1
|
Mast N, Butts M, Pikuleva IA. Unbiased insights into the multiplicity of the CYP46A1 brain effects in 5XFAD mice treated with low dose-efavirenz. J Lipid Res 2024; 65:100555. [PMID: 38719151 PMCID: PMC11176809 DOI: 10.1016/j.jlr.2024.100555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 03/12/2024] [Accepted: 05/01/2024] [Indexed: 05/30/2024] Open
Abstract
Cytochrome P450 46A1 (CYP46A1) is the CNS-specific cholesterol 24-hydroxylase that controls cholesterol elimination and turnover in the brain. In mouse models, pharmacologic CYP46A1 activation with low-dose efavirenz or by gene therapy mitigates the manifestations of various brain disorders, neurologic, and nonneurologic, by affecting numerous, apparently unlinked biological processes. Accordingly, CYP46A1 is emerging as a promising therapeutic target; however, the mechanisms underlying the multiplicity of the brain CYP46A1 activity effects are currently not understood. We proposed the chain reaction hypothesis, according to which CYP46A1 is important for the three primary (unifying) processes in the brain (sterol flux through the plasma membranes, acetyl-CoA, and isoprenoid production), which in turn affect a variety of secondary processes. We already identified several processes secondary to changes in sterol flux and herein undertook a multiomics approach to compare the brain proteome, acetylproteome, and metabolome of 5XFAD mice (an Alzheimer's disease model), control and treated with low-dose efavirenz. We found that the latter had increased production of phospholipids from the corresponding lysophospholipids and a globally increased protein acetylation (including histone acetylation). Apparently, these effects were secondary to increased acetyl-CoA production. Signaling of small GTPases due to their altered abundance or abundance of their regulators could be affected as well, potentially via isoprenoid biosynthesis. In addition, the omics data related differentially abundant molecules to other biological processes either reported previously or new. Thus, we obtained unbiased mechanistic insights and identified potential players mediating the multiplicity of the CYP46A1 brain effects and further detailed our chain reaction hypothesis.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, USA
| | - Makaya Butts
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, USA.
| |
Collapse
|
2
|
El-Darzi N, Mast N, Li Y, Pikuleva IA. APOB100 transgenic mice exemplify how the systemic circulation content may affect the retina without altering retinal cholesterol input. Cell Mol Life Sci 2024; 81:52. [PMID: 38253888 PMCID: PMC10803575 DOI: 10.1007/s00018-023-05056-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 10/24/2023] [Accepted: 11/17/2023] [Indexed: 01/24/2024]
Abstract
Apolipoprotein B (APOB) is a constituent of unique lipoprotein particles (LPPs) produced in the retinal pigment epithelium (RPE), which separates the neural retina from Bruch's membrane (BrM) and choroidal circulation. These LPPs accumulate with age in BrM and contribute to the development of age-related macular degeneration, a major blinding disease. The APOB100 transgenic expression in mice, which unlike humans lack the full-length APOB100, leads to lipid deposits in BrM. Herein, we further characterized APOB100 transgenic mice. We imaged mouse retina in vivo and assessed chorioretinal lipid distribution, retinal sterol levels, retinal cholesterol input, and serum content as well as tracked indocyanine green-bound LPPs in mouse plasma and retina after an intraperitoneal injection. Retinal function and differentially expressed proteins were also investigated. APOB100 transgenic mice had increased serum LDL content and an additional higher density HDL subpopulation; their retinal cholesterol levels (initially decreased) became normal with age. The LPP cycling between the RPE and choroidal circulation was increased. Yet, LPP trafficking from the RPE to the neural retina was limited, and total retinal cholesterol input did not change. There were lipid deposits in the RPE and BrM, and retinal function was impaired. Retinal proteomics provided mechanistic insights. Collectively, our data suggested that the serum LDL/HDL ratio may not affect retinal pathways of cholesterol input as serum LPP load is mainly handled by the RPE, which offloads LPP excess to the choroidal circulation rather than neural retina. Different HDL subpopulations should be considered in studies linking serum LPPs and age-related macular degeneration.
Collapse
Affiliation(s)
- Nicole El-Darzi
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Yong Li
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA.
| |
Collapse
|
3
|
Masson EAY, Serrano J, Leger-Charnay E, Acar N. Cholesterol and oxysterols in retinal neuron-glia interactions: relevance for glaucoma. FRONTIERS IN OPHTHALMOLOGY 2024; 3:1303649. [PMID: 38983043 PMCID: PMC11182186 DOI: 10.3389/fopht.2023.1303649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 12/04/2023] [Indexed: 07/11/2024]
Abstract
Cholesterol is an essential component of cellular membranes, crucial for maintaining their structural and functional integrity. It is especially important for nervous tissues, including the retina, which rely on high amounts of plasma membranes for the transmission of the nervous signal. While cholesterol is by far the most abundant sterol, the retina also contains cholesterol precursors and metabolites, especially oxysterols, which are bioactive molecules. Cholesterol lack or excess is deleterious and some oxysterols are known for their effect on neuron survival. Cholesterol homeostasis must therefore be maintained. Retinal glial cells, especially Müller cells, the principal glial cells of the vertebrate retina, provide mechanical, nutritional, and metabolic support for the neighboring neurons. Several pieces of evidence indicate that Müller cells are major actors of cholesterol homeostasis in the retina, as it is known for other glial cells in the brain. This process is based on a close cooperation with neurons, and sterols can be signaling molecules participating in glia-neuron interactions. While some implication of cholesterol in age-related macular degeneration is now recognized, based on epidemiological and laboratory data, evidence for its role in glaucoma is still scarce. The association between cholesterolemia and glaucoma is controversial, but experimental data suggest that sterols could take part in the pathological processes. It has been demonstrated that Müller glial cells are implicated in the development of glaucoma through an ambivalent reactive retinal gliosis process. The early steps contribute to maintaining retinal homeostasis and favor the survival of ganglion cells, which are targeted during glaucoma. If gliosis persists, dysregulation of the neuroprotective functions, cytotoxic effects of gliotic Müller cells and disruption of glia-neuron interactions lead to an acceleration of ganglion cell death. Sterols could play a role in the glial cell response to glaucomatous injury. This represents an understudied but attractive topic to better understand glaucoma and conceive novel preventive or curative strategies. The present review describes the current knowledge on i) sterol metabolism in retinal glial cells, ii) the potential role of cholesterol in glaucoma, and iii) the possible relationships between cholesterol and oxysterols, glial cells and glaucoma. Focus is put on glia-neuron interactions.
Collapse
Affiliation(s)
- Elodie A Y Masson
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, CNRS, INRAE, Institut Agro, Université de Bourgogne, Dijon, France
| | - Jeanne Serrano
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, CNRS, INRAE, Institut Agro, Université de Bourgogne, Dijon, France
- Sensory Perception, Glia/Neuron Interaction Research Group, Centre des Sciences du Goût et de l'Alimentation, CNRS, INRAE, Institut Agro, Université de Bourgogne, Dijon, France
| | - Elise Leger-Charnay
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, CNRS, INRAE, Institut Agro, Université de Bourgogne, Dijon, France
| | - Niyazi Acar
- Eye and Nutrition Research Group, Centre des Sciences du Goût et de l'Alimentation, CNRS, INRAE, Institut Agro, Université de Bourgogne, Dijon, France
| |
Collapse
|
4
|
McCarty KD, Liu L, Tateishi Y, Wapshott-Stehli HL, Guengerich FP. The multistep oxidation of cholesterol to pregnenolone by human cytochrome P450 11A1 is highly processive. J Biol Chem 2024; 300:105495. [PMID: 38006947 PMCID: PMC10716780 DOI: 10.1016/j.jbc.2023.105495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 11/17/2023] [Accepted: 11/20/2023] [Indexed: 11/27/2023] Open
Abstract
Cytochrome P450 (P450, CYP) 11A1 is the classical cholesterol side chain cleavage enzyme (P450scc) that removes six carbons of the side chain, the first and rate-limiting step in the synthesis of all mammalian steroids. The reaction is a 3-step, 6-electron oxidation that proceeds via formation of 22R-hydroxy (OH) and 20R,22R-(OH)2 cholesterol, yielding pregnenolone. We expressed human P450 11A1 in bacteria, purified the enzyme in the absence of nonionic detergents, and assayed pregnenolone formation by HPLC-mass spectrometry of the dansyl hydrazone. The reaction was inhibited by the nonionic detergent Tween 20, and several lipids did not enhance enzymatic activity. The 22R-OH and 20R,22R-(OH)2 cholesterol intermediates were bound to P450 11A1 relatively tightly, as judged by steady-state optical titrations and koff rates. The electron donor adrenodoxin had little effect on binding; the substrate cholesterol showed a ∼5-fold stimulatory effect on the binding of adrenodoxin to P450 11A1. Presteady-state single-turnover kinetic analysis was consistent with a highly processive reaction with rates of intermediate oxidation steps far exceeding dissociation rates for products and substrates. The presteady-state kinetic analysis revealed a second di-OH cholesterol product, separable by HPLC, in addition to 20R,22R-(OH)2 cholesterol, which we characterized as a rotamer that was also converted to pregnenolone at a similar rate. The first oxidation step (at C-22) is the slowest, limiting the overall rate of cleavage. d3-Cholesterol showed no kinetic deuterium isotope effect on C-22, indicating that C-H bond cleavage is not rate-limiting in the first hydroxylation step.
Collapse
Affiliation(s)
- Kevin D McCarty
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Lu Liu
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Yasuhiro Tateishi
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
| |
Collapse
|
5
|
Pikuleva IA. Challenges and Opportunities in P450 Research on the Eye. Drug Metab Dispos 2023; 51:1295-1307. [PMID: 36914277 PMCID: PMC10506698 DOI: 10.1124/dmd.122.001072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 02/14/2023] [Accepted: 03/06/2023] [Indexed: 03/15/2023] Open
Abstract
Of the 57 cytochrome P450 enzymes found in humans, at least 30 have ocular tissues as an expression site. Yet knowledge of the roles of these P450s in the eye is limited, in part because only very few P450 laboratories expanded their research interests to studies of the eye. Hence the goal of this review is to bring attention of the P450 community to the eye and encourage more ocular studies. This review is also intended to be educational for eye researchers and encourage their collaborations with P450 experts. The review starts with a description of the eye, a fascinating sensory organ, and is followed by sections on ocular P450 localizations, specifics of drug delivery to the eye, and individual P450s, which are grouped and presented based on their substrate preferences. In sections describing individual P450s, available eye-relevant information is summarized and concluded by the suggestions on the opportunities in ocular studies of the discussed enzymes. Potential challenges are addressed as well. The conclusion section outlines several practical suggestions on how to initiate eye-related research. SIGNIFICANCE STATEMENT: This review focuses on the cytochrome P450 enzymes in the eye to encourage their ocular investigations and collaborations between P450 and eye researchers.
Collapse
Affiliation(s)
- Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| |
Collapse
|
6
|
El-Darzi N, Mast N, Li Y, Dailey B, Kang M, Rhee DJ, Pikuleva IA. The normalizing effects of the CYP46A1 activator efavirenz on retinal sterol levels and risk factors for glaucoma in Apoj -/- mice. Cell Mol Life Sci 2023; 80:194. [PMID: 37392222 PMCID: PMC10314885 DOI: 10.1007/s00018-023-04848-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/16/2023] [Accepted: 06/23/2023] [Indexed: 07/03/2023]
Abstract
Apolipoprotein J (APOJ) is a multifunctional protein with genetic evidence suggesting an association between APOJ polymorphisms and Alzheimer's disease as well as exfoliation glaucoma. Herein we conducted ocular characterizations of Apoj-/- mice and found that their retinal cholesterol levels were decreased and that this genotype had several risk factors for glaucoma: increased intraocular pressure and cup-to-disk ratio and impaired retinal ganglion cell (RGC) function. The latter was not due to RGC degeneration or activation of retinal Muller cells and microglia/macrophages. There was also a decrease in retinal levels of 24-hydroxycholesterol, a suggested neuroprotectant under glaucomatous conditions and a positive allosteric modulator of N-methyl-D-aspartate receptors mediating the light-evoked response of the RGC. Therefore, Apoj-/- mice were treated with low-dose efavirenz, an allosteric activator of CYP46A1 which converts cholesterol into 24-hydroxycholesterol. Efavirenz treatment increased retinal cholesterol and 24-hydroxycholesterol levels, normalized intraocular pressure and cup-to-disk ratio, and rescued in part RGC function. Retinal expression of Abcg1 (a cholesterol efflux transporter), Apoa1 (a constituent of lipoprotein particles), and Scarb1 (a lipoprotein particle receptor) was increased in EVF-treated Apoj-/- mice, indicating increased retinal cholesterol transport on lipoprotein particles. Ocular characterizations of Cyp46a1-/- mice supported the beneficial efavirenz treatment effects via CYP46A1 activation. The data obtained demonstrate an important APOJ role in retinal cholesterol homeostasis and link this apolipoprotein to the glaucoma risk factors and retinal 24-hydroxycholesterol production by CYP46A1. As the CYP46A1 activator efavirenz is an FDA-approved anti-HIV drug, our studies suggest a new therapeutic approach for treatment of glaucomatous conditions.
Collapse
Affiliation(s)
- Nicole El-Darzi
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Yong Li
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Brian Dailey
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Min Kang
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Douglas J Rhee
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Science, Case Western Reserve University, Cleveland, OH, 44106, USA.
| |
Collapse
|
7
|
Mast N, El-Darzi N, Li Y, Pikuleva IA. Quantitative characterizations of the cholesterol-related pathways in the retina and brain of hamsters. J Lipid Res 2023:100401. [PMID: 37330011 PMCID: PMC10394389 DOI: 10.1016/j.jlr.2023.100401] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 06/08/2023] [Accepted: 06/13/2023] [Indexed: 06/19/2023] Open
Abstract
The retina and brain are separated from the systemic circulation by the anatomical barriers, which are permeable (the outer blood-retinal barrier) and impermeable (the blood-brain and inner blood-retina barriers) to cholesterol. Herein we investigated whether the whole-body cholesterol maintenance affects cholesterol homeostasis in the retina and brain. We used hamsters, whose whole-body cholesterol handling is more similar to those in humans than in mice and conducted separate administrations of deuterated water and deuterated cholesterol. We assessed the quantitative significance of the retinal and brain pathways of cholesterol input and compared the results with those from our previous studies in mice. The utility of the measurements in the plasma of deuterated 24-hydroxycholesterol, the major cholesterol elimination product from the brain, was investigated as well. We established that despite a 7-fold higher serum LDL to HDL ratio and other cholesterol-related differences, in situ biosynthesis remained the major source of cholesterol for hamster retina, although its quantitative significance was reduced to 53% as compared to 72-78% in mouse retina. In the brain, the principal pathway of cholesterol input was also the same, in situ biosynthesis, accounting for 94% of the total brain cholesterol input (96% in mice); the interspecies differences pertained to the absolute rates of the total cholesterol input and turnover. We documented the correlations between deuterium enrichments of the brain 24-hydroxycholesterol, brain cholesterol, and plasma 24-hydroxycholesterol, which suggested that deuterium enrichment of plasma 24-hydroxycholesteol could be an in vivo marker of cholesterol elimination and turnover in the brain.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - Yong Li
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA.
| |
Collapse
|
8
|
Kakiyama G, Rodriguez-Agudo D, Pandak WM. Mitochondrial Cholesterol Metabolites in a Bile Acid Synthetic Pathway Drive Nonalcoholic Fatty Liver Disease: A Revised "Two-Hit" Hypothesis. Cells 2023; 12:1434. [PMID: 37408268 PMCID: PMC10217489 DOI: 10.3390/cells12101434] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 05/15/2023] [Accepted: 05/17/2023] [Indexed: 07/07/2023] Open
Abstract
The rising prevalence of nonalcoholic fatty liver disease (NAFLD)-related cirrhosis highlights the need for a better understanding of the molecular mechanisms responsible for driving the transition of hepatic steatosis (fatty liver; NAFL) to steatohepatitis (NASH) and fibrosis/cirrhosis. Obesity-related insulin resistance (IR) is a well-known hallmark of early NAFLD progression, yet the mechanism linking aberrant insulin signaling to hepatocyte inflammation has remained unclear. Recently, as a function of more distinctly defining the regulation of mechanistic pathways, hepatocyte toxicity as mediated by hepatic free cholesterol and its metabolites has emerged as fundamental to the subsequent necroinflammation/fibrosis characteristics of NASH. More specifically, aberrant hepatocyte insulin signaling, as found with IR, leads to dysregulation in bile acid biosynthetic pathways with the subsequent intracellular accumulation of mitochondrial CYP27A1-derived cholesterol metabolites, (25R)26-hydroxycholesterol and 3β-Hydroxy-5-cholesten-(25R)26-oic acid, which appear to be responsible for driving hepatocyte toxicity. These findings bring forth a "two-hit" interpretation as to how NAFL progresses to NAFLD: abnormal hepatocyte insulin signaling, as occurs with IR, develops as a "first hit" that sequentially drives the accumulation of toxic CYP27A1-driven cholesterol metabolites as the "second hit". In the following review, we examine the mechanistic pathway by which mitochondria-derived cholesterol metabolites drive the development of NASH. Insights into mechanistic approaches for effective NASH intervention are provided.
Collapse
Affiliation(s)
- Genta Kakiyama
- Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA; (D.R.-A.); (W.M.P.)
- Research Services, Central Virginia Veterans Affairs Healthcare System, Richmond, VA 23249, USA
| | - Daniel Rodriguez-Agudo
- Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA; (D.R.-A.); (W.M.P.)
- Research Services, Central Virginia Veterans Affairs Healthcare System, Richmond, VA 23249, USA
| | - William M. Pandak
- Department of Internal Medicine, Virginia Commonwealth University School of Medicine, Richmond, VA 23298, USA; (D.R.-A.); (W.M.P.)
- Research Services, Central Virginia Veterans Affairs Healthcare System, Richmond, VA 23249, USA
| |
Collapse
|
9
|
El-Darzi N, Mast N, Hammer SS, Dorweiler TF, Busik JV, Pikuleva IA. 2-Hydroxypropyl-β-cyclodextrin mitigates pathological changes in a mouse model of retinal cholesterol dyshomeostasis. J Lipid Res 2022; 64:100323. [PMID: 36586438 PMCID: PMC9883287 DOI: 10.1016/j.jlr.2022.100323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/22/2022] [Accepted: 12/12/2022] [Indexed: 12/30/2022] Open
Abstract
CYP46A1 is a CNS-specific enzyme, which eliminates cholesterol from the brain and retina by metabolism to 24-hydroxycholesterol, thus contributing to cholesterol homeostasis in both organs. 2-Hydroxypropyl-β-cyclodextrin (HPCD), a Food and Drug Administration-approved formulation vehicle, is currently being investigated off-label for treatment of various diseases, including retinal diseases. HPCD was shown to lower retinal cholesterol content in mice but had not yet been evaluated for its therapeutic benefits. Herein, we put Cyp46a1-/- mice on high fat cholesterol-enriched diet from 1 to 14 months of age (control group) and at 12 months of age, started to treat a group of these animals with HPCD until the age of 14 months. We found that as compared with mature and regular chow-fed Cyp46a1-/- mice, control group had about 6-fold increase in the retinal total cholesterol content, focal cholesterol and lipid deposition in the photoreceptor-Bruch's membrane region, and retinal macrophage activation. In addition, aged animals had cholesterol crystals at the photoreceptor-retinal pigment epithelium interface and changes in the Bruch's membrane ultrastructure. HPCD treatment mitigated all these manifestations of retinal cholesterol dyshomeostasis and altered the abundance of six groups of proteins (genetic information transfer, vesicular transport, and cytoskeletal organization, endocytosis and lysosomal processing, unfolded protein removal, lipid homeostasis, and Wnt signaling). Thus, aged Cyp46a1-/- mice on high fat cholesterol-enriched diet revealed pathological changes secondary to retinal cholesterol overload and supported further studies of HPCD as a potential therapeutic for age-related macular degeneration and diabetic retinopathy associated with retinal cholesterol dyshomeostasis.
Collapse
Affiliation(s)
- Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Sandra S. Hammer
- Department of Physiology, Michigan State University, East Lansing, MI, USA
| | - Tim F. Dorweiler
- Department of Physiology, Michigan State University, East Lansing, MI, USA
| | - Julia V. Busik
- Department of Physiology, Michigan State University, East Lansing, MI, USA
| | - Irina A. Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA,For correspondence: Irina A. Pikuleva
| |
Collapse
|
10
|
Lerner AJ, Arnold SE, Maxfield E, Koenig A, Toth ME, Fortin B, Mast N, Trombetta BA, Denker J, Pieper AA, Tatsuoka C, Raghupathy S, Pikuleva IA. CYP46A1 activation by low-dose efavirenz enhances brain cholesterol metabolism in subjects with early Alzheimer's disease. Alzheimers Res Ther 2022; 14:198. [PMID: 36581878 PMCID: PMC9797897 DOI: 10.1186/s13195-022-01151-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 12/20/2022] [Indexed: 12/30/2022]
Abstract
BACKGROUND Efavirenz is an anti-HIV drug, and cytochrome P450 46A1 (CYP46A1) is a CNS-specific enzyme that metabolizes cholesterol to 24-hydroxycholesterol (24HC). We have previously shown that allosteric CYP46A1 activation by low-dose efavirenz in a transgenic mouse model of Alzheimer's disease (AD) enhanced both cholesterol elimination and turnover in the brain and improved animal performance in memory tests. Here, we sought to determine whether CYP46A1 could be similarly activated by a low-dose efavirenz in human subjects. METHODS: This pilot study enrolled 5 subjects with early AD. Participants were randomized to placebo (n = 1) or two daily efavirenz doses (50 mg and 200 mg, n = 2 for each) for 20 weeks and evaluated for safety and CYP46A1 target engagement (plasma 24HC levels). A longitudinal mixed model was used to ascertain the statistical significance of target engagement. We also measured 24HC in CSF and conducted a unique stable isotope labeling kinetics (SILK) study with deuterated water to directly measure CYP46A1 activity changes in the brain. RESULTS In subjects receiving efavirenz, there was a statistically significant within-group increase (P ≤ 0.001) in the levels of plasma 24HC from baseline. The levels of 24HC in the CSF of subjects on the 200-mg dose of efavirenz were also increased. Target engagement was further supported by the labeling kinetics of 24HC by deuterated water in the SILK study. There were no serious adverse effects in any subjects. CONCLUSIONS Our findings suggest efavirenz target engagement in human subjects with early AD. This supports the pursuit of a larger trial for further determination and confirmation of the efavirenz dose that exerts maximal enzyme activation, as well as evaluation of this drug's effects on AD biomarkers and clinical symptomatology. TRIAL REGISTRATION ClinicalTrials.gov, NCT03706885.
Collapse
Affiliation(s)
- Alan J Lerner
- Brain Health and Memory Center, Neurological Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, 44122, USA
- Department of Neurology, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Steven E Arnold
- Alzheimer's Clinical and Translational Research Unit, Massachusetts General Hospital, Charlestown, MA, 02129, USA
| | - Erin Maxfield
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Aaron Koenig
- Alzheimer's Clinical and Translational Research Unit, Massachusetts General Hospital, Charlestown, MA, 02129, USA
| | - Maria E Toth
- Brain Health and Memory Center, Neurological Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, 44122, USA
| | - Brooke Fortin
- Alzheimer's Clinical and Translational Research Unit, Massachusetts General Hospital, Charlestown, MA, 02129, USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Bianca A Trombetta
- Alzheimer's Clinical and Translational Research Unit, Massachusetts General Hospital, Charlestown, MA, 02129, USA
| | - John Denker
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Andrew A Pieper
- Harrington Discovery Institute, University Hospitals Cleveland Medical Center, Cleveland, OH, 44106, USA
- Department of Psychiatry, Case Western Reserve University, Cleveland, OH, 44106, USA
- Geriatric Psychiatry, GRECC, Louis Stokes Cleveland VA Medical Center, Cleveland, OH, 44106, USA
- Institute for Transformative Molecular Medicine, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Curtis Tatsuoka
- Department of Population and Quantitative Health Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Sangeetha Raghupathy
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, 44106, USA.
| |
Collapse
|
11
|
Mast N, Li Y, Pikuleva IA. Increased Acetylcholine Levels and Other Brain Effects in 5XFAD Mice after Treatment with 8,14-Dihydroxy Metabolite of Efavirenz. Int J Mol Sci 2022; 23:ijms23147669. [PMID: 35887013 PMCID: PMC9317559 DOI: 10.3390/ijms23147669] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 07/06/2022] [Accepted: 07/09/2022] [Indexed: 02/08/2023] Open
Abstract
Efavirenz (EFV), an FDA-approved anti-HIV drug, has off-target binding to CYP46A1, the CNS enzyme which converts cholesterol to 24-hydroxycholesterol. At small doses, EFV allosterically activates CYP46A1 in mice and humans and mitigates some of the Alzheimer's disease manifestations in 5XFAD mice, an animal model. Notably, in vitro, all phase 1 EFV hydroxymetabolites activate CYP46A1 as well and bind either to the allosteric site for EFV, neurotransmitters or both. Herein, we treated 5XFAD mice with 8,14-dihydroxyEFV, the binder to the neurotransmitter allosteric site, which elicits the highest CYP46A1 activation in vitro. We found that treated animals of both sexes had activation of CYP46A1 and cholesterol turnover in the brain, decreased content of the amyloid beta 42 peptide, increased levels of acetyl-CoA and acetylcholine, and altered expression of the brain marker proteins. In addition, male mice had improved performance in the Barnes Maze test and increased expression of the acetylcholine-related genes. This work expands our knowledge of the beneficial CYP46A1 activation effects and demonstrates that 8,14-dihydroxyEFV crosses the blood-brain barrier and has therapeutic potential as a CYP46A1 activator.
Collapse
|
12
|
Mast N, Fotinich A, Pikuleva IA. The Hydroxylation Position Rather than Chirality Determines How Efavirenz Metabolites Activate Cytochrome P450 46A1 In Vitro. Drug Metab Dispos 2022; 50:923-930. [PMID: 35489779 PMCID: PMC11022896 DOI: 10.1124/dmd.122.000874] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 04/05/2022] [Indexed: 11/22/2022] Open
Abstract
(S)-Efavirenz (EFV) is a reverse transcriptase inhibitor and an antiviral drug. In addition, (S)-EFV can interact off target with CYP46A1, the major cholesterol hydroxylating enzyme in the mammalian brain, and allosterically activate CYP46A1 at a small dose in mice and humans. Studies with purified CYP46A1 identified two allosteric sites on the enzyme surface, one for (S)-EFV and the second site for L-glutamate (Glu), a neurotransmitter that also activates CYP46A1 either alone or in the presence of (S)-EFV. Previously, we found that racemic (rac)-7-hydroxyefavirenz, (rac)-8-hydroxyefavirenz, (S)-8-hydroxyefavirenz, and (rac)-8,14-dihydroxyefavirenz, compounds with the hydroxylation positions corresponding to the metabolism of (S)-EFV in the liver, activated CYP46A1 in vitro. Yet, these compounds differed from (S)-EFV in how they allosterically interacted with CYP46A1. Herein, we further characterized (rac)-7-hydroxyefavirenz, (rac)-8-hydroxyefavirenz, (S)-8-hydroxyefavirenz, and (rac)-8,14-dihydroxyefavirenz, and, in addition, (R)-EFV, (S)-7-hydroxyefavirenz, (rac)-7,8-dihydroxyefavirenz, (S)-7,8-dihydroxyefavirenz, and (S)-8,14-dihydroxyefavirenz for activation and binding to CYP46A1 in vitro. We found that the spatial configuration of all tested compounds neither affected the CYP46A1 activation nor the sites of binding to CYP46A1. Yet, the hydroxylation position determined whether the hydroxylated metabolite interacted with the allosteric site for (S)-EFV [(R)-EFV, (rac)-7,8-dihydroxyefavirenz, and (S)-7,8-dihydroxyefavirenz], L-Glu [(rac)- and (S)-8,14-dihydroxyefavirenz], or both [(rac)-7-hydroxyefavirenz, (S)-7-hydroxyefavirenz, (rac)-8-hydroxyefavirenz, and (S)-8-hydroxyefavirenz]. This difference in binding to the allosteric sites determined, in turn, how CYP46A1 activity was changed in the coincubations with (S)-EFV and either its metabolite or L-Glu. The results suggest EFV metabolites that could be more potent for CYP46A1 activation in vivo than (S)-EFV. SIGNIFICANCE STATEMENT: This study found that not only efavirenz but also all its hydroxylated metabolites allosterically activate CYP46A1 in vitro. The enzyme activation depended on the hydroxylation position but not the metabolite spatial configuration and involved either one or two allosteric sites-for efavirenz, L-glutamate, or both. The results suggest that the hydroxylated efavirenz metabolites may differ from efavirenz in how they interact with the CYP46A1 allosteric and active sites.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| | - Anna Fotinich
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| |
Collapse
|
13
|
El-Darzi N, Mast N, Buchner DA, Saadane A, Dailey B, Trichonas G, Pikuleva IA. Low-Dose Anti-HIV Drug Efavirenz Mitigates Retinal Vascular Lesions in a Mouse Model of Alzheimer's Disease. Front Pharmacol 2022; 13:902254. [PMID: 35721135 PMCID: PMC9198296 DOI: 10.3389/fphar.2022.902254] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Accepted: 05/02/2022] [Indexed: 12/02/2022] Open
Abstract
A small dose of the anti-HIV drug efavirenz (EFV) was previously discovered to activate CYP46A1, a cholesterol-eliminating enzyme in the brain, and mitigate some of the manifestation of Alzheimer's disease in 5XFAD mice. Herein, we investigated the retina of these animals, which were found to have genetically determined retinal vascular lesions associated with deposits within the retinal pigment epithelium and subretinal space. We established that EFV treatment activated CYP46A1 in the retina, enhanced retinal cholesterol turnover, and diminished the lesion frequency >5-fold. In addition, the treatment mitigated fluorescein leakage from the aberrant blood vessels, deposit size, activation of retinal macrophages/microglia, and focal accumulations of amyloid β plaques, unesterified cholesterol, and Oil Red O-positive lipids. Studies of retinal transcriptomics and proteomics identified biological processes enriched with differentially expressed genes and proteins. We discuss the mechanisms of the beneficial EFV effects on the retinal phenotype of 5XFAD mice. As EFV is an FDA-approved drug, and we already tested the safety of small-dose EFV in patients with Alzheimer's disease, our data support further clinical investigation of this drug in subjects with retinal vascular lesions or neovascular age-related macular degeneration.
Collapse
Affiliation(s)
- Nicole El-Darzi
- Departments of Ophthalmology and Visual Sciences, Cleveland, OH, United States
| | - Natalia Mast
- Departments of Ophthalmology and Visual Sciences, Cleveland, OH, United States
| | - David A. Buchner
- Departments of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Aicha Saadane
- Departments of Ophthalmology and Visual Sciences, Cleveland, OH, United States
| | - Brian Dailey
- Departments of Ophthalmology and Visual Sciences, Cleveland, OH, United States
| | - Georgios Trichonas
- Departments of Ophthalmology and Visual Sciences, Cleveland, OH, United States
| | - Irina A. Pikuleva
- Departments of Ophthalmology and Visual Sciences, Cleveland, OH, United States,*Correspondence: Irina A. Pikuleva,
| |
Collapse
|
14
|
Bryl A, Mrugacz M, Falkowski M, Zorena K. The Effect of Hyperlipidemia on the Course of Diabetic Retinopathy—Literature Review. J Clin Med 2022; 11:jcm11102761. [PMID: 35628887 PMCID: PMC9146710 DOI: 10.3390/jcm11102761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 04/29/2022] [Accepted: 05/11/2022] [Indexed: 12/16/2022] Open
Abstract
Diabetes mellitus is a very important social issue, and its retinal complications continue to be one of the major causes of blindness worldwide. The effect of glucose level on the development of retinal retinopathy has been the subject of numerous studies and is well understood. Hypertension and hyperlipidemia have been known to be important risk factors in the development of diabetes complications. However, the mechanisms of this effect have not been fully explained and raise a good deal of controversy. The latest research results suggest that some lipoproteins are closely correlated with the incidence of diabetic retinopathy and that by exerting an impact on their level the disease course can be modulated. Moreover, pharmacotherapy which reduces the level of lipids, particularly by means of statins and fibrate, has been shown to alleviate diabetic retinopathy. Therefore, we have decided to review the latest literature on diabetic retinopathy with respect to the impact of hyperlipidemia and possible preventive measures
Collapse
Affiliation(s)
- Anna Bryl
- Department of Ophthalmology and Eye Rehabilitation, Medical University of Bialystok, Waszyngtona 17, 15-274 Bialystok, Poland;
- Correspondence:
| | - Małgorzata Mrugacz
- Department of Ophthalmology and Eye Rehabilitation, Medical University of Bialystok, Waszyngtona 17, 15-274 Bialystok, Poland;
| | - Mariusz Falkowski
- PhD Studies, Medical University of Bialystok, 15-089 Bialystok, Poland;
| | - Katarzyna Zorena
- Department of Immunobiology and Environmental Microbiology, Medical University of Gdansk, 80-211 Gdansk, Poland;
| |
Collapse
|
15
|
Jenkins AJ, Grant MB, Busik JV. Lipids, hyperreflective crystalline deposits and diabetic retinopathy: potential systemic and retinal-specific effect of lipid-lowering therapies. Diabetologia 2022; 65:587-603. [PMID: 35149880 PMCID: PMC9377536 DOI: 10.1007/s00125-022-05655-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 12/14/2021] [Indexed: 12/19/2022]
Abstract
The metabolically active retina obtains essential lipids by endogenous biosynthesis and from the systemic circulation. Clinical studies provide limited and sometimes conflicting evidence as to the relationships between circulating lipid levels and the development and progression of diabetic retinopathy in people with diabetes. Cardiovascular-system-focused clinical trials that also evaluated some retinal outcomes demonstrate the potential protective power of lipid-lowering therapies in diabetic retinopathy and some trials with ocular primary endpoints are in progress. Although triacylglycerol-lowering therapies with fibrates afforded some protection against diabetic retinopathy, the effect was independent of changes in traditional blood lipid classes. While systemic LDL-cholesterol lowering with statins did not afford protection against diabetic retinopathy in most clinical trials, and none of the trials focused on retinopathy as the main outcome, data from very large database studies suggest the possible effectiveness of statins. Potential challenges in these studies are discussed, including lipid-independent effects of fibrates and statins, modified lipoproteins and retinal-specific effects of lipid-lowering drugs. Dysregulation of retinal-specific cholesterol metabolism leading to retinal cholesterol accumulation and potential formation of cholesterol crystals are also addressed.
Collapse
Affiliation(s)
- Alicia J Jenkins
- NHMRC Clinical Trials Centre, The University of Sydney, Sydney, NSW, Australia
| | - Maria B Grant
- Department of Ophthalmology and Vision Science, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Julia V Busik
- Department of Physiology, Michigan State University, East Lansing, MI, USA.
| |
Collapse
|
16
|
Léger-Charnay E, Gambert S, Martine L, Dubus E, Maire MA, Buteau B, Morala T, Gigot V, Bron AM, Bretillon L, Masson EAY. Retinal cholesterol metabolism is perturbated in response to experimental glaucoma in the rat. PLoS One 2022; 17:e0264787. [PMID: 35275950 PMCID: PMC8916636 DOI: 10.1371/journal.pone.0264787] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 02/16/2022] [Indexed: 01/26/2023] Open
Abstract
Alterations of cholesterol metabolism have been described for many neurodegenerative pathologies, such as Alzheimer's disease in the brain and age-related macular degeneration in the retina. Recent evidence suggests that glaucoma, which is characterized by the progressive death of retinal ganglion cells, could also be associated with disruption of cholesterol homeostasis. In the present study we characterized cholesterol metabolism in a rat model of laser-induced intraocular hypertension, the main risk factor for glaucoma. Sterol levels were measured using gas-chromatography and cholesterol-related gene expression using quantitative RT-PCR at various time-points. As early as 18 hours after the laser procedure, genes implicated in cholesterol biosynthesis and uptake were upregulated (+49% and +100% for HMG-CoA reductase and LDLR genes respectively, vs. naive eyes) while genes involved in efflux were downregulated (-26% and -37% for ApoE and CYP27A1 genes, respectively). Cholesterol and precursor levels were consecutively elevated 3 days post-laser (+14%, +40% and +194% for cholesterol, desmosterol and lathosterol, respectively). Interestingly, counter-regulatory mechanisms were transcriptionally activated following these initial dysregulations, which were associated with the restoration of retinal cholesterol homeostasis, favorable to ganglion cell viability, one month after the laser-induced ocular hypertension. In conclusion, we report here for the first time that ocular hypertension is associated with transient major dynamic changes in retinal cholesterol metabolism.
Collapse
Affiliation(s)
- Elise Léger-Charnay
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Ségolène Gambert
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
- Laboratoire de Biochimie Médicale, Plateforme de Biologie Hospitalo-Universitaire, Dijon, France
| | - Lucy Martine
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Elisabeth Dubus
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Marie-Annick Maire
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Bénédicte Buteau
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Tristan Morala
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Vincent Gigot
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Alain M. Bron
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
- Département d’Ophtalmologie, Centre Hospitalo-Universitaire de Dijon, Dijon, France
| | - Lionel Bretillon
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
| | - Elodie A. Y. Masson
- Centre des Sciences du Goût et de l’Alimentation, AgroSup Dijon, CNRS, INRAE, Université Bourgogne Franche-Comté, Dijon, France
- * E-mail:
| |
Collapse
|
17
|
Characterizations of Hamster Retina as a Model for Studies of Retinal Cholesterol Homeostasis. BIOLOGY 2021; 10:biology10101003. [PMID: 34681102 PMCID: PMC8533155 DOI: 10.3390/biology10101003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 11/21/2022]
Abstract
Simple Summary This work represents a comprehensive evaluation of hamster retina by state-of-the-art methodologies and provides evidence that hamsters may represent a better model for studies of retinal cholesterol maintenance than mice. The latter is an important finding, as disturbances in retinal cholesterol homeostasis are linked to age-related macular degeneration and diabetic retinopathy, which are blinding diseases. Abstract Cholesterol homeostasis in the retina, a sensory organ in the back of the eye, has been studied in mice but not hamsters, despite the latter being more similar to humans than mice with respect to their whole-body cholesterol maintenance. The goal of this study was to begin to assess hamster retina and conduct initial interspecies comparisons. First, young (3-month old) and mature (6-month old) Syrian (golden) hamsters were compared with 3- and 6-month old mice for ocular biometrics and retinal appearance on optical coherence tomography and fluorescein angiography. Of the 30 evaluated hamsters, seven had retinal structural abnormalities and all had increased permeability of retinal blood vessels. However, hamsters did not carry the mutations causing retinal degenerations 1 and 8, had normal blood glucose levels, and only slightly elevated hemoglobin A1c content. Cholesterol and six other sterols were quantified in hamster retina and compared with sterol profiles in mouse and human retina. These comparisons suggested that cholesterol turnover is much higher in younger than mature hamster retina, and that mature hamster and human retinas share similarities in the ratios of cholesterol metabolites to cholesterol. This study supports further investigations of cholesterol maintenance in hamster retina.
Collapse
|
18
|
Qiang W, Wei R, Chen Y, Chen D. Clinical Pathological Features and Current Animal Models of Type 3 Macular Neovascularization. Front Neurosci 2021; 15:734860. [PMID: 34512255 PMCID: PMC8427186 DOI: 10.3389/fnins.2021.734860] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 07/29/2021] [Indexed: 02/05/2023] Open
Abstract
Type 3 macular neovascularization (MNV3), or retinal angiomatous proliferation (RAP), is a distinct type of neovascular age-related macular degeneration (AMD), which is a leading cause of vision loss in older persons. During the past decade, systematic investigation into the clinical, multimodal imaging, and histopathological features and therapeutic outcomes has provided important new insight into this disease. These studies favor the retinal origin of MNV3 and suggest the involvement of retinal hypoxia, inflammation, von Hippel–Lindau (VHL)–hypoxia-inducible factor (HIF)–vascular endothelial growth factor (VEGF) pathway, and multiple cell types in the development and progression of MNV3. Several mouse models, including the recently built Rb/p107/Vhl triple knockout mouse model by our group, have induced many of the histological features of MNV3 and provided much insight into the underlying pathological mechanisms. These models have revealed the roles of retinal hypoxia, inflammation, lipid metabolism, VHL/HIF pathway, and retinoblastoma tumor suppressor (Rb)–E2F cell cycle pathway in the development of MNV3. This article will summarize the clinical, multimodal imaging, and pathological features of MNV3 and the diversity of animal models that exist for MNV3, as well as their strengths and limitations.
Collapse
Affiliation(s)
- Wei Qiang
- Research Laboratory of Ophthalmology and Vision Sciences, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| | - Ran Wei
- Research Laboratory of Ophthalmology and Vision Sciences, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| | - Yongjiang Chen
- The School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, Canada
| | - Danian Chen
- Research Laboratory of Ophthalmology and Vision Sciences, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| |
Collapse
|
19
|
Abstract
Cholesterol is a quantitatively and biologically significant constituent of all mammalian cell membrane, including those that comprise the retina. Retinal cholesterol homeostasis entails the interplay between de novo synthesis, uptake, intraretinal sterol transport, metabolism, and efflux. Defects in these complex processes are associated with several congenital and age-related disorders of the visual system. Herein, we provide an overview of the following topics: (a) cholesterol synthesis in the neural retina; (b) lipoprotein uptake and intraretinal sterol transport in the neural retina and the retinal pigment epithelium (RPE); (c) cholesterol efflux from the neural retina and the RPE; and (d) biology and pathobiology of defects in sterol synthesis and sterol oxidation in the neural retina and the RPE. We focus, in particular, on studies involving animal models of monogenic disorders pertinent to the above topics, as well as in vitro models using biochemical, metabolic, and omic approaches. We also identify current knowledge gaps and opportunities in the field that beg further research in this topic area.
Collapse
Affiliation(s)
- Sriganesh Ramachandra Rao
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA; Research Service, VA Western NY Healthcare System, Buffalo, NY, USA
| | - Steven J Fliesler
- Departments of Ophthalmology and Biochemistry and Neuroscience Graduate Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York- University at Buffalo, Buffalo, NY, USA; Research Service, VA Western NY Healthcare System, Buffalo, NY, USA.
| |
Collapse
|
20
|
Zhang X, Alhasani RH, Zhou X, Reilly J, Zeng Z, Strang N, Shu X. Oxysterols and retinal degeneration. Br J Pharmacol 2021; 178:3205-3219. [PMID: 33501641 DOI: 10.1111/bph.15391] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 01/13/2021] [Accepted: 01/19/2021] [Indexed: 12/11/2022] Open
Abstract
Retinal degeneration, characterised by the progressive death of retinal neurons, is the most common cause of visual impairment. Oxysterols are the cholesterol derivatives produced via enzymatic and/or free radical oxidation that regulate cholesterol homeostasis in the retina. Preclinical and clinical studies have suggested a connection between oxysterols and retinal degeneration. Here, we summarise early and recent work related to retina oxysterol-producing enzymes and the distribution of oxysterols in the retina. We examine the impact of loss of oxysterol-producing enzymes on retinal pathology and explore the molecular mechanisms associated with the toxic or protective roles of individual oxysterols in different types of retinal degeneration. We conclude that increased efforts to better understand the oxysterol-associated pathophysiology will help in the development of effective retinal degeneration therapies. LINKED ARTICLES: This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.
Collapse
Affiliation(s)
- Xun Zhang
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Reem Hasaballah Alhasani
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, UK.,Department of Biology, Faculty of Applied Science, Umm Al-Qura University, Makkah, Saudi Arabia
| | - Xinzhi Zhou
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, UK
| | - James Reilly
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, UK
| | - Zhihong Zeng
- College of Biological and Environmental Engineering, Changsha University, Changsha, Hunan, China
| | - Niall Strang
- Department of Vision Science, Glasgow Caledonian University, Glasgow, UK
| | - Xinhua Shu
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, UK.,Department of Vision Science, Glasgow Caledonian University, Glasgow, UK.,School of Basic Medical Sciences, Shaoyang University, Shaoyang, Hunan, China
| |
Collapse
|
21
|
Busik JV. Lipid metabolism dysregulation in diabetic retinopathy. J Lipid Res 2021; 62:100017. [PMID: 33581416 PMCID: PMC7892987 DOI: 10.1194/jlr.tr120000981] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 12/15/2020] [Accepted: 12/23/2020] [Indexed: 12/12/2022] Open
Abstract
Lipid metabolic abnormalities have emerged as potential risk factors for the development and progression of diabetic complications, including diabetic retinopathy (DR). This review article provides an overview of the results of clinical trials evaluating the potential benefits of lipid-lowering drugs, such as fibrates, omega-3 fatty acids, and statins, for the prevention and treatment of DR. Although several clinical trials demonstrated that treatment with fibrates leads to improvement of DR, there is a dissociation between the protective effects of fibrates in the retina, and the intended blood lipid classes, including plasma triglycerides, total cholesterol, or HDL:LDL cholesterol ratio. Guided by these findings, plasma lipid and lipoprotein-independent mechanisms are addressed based on clinical, cell culture, and animal model studies. Potential retinal-specific effects of fatty acid oxidation products, cholesterol, and ceramide, as well as lipid-independent effects of PPAR alpha activation, are summarized based on the current literature. Overall, this review highlights promising potential of lipid-based treatment strategies further enhanced by the new knowledge of intraretinal lipids and lipoproteins in DR.
Collapse
Affiliation(s)
- Julia V Busik
- Department of Physiology, Michigan State University, East Lansing, MI, USA.
| |
Collapse
|
22
|
Cao X, Guo Y, Wang Y, Wang H, Liu D, Gong Y, Wang J, Chen X, Zhang W. Effects of high-fat diet and Apoe deficiency on retinal structure and function in mice. Sci Rep 2020; 10:18601. [PMID: 33139746 PMCID: PMC7606505 DOI: 10.1038/s41598-020-75576-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 10/16/2020] [Indexed: 12/17/2022] Open
Abstract
To investigate the effects of a high-fat diet (HFD) and apolipoprotein E (Apoe) deficiency on retinal structure and function in mice. Apoe KO mice and wild-type C57BL/6J mice were given a low-fat diet (LFD) or a HFD for 32 weeks. Blood glucose, serum lipids, body weight and visceral fat weight were evaluated. Retinal sterol quantification was carried out by isotope dilution gas chromatography-mass spectrometry. The cholesterol metabolism related genes SCAP-SREBP expressions were detected by qRT-PCR. Retinal function was recorded using an electroretinogram. The thickness of each layer of the retina was measured by optical coherence tomography. Fundus fluorescein angiography was performed to detect retinal vasculature changes. Immunohistochemical staining was used to determine the expression of NF-κB, TNF-α and VEGFR2 in the retina among HFD, HFD Apoe-/-, LFD Apoe-/- and WT mice retinas. HFD feeding caused the mice to gain weight and develop hypercholesterinemia, while Apoe-/- abnormalities also affected blood lipid metabolism. Both HFD and Apoe deficiency elevated retinal cholesterol, especially in the HFD Apoe-/- mice. No up-regulated expression of SCAP-SREBP was observed as a negative regulator. Impaired retinal functions, thinning retinas and abnormal retinal vasculature were observed in the peripheral retinas of the HFD and Apoe-/- mice compared with those in the normal chow group, particularly in the HFD Apoe-/- mice. Moreover, the expression of NF-κB in the retinas of the HFD and Apoe-/- mice was increased, together with upregulated TNF-α mRNA levels and TNF-α expression in the layer of retinal ganglion cells of the peripheral retina. At the same time, the expression level of VEGFR2 was elevated in the intervention groups, most notably in HFD Apoe-/- mice. HFD or Apoe gene deletion had certain adverse effects on retinal function and structure, which were far below the combined factors and induced harm to the retina. Furthermore, HFD caused retinal ischemia and hypoxia. Additionally, Apoe abnormality increased susceptibility to ischemia. These changes upregulated NF-κB expression in ganglion cells and activated downstream TNF-α. Simultaneously, they activated VEGFR2, accelerating angiogenesis and vascular permeability. All of the aforementioned outcomes initiated inflammatory responses to trigger ganglion cell apoptosis and aggravate retinal neovascularization.
Collapse
Affiliation(s)
- Xiupeng Cao
- Tianjin Medical University, Tianjin, China.,Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China.,Nankai University Affiliated Eye Hospital, Tianjin, China
| | - Yatu Guo
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China. .,Nankai University Affiliated Eye Hospital, Tianjin, China.
| | - Yuchuan Wang
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China.,Nankai University Affiliated Eye Hospital, Tianjin, China
| | - Hao Wang
- State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science and Technology, Tianjin, China
| | - Dong Liu
- State Key Laboratory of Food Nutrition and Safety, Tianjin University of Science and Technology, Tianjin, China
| | - Yibo Gong
- Tianjin Medical University, Tianjin, China.,Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China.,Nankai University Affiliated Eye Hospital, Tianjin, China
| | - Jue Wang
- Tianjin Medical University, Tianjin, China.,Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China.,Nankai University Affiliated Eye Hospital, Tianjin, China
| | - Xia Chen
- Tianjin Medical University, Tianjin, China. .,Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China. .,Nankai University Affiliated Eye Hospital, Tianjin, China.
| | - Wei Zhang
- Tianjin Medical University, Tianjin, China. .,Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin, China. .,Nankai University Affiliated Eye Hospital, Tianjin, China.
| |
Collapse
|
23
|
Mast N, El-Darzi N, Petrov AM, Li Y, Pikuleva IA. CYP46A1-dependent and independent effects of efavirenz treatment. Brain Commun 2020; 2:fcaa180. [PMID: 33305262 PMCID: PMC7713991 DOI: 10.1093/braincomms/fcaa180] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/22/2020] [Accepted: 10/05/2020] [Indexed: 12/15/2022] Open
Abstract
Cholesterol excess in the brain is mainly disposed via cholesterol 24-hydroxylation catalysed by cytochrome P450 46A1, a CNS-specific enzyme. Cytochrome P450 46A1 is emerging as a promising therapeutic target for various brain diseases with both enzyme activation and inhibition having therapeutic potential. The rate of cholesterol 24-hydroxylation determines the rate of brain cholesterol turnover and the rate of sterol flux through the plasma membranes. The latter was shown to affect membrane properties and thereby membrane proteins and membrane-dependent processes. Previously we found that treatment of 5XFAD mice, an Alzheimer's disease model, with a small dose of anti-HIV drug efavirenz allosterically activated cytochrome P450 46A1 in the brain and mitigated several disease manifestations. Herein, we generated Cyp46a1-/- 5XFAD mice and treated them, along with 5XFAD animals, with efavirenz to ascertain cytochrome P450 46A1-dependent and independent drug effects. Efavirenz-treated versus control Cyp46a1-/- 5XFAD and 5XFAD mice were compared for the brain sterol and steroid hormone content, amyloid β burden, protein and mRNA expression as well as synaptic ultrastructure. We found that the cytochrome P450 46A1-dependent efavirenz effects included changes in the levels of brain sterols, steroid hormones, and such proteins as glial fibrillary acidic protein, Iba1, Munc13-1, post-synaptic density-95, gephyrin, synaptophysin and synapsin-1. Changes in the expression of genes involved in neuroprotection, neurogenesis, synaptic function, inflammation, oxidative stress and apoptosis were also cytochrome P450 46A1-dependent. The total amyloid β load was the same in all groups of animals, except lack of cytochrome P450 46A1 decreased the production of the amyloid β40 species independent of treatment. In contrast, altered transcription of genes from cholinergic, monoaminergic, and peptidergic neurotransmission, steroid sulfation and production as well as vitamin D3 activation was the main CYP46A1-independent efavirenz effect. Collectively, the data obtained reveal that CYP46A1 controls cholesterol availability for the production of steroid hormones in the brain and the levels of biologically active neurosteroids. In addition, cytochrome P450 46A1 activity also seems to affect the levels of post-synaptic density-95, the main postsynaptic density protein, possibly by altering the calcium/calmodulin-dependent protein kinase II inhibitor 1 expression and activity of glycogen synthase kinase 3β. Even at a small dose, efavirenz likely acts as a transcriptional regulator, yet this regulation may not necessarily lead to functional effects. This study further confirmed that cytochrome P450 46A1 is a key enzyme for cholesterol homeostasis in the brain and that the therapeutic efavirenz effects on 5XFAD mice are likely realized via cytochrome P450 46A1 activation.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Alexey M Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Young Li
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, USA
| |
Collapse
|
24
|
Cholesterol Regulation in Age-Related Macular Degeneration: A Framework for Mathematical Modelling of Drusen Biogenesis. Bull Math Biol 2020; 82:135. [PMID: 33044644 DOI: 10.1007/s11538-020-00812-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 09/25/2020] [Indexed: 10/23/2022]
Abstract
In age-related macular degeneration (AMD), there is, in common with many other age-related diseases, the need to distinguish between changes in the ageing eye that lead to disease and those changes that are considered part of a healthy, ageing eye. Various studies investigating the multitude of mechanisms involved in the aetiology of AMD exist within the field of ophthalmology and related medical fields, yet many aspects of it remain poorly understood and only a limited number of therapies are available. A recent study relates drusen's topographically cellular characteristics to the neural retina's metabolic needs and associated cholesterol involvement within the retina. In particular, there is a need to fully understand the maintenance of cholesterol homeostasis in the retina to prevent normal ageing processes from being perturbed towards maculopathy. Here, we present an extensive review of the clinical and physiological features of the ageing retina, as well as mechanisms implicated in pathology, synthesised from a vast body of the published literature. We use this novel synthesis to construct a comprehensive process schematic, encompassing all key species and physiological processes such as nutrients, waste and lipoprotein management. We are therefore able to express these processes in a mathematical language via a comprehensive modelling framework, comprising a set of twenty-three equations spanning three distinct biological compartments. This very general modelling framework may now be adapted to more focused studies on individual mechanisms, processes or components underlying of the many facets of AMD. As an example of such a focused application, we conclude this article with a one-compartment, four-species model of the retinal pigment epithelium, which considers the parametric conditions under which either cholesterol homeostasis or unregulated accumulation of cholesterol may obtain in the ageing eye.
Collapse
|
25
|
El-Darzi N, Mast N, Petrov AM, Pikuleva IA. 2-Hydroxypropyl-β-cyclodextrin reduces retinal cholesterol in wild-type and Cyp27a1 -/- Cyp46a1 -/- mice with deficiency in the oxysterol production. Br J Pharmacol 2020; 178:3220-3234. [PMID: 32698250 DOI: 10.1111/bph.15209] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 07/14/2020] [Accepted: 07/16/2020] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND AND PURPOSE 2-Hydroxypropyl-β-cyclodextrin (HPCD) is an FDA approved vehicle for drug delivery and an efficient cholesterol-lowering agent. HPCD was proposed to lower tissue cholesterol via multiple mechanisms including those mediated by oxysterols. CYP27A1 and CYP46A1 are the major oxysterol-producing enzymes in the retina that convert cholesterol to 27- and 24-hydroxycholesterol, respectively. We investigated whether HPCD treatments affected the retina of wild-type and Cyp27a1-/- Cyp46a1-/- mice that do not produce the major retinal oxysterols. EXPERIMENTAL APPROACH HPCD administration was either by i.p., p.o. or s.c. Delivery to the retina was confirmed by angiography using the fluorescently labelled HPCD. Effects on the levels of retinal sterols, mRNA and proteins were evaluated by GC-MS, qRT-PCR and label-free approach, respectively. KEY RESULTS In both wild-type and Cyp27a1-/- Cyp46a1-/- mice, HPCD crossed the blood-retinal barrier when delivered i.p. and lowered the retinal cholesterol content when administered p.o. and s.c. In both genotypes, oral HPCD treatment affected the expression of cholesterol-related genes as well as the proteins involved in endocytosis, lysosomal function and lipid homeostasis. Mechanistically, liver X receptors and the altered expression of Lipe (hormone-sensitive lipase), Nceh1 (neutral cholesterol ester hydrolase 1) and NLTP (non-specific lipid-transfer protein) could mediate some of the HPCD effects. CONCLUSIONS AND IMPLICATIONS HPCD treatment altered retinal cholesterol homeostasis and is a potential therapeutic approach for the reduction of drusen and subretinal drusenoid deposits, cholesterol-rich lesions and hallmarks of age-related macular degeneration. LINKED ARTICLES This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.
Collapse
Affiliation(s)
- Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Alexey M Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, USA
| |
Collapse
|
26
|
Studies of ApoD -/- and ApoD -/-ApoE -/- mice uncover the APOD significance for retinal metabolism, function, and status of chorioretinal blood vessels. Cell Mol Life Sci 2020; 78:963-983. [PMID: 32440710 DOI: 10.1007/s00018-020-03546-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 04/15/2020] [Accepted: 05/07/2020] [Indexed: 12/26/2022]
Abstract
Apolipoprotein D (APOD) is an atypical apolipoprotein with unknown significance for retinal structure and function. Conversely, apolipoprotein E (APOE) is a typical apolipoprotein with established roles in retinal cholesterol transport. Herein, we immunolocalized APOD to the photoreceptor inner segments and conducted ophthalmic characterizations of ApoD-/- and ApoD-/-ApoE-/- mice. ApoD-/- mice had normal levels of retinal sterols but changes in the chorioretinal blood vessels and impaired retinal function. The whole-body glucose disposal was impaired in this genotype but the retinal glucose metabolism was unchanged. ApoD-/-ApoE-/- mice had altered sterol profile in the retina but apparently normal chorioretinal vasculature and function. The whole-body glucose disposal and retinal glucose utilization were enhanced in this genotype. OB-Rb, both leptin and APOD receptor, was found to be expressed in the photoreceptor inner segments and was at increased abundance in the ApoD-/- and ApoD-/-ApoE-/- retinas. Retinal levels of Glut4 and Cd36, the glucose transporter and scavenger receptor, respectively, were increased as well, thus linking APOD to retinal glucose and fatty acid metabolism and suggesting the APOD-OB-Rb-GLUT4/CD36 axis. In vivo isotopic labeling, transmission electron microscopy, and retinal proteomics provided additional insights into the mechanism underlying the retinal phenotypes of ApoD-/- and ApoD-/-ApoE-/- mice. Collectively, our data suggest that the APOD roles in the retina are context specific and could determine retinal glucose fluxes into different pathways. APOD and APOE do not play redundant, complementary or opposing roles in the retina, rather their interplay is more complex and reflects retinal responses elicited by lack of these apolipoproteins.
Collapse
|
27
|
Petrov AM, Mast N, Li Y, Denker J, Pikuleva IA. Brain sterol flux mediated by cytochrome P450 46A1 affects membrane properties and membrane-dependent processes. Brain Commun 2020; 2. [PMID: 32661514 PMCID: PMC7357967 DOI: 10.1093/braincomms/fcaa043] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cytochrome P450 46A1 encoded by CYP46A1 catalyzes cholesterol 24-hydroxylation and is a CNS-specific enzyme that controls cholesterol removal and turnover in the brain. Accumulating data suggest that increases in cytochrome P450 46A1 activity in mouse models of common neurodegenerative diseases affect various, apparently unlinked biological processes and pathways. Yet, the underlying reason for these multiple enzyme activity effects is currently unknown. Herein, we tested the hypothesis that cytochrome P450 46A1-mediated sterol flux alters physico-chemical properties of the plasma membranes and thereby membrane-dependent events. We used 9-month old 5XFAD mice (an Alzheimer's disease model) treated for 6 months with the anti-HIV drug efavirenz. These animals have previously been shown to have improved behavioral performance, increased cytochrome P450 46A1 activity in the brain, and increased sterol flux through the plasma membranes. We further examined 9-month old Cyp46a1 -/- mice, which have previously been observed to have cognitive deficits and decreased sterol flux through brain membranes. Synaptosomal fractions from the brain of efavirenz-treated 5XFAD mice had essentially unchanged cholesterol levels as compared to control 5XFAD mice. However with efavirenz treatment in these mice, there were changes in the membrane properties (increased cholesterol accessibility, ordering, osmotic resistance, and thickness) as well as total glutamate content and ability to release glutamate in response to mild stimulation. Similarly, the cholesterol content in synaptosomal fractions from the brain of Cyp46a1 -/- mice was essentially the same as in wild type mice but knockout of Cyp46a1 was associated with changes in membrane properties and glutamate content and its exocytotic release. Changes in Cyp46a1 -/- mice were in the opposite direction to those observed in efavirenz-treated vs control 5XFAD mice. Incubation of synaptosomal fractions with the inhibitors of glycogen synthase kinase 3, cyclin-dependent kinase 5, protein phosphatase 1/2A or calcineurin, and protein phosphatase 2B revealed that increased sterol flux in efavirenz-treated vs control 5XFAD mice affected the ability of all four enzymes to modulate glutamate release. In contrast, in Cyp46a1 -/- vs wild type mice, decreased sterol flux altered the ability of only cyclin-dependent kinase 5 and protein phosphatase 2B to regulate the glutamate release. Collectively, our results support cytochrome P450 46A1-mediated sterol flux as an important contributor to the fundamental properties of the membranes, protein phosphorylation, and synaptic transmission Also, our data provide an explanation of how one enzyme, cytochrome P450 46A1, can affect multiple pathways and processes and serve as a common potential target for several neurodegenerative disorders.
Collapse
Affiliation(s)
- Alexey M Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - Young Li
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - John Denker
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH USA
| |
Collapse
|
28
|
Choudhary M, Ismail EN, Yao PL, Tayyari F, Radu RA, Nusinowitz S, Boulton ME, Apte RS, Ruberti JW, Handa JT, Tontonoz P, Malek G. LXRs regulate features of age-related macular degeneration and may be a potential therapeutic target. JCI Insight 2020; 5:131928. [PMID: 31829999 DOI: 10.1172/jci.insight.131928] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 12/05/2019] [Indexed: 12/11/2022] Open
Abstract
Effective treatments and animal models for the most prevalent neurodegenerative form of blindness in elderly people, called age-related macular degeneration (AMD), are lacking. Genome-wide association studies have identified lipid metabolism and inflammation as AMD-associated pathogenic pathways. Given liver X receptors (LXRs), encoded by the nuclear receptor subfamily 1 group H members 2 and 3 (NR1H3 and NR1H2), are master regulators of these pathways, herein we investigated the role of LXR in human and mouse eyes as a function of age and disease and tested the therapeutic potential of targeting LXR. We identified immunopositive LXR fragments in human extracellular early dry AMD lesions and a decrease in LXR expression within the retinal pigment epithelium (RPE) as a function of age. Aged mice lacking LXR presented with isoform-dependent ocular pathologies. Specifically, loss of the Nr1h3 isoform resulted in pathobiologies aligned with AMD, supported by compromised visual function, accumulation of native and oxidized lipids in the outer retina, and upregulation of ocular inflammatory cytokines, while absence of Nr1h2 was associated with ocular lipoidal degeneration. LXR activation not only ameliorated lipid accumulation and oxidant-induced injury in RPE cells but also decreased ocular inflammatory markers and lipid deposition in a mouse model, thereby providing translational support for pursuing LXR-active pharmaceuticals as potential therapies for dry AMD.
Collapse
Affiliation(s)
- Mayur Choudhary
- Duke Eye Center, Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Ebraheim N Ismail
- Department of Bioengineering, Northeastern University, Boston, Massachusetts, USA
| | - Pei-Li Yao
- Duke Eye Center, Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Faryan Tayyari
- Duke Eye Center, Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA
| | - Roxana A Radu
- Stein Eye Institute, Department of Ophthalmology, UCLA, Los Angeles, California, USA
| | - Steven Nusinowitz
- Stein Eye Institute, Department of Ophthalmology, UCLA, Los Angeles, California, USA
| | - Michael E Boulton
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Rajendra S Apte
- Department of Ophthalmology and Visual Sciences, Washington University in Saint Louis School of Medicine, Saint Louis, Missouri, USA
| | - Jeffrey W Ruberti
- Department of Bioengineering, Northeastern University, Boston, Massachusetts, USA
| | - James T Handa
- Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, UCLA, Los Angeles, California, USA
| | - Goldis Malek
- Duke Eye Center, Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina, USA.,Department of Pathology, Duke University School of Medicine, Durham, North Carolina, USA
| |
Collapse
|
29
|
Petrov AM, Astafev AA, Mast N, Saadane A, El-Darzi N, Pikuleva IA. The Interplay between Retinal Pathways of Cholesterol Output and Its Effects on Mouse Retina. Biomolecules 2019; 9:biom9120867. [PMID: 31842366 PMCID: PMC6995521 DOI: 10.3390/biom9120867] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/03/2019] [Accepted: 12/10/2019] [Indexed: 12/14/2022] Open
Abstract
In mammalian retina, cholesterol excess is mainly metabolized to oxysterols by cytochromes P450 27A1 (CYP27A1) and 46A1 (CYP46A1) or removed on lipoprotein particles containing apolipoprotein E (APOE). In contrast, esterification by sterol-O-acyltransferase 1 (SOAT) plays only a minor role in this process. Accordingly, retinal cholesterol levels are unchanged in Soat1-/- mice but are increased in Cyp27a1-/-Cyp46a1-/- and Apoe-/- mice. Herein, we characterized Cyp27a1-/-Cyp46a1-/-Soat1-/- and Cyp27a1-/-Cyp46a1-/-Apoe-/- mice. In the former, retinal cholesterol levels, anatomical gross structure, and vasculature were normal, yet the electroretinographic responses were impaired. Conversely, in Cyp27a1-/-Cyp46a1-/-Apoe-/- mice, retinal cholesterol levels were increased while anatomical structure and vasculature were unaffected with only male mice showing a decrease in electroretinographic responses. Sterol profiling, qRT-PCR, proteomics, and transmission electron microscopy mapped potential compensatory mechanisms in the Cyp27a1-/-Cyp46a1-/-Soat1-/- and Cyp27a1-/-Cyp46a1-/-Apoe-/- retina. These included decreased cholesterol biosynthesis along with enhanced formation of intra- and extracellular vesicles, possibly a reserve mechanism for lowering retinal cholesterol. In addition, there was altered abundance of proteins in Cyp27a1-/-Cyp46a1-/-Soat1-/- mice that can affect photoreceptor function, survival, and retinal energy homeostasis (glucose and fatty acid metabolism). Therefore, the levels of retinal cholesterol do not seem to predict retinal abnormalities, and it is rather the network of compensatory mechanisms that appears to determine retinal phenotype.
Collapse
|
30
|
Mast N, Verwilst P, Wilkey CJ, Guengerich FP, Pikuleva IA. In Vitro Activation of Cytochrome P450 46A1 (CYP46A1) by Efavirenz-Related Compounds. J Med Chem 2019; 63:6477-6488. [PMID: 31617715 PMCID: PMC7226586 DOI: 10.1021/acs.jmedchem.9b01383] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
![]()
Cytochrome P450 46A1 (CYP46A1) is a central nervous system-specific
enzyme, which catalyzes cholesterol 24-hydroxylation. Currently CYP46A1
is being evaluated in a clinical trial for activation by small doses
of the anti-HIV drug efavirenz. Eight efavirenz-related compounds
were investigated for CYP46A1 activation in vitro, induction of a
CYP46A1 spectral response, spectral Kd values, interaction with the P450 allosteric sites, and a model
of binding to the enzyme active site. We gained insight into structure–activity
relationships of efavirenz for CYP46A1 activation and found that the
investigated efavirenz primary metabolites are stronger and better
activators of CYP46A1 than efavirenz. We also established that CYP46A1
is activated by racemates and that a conformational-selection mechanism
is operative in CYP46A1. The results suggest structural modifications
of efavirenz to further increase CYP46A1 activation without inhibition
at high compound concentrations. It is possible that not only efavirenz
but its metabolites activate CYP46A1 in vivo.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, United States
| | - Peter Verwilst
- Department of Chemistry, Korea University, Seoul 02841, Korea
| | - Clayton J Wilkey
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106, United States
| |
Collapse
|
31
|
Pariente A, Peláez R, Pérez-Sala Á, Larráyoz IM. Inflammatory and cell death mechanisms induced by 7-ketocholesterol in the retina. Implications for age-related macular degeneration. Exp Eye Res 2019; 187:107746. [DOI: 10.1016/j.exer.2019.107746] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 07/25/2019] [Accepted: 07/25/2019] [Indexed: 12/16/2022]
|
32
|
Petrov AM, Lam M, Mast N, Moon J, Li Y, Maxfield E, Pikuleva IA. CYP46A1 Activation by Efavirenz Leads to Behavioral Improvement without Significant Changes in Amyloid Plaque Load in the Brain of 5XFAD Mice. Neurotherapeutics 2019; 16:710-724. [PMID: 31062296 PMCID: PMC6694340 DOI: 10.1007/s13311-019-00737-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Efavirenz, the FDA-approved anti-retroviral medication, is evaluated in the clinical trial in patients with mild cognitive impairment or early dementia due to Alzheimer's disease. Efavirenz is assessed for activation of cytochrome P450 46A1 (CYP46A1), a CNS-specific enzyme that converts cholesterol to 24-hydroxycholesterol. Cholesterol 24-hydroxylation is the major pathway for brain cholesterol removal, and a mechanism that controls brain cholesterol turnover. The present study tested efavirenz on 5XFAD mice (an Alzheimer's model) at a very low daily dose of 0.1 mg/kg body weight. Efavirenz treatment started from three months of age, after amyloid plague appearance, and continued for 6 months. This treatment led to CYP46A1 activation in the brain, enhancement of brain cholesterol turnover, behavioral improvements, reduction in microglia activation but increased astrocyte reactivity. The levels of the soluble and insoluble amyloid 40 and 42 peptides were unchanged while the number and area of the dense core amyloid plaques were slightly decreased. The measurements of the brain levels of several pre- and post-synaptic proteins (Munc13-1, PSD-95, gephyrin, synaptophysin, synapsin-1, and calbindin-D28k) suggested efavirenz effect at the synaptic level. Efavirenz treatment in the present work seems to represent a model of behavioral and other improvements independent of the levels of the amyloid peptides and provides insight into potential outcomes of the future clinical trial.
Collapse
Affiliation(s)
- Alexey M Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA
| | - Morrie Lam
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA
| | - Jean Moon
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA
| | - Yong Li
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA
| | - Erin Maxfield
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, 2085 Adelbert Rd., Room 303, Cleveland, OH, 44106, USA.
| |
Collapse
|
33
|
Roizenblatt M, Naranjit N, Maia M, Gehlbach PL. The Question of a Role for Statins in Age-Related Macular Degeneration. Int J Mol Sci 2018; 19:ijms19113688. [PMID: 30469381 PMCID: PMC6274767 DOI: 10.3390/ijms19113688] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 11/18/2018] [Accepted: 11/19/2018] [Indexed: 01/22/2023] Open
Abstract
Age-related macular degeneration (AMD) is the leading cause of irreversible central vision loss in patients over the age of 65 years in industrialized countries. Epidemiologic studies suggest that high dietary fat intake is a risk factor for the development and progression of both vascular and retinal disease. These, and other associations, suggest a hypothesis linking elevated cholesterol and AMD progression. It follows, therefore, that cholesterol-lowering medications, such as statins, may influence the onset and progression of AMD. However, the findings have been inconclusive as to whether statins play a role in AMD. Due to the significant public health implications of a potential inhibitory effect of statins on the onset and progression of AMD, it is important to continually evaluate emerging findings germane to this question.
Collapse
Affiliation(s)
- Marina Roizenblatt
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
- Department of Ophthalmology, Federal University of São Paulo, São Paulo 04023-062, Brazil.
- Vision Institute, IPEPO, Department of Ophthalmology, Paulista Medical School, Federal University of São Paulo, São Paulo 04038-032, Brazil.
| | - Nara Naranjit
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
| | - Mauricio Maia
- Department of Ophthalmology, Federal University of São Paulo, São Paulo 04023-062, Brazil.
- Vision Institute, IPEPO, Department of Ophthalmology, Paulista Medical School, Federal University of São Paulo, São Paulo 04038-032, Brazil.
| | - Peter L Gehlbach
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
| |
Collapse
|
34
|
Saadane A, Mast N, Trichonas G, Chakraborty D, Hammer S, Busik JV, Grant MB, Pikuleva IA. Retinal Vascular Abnormalities and Microglia Activation in Mice with Deficiency in Cytochrome P450 46A1-Mediated Cholesterol Removal. THE AMERICAN JOURNAL OF PATHOLOGY 2018; 189:405-425. [PMID: 30448403 DOI: 10.1016/j.ajpath.2018.10.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 09/27/2018] [Accepted: 10/15/2018] [Indexed: 12/11/2022]
Abstract
CYP46A1 is the cytochrome P450 enzyme that converts cholesterol to 24-hydroxycholesterol, a cholesterol elimination product and a potent liver X receptor (LXR) ligand. We conducted retinal characterizations of Cyp46a1-/- mice that had normal fasting blood glucose levels but up to a 1.8-fold increase in retinal cholesterol. The retina of Cyp46a1-/- mice exhibited venous beading and tortuosity, microglia/macrophage activation, and increased vascular permeability, features commonly associated with diabetic retinopathy. The expression of Lxrα and Lxrβ was increased in both the whole Cyp46a1-/- retina and retinal macroglia/macrophages. The LXR-target genes were affected as well, primarily in activated microglial cells and macrophages. In the latter, the LXR-transactivated genes (Abca1, Abcg1, Apod, Apoe, Mylip, and Arg2) were up-regulated; similarly, there was an up-regulation of the LXR-transrepressed genes (Ccl2, Ptgs2, Cxcl1, Il1b, Il6, Nos2, and Tnfa). For comparison, gene expression was investigated in bone marrow-derived macrophages from Cyp46a1-/- mice as well as retinal and bone marrow-derived macrophages from Cyp27a1-/- and Cyp27a1-/-Cyp46a1-/- mice. CYP46A1 expression was detected in retinal endothelial cells, and this expression was increased in the proinflammatory environment. Retinal Cyp46a1-/- phosphoproteome revealed altered phosphorylation of 30 different proteins, including tight junction protein zonula occludens 1 and aquaporin 4. Collectively, the data obtained establish metabolic and regulatory significance of CYP46A1 for the retina and suggest pharmacologic activation of CYP46A1 as a potential therapeutic approach to dyslipidemia-induced retinal damage.
Collapse
Affiliation(s)
- Aicha Saadane
- Department of Ophthalmology and Visual Sciences, the University Hospitals, Case Western Reserve University, Cleveland, Ohio
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, the University Hospitals, Case Western Reserve University, Cleveland, Ohio
| | - George Trichonas
- Department of Ophthalmology and Visual Sciences, the University Hospitals, Case Western Reserve University, Cleveland, Ohio
| | | | - Sandra Hammer
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - Julia V Busik
- Department of Physiology, Michigan State University, East Lansing, Michigan
| | - Maria B Grant
- Department of Ophthalmology, University of Alabama, Birmingham, Alabama
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, the University Hospitals, Case Western Reserve University, Cleveland, Ohio.
| |
Collapse
|
35
|
Curcio CA. Soft Drusen in Age-Related Macular Degeneration: Biology and Targeting Via the Oil Spill Strategies. Invest Ophthalmol Vis Sci 2018; 59:AMD160-AMD181. [PMID: 30357336 PMCID: PMC6733535 DOI: 10.1167/iovs.18-24882] [Citation(s) in RCA: 173] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
AMD is a major cause of legal blindness in older adults approachable through multidisciplinary research involving human tissues and patients. AMD is a vascular-metabolic-inflammatory disease, in which two sets of extracellular deposits, soft drusen/basal linear deposit (BLinD) and subretinal drusenoid deposit (SDD), confer risk for end-stages of atrophy and neovascularization. Understanding how deposits form can lead to insights for new preventions and therapy. The topographic correspondence of BLinD and SDD with cones and rods, respectively, suggest newly realized exchange pathways among outer retinal cells and across Bruch's membrane and the subretinal space, in service of highly evolved, eye-specific physiology. This review focuses on soft drusen/BLinD, summarizing evidence that a major ultrastructural component is large apolipoprotein B,E-containing, cholesterol-rich lipoproteins secreted by the retinal pigment epithelium (RPE) that offload unneeded lipids of dietary and outer segment origin to create an atherosclerosis-like progression in the subRPE-basal lamina space. Clinical observations and an RPE cell culture system combine to suggest that soft drusen/BLinD form when secretions of functional RPE back up in the subRPE-basal lamina space by impaired egress across aged Bruch's membrane-choriocapillary endothelium. The soft drusen lifecycle includes growth, anterior migration of RPE atop drusen, then collapse, and atrophy. Proof-of-concept studies in humans and animal models suggest that targeting the “Oil Spill in Bruch's membrane” offers promise of treating a process in early AMD that underlies progression to both end-stages. A companion article addresses the antecedents of soft drusen within the biology of the macula.
Collapse
Affiliation(s)
- Christine A Curcio
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
| |
Collapse
|
36
|
Saadane A, Petrov A, Mast N, El-Darzi N, Dao T, Alnemri A, Song Y, Dunaief JL, Pikuleva IA. Mechanisms that minimize retinal impact of apolipoprotein E absence. J Lipid Res 2018; 59:2368-2382. [PMID: 30333155 DOI: 10.1194/jlr.m090043] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Revised: 10/17/2018] [Indexed: 01/28/2023] Open
Abstract
Apolipoprotein E (APOE) is a component of lipid-transporting particles and a recognition ligand for receptors, which bind these particles. The APOE isoform ε2 is a risk factor for age-related macular degeneration; nevertheless, APOE absence in humans and mice does not significantly affect the retina. We found that retinal cholesterol biosynthesis and the levels of retinal cholesterol were increased in Apoe-/- mice, whereas cholesterol elimination by metabolism was decreased. No focal cholesterol deposits were observed in the Apoe-/- retina. Retinal proteomics identified the most abundant cholesterol-related proteins in WT mice and revealed that, of these cholesterol-related proteins, only APOA4 had increased expression in the Apoe-/- retina. In addition, there were changes in retinal abundance of proteins involved in proinflammatory and antiinflammatory responses, cellular cytoskeleton maintenance, vesicular traffic, and retinal iron homeostasis. The data obtained indicate that when APOE is absent, particles containing APOA1, APOA4, and APOJ still transport cholesterol in the intraretinal space, but these particles are not taken up by retinal cells. Therefore, cholesterol biosynthesis inside retinal cells increase, whereas metabolism to oxysterols decreases to prevent cells from cholesterol depletion. These and other compensatory changes underlie only a minor retinal phenotype in Apoe-/- mice.
Collapse
Affiliation(s)
- Aicha Saadane
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Alexey Petrov
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Tung Dao
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| | - Ahab Alnemri
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Ying Song
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Joshua L Dunaief
- F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH
| |
Collapse
|
37
|
Additive neuroprotective effects of 24(S)-hydroxycholesterol and allopregnanolone in an ex vivo rat glaucoma model. Sci Rep 2018; 8:12851. [PMID: 30150786 PMCID: PMC6110753 DOI: 10.1038/s41598-018-31239-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 08/15/2018] [Indexed: 11/25/2022] Open
Abstract
In a rat ex vivo acute glaucoma model, high pressure (75 mmHg) causes swelling of ganglion cell axons and elevates levels of the endogenous steroids 24(S)-hydroxycholesterol (24SH) and allopregnanolone (AlloP). Furthermore, 24SH (0.1 µM) alone elevates AlloP levels via NMDA receptors. With this model, we now investigate possible interactions between 24SH and AlloP. We found that inhibition of AlloP synthesis with dutasteride under high pressure results in severe excitotoxicity in addition to axonal swelling. The excitotoxicity is prevented by exogenous AlloP but not 24SH, indicating that endogenous AlloP is crucial for protection. However, inhibition of 24SH synthesis with voriconazole induces severe excitotoxicity under normal pressure. Paradoxically, the excitotoxicity by voriconazole is better prevented by AlloP than 24SH. These findings suggest that inhibition of 24SH synthesis becomes excitotoxic in the absence of AlloP. We also observed that co-administration of sub-micromolar 24SH (0.1 µM) and AlloP (0.1 µM), concentrations that are only partially effective when administered alone, prevents axonal swelling under high pressure. This apparent enhanced protection indicates strong interaction between the two neurosteroids to preserve neuronal integrity, with 24SH contributing to AlloP synthesis via NMDA receptors and with AlloP playing an essential role in neuroprotection via GABAA receptors.
Collapse
|
38
|
Mast N, Bederman IR, Pikuleva IA. Retinal Cholesterol Content Is Reduced in Simvastatin-Treated Mice Due to Inhibited Local Biosynthesis Albeit Increased Uptake of Serum Cholesterol. Drug Metab Dispos 2018; 46:1528-1537. [PMID: 30115644 DOI: 10.1124/dmd.118.083345] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 08/14/2018] [Indexed: 12/18/2022] Open
Abstract
Statins, a class of cholesterol-lowering drugs, are currently being investigated for treatment of age-related macular degeneration, a retinal disease. Herein, retinal and serum concentrations of four statins (atorvastatin, simvastatin, pravastatin, and rosuvastatin) were evaluated after mice were given a single drug dose of 60 mg/kg body weight. All statins, except rosuvastatin, were detected in the retina: atorvastatin and pravastatin at 1.6 pmol and simvastatin at 4.1 pmol. Serum statin concentrations (pmol/ml) were 223 (simvastatin), 1401 (atorvastatin), 2792 (pravastatin), and 9050 (rosuvastatin). Simvastatin was then administered to mice daily for 6 weeks at 60 mg/kg body weight. Simvastatin treatment reduced serum cholesterol levels by 18% and retinal content of cholesterol and lathosterol (but not desmosterol) by 24% and 21%, respectively. The relative contributions of retinal cholesterol biosynthesis and retinal uptake of serum cholesterol to total retinal cholesterol input were changed as well. These contributions were 79% and 21%, respectively, in vehicle-treated mice and 69% and 31%, respectively, in simvastatin-treated mice. Thus, simvastatin treatment lowered retinal cholesterol because a compensatory upregulation of retinal uptake of serum cholesterol was not sufficient to overcome the effect of inhibited retinal biosynthesis. Simultaneously, simvastatin-treated mice had a 2.9-fold increase in retinal expression of Cd36, the major receptor clearing oxidized low-density lipoproteins from Bruch's membrane. Notably, simvastatin treatment essentially did not affect brain cholesterol homeostasis. Our results reveal the statin effect on the retinal and brain cholesterol input and are of value for future clinical investigations of statins as potential therapeutics for age-related macular degeneration.
Collapse
Affiliation(s)
- Natalia Mast
- Departments of Ophthalmology and Visual Sciences (N.M., I.A.P.) and Pediatrics (I.R.B.), Case Western Reserve University, Cleveland, Ohio
| | - Ilya R Bederman
- Departments of Ophthalmology and Visual Sciences (N.M., I.A.P.) and Pediatrics (I.R.B.), Case Western Reserve University, Cleveland, Ohio
| | - Irina A Pikuleva
- Departments of Ophthalmology and Visual Sciences (N.M., I.A.P.) and Pediatrics (I.R.B.), Case Western Reserve University, Cleveland, Ohio
| |
Collapse
|
39
|
El-Darzi N, Astafev A, Mast N, Saadane A, Lam M, Pikuleva IA. N, N-Dimethyl-3β-hydroxycholenamide Reduces Retinal Cholesterol via Partial Inhibition of Retinal Cholesterol Biosynthesis Rather Than its Liver X Receptor Transcriptional Activity. Front Pharmacol 2018; 9:827. [PMID: 30090064 PMCID: PMC6069453 DOI: 10.3389/fphar.2018.00827] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 07/09/2018] [Indexed: 12/19/2022] Open
Abstract
N,N-dimethyl-3β-hydroxycholenamide (DMHCA) is an experimental pharmaceutical and a steroidal liver X receptor (LXR) agonist, which does not induce undesired hepatic lipogenesis. Herein, DMHCA was evaluated for its retinal effects on normal C57BL/6J and Cyp27a1−/−Cyp46a1−/− mice; the latter having higher retinal total and esterified cholesterol in addition to retinal vascular abnormalities. Different doses and two formulations were used for DMHCA delivery either via drinking water (C57BL/6J mice) or by oral gavage (Cyp27a1−/−Cyp46a1−/− mice). The duration of treatment was 1 week for C57BL/6J mice and 2 or 4 weeks for Cyp27a1−/−Cyp46a1−/− mice. In both genotypes, the higher DMHCA doses (37–80 mg/kg of body weight/day) neither increased serum triglycerides nor serum cholesterol but altered the levels of retinal sterols. Total retinal cholesterol was decreased in the DMHCA-treated mice, mainly due to a decrease in retinal unesterified cholesterol. In addition, retinal levels of cholesterol precursors lanosterol, zymosterol, desmosterol, and lathosterol were changed in Cyp27a1−/−Cyp46a1−/− mice. In both genotypes, DMHCA effect on retinal expression of the LXR target genes was only moderate and gender-specific. Collectively, the data obtained provide evidence for a decrease in retinal cholesterol as a result of DMHCA acting in the retina as an enzyme inhibitor of cholesterol biosynthesis rather than a LXR transcriptional activator. Specifically, DMHCA appears to partially inhibit the cholesterol biosynthetic enzyme Δ24-dehydrocholesterol reductase rather than upregulate the expression of LXR target genes involved in reverse cholesterol transport. The identified DMHCA dosages, formulations, and routes of delivery as well as the observed effects on the retina should be considered in future studies using DMHCA as a potential therapeutic for age-related macular degeneration and diabetic retinopathy.
Collapse
Affiliation(s)
- Nicole El-Darzi
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Artem Astafev
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Aicha Saadane
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Morrie Lam
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, United States
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH, United States
| |
Collapse
|
40
|
Lam M, Mast N, Pikuleva IA. Drugs and Scaffold That Inhibit Cytochrome P450 27A1 In Vitro and In Vivo. Mol Pharmacol 2017; 93:101-108. [PMID: 29192124 DOI: 10.1124/mol.117.110742] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/27/2017] [Indexed: 11/22/2022] Open
Abstract
Cytochrome P450 27A1 (CYP27A1) is a ubiquitous enzyme that hydroxylates cholesterol and other sterols. Complete CYP27A1 deficiency owing to genetic mutations is detrimental to human health, whereas 50% of activity retention is not and does not affect the whole body cholesterol levels. CYP27A1 is considered a potential therapeutic target in breast cancer and age-related neurodegenerative diseases; however, CYP27A1 inhibition should be ≤50%. Herein, 131 pharmaceuticals were tested for their effect on CYP27A1-mediated cholesterol 27-hydroxylation by in vitro enzyme assay. Of them, 14 drugs inhibited CYP27A1 by ≥75% and were evaluated for in vitro binding to the enzyme active site and for inhibition constants. All drugs except one (dasatinib) elicited a spectral response in CYP27A1 and had Ki values for cholesterol 27-hydroxylation either in the submicromolar (clevidipine, delavirdine, etravirine, felodipine, nicardipine, nilotinib, and sorafenib) or low micromolar range (abiratone, candesartan, celecoxib, dasatinib, nilvadipine, nimodipine, and regorafenib). Clevidipine, felodipine, nicardipine, nilvadipine, and nimodipine have the same 1,4-dihydropyridine scaffold and are indicated for hypertension. We used two of these antihypertensives (felodipine and nilvadipine) for administration to mice at a 1-mg/kg of body weight dose, daily, for 7 days. Mouse 27-hydroxycholesterol levels in the plasma, brain, and liver were reduced, whereas tissue levels of total cholesterol were unchanged. Structure-activity relationships within the 1,4-dihydropyridine scaffold were investigated, and features important for CY27A1 inhibition were identified. We confirmed our previous finding that CYP27A1 is a druggable enzyme and found additional drugs as well as the scaffold with potential for partial CYP27A1 inhibition in humans.
Collapse
Affiliation(s)
- Morrie Lam
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio
| |
Collapse
|
41
|
Mast N, Lin JB, Anderson KW, Bjorkhem I, Pikuleva IA. Transcriptional and post-translational changes in the brain of mice deficient in cholesterol removal mediated by cytochrome P450 46A1 (CYP46A1). PLoS One 2017; 12:e0187168. [PMID: 29073233 PMCID: PMC5658173 DOI: 10.1371/journal.pone.0187168] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 10/13/2017] [Indexed: 01/12/2023] Open
Abstract
Cytochrome P450 46A1 (CYP46A1) converts cholesterol to 24-hydroxycholesterol and thereby controls the major pathways of cholesterol removal from the brain. Cyp46a1-/- mice have a reduction in the rate of cholesterol biosynthesis in the brain and significant impairments to memory and learning. To gain insights into the mechanisms underlying Cyp46a1-/- phenotype, we used Cyp46a1-/- mice and quantified their brain sterol levels and the expression of the genes pertinent to cholesterol homeostasis. We also compared the Cyp46a1-/- and wild type brains for protein phosphorylation and ubiquitination. The data obtained enable the following inferences. First, there seems to be a compensatory upregulation in the Cyp46a1-/- brain of the pathways of cholesterol storage and CYP46A1-independent removal. Second, transcriptional regulation of the brain cholesterol biosynthesis via sterol regulatory element binding transcription factors is not significantly activated in the Cyp46a1-/- brain to explain a compensatory decrease in cholesterol biosynthesis. Third, some of the liver X receptor target genes (Abca1) are paradoxically upregulated in the Cyp46a1-/- brain, possibly due to a reduced activation of the small GTPases RAB8, CDC42, and RAC as a result of a reduced phosphorylation of RAB3IP and PAK1. Fourth, the phosphorylation of many other proteins (a total of 146) is altered in the Cyp46a1-/- brain, including microtubule associated and neurofilament proteins (the MAP and NEF families) along with proteins related to synaptic vesicles and synaptic neurotransmission (e.g., SLCs, SHANKs, and BSN). Fifth, the extent of protein ubiquitination is increased in the Cyp46a1-/- brain, and the affected proteins pertain to ubiquitination (UBE2N), cognition (STX1B and ATP1A2), cytoskeleton function (TUBA1A and YWHAZ), and energy production (ATP1A2 and ALDOA). The present study demonstrates the diverse potential effects of CYP46A1 deficiency on brain functions and identifies important proteins that could be affected by this deficiency.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Joseph B. Lin
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Kyle W. Anderson
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States of America
- Institute for Bioscience and Biotechnology Research, Rockville, Maryland, United States of America
| | - Ingemar Bjorkhem
- Department of Laboratory Medicine, Division of Clinical Chemistry, Karolinska Institute, Huddinge, Sweden
| | - Irina A. Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail:
| |
Collapse
|
42
|
Mast N, Saadane A, Valencia-Olvera A, Constans J, Maxfield E, Arakawa H, Li Y, Landreth G, Pikuleva IA. Cholesterol-metabolizing enzyme cytochrome P450 46A1 as a pharmacologic target for Alzheimer's disease. Neuropharmacology 2017; 123:465-476. [PMID: 28655608 PMCID: PMC5546235 DOI: 10.1016/j.neuropharm.2017.06.026] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 06/21/2017] [Accepted: 06/23/2017] [Indexed: 12/27/2022]
Abstract
Cytochrome P450 46A1 (CYP46A1 or cholesterol 24-hydroxylase) controls cholesterol elimination from the brain and plays a role in higher order brain functions. Genetically enhanced CYP46A1 expression in mouse models of Alzheimer's disease mitigates the manifestations of this disease. We enhanced CYP46A1 activity pharmacologically by treating 5XFAD mice, a model of rapid amyloidogenesis, with a low dose of the anti-HIV medication efavirenz. Efavirenz was administered from 1 to 9 months of age, and mice were evaluated at specific time points. At one month of age, cholesterol homeostasis was already disturbed in the brain of 5XFAD mice. Nevertheless, efavirenz activated CYP46A1 and mouse cerebral cholesterol turnover during the first four months of administration. This treatment time also reduced amyloid burden and microglia activation in the cortex and subiculum of 5XFAD mice as well as protein levels of amyloid precursor protein and the expression of several genes involved in inflammatory response. However, mouse short-term memory and long-term spatial memory were impaired, whereas learning in the context-dependent fear test was improved. Additional four months of drug administration (a total of eight months of treatment) improved long-term spatial memory in the treated as compared to the untreated mice, further decreased amyloid-β content in 5XFAD brain, and also decreased the mortality rate among male mice. We propose a mechanistic model unifying the observed efavirenz effects. We suggest that CYP46A1 activation by efavirenz could be a new anti-Alzheimer's disease treatment and a tool to study and identify normal and pathological brain processes affected by cholesterol maintenance.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Aicha Saadane
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Ana Valencia-Olvera
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - James Constans
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Erin Maxfield
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Hiroyuki Arakawa
- Behavioral Core, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Young Li
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Gary Landreth
- Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
| |
Collapse
|
43
|
Hammer SS, Beli E, Kady N, Wang Q, Wood K, Lydic TA, Malek G, Saban DR, Wang XX, Hazra S, Levi M, Busik JV, Grant MB. The Mechanism of Diabetic Retinopathy Pathogenesis Unifying Key Lipid Regulators, Sirtuin 1 and Liver X Receptor. EBioMedicine 2017; 22:181-190. [PMID: 28774737 PMCID: PMC5552206 DOI: 10.1016/j.ebiom.2017.07.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 07/06/2017] [Accepted: 07/07/2017] [Indexed: 12/30/2022] Open
Abstract
Diabetic retinopathy (DR) is a complication secondary to diabetes and is the number one cause of blindness among working age individuals worldwide. Despite recent therapeutic breakthroughs using pharmacotherapy, a cure for DR has yet to be realized. Several clinical trials have highlighted the vital role dyslipidemia plays in the progression of DR. Additionally, it has recently been shown that activation of Liver X receptor (LXRα/LXRβ) prevents DR in diabetic animal models. LXRs are nuclear receptors that play key roles in regulating cholesterol metabolism, fatty acid metabolism and inflammation. In this manuscript, we show insight into DR pathogenesis by demonstrating an innovative signaling axis that unifies key metabolic regulators, Sirtuin 1 and LXR, in modulating retinal cholesterol metabolism and inflammation in the diabetic retina. Expression of both regulators, Sirtuin 1 and LXR, are significantly decreased in diabetic human retinal samples and in a type 2 diabetic animal model. Additionally, activation of LXR restores reverse cholesterol transport, prevents inflammation, reduces pro-inflammatory macrophages activity and prevents the formation of diabetes-induced acellular capillaries. Taken together, the work presented in this manuscript highlights the important role lipid dysregulation plays in DR progression and offers a novel potential therapeutic target for the treatment of DR. Diabetes affects retinal Liver X Receptor and Sirtuin 1 expression levels. Liver X Receptor normalized reverse cholesterol transport and prevented diabetes-induced inflammation in retinal cells. Liver X Receptor activation reduced the number of pro-inflammatory macrophages and prevented DR-like pathology.
Results of recent clinical trials demonstrate strong association between lipid abnormalities and progression of diabetic retinopathy (DR), the sight-threatening secondary complication of diabetes. This study addresses the role of key metabolic lipid regulators, SIRT1 and LXR in the progression of DR. All the components of SIRT1-LXR axis were downregulated in retinal cells isolated from human donor tissue or a DR animal model. Activation of LXR normalized reverse cholesterol transport, prevented diabetes-induced inflammation, reduced the number of pro-inflammatory macrophages and prevented DR-like pathology, suggesting that control of SIRT1-LXR axis could be a promising therapeutic target for treatment of DR.
Collapse
Affiliation(s)
- Sandra S Hammer
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Eleni Beli
- Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Nermin Kady
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Qi Wang
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Kiana Wood
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Todd A Lydic
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Goldis Malek
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC, United States
| | - Daniel R Saban
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC, United States
| | - Xiaoxin X Wang
- Department of Medicine, University of Colorado, Aurora, CO, United States
| | - Sugata Hazra
- Department of Pharmacology, University of Florida, Gainesville, FL, United States
| | - Moshe Levi
- Department of Medicine, University of Colorado, Aurora, CO, United States
| | - Julia V Busik
- Department of Physiology, Michigan State University, East Lansing, MI, United States.
| | - Maria B Grant
- Department of Ophthalmology, Indiana University School of Medicine, Indianapolis, IN, United States.
| |
Collapse
|
44
|
Mast N, Anderson KW, Johnson KM, Phan TTN, Guengerich FP, Pikuleva IA. In vitro cytochrome P450 46A1 (CYP46A1) activation by neuroactive compounds. J Biol Chem 2017. [PMID: 28642370 DOI: 10.1074/jbc.m117.794909] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome P450 46A1 (CYP46A1, cholesterol 24-hydroxylase) is the enzyme responsible for the majority of cholesterol elimination from the brain. Previously, we found that the anti-HIV drug efavirenz (EFV) can pharmacologically activate CYP46A1 in mice. Herein, we investigated whether CYP46A1 could also be activated by endogenous compounds, including major neurotransmitters. In vitro experiments with purified recombinant CYP46A1 indicated that CYP46A1 is activated by l-glutamate (l-Glu), l-aspartate, γ-aminobutyric acid, and acetylcholine, with l-Glu eliciting the highest increase (3-fold) in CYP46A1-mediated cholesterol 24-hydroxylation. We also found that l-Glu and other activating neurotransmitters bind to the same site on the CYP46A1 surface, which differs from the EFV-binding site. The other principal differences between EFV and l-Glu in CYP46A1 activation include an apparent lack of l-Glu binding to the P450 active site and different pathways of signal transduction from the allosteric site to the active site. EFV and l-Glu similarly increased the CYP46A1 kcat, the rate of the "fast" phase of the enzyme reduction by the redox partner NADPH-cytochrome P450 oxidoreductase, and the amount of P450 reduced. Spectral titrations with cholesterol, in the presence of EFV or l-Glu, suggest that water displacement from the heme iron can be affected in activator-bound CYP46A1. Moreover, EFV and l-Glu synergistically activated CYP46A1. Collectively, our in vitro data, along with those from previous cell culture and in vivo studies by others, suggest that l-Glu-induced CYP46A1 activation is of physiological relevance.
Collapse
Affiliation(s)
- Natalia Mast
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106
| | - Kyle W Anderson
- Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899; Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850
| | - Kevin M Johnson
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Thanh T N Phan
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - F Peter Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio 44106.
| |
Collapse
|
45
|
Hammer SS, Busik JV. The role of dyslipidemia in diabetic retinopathy. Vision Res 2017; 139:228-236. [PMID: 28545981 DOI: 10.1016/j.visres.2017.04.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/06/2017] [Accepted: 04/13/2017] [Indexed: 02/08/2023]
Abstract
Diabetic retinopathy (DR) affects over 93million people worldwide and is the number one cause of blindness among working age adults. These indicators coupled with the projected rise of patients diagnosed with diabetes, makes DR a serious and prevalent vision threating disease. Data from recent clinical trials demonstrate that in addition to the well accepted role of hyperglycemia, dyslipidemia is an important, but often overlooked factor in the development of DR. The central aim of this review article is to showcase the critical role of dyslipidemia in DR progression as well as highlight novel therapeutic solutions that take advantage of the vital roles lipid metabolism plays in DR progression.
Collapse
Affiliation(s)
- Sandra S Hammer
- Department of Physiology, Michigan State University, East Lansing, MI, United States
| | - Julia V Busik
- Department of Physiology, Michigan State University, East Lansing, MI, United States.
| |
Collapse
|
46
|
Mast N, Anderson KW, Lin JB, Li Y, Turko IV, Tatsuoka C, Bjorkhem I, Pikuleva IA. Cytochrome P450 27A1 Deficiency and Regional Differences in Brain Sterol Metabolism Cause Preferential Cholestanol Accumulation in the Cerebellum. J Biol Chem 2017; 292:4913-4924. [PMID: 28190002 DOI: 10.1074/jbc.m116.774760] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 02/10/2017] [Indexed: 01/04/2023] Open
Abstract
Cytochrome P450 27A1 (CYP27A1 or sterol 27-hydroxylase) is a ubiquitous, multifunctional enzyme catalyzing regio- and stereospecific hydroxylation of different sterols. In humans, complete CYP27A1 deficiency leads to cerebrotendinous xanthomatosis or nodule formation in tendons and brain (preferentially in the cerebellum) rich in cholesterol and cholestanol, the 5α-saturated analog of cholesterol. In Cyp27a1-/- mice, xanthomas are not formed, despite a significant cholestanol increase in the brain and cerebellum. The mechanism behind cholestanol production has been clarified, yet little is known about its metabolism, except that CYP27A1 might metabolize cholestanol. It also is unclear why CYP27A1 deficiency results in preferential cholestanol accumulation in the cerebellum. We hypothesized that cholestanol might be metabolized by CYP46A1, the principal cholesterol 24-hydroxylase in the brain. We quantified sterols along with CYP27A1 and CYP46A1 in mouse models (Cyp27a1-/-, Cyp46a1-/-, Cyp27a1-/-Cyp46a1-/-, and two wild type strains) and human brain specimens. In vitro experiments with purified P450s were conducted as well. We demonstrate that CYP46A1 is involved in cholestanol removal from the brain and that several factors contribute to the preferential increase in cholestanol in the cerebellum arising from CYP27A1 deficiency. These factors include (i) low cerebellar abundance of CYP46A1 and high cerebellar abundance of CYP27A1, the lack of which probably selectively increases the cerebellar cholestanol production; (ii) spatial separation in the cerebellum of cholesterol/cholestanol-metabolizing P450s from a pool of metabolically available cholestanol; and (iii) weak cerebellar regulation of cholesterol biosynthesis. We identified a new physiological role of CYP46A1, an important brain enzyme and cytochrome P450 that could be activated pharmacologically.
Collapse
Affiliation(s)
- Natalia Mast
- From the Departments of Ophthalmology and Visual Sciences and
| | - Kyle W Anderson
- the Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.,the Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, and
| | - Joseph B Lin
- From the Departments of Ophthalmology and Visual Sciences and
| | - Yong Li
- From the Departments of Ophthalmology and Visual Sciences and
| | - Illarion V Turko
- the Biomolecular Measurement Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.,the Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, and
| | - Curtis Tatsuoka
- Neurology, Case Western Reserve University, Cleveland, Ohio 44106
| | - Ingemar Bjorkhem
- the Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institute, 141 86 Huddinge, Sweden
| | | |
Collapse
|
47
|
High Cholesterol Diet Increases Expression of Cholesterol 24-Hydroxylase and BACE1 in Rat Hippocampi: Implications for the Effect of Diet Cholesterol on Memory. IRANIAN RED CRESCENT MEDICAL JOURNAL 2016. [DOI: 10.5812/ircmj.35677] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
48
|
Saadane A, Mast N, Dao T, Ahmad B, Pikuleva IA. Retinal Hypercholesterolemia Triggers Cholesterol Accumulation and Esterification in Photoreceptor Cells. J Biol Chem 2016; 291:20427-39. [PMID: 27514747 DOI: 10.1074/jbc.m116.744656] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Indexed: 01/01/2023] Open
Abstract
The process of vision is impossible without the photoreceptor cells, which have a unique structure and specific maintenance of cholesterol. Herein we report on the previously unrecognized cholesterol-related pathway in the retina discovered during follow-up characterizations of Cyp27a1(-/-)Cyp46a1(-/-) mice. These animals have retinal hypercholesterolemia and convert excess retinal cholesterol into cholesterol esters, normally present in the retina in very small amounts. We established that in the Cyp27a1(-/-)Cyp46a1(-/-) retina, cholesterol esters are generated by and accumulate in the photoreceptor outer segments (OS), which is the retinal layer with the lowest cholesterol content. Mouse OS were also found to express the cholesterol-esterifying enzyme acyl-coenzyme A:cholesterol acyltransferase (ACAT1), but not lecithin-cholesterol acyltransferase (LCAT), and to differ from humans in retinal expression of ACAT1. Nevertheless, cholesterol esters were discovered to be abundant in human OS. We suggest a mechanism for cholesterol ester accumulation in the OS and that activity impairment of ACAT1 in humans may underlie the development of subretinal drusenoid deposits, a hallmark of age-related macular degeneration, which is a common blinding disease. We generated Cyp27a1(-/-)Cyp46a1(-/-)Acat1(-/-) mice, characterized their retina by different imaging modalities, and confirmed that unesterified cholesterol does accumulate in their OS and that there is photoreceptor apoptosis and OS degeneration in this line. Our results provide insights into the retinal response to local hypercholesterolemia and the retinal significance of cholesterol esterification, which could be cell-specific and both beneficial and detrimental for retinal structure and function.
Collapse
Affiliation(s)
- Aicha Saadane
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| | - Natalia Mast
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| | - Tung Dao
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| | - Baseer Ahmad
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and the University Hospitals, Cleveland, Ohio 44106
| | - Irina A Pikuleva
- From the Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, Ohio and
| |
Collapse
|
49
|
Lin JB, Mast N, Bederman IR, Li Y, Brunengraber H, Björkhem I, Pikuleva IA. Cholesterol in mouse retina originates primarily from in situ de novo biosynthesis. J Lipid Res 2015; 57:258-64. [PMID: 26630912 DOI: 10.1194/jlr.m064469] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Indexed: 12/18/2022] Open
Abstract
The retina, a thin tissue in the back of the eye, has two apparent sources of cholesterol: in situ biosynthesis and cholesterol available from the systemic circulation. The quantitative contributions of these two cholesterol sources to the retinal cholesterol pool are unknown and have been determined in the present work. A new methodology was used. Mice were given separately deuterium-labeled drinking water and chow containing 0.3% deuterium-labeled cholesterol. In the retina, the rate of total cholesterol input was 21 μg of cholesterol/g retina • day, of which 15 μg of cholesterol/g retina • day was provided by local biosynthesis and 6 μg of cholesterol/g retina • day was uptaken from the systemic circulation. Thus, local cholesterol biosynthesis accounts for the majority (72%) of retinal cholesterol input. We also quantified cholesterol input to mouse brain, the organ sharing important similarities with the retina. The rate of total cerebral cholesterol input was 121 μg of cholesterol/g brain • day with local biosynthesis providing 97% of total cholesterol input. Our work addresses a long-standing question in eye research and adds new knowledge to the potential use of statins (drugs that inhibit cholesterol biosynthesis) as therapeutics for age-related macular degeneration, a common blinding disease.
Collapse
Affiliation(s)
- Joseph B Lin
- Department of Ophthalmology and Visual Sciences,Case Western Reserve University, Cleveland, OH 44106
| | - Natalia Mast
- Department of Ophthalmology and Visual Sciences,Case Western Reserve University, Cleveland, OH 44106
| | - Ilya R Bederman
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH 44106
| | - Yong Li
- Department of Ophthalmology and Visual Sciences,Case Western Reserve University, Cleveland, OH 44106
| | - Henri Brunengraber
- Department of Nutrition, Case Western Reserve University, Cleveland, OH 44106
| | - Ingemar Björkhem
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska University Hospital, Karolinska Institute, Huddinge, Stockholm 141 86 Sweden
| | - Irina A Pikuleva
- Department of Ophthalmology and Visual Sciences,Case Western Reserve University, Cleveland, OH 44106
| |
Collapse
|
50
|
Cascio C, Deidda I, Russo D, Guarneri P. The estrogenic retina: The potential contribution to healthy aging and age-related neurodegenerative diseases of the retina. Steroids 2015; 103:31-41. [PMID: 26265586 DOI: 10.1016/j.steroids.2015.08.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Revised: 07/29/2015] [Accepted: 08/04/2015] [Indexed: 12/18/2022]
Abstract
These last two decades have seen an explosion of clinical and epidemiological research, and basic research devoted to envisage the influence of gender and hormonal fluctuations in the retina/ocular diseases. Particular attention has been paid to age-related disorders because of the overlap of endocrine and neuronal dysfunction with aging. Hormonal withdrawal has been considered among risk factors for diseases such as glaucoma, diabetic retinopathy and age-related macular disease (AMD), as well as, for Alzheimer's disease, Parkinson's disease, or other neurodegenerative disorders. Sex hormones and aging have been also suggested to drive the incidence of ocular surface diseases such as dry eye and cataract. Hormone therapy has been approached in several clinical trials. The discovery that the retina is another CNS tissue synthesizing neurosteroids, among which neuroactive steroids, has favored these studies. However, the puzzling data emerged from clinical, epidemiological and experimental studies have added several dimensions of complexity; the current landscape is inherently limited to the weak information on the influence and interdependence of endocrine, paracrine and autocrine regulation in the retina, but also in the brain. Focusing on the estrogenic retina, we here review our knowledge on local 17β-oestradiol (E2) synthesis from cholesterol-based neurosteroidogenic path and testosterone aromatization, and presence of estrogen receptors (ERα and ERβ). The first cholesterol-limiting step and the final aromatase-limiting step are discussed as possible check-points of retinal functional/dysfunctional E2. Possible E2 neuroprotection is commented as a group of experimental evidence on excitotoxic and oxidative retinal paradigms, and models of retinal neurodegenerative diseases, such as glaucoma, diabetic retinopathy and AMD. These findings may provide a framework to support clinical studies, although further basic research is needed.
Collapse
Affiliation(s)
- Caterina Cascio
- CNR Institute of Biomedicine and Molecular Immunology, Neuroscience Unit, Palermo, Italy
| | - Irene Deidda
- CNR Institute of Biomedicine and Molecular Immunology, Neuroscience Unit, Palermo, Italy
| | - Domenica Russo
- CNR Institute of Biomedicine and Molecular Immunology, Neuroscience Unit, Palermo, Italy
| | - Patrizia Guarneri
- CNR Institute of Biomedicine and Molecular Immunology, Neuroscience Unit, Palermo, Italy.
| |
Collapse
|