7-Ketocholesterol

Minimally Invasive Vacuum-Aided Extraction Technique for the Lipid Analysis of Historic Parchment

Parchment is an ancient writing support formed from dehaired animal skins. Its manufacture comprises a series of liming and scraping steps before being stretched and dried under tension. Historical parchment represents a valuable source of cultural heritage which, until now, has limited investigations to noninvasive analyses to infer ink composition, degradation, or physical changes over time. We highlight the prospect of the molecular and isotope compositions of animal lipids from parchment as an untapped record of its production and the animal's diet and environment. We report a minimally invasive, total lipid extraction aided by a vacuum for historical parchments. The quantitative and qualitative compositions of lipid extracts obtained using this method are compared with those obtained using invasive sampling for nine sacrificial membranes dated 1765-1825 CE. This extraction method is then applied to membranes from the Chancery Parliament Rolls (1814-1820 CE) held by The National Archives, UK to obtain lipids and derive taxonomic and dietary information using their stable carbon isotope compositions. This novel vacuum-aided extraction allows, for the first time, animal lipids to be obtained from parchment minimally invasively, paving the way for dietary and paleoclimate studies using this well-dated and common material.

Multi-omics study on the molecular mechanism of anlotinib in regulating tumor metabolism

Anlotinib, an orally administered small molecule inhibitor of receptor tyrosine kinases (RTKs), exerts significant anti-angiogenic and vascular normalization effects. However, the mechanisms underlying its involvement in tumor metabolic reprogramming are still unclear. This study aims to investigate the distribution and expression levels of metabolites within tumors after anlotinib treatment using spatial metabolomics analysis. Subsequently, by integrating the transcriptomics and proteomics analyses, we identified that anlotinib treatment primarily modulated four metabolic pathways, including taurine and hypotaurine metabolism, steroid synthesis, pentose phosphate pathway, and lipid biosynthesis. This regulation significantly influenced the metabolic levels of compounds such as sulfonic acids, cholesterol, inositol phosphate pyrophosphate, and palmitoyl-CoA in the tumor, thereby impacting tumor initiation and progression. This study provides potential metabolic biomarkers for anlotinib treatment in tumors.

Protective Effect of Ergothioneine against 7-Ketocholesterol-Induced Mitochondrial Damage in hCMEC/D3 Human Brain Endothelial Cells

Recent findings have suggested that the natural compound ergothioneine (ET), which is synthesised by certain fungi and bacteria, has considerable cytoprotective potential. We previously demonstrated the anti-inflammatory effects of ET on 7-ketocholesterol (7KC)-induced endothelial injury in human blood-brain barrier endothelial cells (hCMEC/D3). 7KC is an oxidised form of cholesterol present in atheromatous plaques and the sera of patients with hypercholesterolaemia and diabetes mellitus. The aim of this study was to elucidate the protective effect of ET on 7KC-induced mitochondrial damage. Exposure of human brain endothelial cells to 7KC led to a loss of cell viability, together with an increase in intracellular free calcium levels, increased cellular and mitochondrial reactive oxygen species, a decrease in mitochondrial membrane potential, reductions in ATP levels, and increases in mRNA expression of TFAM, Nrf2, IL-1β, IL-6 and IL-8. These effects were significantly decreased by ET. Protective effects of ET were diminished when endothelial cells were coincubated with verapamil hydrochloride (VHCL), a nonspecific inhibitor of the ET transporter OCTN1 (SLC22A4). This outcome demonstrates that ET-mediated protection against 7KC-induced mitochondrial damage occurred intracellularly and not through direct interaction with 7KC. OCTN1 mRNA expression itself was significantly increased in endothelial cells after 7KC treatment, consistent with the notion that stress and injury may increase ET uptake. Our results indicate that ET can protect against 7KC-induced mitochondrial injury in brain endothelial cells.

Methods on LDL particle isolation, characterization, and component fractionation for the development of novel specific oxidized LDL status markers for atherosclerotic disease risk assessment

The present study uses simple, innovative methods to isolate, characterize and fractionate LDL in its main components for the study of specific oxidations on them that characterize oxidized low-density lipoprotein (oxLDL) status, as it causatively relates to atherosclerosis-associated cardiovascular disease (CVD) risk assessment. These methods are: (a) A simple, relatively time-short, low cost protocol for LDL isolation, to avoid shortcomings of the currently employed ultracentrifugation and affinity chromatography methodologies. (b) LDL purity verification by apoB100 SDS-PAGE analysis and by LDL particle size determination; the latter and its serum concentration are determined in the present study by a simple method more clinically feasible as marker of CVD risk assessment than nuclear magnetic resonance. (c) A protocol for LDL fractionation, for the first time, into its main protein/lipid components (apoB100, phospholipids, triglycerides, free cholesterol, and cholesteryl esters), as well as into LDL carotenoid/tocopherol content. (d) Protocols for the measurement, for the first time, of indicative specific LDL component oxidative modifications (cholesteryl ester-OOH, triglyceride-OOH, free cholesterol-OOH, phospholipid-OOH, apoB100-MDA, and apoB100-DiTyr) out of the many (known/unknown/under development) that collectively define oxLDL status, which contrasts with the current non-specific oxLDL status evaluation methods. The indicative oxLDL status markers, selected in the present study on the basis of expressing early oxidative stress-induced oxidative effects on LDL, are studied for the first time on patients with end stage kidney disease on maintenance hemodialysis, selected as an indicative model for atherosclerosis associated diseases. Isolating LDL and fractionating its protein and main lipid components, as well as its antioxidant arsenal comprised of carotenoids and tocopherols, paves the way for future studies to investigate all possible oxidative modifications responsible for turning LDL to oxLDL in association to their possible escaping from LDL's internal antioxidant defense. This can lead to studies to identify those oxidative modifications of oxLDL (after their artificial generation on LDL), which are recognized by macrophages and convert them to foam cells, known to be responsible for the formation of atherosclerotic plaques that lead to the various CVDs.

Ultra-high-performance liquid chromatography-tandem mass spectrometry analysis of serum metabolomic characteristics in people with different vitamin D levels

Vitamin D is a fat-soluble vitamin with multiple functions. However, the metabolism of people with different vitamin D concentrations is still unclear. Herein, we collected clinical data and analysed the serum metabolome of people with 25-hydroxyvitamin D (25[OH]D) ≥40 ng/mL (A), 30 ng/mL ≤25(OH)D <40 ng/mL (B) and 25(OH)D <30 ng/mL (C) by the ultra-high-performance liquid chromatography-tandem mass spectrometry method. We found that haemoglobin A1c, fasting blood glucose, fasting insulin, homeostasis model assessment of insulin resistance and thioredoxin interaction protein were enhanced, while HOMA-β was reduced with the decrease of 25(OH)D concentration. In addition, people in the C group were diagnosed with prediabetes or diabetes. Metabolomics analysis showed that seven, thirty-four and nine differential metabolites were identified in the groups B vs A, C vs A and C vs B, respectively. Metabolites associated with cholesterol metabolism and bile acid biosynthesis, such as 7-ketolithocholic acid, 12-ketolithocholic acid, apocholic acid, N-arachidene glycine and d-mannose 6-phosphate, were significantly upregulated in the C group compared with the A or B groups. In conclusion, the disorder of vitamin D metabolism may be related to cholesterol metabolism and bile acid biosynthesis. This study provided a basis for exploring the possible mechanism leading to abnormal vitamin D metabolism.

Interaction between Plasma Metabolomics and Intestinal Microbiome in db/db Mouse, an Animal Model for Study of Type 2 Diabetes and Diabetic Kidney Disease

Evidence has demonstrated that either metabolites or intestinal microbiota are involved in the pathogenesis of type 2 diabetes (T2D) and diabetic kidney disease (DKD). To explore the interaction between plasma metabolomics and intestinal microbiome in the progress of T2D-DKD, in the current study, we analyzed metabolomics in the plasma of db/db mice with liquid chromatography–mass spectrometry and also examined intestinal prokaryotes and entire gut microbiome dysbiosis at the genus level with both 16S rDNA and metagenomic sequencing techniques. We found that Negativibacillus and Rikenella were upregulated, while Akkermansia, Candidatus, Erysipelatoclostridium and Ileibacterium were downregulated in the colon of db/db mice compared with non-diabetic controls. In parallel, a total of 91 metabolites were upregulated, while 23 were downregulated in the plasma of db/db mice. The top five upregulated metabolites included D-arabinose 5-phosphate, estrone 3-sulfate, L-theanine, 3′-aenylic acid and adenosine 5′-monophosphate, and the five most significantly downregulated metabolites were aurohyocholic acid sodium salt, calcium phosphorylcholine chloride, tauro-alpha-muricholic acid sodium salt, galactinol and phosphocholine. These plasma metabolites were interacted with intestinal microbiomes, which are mainly involved in the pathways related to the biosynthesis of unsaturated fatty acids, fatty acid elongation, steroid biosynthesis, and D-arginine and D-ornithine metabolism. In the differential metabolites, N-acetyl-L-ornithine, ornithine and L-kyn could be metabolized by the correspondingly differential ontology genes in the intestinal metagenome. The current study thereby provides evidence for a gut–metabolism–kidney axis in the metabolism of db/db mice, in which the gut microbiome and circulating metabolomics interact, and suggests that information from this axis may contribute to our understanding of T2D and DKD pathogenesis.

7-Ketocholesterol Induces Lipid Metabolic Reprogramming and Enhances Cholesterol Ester Accumulation in Cardiac Cells

7-Ketocholesterol (7KCh) is a major oxidized cholesterol product abundant in lipoprotein deposits and atherosclerotic plaques. Our previous study has shown that 7KCh accumulates in erythrocytes of heart failure patients, and further investigation centered on how 7KCh may affect metabolism in cardiomyocytes. We applied metabolomics to study the metabolic changes in cardiac cell line HL-1 after treatment with 7KCh. Mevalonic acid (MVA) pathway-derived metabolites, such as farnesyl-pyrophosphate and geranylgeranyl-pyrophosphate, phospholipids, and triacylglycerols levels significantly declined, while the levels of lysophospholipids, such as lysophosphatidylcholines (lysoPCs) and lysophosphatidylethanolamines (lysoPEs), considerably increased in 7KCh-treated cells. Furthermore, the cholesterol content showed no significant change, but the production of cholesteryl esters was enhanced in the treated cells. To explore the possible mechanisms, we applied mRNA-sequencing (mRNA-seq) to study genes differentially expressed in 7KCh-treated cells. The transcriptomic analysis revealed that genes involved in lipid metabolic processes, including MVA biosynthesis and cholesterol transport and esterification, were differentially expressed in treated cells. Integrated analysis of both metabolomic and transcriptomic data suggests that 7KCh induces cholesteryl ester accumulation and reprogramming of lipid metabolism through altered transcription of such genes as sterol O-acyltransferase- and phospholipase A2-encoding genes. The 7KCh-induced reprogramming of lipid metabolism in cardiac cells may be implicated in the pathogenesis of cardiovascular diseases.

Modulation of 11β-hydroxysteroid dehydrogenase functions by the cloud of endogenous metabolites in a local microenvironment: The glycyrrhetinic acid-like factor (GALF) hypothesis

11β-Hydroxysteroid dehydrogenase (11β-HSD)-dependent conversion of cortisol to cortisone and corticosterone to 11-dehydrocorticosterone are essential in regulating transcriptional activities of mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Inhibition of 11β-HSD by glycyrrhetinic acid metabolites, bioactive components of licorice, causes sodium retention and potassium loss, with hypertension characterized by low renin and aldosterone. Essential hypertension is a major disease, mostly with unknown underlying mechanisms. Here, we discuss a putative mechanism for essential hypertension, the concept that endogenous steroidal compounds acting as glycyrrhetinic acid-like factors (GALFs) inhibit 11β-HSD dehydrogenase, and allow for glucocorticoid-induced MR and GR activation with resulting hypertension. Initially, several metabolites of adrenally produced glucocorticoids and mineralocorticoids were shown to be potent 11β-HSD inhibitors. Such GALFs include modifications in the A-ring and/or at positions 3, 7 and 21 of the steroid backbone. These metabolites may be formed in peripheral tissues or by gut microbiota. More recently, metabolites of 11β-hydroxy-Δ4androstene-3,17-dione and 7-oxygenated oxysterols have been identified as potent 11β-HSD inhibitors. In a living system, 11β-HSD isoforms are not exposed to a single substrate but to several substrates, cofactors, and various inhibitors simultaneously, all at different concentrations depending on physical state, tissue and cell type. We propose that this "cloud" of steroids and steroid-like substances in the microenvironment determines the 11β-HSD-dependent control of MR and GR activity. A dysregulated composition of this cloud of metabolites in the respective microenvironment needs to be taken into account when investigating disease mechanisms, for forms of low renin, low aldosterone hypertension.

An insight on 7- ketocholesterol mediated inflammation in atherosclerosis and potential therapeutics

7-ketocholesterol, a toxic oxidative product of oxysterol is a causative agent of several diseases and disabilities concomitant to aging including cardiovascular diseases like atherosclerosis. Auto-oxidation of cholesterol esters present in low-density lipoprotein (LDL) deposits lead to the formation of oxidized LDL (Ox-LDL) along with its byproducts, namely 7KCh. It is predominantly found in atherosclerotic plaque and also found to be more atherogenic than cholesterol by being cytotoxic, interfering with cellular homeostasis. This makes it a serious threat by being the foremost cause of morbidity and mortality worldwide and is likely to become more serious during forth coming years. It involves in mediating inflammatory mechanisms characterized by the advancement of fibroatheroma plaques. The atherosclerotic lesion is composed of Ox-LDL along with fibrotic mass consisting of immune cells and molecules. Macrophages being the specialized phagocytic cells, contribute to removal of detrimental contents of the lesion along with accumulated lipids leading to alteration of its biology and functionality due to its plasticity. Here, we have explored the known as well as proposed mechanisms involved with 7KCh associated atherogenesis along with potential therapeutic strategies for targeting 7KCh as a diagnostic and target in medicine.

Safety and feasibility of arterial wall targeting with robot-assisted high intensity focused ultrasound: a preclinical study

PURPOSE

High-intensity focused ultrasound (HIFU) is a potential noninvasive thermal ablation method for the treatment of peripheral artery disease. Dual-mode ultrasound arrays (DMUA) offer the possibility of simultaneous imaging and treatment. In this study, safety and feasibility of femoral artery robot-assisted HIFU/DMUA therapy was assessed.

METHODS

In 18 pigs (∼50kg), angiography and diagnostic ultrasound were used to visualize diameter and blood flow of the external femoral arteries (EFA). HIFU/DMUA-therapy was unilaterally applied to the EFA dorsal wall using a 3.5 MHz, 64-element transducer, closed-loop-control was used to automatically adjust energy delivery to control thermal lesion formation. A continuous lesion of at least 25 mm was created by delivering 6-8 HIFU shots per imaging plane perpendicular to the artery spaced 1 mm apart. Directly after HIFU/DMUA-therapy and after 0, 3 or 14 days follow up, diameter and blood flow were measured and the skin was macroscopically examined for thermal damage. The tissue was removed for histological analysis.

RESULTS

No complications were observed. The most frequently observed treatment effect was formation of scar tissue, predominantly in the adventitia and the surrounding tissue. No damage to the endothelium or excessive damage of the surrounding tissue was observed. There was no significant decrease in the mean arterial diameter after HIFU/DMUA-therapy.

CONCLUSION

HIFU/DMUA therapy successfully targeted the vessel walls of healthy porcine arteries, without causing endothelial damage or other vascular complications. Therefore, this therapy can be safely applied to healthy arterial walls in animals. Future studies should focus on safety and dose-finding in atherosclerotic diseased arteries.

Prevention by Dietary Polyphenols (Resveratrol, Quercetin, Apigenin) Against 7-Ketocholesterol-Induced Oxiapoptophagy in Neuronal N2a Cells: Potential Interest for the Treatment of Neurodegenerative and Age-Related Diseases

The Mediterranean diet is associated with health benefits due to bioactive compounds such as polyphenols. The biological activities of three polyphenols (quercetin (QCT), resveratrol (RSV), apigenin (API)) were evaluated in mouse neuronal N2a cells in the presence of 7-ketocholesterol (7KC), a major cholesterol oxidation product increased in patients with age-related diseases, including neurodegenerative disorders. In N2a cells, 7KC (50 µM; 48 h) induces cytotoxic effects characterized by an induction of cell death. When associated with RSV, QCT and API (3.125; 6.25 µM), 7KC-induced toxicity was reduced. The ability of QCT, RSV and API to prevent 7KC-induced oxidative stress was characterized by a decrease in reactive oxygen species (ROS) production in whole cells and at the mitochondrial level; by an attenuation of the increase in the level and activity of catalase; by attenuating the decrease in the expression, level and activity of glutathione peroxidase 1 (GPx1); by normalizing the expression, level and activity of superoxide dismutases 1 and 2 (SOD1, SOD2); and by reducing the decrease in the expression of nuclear erythroid 2-like factor 2 (Nrf2) which regulates antioxidant genes. QCT, RSV and API also prevented mitochondrial dysfunction in 7KC-treated cells by counteracting the loss of mitochondrial membrane potential (ΨΔm) and attenuating the decreased gene expression and/or protein level of AMP-activated protein kinase α (AMPKα), sirtuin 1 (SIRT1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) implicated in mitochondrial biogenesis. At the peroxisomal level, QCT, RSV and API prevented the impact of 7KC by counteracting the decrease in ATP binding cassette subfamily D member (ABCD)3 (a peroxisomal mass marker) at the protein and mRNA levels, as well as the decreased expresssion of genes associated with peroxisomal biogenesis (Pex13, Pex14) and peroxisomal β-oxidation (Abcd1, Acox1, Mfp2, Thiolase A). The 7KC-induced decrease in ABCD1 and multifunctional enzyme type 2 (MFP2), two proteins involved in peroxisomal β-oxidation, was also attenuated by RSV, QCT and API. 7KC-induced cell death, which has characteristics of apoptosis (cells with fragmented and/or condensed nuclei; cleaved caspase-3; Poly(ADP-ribose) polymerase (PARP) fragmentation) and autophagy (cells with monodansyl cadaverine positive vacuoles; activation of microtubule associated protein 1 light chain 3–I (LC3-I) to LC3-II, was also strongly attenuated by RSV, QCT and API. Thus, in N2a cells, 7KC induces a mode of cell death by oxiapoptophagy, including criteria of OXIdative stress, APOPTOsis and autoPHAGY, associated with mitochondrial and peroxisomal dysfunction, which is counteracted by RSV, QCT, and API reinforcing the interest for these polyphenols in prevention of diseases associated with increased 7KC levels.

Integrating Molecular Networking and 1H NMR Spectroscopy for Isolation of Bioactive Metabolites from the Persian Gulf Sponge Axinella sinoxea

The geographic position, highly fluctuating sea temperatures and hypersalinity make Persian Gulf an extreme environment. Although this unique environment has high biodiversity dominated by invertebrates, its potential in marine biodiscovery has largely remained untapped. Herein, we aimed at a detailed analysis of the metabolome and bioactivity profiles of the marine sponge Axinella sinoxea collected from the northeast coast of the Persian Gulf in Iran. The crude extract and its Kupchan subextracts were tested in multiple in-house bioassays, and the crude extract and its CHCl₃-soluble portion showed in vitro antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecium (Efm). A molecular networking (MN)-based dereplication strategy by UPLC-MS/MS revealed the presence of phospholipids and steroids, while ¹H NMR spectroscopy indicated the presence of additional metabolites, such as diketopiperazines (DKPs). Integrated MN and ¹H NMR analyses on both the crude and CHCl₃ extracts combined with an antibacterial activity-guided isolation approach afforded eight metabolites: a new diketopiperazine, (-)-cyclo(L-trans-Hyp-L-Ile) (8); a known diketopiperazine, cyclo(L-trans-Hyp-L-Phe) (7); two known phospholipids, 1-O-hexadecyl-sn-glycero-3-phosphocholine (1) and 1-O-octadecanoyl-sn-glycero-3-phosphocholine (2); two known steroids, 3β-hydroxycholest-5-ene-7,24-dione (3) and (22E)-3β-hydroxycholesta-5,22-diene-7,24-dione (4); two known monoterpenes, loliolide (5) and 5-epi-loliolide (6). The chemical structures of the isolates were elucidated by a combination of NMR spectroscopy, HRMS and [α]_D analyses. All compounds were tested against MRSA and Efm, and compound 3 showed moderate antibacterial activity against MRSA (IC₅₀ value 70 μg/mL). This is the first study that has dealt with chemical and bioactivity profiling of A.sinoxea leading to isolation and characterization of pure sponge metabolites.

Endoplasmic reticulum stress and mitochondrial biogenesis are potential therapeutic targets for abdominal aortic aneurysm

Endoplasmic reticulum (ER) and mitochondria are crucial organelles for cell homeostasis and alterations of these organelles have been implicated in cardiovascular disease. However, their roles in abdominal aortic aneurysm (AAA) pathogenesis remain largely unknown. In a recent issue of Clinical Science, Navas-Madronal et al. ((2019), 133(13), 1421-1438) reported that enhanced ER stress and dysregulation of mitochondrial biogenesis are associated with AAA pathogenesis in humans. The authors also proposed that disruption in oxysterols network such as an elevated concentration of 7-ketocholestyerol in plasma is a causative factor for AAA progression. Their findings highlight new insights into the underlying mechanism of AAA progression through ER stress and dysregulation of mitochondrial biogenesis. Here, we will discuss the background, significance of the study, and future directions.

Oxysterol concentrations are associated with cholesterol concentrations and anemia in pediatric patients with sickle cell disease

Sickle cell disease (SCD) causes anemia, oxidative stress, chronic inflammation, and lipid abnormalities. Oxysterols are oxidized derivatives of cholesterol and affect cholesterol metabolism and eryptosis. Our aim was to determine whether the plasma concentrations of 7-ketocholesterol (7-KC) and cholestane-3β,5α,6β-triol (C-triol) were associated with hemolysis and lipid profile in patients with SCD. A total of 32 steady-state pediatric patients with SCD (22 HbSS and 10 HbSß⁺) and 25 healthy controls were included in the study. Hemolysis parameters, ferritin, serum iron, lipids, 7-KC and C-triol concentrations of all subjects were measured. Oxysterols were quantified with N,N-dimethylglycine derivatization via LC-MS/MS. 7-KC and C-triol concentrations were found to be increased in SCD patients, while there was no difference between the HbSS and HbSß⁺ subgroups. 7-KC concentrations s were correlated negatively with hemoglobin and positively with lactate dehydrogenase concentrations, while C-triol concentrations were negatively correlated with HDL cholesterol. Furthermore, while 7-KC and C-triol concentrations were highly correlated among controls, there was no correlation in patients. The findings of our study suggest that 7-KC and C-triol may have a role in SCD pathophysiology. The lack of correlation in patients' 7-KC and C-triol concentrations suggest alterations in oxysterol production in patients with SCD.

The Oxysterol 7-Ketocholesterol Reduces Zika Virus Titers in Vero Cells and Human Neurons

Zika virus (ZIKV) is an emerging flavivirus responsible for a major epidemic in the Americas beginning in 2015. ZIKV associated with maternal infection can lead to neurological disorders in newborns, including microcephaly. Although there is an abundance of research examining the neurotropism of ZIKV, we still do not completely understand the mechanism by which ZIKV targets neural cells or how to limit neural cell infection. Recent research suggests that flaviviruses, including ZIKV, may hijack the cellular autophagy pathway to benefit their replication. Therefore, we hypothesized that ZIKV replication would be impacted when infected cells were treated with compounds that target the autophagy pathway. We screened a library of 94 compounds known to affect autophagy in both mammalian and insect cell lines. A subset of compounds that inhibited ZIKV replication without affecting cellular viability were tested for their ability to limit ZIKV replication in human neurons. From this second screen, we identified one compound, 7-ketocholesterol (7-KC), which inhibited ZIKV replication in neurons without significantly affecting neuron viability. Interestingly, 7-KC induces autophagy, which would be hypothesized to increase ZIKV replication, yet it decreased virus production. Time-of-addition experiments suggest 7-KC inhibits ZIKV replication late in the replication cycle. While 7-KC did not inhibit RNA replication, it decreased the number of particles in the supernatant and the relative infectivity of the released particles, suggesting it interferes with particle budding, release from the host cell, and particle integrity.

Induction of peroxisomal changes in oligodendrocytes treated with 7-ketocholesterol: Attenuation by α-tocopherol

The involvement of organelles in cell death is well established especially for endoplasmic reticulum, lysosomes and mitochondria. However, the role of the peroxisome is not well known, though peroxisomal dysfunction favors a rupture of redox equilibrium. To study the role of peroxisomes in cell death, 158 N murine oligodendrocytes were treated with 7-ketocholesterol (7 KC: 25-50 μM, 24 h). The highest concentration is known to induce oxiapoptophagy (OXIdative stress + APOPTOsis + autoPHAGY), whereas the lowest concentration does not induce cell death. In those conditions (with 7 KC: 50 μM) morphological, topographical and functional peroxisome alterations associated with modifications of the cytoplasmic distribution of mitochondria, with mitochondrial dysfunction (loss of transmembrane mitochondrial potential, decreased level of cardiolipins) and oxidative stress were observed: presence of peroxisomes with abnormal sizes and shapes similar to those observed in Zellweger fibroblasts, lower cellular level of ABCD3, used as a marker of peroxisomal mass, measured by flow cytometry, lower mRNA and protein levels (measured by RT-qPCR and western blotting) of ABCD1 and ABCD3 (two ATP-dependent peroxisomal transporters), and of ACOX1 and MFP2 enzymes, and lower mRNA level of DHAPAT, involved in peroxisomal β-oxidation and plasmalogen synthesis, respectively, and increased levels of very long chain fatty acids (VLCFA: C24:0, C24:1, C26:0 and C26:1, quantified by gas chromatography coupled with mass spectrometry) metabolized by peroxisomal β-oxidation. In the presence of 7 KC (25 μM), slight mitochondrial dysfunction and oxidative stress were found, and no induction of apoptosis was detected; however, modifications of the cytoplasmic distribution of mitochondria and clusters of mitochondria were detected. The peroxisomal alterations observed with 7 KC (25 μM) were similar to those with 7 KC (50 μM). In addition, data obtained by transmission electron microcopy and immunofluorescence microscopy by dual staining with antibodies raised against p62, involved in autophagy, and ABCD3, support that 7 KC (25-50 μM) induces pexophagy. 7 KC (25-50 μM)-induced side effects were attenuated by α-tocopherol but not by α-tocotrienol, whereas the anti-oxidant properties of these molecules determined with the FRAP assay were in the same range. These data provide evidences that 7 KC, at concentrations inducing or not cell death, triggers morphological, topographical and functional peroxisomal alterations associated with minor or major mitochondrial changes.

7-Ketocholesterol induces ATM/ATR, Chk1/Chk2, PI3K/Akt signalings, cytotoxicity and IL-8 production in endothelial cells

Cardiovascular diseases (atherosclerosis, stroke, myocardiac infarction etc.) are the major systemic diseases of elder peoples in the world. This is possibly due to increased levels of oxidized low-density lipoproteins (oxLDLs) such as 7-ketocholesterol (7-KC) and lysophosphatidylcholine (LPC) that damage vascular endothelial cells, induce inflammatory responses, to elevate the risk of cardiovascular diseases, Alzheimer's disease, and age-related macular degeneration. However the toxic effects of 7-KC on endothelial cells are not known. In this study, 7-KC showed cytotoxicity to endothelial cells at concentrations higher than 10 µg/ml. 7-KC stimulated ATM/Chk2, ATR-Chk1 and p53 signaling pathways in endothelial cells. 7-KC also induced G0/G1 cell cycle arrest and apoptosis with an inhibition of Cyclin dependent kinase 1 (Cdk1) and cyclin B1 expression. Secretion and expression of IL-8 in endothelial cells were stimulated by 7-KC. 7-KC further induced intracellular ROS production as shown by increase in DCF fluorescence and Akt phosphorylation. LY294002 attenuated the 7-KC-induced apoptosis and IL-8 mRNA expression of endothelial cells. These results indicate that oxLDLs such as 7-KC may contribute to the pathogenesis of atherosclerosis, thrombosis and cardiovascular diseases by induction of endothelial damage, apoptosis and inflammatory responses. These events are associated with ROS production, activation of ATM/Chk2, ATR/Chk1, p53 and PI3K/Akt signaling pathways.

Oxidative alterations in sickle cell disease: Possible involvement in disease pathogenesis

Sickle cell disease (SCD) is the first molecular disease in the literature. Although the structural alteration and dysfunction of the sickle hemoglobin (HbS) are well understood, the many factors modifying the clinical signs and symptoms of the disease are under investigation. Besides having an abnormal electrophoretic mobility and solubility, HbS is unstable. The autooxidation rate of the abnormal HbS has been reported to be almost two times of the normal. There are two more components of the oxidative damage in SCD: Free radical induced oxidative damage during vaso-occlusion induced ischemia-reperfusion injury and decreased antioxidant capacity in the erythrocyte and in the circulation. We will discuss the effects of oxidative alterations in the erythrocyte and in the plasma of SCD patients in this review.

Association of Plasma 7-Ketocholesterol With Cardiovascular Outcomes and Total Mortality in Patients With Coronary Artery Disease

Rationale:

7-Ketocholesterol (7-KC), a form of cholesterol oxidation product, plays an essential role in the atherogenesis in animal models.

Objective:

We sought to determine the association of circulating 7-KC with clinical cardiovascular outcomes and total mortality in patients with stable coronary artery disease.

Methods and Results:

We measured the plasma 7-KC levels by high-performance liquid chromatography in a prospective cohort study of 1016 patients (mean age, 63.2 years; male 61.1%) with stable coronary artery disease who were recruited from December 2008 to December 2011 and followed up for a median of 4.6 years. We adjudicated myocardial infarction, hospitalization of heart failure, cardiovascular death, all-cause death, and composite end points of myocardial infarction/heart failure/death by review of medical records and death certificates. We used multivariable Cox proportional hazards analysis to compare the incidence rate of cardiovascular events and all-cause death according to the quartile of the plasma 7-KC. During the median 4.6 years follow-up, totally 221 participants (21.8%) experienced a cardiovascular event or death. The adjusted risk of the composite end points was higher in the highest 7-KC quartile than in the lowest quartile (hazard ratio, 1.76; 95% confidence interval, 1.42–2.21; P <0.001). After adjustment for demographic and clinical variables and other biomarkers, including high-sensitivity C-reactive protein and NT-proBNP (N-terminal pro-B-type natriuretic peptide), 1 SD increase in the 7-KC level remained associated with a 36% higher rate of composite outcomes (hazard ratio, 1.36; 95% confidence interval, 1.22–1.48; P =0.007). Plasma 7-KC clearly improved various model performance measures, including C statistics, integrated discrimination, and category-free net reclassification.

Conclusions:

High 7-KC levels are associated with increased risk of cardiovascular events, total death, and composite outcomes in patients with stable coronary artery disease.

Mitochondrial dysfunctions in 7-ketocholesterol-treated 158N oligodendrocytes without or with α-tocopherol: Impacts on the cellular profil of tricarboxylic cycle-associated organic acids, long chain saturated and unsaturated fatty acids, oxysterols, cholesterol and cholesterol precursors

In multiple sclerosis (MS) a process of white matter degradation leading to demyelination is observed. Oxidative stress, inflammation, apoptosis, necrosis and/or autophagy result together into a progressive loss of oligodendrocytes. 7-ketocholesterol (7KC), found increased in the cerebrospinal fluid of MS patients, triggers a rupture of RedOx homeostasis associated with mitochondrial dysfunctions, aptoptosis and autophagy (oxiapoptophagy) in cultured murine oligodendrocytes (158N). α-tocopherol is able to mild the alterations induced by 7KC partially restoring the cellular homeostasis. In presence of 7KC, the amount of adherent 158N cells was decreased and oxidative stress was enhanced. An increase of caspase-3 and PARP degradation (evidences of apoptosis), and an increased LC3-II/LC3-I ratio (criterion of autophagy), were detected. These events were associated with a decrease of the mitochondrial membrane potential (ΔΨ_m) and by a decrease of oxidative phosphorylation revealed by reduced NAD⁺ and ATP. The cellular lactate was higher while pyruvate, citrate, fumarate, succinate (tricarboxylic acid (TCA) cycle intermediates) were significantly reduced in exposed cells, suggesting that an impairment of mitochondrial respiratory functions could lead to an increase of lactate production and to a reduced amount of ATP and acetyl-CoA available for the anabolic pathways. The concentration of sterol precursors lathosterol, lanosterol and desmosterol were significantly reduced together with satured and unsatured long chain fatty acids (C16:0 - C18:0, structural elements of membrane phospholipids). Such reductions were milder with α-tocopherol. It is likely that the cell death induced by 7KC is associated with mitochondrial dysfunctions, including alterations of oxidative phosphorylation, which could result from lipid anabolism dysfunctions, especially on TCA cycle intermediates. A better knowledge of mitochondrial associated dysfunctions triggered by 7KC will contribute to bring new information on the demyelination processes which are linked with oxidative stress and lipid peroxidation, especially in MS.

Monocytic MKP-1 is a Sensor of the Metabolic Environment and Regulates Function and Phenotypic Fate of Monocyte-Derived Macrophages in Atherosclerosis

Diabetes promotes the S-glutathionylation, inactivation and subsequent degradation of mitogen-activated protein kinase phosphatase 1 (MKP-1) in blood monocytes, and hematopoietic MKP-1-deficiency in atherosclerosis-prone mice accelerates atherosclerotic lesion formation, but the underlying mechanisms were not known. Our aim was to determine the mechanisms through which MKP-1 deficiency in monocytes and macrophages promotes atherogenesis. Transplantation of MKP-1-deficient bone marrow into LDL-R^−/− (MKP-1_LeuKO) mice accelerated high-fat diet (HFD)-induced atherosclerotic lesion formation. After 12 weeks of HFD feeding, MKP-1_LeuKO mice showed increased lesion size in both the aortic root (1.2-fold) and the aorta (1.6-fold), despite reduced plasma cholesterol levels. Macrophage content was increased in lesions of MKP-1_LeuKO mice compared to mice that received wildtype bone marrow. After only 6 weeks on a HFD, in vivo chemotactic activity of monocytes was already significantly increased in MKP-1_LeuKO mice. MKP-1 deficiency in monocytes and macrophages promotes and accelerates atherosclerotic lesion formation by hyper-sensitizing monocytes to chemokine-induced recruitment, predisposing macrophages to M1 polarization, decreased autophagy and oxysterol-induced cell death whereas overexpression of MKP-1 protects macrophages against metabolic stress-induced dysfunction. MKP-1 serves as a master-regulator of macrophage phenotype and function and its dysregulation by metabolic stress may be a major contributor to atherogenesis and the progression of atherosclerotic plaques.

Biodegradation of cytotoxic 7-Ketocholesterol by Pseudomonas aeruginosa PseA

The present study aims to degrade 7-Ketocholesterol (7KC), a major oxysterol implicated in many age-related disorders, through microbial means and find candidate enzymes involved for further application in food systems and as a therapeutic. During initial screening of previously isolated bacteria from our laboratory, Pseudomonas aeruginosa PseA was found to be a potential degrader strain using 7KC as a sole carbon source. Under optimized conditions, it is able to degrade 88% of an initial concentration of 1000ppm (1g/l) 7KC. Preliminary in vitro studies with extra-cellular extract has shown degradation of the compound, thus reinforcing the occurrence of suitable enzymatic systems involved in the process. We have been able to identify cholesterol oxidase as one such potential enzyme. Some intermediate products of degradation have also been identified. This is the first detailed report of 7KC degradation by a P. aeruginosa strain.

Differential cytotoxic effects of 7-dehydrocholesterol-derived oxysterols on cultured retina-derived cells: Dependence on sterol structure, cell type, and density

Tissue accumulation of 7-dehydrocholesterol (7DHC) is a hallmark of Smith-Lemli-Opitz Syndrome (SLOS), a human inborn error of the cholesterol (CHOL) synthesis pathway. Retinal 7DHC-derived oxysterol formation occurs in the AY9944-induced rat model of SLOS, which exhibits a retinal degeneration characterized by selective loss of photoreceptors and associated functional deficits, Müller cell hypertrophy, and engorgement of the retinal pigment epithelium (RPE) with phagocytic inclusions. We evaluated the relative effects of four 7DHC-derived oxysterols on three retina-derived cell types in culture, with respect to changes in cellular morphology and viability. 661W (photoreceptor-derived) cells, rMC-1 (Müller glia-derived) cells, and normal diploid monkey RPE (mRPE) cells were incubated for 24 h with dose ranges of either 7-ketocholesterol (7kCHOL), 5,9-endoperoxy-cholest-7-en-3β,6α-diol (EPCD), 3β,5α-dihydroxycholest-7-en-6-one (DHCEO), or 4β-hydroxy-7-dehydrocholesterol (4HDHC); CHOL served as a negative control (same dose range), along with appropriate vehicle controls, while staurosporine (Stsp) was used as a positive cytotoxic control. For 661W cells, the rank order of oxysterol potency was: EPCD > 7kCHOL >> DHCEO > 4HDHC ≈ CHOL. EC50 values were higher for confluent vs. subconfluent cultures. 661W cells exhibited much higher sensitivity to EPCD and 7kCHOL than either rMC-1 or mRPE cells, with the latter being the most robust when challenged, either at confluence or in sub-confluent cultures. When tested on rMC-1 and mRPE cells, EPCD was again an order of magnitude more potent than 7kCHOL in compromising cellular viability. Hence, 7DHC-derived oxysterols elicit differential cytotoxicity that is dose-, cell type-, and cell density-dependent. These results are consistent with the observed progressive, photoreceptor-specific retinal degeneration in the rat SLOS model, and support the hypothesis that 7DHC-derived oxysterols are causally linked to that retinal degeneration as well as to SLOS.

Cholesterol Oxidation in Fish and Fish Products

Fish and fish products are important from a nutritional point of view due to the presence of high biological value proteins and the high content of polyunsaturated fatty acids, especially those of the n-3 series, and above all eicosapentaenoic acid and docosahexaenoic acid. However, these important food products also contain significant amounts of cholesterol. Although cholesterol participates in essential functions in the human body, it is unstable, especially in the presence of light, oxygen, radiation, and high temperatures that can cause the formation of cholesterol oxidation products or cholesterol oxides, which are prejudicial to human health. Fish processing involves high and low temperatures, as well as other methods for microbiological control, which increases shelf life and consequently added value; however, such processes favor the formation of cholesterol oxidation products. This review brings together data on the formation of cholesterol oxides during the preparation and processing of fish into food products which are recognized and recommended for their nutritional properties.

Induction of oxiapoptophagy on 158N murine oligodendrocytes treated by 7-ketocholesterol-, 7β-hydroxycholesterol-, or 24(S)-hydroxycholesterol: Protective effects of α-tocopherol and docosahexaenoic acid (DHA; C22:6 n-3)

In demyelinating or non-demyelinating neurodegenerative diseases, increased levels of 7-ketocholesterol (7KC), 7β-hydroxycholesterol (7β-OHC) and 24(S)-hydroxycholesterol (24S-OHC) can be observed in brain lesions. In 158N murine oligodendrocytes, 7KC triggers a complex mode of cell death defined as oxiapoptophagy, involving simultaneous oxidative stress, apoptosis and autophagy. In these cells, 7KC as well as 7β-OHC and 24S-OHC induce a decrease of cell proliferation evaluated by phase contrast microscopy, an alteration of mitochondrial activity quantified with the MTT test, an overproduction of reactive oxygen species revealed by staining with dihydroethidium and dihydrorhodamine 123, caspase-3 activation, PARP degradation, reduced expression of Bcl-2, and condensation and/or fragmentation of the nuclei which are typical criteria of oxidative stress and apoptosis. Moreover, 7KC, 7β-OHC and 24S-OHC promote conversion of microtubule-associated protein light chain 3 (LC3-I) to LC3-II which is a characteristic of autophagy. Consequently, 7β-OHC and 24S-OHC, similarly to 7KC, can be considered as potent inducers of oxiapoptophagy. Furthermore, the different cytotoxic effects associated with 7KC, 7β-OHC and 24S-OHC-induced oxiapoptophagy are attenuated by vitamin E (VitE, α-tocopherol) and DHA which enhances VitE protective effects. In 158N murine oligodendrocytes, our data support the concept that oxiapoptophagy, which can be inhibited by VitE and DHA, could be a particular mode of cell death elicited by cytotoxic oxysterols.

Phosphorescence monitoring of hypoxic microenvironment in solid-tumors to evaluate chemotherapeutic effects using the hypoxia-sensitive iridium (III) coordination compound

Objectives

To utilize phosphorescence to monitor hypoxic microenvironment in solid-tumors and investigate cancer chemotherapeutic effects in vivo.

Methods

A hypoxia-sensitive probe named BTP was used to monitor hypoxic microenvironment in solid-tumors. The low-dose metronomic treatment with cisplatin was used in anti-angiogenetic chemotherapeutic programs. The phosphorescence properties of BTP were detected by a spectrofluorometer. BTP cytotoxicity utilized cell necrosis and apoptosis, which were evaluated by trypan blue dye exclusion and Hoechst33342 plus propidium iodide assays. Tumor-bearing mouse models of colon adenocarcinoma were used for tumor imaging in vivo. Monitoring of the hypoxic microenvironment in tumors was performed with a Maestro 2 fluorescence imaging system. Tumor tissues in each group were harvested regularly and treated with pathological hematoxylin and eosin and immunohistochemical staining to confirm imaging results.

Results

BTP did not feature obvious cytotoxicity for cells, and tumor growth in low-dose metronomic cisplatin treated mice was significantly inhibited by chemotherapy. Hypoxic levels significantly increased due to cisplatin, as proven by the expression level of related proteins. Phosphorescence intensity in the tumors of mice in the cisplatin group was stronger and showed higher contrast than that in tumors of saline treated mice.

CD1d serves as a surface receptor for oxidized cholesterol induction of peroxisome proliferator-activated receptor-γ

OBJECTIVE

The cluster of differentiation-1d (CD1d) recognizes and presents the lipid antigens to NK-T lymphocytes. Atherosclerotic lesions contain atherogenic lipids, mainly cholesterol and its oxides. Peroxisome proliferator-activated receptor-γ (PPARγ) is also known to exist in atherosclerotic lesions, participating in regulation of lipid metabolism. The current study tested whether CD1d acts as a surface receptor that mediates induction and activation of PPARγ by oxysterols commonly found in atherosclerotic lesions.

METHODS AND RESULTS

CD1d overexpression in HEK 293 cells transfected with CD1d cDNA was confirmed by fluorescence, flow cytometry, Western blotting and mRNA expression. Tritiated ((3)H) 7-ketocholesterol (7K) was used for lipid binding assays. Radioactive assessment demonstrated an increased 7K-binding activity HEK 293 cells with CD1d overexpression. The 7K binding could be blocked by another oxysterol, 25-hydroxycholesterol, but not by native free cholesterol. Addition of CD1d:IgG dimer protein or an anti-CD1d antibody, but not control IgG, significantly diminished 7K binding to CD1d-expressing HEK 293 cells. CD1d deficiency markedly diminished the 7K-binding in macrophages and smooth muscle cells. Western blot and gel shift assays demonstrated that CD1d-mediated 7K binding induced expression and activation of PPARγ. The PPARγ agonist PGJ2 enhances the 7K stimulatory effect on PPARγ expression and activity but the antagonist GW9662 inhibits the 7K effect on the CD1d-expressing cells.

CONCLUSIONS

CD1d acts as a cell surface receptor that recognizes and binds oxysterols and initializes a pathway connecting oxysterol binding to PPARγ activation.

Structural characterization of human cholesterol 7α-hydroxylase

Hepatic conversion to bile acids is a major elimination route for cholesterol in mammals. CYP7A1 catalyzes the first and rate-limiting step in classic bile acid biosynthesis, converting cholesterol to 7α-hydroxycholesterol. To identify the structural determinants that govern the stereospecific hydroxylation of cholesterol, we solved the crystal structure of CYP7A1 in the ligand-free state. The structure-based mutation T104L in the B' helix, corresponding to the nonpolar residue of CYP7B1, was used to obtain crystals of complexes with cholest-4-en-3-one and with cholesterol oxidation product 7-ketocholesterol (7KCh). The structures reveal a motif of residues that promote cholest-4-en-3-one binding parallel to the heme, thus positioning the C7 atom for hydroxylation. Additional regions of the binding cavity (most distant from the access channel) are involved to accommodate the elongated conformation of the aliphatic side chain. Structural complex with 7KCh shows an active site rigidity and provides an explanation for its inhibitory effect. Based on our previously published data, we proposed a model of cholesterol abstraction from the membrane by CYP7A1 for metabolism. CYP7A1 structural data provide a molecular basis for understanding of the diversity of 7α-hydroxylases, on the one hand, and cholesterol-metabolizing enzymes adapted for their specific activity, on the other hand.

Plant sterols from foods in inflammation and risk of cardiovascular disease: a real threat?

High dietary intakes of cholesterol together with sedentary habits have been identified as major contributors to atherosclerosis. The latter has long been considered a cholesterol storage disease; however, today atherosclerosis is considered a more complex disease in which both innate and adaptive immune-inflammatory mechanisms as well as bacteria play a major role, in addition to interactions between the arterial wall and blood components. This scenario has promoted nutritional recommendations to enrich different type of foods with plant sterols (PS) because of their cholesterol-lowering effects. In addition to cholesterol, PS can also be oxidized during food processing or storage, and the oxidized derivatives, known as phytosterol oxidation products (POPs), can make an important contribution to the negative effects of both cholesterol and cholesterol oxidation oxides (COPs) in relation to inflammatory disease onset and the development of atherosclerosis. Most current research efforts have focused on COPs, and evaluations of the particular role and physiopathological implications of specific POPs have been only inferential. Appreciation of the inflammatory role described for both COPs and POPs derived from foods also provides additional reasons for safety studies after long-term consumption of PS. The balance and relevance for health of all these effects deserves further studies in humans. This review summarizes current knowledge about the presence of sterol oxidation products (SOPs) in foods and their potential role in inflammatory process and cardiovascular disease.

Oxysterols and redox signaling in the pathogenesis of non-alcoholic fatty liver disease

Oxysterols are oxidized species of cholesterol coming from exogenous (e.g. dietary) and endogenous (in vivo) sources. They play critical roles in normal physiologic functions such as regulation of cellular cholesterol homeostasis. Most of biological effects are mediated by interaction with nuclear receptor LXRα, highly expressed in the liver as well as in many other tissues. Such interaction participates in the regulation of whole-body cholesterol metabolism, by acting as "lipid sensors". Moreover, it seems that oxysterols are also suspected to play key roles in several pathologies, including cardiovascular and inflammatory disease, cancer, and neurodegeneration. Growing evidence suggests that oxysterols may contribute to liver injury in non-alcoholic fatty liver disease. The present review focuses on the current status of knowledge on oxysterols' biological role, with an emphasis on LXR signaling and oxysterols' physiopathological relevance in NAFLD, suggesting new pharmacological development that needs to be addressed in the near future.

Regulation of autophagic flux by dynein-mediated autophagosomes trafficking in mouse coronary arterial myocytes

Autophagic flux is an important process during autophagy maturation in coronary arterial myocytes (CAMs). Here, we defined the role and molecular mechanism of the motor protein dynein in the regulation of autophagic flux in CAMs. In mouse CAMs, dynein protein is abundantly expressed. Pharmacological or genetic inhibition of dynein activity dramatically enhanced 7-ketocholesterol (7-Ket)-induced expression of the autophagic marker LC3B and increased the cellular levels of p62, a selective substrate for autophagy. Inhibition of dynein activity increased 7-Ket-induced formation of autophagosomes (APs), but reduced the number of autophagolysosomes (APLs) in CAMs. Furthermore, 7-Ket increased the fusion of APs with lysosomes and the velocity of APs movement in mouse CAMs, which was abolished when the dynein activity in these cells was inhibited. Interestingly, 7-Ket increased lysosomal Ca(2+) release and stimulated dynein ATPase activity, both of which were abolished by NAADP antagonists, NED-19 and PPADS. Taken together, our data suggest that NAADP-mediated Ca(2+) release plays a crucial role in regulating dynein activity, which mediates APs trafficking and fusion with lysosomes to form APLs thus regulating autophagic flux in CAMs under atherogenic stimulation.

Placental ABC transporters, cellular toxicity and stress in pregnancy

The human placenta, in addition to its roles as a nutrient transfer and endocrine organ, functions as a selective barrier to protect the fetus against the harmful effects of exogenous and endogenous toxins. Members of the ATP-binding cassette (ABC) family of transport proteins limit the entry of xenobiotics into the fetal circulation via vectorial efflux from the placenta to the maternal circulation. Several members of the ABC family, including proteins from the ABCA, ABCB, ABCC and ABCG subfamilies, have been shown to be functional in the placenta with clinically significant roles in xenobiotic efflux. However, recent findings suggest that these transporters also protect placental tissue by preventing the cellular accumulation of cytotoxic compounds such as lipids, sterols and their derivatives. Such protective functions are likely to be particularly important in pregnancies complicated by inflammatory or oxidative stress, where the generation of toxic metabolites is enhanced. For example, ABC transporters have been shown to protect against the harmful effects of hypoxia and oxidative stress through increased expression and efflux of oxysterols and glutathione conjugated xenobiotics. However, this protective capacity may be diminished in response to the same stressors. Several studies in primary human trophoblast cells and animal models have demonstrated decreased expression and activity of placental ABC transporters with inflammatory, oxidative or metabolic stress. Several clinical studies in pregnancies complicated by inflammatory conditions such as preeclampsia and gestational diabetes support these findings, although further studies are required to determine the clinical relevance of the relationships between placental ABC transporter expression and activity, and placental function in stressed pregnancies. Such studies are necessary to fully understand the consequences of pregnancy disorders on placental function and viability in order to optimise pregnancy care and maximise fetal growth and health.

Perilipin 2 (PLIN2)-deficiency does not increase cholesterol-induced toxicity in macrophages

Interventions on macrophages/foam cells to redirect intracellular cholesterol towards efflux pathways could become a very valuable addition to our therapeutic arsenal against atherosclerosis. However, certain manipulations of the cholesteryl ester cycle, such as the inhibition of ACAT1, an ER-resident enzyme that re-esterifies cholesterol, are not well tolerated. Previously we showed that targeting perilipin-2 (PLIN2), a major lipid droplet (LD)-associated protein in macrophages, prevents foam cell formation and protects against atherosclerosis. Here we have assessed the tolerance of PLIN2-deficient bone marrow derived macrophages (BMM) to several lipid loading conditions similar to the found during atherosclerosis development, including exposure to modified low-density lipoprotein (mLDL) and 7-ketocholesterol (7-KC), a free cholesterol (FC) metabolite, in media with or without cholesterol acceptors. BMM isolated from mice that do or do not express PLIN2 were tested for apoptosis (TUNEL and cleaved caspase-3), ER stress (CHOP induction and XBP-1 splicing), and inflammation (TNF-α and IL-6 mRNA levels). Like in other cell types, PLIN2 deficiency impairs LD buildup in BMM. However, while most stress parameters were elevated in macrophages under ACAT inhibition and 7-KC loading, PLIN2 inactivation was well tolerated. The data support the safety of targeting PLIN2 to prevent foam cell formation and atherosclerosis.

Cholesterol oxidation in the retina: implications of 7KCh formation in chronic inflammation and age-related macular degeneration

This review will discuss the formation and potential implications of 7-ketocholesterol (7KCh) in the retina. 7KCh is a proinflammatory oxysterol known to be present in high amounts in oxidized LDL deposits associated with atheromatous plaques. 7KCh is generated in situ in these lipoprotein deposits where it can accumulate and reach very high concentrations. In normal primate retina, 7KCh has been found associated with lipoprotein deposits in the choriocapillaris, Bruch's membrane, and the retinal pigment epithelium (RPE). In photodamaged rats, 7KCh has been found in the neural retina in areas of high mitochondrial content, ganglion cells, photoreceptor inner segments and synapses, and the RPE. Intermediates found by LCMS indicate 7KCh is formed via a free radical-mediated mechanism catalyzed by iron. 7KCh seems to activate several kinase signaling pathways that work via nuclear factor κB and cause the induction of vascular endothelial growth factor, interleukin (IL)-6, and IL-8. There seems to be little evidence of 7KCh metabolism in the retina, although some form of efflux mechanism may be active. The chronic mode of formation and the potent inflammatory properties of 7KCh indicate it may be an "age-related" risk factor in aging diseases such as atherosclerosis, Alzheimer's, and age-related macular degeneration.

Methionine sulfoxide reductase B2 is highly expressed in the retina and protects retinal pigmented epithelium cells from oxidative damage

Methionine sulfoxide reductase B2 (MSRB2) is a mitochondrial enzyme that converts methionine sulfoxide (R) enantiomer back to methionine. This enzyme is suspected of functioning to protect mitochondrial proteins from oxidative damage. In this study we report that the retina is one of the human tissues with highest levels of MSRB2 mRNA expression. Other tissues with high expression were heart, kidney and skeletal muscle. Overexpression of an MSRB2-GFP fusion protein increased the MSR enzymatic activity three-fold in stably transfected cultured RPE cells. This overexpression augmented the resistance of these cells to the toxicity induced by 7-ketocholesterol, tert-butyl hydroperoxide and all-trans retinoic acid. By contrast, knockdown of MSRB2 by a miRNA in stably transfected cells did not convey increased sensitivity to the oxidative stress. In the monkey retina MSRB2 localized to the ganglion cell layer (GLC), the outer plexiform layer (OPL) and the retinal pigment epithelium (RPE). MSRB2 expression is most pronounced in the OPL of the macula and foveal regions suggesting an association with the cone synaptic mitochondria. Our data suggests that MSRB2 plays an important function in protecting cones from multiple type of oxidative stress and may be critical in preserving central vision.

Photodamage generates 7-keto- and 7-hydroxycholesterol in the rat retina via a free radical-mediated mechanism

Albino Sprague-Dawley rats are known to undergo photoreceptor degeneration after exposure to constant light, but the molecular mechanism(s) by which the photoreceptors degenerate is not fully understood. We hypothesized that cytotoxic oxysterols are generated in situ in the retina under such conditions and may be involved in the degenerative mechanism. Thus, photodamaged and control rat retinas were analyzed for oxysterols by liquid chromatography mass spectroscopy. Elevated levels of two known cytotoxic oxysterols, 7-ketocholesterol (7KCh) and 7alphabeta-hydroxycholesterol (7HCh), were found in the photodamaged retinas, at levels six-fold and 50-fold greater, respectively, than those found in non photodamaged controls. Notably, two key intermediates, 5,6alpha,beta-epoxycholesterol (5,6-epoxyCh) and 7alphabeta-hydroperoxy-cholesterol, were also identified, indicating that the formation of 7KCh and 7HCh is mediated by a free radical mechanism. By immunohistochemistry, 7KCh was localized to the ganglion cell layer, photoreceptor inner segments and retinal pigment epithelium (RPE), which coincides with the localization of ferritin in the retina. Exposure of a mixture of ferritin and low-density lipoprotein to intense white light in vitro produced similar oxysterol species as seen in vivo. We propose that the increased levels of 7KCh and 7HCh, especially in photoreceptor inner segments and RPE, may arise due to ferritin-catalyzed reactions and may be important contributors to the photoreceptor degeneration observed in photodamaged rats.

Transport of lipids by ABC proteins: interactions and implications for cellular toxicity, viability and function

Members of the ATP-binding cassette (ABC) family of membrane-bound transporters are involved in multiple aspects of transport and redistribution of various lipids and their conjugates. Most ABC transporters localize to the plasma membrane; some are associated with liquid-ordered cholesterol-/sphingolipid-rich microdomains, and to a lesser extent the membranes of the Golgi and endoplasmic reticulum. Hence, ABC transporters are well placed to regulate plasma membrane lipid composition and the efflux and redistribution of structural phospholipids and sphingolipids during periods of cellular stress and recovery. ABC transporters can also modulate cellular sensitivity to extrinsic pro-apoptotic signals through regulation of sphingomyelin-ceramide biosynthesis and metabolism. The functionality of ABC transporters is, in turn, modulated by the lipid content of the microdomains in which they reside. Cholesterol, a major membrane microdomain component, is not only a substrate of several ABC transporters, but also regulates ABC activity through its effects on microdomain structure. Several important bioactive lipid mediators and toxic lipid metabolites are also effluxed by ABC transporters. In this review, the complex interactions between ABC transporters and their lipid/sterol substrates will be discussed and analyzed in the context of their relevance to cellular function, toxicity and apoptosis.

A novel NADP(+)-dependent dehydrogenase activity for 7alpha/beta- and 11beta-hydroxysteroids in human liver nuclei: A third 11beta-hydroxysteroid dehydrogenase

Human tissue from uninvolved liver of cancer patients was fractionated using differential centrifugation and characterized for 11betaHSD enzyme activity against corticosterone, dehydrocorticosterone, 7alpha- and 7beta-hydroxy-dehydroepiandrosterone, and 7-oxo-dehydroepiandrosterone. An enzyme activity was observed in nuclear protein fractions that utilized either NADP(+) or NAD(+), but not NADPH and NADH, as pyridine nucleotide cofactor with K(m) values of 12+/-2 and 390+/-2microM, compared to the K(m) for microsomal 11betaHSD1 of 43+/-8 and 264+/-24microM, respectively. The K(m) for corticosterone in the NADP(+)-dependent nuclear oxidation reaction was 102+/-16nM, compared to 4.3+/-0.8microM for 11betaHSD1. The K(cat) values for nuclear activity with NADP(+) was 1687nmol/min/mg/micromol, compared to 755nmol/min/mg/micromol for microsomal 11betaHSD1 activity. Inhibitors of 11betaHSD1 decreased both nuclear and microsomal enzyme activities, suggesting that the nuclear activity may be due to an enzyme similar to 11betaHSD Type 1 and 2.

Human carotid atherosclerotic plaque increases oxidative state of macrophages and low-density lipoproteins, whereas paraoxonase 1 (PON1) decreases such atherogenic effects

Human atherosclerotic plaque contains a variety of oxidized lipids, which can facilitate further oxidation. Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated esterase (lipolactonase), exhibiting antiatherogenic properties. The aims of the present study were to examine the oxidizing potency of the human carotid plaque lipid extract (LE), and the antiatherogenic role of PON1 on LE oxidation competence. Human carotid plaques were extracted by organic solvent, and the extract was incubated with lipoprotein particles, with macrophages, or with probes sensitive to oxidative stress, with or without preincubation with PON1, followed by oxidative-stress assessment. Our findings imply that the LE oxidized LDL, macrophages, and exogenous probes and decreases HDL-mediated cholesterol efflux from macrophages, in a dose-dependent manner. Incubation of PON1 with LE significantly affects LE composition, reduces LE atherogenic properties, and decreases the extract's total peroxide concentration by 44%, macrophage oxidation by 25%, and probe oxidation by up to 52%. We conclude that these results expand our understanding of how the plaque itself accelerates atherogenesis and provides an important mechanism for attenuation of atherosclerosis development by the antioxidant action of PON1 on the atherosclerotic plaque.

7-Ketocholesterol is present in lipid deposits in the primate retina: potential implication in the induction of VEGF and CNV formation

PURPOSE

7-Ketocholesterol is a highly toxic oxysterol found in abundance in atherosclerotic plaques and is believed to play a critical role in atherosclerosis. The purpose of this study was to identify and localize 7-ketocholesterol (7kCh) in the primate retina and to examine the potential consequences of its presence in oxidized lipid deposits in the retina.

METHODS

Unsterified 7kCh was identified and quantified by high-performance liquid chromatography-mass spectrometry. Localization of 7kCh was performed by immunohistochemistry. VEGF induction was determined by qRT-PCR. Cell viability was determined by measuring cellular dehydrogenase activity. Analyses were performed using ARPE19 and human vascular endothelial cells (HMVECs).

RESULTS

7-Ketocholesterol is localized mainly to deposits in the choriocapillaris and Bruch's membrane and on the surfaces of vascular endothelial cells of the neural retina. RPE/choriocapillaris regions contained approximately four times more 7kCh than the neural retina. In ARPE19 cells and HMVECs, oxidized LDL and 7kCh induced VEGF 8- to 10-fold above controls. Hypoxia inducible factor (HIF)-1alpha levels did not increase as a result of 7kCh treatment, suggesting an HIF-independent induction pathway. Cholesterol sulfate, a liver X receptor (LXR) antagonist, had marked attenuation of the 7kCh-mediated VEGF induction. LXR-specific siRNAs also reduced VEGF induction. Inhibition of NF-kappaB with BAY 11-7082 reduced IL-8 but not VEGF induction.

CONCLUSIONS

The location of 7-kCh in the retina and its induction of VEGF in cultured RPE cells and HMVECs suggest it may play a critical role in choroidal neovascularization. The pathway for VEGF induction seems to be independent of HIF-1alpha and NF-kappaB but seems to be partially regulated by LXRs.