Lipid accumulation and lysosomal pathways contribute to dysfunction and apoptosis of human endothelial cells caused by 7-oxysterols

Transcriptomics Analysis Revealed Key Genes Associated with Macrophage Autophagolysosome in Male ApoE-/- Mice Aortic Atherosclerosis

Purpose

Atherosclerosis (AS) is the most common cause of cardiovascular and cerebrovascular diseases. However, the mechanisms underlying atherosclerotic plaque progression remain unclear. This study aimed to investigate the genes associated with the development of atherosclerosis in the aorta of ApoE-/- male mice, which could serve as novel biomarkers and therapeutic targets in interventions to halt plaque progression.

Methods

Eight-week-old ApoE-/- mice were fed a normal purified laboratory diet or a Western Diet (WD) for 6 or 22 weeks. High-throughput sequencing technology was used to analyze the transcriptomes of the aortas of four groups of mice that were exposed to different dietary conditions. We retrieved and downloaded the human Arteriosclerosis Disease Chip dataset GSE100927 from the Gene Expression Omnibus (GEO) database and selected 29 cases of carotid atherosclerotic lesions and 12 cases of normal carotid tissues as the experimental and control groups, respectively, to further verify our dataset. In addition, we used quantitative reverse transcription polymerase chain reaction (QT-PCR) to verify the expression levels of the core genes in an atherosclerosis mouse model.

Results

There were 265 differentially expressed genes (DEGs) between the ApoE-/- Male mice AS22W group and Sham22W group. In addition to the well-known activation of inflammation and immune response, t the autophagy-lysosome system is also an important factor that affects the development of atherosclerosis. We identified five core genes (Atp6ap2, Atp6v0b, Atp6v0d2, Atp6v1a, and Atp6v1d) in the protein-protein interaction (PPI) network that were closely related to autophagosomes. Hub genes were highly expressed in the carotid atherosclerosis group in the GSE100927 dataset (P < 0.001). QT-PCR showed that the RNA level of Atp6v0d2 increased significantly during the development of atherosclerotic plaque in ApoE-/- male mice.

Conclusion

Five core genes which affect the development of aortic atherosclerosis through the autophagy-lysosome system, especially Atp6v0d2, were screened and identified using bioinformatic techniques.

Prognostic value of plasma 7-ketocholesterol in sepsis

BACKGROUND

Early evaluation of the severity of sepsis and estimation of its prognosis remains one of the main challenges in current therapeutic strategies. This study aimed to evaluate the prognostic value of plasma 7-ketocholesterol (7-KC) in sepsis.

METHODS

We retrospectively measured by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) the plasma 7-KC concentration in 176 patients with sepsis and 90 healthy volunteers. A multivariate Cox proportional hazard model was introduced to identify independent factors, including plasma 7-KC and clinical features, for the 28-day mortality of sepsis, and a nomogram for predicting the 28-day mortality of sepsis was established. Decision curve analysis (DCA) was performed to assess the prediction model of death risk of sepsis.

RESULTS

The area under the curve (AUC) of plasma 7-KC in diagnosing sepsis was 0.899 (95% CI = 0.862-0.935, P < 0.001), while it was 0.830 (95% CI = 0.764-0.894, P < 0.001) in diagnosing septic shock. The AUCs of plasma 7-KC in predicting the survival of sepsis patients in the training cohort and the test cohort were 0.770 (95% CI = 0.692-0.848, P < 0.05) and 0.869 (95% CI = 0.763-0.974, P < 0.05), respectively. In addition, high plasma 7-KC expression predicts poor prognosis in sepsis. Then, 7-KC and platelet count were identified as the two factors with significant differences by a multivariate Cox proportional hazard model, and the 28-day mortality probability ranged from 0.002 to 0.985 and was assessed using a nomogram. DCA results revealed that the combination of plasma 7-KC and platelet count showed the best prognostic efficiency of the risk threshold compared to a single factor in both the training cohort and test cohort.

CONCLUSIONS

Collectively, the elevated plasma 7-KC level is an indicator of sepsis and was identified as a prognostic indicator for sepsis patients, providing a landscape for predicting survival in early sepsis with potential clinical utility.

Plasma metabolomics in a deep vein thrombosis rat model based on ultra-high performance liquid chromatography-electrostatic field orbitrap high resolution mass spectrometry

深静脉血栓(DVT)是一种血栓栓塞性疾病,具有高发病率、高死亡率和高后遗症3大特点。采用左股静脉不完全结扎加高渗盐水刺激建立DVT大鼠模型,使用超高效液相色谱-静电场轨道阱高分辨质谱(UHPLC-Orbitrap HRMS)检测假手术组与DVT模型组的血浆代谢谱,用主成分分析(PCA)及正交偏最小二乘-判别分析(OPLS-DA)对代谢组数据进行多元统计分析,观察两组间的代谢表型差异,将多变量模型分析中的变量重要性值(VIP>1)以及代谢物在模型组中的变化倍数(FC≤0.5或FC≥2,且P<0.05)作为差异代谢物筛选条件。最终在DVT模型组与假手术组间筛选得到27种差异代谢物,这些代谢物反映了DVT大鼠的代谢紊乱情况。具体表现为与假手术组相比,DVT模型组中三甲基胺氮氧化物(TMAO)、维生素K、鹅去氧胆酸、牛磺酸、1-甲基烟酰胺、7-酮胆固醇、反式十六烷基-2-烯醇肉碱、乙烯基乙酰甘氨酸、丙酰脯氨酸、咪唑乙酸、咪唑乙酸核糖苷、1,3,7-三甲基尿酸、1-丁胺、2-羟基异丙酸、吡哆醛、5α-四氢皮质酮、苯乳酸的水平显著升高;而3-脱氢肉碱、磷脂酰胆碱22∶6/20∶2(PC 22∶6/20∶2)、甘油二酯18∶3/20∶4(DG 18∶3/20∶4)、溶血磷脂酰胆碱20∶2(LysoPC 20∶2)、波维酸、鹅肌肽、L-肌肽、辛酸、羟基丙酮酸、3-羟基癸酸的水平显著降低。基于京都基因与基因组百科全书数据库(KEGG)代谢通路的差异丰度(DA)分析显示DVT模型大鼠与假手术组的代谢通路差异主要集中在初级胆汁酸生物合成、胆汁分泌、组氨酸代谢、亚油酸代谢、甘油磷脂代谢和β-丙氨酸代谢。紊乱的代谢物和代谢途径可为进一步深入理解DVT的病理机制、寻找诊断标志物及药物作用靶点提供参考。

Effect of Withanolide A on 7-Ketocholesterol Induced Cytotoxicity in hCMEC/D3 Brain Endothelial Cells

Withanolide A is a naturally occurring phytochemical that is found in Ashwagandha (Withania somnifera, fam. Solanaceae) or Indian Ginseng. In the current study, we elucidated the effect of withanolide A on 7-ketocholesterol (7KC) induced injury in hCMEC/D3 human brain endothelial cells. 7KC is a cholesterol oxidation product or oxysterol that is present in atherosclerotic plaques and is elevated in the plasma of patients with hypercholesterolemia and/or diabetes mellitus. Results showed that withanolide A significantly reduced the effects of 7KC, which include loss of endothelial cell viability, increase in expression of pro-inflammatory genes-IL-1β, IL-6, IL-8, TNF-α, cyclooxygenase-2 (COX-2), increased COX-2 enzyme activity, increased ROS formation, increased expression of inducible nitric oxide synthase and genes associated with blood clotting, including Factor 2/thrombin, Factor 8, von Willebrand factor, and thromboxane A synthase, and increased human thrombin enzyme activity. Some of the above effects of withanolide A on 7KC were reduced in the presence of the glucocorticoid receptor antagonist, mifepristone (RU486). These findings suggest that the glucocorticoid receptor could play a role in the cytoprotective, antioxidant, and anti-clotting effects of withanolide A against 7KC. Further studies are necessary to elucidate the detailed mechanisms of action of withanolide A against oxysterol-induced injury.

Oxysterols in the Immune Response to Bacterial and Viral Infections

Oxidized cholesterols, the so-called oxysterols, are widely known to regulate cholesterol homeostasis. However, more recently oxysterols have emerged as important lipid mediators in the response to both bacterial and viral infections. This review summarizes our current knowledge of selected oxysterols and their receptors in the control of intracellular bacterial growth as well as viral entry into the host cell and viral replication. Lastly, we briefly discuss the potential of oxysterols and their receptors as drug targets for infectious and inflammatory diseases.

Influential role of 7-Ketocholesterol in the progression of Alzheimer's disease

Millions of people are affected by neurodegenerative diseases worldwide. They occur due to the loss of brain functions or peripheral nervous system dysfunction. If untreated, prolonged condition ultimately leads to death. Mostly they are associated with stress, altered cholesterol metabolism, inflammation and organelle dysfunction. Endogenous cholesterol and phospholipids in brain undergo auto-oxidation by enzymatic as well as non-enzymatic modes leading to the formation of by-products such as 4-hydroxynonenal and oxysterols. Among various oxysterols, 7-ketocholesterol (7KCh) is one of the major toxic components involved in altering neuronal lipid metabolism, contributing to inflammation and nerve cell damage. More evidently 7KCh is proven to induce oxidative stress and affects membrane permeability. Loss in mitochondrial membrane potential affects metabolism of cell organelles such as lysosomes and peroxisomes which are involved in lipid and protein homeostasis. This in turn could affect amyloidogenesis, tau protein phosphorylation and accumulation in pathological conditions of neurodegenerative diseases. Lipid alterations and the consequent pathogenic protein accumulation, results in the damage of cell organelles and microglial cells. This could be a reason behind disease progression and predominantly reported characteristics of neurodegenerative disorders such as Alzheimer's disease. This review focuses on the role of 7KCh mediated neurodegenerative Alzheimer's disease with emphasis on alterations in the lipid raft microdomain. In addition, current trends in the significant therapies related to 7KCh inhibition are highlighted.

Attenuation of 7-ketocholesterol- and 7β-hydroxycholesterol-induced oxiapoptophagy by nutrients, synthetic molecules and oils: Potential for the prevention of age-related diseases

Age-related diseases for which there are no effective treatments include cardiovascular diseases; neurodegenerative diseases such as Alzheimer's disease; eye disorders such as cataract and age-related macular degeneration; and, more recently, Severe Acute Respiratory Syndrome (SARS-CoV-2). These diseases are associated with plasma and/or tissue increases in cholesterol derivatives mainly formed by auto-oxidation: 7-ketocholesterol, also known as 7-oxo-cholesterol, and 7β-hydroxycholesterol. The formation of these oxysterols can be considered as a consequence of mitochondrial and peroxisomal dysfunction, leading to increased in oxidative stress, which is accentuated with age. 7-ketocholesterol and 7β-hydroxycholesterol cause a specific form of cytotoxic activity defined as oxiapoptophagy, including oxidative stress and induction of death by apoptosis associated with autophagic criteria. Oxiaptophagy is associated with organelle dysfunction and in particular with mitochondrial and peroxisomal alterations involved in the induction of cell death and in the rupture of redox balance. As the criteria characterizing 7-ketocholesterol- and 7β-hydroxycholesterol-induced cytotoxicity are often simultaneously observed in major age-related diseases (cardiovascular diseases, age-related macular degeneration, Alzheimer's disease) the involvement of these oxysterols in the pathophysiology of the latter seems increasingly likely. It is therefore important to better understand the signalling pathways associated with the toxicity of 7-ketocholesterol and 7β-hydroxycholesterol in order to identify pharmacological targets, nutrients and synthetic molecules attenuating or inhibiting the cytotoxic activities of these oxysterols. Numerous natural cytoprotective compounds have been identified: vitamins, fatty acids, polyphenols, terpenes, vegetal pigments, antioxidants, mixtures of compounds (oils, plant extracts) and bacterial enzymes. However, few synthetic molecules are able to prevent 7-ketocholesterol- and/or 7β-hydroxycholesterol-induced cytotoxicity: dimethyl fumarate, monomethyl fumarate, the tyrosine kinase inhibitor AG126, memantine, simvastatine, Trolox, dimethylsufoxide, mangafodipir and mitochondrial permeability transition pore (MPTP) inhibitors. The effectiveness of these compounds, several of which are already in use in humans, makes it possible to consider using them for the treatment of certain age-related diseases associated with increased plasma and/or tissue levels of 7-ketocholesterol and/or 7β-hydroxycholesterol.

Toward Raman Subcellular Imaging of Endothelial Dysfunction

Multiple diseases are at some point associated with altered endothelial function, and endothelial dysfunction (ED) contributes to their pathophysiology. Biochemical changes of the dysfunctional endothelium are linked to various cellular organelles, including the mitochondria, endoplasmic reticulum, and nucleus, so organelle-specific insight is needed for better understanding of endothelial pathobiology. Raman imaging, which combines chemical specificity with microscopic resolution, has proved to be useful in detecting biochemical changes in ED at the cellular level. However, the detection of spectroscopic markers associated with specific cell organelles, while desirable, cannot easily be achieved by Raman imaging without labeling. This critical review summarizes the current advances in Raman-based analysis of ED, with a focus on a new approach involving molecular Raman reporters that could facilitate the study of biochemical changes in cellular organelles. Finally, imaging techniques based on both conventional spontaneous Raman scattering and the emerging technique of stimulated Raman scattering are discussed.

7-ketocholesterol induces endothelial-mesenchymal transition and promotes fibrosis: implications in neovascular age-related macular degeneration and treatment

Oxidized cholesterols and lipids accumulate in Bruch's membrane in age-related macular degeneration (AMD). It remains unknown what causal relationship exists between these substances and AMD pathophysiology. We addressed the hypothesis that a prevalent form, 7-ketocholesterol (7KC), promotes choroidal endothelial cell (CEC) migration and macular neovascularization in AMD. Compared to control, 7KC injection caused 40% larger lectin-stained lesions, but 70% larger lesions measured by optical coherence tomography one week after laser-injury. At two weeks, 7KC-injected eyes had 86% larger alpha smooth muscle actin (αSMA)-labeled lesions and more collagen-labeling than control. There was no difference in cell death. 7KC-treated RPE/choroids had increased αSMA but decreased VE-cadherin. Compared to control-treated CECs, 7KC unexpectedly reduced endothelial VE-cadherin, CD31 and VEGFR2 and increased αSMA, fibroblast activation protein (FAP) and transforming growth factor beta (TGFβ). Inhibition of TGFβ receptor-mediated signaling by SB431542 abrogated 7KC-induced loss of endothelial and increase in mesenchymal proteins in association with decreased transcription factor, SMAD3. Knockdown of SMAD3 partially inhibited 7KC-mediated loss of endothelial proteins and increase in αSMA and FAP. Compared to control, 7KC-treatment of CECs increased Rac1GTP and migration, and both were inhibited by the Rac1 inhibitor; however, CECs treated with 7KC had reduced tube formation. These findings suggest that 7KC, which increases in AMD and with age, induces mesenchymal transition in CECs making them invasive and migratory, and causing fibrosis in macular neovascularization. Further studies to interfere with this process may reduce fibrosis and improve responsiveness to anti-VEGF treatment in non-responsive macular neovascularization in AMD.

Effect of Ergothioneine on 7-Ketocholesterol-Induced Endothelial Injury

Ergothioneine (ET) is a naturally occurring antioxidant that is synthesized by non-yeast fungi and certain bacteria. ET is not synthesized by animals, including humans, but is avidly taken up from the diet, especially from mushrooms. In the current study, we elucidated the effect of ET on the hCMEC/D3 human brain endothelial cell line. Endothelial cells are exposed to high levels of the cholesterol oxidation product, 7-ketocholesterol (7KC), in patients with cardiovascular disease and diabetes, and this process is thought to mediate pathological inflammation. 7KC induces a dose-dependent loss of cell viability and an increase in apoptosis and necrosis in the endothelial cells. A relocalization of the tight junction proteins, zonula occludens-1 (ZO-1) and claudin-5, towards the nucleus of the cells was also observed. These effects were significantly attenuated by ET. In addition, 7KC induces marked increases in the mRNA expression of pro-inflammatory cytokines, IL-1β IL-6, IL-8, TNF-α and cyclooxygenase-2 (COX2), as well as COX2 enzymatic activity, and these were significantly reduced by ET. Moreover, the cytoprotective and anti-inflammatory effects of ET were significantly reduced by co-incubation with an inhibitor of the ET transporter, OCTN1 (VHCL). This shows that ET needs to enter the endothelial cells to have a protective effect and is unlikely to act via extracellular neutralizing of 7KC. The protective effect on inflammation in brain endothelial cells suggests that ET might be useful as a nutraceutical for the prevention or management of neurovascular diseases, such as stroke and vascular dementia. Moreover, the ability of ET to cross the blood-brain barrier could point to its usefulness in combatting 7KC that is produced in the CNS during neuroinflammation, e.g. after excitotoxicity, in chronic neurodegenerative diseases, and possibly COVID-19-related neurologic complications.

Diverse Immunoregulatory Roles of Oxysterols-The Oxidized Cholesterol Metabolites

Intermediates of both cholesterol synthesis and cholesterol metabolism can have diverse roles in the control of cellular processes that go beyond the control of cholesterol homeostasis. For example, oxidized forms of cholesterol, called oxysterols have functions ranging from the control of gene expression, signal transduction and cell migration. This is of particular interest in the context of immunology and immunometabolism where we now know that metabolic processes are key towards shaping the nature of immune responses. Equally, aberrant metabolic processes including altered cholesterol homeostasis contribute to immune dysregulation and dysfunction in pathological situations. This review article brings together our current understanding of how oxysterols affect the control of immune responses in diverse immunological settings.

7-Ketocholesterol in disease and aging

7-Ketocholesterol (7KC) is a toxic oxysterol that is associated with many diseases and disabilities of aging, as well as several orphan diseases. 7KC is the most common product of a reaction between cholesterol and oxygen radicals and is the most concentrated oxysterol found in the blood and arterial plaques of coronary artery disease patients as well as various other disease tissues and cell types. Unlike cholesterol, 7KC consistently shows cytotoxicity to cells and its physiological function in humans or other complex organisms is unknown. Oxysterols, particularly 7KC, have also been shown to diffuse through membranes where they affect receptor and enzymatic function. Here, we will explore the known and proposed mechanisms of pathologies that are associated with 7KC, as well speculate about the future of 7KC as a diagnostic and therapeutic target in medicine.

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.

Oxysterols and 4-hydroxy-2-nonenal contribute to atherosclerotic plaque destabilization

A growing bulk of evidence suggests that cholesterol oxidation products, known as oxysterols, and 4-hydroxy-2-nonenal (HNE), the major proatherogenic components of oxidized low density lipoproteins (oxLDLs), significantly contribute to atherosclerotic plaque progression and destabilization, with eventual plaque rupture. These oxidized lipids are involved in various key steps of this complex process, mainly thanks to their ability to induce inflammation, oxidative stress, and apoptosis. This review summarizes the current knowledge of the effects induced by these compounds on vascular cells, after their accumulation in the arterial wall and in the atherosclerotic plaque.

Exposure to atheroma-relevant 7-oxysterols causes proteomic alterations in cell death, cellular longevity, and lipid metabolism in THP-1 macrophages

The 7-oxysterols are recognised as strong enhancers of inflammatory processes in foamy macrophages. Atheroma-relevant 7-oxysterol mixtures induce a mixed type of cell death in macrophages, and trigger cellular oxidative stress responses, which mimic oxidative exposures observed in atherosclerotic lesions. However, the macrophage proteome has not previously been determined in the 7-oxysterol treated cell model. The aim of the present study was to determine the specific effects of an atheroma-relevant 7-oxysterol mixture on human macrophage proteome. Human THP-1 macrophages were exposed to an atheroma-relevant mixture of 7β-hydroxycholesterol and 7-ketocholesterol. Two-dimensional gel electrophoresis and mass spectrometry techniques were used to analyse the alterations in macrophage proteome, which resulted in the identification of 19 proteins with significant differential expression upon oxysterol loading; 8 increased and 11 decreased. The expression patterns of 11 out of 19 identified significant proteins were further confirmed by tandem-mass spectrometry, including further validation of increased histone deacetylase 2 and macrophage scavenger receptor types I and II expressions by western blot analysis. Identified proteins with differential expression in the cell model have been associated with i) signalling imbalance in cell death and cellular longevity; ii) lipid uptake and metabolism in foam cells; and iii) inflammatory proteins. The presented findings highlight a new proteomic platform for further studies into the functional roles of macrophages in atherosclerosis, and present a cell model for future studies to modulate the macrophage proteome by potential anti-atherosclerotic agents.

7-Ketocholesterol overcomes drug resistance in chronic myeloid leukemia cell lines beyond MDR1 mechanism

Chronic myeloid leukemia (CML) is a myeloproliferative disease with a characteristic BCR-ABL tyrosine kinase (TK) fusion protein. Despite the clinical efficacy accomplished by TKIs therapies, disease progression may affect patient response rate to these inhibitors due to a multitude of factors that could lead to development of a mechanism known as multidrug resistance (MDR). 7-Ketocholesterol (7KC) is an oxidized cholesterol derivative that has been extensively reported to cause cell death in a variety of cancer models. In this study, we showed the in vitro efficacy of 7KC against MDR leukemia cell line, Lucena. 7KC treatment induced reduction in cell viability, together with apoptosis-mediated cell death. Moreover, downregulation of MDR protein caused intracellular drug accumulation and 7KC co-incubation with either Daunorubicin or Vincristine reduced cell viability compared to the use of each drug alone. Additionally, quantitative label-free mass spectrometry-based protein quantification showed alteration of different molecular pathways involved in cell cycle arrest, induction of apoptosis and misfolded protein response. Conclusively, this study highlights the effect of 7KC as a sensitizing agent of multidrug resistance CML and elucidates its molecular mechanisms.

SIGNIFICANCE

CML patients treated with tyrosine kinase inhibitors (TKIs) have showed a 5-year estimated overall survival of 89%, with cumulative complete cytogenetic response of 87%. However, development of drug resistance is a common feature of the disease progression. This study aimed at showing the effect of 7KC as a cytotoxic and sensitizing agent of multidrug resistance CML cell lines. The cellular and molecular basis of this compound were elucidated using a comprehensive strategy based on quantitative proteomic and cell biology assays. We showed that 7KC induced cell death and overcomes drug resistance in CML through mechanisms that go beyond the classical MDR1 pathways.

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.

The role of oxysterols in vascular ageing

The ageing endothelium progressively loses its remarkable and crucial ability to maintain homeostasis of the vasculature, as it acquires a proinflammatory phenotype. Cellular and structural changes gradually accumulate in the blood vessels, and markedly in artery walls. Most changes in aged arteries are comparable to those occurring during the atherogenic process, the latter being more marked: pro-oxidant and proinflammatory molecules, mainly deriving from or triggered by oxidized low density lipoproteins (oxLDLs), are undoubtedly a major driving force of this process. Oxysterols, quantitatively relevant components of oxLDLs, are likely candidate molecules in the pathogenesis of vascular ageing, because of their marked pro-oxidant, proinflammatory and proapoptotic properties. An increasing bulk of experimental data point to the contribution of a variety of oxysterols of pathophysiological interest, also in the age-related genesis of endothelium dysfunction, intimal thickening due to lipid accumulation, and smooth muscle cell migration and arterial stiffness due to increasing collagen deposition and calcification. This review provides an updated analysis of the molecular mechanisms whereby oxysterols accumulating in the wall of ageing blood vessels may 'activate' endothelial and monocytic cells, through expression of an inflammatory phenotype, and 'convince' smooth muscle cells to proliferate, migrate and, above all, to act as fibroblast-like cells.

Hair sterol signatures coupled to multivariate data analysis reveal an increased 7β-hydroxycholesterol production in cognitive impairment

Altered cholesterol metabolism could be associated with cognitive impairment. The quantitative profiling of 19 hair sterols was developed using gas chromatography-mass spectrometry coupled to multivariate data analysis. The limit of quantification of all sterols ranged from 5 to 20 ng/g, while the calibration linearity was higher than 0.98. The precision (% CV) and accuracy (% bias) ranged from 3.2% to 9.8% and from 83.2% to 119.4%, respectively. Among the sterols examined, 8 were quantitatively detected from two strands of 3-cm-long scalp hair samples of female participants, including mild cognitive impairment (MCI, n=15), Alzheimer's disease (AD, n=31), and healthy controls (HC, n=36). The cognitive impairment (MCI or AD) was correlated with a higher metabolic rate than that of HCs based on 7β-hydroxycholesterol (P<0.005). Significant negative correlations (r=-0.822) were detected between Mini-Mental State Examination (MMSE) scores and hair sample metabolic ratios of 7β-hydroxycholesterol to cholesterol, which is an accepted, sensitive, and specific tool for discriminating HCs from individuals with MCI or AD. In conclusion, improved diagnostic values can be obtained using hair sterol signatures coupled with MMSE scores. This method may prove useful for predictive diagnosis in population screening of cognitive impairment.

7-Ketocholesterol-induced lysosomal dysfunction exacerbates vascular smooth muscle cell calcification via oxidative stress

Vascular calcification is known to reduce the elasticity of aorta. Several studies have suggested that autophagy-lysosomal pathway (ALP) in vascular smooth muscle cells (VSMCs) is associated with vascular calcification. A major component of oxidized low-density lipoproteins, 7-ketocholesterol (7-KC), has been reported to promote inorganic phosphorus (Pi)-induced vascular calcification and induce ALP. The aim of this study was to unravel the relationship between ALP and the progression of calcification by 7-KC. Calcification of human VSMCs was induced by Pi stimulation in the presence or absence of 7-KC. FACS analysis showed that 7-KC-induced apoptosis at a high concentration (30 μM), but not at a low concentration (15 μM). Interestingly, 7-KC promoted calcification in VSMCs regardless of apoptosis. Immunoblotting and immunostaining showed that 7-KC inhibits not only the fusion of autophagosomes and lysosomes but also causes a swell of lysosomes with the reduction of cathepsin B and D. Moreover, lysosomal protease inhibitors exacerbated the apoptosis-independent calcification by 7-KC although inhibition of autophagosome formation by Atg5 siRNA did not. Finally, the 7-KC-induced progression of calcification was alleviated by the treatment with antioxidant. Taken together, our data showed that 7-KC promotes VSMC calcification through lysosomal-dysfunction-dependent oxidative stress.

A new quinoxaline-containing peptide induces apoptosis in cancer cells by autophagy modulation

The most cytotoxic compound from a library of quinoxaline-containing peptides is endocyted into HeLa cells, accumulates in acidic compartments, and blocks autophagy by altering lysosomal function, leading to apoptosis activation.

The synthesis of a new small library of quinoxaline-containing peptides is described. After cytotoxic evaluation in four human cancer cell lines, as well as detailed biological studies, it was found that the most active compound, RZ2, promotes the formation of acidic compartments, where it accumulates, blocking the progression of autophagy. Further disruption of the mitochondrial membrane potential and an increase in mitochondrial ROS was observed, causing cells to undergo apoptosis. Given its cytotoxic activity and protease-resistant features, RZ2 could be a potential drug candidate for cancer treatment and provide a basis for future research into the crosstalk between autophagy and apoptosis and its relevance in cancer therapy.

Rescuing apoptotic neurons in Alzheimer's disease using wheat germ agglutinin-conjugated and cardiolipin-conjugated liposomes with encapsulated nerve growth factor and curcumin

Liposomes with cardiolipin (CL) and wheat germ agglutinin (WGA) were developed to permeate the blood–brain barrier and treat Alzheimer’s disease. WGA-conjugated and CL-incorporated liposomes (WGA-CL-liposomes) were used to transport nerve growth factor (NGF) and curcumin (CUR) across a monolayer of human brain-microvascular endothelial cells regulated by human astrocytes and to protect SK-N-MC cells against apoptosis induced by β-amyloid_1–42 (Aβ_1–42) fibrils. An increase in the CL mole percentage in lipids increased the liposomal diameter, absolute zeta potential value, entrapment efficiency of NGF and CUR, release of NGF, biocompatibility, and viability of SK-N-MC cells with Aβ_1–42, but decreased the atomic ratio of nitrogen to phosphorus and release of CUR. In addition, an increase in the WGA concentration for grafting enhanced the liposomal diameter, atomic ratio of nitrogen to phosphorus, and permeability of NGF and CUR across the blood–brain barrier, but reduced the absolute zeta potential value and biocompatibility. WGA-CL-liposomes carrying NGF and CUR could be promising colloidal delivery carriers for future clinical application in targeting the blood–brain barrier and inhibiting neurotoxicity.

Involvement of oxysterols in age-related diseases and ageing processes

Ageing is accompanied by increasing vulnerability to major pathologies (atherosclerosis, Alzheimer's disease, age-related macular degeneration, cataract, and osteoporosis) which can have similar underlying pathoetiologies. All of these diseases involve oxidative stress, inflammation and/or cell death processes, which are triggered by cholesterol oxide derivatives, also named oxysterols. These oxidized lipids result either from spontaneous and/or enzymatic oxidation of cholesterol on the steroid nucleus or on the side chain. The ability of oxysterols to induce severe dysfunctions in organelles (especially mitochondria) plays key roles in RedOx homeostasis, inflammatory status, lipid metabolism, and in the control of cell death induction, which may at least in part contribute to explain the potential participation of these molecules in ageing processes and in age related diseases. As no efficient treatments are currently available for most of these diseases, which are predicted to become more prevalent due to the increasing life expectancy and average age, a better knowledge of the biological activities of the different oxysterols is of interest, and constitutes an important step toward identification of pharmacological targets for the development of new therapeutic strategies.

The effect of 7-ketocholesterol and 25-hydroxycholesterol on the integrity of the human aortic endothelial and intestinal epithelial barriers

OBJECTIVE AND DESIGN

The damage of barrtier tissues, such as the vascular endothelium and intestinal epithelium, may lead to disturbances of local immune homeostasis. The aim of the study was to assess and compare the effect of oxidized cholesterols (7-ketocholesterol and 25-hydroxycholesterol) on the barrier properties of human primary aortic endothelium (HAEC) and intestinal epithelium Caco-2 cells using a realtime cell electric impedance sensing system (RTCA-DP).

MATERIALS AND METHODS

HAEC and Caco-2 cells were stimulated with 7-ketocholesterol and 25-hydroxycholesterol by the RTCA-DP system. Apoptosis was assessed by flow cytometry and cell monolayer morphology was assessed under a light microscope.

RESULTS

7-ketocholesterol decreased impedance (nCI) in both the endothelium and epithelium. However, the decrease was more profound in the endothelium. Similarly, although 25-hydroxycholesterol decreased nCI in both the endothelium and epithelium, the effect was weaker than that of 7-ketocholesterol, which caused extensive damage to the endothelial monolayer, while 25-hydroxycholesterol caused partial damage and did not affect the epithelial monolayer. 7-ketocholesterol, but not 25-hydroxycholesterol, increased endothelial cell apoptosis and decreased the viability of endothelial cells. However, 7-ketocholesterol and 25-hydroxycholesterol decreased epithelial cell apoptosis and increased viability.

CONCLUSION

Oxidized cholesterols destroy the HAEC, but not the Caco-2 epithelial barrier, via cell apoptosis dependent on the site of oxidation. Damage to the endothelium by oxidized cholesterol may disrupt local homeostasis and provide open access to inner parts of the vascular wall for lipids, other peripheral blood-derived agents, and immune cells, leading to inflammation and atherogenesis.

Oxysterols and symptomatic versus asymptomatic human atherosclerotic plaque

Atherosclerosis is the most common cause of mortality in the Western world, contributing to about 50% of all deaths. Atherosclerosis is characterized by deposition of lipids onto the coronary or carotid arterial wall and formation of an atherosclerotic plaque. Atherosclerotic plaques are categorized into two groups: symptomatic and asymptomatic. The symptomatic plaques tend to be unstable and prone to rupture, and are associated with an increase in ischemic events. Oxysterols, products of cholesterol oxidation, are cytotoxic materials. Their level and type may be associated with plaque formation, development and stability. Oxysterols stimulate the formation of foam cells, advance atherosclerotic plaque progression, and contribute to plaque vulnerability and instability due to their cytotoxicity and their ability to induce cell apoptosis. Studies indicate that plasma 7β-OH CH level can be used as a biomarker for detecting carotid and coronary artery disease. Further clinical studies are needed to evaluate the potential of oxysterols for use as biomarkers for plaque vulnerability and instability. The identification of biomarkers in the blood that can distinguish between symptomatic and asymptomatic plaques remains an unresolved issue.

Toxicity of 7-ketocholesterol on lethality, growth, reproduction, and germline apoptosis in the nematode Caenorhabditis elegans

7-Ketocholesterol is one of the most abundant cholesterol oxides, and is known to be cytotoxic to various types of cultured mammalian cells; however, little is known regarding its effects in vivo. With the use of the nematode Caenorhabditis elegans as model organism, in vivo toxicity of 7-ketocholesterol was investigated. The aim of the study was to examine the effects on life span, as well as short-term effects on reproduction, thermotolerance, germline apoptosis, and reactive oxygen species (ROS) generation resulting from C. elegans exposure to 7-ketocholesterol at concentrations ranging from 0 to 200 μg/ml. Results indicated that 7-ketocholesterol reduced reproductive capacity, shortened the life span in a concentration-dependent manner, and impaired thermotolerance of the adult nematode. 7-Ketocholesterol also induced germline apoptotic cell death and increased ROS generation in adult worms. Thus, the model organism C. elegans is recommended for assessment of the safety and bioactivity of cholesterol oxides.

7-ketocholesterol-induced caspase-mediated apoptosis in Saccharomyces cerevisiae

The cytotoxicity of cholesterol oxidation products has been documented in several mammalian cell lines. It can lead to a wide range of diseases. However, the molecular mechanisms underlying this toxicity in vivo are scarce. The objective of the present study was to assess the potential toxic effects of 7-ketocholesterol, an important cholesterol oxidation product, on Saccharomyces cerevisiae. Our data show for the first time that 7-ketocholesterol can induce dose-dependent cell death in S. cerevisiae. These results suggest that the death induced by this compound is apoptotic and accompanied by chromatin condensation, the production of ROS, and translocation of phosphatidylserine from the inner to the outer leaflet of the cytoplasmic membrane. We further showed that 7-ketocholesterol-induced cell death was partially rescued after pretreatment with caspase inhibitor (Z-VAD-fmk). In addition, caspase deletion resulted in promotion of cell viability. All these results strongly indicated that 7-ketocholesterol induces apoptosis in yeast cells through a caspase-dependent pathway.

Telmisartan exerts pleiotropic effects in endothelial cells and promotes endothelial cell quiescence and survival

OBJECTIVE

Telmisartan, an angiotensin II type 1 receptor blocker, and amlodipine, a calcium channel blocker, are antihypertensive agents clinically used as monotherapy or in combination. They exert beneficial cardiovascular effects independently of blood pressure lowering and classic mechanisms of action. In this study, we investigate molecular mechanisms responsible for the off-target effects of telmisartan and telmisartan-amlodipine in endothelial cells (ECs), using an unbiased genomic approach.

APPROACH AND RESULTS

In human umbilical vein ECs, microarray analysis of gene expression followed by pathway enrichment analysis and quantitative polymerase chain reaction validation revealed that telmisartan modulates the expression of key genes responsible for cell cycle progression and apoptosis. Amlodipine's effect was similar to control. ECs exposed to telmisartan, but not amlodipine, losartan, or valsartan, exhibited a dose-dependent impairment of cell growth and failed to enter the S-phase of the cell cycle. Similarly, telmisartan inhibited proliferation in COS-7 cells lacking the angiotensin II type 1 receptor. In telmisartan-treated ECs, phosphorylation and activation of Akt, as well as MDM2, were reduced, leading to accumulation of p53 in the nucleus, where it represses the transcription of cell cycle-promoting genes. Phosphorylation of glycogen synthase kinase-3β was also reduced, resulting in rapid proteolytic turnover of CyclinD1. Telmisartan induced downregulation of proapoptotic genes and protected ECs from serum starvation-induced and 7-ketocholesterol-induced apoptosis.

CONCLUSIONS

Telmisartan exerts antiproliferative and antiapoptotic effects in ECs. This may account for the improved endothelial dysfunction observed in the clinical setting.

Oxysterols in cancer cell proliferation and death

Oxysterols have been shown to interfere with proliferation and cause the death of many cancer cell types, such as leukaemia, glioblastoma, colon, breast and prostate cancer cells, while they have little or no effect on senescent cells. The mechanisms by which oxysterols may influence proliferation are manifold: they control the transcription and the turnover of the key enzyme in cholesterol synthesis, 3-hydroxy-3-methylglutaryl CoA reductase, by binding to Insig-1, Insig-2 and liver X receptors. Oxysterols are thought to be generated in proportion to the rate of cholesterol synthesis. Although there is no consensus about the mechanism by which these oxysterols are generated in vivo, it clearly has to be ubiquitous. The 25- and the 27-cholesterol hydroxylases, present in almost all tissues, are possible candidates. Cholesterol uptake from lipoproteins, intracellular vesicle transport and lipid transfer are also modified by oxysterols. Oxysterols interfere with ERK, hedgehog and wnt pathways of proliferation and differentiation. When administered in vitro to cancer cell lines, oxysterols invariably both slow down proliferation and provoke cell death. Perhaps is it sufficient to stop proliferation of a cancer to provoke its eradication. Therefore, the two facets of oxysterol action that seem important for cancer treatment, cytostaticity and cytotoxicity, will be discussed.

Relationships of coronary heart disease with 27-hydroxycholesterol, low-density lipoprotein cholesterol, and menopausal hormone therapy

BACKGROUND

Menopausal hormone therapy (MHT) increases the risk of coronary heart disease (CHD) in older women with elevated low-density lipoprotein (LDLC) levels. The endogenous estrogen receptor antagonist 27-hydroxycholesterol (27OHC) is correlated with LDLC levels and may block the beneficial effects of estrogen on the cardiovascular system.

METHODS AND RESULTS

We conducted a nested case-control study in the Women's Health Initiative trials of 350 CHD cases and 813 matched controls to explore potential mediation by 27OHC of the dependence of the CHD risk elevation with MHT on LDLC. Baseline levels of 27OHC were not associated with CHD risk when LDLC was included in the multivariable models. The odds ratio for CHD associated with increased LDLC was 1.15 (95% confidence interval, 1.08-1.23) and was unchanged at 1.14 (95% confidence interval, 1.07-1.22) when 27OHC was added to the model. Baseline 27OHC did not interact with MHT on CHD risk (P=0.81). In contrast, LDLC levels modified the effect of MHT on CHD risk (P for interaction=0.02), and adding 27OHC did not affect this result. With the use of log scales, the effect of MHT on CHD increased linearly with increasing level of baseline LDLC, with a transition from no risk to increased risk at ≈3.36 mmol/L (130 mg/dL).

CONCLUSIONS

This study found that 27OHC does not independently increase the risk of CHD, does not modify the increased risk of CHD resulting from MHT, and does not mediate the interaction of LDLC with MHT. Measuring blood lipids may aid in counseling individual women about initiating MHT and cardiovascular risk mitigation.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00000611.