Homocysteine accelerates atherosclerosis via inhibiting LXRα-mediated ABCA1/ABCG1-dependent cholesterol efflux from macrophages

The association between hyperhomocysteinemia and the prevalence of bilateral carotid atherosclerotic plaques in a middle-aged population

OBJECTIVE

We conducted a cross-sectional study to investigate the impact of hyperhomocysteinemia (HHcy) on the prevalence of CASP among middle-aged individuals, aiming to provide insights for CASP prevention.

METHODS

1105 subjects were categorized into HHcy group or normal tHcy group based on their plasma total homocysteine (tHcy). All participants underwent carotid artery ultrasonography to assess the presence of unilateral and bilateral CASP. Comparative analyses of demographic and clinical data were conducted between the two groups. Logistic regression and prespecified subgroup analyses were performed to determine whether HHcy independently contributed to bilateral CASP.

RESULTS

132 individuals exhibited bilateral CASP. The prevalence of bilateral CASP was significantly higher in the HHcy group compared to the normal tHcy group (21.55 % vs. 10.82 %, p = 0.003). Univariate logistic analysis showed a significant association between HHcy and the prevalence of bilateral CASP (OR = 2.056, 95 %CI 1.089-3.881, p = 0.026). In all four models of multivariate logistic analysis, HHcy consistently emerged as an independent risk factor for bilateral CASP, with odd ratios of 1.958, 2.047, 2.023, and 2.186. This association remained significant across all five subgroups stratified by age, sex, hypertension, diabetes, and BMI.

CONCLUSION

Our studies demonstrated HHcy was an independent risk factor for the prevalence of bilateral CASP in the middle-aged population. Theses results emphasized the importance of addressing HHcy in preventive strategies aimed at mitigating the burden of CASP among middle-aged individuals.

Curcumin Equipped Nanozyme-Like Metal-Organic Framework Platform for the Targeted Atherosclerosis Treatment with Lipid Regulation and Enhanced Magnetic Resonance Imaging Capability

Atherosclerotic cardiovascular disease (ASCVD) has become the leading cause of death worldwide, and early diagnosis and treatment of atherosclerosis (AS) are crucial for reducing the occurrence of acute cardiovascular events. However, early diagnosis of AS is challenging, and oral anti-AS drugs suffer from limitations like imprecise targeting and low bioavailability. To overcome the aforementioned shortcomings, Cur/MOF@DS is developed, a nanoplatform integrating diagnosis and treatment by loading curcumin (Cur) into metal-organic frameworks with nanozymes and magnetic resonance imaging (MRI) properties. In addition, the surface-modification of dextran sulfate (DS) enables PCN-222(Mn) effectively target scavenger receptor class A in macrophages or foam cells within the plaque region. This nanoplatform employs mechanisms that effectively scavenge excessive reactive oxygen species in the plaque microenvironment, promote macrophage autophagy and regulate macrophage polarization to realize lipid regulation. In vivo and in vitro experiments confirm that this nanoplatform has outstanding MRI performance and anti-AS effects, which may provide a new option for early diagnosis and treatment of AS.

Relationship between homocysteine and chronic total coronary occlusion: a cross-sectional study from southwest China

BACKGROUND

Chronic total coronary occlusion is among the most complex coronary artery diseases. Elevated homocysteine is a risk factor for coronary artery diseases. However, few studies have assessed the relationship between homocysteine and chronic total coronary occlusion.

METHODS

1295 individuals from Southwest China were enrolled in the study. Chronic total coronary occlusion was defined as complete occlusion of coronary artery for more than three months. Homocysteine was divided into quartiles according to its level. Univariate and multivariate logistic regression models, receiver operating characteristic curves, and subgroup analysis were applied to assess the relationship between homocysteine and chronic total coronary occlusion.

RESULTS

Subjects in the higher homocysteine quartile had a higher rate of chronic total coronary occlusion (P < 0.001). After adjustment, the odds ratio for chronic total coronary occlusion in the highest quartile of homocysteine compared with the lowest was 1.918 (95% confidence interval 1.237-2.972). Homocysteine ≥ 15.2 μmol/L was considered an independent indicator of chronic total coronary occlusion (odds ratio 1.53, 95% confidence interval 1.05-2.23; P = 0.0265). The area under the receiver operating characteristic curve was 0.659 (95% confidence interval, 0.618-0.701; P < 0.001). Stronger associations were observed in elderly and in those with hypertension and diabetes.

CONCLUSIONS

Elevated homocysteine is significantly associated with chronic total coronary occlusion, particularly in elderly and those with hypertension and diabetes.

Association between homocysteine level and length of stay in patients with lower extremity atherosclerotic disease: a retrospective cohort study

OBJECTIVES

Homocysteine (Hcy) level has been widely identified as a risk factor associated with adverse outcomes in patients with lower extremity atherosclerotic disease (LEAD). However, there are still some knowledge gaps in research on the association between Hcy level and downstream adverse outcomes, such as length of stay (LOS). This study aims to explore whether and to what extent Hcy level is associated with LOS in patients with LEAD.

DESIGN

Retrospective cohort study.

SETTING

China.

PARTICIPANTS, PRIMARY AND SECONDARY OUTCOMES

We conducted a retrospective cohort study of 748 patients from inpatients with LEAD between January 2014 and November 2021 at the First Hospital of China Medical University in China. We used a slew of generalised linear models to evaluate the association between Hcy level and LOS.

RESULTS

The patients' median age was 68 years and 631 (84.36%) were males. A dose-response curve with an inflection point at 22.63 µmol/L was observed between Hcy level and LOS after the adjustment of potential confounders. LOS increased before Hcy level reached the inflection point (β: 0.36; 95% CI: 0.18 to 0.55; p<0.001).ConclusionOur results show that an Hcy level <22.63 µmol/L is associated with increased LOS in patients with LEAD, which was independent of some other risk factors. This might shed light on how Hcy can be used as a key marker in the comprehensive management of patients with LEAD during hospitalisation.

H-type hypertension is a risk factor for chronic total coronary artery occlusion: a cross-sectional study from southwest China

BACKGROUND

Chronic total coronary occlusion (CTO) is serious and the "last bastion" of percutaneous coronary intervention. Hypertension and hyperhomocysteinemia (HHCY) are synergistic and significantly increase cardiovascular event risk. The relationship between H-type hypertension and CTO remains unclear; thus, this cross-sectional study investigated this potential association.

METHODS

Between January 2018 and June 2022, 1446 individuals from southwest China were recruited to participate in this study. CTO was defined as complete coronary artery occlusion persisting for over three months. H-type hypertension was defined as hypertension with plasma homocysteine levels ≥ 15 µmol/L. Multivariate logistic regression models were applied to assess the association between H-type hypertension and CTO. Receiver operating characteristic (ROC) curves were generated to determine the accuracy of H-type hypertension in predicting CTO.

RESULTS

Of the 1446 individuals, 397 had CTO, and 545 had H-type hypertension. After multivariate adjustment, the odds ratio (OR) for CTO in individuals with H-type hypertension was 2.3-fold higher (95% CI 1.01-5.26) than that in healthy controls. The risk of CTO is higher in individuals with H-type hypertension than in those with isolated HHCY and hypertension. The area under the ROC curve for CTO was 0.685 (95% CI, 0.653-0.717) for H-type hypertension.

CONCLUSIONS

In southwest China, H-type hypertension is significantly related to the occurrence of CTO.

TRIAL REGISTRATION

This retrospective study was registered with the Chinese Clinical Trials Registry ( http://www.chictr.org.cn , ChiCTR2100050519.2.2).

Plasma Homocysteine (Hcy) Concentration Functions as a Predictive Biomarker of SPECT-Evaluated Post-Ischemic Hyperperfusion in Acute Ischemic Stroke

Introduction

Homocysteine (Hcy) concentration has been reported to be associated with ischemic stroke. In this study, we aimed to investigate the potential of plasma Hcy in the prediction of post-ischemic hyperperfusion in AIS patients, which was diagnosed with the single-photon emission computed tomography (SPECT) method.

Methods

A total of 112 ischemic stroke patients were recruited in this study. According to whether the patients were subjected to post-ischemic hyperperfusion, all recruited subjects were divided into a post-ischemic hyperperfusion (+) group (N=48) and post-ischemic hyperperfusion (-) group (N=64). The basic demographical data, clinicopathological data and laboratory biochemical data were collected and compared. Level of homocysteine (Hcy) and cystatin-C (Cys-C) and their potential as predictive biomarker are also investigated.

Results

No significant differences were spotted between the post-ischemic hyperperfusion group (+) and post-ischemic hyperperfusion (-) group in respect to the basic demographical and clinicopathological data. And the serum Hcy levels were lower in the post-ischemic hyperperfusion (+) group. Moreover, ROC analysis indicated significant relationships between Hcy levels and the onset of post-ischemic hyperperfusion.

Conclusion

In conclusion, we validated that the plasma Hcy concentration can be used as a predictive biomarker of SPECT-evaluated post-ischemic hyperperfusion in patients suffering from acute ischemic stroke.

Activation of NR1H3 attenuates the severity of septic myocardial injury by inhibiting NLRP3 inflammasome

Most sepsis deaths are due to the development of multiple organ failure, in which heart failure is a recognized manifestation of sepsis. To date, the role of liver X receptors α (NR1H3) in sepsis is still uncertain. Here, we hypothesized that NR1H3 mediates multiple essential sepsis-related signalings to attenuate septic heart failure. Adult male C57BL/6 or Balbc mice and HL-1 myocardial cell line were performed for in vivo and in vitro experiments, respectively. NR1H3 knockout mice or NR1H3 agonist T0901317 was applied to evaluate the impact of NR1H3 on septic heart failure. We found decreased myocardial expression levels of NR1H3-related molecules while increased NLRP3 level in septic mice. NR1H3 knockout worsensed cardiac dysfunction and injury in mice subjected to cecal ligation and puncture (CLP), in association with exacerbated NLRP3-mediated inflammation, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, and apoptosis-related markers. The administration of T0901317 reduced systemic infection and improve cardiac dysfunction in septic mice. Moreover, Co-IP assays, luciferase reporter assays, and chromatin immunoprecipitation analysis, confirmed that NR1H3 directly repressed NLRP3 activity. Finally, RNA-seq detection further clarified an overview of the roles of NR1H3 in sepsis. In general, our findings indicate that NR1H3 had a significant protective effect against sepsis and sepsis-induced heart failure.

The relationship between hyperhomocysteinemia and total coronary artery occlusion: a cross-sectional study from Southwest China

BACKGROUND

Increasing evidence points to hyperhomocysteinemia as an independent risk factor for coronary artery disease in addition to traditional cardiovascular risks, but few have studied the association between hyperhomocysteinemia and total coronary artery occlusion (TCAO). To understand the risk factors for TCAO, we investigated the potential relationship between hyperhomocysteinemia and TCAO, and the interactions between cardiovascular risk factors and hyperhomocysteinemia.

METHODS

A total of 890 adult patients from Southwest China participated in this cross-sectional study between February 2018 and February 2021. TCAO was defined as complete occlusion of more than one of the 15 coronary segments. Hyperhomocysteinemia was defined as serum homocysteine levels ≥15 μmol/L. Multivariable logistic regression models were used to determine the relationship between hyperhomocysteinemia and TCAO. The relationship between homocysteine as a continuous variable and TCAO was also analyzed. Subgroup analyses by sex, age, weight, smoking, hypertension, diabetes, and dyslipidemia were done, and interactions between subgroup variables and hyperhomocysteinemia were performed.

RESULTS

Individuals with hyperhomocysteinemia showed an increased risk for TCAO. The adjusted odds ratio for TCAO in individuals with hyperhomocysteinemia was 1.74 (95% confidence interval, 1.28-2.36). When analyzed as a continuous variable, homocysteine was associated with an increased risk for TCAO. Subgroup analysis showed that the association between hyperhomocysteinemia and TCAO was statistically significant in men, elderly, overweight, smokers, and non-diabetic people. Interaction analysis showed no significant interactions between hyperhomocysteinemia and group variables.

CONCLUSIONS

In Southwest China, hyperhomocysteinemia was significantly associated with TCAO. This association was particularly significant in men, elderly, overweight, smokers, and non-diabetic people.

Anti-Atherogenic Actions of the Lab4b Consortium of Probiotics In Vitro

Probiotic bacteria have many protective effects against inflammatory disorders, though the mechanisms underlying their actions are poorly understood. The Lab4b consortium of probiotics contains four strains of lactic acid bacteria and bifidobacteria that are reflective of the gut of newborn babies and infants. The effect of Lab4b on atherosclerosis, an inflammatory disorder of the vasculature, has not yet been determined and was investigated on key processes associated with this disease in human monocytes/macrophages and vascular smooth muscle cells in vitro. The Lab4b conditioned medium (CM) attenuated chemokine-driven monocytic migration, monocyte/macrophage proliferation, uptake of modified LDL and macropinocytosis in macrophages together with the proliferation and platelet-derived growth factor-induced migration of vascular smooth muscle cells. The Lab4b CM also induced phagocytosis in macrophages and cholesterol efflux from macrophage-derived foam cells. The effect of Lab4b CM on macrophage foam cell formation was associated with a decrease in the expression of several key genes implicated in the uptake of modified LDL and induced expression of those involved in cholesterol efflux. These studies reveal, for the first time, several anti-atherogenic actions of Lab4b and strongly implicate further studies in mouse models of the disease in vivo and in clinical trials.

Lipid Droplet Protein PLIN1 Regulates Inflammatory Polarity in Human Macrophages and is Involved in Atherosclerotic Plaque Development by Promoting Stable Lipid Storage

AIM

Perilipins (PLINs), peripheral lipid droplet (LD) proteins, play important roles in lipid accumulation and maturation in adipocytes. The relationship between PLIN family proteins and macrophage polarization in atherosclerosis has not been elucidated.

METHODS

The experiments used tissues from human arteries of 65 patients who had undergone a carotid endarterectomy, and cultured macrophages generated from healthy human peripheral blood mononuclear cells.

RESULTS

Plaque immunohistochemistry demonstrated co-expression of PLIN1 and PLIN2 in both symptomatic (n=31) and asymptomatic patients (n=34). PLIN2 mRNA expression increased 3.38-fold in the symptomatic group compared with those from asymptomatic. PLIN1 was not expressed on small LDs at a shorter incubation but was on large LDs at longer incubation with oxidized LDL and VLDL, while PLIN2 was observed after 24 h and increased with a longer incubation in cultured M1 macrophage. In M2 macrophages, PLIN1 was seen as early as 24 h following incubation with VLDL, and LD size increased with longer incubation. PLIN1 overexpression increased the size of LDs in M1 macrophages, even after a short incubation, and reduced the RNA expression of TNFA, MMP2, ABCA1, and ABCG1 versus the M1 control. Conversely, silencing of PLIN1 in M2 macrophages had the opposite effects on LD size and RNA expression.

CONCLUSION

There was a relationship between macrophage polarity, cytosolic LD size, and PLIN1/PLIN2 expression levels. PLIN2 was mainly expressed in arterial plaques in symptomatic stroke patients, and associated with the inflammatory phenotype of human macrophages, while PLIN1 expression is closely associated with plaque stability and the anti-inflammatory phenotype.

Soluble epoxide hydrolase inhibitor, TPPU, attenuates progression of atherosclerotic lesions and vascular smooth muscle cell phenotypic switching

Atherosclerosis manifests as a chronic inflammation resulting from multiple interactions between circulating factors and various cell types in blood vessel walls. Growing evidence shows that phenotypic switching and proliferation of vascular smooth muscle cells (VSMCs) plays an important role in the progression of atherosclerosis. Soluble epoxide hydrolase (sEH)/epoxyeicosatrienoic acids are mediated by vascular inflammation. N-[1-(1-oxopropyl)-4-piperidinyl]-N'-[4-(trifluoromethoxy)phenyl]-urea (TPPU) is an sEH inhibitor. This study investigated the therapeutic effect of TPPU on atherosclerosis in vivo and homocysteine-induced vascular inflammation in vitro and explored their molecular mechanisms. We found that TPPU decreased WD-induced atherosclerotic plaque lesions, inflammation, expression of sEH, and nicotinamide adenine dinucleotide phosphate oxidase-4 (Nox4), and increased the expression of contractile phenotype marker of aortas in ApoE (-/-) mice. TPPU also inhibited homocysteine-stimulated VSMC proliferation, migration, and phenotypic switching, and reduced Nox4 in human-aorta-VSMC regulation. We conclude that TPPU has anti-atherosclerotic effects, potentially because of the suppression of VSMC phenotype switching. Thus, TPPU could be a potential therapeutic target for phenotypic switching attenuation in atherosclerosis.

Impact of H-Type Hypertension on Intraplaque Neovascularization Assessed by Contrast-Enhanced Ultrasound

AIM

H-type hypertension is connected with carotid atherosclerotic plaques and stroke, whereas neovascularization is a dominant contributor to plaque vulnerability. However, the correlation between H-type hypertension and plaque vulnerability remains unclear. This study aims to explore the influence of H-type hypertension on intraplaque neovascularization (IPN).

METHODS

We enrolled 235 patients with carotid plaques into the investigation and classified them into four groups: H-type hypertension group, simple hypertension group, isolated hyperhomocysteinemia group, and control group. Contrast-enhanced ultrasound (CEUS) was performed on them and IPN was evaluated using semi-quantitative visual grading: grade 1 (no microbubbles or microbubbles limited to the adventitial side and/or shoulder of plaque) and, grade 2 (diffused microbubbles within plaque or microbubbles enter plaque core). To analyze the correlation between H-type hypertension and the degree of plaque enhancement, logistic regression was used.

RESULTS

Compared with those with CEUS grade 1 plaques, those with CEUS grade 2 plaques had higher frequency of ischemic stroke (29.0% vs. 45.1%, P＜0.05), hypertension (41.0% vs. 56.3%, P＜0.05), and H-type hypertension (18.0% vs. 29.6%, P＜0.05). No significant differences existed in plaque morphology, plaque echogenicity, and the severity of carotid artery stenosis between the degree of plaque enhancement (all P＞0.05). H-type hypertension (multivariate-adjusted OR: 3.036, 95% CI: 1.258-7.329) was independently connected with the degree of plaque enhancement even after adjusting for other covariates.

CONCLUSION

H-type hypertension is expressly connected with the degree of plaque enhancement and may facilitate plaque vulnerability. Our findings may offer a new insight for treating vulnerable plaque, lowering blood pressure, and lowering homocysteine equally crucial.

Acid-Sensing Ion Channel 1/Calpain1 Activation Impedes Macrophage ATP-Binding Cassette Protein A1-Mediated Cholesterol Efflux Induced by Extracellular Acidification

Background

Extracellular acidification is a common feature of atherosclerotic lesions, and such an acidic microenvironment impedes ATP-binding cassette transporter A1 (ABCA1)-mediated cholesterol efflux and promotes atherogenesis. However, the underlying mechanism is still unclear. Acid-sensing ion channel 1 (ASIC1) is a critical H⁺ receptor, which is responsible for the perception and transduction of extracellular acidification signals.

Aim

In this study, we explored whether or how ASIC1 influences extracellular acidification-induced ABCA1-mediated cholesterol efflux from macrophage-derived foam cells.

Methods

RAW 264.7 macrophages were cultured in an acidic medium (pH 6.5) to generate foam cells. Then the intracellular lipid deposition, cholesterol efflux, and ASIC1/calpain1/ABCA1 expressions were evaluated.

Results

We showed that extracellular acidification enhanced ASIC1 expression and translocation, promoted calpain1 expression and lipid accumulation, and decreased ABCA1 protein expression as well as ABCA1-mediated cholesterol efflux. Of note, inhibiting ASIC1 activation with amiloride or Psalmotoxin 1 (PcTx-1) not only lowered calpain1 protein level and lipid accumulation but also enhanced ABCA1 protein levels and ABCA1-mediated cholesterol efflux of macrophages under extracellular acidification conditions. Furthermore, similar results were observed in macrophages treated with calpain1 inhibitor PD150606.

Conclusion

Extracellular acidification declines cholesterol efflux via activating ASIC1 to promote calpain1-mediated ABCA1 degradation. Thus, ASIC1 may be a novel therapeutic target for atherosclerosis.

PPARα/γ signaling pathways are involved in Chlamydia pneumoniae-induced foam cell formation via upregulation of SR-A1 and ACAT1 and downregulation of ABCA1/G1

Chlamydia pneumoniae (Cpn) has been reported to be involved in the pathogenesis of early atherosclerosis by inducing macrophage-derived foam cell formation in the presence of low-density lipoprotein (LDL). However, the biochemical mechanisms underlying Cpn-induced foam cell formation are still not fully elucidated. The present study showed that in LDL-treated THP-1-derived macrophages, Cpn not only upregulated the expression of scavenger receptor A1 (SR-A1) and acyl-coenzyme A: cholesterol acyltransferase 1 (ACAT1), but it also downregulated the expression of ATP binding cassette transporters (ABCA1 and ABCG1) at both the mRNA and protein levels. These processes facilitated cholesterol accumulation and promoted macrophage-derived foam cell formation. Treatment with the peroxisome proliferator-activated receptor (PPAR)-γ agonist rosiglitazone or the PPARα agonist fenofibrate decreased the number of foam cells induced by Cpn, while the PPARγ antagonist GW9662, the PPARα antagonist MK886, or PPARα/γ siRNAs enhanced the effect of Cpn on foam cell formation and gene expression of SR-A1, ACAT1, and ABCA1/G1. Moreover, the PPARγ agonist rosiglitazone reversed the downregulation of CD36 by Cpn, while PPARγ siRNA and the PPARγ inhibitor GW9662 further suppressed CD36 expression. However, the PPARα agonist, inhibitor, and siRNA all showed no effect on CD36 expression. In conclusion, the PPARα and PPARγ pathways are both involved in Cpn-induced macrophage-derived foam cell formation by upregulating SR-A1 and ACAT1 and downregulating ABCA1/G1 expression.

Role of PCSK9 in Homocysteine-Accelerated Lipid Accumulation in Macrophages and Atherosclerosis in ApoE-/- Mice

Background: Homocysteine (Hcy) has been established as an independent risk factor for atherosclerosis, and the involvement of hyperhomocysteinemia (HHcy) in atherosclerotic lesions is complex. Proprotein convertase subtilisin kexin 9 (PCSK9) has vital importance in lipid metabolism, and its inhibitors have intense lipid-lowering and anti-atherosclerotic effects. However, the underlying effect of PCSK9 on HHcy-accelerated dyslipidemia of macrophages is still uncertain. The purpose of this study was to investigate the potential role of PCSK9 in Hcy-induced lipid accumulation and atherosclerotic lesions.

Methods:In vitro, gene and protein expressions were assessed by real-time quantitative PCR and western blot in THP-1 macrophages with Hcy incubation. Lipid accumulation and cholesterol efflux were evaluated with Hcy treatment. SBC-115076 was used to examine the role of PCSK9 in ATP-binding cassette transporter A1 and G1 (ABCA1 and ABCG1)-dependent cholesterol efflux. In vivo, lesion area, lipid deposition and collagen contents were determined in aortas of ApoE^−/− mice under a methionine diet. SBC-115076 was subcutaneously injected to explore the potential effects of PCSK9 inhibition on alleviating the severity of HHcy-related atherosclerotic lesions.

Results: In THP-1 macrophages, Hcy dose- and time-dependently promoted PCSK9 gene and protein levels without regulating the translation of Low-density lipoprotein receptor (LDLR). SBC-115076 used to inhibit PCSK9 largely alleviated lipid accumulation and reversed the cholesterol efflux to apolipoprotein-I(apoA-I) and high-density lipoprotein (HDL) mediated by ABCA1 and ABCG1. In ApoE^−/− mice, methionine diet induced HHcy caused larger lesion area and more lipid accumulation in aortic roots. SBC-115076 reduced atherosclerotic severity by reducing the lesion area and lipid accumulation and increasing expressions of ABCA1 and ABCG1 in macrophages from atherosclerotic plaque. In addition, SBC-115076 decreased plasma Hcy level and lipid profiles significantly.

Conclusion: PCSK9 promoted lipid accumulation via inhibiting cholesterol efflux mediated by ABCA1 and ABCG1 from macrophages and accelerated atherosclerotic lesions under HHcy treatment. Inhibiting PCSK9 may have anti-atherogenic properties in HHcy-accelerated atherosclerosis.

The regulation of Ero1-alpha in homocysteine-induced macrophage apoptosis and vulnerable plaque formation in atherosclerosis

BACKGROUND AND AIMS

Hyperhomocysteinemia (HHcy) is an independent risk factor for atherosclerosis and plaque vulnerability. Macrophage apoptosis mediated by endoplasmic reticulum (ER) stress plays an important role in the pathogenesis of HHcy-aggravated atherosclerosis. Endoplasmic reticulum oxidoreductase 1α (Ero1α) is critical for ER stress-induced apoptosis. We hypothesized that Ero1α may contribute to ER-stress induced macrophage apoptosis and plaque stability in advanced atherosclerotic lesions by HHcy.

METHODS

Apoe^-/- mice were maintained on drinking water containing homocysteine (Hcy, 1.8 g/L) to establish HHcy atherosclerotic models. The role of Ero1α in atherosclerotic plaque stability, macrophage apoptosis and ER stress were monitored in the plaque of aortic roots in HHcy Apoe^-/- mice with or without silence or overexpression of Ero1α through lentivirus. Mouse peritoneal macrophages were used to confirm the regulation of Ero1α on ER stress dependent apoptosis in the presence of HHcy.

RESULTS

Atherosclerotic plaque vulnerability and macrophage apoptosis were promoted in Apoe^-/- mice by high Hcy diet, accompanied by the upregulation of Ero1α expression and ER stress. Inhibition of Ero1α prevented macrophage apoptosis and atherosclerotic plaque vulnerability, and vice versa. Consistently, in mouse peritoneal macrophages, ER stress and apoptosis were attenuated by Ero1α deficiency, but enhanced by Ero1α overexpression.

CONCLUSIONS

Hcy, via upregulation of Ero1α expression, activates ER stress-dependent macrophage apoptosis to promote vulnerable plaque formation in atherosclerosis. Ero1α may be a potential therapeutic target for atherosclerosis induced by Hcy.

Antiatherogenic Effects of Quercetin in the THP-1 Macrophage Model In Vitro, With Insights Into Its Signaling Mechanisms Using In Silico Analysis

Background: Atherosclerosis (AS), a major risk factor for stroke and brain tissue destruction, is an inflammatory disease of the blood vessels, and the underlying pathology is inflammation mediated by various chemokines and cytokines. Quercetin, a natural flavonol, is reported to have both anti-inflammatory and antioxidant properties. As such, in the present study, we evaluated the antiatherogenic effects of quercetin in a human THP-1 cell line in vitro and also the signaling mechanisms using in silico analysis.

Materials and Methods: THP-1 macrophages exposed to different concentrations of quercetin (5–100 μM for 24 h) were tested for cytotoxicity. Real-time gene expression assay for intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) was carried out following treatment with quercetin at 15 and 30 μM for 24 h either in the absence or presence of interferon (IFN-γ) for 3 h to induce inflammation. Monocyte migration and cholesterol efflux were also assessed.

Results: Quercetin did not exert any cytotoxic effects on THP-1 cells at the various concentrations tested. The gene expression assay showed a significant decrease in ICAM-1 (by 3.05 and 2.70) and MCP-1 (by 22.71 and 27.03), respectively. Quercetin at 15 µM decreased THP-1 monocyte migration by 33% compared to the MCP-1-treated cells. It also increased cholesterol efflux significantly by1.64-fold and 1.60-fold either alone or in combination with IFN-γ, respectively. Ingenuity Pathway Analysis of the molecular interactions of quercetin identified canonical pathways directly related to lipid uptake and cholesterol efflux. Furthermore, CD36, SR-A, and LXR-α also demonstrated significant increases by 72.16-, 149.10-, and 29.68-fold, respectively.

Conclusion: Our results from both in vitro and in silico studies identified that quercetin inhibited the THP-1 monocyte migration, MCP-1, and ICAM-1 and increased cholesterol efflux probably mediated via the LXR/RXR signaling pathway. Therefore, quercetin will help prevent cell infiltration in atherosclerotic plaques and reduce the risk of stroke or brain destruction.

Four Weeks of Aerobic Training Affects Cardiac Tissue Matrix Metalloproteinase, Lactate Dehydrogenase and Malate Dehydrogenase Enzymes Activities, and Hepatorenal Biomarkers in Experimental Hyperhomocysteinemia in Rats

The aim of this study was to investigate the effect of the application of homocysteine as well as its effect under the condition of aerobic physical activity on the activities of matrix metalloproteinases (MMP), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) in cardiac tissue and on hepato-renal biochemical parameters in sera of rats. Male Wistar albino rats were divided into four groups (n = 10, per group): C: 0.9% NaCl 0.2 mL/day subcutaneous injection (s.c.); H: homocysteine 0.45 µmol/g b.w./day s.c.; CPA saline (0.9% NaCl 0.2 mL/day s.c.) and a program of physical activity on a treadmill; and HPA homocysteine (0.45 µmol/g b.w./day s.c.) and a program of physical activity on a treadmill. Subcutaneous injection of substances was applied 2 times a day at intervals of 8 h during the first two weeks of experimental protocol. Hcy level in serum was significantly higher in the HPA group compared to the CPA group (p < 0.05). Levels of glucose, proteins, albumin, and hepatorenal biomarkers were higher in active groups compared with the sedentary group. It was demonstrated that the increased activities of LDH (mainly caused by higher activity of isoform LDH2) and mMDH were found under the condition of homocysteine-treated rats plus aerobic physical activity. Independent application of homocysteine did not lead to these changes. Physical activity leads to activation of MMP-2 isoform and to increased activity of MMP-9 isoform in both homocysteine-treated and control rats.

Inhibition of miR-200b-3p alleviates lipid accumulation and promotes cholesterol efflux by targeting ABCA1 in macrophage-derived foam cells

Atherosclerosis (As) is a chronic cardiovascular disease characterized by abnormal of lipid accumulation and cholesterol efflux. The present study aimed to investigate whether the micro-RNA (miR)-200b-3p could exacerbate As by promoting lipid accumulation and inhibiting cholesterol efflux via ATP-binding cassette transporter A1 (ABCA1) in macrophage-derived foam cells. Blood samples from 30 patients with As and 30 healthy people were collected at Quanzhou First Hospital. RAW264.7 cells were used to establish foam cells using oxidized low-density lipoprotein. The expression of miR-200b-3p and ABCA1 was evaluated by reverse transcription quantitative PCR and western blotting. Lipid accumulation was analyzed by Oil Red O staining and cholesterol content was assessed by ELISA. A targeting relationship between miR-200b-3p and ABCA1 was demonstrated by luciferase reporter assays. Compared with healthy volunteers and RAW264.7 cells, the expression level of miR-200b-3p was significantly increased whereas the expression level of ABCA1 was significantly decreased in patients with As and foam cells. Furthermore, miR-200b-3p expression was negatively correlated with ABCA1 expression in the blood of the patients with As. Lipid content was significantly decreased and cholesterol efflux was significantly increased in foam cells transfected with the miR-200b-3p inhibitor compared with inhibitor control cells. In addition, ABCA1 was shown to be targeted by miR-200b-3p. Furthermore, the lipid content in foam cells transfected with the miR-200b-3p inhibitor and small interfering-ABCA1 was significantly increased, while the cholesterol efflux was significantly decreased compared with foam cells transfected with the miR-200b-3p inhibitor. In conclusion, the findings from the present study indicated that inhibition of miR-200b-3p may alleviate lipid accumulation and promote cholesterol efflux by targeting ABCA1 in macrophage-derived foam cells.

TIGAR mitigates atherosclerosis by promoting cholesterol efflux from macrophages

BACKGROUND AND AIMS

TP53-induced glycolysis and apoptosis regulator (TIGAR) is now characterized as a fructose-2,6-bisphosphatase to reduce glycolysis and protect against oxidative stress. Recent studies have demonstrated that TIGAR is associated with cardiovascular disease. However, little is known about its role in atherosclerogenesis. In this study, we aimed to investigate the effect of TIGAR on atherosclerosis and explore the underlying molecular mechanism.

METHODS

The Gene Expression Omnibus (GEO) datasets were used to analyze the differential expression of relative proteins. THP-1-derived macrophages were used as an in vitro model and apolipoprotein E-deficient (Apoe^-/-) mice were used as an in vivo model. [³H] labeled cholesterol was used to assess the capacity of cholesterol efflux and reverse cholesterol transport (RCT). Both qPCR and Western blot were used to evaluate the mRNA and protein expression, respectively. Lentiviral vectors were used to disturb the expression of TIGAR in vitro and in vivo. Oil Red O, hematoxylin-eosin, and Masson staining were performed to evaluate atherosclerotic plaques in Apoe^-/- mice fed a Western diet. Conventional assay kits were used to measure the levels of reactive oxygen species (ROS), plasma lipid profiles and 27-hydroxycholesterol (27-HC).

RESULTS

Our results showed that TIGAR is increased upon the formation of macrophage foam cells and atherosclerosis. TIGAR knockdown markedly promoted lipid accumulation in macrophages. Silencing of TIGAR impaired cholesterol efflux and down-regulated the expression of ATP-binding cassette transporter A1 (ABCA1) and ABCG1 by interfering with liver X receptor α (LXRα) expression and activity, but did not influence cholesterol uptake by macrophages. Additionally, this inhibitory effect of TIGAR deficiency on cholesterol metabolism was mediated through the ROS/CYP27A1 pathway. In vivo experiments revealed that TIGAR deficiency decreased the levels of ABCA1 and ABCG1 in plaques and aorta and impaired the capacity of RCT, thereby leading to the progression of atherosclerosis in Apoe^-/- mice.

CONCLUSIONS

TIGAR mitigates the development of atherosclerosis by up-regulating ABCA1 and ABCG1 expression via the ROS/CYP27A1/LXRα pathway.

CTRP12 ameliorates atherosclerosis by promoting cholesterol efflux and inhibiting inflammatory response via the miR-155-5p/LXRα pathway

C1q tumor necrosis factor-related protein 12 (CTRP12), a conserved paralog of adiponectin, is closely associated with cardiovascular disease. However, little is known about its role in atherogenesis. The aim of this study was to examine the influence of CTRP12 on atherosclerosis and explore the underlying mechanisms. Our results showed that lentivirus-mediated CTRP12 overexpression inhibited lipid accumulation and inflammatory response in lipid-laden macrophages. Mechanistically, CTRP12 decreased miR-155-5p levels and then increased its target gene liver X receptor α (LXRα) expression, which increased ATP binding cassette transporter A1 (ABCA1)- and ABCG1-dependent cholesterol efflux and promoted macrophage polarization to the M2 phenotype. Injection of lentiviral vector expressing CTRP12 decreased atherosclerotic lesion area, elevated plasma high-density lipoprotein cholesterol levels, promoted reverse cholesterol transport (RCT), and alleviated inflammatory response in apolipoprotein E-deficient (apoE-/-) mice fed a Western diet. Similar to the findings of in vitro experiments, CTRP12 overexpression diminished miR-155-5p levels but increased LXRα, ABCA1, and ABCG1 expression in the aortas of apoE-/- mice. Taken together, these results suggest that CTRP12 protects against atherosclerosis by enhancing RCT efficiency and mitigating vascular inflammation via the miR-155-5p/LXRα pathway. Stimulating CTRP12 production could be a novel approach for reducing atherosclerosis.

The Role of Ubiquitin E3 Ligase in Atherosclerosis

Atherosclerosis is a chronic inflammatory vascular disease. Atherosclerotic cardiovascular disease is the main cause of death in both developed and developing countries. Many pathophysiological factors, including abnormal cholesterol metabolism, vascular inflammatory response, endothelial dysfunction and vascular smooth muscle cell proliferation and apoptosis, contribute to the development of atherosclerosis and the molecular mechanisms underlying the development of atherosclerosis are not fully understood. Ubiquitination is a multistep post-translational protein modification that participates in many important cellular processes. Emerging evidence suggests that ubiquitination plays important roles in the pathogenesis of atherosclerosis in many ways, including regulation of vascular inflammation, endothelial cell and vascular smooth muscle cell function, lipid metabolism and atherosclerotic plaque stability. This review summarizes important contributions of various E3 ligases to the development of atherosclerosis. Targeting ubiquitin E3 ligases may provide a novel strategy for the prevention of the progression of atherosclerosis.

Over-activation of NMDA receptors promotes ABCA1 degradation and foam cell formation

ATP-binding cassette transporter A1 (ABCA1) is an essential regulator of intracellular cholesterol efflux. Secreted cholesterol binds to lipid-free apolipoprotein A-I (apoA-I) in peripheral blood to constitute high-density lipoprotein cholesterol (HDL) complexes. ABCA1 protein on the surface of macrophages acts as a crucial controller in preventing cholesterol accumulation. Importantly, ABCA1 is unstable and easily degraded via a series of biochemical activities, including but not limited to calpain-mediated and ubiquitin-proteasome system-mediated processes. How accelerated ABCA1 degradation impacts disordered lipid metabolism in macrophages and foam cell formation is unclear. N-methyl d-aspartate receptors (NMDARs) are ionotropic glutamate receptors with high calcium permeability. Calcium influx via NMDARs activates downstream signaling pathways. Over-activation of NMDARs stimulated by NMDA contributes to dysfunctional lipid metabolism in macrophages and foam cell formation via promotion of calpain-mediated ABCA1 proteolysis. However, increased NMDAR activity does not affect liver X receptor expression or ABCA1 mRNA levels. Following NMDA receptor silencing or calpain inhibition, NMDA treatment did not reduce ABCA1 protein levels, nor caused lipid accumulation in macrophages. In addition, NMDAR over-activation activates NF-κB signaling to promote IL-1β and IL-6 macrophage marker expression. However, NMDAR silencing and calpain inhibition reduce inflammatory macrophage responses. In summary, our study suggests that NMDAR activation reduces surface ABCA1 protein, promotes lipid accumulation, and induces the production and secretion of many inflammatory mediators in macrophages, possibly through enhanced calpain-mediated ABCA1 protein degradation. Thus, the NMDAR receptor may be a novel pharmacologic target for atherosclerosis therapy.

Impact of homocysteine levels on clinical outcome in patients with acute ischemic stroke receiving intravenous thrombolysis therapy

Background

The purpose of this study was to retrospectively assess the potential correlation between clinical outcomes and homocysteine (Hcy) levels in acute ischemic stroke (AIS) patients after recombinant tissue plasminogen activator (rtPA) treatment.

Methods

AIS patients treated by rtPA were enrolled between September 2018 and March 2019 in the Stroke Center (Department of Neurology and Neurosurgery), Shanghai Tenth People’s Hospital, Tongji University School of Medicine. Demographics, baseline and clinical characteristics, and modified Rankin Scale (mRS) score after three months from the onset were retrospectively analyzed. Then we compared data about demographics, baseline and clinical characteristics between patients with favorable (mRS score 0–2) and unfavorable (mRS score 3–6) outcomes.

Results

Among 141 patients, 36 patients had poor outcome, for an incidence of 25.53%. Univariate analysis showed that higher Hcy levels (OR = 1.07, 95% CI [1.02–1.12]), older age (OR = 1.06, 95% CI [1.02–1.10]), longer door to needle time (DNT) (OR = 1.03, 95% CI [1.01–1.05]), higher D-Dimer levels (OR = 1.33, 95% CI [1.03–1.71]), and higher National Institutes of Health Stroke Scale (NIHSS) score before treatment (OR = 1.21, 95% CI [1.08–1.35]) were each associated with poor outcome. Also, without internal carotid artery plaque (OR = 0.30, 95% CI [0.10–0.92]) showed a protective effect on patients’ clinical outcome. Patients with higher levels of Hcy decline also showed an increased risk of poor outcome for AIS patients obtaining rtPA treatment (Non-adjusted: OR = 1.07, 95% CI [1.02–1.12]; Adjust model I adjusts for demographics (age, male): OR = 1.06, 95% CI [1.02–1.11]; Adjust model II adjusts for hospital care factors (onset to treatment, DNT): OR = 1.08, 95% CI [1.03–1.13]; Adjust model III adjusts for health and stroke factors (INR, D-Dimer, HGB, NIHSS score before treatment, smoking, drinking, hypertension, diabetes, coronary disease, hyperlipidemia, previous stroke, atrial fibrillation, hemorrhagic transformation, internal carotid artery plaque): OR = 1.06, 95% CI [1.02–1.11]). The results are very stable in all three models constructed.

Conclusion

The results of this study indicate that increased Hcy level independently predicts unfavorable outcome in AIS patients accepting thrombolytic therapy. However, the contribution of Hcy to the outcome, although significant, is relatively small and perhaps not clinically significant when all the other confounders are considered.

Negative Correlation Between Serum Levels of Homocysteine and Apolipoprotein M

BACKGROUND

Homocysteine (Hcy) has been suggested as an independent risk factor for atherosclerosis. Apolipoprotein M (apoM) is a constituent of the HDL particles. The goal of this study was to examine the serum levels of homocysteine and apoM and to determine whether homocysteine influences apoM synthesis.

METHODS

Serum levels of apoM and Hcy in 17 hyperhomocysteinemia (HHcy) patients and 19 controls were measured and their correlations were analyzed. Different concentrations of homocysteine (Hcy) and LY294002, a specific phosphoinositide 3- kinase (PI3K) inhibitor, were used to treat HepG2 cells. The mRNA levels were determined by RT-PCR and the apoM protein mass was measured by western blot.

RESULTS

We found that decreased serum apoM levels corresponded with serum HDL levels in HHcy patients, while the serum apoM levels showed a statistically significant negative correlation with the serum Hcy levels. Moreover, apoM mRNA and protein levels were significantly decreased after the administration of Hcy in HepG2 cells, and this effect could be abolished by addition of LY294002.

CONCLUSIONS

Present study demonstrates that Hcy downregulates the expression of apoM by mechanisms involving the PI3K signal pathway.

Homocysteine accelerates atherosclerosis by inhibiting scavenger receptor class B member1 via DNMT3b/SP1 pathway

Homocysteine (Hcy) is an independent risk factor for atherosclerosis, which is characterized by lipid accumulation in the atherosclerotic plaque. Increasing evidence supports that as the main receptor of high-density lipoprotein, scavenger receptor class B member 1 (SCARB1) is protective against atherosclerosis. However, the underlying mechanism regarding it in Hcy-mediated atherosclerosis remains unclear. Here, we found the remarkable inhibition of SCARB1 expression in atherosclerotic plaque and Hcy-treated foam cells, whereas overexpression of SCARB1 can suppress lipid accumulation in foam cells following Hcy treatment. Analysis of SCARB1 promoter showed that no significant change of methylation level was observed both in vivo and in vitro under Hcy treatment. Moreover, it was found that the negative regulation of DNMT3b on SCARB1 was due to the decreased recruitment of SP1 to SCARB1 promoter. Thus, we concluded that inhibition of SCARB1 expression induced by DNMT3b at least partly accelerated Hcy-mediated atherosclerosis through promoting lipid accumulation in foam cells, which was attributed to the decreased binding of SP1 to SCARB1 promoter. In our point, these findings will provide novel insight into an epigenetic mechanism for atherosclerosis.

Mangiferin promotes macrophage cholesterol efflux and protects against atherosclerosis by augmenting the expression of ABCA1 and ABCG1

Mangiferin has been identified as a potent cardioprotective factor that enhances high-density lipoprotein cholesterol levels in plasma. The aim of this study was to investigate the impact of mangiferin on macrophage cholesterol efflux and the development of atherosclerosis. The results showed that mangiferin injection significantly decreased atherosclerotic plaque size, and reduced plasma levels of low-density lipoprotein cholesterol, triglyceride, and total cholesterol in apoE knockout mice, whereas reverse cholesterol transport efficiency and high-density lipoprotein cholesterol levels were enhanced. In vitro study showed that mangiferin prevented lipid accumulation and promoted [³H]-cholesterol efflux from acetylated LDL-loaded RAW264.7 macrophages with an increase in the expression of ATP binding cassette A1/G1 (ABCA1/G1), liver X receptor-α (LXRα) and peroxisome proliferator-activated receptor-γ (PPARγ). Moreover, transfection of PPARγ siRNA or LXRα siRNA markedly abolished the positive effects of mangiferin on ABCA1/G1 expression and cholesterol efflux. The opposite effects were observed after treatment with PPARγ agonist rosiglitazone or LXRα agonist T0901317. In conclusion, mangiferin may attenuate atherogenesis by promoting cholesterol efflux from macrophages via the PPARγ-LXRα-ABCA1/G1 pathway.

Gut Microbiota-Dependent Marker TMAO in Promoting Cardiovascular Disease: Inflammation Mechanism, Clinical Prognostic, and Potential as a Therapeutic Target

Cardiovascular disease (CVD) is the leading cause of death worldwide, especially in developed countries, and atherosclerosis (AS) is the common pathological basis of many cardiovascular diseases (CVDs) such as coronary heart disease (CHD). The role of the gut microbiota in AS has begun to be appreciated in recent years. Trimethylamine N-oxide (TMAO), an important gut microbe-dependent metabolite, is generated from dietary choline, betaine, and L-carnitine. Multiple studies have suggested a correlation between plasma TMAO levels and the risk of AS. However, the mechanism underlying this relationship is still unclear. In this review, we discuss the TMAO-involved mechanisms of atherosclerotic CVD from the perspective of inflammation, inflammation-related immunity, cholesterol metabolism, and atherothrombosis. We also summarize available clinical studies on the role of TMAO in predicting prognostic outcomes, including major adverse cardiovascular events (MACE), in patients presenting with AS. Finally, since TMAO may be a novel therapeutic target for AS, several therapeutic strategies including drugs, dietary, etc. to lower TMAO levels that are currently being explored are also discussed.

Hyperhomocysteinemia induces vascular calcification by activating the transcription factor RUNX2 via Krüppel-like factor 4 up-regulation in mice

One of the main characteristics of atherosclerosis is vascular calcification, which is linked to adverse cardiovascular events. Increased homocysteine (Hcy), a feature of hyperhomocysteinemia, is correlated with advanced vascular calcification and phenotypic switching of vascular smooth muscle cells (VSMCs). Oxidative stress and high phosphate levels also induce VSMC calcification, suggesting that the Krüppel-like factor 4 (KLF4) signaling pathway may also contribute to vascular calcification. In this study, we investigated this possibility and the role and mechanisms of Hcy in vascular calcification. We found that in atherosclerotic apolipoprotein E-deficient (ApoE^-/-) mice, Hcy significantly increases vascular calcification in vivo, as well as VSMC calcification in vitro Of note, the Hcy-induced VSMC calcification was correlated with elevated KLF4 levels. Hcy promoted KLF4 expression in calcified atherosclerotic lesions in vivo and in calcified VSMCs in vitro shRNA-mediated KLF4 knockdown blocked the Hcy-induced up-regulation of runt-related transcription factor 2 (RUNX2) and VSMC calcification. RUNX2 inhibition abolished Hcy-induced VSMC calcification. Using ChIP analysis, we demonstrate that KLF4 interacts with RUNX2, an interaction promoted by Hcy stimulation. Our experiments also revealed that the KLF4 knockdown attenuates Hcy-induced RUNX2 transactivity, indicating that KLF4 is important in modulating RUNX2 transactivity. These findings support a role for Hcy in regulating vascular calcification through a KLF4-RUNX2 interaction and indicate that Hcy-induced, enhanced RUNX2 transactivity increases VSMC calcification. These insights reveal possible opportunities for developing interventions that prevent or manage vascular calcification.

Impaired autophagy mediates hyperhomocysteinemia-induced HA-VSMC phenotypic switching

Hyperhomocysteinemia (HHcy) is a highly-related risk factor in vascular smooth muscle cell (VSMC) phenotypic modulation and atherosclerosis. Growing evidence indicated that autophagy is involved in pathological arterial changes. However, the risk mechanisms by which homocysteine and VSMC autophagy interact with cardiovascular disease are poorly understood. This study verified the homocysteine-responsive endoplasmic reticulum protein promotion of VSMC phenotypic switching, and the formation of atherosclerotic plaque in vitro. We found that impaired autophagy, as evidenced by decreased levels of MAP1LC3B II/MAP1LC3B I, has a vital role in HHcy-induced human aortic (HA)-VSMC phenotypic switching, with a decrease in contractile proteins (SM α-actin and calponin) and an increase in osteopontin. Knockdown of the essential autophagy gene Atg7 by small interfering RNA promoted HA-VSMC phenotypic switching, indicating that impaired autophagy induces phenotypic switching in these cells. HHcy co-treatment with rapamycin triggered autophagy, which alleviated HA-VSMC phenotypic switching. Finally, we found that Krüppel-like factor 4 (KLF4), a zinc-finger transcription factor for maintaining genomic stability by resisting oxidative stress and restoring autophagy, is closely involved in this process. HHcy clearly decreased KLF4 expression. KLF4-specific siRNA aggravated defective autophagy and phenotypic switching. Mechanistically, KLF4 regulated the HHcy-induced decrease in HA-VSMC autophagy via the m-TOR signaling pathway. In conclusion, these results demonstrated that the KLF4-dependent rapamycin signaling pathway is a novel mechanism underlying HA-VSMC phenotypic switching and is crucial for HHcy-induced HA-VSMCs with defective autophagy to accelerate early atherosclerosis.