Oxidized low-density lipoprotein is associated with viral load and disease activity in patients with chronic hepatitis C

Ezetimibe treatment reduces oxidized low-density lipoprotein in biliary cirrhotic rats

BACKGROUND

In liver cirrhosis, chronic inflammation is associated with an increase in oxidative stress, and subsequently an increase in the concentration of oxidized low-density lipoprotein (ox-LDL). Ezetimibe is a lipid-lowering agent with anti-inflammation and anti-oxidative stress activities. This study aimed to investigate the effect of ezetimibe treatment on ox-LDL in cirrhotic rats.

METHODS

Biliary cirrhosis was induced in Sprague-Dawley rats with common bile duct ligation (BDL). Sham-operated rats served as surgical controls. Ezetimibe (10 mg/kg/d) or vehicle was administered in the sham-operated or BDL rats for 4 weeks, after which hemodynamic parameters, biochemistry data, and oxidative stress were evaluated. Plasma and intrahepatic ox-LDL levels were also examined, and hepatic proteins were analyzed to explore the mechanism of ezetimibe treatment.

RESULTS

The BDL rats had typical features of cirrhosis including jaundice, impaired liver function, hyperlipidemia, and elevated ox-LDL levels compared to the sham-operated rats. Ezetimibe treatment did not affect hemodynamics, liver biochemistry, or plasma lipid levels. However, it significantly reduced oxidative stress, plasma levels of ox-LDL, and tumor necrosis factor α. In addition, ezetimibe upregulated the hepatic protein expression of an ox-LDL scavenger (lectin-like ox-LDL rececptor-1), which resulted in reductions in intrahepatic ox-LDL and fat accumulation in the BDL rats. Nevertheless, ezetimibe treatment did not ameliorate hepatic inflammation or liver fibrosis.

CONCLUSION

Ezetimibe reduced plasma and intrahepatic ox-LDL levels in the cirrhotic rats. Furthermore, it ameliorated intrahepatic fat accumulation and oxidative stress. However, ezetimibe did not alleviate hepatic fibrosis or inflammation in the biliary cirrhotic rats.

Genetic and pharmacological perturbation of hepatitis-C virus entry

Hepatitis-C virus (HCV) chronically infects 58 million individuals worldwide with variable disease outcome. While a subfraction of individuals exposed to the virus clear the infection, the majority develop chronic infection if untreated. Another subfraction of chronically ill proceeds to severe liver disease. The underlying causes of this interindividual variability include genetic polymorphisms in interferon genes. Here, we review available data on the influence of genetic or pharmacological perturbation of HCV host dependency factors on the clinically observed interindividual differences in disease outcome. We focus on host factors mediating virus entry into human liver cells. We assess available data on genetic variants of the major entry factors scavenger receptor class-B type I, CD81, claudin-1, and occludin as well as pharmacological perturbation of these entry factors. We review cell culture experimental and clinical cohort study data and conclude that entry factor perturbation may contribute to disease outcome of hepatitis C.

Effects of PCSK-9 Inhibition by Alirocumab Treatments on Biliary Cirrhotic Rats

Hyperlipidemia and oxidative stress with elevated oxidized low-density lipoprotein (ox-LDL) exacerbate hepatic inflammation and fibrosis. The plasma level of low-density lipoprotein (LDL) is controlled by proprotein convertase subtilisin/kexin 9 (PCSK9). Alirocumab is a monoclonal antibody that decreases LDL via inhibiting PCSK9 function. Apart from lipid-lowering effects, alirocumab exerts anti-inflammation, anti-angiogenesis and anti-oxidant effects. This study aims to investigate the impact of alirocumab treatment on common bile duct ligation (BDL)-induced biliary cirrhotic rats. After a 4-week treatment of alirocumab, the hemodynamic data, blood biochemistry, ox-LDL level, oxidative stress markers, severity of hepatic encephalopathy and abnormal angiogenesis of BDL rats were measured and compared to the control group. BDL rats presented cirrhotic pictures and elevated ammonia, total cholesterol, LDL and ox-LDL levels compared to the control group. Alirocumab decreased plasma levels of total cholesterol, LDL, and oxidative stress markers; however, it did not affect the hemodynamics, liver and renal biochemistry, and the plasma levels of ammonia and ox-LDL. The motor activities, portal-systemic collaterals and mesenteric vascular density were not significantly different between alirocumab-treated and control groups. In addition, it did not affect hepatic inflammation, intrahepatic angiogenesis, liver fibrosis and free cholesterol accumulation in the liver of BDL rats. In conclusion, PCSK9 inhibition by alirocumab treatment ameliorates hyperlipidemia and systemic oxidative stress in biliary cirrhotic rats. However, it does not affect the plasma level of ox-LDL, intrahepatic inflammation and fibrosis. In addition, PCSK9 inhibition has a neutral effect on abnormal angiogenesis and hepatic encephalopathy in biliary cirrhotic rats.

Pathological Crosstalk Between Oxidized LDL and ER Stress in Human Diseases: A Comprehensive Review

The oxidative modification of the major cholesterol carrying lipoprotein, oxLDL, is a biomarker as well as a pathological factor in cardiovascular diseases (CVD), type 2 diabetes mellitus (T2DM), obesity and other metabolic diseases. Perturbed cellular homeostasis due to physiological, pathological and pharmacological factors hinder the proper functioning of the endoplasmic reticulum (ER), which is the major hub for protein folding and processing, lipid biosynthesis and calcium storage, thereby leading to ER stress. The cellular response to ER stress is marked by a defensive mechanism called unfolded protein response (UPR), wherein the cell adapts strategies that favor survival. Under conditions of excessive ER stress, when the survival mechanisms fail to restore balance, UPR switches to apoptosis and eliminates the defective cells. ER stress is a major hallmark in metabolic syndromes such as diabetes, non-alcoholic fatty liver disease (NAFLD), neurological and cardiovascular diseases. Though the pathological link between oxLDL and ER stress in cardiovascular diseases is well-documented, its involvement in other diseases is still largely unexplored. This review provides a deep insight into the common mechanisms in the pathogenicity of diseases involving oxLDL and ER stress as key players. In addition, the potential therapeutic intervention of the targets implicated in the pathogenic processes are also explored.

Oxidized Low-Density Lipoprotein Drives Dysfunction of the Liver Lymphatic System

BACKGROUND AND AIMS

As the incidence of nonalcoholic steatohepatitis (NASH) continues to rise, understanding how normal liver functions are affected during disease is required before developing novel therapeutics which could reduce morbidity and mortality. However, very little is understood about how the transport of proteins and cells from the liver by the lymphatic vasculature is affected by inflammatory mediators or during disease.

METHODS

To answer these questions, we utilized a well-validated mouse model of NASH and exposure to highly oxidized low density lipoprotein (oxLDL). In addition to single cell sequencing, multiplexed immunofluorescence and metabolomic analysis of liver lymphatic endothelial cells (LEC)s we evaluated lymphatic permeability and transport both in vitro and in vivo.

RESULTS

Confirming similarities between human and mouse liver lymphatic vasculature in NASH, we found that the lymphatic vasculature expands as disease progresses and results in the downregulation of genes important to lymphatic identity and function. We also demonstrate, in mice with NASH, that fluorescein isothiocyanate (FITC) dextran does not accumulate in the liver draining lymph node upon intrahepatic injection, a defect that was rescued with therapeutic administration of the lymphatic growth factor, recombinant vascular endothelial growth factor C (rVEGFC). Similarly, exposure to oxLDL reduced the amount of FITC-dextran in the portal draining lymph node and through an LEC monolayer. We provide evidence that the mechanism by which oxLDL impacts lymphatic permeability is via a reduction in Prox1 expression which decreases lymphatic specific gene expression, impedes LEC metabolism and reorganizes the highly permeable lymphatic cell-cell junctions which are a defining feature of lymphatic capillaries.

CONCLUSIONS

We identify oxLDL as a major contributor to decreased lymphatic permeability in the liver, a change which is consistent with decreased protein homeostasis and increased inflammation during chronic liver disease.

Emerging Roles for Lymphatics in Chronic Liver Disease

Chronic liver disease (CLD) is a global health epidemic causing ∼2 million deaths annually worldwide. As the incidence of CLD is expected to rise over the next decade, understanding the cellular and molecular mediators of CLD is critical for developing novel therapeutics. Common characteristics of CLD include steatosis, inflammation, and cholesterol accumulation in the liver. While the lymphatic system in the liver has largely been overlooked, the liver lymphatics, as in other organs, are thought to play a critical role in maintaining normal hepatic function by assisting in the removal of protein, cholesterol, and immune infiltrate. Lymphatic growth, permeability, and/or hyperplasia in non-liver organs has been demonstrated to be caused by obesity or hypercholesterolemia in humans and animal models. While it is still unclear if changes in permeability occur in liver lymphatics, the lymphatics do expand in number and size in all disease etiologies tested. This is consistent with the lymphatic endothelial cells (LEC) upregulating proliferation specific genes, however, other transcriptional changes occur in liver LECs that are dependent on the inflammatory mediators that are specific to the disease etiology. Whether these changes induce lymphatic dysfunction or if they impact liver function has yet to be directly addressed. Here, we will review what is known about liver lymphatics in health and disease, what can be learned from recent work on the influence of obesity and hypercholesterolemia on the lymphatics in other organs, changes that occur in LECs in the liver during disease and outstanding questions in the field.

Hepatitis C, systemic inflammation and oxidative stress: correlations with metabolic diseases

Introduction: Hepatitis C chronic infection has long been correlated with numerous systemic diseases, such as diabetes mellitus and hepatic steatosis. Recent studies have also revealed an association with atherosclerosis.Areas covered: An analysis is presented on the mechanisms through which the hepatitis C viral infection can lead to a systemic increase in pro-inflammatory markers, especially tumor necrosis factor-a and interleukin-6. The immunological imbalance created may, through different mechanisms, act on the metabolic pathways that contribute to the development of insulin resistance, the accumulation of lipids in the liver, and even the formation of atherosclerotic plaques. Moreover, an additional contributing factor to the above-mentioned metabolic derangements is the unopposed oxidative stress observed in chronic hepatitis C viral infection. The virus itself contributes to the formation of oxidative stress, through alterations in the trace metal homeostasis and its effect on pro-inflammatory cytokines, such as tumor necrosis factor-a.Expert opinion: The scope of this review is to emphasize the importance of the metabolic manifestations of hepatitis C viral infection and to elucidate the pathophysiological mechanisms behind their emergence.

Immunometabolic Effect of Cholesterol in Hepatitis C Infection: Implications in Clinical Management and Antiviral Therapy

Hepatitis C virus (HCV) is a lipid-enveloped virion particle that causes infection to the liver, and as part of its life cycle, it disrupts the host lipid metabolic machinery, particularly the cholesterol synthesis pathway. The innate immune response generated by liver resident immune cells is responsible for successful viral eradication. Unfortunately, most patients fail to eliminate HCV and progress to chronic infection. Chronic infection is associated with hepatic fat accumulation and inflammation that triggers fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Despite that the current direct-acting antiviral agents have increased the cure rate of HCV infection, viral genotype and the host genetic background influence both the immune response and lipid metabolism. In this context, recent evidence has shown that cholesterol and its derivatives such as oxysterols might modulate and potentialize the hepatic innate immune response generated against HCV. The impairment of the HCV life cycle modulated by serum cholesterol could be relevant for the clinical management of HCV-infected patients before and after treatment. Alongside, cholesterol levels are modulated either by genetic variations in IL28B, ApoE, and LDLR or by dietary components. Indeed, some nutrients such as unsaturated fatty acids have demonstrated to be effective against HCV replication. Thus, cholesterol modifications may be considered as a new adjuvant strategy for HCV infection therapy by providing a biochemical tool that guides treatment decisions, an improved treatment response and favoring viral clearance. Herein, the mechanisms by which cholesterol contributes to the immune response against HCV infection and how genetic and environmental factors may affect this role are reviewed.

Interactions between Hepatitis C Virus and the Human Apolipoprotein H Acute Phase Protein: A Tool for a Sensitive Detection of the Virus

The Hepatitis C virus (HCV) infection exhibits a high global prevalence frequently associated with hepatocellular carcinoma, taking years to develop. Despite the standardization of highly sensitive HCV quantitative RT-PCR (qRT-PCR) detection methods, false-negative diagnoses may be generated with current methods, mainly due to the presence of PCR inhibitors and/or low viral loads in the patient’s sample. These false-negative diagnoses impact both public health systems, in developing countries, and an in lesser extent, in developed countries, including both the risk of virus transmission during organ transplantation and/or blood transfusion and the quality of the antiviral treatment monitoring. To adopt an appropriate therapeutic strategy to improve the patient’s prognosis, it is urgent to increase the HCV detection sensitivity. Based upon previous studies on HBV, we worked on the capacity of the scavenger acute phase protein, Apolipoprotein H (ApoH) to interact with HCV. Using different approaches, including immunoassays, antibody-inhibition, oxidation, ultracentrifugation, electron microscopy and RT-PCR analyses, we demonstrated specific interactions between HCV particles and ApoH. Moreover, when using a two-step HCV detection process, including capture of HCV by ApoH-coated nanomagnetic beads and a home-made real-time HCV-RT-PCR, we confirmed the presence of HCV for all samples from a clinical collection of HCV-seropositive patients exhibiting an RT-PCR COBAS® TaqMan® HCV Test, v2.0 (COBAS)-positive result. In contrast, for HCV-seropositive patients with either low HCV-load as determined with COBAS or exhibiting HCV-negative COBAS results, the addition of the two-step ApoH-HCV-capture and HCV-detection process was able to increase the sensitivity of HCV detection or more interestingly, detect in a genotype sequence-independent manner, a high-proportion (44%) of HCV/RNA-positive among the COBAS HCV-negative patients. Thus, the immune interaction between ApoH and HCV could be used as a sample preparation tool to enrich and/or cleanse HCV patient’s samples to enhance the detection sensitivity of HCV and therefore significantly reduce the numbers of false-negative HCV diagnosis results.

Oxidized Low-Density Lipoprotein Is a Novel Predictor of Interferon Responsiveness in Chronic Hepatitis C Infection

BACKGROUND & AIMS

Hepatitis C virus (HCV) cell entry is mediated by several cell surface receptors, including scavenger receptor class B type I (SR-BI). Oxidized low density lipoprotein (oxLDL) inhibits the interaction between HCV and SR-BI in a noncompetitive manner. We tested whether serum oxLDL levels correlate with sustained virologic response (SVR) rates after interferon-based treatment of chronic hepatitis C.

METHODS

Baseline oxLDL was determined in 379 participants with chronic HCV genotype 1 infection from the INDIV-2 study using a commercial enzyme-linked immunosorbent assay. The mechanistic in vitro studies used full-length and subgenomic HCV genomes replicating in hepatoma cells.

RESULTS

In the multivariate analysis, oxLDL was found to be an independent predictor of SVR. Oxidized LDL did not correlate with markers of inflammation (alanine transaminase, ferritin), nor was serum oxLDL affected by exogenous interferon administration. Also, oxLDL did not alter the sensitivity of HCV replication to interferon. However, oxLDL was found to be a potent inhibitor of cell-to-cell spread of HCV between adjacent cells in vitro. It could thus reduce the rate at which new cells are infected by HCV through either the cell-free or cell-to-cell route. Finally, serum oxLDL was significantly associated with the estimated infected cell loss rate under treatment.

CONCLUSIONS

Oxidized LDL is a novel predictor of SVR after interferon-based therapy and may explain the previously observed association of LDL with SVR. Rather than being a marker of activated antiviral defenses it may improve chances of SVR by limiting spread of infection to naive cells through the cell-to-cell route.

Mitochondrial dysfunctions and altered metals homeostasis: new weapons to counteract HCV-related oxidative stress

The hepatitis C virus (HCV) infection produces several pathological effects in host organism through a wide number of molecular/metabolic pathways. Today it is worldwide accepted that oxidative stress actively participates in HCV pathology, even if the antioxidant therapies adopted until now were scarcely effective. HCV causes oxidative stress by a variety of processes, such as activation of prooxidant enzymes, weakening of antioxidant defenses, organelle damage, and metals unbalance. A focal point, in HCV-related oxidative stress onset, is the mitochondrial failure. These organelles, known to be the "power plants" of cells, have a central role in energy production, metabolism, and metals homeostasis, mainly copper and iron. Furthermore, mitochondria are direct viral targets, because many HCV proteins associate with them. They are the main intracellular free radicals producers and targets. Mitochondrial dysfunctions play a key role in the metal imbalance. This event, today overlooked, is involved in oxidative stress exacerbation and may play a role in HCV life cycle. In this review, we summarize the role of mitochondria and metals in HCV-related oxidative stress, highlighting the need to consider their deregulation in the HCV-related liver damage and in the antiviral management of patients.

Investigation of the factors associated with circulating soluble CD36 levels in patients with HCV-related chronic liver disease

BACKGROUND

CD36, a class B scavenger receptor, participates in the pathogenesis of metabolic dysregulation such as insulin resistance, hepatic steatosis, and atherosclerosis. Persistent hepatitis C virus (HCV) infection often evokes these metabolic abnormalities. The primary purpose of this study was to investigate the role of CD36 in the pathogenesis of insulin resistance and hepatic steatosis caused by chronic HCV infection.

METHODS

Forty-five patients with HCV-related chronic liver disease (CLD-C) were enrolled in this study. CD36 expression in the liver specimen was examined by an immunohistochemical procedure. The concentrations of circulating soluble form of CD36 (sCD36) and oxLDL were determined by the enzyme-linked innunosorbent assay. Insulin resistance was estimated by the values of HOMA-IR.

RESULTS

Moderate to extensive hepatic CD36 expression was observed in the sinusoids of all enrolled CLD-C patients. CD36-positive sinusoids appeared to be identical to Kupffer cells. The severity of CD36 expression in the hepatic sinusoids was significantly correlated with the sCD36 level in sera of patients with CLD-C. The serum sCD36 levels were significantly correlated with body mass index and serum oxLDL levels in those patients. However, the serum sCD36 concentrations were independent of the values of HOMA-IR and the severity of hepatic steatosis.

CONCLUSIONS

These data suggest that the serum sCD36 levels reflect the severity of CD36 expression on the Kupffer cells in patients with CLD-C, and that the serum sCD36 levels were associated with obesity, although the levels were independent of insulin resistance and hepatic steatosis in those patients.

Characterization of the inhibition of hepatitis C virus entry by in vitro-generated and patient-derived oxidized low-density lipoprotein

Oxidized low-density lipoprotein (oxLDL) has been reported as an inhibitor of hepatitis C virus (HCV) cell entry, making it the only known component of human lipid metabolism with an antiviral effect on HCV. However, several questions remain open, including its effect on full-length cell-culture-grown HCV (HCVcc) of different genotypes or on other steps of the viral replication cycle, its mechanism of action, and whether endogenous oxLDL shares the anti-HCV properties of in vitro-generated oxLDL. We combined molecular virology tools with oxLDL serum measurements in different patient cohorts to address these questions. We found that oxLDL inhibits HCVcc at least as potently as HCV pseudoparticles. There was moderate variation between genotypes, with genotype 4 appearing the most oxLDL sensitive. Intracellular RNA replication and assembly and release of new particles were unaffected. HCV particles entering target cells lost oxLDL sensitivity with time kinetics parallel to anti-SR-BI (scavenger receptor class B type I), but significantly earlier than anti-CD81, suggesting that oxLDL acts by perturbing interaction between HCV and SR-BI. Finally, in chronically HCV-infected individuals, endogenous serum oxLDL levels did not correlate with viral load, but in HCV-negative sera, high endogenous oxLDL had a negative effect on HCV infectivity in vitro.

CONCLUSION

oxLDL is a potent pangenotype HCV entry inhibitor that maintains its activity in the context of human serum and targets an early step of HCV entry.

Trace metal imbalance associated with oxidative stress and inflammatory status in anti-hepatitis C virus antibody positive subjects

Toxic and essential trace metals, oxidative stress, and inflammatory status were evaluated in anti-hepatitis C virus (HCV) antibody-positive subjects. Blood biochemical parameters were determined in anti-HCV antibody-positive (n=17) and -negative controls (n=46). Compared with controls, anti-HCV antibody-positive individuals had significantly lower concentrations of plasma zinc (Zn); higher copper (Cu), iron (Fe), lead (Pb), cadmium (Cd), and aluminum (Al); and lower activities of erythrocyte antioxidant enzymes glutathione peroxidase and catalase, and elevated superoxide dismutase. Significantly increased lipid peroxidation malondialdehyde (MDA), and inflammatory markers such as alanine aminotransferase (ALT), high sensitivity C-reactive protein (hs-CRP), ferritin, and Cu/Zn ratios, as well as decreased albumin and high density lipoprotein (HDL) concentrations were observed. We have found significant interactions between toxic (e.g., Pb, Cd, and Al) and essential metals (e.g., Zn, Cu, Fe), which correlated with MDA. In conclusion, anti-HCV antibody-positive subjects had abnormal distributions of trace metals that may aggravate oxidative stress and inflammation, and exacerbate hepatic damage.