A Phase 3, Randomized, Controlled Trial of Resmetirom in NASH with Liver Fibrosis.

BACKGROUND: Nonalcoholic steatohepatitis (NASH) is a progressive liver disease with no approved treatment. Resmetirom is an oral, liver-directed, thyroid hormone receptor beta-selective agonist in development for the treatment of NASH with liver fibrosis. METHODS: We are conducting an ongoing phase 3 trial involving adults with biopsy-confirmed NASH and a fibrosis stage of F1B, F2, or F3 (stages range from F0 [no fibrosis] to F4 [cirrhosis]). Patients were randomly assigned in a 1:1:1 ratio to receive once-daily resmetirom at a dose of 80 mg or 100 mg or placebo. The two primary end points at week 52 were NASH resolution (including a reduction in the nonalcoholic fatty liver disease [NAFLD] activity score by ≥2 points; scores range from 0 to 8, with higher scores indicating more severe disease) with no worsening of fibrosis, and an improvement (reduction) in fibrosis by at least one stage with no worsening of the NAFLD activity score. RESULTS: Overall, 966 patients formed the primary analysis population (322 in the 80-mg resmetirom group, 323 in the 100-mg resmetirom group, and 321 in the placebo group). NASH resolution with no worsening of fibrosis was achieved in 25.9% of the patients in the 80-mg resmetirom group and 29.9% of those in the 100-mg resmetirom group, as compared with 9.7% of those in the placebo group (P<0.001 for both comparisons with placebo). Fibrosis improvement by at least one stage with no worsening of the NAFLD activity score was achieved in 24.2% of the patients in the 80-mg resmetirom group and 25.9% of those in the 100-mg resmetirom group, as compared with 14.2% of those in the placebo group (P<0.001 for both comparisons with placebo). The change in low-density lipoprotein cholesterol levels from baseline to week 24 was -13.6% in the 80-mg resmetirom group and -16.3% in the 100-mg resmetirom group, as compared with 0.1% in the placebo group (P<0.001 for both comparisons with placebo). Diarrhea and nausea were more frequent with resmetirom than with placebo. The incidence of serious adverse events was similar across trial groups: 10.9% in the 80-mg resmetirom group, 12.7% in the 100-mg resmetirom group, and 11.5% in the placebo group. CONCLUSIONS: Both the 80-mg dose and the 100-mg dose of resmetirom were superior to placebo with respect to NASH resolution and improvement in liver fibrosis by at least one stage. (Funded by Madrigal Pharmaceuticals; MAESTRO-NASH ClinicalTrials.gov number, NCT03900429.).

Resmetirom (MGL-3196) for the treatment of non-alcoholic steatohepatitis: a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial.

BACKGROUND: Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis, inflammation, hepatocellular injury, and progressive liver fibrosis. Resmetirom (MGL-3196) is a liver-directed, orally active, selective thyroid hormone receptor-ß agonist designed to improve NASH by increasing hepatic fat metabolism and reducing lipotoxicity. We aimed to assess the safety and efficacy of resmetirom in patients with NASH. METHODS: MGL-3196-05 was a 36-week randomised, double-blind, placebo-controlled study at 25 centres in the USA. Adults with biopsy confirmed NASH (fibrosis stages 1-3) and hepatic fat fraction of at least 10% at baseline when assessed by MRI-proton density fat fraction (MRI-PDFF) were eligible. Patients were randomly assigned 2:1 by a computer-based system to receive resmetirom 80 mg or matching placebo, orally once a day. Serial hepatic fat measurements were obtained at weeks 12 and 36, and a second liver biopsy was obtained at week 36. The primary endpoint was relative change in MRI-PDFF assessed hepatic fat compared with placebo at week 12 in patients who had both a baseline and week 12 MRI-PDFF. This trial is registered with ClinicalTrials.gov, number NCT02912260. FINDINGS: 348 patients were screened and 84 were randomly assigned to resmetirom and 41 to placebo at 18 sites in the USA. Resmetirom-treated patients (n=78) showed a relative reduction of hepatic fat compared with placebo (n=38) at week 12 (-32·9% resmetirom vs -10·4% placebo; least squares mean difference -22·5%, 95% CI -32·9 to -12·2; p<0·0001) and week 36 (-37·3% resmetirom [n=74] vs -8·5 placebo [n=34]; -28·8%, -42·0 to -15·7; p<0·0001). Adverse events were mostly mild or moderate and were balanced between groups, except for a higher incidence of transient mild diarrhoea and nausea with resmetirom. INTERPRETATION: Resmetirom treatment resulted in significant reduction in hepatic fat after 12 weeks and 36 weeks of treatment in patients with NASH. Further studies of resmetirom will allow assessment of safety and effectiveness of resmetirom in a larger number of patients with NASH with the possibility of documenting associations between histological effects and changes in non-invasive markers and imaging. FUNDING: Madrigal Pharmaceuticals.

Sofosbuvir, Velpatasvir, and Voxilaprevir for Previously Treated HCV Infection.

BACKGROUND: Patients who are chronically infected with hepatitis C virus (HCV) and who do not have a sustained virologic response after treatment with regimens containing direct-acting antiviral agents (DAAs) have limited retreatment options. METHODS: We conducted two phase 3 trials involving patients who had been previously treated with a DAA-containing regimen. In POLARIS-1, patients with HCV genotype 1 infection who had previously received a regimen containing an NS5A inhibitor were randomly assigned in a 1:1 ratio to receive either the nucleotide polymerase inhibitor sofosbuvir, the NS5A inhibitor velpatasvir, and the protease inhibitor voxilaprevir (150 patients) or matching placebo (150 patients) once daily for 12 weeks. Patients who were infected with HCV of other genotypes (114 patients) were enrolled in the sofosbuvir-velpatasvir-voxilaprevir group. In POLARIS-4, patients with HCV genotype 1, 2, or 3 infection who had previously received a DAA regimen but not an NS5A inhibitor were randomly assigned in a 1:1 ratio to receive sofosbuvir-velpatasvir-voxilaprevir (163 patients) or sofosbuvir-velpatasvir (151 patients) for 12 weeks. An additional 19 patients with HCV genotype 4 infection were enrolled in the sofosbuvir-velpatasvir-voxilaprevir group. RESULTS: In the three active-treatment groups, 46% of the patients had compensated cirrhosis. In POLARIS-1, the rate of sustained virologic response was 96% with sofosbuvir-velpatasvir-voxilaprevir, as compared with 0% with placebo. In POLARIS-4, the rate of response was 98% with sofosbuvir-velpatasvir-voxilaprevir and 90% with sofosbuvir-velpatasvir. The most common adverse events were headache, fatigue, diarrhea, and nausea. In the active-treatment groups in both trials, the percentage of patients who discontinued treatment owing to adverse events was 1% or lower. CONCLUSIONS: Sofosbuvir-velpatasvir-voxilaprevir taken for 12 weeks provided high rates of sustained virologic response among patients across HCV genotypes in whom treatment with a DAA regimen had previously failed. (Funded by Gilead Sciences; POLARIS-1 and POLARIS-4 ClinicalTrials.gov numbers, NCT02607735 and NCT02639247 .).

A Roadmap for Value-Based Payment Models Among Patients With Cirrhosis.

Healthcare reimbursement is shifting from fee-for-service to fee-for-value. Cirrhosis, which costs the U.S. healthcare system as much as heart failure, is a prime target for value-based care. This article describes models in which physician groups or health systems are paid for improving quality and lowering costs for a given population of patients with cirrhosis. If done correctly, we believe that such frameworks, once adopted, could help reduce burnout by freeing physicians of the burden of checking boxes in the electronic medical record so that they can devote their energies to managing populations. Conclusion: Value-based payment models for cirrhosis have the potential to benefit patients, physicians, and healthcare insurers.

Hepatitis C virus double-stranded RNA is the predominant form in human liver and in interferon-treated cells.

Hepatitis C virus (HCV) is unique among RNA viruses in its ability to establish chronic infection in the majority of exposed adults. HCV persists in the liver despite interferon (IFN)-stimulated gene (ISG) induction; robust induction actually predicts treatment failure and viral persistence. It is unclear which forms of HCV RNA are associated with ISG induction and IFN resistance during natural infections. To thoroughly delineate HCV RNA populations, we developed conditions that fully separate the strands of long double-stranded RNA (dsRNA) and allow the released RNAs to be quantified in reverse transcription/polymerase chain reaction assays. These methods revealed that dsRNA, a pathogen-associated molecular pattern (PAMP), comprised 52% (standard deviation, 28%) of the HCV RNA in the livers of patients with chronic infection. HCV dsRNA was proportionally higher in patients with the unfavorable IL28B TT (rs12979860) genotype. Higher ratios of HCV double-stranded to single-stranded RNA (ssRNA) correlated positively with ISG induction. In Huh-7.5 cells, IFN treatment increased the total amount of HCV dsRNA through a process that required de novo viral RNA synthesis and shifted the ratio of viral dsRNA/ssRNA in favor of dsRNA. This shift was blocked by ribavirin (RBV), an antiviral drug that reduces relapse in HCV patients. Northern blotting established that HCV dsRNA contained genome-length minus strands. CONCLUSION: HCV dsRNA is the predominant form in the HCV-infected liver and has features of both a PAMP and a genomic reservoir. Interferon treatment increased rather than decreased HCV dsRNA. This unexpected finding suggests that HCV produces dsRNA in response to IFN, potentially to antagonize antiviral defenses. (Hepatology 2017;66:357-370).

Estrogen decreases tight junction protein ZO-1 expression in human primary gut tissues.

Females have a higher prevalence of most autoimmune diseases; however, the mechanism is unknown. In this study, we examined the expression of tight junction protein zonula occludens 1 (ZO-1) and estrogen receptor (ER)-α/ß in human primary gut tissues by immunohistochemistry, immunofluorescence and qPCR. The expression of ZO-1 and ER-ß but not ER-α was present in both male and female gut tissues. There was no sex difference in ER-ß expression, but ZO-1 expression was decreased in females compared to males. In vitro, estrogen treatment decreased ZO-1 mRNA and protein expression, ZO-1 promoter activity, IL-6 production, and NF-κB activation in human primary gut tissues or the Caco-2 cells, but increased the ER-ß expression in Caco-2 cells. Consistently, plasma IL-6 levels in females were reduced relative to males in vivo. Our finding indicates that estrogen may play a role in gut tight junction expression and permeability.

Biliary Epithelial Cells Are Not the Predominant Source of Hepatic CXCL12.

Hepatic expression levels of CXCL12, a chemokine important in inflammatory and stem cell recruitment, and its receptor, C-X-C chemokine receptor 4, are increased during all forms of liver injury. CXCL12 is expressed by both parenchymal and nonparenchymal hepatic cells, and on the basis of immunohistochemistry, biliary epithelial cells (BECs) are thought to be a predominant source of hepatic CXCL12, thereby promoting periportal recruitment of C-X-C chemokine receptor 4-expressing lymphocytes. Our study aims to show that BECs may, in fact, not be the predominant source of hepatic CXCL12. We measured CXCL12 secretion and expression from human and murine BECs using enzyme-linked immunosorbent assay and Western blot analysis from cell culture supernatants and whole cell lysates, respectively, whereas CXCL12 expression in murine livers was analyzed in a Cxcl12-Gfp reporter mouse. Cell culture supernatants and whole cell lysates from BECs failed to demonstrate their expression of CXCL12. Furthermore, we confirmed these results with a Cxcl12-Gfp reporter mouse in which green fluorescent protein expression is notably absent from BECs. Interestingly, on the basis of green fluorescent protein expression, we demonstrate a population of CXCL12-expressing cells within the portal tract that are distinct, yet intimately associated with BECs. These findings indicate that BECs are not a predominant source of CXCL12.

Inhibition of the CXCL12/CXCR4 chemokine axis with AMD3100, a CXCR4 small molecule inhibitor, worsens murine hepatic injury.

AIM: Activation of hepatic stellate cells and development of chronic inflammation are two key features in the progression of hepatic fibrosis. We have shown that in vitro activated stellate cells increase their expression of CXCL12 as well as the receptor CXCR4 and that receptor engagement promotes a profibrogenic phenotype. Furthermore, injury promotes increased hepatic expression of CXCL12 and a massive infiltration of CXCR4-expressing leukocytes, granulocytes and myeloid cells. The primary site of inflammatory cell accumulation is around the CXCL12-rich portal tracts and within fibrotic septae, indicating a role for CXCR4 during injury. In order to characterize the relevance of the CXCR4/CXCL12 chemokine axis during hepatic injury we inhibited the axis using AMD3100, a CXCR4 small molecule inhibitor, in models of chronic and acute liver injury. METHODS: Mice were subjected to acute and chronic CCl4 liver injury with and without AMD3100 administration. The degree of liver injury, fibrosis and the composition of the intrahepatic inflammatory response were characterized. RESULTS: Treatment of mice with AMD3100 in the chronic CCl4 model of liver injury led to an increase in hepatic inflammation and fibrosis with a specific increase in intrahepatic neutrophils. Furthermore, in an acute model of CCl4 -induced liver injury, AMD3100 led to an increase in the number of intrahepatic neutrophils and a trend towards worse necrosis. CONCLUSION: Together, this data suggests that inhibition of the CXCR4/CXCL12 chemokine axis is injurious through modulation of the hepatic inflammatory response and that this axis may serve a protective role in liver injury.

Pathogenesis of MASLD and MASH - role of insulin resistance and lipotoxicity.

BACKGROUND: Insulin resistance and lipotoxicity are extremely interconnected but fundamental in setting the stage for the development of MASLD/MASH. AIM/METHODS: A comprehensive literature search was performed and key themes were synthesised to provide insight into the underlying molecular mechanisms of insulin resistance and lipotoxicity in the liver, muscle, pancreas and adipose tissue and how organ cross-talk is fundamental to driving disease pathogenesis. RESULTS: Classical thinking postulates that excess FFA load exceeds the storage capacity of adipose tissue, which is predicated upon both genetic and environmental factors. This results in insulin resistance and compensatory hyperinsulinaemia by pancreatic beta cells to overcome target organ insulin resistance. As adipocyte dysfunction worsens, not only are excess FFA delivered to other organs, including skeletal muscle, pancreas and liver but a pro-inflammatory milieu is established with increases in IL-6, TNF-α and changes in adipokine levels (increased leptin and decreased adiponectin). With increased intramuscular lipid accumulation, lipotoxic species decrease insulin signalling, reduce glucose uptake by downregulation of GLUT4 and decrease glycogen synthesis. With this additional reduced capacity, hyperglycaemia is further exacerbated and increased FFA are delivered to the liver. The liver has the largest capacity to oxidise fat and to adapt to these stressors and, therefore, has become the last line of defence for excess lipid storage and utilisation, the capacity of which may be impacted by genetic and environmental factors. However, when the liver can no longer keep up with increasing FFA delivery and DNL, lipotoxic species accumulate with ensuing mitochondrial dysfunction, increased ER stress, oxidant stress and inflammasome activation, all of which drive hepatocyte injury and apoptosis. The resulting wound healing response, marked by stellate cell activation, drives collagen accumulation, progressive fibrosis, and, ultimately, end organ failure and death. This vicious cycle and complex interplay between insulin resistance, hyperinsulinaemia, lipotoxicity and multi-directional cross-talk among different target organs are critical drivers of MASLD/MASH. CONCLUSIONS: Targeting tissue-specific insulin resistance and hyperinsulinaemia while decreasing FFA load (lipotoxicity) through dietary and lifestyle changes remain the best upstream interventions.

CXCL12 induces hepatic stellate cell contraction through a calcium-independent pathway.

Liver fibrosis, with subsequent development of cirrhosis and ultimately portal hypertension, results in the death of patients with end-stage liver disease if liver transplantation is not performed. Hepatic stellate cells (HSCs), central mediators of liver fibrosis, resemble tissue pericytes and regulate intrahepatic blood flow by modulating pericapillary resistance. Therefore, HSCs can contribute to portal hypertension in patients with chronic liver disease (CLD). We have previously demonstrated that activated HSCs express functional chemokine receptor, CXCR4, and that receptor engagement by its ligand, CXCL12, which is increased in patients with CLD, leads to further stellate cell activation in a CXCR4-specific manner. We therefore hypothesized that CXCL12 promotes HSC contraction in a CXCR4-dependent manner. Stimulation of HSCs on collagen gel lattices with CXCL12 led to gel contraction and myosin light chain (MLC) phosphorylation, which was blocked by addition of AMD3100, a CXCR4 small molecule inhibitor. These effects were further mediated by the Rho kinase pathway since both Rho kinase knockdown or Y-27632, a Rho kinase inhibitor, blocked CXCL12 induced phosphorylation of MLC and gel contraction. BAPTA-AM, a calcium chelator, had no effect, indicating that this pathway is calcium sensitive but not calcium dependent. In conclusion, CXCL12 promotes stellate cell contractility in a predominantly calcium-independent fashion. Our data demonstrates a novel role of CXCL12 in stellate cell contraction and the availability of small molecule inhibitors of the CXCL12/CXCR4 axis justifies further investigation into its potential as therapeutic target for portal hypertension.

Resmetirom: An Orally Administered, Smallmolecule, Liver-directed, ß-selective THR Agonist for the Treatment of Non-alcoholic Fatty Liver Disease and Non-alcoholic Steatohepatitis.

Non-alcoholic fatty liver disease (NAFLD) encompasses a spectrum of fatty liver disease, including non-alcoholic fatty liver (NAFL) and its more progressive form, non-alcoholic steatohepatitis (NASH). The prevalence of NAFLD/NASH along with type 2 diabetes and obesity is rising worldwide. In those who develop NASH, unlike those with bland steatosis (NAFL), lipotoxic lipids drive hepatocyte injury, inflammation and stellate cell activation leading to progressive accumulation of collagen or fibrosis, ultimately leading to cirrhosis and increased risk of hepatocellular carcinoma. Hypothyroidism is associated with NAFLD/NASH; specifically, intrahepatic hypothyroidism drives lipotoxicty in preclinical models. Agonists of thyroid hormone receptor (THR)-ß, which is primarily found in the liver, can promote lipophagy, mitochondrial biogenesis and mitophagy, stimulating increased hepatic fatty acid ß-oxidation, and thereby decreasing the burden of lipotoxic lipids, while promoting low-density lipoprotein (LDL) uptake and favourable effects on lipid profiles. A number of THR-ß agonists are currently being investigated for NASH. This review focuses on resmetirom, an orally administered, once-daily, small-molecule, liver-directed, ß-selective THR agonist, as it is furthest along in development. Data from completed clincal studies outlined in this review demonstrate that resmetirom is effective in reducing hepatic fat content as measured by magnetic resonance imaging-derived proton density fat fraction, reduces liver enzymes, improves non-i nvasive markers of liver fibrogenesis and decreases liver stiffness, while eliciting a favourable cardiovascular profile with a reduction in serum lipids, including LDL cholesterol. Topline phase III biopsy data showed resolution of NASH and/or fibrosis improvement after 52 weeks of treatment, with more detailed peer-reviewed findings anticipated in order to certify these findings. Longer term clinical outcomes from both MAESTRO-NASH and MAESTRO-NASH OUTCOMES will be a pivotal juncture in the drug's road towards being approved as a NASH therapeutic.

Update on Clinical Trials for Nonalcoholic Steatohepatitis.

Tremendous effort has been put forth over the past 2 decades in understanding the pathophysiology of nonalcoholic fatty liver disease/nonalcoholic steatohepatitis (NAFLD/NASH). Although multiple potential targets for drug development exist, there have been no approved therapies for NAFLD/NASH. Lipotoxicity, owing to increased delivery of fatty acids to the liver, and hepatic de novo lipogenesis are key drivers of disease pathogenesis. Moreover, genetics, environmental factors, and comorbid conditions converge to determine disease progression in individual patients. Given the complexity and heterogeneity of disease pathogenesis, numerous therapeutic targets have emerged and have been tested in clinical trials. Early trial failures have provided key lessons and foundational insights to move the field forward. Current ongoing phase 3 trials and emerging phase 2 trials are reasons for optimism, and 2 drugs, obeticholic acid and resmetirom, are being evaluated for accelerated approval by the US Food and Drug Administration this year. This article highlights key features of NASH pathophysiology and drug targets, the lessons learned from completed trials, and the current landscape of phase 2 and 3 clinical trials in NASH.

Environmental exposures are important risk factors for advanced liver fibrosis in African American adults.

Background & Aims: The prevalence and aetiology of liver fibrosis vary over time and impact racial/ethnic groups unevenly. This study measured time trends and identified factors associated with advanced liver fibrosis in the United States. Methods: Standardised methods were used to analyse data on 47,422 participants (≥20 years old) in the National Health and Nutrition Examination Survey (1999-2018). Advanced liver fibrosis was defined as Fibrosis-4 ≥2.67 and/or Forns index ≥6.9 and elevated alanine aminotransferase. Results: The estimated number of people with advanced liver fibrosis increased from 1.3 million (95% CI 0.8-1.9) to 3.5 million (95% CI 2.8-4.2), a nearly threefold increase. Prevalence was higher in non-Hispanic Black and Mexican American persons than in non-Hispanic White persons. In multivariable logistic regression analysis, cadmium was an independent risk factor in all racial/ethnic groups. Smoking and current excessive alcohol use were risk factors in most. Importantly, compared with non-Hispanic White persons, non-Hispanic Black persons had a distinctive set of risk factors that included poverty (odds ratio [OR] 2.09; 95% CI 1.44-3.03) and susceptibility to lead exposure (OR 3.25; 95% CI 1.95-5.43) but did not include diabetes (OR 0.88; 95% CI 0.61-1.27; p =0.52). Non-Hispanic Black persons were more likely to have high exposure to lead, cadmium, polychlorinated biphenyls, and poverty than non-Hispanic White persons. Conclusions: The number of people with advanced liver fibrosis has increased, creating a need to expand the liver care workforce. The risk factors for advanced fibrosis vary by race/ethnicity. These differences provide useful information for designing screening programmes. Poverty and toxic exposures were associated with the high prevalence of advanced liver fibrosis in non-Hispanic Black persons and need to be addressed. Impact and Implications: Because liver disease often produces few warning signs, simple and inexpensive screening tests that can be performed by non-specialists are needed to allow timely diagnosis and linkage to care. This study shows that non-Hispanic Black persons have a distinctive set of risk factors that need to be taken into account when designing liver disease screening programs. Exposure to exogenous toxins may be especially important risk factors for advanced liver fibrosis in non-Hispanic Black persons.

Activated hepatic stellate cells upregulate transcription of ecto-5'-nucleotidase/CD73 via specific SP1 and SMAD promoter elements.

Adenosine is a potent modulator of liver fibrosis and inflammation. Adenosine has been shown to regulate such diverse activities as chemotaxis, contraction, and matrix production in hepatic stellate cells (HSC). Ecto-5'-nucleotidase/CD73 [EC 3.1.3.5] is the rate-limiting enzyme in adenosine production. Cd73-deficient mice are resistant to experimental liver fibrosis and have impaired adenosine generation. However, cell-specific expression and regulation of CD73 within the fibrotic liver have not been defined. In particular, prior evidence demonstrating that liver myofibroblasts, the cells believed to be responsible for matrix formation in the liver, express CD73 is lacking. Thus we tested the hypothesis that HSC and portal fibroblasts (PF), cells that undergo differentiation into liver myofibroblasts, express CD73 in a regulated fashion. We found that CD73 is weakly expressed in quiescent HSC and PF but is markedly upregulated at the transcriptional level in myofibroblastic HSC and PF. We furthermore found that CD73 protein and its functional activity are strongly increased in fibrous septa in rats subjected to experimental fibrosis. To determine the mechanism for the upregulation of Cd73 gene, we cloned the rat Cd73 promoter and then used serial truncation and site-directed mutagenesis to identify key regulatory elements. We identified two consensus SP1 motifs and one SMAD binding site, each of which was necessary for Cd73 gene upregulation. In conclusion, activated HSC upregulate Cd73 gene expression, via specific SP1 and SMAD promoter elements, after myofibroblastic differentiation. The ecto-5'-nucleotidase/CD73 enzyme is a novel cellular marker of activated liver myofibroblasts in vivo and in vitro and thus represents a promising molecular target for antifibrotic therapies in liver diseases.

Human immunodeficiency virus (HIV)-1 infects human hepatic stellate cells and promotes collagen I and monocyte chemoattractant protein-1 expression: implications for the pathogenesis of HIV/hepatitis C virus-induced liver fibrosis.

UNLABELLED: Patients coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) develop more rapid fibrosis than those infected with HCV only. In HIV/HCV-coinfected patients, fibrosis progression correlates with HIV RNA levels, suggesting a direct role of HIV in liver fibrogenesis. Chemokine (C-C motif) receptor 5 (CCR5) and cysteine-X-cysteine receptor 4 (CXCR4), the two major coreceptors required for HIV entry into cells, are expressed on activated hepatic stellate cells (HSCs), the principle fibrogenic cell type in the liver. We therefore examined whether HIV can infect HSCs, explored the potential mechanisms of viral entry, and assessed the impact of infection as reflected by the ability of HSCs to transfer virus to T lymphocytes and elicit a proinflammatory and profibrogenic response. We report that the laboratory-adapted viruses HIV-IIIB (CXCR4-tropic or X4) and HIV-BaL (CCR5-tropic or R5) and primary HIV isolates can infect both a human stellate cell line, LX-2, and primary human HSCs. HIV entry and gene expression in HSCs was confirmed using HIV-green fluorescent protein (GFP) expression viral constructs in the presence or absence of the reverse-transcriptase inhibitor azidothymidine. CD4 expression on a subset of primary HSCs was demonstrated using fluorescence-activated cell sorting and immunofluorescence staining. Blocking experiments in the presence of anti-CD4, anti-CXCR4, and anti-CCR5 revealed that HIV entry into HSCs is predominantly CD4/chemokine coreceptor-independent. HIV infection promoted HSC collagen I expression and secretion of the proinflammatory cytokine monocyte chemoattractant protein-1. Furthermore, infected LX-2 cells were capable of transferring GFP-expressing virus to T lymphocytes in a coculture system. CONCLUSION: Taken together, our results suggest a potential role of HIV in liver fibrosis/inflammation mediated through effects on HSCs. The role of early highly active antiretroviral therapy initiation in patients with HIV/HCV coinfection warrants further investigation.

Loss of matrix metalloproteinase-2 amplifies murine toxin-induced liver fibrosis by upregulating collagen I expression.

BACKGROUND AND AIMS: Matrix metalloproteinase-2 (MMP-2), a type IV collagenase secreted by activated hepatic stellate cells (HSCs), is upregulated in chronic liver disease and is considered a profibrotic mediator due to its proliferative effect on cultured HSCs and ability to degrade normal liver matrix. Although associative studies and cell culture findings suggest that MMP-2 promotes hepatic fibrogenesis, no in vivo model has definitively established a pathologic role for MMP-2 in the development and progression of liver fibrosis. We therefore examined the impact of MMP-2 deficiency on liver fibrosis development during chronic CCl(4) liver injury and explored the effect of MMP-2 deficiency and overexpression on collagen I expression. METHODS: Following chronic CCl(4) administration, liver fibrosis was analyzed using Sirius Red staining with quantitative morphometry and real-time polymerase chain reaction (PCR) in MMP-2-/- mice and age-matched MMP-2+/+ controls. These studies were complemented by analyses of cultured human stellate cells. RESULTS: MMP-2-/- mice demonstrated an almost twofold increase in fibrosis which was not secondary to significant differences in hepatocellular injury, HSC activation or type I collagenase activity; however, type I collagen messenger RNA (mRNA) expression was increased threefold in the MMP-2-/- group by real-time PCR. Furthermore, targeted reduction of MMP-2 in cultured HSCs using RNA interference significantly increased collagen I mRNA and protein, while overexpression of MMP-2 resulted in decreased collagen I mRNA. CONCLUSIONS: These findings suggest that increased MMP-2 during the progression of liver fibrosis may be an important mechanism for inhibiting type I collagen synthesis by activated HSCs, thereby providing a protective rather than pathologic role.

Hepatic stellate cells express functional CXCR4: role in stromal cell-derived factor-1alpha-mediated stellate cell activation.

UNLABELLED: Chemokine interactions with their receptors have been implicated in hepatic stellate cell (HSC) activation. The hepatic expression of CXCR4 messenger RNA is increased in hepatitis C cirrhotic livers and plasma levels of its endogenous ligand, stromal cell-derived factor-1alpha (SDF-1alpha), correlate with increased fibrosis in these patients. The expression of CXCR4 by HSCs has not been reported. We therefore examined whether HSCs express CXCR4 in vivo and in vitro and explored whether SDF-1alpha/CXCR4 receptor engagement promotes HSC activation, fibrogenesis, and proliferation. The hepatic protein expression of both CXCR4 and SDF-1alpha is increased in hepatitis C cirrhotic livers and immunoflourescent and immunohistochemical staining confirms that HSCs express CXCR4 in vivo. Immortalized human stellate cells as well as primary human HSCs express CXCR4, and cell surface receptor expression increases with progressive culture-induced activation. Treatment of stellate cells with recombinant SDF-1alpha increases expression of alpha-smooth muscle actin and collagen I and stimulates a dose-dependent increase in HSC proliferation. Inhibitor studies suggest that SDF-1alpha/CXCR4-dependent extracellular signal-regulated kinase 1/2 and Akt phosphorylation mediate effects on collagen I expression and stellate cell proliferation. CONCLUSION: HSCs express CXCR4 receptor in vivo and in vitro. CXCR4 receptor activation by SDF-1alpha is profibrogenic through its effects on HSC activation, fibrogenesis, and proliferation. Extracellular signal-regulated kinase 1/2 and phosphoinositide 3-kinase pathways mediate SDF-1alpha-induced effects on HSC expression of collagen I and proliferation. The availability of small molecule inhibitors of CXCR4 make this receptor an appealing target for antifibrotic approaches.

Role of Kupffer Cells in Driving Hepatic Inflammation and Fibrosis in HIV Infection.

While the interactions between HIV and various liver cell populations have been explored, the relevance of these interactions when patients are well-controlled on ART is less clear. Therefore, we focus this perspective on HIV-related alterations that may drive hepatic inflammation and fibrosis in aviremic patients, with a focus on Kupffer cells and Hepatic Stellate Cells. Persistent CD4+ T cell depletion in the gut resulting in increased gut permeability has been postulated to play a role in systemic immune activation in HIV patients. The liver, with its unique location, remains the gatekeeper between the gut and the systemic circulation. The resident liver macrophage, Kupffer cell, is responsible for clearing and responding to these products. We propose that changes in Kupffer cell biology, in the context of HIV infection, creates a mileu that drives hepatic inflammation and fibrosis in response to microbial translocation. Targeting these pathways may be helpful in improving liver-related outcomes in HIV patients.