Obesity and the metabolic syndrome are closely correlated with hepatic steatosis. Simple hepatic steatosis in nonalcoholic fatty liver disease can progress to nonalcoholic steatohepatitis (NASH), which can be a precursor to more serious liver diseases, such as cirrhosis and hepatocellular carcinoma. The pathogenic mechanisms underlying progression of steatosis to NASH remain unclear; however, inflammation, proinflammatory cytokines, and oxidative stress have been postulated to play key roles. We previously reported that patients with NASH have elevated serum levels of proinflammatory cytokines, such as interleukin-8 (IL-8), which are likely to contribute to hepatic injury. This study specifically examines the effect of hepatic steatosis on IL-8 production. We induced lipid accumulation in hepatocytes (HepG2, rat primary hepatocytes, and human primary hepatocytes) by exposing them to pathophysiologically relevant concentrations of palmitic acid to simulate the excessive influx of fatty acids into hepatocytes. Significant fat accumulation was documented morphologically by Oil Red O staining in cells exposed to palmitic acid, and it was accompanied by an increase in intracellular triglyceride levels. Importantly S everal studies suggest that elevated levels of circulating free fatty acids (FFAs) contribute to the complications of obesity and the metabolic syndrome by promoting excess fat deposition in nonadipose tissues not suited for fat storage, such as the liver. 1 A strong correlation exists between obesity and fatty liver (hepatic steatosis); indeed, nonalcoholic fatty liver disease is considered to be the hepatic manifestation of the metabolic syndrome. 2 Liver steatosis is often considered a benign condition, but it can progress to nonalcoholic steatohepatitis (NASH), which may be a precursor to more severe liver diseases such as cirrhosis and hepatocellular carcinoma. 3 NASH is a common liver disease in the United States, and its prevalence is on the rise worldwide. NASH is characterized by microvesicular and macrovesicular steatosis, inflammation with mixed cellularity including neutrophils, hepatocyte degeneration and injury, and sometimes fibrosis. 3 The pathogenesis of NASH and the mechanisms of progression of hepatic steatosis to NASH remain unclear. 4 Current understanding supports the "multiple-hit model" for the development of NASH, wherein hepatic steatosis represents the "first hit," whereas the "second" or "subsequent" hits must induce liver damage and promote inflammation with neutrophil infiltration. The nature of the subsequent hits is hypothesized to include direct lipid toxicity, mitochondrial dys-

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease and can lead to hepatocellular carcinoma and end-stage liver disease. The current FDA-approved treatment for HCV (pegylated interferon-alpha (IFNα) with ribavirin) is effective only in about 50% of patients. Epidemiological evidence suggests that obesity, alcohol, smoking and environmental pollutants may contribute to resistance to IFNα therapy in HCV. Acrolein, a ubiquitous environmental pollutant and major component of cigarette smoke, is also generated endogenously by cellular metabolism and lipid peroxidation. This study examines the effects of acrolein on (i) IFNα-mediated signaling and antiviral gene expression in cultured and primary human hepatocytes, and (ii) HCV replication in an HCV-replicon system. Our data demonstrate that non-toxic concentrations of acrolein significantly inhibited IFNα-induced tyrosine phosphorylation of both cytoplasmic and nuclear STAT1 and STAT2, without altering the total levels. Also, acrolein down-regulated IFNα stimulated gene transcription, resulting in reduced expression of antiviral genes. Importantly, acrolein abolished the IFNα mediated downregulation of HCV viral expression in the HCV-replicon system. This study defines mechanisms involved in resistance to IFNα and identifies the pathogenic role of acrolein, and potentially other environmental pollutants, in suppressing IFNα antiviral activity, and establishes their adverse impact on HCV therapy.

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Hepatitis C virus (HCV) infection is the major cause of chronic liver disease in the US and is a precursor to cirrhosis, end‐stage liver disease, hepatocellular carcinoma and death. The FDA approved standard of care for chronic hepatitis C, is pegylated interferon‐alpha (IFNα) combined with ribavirin which is effective only in about 50% of patients. Studies have identified potential cofactors that contribute to the failure of anti‐HCV therapy, including obesity, elevated lipid peroxidation, oxidative stress and environmental pollutants. Acrolein (ACR), a highly reactive aldehyde, is formed endogenously through cellular lipid peroxidation and is also a common, ubiquitous environmental pollutant. Exposure to ACR induces considerable oxidative stress and disrupts cellular signaling. This study examines the effect of ACR on IFNα mediated anti‐viral signaling in hepatic cells. Our data demonstrate that relevant concentrations of ACR significantly inhibit interferon‐alpha mediated JAK/Stat signaling, leading to reduced expression of anti‐viral proteins. ACR dramatically inhibits IFN‐induced tyrosine phosphorylation of both STAT1 and STAT2, and their upstream kinases, JAK1 and Tyk2. A corresponding decrease is observed in the nuclear translocation of phospho‐STAT1 and 2. Acrolein down regulated IFNα. inducible expression of anti‐HCV proteins such as PKR, OAS, ISG15 and ISG54, primarily by decreasing ISRE‐controlled gene transcription. This study identifies acrolein, a derivative of lipid peroxidation and a common environmental pollutant, as a potential cofactor that contributes to poor treatment outcomes and failure of IFNα therapy.