Interferon alpha and alcohol augment nuclear regulatory factor-kappa B activation in HepG2 cells, and interferon alpha increases pro-inflammatory cytokine production

Background. The mechanisms for decreased therapeutic response to IFN alpha in chronic hepatitis C patients with alcohol are unknown. We investigated t he hypothesis that IFN alpha and alcohol regulate cells both in the liver p arenchyma and the immune system. Methods: We used the hepatocellular carcinoma cells (HepG2) to determine if IFN alpha (500-10,000 U/ml) or ethanol (25-100 mM) modulates NF-kB activat ion alone or in combination with TNF alpha (0.1-20 mug/ml) as determined in electromobility gel shift assays. IkB levels were evaluated in the cytopla smic extracts by western blot. Monocytes from normal donors were activated with LPS (1 mug/ml) in combination with IFN alpha or ethanol overnight and TNF alpha, IL-6, and IL-12 were measured in the supernatants. Results: In HepG2 cells, both IFN alpha and acute alcohol treatment induced NF-kappaB activation and augmented TNT alpha -induced NF-kappaB binding. P retreatment of HepG2 cells with IFN alpha resulted in the highest levels of NF-kappaB activation in response to TNF alpha or TNF alpha plus ethanol st imulation. Supershift experiments confirmed that the NF-kappaB dimer induce d by TNT alpha and its combination with IFN alpha or ethanol contains RelA (p65) and involves rapid degradation of I kappaB alpha. Experiments using t he proteasome inhibitor, MG132, revealed that augmentation of NF-kappaB by ethanol and IFN alpha is mediated via the proteasome pathway. We show that in normal monocytes, IFN alpha augments LPS-induced production of the infla mmatory cytokines TNF alpha, IL-6, and IL-12 (p < 0.06) without further mod ulation by acute alcohol treatment. Conclusions: These results suggest that IFN alpha can increase HepG2 cell s ensitivity to TNF alpha and ethanol-mediated activation. Augmentation of mo nocyte inflammatory cytokines, particularly of IL-12 production, by IFN alp ha could be a key element of the antiviral response in chronic HCV. These r esults support the hypothesis that the therapeutic benefits of IFN alpha li kely involve activation of both immune and parenchymal cells in the liver.