Interferon alpha and alcohol augment nuclear regulatory factor-kappa B activation in HepG2 cells, and interferon alpha increases pro-inflammatory cytokine production
G. Szabo et al., Interferon alpha and alcohol augment nuclear regulatory factor-kappa B activation in HepG2 cells, and interferon alpha increases pro-inflammatory cytokine production, ALC CLIN EX, 25(8), 2001, pp. 1188-1197
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.