Cytokine response and oxidative stress produced by ethanol, acetaldehyde and endotoxin treatment in HepG2 cells

Background: inflammatory mediators. including cytokines and reactive oxygen species, are associated with the pathology of chronic liver disease. Hepat ocytes are generally considered as targets but not producers of these impor tant mediators. Objectives: To investigate whether cells of hepatocellular lineage are a po tential source of Various cytokines we estimated the expression and secreti on of tumor necrosis factor alpha, transforming growth factor beta 1, and i nterleukins 1beta, 6 and 8 in the culture of well-differentiated human HepG 2 cells treated for 24 hours with ethanol, acetaldehyde and lipopolysacchar ide. Lipid peroxidation damage, glutathione content and glutathione peroxid ase, catalase and superoxide dismutase activity were also determined. Methods: HepG2 cells were treated for 24 hours with ethanol (50 mM), acetal dehyde (175 muM) and LPS 1 mug/ml). TNF-alpha, TGF-beta, IL-1 beta IL-6 and IL-8 mRNA were determined by reverse transcriptase polymerase chain reacti on and secretion by enzyme-linked immunoassay. Lipid peroxidation damage, g lutathione content and antioxidant enzyme activities were determined spectr ophotometrically. Results: Exposure to ethanol for 24 hours induced the expression of TNF-alp ha and TGF-beta (1), secretion of IL-1 beta and TGF-beta (1) and decreased catalase activity. Acetaldehyde markedly increased TNF-alpha and IL-8 expre ssion, stimulated IL-1 beta and IL-8 secretion, increased lipid peroxidatio n damage and decreased catalase activity, while LPS exposure induced the ex pression of TNF-alpha, TGF-beta (1), IL-6 and IL-8, the secretion of TGF-be ta (1), IL-1 beta, IL-6 and IL-8, and a decrease in catalase activity. No c hange in GSH, GSHPx or SOD was found in any experimental condition. Conclusions: The present studies confirm and extend the notion that hepatoc ytes respond to ethanol, acetaldehyde and LPS-producing cytokines. Oxidativ e stress produced by the toxic injury plays an important role in this respo nse through upregulation of inflammatory cytokines.