Role of cytokines in ethanol-induced cytotoxicity in vitro in Hep G2 cells

Abstract

Background & Aims: As shown previously by us, ethanol (EtOH) causes time- and concentration-dependent reduction in cytoviability. Tauroursodeoxycholic acid (TUDCA) and ursodeoxycholic acid (UDCA) were shown to reduce cytotoxicity. Long-term EtOH exposure leads to immunoregulatory and detoxification impairment. This study aimed to determine the relationship between cytokine (interleukin [IL]-1α and IL-6 and tumor necrosis factor [TNF]-α) production and expression, glutathione (GSH) status, and EtOH-induced cytotoxicity on Hep G2 cells. Methods: Cells were incubated with 80 mmol/L EtOH or α-minimal essential medium (control) in the presence or absence of 50 μmol/L TUDCA or UDCA. Cytokine release was quantitated by enzyme-linked immunosorbent assay. Cytokine expression was measured by reverse-transcription polymerase chain reaction. GSH content was determined in both the cytosolic and mitochondrial fractions. Results: After 24 hours of EtOH exposure, the release of IL-1α doubled, that of IL-6 increased 10 times, and that of TNF-α increased 3.5 times. Cytokine expression was up-regulated compared with control for IL-1α (42%), IL-6 (26%), and TNF-α (52%). Addition of 50 μmol/L TUDCA or UDCA reduced cytokine release and expression. TNF-α increased cytotoxicity by 18%. Anti–TNF-α antibody almost abolished it. EtOH depleted mGSH levels by 55% ( P < 0.001). TUDCA replenished them by 88%. Conclusions: EtOH up-regulated expression of cytokines in Hep G2 cells is down-regulated by bile acids. Increased amounts of TNF-α and depletion in both cytosolic and mitochondrial GSH contribute to EtOH cytotoxicity. Bile acids prevent toxicity. GASTROENTEROLOGY 1998;115:157-166