Inhibition of TNF-α-mediated NF-κB activation by 4-hydroxynonenal contributes to liver injury in alcoholic liver disease

AIM: To study the role of 4-hydroxynonenal (4-HNE) in hepatocyte death induced by tumor necrosis factor α (TNF-α).METHODS: Human liver cell line HepG2 and primary mouse hepatocytes were used to establish the cell model. The effect of 4-HNE on TNF-α-induced cell death was determined by lactate dehydrogenase (LDH) release and MTT assays. The intracellular levels of 4-HNE-protein adducts were determined by Western blotting. The intranuclear NF-κB (p65) and its DNA binding activity were detected by Western blotting and ELISA, respectively. Long-term intake of alcohol in C57BL/6 mice was performed to establish the animal model. The histological changes of mouse hepatic tissues and the apoptosis of hepatocytes were observed by HE staining and TUNEL assay, respectively. The hepatic levels of triglyceride (TG), TNF-α and 4-HNE-protein adducts, and the plasma activity of alanine aminotransferase (ALT) were also detected.RESULTS: (1) 4-HNE significantly increased the sensitivity of HepG2 cells and primary mouse hepatocytes to the killing effect of TNF-α. (2) 4-HNE significantly increased the intracellular levels of 4-HNE-protein adducts. (3) 4-HNE inhibited TNF-α-mediated NF-κB (p65) activation in HepG2 cells. (4) Long-term intake of alcohol in mice resulted in high hepatic levels of 4-HNE and TNF-α, accompanied with the increases in hepatic TG content, plasma ALT activity and hepatocyte death.CONCLUSION: Long-term intake of alcohol induces oxidative stress and produces 4-HNE as a hepatocyte-sensitizing factor, which inhibits TNF-α-mediated NF-κB anti-apoptotic signaling pathway in hepatocytes, thus inducing alcoholic liver damage.