ABSTRACT
AIM: Glucocorticoid-induced tumor necrosis factor receptor ligand (GITRL) plays pro-inflammatory roles in immune response. Thus, our aim was to assess if dexamethasone attenuates lipopolysaccharide (LPS)-induced liver injury by affecting GITRL in Kupffer cells (KC). METHODS: A BALB/c mouse model of liver injury was established by i.p. injecting with LPS (10 mg/kg) co-treated with or without dexamethasone (3 mg/kg). Blood and liver samples were obtained for analysis of liver morphology, GITRL expression, hepatocellular function and cytokine levels at 24 h after injection. KC were isolated and challenged by LPS (1 µg/mL), with or without dexamethasone (10 µM) co-treatment, or with GITRL siRNA pre-transfection. The GITRL expression and cytokine levels were assayed at 24 h after challenge. RESULTS: Dexamethasone treatment significantly improved the survival rate of endotoxemic mice (P < 0.05), whereas serum alanine aminotransferase, aspartate aminotransferase, tumor necrosis factor (TNF)-α, interleukin (IL)-6 and γ-interferon levels were significantly decreased (P < 0.05, respectively). Concurrently, LPS-induced hepatic tissue injury was attenuated as indicated by morphological analysis; and expression of GITRL in liver tissue and KC was downregulated (P < 0.05). Consistent with these in vivo experiments, inhibited expression of GITRL, TNF-α and IL-6 caused by dexamethasone treatment were also observed in LPS-stimulated KC. The GITRL, TNF-α and IL-6 expression was also significantly inhibited by GITRL gene silencing. CONCLUSION: The TNF-α and IL-6 expression of LPS-stimulated KC was inhibited by GITRL gene silencing. Dexamethasone attenuates LPS-induced liver injury, at least proportionately, by downregulating GITRL in KC.
