C5a/C5a R pathway is essential for up-regulating Sph K1 expression through p38-MAPK activation in acute liver failure

AIM To investigate the role of the complement 5a(C5a)/C5 a receptor(C5a R) pathway in the pathogenesis of acute liver failure(ALF) in a mouse model.METHODS BALB/c mice were randomly assigned to different groups, and intraperitoneal injections of lipopolysaccharide(LPS)/D-galactosamine(D-Gal N)(600 mg/kg and 10 μg/kg) were used to induce ALF. The KaplanMeier method was used for survival analysis. Serum alanine aminotransferase(ALT) levels, at different time points within a 1-wk period, were detected with a biochemistry analyzer. Pathological examination of liver tissue was performed 36 h after ALF induction. Serum complement 5(C5), C5 a, tumor necrosis factor-α(TNF-α), interleukin(IL)-1β, IL-6, high-mobility group protein B1(HMGB1) and sphingosine-1-phosphatelevels were detected by enzyme-linked immunosorbant assay. Hepatic morphological changes at 36 h after ALF induction were assessed by hematoxylin and eosin staining. Expression of C5 a R, sphingosine kinase 1(Sph K1), p38-MAPK and p-p38-MAPK in liver tissue, peripheral blood mononuclear cells(PBMCs) and peritoneal exudative macrophages(PEMs) of mice or RAW 264.7 cells was analyzed by western blotting. C5 a R m RNA levels were detected by quantitative real-time PCR.RESULTS Activation of C5 and up-regulation of C5 a R were observed in liver tissue and PBMCs of mice with ALF. Blockade of C5 a R with a C5 a R antagonist(C5a Ra C5 a Ra) significantly reduced the levels of serum ALT, inflammatory cytokines(TNF-α, IL-1β and IL-6) and HMGB1, as well as the liver tissue damage, but increased the survival rates(P < 0.01 for all). Blockade of C5 a R decreased Sph K1 expression in both liver tissue and PBMCs significantly at 0.5 h after ALF induction. C5 a Ra pretreatment significantly downregulated the phosphorylation of p38-MAPK in liver tissues of ALF mice and C5 a stimulated PEMs or RAW 264.7 cells. Moreover, inhibition of p38-MAPK activity with SB203580 reduced Sph K1 protein production significantly in PEMs after C5 a stimulation.CONCLUSION The C5a/C5 a R pathway is essential for up-regulating Sph K1 expression through p38 MAPK activation in ALF in mice, which provides a potential immunotherapeutic strategy for ALF in patients.