OP05 Cystathionine γ-lyase deficiency protects mice from galactosamine/lipopolysaccharide-induced acute liver failure

Background Acute liver failure (ALF) is a fatal syndrome attributed to massive hepatocyte death. Although a variety of insults including viral infection and drugs can cause ALF, the resulting clinical picture is remarkably similar across the different etiologies, reflecting common patterns of response of the innate immune system and the resulting inflammatory response. Hydrogen sulfide (H 2 S) has been reported to exert cytoprotective or cytotoxic effects. We have recently reported that breathing low concentration of H 2 S prevents lethal endotoxemia and inflammatory liver injury in mice at least in part by increasing thiosulfate, an oxidative metabolite of H 2 S [1] . Nonetheless, role of endogenously produced H 2 S in inflammatory organ injury remains incompletely defined. Here, we examined the role of cystathionine γ -lyase (CSE) in the ALF induced by D-Galactosamine (GalN) and lipopolysaccharide (LPS) in mice. Methods Wild-type C57BL6J (WT) and CSE-deficient mice [2] on C57BL6J background were challenged with saline or GalN (300 mg/kg)/LPS (1 μg/kg). Impact of CSE deficiency on LPS-induced tumor necrosis factor- α (TNF- α ) production by macrophages and GalN/TNF- α -induced hepatocyte death was examined in primary culture. Plasma and liver levels of sulfide metabolites were measured by HPLC after derivatization with monobromobimane. Results WT mice exhibited high mortality rate, prominent liver injury, and increased plasma alanine aminotransferase (ALT) levels after GalN/LPS challenge. Congenital deficiency or chemical inhibition of CSE by DL-propargylglycine (PAG) attenuated GalN/LPS-induced liver injury. CSE-deficiency markedly improved survival rate and attenuated GalN/LPS-induced up-regulation of inflammatory cytokines and activation of caspase 3 and PARP in the liver. CSE-deficiency protected primary hepatocytes from GalN/TNF- α -induced cell death without affecting LPS-induced TNF- α production from primary peritoneal macrophages. CSE-deficient mice exhibited up-regulated NF-E2 p45-related factor 2 (Nrf2) and Nrf2-dependent antioxidant proteins, activated Akt-dependent anti-apoptotic signaling, and markedly attenuated GalN/LPS-induced JNK phosphorylation in the liver. Beneficial effects of CSE-deficiency and administration of PAG were associated with markedly elevated homocysteine and thiosulfate levels in the liver and plasma. Finally, administration of sodium thiosulfate (STS) markedly attenuated GalN/LPS-induced liver injury via activation of Akt- and Nrf2-dependent signaling and inhibition of GalN/LPS-induced JNK phosphorylation in WT mice. Conclusion Using CSE-deficient mice and primary hepatocytes, we unexpectedly revealed cytoprotective effects of CSE deficiency against inflammatory acute liver failure. Our results also showed a profound impact of CSE deficiency on sulfide metabolism that triggered several cytoprotective mechanisms including Akt- and Nrf2-dependent signaling and augmentation of thiosulfate levels. Lastly, we confirmed the robust cytoprotective effects of sodium thiosulfate against inflammatory liver failure, suggesting an important translational potential of our findings.