Hydrogen gas (H2) pretreatment improves lipopolysaccharide-induced acute liver injury in mice by inhibiting NLRP3 inflammasome activation and pyroptosis signaling.

BACKGROUND

The liver is extremely vulnerable to endotoxin-induced damage during sepsis. Hydrogen gas (H2) is a colorless and odorless gas molecule with anti-oxidative and anti-inflammatory actions. However, the effects of H2 intraperitoneal injection on sepsis-induced acute liver injury and the possible mechanisms remain unclear.

METHODS

Biochemical analysis, H&E staining, immunoblotting, immunofluorescence, and TUNEL staining were used to investigate the effects and mechanisms of H2 intraperitoneal injection on lipopolysaccharide (LPS)-induced acute liver injury in mice. AML12 cells and pharmacological rescue experiment were used to confirmed the target of H2.

RESULTS

H2 pretreatment by intraperitoneal injection improved LPS-induced acute liver injury in mice as indicated by reducing inflammatory cells infiltration in the liver, down-regulating serum ALT and AST levels, decreasing hepatic 3-nitrotyrosine, MDA, and MPO levels, and up-regulating hepatic GSH levels. Mechanistically, H2 suppressed TLR4 to IKK-NF-κB and to MAPK (ERK, p38 and JNK) signaling, and thus reducing pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-18 levels in the liver of LPS-challenged mice. Moreover, the hepatic pyroptosis signaling including NLRP3 inflammasome (NLRP3, ASC, and Caspase-1) to GSDMD, Caspase-8/11 to GSDMD, Caspase-3 to GSDME, and TUNEL staining in LPS-challenged mice were all reversed by H2 treatment. The pharmacological rescue experiments by agonist (nigericin) and antagonist (MCC950) of NLRP3 further confirm the action of H2 on NLRP3 in vitro.

CONCLUSIONS

H2 pretreatment by intraperitoneal injection alleviated LPS-induced acute liver injury in mice by modulating redox homeostasis, TLR4-mediated innate immune signaling, NLRP3 inflammasome activation and pyroptosis signaling.