Hydrogen gas alleviates acute alcohol-induced liver injury by inhibiting JNK activation

Hydrogen gas alleviates acute ethanol-induced hepatotoxicity in mice via modulating TLR4/9 innate immune signaling and pyroptosis

Alcoholic liver disease (ALD), which is induced by chronic heavy alcohol consumption, accompanies complicated pathological mechanisms, including oxidative stress, inflammation, cell death, epigenetic changes and acetaldehyde-mediated toxicity. Hydrogen (H2) is the lightest gas with multiple biological effects such as high selective anti-oxidation, anti-inflammation and anti-apoptosis. However, the dose effects and innate immune mechanisms of intraperitoneal injection of H2 on ALD are limited. Here, we used acute ethanol-induced hepatotoxicity mice models to estimate the actions of intraperitoneal injection of H2 on ALD. The effects of H2 on acute ethanol-induced liver damage were examined by hepatic oil red O staining, quantitative PCR (qPCR) for lipid metabolic genes, hepatic triglyceride (TG) and serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Hepatic mitochondrial superoxide (MitoSOX), 3-nitrotyrosine (3-NT), malondialdehyde (MDA), and glutathione (GSH) levels were examined to evaluate oxidative stress. Immunoblot, and immunofluorescence staining were used to further confirm the innate immune molecular targets of H2. Our results showed that intraperitoneal injection of H2 improved acute ethanol-induced liver injury in mice in a dose dependent manner, as indicated by decreasing serum ALT and AST levels, hepatic TG levels, and increasing lipid export genes (Mttp and Apob) mRNA levels and reducing fatty acid uptake gene (CD36) mRNA levels. Mechanistically, H2 inhibited hepatic oxidative stress as indicated by reducing reactive oxygen species (ROS), 3-NT, and MDA levels in the liver, while increasing hepatic GSH levels; inhibited the overactived TLR4/9-NF-κB-TNF-α/IL-1β/IL-18 innate immune signaling; suppressed the canonical Caspase-1-GSDMD pyroptosis signaling, and the non-canonical pyroptosis signaling, such as Caspase-11-GSDMD, Caspase-8-GSDMD and Caspase-3-GSDME signaling. Therefore, our study highlights that intraperitoneal injection of H2 may represent a novel therapeutic and safe strategy for ALD via modulating oxidative stress, innate immunity and pyroptosis.

Hydrogen gas ameliorates acute alcoholic liver injury via anti-inflammatory and antioxidant effects and regulation of intestinal microbiota

Alcoholic liver disease (ALD) is a globally prevalent liver-related disorder characterized by severe oxidative stress and inflammatory liver damage, for which no effective treatment is currently available. Hydrogen gas (H₂) has been demonstrated to be an efficient antioxidant in various diseases in animals as well as humans. However, the protective effects of H₂ on ALD and its underlying mechanisms remain to be elucidated. The present study demonstrated that H₂ inhalation ameliorated liver injury, and attenuated liver oxidative stress, inflammation, and steatosis in an ALD mouse model. Moreover, H₂ inhalation improved gut microbiota, including increasing the abundance of Lachnospiraceae and Clostridia, and decreasing the abundance of Prevotellaceae and Muribaculaceae, and also improved intestinal barrier integrity. Mechanistically, H₂ inhalation blocked activation of the LPS/TLR4/NF-κB pathway in liver. Notably, it was further demonstrated that the reshaped gut microbiota may accelerate alcohol metabolism, regulate lipid homeostasis and maintain immune balance by bacterial functional potential prediction (PICRUSt). Fecal microbiota transplantation from mice that had undergone H₂ inhalation significantly alleviated acute alcoholic liver injury. In summary, the present study showed that H₂ inhalation alleviated liver injury by reducing oxidative stress and inflammation, while also improving intestinal flora and enhancing the intestinal barrier. H₂ inhalation may serve as an effective intervention for preventing and treating ALD in a clinical context.

Alcohol-induced increase in BMP levels promotes fatty liver disease in male prediabetic stage Otsuka Long-Evans Tokushima Fatty rats

Alcohol consumption exacerbates liver abnormalities in animal models, but whether it increases the severity of liver disease in early diabetic or prediabetic rats is unclear. To investigate the molecular mechanisms underlying alcohol-induced liver steatosis or hepatitis, we used a prediabetic animal model. Otsuka Long-Evans Tokushima Fatty (OLETF) and Long-Evans Tokushima Fatty (LETO) rats were pair-fed with an ethanol-containing liquid diet for 6 weeks. Compared with controls, OLETF and LETO rats displayed more pronounced liver steatosis and higher plasma levels of serum glutamic oxaloacetic transaminase (SGOT) and serum glutamate pyruvate transaminase (SPGT), indicating liver injury. Ethanol-fed LETO (Pd-L-E) rats showed mild liver steatosis and no inflammation compared with ethanol-fed OLETF (Pd-O-E) rats. Although precursor and active SREBP-1 levels in the liver of ethanol-fed OLETF rats significantly increased compared with control diet-fed OLETF rats (Pd-O-C), those of Pd-L-E rats did not. Bone morphogenetic protein (BMP) and TGF-β1 balance in Pd-O-E rats was significantly altered because BMP signaling was upregulated by inducing BMP2, BMP4, BMP7, BMP9, Smad1, and Smad4, whereas TGF-β1, Smad3, and Erk were downregulated. Activation of TGF-β/Smad signaling inhibited BMP2 and BMP9 expression and increased epithelial-mesenchymal transition (EMT) marker levels (Hepcidin, Snail, and Twist) in the liver of LETO rats. Livers of ethanol-fed OLETF rats showed increased levels of vimentin, FSP-1, α-SMA, MMP1, MMP13, and collagen III compared with rats of other groups, whereas EMT marker levels did not change. Thus, BMP exerted anti- and/or pro-fibrotic effects in ethanol-fed rats. Therefore, BMP and TGF-β, two key members of the TGF-β superfamily, play important but diverse roles in liver steatosis in young LETO and OLETF rats.