Lactobacillus casei culture supernatant ameliorates acute alcohol-induced liver injury by inhibiting cellular stress and promoting intestinal integrity in mice

Alcohol-associated liver disease (ALD) is a common liver disease worldwide. Probiotics prevent alcohol-induced liver injury and improve intestinal integrity. However, the precise mechanisms behind these effects are not fully understood. In the present study, we investigated the effects of Lactobacillus casei (L. casei) AS1.2435 on ALD in a mouse model. Ten-week-old ICR mice were pretreated with L. casei intracellular product or L. casei supernatants in drinking solution for 2 weeks before gavage administration of one dose of ethanol at 6 g/kg body weight. Alcohol-induced liver injury was examined by measuring plasma alanine aminotransferase levels and histological staining of liver sections. Apoptosis in liver tissue was detected by TUNEL staining. Oxidative stress and endoplasmic reticulum stress-related proteins, including malondialdehyde, superoxide dismutase, glutathione peroxidase, C/Ebp-homologous protein, glucose-regulated protein 78, protein disulfide isomerase, and X box-binding protein-1 in liver tissues were measured using commercial kits and immunohistochemical analysis. Intestinal tissue was examined by histological staining, and the expression of tight junction mRNA and proteins were analyzed by RT-PCR and immunofluorescence. L. casei supernatants supplementation significantly reduced alcohol-induced liver fat accumulation, inflammatory responses, intestinal mucosa injury, and improved liver function. L. casei supernatants prevented alcohol-induced increases in apoptosis, oxidative damage, and endoplasmic reticulum stress in mouse livers. L. casei supernatants pretreatment significantly increased alcohol-reduced mRNA expression of zonula occludens-1, claudin-1, intestine trefoil factor, P-glycoprotein, and cathelin-related antimicrobial peptide. Consistently, the increased protein levels of ZO-1, occludin, and claudin-1 were confirmed by immunofluorescence. However, no effects were observed in the L. casei intracellular product pretreatment groups. L. casei supernatants' extracellular product can alleviate ALD and intestinal injury by inhibiting cellular stress and promoting intestinal integrity.