Nedd4L signaling contributes to carbon tetrachloride-induced liver fibrosis in female mice and is associated with enteric dysbacteriosis.

Background: Liver fibrosis is characterized by hepatic stellate cell (HSC) activation and collagen overproduction, but its pathogenesis remains largely unknown. This study aimed to uncover the role of neural precursor cell expressed developmentally downregulated 4-like (Nedd4L) signaling in liver fibrosis and its relationship with gut microbiota.

Methods: Intraperitoneal injection of carbon tetrachloride (CCl₄) was used to induce liver fibrosis in 8-week-old female C57BL/6J mice with Nedd4L knockout or administration of the Nedd4L protein phosphorylation inhibitor EMD638683. HSCs isolated from mice were activated with transforming growth factor-beta 1 (TGFβ1) with or without EMD638683.

Results: An approximately 3-fold elevation in Nedd4L mRNA was observed in hepatocytes and liver tissues, and significantly higher hepatic Nedd4L phosphorylation was observed in fibrotic mice than in non-fibrotic mice. Nedd4L mRNA level in HSCs isolated from fibrotic livers and Nedd4L protein level in TGFβ1-stimulated HSCs from wild-type livers remained unchanged. In isolated HSCs, TGFβ1-induced Nedd4L phosphorylation and cell activation were suppressed with EMD638683. In CCl₄-treated mice, EMD638683 alleviated liver fibrosis and induced a relative increase in fecal Bacteroides, Parabacteroides, Erysipelatoclostridium, Blautia, and Klebsiella, whereas Nedd4L deficiency predisposed mice to liver injury and liver fibrosis with a remarkable reduction in fecal Lactobacillus, Enterorhabdus, and Bacteroides.

Conclusion: Hepatic Nedd4L signaling contributes to CCl₄-induced liver fibrosis in female mice, which is associated with alterations in the gut microbiota, and Nedd4L phosphorylation is involved in TGFβ1-mediated HSC activation.