Investigation of HO-1 Regulation of Liver Fibrosis Related to Nonalcoholic Fatty Liver Disease Through the SIRT1/TGF-ß/Smad3 Pathway.

BACKGROUND AND AIMS

Heme oxygenase 1 (HO-1) has an influential yet insufficiently investigated effect on Sirtuin 1 (SIRT1), a histone deacetylase activated by nicotinamide adenine dinucleotide, which may impact the transforming growth factor-β (TGF-ß)/Smad3 pathway in nonalcoholic fatty liver disease (NAFLD)-related liver fibrosis. This study aimed to elucidate the regulation of NAFLD-related liver fibrosis induced by HO-1 through the SIRT1/TGF-ß/Smad3 pathway.

METHODS

HO-1 induction and inhibition were established in C57BL/6J mice fed a methionine- and choline-deficient (MCD) diet. Additionally, wild-type mice were fed either a normal diet or an MCD diet. Hematoxylin and eosin, Masson's trichrome, and Sirius Red staining were used to assess hepatic steatosis, inflammation, and fibrosis. , plasmid overexpression and small interfering RNA silencing of HO-1 were performed in LX-2 cells. Cell viability was assessed using the Cell Counting Kit-8, and apoptosis was evaluated via terminal deoxynucleotidyl transferase dUTP nick-end labeling and immunofluorescence. Flow cytometry was employed to assess apoptosis and reactive oxygen species production. Western blot and real-time quantitative reverse transcription polymerase chain reaction were used to analyze the mRNA and protein expression of genes related to HO-1, SIRT1, the TGF-ß signaling pathway, and fibrosis.

RESULTS

MCD-fed mice developed significant liver damage, including steatosis, inflammatory infiltration, and pericellular fibrosis. Zinc protoporphyrin treatment exacerbated these conditions. Corroborating these findings, silencing HO-1 in LX-2 cells increased the expression of fibrosis-related genes. Furthermore, HO-1 overexpression not only increased SIRT1 expression but also reduced the activity of key regulatory factors in the TGF-ß signaling pathway, suggesting a potential interaction between HO-1 and the SIRT1/TGF-ß pathway.

CONCLUSIONS

HO-1 inhibits the activation of the TGF-ß/Smad3 pathway in NAFLD-related liver fibrosis through SIRT1. These findings provide insights into new therapeutic strategies for treating NAFLD-associated liver fibrosis.