HSPA9/HMGB1 regulates myocardial fibrosis in atrial fibrillation via TGF-β1/Smad pathway and autophagy.

Background: Atrial fibrillation (AF) is a common arrhythmia often linked to myocardial fibrosis. This study investigates the molecular mechanisms underlying AF, focusing on HSPA9 as a key regulator of fibrosis and its interaction with the TGF-β1/Smad pathway.

Methods: The GSE79768 dataset was employed for differential gene expression analysis. Weighted Gene Co-expression Network Analysis (WGCNA) identified key modules associated with AF. Functional enrichment analyses and Protein-Protein Interaction (PPI) networks were performed. Mouse cardiac fibroblasts were subjected to Angiotensin II (Ang II), and gene, protein, and functional analyses were conducted using quantitative real-time polymerase chain reaction (qRT-PCR), Western blot (WB), immunofluorescence, Co-immunoprecipitation (Co-IP), Cell Counting Kit-8 (CCK-8), and cell migration assays. In vivo, Ang II-induced mice were detected with immunohistochemistry (IHC) and Hematoxylin and Eosin (H&E) staining for fibrosis.

Results: WGCNA identified a strong correlation with the brown module, highlighting HSPA9 as a key gene in AF. HSPA9 was upregulated in AF tissues and Ang II-treated fibroblasts. Knockdown of HSPA9 suppressed fibroblast proliferation, migration, and fibrosis marker expression. HSPA9 interacts with HMGB1 to stabilize it, activating the TGF-β1/Smad pathway. HMGB1 overexpression reversed the effects of HSPA9 knockdown. In vivo, HSPA9 knockdown alleviated myocardial fibrosis. HSPA9 inhibits autophagy via the TGF-β1/Smad pathway, making it a possible target for treatment for AF and fibrosis.

Conclusion: HSPA9 regulates myocardial fibrosis in AF by interacting with HMGB1 and activating the TGF-β1/Smad pathway. Targeting HSPA9 could be a promising therapeutic strategy for preventing or treating AF-associated myocardial fibrosis.