Integrin subunit β-like 1 mediates angiotensin II-induced myocardial fibrosis by regulating the forkhead box Q1/Snail axis

Cardiac fibrosis is a severe condition with limited therapeutic options and often occurs in chronic cardiovascular diseases such as hypertension and myocardial infarction. There is currently a clear need to identify novel mediators of cardiac fibrosis to facilitate the development of more effective therapeutic strategies targeting cardiac fibrosis. Integrin subunit β-like 1 (ITGBL1), an extracellular matrix protein, has previously been implicated in various fibrotic diseases. However, the precise role of ITGBL1 in regulating myocardial fibrosis remains unknown. The present study was designed to investigate whether ITGBL1 regulates angiotensin II (Ang II)-induced myocardial fibrosis in vitro and in vivo and the possible mechanism of action. It was found that the protein expressions of ITGBL1, Forkhead box Q1 (FOXQ1), and Snail were all increased significantly in fibrotic heart tissues from Ang II-infused mice and Ang II-stimulated cardiac fibroblasts, all of which were inhibited by the Ang II type I (AT1) receptor antagonist losartan. Silencing the ITGBL1/FOXQ1/Snail axis with specific siRNAs reversed Ang II-induced fibrotic effects and upregulation of FOXQ1 and Snail expressions in cardiac fibroblasts. FOXQ1 siRNA inhibited Snail expression in Ang II-induced cardiac fibroblasts. Furthermore, ITGBL1/FOXQ1 interacted with the TGF-β1 signaling to form a positive feedback loop. Our findings suggest that the extracellular matrix protein ITGBL1 mediates Ang II-induced cardiac fibrosis via the FOXQ1/Snail axis, which identifies ITGBL1 as a novel mediator of cardiac fibrosis and represents a potential therapeutic target for cardiac fibrosis.