Angiotensin II and αvβ3 integrin expression in rat neonatal cardiac fibroblasts

We recently demonstrated that alpha(nu)beta(3) integrins are involved in the mechanisms of angiotensin II (Ang II)-induced DNA synthesis and collagen gel contractions in rat cardiac fibroblasts (CFBs), cellular mechanisms that are relevant for cardiac remodeling. The aim of the present study was to elucidate the effect of Ang II and other growth factors on the regulation of the alpha(nu)beta(3) integrins in fibroblasts from neonatal rat hearts. The alpha(nu)beta(3) integrin receptor expression was significantly increased (P<0.05) at the mRNA level after treatment with Ang II, transforming growth factor-beta(1) (TGF-beta(1)), and platelet-derived growth factor (PDGF) for 8 and 16 hours. The surface expression of the alpha(nu) and beta(3) integrin subunits was elevated after 32 and 48 hours (P<0.05) as determined with flow cytometry. To investigate fibroblast motility, we performed chemotaxis experiments with transwell chambers. Ang II was chemotactic for CFBs, as tested with checkerboard experiments. The chemotactic effect was concentration dependent and was completely blocked by Ang II type 1 receptor blockers but not by Ang II type 2 receptor blocker PD 123319. Ang II- and PDGF-BB-mediated chemotaxis could be significantly inhibited by RGD peptides and the blocking antibodies against alpha(nu)beta(3) integrin (both P<0.01). Adhesion of CFBs to vitronectin was partially inhibited by an antibody to alpha(nu)beta(3) integrin but was mainly mediated by an alpha(nu)beta(3) integrin. Relevant in vivo expression of alpha(nu)beta(3) integrin by CFBs was confirmed with in situ hybridization with probes for alpha(nu) and beta(3) mRNA in rat hearts. The present study demonstrates that the expression of alpha(nu)beta(3) integrin is augmented by Ang II, PDGF and TGF-beta(1) in neonatal CFBs. Furthermore, this integrin is involved in the chemotaxis, motility, acid adhesion of CFBs. The present findings support the current concept that integrins participate in the control of fibroblast behavior during cardiac remodeling mechanisms.