Role of integrins in angiotensin II-induced proliferation of vascular smooth muscle cells

Abstract

Angiotensin II (AII) binds to G protein-coupled receptor AT(1) and stimulates extracellular signal-regulated kinase (ERK), leading to vascular smooth muscle cells (VSMC) proliferation. Proliferation of mammalian cells is tightly regulated by adhesion to the extracellular matrix, which occurs via integrins. To study cross-talk between G protein-coupled receptor- and integrin-induced signaling, we hypothesized that integrins are involved in AII-induced proliferation of VSMC. Using Oligo GEArray and quantitative RT-PCR, we established that messages for α(1)-, α(5)-, α(V)-, and β(1)-integrins are predominant in VSMC. VSMC were cultured on plastic dishes or on plates coated with either extracellular matrix or poly-d-lysine (which promotes electrostatic cell attachment independent of integrins). AII significantly induced proliferation in VSMC grown on collagen I or fibronectin, and this effect was blocked by the ERK inhibitor PD-98059, suggesting that AII-induced proliferation requires ERK activity. VSMC grown on collagen I or on fibronectin demonstrated approximately three- and approximately sixfold increases in ERK phosphorylation after stimulation with 100 nM AII, respectively, whereas VSMC grown on poly-d-lysine demonstrated no significant ERK activation, supporting the importance of integrin-mediated adhesion. AII-induced ERK activation was reduced by >65% by synthetic peptides containing an RGD (arginine-glycine-aspartic acid) sequence that inhibit α(5)β(1)-integrin, and by ∼60% by the KTS (lysine-threonine-serine)-containing peptides specific for integrin-α(1)β(1). Furthermore, neutralizing antibody against β(1)-integrin and silencing of α(1), α(5), and β(1) expression by transfecting VSMC with short interfering RNAs resulted in decreased AII-induced ERK activation. This work demonstrates roles for specific integrins (most likely α(5)β(1) and α(1)β(1)) in AII-induced proliferation of VSMC.

<b>Docosahexaenoic acid suppresses angiotensin II-induced A7r5 vascular smooth muscle cell proliferation and migration under pulsatile pressure str</b><b>ess </b>

“…These results were consistent with our previous findings using human aortic SMCs (13). Therefore, it was shown that the In fact, angiotensin II causes VSMC proliferation and migration, an increase in matrix production of fibronectin and collagen, and induction of oxidative stress (2,31,35). In this study, pulsatile pressure stress increased proliferation and migration.…”

Integrin signaling in atherosclerosis

“…AngII induces smooth muscle adhesion to collagen and fibronectin through the AT1 receptor [192–194], resulting in FAK-dependent ERK activation and enhanced cell proliferation [195, 196]. Cytoskeletal stiffening and contraction of smooth muscle cells treated with AngII results in elevated blood pressure [192, 193, 197], thereby enhancing mechanical load on the smooth muscle integrins.…”

“…However, integrin signaling may also contribute to vasoconstriction, as treatment with the integrin inhibitor RGDS reduced vasoconstriction to AngII but not other vasoconstrictors [198]. While α1β1 has largely been implicated in maintaining the contractile phenotype in atherosclerosis, smooth muscle hypertrophy to chronic AngII stimulation is reduced in α1 knockout mice [199], and inhibiting α1β1 using siRNA knockdown or peptide inhibitors blunts AngII-induced ERK activation and proliferation [195, 200]. Consistent with this association, AngII promotes α1 integrin expression [199] along with the expression of multiple provisional matrix-binding integrins, such as α8, β1, and β3 [201, 202].…”

Cross-Talk between Transforming Growth Factor–β1 and Muscarinic M2 Receptors Augments Airway Smooth Muscle Proliferation

“…In addition to their function as a scaffold, ECM proteins also modulate a variety of cellular functions, including migration, differentiation, and proliferation. For example, ASM cells cultured on fibronectin or collagen Type I matrices show enhanced mitogenic responses to growth factors such as platelet-derived growth factor (PDGF) (7)(8)(9)(10)(11)(12). The interaction of these cells with the ECM occurs mainly through integrins, a group of heterodimeric transmembrane glycoproteins.…”

“…The interaction of these cells with the ECM occurs mainly through integrins, a group of heterodimeric transmembrane glycoproteins. Studies on the role of integrins in smooth muscle cell proliferation have indicated an important role for these ECM receptors (e.g., both the angiotensin II-induced and PDGF-induced proliferation of vascular smooth muscle cells requires signaling through a5b1 integrins) (7,13). In addition, the proliferation of human ASM cells can also be mediated by integrins, in particular by the a5b1 integrins (9,14,15).…”