Regulation of collagen synthesis in mouse skin fibroblasts by distinct angiotensin II receptor subtypes

We examined the possibility of whether angiotensin (Ang) II type 1 (AT(1)) and type 2 (AT(2)) receptor stimulation differentially regulates collagen production in mouse skin fibroblasts. Both AT(1) and AT(2) receptors were expressed in neonatal skin fibroblasts prepared from wild-type mice to a similar degree, and the AT(1a) receptor was exclusively expressed as opposed to the AT(1b) receptor. In wild-type fibroblasts, Ang II increased collagen synthesis accompanied by an increase in expression of tissue inhibitor of metalloproteinase (TIMP)-1, and these increases were inhibited by valsartan, an AT(1) receptor blocker, but augmented by PD123319, an AT(2) receptor antagonist. Ang II decreased basal and IGF-I-induced collagen production and inhibited TIMP-1 expression in neonatal skin fibroblasts prepared from AT(1a) knockout (KO) mice. These Ang II-mediated inhibitory effects on collagen production and TIMP-1 expression observed in AT(1a) KO fibroblasts were attenuated by the addition of PD123319 or a tyrosine phosphatase inhibitor, sodium orthovanadate, but not affected by a serine/threonine phosphatase inhibitor, okadaic acid. Moreover, we demonstrated that transfection of a catalytically inactive, dominant negative SHP-1 (Src homology 2-containing protein-tyrosine phosphatase-1) mutant inhibited the Ang II-mediated inhibitory effect on both collagen synthesis and TIMP-1 expression in AT(1a) KO fibroblasts. These results suggest that AT(1a) receptor stimulation increases collagen production in skin fibroblasts at least in part due to the inhibition of collagen degradation via the increase in TIMP-1 expression, whereas AT(2) receptor stimulation exerts inhibitory effects on TIMP-1 expression, which is mediated at least partially by the activation of SHP-1, thereby possibly inhibiting collagen production.