期刊
CIRCULATION
卷 110, 期 19, 页码 3129-3135出版社
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/01.CIR.0000147180.87553.79
关键词
enzymes; hypertrophy; myocardium; peptides
Background-Although increased activity of angiotensin-converting enzyme (ACE) has been associated with increased cardiac collagen, no studies to date have established a direct cause-and-effect relation between the two. Methods and Results-We used transgenic rats that overexpress human ACE selectively in the myocardium. Two independent heterozygous transgenic rat lines were studied, one expressing 2 to 3 copies (L1172) and the other expressing 5 to 10 copies (L1173) of the ACE transgene. These rats were normotensive but developed a proportionate increase in myocardial collagen depending on the ACE gene dose (up to 2.5-fold, P<0.01), but cardiac angiotensin II levels remained normal, whereas collagen content reversed to control levels on ACE inhibition. To explain these changes, we investigated N-acetyl-Ser-Asp-Lys-Pro ( AcSDKP), an alternative substrate that is catabolized exclusively by ACE. Increased cardiac expression of ACE was paralleled by a reciprocal decrease in cardiac AcSDKP and a proportionate increase in phosphorylated Smad2 and Smad3, all of which normalized after both ACE inhibition and AcSDKP infusion. Furthermore, a functional link of this signaling cascade was demonstrated, because AcSDKP inhibited Smad3 phosphorylation in a dose-dependent manner in cultured cardiac fibroblasts and in vivo. Conclusions-Our findings suggest that increased cardiac ACE activity can increase cardiac collagen content by degradation of AcSDKP, an inhibitor of the phosphorylation of transforming growth factor-beta signaling molecules Smad2 and Smad3. This implies that the antifibrotic effects of ACE inhibitors are mediated in part by increasing cardiac AcSDKP, with subsequent inhibition of Smad 2/3 phosphorylation.
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