Hypertension and Vascular Research Division, Henry Ford Hospital, 2799 West Grand Blvd., Detroit, MI 48202, USA.
Am J Physiol Heart Circ Physiol. 2010 May;298(5):H1357-64. doi: 10.1152/ajpheart.00464.2009. Epub 2010 Feb 12.
N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) inhibits collagen production and cell proliferation in cultured rat cardiac fibroblasts, but its effect on differentiation of fibroblasts into myofibroblasts is not known. High amounts of transforming growth factor-beta1 (TGF-beta1) have been found in fibrotic cardiac tissue. TGF-beta1 converts fibroblasts into myofibroblasts, which produce more extracellular matrix proteins than fibroblasts. We hypothesized that 1) Ac-SDKP inhibits TGF-beta1-induced differentiation of fibroblasts into myofibroblasts; and 2) this effect is mediated in part by blocking phosphorylation of small-mothers-against-decapentaplegic (Smad) 2 and extracellular signal-regulated kinase (ERK) 1/2. For this study, we used human fetal cardiac fibroblasts (HCFs), which do not spontaneously become myofibroblasts when cultured at low passages. We investigated the effect of Ac-SDKP on TGF-beta1-induced HCF transformation into myofibroblasts, Smad2 and ERK1/2 phosphorylation, Smad7 expression, cell proliferation, and collagen production. We also investigated TGF-beta1 production by HCFs stimulated with endothelin-1 (ET-1). As expected, HCFs treated with TGF-beta1 transformed into myofibroblasts as indicated by increased expression of alpha-smooth muscle actin and a higher proportion of the embryonic isoform of smooth muscle myosin compared with untreated cells. TGF-beta1 also increased Smad2 and ERK1/2 phosphorylation but did not affect Smad7 expression. In addition, TGF-beta1 stimulated HCF proliferation as indicated by an increase in mitochondrial dehydrogenase activity and collagen production (hydroxyproline assay). Ac-SDKP significantly inhibited all of the effects of TGF-beta1. It also inhibited ET-1-stimulated TGF-beta1 production. We concluded that Ac-SDKP markedly suppresses differentiation of human cardiac fibroblasts into myofibroblasts, probably by inhibiting the TGF-beta/Smad/ERK1/2 signaling pathway, and thus mediating its anti-fibrotic effects.
N-乙酰基-丝氨酰-天冬氨酰-赖氨酰-脯氨酸（Ac-SDKP）可抑制培养的大鼠心脏成纤维细胞胶原的产生和细胞增殖，但它对成纤维细胞分化为肌成纤维细胞的影响尚不清楚。在纤维化的心脏组织中已发现大量的转化生长因子-β1（TGF-β1）。TGF-β1 将成纤维细胞转化为肌成纤维细胞，后者产生的细胞外基质蛋白多于成纤维细胞。我们假设：1）Ac-SDKP 抑制 TGF-β1 诱导的成纤维细胞分化为肌成纤维细胞；2）这种作用部分是通过阻断小母亲抗死亡锥蛋白（Smad）2 和细胞外信号调节激酶（ERK）1/2 的磷酸化来介导的。为此，我们使用人胎儿心脏成纤维细胞（HCF）进行研究，这些细胞在低传代培养时不会自发地转化为肌成纤维细胞。我们研究了 Ac-SDKP 对 TGF-β1 诱导的 HCF 转化为肌成纤维细胞、Smad2 和 ERK1/2 磷酸化、Smad7 表达、细胞增殖和胶原产生的影响。我们还研究了内皮素-1（ET-1）刺激的 HCF 产生 TGF-β1 的情况。正如预期的那样，用 TGF-β1 处理的 HCF 转化为肌成纤维细胞，其特征是与未处理的细胞相比，α-平滑肌肌动蛋白的表达增加，并且胚胎型平滑肌肌球蛋白的比例更高。TGF-β1 还增加了 Smad2 和 ERK1/2 的磷酸化，但不影响 Smad7 的表达。此外，TGF-β1 如线粒体脱氢酶活性和胶原产生（羟脯氨酸测定）的增加所示，刺激 HCF 增殖。Ac-SDKP 显著抑制 TGF-β1 的所有作用。它还抑制 ET-1 刺激的 TGF-β1 产生。我们得出结论，Ac-SDKP 显著抑制人心脏成纤维细胞分化为肌成纤维细胞，可能是通过抑制 TGF-β/Smad/ERK1/2 信号通路，从而介导其抗纤维化作用。
