肾上腺髓质素对血管紧张素Ⅱ促血管外膜成纤维细胞胶原生成作用的影响

目的探讨肾上腺髓质素（ADM）对血管紧张素Ⅱ（AngⅡ）诱导的血管外膜成纤维细胞胶原生成的影响及机制。方法体外培养大鼠主动脉外膜成纤维细胞,通过放射免疫法测定培养上清中ADM含量,采用酶联免疫吸附法（ELISA）测定培养上清中Ⅰ、Ⅲ型胶原蛋白含量,用逆转录一聚合酶链反应（RT—PCR）及Western印迹法检测转化生长因子β1（TGFβ1）和基质金属蛋白酶-2（MMP-2）mRNA及蛋白的表达。结果AngII呈剂量依赖性地刺激血管外膜成纤维细胞分泌ADM,在AngⅡ（10^-6mol／L）刺激前30min加入氯沙坦或（和）PD123319,氯沙坦（10^-5mol／L）可明显降低AngⅡ刺激的ADM分泌,其抑制率为45％（P〈0．01）,而PD123319（10mmol／L）作用后抑制率仅为3％（P〉0．05）,氯沙坦＋PD123319组与单独氯沙坦组相比差异无统计学意义（P〉0．05）;AngⅡ显著增加培养上清中Ⅰ、Ⅲ型胶原蛋白含量,ADM呈剂量依赖地抑制AngⅡ上述作用,其中ADM（10“mol／L）组中I、Ⅲ型胶原合成分别抑制了30％和31％（P〈0．01）,ADM（10^-7mol／L）组则分别抑制了43％和42％（P〈0．01）。ADM受体拈抗剂ADM22-52可增强AngII上述作用,Ⅰ、Ⅲ型胶原合成分别增加了38％和43％（P〈0．01）;ADM呈剂量依赖性抑制AngⅡ刺激的TGFβ1mRNA及蛋白表达,其中ADM（10^-8mol／L）组中TGFβ1mRNA及蛋白表达分别抑制了55％和45％（P〈0．01）,ADM（10^-7mol／L）组则分别抑制了70％和59％（P〈0．01）;AngⅡ明显下调细胞内MMP-2mRNA及蛋白表达,ADM呈剂量依赖性抑制上述作用,其中10^-8mol／LADM组细胞内MMP-2mRNA及蛋白表达分别增加了1．0和0．9倍。结论AngⅡ可刺激血管外膜成纤维细胞释放ADM,而自分泌旁分泌的ADM可能通过下调细胞内TGFN表达和上调MMP-2表达,抑制AngⅡ刺激的Ⅰ、Ⅲ型胶原蛋白生成,从而发挥有效的抗血管重构作用。

Effects of adrenomedullin on angiotensin II-induced collagen synthesis in vascular adventitial fibroblasts

OBJECTIVE: To explore the effects of adrenomedullin (ADM) on Angiotensin II (AngII)-induced collagen synthesis in cultured rat vascular adventitial fibroblasts. METHODS: Rat vascular adventitial fibroblasts were cultured in vitro. ADM produced and secreted from adventitia in the presence of AngII was detected by radioimmunoassay, type I, III collagen contents in adventitia fibroblasts were measured by ELISA and the expressions of TGFbeta1 and MMP-2 were determined by RT-PCR and Western blotting. RESULTS: AngII significantly induced ADM secretion in adventitial fibroblasts in a dose-dependent manner. These effects could be reduced by 45%, 3% and 46%, through pre-treatment with Losartan, PD123319 or both, respectively for 30 min in culture medium. The AngII-induced type I, III collagen secretion in adventitial fibroblasts was significantly reduced by AMD in a dose-dependent manner, (P < 0.01) while ADM agonist ADM(22 - 52) significantly potentiated the effect of AngII; ADM also reduced AngII-induced expression of TGFbeta1 at mRNA and protein levels in a dose-dependent manner. AngII reduced the expression of MMP-2 at mRNA and protein levels in adventitial fibroblasts and these effects could be reversed by AMD (10(-8) mol/L). CONCLUSION: AngII stimulated ADM secretion in adventitia fibroblasts, ADM in turn can inhibit AngII-induced type I, III collagen synthesis in adventitial fibroblasts probably by downregulating the TGFbeta1 expression and upregulating MMP-2 expression. ADM therefore served as an antifibrotic factor in vascular remodeling process.