糖皮质激素对成骨细胞局部的肾素-血管紧张素系统的调节作用

Regulatory effects of glucocorticoids on the local renin-angiotensin system in osteoblasts

目的利用小鼠的MC3T3-E1细胞来观察地塞米松对成骨细胞局部肾素-血管紧张素系统的调节作用。方法常规培养MC3T3-E1细胞,细胞免疫组织化学观察成骨细胞局部肾素-血管紧张素系统组分血管紧张素Ⅱ的Ⅰ型和Ⅱ型受体以及血管紧张素转化酶的表达。然后利用无血清培养基培养12h后,将MC3T3-E1细胞分为4组:对照组、地塞米松组(10-6 mol/L)、地塞米松+米非司酮组以及米非司酮组(10-5 mol/L)。待干预36h后,检测血管紧张素转化酶的活性。利用半定量PCR检测血管紧张素Ⅱ的Ⅰ型和Ⅱ型受体以及血管紧张素转化酶的mRNA的表达水平。利用Western blot方法检测血管紧张素Ⅱ的Ⅰ型和Ⅱ型受体以及血管紧张素转化酶的蛋白表达水平。结果与对照组比较,地塞米松明显增加了成骨细胞的血管紧张素转化酶的活性、同时也增加了血管紧张素Ⅱ的Ⅰ型和Ⅱ型受体以及血管紧张素转化酶的蛋白和mRNA的水平(P<0.05),但当同时给予米非司酮时,地塞米松的这种作用被阻断(P<0.05)。当单独给予米非司酮时,成骨细胞上血管紧张素转化酶的活性、血管紧张素Ⅱ的Ⅰ型和Ⅱ型受体以及血管紧张素转化酶的蛋白和mRNA的水平与对照组比较均无发生明显变化(P>0.05)。结论地塞米松通过成骨细胞上的糖皮质素受体激活成骨细胞局部肾素-血管紧张素系统,这很可能是激素性骨质疏松的发病机制之一。

Objective To investigate the regulatory effects of glucocorticoids on the local renin-angiotensin system in osteoblasts by using MC3T3-E1 cells. Methods Cellular immune histochemistry was carried out to observe the renin-angiotensin system in osteoblasts. And then after 12-hour culture in serum-free solution, MC3T3- E1 cells were divided into four groups： control, dexamethasone （DXM）, dexamethasone -- mifepristone （DXM＋ MIF） and mifepristone （MIF）. Components of the renin-angiotensin system including angiotensin type 1 receptor （AT1R）, angiotensin type 2 receptor （AT2R） and angiotensin converting enzyme （ACE） in osteoblasts were detected at the mRNA and protein levels using Western blot and PCR. The activity of ACE was also measured after 36-hour intervention. Results The results of immunohistochemistry showed that ATIR, AT2R and ACE were all expressed in osteoblasts. The activity of ACE increased obviously after dexamethasone intervention compared with that in the control group, which was blocked by mifepristone. The mRNA levels of AT1R, AT2R and ACE were increased by dexamethasone compared with those in the control group, which was inhibited by mifepristone. The protein levels of AT1R, AT2R and ACE were enhanced by dexamethasone compared with those in the control group, which was blocked when the cells were co-intervened with mifepristone. However, ACE activity and the mRNA andprotein levels of AT1R, AT2R and ACE did not change when the cells were intervened with mifepristone alone （P〉0.05）. Oonclusion The local renin-angiotensin system in osteoblasts is activated by dexamethasone through glucocorticoid receptors on osteoblasts, which may be one of the pathogenesis of glucocorticoid-induced osteoporosis.