血管紧张素Ⅱ诱导RAW264.7细胞Toll样受体4表达及髓过氧化物酶活性的机制研究

AngiotensinⅡ induces toll-like receptor 4 expression and myeloperoxidase activity in RAW264.7 cells

目的:探讨血管紧张素Ⅱ(AngⅡ)对RAW264.7细胞Toll样受体4(TLR4)mRNA、蛋白表达及髓过氧化物酶(MPO)活性的影响及其致炎致动脉粥样硬化(AS)机制。方法:体外培养RAW264.7细胞,用不同浓度的AngⅡ(1、10、100、1000nmol/L)及100μg/L脂多糖(LPS)刺激RAW264.7细胞24h后,RT-PCR法测RAW264.7细胞TLR4 mRNA水平,Western blot检测RAW264.7细胞TLR4蛋白表达,比色法测细胞培养上清中MPO活性。同时,预先加入不同剂量的TLR4阻断剂(1mg/L、5mg/L)后,再用AngⅡ(100nmol/L)刺激RAW264.7细胞24h,检测细胞培养上清中MPO活性。结果:AngⅡ浓度依赖性地增加RAW264.7细胞TLR4 mRNA及蛋白表达(P<0.01),LPS也可诱导RAW264.7细胞TLR4 mRNA及蛋白表达(P<0.01);AngⅡ浓度依赖性地升高RAW264.7细胞MPO活性(P<0.01),LPS也可升高RAW264.7细胞MPO活性(P<0.01),而TLR4阻断剂明显抑制AngⅡ这一效应(P<0.01)。结论:AngⅡ上调RAW264.7细胞TLR4表达,通过跨膜受体TLR4诱导MPO分泌,加重炎症反应,促进AS的形成和发展。

AIM： To investigate the effects of angiotensinⅡ （AngⅡ） on mRNA and protein expressions of toll-like receptor 4 （TLR4） and myeloperoxidase （MPO） activity in RAW264.7 cells, and explore its pro-inflammatory and pro-atherosclerotic mechanisms. METHODS： Murine RAW264.7cells were cultured and stimulated with different concentrations （1, 10, 100 and 1 000 nmol/L） of Ang Ⅱor LPS （100 μg/L） for 24 h. TLR4 mRNA levels were analyzed by RT-PCR, and TLR4 protein expression was measured by Western blot. MPO activity in the supernatant was assayed with colorimetry. Then, the cells were pretreated with TLR4 blocker （1 and 5 mg/L） for 1 h prior to stimulation with 100 nmol/L Ang Ⅱ for 24 h, and MPO activity in the supernatant was detected. RESULTS： Ang Ⅱ increased mRNA and protein expressions of TLR4 in RAW264.7 cells in concentration-dependent manner （P〈0.01）, and LPS also induced mRNA and protein expressions of TLR4 in RAW264.7 cells （P〈0.01）. In addition, AngⅡ concentration-dependently elevated MPO activity in RAW264.7 cells （P〈0.01）, and LPS also enhanced MPO activity of RAW264.7 cells （P〈0.01）, but the TLR4 blocker significantly antagonized the effect of Ang Ⅱ on MPO activity （P〈0.01）. CONCLUSION： Ang Ⅱupregulates TLR4 expressions, and induces MPO secretion via TLR4 in RAW264.7 cells, which mediate the pro-inflammatory effect of AngⅡ to contribute formation and development of atherosclerosis.