维生素D对大鼠心血管保护作用及机制

Mechanism of protective effect of vitamin D on cardiovascular tissue in rats with myocardial infarction

目的了解维生素D对大鼠急性心肌梗死的保护作用机制。方法选取脂多糖(LPS)诱导A7R5细胞Toll样受体(TLR)4表达量最高的浓度和时间点,应用1×10-7mol/L的1,25(OH)2D3进行干预。建立大鼠心肌梗死模型,随机分为2组,I组:心肌梗死模型组(n=16)、II组:维生素D治疗组(n=16),另设III组:假手术组(n=15)。4w后处死大鼠,观察大鼠心肌梗死面积(MIS)及心肌血清酶学变化。real-time PCR和Western blot方法检测TLR4、髓样分化因子(MyD)88和核因子活化B细胞κ轻链增强子(NF-κB)的mRNA和蛋白表达。结果在LPS诱导基础上,维生素D处理0、12和24 h后,TLR4、MyD88和NF-κB的mRNA水平分别为(22.0±5.1)、(15.1±5.1)和(8.0±4.2);(28.8±5.7)、(20.1±4.4)和(14.0±3.7);(25.2±5.3)、(17.7±4.5)和(10.2±3.7);TLR4、MyD88和NF-κB的蛋白水平变化同mRNA水平一致;维生素D可使实验性心肌梗死大鼠的MIS从(37.89±3.24)降至(12.25±1.34)(P<0.01),并改善心肌血清酶学变化(P<0.01);维生素D能够下调实验性心肌梗死大鼠心肌组织TLR4、MyD88和NF-κB的mRNA表达,分别从(4.61±0.42)、(3.81±0.36)和(3.86±0.51)降至(2.73±0.25)、(2.17±0.41)和(1.63±0.39);TLR4、MyD88和NF-κB的蛋白水平变化同mRNA水平一致。结论维生素D通过下调TLR4表达及相关的Myd88和NF-κB途径对大鼠的心血管产生保护作用。

Objective To explore the mechanism of protective effect of vitamin D on cardiovascular tissue in the rats with myocardial infarction. Methods With a pre-experiment, the best time of 1,25 dihydroxyvitamin D3 （ 1,25 [ OH ] 2D3 ） intervention was determined by observing the expressions of Toll like receptor （ TLR4 ） and its related signaling molecules in A7R5 cells treated with both lipopolysaccharide （LPS） and 1 × 10^-7 mol/L 1,25 （OH）2D3. The rats were randomly divided into 2 groups ： myocardial infarction （ MI ） model group （ n = 16 ） and 1, 25 （ OH ） 2D3 treatment group （n = 16）, and a sham-operation group was used as control. The rats in 1,25 （OH）2 D3 treatment group were admin- istered with 1 ×10^-7 mol/L 1,25（OH）2D3 by gavage 48 hours after the MI operation and the rats in other two groups were treated with normal saline; the treatments were performed once a day for 4 weeks. At the end of the treatments, myo cardial infarct size （MIS） and cardiac serum enzymes of the rats were detected. The level of TLR4, myeloid differentiation factor 88 （MyD88）, and nuclear factor kappalight-chain-enhancer of activated B cells （NF-κB） were detected with real-time PCR and Western blot. Results Vitamin D had inhibitive effect on LPS-induced elevations of TLR4, MyD88 and NF-κB in A7R5 cells（ P 〈 0.01 ）. Vitamin D could decrease MIS significantly（ P 〈 0. 01 ） and improve the cardiac serum enzymes（ P 〈 0. 01 ）. Vitamin D could inhibit the expressions of TLR4 ,MyD88 and NF-κB in myocardial tissue （ P 〈 0. 01 ）. Conclusion Vitamin D has cardiovascular protective effect through downregulating TLR4 and its relation signaling molecules MyD88 and NF-κB.