Effect Of Atorvastatin On ERK1/2 Signaling Pathway In Rats With Myocardial Injured Induced By Coronary Microemboliation

Objective To research the mechanism of the extracellular signal-regulated kinases1/2(ERK1/2) pathway of regulation myocardial inflammation in rats with Coronary microembolization(CME), and to explore the effect of atorvastatin on the signal transduction pathway of the intervention and its impact on the protective effect of cardiac function.Methods Coronary microembolization models were produced by injection of 42μm microspheres(3000) into the left ventricle while occlusion the ascending aorta. The Sprague-Dawley rats were randomly divided into the sham group(S group), coronary microembolization group(CME group), Gavage control group, atorvastatin group, atorvastatin loading dose group and PD98059 group(n=15,respectively). The atorvastatin group, atorvastatin loading dose group and Gavage control group rats were orally treated for seven days with 10 mg/kg of atorvastatin or vehicle, once a day. Then atorvastatin loading dose group received a loading dose of 20 mg/kg atorvastatin 4 hours before operation. Before 4 hours operation, the rats of PD98059 group were injected with 1mg/kg of PD98059(the specific inhibitor of ERK1/2) in tail vein. Echocardiography was used to evaluate Cardiac function. Sections of myocardium were stained with hematoxylin-eosin for evaluation Inflammatory cell infiltration. mRNA expression of TNF-αand Macrophage Migration Inhibitory Factor(MIF) in myocardium were semiquantitative analysis by RT-PCR.The protein of p-ERK1/2 in myocardium were detected by Western blot and immunohistochemistry. DNA-binding activity of NF-κB was assessed by electrophoretic mobility shift assay (EMSA).Results 1. CME Significantly activated inflammatory response in myocardial tissue, just as increasing the inflammatory cytokines expression and recruiting the Inflammatory cells. The mRNA of MIF and TNF-αexpression and Inflammatory cells infiltration in CME group and Gavage control group were significantly increased comparing to S group(respectively P<0.05), following with Cardiac function dramatically decreased. Echocardiography showed that Left ventricular ejection fraction(LVEF),short axis fractional shortening(FS) and Cardiac output(CO) decreased ( S group respectively 82.69±3.50%, 42.91±2.00%, 0.164±0.005L/min, CME group respectively 72.97±3.20%, 37.69±1.68%, 0.095±0.015 L/min;all P<0.05), but Left ventricular end-diastolic diameter(LVEDd) increased after CME(S group and CME group respectively 5.10±0.18mm and 6.17±0.16mm;P<0.05). Likewise, the phosphorylation level of the ERK1/2 obviously increased. Comparing to S group, expression of p-ERK1/2 in CME group and Gavage control group were significantly increased (respectively P<0.05) and Immunohistochemistry show that the protein of p-ERK1/2 mainly expression in nucleus of myocardial cell, the cells express a small amount of solute. However, CME was not effect the protein of ERK1/2 expression. EMSA results showed that the NF-κB activity significantly increased after CME, suggesting that NF-κB transcription inflammatory cytokines involved in damaging cardiac function caused by CME.2. Phosphorylation level of the ERK1/2, NF-κB activation, MIF and TNF-αmRNA expression and the amount of inflammatory cell infiltration were dramatically decreased after continuous treating with atorvastatin for seven days before CME, accompanied by significant improvement in cardiac function(The LVEF, FS, CO, LVEDd of atorvastatin group respectively 76.65±4.10%, 39.74±2.23%, 0.141±0.165L/min, 5.65±0.26mm,Compared to Gavage control group ;all P<0.05). We would get greater efficiency after treatment once more doubling the amount of atorvastatin 4 hours before operation(The LVEF, FS, CO and LVEDd of atorvastatin loading dose group respectively 79.99±4.26%, 41.56±2.06%, 0.153±0.014L/min and 5.47±0.26mm,Compare to atorvastatin group all P<0.05).3. Treating with PD98059 got the same efficiency with atorvastatin in rats with CME, for instance, the protein of ERK1/2 expression and NF-κB DNA-binding decreased, TNF-αmRNA expression reduced,Inflammatory cell infiltration diminished and the Cardiac function were also Improved(The LVEF, FS, CO, LVEDd of PD98059 group respectively 76.46±4.46%, 39.47±2.26%, 0.139±0.019L/min, 5.65±0.31mm,Compare to CME group; all P<0.05), but MIF mRNA expression were not effected by PD98059 in CME rats. So we speculate that MIF is not involved in ERK1 / 2 signaling pathway or its regulation as ERK1 / 2 signaling pathway upstream.Conclusion The present study demonstrates a novel role of ERK1/2 signaling pathway in promoting myocardium inflammation and dysfunction in CME. Atorvastatin treatment, especially loading dose of atorvastatin 4 hours before operation significantly reduced the expression of inflammatory cytokines and inflammatory cell infiltration, as well as significant improvement in cardiac function, of which mechanism may be blocking the ERK1/2 signaling pathway.