Effect of metoprolol on myocardial apoptosis after coronary microembolization in rats

BACKGROUND:Coronary microembolization(CME) is a serious complication following percutaneous coronary intervention(PCI) in patients with acute coronary syndromes.The use of metoprolol before PCI can significantly protect ischemic myocardium from myocardial damage,but the function of metoprolol in the treatment of CME is not entirely clear.This study was to explore the effect and significance of metoprolol on myocardial apoptosis and caspase-3 activation after CME in rats.METHODS:Thirty rats were randomly divided into three groups including sham-operation(control group),CME plus saline(CME group),CME plus metoprolol(metoprolol group),10 rats for each group.The CME group was induced by injecting 3 000 polyethylene microspheres(42 urn)into the left ventricle during a 10-second occlusion of the ascending aorta;the control group was injected with physiological saline instead of microembolization ball;the metoprolol or saline group was given three intravenous bolus injections before CME.Echocardiography,TUNEL staining,and Western blotting were used to evaluate cardiac function,proportion of apoptotic cells and activation of caspase-3 respectively at 6 hours after operation.RESULTS:Echocardiography parameters displayed that the metoprolol group improved cardiac function significantly compared with the CME group(PO.05).The myocardial apoptotic rate of the CME group as well as the contents of activated caspase-3 increased significantly(P<0.05),both of which were ameliorated significantly by metoprolol treatment(P<0.05).CONCLUSIONS:This study demonstrates that metoprolol can protect the myocardium during CME in rats by inhibiting apoptosis and improving cardiac function.These results suggest that the inhibition of apoptosis can be a potential therapeutic strategy for the treatment of CME.

Coronary microembolization induced myocardial contractile dysfunction through a p38 mapk pathway

Background Cathepsin S and its endogenous inhibitor cystatin C are implicated in the pathogenesis of atherosclerosis,especially in the plaque destabilization and rupture leading to acute coronary syndrome.However, whether circulating cathepsin S and cystatin C also change in association with coronary plaque morphology is unknown yet. Methods Sprague-Dawley rats were randomly divided into three groups;Sham group,CME group and SB203580 group (n=10 per group).CME rats were produced by injection of 42μm microspheres into the left ventricle with occlusion of the ascending aorta.SB203580,a p38 MAPK inhibitor,was injected into femoral vein after finishing the injection of microspheres in SB203580 group.Left ventricular Ejection Fraction was determined by echocardiography.The level of phosphorylated and total P38 MAPK in myocardium was assessed by Western Blot.Results Left ventricular(LV) Ejection Fraction was depressed at 3 hours and until up to 12 hours in CME group.The increased p38 MAPK activation was observed in CME group.The administration of SB203580 partly inhibited the p38 MAPK activity and preserved cardiac contractile function.Conclusions p38 MAPK is significantly activated by CME and the inhibition of p38 MAPK can partly preserve cardiac contractile function.

Efficacy of Dual Antiplatelet Therapy Combined with Naoxintong Capsules(脑心通胶囊) Following Coronary Microembolization Induced by Homologous Microthrombi in Rats

Objective： To evaluate the efficacy of dual antiplatelet therapy combined with Naoxintong Capsule （脑心通胶囊, NXTC） in a rat model of coronary microembolization （CME）. Methods： A total of 95 rats were randomly divided into 6 groups： control, sham-operation, CME model, NXTC, dual antiplatelet （clopidogrel and aspirin） intervention （DA）, and NXTC combined with DA （NDA） groups. The complete data in 69 rats were obtained. The number of CME, myocardial apoptosis rate, bleeding time, clotting time, and adensosine diphosphate （ADP）-induced platelet aggregation were assessed. Results： Compared with the CME group, the number of CME and myocardial apoptosis rates were significantly decreased in the NXTC, DA, and NDA groups （P〈0.01）. Compared with other intervention groups, the number of CME and myocardial apoptosis rates were the least in the NDA group （P〈0.01）, and the incidence of surgical bleeding was the highest in the DA group （P〈0.01）. Compared with the CME group, ADP-induced maximum platelet aggregation rate was significantly inhibited in the NXTC, DA, and NDA groups （P〈0.01）, both bleeding time and clotting time were significantly increased in the NXTC, DA, and NDA groups （P〈0.01）, while the above parameters were the highest in the DA group （P〈0.05）. Conclusion： The combination therapy of NXTC and DA enhanced the anti-CME effect of either therapy alone and reduced the risk of the DA therapy-associated bleeding, demonstrating an improved benefit/ risk ratio in the rat model of CME.

Shexiang Tongxin Dropping Pill(麝香通心滴丸)Reduces Coronary Microembolization in Rats via Regulation of Mitochondrial Permeability Transition Pore Opening and AKT-GSK3βPhosphorylation

Objective To investigate the protective effects of Shexiang Tongxin Dropping Pill(麝香通心滴丸,STDP)following sodium laurate-induced coronary microembolization(CME)in rats.Methods Forty rats were divided into 4 groups:the control(sham)group,CME group,low-dose STDP pretreatment group(20 mg·kg^(−1)·d^(−1)),and high-dose STDP pretreatment group(40 mg·kg^(−1)·d^(−1)).The rats were intragastric administrated with STDP 2 weeks before operation.Moreover,the histopathological alterations were observed using optical microscopy and transmission electron microscopy.Antioxidant biomarkers were analyzed by enzyme-linked immunosorbent assay.Mitochondrial functions including the mitochondrial permeability transition pore(mPTP)mtDNA copy number were determined and proteins of AKT/GSK3βwere analyzed by Western blot.Results The rats in the CME group showed a significant increase in the fibrinogen-like protein 2 expression level and mitochondrial dysfunction and a decrease in the expression level of antioxidant biomarkers(superoxide dismutase and catalase,P<0.01 for all).In contrast,the rats in the low-and high-dose STDP pretreatment groups showed a significant decrease in coronary microthrombi(P<0.05);moreover,STDP restored the antioxidant-related protein activities and mitochondrial function,inhibited mPTP opening,decreased AKT-Ser473 phosphorylation,and increased GSK3β-Ser9 phosphorylation(P<0.05 or P<0.01).Conclusion STDP may be useful for treatment of CME,possibly via regulation of mPTP opening and AKT/GSK3βphosphorylation.

IRAK1, TRAF6 and AUF1 are involved in myocardial inflammatory response after coronary microembolization in miniature swines

Background Coronary microembolization （CME） is characterized by distal microvascular occlusion. However, the inflammatory mechanisms and therapeutic targets of CME are largely unknown. Methods A total of 11 Guangxi Bama miniature swines were divided into two groups： sham （n = 5） and CME （n = 6）. Microspheres were injected into the left anterior descending artery of the CME group to make an animal model of CME. The expres- sions of microRNA-146a （miR-146a） and IRAK1, TRAF6, and AUF1 in the myocardium were detected by qPCR. Results In the CME group, microspheres, microinfarction, and inflammatory cell infiltration were found under an optical microscope. The expression levels of miR-146a were low in both groups. After CME, the expression levels of IRAK1, TRAF6, and AUF1 in the CME group were upregulated compared with those in the sham group （P 〈 0.01;P 〈 0.05;P 〈 0.05, respectively）. Conclusions AUF1, IRAK1 and TRAF6, but not miR-146a, could be involved, in myocardium inflammation following CME.

Coronary Embolization and Myocardial Microinfarction: MR Imaging and Histopathologic Characterization

Magnetic resonance imaging (MRI) has been proven to reliably assess regional perfusion and left ventricular (LV) function of microembolized myocardium. The visibility of microinfarct on delayed enhancement MRI (DE-MRI) is limited and dependent on technical and biological issues. Furthermore, MRI underestimates total microinfarct size compared with microscopy. MRI studies revealed that the presence of microemboli in pre-existing acute infarct delays infarct healing and magnifies LV remodeling. Discrimination of acute from chronic microinfarct is based on presence of inflammatory cells, edema and scar tissue, respectively. These noninvasive findings highlight the importance of prognostic utility of MRI and warrant larger clinical studies or registries to evaluate the significance of presence of focal microinfarct. Serial microscopic studies revealed that intravascular microemboli migrate into the extravascular space and this migration process is a function of time. This phenomenon may limit the use of microemboli therapy in occluding hemorrhagic blood vessels or treating tumors. Despite current standard of care, existing methods and therapies do not prevent coronary embolization nor reverse their deleterious effects.