Effects of Ang Ⅱ perfusion on transmural heterogeneous of Cx43 in acute myocardial ischemia reperfusion

Objective:To observe the effects of angiotensin Ⅱ(Ang Ⅱ) pefusion on transmural heterogeneity of Cx43 expression in the rabbit model with acute myocardial ischemia reperfusion(MIR),and investigate the role of rennin-angiotensin system in malignant ventricular arrhythmia induced by MIR.Methods:Twenty rabbits were randomly divided into MIR group(n=10) and Ang Ⅱ group(n=10).MIR model was produced with traditional ligation and opening of the anterior descending coronary artery in all animal.The hearts in vitro in the MIR group and the Ang Ⅱ group were perfused with simply improved Tyrode's solution and containing Ang Ⅱ Tyrode's solution respectively.90%monophasic action potential repolarization duration,transmural dispersion of repolarization.Cx43 protein(Cx43-pro) and mRNA(Cx43-Cq) expression in subepicardial,midmyocardial and subendocardial myocardium were measured in both groups.The greatest differences of Cx43-pro and Cx43-Cq among three myocardial layers were calculated and shown with △Cx43-pro and △Cx43-Cq respectively.Results:After Ang Ⅱ perfusion,90%monophasic action potential repolarization duration among three myocardial layer were significantly prolonged(P < 0.05 and P < 0.01),and transmural dispersion of repolarization also significantly increased compared with the MIR group(P < 0.05).Compare with the MIR group,three myocardial Cx43-pro and Cx43-Cq expression in the Ang Ⅱ group were significantly decreased(P < 0.05 and P < 0.01).but△Cx43-pro and △Cx43-Cq were significant increased.Conclusions:Renin-angiotensin system increases transmural heterogeneity of Cx43 expression in the rabbit model with MIR by Ang Ⅱ,and enlarge transmural dispersion of repolarization among three myocardial layers of left ventricular which induces malignant ventricular arrhythmia.

Protective effect of pioglitazone on kidney injury in diabetic rats

Objective:To investigate the protective effect of pioglitazone on kidney injury in diabetic rat model and its mechanisms.Methods:Forty healthy Sprague Dawley rats were selected and randomly divided into five groups,with 8 rats in each group.Group A served as control group and were administered with sterile citrate buffer(i.p.)as placebo.Groups B.C,D and E rats were injected(i.p.)with streptozotocin to induce type I diabetes,Diabetic rats in Group B were intragastrically administered with sterile saline solution alone.Groups C,D and E rats were iutragastrically given pioglitazone hydrochloride suspension at doses of 10,20,30 mg/kg per day.respectively.After eight weeks of treatment,all rats were anesthetized and blood was withdrawn from the abdominal aortic ofr detection of hemoglobin A_(1c),serum creatinine(SCr)and blood ures nitrogen(BUN)levels.Rats were then sacrificed and the left kidney was excised for calculation of kidney hypertrophy index(KHI),observation of renal pathological changes using light microscope and electron microscope.Mean glomerular cross-sectional areas(MGA).mean glomerular volume(MGV).glomerular basement membrane thickness and foot process fusion ratio were ealculated.RT-PCR was employed for detection of podocalyxin(PCX)protein expression.Results:Results showed that levels of hemoglobin A_(1c),BUN.SCr in Groups B,C.D and E rats were significantly higher than those in Group A(P<0.05),while BUN aud SCr levels in rats of Groups C,D and E were significantly lower than those in Group B(P<0.05).KHI,MGA and MGV levels were significantly higher in Groups B.C,D and E rats than those in Group A(P<0.05);KHI and MGA levels in Group B rats were significantly higher than those in Groups C.D and E(P<0.05)and MGV in Groups D and E was significantly lower than that in Gtoups B and C(P<0.05).Histology study showed normal glomerulus structure,morphology,volume,endothelial cells and mesangial cells as well as clear glomerular eapillary in Group A rats.Renal mesangial matrx proliferation and expansion of glomerulus cavities in Groups B.C.D and E were observed.However.damage degree in Groups C.D and E were more moderate than that iu Group B.Conclusions:Pioglitazone can reduce kidney damage in diabetic rats.which may be attributed to its role in increasing glomerular PCX protein expression and inhibiting urinary excretion of PCX,and its effect is dose dependent.

MiR-15a-5p in neutrophil exosomes promotes macrophage apoptosis through targeted inhibition of BCL2L2

Objective:To explore the possible mechanism of neutrophil exosomes regulating macrophage apoptosis.Methods:neutrophils were induced by lipopolysaccharide,inflammatory factors were detected by ELISA,the morphology of exosomes was identified by electron microscope,and the expression of mir-15a-5p in exosomes was detected by RT-PCR;Raw267.4 macrophages was treated with neutrophil exosomes and mir-15a-5p mimic respectively,CCK8 to detect cell viability,flow cytometry to detect apoptosis;The binding sites of mir-15a-5p and BCL2L2 were predicted and verified by double luciferase experiment;RT-PCR and Western blot verified that mir-15a-5p regulate the expression of BCL2L2.Results:lipopolysaccharide induced neutrophil inflammatory factors IL-2,IL-6,IL-10 and TNF-α.The morphological characteristics of exosomes were observed by electron microscope.Mir-15a-5p was significantly overexpressed in neutrophil exosomes induced by lipopolysaccharide;Lipopolysaccharide-induced neutrophil exosomes and mir-15a-5p simulants can promote raw267.4 macrophage apoptosis and inhibit its cell viability;Targetscan database predicted that mir-15a-5p and BCL2L2 had binding sites.Double-luciferase experiment verified that mir-15a-5p and BCL2L2 bound through binding sites;Mir-15a-5p mimic was transfected into raw267.4 macrophages which inhibit the expression of BCL2L2 mRNA and protein.Conclusion:inflammatory neutrophils may promote raw267.4 by secreting exosomes containing mir-15a-5p and inhibiting BCL2L2 by targeting macrophage apoptosis.This may provide a theoretical basis for further understanding the molecular mechanism of inflammatory regulation of neutrophils and macrophages.

Effect and mechanism of dexmedetomidine on ischemic arrhythmia

Objective:To explore the antiarrhythmic effect and mechanism of dexmedetomidine,a myocardialα2 receptor agonist in vitro.Methods:Fifty Wistar rats were randomly divided into five groups(n=10):sham operation group(Ctl),arrhythmia model group(Model),arrhythmia+dexmedetomidine group(Dex),arrhythmia+yohimbine+dexmedetomidine group(Yoh+Dex),arrhythmia+yohimbine group(Yoh).The Ctl group just thread left anterior descending coronary artery without ligation.Model group recorded 10 minutes of normal ECG,ligated the left anterior descending coronary artery,and continued to record the ECG for 2 hours.Dex group,Yoh+Dex group and Yoh group were ligated left anterior descending coronary artery after administration.Use BL-420E system to record ECG;Curtis and Walker arrhythmia scores were used to analyze the severity of arrhythmia;perform survival analysis according to the life span of each group of rats;after 21 days of modeling,measure the area of myocardial infarction by TTC staining.The pH value of extracellular fluid was decreased to simulate myocardial ischemia.Patch clamp technique was used to detect the action potential duration of myocardial cells.Results:Compared with the Ctl group,the arrhythmia score and myocardial infarction area in the Model group was increased(P<0.05),the mortality and myocardial infarction area were alsosignificantly reduced(P<0.05).Compared with Model group and Yoh group,the arrhythmia score of Dex group was significantly lower(P<0.001),the mortality and myocardial infarction area were significantly lower(P<0.05);Dexmedetomidine shortened QTc interval(P<0.01),APD50 and APD90(P<0.05).The α_(2) receptor blocker Yohimbine inhibited the effect of dexmedetomidine.Conclusion:Dexmedetomidine affects the action potential repolarization process by stimulating myocardial α_(2) receptors,and prevents ischemia-induced ventricular arrhythmia.