Downregulation of cardiac PIASy inhibits Cx43 SUMOylation and ameliorates ventricular arrhythmias in a rat model of myocardial ischemia/reperfusion injury

Background:Dysfunction of the gap junction channel protein connexin 43(Cx43)contributes to myocardial ischemia/reperfusion(I/R)-induced ventricular arrhythmias.Cx43 can be regulated by small ubiquitin-like modifier(SUMO)modification.Protein inhibitor of activated STAT Y(PIASy)is an E3 SUMO ligase for its target proteins.However,whether Cx43 is a target protein of PIASy and whether Cx43 SUMOylation plays a role in I/R-induced arrhythmias are largely unknown.Methods:Male Sprague-Dawley rats were infected with PIASy short hairpin ribonucleic acid(shRNA)using recombinant adeno-associated virus subtype 9(rAAV9).Two weeks later,the rats were subjected to 45 min of left coronary artery occlusion followed by 2 h reperfusion.Electrocardiogram was recorded to assess arrhythmias.Rat ventricular tissues were collected for molecular biological measurements.Results:Following 45 min of ischemia,QRS duration and QTc intervals statistically significantly increased,but these values decreased after transfecting PIASy shRNA.PIASy downregulation ameliorated ventricular arrhythmias induced by myocardial I/R,as evidenced by the decreased incidence of ventricular tachycardia and ventricular fibrillation,and reduced arrythmia score.In addition,myocardial I/R statistically significantly induced PIASy expression and Cx43 SUMOylation,accompanied by reduced Cx43 phosphorylation and plakophilin 2(PKP2)expression.Moreover,PIASy downregulation remarkably reduced Cx43 SUMOylation,accompanied by increased Cx43 phosphorylation and PKP2 expression after I/R.Conclusion:PIASy downregulation inhibited Cx43 SUMOylation and increased PKP2 expression,thereby improving ventricular arrhythmias in ischemic/reperfused rats heart.

鞘内注射吗啡预处理激活大鼠δ、κ、μ受体致心肌保护

背景鞘内注射小剂量吗啡可产生与静脉注射吗啡相似的心肌保护作用，但鞘内注射吗啡预处理（IT—MPC）与缺血预处理（IPC）作用强度的差别还未知，IT-MPC是否由阿片类受体所介导也未阐明。因此，本实验比较IT—MPC与IPC作用强度差别并探讨阿片类受体的作用。方法80只SD大鼠麻醉后开胸，成功置入鞘内导管后随机分为13组（n=6—7）。IPC组接受3次5分钟缺血-5分钟再灌注的心肌IPC（阻闭左冠状动脉），随之给予30分钟缺血-2小时再灌注诱导心肌缺血再灌注（IR）损伤。IT-MPC组按剂量不同分为4个亚组（分别是0．03、0．3、3及30μg／kg），以3次5分钟注射-5分钟间停的模式平均注入鞘内，随之诱导IR损伤。静脉注射吗啡预处理组（IV-MPC）组经静脉给予吗啡300μg／kg，对照组鞘内给予10μl生理盐水。受体阻滞剂组选择在IT—MPC（3μg/kg）前分别给予选择性δ、κ、μ受体阻滞剂NTD、nor-BNI及CTOP，以评价阿片类受体亚型的作用。通过2，3，5-tripheny ltetrazolium染色，计算心肌梗死面积（IS），即梗死心肌占缺血危险区（AAR）的百分比。结果与对照组相比，鞘内注射0．3～30μg／kg吗啡降低心肌IS，3组IS／AAR分别为33％±10％（0．3μg／kg）、29％±10％（3μg／kg）、29％±16％（30μg/kg），对照组为53％±8％（P〈0．01）。IT-MPC降低心肌IS／AAR程度与IV-MPC（33％±6％，P=0．84）及IPC（22％±4％，P=0．41）相近。注射选择性受体阻滞剂后，由IT-MPC（3μg/kg）产生的心肌预处理效果降低（NTD＋IT-MPC，50％±9％：nor-BNI＋IT-MPc，43％±6％；CTOP＋IT—MPC，53％±9％；与对照组相比，P=0．14）。结论IT—MPC产生与IPC及IV—MPC相近的心肌保护作用，其机制涉及到δ、κ、μ受体。

Adiponectin:mechanisms and new therapeutic approaches for restoring diabetic heart sensitivity to ischemic post-conditioning

Systemic inflammatory response following myocardial ischemia-reperfusion injury(IRI)to a specific organ may cause injuries.Ischemic post-conditioning(IPostC)has emerged as a promising method for myocardial protection against IRI both in experimental and in clinical settings.Enhancement of endogenous nitric oxide(NO)is one of the major mechanisms by which IPostC confers cardioprotection.However,the sensitivity of the diabetic heart to IPostC is impaired and the underlying mechanism is unknown.Adiponectin(APN)is an adipocyte-derived plasma protein with anti-diabetic and anti-inflammatory properties.Plasma levels of APN are decreased in obese subjects and in patients with type 2 diabetes.APN supplementation has been shown to increase NO production and attenuate myocardial IRI in normal(non-diabetic)animals.However,the effect of APN on myocardial injury in diabetic subjects,especially its potential in restoring the sensitivity of the diabetic heart to IPostC has not been investigated.In the current paper,we discussed the possible reasons why the myocardium of diabetic subjects loses sensitivity to IPostC and also highlighted the potential effectiveness and mechanism of APN in restoring IPostC cardioprotection in diabetes.This review proposes to conduct studies that may facilitate the development of novel and optimal therapies to enhance cardioprotection in patients with severe diseases such as diabetes.