血管钠肽抑制内质网应激减轻糖尿病大鼠缺血/再灌注心肌损伤

Vasonatrin peptide inhibits endoplasmic reticulum stress and attenuates myocardial ischemia/reperfusion injury in diabetic rats

目的观察人工合成的钠尿肽——血管钠肽(VNP)对糖尿病(DM)大鼠心肌缺血/再灌注(MI/R)损伤的影响及机制。方法高脂饲料喂养SD大鼠4周后,注射链脲霉素STZ(25 mg/kg,i.p.),1周后随机血糖≥11.1mmol/L为DM模型构建成功,常规制备MI/R(30 min/4 h)模型。将大鼠随机分为4组:假手术组、MI/R组、DM+假手术组、DM+MI/R组。多导生理记录仪检测左室压上升/下降最大速率(±LVd P/dtm ax),Evans blue-TTC双染色法检测心肌梗死面积,TUNEL法进行心肌细胞凋亡测试、试剂盒检测caspase-3活性,Western blot检测GRP78、Chop和PKG等蛋白表达。结果与对照组相比,DM大鼠MI/R心肌损伤加重。VNP治疗(再灌前10 min,给予100μg/kg,i.v)可显著减轻DM大鼠MI/R损伤,包括增强±LVd P/dtm ax,降低心梗范围、死亡率与Caspase-3活性(n=8,P<0.05)。此外,VNP可降低内质网应激相关蛋白GRP78、CHOP表达(n=3,P<0.01)。VNP上述效应可同时被PKG阻断剂KT-5823(再灌前20 min,给予0.5 mg/kg,i.p)抑制、并被c GMP衍生物8-Br-c GMP(1 mg/kg)模拟(P<0.05,P<0.01)。用内质网应激抑制剂TUDCA(50 mg/kg)预处理DM大鼠,并不能增强VNP的心肌保护作用。结论 VNP治疗可减轻DM性MI/R损伤,其机制可能与通过c GMP-PKG信号抑制内质网应激有关,提示VNP对DM性缺血性心脏病具有潜在治疗价值。

AIM To investigate the effects of vasonatrin peptide （VNP） on myocardial ischemia/reper- fusion （MI/R） injury in diabetic rats and to elucidate its mechanisms. METHODS High-fat diet and low-dose streptozotocin （STZ, 25 mg/kg, i.p. ） injection induced diabetic Sprague Dawley rats with random blood glucose level 〉 11.1 mmol/L 1 week later. Left anterior descending coronary artery was ligated for 30 min and reperfused for 4 h to establish the in vivo model of ischemia-reperfusion. RESULTS VNP treatment （100μg/kg, i. v. , 10 min before R） significantly improved ± LV dP/dtmax and LVSP and reduced LVEDP, apoptosis index, caspase-3 activity, plasma CK and LDH activities. Moreover, VNP inhibited endoplasmic reticulum （ER） stress by suppressing GRP78 and CHOP. These effects were mim- icked by 8-Br-cGMP, a cGMP analogue but were inhibited by KT-5823, a selective inhibitor of PKG. In addition, pretreatment of DM rats with TUDCA, a specific inhibitor of ER stress, did not further promote the cardioprotective effect of VNP. CONCLUSION VNP protects diabetic heart against MI/R injury by inhibiting ER stress via cGMP-PKG signaling pathway. These results suggest that VNP may have some potential therapeutic value for diabetic patients with ischemic heart disease.