MRL-45696 减轻2 型糖尿病大鼠心肌缺血再灌注后的DNA损伤

目的研究摄食二磷酸腺苷核糖聚合酶抑制剂MRL-45696是否减轻2型糖尿病大鼠心肌缺血/再灌注后DNA的损伤。方法大鼠高糖高脂饲料喂食8 周后腹腔注射链脲佐菌素（STZ）（30 mg/kg），构建2型糖尿病大鼠模型，选取2型糖尿病大鼠40只，随机分为糖尿病组（DM）、假手术组（S）、MRL-45696治疗+假手术组（NO）、缺血再灌注损伤模型组（MI/R）、MRL-45696治疗+缺血再灌注损伤组（MRL），每组各8只。灌胃给予2型糖尿病大鼠MRL-45696 (50 mg/kg·d)，1周后以大鼠冠状动脉左前降支结扎30 min 再灌注120 min 的方法制作心肌缺血再灌注损伤模型。检测大鼠血浆心肌肌钙蛋白Ⅰ（cTnI）、血清肌酸激酶（CK）、血清乳酸脱氢酶（LDH）活性和心肌梗死范围、细胞凋亡比例、丙二醛（MDA）、超氧化物歧化酶活性（SOD）。Western blot检测γ-H2AX、cleaved caspase-3、PARP-1、PAR；比色法检测大鼠心肌组织中烟酰胺腺嘌呤二核苷酸（NAD）水平（以NAD+/NADH比例代表）。结果MRL组心肌梗死面积显著小于MI/R 组（P<0.05），MI/R 组cTnI、CK、LDH、MDA、γ-H2AX、cleavedcaspase-3表达水平及细胞凋亡较其它组显著升高（P<0.05），而SOD水平明显降低（P<0.05）；与MI/R组相比，MRL组大鼠cTnI、CK、LDH、MDA、γ-H2AX、cleaved caspase-3、PARP-1、PAR表达水平及细胞凋亡明显降低，SOD及NAD表达水平明显升高，差异有统计学意义（P<0.05）。结论糖尿病加重大鼠心肌细胞缺血再灌注后DNA损伤，MRL-45696 可能通过抑制糖尿病大鼠PARP-1的过度激活，减轻心肌细胞缺血再灌注损伤，减少心肌梗死面积。

Poly(ADP-ribose) polymerases-1 inhibitor MRL-45696 alleviates DNA damage aftermyocardial ischemia-reperfusion in diabetic rats

Objective To study the protective effect of MRL-45696, an inhibitor of poly(ADP- ribose) polymerase-1 (PARP-1),against DNA damage after myocardial ischemia/reperfusion (I/R) in diabetic rats. Methods Rat models of type 2 diabetesmellitus were established by high-fat feeding and a single peritoneal dose of streptozotocin. Forty diabetic rats wererandomized equally into diabetic group, sham-operated group, sham-operated group with MRL-45696 treatment, I/R injurymodel group and I/R injury group with MRL-45696 treatment. The rats in MRL-45696-treated groups were subjected to dailyintragastric administration of MRL-45696 (50 mg/kg) for 7 consecutive days, after which sham operation was performed ormyocardial I/R injury was induced by ligation of the left anterior descending coronary artery for 30 min followed byreperfusion for 120 min. The range of myocardial infarction, plasma cardiac troponin I (cTnI), serum creatine kinase (CK),lactate dehydrogenase (LDH) activity, malondialdehyde (MDA), superoxide dismutase (SOD) activity, and cardiac myocyteapoptosis were detected. The levels of γ-H2AX, cleaved caspase-3, PARP-1, and PAR were detected with Western blotting, andthe level of NAD was detected using colorimetry. Results The infarct size was significantly smaller in MRL-45696 treatmentgroup than in I/R injury group (P<0.05). In I/R model group, the levels of cTnI, CK, and LDH in the plasma or serum andMDA, γ-H2AX, cleaved caspase-3 and apoptotic rate in the cardiac myocytes were significantly higher than those in the othergroups (P<0.05), and SOD activity was significantly decreased (P<0.05). Compared with I/R model group, the rats with MRL-45696 treatment showed significantly decreased levels of cTnI, CK, LDH, MDA, γ-H2AX, cleaved caspase-3, PARP- 1, PARexpression and cell apoptosis with significantly increased levels of SOD and NAD (P<0.05). Conclusion MRL-45696 can inhibitexcessive activation of PARP-1, increase intracellular level of NAD and inhibit cardiac myocyte apoptosis to alleviatemyocardial I/R-induced DNAdamage and reduce myocardial infarct size in diabetic rats.