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 diabetes mellitus were established by high-fat feeding and a single peritoneal dose of streptozotocin. Forty diabetic rats were randomized equally into diabetic group, sham-operated group, sham-operated group with MRL-45696 treatment, I/R injury model group and I/R injury group with MRL-45696 treatment. The rats in MRL-45696-treated groups were subjected to daily intragastric administration of MRL-45696 (50 mg/kg) for 7 consecutive days, after which sham operation was performed or myocardial I/R injury was induced by ligation of the left anterior descending coronary artery for 30 min followed by reperfusion 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 myocyte apoptosis were detected. The levels of γ-H2AX, cleaved caspase-3, PARP-1, and PAR were detected with Western blotting, and the level of NAD was detected using colorimetry.
Results: The infarct size was significantly smaller in MRL-45696 treatment group 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 and MDA, γ-H2AX, cleaved caspase-3 and apoptotic rate in the cardiac myocytes were significantly higher than those in the other groups (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, PAR expression and cell apoptosis with significantly increased levels of SOD and NAD (P < 0.05).
Conclusions: MRL-45696 can inhibit excessive activation of PARP-1, increase intracellular level of NAD and inhibit cardiac myocyte apoptosis to alleviate myocardial I/R-induced DNA damage and reduce myocardial infarct size in diabetic rats.
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、cleaved caspase-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。
Keywords: DNA damage; MRL-45696; diabetic model; ischemia-reperfusion injury; poly(ADP-ribose) polymerase-1.