高铁血红素对心肌缺血／再灌注损伤的防护作用及其机制

目的：在大鼠急性心肌缺血／再灌ii（I／R）模型上，观察高铁血红素在钙激活中性蛋白酶（calpain）介导的心肌I／R损伤中的作用。并初步探讨其可能的机制。方法：64只雄性SD大鼠随机8组（n：8）：假手术组（sham组）、（I／R）组、MDL28170＋I／R组、单纯MDL28170组、高铁血红素＋I／R组、单纯高铁血红素组、锌原卟啉Ⅸ＋高铁血红素＋I／R组、单纯锌原卟啉Ⅸ组。采用大鼠离体心脏Langendorff灌流技术，心脏I／R后，测定左室发展压（LVDP）、心肌梗死面积、冠脉流出液中的乳酸脱氢酶（LDH）释放量。检测calpain、血红素氧化酶（HO）、和半胱氨酸天冬氨酸蛋白酶3（caspase3）活性。Westernblot观察心肌钙蛋白酶抑制蛋白（calpastatin）蛋白表达。结果：①心肌I／R后，calpain、caspase3活性明显增高。calpain抑制剂MDL28170可抑制I／R诱导的LDH释放量增加，增高LVDP，缩小心肌梗死面积。②与单纯I／R组相比，大鼠预先给予高铁血红素后，心脏HO-1活性增加，calpain和caspase3活性下降。同时，LDH释放量减少，LVDP明显增高，心肌梗死面积缩小。③I／R组心肌calpastatin表达量明显低于对照组，高铁血红素组大鼠calpastatin表达量增高。HO-1的抑制剂锌原卟啉Ⅸ可取消高铁血红素对calpastain表达量的影响，并取消其心肌保护作用。结论：高铁血红素预处理可通过抑制calpain的激活，减轻大鼠心肌I／R损伤，其机制可能与增加calpastatin蛋白表达有关。

Protection effect and mechanism of hemin against ischemia /reperfusion injury in rat hearts

Objective： To investigate whether the cardioprotective effect of hemin against ischemia/reperfusion（I/R） injury is through the inhibition of calpain activity, and to explore its underlying mechanism. Methods：Sixty-four SD rats were randomly divided into eight groups（ n = 8） ： sham, I/R, MDL ＋ I/R, MDL, hemin ＋ I/R, hemin, and ZnPP ＋ hemin ＋ I/R, ZnPP. Langendorff isolated rat heart perfusion mod- el was used. The rat hearts were suffered from 40 min of ischemia followed by 30 min of reperfusion. After that, left ventricular developed pressure （LVDP） was recorded. Infarct size and release of lactate dehydrogenase （LDH） were measured. Calpain, heme oxygenase （HO）, and caspase 3 activities were evaluated. Expression of calpastatin protein was detected by Western blot. Results： O After suffered from is- chemia/reperfusion, the calpain activity and caspase 3 activity increased. MDL28170, an inhibitor of calpain, prevented ischemia/reperfusion induced increases in LDH and infarct size, improved the LVDP recovery. QCompared with ischema/repeffusion rat hearts, pretreatment of hemin enhanced the HO-1 activity, decreased the calpain and caspase 3 activities, declined LDH release and infarct size, and improved LVDP recovery. （~）Ischemia/reperfusion reduced the expression of calpastatin protein in rat hearts, which was inhibited by hemin preav.atment. And HO-1 inhibitor could abolish the cardioprotection of hemin. Condusion： Cardioprotective effect of hemin against ischemia/reperfusion injury is through the inhibition of calpain activity, the mechanism might be involved in the increase in calpastatin protein expression.