The Research Of Leptin On Myocardial Ischemia Reperfusion Injury In Mice

Objective:To monitor the changes of interleukin-6(IL-6) and tumornecrosis factor-alpha (TNF-α) levels in the process of myocardial ischemiareperfusion injury(MIRI) in mice and the leptin pretreatment effects on them,and to explore the effects of leptin and tea polyphenols pretreatment on MIRI inmice and cold/hot myocardial ischemia reperfusion injury(MIRI) in a murinecardiac transplant model.Methods:1.Forty males C57BL/6mice were randomly divided intosham-operation group,MIRI model group(established by blocking left coronaryartery anterior descending branch for30min followed by reperfusion), leptinpretreatment group (Leptin+MIRI group),（established by injectingintraperitoneally leptin at30min before ischemia）and leptin post-treatmentgroup (MIRI+Leptin group)(established by injecting intraperitoneally leptin at30min after reperfusion).The blood and heart samples were obtained from eachmouse at3h and6h after reperfusion.The serum IL-6and TNF-α levels and thelevels of leptin in cardiac muscle and serum were detected.2. Syngeneic heart transplants were performed in30male C57BL/6micesand were randomized into3groups:①Cardiac transplant group;②Leptin pretreatment group,Leptin50μg/kg in200μl NS injected intraperitoneallybefore transplantation (at about30min before reperfusion);③MIRI group.Thegrafts were retrieved at6h after reperfusion. Grafts and serum samples werecollected for leptin measurement, cytokines analysis and histological analysis toassess intra-graft inflammation.3. Forty male C57BL/6mice were randomly divided into four groups:(1)The control group.(2) The myocardial ischemia reperfusion group (MIRI group).(3) The tea polyphenols group.(4) The leptin pretreatment group. Heart sampleswere harvested from each mouse at6hours after reperfusion.We then analyzedthe samples for leptin level and NOX-4mRNA expression, myeloperoxidase(MPO) level, hydrogen peroxide(H2O2) and malondialdehyde (MDA) contentsand superoxide dismutase (SOD) activity.Results:1.The serum IL-6and TNF-α levels at3h and6h were increased inLeptin+MIRI group[(420.1±30.8)pg/ml,(320.1±30.8)pg/ml;(6.2±1.9)pg/ml,(7.0±2.0)pg/ml,P＜0.01] compared with sham-operation group[(12.3±5.8)pg/ml,(13.1±5.9)pg/ml;(6.2±1.9)pg/ml,(7.0±2.0)pg/ml,P＜0.01] but weredecreased compared with MIRI model group[(596.6±88.2)pg/ml,(686.2±110.2)pg/ml;(87.3±16.1)pg/ml,(100.3±24.1)pg/ml,P＜0.01]; the leptin level in cardiacmuscle and serum at3h and6h were increased in Leptin+MIRI group[(8.39±4.19)ug/g,(9.21±4.56)ug/g;(14.59±2.68)ug/g,(16.01±3.15)ug/g,P＜0.05]compared with sham-operation group[(1.54±0.70)ug/g,(1.61±0.81)ug/g;(2.61±1.12)ug/g,(2.73±1.52)ug/g,P＜0.05] but were decreased compared withMIRI model group[(16.02±4.22)ug/g,(18.02±5.20);(31.76±6.10) ug/g,(36.11±6.88),P＜0.01].2.The serum troponin I,tumor necrosis factor-alpha, interleukin-1β andinterleukin-6levels and myocardial myeloperoxidase level are not obviouslydifferences（P＞0.05）. 3. Tea polyphenols significantly reduce the myocardial tissue of leptinlevel(P<0.01)、NOX-4mRNA expression(P<0.01)、MPO activity(P<0.01)、H2O2and MDA contents(P<0.01)and increase SOD activity(P<0.01).Conclusions:1.Leptin pretreatment can reduced the serum IL-6and TNF-αexpressions, thus may have cardiac muscle protection, and leptin pretreatmentcan alleviate myocardial ischemia reperfusion injury (MIRI).2. Pretreatment of leptin is a feasible and effective method of attenuatingischemia/reperfusion injury and inflammatory reaction, protecting cardiacfunction.The differences of leptin pretreatment on cold/hot myocardial ischemiareperfusion injury in mice were not statistically significant.3. Tea polyphenols could help prevent myocardial damage on myocardialischemia reperfusion injury in mice. This cardiac protection effect is mediated,in part, via suppression of the leptin level、the neutrophils gathering andinfiltration and ROS generation.