| Objective: At present, it shows that myocardial ischemia/ reperfusion injury has a close correlation with the activation of polymorphonuclear neutrophilic leukocytes, however, many cytokines play important role in this complicated process. Carvedilol, a novel beta adrenoceptor antagonist, not only can blockadeα1-adrenoceptor andβ-adrenoceptor, but also have other usefulness which is independent of the above-mentioned contribution. By now it remains unclear if a short period's using of carvedilol can also have anti-inflammatory effects on myocardial ischemia/reperfusion injury. To investigate this question, we developed different rabbit model in vivo to observe successive change of TNF-αin blood-serum and MDA,MPO in myocardium, furthermore, histopathologic feature of each group was depicted to reflect the degree of polymorphonuclear neutrophilic leukocytes infiltrating in myocardium directly.Materials and Methods: 48 New Zealand White rabbits(2.5-3.0kg) were randomly divided into four groups: (1) Ischemia and Reperfusion group (IR group, n=12, normal saline 5m1/d): The group was divided into three subunits furthermore according to the different ways of the following treatments, the left ventricular branches of coronary were ligated and obstructed for 40 minutes, obstructed for 40 minutes and reperfused for 40 minutes, obstructed for 40 minutes and reperfused for 120 minutes, moreover, each subunit was composed by four rabbit models; (2) Carvedilol precondition group (CAR group, n=12, carvedilol 3mg/kg/d): The same model as IR group; (3) Ischemic precondition group (IPC group, n=12, normal saline 5m1/d): The left ventricular branches of coronary were obstructed for 5 minutes and reperfused for 5 minutes thrice, then the subunits were completed in the same ways as IR group and CAR group; (4) Sham operated group (Sham group, n=12, normal saline 5m1/d): The left ventricular branches of coronary artery were falsely ligated and three subunits were obtained at the same points of IR group and CAR group. After surgical procedures, we detected the concentration of TNF-αin blood-serum and MDA,MPO in myocardium separately. We also chose some models for histological examination (stained with hematoxylin and eosin) of the ischemic myocardial tissue. All data were presented as mean士SD. The statistical significance of the changes in different models were analyzed by SPSS11.5 statistics software. A value of P<0.05 was accepted as statistically significant.Results:1 The concentration changes of MDA in myocardiumOver time, the concentration of MDA in each group increased. But statistical differences occurred only in IR group, CAR group and IPC group: [(4.79±0.12)vs (9.01±0.51 )vs(22.56±1.59)]nmol/mgprot; [(4.69±0.12)vs (6.41±0.54)vs (13.92±0.53)]nmol/mgprot; [(4.71±0.12)vs(6.96±0.45)vs (14.90±0.65)] nmol/mgprot,(F=370.29,491.98,541.60, P<0.01). At the same point, compared with the Sham, CAR and IPC groups, the concentration of MDA in IR group was the highest, and statistical differences were found at reperfusion for 40 minutes and 120 minutes points ( F=59.07,257.80, p<0.01). At the points of reperfusion for 40 minutes and 120 minutes, statistical significances of MDA were found between CAR group and Sham group, IPC group and Sham group (p<0.01), not found between CAR group and IPC group(p=0.13, 0.25).2 The concentration changes of MPO in myocardiumOver time, the concentration of MPO in each group increased. But statistical differences occurred only in IR group, CAR group and IPC group: [(2.60±0.33)vs (5.15±0.85 )vs(8.63±0.25)] mU/mgprot; [(2.54±0.19)vs (4.17±0.78)vs (6.66±0.19)]mU/mgprot; [(2.59±0.30)vs(3.80±0.23)vs (6.94±0.22)] mU/mgprot,(F=498.00,572.71,313.52, p<0.01). At the same point, compared with the Sham, CAR and IPC groups, the concentration of MPO in IR group was the highest, and statistical differences were found at reperfusion for 40 minutes and 120 minutes points(F=13.49, 540.19, p<0.01). At the points of reperfusion for 40 minutes and 120 minutes, statistical significances of MPO were found between CAR group and Sham group, IPC group and Sham group (p<0.01), not found between CAR group and IPC group(p=0.39, 0.10).3 The concentration changes of TNF-αin blood-serumOver time, the concentration of TNF-αin each group increased. But statistical differences occurred only in IR group, CAR group and IPC group: ([12.47±0.99)vs (23.01±0.82 )vs(45.18±1.09)] pg/ml; [(11.14±0.97)vs (15.34±1.15)vs (33.88±0.99)]pg/ml; [(11.64±0.64)vs(16.77±0.66)vs (35.30±0.95)] pg/ml,(F=1177.67,540.28,1063.94, p<0.01). At the same point, compared with the Sham, CAR and IPC groups, the concentration of TNF-αin IR group was the highest, and statistical differences were found at reperfusion for 40 minutes and 120 minutes points(F=101.83,795.40, P<0.01). At the points of reperfusion for 40 minutes and 120 minutes, statistical significances of TNF-αwere found between CAR group and Sham group, between IPC group and Sham group (p<0.01), not found between CAR group and IPC group(p=0.06, 0.07).4 Histopathologic feature of each group HE stained(10×40) Normal myocardium: myocardial fibre arranged in order, with regular bouncary. I/R group: At ischemia for 40 minutes point, few polymorphonuclear neutrophilic leukocytes infiltrated in myocardial interstitium and adhered to vascular endothelial cells of big blood vessel. Myocardial edema could be observed in ischemic region; At reperfusion for 120 minutes point, myocardial interstitium bleeding, sarcoplasm liquefaction and necrosis could be observed, lots of polymorphonuclear neutrophilic leukocytes infiltrated in myocardial interstitium. CAR and IPC group: At reperfusion for 120 minutes point, myocardial edema, degeneration and some of sarcoplasm liquefaction could also be observed, few of polymorphonuclear neutrophilic leukocytes infiltrated in myocardial interstitium and adhered to vascular endothelial cells of blood vessel.Conclusion:1 From this experiment, we could see that over time, the concentrations of MDA, MPO and TNF-αin IR, CAR and IPC groups were increasing. It showed that myocardium injury increased with the accelerating of myocardial inflammatory activity.2 At different points, the concentrations of MDA, MPO and TNF-αin CAR and IPC groups were lower than that in IR group. The degrees of polymorphonuclear neutrophilic leukocytes infiltration were also depressed. It showed that the therapy of carvedilol and ischemic precondition could effectively inhibit TNF-αexpression, diminish polymorphonuclear neutrophilic leukocytes infiltration, which proved the strong anti-inflammatory effects of carvedilol on ischemia/ reperfusion injury, partly explaining its mechanisms of myocardium protection. Its anti-inflammatory effects perhaps were related to the inhibition of NF-κB, reducting the expression of ICAM-1 and TNF-α, protection of vascular endothelial cell function and improvement of NO etc.3 No statistical difference was found between CAR and IPC groups in short period. It implied that carvedilol could prevent myocardial ischemia/reperfusion injury effectively, expected to be a theoretical support for its applying on clinic more widely.
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