[The protective effect of interleukin-1 receptor antagonist on postischemic reperfused myocardium and its possible mechanism].

OBJECTIVE

To observe the dynamic changes of plasma inflammatory cytokine interleukin-1 beta (IL-1 beta) in patients with acute myocardiac infarction (AMI) before and after recanalization of the infarct related artery (IRA) and to observe the effect of recombinant human IL-1 receptor antagonist (rhIL-1ra) on the postischemic reperfused myocardium in experimental rabbits.

METHODS

(1) ELISA was used to measure the plasma IL-1 beta of 22 AMI patients, 20 males and 2 females, aged 64 +/- 12, before emergency percutaneous coronary intervention (PCI), and 12 hours and 24 hours after-intervention, and measure the plasma IL-1 beta of 8 healthy controls, 6 males and 2 females, aged 56 +/- 9. (2) Forty rabbits underwent ligation of the left circumflex branch of coronary artery (LCX) for 50 minutes and reperfusion for 4 hours after the ligatures were untied. The rabbits were randomly divided into 4 groups of 10 rabbits to be injected into the left ventricle immediately before the reperfusion with rhIL-1ra 10 mg/kg (group A), 20 mg/kg (group B), or 40 mg/kg (group C), and normal saline (control group) respectively. After reperfusion of 4 hours, the LCX was re-ligated. Evans blue was injected into the left ventricle. 15% KCl was injected intravenously to kill the rabbits. Their hearts were taken out to weigh the non-ischemic, ischemic, and necrotic cardiac muscles so as to calculate the infarct size. The myoperoxidase (MPO) activity was measured by colorimetry. Sections of myocardium were made. The number of apoptotic cardiomyocytes was evaluated by TUNEL method. The apoptotic rate of cardiomyocyte was measured by annexin V method. The DNA expression of myocardium was detected by DNA laddering method. The expressions of Bcl-2 and Bax apoptosis genes were assessed.

RESULTS

(1) The average plasma IL-1 beta level of the 22 AMI patients before emergency PCI was significantly higher than that of the controls (28 pg/ml +/- 9 pg/ml vs. 20 pg/ml +/- 11 pg/ml, P < 0.05), and became the highest 12 hours after the intervention (86 pg/ml +/- 14 pg/ml), and the high level lasted to 24 hours after emergency PCI. (2) In the ischemia-reperfusion rabbit model, the infarct size was 47% +/- 7% in the group A, 34% +/- 8% in the group B, 31% +/- 6% in the group C, and 61% +/- 11% in the control group (P < 0.05, 0.01, and 0.01 respectively). The activity of myocardial MPO was 16.6 +/- 3.6 min(-1).g.w.w(-1) in the group A, 10.9 min(-1).g.w.w(-1) +/- 1.9 min(-1).g.w.w(-1) in the group B, 7.8 min(-1).g.w.w(-1) +/- 2.2 min(-1).g.w.w(-1) in the group C, and 20.5 min(-1).g.w.w(-1) +/- 4.5 min(-1).g.w.w(-1) in the control group (P < 0.05, 0.01, and 0.01 respectively). The cardiomyocyte apoptosis evaluated by TUNEL was 38.3 n/HP +/- 7.4 n/HP in the group A, 25.6 n/HP +/- 6.8 n/HP in the group B, 12.2 n/HP +/- 3.3 n/HP in the group C, and 44.4 n/HP +/- 9.5 n/HP in the control group (P < 0.05, and P < 0.01 respectively in comparison between the group B and the control group and between the group C and the control group). The apoptotic rate by annexin V method was 11.6% +/- 2.7% in the group A; 7.7% +/- 2.4% in the group B, 4.7% +/- 1.4% in the group C, and 15.6% +/- 3.5% in the control group (P < 0.05, 0.01, and 0.01 respectively). DNA electrophoresis showed scaling ladder pattern only in the control group. The fluorescent density of the apoptosis gene Bax in myocardium was 24.9 +/- 8.2 in the group A; 15.5 +/- 3.4 in the group B, 10.6 +/- 2.5 in the group C, and 33.3 +/- 9.4 in the control group (P = 0.0298, 0091, and 0052 respectively) and no significant difference in the expression of Bcl-2 was shown among the 4 groups. Myocardial MPO was correlated with cardiomyocyte apoptosis (r = 0.86 by TUNEL, P < 0.01; r = 0.75 by Annexin V method, P < 0.05).

CONCLUSION

Inflammatory cytokine IL-1 beta is involved in myocardial ischemia-reperfusion injury. With potential therapeutic value in prevention and treatment of ischemia-reperfusion injury to myocardium, rhIL-1ra may reduce myocardial ischemia-reperfusion injury by suppression of cardiomyocytes apoptosis mediated by IL-als; 0.86 by TUNEL, P < 0.01; r = 0.75 by Annexin V method, P < 0.05).

CONCLUSION

Inflammatory cytokine IL-1 beta is involved in myocardial ischemia-reperfusion injury. With potential therapeutic value in prevention and treatment of ischemia-reperfusion injury to myocardium, rhIL-1ra may reduce myocardial ischemia-reperfusion injury by suppression of cardiomyocytes apoptosis mediated by IL-1.