[Cardioprotection of recombinant human erythropoietin pretreatment on ischemia-reperfused hearts and mechanism thereof: experiment with rats].

OBJECTIVE: To study the cardioprotective effects of recombinant human erythropoietin (rhEPO) on heart with ischemia-reperfusion (I-R) injury and the possible mechanism.

METHODS: 156 SD rats, except 36 in the sham operation group, underwent ligation of the left descending coronary artery for 30 minutes and then reperfusion for 3 hours. 108 rats were randomly divided into 3 equal groups IR + rhEPO group (Group C, intraperitoneally injected with rhEPO 5000 U/kg 24 h before IR insult), IR group (Group B), and sham-operation group (Group A). By the end of reperfusion blood sample were collected by cardiac puncture to detect the plasma content of MB isoenzyme of creatine kinase (CK-MB). Before ischemia, after ischemia, and 30, 60, 120, and 180 min after reperfusion the hearts of 6 rats from each group were killed respectively with their hearts taken out. Another 12 rats were randomly divided into Groups B and C as described above to undergo IR insult, and underwent re-ligation, intravenous injection of Evans blue and pathological examination to observe the area of infarct size. Another 18 rats were divided into 3 equal groups: Groups A, B, and C as described above, and then underwent electron microscopy to observe the ultrastructure of the myocardium. Furthermore, another 18 rats were divided into 3 equal groups: Groups A, B, and C as described above to undergo pathological examination of the heart and neutrophil infiltration. Tumor necrosis-alpha (TNF-alpha) and interleukin-6 (IL-6) concentrations of left ventricle were analyzed by ELISA 1 h and 2 h after reperfusion respectively; and nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) levels were detected by electrophoretic mobility shift assay.

RESULTS: The ratio of infarct size to area at risk (IS%) of Group C was (28.0% +/- 1.3%), significantly lower than that of Group B [(43.3 +/- 2.5)%, P < 0.01]. The plasma CK-MB concentrations of Groups B and C were (2110 +/- 245) U/L and (1689 +/- 138) U/L respectively, both significantly higher than that of Group A [(933 +/- 88) U/L, both P < 0.01], however, the CK-MB level of Group C was significantly lower than that of Group B (P < 0.01). The pathological changes of Group C were remarkably milder than those of Group B. The semi-quantitative scale of Groups B and C were 3.65 +/- 0.51 and 2.37 +/- 0.49 respectively, both significantly higher than that of Group A (1.76 +/- 0.43), and the semi-quantitative scale of Groups C was significantly lower than that of Group B (P < 0.01). The degree of neutrophil infiltration of Group C was remarkably milder than that of Group B. In Group B there were 2 peaks of NF-kappaB expression: 30 min and 180 min after reperfusion, and the AP-1 expression increased 30 min after reperfusion and then gradually decreased. In Group C the expression levels of NF-kappaB and AP-1 increased 30 min after reperfusion in comparison with Group A, and then gradually decreased and were all significantly lower than those of Group B (all P < 0.01). The levels of TNF-alpha and IL-6 1 h after reperfusion of Groups B and C were all significantly higher than those of Group A (all P < 0.01) and the TNF-alpha and IL-6 of Group C were both significantly lower than those of Group B (both P < 0.01).

CONCLUSION: RhEPO pretreatment can elicit potent cardioprotection against I-R injury, which may due in part to the suppression of NF-kappaB and AP-1 activation and downregulation of the downstream proinflammatory cytokines.