Objective: To explore the role of myeloperoxidase (MPO) and tumor necrosis factor-α (TNF-α) in myocardial injury induced by hind-limb ischemia-reperfusion (IR) in rats.
Methods: Rat models of bilateral hindlimb IR established using a tourniquet were randomized into 9 groups, including a normal control group normal, 2 ischemic groups with hindlimb ischemia for 2 and 4 h, and 6 IR groups with a 4-h ischemia followed by reperfusion for 0.5, 2, 4, 6, 12, and 24 h. The plasma and myocardial levels of MPO and TNF-α in each group were measured, and the myocardial expression of TNF-α was determined with immunohistochemistry.
Results: Compared with the normal control group, the rats with a 2-h ischemia showed significantly increased levels of MPO and TNF-α in the plasma and myocardium. Compared with those in rats with a 4-h ischemia, the plasma and myocardial MPO levels increased significantly at 0.5 and 2 h of reperfusion, respectively; the plasma TNF-α level increased significantly at 4 h of reperfusion and myocardial TNF-α level decreased obviously at 12 h; plasma levels of MPO and TNF-α both significantly decreased at 24 h. The plasma MPO and TNF-α and myocardial TNF-α reached the peak levels at 4 h of reperfusion, and the peak myocardial MPO level occurred at 6 h. Immunohistochemistry showed that TNF-α positivity moderately increased after hindlimb ischemia, and further increased at 4 h of reperfusion but obviously reduced at 24 h.
Conclusion: The activation of systemic and local neutrophils and inflammatory cytokines may play an important role in myocardial injury induced by hindlimb IR in rats.