Objective: We previously showed that HSP90 is involved in postconditioning cardioprotection by inhibiting complement C5a. Here, we investigated whether HSP90-mediated C5a/NF-κB inhibition is responsible for the cardioprotection conferred by liraglutide.
Methods: Rat hearts underwent a 30 min occlusion of the anterior descending coronary artery, after which reperfusion was performed for 2 h. A total of 100 rats were randomly assigned to the following groups: ischemia/reperfusion (I/R), sham, liraglutide preconditioning (LP, liraglutide, 0.18 mg/kg, intravenously, 12 h before ischemia), HSP90 inhibitor geldanamycin (GA, 1 mg/kg, intraperitoneally, 30 min before ischemia) plus LP, and C5a receptor antagonist PMX53 (1 mg/kg, intravenously, 30 min before ischemia) plus LP. Cardiac injury, C5a/NF-κB activation, and inflammation were investigated.
Results: LP significantly attenuated I/R-induced cardiomyocyte apoptosis, infarct size, and secretion of creatine kinase-MB, lactate dehydrogenase and cardiac troponin I. These effects were complemented by decreased C5a levels, nuclear factor (NF)-κB signaling, inflammatory cytokine expression, and increased HSP90 levels. GA, an HSP90 inhibitor, promotes C5a activation, NF-κB signaling, and inflammation and suppresses cardioprotection by LP. By contrast, PMX53, a C5a inhibitor, suppressed C5a activation, NF-κB signaling, and inflammation, and enhanced cardioprotection by LP.
Conclusion: HSP90 markedly contributes to LP cardioprotection by inhibiting inflammatory responsesand C5a/NF-κB signaling , ultimately attenuating I/R-induced cardiomyocyte apoptosis by suppressing the proapoptotic factor Bax, and inducing the anti-apoptotic factor Bcl2.
Keywords: C5a; HSP90; Liraglutide preconditioning; NF-κB; inflammation; ischemia/reperfusion.