Identification of a novel role for sphingolipid signaling in TNFα and ischemic preconditioning mediated cardioprotection

TNFα administration mimics ischemic preconditioning and neutralizing antibodies to TNFα and IL-1β abolish exercise-induced preconditioning. However, the pharmacology of TNFα's cardioprotective effects and associated downstream signaling events has not been delineated. We evaluated the temporal and dose specific requirements of TNFα to function as a preconditioning mimetic. Furthermore we postulated that the preconditioning effect of TNFα might be orchestrated via sphingolipid signaling. The cardioprotective effect of TNFα and the role of sphingolipid signaling were assessed using a classical preconditioning protocol in the isolated perfused rat heart with the measurement of infarct size and contractile function modulation in response to index ischemia and reperfusion. Recombinant TNFα at an optimal dose of 0.5 ng/ml mimicked ischemic preconditioning by reducing infarct size by 60% v non-preconditioned ischemia-reperfusion controls (P<0.01). The infarct sparing effect of TNFα required a wash-out period prior to the index ischemic-reperfusion. Moreover, the classic ischemic preconditioning antagonist such as 5-hydroxydecanoate abolished TNFα preconditioning. An inhibitor of the sphingolipid signaling pathway. N-oleoylethanolamine (NOE, 1 μM) attenuated ischemic and TNFα preconditioning. Likewise, cell-permeable C2-ceramide and sphingosine 1-phosphate (sphingolipid signaling intermediates) both reproduced the preconditioning cardioprotective phenotype. Finally. TNFα and ceramide conferred preconditioning-like cardioprotection against post-ischemic contractile dysfunction and this cardioprotective effect was attenuated by NOE. In contrast, NOE did not reverse ischemic preconditioning enhanced post-ischemic contractile function. In conclusion, TNFα activates preconditioning-like tolerance against infarction and contractile dysfunction. This cardioprotection is mediated, in part, via activation of novel sphingolipid signaling intermediates. © 2002 Elsevier Science Ltd. All rights reserved.