Cardioprotective effect of the TD anti-apoptotic peptide: Study of the mechanisms of action

Introduction: Apoptosis is a main contributor of reperfusion injury after myocardial infarction. In a previous study, we evidenced the cardioprotective effect of a synthetic peptide (TD) able to interfere with FAS-DAXX interaction specifically activated during reperfusion-induced apoptosis. Objective: the aim of our study was to study the mechanisms of action of the TD anti-apoptotic peptide. Methods: Hearts from C57Bl6 mice were subjected ex vivo (Langendorff) to 40 minute-ischemia (coronary ligation) and 1 hour reperfusion (IR protocol). TD peptide (1 µM) was perfused during reperfusion. At the end of the protocol, a proteomic analysis by western-blot was realized in TD- versus non-treated IR hearts.Results: Upon TD treatment, the downstream activation of the JNK/caspase 3 pathway was down-regulated. A decrease in both the expression of BAD protein and the level of activated caspase 9, both mediators of the intrinsic pathway, was also observed. TD treatment was able to decrease the FADD-caspase 8 extrinsic pathway probably due to its impact on DAXX-FADD cooperativity within the DISC. Of great interest, TD peptide treatment was not associated neither with a deleterious reduction of DAXX protein level already described to trigger unexpected pro-apoptotic effects (siRNA DAXX) nor with a switch to the necroptotic pathway (RIP1-RIP3-MLKL). Protein levels of HSP70, a hallmark of proteotoxic stress, were also reduced. Interestingly, the anti-apoptotic TD treatment was also related to an activation of the RISK (Reperfusion Injury Salvage Kinase) pathway including ERK1/2 and PI3kinase-AKT. Conclusion: TD peptide treatment appears as a particularly relevant therapeutic strategy to target reperfusion-induced apoptotic pathways. Targeting FAS:DAXX interaction from the extrinsic pathway also indirectly reduced the activation of the intrinsic (JNK-BAX crosstalk) cascade thus allowing a complete inhibition of reperfusion injury with a single pharmacological administration.