pGlu-serpinin protects the normotensive and hypertensive heart from ischemic injury.

Serpinin peptides derive from proteolytic cleavage of Chromogranin-A at C-terminus. Serpinin and the more potent pyroglutaminated-Serpinin (pGlu-Serp) are positive cardiac beta-adrenergic-like modulators, acting through β1-AR/AC/cAMP/PKA pathway. Since in some conditions this pathway and/or other pro-survival pathways, activated by other Chromogranin-A fragments, may cross-talk and may be protective, here we explored whether pGlu-Serp cardioprotects against ischemia/reperfusion injury under normotensive and hypertensive conditions. In the latter condition cardioprotection is often blunted because of the limitations on pro-survival Reperfusion-Injury-Salvage-Kinases (RISK) pathway activation. The effects of pGlu-Serp were evaluated on infarct size (IS) and cardiac function by using the isolated and Langendorff perfused heart of normotensive (WKY) and spontaneously hypertensive (SHR) rats exposed to ischemic pre-conditioning (PreC) and post-conditioning (PostC). In both WKY and SHR rat, pGlu-Serp induced mild cardioprotection in both PreC and in PostC. pGlu-Serp administered at the reperfusion (Serp-PostC) significantly reduced IS, being more protective in SHR than in WKY. Conversely, developed Left Ventricular Pressure (LVDevP) post-ischemic recovery was greater in WKY than in SHR. pGlu-Serp-PostC reduced contracture in both strains. Co-infusion with specific RISK inhibitors (P13K/AkT, MitoKATP channels, and PKC) blocked the pGlu-Serp-PostC protective effects. To show direct effect on cardiomyocytes, we pre-treated H9c2 with pGlu-Serp which were thus protected against hypoxia/reoxygenation. These results suggest pGlu-Serp as a potential modulatory agent implicated in the protective processes which can limit infarct size and overcome the hypertension-induced failure of PostC.