Syntaxin 1A mediates isoflurane but not hypoxia preconditioning-induced alleviation of hypoxia-reoxygenation injury in rat cardiomyocytes.

Preconditioning with ischemia/hypoxia (IPC/HPC) or clinically available volatile anesthetics such as isoflurane (Iso-PC) could activate cardioprotective signaling pathways, thereby reducing myocardial ischemia/reperfusion (IR) injury. However, their molecular targets remain elusive. We herein investigated the roles of syntaxin 1A (Stx-1A) in cardiomyocyte protection induced by HPC and Iso-PC. Both in vivo myocardial IR model and in vitro cardiomyocyte hypoxia/reoxygenation (HR) model were used to test the effects of IR/HR, IPC/HPC and Iso-PC on Stx-1A protein expression. Stx-1A knockdown and overexpression in cardiomyocytes were achieved by adenovirus infection to define the relationship between Stx-1A levels and IPC/Iso-PC-induced cardioprotection. Cardiac troponin T (cTnT), cell apoptosis rate, and cell viability were introduced as indicators for cardiomyocyte HR injury. Changes of cardioprotective signaling pathways activities including PI3K/AKT/GSK3β, ERK1/2, STAT3 and PKC were also detected using Western blot. Rat cardiomyocyte Stx-1A was upregulated 4 hours after IR or HR. IPC/HPC as well as Iso-PC further increased Stx-1A expression compared with IR/HR. Stx-1A knockdown was accompanied with more cell apoptosis and decreased cell viability while overexpression of Stx-1A seemed cardioprotective. Iso-PC induced decrease in cell apoptosis and increase in cell viability but not HPC-induced cardioprotection was reversed by Stx-1A shRNA transfection. No difference in cell apoptosis or cell viability was found before and after Stx-1A overexpression in each group. Moreover, Stx-1A knockdown were accompanied with increased PI3K/AKT/GSK3β activities irrespective of the treatments. Stx-1A is cardioprotective and a potential target of isoflurane induced cardioprotection. Further studies are needed to test whether stx-1A is regulated by AKT/GSK3β signaling.