Role of the O-linked β-N-acetylglucosamine in the Cardioprotection Induced by Isoflurane

Background: Cardiac protection by volatile anesthetic-induced preconditioning and ischemic preconditioning have similar signaling pathways. Recently, it was reported that augmentation of protein modified with O-linked beta-N-acetylglucosamine (O-GlcNAc) contributes to cardiac protection. This study investigated the role of O-GlcNAc in cardiac protection induced by anesthetic-induced preconditioning. Methods: O-GlcNAc-modified proteins were visualized by immunoblotting. Tolerance against ischemia or reperfusion was tested in vivo (n = 8) and in vitro (n = 6). The opening of the mitochondrial permeability transition pore (mPTP) upon oxidative stress was examined in myocytes treated with calcein AM (n = 5). Coimmunoprecipitation and enzymatic labeling were performed to detect the mitochondrial protein responsible for the mPTP opening. Results: Isoflurane treatment and the consequent augmentation of O-GlcNAc concentrations reduced the infarct size (26 +/- 5% [mean +/- SD], P < 0.001) compared with the control. The protective effect of O-GlcNAc was eliminated in the group pretreated with the O-GlcNAc transferase inhibitor alloxan (39 +/- 5%, P < 0.001). Myocyte survival also showed the same result in vitro. Formation of the mPTP was abrogated in the isoflurane-treated cells (86 +/- 4%, P < 0.001) compared with the control and alloxan-plus-isoflurane-treated cells (57 +/- 7%, P < 0.001). Coimmunoprecipitation and enzymatic labeling studies revealed that the O-GlcNAc-modified, voltage-dependent anion channel restained the mPTP opening. Conclusions: Isoflurane induced O-GlcNAc modification of mitochondrial voltage-dependent anion channel. This modification inhibited the opening of the mPTP and conferred resistance to ischemia-reperfusion stress.