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Background/Aims: Acetylcholine (ACh) is known to modulate the cardiac redox environment and thereby suppress reactive oxygen species (ROS) generation during oxidative stress. However, there is little information about its regulation on ROS clearance. Here we investigate the beneficial effects of ACh on superoxide dismutase (SOD) as key ROS-detoxifying enzyme system in cultured rat cardiomyoblasts. Methods: H9c2 cells were subjected to hypoxia/reoxygenation (H/R) to mimic oxidative stress. Western blot was used to detect the expression of SOD and related signaling molecules. Specific protein knockdown was performed with siRNA transfection. Results: ACh treatment on the beginning of reoxygenation decreased ROS and apoptosis. ACh increased ATP synthesis and mitochondrial DNA. Furthermore, ACh significantly reversed H/R-induced reduction in protein expressions and activities of SOD. ACh stimulated peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α) and decreased forkhead box subfamily O3a (FoxO3a) phosphorylation. Atropine (muscarinic receptor antagonist) abolished the cytoprotection afforded by ACh. PGC-1α siRNA blocked ACh-induced invigorating effects on SOD2, whereas it did not alter SOD1 and FoxO3a phosphorylation. FoxOSa siRNA drastically decreased the expressions of SOD2 and PGC-1α, while it did not affect SOD1. Conclusion: ACh activates SOD2 within mitochondria through FoxO3a/PGC-1α pathway and up-regulates SOD1 in the cytoplasm, thus protecting against oxidative injury induced by H/R. Our findings provide new insights into mechanisms underlying the cardioprotection of ACh on ROS detoxifying. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Acetylcholine (ACh), a neurotransmitter of vagal nerve, offers tolerance to ischemia/reperfusion injury. Given the regulation of autophagy in cardioprotection, this study was to examine the role of autophagy in ACh-elicited protection against hypoxia/reoxygenation (HR) injury. Methods: H9c2 cells were subjected to HR injury. Autophagy was determined by transmission electron microscopy, MDC staining and western blot. MTT kit, LDH and CK release, ATP content and TUNEL assay were used to evaluate cardiomyocytes injury. Atg7 and AMPK knockdown was performed with siRNA transfection. Results: Following 4, 8, 12 and 16 h reoxygenation, autophagosomes were decreased along with reduced cell viability. ACh during 4 h reoxygenation facilitated autophagy as evidence by increased autophagosomes and MDC labeling autophagic vacuoles. H9c2 cells treated with ACh also underwent a biochemical changes by increased ratio of LC3-II/LC3-I and autophagy flux (decreased p62), while muscarinic receptor antagonist atropine suppressed these effects. Induction of autophagy was correlated with enhanced cell survival and decreased apoptosis. Autophagy inhibition with chloroquine and Atg7 siRNA significantly attenuated ACh-induced cytoprotection. ACh-elicited autophagy activation could be related to increased AMPK phosphorylation and decreased mTOR phosphorylation. AMPK siRNA exhibited an elevation in mTOR phosphorylation and reduced the ratio of LC3-II/LC3-I. Importantly, AMPK knockdown desensitized H9c2 cells to ACh-mediated protection. Conclusions: These data provided first evidence that ACh-induced autophagy elicited cytoprotective effects through muscarinic receptor activated-AMPK-mTOR pathway, and suggested a novel mechanism of ACh-induced tolerance against HR injury. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]