Activation of Epsilon Protein Kinase C-Mediated Anti-Apoptosis Is Involved in Rapid Tolerance Induced by Electroacupuncture Pretreatment Through Cannabinoid Receptor Type 1

Background and Purpose-Our previous study has demonstrated that the rapid tolerance to cerebral ischemia by electroacupuncture (EA) pretreatment was possibly mediated through an endocannabinoid system-related mechanism. The purpose of this study was to investigate whether activation of epsilon protein kinase C (epsilon PKC) was involved in EA pretreatment-induced neuroprotection via cannabinoid receptor type 1 in a rat model of transient focal cerebral ischemia. Methods-The activation of epsilon PKC in the ipsilateral brain tissues after EA pretreatment was investigated in the presence or absence of cannabinoid receptor antagonists. At 2 hours after the end of EA pretreatment, focal cerebral ischemia was induced by middle cerebral artery occlusion for 120 minutes in rats. The neurobehavioral scores, infarction volumes, neuronal apoptosis, and the expression of Bcl-2 and Bax were evaluated after reperfusion in the presence or absence of epsilon PKC-selective peptide inhibitor (TAT-epsilon V1-2) or activator (TAT-psi epsilon RACK). Results-EA pretreatment enhanced epsilon PKC activation. Systemic delivery of TAT-psi epsilon RACK conferred neuroprotection against a subsequent cerebral ischemic event when delivered 2 hours before ischemia. Pretreatment with EA reduced infarct volumes, improved neurological outcome, inhibited neuronal apoptosis, and increased the Bcl-2-to-Bax ratio after reperfusion, and the beneficial effects were attenuated by TAT-epsilon V1-2. In addition, the blockade of cannabinoid receptor type 1, but not cannabinoid receptor type 2 receptor, reversed the increase in epsilon PKC activation and neuroprotection induced by EA pretreatment. Conclusion-EA pretreatment may activate endogenous epsilon PKC-mediated anti-apoptosis to protect against ischemic damage after focal cerebral ischemia via cannabinoid receptor type 1, which represents a new mechanism of EA pretreatment-induced rapid tolerance to focal cerebral ischemia in rats. (Stroke. 2011; 42: 389-396.)