Activation of STAT3 is involved in neuroprotection by electroacupuncture pretreatment via cannabinoid CB1 receptors in rats
Pretreatment with electroacupuncture (EA) attenuates cerebral ischemic injury through the endocannabinoid system, although the molecular mechanisms mediate this neuroprotection are unknown. It is well-known that signal transducer and activator of transcription 3 (STAT3) plays an essential role in cell survival and proliferation. Therefore, we investigated whether STAT3 is involved in EA pretreatment-induced neuroprotection via cannabinoid CB1 receptors (CB1R) after transient focal cerebral ischemia in rats. Two hours after EA pretreatment, focal cerebral ischemia was induced by middle cerebral artery occlusion (MACO) for 120 minutes. The expression of pSTAT3(Ser727), which is necessary for STAT3 activation, was examined in the ipsilateral ischemic penumbra. Infarct volumes and neurological scores were evaluated at 72 hours after MACO in the presence or absence of the STAT3 inhibitor peptide (PpYLKTK). Neuronal apoptosis and the Bax/Bcl-2 ratio were also evaluated 24 hours after reperfusion. Our results showed that EA pretreatment significantly enhanced neuronal expression of pSTAT3(Ser727) in the ischemic penumbra 6 hours after reperfusion. Moreover, EA pretreatment reduced infarct volume, improved neurological outcome, inhibited neuronal apoptosis and decreased the Bax/Bcl-2 ratio following reperfusion. The beneficial effects of EA were attenuated by PpYLKTK administered 30 minutes before MACO, and PpYLKTK effectively reversed the increase in pSTAT3(Ser727) expression. Furthermore, CB1R antagonist or CB1R knockdown with siRNA blocked the elevation of pSTAT3(Ser727) expression by EA pretreatment, whereas the two CB1R agonists increased STAT3 activation. In conclusion, EA pretreatment enhances STAT3 activation via CB1R to protect against cerebral ischemia, suggesting that STAT3 activation may be a novel target for stroke intervention.
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