Mn-SOD Upregulation by Electroacupuncture Attenuates Ischemic Oxidative Damage via CB1R-Mediated STAT3 Phosphorylation

Abstract

Electroacupuncture (EA) pretreatment elicits the neuroprotective effect against cerebral ischemic injury through cannabinoid receptor type 1 receptor (CB1R). In current study, we aimed to investigate whether the signal transducer and activator of transcription 3 (STAT3) and manganese superoxide dismutase (Mn-SOD) were involved in the antioxidant effect of EA pretreatment through CB1R. At 2 h after EA pretreatment, focal cerebral ischemic injury was induced by transient middle cerebral artery occlusion for 60 min in C57BL/6 mice. The expression of Mn-SOD in the penumbra was assessed by Western blot and immunoflourescent staining at 2 h after reperfusion. In the presence or absence of Mn-SOD small interfering RNA (siRNA), the neurological deficit score, the infarct volume, the terminal deoxynucleotidyl transferase-mediated dUDP-biotin nick end labeling (TUNEL) staining, and oxidative stress were evaluated. Furthermore, the Mn-SOD protein expression and phosphorylation of STAT3 at Y705 were also determined in the presence and absence of CB1R antagonists (AM251, SR141716) and CB1R agonists (arachidonyl-2-chloroethylamide (ACEA), WIN 55,212-2). EA pretreatment upregulated the Mn-SOD protein expression and Mn-SOD-positive neuronal cells at 2 h after reperfusion. EA pretreatment also attenuated oxidative stress, inhibited cellular apoptosis, and induced neuroprotection against ischemic damage, whereas these beneficial effects of EA pretreatment were reversed by knockdown of Mn-SOD. Mn-SOD upregulation and STAT3 phosphorylation by EA pretreatment were abolished by two CB1R antagonists, while pretreatment with two CB1R agonists increased the expression of Mn-SOD and phosphorylation level of STAT3. Mn-SOD upregulation by EA attenuates ischemic oxidative damage through CB1R-mediated STAT3 phosphorylation in stroke mice, which may represent one new mechanism of EA pretreatment-induced neuroprotection against cerebral ischemia.

Keywords: Cannabinoid receptor type 1 receptor (CB1R); Cerebral ischemia; Electroacupuncture; Manganese superoxide dismutase (Mn-SOD); Oxidative damage; Signal transducer and activator of transcription 3 (STAT3).