In this study, we aimed to investigate the effect of electro-acupuncture (EA) pretreatment at zusanli (ST36) acupoint on lipopolysaccharide (LPS)-induced endotoxemic rat model and explore the underlying molecular mechanisms. Rats were treated with EA at ST36 for 7 days before being subjected to LPS. Two hours post-LPS, samples such as serum, local acupoint tissues, and spleens were collected and processed for investigations including cytokine production, cytosolic calcium (Ca2+) concentration, Ca2+ influx, cannabinoid CB2 receptor (CB2R) expression, and TLR4/NF-κB signaling. Our results showed EA pretreatment significantly attenuated LPS-induced inflammatory cytokine production, such as TNF-α, IL-1β, and IL-6. EA also enhanced CB2R expression, inhibited Ca2+ influx, and inactivated TLR4/NF-κB signaling, subsequently resulting in a substantial reduction of Ca2+ concentration. Importantly, CB2R antagonist AM630 effectively abrogated the suppressive effect of EA at ST36 on the endotoxemic rats, suggesting CB2R was involved in the anti-inflammatory effect of EA. EA pretreatment could enhance CB2R expression, inhibit Ca2+ influx, and inactivate TLR4/NF-κB signaling, which contributes to the alleviation of LPS-induced inflammation in rats.
Keywords: TLR4/NF-κB signaling; calcium; cannabinoid CB2 receptor; electro-acupuncture; inflammation; lipopolysaccharide.