Effect of electroacupuncture on inflammatory signal expression in local tissues of rats with chronic pelvic pain syndrome based on purinergic 2X7 receptor/NOD-like receptor pyrin domain-containing 3 signal pathway.

OBJECTIVES
To study the expression of inflammatory signal in local prostate tissue of chronic pelvic pain syndrome (CPPS) rats by electroacupuncture (EA) of Guanyuan (CV4), Zhongji (CV3), Huiyang (BL35) and Sanyinjiao (SP6), and to explore the possible mechanism of anti-inflammatory and analgesic effects of EA. METHODS：A total of 36 Sprague-Dawley male rats were randomly divided into three groups: control, model and EA (n=12 rats/group). The CPPS model was made by injection of CFA into ventral lobes of the prostate (0.1 mL). Electric acupuncture apparatus was applied to stimulate Guanyuan (CV4), Zhongji (CV3), bilateral Huiyang (BL35) and Sanyinjiao (SP6) acupoints in EA group. The general condition of rats was observed and the prostate index (PI) was calculated. The thermal pain threshold was collected after each therapeutic course. Histopathological changes of the prostate tissue were examined by hematoxylin-eosin staining method. The expression levels of tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β) and prostaglandin E2 (PGE2) in prostatic homogenates were measured by enzyme linked immunosorbent assay (ELISA). Moreover, the expression levels of purinergic 2X7 receptor (P2X7R), NOD-like receptor pyrin domain-containing 3 (NLRP3), caspase-1 and interleukin-18 (IL-18) mRNA were quantified by quantitative real-time polymerase chain reaction.


RESULTS
Compared with control group, the PI of rats increased, and the thermal pain threshold decreased significantly in model group. The morphological structure of prostate tissues of rats in model group was severely damaged with a large number of inflammatory cells infiltration. Additionally, the levels of TNF-α, IL-1β and PGE2 were higher, and the expressions of P2X7R, NLRP3, caspase-1 and IL-18 mRNA were higher than those in control group. After EA treatment, the PI was significantly decreased, the thermal pain threshold was significantly increased, and the tissue damage was significantly improved. The expressions of inflammatory cytokines were lower in EA group, and expression of P2X7R/NLRP3 pathway was down-regulated.


CONCLUSION
The effect of EA at Guanyuan (CV4), Zhongji (CV3), Huiyang (BL35) and Sanyinjiao (SP6) can improve inflammation and pain symptoms of CPPS rats induced by Complete Freund's adjuvant (CFA). This suggests that EA at Guanyuan (CV4), Zhongji (CV3), Huiyang (BL35) and Sanyinjiao (SP6) can produce anti-inflammatory analgesia effect by preventing the activation of P2X7R/NLRP3 signal pathway, inhibit the release of inflammatory cytokines in CPPS rats, which may provide a putative novel target for the treatment of CPPS.