Pingchong Jiangni recipe through nerve growth factor/transient receptor potential vanilloid 1 signaling pathway to relieve pain in endometriosis model rats

Ethnopharmacological relevance: Pingchong Jiangni recipe (PJR) is often used in the treatment of endometriosis (EM). This formula has been clinically validated by the State Administration of Traditional Chinese Medicine Key Specialties Collaborative Group for its therapeutic efficacy. Recently, our research team also confirmed that PJR has a shrinking effect on ovarian chocolate cysts. Additionally, PJR was also found to have a shrinking effect on EM lesions; however, the mechanism by which this effect occurs remains unclear.Aim of the study: To explore the mechanisms by which PJR relieves pain in patients with EM.Materials and methods: A rat model of EM was established by autologous transplantation. PJR (3.78 g/kg, 7.56 g/ kg, and 15.12 g/kg) was orally administered for 21 days. The rat grimace scale (RGS) score and paw withdrawal threshold (PWT) were measured at a fixed time during the experiment. Hematoxylin and eosin staining was performed to observe histopathological changes in EM rats after administration, enzyme-linked immunosorbent assay to evaluate the plasma expression of tumor necrosis factor-& alpha; (TNF-& alpha;) and nerve growth factor (NGF), and immunohistochemistry and western blotting to identify differences in the expression of pain-related factors in EM rats.Results: The medium-dose group of PJR (7.56 g/kg) had the best effect on relieving pain in EM rats by reducing RGS, increasing PWT, reducing the ectopic endometrium, improving the cellular structure of the lesion, and reducing TNF-& alpha; and NGF levels. However, PJR significantly decreased the expression of transient receptor potential vanilloid 1 (TRPV1), phosphorylated TRPV1 (p-TRPV1), protein kinase C (PKC), and NGF.Conclusion: The mechanism by which PJR relieves EM pain may be through the downregulation of NGF, PKC, and TRPV1 expression.