Study on the analgesic and anti-inflammatory mechanisms of Jingu Zhitong gel in the treatment of knee osteoarthritis through the IL-17, NGF-TrkA, and COX-2/PGE2 pathways

Introduction: Knee osteoarthritis (KOA) is a degenerative bone and joint disease. Jingu Zhitong Gel (JGZTG) exhibits a promising therapeutic effect in the clinical treatment of knee osteoarthritis (KOA). However, the mechanism of JGZTG in treating KOA remains unclear. Methods: We established a rat model of KOA through surgery and treated rats with JGZTG for 21 days. The pain threshold was measured by the Ugo Basile joint pain tester, the weight bearing on the right foot was detected by a bipedal balance tester, the inflammatory factor levels were measured by ELISA kits, and the joint morphology score was evaluated. Hematoxylin and eosin staining (H&E) was used to evaluate the pathological lesions, while toluidine blue staining was used to observe the proteoglycan depletion. Transcriptomic analysis was conducted to elucidate the potential mechanisms of JGZTG in treating KOA. Real-time quantitative Polymerase Chain Reaction (RT-qPCR), and immunofluorescence (IF) assays were conducted to validate transcriptomic results and investigate the analgesic mechanisms. Results: After 21 days of treatment, JGZTG significantly increased the pain threshold and the weight bearing on the right foot in KOA rats, furthermore, reduced the levels of inflammatory factors (TNF-α, IL-6, IL-1β, and PGE2) in the serum and joint lavage fluid. In addition, JGZTG significantly decreased the joint morphology score, reduced synovial damage, alleviated cartilage injury, and reduced proteoglycan depletion in KOA models. The results of transcriptomic analysis showed that the anti-inflammatory effect of JGZTG in treating KOA was associated with the IL-17 signaling pathway. Further validation revealed that the relative mRNA and protein expression of IL-17RB, FosB, MMP1b, MMP3, MMP13, CCL17, and CXCL6 were regulated by JGZTG. In addition, JGZTG can reduce the mRNA and protein overexpression of NGF, Ntrk1, Trpv1, Ptgs2, PGE2, EP4, TAC1, and Calca, which are the key factors of the NGF-TrkA and COX-2/PGE2 pathways. Conclusion: JGZTG exhibits pain-relieving and anti-inflammatory effects in KOA, which were linked to altered IL-17, NGF-TrkA, and COX-2/PGE2 pathways. These findings have provided experimental evidence for the mechanisms underlying the therapeutic effects of JGZTG in KOA.