ObjectiveThis paper aims to investigate the mechanism of Jinyang Dingtong plaster in improving the peripheral pain sensitization and synovial fibrosis in rats with knee osteoarthritis （KOA） by blocking the ion channels of transient receptor potentials （TRPs）. MethodsThe active components in the transdermal absorption solution of Jinyang Dingtong plaster were identified by using ultra-high performance liquid chromatography-electrospray ionization-quadrupole ion trap tandem mass spectrometry （UPLC-MS/MS） technology. A KOA rat model was established through intra-articular injection of monoiodoacetic acid. The rats were randomly divided into blank control group， KOA group， compound Nanxing Zhitong plaster Group， and Jinyang Dingtong plaster group， with eight rats per group. Among them， the rats in the compound Nanxing Zhitong plaster group and the Jinyang Dingtong plaster group were intervened with external application treatment. After the intervention period， the cold and mechanical stimulus pain thresholds of rats in each group were detected， and the transverse diameter of the knee joint was measured. The levels of inflammatory factors in the serum such as interleukin-1β （IL-1β）， tumor necrosis factor-α （TNF-α）， nerve growth factor （NGF）， and calcitonin gene-related peptide （CGRP） were determined by enzyme-linked immunosorbent assay （ELISA）. Protein expression levels of transient receptor potential ankyrin 1 （TRPA1）， transient receptor potential melastatin 8 （TRPM8）， transient receptor potential vanilloid 1 （TRPV1）， transient receptor potential vanilloid 4 （TRPV4）， transforming growth factor-β （TGF-β）， and vascular endothelial growth factor （VEGF） in synovial tissue were detected by Western blot. Histopathological changes in synovial tissue were observed by using hematoxylin and eosin （HE）， Masson， and Sirius red staining， while the expression of type Ⅰ collagen and alpha-smooth muscle actin （α-SMA） was detected by multiplex immunofluorescence. ResultsA total of 35 active components in the transdermal absorption solution of Jinyang Dingtong plaster were identified by UPLC-MS/MS， including phenolic acids， flavonoids， quinones， alkaloids， terpenes， lignans， and coumarins. Among them， the constituents such as berberine， paeoniflorin， ferulic acid， and caffeic acid exhibit clear anti-inflammatory， analgesic， and anti-fibrotic pharmacological effects. Compared to the blank control group， rats in the KOA group showed a significant decrease in cold and mechanical stimuli pain thresholds （P<0.01）. After 14 and 28 days of Jinyang Dingtong plaster intervention， the pain threshold in this group was significantly increased compared to that in KOA group （P<0.01）， showing no significant difference from that in compound Nanxing Analgesic plaster group. Additionally， Jinyang Dingtong plaster reduced the levels of IL-1β， TNF-α， NGF， and CGRP in the serum of KOA rats （P<0.01）， lowered the expression of TRPA1， TRPM8， TRPV1， TRPV4， TGF-β， and VEGF proteins in synovial tissue （P<0.01）， improved synovial pathological damage in KOA rats， and significantly decreased fluorescence intensity of type Ⅰ collagen and α-SMA （P<0.01）. ConclusionJinyang Dingtong plaster can improve the peripheral pain sensitization and synovial fibrosis in KOA rats by downregulating the expression of ion channels of TRPs and related inflammatory and fibrotic factors.

ObjectiveThis paper aims to investigate the mechanism of Jinyang Dingtong plaster in improving the peripheral pain sensitization and synovial fibrosis in rats with knee osteoarthritis （KOA） by blocking the ion channels of transient receptor potentials （TRPs）. MethodsThe active components in the transdermal absorption solution of Jinyang Dingtong plaster were identified by using ultra-high performance liquid chromatography-electrospray ionization-quadrupole ion trap tandem mass spectrometry （UPLC-MS/MS） technology. A KOA rat model was established through intra-articular injection of monoiodoacetic acid. The rats were randomly divided into blank control group， KOA group， compound Nanxing Zhitong plaster Group， and Jinyang Dingtong plaster group， with eight rats per group. Among them， the rats in the compound Nanxing Zhitong plaster group and the Jinyang Dingtong plaster group were intervened with external application treatment. After the intervention period， the cold and mechanical stimulus pain thresholds of rats in each group were detected， and the transverse diameter of the knee joint was measured. The levels of inflammatory factors in the serum such as interleukin-1β （IL-1β）， tumor necrosis factor-α （TNF-α）， nerve growth factor （NGF）， and calcitonin gene-related peptide （CGRP） were determined by enzyme-linked immunosorbent assay （ELISA）. Protein expression levels of transient receptor potential ankyrin 1 （TRPA1）， transient receptor potential melastatin 8 （TRPM8）， transient receptor potential vanilloid 1 （TRPV1）， transient receptor potential vanilloid 4 （TRPV4）， transforming growth factor-β （TGF-β）， and vascular endothelial growth factor （VEGF） in synovial tissue were detected by Western blot. Histopathological changes in synovial tissue were observed by using hematoxylin and eosin （HE）， Masson， and Sirius red staining， while the expression of type Ⅰ collagen and alpha-smooth muscle actin （α-SMA） was detected by multiplex immunofluorescence. ResultsA total of 35 active components in the transdermal absorption solution of Jinyang Dingtong plaster were identified by UPLC-MS/MS， including phenolic acids， flavonoids， quinones， alkaloids， terpenes， lignans， and coumarins. Among them， the constituents such as berberine， paeoniflorin， ferulic acid， and caffeic acid exhibit clear anti-inflammatory， analgesic， and anti-fibrotic pharmacological effects. Compared to the blank control group， rats in the KOA group showed a significant decrease in cold and mechanical stimuli pain thresholds （P<0.01）. After 14 and 28 days of Jinyang Dingtong plaster intervention， the pain threshold in this group was significantly increased compared to that in KOA group （P<0.01）， showing no significant difference from that in compound Nanxing Analgesic plaster group. Additionally， Jinyang Dingtong plaster reduced the levels of IL-1β， TNF-α， NGF， and CGRP in the serum of KOA rats （P<0.01）， lowered the expression of TRPA1， TRPM8， TRPV1， TRPV4， TGF-β， and VEGF proteins in synovial tissue （P<0.01）， improved synovial pathological damage in KOA rats， and significantly decreased fluorescence intensity of type Ⅰ collagen and α-SMA （P<0.01）. ConclusionJinyang Dingtong plaster can improve the peripheral pain sensitization and synovial fibrosis in KOA rats by downregulating the expression of ion channels of TRPs and related inflammatory and fibrotic factors.