Integrated skin metabolomics and network pharmacology to explore the mechanisms of Goupi Plaster for treating knee osteoarthritis

Background and aim: Goupi Plaster (GP) is topical traditional Chinese medicine preparation. It has been used to treat Knee Osteoarthritis (KOA) in clinical practice of traditional Chinese medicine (TCM). However, the mechanisms of GP relieve KOA are poorly understood. Experimental procedure: Rabbit models of KOA were established and treated with GP. Knee cartilage pathology was analyzed using hematoxylin and eosin staining, while plasma levels of inflammatory factors (interleukin (IL)-4, IL-6, and IL-17) and skin neurotransmitters (calcitonin gene-related peptide (CGRP), substance P (SP), and5-hydroxytryptamine (5-HT)) were measured by enzyme linked immunosorbent assay. Metabolomics based on GC-TOF-MS analysis screened for skin biomarkers as well as relevant pathways. Network pharmacology screened for relevant skin targets as well as relevant pathways, and finally, MetScape software was utilized to integrate the results of metabolomics and network pharmacology to screen for key skin targets, key metabolites, and key pathways for GP treatment of KOA. Results and conclusion: GP administration substantially repaired cartilage surface breaks in KOA and led to relatively intact cartilage structure and normal cell morphology. GP decreased plasma levels of IL-6 and IL-17 and skin levels of CGRP, SP and 5-HT while increased plasma IL-4. GP administration normalized the levels of 15 metabolites which were changed in KOA. Network pharmacology analysis identified 181 targets. Finally, 3 key targets, 5 key metabolites and 3 related pathways were identified, which suggested that GP improved skin barrier function and skin permeability by regulating skin lipid metabolism. GP treatment also regulated skin amino acid levels and subsequently affected neurotransmitters and signaling molecules. In addition, the purinergic signaling pathway was also involved in the treatment of GP against KOA. In conclusion, GP treatment is associated with changes in skin lipid metabolism, neurotransmitters, and the purinergic signaling pathway.