Site-specific transdermal delivery of Qingteng Waifu San in a rheumatoid arthritis rabbit model

Abstract: Background: Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation, joint swelling, pain, cartilage destruction and bone erosion. Qingteng Waifu San is an external sinomenine-containing preparation, but its site-specific transdermal response requires disease-relevant evaluation. Objectives: To compare Zusanli (ST36)-site and adjacent non-acupoint transdermal application of Qingteng Waifu San in an ovalbumin/complete Freund’s adjuvant-induced RA rabbit model and to evaluate formulation, neuropeptide, inflammatory, behavioural and histopathological outcomes. Methods: Forty-eight New Zealand white rabbits were allocated into six groups (n=8 each): normal control, vehicle-only transdermal control, acupuncture, acupoint injection, ST36-site transdermal Qingteng Waifu San and adjacent non-acupoint transdermal Qingteng Waifu San. Gel appearance, pH, viscosity, spreadability, sinomenine content and high-performance liquid chromatography (HPLC) fingerprint similarity were assessed. Substance P (SP), calcitonin gene-related peptide (CGRP), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and interleukin-1 beta (IL-1beta) were measured by enzyme-linked immunosorbent assay (ELISA). SP and CGRP messenger RNA (mRNA) were analysed by real-time polymerase chain reaction (PCR). Arthritis score, paw volume, mechanical withdrawal threshold and histopathological scores were assessed. Results: The vehicle-only group showed RA-related changes compared with normal controls. ST36-site Qingteng Waifu San reduced arthritis score, paw volume, serum cytokines and histopathological injury scores and improved mechanical withdrawal threshold compared with vehicle-only control. SP and CGRP levels were higher after ST36 application than after adjacent non-acupoint application, indicating site-dependent neurocutaneous modulation. Conclusion: ST36-site transdermal Qingteng Waifu San produced stronger neuropeptide modulation and more favourable RA-related outcome profiles than adjacent non-acupoint application.