Water extracts of Tibetan medicine Wuweiganlu attenuates experimental arthritis via inducing macrophage polarization towards the M2 type

Abstract

Ethnopharmacological relevance: Wuweiganlu (WGL) is a well-known formulation described in the "Four Medical Scriptures of Tibetan medicine", which is mainly used for the treatment of Rheumatoid Arthritis (RA) and other chronic ailments prescribed by Tibetan medicine. Nonetheless, the active constituents present in the water extracts of Wuweiganlu (WGLWE) specifically targeting arthritis treatment are largely unknown.

Aim of the study: The aim of this study is to explore the effects and underlying mechanisms of the active components in WGLWE on RA.

Materials and methods: We utilized ultra-performance liquid chromatography coupled with Q-TOF mass spectrometry (UPLC-Q-TOF-MS) to identify the main chemical compositions of WGLWE. The polarization effect of WGLWE on bone marrow-derived macrophages (BMDM) was determined. A rat model of collagen-induced arthritis (CIA) was established by injecting an emulsion of bovine type II collagen mixed with an equal volume of incomplete Freund's adjuvant into the tail, paw and back of rats. A WGLWE-based ointment was topically applied to the legs and paws of the rats for 30 days. The rats' ankles were photographed to measure the degree of swelling. Micro-CT was used to image the knee joint and paw of rats, and the bone mineral density (BMD) and bone volume fraction (BV/TV) of knee joint in rats were analyzed. High-frequency ultrasound imaging of the rat knee joint was performed to observe knee joint effusion. Further, the serum levels of tumor necrosis factor (TNF-α), interleukin-6 (IL-6), IL-10, and arginine (Arg-1) in CIA rats were detected by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry (IHC) and immunofluorescence (IF) co-staining were employed to detect the expression levels of inflammatory factors in synovium.

Results: A total of 28 main components were identified in WGLWE, and these compounds can directly bind to the inflammatory pathway proteins such as JAK2, NFκB and STAT3. In vitro experiments demonstrated that WGLWE promoted the transformation of M1 macrophages into M2 macrophages and suppressed the release of proinflammatory cytokines TNF-α and IL-6. In vivo studies showed that WGLWE effectively reduced ankle swelling, alleviated knee joint effusion, and improved BV/TV while also reducing synovial inflammation levels. Furthermore, WGLWE compounds induced the transition of M1-type macrophages to M2-type macrophages in synovial tissue, resulting in decreased secretion of inflammatory factors TNF-α, WGLWE improved the synovial inflammatory state.

Conclusion: Our results indicated that WGLWE alleviated joint inflammation in CIA rats and the underlying mechanism may be related to inducing the transformation of bone marrow-derived M1 macrophages to M2 macrophages, leading to an increase in the secretion of anti-inflammatory factors and a decrease in pro-inflammatory factors. Therefore, WGLWE may be used as a potential herbal preparation for the treatment of RA.

Keywords: M2 macrophages; Micro-CT; Rheumatoid arthritis; WGLWE.