Key Laboratory of Tropical Translational Medicine of Ministry of Education & Hainan Provincial Key Laboratory of Tropical Medicine, Hainan Medical University, Haikou.
Orthopedic Hospital of Guangdong Province, Academy of Orthopedics•Guangdong Province, Department of Orthopedics, The Third Affiliated Hospital of Southern Medical University.
Rheumatology (Oxford). 2021 Oct 2;60(10):4899-4909. doi: 10.1093/rheumatology/keab018.
Direct inhibition of M1 polarization of synovial macrophages may be a useful therapeutic treatment for OA and OA-associated synovitis. Frugoside (FGS) is a cardiac glycoside compound isolated and extracted from Calotropis gigantea. Cardiac glycosides possess interesting anti-inflammatory potential. However, the corresponding activity of FGS has not been reported. Therefore, our aim was to find direct evidence of the effects of FGS on synovial macrophage M1 polarization and OA control.
Collagenase was used to establish an experimental mouse OA model (CIOA) with considerable synovitis. Then, FGS was intra-articular administered. The mRNA and protein levels of iNOS were analysed by real-time PCR and Western blotting in vitro. Immunohistochemical and immunofluorescence staining were used to measure the expression of F4/80, iNOS, Col2α1 and MMP13 in vivo. The levels of pro-inflammatory cytokines in FGS-treated M1 macrophage culture supernatants were analysed by flow cytometry.
FGS attenuates synovial inflammation and delays the development of OA in CIOA mice. Further results demonstrate that FGS inhibits macrophage M1 polarization in vitro and in vivo, which subsequently decreases the secretion of IL-6 and TNF-α, in turn delaying cartilage and extracellular matrix (ECM) degradation and chondrocyte hypertrophy. FGS inhibits macrophage M1 polarization by partially downregulating miR-155 levels.
This study demonstrates that intra-articular injection of FGS is a potential strategy for OA prevention and treatment, even at an early stage of disease progression. This is a novel function of FGS and has promising future clinical applications.
直接抑制滑膜巨噬细胞 M1 极化可能是治疗 OA 和 OA 相关滑膜炎的有效方法。杠柳苷（FGS）是从杠柳中分离和提取的一种强心苷化合物。强心苷具有有趣的抗炎潜力。然而，FGS 的相应活性尚未报道。因此，我们的目的是寻找 FGS 对滑膜巨噬细胞 M1 极化和 OA 控制的直接作用的直接证据。
使用胶原酶建立具有明显滑膜炎的实验性小鼠 OA 模型（CIOA），然后关节内给予 FGS。通过实时 PCR 和 Western blot 在体外分析 iNOS 的 mRNA 和蛋白水平。免疫组织化学和免疫荧光染色用于测量体内 F4/80、iNOS、Col2α1 和 MMP13 的表达。通过流式细胞术分析 FGS 处理的 M1 巨噬细胞培养上清液中促炎细胞因子的水平。
FGS 可减轻滑膜炎症并延缓 CIOA 小鼠 OA 的发展。进一步的结果表明，FGS 可在体外和体内抑制巨噬细胞 M1 极化，从而减少 IL-6 和 TNF-α 的分泌，进而延迟软骨和细胞外基质（ECM）降解和软骨细胞肥大。FGS 通过部分下调 miR-155 水平抑制巨噬细胞 M1 极化。
本研究表明，关节内注射 FGS 是预防和治疗 OA 的一种潜在策略，即使在疾病进展的早期阶段也是如此。这是 FGS 的一个新功能，具有有前途的临床应用前景。
