Protective effect of glycyrrhizin on articular cartilage in rats with post-traumatic osteoarthritis and its related mechanism

Objective: To investigate the protective effect of glycyrrhizin on articular cartilage in post-traumatic osteoarthritis (PTOA) and the related mechanism thereof. Methods: Twenty-four Sprague Dawley rats were randomly divided into sham, PTOA, 20 mg center dot kg(-1), and 50 mg center dot kg(-1) glycyrrhizin groups, with six rats in each group. The PTOA rat model was established by anterior cruciate ligament transection, and the rats were intragastrically administered with 20 mg center dot kg(-1) and 50 mg center dot kg(-1) glycyrrhizin. The pain indexes, pathology, inflammation, apoptosis, extracellular matrix, and toll-like receptor 4/Nuclear factor kappa B (TLR4/NF-kappa B) signaling pathway proteins were detected after treatment. Results: Compared with the sham group, the pain indexes, proteoglycan content, and the expression of Bcl-2, collagen II, and aggrecan significantly decreased, whereas the Mankin's and Osteoarthritis Research Society International (OARSI) scores, levels of inflammatory factors, and expression of Bax, Caspase-3, MMP-3, MMP-13, ADAMTS5, TLR4, Myd88, and p-p65 were significantly increased in the PTOA group (P<0.05). After 20 mg center dot kg(-1) and 50 mg center dot kg(-1) glycyrrhizin treatment, the proteoglycan content and expression of Bcl-2, collagen II, and aggrecan were significantly increased, whereas the Mankin's and OARSI scores, levels of inflammatory factors, and expression of Bax, Caspase-3, MMP-3, MMP-13, ADAMTS5, TLR4, Myd88, and p-p65 were significantly decreased (P<0.05). The improvement was more significant in the 50 mg center dot kg(-1) glycyrrhizin group (P<0.05). Conclusion: Glycyrrhizin could inhibit inflammation and articular cartilage degeneration by inhibiting the activation of the TLR4/NF-kappa B signaling pathway, thereby improving the function of the knee joint in PTOA modeled rats.