Pyroptosis of chondrocytes activated by synovial inflammation accelerates TMJ osteoarthritis cartilage degeneration via ROS/NLRP3 signaling.

Synovial inflammation and chondrocyte death have been widely acknowledged as key contributors to the pathological progression of temporomandibular joint osteoarthritis (TMJ-OA), a degenerative joint disease currently lacking definitive treatments. This study aims to understand the regulatory role of chondrocyte pyroptosis in condylar cartilage degradation during TMJ-OA. The levels of cytokines, cartilage degeneration markers, and pyroptotic biomarkers in the synovium and synovial fluid of temporomandibular disorders (TMD) patients were examined. The synovitis, cartilage degradation, and chondrocyte pyroptosis in wild-type and alpha-kinase 1 (ALPK1)-deficient TMJ-OA mice were then compared following monosodium iodoacetate (MIA) induction. Subsequently, we investigated the downstream mechanisms of cytokines- or macrophage supernatants-induced metabolic disorders and pyroptosis in chondrocytes using primary TMJ chondrocytes and ATDC5 chondrocyte cultures. We found a positive correlation between pyroptotic biomarkers and cartilage degradation mediators and cytokines in the synovial fluid of TMD patients. MIA-induced TMJ-OA mice demonstrated significant synovitis, cartilage degradation, and chondrocyte pyroptosis, which were mitigated in ALPK1-deficient TMJ-OA mice, inflammation-restrained mice. Ex-vivo study revealed the contribution of reactive oxygen species (ROS) to inflammation-irritated macrophage supernatants-induced pyroptosis and metabolic disorders in chondrocytes. Targeting NOD-like receptor protein 3 (NLRP3) alleviated cytokines- or ROS-induced pyroptosis and metabolic disorders in chondrocytes by inhibiting caspase-1 activation and interleukin-1β (IL-1β) secretion. Our findings offer novel insight into the role of synovial inflammation-induced chondrocyte pyroptosis in promoting cartilage degradation during TMJ-OA via the ROS and NLRP3 signaling pathway.

Liu X ，Li Y ，Zhao J ，Hu Z ，Fang W ，Ke J ，Li W ，Long X ... -  《-》

Resatorvid alleviates experimental inflammatory TMJOA by restraining chondrocyte pyroptosis and synovial inflammation.

Innate immunity plays a significant role in the pathogenesis of temporomandibular joint osteoarthritis (TMJOA), which is characterized by synovial inflammation and condylar cartilage degradation. We are urged to investigate the impact of Resatorvid, a preventative drug that inhibits Toll-like receptor 4 (TLR4), on experimental inflammatory TMJOA pathology. An intra-articular injection of complete Freund's adjuvant (CFA) was used to induce an experimental inflammatory mouse TMJOA model, and TLR4 expression was identified by immunofluorescent labeling. Intraperitoneal injections of Resatorvid were administered to CFA-induced TMJOA mice, and the pathology of TMJOA animals with and without Resatorvid treatment was examined by H&E, Safranin-O/Fast Green, and TRAP staining, as well as micro-CT, immunohistochemistry, and immunofluorescence. The impact of Resatorvid on chondrocyte pyroptosis and macrophage inflammation was further investigated using ATDC5 chondrocytes and RAW264.7 macrophages pretreated with relevant antagonists. CFA-induced TMJOA mice revealed remarkable synovial inflammation, together with a time course of cartilage degradation and bone destruction, with TLR4 elevated in the synovium and condylar cartilage. Prophylactic treatment with Resatorvid mitigated synovial inflammation, cartilage degeneration, and bone destruction in CFA-induced TMJOA mice and downregulated MyD88/NF-κB expression. Ex vivo studies demonstrated that Resatorvid treatment alleviated NOD-like receptor protein 3 (NLRP3)-mediated chondrocyte pyroptosis and degeneration and relieved macrophage inflammation by preventing reactive oxygen species (ROS) production through NLRP3 signaling. Prophylactic treatment with Resatorvid alleviates TMJOA pathology by inhibiting chondrocyte pyroptosis and degeneration, as well as ROS-induced macrophage inflammation, through TLR4/MyD88/NF-κB/NLRP3.

Liu X ，Li H ，Feng Y ，Guo H ，Li Y ，Ke J ，Long X ... -  《-》

P2X7 Receptor Induces Pyroptotic Inflammation and Cartilage Degradation in Osteoarthritis via NF-κB/NLRP3 Crosstalk.

Osteoarthritis (OA) is an urgent public health problem; however, the underlying causal mechanisms remain unclear, especially in terms of inflammatory mediators in cartilage degradation and chondrocyte imbalance. P2X7 receptor (P2X7R) is a critical inflammation switch, but few studies have examined its function and mechanisms in OA-like pyroptotic inflammation of chondrocytes. In this study, Sprague-Dawley rats were injected in the knee with monosodium iodoacetate (MIA) to induce OA, followed by multiple intra-articular injections with P2X7R antagonist A740003, P2X7R agonist BzATP, NF-κB inhibitor Bay 11-7082, and NLRP3 inhibitor CY-09. Primary rat chondrocytes were harvested and treated similarly. We assessed cell viability, damage, and death via cell viability assay, lactate dehydrogenase (LDH) release, and flow cytometry. Concentrations of adenosine triphosphate (ATP) and interleukin- (IL-) 1β in cell culture supernatant and joint cavity lavage fluid were analyzed by enzyme-linked immunosorbent assay. Changes in expression levels of P2X7 and inflammation-related indicators were analyzed by immunofluorescence, quantitative reverse-transcription polymerase chain reaction, and western blotting. Cell morphology changes and pyroptosis were observed using transmission electron microscopy. Histology, immunohistochemistry, and microcomputed tomography were used to analyze damage to bone and cartilage tissues and assess the severity of OA. Similar to MIA, BzATP reduced cell viability and collagen II expression in a dose-dependent manner. Conversely, A740003 ameliorated MIA-induced cartilage degradation and OA-like pyroptotic inflammation by rescuing P2X7, MMP13, NF-κB p65, NLRP3, caspase-1 (TUNEL-positive and active), and IL-1β upregulation. Additionally, A740003 reduced the caspase-1/propidium iodide double-positive rate, LDH concentration, and reactive oxygen species production. These effects also occurred via coincubation with Bay 11-7082 and CY-09. In conclusion, activated P2X7 promoted extracellular matrix degradation and pyroptotic inflammation in OA chondrocytes through NF-κB/NLRP3 crosstalk, thus, aggravating the symptoms of OA. The study findings suggest P2X7 as a potential target for inflammation treatment, providing new avenues for OA research and therapy.

Li Z ，Huang Z ，Zhang H ，Lu J ，Tian Y ，Wei Y ，Yang Y ，Bai L ... -  《-》

The IRF1/GBP5 axis promotes osteoarthritis progression by activating chondrocyte pyroptosis.

Tang H ，Gong X ，Dai J ，Gu J ，Dong Z ，Xu Y ，Hu Z ，Zhao C ，Deng J ，Dong S ... -  《-》

MicroRNA-140-5p represses chondrocyte pyroptosis and relieves cartilage injury in osteoarthritis by inhibiting cathepsin B/Nod-like receptor protein 3.

Zhang L ，Qiu J ，Shi J ，Liu S ，Zou H ... -  《-》