Succinate dehydrogenase mediated ROS production contributes to ASIC1a-induced chondrocyte pyroptosis in rheumatoid arthritis

Our previous study showed that acidic stimuli activate acid-sensitive ion channel 1a (ASIC1a), resulting in chondrocyte destruction associated with rheumatoid arthritis (RA). However, the exact underlying processes remain unclear. Recent evidence suggests that the production of reactive oxygen species (ROS) mediated by succinate dehydrogenase (SDH), contributes to chondrocyte damage. The objective of this study was to investigate the involvement of SDH in ASIC1a-induced chondrocyte destruction in RA and to explore the associated mechanisms both in vivo and in vitro. Our findings revealed that the cartilage of mice with collagen-induced arthritis (CIA) and acid-treated chondrocytes exhibited a substantial increase in SDH expression. Furthermore, SDH inhibition attenuates acidosis-induced pyroptosis in chondrocytes. Notably, ASIC1a activation through acid stimuli increases SDH activity and pyroptosis through the Ca²⁺/CaMKK2/AMPK pathway in chondrocytes. Mechanistically, SDH assembly factor 2 (SDHAF2) was identified as a key modulator of SDH activity induced by ASIC1a in acid-stressed chondrocytes. Moreover, the expression of SDH in CIA mouse chondrocytes decreased and the histological characteristics of ankle joint damage were reduced by the ASIC1a-particular blocker PcTx-1. Overall, these observations suggest that ASIC1a activation under acidic conditions increases SDH activity and modulates SDHAF2, thereby promoting chondrocyte pyroptosis through the Ca²⁺/CaMKK2/AMPK pathway.