VDAC1-mediated cytosolic leakage of mtDNA triggers pyroptosis of nucleus pulposus cells by activating the TLR9 signaling pathway.

Programmed cell death, particularly pyroptosis mediated by inflammatory signaling pathways, plays a critical role in the pathogenesis of intervertebral disc degeneration (IVDD). However, the regulatory mechanisms underlying pyroptosis and inflammation in IVDD remain poorly understood. Voltage-dependent anion channel 1 (VDAC1), a pivotal mitochondrial protein, forms oligomeric structures under inflammatory stimulation, leading to mitochondrial DNA (mtDNA) release into the cytoplasm and extracellular space. This triggers inflammatory cascades and activates pyroptosis signaling pathways, yet its physiological role and regulatory mechanisms in IVDD are still unclear. In this study, we demonstrated that the expression of VDAC1 was increased in degenerated NP tissues, and oxidative stress induced the expression and oligomerization of VDAC1 in NPC. Inhibiting VDAC1 by specific inhibitor NSC15364 or downregulating the expression of VDAC1 by specific siRNAs attenuated the mitochondrial dysfunction and pyroptosis of NPC. Mechanistically, we proved that inhibiting VDAC1 alleviated the cytosolic leakage of mtDNA, which subsequently blocked the TLR9 signaling pathway, ultimately alleviating the pyroptosis of NPC in vitro and in vivo. Our results proved for the first time that VDAC1-mtDNA-TLR9 signaling pathway might be a novel target for the treatment of IVDD.