The Succinate-HIF-1α-NLRP3 Axis in 3-Nitropropionic Acid-Induced Ovarian Dysfunction: A Testable Metabolic-Inflammatory Framework.

3-Nitropropionic acid (3-NPA) is an irreversible inhibitor of succinate dehydrogenase (SDH; mitochondrial complex II) that is widely used to model mitochondrial metabolic stress. Direct reproductive studies now show that 3-NPA can increase ovarian oxidative stress, granulosa-cell apoptosis, follicular atresia, alter ovarian reserve, impair oocyte maturation, and reduce fertility in experimental models. However, no ovarian study has yet demonstrated the complete succinate-HIF-1α-NLRP3 cascade proposed here. We therefore propose a testable framework in which SDH inhibition causes succinate accumulation and impaired respiratory electron flux, while redox stress provides an additional signal for HIF-1α stabilization and NLRP3 activation. Succinate-mediated inhibition of prolyl hydroxylases provides a mechanistic route to HIF-1α stabilization under normoxic or near-normoxic conditions, whereas NLRP3 activation may integrate mitochondrial danger signals with inflammatory signaling. Importantly, HIF-1α is not intrinsically pathogenic in the ovary: physiological HIF-1α signaling supports angiogenesis, ovulation, granulosa-cell survival, autophagy, and luteal remodeling, whereas persistent or excessive activation may become maladaptive. We further refine the proposed metabolic-inflammatory threshold as a measurable state in which combined succinate/redox burden and inflammasome activation exceed the adaptive capacity of a follicular unit. The model predicts that time-resolved measurements of succinate, SDH activity, HIF-1α stabilization, NLRP3 activation, and follicular outcomes should reveal ordered relationships that can be tested by pharmacological and genetic intervention. This review distinguishes direct ovarian evidence from cross-system mechanistic evidence and identifies the experiments required to establish causality.