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

3-NPA is produced by several plants and fungi and is associated with poisoning by contaminated food, particularly moldy sugarcane. Its structural relationship to succinate enables interaction with SDH, and covalent modification of the enzyme underlies its irreversible inhibitory behavior [ 22 , 23 , 24 ] ( Figure 1 ). The reproductive literature supports biological activity at multiple levels. In female mice, repeated systemic exposure increases ovarian oxidative stress and follicular atresia; in granulosa-cell models it reduces viability and increases apoptosis; in oocytes it disrupts maturation; and in more recent studies it alters ovarian reserve and fertility. These observations establish 3-NPA as an experimental reproductive toxicant, but they do not by themselves identify a common downstream signaling cascade [ 12 , 13 , 14 , 16 , 17 , 18 , 19 , 20 , 21 ]. SDH/complex II links the tricarboxylic acid (TCA) cycle to the respiratory chain. It oxidizes succinate to fumarate while reducing FAD to FADH 2 , and transfers electrons through its iron–sulfur centers to ubiquinone. Structural and biochemical studies establish complex II as a specialized respiratory node whose dysfunction can influence both intermediary metabolism and electron-transfer chemistry [ 24 , 25 , 26 ]. 3-NPA therefore has a distinctive metabolic signature: it blocks succinate oxidation rather than directly inhibiting NADH dehydrogenase. The most defensible upstream event is SDH inhibition, followed by succinate accumulation, reduced complex-II electron entry, altered TCA flux, and secondary changes in cellular redox balance [ 23 , 24 , 26 ]. Three consequences are particularly relevant to ovarian toxicity. First, complex-II-dependent respiratory electron flow within the electron transport chain (ETC) is reduced, which can lower respiratory capacity and ATP production when compensatory pathways are insufficient. Second, succinate accumulates because its oxidation to fumarate is blocked. Third, altered respiratory flux can increase ROS generation at mitochondrial redox sites. The magnitude and direction of NADH/NAD + changes are context dependent and should not be described as an obligatory direct consequence of SDH inhibition because complex II is FAD-linked and does not directly produce NADH [ 26 , 27 , 28 ]. The ROS mechanism also requires correction. Reverse electron transport (RET) at complex I is a well-established ROS-generating mechanism under conditions such as succinate-driven reperfusion, when a large reduced succinate pool feeds electrons into an otherwise competent respiratory chain. Irreversible pharmacological blockade of SDH is biochemically different. Under 3-NPA exposure, it is more appropriate to describe ROS as arising from disturbed complex-II redox chemistry, impaired electron flux, altered ubiquinone redox state, and secondary respiratory imbalance. Complex II itself can generate ROS in both forward and reverse reactions, but the extent to which RET contributes during sustained 3-NPA inhibition in ovarian cells remains untested [ 27 , 28 , 29 , 30 ]. A focused PubMed literature search identified a small but expanding body of primary reproductive studies. The evidence is heterogeneous in species, exposure regimen, and endpoint, but it is sufficient to establish direct ovarian and gamete toxicity ( Table 1 ). The studies consistently support oxidative stress, apoptosis, follicular injury, altered ovarian reserve, or impaired oocyte development. In contrast, none of the identified studies simultaneously measured SDH activity/succinate, HIF-1α stabilization, and NLRP3 inflammasome activation in the same ovarian model. This distinction is central to the revised interpretation of the present review. Table 1 demonstrates that the foundational premise of ovarian 3-NPA toxicity is directly supported, but the proposed axis is not yet directly demonstrated. The most reproducible ovarian signals are oxidative stress, apoptosis, follicular atresia, altered ovarian reserve, and impaired oocyte competence. These findings provide biological plausibility for investigating succinate, HIF-1α, and NLRP3, but they should not be retrospectively relabeled as evidence that those nodes mediate 3-NPA toxicity. Direct ovarian toxicity should be distinguished from reproductive consequences secondary to systemic 3-NPA toxicity. Direct evidence is strongest when ovarian tissue, isolated granulosa cells, or oocytes are exposed to 3-NPA and the ovarian phenotype is measured directly. In contrast, maternal exposure, offspring phenotypes, and fertility outcomes after systemic dosing may reflect a combination of ovarian and extra-ovarian effects. Because 3-NPA is a potent mitochondrial toxicant with established neurological and systemic toxicity, differences in dose, route, duration, species, and concurrent neurological, metabolic, endocrine, or general toxic effects may influence ovarian endpoints. Accordingly, systemic in vivo studies are interpreted as evidence of reproductive toxicity rather than proof that the ovary is always the primary site of toxicity.

Direct ovarian studies support mitochondrial and redox disruption after 3-NPA exposure. Reduced SDH activity, altered oxidative-phosphorylation capacity, loss of mitochondrial membrane potential, increased ROS, and impaired antioxidant defenses have been reported in ovarian or granulosa-cell models [ 12 , 14 , 16 , 17 , 18 , 19 , 20 , 31 ] ( Figure 2 ). By contrast, specific remodeling of mitochondrial dynamics, such as DRP1 hyperactivation or coordinated MFN1/2 and OPA1 downregulation, has not been established as a consistent 3-NPA ovarian phenotype. These changes are mechanistically plausible because mitochondrial stress can alter fission/fusion balance, but they should be treated as testable predictions rather than observations [ 3 , 5 ]. The revised manuscript avoids describing granulosa cells as uniformly OXPHOS-dependent. Proliferating granulosa cells can rely substantially on glycolysis, while mitochondrial metabolism remains essential for steroidogenesis, differentiation, redox regulation, and adaptation. HIF-1α-driven glycolysis may therefore be adaptive in some granulosa-cell states and maladaptive in others. The relevant question is not whether glycolysis increases, but whether the shift is sufficient to maintain ATP demand and biosynthetic functions while preserving redox and mitochondrial homeostasis [ 5 , 6 , 32 ]. Oxidative stress and apoptosis are the strongest mechanistic findings across the direct reproductive literature. Mouse and goose granulosa-cell models show increased ROS and activation of apoptotic pathways, while more recent studies implicate TRPM2-dependent Ca 2+ influx, NRF2 signaling, and JNK/ERK responses. Ferroptosis and pyroptosis are biologically relevant forms of granulosa-cell death in other ovarian injury models, but their co-activation by 3-NPA itself remains unproven [ 12 , 14 , 17 , 18 , 19 , 20 , 33 ]. Thus, the revised framework distinguishes three evidence layers: (i) direct 3-NPA reproductive toxicity, (ii) ovarian mechanisms demonstrated with other insults, and (iii) cross-system biochemical mechanisms that generate hypotheses for 3-NPA. The proposed succinate–HIF-1α–NLRP3 axis belongs primarily to the third category, with selected nodes supported by independent ovarian literature.

Succinate is both a TCA-cycle intermediate and a signaling metabolite. Accumulation of succinate can inhibit α-ketoglutarate-dependent dioxygenases, including prolyl hydroxylases (PHDs), thereby altering HIF stability and other oxygen-sensitive or epigenetic processes. This mechanism is well established in non-ovarian systems [ 34 , 35 , 36 ] ( Figure 3 ). For 3-NPA-exposed ovaries, however, succinate accumulation should currently be considered a strong biochemical prediction rather than a universally demonstrated ovarian measurement. The most informative experiment would be a time-resolved analysis of intracellular succinate alongside SDH activity and fumarate, before and after 3-NPA exposure. Extracellular succinate signaling through SUCNR1/GPR91 is also plausible, but functional SUCNR1 signaling specifically in granulosa cells after 3-NPA exposure has not been established and should therefore remain explicitly hypothetical. Under normoxia, PHD enzymes hydroxylate HIF-1α and facilitate recognition by Von Hippel–Lindau tumor suppressor (VHL). Succinate can inhibit PHD activity and stabilize HIF-1α despite the absence of severe tissue hypoxia. This is appropriately termed pseudohypoxia. Importantly, pseudohypoxia refers to activation of hypoxia-responsive signaling without requiring a fall in tissue oxygen tension; because SDH inhibition can also reduce oxygen consumption, local oxygen availability may even increase in some contexts [ 36 , 37 , 38 ]. The proposed ovarian sequence is therefore: SDH inhibition → succinate accumulation → reduced PHD activity → delayed HIF-1α degradation. This sequence is biochemically well supported, but its magnitude, timing, and contribution to 3-NPA-induced ovarian injury require direct ovarian measurements. HIF-1α should not be characterized as inherently pathological. In the ovary, HIF-1α participates in follicular angiogenesis, ovulation, granulosa-cell survival, autophagy, luteinization, and luteal remodeling. In mice, the FSH–HIF-1α–VEGF pathway is required for ovulation and oocyte health, while granulosa-cell HIF-1α can protect against hypoxia-induced apoptosis and contribute to autophagy [ 6 , 32 , 39 , 40 ]. The relevant distinction is therefore between adaptive and maladaptive HIF-1α activity. Transient HIF-1α activation may support survival and tissue remodeling, whereas persistent or excessive activation, especially when coupled to redox stress and inflammatory signaling, could become maladaptive. Accordingly, the metabolic-burden term M in the threshold model refers specifically to persistent or pathological metabolic stress associated with sustained HIF-1α activation, not to physiological HIF-1α pulses required for normal follicular or luteal function. This distinction is essential when interpreting succinate-driven HIF-1α stabilization in a toxicological setting. If succinate is a causal intermediate rather than a bystander, then reducing succinate accumulation or restoring PHD activity should attenuate HIF-1α stabilization without necessarily preventing the initial SDH inhibition. Conversely, direct HIF-1α inhibition should reduce HIF-dependent transcription but should not normalize succinate. These experimentally separable predictions provide a means to distinguish causal order from parallel stress responses.

ROS can promote NLRP3 inflammasome activation through several convergent mechanisms, including disruption of redox-sensitive proteins and mitochondrial stress. The TXNIP–NLRP3 mechanism was initially defined in metabolic and inflammatory systems and should not be treated as a demonstrated 3-NPA granulosa-cell mechanism. In ovarian granulosa cells exposed to other metabolic or inflammatory insults, NLRP3, caspase-1, and GSDMD activation have been directly observed, establishing ovarian competence for this inflammatory cell-death pathway [ 41 , 42 , 43 , 44 ]. For 3-NPA, the most defensible formulation is therefore that mitochondrial redox stress may provide a signal capable of activating NLRP3, rather than that 3-NPA has already been shown to activate a TXNIP-dependent NLRP3 pathway in the ovary. Cross-system studies support bidirectional coupling between HIF-1α and inflammatory signaling. Succinate can stabilize HIF-1α, and HIF-dependent transcription can promote inflammatory outputs such as IL-1β; conversely, inflammatory signaling can reinforce HIF-1α activity in some contexts [ 32 , 35 , 36 ]. Ovarian studies independently demonstrate that HIF-1α and NLRP3 are functional regulators of granulosa-cell biology, but direct evidence connecting these two nodes downstream of 3-NPA is lacking [ 35 , 36 , 41 , 45 , 46 ] ( Figure 4 ). The revised model therefore uses a dashed causal boundary between the demonstrated ovarian modules and the proposed 3-NPA-specific integration. This distinction prevents a cross-system mechanism from being presented as if it were already validated in ovarian tissue. We redefine the previously rhetorical “metabolic–inflammatory threshold” as a measurable state variable rather than a fixed biological constant. Let M represent the combined metabolic/redox burden, approximated by normalized succinate accumulation, SDH inhibition, ROS or lipid-peroxidation indices, and mitochondrial membrane-potential loss. Let I represent inflammatory activation, approximated by NLRP3 abundance/assembly, cleaved caspase-1, GSDMD-N, and mature IL-1β/IL-18. Let A represent adaptive capacity, including NRF2 activity, antioxidant capacity, ATP compensation, autophagy, and cell-survival signaling. The threshold hypothesis predicts that follicular injury becomes progressively more likely when M + I exceeds A for a sufficient duration. This formulation generates testable predictions. First, follicular outcomes should correlate more strongly with the integrated time-dependent burden than with any single endpoint. Second, partial reduction in either metabolic stress or inflammasome activation should shift the dose–response curve if the two inputs are coupled. Third, combined intervention should produce greater protection than either intervention alone if the model contains a true synergistic threshold. Fourth, the threshold should be cell-state dependent rather than universal, because granulosa cells, oocytes, theca cells, and stromal/immune cells have different metabolic reserves and signaling networks. Ovulation is accompanied by a tightly regulated inflammatory-like program, and inflammatory mediators participate in follicular rupture and tissue remodeling. The revised manuscript therefore does not equate NLRP3 activation with pathological injury. The proposed threshold concept instead concerns duration, amplitude, and spatial persistence of inflammatory signaling. A transient inflammatory pulse compatible with ovulation should be distinguished experimentally from sustained NLRP3 activation associated with follicular atresia or granulosa-cell death.

Direct 3-NPA studies support depletion of primordial follicles and development of POI-like phenotypes after repeated exposure. The PI3K–AKT–FOXO3 pathway is a well-established regulator of primordial follicle activation, but the specific sequence 3-NPA → succinate/ROS → PTEN suppression → AKT activation → FOXO3a export has not been demonstrated. It should therefore be treated as a mechanistic prediction rather than an established 3-NPA pathway [ 1 , 31 ]. Inflammation can also influence follicular survival, and ovarian NLRP3 activation is documented in metabolic reproductive disorders. Nevertheless, direct evidence that 3-NPA-induced NLRP3/IL-1β drives abnormal primordial-follicle recruitment is currently lacking. This is an important knowledge gap rather than a settled mechanism [ 45 , 46 ]. Direct 3-NPA studies demonstrate impaired granulosa-cell viability/proliferation, increased apoptosis, and reduced follicular development. As an in-principle supporting observation from a different experimental context, IL-1β has been shown to inhibit estrogen formation in cultured rat granulosa cells. This finding demonstrates that inflammatory signaling can affect granulosa-cell steroidogenesis, but it does not establish IL-1β as a mediator of the specific 3-NPA ovarian phenotype, nor does it establish the proposed succinate–HIF-1α–NLRP3 pathway [ 12 , 14 , 17 , 47 ] ( Figure 5 ). 3-NPA directly impairs oocyte maturation, including first polar body extrusion, spindle organization, cortical-granule distribution, ATP levels, mitochondrial membrane potential, and redox status. These observations provide direct evidence for gamete-level toxicity. Whether succinate accumulation, HIF-1α stabilization, or NLRP3 signaling contributes to these oocyte phenotypes remains unknown [ 4 , 16 ]. Repeated 3-NPA exposure can reduce AMH and estradiol, increase FSH, alter the estrous cycle, reduce primordial follicles, increase atresia, and impair fertility in mice. These outcomes support the use of 3-NPA as an oxidative-stress-associated POI model. However, the causal bridge from these phenotypes to the proposed succinate–HIF-1α–NLRP3 axis remains to be established [ 11 , 15 , 18 , 19 , 31 ] ( Figure 6 ).

POI is characterized by diminished ovarian reserve and impaired endocrine function. Because 3-NPA can induce POI-like phenotypes in mice and metabolic/redox abnormalities are implicated in human POI, the proposed axis may provide a useful mechanistic hypothesis. However, no evidence currently demonstrates that the succinate–HIF-1α–NLRP3 axis is a causal driver of human POI [ 11 , 31 , 48 ] ( Figure 7 ). Ovarian aging is associated with mitochondrial dysfunction, oxidative stress, and chronic low-grade inflammation. These features overlap conceptually with the proposed axis, but overlap is not proof of pathway identity. The strongest value of the model in ovarian aging is therefore as a testable hypothesis linking metabolic stress to inflammatory signaling [ 3 , 8 , 9 , 49 ]. NLRP3 activation and granulosa-cell pyroptosis have been demonstrated in PCOS-related models, and metabolic reprogramming is an important feature of PCOS. These independent findings make NLRP3 and HIF-1α biologically relevant to PCOS, but there is no evidence that 3-NPA-induced succinate accumulation explains PCOS pathogenesis. The proposed axis should therefore be presented as a possible mechanistic analogy, not a disease mechanism [ 45 , 46 , 50 ]. Endometriosis provides a more defensible disease context for discussing HIF-1α because hypoxia-related signaling and angiogenic remodeling are independently established in the disease. Nevertheless, extrapolating the complete succinate–HIF-1α–NLRP3 sequence from 3-NPA toxicity to endometriosis remains speculative and should be tested in disease-specific models [ 51 ].

Melatonin, N-acetylcysteine, coenzyme Q10, NRF2 activation, and related antioxidant strategies are plausible approaches because oxidative stress is a reproducible component of 3-NPA ovarian injury. However, protection by an antioxidant would not prove the succinate–HIF-1α–NLRP3 pathway; it would establish redox dependence. Direct ovarian 3-NPA studies provide proof-of-principle for several antioxidant or redox-supportive interventions, including proanthocyanidins, tannic acid, silibinin, swertiamarin, selenium, and BCAA supplementation [ 14 , 15 , 17 , 18 , 19 , 22 ] ( Figure 8 ). α-ketoglutarate supplementation or pharmacological modulation of PHD activity could test whether HIF-1α stabilization is downstream of succinate accumulation. The critical experimental requirement is temporal ordering: if PHD restoration reduces HIF-1α stabilization without restoring SDH activity, this would support the proposed metabolite-to-HIF branch. Conversely, excessive HIF-1α inhibition may be harmful because physiological HIF-1α signaling supports ovarian vascular and follicular functions [ 6 , 37 , 39 , 40 ]. MCC950 is a well-characterized experimental NLRP3 inhibitor and can be used to test whether inflammasome activation is required for downstream ovarian injury. To the best of our knowledge, MCC950 has not been directly tested as a treatment for 3-NPA-induced ovarian injury. Thus, MCC950 should be described as a mechanistic probe and candidate intervention, not a validated therapy for this model [ 52 ]. SIRT3 is an attractive metabolic node because it regulates mitochondrial homeostasis, antioxidant capacity, and energy metabolism. Yet neither SIRT3/AMPK activation nor direct succinate-lowering strategies have been shown to reverse the full 3-NPA ovarian phenotype. The strongest next step is a factorial design that combines a metabolic intervention with an inflammasome intervention and tests whether combined treatment produces non-additive protection [ 52 , 53 , 54 ].

Several limitations define the current evidence base ( Table 2 ). First, the direct ovarian literature is relatively small and heterogeneous in species, dose, duration, and endpoints. Second, most evidence for succinate–PHD–HIF-1α signaling and HIF-1α–NLRP3 coupling derives from non-ovarian systems. Third, direct measurement of ovarian succinate, HIF-1α hydroxylation/degradation kinetics, NLRP3 assembly, caspase-1 activity, and GSDMD cleavage after 3-NPA is limited or absent. Fourth, 3-NPA is a potent mitochondrial toxicant and may activate parallel pathways, including PARP-1, SIRT1, NRF2, TRPM2, JNK/ERK, autophagy, and glutamine metabolism; the proposed axis may therefore represent one branch of a broader stress response rather than a unique master pathway [ 14 , 17 , 18 , 19 , 20 , 31 ]. Fifth, pharmacological inhibitors may have off-target effects and cannot by themselves establish pathway order. Genetic approaches, orthogonal metabolic measurements, and rescue experiments are required. Sixth, the dose ranges used in rodents and cultured cells cannot be directly translated into human exposure levels. Finally, HIF-1α and NLRP3 both have physiological functions in ovarian biology, so complete pathway suppression may be neither feasible nor desirable. The most informative future experiments are therefore: time-resolved ovarian metabolomics for succinate/fumarate and respiratory measurements; direct measurement of HIF-1α hydroxylation, VHL engagement, and transcriptional output; NLRP3 inflammasome assembly and GSDMD cleavage assays in purified granulosa cells; genetic perturbation of SDH, HIF1A, NLRP3, TXNIP, and SUCNR1; cell-type-resolved single-cell or spatial measurements; and factorial intervention studies designed to test the proposed threshold and interaction effects. The recent maternal-exposure study showing an F1 POI-like phenotype further broadens the reproductive evidence base, but its intergenerational design also underscores the need to distinguish ovarian-intrinsic effects from consequences of maternal systemic toxicity and developmental exposure [ 20 ].

The ovary integrates follicle recruitment, granulosa-cell proliferation and differentiation, steroidogenesis, ovulation, luteal remodeling, and oocyte competence. These processes are governed by endocrine, metabolic, redox, vascular, and immune signals rather than by a single pathway. The size and persistence of the primordial follicle pool are major determinants of reproductive lifespan, while mitochondrial integrity influences oocyte competence and follicular survival [ 1 , 2 , 3 ]. Mitochondria are particularly important in oocytes, which contain a very high mitochondrial complement and rely on oxidative metabolism for maturation and early embryogenesis. Granulosa-cell metabolism, however, is more heterogeneous than a simple oxidative phosphorylation (OXPHOS)-dominant model implies. Proliferating granulosa cells can exhibit substantial glycolytic activity, whereas mitochondrial oxidative metabolism remains important for steroidogenesis, differentiation, redox control, and cellular adaptation. Thus, a reduction in OXPHOS should not automatically be interpreted as energetic collapse; its consequence depends on developmental stage, substrate availability, and the capacity for glycolytic compensation [ 3 , 4 , 5 , 6 ]. Mitochondrial dysfunction and oxidative stress are implicated in ovarian aging, premature ovarian insufficiency (POI), and other reproductive disorders. Recent ovarian studies also show that metabolic perturbations can alter granulosa-cell function and ovarian reserve, supporting an integrated metabolic view of reproductive dysfunction [ 7 , 8 , 9 , 10 , 11 ]. 3-NPA is a naturally occurring toxin and an irreversible inhibitor of SDH. In nervous-system models, its toxicity is closely linked to complex II inhibition, succinate accumulation, impaired respiration, and oxidative stress. Importantly, direct reproductive studies are not absent: mouse, goose, vole, and oocyte models have documented ovarian or gamete toxicity. What remains absent is direct evidence that these ovarian phenotypes are causally organized by a succinate–HIF-1α–NLRP3 pathway [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. The purpose of this review is therefore twofold. First, we synthesize the primary reproductive literature on 3-NPA and explicitly distinguish demonstrated ovarian observations from mechanistic extrapolation. Second, we develop the succinate–HIF-1α–NLRP3 axis as a hypothesis-generating framework rather than an established ovarian mechanism. Particular attention is given to the biochemical feasibility of reactive oxygen species (ROS) generation after irreversible SDH inhibition, the physiological and pathological duality of HIF-1α, the metabolic heterogeneity of granulosa cells, and a measurable definition of the proposed metabolic–inflammatory threshold. About review methodology and evidence classification, this article is a narrative review with a focused, reproducible literature-mapping component rather than a systematic review or meta-analysis. A final focused PubMed search was conducted on 28 August 2026 using combinations of “3-nitropropionic acid”, “3-NPA”, “ovary”, “ovarian”, “granulosa cell”, “oocyte”, “follicle”, “ovarian reserve”, “premature ovarian insufficiency”, and “embryo”. Mechanistic searches additionally combined 3-NPA or succinate with “succinate dehydrogenase”, “HIF-1α”, “PHD”, “NLRP3”, “TXNIP”, “pyroptosis”, “ferroptosis”, “mitochondrial ROS”, and “SUCNR1”. Primary reproductive studies were prioritized, and recent primary literature was preferentially incorporated. Studies were selected for relevance to ovarian/reproductive toxicity, mitochondrial metabolism, redox signaling, HIF-1α biology, inflammasome signaling, or candidate interventions. No formal PRISMA screening, risk-of-bias scoring, or quantitative meta-analysis was performed. Claims were classified as direct 3-NPA reproductive evidence, ovarian mechanistic evidence not specifically downstream of 3-NPA, or cross-system mechanistic evidence; links not directly supported by these tiers are presented as hypotheses.

Direct reproductive studies establish that 3-NPA is capable of inducing ovarian and gamete toxicity characterized by oxidative stress, granulosa-cell apoptosis, follicular atresia, altered ovarian reserve, impaired oocyte maturation, and reduced fertility. The current evidence does not establish the complete succinate–HIF-1α–NLRP3 pathway in the ovary. We therefore propose this axis as a testable mechanistic framework rather than a proven causal cascade. The central hypothesis is that irreversible SDH inhibition creates a metabolic state characterized by succinate accumulation and altered mitochondrial redox chemistry; succinate may stabilize HIF-1α through PHD inhibition, while mitochondrial danger signals may promote NLRP3 activation. Physiological HIF-1α and NLRP3 functions must be distinguished from persistent pathological activation. The proposed metabolic–inflammatory threshold is operationally defined as the point at which combined metabolic/redox burden and inflammatory activation exceed adaptive capacity for sufficient duration to alter follicular fate. The value of this framework is therefore not that it closes the mechanistic question, but that it organizes existing reproductive observations into experimentally separable predictions. Direct measurement and causal perturbation of succinate, HIF-1α, NLRP3, and their temporal relationships will determine whether the proposed axis is a central mechanism, one branch of a broader stress response, or a context-dependent module in 3-NPA-induced ovarian dysfunction.