THE ROLE OF MITOCHONDRIAL CATIONS HOMEOSTASIS IN THE CONTROL OF THE INFLAMMATORY RESPONSE

Mitochondrial calcium (Ca²⁺) and potassium (K⁺) signaling have emerged as key regulators of innate immunity. Mitochondria are essential for both the initiation and maintenance of innate and adaptive immune responses, acting as signaling hubs and modulators of several physio-pathological functions, particularly through their role in cation homeostasis. In this study, we demonstrated that mitochondrial Ca²⁺ uptake via the mitochondrial calcium uniporter (MCU) is crucial for full activation of the NLR family pyrin domain containing 3 (NLRP3) inflammasome in macrophages. Using both pharmacological inhibition and genetic ablation of MCU, we showed that impaired mitochondrial Ca²⁺ accumulation significantly reduces IL-1β release in response to various stimuli (ATP, nigericin, Poly(dA:dT) and monosodium urate crystals (MSU). Notably, reduced mitochondrial Ca²⁺ uptake prevented mitochondrial fragmentation, a process required for optimal inflammasome activation. These findings were further supported by in vivo studies: both MCU heterozygous (MCU⁺/⁻) and macrophage-specific MCU knockout (macMCU⁻/⁻) mice exhibited attenuated NLRP3-driven inflammation following intra-articular MSU injection in a model of acute gout. We also showed that mitochondrial K⁺ flux is also required for NLRP3 inflammasome activation. Genetic deletion of the mitochondrial ATP-sensitive K+ (MitoKATP) channel dampens the inflammatory response, although the mechanistic link between mitochondrial K⁺ flux and inflammasome activation remains to be fully elucidated. Together, these findings identify mitochondrial cations fluxes, particularly Ca²⁺ and K⁺, as critical checkpoints in the regulation of NLRP3 inflammasome activation. Moreover, these data suggest that modulating mitochondrial Ca²⁺ handling could represent a promising therapeutic strategy for controlling inflammation in diseases such as gout.