Hyperthermia induces reductive stress in murine macrophages

Hyperthermia induces heat stress (HS) and injuries in various human organs, or even leads to mortality, yet the underlying mechanism is incompletely uncovered. Our study revealed that HS in macrophages induced concurrent activation of pyroptotic, apoptotic, and necroptotic pathways, and the formation of PANoptosome-like complexes. However, these processes proceeded independently of ROS, as the ROS scavengers N-acetyl cysteine and mito-TEMPO failed to prevent the cell death (PANoptosis) despite effectively suppressing oxidative stress. Instead, HS caused reductive stress marked by NADPH accumulation and thioredoxin (Trx) system dysfunction. Trx1 aggregation impaired redox regulation, leading to aberrant disulfide bonding in mitochondrial proteins (e.g., Drp1, Bcl-2). The Trx reductase exogenous substrate DTNB partially rescued cell viability by restoring redox balance, confirming Trx failure as a key driver of cytotoxicity. Notably, such reductive stress was accompanied by DNA damage and mitochondrial injury during HS. Pharmacologic intervention revealed that pan-caspase inhibition by IDN-6556 abrogated the reductive stress and its consequences (ROS production, DNA damage, and mitochondrial injury), and suppressed the pyroptotic/apoptotic signaling and lytic cell death. However, the caspase inhibition alone triggered compensatory receptor-interaction protein 3 (RIPK3) activation, necessitating dual inhibition with GSK'872 (RIPK3 inhibitor) to fully block PANoptotic cell death. In vivo validation showed protection of the IDN-6556/GSK'872 combination against HS-induced injury on the intestines through reduced DNA damage and PANoptosis suppression. Our study reveals that reductive stress-mediated Trx dysfunction, not oxidative stress, underlies HS-induced PANoptosis. Dual targeting of caspases and RIPK3 provides a novel therapeutic avenue against heat shock-associated diseases.