Self-catalyzed nitric oxide nanocomplexes induce ferroptosis for cancer immunotherapy.

Ferroptosis, triggered by membrane lipid peroxidation (LPO) and diminished antioxidants, can be induced by intracellular iron (II, Fe²⁺). However, the role of nitric oxide (NO) in causing Fe²⁺ overload for ferroptosis remains uncertain. This study reveals that NO can stimulate endogenous Fe²⁺ release by upregulating heme oxygenase 1 (HMOX1) expression. Here, ferritin heavy chain (FHC) siRNA and hyaluronic acid (HA)-modified Arg-stabilized zinc peroxide (AZOSH), a non-ferrous-based nanoagent, is synthesized to trigger ferroptosis by inducing intracellular Fe²⁺ overload. AZOSH, a self-catalyzed NO nanocomplex, effectively generates NO through a reaction of self-supplied Arginine (Arg) and hydrogen peroxide (H₂O₂), which promotes glutathione (GSH) consumption to downregulate glutathione peroxidase 4 (GPX4) expression and produces peroxynitrite (ONOO^-) to enhance LPO. Meanwhile, NO promotes endo/lysosomal escape of siRNA by damaging membrane structures. Moreover, AZOSH significantly triggers Fe²⁺ overload through the synergistic effects of NO-activated HMOX1 expression and FHC siRNA-mediated ferritin sequestration. Additionally, the released Zn²⁺ from AZOSH induces oxidative stress by inhibiting mitochondrial function, further promoting ferroptosis. Consequently, AZOSH-mediated ferroptosis exhibits a strong cellular immunogenic response for T-cell activation and infiltration. Importantly, the integration of AZOSH with an anti-PD-1 antibody results in notable antitumor efficacy in vivo. Therefore, this study provides a novel concept of NO-induced ferroptosis, highlighting its role in enhancing PD-1-based immunotherapeutic efficacy.