MitoSNO inhibits mitochondrial hydrogen peroxide generation by α-ketoglutarate dehydrogenase

Here, we demonstrate mitochondrial hydrogen peroxide (mtH₂O₂) production by α-ketoglutarate dehydrogenase (KGDH) can be inhibited by mitochondria-targeted S-nitrosating agent (MitoSNO), alleviating lipotoxicity. MitoSNO in the nanomolar range inhibits mtH₂O₂ by ∼50% in isolated liver mitochondria without disrupting respiration, whereas the mitochondria-selective derivative used to synthesize MitoSNO, mitochondria-selective N-acetyl-penicillamine, had no effect on either mtH₂O₂ generation or oxidative phosphorylation. Additionally, mtH₂O₂ generation in isolated liver mitochondria was almost abolished when MitoSNO was administered in the low micromolar range. The potent inhibitory effect of MitoSNO was comparable to 2-keto-3-methyl-valeric acid and valproic acid, selective inhibitors for KGDH-mediated mtH₂O₂ production. S1QEL 1.1 (S1) and S3QEL (S3), which are known to selectively suppress mtH₂O₂ genesis through inhibition of complex I and complex III, respectively, without disrupting respiration, had little to no effect on mtH₂O₂ production by liver mitochondria. The MitoSNO also suppressed mtH₂O₂ production and partially rescued mitochondrial respiration in Huh-7 cells subjected to palmitate- and fructose-induced lipotoxicity. MitoSNO also prevented cell death and abrogated intrahepatic lipid accumulation in these Huh-7 cells. MitoSNO nullified mtH₂O₂ overgeneration and partially rescued oxidative phosphorylation in liver mitochondria from mice fed a high-fat diet. Our findings demonstrate that MitoSNO interferes with mtH₂O₂ production through KGDH S-nitrosation and may be useful in alleviating nonalcoholic fatty liver disease.