MitoSNO inhibits mitochondrial hydrogen peroxide generation by α-ketoglutarate dehydrogenase.

Here, we demonstrate mitochondrial hydrogen peroxide (mtH(2)O(2)) production by α-ketoglutarate dehydrogenase (KGDH) can be inhibited by mitochondria-targeted S-nitrosating agent (MitoSNO), alleviating lipotoxicity. MitoSNO in the nanomolar range inhibits mtH(2)O(2) 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 mtH(2)O(2) generation or oxidative phosphorylation. Additionally, mtH(2)O(2) 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 mtH(2)O(2) production. S1QEL 1.1 (S1) and S3QEL (S3), which are known to selectively suppress mtH(2)O(2) genesis through inhibition of complex I and complex III, respectively, without disrupting respiration, had little to no effect on mtH(2)O(2) production by liver mitochondria. The MitoSNO also suppressed mtH(2)O(2) 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 mtH(2)O(2) overgeneration and partially rescued oxidative phosphorylation in liver mitochondria from mice fed a high-fat diet. Our findings demonstrate that MitoSNO interferes with mtH(2)O(2) production through KGDH S-nitrosation and may be useful in alleviating nonalcoholic fatty liver disease.