Figueira 2021 Arch Biochem Biophys

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Figueira TR, Francisco A, Ronchi JA, Dos Santos GRRM, Santos WD, Treberg JR, Castilho RF (2021) NADPH supply and the contribution of NAD(P)+ transhydrogenase (NNT) to H2O2 balance in skeletal muscle mitochondria. Arch Biochem Biophys 707:108934.

» PMID: 34043997

Figueira Tiago R, Francisco Annelise, Ronchi Juliana A, Dos Santos Guilherme R R M, Dos Santos William, Treberg Jason R, Castilho Roger F (2021) Arch Biochem Biophys

Abstract: H2O2 is endogenously generated and its removal in the matrix of skeletal muscle mitochondria (SMM) is dependent on NADPH likely provided by NAD(P)+ transhydrogenase (NNT) and isocitrate dehydrogenase (IDH2). Importantly, NNT activity is linked to mitochondrial protonmotive force. Here, we demonstrate the presence of NNT function in detergent-solubilized and intact functional SMM isolated from rats and wild type (Nnt+/+) mice, but not in SMM from congenic mice carrying a mutated NNT gene (Nnt-/-). Further comparisons between SMM from both Nnt mouse genotypes revealed that the NADPH supplied by NNT supports up to 600 pmol/mg/min of H2O2 removal under selected conditions. Surprisingly, SMM from Nnt-/- mice removed exogenous H2O2 at wild-type levels and exhibited a maintained or even decreased net emission of endogenous H2O2 when substrates that support Krebs cycle reactions were present (e.g., pyruvate plus malate or palmitoylcarnitine plus malate). These results may be explained by a compensation for the lack of NNT, since the total activities of concurrent NADP+-reducing enzymes (IDH2, malic enzymes and glutamate dehydrogenase) were ~70% elevated in Nnt-/- mice. Importantly, respiratory rates were similar between SMM from both Nnt genotypes despite differing NNT contributions to H2O2 removal and their implications for an evolving concept in the literature are discussed. We concluded that NNT is capable of meaningfully sustaining NADPH-dependent H2O2 removal in intact SMM. Nonetheless, if the available substrates favor non-NNT sources of NADPH, the H2O2 removal by SMM is maintained in Nnt-/- mice SMM. Keywords: Antioxidant, C57BL/6J, Krebs cycle, Oxidative stress, Redox balance Bioblast editor: Reiswig R O2k-Network Lab: BR Campinas Vercesi AE, CA Winnipeg Treberg JR


Labels: MiParea: Respiration, Genetic knockout;overexpression 

Stress:Oxidative stress;RONS  Organism: Mouse  Tissue;cell: Skeletal muscle  Preparation: Isolated mitochondria 


Coupling state: LEAK, OXPHOS, ET  Pathway: F, N  HRR: Oxygraph-2k 

2021-07