NADPH supply and the contribution of NAD(P)(+) transhydrogenase (NNT) to H2O2 balance in skeletal muscle mitochondria

Autor(es)

Figueira, Tiago R. ^{[1, 2]} ; Francisco, Annelise ^[2] ; Ronchi, Juliana A. ^[2] ; dos Santos, Guilherme R. R. M. ^[2] ; dos Santos, William ^[3] ; Treberg, Jason R. ^{[3, 4]} ; Castilho, Roger F. ^[2]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Sch Phys Educ & Sport Ribeirao Preto, Ribeirao Preto, SP - Brazil

^[2] Univ Campinas UNICAMP, Fac Med Sci, Dept Pathol, Rua Tessalia Vieira de Camargo 126, BR-13083887 Campinas, SP - Brazil

^[3] Univ Manitoba, Dept Biol Sci, Gen Off 212B Biosci Bldg, Winnipeg, MB R3T 2N2 - Canada

^[4] Univ Manitoba, Ctr Aging, Winnipeg, MB - Canada

• Tipo de documento: Artigo Científico
• Fonte: Archives of Biochemistry and Biophysics; v. 707, AUG 15 2021.
• Citações Web of Science: 0

Resumo

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 similar to 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. (AU)

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