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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

The Contribution of Nicotinamide Nucleotide Transhydrogenase to Peroxide Detoxification Is Dependent on the Respiratory State and Counterbalanced by Other Sources of NADPH in Liver Mitochondria

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Ronchi, Juliana Aparecida ; Francisco, Annelise ; Correa Passos, Luiz Augusto ; Figueira, Tiago Rezende ; Castilho, Roger Frigerio
Total Authors: 5
Document type: Journal article
Source: Journal of Biological Chemistry; v. 291, n. 38, p. 20173-20187, SEP 16 2016.
Web of Science Citations: 24

The forward reaction of nicotinamide nucleotide transhydrogenase (NNT) reduces NADP(+) at the expense of NADH oxidation and H+ movement down the electrochemical potential across the inner mitochondrial membrane, establishing an NADPH/NADP(+) ratio severalfold higher than the NADH/NAD(+) ratio in the matrix. In turn, NADPH drives processes, such as peroxide detoxification and reductive biosynthesis. In this study, we generated a congenic mouse model carrying a mutated Nnt(C57BL/6J) allele from the C57BL/6J substrain. Suspensions of isolated mitochondria from Nnt(+/+), Nnt(+/-), and Nnt(-/-) mouse liver were biochemically evaluated and challenged with exogenous peroxide under different respiratory states. The respiratory substrates were also varied, and the participation of concurrent NADPH sources (i.e. isocitrate dehydrogenase-2, malic enzymes, and glutamate dehydrogenase) was assessed. The principal findings include the following: Nnt(+/-) and Nnt(-/-) exhibit approximate to 50% and absent NNT activity, respectively, but the activities of concurrent NADPH sources are unchanged. The lack of NNT activity in Nnt(-/-) mice impairs peroxide metabolism in intact mitochondria. The contribution of NNT to peroxide metabolism is decreased during ADP phosphorylation compared with the non-phosphorylating state; however, it is accompanied by increased contributions of concurrent NADPH sources, especially glutamate dehydrogenase. NNT makes a major contribution to peroxide metabolism during the blockage of mitochondrial electron transport. Interestingly, peroxide metabolism in the Nnt(+/-) mitochondria matched that in the Nnt(+/+) mitochondria. Overall, this study demonstrates that the respiratory state and/or substrates that sustain energy metabolism markedly influence the relative contribution of NNT (i.e. varies between nearly 0 and 100%) to NADPH-dependent mitochondrial peroxide metabolism. (AU)

FAPESP's process: 11/50400-0 - Mitochondrial energy metabolism, redox state and functionality in cell death and cardiometabolic and neurodegenerative disorders
Grantee:Aníbal Eugênio Vercesi
Support type: Research Projects - Thematic Grants
FAPESP's process: 15/22063-0 - Antioxidant Role of the Nicotinamide Nucleotide Transhydrogenase (NNT) in the Central Nervous System - Morphofunctional characterization in control mice and spontaneously Nnt gene mutant mice.
Grantee:Annelise Francisco
Support type: Scholarships in Brazil - Doctorate