Extraction and Quantitation of Nicotinamide Adenine Dinucleotide Redox Cofactors

Wenyun Lu, Lin Wang, Li Chen, Sheng Hui, Joshua D. Rabinowitz

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Aims: Accurate analysis of dinucleotide redox cofactors nicotinamide adenine dinucleotide phosphate reduced (NADPH), nicotinamide adenine dinucleotide phosphate (NADP+), nicotinamide adenine dinucleotide reduced (NADH), and nicotinamide adenine dinucleotide (NAD+) from biological samples is important to understanding cellular redox homeostasis. In this study, we aimed to develop a simple protocol for quenching metabolism and extracting NADPH that avoids interconversion among the reduced forms and the oxidized forms. Results: We compared seven different solvents for quenching and extraction of cultured mammalian cells and mouse tissues: a cold aqueous buffer commonly used in enzyme assays with and without detergent, hot aqueous buffer, and cold organic mixtures (80% methanol, buffered 75% acetonitrile, and acidic 40:40:20 acetonitrile:methanol:water with either 0.02 M or 0.1 M formic acid). Extracts were analyzed by liquid chromatography-mass spectrometry (LC-MS). To monitor the metabolite interconversion, cells were grown in 13C6-glucose medium, and unlabeled standards were spiked into the extraction solvents. Interconversion between the oxidized and reduced forms was substantial except for the enzyme assay buffer with detergent, 80% methanol and 40:40:20 acetonitrile:methanol:water, with the 0.1 M formic acid mix giving the least interconversion and best recoveries. Absolute NAD+, NADH, NADP+, and NADPH concentrations in cells and mouse tissues were measured with this approach. Innovation: We found that the interconversion between the reduced and oxidized forms during extraction is a major barrier to accurately measuring NADPH/NADP+ and NADH/NAD+ ratios. Such interconversion can be monitored by isotope labeling cells and spiking NAD(P)(H) standards. Conclusion: Extraction with 40:40:20 acetonitrile:methanol:water with 0.1 M formic acid decreases interconversion and, therefore, is suitable for measurement of redox cofactor ratios using LC-MS. This solvent is also useful for general metabolomics. Samples should be neutralized immediately after extraction to avoid acid-catalyzed degradation. When LC-MS is not available and enzyme assays are accordingly used, inclusion of detergent in the aqueous extraction buffer reduces interconversion. Antioxid. Redox Signal. 28, 167-179.

Original languageEnglish (US)
Pages (from-to)167-179
Number of pages13
JournalAntioxidants and Redox Signaling
Volume28
Issue number3
DOIs
StatePublished - Jan 20 2018

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physiology
  • Molecular Biology
  • Clinical Biochemistry
  • Cell Biology

Keywords

  • nicotinamide adenine dinucleotide phosphate

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