fphar-09-01085 September 21, 2018 Time: 16:31 # 1 ORIGINAL RESEARCH published: 25 September 2018 doi: 10.3389/fphar.2018.01085 Metabolomics-Driven Elucidation of Cellular Nitrate Tolerance Reveals Ascorbic Acid Prevents Nitroglycerin-Induced Inactivation of Xanthine Oxidase Elizabeth Rose Axton1,2,3, Eleonso Cristobal1,2, Jaewoo Choi1, Cristobal L. Miranda1,2 and Jan Frederik Stevens1,2* 1 The Linus Pauling Institute, Oregon State University, Corvallis, OR, United States, 2 Department of Pharmaceutical Sciences, Oregon State University, Corvallis, OR, United States, 3 Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR, United States Glyceryl trinitrate (GTN) has found widespread use for the treatment of angina pectoris, a pathological condition manifested by chest pain resulting from insufficient blood supply Edited by: to the heart. Metabolic conversion of GTN, a nitric oxide (NO) pro-drug, into NO induces Pedro D’Orléans-Juste, vasodilation and improves blood flow. Patients develop tolerance to GTN after several Université de Sherbrooke, Canada weeks of continuous use, limiting the potential for long-term therapy. The mechanistic Reviewed by: Carlos F. Sánchez-Ferrer, cause of nitrate tolerance is relatively unknown. We developed a cell culture model 15 Universidad Autonoma de Madrid, of nitrate tolerance that utilizes stable isotopes to measure metabolism of N3-GTN Spain into 15N-nitrite. We performed global metabolomics to identify the mechanism of GTN- InKyeom Kim, Kyungpook National University, induced nitrate tolerance and to elucidate the protective role of vitamin C (ascorbic acid). South Korea Metabolomics analyses revealed that GTN impaired purine metabolism and depleted *Correspondence: intracellular ATP and GTP. GTN inactivated xanthine oxidase (XO), an enzyme that Jan Frederik Stevens
[email protected] is critical for the metabolic bioactivation of GTN into NO.