The effect of inhaled nitric oxide treatment on biomarkers of oxidative/nitrosative damage to proteins and DNA/RNA.

Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator that is used as a treatment for persistent pulmonary hypertension in neonates (PPHN) with hypoxic respiratory failure. The generation of reactive oxygen and nitrogen species might induce oxidative/nitrosative damage to multiple organs. There is an increasing scientific and clinical interest in the determination of specific biomarkers to measure the degree of oxidative/nitrosative stress in non-invasively collected biofluids. A method for the simultaneous detection of a panel of oxidative and nitrosative stress-related biomarkers for quantifying damage to proteins and DNA/RNA in 20 μL of infant urine samples based on reversed-phase ultra-performance liquid chromatography coupled to tandem mass spectrometry operating in positive electrospray ionization mode (ESI) was optimized and validated. Infant urine samples from two different studies were analyzed: (i) term and preterm infants from a nutrition study (Nutrishield, N = 50) and (ii) infants with respiratory insufficiency, including infants with PPHN (N = 16) that required iNO treatment and a control group without treatment (N = 14). Eleven of 14 metabolites were detected in >50 % of infant urine samples, with ranges between 0.008 and 1400 μmol/g creatinine. When comparing across groups, differences in samples collected after iNO treatment in comparison to the rest of the groups were found for m-tyrosine (m-Tyr and m-Tyr/Phe) and ortho-tyrosine (o-Tyr and o-Tyr/Phe) (p-values <0.001, Wilcoxon rank-sum test). Positive linear relationships were found with NO exposure corrected by infant weight for m-Tyr, m-Tyr/Phe, o-Tyr, o-Tyr/Phe and 3-nitrotyrosine. Future studies will focus on the evaluation of the impact of iNO treatment on health and oxidative/nitrosative stress-related morbidities associated with prematurity.