Glutathionylated γG and γA subunits of hemoglobin F: a novel post‐translational modification found in extremely premature infants by LC‐MS and nanoLC‐MS/MS

Oxidative stress plays an important role in the development of various disease processes and is a putative mechanism in the development of bronchopulmonary dysplasia, the most common complication of extreme preterm birth. Glutathione, a major endogenous antioxidant and redox buffer, also mediates cellular functions through protein thiolation. We sought to determine if post‐translational thiol modification of hemoglobin F occurs in neonates by examining erythrocyte samples obtained during the first month of life from premature infants, born at 23 0/7 – 28 6/7 weeks gestational age, who were enrolled at our center in the Prematurity and Respiratory Outcomes Program (PROP). Using liquid chromatography‐mass spectrometry (LC‐MS), we report the novel finding of in vivo and in vitro glutathionylation of γG and γA subunits of Hgb F. Through tandem mass spectrometry (nanoLC‐MS/MS), we confirmed the adduction site as the Cys‐γ94 residue and through high‐resolution mass spectrometry determined that the modification occurs in both γ subunits. We also identified glutathionylation of the β subunit of Hgb A in our patient samples; we did not find modified α subunits of Hgb A or F. In conclusion, we are the first to report that glutathionylation of γG and γA of Hgb F occurs in premature infants. Additional studies of this post‐translational modification are needed to determine its physiologic impact on Hgb F function and if sG‐Hgb is a biomarker for clinical morbidities associated with oxidative stress in premature infants. Copyright © 2014 John Wiley & Sons, Ltd.