Oxidative Stress Early After Hematopoietic Stem Cell Transplant

•We have described the physiological response to oxidative stress post HSCT in 122 pediatric and young adult patients.•We saw a dramatic increase in glutathione reductase (GSR) expression early post HSCT, likely representing a brisk host response to remove ROS released by conditioning.•We found a significant correlation between oxidant damage and HSCT related complications including death, TA-TMA and GVHD.•Our data support the importance of events in the first few weeks after HSCT in the initiation of later adverse events and thus the investigation of early anti-oxidant prophylactic therapies. HSCT conditioning regimens cause massive lysis of hematopoietic cells with release of toxic intracellular molecules into the circulation. To describe the response to oxidative stress early after hemopoietic stem cell transplantation (HSCT) and assess the association of early oxidative stress with later transplant outcomes. Key components of in the body's physiological response to oxidative stress were studied in a cohort of 122 consecutive pediatric allogeneic HSCT recipients. Glutathione reductase (GSR), glutathione peroxidase (GPX) and glutathione synthetase protein expression was measured using ELISA and reduced and oxidized glutathione (GSH and GSSG) levels were quantified using mass spectrometry. GSR is an inducible enzyme which catalyzes the regeneration of reduced glutathione (GSH). Levels of GSR increased by more than 5-fold between start of conditioning chemotherapy and day 0 (median 87ng/mL to 459ng/mL, P < .0001). GPX catalyzes removal of toxic reactive oxygen species (ROS) by oxidation of GSH. GPX4 levels fell briskly by day 0 (median 20.3 ng/mL prior to HSCT to 7.4ng/mL at day 0, P < .0001), likely indicating consumption of the enzyme as cell lysis and subsequent oxidative stress occurred. Levels of the antioxidant substrate reduced glutathione stayed stable from pre-HSCT through day 14, likely maintained by increased glutathione synthesis by the enzyme glutathione synthetase, whose median levels increased from 38.8ng/mL before conditioning to 54ng/mL at day 21 (P = .02). GSR levels were associated with patient outcomes. Median GSR levels were significantly elevated through days 0-21 in those who died in the first year after HSCT compared to those who survived. Similarly, patients who developed high risk transplant-associated thrombotic microangiopathy (TA-TMA) and grade 2 and above graft versus host disease (GVHD) also had significantly higher GSR level