Hypoxia Decreases Trx2 Protein and Activity in Pulmonary Vascular Cells

Abstract

Pulmonary Hypertension (PH) is characterized by the sustained increase in pulmonary arterial pressure. Increased pulmonary vascular pressure and resistance result in right ventricle (RV) hypertrophy and can ultimately lead to RV failure and death. Increased levels of Reactive Oxygen Species (ROS) have been implicated in PH pathogenesis. Endogenous antioxidant mechanisms, such as the Thioredoxin 2 (Trx2) system, are of importance in maintaining cellular ROS levels. Trx2 protein acts as a reducing agent within the mitochondria to maintain proteins in a reduced state. Because hypoxia stimulates ROS and PH, we examined the effects of hypoxia on Trx2 in vitro and in vivo. We hypothesized that hypoxia impacts mitochondria ROS levels by altering Trx2 expression and activity. Human Pulmonary Artery Endothelial Cells (HPAEC) were exposed to hypoxia (1%O2) for 72 hours, and mice were subjected to 3 weeks of hypoxia (10% O2). qRT‐PCR and western blot analysis were used to study the transcriptional, translational and post‐translational effects of hypoxia on Trx2. Hypoxia decreased levels of Trx2 mRNA and protein in HPAEC in vitro and also reduced Trx2 mRNA levels in the lungs of hypoxia‐exposed mice. Similarly, hypoxia increased oxidized Trx2 (inactive) in the mouse lung compared to animals exposed to normoxia. In combination these data suggest that hypoxia decreases in vitro and in vivo. These changes in Trx2 expression and activity may contribute to mitochondrial ROS production and dysfunction associated with PH. This work was supported by NIH RO1 HL 102167 and the T32 Training Program in Academic Pulmonary Medicine.