Oxidative stress induces heme oxygenase 1 in rat lung microvascular endothelial cells (RLMVECs)

Abstract

Heme oxygenase 1 (HO-1) plays an important role in mitigating the deleterious effects of oxidative stress. To examine the anti-oxidant effect of HO-1, we studied the effect of reactive oxygen species (ROS) on HO-1 levels in RLMVECs. Intracellular ROS levels were increased by addition of menadione, which undergoes cellular redox cycling. Cultured, quiesced RLMVEC were incubated with menadione (10nM–100μM) from 30 min to 12 hrs and HO-1 protein expression determined by Western blot analysis. Incubation of RLMVECs with menadione (10nM–100μM) for 30 min or 1 hr failed to induce HO-1 expression. However, a 10-fold increase in HO-1 expression was observed at 2 and 6 hrs incubation with 10 μM menadione. To prevent/reverse menadione-induced ROS production, tempol (0.5 to 500μM), a cell permeable free radical scavenger, was preincubated with RLMVECs for 1hr prior to addition of 10μM menadione. Menadione-induced HO-1 levels (140 ±10% over control; P< 0.01) was reversed by tempol (0.5–5 μM) to 27±2% and 29±3 (P< 0.02), respectively. Higher concentrations of tempol (50–500μM) were ineffective in reducing menadione-induced HO-1 expression (124±40%). Thus, low dose tempol may be effective in mitigating oxidative stress which has been implicated in the development of pulmonary vascular pathologies such as hypoxia- induced pulmonary hypertension Supported by Philip Morris USA Inc. and by Philip Morris International