Change of Heme Oxygenase-1 Expression in Lung Injury Induced by Chrysotile Asbestos In Vivo and In Vitro

Abstract

Oxidative stress is thought to be the pathogenesis of pulmonary fibrosis induced by asbestos, and heme oxygenase-1 (HO-1) protects lung tissue against oxidative stress. We hypothesized that HO-1 is also associated with oxidative lung injury caused by exposure to chrysotile asbestos. This study was conducted to investigate the HO-1 expression of lungs in lung injury by chrysotile asbestos in vivo and in vitro. Male Wistar rats were administered 1 mg or 2 mg chrysotile suspended in saline by a single intratracheal instillation and were sacrificed at 3 days, 1 wk, 1 mo, 3 mo, and 6 mo of recovery time. The expression of HO-1 was observed by Western blot analysis, reverse-transcription polymerase chain reaction, and immunostaining. Protein levels of HO-1 increased at from 3 days to 6 mo following intratracheal instillation of 1 or 2 mg chrysotile. The mRNA levels of HO-1 increased at 3 mo and 6 mo following intratracheal instillation of 1 or 2 mg chrysotile. HO-1-positive cells were mainly found in the alveolar macrophages during immunostaining. We then examined HO-1 protein expression in human alveolar epithelial cells (A549). A549 cells were incubated with chrysotile at concentrations of 0, 12.5, 25, 50, and 100 μ g/ml over 24 h. Increased expression of HO-1 protein was found following exposure to 25 or 50 μ g/ml of chrysotile. Increased expression of HO-1 was also found at 6, 12, 24, and 48 h after exposure to 50 μ g/ml of chrysotile with a peak at 24 h. These findings suggest that HO-1 is related to lung injury arising from exposure to chrysotile asbestos in vivo and in vitro.