Role of thioredoxin nitration in bleomycin-induced pulmonary fibrosis in rats

Abstract

Objective Oxidant stimulation has been reported to play a key role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Thiordoxin (Trx) is an important antioxidant in living cells. Our study aimed to observe the role of Trx nitration in bleomycin (BLM)-induced pulmonary fibrosis in rats. Methods Rat pulmonary fibrosis model was established by intratracheal instillation of BLM. Male Wistar rats were randomly divided into four gruops: control group 1 (7 days), control group 2 (28 days), BLM-treated group A (7 days) and BLM-treated group B (28 days). In BLM-treated groups, rats were intratracheally instilled with a single dose of BLM (5.0 mg/kg in 1.0 ml phosphate buffered saline). Seven or 28 days after instillation, rats were euthanized. Histopathologic and biochemical exams were performed. The expression and activity levels of Trx were determined, and the level of nitrated Trx was determined using immunoprecipitation and immunoblotting. Results Tyrosine nitration of proteins increased in BLM groups as compared with the control groups [At 7th day: (0.78±0.17) vs. (1.26±0.20) μg/mg protein, P<0.05; At 28th day: (0.82±0.25) vs. (2.42±0.32) μg/mg protein P<0.01]. Trx activity decreased in BLM gruops as compared with the control groups [At 7th day: (2.75±0.32) vs. (1.70±0.25) μmol/(min·mg protein), P<0.05; At 28th day: (2.82±0.25) vs. (0.92±0.14) μmol/(min·mg protein), P<0.01], whereas the nitration level of Trx increased dramatically [At 7th day: (3.80±0.78) vs. (6.20±1.40) μmol/(min·mg protein), P<0.05; At 28 day: (3.82±0.62) vs. (8.92±2.11) μmol/(min·mg protein), P<0.01]. Conclusion Our results indicated that Trx nitration might be involved in BLM-induced pulmonary fibrosis in rats. Key words: Pulmonary fibrosis; Thioredoxin; Nitration; Apoptosis