Inhibitory effects of the dietary antioxidants butylated hydroxyanisole and butylated hydroxytoluene on bronchioloalveolar cell proliferation during the bleomycin-induced pulmonary fibrosing process in hamsters

The effects of dietary antioxidants on bleomycin (BLM)-induced pulmonary fibrosis were investigated in Syrian golden hamsters. In addition, the influence on cell proliferative activity in bronchioloalveolar hyperplastic lesions during the lung fibrosing process was evaluated in terms of argyrophil nucleolar organizer regions (AgNORs) and proliferating cell nuclear antigen (PCNA). Male 6-wk-old hamsters were divided into six groups. Groups 1-3 were intratracheally instilled with BLM at a dose of 2.5 U/kg body weight on days 0 and 14, and then given a diet supplemented with 1% butylated hydroxyanisole (BHA), or 1% butylated hydroxytoluene (BHT), or basal diet alone for the following 41 days. Groups 4-6 were given 1% BHA, 1% BHT or basal diet without BLM treatment for the same time period as that in those of groups 1-3. The mortality rate of animals in group 1 (BLM/BHA) (one in 20; 5%) was lower than in those of groups 2 (BLM/BHT) (three in 20; 15%) and 3 (BLM alone) (four in 20; 20%). BHA and BHT treatments significantly inhibited lung weight gains by BLM (P0.05). Histopathologically, both BHA and BHT reduced BLM-induced pulmonary histopathological changes such as fibrosis, macrophage aggregation and epithelial proliferation, with a tendency for correlation with accumulation of type III collagen. In addition, antioxidant treatment significantly lowered the mean numbers of AgNORs (P0.01) and PCNA-labelling indices (P0.05) in the hyperplastic bronchioloalveolar lesions. The results thus indicate that these antioxidants exert inhibitory effects on proliferation of hyperplastic lesions associated with lung fibrosis.