High-dose N-acetylcysteine decreases silica-induced lung fibrosis in the rat

Objective To study the potential of high-dose N-acetylcysteine (NAC) to attenuate silica-induced pulmonary fibrosis in the rat. Methods Rats exposed to intratracheal instillation of silica particles were treated with 500mg/kg NAC orally every day for 7 days, before and up to 28 days after silica administration (n=32), or received no treatment following silica exposure (n=32); a third group received intratracheal saline (n=32). Fibrosis score, and hydroxyproline (HYP) and malondialdehyde (MDA) content, were assessed in lung tissue. Bronchoalveolar lavage fluid (BALF) and serum levels of tumour necrosis factor (TNF)-, interleukin (IL)-8 and high-sensitivity C-reactive protein (hsCRP) were assessed by enzyme-linked immunosorbent assay. Results Histopathology revealed inflammation and fibrosis in lung tissue from rats exposed to silica, but not in saline controls. The fibrosis score was significantly lower in animals treated with NAC compared with silica-exposed untreated rats. HYP and MDA content were significantly lower at all timepoints, following NAC treatment versus no treatment, in silica-exposed rats. NAC attenuated silica-induced increases in TNF-, IL-8 and hsCRP in BALF and serum. Conclusions Oral treatment with high-dose NAC during early silica exposure can ameliorate the activity of proinflammatory cytokines, thus attenuating subsequent lung fibrosis. These results suggest that NAC has potential as a treatment for silica-induced lung fibrosis.