OBJECTIVETo investigate the changes in the levels of inflammatory cytokines in bronchoalveolar lavage fluid (BALF) in rats exposed to silica dust.

METHODSExperimental rats were randomly divided into control group and three experimental groups (doses of dust: 15, 30, and 60 mg/ml), with 42 rats in each group. Each rat in the control group was treated with 1 ml of normal saline by intratracheal instillation, while each rat in the experimental groups was exposed to 1 ml of silica suspension by a single intratracheal instillation. Seven rats in each group were killed at 1, 3, 7, 14, 21, and 28 days after exposure, and then BALF was collected. Enzyme-linked immunosorbent assay was used to measure the levels of interleukin (IL)-1, IL-6, IL-16, macrophage inflammatory protein-1 alpha (MIP-1α), monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), and transforming growth factor-β (TGF-β).

RESULTSThe levels of cytokines in each experimental group were higher than those in the control group at any time point. In the early stage of exposure (day 1-3), BALF IL-1 level increased significantly with the increase in dust dose, and on day 14, BALF IL-6 and IL-16 levels increased significantly with the increase in dust dose; the levels of IL-1, IL-6, and IL-16 in the experimental groups reached the peak on day 14. There were significant differences in the levels of MIP-1α and MCP-1 between the experimental groups (FMIP-1α = 30.106, P<0.01; FMCP-1 = 17.193, P<0.01). In each group, the level of MCP-1 varied significantly at different time points (F = 0.618, P>0.05). On day 1-14, BALF TNF-α level increased with the increase in dust dose, with a significant dose-response relationship (P < 0.05). In each experimental group, TNF-α level reached the peak on day 14. On days 14, 21, and 28, the high-dose group had significantly higher BALF TGF-β levels than the low-dose group (P<0.05); on days 14 and 28, the high-dose group had significantly higher BALF TGF-β levels than the middle-dose group (P<0.05).

CONCLUSIONIL-1, IL-6, IL-16, MIP-1α, MCP-1, and TNF-α play a role in the development and progression of silicosis inflammation. TGF-β may be related to (related to; associated with; correlated with) fibrosis.