OBJECTIVETo study the effect of SiO(2) on the expression of platelet derived growth factor (PDGF) in human silicotic alveolar macrophages (AM) and human embryonic lung fibroblasts (HELF).

METHODSHuman alveolar macrophages were collected from a silicotic patient by bronchoalveolar lavage and exposed to SiO(2) for 3, 6, 12, 18, 24 and 36 h. The cultured supernatant at 24 h was incubated with human embryonic lung fibroblasts for 6, 12, 18, 24, 36 and 48 h. The immunocytochemistry and Western blot were used to detect the level of expression of PDGF in lung fibroblasts and their supernatant respectively. (3)H-proline was used to detect the synthesis and secretion of collagen in HELF.

RESULTSThe expression of the PDGF in the supernatant of alveolar macrophages exposed to SiO(2) increased significantly and reached the peak at 24 h (average optical density: 0.282 +/- 0.019 vs 0.214 +/- 0.014, P < 0.01) with ELISA. The expression of PDGF in lung fibroblasts and their supernatant increased at different time (6, 12, 18, 24, 36 and 48 h) with immunocytochemistry and Western blot respectively when incubated with the cultured supernatant of silicotic AM exposed to SiO(2). The expression of PDGF was significantly different from the control group (P < 0.05). The synthesis and secretion of collagen in FB were increased markedly when incubated with the cultured supernatant of AM stimulated by SiO(2) compared with the control group.

CONCLUSIONSiO(2) may affect the expression of PDGF and synthesis of collagen through AM mediation and participate in the formation of lung fibrosis.