Induced sputum markers of fibrosis and decline in pulmonary function in asbestosis and silicosis: a pilot study

OBJECTIVE: To evaluate the usefulness of fibrogenic cytokines and mediators in the analysis of induced sputum and determine if their levels correlated with previous decline in lung function in asbestosis and silicosis.

DESIGN: In a pilot study for the evaluation of 19 workers with asbestosis and 15 with silicosis, all workers had chart reviews and records of previous lung function tests. Fourteen healthy control subjects were also included in the study. All subjects attended the laboratory for a clinical evaluation, pulmonary function tests and induced sputum sampling. Differential cell counts were performed and the following mediators and cytokines were measured: matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinases 1 (TIMP-1), fibronectin, interleukin 1 beta (IL-1β), IL-6, IL-8, IL-12, transforming growth factor beta (TGF-β) and tumor necrosis factor-alpha (TNF-α).

RESULTS: Levels of IL-1β were higher in the sputum of subjects with asbestosis and silicosis than in controls. Eosinophils, neutrophils and IL-1β levels were significantly correlated with the rate of decline in pulmonary function.

CONCLUSION: The induced sputum levels of certain inflammatory cells and IL-1β correlate with the decline in pulmonary function associated with asbestosis and silicosis. It remains to be established if these markers can help predict the clinical outcome of workers exposed to these mineral particles or fibers in a prospective study.