Expression of surfactant protein-A in exhaled breath condensate of patients with chronic obstructive pulmonary disease.

Pulmonary surfactant protein A (SP-A) has been associated with host defense in the lung, and contributes to the pathogenesis of chronic obstructive pulmonary disease (COPD). The present study aimed to determine a non­invasive method of measurement of SP­A, and further examine the expression levels of SP­A in patients with COPD. SP­A was detected in the exhaled breath condensate (EBC) obtained from patients with COPD and from non­COPD subjects. The individuals recruited for the present study comprised 60 subjects with and without COPD, who underwent lobectomy for a solitary peripheral lung nodule. EBC was collected using a condenser, and an enzyme­linked immunosorbent assay (ELISA) was used to measure the levels of SP­A. Tissue samples were obtained during lobectomy through resection of the adjacent lung tissues, located >5 cm from the nodule. Western blot analysis and immunohistochemistry were used to measure SP­A and SP­A­positive type II pneumocytes. The results demonstrated that SP­A was detectable in the EBC of all subjects. The results of the ELISA and western blotting demonstrated that the expression levels of SP­A were significantly decreased in patients with COPD, compared with the non­COPD subjects. The reduction of SP­A­positive type II pneumocytes was associated with the expression levels of SP­A. Decreased expression levels of SP­A in EBC were associated with a higher degree of airway limitation. These results suggested that the measurement of SP­A levels in the EBC may serve as a method for monitoring airway obstruction in patients with COPD. Further investigations are required in order to examine these observations further and to elucidate the underlying mechanisms.