Abstract
Human alveolar macrophages (PAM) play an important role in host defence in the lung by secreting several biologically active molecules including eicosanoids to elicit inflammatory reactions. We investigated the effect of smoking and pretreatment with lipopolysaccharide (LPS) on the secretion of leukotrienes (LT) and prostaglandins (PG) from PAM. PAM were recovered by bronchoalveolar lavage, and cultured in vitro with or without LPS (500 ng/ml) . After various periods of incubation, PAM were washed and then stimulated with calcium ionophore A23187 (2μM), or phorbol myristate acetate (PMA, 500 ng/ml) . LT and PG in supernatants were quantitated by high performance liquid chromatography. Minimal detectable amount of LT and PG were 1ng. LTB4 was detected in the supernatant of PAM stimulated with A23187 as a sole LT, and PGE2 in the supernatant of nonsmokers' PAM pretreated with LPS and then stimulated with PMA as a sole PG in this assay system.
Smokers' PAM secreted decreased amount of LTB4 compared with nonsmokers' PAM. No PG was detected in the supernatant of smokers' PAM even if they were pretreated with LPS. PAM pretreated with LPS secreted increased amount of LTB4 compared with control. Thirty minutes preincubation was optimal for PAM to secrete LTB4. In contrast, twelve-hour pretreatment was required for nonsmokers' PAM to secrete detectable amount of PGE2, and the secretion of PGE2 increased up to 48-hour pretreatment.
In conclusion, smoking decreased the capacity of PAM to secrete LTB4 and PGE2, and LPS primed PAM for enhanced secretion of LTB4 and PGE2.
