ENDOTOXIN-STIMULATED ALVEOLAR MACROPHAGE RECRUITMENT OF NEUTROPHILS AND MODULATION WITH EXOGENOUS SURFACTANT

Objective: To determine whether endotoxin-stimulated alveolar macropha ges would attract neutrophils and whether exogenous surfactant treatme nt would modulate this chemoattraction. Design: Alveolar macrophages w ere harvested from bronchoalveolar lavage fluid and neutrophils from t he blood of anesthetized guinea pigs. Subjects: Hartley guinea pigs. I nterventions: Alveolar macrophages were suspended in RPMI 1640 and sti mulated with 1 mu g/mL of lipopolysaccharide (LPS), the supernatant re moved and the alveolar macrophages were incubated in either RPMI or RP MI with surfactant at two different doses (292 mu g/mL or 875 mu g/mL) for 16 hrs. Measurements and Main Results: The supernatant was extrac ted from the alveolar macrophages and placed in a chemotaxis plate and the migration of neutrophils was measured. Chemotaxis of all cell typ es to be tested was measured by a change of absorbance on a microplate reader set at 492 nm. Results were compared with alveolar macrophages not stimulated with LPS, RPMI alone, and N formyl-methionyl-leucyl-ph enylalanine (FMLP). The supernatant of the stimulated alveolar macroph ages increased neutrophil chemotaxis as compared with unstimulated alv eolar macrophages, and RPMI (p < .05). surfactant treatment with 292 m u g/mL significantly decreased LPS-stimulated alveolar macrophages ind uced neutrophil chemotaxis. Treatment with 875 mu g/mL of surfactant d id not alter neutrophil chemotaxis. Conclusions: Alveolar macrophages stimulation with LPS increased the chemotaxis of neutrophils. Treatmen t with surfactant at a concentration of 875 mu g/mL did not alter neut rophil migration; however, treatment with 292 mu g/mL significantly de creased neutrophil chemotaxis suggesting that at low concentrations, s urfactant inhibits chemokine release and may reduce pulmonary neutroph il sequestration in vivo.