Phagocytosis of particulate air pollutants by human alveolar macrophages stimulates the bone marrow

Mukae, Hiroshi, James C. Hogg, Dean English, Renaud Vincent, and Stephan F. van Eeden. Phagocytosis of particulate air pollutants by human alveolar macrophages stimulates the bone marrow. Am J Physiol Lung Cell Mol Physiol 279: L924-L931, 2000.--Epidemiologic studies have shown an association between the level of ambient particulate matter [is less than] 10 [micro] m ([PM.sub.10]) and cardiopulmonary mortality. We have shown that exposure of rabbits to P[M.sub.10] stimulates the bone marrow. In this study, we determined whether human alveolar macrophages (AMs) that phagocytose atmospheric [PM.sub.10] produce mediators capable of stimulating the bone marrow. AMs incubated with [PM.sub.l0] for 24 h produced tumor necrosis factor-[Alpha] in a dose-dependent manner (86.8 [+ or -] 53.29 pg/ml with medium alone; 1,087.2 [+ or -] 257.3 pg/ml with 0.1 mg/ml of P[M.sub.10]; P [is less than] 0.02). Instillation of the supernatants from AMs incubated with 0.1 mg/ml of [PM.sub.10] into the lungs of rabbits (n = 6) increased circulating polymorphonuclear leukocyte (PMN) and band cell counts as well as shortened the PMN transit time through the bone marrow (87.9 [+ or -] 3.3 h) compared with unstimulated human AMs (104.9 [+ or -] 2.4 h; P [is less than] 0.01; n = 5 rabbits). The supernatants from rabbit AMs incubated with 0.1 mg/ml of [PM.sub.10] (n = 4 rabbits) caused a similar shortening in the PMN transit time through the bone marrow (91.5 [+ or -] 1.6 h) compared with human AMs. We conclude that mediators released from AMs after phagocytosis of [PM.sub.10] induce a systemic inflammatory response that includes stimulation of the bone marrow. particulate matter less than 10 micrometers; air pollution; bone marrow; leukocytes; cytokines