Calcium dependent and independent cytokine synthesis by air pollution particle-exposed human bronchial epithelial cells.

UNLABELLED

Exposure to ambient air pollution particles with a diameter of <10 microm (PM(10)) has been associated with increased cardiopulmonary morbidity and mortality. We have shown that human bronchial epithelial cells (HBECs) exposed to PM(10) produce pro-inflammatory mediators that contribute to a local and systemic inflammatory response. Changes in intracellular calcium concentrations (Ca(2+)) have been demonstrated to regulate several functions of the airway epithelium including the production of pro-inflammatory mediators. The aim of the present study was to determine the nature and mechanism of calcium responses induced by PM(10) in HBECs and its relationship to cytokine synthesis.

METHODS

Primary HBECs were exposed to urban air pollution particles (EHC-93) and Ca(2+) responses were measured using the fluoroprobe (Fura-2). Cytokine levels were measured at mRNA and protein levels using real-time PCR and ELISA.

RESULTS

PM(10) increased Ca(2+) in a dose-dependent manner. This calcium response was reduced by blocking the influx of calcium into cells (i.e. calcium-free medium, NiCl(2), LaCl(3)). PM(10) also decreased the activity of calcium pumps. PM(10) increased the production of IL-1beta, IL-8, GM-CSF and LIF. Preincubation with intracellular calcium chelator (BAPTA-AM) attenuated IL-1beta and IL-8 production, but not GM-CSF and LIF production.

CONCLUSION

We conclude that exposure to PM(10) induces an increase in cytosolic calcium and cytokine production in bronchial epithelial cells. Our results also suggest that PM(10) induces the production of pro-inflammatory mediators via either intracellular calcium-dependent (IL-1beta, IL-8) or -independent (GM-CSF, LIF) pathways.