Organic chemicals from diesel exhaust particles affects intracellular calcium, inflammation and β-adrenoceptors in endothelial cells

Exposure to diesel exhaust particles (DEP) may contribute to endothelial dysfunction and cardiovascular disease. DEP, extractable organic material from DEP (DEP-EOM) and certain PAHs seem to trigger [Ca2+](i) increase as well as inflammation via GPCRs like beta ARs and PAR-2. In the present study we explored the involvement of beta ARs and PAR-2 in effects of DEP-EOM on [Ca2+](i) and expression of inflammation-associated genes in the endothelial cell-line HMEC-1. We exposed the human microvascular endothelial cell line HMEC-1 to DEP-EOM fractionated by sequential extraction with solvents of increasing polarity: n-hexane (n-Hex-EOM), dichloromethane (DCM-EOM), methanol (Methanol-EOM) and water (Water-EOM). While Methanol-EOM and Water-EOM had no marked effects, n-Hex-EOM and DCM-EOM enhanced [Ca2+](i) (2-3 times baseline) and expression of inflammation-associated genes (IL-1 alpha, IL-1 beta, COX-2 and CXCL8; 2-15 times baseline) in HMEC-1. The expression of beta ARs (60-80% of baseline) and beta AR-inhibitor carazolol suppressed the increase in [Ca2+](i) induced by both n-Hex- and DCM-EOM. Carazolol as well as the Ca2+-channel inhibitor SKF-96365 reduced the DCM-EOM-induced pro-inflammatory gene-expression. Overexpression of beta ARs increased DCM-EOM-induced [Ca2+](i) responses in HEK293 cells, while beta AR-overexpression suppressed [Ca2+](i) responses from n-Hex-EOM. Furthermore, the PAR-2-inhibitor ENMD-1068 attenuated [Ca2+](i) responses to DCM-EOM, but not n-Hex-EOM in HMEC-1. The results suggest that beta AR and PAR-2 are partially involved in effects of complex mixtures of chemicals extracted from DEP on calcium signalling and inflammation-associated genes in the HMEC-1 endothelial cell-line.