Particulate matter initiates inflammatory cytokine release by activation of capsaicin and acid receptors in a human bronchial epithelial cell line

Recent experiments have shown that human bronchial epithelial cells (i.e., BEAS-2B) release pro-inflammatory cytokines (i.e., IL-6 and TNF alpha) in a receptor-mediated fashion in response to the neuropeptides, substance P (S P), calcitonin gene-related protein (CGRP), and the prototype botanical irr itant capsaicin. In the present experiments, we examined the relevance of t hese receptors to particulate matter (PM)-associated cellular inflammation. BEAS-2B cells, exposed to residual oil fly ash particles (ROFA), responded with an immediate (<30 s) increase in intracellular calcium levels ([Ca2+] (i)), increases of key inflammatory cytokine transcripts (i.e., IL-6, IL-8, TNF alpha) within 2 h exposure, and subsequent release of IL-6 and IL-8 cy tokine protein after 4 h exposure. Pretreatment of BEAS-2B cells with pharm acological antagonists selective for the SP or CGRP receptors reduced the R OFA-stimulated IL-6 cytokine production by similar to 25 and 50%, respectiv ely. However, pretreatment of these cells with capsazepine (CPZ), an antago nist for capsaicin (i.e., vanilloid) receptors, inhibited the immediate inc reases in [Ca2+](i), diminished transcript (i.e., IL-6, IL-8, TNF alpha) le vels and reduced IL-6 cytokine release to control levels. BEAS-2B cells exp osed to ROFA in calcium-free media failed to demonstrate increases of [Ca2](i) and showed reduced levels of cytokine transcript (i.e., IL-6, IL-8, TN F alpha) and IL-6 release, suggesting that ROFA-stimulated cytokine formati on was partially dependent on extracellular calcium sources. A final set of experiments compared the inflammatory properties of the soluble and acidic insoluble components of ROFA. BEAS-2B cells, exposed to ROFA or ROFA that had been filtered through a 0.2-mu m pore filter, produced equivocal IL-6. BEAS-2B cells exposed to pH 5.0 media for 15 min released moderate amounts of IL-6, 4 h later. This cytokine release could be blocked by amiloride, a pH receptor antagonist, but not by CPZ. BEAS-2B cells, pretreated with amil oride before ROFA exposure, showed a partial(similar to 25%) reduction of I L-6. Together, these data indicate that the acidic, soluble components of R OFA initiate cytokine release in BEAS-2B cells through activation of both c apsaicin- and PH-sensitive irritant receptors. (C) 1999 Academic Press.