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 TNFalpha) in a receptor-mediated fashion in response to the neuropeptides, substance P (SP), calcitonin gene-related protein (CGRP), and the prototype botanical irritant capsaicin. In the present experiments, we examined the relevance of these 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, TNFalpha) within 2 h exposure, and subsequent release of IL-6 and IL-8 cytokine protein after 4 h exposure. Pretreatment of BEAS-2B cells with pharmacological antagonists selective for the SP or CGRP receptors reduced the ROFA-stimulated IL-6 cytokine production by approximately 25 and 50%, respectively. However, pretreatment of these cells with capsazepine (CPZ), an antagonist for capsaicin (i.e., vanilloid) receptors, inhibited the immediate increases in [Ca2+]i, diminished transcript (i.e., IL-6, IL-8, TNFalpha) levels and reduced IL-6 cytokine release to control levels. BEAS-2B cells exposed 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, TNFalpha) and IL-6 release, suggesting that ROFA-stimulated cytokine formation 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-micrometer 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 amiloride before ROFA exposure, showed a partial (approximately 25%) reduction of IL-6. Together, these data indicate that the acidic, soluble components of ROFA initiate cytokine release in BEAS-2B cells through activation of both capsaicin- and pH-sensitive irritant receptors.
Veronesi
B
B
Neurotoxicology Division, U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratories, Research Triangle Park, North Carolina, 27711, USA.
Oortgiesen
M
M
Carter
J D
JD
Devlin
R B
RB
D000393:Air Pollutants; D000584:Amiloride / Q000494:pharmacology; D001980:Bronchi / Q000378:metabolism*; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000378:metabolism*; D002244:Carbon / Q000494:pharmacology*; D002460:Cell Line; D060729:Coal Ash; D016207:Cytokines / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D064729:Neurokinin-1 Receptor Antagonists; D052638:Particulate Matter; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000502:physiology; D011955:Receptors, Drug / Q000037:antagonists & inhibitors / Q000502:physiology*; D018040:Receptors, Neurokinin-1 / Q000502:physiology; D013373:Substance P / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D000393:Air Pollutants; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D060729:Coal Ash; D016207:Cytokines; D015850:Interleukin-6; D016209:Interleukin-8; D064729:Neurokinin-1 Receptor Antagonists; D052638:Particulate Matter; D018015:Receptors, Calcitonin Gene-Related Peptide; D011955:Receptors, Drug; D018040:Receptors, Neurokinin-1; D014409:Tumor Necrosis Factor-alpha; D013373:Substance P; D002244:Carbon; D000584:Amiloride; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin; D002118:Calcium