Long term exposure to environmental concentrations of diesel exhaust particles does not impact the phenotype of human bronchial epithelial cells

Abstract

Chronic exposure to diesel engine exhausts is associated with an increased risk of pulmonary diseases including lung cancer. Diesel engine exhausts contain large amounts of diesel exhaust particles (DEP) on which are adsorbed several carcinogenic compounds such as polycyclic aromatic hydrocarbons. Acute toxicity of high concentrations of DEP has been largely demonstrated in various in vitro cellular models. In contrast, the cellular and molecular impacts of low environmental concentrations of DEP on the phenotype of chronically exposed lung epithelial cells remain to be investigated. In the present study, we show that long term exposure (6 months) to 2 μg/ml (0.4 μg/cm) DEP (standard reference material 1650b) increased cytochrome P4501A mRNA levels in the human bronchial epithelial BEAS-2B cell line. However, chronic exposure to DEP did not change cell morphology, trigger epithelial-mesenchymal transition or increase anchorage-independent cell growth. Moreover, DEP increase neither the levels of reactive oxygen species or those of γ-histone H2AX, nor the expression of interleukin-6 and interleukin-8. Our results thus demonstrate that the chronic exposure to low DEP concentrations could increase cytochrome P501A gene expression in BEAS-2B cells but did not induce molecular effects related to genotoxicity, oxidative stress or inflammation.

The Biological Effects of Complete Gasoline Engine Emissions Exposure in a 3D Human Airway Model (MucilAirTM) and in Human Bronchial Epithelial Cells (BEAS-2B)

“…As real-life exposures are usually long-term, with periods of higher levels and lower concentrations of air pollutants, such scenarios should ideally be mimicked in toxicological experiments. While animal studies are commonly designed as long-term, lasting for several weeks or even months [23], experiments in vitro with cellular monocultures are usually short-term, limited to the exposure of hours up to single days (e.g., [17,21]), although in one study a 6-month treatment was performed [24]. However, exposure to complete emissions was not seen in any of these studies.…”

Carbon nanotube filler enhances incinerated thermoplastics-induced cytotoxicity and metabolic disruption in vitro

“…Since the current understanding presumes desorption of particle-adsorbed PAHs leads to genotoxicity [ 50 , 51 ], we hypothesized particle-adsorbed PAHs would be bioavailable to cause activation of AhR-mediated XRE-associated machinery in Beas-2B cells, resulting in genotoxicity [ 52 – 55 ] and partially accounting for reductions in PI- observed in acute cytotoxicity assessment. Further, we examined proliferative behaviour of Beas-2B after treatmments in order to correlate particle-mediated effects to B[a]P, the archetypal PAH.…”

Nanodomains in cardiopulmonary disorders and the impact of air pollution

“…The superfamily of CYP1 genes are closely intermingled with the metabolism of xenobiotics, a process mainly regulated by the AHR known to be in turn activated by PAH known to be released by combustion system. Chronic exposure of human bronchial epithelial cells (BEAS-2B) to low concentration of DEP (Standard Reference Material 1650b) with known concentrations of PAH and nitro-PAH, and with a mean particle diameter of 0.18 μm, for 6 months did not change basal mRNA expression of both CYP1A1 and CYP1B1 mRNA [ 83 ]. Moreover, under the outlined experimental design long-term DEP-exposed BEAS-2B did not undergo EMT studied by gene expression of E-cadherin, vimentin and N-cadherin [ 83 ].…”

“…Chronic exposure of human bronchial epithelial cells (BEAS-2B) to low concentration of DEP (Standard Reference Material 1650b) with known concentrations of PAH and nitro-PAH, and with a mean particle diameter of 0.18 μm, for 6 months did not change basal mRNA expression of both CYP1A1 and CYP1B1 mRNA [ 83 ]. Moreover, under the outlined experimental design long-term DEP-exposed BEAS-2B did not undergo EMT studied by gene expression of E-cadherin, vimentin and N-cadherin [ 83 ]. However, in another recent study BEAS-2B were exposed to primary ultrafine particles (UFP) from diesel and transcriptional changes were followed with an RNA-seq time-course.…”

“…Used as in vitro model, exposure of BEAS-2B cells to an ultrafine PM induced phenotypic changes for EMT exemplified by a reduction in the epithelial marker E-cadherin and an increase in the mesenchymal marker α–smooth muscle actin, seen by immunohistochemistry and mRNA expression [ 84 ]. In contrast, chronic exposure of BEAS-2B cells to DEP (Standard Reference Material 1650b) did not induce EMT [ 83 ] ( Table 1 ). Such seemingly differences are most likely due to different types of air pollutions and further point to the importance of studies in subcellular domains in space and time.…”