Endothelial responses of the alveolar barrier in vitro in a dose-controlled exposure to diesel exhaust particulate matter

Abstract

BackgroundDuring the last 250 years, the level of exposure to combustion-derived particles raised dramatically in western countries, leading to increased particle loads in the ambient air. Among the environmental particles, diesel exhaust particulate matter (DEPM) plays a special role because of its omnipresence and reported effects on human health. During recent years, a possible link between air pollution and the progression of atherosclerosis is recognized. A central effect of DEPM is their impact on the endothelium, especially of the alveolar barrier. In the present study, a complex 3D tetraculture model of the alveolar barrier was used in a dose-controlled exposure scenario with realistic doses of DEPM to study the response of endothelial cells.ResultsTetracultures were exposed to different doses of DEPM (SRM2975) at the air-liquid-interface. DEPM exposure did not lead to the mRNA expression of relevant markers for endothelial inflammation such as ICAM-1 or E-selectin. In addition, we observed neither a significant change in the expression levels of the genes relevant for antioxidant defense, such as HMOX1 or SOD1, nor the release of pro-inflammatory second messengers, such as IL-6 or IL-8. However, DEPM exposure led to strong nuclear translocation of the transcription factor Nrf2 and significantly altered expression of CYP1A1 mRNA in the endothelial cells of the tetraculture.ConclusionIn the present study, we demonstrated the use of a complex 3D tetraculture system together with a state-of-the-art aerosol exposure equipment to study the effects of in vivo relevant doses of DEPM on endothelial cells in vitro. To the best of our knowledge, this study is the first that focuses on indirect effects of DEPM on endothelial cells of the alveolar barrier in vitro. Exposure to DEPM led to significant activation and nuclear translocation of the transcription factor Nrf2 in endothelial cells. The considerably low doses of DEPM had a low but measurable effect, which is in line with recent data from in vivo studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-017-0186-4) contains supplementary material, which is available to authorized users.

Pro-inflammatory effects of crystalline- and nano-sized non-crystalline silica particles in a 3D alveolar model

“…The 3D tri-culture model, established as described by Klein and co-workers [43,44], consisted of three different cell-types, A549 epithelial lung cells, PMAdifferentiated THP-1 cells, and EA.hy 926 endothelial cells (from the American Type Culture Collection, Manassas, VA, USA), and has been used by us in a previous study [53]. The Ea.hy 926 cells were maintained in DMEM + Glutamax, with HEPES buffer (DMEM) and 10% FBS.…”

“…The last years increasing attention has been paid to: a) develop in vitro systems for high throughput screening for studying NPs [41] b) identify adverse outcome pathways (AOP) and their critical molecular initiating events (MIEs) for NPs [42] c) develop relevant 3D co-cultures better mimicking the in vivo situations [43][44][45][46][47]. In several studies THP-1 monocytes or PMA-differentiated THP-1 monocytes (THP-1 macrophages), have been included in the apical or basolateral compartment [43,48].…”

“…The last years increasing attention has been paid to: a) develop in vitro systems for high throughput screening for studying NPs [41] b) identify adverse outcome pathways (AOP) and their critical molecular initiating events (MIEs) for NPs [42] c) develop relevant 3D co-cultures better mimicking the in vivo situations [43][44][45][46][47]. In several studies THP-1 monocytes or PMA-differentiated THP-1 monocytes (THP-1 macrophages), have been included in the apical or basolateral compartment [43,48]. The apical compartment in such tri-culture models has been exposed to crystalline silica [49,50], particulate matter [51,52], diesel exhaust particles (DEP) [43,53,54] as well as NPs, including SiNPs [53] and silver (Ag) NPs and nanowires [48,55,56].…”

“…In several studies THP-1 monocytes or PMA-differentiated THP-1 monocytes (THP-1 macrophages), have been included in the apical or basolateral compartment [43,48]. The apical compartment in such tri-culture models has been exposed to crystalline silica [49,50], particulate matter [51,52], diesel exhaust particles (DEP) [43,53,54] as well as NPs, including SiNPs [53] and silver (Ag) NPs and nanowires [48,55,56]. The most common biological endpoints include barrier function, cytotoxicity and pro-inflammatory responses in the apical and basolateral compartment, with some studies reporting endothelial responses [49,[53][54][55][56][57], others not [53,55].…”

“…In the present study, we have examined the potential of SiNPs (Si10), and micrometer-sized crystalline silica particles (quartz; Min-U-Sil), to induce pro-inflammatory responses in a 3D tri-culture cell model, mimicking the lungblood barrier, as introduced by Klein and co-workers [43,44]. The culture is consisting of apical PMA-differentiated THP-1 cells and A549 cells in contact culture, separated from basolateral endothelial cells (Ea.Hy926) by a microporous membrane (1 μm pores).…”