Lipophilic components of diesel exhaust particles induce pro-inflammatory responses in human endothelial cells through AhR dependent pathway(s)

Abstract

BackgroundExposure to traffic-derived particulate matter (PM), such as diesel exhaust particles (DEP), is a leading environmental cause of cardiovascular disease (CVD), and may contribute to endothelial dysfunction and development of atherosclerosis. It is still debated how DEP and other inhaled PM can contribute to CVD. However, organic chemicals (OC) adhered to the particle surface, are considered central to many of the biological effects. In the present study, we have explored the ability of OC from DEP to reach the endothelium and trigger pro-inflammatory reactions, a central step on the path to atherosclerosis.ResultsExposure-relevant concentrations of DEP (0.12 μg/cm2) applied on the epithelial side of an alveolar 3D tri-culture, rapidly induced pro-inflammatory and aryl hydrocarbon receptor (AhR)-regulated genes in the basolateral endothelial cells. These effects seem to be due to soluble lipophilic constituents rather than particle translocation. Extractable organic material of DEP (DEP-EOM) was next fractionated with increasing polarity, chemically characterized, and examined for direct effects on pro-inflammatory and AhR-regulated genes in human microvascular endothelial (HMEC-1) cells and primary human endothelial cells (PHEC) from four healthy donors. Exposure-relevant concentrations of lipophilic DEP-EOM (0.15 μg/cm2) induced low to moderate increases in IL-1α, IL-1β, COX2 and MMP-1 gene expression, and the MMP-1 secretion was increased. By contrast, the more polar EOM had negligible effects, even at higher concentrations. Use of pharmacological inhibitors indicated that AhR and protease-activated receptor-2 (PAR-2) were central in regulation of EOM-induced gene expression. Some effects also seemed to be attributed to redox-responses, at least at the highest exposure concentrations tested. Although the most lipophilic EOM, that contained the majority of PAHs and aliphatics, had the clearest low-concentration effects, there was no straight-forward link between chemical composition and biological effects.ConclusionLipophilic and semi-lipophilic chemicals seemed to detach from DEP, translocate through alveolar epithelial cells and trigger pro-inflammatory reactions in endothelial cells at exposure-relevant concentrations. These effects appeared to be triggered by AhR agonists, and involve PAR-2 signaling.Electronic supplementary materialThe online version of this article (10.1186/s12989-018-0257-1) contains supplementary material, which is available to authorized users.

Concentration‐dependent cytokine responses of silica nanoparticles and role of ROS in human lung epithelial cells

“…In contrast, no attenuation was observed at lower concentrations (100 µg/mL), with lower cytokine responses. This indicates that, at least in the present case, ROS‐dependent mechanisms were predominately a high‐concentration phenomenon, as recently also observed for DEP, possibly acting by exacerbating the effects of other particle‐/NP‐induced pathways. In further support of this, even at the highest Si50 concentrations, ROS inhibition only exerted partial reductions in the cytokine response, suggesting a combination of ROS‐dependent and ROS‐independent mechanisms.…”

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

“…Up-regulation of HO-1, MMP-1 and -9 may possibly be related to downstream effects of earlier cytokine responses. Similarly, exposing the same 3D tri-culture to DEP, MMP-1 was only induced at the latest time point [53].…”

“…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.…”

“…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].…”

Shenlian Extract in the Treatment of Ultrafine Particulate Matter- Aggravated Myocardial Ischemic Injury: Integrating Network Pharmacology and in vivo Pharmacological Evaluation

“…Endotoxins can also stimulate localized or systemic inflammation via the activation of pattern recognition receptors [35]. Several studies reported that the biological and chemical components of particulate matter have synergistic pro-inflammatory effects [36][37][38][39][40].Some researchers have proven that particulate matter is a key cause of cardiovascular morbidity and mortality [41]. Animal experiments have also confirmed that particulate matter exposure triggers inflammation and oxidative stress, which may cause lung and heart injure [42,43].…”