Combination effects of cigarette smoke extract and ambient ultrafine particles on endothelial cells

Abstract

Previous studies have shown that ambient ultrafine particles with diameters less than 100 nm (UFPs) can pass from the lungs to the circulation because of their very small diameter, and induce lung oxidative stress with a resultant dysfunction of lung endothelial cells. However, no studies have addressed the potential combined effects of UFPs and cigarette smoke on vascular endothelial cells. We hypothesized that co-exposure to UFPs and cigarette smoke extract (CSE) may cause combined effects on activation of endothelial cells and dysfunction of endothelium by oxidative stress through activation of NADPH oxidase. We determined the effects of UFPs with or without CSE on mouse pulmonary microvascular endothelial cells (MPMVEC) obtained from C57BL/6J (wild-type) and gp91phox knock-out mice (gp91phox is one of the key components of NADPH oxidase, one of ROS generators). Our results showed that exposure of MPMVEC from wild-type mice to UFPs or CSE, at a non-toxic dose, induced reactive oxygen species (ROS) generation, increased phosphorylation of p38 and Erk1/2, and up-regulated early growth response -1 (Egr-1) and IL-6 genes. These effects were significantly enhanced when cells were co-exposed to both UFPs and CSE. However, exposure of MPMVEC from gp91phox knock-out mice did not induce the above effects. Furthermore, UFPs- and/or CSE-induced Egr-1 mRNA upregulation was attenuated significantly when cells were pre-treated with p38 specific inhibitor, SB 203580, or MEK1/2 inhibitor, PD98059, and Egr-1 siRNA treatment abolished UFPs- and/or CSE- induced overexpression of IL-6. Our results suggest that UFPs and/or CSE caused activation of NADPH oxidase, resulting in ROS generation that led to activation of MAPKs through induced phosphorylation of p38 and ERK1/2 MAPKs and upregulation of Egr-1. Those effects may further result in endothelial dysfunction through production of cytokines such as IL-6. Our results suggest that co-exposure to UFPs and CSE causes enhanced injury to endothelial cells.

Nanoparticle emissions from 11 non-vehicle exhaust sources – A review

“…Active smoking is widely recognised as one of the major causes of coronary artery disease, cancer (particularly lung cancer), and chronic obstructive pulmonary disease in adults (USDHHS, 2006), as well as impacting the function of the endothelium and causing altered gene expression in endothelial cells via their ability to generate ROS and nitrogen species (Bercher et al, 2007;Mo et al, 2012). Insoluble nanoparticles are capable of translocation from the lung to other parts such as the lymph nodes, spleen, heart and bone marrow; their high surface to mass ratio increases biological activity relative to larger particles of the same chemical composition (Oberdörster et al, 2005;Kreyling et al, 2010).…”

“…Insoluble nanoparticles are capable of translocation from the lung to other parts such as the lymph nodes, spleen, heart and bone marrow; their high surface to mass ratio increases biological activity relative to larger particles of the same chemical composition (Oberdörster et al, 2005;Kreyling et al, 2010). Recent research indicate that co-exposure to ambient nanoparticles and cigarette smoke extract causes enhanced injury to endothelial cells and may cause combined effects on activation of endothelial cells and dysfunction of the endothelium by oxidative stress through activation of NADPH oxidase (Mo et al, 2012). However, there are so far no studies available which have apportioned the effect of cigarette derived nanoparticle exposure from effects caused by other ambient nanoparticles.…”

The p-ERK–p-c-Jun–cyclinD1 pathway is involved in proliferation of smooth muscle cells after exposure to cigarette smoke extract

“…The same batch of PBS, but which had not been smoke-bubbled, was used as control. CSE was aliquoted and stored at À80°C until required for use [10,11].…”

Mitochondrial Genetic Background Modifies the Relationship between Traffic-Related Air Pollution Exposure and Systemic Biomarkers of Inflammation

“…Mitochondrial ROS has been implicated in inflammatory cytokine production, providing a possible link between ROS-driven and inflammatory diseases [32]. Studies in cultured human cells have shown that exposure to particulate matter increases mitochondrial ROS [33]–[35], and these mitochondrial ROS increases cause increased IL-6 gene expression [34], [35]. Conversely, inhibition of mitochondrial ROS reduces inflammatory cytokine production in response to inflammatory stimulus [36].…”