Elsevier

Toxicology Letters

Volume 237, Issue 3, 17 September 2015, Pages 167-173
Toxicology Letters

Particulate matter (PM10) induces metalloprotease activity and invasion in airway epithelial cells

https://doi.org/10.1016/j.toxlet.2015.06.001Get rights and content

Highlights

  • PM10 induces metalloproteases expression and activity.

  • PM10 induces invasiveness.

  • PM10 downregulates E-Cadherin/β-Catenin expression.

Abstract

Airborne particulate matter with an aerodynamic diameter ≤10 μm (PM10) is a risk factor for the development of lung diseases and cancer. The aim of this work was to identify alterations in airway epithelial (A549) cells induced by PM10 that could explain how subtoxic exposure (10 μg/cm2) promotes a more aggressive in vitro phenotype. Our results showed that cells exposed to PM10 from an industrial zone (IZ) and an urban commercial zone (CZ) induced an increase in protease activity and invasiveness; however, the cell mechanism is different, as only PM10 from CZ up-regulated the activity of metalloproteases MMP-2 and MMP-9 and disrupted E-cadherin/β-catenin expression after 48 h of exposure. These in vitro findings are relevant in terms of the mechanism action of PM10 in lung epithelial cells, which could be helpful in understanding the pathogenesis of some human illness associated with highly polluted cities.

Introduction

Particulate matter (PM) is strongly linked to cardiovascular and pulmonary diseases, and numerous epidemiological studies have shown that it represents a risk factor for the development of malignancies, including lung cancer (Pope et al., 2002, Pope and Dockery, 2006, Chien et al., 2015, Rice et al., 2015, Wittkopp et al., 2015, Yang et al., 2015). PM with an aerodynamic diameter ≤10 μm (PM10) is a complex mixture of aggregates containing metals, polycyclic aromatic hydrocarbons (PAH), nitrates, and sulfates, among others (Englert, 2004). Composition is directly related to the source of PM10, and traffic and industrial activities have an important impact on that composition. Adverse effects of PM10, specifically on alveolar epithelia, are related to inflammation caused, in part, by phagocytic cells after PM10 internalization (Mukae et al., 2000). A common response after PM10 exposure is an increase in the production of cytokines and chemokines, such as the interleukins (IL-1, IL-6, and IL-8), tumor necrosis factor-α (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) (van Eeden et al., 2001, Sun, 2010). In this regard, sustained inflammation could leads to a lung remodeling, which is a hallmark of several lung diseases, including chronic obstructive pulmonary disease, asthma, lung fibrosis, and lung cancer (Ohbayashi, 2002); lung remodeling involves in connective tissue, smooth muscle, vasculature, and alveolar epithelia. It causes cell turnover, and as a consequence, toxicants such as PM10 can have an important impact in the regeneration and repair process.

While much research has been focused on inflammation, less is known about some consequences of the inflammatory process, which involves an increase in protease activity and the up-regulation of the matrix metalloprotease (MMP) activity (which has low expression under physiological conditions). An unremitting, persistent MMP activity can cause not only epithelial damage but also tissue dysfunction. In addition, MMP activity can trigger E-cadherin and β-catenin disruption, which is involved in the epithelial cells’ capacity to acquire an invasive phenotype (Nawrocki-Raby et al., 2003). However, the effect of PM10 on MMP activity and possible alterations in E-cadherin and β-catenin expression in airway epithelial cells remains unstudied. We hypothesized that PM10 exposure could induce an increase in protease activity and MMP activity and expression in epithelial cells, which in turn can acquire an invasive phenotype accompanied by disruption of E-cadherin or β-catenin expression. For these reasons, we aimed to evaluate the protease activity, MMP activity and expression, and invasive potential of airway epithelial cells exposed to PM10 to determine if E-cadherin or β-catenin expression was altered.

Section snippets

PM10 sampling

PM10 was collected from two zones in Mexico City, an industrial zone (IZ: mainly industrial sources) and a commercial zone (CZ: mainly traffic sources) (Alfaro-Moreno et al., 2002) using a high-volume particle collector with a flux of 1.13 m3/min (GMW model 1200 VFC HVPM10; Sierra Andersen, Smyrna, GA, USA). PM10 was collected on 3.0 μm pore size cellulose nitrate filter (Sartorius AG, Gottingen, Germany), 3 days per week. This filter is located after fractionation of the PM zone, and according

Protease and MMP activity assays

The protease activity was measured by proteolysis assay, and it tended to increase; for PM10 exposure from IZ, an increase of 43.06% after 24 h and 61.35% (***P < 0.001) after 48 h was found (Fig. 1A). Epithelial cells exposed to PM10 from CZ had a protease activity increase of 51.75% (**P < 0.01) after 24 h of exposure and 64.4% (***P < 0.001) after 48 h (Fig. 1A). Then, specific activity of MMPs was determined (Fig. 1B); exposure to PM10 from IZ did not induce any change in MMP-1 and MMP-2 activation,

Discussion

PM10 is considered a risk factor for the development of lung diseases, including cancer (Pope et al., 2002, Bals and Hiemstra, 2004, Pope and Dockery, 2006). In addition, epithelial cells play an important role during lung remodeling, which could lead to progression of lung diseases. Thus, we selected lung epithelial A549 cells, a widely and currently accepted experimental model, to design this study (Deng et al., 2014, Orona et al., 2014). We hypothesized that the imbalance caused in these

Conflicts of interest

The authors declare no conflicts of interest related to this work. All authors have read and approved the manuscript.

Acknowledgments

The authors express their gratitude to Yazmín Segura and Raúl Quintana, participants in the field campaign, and thank to Eva Salinas and Leticia Martínez for their technical support. This work was supported by CONACyT-Mexico grants 43183-M, AC-2006-52830.

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