Original article
Mechanisms of allergic and immune disease
Effects of diesel exhaust particles on primary cultured healthy human conjunctival epithelium

https://doi.org/10.1016/j.anai.2012.10.017Get rights and content

Abstract

Background

Air pollution from road traffic is a serious public health problem. Epidemiologic studies have demonstrated adverse health effects associated with environmental pollution. Diesel exhaust is a major contributor to ambient particulate matter air pollution. We studied the effects of exposure to diesel exhaust particles on allergic conjunctivitis using cultured conjunctival epithelial cells obtained from healthy people.

Objective

To identify the factors involved in the human conjunctival epithelial response to diesel exhaust in vitro.

Methods

Healthy individuals underwent conjunctival biopsy, and the samples were incubated on conjunctival epithelial sheets. We investigated the effects of exposure to diesel exhaust using GeneChip arrays. The adhesion molecules and cytokines showing increased expression on GeneChip arrays were verified by real-time reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay.

Results

The GeneChip array showed increased expression of adhesion molecules, cytokines, chemokines, and growth factors after exposure to diesel exhaust. Real-time reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay confirmed that the expression of intercellular adhesion molecule 1 and interleukin 6, in particular, were significantly upregulated.

Conclusion

Our experimental data confirm that exposure to diesel exhaust particles increases inflammatory factor expression in human conjunctiva and thereby contributes to allergic conjunctival responses.

Introduction

Allergic conjunctivitis is the most common ocular surface allergic disease and affects more than 20% of the population.[1], [2], [3] As a result of changes in the living environment and other factors, the incidence of allergic diseases, including atopic dermatitis and pollinosis, is progressively increasing. The medical community has been challenged to develop effective therapies for these allergic diseases.4 To better understand the pathogenesis of allergic disease, researchers are increasingly focusing on the effects of environmental factors, such as exposure to atmospheric pollutants, UV light, and viral infection. Epidemiologic studies have found that the increased incidence of allergic diseases is at least partly due to increased exposure to atmospheric pollutants.

The effects of diesel exhaust on the pathophysiology of allergic airway disease have been analyzed in animals and humans using in vitro and in vivo models. The components of diesel exhaust as environmental factors have received much attention in these studies. In fact, it was reported that diesel exhaust particles and carbon black can induce dust mite allergy in rats.5 Exposure to diesel exhaust also enhances ozone-induced airway inflammation in healthy humans6 and in people with asthma.7 In the bronchial epithelium, diesel exhaust increases interleukin (IL) 8, growth-regulated oncogene (GRO) α, and IL-13 and activates several transcription factors (eg, nuclear factor–κB and activator protein 1) and mitogen-activated protein kinases (eg, p38 and c-Jun N-terminal kinase).[8], [9] Holgate et al[10], [11] exposed healthy and asthmatic individuals to diesel exhaust for 2 hours and determined messenger RNA expression in bronchial wash fluid. Stenfors et al12 determined cytokine production in lavage fluid after exposing asthmatic and healthy individuals to diesel exhaust for 6 hours. These findings suggest that oxidant pollutants, including diesel exhaust particles, cause allergic inflammation by activating allergic inflammatory response elements.

In this study, we hypothesized that the ocular surface is exposed to diesel exhaust particles, which enhance the expression of cytokines and growth factors, leading to allergic conjunctival inflammation. Using a GeneChip array, we first investigated the effects of exposure to diesel exhaust in vitro.

Section snippets

Culture of human conjunctival epithelial cells

This study was approved by the Ethics Committee of Tokyo Dental College (Chiba, Japan). All experiments were conducted in accordance with principles of the Declaration of Helsinki. Written informed consent was obtained from all volunteers before participation. Human conjunctival samples were collected from 7 healthy volunteers using scissors under 2% Xylocaine anesthesia. To establish primary conjunctival epithelial cells, samples were cultured in supplemented hormonal epithelial medium

Elevated transcripts in deactivated conjunctival cells

The optimal incubation time to measure the apparent increase of the mRNAs in the model was revealed as 6 hours after exposure among 1, 3, and 6 hours. In addition, 24 hours after exposure among 8, 24, and 48 hours was the optimal time to determine protein production.

We used a GeneChip array to examine the expression levels of approximately 12,000 genes in conjunctival cells exposed to diesel exhaust particles. The fold-increase in expression was determined by calculating the mean difference in

Discussion

There is growing evidence that particulate air pollution increases the incidence of allergy and asthma, in addition to augmenting the severity of asthma and allergic diseases.[14], [15], [16], [17] For example, diesel exhaust was reported to increase histamine-induced IL-8 and granulocyte-macrophage colony-stimulating factor production in nasal epithelial cells and endothelial cells.18 Diesel exhaust was also reported to induce cytokine expression in human bronchial epithelial cells.19

Acknowledgments

We thank Ayako Igarashi and Akiko Kujira at the Tokyo Dental College for their technical assistance.

References (42)

  • M.M. Hom et al.

    Allergic conjunctivitis and dry eye syndrome

    Ann Allergy Asthma Immunol

    (2012)
  • T. Manners

    Managing eye conditions in general practice

    BMJ

    (1997)
  • M.B. Abelson

    A review of olopatadine for the treatment of ocular allergy

    Expert Opin Pharmacother

    (2004)
  • M.B. Abelson

    Comparison of the conjunctival allergen challenge model with the environmental model of allergic conjunctivitis

    Acta Ophthalmol Scand Suppl

    (1999)
  • P. Singh et al.

    Effects of diesel exhaust particles and carbon black on induction of dust mite allergy in brown norway rats

    J Immunotoxicol

    (2005)
  • J. Bosson et al.

    Diesel exhaust exposure enhances the ozone-induced airway inflammation in healthy humans

    Eur Respir J

    (2008)
  • J. McCreanor et al.

    Respiratory effects of exposure to diesel traffic in persons with asthma

    N Engl J Med

    (2007)
  • J. Pourazar et al.

    Diesel exhaust increases EGFR and phosphorylated C-terminal Tyr 1173 in the bronchial epithelium

    Part Fibre Toxicol

    (2008)
  • S.T. Holgate et al.

    Health effects of acute exposure to air pollution, part II: Healthy subjects exposed to concentrated ambient particles

    Res Rep Health Eff Inst

    (2003)
  • S.T. Holgate et al.

    Health effects of acute exposure to air pollution, part I: healthy and asthmatic subjects exposed to diesel exhaust

    Res Rep Health Eff Inst

    (2003)
  • N. Stenfors et al.

    Different airway inflammatory responses in asthmatic and healthy humans exposed to diesel

    Eur Respir J

    (2004)
  • Cited by (51)

    • A study on fundamental combustion properties of oxymethylene ether-1, the primary reference fuel 90, and their blend: Experiments and modeling

      2022, Combustion and Flame
      Citation Excerpt :

      The transport sector, due to its heavy dependence on fossil fuels, is a major contributor of CO2, which is the most prominent greenhouse gas (GHG) connected to climate change [1–3].

    • A comprehensive kinetic model for dimethyl ether and dimethoxymethane oxidation and NO<inf>x</inf> interaction utilizing experimental laminar flame speed measurements at elevated pressure and temperature

      2020, Combustion and Flame
      Citation Excerpt :

      Compression ignition (CI) engines are still facing the challenge of a trade-off between emission control for oxides of nitrogen (NOx) and particulate matter (PM), which are harmful to the environment and human health [1,2].

    • Influence of pentanol and dimethyl ether blending with diesel on the combustion performance and emission characteristics in a compression ignition engine under low temperature combustion mode

      2019, Journal of the Energy Institute
      Citation Excerpt :

      Despite an anticipated decline in the overall diesel market share in the years to 2030, demand for diesel is expected to remain above 50% in medium-upper car segments. Compression ignition engines are still facing the challenge of trade-off emission controls for oxides of nitrogen (NOx) and particulate matter (PM), which are harmful to the environment and human health [1–3]. Low-temperature combustion (LTC) is one of the promising techniques to tackle this issue [4–8].

    View all citing articles on Scopus

    Disclosures: Authors have nothing to disclose.

    Funding Sources: This study was supported by a research grant from Santen Pharmaceutical Co, Ltd, Osaka, Japan.

    View full text