Early suppression of NFκB and IL-8 in bronchial epithelium after ozone exposure in healthy human subjects

Abstract

Exposure to elevated concentrations of ozone, a common air pollutant, has been associated with numerous adverse health effects. We have previously reported the time-course of ozone-induced airway inflammation, demonstrating an early up-regulation of vascular endothelial adhesion molecules in bronchial mucosa at 1.5 hours, followed by a neutrophilic infiltration 6 hours after exposure to 0.2 ppm ozone. We hypothesized that the neutrophilic infiltration in the bronchial mucosa would reflect an early increase in bronchial epithelial expression of redox-sensitive transcription factors and kinases regulating neutrophil chemoattractant expression. To test this hypothesis, endobronchial biopsies were obtained from healthy human subjects (n = 11) 1.5 hours after 0.2 ppm of ozone and filtered air exposures (lasting for 2 hours) and stained for mitogen-activated protein kinases (MAPKs), transcription factors, and neutrophil chemoattractants. Total epithelial staining was quantified, as well as the extent of nuclear translocation. Contrary to expectation, ozone significantly suppressed total and nuclear expression of nuclear factor κB (NFκB) in bronchial epithelial cells (p = 0.02 and p = 0.003 respectively). Similarly, the total staining for phosphorylated C-jun was suppressed (p = 0.021). Expression of interleukin 8 (IL-8) in the bronchial epithelium was likewise decreased after ozone (p = 0.018), while GRO-α, ENA-78, C-fos, p-p38, p-JNK, and p-ERK stainings were unchanged. These data suggest that the redox-sensitive NFκB and activator protein 1 (AP-1) pathways within the human bronchial epithelium do not seem to be involved in the early inflammatory cell recruitment pathways in healthy subjects exposed to ozone.

Keywords::

• Transcription factors
• MAP kinases
• cytokines
• air pollution

Acknowledgements

The authors would like to thank Frida Holmström, Annika Johansson, Helena Bogseth, Ann-Britt Lundström, and Maj-Cari Ledin for their excellent technical assistance.

Declaration of interest: Financial support was provided by The Swedish Heart–Lung Foundation and Umeå University.