Cigarette smoke increases TLR4 and TLR9 expression and induces cytokine production from CD8+T cells in chronic obstructive pulmonary disease

Jessica Nadigel,Jean Bourbeau,David H Eidelman,François Maltais,Carolyn J Baglole,David Préfontaine,Qutayba Hamid

doi:10.1186/1465-9921-12-149

Abstract

BackgroundCigarette smoke is a major risk factor for chronic obstructive pulmonary disease (COPD), an inflammatory lung disorder. COPD is characterized by an increase in CD8+ T cells within the central and peripheral airways. We hypothesized that the CD8+ T cells in COPD patients have increased Toll-like receptor (TLR) expression compared to control subjects due to the exposure of cigarette smoke in the airways.MethodsEndobronchial biopsies and peripheral blood were obtained from COPD patients and control subjects. TLR4 and TLR9 expression was assessed by immunostaining of lung tissue and flow cytometry of the peripheral blood. CD8+ T cells isolated from peripheral blood were treated with or without cigarette smoke condensate (CSC) as well as TLR4 and TLR9 inhibitors. PCR and western blotting were used to determine TLR4 and TLR9 expression, while cytokine secretion from these cells was detected using electrochemiluminescence technology.ResultsNo difference was observed in the overall expression of TLR4 and TLR9 in the lung tissue and peripheral blood of COPD patients compared to control subjects. However, COPD patients had increased TLR4 and TLR9 expression on lung CD8+ T cells. Exposure of CD8+ T cells to CSC resulted in an increase of TLR4 and TLR9 protein expression. CSC exposure also caused the activation of CD8+ T cells, resulting in the production of IL-1β, IL-6, IL-10, IL-12p70, TNFα and IFNγ. Furthermore, inhibition of TLR4 or TLR9 significantly attenuated the production of TNFα and IL-10.ConclusionsOur results demonstrate increased expression of TLR4 and TLR9 on lung CD8+ T cells in COPD. CD8+ T cells exposed to CSC increased TLR4 and TLR9 levels and increased cytokine production. These results provide a new perspective on the role of CD8+ T cells in COPD.

Highlights

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide [1], with more than 80% of chronic obstructive pulmonary disease (COPD) cases caused by cigarette smoking [2]
TLR4 and TLR9 are expressed in COPD patients and control subjects Activation of Toll-like receptor (TLR) can lead to the production of proinflammatory mediators, many of which are increased in COPD
In order to further quantify the staining in the subepithelium, the number of positive immune cells per square millimeter were counted from both COPD and control biopsies for each of the TLRs of interest

Summary

Introduction

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide [1], with more than 80% of COPD cases caused by cigarette smoking [2]. TLR4, which recognizes gram-negative bacteria, and TLR9, which binds unmethylated CpG motifs, are two well-studied TLRs. Activation of TL4 or TLR9, results in signal transduction cascades involving downstream pathways including nuclear factor of kappa B (NF-B) and JUN N-terminal kinase (JNK) [16]. Activation of TL4 or TLR9, results in signal transduction cascades involving downstream pathways including nuclear factor of kappa B (NF-B) and JUN N-terminal kinase (JNK) [16] This results in the production of inflammatory cytokines such as IL-1b, IL-6, IL-8, TNFa and IL-10 which can modulate inflammatory responses [17,18,19]. We hypothesized that the CD8+ T cells in COPD patients have increased Toll-like receptor (TLR) expression compared to control subjects due to the exposure of cigarette smoke in the airways

Methods

Results

Discussion

Conclusion