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Epithelial expression of TLR4 is modulated in COPD and by steroids, salmeterol and cigarette smoke.

MacRedmond RE, Greene CM, Dorscheid DR, McElvaney NG, O'Neill SJ - Respir. Res. (2007)

Bottom Line: We found reduced TLR4 gene expression in the nasal epithelium of smokers compared with non-smoking controls, while TLR2 expression was unchanged.Treatment with the corticosteroids fluticasone and dexamethasone resulted in a dose-dependent reduction in TLR4 mRNA and protein.The effect of dexamethasone and salmeterol in combination was additive, with downregulation of TLR4 gene expression, and no change in membrane receptor expression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland. rmacredmond@mrl.ubc.ca

ABSTRACT
The toll-like receptors (TLRs) are a key component of host defense in the respiratory epithelium. Cigarette smoking is associated with increased susceptibility to infection, while COPD is characterised by bacterial colonisation and infective exacerbations. We found reduced TLR4 gene expression in the nasal epithelium of smokers compared with non-smoking controls, while TLR2 expression was unchanged. Severe COPD was associated with reduced TLR4 expression compared to less severe disease, with good correlation between nasal and tracheal expression. We went on to examine the effect of potential modulators of TLR4 expression in respiratory epithelium pertinent to airways disease. Using an airway epithelial cell line, we found a dose-dependent downregulation in TLR4 mRNA and protein expression by stimulation with cigarette smoke extracts. Treatment with the corticosteroids fluticasone and dexamethasone resulted in a dose-dependent reduction in TLR4 mRNA and protein. The functional significance of this effect was demonstrated by impaired IL-8 and HBD2 induction in response to LPS. Stimulation with salmeterol (10-6 M) caused upregulation of TLR4 membrane protein presentation with no upregulation of mRNA, suggesting a post-translational effect. The effect of dexamethasone and salmeterol in combination was additive, with downregulation of TLR4 gene expression, and no change in membrane receptor expression. Modulation of TLR4 in respiratory epithelium may have important implications for airway inflammation and infection in response to inhaled pathogens.

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TLR4 mRNA expression is down-regulated in the nasal mucosa of smokers and in severe COPD in vivo. Outpatients attending for upper GI endoscopy or bronchoscopy were recruited for nasal brush sampling. Subjects were excluded on the basis of pre-existing immunosuppression, pulmonary or nasal pathology other than COPD, including current or recent (within 6 weeks) upper or lower respiratory tract infection. Tracheal brush specimens were also collected on a subset of patients undergoing fibreoptic bronchoscopy (n = 9). A. Table showing demographics of the study population. There was no significant difference between the study groups. B. Total RNA from was reverse transcribed into cDNA and used as a template for semi-quantitative PCR reactions using TLR4, TLR2, HBD2 and GAPDH gene-specific primers. (** P < 0.005 vs non-smoking controls; † P < 0.05 vs all controls; $ P < 0.05 vs COPD FEV1 > 1L). C. TLR4 expression by semi-quantitative RTPCR analysis in tracheal and nasal epithelium.
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Figure 1: TLR4 mRNA expression is down-regulated in the nasal mucosa of smokers and in severe COPD in vivo. Outpatients attending for upper GI endoscopy or bronchoscopy were recruited for nasal brush sampling. Subjects were excluded on the basis of pre-existing immunosuppression, pulmonary or nasal pathology other than COPD, including current or recent (within 6 weeks) upper or lower respiratory tract infection. Tracheal brush specimens were also collected on a subset of patients undergoing fibreoptic bronchoscopy (n = 9). A. Table showing demographics of the study population. There was no significant difference between the study groups. B. Total RNA from was reverse transcribed into cDNA and used as a template for semi-quantitative PCR reactions using TLR4, TLR2, HBD2 and GAPDH gene-specific primers. (** P < 0.005 vs non-smoking controls; † P < 0.05 vs all controls; $ P < 0.05 vs COPD FEV1 > 1L). C. TLR4 expression by semi-quantitative RTPCR analysis in tracheal and nasal epithelium.

Mentions: The demographics of the study population are shown in Figure 1A. There was no significant difference in the characteristics of the COPD subgroups or control subgroups in terms of age, gender or medication use. No patients or control subjects reported a clinical history suggestive of atopy. All COPD subjects were using inhaled LABA and corticosteroids. COPD patients were on average a decade older than the control subjects. There was difficulty in recruiting a population of "normal" older smokers, that is, smokers who had no history of respiratory disease and normal FEV1. The main objective of the study was to observe differences between COPD patients of different degrees of severity. Observed differences with control groups represent a "real world" differences between typical subjects with this condition and healthy control subjects. As all COPD patients were using both inhaled LABA and corticosteroids, differences between subsets of patients may be attributable to the disease process, while differences with control subjects may be the result of disease, smoking or medication.


Epithelial expression of TLR4 is modulated in COPD and by steroids, salmeterol and cigarette smoke.

MacRedmond RE, Greene CM, Dorscheid DR, McElvaney NG, O'Neill SJ - Respir. Res. (2007)

TLR4 mRNA expression is down-regulated in the nasal mucosa of smokers and in severe COPD in vivo. Outpatients attending for upper GI endoscopy or bronchoscopy were recruited for nasal brush sampling. Subjects were excluded on the basis of pre-existing immunosuppression, pulmonary or nasal pathology other than COPD, including current or recent (within 6 weeks) upper or lower respiratory tract infection. Tracheal brush specimens were also collected on a subset of patients undergoing fibreoptic bronchoscopy (n = 9). A. Table showing demographics of the study population. There was no significant difference between the study groups. B. Total RNA from was reverse transcribed into cDNA and used as a template for semi-quantitative PCR reactions using TLR4, TLR2, HBD2 and GAPDH gene-specific primers. (** P < 0.005 vs non-smoking controls; † P < 0.05 vs all controls; $ P < 0.05 vs COPD FEV1 > 1L). C. TLR4 expression by semi-quantitative RTPCR analysis in tracheal and nasal epithelium.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2194695&req=5

Figure 1: TLR4 mRNA expression is down-regulated in the nasal mucosa of smokers and in severe COPD in vivo. Outpatients attending for upper GI endoscopy or bronchoscopy were recruited for nasal brush sampling. Subjects were excluded on the basis of pre-existing immunosuppression, pulmonary or nasal pathology other than COPD, including current or recent (within 6 weeks) upper or lower respiratory tract infection. Tracheal brush specimens were also collected on a subset of patients undergoing fibreoptic bronchoscopy (n = 9). A. Table showing demographics of the study population. There was no significant difference between the study groups. B. Total RNA from was reverse transcribed into cDNA and used as a template for semi-quantitative PCR reactions using TLR4, TLR2, HBD2 and GAPDH gene-specific primers. (** P < 0.005 vs non-smoking controls; † P < 0.05 vs all controls; $ P < 0.05 vs COPD FEV1 > 1L). C. TLR4 expression by semi-quantitative RTPCR analysis in tracheal and nasal epithelium.
Mentions: The demographics of the study population are shown in Figure 1A. There was no significant difference in the characteristics of the COPD subgroups or control subgroups in terms of age, gender or medication use. No patients or control subjects reported a clinical history suggestive of atopy. All COPD subjects were using inhaled LABA and corticosteroids. COPD patients were on average a decade older than the control subjects. There was difficulty in recruiting a population of "normal" older smokers, that is, smokers who had no history of respiratory disease and normal FEV1. The main objective of the study was to observe differences between COPD patients of different degrees of severity. Observed differences with control groups represent a "real world" differences between typical subjects with this condition and healthy control subjects. As all COPD patients were using both inhaled LABA and corticosteroids, differences between subsets of patients may be attributable to the disease process, while differences with control subjects may be the result of disease, smoking or medication.

Bottom Line: We found reduced TLR4 gene expression in the nasal epithelium of smokers compared with non-smoking controls, while TLR2 expression was unchanged.Treatment with the corticosteroids fluticasone and dexamethasone resulted in a dose-dependent reduction in TLR4 mRNA and protein.The effect of dexamethasone and salmeterol in combination was additive, with downregulation of TLR4 gene expression, and no change in membrane receptor expression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medicine, Royal College of Surgeons in Ireland, Dublin, Ireland. rmacredmond@mrl.ubc.ca

ABSTRACT
The toll-like receptors (TLRs) are a key component of host defense in the respiratory epithelium. Cigarette smoking is associated with increased susceptibility to infection, while COPD is characterised by bacterial colonisation and infective exacerbations. We found reduced TLR4 gene expression in the nasal epithelium of smokers compared with non-smoking controls, while TLR2 expression was unchanged. Severe COPD was associated with reduced TLR4 expression compared to less severe disease, with good correlation between nasal and tracheal expression. We went on to examine the effect of potential modulators of TLR4 expression in respiratory epithelium pertinent to airways disease. Using an airway epithelial cell line, we found a dose-dependent downregulation in TLR4 mRNA and protein expression by stimulation with cigarette smoke extracts. Treatment with the corticosteroids fluticasone and dexamethasone resulted in a dose-dependent reduction in TLR4 mRNA and protein. The functional significance of this effect was demonstrated by impaired IL-8 and HBD2 induction in response to LPS. Stimulation with salmeterol (10-6 M) caused upregulation of TLR4 membrane protein presentation with no upregulation of mRNA, suggesting a post-translational effect. The effect of dexamethasone and salmeterol in combination was additive, with downregulation of TLR4 gene expression, and no change in membrane receptor expression. Modulation of TLR4 in respiratory epithelium may have important implications for airway inflammation and infection in response to inhaled pathogens.

Show MeSH
Related in: MedlinePlus