The main rhinovirus respiratory tract adhesion site (ICAM-1) is upregulated in smokers and patients with chronic airflow limitation (CAL)

Abstract

Background: ICAM-1 is a major receptor for ~60% of human rhinoviruses, and non-typeable Haemophilus influenzae, two major pathogens in COPD. Increased cell-surface expression of ICAM-1 in response to tobacco smoke exposure has been suggested. We have investigated epithelial ICAM-1 expression in both the large and small airways, and lung parenchyma in smoking-related chronic airflow limitation (CAL) patients.

Methods: We evaluated epithelial ICAM-1 expression in resected lung tissue: 8 smokers with normal spirometry (NLFS); 29 CAL patients (10 small-airway disease; 9 COPD-smokers; 10 COPD ex-smokers); Controls (NC): 15 normal airway/lung tissues. Immunostaining with anti-ICAM-1 monoclonal antibody was quantified with computerized image analysis. The percent and type of cells expressing ICAM-1 in large and small airway epithelium and parenchyma were enumerated, plus percentage of epithelial goblet and submucosal glands positive for ICAM- 1.

Results: A major increase in ICAM-1 expression in epithelial cells was found in both large (p < 0.006) and small airways (p < 0.004) of CAL subjects compared to NC, with NLFS being intermediate. In the CAL group, both basal and luminal areas stained heavily for ICAM-1, so did goblet cells and sub-mucosal glands, however in either NC or NLFS subjects, only epithelial cell luminal surfaces stained. ICAM-1 expression on alveolar pneumocytes (mainly type II) was slightly increased in CAL and NLFS (p < 0.01). Pack-years of smoking correlated with ICAM-1 expression (r = 0.49; p < 0.03).

Conclusion: Airway ICAM-1 expression is markedly upregulated in CAL group, which could be crucial in rhinoviral and NTHi infections. The parenchymal ICAM-1 is affected by smoking, with no further enhancement in CAL subjects.

Keywords: Chronic airflow limitation; Chronic obstructive pulmonary disease; Epithelial adhesion; Human rhinovirus; Intercellular adhesion molecule-1.

Fig. 1

Intercellular adhesion molecule-1 (ICAM-1) expression in epithelium of large (a-c) and small airways (d-f). a, d Representative section of small airway from a never smoker showing negligible ICAM-1 staining. b, e Typical normal lung function smoker showing positive staining (showed by black arrow). c, f Typical COPD-smoker showing extensive ICAM-1 staining (black arrow). Magnification = x400. BC: basal cells; EC: epithelial cells; GC; goblet cells

Fig. 2

Quantification of ICAM-1-expressing cells in cross-sectional study (a) large airway epithelium. b small airway epithelium. c lung alveolar epithelial cells. Abbreviations: NC, normal control; CAL, chronic airflow limitation; ICAM-1, intercellular adhesion molecule-1; NLFS, normal lung-function smoker

Fig. 3

Correlation between total epithelial cells positive for ICAM-1 with smoking history (pack years). a large airway epithelium. b small airway epithelium. c lung alveolar epithelial cells. Abbreviations: ICAM-1, intercellular adhesion molecule-1

Fig. 4

Photomicrograph showing ICAM-1 expression. (a-b) lung alveolar epithelium. (c-d) submucosal glands. (a) Representative sections from a never smoker. (b) Typical COPD-smoker showing positive staining in alveolar epithelial cells (mainly type II). (c) normal lung function smoker. (d) COPD-smoker showing extensive ICAM-1 staining in submucosal glands. Magnification: A-B=x100; C-D=x200

Fig. 5

Quantification of ICAM-1-expressing goblet cells (a-b) and submucosal glands (c-d) in the cross-sectional study. (a) ICAM-1 expressing goblet cells in large airway epithelium. (b) Intensity of ICAM-1 staining of goblet cells in large airway epithelium. Only ICAM-1 positive goblet cells are included in this comparison. (c) ICAM-1 expressing submucosal glands. (d) Intensity of ICAM-1 staining of submucosal glands. Abbreviations: NC, normal control; CAL, chronic airflow limitation; ICAM-1, intercellular adhesion molecule-1; NLFS, normal lung-function smoker

Fig. 6

Resected lung tissue sections from a COPD-smoker showing goblet cells in of large airway epithelium. (a) ICAM-1 expression, stained with anti-ICAM-1 antibody (brown). (b) goblet cell marker, stained with Periodic Acid-Schiff (purple). Block arrows showing goblet cells expressing both ICAM-1 and PAS staining. Magnification=400x

Fig. 7

Photomicrograph showing ICAM-1 expression in bronchial epithelial cells. a BEAS-2B control cells. b BEAS-2B cells pretreated with CSE (1%, 4 h). c CSE 1% increases ICAM-1 transcript level, assessed by quantitative RT-PCR and normalized for three housekeeping genes. d CSE (1%) also increases protein expression on epithelial cell culture, quantified by computerized image analysis software. Data is presented as mean ± SEM. Magnification = 400x. (Blue: nuclear stain DAPI; Green: Alexa Fluor 488 showing ICAM-1 stain)