CXCR6 EXPRESSION IS INCREASED IN PERIPHERAL BLOOD MONONUCLEAR CELLS FROM COPD PATIENTS

P Escudero1,2, C Rius1,2, L Piqueras2, C González2,3, E Servera2,3, H González2, EJ Morcillo1,2, MJ Sanz1,2. 1University of Valencia, Pharmacology, Spain, 2University Clinic Hospital Research Foundation-INCLIVA, INCLIVA, Spain, 3University Clinic Hospital of Valencia, Pneumology Unit, Spain

Background: Chemokine synthesis and expression by endothelial cells may be an important process underlying cell recruitment within the cardiovascular system in airway inflammatory diseases such as chronic obstructive pulmonary disease (COPD). Chemokine membrane bound CXCL16 promotes the firm adhesion of cells expressing its cognate receptor, CXCR6. The proteolytic cleavage of membrane-bound CXCL16 results in the release of soluble CXCL16, which acts as a chemoattractant for CXCR6+ cells.

Objective: To investigate the expression of CXCR6 receptor in circulating monocytes and lymphocytes from COPD patients and evaluate their adhesiveness to human umbilical arterial endothelial cells (HUAEC).

Methods: Flow cytometry was used to analyze CXCR6 receptor expression in circulating mononuclear cells from COPD patients and age-matched healthy non smoker volunteers. CXCL16 circulating levels were determined in plasma samples by ELISA. Finally, flow chamber was employed to evaluate the functional role of CXCL16 on cigarette smoke extract (CSE)-induced mononuclear cell arrest under dynamic conditions in both populations. 10% CSE was prepared by bubbling smoke from one cigarette 3R4F into 10 ml of EGM-2 culture media without FBS at a rate of 1 cigarette every 2 min, as described previously1.

Results: Whole blood from age matched healthy non smoker volunteers and COPD patients (smoking history of ≥ 10 pack-year, post-bronchodilator FEV1/FVC ratio < 0.7 and a post-bronchodilator FEV1 <80%) were obtained from 20-21 subjects in each group. Flow cytometry analysis revealed increased CXCR6 expression on circulating monocytes and lymphocytes from COPD patients versus control individuals. Interestingly, the number of cells expressing CXCL16 receptor was also enhanced in COPD patients. Despite these findings, no differences in the circulating levels of CXCL16 were detected. Whole blood from both groups was perfused across a monolayer of HUAEC stimulated or not with 1% CSE for 24 h. Significant increases in leukocyte adhesion were observed in HUAEC stimulated with 1% CSE. Neutralization of CXCL16 activity on endothelial cell surface resulted in a significant reduction of 1% CSE-induced leukocyte adhesion to HUAEC being this effect more patent for leukocytes from COPD patients than for those from control individuals.

Conclusions: These results suggest that leukocytes from COPD patients express functional CXCR6 receptor that may explain the increased leukocyte recruitment in vessels distant from the lung. Therefore, targeting CXCL16/CXCR6 axis might prevent cardiovascular diseases in COPD patients.

References:

1,- Edirisinghe et al., FASEB J. 2008;22:2297-2310.

This work was supported by grants SAF2009-08913 SAF2011-23777 CP07/00179, PI08/1875 and RIER RD08/0075/0016 from Spanish Ministry of Science and Innovation, Carlos III Health Institute, Spanish Ministry of Health and several grants from Generalitat Valenciana.