Does leptin play a cytokine-like role within the airways of COPD patients?

The leptin-leptin receptor system might be up-regulated in the airways of chronic obstructive pulmonary disease (COPD). In bronchial biopsies obtained from normal subjects and smokers, with and without COPD, the present study examined leptin and leptin-receptor expression and their co-localisation in airway and inflammatory cells. Combining immunohistochemistry with terminal deoxynucleotidyl transferase dUTP nick end-labelling techniques, apoptosis in airway and inflammatory cells and in leptin and leptin-receptor expressing cells was investigated. In the epithelial cells both leptin and leptin-receptor expression was higher in normal subjects than in smokers and COPD subjects. By contrast, in the sub-mucosa, leptin was over-expressed in COPD when compared with normal subjects and smokers. Leptin and its receptor were co-localised, mainly with activated T cells (CD45R0) and CD8+ T lymphocytes. In smokers, apoptosis was found in some inflammatory cells, whereas in COPD inflammatory cells, leptin and leptin-receptor positive cells were not apoptotic. Leptin expression was related to COPD severity and assessed using the Global initiative for Chronic Obstructive Lung Disease classification. In conclusion, the present study shows an increased leptin expression in bronchial mucosa of chronic obstructive pulmonary disease patients, associated with airway inflammation and airflow obstruction.