Biomarkers in Chronic Obstructive Pulmonary Diseases

APN circulates in different molecular forms in the blood. It has been reported by Miller et al., that by screening bronchoalveolar lavage (BAL) fluids from chronic obstructive pulmonary disease-Emphysema (COPD-E) and control subjects the epithelial cells can also secrete APN. Immuno-histochemistry of lung sections in COPD-E patients’ demonstrated markable levels of adiponectin and adiponectin receptor 1 (AdipoR1) but not AdipoR2 in the epithelial cells. At present, the mechanism of APN participation in the inflammation of COPD remains unknown. To find out its role in COPD inflammation, Miller et al. measured the concentration of APN in the serum and induced sputum in patients and explored its relationship with the percentage of neutrophils in the airway, IL-8, IL-6 and TNF-α. These studies encourage new insights into the expression of lung epithelial cells with adiponectin and functional AdipoR1 is, implying a significant autocrine and/or paracrine pathway for adiponectin to stimulate. Finally, they explained that adiponectin showed high expression in the lungs of human subjects with the COPD-E. Comparatively, people without COPD, when exposed to tobacco smoke shows down-regulation in adiponectin expression. The study summarized that expression of adiponectin by airway epithelium may regulate the inflammatory reaction in COPD by autocrine or paracrine pathways [7].