Lipids in the lung: Respiratory inflammation in COPD

Abstract

Background

There is strong association between COPD and metabolic co-morbidities involving lipids. Abnormalities of lipid metabolism are associated with increased inflammatory responses. The aim of this study was to identify abnormalities of lipid content in the lungs of COPD patients, focusing on lung macrophages.

Methods

Resected lung tissue from patients undergoing surgery for cancer was used; isolated macrophages and macrophages within formalin fixed paraffin embedded (FFPE) tissue were examined. Comparisons were made between 5 subject groups, never smokers (NS), current smokers with normal lung function (S), ex-smokers with normal lung function (E), COPD current smokers (COPDS) and COPD ex-smokers (COPDE). The presence of lipid laden macrophages was identified using oil red o stain (ORO) where positive staining is expressed as % mean (SD).

Results

The number of ORO positive macrophages was increased in COPD patients and controls who were current smokers (COPDS and S) compared to the other groups of ex- or never smokers, in both isolated macrophages and FFPE tissue.

Discussion

We have shown an increase in lipid laden macrophages in the lungs of S and COPDS. Current smoking appears to cause dysfunctional lipid metabolism within lung macrophages that may contribute to respiratory inflammation. Smoking cessation may have benefits in returning lipid metabolism to normal in these cells.