Increased expression of membrane-associated phospholipase A 2 in the lower respiratory tract of asymptomatic cigarette smokers

Abstract

Group II phospholipase A 2 (membrane-associated phospholipase A 2, M-PLA 2) hydrolyses the 2-acyl position of a glycerophospholipid. The concentrations of M-PLA 2 in serum and bronchoalveolar lavage fluid (BALF) were measured in 13 asymptomatic cigarette smokers without clinically detectable lung disease, and the results were compared with those in 13 healthy non-smokers, using a specific radioimmunoassay. In addition, Northern blot analysis of M-PLA 2 mRNA was performed in preparations of total RNA extracted from the cell pellet of BALF from two smokers and two non-smokers. No significant difference was found in serum M-PLA 2 levels between 13 smokers (mean ± sd, 3·48 ± 1·21 ng ml −1) and 13 non-smokers (3·12 ± 1·06 ng ml −1). The smokers' BALFs contained significantly greater levels of M-PLA 2 compared with the non-smokers', whether expressed in terms of BALF volume (0·59 ± 0·34 vs. 0·12 ± 0·09 ng ml −1, P<0·001) or protein content (7·22 ± 3·17 vs. 2·31 ± 1·48 ng mg −1 protein, P<0·001). Northern analysis showed that the levels of M-PLA 2 mRNA in two smokers were greater than those in two non-smokers. Thus, cigarette smoking was associated with increased levels of M-PLA 2 in BALF. This enzyme may be involved in the pathogenesis of pulmonary disease associated with cigarette smoking.