Jm. Samet et al., CHARACTERIZATION OF A SECRETORY PHOSPHOLIPASE A(2) IN HUMAN BRONCHOALVEOLAR LAVAGE FLUID, Experimental lung research, 22(3), 1996, pp. 299-315
Phospholipase A(2) (PLA(2)) is a pivotal enzyme involved in the synthe
sis of the potent lipid inflammatory mediators platelet activating fac
tor (PAF) and the eicosanoids. This study characterizes a PLA(2) recov
ered in the bronchoalveolar lavage fluid (BALF) of healthy adult human
subjects. Human BALF PLA(2) exhibited characteristics of secretory PL
A(2)s that include an activity that is acid stable, sensitive to reduc
ing agents, and optimally requires millimolar calcium. BALF PLA(2) sho
wed marked selectivity for phosphatidylcholine containing arachidonic
acid (AA) over linoleic or palmitic acids. Size exclusion chromatograp
hy showed the BALF PLA(2) protein to be approximately 14 kDa in mass,
consistent with it being a secretory form of PLA(2). The biological si
gnificance of BALF PLA(2) was tested by applying BALF concentrates to
cultures of the human bronchial epithelial cell line BEAS 2B. Cultures
of BEAS 2B cells treated with BALF concentrates released amounts of A
A and produced higher levels of PAF. These data show that the lining f
luid of the human respiratory tract normally contains a secretory PLA(
2), which may be involved in the formation of lipid inflammatory media
tors in normal and pathophysiologic states in the lung.