ANTIGEN-INDUCED GENERATION OF LYSO-PHOSPHOLIPIDS IN HUMAN AIRWAYS

The goal of the current study was to examine the formation of phosphol ipids, 1-radyl-2-lyso-sn-glycero-phospholipids (lyso-PL) and 2-acetyla ted phospholipids (such as PAF) as well as mechanisms responsible for generating these phospholipids in bronchoalveolar lavage fluid (BALF) from allergic subjects challenged with antigen. Bronchoalveolar lavage was performed in normal and allergic subjects before, 5-30 min, 6 h, and 20 h after segmental antigen challenge via a wedged bronchoscope. Levels of 1-hexadecyl-2-lyso-phospholipids and 1-hexadecyl-2-acetyl-ph ospholipids were initially determined by negative ion chemical ionizat ion gas chromatography/mass spectrometry (NICI-GC/MS). Antigen dramati cally elevated quantities of 1-hexadecyl-2-lyso-phospholipids in aller gic subjects 20 h after challenge when compared to non-allergic contro ls. In contrast, there was not a significant increase in levels of 1-h exadecyl-2-acetyl-phospholipids after antigen challenge. Closer examin ation of 1-radyl-2-lyso-sn-glycero-3-phosphocholine (GPC) revealed tha t 1-palmitoyl-2-lyso-GPC, 1-myristoyl-2-lyso-GPC and 1-hexadecyl-2-lys o-GPC were three major molecular species produced after antigen challe nge. 1-palmitoyl-2-lyso-GPC increased sevenfold to levels of 222 +/- 7 5 ng/ml of BALF 20 h after antigen challenge. The elevated levels of l yso-PL. correlated with levels of albumin used to assess plasma exudat ion induced by allergen challenge. In contrast, the time course of pro staglandin D-2 (PGD(2)) or 9 alpha, 11 beta PGF(2) (11 beta PGF(2)) fo rmation did not correlate with lyso-PL generation. To examine the mech anism leading to lyso-phospholipid formation in antigen-challenged all ergic subjects, secretory phospholipase A(2) (PLA(2)) and acetyl hydro lase activities were measured. There was a significant increase in PLA (2) activity found in BALF of allergic subjects challenged with antige n when compared to saline controls. This activity was neutralized by a n antibody directed against low molecular mass, (14 kD) human synovial PLA(2) and dithiothreitol. Acetyl hydrolase activity also markedly in creased in BALF obtained after antigen challenge. This study indicates that high levels of lyso-PLs are present in airways of allergic subje cts challenged with antigen and provides evidence for two distinct mec hanisms that could induce lyso-PL formation. Future studies will be ne cessary to determine the ramifications of these high levels of lyso-ph ospholipids on airway function.