Deletion of secretory group v phospholipase A2 attenuates cell migration and airway hyperresponsiveness in immunosensitized mice

We investigated the role of group V phospholipase A(2) (gVPLA(2)) in OVA-induced inflammatory cell migration and airway hyperresponsiveness (AHR) in C57BL/6 mice. Repeated allergen challenge induced biosynthesis of gVPLA(2) in airways. By aerosol, gVPLA(2) caused dose-related increase in airway resistance in saline-treated mice; in allergic mice, gVPLA(2) caused persistent airway narrowing. Neither group IIa phospholipase A(2), a close homolog of gVPLA(2), nor W31A, an inactive gVPLA(2) mutant with reduced activity, caused airway narrowing in immune-sensitized mice. Pretreatment with MCL-3G1, a blocking Ab against gVPLA(2), before OVA challenge blocked fully gVPLA(2)-induced cell migration and airway narrowing as marked by reduction of migrating leukocytes in bronchoalveolar lavage fluid and decreased airway resistance. We also assessed whether nonspecific AHR caused by methacholine challenge was elicited by gVPLA(2) secreted from resident airway cells of immune-sensitized mice. MCL-3G1 also blocked methacholine-induced airway bronchoconstriction in allergic mice. Blockade of bronchoconstriction by MCL-3G1 was replicated in allergic pla2g5(-/-) mice, which lack the gene encoding gVPLA(2). Bronchoconstriction caused by gVPLA(2) in pla2g4(-/-) mice was comparable to that in pla2g4(+/+) mice. Our data demonstrate that gVPLA(2) is a critical messenger enzyme in the development of AHR and regulation of cell migration during immunosensitization by a pathway that is independent of group IV aphospholipase A(2).