AbstractsBiology & Animal Science

There are a number of isoforms in the PLA2 superfamily, including secretory PLA2s (sPLA2) cytosolic PLA2s (cPLA 2), and calcium independent PLAS (iPLA2beta-short, beta-long, and gamma). In membranous nephropathy, glomerular epithelial cell (GEC) injury by complement C5b-9 leads to morphological changes in GEC and proteinuria, in association with cPLA2alpha activation. The present study addresses the role of iPLA2 in GEC injury. Complement-mediated release of [3H] arachidonic acid was most significantly augmented in GEC overexpressing iPLA2gamma (GEC-iPLA2gamma) as compared with GEC-Neo control. The accelerated AA release was inhibited by the iPLA2-directed catalytic inhibitor bromoenol lactone (BEL). For comparison, GEC-iPLA2gamma also amplified [3H]AA release after incubation of GEC with H2O2, or chemical anoxia followed by re-exposure to glucose, whereas stable clones overexpressing iPLA2gamma only amplified [3H]AA release after incubation with H2O2. Complement-mediated cytotoxicity (measured by release of lactate dehydrogenase) was attenuated significantly in GEC-iPLA2gamma, as compared with GEC-Neo, and the cytoprotective effect of iPLA2gamma was reversed by BEL and partially by Indomethacin. In keeping with previous results, incubation of GEC-cPLA2alpha with complement increased free [3H]AA. This increase in [ 3H]AA was blocked by BEL, although BEL did not block cPLA2alpha activity in cell extracts in vitro. Thus, in addition to cPLA2alpha, iPLA2gamma may be involved in complement-mediated release of AA. Moreover, activation of cPLA2alpha by complement appears to be, at least in part, dependent on iPLA2gamma. Modulation of iPLA2gamma activity may provide a new approach to reducing GEC injury.