Cytosolic phospholipase A(2), (PLA(2)), but not secretory PLA(2), potentiates hydrogen peroxide cytotoxicity in kidney epithelial cells

Phospholipase A(2) (PLA(2)) and reactive oxygen species have been implicated both individually and synergistically in various forms of cellular injury. The form(s) of PLA(2) important for cell injury and the implications of enhanced activity of the enzyme, however, have not been discerned. Previous studies reveal an increase in PLA(2) activity associated with cell injury, but this association does not establish a causal relationship between the increase in activity and the injury. LLC-PK1 cell lines were created that express either the cytosolic PLA(2) or a group II PLA(2). The susceptibility of these cells to hydrogen peroxide toxicity was determined in order to evaluate the relative importance of these two forms of PLA(2) in oxidant injury. Expression of cytosolic PLA(2) in the LLC-cPLA(2) cell line was associated with a 50-fold increase in PLA(2) activity in the cytosolic fraction, an increase in agonist-stimulated arachidonate release, and immunodetection of the cytosolic PLA(2) protein that was undetectable in control cells. Exposure to hydrogen peroxide or menadione, but not mercuric chloride, resulted in significantly greater lactate dehydrogenase release in LLC-cPLA(2) cells when compared with control cells. Exogenous arachidonic acid (150 mu M) did not enhance hydrogen peroxide-induced injury. The intracellular calcium chelator, 1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/tetra(acetoxymethyl) ester, protected the cells against injury, but the calcium ionophore, A23187, did not increase injury. Glycine conferred no protective effect against hydrogen peroxide toxicity. By contrast to these results with cytosolic PLA(2)-expressing cells, secretory PLA(2) expression to very high levels did not increase susceptibility to hydrogen peroxide. Thus, cytosolic PLA(2) may an be an important mediator of oxidant damage to renal epithelial cells.