Prostaglandin E2 and Leukotriene C4 Production in rat Cerebellar Granulocytes and Astrocytes: Possible Roles in Brain Trauma

Abstract

When cells are traumatized, arachidonic acid is released from cell membranes and metabolized into a family of biologically active compounds called eicosanoids. The origin of these compounds in the brain is uncertain, as is their role in trauma conditions. Two cell types were studied as possible producers of eicosanoids: cerebellar granulocytes and astrocytes. Using HPLC to separate tritiated arachidonic acid metabolites, two compounds--prostaglandin E2 (PG E2) and leukotriene C4 (L TC4)-were found to exist in both cell cultures. Time-dependent and dose-dependent responses were measured using calcium ionophore and N-methyl-D-aspartate to stimulate maximum production. Oxidative stress was simulated in cultures by the addition of various concentrations of hydrogen peroxide; energy depletion was simulated by treating cells with sodium iodoacetate. A competitive enzyme immunoassay was used to quantitate eicosanoid concentrations. Cerebellar granulocyt~s were not able to produce any measurable amounts of L TC4 while they did produce substantial levels of PGE2. Rat astrocytes also produced high levels of PGE2; LTC4 production was minimal. When cultures were treated with hydrogen peroxide, it was discovered that neither PGE2 nor L TC4 synthesis was affected in either culture; however, the subsequent addition of calcium ionophore caused significant elevation of PGE2 in both cerebellar granulocytes and astrocytes. Incubation with sodium iodoacetate resulted in increased prostaglandin levels in both cell types while L TC4 production remained minimal. These results show that 1.) neuronal cells are capable of producing PGE2, 2.) PGE2 synthesis is upregulated during oxidative stress when the release of arachidonic acid is stimulated and 3.) PGE2 may be involved in stroke as either a participant or as a manifestation of trauma.