INTERLEUKIN-1-BETA-INDUCED CYTOSOLIC PHOSPHOLIPASE-A(2) ACTIVITY AND PROTEIN-SYNTHESIS IS BLOCKED BY DEXAMETHASONE IN RAT MESANGIAL CELLS

Interleukin-1beta induces gene expression and secretion of the secreto ry phospholipase A, (sPLA2) and prostaglandin E2 (PGE2) release from r at mesangial cells. We have previousy shown that prolonged treatment o f rat mesangial cells with interleukin-1beta (IL-1beta) also enhances the cytosolic phospholipase A2 (cPLA2) activity. This effect of IL-1be ta on the cPLA2 activity is inhibited by actinomycin D and cycloheximi de, indicating that both transcription and translation are involved. H ere, we describe that IL-1beta increases mRNA levels and protein synth esis of cPLA2 itself. In parallel with the effect of dexamethasone on the sPLA2, this glucocorticoid inhibits the IL-1beta-enhanced cPLA2 ac tivity as a result of the suppression of IL-1beta-induced cPLA2 gene e xpression. This report suggests that the pro-inflammatory action of in terleukin-1beta may, in part, be mediated by its effects on cPLA2 acti vity.