Interleukin-1 stimulates phosphatidic acid-mediated phospholipase D activity in human mesangial cells

Abstract

Previous studies suggest that signal transduction mediated by interleukin-1 (IL-1), acting through an IL-1 receptor type found on T-cells and mesangial cells, may use phosphatidylethanolamine (PE) as a signaling molecule. Evidence presented here indicates that stimulation of human mesangial cells by IL-1 results in activation of a phospholipase D (PLD) that hydrolyzes PE to phosphatidic acid (PA). PLD acts on a subfraction of PE enriched in 1-o-alkyl and 1-o-alkenyl, sn-2-unsaturated species, generating a unique PA subspecies 30-120 s after stimulation. This PA species is subsequently converted to diradylglycerols by phosphatidate phosphohydrolase. The PE-directed PLD activity is abolished by antibodies against the IL-1 type I receptor and against IL-1. This specific PLD activity is also stimulated by low concentrations of 1,2-sn-dilinoleoyl PA, but not by high concentrations of 1-palmitoyl or 1-oleoyl lyso-PA. Blockade of PLD activation by IL-1 antibodies or antibody against the IL-1 receptor is bypassed by stimulation of human mesangial cells with 1,2-sn-dilinoleoyl PA. A novel system of signal cytokine mediation through PA self-amplification is indicated.