Interleukin‐1 beta activates expression of cyclooxygenase‐2 and inducible nitric oxide synthase in primary hippocampal neuronal culture: Platelet‐activating factor as a preferential mediator of cyclooxygenase‐2 expression

Abstract

Interleukin-1 beta (IL-1β) is an inflammatory cytokine whose expression is elevated in brain during seizures, ischemia, and injury. Expression of IL-1β and its receptor can also be observed in normal brain. Platelet-activating factor (PAF) is also a dual mediator that promotes neuronal plasticity responses as well as inflammation. We have determined the role of PAF in the regulation of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) genes by IL-1β in rat primary hippocampal cultures. As assessed by reverse transcriptase/polymerase chain reaction (RT/PCR), recombinant mouse IL-1β (1 nM) led to an induction of COX-2 mRNA which peaked at 2 hours, declined to baseline levels by 4 hours, began to rise again by 6 hours, and remained elevated at 24 hours post-treatment. iNOS mRNA was also induced, but unlike COX-2, its abundance peaked at 4 hours and decreased by 6 hours to a plateau lasting through 24 hours. Pretreatment with PAF antagonist BN50730 blocked induction of COX-2 mRNA by 2-hour IL-1β treatment, and 2-hour treatment with the PAF analog mcPAF mimicked the effects of IL-1β on COX-2 mRNA levels. Following injury, synaptic plasticity changes may be affected by IL-1β-PAF-COX-2 neuronal signaling. J. Neurosci. Res. 58:593–598, 1999. © 1999 Wiley-Liss, Inc.