Spontaneous Glutamatergic Synaptic Activity Regulates Constitutive COX-2 Expression in Neurons OPPOSING ROLES FOR THE TRANSCRIPTION FACTORS CREB (cAMP RESPONSE ELEMENT BINDING) PROTEIN AND Sp1 (STIMULATORY PROTEIN-1)

Abstract

Edited by Paul E. FraserBurgeoning evidence supports a role for cyclooxygenase metabolites in regulating membrane excitability in various forms of synaptic plasticity. Two cyclooxygenases, COX-1 and COX-2, catalyze the initial step in the metabolism of arachidonic acid to prostaglandins. COX-2 is generally considered inducible, but in glutamatergic neurons in some brain regions, including the cerebral cortex, it is constitutively expressed. However, the transcriptional mechanisms by which this occurs have not been elucidated. Here, we used quantitative PCR and also analyzed reporter gene expression in a mouse line carrying a construct consisting of a portion of the proximal promoter region of the mouse COX-2 gene upstream of luciferase cDNA to characterize COX-2 basal transcriptional regulation in cortical neurons. Extracts from the whole brain and from the cerebral cortex, hippocampus, and olfactory bulbs exhibited high luciferase activity. Moreover, constitutive COX-2 expression and luciferase activity were detected in cortical neurons, but not in cortical astrocytes, cultured from wild-type and transgenic mice, respectively. Constitutive COX-2 expression depended on spontaneous but not evoked excitatory synaptic activity and was shown to be N-methyl-D-aspartate receptor-dependent. Constitutive promoter activity was reduced in neurons transfected with a dominant-negative cAMP response element binding protein (CREB) and was eliminated by mutating the CRE-binding site on the COX-2 promoter. However, mutation of the stimulatory protein-1 (Sp1)-binding site resulted in an N-methyl-D-aspartate receptor-dependent enhancement of COX-2 promoter activity. Basal binding of the transcription factors CREB and Sp1 to the native neuronal COX-2 promoter was confirmed. In toto, our data suggest that spontaneous glutamatergic synaptic activity regulates constitutive neuronal COX-2 expression via Sp1 and CREB protein-dependent transcriptional mechanisms.The first committed reaction in the metabolism of arachidonic acid to prostaglandins and thromboxanes is catalyzed by two related heme-containing bis-oxygenases, cyclooxygenase (COX) 1 and 2. These enzymes share 90% similarity in amino acid sequence and exhibit nearly identical enzyme kinetics (1, 2). Both catalyze two separate reactions, the first metabolizing arachidonic acid to PGG 2 3 (cyclooxygenase reaction), an intermediate that is subsequently reduced in the second reaction to the product, PGH 2 (peroxidase reaction). PGH 2 is the substrate for various synthases that generate individual biologically active prostaglandins and thromboxanes, often in a cell typespecific manner (3). Although both metabolize arachidonic acid to PGH 2 , the transcriptional regulation of each isoform differs. The PTGS1 gene encoding COX-1 lacks a TATA box motif in its 5Ј promoter region and is generally constitutively active in cells (4, 5). In contrast, the promoter regulatory region of the PTGS2 gene encoding COX-2 is not typically active but can be strongly and rapidly induced under specific...

Postnatal changes in constitutive cyclooxygenase‑2 expression in the mice hippocampus and its function in synaptic plasticity

“…GluN1 transgenic mice were shown to report increases in proliferating neural progenitor cells in the adult sugranular zone of dentate gyrus (41), whereas GluN2A KO mice were described to present better exercise-induced amelioration of proliferating neural progenitor cells compared to WT mice (42). In addition, GluN1 null mutant embryo, COX-2 mRNA expression was significantly decreased compared to that in the wide-type embryo (43). Therefore, the reduction in GluN1 and GluN2A/2B observed in COX-2 KO mice may be closely associated with decreases in both the proliferating activity and synaptic plasticity.…”

“…This result is consistent with a previous study indicating that genetic and pharmacological inhibition of COX-2 prominently decreased the number of pCREB-immunoreactive nuclei in the dentate gyrus (17–19). In addition, luciferase assay demonstrated that CREB was involved in the constitutive expression of COX-2 in neurons (43).…”

Influence of Cyclooxygenase-2 Inhibitors on Kynurenic Acid Production in Rat Brain in Vitro

“…Murray and O’Connor ( 2003 ) reported that cyclooxygenase-2 (COX-2), an enzyme synthesizing prostaglandins involved in inflammatory processes, inhibits long-term potentiation (LTP) in rat dentate gyrus, pointing to COX-2 role in memory and learning. COX-2 was found to be constitutively expressed in both cortical and hippocampal neurons (Yamagata et al 1993 ) and being dependent on N -methyl-D-aspartate (NMDA) receptor activity (Hewett et al 2016 ). The expression of COX-2 could be markedly increased in astroglia and microglia in the presence of inflammatory stimuli (Font-Nieves et al 2012 ).…”

Maintenance of the Innate Seizure Threshold by Cyclooxygenase-2 is Not Influenced by the Translational Silencer, T-cell Intracellular Antigen-1

“…Neuronal expression is coupled to endogenous postsynaptic N-Methyl-D-Aspartate type glutamate receptor (NMDAR) activity and as such, can be modified by changes in excitatory neuronal activity. In this regard, antagonism of the NMDAR or deletion of its gene suppresses basal COX-2 mRNA expression by cortical neurons both in the brain and in culture (Yamagata et al, 1993; Hewett et al, 2016). Moreover, neuronal COX-2 mRNA and protein expression in the brain are upregulated strongly in response to excitatory stimulation (Yamagata et al, 1993).…”

“…While the regulation of COX-2 expression has been studied extensively in non-neuronal cell types, much less is known about its regulation in neurons. Numerous transcriptional regulatory proteins are known to bind to cis -acting elements in the 5′ regulatory region of the COX-2 gene and recent evidence from cultures of cortical neurons indicates that basal COX-2 expression is modulated transcriptionally by both Cyclic AMP Response Element Binding protein and Sp-1 (Hewett et al, 2016). The 3′ untranslated region (3′UTR) ofCOX-2 mRNA is a second regulatory region that has the capacity to bind numerous RNA binding proteins (RBPs), which can affect stability and/or translation of the transcript (Dixon et al, 2000).…”