Transcriptional regulation of human prostaglandin-endoperoxide synthase-2 gene in vascular endothelial cells

The omega-3 fatty acid docosahexaenoate attenuates endothelial cyclooxygenase-2 induction through both NADP(H) oxidase and PKC epsilon inhibition

A high intake of the omega-3 fatty acid docosahexaenoate [docosahexaenoic acid (DHA)] has been associated with systemic antiinflammatory effects and cardiovascular protection. Cyclooxygenase (COX)-2 is responsible for the overproduction of prostaglandins (PG) at inflammatory sites, and its expression is increased in atheroma. We studied the effects of DHA on COX-2 expression and activity in human saphenous vein endothelial cells challenged with proinflammatory stimuli. A>or=24-h exposure to DHA reduced COX-2 expression and activity induced by IL-1, without affecting COX-1 expression. DHA effect depended on the NF-kappaB-binding site in the COX-2 promoter. EMSAs confirmed that DHA attenuated NF-kappaB activation. Because MAPK, PKC, and NAD(P)H oxidase all participate in IL-1-mediated COX-2 expression, we also tested whether these enzymes were involved in DHA effects. Western blots showed that DHA blocked nuclear p65 NF-kappaB subunit translocation by decreasing cytokine-stimulated reactive oxygen species and ERK1/2 activation by effects on both NAD(P)H oxidase and PKCepsilon activities. Finally, to address the question whether DHA itself or DHA-derived products were responsible for these effects, we inhibited the most important enzymes involved in polyunsaturated fatty acid metabolism, showing that 15-lipoxygenase-1 products mediate part of DHA effects. These studies provide a mechanistic basis for antiinflammatory and possibly plaque-stabilizing effects of DHA.

Suppressive effects of furonaphthoquinone NFD-37 on the production of lipopolysaccharide-inducible inflammatory mediators in macrophages RAW 264.7

2-Methyl-2-(2-methylpropenyl)-2,3-dihydronaphthoquinone[2,3-b]furan-4,9-dione (NFD-37) is a synthetic furonaphthoquinone compound. In this study, we determined that NFD-37 could inhibit the lipopolysaccharide (LPS)-induced production of inflammatory mediators in macrophages RAW 264.7. This compound inhibited LPS-induced nitric oxide (NO) or prostaglandin (PG) E2 production in dose-dependent manners, with IC50 values of 7.2 microM and 5.3 microM, respectively. As the positive controls, pyrrolidine dithiocarbamate (30 microM) exhibited a 57% inhibition of NO production, and NS-398 (1 microM) manifested a 48% inhibition of PGE2 production. The inhibitory effects of NFD-37 on NO and PGE2 production were determined to occur in conjunction with the suppression of inducible NO synthase or cyclooxygenase-2 expression. NFD-37 also inhibited the production of LPS-inducible tumor necrosis factor-alpha, interleukin (IL)-1beta and IL-6, at IC50 values of 4.8-8.9 microM. We also determined the anti-inflammatory efficacy of NFD-37 using carrageenin-induced paw edema in experimental mice.

Transcriptional regulation of cyclooxygenase-2 gene in ovine large luteal cells

There is positive feedback pathway in the ovine large luteal cell, such that prostaglandin (PG) F(2 alpha) stimulation induces intraluteal PGF(2 alpha) production as the result of induction of one of the rate-limiting enzymes in PG production, cyclooxygenase-2 (Cox-2). The objective of the present study was to evaluate the intracellular effector systems and important DNA transcriptional element(s) involved in regulating the Cox-2 gene in ovine large luteal cells. In transient transfection assays, Cox-2 promoter was rapidly induced (4 h) by phorbol didecanoate (a protein kinase [PK] C activator), ionomycin, and cloprostenol (PGF(2 alpha) analogue), with a peak induction at 12 h. Cloprostenol-mediated promoter activation was not blocked by inhibition of various second messenger systems, including PKA, calcium calmodulin kinase II, or mitogen-activated protein kinases. However, myristoylated PKC pseudosubstrate peptide inhibited cloprostenol stimulation of Cox-2 promoter, indicating the critical role of PKC in this stimulation. The Cox-2 promoter could be reduced to 282 base pairs (bp) of the 5' flanking sequence with retention of full inducibility by cloprostenol. Mutation of three critical cis-responsive elements within this 282-bp region (C/EBP, cAMP responsive element [CRE], and E-box) indicated that E-box was critical in both basal and cloprostenol-induced promoter activity. However, there was also significant but less dramatic inhibition of cloprostenol stimulation by mutation of C/EBP and CRE in the Cox-2 promoter, and mutation of all three elements eliminated cloprostenol induction of this promoter. Electrophoretic mobility shift assays of nuclear extracts from large luteal cells revealed that upstream stimulatory factor (USF)-1 and USF-2 bound to the E-box in Cox-2. Thus, PKC directly regulates transcription of the Cox-2 gene in large luteal cells by acting through DNA elements close to the putative transcriptional start point, particularly an E-box region at -50 bp.

Molecular characterization of bovine prostaglandin G/H synthase-2 and regulation in uterine stromal cells

Prostaglandin G/H synthase (PGHS) is a key rate-limiting enzyme in the prostaglandin biosynthetic pathway, and prostaglandins play a central role in the control of the reproductive cycle. The objectives of this study were to clone and characterize the primary structure of bovine PGHS-2 and to study its regulation in uterine stromal cells in vitro. The bovine PGHS-2 cDNA was cloned by a combination of reverse transcription-polymerase chain reaction and cDNA library screening. Results showed that the complete bovine PGHS-2 cDNA is composed of a 5'-untranslated region of 128 bp, an open reading frame of 1815 bp, and a 3'-untranslated region of 1565 bp containing multiple repeats (n = 11) of the Shaw-Kamen sequence 5'-ATTTA-3'. The open reading frame encodes a 604-amino acid protein that is 86-97% identical to other mammalian PGHS-2 homologs. The regulation of PGHS-2 mRNA and protein was studied in primary cultures of bovine uterine stromal cells stimulated with phorbol 12-myristate 13-acetate (PMA; 100 nM). Northern and Western blot analyses reveal a marked induction in PGHS-2 transcript (4.0 kilobases) and protein (M(r) = 72 000) after 3-12 h of PMA stimulation (P < 0.05). However, this induction was transient in nature as levels of PGHS-2 mRNA and protein returned to basal levels after 24 h of PMA stimulation. In contrast, PMA had no effect on levels of PGHS-1 (P > 0.05). The PMA-dependent induction of PGHS-2 was associated with a significant increase in prostaglandin E2 secretion in the culture media (P < 0.05). To study promoter activity of the 5'-flanking DNA region of the bovine PGHS-2 gene, the genomic fragment -1574/-2 (+1 = transcription start site), as well as a series of 5'-deletion mutants, were fused upstream of the firefly luciferase gene and transiently transfected into primary cultures of bovine uterine stromal cells. Results showed that a first promoter region located between -1574 and -492 and a second region between -88 and -39 appear to play important roles in PMA-dependent regulation of PGHS-2 promoter activity in bovine uterine cells. Thus, this study characterizes for the first time the structure of the bovine PGHS-2 transcript and the deduced amino acid sequence of its encoded protein and establishes an in vitro model to study the regulation of PGHS-2 gene expression in bovine uterine tissue.

The delayed activation of the prostaglandin G/H synthase-2 promoter in bovine granulosa cells is associated with down-regulation of truncated upstream stimulatory factor-2

To elucidate the molecular mechanisms involved in the delayed induction of PGHS-2 in species with a long ovulatory process, a 1. 6-kilobase fragment of the bovine PGHS-2 promoter was isolated, and its activity was characterized in primary cultures of bovine granulosa cells. Promoter activity assays performed with a series of deletion mutants revealed that the promoter region from -149 to -2 (+1 = transcription start site) confers full-length promoter activity in response to forskolin (10 microM). Four consensus cis-elements were identified within this region, including an E-box, ATF/CRE, C/EBP, and AP2 site. Site-directed mutagenesis showed that the E-box was required for PGHS-2 promoter activity, that disruption of the C/EBP element decreased forskolin inducible activity by 29%, whereas point mutation within the ATF/CRE and AP2 element had no inhibitory effect. Electrophoretic mobility shift assays (EMSAs) performed with the -149/-2 fragment and granulosa cell nuclear extracts obtained before (0 h) and after (18 and 20 h) human chorionic gonadotropin (hCG) revealed the regulation of multiple DNA-protein complexes. The 0-h extract generated four complexes at the E-box, whereas only one complex was produced at this site with the 18-h extract. Supershift EMSAs identified that upstream stimulatory factor-1 and -2 (USF-1 and -2) were part of these complexes. Interestingly, the presence of the amino-terminal truncated USF-2, which lacks the transcription activation domain, was detected in the 0-h extract, but not in extracts prepared post-hCG. Supershift EMSAs also indicated high levels of C/EBPbeta binding to its cis-element in the 0-h extract, which contrasts with results previously reported in rats. Thus, high levels of amino-terminal truncated USF-2 and C/EBPbeta in bovine granulosa cells prior to hCG treatment could repress gene expression, and be involved in the delayed induction of PGHS-2 in species with a long ovulatory process.