Peroxisome-proliferator-activated receptors and the control of levels of prostaglandin-endoperoxide synthase 2 by arachidonic acid in the bovine uterus

Abstract

Arachidonic acid is a potential paracrine agent released by the uterine endometrial epithelium to induce PTGS2 [PG (prostaglandin)-endoperoxide synthase 2] in the stroma. In the present study, bovine endometrial stromal cells were used to determine whether PTGS2 is induced by arachidonic acid in stromal cells, and to investigate the potential role of PPARs (peroxisome-proliferator-activated receptors) in this effect. Arachidonic acid increased PTGS2 levels up to 7.5-fold within 6 h. The cells expressed PPARalpha and PPARdelta (also known as PPARbeta) (but not PPARgamma). PTGS2 protein level was increased by PPAR agonists, including polyunsaturated fatty acids, synthetic PPAR ligands, PGA1 and NSAIDs (non-steroidal anti-inflammatory drugs) with a time course resembling that of arachidonic acid. Use of agonists and antagonists indicated PPARalpha (but not PPARdelta or PPARgamma) was responsible for PTGS2 induction. PTGS2 induction by arachidonic acid did not require PG synthesis. PTGS2 levels were increased by the PKC (protein kinase C) activators 4beta-PMA and PGF(2alpha), and the effects of arachidonic acid, NSAIDs, synthetic PPAR ligands and 4beta-PMA were blocked by PKC inhibitors. This is consistent with PPAR phosphorylation by PKC. Induction of PTGS2 protein by 4beta-PMA in the absence of a PPAR ligand was decreased by the NF-kappaB (nuclear factor kappaB) inhibitors MG132 and parthenolide, suggesting that PKC acted through NF-kappaB in addition to PPAR phosphorylation. Use of NF-kappaB inhibitors allowed the action of arachidonic acid as a PPAR agonist to be dissociated from an effect through PKC. The results are consistent with the hypothesis that arachidonic acid acts via PPARalpha to increase PTGS2 levels in bovine endometrial stromal cells.

An in vitro investigation of the actions of reproductive hormones on the cervix of the ewe in the follicular stage: The effects of 17β-estradiol, oxytocin, FSH, and arachidonic acid on the cervical pathway for the synthesis of prostaglandin E2

“…Increased production of PG in various tissues after stimulation by polyunsaturated fatty acids has been previously reported in rat uterine stromal cells [49] and in endometrial cells from the late-pregnant ewes [25]. In our study, AA increased levels of COX-2 and cPLA 2 after 48 hours of incubation and these results were in agreement with what previously shown in bovine endometrial cells [50]. These observations suggest tissue and cell-specific differences in the induction of cPLA 2 by AA and support a new vision of the importance of AA in the synthesis of PGE 2 .…”

Involvement of the nuclear factor-κB pathway in the pathogenesis of endometriosis

“…MG-132 (47,69,70) In vitro, EEC Y IL-6 and LIF In vitro, bovine ESC Y PTGS-2 and COX-2 Parthenolide (69) In vitro, bovine ESC Y PTGS-2 SN-50 (33,47) In vitro, EEC Y IL-6 and LIF In vivo, nude mouse a Y Ec lesion development Y ICAM-1 and [ apoptosis Curcumin (53,54,67,168) In vitro, ESC and EcSC Y MIF In vivo, human Unknown, Y symptoms? Sulindac (55) In vitro, ESC Y RANTES Thalidomide (62) In vitro, EcSC Y IL-8 TPCK (59) In vitro, EcSC Y IL-8 GnRH-a (59) In vivo, human/in vitro, EcSC b…”

“…In vitro, EcCs have shown IL-1b, TNF-a, or LPS-dependent NF-kB activation, positively modulating the proinflammatory cytokines RANTES, MIF, IL-8, IL-6, TNF-a, ICAM-1, granulocyte macrophage-colony-stimulating factor (GM-CSF), and monocyte chemoattractant protein-1 (MCP-1) (58-61, 64, 65, 67, 68). Possibly COX-2 could also be modulated by NF-kB, as evidenced in bovine ECs (69,70). In endothelial cells, NF-kB activity has been associated with vascular cell adhesion molecule-1 (VCAM-1), ICAM-1, and…”

Functional Role of PPARs in Ruminants: Potential Targets for Fine-Tuning Metabolism during Growth and Lactation

“…Several in vitro studies using synthetic agonists have demonstrated that activation of PPAR isotypes (except gamma) affects fertility by increasing the expression and/or production of prostaglandins, for example, prostaglandin (PG) F2 α , and PGE2 in bovine endometrial cells [44, 77]. Other in vitro studies were carried out in order to test the response to PPAR isotypes in two bovine cell lines (MDBK and MAC-T) with the purpose of determining PPAR α and PPAR γ target genes [26, 28, 36, 61].…”