Prostaglandin Pathway Research Articles

Characterisation of endometrial gene expression and metabolic parameters in beef heifers yielding viable or non-viable embryos on Day 7 after insemination

The aim of the present study was to compare the hormonal and metabolic characteristics and endometrial gene expression profiles in beef heifers yielding either a viable or degenerate embryo on Day 7 after insemination as a means to explain differences in embryo survival. Oestrus was synchronised in cross-bred beef heifers (n = 145) using a controlled internal drug release (CIDR)-prostaglandin protocol. Heifers (n = 102) detected in standing oestrus (within 24-48 h after CIDR removal) were inseminated 12-18 h after detection of oestrus (Day 0) with frozen-thawed semen from a single ejaculate of a bull with proven fertility. Blood samples were collected from Day 4 to Day 7 after oestrus to measure progesterone (on Days 4, 5 and 7), insulin and insulin-like growth factor (IGF)-I (on Days 4 and 6) and urea (on Day 7) concentrations. All animals were killed on Day 7. Uterine pH was determined at the time of death. Animals from which an embryo was recovered were classified as either having a viable embryo (morula/blastocyst stage; n = 32) or a retarded embryo (arrested at the two- to 16-cell stage; n = 19). In addition, 14 single-celled unfertilised oocytes were recovered, giving an overall recovery rate of 64%. There was no significant difference in the blood parameters determined or uterine pH at the time of death between heifers with either a viable or retarded embryo. The relative abundance of nine transcripts (i.e. MOGAT1, PFKB2, LYZ2, SVS8, UHRF1, PTGES, AGPAT4, DGKA and HGPD) of 53 tested in the endometrial tissue differed between heifers with a viable or retarded embryo. Both LYZ2 and UHRF1 are associated with regulation of the immune system; PFKFB2 is a mediator in glycolysis; MOGAT, AGPAT4 and DGKA belong to the triglyceride synthesis pathway; and PTGES and HGPD belong to the prostaglandin pathway. Both these metabolic pathways are important for early embryonic development. In conclusion, retarded embryo development in the present study was not related to serum progesterone, IGF-I, insulin or urea concentrations, nor to uterine pH at the time of death. However, altered expression of genes involved in the prostaglandin and triglyceride pathways, as well as two genes that are closely associated with the regulation of immunity, in the endometrium may indicate a uterine component in the retardation of embryo development in these beef heifers.

Influence of Cyclooxygenase Inhibitors on the Function of the Prostaglandin Transporter Organic Anion-Transporting Polypeptide 2A1 Expressed in Human Gastroduodenal Mucosa

The human organic anion-transporting polypeptide 2A1 (OATP2A1) is a prostaglandin transporter expressed in several tissues and plays an important role for local distribution of prostaglandins, which contribute to the integrity of gastric mucosa. Blockade of prostaglandin pathways by cyclooxygenase (COX) inhibitors has been associated with serious side effects such as gastrointestinal ulceration and bleeding. However, little is known regarding OATP2A1 expression in the upper gastrointestinal tract and the potential impact of cyclooxygenase inhibitors on OATP2A1 function. We first investigated the expression of OATP2A1 mRNA and protein in human gastroduodenal mucosa using human biopsy specimens obtained from antrum, corpus, and duodenum. The results indicate that OATP2A1 is expressed in the neck region and deep pyloric glands of antrum and in parietal cells of gastric corpus. Second, we examined various COX inhibitors for their effects on OATP2A1 transporter activity. Using HEK293 cells expressing OATP2A1, we found that diclofenac and lumiracoxib are potent inhibitors of OATP2A1-mediated transport of prostaglandin (PG) E(2) with IC(50) values of 6.2 +/- 1.2 and 3.1 +/- 1.2 microM. In contrast, indomethacin, ketoprofen, and naproxen led to significant stimulation of OATP2A1-mediated PGE(2) transport by 162.7 +/- 13.9, 77.2 +/- 3.6, and 32.3 +/- 4.9%, respectively. Taken together, our results suggest that various clinically used COX inhibitors have differential impact on the function of the prostaglandin transporter OATP2A1 in human stomach and that these effects may contribute to differences in the gastrointestinal side effects of COX inhibitors.

DOCK2 Is a Microglial Specific Regulator of Central Nervous System Innate Immunity Found in Normal and Alzheimer’s Disease Brain

Neuroinflammation is a hallmark of several neurodegenerative diseases, including Alzheimer's disease (AD). Strong epidemiological and experimental evidence supports the use of nonsteroidal anti-inflammatory drugs to reduce AD risk. However, poor outcome in clinical trials and toxicity in a prevention trial have shifted focus away from these cyclooxygenase (COX) inhibitors to seek additional therapeutic targets in the prostaglandin pathway. Previously, the prostaglandin E2 receptor, EP2, was shown to regulate neuroinflammation and reduce Abeta plaque burden in transgenic mice. Unfortunately, widespread EP2 distribution and a direct effect on COX2 induction make EP2 a less desirable target. In this study, we link dedicator of cytokinesis 2 (DOCK2) to the prostaglandin pathway in the brain. Additionally, we show that DOCK2 regulates microglial innate immunity independent of COX2 induction and that DOCK2+ microglia are associated with human AD pathology. Together, these results suggest DOCK2 as a COX2 expression-independent therapeutic target for neurodegenerative diseases such as AD.

Acute and chronic anti-inflammatory properties of the stem bark aqueous and methanol extracts of Sclerocarya birrea (Anacardiaceae)

Sclerocarya birrea is used in folk medicine for the treatment of inflammatory disorders. The effect of the stem bark aqueous and methanol extracts of S. birrea (150 or 300 mg/kg) was evaluated on carrageenan-, histamine- or serotonin-induced paw oedema in rats. The methanol extract of S. birrea (300 mg/kg) being the most active, exhibited a maximum inhibition of 75.45 and 55.31% on carrageenan- and histamine-induced inflammation, respectively. When administered at 300 mg/kg, the methanol extract of S. birrea also exhibited 80.68% inhibition on the 10th day and 54.43% inhibition on the 21st day in formalin- or complete Freund's adjuvant (CFA)-induced paw oedema in rats. GSH level was significantly increased (75.14%), while MAD level was significantly decreased (31.22%) in the liver of CFA rats treated with S. birrea (300 mg/kg). The results suggest that the anti-inflammatory activity of the aqueous and methanol extracts of S. birrea is due to the inhibition of histamine and prostaglandin pathways and to its antioxidant activity.

Tumor Necrosis Factor (TNF)-Alpha Induces Luteolytic Sensitivity in Porcine Luteal Cells by Activating the Intra-Luteal Prostaglandin (PG) Pathway.

Tumor Necrosis Factor (TNF)-Alpha Induces Luteolytic Sensitivity in Porcine Luteal Cells by Activating the Intra-Luteal Prostaglandin (PG) Pathway.

Synaptotagmin-2 Controls Regulated Exocytosis but Not Other Secretory Responses of Mast Cells

Mast cell degranulation is a highly regulated, calcium-dependent process, which is important for the acute release of inflammatory mediators during the course of many pathological conditions. We previously found that Synaptotagmin-2, a calcium sensor in neuronal exocytosis, was expressed in a mast cell line. We postulated that this protein may be involved in the control of mast cell-regulated exocytosis, and we generated Synaptotagmin-2 knock-out mice to test our hypothesis. Mast cells from this mutant animal conferred an abnormally decreased passive cutaneous anaphylaxis reaction on mast cell-deficient mice that correlated with a specific defect in mast cell-regulated exocytosis, leaving constitutive exocytosis and nonexocytic mast cell effector responses intact. This defect was not secondary to abnormalities in the development, maturation, migration, morphology, synthesis, and storage of inflammatory mediators, or intracellular calcium transients of the mast cells. Unlike neurons, the lack of Synaptotagmin-2 in mast cells was not associated with increased spontaneous exocytosis.

Receptor mediation and nociceptin inhibition of bradykinin-induced plasma extravasation in the knee joint of the rat

Objective and designThe aim was to investigate the signaling mechanisms and regulation of bradykinin (BK)-induced inflammation in rat knee joint.Materials and methodsKnee joints of anesthetized rats were perfused with BK (0.1–1.0 μM), and synovial plasma extravasation (PE) was evaluated by spectrophotometrical measurement of Evans Blue leakage. To examine the signaling pathway, B1 antagonist [des-Arg10]-HOE140 (0.1–1.0 μM) and B2 antagonist HOE140 (0.05–1.0 μM), calcitonin gene-related peptide (CGRP) antagonist CGRP8-37 (0.5–1.0 μM), prostaglandin E2 antagonist AH-6809 (0.1–1.0 μM), and histamine H1 antagonist mepyramine (0.1–1.0 μM) were used. Nociceptin (0.0001–1.0 μM) and antagonist J-113397 were tested for modulation of BK-induced PE. The analyses were compared side-by-side with 5-hydroxytryptamine-induced PE.ResultsBK perfusion dose-dependently induced PE, which was blocked by HOE140, CGRP8-37, AH-6809, and mepyramine. It was also inhibited by nociceptin, which could be reversed by antagonist J-113397. In contrast, 5-hydroxytryptamine-induced PE was biphasically regulated by nociceptin and was not antagonized by CGRP8-37.ConclusionsBK-induced PE is mediated by B2 receptors and may involve CGRP, prostaglandin, and histamine pathways. BK-induced PE is inhibited by nociceptin through the activation of ORL1 receptors. There are differences between BK- and 5-hydroxytryptamine-induced inflammation in signaling and modulation.

Secretin‐induced gastric relaxation is mediated by vasoactive intestinal polypeptide and prostaglandin pathways

Secretin has been shown to delay gastric emptying and inhibit gastric motility. We have demonstrated that secretin acts on the afferent vagal pathway to induce gastric relaxation in the rat. However, the efferent pathway that mediates the action of secretin on gastric motility remains unknown. We recorded the response of intragastric pressure to graded doses of secretin administered intravenously to anaesthetized rats using a balloon attached to a catheter and placed in the body of the stomach. Secretin evoked a dose-dependent decrease in intragastric pressure. The threshold dose of secretin was 1.4 pmol kg(-1) h(-1) and the effective dose, 50% was 5.6 pmol kg(-1) h(-1). Pretreatment with hexamethonium markedly reduced gastric relaxation induced by secretin (5.6 pmol kg(-1) h(-1)). Bilateral vagotomy also significantly reduced gastric motor responses to secretin. Administration of N(G)-nitro-L-arginine methyl ester (10 mg kg(-1)) did not affect gastric relaxation induced by secretin. In contrast, intravenous administration of a vasoactive intestinal polypeptide (VIP) antagonist (30 nmol kg(-1)) reduced the gastric relaxation response to secretin (5.6 pmol kg(-1) h(-1)) by 89 +/- 5%. Indomethacin (2 mg kg(-1)) reduced gastric relaxation induced by secretin (5.6 pmol kg(-1) h(-1)) by 87 +/- 5%. Administration of prostaglandin (48 mg kg(-1) h(-1)) prevented this inhibitory effect. Indomethacin also reduced gastric relaxation induced by VIP (300 pmol kg(-1)) by 90 +/- 7%. These observations indicate that secretin acts through stimulation of presynaptic cholinergic neurons in a vagally mediated pathway. Through nicotinic synapses, secretin stimulates VIP release from postganglionic neurons in the gastric myenteric plexus, which in turn induces gastric relaxation through a prostaglandin-dependent pathway.

Inflammatory cells and chemokines sustain FGF2-induced angiogenesis

Angiogenesis and inflammation are closely integrated processes in a number of physiological and pathological conditions, including wound healing, psoriasis, diabetic retinopathy, rheumatoid arthritis, arteriosclerosis, and cancer. Fibroblast growth factor-2 (FGF2) belongs to the family of the heparin-binding FGF growth factors. FGF2 exerts its pro-angiogenic activity by interacting with various endothelial cell surface receptors, including tyrosine kinase receptors, heparan-sulfate proteoglycans, and integrins. Elevated levels of FGF2 have been implicated in the pathogenesis of several diseases characterized by a deregulated angiogenic/inflammatory response. FGF2 induces the expression of a wide repertoire of inflammation-related genes in endothelial cells, including pro-inflammatory cytokines/chemokines and their receptors, endothelial cell adhesion molecules, and components of the prostaglandin pathway. Consistent with this pro-inflammatory signature, in vivo evidence points to a non-redundant role for chemokines and infiltrating monocytes/macrophages in FGF2-driven neovascularization. This review will focus on the cross-talk between FGF2 and the inflammatory response in the modulation of blood vessel growth.

Gastric and small bowel ileus after severe burn in rats: The effect of cyclooxygenase-2 inhibitors

Gastrointestinal (GI) ileus is a common complication after severe burns. Selective cyclooxygenase-2 inhibitors (COX-2i) improved post-operative ileus, but its effect on burn-induced GI dysmotility is unknown. Our aim was to test whether a COX-2i improves gastric emptying (GE) and small bowel transit (SBT) after burn. Experiment on GE: rats were anesthetized and randomized into sham/scald burn, treated/untreated with COX-2i. Six hours after burn, rats received a phenol red meal and were sacrificed 30 min later. Gastric emptying was determined based on the percentage of phenol red recovered in harvested stomachs. Experiment on SBT: rats received a duodenostomy and were scald/sham burned 5 days later. Six hours after burn, rats received a phenol red meal through the duodenostomy catheter and were sacrificed 100 min later. Geometric center (GC) was calculated for SBT. GE was decreased significantly in burned vs. sham animals ( p < 0.001). SBT was significantly impaired in burned vs. sham animals ( p < 0.001). The COX-2i improved GE in the burn rats but not GE in the control rats or SBT in the burn rats. COX-2i improves burn-induced delayed GE, suggesting the mediation of the latter via the prostaglandin pathway.

Common Polymorphisms in the Prostaglandin Pathway Genes and Their Association with Breast Cancer Susceptibility and Survival

There is evidence that genetic variation in the prostaglandin pathway affects cancer susceptibility and progression. Conflicting data from several studies exist for the association of PTGS2 (cyclooxygenase 2) polymorphisms with breast cancer risk. We investigated associations between common germ-line variations in seven genes in the prostaglandin pathway and breast cancer susceptibility and survival among women with invasive breast cancer in the SEARCH study. DNA samples from 9,030 cases and controls were genotyped for 64 single nucleotide polymorphisms tagging known common variants (minor allele frequency > 0.05) in PTGS1, PTGS2, TBXAS1, PTGIS, PTGES, PTGDS, and PGDS with a two-stage case-control study design. Four tagging single nucleotide polymorphisms showed modest association with breast cancer susceptibility. All four fit a recessive genetic model. Minor allele homozygotes for PTGISrs5602 [odds ratio (OR), 1.15; 95% confidence interval (95% CI), 1.04-1.27; P = 0.005], PTGISrs8183919 (OR, 1.22; 95% CI, 1.06-1.41; P = 0.006), and TBXASrs41727 (OR, 1.83; 95% CI, 1.22-2.73; P = 0.003) are associated with an increased risk compared with common allele carriers. For PTGISrs44627 minor allele homozygotes (OR, 0.66; 95% CI, 0.5-0.86; P = 0.002), a protective effect was observed. Specific PTGIS and TBXAS1 variants may affect breast cancer susceptibility, but common variants in PTGS1, PTGS2, PTGES, PTGDS, and PGDS have no major role in breast cancer susceptibility. None of the variants in the seven genes studied appear to affect survival. Further larger studies correlating clinical and genotypic data are required to establish if the clinical utility of prostaglandin-targeted therapies, as chemoprevention agents, is influenced by an individual's profile of genetic variants in key prostaglandin pathway genes.

Inhibition of prostaglandin synthesis and actions by genistein in human prostate cancer cells and by soy isoflavones in prostate cancer patients

Soy and its constituent isoflavone genistein inhibit the development and progression of prostate cancer (PCa). Our study in both cultured cells and PCa patients reveals a novel pathway for the actions of genistein, namely the inhibition of the synthesis and biological actions of prostaglandins (PGs), known stimulators of PCa growth. In the cell culture experiments, genistein decreased cyclooxygenase-2 (COX-2) mRNA and protein expression in both human PCa cell lines (LNCaP and PC-3) and primary prostate epithelial cells and increased 15-hydroxyprostaglandin dehydrogenase (15-PGDH) mRNA levels in primary prostate cells. As a result genistein significantly reduced the secretion of PGE(2) by these cells. EP4 and FP PG receptor mRNA were also reduced by genistein, providing an additional mechanism for the suppression of PG biological effects. Further, the growth stimulatory effects of both exogenous PGs and endogenous PGs derived from precursor arachidonic acid were attenuated by genistein. We also performed a pilot randomised double blind clinical study in which placebo or soy isoflavone supplements were given to PCa patients in the neo-adjuvant setting for 2 weeks before prostatectomy. Gene expression changes were measured in the prostatectomy specimens. In PCa patients ingesting isoflavones, we observed significant decreases in prostate COX-2 mRNA and increases in p21 mRNA. There were significant correlations between COX-2 mRNA suppression, p21 mRNA stimulation and serum isoflavone levels. We propose that the inhibition of the PG pathway contributes to the beneficial effect of soy isoflavones in PCa chemoprevention and/or treatment.

Reduced bladder cancer recurrence rate with cardioprotective aspirin after intravesical bacille Calmette‐Guérin

To evaluate the recurrence-free survival (RFS) rate of patients taking cardioprotective aspirin after intravesical bacille Calmette-Guérin (BCG) for high-grade noninvasive urothelial carcinoma of the bladder, as preventing the recurrence of superficial bladder cancer might decrease patient morbidity and mortality from this disease, and nonsteroidal anti-inflammatory agents (NSAIDs) have shown promise in preclinical prevention through inhibition of the prostaglandin pathway and other mechanisms. In all, 43 patients with carcinoma in situ (CIS) and/or high-grade papillary bladder cancer were treated with intravesical BCG. Patients were stratified according to whether they took cardioprotective aspirin after treatment, and Kaplan-Meier curves of RFS were compared by log-rank analysis. Multivariable analysis was used for potentially confounding factors, including maintenance BCG, the presence of CIS, and smoking status. Of patients taking cardioprotective aspirin, the 5-year RFS rate was 64.3%, compared with 26.9% for patients not taking aspirin, with a significantly higher RFS by univariable log rank analysis (P = 0.03). Even after adjusting for the other factors by multivariable analysis, aspirin seems to affect recurrence (hazard ratio 0.179, P = 0.001). Maintenance BCG (hazard ratio 0.233, P = 0.02) and smoking history (hazard ratio 3.199, P = 0.05) also significantly affected recurrence. There was a significantly higher RFS rate in patients taking cardioprotective aspirin after intravesical BCG therapy for bladder cancer. The results of this study support the further investigation of aspirin and other NSAIDs as preventive agents in patients being treated for superficial bladder cancer.

Prostaglandin mediates endotoxaemia‐induced hypophagia by activation of pro‐opiomelanocortin and corticotrophin‐releasing factor neurons in rats

Corticotrophin-releasing factor (CRF) and alpha-melanocyte-stimulating hormone (alpha-MSH), both of which are synthesized by hypothalamic neurons, play an essential role in the control of energy homeostasis. Neuroendocrine and behavioural responses induced by lipopolyssacharide (LPS) have been shown to involve prostaglandin-mediated pathways. This study investigated the effects of prostaglandin on CRF and alpha-MSH neuronal activities in LPS-induced anorexia. Male Wistar rats were pretreated with indomethacin (10 mg kg(-1); i.p.) or vehicle; 15 min later they received LPS (500 microg kg(-1); i.p.) or saline injection. Food intake, hormone responses and Fos-CRF and Fos-alpha-MSH immunoreactivity in the paraventricular and arcuate nuclei, respectively, were evaluated. In comparison with saline treatment, LPS administration induced lower food intake and increased plasma ACTH and corticosterone levels, as well as an increase in Fos-CRF and Fos-alpha-MSH double-labelled neurons in vehicle-pretreated rats. In contrast, indomethacin treatment partly reversed the hypophagic effect, blunted the hormonal increase and blocked the Fos-CRF and Fos-alpha-MSH hypothalamic double labelling increase in response to the LPS stimulus. These data demonstrate that the activation of pro-opiomelanocortin and CRF hypothalamic neurons following LPS administration is at least partly mediated by the prostaglandin pathway and is likely to be involved in the modulation of feeding behaviour during endotoxaemia.

Conjugated linoleic acid-mediated inflammation and insulin resistance in human adipocytes are attenuated by resveratrol

Inflammation plays a role in trans-10, cis-12 (10,12)-conjugated linoleic acid (CLA)-mediated delipidation and insulin resistance in adipocytes. Given the anti-inflammatory role of resveratrol (RSV), we hypothesized that RSV would attenuate inflammation and insulin resistance caused by 10,12 CLA in human adipocytes. RSV blocked 10,12 CLA induction of the inflammatory response by preventing activation of extracellular signal-related kinase and induction of inflammatory gene expression (i.e., IL-6, IL-8, IL-1beta) within 12 h. Similarly, RSV suppressed 10,12 CLA-mediated activation of the inflammatory prostaglandin pathway involving phospholipase A(2), cyclooxygenase-2, and PGF(2alpha). In addition, RSV attenuated 10,12 CLA increase of intracellular calcium and reactive oxygen species associated with cellular stress, and activation of stress-related proteins (i.e., activating transcription factor 3, JNK) within 12 h. 10,12 CLA-mediated insulin resistance and suppression of fatty acid uptake and triglyceride content were attenuated by RSV. Finally, 10,12 CLA-mediated decrease of peroxisome proliferator-activated receptor gamma (PPARgamma) protein levels and activation of a peroxisome proliferator response element (PPRE) reporter were prevented by RSV. RSV increased the basal activity of PPRE, suggesting that RSV increases PPARgamma activity. Collectively, these data demonstrate for the first time that RSV prevents 10,12 CLA-mediated insulin resistance and delipidation in human adipocytes by attenuating inflammation and cellular stress and increasing PPARgamma activity.

Activation of PPARγ by human CMV for de novo replication impairs invasiveness of cytotrophoblast from early placenta

Human cytomegalovirus (HCMV) contributes to pathogenic processes in immuno-suppressed individuals, in fetuses and in neonates. Infection during pregnancy is known to cause miscarriages and low-birthweight newborns and we know that in this case infection of the placenta precedes transmission to the fetus. HCMV was shown to benefit from inflammatory conditions by using the cyclooxygenase-2 (Cox-2)-dependent prostaglandin pathway for transcription of the essential immediate-early gene IE2. The fact that Cox-2 activation could serve as a source of ligand for the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ), which is known to play a pivotal role in controlling human trophoblast invasion, led us to hypothesize that HCMV could impair placentation through activation of PPARγ.

Inhibition of prostaglandin synthesis and actions contributes to the beneficial effects of calcitriol in prostate cancer

Our research is aimed at obtaining a better understanding of the molecular mechanisms of the anti-proliferative and cancer preventive effects of calcitriol with the goal of developing strategies to improve the treatment of prostate cancer (PCa). In PCa cells calcitriol inhibits the synthesis and biological actions of prostaglandins (PGs) by three actions: (i) the inhibition of the expression of cyclooxygenase-2 (COX-2), the enzyme that synthesizes PGs, (ii) the upregulation of the expression of 15-prostaglandin dehydrogenase (15-PGDH), the enzyme that inactivates PGs and (iii) decreasing the expression of EP and FP PG receptors that are essential for PG signaling. Since PGs have been shown to promote carcinogenesis and progression of multiple cancers, we hypothesize that the inhibition of the PG pathway contributes to the ability of calcitriol to prevent or inhibit PCa development and growth. We have shown that the combination of calcitriol and non-steroidal anti-inflammatory drugs (NSAIDs) result in a synergistic inhibition of the growth of PCa cell cultures and this combination therapy offers a potential therapeutic strategy. These findings led us to embark on a clinical trial combining the non-selective NSAID naproxen with calcitriol in men with early recurrent PCa. The results indicate that the combination of high dose weekly calcitriol with naproxen slows the rate of rise (doubling time) of PSA in most patients indicating the slowing of disease progression. Further studies are warranted to determine the role of this combination therapy in the management of recurrent PCa.

The role of sulfur dioxide as an endogenous gaseous vasoactive factor in synergy with nitric oxide

To explore the physiological role of endogenous gaseous sulfur dioxide (SO 2) on vascular contractility and its underlying cellular and molecular mechanisms, vasodilation experiment of isolated rat thoracic aortic rings by gaseous SO 2 was carried out and the signal transduction pathways involved in the vascular effects of SO 2 were investigated. In the present study, SO 2 gas and SO 2 gas-bubbled solution (SO 2 stock solution) were first used to relax vascular tissues. The results show: (1) Gaseous SO 2 relaxed rat thoracic aortic rings in a dose-dependent manner (from 1 to 2000 μM). The vasorelaxant effect of SO 2 at physiological relevant and low concentrations (<450 μM) was endothelium-dependent, and at high concentrations (>500 μM) was endothelium-independent. (2) The vasorelaxation by addition of SO 2 stock solution (final concentrations ⩽2 mM) was actually caused by SO 2 molecules, not by sulfite or bisulfite, and the characteristic of vasorelaxation by SO 2 was different from that of sulfite and bisulfite. (3) The vasorelaxant effect of SO 2 was not due to the altered neurotransmitter release from the autonomous or nonadrenergic and noncholinergic (NANC) nerve endings, also not due to superoxide and hydrogen peroxide produced in the vascular tissues, also disapproving the involvement of prostaglandin, PKC, β-adrenoceptor and cAMP pathways. (4) The vasorelaxant effect of SO 2 at the physiological relevant and low concentrations was mediated by the cGMP pathway. (5) There was the synergistic effect on smooth muscle relaxation between much lower concentrations of SO 2 (3 μM) and NO (3 or 5 nM). These findings led to the conclusions: endogenous gaseous SO 2 was a vasoactive factor, which might regulate vascular smooth muscle tone in synergy with NO.

Exercise status affects skin perfusion via prostaglandin, nitric oxide, and EDHF pathways in diabetes

Participation in regular exercise training improves dorsal skin perfusion, while type 2 diabetes mellitus (T2 DM) often limits it via reductions in the action or release of vasodilatory compounds. This study was undertaken to investigate the relative contributions of prostaglandins (PG), nitric oxide (NO), and endothelial-derived hyperpolarizing factor (EDHF) in dorsal foot skin perfusion in individuals with and without T2 DM and a sedentary lifestyle. Participants included 24 individuals with T2 DM and 28 nondiabetic controls whose exercise status was determined via questionnaire. Their dorsal foot skin perfusion was measured at rest using laser Doppler assessment during localized heating to 44 °C with oral aspirin (ASA, 325 mg) treatment. In addition, they received an infusion via a subcutaneous microdialysis probe of either saline (left foot) or L-NAME, a NOS-inhibitor (right foot). Compared to normative data without ASA, heat-stimulated perfusion in regular exercisers ( n = 22) was significantly more suppressed by ASA and by ASA/L-NAME than in sedentary individuals ( n = 30). Chronic exercisers exhibit a greater reliance on PG and lesser involvement of EDHF with unchanged NO compared to sedentary individuals, who rely more on EDHF and less on PG release. One possible exception may be diabetic, sedentary individuals, who may rely somewhat more on NO than EDHF. These results suggest that regular exercise may exhibit the greatest effect on the normal functioning of these vasodilatory pathways, although diabetes and a sedentary state together may somewhat alter their relative importance.

Pirinixic Acid Derivatives as Novel Dual Inhibitors of Microsomal Prostaglandin E2 Synthase-1 and 5-Lipoxygenase

Dual inhibition of the prostaglandin (PG) and leukotriene (LT) biosynthetic pathway is supposed to be superior over single interference, both in terms of efficacy and side effects. Here, we present a novel class of dual microsomal PGE(2) synthase-1/5-lipoxygenase (5-LO) inhibitors based on the structure of pirinixic acid [PA, 2-(4-chloro-6-(2,3-dimethylphenylamino)pyrimidin-2-ylthio)acetic acid, compound 1]. Target-oriented structural modification of 1, particularly alpha substitution with extended n-alkyl or bulky aryl substituents and concomitant replacement of the 2,3-dimethylaniline by a biphenyl-4-yl-methane-amino residue, resulted in potent suppression of mPGES-1 and 5-LO activity, exemplified by 2-(4-(biphenyl-4-ylmethylamino)-6-chloropyrimidin-2-ylthio)octanoic acid (7b, IC(50) = 1.3 and 1 microM, respectively). Select compounds also potently reduced PGE(2) and 5-LO product formation in intact cells. Importantly, inhibition of cyclooxygenases-1/2 was significantly less pronounced. Taken together, these pirinixic acid derivatives constitute a novel class of dual mPGES-1/5-LO inhibitors with a promising pharmacological profile and a potential for therapeutic use.