Why do a wide variety of animals retain multiple isoforms of cyclooxygenase? Prostaglandins Other Lipid Mediat. 2014;109-111:14-22. [PMID: 24721150 DOI: 10.1016/j.prostaglandins.2014.03.002]

Cyclooxygenase (COX) has been cloned from the phyla Cnidaria, Mollusca, Arthropoda, and Chordata of the animal kingdom. Many organisms have multiple COX isoforms that have arisen from gene duplication. It is not well understood why there are multiple COX isoforms in the same organism, or when duplication of the COX gene occurred. Here, we summarize the current knowledge of the evolutionary history of COX in the animal kingdom and discuss the reasons why the multiple COX system has been retained so widely. The phylogenetic analysis suggests that all COX genes in animals may descend from a common ancestor and that the duplication of an ancestral COX gene might occur within each lineage after the divergence of the animal. In most instances, the expressions of multiple COX isoforms are separately regulated and these isoforms play different and important pathophysiological roles in each organism. This may be the reason why multiple COX isoforms are widely retained.

Urethane dimethacrylate induces cytotoxicity and regulates cyclooxygenase-2, hemeoxygenase and carboxylesterase expression in human dental pulp cells

The toxic effect of urethane dimethacrylate (UDMA), a major dental resin monomer, on human dental pulp is not fully clear. In this study, we investigated the influence of UDMA on the cytotoxicity, cell cycle distribution, apoptosis and related gene expression of dental pulp cells. The role of reactive oxygen species, hemeoxygenase-1 (HO-1) and carboxylesterase (CES) in UDMA cytotoxicity, was evaluated. UDMA induced morphological changes of pulp cells and decreased cell viability by 29-49% at concentrations of 0.1-0.35 mM. UDMA induced G0/G1, G2/M cell cycle arrest and apoptosis. The expression of cdc2, cyclinB1 and cdc25C was inhibited by UDMA. Moreover, UDMA stimulated COX-2, HO-1 and CES2 mRNA expression of pulp cells. The cytotoxicity of UDMA was attenuated by N-acetyl-l-cysteine, catalase and esterase, but was enhanced by Zn-protoporphyrin (HO-1 inhibitor), BNPP (CES inhibitor) and loperamide (CES2 inhibitor). Exposure of UDMA may potentially induce the inflammation and toxicity of dental pulp. These findings are important for understanding the clinical response of human pulp to resin monomers after operative restoration and pulp capping, and also provide clues for improvement of dental materials.

Cyclooxygenase-2 mediates induction of the renal stanniocalcin-1 gene by arginine vasopressin

In rats and mice, the renal stanniocalcin-1 (STC-1) gene is expressed in most nephron segments, but is differentially induced in response to dehydration. In cortical segments STC-1 mRNA levels are upregulated by the hypertonicity of dehydration, while hypovolemia causes gene induction in the inner medulla (papilla). In both cases induction is mediated by arginine vasopressin (AVP) acting via the V2 receptor (V2R). The intent of STC-1 gene upregulation during dehydration has yet to be established. Therefore, to narrow down the range of possible actions, we mapped out the pathway by which V2R occupancy upregulates the gene. V2R occupancy activates two different renal pathways in response to dehydration. The first is antidiuretic in nature and is mediated by direct V2R occupancy. The second pathway is indirect and counter-regulates AVP-mediated antidiuresis. It involves COX-2 (cyclooxygenase-2) and the prostanoids, and is activated by the V2R-mediated rise in medullary interstitial osmolality. The resulting prostanoids counter-regulate AVP-mediated antidiuresis. They also upregulate renal cytoprotective mechanisms. The present studies employed models of COX inhibition and COX gene deletion to address the possible involvement of the COX pathway. The results showed that both general and specific inhibitors of COX-2 blocked STC-1 gene induction in response to dehydration. Gene induction in response to dehydration was also abolished in COX-2 null mice (cortex and papilla), but not in COX-1 null mice. STC-1 gene induction in response to V2R occupancy was also uniquely abolished in COX-2 nulls (both regions). These findings therefore collectively suggest that AVP-mediated elevations in STC-1 gene expression are wholly dependent on functional COX-2 activity. As such, a permissive role for STC-1 in AVP-mediated antidiuresis can be ruled out, and its range of possible actions has been narrowed down to AVP counter-regulation and renal cytoprotection.

Rapid and simultaneous quantitation of prostanoids by UPLC-MS/MS in rat brain

The metabolites of arachidonic acid (AA) produced from the cyclooxygenase (COX) pathway, collectively termed as prostanoids, and from the CYP 450 pathway, eicosanoids, have been implicated in various neuro-degenerative and neuroinflammatory diseases. This study developed a quantitative UPLC-MS/MS method to simultaneously measure 11 prostanoids including prostaglandins and cyclopentenone metabolites in the rat brain cortical tissue. Linear calibration curves ranging from 0.104 to 33.3ng/ml were validated. The inter-day and intra-day variance for all metabolites was less than 15%. The extraction recovery efficiency and matrix (deionized water) effects measured at 12.5ng/ml (750pg on column) ranged from 88 to 100% and 3 to 14%, respectively, with CV% values below 20%. Additionally, applying the processing and extraction conditions of this method to our previous CYP450 eicosanoids method resulted in overall improvement in extraction recovery and reduction in matrix effects at low (0.417ng/ml) and high (8.33ng/ml) concentrations. In rat brain cortical tissue samples, concentrations of prostanoids ranged from 10.2 to 937pmol/g wet tissue and concentration of eicosanoids ranged from 2.23 to 793pmol/g wet tissue. These data demonstrate that the successive measurement of prostanoids and eicosanoids from a single extracted sample of rat brain tissue can be achieved with a UPLC-MS/MS system and that this method is necessary for evaluation of these metabolites to delineate their role in various neuroinflammatory and cerebrovascular disorders.

Parenteral and inhaled prostanoid therapy in the treatment of pulmonary arterial hypertension

Since continuous IV epoprostenol was approved in the U.S., parenteral prostanoid therapy has remained the gold standard for the treatment of patients with advanced pulmonary arterial hypertension (PAH). Prostanoid agents can be administered as continuous intravenous infusions, as continuous subcutaneous infusions and by intermittent nebulization therapy. This article presents data from clinical trials of available prostanoid agents, and their varied routes of administration. The varied routes of administration allow for the incremental use of this class of agents in advanced PAH, and if PAH progresses. Prostanoids will remain a major component of PAH therapy for the foreseeable future.

The role of prostaglandin E2 in human vascular inflammation

Prostaglandins (PG) are the product of a cascade of enzymes such as cyclooxygenases and PG synthases. Among PG, PGE2 is produced by 3 isoforms of PGE synthase (PGES) and through activation of its cognate receptors (EP1-4), this PG is involved in the pathophysiology of vascular diseases. Some anti-inflammatory drugs (e.g. glucocorticoids, nonsteroidal anti-inflammatory drugs) interfere with its metabolism or effects. Vascular cells can initiate many of the responses associated with inflammation. In human vascular tissue, PGE2 is involved in many physiological processes, such as increasing vascular permeability, cell proliferation, cell migration and control of vascular smooth muscle tone. PGE2 has been shown to contribute to the pathogenesis of atherosclerosis, abdominal aortic aneurysm but also in physiologic/adaptive processes such as angiogenesis. Understanding the roles of PGE2 and its cognate receptors in vascular diseases could help to identify diagnostic and prognostic biomarkers. In addition, from these recent studies new promising therapeutic approaches like mPGES-1 inhibition and/or EP4-antagonism should be investigated.

Lipidomics of essential fatty acids and oxygenated metabolites

Polyunsaturated fatty acids in mammals may be oxygenated into a myriad of bioactive products through di- and monooxygenases, products that are rapidly degraded to control their action. To evaluate the phenotypes of biological systems regarding this wide family of compounds, a lipidomics approach in function of time and compartments would be relevant. The current review takes into consideration most of the diverse oxygenated metabolites of essential fatty acids at large and their immediate degradation products. Their biological function and life span are considered. Overall, this is a fluxolipidomics approach that is emerging.

Control of human vascular tone by prostanoids derived from perivascular adipose tissue

Perivascular adipose tissue (PVAT) surrounds most vessels and has now been recognized as a regulator of vascular functions. This effect of PVAT has been mostly demonstrated in vessels obtained from rats and mice. Thus, the aim of this study was to investigate anti-contractile effect of PVAT surrounding human coronary bypass grafts such as saphenous vein (SV) and internal mammary artery (IMA). Moreover, we aimed to determine the involvement of prostanoids in the anticontractile effect of PVAT. Human SV and IMA preparations were set up in an organ bath. The presence of PVAT in SV and IMA preparations significantly attenuated the contractile response to noradrenaline (NA). Preincubation with indomethacin, a cyclooxygenase inhibitor, increased NA contraction in SV preparations with PVAT. This effect was not observed in IMA preparation with PVAT incubated with indomethacin. The lower measurements of prostaglandin E2 (PGE2) released from PVAT surrounding IMA versus SV supported these effects. In conclusion, our results show that PVAT of SV could attenuate NA-induced contraction by releasing both PGE2 and prostacyclin (PGI2). In contrast to SV, PVAT of IMA exerts its anti-contractile effect independently from prostanoids. These observations suggest that retaining PVAT in human SV and IMA preparations may have potential clinical implications to improve coronary bypass graft patency.

Pharmacological induction of delayed and prolonged cardiac protection: The role of prostanoids

In 1983, a delayed and prolonged cardioprotection induced by drugs was described. This pharmacologically induced adaptation to stress represents a new trend in cardioprotection as opposed to the classical drug treatment that was based on the presence of drug-receptor binding. Such a long-lasting, delayed adaptation can be induced by non-injurious pharmacological stimuli (eg, prostacyclin and its stable analogues, catecholamines and other substances) and manifests as a marked protection against the severe consequences of ischemia; attenuation of early morphological changes (limitation in infarct size) and reduction in ventricular arrhythmias as results of coronary artery occlusion and reperfusion or ouabain toxication. The protection is time- and dose-dependent; the maximum effects occur 24 h and 48 h after drug treatment. These effects can be prolonged for a longer period by the periodic administration of maintenance doses. Concerning the mechanism of this marked delayed protection, the findings show that these adaptive stresses stimulate the adenylate cyclase/cyclic AMP (cAMP) system and result in elevation in cardiac cAMP level. This triggers the induction of Na(+)/K(+)-ATPase and activates phosphodiesterase (PDE) isoforms, most likely PDE1 and PDE4. The increased amount of PDE isoforms and activated Na(+)/K(+)-ATPase moderates ischemic myocardial potassium loss, and reduces sodium and calcium accumulation during myocardial ischemia. This also attenuates ouabain toxicity. Induction of PDE isoforms may lead to a reduction in the accumulation of excess cAMP and contribute to a lessened response to beta-adrenergic stimuli. The antiarrhythmic effects can be explained by electrophysiological changes, such as prolongations of the effective refractory period and the action potential duration during ischemia and reperfusion. The advantages of pharmacologically induced adaptation to stress in preventive therapy are that an exact dosage can be applied, the risk of the harmful effects is minimal, the protection can be prolonged, and it can be induced under pathological conditions (eg, atherosclerosis, hypercholesterolemia). Pharmacologically induced long-term protection may represent a new approach in the therapy of cardiovascular diseases.