Thromboxane Production Research Articles

A review of the mechanisms and effectiveness of dietary polyphenols in reducing oxidative stress and thrombotic risk

Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, flavonols, catechins and phenolic acids, possess antioxidant properties and therefore might be important in preventing oxidative-stress-induced platelet activation and attenuating adverse haemostatic function. Free radicals, including reactive oxygen and nitrogen species, promote oxidative stress, leading to platelet hyperactivation and the risk of thrombosis. The consumption of antioxidant/polyphenol rich foods might therefore impart anti-thrombotic and cardiovascular protective effects via their inhibition of platelet hyperactivation or aggregation. Most commonly-used anti-platelet drugs such as aspirin block the cyclooxygenase (COX)-1 pathway of platelet activation, similar to the action of antioxidants with respect to neutralising hydrogen peroxide (H2 O2 ), with a similar effect on thromboxane production via the COX-1 pathway. Polyphenols also target various additional platelet activation pathways (e.g. by blocking platelet-ADP, collagen receptors); thus alleviating fibrinogen binding to platelet surface (GPIIb-IIIa) receptors, reducing further platelet recruitment for aggregation and inhibiting platelet degranulation. As a result of the ability of polyphenols to target additional pathways of platelet activation, they may have the potential to substitute or complement currently used anti-platelet drugs in sedentary, obese, pre-diabetic or diabetic populations who can be resistant or sensitive to pharmacological anti-platelet therapy.

Cyclo-oxygenase-2 inhibitors

Non-steroidal anti-inflammatory drugs (NSAIDs) are used by millions of patients for many painful pathological disorders. Studies demonstrate their clinical efficacy in both acute and chronic pain. When compared with placebo, NSAIDs show superior analgesic efficacy across a wide spectrum of conditions including postoperative pain, cancer pain, and musculoskeletal conditions. However, NSAIDs have failed to show any benefit in neuropathic pain. Conventional NSAIDs reversibly inhibit the enzyme cyclooxygenase (COX), thereby preventing the production of both prostaglandins and thromboxanes from membrane phospholipids. There are two isoforms of the COX enzyme, COX-1 and COX-2. These isoforms vary in their distribution and expression but are similar in size, substrate specificity, and kinetics. Conventional NSAIDs inhibit the two isoforms to varying degrees, which can cause adverse effects in the gastrointestinal (GI) tract, kidney, respiratory system, and platelets. These sideeffects led to the development of cyclooxygenase-2 inhibitors (coxibs). Coxibs are selective inhibitors of the COX-2 isoenzyme. As the anti-inflammatory effects of conventional NSAIDs were predominantly believed to be mediated by inhibition of COX-2, and their GI side-effects by inhibition of COX-1, it was hypothesized that selective coxibs would provide a safer alternative to conventional NSAIDs.

Netrin-1 regulates the inflammatory response of neutrophils and macrophages, and suppresses ischemic acute kidney injury by inhibiting COX-2-mediated PGE2 production

Netrin-1 regulates inflammation but the mechanism by which this occurs is unknown. Here we explore the role of netrin-1 in regulating the production of the prostanoid metabolite PGE2 from neutrophils in in vitro and in vivo disease models. Ischemia reperfusion in wild-type and RAG-1 knockout mice induced severe kidney injury that was associated with a large increase in neutrophil infiltration and COX-2 expression in the infiltrating leukocytes. Administration of netrin-1 suppressed COX-2 expression, PGE2 and thromboxane production, and neutrophil infiltration into the kidney. This was associated with reduced apoptosis, inflammatory cytokine and chemokine expression, and improved kidney function. Treatment with the PGE2 receptor EP4 agonist enhanced neutrophil infiltration and renal injury which was not inhibited by netrin-1. Consistent with in vivo data, both LPS and IFNγ-induced inflammatory cytokine production in macrophages and IL-17-induced IFNγ production in neutrophils were suppressed by netrin-1 in vitro by suppression of COX-2 expression. Moreover, netrin-1 regulates COX-2 expression at the transcriptional level through the regulation of NFκB activation. Thus, netrin-1 regulates the inflammatory response of neutrophils and macrophages through suppression of COX-2 mediated PGE2 production. This could be a potential drug for treating many inflammatory immune disorders.

Protection of vascular endothelium by aspirin in a murine model of chronic Chagas’ disease

Chronic Chagas' disease affects 10-30 % of patients infected with Trypanosoma cruzi, and it mainly manifests as cardiomyopathy. Important pathophysiological mechanisms involved in the cardiac lesions include activation of the endothelium and induced microvascular alterations. These processes involve the production of endothelial adhesion molecules and thromboxane A2, which are involved in inflammatory cell recruitment and platelet aggregation, respectively. Cyclooxygenase inhibitors such as aspirin decrease thromboxane production and alter the course of Chagas' disease, both in the acute and chronic phases. We studied the effects of the administration of low and high doses of aspirin during the early phase of T. cruzi infection, following microvascular damage in the context of a chronic murine model of Chagas' disease. The effects of both schedules were assessed at 24 and 90 days postinfection by evaluating parasitemia, mortality, and cardiac histopathological changes as well as the expression of ICAM, VCAM, and E-selectin in cardiac tissue. Thromboxane A2, soluble ICAM, and E-selectin blood levels were also measured. While aspirin did not affect parasitemia or mortality in the infected mice, it decreased both cardiac inflammatory infiltrates and thromboxane levels. Additionally, at 90 days postinfection, aspirin normalized sICAM and sE-selectin levels. Considering the improved endothelial function induced by aspirin, we propose the possibility of including this drug in clinical therapy to treat chronic Chagas' disease.

Estradiol-17β and its Cytochrome P450- and Catechol-O-Methyltransferase–Derived Metabolites Selectively Stimulate Production of Prostacyclin in Uterine Artery Endothelial Cells

Metabolism of estradiol-17β to 2-hydroxyestradiol, 4-hydroxyestradiol, 2-methoxyestradiol, and 4-methoxyestradiol contributes importantly to the vascular effects of estradiol-17β in several vascular beds. However, little is known about the role of estradiol-17β metabolites via the different estrogen receptors (ER-α/ER-β) on de novo endothelial prostacyclin and thromboxane production. We hypothesized that estradiol-17β and its metabolites, via ER-α or ER-β, can enhance the prostacyclin/thromboxane ratio through the classic phospholipase A 2 , cyclooxygenase-1, and prostacyclin synthase pathway in ovine uterine artery endothelial cells (UAECs) derived from pregnant (P-UAECs) versus nonpregnant (NP-UAECs) ewes. Western analyses showed higher expression of phospholipase A 2 , cyclooxygenase-1, and prostacyclin synthase in UAECs from the pregnant state, whereas thromboxane synthase was lowered in UAECs from the pregnant state. In UAECs from the pregnant state, estradiol-17β, 2-hydroxyestradiol, 4-hydroxyestradiol, 2-methoxyestradiol and 4-methoxyestradiol concentration and time-dependently increased prostacyclin compared with controls. Prostacyclin increases in UAECs from the nonpregnant state were of a lower magnitude. Estradiol-17β and its metabolites stimulated higher prostacyclin/thromboxane ratios in UAECs from the pregnant state compared with UAECs from the nonpregnant state. Estradiol-17β–induced prostacyclin increases were abrogated by the antagonists SC-560 (cyclooxygenase-1), U-51605 (Prostacyclin synthase), ICI 182 780 (ICI; both ER-α/β), and 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinyleth oxy)phenol]-1H-pyrazole dihydrochloride (MPP; ER-α), but not by 4-[2-phenyl-5,7-bis (trifluoromethyl) pyrazolo[1,5-a]pyrim idin-3-yl]phenol (PHTPP; ER-β). Prostacyclin increases induced by its metabolites were abolished by SC-560 and U-51605, but unaltered by ICI, MPP, or PHTPP. Our findings demonstrate that estrogen via primarily ER-α and its metabolites via ER-independent mechanisms influence the de novo endothelial biosynthesis of prostacyclin, which may be important in the regulation of vascular tone. These findings also shed light on the complexities of estrogen signaling via its metabolism and the functional heterogeneity of the ERs.

The immunological reactivity of blood cells in early pregnancy for predicting of pregnancy outcomes

The immunological reactivity of blood cells in early pregnancy for predicting of pregnancy outcomes

Cyclooxygenase Expression and Platelet Function in Healthy Dogs Receiving Low‐Dose Aspirin

Low-dose aspirin is used to prevent thromboembolic complications in dogs, but some animals are nonresponsive to the antiplatelet effects of aspirin ("aspirin resistance"). That low-dose aspirin would inhibit platelet function, decrease thromboxane synthesis, and alter platelet cyclooxygenase (COX) expression. Twenty-four healthy dogs. A repeated measures study. Platelet function (PFA-100 closure time, collagen/epinephrine), platelet COX-1 and COX-2 expression, and urine 11-dehydro-thromboxane B(2) (11-dTXB(2)) were evaluated before and during aspirin administration (1 mg/kg Q24 hours PO, 10 days). Based on prolongation of closure times after aspirin administration, dogs were divided into categories according to aspirin responsiveness: responders, nonresponders, and inconsistent responders. Low-dose aspirin increased closure times significantly (62% by Day 10, P < .001), with an equal distribution among aspirin responsiveness categories, 8 dogs per group. Platelet COX-1 mean fluorescent intensity (MFI) increased significantly during treatment, 13% on Day 3 (range, -29.7-136.1%) (P = .047) and 72% on Day 10 (range, -0.37-210%) (P < .001). Platelet COX-2 MFI increased significantly by 34% (range, -29.2-270%) on Day 3 (P = .003) and 74% (range, -19.7-226%) on Day 10 (P < .001). Urinary 11-dTXB(2) concentrations significantly (P = .005, P < .001) decreased at both time points. There was no difference between aspirin responsiveness and either platelet COX expression or thromboxane production. Low-dose aspirin consistently inhibits platelet function in approximately one-third of healthy dogs, despite decreased thromboxane synthesis and increased platelet COX expression in most dogs. COX isoform expression before treatment did not predict aspirin resistance.

Thromboxane Receptors in Smooth Muscle Promote Hypertension, Vascular Remodeling, and Sudden Death

The prostanoid thromboxane A2 has been implicated to contribute to the pathogenesis of many cardiovascular diseases, including hypertension. To study the role of vascular thromboxane-prostanoid (TP) receptors in blood pressure regulation, we generated mice with cell-specific deletion of TP receptors in smooth muscle using Cre/Loxp technology. We crossed the KISM22α-Cre transgenic mouse line expressing Cre recombinase in smooth muscle cells with a mouse line bearing a conditional allele of the Tbxa2r gene (Tp(flox)). In KISM22α-Cre(+)Tp(flox/flox) (TP-SMKO) mice, TP receptors were efficiently deleted from vascular smooth muscle cells. In TP-SMKOs, acute vasoconstrictor responses to the TP agonist U46619 were attenuated to a similar extent in both the peripheral and renal circulations. Yet, acute vascular responses to angiotensin II were unaffected at baseline and after chronic angiotensin II administration. Infusion of high-dose U46619 caused circulatory collapse and death in a majority of control mice but had negligible hemodynamic effects in TP-SMKOs, which were completely protected from U46619-induced sudden death. Baseline blood pressures were normal in TP-SMKOs. However, the absence of TP receptors in vascular smooth muscle cells was associated with significant attenuation of angiotensin II-induced hypertension and diminished vascular remodeling. This was also associated with reduced urinary thromboxane production after chronic angiotensin II. Thus, TP receptors in vascular smooth muscle cells play a major role in mediating the actions of thromboxane A(2) in TP agonist-induced shock, hypertension, and vascular remodeling of the aorta.

The Effects of Cyclosporine on Platelet Function and Cyclooxygenase Expression in Normal Dogs

Cyclosporine has been shown to alter platelet plasma membranes and have a hypercoagulable effect in humans, leading to thromboembolic complications. Our hypothesis was that by modulating platelet reactivity, cyclosporine increases the risk of thromboembolic complications. The objective was to determine the effects of cyclosporine on primary hemostasis in normal dogs. Eight healthy, intact female dogs. A repeated-measures design utilized flow cytometry to evaluate platelet expression of platelet reactivity markers (P-selectin and phosphatidylserine) and COX-1 and COX-2 during the administration of 2 cyclosporine dosages (19 mg/kg q12h [immunosuppressive dosage] and 5 mg/kg q24h [atopy dosage]). Urine 11-dehydro-thromboxane-B(2) (11-dTXB(2) ) concentration was normalized to urine creatinine concentration, and platelet function was analyzed by PFA-100. After a week of the immunosuppressive dosage, all platelet reactivity markers showed a significant decrease in mean fluorescent intensity (MFI). After the atopy dosage, only P-selectin and COX-2 MFI demonstrated a change from baseline, decreasing by 29% (P = .013) and 31% (P = .003), respectively. Urinary 11-dTXB(2) -to-creatinine ratio significantly increased at all time points during the immunosuppressive dosage, but no significant change occurred during administration of the atopy dosage. PFA-100 closure times using collagen/ADP cartridges increased by 62% (P = .008) with the immunosuppressive dosage and decreased by 45% with the atopy dosage (P = .035). No significant changes in closure times occurred with collagen/epinephrine cartridges. Our study suggests that, similar to what is observed in humans, cyclosporine alters the platelet plasma membrane and increases thromboxane production in dogs, especially at immunosuppressive dosages.

High Glucose Inhibits the Aspirin-Induced Activation of the Nitric Oxide/cGMP/cGMP-Dependent Protein Kinase Pathway and Does Not Affect the Aspirin-Induced Inhibition of Thromboxane Synthesis in Human Platelets

Since hyperglycemia is involved in the “aspirin resistance” occurring in diabetes, we aimed at evaluating whether high glucose interferes with the aspirin-induced inhibition of thromboxane synthesis and/or activation of the nitric oxide (NO)/cGMP/cGMP-dependent protein kinase (PKG) pathway in platelets. For this purpose, in platelets from 60 healthy volunteers incubated for 60 min with 5–25 mmol/L d-glucose or iso-osmolar mannitol, we evaluated the influence of a 30-min incubation with lysine acetylsalicylate (L-ASA; 1–300 μmol/L) on 1) platelet function under shear stress; 2) aggregation induced by sodium arachidonate or ADP; 3) agonist-induced thromboxane production; and 4) NO production, cGMP synthesis, and PKG-induced vasodilator-stimulated phosphoprotein phosphorylation. Experiments were repeated in the presence of the antioxidant agent amifostine. We observed that platelet exposure to 25 mmol/L d-glucose, but not to iso-osmolar mannitol, 1) reduced the ability of L-ASA to inhibit platelet responses to agonists; 2) did not modify the L-ASA–induced inhibition of thromboxane synthesis; and 3) prevented the L-ASA–induced activation of the NO/cGMP/PKG pathway. Preincubation with amifostine reversed the high-glucose effects. Thus, high glucose acutely reduces the antiaggregating effect of aspirin, does not modify the aspirin-induced inhibition of thromboxane synthesis, and inhibits the aspirin-induced activation of the NO/cGMP/PKG pathway. These results identify a mechanism by which high glucose interferes with the aspirin action.

Inibição seletiva da ciclo-oxigenase-2: riscos e benefícios

The cyclooxygenase (COX) inhibitors are the most common drugs used worldwide. COX corresponds to an evolutionarily conserved class of enzymes and has two main isoforms: COX-1, which is largely associated with physiological functions, and COX-2, which is largely associated with pathological functions. Their subproducts have an important role in inflammation and pain perception. The COX-2 selective inhibition was designed to minimize gastrointestinal complications of non-selective inhibition. However, this exclusive COX-2 inhibition was associated with serious cardiovascular events, for causing an imbalance between prostacyclin and thromboxane production. The objective of this study is to discuss the mechanisms underlying the cardiovascular effects, pointing out the advantages and disadvantages of the selective or nonselective COX inhibitors.

Reciprocal Relationship Between Reactive Oxygen Species and Cyclooxygenase-2 and Vascular Dysfunction in Hypertension

This study evaluates a possible relationship between reactive oxygen species (ROS) and cyclooxygenase (COX)-2-derived products in conductance and resistance arteries from hypertensive animals. Angiotensin II (Ang II)-infused mice or spontaneously hypertensive rats treated with the NAD(P)H Oxidase inhibitor apocynin, the mitochondrion-targeted SOD2 mimetic Mito-TEMPO, the superoxide dismutase analog tempol, or the COX-2 inhibitor Celecoxib were used. Apocynin, Mito-TEMPO, and Celecoxib treatments prevented Ang II-induced hypertension, the increased vasoconstrictor responses to phenylephrine, and the reduced acetylcholine relaxation. The NOX-2 inhibitor gp91ds-tat, the NOX-1 inhibitor ML171, catalase, and the COX-2 inhibitor NS398 abolished the ex vivo effect of Ang II-enhancing phenylephrine responses. Antioxidant treatments diminished the increased vascular COX-2 expression, prostanoid production, and/or participation of COX-derived contractile prostanoids and thromboxane A(2) receptor (TP) in phenylephrine responses, observed in arteries from hypertensive models. The treatment with the COX-2 inhibitor normalized the increased ROS production (O(2)·(-) and H(2)O(2)), NAD(P)H Oxidase expression (NOX-1, NOX-4, and p22phox) and activity, MnSOD expression, and the participation of ROS in vascular responses in both hypertensive models. Apocynin and Mito-TEMPO also normalized these parameters of oxidative stress. Apocynin, Mito-TEMPO, and Celecoxib improved the diminished nitric oxide (NO) production and the modulation by NO of phenylephrine responses in the Ang II model. This study provides mechanistic evidence of circuitous relationship between COX-2 products and ROS in hypertension. The excess of ROS from NAD(P)H Oxidase and/or mitochondria and the increased vascular COX-2/TP receptor axis act in concert to induce vascular dysfunction and hypertension.

ENDOGENOUS OPIOID SYSTEM AS A MEDIATOR OF ACUTE AND LONG-TERM ADAPTATION TO STRESS. PROSPECTS FOR CLINICAL USE OF OPIOID PEPTIDES

It has been well established that opioid peptides (OPs) affect various hormonal systems. Opioids exhibit stress-limiting and gastro-protective effects in stressed animals, acting via mu- and delta-opioid receptors (OR). Peripheral mu-OR stimulation by endogenous and exogenous opioids increases cardiac tolerance to pathological consequences of stress. Enhancement ofprostacyclin synthesis, decrease of thromboxane production as well as suppression of lipid peroxidation can be directly responsible for cardioprotective effects of OPs in stressed animals. Adaptive responses are accompanied by increased OP levels in blood and tissues. Reduction of ventricular arrhythmias induced by repeated short-term immobilization stress is mediated via mu-OR stimulation by endogenous opioids, while delta-OR account for an antiarrhythmic effect of adaptation to chronic intermittent hypobaric hypoxia. The mechanism of infarct size-limiting effect of continuous normobaric hypoxia involves both mu- and delta-OR stimulation. Peptide OR agonists can be considered in future clinical practice for treatment of withdrawal syndrome, stress-related cardiac disease or myocardial injury caused by ischemia-reperfusion insult.

Thromboxane Inhibitors Attenuate Inflammatory and Fibrotic Changes in Rat Liver Despite Continued Ethanol Administrations

Thromboxane levels are increased in rats fed ethanol (EtOH), whereas thromboxane inhibitors reduce alcoholic liver injury. The aim of this study is to determine whether thromboxane inhibitors could attenuate the already established alcoholic liver injury. Rats were fed EtOH and liquid diet for 6 weeks by intragastric infusion to induce liver injury after which EtOH was continued for 2 more weeks, and the rats were treated with either a thromboxane synthase inhibitor (TXSI) or a thromboxane receptor antagonist (TXRA). Liver pathology, lipid peroxidation, nuclear factor-kappa-B (NF-κB) activity, tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), and transforming growth factor-beta1 (TGF-β(1) ) were evaluated. Administration of fish oil and EtOH caused fatty liver, necrosis, inflammation and fibrosis accompanied by increased in lipid peroxidation, NF-κB activity, and expression of TNF-α, COX-2, and TGF-β(1) . Treatment with the thromboxane inhibitors ameliorated a certain level of the pathological and biochemical abnormalities. In particular, TXSI in addition to reducing necrosis, inflammation and fibrosis also decrease the severity of fatty liver. Thromboxane inhibitors attenuated the alcoholic liver injury, inflammation and fibrotic changes despite continued EtOH administration. Inhibition of the production of thromboxane by thromboxane inhibitor and receptor antagonists may be a useful treatment strategy in clinical alcoholic liver disease.

Laboratory Effect on Platelet Activity within 24 h of the First 300-mg Oral Dose of Aspirin Given in Hospital during the Acute Phase of Ischemic Cerebral Events

Background and Purpose: Aspirin is the most commonly used antiplatelet treatment during the acute phase of cerebral ischemic events. It inhibits the production of thromboxane (TX) A₂, a powerful platelet activator. Despite this protection, early ischemic recurrences are frequent and considered clinical failures of this therapy. Only a few trials have focused on the use of antiplatelet therapy during this phase, and none has described the laboratory effect of the first dose of aspirin given after an ischemic cerebral event. However, this study may help clinicians to understand the mechanisms of early recurrences, and to design new therapeutic strategies, in particular for patients already treated with a daily dose of aspirin. Method: We studied laboratory parameters of the first 300-mg oral dose of aspirin given within 48 h after an ischemic cerebral event. Two blood samples were taken from all of the patients: the first during the third hour following aspirin intake (T1) and the second during the twenty-fourth hour (T2). For patients already treated with a daily dose of aspirin, a supplementary sample was taken before aspirin intake (T0). Platelet reactivity was studied on the basis of serum TXB₂ levels, a metabolite of TXA₂, and light transmission aggregometry after stimulation of platelet-rich plasma by arachidonic acid and by two concentrations of collagen, i.e. 2 µg/ml (Col2), dependent on the TXA₂ pathway, and 20 µg/ml (Col20), independent of the TXA₂ pathway. Results with Col2 were related to results with Col20 (Col2/20 ratio) to limit the impact of variations induced by the effects of preanalytical conditions. Results: Fifty patients were included. TXB₂ values (p < 0.001) and relative values of the Col2/20 ratio (p = 0.037) were significantly higher at T2 compared to T1. For patients already treated with aspirin, TXB₂ levels (p < 0.001) were significantly lower at T1 compared to T0, and the Col2/20 ratio tended to decrease (p = 0.096). Conclusion: Platelet reactivity recovers within 24 h following the first 300-mg oral dose of aspirin during the acute phase of a cerebral ischemic event as demonstrated by an increase in TXB₂ levels, and the Col2/20 ratio, at T2 compared to T1. This would favor early ischemic recurrences. However, for patients already treated with aspirin, this dose is able to decrease TXB₂ levels and to complete the inhibition of the TXA₂ pathway, which shows the utility of this prescription in this case.

Premedication with meloxicam exacerbates intracranial haemorrhage in an immature swine model of non-impact inertial head injury

Meloxicam is a cyclo-oxygenase-2 (COX-2) preferential non-steroidal anti-inflammatory drug with very effective analgesic and anti-inflammatory effects in swine. Previous reports in piglets have demonstrated that meloxicam also inhibits COX-1 and reduces production of thromboxane significantly. We use preinjury analgesia in our immature swine (3-5-day-old piglets) model of brain injury using rapid head rotations without impact. In 23 consecutive subjects we found that premedication with meloxicam (n = 6) produced a significantly higher mortality rate (5/6 or 83%) than buprenorphine (n = 17, 1/17 or 6%, P < 0.02). On gross neuropathological examination of the meloxicam-treated swine, we observed massive subdural and subarachnoid bleeding which were not present in buprenorphine-premedicated animals. To our knowledge there are no previous reports in swine of increased bleeding or platelet inhibition associated with meloxicam administration and further research is needed to define mechanisms of action in piglets. We caution the use of meloxicam in swine when inhibition of platelet aggregation might adversely affect refinement of experimental research protocols, such as in stroke, trauma and cardiac arrest models.

Urinary 11-dehydro-thromboxane B2 and 2,3-dinor-6-keto-prostaglandin-F1α in healthy post-menopausal and pre-menopausal women receiving aspirin 100 mg

The prevalence of cardiovascular diseases in women increases sharply after menopause. In postmenopausal women, thromboxane production increases while prostacyclin decreases. Low dose aspirin reduces the production of both thromboxane and prostacyclin. The present study was an open-label clinical trial with two parallel groups of 15 premenopausal women and 15 postmenopausal women. Twenty-four hours urine was collected from each subject before and after aspirin 100 mg daily for 7 days. The concentration of thromboxane and prostacyclin was measured as their metabolites (11-dehydro-thromboxane B(2) and 2,3-dinor-6-keto-prostaglandin-F(1α)) in urine using enzyme immunoassay methods. This study showed that aspirin significantly reduced thromboxane in both groups with significantly larger percentage reduction in postmenopausal women compared to premenopausal women (73.32 vs. 61.13%, p = 0.021). This study also showed that aspirin reduced prostacyclin significantly in both groups, but the percentage reduction between the groups was not significantly different. The decrease in the ratio of 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) should be compared to assess aspirin efficacy as an antithrombotic. Calculation of the ratio of 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) before aspirin consumption was higher in postmenopausal women than in premenopausal women. The decrease in 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) ratio by aspirin was greater in postmenopausal women than in premenopausal women (1.91 vs. 0.17; p = 0.022). It was concluded that aspirin reduced thromboxane and prostacyclin significantly in each group with significant 11-dTXB(2) percentage reduction between groups and non-significant 2,3-dinor-6-keto-PGF(1α) percentage reduction between groups, but reduced the 11-dTXB(2)/2,3-dinor-6-keto-PGF(1α) ratio much larger in postmenopausal women compared to that in premenopausal women.

−765 G→C and −1195 A→G Promoter Variants of the Cyclooxygenase-2 Gene Decrease the Risk for Preeclampsia

Cyclooxygenase-2 (COX-2) is the inducible isoenzyme of COX that leads to increased production of prostaglandins and thromboxane, the mediators of inflammation. Controversial data regarding COX levels or activities in the placentas of women with preeclampsia have led us to examine whether a single nucleotide polymorphism (SNP) in the COX-2 gene is associated with the onset of preeclampsia. Two polymorphisms in the promoter region of COX-2 gene were examined by the polymerase chain reaction and restriction fragment length polymorphism in 128 controls and 74 preeclamptic patients. Genotype distribution and allelic frequencies for -765G→C polymorphism of COX-2 gene were significantly different between patients and controls (p=0.000 and p=0.042, respectively). The odds ratio (OR) for preeclampsia risk associated to the -765G allelic variant was 4.07 (95% confidence interval [CI]: 0.89-18.56). The AA genotype of the -1195 A→G variant was present at a significantly higher frequency among all preeclamptic subjects (p=0.000 χ(2): 13.4, OR: 3.44, 95% CI: 1.74-6.77). A moderate linkage was observed between the -765G and -1195A variants (D(0): 0.201; r(2): 0.003). These findings suggest that SNPs, -765G→C and -1195 A→G, on the promoter region of COX-2 gene may reduce the risk of preeclampsia, possibly by affecting the rate of gene expression.

Grand Challenge in Inflammation

Acute inflammation is a normal response to infection and is beneficial for the host to survive. However, most human diseases are due to sterile inflammation. When allowed to continue unchecked, sterile inflammation can result in autoinflammatory disorders, neurodegenerative disease, or cancer. A variety of safe and effective anti-inflammatory agents are available for short term control of acute inflammation including aspirin and non-steroidal anti-inflammatory drugs (NSAIDs). For the most part, even short term glucocorticoids are safe and effective. But attacking the upstream causes of inflammation is required for long-term treatment. There is new era of anti-inflammatory agents, which includes “biologicals” such as anti-cytokine therapies, kinase inhibitors, statins, histone deacetylase inhibitors, and PPAR agonists. Reducing pain, inflammation, and fever with salicylate-containing plant extracts can be traced throughout written human history. One hundred fifty years ago, Felix Hoffman acetylated salicylic acid and created aspirin. Aspirin inhibits the cyclooxygenase (COX) enzymes COX-1 and COX-2, which synthesize the inflammatory mediators prostaglandins and thromboxanes. The ability to block production of prostaglandins and thromboxanes accounts for aspirin being the world's most used therapeutic agent. Second to aspirin are NSAIDs, which target COX-2 and hence the synthesis of prostaglandins, particularly PGE2. Synthetic forms of natural cortisol (termed glucocorticoids) are widely used to treat many inflammatory diseases and despite their serious side effects, glucocorticoids remain a mainstay of inflammation reduction. Yet, it is still the challenge of the pharmaceutical chemist to develop more effective and less toxic agents to treat the signs and symptoms of acute inflammation as well as the long-term consequences of chronic inflammatory diseases. Inflammation is a dynamic process with pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1 playing central roles. A number of “biologicals” have been developed to treat inflammation by reducing the activity of specific cytokines or their receptors (anti-cytokine therapies), block lymphocyte trafficking into tissues, prevent the binding of monocyte–lymphocyte co-stimulatory molecules, or deplete B lymphocytes. Current anti-cytokine therapies have found a place in the treatment of autoimmune diseases, such as rheumatoid arthritis, inflammatory bowel disease, psoriasis, and others. Without question, neutralization of specific pro-inflammatory cytokines has demonstrated their causative role in inflammation and has changed the lives of millions of patients with these diseases. One drawback of anti-cytokine therapies is decreased host immune defense against infection and possibly cancer. Nevertheless, the benefits of anti-cytokine therapies outweigh the risks and the risks can be reduced. Compared to the consequences of long-term glucocorticoid treatment to stem inflammation, anti-cytokine therapies are a major improvement. Indeed, organ toxicities are rarely, if ever, observed with anti-cytokine therapies as they operate almost exclusively in extracellular rather than intracellular compartments. Kinases that act downstream of cytokine receptors have become new targets to tame inflammation, and orally active small molecule inhibitors of intracellular signaling kinases will likely be the new frontier of anti-inflammatory agents. However, because many intracellular signaling molecules are involved in normal cellular functions, the effective concentration that does not elicit organ toxicity will need to be carefully determined. Statins, a safe class of drugs used for lowering serum cholesterol, also have anti-inflammatory properties. Orally active inhibitors of histone deacetylases, which are currently in clinical use, are effective anti-inflammatory drugs. Naturally occurring resolvins are also being developed as anti-inflammatory agents. Thus the challenge is to develop anti-inflammatory agents that are orally active, safe, and effective for treating acute or chronic inflammation.

Measurements of thromboxane production and their clinical significance in coronary heart disease

Measurements of thromboxane production and their clinical significance in coronary heart disease -