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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The roles of PGI2 and TXA2 in recurring reduction of carotid artery and cerebral blood flow induced by partial constriction of the common carotid artery and cerebral blood flow induced by partial constriction of the common carotid artery were examined in anesthetized dogs. The recurring reduction was eliminated by OKY 046 and 1580 which inhibit TX synthetase, acetylsalicylic acid which inhibits cyclo-oxygenase and lipoxygenase, PGI2 and by papaverine which enhances PGI synthesis. But the recurring reduction was not eliminated by phentolamine. The recurring reduction was induced by epinephrine which activates phospholipase A2 and cyclo-oxygenase and causes platelet aggregation. It was also induced by tranylcypromine which inhibits PGE2 synthetase and, although infrequently, by TXA2. The recurring reduction was also induced by indomethacin that inhibits cyclo-oxygenase. The indomethacin-induced recurring reduction, however, was eliminated not by OKY 046 and 1580 but by PGI2. It is suggested that TXA2 acted as an inducer and PGI2 as an inhibitor in the recurring reduction of carotid artery and cerebral blood flow.
Stroke
PMID:Role of prostaglandin I2 and thromboxane A2 in recurring reduction of carotid and cerebral blood flow in dogs. 702 92

Patients with human immunodeficiency virus show increased atheroembolism and premature arterial events (stroke, myocardial infarction), but no increased venous thromboembolism. This paper describes an association of elevated lipoprotein(a), a decreased prostaglandin I(2)(PGI(2)) synthesis stimulating plasma factor, diminished PGI(2)-stability in plasma and decreased high-density lipoprotein-cholesterol and apolipoprotein A. It is unclear to what extent these biochemical findings represent an acute phase reaction only or a disturbance in the prostaglandin system. Definitely, they are resulting in severe hemostatic imbalance decreasing local PGI(2)-availability with a dramatic reduction in the cytoprotective capacity favouring the onset of premature arterial events seen in some of the patients.
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PMID:Association of lipoprotein(a), prostaglandin I(2)--synthesis stimulating plasma factor, biological half-life of prostaglandin I(2)and high-density lipoproteins in HIV-1 infection of different stages. 1109 Feb 58

Cyclooxygenases catalyze the first committed step in the formation of prostaglandins and thromboxanes from arachidonic acid. Cyclooxygenase-2 (COX-2), the inducible isoform of cyclooxygenase, is expressed in brain selectively in neurons of hippocampus, cerebral cortex, amygdala, and hypothalamus. Prostaglandins function in many processes in the CNS, including fever induction, nociception, and learning and memory, and are upregulated in paradigms of excitotoxic brain injury such as stroke and epilepsy. To address the varied functions of COX-2 and its prostaglandin products in brain, we have developed a transgenic mouse model in which COX-2 is selectively overexpressed in neurons of the CNS. COX-2 transgenic mice demonstrate elevated levels of all prostaglandins and thromboxane, albeit with a predominant induction of PGE(2) over other prostaglandins, followed by more modest inductions of PGI(2), and relatively smaller increases in PGF(2alpha),PGD(2), and TxB(2). We also examined whether increased neuronal production of prostaglandins would affect fever induction in response to the bacterial endotoxin lipopolysaccharide. COX-2 induction in brain endothelium has been previously determined to play an important role in fever induction, and we tested whether neuronal expression of COX-2 in hypothalamus also contributed to the febrile response. We found that in mice expressing transgenic COX-2 in anterior hypothalamus, the febrile response was significantly potentiated in transgenic as compared to non-transgenic mice, with an accelerated onset of fever by 1 2 hours after LPS administration, suggesting a role for neuronally derived COX-2 in the fever response.
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PMID:Neuronal overexpression of COX-2 results in dominant production of PGE2 and altered fever response. 1266 73

Prostacyclin (PGI(2)) is a potent endogenous inhibitor of platelet function and possesses a strong vasodilator effect. Furthermore, prostacyclin is currently presented as the physiologic antagonist of thromboxane A(2)(TXA(2)), which exhibits pro-aggregatory and vasoconstrictor properties. So, the balance between PGI(2) and TXA(2) production is crucial for the cardiovascular system. Indeed, an imbalance in the production or effect of these products is deleterious for the circulatory system and can lead to characterized vascular diseases such as hypertension, stroke, atherosclerosis or myocardial infarction. Although the biological effects of PGI(2) are considered to be clinically useful, its use as therapeutic agent is largely limited by both its chemical and metabolic instability. Actually, several prostacyclin agonists have been synthesized and pharmacologically evaluated. Among these, some have been clinically evaluated as therapeutic agents in several vascular diseases. This review focuses on the latest chemical and pharmacological developments in the field of the prostacyclin agonists.
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PMID:New developments on thromboxane and prostacyclin modulators part II: prostacyclin modulators. 1513 17

Selective inhibitors of cyclooxygenase (COX)-2 depress prostacyclin (PGI(2)) without a concomitant inhibition of platelet COX-1-derived thromboxane (Tx)A(2). Experiments in gene-deleted mice have shown that ablation of the PGI(2) receptor (the IP) predisposes to an exaggerated response to agonists which elevate blood pressure, accelerate atherogenesis and induce thrombosis. Such a class-based effect would be expected to be modulated by the underlying risk of cardiovascular disease in patients, elements of drug exposure, such as dose, duration of action and duration of dosing, and inter-individual variability of drug response. Five placebo-controlled trials of three structurally distinct selective inhibitors of COX-2 have revealed an increased hazard of myocardial infarction and stroke consistent with a mechanism-based class-specific cardiovascular hazard. Sustained inhibition of platelet TxA(2) by aspirin affords cardiovascular benefit, despite concomitant inhibition of PGI(2). Although there is no information from randomized placebo-controlled trials, traditional non-steroidal anti-inflammatory drugs, such as naproxen, dicofenac and ibuprofen, might differ in their effects of cardiovascular biology.
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PMID:Cardiovascular hazard and non-steroidal anti-inflammatory drugs. 1578 Aug 32

Coxibs, such as rofecoxib, celecoxib, and valdecoxib, selectively inhibit cyclooxygenase (COX)-2, the mainly inducible, pro-inflammatory COX isoform. Unlike traditional non-steroidal anti-inflammatory drugs (NSAIDs) most coxibs do not significantly inhibit COX-1 and are therefore less toxic to the gastrointestinal tract. Hence, coxibs widely replaced traditional NSAIDs for treatment of arthritis and other painful inflammatory conditions. In many, but not all, clinical studies, coxibs became associated with higher risks of myocardial infarction (MI) and stroke. Several mechanisms may be involved in the pathogenesis of such complications. First, selective inhibition of COX-1 lowers platelet synthesis of thromboxane (TXA(2)), a thrombogenic and atherogenic eicosanoid. Selective inhibition of COX-2 limits endothelial cell synthesis of prostacyclin (PGI(2)), an arachidonic acid product that opposes the effects of thromboxane. In apoE-/- mice, interruption of TXA(2) signaling by deletion of its receptor (TP) limits atherogenesis, whereas interruption of PGI2 signaling by deletion of its receptor (IP) accelerates atherogenesis. This suggests that selective inhibition of COX-2 can disrupt the physiological balance between thromboxane and prostacyclin and thus increase atherosclerosis, thrombogenesis, and the risk of cardiovascular complications. Second, COX inhibition can raise levels of arachidonic acid, which can inhibit mitochondrial oxidative phosphorylation (OXPHOS) and increase OXPHOS generation of reactive oxygen species. Several NSAIDs, including coxibs and meloxicam, directly uncouple or inhibit OXPHOS. Studies of apoE-/- mice indicate that mitochondrial dysfunction plays an early role in atherogenesis. Third, many NSAIDs exhibit COX-independent properties. For example, in animal models, short-term treatment with celecoxib reduces monocyte chemotaxis by reducing expression of monocyte chemoattractant protein (MCP)-1. However, long-term treatment results in the opposite effect and accelerates atherogenesis. In conclusion, to reduce the risk of cardiovascular complications during long-term coxib therapy, low-dose aspirin supplementation should be considered. An alternative is to use a less COX-2-selective inhibitor such as meloxicam. Genotyping of -765 alleles of the COX-2 gene promoter and examining the polymorphism of other genes involved in eicosanoid metabolism or NSAID degradation may become helpful in predicting patients who are at higher risk of cardiovascular complications during selective COX-2 inhibitor therapy.
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PMID:Cardiovascular complications of non-steroidal anti-inflammatory drugs. 1625 52

Selective inhibitors of cyclooxygenase (COX)-2, the coxibs, were developed to inhibit inflammatory prostaglandins derived from COX-2, while sparing gastroprotective prostaglandins primarily formed by COX-1. However, COX-2-derived prostaglandins mediate not only pain and inflammation but also affect vascular function, the regulation of hemostasis/ thrombosis, and blood pressure control. All coxibs depress COX-2-dependent prostacyclin (PGI(2)) biosynthesis without effective suppression of platelet COX-1-derived thromboxane (Tx) A(2), unlike aspirin or traditional nonsteroidal anti-inflammatory drugs, which inhibit both COX-1 and COX-2. The actions of PGI(2) oppose mediators, which stimulate platelets, elevate blood pressure, and accelerate atherogenesis, including TxA(2). Indeed, structurally distinct inhibitors of COX-2 have increased the likelihood of hypertension, myocardial infarction and stroke in controlled clinical trials. The detection of these events in patients is related to the duration of exposure and to their baseline risk of cardiovascular disease. Thus, coxibs should be withheld from patients with preexisting cardiovascular risk factors, and exposed patients at low cardiovascular baseline risk should be monitored for changes in their risk factor profile, such as increases in arterial blood pressure.
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PMID:The cardiovascular pharmacology of COX-2 inhibition. 1630 18

We investigated the mechanisms by which inhibitors of prostaglandin G/H synthase-2 (PGHS-2; known colloquially as COX-2) increase the incidence of myocardial infarction and stroke. These inhibitors are believed to exert both their beneficial and their adverse effects by suppression of PGHS-2-derived prostacyclin (PGI(2)) and PGE(2). Therefore, the challenge remains to identify a mechanism whereby PGI(2) and PGE(2) expression can be suppressed while avoiding adverse cardiovascular events. Here, selective inhibition, knockout, or mutation of PGHS-2, or deletion of the receptor for PGHS-2-derived PGI(2), was shown to accelerate thrombogenesis and elevate blood pressure in mice. These responses were attenuated by COX-1 knock down, which mimics the beneficial effects of low-dose aspirin. PGE(2) biosynthesis is catalyzed by the coordinate actions of COX enzymes and microsomal PGE synthase-1 (mPGES-1). We show that deletion of mPGES-1 depressed PGE(2) expression, augmented PGI(2) expression, and had no effect on thromboxane biosynthesis in vivo. Most importantly, mPGES-1 deletion affected neither thrombogenesis nor blood pressure. These results suggest that inhibitors of mPGES-1 may retain their antiinflammatory efficacy by depressing PGE(2), while avoiding the adverse cardiovascular consequences associated with PGHS-2-mediated PGI(2) suppression.
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PMID:Cyclooxygenases, microsomal prostaglandin E synthase-1, and cardiovascular function. 1661 56

Cardiovascular disease (CVD) is a human health crisis that remains the leading cause of death worldwide. The cytochrome P450 (CYP) class of enzymes are key metabolizers of both xenobiotics and endobiotics. Many CYP enzyme families have been identified in the heart, endothelium and smooth muscle of blood vessels. Furthermore, mounting evidence points to the role of endogenous CYP metabolites, such as epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraenoic acids (HETEs), prostacyclin (PGI(2)), aldosterone, and sex hormones, in the maintenance of cardiovascular health. Emerging science and the development of genetic screening have provided us with information on the differences in CYP expression among populations and groups of individuals. With this information, a link between CYP expression and activity and CVD, such as hypertension, coronary artery disease (CAD), myocardial infarction, heart failure, stroke, and cardiomyopathy and arrhythmias, has been established. In fact many currently used therapeutic modalities in CVD owe their therapeutic efficacy to their effect on CYP metabolites. Thus, the evidence for the involvement of CYP in CVD is numerous. Concentrating on treatment modalities that target the CYP pathway makes ethical sense for the affected individuals and decreases the socioeconomic burden of this disease. However, more research is needed to allow the integration of this information into a clinical setting.
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PMID:Cytochrome P450 enzymes: central players in cardiovascular health and disease. 1682 12

Selective inhibitors of cyclooxygenase-2 (COX-2) were designed to minimize gastrointestinal complications of traditional non-steroidal anti-inflammatory drugs (NSAIDs) attributed to the suppression of COX-1-derived prostanoids. Selective COX-2 inhibitors (coxibs) are effective anti-inflammatory and analgesic drugs. However, recently it has become apparent that some coxibs increase the risk of serious cardiovascular events, including myocardial infarction and stroke. This has led to the withdrawal of rofecoxib from markets and has raised the concern about an inherent atherothrombotic risk of this class of drugs. This question should be carefully analyzed in the light of the current knowledge on COX-2 functions in the cardiovascular system. COX-2 is regarded as an inducible enzyme involved in the pathophysiology of inflammation and pain. In the cardiovascular system, COX-2 has also been associated with pro-inflammatory/pro-atherogenic stages, due to its up-regulation in monocyte-derived macrophages present in atherosclerotic lesions. However, experimental and clinical studies suggest that COX-2 is "constitutively" expressed in some tissues, among them in the vascular endothelium, where COX-2-derived prostanoids, especially prostacyclin (PGI(2)), contribute in the maintenance of vascular homeostasis and integrity. This review provides an updated overview on the functions of COX-2 in the cardiovascular system addressing key issues that could help to understand why chronic COX-2 inhibition may have undesirable effects in patients at cardiovascular risk.
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PMID:Mechanisms underlying the cardiovascular effects of COX-inhibition: benefits and risks. 1769 94


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