Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Analysis of the human genome project tells us that there may be as few as 3000 genes that are likely to be good drug targets. Although the number of targets is still very large, these data have been interpreted by some to mean that the pharmaceutical industry may someday run out of novel drug targets. Despite the doom and gloom of such analysis, there is considerable reason for optimism. Drugs may exhibit selectivity of action beyond that predicted by target expression alone. Drugs that act at a single molecular target may have very different pharmacology and, as a result, different therapeutic uses. Three well-characterized model systems are highlighted to illustrate this point. The first model system is exemplified by nifedipine and verapamil, both of which act on L-type calcium channels. Both drugs are used to treat hypertension, but only verapamil can be used to produce atrioventricular block in patients with atrial fibrillation. The second model system describes the therapeutic exploitation of unusual conditions that occur in the ischemic myocardium to produce drugs that are more effective for suppressing ischemia-induced arrhythmias. The third model system discusses the mechanisms through which phosphodiesterase-5 (PDE5) inhibitors act selectively to facilitate penile erection while having little effect in the non-penile vasculature that also expresses PDE5.
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PMID:Mechanism of tissue-selective drug action in the cardiovascular system. 1582 Nov 57

Although pentoxifylline (PTXF), a phosphodiesterase inhibitor, has been reported to exert beneficial effects in cardiac bypass surgery, its effect and mechanisms against ischemia-reperfusion (I/R) injury in heart are poorly understood. Because I/R is known to increase the level of tumor necrosis factor (TNF)-alpha in myocardium and PTXF has been shown to depress the production of TNF-alpha in failing heart, this study examined the hypothesis that PTXF may attenuate cardiac dysfunction and reduce TNF-alpha content in I/R heart. For this purpose, isolated rat hearts were subjected to global ischemia for 30 min followed by reperfusion for 2-30 min. Although cardiac dysfunction due to ischemia was not affected, the recovery of heart function upon reperfusion was markedly improved by PTXF treatment. This cardioprotective effect of PTXF was dose dependent; maximal effect was seen at a concentration of 125 microM. TNF-alpha, nuclear factor-kappaB (NF-kappaB), and phosphorylated NF-kappaB contents were decreased in ischemic heart but were markedly increased within 2 min of starting reperfusion. The ratio of cytosolic-to-homogenate NF-kappaB was decreased, whereas the ratio of particulate-to-homogenate NF-kappaB was increased in I/R hearts. These changes in TNF-alpha and NF-kappaB protein contents as well as in NF-kappaB redistribution due to I/R were significantly attenuated by PTXF treatment. The results of this study indicate that the cardioprotective effects of PTXF against I/R injury may be due to reductions in the activation of NF-kappaB and the production of TNF-alpha content.
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PMID:Pentoxifylline attenuates cardiac dysfunction and reduces TNF-alpha level in ischemic-reperfused heart. 1583 6

The phosphodiesterase type-5 (PDE5) inhibitor, sildenafil, is the first drug developed for treatment of erectile dysfunction in patients. Experimental data in animals show that sildenafil has a preconditioning-like cardioprotective effect against ischemia/reperfusion injury in the intact heart. Mechanistic studies suggest that sildenafil exerts cardioprotection through NO generated from eNOS/iNOS, activation of protein kinase C/ERK signaling and opening of mitochondrial ATP-sensitive potassium channels. Additional studies show that the drug attenuates cell death resulting from necrosis and apoptosis, and increases the Bcl2/Bax ratio through NO signaling in adult cardiomyocytes. Emerging new data also suggest that sildenafil may be used clinically for treatment of pulmonary arterial hypertension and endothelial dysfunction. Future demonstration of the cardioprotective effect in patients with the relatively safe and effective FDA-approved PDE5 inhibitors such as sildenafil could have an enormous impact on bringing the long-studied phenomenon of ischemic and pharmacologic preconditioning to the clinical forefront.
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PMID:Pharmacological preconditioning with sildenafil: Basic mechanisms and clinical implications. 1592 55

Drug-induced delayed cardiac protection (DCP) against the effects of acute myocardial ischemia was first described 22 years ago by the author and his coworkers. It can be initiated by noninjurious pharmacological doses of prostacyclin (PGI2), its stable analogues, and by catecholamines. DCP protects against many consequences of ischemia, attenuating early morphological changes, limiting infarct size and suppressing arrhythmias, and can also protect against ouabain intoxication. DCP operates under a variety of pathological conditions (atherosclerosis, hypercholesterolaemia, and diabetes). DCP can also be evoked by transient myocardial ischemia and by exercise and is known in this context as "ischemic preconditioning", specifically the "second window of protection"; transient ischemia also evokes an immediate but short-lived protection known as "classical preconditioning". DCP is fundamentally different in concept to conventional drug therapy because the process appears to depend on the duration of the trigger and be related in a bell-shaped manner to the strength of the trigger. The exact mechanism is uncertain. Prolongation of the effective refractory period (ERP) and of the action potential duration (APD) may contribute to DCP suppression of arrhythmias. The protection is time and dose dependent, with optimal effects 24 to 48 hr after treatment. It can be sustained by intermittent administration of low maintenance doses. Stimulation of the adenylate-cyclase/cyclic adenosine monophosphate (cAMP) system appears to be a common feature of DCP. Responses to beta-adrenergic stimuli are also diminished. Cardiac cAMP triggers the induction of phosphodiesterase (PDE) 1 and 4 isoforms and of Na/K-ATPase. Increased amount and activity of PDE isoforms subsequently reduces excess myocardial cAMP production. Changes in Na/K-ATPase moderate ischemic myocardial potassium loss, sodium, and calcium accumulation, as well as the toxicity of ouabain. The future therapeutic challenge is to identify new drugs that can mimic DCP.
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PMID:Drug-induced delayed cardiac protection against the effects of myocardial ischemia. 1609 98

Activated leukocytes are implicated in development of ischemia/reperfusion (I/R)-induced organ injuries. Phosphodiesterase 3 inhibitors have anti-inflammatory effects by preventing cyclic adenosine monophosphate (cAMP) degradation. We examined the effects of olprinone, a specific phosphodiesterase 3 inhibitor, on I/R-induced acute renal injury model in rats. Forty-five minute renal I/R was induced in uni-nephrectomized rats. Rats were divided into a vehicle group, an olprinone group, and a dibutyril (DB) cAMP group. Olprinone (0.2 microg/kg/minute) infusion began 30 min after reperfusion and continued for 3 h. DBcAMP (5 mg/kg), a stable analog of cAMP, was intraperitoneally administered 5 min after reperfusion to clarify the effect of cAMP in our model. Olprinone reduced the I/R-induced increases in serum levels of blood urea nitrogen and creatinine, and improved histological changes, including acute tubular necrosis in the outer medulla. Hemodynamic status was not affected by olprinone. I/R-induced a decrease in renal tissue blood flow, an increase in renal vascular permeability, and an enhancement of leukocyte activation, reflected by renal tissue levels of myeloperoxidase activity, and the tissue levels of cytokine-induced neutrophil chemoattractant (an equivalent of human interleukin 8) and tumor necrosis factor-alpha were all significantly decreased by olprinone. Olprinone also increased the renal tissue and plasma levels of cAMP in rats subjected to renal I/R. DBcAMP showed similar effects. Our results indicated that olprinone reduced the I/R-induced acute renal injury, probably by inhibiting leukocyte activation. The effects of olprinone could be explained through its action on cAMP levels.
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PMID:Olprinone reduces ischemia/reperfusion-induced acute renal injury in rats through enhancement of cAMP. 1613 69

cGMP and opening of mitochondrial K(ATP) channel play an important role in preconditioning of the heart following ischemia/reperfusion (I/R) injury. We investigated the cardioprotective effect of vardenafil (VAR) (Levitra), a highly selective and biochemically potent inhibitor of phosphodiesterase-5 (PDE-5) that enhances erectile function in men through up-regulation of cGMP. Rabbits were treated with VAR (0.014 mg/kg, iv) or volume-matched saline, 30 min prior to 30 min of sustained regional ischemia followed by 3 h of reperfusion. 5-hydroxydecanoate (5-HD, 5 mg/kg, iv) or HMR 1098 (HMR, 3 mg/kg, iv), the respective blockers of mitochondrial or sarcolemmal K(ATP) channels were administered 10 min before I/R. Infarct size was measured by computer morphometry of tetrazolium stained sections. Vardenafil treatment caused decrease in mean arterial blood pressure from 93.5+/-2.6 to 82.2+/-1.5 mmHg and increase in heart rate from baseline value of 151+/-20 to 196+/-4.6 bpm (mean+/-standard error of mean (S.E.M.), P<0.05) within 5 min. The infarct size (% of risk area) was reduced from 33.8+/-1.3 in control rabbits to 14.3+/-2.2 (58% reduction, P<0.05). 5-HD abolished VAR-induced protection as demonstrated by increase in infarct size to 34.5+/-2.3 (P<0.05, N=6 per group). In contrast, HMR failed to block the protective effect of VAR (infarct size, 14.3+/-2.2 versus 16.3+/-1.0 in VAR + HMR, P>0.05). Neither inhibitors of the K(ATP) channel influenced the infarct size in the control rabbits, as shown by infarct size of 34.9+/-1.1 and 33.3+/-1.4 in animals treated with 5-HD and HMR, respectively. For the first time, we demonstrate that VAR induces protective effect against I/R injury via opening of mitochondrial K(ATP) channel. These results further support our hypothesis that the novel class of PDE-5 inhibitors induce protective effect in the ischemic heart, in addition to their well known clinical effects in the treatment of erectile dysfunction in men.
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PMID:Vardenafil: a novel type 5 phosphodiesterase inhibitor reduces myocardial infarct size following ischemia/reperfusion injury via opening of mitochondrial K(ATP) channels in rabbits. 1648 Jul 39

Increasing age decreases the number of new neurons in the dentate gyrus and the subventricular zone (SVZ). Sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, enhances neurogenesis in young rats. The present study tested the hypothesis that sildenafil augments neurogenesis in aged rats after focal cerebral ischemia. Nonischemic aged (18 months, n = 6) Wistar rats exhibited a significant reduction of actively proliferating and relatively quiescent cells in the SVZ measured by the number of minichromosome maintenance protein-2-positive (MCM-2+) cells, a marker of the proliferating cells, compared with nonischemic young (3-4 months, n = 8) rats. Occlusion of the middle cerebral artery did not increase the number of MCM-2+ cells in the SVZ of aged rats at 3 months after focal ischemia. However, treatment with sildenafil at a dose of 3 mg/kg (n = 8) daily for 7 consecutive days starting 7 days after focal ischemia significantly increased the number of MCM-2+ cells in the SVZ of aged rats compared with aged rats treated with saline (n = 8). Double immunostaining revealed that substantially more Ki67+ cells (a marker of proliferating cells) were doublecortin+ (a marker of migrating neuroblasts) in sildenafil-treated than in saline-treated aged animals. In addition, treatment with sildenafil significantly improved functional recovery compared with saline-treated rats. These data suggest that inhibition of PDE5 activity by sildenafil augments neurogenesis in the SVZ of aged ischemic rats, although these rats have reduced numbers of neural progenitor and stem cells in the SVZ.
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PMID:Delayed treatment with sildenafil enhances neurogenesis and improves functional recovery in aged rats after focal cerebral ischemia. 1651 65

Although erectile dysfunction (ED) in older subjects needs a holistic approach, the pathophysiology consists mainly in chronic ischemia with deterioration of cavernous smooth muscles followed by development of corporeal fibrosis. Therefore, phosphodiesterase type 5 (PDE5) inhibition, enhancing vasodilatation in corpora cavernosa, represents a first-line therapy for ED. PDE5 is in fact the major cGMP hydrolizing enzyme in penile corpus cavernosum. The mechanisms of action, the pharmacokinetics and the contraindications of selective PDE5 inhibitors, are described in details. Furthermore, attention is focused on the interaction of PDE5 inhibitors on hypothalamus-pituitary gonadol (HPG) function. Finally, considering that androgens may influence sexual behavior by modifying the central nervous system neurotransmitter targeted system, the potentiation of PDE5 inhibitors with testosterone supplementation may be considered to improve erectile function and quality of life in older males.
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PMID:Phosphodiesterase type 5 inhibithors in older males. 1676 Jun 38

Improved preservation of the harvested heart with attenuation of the reperfusion injury is important for successful outcomes of cardiac transplantations. The most commonly used cardioplegic solution, to prevent ischemic changes has been St Thomas' Hospital cardioplegic solution (STHCS). However, it is neither ideal nor sufficient to prevent myocardial ischemia and reperfusion injury. Phosphodiesterase inhibitors can attenuate the damage due to the injuries of ischemia and reperfusion. In this study we sought to enrich STHCS with a phosphodiesterase inhibitor to improve preservation of cardiac functions. The harvested hearts of 24 rats were divided into four groups. All hearts were mounted on a Langendorff perfusion system. After a stabilization period, cardiac arrest was maintained by STHCS. The hearts were stored in STHCS alone or with milrinone, amrinone, or enoximone for 6 hours. The reperfusion was maintained using a modified Tyrode's solution. All hearts were compared for their preischemic and postischemic left ventricular developed pressure, +dp/dtmax, -dp/dtmax, duration of systole, ejection time, and time to reach peak systolic pressure. Coronary effluent was collected for lactate dehydrogenase (LDH) measurements. The initial values for all metrics were comparable between the groups. During the postreperfusion period, all hearts showed lower peak systolic pressures than the initial values. Although the amrinone group seemed to have higher values, the 25-minute result was at the border of significance and the 30-minute value, significantly higher. All hearts showed far lower results of maximum changes in contractility during the time period (+dp/dtmax) versus the initial values; comparisons between groups were not significant. For the parameter of maximum changes in relaxation during the time period (-dp/dtmax), while other hearts showed lower results, the amrinone group displayed values comparable to the initial ones after 20 minutes. Comparisons between groups were insignificant. While other hearts had comparable values for time of systole, the hearts applied with milrinone reached these values after 15 minutes. Group comparison for time of ejection revealed that the results at 5-minute postreperfusion were higher in the enoximone and the amrinone groups than the milrinone group. Postreperfusion 5-minute results were higher in the enoximone and the amrinone groups than the milrinone group for time to reach peak systolic pressure. LDH levels were lowest in the amrinone group. In conclusion, our study revealed that adding phosphodiesterase inhibitors to STHCS improved peak systolic pressure and maximum changes in relaxation during the time period (-dp/dtmax, mm Hg/s). It also decreased the LDH leakage, which corresponded to the degree of ischemic tissue damage. Amrinone seemed to result in more favorable results, which may be attributed to its additional effects on inflammation, including those on cytokines and leukocyte aggregation.
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PMID:Effect of combining phosphodiesterase III inhibitors with St Thomas Hospital's solution used as transplantation preservative solution in isolated rat hearts. 1679 75

The administration of a cyclic nucleotide analog improves cold ischemia/reperfusion injury in several organs. The type 3 phosphodiesterase inhibitor olprinone is a potent stimulus that enhances cellular cAMP levels. The present study was performed to investigate the protective effects of enhanced intracellular cAMP levels by olprinone in rat orthotopic kidney transplantation. Autotransplantation and immediate contralateral nephrectomy were performed in Lewis rats after 18 hours of graft storage at 4 degrees C in University of Wisconsin (UW) solution with or without 25 microg/mL olprinone hydrochloride. At 2 hours after reperfusion, serum and urinary biochemical indicators of renal dysfunction and injury were measured: serum creatinine, fractional excretion of Na+ and urinary N-acetyl-D-glucosaminidase. Additionally, intracellular cAMP in kidney tissues was measured by a radioimmunology method. Compared to the only UW solution group, olprinone hydrochloride significantly reduced the increased in serum creatinine, FENa and NAG caused by renal ischemia/reperfusion injury, after 2 hours of reperfusion. The content of cAMP at the endpoint of 18 hours cold preservation was significantly greater in the UW plus olprinone hydrochloride group than that in the UW group. Two hours after reperfusion, the content of cAMP in the UW plus olprinone hydrochloride group was still significantly higher than that in the UW group without containing olprinone hydrochloride. These results support a beneficial effect of olprinone against cold ischemia and reperfusion injury via an increased intracellular cAMP levels.
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PMID:The enhancement of cellular cAMP with olprinone protects autotransplanted rat kidney against cold ischemia-reperfusion injury. 1679 61


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