Beta Antagonist Research Articles

Noradrenergic modulation of neuronal responses to n-methyl-d-aspartate in the vestibular nuclei: An electrophysiological and immunohistochemical study

Excitatory responses evoked by N-methyl-d-aspartate (NMDA) in the vestibular nuclei (VN) of the rat were studied in vivo during microiontophoretic application of noradrenaline (NA) and/or its agonists and antagonists. Ejection of NA-modified excitatory responses mediated by NMDA receptors (NMDAR) in all neurons tested; the effect was enhancement in 59% of cases and depression in the remaining 41%. Enhancements prevailed in all VN with the exception of the lateral vestibular nucleus, where both effects were recorded in an equal number of cases.The enhancing action of NA on NMDAR-mediated responses was mimicked by the noradrenergic beta-receptor agonist isoproterenol, the beta1 specific agonist denopamine and the alpha2 agonist clonidine. These effects were blocked respectively by the generic beta-receptor antagonist timolol, the beta1 antagonist atenolol and the alpha2 antagonist yohimbine. In contrast, application of the alpha1 receptor agonist cirazoline and the specific alpha1 antagonist prazosin respectively mimicked and partially antagonized the depression of NMDAR-mediated excitations induced by NA.Double-labeling immunohistochemical techniques demonstrated broad colocalization of NMDAR (specifically NR1 and NR2 subunits) with noradrenergic receptors (alpha1, alpha2 and beta1) in many VN neurons; only minor differences were found between nuclei.These results indicate that NA can produce generalized modulation of NMDAR-mediated excitatory neurotransmission in VN, which may in turn modify synaptic plasticity within the nuclei.

Management of Atrial Fibrillation in Critically Ill Patients

Atrial fibrillation (AF) is common in ICU patients and is associated with a two- to fivefold increase in mortality. This paper provides a reappraisal of the management of AF with a special focus on critically ill patients with haemodynamic instability. AF can cause hypotension and heart failure with subsequent organ dysfunction. The underlying mechanisms are the loss of atrial contraction and the high ventricular rate. In unstable patients, sinus rhythm must be rapidly restored by synchronised electrical cardioversion (ECV). If pharmacological treatment is indicated, clinicians can choose between the rate control and the rhythm control strategy. The optimal substance should be selected depending on its potential adverse effects. A beta-1 antagonist with a very short half-life (e.g., esmolol) is an advantage for ICU patients because the effect of beta-blockade on cardiovascular stability is unpredictable in those patients. Amiodarone is commonly used in the ICU setting but has potentially severe cardiac and noncardiac side effects. Digoxin controls the ventricular response at rest, but its benefit decreases in the presence of adrenergic stress. Vernakalant converts new-onset AF to sinus rhythm in approximately 50% of patients, but data on its efficacy and safety in critically ill patients are lacking.

Altered responses to vasopressors of a patient medicated with carvedilol, pilsicainide and enalapril

A patient scheduled for laparoscopic rectal surgery was medicated with carvedilol, an antagonist of beta 1-, beta 2- and alpha 1-adrenergic receptors, pilsicainide, a class Ic antiarrhythmic drug and enalapril, an angiotensin-converting enzyme inhibitor. Because the patient experienced attacks of atrial fibrillation with rapid ventricular response almost weekly, carvedilol and pilsicainide were continued up to the day of surgery, while enalapril was discontinued for 24 h prior to surgery. During the operation, he showed prolonged hypotension that did not respond to usual doses of vasopressors such as ephedrine, phenylephrine and dopamine but responded to higher doses of norepinephrine. Postoperatively, he was given dopamine but exhibited tachyarrhythmia until the dopamine infusion was discontinued.

Resveratrol induced neuroprotection is mediated via both estrogen receptor subtypes, ERα and ERβ

Resveratrol, a dietary polyphenol with antioxidant and anti-inflammatory activity, has been shown to provide neuroprotection in models of ischemia. However, the mechanism of action of resveratrol-induced neuroprotection remains unclear. Previous work in our laboratory has provided evidence that acute, systemic administration of resveratrol is neuroprotective in a permanent model of cerebral ischemia, an effect that was blocked when animals received the non-selective estrogen receptor antagonist, ICI, 182,780. The present study was designed to investigate whether the source of neuroprotection afforded by resveratrol action within the cerebral cortex itself is mediated preferentially via selective activation of either α or β estrogen receptor subtype. Intracortical injection of resveratrol (0.1 and 1.0μM) 10min prior to 30min of ischemia followed by 5.5h of reperfusion significantly reduced infarct volume in the prefrontal cortex. This neuroprotective effect was significantly attenuated when resveratrol injection (1.0μM) was preceded by injection of a selective estrogen receptor α antagonist, 1,3-bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy)phenol]-1N-pyrozole dihydrochloride (MPP) or a selective estrogen receptor beta (ERβ) antagonist, 4-[2-phenyo-5,7-bis(trifluoromrthyl)pyrazolo(1,5-a)pyrimidin-3-yl]phenol (PHTPP). These results provide evidence for rapidly induced neuroprotection mediated by resveratrol activation of either estrogen receptor subtype within the ischemic cortex of rats.

Evaluation of Seven Chromatographic Response Functions on Simulated and Experimentally Obtained Chromatograms in Hydrophilic Interaction Liquid Chromatography System

This paper investigates the ability of seven chromatographic response functions to measure the quality of chromatograms obtained in hydrophilic interaction liquid chromatography (HILIC). First, the functions were tested on a set of simulated chromatograms and differences in their mathematical design were discussed. Second, the functions were evaluated on the experimentally obtained chromatograms in HILIC analysis of model mixture consisted of beta agonists and antagonists. The ranking of chromatograms obtained by different functions was significantly different, implying that the accuracy of the optimization procedure is strongly dependent on the function that was selected as an output. Investigation of potential drawbacks of each function was conducted and general recommendations concerning the use of chromatographic response functions in optimization strategies are proposed.

Estrogen promotes the growth of decidual stromal cells in human early pregnancy

Interleukin-24 (IL-24) is a novel tumor suppressor gene, which has suppressor activity in a broad spectrum of human cancer cells. The present study aimed to elucidate the biological function of IL-24 and its receptors (IL-20R1, IL-20R2 and IL-22R1) in decidual stromal cells (DSCs) at human maternal-fetal interface. The DSCs behaviors in vitro were verified by viability (MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and apoptosis assay, respectively. Additionally, the effects of pregnancy-associated hormones on IL-24 and the effect of IL-24 on the correspondent functional molecules were investigated by ELISA, in-cell western and flow cytometry, respectively. Here we found that DSCs expressed IL-24 and its receptors, and IL-24 obviously suppressed the viability and stimulated the apoptosis in DSCs. On the contrary, both anti-IL-24 and IL-22R1 neutralizing antibodies markedly promoted growth and reduced the apoptosis. Estrogen but not progesterone could significantly decrease IL-24 but not its receptors, and these effects could be abolished by the antagonist of estrogen receptor beta (ERβ). IL-24 significantly restricted the stimulatory effect of estrogen on the viability, anti-apoptosis, anti-apoptosis gene Bcl-2 and proliferation relative gene Ki-67 in DSCs. Our study has demonstrated that IL-24/IL-20R2/IL-22R1 axis is involved in the regulation of estrogen/ERβ signaling on the growth of DSCs through up-regulating the expression of Bcl-2 and Ki67, which suggests that estrogen plays an important role in DSC growth of the early pregnancy through down-regulating IL-24.

Effects of adrenergic beta-1 antagonists on hemodynamics of severe septic patients

To explore the effects of adrenergic beta-1 antagonists on hemodynamics of severe septic patients. A total of 16 severe septic patients underwent mechanical ventilation from June 2012 to December 2012 at Fourth Affiliated Hospital of Nanchang University. There were 14 males and 2 females with a mean age of (58 ± 6) years (range: 48 - 67 years). Among them, there were multiple trauma (n = 4), acute severe pancreatitis (n = 6) and recent tumorectomy for gastrointestinal cancer (n = 6). The adrenergic beta-1 antagonist esmolol was injected through central venous catheter to reduce heart rate by 20% from baseline. Various indices (heart rate, systolic blood pressure, diastolic blood pressure, cardiac output, cardiac index, central venous pressure, pulmonary artery wedge pressure, pulmonary vascular resistance index, systemic vascular resistance index and stroke volume index) were monitored by a multifunctional and hemodynamic monitor connected to pulmonary artery catheter. And other indices of arterial pressure of carbon dioxide (PaCO2), lactate (Lac) concentration, superior vena cava oxygen saturation (ScvO2), superior vena cava carbon dioxide pressure (PcvO2) and central venous-to-arterial carbon dioxide tension difference (Pcv-aCO2) were measured by a blood-gas-analyzer before 10 minutes and after 3 hours of dosing. Heart rate and cardiac index decreased significantly at 3 hours post-dosing compared with that at pre-dosing ((91 ± 13) vs (114 ± 15) beats per minute, (3.4 ± 0.7) vs (4.2 ± 0.8) L×min(-1)×m(-2), P < 0.05), but systolic blood pressure, diastolic blood pressure, central venous pressure, pulmonary wedge pressure, pulmonary vascular resistance index, systemic vascular resistance index and stroke index showed no significant changes ((100 ± 13) vs (108 ± 14) mm Hg (1 mm Hg = 0.133 kPa), (62 ± 7) vs (64 ± 6) mm Hg, (11.8 ± 2.5) vs (12.1 ± 2.4) mm Hg, (13 ± 5) vs (14 ± 4) mm Hg, (201 ± 72) vs (179 ± 95) dyn×s/(cm(5)×m(2)), (1360 ± 520) vs (1366 ± 538) dyn×s/(cm(5)×m(2)), (40 ± 9) vs (38 ± 6) ml/(beat×m(2)), all P > 0.05). ScvO2, Lac and Pcv-aCO2 also showed no significant change ((72.8 ± 5.3)% vs (70.1 ± 4.0)%, (2.11 ± 0.13) vs (2.31 ± 0.23) mmol/L, (3.9 ± 1.0) vs (4.5 ± 0.8) mm Hg, all P > 0.05). Adrenergic beta-1 antagonist may reduce cardiac output in proportion to the percentage decreases in heart rate in severe septic patients without adverse effects upon cardiac function and systemic perfusion.

Effects of salbutamol on non –NMDA glutamate- induced motor neuron loss

Recent data suggests that catecholamine systems might have a trophic role in the spinal cord. These data are based on the clinical evidence that beta-2 agonists produce a relief in spinal motor neuron disorders. Therefore, in the present study we isolated ventral spinal cord cell cultures and we administered either the beta-2 agonist salbutamol alone or in combination with the beta-2 antagonist butoxamine. These experiments were carried out both in baseline conditions and in the presence of a non-NMDA glutamate shock. In fact, increased extracellular glutamate concentration can be toxic for neuronal cells. Glutamate- mediated excitotoxicity relies on the stimulation of both NMDA and non- NMDA receptors although naturally occurring motor neuron loss is thought to depend on an excess of stimulation of non-NMDA receptors. Therefore, primary cell cultures obtained from the ventral spinal cord of 14-days-old mice embryos were preadministered MK-801, a non-competitive antagonist of NMDA receptors, immediately before the non-NMDA (both kainate and AMPA) receptor agonist kainic acid (KA, 50 and 100 μM for 15 min) either in baseline conditions or in combination with salbutamol (10 μM) and butoxamine (50 μM) administered 30 min before KA. We found that the beta-2 antagonist butoxamine did not produce any effect either alone or in combination with kainate. Although butoxamine prevented the effects induced by the beta-2 agonist salbutamol. In particular, salbutamol prevented non-NMDA-induced motor neuron loss and this effect was abolished by the concomitant administration of butoxamine. When salbutamol was administered alone we detected morphological changes at motor neuron level. We also analysed whether salbutamol administration increased the expression of survival motor neuron protein (SMN, an endogenous molecule which provides protective effect for motor neurons) as a possible mechanism of neuroprotection. Unexpectedly, the protective effects induced by salbutamol were accompanied by a reduction of the SMN, while KA induced an increase in SMN levels. These results lend substance that catecholamine receptors subtype beta-2 protect motor neurons in the short term following glutamate excitotoxicity. It is likely that the paradoxical effects observed for SMN level might be due to the need of a compensatory mechanism (following NMDA) or the reduced level of neuronal stress (following salbutamol). Further studies are in progress to unravel the mechanisms responsible for neuroprotection induced at motor neuron level by catecholamine and beta-2 receptors.

Genistein Therapy Reverses Lung Inflammation and Fibrosis during Severe Pulmonary Hypertension through Estrogen Receptor Beta

Pulmonary Hypertension (PH) is a disease of increasing pulmonary arterial pressure characterized by extensive lung inflammation and fibrosis. We have previously shown that Genistein, a soy isoflavone, can rescue severe PH. Since Genistein is a selective Estrogen Receptor Beta agonist, here we examined whether Genistein can reverse fibrosis and inflammation induced by PH via an Estrogen Receptor Beta dependent mechanism. PH was established by treating male rats with monocrotaline (MCT, 60mg/kg, s.c.). At day 21 when severe PH was established, rats were treated with 10 day Genistein therapy (Gen group), Genistein therapy in the presence of selective Estrogen Receptor β antagonist PHTPP (Gen+PHTPP group), or were left untreated to develop right ventricular failure (RVF group). RVF animals developed severe pulmonary hypertension (RVP=72.96±1.39mmHg vs 31.15±0.56 mmHg in CTRL; RVEF=28.76±0.79% vs 66.22±1.40% in CTRL, all p<.05). Genistein therapy restored these abnormalities (RVEF=65.67±1.08%, RVP = 43.34±4.08 mmHg, p<0.05 vs RVF). Interestingly, in the presence of Estrogen Receptor Beta antagonist PHTPP, Genistein failed to rescue these animals (RVP=61.22±4.40, RVEF=42.27±2.7%, p=n.s. vs RVF). Masson's Trichrome staining revealed extensive lung fibrosis in RVF group, which was also restored with Gen therapy. Again, Gen+PHTPP group showed no reversal of pulmonary fibrosis. Immunoperoxidase staining showed an increase in ED-1 positive cells in the lung of RVF-group indicating increased inflammation. This change was reversed entirely by Genistein therapy. RT PCR also revealed that pro-inflammatory molecules TNFα and IL-1β were both elevated more than 2-fold in the lung of RVF animals and reversed with Genistein therapy (all p<0.05). Interestingly, Gen+PHTPP animals still showed significantly elevated ED-1 positive cells in the lung as well as elevated TNFα and IL1β (all p=n.s. vs RVF). These results suggest that genistein induced reversal of lung inflammation and fibrosis during pulmonary hypertension is mediated through Estrogen Receptor β.

The Effects of Cardiac Resynchronization Therapy on Chronotropic Incompetence in Patients Intolerant of Beta Antagonist Therapy. Data from the DECREASE HF Trial

The Effects of Cardiac Resynchronization Therapy on Chronotropic Incompetence in Patients Intolerant of Beta Antagonist Therapy. Data from the DECREASE HF Trial

Pharmacological characterization of the inhibitory activity of βh-endorphin (βh-EP),[Arg9,19,24,28,29]-)βh-EP,[Gln8,Gly31]-βh-EP-Gly-Gly-NH2, in the neuroeffector junction of the mouse vas deferens

The inhibitory opioid activities of beta h-endorphin (beta h-EP), its structurally related peptide analogues [Gln8,Gly31]-beta h-EP-Gly-Gly-NH2 (Gly-Gly-beta h-EP), [Arg9,19,24,28,29]-beta h-EP (Arg-beta h-EP) and methionine enkephalin have been examined in the electrically stimulated mouse vas deferens bioassay. All four peptides behaved as full agonists; methionine enkephalin was the most potent followed by Arg-beta h-EP, beta h-EP and Gly-Gly-beta h-EP. Neither Gly-Gly-beta h-EP nor Arg-beta h-EP antagonized the inhibitory action of beta h-EP or methionine enkephalin. An hour of tissue exposure to 30 nM beta-funaltrexamine followed by thorough washing, displaced to the right, in a parallel fashion, the concentration-response curves of beta h-EP and analogues. Whereas the displacement of the concentration response curves was 8 to 10-fold for beta h-EP and Arg-beta h-EP, it was only about 3-fold for Gly-Gly-beta h-EP and methionine enkephalin. Naltrindole was the most potent antagonist of methionine enkephalin with an apparent pA2 of 9.4; its potency as an antagonist of beta h-EP and related analogues was approximately one-tenth of this with pA2 values approximately 8.5. Norbinaltorphimine also antagonized the action of the opioid peptides with pA2 values close to 7.8.

The soy isoflavone genistein alters cell growth in non‐malignant colonocytes

Numerous studies show that consumption of soy and its primary phytoestrogen genistein (Gen) can inhibit the formation of colon tumors. However, the effect of Gen at dietary levels in non-diseased colonocytes has not been investigated. The presented studies focused on evaluating the effects of Gen in non-malignant colonocytes in vitro and in vivo to determine how the compound influences the physiology of these cells. Gen treatments (1 and 10 μM/L) decreased cell growth, increased apoptosis, and increased p53 transcriptional activity in young adult mouse colonocytes (YAMC), a non-transformed cell line. However, these effects were lost when co-treated with an estrogen receptor beta (ERβ) antagonist. To further study the effects of Gen in healthy colonic epithelia, we evaluated physiologic changes in colonic crypts in ovariectomized mice given an Estradiol (E2) pellet, 1,000 ppm Gen diet, or a phytoestrogen free diet. As seen in vitro, E2 treated animals had significantly higher rates of apoptosis with Gen trending in the same fashion. These data demonstrate that Gen alters the physiology of non-malignant colonocytes which appears to be mediated through ERβ. Collectively, with our previous data, this suggests that Gen influences colonocyte physiology and this state may partially explain how this compound decreases risk of colon cancer. Grant support: American Institute for Cancer Research grant 07B080. Grant Funding Source: American Institute for Cancer Research grant 07B080

Stenotic aortic valves have dysfunctional mechanisms of anti-inflammation: Implications for aortic stenosis

Aortic stenosis is an inflammatory disease, associated with increased tissue levels of interleukin-1 beta. We hypothesized that the antagonist of interleukin-1 beta, interleukin-1 receptor antagonist, is deficient in aortic valves and that its production by aortic valve interstitial cells is less in cells from stenotic valves than from controls. Valve leaflets from stenotic aortic valves (n=6) and from valves from hearts explanted at the time of cardiac transplantation (n=6) were studied by immunostaining for interleukin-1 receptor antagonist. Aortic valve interstitial cells were isolated from valves, and receptor antagonist levels were determined from cell lysates (enzyme-linked immunosorbent assay). Osteogenic phenotype changes in valve cells stimulated by toll-like receptors 2 and 4 were determined by immunoblotting for bone morphogenetic protein-2 after treatment with and without interleukin-1 receptor antagonist (100 μg/mL). Statistics were by analysis of variance. Interleukin-1 receptor antagonist was abundant in nonstenotic aortic valve leaflets and virtually absent in leaflets from stenotic valves. Aortic valve interstitial cells from grossly normal leaflets produced significantly more receptor antagonist at baseline and in response to toll-like receptor 2 and 4 stimulation, than did cells from diseased valves (P<0.05). Interleukin-1 receptor antagonist was able to significantly attenuate toll-like receptor 2, but not toll-like receptor 4, stimulated bone morphogenetic protein-2 production in aortic valve interstitial cells (P<.05). Interleukin-1 receptor antagonist-mediated mechanisms of anti-inflammation are dysfunctional in stenotic valves. We conclude that such impaired mechanisms of anti-inflammation may contribute to the pathogenesis of aortic stenosis.

Neuronal regulation of photo‐induced pineal photoreceptor proteins in carp Catla catla

In the present in vitro study on the pineal in carp Catla catla, specific agonist and antagonists of receptors for different neuronal signals and regulators of intra-cellular Ca(++) and cAMP were used to gather basic information on the neuronal signal transduction cascade mechanisms in the photo-induced expression of rod-like opsin and alpha-transducin-like proteins in any fish pineal. Western-blot analysis followed by quantitative analysis of respective immunoblot data for both the proteins revealed that photo-induced expression of each protein was stimulated by cholinergic (both nicotinic and muscarinic) agonists and a dopaminergic antagonist, inhibited by both cholinergic antagonists and a dopaminergic agonist, but not affected by any agonists or antagonists of adrenergic (alpha(1), alpha(2) and beta(1)) receptors. Moreover, expression of each protein was stimulated by voltage gated L type calcium channel blocker, adenylate cyclase inhibitor and phosphodiesterase activator; but suppressed by the activators of both calcium channel and adenylate cyclase, and by phosphodiesterase inhibitor. Collectively, we report for the first time that both cholinergic and dopaminergic signals play an important, though antagonistic, role in the photo-induced expression of photoreceptor proteins in the fish pineal through activation of a signal transduction pathway in which both calcium and cAMP may act as the intracellular messengers.

Investigation of the Effect of Mutations of Rat Albumin on the Binding Affinity to the α4β1 Integrin Antagonist, 4-[1-[3-Chloro-4-[N′-(2-methylphenyl)ureido]phenylacetyl]-(4S)-fluoro-(2S)-pyrrolidine-2-yl]methoxybenzoic Acid (D01-4582), Using Recombinant Rat Albumins

The authors reported previously rat strain differences in plasma protein binding to alpha(4)beta(1) antagonist D01-4582, resulting in a great strain difference in its pharmacokinetics (19-fold differences in the AUC). The previous study suggested that amino acid changes of V238L and/or T293I in albumin reduced the binding affinity. In order to elucidate the relative significance of these mutations, an expression system was developed to obtain recombinant rat albumins (rRSA) using Pichia pastoris, followed by a binding analysis of four rRSAs by the ultracentrifugation method. The equilibrium dissociation constant (K(d)) of wild-type rRSA was 210 nM, while K(d) of rRSA that carried both V238L and T293I mutations was 974 nM. K(d) of artificial rRSA that carried only V238L was 426 nM, and K(d) of artificial rRSA that carried only T293I was 191 nM. These results suggested that V238L would be more important in the alteration of K(d). However, since none of the single mutations were sufficient to explain the reduction of affinity, the possibility was also suggested that T293I interacted cooperatively to reduce the binding affinity of rat albumin to D01-4582. Further investigation is required to elucidate the mechanism of the possible cooperative interaction.

Synthesis and Evaluation of a Near-Infrared Fluorescent Non-Peptidic Bivalent Integrin αvβ3 Antagonist for Cancer Imaging

Computer modeling approaches to identify new inhibitors are essentially a very sophisticated and efficient way to design drugs. In this study, a bivalent nonpeptide intergrin alpha(v)beta(3) antagonist (bivalent IA) has been synthesized on the basis of an in silico rational design approach. A near-infrared (NIR) fluorescent imaging probe has been developed from this bivalent compound. In vitro binding assays have shown that the bivalent IA (IC(50) = 0.40 +/- 0.11 nM) exhibited improved integrin alpha(v)beta(3) affinity in comparison with the monovalent IA (IC(50) = 22.33 +/- 4.51 nM), resulting in an over 50-fold improvement in receptor affinity. NIR imaging probe, bivalent-IA-Cy5.5 conjugate, also demonstrated significantly increased binding affinity (IC(50) = 0.13 +/- 0.02 nM). Fluorescence microscopy studies showed integrin-mediated endocytosis of bivalent-IA-Cy5.5 in U87 cells which was effectively blocked by nonfluorescent bivalent IA. We also demonstrated tumor accumulation of this NIR imaging probe in U87 mouse xenografts.

99mTc-labeling of Peptidomimetic Antagonist to Selectively Target αvβ3 Receptor-Positive Tumor: Comparison of PDA and EDDA as Co-Ligands

OBJECTIVES: The aim of this research was to synthesize radiolabeled peptidomimetic integrin alpha(v)beta(3) antagonist with (99m)Tc for rapid targeting of integrin alpha(v)beta(3) receptors in tumor to produce a high tumor to background ratio. METHODS: The amino terminus of 4-[2-(3,4,5,6-tetra-hydropyrimidin-2-ylamino)-ethyloxy]benzoyl-2-(S)-[N-(3-amino-neopenta-1-carbamyl)]-aminoethylsulfonyl-amino-beta-alanine hydrochloride (IAC) was conjugated with N-hydroxysuccinimide ester of HYNIC and labeled with (99m)Tc using tricine with either 1,5-pyridinedicarboxylic acid (PDA) or ethylenediamine-N,N'-diacetic acid (EDDA) as the co-ligand. The products, (99m)Tc EDDA(2)/HYNIC-IAC (P1) and (99m)Tc PDA (tricin)/HYNIC-IAC (P2) were subjected to in vitro serum stability, receptor-binding, biodistribution and imaging studies. RESULTS: P1 and P2 were synthesized with an overall yield of >80%. P1 was slightly more stable than P2 when incubated in serum at 37 degrees C for 18 hrs (84 vs 77% intact). The In vitro receptor-binding of P1 was higher than that of P2 (78.02 +/- 13.48 vs 51.05 +/- 14.05%) when incubated with alpha(v)beta(3) at a molar excess (0.8 muM). This receptor binding was completely blocked by a molar excess of an unlabeled peptidomimetic antagonist. Their differences shown in serum stability and the receptor-binding appeared to be related to their biological behaviors in tumor uptake and retention; the 1 h tumor uptakes of P1 and P2 were 3.17+/-0.52 and 2.13+/-0.17 % ID/g, respectively. P1 was retained in the tumor longer than P2. P1 was excreted primarily through the renal system whereas P2 complex was excreted equally via both renal and hepatobiliary systems. Thus, P1 was retained in the whole-body with 27.25 +/- 3.67% ID at 4 h whereas 54.04 +/- 3.57% ID of P2 remained in the whole-body at 4 h. This higher whole-body retention of P2 appeared to be resulted from a higher amount of radioactivity retained in liver and intestine. These findings were supported by imaging studies showing higher tumor-to-abdominal contrast for P1 than for P2 at 3 h postinjection. CONCLUSIONS: P1 showed good tumor targeting properties with a rapid tumor uptake, prolonged tumor retention and fast whole-body clearance kinetics. These findings warrant further investigation of the HYNIC method of (99m)Tc labeling of other peptidomimetic antagonists using EDDA as a coligand.

RGD-ligand mimetic antagonists of integrin alphaIIbbeta3 paradoxically enhance GPVI-induced human platelet activation.

The integrin alpha(IIb)beta(3) is the major mediator of platelet aggregation and has, therefore, become an important target of antithrombotic therapy. Antagonists of alpha(IIb)beta(3), for example abciximab, tirofiban and eptifibatide, are used in the treatment of acute coronary syndromes. However, in addition to effective blockade of the integrin, binding of can induce conformational changes in the integrin and can also induce integrin clustering. This class effect of RGD-ligand mimetics might, therefore, underlie paradoxical platelet activation and thrombosis previously reported. To examine the components of signaling pathways and functional responses in platelets that may underlie this phenomenon of paradoxical platelet activation. We assessed the effect of lotrafiban, and other alpha(IIb)beta(3) antagonists including the clinically used drug tirofiban, on tyrosine phosphorylation of key signaling proteins in platelets by immunoblotting and also platelet functional outputs such as cytosolic calcium responses, phosphatidylserine exposure (pro-coagulant activity) and dense granule release. In all cases, no effect of alpha(IIb)beta(3) antagonists were observed on their own, but these integrin antagonists did lead to a marked potentiation of glycoprotein VI (GPVI)-associated FcR gamma-chain phosphorylation, activation of Src family kinases and Syk kinase. This correlated with increased dense granule secretion, cytosolic calcium response and exposure of phosphatidylserine on the platelet surface. P2Y(12) antagonism abolished the potentiated phosphatidylserine exposure and dense granule secretion but not the cytosolic calcium response. These data provide a mechanism for enhancement of platelet activity by alpha(IIb)beta(3) inhibitors, but also reveal a potentially important signaling pathway operating from the integrin to GPVI signaling.

Inwieweit bilden definierte Tagesdosen (DDD) die tatsächlich verordneten Tagesdosen ab? Eine Analyse ambulanter Verordnungsdaten

Defined daily doses (DDD) are used to analyse drug utilisation. For frequently prescribed drug groups, we studied to what extent the DDD correspond to the average prescribed daily doses (PDD). We analysed all drugs prescribed for more than three months to insured of a large health insurance fund in Mecklenburg-Vorpommern, one federal state in Germany. PDD for plain ACE inhibitors, selective beta-antagonists and some antidiabetics (sulfonylurea compounds) were calculated and compared with their DDD. During the study period, about 38 500 patients received continuous prescriptions of each ACE inhibitors or selective beta-antagonists, and about 9 000 of sulfonylurea compounds. PDD differed from DDD in varying degrees. For ACE inhibitors, PDD ranged between 1.5 DDD (for captopril) and 3.5 (for ramipril). The PDD for beta antagonists were on average 0.9 DDD, similar for bisoprolol (0.8 DDD) and metoprolol (0.9 DDD). As for oral antidiabetics, doctors prescribed 1.0 DDD glibenclamid per day and patient and 2.0 DDD glimepirid. Depending on differences between DDD and PDD, real daily costs for drug therapy differed from the theoretical costs per DDD, for example in the case of ramipril they were 0.24 euros compared to 0.07 euros. The PDD were much higher than the DDD for several frequently prescribed drugs. Consequently, the daily drug costs exceeded the drug costs based on DDD. Evaluations of drug costs on the basis for DDD require careful interpretation. Moreover, the number of DDD alone is not a valid measurement for the appropriateness of drug therapy and can only give a rough estimate of the number of patients treated, at least for the drug groups in this study.

Function and Antagonism of &amp;#946; Integrins in the Development of Cancer Therapy

The integrin family of cell surface receptors integrates cell-extracellular matrix interactions with the cell cytoskeleton and signalling across the cell membrane, resulting in an important role in cell adhesion, mobility and migration, proliferation, and survival. Changes in the number and identity of integrin receptors are common in cancer cells resulting in alteration of the ability of malignant cells to interact with the extracellular matrix, and promoting migration as well as facilitating survival outside the tumour normal environment. beta(3) integrins are potentially involved in every step of the metastatic process and expression of both alpha(IIb)beta(3) and alpha(n)beta(3) is correlated with metastatic ability of tumour cells. The recognition of the RGD binding motif common to the disintegrins and natural integrin ligands such as fibrinogen allowed the development of small molecule beta(3) integrin antagonists, progressing from linear peptides containing the RGD sequence to cyclic peptides with well-defined conformation, and hence to small molecule peptidomimetics with improved pharmacological properties. In this review, we summarize the role of the beta(3)-subfamily of integrins when expressed in normal and tumour tissue, the development of small-molecule antagonists of beta(3) integrins and their potential anti-cancer applications.