Biomedical subjects

S A Mousa

Publications and source records attributed to S A Mousa.

At least 73 records · Page 4Linked to original sources

PubMed1998

Pain control in inflammation governed by selectins.

Opioid-containing immune cells migrate preferentially to inflamed sites, where they release beta-endorphin which activates peripheral opioid receptors to inhibit pain. Immunocyte recruitment is a multistep, sequential engagement of various adhesion molecules located on immune cells and vascular endothelium. Selectins mediate the initial phase of immunoctye extravasation into inflamed sites. Here we show that anti-selectin treatment abolishes peripheral opioid analgesia elicited either endogenously (by stress) or by corticotropin-releasing factor. This results from a blockade of the infiltration of immunocytes containing beta-endorphin and the consequent decrease of the beta-endorphin content in the inflamed tissue. These findings indicate that the immune system uses mechanisms of cell migration not only to fight pathogens but also to control pain in injured tissue. Thus, pain is exacerbated by measures inhibiting the immigration of opioid-producing cells or, conversely, analgesia might be conveyed by adhesive interactions that recruit those cells to injured tissue.

Analgesia↗

PubMed1998

Intravenous and oral antiplatelet/antithrombotic efficacy and specificity of XR300, a novel nonpeptide platelet GPIIb/IIIa antagonist.

Currently used antiplatelet drugs including aspirin, ticlopidine, and others are effective against certain but not all of the many endogenous platelet activators. Because of their limited efficacy, a significant number of serious thromboembolic complications still occur, highlighting the need for a more effective therapy. Thus our study was undertaken to define the antiplatelet efficacy, specificity, and the intravenous and oral antiplatelet/antithrombotic effects of a nonpeptide glycoprotein alphaIIb beta3 integrin (GPIIb/IIIa) antagonist XR300, an ethyl ester prodrug of XR299. XR300, on its conversion to the active form XR299, inhibited human platelet aggregation induced by 100 microM adenosine diphosphate (ADP) with a median inhibitory concentration (IC50) of 0.09 microM. Similarly, XR299 inhibited 125I-fibrinogen binding to human gel-purified platelets (IC50, 0.01 microM) regardless of the agonist used. In purified human GPIIb/IIIa, XR299 demonstrated a competitive high-affinity binding with an IC50 of 1.2 nM. XR299 demonstrated a high degree of specificity for platelet GPIIb/IIIa (alphaIIb beta3) as compared with other integrins including alpha(v)beta3, alpha(v)beta5, and alpha4beta1, where IC50 values were >10 microM. XR300 administered to mongrel dogs either intravenously (0.5-1.0 mg/kg, i.v.) or orally at 1.0-2.0 mg/kg, demonstrated maximal antiplatelet effects with rapid onset and extended duration. XR300 demonstrated maximal antithrombotic efficacy in preventing the incidence of occlusive thrombosis or cyclic flow reduction (CFR) in the carotid or femoral artery thrombosis models induced either electrolytically or by mechanical injury along with stenosis. In conclusion, XR300 is a novel intravenous and oral antiplatelet/antithrombotic agent with high affinity and specificity for platelet GPIIb/IIIa receptors.

Administration, Oral↗

PubMed1998

Oral antiplatelet efficacy and specificity of a novel nonpeptide platelet GPIIb/IIIa receptor antagonist, DMP 802.

This study was undertaken to define the platelet glycoprotein alphaIIb beta3 integrin (GPII/IIIa) affinity, specificity, and oral antiplatelet efficacy of DMP 802, a small-molecule nonpeptide antiplatelet agent. Platelet GPIIb/IIIa integrin binding affinity and specificity for DMP 802 were determined by using binding and adhesion assays with cells from various species, including human. DMP 802 demonstrated a potent antiplatelet efficacy [median inhibitory concentration (IC50), 0.029 +/- 0.0042 microM] in inhibiting human platelet aggregation induced by 10 microM adenosine diphosphate (ADP), as assessed by light-transmittance aggregometry. DMP 802 inhibited 125I-fibrinogen binding to activated (ADP, epinephrine, and arachidonic acid at 100 microM each) gel purified human platelets with an IC50 of 0.012 +/- 0.003 microM. DMP 802 demonstrated tight association with unactivated human, baboon, or canine platelets (t(1/2) of dissociation, 32 +/- 2, 32 +/- 13, and 11 +/- 1 min, respectively). DMP 802 binds with high affinity to both unactivated and activated human platelets (Kd = 0.61 +/- 0.17, 0.57 +/- 0.21 nM, respectively). DMP 802 demonstrated species specificity in inhibiting platelet aggregation with IC50 values ranging from 0.025 to 0.092 microM (human, guinea pig, dog, swine, hamster) and 0.88-1.0 microM (rabbit and rat) in platelets obtained from these various species. DMP 802 demonstrated a high degree of specificity for platelet GPIIb/IIIa (alphaIIb/beta3) as compared with other integrins including alpha(v)beta3 (IC50, >10 microM), alpha(v)beta5 (IC50, >100 microM), alpha4beta1 (IC50, >100 microM), and alpha5beta1 (IC50, >10 microM). Oral antiplatelet efficacy of DMP 802 was examined after single oral (0.05-0.20 mg/kg) and after repeated oral dosing at 0.05 mg/kg daily for 5 days in mongrel dogs. Dose-dependent antiplatelet efficacy with an extended duration of antiplatelet efficacy was demonstrated based on ex vivo inhibition of platelet aggregation induced by 100 microM ADP. DMP 802 has an oral bioavailability of 14.9% in dogs. In conclusion, the alpha sulfonamide isoxazoline analog, DMP 802, is a novel oral antiplatelet agent with high affinity, relatively slow dissociation rate and specificity for human platelet GPIIb/IIIa receptors.

Administration, Oral↗

PubMed1998

XV454, a novel nonpeptide small-molecule platelet GIIb/IIIa antagonist with comparable platelet alpha(IIb)beta3-binding kinetics to c7E3.

XV454 demonstrated high potency (IC50 = 14-25 nM) in inhibiting human platelet aggregation induced by adenosine diphosphate (ADP, 10 microM), thrombin receptor agonist peptide (TRAP) (10 microM), or collagen (20 microg/ml). XV454 exhibited a high degree of selectivity for platelet alpha(IIb)beta3 in comparison with c7E3, which is a nonspecific antagonist for both alpha(IIb)beta3 and alpha(v)beta3. Both XV454 and c7E3 bind with high affinity to either activated (A) or unactivated (U) human, baboon, or canine platelets. XV454 binds with a relatively higher affinity [Kd = 0.5 nM (A), 0.6 nM (U)] as compared with c7E3 [Kd = 9.1 nM (A), 9.2 (U) nM]. XV454 demonstrated a tight association with human, baboon, and, to a lesser extent, with canine platelets (t(1/2) of dissociation = 110 +/- 6, 80 +/- 10, and 23 +/- 2 min, respectively). Both c7E3 and XV454 associate tightly with a slower dissociation rate with unactivated human platelets: t(1/2) of 42 and 116 min, respectively. In non-human primates, oral (0.1 mg/kg, p.o.) and intravenous (0.05 mg/kg, i.v. bolus administration of XV454 methyl ester pro-drug resulted a long-lasting maximal antiplatelet efficacy for < or = 72 h with significant but reversible prolongation of bleeding time and without effects on platelet count, clinical chemistry, or hemodynamic profile. In conclusion, XV454 represents a potent antiplatelet agent in inhibiting platelet aggregation along with a high affinity and relatively slow dissociation rate from human platelet GPIIb/IIIa receptors that allow a long-lasting antiplatelet efficacy after single i.v. or oral administration.

Alanine↗

PubMed1998

Cell adhesion molecules and extracellular matrix proteins: potential therapeutic applications.

Adhesion plays a central role as a recognition system, guiding the interaction between individual cells, and thereby regulating many biological processes. Adhesion can occur via cell-cell or cell-extracellular matrix interactions through several major cell adhesion molecule (CAM) families, including selectins, integrins, immunoglobulins and cadherins. Recent studies have focused on the elucidation of adhesive ligands responsible for the different types of cellular adhesion. Significant breakthroughs in CAM research are a result of various developments, including the purification of various adhesive proteins from different tissue sources and cloned adhesion molecules, the generation of specific monoclonal antibodies, the development of functional assays and the identification of certain genetic disorders linked to CAM defects. This has led to an increased understanding of the importance of CAM as a key therapeutic target.

Journal Article↗

PubMed1998

Novel technetium-99m-labeled platelet GPIIb/IIIa receptor antagonists as potential imaging agents for venous and arterial thrombosis.

OBJECTIVES: Either venous or arterial thrombosis is a potentially life-threatening event and existing diagnostic modalities are inadequate to diagnose and to determine the morphology of the evolving thrombus. Thus development of a noninvasive imaging agent that can detect clot location remains a critical and unmet need in nuclear diagnostic medicine. The present study was undertaken to determine the potential of platelet GPIIb/IIIa receptors compared with direct thrombin inhibitors, in the detection of venous and arterial clots. METHODS: Initially, the validity of exploiting the degree and extent of specific uptake and retention of a potent GPIIb/IIIa receptor antagonist in venous and in arterial thrombus was confirmed in vitro in artificially created arterial- or venous-type clots, using the radiolabeled antagonist, 3H-DMP728. This was followed by comparing the in-vivo clot/blood distribution of various technetium-99m (99mTc)-labeled, DMP728-derived, GPIIb/IIIa receptor antagonists and of thrombin inhibitors, over time, in mixed arterial/venous or venous clots in arteriovenous shunt and in venous clot models in dogs. In addition, we performed noninvasive single-photon emission tomographic imaging of the venous clot in a deep vein thrombosis model in dogs. RESULTS: Our data confirmed that potency for the platelet GPIIb/IIIa receptors was maintained after radiolabeling of the parent active GPIIb/IIIa receptor antagonists. DMP728 demonstrated a relatively greater affinity for activated than for unactivated human platelets, which might be essential for attaining an optimal thrombus/blood (target/background) distribution ratio and the optimal detection of small clots (i.e. greater sensitivity). CONCLUSIONS: These data suggest a potential utility of 99mTc-GPIIb/IIIa receptor antagonists, but not of direct thrombin inhibitors, in the diagnosis of venous clots in deep vein thrombosis, pulmonary embolism and arterial thromboembolic disorders including stroke and coronary and peripheral artery thrombotic disorders.

Analysis of Variance↗

PubMed1998

Antiplatelet efficacy of XV459, a novel nonpeptide platelet GPIIb/IIIa antagonist: comparative platelet binding profiles with c7E3.

Recent advances in the development of i.v. platelet glycoprotein alphaIIb/beta3 integrin (GPIIb/IIIa) antagonists led to the development of either a class of small-molecular-weight antagonists with a short to ultra-short duration of antiplatelet effects (Integrelin, Tirofiban, DMP728) or a very long-acting antagonist (ReoPro). Thus the present study was undertaken to characterize the antiplatelet efficacy of a small-molecule GPIIb/IIIa antagonist, DMP754/XV459, and to determine its platelet GPIIb/IIIa receptor binding profiles. DMP754, upon its conversion with esterases to its free acid form XV459, and XV459 itself, demonstrated high potency (IC50 = 0.030-0.060 microM) in inhibiting human platelet aggregation induced by ADP (100 microM), thrombin receptor agonist peptide (10 microM) or collagen (20 microgram/ml) in citrate or heparin. Maximal platelet aggregation inhibition was achieved at 50 to >/=80% receptor occupancy, depending on the agonist used. Both XV459 and c7E3 bind with high affinity to either activated human platelets (Kd = 0.0008 and 0.0091 microM, respectively) or unactivated human platelets (Kd = 0.0025 and 0.0092 microM, respectively). XV459 demonstrated tight association with human, baboon and (to a lesser extent) canine platelets (t1/2 of dissociation = 7 +/- 0, 8 +/- 1 and 1.4 +/- 0.1 minutes, respectively). Both c7E3 and XV459 associate tightly with slower dissociation rates to unactivated human platelets. XV459 represents a potent antiplatelet agent in inhibiting platelet aggregation along with offering high affinity and a relatively slow dissociation rate from human platelet GPIIb/IIIa receptors that might allow for once-a-day p.o. dosage.

Amino Acids↗

PubMed1997

Dissociation between the anti-aggregatory & anti-secretory effects of platelet integrin alpha IIb beta 3 (GPIIb/IIIa) antagonists, c7E3 and DMP728.

The effects of alpha IIb beta 3 antagonists on the blockade of fibrinogen binding to platelet alpha IIb beta 3 are well documented, however, little is known about their effects on platelet secretion. We compare here the effect of two potent alpha IIb beta 3 antagonists, c7E3 and DMP728, on platelet secretion. Using human platelet-rich plasma, P-selectin expression was measured by flow cytometry and type 1 plasminogen activator inhibitor (PAI-1) secretion as well as beta-thromboglobulin (beta-TG) were determined by ELISA. At various concentrations of the antagonists that inhibited 80-95% of platelet aggregation, neither had any effect on P-selectin expression. In contrast, thrombin-stimulated PAI-1 secretion is only inhibited by c7E3, 49.6% at 3.5 mumol/L (p < 0.05), but not at any other maximally effective anti-aggregatory concentrations of c7E3 or DMP728. Furthermore, a lack of any significant effects on platelet granular secretion of beta-TG induced by either thrombin or ADP was demonstrated with DMP728, c7E3 or LM609. Two protein kinase inhibitors, staurosporine and herbimycin, blocked both ADP and thrombin-induced P-selectin expression at 10 mumol/L, but not PAI-1 secretion. Taken together this suggests that: (1) the mechanism of platelet granular secretion is independent of the integrin alpha IIb beta 3 and (2) the subcellular locations of PAI-1, beta-TG and P-selectin or the signaling mechanisms that regulate their secretion might be different. Although there is no direct effect of platelet alpha IIb beta 3 antagonists on platelet secretion of PAI-1, beta-TG and P-selectin, the present data demonstrates that reduction of platelet number by alpha IIb beta 3 antagonists, via the reduction in thrombus size, might be an alternate mechanism for reduced platelet secretion. In conclusion, a discoupling between the anti-aggregatory and the anti-secretory effects of alpha IIb beta 3 antagonists has been demonstrated.

Abciximab↗

PubMed1997

Discovery of an orally active series of isoxazoline glycoprotein IIb/IIIa antagonists.

Using isoxazoline XR299 (1a) as a starting point for the design of highly potent, long-duration GPIIb/IIIa antagonists, the effect of placing lipophilic substituents at positions alpha and beta to the carboxylate moiety was evaluated. Of the compounds studied, it was found that the n-butyl carbamate 24u exhibited superior potency and duration of ex vivo antiplatelet effects in dogs. Replacement of the benzamidin-4-yl moiety with alternative basic groups, elimination of the isoxazoline stereocenter, and reversal of the orientation of the isoxazoline ring resulted in lowered potency and/or duration of action.

Administration, Oral↗

PubMed1997

Biological matrix-dependent pharmacokinetic and pharmacodynamic parameters of a novel platelet glycoprotein IIB/IIIA receptor antagonist, XU063, in beagle dogs.

The pharmacokinetic-pharmacodynamic (PK/PD) relationship of a novel platelet glycoprotein IIb/IIIa receptor antagonist, XU063, was evaluated as a function of biological matrix in beagle dogs. The disposition of 14C-radioactivity in various blood or plasma matrices and kinetics of inhibition of adenosine diphosphate (ADP) induced platelet aggregation were determined in beagle dogs following an intravenous infusion of 14C-XU063 at 2 micrograms/kg for 45 min. The 14C-radioactivity was maximum in platelet poor plasma (PPP) harvested from blood collected in EDTA and lowest in PPP harvested from blood collected in citrated vacutainers over the entire concentration versus time profile during and post infusion. The 14C-radioactivity values in blood and platelet rich plasma (PRP) were comparable and were between EDTA PPP and citrated PPP values. The resultant estimates of the PK and PD parameters of 14C-XU063 varied widely depending on the type of matrix used. The systemic clearance values for 14C-XU063 were 1 and 10 mL/min/kg for EDTA and citrated PPP, respectively. The values for the volume of distribution at steady-state were 0.2 and 1.3 L/kg, for EDTA and citrated PPP, respectively. The terminal elimination half-life appeared independent of the matrix with a median value of 2 h. The estimated ex vivo IC50 values of XU063 ranged from 0.4 ng/mL (citrated PPP, platelet free drug) to 7 ng/mL (EDTA PPP, total drug). These results demonstrated the dependence of PK and PD parameters of antiplatelet agent XU063 on the type of biological matrix used to determine concentrations of XU063. The pros and cons of various blood sample collection methods for the evaluation of PK/PD relationship of potential antiplatelet agents are presented.

Adenosine Diphosphate↗

PubMed1997

Agonist-activated alphavbeta3 on platelets and lymphocytes binds to the matrix protein osteopontin.

The phosphorylated acidic glycoprotein osteopontin is present in the extracellular matrix of atherosclerotic plaques and the wall of injured but not normal arteries. To determine if osteopontin could serve as a substrate for platelet adhesion, we measured the adherence of resting and agonist-stimulated human platelets to immobilized recombinant human osteopontin. Agonist-stimulated but not resting platelets bound to osteopontin by a process that was mediated primarily by alphavbeta3. alphavbeta3-mediated adherence occurred at physiologic concentrations of calcium and was inhibited by an alphavbeta3-selective cyclic peptide. Assays using phorbol myristate acetate-stimulated transfected B lymphocytes expressing both alphavbeta3 and alphaIIbbeta3 confirmed that activated alphavbeta3 not activated alphaIIbbeta3 was responsible for the cellular adherence we measured. These studies indicate that alphavbeta3 can reside on the cell surface in an inactive state and can be converted to a ligand binding conformation by cellular agonists. Moreover, they suggest that platelet adherence to osteopontin mediated by activated alphavbeta3 could play a role in anchoring platelets to disrupted atherosclerotic plaques and the walls of injured arteries. By inhibiting alphavbeta3 function, it may be possible to inhibit platelet-mediated vascular occlusion with a minimal effect on primary hemostasis.

Adenosine Diphosphate↗

PubMed1997

Corticotropin-releasing factor in antinociception and inflammation.

Corticotropin-releasing factor (CRF) plays a major role at the level of the hypothalamus and pituitary to control the body's response mechanisms to stressful stimuli. The recent discovery of CRF outside the central nervous system suggests that CRF may well play a similar role in peripheral tissues, most likely in a paracrine manner. While its effects in many other peripheral tissues is not known yet, CRF and its receptors are upregulated in inflammatory pain states pointing to a key role under these circumstances. Indeed, locally expressed CRF seems to act on CRF receptors on immune cells which have migrated into the area of the inflamed tissue, and induce the release of opioid peptides synthesized within these immune cells. These opioids subsequently act on peripheral opioid receptors located on peripheral sensory nerves to inhibit the transmission of painful stimuli. CRF may also affect the inflammatory response; however, these data are still controversial. The peripheral paracrine effects of CRF may be similar to those of hypothalamic CRF, i.e., to counterbalance local stressful events, such as inflammation and pain, so that they do not threaten the homeostasis of the body. Interestingly, CRF-like peptides have been identified not only in mammalians, but also in species such as the frog (Stenzel-Poore et al., 1992, Mol. Endocrinol. 6, 1716) and the teleost fish (Okawara et al., 1988, Proc. Natl. Acad. Sci. USA 85, 8439) indicating that this is a peptide that has been conserved over a long period (200 million years) across species (Lederis et al., 1990, Prog. Clin. Biol. Res. 342, 467) and that the release of ACTH-like peptides by peptides of the CRF family may represent an ancestral type of stress response (Ottaviani et al., 1992, Gen. Comp. Endocrinol. 87, 354; Tran et al., 1990, Gen. Comp. Endocrinol. 78, 351).

Analgesia↗

PubMed1997

Discovery of potent isoxazoline glycoprotein IIb/IIIa receptor antagonists.

Using the isoxazoline as a common structural feature, three series of glycoprotein IIb/IIIa receptor antagonists were evaluated, culminating in the discovery of XR299 (30). In an in vitro assay of platelet inhibition, XR299 had an IC50 of 0.24 microM and was a potent antiplatelet agent when dosed intravenously in a canine model. It was shown through X-ray studies of the cinchonidine salt 49 that the receptor required the 5(R)-stereochemistry for high potency. The ethyl ester prodrug of XR299, XR300 (29), was orally active in the dog.

Animals↗

PubMed1997

Selective alpha v beta 3 integrin blockade potently limits neointimal hyperplasia and lumen stenosis following deep coronary arterial stent injury: evidence for the functional importance of integrin alpha v beta 3 and osteopontin expression during neointima formation.

UNLABELLED: Lumen loss from vascular restenosis remains a leading cause of chronic revascularization failure. OBJECTIVE: We hypothesized that cell-matrix adhesion, migration, and differentiation events that underlie restenosis are mediated by alpha v beta 3 integrin-ligand interactions. METHODS: Using immunohistochemistry and in situ hybridization, we examined the spatial and temporal vessel wall expression of alpha v beta 3 and osteopontin following deep coronary arterial injury. Cell migration and adhesion assays were performed to demonstrate the affinity and specificity of XJ 735 for various vessel wall integrins. The effects of XJ 735 (a selective cyclic Arg-Gly-Asp (RGD) peptidomimetic alpha v beta 3 antagonist) on neointimal hyperplasia and lumen stenosis were tested in a porcine coronary injury model. Normolipemic swine underwent oversized stent injury followed by XJ 735 administration (9 animals, 28 lesions; 1 mg/kg bolus + 7 days 4 mg/kg/d infusion + 21 days 2 mg/kg i.v. bolus 12 hourly) or placebo (10 animals, 30 arterial lesions). RESULTS: Maximal alpha v beta 3 immunoreactivity was observed between 7-14 days following injury in the neointima, media, and adventitia. Maximal osteopontin mRNA signal in the neointima, media, and adventitia was observed at 14, 7 and 28 days respectively. IC50 for XJ 735 alpha v beta 3-mediated inhibition of human and porcine endothelial cell adhesion, and vascular smooth muscle cell migration, ranged from 0.6 to 4.4 microM. In contrast, IC50 for porcine or human alpha IIb/beta 3, alpha 4 beta 1, alpha v beta 5, and alpha 5 beta 1 inhibition exceeded 100 microM. Steady state XJ 735 plasma levels exceeded 5 microM. Despite slightly higher injury scores in XJ 735 treated animals, significant reductions in mean neointima area (43% reduction; p = 0.0009), and mean percent lumen stenosis (approximately 2.9 fold reduction; p = 0.04) were observed in XJ 735 treated animals. XJ 735 treatment did not significantly alter the relative size of the arterial injury and reference sites (geometric remodeling). Comparison of neontima area vs. injury score regression lines revealed significant reductions in slope (p = 0.0001) and intercept (p = 0.0001) for XJ 735. CONCLUSIONS: Selective alpha v beta 3 blockade is an effective anti-restenosis strategy that potently limits neointimal growth and lumen stenosis following deep arterial injury. The co-ordinate spatial and temporal upregulation of alpha v beta 3 expression following vessel wall injury, and the high affinity and specificity of XJ 735 for alpha v beta 3, confirms the importance of this integrin in adhesive and migratory cell-matrix events underlying coronary restenosis.

Animals↗

PubMed1997

Intranasal absorption of the platelet glycoprotein IIb/IIIa receptor antagonist, DMP 755, and the effect of anesthesia on nasal bioavailability.

Intranasal absorption and bioavailability of DMP 755, a peptidomimetic, platelet glycoprotein IIb/IIIa receptor antagonist, were examined in anesthetized and lightly sedated dogs. Nasal bioavailability was determined by measuring plasma concentrations relative to those after intravenous dosing. DMP 755 is an ester prodrug, and bioavailability reflects concentrations of the acid hydrolysis product. Nasal bioavailability in dogs anesthetized with pentobarbital was 85 +/- 4%, whereas in dogs anesthetized with the short-acting anesthetic propofol, bioavailability was 32 +/- 7%. Nasal bioavailability was greater than the reported oral bioavailability of DMP 755 in dogs, and was quite consistent. Because anesthesia affects nasal bioavailability, an effect that may depend on the absorption half-life of the test compound, a conscious or lightly sedated animal model is preferred.

Absorption↗

PubMed1997

Prevention of carotid artery thrombosis by oral platelet GPIIb/IIIa antagonist in dogs.

BACKGROUND AND PURPOSE: Current antithrombotic therapy in acute ischemic stroke and myocardial infarction in which a combination of antiplatelet agents (aspirin) and anticoagulants (heparin) was used led to partial reduction of acute thrombotic complications. Recent advances in antiplatelet research led to the discovery of the platelet glycoprotein IIb/IIIa complex (GPIIb/IIIa), the final common pathway for platelet aggregation. The present study was undertaken to determine the oral antithrombotic efficacy of a potent and specific platelet GPIIb/ IIIa antagonist, DMP728, in an electrically induced carotid artery thrombosis model in dogs. Based on the powerful antiplatelet efficacy of this mechanism in inhibiting all agonist-induced platelet aggregation as well as in inhibiting platelet procoagulant activity (thrombin generation and hence fibrin formation), an orally active antagonist for this integrin receptor might have potential benefits in stroke. METHODS: Anesthetized dogs were instrumented for monitoring of arterial blood pressure, heart rate, and carotid artery flow velocity. Animals were treated with saline or DMP728 (0.1 to 1.0 mg/kg PO). Thrombus formation (platelet-rich aggregate with fibrous coating and a few erythrocytes) by anodal electrolytic stimulation (300 microA) to the intimal surface of the right carotid artery was initiated 120 minutes after oral DMP728 administration and continued for 180 minutes. Whole blood cell counts, ex vivo platelet aggregation, and template bleeding time were determined at different time points throughout the study. RESULTS: DMP728 administered at 0.1 to 1.0 mg/kg PO exhibited dose-dependent antithrombotic efficacy in this model. DMP728 was shown to be significantly effective in inhibiting ex vivo platelet aggregation and in inhibiting thrombosis at 0.3 to 1.0 mg/kg PO. The antiplatelet, antithrombotic effects of DMP728 were demonstrated without any significant changes in the different hemodynamic or coagulation parameters. These data demonstrated the oral antithrombotic efficacy of DMP728 in dogs. CONCLUSIONS: Platelet GPIIb/IIIa blockade with an orally active antagonist was shown to be safe and effective in the prevention of carotid artery occlusive thrombosis.

Administration, Oral↗

PubMed1996

Synthesis and solution conformation of cyclo[RGDRGD]: a cyclic peptide with selectivity for the alpha V beta 3 receptor.

Three peptides, cyclo[RGDRGD], cyclo[RGDRGd] (d = D-Asp), and the linear sequence RGDRGD, were prepared via solid phase syntheses. These were tested in binding assays based upon the alpha IIb/beta 3-fibrinogen and the alpha V beta 3-vitronectin interactions and found to be selective for the alpha V beta 3 integrin. The alpha V beta 3-vitronectin is important in bone regeneration, hence the compounds were also tested in an osteoclast regeneration assay; all three compounds, cyclo-[RGDRGD], cyclo[RGDRGd], and RGDRGD, showed modest activities. Molecular modeling, NMR, and CD studies were undertaken to elucidate the conformational preferences of cyclo-[RGDRGD], in aqueous solutions. Results from these studies strongly suggest that the molecule tends to adopt a type I beta-turn conformation with a relatively short distance between the Asp and Arg side chains. These observations are in harmony with the first correlations made between alpha V beta 3 selectivity and solution conformation for a peptide ligand (Pfaff, M.; et al. J. Biol. Chem. 1994, 269, 20233).

Cell Division↗

PubMed1996

Local upregulation of corticotropin-releasing hormone and interleukin-1 receptors in rats with painful hindlimb inflammation.

Opioid peptides derived from immune cells produce analgesia by activating opioid receptors on peripheral sensory nerves in inflammation. Corticotropin-releasing hormone (CRH) and interleukin-1 beta (IL-1 beta) can release these opioids. Here we show that both corticotropin-releasing hormone and interleukin-1 beta elicit receptor-specific antinociception in inflamed paws of rats by an opioid-mediated mechanism. Autoradiographic studies demonstrate 125I-CRH and 125I-IL-1 beta binding sites on immune cells in lymph nodes and inflamed paws. This binding is of high affinity and displaceable by the respective unlabeled agonist and antagonist ligands but not by opioid or adrenergic compounds. 125I-CRH and 125I-IL-1 beta binding sites are absent on nerves and in non-inflamed subcutaneous tissue but their number is greatly enhanced in inflamed paws and lymph nodes. This upregulation of binding sites for the opioid-releasing agents corticotropin-releasing hormone and interleukin-1 beta likely represents part of the body's local response to combat inflammatory pain.

Animals↗