Cerebrovascular characterization of clazosentan, the first nonpeptide endothelin receptor antagonist clinically effective for the treatment of cerebral vasospasm. Part I: Inhibitory effect on endothelinA receptor—mediated contraction

2005 ◽  
Vol 102 (6) ◽  
pp. 1101-1107 ◽  
Author(s):  
Hartmut Vatter ◽  
Michael Zimmermann ◽  
Veronika Tesanovic ◽  
Andreas Raabe ◽  
Lothar Schilling ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Cerebral Vasospasm ◽  
Isometric Force ◽  
Inhibitory Effect ◽  
Affinity Constant ◽  
Dependent Manner ◽  
Content Type ◽  
The Right ◽  
Fine Print

Object. The central role of endothelin (ET)—1 in the development of cerebral vasospasm after subarachnoid hemorrhage is indicated by the successful treatment of this vasospasm in several animal models by using selective ETA receptor antagonists. Clazosentan is a selective ETA receptor antagonist that provides for the first time clinical proof that ET-1 is involved in the pathogenesis of cerebral vasospasm. The aim of the present investigation was, therefore, to define the pharmacological properties of clazosentan that affect ETA receptor—mediated contraction in the cerebrovasculature. Methods. Isometric force measurements were performed in rat basilar artery (BA) ring segments with (E+) and without (E−) endothelial function. Concentration effect curves (CECs) were constructed by cumulative application of ET-1 or big ET-1 in the absence or presence of clazosentan (10−9, 10−8, and 10−7 M). The inhibitory potency of clazosentan was determined by the value of the affinity constant (pA2). The CECs for contraction induced by ET-1 and big ET-1 were shifted to the right in the presence of clazosentan in a parallel dose-dependent manner, which indicates competitive antagonism. The pA2 values for ET-1 were 7.8 (E+) and 8.6 (E−) and the corresponding values for big ET-1 were 8.6 (E+) and 8.3 (E−). Conclusions. The present data characterize clazosentan as a potent competitive antagonist of ETA receptor—mediated constriction of the cerebrovasculature by ET-1 and its precursor big ET-1. These functional data may also be used to define an in vitro profile of an ET receptor antagonist with a high probability of clinical efficacy.

Cerebrovascular characterization of clazosentan, the first nonpeptide endothelin receptor antagonist shown to be clinically effective for the treatment of cerebral vasospasm. Part II: Effect on endothelinB receptor—mediated relaxation

2005 ◽  
Vol 102 (6) ◽  
pp. 1108-1114 ◽  
Author(s):  
Hartmut Vatter ◽  
Michael Zimmermann ◽  
Veronika Tesanovic ◽  
Andreas Raabe ◽  
Volker Seifert ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Cerebral Vasospasm ◽  
Competitive Inhibition ◽  
Isometric Force ◽  
Affinity Constant ◽  
Content Type ◽  
Prostaglandin F ◽  
Cerebrovascular System ◽  
Fine Print

Object. The disturbed balance between nitric oxide and endothelin (ET)—1 in the cerebrovasculature seems to play a major role in the development of cerebral vasospasm after subarachnoid hemorrhage. Endothelin-1 represents the contractile part in this balance. In addition to the prevailing ETA receptor—dependent contractile effect, ET-1 also has ETB receptor—mediated vasodilatory attributes. The aim of the present study was to define the actual selectivity of clazosentan, the first putative highly ETA receptor—selective antagonist clinically proven to be effective in the treatment of vasospasm in the cerebrovasculature. Methods. Rat basilar artery ring segments with endothelial function were used for the measurement of isometric force. Concentration effect curves were constructed by cumulative application of sarafotoxin S6c, ET-1, or big ET-1 in the presence or absence of clazosentan (10−9 to 10−6 M) after a precontraction was induced by prostaglandin F2α. The inhibition by clazosentan was estimated by the value of the affinity constant (pA2). The relaxation induced by sarafotoxin S6c, ET-1, and big ET-1 was inhibited in a competitive manner by clazosentan, yielding pA2 values of 7.1, 6.7, and 6.5, respectively. The selectivity to the ETA receptor in the cerebrovascular system was approximately two logarithmic units. Conclusions. The present investigation shows a competitive inhibition of ETB receptor—mediated relaxation in cerebral vessels by clazosentan in therapeutically relevant concentrations. Thus, additional clinical trials should be undertaken to evaluate clazosentan concentrations in cerebrospinal fluid. Furthermore, the present data may be taken to describe the pharmacological properties for an ET receptor antagonist specifically tailored for the treatment of pathological conditions of impaired cerebral blood flow.

Effect of the novel endothelin(A) receptor antagonist LU 208075 on contraction and relaxation of isolated rat basilar artery

2002 ◽  
Vol 103 (s2002) ◽  
pp. 408S-413S ◽  
Author(s):  
Hartmut VATTER ◽  
Michael ZIMMERMANN ◽  
Carla JUNG ◽  
Edda WEYRAUCH ◽  
Josef LANG ◽  
...  
Keyword(s):  
Receptor Antagonist ◽  
Basilar Artery ◽  
Isometric Force ◽  
Inhibitory Effect ◽  
Percentage Decrease ◽  
Receptor Inhibition ◽  
Endothelin A Receptor ◽  
The Right ◽  
Contraction And Relaxation

Increased levels of endothelin (ET)-1 and bigET-1 may be responsible for enhanced cerebroarterial resistance under pathologic conditions. Therefore, the effect of LU 208075, a novel ET(A)-selective receptor antagonist was determined. The aim of the study was to investigate in vitro the inhibitory effect of LU 208075 on ET-1 and bigET-1 induced contraction and relaxation in rat basilar artery segments. Segments with (E+) and without (E-) endothelium were prepared for the measurement of isometric force. Concentration–effect curves (CECs) were constructed by cumulative application of ET-1 or bigET-1. The shift of the CECs in the presence of LU 208075 against the control curve was determined. Relaxation was investigated on precontracted segments, calculated in percentage decrease of precontraction and compared by the pD2 and Emax. ET-1 and bigET-1 induced contraction was dose dependently inhibited by LU 208075. Shifts of the CECs in the presence of LU 208075 (10-6M and 10-5M) were for ET-1 (1) in E+: 4.4 and 19.7; (2) in E-: 8.1 and 60.4 and for bigET-1 (3) in E+: 10.8 and (4) in E-: 26.0 respectively. LU 208075 (10-5M) completely inhibited bigET-1-induced contraction. Relaxation by ET-1 or bigE-1 was only observed in the presence of LU 208075. CECs were shifted to the right by LU 208075 (10-5 M) by a factor of 24 (ET-1) and 4.5 (bigET-1). Emax values were 45±18% and 51±15% (ET-1; in the presence of 10-5 and 10-6 M LU 208075 respectively), and 56±20% and 49±17% (bigET-1; in the presence of 10-5 and 10-6 M LU 208075 respectively). The data suggests a competitive ET(A)-receptor inhibition by LU 208075. The enhanced inhibitory effect on bigET-1-induced contraction could indicate an additional inhibitory effect on endothelin-converting enzyme activity. The pronounced effect on E-vessels and the inhibition of relaxation may suggest an ET(B) receptor affinity.

Growth hormone receptor expression and function in meningiomas: effect of a specific receptor antagonist

1999 ◽  
Vol 91 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Keith E. Friend ◽  
Robert Radinsky ◽  
Ian E. McCutcheon
Keyword(s):  
Growth Hormone ◽  
Growth Rate ◽  
Receptor Antagonist ◽  
Messenger Rna ◽  
Thymidine Incorporation ◽  
Receptor Expression ◽  
Dependent Manner ◽  
Content Type ◽  
Gh Receptor ◽  
Fine Print

Object. This study was undertaken to explore the effects of growth hormone (GH) and the GH-stimulated peptide insulin-like growth factor—1 (IGF-1) on the growth rate of meningiomas.Methods. Polymerase chain reaction and ribonuclease protection assays were used to demonstrate that GH receptor messenger RNA was present in all 14 meningioma specimens studied, regardless of tumor grade. Both wild type (GHRwt) and a previously described exon 3 deletion isoform (GHRd3) of the GH receptor were identified in individual tumor specimens. The importance of the GH receptor was assessed using a GH receptor antagonist (B2036). Blockade of the GH receptor with B2036 reduced serum-induced DNA synthesis, as measured by thymidine incorporation, by 8 to 33% (mean 20%) in primary meningioma cultures. Tumors that expressed the GHRwt and GHRd3 isoforms, or a combination of the two, were all responsive to antagonist treatment. The importance of IGF-1 in stimulating meningioma cell growth was also assessed. It was found that IGF-1 increased thymidine incorporation in primary meningioma cultures in a dose-dependent manner: 1 ng/ml, 5 ng/ml, and 10 ng/ml resulted in increases in thymidine incorporation of 21%, 43%, and 176%, respectively, over baseline values.Conclusions. In these studies the authors demonstrate that activation of the GH/IGF-1 axis significantly increases the growth rate of meningiomas. Blockade of the GH receptor on tumor cells inhibited tumor growth. If these findings are confirmed in animal studies, agents that downregulate the GH/IGF-1 axis might represent a potential adjuvant therapy in the management of patients with meningioma.

Association between cerebrospinal fluid levels of asymmetric dimethyl-L-arginine, an endogenous inhibitor of endothelial nitric oxide synthase, and cerebral vasospasm in a primate model of subarachnoid hemorrhage

2004 ◽  
Vol 101 (5) ◽  
pp. 836-842 ◽  
Author(s):  
Carla S. Jung ◽  
Brian A. Iuliano ◽  
Judith Harvey-White ◽  
Michael G. Espey ◽  
Edward H. Oldfield ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Cerebrospinal Fluid ◽  
Cerebral Vasospasm ◽  
Primate Model ◽  
Content Type ◽  
Cerebrospinal Fluid Levels ◽  
Delayed Cerebral Vasospasm ◽  
The Right ◽  
Fluid Levels ◽  
Fine Print

Object. Decreased availability of nitric oxide (NO) has been proposed to evoke delayed cerebral vasospasm after subarachnoid hemorrhage (SAH). Asymmetric dimethyl-l-arginine (ADMA) inhibits endothelial NO synthase (eNOS) and, therefore, may be responsible for decreased NO availability in cases of cerebral vasospasm. The goal of this study was to determine whether ADMA levels are associated with cerebral vasospasm in a primate model of SAH. Methods. Twenty-two cynomolgus monkeys (six control animals and 16 with SAH) were used in this study. The levels of ADMA, l-arginine, l-citrulline, nitrites, and nitrates in cerebrospinal fluid (CSF) and serum were determined on Days 0, 7, 14, and 21 following onset of SAH. Cerebral arteriography was performed to assess the degree of vasospasm. Western blot analyses of the right and left middle cerebral arteries (MCAs) were performed to assess the expression of eNOS, type I protein—arginine methyl transferase (PRMT1) and dimethylarginine dimethylaminohydrolase (DDAH2). Cerebrospinal fluid levels of ADMA remained unchanged in the control group (six animals) and in animals with SAH that did not have vasospasm (five animals; p = 0.17), but the levels increased in animals with vasospasm (11 animals) on Day 7 post-SAH (p < 0.01) and decreased on Days 14 through 21 (p < 0.05). Cerebrospinal fluid levels of ADMA correlated directly with the degree of vasospasm (correlation coefficient = 0.7, p = 0.0001; 95% confidence interval: 0.43–0.83). Levels of nitrite and nitrate as well as those of l-citrulline in CSF were decreased in animals with vasospasm. Furthermore, DDAH2 expression was attenuated in the right spastic MCA on Day 7 post-SAH, whereas eNOS and PRMT1 expression remained unchanged. Conclusions. Changes in the CSF levels of ADMA are associated with the development and resolution of vasospasm found on arteriograms after SAH. The results indicate that endogenous inhibition of eNOS by ADMA may be involved in the development of delayed cerebral vasospasm. Inhibition of ADMA production may provide a new therapeutic approach for cerebral vasospasm after SAH.

A Comparative Study of the Effects of Adrenoceptor Antagonists on Platelet Aggregation and Thromboxane Generation

1985 ◽  
Vol 54 (02) ◽  
pp. 480-484 ◽  
Author(s):  
I A Greer ◽  
J J Walker ◽  
M McLaren ◽  
A A Calder ◽  
C D Forbes
Keyword(s):  
Platelet Aggregation ◽  
Vascular Disease ◽  
Platelet Rich Plasma ◽  
Thromboxane A2 ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Wide Range ◽  
The Right

SummaryPlatelet aggregation and thromboxane A2 have been implicated in the pathogenesis of several forms of vascular disease. The aim of this study was to determine the effect of a wide range of adrenoceptor antagonists on platelet aggregation, and thromboxane A2 production, from normal human platelet rich plasma in vitro. Labetalol, pindolol and propranolol inhibited platelet aggregation to collagen in a dose dependent manner. Increasing the concentration of collagen “shifted” the dose response curve to the right. These 3 drugs also significantly inhibited thromboxane A2 generation in response to collagen but not to arachidonic acid. This effect was independent of any inhibitory effect of these drugs on platelet aggregation, and occurred at a drug concentration close to that obtained in vivo. Atenolol, metoprolol, prazosin and timolol were similarly assessed but had no effect on either platelet aggregation or thromboxane A2 generation. This ability of labetalol, pindolol, and propranolol to inhibit platelet aggregation and thromboxane generation, may be of clinical benefit in view of the increasing evidence implicating thromboxane A2 in the pathogenesis of vascular disease.

Effect of intracarotid nitric oxide on primate cerebral vasospasm after subarachnoid hemorrhage

1995 ◽  
Vol 83 (1) ◽  
pp. 118-122 ◽  
Author(s):  
John K. B. Afshar ◽  
Ryszard M. Pluta ◽  
Robert J. Boock ◽  
B. Gregory Thompson ◽  
Edward H. Oldfield
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Subarachnoid Hemorrhage ◽  
Cerebral Vasospasm ◽  
Primate Model ◽  
Content Type ◽  
Continuous Release ◽  
Blood Flow Velocities ◽  
The Right ◽  
Fine Print

✓ The continuous release of nitric oxide (NO) is required to maintain basal cerebrovascular tone. Oxyhemoglobin, a putative spasmogen, rapidly binds NO, implicating loss of NO in the pathogenesis of cerebral vasospasm after subarachnoid hemorrhage (SAH). If vasospasm is mediated by depletion of NO in the vessel wall, it should be reversible by replacement with NO. To investigate this hypothesis, the authors placed blood clots around the right middle cerebral artery (RMCA) of four cynomolgus monkeys; four unoperated animals served as controls. Arteriography was performed before and 7 days after surgery to assess the presence and degree of vasospasm, which was quantified in the anteroposterior (AP) projection by computerized image analysis. On Day 7, cortical cerebral blood flow (CBF) in the distribution of the right MCA was measured during four to six runs in the right internal carotid artery (ICA) of brief infusions of saline followed by NO solution. Arteriography was performed immediately after completing the final NO infusion in three of the four animals with vasospasm. Right MCA blood flow velocities were obtained using transcranial Doppler before, during, and after NO infusion in two vasospastic animals. After ICA NO infusion, arteriographic vasospasm resolved (mean percent of preoperative AP area, 55.9%); that is, the AP areas of the proximal portion of the right MCA returned to their preoperative values (mean 91.4%; range 88%–96%). Compared to ICA saline, during ICA NO infusion CBF increased 7% in control animals and 19% in vasospastic animals (p < 0.002) without significant changes in other physiological parameters. During NO infusion, peak systolic right MCA CBF velocity decreased (130 to 109 cm/sec and 116 to 76 cm/sec) in two vasospastic animals. The effects of ICA NO on CBF and CBF velocity disappeared shortly after terminating NO infusion. Intracarotid infusion of NO in a primate model of vasospasm 1) increases CBF, 2) decreases cerebral vascular resistance, 3) reverses arteriographic vasospasm, and 4) decreases CBF velocity in the vasospastic artery without producing systemic hypotension. These findings indicate the potential for the development of targeted therapy to reverse cerebral vasospasm after SAH.

Antiproliferative effect of trapidil, a platelet-derived growth factor antagonist, on a glioma cell line in vitro

1990 ◽  
Vol 73 (3) ◽  
pp. 436-440 ◽  
Author(s):  
Jun-ichi Kuratsu ◽  
Yukitaka Ushio
Keyword(s):  
Growth Factor ◽  
Cell Lines ◽  
Glioma Cell ◽  
Glioma Cells ◽  
Inhibitory Effect ◽  
Platelet Derived Growth Factor ◽  
Content Type ◽  
Glioma Cell Lines ◽  
Fine Print

✓ Platelet-derived growth factor (PDGF) is produced by glioma cells. However, there is heterogeneity among glioma cell lines in the production of PDGF. It has been demonstrated that U251MG cells produce a PDGF-like molecule while U105MG cells do not. Trapidil, a specific antagonist of PDGF, competes for receptor binding with PDGF. Therefore, the inhibitory effect of trapidil on the proliferation of glioma cells was investigated in vitro using two glioma cell lines. At 100 µg/ml, trapidil significantly inhibited the proliferation of U251MG cells (which produce the PDGF-like molecule). At the same trapidil concentration, the proliferation of U105MG cells (which do not produce the PDGF-like molecule) was not inhibited. The inhibitory effect of trapidil was remarkable on Days 3 and 4 of culture. After 4 days of incubation, the proliferation of U251MG cells was 46% of the control preparation. Trapidil enhanced the antitumor effect of 3-((4-amino-2-methyl-5-pyrimidinyl)ethyl)-1-(2-chloroethyl)-1-nitro-sourea (ACNU) against U251MG cells. The enhancing effect was highest on Days 4 and 6 of culture. After 6 days of incubation in the presence of 100 µg/ml trapidil and 1 µg/ml ACNU, the proliferation of U251MG cells was 18% of the control preparation. These findings suggest that trapidil interrupts the autocrine loop at the PDGF and PDGF-receptor level and that combination therapy with trapidil and ACNU may be useful in the treatment of glioma.

Loss of nitric oxide synthase immunoreactivity in cerebral vasospasm

1996 ◽  
Vol 84 (4) ◽  
pp. 648-654 ◽  
Author(s):  
Ryszard M. Pluta ◽  
B. Gregory Thompson ◽  
Ted M. Dawson ◽  
Solomon H. Snyder ◽  
Robert J. Boock ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Cerebral Vasospasm ◽  
Cerebral Artery ◽  
Cerebral Arteries ◽  
Nerve Fibers ◽  
Content Type ◽  
The Right ◽  
Oxide Synthase ◽  
Fine Print

✓ To determine the distribution of nitric oxide synthase (NOS) in the primate cerebral artery nervi vasorum and to examine the potential role of NOS in cerebral vasospasm after subarachnoid hemorrhage (SAH) in primates, the distribution of NOS immunoreactivity (NOS-IR) in the major cerebral arteries was examined immunohistochemically in cynomolgus monkeys by the use of whole, mounted preparations of the circle of Willis. In four normal monkeys, NOS-IR was localized to the endothelial and adventitial layers of the large cerebral arteries. On the abluminal side, NOS-IR staining was densely concentrated in perivascular nerve fibers (nervi vasorum) of the anterior circulation. Staining was less prominent in the posterior circulation. In six monkeys with vasospasm on Day 7 after placement of preclotted arterial blood to form an SAH around the right middle cerebral artery (MCA) (42% ± 8.3% decrease of MCA area, mean ± standard deviation), NOS-IR was virtually absent in nerve fibers around the spastic right MCA but was normal on the contralateral side. In five monkeys in which vasospasm resolved by Day 14 after SAH (36% ± 14% decrease of right MCA area on Day 7, and 5% ± 14% decrease on Day 14), NOS-IR was also absent in the right MCA adventitial nerve fibers and remained normal in the left MCA. Adventitial NOS-IR was also normal in cerebral vessels of a sham-operated, nonspastic monkey. These findings provide further evidence that nitric oxide (NO) functions as a neuronal transmitter to mediate vasodilation in primates and indicate a role for adventitial NO in the pathogenesis of cerebral vasospasm after SAH in humans.

The effects of dexamethasone on C6 astrocytoma radiosensitivity

1989 ◽  
Vol 70 (5) ◽  
pp. 767-773 ◽  
Author(s):  
Carl D. Lordo ◽  
Eric C. Stroude ◽  
Rolando F. Del Maestro
Keyword(s):  
Three Dimensional ◽  
Inhibitory Effect ◽  
Plating Efficiency ◽  
Dexamethasone Treatment ◽  
Content Type ◽  
Astrocytoma Cells ◽  
C6 Astrocytoma ◽  
Radiation Induced ◽  
Fine Print

✓ Brain-tumor patients often undergo radiation therapy while receiving corticosteroids for the treatment of cerebral edema. Studies have demonstrated that dexamethasone is radioprotective in a number of cell lines. The C6 astrocytoma cell line is well established in vitro and is modulated by dexamethasone treatment. It has therefore been hypothesized that dexamethasone-treated C6 astrocytoma cells would be more resistant to radiation-induced damage. The present study was carried out to assess this hypothesis using both the in vitro C6 astrocytoma monolayer and three-dimensional multicellular spheroid models. Dexamethasone was inhibitory to the C6 astrocytoma cells in the monolayer preparation, increasing their doubling time by 13%. In the spheroid cultures, dexamethasone treatment decreased the number of cells per spheroid by 46%. Dexamethasone did not affect the plating efficiency of either the cells from the monolayer experiment or those dissociated from spheroids, however, suggesting that the inhibitory effect was not tumoricidal. At a clinical concentration (1.94 × 10−5 M), dexamethasone did not significantly influence plating efficiency of irradiated C6 astrocytoma cells in monolayer or three-dimensional spheroid cultures.

Is vasospasm related to proliferative arteriopathy?

1992 ◽  
Vol 77 (5) ◽  
pp. 740-748 ◽  
Author(s):  
Ryszard M. Pluta ◽  
Alois Zauner ◽  
Jay K. Morgan ◽  
Karin M. Muraszko ◽  
Edward H. Oldfield
Keyword(s):  
Cerebral Vasospasm ◽  
Vessel Diameter ◽  
Limited Range ◽  
Primate Model ◽  
Content Type ◽  
Morphological Studies ◽  
Dividing Cells ◽  
The Right ◽  
Fine Print

✓ Although proliferative arteriopathy has been postulated to play a role in the etiology of vasospasm after subarachnoid hemorrhage (SAH), histological and morphological studies examining cerebral vasospasm have produced conflicting results. To help settle this controversy, the authors used an in vivo label of cell division, bromodeoxycytidine, to assess cell proliferation in a primate model of SAH. Fifteen cynomolgus monkeys received a clot of either whole blood (11 animals) or red blood cells (four animals) placed around the right middle cerebral artery (MCA). On the day of surgery continuous intravenous infusion of bromodeoxycytidine was begun and continued until the animal was sacrificed immediately after arteriography on Day 7, 12, or 27 following surgery. Sections from the right and left MCA's were stained with a monoclonal antibody against bromodeoxcytidine, and labeled cells were counted. Arteriographic evidence of vasospasm occurred in nine monkeys on Day 7. On Day 12 and Day 27 no monkeys had persistent vasospasm. Placement of subarachnoid clot around the right MCA increased proliferative activity across all layers of the arterial wall. Most of the labeled cells were in the adventitia and the endothelium. Although there were more dividing cells in all layers of the right MCA than the left MCA (p < 0.01), the number of stained cells per section was limited (range 0.1 to 21.2, mean 8) and the occurrence of vasospasm was not associated with the number of dividing cells in the right MCA on Day 7, 12, 27, or for all days combined (p > 0.6). Cerebral vasospasm after SAH was not associated with the extent of proliferation of cells in the vessel wall, nor could the intensity of the limited proliferative changes have been responsible for narrowing of the vessel diameter.

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