I. Shalaby | University of Maryland School of Medicine (original) (raw)
Papers by I. Shalaby
Final results of a phase I study using oral temozolomide (TMZ) daily for 14 days with weekly paclitaxel in patients (pts) with advanced malignancies
Journal of Clinical Oncology, 2006
12020 Background: TMZ is an alkylating agent with activity in a variety of neoplasms. The optimal... more 12020 Background: TMZ is an alkylating agent with activity in a variety of neoplasms. The optimal schedule of administration for TMZ has not been established and only a few studies have studied it in combination with other agents. Repair of TMZ-induced DNA damage is associated with the activity of O-6 alkylguanine-DNA-alkyl transferase (AGT). Preclinical and clinical data indicate that prolonged exposure to TMZ results, not only in enhanced DNA alkylation, but also in depletion of AGT. This serves as the rationale to study TMZ using protracted schedules. Methods: The aim of this study was to determine the maximum tolerated dose (MTD) and dose limiting toxicity (DLT) of oral TMZ given daily for 14 days with weekly paclitaxel in pts with advanced cancers. Forty-five pts received 136 cycles of TMZ at escalating doses (50, 75, 100, 125 and 150 mg/m2/day × 14 days) plus paclitaxel at 80 mg/m2 on days 1, 8, and 15. Pts were stratified as lightly (LP) or heavily (HP) pretreated and MTD def...
![Research paper thumbnail of Maitotoxin-Induced Release of ?-[3H]Aminobutyric Acid from Cultures of Striatal Neurons](https://attachments.academia-assets.com/100522984/thumbnails/1.jpg)
](Journal of Neurochemistry, 1986
The potent marine toxin, maitotoxin, induced the release of y-[3H]aminobutyric acid (GABA) from r... more The potent marine toxin, maitotoxin, induced the release of y-[3H]aminobutyric acid (GABA) from reaggregate cultures of striatal neurons in a dose-dependent manner. Maitotoxin-induced release occurred following a lag period of several minutes and was persistent. Release induced by 70 m M K + on the other hand was immediate and transient in nature. Co2+ (3 rnM) and Cd2+ (1 mM) inhibited maitotoxin-induced release of GABA as did removal of extracellular Ca2+. However, the organic calcium antagonists nisoldipine, nitrendipine, and D-600 at concentrations of M did not block maitotoxin-induced or 70 m M K+-induced release. High concentrations of D-600 M) partially blocked both maitotoxin-and 70 mM K+-induced release. The dihydropyridine calcium agonist BAY K8644 M) did not enhance maitotoxin-induced or 70 mM K +-induced release. Replacement of N a + in the incubation medium with choline led to an increased basal output of GABA and an apparent inhibition of the effect of maitotoxin. These data are discussed with reference t o the hypothesis that rnaitotoxin can directly activate voltage-sensitive calcium channels. Key Words: Maitotoxin-y-Aminobutyric acid-Striatum-Neurons-Transmitter release. Shalaby I. A. et al. Maitotoxin-induced release of y-[3H]aminobutyric a c i d f r o m c u l t u r e s of striatal neurons.
Biochemical and morphological studies on GABA neurons in reaggregate culture
Brain Research, 1987
Acquired and Congenital Syphilis 095.8
Bioorganic & Medicinal Chemistry Letters, 1993
Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole result... more Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole results in a new series of 'non-traditional' NMDA antagonists. In combination with threo relative stereochemistry. @roved NMDA antagonist potency and selectivity may be achieved.
Neuroprotective effects of the N-methyl-D-aspartate receptor antagonists ifenprodil and SL-82,0715 on hippocampal cells in culture
The Journal of pharmacology and experimental therapeutics, 1992
The N-methyl-D-aspartate (NMDA) antagonists ifenprodil and SL-82,0715 were examined for neuroprot... more The N-methyl-D-aspartate (NMDA) antagonists ifenprodil and SL-82,0715 were examined for neuroprotective efficacy against glutamate toxicity of hippocampal neurons in culture. Hippocampal cells were grown on 96-well culture plates for 2 to 3 weeks and then exposed for a 15-min period to glutamate or NMDA. Neurodegeneration was quantified 24 hr after the excitotoxin exposure, by measuring the activity of lactate dehydrogenase leaked into the culture medium by the damaged cells. Glutamate induced a concentration-dependent increase in lactate dehydrogenase that reached 3-fold the activity of control cultures. The NMDA antagonists MK-801 and AP-7 blocked this neurotoxicity when added either during or after the glutamate exposure. Ifenprodil and SL-82,0715 blocked the neurotoxicity only when added during the excitotoxin exposure. Ifenprodil was 3 times more potent than SL-82,0715 in blocking glutamate or NMDA-induced neurotoxicity. Glycine did not reverse the neuroprotective effects of th...
Glycine reverses 7-Cl kynurenate blockade of glutamate neurotoxicity in cell culture
European Journal of Pharmacology, 1989
UK PubMed Central (UKPMC) is an archive of life sciences journal literature.
(1S, 2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol: A Potent New Neuroprotectant Which Blocks N-Methyl-D-Aspartate Responses
Journal of medicinal …, 1995
(1S,2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (20, CP-101,606) has been... more (1S,2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (20, CP-101,606) has been identified as a potent and selective N-methyl-D-aspartate (NMDA) antagonist through a structure activity relation (SAR) program based on ifenprodil, a known antihypertensive agent with NMDA antagonist activity. Sites on the threo-ifenprodil skeleton explored in this report include the pendent methyl group (H, methyl, and ethyl nearly equipotent; propyl much weaker), the spacer group connecting the C-4 phenyl group to the piperidine ring (an alternating potency pattern with 0 and 2 carbon atoms yielding the greatest potency), and simple phenyl substitution (little effect). While potent NMDA antagonists were obtained with a two atom spacer, this arrangement also increased alpha 1 adrenergic affinity. Introduction of a hydroxyl group into the C-4 position on these piperidine ring resulted in substantial reduction in alpha 1 adrenergic affinity. The combination of these observations was instrumental in the discovery of 20. This compound potently protects cultured hippocampal neurons from glutamate toxicity (IC50 = 10 nM) while possessing little of the undesired alpha 1 adrenergic affinity (IC50 approximately 20 microM) of ifenprodil. Furthermore, 20 appears to lack the psychomotor stimulant effects of nonselective competitive and channel-blocking NMDA antagonists. Thus, 20 shows great promise as a neuroprotective agent and may lack the side effects of compounds currently in clinical trials.
Chronic haloperidol treatment during prenatal and postnatal development was found to induce long-... more Chronic haloperidol treatment during prenatal and postnatal development was found to induce long-term behavioral and psychopharmacological effects. Rats tested shortly after termination of the chronic treatment at weaning or as young adults were hyperactive in the open field and exhibited an attenuated behavioral response t O amphetamine and an accentuated cataleptic response to later doses of haloperidol, when compared with control offspring of the same age. Tests at an intermediate interval (adolescence period) showed no significant difference from control offspring on any of these behavioral measures. Adult rats administered haloperidol chronically for the same duration were also hyperactive after termination of treatment. In contrast to the effects of haloperidol during development, these adults exhibited an accentuated behavioral response to amphetamine and an attenuated cataleptic response to a later dose of haloperidol. Compensatory mechanisms in response to chronic haloperidol treatment during development thus appear to be different from those in adulthood.
CP-101,606, a potent neuroprotectant selective for forebrain neurons
European journal of …, 1997
The neuroprotective activity of (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-pr... more The neuroprotective activity of (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP-101,606), an N-methyl-D-aspartate (NMDA) receptor antagonist structurally similar to ((+/-)-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-++ +piperidineethanol (ifenprodil), was investigated in neurons in primary culture. CP-101,606 potently and efficaciously protected hippocampal neurons from glutamate toxicity but was > 900-fold less effective for cerebellar granule neurons. The neuroprotective activity in the hippocampal neurons is mediated through a high affinity binding site distinct from the agonist and thienylcyclohexylpiperidine (TCP) binding sites of the NMDA receptor. Autoradiography indicates the CP-101,606 binding site is localized in forebrain, most notably in hippocampus and the outer layers of cortex. The functional selectivity for hippocampal neurons, forebrain localization of binding sites, and structural relation to ifenprodil suggest that CP-101,606 is an NMDA antagonist highly selective for NR2B subunit containing receptors.
Separation of. alpha. 1-adrenergic and N-methyl-D-aspartate antagonist activity in a series of ifenprodil compounds
Journal of medicinal …, 1991
Ifenprodil (1) represents a new class of N-methyl-D-aspartate (NMDA) antagonist. This drug also p... more Ifenprodil (1) represents a new class of N-methyl-D-aspartate (NMDA) antagonist. This drug also possesses potent activity at several other brain receptors (most notably alpha 1 adrenergic receptors). We have prepared the enantiomers and diastereomers of ifenprodil along with a series of partial structures in order to explore the basic structure activity relations within this class of compounds. From this study, it is clear that alpha 1 adrenergic and NMDA receptor activities may be separated by selection of the threo relative stereochemistry. Examination of the optical isomers of threo-ifenprodil (2) reveals that no further improvement in receptor selectivity is gained from either antipode. Individual removal of most of the structural fragments from the ifenprodil molecule generally results in less active compounds although fluorinated derivative 9 with threo relative stereochemistry is somewhat more potent and substantially more selective for the NMDA receptor. Finally a minimum structure for activity in this series (14) has been identified. This stripped-down version of ifenprodil possesses nearly equivalent affinity for the NMDA receptor with no selectivity over alpha 1 adrenergic receptors.
Bioorganic & Medicinal Chemistry Letters, 1993
Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole result... more Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole results in a new series of 'non-traditional' NMDA antagonists.
The effects of dihydropyridines on neurotransmitter release from cultured neuronal cells
Life sciences, Jan 17, 1984
Depolarizing stimuli increase the release of transmitter substances from cultured PC12 pheochromo... more Depolarizing stimuli increase the release of transmitter substances from cultured PC12 pheochromocytoma cells and reaggregate cultures of mouse mesencephalic dopamine neurones. We measured the stimulated release of (3H) norepinephrine and (3H) dopamine from these systems respectively. In the cultured mouse dopaminergic neurones, several organic calcium channel blockers including nitrendipine, D-600, verapamil and diltiazem were unable to inhibit potassium-evoked transmitter release. However, release was blocked by 3 mM cobalt. The novel dihydropyridine calcium channel agonist BAY K8644 also had no effect on basal or evoked dopamine release. In contrast, BAY K8644 greatly stimulated the potassium-evoked release of (3H) norepinephrine from PC12 cells. The BAY K8644 enhanced release could be blocked by the dihydropyridine antagonist nitrendipine. These results indicate that while stimulus-secretion coupling in the PC12 cell line involves dihydropyridine sensitive calcium channels, this...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1983
Dissociated dopamine (DA) neurons from 14-day fetal mice were dissected from the rostral mesencep... more Dissociated dopamine (DA) neurons from 14-day fetal mice were dissected from the rostral mesencephalic tegmentum (RMT) and were allowed to reaggregate in vitro with cells from the corpus striatum (CS). As previously demonstrated under these conditions, DA neurons develop punctate fluorescent varicosities and the capacity to synthesize, accumulate, and retain DA (Kotake, C., P. C. Hoffmann, and A. Heller (1982) J. Neurosci. 2: 1307-1315). After 17 to 22 days in culture, the RMT-CS coaggregates were assessed for their ability to release DA. Coaggregates were incubated in 5.6 x 10(-6) M [3H]DA, washed, and then superfused at 100 microliters/min for 2 hr. Fractions were collected every 2 min. Basal efflux of [3H]DA/2 min was 1% of tissue stores of 3H. K+, 70 mM infused for 8 min induced a peak release of 5.87% of tissue stores of 3H, and 50 mM K+ induced a peak release of 2.13%. The potassium-induced release of [3H]DA was calcium dependent. When d-amphetamine was infused for 12 min, 100...
ChemInform Abstract: 5,7-Dihydro-3-(2-(1-(phenylmethyl)-4-piperidinyl)ethyl)-6H-pyrrolo(3,2- f)-1,2-benzisoxazol-6-one: A Potent and Centrally-Selective Inhibitor of Acetylcholinesterase with an Improved Margin of Safety
ChemInform, 1995
Proceedings of the National Academy of Sciences, 1988
We have studied three low molecular weight phosphoproteins, 000,000,000, respectively) in reaggre... more We have studied three low molecular weight phosphoproteins, 000,000,000, respectively) in reaggregate cultures from various regions of fetal mouse brain. ARPP-16 and ARPP-21 were detected only in striatal and cortical cultures. In contrast, ARPP-19, which is structurally related to ARPP-16, was also present in reaggregate cultures prepared from thalamus and ventral and dorsal mesencephalon, as well as in monolayer cultures of astroglial cells. In striatal aggregates cultured over a 3-week period, the relative levels of ARPP-16, ARPP-21, and synapsin I/protein HIa (synaptic vesicle-associated phosphoproteins closely related to each other and treated as a single entity in the present study) increased with time, whereas the level of ARPP-19 decreased. Incubation of striatal aggregates with 8-Br-cAMP, forskolin, or vasoactive intestinal peptide increased the phosphorylation of all these proteins. We conclude that the state of phosphorylation of two proteins enriched in specific neurons (ARPP-16 and ARPP-21) and two more widely distributed proteins (ARPP-19 and synapsin I/protein IIla) is regulated by cAMP and vasoactive intestinal peptide in striatal cells in culture. These phosphoproteins may therefore play a role in mediating some of the actions of vasoactive intestinal peptide in the caudate-putamen.
Neuroscience, 1987
influence of hippocampal target cells on the development of cholinergic septal neurons was studie... more influence of hippocampal target cells on the development of cholinergic septal neurons was studied in rotation-mediated reaggregating cell cultures. Brain cells from 15-day-old mouse embryos were obtained from: (i) septum, containing cholinergic cells which project to the hippocampus; (ii) hippocampus which contains target cells for the septal cholinergic neurons; and (iii) cerebellum, containing cells which are not targets for the septal cholinergic cells. The cells were then cultured for 3 weeks in a rotary incubator in the following combinations: (a) septal cells alone; (b) hippocampal cells alone; (c) cerebellar cells alone; (d) septal-hippocampal cells together; and (e) septal-cerebellar cells together. After harvesting, fixation, and embedding, 50 pm sections were cut and processed for visualization of acctylcholinesterase activity. Sections from reaggregates containing either hippocampal or cerebellar cells alone contained only a few acetylcholinesterase-positive cells, but no positive fibers. Sections from septal-hippocampal coaggregates revealed a pattern of well-defined, fine-caliber acetylcholinesterase-positive fibers with extensive arborizations and varicosities suggesting axonal proliferation. In septal-cerebellar coaggregates, acetylcholinesterase-positive fibers appeared to be degenerating and distinct areas were observed which were essentially devoid of acetylcholinesterase fibers. In some experiments, either cerebellar or hippocampal cells were labeled with wheatgerm agglutinin-rhodamine prior to culture in order to identify these cells in the resulting reaggregates. Analysis of sections from these studies showed that acetylcholinesterase fibers were excluded from regions of coaggregates containing cerebellar cells, but were present in regions of coaggregates containing hippocampal cells. Finally, cell counts of acetylcholinesterase-positive cells in the various combinations revealed that these putative cholinergic neurons were significantly more numerous in septal-hippocampal coaggregates (271 + 19 per lo6 septal cells added) than in septal reaggregates (38 f 6 per lo6 septal cells added) or septal-cerebellar coaggregates (85 f 29 per lo6 septal cells added). These results, taken together, suggest that hippocampal target cells influence the development and survival of cholinergic neurons.
Glutamate Receptor Ion Channel Properties Predict Vulnerability to Cytotoxicity in a Transfected Nonneuronal Cell Line
Molecular and Cellular Neuroscience, 1996
Excessive activation of glutamate receptors is thought to play a critical role in neuronal excito... more Excessive activation of glutamate receptors is thought to play a critical role in neuronal excitotoxicity. To compare the cytotoxic potential of different glutamate receptor subtypes and correlate receptor biophysical properties with cytotoxicity, we have expressed recombinant receptors in human embryonic kidney 293 (HEK-293) cells. Survival of transfected cells was analyzed under conditions of defined agonist concentration and exposure time. For HEK-293 cells transfected with N-methyl-D-aspartate (NMDA) receptors, the EC50 for NMDA-induced cytotoxicity was 300 microM. Experiments using ion substitution, or cells expressing mutant NMDA receptors with low calcium permeability, suggested that both calcium and sodium influx through NMDA receptors contributed to cytotoxicity. In contrast, cytotoxicity was not observed in cells transfected with calcium permeable alpha-amino 3-hydroxy-5-methyl-4-isoxazole propionate- or kainate-type glutamate receptors even at saturating agonist concentrations, unless inhibitors of agonist-dependent desensitization were included. These results directly demonstrate that calcium permeability and desensitization kinetics play important roles in determining the excitotoxic potential of different glutamate receptor subtypes.
Developmental Brain Research, 1990
Key words Dopamlne-and adenosine 3".5"-monophosphate-regulated neuronal phosphoprotem; Ontogeny, ... more Key words Dopamlne-and adenosine 3".5"-monophosphate-regulated neuronal phosphoprotem; Ontogeny, Substantia nlgra, Tyroslne hydroxylase, Reaggregate culture DARPP-32, a dopamlne-and adenosine 3".5"-monophosphate regulated neuronal phosphoproteln, M r 32 kDa, is a phenotypic marker of the medium-size spiny neurons of the mammalian caudate-putamen In the present study, we exammed the ontogeny of DARPP-32 protein and mRNA, and compared it to the ontogeny of tyroslne hydroxylase and synapsln I, a synaptic-veslcle phosphoproteln In VlVO, the amount of DARPP-32 protein per mg total protein increased throughout the first three postnatal weeks, and then declined to plateau at adult levels The mRNA level closely paralleled the protein, except that its rise preceded that of the protein Tyroslne hydroxylase levels rose throughout the first 4 postnatal weeks, and synapsin I levels rose steadily during the same period Primary reaggregate cultures containing cells from the caudate-putamen expressed DARPP-32 with a time course similar to that seen m VlVO The level of expression was not altered by coculturing with dopaminerglc neurons from the rostral mesencephallc tegmentum Thus, the postnatal increase in DARPP-32 levels in the caudate-putamen appears to be independent of transsynaptlc or end-organ influences from the substantla mgra 0165-3806/90/$03 50
Release of dopamine from mesencephalic neurons in aggregate cultures: influence of target and non-target cells
Brain Research, 1984
Spontaneous release of [3H]dopamine (DA) was observed from reaggregates of dissociated cells from... more Spontaneous release of [3H]dopamine (DA) was observed from reaggregates of dissociated cells from fetal rostral mesencephalic tegmentum (RMT) containing DA neurons cocultured with their axonal target cells from striatum (CS) or frontal cortex (FCx), or with non-target cells from occipital cortex (OCx), or tectum. Such release increased in response to 50 mM K+. Tetrodotoxin (TTX) suppressed the spontaneous release from RMT-CS and RMT-FCx reaggregates by 42%; from RMT-tectum reaggregates by 24%, and did not significantly inhibit the release from RMT-OCx cocultures. Since TTX blocks spontaneous neuronal activity, these results suggest that the presence of axonal target cells enhances the activity of the dopamine neurons. DA neurons within RMT-FCx reaggregates released significantly more [3H]DA in response to 50 mM K+ than in RMT-CS cocultures. This result is in accord with the findings in vivo that inhibitory feedback mechanisms on DA release, present in the striatum, are lacking in the frontal cortex.
Final results of a phase I study using oral temozolomide (TMZ) daily for 14 days with weekly paclitaxel in patients (pts) with advanced malignancies
Journal of Clinical Oncology, 2006
12020 Background: TMZ is an alkylating agent with activity in a variety of neoplasms. The optimal... more 12020 Background: TMZ is an alkylating agent with activity in a variety of neoplasms. The optimal schedule of administration for TMZ has not been established and only a few studies have studied it in combination with other agents. Repair of TMZ-induced DNA damage is associated with the activity of O-6 alkylguanine-DNA-alkyl transferase (AGT). Preclinical and clinical data indicate that prolonged exposure to TMZ results, not only in enhanced DNA alkylation, but also in depletion of AGT. This serves as the rationale to study TMZ using protracted schedules. Methods: The aim of this study was to determine the maximum tolerated dose (MTD) and dose limiting toxicity (DLT) of oral TMZ given daily for 14 days with weekly paclitaxel in pts with advanced cancers. Forty-five pts received 136 cycles of TMZ at escalating doses (50, 75, 100, 125 and 150 mg/m2/day × 14 days) plus paclitaxel at 80 mg/m2 on days 1, 8, and 15. Pts were stratified as lightly (LP) or heavily (HP) pretreated and MTD def...
Journal of Neurochemistry, 1986
The potent marine toxin, maitotoxin, induced the release of y-[3H]aminobutyric acid (GABA) from r... more The potent marine toxin, maitotoxin, induced the release of y-[3H]aminobutyric acid (GABA) from reaggregate cultures of striatal neurons in a dose-dependent manner. Maitotoxin-induced release occurred following a lag period of several minutes and was persistent. Release induced by 70 m M K + on the other hand was immediate and transient in nature. Co2+ (3 rnM) and Cd2+ (1 mM) inhibited maitotoxin-induced release of GABA as did removal of extracellular Ca2+. However, the organic calcium antagonists nisoldipine, nitrendipine, and D-600 at concentrations of M did not block maitotoxin-induced or 70 m M K+-induced release. High concentrations of D-600 M) partially blocked both maitotoxin-and 70 mM K+-induced release. The dihydropyridine calcium agonist BAY K8644 M) did not enhance maitotoxin-induced or 70 mM K +-induced release. Replacement of N a + in the incubation medium with choline led to an increased basal output of GABA and an apparent inhibition of the effect of maitotoxin. These data are discussed with reference t o the hypothesis that rnaitotoxin can directly activate voltage-sensitive calcium channels. Key Words: Maitotoxin-y-Aminobutyric acid-Striatum-Neurons-Transmitter release. Shalaby I. A. et al. Maitotoxin-induced release of y-[3H]aminobutyric a c i d f r o m c u l t u r e s of striatal neurons.
Biochemical and morphological studies on GABA neurons in reaggregate culture
Brain Research, 1987
Acquired and Congenital Syphilis 095.8
Bioorganic & Medicinal Chemistry Letters, 1993
Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole result... more Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole results in a new series of 'non-traditional' NMDA antagonists. In combination with threo relative stereochemistry. @roved NMDA antagonist potency and selectivity may be achieved.
Neuroprotective effects of the N-methyl-D-aspartate receptor antagonists ifenprodil and SL-82,0715 on hippocampal cells in culture
The Journal of pharmacology and experimental therapeutics, 1992
The N-methyl-D-aspartate (NMDA) antagonists ifenprodil and SL-82,0715 were examined for neuroprot... more The N-methyl-D-aspartate (NMDA) antagonists ifenprodil and SL-82,0715 were examined for neuroprotective efficacy against glutamate toxicity of hippocampal neurons in culture. Hippocampal cells were grown on 96-well culture plates for 2 to 3 weeks and then exposed for a 15-min period to glutamate or NMDA. Neurodegeneration was quantified 24 hr after the excitotoxin exposure, by measuring the activity of lactate dehydrogenase leaked into the culture medium by the damaged cells. Glutamate induced a concentration-dependent increase in lactate dehydrogenase that reached 3-fold the activity of control cultures. The NMDA antagonists MK-801 and AP-7 blocked this neurotoxicity when added either during or after the glutamate exposure. Ifenprodil and SL-82,0715 blocked the neurotoxicity only when added during the excitotoxin exposure. Ifenprodil was 3 times more potent than SL-82,0715 in blocking glutamate or NMDA-induced neurotoxicity. Glycine did not reverse the neuroprotective effects of th...
Glycine reverses 7-Cl kynurenate blockade of glutamate neurotoxicity in cell culture
European Journal of Pharmacology, 1989
UK PubMed Central (UKPMC) is an archive of life sciences journal literature.
(1S, 2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol: A Potent New Neuroprotectant Which Blocks N-Methyl-D-Aspartate Responses
Journal of medicinal …, 1995
(1S,2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (20, CP-101,606) has been... more (1S,2S)-1-(4-Hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (20, CP-101,606) has been identified as a potent and selective N-methyl-D-aspartate (NMDA) antagonist through a structure activity relation (SAR) program based on ifenprodil, a known antihypertensive agent with NMDA antagonist activity. Sites on the threo-ifenprodil skeleton explored in this report include the pendent methyl group (H, methyl, and ethyl nearly equipotent; propyl much weaker), the spacer group connecting the C-4 phenyl group to the piperidine ring (an alternating potency pattern with 0 and 2 carbon atoms yielding the greatest potency), and simple phenyl substitution (little effect). While potent NMDA antagonists were obtained with a two atom spacer, this arrangement also increased alpha 1 adrenergic affinity. Introduction of a hydroxyl group into the C-4 position on these piperidine ring resulted in substantial reduction in alpha 1 adrenergic affinity. The combination of these observations was instrumental in the discovery of 20. This compound potently protects cultured hippocampal neurons from glutamate toxicity (IC50 = 10 nM) while possessing little of the undesired alpha 1 adrenergic affinity (IC50 approximately 20 microM) of ifenprodil. Furthermore, 20 appears to lack the psychomotor stimulant effects of nonselective competitive and channel-blocking NMDA antagonists. Thus, 20 shows great promise as a neuroprotective agent and may lack the side effects of compounds currently in clinical trials.
Chronic haloperidol treatment during prenatal and postnatal development was found to induce long-... more Chronic haloperidol treatment during prenatal and postnatal development was found to induce long-term behavioral and psychopharmacological effects. Rats tested shortly after termination of the chronic treatment at weaning or as young adults were hyperactive in the open field and exhibited an attenuated behavioral response t O amphetamine and an accentuated cataleptic response to later doses of haloperidol, when compared with control offspring of the same age. Tests at an intermediate interval (adolescence period) showed no significant difference from control offspring on any of these behavioral measures. Adult rats administered haloperidol chronically for the same duration were also hyperactive after termination of treatment. In contrast to the effects of haloperidol during development, these adults exhibited an accentuated behavioral response to amphetamine and an attenuated cataleptic response to a later dose of haloperidol. Compensatory mechanisms in response to chronic haloperidol treatment during development thus appear to be different from those in adulthood.
CP-101,606, a potent neuroprotectant selective for forebrain neurons
European journal of …, 1997
The neuroprotective activity of (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-pr... more The neuroprotective activity of (1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP-101,606), an N-methyl-D-aspartate (NMDA) receptor antagonist structurally similar to ((+/-)-(R*,S*)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-++ +piperidineethanol (ifenprodil), was investigated in neurons in primary culture. CP-101,606 potently and efficaciously protected hippocampal neurons from glutamate toxicity but was > 900-fold less effective for cerebellar granule neurons. The neuroprotective activity in the hippocampal neurons is mediated through a high affinity binding site distinct from the agonist and thienylcyclohexylpiperidine (TCP) binding sites of the NMDA receptor. Autoradiography indicates the CP-101,606 binding site is localized in forebrain, most notably in hippocampus and the outer layers of cortex. The functional selectivity for hippocampal neurons, forebrain localization of binding sites, and structural relation to ifenprodil suggest that CP-101,606 is an NMDA antagonist highly selective for NR2B subunit containing receptors.
Separation of. alpha. 1-adrenergic and N-methyl-D-aspartate antagonist activity in a series of ifenprodil compounds
Journal of medicinal …, 1991
Ifenprodil (1) represents a new class of N-methyl-D-aspartate (NMDA) antagonist. This drug also p... more Ifenprodil (1) represents a new class of N-methyl-D-aspartate (NMDA) antagonist. This drug also possesses potent activity at several other brain receptors (most notably alpha 1 adrenergic receptors). We have prepared the enantiomers and diastereomers of ifenprodil along with a series of partial structures in order to explore the basic structure activity relations within this class of compounds. From this study, it is clear that alpha 1 adrenergic and NMDA receptor activities may be separated by selection of the threo relative stereochemistry. Examination of the optical isomers of threo-ifenprodil (2) reveals that no further improvement in receptor selectivity is gained from either antipode. Individual removal of most of the structural fragments from the ifenprodil molecule generally results in less active compounds although fluorinated derivative 9 with threo relative stereochemistry is somewhat more potent and substantially more selective for the NMDA receptor. Finally a minimum structure for activity in this series (14) has been identified. This stripped-down version of ifenprodil possesses nearly equivalent affinity for the NMDA receptor with no selectivity over alpha 1 adrenergic receptors.
Bioorganic & Medicinal Chemistry Letters, 1993
Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole result... more Replacement of the phenol group in noncompetitive NMDA antagonist ifenprodil with oxindole results in a new series of 'non-traditional' NMDA antagonists.
The effects of dihydropyridines on neurotransmitter release from cultured neuronal cells
Life sciences, Jan 17, 1984
Depolarizing stimuli increase the release of transmitter substances from cultured PC12 pheochromo... more Depolarizing stimuli increase the release of transmitter substances from cultured PC12 pheochromocytoma cells and reaggregate cultures of mouse mesencephalic dopamine neurones. We measured the stimulated release of (3H) norepinephrine and (3H) dopamine from these systems respectively. In the cultured mouse dopaminergic neurones, several organic calcium channel blockers including nitrendipine, D-600, verapamil and diltiazem were unable to inhibit potassium-evoked transmitter release. However, release was blocked by 3 mM cobalt. The novel dihydropyridine calcium channel agonist BAY K8644 also had no effect on basal or evoked dopamine release. In contrast, BAY K8644 greatly stimulated the potassium-evoked release of (3H) norepinephrine from PC12 cells. The BAY K8644 enhanced release could be blocked by the dihydropyridine antagonist nitrendipine. These results indicate that while stimulus-secretion coupling in the PC12 cell line involves dihydropyridine sensitive calcium channels, this...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1983
Dissociated dopamine (DA) neurons from 14-day fetal mice were dissected from the rostral mesencep... more Dissociated dopamine (DA) neurons from 14-day fetal mice were dissected from the rostral mesencephalic tegmentum (RMT) and were allowed to reaggregate in vitro with cells from the corpus striatum (CS). As previously demonstrated under these conditions, DA neurons develop punctate fluorescent varicosities and the capacity to synthesize, accumulate, and retain DA (Kotake, C., P. C. Hoffmann, and A. Heller (1982) J. Neurosci. 2: 1307-1315). After 17 to 22 days in culture, the RMT-CS coaggregates were assessed for their ability to release DA. Coaggregates were incubated in 5.6 x 10(-6) M [3H]DA, washed, and then superfused at 100 microliters/min for 2 hr. Fractions were collected every 2 min. Basal efflux of [3H]DA/2 min was 1% of tissue stores of 3H. K+, 70 mM infused for 8 min induced a peak release of 5.87% of tissue stores of 3H, and 50 mM K+ induced a peak release of 2.13%. The potassium-induced release of [3H]DA was calcium dependent. When d-amphetamine was infused for 12 min, 100...
ChemInform Abstract: 5,7-Dihydro-3-(2-(1-(phenylmethyl)-4-piperidinyl)ethyl)-6H-pyrrolo(3,2- f)-1,2-benzisoxazol-6-one: A Potent and Centrally-Selective Inhibitor of Acetylcholinesterase with an Improved Margin of Safety
ChemInform, 1995
Proceedings of the National Academy of Sciences, 1988
We have studied three low molecular weight phosphoproteins, 000,000,000, respectively) in reaggre... more We have studied three low molecular weight phosphoproteins, 000,000,000, respectively) in reaggregate cultures from various regions of fetal mouse brain. ARPP-16 and ARPP-21 were detected only in striatal and cortical cultures. In contrast, ARPP-19, which is structurally related to ARPP-16, was also present in reaggregate cultures prepared from thalamus and ventral and dorsal mesencephalon, as well as in monolayer cultures of astroglial cells. In striatal aggregates cultured over a 3-week period, the relative levels of ARPP-16, ARPP-21, and synapsin I/protein HIa (synaptic vesicle-associated phosphoproteins closely related to each other and treated as a single entity in the present study) increased with time, whereas the level of ARPP-19 decreased. Incubation of striatal aggregates with 8-Br-cAMP, forskolin, or vasoactive intestinal peptide increased the phosphorylation of all these proteins. We conclude that the state of phosphorylation of two proteins enriched in specific neurons (ARPP-16 and ARPP-21) and two more widely distributed proteins (ARPP-19 and synapsin I/protein IIla) is regulated by cAMP and vasoactive intestinal peptide in striatal cells in culture. These phosphoproteins may therefore play a role in mediating some of the actions of vasoactive intestinal peptide in the caudate-putamen.
Neuroscience, 1987
influence of hippocampal target cells on the development of cholinergic septal neurons was studie... more influence of hippocampal target cells on the development of cholinergic septal neurons was studied in rotation-mediated reaggregating cell cultures. Brain cells from 15-day-old mouse embryos were obtained from: (i) septum, containing cholinergic cells which project to the hippocampus; (ii) hippocampus which contains target cells for the septal cholinergic neurons; and (iii) cerebellum, containing cells which are not targets for the septal cholinergic cells. The cells were then cultured for 3 weeks in a rotary incubator in the following combinations: (a) septal cells alone; (b) hippocampal cells alone; (c) cerebellar cells alone; (d) septal-hippocampal cells together; and (e) septal-cerebellar cells together. After harvesting, fixation, and embedding, 50 pm sections were cut and processed for visualization of acctylcholinesterase activity. Sections from reaggregates containing either hippocampal or cerebellar cells alone contained only a few acetylcholinesterase-positive cells, but no positive fibers. Sections from septal-hippocampal coaggregates revealed a pattern of well-defined, fine-caliber acetylcholinesterase-positive fibers with extensive arborizations and varicosities suggesting axonal proliferation. In septal-cerebellar coaggregates, acetylcholinesterase-positive fibers appeared to be degenerating and distinct areas were observed which were essentially devoid of acetylcholinesterase fibers. In some experiments, either cerebellar or hippocampal cells were labeled with wheatgerm agglutinin-rhodamine prior to culture in order to identify these cells in the resulting reaggregates. Analysis of sections from these studies showed that acetylcholinesterase fibers were excluded from regions of coaggregates containing cerebellar cells, but were present in regions of coaggregates containing hippocampal cells. Finally, cell counts of acetylcholinesterase-positive cells in the various combinations revealed that these putative cholinergic neurons were significantly more numerous in septal-hippocampal coaggregates (271 + 19 per lo6 septal cells added) than in septal reaggregates (38 f 6 per lo6 septal cells added) or septal-cerebellar coaggregates (85 f 29 per lo6 septal cells added). These results, taken together, suggest that hippocampal target cells influence the development and survival of cholinergic neurons.
Glutamate Receptor Ion Channel Properties Predict Vulnerability to Cytotoxicity in a Transfected Nonneuronal Cell Line
Molecular and Cellular Neuroscience, 1996
Excessive activation of glutamate receptors is thought to play a critical role in neuronal excito... more Excessive activation of glutamate receptors is thought to play a critical role in neuronal excitotoxicity. To compare the cytotoxic potential of different glutamate receptor subtypes and correlate receptor biophysical properties with cytotoxicity, we have expressed recombinant receptors in human embryonic kidney 293 (HEK-293) cells. Survival of transfected cells was analyzed under conditions of defined agonist concentration and exposure time. For HEK-293 cells transfected with N-methyl-D-aspartate (NMDA) receptors, the EC50 for NMDA-induced cytotoxicity was 300 microM. Experiments using ion substitution, or cells expressing mutant NMDA receptors with low calcium permeability, suggested that both calcium and sodium influx through NMDA receptors contributed to cytotoxicity. In contrast, cytotoxicity was not observed in cells transfected with calcium permeable alpha-amino 3-hydroxy-5-methyl-4-isoxazole propionate- or kainate-type glutamate receptors even at saturating agonist concentrations, unless inhibitors of agonist-dependent desensitization were included. These results directly demonstrate that calcium permeability and desensitization kinetics play important roles in determining the excitotoxic potential of different glutamate receptor subtypes.
Developmental Brain Research, 1990
Key words Dopamlne-and adenosine 3".5"-monophosphate-regulated neuronal phosphoprotem; Ontogeny, ... more Key words Dopamlne-and adenosine 3".5"-monophosphate-regulated neuronal phosphoprotem; Ontogeny, Substantia nlgra, Tyroslne hydroxylase, Reaggregate culture DARPP-32, a dopamlne-and adenosine 3".5"-monophosphate regulated neuronal phosphoproteln, M r 32 kDa, is a phenotypic marker of the medium-size spiny neurons of the mammalian caudate-putamen In the present study, we exammed the ontogeny of DARPP-32 protein and mRNA, and compared it to the ontogeny of tyroslne hydroxylase and synapsln I, a synaptic-veslcle phosphoproteln In VlVO, the amount of DARPP-32 protein per mg total protein increased throughout the first three postnatal weeks, and then declined to plateau at adult levels The mRNA level closely paralleled the protein, except that its rise preceded that of the protein Tyroslne hydroxylase levels rose throughout the first 4 postnatal weeks, and synapsin I levels rose steadily during the same period Primary reaggregate cultures containing cells from the caudate-putamen expressed DARPP-32 with a time course similar to that seen m VlVO The level of expression was not altered by coculturing with dopaminerglc neurons from the rostral mesencephallc tegmentum Thus, the postnatal increase in DARPP-32 levels in the caudate-putamen appears to be independent of transsynaptlc or end-organ influences from the substantla mgra 0165-3806/90/$03 50
Release of dopamine from mesencephalic neurons in aggregate cultures: influence of target and non-target cells
Brain Research, 1984
Spontaneous release of [3H]dopamine (DA) was observed from reaggregates of dissociated cells from... more Spontaneous release of [3H]dopamine (DA) was observed from reaggregates of dissociated cells from fetal rostral mesencephalic tegmentum (RMT) containing DA neurons cocultured with their axonal target cells from striatum (CS) or frontal cortex (FCx), or with non-target cells from occipital cortex (OCx), or tectum. Such release increased in response to 50 mM K+. Tetrodotoxin (TTX) suppressed the spontaneous release from RMT-CS and RMT-FCx reaggregates by 42%; from RMT-tectum reaggregates by 24%, and did not significantly inhibit the release from RMT-OCx cocultures. Since TTX blocks spontaneous neuronal activity, these results suggest that the presence of axonal target cells enhances the activity of the dopamine neurons. DA neurons within RMT-FCx reaggregates released significantly more [3H]DA in response to 50 mM K+ than in RMT-CS cocultures. This result is in accord with the findings in vivo that inhibitory feedback mechanisms on DA release, present in the striatum, are lacking in the frontal cortex.