Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 7 de 7
Filter
Add more filters










Database
Language
Publication year range
1.
J Neurochem ; 136(4): 692-697, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26561358

ABSTRACT

The enantiomers of erythro-3-hydroxyaspartate were tested for activity at glutamate transporters and NMDA receptors. Both enantiomers inhibited glutamate transporters in rat hippocampal crude synaptosomes and elicited substrate-like activity at excitatory amino acid transporter 1, 2, and 3 as measured by voltage clamp in the Xenopus oocyte expression system. The enantiomers had similar affinities, but the D-enantiomer showed a lower maximal effect at excitatory amino acid transporter 1, 2, and 3 than the L-enantiomer. Surprisingly, D-erythro-3-hydroxyaspartate was a potent NMDA receptor agonist with an EC50 value in rat hippocampal neurons of 320 nM, whereas the L-enantiomer was 100-fold less potent. L-erythro-3-hydroxyaspartate showed activity at both glutamate transporters and NMDA receptors at concentrations that are reported to inhibit serine racemase, indicating a lack of selectivity. This enantiomeric pair may assist in shedding further light on the structural requirements for substrate activity at glutamate transporters and for agonist activity at NMDA receptors. The erythro enantiomers of 3-hydroxyaspartate had interesting and surprising effects on glutamate neurotransmitter systems. L-erythro-3-hydroxyaspartate had activity at both glutamate transporters (EAAT1/2/3) and NMDA receptors. D-erythro-3-hydroxyaspartate acted on EAATs, but was also identified as a highly potent NMDA receptor agonist. These enantiomers shed further light on the structural requirements for activity at EAATs and NMDA receptors.

2.
Neuropharmacology ; 97: 436-46, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26002625

ABSTRACT

Understanding the storage and release of the excitatory neurotransmitter, L-glutamate by synaptic vesicles has lagged behind receptor characterizations due to a lack of pharmacological agents. We report that the glutamate analog, 3-aminoglutarate (3-AG) is a "silent" false transmitter for glutamate neurons that may be a useful tool to study storage and release mechanisms. Like L-glutamate itself, 3-AG is a high-affinity substrate for both the plasma membrane (EAATs) and vesicular (vGLUT) glutamate transporters. As such, EAATs facilitate 3-AG entry into neuronal cytoplasm allowing 3-AG to compete with L-glutamate for transport into vesicles thus reducing glutamate content. In a synaptosomal preparation, 3-AG inhibited calcium-dependent endogenous L-glutamate release. Unlike L-glutamate, 3-AG had low affinity for both ionotropic (NMDA and AMPA) and G-protein coupled (mGlu1-8) receptors. Consequently, 3-AG behaves as a "silent" false transmitter that may be used in physiological experiments to probe synaptic vesicle storage and release mechanisms for L-glutamate. The companion paper by Wu et al. (2015) describes initial experiments that explore the effects of 3-AG on glutamate synaptic transmission under physiological and pathophysiological conditions.


Subject(s)
Glutamates/pharmacology , Glutamic Acid/metabolism , Neurons/drug effects , Neurotransmitter Agents/pharmacology , Animals , Calcium/metabolism , Cell Membrane/drug effects , Cell Membrane/metabolism , Cells, Cultured , Dose-Response Relationship, Drug , Glutamate Plasma Membrane Transport Proteins/genetics , Glutamate Plasma Membrane Transport Proteins/metabolism , Hippocampus/drug effects , Hippocampus/physiology , Humans , Membrane Potentials/drug effects , Membrane Potentials/physiology , Neurons/physiology , Oocytes , Prosencephalon/drug effects , Prosencephalon/physiology , Rats, Wistar , Receptors, G-Protein-Coupled/metabolism , Receptors, Ionotropic Glutamate/metabolism , Synaptic Vesicles/drug effects , Synaptic Vesicles/metabolism , Xenopus
3.
Curr Eye Res ; 34(3): 184-95, 2009 Mar.
Article in English | MEDLINE | ID: mdl-19274525

ABSTRACT

PURPOSE: The prostamide bimatoprost and prostanoid FP receptor agonists are highly efficacious drugs for glaucoma treatment. The presence of both prostamide and prostanoid FP receptors in bimatoprost-sensitive preparations has made prostamide receptor classification difficult. This study investigated a novel bimatoprost-sensitive preparation. METHODS: Human peripheral blood T lymphoblasts (Molt-3) and human osteoblasts (hFOB) were cultured for intracellular calcium signaling studies and quantitative real-time PCR analysis of RNA. RESULTS: Bimatoprost stimulated concentration-related increases in [Ca(2 +)](i) in a human T-cell line that does not express human FP receptor/variants, according to PCR analysis. The calcium signal induced by bimatoprost was not antagonized by prostanoid FP receptor antagonist/partial agonist AL-8810 or selective TP receptor antagonist SQ 29548. Conversely, bimatoprost did not elevate [Ca(2 +)](i) in human osteoblasts, which were confirmed to contain RNA of human FP receptor/variants. CONCLUSIONS: Molt-3 cells have been identified as a bimatoprost-sensitive preparation in which the activity of bimatoprost is independent of prostanoid FP receptors.


Subject(s)
Amides/pharmacology , Antihypertensive Agents/pharmacology , Calcium Signaling/drug effects , Calcium/metabolism , Cloprostenol/analogs & derivatives , Receptors, Prostaglandin/metabolism , Receptors, Thromboxane/metabolism , T-Lymphocytes/metabolism , Bimatoprost , Cell Proliferation/drug effects , Cell Survival , Cells, Cultured , Cloprostenol/pharmacology , Dose-Response Relationship, Drug , Humans , Osteoblasts/metabolism , Receptors, Prostaglandin/agonists , Receptors, Prostaglandin/antagonists & inhibitors , Receptors, Thromboxane/agonists , Receptors, Thromboxane/antagonists & inhibitors , Reverse Transcriptase Polymerase Chain Reaction
5.
Cardiovasc Drug Rev ; 23(3): 231-46, 2005.
Article in English | MEDLINE | ID: mdl-16252016

ABSTRACT

Bimatoprost is a safe and well-tolerated intraocular pressure (IOP) lowering drug that was approved in the United States in 2001 for the treatment of glaucoma and ocular hypertension. It is highly efficacious and produces greater mean reductions in IOP than other currently available antiglaucoma drugs. Conjunctival hyperemia is a common side effect of bimatoprost, but the hyperemia is typically mild and transient. No association has been found between signs of inflammation and the presence of hyperemia in bimatoprost-treated patients. Preclinical studies have elucidated the pharmacological mechanism of bimatoprost-related hyperemia and have examined the possible involvement of inflammation. Bimatoprost, as well as the free acid of latanoprost, elicited endothelium-dependent vasorelaxation in the rabbit jugular vein preparation, a quantitative in vitro model for ocular surface hyperemia (OSH). The vasorelaxant responses to either bimatoprost or latanoprost free acid were significantly inhibited by L-NAME, a nitric oxide synthase inhibitor. Similarly, the in vivo OSH responses to topically applied bimatoprost or latanoprost in dog eyes were significantly inhibited by L-NAME. As predicted, prostaglandin E(2) (PGE(2))-induced conjunctival hyperemia was not inhibited by L-NAME, since PGE(2) has a direct relaxant effect on the vascular smooth muscle. In-life observations and histopathological assessment of ocular surface tissues following bimatoprost treatment were performed for multiple-dose one month, 6 month, or 12 month safety studies in rabbits, dogs, and non-human primates. Results of these studies showed no evidence of bimatoprost-related inflammation in the ocular surface tissues. In summary, OSH related to bimatoprost treatment in laboratory animals occurs by endothelial-derived nitric oxide-mediated vasodilatation and is not associated with inflammation. These studies suggest that conjunctival hyperemia, a side effect of bimatoprost treatment, results from non-inflammatory, pharmacologically based vasodilatation.


Subject(s)
Hyperemia/chemically induced , Lipids/therapeutic use , Administration, Topical , Amides , Animals , Bimatoprost , Clinical Trials as Topic , Cloprostenol/analogs & derivatives , Conjunctiva/drug effects , Conjunctiva/ultrastructure , Drug Evaluation, Preclinical/methods , Enzyme Inhibitors/administration & dosage , Enzyme Inhibitors/therapeutic use , Humans , Hyperemia/prevention & control , Lipids/administration & dosage , Lipids/adverse effects , NG-Nitroarginine Methyl Ester/administration & dosage , NG-Nitroarginine Methyl Ester/therapeutic use , Nitric Oxide Synthase/antagonists & inhibitors
6.
Biochem Biophys Res Commun ; 330(4): 1062-7, 2005 May 20.
Article in English | MEDLINE | ID: mdl-15823551

ABSTRACT

Cannabinoid CB(1) receptors are involved in ocular physiology and may regulate intraocular pressure (IOP). However, endocannabinoid levels in human ocular tissues of cornea, iris, ciliary body, retina, and choroid from normal and glaucomatous donors have not been investigated. Anandamide (N-arachidonoylethanolamine; AEA), 2-arachidonoylglycerol (2-AG), and the anandamide congener, palmitoylethanolamide (PEA), were detected in all the human tissues examined. In eyes from patients with glaucoma, significantly decreased 2-AG and PEA levels were detected in the ciliary body, an important tissue in the regulation of IOP. The findings suggest that these endogenous compounds may have a role in this disease, particularly with respect to regulation of IOP.


Subject(s)
Arachidonic Acids/metabolism , Cannabinoid Receptor Modulators/metabolism , Endocannabinoids , Eye/metabolism , Glaucoma/metabolism , Glycerides/metabolism , Palmitic Acids/metabolism , Aged , Amides , Ciliary Body/metabolism , Ethanolamines , Humans , Middle Aged , Organ Specificity , Polyunsaturated Alkamides
7.
Br J Pharmacol ; 144(4): 493-501, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15678094

ABSTRACT

1. The pharmacology of bimatoprost, a synthetic prostaglandin-amide, was examined in prostaglandin F(2alpha) (PGF(2alpha))-sensitive preparations. Bimatoprost potently contracted the rabbit isolated uterus (pEC(50)=7.92+/-0.16). In contrast, bimatoprost exhibited weak excitatory activity in human myometrium from pregnant and nonpregnant donors, mouse uterus, rat uterus, and endothelium-intact rabbit jugular veins, and did not stimulate DNA synthesis in mouse fibroblasts. 2. The possibility that the effects of bimatoprost may reflect partial agonism at prostanoid FP receptors was examined and the contractile effects of full agonists, 17-phenyl PGF(2alpha) (FP) and U-46619 (TP, a control), were determined in the absence and presence of 1 muM bimatoprost on the mouse uterus. Analyses of the agonist-agonist functional studies showed no antagonism, indicating that bimatoprost is not a partial agonist. 3. Bioassay metabolism studies of bimatoprost and latanoprost (FP receptor agonist prodrug) in the rabbit uterus were conducted using recipient mouse uterus. Results indicated that the potent responses to bimatoprost in the rabbit uterus are produced by the intact molecule and not by its putative free acid metabolite, 17-phenyl PGF(2alpha). Some hydrolysis of latanoprost to latanoprost free acid appears to have occurred in the rabbit uterus, according to biological detection. 4. The pharmacology of bimatoprost could not be explained by its interaction with known prostanoid FP receptors and was independent of species-, tissue-, or preparation-related factors. The potent contractile effects of bimatoprost in the rabbit uterus provide further pharmacological evidence for the presence of a novel receptor population that preferentially recognises bimatoprost.


Subject(s)
Lipids/pharmacology , Receptors, Prostaglandin/agonists , Uterine Contraction/drug effects , Uterus/drug effects , 3T3 Cells , Amides , Animals , Bimatoprost , Cloprostenol/analogs & derivatives , DNA/biosynthesis , Dose-Response Relationship, Drug , Female , Fibroblasts/drug effects , Fibroblasts/metabolism , Humans , In Vitro Techniques , Jugular Veins/drug effects , Jugular Veins/metabolism , Jugular Veins/physiology , Mice , Muscle Contraction/drug effects , Muscle, Smooth, Vascular/drug effects , Muscle, Smooth, Vascular/physiology , Myometrium/drug effects , Myometrium/metabolism , Myometrium/physiology , Pregnancy , Rabbits , Rats , Rats, Sprague-Dawley , Uterus/metabolism , Uterus/physiology
SELECTION OF CITATIONS
SEARCH DETAIL
...