Molecular pharmacology
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Molecular pharmacology · May 1996
Inhibitory effect of E3330, a novel quinone derivative able to suppress tumor necrosis factor-alpha generation, on activation of nuclear factor-kappa B.
(2E)-3-[5-(2,3-Dimethoxy-6-methyl-1,4-benzoquinoyl)]-2-nonyl-2- propenoic acid (E3330), is a novel agent with hepatoprotective activity. We report the effect of E3330 on transcriptional activation of tumor necrosis factor (TNF)-alpha gene and on nuclear factor (NF)-kappa B activation. Nuclear run-on experiments showed that E3330 decreases transcriptional activation of TNF-alpha gene induced by lipopolysaccharide (LPS) stimulation in human peripheral monocytes. ⋯ E3330 decreased activated NF-kappa B in nuclei, suggesting that E3330 inhibits NF-kappa B activation and/or translocation of the nuclei. Western blotting analysis with anti-I kappa B-alpha antibody indicated that E3330 inhibited degradation of I kappa B-alpha, which is an inhibitory protein of NF-kappa B, in LPS-stimulated monocytes. E3330 may suppress the production of active oxygen species serving as common messengers to activate NF-kappa B.
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Molecular pharmacology · May 1996
3 alpha-Hydroxy-3 beta-trifluoromethyl-5 alpha-pregnan-20-one (Co 2-1970): a partial agonist at the neuroactive steroid site of the gamma-aminobutyric acidA receptor.
Neuroactive steroids bind to a unique site on the gamma-aminobutyric acidA (GABAA) receptor complex and allosterically modulate the binding of convulsant ([35S]t-butylbicyclophosphorothionate, [35S]TBPS), GABA ([3H]muscimol), and benzodiazepine ([3H]flunitrazepam) site ligands. In rat cortical membranes, 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha, 5 alpha-P) is a full agonist at the steroid site, inhibiting 96% of specific [35S]TBPS binding and enhancing [3H]flunitrazepam and [3H]muscimol binding 95% and 69% above control levels, respectively. In contrast, the synthetic steroid 3 alpha-hydroxy-3 beta-trifluoromethyl-5 alpha-pregnan-20-one (Co 2-1970) has limited efficacy for modulating the binding of [35S]TBPS (44% inhibition), [3H]flunitrazepam (41% enhancement), and [3H]muscimol (< 10% enhancement). ⋯ Co 2-1970 showed limited efficacy potentiation of GABA-evoked chloride currents relative to 3 alpha, 5 alpha-P (28% and 86% of the GABA maximum current, respectively). Moreover, Co 2-1970 produced a concentration-dependent antagonism of the 3 alpha, 5 alpha-P-induced potentiation that was associated with a reduction in the apparent affinity of 3 alpha, 5 alpha-P (11-fold at 10 microM Co 2-1970). Taken together, these data indicate that Co 2-1970 is a partial agonist at the neuroactive steroid site associated with GABAA receptors.
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Molecular pharmacology · Apr 1996
Comparative StudyCyclic AMP-dependent regulation of fibroblast growth factor-2 messenger RNA levels in rat cortical astrocytes: comparison with fibroblast growth factor-1 and ciliary neurotrophic factor.
The present study was undertaken to investigate the regulatory mechanisms of fibroblast growth factor-1 and -2 (FGF-1 and FGF-2) gene expression compared with ciliary neurotropic factor (CNTF) in rat cortical astrocytes. Glial cells represent a source of different trophic factors and cytokines that can influence the survival of multiple cell populations within the central nervous system. We found that the beta-adrenergic receptor agonist (betaAR) isoproterenol produced a significant induction of FGF-2 gene expression and protein in type I astrocytes. ⋯ Coincubation of isoproterenol with actinomycin D, an inhibitor of gene transcription, prevents the modification of neurotrophic factor biosynthesis, indicating that transcriptional mechanisms are indeed involved in these regulatory pathways. However, the determination of FGF-2 mRNA half-life suggests that the effect of the betaAR agonist can be in part the result of mRNA stabilization. The mechanisms that we describe can be important in the maintenance of neuronal homeostasis and may be relevant in the development of alternative strategies for the treatment of acute and chronic neurodegenerative disorders
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Molecular pharmacology · Dec 1995
Comparative StudySustained exposure to 1-aminocyclopropanecarboxylic acid, a glycine partial agonist, alters N-methyl-D-aspartate receptor function and subunit composition.
Partial agonists at the strychnine-insensitive glycine sites coupled to N-methyl-D-aspartate (NMDA) receptors reduce both glutamate-induced neurotoxicity in vitro and ischemia-induced neurodegeneration in vivo. Paradoxically, sustained exposure of cultured cerebellar granule cell neurons to glycinergic ligands, including glycine and the glycine partial agonists (+/-)-3-amino-1-hydroxy-2-pyrrolidone, 1-aminocyclopropanecarboxylic acid (ACPC), and D-cycloserine, attenuates the neuroprotective effects of (+/-)-3-amino-1-hydroxy-2-pyrrolidone and ACPC. In the present study, we investigated the mechanisms responsible for this attenuated neuroprotection. ⋯ This apparent increase in glutamate sensitivity may be attributable to a change in NMDA receptor subunit composition as sustained ACPC exposure resulted in a approximately 2.5-fold increase in NMDA receptor 2C RNA levels, without concomitant changes in the amounts of RNA encoding the NMDA receptor 2A, 2B, or 1 subunit. This is the first demonstration that sustained exposure to a glycinergic ligand can alter the expression of RNAs encoding NMDA receptor subunits. Because glycinergic ligands are potential clinical candidates, these results may have important implications for the treatment of neurodegenerative disorders.
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Molecular pharmacology · Nov 1995
Role of oxidative stress generated from the mitochondrial electron transport chain and mitochondrial glutathione status in loss of mitochondrial function and activation of transcription factor nuclear factor-kappa B: studies with isolated mitochondria and rat hepatocytes.
Mitochondria are an important source of reactive oxygen intermediates because they are the major consumers of molecular oxygen in cells. Respiration is associated with toxicity, which is related to the activation of oxygen to reactive intermediates. The purpose of the present study was to examine the role of reduced glutathione (GSH) in the maintenance of mitochondrial functions during oxidative stress induced through selective inhibition of the complex III segment of the electron transport chain. ⋯ Thus, our results suggest that GSH protects mitochondria against the endogenous oxidative stress produced at the ubiquinone site of the electron transport chain. Mitochondrial GSH depletion potentiates oxidant-induced loss of mitochondrial functions. Oxidant stress in mitochondria can promote extramitochondrial activation of NF-kappa B and therefore may affect nuclear gene expression.