PubMed Health⌕ Search

Biomedical subjects

Bryan L Roth

Publications and source records attributed to Bryan L Roth.

At least 73 records · Page 4Linked to original sources
PubMed2003

Spiro[9,10-dihydroanthracene]-9,3'-pyrrolidine-a structurally unique tetracyclic 5-HT2A receptor antagonist.

Structural elaboration of phenylethylamine to spiro[9,10-dihydroanthracene]-9,3'-pyrrolidine (SpAMDA) produces an agent with unexpectedly high affinity (K(i)=4 nM) at 5-HT(2A) receptors. It was shown that SpAMDA acts as a 5-HT(2A) receptor antagonist. The structure and molecular geometry of SpAMDA are not consistent with existing pharmacophore features, and a novel 5-HT(2A) antagonist pharmacophore model is proposed for the binding of aminomethyl-9,10-dihydroanthracene analogs. Thus, SpAMDA may be a structurally novel parent of a new class of 5-HT(2A) receptor antagonists that binds to the receptor in a unique fashion that is distinct from the binding topology of existing 5-HT(2A) receptor antagonists.

3T3 Cells↗
PubMed2003

Serotonin receptors represent highly favorable molecular targets for cognitive enhancement in schizophrenia and other disorders.

RATIONALE: Current treatments for schizophrenia adequately treat the positive symptoms of schizophrenia but only modestly improve cognitive deficits. This review provides evidence for and against the use of selective 5-HT receptor drugs as cognition enhancing agents for schizophrenia and other disorders. METHODS: Pre-clinical and clinical literature concerned with the role of the serotonergic system in cognition and memory as it relates to schizophrenia is reviewed. Individual 5-HT receptor subtypes for which selective drugs are available that are likely to improve cognition are reviewed. Recommendations for clinical testing are proposed. RESULTS AND CONCLUSIONS: Four 5-HT receptor systems (5-HT(1A), 5-HT(2A), 5-HT(4), 5-HT(6)) are highlighted as suitable targets for enhancing cognition and memory. Because many clinically available antipsychotic drugs already target 5-HT(1A), 5-HT(2A) and 5-HT(6) receptors, design of clinical trials will need to take into account the serotonergic pharmacology of concurrently administered antipsychotic medications. 5-HT(1A) partial agonists and 5-HT(2A) antagonists have shown modest effectiveness in improving cognition in schizophrenia. 5-HT(6)-selective compounds for cognition enhancement are in late-stage clinical trials, while 5-HT(4) compounds have not yet been tested in humans for cognition enhancement. RECOMMENDATIONS: For stand-alone therapy for enhancing cognition, 5-HT(1A) partial agonists, 5-HT(2A) antagonists, 5-HT(4) partial agonists and 5-HT(6) antagonists are all likely to induce at least modest improvement in cognition in schizophrenia. If "add-on therapy" is contemplated, antipsychotic drugs with weak affinities for serotonin receptors should be used to avoid confounds. It is likely that serotonergic drugs will soon be available as cognition enhancing medications for disorders other than schizophrenia (e.g. dementia).

Animals↗
PubMed2003

Identification of two serine residues essential for agonist-induced 5-HT2A receptor desensitization.

5-HT(2A) serotonin receptors represent the principal molecular targets for LSD-like hallucinogens and atypical antipsychotic drugs. It has been proposed that a dysregulation of 5-HT(2A) receptor-mediated signaling may contribute to the pathogenesis of schizophrenia and related diseases. A major mechanism for the attenuation of GPCR signaling following agonist activation typically involves the phosphorylation of serine and/or threonine residues by various kinases. Ser/Thr phosphorylation leads to the binding of accessory proteins and the uncoupling of the G proteins, thereby preventing further signaling. The molecular mechanisms by which 5-HT(2A) receptors are desensitized are unknown, and to date, no residues essential for agonist-mediated desensitization have been identified. Thus, we mutated, individually or in groups, all of the 37 serines and threonines in the cytoplasmic domains of the 5-HT(2A) receptor and assessed the effects of these mutations on agonist-mediated desensitization. We discovered that mutation of two residues, S421 in the C-terminal tail and S188 in the second intracellular loop, to alanine resulted in a significant block of agonist-induced desensitization. Intriguingly, a single-nucleotide polymorphism, of unreported frequency, at the S421 locus has been reported (S421F); the S421F mutation, like the S421A mutation, significantly attenuated agonist-mediated desensitization. Taken together, these findings indicate that the process of agonist-mediated desensitization of 5-HT(2A) receptors requires the presence of two nonconserved serine residues located in distinct intracellular loops.

Amino Acid Sequence↗
PubMed2003

In vitro characterization of ephedrine-related stereoisomers at biogenic amine transporters and the receptorome reveals selective actions as norepinephrine transporter substrates.

Ephedrine is a long-studied stimulant available both as a prescription and over-the-counter medication, as well as an ingredient in widely marketed herbal preparations, and is also used as a precursor for the illicit synthesis of methamphetamine. Ephedrine is related to phenylpropanolamine, a decongestant removed from the market place due to concerns that its use increased the risk of hemorrhagic stroke. Standard pharmacology texts emphasize that ephedrine is both a direct and indirect adrenergic agonist, activating adrenergic receptors both by direct agonist activity as well as by releasing norepinephrine via a carrier-mediated exchange mechanism. Chemically, ephedrine possesses two chiral centers. In the present study, we characterized the stereoisomers of ephedrine and the closely related compounds pseudoephedrine, norephedrine, pseudonorephedrine (cathine), methcathinone, and cathinone at biogenic amine transporters and a large battery of cloned human receptors (e.g., "receptorome"). The most potent actions of ephedrine-type compounds were as substrates of the norepinephrine transporter (EC50 values of about 50 nM) followed by substrate activity at the dopamine transporter. Screening the receptorome demonstrated weak affinity at alpha2-adrenergic and 5-hydroxytryptamine7 receptors (Ki values 1-10 microM) and no significant activity at beta-adrenergic or alpha1-adrenergic receptors. Viewed collectively, these data indicate that the pharmacological effects of ephedrine-like phenylpropanolamines are likely mediated by norepinephrine release, and although sharing mechanistic similarities with, they differ in important respects from those of the phenylpropanonamines methcathinone and cathinone and the phenyisopropylamines methamphetamine and amphetamine.

Adrenergic Agents↗
PubMed2003

Parkin-deficient mice exhibit nigrostriatal deficits but not loss of dopaminergic neurons.

Loss-of-function mutations in parkin are the major cause of early-onset familial Parkinson's disease. To investigate the pathogenic mechanism by which loss of parkin function causes Parkinson's disease, we generated a mouse model bearing a germline disruption in parkin. Parkin-/- mice are viable and exhibit grossly normal brain morphology. Quantitative in vivo microdialysis revealed an increase in extracellular dopamine concentration in the striatum of parkin-/- mice. Intracellular recordings of medium-sized striatal spiny neurons showed that greater currents are required to induce synaptic responses, suggesting a reduction in synaptic excitability in the absence of parkin. Furthermore, parkin-/- mice exhibit deficits in behavioral paradigms sensitive to dysfunction of the nigrostriatal pathway. The number of dopaminergic neurons in the substantia nigra of parkin-/- mice, however, is normal up to the age of 24 months, in contrast to the substantial loss of nigral neurons characteristic of Parkinson's disease. Steady-state levels of CDCrel-1, synphilin-1, and alpha-synuclein, which were identified previously as substrates of the E3 ubiquitin ligase activity of parkin, are unaltered in parkin-/- brains. Together these findings provide the first evidence for a novel role of parkin in dopamine regulation and nigrostriatal function, and a non-essential role of parkin in the survival of nigral neurons in mice.

Alleles↗
PubMed2003

Ring substituted analogues of 5-aminomethyl-10,11-dihydro-dibenzo[a,d]cycloheptene (AMDH): potential modes of binding to the 5-HT(2A) receptor.

The synthesis and 5-HT(2A) receptor affinities of 2-substituted-5-aminomethyl-10,11-dihydrodibenzo[a,d]cycloheptene (AMDH) derivatives are described. Comparison of the effects of substitution on affinities allowed assignment of potential binding modes in comparison with DOB-like agonists/antagonists and 3-substituted 1-(aminomethyl)-9,10-dihydroanthracene structures.

Cyclopentanes↗
PubMed2003

Aripiprazole, a novel atypical antipsychotic drug with a unique and robust pharmacology.

Atypical antipsychotic drugs have revolutionized the treatment of schizophrenia and related disorders. The current clinically approved atypical antipsychotic drugs are characterized by having relatively low affinities for D(2)-dopamine receptors and relatively high affinities for 5-HT(2A) serotonin receptors (5-HT, 5-hydroxytryptamine (serotonin)). Aripiprazole (OPC-14597) is a novel atypical antipsychotic drug that is reported to be a high-affinity D(2)-dopamine receptor partial agonist. We now provide a comprehensive pharmacological profile of aripiprazole at a large number of cloned G protein-coupled receptors, transporters, and ion channels. These data reveal a number of interesting and potentially important molecular targets for which aripiprazole has affinity. Aripiprazole has highest affinity for h5-HT(2B)-, hD(2L)-, and hD(3)-dopamine receptors, but also has significant affinity (5-30 nM) for several other 5-HT receptors (5-HT(1A), 5-HT(2A), 5-HT(7)), as well as alpha(1A)-adrenergic and hH(1)-histamine receptors. Aripiprazole has less affinity (30-200 nM) for other G protein-coupled receptors, including the 5-HT(1D), 5-HT(2C), alpha(1B)-, alpha(2A)-, alpha(2B)-, alpha(2C)-, beta(1)-, and beta(2)-adrenergic, and H(3)-histamine receptors. Functionally, aripiprazole is an inverse agonist at 5-HT(2B) receptors and displays partial agonist actions at 5-HT(2A), 5-HT(2C), D(3), and D(4) receptors. Interestingly, we also discovered that the functional actions of aripiprazole at cloned human D(2)-dopamine receptors are cell-type selective, and that a range of actions (eg agonism, partial agonism, antagonism) at cloned D(2)-dopamine receptors are possible depending upon the cell type and function examined. This mixture of functional actions at D(2)-dopamine receptors is consistent with the hypothesis proposed by Lawler et al (1999) that aripiprazole has "functionally selective" actions. Taken together, our results support the hypothesis that the unique actions of aripiprazole in humans are likely a combination of "functionally selective" activation of D(2) (and possibly D(3))-dopamine receptors, coupled with important interactions with selected other biogenic amine receptors--particularly 5-HT receptor subtypes (5-HT(1A), 5-HT(2A)).

Antipsychotic Agents↗
PubMed2003

A direct interaction of PSD-95 with 5-HT2A serotonin receptors regulates receptor trafficking and signal transduction.

The serotonin (5-hydroxytryptamine) 2A receptor (5-HT2A) is an important G protein-coupled receptor (GPCR) that mediates the effects of hallucinogens and is the target of a number of commonly prescribed medications including atypical antipsychotics, antidepressants, and anxiolytics. The 5-HT2A receptor possesses a canonical Type I PDZ-binding domain (X-Ser/Thr-X-Phi) at the carboxyl terminus and has been predicted, but never demonstrated, to interact with PDZ domain-containing proteins. We discovered that PSD-95, a prototypic PDZ domain-containing protein, directly associates with the 5-HT2A receptor and regulates 5-HT2A receptor-mediated signaling and trafficking in HEK-293 cells. Co-immunoprecipitation studies revealed that the native 5-HT2A receptor, but not a mutant lacking the PDZ-binding domain, interacted directly with PSD-95. The association with PSD-95 enhanced 5-HT2A receptor-mediated signal transduction, a novel action of PSD-95 on GPCRs. The augmentation of 5-HT2A receptor signaling by PSD-95 was not accompanied by alteration in the kinetics of 5-HT2A receptor desensitization but was associated with the inhibition of agonist-induced 5-HT2A receptor internalization. Additional studies demonstrated that 5-HT2A receptor and PSD-95 were co-localized in clusters on the cell surface of HEK-293 cells. Taken together, the present work elucidates novel roles for PSD-95 in regulating the functional activity and intracellular trafficking of 5-HT2A receptors and possibly other GPCRs.

Amino Acid Motifs↗
PubMed2003

Synthesis and in vitro pharmacology of novel heterocyclic muscarinic ligands.

A set of novel heterocyclic ligands (7a-9a, 7b-9b, and 9c) structurally related to oxotremorine 2 was designed, synthesized, and tested at muscarinic receptor subtypes. In the binding experiments at cloned hm1-5, the presence of the 2-methylimidazole/2-methyl-3-alkylimidazolium moiety in place of the pyrrolidine ring revealed, in derivatives 8a, 8b, and 9c, a moderate selectivity for some receptor subtypes. The functional in vitro assays yielded results that correlated closely to binding data. In general, on passing from agonists bearing the pyrrolidine moiety to their analogues carrying the 2-methylimidazole function, the overall pharmacological efficacy profile is shifted from agonism toward partial agonism. The insertion of the 2-methyl-3-alkylimidazolium moiety advances the effect such that the compounds are pure antagonists. Quite similarly, chiral 3-oxo-Delta(2)-isoxazoline (+/-)-10 behaved as a weak antagonist unable to discriminate the different muscarinic receptor subtypes.

Animals↗
PubMed2003

Salvinorin A: the "magic mint" hallucinogen finds a molecular target in the kappa opioid receptor.

Salvinorin A, a neoclerodane diterpene, is the most potent naturally occurring hallucinogen known and rivals the synthetic hallucinogen lysergic acid diethylamide in potency. Recently, the molecular target of salvinorin A was identified as the kappa opioid receptor (KOR). Salvinorin A represents the only known non-nitrogenous KOR selective agonist. Based on the selectivity of salvinorin A for the KOR, this receptor represents a potential molecular target for the development of drugs to treat disorders characterized by alterations in perception, including schizophrenia, Alzheimer's disease and bipolar disorder.

Animals↗
PubMed2003

H1-histamine receptor affinity predicts short-term weight gain for typical and atypical antipsychotic drugs.

As a result of superior efficacy and overall tolerability, atypical antipsychotic drugs have become the treatment of choice for schizophrenia and related disorders, despite their side effects. Weight gain is a common and potentially serious complication of some antipsychotic drug therapy, and may be accompanied by hyperlipidemia, hypertension and hyperglycemia and, in some extreme cases, diabetic ketoacidosis. The molecular mechanism(s) responsible for antipsychotic drug-induced weight gain are unknown, but have been hypothesized to be because of interactions of antipsychotic drugs with several neurotransmitter receptors, including 5-HT(2A) and 5-HT(2C) serotonin receptors, H(1)-histamine receptors, alpha(1)- and alpha(2)-adrenergic receptors, and m3-muscarinic receptors. To determine the receptor(s) likely to be responsible for antipsychotic-drug-induced weight gain, we screened 17 typical and atypical antipsychotic drugs for binding to 12 neurotransmitter receptors. H(1)-histamine receptor affinities for this group of typical and atypical antipsychotic drugs were significantly correlated with weight gain (Spearman rho=-0.72; p<0.01), as were affinities for alpha(1A) adrenergic (rho=-0.54; p<0.05), 5-HT(2C) (rho=-0.49; p<0.05) and 5-HT(6) receptors (rho=-0.54; p<0.05), whereas eight other receptors' affinities were not. A principal components analysis showed that affinities at the H(1), alpha(2A), alpha(2B), 5-HT(2A), 5-HT(2C), and 5-HT(6) receptors were most highly correlated with the first principal component, and affinities for the D(2), 5-HT(1A), and 5-HT(7) receptors were most highly correlated with the second principal component. A discriminant functions analysis showed that affinities for the H(1) and alpha(1A) receptors were most highly correlated with the discriminant function axis. The discriminant function analysis, as well as the affinity for the H(1)-histamine receptor alone, correctly classified 15 of the 17 drugs into two groups; those that induce weight gain and those that do not. Because centrally acting H(1)-histamine receptor antagonists are known to induce weight gain with chronic use, and because H(1)-histamine receptor affinities are positively correlated with weight gain among typical and atypical antipsychotic drugs, it is recommended that the next generation of atypical antipsychotic drugs be screened to avoid H(1)-histamine receptors.

Animals↗
PubMed2003

Novel diketopiperazine enhances motor and cognitive recovery after traumatic brain injury in rats and shows neuroprotection in vitro and in vivo.

The authors developed a novel diketopiperazine that shows neuroprotective activity in a variety of in vitro models, as well as in a clinically relevant experimental model of traumatic brain injury (TBI) in rats. Treatment with 1-ARA-35b (35b), a cyclized dipeptide derived from a modified thyrotropin-releasing hormone (TRH) analog, significantly reduced cell death associated with necrosis (maitotoxin), apoptosis (staurosporine), or mechanical injury in neuronal-glial cocultures. Rats subjected to lateral fluid percussion-induced TBI and then treated with 1 mg/kg intravenous 35b thirty minutes after trauma showed significantly improved motor recovery and spatial learning compared with vehicle-treated controls. Treatment also significantly reduced lesion volumes as shown by magnetic resonance imaging, and decreased the number of TUNEL-positive neurons observed in ipsilateral hippocampus. Unlike TRH or traditional TRH analogs, 35b treatment did not change mean arterial pressure, body temperature, or thyroid-stimulating hormone release, and did not have analeptic activity. Moreover, in contrast to TRH or typical TRH analogs, 35b administration after TBI did not alter free-magnesium concentration or cellular bioenergetic state. Receptor-binding studies showed that 35b did not act with high affinity at 50 classical receptors, channels, or transporters. Thus, 35b shows none of the typical physiologic actions associated with TRH, but possesses neuroprotective actions in vivo and in vitro, and appears to attenuate both necrotic and apoptotic cell death.

Animals↗
PubMed2003

L-homocysteine sulfinic acid and other acidic homocysteine derivatives are potent and selective metabotropic glutamate receptor agonists.

Moderate hyperhomocysteinemia is associated with several diseases, including coronary artery disease, stroke, Alzheimer's disease, schizophrenia, and spina bifida. However, the mechanisms for their pathogenesis are unknown but could involve the interaction of homocysteine or its metabolites with molecular targets such as neurotransmitter receptors, channels, or transporters. We discovered that L-homocysteine sulfinic acid (L-HCSA), L-homocysteic acid, L-cysteine sulfinic acid, and L-cysteic acid are potent and effective agonists at several rat metabotropic glutamate receptors (mGluRs). These acidic homocysteine derivatives 1) stimulated phosphoinositide hydrolysis in the cells stably expressing the mGluR1, mGluR5, or mGluR8 (plus Galpha(qi9)) and 2) inhibited the forskolin-induced cAMP accumulation in the cells stably expressing mGluR2, mGluR4, or mGluR6, with different potencies and efficacies depending on receptor subtypes. Of the four compounds, L-HCSA is the most potent agonist at mGluR1, mGluR2, mGluR4, mGluR5, mGluR6, and mGluR8. The effects of the four agonists were selective for mGluRs because activity was not discovered when L-HCSA and several other homocysteine derivatives were screened against a large panel of cloned neurotransmitter receptors, channels, and transporters. These findings imply that mGluRs are candidate G-protein-coupled receptors for mediating the intracellular signaling events induced by acidic homocysteine derivatives. The relevance of these findings for the role of mGluRs in the pathogenesis of homocysteine-mediated phenomena is discussed.

Animals↗
PubMed2003

The interaction of a constitutively active arrestin with the arrestin-insensitive 5-HT(2A) receptor induces agonist-independent internalization.

5-HT(2A) serotonin receptors are unusual among G-protein coupled receptors in that they can be internalized and desensitized, in some cell types, in an arrestin-independent manner. The molecular basis of the arrestin-insensitivity of 5-HT(2A) receptors is unknown but is probably caused, in part, by the apparent lack of agonist-induced 5-HT(2A) receptor phosphorylation. Because the arrestin-insensitivity of 5-HT(2A) receptors is cell-type selective, we used a "constitutively active" arrestin mutant that can interact with agonist-activated but nonphosphorylated receptors. We show here that this "constitutively active" arrestin mutant (Arr2-R169E) can force 5-HT(2A) receptors to be regulated by arrestins. Cotransfection of 5-HT(2A) receptors with Arr2-R169E induced agonist-independent 5-HT(2A) receptor internalization, and a constitutive translocation of the Arr2-R169E mutant to the plasma membrane, whereas wild-type Arrestin-2 had no effect. Additionally, Arr2-R169E, unlike wild-type arrestin-2, induced a significant decrease in efficacy of agonist-induced phosphoinositide hydrolysis with an unexpected increase in agonist potency. Radioligand binding assays demonstrated that the fraction of receptors in the high-affinity agonist binding-state increased with expression of Arr2-R169E, indicating that Arr2-R169E stabilizes the agonist-high affinity state of the 5-HT(2A) receptor (R*). Intriguingly, the agonist-independent interaction of Arr2-R169E with 5-HT(2A) receptors was inhibited by inverse agonist treatment and is thus probably caused by the high level of 5-HT(2A) receptor constitutive activity. This is the first demonstration that a constitutively active arrestin mutant can both induce agonist-independent internalization and stabilize the agonist-high affinity state of an arrestin-insensitive G protein coupled receptor.

Amino Acid Substitution↗
PubMed2003

3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy") induces fenfluramine-like proliferative actions on human cardiac valvular interstitial cells in vitro.

Recent findings have implicated the 5-hydroxytryptamine 2B (5-HT2B) serotonin receptor in mediating the heart valve fibroplasia [valvular heart disease (VHD)] and primary pulmonary hypertension observed in patients taking the now-banned appetite suppressant fenfluramine (Pondimin, Redux). Via large-scale, random screening of a portion of the receptorome, we have discovered that the amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy") and its N-demethylated metabolite 3,4-methylenedioxyamphetamine (MDA) each preferentially bind to and activate human recombinant 5-HT2B receptors. We also demonstrate that MDMA and MDA, like fenfluramine and its N-deethylated metabolite norfenfluramine, elicit prolonged mitogenic responses in human valvular interstitial cells via activation of 5-HT2B receptors. We also report that pergolide and dihydroergotamine, two drugs recently demonstrated to induce VHD in humans, potently activate 5-HT2B receptors, thus validating this assay system for its ability to predict medications that might induce VHD. Our discovery that MDMA and a major metabolite, MDA, induce prolonged mitogenic responses in vitro similar to those induced by fenfluramine and norfenfluramine in vivo (i.e., valvular interstitial cell fibroplasia) predict that long-term MDMA use could lead to the development of fenfluramine-like VHD. Because of the widespread abuse of MDMA, these findings have major public health implications. These findings also underscore the necessity of screening current and future drugs at h5-HT2B receptors for agonist actions before their use in humans.

3,4-Methylenedioxyamphetamine↗