Molecular pharmacology
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Molecular pharmacology · Sep 2007
Comparative StudyDistinct profiles of alpha7 nAChR positive allosteric modulation revealed by structurally diverse chemotypes.
Selective modulation of alpha7 nicotinic acetylcholine receptors (nAChRs) is thought to regulate processes impaired in schizophrenia, Alzheimer's disease, and other dementias. One approach to target alpha7 nAChRs is by positive allosteric modulation. Structurally diverse compounds, including PNU-120596, 4-naphthalene-1-yl-3a,4,5,9b-tetrahydro-3-H-cyclopenta[c]quinoline-8-sulfonic acid amide (TQS), and 5-hydroxyindole (5-HI) have been identified as positive allosteric modulators (PAMs), but their receptor interactions and pharmacological profiles remain to be fully elucidated. ⋯ Both types of PAMs also increased the ACh-evoked alpha7 window currents, with type II PAMs generally showing larger potentiation. None of the PAMs tested increased nicotine-evoked Ca(2+) transients in human embryonic kidney 293 cells expressing human alpha4beta2 or alpha3beta4 nAChRs, although some inhibition was noted for 5-HI, genistein, and TQS. In summary, our studies reveal two distinct alpha7 PAM profiles, which could offer unique opportunities for modulating alpha7 nAChRs in vivo and in the development of novel therapeutics for central nervous system indications.
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Molecular pharmacology · Sep 2007
The multikinase inhibitor sorafenib induces apoptosis in highly imatinib mesylate-resistant bcr/abl+ human leukemia cells in association with signal transducer and activator of transcription 5 inhibition and myeloid cell leukemia-1 down-regulation.
The effects of the multikinase inhibitor sorafenib (BAY 43-9006), an agent shown previously to induce apoptosis in human leukemia cells through inhibition of myeloid cell leukemia-1 (Mcl-1) translation, have been examined in Bcr/Abl(+) leukemia cells resistant to imatinib mesylate (IM). When administered at pharmacologically relevant concentrations (10-15 microM), sorafenib potently induced apoptosis in imatinib mesylate-resistant cells expressing high levels of Bcr/Abl, cells exhibiting a Bcr/Abl-independent, Lyn-dependent form of resistance, and CD34(+) cells obtained from imatinib-resistant patients. In addition, Ba/F3 cells expressing mutations rendering them resistant to IM (e.g., E255K, M351T) or to IM, dasatinib, and nilotinib (T315I) remained fully sensitive to sorafenib. ⋯ Ba/F3 cells expressing Bcr/Abl mutations were as sensitive to sorafenib-induced Mcl-1 down-regulation and dephosphorylation of STAT5 and eukaryotic initiation factor 4E as wild-type cells. Finally, stable knockdown of Bcl-2-interacting mediator of cell death (Bim) with short hairpin RNA in K562 cells significantly diminished sorafenib lethality, arguing strongly for a functional role of this proapoptotic Bcl-2 family member in the lethality of this agent. Together, these findings suggest that sorafenib effectively induces apoptosis in highly imatinib-resistant chronic myelogenous leukemia cells, most likely by inhibiting or down-regulating targets (i.e., STAT5 and Mcl-1) downstream or independent of Bcr/Abl.
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Molecular pharmacology · Sep 2007
Comparative StudyModulation of presynaptic beta3-containing GABAA receptors limits the immobilizing actions of GABAergic anesthetics.
Intravenous GABAergic anesthetics are potent hypnotics but are rather ineffective in depressing movements. Immobility is mediated, in part, by the ventral horn of the spinal cord. We hypothesized that the efficacy of these anesthetics in producing immobility is compromised by the activation of GABA(A) receptors located presynaptically, which modulate GABA release onto neurons in the ventral horn. ⋯ Etomidate prolonged the decay time of GABA(A) receptors at all tested concentrations. At concentrations greater than 1.0 microM, anesthetic-induced decrease of GABA release via modulation of presynaptic GABA(A) receptors and enhancement of postsynaptic GABA(A) receptor-function compensated for each other. The results suggest that the limited immobilizing efficacy of these agents is probably due to a presynaptic mechanism and that GABAergic agents with a specificity for post-versus presynaptic receptors would probably have much stronger immobilizing actions, pointing out novel avenues for drug development.
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Molecular pharmacology · Jul 2007
Chronic intermittent ethanol treatment selectively alters N-methyl-D-aspartate receptor subunit surface expression in cultured cortical neurons.
A chronic intermittent ethanol (CIE) exposure regimen consists of repeated episodes of ethanol intoxication and withdrawal. CIE treatment has been reported to result in a significant enhancement of N-methyl-D-aspartate (NMDA) receptor-mediated synaptic responses in vivo, and trafficking of NMDA receptors is emerging a key regulatory mechanism that underlies the channel function. Therefore, in the present study, we examined the effects of CIE on NMDA receptor subunit surface expression. ⋯ In addition, this was accompanied by significant increases in postsynaptic density protein 95 clusters. Protein kinase A inhibitor completely reversed CIE-induced increase in NR1 and partially in NR2B surface level and a long-lasting effect. These changes may contribute to the development of ethanol-induced neurotoxicity and ethanol dependence.
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Molecular pharmacology · May 2007
Activation of TRPA1 channels by the fatty acid amide hydrolase inhibitor 3'-carbamoylbiphenyl-3-yl cyclohexylcarbamate (URB597).
As a member of the transient receptor potential (TRP) ion channel superfamily, the ligand-gated ion channel TRPA1 has been implicated in nociceptive function and pain states. The endogenous ligands that activate TRPA1 remain unknown. However, various agonists have been identified, including environmental irritants (e.g., acrolein) and ingredients of pungent natural products [e.g., allyl isothiocyanate (ITC), cinnamaldehyde, allicin, and gingerol]. ⋯ Furthermore, URB597 activated TRPA1 channels endogenously expressed in a population of rat dorsal root ganglion neurons that also responded to ITC. In contrast to its effect on TRPA1, URB597 inhibited TRPM8 and had no effects on TRPV1 or TRPV4. Thus, we conclude that URB597 is a novel agonist of TRPA1 and probably activates the channel through a direct gating mechanism.