Molecular pharmacology
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Molecular pharmacology · May 2010
Modulation of silent and constitutively active nociceptin/orphanin FQ receptors by potent receptor antagonists and Na+ ions in rat sympathetic neurons.
The pharmacology of G protein-coupled receptors can be influenced by factors such as constitutive receptor activation and Na(+) ions. In this study, we examined the coupling of natively and heterologously expressed nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptors with voltage-dependent Ca(2+) channels after exposure to four high-affinity NOP receptor blockers [[Nphe(1)Arg(14)Lys(15)]N/OFQ-NH(2) (UFP-101), 1-[1-(cyclooctylmethyl)-1,2,3,6-tetrahydro-5-(hydroxymethyl)-4-pyridinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (Trap-101), 1-benzyl-N-{3-[spiroisobenzofuran-1(3H),4'-piperidin-1-yl]propyl}pyrrolidine-2-carboxamide (compound 24), and N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl)benzamide hydrochloride (JTC-801)] in sympathetic neurons. The enhanced tonic inhibition of Ca(2+) currents in the absence of agonists, indicative of constitutively active NOP receptors in transfected neurons, was abolished after pretreatment with pertussis toxin. ⋯ Examination of the allosteric effects of Na(+) on heterologously overexpressed NOP receptors showed that the tonic Ca(2+) current inhibition was abolished in the presence of the monovalent cation. These results demonstrate that constitutively active NOP receptors exhibit differential blocker pharmacology and allosteric regulation by Na(+). Data are also presented demonstrating that heterologously expressed mu opioid receptors in sympathetic neurons are similarly modulated.
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Molecular pharmacology · Apr 2010
Regulation of multidrug resistance protein 1 by tumor necrosis factor alpha in cultured glial cells: involvement of nuclear factor-kappaB and c-Jun N-terminal kinase signaling pathways.
Pharmacotherapy of brain HIV-1 infection may be limited by ABC transporters [i.e., P-glycoprotein (P-gp), multidrug resistance protein 1 (Mrp1)] that export antiretroviral drugs from HIV-1 brain cellular targets (i.e., astrocytes, microglia). Using an in vitro astrocyte model of an HIV-1 associated inflammatory response, our laboratory has shown that cytokines [i.e., tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1 beta, IL-6], which are secreted in response to HIV-1 envelope glycoprotein gp120 exposure, can decrease P-gp functional expression; however, it is unknown whether these same cytokines can alter expression and/or activity of other ABC transporters (i.e., Mrp1). In primary cultures of rat astrocytes, Mrp1 expression was increased by TNF-alpha (2.7-fold) but was not altered by IL-1 beta or IL-6. ⋯ Mrp1 mRNA expression was increased after treatment with gp120 (1.6-fold) or TNF-alpha (1.7-fold), suggesting altered Mrp1 gene transcription. These data suggest that gp120 and TNF-alpha can up-regulate Mrp1 expression in cultured astrocytes. Furthermore, our results imply that both NF-kappaB and JNK signaling are involved in Mrp1 regulation during an HIV-1 associated inflammatory response.
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Molecular pharmacology · Mar 2010
Comparative StudyContext-dependent pharmacology exhibited by negative allosteric modulators of metabotropic glutamate receptor 7.
Phenotypic studies of mice lacking metabotropic glutamate receptor subtype 7 (mGluR7) suggest that antagonists of this receptor may be promising for the treatment of central nervous system disorders such as anxiety and depression. Suzuki et al. (J Pharmacol Exp Ther 323:147-156, 2007) recently reported the in vitro characterization of a novel mGluR7 antagonist called 6-(4-methoxyphenyl)-5-methyl-3-(4-pyridinyl)-isoxazolo[ 4,5-c]pyridin-4(5H)-one (MMPIP), which noncompetitively inhibited the activity of orthosteric and allosteric agonists at mGluR7. We describe that MMPIP acts as a noncompetitive antagonist in calcium mobilization assays in cells coexpressing mGluR7 and the promiscuous G protein G alpha(15). ⋯ Electrophysiological studies reveal that, in contrast to the orthosteric antagonist (2S)-2-amino-2-[(1S,2S)-2-carboxyclycloprop-1-yl]-3-(xanth-9-yl) propanoic acid (LY341495), MMPIP is unable to block agonist-mediated responses at the Schaffer collateral-CA1 synapse, a location at which neurotransmission has been shown to be modulated by mGluR7 activity. Thus, MMPIP and related compounds differentially inhibit coupling of mGluR7 in different cellular backgrounds and may not antagonize the coupling of this receptor to native G(i/o) signaling pathways in all cellular contexts. The pharmacology of this compound represents a striking example of the potential for context-dependent blockade of receptor responses by negative allosteric modulators.
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Molecular pharmacology · Feb 2010
Comparative StudyAnalgesic (omega)-conotoxins CVIE and CVIF selectively and voltage-dependently block recombinant and native N-type calcium channels.
Neuronal (N)-type Ca(2+) channel-selective omega-conotoxins have emerged as potential new drugs for the treatment of chronic pain. In this study, two new omega-conotoxins, CVIE and CVIF, were discovered from a Conus catus cDNA library. Both conopeptides potently displaced (125)I-GVIA binding to rat brain membranes. ⋯ Homology models of CVIE and CVIF suggest that omega-conotoxin/voltage-gated Ca(2+) channel interaction is dominated by ionic/electrostatic interactions. In the rat partial sciatic nerve ligation model of neuropathic pain, CVIE and CVIF (1 nM) significantly reduced allodynic behavior. These N-type Ca(2+) channel-selective omega-conotoxins are therefore useful as neurophysiological tools and as potential therapeutic agents to inhibit nociceptive pain pathways.
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Molecular pharmacology · Feb 2010
Comparative StudyIncreased spinal dynorphin levels and phospho-extracellular signal-regulated kinases 1 and 2 and c-Fos immunoreactivity after surgery under remifentanil anesthesia in mice.
In humans, remifentanil anesthesia enhances nociceptive sensitization in the postoperative period. We hypothesized that activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and the expression of c-Fos, prodynorphin (mRNA), and dynorphin in the spinal cord could participate in the molecular mechanisms underlying postoperative opioid-induced sensitization. In a mouse model of incisional pain, we evaluated thermal (Hargreaves test) and mechanical (von Frey) hyperalgesia during the first 21 postoperative days. ⋯ We also identified an early expression of c-Fos immunoreactivity in the superficial laminae of the dorsal horn of the spinal cord (peak at 4 h; p < 0.001), together with a partial activation of ERK1/2 (4 h; p < 0.001). These findings suggest that activated ERK1/2 could induce c-Fos expression and trigger the transcription of prodynorphin in the spinal cord. This in turn would result in long-lasting increased levels of dynorphin that, in our model, could participate in the persistence of pain but not in the manifestation of first pain.