Orexin receptors in GtoPdb v.2021.3.

Orexin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Orexin receptors [42]) are activated by the endogenous polypeptides orexin-A and orexin-B (also known as hypocretin-1 and -2; 33 and 28 aa) derived from a common precursor, preproorexin or orexin precursor, by proteolytic cleavage and some typical peptide modifications [109]. Currently the only orexin receptor ligands in clinical use are suvorexant and lemborexant, which are used as hypnotics. Orexin receptor crystal structures have been solved [134, 133, 54, 117, 46].

The CNS-penetrant soluble guanylate cyclase stimulator CYR119 attenuates markers of inflammation in the central nervous system.

BACKGROUND: Inflammation in the central nervous system (CNS) is observed in many neurological disorders. Nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate (NO-sGC-cGMP) signaling plays an essential role in modulating neuroinflammation. CYR119 is a CNS-penetrant sGC stimulator that amplifies endogenous NO-sGC-cGMP signaling. We evaluated target engagement and the effects of CYR119 on markers of neuroinflammation in vitro in mouse microglial cells and in vivo in quinolinic acid (QA)-induced and high-fat diet-induced rodent neuroinflammation models. METHODS: Target engagement was verified in human embryonic kidney (HEK) cells, rat primary neurons, mouse SIM-A9 cells, and in rats by measuring changes in cGMP and downstream targets of sGC signaling [phosphorylated vasodilator-stimulated phosphoprotein (pVASP), phosphorylated cAMP-response element binding (pCREB)]. In SIM-A9 cells stimulated with lipopolysaccharides (LPS), markers of inflammation were measured when cells were treated with or without CYR119. In rats, microinjections of QA and vehicle were administered into the right and left hemispheres of striatum, respectively, and then rats were dosed daily with either CYR119 (10 mg/kg) or vehicle for 7 days. The activation of microglia [ionized calcium binding adaptor molecule 1 (Iba1)] and astrocytes [glial fibrillary acidic protein (GFAP)] was measured by immunohistochemistry. Diet-induced obese (DIO) mice were treated daily with CYR119 (10 mg/kg) for 6 weeks, after which inflammatory genetic markers were analyzed in the prefrontal cortex. RESULTS: In vitro, CYR119 synergized with exogenous NO to increase the production of cGMP in HEK cells and in primary rat neuronal cell cultures. In primary neurons, CYR119 stimulated sGC, resulting in accumulation of cGMP and phosphorylation of CREB, likely through the activation of protein kinase G (PKG). CYR119 attenuated LPS-induced elevation of interleukin 6 (IL-6) and tumor necrosis factor (TNF) in mouse microglial cells. Following oral dosing in rats, CYR119 crossed the blood-brain barrier (BBB) and stimulated an increase in cGMP levels in the cerebral spinal fluid (CSF). In addition, levels of proinflammatory markers associated with QA administration or high-fat diet feeding were lower in rodents treated with CYR119 than in those treated with vehicle. CONCLUSIONS: These data suggest that sGC stimulation could provide neuroprotective effects by attenuating inflammatory responses in nonclinical models of neuroinflammation.

Selective orexin 2 receptor antagonism blocks cue-induced reinstatement, but not nicotine self-administration or nicotine-induced reinstatement.

The orexinergic system has been implicated in a number of behaviors, including reward and incentive motivation. Orexin 1 receptor antagonism has been reported to reduce drug self-administration, conditioned place preference, and reinstatement in rodents, but the role of the orexin 2 receptor is unclear. Here we evaluated the impact of the novel and selective orexin 2 receptor antagonist, 2-SORA 18, on motivation for nicotine as measured by responding on a progressive ratio schedule, as well as cue-induced reinstatement of a response previously associated with nicotine reward, and nicotine-induced reinstatement. 2-SORA 18 demonstrated selective effects on these behaviors. Specifically, doses up to 60 mg/kg 2-SORA 18 were without significant effect on nicotine self-administration or nicotine-induced reinstatement, but doses as low as 15 mg/kg 2-SORA 18 completely blocked cue-induced reinstatement. These findings indicate that orexin 2 receptor antagonism might have utility for attenuating relapse, particularly for patients sensitive to environmental stimuli associated with drug taking.

Quantitative proteomics in laser capture microdissected sleep nuclei from rat brain.

The combination of stable isotope labeling of amino acids in mammals (SILAM) and laser capture microdissection (LCM) for selective proteomic analysis of the targeted tissues holds tremendous potential for refined characterization of proteome changes within complex tissues such as the brain. The authors have applied this approach to measure changes in relative protein abundance in ventral tegmental area (VTA) of the rat brain that correlate to pharmacological perturbations. Enriched (13)C6(15)N2-lysine was introduced in vivo via diet. These animals were sacrificed during the middle of the 12-hour light period to extract isotopically "heavy" proteins, which were then used as a reference for extracts from dosed, unlabeled rats. Animals were administered an orexin peptide (Ox-B), an orexin receptor antagonist (ORA), or a mixture of both (Ox-B + ORA). All samples were obtained at same phase of the sleep cycle. Labeled-pair identification and differential quantitation provided protein identification and expression ratio data. Five proteins were found to exhibit decreased relative abundance after administration of an ORA, including α-synuclein and rat myelin basic protein. Conversely, six proteins showed increased relative abundance upon antagonist treatment, including 2',3'-cyclic nucleotide 3'-phosphodiesterase.

Orexin receptor antagonism prevents transcriptional and behavioral plasticity resulting from stimulant exposure.

Orexin is a key neurotransmitter of central arousal and reward circuits in the CNS. Two receptors respond to orexin signaling, Orexin 1 Receptor (OX1R) and Orexin 2 Receptor (OX2R) with partially overlapping brain distributions. Genetic and pharmacological studies suggest orexin receptor antagonists could provide therapeutic benefit for insomnia and other disorders in which sleep/wake cycles are disrupted. Preclinical data has also emerged showing that the orexin system is involved in the behavioral and neurological effects of drugs of abuse (Aston-Jones et al., 2009; Harris et al., 2005). Here we report sleep promoting effects of a recently described small molecule dual orexin receptor OX1R and OX2R antagonist. This dual orexin receptor antagonist (DORA) also inhibits the ability of subchronic amphetamine to produce behavioral sensitization measured 10 days following pre-treatment. Transcriptional profiling of isolated reward and arousal circuits from brains of behaviorally sensitized animals showed that the DORA blocked the significant alteration of gene expression levels in response to amphetamine exposure, particularly those associated with synaptic plasticity in the VTA. Further, DORA attenuates the ability of nicotine to induce reinstatement of extinguished responding for a reinforcer, demonstrating selectivity of the effect to reward pathways and not to food intake. In summary, these data demonstrate efficacy of a dual orexin receptor antagonist for promotion of sleep and suggest that pharmacological inhibition of the orexin system may play a role in both prevention of drug-induced plasticity and drug-relapse.

Distribution of histone deacetylases 1-11 in the rat brain.

Although protein phosphorylation has been characterized more extensively, modulation of the acetylation state of signaling molecules is now being recognized as a key means of signal transduction. The enzymes responsible for mediating these changes include histone acetyl transferases and histone deacetylases (HDACs). Members of the HDAC family of enzymes have been identified as potential therapeutic targets for diseases ranging from cancer to ischemia and neurodegeneration. We initiated a project to conduct comprehensive gene expression mapping of the 11 HDAC isoforms (HDAC1-11) (classes I, II, and IV) throughout the rat brain using high-resolution in situ hybridization (ISH) and imaging technology. Internal and external data bases were employed to identify the appropriate rat sequence information for probe selection. In addition, immunohistochemistry was performed on these samples to separately examine HDAC expression in neurons, astrocytes, oligodendrocytes, and endothelial cells in the CNS. This double-labeling approach enabled the identification of specific cell types in which the individual HDACs were expressed. The signals obtained by ISH were compared to radiolabeled standards and thereby enabled semiquantitative analysis of individual HDAC isoforms and defined relative levels of gene expression in >50 brain regions. This project produced an extensive atlas of 11 HDAC isoforms throughout the rat brain, including cell type localization, providing a valuable resource for examining the roles of specific HDACs in the brain and the development of future modulators of HDAC activity.

Aberrant recombination involving the granzyme locus occurs in Atm-/- T-cell lymphomas.

Ataxia telangiectasia (A-T) is an autosomal recessive disease caused by loss of function of the serine/threonine protein kinase ATM (ataxia telangiectasia mutated). A-T patients have a 250-700-fold increased risk of developing lymphomas and leukemias which are typically highly invasive and proliferative. In addition, a subset of adult acute lymphoblastic leukemias and aggressive B-cell chronic lymphocytic leukemias that occur in the general population show loss of heterozygosity for ATM. To define the specific role of ATM in lymphomagenesis, we studied T-cell lymphomas isolated from mice with mutations in ATM and/or p53 using cytogenetic analysis and mRNA transcriptional profiling. The analyses identified genes misregulated as a consequence of the amplifications, deletions and translocation events arising as a result of ATM loss. A specific recurrent disruption of the granzyme gene family locus was identified resulting in an aberrant granzyme B/C fusion product. The combined application of cytogenetic and gene expression approaches identified specific loci and genes that define the pathway of initiation and progression of lymphoreticular malignancies in the absence of ATM.