Abstract
Background
Negative symptoms in schizophrenia (SCZ) are poorly treated and interfere with the function of patients. Studies focusing on structural and functional imaging and non-invasive ...electrophysiology implicate perturbations of the frontocortico-temporal circuits and disruption of cortico-striatal loops to negative symptoms in SCZ. GPR139 is an orphan GPCR that is specifically expressed in the CNS and enriched in the habenula, a brain structure involved in reward and motivation. Structural and functional alterations of the habenula have been found in SCZ patients, who show deficits in feedback processing and lack habenula activation in response to negative outcomes. Rodent experiments demonstrate the involvement of direct projection from the cortex to the habenula controlling social behavior. Alteration in habenula activity have been correlated with depression, and normalization of aberrant habenula activity has been proposed as therapeutic strategy to reverse anhedonia. Building on data previously reported at SIRS2018, we further explored modulation of GPR139 receptors and habenula circuitry in vivo as a novel mechanism to treat negative symptoms in SCZ.
Methods
Animals were submitted to an unpredictable chronic mild stress (uCMS) protocol, an animal model of depression that produces deficits in several behavioral domains affected in depressed patients. The three-chamber (Crawley’s) paradigm has been used to study social interaction in rodents. Induction of the immediate early gene c-fos expression was studied as marker for habenula neuron activation in vivo. Dopamine release in the nucleus accumbens (NAc) was studied by standard in vivo microdialysis in freely moving rats.
Results
The selective GPR139 agonist TAK-041 increased cFOS expression in the habenula in wild type mice, but not in GPR139 knock out mice. No desensitization of cFOS in the habenula was observed after chronic dosing of TAK-041. Microdialysis studies showed that TAK-041 reduced amphetamine- and nicotine-induced dopamine release in the NAc in rats. TAK-041 dosed acutely and chronically reversed anhedonia caused by uCMS in rats. TAK-041 also reversed anxiety related behavior assessed in the novelty suppressed feeding test and depressive-like behavior in the forced swim test in the uCMS model. uCMS-exposed animals develop a disrupted circadian regulation of corticosterone secretion, which was also normalized by TAK-041 treatment. Furthermore, TAK-041 reversed the uCMS-induced atrophy in the basal dendrites of pyramidal neurons in the hippocampus and the uCMS-induced hypertrophy of medium-spiny neurons in the NAc. These results suggest a potential benefit of TAK-041 in the treatment of anhedonia and possibly depression. TAK-041 also completely reversed social interaction (SI) deficits in the maternal immune activation poly-I:C model of SCZ, the subchronic PCP-SI model and in Balb/C and BTBR mice.
Discussion
The GPR139 agonist TAK-041 is proposed as a modulator of habenula circuitry to treat negative symptoms in SCZ based on efficacy in reversing anhedonia and social interaction deficits in multiple rodent models related to negative symptoms in SCZ.
*Employed by Takeda when the study was done.
Abstract
Background
Individuals with schizophrenia fail to appropriately use negative feedback to guide learning. These learning deficits are thought to arise from abnormalities in midbrain dopamine ...activity. The habenula is a well conserved paired structure that sits in the midline, adjacent to the third ventricle, and dorsal and posterior to the thalamus. Classic studies have shown that it is part of the reward pathway and functions with dopamine neurons in the ventral tegmental area (VTA) to mediate reward related signals, specifically aversive and negative stimulus (Hikosaka, 2010). Several studies point to pathology in the habenula as contributing to schizophrenia (Sandyk, 1992; Caputo et al., 1998; Shepard et al., 2006). Despite the many studies on the habenula, the precise function of the habenula remains unclear. Here we describe functional consequences of regulation of GPR139 an orphan GPCR that is specifically expressed in the CNS and enriched in the habenula (Matsuo et al., 2005) in mouse models of domain of schizophrenia.
Methods
Specific expression of mouse GPR139 in the habenula was evaluated using bacterial artificial chromosome translating ribosome affinity purification (bacTRAP) and confirmed by immunohistochemistry. GPR139-/- mice were generated by removal of a 736bp region encoding the seven transmembrane domain (7TM) domain. Knockout animals were maintained inbred on a 129/SvEv background and evaluated in behavioral models that reflect aspects of negative symptoms. High throughput screen (HTS) for small molecules was performed. We expressed full length GPR139 into CHO cells and screened a 600K library using a calcium assay to identify small molecule agonist. Hits were identified and physical properties optimized to produce a molecule suitable for in vivo evaluation. GPR139 agonist was testedin vivo in social interaction in Poly(I:C) and cognitive test in subchronic PCP, models of schizophrenia.
Results
Using bacTRAP we observed enriched expression of GPR139 in substance P positive- cells of the medial habenula. This expression was confirmed with immunohistochemistry. To determine if GPR139 regulates the known role of the habenula in learning, motivation, and social behaviour, GPR139 -/- animals were generated and phenotyped. These animals appeared normal and performed comparably to wild-type animals in a range of standard tasks. However, they were significantly impaired in models that reflect aspects of negative symptoms such as progressive ratio (Killeen et al., 2009; Heath et al., 2016), a measure of motivation and nest-building (Pedersen et al., 2014; Nakajima et al., 2013), a model of self-neglect. Furthermore, these animals showed deficits in novel object recognition model of working memory (Antunes and Biala, 2012). The small molecule agonist was observed to reverse deficits in models of schizophrenia including cognition in a subchronic PCP induced attentional set-shifting paradigm (Birrell and Brown, 2000) and social interaction in the Poly(I:C) maternal model (Meyer et al., 2008; Bitanihirwe et al., 2010).
Discussion
These findings identify an orphan receptor that plays an important role in habenular function. Modulation of this receptor may provide an opportunity to address an important unmet need in schizophrenia.
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We report a significant decrease in transcription of the G protein-coupled receptor GPR39 in striatal neurons of Parkinson’s disease patients compared to healthy controls, suggesting ...that a positive modulator of GPR39 may beneficially impact neuroprotection. To test this notion, we developed various structurally diverse tool molecules. While we elaborated on previously reported starting points, we also performed an in silico screen which led to completely novel pharmacophores. In vitro studies indicated that GPR39 agonism does not have a profound effect on neuroprotection.
The potassium (K+) ion channel KCNK13 is specifically expressed in human microglia with elevated expression observed in post-mortem human brain tissue from patients with Alzheimer’s disease. ...Modulation of KCNK13 activity by a small-molecule inhibitor is proposed as a potential treatment for neurodegenerative diseases. Herein, we describe the evolution of a series of KCNK13 inhibitors derived from a high-throughput screening campaign, resulting in CVN293, a potent, selective, and brain permeable clinical candidate molecule. CVN293 demonstrated a concentration-dependent inhibition of the NLRP3-inflammasome mediated production of IL-1β from LPS-primed murine microglia. Cross-species pharmacokinetic data of CVN293 are also disclosed. These findings support the advancement of CVN293 in clinical trials.
Irregular
N
-methyl-
d
-aspartate receptor (NMDAR) function is one of the main hypotheses employed to facilitate understanding of the underlying disease state of schizophrenia. Although direct ...agonism of the NMDAR has not yielded promising therapeutics, advances have been made by modulating the NMDAR co-agonist site which is activated by glycine and
d
-serine. One approach to activate the co-agonist site is to increase synaptic
d
-serine levels through inhibition of
d
-amino acid oxidase (DAO), the major catabolic clearance pathway for this and other
d
-amino acids. A number of DAO inhibitors have been developed but most have not entered clinical trials. One exception to this is sodium benzoate which has demonstrated efficacy in small trials of schizophrenia and Alzheimer’s disease. Herein we provide data on the effect of sodium benzoate and an optimised Takeda compound, PGM030756 on ex vivo DAO enzyme occupancy and cerebellar
d
-serine levels in mice. Both compounds achieve high levels of enzyme occupancy; although lower doses of PGM030756 (1, 3 and 10 mg/kg) were required to achieve this compared to sodium benzoate (300, 1000 mg/kg). Cerebellar
d
-serine levels were increased by both agents with a delay of approximately 6 h after dosing before the peak effect was achieved. Our data and methods may be useful in understanding the effects of sodium benzoate that have been seen in clinical trials of schizophrenia and Alzheimer’s disease and to support the potential clinical assessment of other DAO inhibitors, such as PGM030756, which demonstrate good enzyme occupancy and
d
-serine increases following administration of low oral doses.
The low affinity metabotropic glutamate receptor mGluR7 has been implicated in numerous CNS disorders; however, a paucity of potent and selective activators has hampered full delineation of the ...functional role and therapeutic potential of this receptor. In this work, we present the identification, optimization, and characterization of highly potent, novel mGluR7 agonists. Of particular interest is the chromane CVN636, a potent (EC50 7 nM) allosteric agonist which demonstrates exquisite selectivity for mGluR7 compared to not only other mGluRs, but also a broad range of targets. CVN636 demonstrated CNS penetrance and efficacy in an in vivo rodent model of alcohol use disorder. CVN636 thus has potential to progress as a drug candidate in CNS disorders involving mGluR7 and glutamatergic dysfunction.
The low affinity metabotropic glutamate receptor mGluR
has been implicated in numerous CNS disorders; however, a paucity of potent and selective activators has hampered full delineation of the ...functional role and therapeutic potential of this receptor. In this work, we present the identification, optimization, and characterization of highly potent, novel mGluR
agonists. Of particular interest is the chromane
, a potent (EC
7 nM) allosteric agonist which demonstrates exquisite selectivity for mGluR
compared to not only other mGluRs, but also a broad range of targets.
demonstrated CNS penetrance and efficacy in an
rodent model of alcohol use disorder.
thus has potential to progress as a drug candidate in CNS disorders involving mGluR
and glutamatergic dysfunction.
Chromosomes that have undergone crossing over in meiotic prophase must maintain sister chromatid cohesion somewhere along their length between the first and second meiotic divisions. Although many ...eukaryotes use the centromere as a site to maintain cohesion, the holocentric organism
instead creates two chromosome domains of unequal length termed the short arm and long arm, which become the first and second site of cohesion loss at meiosis I and II. The mechanisms that confer distinct functions to the short and long arm domains remain poorly understood. Here, we show that phosphorylation of the synaptonemal complex protein SYP-1 is required to create these domains. Once crossover sites are designated, phosphorylated SYP-1 and PLK-2 become cooperatively confined to short arms and guide phosphorylated histone H3 and the chromosomal passenger complex to the site of meiosis I cohesion loss. Our results show that PLK-2 and phosphorylated SYP-1 ensure creation of the short arm subdomain, promoting disjunction of chromosomes in meiosis I.
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