Orexins increase mRNA expressions of neurotrophin-3 in rat primary cortical neuron cultures

C-terminal peptide of preproorexin enhances brain-derived neurotrophic factor expression in rat cerebrocortical cells and recognition memory in mice

During the production of orexin A and B from preproorexin, a common precursor protein, in hypothalamic orexin neurons, C-terminal peptide (herein called preproorexin C-peptide) is concomitantly produced via post-translational processing. The predicted three-dimensional structure of preproorexin C-peptide is similar among mammalian species, suggestive of a conserved function in the mammalian brain. However, C-peptide has long been regarded as a non-functional peptide. We herein examined the effects of rat and/or mouse preproorexin C-peptide on gene expression and cell viability in cultured rat cerebrocortical cells and on memory behavior in C57BL/6J mice. Rat and mouse C-peptides both increased brain-derived neurotrophic factor (Bdnf) mRNA levels. Moreover, C-peptide enhanced high K+-, glutamate-, and BDNF-induced increases in Bdnf mRNA levels without affecting forskolin-induced Bdnf expression. H-89, a protein kinase A inhibitor, blocked C-peptide-induced Bdnf expression, whereas rolipram, a phosphodiesterase inhibitor, enhanced this effect. Intracellular cyclic AMP concentrations were elevated by C-peptide. These results demonstrate that preproorexin C-peptide promoted Bdnf mRNA expression by a cyclic AMP-dependent mechanism. Eleven amino acids at the N terminus of rat preproorexin C-peptide exerted similar effects on Bdnf expression as full-length preproorexin C-peptide. Preproorexin C-peptide also exerted protective effects against CoCl2-induced neuronal cell death. An intracerebroventricular injection of mouse preproorexin C-peptide induced c-fos and Bdnf expression in the cerebral cortex and hippocampus and enhanced novel object recognition memory in mice. Collectively, the present results show that preproorexin C-peptide is a functional substance, at least in some pharmacological and neuronal settings.

Emphasizing roles of BDNF promoters and inducers in Alzheimer's disease for improving impaired cognition and memory

Brain-derived neurotrophic factor (BDNF) is a crucial neurotrophic factor adding to neurons' development and endurance. The amount of BDNF present in the brain determines susceptibility to various neurodegenerative diseases. In Alzheimer's disease (AD), often it is seen that low levels of BDNF are present, which primarily contributes to cognition deficit by regulating long-term potentiation (LTP) and synaptic plasticity. Molecular mechanisms underlying the synthesis, storage and release of BDNF are widely studied. New molecules are found, which contribute to the signal transduction pathway. Two important receptors of BDNF are TrkB and p75NTR. When BDNF binds to the TrkB receptor, it activates three main signalling pathways-phospholipase C, MAPK/ERK, PI3/AKT. BDNF holds an imperative part in LTP and dendritic development, which are essential for memory formation. BDNF supports synaptic integrity by influencing LTP and LTD. This action is conducted by modulating the glutamate receptors; AMPA and NMDA. This review paper discusses the aforesaid points along with inducers of BDNF. Drugs and herbals promote neuroprotection by increasing the hippocampus' BDNF level in various disease-induced animal models for neurodegeneration. Advancement in finding pertinent molecules contributing to the BDNF signalling pathway has been discussed, along with the areas that require further research and study.

Effects of bright light therapy on neuroinflammatory and neuroplasticity markers in a diurnal rodent model of Seasonal Affective Disorder

BACKGROUND

Bright light therapy (BLT) is widely used for treating Seasonal Affective Disorder (SAD). However, the neural mechanisms underlying the therapeutic effects of BLT remain largely unexplored. The present study used a diurnal rodent (Nile grass rats; Arvicanthis niloticus) to test the hypothesis that the therapeutic effects of BLT could be, in part, due to reduced neuroinflammation and/or enhanced neuroplasticity. Our previous research has demonstrated that compared to grass rats housed in a summer-like daytime bright light condition (1000 lux), those housed in a winter-like daytime dim light condition (50 lux) showed increased depression- and anxiety-like behaviours, as well as impaired sociosexual behaviours and spatial memory, similar to what is observed in patients suffering from SAD.

MATERIALS AND METHODS

In the present study, male and female grass rats were housed under the winter-like dim daytime light condition (lights on 600-1800 hr, 50 lux). The experimental groups received daily 1-h early morning BLT from 0600-0700 using full-spectrum light (10,000 lux), while the control groups received narrowband red light (λmax, 780 nm). Following 4 weeks of treatment, the expression of several neuroinflammatory or plasticity markers was examined in the medial prefrontal cortex (mPFC), basolateral amygdala (BLA), and the CA1 of the dorsal hippocampus.

RESULTS

For the neuroinflammatory markers, BLT reduced TNF-α in the BLA of females, and upregulated CD11b in the mPFC and IL6 in the BLA in males. For the neuroplasticity markers, BLT downregulated BDNF in the CA1 and TrkB in all three brain regions in females but upregulated BDNF in the BLA and CA1 in males.

CONCLUSIONS

These results indicate that the therapeutic effects of BLT on sleep, mood, and cognition may be attributed in part to mechanisms involving neuroinflammation and neuroplasticity in corticolimbic brain regions. Moreover, these effects appear to vary between sexes.

Cerebrospinal fluid proteomics in recent-onset Narcolepsy type 1 reveals activation of the complement system

Introduction

Narcolepsy type 1 (NT1) is a rare, chronic and disabling neurological disease causing excessive daytime sleepiness and cataplexy. NT1 is characterized pathologically by an almost complete loss of neurons producing the orexin neuropeptides in the lateral hypothalamus. Genetic and environmental factors strongly suggest the involvement of the immune system in the loss of orexin neurons. The cerebrospinal fluid (CSF), secreted locally and surrounding the central nervous system (CNS), represents an accessible window into CNS pathological processes.

Methods

To gain insight into the biological and molecular changes in NT1 patients, we performed a comparative proteomics analysis of the CSF from 21 recent-onset NT1 patients and from two control groups: group 1 with somatoform disorders, and group 2 patients with hypersomnia other than NT1, to control for any potential effect of sleep disturbances on CSF composition. To achieve an optimal proteomic coverage analysis, the twelve most abundant CSF proteins were depleted, and samples were analyzed by nano-flow liquid chromatography tandem mass spectrometry (nano-LC-MS/MS) using the latest generation of hybrid Orbitrap mass spectrometer.

Results and discussion

Our study allowed the identification and quantification of up to 1943 proteins, providing a remarkably deep analysis of the CSF proteome. Interestingly, gene set enrichment analysis indicated that the complement and coagulation systems were enriched and significantly activated in NT1 patients in both cohorts analyzed. Notably, the lectin and alternative complement pathway as well as the downstream lytic membrane attack complex were congruently increased in NT1. Our data suggest that the complement dysregulation in NT1 patients can contribute to immunopathology either by directly promoting tissue damage or as part of local inflammatory responses. We therefore reveal an altered composition of the CSF proteome in NT1 patients, which points to an ongoing inflammatory process contributed, at least in part, by the complement system.

Brain fractalkine-CX3CR1 signalling is anti-obesity system as anorexigenic and anti-inflammatory actions in diet-induced obese mice

Fractalkine is one of the CX3C chemokine family, and it is widely expressed in the brain including the hypothalamus. In the brain, fractalkine is expressed in neurons and binds to a CX3C chemokine receptor 1 (CX3CR1) in microglia. The hypothalamus regulates energy homeostasis of which dysregulation is associated with obesity. Therefore, we examined whether fractalkine-CX3CR1 signalling involved in regulating food intake and hypothalamic inflammation associated with obesity pathogenesis. In the present study, fractalkine significantly reduced food intake induced by several experimental stimuli and significantly increased brain-derived neurotrophic factor (BDNF) mRNA expression in the hypothalamus. Moreover, tyrosine receptor kinase B (TrkB) antagonist impaired fractalkine-induced anorexigenic actions. In addition, compared with wild-type mice, CX3CR1-deficient mice showed a significant increase in food intake and a significant decrease in BDNF mRNA expression in the hypothalamus. Mice fed a high-fat diet (HFD) for 16 weeks showed hypothalamic inflammation and reduced fractalkine mRNA expression in the hypothalamus. Intracerebroventricular administration of fractalkine significantly suppressed HFD-induced hypothalamic inflammation in mice. HFD intake for 4 weeks caused hypothalamic inflammation in CX3CR1-deficient mice, but not in wild-type mice. These findings suggest that fractalkine-CX3CR1 signalling induces anorexigenic actions via activation of the BDNF-TrkB pathway and suppresses HFD-induced hypothalamic inflammation in mice.

Atractylenolide-III suppresses lipopolysaccharide-induced inflammation via downregulation of toll-like receptor 4 in mouse microglia

Atractylenolide-III (AIII), a sesquiterpene compound isolated from the rhizome of Atractylodes macrocephala, has been reported to have anti-inflammatory effects in the peripheral organs. However, its effects on brain inflammation remain elusive. The present study investigated the effects of AIII on the response to lipopolysaccharide (LPS) in mouse microglia and clarified the underlying mechanism. In this study, treatment of MG6 cells with AIII (100 μM) significantly decreased the mRNA expression and protein levels of toll-like receptor 4 (TLR4). In addition, pretreatment of MG6 cells and primary cultured microglia cells with AIII (100 μM) significantly decreased the mRNA expression and protein levels of tumor necrosis factor-α, interleukin-1β, interleukin-6, inducible nitric oxide synthase, and cyclooxygenase-2 induced by LPS (5 ng/mL) without cytotoxicity. Subsequently, pretreatment with AIII significantly suppressed the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) and c-Jun NH₂-terminal kinase (JNK) after LPS stimulation in MG6 cells. These results showed that AIII downregulated TLR4 expression, leading to suppression of the p38 MAPK and JNK pathways, which in turn inhibited the production of pro-inflammatory cytokines and enzymes in LPS-stimulated microglia. Our findings, therefore, suggest the potential for AIII as a therapeutic agent for the treatment of brain inflammation, particularly in microglia-associated inflammation.

Impaired brain fractalkine-CX3CR1 signaling is implicated in cognitive dysfunction in diet-induced obese mice

INTRODUCTION

A diet high in saturated fat is well known to affect neuronal function and contribute to cognitive decline in experimental animals and humans. Fractalkine released from neurons acts on its receptor, CX3C chemokine receptor 1 (CX3CR1), in the microglia to regulate several brain functions. The present study addressed whether fractalkine-CX3CR1 signaling in the brain, especially the hippocampus, contributes to the cognitive deficits observed in diet-induced obese (DIO) mice.

RESEARCH DESIGN AND METHODS

Mice were given 60% high-fat diet for 16 weeks. The expression of fractalkine and CX3CR1 in the hippocampus, amygdala and prefrontal cortex of DIO mice was analyzed. Cognitive ability in the Y-maze test and hippocampal glutamate receptors and synaptic markers were observed in DIO and CX3CR1 antagonist-treated mice. Regulation of fractalkine and CX3CR1 expression in the hippocampus was examined following administration of a selective insulin-like growth factor-1 (IGF-1) receptor inhibitor and a tyrosine receptor kinase B (TrkB) antagonist in normal mice.

RESULTS

DIO mice exhibited significant cognitive deficits in the Y-maze test and decrease in fractalkine and CX3CR1 in the hippocampus and amygdala compared with mice fed a control diet (CD mice). Administration of the CX3CR1 antagonist 18a in normal mice induced significant cognitive deficits in the Y-maze test. DIO mice and CX3CR1 antagonist-treated mice exhibited significant decreases in protein levels of NMDA (N-methyl-D-aspartate) receptor subunit (NR2A), AMPA (α-amino-5-methyl-3-hydroxy-4-isoxazole propionate) receptor subunit (GluR1) and postsynaptic density protein 95 in the hippocampus compared with their respective controls. Furthermore, plasma IGF-1 and hippocampal brain-derived neurotrophic factor were significantly decreased in DIO mice compared with CD mice. Administration of a selective IGF-1 receptor inhibitor and a TrkB antagonist in normal mice significantly decreased fractalkine and CX3CR1 in the hippocampus.

CONCLUSIONS

These findings indicate that the cognitive decline observed in DIO mice is due, in part, to reduced fractalkine-CX3CR1 signaling in the corticolimbic system.

Reduced brain fractalkine-CX3CR1 signaling is involved in the impaired cognition of streptozotocin-treated mice

Patients with diabetes mellitus are predisposed to cognitive impairment. Fractalkine-CX3CR1 in the brain signaling represents a primary neuron-microglia inter-regulatory system for several brain functions including learning and memory processes. The present study addressed whether fractalkine-CX3CR1 signaling in the hippocampus contributes to the cognitive deficits observed in streptozotocin (STZ)-treated mice. Our results showed that STZ-treated mice exhibited significant cognitive deficits in the Y-maze test, and a decrease in fractalkine and CX3CR1 levels in the hippocampus. Moreover, intracerebroventricular injection of the CX3CR1 antagonist 18a in normal mice induced significant cognitive deficits in the Y-maze test. STZ-treated mice showed a significant increase in plasma corticosterone levels and a decrease in plasma and hippocampal levels of insulin-like growth factor-1 (IGF-1). Therefore, we examined the effects of corticosterone and IGF-1 on regulation of fractalkine and CX3CR1 expression. Dexamethasone (DEX) application significantly decreased the mRNA expression of fractalkine in primary neuron and astrocyte cultures, and of CX3CR1 in primary microglia cultures. On the other hand, IGF-1 application significantly increased the mRNA expression of fractalkine in primary neuron cultures and CX3CR1 in primary microglia cultures. In addition, administration of DEX and the IGF-1 receptor tyrosine kinase inhibitor picropodophyllin significantly reduced the mRNA expression of fractalkine and CX3CR1 in the hippocampus. These findings indicate that impaired cognition in STZ-treated mice is associated with reduced fractalkine-CX3CR1 signaling in the hippocampus which may be induced by an increase in corticosterone and a decrease in IGF-1.

[Choice of neuroprotective therapy regimens in patients with chronic cerebral ischemia, taking into account the synergy of drug interactions]

OBJECTIVE

Optimization of the choice of neuroprotective treatment regimens in patients with chronic cerebral ischemia that takes into account the synergy of drug interactions gives the doctor an opportunity for personalized approach that increases the effectiveness of treatment.

MATERIAL AND METHODS

Differential chemoreactomic analysis of the synergism of ethyl methyl hydroxypyridine succinate (EMHPS) and a number of monocomponent neuroprotective agents (piracetam, vinpocetine, citicoline, choline alfoscerate); proteomic analysis of polypeptide neuroprotectors (cerebrolysin, etc.); an expert analysis of multicomponent neuroprotector Cytoflavin.

RESULTS

Piracetam, citicoline (Neupilept) and choline alfoscerate (Cereton) effectively enhance the pharmacological properties of EMHPS and vice versa. Expert assessments of the synergism between the properties of EMHPS, polypeptide neuroprotectors (cerebrolysin) and other multicomponent drugs (cytoflavin), which are also used in adjuvant therapy with EMHPS, are presented.

CONCLUSION

In real clinical practice, of particular interest is the objectification of the appointment of combined therapy regimens. This study indicates that EMHPS can provide a favorable background for maximizing the effectiveness of therapy when used with other drugs.

[An analysis of the peptide composition of a 'light' peptide fraction of cerebrolysin]

AIM

To analyze the peptide composition of a light peptide fraction of cerebrolysin.

MATERIAL AND METHODS

Mass spectrometry (MS) with orbital ion traps and modern de novo MS-sequencing algorithms was performed.

RESULTS

The amino acid sequences of 14 635 peptides corresponding to the 1643 porcine proteome neuronal proteins are identified. An analysis of the human proteome annotation shows that these peptides can mimic the corresponding human peptides. In particular, 405 peptide fragments correspond to 300 known biologically active peptides, including fragments of antibacterial peptides (defensins, histatins), immunomodulatory (granulin, manserin) and vasoactive (endothelin, VIP) peptides. At the same time, 8953 of 14 635 peptides can modulate the activity of 275 human signaling proteins, including kinases CDK1, CDK2, TGFBR2, GSK3, MTOR, pro-apoptotic caspases CASP1, CASP3 and CASP6 etc. The results confirm the presence of Leu- and Met-enkephalins, fragments of neuropeptide orexin, neuropeptide VF, galanin and nerve growth factor that have a neurotrophic effect.

CONCLUSION

The results of a proteomic study of the peptide composition of cerebrolysin indicate the widest range of molecular mechanisms responsible for the clinical efficacy of this drug.

Significance of the orexinergic system in modulating stress-related responses in an animal model of post-traumatic stress disorder

Converging evidence indicates that orexins (ORXs), the regulatory neuropeptides, are implicated in anxiety- and depression-related behaviors via the modulation of neuroendocrine, serotonergic, and noradrenergic systems. This study evaluated the role of the orexinergic system in stress-associated physiological responses in a controlled prospective animal model. The pattern and time course of activation of hypothalamic ORX neurons in response to predator-scent stress (PSS) were examined using c-Fos as a marker for neuronal activity. The relationship between the behavioral response pattern 7 days post-exposure and expressions of ORXs was evaluated. We also investigated the effects of intracerebroventricular microinfusion of ORX-A or almorexant (ORX-A/B receptor antagonist) on behavioral responses 7 days following PSS exposure. Hypothalamic levels of ORX-A, neuropeptide Y (NPY), and brain-derived neurotrophic factor (BDNF) were assessed. Compared with rats whose behaviors were extremely disrupted (post-traumatic stress disorder [PTSD]-phenotype), those whose behaviors were minimally selectively disrupted displayed significantly upregulated ORX-A and ORX-B levels in the hypothalamic nuclei. Intracerebroventricular microinfusion of ORX-A before PSS reduced the prevalence of the PTSD phenotype compared with that of artificial cerebrospinal fluid or almorexant, and rats treated with almorexant displayed a higher prevalence of the PTSD phenotype than did untreated rats. Activated ORX neurons led to upregulated expressions of BDNF and NPY, which might provide an additional regulatory mechanism for the modulation of adaptive stress responses. The study indicates that the activated ORX system might promote adaptive responses to PSS probably via stimulation of BDNF and NPY secretion, and early intervention with ORX-A reduces the prevalence of the PTSD phenotype and increases the prevalence of adaptive phenotypes. The findings provide some insights into the mechanisms underlying the involvement of the ORX system in stress-related disorders.

Orexinergic modulation of serotonin neurons in the dorsal raphe of a diurnal rodent, Arvicanthis niloticus

The hypothalamic neuropeptide, orexin (or hypocretin), is implicated in numerous physiology and behavioral functions, including affective states such as depression and anxiety. The underlying mechanisms and neural circuits through which orexin modulates affective responses remain unclear. The objective of the present study was to test the hypothesis that the serotonin (5-HT) system of the dorsal raphe nucleus (DRN) is a downstream target through which orexin potentially manifests its role in affective states. Using a diurnal rodent, the Nile grass rat (Arvicanthis niloticus), we first characterized the expression of the orexin receptors OX1R and OX2R in the DRN using in situ hybridization. The results revealed distinct distributions of OX1R and OX2R mRNAs, with OX1R predominantly expressed in the dorsal and lateral wings of the DRN that are involved in affective processes, while OX2R was mostly found in the ventral DRN that is more involved in sensory-motor function. We next examined how the orexin-OX1R pathway regulates 5-HT in the DRN and some of its projection sites using a selective OX1R antagonist SB-334867 (10 mg/kg, i.p.). A single injection of SB-334867 decreased 5-HT-ir fibers within the anterior cingulate cortex (aCgC); five once-daily administrations of SB-334867 decreased 5-HT-ir not only in the aCgC but also in the DRN, oval bed nucleus of the stria terminalis (ovBNST), nucleus accumbens shell (NAcSh), and periaqueductal gray (PAG). HPLC analysis revealed that five once-daily administrations of SB-334867 did not affect 5-HT turnover to any of the five sites, although it increased the levels of both 5-HT and 5-HIAA in the NAcSh. These results together suggest that orexinergic modulation of DRN 5-HT neurons via OX1Rs may be one pathway through which orexin regulates mood and anxiety, as well as perhaps other neurobiological processes.

Orexin-A Exerts Neuroprotective Effects via OX1R in Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by progressive and selective death of dopaminergic neurons. Orexin-A is involved in many biological effects of the body. It has been reported that orexin-A has protective effects in cellular models of PD. However, little is known about the protective effects of orexin-A in animal parkinsonian models and the cellular mechanism has not yet been fully clarified. The aim of this study was to evaluate the effects of orexin-A in MPTP mice model of PD as well as the possible neuroprotective mechanisms of orexin-A on dopaminergic neurons. The results from animal experiments demonstrated that orexin-A attenuated the loss of dopaminergic neurons and the decrease of tyrosine hydroxylase (TH) expression in the substantia nigra, normalized the striatal dopaminergic fibers, and prevented the depletion of dopamine and its metabolites in the striatum. MPTP-treated mice showed cognitive impairments accompanied with significant motor deficiency. Orexin-A improved MPTP-induced impairments in both motor activity and spatial memory. Importantly, orexin-A increased the protein level of brain-derived neurotrophic factor (BDNF) in dopaminergic neurons of the substantia nigra. Furthermore, the protective effects of orexin-A on MPTP parkinsonian mice could be blocked by orexinergic receptor 1 (OX1R) antagonist, SB334867. In another set of experiments with SH-SY5Y dopaminergic cells, orexin-A significantly induced the expression of BDNF in a dose and time-dependent manner. The upregulation of BDNF is mainly concerned with PI3K and PKC signaling pathways via OX1R. The present study demonstrated that orexin-A exerted neuroprotective effects on MPTP parkinsonian mice, which may imply orexin-A as a potential therapeutic target for PD.

Orexin-A Exerts Neuroprotective Effects via OX1R in Parkinson's Disease

Parkinson’s disease (PD) is a common neurodegenerative disorder characterized by progressive and selective death of dopaminergic neurons. Orexin-A is involved in many biological effects of the body. It has been reported that orexin-A has protective effects in cellular models of PD. However, little is known about the protective effects of orexin-A in animal parkinsonian models and the cellular mechanism has not yet been fully clarified. The aim of this study was to evaluate the effects of orexin-A in MPTP mice model of PD as well as the possible neuroprotective mechanisms of orexin-A on dopaminergic neurons. The results from animal experiments demonstrated that orexin-A attenuated the loss of dopaminergic neurons and the decrease of tyrosine hydroxylase (TH) expression in the substantia nigra, normalized the striatal dopaminergic fibers, and prevented the depletion of dopamine and its metabolites in the striatum. MPTP-treated mice showed cognitive impairments accompanied with significant motor deficiency. Orexin-A improved MPTP-induced impairments in both motor activity and spatial memory. Importantly, orexin-A increased the protein level of brain-derived neurotrophic factor (BDNF) in dopaminergic neurons of the substantia nigra. Furthermore, the protective effects of orexin-A on MPTP parkinsonian mice could be blocked by orexinergic receptor 1 (OX1R) antagonist, SB334867. In another set of experiments with SH-SY5Y dopaminergic cells, orexin-A significantly induced the expression of BDNF in a dose and time-dependent manner. The upregulation of BDNF is mainly concerned with PI3K and PKC signaling pathways via OX1R. The present study demonstrated that orexin-A exerted neuroprotective effects on MPTP parkinsonian mice, which may imply orexin-A as a potential therapeutic target for PD.

Orexin-A inhibits capsaicin-induced changes in cyclooxygenase-2 and brain-derived neurotrophic factor expression in trigeminal nucleus caudalis of rats

Background

The trigeminal nucleus caudalis (Vc) is a primary central site for trigeminal transmitting. Noxious stimulation of the trigeminal nociceptors alters the central synaptic releases and neural expression of some inflammatory and trophic agents. Orexin-A and the orexin 1 receptor (OX1R) are expressed in pain pathways including trigeminal pain transmission. However, the the mechanism(s) underling orexin-A effects on trigeminal pain modulation have not been fully clarified.

Methods

Trigeminal pain was induced by subcutaneous injection of capsaicin in the upper lip in rats. The effect of trigeminal pain on cyclooxygenase-2 (COX-2) and brain-derived neurotrophic factor (BDNF) expression in the Vc of animals was determined by immunofluorescence. Subsequently, OX1R agonist (orexin-A) and antagonist (SB-334867-A) was administrated in the Vc to investigate the possible roles of the Vc OX1R on changes in COX-2 and BDNF levels following pain induction.

Results

The data indicated an increase in COX-2 and decrease in BDNF immuno-reactivity in the Vc of capsaicin, and capsaicin- pretreated with SB-334867-A (80 nM), groups of rat. However, the effect of capsaicin on COX-2 and BDNF expressions was reversed by a Vc microinjection of orexin-A (100 pM).

Conclusions

Overall, the present data reveals that orexin-A can attenuate capsaicin-induced trigeminal pain through the modulation of pain effects on COX-2 and BDNF expressions in the Vc of rats.

RNA-seq expression profiling of rat MCAO model following reperfusion Orexin-A

Orexin-A is a neuropeptide with potent neuroprotective activity towards cerebral ischemia-reperfusion (I/R) injury, but few studies have attempted to elucidate the mechanism. Herein, we performed global gene expression profiling of the hippocampus following reperfusion with Orexin-A using RNA sequencing (RNA-seq). RNA-seq identified 649 differentially expressed genes (DEGs) in the Orexin-A group compared with saline controls (I/R group), of which 149 were up-regulated and 500 were down-regulated. DEGs were confirmed using qRT-PCR, their molecular functions, biological processes and molecular components were explored using Gene Ontology (GO) analysis and 206 KEGG pathways were associated with Orexin-A treatment. MAPK, chemokine and calcium signalling pathways were mainly responsible for the neuroprotective effects of Orexin-A. Hspb1, Igf2 and Ptk2b were selected for functional interaction analysis by GeneMANIA. The results suggest that Orexin-A modifies gene expression in the hippocampus, leading to neuroprotection from I/R injury. The study provides a basis for future elucidation of the molecular mechanisms underlying Orexin-A.

Neuronal cells derived from human induced pluripotent stem cells as a functional tool of melanocortin system

BACKGROUND

The preparation of human neurons derived from human induced pluripotent stem (iPS) cells can serve as a potential tool for evaluating the physiological and pathophysiological properties of human neurons and for drug development.

METHODS

In the present study, the functional activity in neuronal cells differentiated from human iPS cells was observed.

RESULTS

The differentiated cells expressed mRNAs for classical neuronal markers (microtubule-associated protein 2, β-tubulin III, calbindin 1, synaptophysin and postsynaptic density protein 95) and for subunits of various excitatory and inhibitory transmitters (NR1, NR2A, NR2B, GABA_A α1). Moreover, the differentiated cells expressed neuropeptides and receptors which are predominantly present in the hypothalamus. The expression of mRNA for preopiomelanocortin, agouti-related protein (AgRP), melanocortin-3 receptor (MC3R) and melanocortin-4 receptor (MC4R) increased in culture with a peak on Day 30 which subsequently decreased at Day 45. Immunoreactivities for MC3R and MC4R were also observed in cells differentiated from human iPS cells. Application of a potent agonist for MC3R and MC4R, [Nle4, D-Phe7]-α-melanocyte-stimulating hormone, significantly increased intracellular cAMP levels, but this was suppressed by AgRP (83-132) and SHU9119.

CONCLUSIONS

These findings offer the possibility for drug developments using neurons differentiated from normal or disease-associated human iPS cells.

Inhibition of TrkB at the nucleus accumbens, using ANA-12, regulates basal and stress-induced orexin A expression within the mesolimbic system and affects anxiety, sociability and motivation

Repeated stress exposure can lead to the development of anxiety and mood disorders. An emerging biological substrate of depression and associated pathology is the nucleus accumbens (NAc), which through interactions with limbic, cognitive and motor circuits can regulate a variety of stress responses. Within these circuits, orexin neurons are involved in arousal and stress adaptability, effects proposed mediated via brain-derived neurotrophic factor signaling. This study tested the hypotheses that 1) repeated exposure to heterotypic stress alters social ability and preference and passive avoidant behaviors, 2) TrkB receptors at the NAc shell regulates stress-induced behavioral responses and orexin expression within the mesocorticolimbic system. Our findings indicate that ANA-12 (0.25 μg/0.5 μl) enhanced sociability during the social interaction test, although treatment had no effect on social preference. The development of conditioned place preference, and fear retention in the passive avoidance test were also facilitated by ANA-12. Biochemical assessments on brain tissues collected within 2 h of a forced swim exposure revealed that ANA-12 increased orexin A immunoreactivity (ir) in the hypothalamic perifornical area, while expression was reduced in the ventral portion of the hippocampal CA1 layer, irrespective of the stress condition. This contrasts changes at the VTA characterized by elevated versus reduced orexin A-ir in ANA-12-treated stress and non-stress rats, respectively. Colocalized orexin A- and tyrosine hydroxylase (TH)-ir at the VTA supports a different temporal expression post stress, TH-ir being unaffected 9 days post stress. These findings support a role for TrkB receptors in regulating basal and stress-induced social, cognitive and motivational behavior, and modulatory actions of BDNF, via TrkB signaling, on orexin A signaling upon stress exposure.

Exercise Influence on Hippocampal Function: Possible Involvement of Orexin-A

In the present article, we provide a brief review of current knowledge regarding the effects induced by physical exercise on hippocampus. Research involving animals and humans supports the view that physical exercise, enhancing hippocampal neurogenesis and function, improves cognition, and regulates mood. These beneficial effects depend on the contribute of more factors including the enhancement of vascularization and upregulation of growth factors. Among these, the BDNF seems to play a significant role. Another putative factor that might contribute to beneficial effects of exercise is the orexin-A. In support of this hypothesis there are the following observations: (1) orexin-A enhances hippocampal neurogenesis and function and (2) the levels of orexin-A increase with physical exercise. The beneficial effects of exercise may represent an important resource to hinder the cognitive decline associated with the aging-related hippocampal deterioration and ameliorate depressive symptoms.

[Molecular mechanisms of pidolate magnesium action and its neurotropic affects]

AIM

A complex study of pharmacological properties of magnesium pyroglutamate using the modern methods of chemoinformatics and bioinformatics.

MATERIAL AND METHODS

Pharmacological properties of magnesium pyroglutamate were studied using chemoinformatic and bioinformatic analyses.

RESULTS

Neurotropic effects of magnesium pyroglutamate are due to an influence on the synthesis of neuropeptides containing pyroglutamate (orexin, thyroliberin, neurotensin etc) and due to the similarity between pyroglutamate-anion with some neuroactive components (L-theanine, 2-pirrolydinone, piracetam).

CONCLUSION

The results of the study suggest neuroprotective, sedative and antidepressive properties of magnesium pyroglutamate which are realized by pyroglutamate-anion in the synergism with magnesium cation.

Spatiotemporal Development of the Orexinergic (Hypocretinergic) System in the Central Nervous System of Xenopus laevis

The present immunohistochemical study represents a detailed spatiotemporal analysis of the localization of orexin-immunoreactive (OX-ir) cells and fibers throughout development in the brain of the anuran amphibian Xenopus laevis, a model frequently used in developmental studies. Anurans undergo remarkable physiological changes during the early life stages, and very little is known about the ontogeny and the localization of the centers that control functions such as appetite and feed ingestion in the developing brain. We examined the onset of the orexinergic system, demonstrated to be involved in appetite regulation, using antibodies against mammalian orexin-A and orexin-B peptides. Simultaneous detection of orexins with other territorial markers was used to assess the precise location of the orexinergic cells in the hypothalamus, analyzed within a segmental paradigm. Double staining of orexins and tyrosine hydroxylase served to evaluate possible interactions with the catecholaminergic systems. At early embryonic stages, the first OX-ir cells were detected in the hypothalamus and, soon after, long descending projections were observed through the brainstem to the spinal cord. As brain development proceeded, the double-staining techniques demonstrated that this OX-ir cell group was located in the suprachiasmatic nucleus within the alar hypothalamus. Throughout larval development, the number of OX-ir cells increased notably and a widespread fiber network that innervated the main areas of the forebrain and brainstem was progressively formed, including innervation in the posterior tubercle and mesencephalon, the locus coeruleus, and the nucleus of the solitary tract where catecholaminergic cells are present. In addition, orexinergic cells were detected in the preoptic area and the tuberal hypothalamus only at late prometamorphic stages. The final distribution pattern, largely similar to that of the adult, was achieved through metamorphic climax. The early expression of orexins in Xenopus suggests important roles in brain development in the embryonic period before feeding, and the progression of the temporal and spatial complexity of the orexinergic system might be correlated to the maturation of appetite control regulation, among other functions.

Blockade of orexin receptors attenuates the cardiovascular response to air-jet stress in spontaneously hypertensive rats

This study tested the hypothesis that orexin plays a role in the elevated pressor response to acute stress in the spontaneously hypertensive rat (SHR). The pressor response to air jet stress (AJS) (n=11/group) was 2.5 times greater in vehicle treated SHR versus Wistar (WIS) rats. Systemic delivery of 30mg/kg of the dual orexin receptor antagonist almorexant did not significantly change resting mean arterial pressure (MAP) but did attenuate the pressor response elicited by AJS to a greater extent in the SHR compared to the Wistar rats (~65% versus ~33% reduction respectively; n=6/group). Alternatively 100mg/kg almorexant reduced resting MAP in the SHR (~25mm Hg drop) and attenuated both the heart rate (HR; ~50% reduction) and MAP (~62% reduction) response to AJS in both strains (n=6/group). Systemic application of SB-334867 (3mg/kg), an orexin receptor type 1 antagonist (n=5/group), selectively reduced resting MAP and attenuated the HR response to AJS in the SHR but had no effect on the pressor response in either strain. The potential role of endogenous orexin release in cardiovascular control in the SHR was linked to a significant increase in brain-derived neurotrophic factor mRNA expression in the hypothalamus and elevated orexin receptor expression (type 2 only) in the dorsal pons when compared to WIS (n=4/group). These results demonstrate that the exaggerated pressor response in the SHR to stress is linked to increased orexin receptor activation and possibly altered orexin receptor expression in the dorsal pons and BDNF expression in the hypothalamus.

7,8-Dihydroxyflavone reduces sleep during dark phase and suppresses orexin A but not orexin B in mice

Brain-derived neurotrophic factor (BDNF) binds to Tropomyosin-receptor-kinase B (TrkB) receptors that regulate synaptic strength and plasticity in the mammalian nervous system. 7,8-Dihydroxyflavone (DHF) is a recently identified small molecule Trk B agonist that has been reported to ameliorate depression, attenuate the fear response, improve memory consolidation, and exert neuroprotective effects. Poor and disturbed sleep remains a symptom of major depressive disorder and most current antidepressants affect sleep. Therefore, we conducted sleep/wake recordings and concomitant measurement of brain orexins, endogenous peptides that suppress sleep, in mice for this study. Baseline polysomnograph recording was performed for 24 h followed by treatment with either 5 mg/kg of DHF or vehicle at the beginning of the dark phase. Animals were sacrificed the following day, one hour after the final treatment with DHF. Orexin A and B were quantified using ELISA and radioimmunoassay, respectively. Total sleep was significantly decreased in the DHF group, 4 h after drug administration in the dark phase, when compared with vehicle-treated animals. This difference was due to a significant decrease of non-rapid eye movement sleep, but not rapid eye movement sleep. DHF increased power of alpha and sigma bands but suppressed power of gamma band during sleep in dark phase. Interestingly, hypothalamic levels of orexin A were also significantly decreased in the DHF group (97 pg/mg) when compared with the vehicle-treated group (132 pg/mg). However, no significant differences of orexin B were observed between groups. Additionally, no change was found in immobility tests.

The role of orexin in post-stroke inflammation, cognitive decline, and depression

Ischemic stroke results in diverse pathophysiologies, including cerebral inflammation, neuronal loss, cognitive dysfunction, and depression. Studies aimed at identifying therapeutic solutions to alleviate these outcomes are important due to the increase in the number of stroke patients annually. Recently, many studies have reported that orexin, commonly known as a neuropeptide regulator of sleep/wakefulness and appetite, is associated with neuronal cell apoptosis, memory function, and depressive symptoms. Here, we briefly summarize recent studies regarding the role and future perspectives of orexin in post-ischemic stroke. This review advances our understanding of the role of orexin in post-stroke pathologies, focusing on its possible function as a therapeutic regulator in the post-ischemic brain. Ultimately, we suggest the clinical potential of orexin to regulate post-stroke pathologies.

Impaired CNS leptin action is implicated in depression associated with obesity

Recent epidemiological studies indicate that obesity increases the incidence of depression. We examined the implication of leptin for obesity-associated depression. Leptin induced antidepressive behavior in normal mice in a forced swimming test (FST), and leptin-overexpressing transgenic mice with hyperleptinemia exhibited more antidepressive behavior in the FST than nontransgenic mice. In contrast, leptin-deficient ob/ob mice showed more severe depressive behavior in the FST than normal mice, and leptin administration substantially ameliorated this depressive behavior. Diet-induced obese (DIO) mice fed a high-fat diet showed more depressive behavior in the FST and in a sucrose preference test compared with mice fed a control diet (CD). In DIO mice, leptin induced neither antidepressive action nor increment of the number of c-Fos immunoreactive cells in the hippocampus. Diet substitution from high-fat diet to CD in DIO mice ameliorated the depressive behavior and restored leptin-induced antidepressive action. Brain-derived neurotrophic factor concentrations in the hippocampus were significantly lower in DIO mice than in CD mice. Leptin administration significantly increased hippocampal brain-derived neurotrophic factor concentrations in CD mice but not in DIO mice. The antidepressant activity of leptin in CD mice was significantly attenuated by treatment with K252a. These findings demonstrated that leptin induces an antidepressive state, and DIO mice, which exhibit severe depressive behavior, did not respond to leptin in both the FST and the biochemical changes in the hippocampus. Thus, depression associated with obesity is due, at least in part, to impaired leptin activity in the hippocampus.

Orexin-A and orexin-B during the postnatal development of the rat brain

Orexin-A and orexin-B are hypothalamic neuropeptides isolated from a small group of neurons in the hypothalamus, which project their axons to all major parts of the central nervous system. Despite the extensive information about orexin expression and function at different parts of the nervous system in adults, data about the development and maturation of the orexin system in the brain are a bit contradictory and insufficient. A previous study has found expression of orexins in the hypothalamus after postnatal day 15 only, while others report orexins detection at embryonic stages of brain formation. In the present study, we investigated the distribution of orexin-A and orexin-B neuronal cell bodies and fibers in the brain at three different postnatal stages: 1-week-, 2-week-old and adult rats. By means of immunohistochemical techniques, we demonstrated that a small subset of cells in the lateral hypothalamus, and the perifornical and periventricular areas were orexin-A and orexin-B positive not only in 2-week-old and adult rats but also in 1-week-old animals. In addition, orexin-A and orexin-B expressing neuronal varicosities were found in many other brain regions. These results suggest that orexin-A and orexin-B play an important role in the early postnatal brain development. The widespread distribution of orexinergic projections through all these stages may imply an involvement of the two neurotransmitters in a large variety of physiological and behavioral processes also including higher brain functions like learning and memory.