TRMT10A dysfunction perturbs codon translation of initiator methionine and glutamine and impairs brain functions in mice.

In higher eukaryotes, tRNA methyltransferase 10A (TRMT10A) is responsible for N1-methylguanosine modification at position nine of various cytoplasmic tRNAs. Pathogenic mutations in TRMT10A cause intellectual disability, microcephaly, diabetes, and short stature in humans, and generate cytotoxic tRNA fragments in cultured cells; however, it is not clear how TRMT10A supports codon translation or brain functions. Here, we generated Trmt10a null mice and showed that tRNAGln(CUG) and initiator methionine tRNA levels were universally decreased in various tissues; the same was true in a human cell line lacking TRMT10A. Ribosome profiling of mouse brain revealed that dysfunction of TRMT10A causes ribosome slowdown at the Gln(CAG) codon and increases translation of Atf4 due to higher frequency of leaky scanning of its upstream open reading frames. Broadly speaking, translation of a subset of mRNAs, especially those for neuronal structures, is perturbed in the mutant brain. Despite not showing discernable defects in the pancreas, liver, or kidney, Trmt10a null mice showed lower body weight and smaller hippocampal postsynaptic densities, which is associated with defective synaptic plasticity and memory. Taken together, our study provides mechanistic insight into the roles of TRMT10A in the brain, and exemplifies the importance of universal tRNA modification during translation of specific codons.

Structural polymorphism of the nucleic acids in pentanucleotide repeats associated with the neurological disorder CANVAS.

Short tandem repeats are inherently unstable during DNA replication depending on repeat length, and the expansion of the repeat length in the human genome is responsible for repeat expansion disorders. Pentanucleotide AAGGG and ACAGG repeat expansions in intron 2 of the gene encoding replication factor C subunit 1 (RFC1) cause cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) and other phenotypes of late-onset cerebellar ataxia. Herein, we reveal the structural polymorphism of the RFC1 repeats associated with CANVAS in vitro. Single-stranded AAGGG repeat DNA formed a hybrid-type G-quadruplex, whereas its RNA formed a parallel-type G-quadruplex with three layers. The RNA of the ACAGG repeat formed hairpin structure comprising C-G and G-C base pairs with A:A and GA:AG mismatched repeats. Furthermore, both pathogenic repeat RNAs formed more rigid structures than those of the nonpathogenic repeat RNAs. These findings provide novel insights into the structural polymorphism of the RFC1 repeats, which may be closely related to the disease mechanism of CANVAS.

An α-synuclein decoy peptide prevents cytotoxic α-synuclein aggregation caused by fatty acid binding protein 3.

α-synuclein (αSyn) is a protein known to form intracellular aggregates during the manifestation of Parkinson's disease. Previously, it was shown that αSyn aggregation was strongly suppressed in the midbrain region of mice that did not possess the gene encoding the lipid transport protein fatty acid binding protein 3 (FABP3). An interaction between these two proteins was detected in vitro, suggesting that FABP3 may play a role in the aggregation and deposition of αSyn in neurons. To characterize the molecular mechanisms that underlie the interactions between FABP3 and αSyn that modulate the cellular accumulation of the latter, in this report, we used in vitro fluorescence assays combined with fluorescence microscopy, transmission electron microscopy, and quartz crystal microbalance assays to characterize in detail the process and consequences of FABP3-αSyn interaction. We demonstrated that binding of FABP3 to αSyn results in changes in the aggregation mechanism of the latter; specifically, a suppression of fibrillar forms of αSyn and also the production of aggregates with an enhanced cytotoxicity toward mice neuro2A cells. Because this interaction involved the C-terminal sequence region of αSyn, we tested a peptide derived from this region of αSyn (αSynP130-140) as a decoy to prevent the FABP3-αSyn interaction. We observed that the peptide competitively inhibited binding of αSyn to FABP3 in vitro and in cultured cells. We propose that administration of αSynP130-140 might be used to prevent the accumulation of toxic FABP3-αSyn oligomers in cells, thereby preventing the progression of Parkinson's disease.

Crucial Role of FABP3 in αSyn-Induced Reduction of Septal GABAergic Neurons and Cognitive Decline in Mice.

In synucleinopathies, while motor symptoms are thought to be attributed to the accumulation of misfolded α-synuclein (αSyn) in nigral dopaminergic neurons, it remains to be elucidated how cognitive decline arises. Here, we investigated the effects of distinct αSyn strains on cognition and the related neuropathology in the medial septum/diagonal band (MS/DB), a key region for cognitive processing. Bilateral injection of αSyn fibrils into the dorsal striatum potently impaired cognition in mice. The cognitive decline was accompanied by accumulation of phosphorylated αSyn at Ser129 and reduction of gamma-aminobutyric acid (GABA)-ergic but not cholinergic neurons in the MS/DB. Since we have demonstrated that fatty acid-binding protein 3 (FABP3) is critical for αSyn neurotoxicity in nigral dopaminergic neurons, we investigated whether FABP3 also participates in αSyn pathology in the MS/DB and cognitive decline. FABP3 was highly expressed in GABAergic but rarely in cholinergic neurons in the MS/DB. Notably, Fabp3 deletion antagonized the accumulation of phosphorylated αSyn, decrease in GABAergic neurons, and cognitive impairment caused by αSyn fibrils. Overall, the present study indicates that FABP3 mediates αSyn neurotoxicity in septal GABAergic neurons and the resultant cognitive impairment, and that FABP3 in this subpopulation could be a therapeutic target for dementia in synucleinopathies.

Dopamine D2L Receptor Deficiency Causes Stress Vulnerability through 5-HT1A Receptor Dysfunction in Serotonergic Neurons.

Mental disorders are caused by genetic and environmental factors. We here show that deficiency of an isoform of dopamine D2 receptor (D2R), D2LR, causes stress vulnerability in mouse. This occurs through dysfunction of serotonin [5-hydroxytryptamine (5-HT)] 1A receptor (5-HT1AR) on serotonergic neurons in the mouse brain. Exposure to forced swim stress significantly increased anxiety- and depressive-like behaviors in D2LR knock-out (KO) male mice compared with wild-type mice. Treatment with 8-OH-DPAT, a 5-HT1AR agonist, failed to alleviate the stress-induced behaviors in D2LR-KO mice. In forced swim-stressed D2LR-KO mice, 5-HT efflux in the medial prefrontal cortex was elevated and the expression of genes related to 5-HT levels was upregulated by the transcription factor PET1 in the dorsal raphe nucleus. Notably, D2LR formed a heteromer with 5-HT1AR in serotonergic neurons, thereby suppressing 5-HT1AR-activated G-protein-activated inwardly rectifying potassium conductance in D2LR-KO serotonergic neurons. Finally, D2LR overexpression in serotonergic neurons in the dorsal raphe nucleus alleviated stress vulnerability observed in D2LR-KO mice. Together, we conclude that disruption of the negative feedback regulation by the D2LR/5-HT1A heteromer causes stress vulnerability.SIGNIFICANCE STATEMENT Etiologies of mental disorders are multifactorial, e.g., interactions between genetic and environmental factors. In this study, using a mouse model, we showed that genetic depletion of an isoform of dopamine D2 receptor, D2LR, causes stress vulnerability associated with dysfunction of serotonin 1A receptor, 5-HT1AR in serotonergic neurons. The D2LR/5-HT1AR inhibitory G-protein-coupled heteromer may function as a negative feedback regulator to suppress psychosocial stress.

Pharmacological prospects of G-quadruplexes for neurological diseases using porphyrins.

Genomic regions with guanine (G)-rich sequences make non-Watson-Crick base pairs, which result in the formation of unique nucleic acid structures called G-quadruplexes (G4s) in cells. Studies have suggested that abnormal G4s are involved in neurological diseases. For example, the formation of G4s caused by expansion of G-rich sequences is implicated in C9orf72-mediated amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD), and fragile X-related tremor/ataxia syndrome (FXTAS). In addition, the disruption and/or mutation of G4 binding proteins (G4BPs), such as heterogeneous nuclear ribonucleoproteins (hnRNPs) and DNA/RNA helicases, is related to neurological diseases. For instance, mutations in a G4BP called ATRX lead to a neurodevelopmental disorder, ATR-X syndrome, which is associated with intellectual disability. We found that porphyrins are potential candidate drugs for treating ATR-X syndrome through their G4 binding ability. Importantly, intracellular porphyrins are produced from 5-aminolevulinic acid (5-ALA) in vivo. Oral administration of 5-ALA improved cognitive dysfunction in an ATR-X syndrome model mouse, and language ability in an ATR-X syndrome patient. In this review, we suggest a novel therapeutic strategy targeting G4s using porphyrins in neurological diseases.

Identification and immunohistochemical characterization of G-quadruplexes in mouse brain.

Guanine-rich DNA and RNA can form a four-stranded structure, termed G-quadruplexes (G4s) in vitro as well as in cells. The formation of G4 is implicated in many physiological events, such as gene transcription, translation, and epigenetics. However, the presence of G4 has not been revealed in the brain. Here, we demonstrate the localization of G4 in the mouse brain by immunohistochemical analysis. In cultured mouse forebrain neurons, numerous punctate G4 foci were observed in nuclei as well as in cytoplasmic areas, including axons, dendrites, and postsynapses. Interestingly, the G4 foci in nuclei show more marked co-localizations with the bright spots of DAPI-positive heterochromatin clusters in mature neurons compared to immature ones. In slices from adult mouse brain, the G4 foci were distributed throughout the brain but were particularly prominent in the hippocampus, olfactory bulb, and cerebellum. In the hippocampus, G4 foci were strongly expressed in neurons and weakly in astrocytes. Consistent with the results in cultured neurons, the nuclear G4 foci were co-localized with heterochromatin in calbindin-positive mature granule cells but less in doublecortin-positive neuronal progenitor cells in the dentate gyrus. Electron microscopic immunolabeling revealed G4 foci on nucleolus-associated chromosomal domains (NADs) and cytoplasm in the adult mouse hippocampal CA1 region. These observations suggest potentially critical roles of G4 in neuronal developmental stages through regulating chromatin structures and cytoplasmic metabolism of RNA.

Anti-Epileptic Effects of FABP3 Ligand MF1 through the Benzodiazepine Recognition Site of the GABAA Receptor.

Recently, we developed the fatty acid-binding protein 3 (FABP3) ligand MF1 (4-(2-(1-(2-chlorophenyl)-5-phenyl-1H-pyrazol-3-yl)phenoxy) butanoic acid) as a therapeutic candidate for α-synucleinopathies. MF1 shows affinity towards γ-aminobutyric acid type-A (GABAA) receptor, but its effect on the receptor remains unclear. Here, we investigate the pharmacological properties of MF1 on the GABAA receptor overexpressed in Neuro2A cells. While MF1 (1-100 µm) alone failed to evoke GABA currents, MF1 (1 µm) promoted GABA currents during GABA exposure (1 and 10 µm). MF1-promoted GABA currents were blocked by flumazenil (10 µm) treatment, suggesting that MF1 enhances receptor function via the benzodiazepine recognition site. Acute and chronic administration of MF1 (0.1, 0.3 and 1.0 mg/kg, p.o.) significantly attenuated status epilepticus (SE) and the mortality rate in pilocarpine (PILO: 300 mg/kg, i.p.)-treated mice, similar to diazepam (DZP: 5.0 mg/kg, i.p.). The anti-epileptic effects of DZP (5.0 mg/kg, i.p.) and MF1 (0.3 mg/kg, p.o.) were completely abolished by flumazenil (25 mg/kg, i.p.) treatment. Pentylenetetrazol (PTZ: 90 mg/kg, i.p.)-induced seizures in mice were suppressed by DZP (5.0 mg/kg, i.p.), but not MF1. Collectively, this suggests that MF1 is a mild enhancer of the GABAA receptor and exercises anti-epileptic effects through the receptor's benzodiazepine recognition site in PILO-induced SE models.

Fatty Acid Binding Protein 3 Enhances the Spreading and Toxicity of α-Synuclein in Mouse Brain.

Oligomerization and/or aggregation of α-synuclein (α-Syn) triggers α-synucleinopathies such as Parkinson's disease and dementia with Lewy bodies. It is known that α-Syn can spread in the brain like prions; however, the mechanism remains unclear. We demonstrated that fatty acid binding protein 3 (FABP3) promotes propagation of α-Syn in mouse brain. Animals were injected with mouse or human α-Syn pre-formed fibrils (PFF) into the bilateral substantia nigra pars compacta (SNpc). Two weeks after injection of mouse α-Syn PFF, wild-type (WT) mice exhibited motor and cognitive deficits, whereas FABP3 knock-out (Fabp3-/-) mice did not. The number of phosphorylated α-Syn (Ser-129)-positive cells was significantly decreased in Fabp3-/- mouse brain compared to that in WT mice. The SNpc was unilaterally infected with AAV-GFP/FABP3 in Fabp3-/- mice to confirm the involvement of FABP3 in the development of α-Syn PFF toxicity. The number of tyrosine hydroxylase (TH)- and phosphorylated α-Syn (Ser-129)-positive cells following α-Syn PFF injection significantly decreased in Fabp3-/- mice and markedly increased by AAV-GFP/FABP3 infection. Finally, we confirmed that the novel FABP3 inhibitor MF1 significantly antagonized motor and cognitive impairments by preventing α-Syn spreading following α-Syn PFF injection. Overall, FABP3 enhances α-Syn spreading in the brain following α-Syn PFF injection, and the FABP3 ligand MF1 represents an attractive therapeutic candidate for α-synucleinopathy.

Cognitive enhancer ST101 improves schizophrenia-like behaviors in neonatal ventral hippocampus-lesioned rats in association with improved CaMKII/PKC pathway.

Atypical antipsychotics improve positive and negative symptoms but are not effective for treating cognitive impairments in patients with schizophrenia. We previously reported that cognitive impairments in neonatal ventral hippocampus (NVH)-lesioned rats show resistance to atypical antipsychotics risperidone and are associated with reduced calcium/calmodulin-dependent protein kinase II (CaMKII) and protein kinase C (PKC) signaling in memory-related regions. The cognitive enhancer ST101 (spiro[imi-dazo[1,2-a]pyridine-3,2-indan]-2(3H)-one) stimulates CaMKII activity in the hippocampus and medial prefrontal cortex (mPFC). We thus tested ST101 on cognitive impairments in NVH-lesioned rats. Chronic ST101 administration (0.1 and/or 0.5 mg/kg, p.o.) significantly improved deficits in prepulse inhibition (PPI), social interaction, and cognitive function in NVH-lesioned rats. ST101 administration (0.5 mg/kg, p.o.) significantly restored the decreased CaMKII autophosphorylation (Thr-286) in the mPFC and hippocampal CA1 regions of NVH-lesioned rats when assessed by immunohistochemistry. Chronic ST101 administration (0.1 mg/kg, p.o.) improved the decline in phosphorylation levels of CaMKII (Thr-286), PKCα (Ser-657), α-amino-3-hydroxy-5-methyl-4-isoxazol- propionic acid (AMPA)-type glutamate receptor subunit 1 (GluA1: Ser-831), and N-methyl-d-aspartate (NMDA) receptor subunit 1 (GluN1: Ser-896) in the mPFC and hippocampal CA1 regions. Taken together, these results suggest that ST101 improves schizophrenia-like behaviors and cognitive impairment by enhancing CaMKII/PKCα signaling in the mPFC and hippocampus in NVH-lesioned rats.

Alzheimer's disease therapeutic candidate SAK3 is an enhancer of T-type calcium channels.

Low-threshold Ca2+ spikes are mediated by T-type Ca2+ channels, which have electrophysiological properties of fast inactivation and slow deactivation kinetics. A low membrane potential of approximately -60 mV is sufficient to trigger channel opening. We recently introduced a novel T-type Ca2+ channel enhancer that improves cognition and inhibits amyloid beta aggregation in an Alzheimer's disease (AD) mouse model. The enhancer stimulates ACh release, Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, and neurogenesis in the hippocampus. Then, we discuss how T-type Ca2+ channel enhancer improves cognition and impaired neurogenesis and how CaMKII signaling in neurodegenerative diseases reduces amyloid beta aggregation. We provide a perspective of the potential AD therapies to target CaMKII signaling. In this context, we overview our attempts leading to the development of a T-type Ca2+ channel enhancer as cognitive enhancer, the action of which has been associated with CaMKII and presumably proteasome activity.

Combined citicoline and docosahexaenoic acid treatment improves cognitive dysfunction following transient brain ischemia.

Phospholipids are structural components of cellular membranes that play important roles as precursors for various signaling pathways in modulating neuronal membrane function and maintenance of the intracellular environment. Phosphatidylcholine (PtdCho) is the most abundant cellular phospholipid. Citicoline and docosahexaenoic acid (DHA) are essential intermediates in the synthesis of PtdCho. Both PtdCho intermediates have independently shown neuroprotective effects in cerebral ischemia, but their combined effect is unknown. This study aimed to investigate the combined effect of oral citicoline and DHA treatment on improvement of cognitive deficits following cerebral ischemia using a 20-min bilateral common carotid artery occlusion (BCCAO) mouse model. BCCAO ischemic mice were treated for a total of 11 days with a combination of citicoline (40 mg/kg body weight/day) and DHA (300 mg/kg body weight/day) or each alone. Combined citicoline and DHA synergistically and significantly improved learning and memory ability of ischemic mice compared with either alone. Further, citicoline and DHA treatment significantly prevented neuronal cell death, and slightly increased DHA-containing PtdCho in the hippocampus, albeit not significantly. Taken together, these findings suggest that combined citicoline and DHA treatment may have synergistic benefits for partially improving memory deficits following transient brain ischemia.

Clinical Therapeutic Strategy and Neuronal Mechanism Underlying Post-Traumatic Stress Disorder (PTSD).

Post-traumatic stress disorder (PTSD) is characterized by an exaggerated response to contextual memory and impaired fear extinction, with or without mild cognitive impairment, learning deficits, and nightmares. PTSD is often developed by traumatic events, such as war, terrorist attack, natural calamities, etc. Clinical and animal studies suggest that aberrant susceptibility of emotion- and fear-related neurocircuits, including the amygdala, prefrontal cortex (PFC), and hippocampus may contribute to the development and retention of PTSD symptoms. Psychological and pharmacological therapy, such as cognitive behavioral therapy (CBT), and treatment with anti-depressive agents and/or antipsychotics significantly attenuate PTSD symptoms. However, more effective therapeutics are required for improvement of quality of life in PTSD patients. Previous studies have reported that ω3 long-chain polyunsaturated fatty acid (LCPUFA) supplements can suppress the development of PTSD symptoms. Fatty acid binding proteins (FABPs) are essential for LCPUFA intracellular trafficking. In this review, we have introduced Fabp3 null mice as an animal model of PTSD with impaired fear extinction. Moreover, we have addressed the neuronal circuits and novel therapeutic strategies for PTSD symptoms.

trans-Fatty acids promote proinflammatory signaling and cell death by stimulating the apoptosis signal-regulating kinase 1 (ASK1)-p38 pathway.

Food-borne trans-fatty acids (TFAs) are mainly produced as byproducts during food manufacture. Recent epidemiological studies have revealed that TFA consumption is a major risk factor for various disorders, including atherosclerosis. However, the underlying mechanisms in this disease etiology are largely unknown. Here we have shown that TFAs potentiate activation of apoptosis signal-regulating kinase 1 (ASK1) induced by extracellular ATP, a damage-associated molecular pattern leaked from injured cells. Major food-associated TFAs such as elaidic acid (EA), linoelaidic acid, and trans-vaccenic acid, but not their corresponding cis isomers, dramatically enhanced extracellular ATP-induced apoptosis, accompanied by elevated activation of the ASK1-p38 pathway in a macrophage-like cell line, RAW264.7. Moreover, knocking out the ASK1-encoding gene abolished EA-mediated enhancement of apoptosis. We have reported previously that extracellular ATP induces apoptosis through the ASK1-p38 pathway activated by reactive oxygen species generated downstream of the P2X purinoceptor 7 (P2X7). However, here we show that EA did not increase ATP-induced reactive oxygen species generation but, rather, augmented the effects of calcium/calmodulin-dependent kinase II-dependent ASK1 activation. These results demonstrate that TFAs promote extracellular ATP-induced apoptosis by targeting ASK1 and indicate novel TFA-associated pathways leading to inflammatory signal transduction and cell death that underlie the pathogenesis and progression of TFA-induced atherosclerosis. Our study thus provides insight into the pathogenic mechanisms of and proposes potential therapeutic targets for these TFA-related disorders.

T-type calcium channel enhancer SAK3 produces anti-depressant-like effects by promoting adult hippocampal neurogenesis in olfactory bulbectomized mice.

T-type calcium channels are involved in the pathophysiology of epilepsy, pain, and sleep. Recently, we developed a novel spiroimidazopyridine compound, SAK3 (ethyl 8'-methyl-2',4-dioxo-2-(piperidin-1-yl)-2'H-spiro[cyclopentane-1,3'-imidazo[1,2-a]pyridine]-2-ene-3-carboxylate), which enhances T-type calcium channel currents and improves memory deficits in olfactory bulbectomized (OBX) mice. Here, we demonstrated the anti-depressant effects of SAK3 in OBX mice. Chronic SAK3 administration (0.5 or 1.0 mg/kg, p.o.) improved depressive-like behaviors in OBX mice. The impaired adult neurogenesis in the hippocampal dentate gyrus (DG) that occurred 4 weeks after OBX administration was significantly restored by chronic SAK3 administration (0.5 or 1.0 mg/kg, p.o.). Additionally, SAK3 (0.5 mg/kg, p.o.) promoted the proliferation and survival of newborn cells in the naïve DG. Moreover, SAK3 administration (0.5 mg/kg, p.o.) antagonized the reduction of calcium/calmodulin-dependent protein kinase II (CaMKII) and CaMKIV phosphorylation levels, thereby rescuing the decreased levels of cAMP response element-binding protein (CREB)/brain derived neurotrophic factor (BDNF) signaling in the OBX DG. The effects of SAK3 were completely blocked by the T-type calcium channel selective blocker NNC 55-0396 (12.5 mg/kg, i.p.). Altogether, these results suggest that SAK3 improves depressive-like behaviors by promoting adult neurogenesis via T-type calcium channel stimulation in the hippocampus.

Acute Treatment with T-Type Calcium Channel Enhancer SAK3 Reduces Cognitive Impairments Caused by Methimazole-Induced Hypothyroidism Via Activation of Cholinergic Signaling.

Hypothyroidism is a common disorder that is associated with psychological disturbances such as dementia, depression, and psychomotor disorders. We recently found that chronic treatment with the T-type calcium channel enhancer SAK3 prevents the cholinergic neurodegeneration induced by a single intraperitoneal (i.p.) injection of methimazole (MMI; 75 mg/kg), thereby improving cognition. Here, we evaluated the acute effect of SAK3 on cognitive impairments and its mechanism of action following the induction of hypothyroidism. Hypothyroidism was induced by 2 injections of MMI (75 mg/kg, i.p.) administered once per week. Four weeks after the final MMI treatment, MMI-treated mice showed reduced serum thyroxine (T4) levels and cognitive impairments without depression-like behaviors. Although acute SAK3 (1.0 mg/kg, p.o.) administration failed to ameliorate the decreased T4 levels and histochemical destruction of the glomerular structure, acute SAK3 (1.0 mg/kg, p.o.) administration significantly reduced cognitive impairments in MMI-treated mice. Importantly, the α7 nicotinic acetylcholine receptor (nAChR)-selective inhibitor methyllycaconitine (MLA; 12 mg/kg, i.p.) and T-type calcium channel-specific blocker NNC 55-0396 (25 mg/kg, i.p.) antagonized the acute effect of SAK3 on memory deficits in MMI-treated mice. We also confirmed that acute SAK3 administration does not rescue reduced olfactory marker protein or choline acetyltransferase immunoreactivity levels in the olfactory bulb or medial septum. Taken together, these results suggest that SAK3 has the ability to improve the cognitive decline caused by hypothyroidism directly through activation of nAChR signaling and T-type calcium channels.

SA4503, A Potent Sigma-1 Receptor Ligand, Ameliorates Synaptic Abnormalities and Cognitive Dysfunction in a Mouse Model of ATR-X Syndrome.

α-thalassemia X-linked intellectual disability (ATR-X) syndrome is caused by mutations in ATRX. An ATR-X model mouse lacking Atrx exon 2 displays phenotypes that resemble symptoms in the human intellectual disability: cognitive defects and abnormal dendritic spine formation. We herein target activation of sigma-1 receptor (Sig-1R) that can induce potent neuroprotective and neuroregenerative effects by promoting the activity of neurotrophic factors, such as brain-derived neurotrophic factor (BDNF). We demonstrated that treatment with SA4503, a potent activator of Sig-1R, reverses axonal development and dendritic spine abnormalities in cultured cortical neurons from ATR-X model mice. Moreover, the SA4503 treatment rescued cognitive deficits exhibited by the ATR-X model mice. We further found that significant decreases in the BDNF-protein level in the medial prefrontal cortex of ATR-X model mice were recovered with treatment of SA4503. These results indicate that the rescue of dendritic spine abnormalities through the activation of Sig-1R has a potential for post-diagnostic therapy in ATR-X syndrome.

Combined Memantine and Donepezil Treatment Improves Behavioral and Psychological Symptoms of Dementia-Like Behaviors in Olfactory Bulbectomized Mice.

Memantine, an uncompetitive N-methyl-D-aspartate receptor antagonist, and the cholinesterase inhibitor, donepezil, are approved in most countries for treating moderate-to-severe Alzheimer's disease (AD). These drugs have different molecular targets; thus, it is expected that the effects of combined treatment would be synergistic. Some reports do show memantine/donepezil synergy in ameliorating cognition in AD model animals, but their combined effects on behavioral and psychological symptoms of dementia (BPSD)-like behaviors have not been addressed. Here, we investigate combined memantine/donepezil effects on cognitive impairment and BPSD-like behaviors in olfactory bulbectomized (OBX) mice. Interestingly, combined administration synergistically improved both depressive-like behaviors and impaired social interaction in OBX mice, whereas only weak synergistic effects on cognitive performance were seen. To address mechanisms underlying these effects, we used in vivo microdialysis study and observed impaired nicotine-induced serotonin (5-HT) release in OBX mouse hippocampus. Combined memantine/donepezil administration, but not single administration of either, significantly antagonized the decrease in nicotine-induced 5-HT release seen in OBX mouse hippocampus. Furthermore, decreased autophosphorylation of calcium/calmodulin dependent protein kinase II (CaMKII) was rescued in hippocampal CA1 and dentate gyrus of OBX mice by combined memantine/donepezil administration. These results suggest that improvement of BPSD-like behaviors by the co-administration of both drugs is in part mediated by enhanced 5-HT release and CaMKII activity in OBX mouse hippocampus.

FABP3 protein promotes α-synuclein oligomerization associated with 1-methyl-1,2,3,6-tetrahydropiridine-induced neurotoxicity.

α-Synuclein (αSyn) accumulation in dopaminergic (DA) neurons is partly regulated by long-chain polyunsaturated fatty acids. We found that fatty acid-binding protein 3 (FABP3, H-FABP), a factor critical for arachidonic acid (AA) transport and metabolism in brain, is highly expressed in DA neurons. Fabp3 knock-out (Fabp3(-/-)) mice were resistant to 1-methyl-1,2,3,6-tetrahydropiridine-induced DA neurodegeneration in the substantia nigra pars compacta and showed improved motor function. Interestingly, FABP3 interacted with αSyn in the substantia nigra pars compacta, and αSyn accumulation following 1-methyl-1,2,3,6-tetrahydropiridine treatment was attenuated in Fabp3(-/-) compared with wild-type mice. We confirmed that FABP3 overexpression aggravates AA-induced αSyn oligomerization and promotes cell death in PC12 cells, whereas overexpression of a mutant form of FABP3 lacking fatty-acid binding capacity did not. Taken together, αSyn oligomerization in DA neurons is likely aggravated by AA through FABP3 in Parkinson disease pathology.

Melatonin reverses the decreases in hippocampal protein serine/threonine kinases observed in an animal model of autism.

Lower global cognitive function scores are a common symptom of autism spectrum disorders (ASDs). This study investigates the effects of melatonin on hippocampal serine/threonine kinase signaling in an experimental ASD model. We found that chronic melatonin (1.0 or 5.0 mg/kg/day, 28 days) treatment significantly rescued valproic acid (VPA, 600 mg/kg)-induced decreases in CaMKII (Thr286), NMDAR1 (Ser896), and PKA (Thr197) phosphorylation in the hippocampus without affecting total protein levels. Compared with control rats, the immunostaining of pyramidal neurons in the hippocampus revealed a decrease in immunolabeling intensity for phospho-CaMKII (Thr286) in the hippocampus of VPA-treated rats, which was ameliorated by chronic melatonin treatment. Consistent with the elevation of CaMKII/PKA/PKC phosphorylation observed in melatonin-treated rat, long-term potentiation (LTP) was enhanced after chronic melatonin (5.0 mg/kg) treatment, as reflected by extracellular field potential slopes that increased from 56 to 60 min (133.4 ± 3.9% of the baseline, P < 0.01 versus VPA-treated rats) following high-frequency stimulation (HFS) in hippocampal slices. Accordingly, melatonin treatment also significantly improved social behavioral deficits at postnatal day 50 in VPA-treated rats. Taken together, the increased phosphorylation of CaMKII/PKA/PKC signaling might contribute to the beneficial effects of melatonin on autism symptoms.