Toshitaka Nabeshima

ObjectivesReports have shown that the kynurenine pathway, one of the pathways by which tryptophan is metabolized, is activated in patients with diffuse large B-cell lymphoma (DLBCL). Activation of the kynurenine pathway triggers the production of various metabolites, such as kynurenine (Kyn), 3-hydroxykynurenine (3-HK), 3-hydroxyanthranilic acid (3-HAA), kynurenic acid (KA), and anthranilic acid (AA), which contribute to immune tolerance. The current study aimed to investigate the changes in metabolites of kynurenine pathway in DLBCL patients and evaluate their performance predicting DLBCL.MethodsChanges in metabolites of kynurenine pathway were examined using high-performance liquid chromatography in 35 DLBCL patients (age 61.2 ± 13.5 years) and 44 healthy controls (age 58.5 ± 12.5 years).ResultsDLBCL patients had significantly higher levels of 3-HK, AA, and 3-HAA but lower levels of tryptophan (Trp) and KA compared to healthy controls. Given that the ratio of each metabolite represents the change in the Kyn pathway, the 3-HK/KA ratio was examined. Notably, DLBCL patients had a significantly higher 3-HK/KA ratio compared to healthy controls. In DLBCL, the area under the receiver operative characteristic (ROC) curve for 3-HK/KA (0.999) was higher than that for lactate dehydrogenase (0.885) and comparable to that for soluble interleukin-2 receptor (sIL-2R) (0.997). Based on ROC curve analysis, the 3-HK/KA ratio was found to be useful biomarker for the diagnosis of DLBCL.ConclusionOur results suggest that the 3-HK/KA ratio is a clinically useful biomarker of DLBCL. Moreover, its combination with existing markers, such as sIL-2R, can improve its effectiveness of diagnosing DLBCL.

Abstract Background Rho-kinase is a serine/threonine kinase and regulates actin dynamics. There are two subtypes: Rho-kinase 1 and Rho-kinase 2. Recently, we found that a Rho-kinase1/2 inhibitor, fasudil, ameliorated schizophrenia-like behaviors in MK-801-treated mice (Takase et al., 2022). However, fasudil has been shown side effects, such as hypotension, which may hinder its clinical application for schizophrenia. Since Rho-kinase 2 is predominantly expressed in brain, we hypothesized that selective inhibition of Rho-kinase 2 might exhibit antipsychotic-like effects with fewer cardiovascular side effects. Aims & Objectives To investigate the potential of a Rho-kinase 2 inhibitor as a therapeutic agent for schizophrenia, we evaluated the effect of a selective Rho-kinase 2 inhibitor, belumosudil (KD025), on MK-801-indued schizophrenia-like behaviors and blood pressure in mice. Method Effects of KD025 on schizophrenia-like behaviors in MK-801-treated mice were evaluated by locomotor activity test, novel object recognition test (NORT), and visual discrimination test (VD). KD025 (100-200 mg/kg) was orally administered 120 min before the behavioral tests. The blood pressure was also measured after KD025 treatment by tail-cuff method. Furthermore, we evaluated the depolarization-evoked extracellular dopamine and serotonin levels in the nucleus accumbens (NAc) using an in vivo microdialysis method. Results KD025 (100 or 200 mg/kg) restored MK-801-induced hyperlocomotion and the cognitive impairments in the NORT and VD, while KD025 showed little effect on systolic blood pressure, not like fasudil. In addition, local perfusion of KD025 (10-20 μ M) in the NAc suppressed the depolarization- evoked serotonin-, but not dopamine-release in the NAc. Discussion & Conclusion Our findings indicate that Rho-kinase 2 has potential as a therapeutic target for schizophrenia and KD025 may be a candidate as an antipsychotic for schizophrenia. References TAKASE, S., LIAO, J., LIU, Y., TANAKA, R., MIYAGAWA, Y., SAWAHATA, M., SOBUE, A., MIZOGUCHI, H., NAGAI, T., KAIBUCHI, K., OZAKI, N. &YAMADA, K. 2022. Antipsychotic-like effects of fasudil, a Rho- kinase inhibitor, in a pharmacologic animal model of schizophrenia. Eur J Pharmacol, 931, 175207.

Background and Purpose Alterations in tryptophan‐kynurenine (TRP‐KYN) pathway are implicated in major depressive disorder (MDD). α7 nicotinic acetylcholine (α7nACh) receptor regulates the hypothalamic–pituitary–adrenal (HPA) axis. We have shown that deficiency of kynurenine 3‐monooxygenase (KMO) induces depression‐like behaviour via kynurenic acid (KYNA; α7nACh antagonist). In this study, we investigated the involvement of the TRP‐KYN pathway in stress‐induced behavioural changes and the regulation of the HPA axis. Experimental Approach Mice were exposed to chronic unpredictable mild stress (CUMS) and subjected to behavioural tests. We measured TRP‐KYN metabolites and the expression of their enzymes in the hippocampus. KMO heterozygous mice were used to investigate stress vulnerability. We also evaluated the effect of nicotine (s.c.) on CUMS‐induced behavioural changes and an increase in serum corticosterone (CORT) concentration. Key Results CUMS decreased social interaction time but increased immobility time under tail suspension associated with increased serum corticosterone concentration. CUMS increased KYNA levels via KMO suppression with microglial decline in the hippocampus. Kmo^+/− mice were vulnerable to stress: they exhibited social impairment and increased serum corticosterone concentration even after short‐term CUMS. Nicotine attenuated CUMS‐induced behavioural changes and increased serum corticosterone concentration by inhibiting the increase in corticotropin‐releasing hormone. Methyllycaconitine (α7nACh antagonist) inhibited the attenuating effect of nicotine. Conclusions and Implications CUMS‐induced behavioural changes and the HPA axis dysregulation could be induced by the increased levels of KYNA via KMO suppression. KYNA plays an important role in the pathophysiology of MDD as an α7nACh antagonist. Therefore, α7nACh receptor is an attractive therapeutic target for MDD.

Abstract Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by repetitive behaviors, social deficits, and cognitive impairments. Maternal use of valproic acid (VPA) during pregnancy is associated with an increased risk of ASD in offspring. The prevailing pathophysiological hypothesis for ASD involves excitation/inhibition (E/I) imbalances and serotonergic dysfunction. Here, we investigated the association between glutamatergic-serotonergic neuronal interactions and ASD-like behaviors in mice exposed to prenatal VPA. Prenatal VPA exposure induced excessive repetitive self-grooming behavior and impaired social behavior and object recognition memory in young adult period. Prenatal VPA mice showed hyper-glutamatergic function (increase in basal extracellular glutamate levels and CaMKII phosphorylation) and hypo-serotonergic function (decrease in 5-hydroxyindoleacetic acid and stimulation-induced serotonin [5-HT] release, but an increase in 5-HT transporter expression) in the prefrontal cortex. Treatment with a low-affinity NMDA receptor antagonist (memantine), a selective 5-HT reuptake inhibitor (fluoxetine), and a 5-HT_1A receptor agonist (tandospirone) attenuated both the increase in CaMKII phosphorylation and ASD-like behavior of prenatal VPA mice. Opto-genetic activation of the serotonergic neuronal system attenuated impairments in social behavior and object recognition memory in prenatal VPA mice. WAY-100635—a 5-HT_1A receptor antagonist—antagonized the effect of fluoxetine on impaired social behavior and object recognition memory. These results suggest that E/I imbalance and ASD-like behavior are associated with hypo-serotonergic receptor signaling through 5-HT_1A receptors in prenatal VPA mice.

High salt (HS) intake induces hypertension and cognitive impairment. Preventive strategies include against dietary supplements. Soybean lecithin is a widely used phospholipid supplement. Lysolecithin is important in cell signaling, digestion, and absorption. This study aimed to investigate the effects of lysophosphatidylcholine containing >70% of the total phospholipids (LPC70), on hypertension and cognitive impairment induced in mice by HS intake. Mice were provided with HS solution (2% NaCl in drinking water) with or without LPC70 for 12 weeks. Blood pressure, cognitive function, and inflammatory response of intestine were determined. Hypertension and impaired object recognition memory induced by HS intake were implicated with increased inducible nitric oxide synthase in the small intestine and tau hyperphosphorylation in the prefrontal cortex. LPC70 treatment prevented cognitive impairment by suppressing inducible nitric oxide synthase and tau hyperphosphorylation. LPC70 may be valuable as a functional food component in preventing HS-induced cognitive impairment.

Abstract Stressful life events contribute to the onset of major depressive disorder (MDD). We recently demonstrated abnormalities in ubiquitination in the pathophysiology of MDD. However, the underlying molecular mechanisms remain unclear. We investigated the involvement of the ubiquitination system‐mediated glutamatergic dysfunction in social impairment induced by chronic social defeat stress (CSDS). Adult C57BL/6J mice were exposed to aggressor ICR male mice for 10 consecutive days. Social impairment was induced by CSDS in the social interaction test 1 days after the last stress exposure. In terms of brain microdialysis, CSDS reduced depolarization‐evoked glutamate release in the prefrontal cortex (PFC), which was reversed by a glutamate transporter 1 (GLT‐1) inhibitor. Interestingly, the expression of ubiquitinated, but not total GLT‐1, was decreased in the PFC of mice exposed to CSDS. The expression of neural precursor cells expressing developmentally downregulated gene 4‐like (Nedd4L: E3 ligase for GLT‐1), and ubiquitin‐conjugating enzyme E2D2 (Ube2d2: E2 ubiquitin‐conjugating enzyme for Nedd4L) was also reduced in CSDS mice. Furthermore, the downregulation of the Nedd4L‐GLT‐1 ubiquitination pathway decreased SIT ratio, but up‐regulation increased it even in non‐CSDS mice. Taken together, the decrease in GLT‐1 ubiquitination may reduce the release of extracellular glutamate induced by high‐potassium stimulation, which may lead to social impairment, while we could not find differences in GLT‐1 ubiquitination between susceptible and resistant CSDS mice. In conclusion, GLT‐1 ubiquitination could play a crucial role in the pathophysiology of MDD and is an attractive target for the development of novel antidepressants.

Indoleamine 2,3-dioxygenase 2 (IDO2) is an enzyme of the tryptophan-kynurenine pathway that is constitutively expressed in the brain. To provide insight into the physiological role of IDO2 in the brain, behavioral and neurochemical analyses in IDO2 knockout (KO) mice were performed. IDO2 KO mice showed stereotyped behavior, restricted interest and social deficits, traits that are associated with behavioral endophenotypes of autism spectrum disorder (ASD). IDO2 was colocalized immunohistochemically with tyrosine-hydroxylase-positive cells in dopaminergic neurons. In the striatum and amygdala of IDO2 KO mice, decreased dopamine turnover was associated with increased α-synuclein level. Correspondingly, levels of downstream dopamine D1 receptor signaling molecules such as brain-derived neurotrophic factor and c-Fos positive proteins were decreased. Furthermore, decreased abundance of ramified-type microglia resulted in increased dendritic spine density in the striatum of IDO2 KO mice. Both chemogenetic activation of dopaminergic neurons and treatment with methylphenidate, a dopamine reuptake inhibitor, ameliorated the ASD-like behavior of IDO2 KO mice. Sequencing analysis of exon regions in IDO2 from 309 ASD samples identified a rare canonical splice site variant in one ASD case. These results suggest that the IDO2 gene is, at least in part, a factor closely related to the development of psychiatric disorders.

Abstract Chronic orofacial pain (COP) is relieved by duloxetine (DLX) and frequently causes depressive symptoms. The aim of this study was to confirm effects of DLX on pain and depressive symptoms, and to associate with their effectiveness in platelet serotonin transporter (SERT) expression, which is a target molecule of DLX and plasma serotonin concentration in COP patients with depressive symptoms. We assessed for the severity of pain and depressive symptoms using the Visual Analog Scale (VAS) and 17-item Hamilton Depression Rating Scale (HDRS), respectively. Chronic orofacial pain patients were classified into 2 groups based on their HDRS before DLX-treatment: COP patients with (COP-D) and without (COP-ND) depressive symptoms. We found that the VAS and HDRS scores of both groups were significantly decreased after DLX treatment compared with those before DLX treatment. Upregulation of total SERT and downregulation of ubiquitinated SERT were observed before DLX treatment in both groups compared with healthy controls. After DLX treatment, there were no differences in total SERT of both groups and in ubiquitinated SERT of COP-D patients compared with healthy controls; whereas, ubiquitinated SERT of COP-ND patients remained downregulated. There were positive correlations between changes of serotonin concentrations and of VAS or HDRS scores in only COP-D patients. Our findings indicate that DLX improves not only pain but also comorbid depressive symptoms of COP-D patients. Duloxetine also reduces platelet SERT through upregulation of ubiquitinated SERT. As the result, decrease of plasma serotonin concentrations may be related to the efficacy of DLX in relieving pain and depression in COP patients.

Schizophrenia (SCZ) is a severe psychiatric disorder characterized by positive symptoms, negative symptoms, and cognitive deficits. Current antipsychotic treatment in SCZ improves positive symptoms but has major side effects and little impact on negative symptoms and cognitive impairment. The pathoetiology of SCZ remains unclear, but is known to involve small GTPase signaling. Rho kinase, an effector of small GTPase Rho, is highly expressed in the brain and plays a major role in neurite elongation and neuronal architecture. This study used a touchscreen-based visual discrimination (VD) task to investigate the effects of Rho kinase inhibitors on cognitive impairment in a methamphetamine (METH)-treated male mouse model of SCZ. Systemic injection of the Rho kinase inhibitor fasudil dose-dependently ameliorated METH-induced VD impairment. Fasudil also significantly suppressed the increase in the number of c-Fos-positive cells in the infralimbic medial prefrontal cortex (infralimbic mPFC) and dorsomedial striatum (DMS) following METH treatment. Bilateral microinjections of Y-27632, another Rho kinase inhibitor, into the infralimbic mPFC or DMS significantly ameliorated METH-induced VD impairment. Two proteins downstream of Rho kinase, myosin phosphatase-targeting subunit 1 (MYPT1; Thr696) and myosin light chain kinase 2 (MLC2; Thr18/Ser19), exhibited increased phosphorylation in the infralimbic mPFC and DMS, respectively, after METH treatment, and fasudil inhibited these increases. Oral administration of haloperidol and fasudil ameliorated METH-induced VD impairment, while clozapine had little effect. Oral administration of haloperidol and clozapine suppressed METH-induced hyperactivity, but fasudil had no effect. These results suggest that METH activates Rho kinase in the infralimbic mPFC and DMS, which leads to cognitive impairment in male mice. Rho kinase inhibitors ameliorate METH-induced cognitive impairment, perhaps via the cortico-striatal circuit.

地域住民を対象とした「くすり実験教室」の取組が参加者の医薬品の適正使用に関する知識の向上につながったかどうか評価した。2017～2020年に愛知県と山梨県で実施した「くすり実験教室」の参加者を対象に、医薬品の使用状況と医薬品の適正使用に関するアンケートを実施した。参加者の総人数は219名で有効回答者数は211名であった。非高齢者と高齢者に分けて解析した。その結果、非高齢者の「はい」と回答した割合が高齢者と比較して有意に高かった設問は「薬を飲み込み難いと感じたことがありますか」であった。高齢者で「はい」と回答した割合が非高齢者と比較して有意に高かった設問は「現在定期的に薬を服用・使用していますか」と「目薬を使っていますか」であった。理解度または正答率が有意に上昇した項目は「薬を飲み込み易くする工夫」、「食直前とは食前1時間以内に服用することである」、「目薬の正しい使い方」、「湿布の正しい使い方」、「お薬手帳の使い方」、「薬の相談は薬剤師にする」であり、地域住民の医薬品の適正使用に関する知識が向上したことが明らかになった。

BACKGROUND AND PURPOSE: High salt (HS) intake has been associated with hypertension and cognitive impairment. It is well-known that angiotensin II (Ang II)-AT1 and prostaglandin E2 (PGE2)-EP1 systems are involved in hypertension and neurotoxicity. However, the involvement of these systems in HS-mediated hypertension and emotional and cognitive impairments remains unclear. EXPERIMENTAL APPROACH: Mice were loaded with HS solution (2% NaCl drinking water) for 12 weeks and blood pressure was monitored. Subsequently, effects of HS intake on emotional and cognitive function and tau phosphorylation in the prefrontal cortex (PFC) and hippocampus (HIP) were investigated. The involvement of Ang II-AT1 and PGE2-EP1 systems in HS-induced hypertension and neuronal and behavioral impairments was examined by treatment with losartan, an AT1 receptor blocker (ARB), or EP1 gene knockout. KEY RESULTS: We demonstrated that hypertension and impaired social behavior and object recognition memory following HS intake could be associated with tau hyperphosphorylation, decreased phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII), and postsynaptic density protein 95 (PSD95) expression in the PFC and HIP of mice. These changes were blocked by pharmacological treatment with losartan or EP1 gene knockout. CONCLUSIONS AND IMPLICATIONS: Our findings suggest that the interaction of Ang II-AT1 and PGE2-EP1 systems could be novel therapeutic targets for hypertension-induced cognitive impairment.

The monoamine hypothesis has been common hypotheses for the pathophysiology of major depressive disorder (MDD). Since mainstream antidepressants are selective serotonin (5-HT) reuptake inhibitors, hypo-serotonergic function has been implicated in the MDD. However, one-third of patients are refractory to the treatment with antidepressants. Tryptophan (TRP) is metabolized via the kynurenine (KYN) and 5-HT pathways. Indoleamine 2,3-dioxygenase 1 (IDO1) is the first metabolizing enzyme in the TRP-KYN pathway which is inducible by pro-inflammatory cytokines, involved depression-like behavior via 5-HT depletion due to decreased level of TRP in the 5-HT pathway. Kynurenine 3-monooxygenase (KMO) is the enzyme in the metabolism of KYN to 3-hydroxykynurenine. KMO deficiency increases level of kynurenic acid (KA), a KYN metabolite by kynurenine aminotransferases (KATs) and induces depression-like behavior. Interestingly, Chronic unpredictable mild stress (CUMS) is associated with a disruption of the hypothalamus-pituitary-adrenocortical (HPA) system and increases KA level with decreased KMO expression in the prefrontal cortex. The decrease of KMO may be related to the reduction in expression of microglia, since KMO is mainly found in microglia in the nervous system. CUMS increases KA level via alternation of enzymes from KMO to KAT. KA is α7 nicotinic acetylcholine receptor (α7nAChR) antagonist. Activation of α7nAChR by nicotine or galantamine attenuates CUMS-induced depression-like behaviors. Taken together, depletion of 5-HT by induction of IDO1 and α7nAChR antagonism by KA via decreased KMO expression cause depression-like behavior, suggesting that metabolic alterations in TRP-KYN pathway are highly involved in the pathophysiology of MDD. Therefore, TRP-KYN pathway is expected to be an attractive target for the development of novel diagnosis of MDD and antidepressants.

Copy number variants in the ARHGAP10 gene are associated with schizophrenia (SCZ). We have previously demonstrated that Rho-kinase (ROCK) inhibitor, fasudil, ameliorates the decreased spine density in the medial prefrontal cortex (mPFC) of Arhgap10 S490P/NHEJ mice carrying the variants that mimic the ARHGAP10 variants found in a Japanese SCZ patient. Accordingly, we have proposed that ROCK is a potentially novel therapeutic target in SCZ. It is well known that there are two subtypes of ROCK, ROCK1 and ROCK2, and that fasudil inhibits both subtypes. Since ROCK2 is highly expressed in the brain, here we evaluated the effect of a selective ROCK2 inhibitor, belumosudil (KD025), on spine density in Arhgap10 S490P/NHEJ mice. We measured the spine density of pyramidal neurons in layer 2/3 of the mPFC in Arhgap10 S490P/NHEJ mice following daily oral administration of KD025 for one week. Moreover, we evaluated the general behaviors in an open field and systolic blood pressure after KD025 treatment. KD025 ameliorated decreased spine density of cortical neurons in the mPFC of Arhgap10 S490P/NHEJ mice, but had little effects on general behaviors and systolic blood pressure induced by fasudil. These observations suggest that ROCK2 is a more appropriate therapeutic target in SCZ, with little inducibility of hypotension.

The monoamine hypothesis has been common hypotheses for the pathophysiology of major depressive disorder (MDD). Since mainstream antidepressants are selective serotonin (5-HT) reuptake inhibitors, hypo-serotonergic function has been implicated in the MDD. However, one-third of patients are refractory to the treatment with antidepressants. Tryptophan (TRP) is metabolized via the kynurenine (KYN) and 5-HT pathways. Indoleamine 2,3-dioxygenase 1 (IDO1) is the first metabolizing enzyme in the TRP-KYN pathway which is inducible by pro-inflammatory cytokines, involved depression-like behavior via 5-HT depletion due to decreased level of TRP in the 5-HT pathway. Kynurenine 3-monooxygenase (KMO) is the enzyme in the metabolism of KYN to 3-hydroxykynurenine. KMO deficiency increases level of kynurenic acid (KA), a KYN metabolite by kynurenine aminotransferases (KATs) and induces depression-like behavior. Interestingly, Chronic unpredictable mild stress (CUMS) is associated with a disruption of the hypothalamus-pituitary-adrenocortical (HPA) system and increases KA level with decreased KMO expression in the prefrontal cortex. The decrease of KMO may be related to the reduction in expression of microglia, since KMO is mainly found in microglia in the nervous system. CUMS increases KA level via alternation of enzymes from KMO to KAT. KA is α7 nicotinic acetylcholine receptor (α7nAChR) antagonist. Activation of α7nAChR by nicotine or galantamine attenuates CUMS-induced depression-like behaviors. Taken together, depletion of 5-HT by induction of IDO1 and α7nAChR antagonism by KA via decreased KMO expression cause depression-like behavior, suggesting that metabolic alterations in TRP-KYN pathway are highly involved in the pathophysiology of MDD. Therefore, TRP-KYN pathway is expected to be an attractive target for the development of novel diagnosis of MDD and antidepressants.

Recently we have identified Arhgap10 gene mutations in Japanese schizophrenia patients by the genome-wide CNV analysis. ARHGAP10 negatively regulates Rho family small GTPases that play roles in the regulation of spine morphology. We also found that Arhgap10 S490P/NHEJ mice which were generated to mimic the patient case were highly sensitive to methamphetamine (METH) and spine density of the secondary dendrites of medium spiny neurons (MSNs) in the striatum was increased in the mutant mice. Because spine density is well associated with neuronal activity, in this study we sought to establish wireless photometry system to measure Ca²⁺ level in the striatal MSNs of Arhgap10 S490P/NHEJ mice.  Firstly, we measured the number of the c-Fos positive cells in the striatum of Arhgap10 S490P/NHEJ mice by immunohistochemistry 2 h after METH (0.3 mg/kg, i.p.) treatment. METH increased the number of c-Fos positive cells in the dorsomedial striatum in Arhgap10 S490P/NHEJ mice but not wild-type mice. We generated mice expressing selectivity GCaMP6 in dopamine D1 receptor-expressing MSNs (D1-MSNs) of the striatum by Cre-loxP system. In a mean while we inserted optic fiber and detected GCaMP6 signal of the striatal D1-MSNs in Drd1-Cre mice under a free moving condition. Treatment of METH (2 mg/kg, i.p.) increased Ca²⁺ signal in striatal D1-MSNs as well as locomotor activity.

Introduction: Burning mouth syndrome and atypical odontalgia (BMS/AO) are chronic orofacial pain conditions in the absence of any identifiable odontogenic pathology. The pain is treatment-resistant and frequently causes depressive symptoms. Duloxetine (DLX), a serotonin-noradrenaline reuptake inhibitor, is not only used as therapy for depression, but also for chronic orofacial pain. Since their mechanisms in detail remains unknown, in this study, we focused on serotonin transporter (SERT), one of DLX action site, and investigated association between expression of SERT and effect of DLX on pain in BMS/AO. Methods: The patients with BMS/AO, were assessed for severity of pain using the visual analog scale (VAS) and for signs of depression using the Hamilton Depression Rating Scale (HDRS). In their platelets before (baseline) and 12 weeks after DLX-treatment, the expression of total and ubiquitinated SERT proteins was confirmed by Western blot. This study was approved by the Ethics Review Committees of Nagoya, Aichi Gakuin, and Meijo Universities. Results: The expression of total and ubiquitinated SERT protein at baseline in all patients were higher and lower, respectively, compared to those in controls. After the DLX-treatment, there was no difference in the total SERT protein levels between the patients and controls. The mean of VAS and HDRS scores or the expression of total SERT protein were significantly decreased after the treatment, compared to those at baseline.  Conclusions: These results indicate that DLX relieves chronic orofacial pain in patients with BMS/AO, and such effect may be mediated via SERT downregulation.

Maternal use of valproic acid (VPA) during pregnancy is associated with an increased risk of autism spectrum disorder (ASD) in the offspring. In the pathophysiological hypothesis of ASD, excitation/inhibition (E/I) imbalance is attracted. Dysfunction of serotonergic system is also suggested to be involved in ASD. In this study, we investigated glutamatergic-serotonergic neuronal interaction in the ASD-like behavior induced by prenatal VPA exposure in mice. Prenatal VPA exposure induced not only excessive repetitive self-grooming behavior, impairments of social behavior and object recognition memory, but also increased glutamatergic signaling (CaMKII phosphorylation) and decreased serotonin contents in the prefrontal cortex. Memantine (low-affinity NMDA antagonist) suppressed both the increase of CaMKII phosphorylation and ASD-like behaviors. Activation of serotonergic signaling via 5-HT_1A receptor by fluoxetine, tandospirone (5-HT_1A receptor agonist) and optogenetics attenuated the ASD-like behaviors in prenatal VPA-exposed mice. WAY-100635 (5-HT_1A receptor antagonist) antagonized the effect of fluoxetine on the ASD-like behaviors. These results suggest that the hyper-NMDA receptor signaling and ASD-like behaviors are associated with hypo-signaling of 5-HT_1A receptor in the prenatal VPA-exposed mice.

Chronic stress contributes to the pathogenesis of major depressive disorder (MDD). In the kynurenine pathway (KP), kynurenine is metabolized to 3-hydroxykynurenine (3-HK) by kynurenine 3-monooxygenase (KMO) and to kynurenic acid (KA) by kynurenine aminotransferase. KP alternation has been reported to be associated with the pathogenesis of MDD. We investigated the involvement of KP in the depressive-like behavior induced by chronic unpredictable mild stress (CUMS). Mice were randomly exposed to 9 kinds of mild stressors for 4 weeks. Corticosterone level in the serum and corticotropin-releasing hormone (CRH) mRNA level in the hypothalamus (HT) elevated immediately after CUMS. Further, KMO mRNA level was decreased, but KA content was increased in the prefrontal cortex (PFC). Because KA is α7 nicotinic acetylcholine receptor (α7nAChR) antagonist, we investigated the effects of nicotine (Nic) and galantamine (Gal :α7nAChR agonist) on the depressive-like behavior and dysregulation of HPA axis induced by CUMS. When Nic and Gal were administrated before exposure to each stressor during CUMS, they attenuated CUMS-induced decreased sociability. Although Nic failed to inhibit elevated corticosterone level in the serum immediately after CUMS, but suppressed that sustained elevation 1 week after CUMS. Alternation of KP from 3-HK to KA through downregulation of KMO may be involved in the depressive-like behavior and the sustained elevation of serum corticosterone 1 week after CUMS.

Adolescent binge drinking represents a major public health challenge and lead to persistent psychiatric disorders. However, the underlying pathogenic mechanisms remain poorly understood. Myelin abnormalities were observed in human subjects with alcohol abuse. Gray matter myelination in the prefrontal cortex and hippocampus during adolescence are vulnerable to alcohol.In the present study, we investigated whether myelin abnormalities in the gray matter are involved in behavioral abnormalities induced by adolescent binge ethanol treatment (ABET). To produce ABET, C57BL/6J mouse was given EtOH (3.0g/kg, i.e. 25% ethanol w/v) once a day during adolescence (P28-46) in an intermittent fashion. ABET persistently developed behavioral abnormalities such as anxiety-like behaviors in the marble burying test and the novelty suppressed feeding test, impaired memory function in the novel object recognition test, and impairments of social behavior in social interaction test. ABET decreased myelin-related protein and oligodendrocyte lineage cells in the prefrontal cortex and hippocampus. Clemastine, which promotes oligodendroglial differentiation and myelination, rescues the behavioral abnormalities. These findings suggest that myelin abnormalities in the gray matter may be involved in the behavioral abnormalities caused by ABET in adulthood.

Dopamine contributes to attention as a key neurotransmitter in the nervous system projecting to the forebrain. Numerous animal models have been generated to model attentional impairment with dopaminergic dysregulation. We previously generated mice lacking Shati, an N-acetyltransferase-8-like protein, on a C57BL/6J genetic background (Shati/Nat8l^−/−). Modulation of this gene leads to changes in behavioral phenotypes such as attentional impairment associated with hypodopaminergic neurotransmission in mice. In this study, the effect of Shati/Nat8l deficit in dopaminergic projections was investigated using an object-based attention test (OBAT). Shati/Nat8l^−/− mice showed attentional impairment in the OBAT, accompanied by reduced neuronal activity in the prefrontal cortex (PFC) and the hypodopaminergic function indicated by the reduced expression of tyrosine hydroxylase (dopaminergic marker) protein and dopamine-related genes in the ventral tegmental area (VTA). The activation of dopaminergic projections of the VTA-PFC by chemogenetic stimulation ameliorated the attentional impairment in Shati/Nat8l^−/− mice. These results confirm previous findings that Shati/Nat8l deficiency interrupts the dopaminergic system and contributes to novel evidence that Shati/Nat8l is implicated in the dopaminergic projections of the VTA-PFC, which play important roles in the regulation of attention in the OBAT.

Tryptophan (TRP) is metabolized via the kynurenine (KYN) pathway, which is related to the pathogenesis of major depressive disorder (MDD). Kynurenine 3-monooxygenase (KMO) is a pivotal enzyme in the metabolism of KYN to 3-hydroxykynurenine. In rodents, KMO deficiency induces a depression-like behavior and increases the levels of kynurenic acid (KA), a KYN metabolite formed by kynurenine aminotransferases (KATs). We will introduce the involvement of TRP metabolism in the depression-like behavior induced by chronic unpredictable mild stress (CUMS). Corticosterone level in the serum and corticosterone-releasing hormone (CRH) mRNA level in the hypothalamus (HT) were elevated immediately after CUMS. Associated with the dysregulation of hypothalamic-pituitary-adrenal (HPA) axis, KMO mRNA level was decreased, and KA content was increased in the prefrontal cortex (PFC). Microglia marker Iba-1 was decreased immediately after CUMS. Because KMO is mainly found in microglia in the central nervous system, these results suggests that CUMS increased KA contents via alternation of kynurenine metabolic enzyme from KMO to KATs due to the reduction of microglia. Because KA is α7 nicotinic acetylcholine receptor (α7nAChR) antagonist, we investigated the effect of nicotine and galantamine (allosteric potentiating ligand for α7nAChR ) on the depression-like behavior and dysregulation of HPA axis induced by CUMS. When nicotine and galantamine were administrated before exposure to each stressor, they attenuated CUMS-induced depression-like behaviors. Although nicotine didn't affect elevated corticosterone level in the serum immediately after CUMS, it suppressed the sustained elevation 1 week after CUMS. Increase of KA associative with downregulation of KMO in microglia was involved in the depressive-like behavior and the sustained elevation of serum corticosterone after CUMS. The ameliorating effects of nicotine and galantamine on depression-like behaviors induced by CUMS are associated with the activation of α7nAChR.

High salt (HS) intake is known as a risk factor for hypertension and dementia. Prostaglandin E2 (PGE2) has various effects on vascular function and central nervous system via four types of PGE2 receptors (EP1-EP4). However, an involvement of PGE2/EP1 signaling in the HS intake-induced hypertension and emotional and cognitive dysfunctions is still unclear. In this study, we confirmed the effect of HS intake on the blood pressure and emotional and cognitive functions in mice. Mice showed hypertension and impairments of social behavior in social interaction test and object recognition memory in novel object recognition test 12 weeks after HS intake. HS intake increased phosphorylation of tau, but decreased phosphorylation of Ca2+ / calmodulin-dependent protein kinase II and expression of PSD95 in the prefrontal cortex. HS intake increased expressions of mRNA of EP1 receptor in the kidney and prefrontal cortex. The HS intake-induced hypertension, abnormal behaviors and increased phosphorylation of tau were not observed in the EP1 heterozygous knockout mice. These findings suggest that PGE2/EP1-tau phosphorylation signaling is involved in the HS intake-induced hypertension and emotional and cognitive dysfunctions.

<title>Abstract</title>Dopamine is a key neurotransmitter that regulates attention through dopamine D1 and D2-receptors in the prefrontal cortex (PFC). We previously developed an object-based attention test (OBAT) to evaluate attention in mice. Disruption of the dopaminergic neuronal system in the PFC induced attentional impairment in the OBAT. However, previous studies have not systematically examined which specific brain regions are associated with the blockade of PFC dopamine D1 and D2-receptors in the OBAT. In this study, we investigated the association of dopamine D1 and D2-receptors in the PFC with attention and neuronal activity in diverse brain regions. We found that both dopamine D1 and D2-receptor antagonists induced attentional impairment in the OBAT by bilateral microinjection into the PFC of mice, suggesting that both dopamine D1 and D2-receptors were associated with attention in the OBAT. Our analysis of the neuronal activity as indicated by c-Fos expression in 11 different brain regions showed that based on the antagonist types, there was selective activation of several brain regions. Overall, this study suggests that both dopamine D1 and D2-receptors play a role in attention through different neuronal circuits in the PFC of mice.

The importance of glutamate transporters in learning, memory, and emotion remains poorly understood; hence, in the present study, we investigated whether deficiency of pharmacological GLAST in neurodevelopmental processes affects cognitive and/or emotional behaviors in mice. The mice were injected with a glutamate transporter inhibitor, dl-threo-β-benzyloxyaspartate (dl-TBOA), during the early postnatal period. At 8 weeks of age, they showed impairments in cognitive or emotional behaviors; dysfunction of glutamatergic neurotransmission (increased expressions of GLAST, GLT-1, or GFAP protein, and decreased ability of glutamate release) in the cortex or hippocampus; morphological changes (decreased cell size in the cortex and thickness of the pyramidal neuronal layer of the CA1 area in the hippocampus). Such behavioral and morphological changes were not observed in adult mice injected with dl-TBOA. These results suggest that GLAST plays an important role in the regulation of cognitive and emotional behaviors. Early postnatal glutamatergic facilitation by GLAST dysfunction leads to cognitive and emotional abnormalities due to neurodevelopmental abnormalities such as morphological changes.