山本 康子

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.

プログラニュリン(PGRN)の測定方法の確立を目的として新たに開発されたPGRN測定試薬の基礎的検討をおこなった。未治療の関節リウマチ(RA)患者50例と変形性ひざ関節症(OA)患者37例,健常者100例についてPGRN測定試薬を用いて測定した。さらにRA治療薬のTNF関連生物学的製剤Infliximab(IFX)投与患者5例について経時変を観察した。再現性は2濃度の併行精度4.4%,4.2%,5日間の室内再現精度8.7%,7.8%であった。健常者のPGRN(Mean±SDng/mL)は男性37.9±8.9ng/ml,女性40.5±8.7ng/mlであった。RA患者は62.9±12.4ng/ml,OA患者55.1±12.0ng/mlでありRA患者が有意に高値であった。またIFX治療患者では治療前から約1年後のPGRNは軽度(約20%)の上昇が認められた。本試薬の基礎的検討は良好であり,RA患者ではOA患者,健常者対照に比べて有意に高く従来の報告と一致していた。(著者抄録)

OBJECTIVES: We evaluated the applicability of a machine learning based Low-density lipoprotein-cholesterol (LDL-C) estimation method and the influence of the characteristics of the training datasets. METHODS: Three training datasets were chosen from training datasets: health check-up participants at the Resource Center for Health Science (N = 2664), clinical patients at Gifu University Hospital (N = 7409), and clinical patients at Fujita Health University Hospital (N = 14842). Nine different machine learning models were constructed through hyperparameter tuning and 10-fold cross-validation. Another test dataset of another 3711 clinical patients at Fujita Health University Hospital was selected as the test set used for comparing and validating the model against the Friedewald formula and the Martin method. RESULTS: The coefficients of determination of the models trained on the health check-up dataset produced coefficients of determination that were equal to or inferior to those of the Martin method. In contrast, the coefficients of determination of several models trained on clinical patients exceeded those of the Martin method. The means of the differences and the convergences to the direct method were higher for the models trained on the clinical patients' dataset than for those trained on the health check-up participants' dataset. The models trained on the latter dataset tended to overestimate the 2019 ESC/EAS Guideline for LDL-cholesterol classification. CONCLUSION: Although machine learning models provide valuable method for LDL-C estimates, they should be trained on datasets with matched characteristics. The versatility of machine learning methods is another important consideration.

Cisplatin is a chemotherapeutic agent used to treat many types of malignant tumors. However, irrespective of its potent anticancer properties and efficacy, nephrotoxicity is the dose-limiting factor of cisplatin treatment. Cisplatin infiltrates renal tubular cells in the kidneys and is metabolized by cysteine conjugate-beta lyase 1 (CCBL1) to form highly reactive thiol-cisplatin; this may mediate cisplatin's nephrotoxicity. Therefore, CCBL1 inhibition may prevent cisplatin-induced nephrotoxicity. Using a high-throughput screening assay, we identified 2',4',6'-trihydroxyacetophenone (THA) as an inhibitor of CCBL1. THA inhibited human CCBL1 beta-elimination activity in a concentration-dependent manner. We further investigated the preventive effect of THA on cisplatin-induced nephrotoxicity. THA attenuated the effect of cisplatin on the viability of confluent renal tubular cells (LLC-PK1 cells) but had no effect on cisplatin-induced reduction of proliferation in the tumor cell lines (LLC and MDA-MB-231). THA pre-treatment significantly attenuated cisplatin-induced increases in blood urea nitrogen, creatinine, cell damage score, and apoptosis of renal tubular cells in mice in a dose-dependent manner. Furthermore, THA pre-treatment attenuated cisplatin-induced nephrotoxicity without compromising its anti-tumor activities in mice bearing subcutaneous syngeneic LLC tumors. THA could help prevent cisplatin-induced nephrotoxicity and may provide a new strategy for cisplatin-inclusive cancer treatments.

The partial loss of liver due to liver transplantation or acute liver failure induces rapid liver regeneration. Recently, we reported that the selective inhibition of indoleamine 2,3‑dioxygenase (Ido) 1 promotes early liver regeneration. However, the role of Ido2 in liver regeneration remains unclear. Wild‑type (WT) and Ido2‑deficient (Ido2‑KO) mice were subjected to 70% partial hepatectomy (PHx). Hepatocyte growth was measured using immunostaining. The mRNA expression of inflammatory cytokines and production of kynurenine in intrahepatic mononuclear cells (MNCs) were analyzed using reverse transcription‑quantitative PCR and high‑performance liquid chromatography. The activation of NF‑κB was determined by both immunocytochemistry and western blotting analysis. The ratio of liver to body weight and the frequency of proliferation cells after PHx were significantly higher in Ido2‑KO mice compared with in WT mice. The expression of IL‑6 and TNF‑α in MNCs were transiently increased in Ido2‑KO mice. The nuclear transport of NF‑κB was significantly higher in peritoneal macrophages of Ido2‑KO mice compared with WT mice. These results suggested that Ido2 deficiency resulted in transiently increased production of inflammatory cytokines through the activation of NF‑kB, thereby promoting liver regeneration. Therefore, the regulation of Ido2 expression in MNCs may play a therapeutic role in liver regeneration under injury and disease conditions.

The COVID-19 vaccine will be safe and effective in solid organ transplant recipients (SOTs). However, the blunted antibody responses were also of concern. Few studies have reported prolonged serologic follow-up after 2 doses of BNT162b2 vaccine in SOTs. We performed a single-center, prospective observational study of 78 SOTs who received 2 doses of BNT162b2 vaccine. We identified the trajectory of antibody titers after vaccination among SOTs with or without mycophenolate mofetil (MMF) or withdrawn from MMF. We found low seroconversion rates (29/42: 69%) and low antibody titers in SOTs treated with MMF. An inverse linear relationship between neutralizing antibody titers and MMF concentration was confirmed in restricted cubic spline plots (P for effect < .01, P for nonlinearity = .08). For the trajectory of antibody responses, seroconversion and improved antibody titers were observed after withdrawal from MMF in SOTs who showed seronegative or low antibody titers at the first visit after 2 doses of vaccine (P for effect < .01, P for nonlinearity < .05, and P for interaction < .01). We identified increased B-cell counts after withdrawal from MMF (P < .01). The recovery of antibody responses was seen in SOTs withdrawn from MMF. The trajectories of antibody responses were modified by MMF administration.

OBJECTIVES: High concentrations of low-density lipoprotein cholesterol (LDL-C) are a risk factor for cardiovascular disease. We validated the efficacy of the Martin method is useful in the estimation of LDL-C concentrations was validated in Japanese populations and derived a modified Martin method for easy laboratory information system applications. METHODS: We created 3 subject groups, including 2664 health check-up participants registered with the Resource Center for Health Science, 29,806 clinical patients (A) in the Gifu University Hospital, and 113,716 clinical patients (B) in the Fujita Health University Hospital. Each method to estimate serum LDL-C concentrations (Friedewald formula, Martin method and modified Martin method) was validated by correlation analysis with serum LDL-C concentrations measured using a direct method. RESULTS: The correlation coefficients with the direct method in terms of the Friedewald formula, Martin method, and modified Martin method were 0.963, 0.972 and 0.970 in the health check-up participants; 0.946, 0.962 and 0.961 in clinical patients A; and 0.961, 0.979 and 0.978 in clinical patients B, respectively. Concordance ratios with using the direct method in the Friedewald formula, Martin method and modified Martin method were 82.8%, 85.5% and 85.3% in the health check-up participants; 76.4%, 80.5% and 80.2% in clinical patients A; and 76.1%, 82.6% and 82.6% in clinical patients B, respectively. CONCLUSION: Our results show that the Martin and modified Martin methods display good performance in terms of the estimation of LDL-C concentrations among triglyceride concentrations of a wide range, and they may thus be useful for estimating LDL-C concentrations.

LPSは炎症の成立に重要な役割を果たしている。LPSはLPS結合蛋白(LBP)と結合し、さらにCD14が結合することで炎症シグナルを細胞内に誘導する。今回、我々は長期療養(5年以上)のRA患者を対象に、高感度法によるLBPの定量とACPA抗体の変動を調査した。また炎症の指標とされているCRPおよびIL-6の測定を同時に行いバイオマーカーとしてのLBPの臨床的意義について検討を行った。血中LBP値(Mean±SD)は健常者3.69±1.26μg/mL、OA群6.05±2.40μg/mL、RA群11.10±5.16μg/mLであり、RA群で最も有意に高値を示した(p<0.0001)。さらにstage、classの亢進に伴いLBPが増加した。また、ACPAとは相関(r=0.410)を認め、陽性群と陰性群での比較では陽性例が有意(p<0.002)に高値であった。このことから高感度法によるLBPの測定はRAの新たな病態解析の指標の一つになる可能性が有るものと考える。(著者抄録)

ADVIAシリーズ用に開発されたIL-6測定試薬をCentaur XPTを用いてその有用性について検討した。併行精度(%)2.2〜7.7,室内再現精度(%)2.9〜6.8で精度について問題ないと考えられる。また従来法のELISA法(r=0.966),CLEIA法(r=0.977)との相関は良好であった。健常者(1.35±0.70pg/mL),不明関節炎患者(3.49±6.29pg/mL)と関節リウマチ患者(17.56±31.28pg/mL)の比較において関節リウマチ患者が有意(p<0.001)に高値であった。さらに操作性については,既に検査室に設置されている装置を用いるため操作手順を大きく変更することはなく日常検査項目と同時測定が可能である。今後,炎症性疾患や感染症などの早期診断バイオマーカーとして臨床の場における新たな診断価値が提唱されるものと考えている。(著者抄録)

汎用生化学自動分析装置を用いたSARS-CoV-2抗体定量の有用性について基礎的検討を行った。陰性検体としてSARS-CoV-2流行以前に健康診断を受診した300名から得られた300検体の血清を用い、新型コロナワクチンを2回接種した本学教職員30名から経時的に得られた血清150検体を用いた。異なる2種類の精度管理血清(血清1:陰性域、血清2:陽性域)を20回連続測定した。その結果、血清1と血清2の測定値はそれぞれ1.69±0.58、31.70±0.89、変動係数はそれぞれ34.5%と2.8%であった。期待値を大きく外れるポイントは認められず良好な希釈直線性が得られ、理論値3000BAU/mLの検体を2n倍希釈し測定した。その結果、300BAU/mLから400BAU/mL付近においてフッキング現象が観察され、プロゾーンの存在が示された。本試薬は多くの検査室が所有する汎用自動分析装置で使用できると考えられた。

BACKGROUND: Coronavirus disease 2019 (COVID-19) is known to cause not only respiratory but also neuropsychiatric symptoms, which are assumed to be derived from a cytokine storm and its effects on the central nervous systems. Patients with COVID-19 who develop severe respiratory symptoms are known to show severe neuropsychiatric symptoms such as cerebrovascular disease and encephalopathy. However, the detailed clinical courses of patients with neuropsychiatric symptoms caused by mild or asymptomatic COVID-19 remain poorly understood. Here, we present a case of COVID-19 who presented with severe and prolonged neuropsychiatric symptoms subsequent to mild respiratory symptoms. CASE PRESENTATION: A 55-year-old female with COVID-19 accompanied by mild respiratory symptoms showed delusion, psychomotor excitement, and poor communication ability during quarantine outside the hospital. Considering her diminished respiratory symptoms, her neuropsychiatric symptoms were initially regarded as psychogenic reactions. However, as she showed progressive disturbance of consciousness accompanied by an abnormal electroencephalogram, she was diagnosed with post-COVID-19 encephalopathy. Although her impaired consciousness and elevated cytokine level improved after steroid pulse therapy, several neuropsychiatric symptoms, including a loss of concentration, unsteadiness while walking, and fatigue, remained. CONCLUSIONS: This case suggests the importance of both recognizing that even apparently mild COVID-19-related respiratory symptoms can lead to severe and persistent neuropsychiatric symptoms, and elucidating the mechanisms, treatment, and long-term course of COVID-19-related neuropsychiatric symptoms in the future.

Mass vaccination campaigns using mRNA vaccines against SARS-CoV-2 have begun in many countries. Serological assays to detect antibody production may be a useful tool to monitor the efficacy of SARS-CoV-2 vaccination in individuals.

LPS結合蛋白(LBP)はLPSを単球に提示するなど,前炎症段階における初期免疫に関与する。今回我々は化学発光免疫測定装置へ搭載可能な新規LBP測定試薬の基本性能評価を行った。再現性は4%未満であり,共存物質の影響を受けないこと,良好な希釈直線性を有することが確認された。健常対照群のLBP値はELISA法やLA法の既報よりも高値であった。また,RA患者において健常対照群よりも有意に高値であった。本試薬は良好な基本性能を有しており新たな炎症関連マーカーとしての活用が期待される。(著者抄録)

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.

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.

Background: Progranulin (GP88) is an 88-kDa glycoprotein growth factor with important biological effects in tumorigenesis and tumour survival. We investigated the usefulness of measuring serum GP88 concentrations as a predictive biomarker for hepatocellular carcinoma in patients with viral hepatitis C after treatment with direct-acting antiviral agents. Methods: We measured the serum GP88 concentrations by using a sandwich enzyme-linked immunoassay from 67 healthy control subjects and 29 patients (20 patients who did not develop hepatocellular carcinoma and 9 patients who developed hepatocellular carcinoma after treatment) with viral hepatitis C after treatment with asunaprevir and daclatasvir. Results: The serum GP88 concentrations of patients with chronic hepatitis C prior to antiviral treatment were significantly higher than those of healthy control subjects. After antiviral treatment, the serum GP88 concentrations of patients who eventually developed hepatocellular carcinoma were significantly higher than those who did not develop hepatocellular carcinoma. The changes in the serum GP88 concentrations before and after treatment in patients who developed hepatocellular carcinoma were significantly lower than those in patients who did not develop hepatocellular carcinoma. The cumulative incidence of hepatocellular carcinoma was significantly higher in either patients with high serum GP88 concentrations after treatment or those with small changes of serum GP88 concentrations pre- and post-treatment. Conclusions: Sustained high concentrations of serum GP88 in patients treated with direct-acting antiviral agents are correlated with the risk of developing hepatocellular carcinoma.

Despite advances in our understanding of endotoxic shock, novel therapeutic interventions that can reduce the burden of sepsis remain elusive. Current treatment options are limited, and it is only through refinements in the ways that we deliver supportive care that mortality has fallen over the years. In this study, the role of kynurenine 3-monooxygenase (KMO) in immune regulation was examined in LPS-induced endotoxemia using KMO-/- and KMO+/+ mice treated with the KMO inhibitor Ro61-8048. We showed that LPS-induced or cecal ligation and puncture-induced mortality and hepatic IL-6 production increased in the absence of KMO, possibly involving increased activating transcription factor 4 (ATF4) signaling in hepatic macrophages. Moreover, treatment of septic mice with 3-hydroxykynurenine reduced mortality rates and inflammatory responses regardless of the presence or absence of KMO. According to our results, the administration of 3-hydroxykynurenine as part of the treatment approach for sepsis or as an adjuvant therapy might reduce the overproduction of IL-6, which is responsible for severe endotoxemia, and ultimately improve the survival rates of patients with sepsis.

Indoleamine 2,3-dioxygenase 1 (IDO1) is a key enzyme associated with immunomodulation through its regulation of the tryptophan-kynurenine (Kyn) pathway in advanced cancers, including metastatic renal cell carcinoma (mRCC). However, the failure of IDO1 inhibitors when used in combination with immune checkpoint inhibitors (ICIs), as observed in clinical trials, raises a number of questions. This study aimed to investigate the association of tryptophan 2,3-dioxygenase (TDO) and IDO1 with cancer development and resistance to immunotherapy in patients with RCC. In our analysis of RCC tissue samples, tissue Kyn levels were elevated in advanced-stage RCC and correlated well with TDO expression levels in RCC tumor cells. In patients with mRCC, TDO rather than IDO1 was expressed in RCC tumor cells, showing a strong association with Kyn expression. Furthermore, immunohistochemical staining of TDO was strongly associated with the staining intensity of forkhead box P3, as well as ICI therapy response and survival in patients with mRCC. Our study is the first to show that TDO expression in tumor tissues is associated with progression and survival, confirming its potential as a predictive biomarker of primary resistance to immunotherapy in patients with mRCC. Our findings suggest that strategies aimed at inhibiting TDO, rather than IDO1, in combination with ICI therapy may aid in the control of mRCC progression.

Hematologic neoplasms, Progranulin, Mechanistic target of rapamycin complex 1, Transforming growth factor beta.

Major depressive disorder (MDD) is a common mental disorder characterized by reduced motivation, diminished interest and pleasure, and anhedonia. We have proposed melanoma-associated antigen D1 (MAGE-D1) knock out (KO) mouse is a MDD model, and which involves the serotonergic hypofunction. However, not only serotonergic but also noradrenergic neuronal malfunctions are involved in depressive behaviors. Here, we investigate the involvement of noradrenergic neuronal system in depression-like behaviors of MAGE-D1 KO mice. MAGE-D1 KO mice showed decreases in locomotor activity, social interaction time and sucrose preference, but increases in immobility time in the forced swimming test (FST), and feeding latency in the novelty suppression feeding test. Noradrenaline (NA) tissue contents in the prefrontal cortex, hippocampus, and amygdala, and potassium-evoked noradrenaline releases in the prefrontal cortex and hippocampus were decreased in MAGE-D1 KO mice. The protein expression of noradrenaline transporter (NAT) was increased in the prefrontal cortex of the MAGE-D1 KO mice. Phosphorylation of NAT at threonine and protein expression of its kinase, protein kinase C (PKC) were decreased, but not changed in ubiquitination or expression of NAT mRNA. Acute administration of NA reuptake inhibitors (desipramine and atomoxetine) attenuated increase in immobility time in the FST and decrease in sucrose preference, but not other behavior changes in MAGE-D1 KO mice. These results suggested that depression-like behaviors in MAGE-D1 KO mice might be associated with hypofunction of noradrenergic neuronal system due to NAT overexpression through decrease in PKC-dependent phosphorylation of NAT.

White matter abnormalities have been implicated in psychiatric diseases such as major depressive disorder (MDD) ; however, the underlying mechanisms remain poorly understood. The structure and function of the corpus callosum are particularly vulnerable to stress, which may lead to MDD. In the present study, we investigated whether chronic social defeat stress (CSDS) induces myelin abnormalities of the corpus callosum through inflammation that contributes to the pathogenesis of MDD. To produce CSDS, the adult C57BL/6J mouse was exposed to an aggressor ICR mouse for 10 consecutive days. CSDS decreased mature oligodendrocytes in the corpus callosum, and persistently developed depression-like behaviors such as increased immobility in the forced swimming test and impaired social interaction. On transmission electron microscopy, myelin abnormalities and axonal degeneration were observed with necrosis-like cell death of oligodendrocytes in the corpus callosum. Interestingly, CSDS significantly increased the Gasdermin D (Gsdmd), a marker of pyroptosis, concomitantly with enhanced IL-1β production in the corpus callosum. Administration of IL-1β inhibitor prevented the decrease of oligodendrocytes and CSDS-induced depression-like behaviors. These findings suggest that IL-1β acts as a crucial mediator of oligodendroglial pyroptosis induced by the CSDS, which may be responsible for the development of MDD.

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder characterized by social deficit and stereotyped, repetitive patterns of behaviors and interests. Maternal use of valproic acid (VPA) during pregnancy is associated with an increased risk of ASD in the offspring. In the pathophysiological hypothesis of ASD, excitation/inhibition (E/I) imbalance is attracted. In this study, we investigated how VPA (500 mg/kg) at embryonic day 12.5 changes the emotional, cognitive and glutamatergic functions in the offspring of mice. Prenatal VPA exposure induced excessive repetitive self-grooming behavior, impairments of social behavior and object recognition memory, increased glutamatergic signaling [i.e. phospho-Ca²+/calmodulin-dependent protein kinase II (CaMKⅡ)and phospho-protein kinase C (PKC) levels] and decreased serotonin contents in the prefrontal cortex. These results suggested that VPA-exposure induced ASD-like behaviors associated with hyper-excitation of glutamatergic and hypo-serotonergic functions in the prefrontal cortex. Activation of serotonergic system by fluoxetine (20mg/kg) attenuated the VPA-induced ASD-like behaviors and hyper-glutamatergic signaling in the prefrontal cortex. These results suggest that hypo-serotonergic function is involved in the prenatal VPA-induced ASD-like behaviors and hyper-excitation in the prefrontal cortex.

Major depressive disorder (MDD) is a worldwide serious psychiatric disease, and more than 300 million people suffer from MDD. Chronic stress contributes to the pathogenesis of MDD. Cigarette smoking is strongly associated with MDD. Epidemiological and clinical studies claim that the smoking is assumed as self-medication for stress and depression. In this study, we investigated the effect of nicotine on the depression-like behavior induced by chronic unpredictable mild stress (CUMS). At the age of 6 weeks, C57BL6J mice were randomly exposed to 9 kinds of mild stressors for 4 weeks. Nicotine (0.2mg/kg), galantamine (1mg/kg) and varenicline (1mg/kg) were administrated 30 min before exposure to each stressor during CUMS. After CUMS, mice were subjected social interaction test and measured serum corticosterone levels and mRNA levels of  nicotinic acetylcholine receptor (nAChR) subunits in the prefrontal cortex (PFC). Nicotine attenuated decrease in social interaction time of CUMS mice. Nicotine did not affect elevated serum corticosterone levels immediately after CUMS but reversed the sustained elevation after behavioral test. CUMS did not affect mRNA levels of α7, α4 or β2 nAChR subunit in the PFC. Finally, we evaluated the efficacies of galantamine, α7 nAChR allosteric modulator and varenicline, α4β2 nAChR partial agonist on CUMS mice. Administration of galantamine, but not varenicline attenuated decrease in social interaction time of CUMS mice. These data suggested that α7 nAChR is an important target for stress resilience and development of antidepressant.

Chronic stress contributes to the pathogenesis of major depressive disorder (MDD). The efficacy of ketamine on the treatment-resistant MDD implies the involvement of glutamatergic dysregulation in its pathophysiology. We recently demonstrated the abnormalities of ubiquitin-proteasome system (UPS) in the pathophysiology of MDD. In the present study, we investigated the involvement of glutamatergic dysregulation by UPS in chronic social defeat stress (CSDS)-induced depression-like behavior. To induce CSDS, the adult C57BL/6J mouse was exposed to aggressor ICR mouse for 10 consecutive days. CSDS reduced the duration of time spent at the interaction zone in the social interaction test. Increase in high potassium-induced release of glutamate was diminished in the prefrontal cortex (PFC) of the stressed mice. Interestingly, ubiquitinated but not total glutamate transporter 1 (GLT-1) was decreased in the PFC of the stressed mice. Protein levels of neural precursor cell expressed developmentally downregulated gene 4-like (Nedd4L) and ubiquitin-conjugating enzyme E2D2 (Ube2d2) were also reduced in the stressed mice. Injection of adeno-associated virus (AAV) expressing shRNA against Nedd4L into the PFC exacerbated the social impairments induced by CSDS. These results suggest that CSDS induces depressive-like behavior and glutamatergic dysfunction, through the decrease of GLT-1 ubiquitination by down-regulation of Ube2d2-Nedd4L pathway. Taken together, GLT-1 ubiquitination could play crucial roles in the pathophysiology of MDD.

High salt (HS) intake is known as a risk factor for hypertension and dementia. However, an involvement of the brain-peripheral interaction in the HS-induced hypertension and cognitive dysfunction is still unclear. In this study, we confirmed the effect of HS intake on the blood pressure and cognitive and emotional functions in mice. Mice showed hypertension and impairments of object recognition memory in novel object recognition test and social behavior in social interaction test 12 weeks after HS intake. We investigated the mechanism of HS intake-induced hypertension and abnormal behaviors. HS intake increased phosphorylation of tau and decreased phosphorylation of Ca2+ / calmodulin-dependent protein kinase II (CaMKII) and expression of PSD95 in the prefrontal cortex and hippocampus, suggesting HS intake induces neuronal dysfunction. On the other hand, HS intake increased mRNA levels of inducible nitric oxide synthase (iNOS) and serum amyloid A (SAA) in the small intestine and picolinic acid levels in the serum, suggesting HS intake induces peripheral inflammatory response. The present findings suggest that HS intake induces hypertension and abnormal behaviors with peripheral inflammatory response.

Indoleamine 2,3-dioxygenase 1 (IDO1) is the first rate-limiting enzyme that metabolizes tryptophan to the kynurenine pathway. Its activity is highly inducible by pro-inflammatory cytokines and correlates with the severity of major depressive disorder (MDD). MicroRNAs (miRNAs) are involved in gene regulation and the development of neuropsychiatric disorders including MDD. However, the role of miRNAs in targeting IDO1 in the pathophysiology of MDD is still unknown. In this study, we investigated the role of novel miRNAs in the regulation of IDO1 activity and its effect on lipopolysaccharide (LPS)-induced depression-like behavior in mice. LPS up-regulated miR-874-3p concomitantly with increase in IDO1 expression in the prefrontal cortex (PFC), increase in immobility in the forced swimming test as depression-like behavior and decrease in locomotor activity as sickness behavior without motor dysfunction. The miR-874-3p increased in both neuron and microglia after LPS. Its mimic significantly suppressed LPS-induced IDO1 expression in the PFC. Infusion of IDO1 inhibitor (1-methyl-l-tryptophan) and miR-874-3p into PFC prevented an increase in immobility in the forced swimming test, but did not decrease in locomotor activity induced by LPS. These results suggest that miR-874-3p may play an important role in preventing the LPS-induced depression-like behavior through inhibition of IDO1 expression. This may also serve as a novel potential target molecule for the treatment of MDD.

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Indoleamine 2,3-dioxygenase 1 (IDO1) is an enzyme known to suppress immune responses, and several reports have showed that it is associated with psoriasis. IDO2 is an isoform of IDO1, recently identified as a catalytic enzyme in the tryptophan-kynurenine pathway, which is expressed in dendritic cells and monocytes. The expression of IDO2 in immune cells suggests that IDO2 may contribute to immune functions. However, the role of IDO2 in the pathogenesis of psoriasis remains unclear. In this study, to elucidate the role of IDO2 in psoriasis, we assessed imiquimod (IMQ)-induced psoriasis-like dermatitis in IDO2 knockout (KO) mice. Skin inflammation, evaluated by scoring erythema, scaling, and ear thickness, was significantly worse in the IDO2 KO mice than in the wild-type (WT) mice. The mRNA expression levels of TNF-α, IL-23p19, and IL-17A, key cytokines involved in the development of psoriasis, were also increased in the IDO2 KO mice. Furthermore, immunohistochemistry revealed that the number of Ki67-positive cells in the epidermis and CD4-, CD8-, and IL-17-positive lymphocytes infiltrating the dermis were significantly increased in the IDO2 KO mice. These results suggest that IDO2 might decrease IL-17 expression, thereby resulting in the suppression of skin inflammation in IMQ-induced psoriasis-like dermatitis.

Kynurenine (Kyn) plays an important role as an immune check-point molecule and regulates various immune responses through its aryl hydrocarbon receptor (Ahr). Kyn is synthesized by indoleamine 2,3-dioxygenase (Ido) and tryptophan 2,3-dioxygenase (Tdo). Ido contributes approximately 90% of tryptophan catabolism. Although Kyn is increased in various liver disorders, the roles of Kyn in liver injury are complicated because Ido1, Ido2, and Tdo are activated in different cell types. In this study, the roles of Ido2 in carbon tetrachloride (CCl4; 1 ml/kg, i.p.)-induced acute liver injury were examined using Ido2 knockout mice and Ido2 inhibitor. After CCl4 treatment, the ratio of Kyn to tryptophan and levels of Kyn in the liver were increased, accompanied by activation of Ahr-mediated signaling, as revealed by increased nuclear Ahr and Cyp1a1 mRNA. Knockout of Ido2 (Ido2-/-) and treatment with Ido2 inhibitor 1-methyl-D-tryptophan (D-1MT; 100 mg/kg, i.p.) attenuated CCl4-induced liver injury, with decreased induction of Ahr-mediated signaling. Administration of D-Kyn (100 mg/kg, i.p.) to Ido2-/- mice canceled the effect of Ido2 deficiency and exacerbated acute liver damage by CCl4 treatment. In addition, liver fibrosis induced by repeated CCl4 administration was suppressed in Ido2-/- mice. In conclusion, the action of Ido2 and Kyn in the liver may prevent severe hepatocellular damage and liver fibrosis.

BACKGROUND: Inflammatory bowel disease, such as Crohn's disease and ulcerative colitis, is characterized by chronic intestinal inflammation leading to intestinal mucosal damage. Inflammatory bowel disease causes dysregulation of mucosal T cell responses, especially the responses of CD4+ T cells. Previously, we demonstrated that indoleamine-2,3-dioxygenase plays an immunosuppressive role in 2,4,6-trinitrobenzene sulfate (TNBS)-induced colitis. Although indoleamine-2,3-dioxygenase exerts immunosuppressive effects by altering the local concentration of tryptophan (Trp) and immunomodulatory Trp metabolites, the specific changes in immune regulation during colitis caused by Trp metabolites and its related enzymes remain unclear. AIM: To investigate role of kynurenine 3-monooxygenase (KMO) in TNBS-induced colitis and involvement of Trp metabolites in maintenance of intestinal homeostasis. METHODS: Colitis was induced in eight-week-old male KMO+/+ or KMO-/- mice of C57BL/6N background using TNBS. Three days later, the colon was used for hematoxylin-eosin staining for histological grading, immunohistochemical or immunofluorescence staining for KMO, cytokines, and immune cells. Inflammatory and anti-inflammatory cytokines were measured using quantitative RT-PCR, and kynurenine (Kyn) pathway metabolites were measured by high-performance liquid chromatography. The cell proportions of colonic lamina propria and mesenteric lymph nodes were analyzed by flow cytometry. RESULTS: KMO expression levels in the colonic mononuclear phagocytes, including dendritic cells and macrophages increased upon TNBS induction. Notably, KMO deficiency reduced TNBS-induced colitis, resulting in an increased frequency of Foxp3+ regulatory T cells and increased mRNA and protein levels of anti-inflammatory cytokines, including transforming growth factor-β and interleukin-10. CONCLUSION: Absence of KMO reduced TNBS-induced colitis via generation of Foxp3+ regulatory T cells by producing Kyn. Thus, Kyn may play a therapeutic role in colon protection during colitis.