Research Themes

• MHCクラスI抗原提示の機能不全が惹起する脳内セロトニン過剰疾患「不安障害」
  01 Apr. 2022 - 31 Mar. 2025
• Dysfunction of ERAP1 induces anxiety disorder via excess serotonin synthesis
  Grant-in-Aid for Scientific Research (C)
  Teikyo Heisei University
  01 Apr. 2019 - 31 Mar. 2022
  Reduction of enzymatic activity of ERAP1 promotes anxious behaviors. In this study, we elucidated the mechanisms promoting anxious behavior associated with ERAP1 gene deletion.
  We found that loss of ERAP1 enzyme activity in the raphe nucleus of the brain promotes excessive serotonin synthesis by suppressing the expression of the tryptophan hydroxylase 2-transcriptional repressor, REST. We also showed that the stress behavior elicited by ERAP1 gene deficiency is due to excess serotonin. Thus, ERAP1 is one of the regulators of serotonin synthesis in the brain and dysfunction of ERAP1 can induce anxiety disorders.
• Mechanism of mucosal immunity activation by exosome
  Grant-in-Aid for Scientific Research (C)
  Teikyo Heisei University
  21 Oct. 2016 - 31 Mar. 2019
  Human whole saliva contains exosomes that have mucosal immunomodulatory potential. Immune-related proteins such as DPP IV and IgA, salivary proteins such as mucin 5B, and lipopolysaccharide (LPS) derived from oral bacteria were associated with surface of the exosomes.
  Mucin 5B was digested with gastrointestinal enzymes. Although IgA and LPS were dissociated by size-exclusion chromatography, a part of them was tightly associated with the exosomes. Salivary exosome without the surface molecules increased production of nitric oxide (NO) from murine macrophages. In addition, we found that DPP IV may contribute to the NO production by collaboration with LPS. Salivary exosome is presumed to suppress the excessive activation in oral cavity and cause the activation of mucosal immunity after exposure to the gastrointestinal condition.
• Roles of ER aminopeptidase 1 in inflammation of Behcet's disease
  Grant-in-Aid for Scientific Research (C)
  Teikyo Heisei University
  01 Apr. 2016 - 31 Mar. 2019
  It has been known that ERAP1 mutation is associated with Behcet's disease. In this study, to elucidate the molecular mechanisms in the disease, roles of ERAP1 in inflammation were evaluated.
  To construct a disease model, uveitis was induced by lipopolysaccharide(LPS) injection into peritoneal cavity of wild-type and ERAP1-knock out (KO) mice. Although nitric oxie（NO) in the blood was increased together with ERAP1 secretion therein after injection, ERAP1-KO caused the reduction of NO and Arg synthesis. These results suggest that secreted ERAP1 is involved in the NO synthesis via producing Arg. On the other hand, we found that secreted ERAP1 binds to exosome derived from activated macrophages and its complex lead to activation of naive macrophage mediating facilitaion of Arg production, iNOS expression and phagocytosis.
  Our data provide the evidence that free ERAP1 and ERAP1 associated with exosomes plays important roles in inflammation through macrophage activation.
• Role of ERAP1 in the pathogenesis of mental disorders
  Grant-in-Aid for Challenging Exploratory Research
  Teikyo Heisei University
  01 Apr. 2015 - 31 Mar. 2017
  Role of ERAP1 in the pathogenesis of mental disorder was investigated using ERAP1 knock out mouse. All the pharmacological measurements tested including, tail suspension test, forced swim test, elevated plus maze test and three chamber test, showed a significant difference between ERAP1 knockout mouse and wild-type mouse and thus suggested that knockout mouse were suffering mental disorder. Measurement of neuronal signal molecules indicated an increase of serotonin in the brain via activation of serotonin synthetic pathway.
  Considering that ERAP1 can be secreted into outside of the cells by certain stimuli, these results strongly suggest that the enzyme plays a critical role in the pathogenesis of certain mental disorders via affecting gene expression of serotonin biosynthesis. Our data presented in this study might confirm new pathological functions of the enzyme and bring new insights into the pathogenesis of certain mental disorders.
• Molecular mechanism and regulation of immune activation cascade by aminopeptidase contained exosome.
  Grant-in-Aid for Scientific Research (C)
  Teikyo Heisei University
  01 Apr. 2013 - 31 Mar. 2016
  Human whole saliva contains two types of extracellular vesicles. One type highly expresses dipeptidyl peptidase-4 (DPP4) and the other type rarely expresses them. We designate former as DPP IV-exosome (DPP4exo), and later as deficient DPP IV-exosome (dDPP4exo). DPP4exo contained lipopolysaccharide (LPS) abundantly, and dDPP4exo contained it slightly. Although large amount of LPS interacted weakly with DPP4exo or existed separately forming micelle, part of LPS bind DPP4exo tightly. DPP4exo alone did not activate murine macrophage, however, DPP4exo with interferon-gamma produce high level of nitric oxide (NO) from murine macrophage. dDPP4exo did not cause NO production, even when interferon-gamma was added. DPP4exo is presumed to induce NO production from macrophage, when inflammation caused by bacterial infection, and associated with increased levels of interferon-gamma in oral cavity.
• Pathophysiological roles of M1 aminopeptidases
  Grant-in-Aid for Scientific Research (B)
  Teikyo Heisei University
  01 Apr. 2013 - 31 Mar. 2016
  Endoplasmic reticulum aminopeptidase (ERAP)1 was secreted under infectious conditions. When analyzed the mechanism, several cytokines were expressed in macrophages in response to LPS and IFN-gamma and their synergistic action caused the secretion via induction of calcium mobilization. Then we found that ERAP1 contributed to the NO production in vivo when analyzed by employing ERAP1-knockout mice.
  In the serum of knockout mice, decrease in free arginine level was observed, suggesting that ERAP1 caused the cleavage of N-terminal arginine of substrate peptides and thus increased NO production. Further works are now in progress to elucidate the pathophysiological roles of ERAP1.
  By molecular modeling, we elucidated the characteristic features of the substrate pocket of M1 aminopeptidases. Based on these results, we screened the inhibitor of ERAP1 and found a candidate. After optimization, we will develop a therapeutically useful inhibitor to pathological conditions caused by ERAP1.
• Contribution of ER-aminopeptidase secretion to classical activation of macrophages
  Grant-in-Aid for Young Scientists (B)
  Teikyo Heisei University
  01 Apr. 2012 - 31 Mar. 2015
  Recently we demonstrated that endoplasmic reticulum aminopeptidase 1 (ERAP1) was secreted from macrophages in response to LPS and IFN-γ, and it enhanced their phagocytic activity. In this study, we analyzed the mechanisms of ERAP1 secretion and phagocytosis activation by secreted ERAP1. TLR ligands such as exogenous lipopolysaccharide, lipoprotein and DNA induced secretion of the enzyme from the murine macrophage cell line RAW264.7 and murine peritoneal macrophages. These secretions were suppressed by deletion of either TNF-α or type 1 IFNR gene, suggesting that TNF-α and type I IFN expressed by TLR signaling are important for ERAP1 secretion. On the other hand, we found the exon 10 sequence of ERAP1 gene is crucial for ER-retantion and extracellular ERAP1 complexed with several cytokines showed more effective on phagocytosis than ERAP1 only. These results suggest that ERAP1 secretion is key event for classical activation of macrophages.
• Role of aminopeptidases in atherosclerosis
  Grant-in-Aid for Challenging Exploratory Research
  Teikyo Heisei University
  Apr. 2012 - Mar. 2014
  Endoplasmic reticulum aminopeptidase (ERAP) 1 is secreted from macrophages in response to IFN-γ and LPS, suggesting that it can regulate blood pressure via cleavage of peptide hormones in the blood vessels and thus affect the formation of atherosclerosis.
  In this study, we initially analyzed the secretion mechanism of ERAP1. We found that IFN-γ/LPS treatment caused the expression of several cytokines in macrophages such as IFN-β and TNF-α. Synergistic action of these cytokines induced the mobilization of calcium in the cytosol to cause the ERAP1 secretion. We also found that secreted ERAP1 mediated NO production via cleavage of peptide hormones having N-terminal arginine. Taken together, our data suggest that ERAP1 was secreted via calcium mobilization in the cytosol in response to infectious states caused by either bacteria or virus infection and could regulate blood pressure via cleavage of peptide hormones and thus might play roles in the formation of atherosclerosis.
• Regulation of blood pressure by secreted adipocyte-derived leucine aminopeptidase
  Grant-in-Aid for Young Scientists (B)
  Apr. 2009 - Mar. 2011
  Adipocyte-derived leucine amnopeptidase (A-LAP) may play role in the blood pressure regulation. In this study, it is revealed that ER-retained A-LAP is secreted from macrophages in response to activation by treatment with lipopolysaccharide and interferon-γ, and supply of arginine for nitric oxide synthesis from peptide to cells. These results suggest that secretion of A-LAP is important for hypertensive action.
• Mechanisms of Enzymatic Action of the Oxytocinase Subfamily of Aminopeptidases
  Grant-in-Aid for Scientific Research (B)
  The Institute of Physical and Chemical Research
  2006 - 2008
• 脂肪細胞由来ロイシンアミノペプチダーゼの分泌を介した新規血圧調節作用の機構解明と高血圧療法への応用　　　　　　　　　　　　　　　
  2008