Faculty Profiles - IWAI Haruki

Eriko Kuramoto, Makoto Fukushima, Ryozo Sendo, Sachi Ohno, Haruki Iwai, Atsushi Yamanaka, Mitsutaka Sugimura, Tetsuya Goto . Three-dimensional topography of rat trigeminal ganglion neurons using a combination of retrograde labeling and tissue-clearing techniques . Journal of Comparative Neurology532 ( 2 ) e25584 2024.2Reviewed International journal

Language：Japanese Publishing type：Research paper (scientific journal)

The trigeminal nerve is the sensory afferent of the orofacial regions and divided into three major branches. Cell bodies of the trigeminal nerve lie in the trigeminal ganglion and are surrounded by satellite cells. There is a close interaction between ganglion cells via satellite cells, but the function is not fully understood. In the present study, we clarified the ganglion cells’ three-dimensional (3D) localization, which is essential to understand the functions of cell–cell interactions in the trigeminal ganglion. Fast blue was injected into 12 sites of the rat orofacial regions, and ganglion cells were retrogradely labeled. The labeled trigeminal ganglia were cleared by modified 3DISCO, imaged with confocal laser-scanning microscopy, and reconstructed in 3D. Histograms of the major axes of the fast blue-positive somata revealed that the peak major axes of the cells innervating the skin/mucosa were smaller than those of cells innervating the deep structures. Ganglion cells innervating the ophthalmic, maxillary, and mandibular divisions were distributed in the anterodorsal, central, and posterolateral portions of the trigeminal ganglion, respectively, with considerable overlap in the border region. The intermingling in the distribution of ganglion cells within each division was also high, in particular, within the mandibular division. Specifically, intermingling was observed in combinations of tongue and masseter/temporal muscles, maxillary/mandibular molars and masseter/temporal muscles, and tongue and mandibular molars. Double retrograde labeling confirmed that some ganglion cells innervating these combinations were closely apposed. Our data provide essential information for understanding the function of ganglion cell–cell interactions via satellite cells.

DOI： 10.1002/cne.25584

Junya Kusumoto, Koji Ataka, Haruki Iwai, Yasuhiko Oga, Keita Yamagata, Kanako Marutani, Takanori Ishikawa, Akihiro Asakawa, Shouichi Miyawaki . Malocclusion impairs cognitive behavior via AgRP signaling in adolescent mice. . Frontiers in neuroscience17 1156523 - 1156523 2023Reviewed International journal

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

INTRODUCTION: Occlusal disharmony induced by deteriorating oral health conditions, such as tooth loss and decreased masticatory muscle due to sarcopenia, is one of the causes of cognitive impairment. Chewing is an essential oral function for maintaining cognitive function not only in the elderly but also in young people. Malocclusion is an occlusal disharmony that commonly occurs in children. The connection between a decline in cognitive function and malocclusion in children has been shown with chronic mouth breathing, obstructive sleep apnea syndrome, and thumb/digit sucking habits. However, the mechanism of malocclusion-induced cognitive decline is not fully understood. We recently reported an association between feeding-related neuropeptides and cognitive decline in adolescent mice with activity-based anorexia. The aim of the present study was to assess the effects of malocclusion on cognitive behavior and clarify the connection between cognitive decline and hypothalamic feeding-related neuropeptides in adolescent mice with malocclusion. METHODS: Four-week-old mice were randomly assigned to the sham-operated solid diet-fed (Sham/solid), sham-operated powder diet-fed (Sham/powder), or malocclusion-operated powder diet-fed (Malocclusion/powder) group. We applied composite resin to the mandibular anterior teeth to simulate malocclusion. We evaluated cognitive behavior using a novel object recognition (NOR) test, measured hypothalamic feeding-related neuropeptide mRNA expression levels, and enumerated c-Fos-positive cells in the hypothalamus 1 month after surgery. We also evaluated the effects of central antibody administration on cognitive behavior impairment in the NOR test. RESULTS: The NOR indices were lower and the agouti-related peptide (AgRP) mRNA levels and number of c-Fos-positive cells were higher in the malocclusion/powder group than in the other groups. The c-Fos-positive cells were also AgRP-positive. We observed that the central administration of anti-AgRP antibody significantly increased the NOR indices. DISCUSSION: The present study suggests that elevated cerebral AgRP signaling contributes to malocclusion-induced cognitive decline in adolescents, and the suppression of AgRP signaling can be a new therapeutic target against cognitive decline in occlusal disharmony.

DOI： 10.3389/fnins.2023.1156523

Koji Ataka, Akihiro Asakawa, Haruki Iwai, Ikuo Kato . Musclin prevents depression-like behavior in male mice by activating urocortin 2 signaling in the hypothalamus. . Frontiers in endocrinology14 1288282 - 1288282 2023Reviewed International journal

Language：English Publishing type：Research paper (scientific journal)

INTRODUCTION: Physical activity is recommended as an alternative treatment for depression. Myokines, which are secreted from skeletal muscles during physical activity, play an important role in the skeletal muscle-brain axis. Musclin, a newly discovered myokine, exerts physical endurance, however, the effects of musclin on emotional behaviors, such as depression, have not been evaluated. This study aimed to access the anti-depressive effect of musclin and clarify the connection between depression-like behavior and hypothalamic neuropeptides in mice. METHODS: We measured the immobility time in the forced swim (FS) test, the time spent in open arm in the elevated-plus maze (EPM) test, the mRNA levels of hypothalamic neuropeptides, and enumerated the c-Fos-positive cells in the paraventricular nucleus (PVN), arcuate nucleus (ARC), and nucleus tractus solitarii (NTS) in mice with the intraperitoneal (i.p.) administration of musclin. Next, we evaluated the effects of a selective corticotropin-releasing factor (CRF) type 1 receptor antagonist, selective CRF type 2 receptor antagonist, melanocortin receptor (MCR) agonist, and selective melanocortin 4 receptor (MC4R) agonist on changes in behaviors induced by musclin. Finally we evaluated the antidepressant effect of musclin using mice exposed to repeated water immersion (WI) stress. RESULTS: We found that the i.p. and i.c.v. administration of musclin decreased the immobility time and relative time in the open arms (open %) in mice and increased urocortin 2 (Ucn 2) levels but decreased proopiomelanocortin levels in the hypothalamus. The numbers of c-Fos-positive cells were increased in the PVN and NTS but decreased in the ARC of mice with i.p. administration of musclin. The c-Fos-positive cells in the PVN were also found to be Ucn 2-positive. The antidepressant and anxiogenic effects of musclin were blocked by central administration of a CRF type 2 receptor antagonist and a melanocortin 4 receptor agonist, respectively. Peripheral administration of musclin also prevented depression-like behavior and the decrease in levels of hypothalamic Ucn 2 induced by repeated WI stress. DISCUSSION: These data identify the antidepressant effects of musclin through the activation of central Ucn 2 signaling and suggest that musclin and Ucn 2 can be new therapeutic targets and endogenous peptides mediating the muscle-brain axis.

DOI： 10.3389/fendo.2023.1288282

Kento Igarashi, Haruki Iwai, Koh-Ichi Tanaka, Yoshikazu Kuwahara, Junichi Kitanaka, Nobue Kitanaka, Akihiro Kurimasa, Kazuo Tomita, Tomoaki Sato . Neuroprotective effect of oxytocin on cognitive dysfunction, DNA damage, and intracellular chloride disturbance in young mice after cranial irradiation. . Biochemical and biophysical research communications612 1 - 7 2022.4Reviewed International journal

Language：English Publishing type：Research paper (scientific journal)

Cranial radiation therapy (CRT) is an effective treatment for brain tumors; however, it also causes brain injuries. The pediatric brain is considered especially vulnerable compared to the adult brain; thus, brain injuries caused by CRT may severely affect their quality of life. In this study, we determined the neuroprotective effects of nasal oxytocin administration following cranial radiation in mice. We investigated the cognitive behavior of mice (novel object recognition test and novel object location test), phosphorylated histone H2AX (γ-H2AX) and K+-Cl- transporter (KCC2) by immunohistochemical analysis of the hippocampal sections, and neuronal cells by immunocytochemistry after radiation and oxytocin administration. We found that the number of γ-H2AX foci was increased, and the surface signal intensity of KCC2 immunofluorescence was decreased in cells that were irradiated with X-rays (1.5 Gy, for three consecutive days) compared with cells that were not. Furthermore, using MQAE, we found that the intracellular chloride ion concentration was downregulated in oxytocin-treated cells by increasing surface KCC2 expression. These results indicate that nasal oxytocin administration after cranial irradiation attenuates cognitive dysfunction in mice and exerts multifaceted neuroprotective effects on DNA damage and maintains chloride ion concentration in neuronal cells.

DOI： 10.1016/j.bbrc.2022.04.099

Eriko Kuramoto, Ayano Kitawaki, Takakazu Yagi, Hiroshi Kono, Shin-Ei Matsumoto, Hiromitsu Hara, Yasumasa Ohyagi, Haruki Iwai, Atsushi Yamanaka, Tetsuya Goto . Development of a system to analyze oral frailty associated with Alzheimer's disease using a mouse model. . Frontiers in aging neuroscience14 935033 - 935033 2022Reviewed International journal

Language：English Publishing type：Research paper (scientific journal)

The rapid aging of the population makes the detection and prevention of frailty increasingly important. Oral frailty has been proposed as a novel frailty phenotype and is defined as a decrease in oral function coexisting with a decline in cognitive and physical functions. Oral frailty has received particular attention in relation to Alzheimer's disease (AD). However, the pathomechanisms of oral frailty related to AD remain unknown. It is assumed that the mesencephalic trigeminal nucleus (Vmes), which controls mastication, is affected by AD pathology, and as a result, masticatory function may be impaired. To investigate this possibility, we included male 3 × Tg-AD mice and their non-transgenic counterpart (NonTg) of 3-4 months of age in the present study. Immunohistochemistry revealed amyloid-β deposition and excessive tau phosphorylation in the Vmes of 3 × Tg-AD mice. Furthermore, vesicular glutamate transporter 1-immunopositive axon varicosities, which are derived from Vmes neurons, were significantly reduced in the trigeminal motor nucleus of 3 × Tg-AD mice. To investigate whether the AD pathology observed in the Vmes affects masticatory function, we analyzed electromyography of the masseter muscle during feeding. The 3 × Tg-AD mice showed a significant delay in masticatory rhythm compared to NonTg mice. Furthermore, we developed a system to simultaneously record bite force and electromyography of masseter, and devised a new method to estimate bite force during food chewing in mice. Since the muscle activity of the masseter showed a high correlation with bite force, it could be accurately estimated from the muscle activity. The estimated bite force of 3 × Tg-AD mice eating sunflower seeds was predominantly smaller than that of NonTg mice. However, there was no difference in masseter weight or muscle fiber cross-sectional area between the two groups, suggesting that the decreased bite force and delayed mastication rhythm observed in 3 × Tg-AD mice were not due to abnormality of the masseter. In conclusion, the decreased masticatory function observed in 3 × Tg-AD mice was most likely caused by AD pathology in the Vmes. Thus, novel quantitative analyses of masticatory function using the mouse model of AD enabled a comprehensive understanding of oral frailty pathogenesis.

DOI： 10.3389/fnagi.2022.935033

Haruki Iwai, Koji Ataka, Hajime Suzuki, Ashis Dhar, Eriko Kuramoto, Atsushi Yamanaka, Tetsuya Goto . Tissue-resident M2 macrophages directly contact primary sensory neurons in the sensory ganglia after nerve injury. . Journal of neuroinflammation18 ( 1 ) 227 - 227 2021.10Reviewed International journal

Language：English Publishing type：Research paper (scientific journal)

BACKGROUND: Macrophages in the peripheral nervous system are key players in the repair of nerve tissue and the development of neuropathic pain due to peripheral nerve injury. However, there is a lack of information on the origin and morphological features of macrophages in sensory ganglia after peripheral nerve injury, unlike those in the brain and spinal cord. We analyzed the origin and morphological features of sensory ganglionic macrophages after nerve ligation or transection using wild-type mice and mice with bone-marrow cell transplants. METHODS: After protecting the head of C57BL/6J mice with lead caps, they were irradiated and transplanted with bone-marrow-derived cells from GFP transgenic mice. The infraorbital nerve of a branch of the trigeminal nerve of wild-type mice was ligated or the infraorbital nerve of GFP-positive bone-marrow-cell-transplanted mice was transected. After immunostaining the trigeminal ganglion, the structures of the ganglionic macrophages, neurons, and satellite glial cells were analyzed using two-dimensional or three-dimensional images. RESULTS: The number of damaged neurons in the trigeminal ganglion increased from day 1 after infraorbital nerve ligation. Ganglionic macrophages proliferated from days 3 to 5. Furthermore, the numbers of macrophages increased from days 3 to 15. Bone-marrow-derived macrophages increased on day 7 after the infraorbital nerve was transected in the trigeminal ganglion of GFP-positive bone-marrow-cell-transplanted mice but most of the ganglionic macrophages were composed of tissue-resident cells. On day 7 after infraorbital nerve ligation, ganglionic macrophages increased in volume, extended their processes between the neurons and satellite glial cells, and contacted these neurons. Most of the ganglionic macrophages showed an M2 phenotype when contact was observed, and little neuronal cell death occurred. CONCLUSION: Most of the macrophages that appear after a nerve injury are tissue-resident, and these make direct contact with damaged neurons that act in a tissue-protective manner in the M2 phenotype. These results imply that tissue-resident macrophages signal to neurons directly through physical contact.

DOI： 10.1186/s12974-021-02283-z

Kento Igarashi, Toshiko Kuchiiwa, Satoshi Kuchiiwa, Haruki Iwai, Kazuo Tomita, Tomoaki Sato . Kamishoyosan (a Japanese traditional herbal formula), which effectively reduces the aggressive biting behavior of male and female mice, and potential regulation through increase of Tph1, Tph2, and Esr2 mRNA levels. . Brain research1768 147580 - 147580 2021.10Reviewed International journal

Language：English Publishing type：Research paper (scientific journal)

Kamishoyosan (KSS), a Japanese traditional herbal formula, is used to treat symptoms related to the autonomic nervous system in men and women; it is especially known for improving the symptoms of irritability (e.g., bad temper and persistent anger). Although clinical and ethological studies of KSS have been conducted, its efficacy in reducing irritability remains to be validated. In the present study, male and female ddY-strain mice were isolation-reared for 8 weeks (from the third postnatal week) to induce pathologically aggressive biting behavior (ABB), which was used as an indicator of irritability. The ABB of mice toward metal rods was measured using the Aggressive Response Meter. An intraperitoneal administration of KSS (100 mg/kg) effectively reduced ABB in male and female mice at 2 h after the administration; however, this effect was canceled by prior administration of WAY-100635 [a 5-hydroxytryptoamine (5-HT)-1A receptor antagonist; 0.5 mg/kg] and bicuculline (a type-A gamma-aminobutyric acid receptor antagonist; 1.0 mg/kg). Additionally, tamoxifen, ICI-182780, and G-15 (all estrogen receptor antagonists) inhibited the action of KSS in a dose-dependent manner. Furthermore, gene expression of tryptophan hydroxylase (Tph) 1 and Tph2 were increased and 5-HT immunofluorescence was slightly increased in the dorsal raphe nucleus (DRN) of isolation-reared mice administered with KSS. Collectively, these results indicate that KSS effectively reduces ABB in isolation-reared male and female mice through stimulation of 5-HT production in the DRN. Our findings also suggest that gene expression of estrogen receptor (Esr) 2 increased in the DRN might be associated with the reduction of ABB.

DOI： 10.1016/j.brainres.2021.147580

Natasya Trivena Rokot, Koji Ataka, Haruki Iwai, Hajime Suzuki, Homare Tachibe, Timothy Sean Kairupan, Kai-Chun Cheng, Haruka Amitani, Akio Inui, Akihiro Asakawa . Antagonism for NPY signaling reverses cognitive behavior defects induced by activity-based anorexia in mice . Psychoneuroendocrinology126 105133 - 105133 2021.4Reviewed International journal

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：Elsevier BV

Patients with AN often express psychological symptoms such as body image distortion, cognitive biases, abnormal facial recognition, and deficits in working memory. However, the molecular mechanisms underlying the impairment of cognitive behaviors in AN remain unknown. In the present study, we measured cognitive behavior using novel object recognition (NOR) tasks and mRNA expressions in hypothalamic neuropeptides in female C57BL/6J mice with activity-based anorexia (ABA). Additionally, we evaluated the effects of antagonists with intracerebroventricular (icv) administration on the impairment of cognitive behavior in NOR tasks. Our results showed that NOR indices were lowered, subsequently increasing mRNA levels of agouti-related peptide (AgRP) and neuropeptide Y (NPY), and c-Fos- and AgRP- or NPY-positive cells in the hypothalamic arcuate nucleus in ABA mice. We also observed that icv administration of anti-NPY antiserum (2 µl), anti-AgRP antibody (0.1 μg), and Y5 receptor antagonist CPG71683 (15 nmol) significantly reversed the decreased NOR indices. Therefore, our results suggest that increased NPY and AgRP signaling in the brain might contribute to the impairment of cognitive behavior in AN.

DOI： 10.1016/j.psyneuen.2021.105133

Ashis Dhar, Eriko Kuramoto, Makoto Fukushima, Haruki Iwai, Atsushi Yamanaka, Tetsuya Goto . The Periodontium Damage Induces Neuronal Cell Death in the Trigeminal Mesencephalic Nucleus and Neurodegeneration in the Trigeminal Motor Nucleus in C57BL/6J Mice. . Acta histochemica et cytochemica54 ( 1 ) 11 - 19 2021.2The Periodontium Damage Induces Neuronal Cell Death in the Trigeminal Mesencephalic Nucleus and Neurodegeneration in the Trigeminal Motor Nucleus in C57BL/6J Mice.Reviewed International journal

Tetsuya Goto, Eriko Kuramoto, Ashis Dhar, Rachel Pei-Hsuan Wang, Haruka Seki, Haruki Iwai, Atsushi Yamanaka, Shin-Ei Matsumoto, Hiromitsu Hara, Makoto Michikawa, Yasumasa Ohyagi, Wai Keung Leung, Raymond Chuen-Chung Chang . Neurodegeneration of Trigeminal Mesencephalic Neurons by the Tooth Loss Triggers the Progression of Alzheimer's Disease in 3×Tg-AD Model Mice . Journal of Alzheimer's disease76 ( 4 ) 1443 - 1459 2020.8Neurodegeneration of Trigeminal Mesencephalic Neurons by the Tooth Loss Triggers the Progression of Alzheimer's Disease in 3×Tg-AD Model MiceReviewed International journal

Kazuhiro Shiozaki , Momoko Kawabe , Kiwako Karasuyama , Takayoshi Kurachi , Akito Hayashi , Koji Ataka , Haruki Iwai , Hinako Takeno , Oki Hayasaka , Tomonari Kotani , Masaharu Komatsu , Akio Inui . Neuropeptide Y deficiency induces anxiety-like behaviours in zebrafish (Danio rerio). . Scientific reports10 ( 1 ) 5913 - 5913 2020.4Neuropeptide Y deficiency induces anxiety-like behaviours in zebrafish (Danio rerio). Reviewed International journal

Hajime Suzuki, Koji Ataka, Akihiro Asakawa, Kai-Chun Cheng, Miharu Ushikai, Haruki Iwai, Takakazu Yagi, Takeshi Arai, Kinnosuke Yahiro, Katsuhiro Yamamoto, Yoshito Yokoyama, Masayasu Kojima, Toshihiko Yada, Toshiya Hirayama, Norifumi Nakamura, Akio Inui . Helicobacter pylori Vacuolating Cytotoxin A Causes Anorexia and Anxiety via Hypothalamic Urocortin 1 in Mice. . Scientific reports9 ( 1 ) 6011 - 6011 2019.4Reviewed International journal

Language：English Publishing type：Research paper (scientific journal)

Helicobacter pylori (Hp) infection is related to the pathogenesis of chronic gastric disorders and extragastric diseases. Here, we examined the anorexigenic and anxiogenic effects of Hp vacuolating cytotoxin A (VacA) through activation of hypothalamic urocortin1 (Ucn1). VacA was detected in the hypothalamus after peripheral administration and increased Ucn1 mRNA expression and c-Fos-positive cells in the hypothalamus but not in the nucleus tractus solitarius. c-Fos and Ucn1-double positive cells were detected. CRF1 and CRF2 receptor antagonists suppressed VacA-induced anxiety and anorexia, respectively. VacA activated single paraventricular nucleus neurons and A7r5 cells; this activation was inhibited by phospholipase C (PLC) and protein kinase C (PKC) inhibitors. VacA causes anorexia and anxiety through the intracellular PLC-PKC pathway, migrates across the blood-brain barrier, and activates the Ucn1-CRF receptor axis.

DOI： 10.1038/s41598-019-42163-4