Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Koichi Iwasa is active.

Publication


Featured researches published by Koichi Iwasa.


The Journal of Steroid Biochemistry and Molecular Biology | 2000

Atheroprotective effect of estriol and estrone sulfate on human vascular smooth muscle cells

Noriko Kikuchi; Mamoru Urabe; Koichi Iwasa; Tomoharu Okubo; Hiroshi Tsuchiya; Tetsuya Hosoda; Hiroshi Tatsumi; Hideo Honjo

In patients with atherosclerosis, fibrosclerotic focuses are induced by multiplication of vascular smooth muscle cells (VSMC), and they are regulated by cytokines and regulators. There have been few reports about the atheroprotective effect of estriol (E(3)). Estrone sulfate (E(1)-S) is the predominant estrogen of conjugated equiline estrogens, which is commonly used in hormone replacement therapy, but it should be hydrolyzed by steroid sulfatase (STS) to enter the cells of target tissues. The purpose of this study was to detect STS in VSMC and to investigate whether E(3) and E(1)-S have atheroprotective effects like E(2). First, we detected the presence of STS mRNA in VSMC by in situ hybridization. We then examined the changes in the expression of mRNAs of cytokines, namely, PDGF-A chain, IL-1, IL-6 and TGF-beta, in VSMC, in the presence and absence of E(3) and estrogens. As a result, the expression of PDGF-A chain, IL-1 and IL-6 mRNAs was suppressed by E(3) (P<0.05 vs control) significantly like E(1)-S and E(2), but that of TGF-beta mRNA was not significantly affected by any estrogen. These results indicate that E(1)-S can be hydrolyzed by STS in VSMC, and that E(3) may regulate the cytokines by suppressing the production of mRNAs. It is suggested that there is a possibility of E(1)-S and E(3) having a direct effect on vessels in atherogenesis.


The Journal of Steroid Biochemistry and Molecular Biology | 2007

Effects of estrogens on cholinergic neurons in the rat basal nucleus

Hiroki Yamamoto; Jo Kitawaki; Noriko Kikuchi; Tomoharu Okubo; Koichi Iwasa; Mitsuhiro Kawata; Hideo Honjo

Estrogen replacement in postmenopausal women may help prevent or delay development of Alzheimers disease. Because loss of basal forebrain cholinergic neurons with reductions in choline acetyltransferase (ChAT) concentration are associated with Alzheimers disease, we investigated the effect of estradiol (E(2)) and J 861, a non-feminizing estrogen, on cholinergic neurons in the basal forebrain. Ovariectomized rats received E(2), J 861 or vehicle, and basal forebrain sections through the substantia innominata, medial septum, and nucleus of the diagonal band were immunostained for ChAT. ChAT-immunoreactive cells in the basal forebrain were significantly reduced in the ovariectomized rats compared to intact rats, but those ovariectomized rats receiving estrogen replacement with E(2) and J 861 had near normal levels of ChAT-positive neurons. While retrograde tracing experiments with fluorogold injected into the prefrontal cortex showed no significant differences in the number of fluorogold-labeled cells among the groups, ChAT-immunoreactive cells and double-labeled cells were significantly lower in OVX rats than in intact and E(2) rats. Some substantia innominata cells in the J 861 rats were ChAT/estrogen receptor alpha-positive. These results suggest that E(2) and J 861 have positive effects on cholinergic neurons that project from the basal nucleus to the forebrain cortex.


The Journal of Steroid Biochemistry and Molecular Biology | 2005

Progestins and estrogens and Alzheimer's disease.

Hideo Honjo; Koichi Iwasa; Mitsuhiro Kawata; Shinji Fushiki; Tetsuya Hosoda; Hiroshi Tatsumi; Naochika Oida; Masaya Mihara; Yoshiichiro Hirasugi; Hiroki Yamamoto; Noriko Kikuchi; Jo Kitawaki

Sex-specific incidence rates for Alzheimers disease (AD) are higher in women than men. Many fundamental researches and some clinical investigations have reported therapeutic and preventive effects of estrogens on AD. But WHIMS [S.A. Shumaker, C. Legault, S.R. Rapp, L. Thal, R.B. Wallace, J.K. Ockene, S.L. Hendrix, B.N. Jones IIIrd, A.R. Assaf, R.D. Jackson, J.M. Kotchen, S. Wabertheil-Smoller, J. Wactawsk-Wende, WHIMS investigators, Estrogen plus progestin and the incidence of dementia and mild cognitive impairment in postmenopausal women. The womens health initiative memory study: a randomized controlled trial, JAMA 289 (2003) 2651-2662], which used daily continuous hormone replacement therapy (HRT), reported that the hazard ratio of the HRT for probable dementia was 2.05. Effect of progestins, and continuous (not cyclically) HRT, even only with estrogen should be reconsidered. In our clinical study, conjugated equine estrogen (CEE) alone showed good changes of psychiatric tests for AD on the 3rd week, but addition of medroxyprogesterone acetate (MPA) or norethindrone since 4th week suppressed these tests. Using human umbilical vein epithelial cell (HUVEC), levonorgestrel (LNG), norethindrone acetate (NETA), MPA increased intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-secretin but dienogest (DNG) showed no effect. In vitro flow system, estradiol (E2), suppressed adhesion of white cell, but LNG, NETA, MPA increased the adhesions. DNG showed less effect. Non-feminizing estrogen J 861, which has delta8,9 double bond and straight in its structure and has less effect on sexual organs. J 861 has shown ameliorative effects on central nervous system (CNS) (increasing of cholineacetyltransferase immunoreactive cells in substantia innominata (SI), etc.) like E2. More investigations about progestins and estrogens and AD should be done.


The Journal of Steroid Biochemistry and Molecular Biology | 2001

Alzheimer's disease and estrogen

Hideo Honjo; Noriko Kikuchi; Tetsuya Hosoda; Keiko Kariya; Yoshiyuki Kinoshita; Koichi Iwasa; Tomoharu Ohkubo; Kazunori Tanaka; Takaya Tamura; Mamoru Urabe; Mitsuhiro Kawata

The preventive effect of estrogen on Alzheimers disease (AD) has become clear with epidemiological data. Therapeutic effects of estrogen have not yet been established. In this presentation, we report our new basic and clinical data. The estrogen receptor, (ER)alpha, and ERbeta mRNA were investigated in rat brain. Estradiol-17beta (E(2)) treatment following OVX reduced the levels of ERalpha mRNA in the hypothalamus. In the substantia innominata (SI), the number of choline acetyltransferase immunoreacive cells increased significantly in the estrogen treatment rat. The neurons in SI projecting to the forebrain cortex contained ERalpha. Increasing amounts of intracellular calcium, peroxidation, and apoptosis with amyloid beta were suppressed in neuronal cells from rat pheochromocytoma (PC12) cells with E(2). ERalpha cDNA transfected PC 12 cells elaborated more neurite-like processes with E(2). In clinics, we are currently preparing vaginal progesterone tablets, which essentially may concentrate in the endometrium to prevent endometrial cancer, with few general circulation of progesterone inviting less depression. The therapeutic effects of cyclic estrogen, such as its preventive effect, are suggested in these studies, at least on mild AD.


Biochemical and Biophysical Research Communications | 2011

17β-Estradiol attenuates saturated fatty acid diet-induced liver injury in ovariectomized mice by up-regulating hepatic senescence marker protein-30.

Michiaki Fukui; Takafumi Senmaru; Goji Hasegawa; Masahiro Yamazaki; Mai Asano; Yayoi Kagami; Akihito Ishigami; Naoki Maruyama; Koichi Iwasa; Jo Kitawaki; Yoshito Itoh; Takeshi Okanoue; Mitsuhiro Ohta; Hiroshi Obayashi; Naoto Nakamura

Senescence marker protein-30 (SMP30) plays an important role in intracellular Ca(2+) homeostasis. The aim of the present study was to investigate the effects of estrogens on liver apoptotic damage and changes in SMP30 expression induced by a high saturated fatty acid diet (HSFD). Ovariectomized mice (OVX) and sham-operated mice (SHAM) were randomly divided into five groups: SHAM fed a normal diet (SHAM/ND), SHAM fed HSFD (SHAM/HSFD), OVX fed ND (OVX/ND), OVX fed HSFD (OVX/HSFD) and OVX fed HSFD with 17β-estradiol (E2) supplementation using an implanted slow-release pellet (OVX/HSFD+E2). After 8 weeks, markers of endoplasmic reticulum (ER) stress and apoptosis, and levels of tumor necrosis factor-α (TNFα and SMP30 expression were investigated. Compared with SHAM/ND, OVX/HSFD mice showed significantly increased spliced X-box protein-1 (s-XBP1), phosphorylated eukaryotic initiation factor-2α (p-eIF2α), glucose-regulated protein 78 (GPR78), C/EBP homologous protein (CHOP), cytosolic cytochrome c, caspase-3 activity, and TNFα, and significantly decreased SMP30. These differences in OVX/HSFD mice were restored to the levels of SHAM/ND mice by E2 supplementation. These results suggest that E2 supplementation attenuates HSFD-induced liver apoptotic death in ovariectomized mice by up-regulating SMP30.


Journal of Obstetrics and Gynaecology Research | 2013

Premature delivery due to intrauterine Candida infection that caused neonatal congenital cutaneous candidiasis: A case report

Fumitake Ito; Tomoharu Okubo; Tadahiro Yasuo; Taisuke Mori; Koichi Iwasa; Kazuhiro Iwasaku; Jo Kitawaki

Congenital cutaneous candidiasis is a very rare disease with less than 100 cases published in the medical literature. Neonates having this disease present with systemic skin lesions caused by intrauterine Candida infections. We present a case of threatened premature delivery due to Candida chorioamnionitis, which caused both maternal postpartum endometritis and neonatal congenital cutaneous candidiasis. A 34‐year‐old woman who was admitted for fetal membrane bulging at 20 weeks of gestation underwent McDonald cervical cerclage. We diagnosed threatened premature delivery due to intrauterine infection; therefore, we terminated the gestation by cesarean section at 24 weeks of gestation. Fungi‐like yeast was detected in infantile gastric juice. Histopathological findings of the placenta revealed that Candida albicans mycelium invaded the placenta, chorioamniotic membrane and umbilical cord.


Acta Obstetricia et Gynecologica Scandinavica | 2006

New ultrasonographic criteria for the prenatal diagnosis of Chiari type 2 malformation

Hidetoshi Fujisawa; Jo Kitawaki; Koichi Iwasa; Hideo Honjo

Background. During prenatal ultrasonography, characteristic malformations including the lemon sign, the banana sign, and obliteration of the cisterna magna are widely used for diagnosis of Chiari type 2 malformation (Arnold Chiari malformation). However, these signs are often obscured by 25 weeks’ gestation. Here, we report an investigation of ultrasonographic markers of Chiari type 2 malformation for diagnosis after 24 weeks’ gestation. Methods. Twenty‐two cases of 24–37 weeks’ gestation referred as fetal ventriculomegaly were analyzed prospectively. Fetuses were examined with ultrasonography by axial section of the head to detect conventional signs, and then by coronary section of the posterior horn of the lateral ventricle to detect two prospective new signs: bilateral downward‐triangle shape (triangle sign) and quadrilateral angular shape (square sign). Results. From the axial sections, three cases were diagnosed with holoprosencephaly, but the remaining 19 cases did not show the lemon sign. In the coronar sections, the eight cases that showed the triangle sign were associated with open spina bifida at the lower vertebral site. The four cases that displayed the square sign showed upper spinal lesions. Chiari type 2 malformation was suspected in these 12 cases. Four of the other seven cases were suspected to be agenesis of the corpus callosum, and the remaining three were normal. All ultrasonographic findings were consistent with the subsequent MRI and postpartum definitive diagnoses. Conclusions. At 24 weeks’ gestation or later, Chiari type 2 malformation can be precisely and efficiently diagnosed by two new characteristics detected during ultrasonography: triangular shape and quadrilateral angular shape.


The Journal of Clinical Endocrinology and Metabolism | 2014

Medroxyprogesterone Acetate Enhances Monocyte-Endothelial Interaction Under Flow Conditions by Stimulating the Expression of Cell Adhesion Molecules

Fumitake Ito; Hiroshi Tatsumi; Taisuke Mori; Izumi Suganuma; Yukiko Tanaka; Aya Sasaki; Seiki Matsuo; Koichi Iwasa; Jo Kitawaki

CONTEXT Monocyte adhesion to endothelial cells is an important initial event in atherosclerosis and is partially mediated by adhesion molecule expression on the cell surface. Although estrogens inhibit atherosclerosis development, effects of coadministered progestogen remain controversial. OBJECTIVE We examined the effects of progestogen on cytokine-stimulated human umbilical venous endothelial cell (HUVEC) expression of adhesion molecules. DESIGN In HUVECs, adhesion molecule mRNA levels were measured by real-time PCR. Protein expression was quantified by immunocytochemistry and ELISAs. To mimic the monocyte adherence to endothelial cells, we used a flow chamber system to assess progestogen effects on U937 monocytoid cell adherence to HUVEC monolayers. We also examined the suppression effects of adhesion molecules with small interference RNAs. RESULTS mRNA levels of adhesion molecules in HUVECs treated with medroxyprogesterone acetate (MPA) or 17β-estradiol + MPA were 1.7- to 2.5-fold higher than those in the control. MPA increased the protein expression of E-selectin, P-selectin, and intercellular adhesion molecule-1 compared with that for the control (83.0 ± 0.7, 34.8 ± 1.2, and 5.4 ± 0.0 ng/mL, respectively), whereas other progestogens or 17β-estradiol additive to progestogens did not significantly change expression. MPA significantly increased U937 monocytoid cell adherence compared with the control (56.0 ± 1.5 vs 46.5 ± 3.5 adherent cells per 10 fields) but did not increase adherence to HUVECs with knocked down intercellular adhesion molecule-1. CONCLUSIONS MPA increases cell adhesion molecule expression on HUVECs, causing increased numbers of monocytoid cells to adhere to HUVECs. These MPA effects may be a risk factor for atherogenesis on endothelial cells in postmenopausal women receiving hormone replacement therapy.


Archives of Gerontology and Geriatrics | 2017

Association between loss of bone mass due to short sleep and leptin-sympathetic nervous system activity

Nagato Kuriyama; Masaaki Inaba; Etsuko Ozaki; Yutaro Yoneda; Daisuke Matsui; Kanae Hashiguchi; Teruhide Koyama; Komei Iwai; Isao Watanabe; Rika Tanaka; Chie Omichi; Shigeto Mizuno; Masao Kurokawa; Motoyuki Horii; Fumitoshi Niwa; Koichi Iwasa; Shinsuke Yamada; Yoshiyuki Watanabe

BACKGROUND Sleep has been reported to be an important factor in bone metabolism, and sympathetic nervous system activity has been reported to regulate bone metabolism. In this study, we evaluated the association between sleep, sympathetic nervous system activity, and bone mass. METHODS The study subjects were 221 individuals (108 males; 113 females; mean age: 55.1±7.0years) divided into two groups: those who slept for less than 6h a day (short sleep [SS] group), and those who slept 6h or longer (normal sleep [NS] group). The groups were compared with regard to lifestyle, cortical bone thickness, cancellous bone density, bone metabolism markers, blood leptin levels, and sympathetic nervous system activity as evaluated by heart rate variability analysis. RESULTS Significant differences were observed between the two groups in cortical bone thickness, blood TRACP-5b, and leptin levels. The L/H ratio (an index of sympathetic nervous system activity) was higher in the SS group than in the NS group. Significant negative correlations were observed between cortical bone thickness and both the L/H ratio and leptin levels, and a significant positive correlation was observed between the L/H ratio and leptin levels. CONCLUSIONS Short sleep was associated with a decline in cortical bone thickness due to the promotion of bone resorption and sympathetic nervous system hyperactivity in the middle-aged group. Leptin levels and cortical bone thickness were found to be closely related, suggesting that cortical bone mass may be regulated via interaction with the leptin-sympathetic nervous system.


European Journal of Obstetrics & Gynecology and Reproductive Biology | 2016

Effects of drospirenone on adhesion molecule expression and monocyte adherence in human endothelial cells

Fumitake Ito; Taisuke Mori; Osamu Takaoka; Yukiko Tanaka; Akemi Koshiba; Hiroshi Tatsumi; Koichi Iwasa; Jo Kitawaki

OBJECTIVE A major concern in hormone replacement therapy is the associated increased risk of cardiovascular diseases. A progestogen without the unfavorable effects on cardiovascular disease should be explored. Monocyte adhesion to endothelial cells is an important initial event in atherosclerosis. In this study, the effects of the alternative progestogen drospirenone (DRSP) on monocyte adhesion in human umbilical venous endothelial cells (HUVECs) were examined. STUDY DESIGN In HUVECs treated with estrogens and progestogens, including DRSP and medroxyprogesterone acetate (MPA), the expression of the adhesion molecules E-selectin, P-selectin, ICAM-1, and VCAM-1 were examined by real-time PCR and using an enzyme-linked immunosorbent assay. A flow chamber system was used to investigate the effects of DRSP on U937 monocytoid cell adherence to HUVEC monolayers. All experimental data were compared using one-way Analysis of Variance. RESULTS Upregulation of adhesion molecule mRNA or protein was not seen in HUVECs treated with DRSP alone or with 17β-estradiol+DRSP. DRSP alone, 17β-estradiol+DRSP or ethinylestradiol+DRSP did not increase the number of adherent monocytoid cells to HUVECs in the flow chamber system. However, MPA significantly enhanced the monocytoid cell adherence (P<0.05). CONCLUSIONS DRSP did not increase the expression of adhesion molecules or monocytoid cell adherence to endothelial cells, indicating that DRSP could reduce the risk of atherogenesis caused by MPA. These results suggest that DRSP may be an alternative to MPA in hormone replacement therapy.

Collaboration


Dive into the Koichi Iwasa's collaboration.

Top Co-Authors

Avatar

Jo Kitawaki

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Hideo Honjo

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Hiroshi Tatsumi

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Noriko Kikuchi

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Fumitake Ito

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Tomoharu Okubo

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Taisuke Mori

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Kazuhiro Iwasaku

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Mamoru Urabe

Kyoto Prefectural University of Medicine

View shared research outputs
Top Co-Authors

Avatar

Mitsuhiro Kawata

Kyoto Prefectural University of Medicine

View shared research outputs
Researchain Logo
Decentralizing Knowledge