Search

The precise mechanism about drug resistance of cancer stem cells (CSCs) has not yet been completely understood. Based on the expression of CD44 and CD133, two well-recognized cell surface markers for CSC identification, we tried to separate HCT8 colorectal cancer cells into different subpopulations and then investigated how the expression of CD44 and CD133 associated with doxorubicin (DXR) resistance. Interestingly, DXR resistance was observed in CD44+CD133+ (P<0.01vs. all other subpopulations), but not in CD44+CD133- cells. CD44+CD133+ cells also showed an enhanced expression of ABCB1 and drug efflux ability (P<0.001vs. all other subpopulations), but verapamil, an inhibitor of ABCB1, only partially mitigated the DXR resistance. Independent on the accumulation of DXR, lower level of reactive oxygen species and higher expression of Nrf2 were detected in CD44+CD133+ than CD44+CD133- cells (P<0.05). Unexpectedly, silencing CD133 by siRNA only partially enhanced the cytotoxicity of DXR, but did not obviously change the expression of ABCB1 and the accumulation of DXR in CD44+CD133+ cells. Complex mechanisms, including drug excretion and redox regulation, are likely involved in the DXR resistance of CD133-positive cells, suggesting the difficulty of drug resistance problem in cancer chemotherapy., Stem Cells International, 2020, art.no.8868849; 2020

Radiotherapy for cancer patients damages normal tissues, thereby inducing an inflammatory response and promoting cancer metastasis. We investigated whether nicaraven, a compound with radioprotective and anti-inflammatory properties, could attenuate radiation-induced cancer metastasis to the lungs of mice. Nicaraven and amifostine, another commercial radioprotective agent, had limited effects on both the radiosensitivity of Lewis lung carcinoma cells in vitro and radiation-induced tumor growth inhibition in vivo. Using experimental and spontaneous metastasis models, we confirmed that thorax irradiation with 5 Gy X-rays dramatically increased the number of tumors in the lungs. Interestingly, the number of tumors in the lungs was significantly reduced by administering nicaraven but not by administering amifostine daily after radiation exposure. Furthermore, nicaraven administration effectively inhibited CCL8 expression and macrophage recruitment in the lungs 1 day after thorax irradiation. Our data suggest that nicaraven attenuates radiation-induced lung metastasis, likely by regulating the inflammatory response after radiation exposure., Cancer Letters, 418, pp.204-210; 2018

Cardiosphere-derived cells (CDCs), one of the promising stem cell sources for myocardial repair, have been tested in clinical trials and resulted in beneficial effects; however, the relevant mechanisms are not fully understood. In this study, we examined the hypothesis that CDCs favor heart repair by switching the macrophages from a pro-inflammatory phenotype (M1) into a regulatory anti-inflammatory phenotype (M2). Macrophages from mice were cultured with CDCs-conditioned medium or with fibroblasts-conditioned medium as a control. Immunostaining showed that CDCs-conditioned medium significantly enhanced the expression of CD206 (a marker for M2 macrophages), but decreased the expression of CD86 (a marker for M1 macrophages) 3 days after culture. For animal studies, we used an acute myocardial infarction model of mice. We injected CDCs, fibroblasts, or saline only into the border zone of infarction. Then we collected the heart tissues for histological analysis 5 and 14 days after treatment. Compared with control animals, CDCs treatment significantly decreased M1 macrophages and neutrophils but increased M2 macrophages in the infarcted heart. Furthermore, CDCs-treated mice had reduced infarct size and fewer apoptotic cells compared to the controls. Our data suggest that CDCs facilitate heart repair by modulating M1/M2 macrophage polarization and neutrophil recruitment, which may provide a new insight into the mechanisms of stem cell-based myocardial repair., PLOS ONE, 11(10), e0165255; 2016

Satellite cells are resident skeletal muscle stem cells that supply myonuclei for homeostasis, hypertrophy, and repair in adult muscle. Scrib is one of the major cell-polarity proteins, acting as a potent tumor suppressor in epithelial cells. Here, we show that Scrib also controls satellite-cell-fate decisions in adult mice. Scrib is undetectable in quiescent cells but becomes expressed during activation. Scrib isasymmetrically distributed in dividing daughter cells, with robust accumulation in cells committed to myogenic differentiation. Low Scrib expression is associated with the proliferative state and preventing self-renewal, whereas high Scrib levels reduce satellite cell proliferation. Satellite-cell-specific knockout of Scrib in mice causes a drastic andinsurmountable defect in muscle regeneration. Thus, Scrib is a regulator of tissue stem cells, controlling population expansion and self-renewal with Scrib expression dynamics directing satellite cell fate., Cell Reports, 10(7), pp.1135-1148; 2015

Effects of antioxidants on the quality and genomic stability of induced pluripotent stem (iPS) cells were investigated with two human iPS cell lines (201B7 and 253G1). Cells used in this study were expanded from a single colony of each cell line with the addition of proprietary antioxidant supplement or homemade antioxidant cocktail in medium, and maintained in parallel for 2 months. The cells grew well in all culture conditions and kept "stemness". Although antioxidants modestly decreased the levels of intracellular reactive oxygen species, there were no differences in the expression of 53BP1 and pATM, two critical molecules related with DNA damage and repair, under various culture conditions. CGH analysis showed that the events of genetic aberrations were decreased only in the 253G1 iPS cells with the addition of homemade antioxidant cocktail. Long-term culture will be necessary to confirm whether low dose antioxidants improve the quality and genomic stability of iPS cells., Scientific reports, 4, 3779; 2014

Although stem cells are generally thought to be resistant to oxidative stress, the fact and in detail molecular mechanism are still to be clearly identified. We herein tried to understand the overall characterization of redox regulatory signaling in hematopoietic stem cells. We purified c-kit-positive hematopoietic stem/progenitor cells from the bone marrow of healthy mice, and then evaluated their redox regulatory property. Compared to the c-kit-negative matured mononuclear cells, c-kit-positive stem/progenitor cells showed lower basic levels of intracellular reactive oxygen species, faster clearance of the accumulated intracellular reactive oxygen species, and higher resistant to oxidative stress. An overall view on the gene expression profile associated with redox regulation showed to be widely differed between cell types. We confirmed that the c-kit-positive stem/progenitor cells expressed significantly higher of Nox1 and catalase, but less of lactoperoxidase than these matured mononuclear cells. Our data suggests that stem cells keep specific redox regulatory property for defensing against oxidative stress., Biochemical and Biophysical Research Communications, 454(3), pp.376-380; 2014

It is known that dehydroepiandrosterone (DHEA) inhibits a phenotypic switch in vascular smooth muscle cells (VSMC) induced by platelet-derived growth factor (PDGF)-BB. However, the mechanism behind the effect of DHEA on VSMC is not clear. Previously we reported that low molecular weight-protein tyrosine phosphatase (LMW-PTP) dephosphorylates PDGF receptor (PDGFR)-beta via a redox-dependent mechanism involving glutathione (GSH)/glutaredoxin (GRX)1. Here we demonstrate that the redox regulation of PDGFR-beta is involved in the effect of DHEA on VSMC. DHEA suppressed the PDGF-BB-dependent phosphorylation of PDGFR-beta. As expected, DHEA increased the levels of GSH and GRX1, and the GSH/GRX1 system maintained the redox state of LMW-PTP. Down-regulation of the expression of LMW-PTP using siRNA restored the suppression of PDGFR-beta-phosphorylation by DHEA. A promoter analysis of GRX1 and gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of GSH synthesis, showed that DHEA up-regulated the transcriptional activity at the peroxisome proliferator-activated receptor (PPAR) response element, suggesting PPARalpha plays a role in the induction of GRX1 and gamma-GCS expression by DHEA. In conclusion, the redox regulation of PDGFR-beta is involved in the suppressive effect of DHEA on VSMC proliferation through the up-regulation of GSH/GRX system., Biochemical and biophysical research communications, 396(2), pp.489-494; 2010

筑波大学教育学博士学位論文・昭和63年3月25日授与 (甲第581号)

体脂肪は人体の水中体重を小さくするから, 水泳には体脂肪の多いことが有利な条件となる可能性がある。本研究は水泳の際に浮くために使われるV̇O2と推進のために使われるV̇O2を測定し, 水中体重の大小が実際の水泳にどれほどの影響を与えているかという点について検討したものである。 男女各3名, 計6名の泳者に, 泳速が0.6, 0.8及び1.0m/secのクロール泳を行わせ, V̇O2を測定した。その際腰に錘をつけて水中体重を増加させ, あるいは滑車を介した錘で腰を引き上げるようにして水中体重を減少させ, 各水中体重において上記の測定を行った。V̇O2値を水中体重に対してプロットすることによって得られる回帰直線の勾配から浮くためのV̇O2を, またY切片から安静時V̇O2を差し引くことによって推進のためのV̇O2を求めた。 1 浮くために必要なV̇O2は泳速とは無関係であり, その平均値は男子の方(352±140ml/min)が女子のそれ(186±83ml/min)より有意に大であった。この差は水中体重に大きく依存していて, 単位水中体重当りに換算すると男女の値は接近した(男子: 117±46ml/min, 女子: 91±36ml/min)。 2 推進のために用いられるV̇O2は, 泳速の増加に伴って指数関数的に増大した。その増加率は男子よりも女子の方が大であったが, それは女子の水泳能力が男子のそれより劣ることに関連していると考えられる。 3 総V̇O2に対する推進のためのV̇O2の割合は, 男子よりも女子において大きく, この点女子の水中体重の小さいことは水泳において有利な条件になっている。男子の世界記録に対する女子のそれの比率は, 競泳の場合には競走の場合より大きいが, この差は女子の体脂肪の多いことが水泳では有利に作用していることに由来するものと考えられる。, Body fat lessens underwater body weight and may offer an advantage for swimming performance. The present study was undertaken to measure separately V̇O2 for buoyancy and that for propulsion during swimming in the swimming flume and to elucidate the advantage of lower underwater body weight in female. Three male swimmers and three female swimmers participated as the subjects. V̇O2 was measured during free style swimming at a constant speed of 0.6, 0.8 and l.0m/sec.Underwater weight was increased stepwisely by loading an extra-weight around the subject's waist or decreased by suspending a weight which pulls the waist upward via a wire and pulleies. V̇O2 at a given speed depended proportionally on the underwater weight. V̇O2 for propu1sion was estimated by subtracting resting V̇O2 from the intercept on the ordinate, and V̇O2 for buoyancy was calculated from the slope. 1) V̇O2 for buoyancy was independent of swimming speed and the average value for female swimmers was much smaller than that for male swimmers (352±140m1/min for male, 186±83m1/min for female). This difference in V̇O2 for buoyancy depended largely on the difference in underwater weight as the calculated values of V̇O2 for buoyancy per kg of underwater weight revealed much smaller difference between sexes (117±46m1/min for male, 91±36m1/min for female). 2) V̇O2 for propulsion increased exponentially with increasing speed. The increasing rate was larger in female than in male. This is probably because of relative inferiority of swimming ability in the female group in this study. 3) The rate of propulsion V̇O2 to total V̇O2 during swimming was larger in female than in male. This represents the advantage of lower underwater weight in female for swimming. This result offers the probable explanation for the discrepancy which exists in male-female ratio of the world records between swimming and running.