Updated on 2026/05/21

写真a

 
SAGA Yukika
 
Organization
School of Medicine Department of Pharmacology Assistant Professor
Title
Assistant Professor
External link

Papers

  • Enhancing radiation sensitivity in malignant brain tumors with chloroquine: a systematic review. International journal

    Paul M Harary, Yusuke S Hori, Shreyas Annagiri, Koki Abe, Yuki Tatekoshi, Ryusuke Hosoda, Yukika Saga, David J Park, Atsushi Kuno, Steven D Chang

    Journal of neuro-oncology   176 ( 1 )   106 - 106   2025.12

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    PURPOSE: Chloroquine (CQ) has been studied for over 50 years as a potential adjuvant to cancer therapy. However, clinical studies investigating CQ combined with radiotherapy for brain tumors have yielded conflicting results. We aimed to synthesize existing evidence on the safety and efficacy of adjuvant CQ with radiotherapy for treatment of high-grade gliomas (HGG) and brain metastases. METHODS: We conducted a systematic review using the PubMed, Embase, Scopus, and Web of Science databases with no date restrictions. We included English-language clinical studies (n ≥ 5 patients) that evaluated the combination of CQ or its analogues with radiotherapy for HGG or brain metastases and reported overall survival (OS) outcomes. Pre-clinical studies and reviews were excluded. RESULTS: We identified 13 eligible studies with 789 patients. Across both HGG and brain metastases, the median CQ dose was 250 mg daily, with whole-brain radiotherapy as the most common radiotherapy modality. For HGG, 3 out of 8 controlled trials reported significant benefit from treatment, with median survival ranging from 7.9 to 36.6 months. By comparison, only a single study of brain metastases found significantly improved progression-free survival relative to control. The safety profile of adjuvant CQ was generally favorable, with mild adverse effects reported in both patient populations. CONCLUSIONS: For HGG, CQ combined with radiotherapy shows promise but modest, inconsistent survival benefits. For brain metastases, evidence is limited and less favorable, with no consistent benefit across tumor types or study designs. Adverse events are generally mild, though most studies used low CQ doses and long‑term safety remains uncertain.

    DOI: 10.1007/s11060-025-05362-w

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  • Resveratrol promotes autophagosome elimination via SIRT1 in cardiomyocytes.

    Atsushi Kuno, Ryusuke Hosoda, Yukika Saga, Naotoshi Iwahara, Yuki Tatekoshi, Ryo Numazawa, Yoshiyuki Horio

    Journal of pharmacological sciences   157 ( 1 )   25 - 34   2025.1

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    The processes of autophagy, including autophagosome formation, fusion of autophagosomes with lysosomes, and degradation of autophagosomes by lysosomes, are regulated by various mechanisms. We recently found that treatment with resveratrol, an activator of the NAD+-dependent protein deacetylase Sirtuin-1 (SIRT1), in a mouse model prevented autophagosome accumulation in the heart with high mTORC1 activity. In this study, we investigated whether SIRT1 mediates the effects of resveratrol on autophagosome elimination using a cardiomyocyte model. In H9c2 cardiomyocytes, treatment with the mTORC1 activator MHY1485 induced autophagosome accumulation accompanied by increases in fragmented mitochondria within the autophagosomes and levels of intracellular reactive oxygen species (ROS), indicative of impaired autophagy-mediated elimination of mitochondria and resultant oxidative stress. MHY1485 suppressed the fusion of autophagosomes with lysosomes. Co-treatment with resveratrol attenuated the MHY1485-induced increases in autophagosomes, mitochondria within autophagosomes, and levels of ROS. Knockdown of Sirt1 reversed the reductions in autophagosomes and ROS levels induced by resveratrol under the condition of MHY1485 treatment. Neither resveratrol treatment nor Sirt1 knockdown modulated the phosphorylation levels of UVRAG, a target of mTORC1 for suppression of autophagosome-lysosome fusion. Our findings suggest that SIRT1 mediates the resveratrol-induced promotion of autophagosome elimination in cells with high mTORC1 activity.

    DOI: 10.1016/j.jphs.2024.11.006

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  • Transcriptional dysregulation of autophagy in the muscle of a mouse model of Duchenne muscular dystrophy. International journal

    Ryuta Nakashima, Ryusuke Hosoda, Yuki Tatekoshi, Naotoshi Iwahara, Yukika Saga, Atsushi Kuno

    Scientific reports   14 ( 1 )   1365 - 1365   2024.1

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    It has been reported that autophagic activity is disturbed in the skeletal muscles of dystrophin-deficient mdx mice and patients with Duchenne muscular dystrophy (DMD). Transcriptional regulations of autophagy by FoxO transcription factors (FoxOs) and transcription factor EB (TFEB) play critical roles in adaptation to cellular stress conditions. Here, we investigated whether autophagic activity is dysregulated at the transcription level in dystrophin-deficient muscles. Expression levels of autophagy-related genes were globally decreased in tibialis anterior and soleus muscles of mdx mice compared with those of wild-type mice. DNA microarray data from the NCBI database also showed that genes related to autophagy were globally downregulated in muscles from patients with DMD. These downregulated genes are known as targets of FoxOs and TFEB. Immunostaining showed that nuclear localization of FoxO1 and FoxO3a was decreased in mdx mice. Western blot analyses demonstrated increases in phosphorylation levels of FoxO1 and FoxO3a in mdx mice. Nuclear localization of TFEB was also reduced in mdx mice, which was associated with elevated phosphorylation levels of TFEB. Collectively, the results suggest that autophagy is disturbed in dystrophin-deficient muscles via transcriptional downregulation due to phosphorylation-mediated suppression of FoxOs and TFEB.

    DOI: 10.1038/s41598-024-51746-9

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  • Resveratrol, a SIRT1 activator, attenuates aging-associated alterations in skeletal muscle and heart in mice.

    Ryusuke Hosoda, Ryuta Nakashima, Masaki Yano, Naotoshi Iwahara, Seidai Asakura, Iyori Nojima, Yukika Saga, Risa Kunimoto, Yoshiyuki Horio, Atsushi Kuno

    Journal of pharmacological sciences   152 ( 2 )   112 - 122   2023.6

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    Aging is associated with impairment of multiple organs, including skeletal muscle and heart. In this study, we investigated whether resveratrol, an activator of an NAD+-dependent protein deacetylase Sirtuin-1 (SIRT1), attenuates age-related sarcopenia and cardiomyocyte hypertrophy in mice. Treatment of mice with resveratrol (0.4 g/kg diet) from 28 weeks of age for 32 weeks prevented aging-associated shortening of rotarod riding time. In the tibialis anterior (TA) muscle, histogram analysis showed that the atrophic muscle was increased in 60-week-old (wo) mice compared with 20-wo mice, which was attenuated by resveratrol. In the heart, resveratrol attenuated an aging-associated increase in the cardiomyocyte diameter. Acetylated proteins were increased and autophagic activity was reduced in the TA muscle of 60-wo mice compared with those of 20-wo mice. Resveratrol treatment reduced levels of acetylated proteins and restored autophagic activity in the TA muscle. Aging-related reduction in myocardial autophagy was also suppressed by resveratrol. Skeletal muscle-specific SIRT1 knockout mice showed increases in acetylated proteins and atrophic muscle fibers and reduced autophagic activity in the TA muscle. These results suggest that activation of SIRT1 by treatment with resveratrol suppresses sarcopenia and cardiomyocyte hypertrophy by restoration of autophagy in mice.

    DOI: 10.1016/j.jphs.2023.04.001

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  • The cytosolic lncRNA dutA affects STATa signaling and developmental commitment in Dictyostelium. International journal

    Yukika Saga, Yudai Shimoyama, Yoko Yamada, Naoki Morikawa, Takefumi Kawata

    Genes to cells : devoted to molecular & cellular mechanisms   28 ( 2 )   111 - 128   2023.2

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    STATa is a pivotal transcription factor for Dictyostelium development. dutA is the most abundant RNA transcribed by RNA polymerase II in Dictyostelium, and its functional interplay with STATa has been suggested. This study demonstrates that dutA RNA molecules are distributed as spot-like structures in the cytoplasm, and that its cell type-specific expression changes dramatically during development. dutA RNA was exclusively detectable in the prespore region of slugs and then predominantly localized in prestalk cells, including the organizer region, at the Mexican hat stage before most dutA transcripts, excluding those in prestalk O cells, disappeared as culmination proceeded. dutA RNA was not translated into small peptides from any potential open reading frame, which confirmed that it is a cytoplasmic lncRNA. Ectopic expression of dutA RNA in the organizer region of slugs caused a prolonged slug migration period. In addition, buffered suspension-cultured cells of the strain displayed reduced STATa nuclear translocation and phosphorylation on Tyr702. Analysis of gene expression in various dutA mutants revealed changes in the levels of several STATa-regulated genes, such as the transcription factors mybC and gtaG, which might affect the phenotype. dutA RNA may regulate several mRNA species, thereby playing an indirect role in STATa activation.

    DOI: 10.1111/gtc.12997

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  • SIRT1 in the cardiomyocyte counteracts doxorubicin-induced cardiotoxicity via regulating histone H2AX. International journal

    Atsushi Kuno, Ryusuke Hosoda, Miki Tsukamoto, Tatsuya Sato, Hiromi Sakuragi, Nami Ajima, Yukika Saga, Kouhei Tada, Yoshiki Taniguchi, Naotoshi Iwahara, Yoshiyuki Horio

    Cardiovascular research   118 ( 17 )   3360 - 3373   2023.1

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    AIMS: Cardiotoxicity by doxorubicin predicts worse prognosis of patients. Accumulation of damaged DNA has been implicated in doxorubicin-induced cardiotoxicity. SIRT1, an NAD+-dependent histone/protein deacetylase, protects cells by deacetylating target proteins. We investigated whether SIRT1 counteracts doxorubicin-induced cardiotoxicity by mediating Ser139 phosphorylation of histone H2AX, a critical signal of the DNA damage response. METHODS AND RESULTS: Doxorubicin (5 mg/kg per week, x4) was administered to mice with intact SIRT1 (Sirt1f/f) and mice that lack SIRT1 activity in cardiomyocytes (Sirt1f/f;MHCcre/+). Reductions in left ventricular fractional shortening and ejection fraction by doxorubicin treatment were more severe in Sirt1f/f;MHCcre/+ than in Sirt1f/f. Myocardial expression level of type-B natriuretic peptide was 2.5-fold higher in Sirt1f/f;MHCcre/+ than in Sirt1f/f after doxorubicin treatment. Sirt1f/f;MHCcre/+ showed larger fibrotic areas and higher nitrotyrosine levels in the heart after doxorubicin treatment. Although doxorubicin-induced DNA damage evaluated by TUNEL staining was enhanced in Sirt1f/f;MHCcre/+, the myocardium from Sirt1f/f;MHCcre/+ showed blunted Ser139 phosphorylation of H2AX by doxorubicin treatment. In H9c2 cardiomyocytes, SIRT1 knockdown attenuated Ser139 phosphorylation of H2AX, increased DNA damage, and enhanced caspase-3 activation under doxorubicin treatment. Immunostaining revealed that acetylation level of H2AX at Lys5 was higher in hearts from Sirt1f/f;MHCcre/+. In H9c2 cells, acetyl-Lys5-H2AX level was increased by SIRT1 knockdown and reduced by SIRT1 overexpression. Ser139 phosphorylation in response to doxorubicin treatment was blunted in a mutant H2AX with substitution of Lys5 to Gln (K5Q) that mimics acetylated lysine compared with that in wild-type H2AX. Expression of K5Q-H2AX as well as S139A-H2AX, which cannot be phosphorylated at Ser139, augmented doxorubicin-induced caspase-3 activation. Treatment of mice with resveratrol, a SIRT1 activator, attenuated doxorubicin-induced cardiac dysfunction, which was associated with a reduction in acetyl-Lys5-H2AX level and a preserved phospho-Ser139-H2AX level. CONCLUSION: These findings suggest that SIRT1 counteracts doxorubicin-induced cardiotoxicity by mediating H2AX phosphorylation through its deacetylation in cardiomyocytes.

    DOI: 10.1093/cvr/cvac026

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  • Analysis of DrkA kinase's role in STATa activation. International journal

    Yukika Saga, Yumi Iwade, Tsuyoshi Araki, Megumi Ishikawa, Takefumi Kawata

    Genes to cells : devoted to molecular & cellular mechanisms   24 ( 6 )   422 - 435   2019.6

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    Dictyostelium STATa is a homologue of metazoan signal transducers and activators of transcription (STATs) and is important for morphogenesis. STATa is activated by phosphorylation on Tyr702 when cells are exposed to extracellular cAMP. Although two tyrosine kinase-like (TKL) proteins, Pyk2 and Pyk3, have been definitively identified as STATc kinases, no kinase is known for STATa activation. Based on homology to the previously identified tyrosine-selective TKLs, we identified DrkA, a member of the TKL family and the Dictyostelium receptor-like kinase (DRK) subfamily, as a candidate STATa kinase. The drkA gene is almost exclusively expressed in prestalk A (pstA) cells, where STATa is activated. Transient over-expression of DrkA increased STATa phosphorylation, although over-expression of the protein causes a severe growth defect and cell death. Furthermore, recombinant DrkA protein is auto-phosphorylated on tyrosine and threonine residues, and an in vitro kinase assay shows that DrkA can phosphorylate STATa on Tyr702 in a STATa-SH2 (phosphotyrosine binding) domain-dependent manner. These observations strongly suggest that DrkA is one of the key regulators of STATa tyrosine phosphorylation and is consistent with it being the kinase that directly activates STATa.

    DOI: 10.1111/gtc.12686

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  • Regulation of ecmF gene expression and genetic hierarchy among STATa, CudA, and MybC on several prestalk A-specific gene expressions in Dictyostelium.

    Yukika Saga, Tomoka Inamura, Nao Shimada, Takefumi Kawata

    Development, growth & differentiation   58 ( 4 )   383 - 99   2016.5

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    STATa, a Dictyostelium homologue of metazoan signal transducer and activator of transcription, is important for the organizer function in the tip region of the migrating Dictyostelium slug. We previously showed that ecmF gene expression depends on STATa in prestalk A (pstA) cells, where STATa is activated. Deletion and site-directed mutagenesis analysis of the ecmF/lacZ fusion gene in wild-type and STATa null strains identified an imperfect inverted repeat sequence, ACAAATANTATTTGT, as a STATa-responsive element. An upstream sequence element was required for efficient expression in the rear region of pstA zone; an element downstream of the inverted repeat was necessary for sufficient prestalk expression during culmination. Band shift analyses using purified STATa protein detected no sequence-specific binding to those ecmF elements. The only verified upregulated target gene of STATa is cudA gene; CudA directly activates expL7 gene expression in prestalk cells. However, ecmF gene expression was almost unaffected in a cudA null mutant. Several previously reported putative STATa target genes were also expressed in cudA null mutant but were downregulated in STATa null mutant. Moreover, mybC, which encodes another transcription factor, belonged to this category, and ecmF expression was downregulated in a mybC null mutant. These findings demonstrate the existence of a genetic hierarchy for pstA-specific genes, which can be classified into two distinct STATa downstream pathways, CudA dependent and independent. The ecmF expression is indirectly upregulated by STATa in a CudA-independent activation manner but dependent on MybC, whose expression is positively regulated by STATa.

    DOI: 10.1111/dgd.12285

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  • Implications of expansin-like 3 gene in Dictyostelium morphogenesis. International journal

    Takefumi Kawata, Yuri Nakamura, Yukika Saga, Yumi Iwade, Megumi Ishikawa, Aya Sakurai, Nao Shimada

    SpringerPlus   4   190 - 190   2015

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    Dictyostelium harbors multiple expansin-like genes with generally unknown functions. Thus, we analyzed the expansin-like 3 (expL3) gene and found that its expression was reduced in a null mutant for a STATa gene encoding a transcription factor. The expression of expL3 was developmentally regulated and its transcript was spliced only in the multicellular stages. The expL3 promoter was activated in the anterior prestalk region of the parental strain and downregulated in the STATa null slug, although the expL3 promoter was still expressed in the prestalk region. The expL3 overexpressing strain exhibited delayed development and occasionally formed an aberrant structure, i.e., a fruiting body-like structure with a short stalk. The ExpL3-myc protein bound cellulose.

    DOI: 10.1186/s40064-015-0964-0

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Books

MISC

  • NAD<sup>+</sup>前駆体ニコチンアミド・モノヌクレオチドの投与はドキソルビシンによる心・腎障害とカヘキシアを軽減する

    久野篤史, 齊藤圭司, 細田隆介, 舘越勇輝, 嵯峨幸夏

    日本腫瘍循環器学会学術集会抄録集(Web)   7th   2024

  • SIRT1活性化薬はドキソルビシンによる腎尿細管のミトコンドリア形態異常を抑制する

    齊藤圭司, 細田隆介, 岩原直敏, 野島伊世里, 嵯峨幸夏, 久野篤史

    日本薬理学雑誌   159 ( Supplement )   2024

  • 糖尿病腎におけるオートファジー障害はネクロプトーシス経路を亢進させる

    高橋怜央, 嵯峨幸夏, 細田隆介, 舘越勇輝, 久野篤史

    日本薬理学雑誌   159 ( Supplement )   2024

  • SIRT1によるオートリソソーム形成の制御におけるRab7の役割解明

    嵯峨幸夏, 細田隆介, 久野篤史

    日本分子生物学会年会プログラム・要旨集(Web)   47th   2024

  • 糖尿病腎における虚血再灌流時のオートファジー障害とネクロプトーシス経路亢進の関連

    高橋怜央, 嵯峨幸夏, 細田隆介, 舘越勇輝, 久野篤史

    日本分子生物学会年会プログラム・要旨集(Web)   47th   2024

  • NAD<sup>+</sup>の前駆体であるニコチンアミドモノヌクレオチドの投与は,ドキソルビシンによる心臓および腎臓の毒性を抑制する

    宮崎瑞菜, 斉藤圭司, 細田隆介, 嵯峨幸夏, 舘越勇輝, 久野篤史

    日本分子生物学会年会プログラム・要旨集(Web)   47th   2024

  • 糖尿病心におけるβ酸化の候補制御因子としてのアセチル化電子伝達フラビンタンパク質αの同定

    矢野雅貴, 舘越勇輝, 細田隆介, 嵯峨幸夏, 久野篤史

    日本分子生物学会年会プログラム・要旨集(Web)   47th   2024

  • ドキソルビシンによる臓器毒性はニコチンアミド・モノヌクレオチドにより軽減する

    久野篤史, 細田隆介, 岩原直敏, 野島伊世里, 嵯峨幸夏, 齊藤圭司

    日本薬理学雑誌   158 ( Supplement )   2023

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Research Projects

  • オートファジーにおけるRab7アセチル化修飾の機能解明

    Grant number:24K18277  2024.4 - 2027.3

    日本学術振興会  科学研究費助成事業  若手研究

    嵯峨 幸夏

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    Grant amount:\4680000 ( Direct Cost: \3600000 、 Indirect Cost:\1080000 )

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  • SIRT1によるオートファゴソーム分解制御機構の解明

    Grant number:23K19373  2023.8 - 2025.3

    日本学術振興会  科学研究費助成事業  研究活動スタート支援

    嵯峨 幸夏

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    Grant amount:\2860000 ( Direct Cost: \2200000 、 Indirect Cost:\660000 )

    心不全患者の5年生存率は非常に低く、病態の解明と新規治療法の開発が急がれる。本研究では老化抑制因子SIRT1によるオートファジー制御機構を、細胞内小胞輸送の調節因子であるRab7との関連から明らかにし、心不全心筋におけるオートファジー不全の機序解明と新しい心不全治療の開発につながる知見を得ることを目指している。
    令和5年度の研究では、SIRT1過剰発現によりRab7タンパクのアセチル化レベルが減少することを確認した。一方で、SIRT1ノックダウンではRab7タンパクのアセチル化に有意な増加はみられなかった。質量解析を行った結果、SIRT1阻害薬であるEx527未処置/ 処置のタンパクサンプル両群で予想より多くのRab7アセチル化リジンが検出され、Ex527処置群で特異的にアセチル化されているリジン残基も複数検出された。以上からRab7は複数のリジン残基がアセチル化修飾を受けており、SIRT1はその内のいくつかの脱アセチル化に関与する可能性が示唆された。
    令和6年度では、CRISPR/Cas9 systemを用いてSIRT1遺伝子をノックアウト(以下KO)した培養細胞株や、同定したリジン残基を置換変異させた点変異Rab7を発現する培養細胞株を作製する。これらの細胞を用いてSIRT1によるRab7脱アセチル化の詳細を調べることで、SIRT1によるRab7を介したオートファジー制御のメカニズムを明らかにしたい。

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  • 細胞質特異的な長鎖非コードRNAがSTATシグナルに及ぼす機能の理解

    Grant number:18J10428  2018.4 - 2020.3

    日本学術振興会  科学研究費助成事業  特別研究員奨励費

    嵯峨 幸夏

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    Grant amount:\1700000 ( Direct Cost: \1700000 )

    本研究は、細胞性粘菌の細胞質長鎖非コードRNA (lncRNA)であるdutA RNAについて、結合タンパク質の同定とそれらの機能解析、及びdutA RNAの局在解析を通し、細胞性粘菌の最終分化に重要なSTATaシグナルにおける細胞質lncRNAの作用機序の解明を目的とした。
    dutA RNAの発生時期依存的な局在変化の原因を探るため、lacZ遺伝子を利用したdutAのプロモーター解析を行い、dutA RNAの局在変化は転写段階である程度制御されることを示した。また、FLAGタグ発現株を作製してdutA RNAがsmall peptideに翻訳されないことも示した。非リン酸化STATaとdutA RNAとの関係を調べるため、panSTATa抗体の作製とYFP-STATa発現株の作製を行った。今後これらを用いて実験を行う。dutA RNA結合タンパク質の精製は、マルトース結合タンパク質 (MBP)をタグとしたMBP-Trap法を立ち上げ、細胞性粘菌レクチンのDscEなど複数の候補タンパク質を同定した。それらについてRNA免疫沈降も行いdutA RNAとの特異的結合を検証し、結合タンパク質精製の収量を上げる改良も行った。今後この方法で更なる新規タンパク質の同定を進める。RNA-seq解析のデータから、野生株とdutA RNA変異株3種を比較して発現変動遺伝子を選別した。さらに、データベースから発現時期特異性や組織特異性の特徴を抽出して照合し、RT-qPCRを行ってdutA RNAの変動によりmRNA量が変動する遺伝子を幾つか同定した。2年間の研究を通し、得られた研究成果は未知の部分が多い細胞質lncRNAの機能を理解する上で重要と言える。以上の成果について投稿論文を執筆中である。

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