Akio Tomoda

Bio: Akio Tomoda is an academic researcher from Tokyo Medical University. The author has contributed to research in topics: Apoptosis & Cell culture. The author has an hindex of 20, co-authored 68 publications receiving 1168 citations.

Combined treatment with bortezomib plus bafilomycin A1 enhances the cytocidal effect and induces endoplasmic reticulum stress in U266 myeloma cells: Crosstalk among proteasome, autophagy-lysosome and ER stress

Abstract: Bortezomib (BZ), a first line 26S proteasome inhibitor, induces a potent cytocidal effect with caspase-3 activation in multiple myeloma (MM) cell lines. Since IκBα is a substrate of the proteasome, the initial rationale for using BZ in MM has been to inhibit NF-κB. However, BZ rather activated NF-κB activity in U266 cells. BZ induces autophagy as well as endoplasmic reticulum (ER) stress in various cell lines tested. Inhibition of initial autophagosome formation by treatment with either 3-methyladenine or siRNA for LC3B in U266 cells and knockdown of the atg5 gene in a murine embryonic fibroblastic cell line all resulted in attenuation of BZ-induced cell death. In contrast, combined treatment with BZ and bafilomycin A1 (BAF), which is a specific inhibitor of vacuolar-ATPase and is used as an autophagy inhibitor at the late stage, resulted in synergistic cytotoxicity, compared with that by either BZ or BAF alone. BAF treatment also induced ER stress, but the kinetics of inductions of ER stress-related genes [e.g. CHOP (GADD153) and GRP78] completely differed between BZ- and BAF-treatments: BZ induced these ER stress markers within 8 h, whereas treatment with BAF required more than 48 h in U266 cells. In order to synchronize ER stress, we pre-treated U266 cells with BAF for 48 h, followed with BZ for 48 h. The sequential treatment with BAF and BZ induced a further enhanced cytotoxicity, compared with the simultaneous combination of BAF and BZ. These data suggest crosstalk among the ubiquitin-proteasome system, the autophagy-lysosome system, and ER stress. Controlling these interactions and kinetics appears to have important implications for optimizing clinical cancer treatment including MM-therapy.

Macrolide antibiotics block autophagy flux and sensitize to bortezomib via endoplasmic reticulum stress-mediated CHOP induction in myeloma cells

Abstract: The specific 26S proteasome inhibitor bortezomib (BZ) potently induces autophagy, endoplasmic reticulum (ER) stress and apoptosis in multiple myeloma (MM) cell lines (U266, IM-9 and RPMI8226). The macrolide antibiotics including concanamycin A, erythromycin (EM), clarithromycin (CAM) and azithromycin (AZM) all blocked autophagy flux, as assessed by intracellular accumulation of LC3B-II and p62. Combined treatment of BZ and CAM or AZM enhanced cytotoxicity in MM cell lines, although treatment with either CAM or AZM alone exhibited almost no cytotoxicity. This combination also substantially enhanced aggresome formation, intracellular ubiquitinated proteins and induced the proapoptotic transcription factor CHOP (CADD153). Expression levels of the proapoptotic genes transcriptionally regulated by CHOP (BIM, BAX, DR5 and TRB3) were all enhanced by combined treatment with BZ plus CAM, compared with treatment with each reagent alone. Like the MM cell lines, the CHOP+/+ murine embryonic fibroblast (MEF) cell line exhibited enhanced cytotoxicity and upregulation of CHOP and its transcriptional targets with a combination of BZ and one of the macrolides. In contrast, CHOP−/− MEF cells exhibited resistance against BZ and almost completely canceled enhanced cytotoxicity with a combination of BZ and a macrolide. These data suggest that ER stress-mediated CHOP induction is involved in pronounced cytotoxicity. Simultaneously targeting two major intracellular protein degradation systems such as the ubiquitin-proteasome system by BZ and the autophagy-lysosome system by a macrolide antibiotic enhances ER stress-mediated apoptosis in MM cells. This result suggests the therapeutic possibility of using a macrolide antibiotic with a proteasome inhibitor for MM therapy.

Phenoxazine Compounds Produced by the Reactions with Bovine Hemoglobin Show Antimicrobial Activity Against Non-tuberculosis Mycobacteria

Abstract: We studied the anti-microbial effects of phenoxazines produced by the reaction of o-aminophenol or its derivatives with bovine hemoglobin, on seven species of mycobacteria such as Mycobacterium tuberculosis, Mycobacterium marinum, Mycobacterium intracellulare, Mycobacterium scrofulaceum, Mycobacterium fortuitum, Mycobacterium kansasii and Mycobacterium smegmatis and some bacteria such as Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica serovar Typhimurium, Staphylococcus aureus, Listeria monocytogeneses. These phenoxazines, including 2-amino-4,4α-dihydro-4α,7-dimethyl-3H-phenoxzine-3-one (Phx-1),3-amino-1,4α-dihydro-4α,8-dimethyl-2H-phenoxazine-2-one (Phx-2), and 2-aminophenoxazine-3-one (Phx-3), prevented the proliferation of four non-tuberculosis mycobacteria including M. scrofulaceum, M. kansasii, M. marinum, and M. intracellulare dose-dependently, though the inhibitory effects of these phenoxazines differed according to the species of mycobacteria. However these phenoxazines failed to prevent the proliferation of M. tuberculosis, M. fortuitum, and M. smegmatis, and the concerned bacteria other than mycobacteria. The present results may contribute to development of novel antibiotics against non-tuberculolsis mycobacteria.

Antitumor Effects of a Novel Phenoxazine Derivative on Human Leukemia Cell Lines in Vitro and in Vivo

Abstract: 2-Amino-4,4alpha-dihydro-4alpha,7-dimethyl-3H-phenoxazine-3-one (Phx) was synthesized by reacting 2-amino-5-methylphenol with bovine hemolysates. Because Phx is a phenoxazine derivative like actinomycin D, we examined its effects on the proliferation of the human leukemia cell lines K562, HL-60, and HAL-01. Phx inhibited proliferation and induced apoptosis in all of the leukemia cell lines we tested, in a dose-dependent manner. We further investigated the antitumor effect of this compound on HAL-01-bearing nude mice. Treatment with Phx markedly reduced the tumor growth rate in the experimental group, as compared with the control group. Moreover, Phx was found to have few adverse effects on weight loss and WBC count. In addition, we examined the effects of Phx on human normal hematopoietic progenitor cells by a clonogenic assay, and we observed less suppression of normal progenitor cells than of leukemic progenitors. These results suggest that Phx may be used to treat patients affected by different types of leukemia.

Functional expression of the organic cation/carnitine transporter 2 in rat astrocytes

Abstract: In this study, we sought to identify the transporters that mediate the uptake of L-carnitine and acetyl-L-carnitine in cultured rat cortical astrocytes. L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine uptake were both saturable, and mediated by a single Na(+)-dependent transport system. Uptake of both was inhibited by L-carnitine, D-carnitine, acetyl-L-carnitine and various organic cations. Acylcarnitines (acetyl-, butyryl-, hexanoyl-, octanoyl- and palmitoyl-L-carnitine) also interacted with L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine transport. 2-Amino-2-norbornane carboxylic acid, a known inhibitor of amino acid transporter B(0,+) (ATB(0,+)), did not cause any significant inhibition. A highly significant correlation was found between the potencies of acylcarnitines in the inhibition of L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine uptake and the acyl chain length of acylcarnitines. The expression of mRNA for organic cation/carnitine transporters (OCTNs), carnitine transporter 2 (CT2) and ATB(0,+) in astrocytes was investigated by reverse transcription (RT)-PCR. OCTN2 mRNA was expressed in astrocytes, whereas the expression of OCTN1, OCTN3 and CT2 mRNA could not be detected. ATB(0,+) mRNA was expressed at very low levels in astrocytes. Western blotting analysis indicated that anti-OCTN2 polyclonal antibody recognized a band of 70 kDa in both kidney and astrocyte preparations. OCTN2 immunoreactivity was detected in rat astrocytes by immunocytochemical staining. Inhibition of OCTN2 expression by RNA interference significantly inhibited L-[(3)H]carnitine and acetyl-L-[(3)H]carnitine uptake into astrocytes. These results suggest that OCTN2 is functionally expressed in rat astrocytes, and is responsible for L-carnitine and acetyl-L-carnitine uptake in these cells.

Medscape

Abstract: Secret History: Return of the Black Death Channel 4, 7-8pm In 1348 the Black Death swept through London, killing people within days of the appearance of their first symptoms. Exactly how many died, and why, has long been a mystery. This Secret History documentary follows experts as they pick through the evidence and reveal why the plague killed on such a scale. And they ask, what might be coming next?

Combination therapy in combating cancer.

Abstract: // Reza Bayat Mokhtari 1,2,4 , Tina S. Homayouni 1 , Narges Baluch 3 , Evgeniya Morgatskaya 1 , Sushil Kumar 1 , Bikul Das 4 and Herman Yeger 1,2 1 Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada 2 Department of Paediatric Laboratory Medicine, The Hospital for Sick Children and Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada 3 Department of Pathology and Molecular Medicine, Queen’s University, Kingston, Ontario, Canada 4 Department of Immunology and Infectious Diseases, The Forsyth Institute, Cambridge, Massachusetts, USA Correspondence to: Herman Yeger, email: // Reza Bayat Mokhtari, email: // Keywords : Nrf2-Keap1, HIF-1alpha, carbonic anhydrase 9 (CAIX), histone deacetylase inhibitor (HDACi), carbonic anhydrase inhibitor (CAI) Received : October 19, 2016 Accepted : February 27, 2017 Published : March 30, 2017 Abstract Combination therapy, a treatment modality that combines two or more therapeutic agents, is a cornerstone of cancer therapy. The amalgamation of anti-cancer drugs enhances efficacy compared to the mono-therapy approach because it targets key pathways in a characteristically synergistic or an additive manner. This approach potentially reduces drug resistance, while simultaneously providing therapeutic anti-cancer benefits, such as reducing tumour growth and metastatic potential, arresting mitotically active cells, reducing cancer stem cell populations, and inducing apoptosis. The 5-year survival rates for most metastatic cancers are still quite low, and the process of developing a new anti-cancer drug is costly and extremely time-consuming. Therefore, new strategies that target the survival pathways that provide efficient and effective results at an affordable cost are being considered. One such approach incorporates repurposing therapeutic agents initially used for the treatment of different diseases other than cancer. This approach is effective primarily when the FDA-approved agent targets similar pathways found in cancer. Because one of the drugs used in combination therapy is already FDA-approved, overall costs of combination therapy research are reduced. This increases cost efficiency of therapy, thereby benefiting the “medically underserved”. In addition, an approach that combines repurposed pharmaceutical agents with other therapeutics has shown promising results in mitigating tumour burden. In this systematic review, we discuss important pathways commonly targeted in cancer therapy. Furthermore, we also review important repurposed or primary anti-cancer agents that have gained popularity in clinical trials and research since 2012.

Polyspecific organic cation transporters: structure, function, physiological roles, and biopharmaceutical implications.

Abstract: The body is equipped with broad-specificity transporters for the excretion and distribution of endogeneous organic cations and for the uptake, elimination and distribution of cationic drugs, toxins and environmental waste products. This group of transporters consists of the electrogenic cation transporters OCT1-3 (SLC22A1-3), the cation and carnitine transporters OCTN1 (SLC22A4), OCTN2 (SLC22A5) and OCT6 (SLC22A16), and the proton/cation antiporters MATE1, MATE2-K and MATE2-B. The transporters show broadly overlapping sites of expression in many tissues such as small intestine, liver, kidney, heart, skeletal muscle, placenta, lung, brain, cells of the immune system, and tumors. In epithelial cells they may be located in the basolateral or luminal membranes. Transcellular cation movement in small intestine, kidney and liver is mediated by the combined action of electrogenic OCT-type uptake systems and MATE-type efflux transporters that operate as cation/proton antiporters. Recent data showed that OCT-type transporters participate in the regulation of extracellular concentrations of neurotransmitters in brain, mediate the release of acetylcholine in non-neuronal cholinergic reactions, and are critically involved in the regulation of histamine release from basophils. The recent identification of polymorphisms in human OCTs and OCTNs allows the identification of patients with an increased risk for adverse drug reactions. Transport studies with expressed OCTs will help to optimize pharmacokinetics during development of new drugs.

Xenobiotic, Bile Acid, and Cholesterol Transporters: Function and Regulation

Abstract: Transporters influence the disposition of chemicals within the body by participating in absorption, distribution, and elimination. Transporters of the solute carrier family (SLC) comprise a variety of proteins, including organic cation transporters (OCT) 1 to 3, organic cation/carnitine transporters (OCTN) 1 to 3, organic anion transporters (OAT) 1 to 7, various organic anion transporting polypeptide isoforms, sodium taurocholate cotransporting polypeptide, apical sodium-dependent bile acid transporter, peptide transporters (PEPT) 1 and 2, concentrative nucleoside transporters (CNT) 1 to 3, equilibrative nucleoside transporter (ENT) 1 to 3, and multidrug and toxin extrusion transporters (MATE) 1 and 2, which mediate the uptake (except MATEs) of organic anions and cations as well as peptides and nucleosides. Efflux transporters of the ATP-binding cassette superfamily, such as ATP-binding cassette transporter A1 (ABCA1), multidrug resistance proteins (MDR) 1 and 2, bile salt export pump, multidrug resistance-associated proteins (MRP) 1 to 9, breast cancer resistance protein, and ATP-binding cassette subfamily G members 5 and 8, are responsible for the unidirectional export of endogenous and exogenous substances. Other efflux transporters [ATPase copper-transporting β polypeptide (ATP7B) and ATPase class I type 8B member 1 (ATP8B1) as well as organic solute transporters (OST) α and β] also play major roles in the transport of some endogenous chemicals across biological membranes. This review article provides a comprehensive overview of these transporters (both rodent and human) with regard to tissue distribution, subcellular localization, and substrate preferences. Because uptake and efflux transporters are expressed in multiple cell types, the roles of transporters in a variety of tissues, including the liver, kidneys, intestine, brain, heart, placenta, mammary glands, immune cells, and testes are discussed. Attention is also placed upon a variety of regulatory factors that influence transporter expression and function, including transcriptional activation and post-translational modifications as well as subcellular trafficking. Sex differences, ontogeny, and pharmacological and toxicological regulation of transporters are also addressed. Transporters are important transmembrane proteins that mediate the cellular entry and exit of a wide range of substrates throughout the body and thereby play important roles in human physiology, pharmacology, pathology, and toxicology.