Hisao Tomida

Fukuyama University, Hukuyama, Hiroshima, Japan

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Publications (15)23.3 Total impact

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    ABSTRACT: The preparation of water-soluble chitosans such as polyethylene glycol (PEG)-grafted derivatives is essential for improving the biocompatibility and water solubility of these types of polysaccharides. In this study, chitosans (CS1; 22kDa, CS2; 38kDa, CS3; 52kDa) with different molecular weights were modified with a succinyl ester derivative of monomethoxypolyethylene glycol (mPEG-COONSu; 2kDa), and the properties of the resulting conjugates (mPEG-CS1, mPEG-CS2, mPEG-CS3) were investigated. The antioxidant properties of these mPEG-CSs were examined using 1) N-centered radicals derived from 1,1'-diphenyl-2-picrylhydrazyl (DPPH), 2) reducing power, based on their ability to reduce Cu(2+) and 3) hydroxyl radicals via the use of ESR spectrometry. The order of their effectiveness was mPEG-CS1> mPEG-CS2> mPEG-CS3, i.e. mPEG-CS1 with a low particle size had the highest scavenging activity of the mPEG-CSs tested. In an in vivo study, we examined the effect of mPEG-CS1 on liver injury, caused by injecting mice with Concanavalin A (Con A). The livers of mice that were treated with mPEG-CS1 were protected from Con A-induced injury. Further, pre-treatment with mPEG-CS1 dramatically reduced the mortality associated with Con A-induced mortality. These findings suggest that mPEG-CS1 could be potentially useful in the treatment of immune-mediated liver injury.
    International journal of biological macromolecules. 06/2014;
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    ABSTRACT: Antioxidant activities of 3-oxygenated and 3,4-dioxygenated carbazole alkaloids and their related carbazoles were comprehensively evaluated. In all assay systems, the 3,8-dihydroxycarbazoles carbazomadurin A (2) and B (3), and their synthetic precursors 2a and 3a exhibited higher antioxidant activities than the 3-monohydroxycarbazoles carazostatin (1), and the synthetic precursors 4a and 4b of carquinostatin A (4). In particular, 2a and 3a exhibited strong scavenging activities due to the reducing ability of formyl group at the C-5 position of carbazoles. The results suggest that these compounds could serve as useful clues for designing and developing novel antioxidants.
    Bioorganic & medicinal chemistry letters. 05/2014;
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    Bioorganic & Medicinal Chemistry Letters. 01/2014;
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    ABSTRACT: The effect of chitosan on oxidative stress and chronic renal failure was investigated using 5/6 nephrectomized rats. The ingestion of chitosan over a 4-week period resulted in a significant decrease in total body weight, glucose, serum creatinine and indoxyl sulfate levels (P = 0.0011, P = 0.0006, P = 0.0012, and P = 0.0005, respectively), compared with the non-treated nephrectomized group. The ingestion of chitosan also resulted in a lowered ratio of oxidized to reduced albumin (P = 0.003) and an increase in biological antioxidant potential (P = 0.023). Interestingly, the oxidized albumin ratio was correlated with serum indoxyl sulfate levels in vivo. These results suggest that the ingestion of chitosan results in a significant reduction in the levels of pro-oxidants, such as uremic toxins, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation.
    Carbohydrate Polymers 06/2012; 89(1):302–304. · 3.92 Impact Factor
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    ABSTRACT: Dipeptidyl peptidase III (DPP III), the zinc peptidase, has a unique helix portion in the metal-binding motif (HELLGH). The enzyme activity of the cupric derivative of rat DPP III (Cu(II)-rat DPP III) for Lys-Ala-β-NA is about 30% of that of the wild-type enzyme. On the other hand, the enzyme activity of Cu(II)-rat del-DPP III, in which Leu453 is deleted from the metal-binding motif, possesses only 1-2% of the enzyme activity of rat del-DPP III. The EPR spectra of Cu(II)-rat DPP III in the presence of various concentrations of the substrate, Lys-Ala-β-NA, changed dramatically, showing formation of the enzyme-metal-substrate complex. The EPR spectra of Cu(II)-rat del-DPP III did not change in the presence of excess Lys-Ala-β-NA. The deletion of Leu453 from the HELLGH motif of rat DPP III leads to a complete loss of flexibility in the ligand geometry around the cupric ions. Under the formation of the enzyme-metal-substrate complex, Glu451 of Cu(II)-rat DPP III is sufficiently able to approach the water molecule via a very different orientation from that of the resting state; however, Glu451 of Cu(II)-rat del-DPP III is not able to access the water molecule.
    Archives of Biochemistry and Biophysics 06/2012; 525(1):71-81. · 3.37 Impact Factor
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    ABSTRACT: In recent years, it is necessary to acquire knowledge not only about medicine but also over-the-counter (OTC) drugs and health food for children, because lowering trend in the age of the health hazard by improper use of health food is reported. Therefore, in order to estimate the extent of use of OTC drugs and health food, the school pharmacists administered a questionnaire to students in grade-school (n=123), junior high school (n=303), and high school (n=115) in Fukuyama city. As a result of the questionnaire survey, surprisingly, the usage ratio of OTC drugs and health food showed the most increase in grade-schooler. The trigger of use of health food is "parents' recommendations" in the lower grades, otherwise the ratio of "use by themselves" was increased in the higher grades. Moreover, a remarkable difference was observed by the kinds of use in students with or without exercise. Interestingly, exercise group expected "physical strength" effects than no exercise group. In addition, the ratio of consultation to the pharmacist at the time of purchase of OTC drugs and health food was low in all grade students. In particular, the ratio of consultation to the pharmacist at the time of purchase of health food was very low in high school students. Therefore, to provide accurate information of medicine and health food for students, the school pharmacist should engage not only in routine work but also in positive guidance about OTC drugs and health food in the future.
    YAKUGAKU ZASSHI 01/2011; 131(5):835-42. · 0.37 Impact Factor
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    ABSTRACT: The spontaneously hypertensive rat (SHR)/NDmcr-cp (SHR-cp), which is a metabolic syndrome model rat, was reported to show hypercholesteremia, as compared with lean littermates. The serum total cholesterol level in SHR-cp at 18 weeks of age is higher than that of normotensive Wistar Kyoto rat (WKY), but that in SHR-cp at 10 weeks of age is the same. The objective of this study is to clarify whether there are differences in the system regulating serum cholesterol levels between SHR-cp and WKY at 10 weeks of age. Total serum cholesterol levels, and cholesterol levels of high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein (VLDL) were similar in the two strains. However, the cholesterol levels in the liver of SHR-cp were lower than those of WKY. Next, mRNA levels of receptors (scavenger receptor class B type 1 [SRB1], LDL receptor [LDLR]) involved in uptake from serum to liver or enzymes of cholesterol catabolism (CYP7A1 and CYP8B1) and biosynthesis (mevalonate pyrophosphate decarboxylases [MPD]) in liver were compared between SHR-cp and WKY. High levels of MPD and LDLR and low levels of SRB1 were shown in SHR-cp, as compared with WKY. CYP7A1 and CYP8B1 levels were similar between SHR-cp and WKY. These results suggest that the serum cholesterol level in SHR-cp by the balance or regulation between the rise in cholesterol uptake and reduction in cholesterol biosynthesis in the liver is the same as that in WKY.
    Biological & Pharmaceutical Bulletin 01/2011; 34(7):1116-9. · 1.85 Impact Factor
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    ABSTRACT: The effect of high molecular weight chitosan supplement (HMCS), a natural polymer derived from chitin, on indices of oxidative stress was investigated in normal volunteers. The use of HMCS for 8 weeks resulted in a significant decrease in total cholesterol levels and atherogenic index, and increased levels of high density lipoprotein (HDL) cholesterol. HMCS treatment also resulted in a lowered ratio of oxidized to reduced albumin and an increase in total plasma antioxidant activity. A good correlation between the atherogenic index and oxidized albumin ratio was found. The results suggest that the ratio of oxidized to reduced albumin ratio represents a potentially useful marker of the metabolic syndrome. In in vitro studies, HMCS slightly reduced the levels of two stable radicals in a dose- and time-dependent manner. The strong binding capacity of indoxyl sulfate and low density lipoprotein (LDL) cholesterol was also observed with HMCS. These results suggest that HMCS reduces significant levels of pro-oxidants such as cholesterol and uremic toxins in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation in humans.
    Carbohydrate Polymers. 01/2011;
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    ABSTRACT: To estimate the extent of use of over-the-counter (OTC) drugs and health food, we administered a questionnaire to the parents of children in a nursery school and to elderly people in a daycare center in Fukuyama city. The aim of the questionnaire was to determine the percentage of children and elderly people who use OTC drugs and health food, the purpose of using them, and the types of OTC drugs and health food used. Other questions concerned the person advising them on the use of OTC and health food, the side effects of OTC drugs and health food, and the awareness of children and elderly people regarding possible interactions between prescription drugs and OTC drugs. In children, the most frequently consumed OTC drugs were cold medicines (32.1%), followed by topical creams (22.6%) and eye lotion (14.3%). In elderly people, the most frequently consumed OTC products were eye lotion (18.0%), followed by laxatives (14.8%) and fomentation agents (13.1%). The purchase ratio of health food for children and elderly people were 4.8% and 11.5%, respectively. These results suggest that the need for OTC drugs and health food in children are very different from those in elderly people. In addition, in promoting self-medication, the demand for the opinion of a specialist occupied about 80% or 70% of the total specialist time among children and elderly people, respectively. Therefore, when providing information on health food and OTC drugs, the needs of each generation should be taken into account. The information obtained from the responses received will allow us to provide better pharmaceutical care for both children and elderly people in Fukuyama city.
    Yakugaku zasshi journal of the Pharmaceutical Society of Japan 08/2010; 130(8):1093-103. · 0.46 Impact Factor
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    ABSTRACT: In the present study, we examined levels of oxidative stress in the serum, brain and kidneys of normotensive Wistar Kyoto rats (WKY) and stroke prone spontaneously hypertensive rats (SHRSP) at 10 weeks of age. Levels of advanced oxidation protein products (AOPP), oxidized albumin and oxidized proteins, markers of oxidative stress, were significantly decreased in serum among SHRSP as compared with WKY. Levels of oxidized proteins determined by immunoblotting were significantly increased in the brain, but not kidney, of SHRSP. The mRNA level of super oxide dismutase (SOD) determined by real time polymerase chain reaction (PCR) and the protein level of catalase assessed by immunoblotting were significantly increased in the brain of SHRSP. From these results, it was suggested that levels of oxidative stress were higher in the brain than serum or kidneys of SHRSP at 10 weeks of age, but are not caused by decreases in the expression of SOD and catalase.
    Biological & Pharmaceutical Bulletin 01/2010; 33(3):518-21. · 1.85 Impact Factor
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    ABSTRACT: The effect of high and low molecular weight chitosans (HMC; 1000 kDa, LMC; 30 kDa) on oxidative stress and hypercholesterolemia was investigated using male 6-week-old Wistar Kyoto rats as a normal model (Normal-rats) and spontaneously hypertensive rat/ND mcr-cp (SHP/ND) as a metabolic syndrome model (MS-rats), respectively. In Normal-rats, the ingestion of both chitosans over a 4 week period resulted in a significant decrease in total body weight (BW), glucose (Gl), triglyceride (TG), low density lipoprotein (LDL) and serum creatinine (Cre) levels. The ingestion of both chitosans also resulted in a lowered ratio of oxidized to reduced albumin and an increase in total plasma antioxidant activity. In addition to similar results in Normal-rats, the ingestion of only HMC over a 4 week period resulted in a significant decrease in total cholesterol levels in MS-rats. Further, the ingestion of LMC resulted in a significantly higher antioxidant activity than was observed for HMC in both rat models. In in vitro studies, LMC caused a significantly higher reduction in the levels of two stable radicals, compared to HMC, and the effect was both dose- and time-dependent. The findings also show that LDL showed strong binding in the case of HMC. These results suggest that LMC has a high antioxidant activity as well as antilipidemic effects, while HMC results in a significant reduction in the levels of pro-oxidants such as LDL in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress in the systemic circulation in metabolic model rats.
    Biological & Pharmaceutical Bulletin 01/2010; 33(12):1994-8. · 1.85 Impact Factor
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    ABSTRACT: The objective of this study was to identify polysaccharides with antioxidant properties for use as potential antioxidative compounds for extended-release matrix tablets. The antioxidant properties of five different polysaccharides, high molecular weight alginate (H-ALG), low molecular weight alginate (L-ALG), high molecular weight chitosan (H-chitosan), low molecular weight chitosan (L-chitosan), and pectic acid (PA) were examined using N-centered radicals from 1,1'-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and reducing power, based on their ability to reduce Cu(2+). L-chitosan and PA had acceptable scavenging abilities and were good radical scavengers, with good reducing power, but the H-chitosan and alginate derivatives were much less effective. The results suggest that L-chitosan and PA could be useful in combating oxidative stress. A PA and L-chitosan interpolymer complex (IPC) tablet was prepared and evaluated as an extended-release tablet matrix using theophylline (TPH) as a model drug. The release of TPH from the matrix tablet (TPH/PA/L-chitosan=200 mg:150 mg:50 mg) was slower than that from PA only (TPH/PA/chitosans=200 mg:200 mg:0 mg) or L-chitosan only (TPH/PA/L-chitosan=200 mg:0 mg:200 mg) tablet. Turbidity measurements also indicated the optimum complexation ratio for IPC between PA/L-chitosan to be 1/3, indicating an acceptable relationship between the turbidity of the complex and the release ratio of TPH. These results suggest that an L-chitosan/PA complex would be potentially useful in an extended-release IPC tablet with high antioxidant activity.
    Carbohydrate research 10/2009; 345(1):82-6. · 2.03 Impact Factor
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    ABSTRACT: Chitosan, a cationic polysaccharide, is widely employed as dietary supplement and in pharmacological and biomedical applications. Although numerous studies have focused on its applications as pharmaceutical excipients or bioactive reagents, relationships between molecular weight (Mr) and biological properties remain unclear. The focus of this study was on the antioxidant properties of several Mr chitosans. We measured the ability of seven Mr chitosans (CT1; 2.8 kDa, CT2; 17.0 kDa, CT3; 33.5 kDa, CT4; 62.6 kDa, CT5; 87.7 kDa, CT6; 604 kDa, CT7; 931 kDa) to protect plasma protein from oxidation by peroxyl radicals derived from 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH). A comparison of the antioxidant action of high Mr chitosans (CT6-CT7) with that of low Mr chitosans (CT1-CT5) showed that low Mr chitosans (CT1-CT5) were more effective in preventing the formation of carbonyl groups in plasma protein exposed to peroxyl radicals. AAPH substantially increases plasma protein carbonyl content via the oxidation of human serum albumin (HSA). We also measured the ability of these chitosans to protect HSA against oxidation by AAPH. Low Mr chitosans (CT1-CT5) were found to effectively prevent the formation of carbonyl groups in HSA, when exposed to peroxyl radicals. Low Mr chitosans were also good scavengers of N-centered radicals, but high Mr chitosans were much less effective. We also found a strong correlation between antioxidant activity and the Mr of chitosans in vitro. These activities were also determined by using the 'TPAC' test. These results suggest that low Mr chitosans (CT1-CT3) may be absorbed well from the gastrointestinal tract and inhibit neutrophil activation and oxidation of serum albumin that is frequently observed in patients plasma undergoing hemodialysis, resulting in a reduction in oxidative stress associated with uremia.
    Carbohydrate research 06/2009; 344(13):1690-6. · 2.03 Impact Factor
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    ABSTRACT: The effect of water-soluble chitosan, a natural polymer derived from chitin, on indices of oxidative stress was investigated in normal volunteers. Treatment with chitosan for 4 weeks produced a significant decrease in levels of plasma glucose, atherogenic index and led to increase in high density lipoprotein cholesterol (HDL). Chitosan treatment also lowered the ratio of oxidized to reduced albumin and increased total plasma antioxidant activity (TPA). There was good correlation between TPA and oxidized albumin ratio. The results indicate that oxidized albumin ratio represents a potentially useful marker of oxidative stress. In in vitro studies, albumin carbonyls and hydroperoxides were significantly decreased in a time-dependent manner in the presence of chitosan, compared with controls (p<0.05). Chitosan also reduced two stable radicals in a dose- and time-dependent manner. The results suggest that chitosan has a direct antioxidant activity in systemic circulation by lowering the indices of oxidative stress in both in vitro and in vivo studies. This may confer benefits additional to the reduction in plasma carbohydrate and increase in HDL levels. It may also inhibit oxidation of serum albumin commonly observed in patients undergoing hemodialysis, resulting in reduction of oxidative stress associated with uremia.
    Food and chemical toxicology: an international journal published for the British Industrial Biological Research Association 10/2008; 47(1):104-9. · 2.99 Impact Factor
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    ABSTRACT: Inhibition of protein oxidation by reactive oxygen species (ROS) would confer benefit to living organisms exposed to oxidative stress, because oxidized proteins are associated with many diseases and can propagate ROS-induced damage. We measured the ability of 2800Da chitosan, D-glucosamine and N-acetyl glucosamine to protect human serum albumin from oxidation by peroxyl radicals derived from 2,2'-azobis(2-amidinopropane)dihydrochloride and N-centered radicals from 1,1'-diphenyl-2-picrylhydrazyl and from 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Comparison with the antioxidant action of vitamin C showed that, on a molar basis, chitosan was equally effective in preventing formation of carbonyl and hydroperoxide groups in human serum albumin exposed to peroxyl radicals. It was also a potent inhibitor of conformational changes in the protein, assessed by absorption spectrum and intrinsic fluorescence. D-glucosamine was much less effective and N-acetyl glucosamine was not a useful antioxidant. Protection of the albumin from peroxyl radicals was achieved by scavenging of peroxyl radical. Chitosan was also a good scavenger of N-centered radicals, with glucosamine and N-acetyl glucosamine much less effective. The results suggest that administration of low molecular weight chitosans may inhibit neutrophil activation and oxidation of serum albumin commonly observed in patients undergoing hemodialysis, resulting in reduction of oxidative stress associated with uremia.
    International Journal of Biological Macromolecules 05/2008; 43(2):159-64. · 2.60 Impact Factor