Biomedical subjects

Jun Shimada

Publications and source records attributed to Jun Shimada.

36 records · Page 2Linked to original sources

PubMed2002

A structure-based method for derivation of all-atom potentials for protein folding.

A method for deriving all-atom protein folding potentials is presented and tested on a three-helix bundle protein, as well as on hairpin and helical sequences. The potentials obtained are composed of a contact term between pairs of atoms, and a local density term for each atom, mimicking solvent exposure preferences. Using this potential in an all-atom protein folding simulation, we repeatedly folded the three-helix bundle, with the lowest energy conformations having a C(alpha) distance rms from the native structure of less than 2 A. Similar results were obtained for the hairpin and helices by using different potentials. We derived potentials for several different proteins and found a high correlation between the derived parameters, suggesting that a potential of this form eventually could be found that folds multiple, unrelated proteins at the atomic level of detail.

Biophysics↗

PubMed2002

Weak, improper, C-O...H-C hydrogen bonds in the dimethyl ether dimer.

The ground-state rotational spectrum of the dimethyl ether dimer, (DME)(2), has been studied by molecular beam Fourier transform microwave and free jet millimeter wave absorption spectroscopies. The molecular beam Fourier transform microwave spectra of the (DME-d(6))(2), (DME-(13)C)(2), (DME-d(6))...(DME), (DME-(13)C)...(DME), and (DME)...(DME-(13)C) isotopomers have also been assigned. The rotational parameters have been interpreted in terms of a C(s) geometry with the two monomers bound by three weak C-H...O hydrogen bonds, each with an average interaction energy of about 1.9 kJ/mol. The experimental data combined with high-level ab initio calculations show this kind of interaction to be improper, blue-shifted hydrogen bonding, with an average shortening of the C-H bonds involved in the hydrogen bonding of 0.0014 A. The length of the C-H...O hydrogen bonds, r(O...H), is in the range 2.52-2.59 A.

Dimerization↗

PubMed2002

Retinoids in liver fibrosis and cancer.

Pathobiological functions and metabolism of retinoids (vitamin A and its derivatives) in liver fibrosis and hepatocellular carcinoma (HCC) are discussed in the present review. Retinoic acid (RA, active metabolite) exacerbates liver fibrosis that is not accompanied by hepatic necroinflammation, in which RA acts directly on hepatic stellate cells (HSCs); RA enhances plasminogen activator/plasmin levels and thereby induces proteolytic activation of latent transforming growth factor-beta (TGF-beta), a strong fibrogenic cytokine, resulting in enhanced collagen production. We have developed a protease inhibitor, camostat mesilate, that suppresses TGF-beta activation and thereby inhibits the transformation of HSCs, leading to reduced matrix production by the cells. The compound is effective not only in preventing but also in reducing hepatic fibrosis in rats when administered orally. HCC is refractory to RA due to its local depletion in the tumors and also due to malfunction of its nuclear receptor, retinoid X receptor-alpha (RXRalpha) Oral supplementation of a synthetic retinoid named acyclic retinoid led to the disappearance of serum lectin-reactive alpha-fetoprotein (AFP-L3) and subsequently suppressed posttherapeutic recurrence of HCC in cirrhotic patients. These results suggest eradication of AFP-L3-producing latent malignant clones from the liver by the retinoid. We propose the concept of "clonal deletion" therapy for cancer chemoprevention, a new category of cancer chemotherapy.

Animals↗

PubMed2002

From knowledge-based potentials to combinatorial lead design in silico.

Computational methods are becoming increasingly used in the drug discovery process. In this Account, we review a novel computational method for lead discovery. This method, called CombiSMoG for "combinatorial small molecule growth", is based on two components: a fast and accurate knowledge-based scoring function used to predict binding affinities of protein-ligand complexes, and a Monte Carlo combinatorial growth algorithm that generates large numbers of low-free-energy ligands in the binding site of a protein. We illustrate the advantages of the method by describing its application in the design of picomolar inhibitors for human carbonic anhydrase.

Algorithms↗

PubMed2002

Synergistic induction of apoptosis by acyclic retinoid and interferon-beta in human hepatocellular carcinoma cells.

Acyclic retinoid, a synthetic retinoid analog, as well as interferon alfa (IFN-alpha) and IFN-beta induce apoptosis in hepatocellular carcinoma (HCC) cells and are used clinically in the prevention of HCC. Here, we show that acyclic retinoid acts synergistically with IFNs in suppressing the growth and inducing apoptosis (as characterized by DNA fragmentation and chromatin condensation) in 5 human HCC cell lines (JHH7, HuH7, PLC/PRF/5, HLE, and HLF). This synergism was only observed when cells were pretreated with the acyclic retinoid, whereas natural retinoic acids (all-trans and 9-cis retinoic acid) were ineffective. This promotion may be due to up-regulation of type 1 IFN receptor (IFNR) expression by the retinoid. Accordingly, incubation with antitype 1 IFNR antibody abolished the synergy. Enhanced IFNR expression was accompanied by increased expression and DNA-binding activity of STAT1, an intracellular signal transducing molecule of IFNR, and increased induction of 2', 5'-oligoadenyl-5'-triphosphate synthetase, which is a target gene of STAT1. Acyclic retinoid did not have any effects on the growth of normal human hepatocytes (Hc) probably because of a lack of IFNR and STAT1 up-regulation. In conclusion, these results provide a rationale for combined biochemoprevention of HCC using acyclic retinoid and IFN-beta.

Antineoplastic Agents↗

PubMed2002

Nasopharyngeal carriage of drug-resistant Streptococcus pneumoniae in children with acute otitis media evaluated by polymerase chain reaction-based genotyping of penicillin-binding proteins.

A polymerase chain reaction (PCR)-based genotyping of the penicillin-binding protein (PBP) genes pbp1a, pbp2x and pbp2b was used to characterize Streptococcus pneumoniae isolated from the nasopharynx of children with acute otitis media (AOM). Mutations were observed in pbp1a, pbp2x and pbp2b genes in 36.5% of the strains. Decreased susceptibility to beta-lactam antibiotics was closely associated with the frequency of mutations in the three PBP genes. Of penicillin-intermediately-resistant S. pneumoniae strains, 54.5% appeared to be genetically similar to penicillin-resistant S. pneumoniae strains. Of penicillin-susceptible S. pneumoniae strains, 33.3% had mutations in the pbp2x gene and showed relatively high MICs to cephalosporins. Strains with mutations in the three PBP genes were often isolated from children < or = 2 years old. Evaluation of mutations in PBP genes using PCR will prove useful for studying the epidemiology of antibiotic resistance.

Acute Disease↗

PubMed2002

Household transmission of Streptococcus pneumoniae among siblings with acute otitis media.

Nasopharyngeal transmission of Streptococcus pneumoniae was evaluated among 23 siblings with acute otitis media (AOM). Restriction fragment length polymorphism revealed that the nasopharyngeal strains were identical between siblings in 12 of 13 clusters of AOM experienced in 11 families. This study demonstrated person-to-person transmission of S. pneumoniae, especially drug-resistant strains, among siblings with AOM.

Acute Disease↗

PubMed2002

Intracerebral adenosine infusion improves neurological outcome after transient focal ischemia in rats.

Second Institute of New Drug Research, Otsuka Pharmaceutical Co., Ltd., Tokushima, Japan In order to elucidate the role of adenosine in brain ischemia, the possible protective effects of adenosine on ischemic brain injury were investigated in a rat model of brain ischemia both in vitro and in vivo. Exogenous adenosine dose-dependently rescued cortical neuronal cells from injury after glucose deprivation in vitro. Adenosine (1 mM) also significantly reduced hypoglycemia/hypoxia-induced glutamate release from the hippocampal slice. In a rat model of transient middle cerebral artery occlusion (MCAO), extracellular adenosine concentration was increased immediately after occlusion, and then returned to the baseline by 30 min after reperfusion. Adenosine infusion through a microdialysis probe into the ipsilateral striatum (1 mM adenosine, 2 microl min(-1), total 4.5 h from the occlusion to 3 h after reperfusion) showed a significant improvement in the neurological outcome, and about 25% reduction of infarct volume, although the effect did not reach statistical significance, compared with the vehicle-treated group at 20 h after 90 min of MCAO. These results demonstrated the neuroprotective effect of adenosine against ischemic brain injury both in vitro and in vivo, suggesting the possible therapeutic application of adenosine regulating agents, which inhibit adenosine uptake or metabolism to enhance or maintain extracellular endogenous adenosine levels, for stroke treatment.

Adenosine↗

PubMed2002

Lack of association between Y chromosome Alu insertion polymorphism and hypertension.

There is an inherited paternal predisposition to hypertension. Y chromosome alphoid satellite variation was recently reported to be linked to diastolic blood pressure. To determine whether there is also a Y chromosome marker linked to hypertension, we investigated the prevalence of the Y chromosome Alu insertion polymorphism (YAP) at DYS287 and its association with hypertension in the Aomori population in the northern area of Honshu Island, Japan. YAP was present in 98 of 285 male residents and absent in the rest. The YAP prevalence in the present study would appear to suggest that the present study population represents the general male population in central Japan. Within the study population, there were 110 hypertensive subjects and 104 normotensive subjects. YAP frequency in the hypertensive subjects was not different from that in the normotensive subjects. These results suggest that the YAP is not likely to be a genetic-susceptibility factor for hypertension in the Aomori population.

Adult↗

PubMedDate not supplied

Dendritic cells in human squamous cell carcinoma of the oral cavity.

Dendritic cells (DCs) are antigen-presenting cells that initiate and modulate immune responses, including tumor immunity. In this study we examined, immunohistochemically, the distribution of DC subsets in the primary tumor, adjacent tissue and regional lymph nodes (RLNs) of patients with oral squamous cell carcinoma (OSCC). The numbers of S100+ and CD1a+ DCs in tissue adjacent to the primary tumor were greater in patients without metastasis to RLNs (PN- cases), compared with those with metastasis (PN+ cases), while greater numbers of CD83+ DCs in the primary tumors were found in PN+ cases. In the RLNs, the numbers of S100+ and CD1a+ DCs were less in PN+ cases than in PN- cases, while the numbers of CD83+ DCs were greater in PN+ cases compared with those in PN- cases. These results suggest that the distribution of DC subsets in OSCC may reflect the degree of tumor immunity induced in the host bearing OSCC.

Adult↗

PubMedDate not supplied

Effect of antitumor agents on cytotoxicity induction by sodium fluoride.

We have recently found that sodium fluoride (NaF) induced apoptotic cell death in tumor cell lines. We investigated here whether 6 popular antitumor compounds modify the cytotoxic activity of NaF against human squamous cell carcinoma (HSC-2) and human promyelocytic leukemia (HL-60) cell lines. Cytotoxic concentrations of cisplatin, etoposide, doxorubicin or peplomycin (tentatively termed as Group I compounds), but not methotrexate and 5-FU (tentatively termed as Group II compounds), enhanced the cytotoxic activity of NaF. NaF and Group I compounds induced internucleosomal DNA fragmentation in HL-60 cells, whereas Group II compounds were inactive even in the presence of NaF. Most Group I compounds except doxorubicin (which induced DNA fragmentation less effectively than others) activated caspase 3 more efficiently than Group II compounds. Caspase 8 (involved in non-mitochondrial extrinsic pathway) and caspase 9 (involved in mitochondrial intrinsic pathway) were also activated, but to a much lesser extent. NaF reduced the glucose consumption at early stage, possibly by inhibition of glycolysis, whereas cisplatin and etoposide reduced the glucose consumption at later stage, suggesting that early decline of glucose consumption is rather specific to NaF.

Antineoplastic Agents↗

PubMedDate not supplied

Apoptosis-inducing activity of cisplatin (CDDP) against human hepatoma and oral squamous cell carcinoma cell lines.

The sensitivity of human hepatoma (HepG2) and oral squamous cell carcinoma (HSC-2) cell lines against various apoptosis-inducing agents was compared. HepG2 cells were generally more resistant to an oxidant (H2O2), antioxidants (sodium ascorbate, gallic acid, epigallocatechin gallate) and anticancer drugs (doxorubicin, methotrexate, cisplatin (CDDP), etoposide, 5-fluoro-2,4(1H,3H)-pyrimidinedione (5-FU), peplomycin sulfate) as compared to HSC-2 cells. Lower concentrations of CDDP, but not other anticancer drugs, induced comparable cytostatic effects on both HSC-2 and HepG2 cells. CDDP induced internucleosomal DNA fragmentation and activation of caspases 3, 8 and 9 in HepG2 cells. On the other hand, CDDP did not induce DNA fragmentation and activated caspase 3 only marginally in HSC-2 cells. Combination treatment with CDDP (10 microM) and 5-FU (100 microM) additively activated all three caspases in HepG2 cells, but not in HSC-2 cells. The present study demonstrated the chemotherapeutic potential of combined treatment of CDDP and 5-FU against hepatoma cells and the considerable variation of drug sensitivity between cancer cell lines.

Antineoplastic Agents↗

PubMedDate not supplied

Cytotoxicity and radical modulating activity of Moxa smoke.

The biological activities of Moxa, used as moxibustion, have not been well documented. We investigated here Moxa smoke for its tumor-specific cytotoxicity, anti-HIV activity, radical intensity and radical scavenging activity, in comparison with previously published data of Moxa extract. Moxa smoke showed slightly higher cytotoxicity against human tumor cell lines (oral squamous cell carcinoma HSC-2, HSC-3, promyelocytic leukemia HL-60) than against normal oral cells (gingival fibroblast HGF, pulp cell HPC, periodontal ligament fibroblast HPLF), yielding a tumor specificity index of 1.29. Moxa smoke dose-dependently induced internucleosomal DNA fragmentation, activation of caspases 3, 8 and 9, and slightly modified the expression of apoptosis-related proteins (Bcl-2, Bad, Bax) in HL-60 cells, but to much lesser extents than attained by positive controls (UV irradiation, actinomycin D treatment). ESR spectroscopy showed that Moxa smoke generated semiquinone-type radicals under alkaline conditions, and scavenged O2(-), hydroxyl radical, singlet oxygen and NO. All Moxa smoke preparations showed no apparent anti-HIV activity. These data demonstrate the antitumor potential of Moxa smoke.

Anti-HIV Agents↗

PubMedDate not supplied

Inhibition by Moxa smoke of NO production and iNOS expression in mouse macrophage-like cells Raw 264.7.

The biological activities of Moxa, used as moxibustion, have not been well documented. We investigated the effect of Moxa smoke on nitric oxide (NO) production by mouse macrophage-like Raw 264.7 cells. Moxa smoke failed to stimulate the Raw 264.7 cells to produce detectable amounts of NO, but rather inhibited the NO production by lipopolysaccharide (LPS)-activated Raw 264.7 cells. The 50% inhibitory concentration (IC50) of NO production by Moxa smoke (0.16%) was one order lower than the 50% cytotoxic concentration (CC50) (4.67%). Western blot and RT-PCR analyses demonstrated that a slightly higher concentration of Moxa is required to reduce the iNOS expression at protein and mRNA levels (IC50 = 0.99 and 2.03%, respectively). The inhibition of NO production by Moxa smoke is, thus, probably due to both the inhibition of iNOS expression and radical-scavenging activity. The present data suggest the possible anti-inflammatory effect of Moxa smoke.

Animals↗

PubMedDate not supplied

Induction of tumor-specific cytotoxicity and apoptosis by doxorubicin.

Doxorubicin (adriamycin), an anthracycline antibiotic, showed higher cytotoxic activity against human tumor cell lines (oral squamous cell carcinoma HSC-2, HSC-3, submandibular gland carcinoma HSG, promyelocytic leukemia HL-60) than against normal human cells (gingival fibroblast HGF, pulp cell HPC, periodontal ligament fibroblast HPLF). Doxorubicin activated caspases 3, 8 and 9 in both HSC-2 and HL-60 cells, but induced internucleosomal DNA fragmentation only in HL-60 cells. Western blot analysis showed that doxorubicin did not significantly change the intracellular concentration of Bcl-2, Bax and Bad in HL-60 cells. Real-time PCR analysis showed that HPC cells expressed the highest amount of mdr1 mRNA, followed by HSC-2 > HGF > HSC-3 > HPLF > HSG > HL-60. ESR spectroscopy showed that doxorubicin produced no discernible radical under alkaline conditions (pH 7.4 to 10.5) except at pH 12.5, and it did not scavenge O2-, NO and DPPH radicals. The present study demonstrates that doxorubicin induces the tumor-specific cytotoxicity and some, but not all, apoptosis markers possibly by a radical-independent mechanism, and that mdr1 expression in the tumor cells is not related to the tumor specificity of doxorubicin.

Antibiotics, Antineoplastic↗

PubMedDate not supplied

Biological impact of contact with metals on cells.

In order to investigate the in vivo effect of metals used in dentistry, we investigated the effect of direct contact with metal plates (20 x 20 x 0.5 mm3) made of gold (Au), silver (Ag), copper (Cu) or palladium (Pd) on human promyelocytic leukemic HL-60 cells grown in RPMI1640 medium supplemented with 10% fetal bovine serum. When 0.5 mL of cell suspension was applied to the metal plates, cells were precipitated on the surface of the metal plate within 10 min. Contact with Cu induced a rapid decline of cell viability, the smear pattern of DNA fragmentation, and only minor activation of caspase-3. These effects were accompanied by a progressive decrease in the extracellular concentration of methionine, cysteine and histidine, with a corresponding increase in the concentration of methionine sulfoxide. Electron microscopy showed that contact with Cu induced vacuolization and cytoplasmic damage, prior to nuclear damage, without affecting the cell surface microvilli or mitochondrial integrity. Contact with the other metals did not induce such changes during the 3 h incubation, nor was any hormetic response (beneficial action at lower concentration) observed in the cells with any metals. Addition of N-acetyl-L-cysteine (4-5 mM) almost completely abrogated the Cu-induced cytotoxicity, whereas sodium ascorbate (0.1-0.5 mM) and catalase (6,000(1)-30,000 units/mL) were ineffective. Numerous serum proteins were adsorbed to the Ag plate, while bovine serum albumin was the major protein adsorbed to other metal plates. The present study suggests that direct contact with Cu induced non-apoptotic cell death by an oxidation-involved mechanism. The present model system may be applicable to the study of the interaction between cells and dental restorative materials.

Acetylcysteine↗

PubMedDate not supplied

Re-evaluation of tumor-specific cytotoxicity of mitomycin C, bleomycin and peplomycin.

Three antitumor antibiotics, mitomycin C, bleomycin sulfate and peplomycin sulfate, were compared for their tumor-specific cytotoxicity, using human oral squamous cell lines (HSC-2, HSC-3, HSC-4, Ca9-22 and NA), human promyelocytic leukemic cell line HL-60 and human normal oral cell types (gingival fibroblast HGF, pulp cell HPC and periodontal ligament fibroblast HPLF). Among these three compounds, mitomycin C showed the highest tumor-specificity, due to its higher cytotoxic activity against human oral tumor cell lines than bleomycin and peplomycin. However, there was considerable variation of drug sensitivity among the six tumor cell lines. Mitomycin C induced internucleosomal DNA fragmentation and caspase-3, -8 and -9 activation in HL-60 cells only after 24 h. On the other hand, mitomycin C induced no clear-cut DNA fragmentation in HCS-2 cells, although it activated caspase-3, -8 and -9 to a slightly higher extent. Western blot analysis demonstrated that mitomycin C did not induce any apparent change in the intracellular concentration of anti-apoptotic protein (Bcl-2) and pro-apoptotic proteins (Bax, Bad). Electron microscopy of mitomycin C-treated HL-60 cells showed intact mitochondria (as regards to integrity and size) and cell surface microvilli, without production of an apoptotic body or autophagosome, at an early stage after treatment. The present study suggests the incomplete induction of apoptosis or the induction of another type of cell death by mitomycin C treatment.

Antibiotics, Antineoplastic↗

PubMedDate not supplied

Cytotoxic activity of selected trifluoromethyl ketones against oral tumor cells.

Several trifluoromethyl ketones (TF1-4) and related non-fluorinated ketones (TF5 and 6) were tested for their relative cytotoxicity on four human tumor cell lines (oral squamous cell carcinoma HSC-2, HSC-3, HSC-4 and promyelocytic leukemia HL-60) and three normal human cells [gingival fibroblasts (HGF), pulp cells (HPC) and periodontal ligament fibroblasts (HPLF)]. Trifluoromethylated a-diketone (TF1, CF3COCOPh) and alpha-hydroxy ketones (TF2, CF3CH(OH)COPh; TF3, CF3CH(OH)COCH2Ph) showed higher tumor-specific cytotoxic activity than the corresponding non-fluorinated analogs (TF5, CH3COCOPh; TF6, CH3CH(OH)COPh), while the anti-tumor potency of trifluoromethyl ketone (TF4, CF3COCH2Ph) was lower. Among four tumor cell lines, HL-60 cells were the most sensitive to TF1-4, followed by HSC-2 and HSC-3 cells. HSC-4 cells were the most resistant in most cases. Agarose gel electrophoresis showed that TF1-3 did not induce intemucleosomal DNA fragmentation nor activated caspase-3. The cytotoxic activities of TF1-3 were not significantly affected by FeCl3. Electron microscopy of TF2- or 3-treated HL-60 cells showed the development of autophagosomes in HL-60 cells, without the production of an apoptotic body, or affecting the mitochondria and cell surface microvilli. The autophagy inhibitor, 3-methyladenine (3-MA), partially inhibited the TF2- or 3-induced cytotoxicity. These data suggest the induction of non-apoptotic cell death by TF2 or 3.

Carcinoma, Squamous Cell↗