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T Sawa

Publications and source records attributed to T Sawa.

At least 19 recordsLinked to original sources
PubMed2000

Tumor-targeting chemotherapy by a xanthine oxidase-polymer conjugate that generates oxygen-free radicals in tumor tissue.

Xanthine oxidase (XO) mediates anticancer activity because of its ability to generate cytotoxic reactive oxygen species (ROS), including superoxide anion radical and hydrogen peroxide. However, the high binding affinity of XO to blood vessels would cause systemic vascular damage and hence limits the use of native XO in clinical settings. We demonstrate here that chemical conjugation of XO with poly(ethylene glycol) (PEG; the conjugates hereafter referred to as PEG-XO) significantly enhanced the tumor-targeting efficacy and the antitumor activity of XO. By using a succinimide-activated PEG derivative, PEG was conjugated to epsilon-amino groups of lysine residues of XO, which play a crucial role in binding of XO to blood vessels. PEG-XO administered i.v. showed a 2.8-fold higher accumulation in solid tumor compared with that of native XO 24 h after injection, whereas a slight or negligible increase in accumulation of PEG-XO was observed in normal organs. The highest PEG-XO enzyme activity was detected in tumor compared with normal organs or tissues except blood; enzyme activity in tumor was 5.0, 3.9, and 9.4 times higher than that in liver, kidney, and spleen, respectively. Intratumor activity remained high for >48 h. Administration of hypoxanthine, a substrate of XO, at 33 mg/kg body weight i.p. 12 h after the administration of PEG-XO (0.6 unit/mouse, i.v.) resulted in significant suppression of tumor growth (P < 0.001), with no tumor growth even after 52 days. However, either PEG-XO or hypoxanthine alone, or native XO with hypoxanthine, showed no effect on the inhibition of tumor growth under present experimental conditions. These findings suggest that PEG-XO, which accumulates preferentially in tumor tissue, warrants further investigation as a novel anticancer agent.

Animals↗
PubMed1999

Involvement of vesicle-cytoskeleton interaction in AQP5 trafficking in AQP5-gene-transfected HSG cells.

A cDNA of rat aquaporin 5 (AQP5) was used to transfect to HSG (human salivary gland cells), and the trafficking mechanism was studied in vitro by confocal laser microscopy. The trafficking of AQP5 to the plasma membrane was induced by stimulation of AQP5-gene-transfected human salivary gland cells (HSGAQP5 cells) with thapsigargin, an inhibitor of endoplasmic Ca(2+)-ATPase, and or with A-23187, a calcium ionophore. Pretreatment of these cells with colchicine or vinblastine, microtubule inhibitors, prevented the trafficking induced by thapsigargin or A-23187. The trafficking event was not completely inhibited by cytochalasin B, a microfilament inhibitor. These results demonstrate that the trafficking of AQP5 vesicles to the plasma membrane is triggered by an increase in intracellular Ca(2+) and that the interaction of AQP5-containing vesicles with the cytoskeleton is involved in this trafficking.

Amino Acid Sequence↗
PubMed1999

Nitrosothiol formation catalyzed by ceruloplasmin. Implication for cytoprotective mechanism in vivo.

Ceruloplasmin (CP) is a major multicopper-containing plasma protein that is not only involved in iron metabolism through its ferroxidase activity but also functions as an antioxidant. However, physiological substrates for CP have not been fully identified nor has the role of CP been fully understood. The reaction of nitric oxide (NO) with CP was investigated in view of nitrosothiol (RS-NO) formation. First, formation of heavy metal- or CP-catalyzed RS-NO was examined with physiologically relevant concentrations of NO and various thiol compounds (RSH) such as glutathione (GSH). Among the various heavy metal ions and copper-containing enzymes and proteins examined, only copper ion (Cu(2+)) and CP showed potent RS-NO (S-nitrosoglutathione)-producing activity. Also, RS-NO-forming catalytic activity was evident for CP added exogenously to RAW264 cells expressing inducible NO synthase in culture, but this was not the case for copper ion. Similarly, CP produced endogenously by HepG2 cells showed potent RS-NO-forming activity in the cell culture. One-electron oxidation of NO appears to be operative for RS-NO production via electron transfer from type 1 copper to a cluster of types 2 and 3 copper in CP. Neurological disorders are associated with aceruloplasminemia; besides RS-NO, S-nitrosoglutathione particularly has been shown to have neuroprotective effect against oxidative stress induced by iron overload. Thus, we suggest that CP plays an important catalytic role in RS-NO formation, which may contribute to its potent antioxidant and cytoprotective activities in vivo in mammalian biological systems.

Animals↗
PubMed1999

Free radical generation from heterocyclic amines by cytochrome b5 reductase in the presence of NADH.

We previously reported findings that NADPH/cytochrome P450 reductase can generate superoxide anion radical (O2*-) from heterocyclic amines (HCA) and from many anticancer agents in vitro. Here we present more evidence in which O2*- is generated when recombinant human cytochrome b5 reductase (rh-Cytb5Rd) was incubated with HCAs such as IQ and MeIQ in the presence of NADH in vitro. This indicates that free radical generation by rh-Cytb5Rd in the presence of HCA may add new insight into the damage of DNA in addition to the previously known mechanism: interaction of activated HCA-intermediates to form DNA adduct.

Cytochrome Reductases↗
PubMed1999

Intracellular signalling pathways of okadaic acid leading to mitogenesis in Rat1 fibroblast overexpressing insulin receptors: okadaic acid regulates Shc phosphorylation by mechanisms independent of insulin.

Okadaic acid is a powerful inhibitor of serine/threonine protein phosphatases 1 and 2A. Although it is known as a potent tumour promoter, the intracellular mechanism by which okadaic acid mediates its mitogenic effect remains to be clarified. We investigated the effect of okadaic acid on the activation of mitogenesis in Rat1 fibroblasts overexpressing insulin receptors. As previously reported, insulin induced Shc phosphorylation, Shc-Grb2 association, MAP kinase activation, and BrdU incorporation. Okadaic acid also stimulated tyrosine phosphorylation of Shc and its subsequent association with Grb2 in a time- and dose-dependent manner without affecting tyrosine phosphorylation of insulin receptor beta-subunit and IRS. However, to a lesser extent, okadaic acid stimulated MAP kinase activity and BrdU incorporation. Interestingly, preincubation of okadaic acid potentiated insulin stimulation of tyrosine phosphorylation of Shc (213% of control), Shc-Grb2 association (150%), MAP kinase activity (152%), and BrdU incorporation (148%). These results further confirmed the important role of Shc, but not IRS, in cell cycle progression in Rat1 fibroblasts. Furthermore, serine/ threonine phosphorylation appears to be involved in the regulation of Shc tyrosine phosphorylation leading to mitogenesis by mechanisms independent of insulin signalling.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Alkylperoxyl radical-scavenging activity of various flavonoids and other phenolic compounds: implications for the anti-tumor-promoter effect of vegetables.

We recently reported that alkylperoxyl radical (ROO(*)) enhanced carcinogenesis in rats treated with carcinogen (Sawa et al. Cancer Epidemiol. Biomarkers Prev. 1998, 7, 1007-1012), and the tumor promoting action of ROO(*) could be reduced by addition of hot-water extracts of vegetables (Maeda et al. Jpn. J. Cancer Res. 1992, 83, 923-928). Here we described the ROO(*)-scavenging activity of flavonoids and nonflavonoid phenolics and their role in anti-tumor-promoter effects. A model molecular species, ROO(*), was generated from tert-butyl hydroperoxide (t-BuOOH) and heme iron, and the scavenging of t-BuOO(*) was determined by (a) bioassay based on the bactericidal action of ROO(*), (b) luminol-enhanced chemiluminescence, and (c) electron spin resonance. Of 17 authentic plant phenolics tested, 9 compounds (including rutin, chlorogenic acid, vanillin, vanillic acid, neohesperidin, gallic acid, shikimic acid, rhamnetin, and kaempferol) showed remarkably high ROO(*)-scavenging activity. Some of them were detected and quantified in hot-water extracts of mung bean sprouts, used as the model vegetable, and their contents increased after germination, which paralleled very well to the ROO(*)-scavenging capacity of the vegetable extracts. Thus, a diet rich in these radical scavengers would reduce the cancer-promoting action of ROO(*). Consequently, the carcinogenic potentials of oxygen-related radicals may be suppressed.

Anticarcinogenic Agents↗
PubMed1999

Active and passive immunization with the Pseudomonas V antigen protects against type III intoxication and lung injury.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that can cause fatal acute lung infections in critically ill individuals. Damage to the lung epithelium is associated with the expression of toxins that are directly injected into eukaryotic cells through a type Ill-mediated secretion and translocation mechanism. Here we show that the P. aeruginosa homolog of the Yersinia V antigen, PcrV, is involved in the translocation of type III toxins. Vaccination against PcrV ensured the survival of challenged mice and decreased lung inflammation and injury. Antibodies to PcrV inhibited the translocation of type III toxins.

Animals↗
PubMed1999

The effects of two antiinflammatory pretreatments on bacterial-induced lung injury.

BACKGROUND: Two antiinflammatory therapies that have been effective in preventing acid-induced lung injury were evaluated. Specifically, their effects on a subsequent bacterial-airspace challenge were compared. Bacteria were instilled 24 h after acid-induced lung injury. Pseudomonas aeruginosa PAO-1 was used as the bacteria, because its effects in healthy lungs was documented previously. METHODS: New Zealand white rabbits were anesthetized and three pretreatments were administered: (1) pentoxifylline pretreatment (a 20-mg/kg bolus dose and then 6 mg x kg(-1) x h(-1) given intravenously), (2) 1 ml anti-tumor necrosis factor alpha antiserum given intravenously, or (3) normal saline given intravenously. The pretreatment doses were shown previously to prevent acid-induced lung injury. Then 1.2 ml/kg hydrochloric acid (HCl), pH 1.25, was instilled into the rabbits' right lungs. All the animals underwent mechanical ventilation for 8 h. Twenty-four hours after the acid instillation, the rabbits were anesthetized again and 2 ml/kg (10(9) colony forming units/ml) PAO-1 was instilled into their left lungs. The rabbits' breathing was aided by mechanical ventilation for another 8 h, and then they were killed and exsanguinated. RESULTS: Both pretreatments attenuated the acid-induced lung injury of the noninstilled left lungs. Arterial oxygen tension and the lung edema of pretreated, acid-exposed animals were significantly and almost equally improved (compared with no pretreatments) by either of the pretreatments. However, when the bacteria were instilled into the left lungs 24 h after the acid injury, the pentoxifylline pretreatment but not the anti-tumor necrosis factor alpha pretreatment prevented much of the bacteria-induced lung injury. Pentoxifylline pretreatment significantly improved the measurements of left lung edema and epithelial and endothelial permeability. There was also a trend for improved oxygenation in the pentoxifylline-pretreated and infected animals. In contrast, the anti-tumor necrosis factor alpha pretreatment did not prevent the bacteria-induced lung injury and increased some of the measurements of lung injury. CONCLUSIONS: Two antiinflammatory therapies that prevented acid-induced lung injury to the noninstilled left lungs had significantly different effects on a subsequent bacteria-induced lung injury to the left lungs. The therapies differed in their mechanism of tumor necrosis factor alpha blockade, and this may have affected the bacteria-induced injury to the lungs.

Animals↗
PubMed1999

Effects of antibiotic therapy on Pseudomonas aeruginosa-induced lung injury in a rat model.

The effect of antibiotics on the acute lung injury induced by virulent Pseudomonas aeruginosa PA103 was quantitatively analyzed in a rat model. Lung injury was induced by the instillation of PA103 directly into the right lower lobes of the lungs of anesthetized rats. The alveolar epithelial injury, extravascular lung water, and total plasma equivalents were measured as separate, independent parameters of acute lung injury. Four hours after the instillation of PA103, all the parameters were increased linearly depending on the dose of P. aeruginosa. Next, we examined the effects of intravenously administered antibiotics on the parameters of acute lung injury in D-galactosamine-sensitized rats. One hour after the rats received 10(7) CFU of PA103, an intravenous bolus injection of aztreonam (60 mg/kg) or imipenem-cilastatin (30 mg/kg) was administered. Despite an MIC indicating resistance, imipenem-cilastatin improved all the measurements of lung injury; in contrast, aztreonam, which had an MIC indicating sensitivity, did not improve any of the lung injury parameters. The antibiotics did not generate different quantities of plasma endotoxin; therefore, endotoxin did not appear to explain the differences in lung injury. This in vivo model is useful to quantitatively compare the efficacies of parenteral antibiotic administration on Pseudomonas airspace infections.

Animals↗
PubMed1999

In vitro induction of activation-induced cell death in lymphocytes from chronic periodontal lesions by exogenous Fas ligand.

Periodontitis is a chronic inflammatory disease which gradually destroys the supporting tissues of the teeth, leading to tooth loss in adults. The lesions are characterized by a persistence of inflammatory cells in gingival and periodontal connective tissues. To understand what mechanisms are involved in the establishment of chronic lesions, we hypothesized that infiltrating lymphocytes might be resistant to apoptosis. However, both Bcl-2 and Bcl-xL were weakly detected in lymphocytes from the lesions, compared with those from peripheral blood, suggesting that these cells are susceptible to apoptosis. Nevertheless, very few apoptotic cells were observed in tissue sections from the lesions. Lymphocytes from the lesions expressed mRNA encoding Fas, whereas Fas-ligand mRNA was very weakly expressed in lymphocytes from the lesions and in periodontal tissues. Since the results indicated that lymphocytes in the lesions might be susceptible to Fas-mediated apoptosis but lack the death signal, we next investigated if these lymphocytes actually undergo apoptosis by the addition of anti-Fas antibodies in vitro. Fas-positive lymphocytes from the lesions underwent apoptosis by these antibodies, but Fas-negative lymphocytes and Fas-positive peripheral lymphocytes did not undergo apoptosis by these antibodies. These results indicate that lymphocytes in the lesions are susceptible to activation-induced cell death and are induced to die by apoptosis after the addition of exogenous Fas ligand.

Adult↗
PubMed1999

Pathogenesis of septic shock in Pseudomonas aeruginosa pneumonia.

The pathogenesis of septic shock occurring after Pseudomonas aeruginosa pneumonia was studied in a rabbit model. The airspace instillation of the cytotoxic P. aeruginosa strain PA103 into the rabbit caused a consistent alveolar epithelial injury, progressive bacteremia, and septic shock. The lung instillation of a noncytotoxic, isogenic mutant strain (PA103DeltaUT), which is defective for production of type III secreted toxins, did not cause either systemic inflammatory response or septic shock, despite a potent inflammatory response in the lung. The intravenous injection of PA103 did not cause shock or an increase in TNF-alpha, despite the fact that the animals were bacteremic. The systemic administration of either anti-TNF-alpha serum or recombinant human IL-10 improved both septic shock and bacteremia in the animals that were instilled with PA103. Radiolabeled TNF-alpha instilled in the lung significantly leaked into the circulation only in the presence of alveolar epithelial injury. We conclude that injury to the alveolar epithelium allows the release of proinflammatory mediators into the circulation that are primarily responsible for septic shock. Our results demonstrate the importance of compartmentalization of inflammatory mediators in the lung, and the crucial role of bacterial cytotoxins in causing alveolar epithelial damage in the pathogenesis of acute septic shock in P. aeruginosa pneumonia.

Animals↗
PubMed1999

Migration inhibitory factor related protein-8 (MRP-8) is an autocrine chemotactic factor for periodontal ligament cells.

Previous studies have suggested that human periodontal ligament (PDL) cells secrete a chemotactic factor which stimulates motility in an autocrine manner. Here we report the partial amino acid sequence of a purified factor which shows 100% homology with human migration inhibitory factor related protein-8 (MRP-8). In addition, reverse-transcription polymerase chain-reaction (RT-PCR) analysis revealed that mRNA encoding MRP-8 was expressed in cultured human PDL cells. To confirm that MRP-8 is chemotactic for PDL cells, we synthesized 25 mer peptides overlapped by 5 amino acids covering the entire MRP-8 protein and tested them for their chemotactic activities. The data indicated that amino acid residues 21-45 showed chemotactic activity for cultured human PDL cells. The maximum chemotactic response was observed at the concentration of 10(-15) mol/mL for human PDL cells. The chemotactic activity was estimated to be approximately 1000-fold higher than that of platelet-derived growth factor (PDGF), insulin-like growth factors-I and -II (IGF-I, -II), and epidermal growth factor (EGF) when compared on a molar basis. Since MRP-8 is reported to be produced mainly by neutrophils and monocytes, the result of the current study may suggest another important role of MRP-8 in human PDL cells.

Amino Acid Sequence↗
PubMed1999

Lactonamycin, a new antimicrobial antibiotic produced by Streptomyces rishiriensis MJ773-88K4. II. Structure determination.

The absolute structure of a new antibiotic lactonamycin is described. The NMR studies deduced one of four possible structures for the aglycon attached by a rhodinose through glycosidic bond. The stereochemistry of the sugar obtained by an acid hydrolysis was determined to be L-form by measuring optical rotation. The stereochemistry of the aglycon was determined by X-ray crystallographic analysis.

Anti-Bacterial Agents↗
PubMed1999

[Current topics in the regulation of prostanoids--3. Prostanoid synthases and prostanoid receptors].

Formation of biologically active prostanoids from PGH2 occurs through a set of synthases for PGD, PGE, PGF, PGI and TXA2, following the cyclooxygenase reaction. Over the past few years, the genes of several prostanoid synthases have been cloned and the characteristics of the enzymes are now determined. In addition, receptors for prostanoids were also cloned and their structures were determined as G-protein coupled seven-transmembrane domain types belonging to the rhodopsin-type receptor superfamily. Based on these molecular biological findings, the mechanism of the diverse effects of prostanoids are being clarified. Selective inhibitors against the synthases and the selective agonists and antagonists for the prostanoid receptors are now being investigated rapidly for clinical application.

Animals↗
PubMed1999

[Current topics in the regulation of prostanoids--4. The feedback regulation by PPAR-gamma].

Recently, it has become known that lipophilic hormones such as steroids and thyroid hormones, or fat-soluble vitamins (vitamins A and D) pass through the cellular membrane and bind to the nuclear receptor superfamily to act as transcription factors. The metabolite of prostaglandin (PG) D2, 15-deoxy-D12,14PGJ2, has been identified as the ligand for peroxisome proliferator-activated receptor gamma (PPAR-gamma), a member of the nuclear receptor superfamily. It forms a transcription factor and is responsible not only for the differentiation of fibroblasts to adipocytes, but also for the regulation of activated macrophages. It is now known that thiazolidinediones and non-steroidal anti-inflammatory drugs classified as cyclooxygenase blockers such as indomethacine and ibuprofen also act as PPAR-gamma agonists and inhibit cytokine production from activated macrophages. PPAR-gamma has become recognized as a new therapeutic target for inflammation control.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

[Intratumoral ethanol injection therapy using endoscopic video information system].

Bronchoscopic ethanol injection (BEI) therapy for endobronchial malignant tumor is thought to be an effective modality for airway dilatation and hemostasis without expensive special equipment. But if ethanol leaks into the airway, it causes severe coughing and erosion of bronchial wall. Using endoscopic video information system (EVIS), an assistant operator can observe an ethanol leak and inject an adequate volume. To evaluate the efficacy and adverse effect of BEI therapy, we treated 8 patients with endobronchial malignant tumor using EVIS. Under local anesthesia, a video-bronchoscope (Olympus BF200 or BF 1T200) was inserted orally, a transbronchial aspiration cytology (TBAC) needle was inserted via the biopsy channel, and injections of 0.2 ml of 99% ethanol into the tumor were repeated. After the tumor degenerated to necrotic tissue, it was removed with a biopsy forceps, and this maneuver was repeated for the existing fresh lesion. The total volume of injected ethanol was 4.5 + 1.6 ml (mean + SD). Airway obstruction and atelectasis were relieved in 4 cases, and hemostasis was obtained in 2 cases. In 2 cases, airway dilatation and hemostasis were not obtained. BEI was more effective in the patients with polypoid or nodular tumor protruding into the airway lumen. As for adverse effects, ethanol leaks caused a severe cough in 2 cases, although they were tolerable and treatment could be continued. BEI therapy using EVIS was thought to be useful to control airway obstruction by endobronchial polypoid tumor with good cost-effectiveness and fewer adverse effects.

Bronchial Neoplasms↗