Biomedical subjects

S Iwata

Publications and source records attributed to S Iwata.

At least 37 records · Page 2Linked to original sources

PubMed2001

Recognition of cell surface GD3 by monoclonal antibody anti-6C2 in rheumatoid arthritis synovial fluid: expression on human T cells with transendothelial migratory activity.

OBJECTIVE: We have previously reported that the anti-6C2 monoclonal antibody (mAb) defines a subset of human CD4+ memory T cells. The present study sought to determine the nature of the 6C2 molecule and the function associated with 6C2+ T cells, and to examine whether this T cell subset is involved in the pathophysiology of rheumatoid arthritis (RA). METHODS: Cytofluorographic analysis was performed for identification of T cell surface molecules displaying a distribution similar to that of the 6C2 molecule. T cells in the synovial fluid of RA patients were examined for expression of the 6C2 molecule. Transendothelial migratory activity was assessed by assay using monolayers of human endothelial cells. Specific reactivity of the anti-6C2 mAb was determined by immunoblotting on gangliosides separated by thin-layer chromatography, and flow cytometric analysis of the cells transfected with complementary DNA (cDNA) was performed for determination of the glycosyltransferases involved in biosynthesis of the gangliosides. RESULTS: On human peripheral T cells, the 6C2 molecule was distributed, by and large, in a pattern similar to that of CDw60, or O-acetyl-GD3. The majority (>70%) of synovial fluid T cells from patients with RA were found to be 6C2 positive, and those 6C2+ T cells exhibited a transendothelial migratory capacity that was inhibited by pretreatment of T cells with anti-6C2 mAb. Moreover, treatment of T cells with neuraminidase resulted in a loss of 6C2 expression as well as a reduction in the transendothelial migratory activity. Anti-6C2 mAb reacted specifically with GD3, but not with O-acetyl-GD3. The reactivity of anti-6C2 mAb was induced on the cell surface only by transfection with cDNA for GD3 synthase. CONCLUSION: The 6C2 molecule is a disialoganglioside, GD3, and is present on a subset of T cells with transendothelial migratory capacity. The 6C2/GD3 molecules, as well as 6C2/GD3+ T cells, appear to play a role in T cell migration and in the inflammation of RA.

Antibodies, Monoclonal↗

PubMed2001

Treatment of unruptured intracranial aneurysms--a clinicopathological correlation.

OBJECT: Brain check-up is very important for detecting the incidence and prevalence of aneurysms in the population and to get the definite strategy for the treatment of intracranial aneurysms. METHODS: This is a retrospective study of 116 aneurysms detected by brain check-up between 1998-1999 which were treated either by clipping or endovascular coiling. In some cases the aneurysmal wall was resected for histopathological examination and compared with five normal autopsy cases. CONCLUSIONS: Direct surgery is the primary option for a patient with an aneurysm in the anterior circulation especially in young patients. Intravascular therapy is suitable for aneurysms in the posterior circulation and in intracavernous site.

Aged↗

PubMed2001

Macular fold after limited macular translocation treated with scleral shortening release and intravitreal gas.

PURPOSE: To describe a case developing a macular fold as a complication of limited macular translocation, which was successfully managed without repeat vitrectomy. METHODS: Interventional case report. A 34-year-old woman who underwent limited macular translocation for subfoveal choroidal neovascularization secondary to myopic degeneration developed a postoperative macular fold. Her visual acuity deteriorated from 20/100 to 20/200 postoperatively. RESULTS: She underwent scleral shortening release and intravitreal gas injection 4 days after the initial surgery and had a resolution of macular fold with adequate foveal displacement. Her visual acuity had improved to 20/40 3 months postoperatively. CONCLUSION: Scleral shortening release and intravitreal gas injection may be considered for the management of severe macular fold caused by limited macular translocation.

Adult↗

PubMed2001

Recommended method of the Japanese Association of Medical Technologists for the determination of protein in urine by HPLC.

A recommended method for the determination of total urinary proteins as a designated comparative method (DCM) is described. The method is based on gel permeation high performance liquid chromatography (HPLC). A total of 20 microl of urine diluted 5-fold with saline solution were applied to a column, eluted with 0.13 mol/l phosphate buffer (pH 7.0) at a flow rate of 1.0 ml/min at 35 degrees C, and the absorbance is monitored at 220 nm. The fraction eluted in the void volume was quantified for urinary protein, using bovine serum albumin (NIST SRM 927) as the standard. The linear range of the assay was 10--5000 mg/l, and the precision was 1.5% in two samples with concentrations of 1037 and 4338, respectively. The analytical recovery was 96--104%. Low molecular weight substances such as glucose, ascorbic acid and bilirubin did not interfere the assay. The assay was satisfactorily applied to a variety of proteins regardless of their nature or molecular weights (12.4 kDa) including beta2-microglobulin and Bence Jones Proteins. Surveys in five clinical laboratories, employing different types of HPLC apparatus with the same column type, showed satisfactory measurement precision (CV 2.1%) for three urine samples with different protein concentrations.

Artifacts↗

PubMed2001

Improved nasal absorption of drugs using poly-L-arginine: effects of concentration and molecular weight of poly-L-arginine on the nasal absorption of fluorescein isothiocyanate-dextran in rats.

The effects of the concentration and molecular weight of poly-L-arginine (poly-L-Arg) on the in vivo nasal absorption of fluorescein isothiocyanate-labeled dextran (MW, 4 kDa, FD-4) in rats were studied. When poly-L-Arg with a range of different molecular weights (MW, 8.9, 45.5 and 92.0 kDa) was applied intranasally at various concentrations, the bioavailability (F(0-9 h)) of FD-4 increased with the increasing concentration of poly-L-Arg. The enhanced absorption was also dependent on the molar concentration, in that the poly-L-Arg with a higher molecular weight increased F(0-9 h) at a lower molar concentration. In addition, for each applied concentration, the poly-L-Arg exhibited a molecular weight-dependence as far as the enhancement of FD-4 absorption was concerned. On the other hand, the maximum absorption rate (MAR) of FD-4, calculated by means of a deconvolution method, tended to reach a maximum plateau level at a lower applied concentration for the poly-L-Arg with the highest molecular weight, but this plateau level was almost the same for poly-L-Arg with molecular weights of 45.5 and 92.0 kDa. Moreover, the simulated absorption profiles of FD-4 indicate that the degree of enhancement (the level of MAR and the subsequent reduction in the absorption rate) was dependent on the molecular weight of poly-L-Arg, while the effect of poly-L-Arg was maintained for a longer period, depending on the applied concentration, although the MAR was relatively similar. These results indicate that the molecular weight of poly-L-Arg appears to affect both the enhancing efficiency (absorption rate) and the time-frame of this enhancing effect, whereas the concentrations of each poly-L-Arg system applied only have an effect on the time-frame. These effects may also be associated with the charge density of a poly-L-Arg molecule.

Absorption↗

PubMed2001

[The trend of childhood bacterial meningitis in Japan (1997.7-2000.6)].

We surveyed the epidemiology of purulent meningitis in pediatrics for 3 years between July 1997 and June 2000 in Japan and obtained the following results. The number of cases of purulent meningitis was 428, which was equivalent of 1.1-1.7 children out of 1,000 hospitalized those in pediatrics per year. The age-distribution for the infections was the highest under 1 year of age and it decreased as the age increased. Under 1 year of age, the highest distribution was observed in one month of age and under 1 month of age, the highest distribution was observed in 7 days of or younger ages. Haemophilus influenzae was the most common pathogen causing the infections, followed by Streptococcus pneumoniae, group B streptococcus, and Escherichia coli. Relationship between causing pathogens and age-distribution was as follows: group B streptococcus and E. coli were major pathogens under 4 months of age and H. influenzae and S. pneumoniae were major pathogens over 3 months of age. Susceptibility tests performed at each facility demonstrated that 25.3% of H. influenzae isolates and 38.7% of S. pneumoniae isolates were drug-resistant. Analysis of resistant genes for H. influenzae and S. pneumoniae isolates, which were stored and sent, demonstrated higher rates of resistance than those observed in susceptibility tests. These results suggest that the increase in insufficient efficacy of usual treatment with combination of ampicillin and cefotaxime is predictable against the infections. Therefore, the treatment for the infections should be reconsidered.

Female↗

PubMed2001

[Pharmacological treatments of Parkinson's disease].

Antiparkinsonian agents applied or under the investigation for the treatment of patients with Parkinson's disease were reviewed. Tremor, akinesia, rigidity and postual instability are key signs of Parkinson's disease. The most important one is akinesia, which includes decreased spontaneous locomotor activity, slowness of movement, awkwardness and freezing. The main pathophysiology of Parkinson's disease is neurodegeneration of nigrostriatal dopaminergic neurons. Neurotoxins or oxidative stress to the dopaminergic neurons have been discussed as one of the etiologies of degeneration. Antioxidant or neuroprotective agents will be the future drugs for Parkinson's disease. At present, supplement of dopamine by levodopa administration, retarding the metabolism of levodopa or dopamine by a dopa decarboxylase inhibitor (DCI), MAO-B (monoamine oxidase inhibitor type B) inhibitor or catechol-O-methyltransferase (COMT) inhibitor, dopamine receptor agonists, anticholinergic agents, dopamine release enhancer/uptake inhibitor, N-methyl-D-aspartate (NMDA) receptor antagonists are applied for the treatment of Parkinson's disease. New agents such as adenosine receptor antagonists, serotonergic agents and nicotinic receptor agonists are under investigation. Agents to facilitate the growth of nerves or to inhibit degeneration of nerves are also studied and will be developed for the treatment of Parkinson's disease in the future. In the case of familial Parkinson's disease, abnormal genes were identified. Gene therapy might be another future treatment for these cases.

Amantadine↗

PubMed2000

TH protein and mRNA in nigrostriatal dopaminergic neurons are down-regulated by continuous but not intermittent apomorphine.

Levels of tyrosine hydroxylase (TH) and TH mRNA were measured after administration of dopamine agonists for a long period of time to elucidate the long-term feedback inhibition of dopamine synthesis in nigrostriatal dopaminergic neurons. Continuous infusion, which desensitized presynaptic dopamine receptors, but not repeated administration, down-regulated TH and TH mRNA levels. This suggests levels of TH protein and mRNA are only feedback inhibited by the continuous stimulation of postsynaptic dopamine receptors.

Animals↗

PubMed2000

Fusion protein approach to improve the crystal quality of cytochrome bo(3) ubiquinol oxidase from Escherichia coli.

Crystals of cytochrome bo(3) ubiquinol oxidase from E. coli diffract X-rays to 3.5 A and the structure determination is in progress. The limiting factor to the elucidation of the structural detail is the quality of the crystals; the diffraction spots from the crystals are diffused which leads to difficulties in processing the data beyond 4.0 A. Weak protein-protein contacts within the crystal lattice is assumed to be the cause of this problem. To improve these contacts, we have introduced protein Z to the C-terminal end of the subunit IV of cytochrome bo(3) and expressed both proteins as a single fusion. We have successfully obtained crystals of this fusion protein. The spot shape problem has clearly been solved in the crystals of the fusion protein although further optimization is necessary to obtain higher resolution. We also discuss the potential applications of this approach to the crystallization of membrane proteins in general.

Bacterial Proteins↗

PubMed2000

Internalization of CD26 by mannose 6-phosphate/insulin-like growth factor II receptor contributes to T cell activation.

CD26 is a T cell activation antigen known to bind adenosine deaminase and have dipeptidyl peptidase IV activity. Cross-linking of CD26 and CD3 with immobilized mAbs can deliver a costimulatory signal that contributes to T cell activation. Our earlier studies revealed that cross-linking of CD26 induces its internalization, the phosphorylation of a number of proteins involved in the signaling pathway, and subsequent T cell proliferation. Although these findings suggest the importance of internalization in the function of CD26, CD26 has only 6 aa residues in its cytoplasmic region with no known motif for endocytosis. In the present study, we have identified the mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGFIIR) as a binding protein for CD26 and that mannose 6-phosphate (M6P) residues in the carbohydrate moiety of CD26 are critical for this binding. Activation of peripheral blood T cells results in the mannose 6 phosphorylation of CD26. In addition, the cross-linking of CD26 with an anti-CD26 antibody induces not only capping and internalization of CD26 but also colocalization of CD26 with M6P/IGFIIR. Finally, both internalization of CD26 and the T cell proliferative response induced by CD26-mediated costimulation were inhibited by the addition of M6P, but not by glucose 6-phosphate or mannose 1-phosphate. These results indicate that internalization of CD26 after cross-linking is mediated in part by M6P/IGFIIR and that the interaction between mannose 6-phosphorylated CD26 and M6P/IGFIIR may play an important role in CD26-mediated T cell costimulatory signaling.

Carbohydrate Metabolism↗

PubMed2000

Affinity partitioning of a poly(histidine)-tagged integral membrane protein, cytochrome bo3 ubiquinol oxidase, in a detergent--polymer aqueous two-phase system containing metal-chelating polymer.

A system has been developed for selective partitioning of membrane proteins. For the first time, an integral membrane protein, cytochrome bo3 ubiquinol oxidase from Escherichia coli, has been affinity partitioned in an aqueous two-phase system. The systems used were different detergent/polymer aqueous two-phase systems containing a metal-chelating polymer, such as poly(ethyleneglycol)-iminodiacetic acid-Cu(II) as well as dextran-iminodiacetic acid-Cu(II). Many non-ionic detergents, such as alkyl(polyethyleneoxide) (CmEOn), Triton, Tween and alkylglucosides, form two-phase systems in mixture with polymers, such as dextran and poly(ethyleneglycol), i.e., a micelle-enriched phase in equilibrium with a polymer-enriched phase are formed. In general, membrane proteins partition strongly to the micelle phase. We show that it is possible to selectively partition a poly(histidine)-tagged integral membrane protein into the polymer phase by metal affinity partitioning, with a shift in the partitioning coefficient from 0.015 to 4.8 (300-fold). The affinity partitioning was characterized and the effects of ligand concentration, pH, time, salts, buffer type, imidazole and charged detergent are discussed. Thus, a fast and mild affinity procedure for the purification of integral membrane proteins can be developed in affinity detergent/polymer aqueous two-phase systems, and the method is especially suitable for the purification of labile integral membrane proteins, such as receptors.

Chelating Agents↗

PubMed2000

Novel in vitro effects of bucillamine: inhibitory effects on proinflammatory cytokine production and transendothelial migration of T cells.

OBJECTIVE: To investigate the novel antiinflammatory mechanism of a disease-modifying antirheumatic drug, bucillamine, on activated T cells, specifically its effect on T cell proliferation, cytokine production, and migration of T cells. METHODS: T cells were cultured in wells coated with anti-CD3 monoclonal antibodies (mAb) plus anti-CD26 mAb or anti-CD3 plus anti-CD28 mAb, with or without bucillamine. Proliferative responses and the production of interleukin-2 (IL-2), interferon-gamma (IFNgamma), tumor necrosis factor alpha (TNFalpha), IL-6, IL-4, and IL-5 were measured under these costimulatory conditions. Phytohemagglutinin (PHA)-activated T cells were cultured on human umbilical vein endothelial cell-coated transwells in the presence or absence of bucillamine, and T cells migrating through the endothelial cell layer were counted. Immunofluorescence analysis was also performed to analyze the effect of bucillamine on the surface expression of adhesion molecules on T cells. RESULTS: Bucillamine (64 microM) significantly inhibited T cell proliferation and the production of IL-2, IFNgamma, TNFalpha, and IL-6, whereas it had no inhibitory effects on the production of IL-4 and IL-5 in the cultures with anti-CD3 plus anti-CD26 mAb. In contrast, bucillamine had no effects on T cell proliferation or any cytokine production in the cultures with anti-CD3 plus anti-CD28 mAb. Furthermore, the same concentration of bucillamine inhibited transendothelial migration of PHA-activated T cells, and reduced the expression level of CD44 on T cells. CONCLUSION: This study demonstrated the novel effects of bucillamine in vitro, showing inhibition of type 1 T helper-type cytokine production and proinflammatory cytokine production induced by certain costimulatory conditions, and inhibition of transendothelial migration of T cells. The inhibition of T cell migration appeared to be mediated partly through the reduced expression of CD44, an adhesion molecule on the T cell surface.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

The metabolic rate and vulnerability of dopaminergic neurons, and adenosine dynamics in the cerebral cortex, nucleus accumbens, caudate nucleus, and putamen of the common marmoset.

The pathophysiology of the striatum and cerebral cortex were studied from the pharmacological aspect. Investigation of the dopamine content in the cerebral cortex revealed that the premotor and motor area showed the highest level (61+/-6.2 ng/g). Intravenous injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at a dose of 10 mg/kg reduced the dopamine content in the caudate nucleus and putamen to 2-3% of the control level in common marmosets, while it fell to 60% in the nucleus accumbens. There was no alteration of the dopamine content in the cerebral cortex. Immunohistochemical staining for tyrosine hydroxylase in the midbrains of MPTP-treated marmosets showed almost complete disappearance of dopaminergic cells from the substantia nigra and good preservation of cells in the ventrotegmental area. Dopaminergic cells projecting to the caudate/putamen, nucleus accumbens, and cerebral cortex showed marked, moderate, and no vulnerability to MPTP, respectively. After systemic administration of MPTP, dopaminergic neurons projecting to the caudate nucleus and putamen were damaged equally. However, the compensatory increase of dopamine turnover was more prominent in the putamen than in the caudate nucleus. Thus, nigroputaminal dopaminergic neurons may have a higher level of activity than neurons in the caudate. The neural connections and functions of the caudate nucleus and putamen have already been differentiated anatomically or physiologically. This compensatory increase of the dopamine turnover rate is another aspect of functional differences between the caudate nucleus and putamen. Investigation of the dopamine content in the head, body, and tail of the caudate nucleus showed no differences in the concentration of dopamine. However, a study of the metabolic rate of dopamine using alpha-methyl-p-tyrosine, a tyrosine hydoxylase inhibitor, showed higher metabolism of dopamine in the head of the caudate nucleus in common marmosets. Thus, dopaminergic neurons projecting to the caudate nucleus may show topographical differences in their firing rates. A microdialysis study indicated an increase in the metabolism of adenosine in the striatum of MPTP-treated animals. Cholinergic neurons are interneurons and are one of the main sources of adenosine in the striatum. Dopaminergic input from the substantia nigra acting on cholinergic neurons was decreased following MPTP treatment. The increase of adenosine metabolism suggested that cholinergic neurons in the striatum receive inhibitory inputs from nigrostriatal dopaminergic neurons.

Adenosine↗

PubMed2000

Beta 1-integrin-mediated cell signaling in T lymphocytes.

beta1-integrins play crucial roles in a variety of cell processes such as adhesion, migration, proliferation, and differentiation of lymphocytes. For understanding the molecular mechanisms of these various biological effects, it may be particularly important to analyze cell signaling through the beta1-integrins. Our previous study had shown that PLC-gamma, pp125FAK (focal adhesion kinase), pp105, paxillin, p59fyn, p56lck and ERK1/2 are phosphorylated in their tyrosine residues upon engagement of beta1-integrins. We identified pp105 as Cas (Crk-associated substrate)-related protein and successfully cloned its cDNA. pp105 is a Cas homologue predominantly expressed in the cells of lymphoid lineage, which led us to designate it as Cas-L. Like p130Cas, Cas-L contains a single SH3 domain and multiple SH2 binding sites (YXXP motif), which is suggested to bind SH2 domains of Crk, Nck, and SHPTP2. Subsequent studies revealed that pp125FAK binds Cas-L on its SH3 domain and phosphorylates its tyrosine residues upon beta1-integrin stimulation. Since Cas-L is preferentially expressed in lymphocytes, it is conceivable that Cas-L plays an important role in lymphocyte-specific signals. We have shown that Cas-L is involved in the T-cell receptor (TCR)/CD3 signaling pathway as well as the beta1-integrin signaling pathway. Cas-L is transiently phosphorylated following CD3 cross-linking, and tyrosine-phosphorylated Cas-L binds to Crk and C3G. Furthermore, a Cas-L mutant (Cas-LDeltaSH3), which lacks the binding site for FAK, is still tyrosine-phosphorylated upon CD3 cross-linking, but not upon beta1-integrin cross-linking, suggesting that FAK is not involved in CD3-dependent Cas-L phosphorylation. Finally, we have identified a crucial role of Cas-L in beta1-integrin-mediated T-cell co-stimulation. beta1-integrins have known to provide a co-stimulus for TCR/CD3-driven interleukin-2 production and proliferation of peripheral T-cells. We have found that this co-stimulatory pathway is impaired in the Jurkat T-cell line, and that the expression level of Cas-L is reduced in Jurkat cells compared with peripheral T-cells. The transfection of Cas-L cDNA into Jurkat cells restored the beta1-integrin-mediated co-stimulation, while the transfection of Cas-LDeltaSH3 mutant failed to do so, showing a contrast to the case with CD3-mediated signaling. These results indicate that Cas-L plays a key role through the association and phosphorylation by FAK in the beta1-integrin-mediated T-cell co-stimulation. Taken together, Cas-L might be the bi-modal docking protein that assembles the signals through beta1-integrins and TCR/CD3, and participates in a variety of T-cell functions.

Animals↗

PubMed2000

The structure of the ubiquinol oxidase from Escherichia coli and its ubiquinone binding site.

Cell respiration is catalyzed by the heme-copper oxidase superfamily of enzymes, which comprises cytochrome c and ubiquinol oxidases. These membrane proteins utilize different electron donors through dissimilar access mechanisms. We report here the first structure of a ubiquinol oxidase, cytochrome bo3, from Escherichia coli. The overall structure of the enzyme is similar to those of cytochrome c oxidases; however, the membrane-spanning region of subunit I contains a cluster of polar residues exposed to the interior of the lipid bilayer that is not present in the cytochrome c oxidase. Mutagenesis studies on these residues strongly suggest that this region forms a quinone binding site. A sequence comparison of this region with known quinone binding sites in other membrane proteins shows remarkable similarities. In light of these findings we suggest specific roles for these polar residues in electron and proton transfer in ubiquinol oxidase.

Amino Acid Sequence↗

PubMed2000

Endoscope-assisted microsurgery for cerebral aneurysms.

We performed endoscope-assisted microsurgery for 64 patients with cerebral aneurysms from June 1998 to January 1999. Two patients were treated under picture-in-picture imaging using a surgical microscope connected with an endoscopic-image display system. The study included 34 patients with incidental discovery: 3 IC oph, aneurysm, 1 from cavernous (C3) portion, 8 at ICPC, 1 from infundibular dilatation, 2 at IC bifurcation, 6 at AcoA, 1 at A1A2, 8 at MCA, 1 at P1, 1 from basilar tip, 1 at AICA, 1 at VA and 1 from PICA. The study also included 30 patients with subarachnoid hemorrhage: 5 ICPC, 2 from anterior choroidal, 1 from IC infundibular dilatation, 10 from AcoA, 2 from A2A3, 7 from MCA, 2 from basilar tip and 1 from PICA. They were classified into gr. 1 for 2, gr. 2 for 8, gr. 3 for 10, gr. 4 for 7, and gr. 5 for 3 cases.

Carotid Artery Diseases↗

PubMed2000

Nitric oxide induces a decrease in the mitochondrial membrane potential of peripheral blood lymphocytes, especially in natural killer cells.

Increased levels of nitric oxide (NO) at an inflammatory site may affect the biological activity of lymphoid cells. To investigate the effects of NO on the immune system, we measured the mitochondrial membrane potential (delta psi m) of the peripheral blood lymphocytes (PBL) cultured with a chemical NO donor. PBL from healthy volunteers were cultured with NOC18, a NO-generating compound, at various concentrations. The delta psi m of the PBL was measured by flow-cytometry using 3,3-dihexyloxacarbocyanine iodide (DiOC6(3)). NOC18 induced a decrease in the delta psi m of the PBL in a dose-dependent fashion, induced an increase in the levels of reactive oxygen species (ROS), and caused these cells to undergo apoptosis. Dual-color staining of the delta psi m and lymphocyte surface markers demonstrated that CD3-CD56+ natural killer (NK) cells were responsive to NO. Trolox, a vitamin E analog, partially reversed the NO-induced decrease in the delta psi m of the PBL. We showed that the delta psi m of peripheral NK cells were decreased by NO, which suggests that abundant NO at an inflammatory site may impair NK cell function.

Antioxidants↗

PubMed2000

Secretion of thioredoxin enhances cellular resistance to cis-diamminedichloroplatinum (II).

Thioredoxin (TRX) is a redox-active protein induced by a variety of stress and secreted from cells. Collecting evidence revealed that extracellular TRX shows cytokine- and chemokine-like activities. In the present study, we studied the role of secreted TRX on cellular resistance to cis-diamminedichloroplatinum (II) (CDDP). The CDDP-resistant variants of HeLa cells not only have enhanced expression of intracellular TRX, but also show increased secretion of TRX into the culture medium, compared to the parental cells. The CDDP-resistant cells also exhibit an enhanced L-cystine uptake capability, which results in a significant increase in the intracellular sulfhydryl content, including glutathione (GSH). Exogenous administration of recombinant TRX (rTRX) increases cellular resistance to CDDP and augments the L-cystine uptake in the parental HeLa cells. Moreover, depletion of L-cystine from the culture medium or combined treatment with L-cystine uptake inhibitors increases cellular sensitivity to CDDP in the CDDP-resistant cells. These findings suggest that secreted TRX may play an important role in the acquisition of cellular CDDP resistance through enhancement of the L-cystine uptake activity, and that the L-cystine transport system, as well as the TRX system, may be a novel therapeutic target in CDDP-resistant cancer cells.

Biological Transport, Active↗