Rintarou Moriguchi

Tumor Necrosis Factor-α–Induced Iron Sequestration and Oxidative Stress in Human Endothelial Cells

Objective—Tumor necrosis factor (TNF)-&agr;–induced endothelial injury, which is associated with atherosclerosis, is mediated by intracellular reactive oxygen species. Iron is essential for the amplification of oxidative stress. We tested whether TNF-&agr; accelerated iron accumulation in vascular endothelium, favoring synthesis of hydroxyl radical. Methods and Results—Diverse iron transporters, including iron import proteins (transferrin receptor [TfR] and divalent metal transporter 1 [DMT1]) and an iron export protein (ferroportin 1 [FP1]) coexist in human umbilical endothelial cells (HUVECs). TNF-&agr; caused upregulation of TfR and DMT1 and downregulation of FP1, which were demonstrated in mRNA as well as protein levels. These changes in iron transporters were accompanied by accumulation of iron that was both transferrin-dependent and transferrin-independent. Modifications of these mRNAs were regulated post-transcriptionally, and were coordinated with activation of binding activity of iron regulatory protein 1 to the iron responsive element on transporter mRNAs. Using a salicylate trap method, we observed that only simultaneous exposure of endothelial cells to iron and TNF-&agr; accelerated hydroxyl radical production. Conclusions—TNF-&agr; could cause intracellular iron sequestration, which may participate importantly in the pathophysiology of atherosclerosis and cardiovascular disease.

An outbreak of fulminant hepatitis B in immunocompromised hemodialysis patients

BackgroundWe aimed to clarify the pathogenesis of an outbreak of fulminant hepatitis B in hemodialysis (HD) patients whose compromised cell-mediated immunity in turn contributed to chronic hepatitis B virus (HBV) carriage.MethodsFive consecutive adult HD patients with acute hepatitis B were evaluated. Viral genotype, mutations, and HBV-DNA levels were studied in relation to viral clearance, liver disease severity, and liver histology by immunostaining.ResultsAll five patients had hepatitis B surface antigen (HBsAg) genotype C, a G-to-A stop codon mutation at nucleotide (nt) 1896 in the precore region, an A-to-T mutation at nt 1762 and an G-to-A mutation at nt 1764 in the basal core promoter. The possible index patient, who suffered from liver cirrhosis, had HBsAg genotype C, anti-hepatitis B envelope (HBe), and these mutations. The level of HBV-DNA declined by about 10 percent per week and no difference in viral kinetics between the patients who died and the survivor was found, irrespective of therapies. The amount of liver cell apoptosis, as assessed by single-stranded DNA, was scarce. The risk of fulminant hepatic failure did not correlate with the preexistent liver histopathological changes. Acute HBV superinfection was associated with hepatitis C virus (HCV) elimination and increased mortality.ConclusionsThis outbreak of fulminant hepatitis B suggests that HD patients can foster highly virulent HBV strains (possibly owing to their compromised immune responses), which may place others at risk of severe, life-threatening acute liver damage and at increased risk of mortality if chronic carriers of HCV should be infected.

Comparison of Cytotoxicity of Cysteine and Homocysteine for Renal Epithelial Cells

Background: Although the cytotoxic effects of cysteine (Cys) on renal cells have been established, the effects of homocysteine (Hcy), which causes endothelial cell dysfunction, have not been well tested. We compared the direct toxicity of Hcy on renal tubular cells to that of Cys and examined the mechanism of cell toxicity. Methods: LLC-PK1 cells were incubated with test media containing 500 µM Cys or Hcy in the presence or absence of 100 µM copper. Lactate dehydrogenase release and thiobarbituric acid reactive substance were measured for estimating cytolysis and lipid peroxidation, respectively. The generation of hydrogen peroxide and hydroxyl radical, and the cell redox state were analyzed using the scopoletin method, salicylate-trap method, and glutathione (GSH) content, respectively. Superoxide dismutase, catalase, and vitamin E also were used for clarifying the mechanism of toxicity. Results: In the presence of copper (+ Cu), cytolysis at 16 h was more prominent in cells exposed to Cys than Hcy. In accordance with cytotoxicity, lipid peroxidation at 4 h of incubation, as well as hydrogen peroxide and hydroxyl radical formation in a shorter incubation, were remarkably greater in Cys + Cu than Hcy + Cu. The addition of Hcy, but not Cys, decreased GSH content significantly. Conclusion: In the presence of copper, Cys was extraordinarily more cytotoxic to renal cells than Hcy. Cytotoxicity from Hcy may be dependent upon depletion of cellular GSH, while Cys cytotoxicity is primarily dependent upon the generation of reactive oxygen species and lipid peroxidation.

High Levels of Tumor Necrosis Factor-α Downregulate Antimicrobial Iron Transport Protein, Nramp1, in Chronic Hemodialysis Patients: A Key Factor for Infection Risk

Background/Aims: The susceptibility of patients on maintenance hemodialysis (MHD) to infections is a major cause of mortality and morbidity. Natural resistance-associated macrophage protein 1 (Nramp1) regulates intracellular pathogen proliferation, and its mRNA expression is highest in polymorphonuclear leukocytes (PMNLs). The purpose of this study was to determine the level of Nramp1 in PMNLs from MHD patients and the factors affecting its expression. Methods: Twenty MHD patients and 24 healthy volunteers (controls) were recruited. Relative quantitative PCR was used to measure Nramp1 mRNA, and protein levels were semiquantified by means of real-time PCR and Western blot analysis or immunohistochemistry. The effect of tumor necrosis factor-α (TNF-α) or interleukin-6 (IL-6) on Nramp1 expression in PMNLs from controls was also examined. Results: Nramp1 mRNA and protein levels were substantially lower in PMNLs from MHD than control subjects. Serum TNF-α levels were significantly higher in the MHD group and were inversely correlated with Nramp1 mRNA levels. The addition of TNF-α to PMNLs from control subjects decreased mRNA and protein levels of Nramp1. IL-6 did not alter Nramp1 mRNA or protein expression. Conclusion: We found that Nramp1 was downregulated in the PMNLs of MHD patients, which constitute the first defense barrier against bacterial challenges. High levels of TNF-α may be associated with the downregulation of Nramp1. Our findings indicate that the susceptibility to infection observed in MHD patients could be partly due to the impairment of the intracellular handling of iron and the donation of more iron to the bacteria.

Deep venous thrombosis, myocardial infarction, and occlusion of vascular access associated with heparin-induced thrombocytopenia in a diabetic hemodialysis patient

We report a patient with diabetic endstage renal disease with an initial platelet count of 17.6 × 104/mm3 who developed type-II heparin-induced thrombocytopenia (HIT) during the induction period of hemodialysis (HD) when unfractionated heparin was used. Because the recognition of the condition and the treatment of this patient with HIT was unsatisfactory, she developed deep venous thrombosis, myocardial infarction, and occlusion of vascular access, at times of platelet counts of 4.1 × 104, 7.7 × 104, and 6.4 × 104/mm3, respectively, with antibodies to heparin/platelet factor 4 complex. Unfortunately, we misjudged in our belief that the thromboembolic events might be associated with an underlying procoagulant state in diabetic nephrotic syndrome, rather than being associated with the clinical picture of HIT. This case report suggests that the clinician must consider HIT in the differential diagnosis for thromboembolic complications during the induction period of HD, because unfractionated heparin is the major anticoagulant used in HD.

Role of Aldose Reductase in the Peritoneal Changes of Patients Undergoing Peritoneal Dialysis

Background/Aims: The mesothelium of patients undergoing peritoneal dialysis (PD) is exposed to glucose in dialysate. Glucose metabolites 3-deoxyglucosone and advanced glycation endproducts (AGEs) in the PD fluid induce peritoneal damage. Circulating factors also affect the peritoneum in the uremic model and predialysis patients. Aldose reductase (AR) generates precursors of 3-deoxyglucosone. We have reported AR acceleration in uremic patients. Therefore, AR acceleration might affect the peritoneum. The purpose of this study was to evaluate the AR level in PD patients and to determine the factors that change the peritoneum of these patients. Methods: We measured the PD effluent (eff-) concentration of cancer antigen 125 (CA125) as a marker of mesothelial viability in PD patients. Erythrocyte AR, eff-, and plasma (p-) concentrations of 3-deoxyglucosone, AGEs, and malondialdehyde were also studied in 30 PD patients, 18 patients undergoing hemodialysis, and 8 control subjects. Results: In the PD group, AR, p-3-deoxyglucosone, p-AGEs, and p-malondialdehyde were higher than in the control group. The predictors for eff-CA125 were not only PD duration and eff-3-deoxyglucosone, but also AR. Conclusion: AR was upregulated in PD patients. AR acceleration may affect the peritoneum in these patients. Further studies are needed to clarify the role of AR in PD patients.

Consultants for the American Journal of Nephrology 2007

Mario Cozzolino Farhard Danesh Robert Danziger John Daugirdas Katherine Dell Luca De Nicola Janice Douglas Thomas DuBose Carolyn Ecelbarger Allison Eddy Charles Edelstein Beatrice Edwards Belkıs Erbas Ronald Falk Ken Farrington Sahar Fathallah-Shaykh Murray Favus Leon Ferder Albert Ferro Michael Fischer Steven Fishbane Barry Freedman Gordon Freeman Elena Gagliardini C. Garlichs Fumitake Gejyo P. Gentilini Cheryl Gilmartin Richard Glassock Ehud Goldhammer David Goldsmith Stuart Goldstein Jennifer Gooch Laurence Greenbaum Dimitrios Grekas Hans Grosse-Wilde Mehmet Haberal Peter Hart Tomoko Hayashida Peter Heering Klaus Hocherl Radovan Hojs Susan Hou Priscilla How Reiko Inagi Ajay Israni Edwin Jackson Sara Jandeska Vanita Jassal Kevin Abbott Dale Abrahamson Adel Afifi Rajiv Agarwal Cu-Rie Ahn Maie Albader Farah Ali Ahsan Arozullah John Asplin Brad Astor Aslihan Avci Carla Avesani Mindy Banks Vinod Bansal Mary Barchman Amelia Bartholomew Amy Barton Pai David Basile F. Baud John Beltrame Carsten Bergmann Rajendra Bhimma Daniel Bichet Peter Blake Amy Bobrowski W. Kline Bolton Michael Braun Carolyn Brecklin Ellen Brooks Edward Brown Vito Campese Caterina Canavese Zemin Cao Lucio Cardoso Daniel Catanzaro Tak Mao Chan Rene Chang Julie Chao Monique Cho Yongwon Choi Nina Clark Steven Coca David Cohen Gabriel Contreras Mark Cooper Dominic Cosgrove Scott Cotler Adrian Covic Daniel Coyne