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      Down-Regulation of Renal Klotho Expression by Shiga Toxin 2

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          Abstract

          Background/Aims: Shiga toxin 2 may trigger classical hemolytic uremic syndrome (HUS) eventually leading to renal failure. Klotho, a transmembrane protein, protease and hormone mainly expressed in kidney is involved in the regulation of renal phosphate excretion and also retains renal protective effects. Renal failure is associated with renal depletion of klotho. The present study explored the influence of Shiga toxin 2 on renal klotho expression. Methods: Mice were injected with either solvent or Shiga toxin 2 and urinary flow rate and phosphate excretion were determined in metabolic cages. Renal transcript levels were measured by quantitative RT-PCR and renal protein abundance by Western blotting. Plasma concentrations of 1,25(OH)<sub>2</sub>D<sub>3</sub> and FGF23 were determined by ELISA and plasma phosphate and urea concentrations by photometry. Results: Shiga toxin 2 treatment was followed by increase of plasma urea concentration, urinary flow rate and renal phosphate excretion but not of plasma phosphate concentration. Shiga toxin 2 treatment strongly decreased klotho mRNA expression and klotho protein abundance in renal tissue. Shiga toxin 2 treatment further increased tumor necrosis factor ( TnfE) mRNA levels, as well as protein abundance of phosphorylated p38 MAPK in renal tissue. The treatment significantly increased renal Cyp27b1 and decreased renal Cyp24a1 mRNA levels without significantly altering plasma 1,25(OH)<sub>2</sub>D<sub>3</sub> levels. Shiga toxin 2 treatment was further followed by increase of plasma FGF23 concentrations . Conclusion: Shiga toxin 2 treatment stimulated TnfE transcription, down-regulated renal klotho expression and increased FGF23 formation, effects presumably contributing to renal tissue injury. i 2015 S. Karger AG, Basel

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          Most cited references 43

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          Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome.

          Most cases of diarrhoea-associated haemolytic uraemic syndrome (HUS) are caused by Shiga-toxin-producing bacteria; the pathophysiology differs from that of thrombotic thrombocytopenic purpura. Among Shiga-toxin-producing Escherichia coli (STEC), O157:H7 has the strongest association worldwide with HUS. Many different vehicles, in addition to the commonly suspected ground (minced) beef, can transmit this pathogen to people. Antibiotics, antimotility agents, narcotics, and non-steroidal anti-inflammatory drugs should not be given to acutely infected patients, and we advise hospital admission and administration of intravenous fluids. Management of HUS remains supportive; there are no specific therapies to ameliorate the course. The vascular injury leading to HUS is likely to be well under way by the time infected patients seek medical attention for diarrhoea. The best way to prevent HUS is to prevent primary infection with Shiga-toxin-producing bacteria.
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            Klotho deficiency causes vascular calcification in chronic kidney disease.

            Soft-tissue calcification is a prominent feature in both chronic kidney disease (CKD) and experimental Klotho deficiency, but whether Klotho deficiency is responsible for the calcification in CKD is unknown. Here, wild-type mice with CKD had very low renal, plasma, and urinary levels of Klotho. In humans, we observed a graded reduction in urinary Klotho starting at an early stage of CKD and progressing with loss of renal function. Despite induction of CKD, transgenic mice that overexpressed Klotho had preserved levels of Klotho, enhanced phosphaturia, better renal function, and much less calcification compared with wild-type mice with CKD. Conversely, Klotho-haploinsufficient mice with CKD had undetectable levels of Klotho, worse renal function, and severe calcification. The beneficial effect of Klotho on vascular calcification was a result of more than its effect on renal function and phosphatemia, suggesting a direct effect of Klotho on the vasculature. In vitro, Klotho suppressed Na(+)-dependent uptake of phosphate and mineralization induced by high phosphate and preserved differentiation in vascular smooth muscle cells. In summary, Klotho is an early biomarker for CKD, and Klotho deficiency contributes to soft-tissue calcification in CKD. Klotho ameliorates vascular calcification by enhancing phosphaturia, preserving glomerular filtration, and directly inhibiting phosphate uptake by vascular smooth muscle. Replacement of Klotho may have therapeutic potential for CKD.
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              Secreted Klotho protein in sera and CSF: implication for post-translational cleavage in release of Klotho protein from cell membrane.

              Klotho mutant mice exhibit a set of phenotypes resembling human ageing. Although the function of Klotho remains unclear, mediation of its pleiotropic functions by putative humoral factor(s) has been presumed. Newly established antibodies against Klotho allowed the detection of secreted Klotho, a candidate for the putative humoral factor, in sera and cerebrospinal fluid. Surprisingly the secreted Klotho was 130 kDa, in contrast to the 70 kDa predicted form from klotho gene transcripts. The secreted as well as the membrane-bound Klotho proteins were suggested to form oligomerized complex. These results delineate post-translation processing of Klotho and possible regulatory mechanisms for secretion of Klotho in vivo.
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                Author and article information

                Journal
                KBR
                Kidney Blood Press Res
                10.1159/issn.1420-4096
                Kidney and Blood Pressure Research
                S. Karger AG
                1420-4096
                1423-0143
                2014
                December 2014
                19 November 2014
                : 39
                : 5
                : 441-449
                Affiliations
                aDepartment of Physiology, University of TRbingen, TRbingen; bDepartment of Dermatology, University Medical Center Mannheim, Ruprecht-Karls-University of Heidelberg, Mannheim; cDepartment of Immunogenetics, German Cancer Research Center, Heidelberg, Germany
                Author notes
                *Prof. Dr. Florian Lang, Physiologisches Institut, Universit(t TRbingen, Gmelinstr. 5, D-72076 TRbingen (Germany), Tel. +49 7071 29 72194, Fax +49 7071 29 5618, E-Mail florian.lang@uni-tuebingen.de
                Article
                368457 Kidney Blood Press Res 2014;39:441-449
                10.1159/000368457
                25471359
                © 2015 S. Karger AG, Basel

                Open Access License: This is an Open Access article licensed under the terms of the Creative Commons Attribution-NonCommercial 3.0 Unported license (CC BY-NC) ( http://www.karger.com/OA-license), applicable to the online version of the article only. Distribution permitted for non-commercial purposes only. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Pages: 9
                Categories
                Original Paper

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