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30, No. 1, 2012
Issue release date: June 2012
Cell Physiol Biochem 2012;30:33-48
(DOI:10.1159/000339047)

Inhibition of Na+-K+-2Cl Cotransporter isoform 1 Accelerates Temozolomidemediated Apoptosis in Glioblastoma Cancer Cells

Algharabil J.2 · Kintner D.B.2 · Wang Q.3 · Begum G.1 · Clark P.A.2 · Yang S.-S.4 · Lin S.-H.4 · Kahle K.T.5 · Kuo J.S.2 · Sun D.1,2
1Dept. of Neurology, Univ. of Pittsburgh, Pittsburgh, PA; 2Dept. of Neurosurgery, 3Cellular and Molecular Pathology Training Program, Univ. of Wisconsin School of Medicine and Public Health, Madison; 4Division of Nephrology, Dept. of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan; 5Dept. of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
email Corresponding Author

Abstract

The hallmark of apoptosis is a significant reduction in cell volume (AVD) resulting from loss of K+i and Cl-i. Loss of cell volume and lowering of ionic strength of intracellular K+ and Cl-occur before any other detectable characteristics of apoptosis. In the present study, temozolomide (TMZ) triggered loss of K+i and Cli and AVD in primary glioblastoma multiforme (GBM) cancer cells (GC) and GC cancer stem cells (GSC). We hypothesize that Na+-K+-2Clcotransporter isoform 1 (NKCC1) counteracts AVD during apoptosis in GBM cancer cells by regulating cell volume and Cl-homeostasis. NKCC1 protein was expressed in both GC and GSC and played an essential role in regulatory volume increase (RVI) in response to hypertonic cell shrinkage and isotonic cell shrinkage. Blocking NKCC1 activity with its potent inhibitor bumetanide abolished RVI. These cells maintained a basal [Cl]i ( ∼ 68 mM) above the electrochemical equilibrium for Cli. NKCC1 also functioned to replenish Cli levels following the loss of Cli. TMZ-treated cells exhibited increased phosphorylation of NKCC1 and its up-stream novel Cl/volume-sensitive regulatory kinase WNK1. Inhibition of NKCC1 activity with bumetanide accelerated AVD, early apoptosis, as well as activation of caspase-3 and caspase-8. Taken together, this study strongly suggests that NKCC1 is an essential mechanism in GBM cells to maintain K+, Cl, and volume homeostasis to counteract TMZ-induced loss of K+, Cl and AVD. Therefore, blocking NKCC1 function augments TMZ-induced apoptosis in glioma cells.


 Outline


 goto top of outline Key Words

  • Glioblastoma multiforme
  • Apoptosis
  • Caspase
  • Apoptotic volume decrease
  • Temozolomide
  • Bumetanide

 goto top of outline Abstract

The hallmark of apoptosis is a significant reduction in cell volume (AVD) resulting from loss of K+i and Cl-i. Loss of cell volume and lowering of ionic strength of intracellular K+ and Cl-occur before any other detectable characteristics of apoptosis. In the present study, temozolomide (TMZ) triggered loss of K+i and Cli and AVD in primary glioblastoma multiforme (GBM) cancer cells (GC) and GC cancer stem cells (GSC). We hypothesize that Na+-K+-2Clcotransporter isoform 1 (NKCC1) counteracts AVD during apoptosis in GBM cancer cells by regulating cell volume and Cl-homeostasis. NKCC1 protein was expressed in both GC and GSC and played an essential role in regulatory volume increase (RVI) in response to hypertonic cell shrinkage and isotonic cell shrinkage. Blocking NKCC1 activity with its potent inhibitor bumetanide abolished RVI. These cells maintained a basal [Cl]i ( ∼ 68 mM) above the electrochemical equilibrium for Cli. NKCC1 also functioned to replenish Cli levels following the loss of Cli. TMZ-treated cells exhibited increased phosphorylation of NKCC1 and its up-stream novel Cl/volume-sensitive regulatory kinase WNK1. Inhibition of NKCC1 activity with bumetanide accelerated AVD, early apoptosis, as well as activation of caspase-3 and caspase-8. Taken together, this study strongly suggests that NKCC1 is an essential mechanism in GBM cells to maintain K+, Cl, and volume homeostasis to counteract TMZ-induced loss of K+, Cl and AVD. Therefore, blocking NKCC1 function augments TMZ-induced apoptosis in glioma cells.

Copyright © 2012 S. Karger AG, Basel


 goto top of outline Author Contacts

Dandan Sun, M.D., Ph.D., Department of Neurology University of Pittsburgh Medical School, S-598 South Biomedical Science Tower (BST) 3500 Terrace St. Pittsburgh PA 15213 (USA), Tel. (412) 624-0418, Fax: (412) 648-3321, E-Mail sund@upmc.edu


 goto top of outline Article Information

Accepted: April 24, 2012
Published online: June 08, 2012
Number of Print Pages : 16


 goto top of outline Publication Details

Cellular Physiology and Biochemistry (International Journal of Experimental Cellular Physiology, Biochemistry and Pharmacology)

Vol. 30, No. 1, Year 2012 (Cover Date: June 2012)

Journal Editor: Guggino W. (Baltimore, Md.), Lang F. (Tübingen)
ISSN: 1015-8987 (Print), eISSN: 1421-9778 (Online)

For additional information: http://www.karger.com/CPB


Copyright / Drug Dosage / Disclaimer

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
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 goverment 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.

Abstract

The hallmark of apoptosis is a significant reduction in cell volume (AVD) resulting from loss of K+i and Cl-i. Loss of cell volume and lowering of ionic strength of intracellular K+ and Cl-occur before any other detectable characteristics of apoptosis. In the present study, temozolomide (TMZ) triggered loss of K+i and Cli and AVD in primary glioblastoma multiforme (GBM) cancer cells (GC) and GC cancer stem cells (GSC). We hypothesize that Na+-K+-2Clcotransporter isoform 1 (NKCC1) counteracts AVD during apoptosis in GBM cancer cells by regulating cell volume and Cl-homeostasis. NKCC1 protein was expressed in both GC and GSC and played an essential role in regulatory volume increase (RVI) in response to hypertonic cell shrinkage and isotonic cell shrinkage. Blocking NKCC1 activity with its potent inhibitor bumetanide abolished RVI. These cells maintained a basal [Cl]i ( ∼ 68 mM) above the electrochemical equilibrium for Cli. NKCC1 also functioned to replenish Cli levels following the loss of Cli. TMZ-treated cells exhibited increased phosphorylation of NKCC1 and its up-stream novel Cl/volume-sensitive regulatory kinase WNK1. Inhibition of NKCC1 activity with bumetanide accelerated AVD, early apoptosis, as well as activation of caspase-3 and caspase-8. Taken together, this study strongly suggests that NKCC1 is an essential mechanism in GBM cells to maintain K+, Cl, and volume homeostasis to counteract TMZ-induced loss of K+, Cl and AVD. Therefore, blocking NKCC1 function augments TMZ-induced apoptosis in glioma cells.



 goto top of outline Author Contacts

Dandan Sun, M.D., Ph.D., Department of Neurology University of Pittsburgh Medical School, S-598 South Biomedical Science Tower (BST) 3500 Terrace St. Pittsburgh PA 15213 (USA), Tel. (412) 624-0418, Fax: (412) 648-3321, E-Mail sund@upmc.edu


 goto top of outline Article Information

Accepted: April 24, 2012
Published online: June 08, 2012
Number of Print Pages : 16


 goto top of outline Publication Details

Cellular Physiology and Biochemistry (International Journal of Experimental Cellular Physiology, Biochemistry and Pharmacology)

Vol. 30, No. 1, Year 2012 (Cover Date: June 2012)

Journal Editor: Guggino W. (Baltimore, Md.), Lang F. (Tübingen)
ISSN: 1015-8987 (Print), eISSN: 1421-9778 (Online)

For additional information: http://www.karger.com/CPB


Copyright / Drug Dosage

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
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 goverment 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.