Interactions of Glutathione S-Transferase-Pi with Ethacrynic Acid and Its Glutathione Conjugate

Details

• Personal Author:
  Ahmad F ; Ahmad H ; Ansari GAS ; Awasthi S ; Srivastava SK
• Description:
  Ethacrynic acid, a diuretic drug known to be an inhibitor of glutathione S-transferases (GSTs), has been shown to enhance the cytotoxicity of the alkylating agent class of chemotherapeutic drugs in cultured cancer cells resistant to alkylating agents. This action of ethacrynic acid is presumably mediated by inhibition of GSTs which are implicated in detoxification of alkylating agents. In addition to being an inhibitor of GSTs, ethacrynic acid also interacts with GSTs as a substrate for conjugation with GSH to yield an ethacrynic acid-GSH conjugate. This conjugate is formed both enzymatically and non-enzymatically and itself is a GST inhibitor. Since ethacrynic acid-GSH conjugate is itself likely to be able to mediate reversal of alkylating agents through GST inhibition, we have synthesized and purified the ethacrynic acid-GSH conjugate, studied the kinetics of inhibition of human lung p-class GST by ethacrynic acid and the conjugate, and compared the kinetics of the enzymatic and non-enzymatic formation of the conjugate using an HPLC method. Results of our studies showed that the ethacrynic acid-GSH conjugate was a more potent inhibitor of human lung GST-p than ethacrynic acid (Ki = 1.5 vs. 11.5 uM, respectively) and that their mechanisms for GST inhibition were distinct (competitive and non-competitive, respectively). Comparison of enzymatic and non-enzymatic rates of conjugate formation in vitro indicated that GST-y catalyzed a rapid conjugation of ethacrynic acid with GSH at a concentration of ethacrynic acid an order of magnitude above that required to nearly completely inhibit GST catalyzed conjugation of 1-chloro-2,4-dinitrobenzene. However, because of the rapid non-enzymatic reaction, and the inhibition of GST-p with the accumulation of the conjugate in the reaction mixture, the overall quantity of the conjugate formed after 150 min was nearly identical in the presence or absence of GST-p. Results of these studies suggest that inhibition of GSTs by ethacrynic acid-GSH conjugate may be the main mechanism through which ethacrynic acid reverses alkylating agent resistance. [Description provided by NIOSH]
• Subjects:
  Cytotoxins Enzymes Neoplasms Occupational Health Safety
• Keywords:
  Author Keywords: Ethacrynic Acid Chemotherapy Conjugate Cytotoxicity Enzymatic Effects Enzyme Complexes Enzyme Inhibition Glutathione Glutathione S-transferase
• ISSN:
  0006-3002
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  OSHA Region 6 ; Texas
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  173-178
• Volume:
  1164
• Issue:
  2
• NIOSHTIC Number:
  nn:20056723
• Citation:
  Biochim Biophys Acta 1993 Jul; 1164(2):173-178
• Contact Point Address:
  S. Awasthi, Division of Hematology and Oncology, 4.164 Old John Sealy, Route E-65, University of Texas Medical Branch Galveston, TX 77555-0565, USA
• CAS Registry Number:
  Glutathione (CAS RN 70-18-8)
• Federal Fiscal Year:
  1993
• Performing Organization:
  University of Texas Medical Branch, Galveston, Texas
• Peer Reviewed:
  True
• Start Date:
  19860101
• Source Full Name:
  Biochimica et Biophysica Acta
• End Date:
  19960630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:7d498acebc250330015d8ab9c43e1a32cbfa695f8ffa314ff00d8b2c07d340e6f986cc2d32134ed47e7c80642c5ceab1d001d4a7cbcdfd603c2d84cb1d3c4a7d
• Download URL:
  https://stacks.cdc.gov/view/cdc/214275/cdc_214275_DS1.pdf
• File Type:
  [PDF - 570.15 KB ]