RT Journal Article SR Electronic T1 Exposure of Rats to Multiple Oral Doses of Dichloroacetate Results in Upregulation of Hepatic GSTs and NQO1 JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP DMD-AR-2020-000143 DO 10.1124/dmd.120.000143 A1 Edwin J. Squirewell A1 Ricky Mareus A1 Lloyd P. Horne A1 Peter W. Stacpoole A1 Margaret O. James YR 2020 UL http://dmd.aspetjournals.org/content/early/2020/08/31/dmd.120.000143.abstract AB Dichloroacetate is an investigational drug that is used in the treatment of various congenital and acquired disorders of energy metabolism. Although DCA is generally well-tolerated, some patients experience peripheral neuropathy, a side effect more common in adults than children. Repetitive DCA dosing causes downregulation of its metabolizing enzyme, GSTZ1, which is also critical in the detoxification of maleylacetoacetate and maleylacetone. GSTZ1 (-/-) knockout mice show upregulation of GSTs and antioxidant enzymes as well as an increase in GSSG:GSH, suggesting GSTZ1 deficiency causes oxidative stress. We hypothesized that DCA-mediated depletion of GSTZ1 causes oxidative stress and used the rat to examine induction of GSTs and antioxidant enzymes after repeated DCA exposure. We determined the expression of A, M, P, and O-class GSTs, NAD(P)H quinone dehydrogenase 1 (NQO1), gamma-glutamylcysteine ligase complex (GCLC), and glutathione synthetase (GSS). GSH and GSSG levels were measured by LC/MS/MS. Enzyme activity was measured in hepatic cytosol using 1-chloro-2,4-dinitrobenzene (CDNB), 1,2-dichloro-4-nitrobenzene (DCNB), and 2,6-dichloroindophenol (DCPIP) as substrates. In comparison to acetate-treated controls, DCA dosing increased the relative expression of GSTA1/A2 irrespective of rodent age, whereas only adults displayed higher levels of GSTM1 and GSTO1. NQO1 expression and activity were higher in juveniles after DCA dosing. GSH concentrations were increased by DCA in adults but the GSH:GSSG ratio was not changed. Levels of GCLC and GSS were higher and lower, respectively, in adults treated with DCA. We conclude that DCA-mediated depletion of GSTZ1 causes oxidative stress and promotes the induction of antioxidant enzymes that may vary between age groups. Significance Statement Treatment with the investigational drug, DCA, results in loss of GSTZ1 and subsequent increases in body burden of the electrophilic tyrosine metabolites, maleylacetoacetate and maleylacetone. Loss of GSTZ1 in genetically-modified mice is associated with induction of GSTs and alteration of the GSSG:GSH ratio. Therefore, we determined whether pharmacological depletion of GSTZ1 through repeat administration of DCA produced similar changes in the liver, which could affect responses to other drugs and toxicants.