Hepatic GSTZ1 Expression in Pregnant Ewes and Their Offspring: Influence of Treatment with Dichloroacetate

Abstract

Dichloroacetate (DCA) is an investigational drug that can stimulate mitochondrial energy metabolism by inhibiting pyruvate dehydrogenase kinase. We hypothesize that DCA could be used in high‐risk pregnancy to reduce perinatal mitochondrial deficiency and resulting cardiac dysfunction in at‐risk fetuses and are testing this postulate in a pregnant sheep model. DCA is metabolized by the enzyme glutathione transferase zeta1 (GSTZ1) to glyoxylate. GSTZ1 is not expressed in human fetal liver, but expression rises after birth. Furthermore, DCA inactivates GSTZ1, resulting in altered pharmacokinetics with repeated dosing. The objectives of this research were (1) to investigate the relative expression of GSTZ1 in maternal and fetal sheep liver from untreated controls close to full term (140 days gestation) and (2) to determine if treatment of sheep with DCA resulted in reduced expression of GSTZ1. We administered DCA intravenously to either the ewe or the fetus at daily divided doses of 25 mg/kg for three to five days prior to sacrifice 24 h after the last dose. We used samples of maternal and fetal liver to prepare cytosol and mitochondria and employed a custom‐made polyclonal antibody to rat GSTZ1 to measure expression relative to a single rat hepatic cytosol standard by Western blot. The sheep liver samples exhibited good cross‐reactivity to the rat antibody. Surprisingly, expression of GSTZ1 in the full‐term fetal liver cytosol fractions from controls was similar to that in the control maternal liver. Treatment with DCA resulted in reduced expression in both maternal and fetal liver cytosol fractions to less than 10% of the control values. In control fetuses, mitochondrial expression of GSTZ1 was 17.6 ± 7.6% of the cytosolic expression. In the DCA‐treated group, mitochondrial expression decreased and levels were undetectable in one‐half of the fetal sheep. These studies demonstrate that (1) GSTZ1 expression in liver cytosol and mitochondria in the late fetal period varies with animal species and (2) repeated treatment with DCA results in reduced GSTZ1 expression, which is likely to alter DCA pharmacokinetics.Support or Funding InformationSupported in part by the US Public Health Service, grant R21HD91599This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.