Overexpression of Cellular Glutathione Peroxidase Does Not Affect Expression of Plasma Glutathione Peroxidase or Phospholipid Hydroperoxide Glutathione Peroxidase in Mice Offered Diets Adequate or Deficient in Selenium

Abstract

Selenium-dependent cellular glutathione peroxidase (GPX1) overexpressing [GPX1(+)] mice were derived by microinjecting a 5.3-kb cloned entire mouse GPX1 genomic DNA into fertilized eggs. The objective of this study was to determine the effect of GPX1 overexpression and dietary selenium on the expression of selenoperoxidases and the status of lipid peroxidation of these transgenic animals. An experiment with a 2 × 2 factorial arrangement of treatments with 15 GPX1(+) and 15 control mice (2 mo old) was conducted for 8 wk. Ten mice of each group (half males and females) were fed a Se-deficient, Torula yeast basal diet (0.02 mg Se/kg, no supplemental vitamin E) and five mice (three males and two females) were fed the basal diet supplemented with 0.51 mg Se/kg as Na₂SeO₃. The GPX1(+) mice had greater GPX1 activities (one- to sixfold, P < 0.0001) than the control mice at both levels of dietary selenium in all tissues except for liver, in which such difference (100%, P < 0.05) was observed only in Se-deficient mice. The GPX1 mRNA level in kidney and in lung of the Se-deficient GPX1(+) mice was 81% and 7.5-fold greater (P < 0.003) than the respective control level. Overexpression of GPX1 did not alter phospholipid hydroperoxide glutathione peroxidase (GPX4) activities and mRNA levels or glutathione S-transferase (GST) activities in most of the tissues, plasma glutathione peroxidase (GPX3) activity or plasma Se concentrations. No differences in lipid peroxidation in kidney, lung or intestine were observed between the Se-deficient GPX1(+) and control mice. In conclusion, the overexpression of the GPX1 gene in these mice was tissue specific and did not affect the expression of GPX3, GPX4 or GST and plasma Se levels; dietary Se appeared to affect the GPX1 overexpression at its mRNA level.