Tissue-specific regulation of glutathione homeostasis and the activator protein-1 (AP-1) response in the rat conceptus.
Oxidative stress in the conceptus is characterized by an increased oxidized to reduced glutathione (GSSG:GSH) ratio and the induction of fos and jun mRNAs, transcripts for components of the activator protein-1 (AP-1) transcription factor. We investigated the role of glutathione homeostasis in the rat conceptus in the regulation of: (1) AP-1 expression and activity, and (2) the activities of glutathione-dependent cytoprotective enzymes. Glutathione content was enhanced with the addition of l-2-oxothiazolidine-4-carboxylate (OTC), a precursor of cysteine, a rate-limiting substrate in glutathione biosynthesis. Day 10 rat conceptuses were cultured for 44 hr with 0, 5, 10, or 20 mM OTC. High concentrations (10 and 20 mM) of OTC were embryotoxic. Incubation of the conceptus in 5 mM OTC caused mild (not statistically significant) embryotoxicity, increased significantly the embryonic glutathione content, prevented culture-induced oxidative stress, and inhibited the induction of AP-1 transcripts and DNA binding activity in the embryo. In contrast, in the yolk sac, 5 mM OTC failed to increase glutathione content or to prevent oxidative stress or AP-1 induction. Thus, regulation of glutathione status in the conceptus is tissue-specific. Glutathione S-transferase and glutathione peroxidase activities were increased approximately 50% in cultured embryos and yolk sacs. OTC treatment (5 mM) prevented this induction in the embryo, but not in the yolk sac, suggesting a role for glutathione homeostasis in the regulation of these enzymes. Tissue-specific regulation of glutathione status and of cytoprotective enzymes in the conceptus during organogenesis may impact on the consequences of insult with oxidative stress.
Department of Pharmacology and Therapeutics, McGill University, Montréal, Québec, Canada.
T R
TR
Ozolins
B F
BF
Hales
D000818:Animals; D019610:Cytoprotection / Q000187:drug effects; D004247:DNA / Q000187:drug effects / Q000378:metabolism; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D005978:Glutathione / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects; D011761:Pyrrolidonecarboxylic Acid; D012333:RNA, Messenger / Q000096:biosynthesis / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism*; D015017:Yolk Sac / Q000201:enzymology / Q000378:metabolism*
D012333:RNA, Messenger; D013844:Thiazoles; D053778:Thiazolidines; D018808:Transcription Factor AP-1; D004247:DNA; D005978:Glutathione; D011761:Pyrrolidonecarboxylic Acid; C029536:2-oxothiazolidine-4-carboxylic acid