Effect of diquat-induced oxidative stress on iron metabolism in male Fischer-344 rats

Abstract

Diquat toxicity causes iron-mediated oxidative stress; however, it remains unclear how diquat affects iron metabolism. Here, we examined the effect of diquat-induced oxidative stress on iron metabolism in male Fischer-344 rats, with particular focus on gene expression. Hepatic nonheme iron content was unchanged until 20 h after diquat treatment. Hepatic free iron levels increased markedly in the early stages following treatment and remained elevated for at least 6 h, resulting in severe hepatotoxicity, until returning to control levels at 20 h. The level of hepatic ferritin, especially the H-subunit, increased 20 h after diquat treatment due to elevated hepatic ferritin-H mRNA expression. These results indicate that early elevated levels of free iron in the liver of diquat-treated rats cause hepatotoxicity, and that this free iron is subsequently sequestered by ferritin synthesized under conditions of oxidative stress, thus limiting the pro-oxidant challenge of iron. The plasma iron concentration decreased at 6 and 20 h after diquat treatment, whereas the level of plasma interleukin-6 increased markedly at 3 h and remained high until 20 h. In the liver of diquat-treated rats, expression of hepcidin mRNA was markedly upregulated at 3 and 6 h, whereas ferroportin mRNA expression was downregulated slightly at 20 h. Transferrin receptor 1 mRNA expression was significantly upregulated at 3, 6, and 20 h. These results indicate that inhibition of iron release from iron-storage tissues, through stimulation of the interleukin-6-hepcidin-ferroportin axis, and enhanced iron uptake into hepatocytes, mediated by transferrin receptor 1, cause hypoferremia.

Effects of Oxidative Stress Caused by <i>tert</i>-Butylhydroquinone on Cytotoxicity in MDCK Cells

“…Prooxidants did not seem to cause cell membrane injury due to formation of lipid peroxidation products by prooxidants in kidney cells for an unknown reason. Additionally, DQ showed a decrease in MDA formation, although DQ was shown to cause liver and kidney damage in male Fisher-344 rats [7]. However, quantification of lactate dehydrogenase release is needed in a future experiment.…”

“…H 2 O 2 is an ROS rather than a prooxidant and produces the most toxic hydroxyl radical through the iron-mediated Fenton reaction [17]. DQ is a metabolic oxidant, which results in DQ radical formation by accepting an electron from NADPH-dependent P450 reductase and successive superoxide radical formation by surrendering an electron to the unpaired molecular oxygen from its radical [7,23]. β-NF is a ligand of the aryl hydrocarbon receptor (AhR), and the AhR ligand generates intracellular ROS [5].…”

“…Hydrogen peroxide (H 2 O 2 ), tert-butylhydroquinone (t-BHQ), diethyl maleate (DEM), diquat (DQ), and β-naphthoflavone (β-NF) are known as prooxidants [3,5,7,13,18,21,23]. These prooxidants, however, can become antioxidants by transcription enhancement of phase II detoxification enzymes, such as glutathione-S-transferase, NAD (P) H:(quinone-acceptor) oxidoreductase, γ-glutamylcysteine synthetase, heme oxygenase and ferritin [11,22,24,26,27,29].…”

“…Although the cellular chemopreventive effect of prooxidants is a complex interplay of events including cellular expression of phase II detoxification enzymes and cellular metal metabolism, antioxidant and oxidative stress seem to be cell-or tissue-specific [7,22,27,28]. The expression of iron storage protein, ferritin, is induced by oxidative stress as an antioxidant, indicating that ferritin has a dual function to store iron in a bioavailable and nontoxic form, as iron (Fe 2+ ) produces the most toxic hydroxyl radical through the Fenton reaction [17,20].…”

“…The expression of iron storage protein, ferritin, is induced by oxidative stress as an antioxidant, indicating that ferritin has a dual function to store iron in a bioavailable and nontoxic form, as iron (Fe 2+ ) produces the most toxic hydroxyl radical through the Fenton reaction [17,20]. On the other hand, cytoprotection of ferritin against oxidative stress is controversial due to the release of Fe 2+ by superoxide anion and/ or radical products [7,22], suggesting that intracellular ferritin protein and iron levels may affect the detoxification capacity of ROS. Therefore, more detailed studies are required to clarify the effects of prooxidants on cells or tissue, with focus on iron metabolism.…”