Increased reactive oxygen species contribute to high NaCl-induced activation of the osmoregulatory transcription factor TonEBP/OREBP.
The signaling pathways leading to high NaCl-induced activation of the transcription factor tonicity-responsive enhancer binding protein/osmotic response element binding protein (TonEBP/OREBP) remain incompletely understood. High NaCl has been reported to produce oxidative stress. Reactive oxygen species (ROS), which are a component of oxidative stress, contribute to regulation of transcription factors. The present study was undertaken to test whether the high NaCl-induced increase in ROS contributes to tonicity-dependent activation of TonEBP/OREBP. Human embryonic kidney 293 cells were used as a model. We find that raising NaCl increases ROS, including superoxide. N-acetylcysteine (NAC), an antioxidant, and MnTBAP, an inhibitor of superoxide, reduce high NaCl-induced superoxide activity and suppress both high NaCl-induced increase in TonEBP/OREBP transcriptional activity and high NaCl-induced increase in expression of BGT1mRNA, a transcriptional target of TonEBP/OREBP. Catalase, which decomposes hydrogen peroxide, does not have these effects, whether applied exogenously or overexpressed within the cells. Furthermore, NAC and MnTBAP, but not catalase, blunt high NaCl-induced increase in TonEBP/OREBP transactivation. N(G)-monomethyl-l-arginine, a general inhibitor of nitric oxide synthase, has no significant effect on either high NaCl-induced increase in superoxide or TonEBP/OREBP transcriptional activity, suggesting that the effects of ROS do not involve nitric oxide. Ouabain, an inhibitor of Na-K-ATPase, attenuates high NaCl-induced superoxide activity and inhibits TonEBP/OREBP transcriptional activity. We conclude that the high NaCl-induced increase in ROS, including superoxide, contributes to activation of TonEBP/OREBP by increasing its transactivation.
Zhou
Xiaoming
X
Division of Nephrology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Ferraris
Joan D
JD
Cai
Qi
Q
Agarwal
Anupam
A
Burg
Maurice B
MB
D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics; D002374:Catalase / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050485:GABA Plasma Membrane Transport Proteins; D006801:Humans; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010042:Ouabain / Q000494:pharmacology; D016877:Oxidants / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012965:Sodium Chloride / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D013481:Superoxides / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000235:genetics*
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D050485:GABA Plasma Membrane Transport Proteins; C118125:NFAT5 protein, human; D016877:Oxidants; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D013481:Superoxides; C072207:betaine plasma membrane transport proteins; D012965:Sodium Chloride; D010042:Ouabain; D002374:Catalase; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester