Requirement of hydrogen peroxide and Sp1 in the stimulation of Na,K-ATPase by low potassium in MDCK epithelial cells

We have previously implicated reactive oxygen species oxygen (ROS) as a critical signal transducer in the upregulation. of Na,K-ATPase by low K+ in MDCK cells, but how ROS mediate this process has not been well defined. We reported here that both of hydrogen peroxide (H2O2) and superoxide anion (O-2 degrees(-)) were rapidly produced at the early stage of low K+-treated MDCK cells. Further analysis revealed that NADP/NADPH oxidase-derived H2O2 was specifically involved in low K+-induced Na,K-ATPase et I gene transcription as well as alpha 1 and beta 1 subunits expressions. Exogenous H2O2 even mimicked the stimulatory effect of low K+ on Na,K-ATPase alpha 1 gene transcription. Low K+ triggered a H2O2-dependnet ERK1/2 phosphorylation in MDCK cells, nonetheless, this ERK1/2 activation did not finally lead to the upregulation of Na,K-ATPase. Similar to previous findings that Na,K-ATPase beta 1 gene transcription was mediated by Sp1, Na,K-ATPase alpha 1 gene transcription in low K+-treated MDCK cells was also closely relevant to Sp1 participation, as confirmed by siRNA as well as PCR mutagenesis technologies. Furthermore, Sp1 activation was dependent on H2O2 generation triggered by low K+. Taken together, the data described in this study outlines an essential role of H2O2 and Sp1 in mediating the upregulation of Na,K-ATPase in MDCK cells by low external K+. (C) 2007 Elsevier Ltd. All rights reserved.