Abstract
Previously, we reported that ouabain and other cardiotonic steroids (CTS) kill renal epithelial and vascular endothelial cells via their interaction with the Na +,K +-ATPase α-subunit, but independently of elevation of the [Na +] i/[K +] i ratio. In distinct cell types, side-by-side with inhibition of Na +,K +-ATPase-mediated ion fluxes, CTS trigger [Ca 2+] i oscillation, activation of Ras, mitogen-activated protein kinases (MAPK), phosphoinositide-3 kinase (PI3K), and protein kinase C as well as the production of reactive oxygen species and cytoskeleton reorganization. This study examined the potential involvement of the above-listed intermediates in death signaling triggered by ouabain in C7-Madin–Darby canine kidney cells. In these cells, twofold decreased staining with dimethylthiazol diphenyltetrazolium (MTT) and detachment of up to 80% of dead cells were detected in 6 and 24 h of ouabain addition, respectively. We did not observe any effect of extra- (EGTA) and intracellular (BAPTA) Ca 2+-chelators, [Ca 2+] i-raising compounds (thapsigargin, ATP), inhibitors of Ras signaling (α-hydroxyfarnesyl-sulphosphoric acid), PI3K (wortmannin), MAPK ERK1/2 kinase (PD98059), tyrosine kinases (genistein) as well as activators (4β-PMA, 8-Br-cAMP, 8-Br-cGMP, forskolin) and inhibitors (calphostin) of serine–threonine kinases on MTT staining and death of ouabain-treated cells. Ouabain did not affect cellular redox state and the production of superoxide anion and hydroperoxide. Neither N-acetylcysteine nor reduced gluthatione suppressed the death of ouabain-treated cells. Thus, our results show that none of the above-listed signaling systems plays a major role in the development of N a i + , K i + -independent death machinery triggered by CTS interaction with the Na +,K +-ATPase α-subunit.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.