Abstract
Ouabain is Na^+^/K^+_^ATPase inhibitor and an endogenous regulator of blood pressure, it has dual effect on vascular endothelial cells(VEC) cell growth and VEC apoptosis is contributed to vascular dysfunction involved in vascular remolding. However, the precise mechanisms of apoptosis induced by ouabain remained unclear. The objective of this study was to identify the differently expressed proteins involved in VEC apoptosis induced by ouabain in order to explore cellular and subcellular mechanisms related to ouabain actions. Human umbilical vein endothelial cells (HUVEC) were exposed to increasing concentrations (0.1 nM to 10 µM) of ouabain at 12–48 h intervals. Cell viability tests revealed that high concentrations of ouabain inhibited cell growth. Flow cytometry and caspase‐3 activity analysis confirmed that apoptosis was primarily responsible for ouabain induced cell death. Two‐dimensional electrophoresis in conjunction with mass spectrometry revealed that the ouabain‐induced apoptosis was accompanied by regulated expression of programmed cell death protein 6, cytochrome C1, endothelin converting enzyme, claudin‐1, reticulon‐4, galectin‐1, ras‐related protein rab‐11B, calnexin, profilin‐1 and heat shock protein 60 (HSP60). Further study on cytochrome c and HSP60 demonstrated that levels of mitochondria and cytosol cytochrome c and HSP60 changed in response to ouabain treatment. Data showed that mitochondria proteins such as HSP60 interferes with HSP60‐Bax interactions played an important role in ouabain induced apoptosis. These data bring new sights into physiological role for ouabain in VEC apoptosis and vascular remodeling, thus provide new strategies for new anti‐cardiovascular disease drug development or the identification of biomarkers for vascular dysfunction in ouabain related hypertension. J. Cell. Biochem. 104: 1054–1064, 2008. © 2008 Wiley‐Liss, Inc.