Cobalt inhibits prolyl hydroxylases leading to the accumulation of hypoxia-inducible factor-1α(HIF-1α) and a concomitant increase in the transcriptional activity of HIF-1. Therefore, cobalt has been under the development as a drug to activate HIF-1 under some disease conditions. However, it has been shown that ischemic conditions resulted in the loss of copper (Cu), under which condition the activation of HIF-1 would not occur unless Cu was supplemented. The present study was undertaken to test the hypothesis that Cu is also required for cobalt activation of HIF-1 transcriptional activity. Human umbilical vein endothelial cells subjected to the treatment with CoCl2 above 25 µM CoCl2 for 2 hrs resulted in an accumulation of HIF-1α, determined by western blot analysis, and an increase in the expression of vascular endothelial growth factor (VEGF), determined by a real-time RT-PCR analysis for mRNA levels and ELISA analysis for protein levels. Cu chelator, tetraethylenepentamine (TEPA), at 25 µM did not significantly affect the accumulation of HIF-1αbut blocked the increase in the VEGF mRNA and protein levels, an effect that could be reversed by an addition of 25 µM CuSO4. In addition, gene-silencing of copper chaperone for Cu,Zn-SOD (CCS) also blocked VEGF expression with little effect on cobalt-induced HIF-1α accumulation. The present study thus demonstrated that Cu was required for cobalt-activated transcriptional activity of HIF-1, although Cu did not affect cobalt-induced accumulation of HIF-α in the cells.
- Received March 27, 2012.
- Revision received May 1, 2012.
- Accepted May 14, 2012.
- The American Society for Pharmacology and Experimental Therapeutics