Abstract
Background
In many studies, endothelial progenitor cells (EPCs) highly expressing antioxidant protein were induced oxidative stress and apoptosis by Oxidized-low density lipoprotein (ox-LDL). Nrf2 which was resently reported to regulate the antioxidant genes and cellular redox regulators was highly expressed in EPCs. However, its role in ox-LDL induced EPCs oxidative stress and apoptosis has not been fully illustrated.
Methods
EPCs isolated from human peripheral blood mononuclear cells were treated with different concentration of ox-LDL, Keap1 siRNA and a specific p38 MAPK inhibitor SB203580, then used to assay the whole cellular Nrf2 (total Nrf2, t-Nrf2), cytoplasmic Nrf2 (c-Nrf2), nuclear Nrf2 (n- Nrf2), NAD(P) H:quinone oxidoreductase 1 (NQO1) protein levels and Bax /Bcl-2 with western blot, NQO1 mRNA levels with RT-PCR, ROS level with H2DCF-DA, the loss/disruption of mitochondrial membrane potential (MMP) with JC-1, apoptosis with Annexin-V and PI,migration ability with transwell chambers and tube formation.
Results
The ox-LDL treatment decreased the n-Nrf2/Histone H3 to c-Nrf2/GAPDH ratio, NQO1 mRNA and protein expression levels. Treatment of ox-LDL enhanced the ROS production, induced loss of membrane potential, increase in cell shrinkage, pyknotic nuclei and apoptosis of EPCs. The Keap1 knockdown with Keap1 siRNA increased the nuclear translocation of Nrf2, the NQO1 mRNA and protein transcription levels, and prevented ox-LDL induced ROS generation and formation of JC-1 monomers. Treatment of ox-LDL increased the activation of p38. Pretreatment with SB203580 significantly eliminated ox-LDL induced the inhibition of Nrf2 nuclear translocation, the depression of the mRNA transcription levels of NQO-1, the ROS generation and the formation of JC-1 monomers in EPCs. The pretreatment of Keap1 siRNA decreased the Bax/Bcl-2 ratio which was increased by the treatment of ox-LDL in EPCs. The ox-LDL treatment decreased EPCs migration activity and tube formation. Whereas the pre-treatment with Keap1 siRNA preserved the migration ability and tube formation of EPCs
Conclusion
Ox-LDL induced EPCs oxidative stress and apoptosis via p38/Keap1/Nrf2 pathway.
High Glucose Impairs Early and Late Endothelial Progenitor Cells by Modifying Nitric Oxide-Related but Not Oxidative Stress-Mediated Mechanisms
