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PKC/Raf/MEK/ERK signaling pathway modulates native-LDL-induced E2F-1 gene expression and endothelial cell
Gianfranco Pintus1, Bruna Tadolini, Anna M Posadino
1Department of Biomedical Sciences, Division of Biochemistry, Laboratory of Cardiovascular Research, University of Sassari, Viale San Pietro 43/B, 07100 Sassari, Italy. gpintus@uniss.it
Background And Objectives:
The interactions of low-density lipoprotein (LDL) with the endothelium are thought to play a major role in the development of atherosclerosis. Due to this reason, the molecular sequelae of events resulting from native LDL (N-LDL) interaction with human endothelial cells (HECs) are largely under investigation.
Methods And Results:
Here, we report that the exposure of serum-free HECs to different concentrations of N-LDL-cholesterol (LDL-chol) elicited a time- and dose-dependent induction of DNA synthesis. The exposure of serum-free HECs to N-LDL was able to elicit a time- and dose-dependent increase of protein kinase C (PKC) activity that, along with the activation of the Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling pathway, leads to an increase in E2F-1 gene expression. In addition, the treatment of HECs with N-LDL was also able to induce both E2F-1 gene transcription and protein expression. These N-LDL-aroused responses were dramatically counteracted by PKC inhibition or down regulation. Similarly to what observed for Raf/MEK/ERK activation and E2F-1 gene expression, the inhibition of PKC as well as its down regulation, significantly lowered the DNA synthesis induced by N-LDL in serum-free HECs.
Conclusions:
These results suggest that the activation of PKC/Raf/MEK/ERK-mediated events controlling E2F-1 gene expression by N-LDL may represent an important mechanism in the regulation of HECs proliferation during normal and pathological processes.