Oxidized LDL Induces Proliferation and Hypertrophy in Human Umbilical Vein Endothelial Cells via Regulation of p27Kip1 Expression: Role of RhoA

Oxidized LDL (OxLDL) induces proliferation in hu- man umbilical vein endothelial cells (HUVEC). The influence of OxLDL on the cyclin-dependent kinase inhibitor p27 Kip1 ,o n the activity of the small GTPase RhoA as a known regulator of p27 Kip1 , and on resulting cell proliferation and hypertrophy was studied. HUVEC were stimulated with OxLDL (1 to 50 g/ml). Proliferation was quantified by 3 H-thymidine incorporation, col- orimetric 3-(4,5-dimethyl-2-thiazyl)-2,5-diphenyl-2h-tetrazolium bromide assay, and cell count and was compared with prolifera- tion of HUVEC that were transfected with dominant negative RhoA or treated with the Rho-kinase inhibitor Y27632. Hy- pertrophy was quantified by 3 H-leucine incorporation and by planimetry. p27 Kip1 expression was determined by Western blot analysis. p27 Kip1 was downregulated by transient transfec- tion with antisense oligonucleotides. Low concentrations of OxLDL induced proliferation of HUVEC, paralleled by a persistent decrease of p27 Kip1 expression. With the use of