Protein kinase C β1 overexpression augments phorbol ester-induced increase in endothelial permeability

Abstract

We studied the postulated involvement of the protein kinase C β1 (PKCβ1) isoform in the regulation of endothelial permeability using human dermal microvascular endothelial cell line (HMEC-1). We overexpressed the recombinant PKCβ1 gene via retroviral-mediated transduction in these cells. PKCβ1 gene transfer was stable, and PKCβ1 protein production was persistent for at least 1 month posttransduction. Addition of 2 x 10-9 M and 2 x 10-8 M phorbol 12-myristate 13-acetate (PMA) to the control (nontransduced) HMEC-1 cells increased the transendothelial 125I-albumin clearance rate (an index of endothelial permeability) from 2.5 ± 0.2 x 10-2 μl/min to 5.4 ± 1.2 x 10-2 μl/min and 16.8 ± 3.1 x 10-2 μl/min, respectively. However, addition of 2 x 10-9 M PMA to PKCβ1-overexpressing HMEC-1 cells produced a maximal increase in the transendothelial 125I-albumin clearance rate of 15.9 ± 2.0 x 10-2 μl/min. Challenge of these cells with 2 x 10-8 M PMA did not further augment the increase in permeability. Activation with PMA was associated with the translocation of the PKCβ1 from the cytosol to the membrane. These data show that PKCβ1 overexpression augments the increase in endothelial permeability in response to PKC activation, suggesting an important function for the PKCβ1, isoform in the regulation of endothelial barrier.