Protein kinase C-dependent effects of 12(S)-HETE on endothelial cell vitronectin receptor and fibronectin receptor

Abstract

12(S)-HETE, a lipoxygenase metabolite of arachidonic acid induced a nondestructive and reversible endothelial cell (EC) retraction. 12(S)-HETE induced EC retraction was inhibited by protein kinase C inhibitors calphostin C and staurosporine but not by the protein kinase A inhibitor H8. The role of EC integrins αvβ3 and α5β1 in 12(S)-HETE induced EC retraction was investigated. In confluent EC cultures, αvβ3 is localized to focal adhesions at both the cell body and cell-cell borders and is colocalized with vinculin-containing focal adhesions. In contrast, α5β1 is primarily enriched at the cell-cell borders, demonstrating codistribution with cell cortical microfilaments and extracellular fibronectin. Both receptors were functional in mediating cell-cell or cell-matrix interactions based on the observations that specific antibodies inhibited EC adhesion to intact subendothelial matrix and disrupted the monolayer integrity. 12(S)-HETE induced a multistep, temporally defined redistribution of the αvβ3-containing focal adhesions, leading to an eventual decrease in αvβ3 plaques in the retracted ECs. This effect of 12(S)-HETE was inhibited by calphostin C but not by H8. The alterations of αvβ3-containing focal adhesions preceded the development of EC retraction. 12(S)-HETE also enhanced EC αvβ3 surface expression as revealed by immunofluorescence, flow cytometry, and digitized image analysis. 12(S)-HETE-induced αvβ3 rearrangement (i.e., decreased focal adhesion localization and enhanced surface expression) did not result from altered mRNA transcription (as revealed by semi-quantitative RT-PCR analysis) or protein translation (as revealed by Western blotting). In contrast to its effect on αvβ3, 12(S)-HETE did not demonstrate a temporally related, well-defined effect on the distribution pattern and the surface expression of α5β1, although the cell-cell border staining pattern of α5β1 was disrupted due to EC retraction. It is concluded that 12(S)-HETE-induced decrease of αvβ3 localization to focal adhesions may contribute to the development of EC retraction and that 12(S)-HETE induced increase in αvβ3 surface expression may promote adhesion of inflammatory leukocytes as well as tumor cells to endothelium.