Modification of PI3K- and MAPK-Dependent Chemotaxis in Aortic Vascular Smooth Muscle Cells by Protein Kinase C βII

Abstract

Hyperglycemia increases expression of platelet-derived growth factor (PDGF)-β receptor and potentiates chemotaxis to PDGF-BB in human aortic vascular smooth muscle cells (VSMCs) via PI3K and ERK/MAPK signaling pathways. The purpose of this study was to determine whether increased activation of protein kinase C (PKC) isoforms had a modulatory effect on the PI3K and ERK/MAPK pathways, control of cell adhesiveness, and movement. All known PKC isoforms were assessed but only PKC α and PKC βII levels were increased in 25 mmol/L glucose. However, only PKC βII inhibition affected (decreased) PI3K pathway and MAPK pathway activities and inhibited PDGF-β receptor upregulation in raised glucose, and specific MAPK inhibition was required to completely block the effect of glucose. In raised glucose conditions, activity of the ERK/MAPK pathway, PI3K pathway, and PKC βII were all sensitive to aldose reductase inhibition. Chemotaxis to PDGF-BB (360 pmol/L), absent in 5 mmol/L glucose, was present in raised glucose and could be blocked by PKC βII inhibition. Formation of lamellipodia was dependent on PI3K activation and filopodia on MAPK activation; both lamellipodia and filopodia were eliminated when PKC βII was inhibited. FAK phosphorylation and cell adhesion were reduced by PI3K inhibition, and although MAPK inhibition prevented chemotaxis, it did not affect FAK phosphorylation or cell adhesiveness. In conclusion, chemotaxis to PDGF-BB in 25 mmol/L glucose is PKC βII -dependent and requires activation of both the PI3K and MAPK pathways. Changes in cell adhesion and migration speed are mediated mainly through the PI3K pathway.