Glucosamine enhances platelet-derived growth factor-induced DNA synthesis via phosphatidylinositol 3-kinase pathway in rat aortic smooth muscle cells

Vascular smooth muscle cells play a key role in the development of atherosc lerosis. Culture of vascular smooth muscle A10 cells with high glucose for 4 weeks enhanced platelet-derived growth factor (PDGF)-induced BrdU incorpo ration. Since a long period of high glucose incubation was required for the effect, and it was inhibited by co-incubation with azaserine, the role of hexosamine biosynthesis in the development of atherosclerosis in diabetes w as studied in A10 cells. Addition of glucosamine to the culture media enhan ced PDGF-stimulated BrdU incorporation, and PDGF-induced tyrosine phosphory lation of the PDGF P-receptor was increased by glucosamine treatment. Of th e subsequent intracellular signaling pathways, PDGF-induced PDGF P-receptor association with PLC gamma was not affected, whereas tyrosine phosphorylat ion of She, subsequent association of Shc with Grb2, and MAP kinase activat ion were relatively decreased. In contrast, PDGF-induced PDGF P-receptor as sociation with the p85 regulatory subunit of PI3-kinase and PI3-kinase acti vation were increased by 20% (P < 0.01) and 36% (P < 0.01), respectively. T he intracellular signaling molecules responsible for the glucosamine effect were further examined using pharmacological inhibitors. Pretreatment with PLC inhibitor (U73122) had negligible effects, and MEK1 inhibitor (PD98059) showed only a slight inhibitory effect on the PDGF-induced BrdU incorporat ion. In contrast, pretreatment with PI3-kinase inhibitor (LY294002) signifi cantly inhibited glucosamine enhancement of PDGF-induced BrdU incorporation . These findings suggest that glucosamine is involved in the development of atherosclerosis by enhancing PDGF-induced mitogenesis specifically via the PI3-kinase pathway. <(c)> 2001 Elsevier Science Ireland Ltd. All rights re served.