Regulation of vascular smooth muscle cell proliferation and migration by sphingosine-1-phosphate

Date of Completion

January 2004

Keywords

Biology, Molecular|Biology, Cell

Degree

Ph.D.

Abstract

Vascular smooth muscle cells (VSMC) exhibit a range of functional phenotypes important in cardiovascular development and disease. Recently, sphingosine-1-phosphate (S1P), a platelet-derived sphingolipid metabolite, has been demonstrated to regulate VSMC function both in vitro and in vivo . ^ In order to improve our understanding of S1P signaling in VSMC, we determined the expression of S1P receptor isoforms (S1Pn/EDG-n) in two different rat VSMC phenotypes: Pup-intimal VSMC and adult-medial VSMC. ^ Herein, pup-intimal VSMC were found to express higher levels of S1P 1/EDG-1 mRNA than adult-medial VSMC. Exogenous expression of S1P 1/EDG-1 in adult-medial cells enhanced S1P-induced proliferation, concomitant with activation of p70 S6 kinase and increases in cyclin D1. Pertussis toxin impaired S1P-induced p70 S6 kinase activation, cyclin D1 induction and proliferation, suggesting that S1P1/EDG-1-coupling to Gi is critical. Furthermore, blocking p70 S6 kinase phosphorylation with rapamycin reduced cyclin D1 induction and proliferation, suggesting that p70 S6 kinase activation is also critical in S1P1/EDG-1/Gi-mediated proliferation. ^ Recently, sphingosine kinase (SK), the enzyme which synthesizes S1P by phosphorylating sphingosine, has been reported to regulate VSMC function in vitro. In order to elucidate the role of SK in VSMC function in vivo, we attempted to develop transgenic mice expressing a sphingosine kinase/β-galactosidase transgene in arterial VSMC. Transgenic mice were successfully generated and transmitted the transgene to offspring. (Abstract shortened by UMI.) ^

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