Short-Term and Long-Term Fluvastatin Inhibit Effects of Thrombospondin-1 on Human Vascular Smooth Muscle Cells

Vascular smooth muscle cells are important in intimal hyperplasia. Thrombospondin-1 is a matricellular protein involved in the vascular injury response. Statins are cholesterol lowering drugs that have beneficial cardiovascular effects. Statis have been shown to inhibit smooth muscle migration through the mevalonate pathway. This effect is thought to be mediated by small G protein Ras and Rho turnover which requires many hours. While many patients undergoing treatment for vascular disease are on statins, many are not. Thus immediate pretreatment with statins before surgery may be beneficial. We hypothesized that statins have effects independent of the mevalonate pathway and thus have an immediate effect.

Human vascular smooth muscle cells were pretreated for 20 h (long-term) or 20 min (short-term) with fluvastatin, or mevalonolactone plus fluvastatin. Thrombospondin-1-induced migration, activation of p42/p44 extracellular signal-regulated kinase, c-Src, focal adhesion kinase and PI3 kinase was determined. The effect of fluvastatin on thrombospondin-1-induced expression of THBS1, FOS, HAS2 and TGFB2 was examined.

Both treatments inhibited thrombospondin-1-induced chemotaxis back to the control group. Mevalonolactone reversed the long-term statin effect by increasing migration but had no effect on the short-term statin response. p42/p44 extracellular signal-regulated kinase was activated by thrombospondin-1 and both treatments augmented activation. Neither treatment affected c-Src activity, but both inhibited focal adhesion kinase and PI3 kinase activity. Only long-term statin treatment inhibited THBS1 expression while both treatments inhibited FOS and TGFB2 expression. Neither treatment affected HAS2. FOS knockdown inhibited thrombospondin-1-induced HAS2 but not TGFβ2 gene expression.

Long-term fluvastatin inhibited thrombospondin-1-induced chemotaxis through the mevalonate pathway while short-term fluvastatin inhibited chemotaxis through an alternate mechanism. Short-term stains have immediate effects independent of the mevalonate pathway. Acute local treatment with statins followed by longer term therapy may limit the vascular response to injury.