The sphingosine kinase inhibitor N,N‐dimethylsphingosine inhibits neointimal hyperplasia

Background and purpose: Sphingosine‐1‐phosphate and its receptors may be involved in vascular smooth muscle cell (VSMC) proliferation following vascular injury. Here, we evaluate the effect of d‐erythro‐N,N‐dimethylsphingosine (DMS), a sphingosine kinase (SK) inhibitor, on VSMC proliferation, apoptosis and neointimal formation. Experimental approach: Growth responses in vitro to fetal calf serum (FCS) were measured by [3H]‐thymidine incorporation and extracellular signal‐regulated kinase‐1/2 (ERK‐1/2) activation in quiescent primary cultures of porcine VSMC in the presence and absence of various concentrations of the SK inhibitor DMS. In vivo treatment with DMS was delivered with a local endoluminal catheter, following balloon injury of coronary arteries. The artery intimal formation was investigated by angiography, myography and histomorphometry. Key results: In vitro experiments indicated that DMS induced a dose‐dependent reduction in [3H]‐thymidine incorporation and ERK‐1/2 activation via a protein kinase C (PKC) independent mechanism with an IC50 value of 12 ± 6 and 15 ± 10 µM respectively. DMS also reduced Akt signalling. Four weeks following in vivo delivery of DMS, complete functional endothelial regeneration was observed in all treatment groups, with significant reduction of intimal formation (vehicle 23.7 ± 4.6% vs. DMS infusion 8.92 ± 2.9%, P