Abstract WP437: The Relationship Between Cholesterol And Cerebral Vasospasm In A Rat Model Of Subarachnoid Hemorrhage: A Mechanistic Role For Lipid Rafts

Abstract

Objective: Rho-kinase (ROK)-mediated vascular smooth muscle (VSM) contraction plays a pivotal role in cerebral vasospasm (CV). Sphingosylphosphorylcholine (SPC), a sphingolipid, induces ROK-mediated VSM contraction, and hypercholesterolemia increases SPC-ROK-mediated VSM contraction. Lipid rafts are cholesterol-enriched membrane microdomains that influence signal transduction. In this study, we report the effect of cholesterol and lipid rafts on CV. Methods: Adult male Sprague-Dawley rats (400-500g, n=53) were fed control, 1% cholesterol or 1% cholesterol +5% β-cyclodextrin (β-CD), which depletes VSM cholesterol, diets for 8 weeks. We used a double-hemorrhage rat subarachnoid hemorrhage (SAH) model, and investigated CV of the basilar artery (BA) at Day5 using a cranial window. T-Cho levels in the internal carotid artery (ICA) were measured using Gas Chromatography. The expression of Flotillin-1, a raft marker, and Flotillin-1 mRNA in the ICA were analysed by Western blot and real-time RT-PCR, respectively. Results: The BA diameters were 358.94±32.05μm and 302.21±38.36μm in control diet (non-treated) and SAH rats, respectively (n=9/group, p<0.05 vs. non-treated). SAH-induced BA contraction was markedly reversed by intracisternal infusion of 10μM Y27632 (n=4, p<0.05), a ROK inhibitor. The BA diameter in SAH rats fed the cholesterol diet was 248.11±34.56μm (n=6, p<0.05 vs. control SAH-rats), compared with 305±25.28μm in SAH rats fed a β-CD diet (n=6, p<0.05 vs. SAH-rat fed a cholesterol diet). T-Cho levels in the ICA were significantly higher in rats fed a cholesterol diet compared with the control diet (0.82±0.24 vs. 0.49±0.09mg/g, n=5/group, p=0.028) or the β-CD diet (0.47±0.06 mg/g, n=5, p=0.016 vs. cholesterol diet). Western blot analysis and real-time RT-PCR revealed increases in Flotillin-1 and Flotillin-1 mRNA expression in the ICA from rats fed a cholesterol diet, whereas Flotillin-1 and Flotillin-1 mRNA expression were not altered in the ICA from rats fed the β-CD diet. Conclusions: These results indicate that cholesterol potentiates SAH-induced CV and are compatible with a role for lipid rafts in this process.