Diminished Lipid Raft SNAP23 Increases Blood Pressure by Inhibiting the Membrane Fluidity of Vascular Smooth-Muscle Cells.

Synaptosomal-associated protein 23 (SNAP23) is involved in microvesicle trafficking and exocytosis in various cell types, but its functional role in blood pressure (BP) regulation has not yet been defined. Here, we found that lipid raft SNAP23 expression was much lower in vascular smooth-muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) than in those from normotensive Wistar-Kyoto (WKY) rats. This led us to investigate the hypothesis that this lower expression may be linked to the spontaneous hypertension found in SHR. The expression level of lipid raft SNAP23 and the fluidity in the plasma membrane of VSMCs were lower in SHR than in WKY rats. Cholesterol content in the VSMC membrane was higher, but the secreted cholesterols found in VSMC-conditioned medium and in the blood serum were lower in SHR than in WKY rats. SNAP23 knockdown in WKY rat VSMCs reduced the membrane fluidity and increased the membrane cholesterol level. Systemic overexpression of SNAP23 in SHR resulted in an increase of cholesterol content in their serum, a decrease in cholesterol in their aorta and the reduction of their BP. Our findings suggest that the low expression of the lipid raft SNAP23 in VSMCs might be a potential cause for the characteristic hypertension of SHR.