The Regulatory Role of Pravastatin™ in the Venous Shear Stress Dependent Induction of Aquaporin 1 Protein Expression in Human Umbilical Vein Endothelial Cells in vitro.

Background: Aquaporins (AQPs) are transmembrane water channels that facilitate osmotically-driven water flux. AQP1 is expressed in vascular endothelium. AQP1 protein abundance is enhanced in cultured human umbilical vein endothelial cells (HUVECs) in response to fluid shear stress. The cholesterol-lowering statin drugs have been shown to regulate the expression of specific AQPs by altering their abundance and/or subcellular localization. Therefore, it is hypothesized that AQP1 may function as a component of the mechanosensory complex in endothelial cells, and therefore, is subject to shear-stress induced gene regulation and modulation of expression by statins. Methods: HUVECs were cultured under static (0 dynes/cm2) and venous fluid shear stress (6 dynes/cm2) in the presence or absence of 5 µM Pravastatin™. Fluorescent immunocytochemistry was used to detect AQP1 protein expression. Images were captured using confocal laser scanning microscopy. Mean fluorescent intensity (in arbitrary units) of AQP1immunofluorescence was determined using ImageJ software, and normalized to control conditions (time zero, static culture with no Pravastatin™). 25-30 cells from two independent experiments were analyzed for each experimental condition. Results: AQP1 immunofluorescence increased 1.3-fold (p\u3c0.05) after 24 hours, and 1.7-fold (p\u3c0.05) after 48 hours in cells cultured under venous fluid shear as comparted to the control. This shear stress-induced expression was blocked by incubation with Pravastatin™ (p\u3e0.05; control vs. venous shear with Pravastatin™). Pravastatin™ had no effect on AQP1 immunofluorescence in static cultures (p\u3e0.05 vs. control). These data indicate that Pravastatin™ prevents shear stress induction of AQP1 in cultured HUVECs. Conclusions: The results presented show that the shear stress induction of AQP1 protein expression is prevented by Pravastatin™. These results further demonstrate a possible tissue-independent function of statin drugs in regulating the expression of AQPs in general and specifically a potential cardioprotective benefit of statins, independent of their cholesterol-lowering function, related to the regulation of AQP1 in vascular endothelial cells