SIRT4 Regulated by a Mechanosensor, PIEZO1 Shows a Protective Function to Suppress Ox-LDL Uptake in Endothelial Cells.

BACKGROUND: Endothelial cells (ECs) are key regulators of vascular function, adapting to mechanical forces, such as shear stress to maintain vascular homeostasis. Disruption of this adaptation, particularly in the regions of disturbed flow, contributes to endothelial dysfunction and the development of atherosclerosis later on. METHODS: We prepared a custom-designed PDMS-based flow chamber to apply controlled shear stress (2 or 7 dynes/cm(2)) to human umbilical vein endothelial cells. ECs were cultured on gelatin-coated coverslips and exposed to different shear flows for up to 12 h. Cell alignment was confirmed by angle measurements using ImageJ. Gene expression of SIRT4, PIEZO1, NOTCH1, and LOX-1 was determined via qPCR, and protein levels were assessed by western blot. Specific gene knockdown was also conducted using siRNAs, targeting either PIEZO1 or SIRT4. Oxidized LDL uptake was evaluated using DiI-labeled Ox-LDL and quantified by fluorescence imaging. Immunofluorescence staining of ECs was performed to visualize VE-cadherin, F-actin, and nuclei. All quantitative data were subjected to statistical analysis. RESULTS: We demonstrated that the mechanosensitive ion channel PIEZO1, regulates SIRT4 expression in response to shear stress. Under atheroprotective shear stress (7 dyne/cm(2)), PIEZO1-mediated upregulation of SIRT4 was observed, while atheroprone shear stress (2 dyne/cm(2)) led to reduced expression. Functional assays showed that SIRT4 protects endothelial cells from Ox-LDL uptake, a key factor in atherosclerosis. SIRT4 silencing increased Ox-LDL accumulation even under protective flow. This effect, and its link to LOX-1, was dependent on PIEZO1 signaling. CONCLUSION: Current findings suggest that the PIEZO1-SIRT4 axis may modulate endothelial responses to shear stress, offering a protective mechanism against Ox-LDL-induced dysfunction and pathology. Our study underscores the potential of SIRT4 as a therapeutic target to mitigate vascular disorders associated with oxidative stress and disturbed blood flow.