Sigma-1 Receptor Activation-Induced Glycolytic ATP Production and Endothelial Barrier Enhancement.

OBJECTIVE: We tested the hypothesis that sigma receptor-1 (sigma1) modulates endothelial barrier function due to its influence on endothelial bioenergetics. METHODS: Cultured human umbilical vein endothelial cell (HUVEC) monolayers were used to model the endothelial barrier. Electric cell-substrate impedance sensing (ECIS), Transwell assays, and immunofluorescence labeling of junctional proteins were used to evaluate endothelial barrier function. Endothelial cell bioenergetics were determined using extracellular flux analysis and direct ATP level measurements. The endothelial-specific contribution of sigma1 was tested using the sigma1-selective agonist, PRE-084, and with targeted knockdown of sigma1 expression using siRNA. RESULTS: Activation of sigma1 with PRE-084 significantly enhanced endothelial barrier function and decreased permeability to albumin and dextran. Knockdown of sigma1 with siRNA reduced barrier function and abolished PRE-084-induced endothelial barrier enhancement. PRE-084 upregulated endothelial glycolysis and glycolytic ATP production, but this response was abolished by siRNA-mediated knockdown of sigma1 expression. PRE-084 also reduced the degree of endothelial barrier dysfunction caused by the mitochondrial oxidative phosphorylation uncoupler CCCP. CONCLUSION: Activation of sigma1 enhances endothelial barrier function and modulates the ratio of glycolytic versus mitochondrial ATP production. These novel findings suggest that endothelial sigma1 may prove beneficial as a novel therapeutic target for reducing microvascular hyperpermeability and counteracting mitochondrial dysfunction.