Intracellular calcium ions facilitate dengue virus entry into endothelial cells and compromise endothelial barrier integrity

Objective:To investigate the involvement of Ca^(2+)in dengue virus(DENV)-infected human umbilical vein endothelial cells(HUVECs)and the disruption of endothelial integrity.Methods:HUVECs were infected with DENV-2 in the presence of intracellular Ca^(2+)or endoplasmic reticulum Ca^(2+)chelators.Virus infectivity was measured by focus-forming assay and quantitative RT-PCR.Intracellular Ca^(2+)was measured using Fluo-4-AM dye.VE-cadherin and focal adhesion kinase(FAK)expressions were investigated by immunofluorescence and immunoblotting assays,respectively.Results:DENV infection increased intracellular cytosolic Ca^(2+)levels and caused disassembly of the adherens junction protein,VEcadherin as evidenced by decreased VE-cadherin expression at the periphery of DENV-2 infected HUVECs.Depletion of intracellular Ca^(2+)stores,particularly those of the endoplasmic reticulum Ca^(2+),significantly decreased DENV yield in HUVECs.Decreased virus yield following the depletion of intracellular Ca^(2+)was caused by the inhibition of viral entry into HUVECs and not the inhibition of viral binding or attachment.DENV-2 infection also resulted in Ca^(2+)-dependent activation of FAK.Conclusions:Intracellular Ca^(2+)is required for the early phases of DENV infection in endothelial cells.Increased cytosolic Ca^(2+)levels in endothelial cells during DENV infection activated FAK,disrupted adherens junctions and compromised barrier integrity.Thus,Ca^(2+)plays an important role in DENV infection in endothelial cells.