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

Abstract

Objective: To investigate the involvement of Ca2+ 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 Ca2+ or endoplasmic reticulum Ca2+ chelators. Virus infectivity was measured by focus-forming assay and quantitative RT-PCR. Intracellular Ca2+ 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 Ca2+ levels and caused disassembly of the adherens junction protein, VE- cadherin as evidenced by decreased VE-cadherin expression at the periphery of DENV-2 infected HUVECs. Depletion of intracellular Ca2+ stores, particularly those of the endoplasmic reticulum Ca2+, significantly decreased DENV yield in HUVECs. Decreased virus yield following the depletion of intracellular Ca2+ 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 Ca2+-dependent activation of FAK. Conclusions: Intracellular Ca2+ is required for the early phases of DENV infection in endothelial cells. Increased cytosolic Ca2+ levels in endothelial cells during DENV infection activated FAK, disrupted adherens junctions and compromised barrier integrity. Thus, Ca2+ plays an important role in DENV infection in endothelial cells.

Keywords

• endothelial cells; calcium signalling; dengue virus; endothelium permeability; intracellular calcium