Endothelial cell apoptosis induced by Dengue virus

Vascular leakage and hemorrhagic diathesis are life-threatening complications that occur to dengue hemorrhagic patients. However, the pathogenic mechanism of hemorrhage is not well understood. It has been shown that endothelial cells are permissive to dengue virus (DV) infection in vitro and DV antigen is found in endothelial cells of autopsy specimens collected from patients who died of DHF. Therefore, the study of interaction between DV and endothelial cells will shed light on the mechanism of dengue hemorrhage. We established a dengue hemorrhage mouse model in immunocompetent C57BL/6 mice by injecting DV serotype 2 strain 16681 intradermally. While high dose DV inoculation induced hemorrhage in all of the mice, 1/3 of those injected with 4-8 x 107 PFU developed hemorrhage in the subcutaneous tissues by day 3 of infection. Importantly, hemorrhage was accompanied by severe thrombocytopenia and vascular leakage. Double immunofluorescence staining revealed that DV targeted both macrophages and endothelial cells in the subcutaneous tissues. In vitro studies showed that human umbilical cord vein endothelial cells (HUVEC) and microvascular endothelial cell line (HMEC) were susceptible to DV and TNF-α enhanced DV-induced apoptosis. In addition, DV infection induced endothelial cell NOS and ROS production and endothelial cell apoptosis, which were also enhanced by TNF-α. These findings demonstrate that dengue virus and TNF-α-induced endothelial cell apoptosis is mediated by ROS and NO