Potential Dengue Virus-Triggered Apoptotic Pathway in Human Neuroblastoma Cells: Arachidonic Acid, Superoxide Anion, and NF-κB Are Sequentially Involved

Abstract

Direct in vivo evidence for the susceptibility of human neuronal cells to dengue virus has not been reported.In this study, we demonstrated that type 2 dengue (DEN-2) virus infection induced extensive apoptosis in the human neuroblastoma cell line SK-N-SH. Phospholipase A 2 (PLA 2 ) was activated by DEN-2 infection, which led to the generation of arachidonic acid (AA). Inhibition of PLA 2 activity by the PLA 2 inhibitors, AACOCF 3 and ONO-RS-082, diminished DEN-2 virus-induced apoptosis. In contrast, the cyclooxygenase inhibitors aspirin and indomethacin, thought to increase AA accumulation by blocking AA catabolism, enhanced apoptosis. Exogenous AA induced apoptosis in a dose-dependent manner. Superoxide anion, which is thought to be generated through the AA-activated NADPH oxidase, was increased after infection. Pretreatment with superoxide dismutase (SOD) protected cells against DEN-2 virus-induced apoptosis. Furthermore, generation of superoxide anion was blocked by AACOCF 3 . In addition, the transcription factors, NF-B and c-Jun, were found to be activated after DEN-2 virus infection. However, pretreatment of cells with oligodeoxynucleotides containing NF-B, but not c-Jun, binding sites (transcription factor decoy) strongly prevented dengue virusinduced apoptosis. The finding that AACOCF 3 and SOD significantly block activation of NF-B suggests that this activation is derived from the AA-superoxide anion pathway. Our results indicate that DEN-2 virus infection of human neuroblastoma cells triggers an apoptotic pathway through PLA 2 activation to superoxide anion generation and subsequently to NF-B activation. This apoptotic effect can be either directly derived from the action of AA and superoxide anion on mitochondria or indirectly derived from the products of apoptosis-related genes activated by NF-B.Dengue virus, a mosquito-borne human pathogen, is a member of the Flaviviridae and is classified into four serotypes (Dengue virus type 1 through 4, designated here DEN-1, -2, -3, and -4 virus) (27,74). Dengue disease, which is caused by dengue virus infection, is considered a major public health problem in Southeast Asia and Central America (25, 58). As a consequence of increasing travel to areas of endemicity, dengue infection has been imported to many parts of the world. Classic dengue fever generally presents in older children and adults with high fever, severe headache and retro-orbital pain, myalgia, arthralgia, nausea, and rash. The acute phase may last for up to a week, but prolonged recovery is common and is sometimes associated with fatigue and depression. In some cases, hemorrhagic manifestations (dengue hemorrhagic fever) and signs of circulatory failure occur, leading to sudden and often hypovolemic shock (dengue shock syndrome) (26,88). An increasing number of cases have been reported with manifestations of encephalopathy and encephalitis, which cover a wide range of symptoms and signs from headache and clouded sensorium to convulsion, spasticity, and coma (34,49,73,79). As a result, the etiolo...

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Heat Shock Protein 90 and Heat Shock Protein 70 Are Components of Dengue Virus Receptor Complex in Human Cells

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