Apoptosis of hepatocytes caused by Punta Toro virus (Bunyaviridae: Phlebovirus) and its implication for Phlebovirus pathogenesis.
Experimental infection of hamsters with Punta Toro virus (PTV) produces a disease with clinical and pathological similarities to the severe human hemorrhagic fever caused by Rift Valley fever virus (RVFV), thus providing an animal model for RVFV pathogenesis. In this model, hepatocytic apoptosis is the main pathological component of liver injuries that are responsible for severe hemorrhagic manifestations. To further elucidate whether viral replication in hepatocytes directly causes apoptosis, we studied the morphological and biochemical changes of apoptosis in HepG2 cells at different time points after PTV infection. Cellular viability began to decrease 12 hours after infection compared with controls. Caspases 3/7 were activated significantly at 48 and 72 hours after infection, and phosphatidylserine translocation and DNA fragmentation were also detected at 48 and 72 hours. Cell cycle analysis by flow cytometry showed that infected HepG2 cells were arrested at G(0)/G(1) phase. Furthermore, virus titer increased with apoptosis progression, suggesting that viral replication is necessary for the apoptotic process. These results indicate that PTV infection alone, without a secondary inflammatory cellular reaction, induces hepatocytic apoptosis and suggest that future therapeutics for RVFV hemorrhagic disease might target inhibition of cellular apoptotic pathways during the acute infection.
Ding
Xiaohua
X
Department of Pathology, University of Texas Medical Branch, 301 University Blvd., Galveston, TX 77555-0588, USA.
Xu
Fangling
F
Chen
Hongli
H
Tesh
Robert B
RB
Xiao
Shu-Yuan
SY
D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D002044:Bunyaviridae Infections / Q000473:pathology / Q000821:virology*; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000032:analysis / Q000378:metabolism; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002470:Cell Survival; D002522:Chlorocebus aethiops; D002999:Clone Cells; D053938:DNA Fragmentation; D004789:Enzyme Activation; D019793:Fluorescein; D005456:Fluorescent Dyes; D016193:G1 Phase; D015870:Gene Expression; D005814:Genes, Viral; D022781:Hepatocytes / Q000201:enzymology / Q000821:virology*; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000473:pathology / Q000821:virology; D008113:Liver Neoplasms / Q000473:pathology; D008856:Microscopy, Fluorescence; D016856:Phlebovirus / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D014709:Vero Cells; D014779:Virus Replication
D017304:Annexin A5; D005456:Fluorescent Dyes; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases; D019793:Fluorescein