Apoptosis induced in chicken embryo fibroblasts in vitro by a polyinosinic:polycytidylic acid copolymer

This study investigated apoptosis induced in chicken embryo fibroblast (CEF) cells by the toxic effects of polyinosinic:polycytidylic acid copolymer (Poly I:C). Along with cell viability and morphological changes, other indicators were measured in vitro after incubation of the cells with Poly I:C, including phosphatidylserine translocation, the formation of DNA fragments, activity of caspase-3, caspase-8 and caspase-9, and the expression levels of RIPK1 mRNA and TNRSF8 mRNA. An inhibition of proliferation was found with increasing levels of Poly I:C, showing that Poly I:C was toxic to the cells. The findings of phosphatidylserine translocation and formation of DNA fragmentation suggested that Poly I:C induced apoptosis. With increased incubation time, the activities of caspase-3 and caspase-8 increased, while there was no significant change in caspase-9 activity. Accordingly, it is concluded that the apoptosis induced by Poly I:C involves a cell death receptor-mediated pathway. The transcription level of RIPK1 mRNA decreased, while that of TNFRSF8 mRNA increased, indicating that Poly I:C-induced apoptosis was related to upregulation of TNFRSF8. These observations provide insight into the potential mechanism of Poly I:C-induced toxicity.