Quercetin 7-rhamnoside reduces porcine epidemic diarrhea virus replication via independent pathway of viral induced reactive oxygen species

We were investigated the effects of Q7R on the cytopathic effects (CPE) by CPE reduction assay. Production of DNA fragment and reactive oxygen species (ROS) induced by PEDV infection were studied using DNA fragmentation assay and flow cytometry.In the course of this study it was discovered that Q7R is an extremely potent compound against PEDV. The addition of Q7R to PEDV-infected Vero cells directly reduced the formation of a visible cytopathic effect (CPE). Also, Q7R did not induce DNA fragmentation. Furthermore, ROS increased the infection of PEDV, which was strongly decreased by N-acetyl-L-cysteins (NAC). However, the increased ROS was not decreased by Q7R. Antiviral activity of antioxidants such as NAC, pyrrolidine dithiocarbamate (PDTC), and the vitamin E derivative, trolox, were hardly noticed.We concluded that the inhibition of PEDV production by Q7R is not simply due to a general action as an antioxidants and is highly specific, as several other antioxidants (NAC, PDTC, trolox) are inactive against PEDV infection.Many viruses are capable of inducing cell death, leading to lysis of the infected cells [1-7]. In late stages of virus infections, morphological changes, commonly known as cytopathic effect (CPE), can be microscopically observed. Virus-induced CPE is characterized by cell rounding, shinkage, deformation of nuclei and chomatin condensation. However, early death of infected cells may limit virus replication [8]. Also, apoptosis, or programmed cell death (PCD), during the late phase of viral infection has been suggested to play an important role in virus life cycle by facilitating viral progeny release and propagation [9,10]. PCD is a process by which damaged, aged, or otherwise unwanted cells are eliminated though a series of steps that results in the destruction of their genome. The form of PCD known as apoptosis is characterized by a series of morphological changes, including nuclear condensation and fragmentation, cytoplasmic blebbing, and cell shi