Feline calicivirus- and murine norovirus-induced COX-2/PGE2 signaling pathway has proviral effects

Cyclooxygenases (COXs)/prostaglandin E-2 (PGE(2)) signaling pathways are known to modulate a variety of homeostatic processes and are involved in various pathophysiological conditions. COXs/PGE(2) signaling pathways have also been demonstrated to have proviral or antiviral effects, which appeared different even in the same virus family. A porcine sapovirus Cowden strain, a member of genus Sapovirus within the Caliciviridae family, induces strong COX-2/PGE(2) but transient COX-1/PGE(2) signaling to enhance virus replication. However, whether infections of other viruses in the different genera activate COXs/PGE(2) signaling, and thus affect the replication of viruses, remains unknown. In the present study, infections of cells with the feline calicivirus (FCV) F9 strain in the genus Vesivirus and murine norovirus (MNV) CW-1 strain in the genus Norovirus only activated the COX-2/PGE(2) signaling in a time-dependent manner. Treatment with pharmacological inhibitors or transfection of small interfering RNAs (siRNAs) against COX-2 enzyme significantly reduced the production of PGE(2) as well as FCV and MNV replications. The inhibitory effects of these pharmacological inhibitors against COX-2 enzyme on the replication of both viruses were restored by the addition of PGE(2). Silencing of COX-1 via siRNAs and inhibition of COX-1 via an inhibitor also decrease the production of PGE(2) and replication of both viruses, which can be attributed to the inhibition COX-1/PGE(2) signaling pathway. These data indicate that the COX-2/PGE(2) signaling pathway has proviral effects for the replication of FCV and MNV, and pharmacological inhibitors against these enzymes serve as potential therapeutic candidates for treating FCV and MNV infections.