Rosmarinic acid interferes with influenza virus A entry and replication by decreasing GSK3β and phosphorylated AKT expression levels

Background: The purpose of this study was to examine the in vivo activity of rosmarinic acid (RA) – a phytochemical with antioxidant, anti-inflammatory, and antiviral properties – against influenza virus (IAV). An antibody-based kinase array and different in vitro functional assays were also applied to identify the mechanistic underpinnings by which RA may exert its anti-IAV activity. Methods: We initially examined the potential efficacy of RA using an in vivo mouse model. A time-of-addition assay and an antibody-based kinase array were subsequently applied to investigate mechanism-of-action targets for RA. The hemagglutination inhibition assay, neuraminidase inhibition assay, and cellular entry assay were also performed. Results: RA increased survival and prevented body weight loss in IAV-infected mice. In vitro experiments revealed that RA inhibited different IAV viruses – including oseltamivir-resistant strains. From a mechanistic point of view, RA downregulated the GSK3β and Akt signaling pathways – which are known to facilitate IAV entry and replication into host cells. Conclusions: RA has promising preclinical efficacy against IAV, primarily by interfering with the GSK3β and Akt signaling pathways.