Saururus chinensis (Lour.) Baill blocks enterovirus 71 infection by hijacking MEK1-ERK signaling pathway

The aerial parts of Saururus chinensis (Lour.) Baill are a Chinese herbal medicine used for the treatment of edema and inflammatory diseases. However, the effect of this medicine on enterovirus 71 (EV71) infection has not been explored. Previous studies showed that MEK1-ERK signal pathway was required for efficient replication of EV71 infection and inhibition of this signal pathway has been shown to suppress virus infection. Here we show that the water extract of S. chinensis (Lour.) Baill (SCB) significantly blocks EV71 infection by inhibiting the activation of MEK1-ERK signal pathway with an IC50 of 8.9μg/mL. SCB at 30 and 60 μg/mL blocked EV71-induced cytopathic effect (CPE) and production of infectious virion by 1.9 and 5.1 logs, respectively. Virucidal assay suggested that SCB had no virucidal activity against EV71 and probably exerted its effect by targeting multiple steps in EV71 infection. Knockdown of MEK1 but not MEK2 blocked EV71 replication. And SCB treatment inhibited the activation of MEK1-ERK signal during EV71 infection. Furthermore, we found that rutin at 200 μM, one of the major components of SCB, significantly suppressed EV71 induced CPE and inhibited viral replication in a dose dependent manner. Taken together, SCB inhibited EV71 infection by hijacking MEK1-ERK signal pathway and rutin was the responsible antiviral component of SCB.