Enterovirus 71 (EV71) is the main causative pathogen of
hand, foot, and mouth disease (HFMD). The severe neurological complications caused by EV71
infection and the lack of effective therapeutic medicine underline the importance of searching for
antiviral substances.
Pyrrolidine dithiocarbamate (
PDTC), an
antioxidant, has been reported to inhibit the replication of coxsackievirus B (CVB) through dysregulating
ubiquitin-
proteasome system (UPS). In this study, we demonstrated that
PDTC exerted potent
antiviral effect on EV71.
Viral RNA synthesis,
viral protein expression, and the production of viral progeny were significantly reduced by the treatment of
PDTC in Vero cells infected with EV71. Similar to the previous report about the inhibitory effect of
PDTC on UPS, we found that
PDTC treatment led to decreased levels of polyubiquitinated
proteins in EV71-infected cells. The inhibitory effect of
PDTC on UPS was further confirmed by the increased accumulation of
cell cycle regulatory proteins p21 and p53, which are normally degraded through UPS, while the expression levels of both
proteins remained unchanged. We also showed that
PDTC had no impact on the activity of
proteasome. Thus, we demonstrated that the down-regulation of
PDTC on UPS was the result of its inhibition on ubiquitination. More importantly, this study provides evidence that the inhibition on UPS was required for the
antiviral activity of
PDTC, since
MG132, a potent
proteasome inhibitor, significantly inhibited the cytopathic effect and
viral protein synthesis in EV71-infected cells. We also found that the
antioxidant property of
PDTC did not contribute to its
antiviral effect, since
N-acetyl-l-cysteine, a potent
antioxidant, could not inhibit viral replication. In addition, CPE and
viral protein synthesis were not inhibited in the cells pretreated with
PDTC 2h before
viral infection and then cultured in the media with no
PDTC supplement, while the
antioxidant effect of
PDTC was retained.
PDTC also showed significant inhibition on apoptosis induced by EV71
infection when it was applied at the early stage of
viral infection. Our results collectively suggest that
PDTC could be a potential anti-EV71 compound which possesses both
antiviral and anti-apoptotic capacity.