Natural antiviral compound silvestrol modulates human monocyte-derived macrophages and dendritic cells

Outbreaks of infections with viruses like Sars-CoV-2, Ebola virus and Zika virus lead to major global health and economic problems because of limited treatment options. Therefore, new antiviral drug candidates are urgently needed. The promising new antiviral drug candidate silvestrol effectively inhibited replication of Corona-, Ebola-, Zika-, Picorna-, Hepatis E and Chikungunya viruses. Besides a direct impact on pathogens, modulation of the host immune system provides an additional facet to antiviral drug development because suitable immune modulation can boost innate defence mechanisms against the pathogens. In the present study, silvestrol down-regulated several pro- and anti-inflammatory cytokines (IL-6, IL-8, IL-10, CCL2, CCL18) and increased TNF-alpha during differentiation and activation of M1-macrophages, suggesting that the effects of silvestrol might cancel each other out. However, silvestrol amplified the anti-inflammatory potential of M2-macrophages by increasing expression of anti-inflammatory surface markers CD206, TREM2 and reducing release of pro-inflammatory IL-8 and CCL2. The differentiation of dendritic cells in the presence of silvestrol is characterized by down-regulation of several surface markers and cytokines indicating that differentiation is impaired by silvestrol. In conclusion, silvestrol influences the inflammatory status of immune cells depending on the cell type and activation status.