Abstract:
Type 1 interferons (IFN-1) are pleiotropic cytokines with well-established anticancer and antiviral properties, particularly in
mucosal tissues. Hence, natural IFN-1-inducing treatments are highly sought after in the clinic. Here, we report for the first
time that cryptolepine, a pharmacoactive alkaloid in the medicinal plant Cryptolepis sanguinolenta, is a potent IFN-1 pathway
inducer. Cryptolepine increased the transcript levels of JAK1, TYK2, STAT1, STAT2, IRF9, and OAS3, as well as increased the
accumulation of STAT1 and OAS3 proteins, similar to recombinant human IFN-α. Cryptolepine effects were observed in
multiple cell types including a model of human macrophages. This response was maintained in MAVS and STING-deficient
cell lines, suggesting that cryptolepine effects are not mediated by nucleic acids released upon nuclear or organelle damage. In
agreement, cryptolepine did not affect cell viability in concentrations that triggered potent IFN-1 activation. In addition, we
observed no differences in the presence of a pharmacological inhibitor of TBK1, a pleiotropic kinase that is a converging point
for Toll-like receptors (TLRs) and nucleic acid sensors. Together, our results demonstrate that cryptolepine is a strong inducer
of IFN-1 response and suggest that cryptolepine-based medications such as C. sanguinolenta extract could be potentially tested
in resource-limited regions of the world for the management of chronic viral infections as well as cancers.
