Abstract
Background
Malaria is a serious public health concern. Artemisinin and its derivatives are first-line drugs for the treatment of Plasmodium falciparum malaria. In mammals, artemisinin exhibits potent anti-inflammatory and immunoregulatory properties. However, it is unclear whether artemisinin plays a regulatory role in the innate immunity of mosquitoes, thereby affecting the development of Plasmodium in Anopheles when Artemisinin and its metabolites enter mosquitoes. This study aimed to determine the effect of DHA, a first-generation semisynthetic derivative of artemisinin, on innate immunity and malaria vector competence of Anopheles stephensi.
Methods
Anopheles stephensi was fed Plasmodium-infected mice treated with dihydroartemisinin (DHA) via gavage, Plasmodium-infected blood containing DHA in vitro, or DHA-containing sugar, followed by Plasmodium yoelii infection. The engorged female mosquitoes were separated and dissected 8 days after infection. Plasmodium oocysts were counted and compared between the control and DHA-treated groups. Additionally, total RNA and proteins were extracted from engorged mosquitoes 24 and 72 h post-infection (hpi). Real-time PCR and western blotting were performed to detect the transcriptional levels and protein expression of immune molecules in mosquitoes. Finally, the Toll signaling pathway was inhibited via RNAi and the infection intensity was analyzed to confirm the role of the Toll signaling pathway in the effect of DHA on the vector competence of mosquitoes.
Results
DHA treatment via different approaches significantly reduced the number of Plasmodium oocysts in mosquitoes. The transcriptional levels of anti-Plasmodium immune genes, including TEP1, LRIM1, and APL1C; Toll pathway genes, including Tube, MyD88, and Rel1; and the effector Defensin 1, were upregulated by DHA treatment at 24 and 72 hpi. TEP1 and Rel1 protein expression was significantly induced under DHA treatment. However, Rel1 knockdown in DHA-treated mosquitoes abrogated DHA-mediated refractoriness to Plasmodium infection.
Conclusions
DHA treatment effectively inhibited the development of P. yoelii in An. stephensi by upregulating mosquitoes’ Toll signaling pathway, thereby influencing the susceptibility of Anopheles to Plasmodium.