The antimalarial activity of transdermal N-89 mediated by inhibiting ERC gene expression in P. Berghei-infected mice

Through studies of new antimalarial drugs, we identified 1,2,6,7-tetraoxaspiro[7.11]nonadecane (N-89) as a potential drug candidate. Here, we analyzed the antimalarial action of a transdermal formulation (td) of N-89, designed for easy use by children, using Plasmodium berghei-infected mice as a model for malaria patients. The td N-89 or artemisinin (ART) formulation was transdermally administered to P. berghei-infected mice with 0.2-0.4 % parasitemia, twice daily for four days, at an effective dose of 90 % for malaria. Parasitemia was decreased in td N-89 and td ART groups during the drug treatment; then, three of the eight mice in td N-89 group were completely cured without relapse. Additionally, abnormal trophozoites in td N-89 group were observed 8 h after administration and increased up to 24 h. To study the change in endoplasmic reticulum-resident calcium-binding protein (ERC) gene expression with td N-89, we investigated the gene expression of P. berghei ERC (PbERC) after td N-89 treatment. PbERC gene expression was increased time-dependently in control group, and was statistically decreased at 4 and 8 h and then increased similar to that of control group at 12 h in td ART group. In contrast, the expression in td N-89 group was almost steady starting from 0 h. We also studied parasite egress-related genes expression after td N-89 treatment, plasmepsin X, subtilisin-like protease 1 and merozoite surface protein 1, were suppressed at 12 h compared to control group. These results suggest that N-89 affects function of endoplasmic reticulum via regulating gene suppression and subsequently parasite growth is inhibited.