harmine and artemisinin

The emergence of artemisinin-resistant Plasmodium falciparum strains poses a serious challenge to the control of malaria. This necessitates the development of new anti-malarial drugs. Previous studies have shown that the natural beta-carboline alkaloid harmine is a promising anti-malarial agent targeting the P. falciparum heat-shock protein 90 (PfHsp90). The aim of this study was to test the anti-malarial activity of harmine analogues.. Forty-two harmine analogues were synthesized and the binding of these analogues to P. falciparum heat shock protein 90 was investigated. The in vitro anti-malarial activity of two of the analogues, 17A and 21A, was evaluated using a 72-h growth inhibition assay. The in vivo anti-malarial activity was tested in Plasmodium berghei infection of BALB/c mice. The potential of 21A for a combination treatment with artemisinin was evaluated using in vivo combination study with dihydro-artemisinin in BALB/c mice. Cytotoxicity of the harmine analogues was tested in vitro using HepG2 and HeLa cell lines.. A novel and non-toxic harmine analogue has been synthesized which binds to PfHsp90 protein, inhibits P. falciparum in vitro at micromolar concentration, reduces parasitaemia and prolongs survival of P. berghei-infected mice with an additive anti-malarial effect when combined with DHA.

Topics: Animals; Antimalarials; Artemisinins; Cell Line; Cell Survival; Disease Models, Animal; Drug Synergism; Female; Harmine; HSP90 Heat-Shock Proteins; Humans; Inhibitory Concentration 50; Malaria; Mice, Inbred BALB C; Plasmodium berghei; Plasmodium falciparum; Protein Binding; Protozoan Proteins; Treatment Outcome

Previous studies have shown an antimalarial effect of total alkaloids extracted from leaves of Guiera senegalensis from Mali in West Africa. We independently observed that the beta-carboline alkaloid harmine obtained from a natural product library screen inhibited Plasmodium falciparum heat shock protein 90 (PfHsp90) ATP-binding domain. In this study, we confirmed harmine-PfHsp90-specific affinity using surface plasmon resonance analysis (dissociation constant [K(d)] of 40 μM). In contrast, the related compound harmalol bound human Hsp90 (HsHsp90) (K(d) of 224 μM) more tightly than PfHsp90 (K(d) of 7,010 μM). Site-directed mutagenesis revealed that Arg98 in PfHsp90 is essential for harmine selectivity. In keeping with our model indicating that Hsp90 inhibition affords synergistic combinations with existing antimalarials, we demonstrated that harmine potentiates the effect of chloroquine and artemisinin in vitro and in the Plasmodium berghei mouse model. These findings have implications for the development of novel therapeutic combinations that are synergistic with existing antimalarials.

Topics: Animals; Antimalarials; Artemisinins; Chloroquine; Drug Synergism; Harmaline; Harmine; HSP90 Heat-Shock Proteins; Malaria; Mice; Mice, Inbred BALB C; Mutagenesis, Site-Directed; Plasmodium berghei; Plasmodium falciparum; Protein Structure, Quaternary; Protein Structure, Tertiary; Surface Plasmon Resonance