In vitro and in vivo anti-malarial activity of novel harmine-analog heat shock protein 90 inhibitors: a possible partner for artemisinin

Abstract

BackgroundThe 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.MethodsForty-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.Results17A and 21A bound to PfHsp90 with average IC50 values of 12.2 ± 2.3 and 23.1 ± 8.8 µM, respectively. They also inhibited the P. falciparum W2 strain with average IC50 values of 4.2 ± 1.3 and 5.7 ± 1.7 µM, respectively. In vivo, three daily injections of P. berghei-infected BALB/c mice with 100 mg/kg of either 17A or 21A showed significant reduction in parasitaemia with a 51.5 and 56.1% reduction, respectively. Mice treated with 17A and 21A showed a median survival time of 11 and 14 days, respectively, while the vehicle control mice survived a median of only 8.5 days. A dose-ranging experiment with 21A showed that the compound has a dose-dependent anti-malarial effect. Furthermore, treatment of infected mice with a combination of 21A and dihydroartemisinin (DHA) showed a dramatic reduction in parasitaemia compared to treatment with DHA alone.ConclusionA 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.

In Vitro and In Vivo Antimalarial Activity of LZ1, a Peptide Derived from Snake Cathelicidin

“…A 72 h in vitro growth inhibition assay [40,41] was used to test the antimalarial activity of LZ1. P. falciparum line 3D7 was cultured in complete RPMI-1640 medium with 2% hematocrit and incubated in a humidified atmosphere with 5% O 2 , 5% CO 2 , and 90% N 2 at 37 °C.…”

Harmine and its derivatives: Biological activities and therapeutic potential in human diseases

“…Similarly, 17A and 21A, two harmine derivatives acting as anti-malarial agents. These were found more active as compared to chloroquine and artemisinin due to the substitution of halogens (Bayih et al, 2016).…”

“…Primitive studies have declared that harmine is an auspicious anti-malarial agent selectively targeting P. falciparum PfHsp90. The unique and non-toxic harmine analogues 17A and 21A have the affinity to bind with heat shock protein-90, inhibits P. falciparum at concentration of 4.2 ± 1.3 µM and 5.7 ± 1.7 µM during in vitro investigation, decreases parasitaemia and extends survival of P. berghei-affected BALB/c mice (100 mg/kg) in vivo (Bayih et al, 2016).…”

Small Molecule Inhibitors Targeting the Heat Shock Protein System of Human Obligate Protozoan Parasites

“…Targeting of Hsp90 in combination therapy has been shown to be effective in reversing resistance to chloroquine by P. falciparum [60]. In addition, two harmine-based inhibitors of PfHsp90 (harmine 17A and harmine 21A) were reportedly effective at reversing both chloroquine and artemisinin resistance based on a mouse malaria model (Figure 2) [60,64,75]. This further highlights the prospects of targeting heat shock proteins in combination therapies against parasites to recover the efficacy of traditional drugs to which parasites are currently resistant.…”