Natural Product Inspired Novel Indole based Chiral Scaffold Kills Human Malaria Parasites via Ionic Imbalance Mediated Cell Death

Abstract

Natural products offer an abundant source of diverse novel scaffolds that inspires development of next generation anti-malarials. With this vision, a library of scaffolds inspired by natural biologically active alkaloids was synthesized from chiral bicyclic lactams with steps/scaffold ratio of 1.7:1. On evaluation of library of scaffolds for their growth inhibitory effect against malaria parasite we found one scaffold with IC50 in low micro molar range. It inhibited parasite growth via disruption of Na+ homeostasis. P-type ATPase, PfATP4 is responsible for maintaining parasite Na+ homeostasis and is a good target for anti-malarials. Molecular docking with our scaffold showed that it fits well in the binding pocket of PfATP4. Moreover, inhibition of Na+-dependent ATPase activity by our potent scaffold suggests that it targets parasite by inhibiting PfATP4, leading to ionic imbalance. However how ionic imbalance attributes to parasite’s death is unclear. We show that ionic imbalance caused by scaffold 7 induces autophagy that leads to onset of apoptosis in the parasite evident by the loss of mitochondrial membrane potential (ΔΨm) and DNA degradation. Our study provides a novel strategy for drug discovery and an insight into the molecular mechanism of ionic imbalance mediated death in malaria parasite.

A De novo Peptide from a High Throughput Peptide Library Blocks Myosin A -MTIP Complex Formation in Plasmodium falciparum

“…4.15. Parasite Culture P. falciparum 3D7 strain was thawed and cultured in vitro in human O+ erythrocytes at 4% hematocrit using the method described previously [55]. Briefly, parasites were cultured in medium containing RPMI 1640 (Invitrogen, Carlsbad, CA, USA), supplemented with 2 g/L NaHCO 3 (Sigma, St. Louis, MO, USA), 5 g/L albumax (Invitrogen), 50 mg/L hypoxanthine (Sigma), and 10 µg/mL gentamicin sulfate (Invitrogen, Carlsbad, CA, USA) at a pH of 7.2 under mixed gas condition (5% CO 2 , 5% O 2 , 95% N 2 ) at 37 • C.…”

<p>Indole: The After Next Scaffold of Antiplasmodial Agents?</p>

“…Another homology model using a rabbit Ca 2+ ATPase (PDB 2DQS) as a template is reported for the binding interactions of indole-based chiral bicyclic lactam derivatives. 53 Structural features essential in the spiroindolones or isoquinoline series of PfATP4 inhibitors and in the quinoline based inhibitors of hemozoin formation can be hybridized for optimization of the indole scaffold as a dual-acting antimalarial agent.…”

Interaction of 14-3-3I and CDPK1 mediates the growth of human malaria parasite

“…IFAs were performed on synchronized P. falciparum 3D7 culture to check for expression of 14-3-3I and its co-localization with CDPK1 in mature stages of the parasite, as described earlier (74). Briefly, mature schizonts (44-46 hpi) & merozoites were isolated, smeared on glass slides, dried and fixed with pre-chilled methanol for overnight at -20 o C. Non-specific binding sites in the parasite were blocked with 3% BSA (in 1X PBS) for 1 hour at room temperature (RT, 293K) and probed with anti-Pf14-3-3I mouse serum and anti-PfCDPK1 rabbit serum at dilutions of 1:50, for 1 hour at RT.…”