A novel pharmacophore model to identify leads for simultaneous inhibition of anti-coagulation and anti-inflammatory activities of snake venom phospholipase A(2)

In silico identification of promiscuous scaffolds as potential inhibitors of 1-deoxy-d-xylulose 5-phosphate reductoisomerase for treatment of Falciparum malaria

CONTEXT

Malaria remains one of the prevalent infectious diseases worldwide. Plasmodium falciparum 1-deoxy-d-xylulose-5-phosphate reductoisomerase (PfDXR) plays a role in isoprenoid biosynthesis in the malaria parasite, making this parasite enzyme an attractive target for antimalarial drug design. Fosmidomycin is a promising DXR inhibitor, which showed safety as well as efficacy against Plasmodium falciparum malaria in clinical trials. However, due to its poor oral bioavailability and non-drug-like properties, the focus of medicinal chemists is to develop inhibitors with improved pharmacological properties.

OBJECTIVE

This study described the computational design of new and potent inhibitors for deoxyxylulose 5-phosphate reductoisomerase and the prediction of their pharmacokinetic and pharmacodynamic properties.

MATERIAL AND METHODS

A complex-based pharmacophore model was generated from the complex X-ray crystallographic structure of PfDXR using MOE (Molecular Operating Environment). Furthermore, MOE-Dock was used as docking software to predict the binding modes of hits and target enzyme.

RESULTS

Finally, 14 compounds were selected as new and potent inhibitors of PfDXR on the basis of pharmacophore mapping, docking score, binding energy and binding interactions with the active site residues of the target protein. The predicted pharmacokinetic properties showed improved permeability by efficiently crossing blood-brain barrier. While, in silico promiscuity binding data revealed that these hits also have the ability to bind with other P. falciparum drug targets.

DISCUSSION AND CONCLUSION

In conclusion, innovative scaffolds with novel modes of action, improved efficacy and acceptable physiochemical/pharmacokinetic properties were computationally identified.

In silico identification and evaluation of leads for the simultaneous inhibition of protease and helicase activities of HCV NS3/4A protease using complex based pharmacophore mapping and virtual screening

Hepatitis C virus (HCV) infection is an alarming and growing threat to public health. The present treatment gives limited efficacy and is poorly tolerated, recommending the urgent medical demand for novel therapeutics. NS3/4A protease is a significant emerging target for the treatment of HCV infection. This work reports the complex-based pharmacophore modeling to find out the important pharmacophoric features essential for the inhibition of both protease and helicase activity of NS3/4A protein of HCV. A seven featured pharmacophore model of HCV NS3/4A protease was developed from the crystal structure of NS3/4A protease in complex with a macrocyclic inhibitor interacting with both protease and helicase sites residues via MOE pharmacophore constructing tool. It consists of four hydrogen bond acceptors (Acc), one hydrophobic (Hyd), one for lone pair or active hydrogen (Atom L) and a heavy atom feature (Atom Q). The generated pharmacophore model was validated by a test database of seventy known inhibitors containing 55 active and 15 inactive/least active compounds. The validated pharmacophore model was used to virtually screen the ChemBridge database. As a result of screening 1009 hits were retrieved and were subjected to filtering by Lipinski’s rule of five on the basis of which 786 hits were selected for further assessment using molecular docking studies. Finally, 15 hits of different scaffolds having interactions with important active site residues were predicted as lead candidates. These candidates having unique scaffolds have a strong likelihood to act as further starting points in the development of novel and potent NS3/4A protease inhibitors.

AhV_aPA-induced vasoconstriction involves the IP₃Rs-mediated Ca²⁺ releasing

AhV_aPA, the acidic PLA₂ purified from Agkistrodon halys pallas venom, was previously reported to possess a strong enzymatic activity and can remarkably induce a further contractile response on the 60 mM K⁺-induced contraction with an EC₅₀ in 369 nM on mouse thoracic aorta rings. In the present study, we found that the p-bromo-phenacyl-bromide (pBPB), which can completely inhibit the enzymatic activity of AhV_aPA, did not significantly reduce the contractile response on vessel rings induced by AhV_aPA, indicating that the vasoconstrictor effects of AhV_aPA are independent of the enzymatic activity. The inhibitor experiments showed that the contractile response induced by AhV_aPA is mainly attributed to the Ca²⁺ releasing from Ca²⁺ store, especially sarcoplasmic reticulum (SR). Detailed studies showed that the Ca²⁺ release from SR is related to the activation of inositol trisphosphate receptors (IP₃Rs) rather than ryanodine receptors (RyRs). Furthermore, the vasoconstrictor effect could be strongly reduced by pre-incubation with heparin, indicating that the basic amino acid residues on the surface of AhV_aPA may be involved in the interaction between AhV_aPA and the molecular receptors. These findings offer new insights into the functions of snake PLA₂ and provide a novel pathogenesis of A. halys pallas venom.