A novel validated assay to support the discovery of new anti-malarial gametocytocidal agents

The bacterial thiopeptide thiostrepton. An update of its mode of action, pharmacological properties and applications

The bacterial thiopeptide thiostrepton (TS) is used as a veterinary medicine to treat bacterial infections. TS is a protein translation inhibitor, essentially active against Gram-positive bacteria and some Gram-negative bacteria. In procaryotes, TS abrogates binding of GTPase elongation factors to the 70S ribosome, by altering the structure of rRNA-L11 protein complexes. TS exerts also antimalarial effects by disrupting protein synthesis in the apicoplast genome of Plasmodium falciparum. Interestingly, the drug targets both the infectious pathogen (bacteria or parasite) and host cell, by inducing endoplasmic reticulum stress-mediated autophagy which contributes to enhance the host cell defense. In addition, TS has been characterized as a potent chemical inhibitor of the oncogenic transcription factor FoxM1, frequently overexpressed in cancers or other diseases. The capacity of TS to crosslink FoxM1, and a few other proteins such as peroxiredoxin 3 (PRX3) and the 19S proteasome, contributes to the anticancer effects of the thiopeptide. The anticancer activities of TS evidenced using diverse tumor cell lines, in vivo models and drug combinations are reviewed here, together with the implicated targets and mechanisms. The difficulty to formulate TS is a drag on the pharmaceutical development of the natural product. However, the design of hemisynthetic analogues and the use of micellar drug delivery systems should facilitate a broader utilization of the compound in human and veterinary medicines. This review shed light on the many pharmacological properties of TS, with the objective to promote its use as a pharmacological tool and medicinal product.

High-Throughput Screen Identifying the Thiosemicarbazone NSC319726 Compound as a Potent Antimicrobial Lead Against Resistant Strains of Escherichia coli

Antibiotic discovery is vital when considering the increasing antimicrobial resistance threat. The aim of this work was to provide a high-throughput screen (HTS) assay using multidrug-resistant Escherichia coli strains to enable further research into antimicrobial lead discovery and identify novel antimicrobials. This study describes a primary HTS of a diverse library of 7884 small molecules against a susceptible E. coli strain. A secondary screening of 112 molecules against four E. coli strains with different susceptibility profiles revealed NSC319726 as a potential antimicrobial lead serving as a novel template. NSC319726 is a good candidate for an analoguing program.

Critical examination of approaches exploited to assess the effectiveness of transmission-blocking drugs for malaria

In the absence of clinically proven vaccines and emerging resistance to common antimalarials and insecticides, the onus of interrupting the life cycle of Plasmodium falciparum, is upon the transmission-blocking drugs. Current transmission-blocking drug primaquine finds its use restricted because of associated hemolytic toxicity issues in Glucose-6-Phosphate-Dehydrogenase deficient individuals. This article provides an extensive review of the assays used by the investigators to evaluate the transmission-blocking activity of drugs. Furthermore, limitations in existing transmission-blocking assessment approaches/studies are also covered in detail. This review is expected to help in the identification of lacunae in current understanding of transmission-blocking strategies, which are hindering our efforts to develop sustainable and effective transmission-blocking interventions.

Inhibitory effect of dihydroartemisinin on chondrogenic and hypertrophic differentiation of mesenchymal stem cells

Chondrocytes located in hyaline cartilage may maintain phenotype while the chondrocytes situated in calcified cartilage differentiate into hypertrophy. Chondrogenic and hypertrophic differentiation of mesenchymal stem cells (MSCs) are two subsequent processes during endochondral ossification. However, it is necessary for chondrocytes to hold homeostasis and to inhibit hypertrophic differentiation in stem cell-based regenerated cartilage. Dihydroartemisinin (DHA) is derived from artemisia apiacea which has many biological functions such as anti-malarial and anti-tumor. Whereas the effects of DHA on chondrogenic and hypertrophic differentiation are poorly understand. In this study, the cytotoxicity of DHA was determined by CCK8 assay and the cell apoptosis was analyzed by flow cytometry. Additionally, the effects of DHA on chondrogenic and hypertrophic differentiation of MSCs are explored by RT-PCR, western blotting and immunohistochemistry. The results showed that DHA inhibited expression of chondrogenic markers including Sox9 and Col2a1 by activating Nrf2 and Notch signaling. After induced to chondrogenesis, cells were treated with hypertrophic induced medium with DHA. The results revealed that hypertrophic markers including Runx2 and Col10a1 were down-regulated following DHA treatment through Pax6/HOXA2 and Gli transcription factors. These findings indicate that DHA is negative to chondrogenesis and is protective against chondrocyte hypertrophy to improve chondrocytes stability. Therefore, DHA might be not suited for chondogenesis but be potential as a new therapeutic candidate to maintain the biological function of regenerated cartilage.