Diversity-oriented synthesis derived indole based spiro and fused small molecules kills artemisinin-resistant Plasmodium falciparum.

BACKGROUND: Despite numerous efforts to eradicate the disease, malaria continues to remain one of the most dangerous infectious diseases plaguing the world. In the absence of any effective vaccines and with emerging drug resistance in the parasite against the majority of anti-malarial drugs, the search for new drugs is urgently needed for effective malaria treatment. METHODS: The goal of the present study was to examine the compound library, based on indoles generated through diversity-oriented synthesis belonging to four different architecture, i.e., 1-aryltetrahydro/dihydro-ß-carbolines and piperidine/pyrrolidine-fused indole derivatives, for their in vitro anti-plasmodial activity. Trifluoroacetic acid catalyzed transformation involving tryptamine and various aldehydes/ketones provided the library. RESULTS: Among all the compounds screened, 1-aryltetrahydro-ß-carbolines 2 and 3 displayed significant anti-plasmodial activity against both the artemisinin-sensitive and artemisinin-resistant strain of Plasmodium falciparum. It was observed that these compounds inhibited the overall parasite growth in intra-erythrocytic developmental cycle (IDC) via reactive oxygen species-mediated parasitic death and thus could be potential anti-malarial compounds. CONCLUSION: Overall the compounds 2 and 3 identified in this study shows promising anti-plasmodial activity that can kill both artemisinin-sensitive and artemisinin-resistant strains of P. falciparum.

Inhibition of PfMYST Histone Acetyltransferase Activity Blocks Plasmodium falciparum Growth and Survival.

One of the major barriers in the prevention and control of malaria programs worldwide is the growing emergence of multidrug resistance in Plasmodium parasites, and this necessitates continued efforts to discover and develop effective drug molecules targeting novel proteins essential for parasite survival. In recent years, epigenetic regulators have evolved as an attractive drug target option owing to their crucial role in survival and development of Plasmodium at different stages of its life cycle. PfMYST, a histone acetyltransferase protein, is known to regulate key cellular processes, such as cell cycle progression, DNA damage repair, and antigenic variation, that facilitate parasite growth, adaptation, and survival inside its host. With the aim of assessing the therapeutic potential of PfMYST as a novel drug target, we examined the effect of NU9056 (an HsTIP60 inhibitor) on the rate of parasite growth and survival. In the present study, by using a yeast complementation assay, we established that PfMYST is a true homolog of TIP60 and showed that NU9056 can inhibit PfMYST catalytic activity and kill P. falciparum parasites in culture. Inhibiting the catalytic activity of PfMYST arrests the parasite in the trophozoite stage and inhibits its further transition to the schizont stage, eventually leading to its death. Overall, our study provides proof of concept that PfMYST catalytic activity is essential for parasite growth and survival and that PfMYST can be a potential target for antimalarial therapy.

Plasmodium falciparum RUVBL3 protein: a novel DNA modifying enzyme and an interacting partner of essential HAT protein MYST.

RUVBLs constitute a conserved group of ATPase proteins that play significant role in a variety of cellular processes including transcriptional regulation, cell cycle and DNA damage repair. Three RUVBL homologues, namely, PfRUVBL1, PfRUVBL2 and PfRUVBL3 have been identified in P. falciparum, unlike its eukaryotic counterparts, which have two RUVBL proteins (RUVBL1 & RUVBL2). The present study expands our understanding of PfRUVBL3 protein and thereby basic biology of Plasmodium in general. Here, we have shown that parasite PfRUVBL3 is a true homolog of human/yeast RUVBL2 protein. Our result show that PfRUVBL3 constitutively expresses throughout the stages of intra-erythrocytic cycle (IDC) with varied localization. In addition to ATPase and oligomerization activity, we have for the first time shown that PfRUVBL3 possess DNA cleavage activity which interestingly is dependent on its insertion domain. Furthermore, we have also identified RUVBL3 to be an interacting partner of an essential chromatin remodeling protein PfMYST and together they colocalize with H3K9me1 histone in parasitophorous vacuole during the ring stage of IDC suggesting their potential involvement in chromatin remodeling and gene transcription.

Pharmacological approach to increasing the retention of radiation-induced γ-H2AX foci using phosphatase inhibitors: significance in radiation biodosimetry.

In a scenario of accidental mass radiation exposure transportation and analysis of samples may take some time, resulting in loss of biomarker information over this period. The present study aims to use phosphatase inhibitors for longer retention of focal signals to adopt γ-H2AX as a biodosimetric biomarker for the management of early triage. Peripheral blood lymphocytes isolated from healthy individuals were irradiated in vitro with x-rays and γ-H2AX foci were analysed using fluorescent microscopy and flow cytometric methods. Further, the effect of protein phosphatase 2A inhibitors such as calyculin A, fostriecin and okadiac acid on the retention of foci was studied. Fluorescent microscopy was found to be a more sensitive method than flow cytometry. Calyculin A showed significant retention of focal signals at 6 h with 1.5-fold increased retention compared to radiation alone; this may prove beneficial in early triage management because of a better dose approximation.

Pharmacological approach to increase the retention of radiation induced gamma-H2AX foci using phosphatase inhibitors: significance in radiation biodosimetry.

In a scenario of accidental mass radiation exposure, transportation and analyzing samples may take its time resulting in loss of biomarker information over this period. The present study aims to use phosphatases inhibitors for longer retention of foci signals to adopt γ-H2AX as a biodosimetric biomarker for the management of early triage. Peripheral blood lymphocytes isolated from healthy individuals irradiated in vitro with X-rays, and γ-H2AX analysed using fluorescent microscopy and flow cytometric methods. Further, the effect of protein phosphatase 2A inhibitors like Calyculin A, Fostriecin and Okadiac acid on the retention of foci were studied. The fluorescent microscopy to be more sensitive method when compared to flow cytometry. Calyculin A showed significant retention of foci signals at 6h with 1.5 fold increased retention of foci signals, this may prove beneficial in early triage management, because of a better dose approximation.