Correction to: Enhanced uptake, high selective and microtubule disrupting activity of carbohydrate fused pyrano-pyranones derived from natural coumarins attributes to its anti-malarial potential.

Please note, following publication of the original article [1], the authors have advised of two errors that are present in the published article.

Enhanced uptake, high selective and microtubule disrupting activity of carbohydrate fused pyrano-pyranones derived from natural coumarins attributes to its anti-malarial potential.

BACKGROUND: Malaria is one of the deadliest infectious diseases caused by protozoan parasite of Plasmodium spp. Increasing resistance to anti-malarials has become global threat in control of the disease and demands for novel anti-malarial interventions. Naturally-occurring coumarins, which belong to a class of benzo-α-pyrones, found in higher plants and some essential oils, exhibit therapeutic potential against various diseases. However, their limited uptake and non-specificity has restricted their wide spread use as potential drug candidates. METHODS: Two series of carbohydrate fused pyrano[3,2-c]pyranone carbohybrids which were synthesized by combination of 2-C-formyl galactal and 2-C-formyl glucal, with various freshly prepared 4-hydroxycoumarins were screened against Plasmodium falciparum. The anti-malarial activity of these carbohybrids was determined by growth inhibition assay on P. falciparum 3D7 strain using SYBR green based fluorescence assay. Haemolytic activity of carbohybrid 12, which showed maximal anti-malarial activity, was determined by haemocompatibility assay. The uptake of the carbohybrid 12 by parasitized erythrocytes was determined using confocal microscopy. Growth progression assays were performed to determine the stage specific effect of carbohybrid 12 treatment on Pf3D7. In silico studies were conducted to explore the mechanism of action of carbohybrid 12 on parasite microtubule dynamics. These findings were further validated by immunofluorescence assay and drug combination assay. RESULTS: 2-C-formyl galactal fused pyrano[3,2-c]pyranone carbohybrid 12 exhibited maximum growth inhibitory potential against Plasmodium with IC50 value of 5.861 µM and no toxicity on HepG2 cells as well as no haemolysis of erythrocytes. An enhanced uptake of this carbohybrid compound was observed by parasitized erythrocytes as compared to uninfected erythrocytes. Further study revealed that carbohybrid 12 arrests the growth of parasite at trophozoite and schizonts stage during course of progression through asexual blood stages. Mechanistically, it was shown that the carbohybrid 12 binds to α,ß-heterodimer of tubulin and affects microtubule dynamics. CONCLUSION: These findings show carbohydrate group fusion to 4-hydroxycoumarin precursor resulted in pyrano-pyranones derivatives with better solubility, enhanced uptake and improved selectivity. This data confirms that, carbohydrate fused pyrano[3,2-c]pyranones carbohybrids are effective candidates for anti-malarial interventions against P. falciparum.

A Fast-Track Phenotypic Characterization of Plasmodium falciparum Vaccine Antigens through Lyse-Reseal Erythrocytes Mediated Delivery (LyRED) of RNA Interference for Targeted Translational Repression.

The minimal success of the malaria vaccine with available antigens indicates the need for intensive and accelerated research to identify and characterize new antigens that confer protection against infection, clinical manifestation, and even malaria transmission. Further, the genetic manipulation tools to characterize such antigens are very time-consuming and laborious due to the very low efficiency of transfection in the malaria parasite. Here, we report a human miRNA-mediated translational repression of antigens in Plasmodium falciparum as a fast-track method for understanding and validating their function. In this method, candidate miRNAs are designed based on favorable hybridization energy against a parasite gene, and miRNA mimics are delivered to the parasite by loading them as cargo in the erythrocytes by simple lyse-reseal method. Incubation of the miRNA loaded erythrocytes with purified mature trophozoites or schizonts results in the loaded erythrocytes' infection. The miRNA mimics are translocated to parasites, and the effect of miRNA-mediated translation repression can be monitored within 48-72 h post-invasion. Unlike other transfection based methods, this method is fast, reproducible, and robust. We call this method as lyse-reseal erythrocytes for delivery (LyRED) of miRNA, which is a rapid and straight-forward method providing an efficient alternative to the existing genetic tools for P. falciparum to characterize the function of antigens or genes. The identification of crucial antigens from the different stages of the Plasmodium falciparum life cycle by the miRNA targeting approach can fuel the development of efficacious subunit vaccines against malaria.

Interaction of Plasmodium falciparum apicortin with α- and ß-tubulin is critical for parasite growth and survival.

Cytoskeletal structures of Apicomplexan parasites are important for parasite replication, motility, invasion to the host cell and survival. Apicortin, an Apicomplexan specific protein appears to be a crucial factor in maintaining stability of the parasite cytoskeletal assemblies. However, the function of apicortin, in terms of interaction with microtubules still remains elusive. Herein, we have attempted to elucidate the function of Plasmodium falciparum apicortin by monitoring its interaction with two main components of parasite microtubular structure, α-tubulin-I and ß-tubulin through in silico and in vitro studies. Further, a p25 domain binding generic drug Tamoxifen (TMX), was used to disrupt PfApicortin-tubulin interactions which led to the inhibition in growth and progression of blood stage life cycle of P. falciparum.

Targeted repression of Plasmodium apicortin by host microRNA impairs malaria parasite growth and invasion.

Mature human erythrocytes contain a rich pool of microRNAs (miRNAs), which result from differentiation of the erythrocytes during the course of haematopoiesis. Recent studies have described the effect of erythrocytic miRNAs on the invasion and growth of the malaria parasite Plasmodium falciparum during the asexual blood stage of its life cycle. In this work, we have identified two erythrocytic miRNAs, miR-150-3p and miR-197-5p, that show favourable in silico hybridization with Plasmodium apicortin, a protein with putative microtubule-stabilizing properties. Co-expression of P. falciparum apicortin and these two miRNAs in a cell line model resulted in downregulation of apicortin at both the RNA and protein level. To create a disease model of erythrocytes containing miRNAs, chemically synthesized mimics of miR-150-3p and miR-197-5p were loaded into erythrocytes and subsequently used for invasion by the parasite. Growth of the parasite was hindered in miRNA-loaded erythrocytes, followed by impaired invasion; micronemal secretion was also reduced, especially in the case of miR-197-5p. Apicortin expression was found to be reduced in miRNA-loaded erythrocytes. To interpret the effect of downregulation of apicortin on parasite invasion to host erythrocytes, we investigated the secretion of the invasion-related microneme protein apical membrane antigen 1 (AMA1). AMA1 secretion was found to be reduced in miRNA-treated parasites. Overall, this study identifies apicortin as a novel target within the malaria parasite and establishes miR-197-5p as its miRNA inhibitor. This miRNA represents an unconventional nucleotide-based therapeutic and provides a new host factor-inspired strategy for the design of antimalarial molecular medicine.This article has an associated First Person interview with the first author of the paper.

Chorismate synthase mediates cerebral malaria pathogenesis by eliciting salicylic acid-dependent autophagy response in parasite.

Cerebral malaria caused by Plasmodium falciparum is the severest form of the disease resulting in the morbidity of a huge number of people worldwide. Development of effective curatives is essential in order to overcome the fatality of cerebral malaria. Earlier studies have shown the presence of salicylic acid (SA) in malaria parasite P. falciparum, which plays a critical role in the manifestation of cerebral malaria. Further, the application of SA for the treatment of acute symptoms in cerebral malaria increases the activity of iNOS leading to severe inflammation-mediated death, also called as Reye's syndrome. Therefore, modulation of the level of SA might be a novel approach to neutralize the symptoms of cerebral malaria. The probable source of parasite SA is the shikimate pathway, which produces chorismate, a precursor to aromatic amino acids and other secondary metabolites like SA in the parasite. In this work, we performed the immunological, pathological and biochemical studies in mice infected with chorismate synthase knocked-out Plasmodium berghei ANKA, which does not produce SA. Fewer cerebral outcomes were observed as compared to the mice infected with wild-type parasite. The possible mechanism behind this protective effect might be the hindrance of SA-mediated induction of autophagy in the parasite, which helps in its survival in the stressed condition of brain microvasculature during cerebral malaria. The absence of SA leading to reduced parasite load along with the reduced pathological symptoms contributes to less fatality outcome by cerebral malaria.

Stenotrophomonas maltophilia Phenotypic and Genotypic Diversity during a 10-year Colonization in the Lungs of a Cystic Fibrosis Patient.

The present study was carried out to understand the adaptive strategies developed by Stenotrophomonas maltophilia for chronic colonization of the cystic fibrosis (CF) lung. For this purpose, 13 temporally isolated strains from a single CF patient chronically infected over a 10-year period were systematically characterized for growth rate, biofilm formation, motility, mutation frequencies, antibiotic resistance, and pathogenicity. Pulsed-field gel electrophoresis (PFGE) showed over time the presence of two distinct groups, each consisting of two different pulsotypes. The pattern of evolution followed by S. maltophilia was dependent on pulsotype considered, with strains belonging to pulsotype 1.1 resulting to be the most adapted, being significantly changed in all traits considered. Generally, S. maltophilia adaptation to CF lung leads to increased growth rate and antibiotic resistance, whereas both in vivo and in vitro pathogenicity as well as biofilm formation were decreased. Overall, our results show for the first time that S. maltophilia can successfully adapt to a highly stressful environment such as CF lung by paying a "biological cost," as suggested by the presence of relevant genotypic and phenotypic heterogeneity within bacterial population. S. maltophilia populations are, therefore, significantly complex and dynamic being able to fluctuate rapidly under changing selective pressures.

Function and toxicity of amyloid beta and recent therapeutic interventions targeting amyloid beta in Alzheimer's disease.

Amyloidogenesis has been implicated in a broad spectrum of diseases in which amyloid protein is invariably misfolded and deposited in cells and organs. Alzheimer's disease is one of the most devastating ailments among amyloidogenesis induced dementia. The amyloid beta (Aß) peptide derived from amyloid precursor protein (APP) is misfolded and deposited as plaques in the brain, which are said to be the hallmark of Alzheimer's disease. In normal brains physiological concentration of the Aß peptide has been indicated to be involved in modulating neurogenesis and synaptic plasticity. However, excess Aß production, its aggregation and deposition deleteriously affect a large number of biologically important pathways leading to neuronal cell death. Targeting Aß production, Aß aggregation or its clearance from the brain has been an active area of research for preventing or curing AD. Our Feature Article intends to detail the aggregation mechanism, the physiological role of the Aß peptide, elaborate its toxic effects, and outline the different classes of molecules designed in the last two years to inhibit amyloidogenic APP processing, Aß oligomerization or fibrillogenesis and to modulate different pathways for active clearance of Aß from the brain.