Entamoeba histolytica Adaption to Auranofin: A Phenotypic and Multi-Omics Characterization

Role of various virulence factors involved in the pathogenesis of Entamoeba histolytica

Developing countries continuously face challenges to get rid of amoebiasis, a protozoan disease caused by Entamoeba histolytica. Every year around 900 million people get affected by amoebiasis, among them only 10 % of people show the symptoms of the disease while 90 % of people do not show any symptoms but still, serve as carriers of the disease. Asymptomatic persons carry cysts of Entamoeba in their fecal matter, which is carried by house flies to contaminate the food and water. Entamoeba histolytica is a very successful pathogen because it has very well-developed virulence factors that function in infection to host as well as in overcoming the host's immune response. However, researchers have very little information about the clear relationship between virulence factors and the virulence of Entamoeba histolytica, through various research, researchers have been able to identify key pathogenic factors that are crucial to the pathogenesis of amoebiasis and have provided valuable insights into the development of the disease. The objective of this review is to underscore various virulence factors (Monosaccharides, Gal/GalNAc lectin, extracellular vesicles, cysteine proteases, amoeba-pores, and actin microfilament) involved in pathogenesis which may be helpful for designing of future drug or therapy.

Identification and characterization of archaeal-type FAD synthase as a novel tractable drug target from the parasitic protozoa Entamoeba histolytica

Flavin adenine dinucleotide (FAD) is an essential cofactor for numerous flavoenzymes present in all living organisms. The biosynthesis of FAD from riboflavin involves two sequential reactions catalyzed by riboflavin kinase and flavin adenine dinucleotide synthase (FADS). Entamoeba histolytica, the protozoan parasite responsible for amebiasis, apparently lacks a gene encoding FADS that share similarity with bacterial and eukaryotic canonical FADS, yet it can synthesize FAD. In this study, we have identified the gene responsible for FADS and thoroughly characterized physiological and biochemical properties of FADS from E. histolytica. Phylogenetic analysis revealed that the gene was likely laterally transferred from archaea. The kinetic properties of recombinant EhFADS were consistent with the notion that EhFADS is of archaeal origin, exhibiting KM and kcat values similar to those of the arachaeal enzyme while significantly differing from the human counterpart. Repression of gene expression of EhFADS by epigenetic gene silencing caused substantial reduction in FAD levels and parasite growth, underscoring the importance of EhFADS for the parasite. Furthermore, we demonstrated that EhFADS gene silencing reduced thioredoxin reductase activity, which requires FAD as a cofactor and makes the ameba more susceptible to metronidazole. In summary, this study unveils unique evolutionary and biochemical features of EhFADS and underscores its significance as a promising drug target in combating human amebiasis.IMPORTANCEFAD is important for all forms of life, yet its role and metabolism are still poorly studied in E. histolytica, the protozoan parasite causing human amebiasis. Our study uncovers the evolutionary unique key enzyme, archaeal-type FADS for FAD biosynthesis from E. histolytica for the first time. Additionally, we showed the essentiality of this enzyme for parasite survival, highlighting its potential as target for drug development against E. histolytica infections.

Identification of Small Molecule Inhibitors Targeting Phosphoserine Phosphatase: A Novel Target for the Development of Antiamoebic Drugs

Amoebiasis, a widespread disease caused by the protozoan parasite Entamoeba histolytica, poses challenges due to the adverse effects of existing antiamoebic drugs and rising drug resistance. Novel targeted drugs are in need of the hour to combat the prevalence of this disease. Given the significance of cysteine for Entamoeba survival, the rate-determining step in the serine (the sole substrate of cysteine synthesis) biosynthetic pathway, i.e., the conversion of 3-phosphoserine to l-serine catalyzed by phosphoserine phosphatase (PSP), emerges as a promising drug target. Our previous study unveils the essential role of EhPSP in amoebas' survival, particularly under oxidative stress, by increasing cysteine production. The study also revealed that EhPSP differs significantly from its human counterpart, both structurally and biochemically, highlighting its potential as a viable target for developing new antiamoebic drugs. In the present study, employing in silico screening of vast natural and synthetic small chemical compound libraries, we identified 21 potential EhPSP inhibitor molecules. Out of the 21 compounds examined, only five could inhibit the catalytic activity of EhPSP. The inhibition capability of these five compounds was subsequently validated by in silico binding free energy calculations, SPR-based real-time binding studies, and molecular simulations to assess the stability of the EhPSP-inhibitor complexes. By identifying the five potential inhibitors that can target cysteine synthesis via EhPSP, our findings establish EhPSP as a drug candidate that can serve as a foundation for antiamoebic drug research.

Transcriptome analysis of Tetrahymena thermophila response to exposure with dihydroartemisinin

Dihydroartemisinin (DHA) is a derivative of artemisinin and is toxic to parasites. We used the Tetrahymena thermophila (T. thermophila) as a model to explore DHA toxicity. Results showed that low concentration of DHA (20 μmol/L) promoted cell proliferation, whereas high concentrations of DHA (40-1280 μmol/L) inhibited that. Appearance of nucleus was pycnosis by laser scanning confocal microscope. DHA significantly elevated activities of SOD and GSH-Px (P < 0.01) and MDA was markedly increased at high level but decreased at low level (P < 0.01). Further results of transcriptome in T. thermophila treated with different concentration DHA group (0, 20, 160 μmol/L) showed that differentially expressed genes (DEGs) were involved in oxidation-reduction and metabolism of exogenous substances indicated oxidative stress stimulation. Kyoto Encyclopedia of Genes and Genomes showed that DEGs were involved in the cytochrome P450-mediated metabolism of exogenous substances, glutathione metabolism and ABC transport. Remarkably, DNA replication was significantly enriched in low concentration DHA, energy metabolism related pathways and necrotic process were considerably enriched in high concentration DHA. The results of RT-qPCR of 13 DEGs were the same as that of transcriptome, in which the expression of GST and GPx family genes were significantly altered after exposed to high-DHA group. DHA induced oxidative stress damage through disturbing with energy. However, detoxification pathways in T. thermophila to resist oxidative damage and cell alleviated low concentration DHA stress by regulating antioxidant enzyme. This study provides good practice on pharmacological mechanism of artemisinin-based drugs in antiparasitic.

Multi-omics analysis to characterize molecular adaptation of Entamoeba histolytica during serum stress

Entamoeba histolytica is responsible for dysentery and extraintestinal disease in humans. To establish successful infection, it must generate adaptive response against stress due to host defense mechanisms. We have developed a robust proteomics workflow by combining miniaturized sample preparation, low flow-rate chromatography, and ultra-high sensitivity mass spectrometry, achieving increased proteome coverage, and further integrated proteomics and RNA-seq data to decipher regulation at translational and transcriptional levels. Label-free quantitative proteomics led to identification of 2344 proteins, an improvement over the maximum number identified in E. histolytica proteomic studies. In serum-starved cells, 127 proteins were differentially abundant and were associated with functions including antioxidant activity, cytoskeleton, translation, catalysis, and transport. The virulence factor, Gal/GalNAc-inhibitable lectin subunits, was significantly altered. Integration of transcriptomic and proteomic data revealed that only 30% genes were coordinately regulated at both transcriptional and translational levels. Some highly expressed transcripts did not change in protein abundance. Conversely, genes with no transcriptional change showed enhanced protein abundance, indicating post-transcriptional regulation. This multi-omics approach enables more refined gene expression analysis to understand the adaptive response of E. histolytica during growth stress.

Insights into the Mechanisms of Lactobacillus acidophilus Activity against Entamoeba histolytica by Using Thiol Redox Proteomics

Amebiasis is an intestinal disease transmitted by the protist parasite, Entamoeba histolytica. Lactobacillus acidophilus is a common inhabitant of healthy human gut and a probiotic that has antimicrobial properties against a number of pathogenic bacteria, fungi, and parasites. The aim of this study was to investigate the amebicide activity of L. acidophilus and its mechanisms. For this purpose, E. histolytica and L. acidophilus were co-incubated and the parasite's viability was determined by eosin dye exclusion. The level of ozidized proteins (OXs) in the parasite was determined by resin-assisted capture RAC (OX-RAC). Incubation with L. acidophilus for two hours reduced the viability of E. histolytica trophozoites by 50%. As a result of the interaction with catalase, an enzyme that degrades hydrogen peroxide (H2O2) to water and oxygen, this amebicide activity is lost, indicating that it is mediated by H2O2 produced by L. acidophilus. Redox proteomics shows that L. acidophilus triggers the oxidation of many essential amebic enzymes such as pyruvate: ferredoxin oxidoreductase, the lectin Gal/GalNAc, and cysteine proteases (CPs). Further, trophozoites of E. histolytica incubated with L. acidophilus show reduced binding to mammalian cells. These results support L. acidophilus as a prophylactic candidate against amebiasis.