Toward incorporating epigenetics into regulation of gene expression in the parasite Trichomonas vaginalis

Targeting histone acetylation to overcome drug resistance in the parasite Trichomonas vaginalis

Trichomoniasis, caused by the parasite Trichomonas vaginalis, is the most common non-viral sexually transmitted infection. Current treatment relies exclusively on 5-nitroimidazole drugs, with metronidazole (MTZ) as the primary option. However, the increasing prevalence of MTZ-resistant strains poses a significant challenge, particularly in the current absence of alternative therapies. Several studies have revealed that the development of metronidazole resistance in T. vaginalis is linked to genomic and transcriptional alterations. Given the role of epigenetic regulation in controlling gene expression, we investigated whether targeting histone deacetylase (HDAC) enzymes could influence drug resistance. Treatment of an MTZ-resistant strain (B7268) with the HDAC inhibitor, trichostatin A (TSA), in combination with MTZ enhanced drug sensitivity and induced significant genome-wide transcriptional changes, as revealed by RNA-seq analysis. To identify drug-related genes epigenetically silenced in the resistant strain but highly active in a sensitive strain, we compared the expression levels of the genes affected by TSA and MTZ treatment with their baseline expression profiles in both resistant and sensitive strains. This analysis identified 130 candidate genes differentially expressed in the sensitive strain NYH209, less expressed in the resistant B7268 strain, that exhibited significant expression changes upon TSA and MTZ treatment. Functional validation involved transfecting the B7268 strain with plasmids encoding four individual candidate genes: a thioredoxin reductase (TrxR), a cysteine synthase (CS), and two genes containing Myb domains (Myb5 and Myb6). Overexpression of three of these genes resulted in a marked reduction in MTZ resistance, demonstrating their role in modulating drug sensitivity. Our findings identified three novel genes that modulate drug resistance in T. vaginalis. This study reveals a previously unknown epigenetic mechanism underlying drug resistance and highlights the therapeutic potential of targeting epigenetic factors, such as HDACs, to overcome resistance and improve treatment efficacy.

Chromatin accessibility and gene expression in the parasite Trichomonas vaginalis

Trichomonas vaginalis, the most common non-viral sexually transmitted parasite, causes more than 270 million infections annually. The infection's outcome varies greatly depending on different factors that include variation in human immune responses, the vaginal microbiome, and the inherent virulence of the strain. Although the pathogenicity of the different strains depends, at least partially, on differential gene expression of virulence genes; the regulatory mechanisms governing this transcriptional control remain incompletely understood. While many studies have reported a positive correlation between gene expression and chromatin accessibility in other cells, this relationship has not been analyzed in T. vaginalis. To address these questions, we selected two contrasting T. vaginalis strains based on their interactions with host cells: B7268 strain, a highly adherent one and resistant to metronidazole, and NYH209 strain, a poorly adherent one and sensitive to metronidazole. Next, we combined the assay for transposase-accessible chromatin using sequencing (ATAC-seq) with RNA sequencing (RNA-seq), to delve into the relationship between chromatin accessibility and gene expression in these distinct T. vaginalis strains. Our findings demonstrate a correlation between chromatin accessibility and gene expression across both strains. Moreover, we found that chromatin accessibility plays a pivotal role in modulating mRNA expression levels of several established genes linked to parasite pathogenesis and drug resistance. We also identified several open chromatin peaks residing at intergenic regions, revealing possible distal regulatory elements that may control gene expression. These results highlight the importance of chromatin accessibility in modulating gene expression in the parasite T. vaginalis, with possible consequences in pathogenesis and/or drug treatment.

The Fimbrin TvFim1, an immunogenic protein involved in male trichomoniasis

An active immunoproteome of Trichomonas vaginalis was obtained by 2D-Western blotting (2D-WB). Subsequent proteoform identification by mass spectrometry (MS) showed differential expression and specific immunoreactions of multiple proteins mediated by the presence of Zn2+. A total of 25 proteoforms were immunologically reactive, generally under Zn2+ conditions, and MS analysis revealed that the fimbrin (plastin) of T. vaginalis (TvFim1) was recognized by the sera of male patients with trichomoniasis but not by the sera of infected female patients. These findings suggest that the protein is immunogenic during active male trichomoniasis and that cytoskeletal proteins, including fimbrins, may also act as virulence factors in addition to their role in parasite morphogenesis.

Advances in Protozoan Epigenetic Targets and Their Inhibitors for the Development of New Potential Drugs

Protozoan parasite diseases cause significant mortality and morbidity worldwide. Factors such as climate change, extreme poverty, migration, and a lack of life opportunities lead to the propagation of diseases classified as tropical or non-endemic. Although there are several drugs to combat parasitic diseases, strains resistant to routinely used drugs have been reported. In addition, many first-line drugs have adverse effects ranging from mild to severe, including potential carcinogenic effects. Therefore, new lead compounds are needed to combat these parasites. Although little has been studied regarding the epigenetic mechanisms in lower eukaryotes, it is believed that epigenetics plays an essential role in vital aspects of the organism, from controlling the life cycle to the expression of genes involved in pathogenicity. Therefore, using epigenetic targets to combat these parasites is foreseen as an area with great potential for development. This review summarizes the main known epigenetic mechanisms and their potential as therapeutics for a group of medically important protozoal parasites. Different epigenetic mechanisms are discussed, highlighting those that can be used for drug repositioning, such as histone post-translational modifications (HPTMs). Exclusive parasite targets are also emphasized, including the base J and DNA 6 mA. These two categories have the greatest potential for developing drugs to treat or eradicate these diseases.

Natural marine products as antiprotozoal agents against amitochondrial parasites

The goal of this work is to compile and discuss molecules of marine origin reported in the scientific literature with anti-parasitic activity against Trichomonas, Giardia, and Entamoeba, parasites responsible for diseases that are major global health problems, and Microsporidial parasites as an emerging problem. The presented data correspond to metabolites with anti-parasitic activity in human beings that have been isolated by chromatographic techniques from marine sources and structurally elucidated by spectroscopic and spectrometric procedures. We also highlight some semi-synthetic derivatives that have been successful in enhancing the activity of original compounds. The biological oceanic reservoir offers the possibility to discover new biologically active molecules as lead compounds to develop new drug candidates. The molecular variety is extensive and must be correctly explored and managed. Also, it will be necessary to take some actions to preserve the source species from extinction or overharvest (e.g., by cryopreservation of coral spermatozoa, oocytes, embryos, and larvae) and coordinate appropriate exploitation to increase the chemical knowledge of the natural products generated in the oceans. Additional initiatives such as the total synthesis of complex natural products and their derivatives can help to prevent overharvest of the marine ecosystems and at the same time contribute to the discovery of new molecules.