The repositioning of epigenetic probes/inhibitors identifies new anti-schistosomal lead compounds and chemotherapeutic targets

Abstract

BackgroundPraziquantel represents the frontline chemotherapy used to treat schistosomiasis, a neglected tropical disease (NTD) caused by infection with macro-parasitic blood fluke schistosomes. While this drug is safe, its inability to kill all schistosome lifecycle stages within the human host often requires repeat treatments. This limitation, amongst others, has led to the search for novel anti-schistosome replacement or combinatorial chemotherapies. Here, we describe a repositioning strategy to assess the anthelmintic activity of epigenetic probes/inhibitors obtained from the Structural Genomics Consortium.Methodology/Principle findingsThirty-seven epigenetic probes/inhibitors targeting histone readers, writers and erasers were initially screened against Schistosoma mansoni schistosomula using the high-throughput Roboworm platform. At 10 μM, 14 of these 37 compounds (38%) negatively affected schistosomula motility and phenotype after 72 hours of continuous co-incubation. Subsequent dose-response titrations against schistosomula and adult worms revealed epigenetic probes targeting one reader (NVS-CECR2-1), one writer (LLY-507 and BAY-598) and one eraser (GSK-J4) to be particularly active. As LLY-507/BAY-598 (SMYD2 histone methyltransferase inhibitors) and GSK-J4 (a JMJD3 histone demethylase inhibitor) regulate an epigenetic process (protein methylation) known to be critical for schistosome development, further characterisation of these compounds/putative targets was performed. RNA interference (RNAi) of one putative LLY-507/BAY-598 S. mansoni target (Smp_000700) in adult worms replicated the compound-mediated motility and egg production defects. Furthermore, H3K36me2, a known product catalysed by SMYD2 activity, was also reduced by LLY-507 (25%), BAY-598 (23%) and siSmp_000700 (15%) treatment of adult worms. Oviposition and packaging of vitelline cells into in vitro laid eggs was also significantly affected by GSK-J4 (putative cell permeable prodrug inhibitor of Smp_034000), but not by the related structural analogue GSK-J1 (cell impermeable inhibitor).Conclusion/SignificanceCollectively, these results provide further support for the development of next-generation drugs targeting schistosome epigenetic pathway components. In particular, the progression of histone methylation/demethylation modulators presents a tractable strategy for anti-schistosomal control.

Structural requirements for dihydrobenzoxazepinone anthelmintics: actions against medically important and model parasites -Trichuris muris,Brugia malayi,Heligmosomoides polygyrusandSchistosoma mansoni

“…The results are shown in Fig 5. The cut-offs for defining hit compounds in this assay have been previously defined [37,55]. Nine compounds were hits in this assay for both motility and phenotype measurements.…”

“…Auranofin was the positive control (screened at 10 μM). Dotted box indicates the threshold for activity in this assay: −0.15 for phenotype and −0.35 for motility; compounds must be below this threshold for both parameters to be considered a hit [37,55]. Compounds were screened in duplicate on two or three separate occasions and the data represents the average scores of these experiments.…”

“…Auranofin, an inhibitor of S. mansoni thioredoxin glutathione reductase (TGR) activity [54] was the positive control in this experiment. The results are shown in Fig 5. The cut-offs for defining hit compounds in this assay have been previously defined [37,55]. Nine compounds were hits in this assay for both motility and phenotype measurements.…”

Long non-coding RNA levels can be modulated by 5-azacytidine in Schistosoma mansoni

“…It is now clear that epigenetic processes play important roles on schistosomes [81][82][83] . In fact, epigenetic mechanisms participate in schistosome phenotypic plasticity 84,85 , in egg production and adult worm viability 34,86,87 as well as in schistosomula survival [88][89][90][91][92] . DNA methylation, one of the most studied epigenetic mechanisms, has been detected in S. mansoni 15 , although the significance of DNA cytosine methylation (5mC) in this parasite has been somewhat controversial [93][94][95] .…”

Epigenetic markers associated with schistosomiasis

“…Inhibitors and miRNAs from these orthologues were supplemented in the cultures of adults and schistosomula causing morphological changes, and the inhibition of a specific HMT resulted in a decrease in the epigenetic mark H3K36me associated with a reduction in motility and in the quantity of eggs produced. These assays open perspectives of treatment during the schistosomula stage ( Whatley et al, 2019 ).…”