Using C. elegans Forward and Reverse Genetics to Identify New Compounds with Anthelmintic Activity

Abstract

BackgroundThe lack of new anthelmintic agents is of growing concern because it affects human health and our food supply, as both livestock and plants are affected. Two principal factors contribute to this problem. First, nematode resistance to anthelmintic drugs is increasing worldwide and second, many effective nematicides pose environmental hazards. In this paper we address this problem by deploying a high throughput screening platform for anthelmintic drug discovery using the nematode Caenorhabditis elegans as a surrogate for infectious nematodes. This method offers the possibility of identifying new anthelmintics in a cost-effective and timely manner.Methods/Principal findingsUsing our high throughput screening platform we have identified 14 new potential anthelmintics by screening more than 26,000 compounds from the Chembridge and Maybridge chemical libraries. Using phylogenetic profiling we identified a subset of the 14 compounds as potential anthelmintics based on the relative sensitivity of C. elegans when compared to yeast and mammalian cells in culture. We showed that a subset of these compounds might employ mechanisms distinct from currently used anthelmintics by testing diverse drug resistant strains of C. elegans. One of these newly identified compounds targets mitochondrial complex II, and we used structural analysis of the target to suggest how differential binding of this compound may account for its different effects in nematodes versus mammalian cells.Conclusions/SignificanceThe challenge of anthelmintic drug discovery is exacerbated by several factors; including, 1) the biochemical similarity between host and parasite genomes, 2) the geographic location of parasitic nematodes and 3) the rapid development of resistance. Accordingly, an approach that can screen large compound collections rapidly is required. C. elegans as a surrogate parasite offers the ability to screen compounds rapidly and, equally importantly, with specificity, thus reducing the potential toxicity of these compounds to the host and the environment. We believe this approach will help to replenish the pipeline of potential nematicides.

Plant-Based Natural Products for the Discovery and Development of Novel Anthelmintics against Nematodes

“…However, even in one species (C. elegans), the values span a wide range. This range is similar to that for active compounds from a chemical library [44] and overlaps in its lower range with IC 50 values for some clinically used anthelmintics. This is perhaps not surprising since many of the compounds were purified from plants traditionally used to treat intestinal worms.…”

“…It has a short life cycle (2-3 weeks) and can be easily maintained in the laboratory at low cost, making it amenable to high-throughput screening. The extensive sequence similarity across the nematode phylum has been demonstrated by comparative genomic studies: C. elegans shares almost 13,000 genes (~70%) with various other nematode species [43,44]. C. elegans has been extensively proven to be an excellent model of intestinal parasitic nematodes for anthelmintic drug discovery thanks to its similarity to parasitic species [41,45,46].…”

“…One of these, 3geranyl-1-(2′-methylbutanoyl)-phloroglucinol, showed significant anthelmintic activity against C. elegans, inducing death in 37% after 30 min treatment at 100 μg/mL (285.3 μM) [95]. (38,39), terpenoids (41,42,43,44,49,50,51,53), steroids (45,46,47), miscellaneous (48,54,55).…”

Caenorhabditis elegans: a model to study the anthelmintic effects of polyphenolic compounds on the fertility of parasitic gastrointestinal nematodes?

“…C. elegans´ culture in liquid mediums is considered a low costly excellent option for a rapid proliferation in a short period. Several trials can be run simultaneously, allowing you to easily screen lethal effects on worms exposed to different monomers concentrations and solvents, evaluating potential effects on host and environment consequences of the compounds tested (Mathew et al, 2016). Thus, we first set up a protocol in a complete S Medium inoculated with E. coli (OD.…”

“…Besides the nematocidal effect, effects on reproduction, behavior and/or locomotion can be examined (Rand and Johnson, 1995;Sangster and Gill, 1999;Strange, 2006). Until now, many other parasitologists have also included this model in the screening of plant extracts (McGaw et al, 2007;Waterman et al), purified fractions, plant compounds (Katiki et al, 2011;Smith et al, 2009) and novel molecules tested in a liquid medium (Mathew et al, 2016). Based on published reports, the aim of this work was: 1) to set up an appropriate, easily reproducible, nematode grown medium and protocol for the evaluation of C. elegans fecundity rate.…”