Altered Gene Expression in the Schistosome-Transmitting Snail Biomphalaria glabrata following Exposure to Niclosamide, the Active Ingredient in the Widely Used Molluscicide Bayluscide

Abstract

In view of the call by the World Health Organization (WHO) for elimination of schistosomiasis as a public health problem by 2025, use of molluscicides in snail control to supplement chemotherapy–based control efforts is likely to increase in the coming years. The mechanisms of action of niclosamide, the active ingredient in the most widely used molluscicides, remain largely unknown. A better understanding of its toxicology at the molecular level will both improve our knowledge of snail biology and may offer valuable insights into the development of better chemical control methods for snails. We used a recently developed Biomphalaria glabrata oligonucleotide microarray (31K features) to investigate the effect of sublethal exposure to niclosamide on the transcriptional responses of the snail B. glabrata relative to untreated snails. Most of the genes highly upregulated following exposure of snails to niclosamide are involved in biotransformation of xenobiotics, including genes encoding cytochrome P450s (CYP), glutathione S-transferases (GST), and drug transporters, notably multi-drug resistance protein (efflux transporter) and solute linked carrier (influx transporter). Niclosamide also induced stress responses. Specifically, six heat shock protein (HSP) genes from three super-families (HSP20, HSP40 and HSP70) were upregulated. Genes encoding ADP-ribosylation factor (ARF), cAMP response element-binding protein (CREB) and coatomer, all of which are involved in vesicle trafficking in the Golgi of mammalian cells, were also upregulated. Lastly, a hemoglobin gene was downregulated, suggesting niclosamide may affect oxygen transport. Our results show that snails mount substantial responses to sublethal concentrations of niclosamide, at least some of which appear to be protective. The topic of how niclosamide’s lethality at higher concentrations is determined requires further study. Given that niclosamide has also been used as an anthelmintic drug for decades and has been found to have activity against several types of cancer, our findings may be of relevance in understanding how both parasites and neoplastic cells respond to this compound.

Pathogen-associated molecular patterns activate expression of genes involved in cell proliferation, immunity and detoxification in the amebocyte-producing organ of the snail Biomphalaria glabrata

“…Except for studies involving hemocytes (Lockyer et al, 2012; Zahoor et al, 2014), studies of gene expression in snails have involved whole-body extraction of nucleic acid (Adema et al, 2010; Hanington et al, 2010, 2012; Lockyer et al, 2007, 2008; Zhang et al, 2015). The amount and quality of RNA we obtained from the APO shows the feasibility of conducting transcriptomic studies on individual snail organs.…”

“…The amount and quality of RNA we obtained from the APO shows the feasibility of conducting transcriptomic studies on individual snail organs. Although the present microarray contained a large number of features (31K features) (Zhang et al, 2015) compared to previous studies (i.e., arrays with 1.1K features (Adema et al, 2010) and 5K features (Lockyer et al, 2012)), it is possible additional transcriptional information remains to be captured. Genome-wide transcriptome analysis certainly provides an alternative, powerful tool for understanding gene expression in response to PAMPs for future studies.…”

“…Using the same array, we found expression of six HSP genes was highly up-regulated in the whole body of B . glabrata in response to sublethal doses of niclosamide, the active ingredient of the molluscicide Bayluscide (Zhang et al, 2015). Therefore, it is suggested that the pattern of gene expression revealed by the present study is more indicative of immune responses, rather than stress responses, to PAMPs.…”

“…Indeed, we observed differential expression of a number of genes associated with degradation or detoxification, including CYP (c29331_rc), GST (contig_6441, contig_2097), and multidrug resistance protein (c27924_rc) in snails injected with PAMPs. Not unexpectedly, a larger number of genes associated with biotransformation activities was activated by exposure to niclosamide (Zhang et al, 2015). For example, 10 CYP genes were expressed differentially in response to niclosamide, with 9 up-regulated and 1 down-regulated (Zhang et al, 2015).…”

“…This array has been successfully applied to reveal molecular mechanisms underlying toxicological effects of niclosamide, the active ingredient of a widely used molluscicide, on the snail B. glabrata (Zhang et al, 2015). Details of microarray design are available at Gene Expression Omnibus (GEO) at the Platform Accession Number GPL20716 (www.ncbi.nih.gov/geo/).…”