The effects of environmentally relevant concentrations of aqueous atorvastatin on Xenopus laevis
Numerous studies report active pharmaceutical compounds detected in both wastewater effluent and surface waters.  Exposure to statin drugs in general, and atorvastatin in particular, is likely to be a concern.  We hypothesized that chronic exposure to low concentrations of atorvastatin in water would result in an adverse effect on production of steroids regulating growth and development of the model amphibian Xenopus laevis.  To assess the potential for impacts we used three experimental assays.  The FETAX assay was used to evaluate the effects of a range of doses of atorvastatin on developing embryos.  A 60 day metamorphosis assay assessed the effects of aqueous atorvastatin exposure at environmentally concentrations on metamorphosing tadpoles.  A 60 day chronic flow-through exposure evaluated the effects of chronic low concentrations of atorvastatin on adults.  The data from the FETAX assay confirmed uptake, activity, and effect of atorvastatin in X. laevis tadpoles. The results of the 60-day flow-through exposure on metamorphosing tadpoles showed significant evidence of altered cholesterol biosynthesis.  The dose-dependent increase in cyp19a1 expression also indicated that the steroidogenesis pathway was affected.  The RNAseq analysis confirmed that exposure to environmentally relevant concentrations of atorvastatin does cause significant alterations to global transcriptional profiles in a manner consistent with dysregulation of the cholesterol biosynthesis pathway, both through the downregulation of many genes involved in that pathway, but also in the impacts to other, related pathways.  The qPCR data for both adult males and adult females indicated only slight changes in expression with the exception that hmgcr was significantly downregulated in males, and cyp3a4 expression was significantly downregulated in females.  The data we present here indicated that chronic exposure to environmentally relevant concentrations of atorvastatin does have the potential to impact early life stage frogs, particularly by altering expression of genes involved in critical molecular pathways. Overall design: Comparative gene expression profiling analysis of RNA-seq data for metamorphosing X. laevis tadpoles exposed to aqueous atorvastation.  Control and exposed treatments in triplicate.