Cross‐species sensitivity to a novel androgen receptor agonist of potential environmental concern, spironolactone

Abstract

Spironolactone is a pharmaceutical that in humans is used to treat conditions like hirsutism, various dermatologic afflictions, and female-pattern hair loss through antagonism of the androgen receptor. Although not routinely monitored in the environment, spironolactone has been detected downstream of a pharmaceutical manufacturer, indicating a potential for exposure of aquatic species. Furthermore, spironolactone has been reported to cause masculinization of female western mosquitofish, a response indicative of androgen receptor activation. Predictive methods to identify homologous proteins to the human and western mosquitofish androgen receptor suggest that vertebrates would be more susceptible to adverse effects mediated by chemicals like spironolactone that target the androgen receptor compared with invertebrate species that lack a relevant homolog. In addition, an adverse outcome pathway previously developed for activation of the androgen receptor suggests that androgen mimics can lead to reproductive toxicity in fish. To assess this, 21-d reproduction studies were conducted with 2 fish species, fathead minnow and Japanese medaka, and the invertebrate Daphnia magna. Spironolactone significantly reduced the fecundity of medaka and fathead minnows at 50 μg/L, whereas daphnia reproduction was not affected by concentrations as large as 500 μg/L. Phenotypic masculinization of females of both fish species was observed at 5 μg/L as evidenced by formation of tubercles in fathead minnows and papillary processes in Japanese medaka. Effects in fish occurred at concentrations below those reported in the environment. These results demonstrate how a priori knowledge of an adverse outcome pathway and the conservation of a key molecular target across vertebrates can be utilized to identify potential chemicals of concern in terms of monitoring and highlight potentially sensitive species and endpoints for testing.

Leveraging existing data for prioritization of the ecological risks of human and veterinary pharmaceuticals to aquatic organisms

“…R. Soc. B 369: 20140022 [24,27,30,31] anti-androgens androgen receptor antagonism -impaired ovulation and spawning -impaired sexual differentiation -decreased nest defence -reproductive impairment -reduced probability of young of year survival** [32 -37] hormonal contraceptive oestrogen receptor activation -impaired ovulation and spawning -impaired sexual development -reproductive impairment [27] hormonal contraceptive oestrogen receptor antagonism* -impaired vitellogenesis, ovulation and spawning -impaired sexual differentiation -reproductive impairment** [38 -42] hormonal contraceptive progesterone receptor activation -reduced fecundity -reduced sperm motility -reproductive impairment [43 -46] anti-inflammatory glucocorticoid receptor activation -reduced oestradiol synthesis and fecundity -morphological abnormalities -decreased immune response -reproductive impairment -reduced probability of young of year survival** [47 -49] anti-depressants serotonin reuptake inhibition -morphological abnormalities -reduced fecundity -decreased food intake -impaired predator avoidance -reproductive impairment -reduced probability of young of year survival** [50 -55] anti-convulsant gamma-aminobutyric-acid receptor opening** sodium-channel inhibition -impaired predator avoidance -reduced probability of young of year survival** [56,57] non-steroidal anti-inflammatory drugs cyclooxygenase inhibition -impaired growth -impaired hatching -decreased spawning behaviour a -reduced fecundity a -increased probability of mortality** -reduced probability of young of year survival** -impaired reproduction a [58 -60] fibrates peroxisome proliferator-activated receptor activation -reduced fecundity -impaired reproduction [61] beta-blockers beta-adrenergic receptor antagonist -reduced growth -reduced probability of young of year survival** -increased probability of mortality** [62 -64] Aromatase inhibition is an established molecular initiating event for propiconazole, however other conazoles have been shown to inhibit other cytochrome P450 enzymes [76].…”

“…Owing to the critical role of the AR in endocrine function, it is an important drug target in humans for treating certain cancers, testosterone deficiencies, hypogonadism, dermatological conditions, hirsutism and delayed puberty in males, and in livestock, particularly beef cattle, for increasing muscle mass [24]. Using our ADME database, DrugBank and the Veterinary Substance Database [77], we first identified human and veterinary pharmaceuticals whose therapeutic MOA involved an interaction with the AR (table 2).…”

In Summary

“…In support of predicting function base on sequence conservation, Lalone et al [24] developed a quantitative bioinformatics strategy to predict species sensitivities and adverse outcomes of prototypic (pharmaceuticals, pesticides) ER and androgen receptor (AR) agonists through comparison of conserved functional domains of these NRs.…”

The pros and cons of ecological risk assessment based on data from different levels of biological organization

“…PCR, microarrays, RNA-seq) and hormone levels (e.g. ELISAs), to link MIEs to AOs and to enhance the interpretation of sub-individual responses (Ankley et al 2010, Berninger et al 2014, LaLone, Villeneuve, Burgoon, et al 2013, LaLone, Villeneuve, Cavallin, et al 2013, Martinovic-Weigelt et al 2014). Once AOPs are well-described, regulatory agencies have encouraged scientists to make them accessible in an AOP knowledge-base and wiki.…”

“…After which, researchers would ideally evaluate the conservation of AOPs across taxa. However, very little progress has been made on this latter goal given how nascent the AOP framework is (but see Ankley and Gray 2013, LaLone, Villeneuve, Burgoon, et al 2013, LaLone, Villeneuve, Cavallin, et al 2013). …”