Melanosome aggregation by corticosteroids: evidence for a novel type of steroid action

Estrogen contamination increases vulnerability of amphibians to the deadly chytrid fungus

Aquatic contaminants and infectious diseases are among the major drivers of global amphibian declines. However, the interaction of these factors is poorly explored and could better explain the amphibian crisis. We exposed males and females of the Brazilian Cururu Toad, Rhinella icterica, to an environmentally relevant concentration of the estrogen 17-alpha-ethinylestradiol (an emerging contaminant) and to the chytrid infection (Batrachochytrium dendrobatidis), in their combined and isolated forms, and the ecotoxicity was determined by multiple biomarkers: cutaneous, hematological, cardiac, hepatic, and gonadal analysis. Our results showed that Cururu toads had many physiological alterations in response to the chytrid infection, including the appearance of cutaneous Langerhans's cells, increased blood leukocytes, increased heart contraction force and tachycardia, increased hepatic melanomacrophage cells, which in turn led to gonadal atrophy. The estrogen, in turn, increased the susceptibility of the toads to the chytrid infection (higher Bd loads) and maximized the deleterious effects of the pathogen: reducing leukocytes, decreasing the contraction force, and causing greater tachycardia, increasing hepatic melanomacrophage cells, and leading to greater gonadal atrophy, which were more extreme in females. The exposure to estrogen also revealed important toxicodynamic pathways of this toxicant, as shown by the immunosuppression of exposed animals, and the induction of the first stages of feminization in males, which corroborates that the synthetic estrogen acts as an endocrine disruptor. Such an intricate relationship is unprecedented and reinforces the importance of studying the serious consequences that multiple environmental stressors can cause to aquatic populations.

Dicyclohexane derivatives that bind to androgen-binding protein (ABP) also inhibit hormone stimulated aromatase activity in rat Sertoli cells

Dicyclohexane derivatives are known to inhibit testosterone binding to rat androgen-binding protein (ABP) a secretory product of Sertoli cells. In this paper we show that these compounds also inhibit the aromatization of testosterone by Sertoli cells in response to cyclic AMP and to hormones that act via this nucleotide. The inhibitory activity of the nonsteroidal androgen analogues is dose-dependent and roughly parallels their ability to interfere with the aromatase activity in human placental microsomes and their affinity for ABP. Diethylstilbestrol and mesohexestrol--two nonsteroidal estrogens which resemble the dicyclohexane derivatives--also inhibit aromatase activity in Sertoli cells and placental microsomes. The effects of the synthetic estrogens on Sertoli cells, however, are less specific. Unlike the dicyclohexane derivatives they also block hormone induced activation of the adenylate cyclase. We conclude that dicyclohexane derivatives are representative of a novel series of inhibitors of aromatase activity.