Antiandrogenic Effects in Vitro and in Vivo of the Fungicide Prochloraz

Abstract

The commonly used imidazole fungicide prochloraz was tested for antiandrogenic effects in vitro and in vivo. Prochloraz, but not the metabolites 2,4,6-trichlorophenoxyacetic acid or 2,4,6-trichlorophenol, inhibited the R1881-induced response in an androgen receptor reporter gene assay. In the Hershberger assay, prochloraz exposure at all dose levels (50, 100, and 200 mg/kg) given orally to castrated testosterone (T)-treated males markedly reduced weights of ventral prostate, seminal vesicles, musc. levator ani/bulbocavernosus, and bulbourethral gland. These effects were accompanied by an increase in LH and a reduction of the T(4) and TSH level. The effects on seminal vesicles, LH, T(4), and TSH were also evident in intact prochloraz-exposed young adult rats. Body weights were unaffected whereas liver weights were increased in prochloraz-treated animals. Changes in androgen-regulated gene expression were determined in ventral prostates by real-time RT-PCR. A pronounced decrease of ornithin decarboxylase and PBP C3 mRNA levels was observed for both prochloraz and flutamide. These results indicate that prochloraz antagonizes the peripheral androgen receptors resulting in decreased growth of androgen-dependent tissues and that it antagonizes central androgen receptors blocking the negative feed-back mechanism of testosterone resulting in increased LH secretion from the pituitary. The antiandrogenic effects of prochloraz were in many ways qualitatively comparable, although weaker, to the effects of flutamide. However, differential effects on levels of FSH, T(4), and TSH indicate that other modes of action apart from the pure AR antagonism might play a role in vivo.

Applicability of Computational Systems Biology in Toxicology

“…1) out of a total of several thousand diseases. These predictions for effects of prochloraz on human health are in line with experimental data from rats indicating that the main adverse outcomes after exposure to prochloraz are diseases related to reproductive health [35][36][37][38]. Another pesticide, mancozeb, underwent the same network analysis and was found to be associated with, for example, inflammatory targets and had no targets in common with prochloraz or other tested pesticides [20].…”

“…Prochloraz is a widely used pesticide that has been demonstrated to have endocrine activity. In animals, it has been shown to cause adverse reproductive outcomes in the male offspring after exposure during foetal life [35][36][37][38]. Prochloraz is known to demasculinize male rat foetuses and virilize female foetuses; however, as clinical studies of environmental chemicals are not carried out, little is known about human effects of this compound.…”

Dynamic Nature of Alterations in the Endocrine System of Fathead Minnows Exposed to the Fungicide Prochloraz

“…For example, studies have shown that the fungicide effectively inhibits aromatase (CYP19) activity in both fish and mammals, blocking the conversion of testosterone (T) to 17b-estradiol (E2) and acting in vivo as an antiestrogen (Ankley et al, 2005;Mason et al, 1987;Sanderson et al, 2002;Thorpe et al, 2007;Vinggaard et al, 2000). Prochloraz also can cause antiandrogenic effects in vertebrates either through direct antagonism of the androgen receptor or through inhibition of cytochrome P450 c17a-hydroxylase/17,20-lyase (CYP17), a steroidogenic enzyme involved in T production (Blystone et al, 2007;Noriega et al, 2005;Vinggaard et al, 2002Vinggaard et al, , 2005. Due to its varied effects on the vertebrate hypothalamic-pituitary-gonadal (HPG) axis, prochloraz has been used as a model compound for studies focused on different mechanisms of endocrine disruption (Gray et al, 2006;USEPA, 2007).…”

“…This could be in response to decreased T in the males (Villeneuve et al, 2007b), or it might be indicative of adaptation to a different mechanism of action of prochloraz. Specifically, in addition to inhibiting CYPs, it has been proposed that prochloraz can affect the vertebrate endocrine system through direct antagonism of the AR (Vinggaard et al, 2002(Vinggaard et al, , 2005; as such, upregulation of the gene coding for the receptor could be viewed as adaptive. Zhang et al (2008) used QPCR to examine expression of a number of the same genes we evaluated in various tissues from male and female Japanese medaka exposed to prochloraz.…”

Evolutionary Perspectives on Sex Steroids in the Vertebrates

“…In these studies, androgen action in utero, or on pubertal development were examined Owens et al 2007). Recognized antiandrogens fell into classes including dicarboximide (Gray et al 1994;Kelce & Wilson 1997) and imidazole fungicides (Vinggaard et al 2002;Noriega et al 2005), organochlorine insecticides (Kelce et al 1995), urea-based herbicides (Gray et al 1999;Lambright et al 2000), phthalate esters used as plasticizers (Parks et al 2000;Howdeshell et al 2007), and polybrominated diphenyl ethers (PBDEs) used as flame retardants (Stoker et al 2005). Natural hormones (Stumm-Zollinger & Fair 1965) and birth control agents (Tabak et al 1981) occurring in wastewater prompted concern over sewage effluents.…”