Neural Mechanisms Underlying the Disruption of Male Courtship Behavior by Adult Exposure to Di(2-ethylhexyl) Phthalate in Mice

Abstract

Background:Courtship behavior plays a critical role in attracting females and reproduction success. However, the effects of exposure to a ubiquitous contaminant di(2-ethylhexyl) phthalate (DEHP) on these behaviors and, in particular, on courtship vocalizations have not been examined.Objective:The effects of adult exposure to DEHP on courtship and mating behaviors and gonadotropic axis and neural mechanisms involved in DEHP-induced effects were analyzed in male mice.Methods:Adult C57BL/6J males were orally exposed to DEHP (0, 0.5, 5, and 50μg/kg/d) for 4 wk. Olfactory preference, ultrasonic vocalizations (USVs), partner preference and mating, as well as locomotor activity and motor coordination, were measured. The kisspeptin system and testosterone levels were analyzed. Proteomic and molecular studies were conducted on the hypothalamic preoptic nucleus, the key region involved in sexual motivation to vocalize and mate.Results:DEHP at 50μg/kg/d reduced the emission of USVs, whereas lower doses changed the ratio of syllable categories. This was associated with diminished sexual interest of female partners toward males exposed to 5 or 50μg/kg/d and increased latency to mate, despite normal olfactory preference. The kisspeptin system and circulating testosterone levels were unaffected. In DEHP-exposed males, proteomic analysis of the preoptic nucleus identified differentially expressed proteins connected to the androgen receptor (AR). Indeed, exposure to 5 or 50μg/kg/d of DEHP induced selective AR downregulation in this nucleus and upstream chemosensory regions. The involvement of AR changes in the observed alterations was further supported by the reduced emission of courtship vocalizations in males with disrupted neural AR expression.Conclusions:These data demonstrate the critical role of neural AR in courtship vocalizations and raises the possibility that the vulnerability of this signaling pathway to exposure to endocrine disrupters may be detrimental for courtship communication and mating in several species. https://doi.org/10.1289/EHP1443

Adult male mice exposure to nonylphenol alters courtship vocalizations and mating

“…In this context, no studies evaluated the potential effects of adult exposure to low doses of NP on male neuroendocrine and behavioral responses. Such an evaluation is particularly pertinent in light of our recent results that demonstrate a high sensitivity of adult neural circuits processing sexual behavior toward endocrine disruptors with estrogenic and anti-androgenic activities 24 , 25 .…”

Sexual Behavior: From Hormonal Regulation to Endocrine Disruption

“…This finding strongly suggests that EDC may act, at least partly, through changes in the neural signaling pathways underlying sexual behavior, either directly through epigenetic modifications to the ERα promoter, as reported for developmental exposure to BPA [103], or through as yet unidentified pathways, as for the down-regulation of AR induced by the exposure of adults to DEHP [98]. …”

“…One recent study addressed the effects of adult exposure to low doses of DEHP on male sexual behavior. Such exposure decreased ultrasonic vocalizations, reduced female attraction and delayed the initiation of mating, without affecting olfactory preference for receptive females [98]. …”

“…In mice, the impairment of sexual behavior following chronic adult exposure to BPA, NP or DEHP was associated with unchanged hormonal levels and integrity of the hypothalamic-pituitary-gonadal axis, together with changes in the level of sex steroid receptor expression [63, 70, 98]. In particular, DEHP down-regulated AR protein and mRNA levels in the neural circuitry involved in sexual behavior [98], while both the numbers of AR and ERα-immunoreactive cells were affected by NP exposure [70]. …”

Kisspeptin as a Behavioral Hormone

“…32 In response to a receptive female, male rodents emit song-like "ultrasonic vocalizations" (USV) to convey information about the males' motivational status and enhance female sexual approach. 33 To this end, kisspeptin receptor expression has been observed in the rodent dorsal cochlear nucleus 34 revealing a conceivable role for kisspeptin signaling in auditory processing.…”