Exposure of Adult Female Mice to Low Doses of di(2-ethylhexyl) Phthalate Alone or in an Environmental Phthalate Mixture: Evaluation of Reproductive Behavior and Underlying Neural Mechanisms

Abstract

BACKGROUND:We have previously shown that adult male mice exposure to low doses of an ubiquitous endocrine disruptor, di(2-ethylhexyl) phthalate (DEHP), alters courtship behavior. OBJECTIVE: The effects of adult exposure to low doses of DEHP alone or in an environmental phthalate mixture on estrous cyclicity, reproductive behavior, and underlying neural structures were analyzed in female mice. METHODS: Two-month-old C57BL/6J females were exposed orally for 6 wk to DEHP alone (0, 5 or 50 lg=kg=d) or to DEHP (5 lg=kg=d) in a phthalate mixture. Estrous cyclicity was analyzed in intact mice, and behavior [lordosis, olfactory preference, partner preference, ability to stimulate male ultrasonic vocalizations (USVs)] was measured in ovariectomized mice primed with estradiol and progesterone. Immunohistochemical studies were conducted in the neural structures involved in behavior for estrogen receptor (ER) a and progesterone receptor (PR). RESULTS: Exposure to DEHP alone or in mixture lengthened the estrous cycle duration, with a shorter proestrus and longer estrus and metestrus stages. Under normalized hormonal levels, females exposed to DEHP alone or in mixture exhibited altered olfactory preference. A lower lordosis behavior and ability to attract and stimulate male emission of courtship USVs was observed, probably due to modifications of pheromonal emission in exposed females. The behavioral alterations were associated with a lower number of PR-expressing neurons, without changes in ERa, in the neural circuitry underlying sexual behavior. The majority of effects observed was comparable between the two DEHP doses and were driven by DEHP in the mixture. CONCLUSIONS: Exposure to environmental doses of DEHP alone or in mixture altered several components of female sexual behavior in mice, probably through selective disruption of neural PR signaling. Together with the previously reported vulnerability of male mice, this finding suggests a major impact of exposure to phthalates on sexual reproduction, including in other species with similar neural regulatory processes.

Prenatal Exposure to an EDC Mixture, NeuroMix: Effects on Brain, Behavior, and Stress Responsiveness in Rats

“…This result is also comparable to our previous two-hit work in which rats were exposed to PCBs during perinatal development, as juveniles, or both [ 21 , 35 ], and wherein single hits at either age did not predict effects of their combination. Our findings are also consistent with the numerous studies suggesting that mate preference is impaired by developmental EDC exposures [ 6 , 99 , 106 , 107 ]. Collectively, we believe that this body of work is important because the vulnerability of mate preference and sexual selection more broadly to EDCs can have consequences on the reproduction and fitness of a species [ 108 ].…”

Behavioral Effects of Exposure to Phthalates in Female Rodents: Evidence for Endocrine Disruption?

“…Adult exposure. To our knowledge, only one study investigated the effects of chronic adult exposure to phthalates on female sexual behavior [ 4 ]. This analysis was performed on ovariectomized females, which were supplemented with estradiol and primed with progesterone before tests to normalize their hormonal levels.…”

“…These behavioral alterations were associated with a selective reduced number of PR-immunoreactive neurons in the neural circuitry that underlies sexual behavior (arcuate nucleus, preoptic area, ventromedial hypothalamus, medial amygdala, and bed nucleus of the stria terminalis) [ 4 ]. In these regions, no effects were found on the number of ERα-immunoreactive neurons.…”

“…In recent studies, we showed that the adult rodent nervous system is also vulnerable to exposure to DEHP on its own or in a phthalate mixture. The observed effects on reproductive behavior were linked to an endocrine mode of action involving the neural alteration of androgen receptors in males and progesterone receptors in females [ 4 , 5 ]. Interestingly, these effects were observed at doses equivalent to or below the tolerable daily intake (TDI) dose of 50 µg/kg/d in both male and female mice.…”

“…Interestingly, these effects were observed at doses equivalent to or below the tolerable daily intake (TDI) dose of 50 µg/kg/d in both male and female mice. Moreover, the females appeared more sensitive to phthalate exposure than males since, under comparable experimental conditions, several components of sexual behavior were affected in females [ 4 ].…”