Dibutyl Phthalate (DBP)-Induced Apoptosis and Neurotoxicity are Mediated via the Aryl Hydrocarbon Receptor (AhR) but not by Estrogen Receptor Alpha (ERα), Estrogen Receptor Beta (ERβ), or Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) in Mouse Cortical Neurons

Abstract

Dibutyl phthalate (di-n-butyl phthalate, DBP) is one of the most commonly used phthalate esters. DBP is widely used as a plasticizer in a variety of household industries and consumer products. Because phthalates are not chemically bound to products, they can easily leak out to enter the environment. DBP can pass through the placental and blood–brain barriers due to its chemical structure, but little is known about its mechanism of action in neuronal cells. This study demonstrated the toxic and apoptotic effects of DBP in mouse neocortical neurons in primary cultures. DBP stimulated caspase-3 and LDH activities as well as ROS formation in a concentration (10 nM–100 µM) and time-dependent (3–48 h) manner. DBP induced ROS formation at nanomolar concentrations, while it activated caspase-3 and LDH activities at micromolar concentrations. The biochemical effects of DBP were accompanied by decreased cell viability and induction of apoptotic bodies. Exposure to DBP reduced Erα and Pparγ mRNA expression levels, which were inversely correlated with protein expression of the receptors. Treatment with DBP enhanced Ahr mRNA expression, which was reflected by the increased AhR protein level observed at 3 h after exposure. ERα, ERβ, and PPARγ antagonists stimulated DBP-induced caspase-3 and LDH activities. AhR silencing demonstrated that DBP-induced apoptosis and neurotoxicity are mediated by AhR, which is consistent with the results from DBP-induced enhancement of AhR mRNA and protein expression. Our study showed that AhR is involved in DBP-induced apoptosis and neurotoxicity, while the ERs and PPARγ signaling pathways are impaired by the phthalate.

Perinatal Exposure to an Environmentally Relevant Mixture of Phthalates Results in a Lower Number of Neurons and Synapses in the Medial Prefrontal Cortex and Decreased Cognitive Flexibility in Adult Male and Female Rats

“…As a class of endocrine-disrupting chemicals, phthalates have a promiscuous set of mechanistic actions that are specific to each phthalate and to the various metabolites (e.g., Chauvigné et al, 2009). Collectively, though, phthalates are known to have antiandrogenic, estrogenic, and antiestrogenic activity (Takeuchi et al, 2005); but given that both sexes were similarly affected by perinatal exposure, phthalates may not be disrupting gonadal steroid effects on sexual differentiation. Although there are indications that neonatal androgens can affect apoptosis in the visual cortex (Nuñez et al, 2000), whether there is a role for sex hormones in the perinatal development of the mPFC is not known.…”

“…Indeed, gonadal hormones play a critical role during perinatal development in regulating apoptosis (Nuñez et al, 2000;Forger, 2009) and synaptic number (Nishizuka and Arai, 1981;Pérez et al, 1990;Simerly, 2002). Although much of this work has focused on subcortical regions where sex hormone receptors are particularly abundant, it is known that these receptors are also present during development in other brains areas, including the cerebral cortex (Pérez et al, 2003;Westberry and Wilson, 2012;Tsai et al, 2015).…”

An Aliphatic Ester Diisopropyl Sebacate Exhibited an Adjuvant Effect on Fluorescein Isothiocyanate-Induced Contact Hypersensitivity Mouse Models

“…DBP has become a primary target for the reduction of childrens' exposure due to the reproductive toxicity, endocrine disruption and neurotoxicity. 1,11,12) Reflecting this situation, the use of alternative plasticizers has been increasing.…”

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

“…In respect to low molecular weight phthalates, prenatal and postnatal DBP exposure upregulates aromatase, an enzyme that has an important role in reproduction and neuroprotection, and downregulates estrogen receptor beta (ER β ), which in turn reduces the expression of phosphate CREB and BDNF, two important neuroprotective proteins, in the rat hippocampus [93]. In line with these results, recently, in mouse neocortical neuronal cultures, treatment with DBP has been shown to impair the estrogen receptor pathway and induce neurotoxicity in a mechanism involved in the aryl hydrocarbon pathway [94]. …”