Abstract
ObjectivesThe aim of this work is to explore the association between chronic exposure to nonylphenol (NP), a representative environmental endocrine disruptor (EED), and the risk of depression and its potential mechanism.MethodsA hospital-based case control study was conducted from August to December 2018. Forty-one patients with confirmed depression and 47 healthy volunteers were recruited. In vitro, 20 rats were randomly divided into the control group (corn oil) and NP exposure group (n=10 per group), which were gavaged at a dose of 4 mg/kg w/day for 180 days.ResultsThe depressed patient group had higher Zung Self-Rating Depression Scale (SDS) (P<0.001) and Self-Rating Anxiety Scale (SAS) (P<0.001) scores than the healthy group. The serum NP level (P=0.009) in the depressed group was higher than that in the healthy group, and the BDNF level (P=0.001) was lower. The serum levels of monoamine neurotransmitters dopamine (DA) (P=0.070), epinephrine (E) (P=0.001), and noradrenaline (NE) (P=0.000) were lower than those in the healthy group. In the sucrose preference test, the sucrose preference time for the exposure group of rats was lower than that of the control group (P<0.001). In the forced swim test, a longer resting time was measured for the exposure group of rats as compared to the control group (P<0.05). The level of NP (P<0.001) in the brain tissue of the NP exposure group was higher than that in the control group, and the serum level of brain-derived neurotrophic factor (BDNF) (P=0.004) was lower. Histopathological examination of the brain biopsies illustrated that the neuronal cells and nuclei in the hippocampus of the exposed group exhibited slight shrinkage.ConclusionChronic exposure to NP at environmental doses will result in the accumulation of NP in the brain and blood, and induction of depression, which might be associated with the alterations in the expression levels of BDNF and monoamine neurotransmitters.
Highlights
Depression has become a common psychiatric disorder that seriously threatens people’s physical and mental health, and it is a serious global public health problem
The neuronal cells and nuclei in the hippocampus of the exposed group exhibited slight shrinkage (Fig. 8). Through this hospital-based case control study and animal experiments, we found that the serum NP levels in the depressed group were higher than those of the healthy group, and the levels of monoamine neurotransmitters and brain-derived neurotrophic factor (BDNF) were lower, which was consistent with the monoamine neurotransmitter hypothesis and Hayley and Kuhlmann’s study (Lee et al, 2017)
Our study found that serum catecholamine neurotransmitter levels in the depressed group were significantly lower than those in the healthy group, and the NP exposure group in the animal experiment exhibited higher NP levels than those in the control group, which indicates consistent results between human and animal experiments
Summary
Depression has become a common psychiatric disorder that seriously threatens people’s physical and mental health, and it is a serious global public health problem. Depression has a high prevalence and recurrence rate, and is associated with suicide, which is the main cause of death of people aged 15-44 years (Zhang, Yang & Wu, 2017). Exposure to BPA during pregnancy and lactation in female rats leads to prolonged forced swim time and depression-like behavioral changes in F1 male offspring (Borrow & Cameron, 2014). A population-based study reported that the higher level of phthalate (an EED), the higher the score of autistic features in Canadian women’s offspring during pregnancy. Prenatal exposure to BPA is associated with anxiety and depression in boys aged 10-12 years, and childhood exposure to BPA impacts behavior. Exposure to EEDs during adolescence was associated with the emotional and social behavior of rats in adulthood (Jennifer et al, 2013; Frederica et al, 2016; Ying et al, 2018)
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