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Dysregulation of Intestinal Health by Environmental Pollutants: Involvement of the Estrogen Receptor and Aryl Hydrocarbon Receptor Lianguo Chen, Weipeng Zhang, Jianghuan Hua, Chenyan Hu, Nelson LokShun Lai, Pei-Yuan Qian, Paul K.S. Lam, James C.W. Lam, and Bingsheng Zhou Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b06322 • Publication Date (Web): 22 Jan 2018 Downloaded from http://pubs.acs.org on January 23, 2018
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Environmental Science & Technology
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Dysregulation of Intestinal Health by Environmental Pollutants: Involvement
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of the Estrogen Receptor and Aryl Hydrocarbon Receptor
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Lianguo Chen
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Lok-Shun Lai †, Pei-Yuan Qian §, Paul K.S. Lam †, James C.W. Lam †,□,*, Bingsheng
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Zhou ‡,*
†,‡,⊥
, Weipeng Zhang
§,⊥,
Jianghuan Hua ‡, Chenyan Hu #, Nelson
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†
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Kowloon, Hong Kong SAR, China
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‡
State Key Laboratory in Marine Pollution, City University of Hong Kong,
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of
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Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
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§
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Water Bay, Hong Kong SAR, China
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#
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Technology, Wuhan 430072, China
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□
Division of Life Science, Hong Kong University of Science and Technology, Clear
School of Chemistry and Environmental Engineering, Wuhan Institute of
Department of Science and Environmental Studies, The Education University of
Hong Kong, Hong Kong SAR, China
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* Corresponding authors:
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Dr. James C.W. Lam
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Tel: 0852-2948-8537
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Fax: 0852-2948-7676
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E-mail:
[email protected] 24 25
Dr. Bingsheng Zhou
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Tel: +86 27 68780042
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Fax: +86 27 68780123
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E-mail:
[email protected] 1
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ABSTRACT
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To determine how environmental pollutants induce dysbiosis of the gut microbiota,
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we exposed adult zebrafish to model pollutants with varied modes of action (atrazine,
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estradiol, polychlorinated biphenyl [PCB]126, and PCB153) for 7 days.
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Subsequently, metagenomic sequencing of the intestines was performed to compare
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the gut microbiomes among the groups. We observed clear compound- and
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sex-specific responses to xenobiotic stress. Principal component analysis revealed
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involvement of the aryl hydrocarbon receptor (AhR) and, to a lesser extent, the
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estrogen receptor (ER) in the dysregulation of the intestinal microbiota. The model
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pollutants differentially impaired intestinal and hepatic physiological activities, as
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indicated by assessments of gut motility, epithelial permeability, inflammation, and
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oxidative stress. Correlation analysis showed that abnormal Aeromonas reproduction,
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especially in the PCB126 groups, was significantly positively associated with
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oxidative damage. Aeromonas closely interacted with Mannheimia and Blastococcus
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to regulate intestinal permeability. In summary, we demonstrated that ER and AhR
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signaling regulated the dynamics of the gut microbiota. Our findings provide new
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mechanistic insight into the complex interactions between the host metabolism and
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gut microbiota, which may contribute to the grouped assessment of environmental
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pollutants in future.
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INTRODUCTION
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Gut microbiota, which is referred to as the large diversity and quantity of microbes
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residing in the intestines of animals, is increasingly known to play pivotal roles in
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the maintenance of host health.1–3 Multiple physiological processes are associated
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with the gut microbiota, including energy metabolism, immune function, and
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neurobehavioral modulation.4–6 It has been established that alterations in the
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composition of gut microbial community will lead to the dysfunction of host
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physiological activities, contributing to the incurrence of many diseases such as
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obesity and diabetes.7–9 Because of the susceptibility of the gut microbiota to
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exogenous stressors, dysbiosis of the intestinal microbiome is becoming a focus of
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research to improve human health and environmental safety.
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Environmental pollutants are disruptors of gut microbiota dynamics. Aberrant
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gut microbiomic composition and abundance are caused by various pollutants,
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including antibiotics, heavy metals, persistent organic pollutants, and pesticides.10
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For example, oral exposure to the polychlorinated biphenyl (PCB) congeners
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(PCB153, PCB138, and PCB180) significantly alters bacterial abundance in the
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mouse intestine by reducing Proteobacteria levels.11 Dietary exposure to
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2,3,7,8-tetrachlorodibenzofuran (TCDF), a dioxin-like pollutant, shifts the
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Firmicutes/Bacteroidetes (F/B) ratio in the mouse gut, inducing host metabolic
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disorders.12 Furthermore, exposure to endocrine disruptors is also capable of
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changing gut bacterial community in animals, such as goldfish (Carassius auratus) 3
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by pentachlorophenol,13 and California mice (Peromyscus californicus) by bisphenol
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A and ethinyl estradiol,14 to significantly increase the abundance of Bacteroides
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genus in the intestines and induce the detriment of host health. Therefore, the
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increasing environmental pollution and continuous emergence of pollutants of
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concern necessitate identification of the compound- and species-specific responses
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of the gut microbiome.
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However, information about the effects of environmental pollutants on the
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intestinal microbiota remains limited. The disruptive effects of most environmental
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pollutants have not been explored, and current studies mainly focus on mammals. In
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view of the complexity of environmental pollutants, the intensive labor and cost
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associated with their investigation make it impossible to study them one by one. It is
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therefore necessary to identify the common mechanisms and indicative bacteria
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underlying the toxicity of environmental pollutants on gut microbiota, typically
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signaling mediated through estrogen receptor (ER) and aryl hydrocarbon receptor
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(AhR). In this study, adult zebrafish (Danio rerio) were exposed to the following
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environmental pollutants with varied modes of action: atrazine, estradiol (E2),
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PCB126, and PCB153. E2 mainly functions by binding to ER, whereas atrazine acts
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as an endocrine disruptor because of its target effect on aromatase but lacks affinity
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for ER.15 Although PCB126 is a dioxin-like coplanar congener with high affinity for
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the AhR, the non-coplanar congener PCB153 does not bind to the AhR.16 Comparing
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the effects of these model chemicals may reveal the roles of ER and AhR signaling 4
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in the dysregulation of the gut microbiota and provide insight into the relationship
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between gut microbes and host health.
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MATERIALS AND METHODS
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Chemicals
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Atrazine and E2 with purities >98% were purchased from Sigma-Aldrich Corp. (St.
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Louis, MO, USA). PCB126 and PCB153 with purities >99% were obtained from
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AccuStandard (New Haven, CT, USA). Stock solutions of model pollutants were
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prepared in dimethyl sulfoxide of high-performance liquid chromatography-grade
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(DMSO; Sigma-Aldrich Corp.). All other reagents were of analytic grade.
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Fish Maintenance and Exposure
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Adult zebrafish aged 4 months were cultured in a semi-static system containing
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charcoal-filtered fully-aerated tap water at a constant ambient temperature (28 ±
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0.5°C) under a light/dark cycle of 14/10 h.17 The fish were fed twice daily with flake
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food and newly hatched Artemia nauplii. After 2 weeks’ acclimation, the fish were
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aqueously exposed to 1.0 µg/L nominal concentrations of various environmental
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pollutants (atrazine, E2, PCB126, and PCB153). The control group received an equal
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volume of DMSO alone. The final DMSO concentrations in the control and
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exposure groups were
