Developmental nicotine exposure and masculinization of the rat preoptic area.

Abstract

Nicotine is a neuroteratogenic component of tobacco smoke, e-cigarettes, and other products and can exert sex-specific effects in the developing brain, likely mediated through sex hormones. Estradiol modulates expression of nicotinic acetylcholine receptors in rats, and plays critical roles in neurodevelopmental processes, including sexual differentiation of the brain. Here, we examined the effects of developmental nicotine exposure on the sexual differentiation of the preoptic area (POA), a brain region that normally displays robust structural sexual dimorphisms and controls adult mating behavior in rodents. Using a rat model of gestational exposure, developing pups were exposed to nicotine (2 mg/kg/day) via maternal osmotic minipump (subcutaneously, sc) throughout the critical window for brain sexual differentiation. At postnatal day (PND) 4, a subset of offspring was analyzed for epigenetic effects in the POA. At PND40, all offspring were gonadectomized, implanted with a testosterone-releasing capsule (sc), and assessed for male sexual behavior at PND60. Following sexual behavior assessment, the area of the sexually dimorphic nucleus of the POA (SDN-POA) was measured using immunofluorescent staining techniques. In adults, normal sex differences in male sexual behavior and in the SDN-POA area were eliminated in nicotine-treated animals. Using novel analytical approaches to evaluate overall masculinization of the adult POA, we identified significant masculinization of the nicotine-treated female POA. In neonates (PND4), nicotine exposure induced trending alterations in methylation-dependent masculinizing gene expression and DNA methylation levels at sexually-dimorphic differentially methylated regions, suggesting that developmental nicotine exposure is capable of triggering masculinization of the rat POA via epigenetic mechanisms.

Type

Journal article

Department

Description

Provenance

Subjects

Preoptic Area, Animals, Rats, Nicotine, Testosterone, Sex Differentiation, Sex Characteristics, Female, Male, Electronic Nicotine Delivery Systems

Citation

Published Version (Please cite this version)

10.1016/j.neuro.2022.01.005

Publication Info

Joglekar, Rashmi, Marty Cauley, Taylor Lipsich, David L Corcoran, Heather B Patisaul, Edward D Levin, Joel N Meyer, Margaret M McCarthy, et al. (2022). Developmental nicotine exposure and masculinization of the rat preoptic area. Neurotoxicology, 89. pp. 41–54. 10.1016/j.neuro.2022.01.005 Retrieved from https://hdl.handle.net/10161/29480.

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Scholars@Duke

Levin

Edward Daniel Levin

Professor in Psychiatry and Behavioral Sciences

Dr. Levin is Chief of the Neurobehavioral Research Lab in the Psychiatry Department of Duke University Medical Center. His primary academic appointment is as Professor in the Department of Psychiatry and Behavioral Sciences. He also has secondary appointments in the Department Pharmacology and Cancer Biology, the Department of Psychological and Brain Sciences and the Nicholas School of the Environment at Duke. His primary research effort is to understand basic neural interactions underlying cognitive function and addiction and to apply this knowledge to better understand cognitive dysfunction and addiction disorders and to develop novel therapeutic treatments.

The three main research components of his laboratory are focused on the themes of the basic neurobiology of cognition and addiction, neurobehavioral toxicology and the development of novel therapeutic treatments for cognitive dysfunction and substance abuse. Currently, our principal research focus concerns nicotine. We have documented the basic effects of nicotine on learning memory and attention as well as nicotine self-administration. We are continuing with more mechanistic studies in rat models using selective lesions, local infusions and neurotransmitter interaction studies. We have found that nicotine improves memory performance not only in normal rats, but also in rats with lesions of hippocampal and basal forebrain connections. We are concentrating on alpha7 and alpha4beta2 nicotinic receptor subtypes in the hippocampus, amygdala , thalamus and frontal cortex and how they interact with dopamine D1 and D2 and glutamate NMDA systems with regard to memory and addiction. I am also conducting studies on human cognitive behavior. We have current studies to assess nicotine effects on attention, memory and mental processing speed in schizophrenia, Alzheimer's Disease and Attention Deficit Hyperactivity Disorder. In the area of neurobehavioral toxicology, I have continuing projects to characterize the adverse effects of prenatal and adolescent nicotine exposure. Our primary project in neurobehavioral toxicology focuses on the cognitive deficits caused by the marine toxins. The basic and applied aims of our research complement each other nicely. The findings concerning neural mechanisms underlying cognitive function help direct the behavioral toxicology and therapeutic development studies, while the applied studies provide important functional information concerning the importance of the basic mechanisms under investigation.

Meyer

Joel Meyer

Professor of Environmental Genomics in the Division of Environmental Sciences and Policy

Dr. Meyer studies the effects of toxic agents and stressors on human and wildlife health. He is particularly interested in understanding the mechanisms by which environmental agents cause DNA damage, the molecular processes that organisms employ to protect prevent and repair DNA damage, and genetic differences that may lead to increased or decreased sensitivity to DNA damage. Mitochondrial DNA damage and repair, as well as mitochondrial function in general, are a particular focus. He studies these effects in the nematode Caenorhabditis elegans, in cell culture, and collaboratively in other laboratory model organisms as well as in human populations in the USA and globally.

Murphy

Susan Kay Murphy

Associate Professor in Obstetrics and Gynecology

Dr. Murphy is a tenured Associate Professor in the Department of Obstetrics and Gynecology and serves as Chief of the Division of Reproductive Sciences. As a molecular biologist with training in human epigenetics, her research interests are largely centered around the role of epigenetic modifications in health and disease. 

Dr. Murphy has ongoing projects on gynecologic malignancies, including approaches to eradicate ovarian cancer cells that survive chemotherapy and later give rise to recurrent disease. Dr. Murphy is actively involved in many collaborative projects relating to the Developmental Origins of Health and Disease (DOHaD).

Her lab is currently working on preconception environmental exposures in males, particularly on the impact of cannabis on the sperm epigenome and the potential heritability of these effects. They are also studying the epigenetic and health effects of in utero exposures, with primary focus on children from the Newborn Epigenetics STudy (NEST), a pregnancy cohort she co-founded who were recruited from central North Carolina between 2005 and 2011. Dr. Murphy and her colleagues continue to follow NEST children to determine relationships between prenatal exposures and later health outcomes.


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