Sex differences in cognition following variations in endocrine status

Impact of benzo[a]pyrene, PCB153 and sex hormones on human ESC-Derived thyroid follicles using single cell transcriptomics

INTRODUCTION

Endocrine disruptors are compounds of manmade origin able to interfere with the endocrine system and constitute an important environmental concern. Indeed, detrimental effects on thyroid physiology and functioning have been described. Differences exist in the susceptibility of human sexes to the incidence of thyroid disorders, like autoimmune diseases or cancer.

METHODS

To study how different hormonal environments impact the thyroid response to endocrine disruptors, we exposed human embryonic stem cell-derived thyroid organoids to physiological concentrations of sex hormones resembling the serum levels of human females post-ovulation or males of reproductive age for three days. Afterwards, we added 10 µM benzo[a]pyrene or PCB153 for 24 h and analyzed the transcriptome changes via single-cell RNA sequencing with differential gene expression and gene ontology analysis.

RESULTS

The sex hormones receptors genes AR, ESR1, ESR2 and PGR were expressed at low levels. Among the thyroid markers, only TG resulted downregulated by benzo[a]pyrene or benzo[a]pyrene with the "male" hormones mix. Both hormone mixtures and benzo[a]pyrene alone upregulated ribosomal genes and genes involved in oxidative phosphorylation, while their combination decreased the expression compared to benzo[a]pyrene alone. The "male" mix and benzo[a]pyrene, alone or in combination, upregulated genes involved in lipid transport and metabolism (APOA1, APOC3, APOA4, FABP1, FABP2, FABP6). The combination of "male" hormones and benzo[a]pyrene induced also genes involved in inflammation and NFkB targets. Benzo[a]pyrene upregulated CYP1A1, CYP1B1 and NQO1 irrespective of the hormonal context. The induction was stronger in the "female" mix. Benzo[a]pyrene alone upregulated genes involved in cell cycle regulation, response to reactive oxygen species and apoptosis. PCB153 had a modest effect in presence of "male" hormones, while we did not observe any changes with the "female" mix.

CONCLUSION

This work shows how single cell transcriptomics can be applied to selectively study the in vitro effects of endocrine disrupters and their interaction with different hormonal contexts.

Behavioural traits related with resilience or vulnerability to the development of cocaine-induced conditioned place preference after exposure of female mice to vicarious social defeat

Exposure to stress induced by intermittent repeated social defeat (IRSD) increases vulnerability to the development of cocaine-induced conditioned place preference (CPP) among male mice; however, some defeated mice are resilient to these effects of stress. In the present study we evaluated the effects of vicarious IRSD (VIRSD) in female mice and explored behavioural traits that are potentially predictive of resilience. C57BL/6 female mice (n = 28) were exposed to VIRSD, which consisted of the animals witnessing a short experience of social defeat by a male mouse on postnatal day (PND) 47, 50, 53 and 56. The control group (n = 10) was not exposed to stress. Blood samples were collected on PND 47 and 56 for corticosterone and interleukin-6 determinations. On PND 57-58, female mice performed several behavioural tests (elevated plus maze, hole-board, object recognition, social interaction, TST and splash tests). Three weeks later, the effects of cocaine (1.5 mg/kg) on the CPP paradigm were assessed. VIRSD decreased corticosterone levels (on PND 56), increased interleukin-6 levels, enhanced novelty-seeking, improved recognition memory and induced anxiety- and depression-like symptoms. Control and VIRSD female mice did not acquire CPP, although some stressed individuals with certain behavioural traits - including a high novelty-seeking profile or the development of depression-like behaviour in the splash test shortly after VIRSD - acquired cocaine CPP. Our results confirm that some behavioural traits of female mice are associated with vulnerability or resilience to the long-term effects of social stress on cocaine reward, as previously observed in males.

Ageing perspective on cognitive outcomes from reproductive hormone adjustments

In addition to primary reproductive functions, gonadal hormones play an important role in an array of neural mechanisms across the human lifespan. The ageing-related decline in their activity has been linked to the deterioration of cognitive functions in otherwise healthy women, associated with menopause transition, contributing to higher incidents of post-menopause dementia. Given the growing utility of gonadal steroids for birth control, as well as for compensatory treatment of menopause and oophorectomy symptoms, and adjuvant transgender therapy, their long-term effects on neural mechanisms warrant comprehensive assessment. In this article, we present an ageing perspective on the cognitive outcomes from contraceptive and replacement therapeutic use of gonadal hormones and discuss their effects on the risk of developing Alzheimer's and Parkinson's dementia. Despite rising data supporting the ameliorative effects of reproductive hormones on cognitive facilities, their impact varies depending on study design and type of intervention, thus, implying dynamic neuro-endocrine interactions with complex compensatory mechanisms. Elucidating differential effects of reproductive hormone adjustments on cognition with underlying mechanisms is expected not only to shed light on important aspects of brain ageing and dementia but to facilitate their use in personalized medicine with improved safety margins and therapeutic outcomes.

The Impact of Mild Chronic Stress and Maternal Experience in the Fmr1 Mouse Model of Fragile X Syndrome

Fragile X syndrome (FXS) is a pervasive developmental disorder and the most common monogenic cause of autism spectrum disorder (ASD). Female heterozygous (HET) carriers play a major role in the transmission of the pathology and present several FXS- and ASD-like behavioral alterations. Despite their clear genetic origins, FXS symptoms are known to be modulated by environmental factors, e.g., exposure to chronic stress, especially during critical life periods, such as pregnancy. Pregnancy, together with pups' care, constitutes maternal experience, i.e., another powerful environmental factor affecting several neurobehavioral functions in females. Here we investigated the impact of maternal experience on the long-term effects of stress in Fmr1-HET female mice. Our findings demonstrated that the behavioral abnormalities of HET females, i.e., hyperactivity and memory deficits, were unaffected by stress or maternal experience. In contrast, stress, independently of maternal experience, induced the appearance of cognitive deficits in WT mice. Maternal experience increased anxiety levels in all mice and enhanced their corticosterone levels, concomitantly promoting the effects of stress on social communication and adrenal glands. In translational terms, these results advance our understanding of the environmental modulation of the behavioral alterations observed in FXS female carriers and highlight the long-term impact of maternal experience and its interactions with chronic stress.

The power of effective study design in animal Experimentation: Exploring the statistical and ethical implications of asking multiple questions of a data set

One of the chief advantages of using highly standardised biological models including model organisms is that multiple variables can be precisely controlled so that the variable of interest is more easily studied. However, such an approach often obscures effects in sub-populations resulting from natural population heterogeneity. Efforts to expand our fundamental understanding of multiple sub-populations are in progress. However, such stratified or personalised approaches require fundamental modifications of our usual study designs that should be implemented in Brain, Behavior and Immunity (BBI) research going forward. Here we explore the statistical feasibility of asking multiple questions (including incorporating sex) within the same experimental cohort using statistical simulations of real data. We illustrate and discuss the large explosion in sample numbers necessary to detect effects with appropriate power for every additional question posed using the same data set. This exploration highlights the strong likelihood of type II errors (false negatives) for standard data and type I errors when dealing with complex genomic data, where studies are too under-powered to appropriately test these interactions. We show this power may differ for males and females in high throughput data sets such as RNA sequencing. We offer a rationale for the use of alternative experimental and statistical strategies based on interdisciplinary insights and discuss the real-world implications of increasing the complexities of our experimental designs, and the implications of not attempting to alter our experimental designs going forward.

Steroid Hormone Interaction with Dendritic Spines: Implications for Neuropsychiatric Disease

Dendritic spines, key sites for neural plasticity, are influenced by gonadal steroids. In this chapter, we review the effects of gonadal steroids on dendritic spine density in areas important to cognitive function, the hippocampus, and prefrontal cortex. Most of these animal model studies investigated the effects of estrogen in females, but we also include more recent data on androgen effects in both males and females. The underlying genomic and non-genomic mechanisms related to gonadal steroid-induced spinogenesis are also reviewed. Subsequently, we discuss possible reasons for the observed sex differences in many neuropsychiatric diseases, which appear to be caused, in part, by aberrant synaptic connections that may involve dendritic spine pathology. Overall, knowledge concerning the regulation of dendritic spines by gonadal hormones has grown since the initial discoveries in the 1990s, and current research points to a potential role for aberrant spine functioning in many neuropsychiatric disorders.