Estrogen Formation and Inactivation Following TBI: What we Know and Where we Could go

Neurological Health in Sexual and Gender Minority Individuals

Despite representing a significant proportion of the U.S. population, there is a paucity of population-based research on the health status and health needs of sexual and gender minority (SGM) individuals in neurology. Compared with heterosexual peers, some SGM populations have a higher burden of chronic health conditions. In parallel, SGM individuals are more likely to experience stigma and discrimination producing psychological distress, which may contribute to and be compounded by reduced health care access and utilization. In this narrative review, we summarize the existing literature on common neurological health conditions such as stroke, headache, epilepsy, movement disorders, and traumatic brain injury through the lens of intersection of SGM identity. Special focus is attuned to social determinants of health and gender-affirming hormonal therapy. Given the limitations in the available literature, there is an urgent unmet need for datasets that include sexual orientation and gender identity information, as well as funding for research that will characterize the prevalence of neurological conditions, unique risk factors, and health outcomes in SGM populations. In the health care community, providers should address deficiencies in their professional training and integrate inclusive language into their clinical skillset to build trust with SGM patients. There is an opportunity in neurology to proactively engage SGM communities, collaborate to remove barriers to care, promote resilience, and develop targeted interventions to ensure high-quality, culturally competent care for SGM populations to improve neurological health for all.

Neuroprotection or Sex Bias: A Protective Response to Traumatic Brain Injury in the Females

Traumatic brain injury (TBI) is a major healthcare problem and a common cause of mortality and morbidity. Clinical and preclinical research suggests sex-related differences in short- and longterm outcomes following TBI; however, males have been the main focus of TBI research. Females show a protective response against TBI. Female animals in preclinical studies and women in clinical trials have shown comparatively better outcomes against mild, moderate, or severe TBI. This reflects a favorable protective nature of the females compared to the males, primarily attributed to various protective mechanisms that provide better prognosis and recovery in the females after TBI. Understanding the sex difference in the TBI pathophysiology and the underlying mechanisms remains an elusive goal. In this review, we provide insights into various mechanisms related to the anatomical, physiological, hormonal, enzymatic, inflammatory, oxidative, genetic, or mitochondrial basis that support the protective nature of females compared to males. Furthermore, we sought to outline the evidence of multiple biomarkers that are highly potential in the investigation of TBI's prognosis, pathophysiology, and treatment and which can serve as objective measures and novel targets for individualized therapeutic interventions in TBI treatment. Implementations from this review are important for the understanding of the effect of sex on TBI outcomes and possible mechanisms behind the favorable response in females. It also emphasizes the critical need to include females as a biological variable and in sufficient numbers in future TBI studies.

ANTI-CD49D ANTIBODY TREATMENT IMPROVES SURVIVAL AND ATTENUATES NEUROCOGNITIVE DEFICITS AFTER TRAUMATIC BRAIN INJURY IN AGED MICE

ABSTRACT

Patients 65 years and older account for an increasing proportion of traumatic brain injury (TBI) patients. Aged TBI patients experience increased morbidity and mortality compared with young TBI patients. We previously demonstrated a marked accumulation of CD8 + T-cells within the brains of aged TBI mice compared with young TBI mice. Therefore, we hypothesized that blocking peripheral T-cell infiltration into the injured brain would improve neurocognitive outcomes in aged mice after TBI. Young and aged male C57BL/6 mice underwent TBI via controlled cortical impact versus sham injury. Two hours after injuries, mice received an anti-CD49d antibody (aCD49d Ab) to block peripheral lymphocyte infiltration or its isotype control. Dosing was repeated every 2 weeks. Mortality was tracked. Neurocognitive testing for anxiety, associative learning, and memory was assessed. Motor function was evaluated. Plasma was collected for cytokine analysis. Flow cytometry was used to phenotype different immune cells within the brains. Consequently, aCD49d Ab treatment significantly improved post-TBI survival, anxiety level, associative learning, memory, and motor function in aged mice 2 months after TBI compared with isotype control treated mice. aCD49d Ab treatment augmented T H 2 response in the plasma of aged mice 2 months after TBI compared with isotype control-treated mice. Notably, aCD49d Ab treatment significantly reduced activated CD8 + cytotoxic T-cells within aged mouse brains after TBI. Contrastingly, no difference was detected in young mice after aCD49d Ab treatment. Collectively, aCD49 Ab treatment reduced T-cells in the injured brain, improved survival, and attenuated neurocognitive and gait deficits. Hence, aCD49d Ab may be a promising therapeutic intervention in aged TBI subjects-a population often excluded in TBI clinical trials.

Systemic inflammation induced from remote extremity trauma is a critical driver of secondary brain injury

Blast exposure, commonly experienced by military personnel, can cause devastating life-threatening polysystem trauma. Despite considerable research efforts, the impact of the systemic inflammatory response after major trauma on secondary brain injury-inflammation is largely unknown. The aim of this study was to identify markers underlying the susceptibility and early onset of neuroinflammation in three rat trauma models: (1) blast overpressure exposure (BOP), (2) complex extremity trauma (CET) involving femur fracture, crush injury, tourniquet-induced ischemia, and transfemoral amputation through the fracture site, and (3) BOP+CET. Six hours post-injury, intact brains were harvested and dissected to obtain biopsies from the prefrontal cortex, striatum, neocortex, hippocampus, amygdala, thalamus, hypothalamus, and cerebellum. Custom low-density microarray datasets were used to identify, interpret and visualize genes significant (p < 0.05 for differential expression [DEGs]; 86 neuroinflammation-associated) using a custom python-based computer program, principal component analysis, heatmaps and volcano plots. Gene set and pathway enrichment analyses of the DEGs was performed using R and STRING for protein-protein interaction (PPI) to identify and explore key genes and signaling networks. Transcript profiles were similar across all regions in naïve brains with similar expression levels involving neurotransmission and transcription functions and undetectable to low-levels of inflammation-related mediators. Trauma-induced neuroinflammation across all anatomical brain regions correlated with injury severity (BOP+CET > CET > BOP). The most pronounced differences in neuroinflammatory-neurodegenerative gene regulation were between blast-associated trauma (BOP, BOP+CET) and CET. Following BOP, there were few DEGs detected amongst all 8 brain regions, most were related to cytokines/chemokines and chemokine receptors, where PPI analysis revealed Il1b as a potential central hub gene. In contrast, CET led to a more excessive and diverse pro-neuroinflammatory reaction in which Il6 was identified as the central hub gene. Analysis of the of the BOP+CET dataset, revealed a more global heightened response (Cxcr2, Il1b, and Il6) as well as the expression of additional functional regulatory networks/hub genes (Ccl2, Ccl3, and Ccl4) which are known to play a critical role in the rapid recruitment and activation of immune cells via chemokine/cytokine signaling. These findings provide a foundation for discerning pathophysiological consequences of acute extremity injury and systemic inflammation following various forms of trauma in the brain.

Endometrial proteomic profile of patients with repeated implantation failure

Introduction

Successful embryo implantation, is the initiating step of pregnancy, relies on not only the high quality of the embryo but also the synergistic development of a healthy endometrium. Characterization and identification of biomarkers for the receptive endometrium is an effective method for increasing the probability of successful embryo implantation.

Methods

Endometrial tissues from 22 women with a history of recurrent implantation failure (RIF) and 19 fertile controls were collected using biopsy catheters on 7-9 days after the peak of luteinizing hormone. Differentially expressed proteins (DEPs) were identified in six patients with RIF and six fertile controls using isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomics analysis.

Results

Two hundred and sixty-three DEPs, including proteins with multiple bioactivities, such as protein translation, mitochondrial function, oxidoreductase activity, fatty acid and amino acid metabolism, were identified from iTRAQ. Four potential biomarkers for receptive endometrium named tubulin polymerization-promoting protein family member 3 TPPP3, S100 Calcium Binding Protein A13 (S100A13), 17b-hydroxysteroid dehydrogenase 2 (HSD17B2), and alpha-2-glycoprotein 1, zinc binding (AZGP1) were further verified using ProteinSimple Wes and immunohistochemical staining in all included samples (n=22 for RIF and n=19 for controls). Of the four proteins, the protein levels of TPPP3 and HSD17B2 were significantly downregulated in the endometrium of patients with RIF.

Discussion

Poor endometrial receptivity is considered the main reason for the decrease in pregnancy success rates in patients suffering from RIF. iTRAQ techniques based on isotope markers can identify and quantify low abundance proteomics, and may be suitable for identifying differentially expressed proteins in RIF. This study provides novel evidence that TPPP3 and HSD17B2 may be effective targets for the diagnosis and treatment of non-receptive endometrium and RIF.

Research progress on pleiotropic neuroprotective drugs for traumatic brain injury

Traumatic brain injury (TBI) has become one of the most important causes of death and disability worldwide. A series of neuroinflammatory responses induced after TBI are key factors for persistent neuronal damage, but at the same time, such inflammatory responses can also promote debris removal and tissue repair after TBI. The concept of pleiotropic neuroprotection delves beyond the single-target treatment approach, considering the multifaceted impacts following TBI. This notion embarks deeper into the research-oriented treatment paradigm, focusing on multi-target interventions that inhibit post-TBI neuroinflammation with enhanced therapeutic efficacy. With an enriched comprehension of TBI's physiological mechanisms, this review dissects the advancements in developing pleiotropic neuroprotective pharmaceuticals to mitigate TBI. The aim is to provide insights that may contribute to the early clinical management of the condition.

Neurons and glial cells acquire a senescent signature after repeated mild traumatic brain injury in a sex-dependent manner

Mild traumatic brain injury (mTBI) is an important public health issue, as it can lead to long-term neurological symptoms and risk of neurodegenerative disease. The pathophysiological mechanisms driving this remain unclear, and currently there are no effective therapies for mTBI. In this study on repeated mTBI (rmTBI), we have induced three mild closed-skull injuries or sham procedures, separated by 24 h, in C57BL/6 mice. We show that rmTBI mice have prolonged righting reflexes and astrogliosis, with neurological impairment in the Morris water maze (MWM) and the light dark test. Cortical and hippocampal tissue analysis revealed DNA damage in the form of double-strand breaks, oxidative damage, and R-loops, markers of cellular senescence including p16 and p21, and signaling mediated by the cGAS-STING pathway. This study identified novel sex differences after rmTBI in mice. Although these markers were all increased by rmTBI in both sexes, females had higher levels of DNA damage, lower levels of the senescence protein p16, and lower levels of cGAS-STING signaling proteins compared to their male counterparts. Single-cell RNA sequencing of the male rmTBI mouse brain revealed activation of the DNA damage response, evidence of cellular senescence, and pro-inflammatory markers reminiscent of the senescence-associated secretory phenotype (SASP) in neurons and glial cells. Cell-type specific changes were also present with evidence of brain immune activation, neurotransmission alterations in both excitatory and inhibitory neurons, and vascular dysfunction. Treatment of injured mice with the senolytic drug ABT263 significantly reduced markers of senescence only in males, but was not therapeutic in females. The reduction of senescence by ABT263 in male mice was accompanied by significantly improved performance in the MWM. This study provides compelling evidence that senescence contributes to brain dysfunction after rmTBI, but may do so in a sex-dependent manner.

Steroid profiling in brain and plasma of adult zebra finches following traumatic brain injury

Traumatic brain injury (TBI) is a serious health concern and a leading cause of death. Emerging evidence strongly suggests that steroid hormones (estrogens, androgens, and progesterone) modulate TBI outcomes by regulating inflammation, oxidative stress, free radical production, and extracellular calcium levels. Despite this growing body of evidence on steroid-mediated neuroprotection, very little is known about the local synthesis of these steroids following injury. Here, we examine the effect of TBI on local neurosteroid levels around the site of injury and in plasma in adult male and female zebra finches. Using ultrasensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS), we examined estrogens, androgens, and progesterone in the entopallium and plasma of injured and uninjured animals. Three days after injury, elevated levels of 17β-estradiol (E₂ ), estrone (E₁ ), and testosterone (T) were detected near injured brain tissue with a corresponding increase in E₂ also detected in plasma. Taken together, these results provide further evidence that TBI alters neurosteroid levels and are consistent with studies showing that neurosteroids provide neuroprotection following injury.

Exploring Sex-Related Differences in Microglia May Be a Game-Changer in Precision Medicine

One area of microglial biology that has been relatively neglected until recently is sex differences and this is in spite of the fact that sex is a risk factor in several diseases that are characterized by neuroinflammation and, by extension, microglial activation. Why these sex differences exist is not known but the panoply of differences extend to microglial number, genotype and phenotype. Significantly, several of these sex-related differences are also evident in health and change during life emphasizing the dynamic and plastic nature of microglia. This review will consider how age impacts on sex-related differences in microglia and ask whether the advancement of personalized medicine demands that a greater focus is placed on studying sex-related differences in microglia in Alzheimer's disease, Parkinson's disease and models of inflammatory stress and trauma in order to make true progress in dealing with these conditions.

Endogenous and Exogenous Estrogen Exposures: How Women's Reproductive Health Can Drive Brain Aging and Inform Alzheimer's Prevention

After advanced age, female sex is the major risk factor for late-onset Alzheimer's disease (AD), the most common cause of dementia affecting over 24 million people worldwide. The prevalence of AD is higher in women than in men, with postmenopausal women accounting for over 60% of all those affected. While most research has focused on gender-combined risk, emerging data indicate sex and gender differences in AD pathophysiology, onset, and progression, which may help account for the higher prevalence in women. Notably, AD-related brain changes develop during a 10-20 year prodromal phase originating in midlife, thus proximate with the hormonal transitions of endocrine aging characteristic of the menopause transition in women. Preclinical evidence for neuroprotective effects of gonadal sex steroid hormones, especially 17β-estradiol, strongly argue for associations between female fertility, reproductive history, and AD risk. The level of gonadal hormones to which the female brain is exposed changes considerably across the lifespan, with relevance to AD risk. However, the neurobiological consequences of hormonal fluctuations, as well as that of hormone therapies, are yet to be fully understood. Epidemiological studies have yielded contrasting results of protective, deleterious and null effects of estrogen exposure on dementia risk. In contrast, brain imaging studies provide encouraging evidence for positive associations between greater cumulative lifetime estrogen exposure and lower AD risk in women, whereas estrogen deprivation is associated with negative consequences on brain structure, function, and biochemistry. Herein, we review the existing literature and evaluate the strength of observed associations between female-specific reproductive health factors and AD risk in women, with a focus on the role of endogenous and exogenous estrogen exposures as a key underlying mechanism. Chief among these variables are reproductive lifespan, menopause status, type of menopause (spontaneous vs. induced), number of pregnancies, and exposure to hormonal therapy, including hormonal contraceptives, hormonal therapy for menopause, and anti-estrogen treatment. As aging is the greatest risk factor for AD followed by female sex, understanding sex-specific biological pathways through which reproductive history modulates brain aging is crucial to inform preventative and therapeutic strategies for AD.

Glial estradiol synthesis after brain injury

Glial cells are important contributors to the hormonal milieu of the brain, particularly following damage. In birds and mammals, neural injury induces the expression of aromatase in astroglia at and around the site of damage. This review describes the progression of our understanding about the incidence, regulation, and function of estrogens synthesized in glia. Following a quick discussion of the landmark studies that first demonstrated steroidogenesis in glia, I go on to describe how the inflammatory response following perturbation of the brain results in the transcription of aromatase and the resultant rise in local estradiol. I end with several unanswered questions, the answers to which may reveal the precise manner in which neurosteroids protect the brain from injury, both prior to and immediately following injury.

Sex Differences in Peritraumatic Inflammatory Cytokines and Steroid Hormones Contribute to Prospective Risk for Nonremitting Posttraumatic Stress Disorder

Women are at higher risk for developing posttraumatic stress disorder (PTSD) compared to men, yet little is known about the biological contributors to this sex difference. One possible mechanism is differential immunological and neuroendocrine responses to traumatic stress exposure. In the current prospective study, we aimed to identify whether sex is indirectly associated with the probability of developing nonremitting PTSD through pro-inflammatory markers and whether steroid hormone concentrations influence this effect. Female (n = 179) and male (n = 197) trauma survivors were recruited from an emergency department and completed clinical assessment within 24 h and blood samples within ∼three hours of trauma exposure. Pro-inflammatory cytokines (IL-6, IL-1 β , TNF, IFNγ), and steroid hormone (estradiol, testosterone, progesterone, cortisol) concentrations were quantified in plasma. Compared to men, women had a higher probability of developing nonremitting PTSD after trauma (p = 0.04), had lower pro-inflammatory cytokines and testosterone (p's<0.001), and had higher cortisol and progesterone (p's<0.001) concentrations. Estradiol concentrations were not different between the sexes (p = 0.24). Pro-inflammatory cytokines were a significant mediator in the relationship between sex and probability of developing nonremitting PTSD (p < 0.05), such that men had higher concentrations of pro-inflammatory cytokines which were associated with lower risk of nonremitting PTSD development. This effect was significantly moderated by estradiol (p < 0.05), as higher estradiol levels in men were associated with higher pro-inflammatory cytokine concentrations and lower risk for developing nonremitting PTSD. The current results suggest that sex differences in the pro-inflammatory cytokine response to trauma exposure partially mediate the probability of developing nonremitting PTSD, and that the protective ability to mount an pro-inflammatory cytokine response in men may depend on higher estradiol levels in the aftermath of trauma exposure.

Moderators of gene-outcome associations following traumatic brain injury

The field of genomics is the principal avenue in the ongoing development of precision/personalised medicine for a variety of health conditions. However, relating genes to outcomes is notoriously complex, especially when considering that other variables can change, or moderate, gene-outcome associations. Here, we comprehensively discuss moderation of gene-outcome associations in the context of traumatic brain injury (TBI), a common, chronically debilitating, and costly neurological condition that is under complex polygenic influence. We focus our narrative review on single nucleotide polymorphisms (SNPs) of three of the most studied genes (apolipoprotein E, brain-derived neurotrophic factor, and catechol-O-methyltransferase) and on three demographic variables believed to moderate associations between these SNPs and TBI outcomes (age, biological sex, and ethnicity). We speculate on the mechanisms which may underlie these moderating effects, drawing widely from biomolecular and behavioural research (n = 175 scientific reports) within the TBI population (n = 72) and other neurological, healthy, ageing, and psychiatric populations (n = 103). We conclude with methodological recommendations for improved exploration of moderators in future genetics research in TBI and other populations.

Steroid sulfatase inhibitors: the current landscape

Introduction: Steroid sulfatase (STS) enzyme is responsible for transforming the inactive sulfate metabolites of steroid sex hormones into the active free steroids. Both the deficiency and the over-expression of STS are associated with the pathophysiology of certain diseases. This article provides the readership with a comprehensive review about STS enzyme and its recently reported inhibitors.Areas covered: In the present article, we reviewed the structure, location, and substrates of STS enzyme, physiological functions of STS, and disease states related to over-expression or deficiency of STS enzyme. STS inhibitors reported during the last five years (2016-present) have been reviewed as well.Expert opinion: Irosustat is the most successful STS inhibitor drug candidate so far. It is currently under investigation in clinical trials for treatment of estrogen-dependent breast cancer. Non-steroidal sulfamate is the most favorable scaffold for STS inhibitor design. They can be beneficial for the treatment of hormone-dependent cancers and neurodegenerative disorders without significant estrogenic side effects. Moreover, dual-acting molecules (inhibitors of STS + another synergistic mechanism) can be therapeutically efficient.

The Role of Estradiol in Traumatic Brain Injury: Mechanism and Treatment Potential

Patients surviving traumatic brain injury (TBI) face numerous neurological and neuropsychological problems significantly affecting their quality of life. Extensive studies over the past decades have investigated pharmacological treatment options in different animal models, targeting various pathological consequences of TBI. Sex and gender are known to influence the outcome of TBI in animal models and in patients, respectively. Apart from its well-known effects on reproduction, 17β-estradiol (E2) has a neuroprotective role in brain injury. Hence, in this review, we focus on the effect of E2 in TBI in humans and animals. First, we discuss the clinical classification and pathomechanism of TBI, the research in animal models, and the neuroprotective role of E2. Based on the results of animal studies and clinical trials, we discuss possible E2 targets from early to late events in the pathomechanism of TBI, including neuroinflammation and possible disturbances of the endocrine system. Finally, the potential relevance of selective estrogenic compounds in the treatment of TBI will be discussed.