The effect of endurance training and testosterone supplementation on the expression of blood spinal cord barrier proteins in rats

Sex, hormones and cerebrovascular function: from development to disorder

Proper cerebrovascular development and neurogliovascular unit assembly are essential for brain growth and function throughout life, ensuring the continuous supply of nutrients and oxygen. This involves crucial events during pre- and postnatal stages through key pathways, including vascular endothelial growth factor (VEGF) and Wnt signaling. These pathways are pivotal for brain vascular growth, expansion, and blood-brain barrier (BBB) maturation. Interestingly, during fetal and neonatal life, cerebrovascular formation coincides with the early peak activity of the hypothalamic-pituitary-gonadal axis, supporting the idea of sex hormonal influence on cerebrovascular development and barriergenesis.Sex hormonal dysregulation in early development has been implicated in neurodevelopmental disorders with highly sexually dimorphic features, such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). Both disorders show higher prevalence in men, with varying symptoms between sexes, with boys exhibiting more externalizing behaviors, such as aggressivity or hyperactivity, and girls displaying higher internalizing behaviors, including anxiety, depression, or attention disorders. Indeed, ASD and ADHD are linked to high prenatal testosterone exposure and reduced aromatase expression, potentially explaining sex differences in prevalence and symptomatology. In line with this, high estrogen levels seem to attenuate ADHD symptoms. At the cerebrovascular level, sex- and region-specific variations of cerebral blood flow perfusion have been reported in both conditions, indicating an impact of gonadal hormones on the brain vascular system, disrupting its ability to respond to neuronal demands.This review aims to provide an overview of the existing knowledge concerning the impact of sex hormones on cerebrovascular formation and maturation, as well as the onset of neurodevelopmental disorders. Here, we explore the concept of gonadal hormone interactions with brain vascular and BBB development to function, with a particular focus on the modulation of VEGF and Wnt signaling. We outline how these pathways may be involved in the underpinnings of ASD and ADHD. Outstanding questions and potential avenues for future research are highlighted, as uncovering sex-specific physiological and pathological aspects of brain vascular development might lead to innovative therapeutic approaches in the context of ASD, ADHD and beyond.

Disruption of neurosteroid synthesis and release by tris(2,3-dibromopropyl)isocyanurate in primary mouse cortical astrocytes in vitro

Neurosteroidogenesis in astrocytes is crucial for the proper development and functioning of the brain. During this process, key neurohormones such as progesterone (P4 ), testosterone (T), and estradiol (E2 ) are produced. Proper production and release of neurosteroids can be affected by substances referred to as endocrine-disrupting compounds (EDCs). Tris-(2,3-dibromopropyl)isocyanurate (TBC) is a representative of novel brominated flame retardants used to stop ignition or reduce fire-related property damage to plastics, polyolefin, polyphenyl alkene, unsaturated polyester, synthetic rubber, and fibers. Interestingly, previous studies have shown that TBC can enhance the proliferation of estradiol-sensitive breast cancers in vitro, which suggests that TBC has EDC properties. Therefore, given the suspected endocrine-disrupting properties of TBC, the aim of the present study was to determine the impact of TBC on the neurosteroid (P4 , T, and E2 ) production and secretion as well as the mRNA expression of key enzymes involved in its production in mouse astrocytes in vitro. Our paper shows that TBC increases P4 production with a strong decrease in T production, which is accompanied by a decrease in Cyp17a1 mRNA expression, that is, the main enzyme metabolizing P4 to T. Moreover, TBC in both studied concentrations increases P4 secretion in the culture medium. Finally, our studies have demonstrated an increase in the expression of Cyp19a1 mRNA, an enzyme metabolizing T to E2 , with a simultaneous increase in the amount of E2 in cells. Our data clearly show that TBC in an in vitro environment acts as EDCs, which may lead to serious consequences for the proper development and functioning of the brain.

Sex differences in the blood-brain barrier: Implications for mental health

Prevalence of mental disorders, including major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ) are increasing at alarming rates in our societies. Growing evidence points toward major sex differences in these conditions, and high rates of treatment resistance support the need to consider novel biological mechanisms outside of neuronal function to gain mechanistic insights that could lead to innovative therapies. Blood-brain barrier alterations have been reported in MDD, BD and SZ. Here, we provide an overview of sex-specific immune, endocrine, vascular and transcriptional-mediated changes that could affect neurovascular integrity and possibly contribute to the pathogenesis of mental disorders. We also identify pitfalls in current literature and highlight promising vascular biomarkers. Better understanding of how these adaptations can contribute to mental health status is essential not only in the context of MDD, BD and SZ but also cardiovascular diseases and stroke which are associated with higher prevalence of these conditions.

Fetal glucocorticoid exposure leads to sex-specific changes in drug-transporter function at the blood-brain barrier in juvenile guinea pigs

Antenatal synthetic glucocorticoids (sGCs) are a life‐saving treatment in managing pre‐term birth. However, off‐target effects of sGCs can impact blood‐brain barrier (BBB) drug transporters essential for fetal brain protection, including P‐glycoprotein (P‐gp/Abcb1) and breast cancer resistance protein (BCRP/Abcg2). We hypothesized that maternal antenatal sGC treatment modifies BBB function in juvenile offspring in a sex‐dependent manner. Thus, the objective of this study was to determine the long‐term impact of a single or multiple courses of betamethasone on P‐gp/Abcb1 and BCRP/Abcg2 expression and function at the BBB. Pregnant guinea pigs (N = 42) received 3 courses (gestation days (GDs) 40, 50, and 60) or a single course (GD50) of betamethasone (1 mg/kg) or vehicle (saline). Cerebral microvessels and brain endothelial cells (BEC) were collected from the post‐natal day (PND) 14 offspring to measure protein, gene expression, and function of the drug transporters P‐gp/Abcb1 and BCRP/Abcg2. P‐gp protein expression was decreased (p < .05) in microvessels from male offspring that had been exposed to multiple courses and a single course of sGC, in utero. Multiple courses of sGC resulted in a significant decrease in P‐gp function in BECs from males (p < .05), but not females. There was a very strong trend for increased P‐gp function in males compared to females (p = .055). Reduced P‐gp expression and function at the BBB of young male offspring following multiple prenatal sGC exposures, is clinically relevant as many drugs administered postnatally are P‐gp substrates. These novel sex differences in drug transporter function may underlie potential sexual dimorphism in drug sensitivity and toxicity in the newborn and juvenile brain.

Sex hormones regulate NHE1 functional expression and brain endothelial proteome to control paracellular integrity of the blood endothelial barrier

BACKGROUND

Sex hormones have been implicated in pH regulation of numerous physiological systems. One consistent factor of these studies is the sodium-hydrogen exchanger 1 (NHE1). NHE1 has been associated with pH homeostasis at epithelial barriers. Hormone fluctuations have been implicated in protection and risk for breaches in blood brain barrier (BBB)/blood endothelial barrier (BEB) integrity. Few studies, however, have investigated BBB/BEB integrity in neurological disorders in the context of sex-hormone regulation of pH homeostasis.

METHODS//RESULTS

Physiologically relevant concentrations of 17-β-estradiol (E2, 294 pM), progesterone (P, 100 nM), and testosterone (T,3.12 nM) were independently applied to cultured immortalized bEnd.3 brain endothelial cells to study the BEB. Individual gonadal hormones showed preferential effects on extracellular pH (E2), 14C-sucrose uptake (T), stimulated paracellular breaches (P) with dependence on functional NHE1 expression without impacting transendothelial resistance (TEER) or total protein expression. While total NHE1 expression was not changed as determined via whole cell lysate and subcellular fractionation experiment, biotinylation of NHE1 for surface membrane expression showed E2 reduced functional expression. Quantitative proteomic analysis revealed divergent effects of 17-β-estradiol and testosterone on changes in protein abundance in bEnd.3 endothelial cells as compared to untreated controls.

CONCLUSIONS

These data suggest that circulating levels of sex hormones may independently control BEB integrity by 1) regulating pH homeostasis through NHE1 functional expression and 2) modifying the endothelial proteome.

Androgens' effects on cerebrovascular function in health and disease

Androgens affect the cerebral vasculature and may contribute to sex differences in cerebrovascular diseases. Men are at a greater risk for stroke and vascular contributions to cognitive impairment and dementia (VCID) compared to women throughout much of the lifespan. The cerebral vasculature is a target for direct androgen actions, as it expresses several sex steroid receptors and metabolizing enzymes. Androgens’ actions on the cerebral vasculature are complex, as they have been shown to have both protective and detrimental effects, depending on factors such as age, dose, and disease state. When administered chronically, androgens are shown to be pro-angiogenic, promote vasoconstriction, and influence blood-brain barrier permeability. In addition to these direct effects of androgens on the cerebral vasculature, androgens also influence other vascular risk factors that may contribute to sex differences in cerebrovascular diseases. In men, low androgen levels have been linked to metabolic and cardiovascular diseases including hypertension, diabetes, hyperlipidemia, and obesity, which greatly increase the risk of stroke and VCID. Thus, a better understanding of androgens’ interactions with the cerebral vasculature under physiological and pathological conditions is of key importance.

Elastin-Derived Peptide VGVAPG Affects Production and Secretion of Testosterone in Mouse Astrocyte In Vitro

Astrocytes play many distinct roles in the nervous system providing structural support for neurons and maintaining blood-brain barrier integrity. Steroid hormones exhibit a broad spectrum of actions in the central and peripheral nervous system, acting as trophic factors affecting cell differentiation and synaptic plasticity. In steroidogenesis, astrocytes play a key role by producing cholesterol, progesterone (P₄), testosterone (T), and estradiol (E₂). Currently there are only few studies which show that the Gly-Val-Ala-Pro-Gly (VGVAPG) peptide may affect the metabolism of astrocytes. Therefore, due to the role of neurosteroids, it is necessary to determine whether VGVAPG affects the level of E₂, P₄, and T in astrocytes. Primary mouse astrocytes were maintained in DMEM/F12 without phenol red, and supplemented with 10% charcoal/dextran-treated fetal bovine serum. Cells were exposed to 10 nM and 1 µM VGVAPG peptide and co-treated with cSrc kinase inhibitor I. After cell stimulation, we measured the Ki67 protein level and the production and secretion of P₄, T, and E₂. Our report presents the novel finding that the VGVAPG peptide affects the production and secretion of neurosteroids in astrocytes in vitro. The VGVAPG peptide increases the production of P₄; however, at the same time, it decreases the secretion of P₄ by astrocytes. On the other hand, it stimulates the production and secretion of T. Interestingly, the production of E₂ did not change in any studied time interval. The expression of Ki67 protein increased after 48 h of exposition to the VGVAPG peptide. The cSrc kinase inhibitor I prevented most of the effects of VGVAPG peptide. Therefore, we postulate that T and cSrc kinase may be responsible for increasing astrocyte proliferation.