Roles of Progesterone, Testosterone and Their Nuclear Receptors in Central Nervous System Myelination and Remyelination

The gut microbiota-oligodendrocyte axis: A promising pathway for modulating oligodendrocyte homeostasis and demyelination-associated disorders

The bidirectional regulation between the gut microbiota and brain, known as gut-brain axis, has received significant attention. The myelin sheath, produced by oligodendrocytes or Schwann cells, is essential for efficient nervous signal transmission and the maintenance of brain function. Growing evidence shows that both oligodendrogenesis and myelination are modulated by gut microbiota and its metabolites, and when dysbiosis occurs, changes in the microbiota composition and/or associated metabolites may impact developmental myelination and the occurrence of neurodevelopmental disabilities. Although the link between the microbiota and demyelinating disease such as multiple sclerosis has been extensively studied, our knowledge about the role of the microbiota in other myelin-related disorders, such as neurodegenerative diseases, is limited. Mechanistically, the microbiota-oligodendrocyte axis is primarily mediated by factors such as inflammation, the vagus nerve, endocrine hormones, and microbiota metabolites as evidenced by metagenomics, metabolomics, vagotomy, and morphological and molecular approaches. Treatments targeting this axis include probiotics, prebiotics, microbial metabolites, herbal bioactive compounds, and specific dietary management. In addition to the commonly used approaches, viral vector-mediated tracing and gene manipulation, integrated multiomics and multicenter clinical trials will greatly promote the mechanistic and interventional studies and ultimately, the development of new preventive and therapeutic strategies against gut-oligodendrocyte axis-mediated brain impairments. Interestingly, recent findings showed that microbiota dysbiosis can be induced by hippocampal myelin damage and is reversible by myelin-targeted drugs, which provides new insights into understanding how hippocampus-based functional impairment (such as in neurodegenerative Alzheimer's disease) regulates the peripheral homeostasis of microbiota and associated systemic disorders.

Relating sex-bias in human cortical and hippocampal microstructure to sex hormones

Determining sex-bias in brain structure is of great societal interest to improve diagnostics and treatment of brain-related disorders. So far, studies on sex-bias in brain structure predominantly focus on macro-scale measures, and often ignore factors determining this bias. Here we study sex-bias in cortical and hippocampal microstructure in relation to sex hormones. Investigating quantitative intracortical profiling in-vivo using the T1w/T2w ratio in 1093 healthy females and males of the cross-sectional Human Connectome Project young adult sample, we find that regional cortical and hippocampal microstructure differs between males and females and that the effect size of this sex-bias varies depending on self-reported hormonal status in females. Microstructural sex-bias and expression of sex hormone genes, based on an independent post-mortem sample, are spatially coupled. Lastly, sex-bias is most pronounced in paralimbic areas, with low laminar complexity, which are predicted to be most plastic based on their cytoarchitectural properties. Albeit correlative, our study underscores the importance of incorporating sex hormone variables into the investigation of brain structure and plasticity.

Investigating the influence of oral contraceptive pill use on multiple sclerosis risk using UK Biobank data

OBJECTIVE

To investigate the association between oral contraceptive (OC) pill use and the risk of developing multiple sclerosis (MS), attempting to address the limitations present in previous studies that produced conflicting results.

DESIGN

A population-based cohort study using data from the UK Biobank.

PATIENTS

The study included 181,058 women of white ethnicity born in England between 1937 and 1970, among which 1,131 had an MS diagnosis.

INTERVENTION

Oral contraceptive use, considering the self-reported age of initiation and discontinuation. The exposures of interest include the following: ever-use, current use, duration of current use in years, and age and year at initiation.

MAIN OUTCOME MEASURES

Multiple sclerosis diagnosis (International Classification of Disease, 10th revision: G35) was used as an outcome of interest, and the associations with the exposures of interest were investigated using marginal structural models with a time-to-event approach. To adjust for confounding, we included in the models several variables, including MS polygenic risk score, education level, parity, smoking, fertility problems, obesity, and mononucleosis. We further aimed to evaluate the influence of parity using a mediation analysis.

RESULTS

The association of both ever and current OC use did not result in a statistically significant MS hazard increase (ever vs. never-users, hazard ratio [HR] = 1.30 [95% confidence interval {CI}: 0.93,1.82]; current vs. never-users, HR = 1.35 [95% CI: 0.81, 2.25]). However, we highlighted parity as an effect modifier for this association. In nulliparous women, ever and current use resulted in a significant twofold and threefold MS hazard increase (HR = 2.08 [95% CI: 1.04, 4.17] and HR = 3.15 [95% CI: 1.43, 6.9]). These associations were supported by significant MS hazard increases for a higher duration of current use and for an earlier age at initiation. We further highlighted genetic MS susceptibility as another effect modifier, as a stronger OC-MS hazard association was found in women with a low MS polygenic risk score.

CONCLUSION

Our findings highlighted how the association between OC use and MS varies on the basis of individual characteristics such as parity and genetic MS susceptibility. Importantly, current use in nulliparous women was found to be associated with a threefold increase in MS hazard. We acknowledge the need for cautious causal interpretation and further research to validate these findings across diverse populations and OC types.

The Interaction of Vasopressin with Hormones of the Hypothalamo-Pituitary-Adrenal Axis: The Significance for Therapeutic Strategies in Cardiovascular and Metabolic Diseases

A large body of evidence indicates that vasopressin (AVP) and steroid hormones are frequently secreted together and closely cooperate in the regulation of blood pressure, metabolism, water-electrolyte balance, and behavior, thereby securing survival and the comfort of life. Vasopressin cooperates with hormones of the hypothalamo-pituitary-adrenal axis (HPA) at several levels through regulation of the release of corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), and multiple steroid hormones, as well as through interactions with steroids in the target organs. These interactions are facilitated by positive and negative feedback between specific components of the HPA. Altogether, AVP and the HPA cooperate closely as a coordinated functional AVP-HPA system. It has been shown that cooperation between AVP and steroid hormones may be affected by cellular stress combined with hypoxia, and by metabolic, cardiovascular, and respiratory disorders; neurogenic stress; and inflammation. Growing evidence indicates that central and peripheral interactions between AVP and steroid hormones are reprogrammed in cardiovascular and metabolic diseases and that these rearrangements exert either beneficial or harmful effects. The present review highlights specific mechanisms of the interactions between AVP and steroids at cellular and systemic levels and analyses the consequences of the inappropriate cooperation of various components of the AVP-HPA system for the pathogenesis of cardiovascular and metabolic diseases.

Testosterone Reduces Myelin Abnormalities in the Wobbler Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal motoneuron degenerative disease that is associated with demyelination. The Wobbler (WR) mouse exhibits motoneuron degeneration, gliosis and myelin deterioration in the cervical spinal cord. Since male WRs display low testosterone (T) levels in the nervous system, we investigated if T modified myelin-relative parameters in WRs in the absence or presence of the aromatase inhibitor, anastrozole (A). We studied myelin by using luxol-fast-blue (LFB) staining, semithin sections, electron microscopy and myelin protein expression, density of IBA1+ microglia and mRNA expression of inflammatory factors, and the glutamatergic parameters glutamine synthetase (GS) and the transporter GLT1. Controls and WR + T showed higher LFB, MBP and PLP staining, lower g-ratios and compact myelin than WRs and WR + T + A, and groups showing the rupture of myelin lamellae. WRs showed increased IBA1+ cells and mRNA for CD11b and inflammatory factors (IL-18, TLR4, TNFαR1 and P2Y12R) vs. controls or WR + T. IBA1+ cells, and CD11b were not reduced in WR + T + A, but inflammatory factors' mRNA remained low. A reduction of GS+ cells and GLT-1 immunoreactivity was observed in WRs and WR + T + A vs. controls and WR + T. Clinically, WR + T but not WR + T + A showed enhanced muscle mass, grip strength and reduced paw abnormalities. Therefore, T effects involve myelin protection, a finding of potential clinical translation.

Cerebrospinal fluid metabolomic and proteomic characterization of neurologic post-acute sequelae of SARS-CoV-2 infection

The mechanism by which SARS-CoV-2 causes neurological post-acute sequelae of SARS-CoV-2 (neuro-PASC) remains unclear. Herein, we conducted proteomic and metabolomic analyses of cerebrospinal fluid (CSF) samples from 21 neuro-PASC patients, 45 healthy volunteers, and 26 inflammatory neurological diseases patients. Our data showed 69 differentially expressed metabolites and six differentially expressed proteins between neuro-PASC patients and healthy individuals. Elevated sphinganine and ST1A1, sphingolipid metabolism disorder, and attenuated inflammatory responses may contribute to the occurrence of neuro-PASC, whereas decreased levels of 7,8-dihydropterin and activation of steroid hormone biosynthesis may play a role in the repair process. Additionally, a biomarker cohort consisting of sphinganine, 7,8-dihydroneopterin, and ST1A1 was preliminarily demonstrated to have high value in diagnosing neuro-PASC. In summary, our study represents the first attempt to integrate the diagnostic benefits of CSF with the methodological advantages of multi-omics, thereby offering valuable insights into the pathogenesis of neuro-PASC and facilitating the work of neuroscientists in disclosing different neurological dimensions associated with COVID-19.

Assisted Reproductive Technology and Disease Management in Infertile Women with Multiple Sclerosis

Multiple sclerosis (MS) predominantly affects women of fertile age. Various aspects of MS could impact on fertility, such as sexual dysfunction, endocrine alterations, autoimmune imbalances, and disease-modifying therapies (DMTs). The proportion of women with MS (wMS) requesting infertility management and assisted reproductive technology (ART) is increasing over time. In this review, we report on data regarding ART in wMS and address safety issues. We also discuss the clinical aspects to consider when planning a course of treatment for infertility, and provide updated recommendations to guide neurologists in the management of wMS undergoing ART, with the goal of reducing the risk of disease activation after this procedure. According to most studies, there is an increase in relapse rate and magnetic resonance imaging activity after ART. Therefore, to reduce the risk of relapse, ART should be considered in wMS with stable disease. In wMS, especially those with high disease activity, fertility issues should be discussed early as the choice of DMT, and fertility preservation strategies might be proposed in selected cases to ensure both disease control and a safe pregnancy. For patients with stable disease taking DMTs compatible with pregnancy, treatment should not be interrupted before ART. If the ongoing therapy is contraindicated in pregnancy, then it should be switched to a compatible therapy. Prior to beginning fertility treatments in wMS, it would be reasonable to assess vitamin D serum levels, thyroid function and its antibody serum levels; start folic acid supplementation; and ensure smoking and alcohol cessation, adequate sleep, and food hygiene. Cervico-vaginal swabs for Ureaplasma urealyticum, Mycoplasma hominis, and Chlamydia trachomatis, as well as serology for viral hepatitis, HIV, syphilis, and cytomegalovirus, should be performed. Steroids could be administered under specific indications. Although the available data do not clearly show a definite raised relapse risk associated with a specific ART protocol, it seems reasonably safe to prefer the use of gonadotropin-releasing hormone (GnRH) antagonists for ovarian stimulation. Close clinical and radiological monitoring is reasonably recommended, particularly after hormonal stimulation and in case of pregnancy failure.

Regulation of Bone by Mechanical Loading, Sex Hormones, and Nerves: Integration of Such Regulatory Complexity and Implications for Bone Loss during Space Flight and Post-Menopausal Osteoporosis

During evolution, the development of bone was critical for many species to thrive and function in the boundary conditions of Earth. Furthermore, bone also became a storehouse for calcium that could be mobilized for reproductive purposes in mammals and other species. The critical nature of bone for both function and reproductive needs during evolution in the context of the boundary conditions of Earth has led to complex regulatory mechanisms that require integration for optimization of this tissue across the lifespan. Three important regulatory variables include mechanical loading, sex hormones, and innervation/neuroregulation. The importance of mechanical loading has been the target of much research as bone appears to subscribe to the "use it or lose it" paradigm. Furthermore, because of the importance of post-menopausal osteoporosis in the risk for fractures and loss of function, this aspect of bone regulation has also focused research on sex differences in bone regulation. The advent of space flight and exposure to microgravity has also led to renewed interest in this unique environment, which could not have been anticipated by evolution, to expose new insights into bone regulation. Finally, a body of evidence has also emerged indicating that the neuroregulation of bone is also central to maintaining function. However, there is still more that is needed to understand regarding how such variables are integrated across the lifespan to maintain function, particularly in a species that walks upright. This review will attempt to discuss these regulatory elements for bone integrity and propose how further study is needed to delineate the details to better understand how to improve treatments for those at risk for loss of bone integrity, such as in the post-menopausal state or during prolonged space flight.

Neurosteroid enantiomers as potentially novel neurotherapeutics

Endogenous neurosteroids and synthetic neuroactive steroids (NAS) are important targets for therapeutic development in neuropsychiatric disorders. These steroids modulate major signaling systems in the brain and intracellular processes including inflammation, cellular stress and autophagy. In this review, we describe studies performed using unnatural enantiomers of key neurosteroids, which are physiochemically identical to their natural counterparts except for rotation of polarized light. These studies led to insights in how NAS interact with receptors, ion channels and intracellular sites of action. Certain effects of NAS show high enantioselectivity, consistent with actions in chiral environments and likely direct interactions with signaling proteins. Other effects show no enantioselectivity and even reverse enantioselectivity. The spectrum of effects of NAS enantiomers raises the possibility that these agents, once considered only as tools for preclinical studies, have therapeutic potential that complements and in some cases may exceed their natural counterparts. Here we review studies of NAS enantiomers from the perspective of their potential development as novel neurotherapeutics.

Sex differences in the effects of high fat diet on underlying neuropathology in a mouse model of VCID

BACKGROUND

Damage to the cerebral vasculature can lead to vascular contributions to cognitive impairment and dementia (VCID). A reduction in blood flow to the brain leads to neuropathology, including neuroinflammation and white matter lesions that are a hallmark of VCID. Mid-life metabolic disease (obesity, prediabetes, or diabetes) is a risk factor for VCID which may be sex-dependent (female bias).

METHODS

We compared the effects of mid-life metabolic disease between males and females in a chronic cerebral hypoperfusion mouse model of VCID. C57BL/6J mice were fed a control or high fat (HF) diet starting at ~ 8.5 months of age. Three months after diet initiation, sham or unilateral carotid artery occlusion surgery (VCID model) was performed. Three months later, mice underwent behavior testing and brains were collected to assess pathology.

RESULTS

We have previously shown that in this VCID model, HF diet causes greater metabolic impairment and a wider array of cognitive deficits in females compared to males. Here, we report on sex differences in the underlying neuropathology, specifically white matter changes and neuroinflammation in several areas of the brain. White matter was negatively impacted by VCID in males and HF diet in females, with greater metabolic impairment correlating with less myelin markers in females only. High fat diet led to an increase in microglia activation in males but not in females. Further, HF diet led to a decrease in proinflammatory cytokines and pro-resolving mediator mRNA expression in females but not males.

CONCLUSIONS

The current study adds to our understanding of sex differences in underlying neuropathology of VCID in the presence of a common risk factor (obesity/prediabetes). This information is crucial for the development of effective, sex-specific therapeutic interventions for VCID.

Rat Ovarian Function Is Impaired during Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is an autoimmune disease affecting the CNS and occurring far more prevalently in women than in men. In both MS and its animal models, sex hormones play important immunomodulatory roles. We have previously shown that experimental autoimmune encephalomyelitis (EAE) affects the hypothalamic-pituitary-gonadal axis in rats of both sexes and induces an arrest in the estrous cycle in females. To investigate the gonadal status in female rats with EAE, we explored ovarian morphometric parameters, circulating and intraovarian sex steroid levels, and the expression of steroidogenic machinery components in the ovarian tissue. A prolonged state of diestrus was recorded during the peak of EAE, with maintenance of the corpora lutea, elevated intraovarian progesterone levels, and increased gene and protein expression of StAR, similar to the state of pseudopregnancy. The decrease in CYP17A1 protein expression was followed by a decrease in ovarian testosterone and estradiol levels. On the contrary, serum testosterone levels were slightly increased. With unchanged serum estradiol levels, these results point at extra-gonadal sites of sex steroid biosynthesis and catabolism as important regulators of their circulating levels. Our study suggests alterations in the function of the female reproductive system during central autoimmunity and highlights the bidirectional relationships between hormonal status and EAE.

Molecular docking and molecular dynamics simulation study the mechanism of progesterone in the treatment of spinal cord injury

PURPOSE

Spinal cord injury can lead to incomplete or complete loss of voluntary movement and sensory function, leading to serious complications. Numerous studies have shown that progesterone exhibits strong therapeutic potential for spinal cord injury. However, the mechanism by which progesterone treats spinal cord injury remains unclear. Therefore, this article explores the mechanism of progesterone in the treatment of spinal cord injury by means of molecular docking and molecular dynamics simulation.

METHODS

We used bioinformatics to screen active pharmaceutical ingredients and potential targets, and molecular docking and molecular dynamics were used to validate and analysis by the supercomputer platform.

RESULTS

Progesterone had 3606 gene targets, spinal cord injury had 6560 gene targets, the intersection gene targets were 2355. GO and KEGG analysis showed that the abundant pathways involved multiple pathways related to cell metabolism and inflammation. Molecular docking showed that progesterone played a role in treating spinal cord injury by acting on BDNF, AR, NGF and TNF. Molecular dynamics was used to prove and analyzed the binding stability of active ingredients and protein targets, and AR/Progesterone combination has the strongest binding energy.

CONCLUSION

Progesterone promotes recovery from spinal cord injury by promoting axonal regeneration, remyelination, neuronal survival and reducing inflammation.

The effects of long-term testosterone treatment on endocrine parameters in hypogonadal men: 12-year data from a prospective controlled registry study

Testosterone therapy (TTh) is the primary treatment for aging men with functional hypogonadism. Whilst the benefits of testosterone (T) replacement are well-evidenced, the long-term data for TTh on metabolic and endocrine parameters is limited. Here we present the effect of TTh on endocrine parameters in hypogonadal men at a 12-year follow-up. In this single-centre, cumulative, prospective, registry study, 321 hypogonadal men (mean age: 58.9 years) received testosterone undecanoate injections in 12-week intervals for up to 12 years. Blood samples were taken at every other visit to measure levels of total T (TT), calculated free T, sex hormone-binding globulin (SHBG), estradiol, luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone and prolactin. We observed an increase in TT of 15.5 nmol/L (p < 0.0001), a reduction in SHBG of 10.5 nmol/L (p < 0.0001) and an increase in calculated free T of 383.04 pmol/L (p < 0.0001) over the study period. This was accompanied by an increase in estradiol levels by 14.9 pmol/L (p < 0.0001), and decreases in progesterone (0.2 ng/mL, p < 0.0001), LH (10.4 U/L, p < 0.0001) and FSH (8.4 U/L, p < 0.0001) were demonstrated at 12-years. The levels of prolactin remained unchanged. Long-term TTh altered hormonal parameters to predictably modify the endocrine system. These effects were sustained during the entire observation time of 12 years.

Pathophysiology and Therapeutic Approaches for Spinal Cord Injury

Spinal cord injury (SCI) is a disabling condition that disrupts motor, sensory, and autonomic functions. Despite extensive research in the last decades, SCI continues to be a global health priority affecting thousands of individuals every year. The lack of effective therapeutic strategies for patients with SCI reflects its complex pathophysiology that leads to the point of no return in its function repair and regeneration capacity. Recently, however, several studies started to uncover the intricate network of mechanisms involved in SCI leading to the development of new therapeutic approaches. In this work, we present a detailed description of the physiology and anatomy of the spinal cord and the pathophysiology of SCI. Additionally, we provide an overview of different molecular strategies that demonstrate promising potential in the modulation of the secondary injury events that promote neuroprotection or neuroregeneration. We also briefly discuss other emerging therapies, including cell-based therapies, biomaterials, and epidural electric stimulation. A successful therapy might target different pathologic events to control the progression of secondary damage of SCI and promote regeneration leading to functional recovery.

Nuclear hormone receptors in demyelinating diseases

Demyelination results from the pathological loss of myelin and is a hallmark of many neurodegenerative diseases. Despite the prevalence of demyelinating diseases, there are no disease modifying therapies that prevent the loss of myelin or promote remyelination. This review aims to summarize studies in the field that highlight the importance of nuclear hormone receptors in the promotion and maintenance of myelination and the relevance of nuclear hormone receptors as potential therapeutic targets for demyelinating diseases. These nuclear hormone receptors include the estrogen receptor, progesterone receptor, androgen receptor, vitamin D receptor, thyroid hormone receptor, peroxisome proliferator-activated receptor, liver X receptor, and retinoid X receptor. Pre-clinical studies in well-established animal models of demyelination have shown a prominent role of these nuclear hormone receptors in myelination through their promotion of oligodendrocyte maturation and development. The activation of the nuclear hormone receptors by their ligands also promotes the synthesis of myelin proteins and lipids in mouse models of demyelination. There are limited clinical studies that focus on how the activation of these nuclear hormone receptors could alleviate demyelination in patients with diseases such as multiple sclerosis (MS). However, the completed clinical trials have reported improved clinical outcome in MS patients treated with the ligands of some of these nuclear hormone receptors. Together, the positive results from both clinical and pre-clinical studies point to nuclear hormone receptors as promising therapeutic targets to counter demyelination.

EphA4 regulates white matter remyelination after ischemic stroke through Ephexin-1/RhoA/ROCK signaling pathway

Ischemic stroke, which accounts for nearly 80% of all strokes, leads to white matter injury and neurobehavioral dysfunction, but relevant therapies to inhibit demyelination or promote remyelination after white matter injury are still unavailable. In this study, the middle cerebral artery occlusion/reperfusion (MCAO/R) in vivo and oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro were used to establish the ischemic models. We found that Eph receptor A4 (EphA4) had no effect on the apoptosis of oligodendrocytes using TUNEL staining. In contrast, EphA4 promoted proliferation of oligodendrocyte precursor cells (OPCs), but reduced the numbers of mature oligodendrocytes and the levels of myelin-associated proteins (MAG, MOG, and MBP) in the process of remyelination in ischemic models in vivo and in vitro as determined using PDGFRα-EphA4-shRNA and LV-EphA4 treatments. Notably, conditional knockout of EphA4 in OPCs (EphA4^fl/fl  + AAV-PDGFRα-Cre) improved the levels of myelin-associated proteins and functional recovery following ischemic stroke. In addition, regulation of remyelination by EphA4 was mediated by the Ephexin-1/RhoA/ROCK signaling pathway. Therefore, EphA4 did not affect oligodendrocyte (OL) apoptosis but regulated white matter remyelination after ischemic stroke through the Ephexin-1/RhoA/ROCK signaling pathway. EphA4 may provide a novel and effective therapeutic target in clinical practice of ischemic stroke.

Tibolone restrains neuroinflammation in mouse experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an immune-mediated and degenerating disease in which myelin sheaths are damaged as a result of chronic progressive inflammation of the central nervous system. Tibolone [(7α,17α)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-in-3-one], a synthetic estrogenic compound with tissue-specific actions and used for menopausal hormone therapy, shows neuroprotective and antioxidant properties both in vivo and in vitro. In the present study, we analyzed whether tibolone plays a therapeutic role in experimental autoimmune encephalomyelitis (EAE) mice, a commonly used model of MS. Female C57BL/6 mice were induced with the myelin oligodendrocyte glycoprotein MOG_35-55 and received s.c. tibolone (0.08 mg kg^-1 ) injection every other day from the day of induction until death on the acute phase of the disease. Reactive gliosis, Toll like receptor 4 (TLR4), high mobility group box protein 1 (HMGB1), inflammasome parameters, activated Akt levels and myelin were assessed by a real-time polymerase chain reaction, immunohistochemistry, and western blot analysis. Our findings indicated that, in the EAE spinal cord, tibolone reversed the astrocytic and microglial reaction, and reduced the hyperexpression of TLR4 and HMGB1, as well as NLR family pyrin domain containing 3-caspase 1-interleukin-1β inflammasome activation. At the same time, tibolone attenuated the Akt/nuclear factor kappa B pathway and limited the white matter demyelination area. Estrogen receptor expression was unaltered with tibolone treatment. Clinically, tibolone improved neurological symptoms without uterine compromise. Overall, our data suggest that tibolone may serve as a promising agent for the attenuation of MS-related inflammation.

Association of Second-generation Antiandrogens With Depression Among Patients With Prostate Cancer

IMPORTANCE

Previous studies have shown a consistent association between hormone therapy (HT), such as androgen deprivation therapy, to treat prostate cancer and depression risk. However, the association between second-generation antiandrogens (AAs) and depression is unknown.

OBJECTIVE

To test the a priori hypothesis that second-generation AAs are associated with an increased risk of depression, including compared with traditional forms of HT.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study analyzed patients aged 66 years and older who were diagnosed with prostate cancer without a second cancer in 12 months from January 2011 to December 2015. Patients with continuous Medicare Parts A, B, and D coverage were included. Individuals who received any form of HT prior to prostate cancer diagnosis and those previously diagnosed with depression were excluded. Data were collected from the Surveillance, Epidemiology, and End Results-Medicare and Texas Cancer Registry-Medicare linked databases. Data were analyzed from February to May 2021.

EXPOSURES

The following treatment groups were compared: (1) no HT group, (2) traditional HT group (HT without second-generation AA exposure), and (3) second-generation AA group.

MAIN OUTCOMES AND MEASURES

Risk of depression in the second-generation AA group compared with the no HT and traditional HT groups, determined prior to data collection, stratified by diagnosis stage.

RESULTS

Of 210 804 patients diagnosed with prostate cancer during the study window, 30 069 men (11 484 [38%] aged 66-70 years; 22 594 [75%] White) who met inclusion criteria were identified. Overall, 17 710 (59%) received no HT, 11 311 (38%) received traditional HT only, and 1048 (3%) received a second-generation AA. Those receiving a second-generation AA were more likely to be older (aged ≥81 years: second-generation AA group, 246 [24%]; traditional HT group, 1997 [18%]; no HT group, 1173 [7%]) and present with advanced disease (eg, distant disease: second-generation AA group, 562 [24%]; traditional HT group, 876 [8%]; no HT group, 129 [0.7%]). Multivariable Cox proportional hazards analysis showed that the second-generation AA group had an increased risk of depression compared with the no HT group (hazard ratio [HR], 2.15; 95% CI, 1.79-2.59; P < .001) and the traditional HT group (HR, 2.26; 95% CI, 1.88-2.73; P < .001), including specifically among those with metastatic disease at diagnosis (HR, 2.40; 95% CI, 1.38-4.15; P = .002).

CONCLUSIONS AND RELEVANCE

In this cohort study, patients with prostate cancer who received a second-generation AA had a large and clinically significant increased risk of depression compared with patients who received traditional HT alone or no HT, including when limiting our analysis to individuals with metastatic disease at diagnosis.

Medroxyprogesterone acetate attenuates demyelination, modulating microglia activation, in a cuprizone neurotoxic demyelinating mouse model

Clinical data reported a reduction of Multiple sclerosis (MS) symptoms during pregnancy when progesterone levels are high. Medroxyprogesterone acetate (MPA) is a synthetic progestin contraceptive with unknown neuroprotective effects. This study investigated the effect of a contraceptive dose of MPA on microglia polarization and neuroinflammation in the neurotoxic cuprizone (CPZ)-induced demyelinating mouse model of MS. Mice received 1 mg of MPA weekly, achieving similar serum concentrations in human contraceptive users. Results revealed that MPA therapy significantly reduced the demyelination in the corpus callosum. In addition, MPA treatment induced a significant reduction in microglia M1-markers (iNOS, IL-1β and TNF-α) while M2-markers (Arg-1, IL-10 and TGF-β) were significantly increased. Moreover, MPA resulted in a significant decrease in the number of iNOS positive cells (M1), whereas TREM-2 positive cells (M2) significantly increased. Furthermore, MPA decreased the protein expression levels of NF-κB and NLRP3 inflammasome as well as mRNA expression levels of the downstream product IL-18. In summary, MPA reduces the level of demyelination and has an anti-inflammatory role in CNS demyelination by inducing M2 microglia polarization and suppressing the M1 phenotype through the inhibition of NF-κB and NLRP3 inflammasome. Our results suggest that MPA should be a suitable contraceptive pharmacological agent in demyelinating diseases.

Critical Role of Astrocyte NAD+ Glycohydrolase in Myelin Injury and Regeneration

Western-style diets cause disruptions in myelinating cells and astrocytes within the mouse CNS. Increased CD38 expression is present in the cuprizone and experimental autoimmune encephalomyelitis models of demyelination and CD38 is the main nicotinamide adenine dinucleotide (NAD⁺)-depleting enzyme in the CNS. Altered NAD⁺ metabolism is linked to both high fat consumption and multiple sclerosis (MS). Here, we identify increased CD38 expression in the male mouse spinal cord following chronic high fat consumption, after focal toxin [lysolecithin (LL)]-mediated demyelinating injury, and in reactive astrocytes within active MS lesions. We demonstrate that CD38 catalytically inactive mice are substantially protected from high fat-induced NAD⁺ depletion, oligodendrocyte loss, oxidative damage, and astrogliosis. A CD38 inhibitor, 78c, increased NAD⁺ and attenuated neuroinflammatory changes induced by saturated fat applied to astrocyte cultures. Conditioned media from saturated fat-exposed astrocytes applied to oligodendrocyte cultures impaired myelin protein production, suggesting astrocyte-driven indirect mechanisms of oligodendrogliopathy. In cerebellar organotypic slice cultures subject to LL-demyelination, saturated fat impaired signs of remyelination effects that were mitigated by concomitant 78c treatment. Significantly, oral 78c increased counts of oligodendrocytes and remyelinated axons after focal LL-induced spinal cord demyelination. Using a RiboTag approach, we identified a unique in vivo brain astrocyte translatome profile induced by 78c-mediated CD38 inhibition in mice, including decreased expression of proinflammatory astrocyte markers and increased growth factors. Our findings suggest that a high-fat diet impairs oligodendrocyte survival and differentiation through astrocyte-linked mechanisms mediated by the NAD⁺ase CD38 and highlights CD38 inhibitors as potential therapeutic candidates to improve myelin regeneration.SIGNIFICANCE STATEMENT Myelin disturbances and oligodendrocyte loss can leave axons vulnerable, leading to permanent neurologic deficits. The results of this study suggest that metabolic disturbances, triggered by consumption of a diet high in fat, promote oligodendrogliopathy and impair myelin regeneration through astrocyte-linked indirect nicotinamide adenine dinucleotide (NAD⁺)-dependent mechanisms. We demonstrate that restoring NAD⁺ levels via genetic inactivation of CD38 can overcome these effects. Moreover, we show that therapeutic inactivation of CD38 can enhance myelin regeneration. Together, these findings point to a new metabolic targeting strategy positioned to improve disease course in multiple sclerosis and other conditions in which the integrity of myelin is a key concern.

Neurosteroids: A novel promise for the treatment of stroke and post-stroke complications

Stroke is the primary reason for death and disability worldwide, with few treatment strategies to date. Neurosteroids, which are natural molecules in the brain, have aroused great interest in the field of stroke. Neurosteroids are a kind of steroid that acts on the nervous system, and are synthesized in the mitochondria of neurons or glial cells using cholesterol or other steroidal precursors. Neurosteroids mainly include estrogen, progesterone (PROG), allopregnanolone, dehydroepiandrosterone (DHEA), and vitamin D (VD). Most of the preclinical studies have confirmed that neurosteroids can decrease the risk of stroke, and improve stroke outcomes. In the meantime, neurosteroids have been shown to have a positive therapeutic significance in some post-stroke complications, such as epilepsy, depression, anxiety, cardiac complications, movement disorders, and post-stroke pain. In this review, we report the historical background, modulatory mechanisms of neurosteroids in stroke and post-stroke complications, and emphasize on the application prospect of neurosteroids in stroke therapy.

Secondary White Matter Injury and Therapeutic Targets After Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (SAH) is one of the special stroke subtypes with high mortality and mobility. Although the mortality of SAH has decreased by 50% over the past two decades due to advances in neurosurgery and management of neurocritical care, more than 70% of survivors suffer from varying degrees of neurological deficits and cognitive impairments, leaving a heavy burden on individuals, families, and the society. Recent studies have shown that white matter is vulnerable to SAH, and white matter injuries may be one of the causes of long-term neurological deficits caused by SAH. Attention has recently focused on the pivotal role of white matter injury in the pathophysiological processes after SAH, mainly related to mechanical damage caused by increased intracerebral pressure and the metabolic damage induced by blood degradation and hypoxia. In the present review, we sought to summarize the pathophysiology processes and mechanisms of white matter injury after SAH, with a view to providing new strategies for the prevention and treatment of long-term cognitive dysfunction after SAH.

Progesterone and Allopregnanolone Neuroprotective Effects in the Wobbler Mouse Model of Amyotrophic Lateral Sclerosis

Progesterone regulates a number of processes in neurons and glial cells not directly involved in reproduction or sex behavior. Several neuroprotective effects are better observed under pathological conditions, as shown in the Wobbler mouse model of amyotrophic laterals sclerosis (ALS). Wobbler mice are characterized by forelimb atrophy due to motoneuron degeneration in the spinal cord, and include microgliosis and astrogliosis. Here we summarized current evidence on progesterone reversal of Wobbler neuropathology. We demonstrated that progesterone decreased motoneuron vacuolization with preservation of mitochondrial respiratory complex I activity, decreased mitochondrial expression and activity of nitric oxide synthase, increased Mn-dependent superoxide dismutase, stimulated brain-derived neurotrophic factor, increased the cholinergic phenotype of motoneurons, and enhanced survival with a concomitant decrease of death-related pathways. Progesterone also showed differential effects on glial cells, including increased oligodendrocyte density and downregulation of astrogliosis and microgliosis. These changes associate with reduced anti-inflammatory markers. The enhanced neurochemical parameters were accompanied by longer survival and increased muscle strength in tests of motor behavior. Because progesterone is locally metabolized to allopregnanolone (ALLO) in nervous tissues, we also studied neuroprotection by this derivative. Treatment of Wobbler mice with ALLO decreased oxidative stress and glial pathology, increased motoneuron viability and clinical outcome in a progesterone-like manner, suggesting that ALLO could mediate some progesterone effects in the spinal cord. In conclusion, the beneficial effects observed in different parameters support the versatile properties of progesterone and ALLO in a mouse model of motoneuron degeneration. The studies foresee future therapeutic opportunities with neuroactive steroids for deadly diseases like ALS.

Progesterone Modulates Mitochondrial Functions in Human Glioblastoma Cells

A substantial literature supports the notion that cancer is a metabolic disease. Mitochondria are sexually dimorphic, and progesterone (P4) plays a key regulatory role in mitochondrial functions. We investigated the effect of P4 on mitochondrial functions in three human glioblastoma multiforme (GBM) cell lines. In dose-response and time-response studies, GBM cells were exposed to different concentrations of P4 followed by mitochondrial stress-testing with a Seahorse analyzer. Data were analyzed for oxygen consumption rate (OCR), extracellular acidification rate (ECAR), and spare respiratory capacity (SRC) to determine the effects of P4 exposure on mitochondrial respiration and rate of glycolysis. We also examined the effect of P4 on mitochondrial superoxide radical generation by confocal microscopy. As early as 1h post-P4 exposure, we found a substantial dose-dependent inhibitory effect of P4 on OCR, ECAR, and SRC in all GBM cell lines. P4 treatment altered the levels of basal respiration, maximum respiration, nonmitochondrial oxygen consumption, ATP production, and proton leak. P4 given at 80-μM concentration showed the maximum inhibitory effect compared to controls. Live imaging data showed an 11-22% increase in superoxide radical generation in all three GBM cell lines following 6h exposure to a high concentration of P4. Our data show that high-dose P4 exerts an inhibitory effect on both mitochondrial respiration and glycolysis in GBM cells. These effects would lead to decreased tumor size and rate of growth, representing a potential treatment to control the spread of GBM.

Uncovering sex differences of rodent microglia

There are inherent structural and functional differences in the central nervous systems (CNS) of females and males. It has been gradually established that these sex-specific differences are due to a spectrum of genetic, epigenetic, and hormonal factors which actively contribute to the differential incidences, disease courses, and even outcomes of CNS diseases between sexes. Microglia, as principle resident macrophages in the CNS, play a crucial role in both CNS physiology and pathology. However, sex differences of microglia have been relatively unexplored until recently. Emerging data has convincingly demonstrated the existence of sex-dependent structural and functional differences of rodent microglia, consequently changing our current understanding of these versatile cells. In this review, we attempt to comprehensively outline the current advances revealing microglial sex differences in rodent and their potential implications for specific CNS diseases with a stark sex difference. A detailed understanding of molecular processes underlying microglial sex differences is of major importance in design of translational sex- and microglia-specific therapeutic approaches.

Nuclear receptors and differentiation of oligodendrocyte precursor cells

Oligodendrocytes are the cells responsible for myelin formation during development and in adulthood, both for normal myelin turnover and myelin repair. These highly specialized cells derive from the oligodendrocyte precursor cells (OPCs), through a complex differentiation process involving genetic and epigenetic regulation mechanisms, which switch the phenotype from a migratory and replicative precursor to a mature post-mitotic cell. The process is regulated by a plethora of molecules, involving neurotransmitters, growth factors, hormones and other small molecules, and is mainly driven by nuclear receptors (NRs). NRs are transcription factors with heterogeneous ligand-dependent and independent actions which differ for the cell target, the responsive gene and the formation of NR homo- or heterodimers. This chapter highlights the role of NRs in regulating OPC differentiation, also in view of drug discovery strategies aimed at targeting pathological conditions which interfere with both developmental myelination and remyelination in adulthood.

Developmental expression of genes involved in progesterone synthesis, metabolism and action during the post-natal cerebellar myelination

Progesterone is involved in dendritogenesis, synaptogenesis and maturation of cerebellar Purkinge cells, major sites of steroid synthesis in the brain. To study a possible time-relationship between myelination, neurosteroidogenesis and steroid receptors during development of the postnatal mouse cerebellum, we determined at postnatal days 5 (P5),18 (P18) and 35 (P35) the expression of myelin basic protein (MBP), components of the steroidogenic pathway, levels of endogenous steroids and progesterone's classical and non-classical receptors. In parallel with myelin increased expression during development, P18 and P35 mice showed higher levels of cerebellar progesterone and its reduced derivatives, higher expression of steroidogenic acute regulatory protein (StAR) mRNA, cholesterol side chain cleavage enzyme (P450scc) and 5α-reductase mRNA vs. P5 mice. Other steroids such as corticosterone and its reduced derivatives and 3β-androstanodiol (ADIOL) showed a peak increase at P18 compared to P5. Progesterone membrane receptors and binding proteins (PGRMC1, mPRα, mPRβ, mPRγ, and Sigma1 receptors) mRNAs levels increased during development while that of classical progesterone receptors (PR) remained invariable. PRKO mice showed similar MBP levels than wild type. Thus, these data suggests that progesterone and its neuroactive metabolites may play a role in postnatal cerebellar myelination.

Hormonal Regulation of Oligodendrogenesis II: Implications for Myelin Repair

Alterations in myelin, the protective and insulating sheath surrounding axons, affect brain function, as is evident in demyelinating diseases where the loss of myelin leads to cognitive and motor dysfunction. Recent evidence suggests that changes in myelination, including both hyper- and hypo-myelination, may also play a role in numerous neurological and psychiatric diseases. Protecting myelin and promoting remyelination is thus crucial for a wide range of disorders. Oligodendrocytes (OLs) are the cells that generate myelin, and oligodendrogenesis, the creation of new OLs, continues throughout life and is necessary for myelin plasticity and remyelination. Understanding the regulation of oligodendrogenesis and myelin plasticity within disease contexts is, therefore, critical for the development of novel therapeutic targets. In our companion manuscript, we review literature demonstrating that multiple hormone classes are involved in the regulation of oligodendrogenesis under physiological conditions. The majority of hormones enhance oligodendrogenesis, increasing oligodendrocyte precursor cell differentiation and inducing maturation and myelin production in OLs. Thus, hormonal treatments present a promising route to promote remyelination. Here, we review the literature on hormonal regulation of oligodendrogenesis within the context of disorders. We focus on steroid hormones, including glucocorticoids and sex hormones, peptide hormones such as insulin-like growth factor 1, and thyroid hormones. For each hormone, we describe whether they aid in OL survival, differentiation, or remyelination, and we discuss their mechanisms of action, if known. Several of these hormones have yielded promising results in both animal models and in human conditions; however, a better understanding of hormonal effects, interactions, and their mechanisms will ultimately lead to more targeted therapeutics for myelin repair.

Hormonal Regulation of Oligodendrogenesis I: Effects across the Lifespan

The brain’s capacity to respond to changing environments via hormonal signaling is critical to fine-tuned function. An emerging body of literature highlights a role for myelin plasticity as a prominent type of experience-dependent plasticity in the adult brain. Myelin plasticity is driven by oligodendrocytes (OLs) and their precursor cells (OPCs). OPC differentiation regulates the trajectory of myelin production throughout development, and importantly, OPCs maintain the ability to proliferate and generate new OLs throughout adulthood. The process of oligodendrogenesis, the creation of new OLs, can be dramatically influenced during early development and in adulthood by internal and environmental conditions such as hormones. Here, we review the current literature describing hormonal regulation of oligodendrogenesis within physiological conditions, focusing on several classes of hormones: steroid, peptide, and thyroid hormones. We discuss hormonal regulation at each stage of oligodendrogenesis and describe mechanisms of action, where known. Overall, the majority of hormones enhance oligodendrogenesis, increasing OPC differentiation and inducing maturation and myelin production in OLs. The mechanisms underlying these processes vary for each hormone but may ultimately converge upon common signaling pathways, mediated by specific receptors expressed across the OL lineage. However, not all of the mechanisms have been fully elucidated, and here, we note the remaining gaps in the literature, including the complex interactions between hormonal systems and with the immune system. In the companion manuscript in this issue, we discuss the implications of hormonal regulation of oligodendrogenesis for neurological and psychiatric disorders characterized by white matter loss. Ultimately, a better understanding of the fundamental mechanisms of hormonal regulation of oligodendrogenesis across the entire lifespan, especially in vivo, will progress both basic and translational research.

Neuroprotective Effects of Testosterone in Male Wobbler Mouse, a Model of Amyotrophic Lateral Sclerosis

Patients suffering of amyotrophic lateral sclerosis (ALS) present motoneuron degeneration leading to muscle atrophy, dysphagia, and dysarthria. The Wobbler mouse, an animal model of ALS, shows a selective loss of motoneurons, astrocytosis, and microgliosis in the spinal cord. The incidence of ALS is greater in men; however, it increases in women after menopause, suggesting a role of sex steroids in ALS. Testosterone is a complex steroid that exerts its effects directly via androgen (AR) or Sigma-1 receptors and indirectly via estrogen receptors (ER) after aromatization into estradiol. Its reduced-metabolite 5α-dihydrotestosterone acts via AR. This study analyzed the effects of testosterone in male symptomatic Wobblers. Controls or Wobblers received empty or testosterone-filled silastic tubes for 2 months. The cervical spinal cord from testosterone-treated Wobblers showed (1) similar androgen levels to untreated control and (2) increased levels of testosterone, and its 5α-reduced metabolites, 5α- dihydrotestosterone, and 3β-androstanediol, but (3) undetectable levels of estradiol compared to untreated Wobblers. Testosterone-treated controls showed comparable steroid concentrations to its untreated counterpart. In testosterone- treated Wobblers a reduction of AR, ERα, and aromatase and high levels of Sigma-1 receptor mRNAs was demonstrated. Testosterone treatment increased ChAT immunoreactivity and the antiinflammatory mediator TGFβ, while it lessened vacuolated motoneurons, GFAP+ astrogliosis, the density of IBA1+ microgliosis, proinflammatory mediators, and oxidative/nitrosative stress. Clinically, testosterone treatment in Wobblers slowed the progression of paw atrophy and improved rotarod performance. Collectively, our findings indicate an antiinflammatory and protective effect of testosterone in the degenerating spinal cord. These results coincided with a high concentration of androgen-reduced derivatives after testosterone treatment suggesting that the steroid profile may have a beneficial role on disease progression.

The role of sex hormones in women with multiple sclerosis: From puberty to assisted reproductive techniques

BACKGROUND

Multiple Sclerosis is a multifactorial chronic autoimmune disease, affecting predominantly females in the fertile age. Sex hormones changes during a woman's life, from puberty to menopause, including pregnancy and puerperium, may influence the onset and course of Multiple Sclerosis. The effect of estrogen levels on immune, clinical and radiological aspects of Multiple Sclerosis, also stimulated investigation on the effect of sexual hormones therapies, such as oral contraceptives and assisted reproductive technique, on the Multiple Sclerosis course.

SEARCH STRATEGY AND SELECTION CRITERIA

A literature search for original articles and reviews was conducted in the databases, including PubMed, Scopus, and ClinicalTrials.gov of the U.S. National Library of Medicine site from 1988 to 2020.

RESULTS AND CONCLUSION

This review reports the effects of the physiological and iatrogenic hormonal changes either on immune or clinical or paraclinical features in the different life stages of women affected by Multiple Sclerosis.

Activin A improves the neurological outcome after ischemic stroke in mice by promoting oligodendroglial ACVR1B-mediated white matter remyelination

Activin A plays important roles in ischemic injury and white matter remyelination, but its mechanisms are unclear. In this study, the adult male C57BL/6 J mice were used to establish the model of 1 h middle cerebral artery occlusion/reperfusion (MCAO/R) 1 d to 28 d-induced ischemic stroke in vivo. We found that the neurological outcome was positively correlated with the levels of myelin associated proteins (include MAG, CNPase, MOG and MBP, n = 6 per group) both in corpus callosum and internal capsule of mice with ischemic stroke. The dynamic changes of Luxol fast blue (LFB) staining intensity, oligodendrocyte (CC1⁺) and proliferated oligodendrocyte precursor (Ki67⁺/PDGFRα⁺) cell numbers indicated demyelination and spontaneous remyelination occurred in the corpus callosum of mice after 1 h MCAO/R 1 d-28 d (n = 6 per group). Activin receptor type I (ACVR1) inhibitor SB431542 aggregated neurological deficits, and reduced MAG, MOG and MBP protein levels of mice with ischemic stroke (n = 6 per group). Meanwhile, recombinant mouse (rm) Activin A enhanced the neurological function recovery, MAG, MOG and MBP protein levels of mice with 1 h MCAO/R 28 d. In addition, the injection of AAV-based ACVR1B shRNA with Olig2 promoter could reverse rmActivin A-induced the increases of CC1⁺ cell number, LFB intensity, MAG, MOG and MBP protein levels in the corpus callosum (n = 6 per group), and neurological function recovery (n = 10 per group) of mice with 1 h MCAO/R 28 d. These results suggested that Activin A improves the neurological outcome through promoting oligodendroglial ACVR1B-mediated white matter remyelination of mice with ischemic stroke, which may provide a potential therapeutic strategy for ischemic stroke.

Low-Field Magnetic Stimulation Accelerates the Differentiation of Oligodendrocyte Precursor Cells via Non-canonical TGF-β Signaling Pathways

Demyelination and oligodendrocyte loss are characteristic changes in demyelinating disorders. Low-field magnetic stimulation (LFMS) is a novel transcranial neuromodulation technology that has shown promising therapeutic potential for a variety of neuropsychiatric conditions. The cellular and molecular mechanisms of magnetic stimulation remain unclear. Previous studies mainly focused on the effects of magnetic stimulation on neuronal cells. Here we aimed to examine the effects of a gamma frequency LFMS on the glial progenitor cells. We used rat central glia-4 (CG4) cell line as an in vitro model. CG4 is a bipotential glial progenitor cell line that can differentiate into either oligodendrocyte or type 2-astrocyte. The cells cultured in a defined differentiation media were exposed to a 40-Hz LFMS 20 min daily for five consecutive days. We found that LFMS transiently elevated the level of TGF-β1 in the culture media in the first 24 h after the treatment. In correlation with the TGF-β1 levels, the percentage of cells possessing complex branches and expressing the late oligodendrocyte progenitor marker O4 was increased, indicating the accelerated differentiation of CG4 cells towards oligodendrocyte in LFMS-treated cultures. LFMS increased phosphorylation of Akt and Erk1/2 proteins, but not SMAD2/3. TGF-β1 receptor I specific inhibitor LY 364947 partially suppressed the effects of LFMS on differentiation and on levels of pAkt and pErk1/2, indicating that LFMS enhances the differentiation of oligodendrocyte progenitor cells via activation of non-canonical TGF-β-Akt and TGF-β-Erk1/2 pathways but not the canonical SMAD pathway. The data from this study reveal a novel mechanism of magnetic stimulation as a potential therapy for demyelination disorders.