Progesterone protective effects in neurodegeneration and neuroinflammation

Investigating the Potential Therapeutic Mechanisms of Puerarin in Neurological Diseases

Plants and their derived phytochemicals have a long history of treating a wide range of illnesses for several decades. They are believed to be the origin of a diverse array of medicinal compounds. One of the compounds found in kudzu root is puerarin, a isoflavone glycoside commonly used as an alternative medicine to treat various diseases. From a biological perspective, puerarin can be described as a white needle crystal with the chemical name of 7-hydroxy-3-(4-hydroxyphenyl)-1-benzopyran-4-one-8-D-glucopyranoside. Besides, puerarin is sparingly soluble in water and produces no color or light yellow solution. Multiple experimental and clinical studies have confirmed the significant therapeutic effects of puerarin. These effects span a wide range of pharmacological effects, including neuroprotection, hepatoprotection, cardioprotection, immunomodulation, anticancer properties, anti-diabetic properties, anti-osteoporosis properties, and more. Puerarin achieves these effects by interacting with various cellular and molecular pathways, such as MAPK, AMPK, NF-κB, mTOR, β-catenin, and PKB/Akt, as well as different receptors, enzymes, and growth factors. The current review highlights the molecular mechanism of puerarin as a neuroprotective agent in the treatment of various neurodegenerative and neurological diseases. Extensive cellular, animal, and clinical research has provided valuable insights into its effectiveness in conditions such as Alzheimer's disease, Parkinson's disease, epilepsy, cerebral stroke, depression, and more.

Sex-associated microRNAs potentially implicated in sporadic Alzheimer's disease (sAD)

BACKGROUND

The onset and pathology of sporadic Alzheimer's disease (sAD) seem to be affected by both sex and genetic mechanisms. Evidence supports that the high prevalence of sAD in women, worldwide, may be attributed to an interplay among aging, sex, and lifestyle, influenced by genetics, metabolic changes, and hormones. Interestingly, epigenetic mechanisms such as microRNAs (miRNAs), known as master regulators of gene expression, may contribute to this observed sexual dimorphism in sAD.

OBJECTIVES

To investigate the potential impact of sex-associated miRNAs on processes manifesting sAD pathology, as described by the Tau-driven Adverse Outcome Pathway (AOP) leading to memory loss.

METHODS

Using publicly available human miRNA datasets, sex-biased miRNAs, defined as differentially expressed by sex in tissues possibly affected by sAD pathology, were collected. In addition, sex hormone-related miRNAs were also retrieved from the literature. The compiled sex-biased and sex hormone-related miRNAs were further plugged into the dysregulated processes of the Tau-driven AOP for memory loss.

RESULTS

Several miRNAs, previously identified as sex-associated, were implicated in dysregulated processes associated with the manifestation of sAD pathology. Importantly, the described pathology processes were not confined to a particular sex. A mechanistic-based approach utilizing miRNAs was adopted in order to elucidate the link between sex and biological processes potentially involved in the development of memory loss.

CONCLUSIONS

The identification of sex-associated miRNAs involved in the early processes manifesting memory loss may shed light to the complex molecular mechanisms underlying sAD pathogenesis in a sex-specific manner.

Progesterone improved the behavior of PC12 cells under OGD/R by reducing FABP5 expression and inhibiting TLR4/NF-κB signaling pathway

Herein, PC12 cells were applied to detect the impact of progesterone under oxygen glucose deprivation/reperfusion (OGD/R) stimulation. The cell proliferation of PC12 cells was evaluated by cell counting kit-8 assay, and the concentrations of MDA, ROS and SOD were examined by their corresponding Enzyme Linked Immunosorbent Assay kits. The invasion and migration properties of PC12 cells were evaluated by transwell and wound healing assays, respectively. The expression patterns of related genes were evaluated by western blot and qPCR. Under OGD/R stimulation, progesterone treatment could elevate the viability of PC12 cells, reduce the levels of MDA and ROS, and elevate the concentration of SOD. Moreover, progesterone treatment could strengthen the invasion and migration abilities of PC12 cells under OGD/R condition, as well as decrease the apoptosis and inflammation. FABP5 expression was significantly increased in PC12 cells under OGD/R stimulation, which was reversed after progesterone stimulation. Under OGD/R stimulation, the protective effects of progesterone on PC12 cells were strengthened after si-FABP5 treatment. The protein levels of TLR4, p-P65 NF-κB, and P65 NF-κB in OGD/R-induced PC12 cells were increased, which were inhibited after progesterone treatment. Progesterone exerted protective effects on PC12 cells by targeting FABP5 under OGD/R stimulation.

Biomaterials-based anti-inflammatory treatment strategies for Alzheimer's disease

The current therapeutic drugs for Alzheimer's disease only improve symptoms, they do not delay disease progression. Therefore, there is an urgent need for new effective drugs. The underlying pathogenic factors of Alzheimer's disease are not clear, but neuroinflammation can link various hypotheses of Alzheimer's disease; hence, targeting neuroinflammation may be a new hope for Alzheimer's disease treatment. Inhibiting inflammation can restore neuronal function, promote neuroregeneration, reduce the pathological burden of Alzheimer's disease, and improve or even reverse symptoms of Alzheimer's disease. This review focuses on the relationship between inflammation and various pathological hypotheses of Alzheimer's disease; reports the mechanisms and characteristics of small-molecule drugs (e.g., nonsteroidal anti-inflammatory drugs, neurosteroids, and plant extracts); macromolecule drugs (e.g., peptides, proteins, and gene therapeutics); and nanocarriers (e.g., lipid-based nanoparticles, polymeric nanoparticles, nanoemulsions, and inorganic nanoparticles) in the treatment of Alzheimer's disease. The review also makes recommendations for the prospective development of anti-inflammatory strategies based on nanocarriers for the treatment of Alzheimer's disease.

Pseudorabies virus inhibits progesterone-induced inactivation of TRPML1 to facilitate viral entry

Viral infection is a significant risk factor for fertility issues. Here, we demonstrated that infection by neurotropic alphaherpesviruses, such as pseudorabies virus (PRV), could impair female fertility by disrupting the hypothalamus-pituitary-ovary axis (HPOA), reducing progesterone (P4) levels, and consequently lowering pregnancy rates. Our study revealed that PRV exploited the transient receptor potential mucolipin 1 (TRPML1) and its lipid activator, phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), to facilitate viral entry through lysosomal cholesterol and Ca2+. P4 antagonized this process by inducing lysosomal storage disorders and promoting the proteasomal degradation of TRPML1 via murine double minute 2 (MDM2)-mediated polyubiquitination. Overall, the study identifies a novel mechanism by which PRV hijacks the lysosomal pathway to evade P4-mediated antiviral defense and impair female fertility. This mechanism may be common among alphaherpesviruses and could contribute significantly to their impact on female reproductive health, providing new insights for the development of antiviral therapies.

A Narrative Review on Axonal Neuroprotection in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) resulting in demyelination and neurodegeneration. The therapeutic strategy is now largely based on reducing inflammation with immunosuppressive drugs. Unfortunately, when disease progression is observed, no drug offers neuroprotection apart from its anti-inflammatory effect. In this review, we explore current knowledge on the assessment of neurodegeneration in MS and look at putative targets that might prove useful in protecting the axon from degeneration. Among them, Bruton's tyrosine kinase inhibitors, anti-apoptotic and antioxidant agents, sex hormones, statins, channel blockers, growth factors, and molecules preventing glutamate excitotoxicity have already been studied. Some of them have reached phase III clinical trials and carry a great message of hope for our patients with MS.

Amelioration of clinical course and demyelination in the cuprizone mouse model in relation to ketogenic diet

Ketogenic diet (KD) is defined as a high-fat, low-carbohydrate diet with appropriate amounts of protein, which has broad neuroprotective effects. However, the mechanisms of ameliorating the demyelination and of the neuroprotective effects of KD have not yet been completely elucidated. Therefore, the present study investigated the protection mechanism of KD treatment in the cuprizone (bis-cyclohexanone oxalydihydrazone, CPZ)-induced demyelination mice model, with special emphasis on neuroinflammation. After the KD treatment, an increased ketone body level in the blood of mice was detected, and a significant increase in the distance traveled within the central area was observed in the open field test, which reflected the increased exploration and decreased anxiety of mice that received CPZ. The results of Luxol fast blue and myelin basic protein (MBP) immunohistochemistry staining for the evaluation of the myelin content within the corpus callosum revealed a noticeable increase in the number of myelinated fibers and myelin score after KD administration in these animals. Concomitant, the protein expressions of glial fibrillary acidic protein (GFAP, an astrocyte marker), ionized calcium-binding adaptor molecule 1 (Iba-1, a microglial marker), CD68 (an activated microglia marker) and CD16/32 (a M1 microglial marker) were down-regulated, while the expression of oligodendrocyte lineage transcription factor 2 (OLIG2, an oligodendrocyte precursor cells marker) was up-regulated by the KD treatment. In addition, the KD treatment not only reduced the level of the C-X-C motif chemokine 10 (CXCL10), which is correlated to the recruitment of activated microglia, but also inhibited the production of proinflammatory cytokines, including interleukin 1β (IL-1β) and tumor necrosis factor-α (TNF-α), which are closely correlated to the M1 phenotype microglia. It is noteworthy, that the expression levels of histone deacetylase 3 (HADC3) and nod-like receptor pyrin domain containing 3 (NLRP3) significantly decreased after KD administration. In conclusion, these data demonstrate that KD decreased the reactive astrocytes and activated the microglia in the corpus callosum, and that KD inhibited the HADC3 and NLRP3 inflammasome signaling pathway in CPZ-treated mice. This suggests that the inhibition of the HADC3 and NLRP3 signaling pathway may be a novel mechanism by which KD exerts its protective actions for the treatment of demyelinating diseases.

Botanical Drug Puerarin Promotes Neuronal Survival and Neurite Outgrowth against MPTP/MPP+-Induced Toxicity via Progesterone Receptor Signaling

Background

Progesterone receptor (PR) modulates neuroprotective and regenerative responses in Parkinson's disease and related neurological diseases.

Objectives

The present study was designed to determine whether botanical drug puerarin could exhibit neuroprotective and neurorestorative activities via PR signaling.

Methods

The neuroprotective and neurotrophic activities of puerarin were investigated in MPTP-lesioned mice and MPP⁺-challenged primary rat midbrain neurons. Rotarod performance test and tail suspension test were used to assess motor functions. Tyrosine hydroxylase (TH) and PR were determined by immunostaining, Western blotting, and luciferase reporter assays. Neurite outgrowth was assessed by fluorescence staining and immunostaining.

Results

Puerarin effectively ameliorated the MPTP-induced motor abnormalities in MPTP-lesioned mice and protected primary rat midbrain neurons against MPP⁺-induced toxicity via PR signaling although progesterone exhibited the neuroprotection. PR antagonist mifepristone (RU486) diminished the neuroprotection of puerarin in MPTP-lesioned mice and MPP⁺-induced primary rat midbrain neurons. Moreover, puerarin promoted the differentiation of primary rat midbrain neurons and potentiated NGF to induce neuritogenesis in PC12 cells. RU486 and PR-siRNA could inhibit the effect of puerarin. Puerarin and progesterone could enhance the PR promoter.

Conclusion

Puerarin attenuated MPTP- and MPP⁺-induced toxicity and potentiated neurite outgrowth via PR. These results suggested that puerarin may become an alternative hormone for suppressing MPTP- and MPP⁺-induced toxicity in neurodegenerative diseases.

Mammary tumors suppress aging-induced neuroinflammation in female Balb/c mice

Neuroinflammation confers changes in brain function (i.e., behavior) that are hypothesized to be adaptive in the short-term, but detrimental (e.g., depression, anxiety) if they persist. Both peripheral tumor growth (outside of the brain) and natural aging independently cause neuroinflammation in rodents, which is corroborated by clinical studies. Mammary tumor effects on neuroinflammation and behavior, however, are typically studied in young rodents, whereas most breast cancer patients are middle-aged. Therefore, the existing literature likely underestimates the resulting neuroinflammation that may occur in clinical cancer populations. The present study tested the hypothesis that aging exacerbates mammary tumor-induced neuroinflammation in female mice. Aging (16 months and ovariectomized) increased body and spleen masses, whereas tumors grew faster and increased spleen mass in young mice (12 weeks) only. Tumors (IL-6, IL-10, TNFα, MCP-1, CXCL1, IP-10) and aging (IL-10, IFNγ) independently increased circulating inflammatory markers, although these variables were only significantly additive in one case (TNFα). In contrast to our prediction, the interaction between tumors and aging resulted in reduced mRNA and protein expression of select inflammatory markers in the hippocampus of tumor-bearing aged mice relative to aged controls. These results indicate that tumors reduce inflammatory activation in the brains of aged mice, a deficit that is likely disadvantageous. Further understanding of how aging and cancer interact to affect brain function is necessary to provide clinically-relevant results and identify mechanisms underlying persistent behavioral issues hampering adult cancer patients.

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Tumors grew more slowly in aged mice.

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Tumors and aging independently increased circulating inflammatory markers.

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Tumors reduced mRNA and protein expression of inflammatory markers in the hippocampus in aged mice.

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Reduced inflammatory activation in the brains of aged mice is likely not adaptive.

Progesterone receptor-mediated actions and the treatment of central nervous system disorders: An up-date of the known and the challenge of the unknown

Progesterone has been shown to exert a wide range of remarkable protective actions in experimental models of central nervous system injury or disease. However, the intimate mechanisms involved in each of these beneficial effects are not fully depicted. In this review, we intend to give the readers a thorough revision on what is known about the participation of diverse receptors and signaling pathways in progesterone-mediated neuroprotective, pro-myelinating and anti-inflammatory outcomes, as well as point out to novel regulatory mechanisms that could open new perspectives in steroid-based therapies.

A preliminary study of association between adolescent estradiol level and dorsolateral prefrontal cortex activity during emotion regulation

Non-human primate models have been useful in clarifying estradiol's role in cognitive processing. These animal studies indicate estradiol impacts cognitive processes supported by regions within dorsolateral prefrontal cortex (DLPFC). Although human functional neuroimaging studies have begun to find similar relationships between estradiol in women for some forms of 'cold' cognitive control, to date no studies have examined the relationship between estradiol and DLPFC function in the context of active attempts to regulate one's emotions. Here, we asked whether peripheral 17-beta estradiol levels in adolescent girls in different pubertal developmental stages (age = 14.9 years ± 1.74) were related to engagement of DLPFC regions during the use of a cognitive strategy for regulating emotion known as reappraisal using functional Magnetic Resonance Imaging. Findings indicated that higher estradiol levels predicted greater DLPFC activity during the down-regulation of negative emotion using reappraisal. This is the first report of an association between estradiol level and DLPFC activity during cognitive reappraisal of negative emotion. The study suggests a possibility that estradiol might positively contribute to regulatory function of a cortical system important for emotional experiences.

Tissue-specific progesterone receptor-chromatin binding and the regulation of progesterone-dependent gene expression

Progesterone receptor (PGR) co-ordinately regulates ovulation, fertilisation and embryo implantation through tissue-specific actions, but the mechanisms for divergent PGR action are poorly understood. Here we characterised PGR activity in mouse granulosa cells using combined ChIP-seq for PGR and H3K27ac and gene expression microarray. Comparison of granulosa, uterus and oviduct PGR-dependent genes showed almost complete tissue specificity in PGR target gene profiles. In granulosa cells 82% of identified PGR-regulated genes bound PGR within 3 kb of the gene and PGR binding sites were highly enriched in proximal promoter regions in close proximity to H3K27ac-modified active chromatin. Motif analysis showed highly enriched PGR binding to the PGR response element (GnACAnnnTGTnC), but PGR also interacted significantly with other transcription factor binding motifs. In uterus PGR showed far more tendency to bind intergenic chromatin regions and low evidence of interaction with other transcription factors. This is the first genome-wide description of PGR action in granulosa cells and systematic comparison of diverse PGR action in different reproductive tissues. It clarifies finely-tuned contextual PGR-chromatin interactions with implications for more targeted reproductive medicine.

Hormone replacement therapy attenuates hearing loss: Mechanisms involving estrogen and the IGF-1 pathway

Estradiol (E) is a multitasking hormone that plays a prominent role in the reproductive system, and also contributes to physiological and growth mechanisms throughout the body. Frisina and colleagues have previously demonstrated the beneficial effects of this hormone, with E‐treated subjects maintaining low auditory brainstem response (ABR) thresholds relative to control subjects (Proceedings of the National Academy of Sciences of the United States of America, 2006;103:14246; Hearing Research, 2009;252:29). In the present study, we evaluated the functionality of the peripheral and central auditory systems in female CBA/CaJ middle‐aged mice during and after long‐term hormone replacement therapy (HRT) via electrophysiological and molecular techniques. Surprisingly, there are very few investigations about the side effects of HRT in the auditory system after it has been discontinued. Our results show that the long‐term effects of HRT are permanent on ABR thresholds and ABR gap‐in‐noise (GIN) amplitude levels. E‐treated animals had lower thresholds and higher amplitude values compared to other hormone treatment subject groups. Interestingly, progesterone (P)‐treated animals had ABR thresholds that increased but amplitude levels that remained relatively the same throughout treatment. These results were consistent with qPCR experiments that displayed high levels of IGF‐1R in the stria vascularis (SV) of both E and P animal groups compared to combination treatment (E + P) animals. IGF‐1R plays a vital role in mediating anti‐apoptotic responses via the PI3K/AKT pathway. Overall, our findings gain insights into the neuro‐protective properties of E hormone treatments as well as expand the scientific knowledge base to help women decide whether HRT is the right choice for them.

Differential effects of completed and incomplete pregnancies on the risk of Alzheimer disease

OBJECTIVE

To investigate the effects of completed pregnancy with childbirth and incomplete pregnancy without childbirth on the late-life cognition and the risk of Alzheimer disease (AD) in women.

METHODS

Using the pooled data of 3,549 women provided by 2 population-based cohort studies, we conducted logistic regression analyses to examine retrospectively the associations of completed and incomplete pregnancy with the risks of mild cognitive impairment and AD. For women without dementia, we also conducted analyses of covariance to examine the associations of completed and incomplete pregnancy with Mini-Mental State Examination (MMSE) score.

RESULTS

Grand multiparous women who experienced ≥5 completed pregnancies showed an ≈1.7-fold higher risk of AD than those who experienced 1 to 4 completed pregnancies (odds ratio [OR] 1.68, 95% confidence interval [CI] 1.04-2.72), while those who had incomplete pregnancies showed half the level of AD risk compared with those who never experienced an incomplete pregnancy (OR 0.43, 95% CI 0.24-0.76 for 1 incomplete pregnancy; OR 0.56, 95% CI 0.34-0.92 for ≥2 incomplete pregnancies). In women without dementia, the grand multiparous had worse MMSE scores than those with 1 to 4 completed pregnancies (p < 0.001), while those who experienced ≥1 incomplete pregnancies had better MMSE scores than those who never experienced an incomplete pregnancy (p = 0.008).

CONCLUSIONS

Grand multiparity was associated with high risk of AD, while incomplete pregnancy was associated with low risk of AD in late life.

Brain inflammasomes in stroke and depressive disorders: Regulation by oestrogen

Neuroinflammation is a devastating pathophysiological process that results in brain damage and neuronal death. Pathogens, cell fragments and cellular dysfunction trigger inflammatory responses. Irrespective of the cause, inflammasomes are key intracellular multiprotein signalling platforms that sense neuropathological conditions. The activation of inflammasomes leads to the auto-proteolytic cleavage of caspase-1, resulting in the proteolysis of the pro-inflammatory cytokines interleukin (IL)1β and IL18 into their bioactive forms. It also initiates pyroptosis, a type of cell death. The two cytokines contribute to the pathogenesis in acute and chronic brain diseases and also play a central role in human aging and psychiatric disorders. Sex steroids, in particular oestrogens, are well-described neuroprotective agents in the central nervous system. Oestrogens improve the functional outcome after ischaemia and traumatic brain injury, reduce neuronal death in Parkinson's and Alzheimer's disease, as well as in amyotrophic lateral sclerosis, attenuate glutamate excitotoxicity and the formation of radical oxygen species, and lessen the spread of oedema after damage. Moreover, oestrogens alleviate menopause-related depressive symptoms and have a positive influence on depressive disorders probably by influencing growth factor production and serotonergic brain circuits. Recent evidence also suggests that inflammasome signalling affects anxiety- and depressive-like behaviour and that oestrogen ameliorates depression-like behaviour through the suppression of inflammasomes. In the present review, we highlight the most recent findings demonstrating that oestrogens selectively suppress the activation of the neuroinflammatory cascade in the brain in acute and chronic brain disease models. Furthermore, we aim to describe putative regulatory signalling pathways involved in the control of inflammasomes. Finally, we consider that psychiatric disorders such as depression also contain an inflammatory component that could be modulated by oestrogen.

Role of Estrogen and Other Sex Hormones in Brain Aging. Neuroprotection and DNA Repair

Aging is an inevitable biological process characterized by a progressive decline in physiological function and increased susceptibility to disease. The detrimental effects of aging are observed in all tissues, the brain being the most important one due to its main role in the homeostasis of the organism. As our knowledge about the underlying mechanisms of brain aging increases, potential approaches to preserve brain function rise significantly. Accumulating evidence suggests that loss of genomic maintenance may contribute to aging, especially in the central nervous system (CNS) owing to its low DNA repair capacity. Sex hormones, particularly estrogens, possess potent antioxidant properties and play important roles in maintaining normal reproductive and non-reproductive functions. They exert neuroprotective actions and their loss during aging and natural or surgical menopause is associated with mitochondrial dysfunction, neuroinflammation, synaptic decline, cognitive impairment and increased risk of age-related disorders. Moreover, loss of sex hormones has been suggested to promote an accelerated aging phenotype eventually leading to the development of brain hypometabolism, a feature often observed in menopausal women and prodromal Alzheimer's disease (AD). Although data on the relation between sex hormones and DNA repair mechanisms in the brain is still limited, various investigations have linked sex hormone levels with different DNA repair enzymes. Here, we review estrogen anti-aging and neuroprotective mechanisms, which are currently an area of intense study, together with the effect they may have on the DNA repair capacity in the brain.

Progesterone treatment shows greater protection in brain vs. retina in a rat model of middle cerebral artery occlusion: Progesterone receptor levels may play an important role

BACKGROUND/OBJECTIVE

To determine whether inflammation increases in retina as it does in brain following middle cerebral artery occlusion (MCAO), and whether the neurosteroid progesterone, shown to have protective effects in both retina and brain after MCAO, reduces inflammation in retina as well as brain.

METHODS

MCAO rats treated systemically with progesterone or vehicle were compared with shams. Protein levels of cytosolic NF-κB, nuclear NF-κB, phosphorylated NF-κB, IL-6, TNF-α, CD11b, progesterone receptor A and B, and pregnane X receptor were assessed in retinas and brains at 24 and 48 h using western blots.

RESULTS

Following MCAO, significant increases were observed in the following inflammatory markers: pNF-κB and CD11b at 24 h in both brain and retina, nuclear NF-κB at 24 h in brain and 48 h in retina, and TNF-α at 24 h in brain.Progesterone treatment in MCAO animals significantly attenuated levels of the following markers in brain: pNF-κB, nuclear NF-κB, IL-6, TNF-α, and CD11b, with significantly increased levels of cytosolic NF-κB. Retinas from progesterone-treated animals showed significantly reduced levels of nuclear NF-κB and IL-6 and increased levels of cytosolic NF-κB, with a trend for reduction in other markers. Post-MCAO, progesterone receptors A and B were upregulated in brain and downregulated in retina.

CONCLUSION

Inflammatory markers increased in both brain and retina after MCAO, with greater increases observed in brain. Progesterone treatment reduced inflammation, with more dramatic reductions observed in brain than retina. This differential effect may be due to differences in the response of progesterone receptors in brain and retina after injury.

Role of Estrogen and Other Sex Hormones in Brain Aging. Neuroprotection and DNA Repair

Aging is an inevitable biological process characterized by a progressive decline in physiological function and increased susceptibility to disease. The detrimental effects of aging are observed in all tissues, the brain being the most important one due to its main role in the homeostasis of the organism. As our knowledge about the underlying mechanisms of brain aging increases, potential approaches to preserve brain function rise significantly. Accumulating evidence suggests that loss of genomic maintenance may contribute to aging, especially in the central nervous system (CNS) owing to its low DNA repair capacity. Sex hormones, particularly estrogens, possess potent antioxidant properties and play important roles in maintaining normal reproductive and non-reproductive functions. They exert neuroprotective actions and their loss during aging and natural or surgical menopause is associated with mitochondrial dysfunction, neuroinflammation, synaptic decline, cognitive impairment and increased risk of age-related disorders. Moreover, loss of sex hormones has been suggested to promote an accelerated aging phenotype eventually leading to the development of brain hypometabolism, a feature often observed in menopausal women and prodromal Alzheimer's disease (AD). Although data on the relation between sex hormones and DNA repair mechanisms in the brain is still limited, various investigations have linked sex hormone levels with different DNA repair enzymes. Here, we review estrogen anti-aging and neuroprotective mechanisms, which are currently an area of intense study, together with the effect they may have on the DNA repair capacity in the brain.

Roles of sigma-1 receptors on mitochondrial functions relevant to neurodegenerative diseases

The sigma-1 receptor (Sig-1R) is a chaperone that resides mainly at the mitochondrion-associated endoplasmic reticulum (ER) membrane (called the MAMs) and acts as a dynamic pluripotent modulator in living systems. At the MAM, the Sig-1R is known to play a role in regulating the Ca2+ signaling between ER and mitochondria and in maintaining the structural integrity of the MAM. The MAM serves as bridges between ER and mitochondria regulating multiple functions such as Ca2+ transfer, energy exchange, lipid synthesis and transports, and protein folding that are pivotal to cell survival and defense. Recently, emerging evidences indicate that the MAM is critical in maintaining neuronal homeostasis. Thus, given the specific localization of the Sig-1R at the MAM, we highlight and propose that the direct or indirect regulations of the Sig-1R on mitochondrial functions may relate to neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS). In addition, the promising use of Sig-1R ligands to rescue mitochondrial dysfunction-induced neurodegeneration is addressed.

Progesterone therapy induces an M1 to M2 switch in microglia phenotype and suppresses NLRP3 inflammasome in a cuprizone-induced demyelination mouse model

Demyelination of the central nervous system (CNS) has been associated to reactive microglia in neurodegenerative disorders, such as multiple sclerosis (MS). The M1 microglia phenotype plays a pro-inflammatory role while M2 is involved in anti-inflammatory processes in the brain. In this study, CPZ-induced demyelination mouse model was used to investigate the effect of progesterone (PRO) therapy on microglia activation and neuro-inflammation. Results showed that progesterone therapy (CPZ+PRO) decreased neurological behavioral deficits, as demonstrated by significantly decreased escape latencies, in comparison to CPZ mice. In addition, CPZ+PRO caused a significant reduction in the mRNA expression levels of M1-markers (iNOS, CD86, MHC-II and TNF-α) in the corpus callosum region, whereas the expression of M2-markers (Trem-2, CD206, Arg-1 and TGF-β) was significantly increased, in comparison to CPZ mice. Moreover, CPZ+PRO resulted in a significant decrease in the number of iNOS⁺ and Iba-1⁺/iNOS⁺ cells (M1), whereas TREM-2⁺ and Iba-1⁺/TREM-2⁺ cells (M2) significantly increased, in comparison to CPZ group. Furthermore, CPZ+PRO caused a significant decrease in mRNA and protein expression levels of NLRP3 and IL-18 (~2-fold), in comparison to the CPZ group. Finally, CPZ+PRO therapy was accompanied with reduced levels of demyelination, compared to CPZ, as confirmed by immunofluorescence to myelin basic protein (MBP) and Luxol Fast Blue (LFB) staining, as well as transmission electron microscopy (TEM) analysis. In summary, we reported for the first time that PRO therapy causes polarization of M2 microglia, attenuation of M1 phenotype, and suppression of NLRP3 inflammasome in a CPZ-induced demyelination model of MS.

Non-Neuronal Cells in the Hypothalamic Adaptation to Metabolic Signals

Although the brain is composed of numerous cell types, neurons have received the vast majority of attention in the attempt to understand how this organ functions. Neurons are indeed fundamental but, in order for them to function correctly, they rely on the surrounding "non-neuronal" cells. These different cell types, which include glia, epithelial cells, pericytes, and endothelia, supply essential substances to neurons, in addition to protecting them from dangerous substances and situations. Moreover, it is now clear that non-neuronal cells can also actively participate in determining neuronal signaling outcomes. Due to the increasing problem of obesity in industrialized countries, investigation of the central control of energy balance has greatly increased in attempts to identify new therapeutic targets. This has led to interesting advances in our understanding of how appetite and systemic metabolism are modulated by non-neuronal cells. For example, not only are nutrients and hormones transported into the brain by non-neuronal cells, but these cells can also metabolize these metabolic factors, thus modifying the signals reaching the neurons. The hypothalamus is the main integrating center of incoming metabolic and hormonal signals and interprets this information in order to control appetite and systemic metabolism. Hence, the factors transported and released from surrounding non-neuronal cells will undoubtedly influence metabolic homeostasis. This review focuses on what is known to date regarding the involvement of different cell types in the transport and metabolism of nutrients and hormones in the hypothalamus. The possible involvement of non-neuronal cells, in particular glial cells, in physiopathological outcomes of poor dietary habits and excess weight gain are also discussed.

Short-term effects of diabetes on neurosteroidogenesis in the rat hippocampus

Diabetes may induce neurophysiological and structural changes in the central nervous system (i.e., diabetic encephalopathy). We here explored whether the levels of neuroactive steroids (i.e., neuroprotective agents) in the hippocampus may be altered by short-term diabetes (i.e., one month). To this aim, by liquid chromatography-tandem mass spectrometry we observed that in the experimental model of the rat raised diabetic by streptozotocin injection, one month of pathology induced changes in the levels of several neuroactive steroids, such as pregnenolone, progesterone and its metabolites (i.e., tetrahydroprogesterone and isopregnanolone) and testosterone and its metabolites (i.e., dihydrotestosterone and 3α-diol). Interestingly these brain changes were not fully reflected by the plasma level changes, suggesting that early phase of diabetes directly affects steroidogenesis and/or steroid metabolism in the hippocampus. These concepts are also supported by the findings that crucial steps of steroidogenic machinery, such as the gene expression of steroidogenic acute regulatory protein (i.e., molecule involved in the translocation of cholesterol into mitochondria) and cytochrome P450 side chain cleavage (i.e., enzyme converting cholesterol into pregnenolone) and 5α-reductase (enzyme converting progesterone and testosterone into their metabolites) are also affected in the hippocampus. In addition, cholesterol homeostasis as well as the functionality of mitochondria, a key organelle in which the limiting step of neuroactive steroid synthesis takes place, are also affected. Data obtained indicate that short-term diabetes alters hippocampal steroidogenic machinery and that these changes are associated with impaired cholesterol homeostasis and mitochondrial dysfunction in the hippocampus, suggesting them as relevant factors for the development of diabetic encephalopathy.

Progesterone treatment modulates mRNA OF neurosteroidogenic enzymes in a murine model of multiple sclerosis

Previous studies of experimental autoimmune encephalomyelitis (EAE) have shown that progesterone decreases inflammatory cell infiltration and proinflammatory factors, increases myelination and attenuates clinical grade of EAE mice. To elucidate potential mediators of these effects, we analyzed the mRNA expression of neurosteroidogenic enzymes in the spinal cord, in view of the protective role of steroids in EAE. We also analyzed mitochondrial morphology and dynamics (fusion and fission proteins), considering the role of mitochondria in neurosteroidogenesis. EAE was induced in C57Bl6 mice using MOG_40-54 and killed on day 16 after induction. Using qPCR, we found in steroid-untreated EAE mice decreased mRNAs for the steroidogenic acute regulatory protein (Star), voltage-dependent anion channel (VDAC), P450scc (cholesterol side-chain cleavage), 5α-reductase, 3α-hydroxysteroid dehydrogenase (3α-HSD) and aromatase, whereas levels of 3β-hydroxysteroid dehydrogenase (3β-HSD) showed a large intra-group variance. We also found increased mRNA expression of 18Kd translocator protein (TSPO), which likely resulted from the reactive microgliosis in this model. EAE mice also showed pathological mitochondrial morphology and reduced expression of fission and fusion protein mRNAs. Most importantly, pretreatment with progesterone a week before EAE induction increased Star,VDAC, P450scc, 5α-reductase type I, 3α-HSD and aromatase mRNAs and did not modify 3β-HSD. TSPO mRNA was decreased, consequent with the inhibition of microgliosis. Mitochondrial morphology was improved and fission/fusion protein mRNAs were enhanced by progesterone treatment. Furthermore, progesterone protective effects on mitochondrial and endoplasmic reticulum may allow the recovery of neurosteroidogenesis. In this way, endogenously synthesized neurosteroids may reinforce the beneficial effects of exogenous progesterone previously shown in MS mice.

Progesterone for acute traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of death and disability, and the identification of effective, inexpensive and widely practicable treatments for brain injury is of great public health importance worldwide. Progesterone is a naturally produced hormone that has well-defined pharmacokinetics, is widely available, inexpensive, and has steroidal, neuroactive and neurosteroidal actions in the central nervous system. It is, therefore, a potential candidate for treating TBI patients. However, uncertainty exists regarding the efficacy of this treatment. This is an update of our previous review of the same title, published in 2012.

OBJECTIVES

To assess the effects of progesterone on neurologic outcome, mortality and disability in patients with acute TBI. To assess the safety of progesterone in patients with acute TBI.

SEARCH METHODS

We updated our searches of the following databases: the Cochrane Injuries Group's Specialised Register (30 September 2016), the Cochrane Central Register of Controlled Trials (CENTRAL; Issue 9, 2016), MEDLINE (Ovid; 1950 to 30 September 2016), Embase (Ovid; 1980 to 30 September 2016), Web of Science Core Collection: Conference Proceedings Citation Index-Science (CPCI-S; 1990 to 30 September 2016); and trials registries: Clinicaltrials.gov (30 September 2016) and the World Health Organization (WHO) International Clinical Trials Registry Platform (30 September 2016).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of progesterone versus no progesterone (or placebo) for the treatment of people with acute TBI.

DATA COLLECTION AND ANALYSIS

Two review authors screened search results independently to identify potentially relevant studies for inclusion. Independently, two review authors selected trials that met the inclusion criteria from the results of the screened searches, with no disagreement.

MAIN RESULTS

We included five RCTs in the review, with a total of 2392 participants. We assessed one trial to be at low risk of bias; two at unclear risk of bias (in one multicentred trial the possibility of centre effects was unclear, whilst the other trial was stopped early), and two at high risk of bias, due to issues with blinding and selective reporting of outcome data.All included studies reported the effects of progesterone on mortality and disability. Low quality evidence revealed no evidence of a difference in overall mortality between the progesterone group and placebo group (RR 0.91, 95% CI 0.65 to 1.28, I² = 62%; 5 studies, 2392 participants, 2376 pooled for analysis). Using the GRADE criteria, we assessed the quality of the evidence as low, due to the substantial inconsistency across studies.There was also no evidence of a difference in disability (unfavourable outcomes as assessed by the Glasgow Outcome Score) between the progesterone group and placebo group (RR 0.98, 95% CI 0.89 to 1.06, I² = 37%; 4 studies; 2336 participants, 2260 pooled for analysis). We assessed the quality of this evidence to be moderate, due to inconsistency across studies.Data were not available for meta-analysis for the outcomes of mean intracranial pressure, blood pressure, body temperature or adverse events. However, data from three studies showed no difference in mean intracranial pressure between the groups. Data from another study showed no evidence of a difference in blood pressure or body temperature between the progesterone and placebo groups, although there was evidence that intravenous progesterone infusion increased the frequency of phlebitis (882 participants). There was no evidence of a difference in the rate of other adverse events between progesterone treatment and placebo in the other three studies that reported on adverse events.

AUTHORS' CONCLUSIONS

This updated review did not find evidence that progesterone could reduce mortality or disability in patients with TBI. However, concerns regarding inconsistency (heterogeneity among participants and the intervention used) across included studies reduce our confidence in these results.There is no evidence from the available data that progesterone therapy results in more adverse events than placebo, aside from evidence from a single study of an increase in phlebitis (in the case of intravascular progesterone).There were not enough data on the effects of progesterone therapy for our other outcomes of interest (intracranial pressure, blood pressure, body temperature) for us to be able to draw firm conclusions.Future trials would benefit from a more precise classification of TBI and attempts to optimise progesterone dosage and scheduling.

The Serum Changes of Neuron-Specific Enolase and Intercellular Adhesion Molecule-1 in Patients With Diffuse Axonal Injury Following Progesterone Administration: A Randomized Clinical Trial

Background

Improvement of neurologic outcome in progesterone-administered patients with diffuse axonal injury (DAI) has been found in a recent study. Also, there has been interest in the importance of serum parameters as predictors of outcome in traumatic brain injury.

Objectives

The aim of this study was to examine the effect of progesterone administration on serum levels of neuron-specific enolase (NSE), and intercellular adhesion molecule-1 (ICAM-1) in clinical DAI.

Patients and Methods

In this study, the serum levels of ICAM-1 and NSE of 32 male DAI patients (18 - 60 years of age, a Glasgow coma scale of 12 or less, and admitted within 4 hours after injury) who were randomized for a controlled phase II trial of progesterone were analyzed. The analysis was performed between the control and progesterone groups at admission time, and 24 hours and six days after DAI, respectively.

Results

A reduction in the serum level of ICAM-1 was noticed in the progesterone group 24 hours after the injury (P < 0.05). There was no significant difference in the serum level of NSE between the study groups during evaluation. At 24 hours after the injury, the level of ICAM-1 in the control group was higher than that at admission time (P < 0.05). The lowest level of NSE in the two groups was seen six days after DAI (P < 0.01).

Conclusions

In summary, progesterone administration reduced serum ICAM-1, and whereby may attenuate blood brain barrier disruption, the latter needs further investigation for confirmation.

Feasibility of progesterone treatment for ischaemic stroke

Two multi-centre phase III clinical trials examining the protective potential of progesterone following traumatic brain injury have recently failed to demonstrate any improvement in outcome. Thus, it is timely to consider how this impacts on the translational potential of progesterone treatment for ischaemic stroke. A wealth of experimental evidence supports the neuroprotective properties of progesterone, and associated metabolites, following various types of central nervous system injury. In particular, for ischaemic stroke, studies have also begun to reveal possible mechanisms of such neuroprotection. However, the results in traumatic brain injury now question whether further clinical development of progesterone for ischaemic stroke is relevant.

Sex-Specific Effects of Progesterone on Early Outcome of Intracerebral Hemorrhage

BACKGROUND

Preclinical evidence suggests that progesterone improves recovery after intracerebral hemorrhage (ICH); however, gonadal hormones have sex-specific effects. Therefore, an experimental model of ICH was used to assess recovery after progesterone administration in male and female rats.

METHODS

ICH was induced in male and female Wistar rats via stereotactic intrastriatal injection of clostridial collagenase (0.5 U). Animals were randomized to receive vehicle or 8 mg/kg progesterone intraperitoneally at 2 h, then subcutaneously at 5, 24, 48, and 72 h after injury. Outcomes included relevant physiology during the first 3 h, hemorrhage and edema evolution over the first 24 h, proinflammatory transcription factor and cytokine regulation at 24 h, rotarod latency and neuroseverity score over the first 7 days, and microglial activation/macrophage recruitment at 7 days after injury.

RESULTS

Rotarod latency (p = 0.001) and neuroseverity score (p = 0.01) were improved in progesterone-treated males, but worsened in progesterone-treated females (p = 0.028 and p = 0.008, respectively). Progesterone decreased cerebral edema (p = 0.04), microglial activation/macrophage recruitment (p < 0.001), and proinflammatory transcription factor phosphorylated nuclear factor-x03BA;B p65 expression (p = 0.0038) in males but not females, independent of tumor necrosis factor-α, interleukin-6, and toll-like receptor-4 expression. Cerebral perfusion was increased in progesterone-treated males at 4 h (p = 0.043) but not 24 h after injury. Hemorrhage volume, arterial blood gases, glucose, and systolic blood pressure were not affected.

CONCLUSIONS

Progesterone administration improved early neurobehavioral recovery and decreased secondary neuroinflammation after ICH in male rats. Paradoxically, progesterone worsened neurobehavioral recovery and did not modify neuroinflammation in female rats. Future work should isolate mechanisms of sex-specific progesterone effects after ICH.

Analytical challenges for measuring steroid responses to stress, neurodegeneration and injury in the central nervous system

Levels of steroids in the adult central nervous system (CNS) show marked changes in response to stress, degenerative disorders and injury. However, their analysis in complex matrices such as fatty brain and spinal cord tissues, and even in plasma, requires accurate and precise analytical methods. Radioimmunoassays (RIA) and enzyme-linked immunosorbent assays, even with prepurification steps, do not provide sufficient specificity, and they are at the origin of many inconsistent results in the literature. The analysis of steroids by mass spectrometric methods has become the gold standard for accurate and sensitive steroid analysis. However, these technologies involve multiple purification steps prone to errors, and they only provide accurate reference values when combined with careful sample workup. In addition, the interpretation of changes in CNS steroid levels is not an easy task because of their multiple sources: the endocrine glands and the local synthesis by neural cells. In the CNS, decreased steroid levels may reflect alterations of their biosynthesis, as observed in the case of chronic stress, post-traumatic stress disorders or depressive episodes. In such cases, return to normalization by administering exogenous hormones or by stimulating their endogenous production may have beneficial effects. On the other hand, increases in CNS steroids in response to acute stress, degenerative processes or injury may be part of endogenous protective or rescue programs, contributing to the resistance of neural cells to stress and insults. The aim of this review is to encourage a more critical reading of the literature reporting steroid measures, and to draw attention to the absolute need for well-validated methods. We discuss reported findings concerning changing steroid levels in the nervous system by insisting on methodological issues. An important message is that even recent mass spectrometric methods have their limits, and they only become reliable tools if combined with careful sample preparation.

Therapeutic actions of translocator protein (18 kDa) ligands in experimental models of psychiatric disorders and neurodegenerative diseases

Translocator protein (TSPO) is an 18kDa protein located at contact sites between the outer and the inner mitochondrial membrane. Numerous studies have associated TSPO with the translocation of cholesterol across the aqueous mitochondrial intermembrane space and the regulation of steroidogenesis, as well as with the control of some other mitochondrial functions, such as mitochondrial respiration, mitochondrial permeability transition pore opening, apoptosis and cell proliferation. In the brain, changes in TSPO expression occur in several neuropathological conditions including neurodegenerative diseases and psychiatric disorders. Furthermore, TSPO ligands have been shown to promote neuroprotection in animal models of brain pathology. At least in some cases, the mechanisms of neuroprotection are associated with modifications in brain steroidogenesis. In addition, regulation of neuroinflammation seems to be a common mechanism in the neuroprotective actions of TSPO ligands in different animal models of brain pathology.

Distinct cognitive effects of estrogen and progesterone in menopausal women

The effects of postmenopausal hormone treatment on cognitive outcomes are inconsistent in the literature. Emerging evidence suggests that cognitive effects are influenced by specific hormone formulations, and that progesterone is more likely to be associated with positive outcomes than synthetic progestin. There are very few studies of unopposed progesterone in postmenopausal women, and none that use functional neuroimaging, a sensitive measure of neurobiological function. In this study of 29 recently postmenopausal women, we used functional MRI and neuropsychological measures to separately assess the effects of estrogen or progesterone treatment on visual and verbal cognitive function. Women were randomized to receive 90 days of either estradiol or progesterone counterbalanced with placebo. After each treatment arm, women were given a battery of verbal and visual cognitive function and working memory tests, and underwent functional MRI including verbal processing and visual working memory tasks. We found that both estradiol and progesterone were associated with changes in activation patterns during verbal processing. Compared to placebo, women receiving estradiol treatment had greater activation in the left prefrontal cortex, a region associated with verbal processing and encoding. Progesterone was associated with changes in regional brain activation patterns during a visual memory task, with greater activation in the left prefrontal cortex and right hippocampus compared to placebo. Both treatments were associated with a statistically non-significant increase in number of words remembered following the verbal task performed during the fMRI scanning session, while only progesterone was associated with improved neuropsychological measures of verbal working memory compared to placebo. These results point to potential cognitive benefits of both estrogen and progesterone.

Inflammasomes are neuroprotective targets for sex steroids

Neuroinflammation in the central nervous system is triggered by toxic stimuli or degenerative events, orchestrates the interplay of brain-intrinsic immune cells and neighboring neural cells, and sequentially allows leukocyte extravasation from the periphery into the brain parenchyma. During the inflammatory cascade, immune-competent cells become activated and secrete a plethora of cytokines and chemokines which form a local inflammatory signaling network important for warding off harmful stimuli to the host but are likewise necessary to preserve damaged brain tissue. Inflammatory responses are initiated by extra- and intra-cellular pathogen and danger-associated receptors. These signals are processed by multi-protein complexes termed inflammasomes which trigger the production of biologically active interleukins-1 and 18 after the cleavage of caspase-1. Estrogens and progesterone are neuroprotective and anti-inflammatory in diverse disease models of the brain in particular under acute inflammatory conditions such as stroke and traumatic brain injury. Both steroids are able to attenuate pro-inflammatory cytokine activity. Recent literature and our own studies provide convincing evidence that the anti-inflammatory potency of these steroids result from a complex interaction with the inflammasome activation and their up-stream regulatory network of miRNAs in brain-intrinsic innate immune cells. This article examines steroid-inflammasome interactions in the brain during brain injury and illuminates the importance of regulation initial upstream events during neuroinflammation. This article is part of a Special Issue entitled 'Steroid Perspectives'.

Progesterone and allopregnanolone in the central nervous system: response to injury and implication for neuroprotection

Progesterone is a well-known steroid hormone, synthesized by ovaries and placenta in females, and by adrenal glands in both males and females. Several tissues are targets of progesterone and the nervous system is a major one. Progesterone is also locally synthesized by the nervous system and qualifies, therefore, as a neurosteroid. In addition, the nervous system has the capacity to bio-convert progesterone into its active metabolite allopregnanolone. The enzymes required for progesterone and allopregnanolone synthesis are widely distributed in brain and spinal cord. Increased local biosynthesis of pregnenolone, progesterone and 5α-dihydroprogesterone may be a part of an endogenous neuroprotective mechanism in response to nervous system injuries. Progesterone and allopregnanolone neuroprotective effects have been widely recognized. Multiple receptors or associated proteins may contribute to the progesterone effects: classical nuclear receptors (PR), membrane progesterone receptor component 1 (PGRMC1), membrane progesterone receptors (mPR), and γ-aminobutyric acid type A (GABAA) receptors after conversion to allopregnanolone. In this review, we will succinctly describe progesterone and allopregnanolone biosynthetic pathways and enzyme distribution in brain and spinal cord. Then, we will summarize our work on progesterone receptor distribution and cellular expression in brain and spinal cord; neurosteroid stimulation after nervous system injuries (spinal cord injury, traumatic brain injury, and stroke); and on progesterone and allopregnanolone neuroprotective effects in different experimental models including stroke and spinal cord injury. We will discuss in detail the neuroprotective effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABAA receptors.

Effect of the -2081G/A polymorphism of the TLR4 gene and its interaction with Helicobacter pylori infection on the risk of gastric cancer in Chinese individuals

AIMS

Toll-like receptor 4 (TLR4) plays an important role in gastric carcinoma. Using a case-control study, we analyzed the genotypic distribution of TLR4 rs10983755 (-2081G/A) and rs11536878 in a Chinese population and investigated the effect of their interactions with Helicobacter pylori infection on susceptibility to gastric cancer (GC) and atrophic gastritis (AG).

METHODS

In this study, 409 and 581 cases of GC and AG, respectively, were selected for analyses along with an equal number of matched controls. The TLR4 polymorphisms were genotyped using Sequenom MassARRAY. Serum levels of anti-H. pylori IgG were determined by enzyme-linked immunosorbent assay.

RESULTS

The TLR4-2081G/A polymorphism was negatively associated with GC (AG+AA vs. GG: odds ratio [OR]=0.70, 95% confidence interval [CI]=0.53-0.93, p=0.012). A decreased risk of GC was observed in H. pylori negative and TLR4-2081(AG+AA) genotype subjects [H. pylori(-)/AG+AA vs. H. pylori(+)/GG: OR=0.16, 95% CI=0.09-0.27, p<0.001]. The rs11536878 polymorphism was not associated with GC or AG.

CONCLUSIONS

The TLR4-2081G/A polymorphism seems to affect the risk of gastric carcinogenesis and may to some degree play a protective role against H. pylori infection.

Role of astrocytes in the neuroprotective actions of 17β-estradiol and selective estrogen receptor modulators

Neuroprotective actions of 17β-estradiol (estradiol) are in part mediated by direct actions on neurons. Astrocytes, which play an essential role in the maintenance of the homeostasis of neural tissue, express estrogen receptors and are also involved in the neuroprotective actions of estradiol in the brain. Estradiol controls gliosis and regulates neuroinflammation, edema and glutamate transport acting on astrocytes. In addition, the hormone regulates the release of neurotrophic factors and other neuroprotective molecules by astrocytes. In addition, reactive astrocytes are a local source of neuroprotective estradiol for the injured brain. Since estradiol therapy is not free from peripheral risks, alternatives for the hormone have been explored. Some selective estrogen receptor modulators (SERMs), which are already in use in clinical practice for the treatment of breast cancer, osteoporosis or menopausal symptoms, exert similar actions to estradiol on astrocytes. Therefore, SERMs represent therapeutic alternatives to estradiol for the activation of astroglia-mediated neuroprotective mechanisms.

Progesterone attenuates experimental subarachnoid hemorrhage-induced vasospasm by upregulation of endothelial nitric oxide synthase via Akt signaling pathway

Cerebral vasospasm is the leading cause of mortality and morbidity in patients after aneurysmal subarachnoid hemorrhage (SAH). However, the mechanism and adequate treatment of vasospasm are still elusive. In the present study, we evaluate the effect and possible mechanism of progesterone on SAH-induced vasospasm in a two-hemorrhage rodent model of SAH. Progesterone (8 mg/kg) was subcutaneously injected in ovariectomized female Sprague-Dawley rats one hour after SAH induction. The degree of vasospasm was determined by averaging the cross-sectional areas of basilar artery 7 days after first SAH. Expressions of endothelial nitric oxide synthase (eNOS) and phosphorylated Akt (phospho-Akt) in basilar arteries were evaluated. Prior to perfusion fixation, there were no significant differences among the control and treated groups in physiological parameters recorded. Progesterone treatment significantly (P < 0.01) attenuated SAH-induced vasospasm. The SAH-induced suppression of eNOS protein and phospho-Akt were relieved by progesterone treatment. This result further confirmed that progesterone is effective in preventing SAH-induced vasospasm. The beneficial effect of progesterone might be in part related to upregulation of expression of eNOS via Akt signaling pathway after SAH. Progesterone holds therapeutic promise in the treatment of cerebral vasospasm following SAH.

Sex differences in a mouse model of multiple sclerosis: neuropathic pain behavior in females but not males and protection from neurological deficits during proestrus

BACKGROUND

Multiple sclerosis (MS), a demyelinating disease of the central nervous system, is one of the most prevalent neurological disorders in the industrialized world. This disease afflicts more than two million people worldwide, over two thirds of which are women. MS is typically diagnosed between the ages of 20-40 and can produce debilitating neurological impairments including muscle spasticity, muscle paralysis, and chronic pain. Despite the large sex disparity in MS prevalence, clinical and basic research investigations of how sex and estrous cycle impact development, duration, and severity of neurological impairments and pain symptoms are limited. To help address these questions, we evaluated behavioral signs of sensory and motor functions in one of the most widely characterized animal models of MS, the experimental autoimmune encephalomyelitis (EAE) model.

METHODS

C57BL/6 male and female mice received flank injection of complete Freund's adjuvant (CFA) or CFA plus myelin oligodendrocyte glycoprotein 35-55 (MOG35-55) to induce EAE. Experiment 1 evaluated sex differences of EAE-induced neurological motor deficits and neuropathic pain-like behavior over 3 weeks, while experiment 2 evaluated the effect of estrous phase in female mice on the same behavioral measures for 3 months. EAE-induced neurological motor deficits including gait analysis and forelimb grip strength were assessed. Neuropathic pain-like behaviors evaluated included sensitivity to mechanical, cold, and heat stimulations. Estrous cycle was determined daily via vaginal lavage.

RESULTS

MOG35-55-induced EAE produced neurological impairments (i.e., motor dysfunction) including mild paralysis and decreases in grip strength in both females and males. MOG35-55 produced behavioral signs of neuropathic pain-mechanical and cold hypersensitivity-in females, but not males. MOG35-55 did not change cutaneous heat sensitivity in either sex. Administration of CFA or CFA + MOG35-55 prolonged the time spent in diestrus for 2 weeks, after which normal cycling returned. MOG35-55 produced fewer neurological motor deficits when mice were in proestrus relative to non-proestrus phases.

CONCLUSIONS

We conclude that female mice are superior to males for the study of neuropathic pain-like behaviors associated with MOG35-55-induced EAE. Further, proestrus may be protective against EAE-induced neurological deficits, thus necessitating further investigation into the impact that estrous cycle exerts on MS symptoms.

Sex steroids and neuroprotection in spinal cord injury: a review of preclinical investigations

Spinal cord injury (SCI) is a debilitating condition that affects motor, sensory and autonomic functions. Subsequent to the first mechanical trauma, secondary events, which include inflammation and glial activation, exacerbate tissue damage and worsen functional deficits. Although these secondary injury mechanisms are amenable to therapeutic interventions, the efficacy of current approaches is inadequate. Further investigations are necessary to implement new therapies that can protect neural cells and attenuate some of the detrimental effects of inflammation while promoting regeneration. Studies on different animal models of SCI indicated that sex steroids, especially 17β-estradiol and progesterone, exert neuroprotective, anti-apoptotic and anti-inflammatory effects, ameliorate tissue sparing and improve functional deficits in SCI. As sex steroid receptors are expressed in a variety of cells including neurons, glia and immune system-related cells which infiltrate the injury epicenter, sex steroids could impact multiple processes simultaneously and in doing so, influence the outcomes of SCI. However, the translation of these pre-clinical findings into the clinical setting presents challenges such as the narrow therapeutic time window of sex steroid administration, the diversity of treatment regimens that have been employed in animal studies and the lack of sufficient information regarding the persistence of the effects in chronic SCI. The current review will summarize some of the major findings in this field and will discuss the challenges associated with the implementation of sex steroids as a promising treatment in human SCI.