Sex-specific therapeutic strategies based on neuroactive steroids: In search for innovative tools for neuroprotection

Associations of schizophrenia with the activities of the HPA and HPG axes and their interactions characterized by hair-based biomarkers

BACKGROUND

Past studies on schizophrenia (SCZ) and the stress-sensitive neuroendocrine systems have mostly focused on a single system and traditionally utilized acute biomarkers (e.g., biomarkers from blood, urine and saliva) that poorly match the chronic course of schizophrenia in time span. Using eight biomarkers in hair, this study aimed to explore the functional characteristics of SCZ patients in the hypothalamic-pituitary-adrenocortical (HPA) and hypothalamic-pituitary-gonadal (HPG) axes and the interaction between the two axes.

METHODS

Hair samples were taken from 137 SCZ patients and 73 controls. The SCZ patients were diagnosed by their attending physician according to the Diagnostic and Statistical Manual of Mental Disorders IV and were clinically stable after treatment. Gender, age, BMI, frequency of hair washing, marital status, education level, family history of mental illness and clozapine dosage were concurrently collected as covariates. The 10-item perceived stress scale (PSS-10) and the social readjustment rating scale were used to assess chronic stress status in SCZ patients. Eight hair biomarkers, cortisol, cortisone, dehydroepiandrosterone (DHEA), testosterone, progesterone, cortisol/cortisone, cortisol/DHEA and cortisol/testosterone, were measured by high performance liquid chromatography tandem mass spectrometer. Among them, cortisol, cortisone, DHEA and cortisol/DHEA reflected the functional activity of the HPA axis, and testosterone and progesterone reflected the functional activity of the HPG axis, and cortisol/cortisone reflected the activity of 11β-hydroxysteroid dehydrogenase types 2 (11β-HSD 2), and cortisol/testosterone reflected the HPA-HPG interaction.

RESULTS

SCZ patients showed significantly higher cortisone and cortisol/testosterone than controls (p<0.001, η²p=0.180 and p=0.015, η²p=0.031), lower testosterone (p=0.009, η²p=0.034), progesterone (p<0.001, η²p=0.069) and cortisol/cortisone (p=0.001, η²p=0.054). There were significant intergroup differences in male and female progesterone (p=0.003, η²p=0.088 and p=0.030, η²p=0.049) and female testosterone (p=0.028, η²p=0.051). In SCZ patients, cortisol, cortisol/cortisone, cortisol/DHEA and cortisol/testosterone were positively associated with PSS-10 score (ps<0.05, 0.212

CONCLUSION

The function of the HPA and HPG axes, the activity of 11β-HSD 2 and the HPA-HPG interaction were abnormal in SCZ patients. The abnormality of neuroendocrine systems was associated with chronic stress status in SCZ patients. This study provided evidence for abnormalities in the neuroendocrine systems in SCZ patients.

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Key Words

• 11β-HSD 2
• HPA axis
• HPG axis
• Hair biomarkers
• Schizophrenia

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MESH Headings

• Humans
• Female
• Male
• Hypothalamo-Hypophyseal System/metabolism
• Schizophrenia/metabolism
• Pituitary-Adrenal System/metabolism
• Pituitary-Adrenal System/physiopathology
• Hair/chemistry
• Hair/metabolism
• Biomarkers/metabolism
• Adult
• Hydrocortisone/metabolism
• Hydrocortisone/analysis
• Cortisone/metabolism
• Cortisone/analysis
• Testosterone/metabolism
• Testosterone/analysis
• Dehydroepiandrosterone/metabolism
• Dehydroepiandrosterone/analysis
• Stress, Psychological/metabolism
• Middle Aged
• Progesterone/metabolism
• Progesterone/analysis
• Case-Control Studies

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Affiliation(s)

Deyi Qi Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China
Weiliang Wang School of Nursing, Harbin Medical University, Harbin 163319, China.
Liuxi Chu Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China
Yan Wu Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China
Wei Wang Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China
Minhui Zhu Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China
Lin Yuan Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China
Wei Gao Institute of Child Development and Education, Southeast University, Nanjing 211189, China; School of Psychology, Nanjing Normal University, Nanjing 210024, China
Huihua Deng Department of Brain and Learning Science, School of Biological Science & Medical Engineering, Southeast University, Nanjing 211189, China; Key Laboratory of Child Development and Learning Science (Southeast University), Ministry of Education, Nanjing 211189, China; Institute of Child Development and Education, Southeast University, Nanjing 211189, China.

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Symptoms, Lifetime Duration of Estrogen Exposure, and Ovarian Reserve Among Women Living With HIV: A Cross-Sectional Observational Study

ABSTRACT

This cross-sectional observational study examined associations among symptom burden, lifetime duration of estrogen exposure, and serum antimüllerian hormone (AMH) levels among women living with HIV (n = 98) using bivariate bias-corrected Pearson correlations and multiple correspondence analyses. The mostly Black (85.6%) sample of women, with a mean age of 50 years (SD 12.6 years), exhibited no significant reproductive history factors and symptom burden interrelationships or significant associations between lifetime duration of estrogen exposure and symptoms. Predictably, serum AMH levels were lower among older women; however, less predictable were its significant relationships with months living with HIV (r = -0.362), months on ART (r = -0.270), and CD4+ T-cell nadir (r = 0.347). Symptom-symptom relationships support a fatigue, pain, sleep, anxiety, and depression symptom cluster. The hypotheses were not supported by cross-sectional observation. Further studies should explore variation in relationships between HIV, estrogen exposure, ovarian reserve, and AMH levels over time.

Neuroactive Steroid-Gut Microbiota Interaction in T2DM Diabetic Encephalopathy

The pathological consequences of type 2 diabetes mellitus (T2DM) also involve the central nervous system; indeed, T2DM patients suffer from learning and memory disabilities with a higher risk of developing dementia. Although several factors have been proposed as possible contributors, how neuroactive steroids and the gut microbiome impact brain pathophysiology in T2DM remain unexplored. On this basis, in male Zucker diabetic fatty (ZDF) rats, we studied whether T2DM alters memory abilities using the novel object recognition test, neuroactive steroid levels by liquid chromatography-tandem mass spectrometry, hippocampal parameters using molecular assessments, and gut microbiome composition using 16S next-generation sequencing. Results obtained reveal that T2DM worsens memory abilities and that these are correlated with increased levels of corticosterone in plasma and with a decrease in allopregnanolone in the hippocampus, where neuroinflammation, oxidative stress, and mitochondrial dysfunction were reported. Interestingly, our analysis highlighted a small group of taxa strictly related to both memory impairment and neuroactive steroid levels. Overall, the data underline an interesting role for allopregnanolone and microbiota that may represent candidates for the development of therapeutic strategies.

Allopregnanolone: An overview on its synthesis and effects

Allopregnanolone, a 3α,5α-progesterone metabolite, acts as a potent allosteric modulator of the γ-aminobutyric acid type A receptor. In the present review, the synthesis of this neuroactive steroid occurring in the nervous system is discussed with respect to physiological and pathological conditions. In addition, its physiological and neuroprotective effects are also reported. Interestingly, the levels of this neuroactive steroid, as well as its effects, are sex-dimorphic, suggesting a possible gender medicine based on this neuroactive steroid for neurological disorders. However, allopregnanolone presents low bioavailability and extensive hepatic metabolism, limiting its use as a drug. Therefore, synthetic analogues or a different therapeutic strategy able to increase allopregnanolone levels have been proposed to overcome any pharmacokinetic issues.

High-fat diet alters stress behavior, inflammatory parameters and gut microbiota in Tg APP mice in a sex-specific manner

Long-term high-fat diet (HFD) consumption commonly leads to obesity, a major health concern of western societies and a risk factor for Alzheimer's disease (AD). Both conditions present glial activation and inflammation and show sex differences in their incidence, clinical manifestation, and disease course. HFD intake has an important impact on gut microbiota, the bacteria present in the gut, and microbiota dysbiosis is associated with inflammation and certain mental disorders such as anxiety. In this study, we have analyzed the effects of a prolonged (18 weeks, starting at 7 months of age) HFD on male and female mice, both wild type (WT) and TgAPP mice, a model for AD, investigating the behavioral profile, gut microbiota composition and inflammatory/phagocytosis-related gene expression in hippocampus. In the open-field test, no overt differences in motor activity were observed between male and female or WT and TgAPP mice on a low-fat diet (LFD). However, HFD induced anxiety, as judged by decreased motor activity and increased time in the margins in the open-field, and a trend towards increased immobility time in the tail suspension test, with increased defecation. Intriguingly, female TgAPP mice on HFD showed less immobility and defecation compared to female WT mice on HFD. HFD induced dysbiosis of gut microbiota, resulting in reduced microbiota diversity and abundance compared with LFD fed mice, with some significant differences due to sex and little effect of genotype. Gene expression of pro-inflammatory/phagocytic markers in the hippocampus were not different between male and female WT mice, and in TgAPP mice of both sexes, some cytokines (IL-6 and IFNγ) were higher than in WT mice on LFD, more so in female TgAPP (IL-6). HFD induced few alterations in mRNA expression of inflammatory/phagocytosis-related genes in male mice, whether WT (IL-1β, MHCII), or TgAPP (IL-6). However, in female TgAPP, altered gene expression returned towards control levels following prolonged HFD (IL-6, IL-12β, TNFα, CD36, IRAK4, PYRY6). In summary, we demonstrate that HFD induces anxiogenic symptoms, marked alterations in gut microbiota, and increased expression of inflammatory genes, except for female TgAPP that appear to be resistant to the diet effects. Lifestyle interventions should be introduced to prevent AD onset or exacerbation by reducing inflammation and its associated symptoms; however, our results suggest that the eventual goal of developing prevention and treatment strategies should take sex into consideration.

Gender-specific approach in psychiatric diseases: Because sex matters

In both animals and human beings, males and females differ in their genetic background and hormonally driven behaviour and show sex-related differences in brain activity and response to internal and external stimuli. Gender-specific medicine has been a neglected dimension of medicine for long time, and only in the last three decades it is receiving the due scientific and clinical attention. Research has recently begun to identify factors that could provide a neurobiological basis for gender-based differences in health and disease and to point to gonadal hormones as important determinants of male-female differences. Animal studies have been of great help in understanding factors contributing to sex-dependent differences and sex hormones action. Here we review and discuss evidence provided by clinical and animal studies in the last two decades showing gender (in humans) and sex (in animals) differences in selected psychiatric disorders, namely eating disorders (anorexia nervosa, bulimia nervosa, binge eating disorder), schizophrenia, mood disorders (anxiety, depression, obsessive-compulsive disorder) and neurodevelopmental disorders (autism spectrum disorders, attention-deficit/hyperactivity disorder).

Sex-Mediated Differences in LPS Induced Alterations of TNFα, IL-10 Expression, and Prostaglandin Synthesis in Primary Astrocytes

Although many neurological and psychiatric disorders reveal clear sex-dependent variations, the molecular mechanism of this process is not clear enough. Astrocytes are involved in the response of neural tissue to injury and inflammation, produce steroid hormones, and sense steroid presence. To explore the hypothesis that astrocytes may participate in sex-mediated differences of inflammatory responses, we have examined whether male and female primary rat astrocytes show different responses to lipopolysaccharide (LPS) as a toll-like receptor 4 (TLR4) agonist. Levels of mRNA and proteins of tumor necrosis factor alpha (TNFα), interleukin-10 (IL-10), and cyclooxygenase (COX)-2 were assessed using qPCR, immunoblotting, and ELISA. UPLC-MS/MS was used to detect prostaglandins (PGs). LPS stimulation resulted in different levels of cytokine production; more TNFα and less IL-10 were produced in female cells compared with male astrocytes. Although the levels of the COX-2 expression were not altered, LPS significantly induced the synthesis of PGs with notable sex-related differences. PGE₂ and PGD₂ were less and 6-keto-PGF_1α was more upregulated in female astrocytes, and TXB₂ had similar levels in cells obtained from males and females. Trilostane, an inhibitor of 3β-Hydroxysteroid dehydrogenase (3β-HSD), inhibited the LPS-induced TNFα production and the release of PGE₂, PGD₂, and 6-keto-PGF_1α in female astrocytes. Thus, male and female astrocytes differentially respond to inflammatory challenges on the level of production of cytokines and steroid hormones. Sex-mediated differences in pro- and anti-inflammatory responses should be taken into consideration for the effective treatment of disorders with neuroinflammation.

Identification of key target genes and biological pathways in multiple sclerosis brains using microarray data obtained from the Gene Expression Omnibus database

OBJECTIVE

The purpose of this study was to investigate critical genes in multiple sclerosis (MS) using microarray data from brain tissue in MS.

MATERIALS

The expression profile data set of MS (GSE38010) downloaded from the Gene Expression Omnibus database contained gene information from five plaque tissues from MS brains and two white matter tissues from healthy controls. An R package was applied to process these raw chip data. Gene Ontology (GO) functional analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and protein-protein interaction (PPI) network analysis were performed to investigate interactions between differentially expressed genes (DEGs) in MS brain tissues.

RESULTS

This study identified a total of 1065 DEGs, including 530 up-regulated genes and 535 down-regulated genes, in MS brain tissue samples compared to those in normal white matter tissue samples. GO and KEGG pathway enrichment analyses showed that the up-regulated DEGs were mainly related to neuron development, neuron projection morphogenesis and neuron differentiation. Furthermore, the down-regulated DEGs were largely related to axon ensheathment, ensheathment of neurons and nervous system development. Seven key genes were found as hub genes in the maintenance of the PPI network.

CONCLUSION

Several key target genes and their GO and KEGG pathway enrichment identified in the present study may serve as feasible targets for MS therapies.

Post-finasteride syndrome and post-SSRI sexual dysfunction: two sides of the same coin?

Sexual dysfunction is a clinical condition due to different causes including the iatrogenic origin. For instance, it is well known that sexual dysfunction may occur in patients treated with antidepressants like selective serotonin reuptake inhibitors (SSRI). A similar side effect has been also reported during treatment with finasteride, an inhibitor of the enzyme 5alpha-reductase, for androgenetic alopecia. Interestingly, sexual dysfunction persists in both cases after drug discontinuation. These conditions have been named post-SSRI sexual dysfunction (PSSD) and post-finasteride syndrome (PFS). In particular, feeling of a lack of connection between the brain and penis, loss of libido and sex drive, difficulty in achieving an erection and genital paresthesia have been reported by patients of both conditions. It is interesting to note that the incidence of these diseases is probably so far underestimated and their etiopathogenesis is not sufficiently explored. To this aim, the present review will report the state of art of these two different pathologies and discuss, on the basis of the role exerted by three different neuromodulators such as dopamine, serotonin and neuroactive steroids, whether the persistent sexual dysfunction observed could be determined by common mechanisms.

Neuroactive steroids and diabetic complications in the nervous system

Important complications of diabetes mellitus in the nervous system are represented by diabetic peripheral neuropathy and diabetic encephalopathy. In this context, an important link is represented by neuroactive steroids (i.e., steroids coming from peripheral glands and affecting nervous functionality as well as directly synthesized in the nervous system). Indeed, diabetes does not only affect the reproductive axis and consequently the levels of sex steroid hormones, but also those of neuroactive steroids. Indeed, as will be here summarized, the levels of these neuromodulators present in the central and peripheral nervous system are affected by the pathology in a sex-dimorphic way. In addition, some of these neuroactive steroids, such as the metabolites of progesterone or testosterone, as well as pharmacological tools able to increase their levels have been demonstrated, in experimental models, to be promising protective agents against diabetic peripheral neuropathy and diabetic encephalopathy.

Sex differences in the phagocytic and migratory activity of microglia and their impairment by palmitic acid

Sex differences in the incidence, clinical manifestation, disease course, and prognosis of neurological diseases, such as autism spectrum disorders or Alzheimer's disease, have been reported. Obesity has been postulated as a risk factor for cognitive decline and Alzheimer's disease and, during pregnancy, increases the risk of autism spectrum disorders in the offspring. Obesity is associated with increased serum and brain levels of free fatty acids, such as palmitic acid, which activate microglial cells triggering a potent inflammatory cascade. In this study, we have determined the effect of palmitic acid in the inflammatory profile, motility, and phagocytosis of primary male and female microglia, both in basal conditions and in the presence of a pro-inflammatory stimulus (interferon-γ). Male microglia in vitro showed higher migration than female microglia under basal and stimulated conditions. In contrast, female microglia had higher basal and stimulated phagocytic activity than male microglia. Palmitic acid did not affect basal migration or phagocytosis, but abolished the migration and phagocytic activity of male and female microglia in response to interferon-γ. These findings extend previous observations of sex differences in microglia and suggest that palmitic acid impairs the protective responses of these cells.

Pregnenolone as an adjunct to risperidone for treatment of women with schizophrenia: A randomized double-blind placebo-controlled clinical trial

There have been few studies of pregnenolone therapy in schizophrenia and those that exist have been subject to several critical limitations, thus yielding inconsistent results. We attempted to assess the therapeutic effect of pregnenolone in a patient sample as homogeneous as possible. In this randomized double-blind clinical trial, 82 female inpatients with chronic schizophrenia, who had discontinued their antipsychotic medications for at least one week in case of any oral antipsychotic medication or a month for any depot antipsychotic medication, received risperidone plus either pregnenolone (50 mg/day) or placebo for 8 weeks. Inclusion criteria were acute illness with a baseline Positive and Negative Syndrome Scale (PANSS) negative subscale score of ≥20. Exclusion criteria were the presence of severe depression or other concomitant psychiatric disorders. Primary outcome was defined as the difference in the PANSS total score change from baseline to week 8 in the pregnenolone group compared to the placebo group. No significant difference was found in the PANSS total score changes between the two arms (mean difference (CI 95%) = -9.41 (-20.24 to 1.41); p = 0.087). Significant differences were initially found for PANSS negative change scores (mean difference (CI 95%) = -2.61 (-5.03 to -0.19); p = 0.035) and general psychopathology change scores (mean difference (CI 95%) = -5.93 (-11.37 to -0.48); p = 0.033). However, these findings did not survive Bonferroni correction for multiple testing. While this trial may suggest a potential effect of pregnenolone on schizophrenia symptoms, further studies are warranted.

Exploring the potential of natural and synthetic neuroprotective steroids against neurodegenerative disorders: A literature review

Neurodegeneration is a complex process, which leads to progressive brain damage due to loss of neurons. Despite exhaustive research, the cause of neuronal loss in various degenerative disorders is not entirely understood. Neuroprotective steroids constitute an important line of attack, which could play a major role against the common mechanisms associated with various neurodegenerative disorders like Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. Natural endogenous steroids induce the neuroprotection by protecting the nerve cells from neuronal injury through multiple mechanisms, therefore the structural modifications of the endogenous steroids could be helpful in the generation of new therapeutically useful neuroprotective agents. The review article will keep the readers apprised of the detailed description of natural as well as synthetic neuroprotective steroids from the medicinal chemistry point of view, which would be helpful in drug discovery efforts aimed toward neurodegenerative diseases.

Neuroprotective effects of low fat-protein diet in the P301L mouse model of tauopathy

Tauopathies are a class of neurodegenerative diseases associated with the pathological aggregation of tau protein in the human brain. Although numerous studies in mouse models of Alzheimer disease (AD) have shown a correlation among diet, beta-amyloid and AD onset, little is known about the impact of diet on Tau. We investigated whether a low fat-protein diet (LFPD) may improve lifespan, cognitive and locomotor activity in P301L-tg mouse model of tauopathy. Our data indicate that LFPD has a beneficial effect on these parameters. Tg mice fed with standard diet shown a decrease in body weight, food intake and survival rate if compared to wild type animals. In contrast, LFPD counteracted weight loss, increased mortality and ameliorated cognitive and locomotor performances in tg mice. LFPD also reduced the abnormal accumulation of agglomerates of P-Tau (pathological features of tauopathies) and the expression of apoptotic markers (i.e., TUNEL immunopositive neurons) in the prefrontal cerebral cortex and hippocampus of P301L-tg mice. Interestingly, some of these effects are sex-dependent. For instance, tg females, but not males, fed with LFPD had a significant increase of body weight and a reduction of P-Tau agglomerates compared to tg fed with standard diet. These changes correlated with a more pronounced improvement of cognition and locomotor activity in females than in male tg fed with LFPD. Altogether, these results suggest a sex dependent neuroprotective effect of LFPD in P301L-tg mice, suggesting that lifestyle intervention strategies may be clinically relevant for delaying the onset of cognitive impairment and dementia, especially in females.

The choroid plexus as a sex hormone target: Functional implications

The choroid plexuses (CPs) are highly vascularized branched structures that protrude into the ventricles of the brain, and form a unique interface between the blood and the cerebrospinal fluid (CSF). In recent years, novel functions have been attributed to this tissue such as in immune and chemical surveillance of the central nervous system, brain development, adult neurogenesis and circadian rhythm regulation. Sex hormones (SH) are widely recognized as modulators in several neurodegenerative diseases, and there is evidence that estrogens and androgens regulate several fundamental biological functions in the CPs. Therefore, SH are likely to affect the composition of the CSF impacting on brain homeostasis. This review will look at implications of the CPs' sex-related specificities.

DNA methylation patterns of protein-coding genes and long non-coding RNAs in males with schizophrenia

Schizophrenia (SCZ) is one of the most complex mental illnesses affecting ~1% of the population worldwide. SCZ pathogenesis is considered to be a result of genetic as well as epigenetic alterations. Previous studies have aimed to identify the causative genes of SCZ. However, DNA methylation of long non-coding RNAs (lncRNAs) involved in SCZ has not been fully elucidated. In the present study, a comprehensive genome-wide analysis of DNA methylation was conducted using samples from two male patients with paranoid and undifferentiated SCZ, respectively. Methyl-CpG binding domain protein-enriched genome sequencing was used. In the two patients with paranoid and undifferentiated SCZ, 1,397 and 1,437 peaks were identified, respectively. Bioinformatic analysis demonstrated that peaks were enriched in protein-coding genes, which exhibited nervous system and brain functions. A number of these peaks in gene promoter regions may affect gene expression and, therefore, influence SCZ-associated pathways. Furthermore, 7 and 20 lncRNAs, respectively, in the Refseq database were hypermethylated. According to the lncRNA dataset in the NONCODE database, ~30% of intergenic peaks overlapped with novel lncRNA loci. The results of the present study demonstrated that aberrant hypermethylation of lncRNA genes may be an important epigenetic factor associated with SCZ. However, further studies using larger sample sizes are required.

The other side of progestins: effects in the brain

Progestins are a broad class of progestational agents widely differing in their chemical structures and pharmacological properties. Despite emerging data suggest that progestins, besides their action as endometrial protection, can also have multiple nonreproductive functions, much remains to be discovered regarding the actions exerted by these molecules in the nervous system. Here, we report the role exerted by different progestins, currently used for contraception or in postmenopausal hormone replacement therapies, in regulating cognitive functions as well as social behavior and mood. We provide evidence that the effects and mechanisms underlying their actions are still confusing due to the use of different estrogens and progestins as well as different doses, duration of exposure, route of administration, baseline hormonal status and age of treated women. We also discuss the emerging issue concerning the relevant increase of these substances in the environment, able to deeply affect aquatic wildlife as well as to exert a possible influence in humans, which may be exposed to these compounds via contaminated drinking water and seafood. Finally, we report literature data showing the neurobiological action of progestins and in particular their importance during neurodegenerative events. This is extremely interesting, since some of the progestins currently used in clinical practice exert neuroprotective and anti-inflammatory effects in the nervous system, opening new promising opportunities for the use of these molecules as therapeutic agents for trauma and neurodegenerative disorders.

Assessment of neuroactive steroids in cerebrospinal fluid comparing acute relapse and stable disease in relapsing-remitting multiple sclerosis

Previous studies have reported an involvement of neuroactive steroids as neuroprotective and anti-inflammatory agents in neurological disorders such as multiple sclerosis (MS); an analysis of their profile during a specific clinical phase of MS is largely unknown. The pregnenolone (PREG), dehydroepiandrosterone (DHEA), and allopregnanolone (ALLO) profile was evaluated in cerebrospinal fluid (CSF) in relapsing-remitting multiple sclerosis (RR-MS) patients as well as those in patients affected by non-inflammatory neurological (control group I) and without neurological disorders (control group II). An increase of PREG and DHEA values was shown in CSF of male and female RR-MS patients compared to those observed in both control groups. The ALLO values were significantly lower in female RR-MS patients than those found in male RR-MS patients and in female without neurological disorder. During the clinical relapse, we observed female RR-MS patients showing significantly increased PREG values compared to female RR-MS patients in stable phase, while their ALLO values showed a significant decrease compared to male RR-MS patients of the same group. Male RR-MS patients with gadolinium-enhanced lesions showed PREG and DHEA values higher than those found in female RR-MS patients with gadolinium-enhanced lesions. Similary, male RR-MS patients with gadolinium-enhanced lesions showed PREG and DHEA values higher than male without gadolinium-enhanced lesions. Female RR-MS patients with gadolinium-enhanced lesions showed DHEA values higher than those found in female RR-MS patients with gadolinium-enhanced lesions. Male and female RR-MS patients with gadolinium-enhanced lesions showed ALLO values higher than those found in respective gender groups without gadolinium-enhanced lesions. ALLO values were lower in male than in female RR-MS patients without gadolinium-enhanced lesions. Considering the pharmacological properties of neuroactive steroids and the observation that neurological disorders influence their concentrations, these endogenous compounds may have an important role as prognostic factors of the disease and used as markers of MS activity such as relapses.

Adverse effects of 5α-reductase inhibitors: What do we know, don't know, and need to know?

Steroids are important physiological orchestrators of endocrine as well as peripheral and central nervous system functions. One of the key processes for regulation of these molecules lies in their enzymatic processing by a family of 5α-reductase (5α-Rs) isozymes. By catalyzing a key rate-limiting step in steroidogenesis, this family of enzymes exerts a crucial role not only in the physiological control but also in pathological events. Indeed, both 5α-R inhibition and supplementation of 5α-reduced metabolites are currently used or have been proposed as therapeutic strategies for a wide array of pathological conditions. In particular, the potent 5α-R inhibitors finasteride and dutasteride are used in the treatments of benign prostatic hyperplasia (BPH), as well as in male pattern hair loss (MPHL) known as androgenetic alopecia (AGA). Recent preclinical and clinical findings indicate that 5α-R inhibitors evoke not only beneficial, but also adverse effects. Future studies should investigate the biochemical and physiological mechanisms that underlie the persistence of the adverse sexual side effects to determine why a subset of patients is afflicted with such persistence or irreversible adverse effects. Also a better focus of clinical research is urgently needed to better define those subjects who are likely to be adversely affected by such agents. Furthermore, research on the non-sexual adverse effects such as diabetes, psychosis, depression, and cognitive function are needed to better understand the broad spectrum of the effects these drugs may elicit during their use in treatment of AGA or BPH. In this review, we will summarize the state of art on this topic, overview the key unresolved questions that have emerged on the pharmacological targeting of these enzymes and their products, and highlight the need for further studies to ascertain the severity and duration of the adverse effects of 5α-R inhibitors, as well as their biological underpinnings.

New steps forward in the neuroactive steroid field

Evidence accumulated in recent years suggests that the systemic treatment with neuroactive steroids, or the pharmacological modulation of its production by brain cells, represent therapeutic options to promote neuroprotection. However, new findings, which are reviewed in this paper, suggest that the factors to be considered for the design of possible therapies based on neuroactive steroids are more complex than previously thought. Thus, although as recently reported, the nervous system regulates neuroactive steroid synthesis and metabolism in adaptation to modifications in peripheral steroidogenesis, the neuroactive steroid levels in the brain do not fully reflect its levels in plasma. Even, in some cases, neuroactive steroid level modifications occurring in the nervous tissues, under physiological and pathological conditions, are in the opposite direction than in the periphery. This suggests that the systemic treatment with these molecules may have unexpected outcomes on neural steroid levels. In addition, the multiple metabolic pathways and signaling mechanisms of neuroactive steroids, which may change from one brain region to another, together with the existence of regional and sex differences in its neural levels are additional sources of complexity that should be clarified. This complexity in the levels and actions of these molecules may explain why in some cases these molecules have detrimental rather than beneficial actions for the nervous system. This article is part of a Special Issue entitled 'Steroid Perspectives'.

Just like a circus: the public consumption of sex differences

The study of sex differences is a rich, productive area of neuroscience, yielding findings that inform our understanding of basic biology and hold promise for clinical applications. There is a tremendous, problematic mismatch, however, between the actual implications of this research and what has generally been communicated to the public. The message communicated by the media, popular press, and in some cases researchers is often inaccurate with respect to what can and cannot be concluded from the data. This misrepresentation of findings has led to a crisis in public education and threatens to do the same in public health. Here, I suggest a number of ways that neuroscientists might address this growing problem. First, we should acknowledge that the term 'sex difference' is usually interpreted by the media and the public as evidence for dichotomous categories that do not actually exist. Because data rarely sort so cleanly into sex-specific categories, clearer presentation of the nature and size of sex differences is warranted. The term 'sex effect' may be preferable to 'sex difference' when the effect is not large. Second, factors that covary with sex, particularly experience, should be considered as causes of sex differences before the idea of "hardwiring" is invoked. Finally, we should be more vigilant about how our own findings are conveyed to policymakers and the public and speak out when they are misrepresented.

Neuroactive steroid levels in plasma and cerebrospinal fluid of male multiple sclerosis patients

Neuroactive steroid family includes molecules synthesized in peripheral glands (i.e., hormonal steroids) and directly in the nervous system (i.e., neurosteroids) which are key regulators of the nervous function. As already reported in clinical and experimental studies, neurodegenerative diseases affect the levels of neuroactive steroids. However, a careful analysis comparing the levels of these molecules in cerebrospinal fluid (CSF) and in plasma of multiple sclerosis (MS) patients is still missing. To this aim, the levels of neuroactive steroids were evaluated by liquid chromatography-tandem mass spectrometry in CSF and plasma of male adults affected by Relapsing-Remitting MS and compared with those collected in control patients. An increase in pregnenolone and isopregnanolone levels associated with a decrease in progesterone metabolites, dihydroprogesterone, and tetrahydroprogesterone was observed in CSF of MS patients. Moreover, an increase of 5α-androstane-3α,17β-diol and of 17β-estradiol levels associated with a decrease of dihydrotestosterone also occurred. In plasma, an increase in pregnenolone, progesterone, and dihydrotestosterone and a decrease in dihydroprogesterone and tetrahydroprogesterone levels were reported. This study shows for the first time that the levels of several neuroactive steroids, and particularly those of progesterone and testosterone metabolites, are deeply affected in CSF of relapsing-remitting MS male patients. We here demonstrated that, the cerebrospinal fluid and plasma levels of several neuroactive steroids are modified in relapsing remitting multiple sclerosis male patients. Interestingly, we reported for the first time that, the levels of progesterone and testosterone metabolites are deeply affected in cerebrospinal fluid. These findings may have an important relevance in therapeutic and/or diagnostic field of multiple sclerosis.

Comparison of plasma and cerebrospinal fluid levels of neuroactive steroids with their brain, spinal cord and peripheral nerve levels in male and female rats

Physiological changes and pathological alterations in the nervous system of rodents are associated with modifications in the levels of neuroactive steroids in the brain, spinal cord and/or peripheral nerves. Measures of tissue levels of steroids in the nervous system present serious limitations for human studies and for longitudinal studies in animals. In this study we have explored whether levels of neuroactive steroids in plasma and the cerebrospinal fluid reflect their levels in neural tissues. To this aim, we have evaluated by liquid chromatography-tandem mass spectrometry the levels of several neuroactive steroids in plasma, cerebrospinal fluid, cerebral cortex, cerebellum, hippocampus, spinal cord and sciatic nerve of male and female rats. Data indicate that plasma and cerebrospinal fluid levels of steroids do not fully reflect their tissue levels. However, the interindividual variations in the levels of all the steroids assessed, with the exception of dehydroepiandrosterone, showed a positive correlation in plasma and cerebral cortex. Most steroids also showed a positive correlation in plasma and the cerebellum, the spinal cord and the sciatic nerve. In the hippocampus, the levels of tetrahydroprogesterone, testosterone and testosterone metabolites showed a significant positive correlation with their respective levels in plasma. The cerebrospinal fluid levels of some steroids, such as testosterone and dihydrotestosterone, showed a full correlation with tissue levels. In addition, cerebrospinal fluid levels of pregnenolone, progesterone, and 17β-estradiol showed a positive correlation with their corresponding levels in the majority of the neural structures analyzed. These findings suggest that the levels of some neuroactive steroids in cerebrospinal fluid as well as in plasma may be valuable to predict their levels in the nervous system.

Liver X receptors, nervous system, and lipid metabolism

Lipids in the nervous system are represented by cholesterol and phospholipids as constituents of cell membranes and, in particular, of myelin. Therefore, lipids are finely regulated to guarantee physiological functions. In the central nervous system, cholesterol is locally synthesized due to the presence of the blood brain barrier. In the peripheral nervous system cholesterol is either up-taken by lipoproteins and/or produced by de novo biosynthesis. Defects in lipid homeostasis in these tissues lead to structural and functional changes that often result in different pathological conditions depending on the affected pathways (i.e. cholesterol biosynthesis, cholesterol efflux, fatty acid biosynthesis etc.). Alterations in cholesterol metabolism in the central nervous system are linked to several disorders such as Alzheimer's disease, Huntington disease, Parkinson disease, Multiple sclerosis, Smith-Lemli-Opitz syndrome, Niemann-Pick type C disease, and glioblastoma. In the peripheral nervous system changes in lipid metabolism are associated with the development of peripheral neuropathy that may be caused by metabolic disorders, injuries, therapeutics, and autoimmune diseases. Transcription factors, such as the Liver X receptors (LXR), regulate both cholesterol and fatty acid metabolism in several tissues including the nervous system. In the last few years several studies elucidated the biology of LXR in the nervous system due to the availability of knock-out mice and the development of synthetic ligands. Here, we review a survey of the literature focused on the central and peripheral nervous system and in physiological and pathological settings with particular attention to the roles played by LXR in both districts.

The role of estrogen in the treatment of men with schizophrenia

Schizophrenia is a debilitating and pervasive mental illness with devastating effects on many aspects of psychological, cognitive and social wellbeing. Epidemiological and life-cycle data point to significant differences in the incidence and course of schizophrenia between men and women, suggesting that estrogen plays a "protective" role . Adjunctive estrogen therapy has been shown to be effective in enhancing the treatment of schizophrenia in women. In men, consideration of estrogen therapy has been impacted by concerns of feminisation, however, clinical trials using estrogen to treat prostate cancer, bone density loss and even aggression in men with dementia or traumatic brain injury, show estrogen to be a safe and effective therapy. Findings do, however, suggest that further exploration of a therapeutic role for adjunctive estradiol treatment in men with schizophrenia is warranted. The development of the new estrogen compounds - Selective Estrogen Receptor Modulators (SERMs) which do not cause feminisation - opens up the possibility of using a different type of estrogen for a longer period of time at higher doses. Estrogen could therefore prove to be an important component in the treatment of psychotic symptoms in men with schizophrenia. This review explains the scientific rationale behind the estrogen hypothesis and how it can be clinically utilised to address concerns unique to the care of men with schizophrenia.

Special biological issues in the management of women with schizophrenia

Schizophrenia is a debilitating and pervasive mental illness with devastating effects on psychological, cognitive and social wellbeing, and for which current treatment options are far from ideal. Gender differences and the influence of the female reproductive life cycle on the onset, course and symptoms of schizophrenia and the discovery of estrogen's remarkable psychoprotective properties in animal models led to the proposal of the 'estrogen protection hypothesis' of schizophrenia. This has fueled the recent successful investigation of estradiol as a potential adjuvant therapeutic agent in the management of schizophrenia in women. This review explains the scientific rationale behind the estrogen hypothesis and how it can be clinically utilized to address concerns unique to the care of women with schizophrenia.

Neuroactive steroids, their metabolites, and neuroinflammation

Neuroinflammation represents a common feature of many neurodegenerative diseases implicated both in their onset and progression. Neuroactive steroids act as physiological regulators and protective agents in the nervous system. Therefore, the attention of biomedical research has been recently addressed in evaluating whether neuroactive steroids, such as progestagens, androgens, and estrogens may also affect neuroinflammatory pathways. Observations so far obtained suggest a general anti-inflammatory effect with a beneficial relapse on several neurodegenerative experimental models, thus confirming the potentiality of a neuroprotective strategy based on neuroactive steroids. In this scenario, neuroactive steroid metabolism and the sophisticated machinery involved in their signaling are becoming especially attractive. In particular, because metabolism of neuroactive steroids as well as expression of their receptors is affected during the course of neurodegenerative events, a crucial role of progesterone and testosterone metabolites in modulating neuroinflammation and neurodegeneration may be proposed. In the present review, we will address this issue, providing evidence supporting the hypothesis that the efficacy of neuroactive steroids could be improved through the use of their metabolites.

Age-related changes in neuroactive steroid levels in 3xTg-AD mice

Although neuroactive steroids exert neuroprotective actions in different experimental models of neurodegenerative diseases, including those of Alzheimer's disease (AD), their relationships with aged related physiologic and pathologic brain changes remain to be clarified. In this study the levels of pregnenolone, dehydroepiandrosterone, progesterone, dihydroprogesterone, tetrahydroprogesterone, isopregnanolone, testosterone, dihydrotestosterone, 5α-androstane-3α,17β-diol, 5α-androstane-3β,17β-diol, 17α-estradiol, and 17β-estradiol were assessed in the limbic region of young adult (7 months) and aged (24 months) male wild type and triple transgenic AD mice. Age related neuropathological changes in AD brains, such as β-amyloid accumulation and gliosis, were associated with modified levels of specific neuroactive steroids and particularly with changes in the levels of progesterone and testosterone metabolites. The altered levels of neuroactive steroids in aged AD brains might impact on the activation of neuroprotective signaling mediated by classic and nonclassic steroid receptors, like the gamma-aminobuttyric acid (GABA)-A receptor.

Role of estrogen treatment in the management of schizophrenia

Increasing evidence from epidemiological, preclinical and clinical studies suggests that estrogens may exert psychoprotective effects in schizophrenia. Observations of gender differences in the onset and course of schizophrenia have prompted exploration of the effects of estrogen on the CNS. The aim of this paper is to provide an overview of different applications of adjunctive estrogen as a possible treatment for symptoms of schizophrenia in both men and women. Recent trials have suggested that estrogen augmentation therapy may be able to enhance the management of schizophrenia; however, the clinical application of estrogen as a treatment has been limited by potential side effects, the most worrying being breast and uterine cancer in women, and feminization in men. Selective estrogen receptor modulators (SERMs), however, may offer therapeutic benefits for both men and women with schizophrenia without posing threat to breast and uterine tissue and without feminizing effects. The use of estrogen opens up new possibilities for both men and women in the treatment of severe mental illnesses such as schizophrenia. With further preclinical and clinical research, it is hoped that this promising field of hormone modulation can continue to evolve and eventually be translated into real therapeutic potential.

Neuroprotective effects of progesterone in chronic experimental autoimmune encephalomyelitis

Observations so far obtained in experimental autoimmune encephalomyelitis (EAE) have revealed the promising neuroprotective effects exerted by progesterone (PROG). The findings suggest that this neuroactive steroid may potentially represent a therapeutic tool for multiple sclerosis (MS). However, up to now, the efficacy of PROG has been only tested in the acute phase of the disease, whereas it is well known that MS expresses different features depending on the phase of the disease. Accordingly, we have evaluated the effect of PROG treatment in EAE induced in Dark Agouti rats (i.e. an experimental model showing a protracted relapsing EAE). Data obtained 45 days after EAE induction show that PROG treatment exerts a beneficial effect on clinical score, confirming surrogate parameters of spinal cord damage in chronic EAE (i.e. reactive microglia, cytokine levels, activity of the Na(+) ,K(+) -ATPase pump and myelin basic protein expression). An increase of the levels of dihydroprogesterone and isopregnanolone (i.e. two PROG metabolites) was also observed in the spinal cord after PROG treatment. Taken together, these results indicate that PROG is effective in reducing the severity of chronic EAE and, consequently, may have potential with respect to MS treatment.

LXR and TSPO as new therapeutic targets to increase the levels of neuroactive steroids in the central nervous system of diabetic animals

Neuroactive steroid levels are decreased in the central nervous system (CNS) of streptozotocin (STZ) diabetic rats. In agreement, they exert protective effects in this experimental model, counteracting degenerative events occurring in the CNS. Therefore, an interesting therapeutic strategy could be to increase their levels directly in the CNS. In this study we have evaluated whether activation of translocator protein-18kDa (TSPO) or liver X receptors (LXRs) may affect the levels of neuroactive steroids present in the CNS of diabetic and non-diabetic animals. We observed that the treatment with either Ro5-4864 (i.e., a ligand of TSPO) or with GW3965 (i.e., a ligand of LXRs) induced an increase of neuroactive steroids in the spinal cord, the cerebellum and the cerebral cortex of STZ-rats, but not in the CNS of non-pathological animals. Interestingly, the pattern of induction was different among the three CNS areas analyzed and between the two pharmacological tools. In particular, the activation of LXRs might represent a promising neuroprotective strategy, because the treatment with GW3965, at variance to Ro5-4864 treatment, did not induce significant changes in the plasma levels of neuroactive steroids. This suggests that activation of LXRs may selectively increase the CNS levels of neuroactive steroids avoiding possible endocrine side effects exerted by the systemic treatment with these molecules. Interestingly GW3965 treatment induced an increase of dihydroprogesterone in the spinal cord of diabetic animals in association with an increase of myelin basic protein expression. Thus we demonstrated that LXR activation was able to rescue CNS symptoms of diabetes.

Hormones and schizophrenia

PURPOSE OF REVIEW

It is a well established fact that many serious mental illnesses, in particular psychoses such as schizophrenia, may have a significant hormonal aetiological component. This study aims to discuss the oestrogen protection hypothesis of schizophrenia in particular, with an emphasis on findings from the recent literature in support of this theory.

RECENT FINDINGS

Epidemiological and life-cycle data point to significant differences in the incidence and course of schizophrenia between men and women, suggesting a protective role of oestrogen. In-vitro and in-vivo preclinical research has confirmed oestradiol's interactions with central neurotransmitter systems implicated in the pathogenesis of schizophrenia, whereas results from randomized controlled trials investigating the antipsychotic potential of oestrogen have been promising. Research into other neuroactive hormones with possible effects on mental state is a field still in its infancy but is evolving rapidly.

SUMMARY

Schizophrenia and related psychoses are pervasive and debilitating conditions, for which currently available treatments are often only partially effective and entail a high risk of serious side effects. Thus, new therapeutic strategies are needed, and the literature reviewed here suggests that hormones such as oestrogen could be a viable option. It is hoped that, with further research and larger trials, the oestrogen hypothesis can be translated into effective clinical practice.

Gender effect on neurodegeneration and myelin markers in an animal model for multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) varies considerably in its incidence and progression in females and males. In spite of clinical evidence, relatively few studies have explored molecular mechanisms possibly involved in gender-related differences. The present study describes possible cellular- and molecular-involved markers which are differentially regulated in male and female rats and result in gender-dependent EAE evolution and progression. Attention was focused on markers of myelination (MBP and PDGFαR) and neuronal distress and/or damage (GABA synthesis enzymes, GAD65 and GAD67, NGF, BDNF and related receptors), in two CNS areas, i.e. spinal cord and cerebellum, which are respectively severely and mildly affected by inflammation and demyelination. Tissues were sampled during acute, relapse/remission and chronic phases and results were analysed by two-way ANOVA.

RESULTS

1. A strong gender-dependent difference in myelin (MBP) and myelin precursor (PDGFαR) marker mRNA expression levels is observed in control animals in the spinal cord, but not in the cerebellum. This is the only gender-dependent difference in the expression level of the indicated markers in healthy animals; 2. both PDGFαR and MBP mRNAs in the spinal cord and MBP in the cerebellum are down-regulated during EAE in gender-dependent manner; 3. in the cerebellum, the expression profile of neuron-associated markers (GAD65, GAD67) is characterized by a substantial down-regulation during the inflammatory phase of the disease, which does not differ between male and female rats (two-way ANOVA); 4. there is an up-regulation of NGF, trkA and p75 mRNA expression in the early phases of the disease (14 and 21 days post-immunization), which is not different between male and female.

CONCLUSIONS

It is reported herein that the regulation of markers involved in demyelination and neuroprotection processes occurring during EAE, a well-established MS animal model, is gender- and time-dependent. These findings might contribute to gender- and phase disease-based therapy strategies.

Milestones on Steroids and the Nervous System: 10 years of basic and translational research

During the last 10 years, the conference on 'Steroids and Nervous System' held in Torino (Italy) has been an important international point of discussion for scientists involved in this exciting and expanding research field. The present review aims to recapitulate the main topics that have been presented through the various meetings. Two broad areas have been explored: the impact of gonadal hormones on brain circuits and behaviour, as well as the mechanism of action of neuroactive steroids. Relationships among steroids, brain and behaviour, the sexual differentiation of the brain and the impact of gonadal hormones, the interactions of exogenous steroidal molecules (endocrine disrupters) with neural circuits and behaviour, and how gonadal steroids modulate the behaviour of gonadotrophin-releasing hormone neurones, have been the topics of several lectures and symposia during this series of meetings. At the same time, many contributions have been dedicated to the biosynthetic pathways, the physiopathological relevance of neurosteroids, the demonstration of the cellular localisation of different enzymes involved in neurosteroidogenesis, the mechanisms by which steroids may exert some of their effects, both the classical and nonclassical actions of different steroids, the role of neuroactive steroids on neurodegeneration, neuroprotection, and the response of the neural tissue to injury. In these 10 years, this field has significantly advanced and neuroactive steroids have emerged as new potential therapeutic tools to counteract neurodegenerative events.

The role of oestrogen and other hormones in the pathophysiology and treatment of schizophrenia

The theory that many serious mental illnesses, in particular psychoses such as schizophrenia, may have a significant hormonal aetiological component is fast gaining popularity and the support of scientific evidence. Oestrogen in particular has been substantially investigated as a potential mediator of brain function in schizophrenia. Epidemiological and life-cycle data point to significant differences in the incidence and course of schizophrenia between men and women suggests a protective role of oestrogen. In vitro and in vivo preclinical research confirms oestradiol's interactions with central neurotransmitter systems implicated in the pathogenesis of schizophrenia, while results from randomised controlled trials investigating the antipsychotic potential of oestrogen have been positive. Research into other neuroactive hormones with possible effects on mental state is a rapidly evolving field that may hold new promise. Given that schizophrenia and related psychoses are pervasive and debilitating conditions for which currently available treatments are often only partially effective and entail a high risk of serious side-effects, novel therapeutic strategies are needed. The literature reviewed in this paper suggests that hormones such as oestrogen could be a viable option, and it is hoped that with further research and larger trials, the oestrogen hypothesis can be translated into effective clinical practice.

Sex differences in the inflammatory response of primary astrocytes to lipopolysaccharide

Background

Numerous neurological and psychiatric disorders show sex differences in incidence, age of onset, symptomatology or outcome. Astrocytes, one of the glial cell types of the brain, show sex differences in number, differentiation and function. Since astrocytes are involved in the response of neural tissue to injury and inflammation, these cells may participate in the generation of sex differences in the response of the brain to pathological insults. To explore this hypothesis, we have examined whether male and female astrocytes show a different response to an inflammatory challenge and whether perinatal testosterone influences this response.

Methods

Cortical astrocyte cultures were prepared from postnatal day 1 (one day after birth) male or female CD1 mice pups. In addition, cortical astrocyte cultures were also prepared from female pups that were injected at birth with 100 μg of testosterone propionate or vehicle. Cultures were treated for 5 hours with medium containing lipopolysaccharide (LPS) or with control medium. The mRNA levels of IL6, interferon-inducible protein 10 (IP10), TNFα, IL1β, Toll-like receptor 4 (TLR4), steroidogenic acute regulatory protein and translocator protein were assessed by quantitative real-time polymerase chain reaction. Statistical significance was assessed by unpaired t-test or by one-way analysis of variance followed by the Tukey post hoc test.

Results

The mRNA levels of IL6, TNFα and IL1β after LPS treatment were significantly higher in astrocytes derived from male or androgenized females compared to astrocytes derived from control or vehicle-injected females. In contrast, IP10 mRNA levels after LPS treatment were higher in astrocytes derived from control or vehicle-injected females than in those obtained from males or androgenized females. The different response of male and female astrocytes to LPS was due neither to differences in the basal expression of the inflammatory molecules nor to differences in the expression of the LPS receptor TLR4. In contrast, the different inflammatory response was associated with increased mRNA levels of translocator protein, a key steroidogenic regulator, in female astrocytes that were treated with LPS.

Conclusions

Male and female cortical astrocytes respond differentially to an inflammatory challenge and this may be predetermined by perinatal testosterone exposure.

Sex differences in the injured brain

Observations obtained in human and in experimental models clearly demonstrate sex differences in degenerative events occurring in the central nervous system. The present review focuses on potential factors that may contribute to these sex-dimorphic features; in particular, morphological organization of the central nervous system and functional influence by neuroactive steroids, genes, and immune system are considered.

Role of neuroactive steroids in the peripheral nervous system

Several reviews have so far pointed out on the relevant physiological and pharmacological role exerted by neuroactive steroids in the central nervous system. In the present review we summarize observations indicating that synthesis and metabolism of neuroactive steroids also occur in the peripheral nerves. Interestingly, peripheral nervous system is also a target of their action. Indeed, as here reported neuroactive steroids are physiological regulators of peripheral nerve functions and they may also represent interesting therapeutic tools for different types of peripheral neuropathy.