Role of estrogen treatment in the management of schizophrenia

Exploring the physiological role of the G protein-coupled estrogen receptor (GPER) and its associations with human diseases

Estrogen is a group of hormones that collaborate with the nervous system to impact the overall well-being of all genders. It influences many processes, including those occurring in the central nervous system, affecting learning and memory, and playing roles in neurodegenerative diseases and mental disorders. The hormone's action is mediated by specific receptors. Significant roles of classical estrogen receptors, ERα and ERβ, in various diseases were known since many years, but after identifying a structurally and locationally distinct receptor, the G protein-coupled estrogen receptor (GPER), its role in human physiology and pathophysiology was investigated. This review compiles GPER-related information, highlighting its impact on homeostasis and diseases, while putting special attention on functions and dysfunctions of this receptor in neurobiology and biobehavioral processes. Understanding the receptor modulation possibilities is essential for therapy, as disruptions in receptors can lead to diseases or disorders, irrespective of correct estrogen levels. We conclude that studies on the GPER receptor have the potential to develop therapies that regulate estrogen and positively impact human health.

Gender-related Characteristics of Oxidative Stress Severity and Cognitive Impairment in Patients With Schizophrenia

The gender specificity of the clinical and psychopathological features of schizophrenia is an important factor in this disease. Gender features of neurocognitive deficit in schizophrenia and associated functional and structural disorders of the brain activity are of particular interest to researchers. There are several potential pathogenetic factors of this disease associated with gender, one of which is considered to be oxidative stress. Stress-induced cell death in the prefrontal and anterior frontal regions and reduced brain volume in these regions lead to cognitive and executive decline in patients with schizophrenia. Despite the great interest in the gender factor in schizophrenia pathogenesis, there are currently very few studies on gender differences in the severity of redox imbalance in patients with schizophrenia and their association with neurocognitive deficit. The aim of the study was to reveal the gender specificity of oxidative stress severity in patients with schizophrenia and assess its association with the severity of neurocognitive deficit. The study included 125 patients with schizophrenia and 75 sex- and age-matched healthy volunteers. Sociodemographic and clinical data were studied. Cognitive functions were evaluated using BACS. Blood samples were taken for biochemical studies of the levels of reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) in erythrocyte hemolysate, malonic dialdehyde (MDA), aldehyde-2,4-dinitrophenylhydrazones (ADNPH), ketone-2,4-dinitrophenylhydrazones (KDNPH) in plasma. Levels of oxidative stress markers were assessed by spectrophotometric method. In a sample of patients with schizophrenia, a statistically significantly higher activity of CAT was revealed among women compared to men (T=2.25; p=0.025), however, it was lower than in healthy volunteers. But, at the same time, a higher concentration of protein peroxidation products was found in the peripheral blood of women than in men (ADNPH MCO: T=2.52; p=0.013; KDNPH MCO: Z=-2.26; p=0.017). In the group of healthy volunteers, in contrast to patients with schizophrenia, gender differences in markers of oxidative stress were not found. In women with schizophrenia, single correlations were found between the level of the lipid peroxidation product MDA and the test scores for verbal memory (R=-0.36; p=0.006) and working memory (R=-0.36; p=0.006), antioxidant enzyme activity SOD and motor skills (R=-0.26; p=0.047). In men, on the contrary, multiple correlations of both antioxidants and, mainly, products of lipid and protein peroxidation with cognitive functions assessed using BACS were found. Despite the fact that oxidative stress is more pronounced in women than in men with schizophrenia, associations of redox imbalance with neurocognitive deficit in women is much less pronounced than in men.

Sex representation in neurodegenerative and psychiatric disorders' preclinical and clinical studies

Many studies show the importance of biological sex for the onset, progression, and response to treatment in brain disorders. In line with these reports, health agencies have requested that all trials, both at the clinical and preclinical level, use a similar number of male and female subjects to correctly interpret the results. Despite these guidelines, many studies still tend to be unbalanced in the use of male and female subjects. In this review we consider three neurodegenerative disorders: Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, and three psychiatric disorders: Depression, Attention Deficit Hyperactivity Disorder, and Schizophrenia. These disorders were chosen because of their prevalence and their recognized sex-specific differences in onset, progression, and response to treatment. Alzheimer's disease and Depression demonstrate higher prevalence in females, whereas Parkinson's Disease, Amyotrophic lateral sclerosis, Attention Deficit Hyperactivity Disorder, and schizophrenia show higher prevalence in males. Results from preclinical and clinical studies examining each of these disorders revealed sex-specific differences in risk factors, diagnostic biomarkers, and treatment response and efficacy, suggesting a role for sex-specific therapies in neurodegenerative and neuropsychiatric disorders. However, the qualitative analysis of the percentage of males and females enrolled in clinical trials in the last two decades shows that for most of the disorders, there is still a sex bias in the patients' enrolment.

The Hypothalamic-Pituitary-Gonadal Axis in Men with Schizophrenia

Schizophrenia is a severe mental disorder with a chronic, progressive course. The etiology of this condition is linked to the interactions of multiple genes and environmental factors. The earlier age of onset of schizophrenia, the higher frequency of negative symptoms in the clinical presentation, and the poorer response to antipsychotic treatment in men compared to women suggests the involvement of sex hormones in these processes. This article aims to draw attention to the possible relationship between testosterone and some clinical features in male schizophrenic patients and discuss the complex nature of these phenomena based on data from the literature. PubMed, Web of Science, and Google Scholar databases were searched to select the papers without limiting the time of the publications. Hormone levels in the body are regulated by many organs and systems, and take place through the neuroendocrine, hormonal, neural, and metabolic pathways. Sex hormones play an important role in the development and function of the organism. Besides their impact on secondary sex characteristics, they influence brain development and function, mood, and cognition. In men with schizophrenia, altered testosterone levels were noted. In many cases, evidence from available single studies gave contradictory results. However, it seems that the testosterone level in men affected by schizophrenia may differ depending on the phase of the disease, types of clinical symptoms, and administered therapy. The etiology of testosterone level disturbances may be very complex. Besides the impact of the illness (schizophrenia), stress, and antipsychotic drug-induced hyperprolactinemia, testosterone levels may be influenced by, i.a., obesity, substances of abuse (e.g., ethanol), or liver damage.

Estrogen receptors observed at extranuclear neuronal sites and in glia in the nucleus accumbens core and shell of the female rat: Evidence for localization to catecholaminergic and GABAergic neurons

Estrogens affect dopamine-dependent diseases/behavior and have rapid effects on dopamine release and receptor availability in the nucleus accumbens (NAc). Low levels of nuclear estrogen receptor (ER) α and ERβ are seen in the NAc, which cannot account for the rapid effects of estrogens in this region. G-protein coupled ER 1 (GPER1) is observed at low levels in the NAc shell, which also likely does not account for the array of estrogens' effects in this region. Prior studies demonstrated membrane-associated ERs in the dorsal striatum; these experiments extend those findings to the NAc core and shell. Single- and dual-immunolabeling electron microscopy determined whether ERα, ERβ, and GPER1 are at extranuclear sites in the NAc core and shell and whether ERα and GPER1 were localized to catecholaminergic or γ-aminobutyric acid-ergic (GABAergic) neurons. All three ERs are observed, almost exclusively, at extranuclear sites in the NAc, and similarly distributed in the core and shell. ERα, ERβ, and GPER1 are primarily in axons and axon terminals suggesting that estrogens affect transmission in the NAc via presynaptic mechanisms. About 10% of these receptors are found on glia. A small proportion of ERα and GPER1 are localized to catecholaminergic terminals, suggesting that binding at these ERs alters release of catecholamines, including dopamine. A larger proportion of ERα and GPER1 are localized to GABAergic dendrites and terminals, suggesting that estrogens alter GABAergic transmission to indirectly affect dopamine transmission in the NAc. Thus, the localization of ERs could account for the rapid effects of estrogen in the NAc.

Sex Differences in Psychosis: Focus on Animal Models

Most psychiatric illnesses, such as schizophrenia, show profound sex differences in incidence, clinical presentation, course, and outcome. Fortunately, more recently the literature on sex differences and (to a lesser extent) effects of sex steroid hormones is expanding, and in this review we have focused on such studies in psychosis, both from a clinical/epidemiological and preclinical/animal model perspective. We begin by briefly describing the clinical evidence for sex differences in schizophrenia epidemiology, symptomatology, and pathophysiology. We then detail sex differences and sex hormone effects in behavioral animal models of psychosis, specifically psychotropic drug-induced locomotor hyperactivity and disruption of prepulse inhibition. We expand on the preclinical data to include developmental and genetic models of psychosis, such as the maternal immune activation model and neuregulin transgenic animals, respectively. Finally, we suggest several recommendations for future studies, in order to facilitate a better understanding of sex differences in the development of psychosis.

The Role of Estrogen Receptors and Their Signaling across Psychiatric Disorders

Increasing evidence suggests estrogen and estrogen signaling pathway disturbances across psychiatric disorders. Estrogens are not only crucial in sexual maturation and reproduction but are also highly involved in a wide range of brain functions, such as cognition, memory, neurodevelopment, and neuroplasticity. To add more, the recent findings of its neuroprotective and anti-inflammatory effects have grown interested in investigating its potential therapeutic use to psychiatric disorders. In this review, we analyze the emerging literature on estrogen receptors and psychiatric disorders in cellular, preclinical, and clinical studies. Specifically, we discuss the contribution of estrogen receptor and estrogen signaling to cognition and neuroprotection via mediating multiple neural systems, such as dopaminergic, serotonergic, and glutamatergic systems. Then, we assess their disruptions and their potential implications for pathophysiologies in psychiatric disorders. Further, in this review, current treatment strategies involving estrogen and estrogen signaling are evaluated to suggest a future direction in identifying novel treatment strategies in psychiatric disorders.

Friend or enemy? Review of 17β-HSD10 and its role in human health or disease

17β-hydroxysteroid dehydrogenase (17β-HSD10) is a multifunctional human enzyme with important roles both as a structural component and also as a catalyst of many metabolic pathways. This mitochondrial enzyme has important functions in the metabolism, development and aging of the neural system, where it is involved in the homeostasis of neurosteroids, especially in regard to estradiol, changes in which make it an essential part of neurodegenerative pathology. These roles therefore, indicate that 17β-HSD10 may be a possible druggable target for neurodegenerative diseases including Alzheimer's disease (AD), and in hormone-dependent cancer. The objective of this review was to provide a summary about physiological functions and pathological roles of 17β-HSD10 and the modulators of its activity.

Sex differences in schizophrenia, bipolar disorder, and post-traumatic stress disorder: Are gonadal hormones the link?

In this review, we describe the sex differences in prevalence, onset, symptom profiles, and disease outcome that are evident in schizophrenia, bipolar disorder, and post-traumatic stress disorder. Women with schizophrenia tend to exhibit less disease impairment than men. By contrast, women with post-traumatic stress disorder are more affected than men. The most likely candidates to explain these sex differences are gonadal hormones. This review details the clinical evidence that oestradiol and progesterone are dysregulated in these psychiatric disorders. Notably, existing data on oestradiol, and to a lesser extent, progesterone, suggest that low levels of these hormones may increase the risk of disease development and worsen symptom severity. We argue that future studies require a more inclusive, considered analysis of gonadal steroid hormones and the intricacies of the interactions between them, with methodological rigour applied, to enhance our understanding of the roles of steroid hormones in psychiatric disorders. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Both Val158Met Polymorphism of Catechol-O-Methyltransferase Gene and Menstrual Cycle Affect Prepulse Inhibition but Not Attentional Modulation of Prepulse Inhibition in Younger-Adult Females

Prepulse inhibition (PPI) can be modulated by both the Val158Met (rs4680) polymorphism of the Catechol-O-Methyltransferase (COMT) gene and the menstrual-cycle-related hormone fluctuations, each of which affects the subcortical/cortical dopamine metabolism. PPI can also be modulated by attention. The attentional modulation of PPI (AMPPI) is sensitive to psychoses. Whether the Val158Met polymorphism affects the AMPPI in female adults at different menstrual-cycle phases is unknown. This study examined whether AMPPI and/or PPI are affected by the Val158Met polymorphism in 177 younger-adult females whose menstrual cycles were mutually different across the menstruation, proliferative, or secretory phases. The AMPPI was evaluated by comparing PPI under the condition of the auditory precedence-effect-induced perceptual spatial separation between the prepulse stimulus and a masking noise (PPI_PSS) against that under the condition of the precedence-effect-induced perceptual spatial co-location (PPI_PSC). The results showed that both the menstrual cycle and the COMT Val158Met polymorphism affected both PPI_PSC and PPI_PSS, but not the AMPPI (difference between PPI_PSS and PPI_PSC). Moreover, throughout the menstrual cycle, both PPI_PSC and PPI_PSS decreased monotonously in Val/Val-carrier participants. However, the decreasing pattern was not overserved in either Met/Met-carrier or Met/Val-carrier participants. Thus, in healthy younger-adult females, PPI_PSC and PPI_PSS, but not the AMPPI, is vulnerable to changes of ovarian hormones, and the COMT Val158Met polymorphism also has a modulating effect on this menstrual-cycle-dependent PPI variation. In contrast, the AMPPI seems to be more steadily trait-based, less vulnerable to ovarian hormone fluctuations, and may be useful in assisting the diagnosis of schizophrenia in female adults.

Women who suffer from schizophrenia: Critical issues

Many brain diseases, including schizophrenia, affect men and women unequally - either more or less frequently, or at different times in the life cycle, or to varied degrees of severity. With updates from recent findings, this paper reviews the work of my research group over the last 40 years and underscores issues that remain critical to the optimal care of women with schizophrenia, issues that overlap with, but are not identical to, the cares and concerns of men with the same diagnosis. Clinicians need to be alert not only to the overarching needs of diagnostic groups, but also to the often unique needs of women and men.

Adjunctive raloxifene for postmenopausal women with schizophrenia: A meta-analysis of randomized, double-blind, placebo-controlled trials

OBJECTIVE

Raloxifene, a selective estrogen receptor modulator, has been used in treating postmenopausal women with schizophrenia with inconsistent results. This meta-analysis of randomized, double-blind, placebo-controlled trials (RCTs) examined its efficacy and safety for postmenopausal women with schizophrenia.

METHOD

Standardized mean differences (SMDs) and risk ratio (RR) together with their 95% confidence intervals (CIs) were calculated using the random effects model.

RESULTS

The meta-analysis included 5 RCTs (n = 240) comparing raloxifene (n = 125, 60 or 120 mg/day) with placebo (n = 115). Adjunctive raloxifene outperformed placebo with regard to the Positive and Negative Syndrome Scale (PANSS) total psychopathology [n = 240, SMD:-0.64 (95%CI:-0.90, -0.37), P < 0.00001; I² = 0%], positive symptoms [n = 240, SMD:-0.49 (95%CI:-0.81, -0.16), P = 0.003; I² = 29%], negative symptoms [n = 240, SMD:-0.43 (95%CI:-0.68, -0.17), P = 0.001; I² = 0%], and general psychopathology scores [n = 240, SMD:-0.66 (95%CI:-0.92, -0.39), P < 0.00001; I² = 0%]. Both groups had similar rates of adverse events and discontinuation (n = 159, RR: 1.32 (95%CI: 0.65, 2.70), P = 0.44, I² = 0%).

CONCLUSION

Adjunctive raloxifene appears to be effective and safe in improving psychotic symptoms for postmenopausal women with schizophrenia. Review registration: CRD 42017059946.

Evaluation of estrogen and G protein-coupled estrogen receptor 1 (GPER) levels in drug-naïve patients with attention deficit hyperactivity disorder (ADHD)

Estrogen has a crucial role in the regulation of reproductive and neuroendocrine function and exerts its effects through two classes of receptors, nuclear and membrane estrogen receptors (mERs). G protein-coupled estrogen receptor 1 (GPER) is a member of mERs, and despite limited research on the levels of GPER in patients with psychiatric diseases, a role of GPER in such conditions has been suggested. Here we evaluated serum estrogen and GPER levels in children with attention deficit hyperactivity disorder (ADHD) in relation to their age- and gender-matched healthy controls. A total of 82 children were included in the study, 47 drug- naïve patients with ADHD (age: 6-12 years; male/female: 34/13) and 35 healthy controls (age: 6-12 years; male/female: 19/16). The subgroups according to ADHD types were inattentive, hyperactive/impulsive, and combined. Serum estrogen was measured using an immunoassay system, while serum GPER was determined using a commercial sandwich enzyme-linked immunosorbent assay kit. Estrogen levels in children with ADHD were similar as in control group, while GPER levels were significantly lower in ADHD group compared to controls (p < 0.05). Logistic regression analysis showed a significant association between GPER levels and ADHD (p < 0.05), and no association between estrogen levels and ADHD (p > 0.05). No significant differences were found in GPER and estrogen levels between ADHD subgroups (p > 0.05). To the best of our knowledge, this study is the first to investigate estrogen and GPER levels in ADHD. Our preliminary findings suggest a relationship between serum GPER levels and ADHD, and this should be further investigated.

Raloxifene as an adjunctive treatment for postmenopausal women with schizophrenia: a meta-analysis of randomized controlled trials

The aim of this study is to meta-analytically assess the efficacy and safety of adjunctive raloxifene for postmenopausal women with schizophrenia. Six studies with 440 patients, including 225 (51.14%) patients on raloxifene and 215 (48.86%) on placebo who completed 13.71 ± 5.09 weeks of treatment, were included in this study. Meta-analysis of Positive and Negative Syndrome Scale total scores and positive, negative, and general symptom scores [standard mean difference (SMD) -0.22 to -0.55, 95% confidence interval (CI) -1.01 to -0.02, p = 0.04-0.01; I ² = 74-79%] revealed an advantage of adjunctive raloxifene treatment over placebo treatment. There was no significant difference regarding discontinuation rate [risk ratio (RR) = 1.38, p = 0.51] and adverse drug reactions (RR = 1.27, p = 0.57) between the two groups. This meta-analysis showed that adjunctive raloxifene appears to be efficacious and safe for postmenopausal women with schizophrenia. Moreover, raloxifene may be efficacious for patients with less severe symptoms. Future studies with a large sample size are needed to confirm these findings.

Translational Significance of Selective Estrogen Receptor Modulators in Psychiatric Disorders

Accumulating data from various clinical trial studies suggests that adjuvant therapy with ovarian hormones (estrogens) could be effective in reducing cognitive deficit and psychopathological symptoms in women with psychiatric disorders. However, estrogen therapy poses serious limitations and health issues including feminization in men and increased risks of thromboembolism, hot flashes, breast hyperplasia, and endometrium hyperplasia when used for longer duration in older women (aged ≥ 60 years) or in women who have genetic predispositions. On the other hand, selective estrogen receptor modulators (SERMs), which may (or may not) carry some risks of hot flashes, thromboembolism, breast hyperplasia, and endometrial hyperplasia, are generally devoid of feminization effect. In clinical trial studies, adjuvant therapy with tamoxifen, a triphenylethylene class of SERM, has been found to reduce the frequency of manic episodes in patients with bipolar disorder, whereas addition of raloxifene, a benzothiophene class of SERM, to regular doses of antipsychotic drugs has been found to reduce cognitive deficit and psychological symptoms in men and women with schizophrenia, including women with treatment refractory psychosis. These outcomes together with potent neurocognitive, neuroprotective, and cardiometabolic properties suggest that SERMs could be the potential targets for designing effective and safer therapies for psychiatric disorders.

Investigating the link between drug-naive first episode psychoses (FEPs), weight gain abnormalities and brain structural damages: Relevance and implications for therapy

Evidence suggests that obesity and overweight may be associated with severe brain structural abnormalities and poor cognitive and functional outcomes in the general population. Despite these observations and the high prevalence of weight gain abnormalities in patients with psychosis spectrum disorders (PSDs), no studies have investigated the impact that these metabolic disturbances may have on brain structures and development in the earliest stages of PSDs. In the present review we shed light on the association between weight gain and brain structural abnormalities that may affect the course of illness in drug-naïve FEPs. Given the lack of studies directly investigating this issue, we firstly identified and critically evaluated the literature assessing weight gain abnormalities and gray or white matter (GM, WM) volumes (either globally or in specific regions of interest) in otherwise healthy obese/overweight adolescents and young adults. We then compared the results of this systematic review with those of two recent meta-analysis investigating GM and WM abnormalities in drug-naïve FEPs. Weight gain in otherwise healthy subjects was consistently associated with frontal and temporal GM atrophy and with reduced integrity of WM in the corpus callosum. Of relevance, all these brain regions are affected in drug-naïve FEPs, and their integrity is associated with clinical, cognitive and functional outcomes. The underlying mechanisms that may explain the association between weight gain, adiposity, and brain damage in both healthy subjects and drug-naïve FEPs are widely discussed. On the basis of this knowledge, we tried: a) to deduce an integrative model for the development of obesity in psychosis spectrum disorders; b) to identify the key vulnerability factors underlying the association between weight gain and psychosis; c) to provide information on new potential targets of intervention.

Effects of immune activation during early or late gestation on schizophrenia-related behaviour in adult rat offspring

Maternal exposure to infectious agents during gestation has been identified as a significant risk factor for schizophrenia. Using a mouse model, past work has demonstrated that the gestational timing of the immune-activating event can impact the behavioural phenotype and expression of dopaminergic and glutamatergic neurotransmission markers in the offspring. In order to determine the inter-species generality of this effect to rats, another commonly used model species, the current study investigated the impact of a viral mimetic Poly (I:C) at either an early (gestational day 10) or late (gestational day 19) time-point on schizophrenia-related behaviour and neurotransmitter receptor expression in rat offspring. Exposure to Poly (I:C) in late, but not early, gestation resulted in transient impairments in working memory. In addition, male rats exposed to maternal immune activation (MIA) in either early or late gestation exhibited sensorimotor gating deficits. Conversely, neither early nor late MIA exposure altered locomotor responses to MK-801 or amphetamine. In addition, increased dopamine 1 receptor mRNA levels were found in the nucleus accumbens of male rats exposed to early gestational MIA. The findings from this study diverge somewhat from previous findings in mice with MIA exposure, which were often found to exhibit a more comprehensive spectrum of schizophrenia-like phenotypes in both males and females, indicating potential differences in the neurodevelopmental vulnerability to MIA exposure in the rat with regards to schizophrenia related changes.

Estrogens in Male Physiology

Estrogens have historically been associated with female reproduction, but work over the last two decades established that estrogens and their main nuclear receptors (ESR1 and ESR2) and G protein-coupled estrogen receptor (GPER) also regulate male reproductive and nonreproductive organs. 17β-Estradiol (E2) is measureable in blood of men and males of other species, but in rete testis fluids, E2 reaches concentrations normally found only in females and in some species nanomolar concentrations of estrone sulfate are found in semen. Aromatase, which converts androgens to estrogens, is expressed in Leydig cells, seminiferous epithelium, and other male organs. Early studies showed E2 binding in numerous male tissues, and ESR1 and ESR2 each show unique distributions and actions in males. Exogenous estrogen treatment produced male reproductive pathologies in laboratory animals and men, especially during development, and studies with transgenic mice with compromised estrogen signaling demonstrated an E2 role in normal male physiology. Efferent ductules and epididymal functions are dependent on estrogen signaling through ESR1, whose loss impaired ion transport and water reabsorption, resulting in abnormal sperm. Loss of ESR1 or aromatase also produces effects on nonreproductive targets such as brain, adipose, skeletal muscle, bone, cardiovascular, and immune tissues. Expression of GPER is extensive in male tracts, suggesting a possible role for E2 signaling through this receptor in male reproduction. Recent evidence also indicates that membrane ESR1 has critical roles in male reproduction. Thus estrogens are important physiological regulators in males, and future studies may reveal additional roles for estrogen signaling in various target tissues.

Women and schizophrenia: planning for the future

The aim of this narrative review is to provide readers with a summary of the recent literature on women and schizophrenia and to address commonly asked questions about the role of gender in this illness. Important gender distinctions were found in the knowledge base around schizophrenia, particularly in the areas of symptom onset, hormonal and immune effects, and antipsychotic drug kinetics and their consequences. We also discuss and address commonly asked questions about gender and schizophrenia. This review concludes that gender differences influence the effectiveness of various treatments and need to be taken into account when planning comprehensive care services for individuals with schizophrenia.

Interactions between estradiol and haloperidol on perseveration and reversal learning in amphetamine-sensitized female rats

There are sex differences associated with schizophrenia, as women exhibit later onset of the disorder, less severe symptomatology, and better response to antipsychotic medications. Estrogens are thought to play a role in these sex differences; estrogens facilitate the effects of antipsychotic medications to reduce the positive symptoms of schizophrenia, but it remains unclear whether estrogens protect against the cognitive symptoms of this disorder. Amphetamine sensitization is used to model some symptoms of schizophrenia in rats, including cognitive deficits like excessive perseveration and slower reversal learning. In this experiment female rats were administered a sensitizing regimen of amphetamine to mimic these cognitive symptoms. They were ovariectomized and administered either low or high estradiol replacement as well as chronic administration of the antipsychotic haloperidol, and were assessed in tests of perseveration and reversal learning. Results of these experiments demonstrated that, in amphetamine-sensitized rats, estradiol alone does not affect perseveration or reversal learning. However, low estradiol facilitates a 0.25mg/day dose of haloperidol to reduce perseveration and improve reversal learning. Combined high estradiol and 0.25mg/day haloperidol has no effect on perseveration or reversal learning, but high estradiol facilitates the effects of 0.13mg/day haloperidol to reduce perseveration and improve reversal learning. Thus, in amphetamine-sensitized female rats, 0.25mg/day haloperidol only improved perseveration and reversal learning when estradiol was low, while 0.13mg/day haloperidol only improved these cognitive processes when estradiol was high. These findings suggest that estradiol facilitates the effects of haloperidol to improve perseveration and reversal learning in a dose-dependent manner.

Estrogen Signaling as a Therapeutic Target in Neurodevelopmental Disorders

Estrogens, the primary female sex hormones, were originally characterized through their important role in sexual maturation and reproduction. However, recent studies have shown that estrogens play critical roles in a number of brain functions, including cognition, learning and memory, neurodevelopment, and adult neuroplasticity. A number of studies from both clinical as well as preclinical research suggest a protective role of estrogen in neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia. Alterations in the levels of estrogen receptors have been found in subjects with ASD or schizophrenia, and adjunctive estrogen therapy has been shown to be effective in enhancing the treatment of schizophrenia. This review summarizes the findings on the role of estrogen in the pathophysiology of neurodevelopmental disorders with a focus on ASD and schizophrenia. We also discuss the potential of estrogen as a therapeutic target in the above disorders.

L-Type Calcium Channels Modulation by Estradiol

Voltage-gated calcium channels are key regulators of brain function, and their dysfunction has been associated with multiple conditions and neurodegenerative diseases because they couple membrane depolarization to the influx of calcium-and other processes such as gene expression-in excitable cells. L-type calcium channels, one of the three major classes and probably the best characterized of the voltage-gated calcium channels, act as an essential calcium binding proteins with a significant biological relevance. It is well known that estradiol can activate rapidly brain signaling pathways and modulatory/regulatory proteins through non-genomic (or non-transcriptional) mechanisms, which lead to an increase of intracellular calcium that activate multiple kinases and signaling cascades, in the same way as L-type calcium channels responses. In this context, estrogens-L-type calcium channels signaling raises intracellular calcium levels and activates the same signaling cascades in the brain probably through estrogen receptor-independent modulatory mechanisms. In this review, we discuss the available literature on this area, which seems to suggest that estradiol exerts dual effects/modulation on these channels in a concentration-dependent manner (as a potentiator of these channels in pM concentrations and as an inhibitor in nM concentrations). Indeed, estradiol may orchestrate multiple neurotrophic responses, which open a new avenue for the development of novel estrogen-based therapies to alleviate different neuropathologies. We also highlight that it is essential to determine through computational and/or experimental approaches the interaction between estradiol and L-type calcium channels to assist these developments, which is an interesting area of research that deserves a closer look in future biomedical research.

Neurocognitive, Neuroprotective, and Cardiometabolic Effects of Raloxifene: Potential for Improving Therapeutic Outcomes in Schizophrenia

Raloxifene is a selective estrogen receptor modulator that has been approved for treating osteoporosis and breast cancer in high-risk postmenopausal women. However, recent evidence suggests that raloxifene adjunct therapy improves cognition and reduces symptom severity in men and women with schizophrenia. In animal models, raloxifene increases forebrain neurogenesis and enhances working memory and synaptic plasticity. It may consequently repair the neuronal and synaptic connectivity that is disrupted in schizophrenia. It also reduces oxidative stress and neuroinflammation, which are potent etiological factors in the neuropathology of schizophrenia. Furthermore, in postmenopausal women, raloxifene reduces the risks for atherosclerosis, diabetes mellitus, and weight gain, which are serious adverse effects associated with long-term antipsychotic treatment in schizophrenia; therefore, it may improve the safety and efficacy of antipsychotic drugs. In this review, recent insights into the neurocognitive, neuroprotective, and cardiometabolic effects of raloxifene in relation to therapeutic outcomes in schizophrenia are discussed.

Sex/gender differences in the brain and cognition in schizophrenia

The early conceptualizations of schizophrenia have noted some sex/gender differences in epidemiology and clinical expression of the disorder. Over the past few decades, the interest in differences between male and female patients has expanded to encompass brain morphology and neurocognitive function. Despite some variability and methodological shortcomings, a few patterns emerge from the available literature. Most studies of gross neuroanatomy show more enlarged ventricles and smaller frontal lobes in men than in women with schizophrenia; finding reflecting normal sexual dimorphism. In comparison, studies of brain asymmetry and specific corticolimbic structures, suggest a disturbance in normal sexual dimorphism. The neurocognitive findings are somewhat consistent with this picture. Studies of cognitive functions mediated by the lateral frontal network tend to show sex differences in patients which are in the same direction as those observed in the general population, whereas studies of processes mediated by the corticolimbic system more frequently reveal reversal of normal sexual dimorphisms. These trends are faint and future research would need to delineate neurocognitive differences between men and women with various subtypes of schizophrenia (e.g., early versus late onset), while taking into consideration hormonal status and gender of tested participants.

Schizophrenia and the influence of male gender

Adolescent boys are the demographic group most likely to receive a diagnosis of schizophrenia. Before adulthood, boys accumulate more potential brain hazards than girls, and this may predispose them to disordered neurodevelopment during adolescence. Hormonal and immune gender differences that emerge at this time likely play an additional and significant role. Very recently, gender differences can be examined even before the onset of full-blown illness, in individuals at "clinically high risk."

Raloxifene trial in postmenopausal woman with treatment-resistant schizophrenia

Raloxifene augmentation in postmenopausal women with schizophrenia has shown promising results. Younger patients diagnosed as treatment-resistant schizophrenia and treated with raloxifene (120 mg/day) have reported significant improvement in symptoms. This case highlights how raloxifene, a selective estrogen receptor modulator (SERM), can play a major role in alleviating positive and negative symptoms in postmenopausal women with treatment-resistant schizophrenia.

A Role for Estrogen in Schizophrenia: Clinical and Preclinical Findings

Gender differences in schizophrenia have been extensively researched and it is being increasingly accepted that gonadal steroids are strongly attributed to this phenomenon. Of the various hormones implicated, the estrogen hypothesis has been the most widely researched one and it postulates that estrogen exerts a protective effect by buffering females against the development and severity of the illness. In this review, we comprehensively analyse studies that have investigated the effects of estrogen, in particular 17β-estradiol, in clinical, animal, and molecular research with relevance to schizophrenia. Specifically, we discuss the current evidence on estrogen dysfunction in schizophrenia patients and review the clinical findings on the use of estradiol as an adjunctive treatment in schizophrenia patients. Preclinical research that has used animal models and molecular probes to investigate estradiol's underlying protective mechanisms is also substantially discussed, with particular focus on estradiol's impact on the major neurotransmitter systems implicated in schizophrenia, namely, the dopamine, serotonin, and glutamate systems.

Neurodevelopmental Animal Models Reveal the Convergent Role of Neurotransmitter Systems, Inflammation, and Oxidative Stress as Biomarkers of Schizophrenia: Implications for Novel Drug Development

Schizophrenia is a life altering disease with a complex etiology and pathophysiology, and although antipsychotics are valuable in treating the disorder, certain symptoms and/or sufferers remain resistant to treatment. Our poor understanding of the underlying neuropathological mechanisms of schizophrenia hinders the discovery and development of improved pharmacological treatment, so that filling these gaps is of utmost importance for an improved outcome. A vast amount of clinical data has strongly implicated the role of inflammation and oxidative insults in the pathophysiology of schizophrenia. Preclinical studies using animal models are fundamental in our understanding of disease development and pathology as well as the discovery and development of novel treatment options. In particular, social isolation rearing (SIR) and pre- or postnatal inflammation (PPNI) have shown great promise in mimicking the biobehavioral manifestations of schizophrenia. Furthermore, the "dual-hit" hypothesis of schizophrenia states that a first adverse event such as genetic predisposition or a prenatal insult renders an individual susceptible to develop the disease, while a second insult (e.g., postnatal inflammation, environmental adversity, or drug abuse) may be necessary to precipitate the full-blown syndrome. Animal models that emphasize the "dual-hit" hypothesis therefore provide valuable insight into understanding disease progression. In this Review, we will discuss SIR, PPNI, as well as possible "dual-hit" animal models within the context of the redox-immune-inflammatory hypothesis of schizophrenia, correlating such changes with the recognized monoamine and behavioral alterations of schizophrenia. Finally, based on these models, we will review new therapeutic options, especially those targeting immune-inflammatory and redox pathways.

Associations between DNA methylation and schizophrenia-related intermediate phenotypes - a gene set enrichment analysis

Multiple genetic approaches have identified microRNAs as key effectors in psychiatric disorders as they post-transcriptionally regulate expression of thousands of target genes. However, their role in specific psychiatric diseases remains poorly understood. In addition, epigenetic mechanisms such as DNA methylation, which affect the expression of both microRNAs and coding genes, are critical for our understanding of molecular mechanisms in schizophrenia. Using clinical, imaging, genetic, and epigenetic data of 103 patients with schizophrenia and 111 healthy controls of the Mind Clinical Imaging Consortium (MCIC) study of schizophrenia, we conducted gene set enrichment analysis to identify markers for schizophrenia-associated intermediate phenotypes. Genes were ranked based on the correlation between DNA methylation patterns and each phenotype, and then searched for enrichment in 221 predicted microRNA target gene sets. We found the predicted hsa-miR-219a-5p target gene set to be significantly enriched for genes (EPHA4, PKNOX1, ESR1, among others) whose methylation status is correlated with hippocampal volume independent of disease status. Our results were strengthened by significant associations between hsa-miR-219a-5p target gene methylation patterns and hippocampus-related neuropsychological variables. IPA pathway analysis of the respective predicted hsa-miR-219a-5p target genes revealed associated network functions in behavior and developmental disorders. Altered methylation patterns of predicted hsa-miR-219a-5p target genes are associated with a structural aberration of the brain that has been proposed as a possible biomarker for schizophrenia. The (dys)regulation of microRNA target genes by epigenetic mechanisms may confer additional risk for developing psychiatric symptoms. Further study is needed to understand possible interactions between microRNAs and epigenetic changes and their impact on risk for brain-based disorders such as schizophrenia.

Evidence of a sex-dependent restrictive epigenome in schizophrenia

When compared to women, men have a higher incidence of schizophrenia, with increases in negative and cognitive symptoms, and an overall poorer disease course. Schizophrenia is conceptualized as a disorder of aberrant gene transcription and regulation. Thus, epigenetics, the study of environmentally induced changes in gene regulation, could advance our understanding of the molecular underpinnings of schizophrenia. Peripheral histone methyltransferase (HMT) mRNA levels have been previously shown to be significantly increased in patients with schizophrenia and correlate with symptomology. In this independent study, peripheral lymphocytes were extracted and clinical symptoms were measured on 74 participants, (40 patients with schizophrenia (19 women, 21 men) and 34 healthy individuals (19 women, 15 men)). HMT (G9α, SETDB1 and GLP) mRNA levels and their resulting histone modification H3K9me2 were measured with RT-PCR and ELISA respectively. Plasma estradiol levels were also measured via ELISA and correlated with HMT mRNA. Clinical symptoms were measured utilizing the Positive and Negative Syndrome Scale (PANSS) and the Heinrichs Carpenter Quality of Life Scale (QLS). The results indicate that men with schizophrenia expressed the highest levels of G9α, SETDB1 mRNA and H3K9me2 protein levels. Additionally, higher levels of symptom presentation and an overall poorer quality of life were correlated with higher HMT mRNA and H3K9me2 protein levels in a sex-dependent pattern. These data support the hypothesis of a sex-dependent restrictive epigenome contributing towards the etiology of schizophrenia. The histone methyltransferases measured here could be potential future therapeutic targets for small molecule pharmacology.

Raloxifene adjunctive therapy for postmenopausal women suffering from chronic schizophrenia: a randomized double-blind and placebo controlled trial

Background

Cumulative evidence from epidemiological, preclinical and clinical studies suggests estrogens may have psychoprotective effects in schizophrenic patients. Selective Estrogen Receptor Modulators could have therapeutic benefits in schizophrenia for both sexes without being hazardous to gynecological tissues or having feminizing effects. Few studies have been conducted regarding the effects of raloxifene on postmenopausal women suffering from schizophrenia. We conducted this placebo-controlled trial to compare the add-on effect of raloxifene to risperidone versus risperidone with placebo.

Methods

This was an 8-week, parallel-group, placebo-controlled trial undertaken at two universities affiliated psychiatric Hospitals in Iran. Forty-six postmenopausal women with the definite diagnosis of schizophrenia were enrolled in the study. Patients received risperidone (6 mg/day in 3 divided doses) combined with either placebo (N = 23) or 120 mg/day of raloxifene (N = 23) for 8 weeks. Patients were assessed by a psychiatrist at baseline and at 2 and 8 weeks after the start of medical therapy. Efficacy was defined as the change from baseline to endpoint in score on Positive and Negative Syndrome Scale (PANSS).

Results

For PANSS scores, the main effect comparing two types of intervention was not significant [F (1, 48) = 1.77, p = 0.18]. For positive subscale scores, there was marginal significant interaction between intervention type and time [F (2, 47) = 2.93, p = 0.06] and there was substantial main effect for time [F (2, 47) = 24.39, p = 0.001] within both groups showing reduction in positive subscale scores across the three time periods. In addition, the main effect comparing two types of intervention was significant [F (1, 48) = 3.78, p = 0.02]. On the other hand, for negative subscale scores, the main effect comparing two types of intervention was not significant [F (1, 48) = 1.43, p = 0.23]. For general subscale scores, the main effect comparing two types of intervention was not significant [F (1, 48) = 0.03, p = 0.86].

Conclusions

According to our findings, raloxifene as an adjunctive treatment to risperidone was only superior in improvement of positive symptoms and it was not effective in treating negative and general psychopathology symptoms.

Trial registration

The trial was registered at the Iranian registry of clinical trials: IRCT201205131556N42

Inflammation and the two-hit hypothesis of schizophrenia

The high societal and individual cost of schizophrenia necessitates finding better, more effective treatment, diagnosis, and prevention strategies. One of the obstacles in this endeavor is the diverse set of etiologies that comprises schizophrenia. A substantial body of evidence has grown over the last few decades to suggest that schizophrenia is a heterogeneous syndrome with overlapping symptoms and etiologies. At the same time, an increasing number of clinical, epidemiological, and experimental studies have shown links between schizophrenia and inflammatory conditions. In this review, we analyze the literature on inflammation and schizophrenia, with a particular focus on comorbidity, biomarkers, and environmental insults. We then identify several mechanisms by which inflammation could influence the development of schizophrenia via the two-hit hypothesis. Lastly, we note the relevance of these findings to clinical applications in the diagnosis, prevention, and treatment of schizophrenia.

The structural biology of oestrogen metabolism

Many enzymes catalyse reactions that have an oestrogen as a substrate and/or a product. The reactions catalysed include aromatisation, oxidation, reduction, sulfonation, desulfonation, hydroxylation and methoxylation. The enzymes that catalyse these reactions must all recognise and bind oestrogen but, despite this, they have diverse structures. This review looks at each of these enzymes in turn, describing the structure and discussing the mechanism of the catalysed reaction. Since oestrogen has a role in many disease states inhibition of the enzymes of oestrogen metabolism may have an impact on the state or progression of the disease and inhibitors of these enzymes are briefly discussed. This article is part of a Special Issue entitled 'CSR 2013'.

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.