Protective actions of ovarian hormones in the serotonin system of macaques

Neuroprotective effects of goji berry (Lycium barbarum L.) polysaccharides on depression-like behavior in ovariectomized rats: behavioral and biochemical evidence

AIM

To assess the protective effects of goji berry (Lycium barbarum L.) polysaccharides (LBP) on depression-like behavior in ovariectomized rats and to elucidate the mechanisms underlying these effects.

METHODS

One hundred female Wistar albino rats (three months old) were randomly assigned either to ovariectomy (n=50) or sham surgery (n=50). After a 14-day recovery period, the groups were divided into five treatment subgroups (10 per group): high-dose LBP (200 mg/kg), low-dose LBP (20 mg/kg), imipramine (IMP, 2.5 mg/kg), 17-beta estradiol (E2, 1 mg/kg), and distilled water. Then, rats underwent a forced swimming test. We also determined the levels of serum antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde), E2 levels, hippocampal brain-derived neurotrophic factor (BDNF), 5HT2A receptor, and transferase dUTP nick end labeling (TUNEL)-positive cells.

RESULTS

Both low-dose LBP and imipramine decreased depression-like behavior by increasing serum superoxide dismutase activity and by decreasing serum malondialdehyde level. Furthermore, low-dose LPB, high-dose LBP, and imipramine increased the number of 5-HT2A receptor- and BDNF-positive cells but decreased the number of TUNEL-positive cells in the hippocampus.

CONCLUSION

This is the first study to show the antidepressant effect of LBP. Although additional research is needed, LBP may be considered a potential new antidepressant.

The Role of Hormonal Replacement Therapy in BRCA Mutated Patients: Lights and Shadows

All cancers develop as a result of mutations in genes. DNA damage induces genomic instability and subsequently increases susceptibility to tumorigenesis. Women who carry mutations of BRCA 1 and BRCA2 genes have an augmented risk of breast and ovarian cancer and a markedly augmented probability of dying because of cancer compared to the general population. As a result, international guidelines recommend that all BRCA1\2 mutation carriers be offered risk-reducing bilateral salpingo-oophorectomy at an early age to reduce the risk of cancer and decrease the mortality rate of this high-risk population. NCCN guidelines recommend risk-reducing bilateral salpingo-oophorectomy in pre-menopausal women, between 35-40 years in BRCA1 mutation carriers and between 40-45 years in BRCA2 mutation carriers. Unfortunately, the well-documented reduction of cancer risk is counterbalanced by early sterility and premature ovarian failure with an early onset of secondary menopausal syndromes such as neuromotor, cardiovascular, cognitive and urogenital deficiency. Hormonal replacement therapy significantly compensates for hormonal deprivation and counteracts menopausal syndrome morbidity and mortality; however, some data suggest a possible correlation between hormonal medications and cancer risk, especially in BRCA1\2 carriers who undergo long-term regimens. Conversely, short-term treatment before the age of natural menopause does not appear to increase the cancer risk in BRCA1 mutation carriers without a personal history of breast cancer after prophylactic surgery. Few data are available on BRCA2 mutation carriers and more well-designed studies are needed. In conclusion, clinicians should propose short-term hormone replacement therapy to BRCA 1 carriers to counteract hormonal deprivation; personalized counselling should be offered to BRCA2 mutation carriers for a balance between the risks and benefits of the treatment.

The role of central serotonergic markers and estradiol changes in perinatal mental health

OBJECTIVE

Women have an increased risk for mental distress and depressive symptoms in relation to pregnancy and birth. The serotonin transporter (SERT) may be involved in the emergence of depressive symptoms postpartum and during other sex-hormone transitions. It may be associated with cerebrospinal fluid (CSF) levels of the main serotonin metabolite 5-hydroxyindolacetic acid (5-HIAA). In 100 healthy pregnant women, who were scheduled to deliver by cesarean section (C-section), we evaluated 5-HIAA and estradiol contributions to mental distress 5 weeks postpartum.

METHODS

Eighty-two women completed the study. CSF collected at C-section was analyzed for 5-HIAA, with high performance liquid chromatography. Serum estradiol concentrations were quantified by liquid chromatography tandem mass spectrometry before C-section and postpartum. Postpartum mental distress was evaluated with the Edinburgh Postnatal Depression Scale (EPDS). Associations between EPDS, 5-HIAA, and Δestradiol were evaluated in linear regression models adjusted for age, parity and SERT genotype.

RESULTS

Higher levels of postpartum mental distress symptoms were negatively associated with a large decrease in estradiol concentrations (β_ΔE2  = 0.73, p = 0.007) and, on a trend level, positively associated with high antepartum 5-HIAA levels (β_5-HIAA  = 0.002, p = 0.06).

CONCLUSION

In a cohort of healthy pregnant women, postpartum mental distress was higher in women with high antepartum 5-HIAA (trend) and lower in women with a large perinatal estradiol decrease. We speculate that high antepartum 5-HIAA is a proxy of SERT levels, that carry over to the postpartum period and convey susceptibility to mental distress. In healthy women, the postpartum return to lower estradiol concentrations may promote mental well-being.

Towards individualised contraceptive counselling: clinical and reproductive factors associated with self-reported hormonal contraceptive-induced adverse mood symptoms

OBJECTIVE

The study aim was to establish which demographic, clinical, reproductive and psychiatric factors are associated with self-reported hormonal contraceptive (HC)-induced adverse mood symptoms.

STUDY DESIGN

We compiled baseline data from two Swedish studies: one cross-sectional study on combined oral contraceptive (COC)-induced adverse mood symptoms (n=118) and one randomised controlled trial on adverse mood symptoms on COC (n=184). Both included women eligible for COC use, aged over 18 years. All women answered a questionnaire on HC use and associated mood problems. The Mini-International Neuropsychiatric Interview (M.I.N.I.) was used to capture mood and anxiety disorders. Women who acknowledged HC-induced adverse mood symptoms, ongoing or previously (n=145), were compared with women without any such experience (n=157).

RESULTS

Compared with women without self-reported HC-induced adverse mood symptoms, women with these symptoms were younger at HC start (adjusted odds ratio (aOR) 0.83, 95% CI 0.72 to 0.95), had more often undergone induced abortion (OR 3.36, 95% CI 1.57 to 7.23), more often suffered from an ongoing minor depressive disorder (n=12 vs n=0) and had more often experienced any previous mental health problem (aOR 1.90, 95% CI 1.01 to 3.59).

CONCLUSIONS

In line with previous research, this study suggests that women with previous or ongoing mental health problems and women who are younger at HC start are more likely to experience HC-induced adverse mood symptoms. Former and current mental health should be addressed at contraceptive counselling, and ongoing mental health disorders should be adequately treated.

IMPLICATIONS

This study adds valuable knowledge for identification of women susceptible to HC-induced adverse mood symptoms. It should facilitate the assessment of whether or not a woman has an increased risk of such symptoms, and thus enable clinicians to adopt a more personalised approach to contraceptive counselling.

Progesterone - Friend or foe?

Estradiol is the "prototypic" sex hormone of women. Yet, women have another sex hormone, which is often disregarded: Progesterone. The goal of this article is to provide a comprehensive review on progesterone, and its metabolite allopregnanolone, emphasizing three key areas: biological properties, main functions, and effects on mood in women. Recent years of intensive research on progesterone and allopregnanolone have paved the way for new treatment of postpartum depression. However, treatment for premenstrual syndrome and premenstrual dysphoric disorder as well as contraception that women can use without risking mental health problems are still needed. As far as progesterone is concerned, we might be dealing with a two-edged sword: while its metabolite allopregnanolone has been proven useful for treatment of PPD, it may trigger negative symptoms in women with PMS and PMDD. Overall, our current knowledge on the beneficial and harmful effects of progesterone is limited and further research is imperative.

Neural regeneration therapies for Alzheimer's and Parkinson's disease-related disorders

Neurodegenerative diseases are devastating mental illnesses without a cure. Alzheimer's disease (AD) characterized by memory loss, multiple cognitive impairments, and changes in personality and behavior. Although tremendous progress has made in understanding the basic biology in disease processes in AD and PD, we still do not have early detectable biomarkers for these diseases. Just in the United States alone, federal and nonfederal funding agencies have spent billions of dollars on clinical trials aimed at finding drugs, but we still do not have a drug or an agent that can slow the AD or PD disease process. One primary reason for this disappointing result may be that the clinical trials enroll patients with AD or PD at advances stages. Although many drugs and agents are tested preclinical and are promising, in human clinical trials, they are mostly ineffective in slowing disease progression. One therapy that has been promising is 'stem cell therapy' based on cell culture and pre-clinical studies. In the few clinical studies that have investigated therapies in clinical trials with AD and PD patients at stage I. The therapies, such as stem cell transplantation - appear to delay the symptoms in AD and PD. The purpose of this article is to describe clinical trials using 1) stem cell transplantation methods in AD and PD mouse models and 2) regenerative medicine in AD and PD mouse models, and 3) the current status of investigating preclinical stem cell transplantation in patients with AD and PD.

Serotonin-estrogen interactions: What can we learn from pregnancy?

We have reviewed the scientific literature related to four diseases in which to serotonin (5-HT) is involved in the etiology, herein named 5-HT-linked diseases, and whose prevalence is influenced by estrogenic status: depression, migraine, irritable bowel syndrome and eating disorders. These diseases all have in common a sex-dimorphic prevalence, with women more frequently affected than men. The co-occurrence between these 5-HT-linked diseases suggests that they have common physiopathological mechanisms. In most 5-HT-linked diseases (except for anorexia nervosa and irritable bowel syndrome), a decrease in the serotonergic tone is observed and estrogens are thought to contribute to the improvement of symptoms by stimulating the serotonergic system. Human pregnancy is characterized by a unique 5-HT and estrogen synthesis by the placenta. Pregnancy-specific disorders, such as hyperemesis gravidarum, gestational diabetes mellitus and pre-eclampsia, are associated with a hyperserotonergic state and decreased estrogen levels. Fetal programming of 5-HT-linked diseases is a complex phenomenon that involves notably fetal-sex differences, which suggest the implication of sex steroids. From a mechanistic point of view, we hypothesize that estrogens regulate the serotonergic system, resulting in a protective effect against 5-HT-linked diseases, but that, in turn, 5-HT affects estrogen synthesis in an attempt to retrieve homeostasis. These two processes (5-HT and estrogen biosynthesis) are crucial for successful pregnancy outcomes, and thus, a disruption of this 5-HT-estrogen relationship may explain pregnancy-specific pathologies or pregnancy complications associated with 5-HT-linked diseases.

Sex differences and the neurobiology of affective disorders

Observations of the disproportionate incidence of depression in women compared with men have long preceded the recent explosion of interest in sex differences. Nonetheless, the source and implications of this epidemiologic sex difference remain unclear, as does the practical significance of the multitude of sex differences that have been reported in brain structure and function. In this article, we attempt to provide a framework for thinking about how sex and reproductive hormones (particularly estradiol as an example) might contribute to affective illness. After briefly reviewing some observed sex differences in depression, we discuss how sex might alter brain function through hormonal effects (both organizational (programmed) and activational (acute)), sex chromosome effects, and the interaction of sex with the environment. We next review sex differences in the brain at the structural, cellular, and network levels. We then focus on how sex and reproductive hormones regulate systems implicated in the pathophysiology of depression, including neuroplasticity, genetic and neural networks, the stress axis, and immune function. Finally, we suggest several models that might explain a sex-dependent differential regulation of affect and susceptibility to affective illness. As a disclaimer, the studies cited in this review are not intended to be comprehensive but rather serve as examples of the multitude of levels at which sex and reproductive hormones regulate brain structure and function. As such and despite our current ignorance regarding both the ontogeny of affective illness and the impact of sex on that ontogeny, sex differences may provide a lens through which we may better view the mechanisms underlying affective regulation and dysfunction.

The role of tryptophan metabolism in postpartum depression

The Postpartum depression (PPD) is the most common postpartum psychiatric disorder, afflicting approximately 10%-20% of new mothers. Clinical symptoms of the PPD include depressive disorder, agitation, insomnia, anxiety and confusion, resulting in an increase in suicidal tendencies, thereby having significant impacts on the puerpera, newborn and their family. A growing body of data indicate a role for alterations in tryptophan metabolism in the PPD. The metabolism of tryptophan produces an array of crucial factors that can differentially regulate key physiological processes linked to the PPD. Importantly, an increase in stress hormones and immune-inflammatory activity drives tryptophan to the production of neuroregulatory kynurenine pathway products and away from the serotonin and melatonin pathways. This links the PPD to other disorders of depressed mood, which are classically associated with decreased serotonin and melatonin, coupled to increases in kynurenine pathway products. Several kynurenine pathway products, such as kynurenic acid and quinolinic acid, can have neuroregulatory effects, with consequences pathological underpinnings of the PPD. The current article reviews the role of alterations in tryptophan metabolism in the PPD.

Modulation of Tryptophan and Serotonin Metabolism as a Biochemical Basis of the Behavioral Effects of Use and Withdrawal of Androgenic-Anabolic Steroids and Other Image- and Performance-Enhancing Agents

Modulation of tryptophan (Trp) metabolism may underpin the behavioral effects of androgenic-anabolic steroids (AAS) and associated image and performance enhancers. Euphoria, arousal, and decreased anxiety observed with moderate use and exercise may involve enhanced cerebral serotonin synthesis and function by increased release of albumin-bound Trp and estrogen-mediated liver Trp 2,3-dioxygenase (TDO) inhibition and enhancement of serotonin function. Aggression, anxiety, depression, personality disorders, and psychosis, observed on withdrawal of AAS or with use of large doses, can be caused by decreased serotonin synthesis due to TDO induction on withdrawal, excess Trp inhibiting the 2 enzymes of serotonin synthesis, and increased cerebral levels of neuroactive kynurenines. Exercise and excessive protein and branched-chain amino acid intakes may aggravate the effects of large AAS dosage. The hypothesis is testable in humans and experimental animals by measuring parameters of Trp metabolism and disposition and related metabolic processes.

Effects of obesogenic diet and estradiol on dorsal raphe gene expression in old female macaques

The beneficial effects of bioidentical ovarian steroid hormone therapy (HT) during the perimenopause are gaining recognition. However, the positive effects of estrogen (E) plus or minus progesterone (P) administration to ovariectomized (Ovx) lab animals were recognized in multiple systems for years before clinical trials could adequately duplicate the results. Moreover, very large numbers of women are often needed to find statistically significant results in clinical trials of HT; and there are still opposing results being published, especially in neural and cardiovascular systems. One of the obvious differences between human and animal studies is diet. Laboratory animals are fed a diet that is low in fat and refined sugar, but high in micronutrients. In the US, a large portion of the population eats what is known as a "western style diet" or WSD that provides calories from 36% fat, 44% carbohydrates (includes 18.5% sugars) and 18% protein. Unfortunately, obesity and diabetes have reached epidemic proportions and the percentage of obese women in clinical trials may be overlooked. We questioned whether WSD and obesity could decrease the positive neural effects of estradiol (E) in the serotonin system of old macaques that were surgically menopausal. Old ovo-hysterectomized female monkeys were fed WSD for 2.5 years, and treated with placebo, Immediate E (ImE) or Delayed E (DE). Compared to old Ovx macaques on primate chow and treated with placebo or E, the WSD-fed monkeys exhibited greater individual variance and blunted responses to E-treatment in the expression of genes related to serotonin neurotransmission, CRH components in the midbrain, synapse assembly, DNA repair, protein folding, ubiquitylation, transport and neurodegeneration. For many of the genes examined, transcript abundance was lower in WSD-fed than chow-fed monkeys. In summary, an obesogenic diet for 2.5 years in old surgically menopausal macaques blunted or increased variability in E-induced gene expression in the dorsal raphe. These results suggest that with regard to function and viability in the dorsal raphe, HT may not be as beneficial for obese women as normal weight women.

Genetic variants of the kynurenine-3-monooxygenase and postpartum depressive symptoms after cesarean section in Chinese women

BACKGROUND

New conceptualizations of depression have emphasized the role of the kynurenine pathway (KP) in the pathogenesis of postpartum depressive symptoms (PDS). Kynurenine 3-monooxygenase (KMO) is a rate-limiting enzyme of the KP, where it catalyzes the conversion of kynurenine (KYN) to 3-hydroxykynurenine (3-HK). Previous work indicates that KMO is closely linked to the pathophysiology of depressive disorders. The purpose of this study is to investigate whether variations in the KMO gene affect PDS development after cesarean section.

METHODS

A total of 710 Chinese women receiving cesarean section were enrolled in this study. PDS was determined by an Edinburgh Postnatal Depression Scale (EPDS) score ≥13. Subsequently, 24 women with PDS and 48 matched women without PDS were randomly selected for investigation of perinatal serum concentrations of KYN, 3-HK and the 3-HK/KYN ratio. The 3-HK/KYN ratio indicates the activity of KMO. In addition, 6 single nucleotide polymorphisms of the KMO gene were examined. Following this genotyping, 36 puerperant women carrying the KMO rs1053230 AG genotype and 72 matched puerperant women carrying the KMO rs1053230 GG genotype were selected for comparisons of KYN, 3-HK and 3-HK/KYN ratio levels.

RESULTS

The results show the incidence of PDS in the Chinese population to be 7.3%, with PDS characterized by increased serum 3-HK concentration and 3-HK/KYN ratio, versus matched postpartum women without PDS (P<0.05). Furthermore, polymorphisms of KMO rs1053230 are significantly associated with the incidence of PDS (P<0.05). The serum concentrations of 3-HK and the 3-HK/KYN ratio in postpartum women carrying the KMO rs1053230 AG genotype are significantly higher than those in matched postpartum women carrying the KMO rs1053230 GG genotype.

CONCLUSIONS

The presented data highlight the contribution of alterations in the KP to the pathogenesis of postpartum depression. Heightened KMO activity, including as arising from KMO rs1053230 G/A genetic variations, are indicated as one possible mechanism driving the biological underpinnings of PDS.

Progesterone increased β-endorphin innervation of the locus coeruleus, but ovarian steroids had no effect on noradrenergic neurodegeneration

With the decline of ovarian steroids levels at menopause, many women experience an increase in anxiety and stress sensitivity. The locus coeruleus (LC), a central source of noradrenaline (NE), is activated by stress and is inhibited by β-endorphin. Moreover, increased NE has been implicated in pathological anxiety syndromes. Hormone replacement therapy (HRT) in menopause appears to decrease anxiety and vulnerability to stress. Therefore, we questioned the effect of HRT on the inhibitory β-endorphin innervation of the LC. In addition, we found that progesterone protects serotoninergic neurons in monkeys, leading us to question whether ovarian steroids are also neuroprotective in LC neurons in monkeys. Adult Rhesus monkeys (Macaca mulatta) were ovariectomized, and either treated with Silastic capsules that contained estradiol, estradiol+progesterone, progesterone alone or that were empty (ovariectomized; control). After 1month, the LC was obtained and processed for immunohistochemistry for β-endorphin and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL). The density of β-endorphin axons was determined with image analysis using ImageJ. The TUNEL-positive neurons were counted in the entire LC. Progesterone-alone significantly increased the density of the β-endorphin axons in the LC (p<0.01). No significant differences between groups in the number of TUNEL-positive cells in the LC were found. In conclusion, we found that HRT increases the inhibitory influence of β-endorphin in the LC, which could, in turn, contribute to reduce anxiety and increase stress resilience. In addition, we did not find compelling evidence of neurodegeneration or neuroprotection by HRT in the LC of Rhesus monkeys.

Pharmacologically Induced Sex Hormone Fluctuation Effects on Resting-State Functional Connectivity in a Risk Model for Depression: A Randomized Trial

Women are at relatively greater lifetime risk for depression than men. This elevated risk in women is partly due to heightened risk during time periods characterized by marked fluctuations in sex hormones, including postpartum and perimenopausal periods. How sex hormone fluctuations contribute to heightened risk is not fully understood but may involve intrinsic functional connectivity. We induced a biphasic ovarian sex hormone fluctuation using the gonadotropin-releasing hormone agonist (GnRHa) goserelin to determine, with a randomized placebo-controlled design, intervention effects on or GnRHa-provoked depressive symptoms associations with change in resting-state functional connectivity (rs-FC) in 58 healthy women for six seeds (amygdala, hippocampus, anterior cingulate cortex, dorsal raphe, median raphe, and posterior cingulate cortex). GnRHa intervention did not significantly affect rs-FC in any seeds. Considering the GnRHa group only, the emergence of depressive symptoms following intervention was positively associated with amygdala-right temporal cortex and negatively associated with hippocampus-cingulate rs-FC. A test for mediation suggested that rs-FC changes in these networks marginally mediated the association between decrease in estradiol and increase in depressive symptoms in the GnRHa group (p=0.07). Our findings provide novel evidence-linking changes in rs-FC networks, the emergence of depressive symptoms and sex hormone fluctuations. Notably, we observed evidence that changes in rs-FC may represent a key neurobiological intermediary between molecular changes induced by hormone fluctuations and the emergence of depressive symptoms. Taken together, our findings indicate that sex hormone fluctuations may contribute to heightened risk for developing depressive symptoms by affecting intrinsic functional connectivity of key limbic brain structures.

How Studies of the Serotonin System in Macaque Models of Menopause Relate to Alzheimer's Disease1

Serotonin plays a key role in mood or affect, and dysfunction of the serotonin system has been linked to depression in humans and animal models. Depression appears prior to or coincident with overt symptoms of Alzheimer's disease (AD) in about 50% of patients, and some experts consider it a risk factor for the development of AD. In addition, AD is more prevalent in women, who also show increased incidence of depression. Indeed, it has been proposed that mechanisms underlying depression overlap the mechanisms thought to hasten AD. Women undergo ovarian failure and cessation of ovarian steroid production in middle age and the postmenopausal period correlates with an increase in the onset of depression and AD. This laboratory has examined the many actions of ovarian steroids in the serotonin system of non-human primates using a rhesus macaque model of surgical menopause with short or long-term estradiol (E) or estradiol plus progesterone (E+P) replacement therapy. In this mini-review, we present a brief synopsis of the relevant literature concerning AD, depression, and serotonin. We also present some of our data on serotonin neuron viability, the involvement of the caspase-independent pathway, and apoptosis-inducing factor in serotonin-neuron viability, as well as gene expression related to neurodegeneration and neuron viability in serotonin neurons from adult and aged surgical menopausal macaques. We show that ovarian steroids, particularly E, are crucial for serotonin neuron function and health. In the absence of E, serotonin neurons are endangered and deteriorating toward apoptosis. The possibility that this scenario may proceed or accompany AD in postmenopausal women seems likely.

Estradiol Valerate and Remifemin ameliorate ovariectomy-induced decrease in a serotonin dorsal raphe-preoptic hypothalamus pathway in rats

Perimenopausal syndromes begin as ovarian function ceases and the most common symptoms are hot flushes. Data indicate that the projections of serotonin to hypothalamus may be involved in the mechanism of hot flushes. Therefore, the aim of this study is to investigate the potential role of the serotonin dorsal raphe-preoptic hypothalamus pathway for hot flushes in an animal model of menopause. We determined the changes in serotonin expression in the dorsal raphe (DR) and preoptic anterior hypothalamus (POAH) in ovariectomized rats. We also explored the therapeutical effects of estradiol valerate and Remifemin in this model. Eighty female Sprague-Dawley rats were randomly assigned to sham-operated (SHAM) group, ovariectomy (OVX) group with vehicle, ovariectomy with estradiol valerate treatment (OVX+E) group and ovariectomy with Remifemin (OVX+ICR) group. Serotonin expression was evaluated in the DR and POAH using immunofluorescence and quantified in the DR using an enzyme-linked immunosorbent assay (ELISA). Apoptosis was analyzed in the DR by TUNEL assay. The number of serotonin immunoreactive neurons and the level of serotonin expression in the DR decreased significantly following OVX compared to the SHAM group. No TUNEL-positive cells were detected in the DR in any group. In addition, following OVX, the number of serotonin-positive fibers decreased significantly in the ventromedial preoptic nucleus (VMPO), especially in the ventrolateral preoptic nucleus (VLPO). Treatment with either estradiol or Remifemin for 4 weeks countered the OVX-induced decreases in serotonin levels in both the DR and the hypothalamus, with levels in the treated rats similar to those in the SHAM group. A fluorescently labeled retrograde tracer was injected into the VLPO at the 4-week time point. A significantly lower percentage of serotonin with CTB double-labeled neurons in CTB-labeled neurons was demonstrated after ovariectomy, and both estradiol and Remifemin countered this OVX-induced decrease. We conclude that serotonin pathway is changed after ovariectomy, including the serotonin synthesis in DR and serotonin fibers in PO/AH, both E and Remifemin have an equivalent therapeutic effect on it.

Sex differences and stress across the lifespan

Sex differences in stress responses can be found at all stages of life and are related to both the organizational and activational effects of gonadal hormones and to genes on the sex chromosomes. As stress dysregulation is the most common feature across neuropsychiatric diseases, sex differences in how these pathways develop and mature may predict sex-specific periods of vulnerability to disruption and increased disease risk or resilience across the lifespan. The aging brain is also at risk to the effects of stress, where the rapid decline of gonadal hormones in women combined with cellular aging processes promote sex biases in stress dysregulation. In this Review, we discuss potential underlying mechanisms driving sex differences in stress responses and their relevance to disease. Although stress is involved in a much broader range of diseases than neuropsychiatric ones, we highlight here this area and its examples across the lifespan.

Neurocognitive effects of estrogens across the adult lifespan in nonhuman primates: State of knowledge and new perspectives

This article is part of a Special Issue "Estradiol and cognition". This review discusses the unique contribution of nonhuman primate research to our understanding of the neurocognitive effects of estrogens throughout the adult lifespan in females. Mounting evidence indicates that estrogens affect many aspects of hippocampal, prefrontal and cholinergic function in the primate brain and the underlying mechanisms are beginning to be elucidated. In addition, estrogens may also influence cognitive function indirectly, via the modulation of other systems that impact cognition. We will focus on the effects of estrogens on sleep and emphasize the need for primate models to better understand these complex interactions. Continued research with nonhuman primates is essential for the development of therapies that are optimal for the maintenance of women's cognitive health throughout the lifespan.

Transdermal Estradiol Treatment for Postpartum Depression: A Pilot, Randomized Trial

Postpartum depression occurs in 14.5% of women in the first 3 months after birth. This study was an 8-week acute phase randomized trial with 3 cells (transdermal estradiol [E2], sertraline [SERT], and placebo [PL]) for the treatment of postpartum major depressive disorder. However, the study was stopped after batch analysis revealed that the E2 serum concentrations were lower than prestudy projections. This paper explores our experiences that will inform future investigations of therapeutic E2 use. Explanations for the low E2 concentrations were as follows: (1) study patch nonadhesion, which did not explain the low concentrations across the entire sample. (2) Ineffective transdermal patch preparations, although 2 different patch preparations were used and no significant main effect of patch type on E2 concentrations was found. (3) Obesity, at study entry, E2-treated women had body mass index of 32.9 (7.4) (mean [SD]). No pharmacokinetic data comparing E2 concentrations from transdermal patches in obese women versus normal weight controls are available. (4) Induction of cytochrome P450 (CYP450) 3A4 and other E2 elimination pathways in pregnancy. CYP4503A4 is induced in pregnancy and is a pathway for the metabolism of E2. Conversion to estrone and phase II metabolism via glucuronidation and sulfation, which also increase in pregnancy, are routes of E2 elimination. The time required for these pathways to normalize after delivery has not been elucidated. The observation that transdermal E2 doses greater than 100 μg/d did not increase serum concentrations was unexpected. Another hypothesis consistent with this observation is suppression of endogenous E2 secretion with increasing exogenous E2 dosing.

An analysis of the influence of selected genetic and hormonal factors on the occurrence of depressive symptoms in late-reproductive-age women

BACKGROUND

The aim of this study was to analyze the influence of genetic and hormonal factors on incidences of depressive symptoms in late-reproductive-age women.

METHODS

The study was performed using the Beck Depression Inventory, the PCR, and genetic tests of 347 healthy late-reproductive-age Polish women.

RESULTS

The relationship between the level of anti-Müllerian hormone (AMH) and depressive symptoms was not statistically significant (p > 0.05). Increases in age and FSH levels were accompanied by a decrease in AMH level in a significant way (p < 0.05). There were no statistically significant relationships between the distribution of genotypes and the frequency of alleles of the investigated polymorphisms and depressive symptoms according to the Beck Depression Inventory.

CONCLUSIONS

(1) The presence of the s/s genotype of the 5-HTTLPR polymorphism in the serotonin transporter promoter region and the 3/3 genotype of the 30-bp VNTR polymorphism in the monoamine oxidase A promoter region does not contribute to the development of depressive symptoms in late-reproductive-age women. (2) A relationship between the level of anti-Müllerian hormone and depressive symptoms was not confirmed in the group of healthy late-reproductive-age women. (3) AMH level correlates negatively with FSH level and age, which confirms that AMH can be regarded as a factor reflecting the ovarian reserve.

Effect of a chronic treatment with an mGlu5 receptor antagonist on brain serotonin markers in parkinsonian monkeys

In Parkinson's disease (PD) and l-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesias (LIDs), overactivity of brain glutamate neurotransmission is documented and antiglutamatergic drugs decrease LID. Serotonin (5-HT) receptors and transporter (SERT) are also implicated in LID and we hypothesize that antiglutamatergic drugs can also regulate brain serotoninergic activity. Our aim was to investigate the long-term effect of the prototypal metabotropic glutamate 5 (mGlu5) receptor antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) with L-DOPA on basal ganglia SERT, 5-HT(1A) and 5-HT(2A) receptor levels in monkeys lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP monkeys were treated for one month with L-DOPA and developed LID while those treated with L-DOPA and MPEP (10 mg/kg) developed significantly less LID. Normal controls and saline-treated MPTP monkeys were included for biochemical analysis. The MPTP lesion and experimental treatments left unchanged striatal 5-HT concentrations. MPTP lesion induced an increase of striatal 5-HIAA concentrations similar in all MPTP monkeys as compared to controls. [(3)H]-8-OH-DPAT and [(3)H]-citalopram specific binding levels to 5-HT(1A) receptors and SERT respectively remained unchanged in the striatum and globus pallidus of all MPTP monkeys compared to controls and no difference was observed between groups of MPTP monkeys. [(3)H]-ketanserin specific binding to striatal and pallidal 5-HT2A receptors was increased in L-DOPA-treated MPTP monkeys as compared to controls, saline and L-DOPA+MPEP MPTP monkeys and no difference between the latter groups was observed; dyskinesia scores correlated positively with this binding. In conclusion, reduction of development of LID with MPEP was associated with lower striatal and pallidal 5-HT2A receptors showing that glutamate activity also affects serotoninergic markers.

Interaction of brain 5-HT synthesis deficiency, chronic stress and sex differentially impact emotional behavior in Tph2 knockout mice

RATIONALE

While brain serotonin (5-HT) function is implicated in gene-by-environment interaction (GxE) impacting the vulnerability-resilience continuum in neuropsychiatric disorders, it remains elusive how the interplay of altered 5-HT synthesis and environmental stressors is linked to failure in emotion regulation.

OBJECTIVE

Here, we investigated the effect of constitutively impaired 5-HT synthesis on behavioral and neuroendocrine responses to unpredictable chronic mild stress (CMS) using a mouse model of brain 5-HT deficiency resulting from targeted inactivation of the tryptophan hydroxylase-2 (Tph2) gene.

RESULTS

Locomotor activity and anxiety- and depression-like behavior as well as conditioned fear responses were differentially affected by Tph2 genotype, sex, and CMS. Tph2 null mutants (Tph2(-/-)) displayed increased general metabolism, marginally reduced anxiety- and depression-like behavior but strikingly increased conditioned fear responses. Behavioral modifications were associated with sex-specific hypothalamic-pituitary-adrenocortical (HPA) system alterations as indicated by plasma corticosterone and fecal corticosterone metabolite concentrations. Tph2(-/-) males displayed increased impulsivity and high aggressiveness. Tph2(-/-) females displayed greater emotional reactivity to aversive conditions as reflected by changes in behaviors at baseline including increased freezing and decreased locomotion in novel environments. However, both Tph2(-/-) male and female mice were resilient to CMS-induced hyperlocomotion, while CMS intensified conditioned fear responses in a GxE-dependent manner.

CONCLUSIONS

Our results indicate that 5-HT mediates behavioral responses to environmental adversity by facilitating the encoding of stress effects leading to increased vulnerability for negative emotionality.

Functional and molecular neuroimaging of menopause and hormone replacement therapy

The level of gonadal hormones to which the female brain is exposed considerably changes across the menopausal transition, which in turn, is likely to be of great relevance for neurodegenerative diseases and psychiatric disorders. However, the neurobiological consequences of these hormone fluctuations and of hormone replacement therapy in the menopause have only begun to be understood. The present review summarizes the findings of thirty-five studies of human brain function, including functional magnetic resonance imaging, positron and single-photon computed emission tomography studies, in peri- and postmenopausal women treated with estrogen, or estrogen-progestagen replacement therapy. Seven studies using gonadotropin-releasing hormone agonist intervention as a model of hormonal withdrawal are also included. Cognitive paradigms are employed by the majority of studies evaluating the effect of unopposed estrogen or estrogen-progestagen treatment on peri- and postmenopausal women's brain. In randomized-controlled trials, estrogen treatment enhances activation of fronto-cingulate regions during cognitive functioning, though in many cases no difference in cognitive performance was present. Progestagens seems to counteract the effects of estrogens. Findings on cognitive functioning during acute ovarian hormone withdrawal suggest a decrease in activation of the left inferior frontal gyrus, thus essentially corroborating the findings in postmenopausal women. Studies of the cholinergic and serotonergic systems indicate these systems as biological mediators of hormonal influences on the brain. More, hormonal replacement appears to increase cerebral blood flow in several cortical regions. On the other hand, studies on emotion processing in postmenopausal women are lacking. These results call for well-powered randomized-controlled multi-modal prospective neuroimaging studies as well as investigation on the related molecular mechanisms of effects of menopausal hormonal variations on the brain.

Diphtheria toxin treatment of Pet-1-Cre floxed diphtheria toxin receptor mice disrupts thermoregulation without affecting respiratory chemoreception

In genetically-modified Lmx1b(f/f/p) mice, selective deletion of LMX1B in Pet-1 expressing cells leads to failure of embryonic development of serotonin (5-HT) neurons. As adults, these mice have a decreased hypercapnic ventilatory response and abnormal thermoregulation. This mouse model has been valuable in defining the normal role of 5-HT neurons, but it is possible that developmental compensation reduces the severity of observed deficits. Here we studied mice genetically modified to express diphtheria toxin receptors (DTR) on Pet-1 expressing neurons (Pet-1-Cre/floxed DTR or Pet1/DTR mice). These mice developed with a normal complement of 5-HT neurons. As adults, systemic treatment with 2-35μg of diphtheria toxin (DT) reduced the number of tryptophan hydroxylase-immunoreactive (TpOH-ir) neurons in the raphe nuclei and ventrolateral medulla by 80%. There were no effects of DT on minute ventilation (VE) or the ventilatory response to hypercapnia or hypoxia. At an ambient temperature (TA) of 24°C, all Pet1/DTR mice dropped their body temperature (TB) below 35°C after DT treatment, but the latency was shorter in males than females (3.0±0.37 vs. 4.57±0.29days, respectively; p<0.001). One week after DT treatment, mice were challenged by dropping TA from 37°C to 24°C, which caused TB to decrease more in males than in females (29.7±0.31°C vs. 33.0±1.3°C, p<0.01). We conclude that the 20% of 5-HT neurons that remain after DT treatment in Pet1/DTR mice are sufficient to maintain normal baseline breathing and a normal response to CO2, while those affected include some essential for thermoregulation, in males more than females. In comparison to models with deficient embryonic development of 5-HT neurons, acute deletion of 5-HT neurons in adults leads to a greater defect in thermoregulation, suggesting that significant developmental compensation can occur.

Melatonin and oestrogen treatments were able to improve neuroinflammation and apoptotic processes in dentate gyrus of old ovariectomized female rats

The aim of this study was to determine the outcomes of oestrogen and melatonin treatments following long-term ovarian hormone depletion on neuroinflammation and apoptotic processes in dentate gyrus of hippocampi. Forty-six female Wistar rats of 22 months of age were used. Twelve of them remained intact, and the other 34 were ovariectomized at 12 months of age. Ovariectomized animals were divided into three groups and treated for 10 weeks with oestrogens, melatonin or saline. All rats were killed by decapitation at 24 months of age, and dentate gyri were collected. A group of 2 month-old intact female rats was used as young control. The levels of pro-inflammatory cytokines and heat shock protein 70 (HSP 70) were analysed by ELISA. The expressions of TNFα, IL1β, GFAP, nNOS, iNOS, HO-1, NFκB, Bax, Bad, AIF, Bcl2 and SIRT1 genes were detected by real-time (RT)-PCR. Western blots were used to measure the protein expression of NFκB p65, NFκB p50/105, IκBα, IκBβ, p38 MAPK, MAP-2 and synapsin I. We have assessed the ability of 17β-oestradiol and melatonin administration to downregulate markers of neuroinflammation in the dentate gyrus of ovariectomized female rats. Results indicated that 17β-oestradiol and melatonin treatments were able to significantly decrease expression of pro-inflammatory cytokines, iNOS and HO-1 in the hippocampus when compared to non-treated animals. A similar age- and long-term ovarian hormone depletion- related increase in GFAP was also attenuated after both melatonin and oestradiol treatments. In a similar way to oestradiol, melatonin decreased the activation of p38 MAPK and NFκB pathways. The treatments enhanced the levels of synaptic molecules synapsin I and MAP-2 and have been shown to modulate the pro-antiapoptotic ratio favouring the second and to increase SIRT1 expression. These findings support the potential therapeutic role of melatonin and oestradiol as protective anti-inflammatory agents for the central nervous system during menopause.

Effect of low doses of progesterone in the expression of the GABA(A) receptor α4 subunit and procaspase-3 in the hypothalamus of female rats

Progesterone is a steroid which regulates neural function, thereby modulating neurotransmission, cell survival, and behavior. Previous studies by our group have shown that chronic administration of low doses of progesterone in diestrus II female rats has an antidepressant-like effect in the forced swimming test (FST). Depression is associated with the several neurotransmitters systems, including GABA and serotonin, and with neurodegeneration and cell death in some brain circuits. The aim of this study was to verify the effect of progesterone on the protein expression of the GABA(A) receptor α4 subunit, serotonin transporter (SERT), Akt, extracellular signal-regulated kinase (Erk), and caspase-3 in the hypothalamus of diestrus II female rats exposed to the FST. Female rats were treated with a daily injection of progesterone (0.4 mg/kg) or vehicle, during two complete oestrous cycles. On the day of the experiment, the animals were euthanized 30 min after the FST, the hypothalamus was dissected and protein expression of GABA(A) receptor α4 subunit, SERT, Akt, Erk, and caspase-3 was evaluated. Progesterone increased the expression of GABA(A) receptor α4 subunit but did not change the expression of SERT. Progesterone decreased the expression of procaspase-3 in the hypothalamus without changing the activation of Akt and Erk in this structure. In summary, our results suggest that progesterone acts to increase the expression of the GABA(A) receptor α4 subunit and decrease the expression of procaspase-3 in the hypothalamus of female rats. Such effects may be involved in the antidepressant-like effect of progesterone in female rats exposed to the FST.

Effect of injectable medroxyprogesterone acetate and etonogestrel implants on GABA-A and serotonin receptors in white and gray matter of the brain: experimental study in rats

The aim of this study was to evaluate the time-dependent effect of progesterone-only contraceptives on the brain and to obtain an improved understanding of mood disorders experienced under this medication. A total of 66 Wistar albino rats were divided into three groups: etonogestrel (ENG) implant (group 1, n = 30); depot medroxyprogesterone acetate (MPA)-injectable (group 2, n = 30); and control (group 3, n = 6) groups. Groups 1 and 2 were each divided into five subgroups, which were examined every 10 d for up to 50 d after medication administration, to evaluate its time-dependent effect. There was no difference in terms of gamma-aminobutyric acid (GABA) and serotonin immunohistochemical staining in white and gray matter among the subgroups of group 1. In group 2, there was a significant decrease in serotonin receptor staining intensity in white and gray matter on day 50, when compared to the control group (p = 0.041). When the subgroups of group 2 were compared, there was a significant decrease in serotonin receptor staining intensity in white and gray matter on days 40 and 50 when compared to day 10. In conclusion, we showed that ENG and MPA have no effect on apoptosis and GABA-A receptors in the brain. We also showed that MPA has time-dependent effects on serotonin receptors, which may be a possible mechanism involved in mood disorders during long-term usage of injectable progesterone-only contraceptives.

Ovarian steroids increase PSD-95 expression and dendritic spines in the dorsal raphe of ovariectomized macaques

Estradiol (E) and progesterone (P) promote spinogenesis in several brain areas. Intracellular signaling cascades that promote spinogenesis involve RhoGTPases, glutamate signaling and synapse assembly. We found that in serotonin neurons, E ± P administration increases (a) gene and protein expression of RhoGTPases, (b) gene expression of glutamate receptors, and (c) gene expression of pivotal synapse assembly proteins. Therefore, in this study we determined whether structural changes in dendritic spines in the dorsal raphe follow the observed changes in gene and protein expression. Dendritic spines were examined with immunogold silver staining of a spine marker protein, postsynaptic density-95 (PSD-95) and with Golgi staining. In the PSD-95 study, adult Ovx monkeys received placebo, E, P, or E + P for 1 month (n = 3/group). Sections were immunostained for PSD-95 and the number of PSD-95-positive puncta was determined with stereology. E, P, and E + P treatment significantly increased the total number of PSD-95-positive puncta (ANOVA, P = 0.04). In the golgi study, adult Ovx monkeys received placebo, E or E + P for 1 month (n = 3-4) and the midbrain was golgi-stained. A total of 80 neurons were analyzed with Neurolucida software. There was a significant difference in spine density that depended on branch order (two-way ANOVA). E + P treatment significantly increased spine density in higher-order (3°-5°) dendritic branches relative to Ovx group (Bonferroni, P < 0.05). In summary, E + P leads to the elaboration of dendritic spines on dorsal raphe neurons. The ability of E to induce PSD-95, but not actual spines, suggests either a sampling or time lag issue. Increased spinogenesis on serotonin dendrites would facilitate excitatory glutamatergic input and, in turn, increase serotonin neurotransmission throughout the brain.

Prenatal alcohol exposure results in long-term serotonin neuron deficits in female rats: modulatory role of ovarian steroids

BACKGROUND

Previous studies on male rodents found that prenatal alcohol exposure (PAE) decreases the number of serotonin immunoreactive (5-HT-ir) neurons in the brainstem. However, data on the effects of PAE in females are lacking. In light of known sex differences in responsiveness of the 5-HT system and known effects of estrogen (E2 ) and progesterone (P4 ) in the brain, we hypothesized that sex steroids will modulate the adverse effects of PAE on 5-HT neurons in adult females.

METHODS

Adult females from 3 prenatal groups (Prenatal alcohol-exposed [PAE], Pair-fed [PF], and ad libitum-fed Controls [C]) were ovariectomized (OVX), with or without hormone replacement, or underwent Sham OVX. 5-HT-ir cells were examined in key brainstem areas.

RESULTS

Our data support the hypothesis that PAE has long-term effects on the 5-HT system of females and that ovarian steroids have a modulatory role in these effects. Intact (Sham OVX) PAE females had marginally lower numbers of 5-HT-ir neurons in the dorsal raphe nucleus of the brainstem compared with PF and C females. This marginal difference became significant following removal of hormones by OVX. Replacement with E2 restored the number of 5-HT-ir neurons in PAE females to control levels, while P4 reversed the effects of E2 . Importantly, despite these differential responses of the 5-HT system to ovarian steroids, there were no differences in E2 and P4 levels among prenatal treatment groups.

CONCLUSIONS

These data demonstrate long-term, adverse effects of PAE on the 5-HT system of females, as well as differential sensitivity of PAE compared with control females to the modulatory effects of ovarian steroids on 5-HT neurons. Our findings have important implications for understanding sex differences in 5-HT dysfunction in depression/anxiety disorders and the higher rates of these mental health problems in individuals with fetal alcohol spectrum disorder.

Oestradiol modulation of serotonin reuptake transporter and serotonin metabolism in the brain of monkeys

Serotonin (5-hydroxytryptamine; 5-HT) is an important brain neurotransmitter that is implicated in mental and neurodegenerative diseases and is modulated by ovarian hormones. Nevertheless, the effect of oestrogens on 5-HT neurotransmission in the primate caudate nucleus, putamen and nucleus accumbens, which are major components of the basal ganglia, and the anterior cerebral cortex, mainly the frontal and cingulate gyrus, is not well documented. The present study evaluated 5-HT reuptake transporter (SERT) and 5-HT metabolism in these brain regions in response to 1-month treatment with 17β-oestradiol in short-term (1 month) ovariectomised (OVX) monkeys (Macaca fascicularis). SERT-specific binding was measured by autoradiography using the radioligand [³H]citalopram. Biogenic amine concentrations were quantified by high-performance liquid chromatography. 17β-Oestradiol increased SERT in the superior frontal cortex and in the anterior cingulate cortex, in the nucleus accumbens, and in subregions of the caudate nucleus of OVX monkeys. 17β-Oestradiol left [³H]citalopram-specific binding unchanged in the putamen, as well as the dorsal and medial raphe nucleus. 17β-Oestradiol treatment decreased striatal concentrations of the precursor of 5-HT, 5-hydroxytryptophan, and increased 5-HT, dopamine and 3-methoxytyramine concentrations in the nucleus accumbens, caudate nucleus and putamen, whereas the concentrations of the metabolites 5-hydroxyindoleacetic acid, 3,4-dihydroxyphenylacetic acid and homovanillic acid remained unchanged. No effect of 17β-oestradiol treatment was observed for biogenic amine concentrations in the cortical regions. A significant positive correlation was observed between [³H]citalopram-specific binding and 5-HT concentrations in the caudate nucleus, putamen and nucleus accumbens, suggesting their link. These results have translational value for women with low oestrogen, such as those in surgical menopause or perimenopause.

Is basic research providing answers if adjuvant anti-estrogen treatment of breast cancer can induce cognitive impairment?

Adjuvant treatment of cancer by chemotherapy is associated with cognitive impairment in some cancer survivors. Breast cancer patients are frequently also receiving endocrine therapy with selective estrogen receptor modulators (SERMs) and/or aromatase inhibitors (AIs) to suppress the growth of estradiol sensitive breast tumors. Estrogens are well-known, however, to target brain areas involved in the regulation of cognitive behavior. In this review clinical and basic preclinical research is reviewed on the actions of estradiol, SERMs and AIs on brain and cognitive functioning to see if endocrine therapy potentially induces cognitive impairment and in that respect may contribute to the detrimental effects of chemotherapy on cognitive performance in breast cancer patients. Although many clinical studies may be underpowered to detect changes in cognitive function, current basic and clinical reports suggest that there is little evidence that AIs may have a lasting detrimental effect on cognitive performance in breast cancer patients. The clinical data on SERMs are not conclusive, but some studies do suggest that tamoxifen administration may form a risk for cognitive functioning particularly in older women. An explanation may come from basic preclinical research which indicates that tamoxifen often acts agonistic in the absence of estradiol but antagonistic in the presence of endogenous estradiol. It could be hypothesized that the negative effects of tamoxifen in older women is related to the so-called window of opportunity for estrogen. Administration of SERMs beyond this so-called window of opportunity may not be effective or might even have detrimental effects similar to estradiol.

Serotonin and Female Psychopathology

There are sex differences in the prevalence and presentation of many psychiatric disorders. Various trends in symptomatology have emerged that are thought to be linked to periods of hormonal fluctuations such as with menses, pregnancy or menopause. With data from animal and human studies, it has become clear that there is an important interplay between the serotonergic system and gonadal hormones. The majority of the research to date has focused on the influence that estrogen has within the CNS and, in particular, how it leads to an overall increase in serotonin synthesis and availability. In reviewing this female-specific topic we hope to raise awareness to sex/gender differences in psychopathology, help identify at-risk populations and consider development of new treatment options. Future research will also need to consider the influence that progesterone and oxytocin may have on sex-specific psychopathology as well as incorporate neuroimaging and consider the influence of hormones on the serotonergic system at a genetic level.

The effect of long-term ovariectomy on midbrain stress systems in free ranging macaques

Communication between the serotonin system and the CRF system plays a pivotal role in the mediation of stress and stress reactivity. CRF appears to be inhibitory of serotonin neurotransmission through the CRF receptor type 1 (CRF-R1). Serotonin neurons also detect the urocortins, which are thought to be anxiolytic. Components of the CRF system in the serotonergic dorsal raphe region were examined in macaques that were ovary-intact or ovariectomized for 3 years living in a relatively natural environment. Female Japanese macaques (Macaca fuscata) were ovariectomized or tubal-ligated (n=5/group) and returned to their natal troop for 3 years. Quantitation of (1) CRF innervation of the serotonergic dorsal raphe, (2) CRF-Receptor type 1 (CRF-R1) in the dorsal raphe, (3) Urocortin 1 (UCN1) cells near the Edinger-Westfal nucleus and (4) UCN1 axons, was obtained with immunocytochemical staining and image analysis. There was no statistical difference in CRF axonal staining in the dorsal raphe, or in UCN1 axonal staining near the dorsal raphe. However, the average number of detectable UCN1 postive cells was significantly lower in the Ovx group than in the Intact group (p=0.003). Average CRF-R1 positive pixel number and positive cell number were significantly higher in the Ovx group than in the Intact group (p=0.005 and 0.02, respectivly). The higher expression of CRF-R1 and lower expression of UCN1 in the Ovx group indicates they may be more vulnerable to stress. The greater expression of CRF-R1 could cause a greater inhibition of serotonin upon a stress-induced increase in CRF as well.

Effect of systemic kynurenine on cortical spreading depression and its modulation by sex hormones in rat

BACKGROUND

The aura symptoms in migraine are most likely due to cortical spreading depression (CSD). CSD is favored by NMDA receptor activation and increased cortical excitability. The latter probably explains why migraine with aura may appear when estrogen levels are high, like during pregnancy. Kynurenic acid, a derivative of tryptophan metabolism, is an endogenous NMDA receptor antagonist whose cerebral concentrations can be augmented by systemic administration of its precursor L-kynurenine.

OBJECTIVE

To determine if exogenous administration of L-kynurenine is able to influence KCl-induced CSD in rat, if the effect is sex-dependent and if it differs in females between the phases of the estrous cycle.

METHODS

Adult Sprague-Dawley rats (n=8/group) received intraperitoneal (i.p.) injections of L-kynurenine (L-KYN, 300 mg/kg), L-KYN combined with probenecid (L-KYN+PROB) that increases cortical concentration of KYNA by blocking its excretion from the central nervous system, probenecid alone (PROB, 200 mg/kg) or NaCl. Cortical kynurenic acid concentrations were determined by HPLC (n=7). Thirty minutes after the injections, CSDs were elicited by application of 1M KCl over the occipital cortex and recorded by DC electrocorticogram. In NaCl and L-KYN groups, supplementary females were added and CSD frequency was analyzed respective to the phases of the estrous cycle determined by vaginal smears.

RESULTS

In both sexes, PROB, L-KYN and L-KYN+PROB increased cortical kynurenic acid level. PROB, L-KYN and L-KYN+PROB with increasing potency decreased CSD frequency in female rats, while in males such an effect was significant only for L-KYN+PROB. The inhibitory effect of L-KYN on CSD frequency in females was most potent in diestrus.

CONCLUSION

L-Kynurenine administration suppresses CSD, most likely by increasing kynurenic acid levels in the cortex. Females are more sensitive to this suppressive effect of L-kynurenine than males. These results emphasize the role of sex hormones in migraine and open interesting novel perspectives for its preventive treatment.

Effect of ovarian steroids on gene expression related to synapse assembly in serotonin neurons of macaques

Dendritic spines are the elementary structural units of neural plasticity. In a model of hormone replacement therapy (HT), we sought to determine the effect of estradiol (E) and progesterone (P) on gene expression related to synapse assembly in a laser-captured preparation enriched for serotonin neurons from rhesus macaques. Microarray analysis was conducted (n = 2 animals/treatment), and the results were confirmed for pivotal genes with qRT-PCR on additional laser-captured material (n = 3 animals/treatment). Ovariectomized rhesus macaques were treated with placebo, E, or E + P via Silastic implants for 1 month. The midbrain was obtained, sectioned, and immunostained for tryptophan hydroxylase (TPH). TPH-positive neurons were laser captured using an arcturus laser dissection microscope (Pixel II). RNA from laser-captured serotonin neurons was hybridized to Rhesus Affymetrix GeneChips for screening purposes. There was a twofold or greater change in the expression of 63 probe sets in the cell adhesion molecule (CAM) category, and 31 probe sets in the synapse assembly category were similarly altered in E- and E + P-treated animals. qRT-PCR assays showed that E treatment induced a significant increase in ephrin receptor A4 (EPHA4) and in integrin A8 (ITGA8) but not in ephrin receptor B4 (EPHB4) or integrin B8 (ITGB8) expression. E also increased expression of cadherin 11 (CDH11), neuroligin 3 (NLGN3), neurexin 3 (NRXN3), syndecan 2 (SCD2), and neural cell adhesion molecule (NCAM) compared with placebo. Supplemental P treatment suppressed E-induced gene expression. In summary, ovarian steroids target gene expression of adhesion molecules in serotonin neurons that are important for synapse assembly.

Interactive effects of estrogen and serotonin on brain activation during working memory and affective processing in menopausal women

While cognitive changes and mood instability are frequent symptoms reported by menopausal women, the degree to which the decline in estrogen production is responsible is not yet clear. Several lines of evidence suggest that estrogen may produce its effects on cognition and mood through modulation of serotonergic function. To test this hypothesis, we used the tryptophan depletion (TD) paradigm to lower central serotonin levels and pharmacologically manipulated estrogen levels in healthy menopausal women. We examined the individual and combined effects of estradiol and serotonin on working memory, emotion processing and task-related brain activation. Eight healthy predominantly early postmenopausal women underwent TD or sham depletion followed by functional magnetic resonance imaging (fMRI) both before and after short-term transdermal estradiol 75-150 μg/d administration. There was an estradiol treatment by TD interaction for brain activation during performance on both the N-back Task (working memory) and Emotion Identification Task (affective processing). During the 2-back condition, TD attenuated activation prior to, but not after, estradiol treatment in the right and left dorsal lateral prefrontal and middle frontal/cingulate gyrus. During emotion identification, TD heightened activation in the orbital frontal cortex and bilateral amygdala, and this effect was attenuated by estradiol treatment. These results provide preliminary evidence that serotonergic effects directly mediate the impact of estrogen on brain activation during working memory and affective processing.

Ovarian steroids increase spinogenetic proteins in the macaque dorsal raphe

Dendritic spines are the basic structural units of neuronal plasticity. Intracellular signaling cascades that promote spinogenesis have centered on RhoGTPases. We found that ovarian steroids increase gene expression of RhoGTPases [Ras homolog gene family member A (RhoA), cell division control protein 42 homolog (Cdc42), and ras-related C3 botulinum toxin substrate (Rac)] in laser-captured serotonin neurons. We sought to confirm that the increases observed in gene expression translate to the protein level. In addition, a preliminary study was conducted to determine whether an increase in spines occurs via detection of the spine marker protein, postsynaptic density-95 (PSD-95). Adult ovariectomized (Ovx) monkeys were treated with estradiol (E), progesterone (P), or E+P for 1 month. Sections through the dorsal raphe nucleus were immunostained for RhoA and Cdc42 (n=3-4/group). The number and positive pixel area of RhoA-positive cells and the positive pixel area of Cdc42-positive fibers were determined. On combining E- and E+P-treated groups, there was a significant increase in the average and total cell number and positive pixel area of RhoA-positive cells. E, P, and E+P treatments, individually or combined, also increased the average and total positive pixel area of Cdc42-positive fibers. With remaining sections from two animals in each group, we conducted a preliminary examination of the regulation of PSD-95 protein expression. PSD-95, a postsynaptic scaffold protein, was examined with immunogold silver staining (n=2/group), and the total number of PSD-95-positive puncta was determined with stereology across four levels of the dorsal raphe. E, P, and E+P treatment significantly increased the total number of PSD-95-positive puncta. Together, these findings indicate that ovarian steroids act to increase gene and protein expression of two pivotal RhoGTPases involved in spinogenesis and preliminarily indicate that an increased number of spines and/or synapses result from this action. Increased spinogenesis on serotonin dendrites would facilitate excitatory glutamatergic input and in turn, increase serotonin neuronal activity throughout the brain.

Ovarian steroids increase glutamatergic related gene expression in serotonin neurons of macaques

Dendritic spines are the elementary structural units of neuronal plasticity and their proliferation and stabilization involve components of glutamate neurotransmission. In a model of hormone replacement therapy (HT), we sought the effect of estradiol (E) and progesterone (P) on gene expression related to glutamate neurotransmission in a laser captured preparation enriched for serotonin neurons from rhesus macaques. Microarray analysis was conducted (n=2 animals/treatment) and then confirmed for pivotal genes with qRT-PCR on additional laser captured material (n=3 animals/treatment). Ovariectomized rhesus macaques were treated with either placebo, E or E+P via Silastic implants for 1month prior to euthanasia. The midbrain was obtained, sectioned and immunostained for TPH. TPH-positive neurons were laser captured using an Arcturus Laser Dissection Microscope (Pixel II). RNA from laser captured serotonin neurons (n=2 animals/treatment) was hybridized to Rhesus Affymetrix GeneChips for screening purposes. There was a 2-fold or greater change in the expression of 28 probe sets related to glutamate processes in E and E+P treated animals. Quantitative (q) RT-PCR was conducted for 11 genes with a custom Taqman PCR array containing monkey specific primers and analyzed with ANOVA followed by Bonferroni's test. The log of the relative expression values indicated that in general, the responses to E and E+P were similar. Comparison of the relative expression or log relative expression in Ovx-controls to combined E and E+P treated groups with t-tests showed a significant increase in AMPA1 (GRIA1), AMPA2 (GRIA2), AMPA4 (GRIA4), NMDA2a (GRIN2A), metabotrophic glutamate receptor (GRM1), glutamine synthetase (GLUL), glutamate dehydrogenase (GLUD), glutamate cysteine ligase modifier subunit (GCLM), the glutamate transporter 2 (SLC1A2) and the glutamate transporter 3 (SLC1A3) with steroid treatment. There was no effect of steroid treatment on gene expression of the glutamate cysteine ligase catalytic subunit (GCLC). These data suggest that ovarian steroids target gene expression of ionotrophic and metabotrophic glutamate receptors in serotonin neurons. These receptors are present on dendritic spines and are necessary for spine maturation. The mRNAs coding for glutamate-related enzymes and transporters are likely derived from astrocytes or glutamate-containing terminals. Their induction by ovarian steroids indicates a complex upregulation of multiple components in the glutamate cycle and antioxidation, in addition to spine proliferation.

Long-term ovariectomy modulates the antidepressant-like action of estrogens, but not of antidepressants

Controversial results related to effectiveness of estrogen replacement therapy (ERT) to alleviate depression are frequently reported. The discrepancies could be related to (a) time when ERT is initiated after the beginning of menopause and/or (b) type of estrogen used. Furthermore, estrogens modulate the antidepressant effect of different compounds; therefore, the effectiveness of antidepressant drugs could also depend on the menopausal status. The aim of the present study was to analyze whether the time after estrogen decline can influence antidepressant-like effects of two estrogens and/or two antidepressants. Thus, the antidepressant-like actions of 17β-estradiol (E(2)), 17α-ethynyl-estradiol (EE(2)), fluoxetine (FLX) and desipramine (DMI) were studied at different periods (1, 3 and 12 weeks) after ovariectomy (OVX), using the forced swimming test (FST). Results showed that OVX increased depressive-like behavior only 1 week after OVX. The antidepressant-like actions of E(2), but not those of EE(2), were cancelled 12 weeks after OVX. Conversely, antidepressant-like actions of FLX and DMI were observed at 1, 3 and 12 weeks after OVX. In conclusion, while the antidepressant-like effects of estrogens depended on the time at which treatment is initiated after OVX as well as on the estrogenic compound used, antidepressant-like effects of FLX and DMI were not blocked by OVX.

Long-term ovariectomy alters social and anxious behaviors in semi-free ranging Japanese macaques

Symptoms of anxiety and depression often occur in young women after complete hysterectomy and in older women during menopause. There are many variables that are hard to control in human population studies, but that are absent to a large extent in stable nonhuman primate troops. However, macaques exhibit depressive and anxious behaviors in response to similar situations as humans such as isolation, stress, instability or aggression. Therefore, we hypothesized that examination of behavior in ovariectomized individuals in a stable macaque troop organized along matriarchal lineages and in which individuals have social support from extended family, would reveal effects that were due to the withdrawal of ovarian steroids without many of the confounds of human society. We also tested the hypothesis that ovariectomy would elicit and increase anxious behavior in a stressful situation such as brief exposure to single caging. Japanese macaques (Macaca fuscata) were ovariectomized (Ovx) or tubal-ligated (intact controls) at 3 years of age and allowed to mature for 3 years in a stable troop of approximately 300 individuals. Behaviors were recorded in the outdoor corral in the third year followed by individual temperament tests in single cages. There was no obvious difference in anxiety-related behaviors such as scratching between Ovx and tubal-ligated animals in the corral. Nonetheless, compared to tubal-ligated animals, Ovx animals exhibited a significant decrease in (1) positive social behavior, (2) initiating dominance behavior, (3) time receiving grooming, (4) locomoting, (5) mounting behavior, and in (6) consort behavior. However, Ovx females exhibited a significant increase in (1) consummatory behavior and (2) object play compared to tubal-ligated controls. In the individual temperament tests, Ovx individuals exhibited an increase in anxiety-related behaviors. There was no difference in adrenal weight/body weight suggesting that neither group was under chronic stress. These data indicate that ovarian hormones enable females to successfully navigate their social situation and may reduce anxiety in novel situations.

Long-term ovariectomy decreases serotonin neuron number and gene expression in free ranging macaques

The serotonin system responds to the ovarian steroids, estradiol (E) and progesterone (P), in women and female animal models. In macaques, ovarian steroid administration to ovariectomized (Ovx) individuals improves serotonin neural function through actions on pivotal serotonin-related genes and proteins, such as TPH2 (tryptophan hydroxylase 2), SERT (serotonin reuptake transporter), and the 5HT1A autoreceptor. In addition, ovarian steroid administration reduces gene and protein expression in the caspase-independent pathway and reduces DNA fragmentation in serotonin neurons. This study examines the hypothesis that long-term ovariectomy will lead to a loss of serotonin neurons and compromised gene expression in serotonin neurons. Female Japanese macaques were ovariectomized or tubal ligated (n=5/group) at 3 years of age and returned to their natal troop. After 3 years, the animals were collected, administered a fenfluramine challenge to determine global serotonin availability, and then euthanized. Fev, TPH2, SERT, and 5HT1A expression were examined with digoxigenin in situ hybridization (ISH) and quantitative image analysis. Cell number, positive pixel area, and average pixel density were determined. In the Ovx group, Fev, TPH2, SERT, and 5HT1A showed a significant decease in average and total cell number and positive pixel area. The reduction in Fev-positive neurons suggests that there were fewer serotonin neurons in Ovx animals compared to ovary-intact animals. The decrease in TPH2 in the Ovx animals was consistent with earlier results in 5-month Ovx animals, but it may be due to the decrease in cell number rather than a decrease in expression on an individual cell basis. The decrease in SERT and 5HT1A in long-term Ovx differed from previous studies in short-term Ovx. In summary, long-term ovarian steroid loss resulted in fewer serotonin neurons and overall lower Fev, TPH2, SERT, and 5HT1A gene expression. This may be due to serotonin cell death or to a negative impact on a long-term developmental process in young female macaques.

Epigenetic dysregulation of HTR2A in the brain of patients with schizophrenia and bipolar disorder

INTRODUCTION

HTR2A gene has been the subject of numerous studies in psychiatric genetics because LSD, which resembles serotonin causes psychosis and atypical antipsychotic drugs target the HTR2A receptor. However, evidence for the role of HTR2A polymorphism(s) in schizophrenia (SCZ) and bipolar disorder (BD) has been elusive. We hypothesized that epigenetic dysregulation of HTR2A may be involved in psycho-pathogenesis and analyzed promoter DNA methylome and expression of HTR2A in SCZ, BD and control subjects.

METHOD

DNA derived from post-mortem brains of patients with SCZ and BD and matched control subjects (each 35) were obtained from the Stanley Medical Research Institute. While bisulfite DNA sequencing was used to screen and quantify cytosine methylation in the HTR2A promoter, corresponding gene expression was analyzed by qRT-PCR.

RESULTS

We found strong evidence for epigenetic fine-tuning of HTR2A expression. In general, the expression of HTR2A in individuals carrying the C allele of T102C (or G allele of -1438A/G polymorphism) was higher than TT genotype. Interestingly, promoter DNA of HTR2A was hypermethylated at and around the -1438A/G polymorphic site, but was hypomethylated at and around T102C polymorphic site in SCZ and BD compared to the controls. Furthermore, epigenetic down-regulation of HTR2A was associated with early age of disease onset in SCZ and BD.

CONCLUSION

Epigenetic dysregulation of HTR2A may contribute to SCZ, BD and earlier age of disease onset. Further research is required to delineate the dysregulation of other components of serotoninergic pathway to design new therapeutics based on the downstream effects of serotonin.

Oestrogen: an overlooked mediator in the neuropsychopharmacology of treatment response?

Major depression (MD) and anorexia nervosa (AN) often present comorbidly and both share some affective symptoms, despite obvious phenotypic differences. In the illness phase, pathophysiological evidence indicates similar abnormalities in both clinical groups including dysfunction in the serotonin (5-HT) system (of which some abnormalities persist following recovery) and between 60% and 80% of patients in both groups present with significant hyperactivity of the hypothalamo-pituitary-adrenal (HPA) axis. First-line approach to treatment for MD involves modulation of the 5-HT system using selective serotonin reuptake inhibitors (SSRIs). For AN, treatment with SSRIs has been shown to be considerably less effective compared to MD. Both illnesses show marked dysregulation in the HPA axis. A consequence of SSRI treatment is a reduction and/or normalization of indices of the HPA axis [i.e. cortisol, adrenocorticotropic hormone (ACTH)], which is consistent with recovery levels in both clinical groups. Oestrogen (in high doses) has been shown to exert antidepressant effects and positively impact on MD symptoms as a treatment in its own right, or in combination with antidepressants, in women of menopausal age. It is proposed that a combination of SSRIs and oestrogen therapy may facilitate physiological normalization in MD in women of non-menopausal age and in AN. Preliminary evidence suggests oestrogen treatment alone is of some benefit to patients and it is proposed that a combination of SSRI and oestrogen will precipitate and potentially accelerate symptomatic remission. Should this approach be successful, it offers the capacity for improvement over traditional antidepressant use in women diagnosed with MD and a novel strategy for the treatment of AN, a serious clinical illness associated with the highest mortality of any psychiatric condition.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Potential Antidepressant Role of Neurotransmitter CART: Implications for Mental Disorders

Depression is one of the most prevalent and debilitating public health concerns. Although no single cause of depression has been identified, it appears that interaction among genetic, epigenetic, biochemical, environmental, and psychosocial factors may explain its etiology. Further, only a fraction of depressed patients show full remission while using current antidepressants. Therefore, identifying common pathways of the disorder and using that knowledge to develop more effective pharmacological treatments are two primary targets of research in this field. Brain-enriched neurotransmitter CART (cocaine- and amphetamine-regulated transcript) has multiple functions related to emotions. It is a potential neurotrophic factor and is involved in the regulation of hypothalamic-pituitary-adrenal axis and stress response as well as in energy homeostasis. CART is also highly expressed in limbic system, which is considered to have an important role in regulating mood. Notably, adolescents carrying a missense mutation in the CART gene exhibit increased depression and anxiety. Hence, CART peptide may be a novel promising antidepressant agent. In this paper, we summarize recent progress in depression and CART. In particular, we emphasize a new antidepressant function for CART.

Overexpression or knockdown of rat tryptophan hyroxylase-2 has opposing effects on anxiety behavior in an estrogen-dependent manner

Previous studies showed that chronic estrogen treatment increases tryptophan hydroxylase-2 (TpH2) mRNA in the caudal dorsal raphe nucleus (DRN), and this increase was associated with decreased anxiety. The present study explored the interaction of estrogen and targeted, bidirectional manipulation of TpH2 expression in the caudal DRN by knockdown or viral overexpression, to decrease or increase tryptophan hydroxylase expression respectively, on anxiety behavior. Rats were ovariectomized and replaced with empty or estradiol capsules (OVX, OVX/E, respectively). Animals received microinfusions of either antisense TpH2 or control morpholino oligonucleotides into caudal DRN and were later tested in the open field test. A separate group of animals were microinfused with TpH2-GFP or GFP-only herpes simplex viral vectors into caudal DRN and tested in the open field. The bidirectional impact of manipulations on TpH2 expression was confirmed using a combination of quantitative protein and mRNA measurements; TpH2 expression changes were limited to discrete subregions of DRN that were targeted by the manipulations. Estradiol decreased anxiety in all behavioral measures. In the OVX/E group, TpH2 knockdown significantly decreased time spent in the center of the open field, but not in the OVX group, suggesting that TpH2 knockdown reduced the anxiolytic effects of estrogen. Conversely, TpH2 overexpression in the OVX group mimicked the effects of estrogen, as measured by increased time spent in the center of the open field. These results suggest that estrogen and TpH2 in the caudal DRN have a critical interaction in regulating anxiety-like behavior.