Role of glucocorticoids in dopamine-related neuropsychiatric disorders

The Dichotomy of Threat and Deprivation as Subtypes of Childhood Maltreatment: Differential Functional Connectivity Patterns of Threat and Reward Circuits in an Adult Trauma Sample

BACKGROUND

Childhood maltreatment is associated with reduced activation of the nucleus accumbens, a central region in the reward network, and overactivity in the amygdala, a key region in threat processing. However, the long-lasting impact of these associations in the context of later-life stress is not well understood. The current study explored the association between childhood threat and deprivation and functional connectivity of threat and reward regions in an adult trauma sample.

METHODS

Trauma survivors (N = 169; mean age [SD] = 32.2 [10.3] years; female = 55.6%) were recruited from a level I trauma center. Two weeks after injury, participants completed the Childhood Trauma Questionnaire (measuring experiences of threat and deprivation) and underwent resting-state functional magnetic resonance imaging. Seed-to-voxel analyses evaluated the effect of childhood threat and deprivation on amygdala and nucleus accumbens resting-state connectivity.

RESULTS

Higher levels of threat were associated with increased connectivity between the right nucleus accumbens with temporal fusiform gyrus/parahippocampal gyrus and the left amygdala and the precuneus (false discovery rate-corrected p < .05). After controlling for posttraumatic symptoms 2 weeks posttrauma and lifetime trauma exposure, only the nucleus accumbens findings survived. There were no significant relationships between experiences of childhood deprivation and amygdala or nucleus accumbens connectivity.

CONCLUSIONS

Experiences of threat are associated with increased nucleus accumbens and amygdala connectivity, which may reflect a preparedness to detect salient and visual stimuli. This may also reflect a propensity toward dysregulated reward processing. Overall, these results suggest that childhood threat may be contributing to aberrant neural baseline reward and threat sensitivity later in life in an adult trauma sample.

Gene expression in the primate orbitofrontal cortex related to anxious temperament

Anxiety disorders are among the most prevalent psychiatric disorders, causing significant suffering and disability. Relative to other psychiatric disorders, anxiety disorders tend to emerge early in life, supporting the importance of developmental mechanisms in their emergence and maintenance. Behavioral inhibition (BI) is a temperament that emerges early in life and, when stable and extreme, is linked to an increased risk for the later development of anxiety disorders and other stress-related psychopathology. Understanding the neural systems and molecular mechanisms underlying this dispositional risk could provide insight into treatment targets for anxiety disorders. Nonhuman primates (NHPs) have an anxiety-related temperament, called anxious temperament (AT), that is remarkably similar to BI in humans, facilitating the design of highly translational models for studying the early risk for stress-related psychopathology. Because of the recent evolutionary divergence between humans and NHPs, many of the anxiety-related brain regions that contribute to psychopathology are highly similar in terms of their structure and function, particularly with respect to the prefrontal cortex. The orbitofrontal cortex plays a critical role in the flexible encoding and regulation of threat responses, in part through connections with subcortical structures like the amygdala. Here, we explore individual differences in the transcriptional profile of cells within the region, using laser capture microdissection and single nuclear sequencing, providing insight into the molecules underlying individual differences in AT-related function of the pOFC, with a particular focus on previously implicated cellular systems, including neurotrophins and glucocorticoid signaling.

Cannabidiol versus placebo as adjunctive treatment in early psychosis: study protocol for randomized controlled trial

BACKGROUND

Psychotic disorders are a leading cause of disability in young adults. Antipsychotics have been the primary intervention for psychosis for over 60 years, and yet, we have made little progress in treating negative symptoms, neurocognition, and functional disability. There is growing evidence that cannabidiol (CBD) is effective in treating positive psychotic symptoms, possibly also negative and neurocognitive symptoms, and moreover is well tolerated compared to other psychotropic medications. Anecdotally, patients participating in the Cognitive Assessment and Risk Evaluation (CARE) Early Psychosis Treatment Program at the University of California, San Diego, are self-administering CBD and report subjective improvement in stress, anxiety, and ability to cope with symptoms. The overarching aim of the trial is to explore the effectiveness of CBD augmentation on symptoms and neurocognition in early psychosis while also exploring the mechanism of action of CBD and predictors of response to treatment. The mechanism by which cannabidiol has a therapeutic effect on psychosis is poorly understood. Recent evidence has suggested that CBD may reduce stress and pro-inflammatory biomarker levels. Endocannabinoids also have powerful roles in eating behavior, reward, and mood, indicating these neurotransmitters may play a role in reducing hyperphagia and metabolic abnormalities that are present early in the course of psychotic illness and exacerbated by antipsychotic medication. The neurophysiological effects of CBD have been studied in animal models of psychosis that show improvements in information processing in response to CBD, but there are no studies in individuals with early psychosis.

METHOD

A total of 120 individuals in the early stages of psychosis will be randomized to 1000 mg of CBD versus placebo as an adjunct to existing treatment in a 8-week, double-blind superiority randomized control trial. The primary outcome measures are symptoms and neurocognition.

DISCUSSION

We hypothesized that CBD will improve symptoms and neurocognition as well as secondary outcome measures of neurohormones, inflammation, eating behaviors, and information processing. Importantly, predictors, moderators, and mediators of the CBD effects will be examined. A better understanding of which individuals are likely to respond to CBD can inform treatment planning and personalize treatment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04411225. Registered on June 2, 2020.

Role of Dopamine Transporter in the Relationship Between Plasma Cortisol and Cognition

OBJECTIVE

Cortisol is associated with cognition in both healthy individuals and patients with neuropsychiatric disorders. Regarding the effects of cortisol on the dopamine system and the association between dopamine transporter (DAT) and cognition, DAT might be a central target linking cortisol and cognition. This study explored the role of striatal DAT in the cortisol-cognition relationship.

METHODS

We recruited 33 patients with carbon monoxide poisoning and 33 age- and sex-matched healthy controls. All participants underwent cognitive assessments of attention, memory, and executive function. Single-photon emission computed tomography with 99mTc-TRODAT was used to determine striatal DAT availability. Plasma cortisol, tumor necrosis factor α, and interleukin-10 levels were measured using enzyme-linked immunosorbent assays.

RESULTS

Compared with healthy controls, patients with carbon monoxide poisoning had lower cognitive performance, bilateral striatal DAT availability, and plasma tumor necrosis factor-α levels and higher cortisol and interleukin-10 levels. In all participants, plasma cortisol level and bilateral striatal DAT availability were negatively and positively related to cognition, respectively, including memory and executive function with β from -0.361 (95% confidence interval [CI] = -0.633 to -0.090) to 0.588 (95% CI = 0.319 to 0.858). Moreover, bilateral striatal DAT mediated the cortisol-cognition relationship with indirect effects from -0.067 (95% CI = -0.179 to -0.001) to -0.135 (95% CI = -0.295 to -0.024). The cytokine levels did not influence the mediation effects.

CONCLUSIONS

This is the first study to demonstrate that striatal DAT mediates the cortisol-cognition relationship. Future studies are needed to comprehensively evaluate the role of the dopamine system in cortisol-cognition associations and treatment implications.

Insulin-like Growth Factor II Prevents MPP+ and Glucocorticoid Mitochondrial-Oxidative and Neuronal Damage in Dopaminergic Neurons

Stress seems to contribute to Parkinson’s disease (PD) neuropathology, probably by dysregulation of the hypothalamic–pituitary–adrenal axis. Key factors in this pathophysiology are oxidative stress and mitochondrial dysfunction and neuronal glucocorticoid-induced toxicity. The insulin-like growth factor II (IGF-II), a pleiotropic hormone, has shown antioxidant and neuroprotective effects in some neurodegenerative disorders. Our aim was to examine the protective effect of IGF-II on a dopaminergic cellular combined model of PD and mild to moderate stress measuring oxidative stress parameters, mitochondrial and neuronal markers, and signalling pathways. IGF-II counteracts the mitochondrial-oxidative damage produced by the toxic synergistic effect of corticosterone and 1-methyl-4-phenylpyridinium, protecting dopaminergic neurons from death and neurodegeneration. IGF-II promotes PKC activation and nuclear factor (erythroid-derived 2)-like 2 antioxidant response in a glucocorticoid receptor-dependent pathway, preventing oxidative cell damage and maintaining mitochondrial function. Thus, IGF-II is a potential therapeutic tool for treatment and prevention of disease progression in PD patients suffering mild to moderate emotional stress.

Impact of Glucocorticoid on a Cellular Model of Parkinson's Disease: Oxidative Stress and Mitochondrial Function

Stress seems to contribute to the neuropathology of Parkinson's disease (PD), possibly by dysregulation of the hypothalamic-pituitary-adrenal axis. Oxidative distress and mitochondrial dysfunction are key factors involved in the pathophysiology of PD and neuronal glucocorticoid-induced toxicity. Animal PD models have been generated to study the effects of hormonal stress, but no in vitro model has yet been developed. Our aim was to examine the impact of corticosterone (CORT) administration on a dopaminergic neuronal cell model of PD induced by the neurotoxin MPP⁺, as a new combined PD model based on the marker of endocrine response to stress, CORT, and oxidative-mitochondrial damage. We determined the impact of CORT, MPP⁺ and their co-incubation on reactive oxygen species production (O2^-•), oxidative stress cellular markers (advanced-oxidation protein products and total antioxidant status), mitochondrial function (mitochondrial membrane potential and mitochondrial oxygen consumption rate) and neurodegeneration (Fluoro-Jade staining). Accordingly, the administration of MPP⁺ or CORT individually led to cell damage compared to controls (p < 0.05), as determined by several methods, whereas their co-incubation produced strong cell damage (p < 0.05). The combined model described here could be appropriate for investigating neuropathological hallmarks and for evaluating potential new therapeutic tools for PD patients suffering mild to moderate emotional stress.

Early life stress reduces voluntary exercise and its prevention of diet-induced obesity and metabolic dysfunction in mice

The development of obesity-related metabolic syndrome (MetS) involves a complex interaction of genetic and environmental factors. One environmental factor found to be significantly associated with MetS is early life stress (ELS). We have previously reported on our mouse model of ELS, induced by neonatal maternal separation (NMS), that displays altered regulation of the hypothalamic-pituitary-adrenal (HPA) axis and increased sensitivity in the urogenital organs, which was attenuated by voluntary wheel running. Here, we are using our NMS model to determine if ELS-induced changes in the HPA axis also influence weight gain and MetS. Naïve (non-stressed) and NMS male mice were given free access to a running wheel and a low-fat control diet at 4-weeks of age. At 16-weeks of age, half of the mice were transitioned to a high fat/sucrose (HFS) diet to investigate if NMS influences the effectiveness of voluntary exercise to prevent diet-induced obesity and MetS. Overall, we observed a greater impact of voluntary exercise on prevention of HFS diet-induced outcomes in naïve mice, compared to NMS mice. Although body weight and fat mass were still significantly higher, exercise attenuated fasting insulin levels and mRNA levels of inflammatory markers in epididymal adipose tissue in HFS diet-fed naïve mice. Only moderate changes were observed in exercised NMS mice on a HFS diet, although this could partially be explained by reduced running distance within this group. Interestingly, sedentary NMS mice on a control diet displayed impaired glucose homeostasis and moderately increased pro-inflammatory mRNA levels in epididymal adipose, suggesting that early life stress alone impairs metabolic function and negatively impacts the therapeutic effect of voluntary exercise.

A human minisatellite hosts an alternative transcription start site for NPRL3 driving its expression in a repeat number-dependent manner

Minisatellites, also called variable number of tandem repeats (VNTRs), are a class of repetitive elements that may affect gene expression at multiple levels and have been correlated to disease. Their identification and role as expression quantitative trait loci (eQTL) have been limited by their absence in comparative genomic hybridization and single nucleotide polymorphisms arrays. By taking advantage of cap analysis of gene expression (CAGE), we describe a new example of a minisatellite hosting a transcription start site (TSS) which expression is dependent on the repeat number. It is located in the third intron of the gene nitrogen permease regulator like protein 3 (NPRL3). NPRL3 is a component of the GAP activity toward rags 1 protein complex that inhibits mammalian target of rapamycin complex 1 (mTORC1) activity and it is found mutated in familial focal cortical dysplasia and familial focal epilepsy. CAGE tags represent an alternative TSS identifying TAGNPRL3 messenger RNAs (mRNAs). TAGNPRL3 is expressed in red blood cells both at mRNA and protein levels, it interacts with its protein partner NPRL2 and its overexpression inhibits cell proliferation. This study provides an example of a minisatellite that is both a TSS and an eQTL as well as identifies a new VNTR that may modify mTORC1 activity.

Cognition- and circuit-based dysfunction in a mouse model of 22q11.2 microdeletion syndrome: effects of stress

Genetic microdeletion at the 22q11 locus is associated with very high risk for schizophrenia. The 22q11.2 microdeletion (Df(h22q11)/+) mouse model shows cognitive deficits observed in this disorder, some of which can be linked to dysfunction of the prefrontal cortex (PFC). We used behavioral (n = 10 per genotype), electrophysiological (n = 7 per genotype per group), and neuroanatomical (n = 5 per genotype) techniques to investigate schizophrenia-related pathology of Df(h22q11)/+ mice, which showed a significant decrease in the total number of parvalbumin positive interneurons in the medial PFC. The Df(h22q11)/+ mice when tested on PFC-dependent behavioral tasks, including gambling tasks, perform significantly worse than control animals while exhibiting normal behavior on hippocampus-dependent tasks. They also show a significant decrease in hippocampus-medial Prefrontal cortex (H-PFC) synaptic plasticity (long-term potentiation, LTP). Acute platform stress almost abolished H-PFC LTP in both wild-type and Df(h22q11)/+ mice. H-PFC LTP was restored to prestress levels by clozapine (3 mg/kg i.p.) in stressed Df(h22q11)/+ mice, but the restoration of stress-induced LTP, while significant, was similar between wild-type and Df(h22q11)/+ mice. A medial PFC dysfunction may underlie the negative and cognitive symptoms in human 22q11 deletion carriers, and these results are relevant to the current debate on the utility of clozapine in such subjects.

Emotional Stability Interacts with Cortisol Levels Before fMRI on Brain Processing of Fearful Faces

Functional-Magnetic-Imaging (fMRI) is widely adopted to investigate neurophysiological correlates of emotion processing (EP). However, studies have reported that scanning procedures in neuroimaging protocols may increase or cause anxiety and psychological distress related with the scanning, thus inducing peripheral cortisol release. These phenomena may in turn impact on brain EP. Additionally, previous findings have indicated that inter-individual differences in stress-response intensity are mediated by levels of Emotional Stability (ES), a personality trait that has been associated with brain activity during EP, especially in amygdala and prefrontal cortex (PFC). The aim of this study was to investigate the interaction between indices of stress related to anticipation of fMRI scanning and levels of ES on amygdala and PFC activity during EP. With this aim, 55 healthy volunteers were characterized for trait ES. Furthermore, salivary cortisol levels at baseline and soon before fMRI scanning were measured as an index of stress related to scanning anticipation. During fMRI, participants performed an explicit EP task. We found that variation in salivary cortisol (Δc) interacts with ES on left amygdala and PFC activity during EP. More in details, in the context of a higher ES, the greater the Δc, the lower the activity in left amygdala and PFC. In the context of lower ES, the opposite Δc-brain activity relationship was found. Our results suggest that the stressful potential of fMRI interacts with personality traits in modulating brain activity during EP. These findings should be taken into account when interpreting neuroimaging studies especially exploring brain physiology during EP.

The effects of early life stress on reward processing

Early life stress (ELS), in the form of childhood maltreatment, abuse, or neglect, increases the risk for psychiatric sequelae later in life. The neurobiology of response to early stress and of reward processing overlap substantially, leading to the prediction that reward processing may be a primary mediator of the effects of early life stress. We describe a growing body of literature investigating the effects of early life stressors on reward processing in animals and humans. Despite variation in the reviewed studies, an emerging pattern of results indicates that ELS results in deficits of ventral striatum-related functions of reward responsiveness and approach motivation, especially when the stressor is experienced in early in development. For stressors experienced later in the juvenile period and adolescence, the animal literature suggests an opposite effect, in which ELS results in increased hedonic drive. Future research in this area will help elucidate the transdiagnostic impact of early life stress, and therefore potentially identify and intervene with at-risk youth, prior to the emergence of clinical psychopathology.

Neonatal immune activation by lipopolysaccharide causes inadequate emotional responses to novel situations but no changes in anxiety or cognitive behavior in Wistar rats

Infection during the prenatal or neonatal stages of life is considered one of the major risk factors for the development of mental diseases such as schizophrenia or autism. However, the impacts of such an immune challenge on adult behavior are still not clear. In our study, we used a model of early postnatal immune activation by the application of bacterial endotoxin lipopolysaccharide (LPS) to rat pups at a dose of 2 mg/kg from postnatal day (PD) 5 to PD 9. In adulthood, the rats were tested in a battery of tasks probing various aspects of behavior: spontaneous activity (open field test), social behavior (social interactions and female bedding exploration), anxiety (elevated plus maze), cognition (active place avoidance in Carousel) and emotional response (ultrasonic vocalization recording). Moreover, we tested sensitivity to acute challenge with MK-801, a psychotomimetic drug. Our results show that the application of LPS led to increased self-grooming in the female bedding exploration test and inadequate emotional reactions in Carousel maze displayed by ultrasonic vocalizations. However, it did not have serious consequences on exploration, locomotion, social behavior or cognition. Furthermore, exposition to MK-801 did not trigger social or cognitive deficits in the LPS-treated rats. We conclude that the emotional domain is the most sensitive to the changes induced by neonatal immune activation in rats, including a disrupted response to novel and stressful situations in early adulthood (similar to that observed in human patients suffering from schizophrenia or autism), while other aspects of tested behavior remain unaffected.

Early Life Stress, Depression And Parkinson's Disease: A New Approach

This review aims to shed light on the relationship that involves exposure to early life stress, depression and Parkinson's disease (PD). A systematic literature search was conducted in Pubmed, MEDLINE, EBSCOHost and Google Scholar and relevant data were submitted to a meta-analysis . Early life stress may contribute to the development of depression and patients with depression are at risk of developing PD later in life. Depression is a common non-motor symptom preceding motor symptoms in PD. Stimulation of regions contiguous to the substantia nigra as well as dopamine (DA) agonists have been shown to be able to attenuate depression. Therefore, since PD causes depletion of dopaminergic neurons in the substantia nigra, depression, rather than being just a simple mood disorder, may be part of the pathophysiological process that leads to PD. It is plausible that the mesocortical and mesolimbic dopaminergic pathways that mediate mood, emotion, and/or cognitive function may also play a key role in depression associated with PD. Here, we propose that a medication designed to address a deficiency in serotonin is more likely to influence motor symptoms of PD associated with depression. This review highlights the effects of an antidepressant, Fluvoxamine maleate, in an animal model that combines depressive-like symptoms and Parkinsonism.

To Do or Not to Do: Dopamine, Affordability and the Economics of Opportunity

Five years ago, we introduced the thrift hypothesis of dopamine (DA), suggesting that the primary role of DA in adaptive behavior is regulating behavioral energy expenditure to match the prevailing economic conditions of the environment. Here we elaborate that hypothesis with several new ideas. First, we introduce the concept of affordability, suggesting that costs must necessarily be evaluated with respect to the availability of resources to the organism, which computes a value not only for the potential reward opportunity, but also the value of resources expended. Placing both costs and benefits within the context of the larger economy in which the animal is functioning requires consideration of the different timescales against which to compute resource availability, or average reward rate. Appropriate windows of computation for tracking resources requires corresponding neural substrates that operate on these different timescales. In discussing temporal patterns of DA signaling, we focus on a neglected form of DA plasticity and adaptation, changes in the physical substrate of the DA system itself, such as up- and down-regulation of receptors or release probability. We argue that changes in the DA substrate itself fundamentally alter its computational function, which we propose mediates adaptations to longer temporal horizons and economic conditions. In developing our hypothesis, we focus on DA D2 receptors (D2R), arguing that D2R implements a form of “cost control” in response to the environmental economy, serving as the “brain’s comptroller”. We propose that the balance between the direct and indirect pathway, regulated by relative expression of D1 and D2 DA receptors, implements affordability. Finally, as we review data, we discuss limitations in current approaches that impede fully investigating the proposed hypothesis and highlight alternative, more semi-naturalistic strategies more conducive to neuroeconomic investigations on the role of DA in adaptive behavior.

Infralimbic dopamine D2 receptors mediate glucocorticoid-induced facilitation of auditory fear memory extinction in rats

The infralimbic (IL) cortex of the medial prefrontal cortex plays an important role in the extinction of fear memory. Also, it has been showed that both brain glucocorticoid and dopamine receptors are involved in many processes such as fear extinction that drive learning and memory; however, the interaction of these receptors in the IL cortex remains unclear. We examined a putative interaction between the effects of glucocorticoid and dopamine receptors stimulation in the IL cortex on fear memory extinction in an auditory fear conditioning paradigm in male rats. Corticosterone (the endogenous glucocorticoid receptor ligand), or RU38486 (the synthetic glucocorticoid receptor antagonist) microinfusion into the IL cortex 10 min before test 1 attenuated auditory fear expression at tests 1-3, suggesting as an enhancement of fear extinction. The effect of corticosterone, but not RU38486 was counteracted by the dopamine D2 receptor antagonist sulpiride pre-treatment administered into the IL (at a dose that failed to alter freezing behavior on its own). In contrast, intra-IL infusion of the dopamine D1 receptor antagonist SCH23390 pre-treatment failed to alter freezing behavior. These findings provide evidence for the involvement of the IL cortex D2 receptors in CORT-induced facilitation of fear memory extinction.

Cortisol alters reward processing in the human brain

Dysfunctional reward processing is known to play a central role for the development of psychiatric disorders. Glucocorticoids that are secreted in response to stress have been shown to attenuate reward sensitivity and thereby might promote the onset of psychopathology. However, the underlying neurobiological mechanisms mediating stress hormone effects on reward processing as well as potential sex differences remain elusive. In this neuroimaging study, we administered 30mg cortisol or a placebo to 30 men and 30 women and subsequently tested them in the Monetary Incentive Delay Task. Cortisol attenuated anticipatory neural responses to a verbal and a monetary reward in the left pallidum and the right anterior parahippocampal gyrus. Furthermore, in men, activation in the amygdala, the precuneus, the anterior cingulate, and in hippocampal regions was reduced under cortisol, whereas in cortisol-treated women a signal increase was observed in these regions. Behavioral performance also indicated that reward learning in men is impaired under high cortisol concentrations, while it is augmented in women. These findings illustrate that the stress hormone cortisol substantially diminishes reward anticipation and provide first evidence that cortisol effects on the neural reward system are sensitive to sex differences, which might translate into different vulnerabilities for psychiatric disorders.

Long-term consequences of prenatal stress and neurotoxicants exposure on neurodevelopment

There is a large consensus that the prenatal environment determines the susceptibility to pathological conditions later in life. The hypothesis most widely accepted is that exposure to insults inducing adverse conditions in-utero may have negative effects on the development of target organs, disrupting homeostasis and increasing the risk of diseases at adulthood. Several models have been proposed to investigate the fetal origins of adult diseases, but although these approaches hold true for almost all diseases, particular attention has been focused on disorders related to the central nervous system, since the brain is particularly sensitive to alterations of the microenvironment during early development. Neurobiological disorders can be broadly divided into developmental, neurodegenerative and neuropsychiatric disorders. Even though most of these diseases share genetic risk factors, the onset of the disorders cannot be explained solely by inheritance. Therefore, current understanding presumes that the interactions of environmental input, may lead to different disorders. Among the insults that can play a direct or indirect role in the development of neurobiological disorders are stress, infections, drug abuse, and environmental contaminants. Our laboratories have been involved in the study of the neurobiological impact of gestational stress on the offspring (Dr. Antonelli's lab) and on the effect of gestational exposure to toxicants, mainly methyl mercury (MeHg) and perfluorinated compounds (PFCs) (Dr. Ceccatelli's lab). In this focused review, we will review the specialized literature but we will concentrate mostly on our own work on the long term neurodevelopmental consequences of gestational exposure to stress and neurotoxicants.

Cushing Disease Presenting as Primary Psychiatric Illness: A Case Report and Literature Review

We report the case of a woman with long-standing refractory depression and psychotic features who was eventually diagnosed with Cushing disease. After surgical treatment of a pituitary adenoma, she experienced gradual psychiatric recovery and was eventually able to discontinue all psychotropic medication. We review the psychiatric components of Cushing disease, implications of psychiatric illnesses for the treatment and prognosis of Cushing disease, and potential pathophysiological mechanisms linking glucocorticoid excess to psychiatric illness.

The impact of genome wide supported microRNA-137 (MIR137) risk variants on frontal and striatal white matter integrity, neurocognitive functioning, and negative symptoms in schizophrenia

Although genome wide association studies have highlighted MicroRNA 137 (MIR137) as a novel susceptibility gene for schizophrenia, the mechanisms by which MIR137 risk variants mediate the neurobiology of schizophrenia are not clear. Based on extant data linking MIR 137 gene with structural brain anomalies and functional brain activations in schizophrenia, we hypothesized that MIR137 risk variants rs1625579 and rs1198588 would be associated with reduced fractional anisotropy in frontostriatal brain regions, impaired neurocognitive functioning and worse psychotic symptoms in schizophrenia patients compared with healthy controls. A total of 147 Chinese participants (84 patients with DSM-IV diagnosis of schizophrenia (SCZ) and 63 healthy controls (HC)) were genotyped using blood samples and underwent diffusion tensor imaging. Neurocognitive domains and psychotic symptoms were assessed using The Brief Assessment of Cognition Battery for Schizophrenia and Positive and Negative Syndrome Scale respectively. We found significant diagnosis-genotype interactions in the right orbitofrontal regions (rs1625579: F = 5.44, P = 0.021; rs1198599: F = 7.55, P = 0.005), left striatum (rs1625579: F = 8.09, P=0.007; rs1198599: F=9.56, P = 0.002), and negative symptoms (rs1625579: t = 2.45, P = 0.016; rs1198588: t = 2.29, P = 0.024). Specifically, SCZ carrying the risk TT genotype had worse negative symptoms and decreased FA in the fronto-striatal regions compared to G and A allele carriers for rs1625579 and rs1198588 respectively, and worse attention and processing speed compared with G-allele for rs1625579. Our findings suggested that the MI137 risk variants were associated with decreased fronto-striatal brain white matter integrity which may underlie poorer attention, processing speed, and greater negative symptoms in schizophrenia.

The relationship of serum cortisol levels with depression, cognitive function and sleep disorders in chronic kidney disease and hemodialysis patients

In the present study, the relationships between cortisol, cognitive function, depressive behavior, and sleep quality in chronic kidney disease (CKD) and hemodialysis (HD) patients was investigated. Patients underwent history taking, physical examination, biochemical analysis, 24-h urine collection (for CKD patients only), measurement of dialysis adequacy (for HD patients only), evaluation of cognitive function, depressive behavior and sleep quality. Among study participants 58 had creatinine clearance ≥60 mL/min/1.73 m(2) (Group 1), 41 had creatinine clearance between 30 and 59 mL/min/1.73 m(2) (Group 2), 25 had creatinine clearance between 15 and 29 mL/min/1.73 m(2) (Group 3) and 12 had creatinine clearance <15 mL/min/1.73 m(2) (Group 4). 38 patients were regular HD patients (Group 5). The cortisol levels in Group 1, 2, 3, 4 and 5 patients were 472.3 ± 138.4, 490.2 ± 214.3, 541.6 ± 172.8, 569.9 ± 101.0 and 637.8 ± 153.7 nmol/L, respectively (P < 0.0001 for trend). In both non-dialysis patient group and dialysis patients linear regression analysis showed that cortisol was independently related with Beck depression inventory (BDI) score (P: 0.013 and 0.001, respectively) but not with cognitive function and sleep quality. In conclusion serum cortisol levels were independently associated with depressive behavior both in CKD and HD patients but not with cognitive function and sleep quality.

MicroRNA-137 regulates a glucocorticoid receptor-dependent signalling network: implications for the etiology of schizophrenia

BACKGROUND

Schizophrenia is a highly heritable neurodevelopmental disorder. A genetic variant of microRNA-137 (miR-137) has yielded significant genome-wide association with schizophrenia, suggesting that this miRNA plays a key role in its etiology. Therefore, a molecular network of interacting miR-137 targets may provide insights into the biological processes underlying schizophrenia.

METHODS

We first used bioinformatics tools to obtain and analyze predicted human and mouse miR-137 targets. We then determined miR-137 levels in rat barrel cortex after environmental enrichment (EE), a neuronal plasticity model that induces upregulation of several predicted miR-137 targets. Subsequently, expression changes of these predicted targets were examined through loss of miR-137 function experiments in rat cortical neurons. Finally, we conducted bioinformatics and literature analyses to examine the targets that were upregulated upon miR-137 downregulation.

RESULTS

Predicted human and mouse miR-137 targets were enriched in neuronal processes, such as axon guidance, neuritogenesis and neurotransmission. The miR-137 levels were significantly downregulated after EE, and we identified 5 novel miR-137 targets through loss of miR-137 function experiments. These targets fit into a glucocorticoid receptor-dependent signalling network that also includes 3 known miR-137 targets with genome-wide significant association with schizophrenia.

LIMITATIONS

The bioinformatics analyses involved predicted human and mouse miR-137 targets owing to lack of information on predicted rat miR-137 targets, whereas follow-up experiments were performed with rats. Furthermore, indirect effects in the loss of miR-137 function experiments cannot be excluded.

CONCLUSION

We have identified a miR-137-regulated protein network that contributes to our understanding of the molecular basis of schizophrenia and provides clues for future research into psychopharmacological treatments for schizophrenia.

Stress-mediated modulations in dopaminergic system and their subsequent impact on behavioral and oxidative alterations: an update

CONTEXT

Stress-induced changes in the dopaminergic system and subsequent enhancement of oxidative load and behavior are associated with a wide range of central and peripheral nervous disorders. Dopamine acts as a key neurotransmitter in the brain plays an important role in the regulation of motor and limbic functions.

OBJECTIVE

This article reviews the effect of stress on central dopaminergic system and its subsequent impact on the alterations in behavior and oxidative stress.

METHODS

A literature survey in PubMed (Bethesda, MD), Scopus (Philadelphia, PA), SciFinder (Columbus, OH) and Google Scholar (PMV, CA) was performed to gather information regarding the role of stress on central dopaminergic system and its associated behavioral and oxidative alterations.

RESULTS

Our collective data on behavioral studies and oxidative distress in stressful conditions show the functional reduction in dopaminergic neuronal system that could be one of the factors for the development of stress-induced motor suppression. Collectively, stress caused significant behavioral and oxidative alterations via suppression of neuronal functions of the central dopaminergic system.

CONCLUSIONS

This study provides an insight into the overall pathophysiological alterations in neuronal functions of the central dopaminergic system caused by acute and chronic unpredictable stress that, in our opinion, represent optimal utility as future therapeutic targets for neurodegenerative disorders.

Acute stress-induced cortisol elevations mediate reward system activity during subconscious processing of sexual stimuli

Stress is thought to alter motivational processes by increasing dopamine (DA) secretion in the brain's "reward system", and its key region, the nucleus accumbens (NAcc). However, stress studies using functional magnetic resonance imaging (fMRI), mainly found evidence for stress-induced decreases in NAcc responsiveness toward reward cues. Results from both animal and human PET studies indicate that the stress hormone cortisol may be crucial in the interaction between stress and dopaminergic actions. In the present study we therefore investigated whether cortisol mediated the effect of stress on DA-related responses to -subliminal-presentation of reward cues using the Trier Social Stress Test (TSST), which is known to reliably enhance cortisol levels. Young healthy males (n = 37) were randomly assigned to the TSST or control condition. After stress induction, brain activation was assessed using fMRI during a backward-masking paradigm in which potentially rewarding (sexual), emotionally negative and neutral stimuli were presented subliminally, masked by pictures of inanimate objects. A region of interest analysis showed that stress decreased activation in the NAcc in response to masked sexual cues (voxel-corrected, p<05). Furthermore, with mediation analysis it was found that high cortisol levels were related to stronger NAcc activation, showing that cortisol acted as a suppressor variable in the negative relation between stress and NAcc activation. The present findings indicate that cortisol is crucially involved in the relation between stress and the responsiveness of the reward system. Although generally stress decreases activation in the NAcc in response to rewarding stimuli, high stress-induced cortisol levels suppress this relation, and are associated with stronger NAcc activation. Individuals with a high cortisol response to stress might on one hand be protected against reductions in reward sensitivity, which has been linked to anhedonia and depression, but they may ultimately be more vulnerable to increased reward sensitivity, and addictions. Future studies investigating effects of stress on reward sensitivity should take into account the severity of the stressor and the individual cortisol response to stress.

Repeated aripiprazole treatment regulates Bdnf, Arc and Npas4 expression under basal condition as well as after an acute swim stress in the rat brain

Despite the rapid control of schizophrenic symptoms is due to the ability of antipsychotic drugs (APDs) to block D2 receptors in the mesolimbic pathway, it is now well-established that the therapeutic effects rely on adaptive mechanisms set in motion by their long-term administration. Such neuroplastic mechanisms depend on the pharmacological profile of the drug employed, with marked differences existing between first and second generation APDs. On these bases, the major accomplishment of this work was to investigate neuroadaptive changes set in motion by repeated treatment with aripiprazole, a novel APD that is unique for being a partial agonist at dopamine D2 receptors. Moreover, given that stress plays a critical role in the exacerbation of disease symptoms, we also investigated whether aripiprazole could influence the dynamic response of the brain to an acute challenge. We found that repeated aripiprazole treatment in rats regulates the expression of different markers of neuroplasticity such as Bdnf, Arc and Npas4 in a brain-region specific fashion; more importantly, the expression of these molecules was significantly up-regulated by an acute swim stress only in aripiprazole-treated animals, which is suggestive of increased ability to cope with the adverse event. We indeed found an overall facilitation of Bdnf expression, an effect that is mainly evident in the prefrontal cortex on the pool of transcripts undergoing dendritic localization. Overall, our results provide novel information regarding the mechanisms through which aripiprazole may regulate brain function and could contribute to improve neuroplastic defects that are associated with schizophrenia symptomatology.

Effects of stimulants and atomoxetine on cortisol levels in children with ADHD

Children with attention deficit hyperactivity disorder (ADHD) have lower diurnal cortisol levels than non-ADHD comparison subjects. Aiming at elucidating the effects of medications used to treat ADHD, we investigated saliva cortisol in children with ADHD: 20 without medication, 147 on methylphenidate, and 21 on atomoxetine. The only significant finding was that children on atomoxetine had higher cortisol levels at bedtime than unmedicated children.

Cortisol levels and risk for psychosis: initial findings from the North American prodrome longitudinal study

BACKGROUND

Studies of biomarkers of hypothalamic-pituitary-adrenal activity indicate that psychotic disorders are associated with elevated cortisol. This study examined cortisol levels in healthy control subjects and individuals who met clinical high-risk (CHR) criteria for psychosis. It was hypothesized that cortisol levels would be 1) elevated in the CHR group relative to control subjects, 2) positively correlated with symptom severity, and 3) most elevated in CHR patients who transition to psychotic level severity.

METHODS

Baseline assessments were conducted at eight centers in the North American Prodrome Longitudinal Study. The present CHR sample included 256 individuals meeting the Scale for Prodromal Symptoms criteria and 141 control subjects, all of whom underwent baseline assessment and measurement of salivary cortisol.

RESULTS

Consistent with previous reports, there was an effect of age on cortisol, with increases through the adolescent/early adult years. Analysis of covariance showed a main effect of diagnostic group, with the CHR group showing higher cortisol. There were modest, positive correlations of cortisol with baseline symptom severity, and analysis of covariance revealed higher baseline cortisol in those who transitioned to psychotic level symptoms when compared with healthy control subjects and CHR subjects who remitted.

CONCLUSIONS

The present findings add to accumulating evidence of heightened cortisol secretion in CHR individuals. The findings also indicate nonspecific associations between cortisol levels and symptom severity, as well as symptom progression. The role of hypothalamic-pituitary-adrenal activity in prediction of conversion to psychosis and its relation with other biomarkers of risk should receive attention in future research.

Addiction and the adrenal cortex

Substantial evidence shows that the hypophyseal–pituitary–adrenal (HPA) axis and corticosteroids are involved in the process of addiction to a variety of agents, and the adrenal cortex has a key role. In general, plasma concentrations of cortisol (or corticosterone in rats or mice) increase on drug withdrawal in a manner that suggests correlation with the behavioural and symptomatic sequelae both in man and in experimental animals. Corticosteroid levels fall back to normal values in resumption of drug intake. The possible interactions between brain corticotrophin releasing hormone (CRH) and proopiomelanocortin (POMC) products and the systemic HPA, and additionally with the local CRH–POMC system in the adrenal gland itself, are complex. Nevertheless, the evidence increasingly suggests that all may be interlinked and that CRH in the brain and brain POMC products interact with the blood-borne HPA directly or indirectly. Corticosteroids themselves are known to affect mood profoundly and may themselves be addictive. Additionally, there is a heightened susceptibility for addicted subjects to relapse in conditions that are associated with change in HPA activity, such as in stress, or at different times of the day. Recent studies give compelling evidence that a significant part of the array of addictive symptoms is directly attributable to the secretory activity of the adrenal cortex and the actions of corticosteroids. Additionally, sex differences in addiction may also be attributable to adrenocortical function: in humans, males may be protected through higher secretion of DHEA (and DHEAS), and in rats, females may be more susceptible because of higher corticosterone secretion.

Bone mineral density, quantitative ultrasound parameters and bone metabolism in postmenopausal women with depression

Low bone mineral density, which increases the risk of stress fragility fractures, is a frequent, often persistent finding in patients with major depressive disorder (MDD). The clinical association between major depressive disorder and osteopenia is still unclear, although several factors are associated with a loss of bone mass. The aim of our study, therefore, was to evaluate bone mineral density and bone metabolism in patients with MDD. Bone mineral density was evaluated in fifty postmenopausal women with MDD, and in 50 matched postmenopausal control women by dual-energy X-ray absorptiometry of the lumbar spine and femur, and by ultrasonography of the calcaneus and phalanges. Serum levels of 25-hydroxivitamin D, parathyroid hormone, Osteoprotegerin/Receptor Activator for Nuclear Factor κB Ligand ratio, bone turnover markers, serum and urinary cortisol were examined. Bone mineral density of the lumbar spine (BMD: 0.72 ± 0.06 vs. 0.82 ± 0.09 g/cm(2), p < 0.001), femoral neck (BMD: 0.58 ± 0.04 vs. 0.71 ± 0.07 g/cm(2), p < 0.001) and total femur (BMD 0.66 ± 0.09 vs. 0.54 ± 0.06 g/cm(2), p < 0.001); and ultrasound parameters at calcaneus (SI: 81.30 ± 6.10 vs. 93.80 ± 7.10, p < 0.001) and phalanges (AD-SOS: 1915.00 ± 37.70 vs. 2020.88 ± 39.46, p < 0.001; BTT : 1.30 ± 0.8 vs. 1.45 ± 0.9, p < 0.001) are significantly lower in patients with MDD compared with controls. Moreover bone turnover markers, parathyroid hormone levels and Receptor Activator for Nuclear Factor κB Ligand are significantly higher in MDD patients compared with controls, while serum levels of 25-hydroxivitamin D and osteoprotegerin are significantly lower. There are no differences in urinary excretion and serum cortisol between groups. Postmenopausal women with depressive disorder have an elevated risk for osteoporosis. Our data suggest that a high level of parathyroid hormone may play a role in the pathogenetic process underlying osteopenia in these patients.

Central dopaminergic system and its implications in stress-mediated neurological disorders and gastric ulcers: short review

For decades, it has been suggested that dysfunction of dopaminergic pathways and their associated modulations in dopamine levels play a major role in the pathogenesis of neurological disorders. Dopaminergic system is involved in the stress response, and the neural mechanisms involved in stress are important for current research, but the recent and past data on the stress response by dopaminergic system have received little attention. Therefore, we have discussed these data on the stress response and propose a role for dopamine in coping with stress. In addition, we have also discussed gastric stress ulcers and their correlation with dopaminergic system. Furthermore, we have also highlighted some of the glucocorticoids and dopamine-mediated neurological disorders. Our literature survey suggests that dopaminergic system has received little attention in both clinical and preclinical research on stress, but the current research on this issue will surely identify a better understanding of stressful events and will give better ideas for further efficient antistress treatments.

Stress, depression and Parkinson's disease

In this review, we focus on the relationship among Parkinson's disease (PD), stress and depression. Parkinson's disease patients have a high risk of developing depression, and it is possible that stress contributes to the development of both pathologies. Stress dysfunction may have a role in the etiology of preclinical non-motor symptoms of PD (such as depression) and, later in the course of the disease, may worsen motor symptoms. However, relatively few studies have examined stress or depression and the injured nigrostriatal system. This review discusses the effects of stress on neurodegeneration and depression, and their association with the symptoms and progression of PD.

Neuroprotective and anti-stress effect of A68930 in acute and chronic unpredictable stress model in rats

The neurorescuing effect of A68930 (a potent selective D(1) agonist) and its role on the regulation of hypothalamus-pituitary-adrenal (HPA)-axis have been investigated. Acute (AS) and chronic unpredictable (CUS) stress models were used to evaluate the effect of A68930 on HPA-axis regulation in relation to the change in the fiber density and number of immunoreactive (ir) neurons of tyrosine hydroxylase (TH) and glucocorticoid receptor (GR) in the dopamine (DA) and GR rich brain regions in rats. CUS caused a significant decrease in the number of TH ir neurons in the striatum, medial forebrain bundle, ventral tegmental area and substansia nigra and GR in the cortex, striatum and hippocampus as compared to the non-stress controls (NS). Administration of A68930 (0.25mg/kg i.p.) significantly normalized these CUS-induced alterations. We also examined the role of A68930 on stress-induced brain oxidative status. AS enhanced the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in the cortex and striatum, while CUS reduced the activities of SOD and catalase (CAT) in the cortex, striatum and hippocampus, when compared with NS. Increased GSH-Px activity, with reduced glutathione and increased lipid peroxidation was observed in both AS and CUS in selected brain regions as compared to NS. Administration of A68930 normalized the antioxidant enzyme activities, replenished GSH and decreased the extent of lipid peroxidation. In conclusion, present findings suggest that the stress-induced immunoreactivity of TH and GR in distinct brain regions are modulated by A68930 leading to the normalization of HPA-axis response. Ours results show the therapeutic importance of DA D(1) agonist in stress-induced dopaminergic-related neurological disorders. A68930 also influenced the brain antioxidant machinery probably through the restoration of stress-induced changes in the dopaminergic system and its crosstalk with GR.

How might stress contribute to increased risk for schizophrenia in children with chromosome 22q11.2 deletion syndrome?

The most common human microdeletion occurs at chromosome 22q11.2. The associated syndrome (22q11.2DS) has a complex and variable phenotype with a high risk of schizophrenia. While the role of stress in the etiopathology of schizophrenia has been under investigation for over 30 years (Walker et al. 2008), the stress–diathesis model has yet to be investigated in children with 22q11.2DS. Children with 22q11.2DS face serious medical, behavioral, and socioemotional challenges from infancy into adulthood. Chronic stress elevates glucocorticoids, decreases immunocompetence, negatively impacts brain development and function, and is associated with psychiatric illness in adulthood. Drawing knowledge from the extant and well-developed anxiety and stress literature will provide invaluable insight into the complex etiopathology of schizophrenia in people with 22q11.2DS while suggesting possible early interventions. Childhood anxiety is treatable and stress coping skills can be developed thereby improving quality of life in the short-term and potentially mitigating the risk of developing psychosis.

Activation of the GDNF-inducible transcription factor (GIF) gene promoter by glucocorticoid and progesterone

Steroid hormones, especially glucocorticoids, exert physiologic effects on dopaminergic neurotransmission and have been implicated in several dopamine-mediated neuropsychiatric conditions. D(2) dopamine receptor gene expression is regulated by the zinc finger-type nuclear protein GDNF-inducible transcription factor (GIF). In this study, we sought to investigate if steroids could regulate transcription of the GIF gene itself. Transient co-transfection of the D(2) expressing neuroblastoma cell line NB41A3 with GIF promoter-luciferase constructs along with expression vectors for steroid hormone receptors showed that activation of glucocorticoid receptors but not estrogen receptors up-regulates transcription from the GIF promoter 5.0-fold. Progesterone receptors, which share the same consensus DNA recognition sequence as glucocorticoid receptors, also activated the GIF promoter. Serial 5'-deletion mutants of the GIF gene upstream region localized the glucocorticoid-responsive segment between nucleotides -128 and -66 relative to the transcription start site. This region contains a putative glucocorticoid-responsive element/progesterone-responsive element (GRE/PRE). Additionally, this fragment of the GIF gene 5'-upstream region activated the heterologous herpes simplex virus thymidine kinase (TK) promoter, which is known to be glucocorticoid and progesterone responsive. Furthermore, glucocorticoid receptor activation up-regulated endogenous GIF gene mRNA expression in NB41A3 cells. These observations demonstrate a molecular basis for glucocorticoid and progesterone-induced up-regulation of GIF gene transcription and provide a mechanism for the modulation of dopamine-mediated behaviors by these hormones.

Low bone mineral density and high bone metabolism turnover in premenopausal women with unipolar depression

INTRODUCTION AND HYPOTHESIS

The majority of studies reporting decreased bone mineral density (BMD) in patients with unipolar depression neglected sex and age differences and menopause as the most important risk factor for osteoporosis. We presumed that physically healthy premenopausal women with unipolar depression have decreased BMD and altered bone cell metabolism.

METHODS

BMD at lumbar spine and femoral neck by dual X-ray absorptiometry, bone alkaline phosphatase sera activity, 5b-tartarate resistant acid phosphatase sera activity and urine N-terminal telopeptide were measured in 73 premenopausal women with unipolar depression and compared with 47 healthy, age- and osteoporosis risk factors-matched premenopausal women. The duration and severity of depression, hormonal status (cortisol, prolactin, parathormone, oestradiol), antidepressive treatment, and physical activity through whole and modified QUALEFFO-41 questionnaire were evaluated. The results were statistically elaborated by the chi-square test, Student's t-test for independent samples, one-way analysis of variance - ANOVA, one-sample Kolmogorov-Smirnov test. Correlations were assessed by means of Pearson's coefficient.

RESULTS

Patients with unipolar depression had significantly lower BMD, the decrease of which correlated only with the duration of depression. High bone metabolism turnover was found with a predomination of osteoresorption which, but not osteosynthesis, correlated with the severity of depression, estimated through Hamilton depression scores. Despite higher but not significant levels of cortisol in women with unipolar depression, the BMD decrease and high bone turnover seem not to be the consequence of hormonal changes or medical treatment. The significant correlations between physical activity and osteoresorption markers were found indicating possible underlying mechanism.

CONCLUSIONS

Premenopausal women with unipolar depression have significantly lower BMD because of stimulated bone cell metabolism with predomination of osteoresorption process, mostly due to decreased physical activity in depression. These women should be investigated for osteoporosis and the multidisciplinary team approach is advocated.

Surgical adrenalectomy with diurnal corticosterone replacement slows escalation and prevents the augmentation of cocaine-induced reinstatement in rats self-administering cocaine under long-access conditions

The loss of control over cocaine use and persistently heightened susceptibility to drug relapse that define human cocaine addiction are consequences of drug-induced neuroplasticity and can be studied in rats self-administering cocaine under conditions of daily long access (LgA) as escalating patterns of drug intake and heightened susceptibility to reinstatement. This study investigated the potential contribution of elevated glucocorticoids at the time of LgA cocaine self-administration (SA) to these behavioral indices of addiction-related neuroplasticity. Rats provided 14 days of 6-h access (LgA) to cocaine showed a progressive escalation of SA and were more susceptible to cocaine-induced reinstatement (10 mg/kg, i.p.) compared to rats self-administering under short-access (ShA; 2 h) conditions. A surgical adrenalectomy and corticosterone replacement (ADX/C) regimen that eliminated SA-induced increases in corticosterone (CORT) while maintaining the diurnal pattern of secretion failed to alter SA or reinstatement in ShA rats but slowed escalation and attenuated later reinstatement in LgA rats when applied before but not after chronic LgA SA testing. Although the contribution of other adrenal hormones cannot be ruled out, these data suggest that elevated glucocorticoids at the time of cocaine exposure may be required for the effects of LgA SA on cocaine intake and later reinstatement. The inability of daily CORT administration before daily ShA SA, at a dose that reproduced the response during LgA SA, to mimic the effects of LgA SA suggests that elevated glucocorticoids during SA may play a permissive role in cocaine-induced neuroplasticity that contributes to addiction.

Selective transrepression versus transactivation mechanisms by glucocorticoid receptor modulators in stress and immune systems

Glucocorticoids control immune homeostasis and regulate stress responses in the human body to a large extent via the glucocorticoid receptor. This transcription factor can modulate gene expression either through direct DNA binding (mainly resulting in transactivation) or independent of DNA binding (in the majority of cases resulting in transrepression). The aim of this review is to discuss the mechanistic basis and applicability of different glucocorticoid receptor modulators in various affections, ranging from immune disorders to mental dysfunctions.

Of old and new diseases: genetics of pituitary ACTH excess (Cushing) and deficiency

The pituitary gland orchestrates our endocrine environment: it produces hormones in response to hypothalamic factors that integrate neural inputs and its activity is balanced by the feedback action of peripheral hormones. Disruption of this equilibrium has severe consequences that affect multiple systems and may be fatal. Genetic analysis of pituitary function led to discovery of critical transcription factors that cause hormone deficiencies when mis-expressed. This review will summarize recent findings that led to the first complete clinical description of inherited, isolated corticotropin (ACTH) deficiency (IAD) and to the first molecular mechanism for excessive ACTH production in Cushing's disease. Indeed, mutations in TPIT, a positive or negative regulator of cell fates for different pituitary lineages, cause neonatal IAD, a condition considered anecdotic before discovery of this transcription factor. Cushing's disease is caused by corticotroph adenomas that produce excess ACTH as a result of resistance to glucocorticoids (Gc). Molecular investigation of the normal mechanism of Gc feedback led to identification of two essential proteins for pro-opiomelanocortin repression that are often mis-expressed in corticotroph adenomas thus providing a molecular explanation for Gc resistance. These two proteins, Brg1 and histone deacetylase 2 (HDAC2), are involved in chromatin remodeling and may also participate in the tumorigenic process, as Brg1 is a tumor suppressor. These recent advances have provided improved diagnosis and opened new perspectives for patient management and therapies.

Cushing's disease in dogs: cabergoline treatment

The treatment of pituitary-dependent hyperadrenocorticism (PDH) in dogs has for a long time been focused on inhibiting the adrenal gland using drugs such as o-p'-DDD, Ketoconazole and Trilostane, without attacking the primary cause: the corticotrophinoma. Corticotroph cells can express the D2 dopaminergic receptor; therefore cabergoline (Cbg) could be effective as a treatment. Follow-up over 4 years was carried out in 40 dogs with PDH that were treated with Cbg (0.07 mg/kg/week. Out of the 40 dogs, 17 responded to Cbg (42.5%). A year after the treatment, there was a significant decrease in ACTH (p<0.0001), alpha-MSH (p<0.01), urinary cortisol/creatinine ratio (p<0.001), and of the tumor size (p<0.0001) evaluated by nuclear magnetic resonance. Dogs responding to Cbg lived significantly longer (p<0.001) than those in the control group. To conclude, Cbg is useful in 42.5% of dogs with PDH, justifying its use as a treatment.

Enviromimetics: exploring gene environment interactions to identify therapeutic targets for brain disorders

There is a growing awareness of the central role played by environmental factors in many of the most debilitating neural disorders. Epidemiological studies have suggested a complex balance between genetic and environmental factors in the pathogenesis of neurological and psychiatric conditions. The use of accurate animal models, combined with experimental manipulations such as environmental enrichment, has shown that increased sensory, cognitive and motor stimulation has beneficial effects in a range of CNS disorders, including Huntington's, Alzheimer's, Parkinson's and other neurodegenerative diseases. Various studies have identified molecular, structural and functional correlates of this experience-dependent plasticity. The authors propose that the molecular systems which mediate the therapeutic effects of environmental enrichment may provide novel targets for pharmacotherapies. More specifically, they elaborate a theoretical framework for the development of 'enviromimetics', therapeutics that mimic or enhance the beneficial effects of environmental stimulation, targeted towards a wide range of nervous system disorders.