Neurotransmitters, neurosteroids and neurotrophins: new models of the pathophysiology and treatment of depression

Digital Delivery of Meditative Movement Training Improved Health of Cigarette-Smoke-Exposed Subjects

Many FA who flew prior to the ban on smoking in commercial aircraft exhibit an unusual pattern of long-term pulmonary dysfunction. This randomized controlled study tested the hypothesis that digitally delivered meditative movement (MM) training improves chronic obstructive pulmonary disease (COPD)-related symptoms in flight attendants (FA) who were exposed to second-hand cigarette smoke (SHCS) while flying. Phase I of this two-phase clinical trial was a single-arm non-randomized pilot study that developed and tested methods for MM intervention; we now report on Phase II, a randomized controlled trial comparing MM to a control group of similar FA receiving health education (HE) videos. Primary outcomes were the 6-min walk test and blood levels of high sensitivity C-reactive protein (hs-CRP). Pulmonary, cardiovascular, autonomic and affective measures were also taken. There were significant improvements in the 6-min walk test, the Multidimensional Assessment of Interoceptive Awareness (MAIA) score, and the COPD Assessment Test. Non-significant trends were observed for increased dehydroepiandrosterone sulfate (DHEAS) levels, decreased anxiety scores and reduced blood hs-CRP levels, and increased peak expiratory flow (PEF). In a Survey Monkey questionnaire, 81% of participants who completed pre and post-testing expressed mild to strong positive opinions of the study contents, delivery, or impact, while 16% expressed mild negative opinions. Over the course of the year including the study, participant adoption of the MM practices showed a significant and moderately large correlation with overall health improvement; Pearson's R = 0.62, p < 0.005. These results support the hypothesized benefits of video-based MM training for this population. No adverse effects were reported.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT02612389

Dehydroepiandrosterone: a neuroactive steroid

Dehydroepiandrosterone (DHEA) and its sulfate bound form (DHEAS) are important steroids of mainly adrenal origin. They are produced also in gonads and in the brain. Dehydroepiandrosterone easily crosses the brain-blood barrier and in part is also produced locally in the brain tissue. In the brain, DHEA exerts its effects after conversion to either testosterone and dihydrotestosterone or estradiol via androgen and estrogen receptors present in the most parts of the human brain, through mainly non-genomic mechanisms, or eventually indirectly via the effects of its metabolites formed locally in the brain. As a neuroactive hormone, DHEA in co-operation with other hormones and transmitters significantly affects some aspects of human mood, and modifies some features of human emotions and behavior. It has been reported that its administration can increase feelings of well-being and is useful in ameliorating atypical depressive disorders. It has neuroprotective and antiglucocorticoid activity and modifies immune reactions, and some authors have also reported its role in degenerative brain diseases. Here we present a short overview of the possible actions of dehydroepiandrosterone and its sulfate in the brain, calling attention to various mechanisms of their action as neurosteroids and to prospects for the knowledge of their role in brain disorders.

The influence of aripiprazole, olanzapine and enriched environment on depressant-like behavior, spatial memory dysfunction and hippocampal level of BDNF in prenatally stressed rats

BACKGROUND

Cognitive function deficits caused by impaired neurogenesis of the brain structures are considered an important pathogenic factor in many neurological and mental diseases such as schizophrenia and depression. The aim of the study was to determine the effect of the enriched environment on cognitive functions and antidepressant-like effect of prenatally stressed rats. It was important to determine the effect of aripiprazole ARI and olanzapine OLA and clarify whether the enriched environment induces increases in brain derived neurothropic factor BDNF in the hippocampus in the prenatally stressed group (PSG) and non-stressed control group (NSCG).

METHODS

The effect of chronic stress applied to pregnant rats and the use of ARI (1.5mg/kg ip) and OLA (0.5mg/kg ip) were studied in the Morris water maze (MWM), Porsolt Forced swimming test (FST) and by determining BDNF levels.

RESULTS

The results indicated that enriched environment improved spatial memory and also had an antidepressant-like effect on prenatally stressed rats. ARI improved spatial memory both in the NSCG and PSG, while OLA caused memory improvement only in the PSG. Moreover, both ARI and OLA reduced immobility time in the NSCG and PSG. In PSG rats, BDNF decrease was observed while chronic treatment with ARI and OLA increased BDNF levels in the hippocampi of NSCG and PSG rats.

CONCLUSION

It has been confirmed that enriched environment improves spatial memory of animals, removes symptoms of stress, has an antidepressant-like effect, and that new neuroleptics, such as ARI or OLA, modulate these functions (increased BDNF).

Could the underestimation of bipolarity obstruct the search for novel antidepressant drugs?

INTRODUCTION

Despite the clinical and social relevance of depression, and the availability of numerous antidepressants and non-pharmacological interventions, response rates remain unsatisfactory and novel therapeutic targets are being explored.

AREAS COVERED

This review starts with a brief overview of the evolution of the current antidepressant drug scenario and ends with a focus on the potential influence of the underestimation of bipolarity on the exploration of novel antidepressant drugs.

EXPERT OPINION

The field of antidepressant drug development has suffered from a relative decline recently and, with the exception of agomelatine, innovative non-monoaminergic antidepressants have yet to be developed. The need for more effective compounds is evident. Clinicians and researchers should pay greater attention to the impact of bipolarity in depression. The ultimate goal of this review is not to discourage the use of antidepressants but rather to encourage judicious prescriptions, and also to solicit a better collaboration between clinicians and preclinical researchers so that more reliable diagnostic criteria can be adopted.

Of sound mind and body: depression, disease, and accelerated aging

Major depressive disorder (MDD) is associated with a high rate of developing serious medical comorbidities such as cardiovascular disease, stroke, dementia, osteoporosis, diabetes, and the metabolic syndrome. These are conditions that typically occur late in life, and it has been suggested that MDD may be associated with “accelerated aging.” We review several moderators and mediators that may accompany MDD and that may give rise to these comorbid medical conditions. We first review the moderating effects of psychological styles of coping, genetic predisposition, and epigenetic modifications (eg, secondary to childhood adversity). We then focus on several interlinked mediators occurring in MDD (or at least in subtypes of MDD) that may contribute to the medical comorbidity burden and to accelerated aging: limbic-hypothalamic-pituitary-adrenal axis alterations, diminution in glucocorticoid receptor function, altered glucose tolerance and insulin sensitivity, excitotoxicity, increases in intracellular calcium, oxidative stress, a proinflammatory milieu, lowered levels of “counter-regulatory” neurosteroids (such as allopregnanolone and dehydroepiandrosterone), diminished neurotrophic activity, and accelerated cell aging, manifest as alterations in telomerase activity and as shortening of telomeres, which can lead to apoptosis and cell death. In this model, MDD is characterized by a surfeit of potentially destructive mediators and an insufficiency of protective or restorative ones. These factors interact in increasing the likelihood of physical disease and of accelerated aging at the cellular level. We conclude with suggestions for novel mechanism-based therapeutics based on these mediators.

Ageing and neurodegenerative diseases

Ageing, which all creatures must encounter, is a challenge to every living organism. In the human body, it is estimated that cell division and metabolism occurs exuberantly until about 25 years of age. Beyond this age, subsidiary products of metabolism and cell damage accumulate, and the phenotypes of ageing appear, causing disease formation. Among these age-related diseases, neurodegenerative diseases have drawn a lot of attention due to their irreversibility, lack of effective treatment, and accompanied social and economical burdens. In seeking to ameliorate ageing and age-related diseases, the search for anti-ageing drugs has been of much interest. Numerous studies have shown that the plant polyphenol, resveratrol (3,5,4'-trihydroxystilbene), extends the lifespan of several species, prevents age-related diseases, and possesses anti-inflammatory, and anti-cancer properties. The beneficial effects of resveratrol are believed to be associated with the activation of a longevity gene, SirT1. In this review, we discuss the pathogenesis of age-related neurodegenerative diseases including Alzheimer's disease, Parkinson's disease and cerebrovascular disease. The therapeutic potential of resveratrol, diet and the roles of stem cell therapy are discussed to provide a better understanding of the ageing mystery.

Sleep pathologies in depression and the clinical utility of polysomnography

Abnormal sleep accompanies many psychiatric conditions, but has long been recognized as a particularly conspicuous feature of affective disorders. More than a mere epiphenomenon, the powerful link between sleep and mood regulation is most dramatically demonstrated by the high efficacy of sleep deprivation in alleviating depression. Indeed, the sleep abnormalities that accompany depression may be due to the same neuropathologies that are responsible for its mood and cognitive symptoms. This powerful link between sleep and mood regulation makes polysomnography (PSG) a useful window into the underlying pathophysiology of depression, yet it is underused, particularly in clinical diagnosis. Recent depression research has emphasized the importance of establishing biologically relevant subtypes of depression with treatment specificity and prognostic value. PSG measures, among other biological markers, may be of importance in establishing these subtypes. Two subtypes of depression that appear to have robust biological differences, the melancholic and atypical subtypes, have recently been shown to have different sleep profiles that can aid in differential diagnosis. Further, routine use of PSG in the workup of a depressed patient would minimize the chances of misdiagnosis in those suffering from primary sleep disorders such as sleep apnea, which can present secondary mood symptoms resembling depression. Increased use of PSG in clinical psychiatric practice would enlarge the body of data available for defining new depressive subtypes in the future. It would also serve an immediate purpose in the separation of atypical, compared with melancholic, depression, and the differential diagnosis of depression from primary sleep disorders.

Depression gets old fast: do stress and depression accelerate cell aging?

Depression has been likened to a state of "accelerated aging," and depressed individuals have a higher incidence of various diseases of aging, such as cardiovascular and cerebrovascular diseases, metabolic syndrome, and dementia. Chronic exposure to certain interlinked biochemical pathways that mediate stress-related depression may contribute to "accelerated aging," cell damage, and certain comorbid medical illnesses. Biochemical mediators explored in this theoretical review include the hypothalamic-pituitary-adrenal axis (e.g., hyper- or hypoactivation of glucocorticoid receptors), neurosteroids, such as dehydroepiandrosterone and allopregnanolone, brain-derived neurotrophic factor, excitotoxicity, oxidative and inflammatory stress, and disturbances of the telomere/telomerase maintenance system. A better appreciation of the role of these mediators in depressive illness could lead to refined models of depression, to a re-conceptualization of depression as a whole body disease rather than just a "mental illness," and to the rational development of new classes of medications to treat depression and its related medical comorbidities.

Glucocorticoids. Mood, memory, and mechanisms

Elevated circulating levels of glucocorticoids are associated with psychiatric symptoms across several different conditions. It remains unknown if this hormonal abnormality is a cause or an effect of the psychiatric conditions. For example, the hypercortisolemia observed in a subset of patients with depression may have a direct impact on the symptoms of depression, but it is also possible that the hypercortisolemia merely reflects the stress associated with depression. Further, rather than causing depression, hypercortisolemia could represent a homeostatic attempt to overcome glucocorticoid resistance. Each of these possibilities will be considered, and correlational and causal evidence will be reviewed. This article will focus on the relationships between glucocorticoids and psychiatric symptoms in Cushing's syndrome, major depression, and steroid psychosis/steroid dementia, as well as the effects of exogenously administered glucocorticoids in normal volunteers. Similarities and differences in the relationship of glucocorticoid hormones to psychiatric symptoms in these conditions will be reviewed. Possible mediators of glucocorticoid effects on the brain and behavior, as well as possible "pro-aging" effects of glucocorticoids in certain cells of the body, will be reviewed. The article concludes with a conceptual model of glucocorticoid actions in the brain that may lead to novel therapeutic opportunities.

Neurobiological and neuropsychiatric effects of dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEAS)

DHEA and DHEAS are steroids synthesized in human adrenals, but their function is unclear. In addition to adrenal synthesis, evidence also indicates that DHEA and DHEAS are synthesized in the brain, further suggesting a role of these hormones in brain function and development. Despite intensifying research into the biology of DHEA and DHEAS, many questions concerning their mechanisms of action and their potential involvement in neuropsychiatric illnesses remain unanswered. We review and distill the preclinical and clinical data on DHEA and DHEAS, focusing on (i) biological actions and putative mechanisms of action, (ii) differences in endogenous circulating concentrations in normal subjects and patients with neuropsychiatric diseases, and (iii) the therapeutic potential of DHEA in treating these conditions. Biological actions of DHEA and DHEAS include neuroprotection, neurite growth, and antagonistic effects on oxidants and glucocorticoids. Accumulating data suggest abnormal DHEA and/or DHEAS concentrations in several neuropsychiatric conditions. The evidence that DHEA and DHEAS may be fruitful targets for pharmacotherapy in some conditions is reviewed.

Dehydroepiandrosterone and monoamines in the limbic system of a genetic animal model of childhood depression

Monoamines and dehydroepiandrosterone (DHEA) levels were measured in a genetic animal model for childhood depression in four subcortical structures: nucleus accumbens (Nac), ventral tegmental area (VTA), amygdala and hypothalamus. The "depressive-like" strain was the Flinders Sensitive Line (FSL), compared to their controls, Sprague-Dawley (SD) rats. Prepubertal FSL rats showed abnormal levels of only a few monoamines and their metabolites in these brain regions. This is in contrast to former studies, in which adult FSL rats exhibited significantly higher levels of all the monoamines and their metabolites measured. These different abnormal monoamine patterns between the "depressed" prepubertal rats and their adults, may help to explain why depressed children and adolescents fail to respond to antidepressant treatment as well as adults do. On the other hand, FSL prepubertal rats exhibited the same pattern of abnormal DHEA basal levels as was found in adults in previous experiments. The results from the current study may imply that treatment with DHEA could be a promising novel therapeutic option for depressed children and adolescents that fail to respond to common (monoaminergic) antidepressant treatments.

The "steroid dementia syndrome": a possible model of human glucocorticoid neurotoxicity

Glucocorticoid medications cause neurotoxicity in animals under certain circumstances, but it is not known if this occurs in humans. We present the case of a 10-year-old boy with no prior psychiatric history and no prior exposure to glucocorticoid medication who received a single 5-week course of glucocorticoids for an acute asthma flare. Beginning during steroid treatment, and persisting for over 3 years after stopping treatment, he showed a significant decline from his pre-morbid academic performance and estimated IQ, verified by longitudinally administered testing and school records. Neuropsychological tests that are sensitive to glucocorticoid-induced cognitive impairments revealed global cognitive deficits consistent with primary hippocampal and prefrontal cortical dysfunction. The patient has a fraternal twin brother, who had previously achieved academic milestones in parallel with him; the patient began falling behind his twin in academic, developmental and social areas shortly after the steroid treatment. In the 3 years since stopping steroid medication, the patient has shown gradual but possibly incomplete resolution of his cognitive deficits. Quantitative brain magnetic resonance imaging (MRI), performed 38 months after steroid exposure revealed no gross abnormalities, but the patient's hippocampal volume was 19.5% smaller than that of his twin, despite the patient having a larger overall intracranial volume. Single photon emission computed tomography (SPECT) imaging, performed at the same time, suggested subtly decreased activity in the left posterior frontal and left parietal lobes. This case, along with others reported in the literature, suggests that certain individuals develop a "steroid dementia syndrome" after glucocorticoid treatment. Although this syndrome is uncommon, it is consistent with evolving theories of the neurotoxic or neuroendangering potential of glucocorticoids in some situations.

Progesterone: the forgotten hormone in men?

'Classical' genomic progesterone receptors appear relatively late in phylogenesis, i.e. it is only in birds and mammals that they are detectable. In the different species, they mediate manifold effects regarding the differentiation of target organ functions, mainly in the reproductive system. Surprisingly, we know little about the physiology, endocrinology, and pharmacology of progesterone and progestins in male gender or men respectively, despite the fact that, as to progesterone secretion and serum progesterone levels, there are no great quantitative differences between men and women (at least outside the luteal phase). In a prospective cohort study of 1026 men with and without cardiovascular disease, we were not able to demonstrate any age-dependent change in serum progesterone concentrations. Progesterone influences spermiogenesis, sperm capacitation/acrosome reaction and testosterone biosynthesis in the Leydig cells. Other progesterone effects in men include those on the central nervous system (CNS) (mainly mediated by 5alpha-reduced progesterone metabolites as so-called neurosteroids), including blocking of gonadotropin secretion, sleep improvement, and effects on tumors in the CNS (meningioma, fibroma), as well as effects on the immune system, cardiovascular system, kidney function, adipose tissue, behavior, and respiratory system. A progestin may stimulate weight gain and appetite in men as well as in women. The detection of progesterone receptor isoforms would have a highly diagnostic value in prostate pathology (benign prostatic hypertrophy and prostate cancer). The modulation of progesterone effects on typical male targets is connected with a great pharmacodynamic variability. The reason for this is that, in men, some important effects of progesterone are mediated non-genomically through different molecular biological modes of action. Therefore, the precise therapeutic manipulation of progesterone actions in the male requires completely new endocrine-pharmacological approaches.

DHEAS as a new diagnostic tool

Dehydroepiandrosterone sulfate (DHEAS) is a 19-carbon steroid, situated along the steroid metabolic pathway. It is the most abundant circulating steroid hormone in the body and can be converted to either androgens or estrogens. Their physiological and pathological functions have not yet been fully identified. Serum DHEAS concentrations peak at around age 25 years and then decline steadily over the following decades. Due to its long half-life and high concentration in the blood, the levels of DHEAS remain the same 24 h a day. This makes DHEAS a very interesting new diagnostic tool for both scientific research and clinical diagnostics. Moreover, circulating concentrations of DHEAS can be changed by many factors, such as endogenous production, hormone supplementation, many kinds of drugs, and many types of disease states. As research moves forward to better understand the relationships of DHEAS with health and disease, it is essential that studies should be designed to control for the influence of many factors on serum DHEAS concentrations.