Serotonergic 5-HT2A receptor stimulation induces steroid 5alpha-reductase gene expression in rat C6 glioma cells via transcription factor Egr-1

Psilocybin, a Naturally Occurring Indoleamine Compound, Could Be Useful to Prevent Suicidal Behaviors

The available interventions for people who are at risk of suicide have limited efficacy. Recently, research on new mental health treatments has started to consider psychedelic compounds, particularly psilocybin, a molecule with a few thousand years of history of use in human societies. The possible effects of psilocybin on suicidal ideation and behaviors have not been specifically studied yet; however, the current knowledge on the suicidal process and the available data on es/ketamine suggest that psylocibin could be used to modulate the thoughts and behavioral patterns in individuals who are at risk of suicidal behaviors. Here, we summarize the available evidence on the possible mechanisms underlying psilocybin positive effects on suicide risk. Major pathways related to suicidal behaviors that might be modulated by psylocibin include serotonin receptors. Specifically, psylocibin directly stimulates the serotonin 2A receptor (5HT_2A), targeting the inflammatory and oxidative stress pathways and leading to a rapid increase in brain plasticity and inflammation suppression and increases in cognitive flexibility, spirituality, and empathy. We also present preliminary epidemiological data and provide a rationale for studying psilocybin in individuals with suicidal ideation or who are at risk of suicidal behaviors. This review presents a framework to understand the basis for psilocybin use in individuals who are at risk of suicidal behaviors and calls for clinical studies.

The Chronic Treatment With 5-HT2A Receptor Agonists Affects the Behavior and the BDNF System in Mice

Serotonin 5-HT2A receptors and the brain-derived neurotrophic factor (BDNF) are involved in the pathophysiology and treatment of many psychiatric diseases. However, the interaction between 5-HT2A and BDNF is still poorly understood. In the present paper, the effects of chronic treatment with mixed 5-HT2A/2C receptor agonist DOI, highly selective 5-HT2A agonists TCB-2 and 25CN-NBOH on behavior and the BDNF system have been investigated. Chronic treatment of males of C57Bl/6 mice with DOI, TCB-2 and 25CN-NBOH (1 mg/kg, i.p., 14 days) resulted in desensitization of 5-HT2A receptors. Treatment with 25CN-NBOH significantly increased startle amplitude. At the same time all used drugs failed to affect anxiety, exploratory and stereotyped behavior as well as spatial memory and learning. TCB-2 and 25CN-NBOH increased the BDNF mRNA level. All 5-HT2A agonists increased the proBDNF level but failed to alter the mature BDNF protein level. TrkB and p75NTR mRNA levels were affected by all utilized agonists. All drugs decreased the total level as well as membrane TrkB protein one indicating downregulation of TrkB receptors. All agonists decreased the membrane p75NTR protein level. Thus, we have shown for the first time that the chronic activation of the 5-HT2A receptor with agonists has affected the BDNF system almost on all levels-transcription, proBDNF production, TrkB and p75NTR receptors' level. The obtained data suggested possible suppression in BDNF-TrkB signaling under chronic treatment with 5-HT2A agonists.

Social isolation stress down-regulates cortical early growth response 1 (Egr-1) expression in mice

Social isolation stress induces behavioral disturbances such as aggression, cognitive impairments, and deficits in prepulse inhibition in mice. Social isolation mice have, therefore, been studied as an animal model of neuropsychiatric disorders such as schizophrenia. Recently, the decrease in early growth response (Egr) gene expression levels were reported in the post-mortem brains of schizophrenia patients. In this study, we investigate the effects of social isolation stress on the expression levels of Egr mRNA and protein in the frontal cortex. Social isolation stress exposure significantly down-regulated the expression of Egr-1 protein and Egr-1 gene transcript in nucleus of cortical neurons in a manner dependent on a social isolation period. This stress had no effect on the expression level of Egr-1 in the striatum or the expression levels of other Egr family members (Egr-2, -3, and -4) in the frontal cortex. These results suggest that the decrease in Egr-1 expression in the frontal cortex may be involved in social isolation stress-induced behavioral abnormalities.

Involvement of Egr-1 in HGF-induced elevation of the human 5alpha-R1 gene in human hepatocellular carcinoma cells

Steroid 5alpha-reductase 1 (5alpha-R1), a key enzyme in the conversion of steroids into their respective 5alpha-reduced derivatives, plays a key role in some hormone-dependent tumours and is abundant in the liver, although it is also widely distributed throughout the body. HGF (hepatocyte growth factor) is a pleiotropic cytokine/growth factor involved in the progression of hepatocellular carcinoma. In the present paper, we report the stimulatory effect of HGF on human 5alpha-R1 transcription in hepatocellular carcinoma cells. Pre-treatment with actinomycin D or cycloheximide blocked the up-regulation of 5alpha-R1 mRNA expression by HGF, indicating that the increased level of 5alpha-R1 mRNA expression is regulated by transcriptional activation and was dependent on de novo protein synthesis. Functional analysis of the 5'-flanking region of the 5alpha-R1 gene by transfection analysis showed that the -79 to -50 region functioned as the HGF-responsive region. Mutagenesis and electrophoretic mobility-shift assays demonstrated that induction of 5a-R1 by HGF is mediated by an Egr-1 (early growth-response gene 1)-binding site at -60/-54. In addition, overexpression of Egr-1 was sufficient to transactivate 5alpha-R1 promoter activity, and knockdown of Egr-1 with gene-specific small interfering RNA resulted in inhibition of HGF-induced up-regulation of endogenous 5alpha-R1 expression. These data provide the first evidence that HGF stimulates 5alpha-R1 expression through up-regulation of the transcription factor Egr-1, thus suggesting the possibility that regulation of steroid metabolism by HGF represents a mechanism for high risk of hepatocellular carcinogenesis in males.

The relevance of neuroactive steroids in schizophrenia, depression, and anxiety disorders

1. Neuroactive steroids are steroid hormones that exert rapid, nongenomic effects at ligand-gated ion channels. There is increasing awareness of the possible role of these steroids in the pathology and manifestation of symptoms of psychiatric disorders. The aim of this paper is to review the current knowledge of neuroactive steroid functioning in the central nervous system, and to assess the role of neuroactive steroids in the pathophysiology and treatment of symptoms of schizophrenia, depression, and anxiety disorders. Particular emphasis will be placed on GABAA receptor modulation, given the extensive knowledge of the interactions between this receptor complex, neuroactive steroids, and psychiatric illness. 2. A brief description of neuroactive steroid metabolism is followed by a discussion of the interactions of neuroactive steroids with acute and chronic stress and the HPA axis. Preclinical and clinical studies related to psychiatric disorders that have been conducted on neuroactive steroids are also described. 3. Plasma concentrations of some neuroactive steroids are altered in individuals suffering from schizophrenia, depression, or anxiety disorders compared to values in healthy controls. Some drugs used to treat these disorders have been reported to alter plasma and brain concentrations in clinical and preclinical studies, respectively. 4. Further research is warranted into the role of neuroactive steroids in the pathophysiology of psychiatric illnesses and the possible role of these steroids in the successful treatment of these disorders.

Amitriptyline induces early growth response-1 gene expression via ERK and JNK mitogen-activated protein kinase pathways in rat C6 glial cells

Astrocytes play important roles in guiding the construction of the nervous system, controlling extracellular ions and neurotransmitters, and regulating CNS synaptogenesis. Egr-1 is a transcription factor involved in neuronal differentiation and astrocyte cell proliferation. In this study, we investigated whether the tricyclic antidepressant (TCA) amitriptyline induces Egr-1 expression in astrocytes using rat C6 glioma cells as a model. We found that amitriptyline increased the expression of Egr-1 in a dose- and time-dependent manner. The amitriptyline-induced Egr-1 expression was mediated through serum response elements (SREs) in the Egr-1 promoter. SREs were activated by the Ets-domain transcription factor Elk-1 through the ERK and JNK mitogen-activated protein (MAP) kinase pathways. The inhibition of the ERK and JNK MAP kinase signals attenuated amitriptyline-induced transactivation of Gal4-Elk-1 and Egr-1 promoter activity. Our findings suggest that the induction of Egr-1 expression in astrocytes may be required to attain the therapeutic effects of antidepressant drugs.

Neurosteroids, neuroactive steroids, and symptoms of affective disorders

Neurosteroids (NS) are steroids synthesized by the brain. Neuroactive steroids (NAS) refers to steroids that, independent of their origin, are capable of modifying neural activities. NAS bind and modulate different types of membrane receptors. The gamma amino butyric acid (GABA) and sigma receptor complexes have been the most extensively studied. Oxidized ring A reduced pregnanes, tetrahydroprogesterone (THP), and tetrahydrodeoxycorticosterone (THDOC) bind to the progesterone intracellular receptor (PR), and in this way can also regulate gene expression. Animal experimentation showed that salient symptoms of depression, viz., anxiety, sleep disturbances, and memory and sexual dysfunctions, are modulated by NAS. In turn, psychotropic drugs modulate NS and NAS levels. NS levels as well as NAS plasma concentrations change in patients with depression syndromes, the levels return to normal baseline with recovery, but normalization is not necessary for successful therapy. Results from current studies on the evolution of nervous systems, including evolutionary developmental biology as well as anatomical and physiological findings, almost preclude a categorical classification of the psychiatric ailments the human brain succumbs to. The persistence in maintaining such essentialist classifications may help to explain why up to now the search for biological markers in psychiatry has been an unrewarding effort. It is proposed that it would be more fruitful to focus on relationships between NAS and symptoms of psychiatric disorders, rather than with typologically defined disorders.

Possible involvement of 5α-reduced neurosteroids in adrenergic and serotonergic stimulation of GFAP gene expression in rat C6 glioma cells

Influence of adrenergic and serotonergic stimulation on glial fibrillary acidic protein (GFAP) gene expression in rat C6 glioma cells was first examined as an in vitro model experiment for investigating the neuronal regulation of glial cell differentiation. Stimulation of these cells with isoproterenol and serotonin elevated GFAP mRNA levels followed by an increase in its protein contents, thus suggesting that both adrenergic and serotonergic stimulation might induce the differentiation of the glioma cells. In addition, progesterone and its 5alpha-reduced metabolite dihydroprogesterone also elevated GFAP mRNA levels in rat C6 glioma cells, consistent with their stimulatory actions on GFAP gene expression observed in rat astrocytes. Further studies showed that the elevation of GFAP mRNA levels induced by isoproterenol and serotonin as well as progesterone was abolished by pretreatment of the glioma cells with finasteride, an inhibitor of 5alpha-reduced steroid production. Moreover, the stimulatory actions of isoproterenol and serotonin on GFAP gene expression were inhibited by pretreatment with a GABA(A) receptor antagonist bicuculline and a progesterone receptor antagonist RU486. These findings suggest that both adrenergic and serotonergic stimulation may indirectly activate GFAP gene expression probably through the production of 5alpha-reduced steroid metabolites in rat C6 glioma cells, proposing the possibility that 5alpha-reduced neurosteroids may play a potential role in the neuronal regulation of glial cell differentiation.