Yokukansan normalizes glucocorticoid receptor protein expression in oligodendrocytes of the corpus callosum by regulating microRNA-124a expression after stress exposure

Dysregulated miR-124 mediates impaired social memory behavior caused by paternal early social isolation

Early social isolation (SI) leads to various abnormalities in emotion and behavior during adulthood. However, the negative impact of SI on offspring remains unclear. This study has discovered that paternal early SI causes social memory deficits and anxiety-like behavior in F1 young adult mice, with alterations of myelin and synapses in the medial prefrontal cortex (mPFC). The 2-week SI in the F1 progeny exacerbates social memory impairment and hypomyelination in the mPFC. Furthermore, the down-regulation of miR-124, a key inhibitor of myelinogenesis, or over-expression of its target gene Nr4a1 in the mPFC of the F1 mice improves social interaction ability and enhances oligodendrocyte maturation and myelin formation. Mechanistically, elevated levels of miR-124 in the sperm of paternal SI mice are transmitted epigenetically to offspring, altering the expression levels of miR-124/Nr4a1/glucocorticoid receptors in mPFC oligodendrocytes. This, in turn, impedes the establishment of myelinogenesis-dependent social behavior. This study unveils a novel mechanism through which miR-124 mediates the intergenerational effects of early isolation stress, ultimately impairing the establishment of social behavior and neurodevelopment.

Cnidium officinale Makino: Phytology, Phytochemistry, Toxicology, Pharmacology and Prescriptions (1967-2023)

Cnidium officinale Makino (COM), a perennial herbaceous plant in the Apiaceous family, widely distribute in Eastern Asia and Asia-Temperate. It has a long history application as a traditional medicine for invigorating the blood and removing blood stasis, and also has been employed to diet, pesticide, herbal bathing materials, the cosmetic and skin care industry. However, there has been no associated review of literature in the past half a century (1967-2023). By searching the international authoritative databases and collecting 229 literatures closely related to COM, herewith a comprehensive and systematic review was conducted. The phytology includes plant distribution and botanical characteristics. The phytochemistry covers 8 major categories, 208 compounds in total, and the quantitative determination of 14 monomer compounds, total polyphenols and total flavonoids. The clinical trial in pregnant women and toxic experiments in mice, the pharmacology of 7 aspects and 82 frequently used prescriptions are summarized. It is expected that this paper will provide forward-looking scientific thinking and literature support for the further modern research, development and utilization of COM.

Traditional uses, chemical compounds, pharmacological activities and clinical studies on the traditional Chinese prescription Yi-Gan San

ETHNOPHARMACOLOGICAL RELEVANCE

A widely used traditional prescription, Yi-Gan San (YGS) is a remedy for neurodegenerative disorders. The formulation consists of seven Chinese medicinal materials in specific proportions, namely Uncariae Ramulus cum Uncis (Uncaria rhynchophylla (Miq.) Miq. ex Havil.), Bupleuri Radix (Bupleurum chinense DC.), Angelicae Sinensis Radix (Angelica sinensis (Oliv.) Diels), Chuanxiong Rhizoma (Ligusticum wallichii Franch.), Poria (Poria cocos (Schw.) Wolf), Atractylodis Macrocephalae Rhizoma (Atractylodes macrocephala Koidz.) and Glycyrrhizae Radix et Rhizoma (Glycyrrhiza uralensis Fisch.). Using YGS has been shown to alleviate various behavioural and psychological symptoms of dementia (BPSD).

AIM OF THIS REVIEW

The goal of this review is to give up-to-date information about the traditional uses, chemistry, pharmacology and clinical efficacy of YGS based on the scientific literature and to learn the current focus and provide references in the next step.

MATERIALS AND METHODS

The database search room was accessed using the search terms "Yi-Gan San" and "Yokukansan" to obtain results from resources such as Web of Science, PubMed, Google Scholar and Sci Finder Scholar. We not only consulted the literature of fellow authors for this review but also explored classical medical books.

RESULTS

YGS has been used to cure neurosis, sleeplessness, night weeping and restlessness in infants. Its chemical components primarily consist of triterpenes, flavonoids, phenolics, lactones, alkaloids and other types of compounds. These active ingredients displayed diverse pharmacological activities to ameliorate BPSD by regulating serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmission. In addition, YGS showed neuroprotective, antistress, and anti-inflammatory effects. The majority of cases of neurodegenerative disorders are treated with YGS, including Alzheimer's disease and dementia with Lewy bodies.

CONCLUSIONS

Based on previous studies, YGS has been used as a traditional prescription in East Asia, such as Japan, Korea and China, and it has diverse chemical compounds and multiple pharmacological activities. Nevertheless, few experimental studies have focused on chemical and quantitative YGS studies, suggesting that further comprehensive research on its chemicals and quality assessments is critical for future evaluations of drug efficacy.

Expression of glucocorticoid receptor (GR) and clinical significance in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare endocrine tumor, and most cases present with hormone excess with poor prognosis. Our research aims to determine the clinical and biological significance of glucocorticoid receptor (GR) expression using large cohorts of ACC patients. Immunohistochemistry was used to assess the expression of GR in 78 ACC cases from the West China Hospital (WCH) cohort. RNA-seq data were retrieved from The Cancer Genome Atlas database (TCGA, n=79). Clinicopathological and follow-up data were obtained from two cohorts. The correlation between the GR gene and tumor immune status was estimated using TIMER and GEPIA2. Kaplan-Meier analysis was performed to identify the prognostic value of GR in ACC. In the WCH cohort, positive nuclear GR staining was identified in 90% of the primary ACC cases. Cortisol-secreting ACCs demonstrated significantly lower GR protein expression than did nonfunctioning tumors (P<0.001). This finding was validated by the mRNA data analysis of the TCGA cohort (P = 0.030). GR expression was found to be positively correlated with the immune cell infiltration level and immune-checkpoint-related gene expression in ACC. Survival comparison and multivariate analysis showed that GR expression is an independent prognostic predictor of disease-free survival and overall survival in ACC patients in both cohorts. Our findings suggest that low GR expression is significantly correlated with excess cortisol, immune signatures and poor survival in ACC patients. We propose that GR signaling may play an important role in ACC behavior and thus may be a therapeutic target, which deserves further research.

Acquired Glucocorticoid Resistance Due to Homologous Glucocorticoid Receptor Downregulation: A Modern Look at an Age-Old Problem

For over 70 years, the unique anti-inflammatory properties of glucocorticoids (GCs), which mediate their effects via the ligand-activated transcription factor, the glucocorticoid receptor alpha (GRα), have allowed for the use of these steroid hormones in the treatment of various autoimmune and inflammatory-linked diseases. However, aside from the onset of severe side-effects, chronic GC therapy often leads to the ligand-mediated downregulation of the GRα which, in turn, leads to a decrease in GC sensitivity, and effectively, the development of acquired GC resistance. Although the ligand-mediated downregulation of GRα is well documented, the precise factors which influence this process are not well understood and, thus, the development of an acquired GC resistance presents an ever-increasing challenge to the pharmaceutical industry. Recently, however, studies have correlated the dimerization status of the GRα with its ligand-mediated downregulation. Therefore, the current review will be discussing the major role-players in the homologous downregulation of the GRα pool, with a specific focus on previously reported GC-mediated reductions in GRα mRNA and protein levels, the molecular mechanisms through which the GRα functional pool is maintained and the possible impact of receptor conformation on GC-mediated GRα downregulation.

White matter microstructural alterations in posttraumatic stress disorder: An ROI and whole-brain based meta-analysis

BACKGROUND

Posttraumatic stress disorder (PTSD) is a debilitating mental illness that is thought to be associated with brain white matter (WM) alterations. Individual diffusion tensor imaging (DTI) studies to date have reported inconsistent alterations in FA across different brain regions in patients with PTSD. Here, we aimed to investigate FA in PTSD using both region-of-interest (ROI)-based and whole-brain-based meta-analytic approaches.

OBJECTIVES

Individual ROI-based meta-analysis was carried out in each eligible white matter tract and seed-based D mapping (SDM) meta-analysis was conducted in the whole brain to identify the convergence of FA alterations in PTSD relative to controls.

RESULTS

Seventeen studies were included in ROI-based meta-analysis (≥ 3 studies were included for each ROI, N_PTSD ≥ 80 and N_control ≥ 103 per ROI). Fourteen studies with a total of 322 PTSD and 335 controls were included in whole-brain based meta-analysis. Both ROI and whole-brain meta-analyses showed that patients with PTSD have significantly higher FA in the inferior fronto-occipital fasciculus and lower FA in the genu of corpus callosum. Whole-brain meta-analyses also identified higher FA in the left inferior temporal gyrus and lower FA in the anterior cingulum and left corticospinal tract.

LIMITATIONS

A small number of studies were included in some ROI tracts. Thus the results should be interpreted with caution.

CONCLUSIONS

Our results suggest that PTSD patients have increased FA in areas related to visual processing, but decreased FA in anterior brain regions critical to cognition association and fear regulation.

GR Dimerization and the Impact of GR Dimerization on GR Protein Stability and Half-Life

Pharmacologically, glucocorticoids, which mediate their effects via the glucocorticoid receptor (GR), are a most effective therapy for inflammatory diseases despite the fact that chronic use causes side-effects and acquired GC resistance. The design of drugs with fewer side-effects and less potential for the development of resistance is therefore considered crucial for improved therapy. Dimerization of the GR is an integral step in glucocorticoid signaling and has been identified as a possible molecular site to target for drug development of anti-inflammatory drugs with an improved therapeutic index. Most of the current understanding regarding the role of GR dimerization in GC signaling derives for dimerization deficient mutants, although the role of ligands biased toward monomerization has also been described. Even though designing for loss of dimerization has mostly been applied for reduction of side-effect profile, designing for loss of dimerization may also be a fruitful strategy for the development of GC drugs with less potential to develop GC resistance. GC-induced resistance affects up to 30% of users and is due to a reduction in the GR functional pool. Several molecular mechanisms of GC-mediated reductions in GR pool have been described, one of which is the autologous down-regulation of GR density by the ubiquitin-proteasome-system (UPS). Loss of GR dimerization prevents autologous down-regulation of the receptor through modulation of interactions with components of the UPS and post-translational modifications (PTMs), such as phosphorylation, which prime the GR for degradation. Rational design of conformationally biased ligands that select for a monomeric GR conformation, which increases GC sensitivity through improving GR protein stability and increasing half-life, may be a productive avenue to explore. However, potential drawbacks to this approach should be considered as well as the advantages and disadvantages in chronic vs. acute treatment regimes.

Short- and long-term alterations of FKBP5-GR and specific microRNAs in the prefrontal cortex and hippocampus of male rats induced by adolescent stress contribute to depression susceptibility

Maladaptation of the hypothalamic-pituitary-adrenal (HPA) axis is involved in susceptibility to depression. Glucocorticoid receptors (GRs) and the co-chaperone protein, FK506 binding protein 51 (FKBP5), play crucial roles in dysfunction of the HPA axis. Further, certain microRNAs (miRNAs), such as miR-124a and miR-18a, which could reduce GR protein expression, contribute to affective disorders, while miR-511 as a regulator of FKBP5 is involved in an increased risk of depression. However, the short-term and persistent impacts of adolescent stress on miR-124a, miR-18a, and miR-511 expressions in the brain are unknown. Using depression models of chronic unpredictable mild stress (CUMS) or dexamethasone administration of adolescent rats, the authors of the present study probed the depressive-like behaviors, GR and FKBP5 expressions, and miR-124a, miR-18a, and miR-511 expressions in the prefrontal cortex and hippocampus. The GR antagonist RU486 was used as intervention. The results revealed that both CUMS and dexamethasone administration in the adolescent period resulted in anhedonia, altered locomotor behaviors, anxiety, and cognitive impairment. A remarkable decrease in GR expression, and increase in FKBP5, miR-124a, and miR-18a expressions were detected in the prefrontal cortex and hippocampus of adolescent rats. Furthermore, the similar long-term changes on behaviors and expressions of GR, FKBP5 and GR-related microRNAs were found in the adult rats following CUMS and dexamethasone treatment in adolescence. However, reduced miR-511 expression was observed only in the prefrontal cortex of adult rats exposed to adolescent CUMS or dexamethasone administration. These data suggested that the downregulation of GR, upregulation of FKBP5, miR-124a, and miR-18a in the prefrontal cortex and hippocampus, and downregulation of miR-511 in the prefrontal cortex were relevant to depressive-like behaviors.

Disease- and treatment-associated acquired glucocorticoid resistance

The development of resistance to glucocorticoids (GCs) in therapeutic regimens poses a major threat. Generally, GC resistance is congenital or acquired over time as a result of disease progression, prolonged GC treatment or, in some cases, both. Essentially, disruptions in the function and/or pool of the glucocorticoid receptor α (GRα) underlie this resistance. Many studies have detailed how alterations in GRα function lead to diminished GC sensitivity; however, the current review highlights the wealth of data concerning reductions in the GRα pool, mediated by disease-associated and treatment-associated effects, which contribute to a significant decrease in GC sensitivity. Additionally, the current understanding of the molecular mechanisms involved in driving reductions in the GRα pool is discussed. After highlighting the importance of maintaining the level of the GRα pool to combat GC resistance, we present current strategies and argue that future strategies to prevent GC resistance should involve biased ligands with a predisposition for reduced GR dimerization, a strategy originally proposed as the SEMOGRAM-SEDIGRAM concept to reduce the side-effect profile of GCs.

Novel role for receptor dimerization in post-translational processing and turnover of the GRα

Glucocorticoids (GCs), acting via the glucocorticoid receptor (GRα), remain the mainstay therapeutic choice for the treatment of inflammation. However, chronic GC use, aside from generating undesirable side-effects, results in GRα down-regulation, often coupled to a decrease in GC-responsiveness, which may culminate in acquired GC resistance. The current study presents evidence for a novel role of the dimerization state of the GRα in mediating GC-mediated GRα turnover. Through comparing the effects of dimerization promoting GCs on down-regulation of a transfected human wild type GRα (hGRwt) or a dimerization deficient GRα mutant (hGRdim), we established that a loss of receptor dimerization restricts GRα turnover, which was supported by the use of the dimerization abrogating Compound A (CpdA), in cells containing endogenous GRα. Moreover, we showed that the dimerization state of the GRα influenced the post-translational processing of the receptor, specifically hyper-phosphorylation at Ser404, which influenced the interaction of GRα with the E3 ligase, FBXW7α, thus hampering receptor turnover via the proteasome. Lastly, the restorative effects of CpdA on the GRα pool, in the presence of Dex, were demonstrated in a combinatorial treatment protocol. These results expand our understanding of factors that contribute to GC-resistance and may be exploited clinically.

Inhibitory effect of the Kampo medicinal formula Yokukansan on acute stress-induced defecation in rats

OBJECTIVES

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder with symptoms of abnormal defecation and abdominal discomfort. Psychological factors are well known to be involved in onset and exacerbation of IBS. A few studies have reported effectiveness of traditional herbal (Kampo) medicines in IBS treatment. Yokukansan (YKS) has been shown to have anti-stress and anxiolytic effects. We investigated the effect of YKS on defecation induced by stress and involvement of oxytocin (OT), a peptide hormone produced by the hypothalamus, in order to elucidate the mechanism of YKS action.

METHODS AND RESULTS

Male Wistar rats were divided into four groups; control, YKS (300 mg/kg PO)-treated non-stress (YKS), acute stress (Stress), and YKS (300 mg/kg PO)-treated acute stress (Stress+YKS) groups. Rats in the Stress and Stress+YKS groups were exposed to a 15-min psychological stress procedure involving novel environmental stress. Levels of plasma OT in the YKS group were significantly higher compared with those in the Control group (P < 0.05), and OT levels in the Stress+YKS group were remarkably higher than those in the other groups (P < 0.01). Next, rats were divided into four groups; Stress, Stress+YKS, Atosiban (OT receptor antagonist; 1 mg/kg IP)-treated Stress+YKS (Stress+YKS+B), and OT (0.04 mg/kg IP)-treated acute stress (Stress+OT) groups. Rats were exposed to acute stress as in the previous experiment, and defecation during the stress load was measured. Administration of YKS or OT significantly inhibited defecation; however, administration of Atosiban partially abolished the inhibitory effect of YKS. Finally, direct action of YKS on motility of isolated colon was assessed. YKS (1 mg/mL, 5 mg/mL) did not inhibit spontaneous contraction.

CONCLUSION

These results suggested that YKS influences stress-induced defecation and that increased OT secretion may be a mechanism underlying this phenomenon.

FKBP5 and specific microRNAs via glucocorticoid receptor in the basolateral amygdala involved in the susceptibility to depressive disorder in early adolescent stressed rats

Exposure to stressful events induces depressive-like symptoms and increases susceptibility to depression. However, the molecular mechanisms are not fully understood. Studies reported that FK506 binding protein51 (FKBP5), the co-chaperone protein of glucocorticoid receptors (GR), plays a crucial role. Further, miR-124a and miR-18a are involved in the regulation of FKBP5/GR function. However, few studies have referred to effects of early life stress on depressive-like behaviours, GR and FKBP5, as well as miR-124a and miR-18a in the basolateral amygdala (BLA) from adolescence to adulthood. This study aimed to examine the dynamic alternations of depressive-like behaviours, GR and FKBP5, as well as miR-124a and miR-18a expressions in the BLA of chronic unpredictable mild stress (CUMS) rats and dexamethasone administration rats during the adolescent period. Meanwhile, the GR antagonist, RU486, was used as a means of intervention. We found that CUMS and dexamethasone administration in the adolescent period induced permanent depressive-like behaviours and memory impairment, decreased GR expression, and increased FKBP5 and miR-124a expression in the BLA of both adolescent and adult rats. However, increased miR-18a expression in the BLA was found only in adolescent rats. Depressive-like behaviours were positively correlated with the level of miR-124a, whereas GR levels were negatively correlated with those in both adolescent and adult rats. Our results suggested FKBP5/GR and miR-124a in the BLA were associated with susceptibility to depressive disorder in the presence of stressful experiences in early life.

Cellular Pharmacological Effects of the Traditional Japanese Kampo Medicine Yokukansan on Brain Cells

Yokukansan (YKS) is a traditional Japanese Kampo medicine currently used for the treatment of the behavioral psychological symptoms associated with dementia (BPSD), which is frequently problematic in neurodegenerative disorders such as Alzheimer’s disease. Regarding the pharmacological mechanisms underlying its efficacy, we recently reviewed the multiple effects of YKS on the neurotransmitter systems (e.g., glutamatergic, serotonergic, dopaminergic, cholinergic, GABAergic, and adrenergic neurotransmission) in various brain regions that are related to the psychological, emotional, cognitive, or memory functions. These multiple effects are thought to be caused by multiple components included in YKS. In addition, YKS exhibits various effects on brain cells (i.e., neurons, glial cells including astrocytes, oligodendrocytes, and microglial cells, and endothelial cells). In this review, we summarize recent evidence demonstrating the cellular pharmacological effects of YKS on these brain cells, and discuss the current understanding of its efficacy and mechanism. In particular, YKS maintains the neuronal survival and function by multiple beneficial effects, including anti-apoptosis, anti-oxidation, anti-endoplasmic reticulum stress, and neurogenesis. YKS also acts on glial cells by: facilitating the transport of glutamate into astrocytes; promoting the proliferation and differentiation of oligodendrocytes; and enhancing the anti-inflammatory properties of microglial cells. These glial effects are thought to support neuronal functioning within the brain. Various ingredients involved in these effects have been identified, some of which can pass through the artificial blood–brain barrier without disrupting the endothelial tight junctions. This multitude of interactive effects displayed by YKS on neuronal and glial cells is suggested to be involved in the multitude of neuropsychopharmacological actions of YKS, which are related to the improvement of BPSD.

Multiple Psychopharmacological Effects of the Traditional Japanese Kampo Medicine Yokukansan, and the Brain Regions it Affects

Yokukansan (YKS), a traditional Japanese Kampo medicine, has indications for use in night crying and irritability in children, as well as neurosis and insomnia. It is currently also used for the remedy of the behavioral and psychological symptoms of dementia (BPSD), such as aggressiveness, agitation, and hallucinations. In parallel with clinical evidence, a significant amount of fundamental researches have been undertaken to clarify the neuropsychopharmacological efficacies of YKS, with approximately 70 articles, including our own, being published to date. Recently, we reviewed the neuropharmacological mechanisms of YKS, including its effects on glutamatergic, serotonergic, and dopaminergic neurotransmission, and pharmacokinetics of the ingredients responsible for the effects. This review is aimed to integrate the information regarding the psychopharmacological effects of YKS with the brain regions known to be affected, to facilitate our understanding of the clinical efficacy of YKS. In this review, we first show that YKS has several effects that act to improve symptoms that are similar to BPSDs, like aggressiveness, hallucinations, anxiety, and sleep disturbance, as well as symptoms like tardive dyskinesia and cognitive deficits. We next provide the evidence showing that YKS can interact with various brain regions, including the cerebral cortex, hippocampus, striatum, and spinal cord, dysfunctions of which are related to psychiatric symptoms, cognitive deficits, abnormal behaviors, and dysesthesia. In addition, the major active ingredients of YKS, geissoschizine methyl ether and 18β-glycyrrhetinic acid, are shown to predominantly bind to the frontal cortex and hippocampus, respectively. Our findings suggest that YKS has multiple psychopharmacological effects, and that these are probably mediated by interactions among several brain regions. In this review, we summarize the available information about the valuable effects of a multicomponent medicine YKS on complex neural networks.

Antistress effects of Kampo medicine "Yokukansan" via regulation of orexin secretion

OBJECTIVE

Various stressors induce stress responses through the hypothalamic-pituitary-adrenal and the sympathetic-adrenal-medullary axes, which are regulated, in part, by orexin. For example, secretion of orexin in the hypothalamus is increased in rats exposed to the stress of social isolation for 1 week. In this study, the antistress effects of Kampo medicine Yokukansan (YKS) via the regulation of orexin secretion were investigated using a rat model.

METHODS AND RESULTS

The administration of 300 mg/kg per day of YKS to rats for 1 week significantly decreased the plasma orexin levels compared with non-treated rats, whereas the administration of 1,000 mg/kg of YKS had no effect on orexin levels. Therefore, 300 mg/kg of YKS was an effective dose for controlling orexin secretion. Subsequently, rats were divided into group-housed control (Con), individually housed stress (Stress), and individually housed YKS (300 mg/kg)-treated stress (Stress + YKS) groups. After 1 week, a resident-intruder aggression test was performed, and the plasma levels of orexin and corticosterone were measured. In the Stress group, aggressive behavior and the levels of corticosterone and orexin significantly increased compared with the Con group; however, these effects were inhibited in the Stress + YKS group. Further, an orexin receptor antagonist (TCS 1102; 10 mg/kg) was intraperitoneally administered to rats exposed to isolation stress to determine whether orexin was involved in stress responses. Under these conditions, aggressive behavior and the level of corticosterone significantly decreased compared with the Stress group.

CONCLUSION

These results suggest that orexin is involved in the control of stress response and that YKS exerts an antistress effect via the regulation of orexin secretion.

Neuropharmacological efficacy of the traditional Japanese Kampo medicine yokukansan and its active ingredients

Dementia is a progressive neurodegenerative disorder with cognitive dysfunction, and is often complicated by behavioral and psychological symptoms of dementia (BPSD) including excitement, aggression, and hallucinations. Typical and atypical antipsychotics are used for the treatment of BPSD, but induce adverse events. The traditional Japanese Kampo medicine yokukansan (YKS), which had been originated from the traditional Chinese medicine Yi-Gan-San, has been reported to improve BPSD without severe adverse effects. In the preclinical basic studies, there are over 70 research articles indicating the neuropharmacological efficacies of YKS. In this review, we first describe the neuropharmacological actions of YKS and its bioactive ingredients. Multiple potential actions for YKS were identified, which include effects on serotonergic, glutamatergic, cholinergic, dopaminergic, adrenergic, and GABAergic neurotransmissions as well as neuroprotection, anti-stress effect, promotion of neuroplasticity, and anti-inflammatory effect. Geissoschizine methyl ether (GM) in Uncaria hook and 18β-glycyrrhetinic acid (GA) in Glycyrrhiza were responsible for several pharmacological actions of YKS. Subsequently, we describe the pharmacokinetics of GM and GA in rats. These ingredients were absorbed into the blood, crossed the blood-brain barrier, and reached the brain, in rats orally administered YKS. Moreover, autoradiography showed that [(3)H]GM predominantly distributed in the frontal cortex and [(3)H]GA in the hippocampus. Thus, YKS is a versatile herbal remedy with a variety of neuropharmacological effects, and may operate as a multicomponent drug including various active ingredients.

MicroRNAs Modulate Interactions between Stress and Risk for Cocaine Addiction

Exposure to stress increases vulnerability to drug abuse, as well as relapse liability in addicted individuals. Chronic drug use alters stress response in a manner that increases drug seeking behaviors and relapse. Drug exposure and withdrawal have been shown to alter stress responses, and corticosteroid mediators of stress have been shown to impact addiction-related brain function and drug-seeking behavior. Despite the documented interplay between stress and substance abuse, the mechanisms by which stress exposure and drug seeking interact remain largely unknown. Recent studies indicate that microRNAs (miRNA) play a significant role in stress modulation as well as addiction-related processes including neurogenesis, synapse development, plasticity, drug acquisition, withdrawal and relapse. MiRNAs are short non-coding RNAs that function as bidirectional epigenetic modulators of gene expression through imperfect sequence targeted degradation and/or translational repression of mRNAs. They serve as dynamic regulators of CNS physiology and pathophysiology, and facilitate rapid and long-lasting changes to complex systems and behaviors. MiRNAs function in glucocorticoid signaling and the mesolimbic dopamine reward system, as well as mood disorders related to drug withdrawal. The literature suggests miRNAs play a pivotal role in the interaction between exposures to stress, addiction-related processes, and negative affective states resulting from extended drug withdrawal. This manuscript reviews recent evidence for the role of miRNAs in the modulation of stress and cocaine responses, and discusses potential mediation of the interaction of these systems by miRNAs. Uncovering the mechanism behind the association of stress and drug taking has the potential to impact the treatment of drug abuse and prevention of relapse. Further comprehension of these complex interactions may provide promising new targets for the treatment of drug addiction.

Rapid Down-Regulation of Glucocorticoid Receptor Gene Expression in the Dentate Gyrus after Acute Stress in vivo: Role of DNA Methylation and MicroRNA Activity

BACKGROUND

Although glucocorticoid receptors (GRs) in the hippocampus play a vital role in the regulation of physiological and behavioural responses to stress, the regulation of receptor expression remains unclear. This work investigates the molecular mechanisms underpinning stress-induced changes in hippocampal GR mRNA levels in vivo.

METHODS

Male Wistar rats were killed either under baseline conditions or after forced swim stress (FSS; 15 min in 25°C water). Rat hippocampi were micro-dissected (for mRNA, microRNA, and DNA methylation analysis) or frozen whole (for chromatin immunoprecipitation). In an additional experiment, rats were pre-treated with RU486 (a GR antagonist) or vehicle.

RESULTS

FSS evoked a dentate gyrus-specific reduction in GR mRNA levels. This was related to an increased DNMT3a protein association with a discreet region of the Nr3c1 (GR gene) promoter, shown here to undergo increased DNA methylation after FSS. FSS also caused a time-dependent increase in the expression of miR-124a, a microRNA known to reduce GR mRNA expression, which was inversely correlated with a reduction in GR mRNA levels 30 min after FSS. FSS did not affect GR binding to a putative negative glucocorticoid response element within the Nr3c1 gene.

CONCLUSIONS

Acute stress results in decreased GR mRNA expression specifically in the dentate gyrus. Our results indicate that a complex interplay of multiple molecular mechanisms - including increased DNA methylation of discrete CpG residues within the Nr3c1 gene, most likely facilitated by DNMT3a, and increased expression of miR-124a - could be responsible for these changes.