Hippocampus remodeling by chronic stress accompanied by GR, proteasome and caspase-3 overexpression

Modulation of noradrenergic signalling reverses stress-induced changes in the hippocampus: Involvement of orexinergic systems

Stress can be beneficial for adapting to dangerous situations in the short term but can be damaging in the long term, especially in the hippocampus. The noradrenergic and orexinergic systems play important roles in stress response. This study investigated the effect of noradrenergic activation on changes induced by chronic stress in the hippocampus and the involvement of orexinergic modulation in this process. This study examined five groups of 40 male Wistar rats (4 + 4 animals/ group): control, chronic stress, acute stress, control with noradrenergic activation, and chronic stress with noradrenergic activation. Hippocampal tissue and blood plasma were the primary specimens analyzed. The researchers measured plasma corticosterone (CORT) using a fluorometric method, examined the expression of prepro-orexin (prepro-OX), orexin receptor-1 (OXr1), and glucocorticoid receptor (GR) through RT-PCR, and quantified neuronal populations using Nissl staining. Acute and chronic stress increased plasma CORT levels and gene expression of prepro-OX, OXr1, and GR, while decreasing neuronal numbers, with chronic stress having a more pronounced effect. Yohimbine-treated and/or stressed rats exhibited elevated plasma CORT levels. Chronic stress substantially upregulated GR and increased prepro-OX and OXr1 expressions whereas yohimbine recovered those profiles in chronically stressed animals. Conversely, chronic stress reduced hippocampal neuronal populations, and chronic stress combined with yohimbine partially compensated for the neuronal numbers compared to chronic stress alone. These results suggest that noradrenergic signalling can reverse chronic stress-induced impairments in prepro-OX, OXr1 and GR expressions, and neuronal populations.

Neuroprotective Role of Selenium Nanoparticles Against Behavioral, Neurobiochemical and Histological Alterations in Rats Subjected to Chronic Restraint Stress

Chronic stress induces changes in the prefrontal cortex and hippocampus. Selenium nanoparticles (SeNPs) showed promising results in several neurological animal models. The implementation of SeNPs in chronic restraint stress (CRS) remains to be elucidated. This study was done to determine the possible protective effects of selenium nanoparticles on behavioral changes and brain oxidative stress markers in a rat model of CRS. 50 rats were divided into three groups; control group (n = 10), untreated CRS group (n = 10) and CRS-SeNPs treated group (n = 30). Restraint stress was performed 6 h./day for 21 days. Rats of CRS-SeNPs treated group received 1, 2.5 or 5 mg/kg SeNPs (10 rats each) by oral gavage for 21 days. Rats were subjected to behavioral assessments and then sacrificed for biochemical and histological analysis of the prefrontal cortex and hippocampus. Prefrontal cortical and hippocampal serotonin levels, oxidative stress markers including malondialdehyde (MDA), reduced glutathione (GSH) and glutathione peroxidase (GPx), tumor necrosis factor alpha (TNF-α) and caspase-3 were assessed. Accordingly, different doses of SeNPs showed variable effectiveness in ameliorating disease parameters, with 2.5 mg/kg dose of SeNPs showing the best improving results in all studied parameters. The present study exhibited the neuroprotective role of SeNPs in rats subjected to CRS and proposed their antioxidant, anti-inflammatory and anti-apoptotic effects as the possible mechanism for increased prefrontal cortical and hippocampal serotonin level, ameliorated anxiety-like and depressive-like behaviors and improved prefrontal cortical and hippocampal histological architecture.

The role of astrocytes in depression, its prevention, and treatment by targeting astroglial gliotransmitter release

The role of ventral hippocampus (vHipp) astroglial gliotransmission in depression was studied using chronic restraint stress (CRS) and chronic unpredictable mild stress (CUMS) rodent models. CRS increased Cx43 hemichannel activity and extracellular glutamate levels in the vHipp and blocking astroglial Cx43 hemichannel-dependent gliotransmission during CRS prevented the development of depression and glutamate buildup. Moreover, the acute blockade of Cx43 hemichannels induced antidepressant effects in rats previously subjected to CRS or CUMS. This antidepressant effect was prevented by coinjection of glutamate and D-serine. Furthermore, Cx43 hemichannel blockade decreased postsynaptic NMDAR currents in vHipp slices in a glutamate and D-serine-dependent manner. Notably, chronic microinfusion of glutamate and D-serine, L-serine, or the NMDAR agonist NMDA, into the vHipp induced depressive-like symptoms in nonstressed rats. We also identified a small molecule, cacotheline, which blocks Cx43 hemichannels and its systemic administration induced rapid antidepressant effects, preventing stress-induced increases in astroglial Cx43 hemichannel activity and extracellular glutamate in the vHipp, without sedative or locomotor side effects. In conclusion, chronic stress increases Cx43 hemichannel-dependent release of glutamate and D-/L-serine from astrocytes in the vHipp, overactivating postsynaptic NMDARs and triggering depressive-like symptoms. This study highlights the critical role of astroglial gliotransmitter release in chronic stress-induced depression and suggests it can be used as a target for the prevention and treatment of depression.

The brain insulin receptor gene network and associations with frailty index

OBJECTIVE

To investigate longitudinal associations between variations in the co-expression-based brain insulin receptor polygenic risk score and frailty, as well as change in frailty across follow-up.

METHODS

This longitudinal study included 1605 participants from the Helsinki Birth Cohort Study. Biologically informed expression-based polygenic risk scores for the insulin receptor gene network, which measure genetic variation in the function of the insulin receptor, were calculated for the hippocampal (hePRS-IR) and the mesocorticolimbic (mePRS-IR) regions. Frailty was assessed in at baseline in 2001-2004, 2011-2013 and 2017-2018 by applying a deficit accumulation-based frailty index. Analyses were carried out by applying linear mixed models and logistical regression models adjusted for adult socioeconomic status, birthweight, smoking and their interactions with age.

RESULTS

The FI levels of women were 1.19%-points (95% CI 0.12-2.26, P = 0.029) higher than in men. Both categorical and continuous hePRS-IR in women were associated with higher FI levels than in men at baseline (P < 0.05). In women with high hePRS-IR, the rate of change was steeper with increasing age compared to those with low or moderate hePRS-IR (P < 0.05). No associations were detected between mePRS-IR and frailty at baseline, nor between mePRS-IR and the increase in mean FI levels per year in either sex (P > 0.43).

CONCLUSIONS

Higher variation in the function of the insulin receptor gene network in the hippocampus is associated with increasing frailty in women. This could potentially offer novel targets for future drug development aimed at frailty and ageing.

Intragastric administration of prednisone acetate induced impairment of hippocampal long-term potentiation

Prednisone acetate (PA) has many adverse side effects despite the fact that oral administration of PA is widely administrated in the clinic. However, it is unknown whether PA can cause hippocampal long-term potentiation (LTP) impairment. Therefore, in our study, PA (5 mg/kg·d) through intragastric administration (gavage) was applied to establish a model of impaired hippocampal LTP in C57BL/6 mice, and the method was evaluated by comparing with another method to establish LTP impairment through subcutaneous injection of corticosterone (CORT, 50 mg/kg·d). First, our results showed PA caused a more significant decrease in population spike (PS, %) after high-frequency stimulation (HFS) than CORT, demonstrating PA induced impairment of hippocampal LTP more successfully than CORT. Second, PA caused poorer performance of memory than CORT. Third, PA caused more serious lesions and loss of the granule cell in the dentate gyrus than CORT. Finally, PA caused lower levels of glutamic acid (Glu), N-methyl-d-aspartate receptors (NMDARs) and gamma-aminobutyric acid (GABA) than CORT. All in all, PA (5 mg/kg·d) through intragastric administration (gavage) induced LTP impairment in the hippocampus more successfully than CORT. The neuronal lesions in the dentate gyrus and the consequent decrease of Glu and NMDARs (especially NMDAR2A) may be the cause of LTP impairment.

Xiangshao Granules reduce the aggressive behavior and hippocampal injury of premenstrual irritability in rats by regulating JIK/JNK/p38 signal pathway

ETHNOPHARMACOLOGICAL RELEVANCE

As a typical prescription for soothing the liver, Xiangshao granule has a good effect on the symptoms of irritability and anxiety. Clinical evidence suggests that it has significant efficacy in the treatment of Premenstrual dysphoria disorder (PMDD). However, the underlying mechanism remains unclear.

AIM OF THE STUDY

PMDD is a common disease in women of childbearing age, seriously affecting their family, society, and daily work life. The registered herbal medicine, Xiangshao granules, is used for relieving PMDD dysphoria and irritability symptoms with excellent efficacy in China. This study was focused on the deep intervention mechanism of Xiangshao granules in treating PMDD.

MATERIALS AND METHODS

The vaginal smear and open field test were used to screen rats in nonreception phase of estrus cycle with similar macroscopic behaviors and regular estrus cycle. The rat model of PMDD irritability was established through social isolation and residential invasion, with which, the irritability symptoms of PMDD patients with menstrual cycle dependence was also well simulated. Elevated plus Maze Test and Social interaction activities were used to measure the anxiety-like behavior of rats. TUNEL Staining and Hematoxylin-Eosin staining were used to measure apoptosis of hippocampal neurons. RT-PCR, Western blot and immunofluorescence were used to measure the expression of GR, JIK, p-JIK, p38, P-P38, JNK, caspase 3, and caspase 12.

RESULTS

In this study, Xiangshao granules showed consistent therapeutic effects similar with those in clinic, significantly reducing aggressive and anxiety-like behaviors with improved social skills in PMDD rats. In mechanism, Xiangshao granules lowered the apoptosis of hippocampal neurons and weakened the morphological damage of the hippocampal brain evidenced by the decreased mRNA and protein expression of glucocorticoid receptor, caspase-3, and caspase-12. In addition, administration of Xiangshao granules led to the decreased expression of JIK in the PMDD irritability rat model which agreed well with the previous studies. The JNK/p38 mitogen-activated protein kinases (MAPKs) signaling pathway is abnormally activated in the hippocampal brain region of PMDD rats, while treated with Xiangshao granules could increase JIK expression and inhibit the abnormal activation of the JNK/p38 MAPK signaling pathway, effectively reducing the stress damage in the hippocampus.

CONCLUSIONS

Xiangshao Granules Reduce the Aggressive Behavior and Hippocampal Injury of Premenstrual Irritability in Rats by Regulating JIK/JNK/p38 Signal Pathway.

Post-traumatic Stress Disorder: Focus on Neuroinflammation

Post-traumatic stress disorder (PTSD), gaining increasing attention, is a multifaceted psychiatric disorder that occurs following a stressful or traumatic event or series of events. Recently, several studies showed a close relationship between PTSD and neuroinflammation. Neuroinflammation, a defense response of the nervous system, is associated with the activation of neuroimmune cells such as microglia and astrocytes and with changes in inflammatory markers. In this review, we first analyzed the relationship between neuroinflammation and PTSD: the effect of stress-derived activation of the hypothalamic-pituitary-adrenal (HPA) axis on the main immune cells in the brain and the effect of stimulated immune cells in the brain on the HPA axis. We then summarize the alteration of inflammatory markers in brain regions related to PTSD. Astrocytes are neural parenchymal cells that protect neurons by regulating the ionic microenvironment around neurons. Microglia are macrophages of the brain that coordinate the immunological response. Recent studies on these two cell types provided new insight into neuroinflammation in PTSD. These contribute to promoting comprehension of neuroinflammation, which plays a pivotal role in the pathogenesis of PTSD.

Exploring the Potential Mechanism of Danshen in the Treatment of Concurrent Ischemic Heart Disease and Depression Using Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulation

Objective: This study aimed to explore the potential targets and mechanism of action of Danshen in treating concurrent ischemic heart disease (IHD) and depression using network pharmacology, molecular docking, and molecular dynamics simulation (MDS). Methods: The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was used to obtain active ingredients and targets of Danshen. Candidate targets for IHD and depression were obtained from the Genecards and DisGeNet databases. The protein–protein interaction (PPI) network was constructed using the STRING database and the Cytoscape 3.8.2 software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed using the Metascape database and the GlueGO package of the Cytoscape 3.8.2 software. Molecular docking was performed using Autodock 1.5.6 and Vina, and the MDS was completed using GROMACS 5.1.2. Results: We obtained 65 active ingredients of Danshen with 131 candidate targets and 39 intersection targets of the active ingredients and diseases. Luteolin, tanshinone IIA, and salviolone were the core active ingredients, and AKT1, TNF, IL-6, MMP9, CASP3, IL-10, PTGS2, STAT3, PPARG, IL-4, EGFR, MAPK14, NOS3, and EDN1 were the core targets. The GO and KEGG pathway enrichment analyses revealed that the intersection targets were mainly enriched in positive regulation of protein phosphorylation, blood circulation, IL-17 signaling pathway, VEGF signaling pathway, and JAK/STAT signaling pathway. The molecular docking revealed that the core active ingredients had a good affinity for the core targets. The results of MDS revealed that the protein-ligand complexes were stable. Conclusions: This study used network pharmacology to analyze the potential mechanism of action of Danshen in the treatment of concurrent IHD and depression. Additionally, the study provided a theoretical basis for further studying the pharmacological mechanisms and targets of Danshen.

A Selective Histamine H4 Receptor Antagonist, JNJ7777120, Role on Glutamate Transporter Activity in Chronic Depression

Glutamate release and reuptake play a key role in the pathophysiology of depression. glutamatergic nerves in the hippocampus region are modulated by histaminergic afferents. Excessive accumulation of glutamate in the synaptic area causes degeneration of neuron cells. The H4 receptor is defined as the main immune system histamine receptor with a pro-inflammatory role. To understand the role of this receptor, the drug JNJ7777120 was used to reveal the chronic depression-glutamate relationship. We have important findings showing that the H4 antagonist increases the glutamate transporters’ instantaneous activity. In our experiment, it has been shown that blocking the H4 receptor leads to increased neuron cell viability and improvement in behavioral ability due to glutamate. Therefore, JNJ can be used to prevent neurotoxicity, inhibit membrane phospholipase activation and free radical formation, and minimize membrane disruption. In line with our findings, results have been obtained that indicate that JNJ will contribute to the effective prevention and treatment of depression.

Neonatal Maternal Separation Modifies Proteostasis Marker Expression in the Adult Hippocampus

Exposure to early-life stress (ELS) can persistently modify neuronal circuits and functions, and contribute to the expression of misfolded and aggregated proteins that are hallmarks of several neurodegenerative diseases. The healthy brain is able to clear dysfunctional proteins through the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP). Accumulating evidence indicates that impairment of these pathways contributes to enhanced protein aggregation and neurodegeneration. While stress is a known precipitant of neurological decline, few specific mechanistic links underlying this relationship have been identified. We hypothesized that neonatal maternal separation (MatSep), a well-established model of ELS, has the ability to alter the levels of UPS and ALP components in the brain, and thus has the potential to disrupt proteostasis. The expression of proteostasis-associated protein markers was evaluated by immunoblotting in the hippocampus and cortex of adult Wistar rats that were previously subjected to MatSep. We observed multiple sex- and MatSep-specific changes in the expression of proteins in the ALP, mitophagy, and UPS pathways, particularly in the hippocampus of adult animals. In contrast, MatSep had limited influence on proteostasis marker expression in the cortex of adult animals. Our results indicate that MatSep can selectively modify the intracellular protein degradation machinery in ways that may impact the development and progression of neurodegenerative disease.

Escitalopram Targets Oxidative Stress, Caspase-3, BDNF and MeCP2 in the Hippocampus and Frontal Cortex of a Rat Model of Depression Induced by Chronic Unpredictable Mild Stress

In recent years, escitalopram (ESC) has been suggested to have different mechanisms of action beyond its well known selective serotonin reuptake inhibition. The aim of this study is to investigate the effects of escitalopram on oxidative stress, apoptosis, brain-derived neurotrophic factor (BDNF), Methyl-CpG-binding protein 2 (MeCP2), and oligodendrocytes number in the brain of chronic unpredictable mild stress-induced depressed rats. The animals were randomised in four groups (8 in each group): control, stress, stress + ESC 5 and stress + ESC 5/10. ESC was administered for 42 days in a fixed dose (5 mg/kg b.w.) or in an up-titration regimen (21 days ESC 5 mg/kg b.w. then 21 days ESC 10 mg/kg b.w.). Sucrose preference test (SPT) and elevated plus maze (EPM) were also performed. ESC improved the percentage of sucrose preference, locomotion and anxiety. ESC5/10 reduced the oxidative damage in the hippocampus and improved the antioxidant defence in the hippocampus and frontal lobe. ESC5/10 lowered caspase 3 activity in the hippocampus. Escitalopram had a modulatory effect on BDNF and the number of oligodendrocytes in the hippocampus and frontal lobe and also improved the MeCP2 expressions. The results confirm the multiple pathways implicated in the pathogenesis of depression and suggest that escitalopram exerts an antidepressant effect via different intricate mechanisms.

Do changes in microglial status underlie neurogenesis impairments and depressive-like behaviours induced by psychological stress? A systematic review in animal models

Stress may have a negative effect on mental health and is the primary environmental risk factor in the aetiology of depression. Nevertheless, the neurobiological mechanisms underlying this mood disorder remain poorly characterized. The hippocampus is a target structure of the adverse effects of stress, and hippocampal neurogenesis plays a crucial role. However, we do not know the mechanisms by which stress impacts neurogenesis. Recent studies indicate that changes in neuroinflammation, primarily via microglial cells, may play an essential role in this process. However, the relationship between stress, microglial changes, and alterations in neurogenesis and their involvement in the development of depression is poorly characterized. For this reason, this systematic review aims to synthesise and evaluate current studies that have investigated the relationship between these variables. Taken together, the revised data, although not entirely conclusive, seem to suggest that microglial changes induced by psychological stress regulate neurogenesis and in turn may be responsible for the development of depressive-like behaviours, but other factors that influence these stressful experiences should not be dismissed.

Standardized Bacopa monnieri Extract Ameliorates Learning and Memory Impairments through Synaptic Protein, Neurogranin, Pro-and Mature BDNF Signaling, and HPA Axis in Prenatally Stressed Rat Offspring

Prenatal stress (PNS) influences offspring neurodevelopment, inducing anxiety-like behavior and memory deficits. We investigated whether pretreatment of Bacopa monnieri extract (CDRI-08/BME) ameliorates PNS-induced changes in signaling molecules, and changes in the behavior of Wistar rat offspring. Pregnant rats were randomly assigned into control (CON)/prenatal stress (PNS)/PNS and exposed to BME treatment (PNS + BME). Dams were exposed to stress by placing them in a social defeat cage, where they observed social defeat from gestational day (GD)-16–18. Pregnant rats in the PNS + BME group were given BME treatment from GD-10 to their offspring’s postnatal day (PND)-23, and to their offspring from PND-15 to -30. PNS led to anxiety-like behavior; impaired memory; increased the level of corticosterone (CORT), adrenocorticotropic hormone, glucocorticoid receptor, pro-apoptotic Casepase-3, and 5-HT_2C receptor; decreased anti-apoptotic Bcl-2, synaptic proteins (synaptophysin, synaptotagmin-1), 5-HT_1A, receptor, phosphorylation of calmodulin-dependent protein kinase II/neurogranin, N-methyl-D-aspartate receptors (2A,2B), postsynaptic density protein 95; and conversion of pro and mature brain derived neurotropic factor in their offspring. The antioxidant property of BME possibly inhibiting the PNS-induced changes in observed molecules, anxiety-like behavior, and memory deficits. The observed results suggest that pretreatment of BME could be an effective coping strategy to prevent PNS-induced behavioral impairments in their offspring.

LPA1 receptor and chronic stress: Effects on behaviour and the genes involved in the hippocampal excitatory/inhibitory balance

The LPA₁ receptor, one of the six characterized G protein-coupled receptors (LPA_1-6) through which lysophosphatidic acid acts, is likely involved in promoting normal emotional behaviours. Current data suggest that the LPA-LPA_1-receptor pathway may be involved in mediating the negative consequences of stress on hippocampal function. However, to date, there is no available information regarding the mechanisms whereby the LPA₁ receptor mediates this adaptation. To gain further insight into how the LPA-LPA₁ pathway may prevent the negative consequences of chronic stress, we assessed the effects of the continuous delivery of LPA on depressive-like behaviours induced by a chronic restraint stress protocol. Because a proper excitatory/inhibitory balance seems to be key for controlling the stress response system, the gene expression of molecular markers of excitatory and inhibitory neurotransmission was also determined. In addition, the hippocampal expression of mineralocorticoid receptor genes and glucocorticoid receptor genes and proteins as well as plasma corticosterone levels were determined. Contrary to our expectations, the continuous delivery of LPA in chronically stressed animals potentiated rather than inhibited some (e.g., anhedonia, reduced latency to the first immobility period), though not all, behavioural effects of stress. Furthermore, this treatment led to an alteration in the genes coding for proteins involved in the excitatory/inhibitory balance in the ventral hippocampus and to changes in corticosterone levels. In conclusion, the results of this study reinforce the assumption that LPA is involved in emotional regulation, mainly through the LPA₁ receptor, and regulates the effects of stress on hippocampal gene expression and hippocampus-dependent behaviour.

Antidepressant-like effects of paeoniflorin on post-stroke depression in a rat model

BACKGROUND

Post-stroke depression (PSD) is one of the most prevalent emotional disorders after stroke and often results in poor outcomes. However, the underlying physiopathologic mechanism and effective treatment of PSD remain poorly elucidated.

OBJECTIVE

To investigate whether paeoniflorin has antidepressant-like activity in a rat model of PSD.

METHODS

Rats were randomly divided into four groups: sham-operated control (Sham), PSD, paeoniflorin (with PSD) and fluoxetine group(with PSD). PSD was developed by the right middle cerebral artery occlusion followed 21 days chronic unpredictable mild stress combined (CUMS) with raised alone. Tests of sucrose preference and open field were used to assess the depression-like behavior. Neurological function was evaluated by neurological deficit score and beam balance test. Expression of phosphorylated CREB (p-CREB) and brain-derived neurotrophic factor (BDNF) in the CA1 region of the hippocampal complex was evaluated by western blot and immunofluorescence.

RESULTS

Te depressive-like behaviors markedly improved after paeoniflorin and fluoxetine treatment. Furthermore, paeoniflorin treatment significantly increased BDNF and p-CREB expression in the CA1 region.

CONCLUSIONS

Observed results suggested that paeoniflorin could ameliorate the symptoms and improve the functional capability of PSD rats, similar to the effect of fluoxetine.

ABBREVIATIONS

PSD: post-stroke depression; CUMS: chronic unpredictable mild stress stimulation; MCAO: middle cerebral artery occlusion; OFT: open field test; SPT: sucrose preference test, NDS: neurological deficit score, BBT: beam balance test; BDNF: brain-derived neurotrophic factor protein; p-CREB: phosphorylated Cyclic-AMP responsive element binding protein.

Electroconvulsive treatment prevents chronic restraint stress-induced atrophy of the hippocampal formation-A stereological study

INTRODUCTION

Electroconvulsive therapy (ECT) is one of the most efficient treatments of major depressive disorder (MDD), although the underlying neurobiology remains poorly understood. There is evidence that ECT and MDD exert opposing effects on the hippocampal formation with respect to volume and number of neurons. However, there has been a paucity of quantitative data in experimental models of ECT and MDD.

METHODS

Using design-based stereology, we have measured the effects of a stress-induced depression model (chronic restraint stress, CRS) and ECS on the morphology of the hippocampus by estimating the volume and total number of neurons in the hilus, CA1, and CA2/3, as well as in the entire hippocampus.

RESULTS

We find that CRS induces a significant decrease in volume exclusively of the hilus and that ECS (CRS + ECS) blocks this reduction. Furthermore, ECS alone does not change the volume or total number of neurons in the entire hippocampus or any hippocampal subdivision in our rat model.

Biological Processes and Biomarkers Related to Frailty in Older Adults: A State-of-the-Science Literature Review

The objectives of this literature review were to (1) synthesize biological processes linked to frailty and their corresponding biomarkers and (2) identify potential associations among these processes and biomarkers. In September 2016, PubMed, Cumulative Index to Nursing and Allied Health, Cochrane Library, and Embase were searched. Studies examining biological processes related to frailty in older adults (≥60 years) were included. Studies were excluded if they did not employ specific measures of frailty, did not report the association between biomarkers and frailty, or focused on nonelderly samples (average age < 60). Review articles, commentaries, editorials, and non-English articles were also excluded. Fifty-two articles were reviewed, reporting six biological processes related to frailty and multiple associated biomarkers. The processes (biomarkers) include brain changes (neurotrophic factor, gray matter volume), endocrine dysregulation (growth hormones [insulin-like growth factor-1 and binding proteins], hormones related to glucose and insulin, the vitamin D axis, thyroid function, reproductive axis, and hypothalamic–pituitary–adrenal axis), enhanced inflammation (C-reactive protein, interleukin-6), immune dysfunction (neutrophils, monocytes, neopterin, CD8+CD28−T cells, albumin), metabolic imbalance (micronutrients, metabolites, enzyme-activity indices, metabolic end products), and oxidative stress (antioxidants, telomere length, glutathione/oxidized glutathione ratio). Bidirectional interrelationships exist within and between these processes. Biomarkers were associated with frailty in varied strengths, and the causality remains unclear. In conclusion, frailty is related to multisystem physiological changes. Future research should examine the dynamic interactions among these processes to inform causality of frailty. Given the multifactorial nature of frailty, a composite index of multisystem biomarkers would likely be more informative than single biomarkers in early detection of frailty.

High-fidelity discrete modeling of the HPA axis: a study of regulatory plasticity in biology

BACKGROUND

The hypothalamic-pituitary-adrenal (HPA) axis is a central regulator of stress response and its dysfunction has been associated with a broad range of complex illnesses including Gulf War Illness (GWI) and Chronic Fatigue Syndrome (CFS). Though classical mathematical approaches have been used to model HPA function in isolation, its broad regulatory interactions with immune and central nervous function are such that the biological fidelity of simulations is undermined by the limited availability of reliable parameter estimates.

METHOD

Here we introduce and apply a generalized discrete formalism to recover multiple stable regulatory programs of the HPA axis using little more than connectivity between physiological components. This simple discrete model captures cyclic attractors such as the circadian rhythm by applying generic constraints to a minimal parameter set; this is distinct from Ordinary Differential Equation (ODE) models, which require broad and precise parameter sets. Parameter tuning is accomplished by decomposition of the overall regulatory network into isolated sub-networks that support cyclic attractors. Network behavior is simulated using a novel asynchronous updating scheme that enforces priority with memory within and between physiological compartments.

RESULTS

Consistent with much more complex conventional models of the HPA axis, this parsimonious framework supports two cyclic attractors, governed by higher and lower levels of cortisol respectively. Importantly, results suggest that stress may remodel the stability landscape of this system, favoring migration from one stable circadian cycle to the other. Access to each regime is dependent on HPA axis tone, captured here by the tunable parameters of the multi-valued logic. Likewise, an idealized glucocorticoid receptor blocker alters the regulatory topology such that maintenance of persistently low cortisol levels is rendered unstable, favoring a return to normal circadian oscillation in both cortisol and glucocorticoid receptor expression.

CONCLUSION

These results emphasize the significance of regulatory connectivity alone and how regulatory plasticity may be explored using simple discrete logic and minimal data compared to conventional methods.

Impaired glucocorticoid-mediated HPA axis negative feedback induced by juvenile social isolation in male rats

We previously demonstrated that socially isolated rats at weaning showed a significant decrease in corticosterone and adrenocorticotropic hormone (ACTH) levels, associated with an enhanced response to acute stressful stimuli. Here we shown that social isolation decreased levels of total corticosterone and of its carrier corticosteroid-binding globulin, but did not influence the availability of the free active fraction of corticosterone, both under basal conditions and after acute stress exposure. Under basal conditions, social isolation increased the abundance of glucocorticoid receptors, while it decreased that of mineralocorticoid receptors. After acute stress exposure, socially isolated rats showed long-lasting corticosterone, ACTH and corticotrophin releasing hormone responses. Moreover, while in the hippocampus and hypothalamus of group-housed rats glucocorticoid receptors expression increased with time and reached a peak when corticosterone levels returned to basal values, in socially isolated rats expression of glucocorticoid receptors did not change. Finally, social isolation also affected the hypothalamic endocannabinoid system: compared to group-housed rats, basal levels of anandamide and cannabinoid receptor type 1 were increased, while basal levels of 2-arachidonoylglycerol were decreased in socially isolated rats and did not change after acute stress exposure. The present results show that social isolation in male rats alters basal HPA axis activity and impairs glucocorticoid-mediated negative feedback after acute stress. Given that social isolation is considered an animal model of several neuropsychiatric disorders, such as generalized anxiety disorder, depression, post-traumatic stress disorder and schizophrenia, these data could contribute to better understand the alterations in HPA axis activity observed in these disorders.

Epigenetic modification of glucocorticoid receptor promoter I7 in maternally separated and restraint-stressed rats

Glucocorticoid receptor (GR) promoter I₇ is susceptible to epigenetic changes induced by environmental influences. Early life stress (ELS) has a persistent impact on GR expression, as well as behavior, in adult rodents via epigenetic changes of GR promoter I₇. Moreover, various stressors can induce histone modifications in this region during adulthood. Thus, the present study aimed to investigate whether maternally separated (MS) rats exposed to chronic restraint stress (RS) would exhibit histone modifications of GR promoter I₇ in the hippocampus. Rats were subjected to MS (3h per day) on postnatal days (PND) 1-21. Then, during adulthood (PND 56-77), the rats were exposed to RS (2h per day) followed by treatment with escitalopram (10mg/kg). The MS and RS groups exhibited significant decreases in total and exon I₇ GR mRNA levels and the combination of MS and RS exerted a greater effect on these mRNA levels than either MS or RS alone. Additionally, both the MS and RS groups showed significant reductions in histone H3 acetylation at GR promoter I₇ and the combination of MS and RS had a greater effect than did either MS or RS alone. Chronic escitalopram treatment ameliorated these changes. The present results indicate that postnatal MS and adult RS influence GR expression through histone modification at GR promoter I₇, and that the combination of the two stressors potentiates these changes. Furthermore, epigenetic mechanisms are involved in escitalopram action.

Anxiolytic effects of muscarinic acetylcholine receptors agonist oxotremorine in chronically stressed rats and related changes in BDNF and FGF2 levels in the hippocampus and prefrontal cortex

RATIONALE

In depressive disorders, one of the mechanisms proposed for antidepressant drugs is the enhancement of synaptic plasticity in the hippocampus and cerebral cortex. Previously, we showed that the muscarinic acetylcholine receptor (mAChR) agonist oxotremorine (Oxo) increases neuronal plasticity in hippocampal neurons via FGFR1 transactivation.

OBJECTIVES

Here, we aimed to explore (a) whether Oxo exerts anxiolytic effect in the rat model of anxiety-depression-like behavior induced by chronic restraint stress (CRS), and (b) if the anxiolytic effect of Oxo is associated with the modulation of neurotrophic factors, brain-derived neurotrophic factor (BDNF) and fibroblast growth factor-2 (FGF2), and phosphorylated Erk1/2 (p-Erk1/2) levels in the dorsal or ventral hippocampus and in the medial prefrontal cortex.

METHODS

The rats were randomly divided into four groups: control unstressed, CRS group, CRS group treated with 0.2 mg/kg Oxo, and unstressed group treated with Oxo. After 21 days of CRS, the groups were treated for 10 days with Oxo or saline. The anxiolytic role of Oxo was tested by using the following: forced swimming test, novelty suppressed feeding test, elevated plus maze test, and light/dark box test. The hippocampi and prefrontal cortex were used to evaluate BDNF and FGF2 protein levels and p-Erk1/2 levels.

RESULTS

Oxo treatment significantly attenuated anxiety induced by CRS. Moreover, Oxo treatment counteracted the CRS-induced reduction of BDNF and FGF2 levels in the ventral hippocampus and medial prefrontal cerebral cortex CONCLUSIONS: The present study showed that Oxo treatment ameliorates the stress-induced anxiety-like behavior and rescues FGF2 and BDNF levels in two brain regions involved in CRS-induced anxiety, ventral hippocampal formation, and medial prefrontal cortex.

Coping with the Forced Swim Stressor: Towards Understanding an Adaptive Mechanism

In the forced swim test (FST) rodents progressively show increased episodes of immobility if immersed in a beaker with water from where escape is not possible. In this test, a compound qualifies as a potential antidepressant if it prevents or delays the transition to this passive (energy conserving) behavioural style. In the past decade however the switch from active to passive "coping" was used increasingly to describe the phenotype of an animal that has been exposed to a stressful history and/or genetic modification. A PubMed analysis revealed that in a rapidly increasing number of papers (currently more than 2,000) stress-related immobility in the FST is labeled as a depression-like phenotype. In this contribution we will examine the different phases of information processing during coping with the forced swim stressor. For this purpose we focus on the action of corticosterone that is mediated by the closely related mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) in the limbic brain. The evidence available suggests a model in which we propose that the limbic MR-mediated response selection operates in complementary fashion with dopaminergic accumbens/prefrontal executive functions to regulate the transition between active and passive coping styles. Upon rescue from the beaker the preferred, mostly passive, coping style is stored in the memory via a GR-dependent action in the hippocampal dentate gyrus. It is concluded that the rodent's behavioural response to a forced swim stressor does not reflect depression. Rather the forced swim experience provides a unique paradigm to investigate the mechanistic underpinning of stress coping and adaptation.

Anti-Apoptotic Protein Bcl-xL Expression in the Midbrain Raphe Region Is Sensitive to Stress and Glucocorticoids

Anti-apoptotic proteins are suggested to be important for the normal health of neurons and synapses as well as for resilience to stress. In order to determine whether stressful events may influence the expression of anti-apoptotic protein Bcl-xL in the midbrain and specifically in the midbrain serotonergic (5-HT) neurons involved in neurobehavioral responses to adverse stimuli, adult male rats were subjected to short-term or chronic forced swim stress. A short-term stress rapidly increased the midbrain bcl-xl mRNA levels and significantly elevated Bcl-xL immunoreactivity in the midbrain 5-HT cells. Stress-induced increase in glucocorticoid secretion was implicated in the observed effect. The levels of bcl-xl mRNA were decreased after stress when glucocorticoid elevation was inhibited by metyrapone (MET, 150 mg/kg), and this decrease was attenuated by glucocorticoid replacement with dexamethasone (DEX; 0.2 mg/kg). Both short-term stress and acute DEX administration, in parallel with Bcl-xL, caused a significant increase in tph2 mRNA levels and slightly enhanced tryptophan hydroxylase immunoreactivity in the midbrain. The increasing effect on the bcl-xl expression was specific to the short-term stress. Forced swim repeated daily for 2 weeks led to a decrease in bcl-xl mRNA in the midbrain without any effects on the Bcl-xL protein expression in the 5-HT neurons. In chronically stressed animals, an increase in tph2 gene expression was not associated with any changes in tryptophan hydroxylase protein levels. Our findings are the first to demonstrate that both short-term stress and acute glucocorticoid exposures induce Bcl-xL protein expression in the midbrain 5-HT neurons concomitantly with the activation of the 5-HT synthesis pathway in these neurons.

Updates in the neuroendocrinology of stress and its clinical management

PURPOSE OF REVIEW

This review will provide updates on the neurobiology of stress, with specific focus on the transmitting mechanism of stress, the intricacies of integrating stress-related information, variability in response to stressors and clinical interventions.

RECENT FINDINGS

Neuropeptides have been implicated as a potential modulator for pathological stress via effects on neurogenesis, alterations in functional states of the cortico-limbic circuits and possible neuroprotection. Glucocorticoid receptors and mineralocorticoid receptors have been implicated in limbic modulation of stress and changes in the hypothalamic pituitary adrenal axis activity via corticosteroid signalling and feedback regulation. Chronic stress and genetic susceptibility have been found to promote intracellular mitochondrial and cellular DNA damage resulting in structural and functional alterations of neuroanatomy and neural circuitries.

SUMMARY

The interplay of stress and the neuroendocrine system appears to be influenced by alterations in genetic expression, resulting in neurochemical messenger and inflammatory cytokine alterations that impact neuroanatomy and neural circuitries to affect both central nervous system structure and function. These neurobiological contributions have been alluded to as possible contributors to stress-related psychopathologies. Clinical interventions with psychotropics, mind body therapies and behavioural therapies have been found to attenuate and reverse stress-related responses.

Heat-shock protein 90 (Hsp90) as anticancer target for drug discovery: an ample computational perspective

There are over 100 different types of cancer, and each is classified based on the type of cell that is initially affected. If left untreated, cancer can result in serious health problems and eventually death. Recently, the paradigm of cancer chemotherapy has evolved to use a combination approach, which involves the use of multiple drugs each of which targets an individual protein. Inhibition of heat-shock protein 90 (Hsp90) is one of the novel key cancer targets. Because of its ability to target several signaling pathways, Hsp90 inhibition emerged as a useful strategy to treat a wide variety of cancers. Molecular modeling approaches and methodologies have become 'close counterparts' to experiments in drug design and discovery workflows. A wide range of molecular modeling approaches have been developed, each of which has different objectives and outcomes. In this review, we provide an up-to-date systematic overview on the different computational models implemented toward the design of Hsp90 inhibitors as anticancer agents. Although this is the main emphasis of this review, different topics such as background and current statistics of cancer, different anticancer targets including Hsp90, and the structure and function of Hsp90 from an experimental perspective, for example, X-ray and NMR, are also addressed in this report. To the best of our knowledge, this review is the first account, which comprehensively outlines various molecular modeling efforts directed toward identification of anticancer drugs targeting Hsp90. We believe that the information, methods, and perspectives highlighted in this report would assist researchers in the discovery of potential anticancer agents.

Flupirtine attenuates chronic restraint stress-induced cognitive deficits and hippocampal apoptosis in male mice

Chronic restraint stress (CRS) causes hippocampal neurodegeneration and hippocampus-dependent cognitive deficits. Flupirtine represents neuroprotective effects and we have previously shown that flupirtine can protect against memory impairment induced by acute stress. The present study aimed to investigate whether flupirtine could alleviate spatial learning and memory impairment and hippocampal apoptosis induced by CRS. CRS mice were restrained in well-ventilated Plexiglass tubes for 6h daily beginning from 10:00 to 16:00 for 21 consecutive days. Mice were injected with flupirtine (10mg/kg and 25mg/kg) or vehicle (10% DMSO) 30min before restraint stress for 21 days. After stressor cessation, the spatial learning and memory, dendritic spine density, injured neurons and the levels of Bcl-2, Bax, p-Akt, p-GSK-3β, p-Erk1/2 and synaptophysin of hippocampal tissues were examined. Our results showed that flupirtine significantly prevented spatial learning and memory impairment induced by CRS in the Morris water maze. In addition, flupirtine (10mg/kg and 25mg/kg) treatment alleviated neuronal apoptosis and the reduction of dendritic spine density and synaptophysin expression in the hippocampal CA1 region of CRS mice. Furthermore, flupirtine (10mg/kg and 25mg/kg) treatment significantly decreased the expression of Bax and increased the p-Akt and p-GSK-3β, and flupirtine (25mg/kg) treatment up-regulated the p-Erk1/2 in the hippocampus of CRS mice. These results suggested that flupirtine exerted protective effects on the CRS-induced cognitive impairment and hippocampal neuronal apoptosis, which is possibly associated with the activation of Akt/GSK-3β and Erk1/2 signaling pathways.