The effects of antidepressants "fluoxetine and imipramine" on vascular abnormalities and Toll like receptor-4 expression in diabetic and non-diabetic rats exposed to chronic stress

Environmental enrichment and the combined interventions of EE and metformin enhance hippocampal neuron survival and hippocampal-dependent memory in type 2 diabetic rats under stress through the BDNF-TrkB signaling pathways

BACKGROUND

Type 2 diabetes (T2D) with depression causes severe cognitive impairments. The devastating conditions will further compromise the overall quality of life. The overconsumption of high-fat and high-sucrose (HFS) diet is one of the modifiable risk factors for T2D, depression, and cognitive impairments. Thus, it is essential to identify effective therapeutic strategies to overcome the cognitive impairments in T2D with depression. We proposed environmental enrichment (EE) which encompasses social, cognitive, and physical components as the alternative treatment for such impairments. We also investigated the potential neuroprotective properties of the antidiabetic drug metformin. This study aimed to investigate the effects of EE and metformin interventions on hippocampal neuronal death, and hippocampal-dependent memory impairment in T2D rats under stress.

METHODS

Thirty-two male rats (200-250 g) were divided into four groups: C group (standard diet + conventional cage), DS group [HFS-induced T2D + restraint stress (RS)], DSE group [HFS-induced T2D + RS + EE] and DSEM group [HFS + RS + EE + metformin]. Serum corticosterone (CORT) was measured to evaluate stress levels. The serum Free Oxygen Radicals Testing (FORT) and Free Oxygen Radicals Defence Test (FORD) were measured to evaluate the systemic oxidative status (OS). Serum brain-derived neurotrophic factor (BDNF) and T-maze tasks were performed to evaluate cognitive functions. Rats were humanely sacrificed to collect brains for histological, morphometric, and hippocampal gene expression studies.

RESULTS

The CORT and the serum FORT levels in the DSE and DSEM groups were lower than in the DS group. Meanwhile, the serum BDNF, T-maze scores, histological, and morphometric analysis were improved in the DSE and DSEM groups than in the DS group. These findings supported that EE and the combined interventions of EE and metformin had neuroprotective properties. The hippocampal gene expression analysis revealed that the DSE and DSEM groups showed improved regulation of BDNF-TrkB signalling pathways, including the BDNF/TrkB binding, PI3K - Akt pathway, Ras-MAPK pathway, PLCγ-Ca2+ pathway, and CREB transcription.

CONCLUSION

EE and the combined interventions of EE and metformin improved hippocampal neuron survival and hippocampal-dependent memory in T2D rats under stress by enhancing gene expression regulation of neurogenesis and synaptic plasticity.

The role of Toll-like receptors in neuropsychiatric disorders: Immunopathology, treatment, and management

Neuropsychiatric disorders denote a broad range of illnesses involving neurology and psychiatry. These disorders include depressive disorders, anxiety, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, autism spectrum disorders, headaches, and epilepsy. In addition to their main neuropathology that lies in the central nervous system (CNS), lately, studies have highlighted the role of immunity and neuroinflammation in neuropsychiatric disorders. Toll-like receptors (TLRs) are innate receptors that act as a bridge between the innate and adaptive immune systems via adaptor proteins (e.g., MYD88) and downstream elements; TLRs are classified into 13 families that are involved in normal function and illnesses of the CNS. TLRs expression affects the course of neuropsychiatric disorders, and is influenced during their pharmacotherapy; For example, the expression of multiple TLRs is normalized during the major depressive disorder pharmacotherapy. Here, the role of TLRs in neuroimmunology, treatment, and management of neuropsychiatric disorders is discussed. We recommend longitudinal studies to comparatively assess the cell-type-specific expression of TLRs during treatment, illness progression, and remission. Also, further research should explore molecular insights into TLRs regulation and related pathways.

Sodium Hydrosulfide Reverts Chronic Stress-Induced Cardiovascular Alterations by Reducing Oxidative Stress

ABSTRACT

Chronic stress induces a group of unrecognized cardiovascular impairments, including elevated hemodynamic variables and vascular dysfunction. Moreover, hydrogen sulfide (H 2 S), a gasotransmitter that regulates the cardiovascular system decreases under chronic stress. Thus, this study assessed the impact of sodium hydrosulfide (NaHS) (H 2 S donor) on chronic restraint stress (CRS)-induced cardiovascular changes. For that purpose, male Wistar rats were restrained for 2 hours a day in a transparent acrylic tube over 8 weeks. Then, body weight, relative adrenal gland weight, serum corticosterone, H 2 S-synthesizing enzymes, endothelial nitric oxide synthetize expression, reactive oxygen species levels, lipid peroxidation, and reduced glutathione-to-oxidized glutathione (GSH 2 :GSSG) ratio were determined in the thoracic aorta. The hemodynamic variables were measured in vivo by the plethysmograph method. The vascular function was evaluated in vitro as vasorelaxant responses induced by carbachol or sodium nitroprusside, and norepinephrine (NE)-mediated vasocontractile responses in the thoracic aorta. CRS increased (1) relative adrenal gland weight; (2) hemodynamic variables; (3) vasoconstrictor responses induced by NE, (4) reactive oxygen species levels, and (5) lipid peroxidation in the thoracic aorta. In addition, CRS decreased (1) body weight; (2) vasorelaxant responses induced by carbachol; (3) GSH content, and (4) GSH 2 :GSSG ratio. Notably, NaHS administration (5.6 mg/kg) restored hemodynamic variables and lipid peroxidation and attenuated the vasoconstrictor responses induced by NE in the thoracic aorta. In addition, NaHS treatment increased relative adrenal gland weight and the GSH 2 :GSSG ratio. Taken together, our results demonstrate that NaHS alleviates CRS-induced hypertension by reducing oxidative stress and restoring vascular function in the thoracic aorta.

Harmine prevents 3-nitropropionic acid-induced neurotoxicity in rats via enhancing NRF2-mediated signaling: Involvement of p21 and AMPK

Oxidative stress induced neurotoxicity is increasingly perceived as an important neuropathologic mechanism underlying the motor and behavioral phenotypes associated with Huntington's disease (HD). Repeated exposure to 3-nitropropionic acid (3-NP) induces neurotoxic changes which closely simulate the neuropathological and behavioral characteristics of HD. This study aimed at evaluating the prophylactic effects of the dual-specificity tyrosine phosphorylation regulated kinase 1A (DYRK1A) inhibitor "harmine" against 3-NP-indued neurotoxicity and HD-like symptoms. The potential prophylactic effect of harmine (10 mg/kg/day; intraperitoneal) was investigated on 3-NP-induced motor and cognitive HD-like deficits, nuclear factor erythroid 2 like 2 (NRF2), AMP kinase (AMPK) and p21 protein levels and the gene expression of haem oxygenase-1 (Ho-1), NAD(P)H: quinone oxidoreductase-1 (Nqo-1) and p62 in addition to redox imbalance and histological neurotoxic changes in the striatum, prefrontal cortex, and hippocampus of male Wistar rats. Harmine successfully increased the protein levels of NRF2, AMPK and p21 and the gene expression of Ho-1, Nqo-1 and p62, restored redox homeostasis, and reduced CASPASE-3 level. This was reflected in attenuation of 3-NP-induced neurodegenerative changes and improvement of rats' motor and cognitive performance. This study draws attention to the protective role of harmine against 3-NP-induced motor and cognitive dysfunction that could be mediated via enhancing NRF2-mediated signaling with subsequent amelioration of oxidative stress injury via NRF2 activators, p21 and AMPK, in the striatum, prefrontal cortex, and hippocampus which could offer a promising therapeutic tool to slow the progression of HD.

Off-Target Effects of Antidepressants on Vascular Function and Structure

Depression emerges as a risk factor for cardiovascular disease, and it is thought that successful antidepressant treatment may reduce such a risk. Therefore, antidepressant treatment embodies a potential preventive measure to reduce cardiovascular events in patients with depression. Accumulating evidence indicates that antidepressants have off-target effects on vascular dysfunction and in the early stages of atherosclerosis, which form the basis for cardiovascular disease (CVD) pathogenesis. In this context, we performed a thorough review of the evidence pertaining to the effects of different classes of antidepressant medications on hemodynamic and early atherosclerosis markers. The preclinical and clinical evidence reviewed revealed a preponderance of studies assessing selective serotonin reuptake inhibitors (SSRI), whereas other classes of antidepressants are less well-studied. Sufficient evidence supports a beneficial effect of SSRIs on vascular inflammation, endothelial function, arterial stiffening, and possibly delaying carotid atherosclerosis. In clinical studies, dissecting the hypothesized direct beneficial antidepressant effect of SSRIs on endothelial health from the global improvement upon remission of depression has proven to be difficult. However, preclinical studies armed with appropriate control groups provide evidence of molecular mechanisms linked to endothelial function that are indeed modulated by antidepressants. This suggests at least a partial direct action on vascular integrity. Further research on endothelial markers should focus on the effect of antidepressants on treatment responders versus non-responders in order to better ascertain the possible beneficial vascular effects of antidepressants, irrespective of the underlying course of depression.

Therapy Management of Metabolic Disorder Comorbidity With Depression

Depression is a common disease that seriously endangers the physical and mental health of human beings, and it often coexists with other metabolic disorders such as diabetes and cancer. There have been endless reports on the mechanism, prevention, and cure of comorbidity because of its high incidence and poor prognosis and the increased burden on the family and society. There may be a specific comorbid basis and causal relationship between depression and metabolic diseases. Depression in patients with metabolic disorders can be effectively alleviated through psychotherapy and medication. The timely and effective treatment of depression can significantly improve the quality of life of patients with metabolic disorders, reduce their psychological burden, and promote the effective treatment of metabolic diseases. This study reorganized the research progress on the management of metabolic disorder comorbidity with depression.

Suppression of cigarette smoke induced MMP1 expression by selective serotonin re-uptake inhibitors

Globally, COPD remains a major cause of disability and death. In the United States alone, it is estimated that approximately 14 million people suffer from the disease. Given the high disease burden and requirement for chronic, long‐term medical care associated with COPD, it is essential that new disease modifying agents are developed to complement the symptomatic therapeutics currently available. In the present report, we have identified a potentially novel therapeutic agent through the use of a high throughput screen based on the knowledge that cigarette smoke induces the proteolytic enzyme MMP1 leading to destruction of the lung in COPD. A construct utilizing the cigarette responsive promoter element of MMP‐1 was conjugated to a luciferase reporter and utilized in an in vitro assay to screen the NIH Molecular Libraries Small Molecule Repository to identify putative targets that suppressed luciferase expression in response to cigarette smoke extract (CSE). Selective serotonin reuptake inhibitors potently inhibited luciferase expression and were further validated. SSRI treatment suppressed MMP‐1 production in small airway epithelial cells exposed to (CSE) in vitro as well as in smoke exposed rabbits. In addition, SSRI treatment inhibited inflammatory cytokine production while rescuing cigarette smoke induced downregulation in vivo of the anti‐inflammatory lipid transporter ABCA1, previously shown by our laboratory to be lung protective. Importantly, SSRI treatment prevented lung destruction in smoke exposed rabbits as measured by morphometry. These studies support further investigation into SSRIs as a novel therapeutic for COPD may be warranted.

Validation of prenatal versus postnatal valproic acid rat models of autism: A behavioral and neurobiological study

Despite the increasing prevalence of autism spectrum disorder (ASD), there is still a deficiency in understanding its exact pathophysiology and treatment, therefore validation of translational ASD animal model is warranted. Although strong evidences support the valproic acid (VPA) model of autism, yet a controversy exists regarding the best timing of exposure whether prenatal or postnatal. Accordingly, this study was designed to compare the time dependent effects of VPA exposure as regard its ability to induce autistic like changes in male Wistar rats. In this study, two different protocols of VPA exposure (prenatal and postnatal) were compared at different levels (behavioral, neurochemical and histopathological). Results of this study revealed that both prenatal and postnatal VPA exposures induced autistic-like behaviors manifested by reduced social interaction, increased repetitive stereotyped behavior and anxiety, cognitive dysfunction, lowered sensitivity to pain, and neurodevelopmental delay. Furthermore, inflammatory cytokines and oxidative/nitrosative stress markers were elevated in prefrontal cortex and hippocampal homogenates. Likewise, histopathological and immunohistochemical assessment confirmed the neurodegenerative and the apoptotic changes in prefrontal cortex, hippocampus and cerebellum exhibited by decreased viable cells number and Nissl's granules optical density, and increased caspase-3 immunoreactivity respectively. Interestingly, ASD core symptoms and histopathological changes were significantly (P < 0.05) altered in prenatal VPA model compared to postnatal VPA model. Additionally, postnatal mortality in prenatal model (4.3%) was much lower compared to the postnatal model (22.7%). In conclusion, our study overweighs the ability of prenatal VPA model over postnatal VPA model to induce behavioral and neuropathological alterations that simulate those observed in autistic individuals with a lower postnatal animal mortality, highlighting the privilege of prenatal over postnatal VPA exposure as a translational model for understanding pathophysiology and developing novel targets for management of ASD.

Salidroside Improves Chronic Stress Induced Depressive Symptoms Through Microglial Activation Suppression

Depression is a severe neurological disorder highly associated with chronic mental stress stimulation, which involves chronic inflammation and microglial activation in the central nervous system (CNS). Salidroside (SLDS) has been reported to exhibit anti-neuroinflammatory and protective properties on neurological diseases. However, the mechanism underlying the effect of SLDS on depressive symptoms has not been well elaborated. In the present study, the effects of SLDS on depressive behaviors and microglia activation in mice CNS were investigated. Behavioral tests, including Forced swimming test (FST), Open field test (OFT) and Morris water maze (MWM) revealed that SLDS treatment attenuated the depressive behaviors in stress mice. SLDS treatment significantly reduced the microglial immunoreactivity for both Iba-1 and CD68, characteristic of deleterious M1 phenotype in hippocampus of stress mice. Additionally, SLDS inhibited microglial activation involving the suppression of ERK1/2, P38 MAPK and p65 NF-κB activation and thus reduced the expression and release of neuroinflammatory cytokines in stress mice as well as in lipopolysaccharide (LPS)-induced primary microglia. Also, SLDS changed microglial morphology, attachment and reduced the phagocytic ability in LPS-induced primary microglia. The results demonstrated that SLDS treatment could improve the depressive symptoms caused by unpredictable chronic stress, indicating a potential therapeutic application of SLDS in depression treatment by interfering microglia-mediated neuroinflammation.

Early life stress induces dysregulation of the heme pathway in adult mice

Early life stress (ELS) is associated with cardiovascular disease (CVD) risk in adulthood, but the underlying vascular mechanisms are poorly understood. Increased hemoglobin and heme have recently been implicated to mediate endothelial dysfunction in several vascular diseases. Chronic physiological stress is associated with alterations in the heme pathway that have been well-described in the literature. However, very little is known about the heme pathway with exposure to ELS or chronic psychosocial stress. Utilizing a mouse model of ELS, maternal separation with early weaning (MSEW), we previously reported that MSEW induces endothelial dysfunction via increased superoxide production. We reasoned that heme dysregulation may be one of the culprits induced by MSEW and sustained throughout adulthood; thus, we hypothesized that MSEW induces heme dysfunction. We investigated whether circulating levels of heme, a circulating pro-oxidant mediator, are increased by MSEW and examined the role of the heme metabolic pathway and heme homeostasis in this process. We found that circulating levels of heme are increased in mice exposed to MSEW and that plasma from MSEW mice stimulated higher superoxide production in cultured mouse aortic endothelial cells (MAECs) compared to plasma from normally reared mice. The heme scavenger hemopexin blunted this enhanced superoxide production. Splenic haptoglobin abundance was significantly lower and hemoglobin levels per red blood cell were significantly higher in MSEW versus control mice. These findings lead us to propose that ELS induces increased circulating heme through dysregulation of the haptoglobin-hemoglobin system representing a mechanistic link between ELS and CVD risk in adulthood.

M1/M2 polarization in major depressive disorder: Disentangling state from trait effects in an individualized cell-culture-based approach

Accumulating evidence indicates the specific involvement of inflammatory processes in major depressive disorder (MDD), particularly affecting innate immunity. Most immune alterations have so far been determined based on plasma or cerebrospinal fluid cytokine levels. To precisely characterize putative innate immune-mediated mechanisms in MDD pathogenesis, we sought to disentangle "state" from "trait" effects in a patient-specific cell model by quantifying the impact of patient-derived autologous sera (AS) on patient-specific monocyte-derived macrophages (Mo-MФs) polarization in vitro. Mo-MФs were generated from 28 patients with moderate to severe MDD and 28 age-, sex-, smoking status- and BMI-matched healthy controls (HC). Cells were treated either with AS or fetal calf serum (FCS) and polarized into M1 (LPS), M2 (IL-10, IL-4, TGF-β) or M0 (unstimulated) macrophages. Polarization capacity was quantified by means of specific M1 (CCR7, CD86, CXCL10, IL-12p70, TNF-α, IL-6, IL-1β, IL-12p40, IL-23, IP-10) and M2 (CD206, IL-10, TARC, IL-1RA) markers. Compared to HC, significantly increased M1-polarization was observed for MDD patients in the presence of FCS, however, polarization in AS enriched media determined an increased M2-polarization in patients. Moreover, female MDD patients exhibited increased M1- and decreased M2-polarization in both conditions compared to male MDD patients. Our data suggests that Mo-MФs derived from patients with MDD exhibit facilitated M1-polarization under traditional cell culture conditions and an increased potential for M2-polarization when cultured in AS. Striking inter-individual variation and pronounced gender effects highlight the potential utility of our personalized cell model-based approach to aid diagnostic and therapeutic decisions.

Cognitive effects of the GSK-3 inhibitor "lithium" in LPS/chronic mild stress rat model of depression: Hippocampal and cortical neuroinflammation and tauopathy

Low-dose repeated lipopolysaccharide pre-challenge followed by chronic mild stress (LPS/CMS) protocol has been introduced as a rodent model of depression combining the roles of immune activation and chronic psychological stress. However, the impact of this paradigm on cognitive functioning has not been investigated hitherto.

METHODS

This study evaluated LPS/CMS-induced cognitive effects and the role of glycogen synthase kinase-3β (GSK-3β) activation with subsequent neuroinflammation and pathological tau deposition in the pathogenesis of these effects using lithium (Li) as a tool for GSK-3 inhibition.

RESULTS

LPS pre-challenge reduced CMS-induced neuroinflammation, depressive-like behavior and cognitive inflexibility. It also improved spatial learning but increased GSK-3β expression and exaggerated hyperphosphorylated tau accumulation in hippocampus and prefrontal cortex. Li ameliorated CMS and LPS/CMS-induced depressive and cognitive deficits, reduced GSK-3β over-expression and tau hyperphosphorylation, impeded neuroinflammation and enhanced neuronal survival.

CONCLUSION

This study draws attention to LPS/CMS-triggered cognitive changes and highlights how prior low-dose immune challenge could develop an adaptive capacity to buffer inflammatory damage and maintain the cognitive abilities necessary to withstand threats. This work also underscores the favorable effect of Li (as a GSK-3β inhibitor) in impeding exaggerated tauopathy and neuroinflammation, rescuing neuronal survival and preserving cognitive functions. Yet, further in-depth studies utilizing different low-dose LPS challenge schedules are needed to elucidate the complex interactions between immune activation and chronic stress exposure.

Role of angiotensin receptors in the medial amygdaloid nucleus in autonomic, baroreflex and cardiovascular changes evoked by chronic stress in rats

This study investigated the role of AT₁ , AT₂ and Mas angiotensinergic receptors within the MeA in autonomic, cardiovascular and baroreflex changes evoked by a 10-day (1  hr daily) repeated restraint stress (RRS) protocol. Analysis of cardiovascular function after the end of the RRS protocol indicated increased values of arterial pressure, without heart rate changes. Arterial pressure increase was not affected by acute MeA treatment after the RRS with either the selective AT₁ receptor antagonist losartan, the selective AT₂ receptor antagonist PD123319 or the selective Mas receptor antagonist A-779. Analysis of heart rate variability indicated that RRS increased the sympathetic tone to the heart, which was inhibited by MeA treatment with either losartan, PD123319 or A-779. Baroreflex function assessed using the pharmacological approach via intravenous infusion of vasoactive agents revealed a facilitation of tachycardia evoked by blood pressure decrease in chronically stressed animals, which was inhibited by MeA treatment with losartan. Conversely, baroreflex responses during spontaneous fluctuations of blood pressure were impaired by RRS, and this effect was not affected by injection of the angiotensinergic receptor antagonists into the MeA. Altogether, the data reported in the present study suggest an involvement of both angiotensinergic receptors present in the MeA in autonomic imbalance evoked by RRS, as well as an involvement of MeA AT₁ receptor in the enhanced baroreflex responses during full range of blood pressure changes. Results also indicate that RRS-evoked increase in arterial pressure and impairment of baroreflex responses during spontaneous variations of arterial pressure are independent of MeA angiotensinergic receptors.

Antidepressant effect of Gentiana olivieri Griseb. in male rats exposed to chronic mild stress

Background: The flowering parts of Gentiana olivieri, known as ‘Afat’ in the southeastern Anatolia region of Turkey, are used as a tonic, an appetizer, and for the treatment of several mental disorders, including depression. The purpose of this study is to investigate the antidepressant effect of G. olivieri ethanol extract (GOEE) in a chronic mild stress-induced rat model, which was used to mimic a depressive state in humans, and to compare the effect with that of imipramine.

Methods: Male Sprague-Dawley rats were randomly divided into six groups: control, stress, treated with imipramine (positive control) and treated with GOEE at three different (200, 500, 1000 mg/kg) doses groups. The rats in all groups, except the control group, were exposed to chronic mild stress. At the end of the 3-week experimental period, biochemical and behavioral parameters were examined.

Results: The results showed that treatment with GOEE or imipramine significantly improved rats’ sucrose consumption which was diminished by chronic mild stress, restored serum levels of corticosterone and proinflammatory cytokines (interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α)), prevented the increase of liver index of rats. Moreover, in the hippocampus tissue, decreased serotonin and noradrenaline levels were significantly increased by treatment with GOEE or imipramine, and antioxidant parameters (thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and glutathione (GSH)) were significantly improved by treatment with GOEE though not with imipramine.

Conclusion: The data demonstrate that G. olivieri may exert its antidepressant activity by improving monoaminergic system disorders, and by favorably affecting the antioxidant, inflammatory and the endocrine mechanisms.

[Changes in blood pressure after introduction of an antidepressant in a public institution of mental health]

INTRODUCTION

Primary prescribing of antidepressants is common in general practice. The relationship between antidepressant introduction and blood pressure (BP) changes is not well established in the literature. The purpose of our study was to examine the short-term course of AHR with and without the introduction of an antidepressant into a public institution of mental health (EPSM).

MATERIALS AND METHODS

An exposed/non-exposed single-centre analytical epidemiological study on a retrospective cohort, with a collection of data on stays between 2013 and 2015 at the EPSM in Armentières. The stays were divided into two groups: antidepressant treatment (introduced during the stay) and control (without antidepressant). BP measurements were taken over a 30-day period per stay. To assess the evolution of AHR across groups, we used a nested mixed linear regression model with multivariate adjustment.

RESULTS

Out of 1241 stays analysed, 124 were in the treated group and 1117 in the control group. The average age was 44.6±14.7 years. The two groups were comparable on most of the variables analyzed. The change in systolic BP was associated with systolic BP values at baseline, history of hypertension, presence of an antihypertensive drug and BMI; the change in diastolic BP was associated with diastolic BP values at baseline, presence of an antihypertensive drug, BMI and history of bipolar disorder. We find no significant difference in the evolution of BP over time between the treated group and the control group over the 30 days of measurement per stay, after adjustment (evolution coefficient of +0.12mmHg systolic BP and -0.1mmHg diastolic BP, P=0.45 and 0.38 respectively).

CONCLUSION

These results are reassuring on the early development of BP after the introduction of antidepressants. They should not overlook the frequent effects of depression and antidepressants on cardiovascular risk (decreased physical activity, dyslipidemia, weight gain, etc.).

Effect of Toll-like receptor 4 on depressive-like behaviors induced by chronic social defeat stress

INTRODUCTION

A growing body of evidence suggests that stress is an important factor in depression, and pro-inflammatory cytokines contribute to the occurrence and development of depression in both animal models and human patients. Toll-like receptor 4 (TLR4) has been shown to be a key innate immune pattern recognition receptor involved in the regulation of stress responses and inflammation. However, the exact effects of TLR4 on depressive-like behaviors induced by chronic social defeat stress (CSDS) are not known.

METHODS

In this study, the effects of TLR4 on depressive-like behaviors were investigated in an animal model of depression induced by CSDS. The depressive-like behaviors were assessed by forced swimming test (FST), social interaction test (SIT), and light-dark box test (LDT). The protein expressions of TLR4 and tumor necrosis factor-α (TNF-α) in the hippocampus were measured using Western blotting.

RESULTS

We found that CSDS increased TLR4 protein levels in the hippocampus and induced behavioral despair in FST, social avoidance in SIT, and anxiety-like behavior in LDT. Fluoxetine normalized the increased expression of TLR4 and reversed behavioral despair, social avoidance, as well as anxiety-like behavior induced by CSDS. However, directly blocking TLR4, by using either TLR4 inhibitor TAK-242 or knockout of TLR4, only inhibited behavioral despair, but not social avoidance or anxiety-like behavior induced by CSDS.

CONCLUSIONS

These results demonstrate a specific modulating role of TLR4 in behavioral despair induced by CSDS and suggest that TAK-242 may be a beneficial treatment for patients with behavioral despair.

Behavioral effects of toll-like receptor-4 antagonist 'eritoran' in an experimental model of depression: role of prefrontal and hippocampal neurogenesis and γ-aminobutyric acid/glutamate balance

Depression is the disease of the modern era. The lack of response to the available antidepressants, which were developed on the basis of the monoaminergic deficit hypothesis of depression, has encouraged scientists to think about new mechanisms explaining the pathogenesis of depression. In this context, the inflammatory theory has emerged to clarify many aspects of depression that the previous theories have failed to explain. Toll-like receptor-4 (TLR-4) has a regulatory role in the brain's immune response to stress, and its activation is suggested to play a pivotal role in the pathophysiology of depression. In this study, we tested eritoran (ERI), a TLR-4 receptor-4 antagonist, as a potential antidepressant. We investigated the effect of long-term administration of ERI in three different doses on behavioral changes, hippocampal and prefrontal cortex (PFC) neurogenesis, and γ-aminobutyric acid (GABA)/glutamate balance in male Wistar rats exposed to chronic restraint stress (CRS). Long-term administration of ERI ameliorated CRS-induced depressive-like symptoms and hypothalamic-pituitary-adrenal axis hyperactivity alongside reducing levels of hippocampal and PFC inflammatory cytokines, restoring GABA and glutamate balance, and enhancing PFC and hippocampal neurogenesis, by increasing BDNF gene and protein expression in a dose-dependent manner. The results demonstrate an antidepressant-like activity of ERI in Wistar rats exposed to CRS, which may be largely mediated by its ability to reduce neuroinflammation, increase BDNF, and restore GABA/glutamate balance in prefrontal cortex and hippocampus. Nonetheless, further studies are needed to characterize the mechanism of the antidepressant effect of ERI.

Fluoxetine attenuates neuroinflammation in early brain injury after subarachnoid hemorrhage: a possible role for the regulation of TLR4/MyD88/NF-κB signaling pathway

Background

Neuroinflammation is closely associated with functional outcome in subarachnoid hemorrhage (SAH) patients. Our recent study demonstrated that fluoxetine inhibited NLRP3 inflammasome activation and attenuated necrotic cell death in early brain injury after SAH, while the effects and potential mechanisms of fluoxetine on neuroinflammation after SAH have not been well-studied yet.

Methods

One hundred and fifty-three male SD rats were subjected to the endovascular perforation model of SAH. Fluoxetine (10 mg/kg) was administered intravenously at 6 h after SAH induction. TAK-242 (1.5 mg/kg), an exogenous TLR4 antagonist, was injected intraperitoneally 1 h after SAH. SAH grade, neurological scores, brain water content, Evans blue extravasation, immunofluorescence/TUNEL staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot were performed.

Results

Fluoxetine administration attenuated BBB disruption, brain edema, and improved neurological function after SAH. In addition, fluoxetine alleviated the number of Iba-1-positive microglia/macrophages, neutrophil infiltration, and cell death. Moreover, fluoxetine reduced the levels of pro-inflammatory cytokines, downregulated the expression of TLR4 and MyD88, and promoted the nuclear translocation of NF-κB p65, which were also found in rats with TAK-242 administration. Combined administration of fluoxetine and TAK-242 did not enhance the neuroprotective effects of fluoxetine.

Conclusion

Fluoxetine attenuated neuroinflammation and improved neurological function in SAH rats. The potential mechanisms involved, at least in part, TLR4/MyD88/NF-κB signaling pathway.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1388-x) contains supplementary material, which is available to authorized users.

Sex differences in cardiovascular, neuroendocrine and behavioral changes evoked by chronic stressors in rats

This study investigated the physiological, somatic and behavioral changes evoked by daily exposure to the same type of stressor (homotypic) or different aversive stressor stimuli (heterotypic) in male and female rats. For this, adult Wistar rats were subjected to a 10days regimen of repeated restraint stress (RRS, homotypic stressor) or chronic variable stress (CVS, heterotypic stressor). Effects evoked by CVS included: (i) adrenal hypertrophy and decreased body weight gain in male animals, (ii) a sympathetically-mediated increase in basal heart rate in males, and (iii) a rise in plasma corticosterone concentration and anxiogenic effects in female animals. The homotypic stressor RRS also induced an increase in plasma corticosterone and anxiogenic effects in females, decreased body weight gain in males and evoked a sympathetically-mediated increase in heart rate in both sexes. Changes in cardiovascular function and autonomic activity evoked by both stressors were followed by impairment of baroreflex activity in males, but not female animals. Both chronic stressors evoked changes in blood pressure responsiveness to vasoconstrictor and vasodilator agents in both sexes. Taken together, these results indicate that regardless of chronic stress regimen males are more vulnerable to somatic effects of chronic stressors, while females appear to be more susceptible to neuroendocrine and behavioral changes. Present findings also indicate that females are selectively vulnerable to cardiovascular and autonomic changes evoked by homotypic stressors. Nevertheless, homotypic and heterotypic stressors similarly affect cardiovascular function and autonomic activity in males.

Metformin potentiates cognitive and antidepressant effects of fluoxetine in rats exposed to chronic restraint stress and high fat diet: potential involvement of hippocampal c-Jun repression

Several hypotheses link high fat diet (HFD) with the pathophysiology of depression and its response to antidepressants. This study aimed to determine the effect of metformin (MET) on the cognitive and antidepressant activity of fluoxetine (FLU) through its effect on c-Jun expression. Behavioral, cognitive function, biochemical, and histopathological studies were performed in non-HFD- and HFD-fed rats exposed to chronic restraint stress (CRS). Stressed group showed cognitive impairment, depressive-like symptoms, disturbed glucose homeostasis and lipid profile, reduced adiponectin level, brain-derived neurotrophic factor (BDNF) expression, and increased corticosterone and c-Jun. All these were aggravated by HFD. MET, FLU and their combination produced significant improvement in lipid profile with significant increase in adiponectin and BDNF expression. Corticosterone, body weight and insulin resistance showed significant decrease in the treated groups. Moreover, there was a significant decrease in hippocampal c Jun expression. There was a significant preferable effect toward the combination. Conclusion, MET may decrease the refractoriness to FLU and improves the cognition in individuals who are fed on HFD.

Mechanisms and Therapeutic Targets of Depression After Intracerebral Hemorrhage

The relationship between depression and intracerebral hemorrhage (ICH) is complicated. One of the most common neuropsychiatric comorbidities of hemorrhagic stroke is Post-ICH depression. Depression, as a neuropsychiatric symptom, also negatively impacts the outcome of ICH by enhancing morbidity, disability, and mortality. However, the ICH outcome can be improved by antidepressants such as the frequently-used selective serotonin reuptake inhibitors. This review therefore presents the mechanisms of post-ICH depression, we grouped the mechanisms according to inflammation, oxidative stress (OS), apoptosis and autophagy, and explained them through their several associated signaling pathways. Inflammation is mainly related to Toll-like receptors (TLRs), the NF-kB mediated signal pathway, the PPAR-γ-dependent pathway, as well as other signaling pathways. OS is associated to nuclear factor erythroid-2 related factor 2 (Nrf2), the PI3K/Akt pathway and the MAPK/P38 pathway. Moreover, autophagy is associated with the mTOR signaling cascade and the NF-kB mediated signal pathway, while apoptosis is correlated with the death receptor-mediated apoptosis pathway, mitochondrial apoptosis pathway, caspase-independent pathways and others. Furthermore, we found that neuroinflammation, oxidative stress, autophagy, and apoptosis experience interactions with one another. Additionally, it may provide several potential therapeutic targets for patients that might suffer from depression after ICH.

Chronic administration of fluoxetine and pro-inflammatory cytokine change in a rat model of depression

This study evaluated the chronic effects of fluoxetine, a commonly prescribed SSRI antidepressant, on the peripheral and central levels of inflammatory cytokines including IL-1β, IL-6, TNF-α and IL-17 over a 4-interval in a rat model of chronic mild stress (CMS) which resembles the human experience of depression. Twenty-four Sprague-Dawley rats were randomly assigned to CMS+vehicle (n = 9), CMS+fluoxetine (n = 9) and the control (n = 6) groups. Sucrose preference and forced swim tests were performed to assess behavioral change. Blood samples were collected on day 0, 60, 90 and 120 for measurement of cytokine levels in plasma. On day 120, the brain was harvested and central level of cytokines was tested using Luminex. Four months of fluoxetine treatment resulted in changes in the sucrose preference and immobility time measurements, commensurate with antidepressant effects. The CMS+vehicle group exhibited elevated plasma levels of IL-1β, IL-17, and TNF-α on day 60 or 120. Rats treated with fluoxetine demonstrated lower IL-1β in plasma and brain after 90 and 120-day treatment respectively (p<0.05). There was a trend of reduction of IL-6 and TNF-α concentration. This study revealed the potential therapeutic effects of fluoxetine by reducing central and peripheral levels of IL-1β in the alleviation of depressive symptoms.

The role of macrophages in anti-inflammatory activity of antidepressant drugs

Depression is a common disease influencing patients' quality of life, whose etiology involves complex interactions of environmental, genetic and immunological factors. The latter factors include proinflammatory activation of monocytes and macrophages and increased serum levels of proinflammatory cytokines, altogether formulated as the "macrophage theory of depression". Our current review summarizes the impact of the most commonly used antidepressant drugs on the immune response with special emphasis on the role of macrophages in the clinically observed effects. The anti-inflammatory action of antidepressants mainly results from their direct interaction with immune cells and from changes in the concentration and the relations of neurotransmitters sensed by these cells. The summarized data revealed that Mφs are one of the leading cell populations involved in drug-mediated immune effects that can be observed both in subjects with depression as well as in individuals not suffering from depression. Thus, currently reviewed immunomodulatory effects of the experimental use of different antidepressant drugs suggest the possibility of utilizing them in complex therapeutic strategies dedicated to various inflammatory and immune-mediated diseases. It is worth noting that an excessive inflammatory reaction is also associated with the pathogenesis of various cardiovascular, metabolic and neuro-endocrine diseases. Thus, the inclusion of antidepressants in the complex therapy of these disorders may have beneficial effects through the enhancement of the mood of the patient and alleviation of chronic inflammation. On the other hand, presented data suggest that the influence of chronically used antidepressants on anti-microbial and anti-tumor immunity could also be taken into consideration.

Emotional Stress and Cardiovascular Complications in Animal Models: A Review of the Influence of Stress Type

Emotional stress has been recognized as a modifiable risk factor for cardiovascular diseases. The impact of stress on physiological and psychological processes is determined by characteristics of the stress stimulus. For example, distinct responses are induced by acute vs. chronic aversive stimuli. Additionally, the magnitude of stress responses has been reported to be inversely related to the degree of predictability of the aversive stimulus. Therefore, the purpose of the present review was to discuss experimental research in animal models describing the influence of stressor stimulus characteristics, such as chronicity and predictability, in cardiovascular dysfunctions induced by emotional stress. Regarding chronicity, the importance of cardiovascular and autonomic adjustments during acute stress sessions and cardiovascular consequences of frequent stress response activation during repeated exposure to aversive threats (i.e., chronic stress) is discussed. Evidence of the cardiovascular and autonomic changes induced by chronic stressors involving daily exposure to the same stressor (predictable) vs. different stressors (unpredictable) is reviewed and discussed in terms of the impact of predictability in cardiovascular dysfunctions induced by stress.

Antidepressants normalize elevated Toll-like receptor profile in major depressive disorder

RATIONALE

Abnormalities in Toll-like receptor (TLR) expression in depression have been inferred in part from observed increases in TLR4 levels in peripheral blood mononuclear cells (PBMCs) and postmortem brains of depressed and suicidal patients. Our previous study found differences in the TLR expression in PBMCs between healthy controls and patients with major depressive disorder. Normalization of increased TLR4 in PBMCs by cognitive behavior psychotherapy has been reported. However, the effects of antidepressants remain unknown.

OBJECTIVES

Changes in TLR1-9 expression levels of PBMCs were examined in 56 patients with MDD. The 17-item Hamilton Depression Rating Scale (HAMD-17) and mRNA expression levels of TLRs were assessed in parallel with a housekeeping gene using qRT-PCR before and after treatment with antidepressants.

RESULTS

TLR3, TLR4, TLR5, TLR7, TLR8, and TLR9 were expressed at elevated levels in patients with MDD and were significantly decreased by treatment with antidepressants for 4 weeks. Antidepressant treatment completely normalized TLR3, TLR5, TLR7, TLR8, and TLR9 levels, whereas TLR1, TLR2, TLR4, and TLR6 were decreased to below normal levels. A subgroup analysis found that only TLR3 was significantly higher at baseline in the nonremission group. In addition, a multiple linear regression analysis revealed that only low TLR3 before treatment predicted improvement in HAMD-17 scores.

CONCLUSIONS

These findings suggest that antidepressant treatment exerts anti-inflammatory effects in patients with MDD and identify TLR profiles as a predictor of response to antidepressant therapy. Further studies investigating the effects of manipulating individual TLRs on depression are needed to fully elucidate the underlying mechanism.