Central administration of insulin-like growth factor-I decreases depressive-like behavior and brain cytokine expression in mice

Serum IL-6 levels and oxidation rate of LDL cholesterol were related to depressive symptoms independent of omega-3 fatty acids among female hospital and nursing home workers in Japan

BACKGROUND

Chronic low-grade inflammation and oxidative stress are commonly observed in persons with depression or depressive symptoms. We explored the degree of depressive symptoms under psychological stress in relation to serum LDL oxidation, inflammatory markers, and fatty acid (FA) distribution among female population. The purpose of this study was to identify peripheral factors that are related to depressive symptoms, and to assess how each factor is related to depressive symptoms.

METHODS

133 female workers in a hospital and nursing homes were recruited in Japan. Depressive symptoms were assessed using the Japanese version of the Centre for Epidemiologic Studies Depression Scale (CES-D), and perceived stress was assessed using the visual analogue scale. Cytokine levels and oxidation rate of LDL cholesterol (ox-LDL/LDL) were measured as indices of inflammation and oxidation. Omega-3 FA distribution was also measured. Path analysis and hierarchical regression analysis were used to determine if each factor was predictive of depressive symptoms.

RESULTS

It was identified that serum ox-LDL/LDL was positively connected with depressive symptoms, but was more strongly related to perceived psychological stress. Elevated serum IL-6 was positively correlated with depressive symptoms, though the effect was partly transmitted via ox-LDL/LDL. Additionally, serum ω3 PUFAs were inversely associated with depressive symptoms independently of IL-6 or ox-LDL/LDL.

CONCLUSION

Although this study is unlikely to fully explain the causes of depressive symptoms, it suggests that psychological stress and somatic factors such as inflammation, oxidation and nutrition are related to depressive symptoms. These findings suggest the therapeutic potential of lifestyle targets to alleviate the identified depression risk factors, anti-oxidative therapies, anti-inflammatory therapies and nutritional interventions to prevent depression.

Notch signaling in astrocytes mediates their morphological response to an inflammatory challenge

In the nervous system, Notch pathway has a prominent role in the control of neuronal morphology and in the determination of the astrocyte fate. However, the role of Notch in morphological astrocyte plasticity is unknown. Here, we have explored the role of Notch activity on the morphological reactivity of primary astrocytes in response to LPS, an inflammatory stimulus. We found that LPS induces reactive astrocyte morphology by the inhibition of Notch signaling via NFκB activation and Jagged upregulation. In contrast, IGF-1, an anti-inflammatory molecule, inhibits LPS-induced reactive astrocyte morphological phenotype by enhancing Notch signaling through the inhibition of NFκB and the activation of MAPK. Therefore, Notch signaling pathway emerges as a mediator of the regulation of astrocyte morphology by inflammatory and anti-inflammatory stimuli.

The insulin-like growth factor-1 system in the adult mammalian brain and its implications in central maternal adaptation

Our knowledge on the bioavailability and actions of insulin-like growth factor-1 (IGF-1) has markedly expanded in recent years as novel mechanisms were discovered on IGF binding proteins (IGFBPs) and their ability to release IGF-1. The new discoveries allowed a better understanding of the endogenous physiological actions of IGF-1 and also its applicability in therapeutics. The focus of the present review is to summarize novel findings on the neuronal, neuroendocrine and neuroplastic actions of IGF-1 in the adult brain. As most of the new regulatory mechanisms were described in the periphery, their implications on brain IGF system will also be covered. In addition, novel findings on the effects of IGF-1 on lactation and maternal behavior are described. Based on the enormous neuroplastic changes related to the peripartum period, IGF-1 has great but largely unexplored potential in maternal adaptation of the brain, which is highlighted in the present review.

Salvianolic acid B abolished chronic mild stress-induced depression through suppressing oxidative stress and neuro-inflammation via regulating NLRP3 inflammasome activation

This study was framed to investigate the molecular mechanism behind the anti-depressant effect of salvianolic acid B (SB) against unpredictable chronic mild stress (CMS) induced depression rat model. Control rats received only saline without CMS exposure, whereas CMS model rats were induced to several stress (CMS) for 6 weeks. Treatment group rats were induced with CMS for 6 weeks but received either 20 or 40 mg/kg of SB or 20 mg/kg imipramine (CMS+IMP) from the 4th week to 6th week. Treatment with SB or IMP significantly ameliorated body weight, sucrose consumption rate with shorter immobility time than the control group. Also, administration with SB or IMP could reverse the hyperactivity of hypothalamic-pituitary-adrenal axis as well as decreased inflammatory cytokines with improved antioxidant status. Furthermore, the protein expression of NLRP3 (inflammasome) was markedly downregulated upon treatment with SB (both 20 and 40 mg) or IMP and thereby confirming its potent anti-depressant activity. PRACTICAL APPLICATIONS: Salvianolic acid B (SB) is a phenolic acid extracted from Salvia militiorrhiza Bunge, a popular Chinese herb, which has been prescribed for various pathological conditions. SB has been previously reported with anti-depressant activity but, the in-depth mechanism behind the anti-depressant effect of SB against CMS is still elusive. Hence, the current study was plotted to explore the in-depth mechanism behind the anti-depressant effect of SB against CMS model of depression in rats. The outcome of the current study has confirmed the anti-depressant activity by abolishing oxidative stress, and neuroinflammatory response in the hippocampus through inhibiting NLRP3 inflammasome activation. Hence, SB can be prescribed to major depression patients with standard anti-depressant agents to abolish oxidative stress, neuro-inflammatory response, and related neurological changes.

Elevated Levels of Serum IL-17A in Community-Dwelling Women with Higher Depressive Symptoms

Recent studies indicate that patients with depression have increased concentrations of serum pro-inflammatory cytokines. However, studies of IL-17 and studies on community-dwellers are few. The purpose of this study was to investigate serum cytokine levels, especially IL-17A, among subjects with high and low depressive symptoms of a general population. The participants comprised 20 female community-dwellers aged 40 years or older who contributed to a Shika study in Ishikawa, Japan. Ten participants who showed higher and ten who showed lower depressive symptoms among 208 females assessed by the Japanese version of the Centre for Epidemiologic Studies Depression Scale (CES-D) were selected for this study. Serum samples were analyzed for TNF-alpha, IL-6, IL-10, IL-12, and IL-17A using a multiplex Luminex analysis. For the comparison between the high and low depressive groups statistically, linear regression analyses were applied. The serum level of IL-17A was significantly higher among the high depressive participants (p < 0.05) even after controlling possible confounders, whereas there were no differences in TNF-alpha, IL-6, IL-10, or IL-12 between the high and low depressive groups. Our findings supported an association between serum IL-17A levels and depressive symptoms. Peripheral IL-17A immune response may be a preventive and treatment target for depression.

Endogenous Omega (n)-3 Fatty Acids in Fat-1 Mice Attenuated Depression-Like Behavior, Imbalance between Microglial M1 and M2 Phenotypes, and Dysfunction of Neurotrophins Induced by Lipopolysaccharide Administration

n-3 polyunsaturated fatty acids (PUFAs) have been reported to improve depression. However, PUFA purities, caloric content, and ratios in different diets may affect the results. By using Fat-1 mice which convert n-6 to n-3 PUFAs in the brain, this study further evaluated anti-depressant mechanisms of n-3 PUFAs in a lipopolysaccharide (LPS)-induced model. Adult male Fat-1 and wild-type (WT) mice were fed soybean oil diet for 8 weeks. Depression-like behaviors were measured 24 h after saline or LPS central administration. In WT littermates, LPS reduced sucrose intake, but increased immobility in forced-swimming and tail suspension tests. Microglial M1 phenotype CD11b expression and concentrations of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-17 were elevated, while M2 phenotype-related IL-4, IL-10, and transforming growth factor (TGF)-β1 were decreased. LPS also reduced the expression of brain-derived neurotrophic factor (BDNF) and tyrosine receptor kinase B (Trk B), while increasing glial fibrillary acidic protein expression and pro-BDNF, p75, NO, and iNOS levels. In Fat-1 mice, LPS-induced behavioral changes were attenuated, which were associated with decreased pro-inflammatory cytokines and reversed changes in p75, NO, iNOS, and BDNF. Gas chromatography assay confirmed increased n-3 PUFA levels and n-3/n-6 ratios in the brains of Fat-1 mice. In conclusion, endogenous n-3 PUFAs may improve LPS-induced depression-like behavior through balancing M1 and M2-phenotypes and normalizing BDNF function.

Neurotrophic factors and neuroplasticity pathways in the pathophysiology and treatment of depression

Depression is a major health problem with a high prevalence and a heavy socioeconomic burden in western societies. It is associated with atrophy and impaired functioning of cortico-limbic regions involved in mood and emotion regulation. It has been suggested that alterations in neurotrophins underlie impaired neuroplasticity, which may be causally related to the development and course of depression. Accordingly, mounting evidence suggests that antidepressant treatment may exert its beneficial effects by enhancing trophic signaling on neuronal and synaptic plasticity. However, current antidepressants still show a delayed onset of action, as well as lack of efficacy. Hence, a deeper understanding of the molecular and cellular mechanisms involved in the pathophysiology of depression, as well as in the action of antidepressants, might provide further insight to drive the development of novel fast-acting and more effective therapies. Here, we summarize the current literature on the involvement of neurotrophic factors in the pathophysiology and treatment of depression. Further, we advocate that future development of antidepressants should be based on the neurotrophin theory.

Brain Kynurenine and BH4 Pathways: Relevance to the Pathophysiology and Treatment of Inflammation-Driven Depressive Symptoms

The prevalence of depressive disorders is growing worldwide, notably due to stagnation in the development of drugs with greater antidepressant efficacy, the continuous large proportion of patients who do not respond to conventional antidepressants, and the increasing rate of chronic medical conditions associated with an increased vulnerability to depressive comorbidities. Accordingly, better knowledge on the pathophysiology of depression and mechanisms underlying depressive comorbidities in chronic medical conditions appears urgently needed, in order to help in the development of targeted therapeutic strategies. In this review, we present evidence pointing to inflammatory processes as key players in the pathophysiology and treatment of depressive symptoms. In particular, we report preclinical and clinical findings showing that inflammation-driven alterations in specific metabolic pathways, namely kynurenine and tetrahydrobiopterin (BH4) pathways, leads to substantial alterations in the metabolism of serotonin, glutamate and dopamine that are likely to contribute to the development of key depressive symptom dimensions. Accordingly, anti-inflammatory interventions targeting kynurenine and BH4 pathways may be effective as novel treatment or as adjuvants of conventional medications rather directed to monoamines, notably when depressive symptomatology and inflammation are comorbid in treated patients. This notion is discussed in the light of recent findings illustrating the tight interactions between known antidepressant drugs and inflammatory processes, as well as their therapeutic implications. Altogether, this review provides valuable findings for moving toward more adapted and personalized therapeutic strategies to treat inflammation-related depressive symptoms.

A novel 5HT3 receptor-IGF1 mechanism distinct from SSRI-induced antidepressant effects

Depression is a common mental disorder affecting around 350 million people worldwide. Although selective serotonin reuptake inhibitors (SSRIs) are the most widely used antidepressants, a significant proportion of depressed patients do not achieve remission with SSRIs. In this study, we show that a serotonin type 3 receptor (5HT3R) agonist induces antidepressant effects as well as hippocampal neurogenesis independent of fluoxetine (a commonly used SSRI). Notably, our histological analysis reveals that 5HT3R and insulin-like growth factor 1 (IGF1) are expressed in the same neurons in the subgranular zone of the hippocampal dentate gyrus. Furthermore, our in vivo microdialysis analysis shows that 5HT3R regulates hippocampal extracellular IGF1 levels, and we also show that 5HT3R-dependent hippocampal neurogenesis is mediated by increased IGF1 levels. Altogether, our findings suggest a novel 5HT3R-IGF1 mechanism that is distinct from fluoxetine-induced responses and that provides a new therapeutic target for depression, especially bringing significant benefits for SSRI-resistant depressed patients.

Caffeine and Modafinil Ameliorate the Neuroinflammation and Anxious Behavior in Rats during Sleep Deprivation by Inhibiting the Microglia Activation

Background: Sleep deprivation (SD) plagues modern society due to the professional demands. It prevails in patients with mood and neuroinflammatory disorders. Although growing evidence suggests the improvement in the cognitive performance by psychostimulants during sleep-deprived conditions, the impending involved mechanism is rarely studied. Thus, we hypothesized that mood and inflammatory changes might be due to the glial cells activation induced modulation of the inflammatory cytokines during SD, which could be improved by administering psychostimulants. The present study evaluated the role of caffeine/modafinil on SD-induced behavioral and inflammatory consequences.

Methods: Adult male Sprague-Dawley rats were sleep deprived for 48 h using automated SD apparatus. Caffeine (60 mg/kg/day) or modafinil (100 mg/kg/day) were administered orally to rats once every day during SD. Rats were subjected to anxious and depressive behavioral evaluation after SD. Subsequently, blood and brain were collected for biochemical, immunohistochemical and molecular studies.

Results: Sleep deprived rats presented an increased number of entries and time spent in closed arms in elevated plus maze test and decreased total distance traveled in the open field (OF) test. Caffeine/modafinil treatment significantly improved these anxious consequences. However, we did not observe substantial changes in immobility and anhedonia in sleep-deprived rats. Caffeine/modafinil significantly down-regulated the pro- and up-regulated the anti-inflammatory cytokine mRNA and protein expression in the hippocampus during SD. Similar outcomes were observed in blood plasma cytokine levels. Caffeine/modafinil treatment significantly decreased the microglial immunoreactivity in DG, CA1 and CA3 regions of the hippocampus during SD, however, no significant increase in immunoreactivity of astrocytes was observed. Sholl analysis signified the improvement in the morphological alterations of astrocytes and microglia after caffeine/modafinil administration during SD. Stereological analysis demonstrated a significant improvement in the number of ionized calcium binding adapter molecule I (Iba-1) positive cells (different states) in different regions of the hippocampus after caffeine or modafinil treatment during SD without showing any significant change in total microglial cell number. Eventually, the correlation analysis displayed a positive relationship between anxiety, pro-inflammatory cytokines and activated microglial cell count during SD.

Conclusion: The present study suggests the role of caffeine or modafinil in the amelioration of SD-induced inflammatory response and anxious behavior in rats.

Highlights

- SD induced mood alterations in rats.

- Glial cells activated in association with the changes in the inflammatory cytokines.

- Caffeine or modafinil improved the mood and restored inflammatory changes during SD.

- SD-induced anxious behavior correlated with the inflammatory consequences.

The relation between insulin-like growth factor 1 levels and risk of depression in ischemic stroke

BACKGROUND

The aim of this study is to evaluate whether lower serum levels of insulin-like growth factor 1 (IGF-1) in the acute phase of ischemic stroke are associated with higher risk of post-stroke depression (PSD) over a 1-year period.

METHODS

The subjects were first-ever acute ischemic stroke (AIS) patients who were hospitalized from July 1, 2014 to August 31, 2015. The study also included 120 age-matched and sex-matched healthy controls from the same geographical area. Fasting blood samples were collected within 24 hours of admission for IGF-I measurement. Neurological and neuropsychological evaluations were conducted at a 1-year follow-up.

RESULTS

Two-hundred twenty-five patients were observed for a 1-year follow-up, and 74 of these patients (32.9%, 95%CI: 26.8%-39.0%) were diagnosed with PSD. The depression distribution across the IGF-1 quartiles ranged between 61.4% (first quartile) and 8.9% (fourth quartile). In a multivariate model using the first quartiles of the IGF-1 versus quartiles 2 through 4, together with the significant clinical variables, the marker displayed prognostic information, and the odds ratio (OR) for first quartile was 3.35 [95% CI, 1.88-6.79; P = 0.001].

CONCLUSION

The data showed that low serum IGF-1 levels at admission are associated with a high risk of developing PSD, suggesting that these alterations might be involved in the pathophysiology of depression symptoms in stroke patients.

Mouse Testing Methods in Psychoneuroimmunology 2.0: Measuring Behavioral Responses

The field of psychoneuroimmunology (PNI) aims to uncover the processes and consequences of nervous, immune, and endocrine system relationships. Behavior is a consequence of such interactions and manifests from a complex interweave of factors including immune-to-neural and neural-to-immune communication. Often the signaling molecules involved during a particular episode of neuroimmune activation are not known but behavioral response provides evidence that bioactives such as neurotransmitters and cytokines are perturbed. Immunobehavioral phenotyping is a first-line approach when examining the neuroimmune system and its reaction to immune stimulation or suppression. Behavioral response is significantly more sensitive than direct measurement of a single specific bioactive and can quickly and efficiently rule in or out relevance of a particular immune challenge or therapeutic to neuroimmunity. Classically, immunobehavioral research was focused on sickness symptoms related to bacterial infection but neuroimmune activation is now a recognized complication of diseases and disorders ranging from cancer to diabesity to Alzheimer's. Immunobehaviors include lethargy, loss of appetite, and disinterest in social activity/surrounding environment. In addition, neuroimmune activation can diminish physical activity, precipitate feelings of depression and anxiety, and impair cognitive and executive function. Provided is a detailed overview of behavioral tests frequently used to examine neuroimmune activation in mice with a special emphasis on pre-experimental conditions that can confound or prevent successful immunobehavioral experimentation.

Insulin-Like Growth Factor-1 and Neuroinflammation

Insulin-like growth factor-1 (IGF-1) effects on aging and neurodegeneration is still controversial. However, it is widely admitted that IGF-1 is involved in the neuroinflammatory response. In peripheral tissues, several studies showed that IGF-1 inhibited the expression of inflammatory markers, although other studies concluded that IGF-1 has proinflammatory functions. Furthermore, proinflammatory cytokines such as TNF-α impaired IGF-1 signaling. In the brain, there are controversial results on effects of IGF-1 in neuroinflammation. In addition to direct protective effects on neurons, several studies revealed anti-inflammatory effects of IGF-1 acting on astrocytes and microglia, and that IGF-1 may also inhibit blood brain barrier permeability. Altogether suggests that the aging-related decrease in IGF-1 levels may contribute to the aging-related pro-inflammatory state. IGF-1 inhibits the astrocytic response to inflammatory stimuli, and modulates microglial phenotype (IGF-1 promotes the microglial M2 and inhibits of M1 phenotype). Furthermore, IGF-1 is mitogenic for microglia. IGF-1 and estrogen interact to modulate the neuroinflammatory response and microglial and astrocytic phenotypes. Brain renin-angiotensin and IGF-1 systems also interact to modulate neuroinflammation. Induction of microglial IGF-1 by angiotensin, and possibly by other pro-inflammatory inducers, plays a major role in the repression of the M1 microglial neurotoxic phenotype and the enhancement of the transition to an M2 microglial repair/regenerative phenotype. This mechanism is impaired in aged brains. Aging-related decrease in IGF-1 may contribute to the loss of capacity of microglia to undergo M2 activation. Fine tuning of IGF-1 levels may be critical for regulating the neuroinflammatory response, and IGF-1 may be involved in inflammation in a context-dependent mode.

Insulin-Like Growth Factors in the Pathogenesis of Neurological Diseases in Children

Insulin-like growth factors play a key role for neuronal growth, differentiation, the survival of neurons and synaptic formation. The action of IGF-1 is most pronounced in the developing brain. In this paper we will try to give an answer to the following questions: Why are studies in children important? What clinical studies in neonatal asphyxia, infantile spasms, progressive encephalopathy-hypsarrhythmia-optical atrophy (PEHO) syndrome, infantile ceroid lipofuscinosis (INCL), autistic spectrum disorders (ASD) and subacute sclerosing encephalopathy (SSPE) have been carried out? What are IGF-based therapeutic strategies? What are the therapeutic approaches? We conclude that there are now great hopes for the therapeutic use of IGF-1 for some neurological disorders (particularly ASD).

Desipramine decreases expression of human and murine indoleamine-2,3-dioxygenases

Abundant evidence connects depression symptomology with immune system activation, stress and subsequently elevated levels of kynurenine. Anti-depressants, such as the tricyclic norepinephrine/serotonin reuptake inhibitor desipramine (Desip), were developed under the premise that increasing extracellular neurotransmitter level was the sole mechanism by which they alleviate depressive symptomologies. However, evidence suggests that anti-depressants have additional actions that contribute to their therapeutic potential. The Kynurenine Pathway produces tryptophan metabolites that modulate neurotransmitter activity. This recognition identified another putative pathway for anti-depressant targeting. Considering a recognized role of the Kynurenine Pathway in depression, we investigated the potential for Desip to alter expression of rate-limiting enzymes of this pathway: indoleamine-2,3-dioxygenases (Ido1 and Ido2). Mice were administered lipopolysaccharide (LPS) or synthetic glucocorticoid dexamethasone (Dex) with Desip to determine if Desip alters indoleamine-dioxygenase (DO) expression in vivo following a modeled immune and stress response. This work was followed by treating murine and human peripheral blood mononuclear cells (PBMCs) with interferon-gamma (IFNγ) and Desip. In vivo: Desip blocked LPS-induced Ido1 expression in hippocampi, astrocytes, microglia and PBMCs and Ido2 expression by PBMCs. Ex vivo: Desip decreased IFNγ-induced Ido1 and Ido2 expression in murine PBMCs. This effect was directly translatable to the human system as Desip decreased IDO1 and IDO2 expression by human PBMCs. These data demonstrate for the first time that an anti-depressant alters expression of Ido1 and Ido2, identifying a possible new mechanism behind anti-depressant activity. Furthermore, we propose the assessment of PBMCs for anti-depressant responsiveness using IDO expression as a biomarker.

(Putative) sex differences in neuroimmune modulation of memory

The neuroimmune system is significantly sexually dimorphic, with sex differences evident in the number and activation states of microglia, in the activation of astrocytes, and in cytokine release and function. Neuroimmune cells and signaling are now recognized as critical for many neural functions throughout the life span, including synaptic plasticity and memory function. Here we address the question of how cytokines, astrocytes, and microglia contribute to memory, and specifically how neuroimmune modulation of memory differentially affects males and females. Understanding sex differences in both normal memory processes and dysregulation of memory in psychiatric and neurological disorders is critical for developing treatment and preventive strategies for memory disorders that are effective for both men and women. © 2016 Wiley Periodicals, Inc.

Insulin-like growth factor-1: a possible marker for emotional and cognitive disturbances, and treatment effectiveness in major depressive disorder

Depression and cognitive dysfunction share a common neuropathological platform. Abnormal neural plasticity in the frontolimbic circuits has been linked to changes in the expression of neurotrophic factors, including IGF-1. These changes may result in clinical abnormalities observed over the course of major depressive disorder (MDD), including cognitive dysfunction. The present review aimed to summarize evidence regarding abnormalities of peripheral IGF-1 in MDD patients and assess a marker and predictive role of the neurotrophin for emotional and cognitive disturbances, and treatment effectiveness. A literature search of the PubMed database was conducted for studies, in which peripheral IGF-1 levels were evaluated. Our analysis revealed four main findings: (1) IGF-1 levels in MDD patients mismatch across the studies, which may arise from various factors, e.g., age, gender, the course of the disease, presence of cognitive impairment, ongoing therapy, or general health conditions; (2) the initial peripheral IGF-1 levels may predict the occurrence of depression in future; (3) peripheral IGF-1 levels may reflect cognitive dysfunction, although the data is limited; (4) it is difficult to evaluate the influence of treatment on IGF-1 levels as there is discrepancy of this growth factor among the studies at baseline, although most of them showed a decrease in IGF-1 levels after treatment.

Deciphering Brain Insulin Receptor and Insulin-Like Growth Factor 1 Receptor Signalling

Insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1R) are highly conserved receptor tyrosine kinases that share signalling proteins and are ubiquitously expressed in the brain. Central application of insulin or IGF1 exerts several similar physiological outcomes, varying in strength, whereas disruption of the corresponding receptors in the brain leads to remarkably different effects on brain size and physiology, thus highlighting the unique effects of the corresponding hormone receptors. Central insulin/IGF1 resistance impacts upon various levels of the IR/IGF1R signalling pathways and is a feature of the metabolic syndrome and neurodegenerative diseases such as Alzheimer's disease. The intricacy of brain insulin and IGF1 signalling represents a challenge for the identification of specific IR and IGF1R signalling differences in pathophysiological conditions. The present perspective sheds light on signalling differences and methodologies for specifically deciphering brain IR and IGF1R signalling.

Treatment of autistic spectrum disorder with insulin-like growth factors

There are no treatments for the core symptoms of autistic spectrum disorder (ASD), but there is now more knowledge on emerging mechanisms and on mechanism-based therapies. In autism there are altered synapses: genes affected are commonly related to synaptic and immune function. Dysregulation of activity-dependent signaling networks may have a key role the etiology of autism. There is an over-activation of IGF-AKT-mTor in autism spectrum disorders. Morphological and electro-physiological defects of the cerebellum are linked to system-wide ASD-like behavior defects. The molecular basis for a cerebellar contribution has been demonstrated in a mouse model. These have led to a potential mechanism-based use of drug targets and mouse models. Neurotrophic factors are potential candidates for the treatment. Insulin-like growth factor-1 (IGF-1) is altered in autism. It reduces neuro-inflammation: by causing changes of cytokines such as IL-6 and microglial function. IGF-1 reduces the defects in the synapse. It alleviates NMDA-induced neurotoxicity via the IGF-AKT-mTor pathway in microglia. IGF-1 may rescue function in Rett syndrome and ASD caused by changes of the SCHANK3 gene. There are recently pilot studies of the treatment of Rett syndrome and of SCHANK3 gene deficiency syndromes. The FDA has granted Orphan drug designations for Fragile X syndrome, SCHANK3 gene deficiency syndrome and Rett syndrome.

Immunomodulatory Factors Galectin-9 and Interferon-Gamma Synergize to Induce Expression of Rate-Limiting Enzymes of the Kynurenine Pathway in the Mouse Hippocampus

Elevated levels of circulating pro-inflammatory cytokines are associated with symptomology of several psychiatric disorders, notably major depressive disorder. Symptomology has been linked to inflammation/cytokine-dependent induction of the Kynurenine Pathway. Galectins, like pro-inflammatory cytokines, play a role in neuroinflammation and the pathogenesis of several neurological disorders but without a clearly defined mechanism of action. Their involvement in the Kynurenine Pathway has not been investigated. Thus, we searched for a link between galectins and the Kynurenine Pathway using in vivo and ex vivo models. Mice were administered LPS and pI:C to determine if galectins (Gal's) were upregulated in the brain following in vivo inflammatory challenges. We then used organotypic hippocampal slice cultures (OHSCs) to determine if Gal's, alone or with inflammatory mediators [interferon-gamma (IFNγ), tumor necrosis factor-alpha (TNFα), interleukin-1beta (IL-1β), polyinosine-polycytidylic acid (pI:C), and dexamethasone (Dex; synthetic glucocorticoid)], would increase expression of indoleamine/tryptophan-2,3-dioxygenases (DO's: Ido1, Ido2, and Tdo2; Kynurenine Pathway rate-limiting enzymes). In vivo, hippocampal expression of cytokines (IL-1β, TNFα, and IFNγ), Gal-3, and Gal-9 along with Ido1 and Ido2 were increased by LPS and pI:C (bacterial and viral mimetics). Of the cytokines induced in vivo, only IFNγ increased expression of two Ido1 transcripts (Ido1-FL and Ido1-v1) by OHSCs. Although ineffective alone, Gal-9 accentuated IFNγ-induced expression of only Ido1-FL. Similarly, IFNγ induced expression of several Ido2 transcripts (Ido2-v1, Ido2-v3, Ido2-v4, Ido2-v5, and Ido2-v6). Gal-9 accentuated IFNγ-induced expression of only Ido2-v1. Surprisingly, Gal-9 alone, slightly but significantly, induced expression of Tdo2 (Tdo2-v1 and Tdo2-v2, but not Tdo2-FL). These effects were specific to Gal-9 as Gal-1 and Gal-3 did not alter DO expression. These results are the first to show that brain Gal-9 is increased during LPS- and pI:C-induced neuroinflammation. Increased expression of Gal-9 may be critical for neuroinflammation-dependent induction of DO expression, either acting alone (Tdo2-v1 and Tdo2-v2) or to enhance IFNγ activity (Ido1-FL and Ido2-v1). Although these novel actions of Gal-9 are described for hippocampus, they have the potential to operate as DO-dependent immunomodulatory processes outside the brain. With the expanding implications of Kynurenine Pathway activation across multiple immune and psychiatric disorders, this synergy provides a new target for therapeutic development.

Alterations in anxiety and social behaviour in Npas4 deficient mice following photochemically-induced focal cortical stroke

In addition to causing widespread cell death and loss of brain function, cerebral ischaemia also induces extensive neuroplasticity. In humans, stroke is often accompanied by severe cognitive and psychiatric changes that are thought to arise as a consequence of this infarct-induced remodelling. A candidate for producing these post-stroke neuropsychiatric changes is Npas4, an activity-dependent transcription factor involved in synaptic plasticity whose expression is aberrantly up-regulated following ischaemic injury. In this study we investigated the role of Npas4 in modulating these stroke-induced neuropsychiatric responses by comparing the performance of wildtype and Npas4^-/- mice in various cognitive and behavioural tasks in a photochemical model of focal cortical stroke. We show that this stroke model results in impaired spatial recognition memory and a reduction in despair-like behaviour that affect both genotypes to a similar degree. Moreover, mice lacking Npas4 also show differences in some aspects of post-stroke sociability and anxiety. Specifically, we show that while stroke had no effect on anxiety levels in wildtype mice, Npas4^-/- mice became significantly more anxious following stroke. In addition, Npas4^-/- mice retained a greater level of sociability in the acute post-stroke period in comparison to their wildtype littermates. Thus, our findings suggest that Npas4 may be involved in post-stroke psychiatric changes related to anxiety and sociability.

Microglial dysfunction connects depression and Alzheimer's disease

Alzheimer's disease (AD) and major depressive disorder (MDD) are highly prevalent neuropsychiatric conditions with intriguing epidemiological overlaps. Depressed patients are at increased risk of developing late-onset AD, and around one in four AD patients are co-diagnosed with MDD. Microglia are the main cellular effectors of innate immunity in the brain, and their activation is central to neuroinflammation - a ubiquitous process in brain pathology, thought to be a causal factor of both AD and MDD. Microglia serve several physiological functions, including roles in synaptic plasticity and neurogenesis, which may be disrupted in neuroinflammation. Following early work on the 'sickness behavior' of humans and other animals, microglia-derived inflammatory cytokines have been shown to produce depressive-like symptoms when administered exogenously or released in response to infection. MDD patients consistently show increased circulating levels of pro-inflammatory cytokines, and anti-inflammatory drugs show promise for treating depression. Activated microglia are abundant in the AD brain, and concentrate around senile plaques, hallmark lesions composed of aggregated amyloid-β peptide (Aβ). The Aβ burden in affected brains is regulated largely by microglial clearance, and the complex activation state of microglia may be crucial for AD progression. Intriguingly, recent reports have linked soluble Aβ oligomers, toxins that accumulate in AD brains and are thought to cause memory impairment, to increased brain cytokine production and depressive-like behavior in mice. Here, we review recent findings supporting the inflammatory hypotheses of AD and MDD, focusing on microglia as a common player and therapeutic target linking these devastating disorders.

IGF-1 and Chondroitinase ABC Augment Nerve Regeneration after Vascularized Composite Limb Allotransplantation

Impaired nerve regeneration and inadequate recovery of motor and sensory function following peripheral nerve repair remain the most significant hurdles to optimal functional and quality of life outcomes in vascularized tissue allotransplantation (VCA). Neurotherapeutics such as Insulin-like Growth Factor-1 (IGF-1) and chondroitinase ABC (CH) have shown promise in augmenting or accelerating nerve regeneration in experimental models and may have potential in VCA. The aim of this study was to evaluate the efficacy of low dose IGF-1, CH or their combination (IGF-1+CH) on nerve regeneration following VCA. We used an allogeneic rat hind limb VCA model maintained on low-dose FK506 (tacrolimus) therapy to prevent rejection. Experimental animals received neurotherapeutics administered intra-operatively as multiple intraneural injections. The IGF-1 and IGF-1+CH groups received daily IGF-1 (intramuscular and intraneural injections). Histomorphometry and immunohistochemistry were used to evaluate outcomes at five weeks. Overall, compared to controls, all experimental groups showed improvements in nerve and muscle (gastrocnemius) histomorphometry. The IGF-1 group demonstrated superior distal regeneration as confirmed by Schwann cell (SC) immunohistochemistry as well as some degree of extrafascicular regeneration. IGF-1 and CH effectively promote nerve regeneration after VCA as confirmed by histomorphometric and immunohistochemical outcomes.

Interactions between inflammatory mediators and corticosteroids regulate transcription of genes within the Kynurenine Pathway in the mouse hippocampus

Background

Increased tryptophan metabolism towards the production of kynurenine via indoleamine/tryptophan-2,3-dioxygenases (DOs: Ido1, Ido2, and Tdo2) is strongly associated with the prevalence of major depressive disorder in patients and the induction of depression-like behaviors in animal models. Several studies have suggested that activation of the immune system or elevated corticosteroids drive DO expression; however, mechanisms linking cytokines, corticosteroids, and DOs to psychiatric diseases remain unclear. Various attempts have been made to correlate DO gene expression within the brain to behavior, but disparate results have been obtained. We believe that discrepancies arise as a result of the under-recognized existence of multiple mRNA transcripts for each DO. Unfortunately, there are no reports regarding how the multiple transcripts are distributed or regulated. Here, we used organotypic hippocampal slice cultures (OHSCs) to directly test the ability of inflammatory and stress mediators to differentially regulate DO transcripts.

Methods

OHSCs were treated with pro-inflammatory mediators (interferon-gamma (IFNγ), lipopolysaccharide (LPS), and polyinosine-polycytidylic acid (pI:C)) with or without corticosteroids (dexamethasone (Dex: glucocorticoid receptor (GR) agonist), aldosterone (Aldo: mineralocorticoid receptor (MR) agonist), or corticosterone (Cort: GR/MR agonist)).

Results

IFNγ induced Ido1-full length (FL) and Ido1-variant (v) expression, and surprisingly, Dex, Cort, and Aldo interacted with IFNγ to further elevate expression of Ido1, importantly, in a transcript dependent manner. IFNγ, LPS, and pI:C increased expression of Ido2-v1 and Ido2-v3 transcripts, whereas only IFNγ increased expression of Ido2-v2. Overall Ido2 transcripts were relatively unaffected by GR or MR activation. Naïve mouse brain expresses multiple Tdo2 transcripts. Dex and Cort induced expression of only one of the three Tdo2 transcripts (Tdo2-FL) in OHSCs.

Conclusions

These results establish that multiple transcripts for all three DOs are expressed within the mouse hippocampus, under the control of distinct regulatory pathways. These data identify a previously unrecognized interaction between corticosteroid receptor activation and inflammatory signals on DO gene expression, which suggest that corticosteroids act to differentially enhance gene expression of Ido1, Ido2, and Tdo2.

Forced swimming sabotages the morphological and synaptic maturation of newborn granule neurons and triggers a unique pro-inflammatory milieu in the hippocampus

Recent experimental data suggest that mood disorders are related to inflammatory phenomena and have led to the "inflammatory hypothesis of depression". Given that the hippocampus is one of the most affected areas in these disorders, we used a model of acute stress (the Porsolt test) to evaluate the consequences of forced swimming on two crucial events related to the pathophysiology of major depression: the functional maturation of newborn granule neurons; and the hippocampal inflammatory milieu. Using PSD95:GFP-expressing retroviruses, we found that forced swimming selectively alters the dendritic morphology of newborn neurons and impairs their connectivity by reducing the number and volume of their postsynaptic densities. In addition, acute stress triggered a series of morphological changes in microglial cells, together with an increase in microglial CD68 expression, thus suggesting the functional and morphological activation of this cell population. Furthermore, we observed an intriguing change in the hippocampal inflammatory milieu in response to forced swimming. Importantly, the levels of several molecules affected by acute stress (such as Interleukin-6 and eotaxin) have been described to also be altered in patients with depression and other mood disorders.

Insulin-like growth factor 2 mitigates depressive behavior in a rat model of chronic stress

Depression is a common psychiatric disorder associated with chronic stress. Insulin-like growth factor 2 (IGF2) is a growth factor that serves important roles in the brain during development and at adulthood. Here, the role of IGF2 expression in the hippocampus was investigated in a rat model of depression. A chronic restraint stress (CRS) model of depression was established in rats, exhibiting depression-like behavior as assessed with the sucrose preference test (SPT) and forced swimming test (FST), and with evaluation of the corticosterone levels. Hippocampal IGF2 levels were significantly lower in rats suffering CRS than in controls, as were levels of pERK1/2 and GluR1. Lentivirus-mediated hippocampal IGF2 overexpression alleviated depressive behavior in restrained rats, elevated the levels of pERK1/2 and GluR1 proteins, but it did not affect the expression of pGSK3β, GluR2, NMDAR1, and NMDAR2A. These results suggest the chronic restraint stress induces depressive behavior, which may be mediated by ERK-dependent IGF2 signaling, pointing to an antidepressant role for this molecular pathway.

Role of neuroinflammation in the emotional and cognitive alterations displayed by animal models of obesity

Obesity is associated with a high prevalence of mood disorders and cognitive dysfunctions in addition to being a significant risk factor for important health complications such as cardiovascular diseases and type 2 diabetes. Identifying the pathophysiological mechanisms underlying these health issues is a major public health challenge. Based on recent findings, from studies conducted on animal models of obesity, it has been proposed that inflammatory processes may participate in both the peripheral and brain disorders associated with the obesity condition including the development of emotional and cognitive alterations. This is supported by the fact that obesity is characterized by peripheral low-grade inflammation, originating from increased adipose tissue mass and/or dysbiosis (changes in gut microbiota environment), both of which contribute to increased susceptibility to immune-mediated diseases. In this review, we provide converging evidence showing that obesity is associated with exacerbated neuroinflammation leading to dysfunction in vulnerable brain regions associated with mood regulation, learning, and memory such as the hippocampus. These findings give new insights to the pathophysiological mechanisms contributing to the development of brain disorders in the context of obesity and provide valuable data for introducing new therapeutic strategies for the treatment of neuropsychiatric complications often reported in obese patients.

Integrative neurobiology of metabolic diseases, neuroinflammation, and neurodegeneration

Alzheimer's disease (AD) is a complex, multifactorial disease with a number of leading mechanisms, including neuroinflammation, processing of amyloid precursor protein (APP) to amyloid β peptide, tau protein hyperphosphorylation, relocalization, and deposition. These mechanisms are propagated by obesity, the metabolic syndrome and type-2 diabetes mellitus. Stress, sedentariness, dietary overconsumption of saturated fat and refined sugars, and circadian derangements/disturbed sleep contribute to obesity and related metabolic diseases, but also accelerate age-related damage and senescence that all feed the risk of developing AD too. The complex and interacting mechanisms are not yet completely understood and will require further analysis. Instead of investigating AD as a mono- or oligocausal disease we should address the disease by understanding the multiple underlying mechanisms and how these interact. Future research therefore might concentrate on integrating these by “systems biology” approaches, but also to regard them from an evolutionary medicine point of view. The current review addresses several of these interacting mechanisms in animal models and compares them with clinical data giving an overview about our current knowledge and puts them into an integrated framework.

3,5,6,7,8,3',4'-heptamethoxyflavone, a citrus polymethoxylated flavone, attenuates inflammation in the mouse hippocampus

Citrus polymethoxylated flavones (PMFs) have recently been shown to suppress inflammation in peripheral tissues. In the present study, we investigated the effects of 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF), one of the PMFs, on inflammation in the brain in vivo using mice injected intrahippocampally with lipopolysaccharide (LPS). We demonstrated that subcutaneously injected HMF suppressed: (1) LPS-induced losses in body weight; (2) LPS-induced microglial activation in the hippocampus; and (3) LPS-induced interleukin-1β mRNA expression in the hippocampus. These results suggest that HMF has the ability to reduce neuroinflammation in the brain.

Prenatal stress is a vulnerability factor for altered morphology and biological activity of microglia cells

Several lines of evidence suggest that the dysregulation of the immune system is an important factor in the development of depression. Microglia are the resident macrophages of the central nervous system and a key player in innate immunity of the brain. We hypothesized that prenatal stress (an animal model of depression) as a priming factor could affect microglial cells and might lead to depressive-like disturbances in adult male rat offspring. We investigated the behavioral changes (sucrose preference test, Porsolt test), the expression of C1q and CD40 mRNA and the level of microglia (Iba1 positive) in 3-month-old control and prenatally stressed male offspring rats. In addition, we characterized the morphological and biochemical parameters of potentially harmful (NO, iNOS, IL-1β, IL-18, IL-6, TNF-α, CCL2, CXCL12, CCR2, CXCR4) and beneficial (insulin-like growth factor-1 (IGF-1), brain derived neurotrophic factor (BDNF)) phenotypes in cultures of microglia obtained from the cortices of 1–2 days old control and prenatally stressed pups. The adult prenatally stressed rats showed behavioral (anhedonic- and depression-like) disturbances, enhanced expression of microglial activation markers and an increased number of Iba1-immunopositive cells in the hippocampus and frontal cortex. The morphology of glia was altered in cultures from prenatally stressed rats, as demonstrated by immunofluorescence microscopy. Moreover, in these cultures, we observed enhanced expression of CD40 and MHC II and release of pro-inflammatory cytokines, including IL-1β, IL-18, TNF-α and IL-6. Prenatal stress significantly up-regulated levels of the chemokines CCL2, CXCL12 and altered expression of their receptors, CCR2 and CXCR4 while IGF-1 production was suppressed in cultures of microglia from prenatally stressed rats. Our results suggest that prenatal stress may lead to excessive microglia activation and contribute to the behavioral changes observed in depression in adulthood.

Deferoxamine attenuates lipopolysaccharide-induced neuroinflammation and memory impairment in mice

Background

Neuroinflammation often results in enduring cognitive impairment and is a risk factor for postoperative cognitive dysfunction. There are currently no effective treatments for infection-induced cognitive impairment. Previous studies have shown that the iron chelator deferoxamine (DFO) can increase the resistance of neurons to injury and disease by stimulating adaptive cellular stress responses. However, the impact of DFO on the cognitive sequelae of neuroinflammation is unknown.

Methods

A mouse model of lipopolysaccharide (LPS)-induced cognitive impairment was established to evaluate the neuroprotective effects of DFO against LPS-induced memory deficits and neuroinflammation. Adult C57BL/6 mice were treated with 0.5 μg of DFO 3 days prior to intracerebroventricular microinjection of 2 μg of LPS. Cognitive function was assessed using a Morris water maze from post-injection days 1 to 3. Animal behavioral tests, as well as pathological and biochemical assays were performed to evaluate the LPS-induced hippocampal damage and the neuroprotective effect of DFO.

Results

Treatment of mice with LPS resulted in deficits in cognitive performance in the Morris water maze without changing locomotor activity, which were ameliorated by pretreatment with DFO. DFO prevented LPS-induced microglial activation and elevations of IL-1β and TNF-α levels in the hippocampus. Moreover, DFO attenuated elevated expression of caspase-3, modulated GSK3β activity, and prevented LPS-induced increases of MDA and SOD levels in the hippocampus. DFO also significantly blocked LPS-induced iron accumulation and altered expression of proteins related to iron metabolism in the hippocampus.

Conclusions

Our results suggest that DFO may possess a neuroprotective effect against LPS-induced neuroinflammation and cognitive deficits via mechanisms involving maintenance of less brain iron, prevention of neuroinflammation, and alleviation of oxidative stress and apoptosis.

Insulin-like growth factors inhibit dendritic cell-mediated anti-tumor immunity through regulating ERK1/2 phosphorylation and p38 dephosphorylation

Insulin-like growth factors (IGFs) can promote tumorigenesis via inhibiting the apoptosis of cancer cells. The relationship between IGFs and dendritic cell (DC)-mediated immunity were investigated. Advanced-stage ovarian carcinoma patients were first evaluated to show higher IGF-1 and IGF-2 concentrations in their ascites than early-stage patients. IGFs could suppress DCs' maturation, antigen presenting abilities, and the ability to activate antigen-specific CD8(+) T cell. IGF-treated DCs also secreted higher concentrations of IL-10 and TNF-α. IGF-treated DCs showed decreased ERK1/2 phosphorylation and reduced p38 dephosphorylation. The percentages of matured DCs in the ascites were significantly lower in the IGF-1 or IGF-2 highly-expressing WF-3 tumor-bearing mice. The IGF1R inhibitor - NVP-AEW541, could block the effects of IGFs to rescue DCs' maturation and to restore DC-mediated antigen-specific immunity through enhancing ERK1/2 phosphorylation and p38 dephosphorylation. IGFs can inhibit DC-mediated anti-tumor immunity through suppressing maturation and function and the IGF1R inhibitor could restore the DC-mediated anti-tumor immunity. Blockade of IGFs could be a potential strategy for cancer immunotherapy.

Estrogen-IGF-1 interactions in neuroprotection: ischemic stroke as a case study

The steroid hormone 17b-estradiol and the peptide hormone insulin-like growth factor (IGF)-1 independently exert neuroprotective actions in neurologic diseases such as stroke. Only a few studies have directly addressed the interaction between the two hormone systems, however, there is a large literature that indicates potentially greater interactions between the 17b-estradiol and IGF-1 systems. The present review focuses on key issues related to this interaction including IGF-1 and sex differences and common activation of second messenger systems. Using ischemic stroke as a case study, this review also focuses on independent and cooperative actions of estrogen and IGF-1 on neuroprotection, blood brain barrier integrity, angiogenesis, inflammation and post-stroke epilepsy. Finally, the review also focuses on the astrocyte, a key mediator of post stroke repair, as a local source of 17b-estradiol and IGF-1. This review thus highlights areas where significant new research is needed to clarify the interactions between these two neuroprotectants.

Dietary broccoli mildly improves neuroinflammation in aged mice but does not reduce lipopolysaccharide-induced sickness behavior

Aging is associated with oxidative stress and heightened inflammatory response to infection. Dietary interventions to reduce these changes are therefore desirable. Broccoli contains glucoraphanin, which is converted to sulforaphane (SFN) by plant myrosinase during cooking preparation or digestion. Sulforaphane increases antioxidant enzymes including NAD(P)H quinone oxidoreductase and heme oxygenase I and inhibits inflammatory cytokines. We hypothesized that dietary broccoli would support an antioxidant response in brain and periphery of aged mice and inhibit lipopolysaccharide (LPS)-induced inflammation and sickness. Young adult and aged mice were fed control or 10% broccoli diet for 28 days before an intraperitoneal LPS injection. Social interactions were assessed 2, 4, 8, and 24 hours after LPS, and mRNA was quantified in liver and brain at 24 hours. Dietary broccoli did not ameliorate LPS-induced decrease in social interactions in young or aged mice. Interleukin-1β (IL-1β) expression was unaffected by broccoli consumption but was induced by LPS in brain and liver of adult and aged mice. In addition, IL-1β was elevated in brain of aged mice without LPS. Broccoli consumption decreased age-elevated cytochrome b-245 β, an oxidative stress marker, and reduced glial activation markers in aged mice. Collectively, these data suggest that 10% broccoli diet provides a modest reduction in age-related oxidative stress and glial reactivity, but is insufficient to inhibit LPS-induced inflammation. Thus, it is likely that SFN would need to be provided in supplement form to control the inflammatory response to LPS.

Developmental oestrogen exposure differentially modulates IGF-I and TNF-α expression levels in immune organs of Yersinia ruckeri-challenged young adult rainbow trout (Oncorhynchus mykiss)

Intensified aquaculture has strong impact on fish health by stress and infectious diseases and has stimulated the interest in the orchestration of cytokines and growth factors, particularly their influence by environmental factors, however, only scarce data are available on the GH/IGF-system, central physiological system for development and tissue shaping. Most recently, the capability of the host to cope with tissue damage has been postulated as critical for survival. Thus, the present study assessed the combined impacts of estrogens and bacterial infection on the insulin-like growth factors (IGF) and tumor-necrosis factor (TNF)-α. Juvenile rainbow trout were exposed to 2 different concentrations of 17β-estradiol (E2) and infected with Yersinia ruckeri. Gene expressions of IGF-I, IGF-II and TNF-α were measured in liver, head kidney and spleen and all 4 estrogen receptors (ERα1, ERα2, ERβ1 and ERβ2) known in rainbow trout were measured in liver. After 5 weeks of E2 treatment, hepatic up-regulation of ERα1 and ERα2, but down-regulation of ERß1 and ERß2 were observed in those groups receiving E2-enriched food. In liver, the results further indicate a suppressive effect of Yersinia-infection regardless of E2-treatment on day 3, but not of E2-treatment on IGF-I whilst TNF-α gene expression was not influenced by Yersinia-infection but was reduced after 5 weeks of E2-treatment. In spleen, the results show a stimulatory effect of Yersinia-infection, but not of E2-treatment on both, IGF-I and TNF-α gene expressions. In head kidney, E2 strongly suppressed both, IGF-I and TNF-α. To summarise, the treatment effects were tissue- and treatment-specific and point to a relevant role of IGF-I in infection.

Assessing for unique immunomodulatory and neuroplastic profiles of physical activity subtypes: a focus on psychiatric disorders

Physical activity (PA) is emerging as a safe and effective tool in the prevention and treatment of psychiatric disorders. PA subtypes include aerobic, resistance, flexibility, neuromotor (involving balance, agility and co-ordination), mind-body (e.g. tai chi, qi gong and yoga) and mixed type trainings. Evidence from clinical trials suggests that PA subtypes can have positive clinical effects, however the effects on the symptomatology may vary according to the PA subtype. It therefore stands to reason that various PA subtypes may modulate the immune system and neuroplastic processes differently. This systematic review aims to assess the immunomodulatory and neuroplastic profiles of various PA subtypes, particularly in unipolar depression and age-related cognitive decline (ARCD). The literature suggests several unique immunomodulatory and neuroplastic profiles for PA subtypes (i.e. resistance, aerobic and mind-body) in depression and ARCD. In depression, levels of various cytokines at baseline may predict treatment response to subtypes of PA and pharmacological agents. The pro-neuroplastic effects of resistance and aerobic PA in ARCD may differ due to variances in neurotrophin profiles. At this stage of literature in the field, it is difficult to draw firm conclusions on the specific immunomodulatory and neuroplastic pathways involved in these PA subtypes given of the small number of comparative studies and methodological heterogeneity between studies (e.g. study population age and illness severity, as well as duration and intensity of PA intervention). This important field requires well-designed, high-quality comparative studies to better describe unique immunomodulatory and neuroplastic profiles.

Rodent models of depression: neurotrophic and neuroinflammatory biomarkers

Rodent models are an indispensable tool for studying etiology and progress of depression. Since interrelated systems of neurotrophic factors and cytokines comprise major regulatory mechanisms controlling normal brain plasticity, impairments of these systems form the basis for development of cerebral pathologies, including mental diseases. The present review focuses on the numerous experimental rodent models of depression induced by different stress factors (exteroceptive and interoceptive) during early life (including prenatal period) or adulthood, giving emphasis to the data on the changes of neurotrophic factors and neuroinflammatory indices in the brain. These parameters are closely related to behavioral depression-like symptoms and impairments of neuronal plasticity and are both gender- and genotype-dependent. Stress-related changes in expression of neurotrophins and cytokines in rodent brain are region-specific. Some contradictory data reported by different groups may be a consequence of differences of stress paradigms or their realization in different laboratories. Like all experimental models, stress-induced depression-like conditions are experimental simplification of clinical depression states; however, they are suitable for understanding the involvement of neurotrophic factors and cytokines in the pathogenesis of the disease—a goal unachievable in the clinical reality. These major regulatory systems may be important targets for therapeutic measures as well as for development of drugs for treatment of depression states.

Prenatal stress leads to changes in IGF-1 binding proteins network in the hippocampus and frontal cortex of adult male rat

Depression is a mental disorder of still unknown origin. Currently, much attention is paid to the potential influence of disturbances in the functioning of neurotrophic factors on the onset of this disease. Insulin-like growth factor 1 (IGF-1) is one of the most important growth agents affecting processes that are crucial for brain development. To date, there are no data showing the impact of prenatal stress on the family of six IGF binding proteins (IGFBP 1-6) that regulate IGF-1 bioactivity. The goal of this study was to investigate whether the decreased expression of IGF-1 in the frontal cortex (FCx) and hippocampus (Hp) of adult male rats following a prenatal stress procedure is related to changes in the IGFBP family. Our results show that rats exposed prenatally to stressful stimuli displayed depression-like behavior based on sucrose preference and elevated plus maze tests. In both cases, in the adult rat brain structures that were examined after the prenatal stress procedure, the IGF-1 protein level was reduced. Moreover, we observed changes of varying degrees in the levels of IGFBPs in stressed animals. A decrease in IGFBP-2 and IGFBP-3 accompanied by an increase in the IGFBP-4 concentration in the Hp and the FCx was detected. There were no differences in IGFBP-1 and IGFBP-6 brain levels between the stressed and control animals, whereas IGFBP-5 concentration was decreased in the Hp of prenatally stressed animals. This study demonstrated that stress during pregnancy may lead not only to behavioral disturbances but also to a decrease in IGF-1 level and the dysregulation of the IGF-1 binding protein network in adult rat offspring.

Etazolate abrogates the lipopolysaccharide (LPS)-induced downregulation of the cAMP/pCREB/BDNF signaling, neuroinflammatory response and depressive-like behavior in mice

Increasing evidence has indicated that immune challenge by bacterial lipopolysaccharide (LPS) induces depressive-like behavior, neuroinflammatory response and upregulates phosphodiesterase-4 (PDE4), an enzyme that specifically hydrolyzes cyclic adenosine monophosphate (cAMP). However, whether the potential PDE4 inhibitor etazolate prevents the LPS-induced depressive-like behavior remains unclear. Here using a model of depression induced by the repeated administration of LPS during 16days, and then investigated the influence of LPS on the expression of PDE4, interleukin-1β (IL-1β) and antidepressant action of etazolate in mice through forced swimming, novelty suppressed feeding, sucrose preference and open-field tests. Our results showed that etazolate pretreatment facilitated the recovery from weight loss and prevented the depressive-like behavior induced by repeated LPS administration. Moreover, the antidepressant action of etazolate was paralleled by significantly reducing the expression levels of PDE4A, PDE4B, PDE4D and IL-1β and up-regulating the cAMP/phosphorylated cAMP response-element binding protein (pCREB)/brain-derived neurotrophic factor (BDNF) signaling in the hippocampus and prefrontal cortex of mice. These results indicate that the effects of etazolate on the depressive-like behavior induced by repeated LPS treatment may partially depend on the inhibition of PDE4 subtypes, the activation of the cAMP/pCREB/BDNF signaling and the anti-inflammatory responses in the hippocampus and prefrontal cortex.

Voluntary wheel running does not affect lipopolysaccharide-induced depressive-like behavior in young adult and aged mice

OBJECTIVE(S)

Peripheral stimulation of the innate immune system with lipopolysaccharide (LPS) causes prolonged depressive-like behavior in aged mice that is dependent on indoleamine 2,3 dioxygenase (IDO) activation. Regular moderate-intensity exercise training has been shown to exert neuroprotective effects that might reduce depressive-like behavior in aged mice. The purpose of this study was to test the hypothesis that voluntary wheel running (VWR) would attenuate LPS-induced depressive-like behavior and brain IDO gene expression in 4- and 22-month-old C57BL/6J mice.

METHODS

Mice were housed with a running wheel (VWR) or no wheel (standard) for 30 (young adult mice) or 70 days (aged mice), after which they were intraperitoneally injected with LPS (young adult mice: 0.83 mg/kg; aged mice: 0.33 mg/kg).

RESULTS

Young adult VWR mice ran on average 6.9 km/day, while aged VWR mice ran on average 3.4 km/day. Both young adult and aged VWR mice increased their forced exercise tolerance compared to their respective standard control groups. VWR had no effect on LPS-induced anorexia, weight loss, increased immobility in the tail suspension test and decreased sucrose preference in either young adult or aged mice. Four (young adult mice) and 24 h (aged mice) after injection of LPS, mRNA transcripts for TNF-α, IL-1β, IL-6, and IDO were upregulated in the whole brain independently of VWR.

CONCLUSION

Prolonged physical exercise has no effect on the neuroinflammatory response to LPS and its behavioral consequences in young adult and aged mice.

Peripheral immunomodulation with ginsenoside Rg1 ameliorates neuroinflammation-induced behavioral deficits in rats

Neuroinflammatory disturbances have been closely associated with depression and many other neuropsychiatric diseases. Although targeting neuroinflammatory mediators with centrally acting drugs has shown certain promise, its translation is faced with several challenges especially drug delivery and safety concerns. Here, we report that neuroinflammation-induced behavioral abnormality could be effectively attenuated with immunomodulatory agents that need not to gain brain penetration. In a rat model with intracerebral lipopolysaccharide (LPS) challenge, we validated that ginsenoside Rg1 (Rg1), a well-established anti-inflammatory agent, was unable to produce a direct action in the brain. Interestingly, peripherally restricted Rg1 could effectively attenuate the weight loss, anorexic- and depressive-like behavior as well as neurochemical disturbances associated with central LPS challenge. Biochemical assay of neuroimmune mediators in the periphery revealed that Rg1 could mitigate the deregulation of the hypothalamic-pituitary-adrenal axis and selectively blunt the increase in circulating interleukin-6 levels. Furthermore, these peripheral regulatory effects were accompanied by dampened microglial activation, mitigated expression of pro-inflammatory mediators and neurotoxic species in the central compartment. Taken together, our work suggested that targeting the peripheral immune system may serve as a novel therapeutic approach to neuroinflammation-induced neuropsychiatric disorders. Moreover, our findings provided the rationale for employing peripherally active agents like Rg1 to combat mental disturbances.

Second messenger/signal transduction pathways in major mood disorders: moving from membrane to mechanism of action, part I: major depressive disorder

The etiopathogenesis and treatment of major mood disorders have historically focused on modulation of monoaminergic (serotonin, norepinephrine, dopamine) and amino acid [γ-aminobutyric acid (GABA), glutamate] receptors at the plasma membrane. Although the activation and inhibition of these receptors acutely alter local neurotransmitter levels, their neuropsychiatric effects are not immediately observed. This time lag implicates intracellular neuroplasticity as primary in the mechanism of action of antidepressants and mood stabilizers. The modulation of intracellular second messenger/signal transduction cascades affects neurotrophic pathways that are both necessary and sufficient for monoaminergic and amino acid-based treatments. In this review, we will discuss the evidence in support of intracellular mediators in the pathophysiology and treatment of preclinical models of despair and major depressive disorder (MDD). More specifically, we will focus on the following pathways: cAMP/PKA/CREB, neurotrophin-mediated (MAPK and others), p11, Wnt/Fz/Dvl/GSK3β, and NFκB/ΔFosB. We will also discuss recent discoveries with rapidly acting antidepressants, which activate the mammalian target of rapamycin (mTOR) and release of inhibition on local translation via elongation factor stimulation. Throughout this discourse, we will highlight potential intracellular targets for therapeutic intervention. Finally, future clinical implications are discussed.

The stress response to surgery and postoperative delirium: evidence of hypothalamic-pituitary-adrenal axis hyperresponsiveness and decreased suppression of the GH/IGF-1 Axis

INTRODUCTION

The aim of this study is to determine whether postoperative delirium is associated with dysregulation of hypothalamic-pituitary-adrenal and growth hormone/insulin-like growth factor 1 (GH/IGF-1) responses following acute systemic inflammation.

METHODS

Plasma levels of cortisol, IGF-1, C-reactive protein, interleukin (IL)-6, IL-8, and IL-10 were measured before and after surgery in 101 patients ≥ 60 years without dementia undergoing elective hip arthroplasty. Participants were assessed with confusion assessment method and Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision; DSM-IV-TR) postoperatively and 37 patients fulfilled the DSM-IV-TR criteria for delirium.

RESULTS

Preoperative plasma cortisol levels were similar in delirium and nondelirium groups (405.37 ± 189.04 vs 461.83 ± 219.39; P = .22). Participants with delirium had higher postoperative cortisol levels (821.67 ± 367.17 vs 599.58 ± 214.94; P = .002) with enhanced postoperative elevation in relation to baseline (1.9- vs 1.5-fold; P = .004). The plasma levels of IGF1 did not differ in delirium and nondelirium groups before (18.12 ± 7.58 vs 16.8 ± 7.86; P = .477) and following surgery (13.39 ± 5.94 vs 11.12 ± 6.2; P = .639), but the levels increased in relation to baseline more frequently in patients who developed delirium (24.3% vs 7.8%; P = .034). The magnitude of postoperative cortisol elevation correlated with ΔIL-6 (P = .485; P = .002), ΔIL-8 (P = .429; P = .008), and ΔIL-10 (P = .544; P < .001) only in patients with delirium.

CONCLUSIONS

Hypothalamic-pituitary-adrenal axis hyperresponsiveness and a less frequent suppression of the GH/IGF-1 axis in response to acute stress are possibly involved in delirium pathophysiology.