A pre-conditioning stress accelerates increases in mouse plasma inflammatory cytokines induced by stress

Single administration of a psychedelic [(R)-DOI] influences coping strategies to an escapable social stress

Psychedelic compounds have potentially rapid, long-lasting anxiolytic, antidepressive and anti-inflammatory effects. We investigated whether the psychedelic compound (R)-2,5-dimethoxy-4-iodoamphetamine [(R)-DOI], a selective 5-HT2A receptor partial agonist, decreases stress-related behavior in male mice exposed to repeated social aggression. Additionally, we explored the likelihood that these behavioral changes are related to anti-inflammatory properties of [(R)-DOI]. Animals were subjected to the Stress Alternatives Model (SAM), an escapable social stress paradigm in which animals develop reactive coping strategies - remaining in the SAM arena (Stay) with a social aggressor, or dynamically initiated stress coping strategies that involve utilizing the escape holes (Escape) to avoid aggression. Mice expressing these behavioral phenotypes display behaviors like those in other social aggression models that separate animals into stress-vulnerable (as for Stay) or stress-resilient (as for Escape) groups, which have been shown to have distinct inflammatory responses to social stress. These results show that Stay animals have heightened cytokine gene expression, and both Stay and Escape mice exhibit plasma and neural concentrations of the inflammatory cytokine tumor necrosis factor-α (TNFα) compared to unstressed control mice. Additionally, these results suggest that a single administration of (R)-DOI to Stay animals in low doses, can increase stress coping strategies such as increasing attention to the escape route, promoting escape behavior, and reducing freezing during socially aggressive interaction in the SAM. Lower single doses of (R)-DOI, in addition to shifting behavior to suggest anxiolytic effects, also concomitantly reduce plasma and limbic brain levels of the inflammatory cytokine TNFα.

Transcriptomic Evaluation of a Stress Vulnerability Network Using Single-Cell RNA Sequencing in Mouse Prefrontal Cortex

BACKGROUND

Increased vulnerability to stress is a major risk factor for several mood disorders, including major depressive disorder. Although cellular and molecular mechanisms associated with depressive behaviors following stress have been identified, little is known about the mechanisms that confer the vulnerability that predisposes individuals to future damage from chronic stress.

METHODS

We used multisite in vivo neurophysiology in freely behaving male and female C57BL/6 mice (n = 12) to measure electrical brain network activity previously identified as indicating a latent stress vulnerability brain state. We combined this neurophysiological approach with single-cell RNA sequencing of the prefrontal cortex to identify distinct transcriptomic differences between groups of mice with inherent high and low stress vulnerability.

RESULTS

We identified hundreds of differentially expressed genes (padjusted < .05) across 5 major cell types in animals with high and low stress vulnerability brain network activity. This unique analysis revealed that GABAergic (gamma-aminobutyric acidergic) neuron gene expression contributed most to the network activity of the stress vulnerability brain state. Upregulation of mitochondrial and metabolic pathways also distinguished high and low vulnerability brain states, especially in inhibitory neurons. Importantly, genes that were differentially regulated with vulnerability network activity significantly overlapped (above chance) with those identified by genome-wide association studies as having single nucleotide polymorphisms significantly associated with depression as well as genes more highly expressed in postmortem prefrontal cortex of patients with major depressive disorder.

CONCLUSIONS

This is the first study to identify cell types and genes involved in a latent stress vulnerability state in the brain.

Enhancement of peripheral fatty acyl ethanolamide signaling prevents stress-induced social avoidance and anxiety-like behaviors in male rats

RATIONALE

Exposure to traumatic events can lead to alterations in social and anxiety-related behaviors. Emerging evidence suggests that peripheral host-defense processes are implicated in the expression of stress-induced behavioral responses and may be targeted to mitigate the negative sequalae of stress exposure.

OBJECTIVES

In this study, we used the peripherally restricted FAAH inhibitor URB937 to investigate the effects of the fatty acyl ethanolamide (FAE) family of lipid mediators - which include the endocannabinoid anandamide and the endogenous PPAR-α agonists, oleoylethanolamide and palmitoylethanolamide - on behavioral and peripheral biochemical responses to two ethologically distinct rat models of stress.

METHODS

Male adult rats were exposed to acute social defeat, a model of psychological stress (Experiment 1), or to the predator odor 2,5-dihydro-2,4,5-trimethylthiazoline (TMT), a test of innate predator-evoked fear (Experiment 2), and subsequently treated with URB937 (1 or 3 mg/kg, intraperitoneal) or vehicle. Behavioral analyses were conducted 24 h (Experiment 1) or 7 days (Experiment 2) after exposure.

RESULTS

URB937 administration prevented the emergence of both social avoidance behavior after social defeat stress and anxiety-related behaviors after TMT exposure. Further, URB937 administration blocked social defeat-induced transient increase in plasma concentrations of pro-inflammatory cytokines and the elevation in plasma corticosterone levels observed 24 h after social defeat CONCLUSIONS: Enhancement of peripheral FAAH-regulated lipid signaling prevents the emergence of stress-induced social avoidance and anxiety-like behaviors in male rats through mechanisms that may involve an attenuation of peripheral cytokine release induced by stress exposure.

Effects of chronic stress on bladder morphology of rats and impact of comfort food diet as an ameliorating agent

OBJECTIVES

To investigate the effects of chronic stress on bladder morphology and the impact of food preference (standard or comfort foods) on the bladder of stressed rats.

METHODS

In total, 32 Wistar male rats (3 months old) were divided into four groups: control (C), stressed (S), control + comfort food (C + CF), and stressed + comfort food (S + CF). Groups C and C + CF were maintained under normal conditions, while groups S and S + CF were subjected to chronic stress by the restraint method. Groups C and S received standard rat chow, while groups C + CF and S + CF received comfort food (Froot Loops®) and standard chow. The stress stimuli were induced daily for 2 h over 8 weeks. After 8 weeks, all animals were killed, and the bladders were removed and used for histomorphometric analysis.

RESULTS

Body mass was similar among the groups. Stress did not promote differences regarding food intake, but animals receiving comfort food showed higher calories intake (in kcal/Kg) than animals receiving only standard chow. The C + CF and S + CF groups preferred comfort food over the standard chow; this preference was higher in the S + CF than in the C + CF group. The surface density of smooth muscle was reduced in stressed animals, while connective tissue and elastic system fiber content were increased in stressed groups. Further, epithelial height was increased in rats submitted to chronic stress. The surface density of elastic system fibers was decreased by the consumption of comfort food.

CONCLUSIONS

Chronic stress induces morphological modifications on the bladder wall and epithelium. These modifications may be related to lower urinary tract symptoms. Additionally, chronic stress caused a higher preference for comfort food intake which did not ameliorate or aggravate the stress-induced bladder alterations.

Subcutaneous Mycobacterium vaccae ameliorates the effects of early life adversity alone or in combination with chronic stress during adulthood in male and female mice

Chronic psychosocial stress is a burden of modern society and poses a clear risk factor for a plethora of somatic and affective disorders, of which most are associated with an activated immune status and chronic low-grade inflammation. Preclinical and clinical studies further suggest that a failure in immunoregulation promotes an over-reaction of the inflammatory stress response and, thus, predisposes an individual to the development of stress-related disorders. Therefore, all genetic (i.e., sex) and environmental (i.e., early life adversity; ELA) factors facilitating an adult's inflammatory stress response are likely to increase their stress vulnerability. In the present study we investigated whether repeated subcutaneous (s.c.) administrations with a heat-killed preparation of Mycobacterium vaccae (M. vaccae; National Collection of Type Cultures (NCTC) 11659), an abundant soil saprophyte with immunoregulatory properties, are protective against negative behavioral, immunological and physiological consequences of ELA alone or of ELA followed by chronic psychosocial stress during adulthood (CAS) in male and female mice. ELA was induced by the maternal separation (MS) paradigm, CAS was induced by 19 days of chronic subordinate colony housing (CSC) in males and by a 7-week exposure to the social instability paradigm (SIP) in females. Our data indicate that ELA effects in both sexes, although relatively mild, were to a great extent prevented by subsequent s.c. M. vaccae administrations. Moreover, although the use of different paradigms for males and females impedes a direct comparison, male mice seemed to be more susceptible to CAS than females, with only females benefitting slightly from the stress protective effects of s.c. M. vaccae administrations when given prior to CAS alone. Finally, our data support the hypothesis that female mice are more vulnerable to the additive effects of ELA and CAS than male mice and that s.c. M. vaccae administrations subsequent to ELA but prior to CAS are protective in both sexes. Taken together and considering the limitation that CAS in males and females was induced by different paradigms, our findings are consistent with the hypotheses that murine stress vulnerability during different phases of life is strongly sex dependent and that developing immunoregulatory approaches, such as repeated s.c. administrations with immunoregulatory microorganisms, have potential for prevention/treatment of stress-related disorders.

Effect of Plant Extracts Combinations on TNF-α, IL-6 and IL-10 Levels in Serum of Rats Exposed to Acute and Chronic Stress

Oxydative stress, anxiety and depression are associated with changes in cytokine levels. Natural products, including individual and combined plant extracts, have the potential to be used in the treatment of neuropsychiatric disorders. The goal of this study is to investigate the effects of two combined plant extracts, rich in flavonoids, on the levels of the cytokines TNF-α, IL-6, and IL-10 in rats subjected to models of acute cold stress and chronic unpredictable stress. The study utilized common medicinal plants such as Valeriana officinalis, Melissa officinalis, Crataegus monogyna, Hypericum perforatum, and Serratula coronata, which were combined in two unique combinations-Antistress I and Antistress II. The compositions of the used extracts were determined by HPLC methods. Pro- and anti-inflammatory cytokines in rats' serum were measured with Enzyme-linked immunosorbent assay. The results from the acute stress model revealed that the individual extract of Crataegus monogyna decreased levels of TNF-α, while Serratula coronata, Hypericum perforatum, and Valeriana officinalis effectively reduced IL-6 levels. Both combinations, Antistress I and Antistress II, were effective in reducing TNF-α and IL-6 levels, with Antistress II also increasing IL-10 levels. In the chronic stress model, Hypericum perforatum extract decreased the levels of the pro-inflammatory cytokines TNF-α and IL-6, whereas extracts of Serratula coronata and Valeriana officinalis only reduced TNF-α levels. The two combined extracts, Antistress I and Antistress II, decreased TNF-α and IL-6 levels, while Antistress I also reduced the levels of the anti-inflammatory cytokine IL-10. The combinations of plant extracts used in our experiment have not been previously studied or documented in the available literature. However, based on our own experimental results, we can draw the conclusion that the combinations exhibit a more pronounced effect in reducing cytokine levels compared to the individual plant extracts.

Stress promotes the infiltration of peripheral immune cells to the brain

Immune cells and the brain have a privileged interaction. Here, we report changes in the hippocampal immune microenvironment at the single cell level after stress, uncovering the tight orchestration of immune cell infiltration into the hippocampus after stress to maintain homeostasis. We show the distribution of several immune cell types in the hippocampus associated with their susceptibility or resilience to the learned helplessness paradigm in a sex- and microbiota-dependent manner using single-cell RNA sequencing and bioinformatic tools, flow cytometry, and immunofluorescence. We uncovered the presence of tissue-resident memory T cells that accumulate over time in the hippocampus of learned helpless mice, and the presence of CD74-expressing myeloid cells. These cells were found by a knockdown approach to be critical to induce resilience to learned helplessness. Altogether, these findings provide a novel overview of the neuro-immune repertoire and its impact on the landscape of the hippocampus after learned helplessness.

Chronic stress negatively impacts wound healing, welfare, and stress regulation in internally tagged Atlantic salmon (Salmo salar)

The desire to understand fish welfare better has led to the development of live monitoring sensor tags embedded within individuals for long periods. Improving and understanding welfare must not come at the cost of impaired welfare due to a tag’s presence and implantation process. When welfare is compromised, the individual will experience negative emotions such as fear, pain, and distress, impacting the stress response. In this study, Atlantic salmon (Salmo salar) underwent surgical implantation of a dummy tag. Additionally, half of this group was introduced to daily crowding stress. Both groups and an untagged group were followed for 8 weeks using triplicate tanks per group. Sampling took place once a week, and where stress was given, it was conducted 24 h before sampling. Stress-related measurements were taken to understand if tagging caused chronic stress and explore the chronic stress response and its impact on wound healing. Primary stress response hormones measured included CRH, dopamine, adrenocorticotropic hormone, and cortisol. Secondary stress response parameters measured included glucose, lactate, magnesium, calcium, chloride, and osmolality. Tertiary stress response parameters measured included weight, length, and five fins for fin erosion. Wound healing was calculated by taking the incision length and width, the inflammation length and width, and the inside wound length and width. The wound healing process showed that stressed fish have a larger and longer-lasting inflammation period and a slower wound healing process, as seen from the inside wound. The tagging of Atlantic salmon did not cause chronic stress. In contrast, daily stress led to an allostatic overload type two response. ACTH was elevated in the plasma after 4 weeks, and cortisol followed elevation after 6 weeks, highlighting a breakdown of the stress regulation. Fin erosion was elevated alongside cortisol increase in the stressed group. This data suggests that tagging previously unstressed fish in a controlled environment does not negatively affect welfare regarding stress responses. It also indicates that stress delays wound healing and increases the inflammatory response, highlighting how continued stress causes a breakdown in some stress responses. Ultimately, the tagging of Atlantic salmon can be successful under certain conditions where proper healing is observed, tag retention is high, and chronic stress is not present, which could allow for the possible measurement of welfare indicators via smart-tags.

Stress-inducible IL-6 is regulated by KLF7 in brown adipocytes

Stress-inducible interleukin 6 (IL-6) is generated in brown adipocytes via beta-3 adrenergic receptor (ADRB3) signaling, which is necessary in stress hyperglycemia, the kind of metabolic adaptation enabling "fight or flight" response by means of liver gluconeogenesis. Nevertheless, the mechanism of ADRB3 signaling mediates IL-6 in brown adipocytes remains unclear. As a result, it is critical to understand how brown adipocytes produce IL-6 via ADRB3 signaling. We found that the ADRB3 agonist and cold stimulation promoted the expression of KLF7 and IL-6 in brown adipocytes of mice. In parallel to these results in vivo, treatment with ADRB3 agonist promoted the expression of KLF7 and the release of IL-6 in primary brown adipocytes of mice. Notably, we discovered that KLF7 positively controls the expression of IL-6 and downregulated KLF7 largely blunted ADRB3 agonist induced IL-6 expressions in brown adipocytes. Our findings suggest that KLF7 is required for the generation of IL-6 when ADRB3 signaling is activated in brown adipocytes.

Chronic stress but not acute stress decreases the seizure threshold in PTZ-induced seizure in mice: role of inflammatory response and oxidative stress

Seizure is paroxysmal abnormal electrical discharges in the cerebral cortex. Inflammatory pathways and oxidative stress are involved in the pathophysiology of seizures. Stress can induce an oxidative stress state and increase the production of inflammatory mediators in the brain. We investigated the effects of acute and chronic stresses on the seizure threshold in pentylenetetrazol (PTZ)-induced seizures in mice, considering oxidative stress and inflammatory mediators in the prefrontal cortex. In this study, 30 male Naval Medical Research Institute (NMRI) mice were divided into 3 groups, including acute stress, chronic stress, and control groups. PTZ was used for the induction of seizures. The gene expression of inflammatory markers (IL-1β, TNF-α, NLRP3, and iNOS), malondialdehyde (MDA) level, nitrite level, and total antioxidant capacity (TAC) were assessed in the prefrontal cortex and serum. Our results showed that stress could increase the expression of inflammatory cytokines genes and oxidative stress in the prefrontal cortex of the brain and serum following PTZ-induced seizures, which is associated with increased seizure sensitivity and decreased the seizure threshold. The effects of chronic stress were much more significant than acute stress. We concluded that the effects of chronic stress on seizure sensitivity and enhancement of neuroinflammation and oxidative stress are much greater than acute stress.

Innate lymphoid cells in depression: Current status and perspectives

The recent discovery of innate lymphoid cells (ILCs) has provided new insights into our understanding of the pathogenesis of many disease conditions with immune dysregulation. Type 1 innate lymphoid cells (ILC1s) induce type I immunity and are characterized by the expression of signature cytokine IFN-γ and the master transcription factor T-bet; ILC2s stimulate type II immune responses and are defined by the expression of signature cytokines IL-5 and IL-13, and transcription factors ROR-α and GATA3; ILC3s requires the transcription factor RORγt and produce IL-22 and IL-17. ILCs are largely tissue-resident and are enriched at barrier surfaces of the mammalian body. Increasing evidence shows that inflammation is involved in the pathogenesis of depression. Although few studies have directly investigated the role of ILCs in depression, several studies have examined the levels of cytokines produced by ILCs in depressed subjects. This review summarizes the potential roles of ILCs in depression. A better understanding of the biology of ILCs may lead to the development of new therapeutic strategies for the management of depression.

Post-weaning Social Isolation in Male and Female Prairie Voles: Impacts on Central and Peripheral Immune System

The socially monogamous prairie vole (Microtus ochrogaster) offers a unique opportunity to examine the impacts of adolescent social isolation on the brain, immune system, and behavior. In the current study, male and female prairie voles were randomly assigned to be housed alone or with a same-sex cagemate after weaning (i.e., on postnatal day 21-22) for a 6-week period. Thereafter, subjects were tested for anxiety-like and depressive-like behaviors using the elevated plus maze (EPM) and Forced Swim Test (FST), respectively. Blood was collected to measure peripheral cytokine levels, and brain tissue was processed for microglial density in various brain regions, including the Nucleus Accumbens (NAcc), Medial Amygdala (MeA), Central Amygdala (CeA), Bed Nucleus of the Stria Terminalis (BNST), and Paraventricular Nucleus of the Hypothalamus (PVN). Sex differences were found in EPM and FST behaviors, where male voles had significantly lower total arm entries in the EPM as well as lower latency to immobility in the FST compared to females. A sex by treatment effect was found in peripheral IL-1β levels, where isolated males had a lower level of IL-1β compared to cohoused females. Post-weaning social isolation also altered microglial density in a brain region-specific manner. Isolated voles had higher microglial density in the NAcc, MeA, and CeA, but lower microglial density in the dorsal BNST. Cohoused male voles also had higher microglial density in the PVN compared to cohoused females. Taken together, these data suggest that post-weaning social housing environments can alter peripheral and central immune systems in prairie voles, highlighting a potential role for the immune system in shaping isolation-induced alterations to the brain and behavior.

Correlation between anxiety-depression symptoms and immune characteristics in inpatients with 2019 novel coronavirus in Wuhan, China

BACKGROUND

Coronavirus disease 2019 (COVID-19) is widely acknowledged as a severe traumatic event, and depression, anxiety, and psychological distress are common in diagnosed patients. However, the correlations of biological indicators with emotion are rarely reported. The primary objective of this study was to explore the dysfunction of immune-inflammatory characteristics in patients with depression-anxiety symptoms.

METHODS

We investigated the mental status of inpatients with COVID-19 in Wuhan and compared the differences in cytokines and lymphocytes between patients with and without depression-anxiety symptoms at admission. After two weeks of treatment, we evaluated the mental conditions and measured the cytokines and lymphocytes of the patients with depression and anxiety symptoms and explored the changes and their associations.

RESULTS

Approximately half of the patients with COVID-19 had depression and anxiety symptoms, and the symptoms were related to the ratio of CD4+/CD8+ and the level of CD4⁺T lymphocytes. When compared with patients without depression-anxiety symptoms, CD4⁺T lymphocytes level was significantly higher in COVID-19 patients with depression-anxiety symptoms.

CONCLUSION

This study provided novel evidence regarding the association between depression and anxiety symptoms and immune characteristics, especially CD4⁺T lymphocyte levels, in COVID-19 patients. We emphasized the importance of paying attention to the dynamic immune process of patients diagnosed with COVID-19 with depression/anxiety.

Modeling Neuroimmune Interactions in Human Subjects and Animal Models to Predict Subtype-Specific Multidrug Treatments for Gulf War Illness

Gulf War Illness (GWI) is a persistent chronic neuroinflammatory illness exacerbated by external stressors and characterized by fatigue, musculoskeletal pain, cognitive, and neurological problems linked to underlying immunological dysfunction for which there is no known treatment. As the immune system and the brain communicate through several signaling pathways, including the hypothalamic–pituitary–adrenal (HPA) axis, it underlies many of the behavioral and physiological responses to stressors via blood-borne mediators, such as cytokines, chemokines, and hormones. Signaling by these molecules is mediated by the semipermeable blood–brain barrier (BBB) made up of a monocellular layer forming an integral part of the neuroimmune axis. BBB permeability can be altered and even diminished by both external factors (e.g., chemical agents) and internal conditions (e.g., acute or chronic stress, or cross-signaling from the hypothalamic–pituitary–gonadal (HPG) axis). Such a complex network of regulatory interactions that possess feed-forward and feedback connections can have multiple response dynamics that may include several stable homeostatic states beyond normal health. Here we compare immune and hormone measures in the blood of human clinical samples and mouse models of Gulf War Illness (GWI) subtyped by exposure to traumatic stress for subtyping this complex illness. We do this via constructing a detailed logic model of HPA–HPG–Immune regulatory behavior that also considers signaling pathways across the BBB to neuronal–glial interactions within the brain. We apply conditional interactions to model the effects of changes in BBB permeability. Several stable states are identified in the system beyond typical health. Following alignment of the human and mouse blood profiles in the context of the model, mouse brain sample measures were used to infer the neuroinflammatory state in human GWI and perform treatment simulations using a genetic algorithm to optimize the Monte Carlo simulations of the putative treatment strategies aimed at returning the ill system back to health. We identify several ideal multi-intervention strategies and potential drug candidates that may be used to treat chronic neuroinflammation in GWI.

Photoactivated Indium Phosphide Quantum Dots Treat Multidrug-Resistant Bacterial Abscesses In Vivo

The increasing prevalence of drug-resistant bacterial strains is causing illness and death in an unprecedented number of people around the globe. Currently implemented small-molecule antibiotics are both increasingly less efficacious and perpetuating the evolution of resistance. Here, we propose a new treatment for drug-resistant bacterial infection in the form of indium phosphide quantum dots (InP QDs), semiconductor nanoparticles that are activated by light to produce superoxide. We show that the superoxide generated by InP QDs is able to effectively kill drug-resistant bacteria in vivo to reduce subcutaneous abscess infection in mice without being toxic to the animal. Our InP QDs are activated by near-infrared wavelengths with high transmission through skin and tissues and are composed of biocompatible materials. Body weight and organ tissue histology show that the QDs are nontoxic at a macroscale. Inflammation and oxidative stress markers in serum demonstrate that the InP QD treatment did not result in measurable effects on mouse health at concentrations that reduce drug-resistant bacterial viability in subcutaneous abscesses. The InP QD treatment decreased bacterial viability by over 3 orders of magnitude in subcutaneous abscesses formed in mice. These InP QDs thus provide a promising alternative to traditional small-molecule antibiotics, with the potential to be applied to a wide variety of infection types, including wound, respiratory, and urinary tract infections.

Glucocorticoids: Dr. Jekyll and Mr. Hyde of Hippocampal Neuroinflammation

Glucocorticoids (GCs) are an important component of adaptive response of an organism to stressogenic stimuli, a typical stress response being accompanied by elevation of GC levels in blood. Anti-inflammatory effects of GCs are widely used in clinical practice, while pro-inflammatory effects of GCs are believed to underlie neurodegeneration. This is particularly critical for the hippocampus, brain region controlling both cognitive function and emotions/affective behavior, and selectively vulnerable to neuroinflammation and neurodegeneration. The hippocampus is believed to be the main target of GCs since it has the highest density of GC receptors potentially underlying high sensitivity of hippocampal cells to severe stress. In this review, we analyzed the results of studies on pro- and anti-inflammatory effects of GCs in the hippocampus in different models of stress and stress-related pathologies. The available data form a sophisticated, though often quite phenomenological, picture of a modulatory role of GCs in hippocampal neuroinflammation. Understanding the dual nature of GC-mediated effects as well as causes and mechanisms of switching can provide us with effective approaches and tools to avert hippocampal neuroinflammatory events and as a result to prevent and treat brain diseases, both neurological and psychiatric. In the framework of a mechanistic view, we propose a new hypothesis describing how the anti-inflammatory effects of GCs may transform into the pro-inflammatory ones. According to it, long-term elevation of GC level or preliminary treatment with GC triggers accumulation of FKBP51 protein that suppresses activity of GC receptors and activates pro-inflammatory cascades, which, finally, leads to enhanced neuroinflammation.

Anxiety-like behavior and intestinal microbiota changes as strain-and sex-dependent sequelae of mild food allergy in mouse models of cow's milk allergy

A number of studies have reported comorbidity of food allergies with various neuropsychiatric disorders, such as anxiety, depression, attention-deficit hyperactivity disorder, and autism. However, inconsistent results across clinical studies have left the association between food allergy and behavioral disorders inconclusive. We postulated that the heterogeneities in genetic background among allergic cohorts affect symptom presentation and severity of food allergy, introducing bias in patient selection criteria toward individuals with overt physical reactions. To understand the influence of genetic background on food allergy symptoms and behavioral changes beyond anaphylaxis, we generated mouse models with mild cow's milk allergy by sensitizing male and female C57BL/6J and BALB/cJ mice to a bovine whey protein, β-lactoglobulin (BLG; Bos d 5). We compared strain- and sex-dependent differences in their immediate physical reactions to BLG challenge as well as anxiety-like behavior one day after the challenge. While reactions to the allergen challenge were either absent or mild for all groups, a greater number of BLG-sensitized BALB/cJ mice presented visible symptoms and hypothermia compared to C57BL/6J mice. Interestingly, male mice of both strains displayed anxiety-like behavior on an elevated zero maze without exhibiting cognitive impairment with the cross maze test. Further characterization of plasma cytokines/chemokines and fecal microbiota also differentiated strain- and sex-dependent effects of BLG sensitization on immune-mediator levels and bacterial populations, respectively. These results demonstrated that the genetic variables in mouse models of milk allergy influenced immediate physical reactions to the allergen, manifestation of anxiety-like behavior, levels of immune responses, and population shift in gut microbiota. Thus, stratification of allergic cohorts by their symptom presentations and severity may strengthen the link between food allergy and behavioral disorders and identify a population(s) with specific genetic background that have increased susceptibility to allergy-associated behavioral disorders.

Toll-like receptor 4 methylation grade is linked to depressive symptom severity

This study explores potential associations between the methylation of promoter-associated CpG sites of the toll-like receptor (TLR)-family, plasma levels of pro-inflammatory proteins and depressive symptoms in young female psychiatric patients. Ratings of depressive symptoms and blood samples were obtained from 92 young women seeking psychiatric care. Methylation of 32 promoter-associated CpG sites in TLR1 to TLR10 was analysed using the Illumina Infinium Methylation EPIC BeadChip. Expression levels of 91 inflammatory proteins were determined by proximity extension assay. Statistical correlations between depressive state, TLR1-10 methylation and inflammatory proteins were investigated. Four additional cohorts were studied to evaluate the generalizability of the findings. In the discovery cohort, methylation grade of cg05429895 (TLR4) in blood was inversely correlated with depressive symptoms score in young adults. After correction for multiple testing, plasma levels of macrophage inflammatory protein 1β (MIP-1β/CCL4) were associated with both TLR4 methylation and depressive symptom severity. A similar inverse association between TLR4 methylation in blood and affective symptoms score was also found in a cohort of 148 both males and females (<40 years of age) from the Danish Twin Registry. These findings were not, however, replicated in three other external cohorts; which differed from the first two cohorts by a higher age and mixed ethnicities, thus limiting the generalizability of our findings. However, TLR4 methylation inversely correlated with TLR4 mRNA expression in the Danish Twin Study indicating a functional significance of methylation at this particular CpG. Higher depression scores in young Scandinavian adults was associated with decreased methylation of TLR4 in blood.

Chronic psychological stress and lower urinary tract symptoms

It is well established that lower urinary tract symptoms (LUTS), particularly urinary urgency and incontinence, cause stress and anxiety for patients. However, there is mounting evidence that the relationship between these two factors is bidirectional and that chronic psychological stress itself can result in the development of symptoms such as urinary frequency, urgency, incontinence, and pelvic pain. This review considers the evidence that such a relationship exists and reviews the literature from clinical and animal studies to identify some of the mechanisms that might be involved. Inflammatory responses induced by chronic stress appear to offer the strongest link to bladder dysfunction. There is overwhelming evidence, both in patients and animal models, for a release of pro-inflammatory cytokines and chemokines during periods of chronic stress. Furthermore, cytokines have been shown to cause bladder dysfunction and pain via actions in the central nervous system and locally in the bladder. In the brain and spinal cord, pro-inflammatory cytokines influence the regulation of micturition pathways by corticotropin-releasing factor (CRF) and its receptors, while peripherally cytokines affect bladder function, directly causing detrusor hypertrophy and afferent nerve hypersensitivity. There is little information on which treatments may have most benefit for stressed/anxious patients with LUTS, but animal studies suggest traditional drugs for overactive bladder (solifenacin, mirabegron) are more effective on LUTS than anxiolytic drugs (fluoxetine, imipramine). The preliminary preclinical data for CRF receptor antagonists is not consistent. A clearer understanding of the mechanisms involved in stress-induced LUTS should provide a basis for improved treatment of this condition.

Pulmonary and renal tolerance of cisplatin-based regimens combining intravenous and endotracheal routes for lung cancer treatment in mice

Despite recent advances, platinum-based chemotherapy (partially composed of cisplatin, CIS) remains the backbone of non-small-cell lung cancer treatment. As CIS presents a cumulative and dose-limiting nephrotoxicity, it is currently administered with an interruption phase of 3-4 weeks between treatment cycles. During these periods, the patient recovers from the treatment side effects but so does the tumour. Our strategy is to increase the treatment frequency by delivering a cisplatin controlled-release dry powder for inhalation (CIS-DPI) formulation during these off-cycles to expose the tumour environment for longer to CIS, increasing its effectiveness. This is promising as long as the pulmonary and renal toxicities remain acceptable. The aim of the present investigation was to evaluate the pulmonary and renal tolerance of CIS-DPI (three times per cycle) and CIS using the intravenous (IV) route (CIS-IV) (one time per cycle) as monotherapies and to optimize their combination in terms of dose and schedule. At the maximum tolerated dose (MTD), combining CIS-DPI and CIS-IV impaired the pulmonary and the renal tolerance. Therefore, pulmonary tolerance was improved when the CIS-IV dose was decreased by 25% (to 1.5 mg/kg) while maintaining the MTD for CIS-DPI. In addition to this dose adjustment, a delay of 24 h between CIS-DPI and CIS-IV administrations limited the acute kidney injury.

Animal Models of Depression: What Can They Teach Us about the Human Disease?

Depression is apparently the most common psychiatric disease among the mood disorders affecting about 10% of the adult population. The etiology and pathogenesis of depression are still poorly understood. Hence, as for most human diseases, animal models can help us understand the pathogenesis of depression and, more importantly, may facilitate the search for therapy. In this review we first describe the more common tests used for the evaluation of depressive-like symptoms in rodents. Then we describe different models of depression and discuss their strengths and weaknesses. These models can be divided into several categories: genetic models, models induced by mental acute and chronic stressful situations caused by environmental manipulations (i.e., learned helplessness in rats/mice), models induced by changes in brain neuro-transmitters or by specific brain injuries and models induced by pharmacological tools. In spite of the fact that none of the models completely resembles human depression, most animal models are relevant since they mimic many of the features observed in the human situation and may serve as a powerful tool for the study of the etiology, pathogenesis and treatment of depression, especially since only few patients respond to acute treatment. Relevance increases by the fact that human depression also has different facets and many possible etiologies and therapies.

Neurobiology of resilience in depression: immune and vascular insights from human and animal studies

Major depressive disorder (MDD) is a chronic and recurrent psychiatric condition characterized by depressed mood, social isolation and anhedonia. It will affect 20% of individuals with considerable economic impacts. Unfortunately, 30-50% of depressed individuals are resistant to current antidepressant treatments. MDD is twice as prevalent in women and associated symptoms are different. Depression's main environmental risk factor is chronic stress, and women report higher levels of stress in daily life. However, not every stressed individual becomes depressed, highlighting the need to identify biological determinants of stress vulnerability but also resilience. Based on a reverse translational approach, rodent models of depression were developed to study the mechanisms underlying susceptibility vs resilience. Indeed, a subpopulation of animals can display coping mechanisms and a set of biological alterations leading to stress resilience. The aetiology of MDD is multifactorial and involves several physiological systems. Exacerbation of endocrine and immune responses from both innate and adaptive systems are observed in depressed individuals and mice exhibiting depression-like behaviours. Increasing attention has been given to neurovascular health since higher prevalence of cardiovascular diseases is found in MDD patients and inflammatory conditions are associated with depression, treatment resistance and relapse. Here, we provide an overview of endocrine, immune and vascular changes associated with stress vulnerability vs. resilience in rodents and when available, in humans. Lack of treatment efficacy suggests that neuron-centric treatments do not address important causal biological factors and better understanding of stress-induced adaptations, including sex differences, could contribute to develop novel therapeutic strategies including personalized medicine approaches.

Proton scanning and X-ray beam irradiation induce distinct regulation of inflammatory cytokines in a preclinical mouse model

PURPOSE

Conventional X-ray radiotherapy induces a pro-inflammatory response mediated by altered expression of inflammation-regulating cytokines. Proton scanning and X-ray irradiation produce distinct changes to cytokine gene expression in vitro suggesting that proton beam therapy may induce an inflammatory response dissimilar to that of X-ray radiation. The purpose of the present study was to determine whether proton scanning beam radiation and conventional X-ray photon radiation would induce differential regulation of circulating cytokines in vivo.

MATERIALS AND METHODS

Female CDF1 mice were irradiated locally at the right hind leg using proton pencil beam scanning or X-ray photons. Blood samples were obtained from two separate mice groups. Samples from one group were drawn by retro-orbital puncture 16 months post irradiation, while samples from the other group were drawn 5 and 30 days post irradiation. Concentration of the cytokines IL-6, IL-1β, IL-10, IL-17A, IFN-γ, and TNFα was measured in plasma using bead-based immunoassays.

RESULTS

The cytokines IL-6, IL-1β, IL-10, IFN-γ, and TNFα were expressed at lower levels in plasma samples from proton-irradiated mice compared with X-ray-irradiated mice 16 months post irradiation. The same cytokines were downregulated in proton-irradiated mice 5 days post irradiation when compared to controls, while at day 30 expression had increased to the same level or higher. X-ray radiation did not markedly change expression levels at days 5 and 30.

CONCLUSIONS

The inflammatory response to proton and X-ray irradiation seem to be distinct as the principal pro-inflammatory cytokines are differentially regulated short- and long-term following irradiation. Both the development of normal tissue damage and efficacy of immunotherapy could be influenced by an altered inflammatory response to irradiation.

Repeated social defeat stress induces neutrophil mobilization in mice: maintenance after cessation of stress and strain-dependent difference in response

BACKGROUND AND PURPOSE

Inflammation has been associated with stress-related mental disturbances. Rodent studies have reported that blood-borne cytokines are crucial for stress-induced changes in emotional behaviours. However, the roles and regulation of leukocytes in chronic stress remain unclear.

EXPERIMENTAL APPROACH

Adult male C57BL/6N mice were subjected to repeated social defeat stress (R-SDS) with two protocols which differed in stress durations, stress cycles, and housing conditions, followed by the social interaction test. The numbers of leukocyte subsets in the bone marrow, spleen, and blood were determined by flow cytometry shortly after or several days after R-SDS. These leukocyte changes were studied in two strains of mice with different stress susceptibility, C57BL/6N and BALB/c mice.

KEY RESULTS

R-SDS with both protocols similarly induced social avoidance in C57BL/6N mice. In the bone marrow, neutrophils and monocytes were increased, and T cells, B cells, NK cells, and dendritic cells were decreased with both protocols. In the blood, neutrophils and monocytes were increased with both protocols, whereas T cells, B cells, NK cells, and dendritic cells were decreased with one of these. Neutrophils and monocytes were also increased in the spleen. Changes in the bone marrow and increased levels of circulating neutrophils were maintained for 6 days after R-SDS. BALB/c mice showed greater social avoidance and increase in circulating neutrophils than C57BL/6N mice.

CONCLUSION AND IMPLICATIONS

In two strains of mice, chronic stress induced neutrophil mobilization and its maintenance. These effects were strain-related and may contribute to the pathology of mental illness.

LINKED ARTICLES

This article is part of a themed issue on Neurochemistry in Japan. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.4/issuetoc.

Inflammatory Pathways in Psychiatric Disorders: The case of Schizophrenia and Depression

Purpose of Review

A better understanding of the key molecules/pathways underlying the pathophysiology of depression and schizophrenia may contribute to novel therapeutic strategies. In this review, we have discussed the recent developments on the role of inflammatory pathways in the pathogenesis of depression and schizophrenia.

Recent Findings

Inflammation is an innate immune response that can be triggered by various factors, including pathogens, stress and injury. Under normal conditions, the inflammatory responses quiet after pathogen clearance and tissue repair. However, abnormal long-term or chronic inflammation can lead to damaging effects. Accumulating evidence suggest that dysregulated inflammation is linked to the pathogenesis of neuropsychiatric disorders. In this review, we have discussed the roles of complement system, infiltration of peripheral immune cells into the central nervous system (CNS), the gut-brain axis, and the kynurenine pathway in depression and schizophrenia.

Summary

There is a large body of compelling evidence on the role of inflammatory pathways in depression and schizophrenia. Although most of these findings show their roles in the pathophysiology of the above disorders, additional studies are warranted to investigate the therapeutic potential of various immune signaling targets discussed in this article.

Origin and Function of Stress-Induced IL-6 in Murine Models

Acute psychological stress has long been known to decrease host fitness to inflammation in a wide variety of diseases, but how this occurs is incompletely understood. Using mouse models, we show that interleukin-6 (IL-6) is the dominant cytokine inducible upon acute stress alone. Stress-inducible IL-6 is produced from brown adipocytes in a beta-3-adrenergic-receptor-dependent fashion. During stress, endocrine IL-6 is the required instructive signal for mediating hyperglycemia through hepatic gluconeogenesis, which is necessary for anticipating and fueling "fight or flight" responses. This adaptation comes at the cost of enhancing mortality to a subsequent inflammatory challenge. These findings provide a mechanistic understanding of the ontogeny and adaptive purpose of IL-6 as a bona fide stress hormone coordinating systemic immunometabolic reprogramming. This brain-brown fat-liver axis might provide new insights into brown adipose tissue as a stress-responsive endocrine organ and mechanistic insight into targeting this axis in the treatment of inflammatory and neuropsychiatric diseases.

Animal models of post-traumatic stress disorder and novel treatment targets

Understanding the neurobiological basis of post-traumatic stress disorder (PTSD) is fundamental to accurately diagnose this neuropathology and offer appropriate treatment options to patients. The lack of pharmacological effects, too often observed with the most currently used drugs, the selective serotonin reuptake inhibitors (SSRIs), makes even more urgent the discovery of new pharmacological approaches. Reliable animal models of PTSD are difficult to establish because of the present limited understanding of the PTSD heterogeneity and of the influence of various environmental factors that trigger the disorder in humans. We summarize knowledge on the most frequently investigated animal models of PTSD, focusing on both their behavioral and neurobiological features. Most of them can reproduce not only behavioral endophenotypes, including anxiety-like behaviors or fear-related avoidance, but also neurobiological alterations, such as glucocorticoid receptor hypersensitivity or amygdala hyperactivity. Among the various models analyzed, we focus on the social isolation mouse model, which reproduces some deficits observed in humans with PTSD, such as abnormal neurosteroid biosynthesis, changes in GABAA receptor subunit expression and lack of pharmacological response to benzodiazepines. Neurosteroid biosynthesis and its interaction with the endocannabinoid system are altered in PTSD and are promising neuronal targets to discover novel PTSD agents. In this regard, we discuss pharmacological interventions and we highlight exciting new developments in the fields of research for novel reliable PTSD biomarkers that may enable precise diagnosis of the disorder and more successful pharmacological treatments for PTSD patients.

Chronic Gestational Inflammation: Transfer of Maternal Adaptation over Two Generations of Progeny

Changes in the in utero environment result in generational transfer of maladapted physiology in the context of conditions such as stress, obesity, and anxiety. Given the significant contribution of noncommunicable diseases-which are characterised by chronic inflammation-to population mortality, the potential for chronic maternal inflammation mediating foetal programming is a growing concern. The extent of generational transfer in terms of immune functionality and leukocyte glucocorticoid sensitivity was investigated over two generations of offspring (F1 and F2) in a model of chronic LPS-induced maternal inflammation in C57/BL/6 mice. Maternal inflammation resulted in glucocorticoid hypersensitivity (increased glucocorticoid receptor expression levels) in the majority of leukocyte subpopulations in both F1 and F2 offspring. Furthermore, splenocytes stimulated with LPS in vitro exhibited exacerbated inflammatory cytokine responses, which were even more prominent in F2 than F1; this effect could be ascribed to NLRP3 inflammasome hyperactivity in F1 but not F2. Current data illustrates that parental chronic inflammation may mediate the inflammatory profile in offspring, potentially propagating a maladapted proinflammatory phenotype in subsequent generations.

Maternal deprivation increases microglial activation and neuroinflammatory markers in the prefrontal cortex and hippocampus of infant rats

A relationship between neuroinflammation and the development of psychiatric disorder have been revealed by many studies in the past decade. Although studies have shown that stressors can induce long-term changes that may be related to behavioral responses, these alterations have been poorly studied soon after a stressor, such as maternal deprivation (MD). Thus, this study was designed to investigate the acute effect of experimental induction of MD on inflammatory and microglial activation markers in the brain of infant rats. Early MD was induced from postnatal day (PND) 1-10. On PND 10 the prefrontal cortex (PFC) and hippocampus from MD and control groups were removed to investigate microglial activation and neuroinflammatory markers. In the PFC the expressions of cluster of differentiation molecule 11B (CD11B), toll-like receptor (TLR)-2, and TLR-4 were increased in rats subjected to MD. The arginase expression was elevated in the PFC and hippocampus of maternally deprived rats. The cytokines interleukin-5 (IL-5), -6, -7, -10, tumor necrosis factor (TNF-α), and interferon gamma (INF-γ) were increased in the PFC of MD rats group. In the PFC the macrophage inflammatory proteins (MIP)-1α levels were reduced in MD rats group. In the hippocampus only the levels of TNF-α and INF-γ were elevated in infant rats subjected to MD. In conclusion, our results support the hypothesis that neuroinflammation and microglial activation, mainly in the PFC, could be involved with changes in the brain resident cells following MD, and these alterations could be associated to the development of psychiatric conditions late in life.

The contribution of the locus coeruleus-norepinephrine system in the emergence of defeat-induced inflammatory priming

Exposure to psychosocial stress is known to precipitate the emergence of stress related psychiatric disorders such as depression and anxiety. While mechanisms by which this occurs remain largely unclear, recent evidence points towards a causative role for inflammation. Neurotransmitters, such as norepinephrine (NE), are capable of regulating expression of proinflammatory cytokines and thus may contribute to the emergence of stress-related disorders. The locus coeruleus (LC) is the major source of norepinephrine (NE) to the brain and therefore the current study utilized N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4), an LC selective noradrenergic neurotoxin, to determine the discrete involvement of the LC-NE system in social defeat-induced inflammation in LC projection regions including the central amygdala (CeA), dorsal raphe (DR) and plasma. In the current study, rats were exposed to brief social defeat or control manipulations on 5 consecutive days. To determine whether a history of social defeat enhanced or "primed" the inflammatory response to a subsequent defeat exposure, all rats regardless of stress history were exposed to an acute social defeat challenge immediately preceeding tissue collection. As anticipated, prior history of social defeat primed inflammatory responses in the plasma and CeA while neuroinflammation in the DR was markedly reduced. Notably, DSP-4 treatment suppressed stress-induced circulating inflammatory cytokines independent of prior stress history. In contrast, neuroinflammation in the CeA and DR were greatly augmented selectively in DSP-4 treated rats with a history of social defeat. Together these data highlight the dichotomous nature of NE in stress-induced inflammatory priming in the periphery and the brain and directly implicate the LC-NE system in these processes.

Effect of Sex on Biomarker Response in a Mouse Model of the Hematopoietic Acute Radiation Syndrome

Sex is an important confounding variable in biomarker development that must be incorporated into biomarker discovery and validation. Additionally, understanding of sex as a biological variable is essential for effective translation of biomarkers in animal models to human populations. Toward these ends, we conducted high-throughput targeted metabolomics using liquid chromatography tandem mass spectrometry and multiplexed immunoassay analyses using a Luminex-based system in both male and female mice in a model of total-body irradiation at a radiation dose consistent with the hematopoietic acute radiation syndrome. Metabolomic and immunoassay analyses identified metabolites and cytokines that were significantly different in plasma from naive and irradiated C57BL/6 mice consisting of equal numbers of female and male mice at 3 d after 8.0 or 8.72 Gy, an approximate LD60-70/30 dose of total-body irradiation. An additional number of metabolites and cytokines had sex-specific responses after radiation. Analyses of sham-irradiated mice illustrate the presence of stress-related changes in several cytokines due simply to undergoing the irradiation procedure, absent actual radiation exposure. Basal differences in metabolite levels between female and male were also identified as well as time-dependent changes in cytokines up to 9 d postexposure. These studies provide data toward defining the influence of sex on plasma-based biomarker candidates in a well-defined mouse model of acute radiation syndrome.

Chronic adolescent stress sex-specifically alters central and peripheral neuro-immune reactivity in rats

Adversity during development is a reliable predictor of psychiatric disorders such as depression and anxiety which are increasingly recognized to have an immune component. We have previously demonstrated that chronic adolescent stress (CAS) in rats leads to depressive-like behavior in adulthood along with long-lasting changes to the hypothalamic-pituitary-adrenal axis and pro-inflammatory cytokine induction in the hippocampus. However, the mechanisms by which CAS promotes hippocampal inflammation are not yet defined. Here we tested the hypothesis that a history of CAS exaggerates induction of the pro-inflammatory NFκB pathway in the adult rat hippocampus without compromising the peripheral immune response. We also assessed potential sex differences because it is unclear whether females, who are twice as likely to suffer from mood disorders as males, are disproportionally affected by stress-primed inflammation. Male and female adolescent rats underwent a CAS paradigm or received no stress. Six weeks following the last stressor, all rats received a single systemic injection of either lipopolysaccharide or vehicle to unmask possible immune-priming effects of CAS. An NFκB signaling PCR array demonstrated that CAS exaggerated the expression of NFκB-related genes in the hippocampus of both males and females. Interestingly, targeted qPCR demonstrated that CAS potentiated the induction of hippocampal IL1B and REL mRNA in female rats only, suggesting that some immune effects of CAS are indeed sex-specific. In contrast to the hippocampal findings, indices of peripheral inflammation such as NFκB activity in the spleen, plasma IL-1β, IL-6, TNF-α, and corticosterone were not impacted by CAS in female rats. Despite showing no pro-inflammatory changes to hippocampal mRNA, male CAS rats displayed lower plasma corticosterone response to LPS at 2 h after injection followed by an exaggerated plasma IL-1β response at 4 h. This potentially blunted corticosterone response coupled with excessive innate immune signaling in the periphery is consistent with possible glucocorticoid resistance in males. In contrast, the effects of CAS manifested as excessive hippocampal immune reactivity in females. We conclude that while a history of exposure to chronic adolescent stress enhances adult immune reactivity in both males and females, the mechanism and manifestation of such alterations are sex-specific.

Putative Inflammatory Sensitive Mechanisms Underlying Risk or Resilience to Social Stress

It has been well recognized that exposure to stress can lead to the onset of psychosocial disorders such as depression. While there are a number of antidepressant therapies currently available and despite producing immediate neurochemical alterations, they require weeks of continuous use in order to exhibit antidepressant efficacy. Moreover, up to 30% of patients do not respond to typical antidepressants, suggesting that our understanding of the pathophysiology underlying stress-induced depression is still limited. In recent years inflammation has become a major focus in the study of depression as several clinical and preclinical studies have demonstrated that peripheral and central inflammatory mediators, including interleukin (IL)-1β, are elevated in depressed patients. Moreover, it has been suggested that inflammation and particularly neuroinflammation may be a direct and immediate link in the emergence of stress-induced depression due to the broad neural and glial effects that are elicited by proinflammatory cytokines. Importantly, individual differences in inflammatory reactivity may further explain why certain individuals exhibit differing susceptibility to the consequences of stress. In this review article, we discuss sources of individual differences such as age, sex and coping mechanisms that are likely sources of distinct changes in stress-induced neuroimmune factors and highlight putative sources of exaggerated neuroinflammation in susceptible individuals. Furthermore, we review the current literature of specific neural and glial mechanisms that are regulated by stress and inflammation including mitochondrial function, oxidative stress and mechanisms of glutamate excitotoxicity. Taken together, the impetus for this review is to move towards a better understanding of mechanisms regulated by inflammatory cytokines and chemokines that are capable of contributing to the emergence of depressive-like behaviors in susceptible individuals.

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.

Communication and social interaction anxiety enhance interleukin-1 beta and cortisol reactivity during high-stakes public speaking

BACKGROUND

Worry or fear related to speaking in front of others, or more broadly, communicating and interacting with others, is common. At elevated levels, however, it may contribute to heightened stress reactivity during acute speaking challenges. The purpose of this study was to examine multi-system physiological stress reactivity in the context of high-stakes public speaking while considering the impact of hypothesized individual difference risk factors.

METHODS

University student participants (n = 95) delivering speeches as a heavily-weighted component of their final grade had saliva samples collected immediately prior to speaking, immediately after, and 20 min after speech completion. Saliva samples were assayed for alpha amylase (sAA), cortisol, and interleukin-1 beta (IL-1β). Self-reported communication anxiety, social interaction anxiety, rejection sensitivity, and sex were assessed as risk factors for heightened stress reactivity.

RESULTS

Salivary sAA, cortisol, and IL-1β significantly changed following speech delivery. Multivariate analyses demonstrated that elevated levels of self-reported communication anxiety and social interaction anxiety were independently associated with increased cortisol and IL-1β responses and combined to enhance HPA axis and inflammatory cytokine activity further (i.e., cortisol and IL-1β AUC_I). Sex and rejection sensitivity were unrelated to physiological stress reactivity.

CONCLUSIONS

These findings suggest that individuals with elevated communication and interaction fears may be at increased risk of heightened neuroendocrine and inflammatory responses following exposure to acute social stressors. Both types of anxiety may combine to increase physiological reactivity further, with unknown, though likely insalubrious, health consequences over time.

CD8+ T cells promote cytokine responses to stress

Psychological stress is known to have profound effects on immune function and to promote inflammatory conditions. Elevated circulating levels of cytokines associated with stress are known to increase the risk to several diseases, but little is known about this mechanism. This study assessed the role of T cells on cytokine levels after exposure to stress in the learned helplessness paradigm. Adoptive transfer of CD4⁺ T cells into Rag2^-/- mice did not change cytokine levels to stress while CD8⁺ T cells resulted in an increase in TNF-α, IL-6 and IFN-γ in stressed Rag2^-/- mice. Moreover, depletion of CD8⁺ T cells in WT mice abolished these cytokine responses to stress. Corticosterone and behavioral stress responsiveness was impaired in Rag2^-/- mice reconstituted with CD8⁺ T cells. Notably, depletion of these cells in WT mice had no effect on behavior or corticosterone levels. Exposure to stress did not change the expression of canonical markers of T cell activation including CD62L and CD44 or modified intracellular cytokine content, suggesting that they are not the main producers of circulating cytokines in response to stress. These results show that CD8⁺ T cells promote TNF-α, IL-6 and IFN-γ responses to stress, possibly by stimulating non-lymphoid cells.

Alterations of the Innate Immune System in Susceptibility and Resilience After Social Defeat Stress

Dysregulation of innate immune responses has frequently been reported in stress-associated psychiatric disorders such as major depression. In mice, enhanced circulating cytokine levels as well as altered innate immune cell numbers have been found after stress exposure. In addition, stress-induced recruitment of peripheral monocytes to the brain has been shown to promote anxiety-like behavior. However, it is yet unclear whether specific differences in the innate immune system are associated with stress susceptibility or resilience in mice. Utilizing chronic social defeat, a model of depression and stress vulnerability, we characterized peripheral and brain-invading myeloid cells in stress-susceptible and resilient animals. In all defeated animals, we found reduced percentages of CD11c⁺ dendritic cells (DCs) by flow cytometry in the spleen when compared to non-defeated controls. Exclusively in susceptible mice conventional DCs of the spleen showed up-regulated expression of MHC class II and co-stimulatory CD80 molecules pointing toward an enhanced maturation phenotype of these cells. Susceptible, but not resilient animals further exhibited an increase in inflammatory Ly6C^hi monocytes and higher numbers of spleen-derived CD11b⁺ cells that produced the proinflammatory cytokine tumor necrosis factor (TNF) upon lipopolysaccharide (LPS) stimulation. Increased percentages of peripheral CD45^hi CD11b⁺ cells immigrated into the brain of defeated mice, regardless of resilience or susceptibility. However, cellular infiltrates in the brain of susceptible mice contained higher percentages of CC chemokine receptor 2 (CCR2⁺) Ly6C^hi monocytes representing an inflammatory phenotype. Thus, we defined specific stress-related immune signatures involving conventional DCs and inflammatory Ly6C^hi monocytes in susceptible and resilient mice. Together, our findings suggest an impact of the innate immune system in vulnerability to stress-related disorders such as major depression.

The association between inflammatory markers (iNOS, HO-1, IL-33, MIP-1β) and depression with and without posttraumatic stress disorder

BACKGROUND

Both major depression and posttraumatic stress disorder (PTSD) are characterized by inflammation, increased concentration levels of proinflammatory cytokines, decreased neurogenesis followed by neuroprogression, as well as mitochondrial and the hypothalamic-pituitary-adrenal axis dysfunction. Elevated levels of oxidative stress caused by an increased activity of prooxidants over antioxidants are also observed. Based on several reports, depressive episodes can lead to the sensitization of immune-inflammatory pathways. Thus, depression, PTSD, and depression comorbid with PTSD are associated with immune-inflammatory markers. The study aimed at evaluating concentration levels of iNOS, HO-1, IL-33, and MIP-1β in depression with and without PTSD.

METHODS

A total number of participants enrolled in the study was 460. Out of them, 420 subjects with various levels of depression severity constituted the study group (210 males and 210 females), and 40 subjects (20 males and 20 females) constituted the control group. Each study group comprised 60 patients (30 males and 30 females) with mild depression (MD), moderate depression (MOD), severe depression (SeD), MD and PTSD (MD+PTSD), MOD and PTSD (MOD+PTSD), SeD and PTSD (SeD+PTSD), and with PTSD alone. At 7:00 a.m., all patients had serum concentrations of iNOS, HO-1, IL-33, MIP-1β determined using ELISA.

RESULTS

Both depression exacerbation and PTSD comorbidity led to elevated levels of iNOS, HO-1, IL-33, and MIP-1β.

CONCLUSION

Depression both with and without PTSD leads to elevated levels of inflammation and an oxidant/antioxidant imbalance. Alterations in both cytokines and oxidative stress are related to the mechanisms responsible for the development of depressive symptoms.

Changes in the concentrations of inflammatory and oxidative status biomediators (MIP-1 α, PMN elastase, MDA, and IL-12) in depressed patients with and without posttraumatic stress disorder

BACKGROUND

Both proinflammatory cytokines and oxidative stress are considered an imbalance between the cellular production of reactive oxygen species and the antioxidant defense mechanisms. An inflammatory response that occurs in depression leads to a synergy between pro-inflammatory cytokines and oxidative stress. This synergy induces common signal transduction pathways that boost the inflammatory cascade. The object of this study was to assess the concentrations of inflammatory and oxidative status biomediators such as MIP-1α, PMN elastase, MDA, and IL-12 in depressed patients with and without posttraumatic stress disorder (PTSD), and with PTSD alone.

METHODS

The number of participants enrolled in the study was 460. Out of them, 420 were determined to be suffering from depression, and 40 (20 males and 20 females) comprised the control group. The subjects were divided into groups, each consisting of 60 participants (30 males and 30 females) with: mild depression (MD), moderate depression (MOD), severe depression (SeD), MD and PTSD (MD+PTSD), MOD and PTSD (MOD+PTSD), SeD and PTSD (Sed+PTSD), and PTSD alone. At 7:00 a.m. all patients had blood samples collected to assess serum concentrations of the studied parameters using the Elisa method.

RESULTS

Depression became more severe as the concentration levels of MIP-1α, PMN elastase, MDA, and IL-12 changed.

CONCLUSION

Studied parameters can be used as markers of chronic stress in both depression and PTSD, either comorbid or alone, to make an early diagnosis and evaluate disease severity. Revealed changes confirm the presence of a biological response in depression.

Early Life Stress Alters Adult Inflammatory Responses in a Mouse Model for Depression

Increased levels of pro-inflammatory cytokines and hypothalamic pituitary axis (HPA) activity are strongly associated with depression. Childhood stress and trauma predispose individuals for increased inflammatory tone and major depression in later life, suggesting that early life reprogramming of the stress/immune axis may be involved in the pathogenesis of depression. In this study, we are using a short duration neonatal maternal separation stress (MS) paradigm in mice to test if early life stress can impact plasma and brain inflammatory tone into adulthood. We use ELISA assays to investigate levels of the pro-inflammatory cytokines IL-1beta, IL-2, IL-6 and TNF-alpha, in both plasma and brain tissue of mice exposed to MS (STR), their unseparated littermates (LMC) and unhandled age matched controls (AMC). Cytokine levels are assessed in male and female adult mice with and without a bacterial lipopolysaccharide (LPS) induced immune challenge. We present evidence that stress exposure, during the first week of life, predisposes both male and female mice for increased inflammatory cytokine secretion, peripherally and in brain tissue, upon adult exposure to lipopolysaccharide (LPS).

Physical versus psychological social stress in male rats reveals distinct cardiovascular, inflammatory and behavioral consequences

Repeated exposure to social stress can precipitate the development of psychosocial disorders including depression and comorbid cardiovascular disease. While a major component of social stress often encompasses physical interactions, purely psychological stressors (i.e. witnessing a traumatic event) also fall under the scope of social stress. The current study determined whether the acute stress response and susceptibility to stress-related consequences differed based on whether the stressor consisted of physical versus purely psychological social stress. Using a modified resident-intruder paradigm, male rats were either directly exposed to repeated social defeat stress (intruder) or witnessed a male rat being defeated. Cardiovascular parameters, behavioral anhedonia, and inflammatory cytokines in plasma and the stress-sensitive locus coeruleus were compared between intruder, witness, and control rats. Surprisingly intruders and witnesses exhibited nearly identical increases in mean arterial pressure and heart rate during acute and repeated stress exposures, yet only intruders exhibited stress-induced arrhythmias. Furthermore, re-exposure to the stress environment in the absence of the resident produced robust pressor and tachycardic responses in both stress conditions indicating the robust and enduring nature of social stress. In contrast, the long-term consequences of these stressors were distinct. Intruders were characterized by enhanced inflammatory sensitivity in plasma, while witnesses were characterized by the emergence of depressive-like anhedonia, transient increases in systolic blood pressure and plasma levels of tissue inhibitor of metalloproteinase. The current study highlights that while the acute cardiovascular responses to stress were identical between intruders and witnesses, these stressors produced distinct differences in the enduring consequences to stress, suggesting that witness stress may be more likely to produce long-term cardiovascular dysfunction and comorbid behavioral anhedonia while exposure to physical stressors may bias the system towards sensitivity to inflammatory disorders.

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.