The neurobiology of aggression and rage: role of cytokines

Aggression modulator: Understanding the multifaceted role of the dorsal raphe nucleus

Aggressive behavior is instinctively driven behavior that helps animals to survive and reproduce and is closely related to multiple behavioral and physiological processes. The dorsal raphe nucleus (DRN) is an evolutionarily conserved midbrain structure that regulates aggressive behavior by integrating diverse brain inputs. The DRN consists predominantly of serotonergic (5-HT:5-hydroxytryptamine) neurons and decreased 5-HT activity was classically thought to increase aggression. However, recent studies challenge this 5-HT deficiency model, revealing a more complex role for the DRN 5-HT system in aggression. Furthermore, emerging evidence has shown that non-5-HT populations in the DRN and specific neural circuits contribute to the escalation of aggressive behavior. This review argues that the DRN serves as a multifaceted modulator of aggression, acting not only via 5-HT but also via other neurotransmitters and neural pathways, as well as different subsets of 5-HT neurons. In addition, we discuss the contribution of DRN neurons in the behavioral and physiological aspects implicated in aggressive behavior, such as arousal, reward, and impulsivity, to further our understanding of DRN-mediated aggression modulation.

Inflammation and Behavior Changes in Dogs and Cats

Sickness is a normal response to infections or stress triggered by proinflammatory cytokines that drive local and systemic inflammatory responses. Proinflammatory cytokines act on the brain causing the so called "sickness behavior,"which is thought to improve recovery but can become maladaptive in the long term. Chronic inflammation characterizes many diseases and there is some evidence that dogs and cats experience age-associated increases in inflammation, a condition named "inflammaging." A complex and multifactorial relationship exists between these inflammatory mechanisms, pain, and psychological illness that may complicate veterinary diagnosis and affect the outcome.

Anger: an underappreciated destructive force in healthcare

Anger is an emotional state that occurs when unexpected things happen to or around oneself and is "an emotional state that varies in intensity from mild irritation to intense fury and rage." It is defined as "a strong feeling of displeasure and usually of antagonism," an emotion characterized by tension and hostility arising from frustration, real or imagined injury by another, or perceived injustice. It can manifest itself in behaviors designed to remove the object of the anger (e.g., determined action) or behaviors designed merely to express the emotion. For the Roman philosopher Seneca anger is not an uncontrollable, impulsive, or instinctive reaction. It is, rather, the cognitive assent that such initial reactions to the offending action or words are in fact unjustified. It is, rather, the cognitive assent that such initial reactions to the offending action or words are in fact unjustified. It seems that the year 2022 was a year when many Americans were plainly angry. "Why is everyone so angry?" the New York Times asked in the article "The Year We Lost It." We believe that Seneca is correct in that anger is unacceptable. Anger is a negative emotion that must be controlled, and Seneca provides us with the tools to avoid and destroy anger. Health care professionals will be more effective, content, and happier if they learn more about Seneca's writings about anger and implement his wisdom on anger from over 2000 years ago.

Plasma and cerebrospinal fluid inflammatory markers and human aggression

A growing body of work suggests that individuals with aggressive behavior and/or aggressive tendencies have evidence of chronic, low level, inflammation as manifested by elevated circulating levels of acute phase reactant proteins and pro-inflammatory cytokines. While animal studies report that direct application of pro-inflammatory proteins in brain increase aggressive behavior, there is no data on the relationship of central levels of these proteins and aggression in human subjects. We simultaneously measured levels of both plasma and lumbar cerebrospinal fluid (CSF) C-Reactive Protein (CRP) and IL-6, IL-8, and TNF-α in 77 medically healthy, drug-free, individuals with varying degrees of aggression including 22 individuals with DSM-5 Intermittent Explosive Disorder (IED). Aggression was assessed using the Life History of Aggression (LHA) and the Buss-Perry Aggression Questionnaire (BPAQ). Plasma and CSF levels of CRP, IL-8, and TNF-α, but not IL-6, correlated significantly with each other. Aggressive individuals with IED displayed elevated plasma, but not CSF, levels of proinflammatory markers and this relationship was specific to IED. Similarly, composite aggression scores correlated significantly with plasma, but not CSF, pro-inflammatory markers. Aggressive behavior in humans is correlated with Plasma, but not CSF, proinflammatory markers despite the observation that these two sets of markers are significantly correlated. Since the direct application of proinflammatory proteins in brains of animals increase aggressive behavior, proinflammatory proteins likely influence brain-based behavior in a manner not reflected in lumbar CSF.

Chronic ethanol induces a pro-inflammatory switch in interleukin-1β regulation of GABAergic signaling in the medial prefrontal cortex of male mice

Neuroimmune pathways regulate brain function to influence complex behavior and play a role in several neuropsychiatric diseases, including alcohol use disorder (AUD). In particular, the interleukin-1 (IL-1) system has emerged as a key regulator of the brain's response to ethanol (alcohol). Here we investigated the mechanisms underlying ethanol-induced neuroadaptation of IL-1β signaling at GABAergic synapses in the prelimbic region of the medial prefrontal cortex (mPFC), an area responsible for integrating contextual information to mediate conflicting motivational drives. We exposed C57BL/6J male mice to the chronic intermittent ethanol vapor-2 bottle choice paradigm (CIE-2BC) to induce ethanol dependence, and conducted ex vivo electrophysiology and molecular analyses. We found that the IL-1 system regulates basal mPFC function through its actions at inhibitory synapses on prelimbic layer 2/3 pyramidal neurons. IL-1β can selectively recruit either neuroprotective (PI3K/Akt) or pro-inflammatory (MyD88/p38 MAPK) mechanisms to produce opposing synaptic effects. In ethanol naïve conditions, there was a strong PI3K/Akt bias leading to a disinhibition of pyramidal neurons. Ethanol dependence produced opposite IL-1 effects - enhanced local inhibition via a switch in IL-1β signaling to the canonical pro-inflammatory MyD88 pathway. Ethanol dependence also increased cellular IL-1β in the mPFC, while decreasing expression of downstream effectors (Akt, p38 MAPK). Thus, IL-1β may represent a key neural substrate in ethanol-induced cortical dysfunction. As the IL-1 receptor antagonist (kineret) is already FDA-approved for other diseases, this work underscores the high therapeutic potential of IL-1 signaling/neuroimmune-based treatments for AUD.

The Predictive Value of Monocyte/High-Density Lipoprotein Ratio (MHR) and Positive Symptom Scores for Aggression in Patients with Schizophrenia

Background and Objectives: Schizophrenia with aggression often has an inflammatory abnormality. The monocyte/high-density lipoprotein ratio (MHR), neutrophil/high-density lipoprotein ratio (NHR), platelet/high-density lipoprotein ratio (PHR) and lymphocyte/high-density lipoprotein ratio (LHR) have lately been examined as novel markers for the inflammatory response. The objective of this study was to assess the relationship between these new inflammatory biomarkers and aggression in schizophrenia patients. Materials and Methods: We enrolled 214 schizophrenia inpatients in our cross-sectional analysis. They were divided into the aggressive group (n = 94) and the non-aggressive group (n = 120) according to the Modified Overt Aggression Scale (MOAS). The severity of schizophrenia was assessed using the Positive and Negative Syndrome Scale (PANSS). The numbers of platelets (PLT), neutrophils (NEU), lymphocytes (LYM), monocytes (MON) and the high-density lipoprotein (HDL) content from subjects were recorded. The NHR, PHR, MHR and LHR were calculated. We analyzed the differences between those indexes in these two groups, and further searched for the correlation between inflammatory markers and aggression. Results: Patients with aggression had higher positive symptom scores (p = 0.002). The values of PLT, MON, MHR and PHR in the aggressive group were considerably higher (p < 0.05). The NHR (r = 0.289, p < 0.01), LHR (r = 0.213, p < 0.05) and MHR (r = 0.238, p < 0.05) values of aggressive schizophrenia patients were positively correlated with the total weighted scores of the MOAS. A higher MHR (β = 1.529, OR = 4.616, p = 0.026) and positive symptom scores (β = 0.071, OR = 1.047, p = 0.007) were significant predictors of aggression in schizophrenia patients. Conclusions: The MHR and the positive symptom scores may be predictors of aggressive behavior in schizophrenia patients. The MHR, a cheap and simple test, may be useful as a clinical tool for risk stratification, and it may direct doctors’ prevention and treatment plans in the course of ordinary clinical care.

Mechanisms of sex differentiation and sex reversal in hermaphrodite fish as revealed by the Epinephelus coioides genome

Most grouper species are functional protogynous hermaphrodites, but the genetic basis and the molecular mechanisms underlying the regulation of this unique reproductive strategy remain enigmatic. In this study, we report a high-quality chromosome-level genome assembly of the representative orange-spotted grouper (Epinephelus coioides). No duplication or deletion of sex differentiation-related genes was found in the genome, suggesting that sex development in this grouper may be related to changes in regulatory sequences or environmental factors. Transcriptomic analyses showed that aromatase and retinoic acid are probably critical to promoting ovarian fate determination, and follicle-stimulating hormone triggers the female-to-male sex change. Socially controlled sex-change studies revealed that, in sex-changing fish, the brain's response to the social environment may be mediated by activation of the phototransduction cascade and the melatonin synthesis pathway. In summary, our genomic and experimental results provide novel insights into the molecular mechanisms of sex differentiation and sex change in the protogynous groupers.

Role of β-Klotho and Malondialdehyde in Metabolic Disorders, HIV Infection, and Antiretroviral Therapy

Metabolic alterations, resulting from factors such as obesity or infections (HIV), generate inflammation in the body, affecting the immune system and causing oxidative stress. Prolonged exposure to antiretroviral therapy (ART) conditions the appearance of alterations considered risk factors for metabolic syndrome (MetS), affecting the quality of life in people living with HIV/AIDS (PLWHA). β-klotho is a protein that can counteract levels of oxidative stress. The aim was to determine the relation of β-klotho and oxidative stress with metabolic alterations in PLWHA. We hypothesized that levels of β-klotho and malondialdehyde (MDA) are related in PLWHA on ART with overweight/obesity. As a result of comparing cases versus controls, significant differences were obtained in levels of β-klotho (p = 0.011), MDA (p < 0.0001), body mass index (p = 0.001), and weight (p < 0.0001). The presence of MetS in PLWHA was 21.2% and 10.6% according to the World Health Organization and ATP III (National Cholesterol Education Program Adult Treatment Panel III) criteria, respectively. The founded correlations were of β-klotho (r = 0.019) and MDA (r = 0.0001), both with CD4+ cells in PLWHA. In controls, β-klotho was correlated with very low-density lipoprotein (r = 0.035) and atherogenic index (AI; r = 0.037), MDA with AI (r = 0.039), cholesterol, and low-density lipoprotein (r = 0.002). The increase of inflammation in the organism, owing to HIV infection and/or the presence of obesity, conditions metabolic disruption or depletion of elements needed for homeostasis in the human body.

Neuromodulatory effect of interleukin 1β in the dorsal raphe nucleus on individual differences in aggression

Heightened aggressive behavior is considered as one of the central symptoms of many neuropsychiatric disorders including autism, schizophrenia, and dementia. The consequences of aggression pose a heavy burden on patients and their families and clinicians. Unfortunately, we have limited treatment options for aggression and lack mechanistic insight into the causes of aggression needed to inform new efforts in drug discovery and development. Levels of proinflammatory cytokines in the periphery or cerebrospinal fluid were previously reported to correlate with aggressive traits in humans. However, it is still unknown whether cytokines affect brain circuits to modulate aggression. Here, we examined the functional role of interleukin 1β (IL-1β) in mediating individual differences in aggression using a resident-intruder mouse model. We found that nonaggressive mice exhibit higher levels of IL-1β in the dorsal raphe nucleus (DRN), the major source of forebrain serotonin (5-HT), compared to aggressive mice. We then examined the effect of pharmacological antagonism and viral-mediated gene knockdown of the receptors for IL-1 within the DRN and found that both treatments consistently increased aggressive behavior of male mice. Aggressive mice also exhibited higher c-Fos expression in 5-HT neurons in the DRN compared to nonaggressive mice. In line with these findings, deletion of IL-1 receptor in the DRN enhanced c-Fos expression in 5-HT neurons during aggressive encounters, suggesting that modulation of 5-HT neuronal activity by IL-1β signaling in the DRN controls expression of aggressive behavior.

Gene expression in peripheral blood mononuclear cells in impulsive aggression: Intermittent explosive disorder compared with non-aggressive healthy and psychiatric controls

Evidence of chronic, systemic, low levels of inflammation is present in several stress-related psychiatric conditions including schizophrenia, depression, and intermittent explosive disorder (IED). We analyzed leukocyte gene expression (mRNA) to quantify the activity of pro and anti-inflammatory signaling pathways. Work performed in non-aggressive populations has uncovered a Conserved Transcriptional Response to Adversity (CTRA) characterized by an upregulation of pro-inflammatory gene transcription in chronically stressed individuals. We used pathway-based bioinformatic analyses of genome-wide transcriptional profiles of peripheral blood leukocyte samples from IED study participants (N = 45) and controls [healthy (n = 45) and psychiatric (n = 34)], with analyses focusing on the pro-inflammatory transcription control pathway mediated by the NF-kB family of transcription factors (typically upregulated in CTRA) and the antiviral transcription control pathway mediated by anti-viral response (IRF) family transcription factors (typically downregulated in CTRA). Compared with both healthy and psychiatric controls, individuals with IED had upregulated transcriptional activity of the antiviral response (IRF), but no evidence of pro-inflammatory NF-kB activation. Analyses implicated CD4 + T cells, CD8 + T cells, and B lymphocytes in IED-related transcriptional alterations, but showed no significant indication of monocyte involvement. This suggests that the inflammatory profile of IED differs substantially from that observed previously in other stress-related disorders, and may involve a pathogen-driven adaptive immune etiology.

Global Correlations Between Chronic Inflammation and Violent Incidents: Potential Behavioral Consequences of Inflammatory Illnesses Across Socio-Demographic Levels

Introduction

This review explores the potential correlation between conditions associated with chronic inflammation and measures of violence across five socioeconomic subgroups. The hypothesis being that since chronic inflammation is associated with increased aggression, an extreme version of which is violence, there should be a correlation between incidents of violence and diseases with one or more inflammatory factors, without an equivalent correlation with the contrast group. An extension of this reasoning would predict a higher correlation among lower socio-demographic index (SDI) populations as a result of fewer resources to prevent either inflammatory disease or violent crime.

Methods

In order to examine this potential correlation, an analysis was made comparing rates of change in incidence between violence, inflammatory conditions, and a contrast group disease of noninflammatory nature, as determined by Pearson's correlation coefficient.

Results

In the low socio-demographic index, inflammatory conditions demonstrated 80% correlation with interpersonal violence, middle-low socio-demographic index inflammatory conditions demonstrated 60% correlation with interpersonal violence, middle socio-demographic index inflammatory conditions demonstrated 0% correlation with interpersonal violence, middle-high socio-demographic index inflammatory conditions demonstrated 60% correlation with interpersonal violence, and high socio-demographic index inflammatory conditions demonstrated 40% correlation with interpersonal violence.

Discussion

The majority of socio-demographic groups showed a significant correlation between rates of change in incidence of violence and inflammatory conditions. This correlation was not found with a similar frequency or strength in diseases not causally linked to inflammation. As predicted in the hypothesis, the highest correlations of inflammatory diseases with violence existed in the lower socio-demographic populations, supporting a link between inflammatory levels and incidences of violence.

Response of salivary biomarkers to an empathy triggering film sequence-a pilot study

Empathy is a multifaceted phenomenon that is difficult to measure. Self-report questionnaires are the most common and well-validated measures while currently no validated protein biomarkers associated with the empathic reaction have been established. Trigger films have been previously used in psychological research to evoke emotions. Thus, in the present randomized cross-over study we investigated the responses of nine salivary biomarkers that have been related to emotions and stress following an empathy triggering and a control film sequence. Additionally, questionnaires for empathy (Saarbrucken Personality Questionnaire (SPQ)) and current mental stress were applied and participants were asked to assess the film protagonists’ emotions using the Positive and Negative Affect Schedule. Data from 46 participants were included in the analysis. α-Amylase, IgA, IL-1β and estradiol showed a significantly different response between the empathy and control intervention. Moreover, normalized levels of these biomarkers significantly correlated with single scales of the SPQ (control film sequence: α-amylase and IgA with personal distress; estradiol with empathic concern; IL-1β with fantasy; empathy triggering film sequence: IgA with empathic concern, fantasy and the total empathy score). These findings indicated that the observed changes in salivary biomarker levels were reflective of a physiological response to the empathy triggering film sequence. Future studies using different triggers and settings will show if the identified biomarkers can be considered as surrogate markers for empathic reactions in general.

Neuromodulation by the immune system: a focus on cytokines

Interactions between the immune system and the nervous system have been described mostly in the context of diseases. More recent studies have begun to reveal how certain immune cell-derived soluble effectors, the cytokines, can influence host behaviour even in the absence of infection. In this Review, we contemplate how the immune system shapes nervous system function and how it controls the manifestation of host behaviour. Interactions between these two highly complex systems are discussed here also in the context of evolution, as both may have evolved to maximize an organism's ability to respond to environmental threats in order to survive. We describe how the immune system relays information to the nervous system and how cytokine signalling occurs in neurons. We also speculate on how the brain may be hardwired to receive and process information from the immune system. Finally, we propose a unified theory depicting a co-evolution of the immune system and host behaviour in response to the evolutionary pressure of pathogens.

Infection threat shapes our social instincts

We social animals must balance the need to avoid infections with the need to interact with conspecifics. To that end we have evolved, alongside our physiological immune system, a suite of behaviors devised to deal with potentially contagious individuals. Focusing mostly on humans, the current review describes the design and biological innards of this behavioral immune system, laying out how infection threat shapes sociality and sociality shapes infection threat. The paper shows how the danger of contagion is detected and posted to the brain; how it affects individuals’ mate choice and sex life; why it strengthens ties within groups but severs those between them, leading to hostility toward anyone who looks, smells, or behaves unusually; and how it permeates the foundation of our moral and political views. This system was already in place when agriculture and animal domestication set off a massive increase in our population density, personal connections, and interaction with other species, amplifying enormously the spread of disease. Alas, pandemics such as COVID-19 not only are a disaster for public health, but, by rousing millions of behavioral immune systems, could prove a threat to harmonious cohabitation too.

Toxoplasma gondii, Suicidal Behavior, and Intermediate Phenotypes for Suicidal Behavior

Within the general literature on infections and suicidal behavior, studies on Toxoplasma gondii (T. gondii) occupy a central position. This is related to the parasite's neurotropism, high prevalence of chronic infection, as well as specific and non-specific behavioral alterations in rodents that lead to increased risk taking, which are recapitulated in humans by T. gondii's associations with suicidal behavior, as well as trait impulsivity and aggression, mental illness and traffic accidents. This paper is a detailed review of the associations between T. gondii serology and suicidal behavior, a field of study that started 15 years ago with our publication of associations between T. gondii IgG serology and suicidal behavior in persons with mood disorders. This "legacy" article presents, chronologically, our primary studies in individuals with mood disorders and schizophrenia in Germany, recent attempters in Sweden, and in a large cohort of mothers in Denmark. Then, it reviews findings from all three meta-analyses published to date, confirming our reported associations and overall consistent in effect size [ranging between 39 and 57% elevation of odds of suicide attempt in T. gondii immunoglobulin (IgG) positives]. Finally, the article introduces certain links between T. gondii and biomarkers previously associated with suicidal behavior (kynurenines, phenylalanine/tyrosine), intermediate phenotypes of suicidal behavior (impulsivity, aggression) and state-dependent suicide risk factors (hopelessness/dysphoria, sleep impairment). In sum, an abundance of evidence supports a positive link between suicide attempts (but not suicidal ideation) and T. gondii IgG (but not IgM) seropositivity and serointensity. Trait impulsivity and aggression, endophenotypes of suicidal behavior have also been positively associated with T. gondii seropositivity in both the psychiatrically healthy as well as in patients with Intermittent Explosive Disorder. Yet, causality has not been demonstrated. Thus, randomized interventional studies are necessary to advance causal inferences and, if causality is confirmed, to provide hope that an etiological treatment for a distinct subgroup of individuals at an increased risk for suicide could emerge.

Hierarchical Representations of Aggression in a Hypothalamic-Midbrain Circuit

Although the ventromedial hypothalamus ventrolateral area (VMHvl) is now well established as a critical locus for the generation of conspecific aggression, its role is complex, with neurons responding during multiple phases of social interactions with both males and females. It has been previously unclear how the brain uses this complex multidimensional signal and coordinates a discrete action: the attack. Here, we find a hypothalamic-midbrain circuit that represents hierarchically organized social signals during aggression. Optogenetic-assisted circuit mapping reveals a preferential projection from VMHvl^vGlut2 to lPAG^vGlut2 cells, and inactivation of downstream lPAG^vGlut2 populations results in aggression-specific deficits. lPAG neurons are selective for attack action and exhibit short-latency, time-locked spiking relative to the activity of jaw muscles during biting. Last, we find that this projection conveys male-biased signals from the VMHvl to downstream lPAG^vGlut2 neurons that are sensitive to features of ongoing activity, suggesting that action selectivity is generated by a combination of pre- and postsynaptic mechanisms.

Role of the kynurenine pathway and the endocannabinoid system as modulators of inflammation and personality traits

BACKGROUND

Kynurenine pathway metabolites and endocannabinoids both exert potent regulatory effects on the immune system, but the relationship between these molecules is unknown. The role of these immunobiological mediators in emotionality and personality traits is not previously characterized.

METHODS

Interleukin-6 (IL-6), 2-arachidonoylglycerol (2-AG) and picolinic acid (PIC) were measured in the plasma of physically healthy individuals who had history of mood, anxiety, and personality disorders (n = 96) or who had no history of any psychiatric disorder (n = 56) by DSM-5 Criteria. Dimensional assessments of personality were performed using the Eysenck Personality Questionnaire (EPQ) and the Tridimensional Personality Questionnaire (TPQ).

RESULTS

Plasma IL-6 levels were significantly associated with plasma 2-AG levels and plasma PIC levels across all subjects. PIC levels were also negatively associated with 2-AG levels across all subjects, independent of IL-6 levels. In our analysis of the biological determinants of personality factors, we identified significant associations between IL-6 and novelty seeking assessment, and between PIC and neuroticism assessment.

CONCLUSIONS

These data provide evidence of a biological link between metabolites of the kynurenine pathway, the endocannabinoid system and IL-6 and suggest that these factors may influence personality traits.

Febrile and sleep responses to an immune challenge are affected by trait aggressiveness in rats

Sleep is altered in response to an immune challenge: non-rapid eye movement (NREM) sleep is increased and fragmented, REM sleep is inhibited. Sleep and immune response are affected by stress: several stressors inhibit sleep and increase waking time; stress-induced cortisol secretion affects the immune response, with immunosuppressive effects. Different levels of trait aggressiveness are associated with specific patterns of neuroendocrine and autonomic stress responsiveness. Aim of this study was to test the hypothesis that trait aggressiveness, by affecting response to stressors, modifies sleep alterations induced by the activation of the immune response. To this aim, rats were selected on the basis of their latency time to attack a male intruder in the resident-intruder test. Animals were instrumented for chronic recordings of sleep-wake activity and injected, intraperitoneally, with an immune challenge (250 μg/kg lipopolysaccharide - LPS, a component of gram-negative bacterial cell wall). Here we report that high aggressive (HA) rats responded to an immune challenge with a 24-h long increase in cortical brain temperature. During the first 12 post-injection hours, HA rats also responded with a prolonged increase in NREM sleep amount, and a 5-h long and continuous inhibition of REM sleep. In HA rats, the LPS-induced increase in the amount of time spent in NREM sleep was due to an increase in the number of episodes of this sleep phase, without any change in the bout duration. The LPS-induced REM sleep inhibition observed in HA rats was due to a decrease in both the number and duration of REM sleep bouts. In HA rats, during REM sleep, LPS administration significantly reduced the power of the EEG theta band. In non-aggressive (NA) rats, in response to LPS administration, cortical brain temperature was increased only for two hours, NREM sleep was unaffected, and REM sleep inhibition was scattered along the first 8 post-injection hours. The LPS-induced changes in the number of NREM sleep bouts of NA rats were limited to few and scattered hours, with a change in bout duration only in a single hour. A combination of decreases, in few hours, in both REM sleep bouts and their duration contributed to the REM sleep inhibition observed in NA rats. In NA rats, the power of EEG theta band was not modified, during REM sleep, by LPS administration. Gross motor activity was inhibited in both HA and NA rats. Results of this study show that trait aggressiveness affects febrile and sleep responses to an immune challenge.

Ketamine metabolite (2R,6R)-hydroxynorketamine enhances aggression via periaqueductal gray glutamatergic transmission

(2R,6R)-hydroxynorketamine (HNK), a metabolite of ketamine, has recently been suggested to be a potent antidepressant for treating animal depression and has rapid-onset and long-lasting action through potentiating glutamatergic transmission. However, its other effects are still unclear. In the present study, we tested the effects of (2R,6R)-HNK on offensive aggression. A resident-intruder (RI) test was used as the main model to test elements of offensive aggression, including threats and bites. Electrophysiological recordings in the ventrolateral periaqueductal gray (vlPAG) were used to measure the functions of glutamatergic synaptic transmission. A single systemic injection of (2R,6R)-HNK, but not (2S,6S)-HNK, increased elements of offensive aggression, including threats and bites, in a dose-dependent manner with long-lasting action. Moreover, (2R,6R)-HNK increased the input-output curve, the AMPA-mediated current, and the frequency and amplitude of miniature excitatory postsynaptic currents (mEPSCs) and decreased the paired-pulse ratio (PPR) in the vlPAG. Furthermore, intra-vlPAG application of (2R,6R)-HNK increased aggressive and biting behaviors, which were abolished by an intra-vlPAG pretreatment with the AMPA receptors antagonist, CNQX. Notably, the intra-vlPAG CNQX pretreatment eliminated systemic (2R,6R)-HNK-enhanced aggressive and biting behaviors. The results of this suggest that (2R,6R)-HNK evokes offensive aggression by increasing vlPAG glutamatergic transmission. Although (2R,6R)-HNK is currently suggested to be effective for treating depression, its side effect of increasing offensive aggression should be a subject of concern in future drug development and therapy.

Moderation of the relationship between Toxoplasma gondii seropositivity and trait impulsivity in younger men by the phenylalanine-tyrosine ratio

Previously, we reported that Toxoplasma gondii (T. gondii)-seropositivity is associated with higher impulsive sensation seeking in younger men. As dopaminergic and serotonergic signaling regulate impulsivity, and as T. gondii directly and indirectly affects dopaminergic signaling and induces activation of the kynurenine pathway leading to the diversion of tryptophan from serotonin production, we investigated if dopamine and serotonin precursors or the tryptophan metabolite kynurenine interact with the T. gondii-impulsivity association. In 950 psychiatrically healthy participants, trait impulsivity scores were related to T. gondii IgG seropositivity. Interactions were also identified between categorized levels of phenylalanine (Phe), tyrosine (Tyr), Phe:Tyr ratio, kynurenine (Kyn), tryptophan (Trp) and Kyn:Trp ratio, and age and gender. Only younger T. gondii-positive men with a high Phe:Tyr ratio, were found to have significantly higher impulsivity scores. There were no significant associations in other demographic groups, including women and older men. No significant effects or interactions were identified for Phe, Tyr, Kyn, Trp, or Kyn:Trp ratio. Phe:Tyr ratio, therefore, may play a moderating role in the association between T. gondii seropositivity and impulsivity in younger men. These results could potentially lead to individualized approaches to reduce impulsivity, based on combined demographic, biochemical and serological factors.

Aggression, Social Stress, and the Immune System in Humans and Animal Models

Social stress can lead to the development of psychological problems ranging from exaggerated anxiety and depression to antisocial and violence-related behaviors. Increasing evidence suggests that the immune system is involved in responses to social stress in adulthood. For example, human studies show that individuals with high aggression traits display heightened inflammatory cytokine levels and dysregulated immune responses such as slower wound healing. Similar findings have been observed in patients with depression, and comorbidity of depression and aggression was correlated with stronger immune dysregulation. Therefore, dysregulation of the immune system may be one of the mediators of social stress that produces aggression and/or depression. Similar to humans, aggressive animals also show increased levels of several proinflammatory cytokines, however, unlike humans these animals are more protected from infectious organisms and have faster wound healing than animals with low aggression. On the other hand, subordinate animals that receive repeated social defeat stress have been shown to develop escalated and dysregulated immune responses such as glucocorticoid insensitivity in monocytes. In this review we synthesize the current evidence in humans, non-human primates, and rodents to show a role for the immune system in responses to social stress leading to psychiatric problems such as aggression or depression. We argue that while depression and aggression represent two fundamentally different behavioral and physiological responses to social stress, it is possible that some overlapped, as well as distinct, pattern of immune signaling may underlie both of them. We also argue the necessity of studying animal models of maladaptive aggression induced by social stress (i.e., social isolation) for understanding neuro-immune mechanism of aggression, which may be relevant to human aggression.

Dietary patterns, body mass index and inflammation: Pathways to depression and mental health problems in adolescents

BACKGROUND

Observational studies suggest that dietary patterns may impact mental health outcomes, although biologically plausible pathways are yet to be tested. We aimed to elucidate the longitudinal relationship between dietary patterns, adiposity, inflammation and mental health including depressive symptoms in a population-based cohort of adolescents.

METHODS

Data were provided from 843 adolescents participating in the Western Australian Pregnancy Cohort (Raine) Study at 14 and 17 years (y) of age. Structural equation modelling was applied to test our hypothesised models relating dietary patterns, energy intake and adiposity (body mass index) at 14 y to adiposity and the pro-inflammatory adipokine (leptin) and inflammation (high sensitivity C-reactive protein - hs-CRP) at 17 y, and these inflammatory markers to depressive symptoms (Beck Depression Inventory) and Internalising and Externalising Behavioral Problems (Child Behavior Check List Youth Self- Report) at 17 y. We further tested a reverse hypothesis model, with depression at 14 y as a predictor of dietary patterns at the same time-point.

RESULTS

The tested models provided a good fit to the data. A 'Western' dietary pattern (high intake of red meat, takeaway, refined foods, and confectionary) at 14 y was associated with higher energy intake and BMI at 14 y, and with BMI and biomarkers of inflammation at 17 y (all p < .05). A 'Healthy' dietary pattern (high in fruit, vegetables, fish, whole-grains) was inversely associated with BMI and inflammation at 17 y (p < .05). Higher BMI at 14 y was associated with higher BMI (p < .01), leptin (p < .05), hs-CRP (p < .05), depressive symptoms (p < .05) and mental health problems (p < .05), all at 17 y.

CONCLUSION

A 'Western' dietary pattern associates with an increased risk of mental health problems including depressive symptoms in adolescents, through biologically plausible pathways of adiposity and inflammation, whereas a 'Healthy' dietary pattern appears protective in these pathways. Longitudinal modelling into adulthood is indicated to confirm the complex associations of dietary patterns, adiposity, inflammation and mental health problems, including depressive symptoms.

The Association between Suicide Attempts and Toxoplasma gondii Infection

Objective

Chronic ‘latent’ infection by Toxoplasma gondii is common and most of the hosts have minimal symptoms or they are even asymptomatic. However, there are possible mechanisms by which T. gondii may affect human behavior and it may also cause humans to attempt suicide. This article aimed to investigate the potential pathophysiological relationship between suicide attempts and T. gondii infection in Korea.

Methods

One hundred fifty-five psychiatric patients with a history of suicide attempt and 135 healthy control individuals were examined with enzyme-linked immunoassays and fluorescent antibody technique for T. gondii seropositivity and antibody titers. The group of suicide attempters was interviewed regarding the history of suicide attempt during lifetime and evaluated using 17-item Korean version of Hamilton Depression Scale (HAMD), Columbia Suicide Severity Rating Scale (C-SSRS), State-Trait Anxiety Inventory (STAI) and Korean-Barratt Impulsiveness Scale (BIS).

Results

Immunoglobulin G antibodies were found in 21 of the 155 suicide attempters and in 8 of the 135 controls (p=0.011). The Toxoplasma-seropositive suicide attempters had a higher HAMD score on the depressed mood and feeling of guilt subscales and a higher total score than the seronegative suicide attempters. T. gondii seropositive status was associated with higher C-SSRS in the severity and lethality subscales. T. gondii IgG seropositivity was significantly associated with higher STAI-X1 scores in the suicide attempters group.

Conclusion

Suicide attempters showed higher seroprevalence of T. gondii than healthy controls. Among the suicide attempters, the T. gondii seropositive and seronegative groups showed several differences in the aspects of suicide. These results suggested a significant association between T. gondii infection and psychiatric problems in suicidality.

Genome-Wide DNA Methylation Changes Associated with Intermittent Explosive Disorder: A Gene-Based Functional Enrichment Analysis

BACKGROUND

Intermittent explosive disorder is defined as a recurrent, problematic, and impulsive aggression that affects 3% to 4% of the US population. While behavioral genetic studies report a substantial degree of genetic influence on aggression and impulsivity, epigenetic mechanisms underlying aggression and intermittent explosive disorder are not well known.

METHODS

The sample included 44 subjects (22 with a DSM-5 diagnosis of intermittent explosive disorder and 22 comparable subjects without intermittent explosive disorder). Peripheral blood DNA methylome was profiled using the Illumina Infinium HumanMethylation450 Beadchip. Intermittent explosive disorder-associated genome-wide DNA methylation changes were analyzed using the CpGassoc R package, with covariates age, sex, and race being adjusted. A gene-based functional enrichment analysis was performed to identify pathways that were overrepresented by genes harboring highly differentially methylated CpG sites.

RESULTS

A total of 27 CpG sites were differentially methylated in IED participants (P<5.0×10-5), but none reached genome-wide significant threshold. Functional enrichment analysis revealed that genes mapped by these CpG sites are involved in the inflammatory/immune system, the endocrine system, and neuronal differentiation.

CONCLUSIONS

Consistent with our previous studies showing an association of inflammatory response with aggressive behavior in intermittent explosive disorder subjects, our gene-based pathway analysis using differentially methylated CpG sites supports inflammatory response as an important mechanism involved in intermittent explosive disorder and reveals other novel biological processes possibly associated with intermittent explosive disorder.

Neuroanatomical Substrates of Rodent Social Behavior: The Medial Prefrontal Cortex and Its Projection Patterns

Social behavior encompasses a number of distinctive and complex constructs that form the core elements of human imitative culture, mainly represented as either affiliative or antagonistic interactions with conspecifics. Traditionally considered in the realm of psychology, social behavior research has benefited from recent advancements in neuroscience that have accelerated identification of the neural systems, circuits, causative genes and molecular mechanisms that underlie distinct social cognitive traits. In this review article, I summarize recent findings regarding the neuroanatomical substrates of key social behaviors, focusing on results from experiments conducted in rodent models. In particular, I will review the role of the medial prefrontal cortex (mPFC) and downstream subcortical structures in controlling social behavior, and discuss pertinent future research perspectives.

Effectiveness of conservative interventions for sickness and pain behaviors induced by a high repetition high force upper extremity task

Background

Systemic inflammation is known to induce sickness behaviors, including decreased social interaction and pain. We have reported increased serum inflammatory cytokines in a rat model of repetitive strain injury (rats perform an upper extremity reaching task for prolonged periods). Here, we sought to determine if sickness behaviors are induced in this model and the effectiveness of conservative treatments.

Methods

Experimental rats underwent initial training to learn a high force reaching task (10 min/day, 5 days/week for 6 weeks), with or without ibuprofen treatment (TRHF vs. TRHF + IBU rats). Subsets of trained animals went on to perform a high repetition high force (HRHF) task for 6 or 12 weeks (2 h/day, 3 days/week) without treatment, or received two secondary interventions: ibuprofen (HRHF + IBU) or a move to a lower demand low repetition low force task (HRHF-to-LRLF), beginning in task week 5. Mixed-effects models with repeated measures assays were used to assay duration of social interaction, aggression, forepaw withdrawal thresholds and reach performance abilities. One-way and two-way ANOVAs were used to assay tissue responses. Corrections for multiple comparisons were made.

Results

TRHF + IBU rats did not develop behavioral declines or systemic increases in IL-1beta and IL-6, observed in untreated TRHF rats. Untreated HRHF rats showed social interaction declines, difficulties performing the operant task and forepaw mechanical allodynia. Untreated HRHF rats also had increased serum levels of several inflammatory cytokines and chemokines, neuroinflammatory responses (e.g., increased TNFalpha) in the brain, median nerve and spinal cord, and Substance P and neurokinin 1 immunoexpression in the spinal cord. HRHF + IBU and HRHF-to-LRLF rats showed improved social interaction and reduced inflammatory serum, nerve and brain changes. However, neither secondary treatment rescued HRHF-task induced forepaw allodynia, or completely attenuated task performance declines or spinal cord responses.

Conclusions

These results suggest that inflammatory mechanisms induced by prolonged performance of high physical demand tasks mediate the development of social interaction declines and aggression. However, persistent spinal cord sensitization was associated with persistent behavioral indices of discomfort, despite use of conservative secondary interventions indicating the need for prevention or more effective interventions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12868-017-0354-3) contains supplementary material, which is available to authorized users.

The Valdostana goat: a genome-wide investigation of the distinctiveness of its selective sweep regions

The Valdostana goat is an alpine breed, raised only in the northern Italian region of the Aosta Valley. This breed's main purpose is to produce milk and meat, but is peculiar for its involvement in the "Batailles de Chèvres," a recent tradition of non-cruel fight tournaments. At both the genetic and genomic levels, only a very limited number of studies have been performed with this breed and there are no studies about the genomic signatures left by selection. In this work, 24 unrelated Valdostana animals were screened for runs of homozygosity to identify highly homozygous regions. Then, six different approaches (ROH comparison, Fst single SNPs and windows based, Bayesian, Rsb, and XP-EHH) were applied comparing the Valdostana dataset with 14 other Italian goat breeds to confirm regions that were different among the comparisons. A total of three regions of selection that were also unique among the Valdostana were identified and located on chromosomes 1, 7, and 12 and contained 144 genes. Enrichment analyses detected genes such as cytokines and lymphocyte/leukocyte proliferation genes involved in the regulation of the immune system. A genetic link between an aggressive challenge, cytokines, and immunity has been hypothesized in many studies both in humans and in other species. Possible hypotheses associated with the signals of selection detected could be therefore related to immune-related factors as well as with the peculiar battle competition, or other breed-specific traits, and provided insights for further investigation of these unique regions, for the understanding and safeguard of the Valdostana breed.

Plasma levels of Th17-related cytokines and complement C3 correlated with aggressive behavior in patients with schizophrenia

Increasing evidence indicates that immune inflammatory processes, especially autoimmune reaction, should be considered in the pathophysiology of schizophrenia and aggressive behavior. The present study aimed to explore the correlation between immune factors (C3 and Th17-related cytokines) and aggressive behavior in schizophrenia patients. Forty schizophrenia patients and forty age- and gender-matched healthy controls participated in the study. Blood samples were assessed by ELISA upon enrollment. Positive and negative syndrome scale (PANSS) and modified overt aggression scale (MOAS) were used to estimate the severity and aggressive symptoms of schizophrenia patients. Plasma levels of IL-17, IL-23, and TGF-β1 in schizophrenia patients were significantly higher than those in healthy controls [(37.63±17.82) vs. (29.34±10.38)pg/ml, p=0.02; (101.40±135.26) vs. (13.09±5.94) pg/ml, p=0.01; (2864.57±2163.61) vs. (1839.69±1797.73)pg/ml, p=0.04], whereas C3 levels were significantly lower in schizophrenia patients [( 120,479.67± 65,612.50) vs. ( 208,060.21± 217,008.21)ng/ml, p=0.02]. IL-17, IL-23, and TGF-β1 levels were positively related to total scores of MOAS (p=0.02, p=0.02 and p=0.03, respectively) and PANSS (p=0.04, p=0.04 and p=0.02, respectively), whereas C3 levels were negatively related to total PANSS scores (p=0.03). IL-17 and IL-23 levels were positively correlated with PANSS excited component scores (p=0.04 and p=0.01, respectively). Our findings suggested that the Th17-related cytokine levels were positively related to the severity of schizophrenia and aggressive behavior, whereas C3 levels were negatively related to the severity of schizophrenia. This study demonstrated that elevated levels of Th17-related cytokines and decreased levels of C3 could be potential biomarkers for schizophrenia and aggressive behavior.

Reciprocal moderation by Toxoplasma gondii seropositivity and blood phenylalanine - tyrosine ratio of their associations with trait aggression

We previously reported that trait aggression, proposed as an endophenotype for suicidal behavior, is positively associated with Toxoplasma gondii (T. gondii) seropositivity in females, but not in males. Additionally, older males seropositive for T. gondii had lower scores on measures of trait aggression, including self-aggression. Trait aggression may be influenced by dopaminergic signaling, which is known to be moderated by gender and age, and potentially enhanced in T. gondii positives through the intrinsic production of dopamine by the microorganism. Therefore, we investigated associations between trait aggression and interactions between T. gondii enzyme-linked immunoabsorbant assay (ELISA) IgG titer-determined seropositivity and high-performance liquid chromatography- (HPLC-) measured blood levels of dopamine precursors phenylalanine (Phe), tyrosine (Tyr), and their ratio in a sample of 1000 psychiatrically healthy participants. Aggressive traits were assessed using the questionnaire for measuring factors of aggression (FAF), the German version of the Buss-Durkee hostility questionnaire. We found that 1) the decrease in trait aggression scores in T. gondii-positive older males was only present in individuals with a low Phe:Tyr ratio, and 2) that there was a positive correlation between Phe:Tyr ratio and total aggression and selected subscales of aggression in T. gondii-positive males, but not in T. gondii-negative males. These findings point toward a gender-specific reciprocal moderation by Phe:Tyr ratio and T. gondii seropositivity of their associations with aggression scores, and lead to experimental interventions geared to manipulating levels of dopamine precursors in selected T. gondii positive individuals with increased propensity for aggression.

Tryptophan, kynurenine, and kynurenine metabolites: Relationship to lifetime aggression and inflammatory markers in human subjects

Inflammatory proteins are thought to be causally involved in the generation of aggression, possibly due to direct effects of cytokines in the central nervous system and/or by generation of inflammatory metabolites along the tryptophan-kynurenine (TRP/KYN) pathway, including KYN and its active metabolites kynurenic acid (KA), quinolinic acid (QA), and picolinic acid (PA). We examined plasma levels of TRP, KYN, KA, QA, and PA in 172 medication-free, medically healthy, human subjects to determine if plasma levels of these substances are altered as a function of trait aggression, and if they correlate with current plasma levels of inflammatory markers. Plasma levels of C-reactive protein (CRP), interleukin-6 (IL-6), and soluble interleukin-1 receptor-II (sIL-1RII) protein were also available in these subjects. We found normal levels of TRP but reduced plasma levels of KYN (by 48%), QA (by 6%), and a QA/KA (by 5%) ratio in subjects with Intermittent Explosive Disorder (IED) compared to healthy controls and psychiatric controls. Moreover, the metabolites were not associated with any of the inflammatory markers studied. These data do not support the hypothesis that elevated levels of KYN metabolites would be present in plasma of subjects with IED, and associated with plasma inflammation. However, our data do point to a dysregulation of the KYN pathway metabolites in these subjects. Further work will be necessary to replicate these findings and to understand their role in inflammation and aggression in these subjects.

Discovery of biochemical biomarkers for aggression: A role for metabolomics in psychiatry

Human aggression encompasses a wide range of behaviors and is related to many psychiatric disorders. We introduce the different classification systems of aggression and related disorders as a basis for discussing biochemical biomarkers and then present an overview of studies in humans (published between 1990 and 2015) that reported statistically significant associations of biochemical biomarkers with aggression, DSM-IV disorders involving aggression, and their subtypes. The markers are of different types, including inflammation markers, neurotransmitters, lipoproteins, and hormones from various classes. Most studies focused on only a limited portfolio of biomarkers, frequently a specific class only. When integrating the data, it is clear that compounds from several biological pathways have been found to be associated with aggressive behavior, indicating complexity and the need for a broad approach. In the second part of the paper, using examples from the aggression literature and psychiatric metabolomics studies, we argue that a better understanding of aggression would benefit from a more holistic approach such as provided by metabolomics. © 2016 Wiley Periodicals, Inc.

Relationships of diet-related blood parameters and blood lead levels with psychopathology and aggression in forensic psychiatric inpatients

BACKGROUND

Earlier studies have suggested associations between diet-related blood parameters and both aggression and psychopathological symptoms, but little is known about this in forensic psychiatric inpatients.

AIM

This article aims to explore the levels of diet-related blood parameters and their relationship to aggressive behaviour and/or psychopathology among Dutch forensic psychiatric inpatients.

METHODS

Minerals, vitamins, lead and fatty acid levels were measured in blood samples from 51 inpatients, well enough to consent and participate in the study, from a possible total of 99. Levels of aggression and psychopathology were assessed using questionnaires, observation instruments and clinical data. Associations between blood parameters and behavioural measures were calculated.

RESULTS

Low average levels of vitamin D3 and omega (ω)-3 fatty acids were found, with nearly two-thirds of the patients having below recommended levels of D3 , while vitamin B6 levels were high. Magnesium, iron, zinc, copper and lead were overall within reference values, but copper/zinc ratios were high. Several significant associations between levels of fatty acid measures and both aggression and psychopathology were observed.

CONCLUSION

In our sample of forensic psychiatric inpatients, fatty acids - but not mineral or vitamin levels - were associated with aggression and psychopathology. A potentially causal link between fatty acids and aggression could be tested in a randomised, placebo-controlled trial of fish oil supplements. General health of such patients might be improved by better vitamin D status (increased sun exposure and/or supplement use) and better ω-3 fatty acid status (oily fish or fish oil consumption), but discouraging unnecessary self-prescription of B vitamins where necessary. Copyright © 2015 John Wiley & Sons, Ltd.

Low-dose lipopolysaccharide (LPS) inhibits aggressive and augments depressive behaviours in a chronic mild stress model in mice

Background

Aggression, hyperactivity, impulsivity, helplessness and anhedonia are all signs of depressive-like disorders in humans and are often reported to be present in animal models of depression induced by stress or by inflammatory challenges. However, chronic mild stress (CMS) and clinically silent inflammation, during the recovery period after an infection, for example, are often coincident, but comparison of the behavioural and molecular changes that underpin CMS vs a mild inflammatory challenge and impact of the combined challenge is largely unexplored. Here, we examined whether stress-induced behavioural and molecular responses are analogous to lipopolysaccharide (LPS)-induced behavioural and molecular effects and whether their combination is adaptive or maladaptive.

Methods

Changes in measures of hedonic sensitivity, helplessness, aggression, impulsivity and CNS and systemic cytokine and 5-HT-system-related gene expression were investigated in C57BL/6J male mice exposed to chronic stress alone, low-dose LPS alone or a combination of LPS and stress.

Results

When combined with a low dose of LPS, chronic stress resulted in an enhanced depressive-like phenotype but significantly reduced manifestations of aggression and hyperactivity. At the molecular level, LPS was a strong inducer of TNFα, IL-1β and region-specific 5-HT_2A mRNA expression in the brain. There was also increased serum corticosterone as well as increased TNFα expression in the liver. Stress did not induce comparable levels of cytokine expression to an LPS challenge, but the combination of stress with LPS reduced the stress-induced changes in 5-HT genes and the LPS-induced elevated IL-1β levels.

Conclusions

It is evident that when administered independently, both stress and LPS challenges induced distinct molecular and behavioural changes. However, at a time when LPS alone does not induce any overt behavioural changes per se, the combination with stress exacerbates depressive and inhibits aggressive behaviours.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0572-0) contains supplementary material, which is available to authorized users.

Elevated Plasma Oxidative Stress Markers in Individuals With Intermittent Explosive Disorder and Correlation With Aggression in Humans

BACKGROUND

Animal and clinical studies suggest a link between inflammation and oxidative stress. Because oxidative stress is an inherent part of inflammation, and inflammation is associated with behavioral aggression in lower mammals and humans, we hypothesized that markers of oxidative stress would be related to aggression in human subjects. In this case-control study, markers of oxidative stress and aggression were assessed in human subjects with histories of recurrent, problematic, impulsive aggressive behavior and in nonaggressive comparator subjects.

METHODS

Plasma levels of 8-hydroxy-2'-deoxyguanosine and 8-isoprostane were examined in the context of measures of aggression and impulsivity in physically healthy subjects with intermittent explosive disorder (n = 69), nonaggressive subjects with Axis I or II disorders (n = 61), and nonaggressive subjects with no history of Axis I or II disorders (n = 67).

RESULTS

Levels of plasma 8-hydroxy-2'-deoxyguanosine and 8-isoprostane were significantly higher in subjects with intermittent explosive disorder compared with psychiatric or normal control subjects. In addition, both oxidative stress markers correlated with a composite measure of aggression; more specifically, 8-hydroxy-2'-deoxyguanosine correlated with measures reflecting a history of actual aggressive behavior in all subjects.

CONCLUSIONS

These data suggest a positive relationship between plasma markers of oxidative stress and aggression in human subjects. This finding adds to the complex picture of the central neuromodulatory role of aggression in human subjects.

Inflammatory markers and chronic exposure to fluoxetine, divalproex, and placebo in intermittent explosive disorder

Intermittent Explosive Disorder (IED) is a disorder of impulsive aggression affecting 4-7% of the U.S. population during some period of life. In addition to other biological correlates, elevations of plasma inflammatory markers have been reported in IED, compared with control, subjects. In this study we sought to explore if treatment exposure to anti-aggressive agents, compared with placebo, would be associated with a reduction in circulating levels of inflammatory markers. Thirty IED subjects, from a 12-week, double-blind, randomized, placebo-controlled trial of fluoxetine and divalproex, in which both pre- and post-treatment levels of C-Reactive Protein (CRP), interleukin (IL)-1β, IL-2, IL-6, IL-8, IL-10 and tumor necrosis factor (TNF)-α were obtained. Efficacy measures included the Overt Aggression Scale-Modified (OAS-M) score for Aggression and for Irritability, rate of Clinical Global Impression of Improvement (CGI-I), and rate of IED Remitters at study completion. As compared to placebo, neither fluoxetine nor divalproex reduced any of the measures of aggression. In addition, levels of CRP and pro- and anti-inflammatory cytokines showed no changes from pre- to post-treatment for any treatment condition. Correlations between pre- and post- treatment plasma CRP/cytokines were substantial (mean r=0.71, r(2)=0.50, p<0.001). Overall, circulating markers of inflammation markers were unaffected by treatment with fluoxetine or divalproex, consistent with the absence of change in measures of impulsive aggression.

Immune reactivity in rats selected for the enhancement or elimination of aggressiveness towards humans

This study analyzes immune reactivity in two lines of rats selected for the enhancement or elimination of aggressiveness toward humans. Compared to nonaggressive line, aggressive rats showed increased blood ratio of CD4(+) and CD8(+)T lymphocytes, monocyte chemoattractant protein (MCP)-1 level both before and after immunization with sheep red blood cells (SRBC), enhanced IgM-immune response, as well as decreased level of interleukin (IL)-1α before immunization. However, antigen administration produced IL-1α increase in aggressive rats and its decrease in nonaggressive rats compared to non-immunized rats of the same lines. In addition, line-dependent alterations of T lymphocyte distribution in response to immune activation have been found only in the spleen. It is suggested that genetic differences in aggressive behavior may contribute to differences in immune function.

Childhood trauma and parental style: Relationship with markers of inflammation, oxidative stress, and aggression in healthy and personality disordered subjects

Recent studies suggest that early life trauma is associated with elevations in circulating markers of inflammation in human subjects. History of aggression as a behavior, or aggression as a personality trait, is also associated with elevations of these inflammatory markers. Since early life trauma is associated with the development and maintenance of aggression in later life we examined the relationship of early life adversity, plasma inflammation markers (IL-6 and CRP) and oxidative stress markers (8-OH-DG and 8-ISO), and aggression in adult subjects with (n=79) and without (n=55) personality disorder. We used a series of mediated and moderated path models to test whether the effects of early adversity on later aggression may be mediated through markers of inflammation. Childhood abuse and parental control were associated with basal IL-6 and CRP concentrations. Path modeling suggested that childhood abuse was associated with aggression indirectly through CRP while parental control influenced aggression indirectly through IL-6 and CRP. Furthermore, these effects were independent of the effect of current depression. The results suggest that disruption of inflammatory processes represent one pathway by which early adversity influences aggression.

Emotions, immunity and sport: Winner and loser athlete's profile of fighting sport

Several studies have focused on the relationship between hormonal changes and affective states in sporting contexts relating to an agonistic outcome. More recently, pro-inflammatory cytokines have also been successfully associated with affective state modulation. The aim of this study was to investigate whether athletes who won or lost show different levels of steroid hormones (testosterone and cortisol), pro-inflammatory cytokine IL-1β, or expressions of anger and anxiety during six training fights in seasonal competitions down to the main seasonal competition. In 25 male kick-boxing athletes (age±SD, 28.68±5.34), anger states (RS score) and anxiety states (AS score) were assessed by STAXI-2 and STAI-Y, respectively. Cortisol (C), testosterone (T) and IL-1β salivary levels were measured by the ELISA method. The saliva samples were taken in the afternoon, 30min prior to the start and 30min from the end of both simulated and official competitions. The results showed that the RS score, T, T/C ratio salivary levels increased during the season, whereas the AS score, C and IL-1β suggested an opposite trend. Close to an official competition, the RS score, T, T/C ratio and IL-1β salivary concentrations were significantly higher, and then decreased during competition. By contrast, the AS score and C levels significantly increased throughout the official competition. In addition, significant differences were found for hormones and IL-1β concentrations as well as psychometric assessment close to the outcome of an official match. Athletes who lost showed an higher AS score and C level, while those who won were characterized by an higher level during the pre-competition RS score, T, T/C ratio, and IL-1β. Note that these factors were positively and significantly correlated at the pre-official competition time, while in a linear regression analysis, IL-1β, T and T/C ratio concentrations explained 43% of the variance in the RS score observed at the same time (adjusted R(2)=0.43, ANOVA P<.05). Our data suggest that the beginning of an agonistic event could trigger emotional responses which correspond to different biological processes instead that of a simulated fight. In particular, IL-1β could be a potential new biological marker of anger and the combined measurement of these factors may be a useful way of understanding athletes' change in relation to their performance.

Immune neuroendocrine phenotypes in Coturnix coturnix: do avian species show LEWIS/FISCHER-like profiles?

Immunoneuroendocrinology studies have identified conserved communicational paths in birds and mammals, e.g. the Hypothalamus-Pituitary-Adrenal axis with anti-inflammatory activity mediated by glucocorticoids. Immune neuroendocrine phenotypes (INPs) have been proposed for mammals implying the categorization of a population in subgroups underlying divergent immune-neuroendocrine interactions. These phenotypes were studied in the context of the LEWIS/FISCHER paradigm (rats expressing high or low pro-inflammatory profiles, respectively). Although avian species have some common immunological mechanisms with mammals, they have also evolved some distinct strategies and, until now, it has not been studied whether birds may also share with mammals similar INPs. Based on corticosterone levels we determined the existence of two divergent groups in Coturnix coturnix that also differed in other immune-neuroendocrine responses. Quail with lowest corticosterone showed higher lymphoproliferative and antibody responses, interferon-γ and interleukin-1β mRNA expression levels and lower frequencies of leukocyte subpopulations distribution and interleukin-13 levels, than their higher corticosterone counterparts. Results suggest the existence of INPs in birds, comparable to mammalian LEWIS/FISCHER profiles, where basal corticosterone also underlies responses of comparable variables associated to the phenotypes. Concluding, INP may not be a mammalian distinct feature, leading to discuss whether these profiles represent a parallel phenomenon evolved in birds and mammals, or a common feature inherited from a reptilian ancestor millions of years ago.

Cerebrospinal fluid inflammatory cytokines and aggression in personality disordered subjects

BACKGROUND

Neurochemical studies have pointed to a modulatory role in human aggression for a variety of central neurotransmitters and neuromodulators such as cytokines. While animal studies of cytokines suggest an aggression-facilitating role for central cytokines, especially for interleukin-1β and other cytokines, no cerebrospinal fluid studies of cytokines have yet been reported in regard to human aggression.

METHODS

Basal lumbar cerebrospinal fluid samples were obtained from 38 physically healthy subjects with DSM-5 Personality Disorder and assayed for cerebrospinal fluid interleukin-6 (log IL-6) and cerebrospinal fluid soluble IL-1 Receptor II protein in the context of their relationship with measures of aggression.

RESULTS

Cerebrospinal fluid soluble interleukin-1 Receptor II (r=.35, r(2) = .12, P= .03), but not log interleukin-6 (r = -.05, r(2) = .00, P= .76), levels were positively correlated with a composite measure of aggression. Adding relevant covariates, including cerebrospinal fluid levels of serotonin and dopamine metabolites, to the statistical model doubled the strength of this relationship (partial r = .54, r(2) = .29, P= .002). No relationship was seen with history of suicidal behavior or with any measure of impulsivity, negative affectivity, or of general dimensions of personality.

CONCLUSION

These data suggest a positive relationship between at least one inflammatory cytokine in the central nervous system and aggression in human subjects. This finding adds to the complex picture of the central neurochemistry of impulsive aggression in human subjects.

Depressogenic vulnerability and gender-specific patterns of neuro-immune dysregulation: What the ratio of cortisol to C-reactive protein can tell us about loss of normal regulatory control

We examined whether the ratio of cortisol (CORT) to high-sensitivity C-reactive protein (hsCRP), an index that captures the integrity of homeostatic regulation between the hypothalamic-pituitary-adrenal (HPA) axis and inflammatory processes, is associated with vulnerability to depression in a gender specific manner and whether glucocorticoid receptor (GR) sensitivity plays a role in these associations. Fasting blood samples were collected between 08:45 and 09:15 and assayed for CORT, hsCRP, and leukocyte count in 213 healthy, medication-free men and women. The NEO-Personality Inventory was used to assess neuroticism, extraversion and anxiety. We used the Hamilton Depression Interview to assess depressive symptoms, the Buss-Perry anger subscale to measure anger, and the Pittsburgh Sleep Quality Index to evaluate subjective sleep quality and its components. Log-transformed CORT/CRP values were analyzed using multiple regression with Holms' adjusted p-values and age, body mass index (BMI), and race as covariates. GR sensitivity was estimated using the log-transformed ratio of neutrophils (N)-to-monocytes (M). The log-transformed ratio of CORT/CRP did not differ between men and women but was significantly and negatively associated with age and BMI. Severity of depressive symptoms, extraversion, anxiety, and sleep quality were associated with the CORT/CRP ratio in a gender-specific manner. For women, decreasing CORT/CRP ratios, suggestive of an insufficient release of CORT coupled with a heightened inflammatory state, were associated with increasing severity of depressive symptoms, decreasing quality of sleep, increasing frequency of sleep disturbance, and decreasing extraversion. For men, increasing frequency of daytime disturbance and levels of anxiety were associated with increasing CORT/CRP ratio, suggestive of an enhanced release of CORT relative to attenuated levels of hsCRP. For both genders, increasing anger was associated with decreasing CORT/CRP ratios. Although results suggested GR downregulation in women but not men, such differences did not mediate the observed associations. With the use of the CORT/CRP ratio, we showed that vulnerability factors for depression are associated with a loss of normal regulatory controls resulting in gender-specific patterns of neuro-immune dysregulation. That GR downregulation did not influence these associations suggests that the loss of regulatory controls in at risk individuals is primarily at the level of the hormone. Beyond the individual contribution of each component of the CORT/CRP ratio, disruption of normal neuroimmune regulatory feedback provides a plausible biological framework useful in understanding biobehavioral vulnerabilities to depression in a gender specific manner. The CORT/CRP ratio may be a viable biomarker not only for delineating risk for MDD but also progression and treatment responses among patients with MDD; possibilities that are testable in future studies.

"Latent" infection with Toxoplasma gondii: association with trait aggression and impulsivity in healthy adults

BACKGROUND

Latent chronic infection with Toxoplasma gondii (T. gondii), a common neurotropic pathogen, has been previously linked with suicidal self-directed violence (SSDV). We sought to determine if latent infection with T. gondii is associated with trait aggression and impulsivity, intermediate phenotypes for suicidal behavior, in psychiatrically healthy adults.

METHODS

Traits of aggression and impulsivity were analyzed in relationship to IgG antibody seropositivity for T. gondii and two other latent neurotropic infections, herpes simplex virus 1 (HSV1) and cytomegalovirus (CMV). One thousand community-residing adults residing in the Munich metropolitan area with no Axis I or II conditions by SCID for DSM-IV (510 men, 490 women, mean age 53.6 ± 15.8, range 20-74). Plasma samples were tested for IgG antibodies to T. gondii, HSV-1 and CMV by ELISA. Self-reported ratings of trait aggression scores (Questionnaire for Measuring Factors of Aggression [FAF]) and trait impulsivity (Sensation-Seeking Scale-V [SSS-V]) were analyzed using linear multivariate methods.

RESULTS

T. gondii IgG seropositivity was significantly associated with higher trait reactive aggression scores among women (p < .01), but not among men. T. gondii-positivity was also associated with higher impulsive sensation-seeking (SSS-V Disinhibition) among younger men (p < .01) aged 20-59 years old (median age = 60). All associations with HSV-1 and CMV were not significant.

CONCLUSIONS

Aggression and impulsivity, personality traits considered as endophenotypes for SSDV, are associated with latent T. gondii infection in a gender and age-specific manner, and could be further investigated as prognostic and treatment targets in T. gondii-positive individuals at risk for SSDV.

Inflammation and lithium: clues to mechanisms contributing to suicide-linked traits

Suicide is one of the leading causes of death in the United States, yet it remains difficult to understand the mechanistic provocations and to intervene therapeutically. Stress is recognized as a frequent precursor to suicide. Psychological stress is well established to cause activation of the inflammatory response, including causing neuroinflammation, an increase of inflammatory molecules in the central nervous system (CNS). Neuroinflammation is increasingly recognized as affecting many aspects of CNS functions and behaviors. In particular, much evidence demonstrates that inflammatory markers are elevated in traits that have been linked to suicidal behavior, including aggression, impulsivity and depression. Lithium is recognized as significantly reducing suicidal behavior, is anti-inflammatory and diminishes aggression, impulsivity and depression traits, each of which is associated with elevated inflammation. The anti-inflammatory effects of lithium result from its inhibition of glycogen synthase kinase-3 (GSK3). GSK3 has been demonstrated to strongly promote inflammation, aggressive behavior in rodents and depression-like behaviors in rodents, whereas regulation of impulsivity by GSK3 has not yet been investigated. Altogether, evidence is building supporting the hypothesis that stress activates GSK3, which in turn promotes inflammation, and that inflammation is linked to behaviors associated with suicide, including particularly aggression, impulsivity and depression. Further investigation of these links may provide a clearer understanding of the causes of suicidal behavior and provide leads for the development of effective preventative interventions, which may include inhibitors of GSK3.

Cerebrospinal fluid and plasma C-reactive protein and aggression in personality-disordered subjects: a pilot study

C-reactive protein (CRP), in the plasma, serves as a marker of systemic inflammation and has been shown to correlate with history of actual aggressive behavior, and as a personality trait of aggressive tendency, in human subjects. This pilot study was conducted to determine if plasma CRP levels are correlated with cerebrospinal fluid levels (CSF CRP) and if CSF CRP also correlates with aggression. If so, this would suggest a role for central inflammatory processes in human aggression. Both plasma and basal lumbar CSF samples were obtained from 17 subjects with DSM-5 personality disorder and assayed for CRP. Plasma and CSF CRP levels were correlated (r = 0.65, p = 0.005) and each correlated with aggression (Plasma: r = 0.53, p = 0.029; CSF: r = 0.84, p < 0.001). When considered simultaneously, CSF CRP, but not plasma CRP, uniquely correlated with aggression. No relationship was seen with other measures of psychopathology. These data suggest a positive relationship between central nervous system CRP and aggression in humans.

Association of childhood chronic physical aggression with a DNA methylation signature in adult human T cells

BACKGROUND

Chronic physical aggression (CPA) is characterized by frequent use of physical aggression from early childhood to adolescence. Observed in approximately 5% of males, CPA is associated with early childhood adverse environments and long-term negative consequences. Alterations in DNA methylation, a covalent modification of DNA that regulates genome function, have been associated with early childhood adversity.

AIMS

To test the hypothesis that a trajectory of chronic physical aggression during childhood is associated with a distinct DNA methylation profile during adulthood.

METHODS

We analyzed genome-wide promoter DNA methylation profiles of T cells from two groups of adult males assessed annually for frequency of physical aggression between 6 and 15 years of age: a group with CPA and a control group. Methylation profiles covering the promoter regions of 20 000 genes and 400 microRNAs were generated using MeDIP followed by hybridization to microarrays.

RESULTS

In total, 448 distinct gene promoters were differentially methylated in CPA. Functionally, many of these genes have previously been shown to play a role in aggression and were enriched in biological pathways affected by behavior. Their locations in the genome tended to form clusters spanning millions of bases in the genome.

CONCLUSIONS

This study provides evidence of clustered and genome-wide variation in promoter DNA methylation in young adults that associates with a history of chronic physical aggression from 6 to 15 years of age. However, longitudinal studies of methylation during early childhood will be necessary to determine if and how this methylation variation in T cells DNA plays a role in early development of chronic physical aggression.

DNA methylation signature of childhood chronic physical aggression in T cells of both men and women

Background

High frequency of physical aggression is the central feature of severe conduct disorder and is associated with a wide range of social, mental and physical health problems. We have previously tested the hypothesis that differential DNA methylation signatures in peripheral T cells are associated with a chronic aggression trajectory in males. Despite the fact that sex differences appear to play a pivotal role in determining the development, magnitude and frequency of aggression, most of previous studies focused on males, so little is known about female chronic physical aggression. We therefore tested here whether or not there is a signature of physical aggression in female DNA methylation and, if there is, how it relates to the signature observed in males.

Methodology/Principal Findings

Methylation profiles were created using the method of methylated DNA immunoprecipitation (MeDIP) followed by microarray hybridization and statistical and bioinformatic analyses on T cell DNA obtained from adult women who were found to be on a chronic physical aggression trajectory (CPA) between 6 and 12 years of age compared to women who followed a normal physical aggression trajectory. We confirmed the existence of a well-defined, genome-wide signature of DNA methylation associated with chronic physical aggression in the peripheral T cells of adult females that includes many of the genes similarly associated with physical aggression in the same cell types of adult males.

Conclusions

This study in a small number of women presents preliminary evidence for a genome-wide variation in promoter DNA methylation that associates with CPA in women that warrant larger studies for further verification. A significant proportion of these associations were previously observed in men with CPA supporting the hypothesis that the epigenetic signature of early life aggression in females is composed of a component specific to females and another common to both males and females.

Anger induced by interferon-alpha is moderated by ratio of arachidonic acid to omega-3 fatty acids

OBJECTIVE

Anger worsens in some patients during interferon-alpha (IFN-α) therapy. Elevated anger has also been associated with lower long-chain omega-3 (LCn-3) fatty acid levels. We examined whether fatty acids could influence vulnerability to anger during IFN-α exposure.

METHODS

Plasma arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) levels were determined prior to IFN-α therapy by mass spectroscopy. Repeated-measure analyses examined the relationship between AA/EPA+DHA and the subsequent development of labile anger and irritability in 82 subjects who prospectively completed the Anger, Irritability, and Assault Questionnaire (AIAQ) during the first eight weeks of IFN-α therapy.

RESULTS

Prior to IFN-α therapy, AA/EPA+DHA did not correlate with either labile anger or irritability. Pre-treatment AA/EPA+DHA did correlate with the subsequent maximal increase in labile anger during IFN-α therapy (r=0.33; p=0.005). Over time, labile anger increased more in subjects with above median AA/EPA+DHA ratios (p<0.05). Of the 17 subjects ultimately requiring psychiatric intervention for anger, 14/17 had above-median AA/EPA+DHA ratios (p=0.009). There was also an interaction with the tumor necrosis factor-alpha (TNF-α) promoter polymorphism (A-308G), such that only those with both elevated AA/EPA+DHA and the A allele had increased labile anger (p=0.001). In an additional 18 subjects, we conversely observed that selective serotonin reuptake inhibitor treatment was associated with increased irritability during IFN-α therapy.

CONCLUSION

LCn-3 fatty acid status may influence anger development during exposure to elevated inflammatory cytokines, and may interact with genetic risk for increased brain TNF-α. LCn-3 supplements may be one strategy for minimizing this adverse side effect of IFN-α.

Effects of ethanolic extract of Fumaria indica L. on rat cognitive dysfunctions

Fumaria indica L. in Ayurveda is known as Parpat and traditionally used to calm the brain. Due to lack of scientific validation, 50% ethanolic extract of F. indica L. (FI) was evaluated for putative cognitive function modulating effects. Suspension of FI in 0.3% carboxymethyl cellulose (CMC) was orally administered to rats during the entire experimental period of 16 days at dose levels of 100, 200, and 400 mg/kg/day. Piracetam was used as standard nootropic. Behavioral models of learning and memory used were modified elevated plus-maze (M-EPM) and passive avoidance (PA) tests. Scopolamine (I mg/kg, s.c.), sodium nitrite (25 mg/kg, i.p.), and electroconvulsive shock (150 mA, 0.2 sec) were used to induce amnesia. Acetylcholinesterase (AChE) activity, muscarinic receptor density, oxidative status, and cytokine expressions [tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-10] were also assessed. Piracetam (500 mg/kg/day)-like memory-enhancing and anti-amnesic activity of the extract was observed. FI showed dose-dependent decrease in brain AChE activity and increase in muscarinic receptor density, and such was also the case for its observed beneficial effects on the brain antioxidative status. FI also inhibited the scopolamine-induced overexpression of the three tested cytokines observed in rat's brain. FI possesses nootropic-like beneficial effects on cognitive functions.