Attentional and mnemonic deficits associated with infectious disease in humans

Interoceptive pathways to understand and treat mental health conditions

An increasing recognition that brain and body are dynamically coupled has enriched our scientific understanding of mental health conditions. Peripheral signals interact centrally to influence how we think and feel, generating our sense of the internal condition of the body, a process known as interoception. Disruptions to this interoceptive system may contribute to clinical conditions, including anxiety, depression, and psychosis. After reviewing the nature of interoceptive disturbances in mental health conditions, this review focuses on interoceptive pathways of existing and putative mental health treatments. Emerging clinical interventions may target novel peripheral treatment mechanisms. Future treatment development requires forward- and back-translation to uncover and target specific interoceptive processes in mental health to elucidate their efficacy relative to interventions targeting other factors.

Can COVID-19 pandemic boost the epidemic of neurodegenerative diseases?

The pandemic of Coronavirus Disease 2019 (COVID-19) presents the world with the medical challenge associated with multifactorial nature of this pathology. Indeed COVID-19 affects several organs and systems and presents diversified clinical picture. COVID-19 affects the brain in many ways including direct infection of neural cells with SARS-CoV-2, severe systemic inflammation which floods the brain with pro-inflammatory agents thus damaging nervous cells, global brain ischaemia linked to a respiratory failure, thromboembolic strokes related to increased intravascular clotting and severe psychological stress. Often the COVID-19 is manifested by neurological and neuropsychiatric symptoms that include dizziness, disturbed sleep, cognitive deficits, delirium, hallucinations and depression. All these indicate the damage to the nervous tissue which may substantially increase the incidence of neurodegenerative diseases and promote dementia.

Microglial Ultrastructure in the Hippocampus of a Lipopolysaccharide-Induced Sickness Mouse Model

Sickness behavior is a set of behavioral changes induced by infections and mediated by pro-inflammatory cytokines. It is characterized by fatigue, decreased appetite and weight loss, changes in sleep patterns, cognitive functions, and lost interest in social activity. It can expedite recovery by conserving energy to mount an immune response involving innate immunity. To provide insights into microglial implication in sickness behavior with special focus on cognitive and social impairment, we investigated changes in their ultrastructure and interactions with synapses using a toxemia mouse model. Adult mice were injected with 1 mg/kg lipopolysaccharide (LPS) or saline, and assayed for signs of sickness behavior. LPS treated mice displayed reduced activity in open-field tests 24 h post-injection, while social avoidance and weight gain/loss were not significantly different between treatment groups. Microglia were investigated using electron microscopy to describe changes in their structure and function at nanoscale resolution. Microglial cell bodies and processes were investigated in the hippocampus CA1, a region responsible for learning and memory that is often impacted after peripheral LPS administration. Microglia in LPS treated animals displayed larger cell bodies as well as less complex processes at the time point examined. Strikingly, microglial processes in LPS injected animals were also more likely to contact excitatory synapses and contained more phagocytic material compared with saline injected controls. We have identified at the ultrastructural level significant changes in microglia-synapse interactions shortly after LPS administration, which draws attention to studying the roles of microglia in synaptic rewiring after inflammatory stimuli.

Large-Scale Validation of the Paddling Pool Task in the Clockmaze for Studying Hippocampus-Based Spatial Cognition in Mice

Rationally designed behavioral tests are important tools to assess the function of specific brain regions. The hippocampus is a crucial neural substrate for spatial cognition, and many studies have linked hippocampal dysfunction with defects on spatial learning and memory in neurological conditions ranging from Alzheimer’s disease to autoimmune syndromes, such as neuropsychiatric lupus. While our understanding of hippocampal function, from the molecular to the system levels, has increased dramatically over the last decades, this effort has not yet translated into efficacious therapies for cognitive impairment. We think that the availability of highly validated behavioral paradigms to measure cognition in mouse models is likely to enhance the potential success of preclinical therapeutic modalities. Here, we present an extensive study of the paddling pool task (PPT), first reported by Deacon and Rawlins, in which mice learn to escape from shallow water through a peripheral exit in a circular arena dubbed the clockmaze. We show that the PPT provides highly reliable results when assaying spatial cognition in C57/BL6 mice (120 males, 40 females) and BALB/c mice (40 males, 90 females). Additionally, we develop a robust algorithm for the assessment of escape strategies with clearly quantifiable readouts, enabling fine-granular phenotyping. Notably, the use of spatial strategy increases linearly across trials in the PPT. In a separate cohort of mice, we apply muscimol injections to silence the dorsal CA1 region of the hippocampus and show that the use of the spatial strategy in the PPT relies on the integrity of the dorsal hippocampus. Additionally, we compare directly the PPT and the Morris water maze (MWM) task in C57/BL6 mice (20 males, 20 females) and BALB/c mice (20 males, 20 females) and we find that the PPT induces significantly lower anxiety, exhaustion and hypothermia than the MWM. We conclude that the PPT provides a robust assessment of spatial cognition in mice, which can be applied in conjunction with other tests, to facilitate hypothesis testing and drug development to combat cognitive impairment.

Interoception and Inflammation in Psychiatric Disorders

Despite a historical focus on neurally mediated interoceptive signaling mechanisms, humoral (and even cellular) signals also play an important role in communicating bodily physiological state to the brain. These signaling pathways can perturb neuronal structure, chemistry, and function, leading to discrete changes in behavior. They are also increasingly implicated in the pathophysiology of psychiatric disorders. The importance of these humoral signaling pathways is perhaps most powerfully illustrated in the context of infection and inflammation. Here we provide an overview of how interaction of immune activation of neural and humoral interoceptive mechanisms mediates discrete changes in brain and behavior and highlight how activation of these pathways at specific points in neural development may predispose to psychiatric disorder. As our mechanistic understanding of these interoceptive pathways continues to emerge, it is revealing novel therapeutic targets, potentially heralding an exciting new era of immunotherapies in psychiatry.

Brain Structures Implicated in Inflammation-Associated Depression

Systemic inflammation rapidly impairs mood, motivation, and cognition inducing a stereotyped cluster of symptoms collectively known as "sickness behaviors." When inflammation is severe or chronic, these behavioral changes can appear indistinguishable from major depressive disorder (MDD). Human and rodent neuroimaging combined with experimental inflammatory challenges has clarified the neural circuitry associated with many of the key features of inflammation-induced-sickness behavior, and in so doing revealed often-remarkable commonalities with circuit abnormalities observed in MDD. This review aims to provide the first synthesis of this work illustrating areas of convergence and divergence with the MDD literature as well as highlighting areas for future study.

Impact of propofol anaesthesia on cytokine expression profiles in the developing rat brain: a randomised placebo-controlled experimental in-vivo study

BACKGROUND

Recent experimental data indicate that volatile anaesthetics can induce a neuroinflammatory response in the central nervous system. The questions of to what extent this occurs in the developing brain and whether nonvolatile anaesthetics are also involved remain unanswered.

OBJECTIVES

The objective of this study is to investigate the impact of propofol anaesthesia on cytokine mRNA expression profiles in the neonatal brain at defined stages of the brain growth spurt.

DESIGN

A randomised placebo-controlled experimental in-vivo study.

SETTING

Translational research laboratories at the University of Geneva Medical School.

METHODS

Wistar rats received 6-h propofol anaesthesia at postnatal day 10 or 20. A quantitative real-time PCR was used to evaluate the impact of this treatment paradigm on mRNA expression profiles of selected members of the cytokine family in the prefrontal cortex and hippocampus.

RESULTS

Propofol anaesthesia induced a transient 1.8-fold (interquartile range, IQR 1.7 to 2.2) increase (P = 0.004) in prefrontal but not hippocampal tumour necrosis factor mRNA concentrations in 10-day-old animals. No such effect was detected in 20-day-old animals. No changes in mRNA concentrations of two other pro-inflammatory cytokines, interleukins IL-6 and IL-1β, were detected following drug exposure at any developmental stages or in any studied brain regions. In contrast, propofol anaesthesia at postnatal day 10 induced a transient increase in the mRNA expression patterns of two chemokines: Ccl2 and Ccl3 [for Ccl2 mRNA: 4.4-fold (3.8 to 5.6) increase in the prefrontal cortex, P = 0.0002 and a 3.5-fold (2.8 to 5.3) increase in the hippocampus, P = 0.0001; for Ccl3 mRNA: 2.9-fold (2.6 to 4.31) increase in the prefrontal cortex, P = 0.0001, and a 2.7-fold (2.2 to 3.6) increase in the hippocampus, P = 0.0003]. Propofol did not affect Ccl2 and Ccl3 mRNA concentrations in 20-day-old animals. In addition, it did not impact on two other members of the chemokine family, Cxcl1 and Cx3cl1, at any time points or in any brain regions investigated.

CONCLUSION

This study suggests that propofol anaesthesia does not have a major impact on pro-inflammatory cytokine expression profiles in the developing central nervous system during the brain growth spurt. These results raise arguments against the involvement of neuroinflammatory pathways in propofol-related neurotoxicity observed following the administration of this drug in the early postnatal period.

Brain morphology links systemic inflammation to cognitive function in midlife adults

BACKGROUND

Inflammation is linked to cognitive decline in midlife, but the neural basis for this link is unclear. One possibility is that inflammation associates with adverse changes in brain morphology, which accelerates cognitive aging and later dementia risk. Clear evidence is lacking, however, regarding whether inflammation relates to cognition in midlife via changes in brain morphology. Accordingly, the current study examines whether associations of inflammation with cognitive function are mediated by variation in cortical gray matter volume among midlife adults.

METHODS

Plasma levels of interleukin (IL)-6 and C-reactive protein (CRP), relatively stable markers of peripheral systemic inflammation, were assessed in 408 community volunteers aged 30-54 years. All participants underwent structural neuroimaging to assess global and regional brain morphology and completed neuropsychological tests sensitive to early changes in cognitive function. Measurements of brain morphology (regional tissue volumes and cortical thickness and surface area) were derived using Freesurfer.

RESULTS

Higher peripheral inflammation was associated with poorer spatial reasoning, short term memory, verbal proficiency, learning and memory, and executive function, as well as lower cortical gray and white matter volumes, hippocampal volume and cortical surface area. Mediation models with age, sex and intracranial volume as covariates showed cortical gray matter volume to partially mediate the association of inflammation with cognitive performance. Exploratory analyses of body mass suggested that adiposity may be a source of the inflammation linking brain morphology to cognition.

CONCLUSIONS

Inflammation and adiposity might relate to cognitive decline via influences on brain morphology.

Systemic inflammation and the brain: novel roles of genetic, molecular, and environmental cues as drivers of neurodegeneration

The nervous and immune systems have evolved in parallel from the early bilaterians, in which innate immunity and a central nervous system (CNS) coexisted for the first time, to jawed vertebrates and the appearance of adaptive immunity. The CNS feeds from, and integrates efferent signals in response to, somatic and autonomic sensory information. The CNS receives input also from the periphery about inflammation and infection. Cytokines, chemokines, and damage-associated soluble mediators of systemic inflammation can also gain access to the CNS via blood flow. In response to systemic inflammation, those soluble mediators can access directly through the circumventricular organs, as well as open the blood–brain barrier. The resulting translocation of inflammatory mediators can interfere with neuronal and glial well-being, leading to a break of balance in brain homeostasis. This in turn results in cognitive and behavioral manifestations commonly present during acute infections – including anorexia, malaise, depression, and decreased physical activity – collectively known as the sickness behavior (SB). While SB manifestations are transient and self-limited, under states of persistent systemic inflammatory response the cognitive and behavioral changes can become permanent. For example, cognitive decline is almost universal in sepsis survivors, and a common finding in patients with systemic lupus erythematosus. Here, we review recent genetic evidence suggesting an association between neurodegenerative disorders and persistent immune activation; clinical and experimental evidence indicating previously unidentified immune-mediated pathways of neurodegeneration; and novel immunomodulatory targets and their potential relevance for neurodegenerative disorders.

[Formula: see text]evidence of neuropsychological dysfunction in Stevens-Johnson Syndrome and toxic epidermal necrolysis: case report

Stevens-Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN) is a potentially life-threatening critical illness affecting multiple organ systems including the peripheral and central nervous system. This case report involves a young man who was diagnosed with SJS/TEN at age 16 and underwent neuropsychological assessment at age 21. Results indicate a diffuse pattern of cerebral compromise and represent a decline from premorbid level of functioning. The etiology of the cognitive impairment in this patient is likely multifactorial with possible pathophysiologic mechanisms including hypoxemia, metabolic acid-base perturbations, hyperglycemia, and delirium, as well as sepsis and inflammation.

Neurocognitive disturbances associated with acute infectious mononucleosis, Ross River fever and Q fever: a preliminary investigation of inflammatory and genetic correlates

Disturbances in neurocognitive performance are a core feature of the acute sickness response to infection; however the underlying mechanisms remain unclear. The current study used a computerised battery to assess neurocognitive functioning in subjects enrolled in the Dubbo Infection Outcomes Study (n=107) - a prospective cohort of subjects followed from documented acute infection with Epstein Barr virus, Ross River virus, or Coxiella burnetii until recovery. Subjects were assessed when ill, and a subset again after complete recovery. Associations between sickness-related cognitive disturbances and single nucleotide polymorphisms (SNPs) in cytokine (interleukin [IL]-6, IL-10, tumor necrosis factor-α and interferon-γ) and neurobehavioral genes (serotonin transporter and catechol-O-methyltransferase) were explored. During acute infection, subjects exhibited slower matching-to-sample responses (p=0.03), poorer working memory capacity (p=0.014), mental planning (p=0.045), and dual attention task performance (p=0.02), and required longer to complete discordant Stroop trials (p=0.01) compared to recovery. Objective impairments correlated significantly with self-reported symptoms (p<0.05) as well as levels of the inflammation marker, C-reactive protein (p=0.001). Linear regression analysis identified an association between neurocognitive disturbance during acute illness and functional polymorphisms in inflammatory cytokine genes. Specifically, the high cytokine producing G allele of the IL-6-174G/C SNP was associated with poorer neurocognitive performance when subjects were ill (p=0.027). These findings confirm that acute infection impacts on neurocognitive performance, manifesting as slowed responses and impaired performance on complex tasks requiring higher-order functioning which has important real-world implications. The data provide the first preliminary evidence for a role of a genetic predisposition to more intense inflammatory responses in objective neurocognitive disturbances during acute infections. These associations require replication in a larger sample size.

The contribution of major depression to the global burden of ischemic heart disease: a comparative risk assessment

BACKGROUND

Cardiovascular disease and mental health both hold enormous public health importance, both ranking highly in results of the recent Global Burden of Disease Study 2010 (GBD 2010). For the first time, the GBD 2010 has systematically and quantitatively assessed major depression as an independent risk factor for the development of ischemic heart disease (IHD) using comparative risk assessment methodology.

METHODS

A pooled relative risk (RR) was calculated from studies identified through a systematic review with strict inclusion criteria designed to provide evidence of independent risk factor status. Accepted case definitions of depression include diagnosis by a clinician or by non-clinician raters adhering to Diagnostic and Statistical Manual of Mental Disorders (DSM) or International Classification of Diseases (ICD) classifications. We therefore refer to the exposure in this paper as major depression as opposed to the DSM-IV category of major depressive disorder (MDD). The population attributable fraction (PAF) was calculated using the pooled RR estimate. Attributable burden was calculated by multiplying the PAF by the underlying burden of IHD estimated as part of GBD 2010.

RESULTS

The pooled relative risk of developing IHD in those with major depression was 1.56 (95% CI 1.30 to 1.87). Globally there were almost 4 million estimated IHD disability-adjusted life years (DALYs), which can be attributed to major depression in 2010; 3.5 million years of life lost and 250,000 years of life lived with a disability. These findings highlight a previously underestimated mortality component of the burden of major depression. As a proportion of overall IHD burden, 2.95% (95% CI 1.48 to 4.46%) of IHD DALYs were estimated to be attributable to MDD in 2010. Eastern Europe and North Africa/Middle East demonstrate the highest proportion with Asia Pacific, high income representing the lowest.

CONCLUSIONS

The present work comprises the most robust systematic review of its kind to date. The key finding that major depression may be responsible for approximately 3% of global IHD DALYs warrants assessment for depression in patients at high risk of developing IHD or at risk of a repeat IHD event.

Twenty-five years of research on the behavioural malaise associated with influenza and the common cold

Minor illnesses such as the common cold and influenza are frequent and widespread. As well as specific symptoms such as nasal problems and fever, these illnesses are associated with a behavioural malaise. One feature of this malaise is reduced alertness and this has been confirmed using subjective reports and objective measures of performance. Such effects have been obtained with both experimentally induced infections and in studies of naturally occurring illnesses. The mechanisms underlying the effects are unclear but possibly reflect effects of cytokines on the CNS which result in changes in neurotransmitter functioning that lead to reduced alertness. The malaise induced by these illnesses has many real-life consequences and activities such as driving and safety at work may be at risk. These illnesses not only have direct effects on performance and mood but also make the person more sensitive to effects of other negative influences such as noise, alcohol and prolonged work. Countermeasures include ingestion of caffeine and other drugs known to increase alertness.

PPARγ activation prevents impairments in spatial memory and neurogenesis following transient illness

The detrimental effects of illness on cognition are familiar to virtually everyone. Some effects resolve quickly while others may linger after the illness resolves. We found that a transient immune response stimulated by lipopolysaccharide (LPS) compromised hippocampal neurogenesis and impaired hippocampus-dependent spatial memory. The immune event caused an ∼50% reduction in the number of neurons generated during the illness and the onset of the memory impairment was delayed and coincided with the time when neurons generated during the illness would have become functional within the hippocampus. Broad spectrum non-steroidal anti-inflammatory drugs attenuated these effects but selective Cox-2 inhibition was ineffective while PPARγ activation was surprisingly effective at protecting both neurogenesis and memory from the effects of LPS-produced transient illness. These data may highlight novel mechanisms behind chronic inflammatory and neuroinflammatory episodes that are known to compromise hippocampus-dependent forms of learning and memory.

Treatment for Schistosoma japonicum, reduction of intestinal parasite load, and cognitive test score improvements in school-aged children

Background

To determine whether treatment of intestinal parasitic infections improves cognitive function in school-aged children, we examined changes in cognitive testscores over 18 months in relation to: (i) treatment-related Schistosoma japonicum intensity decline, (ii) spontaneous reduction of single soil-transmitted helminth (STH) species, and (iii) ≥2 STH infections among 253 S. japonicum-infected children.

Methodology

Helminth infections were assessed at baseline and quarterly by the Kato-Katz method. S. japonicum infection was treated at baseline using praziquantel. An intensity-based indicator of lower vs. no change/higher infection was defined separately for each helminth species and joint intensity declines of ≥2 STH species. In addition, S. japonicum infection-free duration was defined in four categories based on time of schistosome re-infection: >18 (i.e. cured), >12 to ≤18, 6 to ≤12 and ≤6 (persistently infected) months. There was no baseline treatment for STHs but their intensity varied possibly due to spontaneous infection clearance/acquisition. Four cognitive tests were administered at baseline, 6, 12, and 18 months following S. japonicum treatment: learning and memory domains of Wide Range Assessment of Memory and Learning (WRAML), verbal fluency (VF), and Philippine nonverbal intelligence test (PNIT). Linear regression models were used to relate changes in respective infections to test performance with adjustment for sociodemographic confounders and coincident helminth infections.

Principal Findings

Children cured (β = 5.8; P = 0.02) and those schistosome-free for >12 months (β = 1.5; P = 0.03) scored higher in WRAML memory and VF tests compared to persistently infected children independent of STH infections. A decline vs. no change/increase of any individual STH species (β:11.5–14.5; all P<0.01) and the joint decline of ≥2 STH (β = 13.1; P = 0.01) species were associated with higher scores in WRAML learning test independent of schistosome infection. Hookworm and Trichuris trichiura declines were independently associated with improvements in WRAML memory scores as was the joint decline in ≥2 STH species. Baseline coinfection by ≥2 STH species was associated with low PNIT scores (β = −1.9; P = 0.04).

Conclusion/Significance

Children cured/S. japonicum-free for >12 months post-treatment and those who experienced declines of ≥2 STH species scored higher in three of four cognitive tests. Our result suggests that sustained deworming and simultaneous control for schistosome and STH infections could improve children's ability to take advantage of educational opportunities in helminth-endemic regions.

Parasitic worm infections are associated with cognitive impairment and lower academic achievement for infected relative to uninfected children. However, it is unclear whether curing or reducing worm infection intensity improves child cognitive function. We examined the independent associations between: (i) Schistosoma japonicum infection-free duration, (ii) declines in single helminth species, and (iii) joint declines of ≥2 soil-transmitted helminth (STH) infections and improvements in four cognitive tests during18 months of follow-up. Enrolled were schistosome-infected school-aged children among whom coinfection with STH was common. All children were treated for schistosome infection only at enrolment with praziquantel. Children cured or schistosome-free for >12 months scored higher in memory and verbal fluency tests compared to persistently infected children. Likewise, declines of single and polyparasitic STH infections predicted higher scores in three of four tests. We conclude that reducing the intensity of certain helminth species and the frequency of multi-species STH infections may have long-term benefits for affected children's cognitive performance. The rapidity of schistosome re-infection and the ubiquity of concurrent multi-species infection highlight the importance of sustained deworming for both schistosome and STH infections to enhance the learning and educational attainment of children in helminth-endemic settings.

Common Respiratory Tract Infections as Psychological Entities: A Review of the Mood and Performance Effects of Being Ill

The clinical manifestations associated with colds and influenza overshadow the equally important mood and performance impairments. While decreased alertness and increased anxiety can be considered side effects of symptomatology, symptoms alone may not be responsible for the psychomotor and attention deficits of colds and influenza, respectively. An alternative hypothesis, as proposed in this review, suggests that the immune response, in the form of a cytokine cascade, may be responsible for both the physical and psychological symptoms. In particular, patterns of cytokine production for each infection will dictate the symptoms and performance deficits both within and between viruses. This hypothesis can be extended to incorporate infectious mononucleosis, as well as colds and influenza. The efficacy of symptom‐based overthe‐counter medications is then called into question.

Role of interleukin-1beta in postoperative cognitive dysfunction

OBJECTIVE

Although postoperative cognitive dysfunction (POCD) often complicates recovery from major surgery, the pathogenic mechanisms remain unknown. We explored whether systemic inflammation, in response to surgical trauma, triggers hippocampal inflammation and subsequent memory impairment, in a mouse model of orthopedic surgery.

METHODS

C57BL/6J, knock out (lacking interleukin [IL]-1 receptor, IL-1R(-/-)) and wild type mice underwent surgery of the tibia under general anesthesia. Separate cohorts of animals were tested for memory function with fear conditioning tests, or euthanized at different times to assess levels of systemic and hippocampal cytokines and microglial activation; the effects of interventions, designed to interrupt inflammation (specifically and nonspecifically), were also assessed.

RESULTS

Surgery caused hippocampal-dependent memory impairment that was associated with increased plasma cytokines, as well as reactive microgliosis and IL-1beta transcription and expression in the hippocampus. Nonspecific attenuation of innate immunity with minocycline prevented surgery-induced changes. Functional inhibition of IL-1beta, both in mice pretreated with IL-1 receptor antagonist and in IL-1R(-/-) mice, mitigated the neuroinflammatory effects of surgery and memory dysfunction.

INTERPRETATION

A peripheral surgery-induced innate immune response triggers an IL-1beta-mediated inflammatory process in the hippocampus that underlies memory impairment. This may represent a viable target to interrupt the pathogenesis of postoperative cognitive dysfunction.

Inflammation causes mood changes through alterations in subgenual cingulate activity and mesolimbic connectivity

BACKGROUND

Inflammatory cytokines are implicated in the pathophysiology of depression. In rodents, systemically administered inflammatory cytokines induce depression-like behavior. Similarly in humans, therapeutic interferon-alpha induces clinical depression in a third of patients. Conversely, patients with depression also show elevated pro-inflammatory cytokines.

OBJECTIVES

To determine the neural mechanisms underlying inflammation-associated mood change and modulatory effects on circuits involved in mood homeostasis and affective processing.

METHODS

In a double-blind, randomized crossover study, 16 healthy male volunteers received typhoid vaccination or saline (placebo) injection in two experimental sessions. Mood questionnaires were completed at baseline and at 2 and 3 hours. Two hours after injection, participants performed an implicit emotional face perception task during functional magnetic resonance imaging. Analyses focused on neurobiological correlates of inflammation-associated mood change and affective processing within regions responsive to emotional expressions and implicated in the etiology of depression.

RESULTS

Typhoid but not placebo injection produced an inflammatory response indexed by increased circulating interleukin-6 and significant mood reduction at 3 hours. Inflammation-associated mood deterioration correlated with enhanced activity within subgenual anterior cingulate cortex (sACC) (a region implicated in the etiology of depression) during emotional face processing. Furthermore, inflammation-associated mood change reduced connectivity of sACC to amygdala, medial prefrontal cortex, nucleus accumbens, and superior temporal sulcus, which was modulated by peripheral interleukin-6.

CONCLUSIONS

Inflammation-associated mood deterioration is reflected in changes in sACC activity and functional connectivity during evoked responses to emotional stimuli. Peripheral cytokines modulate this mood-dependent sACC connectivity, suggesting a common pathophysiological basis for major depressive disorder and sickness-associated mood change and depression.

Neural origins of human sickness in interoceptive responses to inflammation

BACKGROUND

Inflammation is associated with psychological, emotional, and behavioral disturbance, known as sickness behavior. Inflammatory cytokines are implicated in coordinating this central motivational reorientation accompanying peripheral immunologic responses to pathogens. Studies in rodents suggest an afferent interoceptive neural mechanism, although comparable data in humans are lacking.

METHODS

In a double-blind, randomized crossover study, 16 healthy male volunteers received typhoid vaccination or saline (placebo) injection in two experimental sessions. Profile of Mood State questionnaires were completed at baseline and at 2 and 3 hours. Two hours after injection, participants performed a high-demand color word Stroop task during functional magnetic resonance imaging. Blood samples were performed at baseline and immediately after scanning.

RESULTS

Typhoid but not placebo injection produced a robust inflammatory response indexed by increased circulating interleukin-6 accompanied by a significant increase in fatigue, confusion, and impaired concentration at 3 hours. Performance of the Stroop task under inflammation activated brain regions encoding representations of internal bodily state. Spatial and temporal characteristics of this response are consistent with interoceptive information flow via afferent autonomic fibers. During performance of this task, activity within interoceptive brain regions also predicted individual differences in inflammation-associated but not placebo-associated fatigue and confusion. Maintenance of cognitive performance, despite inflammation-associated fatigue, led to recruitment of additional prefrontal cortical regions.

CONCLUSIONS

These findings suggest that peripheral infection selectively influences central nervous system function to generate core symptoms of sickness and reorient basic motivational states.

Intranasal immune challenge induces sex-dependent depressive-like behavior and cytokine expression in the brain

The association between activation of the immune system and mood disorders has been reported by several studies. However, the mechanisms by which the immune system affects mood are only partially understood. In the present study, we detected depressive-like behavior in a rat animal model which involves the induction of inflammation in the nasal cavities by intranasal (i.n.) instillation of bacterial lipopolysaccharides (LPS). Female rats showed depressive-like behavior as evidenced by the forced swim test after repeated i.n. administration of LPS. These responses were not paralleled by alterations in motor activity as measured by the open field test. In the same animals, corticosterone responses after the swimming sessions were the highest of all the groups evaluated. Real-time RT PCR was used to analyze the transcriptional regulation of the cytokines interleukin-1beta, tumor necrosis factor-alpha, and interleukin-6 in several brain regions. Increased tumor necrosis factor-alpha was detected in the hippocampus and brainstem of female rats challenged with i.n. LPS. These results suggest that peripheral inflammation in the upper respiratory tract is an immune challenge capable of inducing depressive-like behavior, promoting exaggerated glucocorticoid responses to stress, and increasing cytokine transcription in the brain. These results further our understanding of the role that the immune system may play in the pathophysiology of depression.

Selective effects of upper respiratory tract infection on cognition, mood and emotion processing: a prospective study

Observational and experimentally induced infection studies show that upper respiratory tract infections (URTI) affect mood and cognition. This study tested the effects of naturally occurring URTI on cognition, mood and emotional processing, using a prospective design, with a broader array of tests than previous research, and with well matched control participants. Eighty participants (42 younger, M age 20.3 years; 38 older, M age 64.3 years) underwent neuropsychological assessment at baseline. Once a participant had URTI symptoms, s/he and a healthy, matched participant were retested. The Cognitive Drug Research computerised assessment battery was used to assess Power and Continuity of Attention, Quality of Episodic and Working Memory, Speed of Memory, and mood. Additionally, emotional processing was measured on matching of emotionally-negative faces with faces and faces with labels. Forty-two of 80 participants were matched (21 well, 21 ill). Well participants improved in Speed of Memory and face-label reaction time. Despite a lack of fever, ill participants demonstrated significantly smaller improvements. Older participants reported feeling less alert if ill, and less stressed if well, than at baseline. All ill participants reported less contentment than at baseline than well participants. Severity of URTI symptoms correlated with changes in Speed of Memory and mood. Even without fever, infectious disease produces large disturbances in speed of cognitive processing, particularly that reflecting retrieval from memory, and these effects are more marked in older participants. URTIs also affect mood. Future studies need to examine the role of inflammatory molecules and the brain regions implicated in mediating these findings.

Genetic Variants in P-Selectin and C-Reactive Protein Influence Susceptibility to Cognitive Decline After Cardiac Surgery

OBJECTIVES

We hypothesized that candidate gene polymorphisms in biologic pathways regulating inflammation, cell matrix adhesion/interaction, coagulation-thrombosis, lipid metabolism, and vascular reactivity are associated with postoperative cognitive deficit (POCD).

BACKGROUND

Cognitive decline is a common complication of coronary artery bypass graft (CABG) surgery and is associated with a reduced quality of life.

METHODS

In a prospective cohort study of 513 patients (86% European American) undergoing CABG surgery with cardiopulmonary bypass, a panel of 37 single-nucleotide polymorphisms (SNPs) was genotyped by mass spectrometry. Association between these SNPs and cognitive deficit at 6 weeks after surgery was tested using multiple logistic regression accounting for age, level of education, baseline cognition, and population structure. Permutation analysis was used to account for multiple testing.

RESULTS

We found that minor alleles of the CRP 1059G/C SNP (odds ratio [OR] 0.37, 95% confidence interval [CI] 0.16 to 0.78; p = 0.013) and the SELP 1087G/A SNP (OR 0.51, 95% CI 0.30 to 0.85; p = 0.011) were associated with a reduction in cognitive deficit in European Americans (n = 443). The absolute risk reduction in the observed incidence of POCD was 20.6% for carriers of the CRP 1059C allele and 15.2% for carriers of the SELP 1087A allele. Perioperative serum C-reactive protein (CRP) and degree of platelet activation were also significantly lower in patients with a copy of the minor alleles, providing biologic support for the observed allelic association.

CONCLUSIONS

The results suggest a contribution of P-selectin and CRP genes in modulating susceptibility to cognitive decline after cardiac surgery, with potential implications for identifying populations at risk who might benefit from targeted perioperative antiinflammatory strategies.

Preliminary evidence of mitochondrial dysfunction associated with post-infective fatigue after acute infection with Epstein Barr virus

BACKGROUND

Acute infectious diseases are typically accompanied by non-specific symptoms including fever, malaise, irritability and somnolence that usually resolve on recovery. However, in some individuals these symptoms persist in what is commonly termed post-infective fatigue. The objective of this pilot study was to determine the gene expression correlates of post-infective fatigue following acute Epstein Barr virus (EBV) infection.

METHODS

We followed 5 people with acute mononucleosis who developed post-infective fatigue of more than 6 months duration and 5 HLA-matched control subjects who recovered within 3 months. Subjects had peripheral blood mononuclear cell (PBMC) samples collected at varying time points including at diagnosis, then every 2 weeks for 3 months, then every 3 months for a year. Total RNA was extracted from the PBMC samples and hybridized to microarrays spotted with 3,800 oligonucleotides.

RESULTS

Those who developed post-infective fatigue had gene expression profiles indicative of an altered host response during acute mononucleosis compared to those who recovered uneventfully. Several genes including ISG20 (interferon stimulated gene), DNAJB2 (DnaJ [Hsp40] homolog and CD99), CDK8 (cyclin-dependent kinase 8), E2F2 (E2F transcription factor 2), CDK8 (cyclin-dependent kinase 8), and ACTN2 (actinin, alpha 2), known to be regulated during EBV infection, were differentially expressed in post-infective fatigue cases. Several of the differentially expressed genes affect mitochondrial functions including fatty acid metabolism and the cell cycle.

CONCLUSION

These preliminary data provide insights into alterations in gene transcripts associated with the varied clinical outcomes from acute infectious mononucleosis.

Interferon-induced depression and cognitive impairment in hepatitis C virus patients: a 72 week prospective study

OBJECTIVES

This study assessed the rates and course of depressive symptomatology and neurocognitive deficits in hepatitis C virus (HCV) patients undergoing interferon treatment, and explored possible predictors of depression and neurocognitive deficits.

DESIGN

In order to obtain objective assessments of depression, and to evaluate cognitive impairment, a 72-week prospective study, comprising 48 weeks of treatment and 24 weeks of post-treatment follow-up was utilized.

METHODS

A total of 50 HCV patients were assessed at baseline, and 14 times during pegylated interferon plus ribavirin treatment. Patients were also assessed on four timepoints after the termination of treatment. All patients have previously been treated for hepatitis C infection with interferon and were judged to be treatment resistant in these treatments. Depression was assessed using the Center for Epidemiological Studies Depression (CES-D) questionnaire, and patients were interviewed regarding problems with memory, attention and concentration.

RESULTS

Eighty-two per cent of interferon-treated patients developed severe enough depressive symptoms to meet the CES-D criteria for possible major depressive disorder (MDD). Possible MDD onset was most frequent by the first week of treatment, and almost all possible MDD cases were observed by week 8. More severe depressive symptoms at baseline were associated with higher depressive symptoms during interferon treatment. Thirty per cent of patients complained about cognitive problems. In half of these patients cognitive impairments were still reported after the termination of treatment. There was no association between depression during interferon treatment and subjective cognitive complaints.

CONCLUSIONS

The findings suggest that depression and cognitive impairments are frequent and persistent side-effects of interferon treatment in treatment-resistant patients.

Maternal behavior changes after immune challenge of neonates with developmental effects on adult social behavior

To examine whether maternal responsiveness during interactions with endotoxin-treated pups contributes to long-term effects on social development, neonatal mice were fostered on postnatal day 1 to dams from three selectively bred lines that differ in social behaviors. On day 5, neonates were administered saline or 0.5 mg/kg endotoxin (lipopolysaccharide, i.p.). Observations of undisturbed dams and litters on days 2, 4, 6, and 8 showed modest line differences in maternal behaviors. At the peak intensity of the transient illness induced by endotoxin (3 hr postinjection on day 5), dams increased licking and decreased time off-nest for endotoxin, but not saline-treated pups. As adults, fostered-reared males were observed in brief social interactions. Males exposed to endotoxin early in life showed changes in adult social behaviors that depended on foster dam line as well as individual differences in maternal responsiveness. Maternal responsiveness to stressed neonates can ameliorate the social-developmental effects of early illness.

The Role of the Immune System in Psychology and Neuroscience

The immune system and the nervous system are connected in a dynamic network that has important implications for psychology. First, if analyzed in functional terms, the immune system and the nervous system are not distinctly separated: The immune system can take part in neuronal signaling through the production of an array of transmitters and hormones, and brain cells can process and present antigen and produce immune proteins. Moreover, synapses seem to be formed between immune and neural cells in lymphoid tissue. The basis of this phenomenon may be a common evolutionary background of physiological systems that by tradition have been viewed as discrete rather than overlapping. Second, the immune system is actively involved in homeostatic regulation. Signals from immune cells can profoundly change the physiological state of the organism, with changes observed in metabolism, stress axes activity, behavior, motivation and cognition. Many of these changes have probably evolved to ease recuperation. Third, the activity in the immune system is dependent of homeostatic regulation by the neuroendocrine system in a biologically important network that is also capable of mediating psychological impact on immunity. In this review, it is argued that immunology should be ecological in nature and thereby related to psychological and neural science. Hypothetically, an ecological immunology will show cross-fertilizing properties, increasing the explanatory power of the seemingly disparate scientific disciplines involved.

The immune system, depression and the action of antidepressants

It is well established that the hypothalamic-pituitary-adrenal axis (HPA) is activated by both external and internal stressors which result in the hypersecretion of adrenal glucocorticoids. In major depression the prolonged elevation of the glucocorticoid concentration leads to a desensitisation of the central glucocorticoid receptors and probably those receptors located on macrophages. These changes may account for the observation that many aspects of cellular immunity are activated in depression (for example, the increased release of pro-inflammatory cytokines from activated macrophages in the periphery and brain, and the increased release of acute phase proteins from the liver) even though other aspects of immunity (for example, natural killer cell activity and T-cell replication) are depressed. It is also known that some of the pro-inflammatory cytokines are potent activators of the HPA axis. Evidence is provided that the consequences of the hypersecretion of glucocorticoids and pro-inflammatory cytokines result in the malfunctioning of noradrenergic and serotonergic neurotransmission in the brain, changes which are reflected in the major symptoms of depression. Support for this view is provided by observations of the effects of some of these cytokines in non-depressed individuals being treated with pro-inflammatory and related cytokines for cancer. This has led to the hypothesis that depression is a form of sickness behaviour which forms the basis of the macrophage theory of depression. The review concludes with a discussion of the role of antidepressants in attenuating the adverse effects of glucocorticoids and pro-inflammatory cytokines on central neurotransmission. Although the precise mechanisms whereby antidepressants these changes is uncertain, there is evidence that they reduce the release of pro-inflammatory cytokines from activated macrophages and thereby facilitate the feedback inhibition of the HPA axis; this results in a reduction in the release of glucocorticoids from the adrenal glands. In addition, many antidepressants have been shown to increase the release of endogenous cytokine antagonists such as interleukin-1 receptor antagonist and interleukin-10. Evidence is also presented to show that different classes of antidepressants act as cyclooxygenase inhibitors which, by lowering the concentration of inflammatory prostaglandins in the brain, reduce the detrimental impact of the inflammatory changes on neurotransmitter function. An advantage of the macrophage hypothesis is that it extends the biogenic amine hypothesis of depression to take account of changes in the endocrine and immune systems which also play a crucial role in the aetiology of depression. In addition, the macrophage hypothesis may broaden the basis of understanding the mechanism of action of antidepressants.

Timing and specificity of the cognitive changes induced by interleukin-2 and interferon-alpha treatments in cancer patients

OBJECTIVE

Neuropsychological changes develop in patients treated by cytokine immunotherapy with interleukin-2 (IL-2) and interferon-alpha (IFN-alpha). However, the time course of appearance of these effects remains unclear, and their precise nature is still incompletely characterized. The objective of this study was to assess and characterize the early cognitive changes induced by IL-2 and IFN-alpha in cancer patients at the end of the first week of treatment and to investigate the subsequent evolution of these changes.

METHODS

The study was conducted in 47 cancer patients who received subcutaneous IL-2, administered alone (N = 17) or with IFN-alpha (N = 7), or IFN-alpha alone, administered subcutaneously at low doses (N = 7) or intravenously at high doses (N = 16). An automated battery of neuropsychological tests (Cambridge Neuropsychological Test Automated Battery) was used to measure reaction time, spatial working memory, and planning tasks. Cognitive tests were performed before treatment (day 1) and after 5 days (day 5) and 1 month of treatment.

RESULTS

On day 5, patients treated with IL-2 alone had impaired spatial working memory and lower accuracy of planning abilities. In contrast, patients treated with IFN-alpha did not show any impairment in performance accuracy in these tasks but showed longer latencies in the test of reaction time. Most of these early alterations persisted at the end of the first month of treatment without any obvious sign of worsening.

CONCLUSIONS

These findings suggest the existence of early differential neuropsychological changes in patients treated with IL-2 and IFN-alpha.

Illness, cytokines, and depression

Various medical conditions that involve activation of the immune system are associated with psychological and neuroendocrine changes that resemble the characteristics of depression. In this review we present our recent studies, designed to investigate the relationship between the behavioral effects of immune activation and depressive symptomatology. In the first set of experiments, we used a double-blind prospective design to investigate the psychological consequences of illness in two models: (1) vaccination of teenage girls with live attenuated rubella virus, and (2) lipopolysaccharide (LPS) administration in healthy male volunteers. In the rubella study, we demonstrated that, compared to control group subjects and to their own baseline, a subgroup of vulnerable individuals (girls from low socioeconomic status) showed a significant virus-induced increase in depressed mood up to 10 weeks after vaccination. In an ongoing study on the effects of LPS, we demonstrated significant LPS-induced elevation in the levels of depression and anxiety as well as memory deficits. These psychological effects were highly correlated with the levels of LPS-induced cytokine secretion. In parallel experiments, we demonstrated in rodents that immune activation with various acute and chronic immune challenges induces a depressive-like syndrome, characterized by anhedonia, anorexia, body weight loss, and reduced locomotor, exploratory, and social behavior. Chronic treatment with antidepressants (imipramine or fluoxetine) attenuated many of the behavioral effects of LPS, as well as LPS-induced changes in body temperature, adrenocortical activation, hypothalamic serotonin release, and the expression of splenic TNF-alpha mRNA. Taken together, these findings suggest that cytokines are involved in the etiology and symptomatology of illness-associated depression.