Effect of single intracerebroventricular injection of alpha-interferon on monoamine concentrations in the rat brain

Increased Parenchymal Macrophages are associated with decreased Tyrosine Hydroxylase mRNA levels in the Substantia Nigra of people with Schizophrenia and Bipolar Disorder

Increased activation of inflammatory macrophages and altered expression of dopamine markers are found in the midbrains of people with schizophrenia (SZ). The relationship of midbrain macrophages to dopamine neurons has not been explored, nor is it known if changes in midbrain macrophages are also present in bipolar disorder (BD) or major depressive disorder (MDD). Herein, we determined whether there were differences in CD163+ cell density in the Substantia Nigra (SN), and cerebral peduncles (CP) of SZ, BD, and MDD compared to controls (CTRL). We also analyzed whether CD163 protein and dopamine-synthesizing enzyme tyrosine hydroxylase (TH) mRNA levels differed among diagnostic groups and if they correlated with the density of macrophages. Overall, perivascular CD163+ cell density was higher in the gray matter (SN) than in the white matter (CP). Compared to CTRL, we found increased density of parenchymal CD163+ cells in the SN of the three psychiatric groups and increased CD163 protein levels in SZ. CD163 protein was positively correlated with density of perivascular CD163+ cells. TH mRNA was reduced in SZ and BD and negatively correlated with parenchymal CD163+ cell density. We provide the first quantitative and molecular evidence of an increase in the density of parenchymal macrophages in the midbrain of major mental illnesses and show that the presence of these macrophages may negatively impact dopaminergic neurons.

Accelerated aging in people living with HIV: The neuroimmune feedback model

People living with HIV (PLWH) experience earlier onset of aging-related comorbidities compared to their counterparts without HIV. This paper lays out a theoretical model to explain why PLWH experience accelerated aging. Briefly, the model is structured as follows. PLWH experience disproportionately heavy burdens of psychosocial stress across the life course. This psychosocial stress increases risks for depressive symptoms and problematic substance use. Depressive symptoms and problematic substance use interfere with long-term adherence to antiretroviral therapy (ART). Lower ART adherence, in turn, exacerbates the elevated systemic inflammation stemming from HIV infection. This inflammation increases risks for aging-related comorbidities. Systemic inflammation also reduces connectivity in the brain's central executive network (CEN), a large-scale brain network that is critical for coping with stressful circumstances. This reduced capacity for coping with stress leads to further increases in depressive symptoms and problematic substance use. Together, these changes form a neuroimmune feedback loop that amplifies the impact of psychosocial stress on aging-related comorbidities. In this paper, I review the existing evidence relevant to this model and highlight directions for future research.

Correlation of catecholamine content and clinical influencing factors in depression among psoriasis patients: a case-control study

Objective

Our study sought to investigate the clinical influencing factors of psoriasis patients with depression, and analyze whether the content of monoamine neurotransmitters in plasma was correlated with depression incidence among psoriasis patients.

Methods

Ninety patients with psoriasis and 40 healthy volunteers (aged from18 to 60) were recruited and interviewed with a piloted questionnaire in both groups to obtain relevant information. The catecholamine in plasma from the two groups was analyzed by radioimmunoassay. The data were analyzed by SPSS statistical software.

Results

The mean Hamilton Depression Scale (HAMD) and mean Athens Insomnia Scale (AIS) scores of the psoriasis patients were higher than the control group. Dopamine content in the plasma was lower (comparing psoriasis patients without depression and the control group, and was negatively correlated with HAMD, AIS, and Psoriasis Area and Severity Index (PASI) scores in the psoriasis patients with depression. There was no significant difference in the epinephrine and norepinephrine contents in all groups. PASI scores were positively correlated with HAMD scores in psoriasis patients. The low dopamine content, Dermatology Life Quality Index, and high PASI scores were the risk factors for depression among the psoriasis patients.

Conclusion

Psoriasis patients have a significantly higher risk of depression than healthy people, and higher PASI scores were linked to a higher incidence of depression. The dopamine levels of patients were influenced by both psoriasis and depression. The risk factors for depression in psoriasis patients are low dopamine levels in the plasma, severe skin lesions, and lower quality of life.

Glycation modulates glutamatergic signaling and exacerbates Parkinson's disease-like phenotypes

Alpha-synuclein (aSyn) is a central player in the pathogenesis of synucleinopathies due to its accumulation in typical protein aggregates in the brain. However, it is still unclear how it contributes to neurodegeneration. Type-2 diabetes mellitus is a risk factor for Parkinson's disease (PD). Interestingly, a common molecular alteration among these disorders is the age-associated increase in protein glycation. We hypothesized that glycation-induced neuronal dysfunction is a contributing factor in synucleinopathies. Here, we dissected the impact of methylglyoxal (MGO, a glycating agent) in mice overexpressing aSyn in the brain. We found that MGO-glycation potentiates motor, cognitive, olfactory, and colonic dysfunction in aSyn transgenic (Thy1-aSyn) mice that received a single dose of MGO via intracerebroventricular injection. aSyn accumulates in the midbrain, striatum, and prefrontal cortex, and protein glycation is increased in the cerebellum and midbrain. SWATH mass spectrometry analysis, used to quantify changes in the brain proteome, revealed that MGO mainly increase glutamatergic-associated proteins in the midbrain (NMDA, AMPA, glutaminase, VGLUT and EAAT1), but not in the prefrontal cortex, where it mainly affects the electron transport chain. The glycated proteins in the midbrain of MGO-injected Thy1-aSyn mice strongly correlate with PD and dopaminergic pathways. Overall, we demonstrated that MGO-induced glycation accelerates PD-like sensorimotor and cognitive alterations and suggest that the increase of glutamatergic signaling may underly these events. Our study sheds new light into the enhanced vulnerability of the midbrain in PD-related synaptic dysfunction and suggests that glycation suppressors and anti-glutamatergic drugs may hold promise as disease-modifying therapies for synucleinopathies.

Paliperidone Reversion of Maternal Immune Activation-Induced Changes on Brain Serotonin and Kynurenine Pathways

Emerging evidence indicates that early-life exposure to environmental factors may increase the risk for schizophrenia via inflammatory mechanisms. Inflammation can alter the metabolism of tryptophan through the oxidative kynurenine pathway to compounds with neurotoxic and neuroprotective activity and compromise serotonin (5-HT) synthesis. Here we investigate the role of serotonergic and kynurenine pathways in the maternal immune activation (MIA) animal model of schizophrenia. The potential reversion exerted by long-term antipsychotic treatment was also evaluated. MIA was induced by prenatal administration of polyinosinic:polycytidylic acid (poly (I:C)) in mice. Expression of different proteins and the content of different metabolites involved in the function of serotonergic and kynurenine pathways was assessed by RT-PCR, immunoblot and ELISA analyses in frontal cortex of the offspring after puberty. MIA decreased tissue 5-HT content and promoted changes in the expression of serotonin transporter, 5-HT_2A and 5-HT_2C receptors. Expression of indoleamine 2,3-dioxygenase 2 (IDO2) and kynurenine 3-monooxygenase (KMO) was increased by poly (I:C) whereas kynurenine aminotransferase II and its metabolite kynurenic acid were not altered. Long-term paliperidone was able to counteract MIA-induced changes in 5-HT and KMO, and to increase tryptophan availability and tryptophan hydroxylase-2 expression in poly (I:C) mice but not in controls. MIA-induced increase of the cytotoxic risk ratio of kynurenine metabolites (quinolinic/kynurenic acid) was also reversed by paliperidone. MIA induces specific long-term brain effects on serotonergic activity. Such effects seem to be related with alternative activation of the kynurenine metabolic pathway towards a cytotoxic status. Atypical antipsychotic paliperodine partially remediates abnormalities observed after MIA.

Intracerebroventricular Administration of Interferon-Alpha Induced Depressive-Like Behaviors and Neurotransmitter Changes in Rhesus Monkeys

Interferon-alpha (IFN-α) is a cytokine widely used in the treatment of brain cancers and virus infections with side effects including causing depression. Monoamine neurotransmitter systems have been found playing important roles in peripheral IFN-α-induced depression, but how peripheral IFN-α accesses the central nervous system and contributes to the development of depression is poorly known. This study aimed to develop a non-human primate model using long-term intracerebroventricular (i.c.v.) administration of IFN-α (5 days/week for 6 weeks), to observe the induced depressive-like behaviors and to explore the contributions of monoamine neurotransmitter systems in the development of depression. In monkeys receiving i.c.v. IFN-α administration, anhedonia was observed as decreases of sucrose consumption, along with depressive-like symptoms including increased huddling behavior, decreases of spontaneous and reactive locomotion in home cage, as well as reduced exploration and increased motionless in the open field. Chronic central IFN-α infusion significantly increased the cerebrospinal fluid (CSF) concentrations of noradrenaline (NA), and 3,4-dihydroxyphenylacetic acid (DOPAC), but not 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA). These CSF monoamine metabolites showed associations with some specific depression-related behaviors. In conclusion, central IFN-α administration induced anhedonia and depression-related behaviors comparable to the results with peripheral administration, and the development of depression was associated with the dysfunction of monoamine neurotransmitters.

Targeting Inflammatory-Mitochondrial Response in Major Depression: Current Evidence and Further Challenges

The prevalence of psychiatric disorders has increased in recent years. Among existing mental disorders, major depressive disorder (MDD) has emerged as one of the leading causes of disability worldwide, affecting individuals throughout their lives. Currently, MDD affects 15% of adults in the Americas. Over the past 50 years, pharmacotherapy, psychotherapy, and brain stimulation have been used to treat MDD. The most common approach is still pharmacotherapy; however, studies show that about 40% of patients are refractory to existing treatments. Although the monoamine hypothesis has been widely accepted as a molecular mechanism to explain the etiology of depression, its relationship with other biochemical phenomena remains only partially understood. This is the case of the link between MDD and inflammation, mitochondrial dysfunction, and oxidative stress. Studies have found that depressive patients usually exhibit altered inflammatory markers, mitochondrial membrane depolarization, oxidized mitochondrial DNA, and thus high levels of both central and peripheral reactive oxygen species (ROS). The effect of antidepressants on these events remains unclear. Nevertheless, the effects of ROS on the brain are well known, including lipid peroxidation of neuronal membranes, accumulation of peroxidation products in neurons, protein and DNA damage, reduced antioxidant defenses, apoptosis induction, and neuroinflammation. Antioxidants such as ascorbic acid, tocopherols, and coenzyme Q have shown promise in some depressive patients, but without consensus on their efficacy. Hence, this paper provides a review of MDD and its association with inflammation, mitochondrial dysfunction, and oxidative stress and is aimed at thoroughly discussing the putative links between these events, which may contribute to the design and development of new therapeutic approaches for patients.

A potential mechanistic role for neuroinflammation in reward processing impairments in autism spectrum disorder

Accumulating evidence suggests that autism spectrum disorder (ASD) may be conceptualized within a framework of reward processing impairments. The Social Motivation Theory of Autism posits that reduced motivation to interact with people and decreased pleasure derived from social interactions may derail typical social development and contribute to the emergence of core social communication deficits in ASD. Neuroinflammation may disrupt the development of mesolimbic dopaminergic systems that are critical for optimal functioning of social reward processing systems. This neuroinflammation-induced disturbance of mesolimbic dopaminergic functioning has been substantiated using maternal immune activation rodent models whose offspring show aberrant dopaminergic corticostriatal function, as well as behavioral characteristics of ASD model systems. Preclinical findings are in turn supported by clinical evidence of increased mesolimbic neuroinflammatory responses in individuals with ASD. This review summarizes evidence for reward processing deficits and neuroinflammatory impairments in ASD and examines how immune inflammatory dysregulation may impair the development of dopaminergic mesolimbic circuitry in ASD. Finally, future research directions examining neuroinflammatory effects on reward processing in ASD are proposed.

Natural Killer Cells may Exert Antidepressant-like Effects in Mice by Controlling the Release of Inflammatory Factors

Depression or stress is reportedly related to the overflow of inflammatory factors in the body and T cells were reported to play important roles in balancing the release of inflammatory factors through vagus nerve circuit. However, few works have been conducted to find if natural killer (NK) cells can also exert the similar function in the reported vagus nerve circuit as T cells and if there was any relationship between depression and this function. In the present study, the behavioral tests on BALB/c mice indicated that the depressant-like symptoms could be improved and simultaneously the concentrations of inflammatory factors in peripheral blood could be reduced significantly by adoptively transferring NK cells into stressed BALB/c mice. The results revealed that NK cells could control the release of inflammatory factors secreted by macrophages and β₂-AR (β₂-adrenergic receptor) on the NK cells were of great importance. Behavioral tests on NCG mice indicated that the antidepressant-like effects of NK cells notably declined after adoptively transferring NK cells with β₂-AR deficiency or with ChAT (choline acetyltransferase) deficiency into stressed NCG mice. Simultaneously, the anti-inflammatory effects also declined significantly both in vivo and in vitro, which indicated that the antidepressant-like property of NK cells may be related to its ability of controlling the release of inflammatory factors. Taken together, we find that NK cells may balance the release of inflammatory factors in our body by transporting the information between the terminal vagal branches and macrophages, which is the mechanism that NK cells may exert antidepressant-like effects.

Role of Inflammation in Depression and Treatment Implications

Approximately one third of depressed patients fail to respond to currently available antidepressant therapies. Therefore, new conceptual frameworks are needed to identify pathophysiologic pathways and neurobiological targets for the development of novel treatment strategies. In this regard, recent evidence suggests that inflammation may contribute to symptoms relevant to a number of psychiatric disorders and particularly depression. Numerous studies (including meta-analyses) have found elevated peripheral and central inflammatory cytokines and acute phase proteins in depression. Chronic exposure to increased inflammation is thought to drive changes in neurotransmitters and neurocircuits that lead to depressive symptoms and that may also interfere with or circumvent the efficacy of antidepressants. Indeed, patients with high inflammation have been shown to exhibit poor response to conventional antidepressant therapies. Recent developments in our ability to understand and measure the effects of inflammation on the brain in patients have opened new doors for the testing of novel treatment strategies that target the immune system or its consequences on neurotransmitter systems. Such recent developments in the field of behavioral immunology and their translational implications for the treatment of depression are discussed herein.

Imaging the Role of Inflammation in Mood and Anxiety-related Disorders

Background

Studies investigating the impact of a variety of inflammatory stimuli on the brain and behavior have reported evidence that inflammation and release of inflammatory cytokines affect circuitry relevant to both reward and threat sensitivity to contribute to behavioral change. Of relevance to mood and anxiety-related disorders, biomarkers of inflammation such as inflammatory cytokines and acute-phase proteins are reliably elevated in a significant proportion of patients with major depressive disorder (MDD), bipolar disorder, anxiety disorders and post-traumatic stress disorder (PTSD).

Methods

This review summarized clinical and translational work demonstrating the impact of peripheral inflammation on brain regions and neurotransmitter systems relevant to both reward and threat sensitivity, with a focus on neuroimaging studies involving administration of inflammatory stimuli. Recent translation of these findings to further understand the role of inflammation in mood and anxiety-related disorders is also discussed.

Results

Inflammation was consistently found to affect basal ganglia and cortical reward and motor circuits to drive reduced motivation and motor activity, as well as anxiety-related brain regions including amygdala, insula and anterior cingulate cortex, which may result from cytokine effects on monoamines and glutamate. Similar relationships between inflammation and altered neurocircuitry have been observed in MDD patients with increased peripheral inflammatory markers, and such work is on the horizon for anxiety disorders and PTSD.

Conclusion

Neuroimaging effects of inflammation on reward and threat circuitry may be used as biomarkers of inflammation for future development of novel therapeutic strategies to better treat mood and anxiety-related disorders in patients with high inflammation.

Immune and Neuroprotective Effects of Physical Activity on the Brain in Depression

Physical activity-a lifestyle factor that is associated with immune function, neuroprotection, and energy metabolism-modulates the cellular and molecular processes in the brain that are vital for emotional and cognitive health, collective mechanisms that can go awry in depression. Physical activity optimizes the stress response, neurotransmitter level and function (e.g., serotonergic, noradrenergic, dopaminergic, and glutamatergic), myokine production (e.g., interleukin-6), transcription factor levels and correlates [e.g., peroxisome proliferator-activated receptor C coactivator-1α [PGC-1α], mitochondrial density, nitric oxide pathway activity, Ca2+ signaling, reactive oxygen specie production, and AMP-activated protein kinase [AMPK] activity], kynurenine metabolites, glucose regulation, astrocytic health, and growth factors (e.g., brain-derived neurotrophic factor). Dysregulation of these interrelated processes can effectuate depression, a chronic mental illness that affects millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility in understanding chronic depression, a need remains to better understand the interrelated mechanisms that contribute to immune dysfunction and the means by which various therapeutics mitigate them. Fortunately, convergent evidence suggests that physical activity improves emotional and cognitive function in persons with depression, particularly in those with comorbid inflammation. Accordingly, the aims of this review are to (1) underscore the link between inflammatory correlates and depression, (2) explicate immuno-neuroendocrine foundations, (3) elucidate evidence of neurotransmitter and cytokine crosstalk in depressive pathobiology, (4) determine the immunomodulatory effects of physical activity in depression, (5) examine protocols used to effectuate the positive effects of physical activity in depression, and (6) highlight implications for clinicians and scientists. It is our contention that a deeper understanding of the mechanisms by which inflammation contributes to the pathobiology of depression will translate to novel and more effective treatments, particularly by identifying relevant patient populations that can benefit from immune-based therapies within the context of personalized medicine.

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

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

Inflammatory Signaling in Hypertension: Regulation of Adrenal Catecholamine Biosynthesis

The immune system is increasingly recognized for its role in the genesis and progression of hypertension. The adrenal gland is a major site that coordinates the stress response via the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal system. Catecholamines released from the adrenal medulla function in the neuro-hormonal regulation of blood pressure and have a well-established link to hypertension. The immune system has an active role in the progression of hypertension and cytokines are powerful modulators of adrenal cell function. Adrenal medullary cells integrate neural, hormonal, and immune signals. Changes in adrenal cytokines during the progression of hypertension may promote blood pressure elevation by influencing catecholamine biosynthesis. This review highlights the potential interactions of cytokine signaling networks with those of catecholamine biosynthesis within the adrenal, and discusses the role of cytokines in the coordination of blood pressure regulation and the stress response.

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.

Inflammation Effects on Motivation and Motor Activity: Role of Dopamine

Motivational and motor deficits are common in patients with depression and other psychiatric disorders, and are related to symptoms of anhedonia and motor retardation. These deficits in motivation and motor function are associated with alterations in corticostriatal neurocircuitry, which may reflect abnormalities in mesolimbic and mesostriatal dopamine (DA). One pathophysiologic pathway that may drive changes in DAergic corticostriatal circuitry is inflammation. Biomarkers of inflammation such as inflammatory cytokines and acute-phase proteins are reliably elevated in a significant proportion of psychiatric patients. A variety of inflammatory stimuli have been found to preferentially target basal ganglia function to lead to impaired motivation and motor activity. Findings have included inflammation-associated reductions in ventral striatal neural responses to reward anticipation, decreased DA and DA metabolites in cerebrospinal fluid, and decreased availability, and release of striatal DA, all of which correlated with symptoms of reduced motivation and/or motor retardation. Importantly, inflammation-associated symptoms are often difficult to treat, and evidence suggests that inflammation may decrease DA synthesis and availability, thus circumventing the efficacy of standard pharmacotherapies. This review will highlight the impact of administration of inflammatory stimuli on the brain in relation to motivation and motor function. Recent data demonstrating similar relationships between increased inflammation and altered DAergic corticostriatal circuitry and behavior in patients with major depressive disorder will also be presented. Finally, we will discuss the mechanisms by which inflammation affects DA neurotransmission and relevance to novel therapeutic strategies to treat reduced motivation and motor symptoms in patients with high inflammation.

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.

Association between serotonin transporter polymorphisms (5-HTTLPR) and the MADRS Dysphoria, Retardation, and Vegetative Subscale scores in the treatment of depression

OBJECTIVE

We investigated the association between serotonin- or 5-hydroxytryptamine (5-HT)-related gene polymorphisms and response to antidepressant treatment in a specific symptom cluster of major depression by using the three-factor model of the Montgomery-Åsberg Depression Rating Scale (MADRS), ie, dysphoria (items of sadness, pessimistic thoughts, and suicidal thoughts), retardation (items of lassitude, inability to feel, apparent sadness, and concentration difficulties), and vegetative symptoms (items of reduced sleep, reduced appetite, and inner tension).

METHODS

This study was an open-label and nonrandomized trial. A total of 160 patients with baseline MADRS scores of ≥21, who were treated with fluvoxamine or milnacipran for 6 weeks, were included in the statistical analysis. Polymorphisms within a 5-HT transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR), a variable number of tandem repeats in the second intron of the 5-HTT gene (5-HTTVNTR), and 5HT2A receptor (1438G/A) were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The 5-HTTLPR polymorphisms affected the MADRS score change in dysphoria, but not in retardation, vegetative, or total symptoms. Dysphoria scores significantly decreased in patients with the S/S genotype compared to those in patients with the short (S)/long (L) + L/L genotype. However, 5-HTTVNTR and 1438G/A polymorphisms were not significantly associated with the treatment response to any cluster of depressive symptoms. When a Bonferroni correction was made, however, our results did not reach the criteria for statistical significance.

CONCLUSION

The use of a single total depression rating scale may not be sufficient to accurately estimate the clinical response to antidepressants. Analyzing a subset of symptoms in psychological scales could be important when performing pharmacogenetic studies.

Interferon-α acutely impairs whole-brain functional connectivity network architecture - A preliminary study

Interferon-alpha (IFN-α) is a key mediator of antiviral immune responses used to treat Hepatitis C infection. Though clinically effective, IFN-α rapidly impairs mood, motivation and cognition, effects that can appear indistinguishable from major depression and provide powerful empirical support for the inflammation theory of depression. Though inflammation has been shown to modulate activity within discrete brain regions, how it affects distributed information processing and the architecture of whole brain functional connectivity networks have not previously been investigated. Here we use a graph theoretic analysis of resting state functional magnetic resonance imaging (rfMRI) to investigate acute effects of systemic interferon-alpha (IFN-α) on whole brain functional connectivity architecture and its relationship to IFN-α-induced mood change. Twenty-two patients with Hepatitis-C infection, initiating IFN-α-based therapy were scanned at baseline and 4h after their first IFN-α dose. The whole brain network was parcellated into 110 cortical and sub-cortical nodes based on the Oxford-Harvard Atlas and effects assessed on higher-level graph metrics, including node degree, betweenness centrality, global and local efficiency. IFN-α was associated with a significant reduction in global network connectivity (node degree) (p=0.033) and efficiency (p=0.013), indicating a global reduction of information transfer among the nodes forming the whole brain network. Effects were similar for highly connected (hub) and non-hub nodes, with no effect on betweenness centrality (p>0.1). At a local level, we identified regions with reduced efficiency of information exchange and a sub-network with decreased functional connectivity after IFN-α. Changes in local and particularly global functional connectivity correlated with associated changes in mood measured on the Profile of Mood States (POMS) questionnaire. IFN-α rapidly induced a profound shift in whole brain network structure, impairing global functional connectivity and the efficiency of parallel information exchange. Correlations with multiple indices of mood change support a role for global changes in brain functional connectivity architecture in coordinated behavioral responses to IFN-α.

Gene-environment interactions linking air pollution and inflammation in Parkinson's disease

Both air pollution exposure and systemic inflammation have been linked to Parkinson's disease (PD). In the PASIDA study, 408 incident cases of PD diagnosed in 2006-2009 and their 495 population controls were interviewed and provided DNA samples. Markers of long term traffic related air pollution measures were derived from geographic information systems (GIS)-based modeling. Furthermore, we genotyped functional polymorphisms in genes encoding proinflammatory cytokines, namely rs1800629 in TNFα (tumor necrosis factor alpha) and rs16944 in IL1B (interleukin-1β). In logistic regression models, long-term exposure to NO₂ increased PD risk overall (odds ratio (OR)=1.06 per 2.94μg/m³ increase, 95% CI=1.00-1.13). The OR for PD in individuals with high NO₂ exposure (≧75th percentile) and the AA genotype of IL1B rs16944 was 3.10 (95% CI=1.14-8.38) compared with individuals with lower NO₂ exposure (<75th percentile) and the GG genotype. The interaction term was nominally significant on the multiplicative scale (p=0.01). We did not find significant gene-environment interactions with TNF rs1800629. Our finds may provide suggestive evidence that a combination of traffic-related air pollution and genetic variation in the proinflammatory cytokine gene IL1B contribute to risk of developing PD. However, as statistical evidence was only modest in this large sample we cannot rule out that these results represent a chance finding, and additional replication efforts are warranted.

Effort-related motivational effects of the pro-inflammatory cytokine interleukin-6: pharmacological and neurochemical characterization

RATIONALE

Motivational dysfunctions such as anergia, fatigue, and reduced effort expenditure are common in patients with depression and other disorders. Pro-inflammatory cytokines are implicated in depression, and cytokine administration induces motivational deficits in humans.

OBJECTIVES

These studies focused on the effects of the cytokine interleukin-6 (IL-6) on effort-related decision-making.

METHODS

Rats were assessed using the concurrent fixed ratio 5-lever pressing/chow feeding choice procedure, which measures the tendency of rats to work for a preferred food (high carbohydrate pellets) in the presence of a concurrently available but less preferred substitute (lab chow).

RESULTS

IL-6 (2.0-8.0 μg/kg IP) shifted choice behavior, significantly decreasing lever pressing and increasing chow intake. Further experiments showed that the adenosine A2A antagonist MSX-3 and the stimulant methylphenidate attenuated the effort-related impairments produced by IL-6, increasing lever pressing and decreasing chow intake in IL-6 treated rats. The same doses of IL-6 did not alter food intake or preference in parallel free-feeding choice studies, demonstrating that these low doses were not altering preference for the high carbohydrate pellets or generally suppressing appetite. Also, IL-6 did not affect body temperature. Microdialysis studies showed that 8.0 μg/kg IL-6 significantly decreased extracellular dopamine in nucleus accumbens core.

CONCLUSIONS

In summary, IL-6 reduces the tendency to work for food, even at low doses that do not produce fever or loss of appetite. Dopaminergic mechanisms may be involved in these effort-related effects. This research has implications for the involvement of cytokines in motivational dysfunctions such as anergia and fatigue.

Lupus brain fog: a biologic perspective on cognitive impairment, depression, and fatigue in systemic lupus erythematosus

Cognitive disturbances, mood disorders and fatigue are common in SLE patients with substantial adverse effects on function and quality of life. Attribution of these clinical findings to immune-mediated disturbances associated with SLE remains difficult and has compromised research efforts in these areas. Improved understanding of the role of the immune system in neurologic processes essential for cognition including synaptic plasticity, long term potentiation and adult neurogenesis suggests multiple potential mechanisms for altered central nervous system function associated with a chronic inflammatory illness such as SLE. This review will focus on the biology of cognition and neuroinflammation in normal circumstances and potential biologic mechanisms for cognitive impairment, depression and fatigue attributable to SLE.

Co-occurring Depression, Chronic Pain and Substance Use Disorders in People with Hepatitis C

Chronic infection with Hepatitis C virus (HCV) is common and can result in serious and sometimes fatal liver complications. The impact of HCV on the liver can be further complicated by medical and psychological comorbidities. Depression, substance use, and pain syndromes are frequent co-morbid conditions in people with HCV and diminish functioning, quality of life, and treatment compliance. Understanding the underlying biological mechanisms of these comorbid conditions within the context of HCV may help elucidate factors contributing to their co-occurrence, perhaps mediatedviapro-inflammatory cytokines. The current review provides a synthesis of the literature on depression, substance use disorders and chronic pain in the presence of HCV. The review includes studies conducted with both veteran and civilian populations. The implications for assessment and antiviral treatment of HCV will be considered.

Depressive symptoms as a side effect of Interferon-α therapy induced by induction of indoleamine 2,3-dioxygenase 1

Depression is known to occur frequently in chronic hepatitis C viral (HCV) patients receiving interferon (IFN)-α therapy. In this study, we investigated whether indoleamine 2,3-dioxygenase1 (IDO1)-mediated tryptophan (TRP) metabolism plays a critical role in depression occurring as a side effect of IFN-α therapy. Increases in serum kynurenine (KYN) and 3-hydroxykynurenine (3-HK) concentrations and in the ratios of KYN/TRP and 3-HK/kynurenic acid (KA) were much larger in depressive HCV patients than in non-depressed patients following therapy. Furthermore, transfection of a plasmid continuously expressing murine IFN-γ into normal mice significantly increased depression-like behavior. IFN-γ gene transfer also resulted in a decrease in serum TRP levels in the mice while KYN and 3-HK levels were significantly increased in both serum and frontal cortex. Genetic deletion of IDO1 in mice abrogated both the increase in depression-like behavior and the elevation in TRP metabolites’ levels, and the turnover of serotonin in the frontal cortex after IFN-γ gene transfer. These results indicate that the KYN pathway of IDO1-mediated TRP metabolism plays a critical role in depressive symptoms associated with IFN-α therapy.

A Neurocomputational Account of How Inflammation Enhances Sensitivity to Punishments Versus Rewards

BACKGROUND

Inflammation rapidly impairs mood and cognition and, when severe, can appear indistinguishable from major depression. These sickness responses are characterized by an acute reorientation of motivational state; pleasurable activities are avoided, and sensitivity to negative stimuli is enhanced. However, it remains unclear how these rapid shifts in behavior are mediated within the brain.

METHODS

Here, we combined computational modeling of choice behavior, experimentally induced inflammation, and functional brain imaging (functional magnetic resonance imaging) to describe these mechanisms. Using a double-blind, randomized crossover study design, 24 healthy volunteers completed a probabilistic instrumental learning task on two separate occasions, one 3 hours after typhoid vaccination and one 3 hours after saline (placebo) injection. Participants learned to select high probability reward (win £1) and avoid high probability punishment (lose £1) stimuli. An action-value learning algorithm was fit to the observed behavior, then used within functional magnetic resonance imaging analyses to identify neural coding of prediction error signals driving motivational learning.

RESULTS

Inflammation acutely biased behavior, enhancing punishment compared with reward sensitivity, through distinct actions on neural representations of reward and punishment prediction errors within the ventral striatum and anterior insula. Consequently, choice options leading to potential rewards were less behaviorally attractive, and those leading to punishments were more aversive.

CONCLUSIONS

Our findings demonstrate the neural mediation of a rapid, state-dependent reorientation of reward versus punishment sensitivity during inflammation. This mechanism may aid the adaptive reallocation of metabolic resources during acute sickness but might also account for maladaptive, motivational changes that underpin the association between chronic inflammation and depression.

The Role of Dopamine in Inflammation-Associated Depression: Mechanisms and Therapeutic Implications

Studies investigating the impact of a variety of inflammatory stimuli on the brain and behavior have consistently reported evidence that inflammatory cytokines affect the basal ganglia and dopamine to mediate depressive symptoms related to motivation and motor activity. Findings have included inflammation-associated reductions in ventral striatal responses to hedonic reward, decreased dopamine and dopamine metabolites in cerebrospinal fluid, and decreased availability of striatal dopamine, all of which correlate with symptoms of anhedonia, fatigue, and psychomotor retardation. Similar relationships between alterations in dopamine-relevant corticostriatal reward circuitry and symptoms of anhedonia and psychomotor slowing have also been observed in patients with major depression who exhibit increased peripheral cytokines and other inflammatory markers, such as C-reactive protein. Of note, these inflammation-associated depressive symptoms are often difficult to treat in patients with medical illnesses or major depression. Furthermore, a wealth of literature suggests that inflammation can decrease dopamine synthesis, packaging, and release, thus sabotaging or circumventing the efficacy of standard antidepressant treatments. Herein, the mechanisms by which inflammation and cytokines affect dopamine neurotransmission are discussed, which may provide novel insights into treatment of inflammation-related behavioral symptoms that contribute to an inflammatory malaise.

Lipopolysaccharide reduces incentive motivation while boosting preference for high reward in mice

Inflammation has been implicated in the development of various psychiatric disorders, including depression. However, the neurobehavioral mechanism involved in this relationship remains elusive. This gap in knowledge may best be filled by evaluating elementary neurobehavioral units affected by inflammation rather than behavioral changes in conventional animal tests of depression. To this end, the current study used a concurrent choice paradigm to evaluate inflammation-induced motivational changes. Male C57BL/6J mice (n=27) were food restricted to between 85 and 90% of their free-feeding weight and were trained to perform a concurrent choice task where they nose-poked for grain rewards on a fixed ratio (FR) 1 schedule (low effort/low reward) and chocolate-flavored rewards on a FR-10 schedule (high effort/high reward). A counterbalanced-within subjects design was used. A single intraperitoneal injection of 0.33 mg/kg lipopolysaccharide (LPS) was used to induce peripheral inflammation. Twenty-four hours after LPS administration, mice showed a reduction in the total number of nose pokes. A proportionally greater reduction in nose pokes was observed for grain, resulting in an increase in percent chocolate pellets earned. These behavioral changes cannot be explained by reduced appetite as feeding before the test led to a similar increase in percent chocolate pellets earned but without any decrease in responding. These results indicate that inflammation modulates incentive motivation by affecting willingness to exert effort for reward and not by reducing sensitivity to reward.

Melanoma tumors alter proinflammatory cytokine production and monoamine brain function, and induce depressive-like behavior in male mice

Depression is a commonly observed disorder among cancer patients; however, the mechanisms underlying the relationship between these disorders are not well known. We used an animal model to study the effects of tumor development on depressive-like behavior manifestation, proinflammatory cytokine expression, and central monoaminergic activity. Male OF1 mice were inoculated with B16F10 melanoma tumor cells and subjected to a 21-day behavioral evaluation comprising the novel palatable food (NPF) test and tail suspension test (TST). The mRNA expression levels of proinflammatory cytokines, interleukin (IL)-1β and IL-6, and tumor necrosis factor-alpha (TNF-α), were measured in the hypothalamus and hippocampus and the levels of IL-6 and TNF-α were measured in the blood plasma. We similarly determined the monoamine turnover in various brain areas. The tumors resulted in increasing the immobility in TST and the expression level of IL-6 in the hippocampus. These increases corresponded with a decrease in dopaminergic activity in the striatum and a decrease in serotonin turnover in the prefrontal cortex. Similarly, a high level of tumor development produced increases in the brain expression levels of IL-6 and TNF-α and plasma levels of IL-6. Our findings suggest that these alterations in inflammatory cytokines and monoaminergic system function might be responsible for the manifestation of depressive-like behaviors in tumor-bearing mice.

Effort-related motivational effects of the pro-inflammatory cytokine interleukin 1-beta: studies with the concurrent fixed ratio 5/ chow feeding choice task

RATIONALE

Effort-related motivational symptoms such as anergia and fatigue are common in patients with depression and other disorders. Research implicates pro-inflammatory cytokines in depression, and administration of cytokines can induce effort-related motivational symptoms in humans.

OBJECTIVES

The present experiments focused on the effects of the pro-inflammatory cytokine interleukin 1-beta (IL-1β) on effort-related choice behavior.

METHODS

Rats were tested on a concurrent fixed ratio 5 lever pressing/chow feeding choice procedure, which assesses the tendency of rats to work for a preferred food (high carbohydrate pellets) in the presence of a concurrently available but less preferred substitute (laboratory chow).

RESULTS

IL-1β (1.0-4.0 μg/kg IP) shifted choice behavior, significantly decreasing lever pressing and increasing intake of the freely available chow. The second experiment assessed the ability of the adenosine A2A antagonist (E)-phosphoric acid mono-[3-[8-[2-(3-methoxyphenyl)vinyl]-7-methyl-2,6-dioxo-1-prop-2-ynyl-1,2,6,7-tetrahydropurin-3-yl] propyl] ester disodium salt (MSX-3) to reverse the behavioral effects of IL-1β. MSX-3 attenuated the effort-related impairments produced by IL-1β, increasing lever pressing and also decreasing chow intake. In the same dose range that shifted effort-related choice behavior, IL-1β did not alter food intake or preference in parallel free-feeding choice studies, indicating that these low doses were not generally suppressing appetite or altering preference for the high carbohydrate pellets. In addition, IL-1β did not affect core body temperature.

CONCLUSIONS

These results indicate that IL-1β can reduce the tendency to work for food, even at low doses that do not produce a general sickness, malaise, or loss of appetite. This research has implications for the involvement of cytokines in motivational symptoms such as anergia and fatigue.

Concomitant interferon alpha stimulation and TLR3 activation induces neuronal expression of depression-related genes that are elevated in the brain of suicidal persons

We have previously identified 15 genes that are associated with the development of severe depressive side effects during the standard therapy with interferon alpha and ribavirin in the peripheral blood of hepatitis C virus infected patients. An enhanced expression of these genes was also found in the blood of psychiatric patients suffering severe depressive episode. Herein, we demonstrate that the same depression-related interferon-inducible genes (DRIIs) are also upregulated in post-mortem brains of suicidal individuals. Using cultured mouse hippocampal and prefrontal neurons we show that costimulation with murine IFN (mIFN) and the TLR3 agonist poly(I:C) promotes the expression of the described DRIIs, at the same time inducing pro-inflammatory cytokine expression through Stat1 and Stat3 activation, promoting neuronal apoptosis. Consequently, the upregulation of selective DRIIs, production of inflammatory cytokines and inhibition of neuronal plasticity may be involved in the pathogenesis of IFN-associated depression.

Research review: the role of cytokines in depression in adolescents: a systematic review

BACKGROUND

While cytokines have been implicated in the pathophysiology of depression in adults, the potential role in younger age groups such as adolescents is less clear. This article therefore reviews the literature (a) to explore the relationship between cytokines and depression in adolescents, and (b) to examine how cytokines may be related to adolescent depression in the context of other neurobiological theories of depression.

METHOD

A systematic review of the scientific literature on the subject was conducted in February 2013, searching the Web of Knowledge, PubMed (Medline), PsycInfo and Cochrane electronic databases.

RESULTS

Eighteen studies were identified measuring both depression or depressive symptoms and cytokines or immune markers in adolescents. Adolescents with depression show age-specific characteristics of the immune and inflammatory system, specifically in NK cell activity and in pro-inflammatory cytokines (such as IL-1β and TNF-α). In addition, the role of cytokines in adolescent depression is influenced by neurodevelopment, hormonal changes, stress and trauma.

CONCLUSIONS

There may be differences in the neurobiology of adolescent major depressive disorder (MDD) compared with adult MDD. Increased understanding of the role of cytokines in adolescent MDD may lead to improved outcomes in the treatment of adolescent depression.

Central administration of murine interferon-α induces depressive-like behavioral, brain cytokine and neurochemical alterations in mice: a mini-review and original experiments

A role for pro-inflammatory cytokines and their neuroinflammatory signaling cascades in depressive pathology has increasingly gained acceptance. In this regard, several lines of evidence suggested that interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) can provoke neurochemical and hormonal changes akin to those associated with psychological stressors, and that these cytokines also induce sickness behaviors that resemble some of the neurovegetative features of depression. Similarly, human depressed patients often display marked changes of pro-inflammatory cytokine levels and immune cell activity. Perhaps more germane in the analysis of the cytokine-depression connection, reports of humans undergoing interferon-α (IFN-α) treatment for certain cancers or viral infections have indicated that the pro-inflammatory cytokine caused signs of major depression in a substantial subset of those treated. In the present investigation, we demonstrated that acute or repeated infusion of IFN-α into the lateral ventricles provoked depressive-like behavior and concomitant changes in serotonin (5-HT) and mRNA expression of particular 5-HT receptors and pro-inflammatory cytokines. These actions were less evident following administration directly into the prefrontal cortex and not apparent at all when administered to the dorsal raphe nucleus. The data are discussed in relation to the induction of depression elicited by IFN-α, and are presented in the context of a mini-review that highlights potential mechanisms through which the cytokine might act to promote psychomotor and affective disturbances and interact with stressors.

Inflammatory cytokines in depression: neurobiological mechanisms and therapeutic implications

Mounting evidence indicates that inflammatory cytokines contribute to the development of depression in both medically ill and medically healthy individuals. Cytokines are important for development and normal brain function, and have the ability to influence neurocircuitry and neurotransmitter systems to produce behavioral alterations. Acutely, inflammatory cytokine administration or activation of the innate immune system produces adaptive behavioral responses that promote conservation of energy to combat infection or recovery from injury. However, chronic exposure to elevated inflammatory cytokines and persistent alterations in neurotransmitter systems can lead to neuropsychiatric disorders and depression. Mechanisms of cytokine behavioral effects involve activation of inflammatory signaling pathways in the brain that results in changes in monoamine, glutamate, and neuropeptide systems, and decreases in growth factors, such as brain-derived neurotrophic factor. Furthermore, inflammatory cytokines may serve as mediators of both environmental (e.g. childhood trauma, obesity, stress, and poor sleep) and genetic (functional gene polymorphisms) factors that contribute to depression's development. This review explores the idea that specific gene polymorphisms and neurotransmitter systems can confer protection from or vulnerability to specific symptom dimensions of cytokine-related depression. Additionally, potential therapeutic strategies that target inflammatory cytokine signaling or the consequences of cytokines on neurotransmitter systems in the brain to prevent or reverse cytokine effects on behavior are discussed.

Not all depression is created equal: sex interacts with disease to precipitate depression

Depression is a common mental disorder that co-occurs in other neurological and somatic diseases. Further, sex differences exist in the prevalence rates of many of these diseases, as well as within non-disease associated depression. In this review, the case is made for needing a better recognition of the source of the symptoms of depression with respect to the sex of the individual; in that, some disease states, which includes the neuroendocrine and immune reactions to the underlying pathophysiology of the disease, may initiate depressive symptoms more often in one sex over the other. The diseases specifically addressed to make this argument are: epilepsy, Alzheimer’s disease, cancer, and cardiovascular disease. For each of these conditions, a review of the following are presented: prevalence rates of the conditions within each sex, prevalence rates of depressive symptoms within the conditions, identified relationships to gonadal hormones, and possible interactions between gonadal hormones, adrenal hormones, and immune signaling. Conclusions are drawn suggesting that an evaluation of the root causes for depressive symptoms in patients with these conditions is necessary, as the underlying mechanisms for eliciting the depressive symptoms may be qualitatively different across the four diseases discussed. This review attempts to identify and understand the mechanisms of depression associated with these diseases, in the context of the known sex differences in the disease prevalence and its age of onset. Hence, more extensive, sex-specific model systems are warranted that utilize these disease states to elicit depressive symptoms in order to create more focused, efficient, and sex-specific treatments for patients suffering from these diseases and concurrent depressive symptoms.

Vulnerability to somatic symptoms of depression during interferon-alpha therapy for hepatitis C: a 16-week prospective study

OBJECTIVE

This study evaluated the distinctive clinical and biological manifestations of depressive symptom subtypes (i.e., cognitive-affective and somatic) in Veterans with hepatitis C viral infection (HCV) before and during interferon-alpha (IFN) based antiviral therapy.

METHODS

Thirty-two Veterans with HCV and no prior history of IFN therapy were followed prospectively during the first 16weeks of therapy to evaluate depressive symptoms and to determine if baseline cytokine and serotonin levels predicted subsequent changes in depressive scores.

RESULTS

IFN therapy resulted in a significant increase in total depressive symptoms from baseline (week 0) to week 16, with neurovegetative and somatic symptoms of depression including loss of appetite, fatigue and irritability increasing within the first two weeks of therapy and continuing to increase throughout IFN therapy. When depressive symptoms were evaluated using a two-factor (i.e., Cognitive-Affective and Somatic) model, the Cognitive-Affective factor score did not change significantly following IFN therapy initiation, while the Somatic factor score showed a significant increase from week 0 to week 16. Veterans with the largest increases in somatic symptoms from week 0 to week 2 had significantly higher levels of tumor necrosis factor-alpha (TNF-α) and lower levels of serotonin at baseline, as compared to Veterans with minimal or no increase in somatic symptoms.

CONCLUSION

Somatic symptoms of depression can be significantly exacerbated during IFN therapy and may be predicted by higher TNF-α levels and lower serotonin levels at baseline.

Hepatitis C infection, antiviral treatment and mental health: a European expert consensus statement

Mental health problems frequently occur in chronic infection with the hepatitis C virus (HCV) and during antiviral treatment with pegylated interferon-alpha (PegIFNα) and ribavirin. Depression is one of the most important complications during antiviral treatment of chronic hepatitis C infection. However, an increased prevalence of depression, fatigue, and cognitive disturbances has also been reported in untreated HCV-positive patients. Patients with psychiatric disorders or drug addiction also have an increased risk of HCV infection. Furthermore, because of possible drug-drug interactions, new antivirals administered together with PegIFNα and ribavirin may complicate psychiatric side effect management, even if no specific psychiatric adverse events are known so far for these new drugs. The European liver patient's organization (ELPA) organised a European expert conference to review the literature and develop expert recommendations for the management of mental health problems in HCV infected patients. This paper results from the output of the 2011 EASL meeting and subsequent dialogue with patient groups and relevant experts in Europe. It summarises the current knowledge of HCV infection and the brain; prevalence, course, and neurobiology of IFN-α associated psychiatric side effects; possible risk factors for IFN-α associated depression and suicide attempts; psychiatric management of HCV infected patients before and during antiviral treatment; prevention of IFN- α associated psychiatric side effects; and psychiatric aspects of the new antivirals. The summarised current knowledge about mental health changes before and during antiviral treatment should improve interdisciplinary management of HCV infected patients.

Cytokines, neurophysiology, neuropsychology, and psychiatric symptoms

Recent research has overcome the old paradigms of the brain as an immunologically privileged organ, and of the exclusive role of neurotransmitters and neuropeptides as signal transducers in the central nervous system. Growing evidence suggests that the signal proteins of the immune system - the cytokines - are also involved in modulation of behavior and induction of psychiatric symptoms. This article gives an overview on the nature of cytokines and the proposed mechanisms of immune-to-brain interaction. The role of cytokines in psychiatric symptoms, syndromes, and disorders like sickness behavior, major depression, and schizophrenia are discussed together with recent immunogenetic findings.

Symptomatic treatment of interferon-α-induced depression in hepatitis C: a systematic review

Despite its efficacy in treating hepatitis C, interferon-α (IFN-α) can cause depression. The purpose of this systematic review is to summarize and discuss the available and effective therapies in treating IFN-α-induced depression. Using PubMed, The Cochrane Library, Scopus, Embase, Ovid of Medline, PsycINFO, and ISI Web of Knowledge, we selected 64 articles concerning IFN-α-induced depression treatment in hepatitis C patients. Selective serotonin reuptake inhibitors can be considered the first choice for the treatment of IFN-α-induced depression, as demonstrated in open-label studies, case reports, and a randomized, double-blind, placebo-controlled trial. Also 5-hydroxytryptophan and tryptophan have been suggested to be effective as monotherapy or as augmentation of selective serotonin reuptake inhibitors. Clinical cases that show positive effects of tricyclic antidepressants, however, do not provide sufficient evidence for the use of these drugs. Two cohort studies have reported the effectiveness of amisulpride, but not of levosulpiride. Mirtazapine has been suggested to be a better choice of treatment in cases where insomnia or anorexia develop. Milnacipram can be useful in cases of concomitant medications, for the unlikely occurrence of drug-drug interactions. Psychostimulants represent an empirical treatment without controlled data to support their use. Two case reports have shown the favorable use of bupropion, particularly if sexual dysfunction or cravings for illicit drugs are present. A single case report suggests electroconvulsive therapy to be a possible choice when antidepressants are ineffective or poorly tolerated. The main limitation of our review is that the quality of the findings varied across the reviewed studies. Our observations may help clinicians with managing IFN-α-induced depression.

Cytokine effects on the basal ganglia and dopamine function: the subcortical source of inflammatory malaise

Data suggest that cytokines released during the inflammatory response target subcortical structures including the basal ganglia as well as dopamine function to acutely induce behavioral changes that support fighting infection and wound healing. However, chronic inflammation and exposure to inflammatory cytokines appears to lead to persisting alterations in the basal ganglia and dopamine function reflected by anhedonia, fatigue, and psychomotor slowing. Moreover, reduced neural responses to hedonic reward, decreased dopamine metabolites in the cerebrospinal fluid and increased presynaptic dopamine uptake and decreased turnover have been described. This multiplicity of changes in the basal ganglia and dopamine function suggest fundamental effects of inflammatory cytokines on dopamine synthesis, packaging, release and/or reuptake, which may sabotage and circumvent the efficacy of current treatment approaches. Thus, examination of the mechanisms by which cytokines alter the basal ganglia and dopamine function will yield novel insights into the treatment of cytokine-induced behavioral changes and inflammatory malaise.

Selective hyper-responsiveness of the interferon system in major depressive disorders and depression induced by interferon therapy

BACKGROUND

Though an important percentage of patients with chronic hepatitis C virus (HCV) undergoing interferon (IFN) therapy develop depressive symptoms, the role of the IFN system in the pathogenesis of depressive disorders is not well understood.

METHODS

50 patients with HCV infection were treated with standard combination therapy (pegylated IFN-α2a/ribavirin). IFN-induced gene expression was analyzed to identify genes which are differentially regulated in patients with or without IFN-induced depression. For validation, PBMC from 22 psychiatric patients with a severe depressive episode (SDE) and 11 controls were cultivated in vitro with pegylated IFN-α2a and gene expression was analyzed.

RESULTS

IFN-induced depression in HCV patients was associated with selective upregulation of 15 genes, including 6 genes that were previously described to be relevant for major depressive disorders or neuronal development. In addition, increased endogenous IFN-production and selective hyper-responsiveness of these genes to IFN stimulation were observed in SDE patients.

CONCLUSIONS

Our data suggest that selective hyper-responsiveness to exogenous (IFN therapy) or endogenous (depressive disorders) type I IFNs may lead to the development of depressive symptoms. These data could lead to the discovery of novel therapeutic approaches to treat IFN-induced and major depressive disorders.

Neurobehavioral effects of interferon-α in patients with hepatitis-C: symptom dimensions and responsiveness to paroxetine

In patients at high risk for recurrence of malignant melanoma, interferon-α (IFN-α), a stimulator of innate immunity, appears to induce distinct neurobehavioral symptom dimensions: a mood and anxiety syndrome, and a neurovegetative syndrome, of which the former is responsive to prophylactic administration of paroxetine. We sought to determine whether symptom dimensions (and treatment responsiveness) arise in patients with hepatitis C administered IFN-α and ribavirin. In a randomized, double-blind, 6-month study, 61 patients with hepatitis C eligible for therapy with IFN-α and ribavirin received the antidepressant paroxetine (n=28) or a placebo (n=33). Study medication began 2 weeks before IFN-α/ribavirin therapy. Neuropsychiatric assessments included the 10-item Montgomery-Asberg Depression Rating Scale (MADRS). The items of the MADRS were grouped into depression, anxiety, cognitive dysfunction, and neurovegetative symptom dimensions, and analyzed using a mixed model. By 2 weeks of IFN-α/ribavirin therapy, all four dimensions increased, with the symptom dimensions of anxiety and cognitive dysfunction fluctuating and worsening, respectively, in both groups over time. The depression symptom dimension was significantly lower in the paroxetine treatment group (p=0.04); severity of the neurovegetative symptom dimension was similar in both groups. Similar to patients with malignant melanoma receiving high-dose IFN-α, the depression symptom dimension is more responsive to paroxetine treatment in individuals undergoing concomitant IFN-α/ribavirin therapy. However, the anxiety, cognitive dysfunction, and neurovegetative symptom dimensions appear less responsive to prophylactic paroxetine administration. Different neurobiologic pathways may contribute to the responsiveness of IFN-α-induced symptom dimensions to antidepressant treatment, requiring relevant psychopharmacologic strategies.

Inflammation-induced anhedonia: endotoxin reduces ventral striatum responses to reward

BACKGROUND

Although inflammatory activity is known to play a role in depression, no work has examined whether experimentally induced systemic inflammation alters neural activity that is associated with anhedonia, a key diagnostic symptom of depression. To investigate this, we examined the effect of an experimental inflammatory challenge on the neural correlates of anhedonia-namely, reduced ventral striatum (VS) activity to reward cues. We also examined whether this altered neural activity related to inflammatory-induced increases in depressed mood.

METHODS

Participants (n = 39) were randomly assigned to receive either placebo or low-dose endotoxin, which increases proinflammatory cytokine levels in a safe manner. Cytokine levels were repeatedly assessed through hourly blood draws; self-reported and observer-rated depressed mood were assessed regularly as well. Two hours after drug administration, neural activity was recorded as participants completed a task in which they anticipated monetary rewards.

RESULTS

Results demonstrated that subjects exposed to endotoxin, compared with placebo, showed greater increases in self-reported and observer-rated depressed mood over time, as well as significant reductions in VS activity to monetary reward cues. Moreover, the relationship between exposure to inflammatory challenge and increases in observer-rated depressed mood was mediated by between-group differences in VS activity to anticipated reward.

CONCLUSIONS

The data reported here show, for the first time, that inflammation alters reward-related neural responding in humans and that these reward-related neural responses mediate the effects of inflammation on depressed mood. As such, these findings have implications for understanding risk of depression in persons with underlying inflammation.

Clinical perspectives on autoimmune processes in schizophrenia

This article reviews the epidemiology of autoimmune conditions in schizophrenia, symptom manifestations of autoimmune conditions resembling schizophrenia, and the immunological changes observed in schizophrenia; and reflects on their associations with neurodevelopment, neurodegeneration, clinical course, and management of schizophrenia.

Norman Cousins Lecture. Mechanisms of cytokine-induced behavioral changes: psychoneuroimmunology at the translational interface

Work in our laboratory has focused on the mechanisms by which cytokines can influence the brain and behavior in humans and non-human primates. Using administration of interferon (IFN)-alpha as a tool to unravel these mechanisms, we have expanded upon findings from the basic science literature implicating cytokine-induced changes in monoamine metabolism as a primary pathway to depression. More specifically, a role for serotonin metabolism has been supported by the clinical efficacy of serotonin reuptake inhibitors in blocking the development of IFN-alpha-induced depression, and the capacity of IFN-alpha to activate metabolic enzymes (indolamine 2,3 dioxygenase) and cytokine signaling pathways (p38 mitogen activated protein kinase) that can influence the synthesis and reuptake of serotonin. Our data also support a role for dopamine depletion as reflected by IFN-alpha-induced changes in behavior (psychomotor slowing and fatigue) and regional brain activity, which implicate the involvement of the basal ganglia, as well as the association of IFN-alpha-induced depressive-like behavior in rhesus monkeys with decreased cerebrospinal fluid concentrations of the dopamine metabolite, homovanillic acid. Neuroimaging data in IFN-alpha-treated patients also suggest that activation of neural circuits (dorsal anterior cingulate cortex) associated with anxiety and alarm may contribute to cytokine-induced behavioral changes. Taken together, these effects of cytokines on the brain and behavior appear to subserve competing evolutionary survival priorities that promote reduced activity to allow healing, and hypervigilance to protect against future attack. Depending on the relative balance between these behavioral accoutrements of an activated innate immune response, clinical presentations may be distinct and warrant individualized therapeutic approaches.

Decreased immobility in swimming test by homologous interferon-alpha in mice accompanied with increased cerebral tryptophan level and serotonin turnover

Animal models are used to decipher the pathophysiology of IFN-alpha-induced psychiatric complications in humans. However, the behavioral effects of IFN-alpha in rodents remain highly controversial. In contrast to homologous IFN-alpha, our recent study revealed that human IFN-alpha, which was used in many previous investigations, had no biological activity in mice. To evaluate the behavioral effects of homologous IFN-alpha in mice, adult C57BL/6J mice were treated with carrier-free murine IFN-alpha and tested on a number of behavioral paradigms. Surprisingly, contrary to previous reports, IFN-alpha treatment decreased the time spent immobile in the forced-swimming test after a single intraperitoneal injection at 2 x 10(6)IU/kg, whereas general locomotor activity was not altered. The elevated plus-maze (EPM) test showed a trend toward an increased anxiety profile in IFN-alpha-treated mice. The tail-suspension and light dark exploration test revealed no difference between IFN-alpha-treated and control animals. Interestingly, neurochemical analysis revealed significantly increased concentrations of tryptophan and 5-hydroxyindoleacetic acid (5-HIAA)/serotonin (5-HT) ratios following IFN-alpha treatment in selected brain regions. Thus, systemic murine IFN-alpha treatment increases swimming time in mice. Increased cerebral serotonin turnover as well as increased tryptophan concentrations, induced by IFN-alpha, implicates serotonergic neurotransmission in behavioral dysfunction caused by this innate immune mediator.

Cerebral immune activation in chronic hepatitis C infection: a magnetic resonance spectroscopy study

BACKGROUND/AIMS

Abnormal cerebral metabolism and cognitive impairments have been reported in patients with chronic hepatitis C (HCV) but studies have failed to demonstrate a relationship between these findings.

METHODS

Twenty-five HCV-positive patients with histologically-mild liver disease were studied with cerebral proton magnetic resonance spectroscopy (MRS), using acquisition parameters to quantify myo-inositol (mI) and other metabolites in frontal white matter (FWM). Patients underwent automated attention and working memory tests (Cognitive Drug Research test system).

RESULTS

The mean mI/ creatine ratio in the HCV+ve patients (0.64, SD 0.21) was significantly higher (p=0.02) than in healthy controls (0.52, SD 0.10). On cognitive testing, the HCV+ve patients showed impairments in 2/4 composite scores, reflecting working memory and attention, compared to normative data from healthy volunteers (p<0.005) and HCV-ve controls (p=0.03). There was a significant association between elevated FWM mI/creatine and prolonged working memory reaction times (R=0.72, p=0.002).

CONCLUSIONS

Elevated FWM mI/ creatine is a feature of HIV-related minor cognitive-motor disorder. It is associated with infection and immune activation of microglial cells. The similar findings in this study suggest that cerebral immune activation may also occur in HCV infection. This may underlie the mild neurocognitive impairment and neuropsychological symptoms observed in a proportion of patients.