Interleukin-2 modulates evoked release of [3H]dopamine in rat cultured mesencephalic cells

Immune and glial cell alterations in the rat brain after repeated exposure to the synthetic cannabinoid JWH-018

The use of synthetic cannabinoid receptor agonists (SCRAs) poses major psychiatric risks. We previously showed that repeated exposure to the prototypical SCRA JWH-018 induces alterations in dopamine (DA) transmission, abnormalities in the emotional state, and glial cell activation in the mesocorticolimbic DA circuits of rats. Despite growing evidence suggesting the relationship between substance use disorders (SUD) and neuroinflammation, little is known about the impact of SCRAs on the neuroimmune system. Here, we investigated whether repeated JWH-018 exposure altered neuroimmune signaling, which could be linked with previously reported central effects. Adult male Sprague-Dawley (SD) rats were exposed to JWH-018 (0.25 mg/kg, i.p.) for fourteen consecutive days, and the expression of cytokines, chemokines, and growth factors was measured seven days after treatment discontinuation in the striatum, cortex, and hippocampus. Moreover, microglial (ionized calcium-binding adaptor molecule 1, IBA-1) and astrocyte (glial fibrillary acidic protein, GFAP) activation markers were evaluated in the caudate-putamen (CPu). Repeated JWH-018 exposure induces a perturbation of neuroimmune signaling specifically in the striatum, as shown by increased levels of cytokines [interleukins (IL) -2, -4, -12p70, -13, interferon (IFN) γ], chemokines [macrophage inflammatory protein (MIP) -1α, -3α], and growth factors [macrophage colony-stimulating factor (M-CSF), vascular endothelial growth factor (VEGF)], together with increased IBA-1 and GFAP expression in the CPu. JWH-018 exposure induces persistant brain region-specific immune alterations up to seven days after drug discontinuation, which may contribute to the behavioral and neurochemical dysregulations in striatal areas that play a role in the reward-related processes that are frequently impaired in SUD.

Dopamine Transmission Imbalance in Neuroinflammation: Perspectives on Long-Term COVID-19

Dopamine (DA) is a key neurotransmitter in the basal ganglia, implicated in the control of movement and motivation. Alteration of DA levels is central in Parkinson’s disease (PD), a common neurodegenerative disorder characterized by motor and non-motor manifestations and deposition of alpha-synuclein (α-syn) aggregates. Previous studies have hypothesized a link between PD and viral infections. Indeed, different cases of parkinsonism have been reported following COVID-19. However, whether SARS-CoV-2 may trigger a neurodegenerative process is still a matter of debate. Interestingly, evidence of brain inflammation has been described in postmortem samples of patients infected by SARS-CoV-2, which suggests immune-mediated mechanisms triggering the neurological sequelae. In this review, we discuss the role of proinflammatory molecules such as cytokines, chemokines, and oxygen reactive species in modulating DA homeostasis. Moreover, we review the existing literature on the possible mechanistic interplay between SARS-CoV-2-mediated neuroinflammation and nigrostriatal DAergic impairment, and the cross-talk with aberrant α-syn metabolism.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

The Role of Glia in Addiction: Dopamine as a Modulator of Glial Responses in Addiction

Addiction is a chronic and potentially deadly disease considered a global health problem. Nevertheless, there is still no ideal treatment for its management. The alterations in the reward system are the most known pathophysiological mechanisms. Dopamine is the pivotal neurotransmitter involved in neuronal drug reward mechanisms and its neuronal mechanisms have been intensely investigated in recent years. However, neuroglial interactions and their relation to drug addiction development and maintenance of drug addiction have been understudied. Many reports have found that most neuroglial cells express dopamine receptors and that dopamine activity may induce neuroimmunomodulatory effects. Furthermore, current research has also shown that pro- and anti-inflammatory molecules modulate dopaminergic neuron activity. Thus, studying the immune mechanisms of dopamine associated with drug abuse is vital in researching new pathophysiological mechanisms and new therapeutic targets for addiction management.

Increased Retinal Ganglion Cell Survival by Exogenous IL-2 Depends on IL-10, Dopamine D1 Receptors, and Classical IL-2/IL-2R Signaling Pathways

Interleukin-2 (IL-2) is a classical pro-inflammatory cytokine known to display neuroprotective roles in the central nervous system including the retina. In the present study, we investigate the molecular targets involved in the neurotrophic effect of IL-2 on retinal ganglion cells (RGC) after optic nerve axotomy. Analysis of retrograde labeling of RGC showed that common cell survival mediators, as Trk receptors, Src, PI3K, PKC, and intracellular calcium do not mediate the neurotrophic effect of IL-2 on RGC. No involvement of MAPK p38 was also observed. However, other MAPKs as MEK and JNK appear to be mediating this IL-2 effect. Our data also indicate that JAK2/3 are important intracellular proteins for the IL-2 effect. Interestingly, we demonstrate that the IL-2 effect depends on dopamine D1 receptors (D1R), the cAMP/PKA pathway, interleukin-10 (IL-10), and NF-κB, suggesting that RGC survival induced by IL-2 encompasses a molecular network of major complexity. In addition, treatment of retinal cells with recombinant IL-10 or 6-Cl-pb (D1R full agonist) was able to increase RGC survival similar to IL-2. Taken together, our results suggest that after optic nerve axotomy, the increase in RGC survival triggered by IL-2 is mediated by IL-10 and D1R along with the intracellular pathways of MAPKs, JAK/STAT, and cAMP/PKA.

Fatigue in inflammatory rheumatic disorders: pathophysiological mechanisms

Today, inflammatory rheumatic disorders are effectively treated, but many patients still suffer from residual fatigue. This work presents pathophysiological mechanisms of fatigue. First, cytokines can interfere with neurotransmitter release at the preterminal ending. Second, a long-term increase in serum concentrations of proinflammatory cytokines increase the uptake and breakdown of monoamines (serotonin, noradrenaline and dopamine). Third, chronic inflammation can also decrease monoaminergic neurotransmission via oxidative stress (oxidation of tetrahydrobiopterin [BH4]). Fourth, proinflammatory cytokines increase the level of enzyme indoleamine-2, 3-dioxygenase activity and shunt tryptophan away from the serotonin pathway. Fifth, oxidative stress stimulates astrocytes to inhibit excitatory amino acid transporters. Sixth, astrocytes produce kynurenic acid that acts as an antagonist on the α7-nicotinic acetylcholine receptor to inhibit dopamine release. Jointly, these actions result in increased glutamatergic and decreased monoaminergic neurotransmission. The above-described pathophysiological mechanisms negatively affect brain functioning in areas that are involved in fatigue.

Alterations in adolescent dopaminergic systems as a function of early mother-toddler attachment: A prospective longitudinal examination

Early experiences have the potential for outsized influence on neural development across a wide number of domains. In humans, many of the most important such experiences take place in the context of the mother-child attachment relationship. Work from animal models has highlighted neural changes in dopaminergic systems as a function of early care experiences, but translational research in humans has been limited. Our goal was to fill this gap by examining the longitudinal associations between early attachment experiences (assessed at 2.5 years) and neural responses to risk and rewards during adolescence (assessed at 13 years). Adolescence is a developmental period where sensitivity to rewards has important implications for behavior and long-term outcomes, providing an important window to study potential influences of early attachment experiences on reward processing. In order to address this question, 50 adolescents completed a risk and reward task during an fMRI scan, allowing us to assess differences in neural sensitivity to changes in risk level and reward amount as a function of early attachment experiences. Adolescents with insecure attachment histories showed blunted sensitivity to increasing risk levels in regions of the dorsal striatum, while also showing heightened sensitivity to increasing reward levels in the same region. These results highlight the importance of early attachment experiences for long-term neural development. Specifically, early exposure to more maladaptive relationships with caregivers may confer dual risks prospectively for adolescents, sensitizing them to rewarding outcomes while de-sensitizing them to potential risks associated with those behaviors, perhaps due to stress-related dopaminergic changes early in development.

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.

[THYMIC HORMONES, ANTIOXIDANT ENZYMES AND NEUROGENESIS OF BULBUS OLFACTORIUS IN RATS WITH PARKINSONISM: THE EFFECT OF MELATONIN]

The adult rats received both neurotoxin 6-hidroxidophamine and neurotoxin and melatonin. It was investigated a link between the disturbances of the brain antioxidant enzymes activity and thymic endocrine function, as possible pathogenic factors of parkinsonism, with changes in the number of neural stem cells (NSC) in the bulbus olfactorius. Rats with motor asymmetry in the apomorphine test and significant damage of the dopaminergic neurons in the-substantia nigra have decreased levels of superoxide dismutase, catalase and glutathione peroxidase activities in striatum (1.3-1.4 times) and blood thymulin content (8 times) compared to control group. On the contrary, examined indices were not changed in rats without motor asymmetry and correspondingly partly damaged neurons. The number of nestin(+)-cells in the bulbus olfactorius of rats without motor asymmetry increased from 91.2% to 99.3% and remained unchanged after melatonin administration course (10 mg/kg during 18 days). Melatonin administration resulted in the decrease in the number of nestin(+)-cells along with significant elevation of the decreased antioxidant enzymes activity and blood thymulin content in rats with circulatory movements. Possibilities of the enhancement of NSC differentiation in bulbus olfactorius into neuronal direction in such animals has been discussed. The conclusion about the potential use of melatonin as a neuroprotector in parkinsonism therapy has been made.

Glial cells as key players in schizophrenia pathology: recent insights and concepts of therapy

The past decade has witnessed an explosion of knowledge on the impact of glia for the neurobiological foundation of schizophrenia. A plethora of studies have shown structural and functional abnormalities in all three types of glial cells. There is convincing evidence of reduced numbers of oligodendrocytes, impaired cell maturation and altered gene expression of myelin/oligodendrocyte-related genes that may in part explain white matter abnormalities and disturbed inter- and intra-hemispheric connectivity, which are characteristic signs of schizophrenia. Earlier reports of astrogliosis could not be confirmed by later studies, although the expression of a variety of astrocyte-related genes is abnormal in psychosis. Since astrocytes play a key role in the synaptic metabolism of glutamate, GABA, monoamines and purines, astrocyte dysfunction may contribute to certain aspects of disturbed neurotransmission in schizophrenia. Finally, increased densities of microglial cells and aberrant expression of microglia-related surface markers in schizophrenia suggest that immunological/inflammatory factors are of considerable relevance for the pathophysiology of psychosis. This review describes current evidence for the multifaceted role of glial cells in schizophrenia and discusses efforts to develop glia-directed therapies for the treatment of the disease.

Latent Toxoplasma gondii infection leads to improved action control

The parasite Toxoplasma gondii has been found to manipulate the behavior of its secondary hosts to increase its own dissemination which is commonly believed to be to the detriment of the host (manipulation hypothesis). The manipulation correlates with an up-regulation of dopaminergic neurotransmission. In humans, different pathologies have been associated with T. gondii infections but most latently infected humans do not seem to display overt impairments. Since a dopamine plus does not necessarily bear exclusively negative consequences in humans, we investigated potential positive consequences of latent toxoplasmosis (and the presumed boosting of dopaminergic neurotransmission) on human cognition and behavior. For this purpose, we focused on action cascading which has been shown to be modulated by dopamine. Based on behavioral and neurophysiological (EEG) data obtained by means of a stop-change paradigm, we were able to demonstrate that healthy young humans can actually benefit from latent T. gondii infection as regards their performance in this task (as indicated by faster response times and a smaller P3 component). The data shows that a latent infection which is assumed to affect the dopaminergic system can lead to paradoxical improvements of cognitive control processes in humans.

Different distribution patterns of lymphocytes and microglia in the hippocampus of patients with residual versus paranoid schizophrenia: further evidence for disease course-related immune alterations?

Certain cytokines have been identified in the peripheral blood as trait markers of schizophrenia, while others are considered relapse-related state markers. Furthermore, data from peripheral blood, cerebrospinal fluid (CSF) and nuclear imaging studies suggest that (1) blood-brain barrier (BBB) dysfunction (e.g., immigration of lymphocytes into brain tissue and intrathecal antibody production) correlates with the development of negative symptoms, while (2) the brain's mononuclear phagocyte system (microglial cells) is activated during acute psychosis. Based on these neuroinflammatory hypotheses, we have quantified the numerical density of immunostained CD3+ T-lymphocytes, CD20+ B-lymphocytes, and HLA-DR+ microglial cells in the posterior hippocampus of 17 schizophrenia patients and 11 matched controls. Disease course-related immune alterations were considered by a separate analysis of residual (prevailing negative symptoms, n=7) and paranoid (prominent positive symptoms, n=10) schizophrenia cases. Higher densities of CD3+ and CD20+ lymphocytes were observed in residual versus paranoid schizophrenia (CD 3: left: P=0.047, right: P=0.038; CD20: left: P=0.020, right: P=0.010) and controls (CD3: left: P=0.057, right: P=0.069; CD20: left: P=0.008, right: P=0.006). In contrast, HLA-DR+ microglia were increased in paranoid schizophrenia versus residual schizophrenia (left: P=0.030, right: P=0.012). A similar trend emerged when this group was compared to controls (left: P=0.090, right: P=0.090). BBB impairment and infiltration of T cells and B cells may contribute to the pathophysiology of residual schizophrenia, while microglial activation seems to play a role in paranoid schizophrenia. The identification of diverse immune endophenotypes may facilitate the development of distinct anti-inflammatory schizophrenia therapies to normalize BBB function, (auto)antibody production or microglial activity.

[Toxoplasma gondii: a potential role in the genesis of psychiatric disorders]

INTRODUCTION

Toxoplasma gondii is the most common protozoan parasite in developed nations. Up to 43% of the French population may be infected, depending on eating habits and exposure to cats, and almost one third of the world human's population may be infected. Two types of infection have been described: a congenital form and an acquired form. Although the medical profession treats these latent cases as asymptomatic and clinically unimportant, results of animal studies and recent studies of personality profiles, behavior, and psychomotor performance have led to reconsider this assumption.

PRECLINICAL DATA

Among rats: parasite cysts are more abundant in amygdalar structures than those found in other regions of the brain. Infection does not influence locomotion, anxiety, hippocampal-dependent learning, fear conditioning (or its extinction) and neophobia in rats. Rats' natural predator is the cat, which is also T. gondii's reservoir. Naturally, rats have an aversion to cat urine, but the parasite suppresses this aversion in rats, thus influencing the infection cycle. Tachyzoites may invade different types of nervous cells, such as neurons, astrocytes and microglial cells in the brain, and Purkinje cells in cerebellum. Intracellular tachyzoites manipulate several signs for transduction mechanisms involved in apoptosis, antimicrobial effectors functions, and immune cell maturation. Dopamine levels are 14% higher in mice with chronic infections. These neurochemical changes may be factors contributing to mental and motor abnormalities that accompany or follow toxoplasmosis in rodents and possibly in humans. Moreover, the antipsychotic haloperidol and the mood stabilizer valproic acid most effectively inhibit Toxoplasma growth in vitro with synergistic activity.

CLINICAL DATA

The effects of the parasite are not due to the manipulation in an evolutionary sense but merely due to neuropathological or neuroimmunological effects of the parasite's presence. Toxoplasmosis and schizophrenia: epidemiological studies point to a role for toxoplasmosis in schizophrenia's etiology, probably during pregnancy and early life, this association being congruent with studies in animal models indicating that animal exposures of the developing brain to infectious agents or immune modulating agents can be associated with behavioral changes that do not appear until the animal reaches full maturity. Psychiatric patients have increased rates of toxoplasmic antibodies, the differences between cases and controls being greatest in individuals who are assayed near the time of the onset of their symptoms. The increase of dopamine in the brain of infected subjects can represent the missing link between toxoplasmosis and schizophrenia. Toxoplasmosis and Obsessive Compulsive Disorder (OCD): the seropositivity rate for anti-T. gondii IgG antibodies among OCD patients is found to be significantly higher than the rate in healthy volunteers. Infection of basal ganglia may be implicated in the pathogenesis of OCD among Toxoplasma seropositive subjects. Toxoplasmosis and personality: infected men appear to be more dogmatic, less confident, more jealous, more cautious, less impulsive and more orderly than others. Conversely, infected women seem warmest, more conscientious, more insecure, more sanctimonious and more persistent than others. It is possible that differences in the level of testosterone may be responsible for the observed behavioral differences between Toxoplasma-infected and Toxoplasma-free subjects.

CONCLUSION

In the future two major avenues for research seem essential. On one hand, prospective studies and research efforts must still be carried out to understand the mechanisms by which the parasite induces these psychiatric disorders. On the other hand, it has not yet been demonstrated that patients with positive toxoplasmic serology may better respond to haloperidol's or valproic acid's antiparasitic activity. These results may appear as a major issue in the drug's prescribing choices and explain variability in response to the treatment of patients with schizophrenia that is not explained by the genetic polymorphism.

Central metabolite changes and activation of microglia after peripheral interleukin-2 challenge

Interleukin (IL)-2 regulates the immune response through the proliferation of activated T-cells and also exerts effects on the central nervous system (CNS). Alongside having marked neurobehavioral effects, IL-2 has been suggested to impact on various psychiatric disorders. The immune-CNS communication of IL-2 remains unclear, although, it is suggested that microglia are the source and target of IL-2. Here, we analyzed changes in brain metabolites following a peripheral IL-2 challenge and examined the contribution of microglia in mediating these effects. Rats were assessed by magnetic resonance spectroscopy (MRS) in a 9.4 T scanner for baseline metabolite levels in the prefrontal cortex (PFC) and the hippocampus. After 7 days animals were scanned again following a single injection of IL-2 (2.5 μg/kg) and then tested on the elevated plus-maze for the correlation of IL-2-induced brain metabolites and measures of anxiety. In another experiment CD25(+) microglia cells were determined. A separate group of rats was injected either with IL-2 or vehicle, and afterward the PFC and hippocampus were dissected and fluorescence activated cell sorting (FACS) analysis was performed. The MRS scans in the intra-individual study design showed a significant increase in myo-inositol in the analyzed regions. A significant correlation of anxiety-like measures and myo-inositol, a marker for microglia activity, was found in the hippocampus. The FACS analysis showed a significant increase in CD25(+) microglia in the hippocampus compared to controls. The results support the role of microglia as a mediator in the immune-CNS communication and the effects of peripheral IL-2.

Immunomodulation in schizophrenia: A study among the Indian schizophrenia patients of Siliguri, West Bengal

Authors investigated the circumstantial evidence for autoimmunity in schizophrenia patients of Siliguri by considering the immune parameters like HLA Class I genes, IL-2 and IL6 and T cell subsets. Low resolution PCR-SSP method was applied for typing the HLA genes. Serum levels of IL-2 and IL-6 were measured by ELISA method. The CD4+ and CD8+ subset count were done using flow cytometry. A significant increase in HLA A*03 gene was observed in patients along with the significant decrease of HLA-A*31 and HLA-B*51. Both IL-2 and IL-6 were found to have decreased levels in the patients. Although the mean percentage of CD4+ and CD8+ cells was higher in patients but not significantly higher than controls. These cumulative preliminary findings are suggestive of alterations in the immune system of schizophrenia patients of this region.

The interaction of nuclear factor-kappa B and cytokines is associated with schizophrenia

BACKGROUND

Many reports suggest that schizophrenia is associated with the inflammatory response mediated by cytokines, and nuclear factor-kappa B (NF-kappaB) regulates the expression of cytokines. However, it remains unclear whether the interaction between NF-kappaB and cytokines is implicated in schizophrenia and whether the effect of neuroleptics treatment for 4 weeks is associated with the alteration of cytokines.

METHODS

Sixty-five healthy subjects and 83 first-episode schizophrenic patients who met DSM-IV criteria and who were never treated with neuroleptics previously were included. Serum levels of cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) were examined by using sandwich enzyme immunoassay (EIA). Peripheral blood mononuclear cell (PBMC) mRNA expressions of cytokines (IL-1beta, TNF-alpha) and NF-kappaB were detected by using semiquantitative reverse transcription polymerase chain reaction (RT-PCR). NF-kappaB activation was examined by using transcription factor assay kits.

RESULTS

Schizophrenic patients showed significantly higher serum levels and PBMC mRNA expressions of IL-1beta and TNF-alpha compared with healthy subjects. However, treatment with the neuroleptic risperidone for 4 weeks significantly decreased serum levels and PBMC mRNA expressions of IL-1beta in schizophrenic patients. NF-kappaB activation and PBMC mRNA expression in patients were significantly higher than those in healthy subjects. Furthermore, PBMC mRNA expressions of IL-1beta and TNF-alpha were positively correlated to NF-kappaB activation in both schizophrenic patients and healthy control subjects.

CONCLUSIONS

Schizophrenic patients showed activation of the cytokine system and immune disturbance. NF-kappaB activation may play a pivotal role in schizophrenia through interaction with cytokines.

Opiate modulation of IL-1alpha, IL-2, and TNF-alpha transport across the blood-brain barrier

Interleukin-1alpha (IL-1alpha), interleukin-2 (IL-2), and tumor necrosis factor alpha (TNF-alpha) are proinflammatory cytokines with potent neuromodulatory effects and are implicated in the etiology and pathogenesis of various psychological and neurological disorders. The findings that chronic morphine treatment alters both blood-brain barrier (BBB) function and cytokine production raises the possibility that morphine can also modulate cytokine transport across the BBB. Here, we found that acute morphine treatment (12 mg/kg i.p.) did not alter blood-to-brain transport of IL-1alpha, IL-2 or TNF-alpha. Whereas chronic morphine treatment (48 h after implantation of 75 mg morphine pellets) and withdrawal from morphine (10-15 min after an i.p. injection of 1mg/kg of naltroxone 48 h after implantation of 75 mg morphine pellets) did not alter blood-to-brain transport of IL-1alpha or TNF-alpha, both the chronic morphine treatment and withdrawal from morphine groups had increased blood-to-brain transport of IL-2. Typically, the permeability of the BBB to IL-2 is dominated by brain-to-blood efflux, with only limited blood-to-brain transport. Here, we found that chronic morphine and withdrawal from morphine did not alter brain-to-blood efflux, but induced a novel saturable blood-to-brain transport system. Whereas IL-1alpha, IL-2, and TNF-alpha are all proinflammatory cytokines, morphine exposure has individualized effects on their blood-to-brain transport.

Effect of unilateral and bilateral lesions of caudate-putamen on immune response in the rat

In the present study we investigated the effect of selectivity destroyed dopaminergic neurons of the caudate-putamen (CP) on immune reactivity in the rat. Unilateral and bilateral lesioning of CP was performed by one direct stereotaxic injection of 6-hydroxydopamine solution. Sham-lesioned and intact rats served as controls. Two weeks after the operation, the animals were immunized with sheep red blood cells or bovine serum albumin for determination of plaque forming cell-response and Arthus and delayed hypersensitivity skin reactions, respectively. Unilateral and bilateral lesions of CP considerably suppressed PFC-response and Arthus and delayed the hypersensitivity reactions in comparison to control rats, while no differences were observed between unilaterally and bilaterally lesioned animals.

Comparative analysis of the expression of c-Fos and interleukin-2 proteins in hypothalamus cells during various treatments

The aim of the present work was to perform a combined analysis of the degree of activation of the anterior hypothalamus of the rat and expression of the interleukin-2 gene during treatments of different types: mild stress ("handling") and adaption to it, as well as intranasal administration of physiological saline and the peptides Vilon (Lys-Glu) and Epitalon (Ala-Glu-Asp-Gly). Changes in the numbers of c-Fos-and IL-2-positive cells in structures of the lateral area (LHA) and anterior (AHN), supraoptic (SON), and paraventricular (PVN) nuclei of the hypothalamus in Wistar rats. Ratios of the quantities of c-Fos-and IL-2-positive cells were determined in intact animals and after activation of brain cells initiated by different treatments; the influences of adaptation to handling on the nature of changes in the expression of these proteins was also studied. Combined analysis of the intensity of expression of these two proteins - c-Fos, a marker of neuron activation and a trans-factor for the IL-2 cytokine gene and other inducible genes, and IL-2 - in intact animals and after various treatments showed that the process of cell activation in most of the hypothalamic structures studied correlated with decreases in the quantity of IL-2-positive cells in these structures; different patterns of changes in the numbers of c-Fos-and IL-2-positive cells were seen in response to different treatments in conditions of stress and adaptation to it.

Immunological aspects in the neurobiology of suicide: elevated microglial density in schizophrenia and depression is associated with suicide

OBJECTIVES

Suicide has a high prevalence in patients with schizophrenia and affective disorder. Our recent postmortem study [Steiner J, Mawrin C, Ziegeler A, Bielau H, Ullrich O, Bernstein HG, Bogerts B. Distribution of HLA-DR-positive microglia in schizophrenia reflects impaired cerebral lateralization. Acta Neuropathologica (Berl) 2006;112:305-16.] revealed increased microglial densities in two schizophrenic patients who had committed suicide. Therefore, the hypothesis of microglial activation during acute psychosis was proposed. Alternatively, "suicide" could be a diagnosis-independent factor leading to microgliosis.

METHODS

To clarify this question, microglial HLA-DR expression was analyzed by immunohistochemistry in the dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), mediodorsal thalamus (MD) and hippocampus of 16 schizophrenics, 14 depressed patients with affective disorder and 10 matched controls. A subgroup of six schizophrenics and seven patients with affective disorder who committed suicide was included.

RESULTS

ANOVA revealed no effect of diagnosis on microglial density (DLPFC: P=0.469; ACC: P=0.349; MD: P=0.569; hippocampus: P=0.497). However, significant microgliosis was observed in the DLPFC (P=0.004), ACC (P=0.012) and MD (P=0.004) of suicide patients. A similar trend was seen in the hippocampus (P=0.057).

CONCLUSION

In conclusion, immunological factors may play a hitherto underestimated role in suicide. First, microglial activation might be interpreted as a consequence of presuicidal stress. Second, one might speculate a causal link between microglial activation and suicidal behaviour, such as neuroendocrine factors, cytokines, and nitric oxide, which are released from microglial cells and are known to modulate noradrenergic or serotonergic neurotransmission and thus may trigger suicidality.

Cytokine levels during pregnancy influence immunological profiles and neurobehavioral patterns of the offspring

The underlying causes of autism spectrum disorders (ASD) are unknown, but clinical and experimental studies indicate immune mechanisms, in general, and cytokine dysregulation, in particular, as contributing factors in their etiology. We developed a prenatal mouse model of autism to demonstrate that circulating levels of defined cytokines in pregnant dams could influence fetal development and behavioral characteristics in their offspring. We administered daily injections of murine IL-2 (0.4 mug in phosphate-buffered saline [PBS]) to pregnant mice during mid-gestation, and analyzed their offspring (IL-2 pups) in comparison to offspring of pregnant mice injected with vehicle only (PBS pups). Significant levels of IL-2 were present in amniotic fluid and tissues from embryos of dams given radiolabeled IL-2, indicating that the injected IL-2 crossed the placenta and entered the fetuses. Lymphocytes from IL-2 pups demonstrated accelerated T cell development, with a skewing toward TH1 cell differentiation. IL-2 pups also showed in vitro proliferative and cytotoxicity responses that were significantly higher than control PBS pups when stimulated with syngeneic B lymphoma cells or allogeneic spleen cells. In addition to their previously shown increases in open-field activity, grooming and rearing behavior, offspring of IL-2-injected (vs. PBS-injected) dams also displayed abnormal new motor learning as assessed through acquisition of the classically conditioned eyeblink response. These results suggest that increases in maternal levels of IL-2 during pregnancy induce in their offspring long-lasting increased vulnerability to neurobehavioral abnormalities associated with autism, and provide a valid animal model to determine the underlying immunological mechanisms.

Effects of toxoplasma on human behavior

Although latent infection with Toxoplasma gondii is among the most prevalent of human infections, it has been generally assumed that, except for congenital transmission, it is asymptomatic. The demonstration that latent Toxoplasma infections can alter behavior in rodents has led to a reconsideration of this assumption. When infected human adults were compared with uninfected adults on personality questionnaires or on a panel of behavioral tests, several differences were found. Other studies have demonstrated reduced psychomotor performance in affected individuals. Possible mechanisms by which T. gondii may affect human behavior include its effect on dopamine and on testosterone.

Poorer results of mice with latent toxoplasmosis in learning tests: impaired learning processes or the novelty discrimination mechanism?

The heteroxenous protozoan parasite Toxoplasma gondii is transmitted from the intermediate host (any warm-blooded animal) to the definitive host (members of the felidae) by carnivory. The infected intermediate hosts develop several specific behavioural changes that are usually considered products of manipulative activity of the parasite aimed to increase the probability of its transmission to the definitive host. Among other changes, the infected rodents were shown to have impaired learning capability. All previous studies were done 2–6 weeks after the infection. Therefore, it was difficult to resolve whether the observed impairment of learning processes was a result of acute or latent toxoplasmosis, i.e. whether it was a side-effect of the disease or a product of manipulation activity. Here we studied the learning capability of Toxoplasma-infected mice in the static rod test and 8-arm radial maze test and their spontaneous activity in the wheel running test 10 weeks after the infection. The infected mice achieved worse scores in the learning tests but showed higher spontaneous activity in the wheel running test. However, a detailed study of the obtained results as well as of the data reported by other authors suggested that the differences between infected and control mice were a result of impaired ability to recognize novel stimuli rather than of impaired learning capacity in animals with latent toxoplasmosis.

Distribution of HLA-DR-positive microglia in schizophrenia reflects impaired cerebral lateralization

Immunological alterations have been demonstrated in peripheral blood and cerebrospinal fluid of patients with schizophrenia, while previous postmortem studies have provided an inconsistent picture as to the role of microglia in the context of schizophrenia. Microglial activation is a sensitive indicator of changes in the CNS microenvironment, such as inflammatory and neurodegenerative processes. The aim of the present postmortem study was to examine HLA class II (HLA-DR) expression on microglia in brain regions which are particularly relevant for schizophrenia, with regard to hemispheric lateralization. Dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), hippocampus and mediodorsal thalamus (MD) were studied in 16 cases with schizophrenia and 16 control subjects. Immunostaining was found in all brain regions and was not restricted to macrophage-like ameboid cells, but also appeared in ramified cells. Region-specific HLA-DR-positive cell density was not significantly different between cases with schizophrenia and controls. However, ameboid microglial cells were lateralized towards the right hemisphere in healthy subjects but not in the schizophrenia group (P=0.01). Postmortem interval correlated with ramified cell numbers in ACC/DLPFC (P=0.01/0.04) and ameboid cell density in hippocampus (P=0.03). Age, gender, duration of disease, medication dosage, storage delay and whole brain volume had no effect. Single case analysis revealed highly elevated microglial cell numbers in ACC and MD of two schizophrenic patients who had committed suicide during acute psychosis. In conclusion, the present data suggest the absence of microgliosis but decreased cerebral lateralization of ameboid microglia in schizophrenia.

Probable neuroimmunological link between Toxoplasma and cytomegalovirus infections and personality changes in the human host

Background

Recently, a negative association between Toxoplasma-infection and novelty seeking was reported. The authors suggested that changes of personality trait were caused by manipulation activity of the parasite, aimed at increasing the probability of transmission of the parasite from an intermediate to a definitive host. They also suggested that low novelty seeking indicated an increased level of the neurotransmitter dopamine in the brain of infected subjects, a phenomenon already observed in experimentally infected rodents. However, the changes in personality can also be just a byproduct of any neurotropic infection. Moreover, the association between a personality trait and the toxoplasmosis can even be caused by an independent correlation of both the probability of Toxoplasma-infection and the personality trait with the third factor, namely with the size of living place of a subject. To test these two alternative hypotheses, we studied the influence of another neurotropic pathogen, the cytomegalovirus, on the personality of infected subjects, and reanalyzed the original data after the effect of the potential confounder, the size of living place, was controlled.

Methods

In the case-control study, 533 conscripts were tested for toxoplasmosis and presence of anti-cytomegalovirus antibodies and their novelty seeking was examined with Cloninger's TCI questionnaire. Possible association between the two infections and TCI dimensions was analyzed.

Results

The decrease of novelty seeking is associated also with cytomegalovirus infection. After the size of living place was controlled, the effect of toxoplasmosis on novelty seeking increased. Significant difference in novelty seeking was observed only in the largest city, Prague.

Conclusion

Toxoplasma and cytomegalovirus probably induce a decrease of novelty seeking. As the cytomegalovirus spreads in population by direct contact (not by predation as with Toxoplasma), the observed changes are the byproduct of brain infections rather than the result of manipulation activity of a parasite. Four independent lines of indirect evidence, namely direct measurement of neurotransmitter concentration in mice, the nature of behavioral changes in rodents, the nature of personality changes in humans, and the observed association between schizophrenia and toxoplasmosis, suggest that the changes of dopamine concentration in brain could play a role in behavioral changes of infected hosts.

Kainate-activated currents in the ventral tegmental area of neonatal rats are modulated by interleukin-2

Interleukin (IL)-2 is a potent modulator of neurotransmission and neuronal development in the mesolimbic and mesostriatal systems. It is also implicated in pathologies (including schizophrenia, Parkinson's disease, autism, cognitive disorders) that are linked with abnormalities in these systems. Since the kainate receptor plays an essential role in mesolimbic neuronal development and excitability, we examined the effects of physiologically relevant concentrations of IL-2 on kainate-activated current (I(KA)) in voltage-clamped neurons freshly isolated from the ventral tegmental area (VTA) of 3- to 14-day-old rats. IL-2 (0.01-10 ng/ml) alone had no effect on membrane conductance. When co-applied with kainate, IL-2 significantly decreased I(KA). IL-2 (2 ng/ml) shifted the kainate concentration-response curve to the right in a parallel manner, significantly increasing the EC(50) without changing the maximal I(KA). IL-2 inhibition of I(KA) was voltage-dependent, being greater at negative potentials. IL-2 did not alter the reversal potential. These findings suggest that IL-2 potently modulates kainate receptors of developing mesolimbic neurons. We suggest that IL-2 plays a role in the excitability of developing neurons in the mesolimbic system. Inasmuch as increased I(KA) is associated with excitotoxicity, coupled with the present observation that IL-2 inhibits I(KA), we suggest an adaptive role for IL-2 in limiting excitotoxicity in the developing brain. IL-2 might thus be required for normal cell development in the mesolimbic and mesostriatal systems.

IL-2 deficiency results in altered septal and hippocampal cytoarchitecture: relation to development and neurotrophins

We have found previously that brain IL-2 receptors are enriched in the hippocampal formation, and that loss of this cytokine results in cytoarchitectural alterations in the hippocampus and septum and related behavioral changes in IL-2 knockout (IL-2 KO) mice. These alterations included decreased cholinergic somata in the medial septum/vertical limb of the diagonal band of Broca (MS/vDB) and decreased distance across the infrapyramidal (IP) granule cell layer (GCL) of the dentate gyrus (DG). To extend our previous findings, several experiments were conducted comparing IL-2 KO mice and wild-type littermates to determine (1) whether the GABAergic projection neurons of IL-2 KO mice in this region were also affected; (2) if the reduction in septal cholinergic projection neurons found in adult IL-2 KO mice is present at weaning (and prior to the development of peripheral autoimmune disease); and (3) if loss of IL-2 may result in changes in the neurotrophins, brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), involved in maintenance of hippocampal neurons. No differences in GABAergic neurons in the MS/vDB were found in adult mice, and the reduction in cholinergic neurons seen in adult IL-2 KO mice was not found in animals at postnatal day 21. The number of neurons in the IP-GCL was also significantly reduced. Compared to wild-type mice, IL-2 KO mice had significantly reduced concentration of BDNF protein and increased concentrations of NGF. These data suggest that the septohippocampal neuronal loss in IL-2 KO mice is selective for the cholinergic neurons and appears to be due to a failure in neuronal maintenance/survival that may be, in part, associated with changes in neurotrophins.

Chlorpromazine and loxapine reduce interleukin-1beta and interleukin-2 release by rat mixed glial and microglial cell cultures

The cytokines IL-1beta and IL-2 are released from activated glial cells in the central nervous system and they are able to enhance catecholaminergic neurotransmission. There is no data concerning influence of antipsychotics on glial cell activity. Antipsychotics reaching the brain act not only on neurons but probably also on glial cells. The aim of this study was to evaluate the effect of chlorpromazine and loxapine on release of IL-1beta and IL-2 by mixed glial and microglial cell cultures. Chlorpromazine in concentrations 2 and 20 muM, and loxapine 0.2, 2 and 20 microM reduced IL-1beta secretion by LPS-activated mixed glia cultures after 1 and 3 days of exposure. Chlorpromazine in concentrations of 0.2, 2 and 20 microM reduced the IL-2 secretion in mixed glial cultures after 3 days of exposure. Loxapine in concentrations of 0.2, 2 and 20 microM reduced IL-2 secretion in mixed glia cultures after 1 and 3 days of exposure, and additionally loxapine decreased IL-1beta and IL-2 secretion in LPS-induced microglia cultures in concentrations of 2, 10 and 20 muM. Quinpirole-a D2 dopaminergic agonist increased LPS-induced IL-1beta and IL-2 secretion in mixed glia cultures only in the highest dose of 20 microM. These findings suggest the absence of functional dopamine receptors on cortical microglial cells. Mixed glia cultures deprived of microglia (by shaking and incubating with L-leucine methyl ester) did not release IL-1beta and IL-2. This observation suggests that microglia can be a source of assessed cytokines. Results of the present study support the view that antipsychotics act not only on neurons but also on glial cells. However, the clinical significance of these observations still remains unclear.

Mycoplasma pneumoniae infection and Tourette's syndrome

An association between infection and Tourette's syndrome (TS) has been described repeatedly. A role for streptococcal infection (PANDAS) has been established for several years, but the involvement of other infectious agents such as Borrelia Burgdorferi or Mycoplasma pneumoniae has only been described in single case reports. We examined antibody titers against M. pneumoniae and various types of antibodies by immunoblot in patients and in a sex- and age-matched comparison group. Participants comprised 29 TS patients and 29 controls. Antibody titers against M. pneumoniae were determined by microparticle agglutination (MAG) assay and confirmed by immunoblot. Elevated titers were found in significantly more TS patients than controls (17 vs. 1). Additionally, the number of IgA positive patients was significantly higher in the TS group than in the control group (9 vs. 1). A higher proportion of increased serum titers and especially of IgA antibodies suggests a role for M. pneumoniae in a subgroup of patients with TS and supports the finding of case reports implicating an acute or chronic infection with M. pneumoniae as one etiological agent for tics. An autoimmune reaction, however, has to be taken into account. In predisposed persons, infection with various agents including M. pneumoniae should be considered as at least an aggravating factor in TS.

Short- and long-term effects of interleukin-2 on weight, food intake, and hedonic mechanisms in the rat

In the present work, we investigated the short- and long-term effects of a single systemic injection of rat recombinant interleukin-2 on weight, food intake, and brain stimulation reward thresholds elicited from the ventral tegmental area. An inverted U-shaped dose-function was obtained with 0.5 microg producing the greatest increases in the threshold for rewarding brain stimulation which were sustained during the month long tests. No differences between groups in terms of maximum response rates, a measure of performance, were observed. Although all injected groups showed a minor decline in the rate of weight gain over time, percent efficiency of food utilization (percent weight gain/food intake) was the same across groups, suggesting that metabolic function was not affected by the cytokine. In animals with bilateral ventral tegmental area implants, there was no consistent correspondence between the threshold change obtained from ipsilateral stimulation and that associated with the contralateral site; side-to-side differences ranged from 0 to 100%, suggesting a specific interaction between cytokine activity and the locus of rewarding brain stimulation. These data suggest that peripheral IL-2 significantly modifies hedonic processes arising from medial forebrain bundle stimulation in a long-term manner. We further suggest that since this modulation appears to be notably site-specific, IL-2 receptors or its metabolites may not be evenly distributed within the medial forebrain bundle.

Permeability of the mouse blood-brain barrier to murine interleukin-2: predominance of a saturable efflux system

Interleukin (IL)-2, a T helper (TH)1 cell-derived glycoprotein with potent neuromodulatory effects, is implicated in the etiology and pathogenesis of various psychiatric and neurological disorders. Paralleling these findings, chronic IL-2 intravenous immunotherapy may induce similar psychopathological outcomes. The findings that acute or repeated injections of IL-2 induce motor and cognitive abnormalities in rodents are consistent with these clinical findings, and raise the possibility that IL-2 crosses the blood-brain barrier (BBB) to alter brain function. However, little is known about the ability of IL-2 to enter the brain or whether its effects vary with the chronicity of IL-2 treatment. Here, we found that radioactively labeled mouse IL-2 (I-IL-2) given intravenously entered the brain at a low rate (Ki=0.142+/-0.044microl/g-min) by a non-saturable process. Repeated injections of either IL-2 or vehicle altered the kinetics of entry without producing a net effect on IL-2 entry. When I-IL-2 was given by brain perfusion, the entry rate greatly increased over 10-fold to 2.2+/-0.805microl/g-min. This suggests a circulating factor is retarding the entry of IL-2 into the brain. A paradoxic increase in the rate of I-IL-2 entry into brain occurred when an excess of unlabeled IL-2 was included in the brain perfusate, suggesting a saturable CNS-to-blood efflux system. Intracerebroventricular injection of I-IL-2 with and without unlabeled IL-2 confirmed the presence of a saturable efflux system. We conclude that IL-2 entry into the brain is low because of the absence of a blood-to-brain transporter and further retarded by circulating factors and a CNS-to-blood efflux system. This is the first description of a saturable CNS-to-blood efflux system for a cytokine. We postulate that this efflux system may protect the brain from circulating IL-2.

Discovering novel phenotype-selective neurotrophic factors to treat neurodegenerative diseases

Astrocytes and neurons in the central nervous system (CNS) interact functionally to mediate processes as diverse as neuroprotection, neurogenesis and synaptogenesis. Moreover, the interaction can be homotypic, implying that astrocyte-derived secreted molecules affect their adjacent neurons optimally vs remote neurons. Astrocytes produce neurotrophic and extracellular matrix molecules that affect neuronal growth, development and survival, synaptic development, stabilization and functioning, and neurogenesis. This new knowledge offers the opportunity of developing astrocyte-derived, secreted proteins as a new class of therapeutics specifically to treat diseases of the CNS. However, primary astrocytes proliferate slowly in vitro, and when induced to immortalize by genetic manipulation, tend to lose their phenotype. These problems have limited the development of astrocytes as sources of potential drug candidates. We have successfully developed a method to induce spontaneous immortalization of astrocytes. Gene expression analysis, karyotyping and activity profiling data show that these spontaneously immortalized type-1 astrocyte cell lines retain the properties of their primary parents. The method is generic, such that cell lines can be prepared from any region of the CNS. To date, a library of 70 cell lines from four regions of the CNS: ventral mesencephalon, striatum, cerebral cortex and hippocampus, has been created. A phenotype-selective neurotrophic factor for dopaminergic neurons has been discovered from one of the cell lines (VMCL1). This mesencephalic astrocyte-derived neurotrophic factor (MANF) is a 20 kD, glycosylated, human secreted protein. Homologs of this protein have been identified in 16 other species including C. elegans. These new developments offer the opportunity of creating a library of astrocyte-derived molecules, and developing the ones with the best therapeutic indices for clinical use.

Tumor necrosis factor-alpha gene promoter polymorphisms in chronic schizophrenia

BACKGROUND

Alterations in cytokine levels in patients with schizophrenia have been documented. Polymorphisms in these cytokine genes are thus potential genetic markers for schizophrenia. The aim of this study was to investigate four biallelic polymorphisms in the tumor necrosis factor-alpha (TNFalpha) gene promoter in relation to susceptibility to schizophrenia.

METHODS

Three hundred two patients and 152 control subjects were genotyped and frequencies of genotypes and alleles were compared for the -1031T/C, -863C/A, -857C/T, and -308G/A polymorphisms. Genotype and allele frequencies were compared between controls and patients.

RESULTS

There were statistically significant differences in genotype distribution and allele frequencies for the -308 polymorphism (p <.001). Genotype distribution and allele frequencies of the other three polymorphisms were not different between patients and reference controls.

CONCLUSIONS

The -308 polymorphism or another genetic variant in linkage disequilibrium with it could be a susceptibility factor for chronic schizophrenia.

Immunity and schizophrenia: autoimmunity, cytokines, and immune responses

As is evident from the present account, there is no single or persuasive argument that signals emanating from the immune system are directly involved in the etiology of schizophrenia. We do not even know if we are dealing with a single disorder with a single causality; almost certainly we are not. The precise etiology of schizophrenia, as with so many neurological disorders, remains obscure. However, there is abundant evidence in schizophrenia of mutual dysregulation of neuronal function and immune system activity. Although this evidence is not always consistent, a pattern emerges suggesting aspects of immune activity being involved in the pathology of neuronal development that characterizes schizophrenia. Exposure to infective agents, HLA associations, autoimmune associations, disturbances in lymphocyte populations, and cytokine imbalances with a skew toward Th2 activity are supportive of this view. That the evidence is not always consistent is a testament to the complexity and heterogeneity of the disorder, to confounding by antipsychotics that themselves are immunomodulatory, and to the multifaceted nature, with all its checks and balances, of the immune system itself.

Cytokines and cognition--the case for a head-to-toe inflammatory paradigm

The brain is not only immunologically active of its own accord, but also has complex peripheral immune interactions. Given the central role of cytokines in neuroimmmunoendocrine processes, it is hypothesized that these molecules influence cognition via diverse mechanisms. Peripheral cytokines penetrate the blood-brain barrier directly via active transport mechanisms or indirectly via vagal nerve stimulation. Peripheral administration of certain cytokines as biological response modifiers produces adverse cognitive effects in animals and humans. There is abundant evidence that inflammatory mechanisms within the central nervous system (CNS) contribute to cognitive impairment via cytokine-mediated interactions between neurons and glial cells. Cytokines mediate cellular mechanisms subserving cognition (e.g., cholinergic and dopaminergic pathways) and can modulate neuronal and glial cell function to facilitate neuronal regeneration or neurodegeneration. As such, there is a growing appreciation of the role of cytokine-mediated inflammatory processes in neurodegenerative diseases such as Alzheimer's disease and vascular dementia. Consistent with their involvement as mediators of bidirectional communication between the CNS and the peripheral immune system, cytokines play a key role in the hypothalamic-pituitary-adrenal axis activation seen in stress and depression. In addition, complex cognitive systems such as those that underlie religious beliefs, can modulate the effects of stress on the immune system. Indirect means by which peripheral or central cytokine dysregulation could affect cognition include impaired sleep regulation, micronutrient deficiency induced by appetite suppression, and an array of endocrine interactions. Given the multiple levels at which cytokines are capable of influencing cognition it is plausible that peripheral cytokine dysregulation with advancing age interacts with cognitive aging.

Interleukin-2-induced increases in climbing behavior: inhibition by dopamine D-1 and D-2 receptor antagonists

Interleukin (IL)-2 is a potent modulator of dopamine activity in the mesocorticolimbic and mesostriatal systems. It is also associated with behavioral changes (increased motor activity) and psychopathological outcomes (schizophrenia, Parkinson's Disease, cognitive deficits) that at least partly reflect aberrations in central dopaminergic transmission. Nonetheless, there is no evidence that a functional link exists between IL-2, dopaminergic processes, and related behavioral changes. We thus determined if IL-2 treatment increases the expression of climbing behavior, a behavior that is linked with dopamine D-1 and/or D-2 receptors and one used to test the efficacy of neuroleptics. IL-2 treatment (5-daily i.p. injections; 0.4 microg/BALB/c mouse) induced a marked 2-fold increase in climbing scores; a single injection had no effect. IL-2-induced increases in climbing behavior were completely blocked by a selective dopamine D-1 receptor antagonist (SCH 23390; 0.05 or 0.2 mg/kg; i.p.), or by a relatively high dose of a D-2 antagonist (sulpiride; 80 mg/kg; i.p.). In contrast, MK-801, a noncompetitive NMDA receptor antagonist, had no effect. This is the first demonstration of a functional link between IL-2, dopaminergic receptors, and behavior. These findings could shed light on the mechanisms by which IL-2 increases vulnerability to psychiatric abnormalities associated with aberrations in central dopaminergic processes.

Neuroleptics normalize increased release of interleukin- 1 beta and tumor necrosis factor-alpha from monocytes in schizophrenia

Some recent reports show that schizophrenia is accompanied by changes in lymphocyte activity. This study investigated the activity of monocytes by determining their release of interleukin- 1 beta (IL- 1 beta) and tumor necrosis factor-alpha (TNF-alpha). Monocytes were immunomagnetically isolated from the peripheral blood of schizophrenic patients before and after neuroleptic medication and stimulated by lipopolisaccharide (LPS) in vitro. The monocytes of schizophrenic patients released significantly higher amounts of IL- 1 beta and TNF-alpha than those of healthy controls. Treatment with the typical neuroleptics haloperidol and perazine decreased the release of IL- 1 beta and TNF-alpha to the control levels. The study has shown that the activity of monocytes is increased in schizophrenia and that neuroleptic treatment normalizes this activity.

An abbreviated review of immune abnormalities in schizophrenia

Initial investigations of the possible interaction between schizophrenia and the immune system began in the early 1900s and have proceeded in a rather halting fashion because of the methodological challenges faced by investigators. However, a confluence of recent data suggests that activation of the inflammatory response system, the cellular immune system, and the humoral immune system may be present in some patients with schizophrenia. Some of the most compelling data support the hypothesis that minor levels of immune activation may be associated with acute psychotic exacerbations. However, a second body of evidence suggests that some individuals with schizophrenia may have chronic, evolving autoimmune processes. This article is an overview of the history, rationale, and some of the recent findings on the interaction between schizophrenia and the immune system.

Interleukin-2 potentiates novelty- and GBR 12909-induced exploratory activity

Interleukin (IL)-2 is a cytokine that influences exploratory behavior and central dopamine activity in rodents, and induces schizophrenic-like behavior and cognitive deficits in humans. We presently report that a single i.p. injection of murine IL-2 (0.05-0.80 microg/mouse) induced significant increases in novelty-induced locomotion and exploration in BALB/c mice. These measures were not significantly altered in mice that were pre-exposed to the test cage prior to cytokine injection. The IL-2-induced behavioral changes were not further augmented by repeated intermittent injections (five daily i.p. injections; 0.4 microg/mouse), however. Nonetheless, during the treatment period, activity scores of IL-2-treated mice significantly exceeded those of mice receiving saline; hence, repeated injections of IL-2 induced a persistent behavioral activation. IL-2 treatment also increased sensitivity to the behavior-stimulating effects of GBR 12909, a highly selective dopamine uptake inhibitor. This effect was a very long-lasting one since the dopamine agonist was administered 6 weeks after cessation of IL-2 treatment. The latter finding indicates that IL-2 interacts with the mesolimbic dopamine system, changing its sensitivity to seemingly different substances. Based on these data, and those of Zalcman and colleagues (S. Zalcman, I. Savina, R.A. Wise, Interleukin-6 increases sensitivity to the locomotor-stimulating effects of amphetamine in rats, Brain Res. 847 (1999) 276-283), it is suggested that cytokines can influence the development of behavioral abnormalities that are characteristic of aberrant mesolimbic dopamine activity via sensitization-like processes.

Interleukin-2 modulates N-methyl-D-aspartate receptors of native mesolimbic neurons

Interleukin (IL)-2 is a brain-derived cytokine that influences mesocorticolimbic dopamine release, and is associated with pathological outcomes that are mediated, at least in part, by aberrations in mesolimbic neurotransmission. The mechanisms by which IL-2 modulates mesolimbic transmission, however, are not known. The NMDA receptor/channel (NMDAR) plays an essential role in neuronal excitability of mesolimbic neurons; we thus examined in neonatal rats the effects of IL-2 on NMDA-activated current (I(NMDA)) in voltage-clamped neurons freshly isolated from the ventral tegmental area (VTA), the site of origin of the mesolimbic system. IL-2 (0.01-500 ng/ml) alone had no effect on membrane conductance. When co-applied with NMDA, IL-2 (50-500 ng/ml) significantly potentiated I(NMDA). In contrast, doses as low as 0.01 ng/ml markedly decreased the NMDA response. Dose-response analysis showed that IL-2 ( > 50 ng/ml) increased the maximal I(NMDA), without changing the EC(50), indicating that IL-2 potentiates I(NMDA) by increasing the efficacy of the NMDAR. Moreover, current-voltage analysis revealed that IL-2 potentiation of I(NMDA) was voltage-dependent, being greater at negative potentials. In contrast, IL-2 inhibition of I(NMDA) was voltage-independent, and IL-2 did not alter the reversal potential. Additionally, IL-2 (1 ng/ml) shifted the NMDA concentration-response curve to the right, significantly increasing the EC(50) for NMDA without changing the maximal I(NMDA), suggesting that IL-2 inhibits the NMDAR by a competitive mechanism. IL-2 thus acts as a potent modulator of the NMDAR. IL-2-induced alterations of responses to NMDAR activation may contribute to synaptic plasticity in the mesolimbic system and to pathological outcomes associated with this system.

Neurochemistry of brain neuroendocrine immune system: signal molecules

The aim of this review is not so much to show the problem of neuroendocrine, neurophysiologic, and neurochemical mechanisms of the immune system regulation of the organism by brain (there is a great deal of literature about it), as to solve the problem of whether the brain itself is an immune organ, and also to define cellular, neurochemical, and immunological properties of the brain for its immune defense when the blood-brain barrier is not damaged in spite of the penetration of the infection to brain. The accumulated literary data on CNS interaction with the immune system, expression of several cytokines and their receptors in the neurons of human brain culture, in astrocytes and microglia, all testify to the existence of a brain immune system. Recently studies appeared on the expression of major histocompatibility complex in brain neurons. It does not exclude the possibility of expression of immunoglobulins (or immunoglobulin-like proteins) in brain cells. Data obtained by us on the biosynthesis of a number of known interleukins and new cytokines in neurosecretory neurons of hypothalamus (N. Paraventricularis and N. Supraopticus) demonstrate that neuroendocrine nuclei of the hypothalamus are the center for neuroendocrine and immune systems of brain.

In-vitro immunomodulatory effects of haloperidol and perazine in schizophrenia

There are some reports describing concurrent changes in lymphocytic and monocytic activities in schizophrenia. In this study we investigated T cell activity in schizophrenic patients by measuring the release of interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R) by T cells and the percentages of CD4+ and CD8+ cells in blood. The release of IL-2 and sIL-2R by T cells was evaluated in dilute whole blood after in-vitro stimulation with phytohemagglutinin. IL-2 levels and the percentage of CD4-cells tended to decrease and sIL-2R levels decreased significantly in schizophrenic patients. Haloperidol and perazine significantly decreased IL-2 levels and increased sIL-2R levels and the percentage CD4-cells. IL-2 and sIL-2R levels were lower in patients with a predominance of positive symptoms. The neuroleptic-induced increase in sIL-2R levels was higher in patients with a predominance of positive symptoms compared with those in whom both positive and negative symptoms were severe. The study has shown that T-cell activity is reduced in schizophrenia and that neuroleptics may have immunomodulatory properties.

Relationships between interleukins, neurotransmitters and psychopathology in drug-free male schizophrenics

It has been postulated that altered interleukin (IL) regulation may be involved in the pathogenesis of schizophrenia. We therefore investigated the relationships between interleukins, neurotransmitters, and psychopathology in schizophrenia. IL-1beta, IL-2, IL-6, homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were measured in the plasma of neuroleptic-free male schizophrenics in comparison to age-matched healthy male controls (n=25 each). The patients' psychopathology was assessed by the Scale for the Assessment of Positive and Negative Symptoms (SAPS, SANS). The above variables were measured during acute states of illness and after eight weeks of treatment with haloperidol. The plasma levels of IL-2 and HVA were significantly higher in patients compared to controls. In schizophrenic patients, there were significant correlations between IL-2 and HVA, IL-2 and SAPS, and HVA and SAPS during the acute state of illness. The level of IL-6 was significantly correlated to SANS and duration of illness. In schizophrenic patients, the plasma levels of IL-2 and HVA were significantly lowered after treatment with haloperidol. Changes in IL-2 and HVA significantly correlated to those in HVA and SAPS, respectively. These results strongly suggest that the cytokines may modulate dopaminergic metabolism and schizophrenic symptomatology in schizophrenia.