The expression of cytokines and their receptors in normal and mildly reactive human brain

Changes in pain during a depressive episode and relationship to cytokine levels in major depressive disorder

BACKGROUND

Depressed patients have an increased incidence of pain. A pathophysiological connection between depression and pain is still not revealed. Immunological activation has been found in both depression and pain. There are few studies of pain and immune activation in patients with depression, without inflammatory and autoimmune disorders.

METHODS

This is a naturalistic follow-up study of 50 patients with a major depressive disorder (MDD) depressive episode, without any inflammatory or autoimmune conditions. We have previously reported on the relationship between depression and cytokine levels. In this study, we obtained data of depression, pain and cytokine levels before and after 12 weeks of depression treatment. All patients were medication-free at inclusion.

RESULTS

At inclusion three out of four patients experienced pain, and the pain scores correlated with the depression scores. After treatment, as depression was relieved, the pain scores dropped significantly and were no longer correlated to the depression scores. There were no correlations between pain scores and cytokine levels. Pain level at inclusion did not correlate with depression treatment outcome.

CONCLUSION

Our findings indicate that pain is a feature of depression. Pain levels and cytokine values didn't correlate. Pain at inclusion did not predict depression treatment outcome.

Impact of maternal immune activation on dendritic spine development

Dendritic spines are small dendritic protrusions that harbor most excitatory synapses in the brain. The proper generation and maturation of dendritic spines are crucial for the regulation of synaptic transmission and formation of neuronal circuits. Abnormalities in dendritic spine density and morphology are common pathologies in autism and schizophrenia. According to epidemiological studies, one risk factor for these neurodevelopmental disorders is maternal infection during pregnancy. This review discusses spine alterations in animal models of maternal immune activation in the context of neurodevelopmental disorders. We describe potential mechanisms that might be responsible for prenatal infection-induced changes in the dendritic spine phenotype and behavior in offspring.

Characterization of the TNF and IL-1 systems in human brain and blood after ischemic stroke

Preclinical and clinical proof-of-concept studies have suggested the effectiveness of pharmacological modulation of inflammatory cytokines in ischemic stroke. Experimental evidence shows that targeting tumor necrosis factor (TNF) and interleukin (IL)-1 holds promise, and these cytokines are considered prime targets in the development of new stroke therapies. So far, however, information on the cellular expression of TNF and IL-1 in the human ischemic brain is sparse.We studied 14 cases of human post-mortem ischemic stroke, representing 21 specimens of infarcts aged 1 to > 8 days. We characterized glial and leukocyte reactions in the infarct/peri-infarct (I/PI) and normal-appearing tissue (NAT) and the cellular location of TNF, TNF receptor (TNFR)1 and TNFR2, IL-1α, IL-1β, and IL-1 receptor antagonist (IL-1Ra). The immunohistochemically stained tissue sections received a score reflecting the number of immunoreactive cells and the intensity of the immunoreactivity (IR) in individual cells where 0 = no immunoreactive cells, 1 = many intermediately to strongly immunoreactive cells, and 2 = numerous and intensively immunoreactive cells. Additionally, we measured blood TNF, TNFR, and IL-1 levels in surviving ischemic stroke patients within the first 8 h and again at 72 h after symptom onset and compared levels to healthy controls.We observed IL-1α and IL-1β IR in neurons, glia, and macrophages in all specimens. IL-1Ra IR was found in glia, in addition to macrophages. TNF IR was initially found in neurons located in I/PI and NAT but increased in glia in older infarcts. TNF IR increased in macrophages in all specimens. TNFR1 IR was found in neurons and glia and macrophages, while TNFR2 was expressed only by glia in I/PI and NAT, and by macrophages in I/PI. Our results suggest that TNF and IL-1 are expressed by subsets of cells and that TNFR2 is expressed in areas with increased astrocytic reactivity. In ischemic stroke patients, we demonstrate that plasma TNFR1 and TNFR2 levels increased in the acute phase after symptom onset compared to healthy controls, whereas TNF, IL-1α, IL-1β, and IL-1Ra did not change.Our findings of increased brain cytokines and plasma TNFR1 and TNFR2 support the hypothesis that targeting post-stroke inflammation could be a promising add-on therapy in ischemic stroke patients.

(Peri)vascular production and action of pro-inflammatory cytokines in brain pathology

In response to tissue injury or infection, the peripheral tissue macrophage induces an inflammatory response through the release of IL-1β (interleukin-1β) and TNFα (tumour necrosis factor α). These cytokines stimulate macrophages and endothelial cells to express chemokines and adhesion molecules that attract leucocytes into the peripheral site of injury or infection. The aims of the present review are to (i) discuss the relevance of brain (peri)vascular cells and compartments to bacterial meningitis, HIV-1-associated dementia, multiple sclerosis, ischaemic and traumatic brain injury, and Alzheimer's disease, and (ii) to provide an overview of the production and action of pro-inflammatory cytokines by (peri)vascular cells in these pathologies of the CNS (central nervous system). The brain (peri)vascular compartments are highly relevant to pathologies affecting the CNS, as infections are almost exclusively blood-borne. Insults disrupt blood and energy flow to neurons, and active brain-to-blood transport mechanisms, which are the bottleneck in the clearance of unwanted molecules from the brain. Perivascular macrophages are the most reactive cell type and produce IL-1β and TNFα after infection or injury to the CNS. The main cellular target for IL-1β and TNFα produced in the brain (peri)vascular compartment is the endothelium, where these cytokines induce the expression of adhesion molecules and promote leucocyte infiltration. Whether this and other effects of IL-1 and TNF in the brain (peri)vascular compartments are detrimental or beneficial in neuropathology remains to be shown and requires a clear understanding of the role of these cytokines in both damaging and repair processes in the CNS.

Pattern of interleukin-6 receptor complex immunoreactivity between cortical regions of rapid autopsy normal and Alzheimer's disease brain

Involvement of the interleukin-6 receptor complex (IL-6RC) in neuroregulatory and immunological processes of the brain and particularly in Alzheimer's disease (AD) has been hypothesized. The functionally active IL-6RC consists of the cytokine IL-6, which acts through the ligand binding IL-6R and the signal transducing gp130. Using a new immunocytochemical protocol on rapid autopsy cryostat brain sections we studied the expression of the IL-6RC in Braak IV-V staged AD patients compared to normal age-matched controls (HC) across five different cortical regions. Inter-rater reliability of the method was high. The "baseline" expression in normal human brain was determined for IL-6,IL-6R and gp130 in all cortical regions. In normal tissue IL-6 expression was lower in parietal cortex. Higher IL-6R expression was shown in frontal, occipital and parietal cortex, lower expression in temporal cortex and cerebellum. In AD IL-6 expression levels were generally increased in parietal cortex and decreased in occipital cortex compared to controls. IL-6R expression levels were strongly increased in AD frontal and occipital cortex and decreased in temporal cortex and cerebellum. Our findings indicate an altered cortical immunoreactivity pattern of the functional IL-6RC in AD supporting the hypothesis of a disease-related role of IL-6 in AD pathophysiology.

Inflammation in the nervous system: the human perspective

Many basic aspects of brain inflammation, recently disclosed in experimental models, are reflected in the pathology of human inflammatory brain diseases. Examples include the key role of T lymphocytes in immune surveillance and in the regulation of the inflammatory response, the essential contributions of adhesion molecules, proinflammatory cytokines, chemokines, and proteases in the recruitment of inflammatory cells into the nervous tissue, the modulating effect of glia cells on the inflammatory process and the termination of T-cell-mediated inflammation by apoptotic cell death. Despite this progress in our understanding of the pathogenesis of brain inflammation, there are still major unresolved questions. Because of technical constraints, most of our knowledge on central nervous system inflammation so far relates to the role of a specific T-cell subset, the so-called T-helper-1 cells. Other T-cell subsets, in particular cytotoxic class I MHC-restricted T lymphocytes, however, appear to be of major importance in human disease. Furthermore, the detailed mechanisms, which are responsible for the profound differences in the patterns of tissue damage in different human inflammatory brain diseases, such as multiple sclerosis or various forms of virus encephalitis, are largely unresolved. We discuss the open questions to be addressed in the future, which, when answered, may help to design novel therapeutic strategies.

Expression of immunoregulatory cytokines in neurons of the lateral hypothalamic area and amygdaloid nuclear complex of rats immunized against human IgG

Present results showed that interleukin-1 (IL-1), IL-6 and transforming growth factor-beta (TGF-beta) were constitutively expressed in the supraoptic and paraventricular nuclei of the rat hypothalamus. Immunoreactive cells were also detected, but to a lesser extent, in other parts of hypothalamus as well as in the cerebral cortex. In rats immunized with IgG, there was moderate increase in immunoreactivities of the cytokines. A notable feature, however, was the induction of the cytokine expression in the lateral hypothalamic area and the amygdaloid nuclear complex, suggesting that the neurons in these two areas are involved in possible immune regulation.

Pararosaniline fixation for detection of co-stimulatory molecules, cytokines, and specific antibody

Integral immunohistochemical analysis of immune responses in frozen sections requires that, in addition to constitutively expressed membrane CD markers, less stable determinants can be reliably visualized. Therefore, we compared the commonly used acetone fixation method with pararosaniline fixation for six determinant categories. These categories included selected constitutively expressed markers, inducible co-stimulatory molecules, pro- and anti-inflammatory cytokines (including the novel cytokine IL-18, also known as IGIF and IL-1gamma), antigen-specific antibody in plasma cells, bacterial peptidoglycan, and lysosomal acid phosphatase activity. Human spleen and mouse spleen activated by agonistic anti-CD40 antibody or TNP-Ficoll immunization were analyzed in parallel with brain tissue from multiple sclerosis (MS) patients and marmoset monkeys with experimental autoimmune encephalomyelitis (EAE), an animal model for MS. Fixation with pararosaniline resulted in better morphology of all tissues and inhibited endogenous alkaline phosphatase activity in brain tissue. Most determinants could be reliably detected. Staining sensitivity and intensity were markedly increased for selected determinant-tissue combinations, e.g., for IL-4 in human spleen and CD40 in human and mouse spleen. These data show that pararosaniline is a useful alternative to acetone, resulting in superior morphology and specific staining for selected determinant-tissue combinations. This provides additional flexibility for in situ analysis of immune reactivity.

The expression of cytokines and their receptors in normal and mildly reactive human brain

There are many inflammatory diseases of the brain such as AIDS, other viral encephalitides and multiple sclerosis all of which are probably influenced by both systemic and focal CNS cytokine release. We have studied the expression of a wide range of pro- and anti-inflammatory cytokines and their receptors, beta2-microglobulin, and MHC Class II, using immunocytochemistry on cryostat sections of normal and mildly reactive human brain. The aim was to try to determine the cytokine 'baseline' expression in normal human brain and the results obtained indicated very low expression of various cytokines and their receptors, mainly by microglia and macrophages with some endothelial expression.