Appearance of cytokine-associated central nervous system myelin damage coincides temporally with serum tumor necrosis factor induction after recombinant interleukin-2 infusion in rats

Neurocognitive effects of chemotherapy and endocrine therapies in the treatment of breast cancer: recent perspectives

With an estimated 207,090 patients diagnosed with breast cancer in 2010, the role of chemotherapy-induced cognitive impairment is of growing importance. Studies to determine the impact of chemotherapy-induced cognitive impairment have been hindered by difficulties in study-design, in particular, study methodology. Here, we present a review of existing studies and discuss several mechanisms for chemotherapy-induced neurocognitive impairment in breast cancer patients, such as direct neurotoxic injury, telomere shortening, oxidative stress, cytokine dysregulation, estrogen-mediated effects, and the role of certain genetic polymorphisms. Decreased estrogen levels may serve as a link between multiple mechanisms potentiating the effects of the chemotherapy-induced cognitive impairment.

Exercise and brain health--implications for multiple sclerosis: Part II--immune factors and stress hormones

Part I of this review addressed the possible modulatory role of exercise on neuronal growth factors to promote brain health in neurodegenerative diseases such as multiple sclerosis (MS), which is characterized by varied patterns of inflammation, demyelination and axonal loss. Part II presents evidence that supports the potential neuroprotective effect of exercise on the modulation of immune factors and stress hormones in MS. Many current therapies used to attenuate MS progression are mediated, at least in part, through alterations in the relative concentrations of pro- and anti-inflammatory cytokines. Exercise-induced alterations in local and systemic cytokine production may also benefit immune function in health and disease. Exercise immunomodulation appears to be mediated by a complex interaction of hormones, cytokines and neural factors that may favorably influence immune variables in MS. The promising interplay between exercise and brain health in MS deserves further investigation.

Cytokines and Brain Injury: Invited Review

The brain reacts to injury or disease by cascades of cellular and molecular responses. Evidence suggests that immune-inflammatory processes are key elements in the physiopathological processes associated with brain injury or damage. Cytokines are among major mediators implicated in these processes. Cytokine responses in the initial phase of brain injury might have a role in aggravating brain damage. However, in later stages, these molecular mediators might contribute to recovery or repair. Hemodynamic stabilization and optimalization of oxygen delivery to the brain remain cornerstones in the management of acute brain injury. New approaches might use anticytokine therapy to limit progression and halt or attenuate secondary brain damage. Progress toward such novel neuroprotection strategies, however, awaits better understanding of the optimal timing and dosing of those neuromodulatory therapies and better knowledge of the numerous interactions of those mediators. This also requires understanding of how and when precisely immune mechanisms shift from noxious to protective or restorative actions.

Cognitive impairment, fatigue, and cytokine levels in patients with acute myelogenous leukemia or myelodysplastic syndrome

BACKGROUND

The objective of the current study was to assess the correlations between cognitive function, fatigue, quality of life, and circulating cytokine levels in patients with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS).

METHODS

Fifty-four patients with AML/MDS were seen for pretreatment evaluation of their cognitive function and symptoms. Fifty percent of the sample was reevaluated 1 month later, when response to protocol chemotherapy was assessed.

RESULTS

A significant proportion of patients had impaired cognitive function prior to the institution of chemotherapy. Sixty-five percent of patients also experienced significant fatigue. Levels of the circulating cytokines interleukin 1 (IL-1), IL-1 receptor antagonist (IL-1RA), IL-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha) were elevated highly compared with normal controls. Higher IL-6 levels were associated with poorer executive function, whereas higher IL-8 levels were associated with better memory performance. IL-6, IL-1RA, and TNF-alpha levels were related to ratings of fatigue. Fatigue and cognitive dysfunction were unrelated. Hemoglobin levels were not associated significantly with either cognitive dysfunction or fatigue. Patients who obtained a complete response tended to have better fine motor control at baseline and lower circulating IL-1 levels. Treatment did not have a significant impact on cognition, although fatigue levels tended to increase.

CONCLUSIONS

Patients with AML/MDS are highly symptomatic and experience cognitive impairment and fatigue before the initiation of their treatment. The current results indicated a correlation between these symptoms and levels of circulating cytokines, providing some support to the hypothesis that cancer-related symptoms are related at least in part to cytokine-immunologic activation. Elucidation of immunologic correlates of symptoms will allow for targeted interventions.

In situ cytokine immune responses in acute disseminated encephalomyelitis: insights into pathophysiologic mechanisms

Acute disseminated encephalomyelitis (ADEM) is thought to be an autoimmune disorder of the central nervous system in which myelin is targeted. Pathological studies on closely related human diseases (eg, multiple sclerosis) and on animal models for these demyelinating disorders have suggested the involvement of cytokines. Studies on peripheral immunocytes and on cerebrospinal fluid revealed the presence of cytokine-mediated responses in ADEM. We carried out this neuroimmunopathologic exploration and report for the first time the in situ expression of "inflammatory" cytokines in ADEM. Moreover, we note a particular spatial and molecular pattern whereby tumor necrosis factor-alpha and interleukin (IL)-1beta are intensely expressed, whereas IL-6 is absent. Differential expression at different levels of the neuraxis was also noticed. Our findings suggest that these cytokines, reported to be toxic to myelin, are implicated in the molecular cascade, resulting in the neural damage. These observations might provide insights into molecular pathways involved in the immunopathogenesis of ADEM and might open new horizons in neuroimmunomodulation and anticytokine treatment.

Involvement of inflammatory cytokines in central nervous system injury

Pro-inflammatory cytokines, interleukin (IL) 1 and tumor necrosis factor (TNF), possess a wide range of biological actions in various tissues. In recent years, there has been increasing evidence that these cytokines are involved in inflammatory reactions in central nervous system (CNS) diseases. Although many studies have demonstrated that IL-1, TNF, and their mRNA are up-regulated in the CNS after injury, the functional roles of these cytokines in the injury are far from completely understood. Overexpression of these cytokines, such as observed during the early stage of injury, can be harmful for the injured tissue. However, low levels of these cytokines, observed during the recovery stage after injury, can enhance repair processes of the injured tissues.

Neurotoxic consequences of central long-term administration of interleukin-2 in rats

Interleukin-2 is an immunoregulatory cytokine with several recently established CNS activities. Central effects of interleukin-2 include growth promotion for neuronal and glial cells as well as modulatory influences on neurotransmission and hormone release. However, little is known about the consequences in the CNS of chronically elevated levels of interleukin-2. Alterations in the interleukin-2/interleukin-2 receptor system are not only associated with CNS trauma, inflammation and certain neuropathologies; elevated interleukin-2 concentrations are especially induced during the therapeutic use of interleukin-2 in cancer treatments. In the present study, intracerebroventricular (i.c.v.) interleukin-2 infusions (5 15 U/h) were performed in Sprague Dawley rats for up to 14 days. Interleukin-2-treated animals showed significantly increased plasma levels of corticosterone indicating an hyperfunctioning of the hypothalamic-pituitary-adrenocortical axis that lasted over the 14 day infusion period. Moreover, the performance of interleukin-2-treated animals in the Morris swim maze task was transiently impaired. Quantitative receptor autoradiographic analyses revealed changes in the binding levels of cholinergic M1 and M2 as well as dopaminergic D1 and D2 receptors in selected brain areas in which interleukin-2 was shown to modulate neurotransmission and which are enriched with interleukin-2 receptor expression. Decreased receptor binding levels were observed in the frontoparietal cortex (M2, D1, D2), hippocampal CA1 region (M1, M2) and the nucleus accumbens (D2). Histological and immunohistochemical examination of the brains of interleukin-2-treated animals revealed multiple alterations. Interleukin-2 treatment resulted in an intracranial accumulation of non-neural, MHC class II-positive cells as well as T and B lymphocytes within the infused brain hemisphere. Cellular infiltrates were associated with angiogenesis and the deposition of extracellular matrix material, such as fibronectin. Adjacent brain regions that were partly invaded and dislodged by the cellular masses were characterized by reactive astrogliosis, microglial activation, endothelial upregulation of adhesion molecules, myelin damage and neuronal loss. Together the data suggest that persistently elevated central levels of interleukin-2 can interfere with several CNS functions and may lead to nervous tissue injury. These findings could be relevant to CNS pathologies characterized by abnormal interleukin-2 production and to central responses to interleukin-2 treatments.

Cellular localization of tumor necrosis factor mRNA in neurological tissue from HIV-infected patients by combined reverse transcriptase/polymerase chain reaction in situ hybridization and immunohistochemistry

HIV-induced neurological disease is postulated to be caused by indirect mechanisms. Tumor necrosis factor (TNF)alpha is increased in the brains in human immunodeficiency virus (HIV)-associated dementia and in the spinal cord in vacuolar myelopathy and may play a pathogenetic role in these diseases. Microglia, astrocytes and infiltrating macrophages can be induced to produce TNF alpha and each has been identified as a source of TNF alpha in neurological disease. Reverse transcriptase synthesis of cDNA and polymerase chain reaction amplification of the cDNA was combined with immunocytochemistry to identify the cellular source of TNF alpha in HIV-induced neurological disease. Cells positive for TNF alpha mRNA were more abundant in white matter than gray matter of the brain from demented individuals. TNF alpha mRNA-positive cells in brains and spinal cords were almost exclusively macrophage-lineage cells. Only rare TNF alpha mRNA-positive cells were astrocytes. We conclude that macrophage-lineage cells are the primary source of elevated central nervous system TNF alpha mRNA in providing further evidence that macrophage activation is an important element in the pathogenesis of HIV-associated neurological disease.

Neurotoxicity induced by interleukin-2: involvement of infiltrating immune cells

Interleukin-2 (IL-2), a key regulator of immune functions, also has potent effects on neurons and glia. IL-2 modulates neural cell growth and survival and transmitter and hormone releases and is thought to mediate neuroimmune interactions. Investigating the neuroendocrine consequences of chronically elevated central nervous system (CNS) levels of IL-2, we recently observed marked neurotoxicity [Hanisch et al. (1994) Endocrinology 135:2465-2472]. In the present study, we characterize in detail the modifications in brain tissue architecture as they result in Sprague-Dawley rats from intracerebroventricular (i.c.v.) administration of low amounts of IL-2 (5 and 15 U/h, respectively, delivered by means of osmotic minipumps for up to 14 days). Histological inspection of the brains revealed massive cellular infiltrates in the ipsilateral hemisphere. The infiltrates were associated with pronounced angiogenesis and changes in the composition of the extracellular matrix. These anatomical changes apparently developed between day 7 and 14. They were specific for IL-2 and were not seen in animals treated, for example, with heat-inactivated IL-2 (controls). We further show that chronic central administration of IL-2 let to T and B lymphocyte invasion of the brain and an intracranial agglomeration of large numbers of MHC class II-positive cells. Immunocytochemistry revealed a widespread inundation of CNS tissue and a decoration of glial cells and neurons by endogenous antibodies. Tissue regions around the IL-2-induced infiltrates showed myelin destruction and neuronal cell loss. Chronically elevated CNS levels of IL-2 may, thus, not only interfere with neurotransmission and endocrine functions but also severely disturb tissue homeostasis. Therefore, the present findings could be relevant to brain injuries, CNS disorders, and clinical treatments associated with increased IL-2 levels or involving an immune component.

CAMPATH-IH in multiple sclerosis

In a pilot study, seven patients with multiple sclerosis were treated with CAMPATH-IH which targets the CD52 antigen present on lymphocytes and monocytes. There was a substantial reduction in disease activity as measured by gadoliunium-enhancing lesions on MRI. Encouraged by this result a further seven patients have been treated with CAMPATH-IH; four also received anti-CD4 antibody. Lymphopaenia developed rapidly and was sustained for at least one year. In 12 patients, the first infusion of antibody was characterised by significant exacerbation or re-awakening of pre-existing symptoms lasting several hours. These clinical effects of antibody treatment correlated with increased levels of circulating cytokines. Peak levels of tumour necrosis factor alpha (TNF alpha) and interferon gamma (IFN gamma) occurred at 2 h whereas the rise in interleukin-6 (IL-6) was significantly delayed and peaked at 4 h after starting antibody treatment. The neurological symptoms could not be attributed directly to pyrexia and were not provoked (in one patient) by an artificial rise in temperature. In the remaining two patients, a single pre-treatment with intravenous methylprednisolone (500 mg) prevented both the transient increase in neurological symptoms and the cytokine release. Our results suggest that soluble immune mediators contribute to symptom production in multiple sclerosis by directly or indirectly blocking conduction through partially demyelinated pathways.

Interleukin-2 as a neuroregulatory cytokine

Interleukin-2 (IL-2), the cytokine also known as T-cell growth factor, has multiple immunoregulatory functions and biological properties not only related to T-cells. In the past decade, substantial evidence accumulated to suggest that IL-2 is also a modulator of neural and neuroendocrine functions. First, extremely potent effects of IL-2 on neural cells were discovered, including activities related to cell growth and survival, transmitter and hormone release and the modulation of bioelectric activities. IL-2 may be involved in the regulation of sleep and arousal, memory function, locomotion and the modulation of the neuroendocrine axis. Second, the concept that IL-2 could act as a neuroregulatory cytokine has been supported by reports on the presence in rodent and human brain tissues of IL-2-like bioactivity, IL-2-like immunoreactivity, IL-2-like mRNA, IL-2 binding sites, IL-2 receptor (IL-2R alpha) and beta chain mRNA and IL-2R immunoreactivity. IL-2 and/or IL-2R molecules mainly localize to the frontal cortex, septum, striatum, hippocampal formation, hypothalamus, locus coeruleus, cerebellum, the pituitary and fiber tracts, such as the corpus callosum, where they are likely expressed by both neuronal and glial cells. Although the molecular biology of the brain IL-2/IL-2R system (including its relation to IL-15/IL-15R alpha) is not yet fully established by cloning and complete sequencing of all respective components, similarities (and to some extent differences) to peripheral counterparts are now apparent. The ability of IL-2 to readily penetrate the blood-brain barrier further suggests that this cytokine could regulate interactions between peripheral tissues and the central nervous system. Taken together, these data suggest that IL-2 of either immune and CNS origin can have access to functional IL-2R molecules on neurons and glia under normal conditions. Additionally, dysregulation of the IL-2/IL-2 receptor system could lead or contribute to functional and pathological alterations in the brain as in the immune system. Understanding the neurobiology of the IL-2/IL-2 receptor system should also help to explain neurologic, neuropsychiatric and neuroendocrine side effects occurring during IL-2 treatment of peripheral and brain tumors. Immunopharmacological manipulation either aiming at the activation or suppression of IL-2 signaling should consider functional interference with constitutive and inducible IL-2 receptors on brain cells in order to fulfil the high expectations associated with the use of this cytokine as a promising agent in immunotherapies, especially of brain tumors.

TNF-alpha increases the frequency of spontaneous miniature synaptic currents in cultured rat hippocampal neurons

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine secreted by activated astrocytes and is known to alter evoked synaptic activity in slices of adult rat hippocampus. In this paper we show that TNF-alpha increases the frequency of spontaneous miniature synaptic currents in cultured hippocampal neurons, acting at nanomolar concentrations. In addition, we show that the mRNA for the 55 kDa TNF-alpha receptor (TNF-R1) is detected in embryonic rat hippocampal cultures, as well as in acutely dissected embryonic and adult rat hippocampi. Possible transduction pathways mediating the TNF-alpha effect are discussed.

Regulation of an oligodendrocyte progenitor cell line by the interleukin-6 family of cytokines

We report pleiotropic actions of the interleukin-6 family of cytokines on a rat cerebral cortical oligodendrocyte cell line, Central Glia-4 (CG-4). This is a bipotential oligodendrocyte type-2 astrocyte (O-2A) progenitor cell line that can be manipulated in vitro to become either a type-2 astrocyte or to follow a linear sequence of events into becoming a mature oligodendrocyte. Using Northern and Western analyses in conjunction with immunocytochemistry we have demonstrated that ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), and interleukin-6 (IL-6) cause a transient increase in glial fibrillary acidic protein (GFAP) in oligodendrocyte type-2 astrocyte (O-2A) progenitor cells. At maximal cytokine concentrations, the largest increase in GFAP protein levels were observed for CNTF and LIF; albeit, IL-6 did increase GFAP but the order of magnitude was 6-7 times less. Moreover, in trophic factor deprived medium, CNTF and LIF protected immature (O4+/MBP-) and mature (MBP+) oligodendrocytes from the apoptotic mode of cell death, while IL-6 had no effect in enhancing oligodendrocyte cell survival. Analysis of the cytokine-induced early response genes (ERGs) revealed a strong degree of overlap for CNTF and LIF. The effect of IL-6 was different in the degree to which the ERGs were up-regulated and in their temporal patterns of expression. These findings suggest that ERGs may be important, at least in part, for determining the extent of functional overlap observed within this cytokine family. Our findings clearly demonstrate differential regulation of oligodendrocyte survival and differentiation by the IL-6 family of cytokines.

Pathogenic and non-pathogenic T lymphocytes specific for the encephalitogenic epitope of myelin basic protein: functional characteristics and vaccination properties

Activated CD4+ T lymphocytes specific for myelin basic protein (MBP) can cause experimental autoimmune encephalomyelitis (EAE) upon their inoculation into syngeneic recipients. In Lewis rats, most of the pathogenic T cell clones that develop following immunization with MBP are reactive against the 72-84 amino acid sequence of MBP, the major encephalitogenic region for Lewis rats. In this study, some MBP-specific T cell clones were found to be non-pathogenic, in spite of their strong reactivity against the encephalitogenic epitope. One of these non-pathogenic clones, designated Znp, and an encephalitogenic clone, Z1a-p, were derived from Z1a encephalitogenic line cells. These subclones were compared for epitope specificity, T cell receptor variable gene expression and for various functional activities, in order to delineate properties crucial for pathogenicity. The Z1a-p and Znp cells expressed comparable levels of the T cell receptor genes and shared strong reactivity against the 72-84 epitope of MBP. The pathogenic Z1a-p cells displayed MBP-specific cytolytic activity in vitro, provided an in-vivo 'help' for elicitation of MBP-specific antibodies, mediated a delayed type hypersensitivity (DTH) response to MBP, caused EAE and vaccinated against the disease, thus demonstrating that a single CD4+ T cell clone is capable of eliciting various functions. The non-pathogenic Znp cells could also carry out most of these various functions, but failed to mediate a DTH response to MBP in normal animals. However, when inoculated into sublethally (650 R) irradiated syngeneic recipients, the Znp cells became highly pathogenic and mediated DTH response to MBP. Local irradiation of the recipient facilitated a DTH response to MBP in the irradiated ear, indicating that Znp cells are equipped with the effector mechanisms required for pathogenicity, and that their failure to cause disease may be accounted for by their inability to migrate into extravascular target tissue. Similar data were obtained with an independently isolated non-pathogenic clone, LB-3, specific for the encephalitogenic epitope of MBP. The ability of these non-pathogenic cells to vaccinate against EAE mediated by pathogenic cells raises the possibility that such non-pathogenic cells may play a role in triggering downregulation of pathogenic T cells.

Intracerebral cytokine messenger RNA expression in acquired immunodeficiency syndrome dementia

The pathogenesis of the dementia associated with human immunodeficiency virus (HIV) infection is unclear, but has been postulated to be due to indirect effects of HIV infection including the local production of cytokines. To determine which cytokines are produced in the nervous system and to identify any correlations with dementia, cytokine and HIV messenger RNA expression was analyzed by reverse transcriptase-polymerase chain reaction in the brains from 24 HIV-infected patients with and without dementia and 9 HIV-uninfected control subjects. Levels of tumor necrosis factor-alpha messenger RNA were significantly higher and levels of interleukin (IL)-4 messenger RNA were significantly lower in demented compared to nondemented HIV-infected patients. Demented patients also had lower IL-1 beta levels than did nondemented patients. No significant differences were detected in the amounts of leukemia inhibitory factor, IL-6, transforming growth factor-beta 1 and -beta 2, monokine induced by gamma interferon-2 (MIG-2), or interferon-gamma messenger RNAs. IL-10 and IL-2 messenger RNAs were undetectable in all brains examined. Cytokine messenger RNA levels in nondemented HIV-positive patients were similar to those in HIV-negative control subjects. HIV transcripts were more abundant in subcortical white matter than in the basal ganglia, cortex, or deep white matter. Our findings suggest a possible role for tumor necrosis factor-alpha in the development of neurological dysfunction. Increased levels of tumor necrosis factor-alpha messenger RNA were not associated with increased levels of IL-1 beta messenger RNA, suggesting differential regulation of these monokines in acquired immunodeficiency syndrome dementia.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated serum levels of tumor necrosis factor-alpha in Guillain-Barré syndrome

Activated T lymphocytes and macrophages play a putative role in the the pathogenesis of Guillain-Barré syndrome. Both cell types secrete tumor necrosis factor-alpha, a cytokine that has well-recognized toxic effects on myelin, Schwann cells, and endothelial cells. We determined serum and cerebrospinal fluid concentrations of tumor necrosis factor alpha in 26 patients with Guillain-Barré syndrome, 27 patients with other polyneuropathies, 30 patients with neurological diseases of the central nervous system, and 14 healthy control subjects. Markedly increased serum levels were detected in 14 patients (54%) with Guillain-Barré syndrome and to a significantly lesser extent, in patients with other polyneuropathies (26%) and in neurological control subjects (23%). Tumor necrosis factor-alpha was not detected in the cerebrospinal fluid of patients with Guillain-Barré syndrome or other polyneuropathies. Increased serum concentrations in patients with Guillain-Barré syndrome correlated directly with disease severity and these concentrations returned to normal in parallel with clinical recovery. These findings emphasize the complexity of the immune response in patients with Guillain-Barré syndrome and suggest that tumor necrosis factor-alpha may be important in the pathogenesis of peripheral demyelination in this disorder.

Delayed neurotoxicity of intraventricular interleukin-2: a case report

A case is reported of a 40 year old woman treated with intraventricular IL-2 for leptomeningeal disease who developed progressive cognitive dysfunction. This deterioration started 3 months post-treatment and worsened over the ensuing 4 years. MRI revealed white matter abnormalities that were not present on the pretreatment scan. Although free of disease, the patient has a subcortical dementia and is unable to work. The potential for progressive brain injury and subsequent disability related to intraventricular IL-2 therapy is discussed.

CNTF protection of oligodendrocytes against natural and tumor necrosis factor-induced death

A proportion of developing oligodendrocytes undergo natural cell death by apoptosis, and mature oligodendrocytes die, either by apoptosis or necrosis, in response to injurious signals such as cytotoxic cytokines and complement. Ciliary neurotrophic factor (CNTF), a trophic factor found in astrocytes in the central nervous system (CNS), promoted the survival and maturation of cultured oligodendrocytes. This trophic factor also protected oligodendrocytes from death induced by tumor necrosis factors (apoptosis) but not against complement (necrosis). These results suggest that CNTF functions in the survival of oligodendrocytes during development and may lead to therapeutic approaches for degenerative diseases of the CNS that involve oligodendrocyte destruction.

Effect of chronic treatment with recombinant interleukin-2 on the central nervous system of adult and old mice

We have studied the effects of chronic treatment with recombinant interleukin-2 on the central nervous system of adult and old mice. Treatment with high doses of recombinant interleukin-2, on a schedule similar to that used in humans, was started at the age of 4 and 17 months, respectively, and ended 3 months later. At that time, all the mice were tested for acquisition of a passive-avoidance task and then sacrificed for histological examination. Three of the four groups (treated and control adults and control old mice) did not differ from one another in task performance or neuron density in frontal cortex, cerebellum, dentate gyrus or CA1-2, CA3, CA4 hippocampal areas. The old treated mice were unique in showing impairment of the mnesic functions and marked neuronal cell loss and degenerative changes limited to the hippocampal regions. Immunohistochemical studies did not show any significant amount of immunoglobulins in affected areas. Our results suggest that in old mice the impairment of the mnesic functions after recombinant interleukin-2 administration is due to hippocampal neuronal damage.