Regulation of intracellular Ca2+ concentration by interleukin-1beta in rat cortical synaptosomes: an age-related study

AP-1 (Activated Protein-1) Transcription Factor JunD Regulates Ischemia/Reperfusion Brain Damage via IL-1β (Interleukin-1β)

Background and Purpose- Inflammation is a major pathogenic component of ischemia/reperfusion brain injury, and as such, interventions aimed at inhibiting inflammatory mediators promise to be effective strategies in stroke therapy. JunD-a member of the AP-1 (activated protein-1) family of transcription factors-was recently shown to regulate inflammation by targeting IL (interleukin)-1β synthesis and macrophage activation. The purpose of the present study was to assess the role of JunD in ischemia/reperfusion-induced brain injury. Methods- WT (wild type) mice randomly treated with either JunD or scramble (control) siRNA were subjected to 45 minutes of transient middle cerebral artery occlusion followed by 24 hours of reperfusion. Stroke size, neurological deficit, plasma/brain cytokines, and oxidative stress determined by 4-hydroxynonenal immunofluorescence staining were evaluated 24 hours after reperfusion. Additionally, the role of IL-1β was investigated by treating JunD siRNA mice with an anti-IL-1β monoclonal antibody on reperfusion. Finally, JunD expression was assessed in peripheral blood monocytes isolated from patients with acute ischemic stroke. Results- In vivo JunD knockdown resulted in increased stroke size, reduced neurological function, and increased systemic inflammation, as confirmed by higher neutrophil count and lymphopenia. Brain tissue IL-1β levels were augmented in JunD siRNA mice as compared with scramble siRNA, whereas no difference was detected in IL-6, TNF-α (tumor necrosis factor-α), and 4-hydroxynonenal levels. The deleterious effects of silencing of JunD were rescued by treating mice with an anti-IL-1β antibody. In addition, JunD expression was decreased in peripheral blood monocytes of patients with acute ischemic stroke at 6 and 24 hours after onset of stroke symptoms compared with sex- and age-matched healthy controls. Conclusions- JunD blunts ischemia/reperfusion-induced brain injury via suppression of IL-1β.

Prognostic value of interleukin-1 beta levels after acute brain injury

Traumatic injury to central nervous system results in the production of inflammatory cytokines via intrinsic mechanisms by neurons, astrocytes and microglia, and extrinsic mechanisms by infiltrating macrophages, lymphocytes and other leukocytes. Interleukin-1 beta is the key mediator of the acute inflammatory host response. While this response is necessary for resolution of the pathologic event, the toxic nature of many of its products can cause significant tissue damage. We analyzed serum interleukin-1 beta levels by enzyme-linked immunosorbent assay in 48 patients with solitary head injury who were transported to our clinic immediately after trauma. We categorized the patients according to their initial Glasgow coma scores in three groups, and compared their serum interleukin-1 beta values both with their Glasgow coma initial and outcome scores. This study helped to provide quantitative data to estimate clinical impressions and prognosis after head injury.

Polyunsaturated fatty acids, neuroinflammation and well being

The innate immune system of the brain is principally composed of microglial cells and astrocytes, which, once activated, protect neurons against insults (infectious agents, lesions, etc.). Activated glial cells produce inflammatory cytokines that act specifically through receptors expressed by the brain. The functional consequences of brain cytokine action (also called neuroinflammation) are alterations in cognition, mood and behaviour, a hallmark of altered well-being. In addition, proinflammatory cytokines play a key role in depression and neurodegenerative diseases linked to aging. Polyunsaturated fatty acids (PUFA) are essential nutrients and essential components of neuronal and glial cell membranes. PUFA from the diet regulate both prostaglandin and proinflammatory cytokine production. n-3 fatty acids are anti-inflammatory while n-6 fatty acids are precursors of prostaglandins. Inappropriate amounts of dietary n-6 and n-3 fatty acids could lead to neuroinflammation because of their abundance in the brain and reduced well-being. Depending on which PUFA are present in the diet, neuroinflammation will, therefore, be kept at a minimum or exacerbated. This could explain the protective role of n-3 fatty acids in neurodegenerative diseases linked to aging.

Mucosal tolerization to E-selectin protects against memory dysfunction and white matter damage in a vascular cognitive impairment model

Vascular cognitive impairment (VCI) is the second most prevalent type of dementia in the world. The white matter damage that characterizes the common subcortical ischemic form of VCI can be modeled by ligating both common carotid arteries in the Wistar rat to induce protracted cerebral hypoperfusion. In this model, we find that repetitive intranasal administration of recombinant E-selectin to induce mucosal tolerance and to target immunomodulation to activating blood vessels potently suppresses both white matter (and possibly gray matter) damage and markers of vessel activation (tumor necrosis factor and E-selectin); it also preserves behavioral function in T-maze spontaneous alternation, T-maze spatial discrimination memory retention, and object recognition tests. Immunomodulation may be an effective novel strategy to prevent progression of VCI.

Endotoxin inhibitor blocks heat exposure-induced expression of brain cytokine mRNA in aged rats

To investigate the age-related changes in the expression of interleukin-1beta (IL-1beta) and its related substances in the brain during heat stress, we measured amounts of mRNAs for IL-1beta, cyclooxygenase-2 (COX-2), and an inhibitor of nuclear factor (NF)-kappaB-beta (IkappaB-beta) that is known to reflect an activation of NF-kappaB, in the cortex, cerebellum, and hippocampus using a quantitative real-time capillary PCR method. The basal levels of IL-1beta mRNA in aged rats (108-110 weeks old) was significantly higher than those in young animals (10-11 weeks old) in these brain regions. Heat exposure (33 degrees C) for 1 h enhanced the expression of IL-1beta and COX-2 mRNAs in aged rats but not in young ones. The amount of lipopolysaccharide (LPS) assessed by its bioactivity in the cortex increased by heat exposure only in aged rats. To further examine an involvement of LPS in the increase in mRNAs, an endotoxin inhibitor (EI), a synthetic peptide that detoxifies LPS by binding to the toxic component of LPS, lipid A, was intraperitoneally injected before heat exposure in aged rats. An intraperitoneal injection of EI significantly attenuated the heat exposure-induced increases in mRNAs for IL-1beta, COX-2, IkappaB-beta, and the LPS activity. Administration of EI also debilitated the heat exposure-induced hyperthermia and responses of plasma ACTH and catecholamines. These findings, taken together, suggest that the bacterial translocation is involved in the mechanisms of the responses to heat exposure in aged rats including the increased expression of mRNAs for IL-1beta and its related substances in the brain.

Changes in mitochondrial status associated with altered Ca2+ homeostasis in aged cerebellar granule neurons in brain slices

In the present work, we investigated the relationship between mitochondrial function and Ca2+ homeostasis in brain slices obtained from mice that aged normally. In acute preparations, the cerebellar neurons had similar values for intracellular free Ca2+ ([Ca2+]i) regardless of their age (range, 6 weeks to 24 months). However, compared with the young slices, the aged neurons (20-24 months) showed an enhanced rate of [Ca2+]i increases as a function of the time the slices were maintained in vitro. When slices were stimulated (KCl depolarization), there were significant differences in the patterns of [Ca2+]i signal displayed by the young and old cerebellar granule neurons. More importantly, the aged neurons showed a significant delay in their capacity to recover the resting [Ca2+]i. The relationship between [Ca2+]i and mitochondrial membrane potential was assessed by recording both parameters simultaneously, using fura-2 and rhodamine-123. In both young and aged neurons, the cytosolic [Ca2+]i signal was associated with a mitochondrial depolarization response. In the aged neurons, the mitochondria had a significantly longer repolarization response, and quantitative analysis showed a direct correlation between the delays in mitochondrial repolarization and [Ca2+]i recovery, indicating the causal relationship between the two parameters. Thus, the present results show that the reported changes in Ca2+ homeostasis associated with aging, which manifest principally in a decreased capacity of maintaining a stable resting [Ca2+]i or recovering the resting [Ca2+]i values after stimulation, are primarily attributable to a metabolic dysfunction in which the mitochondrial impairment plays an important role.

Interleukin-1 beta exerts a myriad of effects in the brain and in particular in the hippocampus: analysis of some of these actions

The realization, in the past decade or so, that bidirectional communication between the central nervous system and the immune system was likely has sparked an explosion of interest in the roles certain cytokines, particularly the proinflammatory cytokine interleukin-1 beta (IL-1 beta), might play in the brain. The observation that IL-1 type I receptor was expressed in highest density in the hypothalamus was of significance in identifying a role for IL-1 beta in neuroendocrine modulation. However, the finding that receptor expression was also high in the hippocampus, an area of the brain which plays a pivotal role in memory and learning, has led to uncovering a role for IL-1 beta in cognitive function. There is now a great deal of evidence suggesting that IL-1 beta plays a significant role in hippocampal synaptic function, and the possibility that IL-1 beta may trigger some of the detrimental changes in certain neurodegenerative diseases is currently being assessed. The review addresses some of the issues relating to the role of IL-1 beta in the brain, specifically in the hippocampus.

Electrochemical monitoring of superoxide anion production and cerebral blood flow: effect of interleukin-1 beta pretreatment in a model of focal ischemia and reperfusion

Conditions associated with systemic infection, such as endotoxinemia, are known to increase the levels of pro-inflammatory cytokines such as interleukin (IL)-1 in the central nervous system. Systemic infection has been shown to be a common preexisting condition in patients with stroke. To examine a possible consequence of systemic infection, we used a novel electrochemical technique, which combines measurement of cerebral blood flow with measurement of superoxide anion concentrations, to examine the effect of pretreatment of pial vasculature with a proinflammatory cytokine, IL-1 beta, on cerebral blood flow and superoxide anion concentration in a rat model of middle cerebral artery occlusion and reperfusion. In addition, neutrophil recruitment was measured using an immunohistochemical technique. Our results indicate that exposure of pial and cerebral vasculature to IL-1 beta significantly accelerates recruitment of neutrophils, reduces cerebral blood flow, and increases superoxide anion concentration at the pial surface during reperfusion. These results support the idea that prior exposure of brain vasculature to IL-1 beta results in acceleration of cerebrovascular injury by accelerating recruitment of neutrophils, which secrete superoxide anion, during reperfusion. This finding has possible implications for the treatment of stroke with reperfusion agents in patients with preexisting infections.

Potential mechanisms of interleukin-1 involvement in cerebral ischaemia

Interleukin-1 (IL-1) has pleiotropic actions in the central nervous system. During the last decade, a growing corpus of evidence has indicated an important role of this cytokine in the development of brain damage following cerebral ischaemia. The expression of IL-1 in the brain is dramatically increased during the early and chronic stage of infarction. The most direct evidence that IL-1 contributes significantly to ischaemic injury is that (1) central administration of IL-1beta exacerbates brain damage, and (2) injection or over-expression of interleukin-1 receptor antagonist, and blockade of interleukin-1beta converting enzyme activity reduce, dramatically, infarction and improve behavioural deficit. The mechanisms underlying IL-1 actions in stroke are not definitively elucidated, and it seems likely that its effects are mediated through stimulation and inhibition of wide range of pathophysiological processes.