Cortical cell death induced by IL-1 is mediated via actions in the hypothalamus of the rat

Downregulation of phosphoglycerate mutase 5 improves microglial inflammasome activation after traumatic brain injury

Traumatic brain injury (TBI) is considered as the most common cause of disability and death, and therefore an effective intervention of cascade pathology of secondary brain injury promptly can be a potential therapeutic direction for TBI prognosis. Further study of the physiological mechanism of TBI is urgent and important. Phosphoglycerate mutase 5 (Pgam5), a mitochondrial protein, mediate mitochondrial homeostasis, cellular senescence, and necroptosis. This study evaluated the effects of Pgam5 on neurological deficits and neuroinflammation of controlled cortical impact-induced TBI mouse model in vivo and LPS + ATP-induced microglia model in vitro. Pgam5 was overexpressed post-TBI. Pgam5 depletion reduced pyroptosis-related molecules and improved microglia activation, neuron damage, tissue lesion, and neurological dysfunctions in TBI mice. RNA-seq analysis and molecular biology experiments demonstrated that Pgam5 might regulate inflammatory responses by affecting the post-translational modification and protein expression of related genes, including Nlrp3, caspase1, Gsdmd, and Il-1β. In microglia, Pgam5-sh abrogated LPS + ATP-induced Il-1β secretion through Asc oligomerization-mediated caspase-1 activation, which was independent of Rip3. The data demonstrate the critical role Pgam5 plays in nerve injury in the progression of TBI, which regulates Asc polymerization and subsequently caspase1 activation, and thus reveals a fundamental mechanism linking microglial inflammasome activation to Asc/caspase1-generated Il-1β-mediated neuroinflammation. Thus, our data indicate Pgam5 worsens physiological and neurological outcomes post-TBI, which may be a potential therapeutic target to improve neuroinflammation after TBI.

Dl-3-n-butylphthalide inhibits neuroinflammation by stimulating foxp3 and Ki-67 in an ischemic stroke model

Dl-3-n-butylphthalide (NBP) has been widely used to treat ischemic stroke in China. To investigate the mechanisms underlying NBP activity, we established a permanent middle cerebral artery occlusion (pMCAO) rat model and injected the rats with 4 mg/kg/d NBP for nine days. We then assessed neuroinflammation, neovascularization and nerve regeneration within the brain. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry imaging (MALDI-TOF MSI) was used to determine the phospholipid distribution, while laser ablation-inductively coupled plasma mass spectrometry imaging (LA-ICP MSI) was used to measure Foxp3, Ki-67 and pCREB levels in the brain. Immunohistochemistry was used to investigate the expression of NLR family pyrin domain containing 3 (NLRP3) and its inflammatory products, caspase-1 and interleukin-1β, in brain tissues. NBP attenuated ischemic damage and ameliorated neurological deficits in rats with pMCAO. In the ischemic brain region, NBP reduced phosphatidylethanolamine (18:0), NLRP3, caspase-1 and interleukin-1β levels, but increased levels of Foxp3, Ki-67, pCREB and several phospholipids. In molecular docking analyses, NBP bound to NLRP3, interleukin-1β, caspase-1, Foxp3, and Ki-67. These results demonstrate that NBP reduces neuroinflammation in brain tissues and promotes nerve and blood vessel regeneration, thus protecting neuromorphology and function.

Clinical Applications of Extracellular Vesicles in the Diagnosis and Treatment of Traumatic Brain Injury

Extracellular vesicles (EVs) have emerged as key mediators of cell-cell communication during homeostasis and in pathology. Central nervous system (CNS)-derived EVs contain cell type-specific surface markers and intralumenal protein, RNA, DNA, and metabolite cargo that can be used to assess the biochemical and molecular state of neurons and glia during neurological injury and disease. The development of EV isolation strategies coupled with analysis of multi-plexed biomarker and clinical data have the potential to improve our ability to classify and treat traumatic brain injury (TBI) and resulting sequelae. Additionally, their ability to cross the blood-brain barrier (BBB) has implications for both EV-based diagnostic strategies and for potential EV-based therapeutics. In the present review, we discuss encouraging data for EV-based diagnostic, prognostic, and therapeutic strategies in the context of TBI monitoring and management.

Analysis of knowledge bases and research focuses of cerebral ischemia-reperfusion from the perspective of mapping knowledge domain

Cerebral ischemia-reperfusion (IR) has attracted wide attention as a serious clinical problem. So far, the field has accumulated a large amount of scientific research literature. To clarify the temporal and spatial distribution characteristics of research resources, knowledge bases and research focuses, a visual analysis was performed on 5814 articles cited in the WoS databases from 2004 to 2019. This analysis was based on bibliometrics and mapping knowledge domain (MKD) analysis with VOSviewer, and CiteSpace 5.4.R4. The results can be elaborated from four aspects. First, the volume of publications in this area is on the rise. Second, the United States and China are the active regions. The USA is the central region of cerebral ischemia-reperfusion research. Third, the knowledge bases of IR have focused on five major areas of "Suitable small-animal models", "A framework with further study", "Molecular signaling targets by oxidative stress", "Finding new potential targets for therapy" and "Protective effect of multiple transient ischemia". Fourth, the research focuses consist of three representative areas: "Oxidative stress closelyd with cerebral ischemia-reperfusion", "Neuronal apoptosis and neuronal protection", and "Neuroprotective effect of the blood-brain barrier".

Serial exposure to ethanol drinking and methamphetamine enhances glutamate excitotoxicity

A significant comorbidity exists between alcohol and methamphetamine (Meth) abuse but the neurochemical consequences of this co-abuse are unknown. Alcohol and Meth independently and differentially affect glutamatergic transmission but the unique effects of their serial exposure on glutamate signaling in mediating damage to dopamine neurons are unknown. Sprague-Dawley rats had intermittent voluntary access to 10% ethanol (EtOH) every other day and water over 28 days and were then administered a binge injection regimen of Meth or saline. EtOH drinking decreased the glutamate aspartate transporter and increased basal extracellular concentrations of glutamate within the striatum when measured after the last day of drinking. Ceftriaxone is known to increase the expression and/or activity of glutamate transporters in the brain and prevented both the decreases in glutamate aspartate transporter and the increases in basal extracellular glutamate when administered during EtOH drinking. EtOH drinking also exacerbated the acute increases in extracellular glutamate observed upon Meth exposure, the subsequent increases in spectrin proteolysis, and the long-term decreases in dopamine content in the striatum, all of which were attenuated by ceftriaxone administration during EtOH drinking only. These results implicate EtOH-induced increases in extracellular glutamate and corresponding decreases in glutamate uptake as mechanisms that contribute to the vulnerability produced by EtOH drinking and the unique neurotoxicity observed after serial exposure to Meth that is not observed with either drug alone. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.

Anti-inflammatory effect of 4-methylcyclopentadecanone in rats submitted to ischemic stroke

This study aimed to investigate the anti-inflammatory effect of 4-methylcyclopentadecanone (4-MCPC) in rats suffering from a cerebral ischemia/reperfusion (I/R) injury. In this study, the focal cerebral ischemia in rats was induced by middle cerebral artery occlusion (MCAO) for 2 h, and the rats were treated with 4-MCPC (8 mg/kg) just 0.5 h before reperfusion. The ischemic infarct volume was recorded 24 h after the MCAO. In addition, myeloperoxidase (MPO) activity and TNF-α and IL-1β levels in the ischemic cerebral cortex were determined by ELISA, while nuclear translocation of NF-κB p65 subunit and expression of p-IκBα were investigated by Western blotting. Our results showed that 4-MCPC treatment decreased infarct volume significantly, compared with I/R group (16.8%±7.5% vs. 39.7%±10.9%); it reduced MPO activity (0.43 ± 0.10 vs. 1.00 ± 0.51 U/g) and expression levels of TNF-α (18.90 ± 3.65 vs. 35.87 ± 4.87 ng/g) and IL-1β (1.68 ± 0.23 vs. 2.67 ± 0.38 ng/g) in ischemic brain tissues of rats. Further study revealed that 4-MCPC treatment markedly reduced nuclear translocation of NF-κB p65 subunit and expression of p-IκBα in ischemic cerebral cortex. Taken together, our results suggest that 4-MCPC protects against cerebral I/R injury and displays anti-inflammatory actions through inhibition of the NF-κB signal pathway.

Increased pro-inflammatory cytokines, glial activation and oxidative stress in the hippocampus after short-term bilateral adrenalectomy

Background

Bilateral adrenalectomy has been shown to damage the hippocampal neurons. Although the effects of long-term adrenalectomy have been studied extensively there are few publications on the effects of short-term adrenalectomy. In the present study we aimed to investigate the effects of short-term bilateral adrenalectomy on the levels of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α; the response of microglia and astrocytes to neuronal cell death as well as oxidative stress markers GSH, SOD and MDA over the course of time (4 h, 24 h, 3 days, 1 week and 2 weeks) in the hippocampus of Wistar rats.

Results

Our results showed a transient significant elevation of pro-inflammatory cytokines IL-1β and IL-6 from 4 h to 3 days in the adrenalectomized compared to sham operated rats. After 1 week, the elevation of both cytokines returns to the sham levels. Surprisingly, TNF-α levels were significantly elevated at 4 h only in adrenalectomized compared to sham operated rats. The occurrence of neuronal cell death in the hippocampus following adrenalectomy was confirmed by Fluoro-Jade B staining. Our results showed a time dependent increase in degenerated neurons in the dorsal blade of the dentate gyrus from 3 days to 2 weeks after adrenalectomy. Our results revealed an early activation of microglia on day three whereas activation of astroglia in the hippocampus was observed at 1 week postoperatively. A progression of microglia and astroglia activation all over the dentate gyrus and their appearance for the first time in CA3 of adrenalectomized rats hippocampi compared to sham operated was seen after 2 weeks of surgery. Quantitative analysis revealed a significant increase in the number of microglia (3, 7 and 14 days) and astrocytes (7 and 14 days) of ADX compared to sham operated rats. Our study revealed no major signs of oxidative stress until 2 weeks after adrenalectomy when a significant decrease of GSH levels and SOD activity as well as an increase in MDA levels were found in adrenalectomized compared to sham rats.

Conclusion

Our study showed an early increase in the pro-inflammatory cytokines followed by neurodegeneration and activation of glial cells as well as oxidative stress. Taking these findings together it could be speculated that the early inflammatory components might contribute to the initiation of the biological cascade responsible for subsequent neuronal death in the current neurodegenerative animal model. These findings suggest that inflammatory mechanisms precede neurodegeneration and glial activation.

Intra-Amniotic LPS Induced Region-Specific Changes in Presynaptic Bouton Densities in the Ovine Fetal Brain

Rationale. Chorioamnionitis has been associated with increased risk for fetal brain damage. Although, it is now accepted that synaptic dysfunction might be responsible for functional deficits, synaptic densities/numbers after a fetal inflammatory challenge have not been studied in different regions yet. Therefore, we tested in this study the hypothesis that LPS-induced chorioamnionitis caused profound changes in synaptic densities in different regions of the fetal sheep brain. Material and Methods. Chorioamnionitis was induced by a 10 mg intra-amniotic LPS injection at two different exposure intervals. The fetal brain was studied at 125 days of gestation (term = 150 days) either 2 (LPS2D group) or 14 days (LPS14D group) after LPS or saline injection (control group). Synaptophysin immunohistochemistry was used to quantify the presynaptic density in layers 2-3 and 5-6 of the motor cortex, somatosensory cortex, entorhinal cortex, and piriforme cortex, in the nucleus caudatus and putamen and in CA1/2, CA3, and dentate gyrus of the hippocampus. Results. There was a significant reduction in presynaptic bouton densities in layers 2-3 and 5-6 of the motor cortex and in layers 2-3 of the entorhinal and the somatosensory cortex, in the nucleus caudate and putamen and the CA1/2 and CA3 of the hippocampus in the LPS2D compared to control animals. Only in the motor cortex and putamen, the presynaptic density was significantly decreased in the LPS14 D compared to the control group. No changes were found in the dentate gyrus of the hippocampus and the piriforme cortex. Conclusion. We demonstrated that LPS-induced chorioamnionitis caused a decreased density in presynaptic boutons in different areas in the fetal brain. These synaptic changes seemed to be region-specific, with some regions being more affected than others, and seemed to be transient in some regions.

IL-1β increases necrotic neuronal cell death in the developing rat hippocampus after status epilepticus by activating type I IL-1 receptor (IL-1RI)

Interleukin-1β (IL-1β) is associated with seizure-induced neuronal cell death in the adult brain. The contribution of IL-1β to neuronal injury induced by status epilepticus (SE) in the immature brain remains unclear. In the present study, we investigated the effects of IL-1β administration on hippocampal neuronal cell death associated with SE in the immature brain, and the role of the type I receptor of IL-1β (IL-1RI). SE was induced with lithium-pilocarpine in 14-days-old (P14) rat pups. Six hours after SE onset, pups were i.c.v. injected in the right ventricle with IL-1β (0, 0.3, 3, 30, or 300 ng), 30 ng of IL-1RI antagonist (IL-1Ra) alone, or 30 ng of IL-1Ra plus 3ng of IL-1β. As control groups, pups without seizures were injected with 3 ng of IL-1β or vehicle. Twenty-four hours after SE onset, neuronal cell death in the CA1 field of dorsal hippocampus was assessed by hematoxylin-eosin, Fluoro-Jade B and in vivo propidium iodide (PI) staining; expression of active caspase-3 (aCas-3) was also determined, using immunohistochemistry. The concentration-response curve of IL-1β showed a bell-shape. Only pups injected with 3 ng of IL-1β after SE showed a significant increase in the number of cells with eosinophilic cytoplasm and pyknotic nuclei, as well as F-JB positive cells with respect to the vehicle group. This effect was prevented when IL-1β was injected with IL-1Ra. Injection of 3 ng of IL-1β increased the number of PI-positive cells in CA1 area after SE. Injection of 3 ng of IL-1β did not produce hippocampal cell death in rats without seizures. Active caspase-3 expression was not observed after treatments in hippocampus. The activation of the IL-1β/IL-1RI system increases necrotic neuronal cell death caused by SE in rat pups.

Fingerprint changes in CSF composition associated with different aetiologies in human neonatal hydrocephalus: inflammatory cytokines

PURPOSE

Hydrocephalus (HC) has a multifactorial and complex picture of pathophysiology due to aetiology, age at and duration since onset. We have previously identified distinctions in markers of cell death associated with different aetiologies. Here, we examined cerebrospinal fluid (CSF) from human HC neonates for cytokines to identify further distinguishing features of different aetiologies.

METHODS

CSF was collected during routine lumbar puncture or ventricular tap from neonates with hydrocephalus, or with no neurological condition (normal controls). Total protein, Fas receptor, Fas ligand, stem cell factor (SCF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), insulin growth factor-1 (IGF-1), tumour necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) were measured and compared between 8 unaffected and 28 HC neonatal CSF samples.

RESULTS

Total protein was significantly (P < 0.05) raised in late-onset hydrocephalus (LOH). Fas receptor was raised (P < 0.05) in post-haemorrhagic hydrocephalus (PHH) and spina bifida with hydrocephalus (SB/HC), but no difference in Fas ligand was found. SCF was raised (P < 0.05) in SB/HC. HGF was found in all HC and was increased (P < 0.01) in PHH. Increased VEGF was found in PHH (P < 0.01) and SB/HC (P < 0.05). Variable levels of IL-6, TNF-α and IGF-1 were found in all HC groups compared with none in normal.

CONCLUSIONS

LOH was unusual with significantly raised total protein indicating an inflammatory state. Increased Fas receptor, VEGF, IGF-1 and HGF suggest anti-apoptotic and repair mechanism activation. By contrast, elevated TNF-α and IL-6 indicate inflammatory processes in these neonatal brains. Taken with our previous study, these data indicate that different pathophysiology, inflammation and repair are occurring in HC of different aetiologies and that additional treatment strategies may benefit these infants in addition to fluid diversion.

Pathogenesis of acute stroke and the role of inflammasomes

Inflammation is an innate immune response to infection or tissue damage that is designed to limit harm to the host, but contributes significantly to ischemic brain injury following stroke. The inflammatory response is initiated by the detection of acute damage via extracellular and intracellular pattern recognition receptors, which respond to conserved microbial structures, termed pathogen-associated molecular patterns or host-derived danger signals termed damage-associated molecular patterns. Multi-protein complexes known as inflammasomes (e.g. containing NLRP1, NLRP2, NLRP3, NLRP6, NLRP7, NLRP12, NLRC4, AIM2 and/or Pyrin), then process these signals to trigger an effector response. Briefly, signaling through NLRP1 and NLRP3 inflammasomes produces cleaved caspase-1, which cleaves both pro-IL-1β and pro-IL-18 into their biologically active mature pro-inflammatory cytokines that are released into the extracellular environment. This review will describe the molecular structure, cellular signaling pathways and current evidence for inflammasome activation following cerebral ischemia, and the potential for future treatments for stroke that may involve targeting inflammasome formation or its products in the ischemic brain.

Association between Interleukin-1 gene single nucleotide polymorphisms and ischemic stroke classified by TOAST criteria in the Han population of northern China

Increasing evidence suggests that IL-1β (C-511T) and IL-1α (C-889T) genes polymorphisms are associated with the susceptibility to cardiocerebral vascular disease. In this paper, we investigated the relationships between these polymorphisms and the risk of ischemic stroke (IS) classified by TOAST criteria in the north Chinese Han population. 440 cases of IS and 486 age- and gender-matched controls of Chinese Han population were enrolled. Association study showed that the TT genotype and T allele of IL-1α-889 C/T were significantly associated with IS of a large artery atherosclerosis (LAA) (TT: OR = 2.01, 95% CI = 1.34–3.0, and P < 0.001; T: OR = 1.44, 95% CI = 1.18–1.78, and P = 0.001). However, there was no significant difference in the distribution of IL-1α-889 C/T genotypes and allele frequencies between the two subgroups (small-artery occlusion (SVD) and cardioembolism (CE)) of IS and control groups. No significant association was also found between the IL-1β-511 TT genotype and T allele (TT: OR = 0.79, 95% CI = 0.56–1.11, and P = 0.175; T: OR = 0.83, 95% CI = 0.68–1.01, and P = 0.066) and IS as well as subgroups of CE and SVD. Our results implicated that IL-1α-889 C/T gene polymorphism might be associated with the susceptibility to IS, especially to IS with LAA, in a north Chinese Han population.

TLR-4-dependent and -independent mechanisms of fetal brain injury in the setting of preterm birth

In this study, we sought to assess how essential activation of toll-like receptor 4 (TLR-4) is to fetal brain injury from intrauterine inflammation. Both wild-type and TLR-4 mutant fetal central nervous system cells were exposed to inflammation using lipopolysaccharide in vivo or in vitro. Inflammation could not induce neuronal injury in the absence of glial cells, in either wild-type or TLR-4 mutant neurons. However, injured neurons could induce injury in other neurons regardless of TLR-4 competency. Our results indicate that initiation of neuronal injury is a TLR-4-dependent event, while propagation is a TLR-4-independent event.

Neutrophil cerebrovascular transmigration triggers rapid neurotoxicity through release of proteases associated with decondensed DNA

Cerebrovascular inflammation contributes to diverse CNS disorders through mechanisms that are incompletely understood. The recruitment of neutrophils to the brain can contribute to neurotoxicity, particularly during acute brain injuries, such as cerebral ischemia, trauma, and seizures. However, the regulatory and effector mechanisms that underlie neutrophil-mediated neurotoxicity are poorly understood. In this study, we show that mouse neutrophils are not inherently toxic to neurons but that transendothelial migration across IL-1-stimulated brain endothelium triggers neutrophils to acquire a neurotoxic phenotype that causes the rapid death of cultured neurons. Neurotoxicity was induced by the addition of transmigrated neutrophils or conditioned medium, taken from transmigrated neutrophils, to neurons and was partially mediated by excitotoxic mechanisms and soluble proteins. Transmigrated neutrophils also released decondensed DNA associated with proteases, which are known as neutrophil extracellular traps. The blockade of histone-DNA complexes attenuated transmigrated neutrophil-induced neuronal death, whereas the inhibition of key neutrophil proteases in the presence of transmigrated neutrophils rescued neuronal viability. We also show that neutrophil recruitment in the brain is IL-1 dependent, and release of proteases and decondensed DNA from recruited neutrophils in the brain occurs in several in vivo experimental models of neuroinflammation. These data reveal new regulatory and effector mechanisms of neutrophil-mediated neurotoxicity (i.e., the release of proteases and decondensed DNA triggered by phenotypic transformation during cerebrovascular transmigration). Such mechanisms have important implications for neuroinflammatory disorders, notably in the development of antileukocyte therapies.

Facts and fiction: the impact of hypothermia on molecular mechanisms following major challenge

Numerous multiple trauma and surgical patients suffer from accidental hypothermia. While induced hypothermia is commonly used in elective cardiac surgery due to its protective effects, accidental hypothermia is associated with increased posttraumatic complications and even mortality in severely injured patients. This paper focuses on protective molecular mechanisms of hypothermia on apoptosis and the posttraumatic immune response. Although information regarding severe trauma is limited, there is evidence that induced hypothermia may have beneficial effects on the posttraumatic immune response as well as apoptosis in animal studies and certain clinical situations. However, more profound knowledge of mechanisms is necessary before randomized clinical trials in trauma patients can be initiated.

CD200-CD200R dysfunction exacerbates microglial activation and dopaminergic neurodegeneration in a rat model of Parkinson's disease

BACKGROUND

Increasing evidence suggests that microglial activation may participate in the aetiology and pathogenesis of Parkinson's disease (PD). CD200-CD200R signalling has been shown to be critical for restraining microglial activation. We have previously shown that expression of CD200R in monocyte-derived macrophages, induced by various stimuli, is impaired in PD patients, implying an intrinsic abnormality of CD200-CD200R signalling in PD brain. Thus, further in vivo evidence is needed to elucidate the role of malfunction of CD200-CD200R signalling in the pathogenesis of PD.

METHODS

6-hydroxydopamine (6-OHDA)-lesioned rats were used as an animal model of PD. CD200R-blocking antibody (BAb) was injected into striatum to block the engagement of CD200 and CD200R. The animals were divided into three groups, which were treated with 6-OHDA/Veh (PBS), 6-OHDA/CAb (isotype control antibody) or 6-OHDA/BAb, respectively. Rotational tests and immunohistochemistry were employed to evaluate motor deficits and dopaminergic neurodegeneration in animals from each group. HPLC analysis was used to measure monoamine levels in striatum. Morphological analysis and quantification of CD11b- (or MHC II-) immunoreactive cells were performed to investigate microglial activation and possible neuroinflammation in the substantia nigra (SN). Finally, ELISA was employed to assay protein levels of proinflammatory cytokines.

RESULTS

Compared with 6-OHDA/CAb or 6-OHDA/Veh groups, rats treated with 6-OHDA/BAb showed a significant increase in counts of contralateral rotation and a significant decrease in TH-immunoreactive (TH-ir) neurons in SN. A marked decrease in monoamine levels was also detected in 6-OHDA/BAb-treated rats, in comparison to 6-OHDA/Veh-treated ones. Furthermore, remarkably increased activation of microglia as well as up-regulation of proinflammatory cytokines was found concomitant with dopaminergic neurodegeneration in 6-OHDA/BAb-treated rats.

CONCLUSIONS

This study shows that deficits in the CD200-CD200R system exacerbate microglial activation and dopaminergic neurodegeneration in a 6-OHDA-induced rat model of PD. Our results suggest that dysfunction of CD200-CD200R signalling may be involved in the aetiopathogenesis of PD.

Volume of white matter hyperintensities in healthy adults: contribution of age, vascular risk factors, and inflammation-related genetic variants

Aging is associated with appearance of white matter hyperintensities (WMH) on MRI scans. Vascular risk and inflammation, which increase with age, may contribute to white matter deterioration and proliferation of WMH. We investigated whether circulating biomarkers and genetic variants associated with elevated vascular risk and inflammation are associated with WMH volume in healthy adults (144 volunteers, 44-77 years of age). We examined association of WMH volume with age, sex, hypertension, circulating levels of total plasma homocysteine (tHcy), cholesterol (low-density lipoprotein), and C-reactive protein (CRP), and four polymorphisms related to vascular risk and inflammation: Apolipoprotein ε (ApoE ε2,3,4), Angiotensin-Converting Enzyme insertion/deletion (ACE I/D), methylenetetrahydrofolate reductase (MTHFR) C677T, C-reactive protein (CRP)-286C>A>T, and interleukin-1β (IL-1β) C-511T. We found that larger WMH volume was associated with advanced age, hypertension, and elevated levels of homocysteine and CRP but not with low-density lipoprotein levels. Homozygotes for IL-1β-511T allele and carriers of CRP-286T allele that are associated with increased inflammatory response had larger WMH than the other allelic combinations. Carriers of the APOE ε2 allele had larger frontal WMH than ε3 homozygotes and ε4 carriers did. Thus, in healthy adults, who are free of neurological and vascular disease, genetic variants that promote inflammation and elevated levels of vascular risk biomarkers can contribute to brain abnormalities. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

IL-1β down-regulates ADAMTS-13 mRNA expression in cells of the central nervous system

ADAMTS-13 is the Von Willebrand factor (vWF) cleaving protease, responsible for the cleavage and down-regulation of the pro-thrombotic properties of ultra large VWF multimers. It is expressed predominantly by the hepatic stellate cells of the liver, but is also found to be expressed in other tissues, including brain. Reduced ADAMTS-13 is associated with a variety of thrombotic microangiopathies. Since the cellular origin and regulation of ADAMTS-13 expression in the brain is unknown, we aimed to investigate this in four different central nervous system (CNS)-derived cell lines, SHSY-5Y (human neuroblastoma), U373 (human astroglioma), CHME-3 (human foetal microglia) and hCMEC/D3 (adult human brain endothelial cells). All cell lines expressed ADAMTS-13 mRNA constitutively with neuroblastoma cells showing the highest expression. Interleukin (IL)-1β down-regulated ADAMTS-13 mRNA expression in astroglioma cells and microglial cells whereas TNF and IL-6 treatment showed no significant differences in ADAMTS-13 mRNA expression in any cell line tested. ADAMTS-13 protein expression was reduced in a dose-dependent manner only in astroglioma cells following stimulation by IL-1β. The ability of IL-1β to significantly reduce ADAMTS-13 mRNA expression in human microglia and astroglioma cells suggests a role in the haemostasis of the local microenvironment under inflammatory conditions. This is the first report of ADAMTS-13 expression in cells of the CNS; however, its function remains to be determined.

Effects of hyperbaric oxygen on the expression of claudins after cerebral ischemia-reperfusion in rats

The malfunction of tight junctions (TJs) between endothelial cells in the blood brain barrier (BBB) is the pathophysiological basis for cerebral ischemia-reperfusion (IR) injury. Claudins, major molecular elements of the TJs, play a key role in the paracellular permeability of the BBB. Although several studies have demonstrated the impact of hyperbaric oxygenation (HBO) on boosting oxygen supply and reducing infarct size, its effect and underlying mechanism on the integrity of the BBB is unknown. To study the function of HBO on claudins and the permeability of the BBB, we replicated the animal model of local cerebral IR. Using Evans blue dye, permeability of the BBB was examined. Transmission electron microscopy (TEM), immunohistochemistry, western blot, and gelatin zymography were used to detect the integrity of the BBB, the expression of claudin-1 and claudin-5, and the activity of matrix metalloproteinases (MMPs) in brain microvessel endothelium. Our data indicate that compared with the sham-operated group, IR increased permeability of the BBB to Evans blue dye (P < 0.01), peaking at 4 h. The BBB ultrastructure was disrupted and the expression of claudin-5 and claudin-1 decreased (P < 0.01) in the 4 and 72 h IR group, respectively. Increased claudin-5 and claudin-1 expression and decreased permeability of the BBB were observed in the HBO + IR group (P < 0.01) via the suppression of MMP-2 and MMP-9, respectively. Our study provides direct evidence that HBO decreases the permeability of the BBB by reducing the enzymatic activity of MMPs and augmenting the expression of claudins at different stages in cerebral IR injury.

Acinetobacter baumannii-induced lung cell death: role of inflammation, oxidative stress and cytosolic calcium

A growing body of evidence supports the notion that susceptible Acinetobacter baumannii strain ATCC 19606 induces human epithelial cells death. However, most of the cellular and molecular mechanisms associated with this cell death remain unknown, and also the degree of the cytotoxic effects of a clinical panresistant strain compared with a susceptible strain has never been studied. Due to the role of proinflammatory cytokine release, oxidative stress and cytosolic calcium increase in the cell death-induced by other Gram-negative bacteria, we investigated whether these intracellular targets were involved in the cell death induced by clinical panresistant 113-16 and susceptible ATCC 19606 strains. Data presented here show that 113-16 and ATCC 19606 induce time-dependent cell death of lung epithelial cells involving a perturbation of cytosolic calcium homeostasis with subsequent calpain and caspase-3 activation. Prevention of this cell death by TNF-α and interleukin-6 blockers and antioxidant highlights the involvement of proinflammatory cytokines and oxidative stress in this phenomenon. These results demonstrate the involvement of calpain calcium-dependent in cell death induced by A. baumannii and the impact of proinflammatory cytokines and oxidative stress in this cell death; it is noteworthy to stress that some mechanisms are less induced by the panresistant strain.

Inflammation-induced preterm birth alters neuronal morphology in the mouse fetal brain

Adverse neurological outcome is a major cause of long-term morbidity in ex-preterm children. To investigate the effect of parturition and inflammation on the fetal brain, we utilized two in vivo mouse models of preterm birth. To mimic the most common human scenario of preterm birth, we used a mouse model of intrauterine inflammation by intrauterine infusion of lipopolysaccharide (LPS). To investigate the effect of parturition on the immature fetal brain, in the absence of inflammation, we used a non-infectious model of preterm birth by administering RU486. Pro-inflammatory cytokines (IL-10, IL-1beta, IL-6 and TNF-alpha) in amniotic fluid and inflammatory biomarkers in maternal serum and amniotic fluid were compared between the two models using ELISA. Pro-inflammatory cytokine expression was evaluated in the whole fetal brains from the two models. Primary neuronal cultures from the fetal cortex were established from the different models and controls in order to compare the neuronal morphology. Only the intrauterine inflammation model resulted in an elevation of inflammatory biomarkers in the maternal serum and amniotic fluid. Exposure to inflammation-induced preterm birth, but not non-infectious preterm birth, also resulted in an increase in cytokine mRNA in whole fetal brain and in disrupted fetal neuronal morphology. In particular, Microtubule-associated protein 2 (MAP2) staining was decreased and the number of dendrites was reduced (P < 0.001, ANOVA between groups). These results suggest that inflammation-induced preterm birth and not the process of preterm birth may result in neuroinflammation and alter fetal neuronal morphology.

[Inhibition effect of IL-1beta on calcium channels currents in cultured cortical neurons of rat]

Interleukin-1beta (IL-1beta) is an important proinflammatory cytokine that exert wide biological functions in the central nervous system (CNS). Voltage-gated Ca2+ channels in plasma membrane are essential components of Ca2+ signal whose change on pathological conditions is closely related to processes of diseases. Although both IL-1beta and Ca2+ channels have key roles in injury and disease of the brain, so far their relations have been reported in few studies. The effects of IL-1beta on Ca2+ channels in cultured cortical neurons of rats were investigated using patch-clamp recording in present research. Our results showed that both 10 and 50 ng/mL of IL-1beta treatment inhibit the Ca2+ currents in time and dose dependent manner, without the change of activation properties of voltage-gated Ca2+ channels (VGCC)s.

Febrile seizures: current views and investigations

Febrile seizures (FSs) are seizures that occur during fever, usually at the time of a cold or flu, and represent the most common cause of seizures in the pediatric population. Up to 5% of children between the ages of six months and five years-of-age will experience a FS. Clinically these seizures are categorized as benign events with little impact on the growth and development of the child. However, studies have linked the occurrence of FSs to an increased risk of developing adult epileptic disorders. There are many unanswered questions about FSs, such as the mechanism of their generation, the long-term effects of these seizures, and their role in epileptogenesis. Answers are beginning to emerge based on results from animal studies. This review summarizes the current literature on animal models of FSs, mechanisms underlying the seizures, and functional, structural, and molecular changes that may result from them.

Interleukin-1beta: a bridge between inflammation and excitotoxicity?

Interleukin-1 (IL-1) is a proinflammatory cytokine released by many cell types that acts in both an autocrine and/or paracrine fashion. While IL-1 is best described as an important mediator of the peripheral immune response during infection and inflammation, increasing evidence implicates IL-1 signaling in the pathogenesis of several neurological disorders. The biochemical pathway(s) by which this cytokine contributes to brain injury remain(s) largely unidentified. Herein, we review the evidence that demonstrates the contribution of IL-1beta to the pathogenesis of both acute and chronic neurological disorders. Further, we highlight data that leads us to propose IL-1beta as the missing mechanistic link between a potential beneficial inflammatory response and detrimental glutamate excitotoxicity.

Inflammatory responses in the rat brain in response to different methods of intra-cerebral administration

Direct intra-cerebral administration of substances into the brain parenchyma is a common technique used by researchers in neuroscience. However, inflammatory responses to the needle may confound the results obtained following injection of these substances. In this paper we show that the use of a glass micro-needle for intra-cerebral injection reduces mechanical injury, blood-brain barrier breakdown and neutrophil recruitment in response to the injection of vehicle or interleukin-1, compared to using a 26-gauge Hamilton syringe. Therefore, the use of a glass micro-needle to inject substances intra-cerebrally appears to cause minimal injection artefact and should be the method of choice.

[The relevance of the inflammatory response in the injured brain]

Research efforts in recent years have defined traumatic brain injury (TBI) as a predominantly immunological and inflammatory disorder. This perception is based on the fact that the overwhelming neuroinflammatory response in the injured brain contributes to the development of posttraumatic edema and to neuropathological sequelae which are, in large part, responsible for the adverse outcome. While the "key" mediators of neuroinflammation, such as the cytokine cascade and the complement system, have been clearly defined by studies in experimental TBI models, their exact pathways of interaction and pathophysiological implications remain to be further elucidated. This lack of knowledge is partially due to the concept of a "dual role" of the neuroinflammatory response after TBI. This notion implies that specific inflammatory molecules may mediate diverse functions depending on their local concentration and kinetics of expression in the injured brain. The inflammation-induced effects range from beneficial aspects of neuroprotection to detrimental neurotoxicity. The lack of success in pushing anti-inflammatory therapeutic concepts from"bench to bedside" for patients with severe TBI strengthens the further need for advances in basic research on the molecular aspects of the neuroinflammatory network in the injured brain. The present review summarizes the current knowledge from experimental studies in this field of research and discusses potential future targets of investigation.

System x(c)- activity and astrocytes are necessary for interleukin-1 beta-mediated hypoxic neuronal injury

The purpose of this study was to elucidate the cellular/biochemical pathway(s) by which interleukin-1beta (IL-1beta) contributes to the pathogenesis of hypoxic-ischemic brain damage. In vivo, IL-1 receptor type I (IL-1RI)-deficient mice showed smaller infarcts and less neurological deficits than wild-type animals after a 90 min reversible middle cerebral artery occlusion. In vitro, IL-1beta mediated an enhancement of hypoxic neuronal injury in murine cortical cultures that was lacking in cultures derived from IL-1RI null mutant animals and was blocked by the IL-1 receptor antagonist or an IL-1RI blocking antibody. This IL-1beta-mediated potentiation of hypoxic neuronal injury was associated with an increase in both cellular cystine uptake ([cystine]i) and extracellular glutamate levels ([glutamate]e) and was prevented by either ionotropic glutamate receptor antagonism or removal of L-cystine, suggesting a role for the cystine/glutamate antiporter (System x(c)-). Indeed, dual System x(c)-/metabotropic glutamate receptor subunit 1 (mGluR1) antagonism but not selective mGluR1 antagonism prevented neuronal injury. Additionally, cultures derived from mGluR1-deficient mice exhibited the same potentiation in injury after treatment with IL-1beta as wild-type cultures, an effect prevented by System x(c)-/mGluR1 antagonism. Finally, assessment of System x(c)- function and kinetics in IL-1beta-treated cultures revealed an increase in velocity of cystine transport (Vmax), in the absence of a change in affinity (Km). Neither the enhancement in [cystine]i, [glutamate]e, or neuronal injury were observed in chimeric cultures consisting of IL-1RI(+/+) neurons plated on top of IL-1RI(-/-) astrocytes, highlighting the importance of astrocyte-mediated alterations in System x(c)- as a novel contributor to the development and progression of hypoxic neuronal injury.

Overexpression of IL-1β by adenoviral-mediated gene transfer in the rat brain causes a prolonged hepatic chemokine response, axonal injury and the suppression of spontaneous behaviour

Acute brain injury induces early and transient hepatic expression of chemokines, which amplify the injury response and give rise to movement of leukocytes into the blood and subsequently the brain and liver. Here, we sought to determine whether an ongoing injury stimulus within the brain would continue to drive the hepatic chemokine response and how it impacts on behaviour and CNS integrity. We generated chronic IL-1beta expression in rat brain by adenoviral-mediated gene transfer, which resulted in chronic leukocyte recruitment, axonal injury and prolonged depression of spontaneous behaviour. IL-1beta could not be detected in circulating blood, but a chronic systemic response was established, including extended production of hepatic and circulating chemokines, leukocytosis, liver damage, weight loss, decreased serum albumin and marked liver leukocyte recruitment. Thus, hepatic chemokine synthesis is a feature of active chronic CNS disease and provides an accessible target for the suppression of CNS inflammation.

Interleukin-1 as a therapeutic target in acute brain injury

Interest in the interactions between the immune and central nervous systems has furthered our understanding of brain function in health and disease. Experimental and clinical studies increasingly reveal an inflammatory component in the pathophysiology of many forms of brain injury. Members of the interleukin (IL)-1 cytokine family are produced by diverse cell types within the brain and may determine the outcome of neuronal injury. This review discusses the neuroprotective potential of IL-1 inhibition in various acute neurological and neurosurgical diseases. The ILs comprise an expanding family of cytokines with diverse physiological and pathological actions, of which IL-1 is a key inflammatory mediator implicated in brain injury. IL-1 expression in the normal CNS is low, but is upregulated rapidly in response to brain injury. In experimental studies, IL-1 and its endogenous, competitive, selective antagonist, IL-1 receptor antagonist (IL-1RA), mediate neurotoxic and neuroprotective outcomes, respectively. Clinical studies support the relationship between inflammation, disease severity and poor prognosis in various neurological and neurosurgical disorders. Recombinant human (rh)IL-1RA shows modest blood–brain barrier penetrance and is safe for clinical use when administered parenterally. Evidence supporting the use of rhIL-1RA and other approaches to targeting IL-1 are discussed in relation to cerebral ischemia, seizures, subarachnoid hemorrhage and traumatic brain injury.

Neurodegenerative actions of interleukin-1 in the rat brain are mediated through increases in seizure activity

The cytokine interleukin-1 (IL-1) is an established and important mediator of diverse forms of neuronal injury in experimental animals. However, its mechanisms of action remain largely unknown. We have reported previously that IL-1 markedly enhances excitotoxic injury induced in the rat by striatal administration of the excitotoxin alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), leading to widespread neuronal loss throughout the ipsilateral cortex. Here we tested the hypothesis that IL-1 causes this injury through induction and/or enhancement of seizure activity in the rat. Consistently with this hypothesis, intrastriatal injection of AMPA or AMPA with IL-1 in the rat brain increased c-Fos expression in regions similar to those in which c-Fos has been reported previously in response to seizures. A significant increase in cortical neuronal activity (number of c-Fos positive cells) was observed in response to AMPA with IL-1 compared with AMPA (8 hr after injection). Increased seizure duration [3,522 +/- 660 sec (SEM) vs. 1,415 +/- 301 sec; P < 0.001] and cell death volume (140 +/- 20 mm3 vs. 52 +/- 6 mm3; P < 0.001) were seen in response to coinfusion of AMPA with IL-1 vs. AMPA alone. In addition, the anticonvulsant diazepam (intraperitoneal) significantly reduced cell death (P < 0.001) and seizure duration (P < 0.001) induced by AMPA with IL-1, and a significant correlation was found between seizure duration and cell death volume. These findings support our hypothesis that IL-1 enhances excitotoxic injury by enhancement of seizures, which may be of relevance to IL-1 actions in other forms of neuronal injury, including cerebral ischemia.

Neuroinflammation and both cytotoxic and vasogenic edema are reduced in interleukin-1 type 1 receptor-deficient mice conferring neuroprotection

BACKGROUND AND PURPOSE

Interleukin-1 (IL-1) is a proinflammatory cytokine implicated in multiple neurodegenerative diseases, including stroke. However, to date, there is no consensus regarding which receptor(s) mediates the detrimental effects of IL-1. We hypothesized that abrogating IL-1 type 1 receptor (IL-1R1) signaling would reduce edema, chemokine expression, and leukocyte infiltration; lower levels of iNOS; and, consequently, decrease free radical damage after mild hypoxia/ischemia (H/I), thus preserving brain cells.

METHODS

IL-1R1 null mice and wild-type mice were subjected to a mild H/I insult. MRI was used to measure the area affected at 30 minutes and 48 hours after H/I. An RNAse protection assay was used to evaluate changes in chemokine mRNA expression. RT-PCR was used to assess inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase mRNA levels. Immunohistochemistry was used to assess leukocyte infiltration. Western blots were used to assess iNOS and glutamate aspartate transporter protein levels.

RESULTS

IL-1R1 null mice had reduced cytotoxic and vasogenic edema. The volume of hyperintense signal on T2-weighted images was reduced on average by 90% at 48 hours after H/I. The induction of multiple chemokine mRNAs was significantly reduced in IL-1R1 null mice compared with wild-type mice at 18 and 72 hours after H/I, which correlated with fewer infiltrating CD3+ leukocytes. Levels of iNOS protein and mRNA (but not glutamate aspartate transporter) were significantly reduced in the IL-1R1 mouse brain.

CONCLUSIONS

These findings indicate that abrogating IL-1R1 signaling could protect brain cells subsequent to a mild stroke by reducing edema and immune cell recruitment, as well as by limiting iNOS-mediated free radical damage.

Differential effects of interleukin-1beta on neurotoxicity, cytokine induction and glial reaction in specific brain regions

An appropriate inflammatory response is crucial for the maintenance of tissue homeostasis. The inflammatory responses seen in the brain parenchyma differ from those elicited in the periphery, ventricles and meninges. However, although an inflammatory component has been associated with many CNS diseases, the differences among parenchymal inflammatory responses in different brain regions have not yet been fully elucidated. Here, we performed a systematic comparison of the effects of a common pro-inflammatory stimulus, IL-1beta, on the hippocampus, substantia nigra, striatum and cortex. We determined various responses, including cytokine mRNA induction, glial activation, immune cell infiltration and changes in neuronal integrity, in both injected and adjacent regions 1 and 6 days after the injection of IL-1beta. We found that the mRNA for TGF-beta was up-regulated in a region-specific manner after IL-1beta administration. Contrary to its response in the periphery, IL-1alpha showed no detectable induction in the tested parenchymal regions. In addition, cytokine induction was also sometimes observed in regions distant from the site of injection. Interestingly, IL-1beta-mediated neurodegeneration was observed in the dentate gyrus of the hippocampus, but not in the other tested regions. The cellular recruitment mediated by IL-1 beta injection consisted mainly of polymorphonuclear cells (PMN), which correlated with IL-1betamRNA induction even in regions far from the injection site. These results indicate that various parenchymal regions show different inflammatory responses and neurodegeneration in response to IL-1beta. Taken together, our results provide a more precise picture of regional inflammation in the brain and should provide a basis for differential interpretation of results based on regional inflammatory differences.

Differential regulation of type I and type II interleukin-1 receptors in focal brain inflammation

Most pathologies of the brain have an inflammatory component, associated with the release of cytokines such as interleukin-1beta (IL-1beta) from resident and infiltrating cells. The IL-1 type I receptor (IL-1RI) initiates a signalling cascade but the type II receptor (IL-1RII) acts as a decoy receptor. Here we have investigated the expression of IL-1beta, IL-1RI and IL-1RII in distinct inflammatory lesions in the rat brain. IL-1beta was injected into the brain to generate an inflammatory lesion in the absence of neuronal cell death whereas neuronal death was specifically induced by the microinjection of N-methyl-D-aspartate (NMDA). Using TaqMan RT-PCR and ELISA, we observed elevated de novo IL-1beta synthesis 2 h after the intracerebral microinjection of IL-1beta; this de novo IL-1beta remained elevated 24 h later. There was a concomitant increase in IL-1RI mRNA but a much greater increase in IL-1RII mRNA. Immunostaining revealed that IL-1RII was expressed on brain endothelial cells and on infiltrating neutrophils. In contrast, although IL-1beta and IL-1RI were elevated to similar levels in response to NMDA challenge, the response was delayed and IL-1RII mRNA expression was unchanged. The lesion-specific expression of IL-1 receptors suggests that the receptors are differentially regulated in a manner not directly related to the endogenous level of IL-1 in the CNS.

Valproate-induced eosinophilia in children with epilepsy: role of interleukin-5

Interleukin-5 contributes both in eosinophilopoiesis and neural development. Serum interleukin-5 levels were measured with enzyme-linked immunosorbent assay technique in 68 children with epilepsy receiving sodium valproate monotherapy and compared with the levels of 60 healthy controls and 14 children with epilepsy receiving carbamazepine. Eosinophilia was observed in 35.3% of children receiving valproate. Interleukin-5 in valproate users was significantly higher compared with children receiving carbamazepine and controls. Valproate users who exhibited eosinophilia had higher interleukin-5 levels compared with those without eosinophilia. However, the interleukin-5 level was also elevated, although to a lesser degree, in children without eosinophilia. The majority of valproate responders had high interleukin-5 levels. A positive correlation between interleukin-5 levels and the eosinophil count was also noted. We postulate that valproate contributes to the pathogenesis of eosinophilia, probably inducing interleukin-5 production. The finding that serum interleukin-5 was significantly elevated in valproate responders and even in valproate users without eosinophilia suggests that the increase in interleukin-5 might represent one of valproate's antiepileptic mechanisms.

Closed head injury--an inflammatory disease?

Closed head injury (CHI) remains the leading cause of death and persisting neurological impairment in young individuals in industrialized nations. Research efforts in the past years have brought evidence that the intracranial inflammatory response in the injured brain contributes to the neuropathological sequelae which are, in large part, responsible for the adverse outcome after head injury. The presence of hypoxia and hypotension in the early resuscitative period of brain-injured patients further aggravates the inflammatory response in the brain due to ischemia/reperfusion-mediated injuries. The profound endogenous neuroinflammatory response after CHI, which is phylogenetically aimed at defending the intrathecal compartment from invading pathogens and repairing lesioned brain tissue, contributes to the development of cerebral edema, breakdown of the blood-brain barrier, and ultimately to delayed neuronal cell death. However, aside from these deleterious effects, neuroinflammation has been recently shown to mediate neuroreparative mechanisms after brain injury as well. This "dual effect" of neuroinflammation was the focus of extensive experimental and clinical research in the past years and has lead to an expanded basic knowledge on the cellular and molecular mechanisms which regulate the intracranial inflammatory response after CHI. Thus, head injury has recently evolved as an inflammatory and immunological disease much more than a pure traumatological, neurological, or neurosurgical entity. The present review will summarize the so far known mechanisms of posttraumatic neuroinflammation after CHI, based on data from clinical and experimental studies, with a special focus on the role of pro-inflammatory cytokines, chemokines, and the complement system.

Stress-induced increases in hypothalamic IL-1: a systematic analysis of multiple stressor paradigms

Exposure to stressors such as footshock, tailshock, and immobilization have been shown to induce hypothalamic IL-1 production, while other stressors such as restraint, maternal separation, social isolation, and predator exposure have no effect on hypothalamic IL-1 levels. This disparity of findings has led to considerable controversy regarding the ability of stressors to induce hypothalamic IL-1 expression. Thus, the goal of the following experiments was to examine hypothalamic IL-1 responses in adult male Sprague-Dawley rats following exposure to a diverse set of stressors. Our data indicate that exposure to 2h of restraint in a Plexiglas tube, glucoprivic challenge induced by administration of 2-deoxyglucose (2-DG), or insulin-induced hypoglycemia all fail to alter hypothalamic IL-1 levels despite robust activation of the pituitary-adrenal response. However, when restraint was administered on an orbital shaker or in combination with insulin-induced hypoglycemia, robust increases in hypothalamic IL-1 were observed. No effects of glucoprivic (2-DG) challenge were observed when combined with restraint, indicating some specificity in the hypothalamic IL-1 response to stress. We also provide a preliminary validation of the ELISA detection method for IL-1, showing that (a) Western blot analyses confirmed strong immunopositive banding at the apparent molecular weight of both mature IL-1beta and the IL-1beta prohormone, and (b) footshock led to a two-fold increase in mRNA for IL-1 in the hypothalamus as detected by RT-PCR. These data provide novel insight into the characteristics of a stressor that may be necessary for the observation of stress-induced increases in hypothalamic IL-1.

In situ detection of intracerebral cytokine expression after human brain contusion

The study was undertaken to analyze intracerebral expression of pro- and anti-inflammatory cytokines after traumatic brain injury (TBI) in man in order to compare the findings with previous experimental data regarding the pathogenesis of secondary brain injury. Contused brain tissue biopsies were obtained from 12 consecutive patients undergoing surgery for brain contusions 3 h to 5 days after trauma. Cytokine expression was analyzed by in situ hybridization and immunohistochemistry. In patients undergoing surgery less than 24 h after trauma, strong expression of both the pro-inflammatory cytokines interleukin (IL)-1-beta, IL-6 and interferon (IFN)-gamma and the anti-inflammatory cytokine IL-4 was detected. In patients undergoing surgery between 3 and 5 days after trauma, IL-4 expression was significantly lower (P < 0.05) compared to the patients operated early. IL-1-beta and IFN-gamma expression remained strong in comparison to IL-6 and IL-4 expression (P < 0.05). Immunohistochemistry for IL-1-beta confirmed that the protein was produced with a temporal and regional pattern that corresponded to in situ hybridization results. The study provides in situ data on intracerebral cytokine expression after contusion in the clinical setting. Strong intracerebral cytokine expression occurs in the perilesional zone both in the early and the delayed phase after traumatic brain injury in humans. The temporal regulation of pro- and anti-inflammatory cytokines differs which reveals different therapeutic windows for pharmacological intervention.

Trisomy 21 and the brain

In fetuses with Down syndrome, neurons fail to show normal dendritic development, yielding a "tree in winter" appearance. This developmental failure is thought to result in mental retardation. In adults with Down syndrome, neuronal loss is dramatic and neurofibrillary and neuritic Abeta plaque pathologies are consistent with Alzheimer disease. These pathological changes are thought to underlie the neuropsychological and physiological changes in older individuals with Down syndrome. Two chromosome 21-based gene products, beta-amyloid precursor protein (betaAPP) and S100B, have been implicated in these neuronal and interstitial changes. Although not necessary for mental retardation and other features, betaAPP gene triplication is necessary, although perhaps not sufficient, for development of Alzheimer pathology. S100B is overexpressed throughout life in Down patients, and mice with extra copies of the S100B gene have dendritic abnormalities. S100B overexpression correlates with Alzheimer pathology in post-adolescent Down syndrome patients and has been implicated in Abeta plaque pathogenesis. Interleukin-1 (IL-1) is a non-chromosome-21-based cytokine that is also overexpressed throughout life in Down syndrome. IL-1 upregulates betaAPP and S100B expression and drives numerous neurodegenerative and self-amplifying cascades that support a neuroinflammatory component in the pathogenesis of sporadic and Down syndrome-related Alzheimer disease.

Glia activation and cytokine increase in rat hippocampus by kainic acid-induced status epilepticus during postnatal development

In adult rats, status epilepticus (SE) induces cytokine production by glia especially when seizures are associated with neuronal injury. This suggests that cytokines may play a role in seizure-induced neuronal damage. As SE-induced injury is age-specific, we used rats of different ages (with distinct susceptibilities to seizure-induced neuronal injury) to elucidate the role of cytokines in this process. Thus, we investigated the activation of microglia and astrocytes, induction of cytokines, and hippocampal neuronal injury 4 and 24 h following kainic acid-induced SE in postnatal day (PN) 9, 15, and 21 rats. At PN9, there was little activation of microglia and astrocytes at any time point studied. Interleukin-1beta (IL), tumor necrosis factor-alpha (TNF), and IL-6 or the naturally occurring IL-1 receptor antagonist (Ra) mRNA expression did not increase. No evidence of cell injury has been detected. At PN15, immunostaining of microglia and astrocytes was enhanced, but only IL-1beta mRNA expression was increased. These changes were observed 4 h after SE. Scattered injured neurons in CA3 and subiculum, but not in any other region, were present 24 h following SE. At PN21, immunostaining of microglia and astrocytes and the mRNA expression of all cytokines studied was significantly increased already 4 h after SE. At 24 h, many injured neurons were present in CA1 and CA3 regions and in 40% of rats in other forebrain areas. These data show that (i) the pattern of glia activation and cytokine gene transcription induced by SE is age-dependent and (ii) neuronal injury in the hippocampus occurs only when cytokines are induced and their synthesis precedes the appearance of neuronal damage. Thus, cytokine expression in immature brain is associated specifically with cell injury rather than with seizures per se, suggesting that proinflammatory cytokines may contribute to the occurence of SE-induced hippocampal damage.

Interleukin-1beta enhances NMDA receptor-mediated intracellular calcium increase through activation of the Src family of kinases

Interleukin (IL)-1beta is a proinflammatory cytokine implicated in various pathophysiological conditions of the CNS involving NMDA receptor activation. Circumstantial evidence suggests that IL-1beta and NMDA receptors can functionally interact. Using primary cultures of rat hippocampal neurons, we investigated whether IL-1beta affects NMDA receptor function(s) by studying (1) NMDA receptor-induced [Ca2+]i increase and (2) NMDA-mediated neurotoxicity. IL1beta (0.01-0.1 ng/ml) dose-dependently enhances NMDA-induced [Ca2+]i increases with a maximal effect of approximately 45%. This effect occurred only when neurons were pretreated with IL-1beta, whereas it was absent if IL-1beta and NMDA were applied simultaneously, and it was abolished by IL-1 receptor antagonist (50 ng/ml). Facilitation of NMDA-induced [Ca2+]i increase by IL-1beta was prevented by both lavendustin (LAV) A (500 nm) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) (1 microm), suggesting an involvement of tyrosine kinases. Increased tyrosine phosphorylation of NMDA receptor subunits 2A and 2B and coimmunoprecipitation of activated Src tyrosine kinase with these subunits was observed after exposure of hippocampal neurons to 0.05 ng/ml IL-1beta. Finally, 0.05 ng/ml IL-1beta increased by approximately 30% neuronal cell death induced by NMDA, and this effect was blocked by both lavendustin A and PP2. These data suggest that IL-1beta increases NMDA receptor function through activation of tyrosine kinases and subsequent NR2A/B subunit phosphorylation. These effects may contribute to glutamate-mediated neurodegeneration.

Interleukin-1beta enhances NMDA receptor-mediated intracellular calcium increase through activation of the Src family of kinases

Interleukin (IL)-1beta is a proinflammatory cytokine implicated in various pathophysiological conditions of the CNS involving NMDA receptor activation. Circumstantial evidence suggests that IL-1beta and NMDA receptors can functionally interact. Using primary cultures of rat hippocampal neurons, we investigated whether IL-1beta affects NMDA receptor function(s) by studying (1) NMDA receptor-induced [Ca2+]i increase and (2) NMDA-mediated neurotoxicity. IL1beta (0.01-0.1 ng/ml) dose-dependently enhances NMDA-induced [Ca2+]i increases with a maximal effect of approximately 45%. This effect occurred only when neurons were pretreated with IL-1beta, whereas it was absent if IL-1beta and NMDA were applied simultaneously, and it was abolished by IL-1 receptor antagonist (50 ng/ml). Facilitation of NMDA-induced [Ca2+]i increase by IL-1beta was prevented by both lavendustin (LAV) A (500 nm) and 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2) (1 microm), suggesting an involvement of tyrosine kinases. Increased tyrosine phosphorylation of NMDA receptor subunits 2A and 2B and coimmunoprecipitation of activated Src tyrosine kinase with these subunits was observed after exposure of hippocampal neurons to 0.05 ng/ml IL-1beta. Finally, 0.05 ng/ml IL-1beta increased by approximately 30% neuronal cell death induced by NMDA, and this effect was blocked by both lavendustin A and PP2. These data suggest that IL-1beta increases NMDA receptor function through activation of tyrosine kinases and subsequent NR2A/B subunit phosphorylation. These effects may contribute to glutamate-mediated neurodegeneration.

Association of interleukin-1 alpha gene polymorphism with cerebral infarction

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 ischemia. The expression of IL-1 in the brain is dramatically increased during the early and chronic stage of infarction. The IL-1 gene cluster on chromosome 2q14 contains three related genes (IL1alpha, IL1beta, and IL1 receptor antagonist) located within a 430-kb region. T and C alleles exist for the IL-1alpha-889 regulatory region and the TT genotype has been reported to increase the production of the protein in lipopolysaccharide (LPS)-stimulated mononuclear cells from IL-1alpha-889 TT carriers. We examined whether the IL-1alpha polymorphism affects the probability of cerebral infarction (CI). We genotyped 360 CI patients and 519 healthy controls for the same polymorphism. A significant increase was found for the IL-1alpha T allele in CI patients compared with controls (chi2=5.026, P=0.025). We conclude that the IL-1alpha-889 polymorphism is a major risk factor for CI in Koreans.

Interleukin-1 and neuronal injury: mechanisms, modification, and therapeutic potential

Interleukin-1 (IL-1) expression in the brain increases in response to acute and chronic insults, and IL-1 contributes directly to experimentally induced ischaemic, excitotoxic, and traumatic brain injury. Release and cleavage of active IL-1 beta may be achieved via purinergic P2X7 receptors and activation of caspase-1. The mechanisms of action of IL-1 are largely unknown, but may involve effects on glia, endothelia, and neurones, or on physical parameters within the brain such as temperature or acidity. The naturally occurring IL-1 receptor antagonist (IL-1ra) is currently being considered for treatment of stroke and other disorders.

Interleukin-1 in the brain: mechanisms of action in acute neurodegeneration

Interleukin-1 (IL-1) exerts a number of diverse actions in the brain, and it is currently well accepted that it contributes to experimentally induced neurodegeneration. Much of this is based on studies using the IL-1 receptor antagonist, which inhibits cell death caused by ischemia, brain injury, or excitotoxins. Our aim is to determine how and where in the brain IL-1 acts to produce these effects. Most of the neurodegenerative effects of IL-1 are thought to be through IL-1 beta. However, we have data implicating IL-1 alpha in excitotoxic cell death. Furthermore mice lacking both IL-1 alpha and IL-1 beta show dramatically reduced ischemic cell death, whereas deletion of IL-1 alpha or IL-1 beta alone fails to modify damage. It has also been demonstrated that IL-1 exacerbates ischemic injury in mice in the absence of the type I IL-1 receptor, suggesting the existence of novel IL-1 receptors in the brain. IL-1 also dramatically exacerbates neuronal loss in response to intrastriatal administration of the excitotoxin AMPA in the rat brain, an effect accompanied by marked increases in cytokine expression in the frontoparietal cortex, which precedes subsequent cell death in this region. Intrastriatal AMPA also results in limbic seizures that are exacerbated by IL-1, and we hypothesize, therefore, that IL-1 exacerbates cell death through increased seizure activity. Therefore, IL-1 appears to induce acute neurodegeneration through a number of mechanisms.

Acute neuroinflammation exacerbates excitotoxicity in rat hippocampus in vivo

Accumulating evidence suggests that inflammation may play an important part in neurodegenerative diseases such as Alzheimer's disease. Inflammation itself, however, is insufficient to produce acute neurodegeneration in vivo. In this report, we determined whether inflammation increases excitotoxicity in hippocampal neurons. A proinflammagen, bacterial endotoxin lipopolysaccharide, was coinjected with ibotenate, an N-methyl-D-aspartate receptor agonist, into rat hippocampus. One week after coinjection, significant neuronal degeneration and severe tissue collapse were observed in the hippocampus. Astroglial and microglial infiltration were also detected. The neurodegeneration was suppressed by dizocilpine maleate, an N-methyl-D-aspartate receptor antagonist. We then examined whether microglial activation takes part in synergistic neuronal loss. One day after the lipopolysaccharide injection into the rat hippocampus, substantial microglial activation and induction of inducible nitric oxide synthase were observed, while neither neuronal nor astrocytic changes were detected. On the other hand, ibotenate injection at the same place 1 day after lipopolysaccharide injection in the hippocampus produced significant neuronal degeneration and gross microglial activation. These results suggest that inflammation by lipopolysaccharide might play an important role in ibotenate/lipopolysaccharide neurotoxicity.

Role of nitric oxide in inflammation-mediated neurodegeneration

Increasing evidence has suggested that inflammation in the brain is closely associated with the pathogenesis of several degenerative neurologic disorders, including Parkinson's disease, Alzheimer's diseases, multiple sclerosis, amyotrophic lateral sclerosis, and AIDS dementia. The hallmark of brain inflammation is the activation of glial cells, especially that of microglia that produce a variety of proinflammatory and neurotoxic factors, including cytokines, fatty acid metabolites, free radicals--such as nitric oxide (NO) and superoxide. Excessive production of NO, as a consequence of nitric oxide synthase induction in activated glia, has been attributed to participate in neurodegeneration. Using primary mixed neuron-glia cultures and glia-enriched cultures prepared from embryonic rodent brain tissues, we have systemically studied the relationship between the production of NO and neurodegeneration in response to stimulation by the inflammagen lipopolysaccharide. This review summarizes our recent findings on the kinetics of NO generation, the relative contribution of microglia and astrocytes to NO accumulation, the relationship between NO production and neurodegeneration, and points of intervention along the pathways associated with NO generation to achieve neuroprotection. We also describe our results relating to the effect of several opioid-related agents on microglial activation and neuroprotection. Among these agents, the opioid receptor antagonist naloxone, especially its non-opioid enantiomer (+)-naloxone, promises to be of potential therapeutic value for the treatment of inflammation-related diseases.

Gulf war syndrome: could it be triggered by biological warfare-vaccines using pertussis as an adjuvant?

Several recent epidemiological studies have shown that vaccinations against biological warfare using pertussis as an adjuvant were associated with the Gulf war syndrome. If such epidemiological findings are confirmed, we propose that the use of pertussis as an adjuvant could trigger neurodegeneration through induction of interleukin-1beta secretion in the brain. In turn, neuronal lesions may be sustained by stress or neurotoxic chemical combinations. Particular susceptibility for IL-1beta secretion and potential distant neuronal damage could provide an explanation for the diversity of the symptoms observed on veterans.