Reduced postischemic apoptosis in the hippocampus of mice deficient in interleukin-1

Research Progress on the Role of Inflammatory Mechanisms in the Development of Postoperative Cognitive Dysfunction

Postoperative cognitive dysfunction (POCD), as one of the common postoperative complications, mainly occurs after surgery and anesthesia, especially in the elderly. It refers to cognitive function changes such as decreased learning and memory ability and inability to concentrate. In severe cases, there could be personality changes and a decline in social behavior. At present, a great deal of research had been carried out on POCD, but its specific mechanism remains unclear. The release of peripheral inflammation-related factors, the degradation and destruction of the blood-brain barrier, the occurrence of central inflammation, and the neuronal apoptosis and synaptic loss could be promoted by neuroinflammation indicating that inflammatory mechanisms may play key roles in the occurrence of POCD.

Decreased angiogenesis as a possible pathomechanism in cervical degenerative myelopathy

Endogenous immune mediated reactions of inflammation and angiogenesis are components of the spinal cord injury in patients with degenerative cervical myelopathy (DCM). The aim of this study was to identify alteration of certain mediators participating in angiogenetic and inflammatory reactions in patients with DCM. A consecutive series of 42 patients with DCM and indication for surgical decompression were enrolled for the study. 28 DCM patients were included, as CSF samples were taken preoperatively. We enrolled 42 patients requiring surgery for a thoracic abdominal aortic aneurysm (TAAA) as neurologically healthy controls. In 38 TAAA patients, CSF samples were taken prior to surgery and thus included. We evaluated the neurological status of patients and controls prior to surgery including NDI and mJOA. Protein-concentrations of factors with a crucial role in inflammation and angiogenesis were measured in CSF via ELISA testing (pg/ml): Angiopoietin 2, VEGF-A and C, RANTES, IL 1 beta and IL 8. Additionally, evaluated the status of the blood-spinal cord barrier (BSCB) by Reibers´diagnostic in all participants. Groups evidently differed in their neurological status (mJOA: DCM 10.1 ± 3.3, TAAA 17.3 ± 1.2, p < .001; NDI: DCM 47.4 ± 19.7, TAAA 5.3 ± 8.6, p < .001). There were no particular differences in age and gender distribution. However, we detected statistically significant differences in concentrations of mediators between the groups: Angiopoietin 2 (DCM 267.1.4 ± 81.9, TAAA 408.6 ± 177.1, p < .001) and VEGF C (DCM 152.2 ± 96.1, TAAA 222.4 ± 140.3, p = .04). DCM patients presented a mild to moderate BSCB disruption, controls had no signs of impairment. In patients with DCM, we measured decreased concentrations of angiogenic mediators. These results correspond to findings of immune mediated secondary harm in acute spinal cord injury. Reduced angiogenic activity could be a relevant part of the pathogenesis of DCM and secondary harm to the spinal cord.

Dim light at night impairs recovery from global cerebral ischemia

Nighttime lighting is one of the great conveniences of modernization; however, there is mounting evidence that inopportune light exposure can disrupt physiological and behavioral functions. Hospital patients may be particularly vulnerable to the consequences of light at night due to their compromised physiological state. Cardiac arrest/cardiopulmonary resuscitation (CA) was used to test the hypothesis in mice that exposure to dim light at night impairs central nervous system (CNS) recovery from a major pathological insult. Mice exposed to dim light at night (5 lx) had higher mortality in the week following cardiac arrest compared to mice housed in dark nights (0 lx). Neuronal damage was significantly greater in surviving mice exposed to dim light at night after CA versus those housed in dark nights. Dim light at night may have elevated neuronal damage by amplifying pro-inflammatory pathways in the CNS; Iba1 immunoreactivity (an indication of microglia activation) and pro-inflammatory cytokine expression were elevated in mice exposed to dim light at night post-CA. Furthermore, selective inhibition of IL-1β or TNFα ameliorated damage in mice exposed to dim light at night. The effects of light at night on CA outcomes were also prevented by using a wavelength of nighttime light that has minimal impact on the endogenous circadian clock, suggesting that replacing broad-spectrum nighttime light with specific circadian-inert wavelengths could be protective. Together, these data indicate that exposure to dim light at night after global cerebral ischemia increases neuroinflammation, in turn exacerbating neurological damage and potential for mortality.

Inhibition of p38 MAPK Signaling Regulates the Expression of EAAT2 in the Brains of Epileptic Rats

Seizures induce the release of excitatory amino acids (EAAs) from the intracellular fluid to the extracellular fluid, and the released EAAs primarily comprise glutamic acid (Glu) and asparaginic acid (Asp). Glu neurotransmission functions via EAA transporters (EAATs) to maintain low concentrations of Glu in the extracellular space and avoid excitotoxicity. EAAT2, the most abundant Glu transporter subtype in the central nervous system (CNS), plays a key role in the regulation of glutamate transmission. Previous studies have shown that SB203580 promotes EAAT2 expression by inhibiting the p38 mitogen-activated protein kinase (MAPK) signaling pathway, but whether SB203580 upregulates EAAT2 expression in epileptic rats is unknown. This study demonstrated that EAAT2 expression was increased in the brain tissue of epileptic rats. Intraperitoneal injection of a specific inhibitor of p38 MAPK, SB203580, reduced the time to the first epileptic seizure and attenuated the seizure severity. In addition, SB203580 treatment increased the EAAT2 expression levels in the brain tissue of epileptic rats. These results suggest that SB203580 could regulate epileptic seizures via EAAT2.

Spontaneous hypothermia ameliorated inflammation and neurologic deficit in rat cardiac arrest models following resuscitation

Cardiac arrest (CA) is a leading cause of mortality worldwide. The majority of the associated mortalities are caused by post-CA syndrome, which includes symptoms, such as neurologic damage, myocardial dysfunction and systemic inflammation. Following CA, return of spontaneous circulation (ROSC) leads to a brain reperfusion injury, which subsequently causes adverse neurologic outcomes or mortality. Therefore, investigating the underlying mechanisms of ROSC-induced neurologic deficits and establishing potential treatments is critical to prevent and treat post-CA syndrome. In the current study, CA rat models were established by asphyxia. Following ROSC, the temperature was controlled to achieve hypothermia. The general neurologic status was assessed using the neurologic deficit scale. Changes in the concentrations of interleukin (IL)-18 and IL-1β were measured with ELISA and the dynamic change in NACHT, LRR and PYD domains-containing protein 3 inflammasome components was determined by western blot analysis and immunohistochemistry. Neuronal death and apoptosis were measured via TUNEL assays. In the CA rat models, increasing the duration of CA before cardiopulmonary resuscitation was found to aggravate the neural deficit and increase the incidence of inflammation. Following ROSC, the expression level of the inflammasome components was observed to increase in CA rat models, which was accompanied by increased secretion of IL-18 and IL-1β, indicating the promotion of inflammation. In addition, the study identified the beneficial role of spontaneous hypothermia in ameliorating the ROSC-induced inflammation and neurologic deficit in CA rat models, including the downregulation of inflammasome components and attenuating neuronal apoptosis. The present study contributes to the understanding of underlying mechanisms in CA-evoked inflammation and the subsequent neurologic damage following ROSC. A novel potential therapeutic strategy that may increase survival times and the quality of life for patients suffering from post-CA syndrome is proposed in the present study.

Experimental animal models and inflammatory cellular changes in cerebral ischemic and hemorrhagic stroke

Stroke, including cerebral ischemia, intracerebral hemorrhage, and subarachnoid hemorrhage, is the leading cause of long-term disability and death worldwide. Animal models have greatly contributed to our understanding of the risk factors and the pathophysiology of stroke, as well as the development of therapeutic strategies for its treatment. Further development and investigation of experimental models, however, are needed to elucidate the pathogenesis of stroke and to enhance and expand novel therapeutic targets. In this article, we provide an overview of the characteristics of commonly-used animal models of stroke and focus on the inflammatory responses to cerebral stroke, which may provide insights into a framework for developing effective therapies for stroke in humans.

Activation of microglia induces symptoms of Parkinson's disease in wild-type, but not in IL-1 knockout mice

Background

Parkinson’s disease (PD) is an age-related progressive neurodegenerative disorder caused by selective loss of dopaminergic neurons from the substantia nigra (SN) to the striatum. The initial factor that triggers neurodegeneration is unknown; however, inflammation has been demonstrated to be significantly involved in the progression of PD. The present study was designed to investigate the role of the pro-inflammatory cytokine interleukin-1 (IL-1) in the activation of microglia and the decline of motor function using IL-1 knockout (KO) mice.

Methods

Lipopolysaccharide (LPS) was stereotaxically injected into the SN of mice brains as a single dose or a daily dose for 5 days (5 mg/2 ml/injection, bilaterally). Animal behavior was assessed with the rotarod test at 2 hr and 8, 15 and 22 days after the final LPS injection.

Results

LPS treatment induced the activation of microglia, as demonstrated by production of IL-1β and tumor necrosis factor (TNF) α as well as a change in microglial morphology. The number of cells immunoreactive for 4-hydroxynonenal (4HNE) and nitrotyrosine (NT), which are markers for oxidative insults, increased in the SN, and impairment of motor function was observed after the subacute LPS treatment. Cell death and aggregation of α-synuclein were observed 21 and 30 days after the final LPS injection, respectively. Behavioral deficits were observed in wild-type and TNFα KO mice, but IL-1 KO mice behaved normally. Tyrosine hydroxylase (TH) gene expression was attenuated by LPS treatment in wild-type and TNFα KO mice but not in IL-1 KO mice.

Conclusions

The subacute injection of LPS into the SN induces PD-like pathogenesis and symptoms in mice that mimic the progressive changes of PD including the aggregation of α-synuclein. LPS-induced dysfunction of motor performance was accompanied by the reduced gene expression of TH. These findings suggest that activation of microglia by LPS causes functional changes such as dopaminergic neuron attenuation in an IL-1-dependent manner, resulting in PD-like behavioral impairment.

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.

Therapeutic time window for edaravone treatment of traumatic brain injury in mice

Traumatic brain injury (TBI) is a major cause of death and disability in young people. No effective therapy is available to ameliorate its damaging effects. Our aim was to investigate the optimal therapeutic time window of edaravone, a free radical scavenger which is currently used in Japan. We also determined the temporal profile of reactive oxygen species (ROS) production, oxidative stress, and neuronal death. Male C57Bl/6 mice were subjected to a controlled cortical impact (CCI). Edaravone (3.0 mg/kg), or vehicle, was administered intravenously at 0, 3, or 6 hours following CCI. The production of superoxide radicals (O₂^∙−) as a marker of ROS, of nitrotyrosine (NT) as an indicator of oxidative stress, and neuronal death were measured for 24 hours following CCI. Superoxide radical production was clearly evident 3 hours after CCI, with oxidative stress and neuronal cell death becoming apparent after 6 hours. Edaravone administration after CCI resulted in a significant reduction in the injury volume and oxidative stress, particularly at the 3-hour time point. Moreover, the greatest decrease in O₂^∙− levels was observed when edaravone was administered 3 hours following CCI. These findings suggest that edaravone could prove clinically useful to ameliorate the devastating effects of TBI.

[Post-resuscitation syndrome. Role of inflammation after cardiac arrest]

Cardiac arrest with subsequent cardiopulmonary resuscitation causes an ischemic reperfusion syndrome of the whole body resulting in localized damage of particularly sensitive organs, such as the brain and heart, together with systemic sequelae. The main factor is a generalized activation of inflammatory reactions resulting in symptoms similar in many aspects to those of sepsis. Systemic inflammation strengthens organ damage due to disorders in the macrocirculation and microcirculation due to metabolic imbalance as well as the effects of direct leukocyte transmitted tissue destruction. The current article gives an overview on the role of inflammation following cardiac arrest and presents in detail the underlying mechanisms, the clinical symptoms and possible therapeutic approaches.

Interleukin-1 participates in the classical and alternative activation of microglia/macrophages after spinal cord injury

Background

Microglia and macrophages (MG/MΦ) have a diverse range of functions depending on unique cytokine stimuli, and contribute to neural cell death, repair, and remodeling during central nervous system diseases. While IL-1 has been shown to exacerbate inflammation, it has also been recognized to enhance neuroregeneration. We determined the activating phenotype of MG/MΦ and the impact of IL-1 in an in vivo spinal cord injury (SCI) model of IL-1 knock-out (KO) mice. Moreover, we demonstrated the contribution of IL-1 to both the classical and alternative activation of MG in vitro using an adult MG primary culture.

Methods

SCI was induced by transection of the spinal cord between the T9 and T10 vertebra in wild-type and IL-1 KO mice. Locomotor activity was monitored and lesion size was determined for 14 days. TNFα and Ym1 levels were monitored to determine the MG/MΦ activating phenotype. Primary cultures of MG were produced from adult mice, and were exposed to IFNγ or IL-4 with and without IL-1β. Moreover, cultures were exposed to IL-4 and/or IL-13 in the presence and absence of IL-1β.

Results

The locomotor activity and lesion area of IL-1 KO mice improved significantly after SCI compared with wild-type mice. TNFα production was significantly suppressed in IL-1 KO mice. Also, Ym1, an alternative activating MG/MΦ marker, did not increase in IL-1 KO mice, suggesting that IL-1 contributes to both the classical and alternative activation of MG/MΦ. We treated primary MG cultures with IFNγ or IL-4 in the presence and absence of IL-1β. Increased nitric oxide and TNFα was present in the culture media and increased inducible NO synthase was detected in cell suspensions following co-treatment with IFNγ and IL-1β. Expression of the alternative activation markers Ym1 and arginase-1 was increased after exposure to IL-4 and further increased after co-treatment with IL-4 and IL-1β. The phenotype was not observed after exposure of cells to IL-13.

Conclusions

We demonstrate here in in vivo experiments that IL-1 suppressed SCI in a process mediated by the reduction of inflammatory responses. Moreover, we suggest that IL-1 participates in both the classical and alternative activation of MG in in vivo and in vitro systems.

Oxygen resuscitation after hypoxia ischemia stimulates prostaglandin pathway in rat cortex

Exposure to hypoxia and hyperoxia in a rodent model of perinatal ischemia results in delayed cell death and inflammation. Hyperoxia increases oxidative stress that can trigger inflammatory cascades, neutrophil activation, and brain microvascular injury. Here we show that 100% oxygen resuscitation in our rodent model of perinatal ischemia increases cortical COX-2 protein levels, S-nitrosylated COX-2cys526, PGE2, iNOS and 5-LOX, all components of the prostaglandin and leukotriene inflammatory pathway.

Involvement of interleukin-1 in lipopolysaccaride-induced microglial activation and learning and memory deficits

We have developed an animal model of learning and memory impairment associated with activation of microglia in the mouse brain. Injection of lipopolysaccharide into the CA1 region of the mouse hippocampus resulted in an increased production of inflammatory cytokines, such as interleukin-1β. Immunostaining for interleukin-1β revealed an increase in the signal at 6 hr after lipopolysaccharide injection. Immunopositive cells for interleukin-1β were colocalized with those immunopositive for CD11b. When subacute lipopolysaccharide treatment (20 μg/2 μl/injection, bilaterally for 5 consecutive days) was performed, long-term activation of microglia and learning and memory deficits as evaluated using a step-through passive avoidance test were observed in the wild-type mice. Gene expression of the N-methyl-D-aspartate receptor NR1 and NR2A subunits was also decreased by the lipopolysaccharide treatment. In contrast, activation of microglia and the associated behavioral deficits were not observed in mice lacking interleukin-1α and -1β following the subacute lipopolysaccharide treatment, together with little change in the gene expression of NR1 and NR2A subunits. However, the subacute lipopolysaccharide treatment produced almost similar changes in those parameters in the tumor necrosis factor-α knockout mice as in the wild-type animals. The injection of interleukin-1β neutralizing antibody with lipopolysaccharide for 5 consecutive days resulted in the improvement of lipopolysaccharide-induced learning and memory deficits. These findings suggest that the expression of interleukin-1 plays an important role in lipopolysaccharide-induced activation of microglia and the associated functional deficits in learning and memory.

Brain plasticity after ischemic episode

Brain plasticity describes the potential of the organ for adaptive changes involved in various phenomena in health and disease. A substantial amount of experimental evidence, received in animal and cell models, shows that a cascade of plastic changes at the molecular, cellular, and tissue levels, is initiated in different regions of the postischemic brain. Underlying mechanisms include neurochemical alterations, functional changes in excitatory and inhibitory synapses, axonal and dendritic sprouting, and reorganization of sensory and motor central maps. Multiple lines of evidence indicate numerous points in which the process of postischemic recovery may be influenced with the aim to restore the full capacity of the brain tissue injured by an ischemic episode.

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.

Increased mitochondrial DNA oxidative damage after transient middle cerebral artery occlusion in mice

Oxidative stress and DNA oxidation play important roles in the induction of ischemic neuronal cell death. However, the subcellular source of oxidized DNA detected by 8-hydroxy-2'-deoxyguanosine (8-OHdG) after ischemia has not been clarified although it is known to increase in the brain after ischemia. One-hour transient ischemia of the middle cerebral artery was induced in mice utilizing an intraluminal filament. The occurrence of superoxide anion as an ethidium (Et) signal, 8-OHdG, cytochrome c release and neuronal cell death were examined using immunohistological and biochemical techniques in sham-operated control (0h) and 1, 3, 6, 24, or 96h after reperfusion. Et signals were prominent in the cortical neurons of ipsilateral hemisphere 3h after reperfusion. Strong 8-OHdG immunoreactivity was observed 3-6h after reperfusion. Immunoassays after cell fractionation revealed a significant increase of 8-OHdG in mitochondria 6h after reperfusion. Immunohistochemistry revealed that the 8-OHdG immunoreactivity colocalized with a neuronal marker, microfilament 200 and a mitochondrial marker, cytochrome oxidase subunit I. Cytochrome c rose in cytoplasm at 6h and TUNEL-positive neurons noted 6-24h after ischemia. The present results suggest the possibility that the mitochondrial damage including mitochondrial DNA oxidation might be responsible for the induction of ischemic neuronal cell death.

CSF orexin A concentrations and expressions of the orexin-1 receptor in rat hippocampus after cardiac arrest

Orexins/hypocretins are neuropeptides that have various physiological effects, including the regulation of feeding behavior, neuroendocrine functions and sleep-wake cycles. Recent studies have suggested that the orexin system may also be involved in brain ischemic reactions. It is also known that changes in sleep patterns, energy homeostasis and neuroendocrine functions are often occur in neurological conditions associated brain ischemia. In the current study, we investigated the time-dependent changes in cerebrospinal fluid (CSF) orexin-A concentration and the expression of the orexin-1 receptor (OX1R) in the rat hippocampus after global ischemia-reperfusion (5 min cardiopulmonary arrest), which is known to induce delayed cell death in the CA1 region of the hippocampus. The CSF orexin-A concentration was elevated transiently at 24 h after ischemia. On days 2 and 4 after ischemia, CSF orexin concentrations were significantly reduced relative to the baseline, and returned to the baseline level by day 7. These changes were correlated with increased expression of OX1R in the CA1 on days 1 and 2 post-ischemia. These results suggest that dynamics of orexin signaling observed may have functional roles for neuronal damage associated with transient ischemia.

Pentoxifylline decreases up-regulated nuclear factor kappa B activation and cytokine production in the rat retina following transient ischemia

AIM

To investigate whether pentoxifylline (PTX) could influence the increased cytokine gene expression in the retina flowing transient ischemia, and if so, whether it acts through the modulation of nuclear factor kappa B (NF-kappaB) activation.

METHODS

Sprague-Dawley rats were randomly divided into three equal groups: control group, saline-treated group, and PTX-treated group. Increased intraocular pressure was applied for 90 min to induce retinal ischemia, and reperfusion was established by lowering the bottle to eye level. The reperfusion period lasted for 48 h. In the PTX-treated group, an initial dose of 20 mg PTX was injected via tail vein at the beginning of reperfusion. Then the rat received infusion of PTX at a rate of 6 mg/kg/h throughout the entire reperfusion period. The retinal tissues were collected at the end of 1, 6, 12, 24, and 48 h of reperfusion, respectively, for biochemical analysis. Histological examination was done on the tissues collected at the end of 48 h after reperfusion.

RESULTS

Histological examination revealed reduction of overall retinal thickness and thinning of the inner retinal layer in saline-treated rats after 48-hour reperfusion. However, PTX treatment significantly reduced the loss of overall retinal thickness and thinning of inner retinal layers. Dramatic increase in NF-kappaB activation, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) production and mRNA expression were observed in the saline-treated group after reperfusion, with the peak reached around 12 h. In the PTX-treated group, NF-kappaB activation, TNF-alpha and IL-1beta production and mRNA expression were significantly reduced at each corresponding time point compared to the saline-treated group.

CONCLUSION

PTX decreased the up-regulated activation of NF-kappaB and the expression of proinflammatory cytokines, TNF-alpha and IL-1beta in rat retinas following ischemia/reperfusion. This may contribute to significantly reduce the loss of overall retinal thickness and thinning of inner retinal layers.

Pharmacological brain cooling with indomethacin in acute hemorrhagic stroke: antiinflammatory cytokines and antioxidative effects

We evaluated the effects of a novel pharmacological brain cooling (PBC) method with indomethacin (IND), a nonselective cyclooxygenase inhibitor, without the use of cooling blankets in patients with hemorrhagic stroke. Forty-six patients with hemorrhagic stroke (subarachnoid hemorrhage; n = 35, intracerebral hemorrhage; n = 11) were enrolled in this study. Brain temperature was measured directly with a temperature sensor. Patients were cooled by administering transrectal IND (100 mg) and a modified nasopharyngeal cooling method (positive selective brain cooling) initially. Brain temperature was controlled with IND 6 mg/kg/day for 14 days. Cerebrospinal fluid concentrations of interleukin-1beta (CSF IL-1beta) and serum bilirubin levels were measured at 1, 2, 4, and 7 days. The incidence of complicating symptomatic vasospasm after subarachnoid hemorrhage was lower than in non-PBC patients. CSF IL-1beta and serum bilirubin levels were suppressed in treated patients. IND has several beneficial effects on damaged brain tissues (anticytokine, free radical scavenger, antiprostaglandin effects, etc.) and prevents initial and secondary brain damage. PBC treatment for hemorrhagic stroke in patients appears to yield favorable results by acting as an antiinflammatory cytokine and reducing oxidative stress.

Controlled normothermia during ischemia is important for the induction of neuronal cell death after global ischemia in mouse

A stable model of neuronal damage after ischemia is needed in mice to enable progression of transgenic strategies. We performed transient global ischemia induced by common carotid artery occlusions with and without maintaining normal rectal temperature (Trec) in order to determine the importance of body temperature control during ischemia. We measured brain temperature (Tb) during ischemia/reperfusion. Mice with normothermia (Trec within +/- 1 degrees C) had increased mortality and neuronal cell death in the CA1 region of hippocampus, which did not occur in hypothermic animals. If the Trec was kept within +/- 1 degrees C, the Tb decreased during ischemia. After reperfusion, Tb in the normothermia group developed hyperthermia, which reached > 40 degrees C and was > 2 degrees C higher than Trec. We suggest that tightly controlled normothermia and prevention of hypothermia (Trec) during ischemia are important factors in the development of a stable neuronal damage model in mice.

Lipopolysaccharide-induced microglial activation induces learning and memory deficits without neuronal cell deathin rats

We used lipopolysaccharide (LPS) to activate microglia that play an important role in the brain immune system. LPS injected into the rat hippocampus CA1 region activated microglial cells resulting in an increased production of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha in the hippocampus during the initial stage of treatment. Immunostaining for IL-1beta was increased at 6 hr after LPS injection. IL-1beta-immunopositive cells were co-localized with immunostaining for CD11b. Subacute treatment with LPS by the same route for 5 days caused long-term activation of microglia and induced learning and memory deficits in animals when examined with a step-through passive avoidance test, but histochemical analysis showed that neuronal cell death was not observed under these experimental conditions. The increased expression of the heme oxygenase-1 (HO-1) gene, an oxidative stress maker, was observed. However, the genetic expression of brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, decreased during the course of LPS treatment. We found decreases in [3H]MK801 binding in the hippocampus CA1 region by LPS-treatment for 5 days. The data shows that glutamatergic transmission was attenuated in the LPS-treated rats. These results suggest that long-term activation of microglia induced by LPS results in a decrease of glutamatergic transmission that leads to learning and memory deficits without neuronal cell death. The physiologic significance of these findings is discussed.

Status epilepticus induces time-dependent neuronal and astrocytic expression of interleukin-1 receptor type I in the rat limbic system

Interleukin-1beta is rapidly synthesized by glia after the induction of seizures. Recent evidence shows that endogenous IL-1beta has proconvulsant actions mediated by interleukin-1 receptor type I. This receptor also mediates interleukin-1beta effects on neuronal susceptibility to neurotoxic insults. In this study, we investigated the basal and seizure-induced expression of interleukin-1 receptor type I in rat forebrain to identify the cells targeted by interleukin-1beta during epileptic activity. Self-sustained limbic status epilepticus was induced in rats by electrical stimulation of the ventral hippocampus. Interleukin-1 receptor type I immunoreactivity was barely detectable in neurons in control brain tissue. During status epilepticus, interleukin-1 receptor type I was induced in the hippocampal neurons firstly, and several hours later in astrocytes localized in limbic and extralimbic areas. Neuronal interleukin-1 receptor type I expression in the hippocampus outlasted the duration of spontaneous electroencephalographic seizure and was not observed in degenerating neurons. Astrocytic expression occurred transiently, between six and 18 h after the induction of status epilepticus and was invariably found in regions of neuronal damage. These time-dependent, cell- and region-specific changes in interleukin-1 receptor type I expression during status epilepticus suggest that interleukin-1 receptor type I in neurons mediates interleukin-1beta-induced fast changes in hippocampal excitability while interleukin-1 receptor type I receptors in astrocytes may mediate interleukin-1beta effects on neuronal survival in hostile conditions.

Inflammation in areas of remote changes following focal brain lesion

Focal brain lesions can lead to metabolic and structural changes in areas distant from but connected to the lesion site. After focal ischemic or excitotoxic lesions of the cortex and/or striatum, secondary changes have been observed in the thalamus, substantia nigra pars reticulata, hippocampus and spinal cord. In all these regions, inflammatory changes characterized by activation of microglia and astrocytes appear. In the thalamus, substantia nigra pars reticulata and hippocampus, an expression of proinflammatory cytokine like tumor necrosis factor-alpha and interleukin-1beta is induced. However, time course of expression and cellular localisation differ between these regions. Neuronal damage has consistently been observed in the thalamus, substantia nigra and spinal cord. It can be present in the hippocampus depending on the procedure of induction of focal cerebral ischemia. This secondary neuronal damage has been linked to antero- and retrograde degeneration. Anterograde degeneration is associated with somewhat later expression of cytokines, which is localised in neurons. In case of retrograde degeneration, the expression of cytokines is earlier and is localised in astrocytes. Pharmacological intervention aiming at reducing expression of tumor necrosis factor-alpha leads to reduction of secondary neuronal damage. These first results suggest that the inflammatory changes in remote areas might be involved in the pathogenesis of secondary neuronal damage.

Orexin-1 receptor expression after global ischemia in mice

Orexins are neuropeptides that have a range of physiological effects including the regulation of feeding behavior and the sleep-wakefulness cycle. Recently, we reported that level of orexin A in spinal fluid was decreased in the patients of some neurodegenerative diseases and it is considered that orexin A and the receptors might be related to central nervous system disorders. However, the expression and localization of orexin receptors is not elicited well. Therefore, the purpose of this study is to investigate the time-dependent changes and the cellular localization of orexin receptor focusing on orexin-1 receptor (OX1R) in the mouse brain after transient common carotid artery occlusion (tCCAO) model by using immunohistochemical techniques. OX1R immunoreactivity dramatically increased and peaked in the hippocampus and cortex 2 days after tCCAO, but remained unchanged in the hypothalamus. Using double-immunohistochemistry, the OX1R immunopositive cells at 2 days after tCCAO were co-localized not only with neuronal marker, NeuN-immunoreactivity but also with astroglial and oligodendroglial markers, GFAP- and CNPase-immunoreactivities, respectively. These results suggested that OX1R is induced other cells in addition to the neurons during stress such as ischemia and orexins and its receptor might play an important role for ischemic insult.

Activation of nuclear factor-kappaB signaling pathway by interleukin-1 after hypoxia/ischemia in neonatal rat hippocampus and cortex

Perinatal hypoxia/ischemia (HI) is a common cause of neurological deficits in children. Interleukin-1 (IL-1) activity has been implicated in HI-induced brain damage. However, the mechanisms underlying its action in HI have not been characterized. We used a 7-day-old rat model to elucidate the role of nuclear factor-kappaB (NF-kappaB) activation in HI stimulation of IL-1 signaling. HI was induced by permanent ligation of the left carotid artery followed by 90 min of hypoxia (7.8% O(2)). Using ELISA assays, we observed increased cell death and caspase 3 activity in hippocampus and cortex 3, 6, 12, 24 and 48 h post-HI. IL-1beta protein expression increased, beginning at 3 h after HI and lasting until 24 h post-HI in hippocampus and 12 h post-HI in cortex. Intracerebroventricular injection of 2 microg IL-1 receptor antagonist (IL-1Ra) 2 h after HI significantly reduced cell death and caspase 3 activity. Electrophoretic mobility shift assay analyses of hippocampus and cortex after HI for NF-kappaB activity showed increased p65/p50 DNA-binding activity at 24 h post-HI. Western blot analyses showed significant nuclear translocation of p65. Protein expression levels of two known inflammatory agents, inducible nitric oxide synthase and cycloxygenase 2, known to be transcriptionally regulated by NF-kappaB, also increased at 24 h after HI. All these HI-induced changes were reversed by IL-1Ra blockade of IL-1 signaling, consistent with IL-1 triggering of inflammatory apoptotic outcomes via NF-kappaB transcriptional activation. The observed increase in cytoplasmic phosphorylated inhibitor kappaBalpha (IkappaBalpha) and nuclear translocation of Bcl-3 24 h after HI was also significantly attenuated by IL-1Ra blockade, suggesting that HI-induced IL-1 activation of NF-kappaB is via both the degradation of IkappaBalpha and the nuclear translocation of Bcl-3.

Inhibitors of iNOS protects PC12 cells against the apoptosis induced by oxygen and glucose deprivation

It has been shown that deletion of the gene encoding the inducible form of nitric oxide synthase (iNOS) results in a reduction of ischemia-induced apoptotic cell death, suggesting the detrimental role of iNOS. The signaling pathways by which iNOS mediates apoptotic cell death under ischemic conditions remain unclear. Understanding the molecular mechanisms of iNOS-mediated apoptotic cell death in ischemia may offer opportunities for potential therapeutic intervention. In the current study, undifferentiated rat pheochromocytoma PC12 cells, exposed to oxygen and glucose deprivation (OGD) followed by reperfusion (adding back oxygen and glucose, OGD-R), were used as an in vitro model of ischemia. The iNOS expression and activity were increased during OGD-R. OGD-R-induced apoptosis was demonstrated by the increase of LDH release, cytosolic release of cytochrome C and caspase-3 activity. Inhibition of iNOS activity by selective iNOS inhibitors, aminoguanidine and 1400W, reduces OGD-R-induced apoptotic cell death, as demonstrated by the decrease of LDH release, cytochrome C release, and caspase-3 activity. These results suggest the critical role of iNOS in mediating apoptosis under ischemic conditions, likely through the induction of caspase-3 activity.

Tenoxicam Exerts a Neuroprotective Action after Cerebral Ischemia in Rats

In this study we investigated the effects of Tenoxicam, a type 2 cyclooxygenase (COX-2) inhibitor, on brain damage induced by ischemia-reperfusion. Male Wistar rats (18-month old average) were anesthetized and submitted to ischemia occlusion of both common carotid arteries (BCAO) for 45 min. After 24 h of reperfusion, rats were decapitated and hippocampi removed for further assays. Animals were divided into sham-operated, ischemia, ischemia + Tenoxicam 2.5 mg/kg, and ischemia + Tenoxicam 10 mg/kg groups. Tenoxicam was administered intraperitoneally immediately after BCAO. Histological analyses show that ischemia produced significant striatal as well as hippocampal lesions which were reversed by the Tenoxicam treatment. Tenoxicam also significantly reduced, to control levels, the increased myeloperoxidase activity in hippocampus homogenates observed after ischemia. However, nitrite concentrations showed only a tendency to decrease in the ischemia + Tenoxicam groups, as compared to that of ischemia alone. On the other hand, hippocampal glutamate and aspartate levels were not altered by Tenoxicam. In conclusion, we showed that ischemia is certainly related to inflammation and to increased free radical production, and selective COX-2 inhibitors might be neuroprotective agents of potential benefit in the treatment of cerebral brain ischemia.

Mechanism for IL-1 beta-mediated neovascularization unmasked by IL-1 beta knock-out mice

We have reported that interleukin-1 beta (IL-1 beta) upregulates cardiac expression of vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2), raising the possibility that IL-1 beta plays an important role in VEGF-mediated neovascularization. In this study, we examined the cellular mechanism for ischemia-induced neovascularization using IL-1 beta knock-out (-/-) mice. Recovery of blood perfusion in ischemic hindlimb in IL-1 beta-/- mice was markedly (43% decrease) impaired as compared with the wild-type mice. CD31(+) vessel numbers and Ki-67(+) neo-capillaries were significantly (P < 0.01) decreased 44% and 68%, respectively. IL-1 beta expression was localized in the capillary vessels in ischemic limb muscles. Ischemia-induced expressions of hypoxia-inducible factor 1 alpha (HIF-1 alpha), VEGF, its receptor VEGFR-2 and vascular cell adhesion molecule-1 (VCAM-1) were markedly inhibited in the IL-1 beta-/- mice. Hindlimb ischemia-induced an increase (1.22% out of total nuclear cell) in CD34(-)/B220(-)/CD3(-)/Flk-1(+) hematopoietic stem cell population in peripheral blood in the wild-type mice, whereas in the IL-1 beta-/- mice such increase was only 0.09%. Injection of IL-1 beta protein into the wild-type mice markedly increased the ratio of the CD34(-)/B220(-)/CD3(-)/Flk-1(+) cell population (from 0.03% to 0.7%) in the peripheral blood associated with an increase in the number of endothelial cells. Such IL-1 beta-mediated increases in cell numbers were blocked by co-injection of anti-VEGF antibody. CD34(-)/B220(-)CD3(-)Flk-1(+) cells trans-differentiated into eNOS- and CD31-expressing endothelial cells in vivo and in vitro. This study demonstrates that IL-1 beta plays a key role in ischemia-induced neovascularization by mobilizing CD34(-)/B220(-)CD3(-)Flk-1(+) endothelial precursor cells in a VEGF-dependent manner as well as by upregulating expressions of VEGF, VEGFR-2 and adhesion molecules on endothelial cells.

Histopathological and behavioral characterization of a novel model of cardiac arrest and cardiopulmonary resuscitation in mice

Cardiac arrest is associated with high mortality and poor neurological outcome. We characterized functional and histological outcome in a novel mouse model of cardiac arrest and cardiopulmonary resuscitation (CPR) in order to study neuroprotective mechanisms. Cardiac arrest was induced in male C57Bl/6 and 129SVEV mice by i.v. injection of KCl. After 10 min cardiac standstill, CPR was initiated by administration of epinephrine, ventilation with 100% oxygen and chest compressions. Twenty-four hours before and 3 or 7 days after CPR, mice were subjected to behavioral testing using a passive avoidance task, locomotor activity in an open field, and spontaneous alternation in a T-maze. Hippocampal and caudoputamen injury was quantified 3 or 7 days after CPR. At both time points, caudoputamen injury was worse in 129SVEV mice. Post-ischemic mice of both strains showed a reduced number of correct choices in the T-maze up to 7 days after CPR, and were temporarily impaired in learning the passive avoidance task with a retention deficit on day 3 but not on day 7. Locomotor activity showed strain differences with C57Bl/6 mice being more active, but little ischemia-related effects. A dissociation between functional and histological outcome was found emphasizing the importance of combining both outcome measures for evaluation of neuroprotective strategies.

Vasoconstriction caused by cocaine is enhanced by sodium salicylate: is inducible nitric oxide synthase mRNA related?

We have previously found that sodium salicylate (NaSal), injected into chicken eggs at nontoxic doses used for quantifying hydroxyl free radicals in hearts and brains of embryos, caused or exacerbated hemorrhages and dramatically reduced hatchability when combined with cocaine (Coc). It has also been reported that inducible nitric oxide synthase (iNOS) gene expression is altered in brain in response to vascular damage and inflammation. In this study we measured diameters of membrane-bound blood vessels (BV) before and after pretreatment with saline (NaCl) or NaSal (100 mg/kg egg), followed by infusion of either NaCl or Coc HCl (total of 67.5 mg/kg egg) during 15 min. Brains and hearts of the embryos were then analyzed for iNOS messenger RNA (mRNA) concentrations. Coc caused vasoconstriction that was significant 5 min postinfusion (5 min PI) of the entire dose (ie after 67.5 mg/kg egg). Significant vasoconstriction was evident within 5 min in the group injected with NaSal followed by infusion with Coc (ie after 22.5 mg Coc/kg egg). Expression of iNOS mRNA was significantly increased only in the brains of the group exposed to NaSal plus Coc, and the increase was inversely related to BV diameter. These data are discussed in relation to effects of salicylate upon prostanoid synthesis and/or nitric oxide synthesis via iNOS inhibition and their possible relationship to Coc-associated cerebral vascular and/or cardiovascular events in abusing humans.

Neuroprotective efficacy and therapeutic time window of peroxynitrite decomposition catalysts in focal cerebral ischemia in rats

Free radicals have been implicated in cerebral ischemia reperfusion (IR) injury. Massive production of nitric oxide and superoxide results in continuous formation of peroxynitrite even several hours after IR insult. This can produce DNA strand nicks, hydroxylation and/or nitration of cytosolic components of neuron, leading to neuronal death. Peroxynitrite decomposition catalysts 5,10,15,20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron (III) (FeTMPyP) and 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) (FeTPPS) have been demonstrated to protect neurons in in vitro cultures; however, their neuroprotective efficacy in cerebral IR injury has not been explored. In the present study, we investigated the efficacy and the therapeutic time window of FeTMPyP and FeTPPS in focal cerebral ischemia (FCI). FCI was induced according to the middle cerebral artery occlusion (MCAO) method. After 2 h of MCAO and 70 h of reperfusion, the extent of neurological deficits, infarct and edema volume were measured in Sprague-Dawley rats. FeTMPyP and FeTPPS were administered at different time points 2, 6, 9 and 12 h post MCAO. FeTMPyP and FeTPPS (3 mg kg(-1), i.v.) treatment at 2 and 6 h post MCAO produced significant reduction in infarct volume, edema volume and neurological deficits. However, treatment at latter time points did not produce significant neuroprotection. Significant reduction of peroxynitrite in blood and nitrotyrosine in brain sections was observed on FeTMPyP and FeTPPS treatment. As delayed treatment of FeTMPyP and FeTPPS produced neuroprotection, we tested whether treatment had any influence over the apoptotic neuronal death. DNA fragmentation and in situ nick end-labeling assays showed that FeTMPyP and FeTPPS treatment reduced IR injury-induced DNA fragmentation. In conclusion, peroxynitrite decomposition catalysts (FeTMPyP and FeTPPS) produced prominent neuroprotection even if administered 6 h post MCAO and the neuroprotective effect is at least in part due to the reduction of peroxynitrite and apoptosis.

IL-1 and TNF-α Play a Pivotal Role in the Host Immune Response in a Mouse Model ofStaphylococcus aureus-Induced Experimental Brain Abscess

Brain abscesses represent a significant medical problem despite recent advances made in detection and therapy. Using an established Staphylococcus aureus-induced brain abscess model, we have sought to define the functional importance of interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and IL-6 in the host anti-bacterial immune response using cytokine gene knockout (KO) mice. Previous studies from our laboratory revealed that these cytokines are among the main proinflammatory mediators produced during the acute stage of brain abscess development. The results presented here demonstrate that although they share many redundant activities, IL-1 and TNF-alpha are important for containing bacterial infection in evolving brain abscesses as evident by increased mortality and bacterial burdens in IL-1 and TNF-alpha KO mice compared to wild type (WT) animals. In contrast, IL-6 was not found to be a major contributor to the host anti-bacterial immune response. Microarray analysis was used to evaluate the downstream consequences originating from the lack of IL-1 on subsequent proinflammatory mediator expression in brain abscesses from IL-1 KO and WT animals. Although numerous genes were significantly induced following S. aureus infection, only IL-1beta and 2 chemokines, CCL9 (macrophage inflammatory protein-1 gamma/MIP-1gamma) and CXCL13 (B lymphocyte chemoattractant/BLC), were differentially regulated in IL-1 KO versus WT animals. These results suggest that IL-1 and TNF-alpha play a pivotal role during the acute stage of brain abscess development through regulating the ensuing anti-bacterial inflammatory response.

[Prevention of delayed neuronal cell death by PACAP and its molecular mechanism]

Ischemic delayed neuronal cell death (apoptosis) in the hippocampus is prevented by PACAP. PACAP inhibits the increasing activity of the MAP kinase family, especially on JNK/SAPK and p38, thereby protecting against apoptotic cell death. After the ischemia-reperfusion, both pyramidal cells and astrocytes increased their expression of PACAP receptors (PAC1-Rs). The pyramidal cells degenerated but reactive astrocytes increased their expression of PAC1-R. PACAP does not only inhibit apoptotic cell death directly, but also affects astrocytes through PAC1-Rs. Interleukin-6 (IL-6), produced in astrocytes, has several effects on the prevention of brain ischemia and trauma and stimulating neuronal growth. IL-6 secretion into the CSF was markedly stimulated after PACAP infusion, suggesting that PACAP stimulates IL-6 secretion from astrocytes. We studied the effects of PACAP on the wild type and IL-6 KO mice after brain ischemia. In wild-type animals, PACAP significantly inhibited cell death, but in IL-6 KO animals, no cytoprotective effect of PACAP was seen. These results suggest that PACAP inhibits apoptotic cell death partly through IL-6. It is considered that PACAP itself and IL-6, stimulated secretion by PACAP, both synergistically inhibit the JNK/SAPK and p38 signaling pathway, thereby protecting against neuronal cell death.

Cardiac arrest/cardiopulmonary resuscitation increases anxiety-like behavior and decreases social interaction

Advances in medical technology have increased the number of individuals who survive cardiac arrest/cardiopulmonary resuscitation (CPR). This increased incidence of survival has created a population of patients with behavioral and physiologic impairments. We used temperature manipulations to characterize the contribution of central nervous system damage to behavioral deficits elicited by 8 minutes of cardiac arrest/CPR in a mouse model. Once sensorimotor deficits were resolved, we examined anxiety-like behavior with the elevated plus maze and social interaction with an ovariectomized female. We hypothesized that anxiety-like behavior would increase and social interaction would decrease in mice subjected to cardiac arrest/CPR and that these changes would be attributable to central nervous system damage rather than damage to peripheral organs or changes orchestrated by the administration of epinephrine. Mice that were subjected to cardiac arrest/CPR while the peripheral organs, but not the brain, were protected by hypothermia exhibited increased anxiety-like behavior and decreased social interaction, whereas mice with hypothermic brains and peripheral organs during cardiac arrest/CPR did not exhibit behavioral impairments. The present study demonstrates that central nervous system damage from cardiac arrest/CPR results in increased anxiety and decreased social interaction and that these behavioral changes are not attributed to underlying sensorimotor deficits, dynamics of arrest and CPR, or peripheral organ damage.

Peroxynitrite and caspase-3 expression after ischemia/reperfusion in mouse cardiac arrest model

NO is a putative neurotransmitter and neuromodulator in the brain. NO is not functioning as a direct neurotoxin. NO with the superoxide radical product peroxynitrite (ONOO-) is much more cytotoxic under tissue impairment conditions. Caspase-3, a potent effector of apoptosis that is triggered via several different signaling pathways, may play a very important role in neuronal cell death caused by various brain injuries. The relationship between mouse caspase-3 and peroxynitrite remains unclear. In the present study, we examined the in vivo expression of 3-nitrotyrosine (a metabolite of peroxinitrite) and caspase-3 after cerebral ischemia produced in a global ischemia model using mice (i.e., a cardiac arrest model). 3-nitrotyrosine immunoreactivity was detected in neuronal cells in the hippocampal dentate nucleus, and cortical regions starting at 12 hrs after ischemia. In particular, numerous neuronal cells were highly immunoreactive for 3-nitrotyrosine in the cortical regions. In hippocampal CA1 pyramidal neurons, 3-nitrotyrosine immunoreactivity was detected from 24 hrs. Caspase-3 immunopositive cells were observed in approximately the same area in which the positive reaction to the anti-nitrotyrosine antibody was observed. These results provide direct evidence for the induction of 3-nitrotyrosine and caspase-3 expression in vivo in an ischemia model using mice. The present findings suggest that peroxynitrite generated by cerebral ischemia/ reperfusion was strongly cytotoxic and induced neuronal cell death (apoptosis) mediated by caspase-3.

Suppression of oxidative stress after transient focal ischemia in interleukin-1 knock out mice

Interleukin-1 (IL-1) contributes to ischemic neurodegeneration. However, the mechanisms regulating action of IL-1 are still poorly understood. In order to clarify this central issue, mice that were gene deficient both IL-1alpha and beta (IL-1 KO) and wild-type mice were subjected to 1 hour transient middle cerebral artery occlusion (tMCAO). The concentration of 8-hydroxy deoxyguanosine (8OHdG) which is considered to be a reliable oxidative DNA damage by superoxide anion, in brain and of total nitric oxide (NO) in plasma were determined by use of HPLC. Twenty-four hours after tMCAO, the ratio of 8OHdG to dG in the ipsilateral hemisphere of wild-type mice were 2.24 x 10(-3) and 4.41 x 10(-3) in the neocortex and striatum, respectively. The concentration of 8OHdG in the ipsilateral hemisphere of the wild-type mice was higher than that of the IL-1 KO mice. The concentration of total NO in the plasma of IL-1 KO mice was also lower than that of the wild-type 24 hours after tMCAO. These results strongly suggest that IL-1 is participated in generating reactive oxygen spices and it aggravates and induces the ischemic neuronal cell death.(183 words).

Evaluation of neuronal cell death after a new global ischemia model in infant mice

For the first time we set up a new model for global ischemia in the infant mice, and time-dependent changes of the blood-brain barrier (BBB) disruption and neuronal cell death were investigated in detail. Infant C57/B16 mice (postnatal 13 days) were anesthetized with inhalation of sevoflurane in N2O/O2 (70/30%) and were subjected to global ischemia by bilateral common carotid artery occlusion (CCAO) for 25 minutes. Disruption of BBB was noted at 4 hours and increased up to 24 hours after the injection of 2% Evan's Blue in the transient CCAO (tCCAO) model. Evaluation of neuronal cell death was determined with toluidine blue staining. Morphological changes of neurons after tCCAO were clearly observed in the hippocampal CA1 region but were slightly detected in the CA3 region. However, there were no morphological changes in the hippocampal dentate gyrus, the neocortex, the striatum and the hypothalamus. The number of survival neurons in the CA1 was significantly decreased at 2 days and sustained up to 4 days after tCCAO. These data indicate that this method is very useful to induce selective vulnerability in mouse hippocampus, and it provides a reliable ischemic model in infant mice.

Retinal ischemia: mechanisms of damage and potential therapeutic strategies

Retinal ischemia is a common cause of visual impairment and blindness. At the cellular level, ischemic retinal injury consists of a self-reinforcing destructive cascade involving neuronal depolarisation, calcium influx and oxidative stress initiated by energy failure and increased glutamatergic stimulation. There is a cell-specific sensitivity to ischemic injury which may reflect variability in the balance of excitatory and inhibitory neurotransmitter receptors on a given cell. A number of animal models and analytical techniques have been used to study retinal ischemia, and an increasing number of treatments have been shown to interrupt the "ischemic cascade" and attenuate the detrimental effects of retinal ischemia. Thus far, however, success in the laboratory has not been translated to the clinic. Difficulties with the route of administration, dosage, and adverse effects may render certain experimental treatments clinically unusable. Furthermore, neuroprotection-based treatment strategies for stroke have so far been disappointing. However, compared to the brain, the retina exhibits a remarkable natural resistance to ischemic injury, which may reflect its peculiar metabolism and unique environment. Given the increasing understanding of the events involved in ischemic neuronal injury it is hoped that clinically effective treatments for retinal ischemia will soon be available.

Nucleoprotamine diet derived from salmon soft roe protects mouse hippocampal neurons from delayed cell death after transient forebrain ischemia

The nutritional benefits of nucleoprotamine (NP), the main component of fish soft roe, have been rarely addressed. In the present study, the preventive effect of oral supplements of nucleoprotamine and its derivatives, DNA and protamine (PT), extracted from salmon soft roe, on survival rate and hippocampal cell death induced by transient brain ischemia, was evaluated in mice. Artificially formulated nucleoprotamine-free (NF) diet with/without nucleoprotamine, DNA or protamine was fed orally. One week after commencement of respective diets, animals were subjected to transient brain ischemia, which was performed by common carotid artery (CCA) occlusion for 25 (severe) or 15 min (mild). After severe ischemia, the survival rate of the NF group was lower than that in the group fed standard diet or NP. Morphological changes in the hippocampal CA1 region were estimated 48 h after mild ischemia. The NP and PT groups significantly decreased the neuronal damage compared with the NF group. The number of cell death in the DNA group, however, was affected similar to that of the NF group. Our data suggests that the nucleoprotamine content in salmon soft roe could be a useful nutritional resource for the prevention of cell damage caused by ischemia such as those occurring with cerebral and/or heart infarction.

Patterns of cerebral inflammatory response in a rabbit model of intrauterine infection-mediated brain lesion

Although the fetal inflammatory response syndrome seems crucial to the association between intrauterine infection and white matter disease in human preterm infants, the underlying mechanisms remain unclear. Using our previously described rabbit model of cerebral cell death in the white matter and hippocampus induced by intrauterine Escherichia coli infection, we investigated inflammatory and astroglial responses in placenta and brain tissues, in correlation with cell death distribution. Brains and placentas were studied 12, 24, or 48 h following intrauterine inoculation of E. coli or saline (groups G12, G24, and G48). Diffuse monocyte-macrophage infiltrates positive for inducible nitric oxide synthase (i-NOS) were significantly more marked in G24 and G48 placentas than in controls. In the G48 fetuses with both diffuse cell death and focal periventricular white matter cysts mimicking cystic periventricular leukomalacia, a strong rabbit macrophage and inducible nitric oxide synthase immunostaining was observed at the border of these cystic lesions. In contrast, in the fetuses with only diffuse and significant cell death, no inflammatory or astroglial responses were detected in the white matter or hippocampus. Cell death was accompanied by i-NOS immunostaining in the hippocampus but not the white matter. Hippocampal cells positive for i-NOS usually displayed a neuronal phenotype. In this model, focal white matter cysts are accompanied by a robust inflammatory response, and diffuse cell death, which may mimic the white matter and hippocampal damage seen in very and extremely pre-term infants, occur in the absence of a detectable brain inflammatory response.

Suppression of oxidative neuronal damage after transient middle cerebral artery occlusion in mice lacking interleukin-1

Interleukin-1 (IL-1) contributes to ischemic neurodegeneration. However, the mechanisms regulating action of IL-1 are still poorly understood. In order to clear this central issue, mice that were gene deficient in IL-1alpha and beta (IL-1 KO) and wild-type mice were subjected to 1-h transient middle cerebral artery occlusion (tMCAO). Expression levels of IL-1beta and IL-1 receptor I (IL-1RI) were then examined. Generation of peroxynitrite and the expression of mRNAs for nitric oxide synthase (NOS) subtypes were also determined. Immunostaining for IL-1beta was increased from 6 h and peaked at 24 h after tMCAO in the microglia and macrophage. The immunoreactivities of IL-1RI were increased progressively in the microvasculature and neuron-like cells of the ipsilateral hemisphere. Infarct volumes were significantly lower in IL-1 KO mice compared with wild-type mice 48 h after tMCAO (P<0.01). The immunoreactivities of 3-nitro-L-tyrosine were determined in the neurons and microvasculature 24 h after tMCAO and were significantly decreased in the IL-1 KO mice compared to wild-type mice. In addition, expression levels of NOS mRNA in IL-1 KO mice were lower than that measured in wild-type mice. These results indicate that IL-1 is up-regulated and may play a role in neurodegeneration by peroxynitrite production during ischemia.