Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats

Regional Differences in the Neuronal Expression of Cyclooxygenase-2 (COX-2) in the Newborn Pig Brain

Cyclooxygenase (COX)-2 is the major constitutively expressed COX isoform in the newborn brain. COX-2 derived prostanoids and reactive oxygen species appear to play a major role in the mechanism of perinatal hypoxic-ischemic injury in the newborn piglet, an accepted animal model of the human term neonate. The study aimed to quantitatively determine COX-2 immunopositive neurons in different brain regions in piglets under normoxic conditions (n=15), and 4 hours after 10 min asphyxia (n=11). Asphyxia did not induce significant changes in neuronal COX-2 expression of any studied brain areas. In contrast, there was a marked regional difference in all experimental groups. Thus, significant difference was observed between fronto-parietal and temporo-occipital regions: 59±4% and 67±3% versus 41±2%* and 31±3%* respectively (mean±SEM, data are pooled from all subjects, n=26, *p<0.05, vs. fronto-parietal region). In the hippocampus, COX-2 immunopositivity was rare (highest expression in CA1 region: 14±2%). The studied subcortical areas showed negligible COX-2 staining. Our findings suggest that asphyxia does not significantly alter the pattern of neuronal COX-2 expression in the early reventilation period. Furthermore, based on the striking differences observed in cortical neuronal COX-2 distribution, the contribution of COX-2 mediated neuronal injury after asphyxia may also show region-specific differences.

MALDI-mass spectrometry imaging of desalted rat brain sections reveals ischemia-mediated changes of lipids

Ischemia-mediated lipidomic changes in rat brains were explored by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) profiling and imaging after in situ desalting which drastically simplified the spectral presentation of tissue lipids. Removal of interference from the massively changed cations in response to tissue damage permitted the revelation of subtle yet important lipidomic changes. The identities of the detected lipids were confirmed by MALDI tandem mass spectrometry (MALDI-MS/MS). The MALDI-MS imaging (MALDI-MSI) result of lysophosphatidylcholine 16:0 (LPC 16:0) in the desalted brain section appeared essentially identical to that of sodiated LPC 16:0 in the adjacent undesalted section and verified the suitability of the desalting method for the MALDI-MSI studies of lipids in tissue. Other than the consistently decreased phosphatidylcholine (PC) 16:0/18:1, images of PCs containing all saturated, or combined saturated and monounsaturated fatty acyl (MUFA) residues revealed their parenchymal increase by ischemia. Images of PCs containing polyunsaturated fatty acyl (PUFA) residues in normal cortex showed laminated patterns similar to cortical lamina. Ischemia reduced the abundance of PC 16:0/20:4 and PC 16:0/22:6 and disrupted the laminated distribution of the former. However, ischemia increased the subcortical abundance of PUFA-PCs containing stearoyl residue and confined their cortical increase within limited areas. Image of parenchymal sphingomyelin 18:0 (SM 18:0) showed its consistent decrease by ischemia that paralleled the increase of ceramide 18:0-H(2)O in region of moderate to high SM abundance. The above results presented the lipidomic changes largely different from previous MALDI-MSI results and suggested a window of intervention that may benefit the management of cerebrovascular accident and other brain injuries.

Bone marrow chimeras in the study of experimental stroke

Inflammation is known to contribute to stroke evolution, and poststroke immune responses have been documented to emanate from the brain via microglia. However, circulating immune cells are increasingly recognized to play a significant role as well. Recent work has demonstrated the importance of the peripheral circulation and stroke pathogenesis. Understanding how the peripheral circulation contributes to ischemic brain injury may reveal important therapeutic targets and strategies. The use of bone marrow chimeras can be a useful tool in understanding the relative contributions of brain resident and peripheral inflammatory responses.

The flavonoid fisetin attenuates postischemic immune cell infiltration, activation and infarct size after transient cerebral middle artery occlusion in mice

The development of the brain tissue damage in ischemic stroke is composed of an immediate component followed by an inflammatory response with secondary tissue damage after reperfusion. Fisetin, a flavonoid, has multiple biological effects, including neuroprotective and antiinflammatory properties. We analyzed the effects of fisetin on infarct size and the inflammatory response in a mouse model of stroke, temporary middle cerebral artery occlusion, and on the activation of immune cells, murine primary and N9 microglial and Raw264.7 macrophage cells and human macrophages, in an in vitro model of inflammatory immune cell activation by lipopolysaccharide (LPS). Fisetin not only protected brain tissue against ischemic reperfusion injury when given before ischemia but also when applied 3 hours after ischemia. Fisetin also prominently inhibited the infiltration of macrophages and dendritic cells into the ischemic hemisphere and suppressed the intracerebral immune cell activation as measured by intracellular tumor necrosis factor α (TNFα) production. Fisetin also inhibited LPS-induced TNFα production and neurotoxicity of macrophages and microglia in vitro by suppressing nuclear factor κB activation and JNK/Jun phosphorylation. Our findings strongly suggest that the fisetin-mediated inhibition of the inflammatory response after stroke is part of the mechanism through which fisetin is neuroprotective in cerebral ischemia.

Ferulic Acid Reduces Cerebral Infarct Through Its Antioxidative and Anti-Inflammatory Effects Following Transient Focal Cerebral Ischemia in Rats

Both Angelica sinensis (Oliv.) Diels (AS) and Ligusticum chuanxiong Hort. (LC) have been used to treat stroke in traditional Chinese medicine for centuries. Ferulic acid (FA), a component in both AS and LC, plays a role in neuroprotection. The purpose of this study was to investigate the effects of FA on cerebral infarct and the involvement of neuroprotective pathway. Rats underwent 2 hours and 24 hours of reperfusion after 90 min middle cerebral artery occlusion (MCAo). The cerebral infarct and neurological deficits were measured after 24 hours of reperfusion. Furthermore, the expression of superoxide radicals, intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO), nuclear factor-κB (NF-κB) immunoreactive cells were assessed after 2 hours and 24 hours of reperfusion. Administration of 80 and 100 mg/kg of FA at the beginning of MCAo significantly reduced cerebral infarct and neurological deficit-score, similar results were obtained by 100 mg/kg of FA administered 30 min after MCAo. FA treatment (100 mg/kg i.v.) effectively suppressed superoxide radicals in the parenchyma lesion, and ICAM-1 immunoreactive vessels in the ischemic striatum after 2 hours of reperfusion. FA (100 mg/kg i.v.) reduced the expression of ICAM-1 and NF-κB in the ischemic cortex and striatum, also down-regulated MPO immunoreactive cells in the ischemic cortex after 24 hours of reperfusion. These results showed that the effect of FA on reducing cerebral infarct area and neurological deficit-score were at least partially attributed to the inhibition of superoxide radicals, ICAM-1 and NF-κB expression in transient MCAo rats.

Magnesium sulfate and nimesulide have synergistic effects on rescuing brain damage after transient focal ischemia

Magnesium sulfate and nimesulide are commonly used drugs with reported neuroprotective effects. Their combination as stroke treatment has the potential benefits of decreasing individual drug dosage and fewer adverse effects. This study evaluated their synergistic effects and compared a low-dose combination with individual drug alone and placebo. Sprague-Dawley rats underwent 90 min of focal ischemia with intraluminal suture occlusion of the middle cerebral artery followed by reperfusion. The rats were randomly assigned to receive one of the following treatments: placebo, magnesium sulfate (MgSO₄; 45 mg/kg) intravenously immediately after the induction of middle cerebral artery occlusion, nimesulide (6 mg/kg) intraperitoneally before reperfusion, and combined therapy. Three days after the ischemia-reperfusion insult, therapeutic outcome was assessed by 2,3,5-triphenyltetrazolium chloride staining and a 28-point neurological severity scoring system. Cyclooxygenase-2, prostaglandin E₂, myeloperoxidase, and caspase-3 expression after treatment were evaluated using Western blot analyses and immunohistochemical staining, followed by immunoreactive cell analysis using tissue cytometry. Only the combination treatment group showed a significant decrease in infarction volume (10.93±6.54% versus 26.43±7.08%, p<0.01), and neurological severity score (p<0.05). Low-dose MgSO₄ or nimesulide showed no significant neuroprotection. There was also significant suppression of cyclooxygenase-2, prostaglandin E₂, myeloperoxidase, and caspase-3 expression in the combination treatment group, suggesting that the combination of the two drugs improved the neuroprotective effects of each individual drug. MgSO₄ and nimesulide have synergistic effects on ischemia-reperfusion insults. Their combination helps decrease drug dosage and adverse effects. Combined treatment strategies may help to combat stroke-induced brain damage in the future.

The CCL2-CCR2 system affects the progression and clearance of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) has been associated with inflammation and apoptosis. The CCL2-CCR2 chemotactic system is one of the major signaling pathways that induce inflammation and apoptosis. However, its role on ICH has not been investigated. We subjected wild-type, CCL2(-/-) , and CCR2(-/-) mice to collagenase-induced ICH, and assessed histological and behavioral outcomes. Lack of CCL2 or CCR2 decreased the hematoma volume early after collagenase-induced ICH but delayed its recovery. The hematoma size was accompanied by brain edema, neuronal death, and neurological scores. Although microglia activation/migration was attenuated in CCL2(-/-) or CCR2(-/-) mice 1 day after injury, more microglia were present at later time points, suggesting that alternative signaling pathways had been activated to recruit them. On the contrary, leukocyte and neutrophil infiltration were decreased in these mice, suggesting a tighter/recovered blood-brain barrier. In addition, we also found that FL- and K104Stop-CCL2 were able to restore the changes found in CCL2(-/-) mice, but K104A-CCL2 failed to do so. These results suggest that plasmin-mediated truncation of CCL2 may be an indispensable step to fully activate the chemokine in vivo. The data also indicate that CCL2-CCR2 signaling pathway may be a molecular target for the treatment of ICH.

Rutin prevents cognitive impairments by ameliorating oxidative stress and neuroinflammation in rat model of sporadic dementia of Alzheimer type

The objective of the present study was to assess the neuroprotective role of rutin (vitamin P) and delineate the mechanism of action. Recent evidence indicates that rutin exhibits antioxidant potential and protects the brain against various oxidative stressors. More precisely, the aim of the present study was to examine the modulating impacts of rutin against cognitive deficits and oxidative damage in intracerebroventricular-streptozotocin (ICV-STZ)-infused rats. Rats were injected bilaterally with ICV-STZ (3 mg/kg), whereas sham rats received the same volume of vehicle. After 2 weeks of streptozotocin (STZ) infusion, rats were tested for cognitive performance using Morris water maze tasks and thereafter euthanized for further biochemical, histopathological, and immunohistochemical studies. Rutin pretreatment (25 mg/kg, orally, once daily for 3 weeks) significantly attenuated thiobarbituric acid reactive substances (TBARS), activity of poly ADP-ribosyl polymerase, and nitrite level and decreased level of reduced glutathione (GSH) and activities of its dependent enzymes (glutathione peroxidase [GPx] and glutathione reductase [GR]) and catalase in the hippocampus of ICV-STZ rats. ICV-STZ rats showed significant cognitive deficits, which was improved significantly by rutin supplementation. The results indicate that rutin attenuates STZ-induced inflammation by reducing the expression of cyclooxygenase-2 (COX-2), glial fibrillary acidic protein (GFAP), interleukin-8 (IL-8), inducible nitric oxide synthase (iNOS), nuclear factor-kB, and preventing the morphological changes in hippocampus. The study thereby suggests the effectiveness of rutin in preventing cognitive deficits and might be beneficial for the treatment of sporadic dementia of Alzheimer type (SDAT).

Significance of marrow-derived nicotinamide adenine dinucleotide phosphate oxidase in experimental ischemic stroke

OBJECTIVE

Reperfusion after stroke leads to infiltration of inflammatory cells into the ischemic brain. Nicotinamide adenine dinucleotide phosphate oxidase (NOX2) is a major enzyme system that generates superoxide in immune cells. We studied the effect of NOX2 derived from the immune cells in the brain and in blood cells in experimental stroke.

METHODS

To establish whether NOX2 plays a role in brain ischemia, strokes were created in mice, then mice were treated with the NOX2 inhibitor apocynin or vehicle and compared to mice deficient in NOX2's gp91 subunit and their wild-type littermates. To determine whether NOX2 in circulating cells versus brain resident cells contribute to ischemic injury, bone marrow chimeras were generated by transplanting bone marrow from wild-type or NOX2-deficient mice into NOX2 or wild-type hosts, respectively.

RESULTS

Apocynin and NOX2 deletion both significantly reduced infarct size, blood-brain barrier disruption, and hemorrhagic transformation of the infarcts, compared to untreated wild-type controls. This was associated with decreased matrix metalloproteinase 9 expression and reduced loss of tight junction proteins. NOX2-deficient mice receiving wild-type marrow had better outcomes compared to the wild-type mice receiving wild-type marrow. Interestingly, wild-type mice receiving NOX2-deficient marrow had even smaller infarct sizes and less hemorrhage than NOX2-deficient mice receiving wild-type marrow.

INTERPRETATION

This indicates that NOX2, whether present in circulating cells or brain resident cells, contributes to ischemic brain injury and hemorrhage. However, NOX2 from the circulating cells contributed more to the exacerbation of stroke than that from brain resident cells. These data suggest the importance of targeting the peripheral immune system for treatment of stroke.

Induction of COX-2 enzyme and down-regulation of COX-1 expression by lipopolysaccharide (LPS) control prostaglandin E2 production in astrocytes

Pathological conditions and pro-inflammatory stimuli in the brain induce cyclooxygenase-2 (COX-2), a key enzyme in arachidonic acid metabolism mediating the production of prostanoids that, among other actions, have strong vasoactive properties. Although low basal cerebral COX-2 expression has been reported, COX-2 is strongly induced by pro-inflammatory challenges, whereas COX-1 is constitutively expressed. However, the contribution of these enzymes in prostanoid formation varies depending on the stimuli and cell type. Astrocyte feet surround cerebral microvessels and release molecules that can trigger vascular responses. Here, we investigate the regulation of COX-2 induction and its role in prostanoid generation after a pro-inflammatory challenge with the bacterial lipopolysaccharide (LPS) in astroglia. Intracerebral administration of LPS in rodents induced strong COX-2 expression mainly in astroglia and microglia, whereas COX-1 expression was predominant in microglia and did not increase. In cultured astrocytes, LPS strongly induced COX-2 and microsomal prostaglandin-E(2) (PGE(2)) synthase-1, mediated by the MyD88-dependent NFκB pathway and influenced by mitogen-activated protein kinase pathways. Studies in COX-deficient cells and using COX inhibitors demonstrated that COX-2 mediated the high production of PGE(2) and, to a lesser extent, other prostanoids after LPS. In contrast, LPS down-regulated COX-1 in an MyD88-dependent fashion, and COX-1 deficiency increased PGE(2) production after LPS. The results show that astrocytes respond to LPS by a COX-2-dependent production of prostanoids, mainly vasoactive PGE(2), and suggest that the coordinated down-regulation of COX-1 facilitates PGE(2) production after TLR-4 activation. These effects might induce cerebral blood flow responses to brain inflammation.

Ablation of cyclooxygenase-2 in forebrain neurons is neuroprotective and dampens brain inflammation after status epilepticus

Cyclooxygenase-2 (COX-2), a source of inflammatory mediators and a multifunctional neuronal modulator, is rapidly induced in select populations of cortical neurons after status epilepticus. The consequences of rapid activity-triggered induction of COX-2 in neurons have been the subject of much study and speculation. To address this issue directly, we created a mouse in which COX-2 is conditionally ablated in selected forebrain neurons. Results following pilocarpine-induced status epilepticus indicate that neuronal COX-2 promotes early neuroprotection and then delayed neurodegeneration of CA1 pyramidal neurons, promotes neurodegeneration of nearby somatostatin interneurons in the CA1 stratum oriens and dentate hilus (which themselves do not express COX-2), intensifies a broad inflammatory reaction involving numerous cytokines and other inflammatory mediators in the hippocampus, and is essential for development of a leaky blood-brain barrier after seizures. These findings point to a profound role of seizure-induced neuronal COX-2 expression in neuropathologies that accompany epileptogenesis.

Blood-brain barrier breakdown in acute and chronic cerebrovascular disease

Disruptions of the blood-brain barrier (BBB) and edema formation both play key roles in the development of neurological dysfunction in acute and chronic cerebral ischemia. Animal studies have revealed the molecular cascades that are initiated with hypoxia/ischemia in the cells forming the neurovascular unit and that contribute to cell death. Matrix metalloproteinases cause reversible degradation of tight junction proteins early after the onset of ischemia, and a delayed secondary opening during a neuroinflammatory response occurring from 24 to 72 hours after. Cyclooxygenases are important in the delayed opening as the neuroinflammatory response progresses. An early opening of the BBB within the 3-hour therapeutic window for tissue-type plasminogen activator can allow it to enter the brain and increase the risk of hemorrhage. Chronic hypoxic hypoperfusion opens the BBB, which contributes to the cognitive changes seen with lacunar strokes and white matter injury in subcortical ischemic vascular disease. This review will describe the molecular and cellular events associated with BBB disruption and potential therapies directed toward restoring the integrity of the neurovascular unit.

Therapeutic neuroprotective effects of ginkgolide B on cortex and basal ganglia in a rat model of transient focal ischemia

Cerebral ischemia and reperfusion is one of the leading causes for death and severe disabilities in the world and often lead to irreversible brain damage over later lifespan. The aim of this study was to investigate the evolution of pathological damage in cerebral cortex and basal ganglia following ischemia and to evaluate the therapeutic neuroprotective effect of ginkgolide B in a rat model of stroke induced by middle cerebral artery occlusion (MCAO). TTC stain, brain water content and Evans-Blue extravasation were used to quantify brain damage. Our results demonstrated that basal ganglia undergo progressive pathological damage earlier following MCAO, and injury was stable and irreversible after 5 h following ischemia. However, onset of ischemia injury in cerebral cortex appeared later than basal ganglia and became evident about 3 h following MCAO, and injury was stable and irreversible after 6 h following ischemia. Blood brain barrier opened progressively, and it seemed to be significantly destroyed after 4 h following MCAO comparing with 0 h. Post-ischemic treatment with ginkgolide B improved neurological function and reduced infarct size in basal ganglia within 3 h and cerebral cortex within 5 h following MCAO. The therapeutic effect of ginkgolide B on extenuate brain edema and decrease blood brain barrier permeability were extended for 5h after ischemia, and more evident reversal effect were observed when administrated at earlier time.

Implications of gliotransmission for the pharmacotherapy of CNS disorders

The seminal discovery that glial cells, particularly astrocytes, can release a number of gliotransmitters that serve as signalling molecules for the cross-talk with neighbouring cellular populations has recently changed our perception of brain functioning, as well as our view of the pathogenesis of several disorders of the CNS. Since glutamate was one of the first gliotransmitters to be identified and characterized, we tackle the mechanisms that underlie its release from astrocytes, including the Ca2+ signals underlying its efflux from astroglia, and we discuss the involvement of these events in a number of relevant physiological processes, from the modulatory control of neighbouring synapses to the regulation of blood supply to cerebral tissues. The relevance of these mechanisms strongly indicates that the contribution of glial cells and gliotransmission to the activities of the brain cannot be overlooked, and any study of CNS physiopathology needs to consider glial biology to have a comprehensive overview of brain function and dysfunction. Abnormalites in the signalling that controls the astrocytic release of glutamate are described in several experimental models of neurological disorders, for example, AIDS dementia complex, Alzheimer's disease and cerebral ischaemia. While the modalities of glutamate release from astrocytes remain poorly understood, and this represents a major impediment to the definition of novel therapeutic strategies targeting this process at the molecular level, some key mediators deputed to the control of the glial release of this excitatory amino acid have been identified. Among these, we can mention, for instance, proinflammatory cytokines, such as tumour necrosis factor-α, and prostaglandins. Agents that are able to block the major steps of tumour necrosis factor-α and prostaglandin production and/or signalling can be proposed as novel therapeutic targets for the treatment of these disorders.

Expression and cellular localization of cyclooxygenases and prostaglandin E synthases in the hemorrhagic brain

Background

Although cyclooxygenases (COX) and prostaglandin E synthases (PGES) have been implicated in ischemic stroke injury, little is known about their role in intracerebral hemorrhage (ICH)-induced brain damage. This study examines the expression and cellular localization of COX-1, COX-2, microsomal PGES-1 (mPGES-1), mPGES-2, and cytosolic PGES (cPGES) in mice that have undergone hemorrhagic brain injury.

Methods

ICH was induced in C57BL/6 mice by intrastriatal injection of collagenase. Expression and cellular localization of COX-1, COX-2, mPGES-1, mPGES-2, and cPGES were examined by immunofluorescence staining.

Results

In the hemorrhagic brain, COX-1, mPGES-2, and cPGES were expressed constitutively in neurons; COX-1 was also constitutively expressed in microglia. The immunoreactivity of COX-2 was increased in neurons and astrocytes surrounding blood vessels at 5 h and then tended to decrease in neurons and increase in astrocytes at 1 day. At 3 days after ICH, COX-2 was observed primarily in astrocytes but was absent in neurons. Interestingly, the immunoreactivity of mPGES-1 was increased in neurons in the ipsilateral cortex and astrocytes in the ipsilateral striatum at 1 day post-ICH; the immunoreactivity of astrocytic mPGES-1 further increased at 3 days.

Conclusion

Our data suggest that microglial COX-1, neuronal COX-2, and astrocytic COX-2 and mPGES-1 may work sequentially to affect ICH outcomes. These findings have implications for efforts to develop anti-inflammatory strategies that target COX/PGES pathways to reduce ICH-induced secondary brain damage.

The neuroprotective effects of cyclooxygenase-2 inhibition in a mouse model of aneurysmal subarachnoid hemorrhage

The CNS inflammatory reaction occurring after aneurysmal subarachnoid hemorrhage (SAH) involves the upregulation of numerous cytokines and prostaglandins. Cyclooxygenase (COX) inhibition is a well-established pharmacological anti-inflammatory agent. Previous studies have shown marked increases in COX-2 expression in neurons, astrocytes, microglia, and endothelial cells following brain injury. COX-2 inhibition has been shown to be beneficial following various types of brain injury. This experiment investigates the role of COX-2 activity in early brain injury following SAH. CD-1 mice were subjected to an endovascular perforation model of SAH or SHAM surgery. Following experimental SAH animals were treated with the specific COX-2 inhibitor, NS398, in dosages of either 10 or 30 mg/kg. Neurological performance and brain edema were evaluated 24 and 72 h after SAH. NS398 at 30 mg/kg significantly reduced SAH-induced neurological deterioration. NS 398 at 30 mg/kg resulted in a trend toward the reduction of SAH-induced cerebral edema. Treatment had no effect on mortality. This experiment provides preliminary evidence that COX-2 inhibition is an effective pharmacological intervention for the prevention of brain edema and the preservation of neurological function following SAH.

Therapeutic targets for neuroprotection and/or enhancement of functional recovery following traumatic brain injury

Traumatic brain injury (TBI) is a significant public health concern. The number of injuries that occur each year, the cost of care, and the disabilities that can lower the victim's quality of life are all driving factors for the development of therapy. However, in spite of a wealth of promising preclinical results, clinicians are still lacking a therapy. The use of preclinical models of the primary mechanical trauma have greatly advanced our knowledge of the complex biochemical sequela that follow. This cascade of molecular, cellular, and systemwide changes involves plasticity in many different neurochemical systems, which represent putative targets for remediation or attenuation of neuronal injury. The purpose of this chapter is to highlight some of the promising molecular and cellular targets that have been identified and to provide an up-to-date summary of the development of therapeutic compounds for those targets.

Cyclooxygenase-2 mediates hyperbaric oxygen preconditioning in the rat model of transient global cerebral ischemia

BACKGROUND AND PURPOSE

Hyperbaric oxygen (HBO) preconditioning (PC) allows brain protection against transient global ischemia. In the present study, we hypothesize that the mechanism of HBO-PC involves the induction of cyclooxygenase-2 (COX-2) in cerebral tissues before ischemia, which leads to a suppression of COX-2 and its downstream targets after global ischemic insult.

METHODS

One hundred twenty-nine male Sprague Dawley rats (body weight 280-300 grams) were allocated to the naive control group and the sham operation group, and 3 groups of animals were subjected to 15-minute 4-vessel occlusion: untreated, preconditioned with HBO 2.5 atmospheres absolutes for 1 hour daily for 5 days, preconditioned as mentioned and administered with COX-2 inhibitor NS-398 (1 mg/kg body weight intraperitoneal) before each preconditioning session, and normal rats preconditioned with HBO without ischemia. The mortality, the incidence of seizures, and T-maze scores were recorded. The quantitative cell count in Nissl stain and TUNEL was conducted on day 7 after ischemia. The brain expression of COX-2 was analyzed with Western blotting and immunofluorescence staining.

RESULTS

HBO-PC increased the number of surviving neurons in the Cornu Ammonis area 1, which was associated with the reduced COX-2 expression in the hippocampus and in the cerebral cortex at 1 and 3 days after ischemia. HBO-PC improved functional performance and tended to decrease mortality and the frequency of seizures. These beneficial effects of HBO-PC were abolished by the COX-2 selective inhibitor NS-398.

CONCLUSIONS

HBO-PC reduced COX-2 expression and provided brain protection after global ischemia. Administration of COX-2 inhibitor with HBO before ischemia abolished preconditioning effect, thereby implicating COX-2 as a mediator of HBO-PC in the ischemic brain.

Direct profiling of phospholipids and lysophospholipids in rat brain sections after ischemic stroke

Stroke, a deleterious cerebrovascular event, is caused by a critical reduction in the blood flow to the brain parenchyma that leads to brain injury and loss of brain functions. The inflammatory responses following ischemia often aggravate the neurological damage. Several pro-inflammatory mediators released after stroke are closely related to the metabolism of phospholipids. In this study we directly profiled the changes in phospholipids in the infarcted rat cerebral cortex 24 hours after middle cerebral artery occlusion (MCAO) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Several phosphatidylcholine (PC) species and sphingomyelin (SM) were significantly decreased after infarction. The cationization pattern of the remaining PCs showed a prominent shift from a mostly potassiated or protonated form to a predominantly sodiated pattern. Stroke also elevated the lysophosphatidylcholines (LPCs) and heme in tissue. The isobaric pairs in PC and LPC classes were resolved by masses through their respective alkali metal adducts in the presence of CsCl. The major fatty acyl LPC species were also structurally confirmed by MALDI-MS/MS. Overall, the results described the changes in PC and LPC species in the infarcted rat cortex. The elevated tissue levels of LPCs and heme signify the ongoing pathological lipid breakdown and the state of parenchymal inflammation. The elevated LPC level in tissue suggests a means of intervention through lysophospholipid metabolism that could potentially benefit the management of stroke and other acute neurological injuries.

Cytosolic phospholipase A2 alpha amplifies early cyclooxygenase-2 expression, oxidative stress and MAP kinase phosphorylation after cerebral ischemia in mice

Background

The enzyme cytosolic phospholipase A₂ alpha (cPLA₂α) has been implicated in the progression of cerebral injury following ischemia and reperfusion. Previous studies in rodents suggest that cPLA₂α enhances delayed injury extension and disruption of the blood brain barrier many hours after reperfusion. In this study we investigated the role of cPLA₂α in early ischemic cerebral injury.

Methods

Middle cerebral artery occlusion (MCAO) was performed on cPLA₂α^+/+ and cPLA₂α^-/- mice for 2 hours followed by 0, 2, or 6 hours of reperfusion. The levels of cPLA₂α, cyclooxygenase-2, neuronal morphology and reactive oxygen species in the ischemic and contralateral hemispheres were evaluated by light and fluorescent microscopy. PGE₂ content was compared between genotypes and hemispheres after MCAO and MCAO and 6 hours reperfusion. Regional cerebral blood flow was measured during MCAO and phosphorylation of relevant MAPKs in brain protein homogenates was measured by Western analysis after 6 hours of reperfusion.

Results

Neuronal cPLA₂α protein increased by 2-fold immediately after MCAO and returned to pre-MCAO levels after 2 hours reperfusion. Neuronal cyclooxygenase-2 induction and PGE₂ concentration were greater in cPLA₂α^+/+ compared to cPLA₂α^-/- ischemic cortex. Neuronal swelling in ischemic regions was significantly greater in the cPLA₂α^+/+ than in cPLA₂α^-/- brains (+/+: 2.2 ± 0.3 fold vs. -/-: 1.7 ± 0.4 fold increase; P < 0.01). The increase in reactive oxygen species following 2 hours of ischemia was also significantly greater in the cPLA₂α^+/+ ischemic core than in cPLA₂α^-/- (+/+: 7.12 ± 1.2 fold vs. -/-: 3.1 ± 1.4 fold; P < 0.01). After 6 hours of reperfusion ischemic cortex of cPLA₂α^+/+, but not cPLA₂α^-/-, had disruption of neuron morphology and decreased PGE₂ content. Phosphorylation of the MAPKs-p38, ERK 1/2, and MEK 1/2-was significantly greater in cPLA₂a^+/+ than in cPLA₂α^-/- ischemic cortex 6 hours after reperfusion.

Conclusions

These results indicate that cPLA₂α modulates the earliest molecular and injury responses after cerebral ischemia and have implications for the potential clinical use of cPLA₂α inhibitors.

Prostanoid EP1 receptor antagonist reduces blood-brain barrier leakage after cerebral ischemia

Disruption of the blood-brain barrier (BBB) after cerebral ischemia is considered to be the initial step in the development of brain injuries, and an increase in the tyrosine phosphorylation of the tight junctional protein occludin has been shown to cause an increase in BBB permeability. Prostaglandin E2 (PGE2) appears to be associated with both toxic and protective effects on neuronal survival in vitro. However, it remains to be determined whether the prostanoid EP1 receptor is involved in the disruption of the BBB after cerebral ischemia. So we examined the effect of a prostanoid EP1 receptor antagonist, SC51089, on BBB leakage and tyrosine phosphorylation of occludin after cerebral ischemia. We demonstrated that SC51089 attenuated the increase in the tyrosine phosphorylation of occludin in isolated brain capillaries, which was coincident with a decrease in BBB leakage. These results suggest that the prostanoid EP1 receptor is involved in the tyrosine phosphorylation of occludin at tight junction, which may lead to disruption of the BBB and be linked to the development of cerebral infarctions.

Antioxidant CR-6 protects against reperfusion injury after a transient episode of focal brain ischemia in rats

Oxidative and nitrosative stress are targets for intervention after ischemia/reperfusion. The aim of this study was to explore the effect of CR-6, a vitamin-E analogue that is antioxidant and scavenger of nitrogen-reactive species. Sprague-Dawley rats had the middle cerebral artery (MCA) occluded either for 90 mins or permanently. Cortical perfusion was continuously monitored by laser-Doppler flowmetry. CR-6 (100 mg/kg) was administered orally either at 2 and 8 h after MCA occlusion, or at 2 h only. Infarct volume, neurological deficit, and signs of reperfusion injury were evaluated. CR-6 was detected in plasma and brain by HPLC. CR-6 reduced glutathione consumption in the ischemic brain and superoxide generation in the isolated MCA. CR-6 decreased infarct volume and attenuated the neurological deficit at 1 and 7 days after ischemia/reperfusion, but not after permanent ischemia. Immediately after reperfusion, cortical blood flow values returned to their baseline (+/-20%) in several animals, whereas others showed hyper-perfusion (>20% of baseline). Reactive hyperemia was associated with adverse events such as increased cortical BBB leakage, edema, protein nitrotyrosination, COX-2 expression, and neutrophil accumulation; and with a poorer outcome, and CR-6 attenuated these effects. In conclusion, oral CR-6 administration after transient ischemia protects the brain from reperfusion injury.

TRPC-mediated actin-myosin contraction is critical for BBB disruption following hypoxic stress

Hypoxia-induced disruption of the blood-brain barrier (BBB) is the result of many different mechanisms, including alterations to the cytoskeleton. In this study, we identified actin-binding proteins involved in cytoskeletal dynamics with quantitative proteomics and assessed changes in subcellular localization of two proteins involved in actin polymerization [vasodilator-stimulated phosphoprotein (VASP)] and cytoskeleton-plasma membrane cross-linking (moesin). We found significant redistribution of both VASP and moesin to the cytoskeletal and membrane fractions of BBB endothelial cells after 1-h hypoxic stress. We also investigated activation of actin-myosin contraction through assessment of phosphorylated myosin light chain (pMLC) with confocal microscopy. Hypoxia caused a rapid and transient increase in pMLC. Blocking MLC phosphorylation through inhibition of myosin light chain kinase (MLCK) with ML-7 prevented hypoxia-induced BBB disruption and relocalization of the tight junction protein ZO-1. Finally, we implicate the transient receptor potential (TRP)C family of channels in mediating these events since blockade of TRPC channels and the associated calcium influx with SKF-96365 prevents hypoxia-induced permeability changes and the phosphorylation of MLC needed for actin-myosin contraction. These data suggest that hypoxic stress triggers alterations to cytoskeletal structure that contribute to BBB disruption and that calcium influx through TRPC channels contributes to these events.

Cyclooxygenase-1 and -2 differentially modulate lipopolysaccharide-induced blood-brain barrier disruption through matrix metalloproteinase activity

Cyclooxygenases (COX) -1 and -2 are key regulators of innate immune responses. We recently demonstrated that the expression of proinflammatory cytokines and chemokines is reduced in COX-1 null ((-/-)), and increased in COX-2(-/-) mice compared with their respective wild type controls during lipopolysaccharide (LPS)-induced innate immune activation. As chemokines are involved in leukocyte recruitment into the inflamed brain, we hypothesized that COX-1 and COX-2 deletion will differentially modulate blood-brain barrier (BBB) permeability in response to LPS. In the present study, using quantitative magnetic resonance imaging, we found that LPS-induced BBB disruption was exacerbated in COX-2(-/-) versus COX-2(+/+) mice. In the hippocampus and cortex of LPS-treated mice, matrix metalloproteinase (MMP)-3 activity was significantly decreased in COX-1(-/-) mice, whereas in COX-2(-/-) mice the activity of both MMP-9 and MMP-3, known to mediate BBB breakdown, was increased. Brain mRNA expression of the leukocyte attracting chemokine Cxcl10, the intercellular interaction molecule Icam-1, the pan-leukocyte marker Cd45 was increased in COX-2(-/-) versus COX-2(+/+) mice, whereas Cxcl10 and Cd45 mRNA expression was decreased in COX-1(-/-) versus COX-1(+/+) mice after LPS. Altogether, these results indicate that COX-2 activity modulates MMP-9 and-3 activities and is necessary to maintain BBB integrity during toll-like receptor 4-dependent innate immune activation.

Effects of genetic deficiency of cyclooxygenase-1 or cyclooxygenase-2 on functional and histological outcomes following traumatic brain injury in mice

Background

Neuroinflammation contributes to the pathophysiology of acute CNS injury, including traumatic brain injury (TBI). Although prostaglandin lipid mediators of inflammation contribute to a variety of inflammatory responses, their importance in neuroinflammation is not clear. There are conflicting reports as to the efficacy of inhibiting the enzymes required for prostaglandin formation, cyclooxygenase (COX) -1 and COX-2, for improving outcomes following TBI. The purpose of the current study was to determine the role of the COX isoforms in contributing to pathological processes resulting from TBI by utilizing mice deficient in COX-1 or COX-2.

Results

Following a mild controlled cortical impact injury, the amount of cortical tissue loss, the level of microglial activation, and the capacity for functional recovery was compared between COX-1-deficient mice or COX-2-deficient mice, and their matching wild-type controls. The deficiency of COX-2 resulted in a minor (6%), although statistically significant, increase in the sparing of cortical tissue following TBI. The deficiency of COX-1 resulted in no detectable effect on cortical tissue loss following TBI. As determined by ³[H]-PK11195 autoradiography, TBI produced a similar increase in microglial activation in multiple brain regions of both COX-1 wild-type and COX-1-deficient mice. In COX-2 wild-type and COX-2-deficient mice, TBI increased ³[H]-PK11195 binding in all brain regions that were analyzed. Following injury, ³[H]-PK11195 binding in the dentate gyrus and CA1 region of the hippocampus was greater in COX-2-deficient mice, as compared to COX-2 wild-type mice. Cognitive assessment was performed in the wild-type, COX-1-deficient and COX-2-deficient mice following 4 days of recovery from TBI. There was no significant cognitive effect that resulted from the deficiency of either COX-1 or COX-2, as determined by acquisition and spatial memory retention testing in a Morris water maze.

Conclusion

These findings suggest that the deficiency of neither COX-1 nor COX-2 is sufficient to alter cognitive outcomes following TBI in mice.

Modulation of inflammatory response by selective inhibition of cyclooxygenase-1 and cyclooxygenase-2 in acute kidney injury

OBJECTIVE AND DESIGN

This work explored the role of inhibition of cyclooxygenases (COXs) in modulating the inflammatory response triggered by acute kidney injury.

MATERIAL

C57Bl/6 mice were used.

TREATMENT

Animals were treated or not with indomethacin (IMT) prior to injury (days -1 and 0).

METHODS

Animals were subjected to 45 min of renal pedicle occlusion and sacrificed at 24 h after reperfusion. Serum creatinine and blood urea nitrogen, reactive oxygen species (ROS), kidney myeloperoxidase (MPO) activity, and prostaglandin E2 (PGE(2)) levels were analyzed. Tumor necrosis factor (TNF)-alpha, t-bet, interleukin (IL)-10, IL-1beta, heme oxygenase (HO)-1, and prostaglandin E synthase (PGES) messenger RNA (mRNA) were studied. Cytokines were quantified in serum.

RESULTS

IMT-treated animals presented better renal function with less acute tubular necrosis and reduced ROS and MPO production. Moreover, the treatment was associated with lower expression of TNF-alpha, PGE(2), PGES, and t-bet and upregulation of HO-1 and IL-10. This profile was mirrored in serum, where inhibition of COXs significantly decreased interferon (IFN)-gamma, TNF-alpha, and IL-12 p70 and upregulated IL-10.

CONCLUSIONS

COXs seem to play an important role in renal ischemia and reperfusion injury, involving the secretion of pro-inflammatory cytokines, activation of neutrophils, and ROS production. Inhibition of COX pathway is intrinsically involved with cytoprotection.

Spatiotemporal correlations between blood-brain barrier permeability and apparent diffusion coefficient in a rat model of ischemic stroke

Variations in apparent diffusion coefficient of water (ADC) and blood-brain barrier (BBB) permeability after ischemia have been suggested, though the correlation between ADC alterations and BBB opening remains to be studied. We hypothesized that there are correlations between the alteration of ADC and BBB permeability. Rats were subjected to 2 h of transient middle cerebral artery occlusion and studied at 3 and 48 h of reperfusion, which are crucial times of BBB opening. BBB permeability and ADC values were measured by dynamic contrast-enhanced MRI and diffusion-weighted imaging, respectively. Temporal and spatial analyses of the evolution of BBB permeability and ADC alteration in cortical and subcortical regions were conducted along with the correlation between ADC and BBB permeability data. We found significant increases in BBB leakage and reduction in ADC values between 3 and 48 h of reperfusion. We identified three MR tissue signature models: high K_i and low ADC, high K_i and normal ADC, and normal K_i and low ADC. Over time, areas with normal K_i and low ADC transformed into areas with high K_i. We observed a pattern of lesion evolution where the extent of initial ischemic injury reflected by ADC abnormalities determines vascular integrity. Our results suggest that regions with vasogenic edema alone are not likely to develop low ADC by 48 h and may undergo recovery.

Nicotine enhances skin necrosis and expression of inflammatory mediators in a rat pressure ulcer model

BACKGROUND

Many bedridden patients develop pressure ulcers, not only in hospital but also at home. Clinical studies have indicated cigarette smoking to be a risk factor for pressure ulcers. However, the contribution of nicotine to pressure ulcer formation has not been identified.

OBJECTIVES

We aimed to clarify the effect of nicotine on pressure ulcer formation, and its mechanism.

METHODS

Ischaemia-reperfusion (I/R) was performed in rat dorsal skin to induce pressure ulcers. The extent of the resulting necrotic area was determined. To clarify the mechanism of the effect of nicotine, mRNA levels of cyclooxygenase-2 (COX-2), interleukin (IL)-1beta, IL-6 and inducible nitric oxide synthase (iNOS) and protein expression of COX-2 and iNOS in the necrotic area were investigated by real-time reverse transcription-polymerase chain reaction and Western blotting, respectively. Furthermore, the effects of the COX-2 inhibitor NS-398 and the iNOS inhibitor aminoguanidine on necrosis were examined.

RESULTS

Skin necrosis in the I/R-treated area was significantly increased by intraperitoneal administration of nicotine (0.175 mg kg(-1) daily). Repeated nicotine administration had little effect on systolic and diastolic blood pressure. I/R treatment increased mRNA levels of COX-2, IL-1beta, IL-6 and iNOS, which were further augmented by nicotine in a dose-dependent manner. Correspondingly, nicotine (0.35 mg kg(-1) daily) markedly enhanced the protein expression of COX-2 and iNOS. Moreover, NS-398 and aminoguanidine showed a tendency to abrogate the increase of I/R-induced skin necrosis caused by nicotine.

CONCLUSIONS

These results suggest that the increased risk of pressure ulcers due to cigarette smoking is mediated, in part, by nicotine. They also indicated that the effect of nicotine is not mediated by a change in blood pressure, but is elicited via an increase of inflammatory mediators in the I/R-treated skin.

Prolonged opportunity for neuroprotection in experimental stroke with selective blockade of cyclooxygenase-2 activity

The post-treatment effects of the selective cyclooxygenase (COX)-2 inhibitor, valdecoxib, were investigated in a rat model of temporary focal ischemia. Valdecoxib reduced basal brain prostaglandin E(2) concentrations at dosages that did not affect serum thromboxane B(2), consistent with a selective COX-2 effect. Temporary focal cerebral ischemia was produced in rats by middle cerebral artery occlusion for 90 min. There was increased expression of COX-2 protein detected by Western blot and immunocytochemistry within neurons in the ischemic cortex at 4 and 24 h after ischemia. Rats were treated with vehicle or valdecoxib 15 min before or 1.5, 3 and 6 h after cerebral ischemia. Rats were sacrificed and brain infarction volume determined 24 h after ischemia. Valdecoxib treatment was associated with a decrease in infarction volume when administered 15 min before, and 1.5 or 3 h but not 6 h after cerebral ischemia. There were no differences in physiological parameters during the procedure. Valdecoxib administered at 1.5 h after ischemia significantly reduced the concentrations of prostaglandin E(2) in ischemic penumbral cortex as compared to the vehicle-treated group and contralateral non-ischemic cortex. These results suggest that COX-2 inhibition with valdecoxib is effective when initiated both before and after middle cerebral artery occlusion.

Post-ischemic brain damage: pathophysiology and role of inflammatory mediators

Neuroinflammatory mediators play a crucial role in the pathophysiology of brain ischemia, exerting either deleterious effects on the progression of tissue damage or beneficial roles during recovery and repair. Within hours after the ischemic insult, increased levels of cytokines and chemokines enhance the expression of adhesion molecules on cerebral endothelial cells, facilitating the adhesion and transendothelial migration of circulating neutrophils and monocytes. These cells may accumulate in the capillaries, further impairing cerebral blood flow, or extravasate into the brain parenchyma. Infiltrating leukocytes, as well as resident brain cells, including neurons and glia, may release pro-inflammatory mediators, such as cytokines, chemokines and oxygen/nitrogen free radicals that contribute to the evolution of tissue damage. Moreover, recent studies have highlighted the involvement of matrix metalloproteinases in the propagation and regulation of neuroinflammatory responses to ischemic brain injury. These enzymes cleave protein components of the extracellular matrix such as collagen, proteoglycan and laminin, but also process a number of cell-surface and soluble proteins, including receptors and cytokines such as interleukin-1beta. The present work reviewed the role of neuroinflammatory mediators in the pathophysiology of ischemic brain damage and their potential exploitation as drug targets for the treatment of cerebral ischemia.

Necrotic neurons enhance microglial neurotoxicity through induction of glutaminase by a MyD88-dependent pathway

Background

Microglia are macrophage-like cells that constantly sense the microenvironment within the central nervous system (CNS). In the event of neuronal stress or injury, microglial cells rapidly react and change their phenotype. This response may lead to a deleterious type of microglial activation, which is often associated with neuroinflammation and neurotoxicity in several neuropathological conditions. We investigated the molecular mechanisms underlying triggering of microglial activation by necrotic neuronal damage.

Methods

Primary cultures of microglia were used to study the effect of necrotic neurons on microglial inflammatory responses and toxicity towards cerebellar granule neurons (CGN). The mouse hippocampal cell line, HT22, was used in this study as the main source of necrotic neurons to stimulate microglia. To identify the signal transduction pathways activated in microglia, primary microglial cultures were obtained from mice deficient in Toll-like receptor (TLR) -2, -4, or in the TLR adapter protein MyD88.

Results

Necrotic neurons, but not other necrotic cell types, induced microglial activation which was characterized by up-regulation of: i) MHC class II; ii) co-stimulatory molecules, i.e. CD40 and CD24; iii) β2 integrin CD11b; iii) pro-inflammatory cytokines, i.e. interleukin 6 (IL-6), IL-12p40 and tumor-necrosis factor (TNF); iv) pro-inflammatory enzymes such as nitric oxide synthase (iNOS, type II NOS), indoleamine 2,3-dioxygenase (IDO) and cyclooxygenase-2 (COX-2) and increased microglial motility. Moreover, microglia-conditioned medium (MCM) obtained from cultures of activated microglia showed increased neurotoxicity mediated through the N-methyl-D-aspartate receptor (NMDAR). The activation of microglia by necrotic neurons was shown to be dependent on the TLR-associated adapter molecule myeloid differentiation primary response gene (MyD88). Furthermore, MyD88 mediated enhanced neurotoxicity by activated microglia through up-regulation of the expression and activity of glutaminase, an enzyme that produces glutamate, which is an NMDAR agonist.

Conclusion

These results show that necrotic neurons activate in microglia a MyD88-dependent pathway responsible for a pro-inflammatory response that also leads to increased neurotoxic activity through induction of glutaminase. This finding contributes to better understanding the mechanisms causing increased neuroinflammation and microglial neurotoxicity in a neurodegenerative environment.

Mangiferin inhibits cyclooxygenase-2 expression and prostaglandin E2 production in activated rat microglial cells

Mangiferin, a naturally occurring glucosylxanthone, has potent antioxidant and anti-inflammatory properties, as demonstrated in several reports. However, very limited information is available on the effects of this natural polyphenol on microglial activation. Thus, the aim of this study was to examine whether mangiferin is able to reduce prostaglandin E(2) (PGE(2)) and 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) production by lipopolysaccharide (LPS)-activated primary rat microglia. Microglial cells were stimulated with 10ng/ml of LPS in the presence or absence of different concentrations of mangiferin (1-50 microM). After 24h incubation, culture media were collected to measure the production of PGE(2) and 8-iso-PGF(2alpha) using enzyme immunoassays. Protein levels of cyclooxygenase (COX)-1 and COX-2 were studied by immunoblotting after 24h of incubation with LPS. Mangiferin potently reduced LPS-induced PGE(2) synthesis and the formation of 8-iso-PGF(2alpha). Interestingly, mangiferin dose-dependently reduced LPS-induced COX-2 protein synthesis without modifying COX-2 transcription. This was due to a decrease in COX-2 transcript stability. However, mangiferin did not modify LPS-mediated phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), a key factor involved in enhancing COX-2 mRNA stability and COX-2 translation in primary microglia. Mangiferin had no effects on LPS-induced expression of inducible nitric oxide synthase (iNOS) or TNF-alpha production. Taken together, results from the present study indicate that mangiferin is able to limit microglial activation, in terms of attenuation of PGE(2) production, free radical formation and reduction in COX-2 synthesis induced by LPS. These data suggest that modulation of microglial activation might contribute to the mechanism of cerebral protection by mangiferin.

Diverse roles of matrix metalloproteinases and tissue inhibitors of metalloproteinases in neuroinflammation and cerebral ischemia

Regulation of the extracellular matrix by proteases and protease inhibitors is a fundamental biological process for normal growth, development and repair in the CNS. Matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) are the major extracellular-degrading enzymes. Two other enzyme families, a disintegrin and metalloproteinase (ADAM), and the serine proteases, plasminogen/plasminogen activator (P/PA) system, are also involved in extracellular matrix degradation. Normally, the highly integrated action of these enzyme families remodels all of the components of the matrix and performs essential functions at the cell surface involved in signaling, cell survival, and cell death. During the inflammatory response induced in infection, autoimmune reactions and hypoxia/ischemia, abnormal expression and activation of these proteases lead to breakdown of the extracellular matrix, resulting in the opening of the blood-brain barrier (BBB), preventing normal cell signaling, and eventually leading to cell death. There are several key MMPs and ADAMs that have been implicated in neuroinflammation: gelatinases A and B (MMP-2 and -9), stromelysin-1 (MMP-3), membrane-type MMP (MT1-MMP or MMP-14), and tumor necrosis factor-alpha converting enzyme (TACE). In addition, TIMP-3, which is bound to the cell surface, promotes cell death and impedes angiogenesis. Inhibitors of metalloproteinases are available, but balancing the beneficial and detrimental effects of these agents remains a challenge.

Detrimental effects of tropisetron on permanent ischemic stroke in the rat

Background

Recent in vitro evidence indicates that blockade of 5-hydroxytryptamine (5-HT) receptor 3 (5-HT₃) is able to confer protection in different models of neuronal injury. The purpose of the present study was to investigate the effect of tropisetron, a 5-HT₃ receptor antagonist, on infarct size and neurological score in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in the rat.

Methods

Two different doses of tropisetron (5 and 10 mg/kg) or vehicle were administered intraperitoneally 30 min before pMCAO. Neurological deficit scores, mortality rate and infarct volume were determined 24 h after permanent focal cerebral ischemia.

Results

Tropisetron failed to reduce cerebral infarction. Animals receiving tropisetron showed a significant increase (p < 0.05) in neurological deficits and mortality rate.

Conclusion

Data from this study indicate that blockade of 5-HT₃ receptors with tropisetron worsens ischemic brain injury induced by pMCAO. These findings could have important clinical implications. Patients taking tropisetron, and possibly other 5-HT₃ antagonists, could potentially have a worse outcome following a brain infarct.

Transcription factor early growth response-1 induction mediates inflammatory gene expression and brain damage following transient focal ischemia

Early growth response-1 (Egr1) is a sequence-specific transcription factor (TF) which is induced under hypoxic conditions. We presently report that transient middle cerebral artery occlusion (MCAO) leads to increased expression of Egr1 in the brains of adult mice and rats between 2 h and 5 days of reperfusion with a peak increase of 8-12-fold at 1 day. When subjected to transient MCAO and 3 days of reperfusion, Egr1-/- mice showed significantly smaller infarcts (by 44.9 +/- 8.4%, p < 0.05) and improved neurological function than Egr1+/+ littermates. Following transient MCAO, brains of Egr1-/- mice showed less water accumulation and decreased neutrophil infiltration (by 42 +/- 8%, p < 0.05) compared to Egr1+/+ mice. The number of activated microglia/macrophages were also significantly lower (OX42+ cells by 53 +/- 9%, p < 0.05 and ED1+ cells by 59 +/- 11%) in the post-ischemic cortex of Egr1-/- mice compared to Egr1+/+ mice. In addition, post-ischemic inflammatory gene expression was less pronounced in the brains of Egr1-/- mice compared to Egr1+/+ mice. Preventing cerebral Egr1 protein induction with small interference RNAs that target Egr1 decreased inflammatory gene expression and led to smaller infarcts (by 40.2 +/- 6.9%, p < 0.05) and reduced neurological deficits in rats subjected to transient MCAO. Conversely, transient MCAO following adenoviral-mediated Egr1 over-expression exacerbated the infarct volume (by 29 +/- 5.3%, p < 0.05) and worsened the neurological deficits in rats. These studies indicate Egr1 as a significant contributor of inflammation and neuronal damage after stroke.

Resveratrol potently reduces prostaglandin E2 production and free radical formation in lipopolysaccharide-activated primary rat microglia

Background

Neuroinflammatory responses are triggered by diverse ethiologies and can provide either beneficial or harmful results. Microglial cells are the major cell type involved in neuroinflammation, releasing several mediators, which contribute to the neuronal demise in several diseases including cerebral ischemia and neurodegenerative disorders. Attenuation of microglial activation has been shown to confer protection against different types of brain injury. Recent evidence suggests that resveratrol has anti-inflammatory and potent antioxidant properties. It has been also shown that resveratrol is a potent inhibitor of cyclooxygenase (COX)-1 activity. Previous findings have demonstrated that this compound is able to reduce neuronal injury in different models, both in vitro and in vivo. The aim of this study was to examine whether resveratrol is able to reduce prostaglandin E₂ (PGE₂) and 8-iso-prostaglandin F_2α (8-iso-PGF_2α) production by lipopolysaccharide (LPS)-activated primary rat microglia.

Methods

Primary microglial cell cultures were prepared from cerebral cortices of neonatal rats. Microglial cells were stimulated with 10 ng/ml of LPS in the presence or absence of different concentrations of resveratrol (1–50 μM). After 24 h incubation, culture media were collected to measure the production of PGE₂ and 8-iso-PGF_2α using enzyme immunoassays. Protein levels of COX-1, COX-2 and microsomal prostaglandin E synthase-1 (mPGES-1) were studied by Western blotting after 24 h of incubation with LPS. Expression of mPGES-1 at the mRNA level was investigated using reverse transcription-polymerase chain reaction (RT-PCR) analysis.

Results

Our results indicate that resveratrol potently reduced LPS-induced PGE₂ synthesis and the formation of 8-iso-PGF_2α, a measure of free radical production. Interestingly, resveratrol dose-dependently reduced the expression (mRNA and protein) of mPGES-1, which is a key enzyme responsible for the synthesis of PGE₂ by activated microglia, whereas resveratrol did not affect the expression of COX-2. Resveratrol is therefore the first known inhibitor which specifically prevents mPGES-1 expression without affecting COX-2 levels. Another important observation of the present study is that other COX-1 selective inhibitors (SC-560 and Valeroyl Salicylate) potently reduced PGE₂ and 8-iso-PGF_2α production by LPS-activated microglia.

Conclusion

These findings suggest that the naturally occurring polyphenol resveratrol is able to reduce microglial activation, an effect that might help to explain its neuroprotective effects in several in vivo models of brain injury.

Cyclooxygenase inhibition limits blood-brain barrier disruption following intracerebral injection of tumor necrosis factor-alpha in the rat

Increased permeability of the blood-brain barrier (BBB) is important in neurological disorders. Neuroinflammation is associated with increased BBB breakdown and brain injury. Tumor necrosis factor (TNF)-alpha is involved in BBB injury and edema formation through a mechanism involving matrix metalloproteinase (MMP) up-regulation. There is emerging evidence indicating that cyclooxygenase (COX) inhibition limits BBB disruption following ischemic stroke and bacterial meningitis, but the mechanisms involved are not known. We used intracerebral injection of TNF-alpha to study the effect of COX inhibition on TNF-alpha-induced BBB breakdown, MMP expression/activity, and oxidative stress. BBB disruption was evaluated by the uptake of (14)C-sucrose into the brain and by magnetic resonance imaging utilizing gadolinium-diethylenetriaminepentaacetic acid as a paramagnetic contrast agent. Using selective inhibitors of each COX isoform, we found that COX-1 activity is more important than COX-2 in BBB opening. TNF-alpha induced a significant up-regulation of gelatinase B (MMP-9), stromelysin-1 (MMP-3), and COX-2. In addition, TNF-alpha significantly depleted glutathione as compared with saline. Indomethacin (10 mg/kg i.p.), an inhibitor of COX-1 and COX-2, reduced BBB damage at 24 h. Indomethacin significantly attenuated MMP-9 and MMP-3 expression and activation and prevented the loss of endogenous radical scavenging capacity following intracerebral injection of TNF-alpha. Our results show for the first time that BBB disruption during neuroinflammation can be significantly reduced by administration of COX inhibitors. Modulation of COX in brain injury by COX inhibitors or agents modulating prostaglandin E(2) formation/signaling may be useful in clinical settings associated with BBB disruption.

Pyrrolidine dithiocarbamate attenuate shock wave induced MDCK cells injury via inhibiting nuclear factor-kappa B activation

Shock wave lithotripsy (SWL)-induced renal damage appears to be multifactorial. Recent data indicated that the mechanism of renal tissue damage secondary to SWL is similar to that of ischemia reperfusion injury. Nuclear factor-kappa B (NFkappaB) and its target genes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), have been demonstrated to play a very important role in a variety of cells or tissues ischemia reperfusion injuries. Thus in the present study, using an in vitro model MDCK cells, we investigated the role of NFkappaB and its target cytotoxic enzyme in shock wave-induced renal cellular damage. We also examined whether inhibition this pathway by pyrrolidine dithiocarbamate (PDTC) is contributed to alleviate SWL-caused cell damage. Suspensions of MDCK cells were placed in containers for shock wave exposure. Three groups of six containers each were examined: control group, no shock wave treatment and SWL group, which received 100 shocks at 18 kV; 3 SWL + PDTC group. PDTC were added to the suspensions before shock wave exposure. After shock wave 0, 2, 4, 6 and 8 h, respectively, the cell supernatants were detected for the level of MDA and release of LDH. At post-shock wave 8 h, cells were harvested to detect the nuclear translocation of NFkappaBp65 by immunofluorescence staining. Degradation of IkappaB-a (an inhibitor protein of NFkappaB) and expression of iNOS and COX-2 were also examined by western blotting. Our results indicated that shock wave initiated the apparent activation of NFkappaB, which in turn induced high expression of iNOS and COX-2. Blocking degradation of IkappaB-a by PDTC was contributed to decrease the expression of iNOS. And the level of MDA and the release of LDH were also significantly reduced by using PDTC. However, the degree of COX-2 expression does not differ significantly between SWL and SWL + PDTC groups. Activation of NFkappaB and subsequent expression of its target cytotoxic enzyme have been demonstrated to be a potential and crucial mechanism in SWL-induced renal cell damage. Blocking this pathway by PDTC is contributed to protect against cellular damage from shock wave.