Rosiglitazone and 15-deoxy-Delta12,14-prostaglandin J2 cause potent neuroprotection after experimental stroke through noncompletely overlapping mechanisms

Stroke triggers an inflammatory cascade which contributes to a delayed cerebral damage, thus implying that antiinflammatory strategies might be useful in the treatment of acute ischaemic stroke. Since two unrelated peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists, the thiazolidinedione rosiglitazone (RSG) and the cyclopentenone prostaglandin 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PGJ2), have been shown to possess antiinflammatory properties, we have tested their neuroprotective effects in experimental stroke. Rosiglitazone or 15d-PGJ2 were administered to rats 10 mins or 2 h after permanent middle cerebral artery occlusion (MCAO). Stroke outcome was evaluated by determination of infarct volume and assessment of neurological scores. Brains were collected for protein expression, gene array analyses and gene shift assays. Our results show that both compounds decrease MCAO-induced infarct size and improve neurological scores. At late times, the two compounds converge in the inhibition of MCAO-induced brain expression of inducible NO synthase and the matrix metalloproteinase 9. Interestingly, at early times, complementary DNA microarrays and gene shift assays show that different mechanisms are recruited. Analysis of early nuclear p65 and late cytosolic IkappaBalpha protein levels shows that both compounds inhibit nuclear factor-kappaB signalling, although at different levels. All these results suggest both PPARgamma-dependent and independent pathways, and might be useful to design both therapeutic strategies and prognostic markers for stroke.

TNFR1 mediates increased neuronal membrane EAAT3 expression after in vivo cerebral ischemic preconditioning

A short ischemic event (ischemic preconditioning) can result in subsequent resistance to severe ischemic injury (ischemic tolerance). Glutamate is released after ischemia and produces cell death. It has been described that after ischemic preconditioning, the release of glutamate is reduced. We have shown that an in vitro model of ischemic preconditioning produces upregulation of glutamate transporters which mediates brain tolerance. We have now decided to investigate whether ischemic preconditioning-induced glutamate transporter upregulation takes also place in vivo, its cellular localization and the mechanisms by which this upregulation is controlled. A period of 10 min of temporary middle cerebral artery occlusion was used as a model of ischemic preconditioning in rat. EAAT1, EAAT2 and EAAT3 glutamate transporters were found in brain from control animals. Ischemic preconditioning produced an up-regulation of EAAT2 and EAAT3 but not of EAAT1 expression. Ischemic preconditioning-induced increase in EAAT3 expression was reduced by the TNF-alpha converting enzyme inhibitor BB1101. Intracerebral administration of either anti-TNF-alpha antibody or of a TNFR1 antisense oligodeoxynucleotide also inhibited ischemic preconditioning-induced EAAT3 up-regulation. Immunohistochemical studies suggest that, whereas the expression of EAAT3 is located in both neuronal cytoplasm and plasma membrane, ischemic preconditioning-induced up-regulation of EAAT3 is mainly localized at the plasma membrane level. In summary, these results demonstrate that in vivo ischemic preconditioning increases the expression of EAAT2 and EAAT3 glutamate transporters the upregulation of the latter being at least partly mediated by TNF-alpha converting enzyme/TNF-alpha/TNFR1 pathway.

Dual role of nitric oxide in adult neurogenesis

In the last decade, it has been demonstrated that neurogenesis persists in the adult mammalian brain and that it is induced after insults, where newborn neurons migrate to damaged areas, differentiate and contribute to the recovery. The understanding of the cellular and molecular events involved in this phenomenon could provide effective therapies not only to promote brain repair in stroke or seizures, but also to facilitate functional improvement in depression or Alzheimer. In this context, many advances have been made, such as the implication of different growth factors, membrane receptors, and most importantly diffusible messengers like nitric oxide (NO). We review here studies in both normal and pathophysiological conditions that suggest a dual role for NO in adult neurogenesis and its relation to different pharmacological strategies stimulating neurogenesis.

Mitochondrial respiratory chain and free radical generation in stroke

Being the second most common cause of death in the industrial countries and one of the major causes of death and disability, stroke has a great effect on public health and is the neurological disease which accounts for the largest number of hospitalizations. In order to develop new treatments, biochemical mechanisms involved in brain damage have been investigated. Among them, oxidant species generated during stroke have been implicated as critical mediators of neuronal injury in this condition, although neuroprotective roles have also been demonstrated. This review is focused on the role of the mitochondrial respiratory chain as both source and target of reactive oxygen and nitrogen species such as nitric oxide, superoxide and peroxynitrite produced in cerebral ischemia. The neuroprotective role of antioxidants or other molecules acting on the mitochondrial respiratory chain and ATP synthesis in the setting of cerebral ischemia is discussed.

The nonthiazolidinedione PPARgamma agonist L-796,449 is neuroprotective in experimental stroke

Some agonists of the peroxisome proliferator-activated receptor gamma (PPARgamma) belonging to the thiazolidinedione (TZD) family, as well as the cyclopentenone prostaglandin 15-dPGJ2, have been shown to cause neuroprotection in animal models of stroke. We have tested whether the TZD-unrelated PPARgamma agonist L-796,449 is neuroprotective after permanent middle cerebral artery occlusion (MCAO) in the rat brain. Our results show that L-796,449 decreases MCAO-induced infarct size and improves neurologic scores. This protection is concomitant to inhibition of MCAO-induced brain expression of inducible NO synthase (iNOS) and the matrix metalloproteinase MMP-9 and to upregulation of the cytoprotective stress protein heme oxygenase-1 (HO-1). Analysis of the NF-kappaB p65 monomer and the NF-kappaB inhibitor IkappaBalpha protein levels as well as gel mobility shift assays indicate that L-796,449 inhibits NF-kappaB signaling, and that it may be recruiting both PPARgamma-dependent and independent pathways. In summary, our results provide new insights for stroke treatment.

The prediction of malignant cerebral infarction by molecular brain barrier disruption markers

BACKGROUND AND PURPOSE

Space-occupying brain edema is a life-threatening complication in patients with large hemispheric stroke. The aim of the study was to determine whether molecular markers of endothelial damage may help to predict secondary brain edema and, secondly, to identify patients who could benefit from aggressive therapies such as decompressive hemicraniectomy or hypothermia.

METHODS

We studied 40 consecutive patients with malignant middle cerebral artery (MCA) infarction and 35 controls with massive MCA infarctions <70 years of age and matched by stroke severity on admission. Cranial computed tomography (CT) was performed at entry and repeated between days 4 and 7, or earlier if there was neurological worsening. Malignant MCA (m-MCA) infarction was diagnosed when follow-up CT detected a more than two-thirds space-occupying MCA infarction with midline shift, compression of the basal cisterns, and neurological deterioration. Plasma concentrations of glutamate, glycine, gamma-aminobutyric acid, interleukin-6 (IL-6), IL-10, tumor necrosis factor-alpha, matrix metalloproteinase-9 (MMP-9), and cellular-fibronectin (c-Fn) were determined in blood samples obtained at admission.

RESULTS

Mean time from stroke onset to blood sampling was 6.3+/-4.8 in m-MCA and 7.7+/-6.0 hours in the control group (P=0.63). Baseline characteristics were comparable in both groups. c-Fn and MMP-9 levels were significantly higher in patients with m-MCA than in controls (all P<0.001). c-Fn >16.6 microg/mL had the highest sensitivity (90%), specificity (100%), and negative and positive predictive values (89% and 100%, respectively) for the prediction of m-MCA infarction.

CONCLUSIONS

A plasma c-Fn concentration >16.6 microg/mL at admission is associated with the development of m-MCA infarction with high sensitivity and specificity, suggesting that c-Fn might be useful in therapeutic decision making.

Immature rat brain slices exposed to oxygen-glucose deprivation as an in vitro model of neonatal hypoxic-ischemic encephalopathy

To analyze whether exposure to oxygen-glucose deprivation (OGD) of immature rat brain slices might reproduce the main pathophysiologic events leading to neuronal death in neonatal hypoxic-ischemic encephalopathy (NHIE), 500 microm-thick brain slices were obtained from 7-day-old Wistar rats, and incubated in oxygenated physiological solution. In OGD group, oxygen and glucose were removed from the medium for 10-30 min (n = 25); then, slices were re-incubated in normal medium. In control group the medium composition remained unchanged (CG, n = 30). Medium samples were obtained every 30 min for 3 h. To analyze neuronal damage, slices were stained with Nissl and CA1 area of hippocampus and cortex were observed under microscopy. In addition, neuronal death was quantified as LDH released to the medium determined by spectrophotometry. Additionally, medium glutamate (Glu) levels were determined by HPLC and those of TNFalpha by ELISA, whereas inducible nitric oxide synthase expression was determined by Western blot performed on slices homogenate. Optimal OGD time was established in 20 min. After OGD, a significant decrease in the number of neurones in hippocampus and cortex was observed. LDH release was maximal at 30 min, when it was five-fold greater than in CG. Furthermore, medium Glu concentrations were 200 times greater than CG levels at the end of OGD period. A linear relationship between Glu and LDH release was demonstrated. Finally, 3 h after OGD a significant induction of iNOS as well as an increase in TNFalpha release were observed. In conclusion, OGD appears as a feasible and reproducible in vitro model, leading to a neuronal damage, which is physiopathologically similar to that found in NHIE.

The anti-inflammatory prostaglandin 15d-PGJ2 decreases oxidative/nitrosative mediators in brain after acute stress in rats

RATIONALE

Immobilisation stress is followed by accumulation of oxidative/nitrosative mediators in brain after the release of tumour necrosis factor-alpha (TNFalpha) and other cytokines, nuclear factor kappa B (NFkappaB) activation, nitric oxide synthase-2 (NOS-2) and cyclooxygenase-2 (COX-2) expression in the brain.

OBJECTIVES

This study was conducted to assess if some of the anti-inflammatory products of COX can modify the accumulation of oxidative/nitrosative species seen in brain after stress and to study the mechanisms by which this effect is achieved.

METHODS

Young-adult male Wistar rats were subjected to a single session of immobilisation during 6 h.

RESULTS

In stressed animals, brain levels of the anti-inflammatory 15d-PGJ2 increases concomitantly with COX-2 expression. Inhibition of COX-2 with NS-398 prevents stress-induced 15d-PGJ2 increase. Injection of supraphysiological doses of 15d-PGJ2 (80-120 microg/kg) decreases stress-induced increase in NOS-2 activity as well as the stress-induced increase in NO metabolites. On the other hand, 15d-PGJ2 decreases stress-induced malondialdehyde (an indicator of lipid peroxidation) accumulation in cortex and prevents oxidation of the main anti-oxidant glutathione. The mechanisms involved in the anti-oxidative properties of 15d-PGJ2 in stress involve NFkappaB blockade (by preventing stress-induced IkappaBalpha decrease) as well as inhibition of TNFalpha release in stressed animals. At the doses tested, 15d-PGJ2 decreases COX-2 expression and PGE2 release during stress, suggesting an alternative mechanism for this endogenous compound.

CONCLUSIONS

These findings demonstrate a role for this anti-inflammatory pathway in the brain response to stress and open the possibility for preventing accumulation of oxidative/nitrosative species and subsequent brain damage.

Increased Plasma Levels of 15-Deoxy Δ Prostaglandin J 2 Are Associated With Good Outcome in Acute Atherothrombotic Ischemic Stroke

Background and Purpose— The 15-deoxy Δ prostaglandin J 2 (15-dPGJ 2 ) is an anti-inflammatory prostaglandin that has been proposed to be the endogenous ligand of peroxisome proliferator-activated receptor-γ (PPARγ), a nuclear receptor that can exert potent anti-inflammatory actions by repressing inflammatory genes when activated. It has been suggested that 15-dPGJ 2 could be beneficial in neurological disorders in which inflammation contributes to cell death such as stroke.

Methods— We investigated the relationship between plasma levels of 15-dPGJ 2 and early neurological deterioration (END), infarct volume, and neurologic outcome in 552 patients with an acute stroke admitted within 24 hours after symptoms onset.

Results— Median [quartiles] plasma 15-dPGJ 2 levels on admission were significantly higher in patients than in controls (60.5 [11.2 to 109.4] versus 5.0 [3.8 to 7.2] pg/mL; P <0.0001). Levels of this prostaglandin were also significantly higher in patients with vascular risk factors (history of hypertension or diabetes) and with atherothrombotic infarcts (113.9 [81.6 to 139.7] pg/mL), than in those with lacunar (58.7 [32.7 to 86.2] pg/mL), cardioembolic (12.1 [6.5 to 39.2] pg/mL), or undetermined origin infarcts (11.4 [5.6 to 24.3] pg/mL) ( P <0.0001). In the subgroup of patients with atherothrombotic infarcts, the adjusted odds ratio of END and poor outcome for 1 pg/mL increase in 15-dPGJ 2 were 0.95 (95% CI, 0.94 to 0.97) and 0.97 (95% CI, 0.96 to 0.98), respectively. In a generalized linear model, by 1 U increase in 15-dPGJ 2 , there was a reduction of 0.47 mL (95% CI, 0.32 to 0.63) in the mean estimated infarct volume.

Conclusions— Increased plasma 15-dPGJ 2 concentration is associated with good early and late neurological outcome and smaller infarct volume. These findings suggest a neuroprotective effect of 15-dPGJ 2 in atherothrombotic ischemic stroke.

Neuroprotection afforded by prior citicoline administration in experimental brain ischemia: effects on glutamate transport

BACKGROUND AND PURPOSE

Cytidine-5'-diphosphocholine (citicoline or CDP-choline), an intermediate in the biosynthesis of phosphatidylcholine, has shown beneficial effects in a number of CNS injury models including cerebral ischemia. Citicoline is the only neuroprotectant that has proved efficacy in patients with moderate to severe stroke. However, the precise mechanism by which citicoline is neuroprotective is not fully known. The present study was designed to search for mechanisms of citicoline neuroprotective properties using in vivo and in vitro models of brain ischemia.

METHODS

Focal brain ischemia was produced in male adult Fischer rats by occluding both the common carotid and middle cerebral arteries. Brain glutamate levels were determined at fixed intervals after occlusion. Animals were then sacrificed, and infarct volume and brain ATP levels were measured. As in vitro model of ischemia, rat cultured cortical neurones or astrocytes, isolated or in co-culture, were exposed to oxygen-glucose deprivation (OGD) either in the absence or in the presence of citicoline (1-100 microM). Viability was studied by measuring LDH release. Glutamate release and uptake, and ATP levels were also determined.

RESULTS

Citicoline (0.5, 1 and 2 g/kg i.p. administered 1 h before the occlusion) produced a reduction of the infarct size measured at striatum (18, 27 and 42% inhibition, respectively, n = 8, P < 0.05 vs. ischemia), effect that correlated with the inhibition caused by citicoline on ischemia-induced increase in glutamate concentrations after the onset of the ischemia. Citicoline also inhibited ischemia-induced decrease in cortical and striatal ATP levels. Incubation of cultured rat cortical neurones with citicoline (10 and 100 microM) prevented OGD-induced LDH and glutamate release and caused a recovery in ATP levels after OGD, confirming our previous results. In addition, citicoline (100 microM) caused an increase in glutamate uptake and in EAAT2 glutamate transporter membrane expression in cultured rat astrocytes.

CONCLUSIONS

Our present findings show novel mechanisms for the neuroprotective effects of citicoline, which cooperate to decrease brain glutamate release after ischemia.

Inhibition of iNOS activity by 1400W decreases glutamate release and ameliorates stroke outcome after experimental ischemia

BACKGROUND AND PURPOSE

It has been shown that the reversed operation of glutamate transporters when ATP levels fall accounts for most glutamate release induced by severe cerebral ischemia. Nitric oxide (NO) is formed after ischemia and causes ATP depletion. Our purpose is to test if NO release from inducible NO synthase (iNOS) after stroke may cause a delayed glutamate release due to ATP depletion that might underlie progression of the ischemic infarct. We have studied the effect of the highly selective inhibitor of iNOS activity 1400W on brain ATP levels, extracellular glutamate, and stroke outcome after transient focal cerebral ischemia in rats.

METHODS

To induce focal ischemia, the middle cerebral artery (MCA) was occluded by using the intraluminal thread technique (tMCAO). 1400W was administered, after tMCAO, by using an Alzet osmotic pump to yield a drug delivery rate of 2.5 mg/kg/h. Results. Postischemic treatment with 1400W induced a reduction in the neurofunctional impairment and in the total volume of brain infarct. Western blot analysis showed ischemia-induced expression of iNOS. Treatment with 1400W partially prevented delayed ATP reduction and produced inhibition of the subsequent delayed increase in glutamate levels caused by the ischemic insult.

CONCLUSIONS

Our data indicate that 1400W improves stroke outcome, an effect concomitant to the inhibition of both ischemia-induced decrease in brain ATP levels and increase in glutamate release. These results provide evidence indicating that the expression of iNOS induced by ischemia may contribute to the progression of the ischemic infarct and have important therapeutic implications for the management of stroke.

Peroxisome proliferator-activated receptor gamma activation decreases neuroinflammation in brain after stress in rats

BACKGROUND

A growing body of evidence has demonstrated that peroxisome proliferator-activated receptor gamma (PPARgamma) play a role in brain inflammatory conditions because various PPARgamma ligands inhibit proinflammatory mediators, such as cytokines (tumor necrosis factor alpha [TNFalpha]) and inducible nitric oxide synthase (NOS-2). As has been previously shown, immobilization stress and stress-related neuropsychologic conditions are followed by accumulation of oxidative/nitrosative mediators in brain after the release of cytokines, nuclear factor kappaB activation, and NOS-2 and cyclooxygenase 2 (COX-2) expression in the brain.

METHODS

To assess whether PPARgamma activation can modify the accumulation of oxidative/nitrosative species seen in brain after stress, and to study the mechanisms by which this effect is achieved, young-adult male Wistar rats (control and immobilized during 6 hours) were injected (IP) with the high-affinity ligand rosiglitazone (RS) at the onset of stress.

RESULTS

Stress increased PPARgamma expression in cortical neurons and glia as assessed by Western blot and immunohistochemistry. In stressed animals, RS (1-3 mg/kg) decreased stress-induced increases in NOS-2 activity. On the other hand, the PPARgamma ligand decreased stress-induced malondialdehyde (an indicator of lipid peroxidation) accumulation in cortex and prevented oxidation of the main antioxidant glutathione. The mechanisms involved in the antioxidative properties of RS in stress involve nuclear factor KB blockade (by preventing stress-induced IkappaBalpha decrease) and inhibition of TNFalpha release in stressed animals. At the doses tested, RS did not decrease COX-2 expression and prostaglandin E2 release during stress. Finally, RS also decreased chronic (repeated immobilization for 21 days) stress-induced accumulation of oxidative/nitrosative mediators.

CONCLUSIONS

Taken together, these findings suggest a role for this antiinflammatory pathway in the brain response to stress and the possibility of pharmacologic modulation for preventing accumulation of oxidative/nitrosative species and subsequent brain damage in stress-related neuropsychologic conditions.

TNFR1 upregulation mediates tolerance after brain ischemic preconditioning

A short ischemic event (ischemic preconditioning (IPC)) can result in subsequent resistance to severe ischemic injury (ischemic tolerance (IT)). The expression and neuroprotective role of tumor necrosis factor (TNF-alpha) have been described in models of IPC and we have showed the participation of its processing enzyme, the TNF-alpha convertase enzyme (TACE) in this process. We have now decided to explore the expression and localization of TNF receptors (TNFR) as well as other signalling mechanisms involved in IT. A period of 10 mins of temporary middle cerebral artery occlusion (tMCAO) was used for focal IPC. To evaluate the ability of IPC to produce IT, permanent MCAO was performed 48 hours after IPC. Ischemic preconditioning produced a reduction in infarct volume, as we showed previously. Ischemic preconditioning caused upregulation of neuronal TNFR1 that was reduced by the selective TACE inhibitor BB1101. Intracerebral administration of TNFR1 antisense oligodeoxynucleotide, which caused a reduction in TNFR1 expression, inhibited the IPC-induced protective effect, showing that TNFR1 upregulation is implicated in IT. Moreover, treatment with BB1101, TNFR1 antisense and lactacystin-a specific proteasome inhibitor-blocked IPC-induced NF-kappaB. Immunohistochemical studies showed the expression of TACE and TNFR1 in neurons. In summary, these data show that IPC produces neuronal upregulation of TACE and TNFR1, and that the pathway TACE/TNF-alpha/TNFR1/NF-kappaB is involved in IT.

TNF-alpha accounts for short-term persistence of oxidative status in rat brain after two weeks of repeated stress

Inducible nitric oxide synthase (NOS-2) accounts for the accumulation of oxidative and nitrosative mediators in brain after stress. To determine whether and when repeated exposure to immobilization stress leads to persistent oxidative status in rat brain, male Wistar rats were immobilized for 6 h/day for 7 or 14 days (S7, S14). Cerebral cortices were obtained immediately after the last session of stress or 1 day later. Stress increased NOS-2 activity after S7 or S14. This enzymatic activity returned to basal values 1 day after S7, but not 1 day after S14. Stress increased malondialdehyde (MDA) accumulation in cortex after S7 and S14. MDA levels returned to basal values 1 day after S7 but not 1 day after S14. In order to elucidate the possible mechanisms involved in this short-term persistence of oxidative status, brain levels of the cytokine tumour necrosis factor alpha (TNF-alpha) were determined. TNF-alpha levels did not increase after S7 or 1 day after S7, but increased after S14 and 1 day after S14. This was paralleled by an increase in TNF-alpha converting enzyme (TACE) activity in brain. When the increase in TNF-alpha at S14 was blocked by BB1101, an inhibitor of TACE, or its effects were blocked with anti-TNF-alpha, the accumulation of MDA and NOS-2 activity 1 day after S14 did not take place. These findings indicate that TACE and TNF-alpha account for stress-induced short-term persistence of NOS-2 activity and MDA accumulation after 14 days of repeated exposure and support a possible neuroprotective role for specific blockers of TNF-alpha in this situation.

Stress increases susceptibility to oxidative/nitrosative mucosal damage in an experimental model of colitis in rats

Inflammatory bowel diseases (IBDs) are multifactorial processes. Clinical and animal studies indicate that emotional stress may contribute to the onset and progress of these diseases. On the other hand, enhanced free radical production in mucosal cells has been also implicated in the pathogenesis of IBD. Using an experimental model of colitis induced by intrarectal instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS) plus ethanol (vehicle), we sought to determine whether prior exposure to immobilization stress modifies the susceptibility to oxidative damage in colonic mucosa. Several groups of Wistar rats were used: control (C) and stressed (by immobilization of 6 hr every day during 10 days; S) groups and rats receiving a colitis-inducing dose of TNBS on day 5 (30 mg; TNBS30) and a noninflammatory dose of TNBS on day 5 (5 mg; TNBS5) with or without stress (prior exposure, days 0-5, and after, days 5-10). At the 10th day, colonic tissue was dissected and processed for biochemical studies. TNBS30 led to body weight loss, macroscopic colonic ulceration, and inflammation (determined by histological parameters and myeloperoxidase [MPO] activity) and to an increase in inducible nitric oxide synthase (NOS-2) activity and expression. TNBS5-instilled animals' body weight and biochemical inflammatory parameters were not significantly different from those in control animals. Interestingly, while stress did not modify body weight, macroscopic aspect of the mucosa, or NOS activity in animals receiving TNBS30, immobilization increased body weight loss, MPO levels, and malondialdehyde (MDA; an indicator of lipid peroxidation) levels after TNBS5. On the other hand, stress increased NOS-2 activity and immunohistochemical expression after instillation of TNBS5. Moreover, constitutive, Ca2+ -dependent NOS activity decreased in stressed animals instilled with TNBS5 compared with nonstressed animals receiving TNBS5 (-28.5 +/- 6.6%; P < 0.05). These findings indicate that previous exposure to stressful stimuli is a factor in susceptibility to oxidative damage in experimental colitis and support a possible protective effect of treatment of stress before and during the development of inflammation in the colon.

Activity of inducible and neuronal nitric oxide synthases in colonic mucosa predicts progression of ulcerative colitis

OBJECTIVE

The present study analyzes inducible and neuronal nitric oxide synthase activity and expression in colonic mucosa of patients with ulcerative colitis, and correlates them with the progression of disease extent.

METHODS

Thirty patients with ulcerative colitis were included. Synthases activity and expression were analyzed both in inflamed and noninflamed mucosa. After 2 yr, disease extent was determined and compared with extent at inclusion.

RESULTS

Ca(2+)-independent activity, expressed as median with (interquartile range), in inflamed mucosa was higher than in noninflamed and control mucosa (102 (165-66), 24 (50-3), 1 (2.5-0.1) pmol.min(-1) mg prot(-1), respectively, p < 0.005), whereas Ca(2+)-dependent activity was significantly lower in inflamed than in noninflamed and control mucosa. Western blot analysis identified inducible and neuronal isoforms and confirmed these differences. Patients with more extended disease after 2 yr had higher levels of Ca(2+)-independent activity in noninflamed mucosa at inclusion and lower levels of Ca(2+)-dependent activity than patients with persistence of similar extent of inflammation (50 (78-29) vs 8 (30-0.1), p < 0.005; 51 (100-36) vs 150 (156-106), p < 0.05, respectively). Values of Ca(2+)-independent activity in noninflamed mucosa greater than 30 pmol. min(-1) mg prot(-1) showed 80% sensitivity and 87.5% specificity in the detection of patients with subsequent progression of disease extent, whereas values of Ca(2+)-dependent activity in noninflamed mucosa greater than 125 pmol. min(-1) mg prot(-1) showed 75% sensitivity and 80% specificity in the detection of patients with stability of disease extent. A ratio of Ca(2+)-independent/Ca(2+)-dependent activities over 0.29 showed 90% sensitivity and 87.5% specificity in the detection of patients with subsequent progression of extent.

CONCLUSIONS

Our results show an up-regulation of inducible nitric oxide synthase and a down-regulation of neuronal isoform not only in inflamed mucosa but also in apparently healthy mucosa of patients with ulcerative colitis. The values of activity of both isoforms in apparently healthy mucosa could predict the disease extent after 2 yr follow-up.

Role of nitric oxide after brain ischaemia

Ischaemic stroke is the second or third leading cause of death in developed countries. In the last two decades substantial research and efforts have been made to understand the biochemical mechanisms involved in brain damage and to develop new treatments. The evidence suggests that nitric oxide (NO) can exert both protective and deleterious effects depending on factors such as the NOS isoform and the cell type by which NO is produced or the temporal stage after the onset of the ischaemic brain injury. Immediately after brain ischaemia, NO release from eNOS is protective mainly by promoting vasodilation; however, after ischaemia develops, NO produced by overactivation of nNOS and, later, NO release by de novo expression of iNOS contribute to the brain damage. This review article summarizes experimental and clinical data supporting the dual role of NO in brain ischaemia and the mechanisms by which NO is regulated after brain ischaemia. We also review NO-based therapeutic strategies for stroke treatment, not only those directly linked with the NO pathway such as NO donors and NOS inhibitors but also those partially related like statins, aspirin or lubeluzole.

In vitro ischemic tolerance involves upregulation of glutamate transport partly mediated by the TACE/ADAM17-tumor necrosis factor-alpha pathway

A short ischemic event [ischemic preconditioning (IPC)] can result in a subsequent resistance to severe ischemic injury (ischemic tolerance). Although tumor necrosis factor-alpha (TNF-alpha) contributes to the brain damage found after cerebral ischemia, its expression and neuroprotective role in models of IPC have also been described. Regarding the role of TNF-alpha convertase (TACE/ADAM17), we have recently shown its upregulation in rat brain after IPC induced by transient middle cerebral artery occlusion and that subsequent TNF-alpha release accounts for at least part of the neuroprotection found in this model. We have now used an in vitro model of IPC using rat cortical cultures exposed to sublethal oxygen-glucose deprivation (OGD) to investigate TACE expression and activity after IPC and the subsequent mechanisms of ischemic tolerance. OGD-induced cell death was significantly reduced in cells exposed to IPC by sublethal OGD 24 hr before, an effect that was inhibited by the TACE inhibitor BB3103 (1 microm) and anti-TNF-alpha antibody (2 microg/ml) and that was mimicked by TNF-alpha (10 pg/ml) preincubation. Western blot analysis showed that TACE expression is increased after IPC. IPC caused TNF-alpha release, an effect that was blocked by the selective TACE inhibitor BB-3103. In addition, IPC diminished the increase in extracellular glutamate caused by OGD and increased cellular glutamate uptake and expression of EAAT2 and EAAT3 glutamate transporters; however, only EAAT3 upregulation was mediated by increased TNF-alpha. These data demonstrate that neuroprotection induced by IPC involves upregulation of glutamate uptake partly mediated by TACE overexpression.

The release of tumor necrosis factor-alpha is associated with ischemic tolerance in human stroke

Tumor necrosis factor (TNF)-alpha overexpression has been related to experimental ischemic tolerance when transient ischemia precedes cerebral infarction. We investigated TNF-alpha and interleukin (IL)-6 plasma concentrations in 283 patients with an acute stroke within 24 hours after symptom onset. An ipsilateral transient ischemic attack (TIA) within 72 hours before stroke was recorded in 38 patients. The infarct volume measured on computed tomography on days 4 to 7 and the frequency of poor outcome (Barthel Index score < 85) at 3 months were significantly lower in patients with prior TIA. Plasma concentrations of TNF-alpha were higher (42.5 +/- 9.9 vs 13.1 +/- 6.4pg/ml, p < 0.0001) and IL-6 levels were lower (10.1 +/- 6.2 vs 28.3 +/- 17.3pg/ml, p < 0.0001) in patients with prior TIA. A new variable termed TNF-alpha/IL-6 index was considered positive when TNF-alpha was greater than 30pg/ml and IL-6 was less than 30pg/ml. Positive TNF-alpha/IL-6 index was found in 92% of patients with prior TIA and in 1% of those without. TNF-alpha/IL-6 index (p = 0.0003) and TIA (p = 0.0001) were associated with good outcome in logistic regression analysis after adjusting for potential confounding factors. Ischemic tolerance in acute stroke is associated with increased plasma levels of TNF-alpha in the presence of reduced concentrations of IL-6.

Relationship between cyclooxygenase-2 and nitric oxide synthase-2 in rat cortex after stress

Many studies have focused on the relationships between distinct enzymatic sources of oxidative mediators. Recently, we have shown that cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (NOS-2) isoforms are up-regulated and account for oxidative damage in brain after stress. To assess the time course of these events, we have used adult male Wistar rats, some of which were immobilized for 6 h. Whereas pretreatment with the specific COX-2 inhibitor NS-398 (5 mg/kg i.p.) decreased Ca2+-independent NOS activity after 6 h of stress, pretreatment with the specific NOS-2 inhibitor 1400 W (4 mg/kg i.p.) did not decrease prostaglandin E2 (PGE2) accumulation induced by stress after 6 h. The observed effects of NS-398 and 1400 W were independent of the general response to stress--neither drug modified stress-induced corticosterone response--which might indicate a possible adaptive role for COX-2 and NOS-2 pathways in this situation. These findings are discussed as possible therapeutic targets in the context of neuropsychiatric disorders related to stress.

[Experimental headache models]

The use of experimental models is so common in most diseases, such as stroke, epilepsy or brain injury, that it does not seem to be necessary to justify in the study of experimental headache models. However, the study of these models was not been possible until 10-15 years ago. Two main reasons made it possible: first, increased basic knowledge about disease mechanisms in the last decade, a requirement necessary before models can be developed and validated; second, the publication of the headache classification of the International Headache Society in 1988 which has permitted an exact diagnosis, avoiding interobserver variability. This review examines the use of animal models to study the neurogenic inflammation described by Moskowitz and those used to study the vascular hypothesis. We have also examined the use of animal experiments to study the neurobiological basis for pain. Finally, we have explored the experimental human headache models not only in sufferers but also in healthy volunteers.

Inhibition of glutamate release by delaying ATP fall accounts for neuroprotective effects of antioxidants in experimental stroke

Excitotoxic neuronal injury related to excessive glutamate release is believed to play a key role in the pathogenesis of focal cerebral ischemia. Reversal of neuronal glutamate transporters caused by ATP fall and subsequent imbalance of membrane ionic gradients accounts for most glutamate release after cerebral ischemia. ATP synthesis from oxidative phosphorylation derives from the coupled functioning of the mitochondrial respiratory chain (MRC) and the ATP synthase; interestingly, the MRC is one of the main sites of cellular reactive oxygen species (ROS) generation even in physiological circumstances. Hence, we have studied the effect of the antioxidants glutathione, superoxide dismutase, and alpha-tocopherol on infarct outcome, brain ATP, and glutamate levels after permanent middle cerebral artery occlusion (MCAO) in Fischer rats; we have also characterized the actions of antioxidants on MRC complexes. Our results show that intraperitoneal administration of antioxidants 2 h before MCAO enhances ATP synthesis and causes a neuroprotective effect concomitant to inhibition of ischemia-induced increase in brain glutamate. Antioxidants also increased mitochondrial ATP and MRC complex I-III activity and respiration, suggesting that these actions are due to removal of the inhibition caused by endogenous ROS on MRC. These findings may possess important therapeutic repercussions in the management of ischemic stroke.

[Consensus review. Pharmacological neuroprotection in cerebral ischemia: is it still a therapeutic option?]

Our increasing knowledge concerning the pathophysiology of cerebral ischemia is leading to a considerable development of drugs that at various levels block or modify the chain of biochemical processes set off as a consequence of hypoperfusion of cerebral parenchyma. In this zone of ischemic penumbra, the interaction between the neuronal ischemia cascade, the response of the glia and changes in the microcirculation, determine the evolution towards either functional recovery of the ischemic fabric or it necrosis. In various types of animal models, the majority of neuroprotective drugs have been shown to have considerable efficacy. However, this has not been translated into human clinical practice. The identification of persistence of recoverable cerebral tissue, together with the development of new designs of clinical trails better adapted to preclinical experiences and to the features of the drugs concerned, may contribute to an improved applicability of the new drugs in human clinical practice.

Induction of cyclooxygenase-2 accounts for restraint stress-induced oxidative status in rat brain

Cyclooxygenase (COX) is the rate-limiting enzyme in the metabolism of arachidonic acid into prostanoids. Although it is constitutively expressed in brain neurons, the inducible isoform (COX-2) is also upregulated in pathological conditions such as seizures, ischemia or some degenerative diseases. To assess whether COX-2 is regulated after stress, we have used adult male Wistar rats, some of which were immobilized during 6 h. An increase in PGE2 concentration occurs in brain cortex after 2-6 h of the onset of stress as well as an enhancement of COX-2 protein. Immunohistochemical studies indicate that COX-2 is expressed in the cortex and hippocampus after stress in cells with morphology of neurons. Administration of PDTC (150 mg/kg), an inhibitor of the transcription factor NF-kappaB or MK-801 (0.2 mg/kg), an N-methyl-D-aspartate receptor blocker, prevents both stress-induced increase in COX-2 activity and protein levels, suggesting an implication of these factors in the mechanism by which stress induces COX-2 in brain. To assess if COX-2 accounts for the oxidative status seen in brain after stress, a group of animals were i.p. injected with NS-398, a specific COX-2 inhibitor 1 h prior to the onset of stress. NS-398 (5 mg/kg) decreases stress-induced malondialdehyde accumulation in cortex as well as prevents the stress-induced oxidation of glutathione. Finally, NS-398 reduced Ca2+-independent inducible nitric oxide synthase (iNOS, NOS-2) activity and lowered the stress-induced accumulation of NO metabolite levels in cortex. These effects of NS-398 seem to be due to the specific inhibition of COX-2, since it has no effect on stress-induced corticosterone release, glutamate release, and NF-kappaB activation. These findings are discussed as possible damaging and/or adaptive roles for stress-induced COX-2 in the brain.