Activation of liver X receptors promotes neuroprotection and reduces brain inflammation in experimental stroke

BACKGROUND

The liver X receptors (LXRs) belong to the nuclear receptor superfamily and act as transcriptional regulators of cholesterol metabolism in several tissues. Recent work also has identified LXRs as potent antiinflammatory molecules in macrophages and other immune cells. Combined changes in lipid and inflammatory profiles are likely mediating the protective role of LXRs in models of chronic injury like atherosclerosis. These beneficial actions, however, have not been illustrated in other models of acute injury such as stroke in which inflammation is an important pathophysiological feature.

METHODS AND RESULTS

We have studied LXR expression and function in the course of experimental stroke caused by permanent middle cerebral artery occlusion in rats and mice. Here, we show that administration of the synthetic LXR agonists GW3965 or TO901317 after the ischemic occlusion improves stroke outcome as shown by decreased infarct volume area and better neurological scores in rats. Neuroprotection observed with LXR agonists correlated with decreased expression of proinflammatory genes in the brain and with reduced nuclear factor-kappaB transcriptional activity. Loss of function studies using LXRalpha,beta(-/-) mice demonstrated that the effect of LXR agonists is receptor specific. Interestingly, infarcted brain area and inflammatory signaling were significantly extended in LXRalpha,beta(-/-) mice compared with control animals, indicating that endogenous LXR signaling mediates neuroprotection in this setting.

CONCLUSIONS

This work highlights the transcriptional action of LXR as a protective pathway in brain injury and the potential use of LXR agonists as therapeutic agents in stroke.

Toll-like receptor 4 is involved in subacute stress-induced neuroinflammation and in the worsening of experimental stroke

BACKGROUND AND PURPOSE

Psychological stress causes an inflammatory response in the brain and is able to exacerbate brain damage caused by experimental stroke. We previously reported that subacute immobilization stress in mice worsens stroke outcome through mechanisms that involve inflammatory mechanisms, such as accumulation of oxidative/nitrosative mediators and expression of inducible nitric oxide synthase and cyclooxygenase-2 in the brain. Some of these inflammatory mediators could be regulated by innate immunity, the activation of which takes place in the brain and produces an inflammatory response mediated by toll-like receptors (TLRs). Recently, we described the implications of TLR4 in ischemic injury, but the role of TLR4 in stress has not yet been examined. We therefore investigated whether inflammation produced by immobilization stress differs in mice that lack a functional TLR4 signaling pathway.

METHODS

We used an experimental paradigm consisting of the exposure of mice to repeated immobilization sessions (1 hour daily for 7 days) before permanent middle cerebral artery occlusion.

RESULTS

We found that TLR4-deficient mice subjected to subacute stress had a better behavioral condition compared with normal mice (C3H/HeN) and that this effect was associated with a minor inflammatory response (cyclooxygenase-2 and inducible nitric oxide synthase expression) and lipid peroxidation (malondialdehyde levels) in brain tissue. Furthermore, previous exposure to stress was followed by a smaller infarct volume after permanent middle cerebral artery occlusion in TLR4-deficient mice than in mice that express TLR4 normally.

CONCLUSIONS

Our results indicate that TLR4 is involved in the inflammatory response after subacute stress and its exacerbating effect on stroke. These data implicate the effects of innate immunity on inflammation and damage in the brain after stroke.

Role of K+ and Ca2+ fluxes in the cerebroarterial vasoactive effects of sildenafil

The aim of this study was to assess the role of K(+) and Ca(2+) fluxes in the cerebroarterial vasoactive effects of the phosphodiesterase-5 inhibitor sildenafil. We used isolated rabbit basilar arteries to assess the effects of extracellular K(+) raising on sildenafil-induced vasodilatation, and studied the pharmacological interaction of sildenafil with selective modulators of membrane K(+) and Ca(2+) channels. Expression of Kv1 subunits of K(+) channels was assessed at messenger and protein levels. Parallel experiments were carried out with zaprinast for comparison. Sildenafil (10 nM-0.1 mM) induced concentration-dependent relaxation of endothelin-1 (10 nM)-precontracted arteries, which was partially inhibited by depolarization with KCl (50 mM), 3 mM tetraethylammonium (non-selective K(+) channel blocker) or 1 mM aminopyridine (inhibitor of K(v) channels), but not by 1 microM glibenclamide (inhibitor of K(ATP) channels) or 50 nM iberiotoxin (inhibitor of K(Ca) channels). Arterial smooth muscle expressed messengers for Kv1.2, Kv1.3, Kv1.4, Kv1.5 and Kv1.6, and proteins of Kv1.1, Kv1.2 and Kv1.4. CaCl(2) (10 microM- 10 mM) induced concentration-dependent contraction in Ca(2+)-free, depolarizing (50 mM KCl) medium. Sildenafil (0.1-100 microM) produced reversible concentration-dependent inhibition of the response to CaCl(2), which was completely abolished by the highest sildenafil concentration. By contrast, only 100 microM zaprinast inhibited the response to CaCl(2). The L-type Ca(2+) channel activator Bay K 8644 (0.1 nM-1 microM) induced concentration-dependent potentiation of the response to CaCl(2) inhibited by 100 microM sildenafil. Moreover, Bay K 8644 (0.1 nM-1 microM) induced concentration-dependent contraction in slightly depolarizing (15 mM) medium, which was inhibited to the same extent and in a concentration-dependent way by sildenafil (0.1-100 microM) and zaprinast (1 or 100 microM). These results show that sildenafil relaxes the rabbit basilar artery by increasing K(+) efflux through K(v) channels, which in turn may affect Ca(2+) signalling. Expression of Kv1 subunits involved in this pharmacological effect occurs at the messenger and, in some cases, at the protein level. In addition to this phosphodiesterase-5-related effect, sildenafil and zaprinast inhibit cerebroarterial vasoconstriction at least in part by directly blocking L-type Ca(2+) channels, although a decrease in the sensitivity of the contractile apparatus to Ca(2+) can not be discarded.

Statin treatment withdrawal in ischemic stroke: a controlled randomized study

BACKGROUND

Pretreatment with statins has been shown to reduce brain injury in cerebral ischemia. In this controlled randomized study, we investigated the influence of statin pretreatment and its withdrawal on the outcome of acute ischemic stroke patients.

METHODS

From 215 patients admitted within 24 hours of a hemispheric ischemic stroke, 89 patients on chronic statin treatment were randomly assigned either to statin withdrawal for the first 3 days after admission (n = 46) or to immediately receive atorvastatin 20 mg/day (n = 43). The primary outcome event was death or dependency (modified Rankin Scale [mRS] score > 2) at 3 months. Early neurologic deterioration (END) and infarct volume at days 4 to 7 were secondary outcome variables. In a secondary analysis, outcome variables were compared with the nonrandomized patients without previous statin therapy (n = 126).

RESULTS

Patients with statin withdrawal showed a higher frequency of mRS score > 2 at the end of follow-up (60.0% vs 39.0%; p = 0.043), END (65.2% vs 20.9%; p < 0.0001), and greater infarct volume (74 [45, 126] vs 26 [12, 70] mL; p = 0.002) compared with the non-statin-withdrawal group. Statin withdrawal was associated with a 4.66 (1.46 to 14.91)-fold increase in the risk of death or dependency, a 8.67 (3.05 to 24.63)-fold increase in the risk of END, and an increase in mean infarct volume of 37.63 mL (SE 10.01; p < 0.001) after adjusting for age and baseline stroke severity. Compared with patients without previous treatment with statins, statin withdrawal was associated with a 19.01 (1.96 to 184.09)-fold increase in the risk of END and an increase in mean infarct volume of 43.51 mL (SE 21.91; p = 0.048).

CONCLUSION

Statin withdrawal is associated with increased risk of death or dependency at 90 days. Hence, this treatment should be continued in the acute phase of ischemic stroke.

The cannabinoid agonist WIN55212 reduces brain damage in an in vivo model of hypoxic-ischemic encephalopathy in newborn rats

Neonatal hypoxic-ischemic encephalopathy (NHIE) is a devastating condition for which effective therapeutic treatments are still unavailable. Cannabinoids emerge as neuroprotective substances in adult animal studies; therefore, we aimed herein to test whether cannabinoids might reduce brain damage induced by hypoxiaischemia (HI) in newborn rats. Thus, 7-d-old Wistar rats (P7) were exposed to 8% O2 for 120 min after left carotid artery ligature, then received s.c. vehicle (VEH) (HI+VEH), the cannabinoid agonist WIN55212 (WIN) (0.1 mg/kg), or WIN with the CB1 or CB2 receptor antagonist SR141617 (SR1) (3 mg/kg) or SR141588 (SR2) (2 mg/kg). Brain damage was assessed by magnetic resonance imaging (MRI) at 1, 3, and 7 d after the insult. At the end of the experiment, MRI findings were corroborated by histology (Nissl staining). HI+VEH showed an area of cytotoxic and vasogenic edema at 24 h after the insult, then evolving to necrosis. HI+WIN showed a similar damaged area at 24 h after the insult, but the final necrotic area was reduced by 66%. Coadministration of either SR1 or SR2 reversed the effects of WIN. In conclusion, likely by activating CB1 and CB2 receptors, WIN afforded robust neuroprotection in newborn rats after HI.

Involvement of IL-1beta in acute stress-induced worsening of cerebral ischaemia in rats

Stress is known to be one of the risk factors of stroke. Most of the knowledge on the effects of stress on cerebrovascular disease in humans is restricted to catecholamines and glucocorticoids effects on blood pressure and/or development of atherosclerosis. However, few experimental studies have examined the possible mechanisms by which stress may affect stroke outcome. We have used an acute stress protocol consisting of the exposure of male Fischer rats to an acute, single exposure immobilisation protocol (6 h) prior to permanent middle cerebral artery occlusion (MCAO), and we have found that stress worsens behavioural and neurological outcomes and increased infarct size after MCAO. The possible regulatory role of the TNFalpha and IL-1beta was studied by looking at the release of these cytokines in brain. The results of the present study showed an increase in IL-1beta release in cerebral cortex after exposure to acute stress. Brain levels of IL-1beta are also higher in previously stressed MCAO rats than in MCAO animals without stress. Pharmacological blockade of IL-1beta with an antibody anti-IL-1beta led to a decrease in the infarct size as well as in neurological and behavioural deficits after MCAO. In summary, our results indicate that IL-1beta, but not TNFalpha, accounts at least partly for the worsening of MCAO consequences in brain of rats exposed to acute stress.

The increase of circulating endothelial progenitor cells after acute ischemic stroke is associated with good outcome

BACKGROUND AND PURPOSE

Increased circulating endothelial progenitor cells (EPC) have been associated with a low cardiovascular risk and may be involved in endothelial cell regeneration. The present study was designed to evaluate the prognostic value of EPC in acute ischemic stroke.

METHODS

Forty-eight patients with a first-ever nonlacunar ischemic stroke were prospectively included in the study within 12 hours of symptoms onset. Stroke severity was evaluated by the National Institutes of Health Stroke Scale, and functional outcome was assessed at 3 months by the modified Rankin Scale (mRS). Infarct volume growth between admission and days 4 to 7 was measured on multiparametric MRI. EPC colonies were defined as early outgrowth colony-forming unit-endothelial cell (CFU-EC). The increment of CFU-EC was quantified during the first week and defined as the absolute difference between the number of CFU-EC at day 7 and admission. The influence of CFU-EC increase on good functional outcome (mRS <or=2) and infarct growth was analyzed by logistic regression and linear models.

RESULTS

Patients with good outcome (n=25) showed a higher CFU-EC increment during the first week (median [quartiles], 23 [11, 36] versus -3 [-7, 1], P<0.0001) compared with patients with poor outcome. CFU-EC increment >or=4 during the first week was associated with good functional outcome at 3 months (odds ratio, 30.7; 95% CI, 2.4 to 375.7; P=0.004) after adjustment for baseline stroke severity, ischemic volume and thrombolytic treatment. For each unit increase in the CFU-EC the mean reduction in the growth of infarct volume was 0.39 (0.03 to 0.76) mL (P=0.033).

CONCLUSIONS

The increase of circulating EPC after acute ischemic stroke is associated with good functional outcome and reduced infarct growth. These findings suggest that EPC might participate in neurorepair after ischemic stroke.

Delayed post-ischemic administration of CDP-choline increases EAAT2 association to lipid rafts and affords neuroprotection in experimental stroke

Glutamate transport is the only mechanism for maintaining extracellular glutamate concentrations below excitotoxic levels. Among glutamate transporters, EAAT2 is responsible for up to 90% of all glutamate transport and has been reported to be associated to lipid rafts. In this context, we have recently shown that CDP-choline induces EAAT2 translocation to the membrane. Since CDP-choline preserves membrane stability by recovering levels of sphingomyelin, a glycosphingolipid present in lipid rafts, we have decided to investigate whether CDP-choline increases association of EAAT2 transporter to lipid rafts. Flotillin-1 was used as a marker of lipid rafts due to its known association to these microdomains. After gradient centrifugation, we have found that flotillin-1 appears mainly in fractions 2 and 3 and that EAAT2 protein is predominantly found colocalised with flotillin-1 in fraction 2. We have also demonstrated that CDP-choline increased EAAT2 levels in fraction 2 at both times examined (3 and 6 h after 1 g/kg CDP-choline administration). In agreement with this, [(3)H] glutamate uptake was also increased in flotillin-associated vesicles obtained from brain homogenates of animals treated with CDP-choline. Exposure to middle cerebral artery occlusion also increased EAAT2 levels in lipid rafts, an effect which was further enhanced in those animals receiving 2 g/kg CDP-choline 4 h after the occlusion. Infarct volume measured at 48 h after ischemia showed a reduction in the group treated with CDP-choline 4 h after occlusion. In summary, we have demonstrated that CDP-choline redistributes EAAT2 to lipid raft microdomains and improves glutamate uptake. This effect is also found after experimental stroke, when CDP-choline is administered 4 h after the ischemic occlusion. Since we have also shown that this delayed post-ischemic administration of CDP-choline induces a potent neuroprotection, our data provides a novel target for neuroprotection in stroke.

Ischemic preconditioning reveals that GLT1/EAAT2 glutamate transporter is a novel PPARgamma target gene involved in neuroprotection

Excessive levels of extracellular glutamate in the nervous system are excitotoxic and lead to neuronal death. Glutamate transport, mainly by glutamate transporter GLT1/EAAT2, is the only mechanism for maintaining extracellular glutamate concentrations below excitotoxic levels in the central nervous system. We recently showed that neuroprotection after experimental ischemic preconditioning (IPC) involves, at least partly, the upregulation of the GLT1/EAAT2 glutamate transporter in astrocytes, but the mechanisms were unknown. Thus, we decided to explore whether activation of the nuclear receptor peroxisome proliferator-activated receptor (PPAR) gamma, known for its antidiabetic and antiinflammatory properties, is involved in glutamate transport. First, we found that the PPARgamma antagonist T0070907 inhibits both IPC-induced tolerance and reduction of glutamate release after lethal oxygen-glucose deprivation (OGD) (70.1%+/-3.4% versus 97.7%+/-5.2% of OGD-induced lactate dehydrogenase (LDH) release and 61.8%+/-5.9% versus 85.9%+/-7.9% of OGD-induced glutamate release in IPC and IPC+T0070907 1 mumol/L, respectively, n=6 to 12, P<0.05), as well as IPC-induced astrocytic GLT-1 overexpression. IPC also caused an increase in nuclear PPARgamma transcriptional activity in neurons and astrocytes (122.1%+/-8.1% and 158.6%+/-22.6% of control PPARgamma transcriptional activity, n=6, P<0.05). Second, the PPARgamma agonist rosiglitazone increased both GLT-1/EAAT2 mRNA and protein expression and [(3)H]glutamate uptake, and reduced OGD-induced cell death and glutamate release (76.3%+/-7.9% and 65.5%+/-15.1% of OGD-induced LDH and glutamate release in rosiglitazone 1 mumol/l, respectively, n=6 to 12, P<0.05). Finally, we have identified six putative PPAR response elements (PPREs) in the GLT1/EAAT2 promoter and, consistently, rosiglitazone increased fourfold GLT1/EAAT2 promoter activity. All these data show that the GLT1/EAAT2 glutamate transporter is a target gene of PPARgamma leading to neuroprotection by increasing glutamate uptake.

The role of PPARgamma on restoration of colonic homeostasis after experimental stress-induced inflammation and dysfunction

BACKGROUND & AIMS

Psychological stress has been implicated in the clinical course of several gastrointestinal diseases, but the mechanisms implicated and the effects of stress on the normal colon are not yet fully understood.

METHODS

Male Wistar rats were exposed to various immobilization periods as a stress paradigm. Colon was processed to assess myeloperoxidase activity, nitric oxide synthase 2, cyclooxygenase 2, and peroxisome proliferator-activated receptor gamma (PPARgamma) expression and production of prostaglandins. Colonic permeability, bacterial translocation, tight junctions ultrastructure, and immunoglobulin (Ig) A levels were also evaluated.

RESULTS

Exposure to acute (6 hours) immobilization stress produced an increase in myeloperoxidase activity and nitric oxide synthase 2 and cyclooxygenase 2 expression. All these parameters remained increased after 5 days of repeated stress exposure, showing a trend to normalize after 10 days. Levels of the anti-inflammatory eicosanoid 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and expression of PPARgamma run parallel with these changes. Colonic epithelial barrier was altered after stress exposure, and a significant decrease in colonic IgA levels after acute stress exposure was observed. Pretreatment with PPARgamma agonists 15d-PGJ(2) and rosiglitazone prevented colonic inflammation and barrier dysfunction as well as the decrease of IgA production induced after acute stress; PPARgamma specific antagonist T0070907 reverted these effects.

CONCLUSIONS

Activation of PPARgamma in rat colon in vivo seems to counteract colonic inflammation and dysfunction induced by stress. On the other hand, PPARgamma ligands may be therapeutically useful in conditions in which inflammation and barrier dysfunction takes place in colon after exposure to stress.

Toll-like receptor 4 is involved in brain damage and inflammation after experimental stroke

BACKGROUND

Stroke is the second to third leading cause of death. Toll-like receptor 4 (TLR4) is a signaling receptor in innate immunity that is a specific immunologic response to systemic bacterial infection and cerebral injury. The role of TLR4 in brain ischemia has not been examined yet. We have therefore investigated whether cerebral ischemia and inflammation produced by permanent occlusion of the middle cerebral artery differ in mice that lack a functional TLR4 signaling pathway.

METHODS AND RESULTS

Permanent occlusion of the middle cerebral artery was performed on 2 strains of TLR4-deficient mice (C3H/HeJ and C57BL/10ScNJ) and respective controls (C3H/HeN and C57BL/10ScSn). Stroke outcome was evaluated by determination of infarct volume and assessment of neurological scores. Brains were collected 24 hours and 7 days after stroke. When compared with control mice, TLR4-deficient mice had lower infarct volumes and better outcomes in neurological and behavioral tests. Mice that lacked TLR4 had minor expression of stroke-induced interferon regulatory factor-1, inducible nitric oxide synthase, and cyclooxygenase-2, mediators implicated in brain damage. The levels of interferon-beta and of the lipid peroxidation marker malondialdehyde were also lower in brains from TLR4-deficient mice than in those from control mice. In addition, the expression of matrix metalloproteinase-9, which is induced and mediates brain damage, was also reduced in TLR4-deficient mice after experimental stroke.

CONCLUSIONS

TLR4-deficient mice have minor infarctions and less inflammatory response after an ischemic insult. These data demonstrate that TLR4 signaling and innate immunity are involved in brain damage and in inflammation triggered by ischemic injury.

A chronic treatment with CDP-choline improves functional recovery and increases neuronal plasticity after experimental stroke

Chronic impairment of forelimb and digit movement is a common problem after stroke that is resistant to therapy. Although in the last years some studies have been performed to increase the efficacy of rehabilitative experience and training, the pharmacological approaches in this context remain poorly developed. We decided to study the effect of a chronic treatment with CDP-choline, a safe and well-tolerated drug that is known to stabilize membranes, on functional outcome and neuromorphological changes after stroke. To assess the functional recovery we have performed the staircase reaching test and the elevated body swing test (EBST), for studying sensorimotor integration and asymmetrical motor function respectively. The treatment with CDP-choline, initiated 24 h after the middle cerebral artery occlusion (MCAO) and maintained during 28 days, improved the functional outcome in both the staircase test (MCAO+CDP=87.0+/-6.6% pellets eaten vs. MCAO+SAL=40.0+/-4.5%; p<0.05) and the EBST (MCAO+CDP=70.0+/-6.8% vs. MCAO+SAL=88.0+/-5.4%; contralateral swing p<0.05). In addition, to study potential neuronal substrates of the improved function, we examined the dendritic morphology of layer V pyramidal cells in the undamaged motor cortex using a Golgi-Cox procedure. The animals treated with CDP-choline showed enhanced dendritic complexity and spine density compared with saline group. Our results suggest that a chronic treatment with CDP-choline initiated 24 h after the insult is able to increase the neuronal plasticity within noninjured and functionally connected brain regions as well as to promote functional recovery.

New-onset hypertension and inflammatory response/poor outcome in acute ischemic stroke

OBJECTIVE

To study the association of previously unknown high blood pressure (HBP) during the acute phase of stroke (new-onset hypertension) with the inflammatory response and clinical outcome.

METHODS

We classified 844 patients with hemispheric ischemic stroke into three groups according to history of hypertension and presence of HBP within the first 24 hours after symptom onset: Group I (n = 412), normotensive patients; Group II (n = 265), chronic hypertensive patients; and Group III (n = 167), new-onset hypertensive patients. Interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and metalloproteinase 9 (MMP-9) were measured in blood samples obtained on admission. The influence of new-onset HBP and markers of inflammation on poor neurologic outcome at 3 months was evaluated by logistic regression analysis.

RESULTS

New-onset HBP was found in 19.9% of patients. Patients in this group had higher plasma concentrations of IL-6, TNF-alpha, ICAM-1, VCAM-1, and MMP-9 than the other two groups. New-onset HBP was associated with poor outcome at 3 months (odds ratio [OR] 2.10; 95% CI 1.54 to 3.52; p < 0.0001) after adjustment for other prognostic factors. However, when markers of inflammation were included in the model, IL-6 (OR 1.01; 95% CI 1.00 to 1.03; p = 0.020) and MMP-9 (OR 1.01; 95% CI 1.00 to 1.01; p < 0.0001), but not new-onset HBP, were independently associated with poor neurologic outcome.

CONCLUSIONS

New-onset high blood pressure in acute ischemic stroke, but not chronic hypertension, is associated with an inflammatory response and poor neurologic outcome.

Micro- and macroalbuminuria predict hemorrhagic transformation in acute ischemic stroke

BACKGROUND

Hemorrhagic transformation (HT) after cerebral ischemia seems to be related to the endothelial disruption secondary to the ischemic process. Albuminuria has recently been found to be a marker of chronic endothelial damage.

OBJECTIVE

To investigate the relationship between albuminuria and HT in patients with acute ischemic stroke.

METHODS

We studied 200 patients (51.5% men, age 72.5 +/- 8.5 years) with ischemic stroke within the first 24 hours of evolution. HT development was assessed on CT performed between days 4 and 7 of evolution and classified according to the ECASS II criteria. Urinary samples were collected within the first 3 hours after admission and the presence of albuminuria, which was considered to be present when the ratio albumin-to-creatinine was > or =30 mg/g creatinine, was determined by nephelometry within the first 24 hours of evolution.

RESULTS

Forty-nine patients (24.5%) had albuminuria and 36 (18%) had HT on the second CT scan. After adjusting for potential confounders including a previous history of diabetes mellitus, hypertension and atrial fibrillation, stroke severity, the presence of early signs of ischemia and leukoaraiosis on the baseline CT scan, and IV anticoagulant treatment, logistic regression analysis showed that albuminuria was independently associated with HT (OR, 7.45; 95% CI 2.30 to 24.16). Moreover, albuminuria was also a significant and independent predictor of parenchymal hemorrhage type 1 and 2 (OR, 8.30; 95% CI 1.77 to 38.89).

CONCLUSION

Albuminuria is an independent predictor of hemorrhagic transformation, and particularly of the most severe bleedings, in patients with acute ischemic stroke. Due to the small number of events, the predictive capacity of albuminuria should be confirmed in larger studies.

Hyperthermia is a surrogate marker of inflammation-mediated cause of brain damage in acute ischaemic stroke

The influence of temperature on the outcome observed in experimental models of ischaemic stroke has not been definitively proved in patients with stroke. Interleukin-6 (IL-6) acts as important endogenous pyrogen, and it is an important regulator of spontaneous body temperature during cerebral ischaemia. The objective of this study was to determine, during the acute phase of cerebral ischaemia, the potential relationship between proinflammatory cytokines and hyperthermia as a cause of larger cerebral infarcts.

PATIENTS AND METHODS

We studied 229 patients with a first-ever acute hemispheric infarction admitted within the first 24 h from onset of symptoms. On admission, axillary temperature was recorded and blood chemistry studies and cranial computed tomography were performed. We classified body temperature into two groups: hyperthermia (>or=37.5 degrees C) and normothermia (<37.5 degrees C). We determined proinflammatory markers [IL-6, tumour necrosis factor-alpha (TNF-alpha), intercellular adhesion molecule (ICAM-1) and vascular cellular adhesion molecule] on admission. Two outcome variables were evaluated: (i) infarct volume; (ii) Canadian Stroke Scale (CSS) at 3 months (CSS <or= 7 was considered poor outcome and CSS > 7 good outcome).

RESULTS

Patients with hyperthermia had higher infarct volume [46.5 (9.8-78.5) cm(3) vs. 19.1 (5.0-23.5) cm(3); P < 0.0001], as well as poor outcome at 3 months. Plasma levels of IL-6, TNF-alpha and ICAM-1 were significantly higher in the group of patients with hyperthermia than in the normothermic group. There was a significant correlation between body temperature on admission and infarct volume (r = 0.302; P < 0.0001), and between proinflammatory markers (IL-6 and TNF-alpha) and infarct volume. A significant association was also found between proinflammatory markers (IL-6, TNF-alpha, and ICAM-1) and poor outcome. However, after adjustment for potential confounders, hyperthermia was not independently associated with either larger infarct volume or with poor outcome at 3 months.

CONCLUSIONS

Inflammatory mediators play a role in acute ischaemic brain damage independently of hyperthermia.

Characterization of the neuroprotective effect of the cannabinoid agonist WIN-55212 in an in vitro model of hypoxic-ischemic brain damage in newborn rats

Brain slices from 7-d-old Wistar rats were exposed to oxygen-glucose deprivation (OGD) for 30 min. OGD slices were incubated with vehicle or with the CB1/CB2 cannabinoid agonist WIN55212 (50 microM), the CB1 agonist arachidonyl-2-chloroethylamide (ACEA) (50 microM), or the CB2 agonist JW133 (50 microM), alone or combined with the CB1 and CB2 receptor antagonist SR 141716 (50 microM) or SR 144528 (50 microM), respectively. Neuronal damage was assessed by histologic analysis and spectrophotometric determination of lactate dehydrogenase (LDH) efflux into the incubation medium. Additionally, medium glutamate levels were determined by high-performance liquid chromatography (HPLC) and those of tumor necrosis factor alpha (TNF-alpha) by enzyme-linked immunosorbent assay. Finally, inducible nitric oxide synthase (iNOS) and CB1/CB2 receptor expression were determined in slices homogenate by Western blot. Both CB1 and CB2 receptors were expressed in slices. OGD increased CB1 expression, cellular damage, LDH efflux, glutamate and TNF-alpha release, and inducible nitric oxide synthase (iNOS) expression; WIN55212 inhibited all these actions. SR141716 and SR144528 inhibited the effect of R(+)-WIN-55212-2 (WIN), as well as the reduction of LDH efflux by ACEA and JW133, respectively. In conclusion, WIN55212 afforded robust neuroprotection in the forebrain slices exposed to OGD, by acting on glutamatergic excitotoxicity, TNF-alpha release, and iNOS expression; this neuroprotective effect seemed to be mediated by CB1 and CB2 receptors.

The role of tumor necrosis factor-alpha in stress-induced worsening of cerebral ischemia in rats

Whereas stress is known to be one of the risk factors of stroke, few experimental studies have examined the possible mechanisms by which stress may affect stroke outcome. Most of the knowledge on the effects of stress on cerebrovascular disease in humans is restricted to catecholamines and glucocorticoids effects on blood pressure and/or development of atherosclerosis. By using an experimental paradigm consisting of the exposure of Fischer rats to repeated immobilization sessions (1 h daily during seven consecutive days) prior to permanent middle cerebral artery occlusion (MCAO), we have found that stress worsens behavioral outcome and increases infarct size after MCAO. These changes occur concomitantly to an increase in inducible nitric oxide synthase (iNOS) expression and to the accumulation of lipid peroxidation markers in brain tissue. The possible regulatory role of TNFalpha was studied by looking at the mechanisms of release of this cytokine as well as to the expression of its receptors (TNFR1 and 2). The results of the present study suggest an increase in TNFalpha expression and release after stress, as well as an increase in the expression of TNFR1. Pharmacological blockade of TNFalpha with anti-TNFalpha led to a decrease in the infarct size as well as in the oxidative/nitrosative biochemical parameters seen after ischemia. In summary, our results indicate that TNFalpha accounts, at least partly, for the worsening of MCAO consequences in brain of rats exposed to stress. Furthermore, the data presented here provide evidence that stress can increase brain ischemic damage and support a possible protective effect of treatment of stressful situations before and during the development of the brain ischemia.

High blood pressure and inflammation are associated with poor prognosis in lacunar infarctions

Lacunar infarction has long been considered to be associated with good prognosis, however a significant percentage of these patients remain functionally dependent. In this study we sought to investigate the factors associated with poor outcome in patients with lacunar infarction.

SUBJECTS AND METHODS

We have performed a secondary study in 113 patients with lacunar infarctions admitted within the first 24 h of symptom onset (mean age 70 years, 57.5% men). Blood pressure, body temperature, serum glucose levels, neurotransmitters and pro-inflammatory markers were measured at admission and during the first 72 h. Stroke severity was assessed by the Canadian Stroke Scale (CSS). Neuroimaging evaluation was performed at admission and between days 4 and 7. Poor functional outcome was considered as a Barthel index <85 at 3 months.

RESULTS

36 patients (31.9%) had poor outcome. Older age (p = 0.009), history of hypertension (p = 0.005), higher body temperature (p < 0.0001), systolic blood pressure (SBP) (p = 0.010), serum glucose (p = 0.002) and interleukin-6 (IL-6) (p < 0.0001) levels, as well as lower CSS score at admission (p < 0.0001) were all predictive factors of poor outcome in bivariate analyses. SBP at admission (OR 2.07, CI 95% 1.04-3.28, p = 0.015) was the only clinical predictor on multivariate analysis. When the logistic model was further adjusted for biomarkers of inflammation and excitotoxicity, IL-6 levels (OR 1.09, CI 95% 1.01-1.26, p = 0.003), but not SBP, was independently associated with poor outcome. This association persisted even after adjusting for potential predictors recorded during the first 72 h of hospitalization.

CONCLUSION

High SBP and IL-6 levels on admission may predict poor outcome in patients with lacunar infarction.

Neurorepair versus neuroprotection in stroke

Stroke is the second to third leading cause of death and the main cause of severe, long-term disability in adults. However, treatment is almost reduced to fibrinolysis, a therapy useful in a low percentage of patients. Given that the immediate treatment for stroke is often unfeasible in the clinical setting, the need for new therapy strategies is imperative. After stroke, the remaining impairment in functions essential for routine activities, such as movement programming and execution, sensorimotor integration, language and other cognitive functions have a deep and life-long impact on the quality of life. An interesting point is that a slow but consistent recovery can be observed in the clinical practice over a period of weeks and months. Whereas the recovery in the first few days likely results from edema resolution and/or from reperfusion of the ischemic penumbra, a large part of the recovery afterwards is due mainly to brain plasticity, by which some regions of the brain assume the functions previously performed by the damaged areas. Neurogenesis and angiogenesis are other possible mechanisms of recovery after stroke. An understanding of the mechanisms underlying functional recovery may shed light on strategies for neurorepair, an alternative with a wide therapeutic window when compared with neuroprotective strategies.

Targets of cytoprotection in acute ischemic stroke: present and future

Although the management of stroke has improved remarkably over the last decade due mainly to the advent of thrombolysis, most neuroprotective agents, although successful in animal studies, have failed in humans. Our increasing knowledge concerning the ischemic cascade is leading to a considerable development of pharmacological tools suggesting that each step of this cascade might be a target for cytoprotection. Glutamate has long been recognized to play key roles in the pathophysiology of ischemia. However, although some trials are still ongoing, the results from several completed trials with drugs interfering with the glutamatergic pathway have been disappointing. Regarding the inhibition of glutamate release as a possible target for cytoprotection, it might be afforded either by decreasing glutamate efflux or by increasing glutamate uptake. In this context, it has been shown that glutamate transport is the primary and only mechanism for maintaining extracellular glutamate concentrations below excitotoxic levels. This transport is executed by the five high-affinity, sodium-dependent plasma membrane glutamate transporters. Among them, the transporter EAAT2 is responsible for up to 90% of all glutamate transport. We will discuss the effect of different neuroprotective tools (membrane stabilizers or endogenous neuroprotection) affecting glutamate efflux and/or expression of EAAT2. We will also describe the finding of a novel polymorphism in the EAAT2 promoter region which could be responsible for differences in both gene function and regulation under pathological conditions such as cerebral ischemia, and which might well account for the failure of glutamate antagonists in the clinical practice. These results may possess important therapeutic implications in the management of patients at risk of ischemic events, since it has been demonstrated that those patients with progressing stroke have higher plasma concentrations of glutamate which remain elevated up to 24 h when compared to the levels in patients without neurological deterioration.

Ischemic preconditioning: a novel target for neuroprotective therapy

Ischemic preconditioning involves a brief exposure to ischemia in order to develop a tolerance to injurious effects of prolonged ischemia. The molecular mechanisms of neuroprotection that lead to ischemic tolerance are not yet completely understood. However, it seems that two distinct phases are involved. Firstly, a cellular defense function against ischemia may be developed by the mechanisms inherent to neurons such as posttranslational modification of proteins or expression of new proteins via a signal transduction system to the nucleus. Secondly, a stress response and synthesis of stress proteins (heat shock proteins) may be activated. These mechanisms are mediated by chaperones. The objective of ischemic preconditioning research is to identify the underlying endogenous protective cellular receptors and signaling cascades, with the long-term goal of allowing therapeutic augmentation of the endogenous protective mechanisms in cerebral ischemia and possibly development of new neuroprotective strategies for ischemic stroke treatment.

TNF–α converting enzyme (TACE) protein expression in different clinical subtypes of multiple sclerosis

Tumor necrosis factor (TNF)-alpha converting enzyme (TACE, also called ADAM17) is a key sheddase that releases TNF-alpha from its inactive cell-bound precursor. TACE protein expression levels in peripheral blood mononuclear cells were measured by Western blot analysis in 20 healthy controls and 80 multiple sclerosis (MS) patients before and after treatment with IFNbeta [20 patients with primary progressive (PP) MS, 20 patients with secondary progressive (SP) MS, and 40 patients with relapsing- remitting (RR) MS (20 patients during clinical remission and 20 patients in relapse)]. TNF-alpha serum levels were also measured by enzyme-linked immunoassay in the MS patients and healthy controls. TACE protein expression levels were lower in healthy controls and PPMS patients compared with SPMS patients and RRMS patient during clinical remission. No differences in TACE protein levels were observed between RRMS patients in relapse and during remission. TACE protein levels were increased in PPMS patients treated with IFNbeta. Serum TNF-alpha levels were higher in RRMS patients in relapse compared with RRMS patients during remission, and positive and negative correlations were found between TACE protein expression and serum TNF-alpha levels in RRMS patients during relapse and during remission respectively. These findings point to different regulatory mechanisms of the TACE-TNF-alpha pathway in the clinical MS subtypes and expand the role of TACE in MS pathogenesis.

A polymorphism in the EAAT2 promoter is associated with higher glutamate concentrations and higher frequency of progressing stroke

It remains unclear why some individuals are susceptible to excitotoxicity after stroke. A possible explanation is impaired glutamate uptake. We have found a highly prevalent polymorphism in the promoter of the glutamate transporter EAAT2 gene that abolishes a putative regulatory site for activator protein–2 (AP-2) and creates a new consensus binding site for the repressor transcription factor GC-binding factor 2 (GCF2). The mutant genotype is associated with increased plasma glutamate concentrations and with a higher frequency of early neurological worsening in human stroke. After transfection into astrocytes, the mutant promoter was not activated by AP-2 and was effectively repressed by GCF2, and its activity in the presence of GCF2 was reduced when compared with the AP-2–cotransfected wild-type promoter. We also show that GCF2 is expressed in ischemic rat brain, suggesting that decreased glutamate uptake occurs in individuals carrying the mutation after stroke. These findings may explain individual susceptibility to excitotoxic damage after stroke as well as the failure of glutamate antagonists in those patients without this polymorphism.