PSD-95 Inhibitors Research Articles

PSD-95 inhibitor Tat-NR2B9c (NA-1) protects the integrity of the blood-brain barrier after transient middle artery occlusion in rats by downregulating matrix metalloprotease-9 and upregulating endothelial nitric oxide synthase

BackgroundProtection against ischemic stroke may be most effective when multiple components of the neurovascular unit are protected, yet current treatments target mainly neurons. Here we explored whether the PSD-95 inhibitor Tat-NR2B9c (NA-1) can protect not only neurons but also the blood-brain barrier. MethodsAdult male Sprague-Dawley rats were randomly divided into three groups, which were subjected to either sham surgery or transient cerebral ischemia-reperfusion, after which some animals were treated with Tat-NR2B9c. The therapeutic efficacy of Tat-NR2B9c was assessed in terms of the degree of neurological deficit and cerebral infarction, integrity of the blood-brain barrier, cerebral water content, as well as expression of PSD-95, nitric oxide synthase, and matrix metalloprotease-9. ResultsTat-NR2B9c (NA-1) ameliorated neurofunctional deficit, reduced cerebral infarction, mitigated blood-brain barrier injury and improved its integrity following ischemia-reperfusion, leading to less cerebral edema. These improvements were associated with upregulation of tight junction proteins in the blood-brain barrier. At the same time, Tat-NR2B9c (NA-1) downregulated neuronal nitric oxide synthase and matrix metalloprotease-9, while reversing the ischemia-induced downregulation of endothelial nitric oxide synthase in brain. We report here the first evidence that PSD-95 is expressed in vascular endothelial cells in the brain. ConclusionOur experiments in a rat model of transient occlusion of the middle cerebral artery suggest that Tat-NR2B9c (NA-1) can mitigate ischemic injury to the blood-brain barrier, and that it may do so by downregulating matrix metalloprotease-9 and upregulating endothelial nitric oxide synthase.

PSD95 as a New Potential Therapeutic Target of Osteoarthritis: A Study of the Identification of Hub Genes through Self-Contrast Model.

Osteoarthritis (OA) is a worldwide joint disease. However, the precise mechanism causing OA remains unclear. Our primary aim was to identify vital biomarkers associated with the mechano-inflammatory aspect of OA, providing potential diagnostic and therapeutic targets for OA. Thirty OA patients who underwent total knee arthroplasty were recruited, and cartilage samples were obtained from both the lateral tibial plateau (LTP) and medial tibial plateau (MTP). GO and KEGG enrichment analyses were performed, and the protein-protein interaction (PPI) assessment was conducted for hub genes. The effect of PSD95 inhibition on cartilage degeneration was also conducted and analyzed. A total of 1247 upregulated and 244 downregulated DEGs were identified. Significant differences were observed between MTP and LTP in mechanical stress-related genes and activated sensory neurons based on a self-contrast model of human knee OA. Cluster analysis identified DLG4 as the hub gene. Cyclic loading stress increased PSD95 (encoded by DLG4) expression in LTP cartilage, and PSD95 inhibitors could alleviate OA progression. This study suggests that inhibiting PSD95 could be a potential therapeutic strategy for preventing articular cartilage degradation.

Hypothalamic Corticotropin-Releasing Hormone Contributes to Hypertension in Spontaneously Hypertensive Rats.

Corticotropin-releasing hormone (CRH) is a neuropeptide regulating neuroendocrine and autonomic function. CRH mRNA and protein levels in the hypothalamic paraventricular nucleus (PVN) are increased in primary hypertension. However, the role of CRH in elevated sympathetic outflow in primary hypertension remains unclear. CRHR1 proteins were distributed in retrogradely labeled PVN presympathetic neurons with an increased level in the PVN tissue in adult spontaneously hypertensive rats (SHRs) compared with age-matched male Wistar-Kyoto (WKY) rats. CRH induced a more significant increase in the firing rate of PVN-rostral ventrolateral medulla (RVLM) neurons and sympathoexcitatory response in SHRs than in WKY rats, an effect that was blocked by preapplication of NMDA receptors (NMDARs) antagonist AP5 and PSD-95 inhibitor, Tat-N-dimer. Blocking CRHRs with astressin or CRHR1 with NBI35965 significantly decreased the firing rate of PVN-RVLM output neurons and reduced arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) in SHRs but not in WKY, whereas blocking CRHR2 with antisauvagine-30 did not. Furthermore, Immunocytochemistry staining revealed that CRHR1 colocalized with NMDARs in PVN presympathetic neurons. Blocking CRHRs significantly decreased the NMDA currents in labeled PVN neurons. PSD-95-bound CRHR1 and PSD-95-bound GluN2A in the PVN were increased in SHRs. These data suggested that the upregulation of CRHR1 in the PVN is critically involved in the hyperactivity of PVN presympathetic neurons and elevated sympathetic outflow in primary hypertension.SIGNIFICANCE STATEMENT Our study found that corticotropin-releasing hormone receptor (CRHR)1 protein levels were increased in the paraventricular nucleus (PVN), and CRHR1 interacts with NMDA receptors (NMDARs) through postsynaptic density protein (PSD)-95 in the PVN neurons in primary hypertension. The increased CRHR1 and CRHR1-NMDAR-PSD-95 complex in the PVN contribute to the hyperactivity of the PVN presympathetic neurons and elevated sympathetic vasomotor tone in hypertension in SHRs. Thus, the antagonism of CRHR1 decreases sympathetic outflow and blood pressure in hypertension. These findings determine a novel role of CRHR1 in elevated sympathetic vasomotor tone in hypertension, which is useful for developing novel therapeutics targeting CRHR1 to treat elevated sympathetic outflow in primary hypertension. The CRHR1 receptor antagonists, which are used to treat health consequences resulting from chronic stress, are candidates to treat primary hypertension.

The Cell-Penetrating Peptide Tat Facilitates Effective Internalization of PSD-95 Inhibitors Into Blood–Brain Barrier Endothelial Cells but less Efficient Permeation Across the Blood–Brain Barrier In Vitro and In Vivo

Inhibition of the interaction between the scaffolding protein PSD-95 and the NMDA receptor has been shown to obstruct ischemic stroke-triggered excitotoxic reactions, leading to neuronal death. The peptides NR2B9c and N-dimer are inhibitors of this interaction. Delivery of the peptides to the brain is challenging due to the general low blood–brain barrier (BBB) permeability. NR2B9c and N-dimer have therefore been conjugated to the cell-penetrating peptide (CPP) Tat, to facilitate blood–brain barrier permeation. However, the BBB permeation of Tat-NR2B9c and Tat-N-dimer has not been fully elucidated. We recently demonstrated that the BBB permeation in vitro and in vivo was lowered upon conjugation of NR2B9c or N-dimer to Tat. In the present study, we aimed to further understand the impact of cargo conjugation to Tat with respect to interaction with and permeation across the BBB in vitro and in vivo. The peptides were labeled with the fluorophore TAMRA (T) and demonstrated efficient Tat-mediated uptake into BBB endothelial cells but differed in their degree of plasma membrane interaction and embedding (T-Tat-NR2B9c = T-Tat > T-Tat-N-dimer) as well as in their chemical stability (T-Tat-N-dimer = T-Tat > T-Tat-NR2B9c). The Tat conjugates all displayed a similar degree of self-association and/or plasma protein adsorption. T-Tat-NR2B9c and T-Tat affected the BBB integrity but not the permeation of the paracellular marker C14-mannitol. T-Tat-NR2B9c and T-Tat-N-dimer displayed less efficient permeation across an in vitro model representing the healthy BBB, when compared to T-Tat, and low BBB permeation in healthy rats.

Intravenous administration of Tat-NR2B9c peptide, a PSD95 inhibitor, attenuates reinstatement of cocaine-seeking behavior in rats

Cocaine use disorder is a serious, chronic and relapsing disease of the nervous system, for which effective treatments do not yet exist. Recently, the role of the N-methyl-d-aspartate (NMDA) receptor subunit GluN2B has been highlighted in cocaine abstinence followed by extinction training. Since the GluN2B subunit is stabilized at synaptic level by the interaction with its scaffolding protein PSD95, in this study we aimed at investigating efficacy of Tat-NR2B9c peptide, a PSD95 inhibitor, which disrupts the interaction of PSD95 with GluN2B, in the attenuation of cocaine seeking-behavior or cue-induced reinstatement. We found that Tat-NR2B9c, administered intravenously, attenuated the reinstatement of active lever presses induced by a priming dose of cocaine or by drug-associated conditioned stimuli. At the same time, the GluN2B/PSD95 complex levels were decreased in the ventral hippocampus of rats that previously self-administered cocaine injected with Tat-NR2B9c during cocaine- or cue-induced reinstatement. In conclusion, we here provide the first evidence showing that the disruption of the GluN2B/PSD95 complexes during cocaine abstinence followed by extinction training may represent a useful strategy to reduce reinstatement of cocaine-seeking behavior.

Plasmin-resistant PSD-95 inhibitors resolve effect-modifying drug-drug interactions between alteplase and nerinetide in acute stroke.

Neuroprotection for acute ischemic stroke is achievable with the eicosapeptide nerinetide, an inhibitor of the protein-protein interactions of the synaptic scaffolding protein PSD-95. However, nerinetide is subject to proteolytic cleavage if administered after alteplase, a standard-of-care thrombolytic agent that nullifies nerinetide's beneficial effects. Here, we showed, on the basis of pharmacokinetic data consistent between rats, primates, and humans, that in a rat model of embolic middle cerebral artery occlusion (eMCAO), nerinetide maintained its effectiveness when administered before alteplase. Because of its short plasma half-life, it can be followed by alteplase within minutes without reducing its neuroprotective effectiveness. In addition, the problem of protease sensitivity is solved by substituting cleavage-prone amino acids from their l- to their d-enantiomeric form. Treatment of rats subjected to eMCAO with such an agent, termed d-Tat-l-2B9c, eliminated protease sensitivity and maintained neuroprotective effectiveness. Our data suggest that both the clinical-stage PSD-95 inhibitor nerinetide and protease-resistant agents such as d-Tat-l-2B9c may be practically integrated into existing stroke care workflows and standards of care.

Effects of the dimeric PSD-95 inhibitor UCCB01-144 on functional recovery after fimbria-fornix transection in rats

Pharmacological inhibition of PSD-95 is a promising therapeutic strategy in the treatment of stroke, and positive effects of monomeric and dimeric PSD-95 inhibitors have been reported in numerous studies. However, whether therapeutic effects will generalize to other types of acute brain injury such as traumatic brain injury (TBI), which has pathophysiological mechanisms in common with stroke, is currently uncertain. We have previously found a lack of neuroprotective effects of dimeric PSD-95 inhibitors in the controlled cortical impact model of TBI in rats. However, as no single animal model is currently able to mimic the complex and heterogeneous pathophysiology of TBI, it is necessary to assess treatment effects across a range of models. In this preliminary study we investigated the neuroprotective abilities of the dimeric PSD-95 inhibitor UCCB01-144 after fimbria-fornix (FF) transection in rats. UCCB01-144 or saline was injected into the lateral tail vein of rats immediately after sham surgery or FF-transection, and effects on spatial delayed alternation in a T-maze were assessed over a 28-day period. Task acquisition was significantly impaired in FF-transected animals, but there were no significant effects of UCCB01-144 on spatial delayed alternation after FF-transection or sham surgery, although decelerated learning curves were seen after treatment with UCCB01-144 in FF-transected animals. The results of the present study are consistent with previous research showing a lack of neuroprotective effects of PSD-95 inhibition in experimental models of TBI.

Effects of Dimeric PSD-95 Inhibition on Excitotoxic Cell Death and Outcome After Controlled Cortical Impact in Rats.

Therapeutic effects of PSD-95 inhibition have been demonstrated in numerous studies of stroke; however only few studies have assessed the effects of PSD-95 inhibitors in traumatic brain injury (TBI). As the pathophysiology of TBI partially overlaps with that of stroke, PSD-95 inhibition may also be an effective therapeutic strategy in TBI. The objectives of the present study were to assess the effects of a dimeric inhibitor of PSD-95, UCCB01-144, on excitotoxic cell death in vitro and outcome after experimental TBI in rats in vivo. In addition, the pharmacokinetic parameters of UCCB01-144 were investigated in order to assess uptake of the drug into the central nervous system of rats. After a controlled cortical impact rats were randomized to receive a single injection of either saline or two different doses of UCCB01-144 (10 or 20mg/kg IV) immediately after injury. Spatial learning and memory were assessed in a water maze at 2weeks post-trauma, and at 4weeks lesion volumes were estimated. Overall, UCCB01-144 did not protect against NMDA-toxicity in neuronal cultures or experimental TBI in rats. Important factors that should be investigated further in future studies assessing the effects of PSD-95 inhibitors in TBI are discussed.

In vitro and invivo effects of a novel dimeric inhibitor of PSD-95 on excitotoxicity and functional recovery after experimental traumatic brain injury.

PSD-95 inhibitors have been shown to be neuroprotective in stroke, but have only to a very limited extent been evaluated in the treatment of traumatic brain injury (TBI) that has pathophysiological mechanisms in common with stroke. The aims of the current study were to assess the effects of a novel dimeric inhibitor of PSD-95, UCCB01-147, on histopathology and long-term cognitive outcome after controlled cortical impact (CCI) in rats. As excitotoxic cell death is thought to be a prominent part of the pathophysiology of TBI, we also investigated the neuroprotective effects of UCCB01-147 and related compounds on NMDA-induced cell death in cultured cortical neurons. Anesthetized rats were given a CCI or sham injury, and were randomized to receive an injection of either UCCB01-147 (10mg/kg), the non-competitive NMDAR-receptor antagonist MK-801 (1mg/kg) or saline immediately after injury. At 2 and 4weeks post-trauma, spatial learning and memory were assessed in a water maze, and at 3months, brains were removed for estimation of lesion volumes. Overall, neither treatment with UCCB01-147 nor MK-801 resulted in significant improvements of cognition and histopathology after CCI. Although MK-801 provided robust neuroprotection against NMDA-induced toxicity in cultured cortical neurons, UCCB01-147 failed to reduce cell death and became neurotoxic at high doses. The data suggest potential differential effects of PSD-95 inhibition in stroke and TBI that should be investigated further in future studies taking important experimental factors such as timing of treatment, dosage, and anesthesia into consideration.

Neuroprotective Effects of a PSD-95 Inhibitor in Neonatal Hypoxic-Ischemic Brain Injury.

The postsynaptic density-95 inhibitor NA-1 uncouples NMDA glutamate receptors from downstream neurotoxic signaling pathways without affecting normal glutamate receptor function. NA-1 attenuates NMDA receptor-mediated neuronal cell death after stroke in multiple models and species. However, its efficacy in providing neuroprotection in models of neonatal hypoxic-ischemic brain injury has not yet been tested. In this study, a modified version of the Rice-Vannucci method for the induction of neonatal hypoxic-ischemic brain injury was performed on postnatal day7 mouse pups. Animals received a single dose of NA-1 intraperitoneally either before or after right common carotid artery occlusion. All experiments were performed in a blinded manner. Infarct volumes were measured 1 and 7days after the injury, while behavioral tests were conducted 1, 3, and 7days after injury. Administration of NA-1 before right common carotid artery occlusion or immediately after ischemia significantly reduced infarct volume and improved neurobehavioral outcomes 1, 3, and 7days post-injury. The neuroprotection and improvement in neurobehavioral outcomes conferred by NA-1 in this mouse neonatal hypoxic-ischemic injury model imply that NA-1 will be effective in reducing neonatal stroke damage and thus could potentially serve as a therapeutic drug for prevention or treatment of neonatal stroke.

Efficacy of the PSD95 inhibitor Tat-NR2B9c in mice requires dose translation between species

Tat-NR2B9c, a clinical-stage stroke neuroprotectant validated in rats and primates, was recently deemed ineffective in mice. To evaluate this discrepancy, we conducted studies in mice subjected to temporary middle cerebral artery occlusion (tMCAO) for either 30 or 60 min according to the established principles for dose-translation between species. Tat-NR2B9c treatment reduced infarct volume by by 24.5% (p = 0.49) and 26.0% (p = 0.03) for 30 and 60 min tMCAO, respectively, at the rat-equivalent dose of 10 nMole/g, but not at the previously reported 3 nMole/g in mice. Dose translation is thus critical when preclinical experiments are conducted in new species.

Advances in Stroke

Translational stroke research continues to move ahead, despite several disappointing clinical trial failures in 2012. There are several factors believed to be contributing to the difficulties in translating experimental studies to human stroke, for example, experimental stroke models might vary too significantly from human stroke, there might be biases in some experimental findings, and the pathophysiology of acute brain injury caused by stroke might be different in humans and animals. The current critical assessment of preclinical studies is driving improvement in the quality of experimental studies and expanding the number of hurdles that a molecule must overcome before proceeding to clinical research. In this short overview, we describe selected translational stroke research that has taken place in 2012. Currently, a candidate drug for successful translation is the postsynaptic density-95 protein (PSD-95) inhibitor, Tat-NR2B9c, which uncouples postsynaptic density protein PSD-95 from neurotoxic signaling pathways.1 PSD-95 binds N-methyl-D-aspartate GluN2 subunits and the neuronal NO synthase.2 Disrupting this complex with PSD-95 inhibitor administered after stroke onset in rodents and nonhuman …

Role of PSD-95 inhibitors in stroke and neuroprotection: A systematic view on NA-1 (Tat-NR2B9c)

MC has received a predoctoral fellowship from the Instituto de Salud Carlos III and DG is a statistical fellow funded by the Spanish stroke network (INVICTUS). MD-G is supported by grant BFU2010-18380/BFI from the Ministerio de Economia y Competitividad.

Role of PSD-95 inhibitors in stroke and neuroprotection: A systematic view on NA-1 (Tat-NR2B9c)

Role of PSD-95 inhibitors in stroke and neuroprotection: A systematic view on NA-1 (Tat-NR2B9c)

Can PSD95 inhibitors widen the therapeutic window?

Can PSD95 inhibitors widen the therapeutic window?

Treatment of stroke with a PSD-95 inhibitor in the gyrencephalic primate brain

All attempts at treating strokes by pharmacologically reducing the human brain's vulnerability to ischaemia have failed, leaving stroke as a leading cause of death, disability and massive socioeconomic loss worldwide. Over decades, research has failed to translate over 1,000 experimental treatments from discovery in cells and rodents to use in humans, a scientific crisis that gave rise to the prevailing belief that pharmacological neuroprotection is not feasible or practicable in higher-order brains. To provide a strategy for advancing stroke therapy, we used higher-order gyrencephalic non-human primates, which bear genetic, anatomical and behavioural similarities to humans and tested neuroprotection by PSD-95 inhibitors--promising compounds that uncouple postsynaptic density protein PSD-95 from neurotoxic signalling pathways. Here we show that stroke damage can be prevented in non-human primates in which a PSD-95 inhibitor is administered after stroke onset in clinically relevant situations. This treatment reduced infarct volumes as gauged by magnetic resonance imaging and histology, preserved the capacity of ischaemic cells to maintain gene transcription in genome-wide screens of ischaemic brain tissue, and significantly preserved neurological function in neurobehavioural assays. The degree of tissue neuroprotection by magnetic resonance imaging corresponded strongly to the preservation of neurological function, supporting the intuitive but unproven dictum that integrity of brain tissue can reflect functional outcome. Our findings establish that tissue neuroprotection and improved functional outcome after stroke is unequivocally achievable in gyrencephalic non-human primates treated with PSD-95 inhibitors. Efforts must ensue to translate these findings to humans.

Imaging of Experimental Stroke Models

The ischemic penumbra is the target of acute stroke therapy. It can be approximated on diffusion/perfusion MRI as the ischemic region with abnormal perfusion and normal diffusion imaging. Using arterial spin labeling perfusion MRI and diffusion MRI, our group has studied the evolution of the diffusion/perfusion mismatch in rat stroke models. Additionally, we have evaluated the effects of high-flow oxygen on the natural history of penumbral evolution, demonstrating that high-flow oxygen "freezes" the evolution of the mismatch and allows for later beneficial use of intravenous tissue plasminogen activator (tPA). Two neuroprotective drugs, Granulocyte colony stimulating factor and a PSD95 inhibitor both impeded the evolution of the mismatch into infarcted tissue in vivo and by histological analysis. Employing a novel technique of clot imaging, our group was able to demonstrate that the combination of tPA plus Annexin-2 was superior to tPA alone in dissolving an embolus and also in reducing the extent of hypoperfused brain tissue of perfusion imaging. The use of these advanced MRI techniques in animal experiments will help to advance clinical imaging of the ischemic penumbra and hopefully contribute to the extension of the therapeutic time window in stroke patients.

Effectiveness of NA-1, a PSD95 inhibitor, in a non-human primate model of embolic stroke

Event Abstract Back to Event Effectiveness of NA-1, a PSD95 inhibitor, in a non-human primate model of embolic stroke Douglas J. Cook1*, L. Teves1 and Michael Tymianski1 1 Toronto Western Hospital Research Institute, Canada Introduction: NA-1 is an inhibitor of the interactions of NMDA glutamate receptors with the submembrane scaffolding protein PSD-95. Treatment with NA-1 decreases stroke volume and improves functional recovery in rodent models of stroke. NA-1 is being evaluated in an ongoing Phase II human clinical trial of its efficacy in reducing the burden of embolic strokes incurred during endovascular aneurysm repair (ENACT trial; clincialtrials.gov NCT00728182). To test whether NA-1 is neuroprotective in embolic strokes in a gyrencephalic non-human primate species we undertook a randomized, blinded, crossover trial of NA-1 vs placebo in a paradigm that simulates the ENACT trial. Methods: Ten adolescent cynomolgus macaques(2.25-4.0 kg) underwent transfemoral, right intracarotid injection of twenty 100um polystyrene spheres followed by treatment with placebo(saline) or NA-1 infused intravenously 1 hour following the embolic procedure. MRI T2 and diffusion weighted imaging(7 Tesla, Bruker Biospin) was obtained at 4, 24 hours and 4 weeks post-stroke. Raw counts and volumetric measurement of diffusion lesions were collected. Primate Stroke Scale scoring was obtained serially for 2 weeks following recovery. Following a 4-week washout period each animal was crossed over to the other treatment group and the procedure was repeated. Results: There were no differences in physiologic parameters between groups. The strokes did not cause gross motor deficits. Animals treated with NA-1 exhibited markedly reduced stroke numbers and volume as compared with placebo-treated animals with the greatest difference observed in the cortex (Figure 1). There was no carry-over effect noted with a 4-week washout. Conclusion: NA-1 significantly reduced embolic stroke number and volume in gyrencephalic non-human primates. This result supports the ENACT paradigm, and the notion that NA-1 should be tested for efficacy in reducing the burden of procedurally-induced strokes in patients. Conference: B.R.A.I.N. platform in Physiology poster day 2009, Toronto, ON, Canada, 16 Dec - 16 Dec, 2009. Presentation Type: Poster Presentation Topic: Poster presentations Citation: Cook DJ, Teves L and Tymianski M (2009). Effectiveness of NA-1, a PSD95 inhibitor, in a non-human primate model of embolic stroke. Front. Neurosci. Conference Abstract: B.R.A.I.N. platform in Physiology poster day 2009. doi: 10.3389/conf.neuro.03.2009.17.009 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 16 Dec 2009; Published Online: 16 Dec 2009. * Correspondence: Douglas J Cook, Toronto Western Hospital Research Institute, Toronto, Canada, dj.cook@me.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Douglas J Cook L. Teves Michael Tymianski Google Douglas J Cook L. Teves Michael Tymianski Google Scholar Douglas J Cook L. Teves Michael Tymianski PubMed Douglas J Cook L. Teves Michael Tymianski Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effectiveness of PSD95 Inhibitors in Permanent and Transient Focal Ischemia in the Rat

Postsynaptic density-95 inhibitors reduce ischemic brain damage without inhibiting excitatory neurotransmission, circumventing the negative consequences of glutamatergic inhibition. However, their efficacy in permanent ischemia and in providing permanent neuroprotection and neurobehavioral improvement in a practical therapeutic window is unproven. These were tested here under conditions that included fever, which is a common occurrence in clinical stroke. Six studies were performed in unfasted Sprague-Dawley rats. Two involved permanent pial vessel occlusion in male and female rats. Two involved permanent middle cerebral artery occlusion, which induced severe hyperthermia, and 2 involved transient middle cerebral artery occlusion. Animals were treated with a single intravenous injection of postsynaptic density-95 inhibitors (Tat-NR2B9c([SDV]) or Tat-NR2B9c([TDV])) 1 hour or 3 hours after stroke. Infarct volumes and neurobehavior were assessed in a blinded manner at 24 hours (pial vessel occlusion and permanent middle cerebral artery occlusion) or at 62 days (transient middle cerebral artery occlusion). Postsynaptic density-95 inhibitors dramatically reduced infarct size in male and female animals exposed to pial vessel occlusion (>50%), in hyperthermic animals with fever exceeding 39 degrees C exposed to permanent middle cerebral artery occlusion (approximately 50%), and at 62 days poststroke in animals exposed to transient middle cerebral artery occlusion (approximately 80%). Effectiveness of postsynaptic density-95 inhibitors was achieved without the drugs affecting body temperature. In transient middle cerebral artery occlusion, a single dose of postsynaptic density-95 inhibitor given 3 hours after stroke onset permanently maintained reduced infarct size and improved neurobehavior. Postsynaptic density-95 inhibitors administrated 3 hours after stroke onset reduced infarct volumes and improved long-term neurobehavioral functions in a wide therapeutic window. This raises the possibility that they may have future clinical usefulness.

Is It Time to Definitely Abandon Neuroprotection in Acute Ischemic Stroke?

See related article, pages 1751–1758. Since the ischemic penumbra was discovered and since a therapeutic window for acute ischemic stroke has been postulated, stroke experts are looking for safe and effective drugs to treat as many acute ischemic stroke patients as possible. Maturation of ischemic damage is a complex process, triggered by hypoperfusion at critical levels and spontaneously evolving toward cell death. It is a self-perpetuating process in which some critical steps (such as ion pumps failure and iNOS production) maintain and enhance the process.1 Reperfusion may reverse the ischemic cascade but, at the same time, induces a further damage. The risk/benefit ratio of reperfusion depends on the amount of penumbral salvageable tissue, that is “individual” and only partially predictable.2,3 Spontaneous reperfusion may occur, and symptoms may reverse, partially or totally, but the percentages of spontaneous reperfusion so far reported account for approximately the 24% of all stroke cases.4 A review of published articles about cerebral angiography in stroke reported that the percentage of spontaneous reperfusion …