Neuroprotection after status epilepticus by targeting protein interactions with postsynaptic density protein 95

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.

Cationic Arginine-Rich Peptides (CARPs): A Novel Class of Neuroprotective Agents With a Multimodal Mechanism of Action

There are virtually no clinically available neuroprotective drugs for the treatment of acute and chronic neurological disorders, hence there is an urgent need for the development of new neuroprotective molecules. Cationic arginine-rich peptides (CARPs) are an expanding and relatively novel class of compounds, which possess intrinsic neuroprotective properties. Intriguingly, CARPs possess a combination of biological properties unprecedented for a neuroprotective agent including the ability to traverse cell membranes and enter the CNS, antagonize calcium influx, target mitochondria, stabilize proteins, inhibit proteolytic enzymes, induce pro-survival signaling, scavenge toxic molecules, and reduce oxidative stress as well as, having a range of anti-inflammatory, analgesic, anti-microbial, and anti-cancer actions. CARPs have also been used as carrier molecules for the delivery of other putative neuroprotective agents across the blood-brain barrier and blood-spinal cord barrier. However, there is increasing evidence that the neuroprotective efficacy of many, if not all these other agents delivered using a cationic arginine-rich cell-penetrating peptide (CCPPs) carrier (e.g., TAT) may actually be mediated largely by the properties of the carrier molecule, with overall efficacy further enhanced according to the amino acid composition of the cargo peptide, in particular its arginine content. Therefore, in reviewing the neuroprotective mechanisms of action of CARPs we also consider studies using CCPPs fused to a putative neuroprotective peptide. We review the history of CARPs in neuroprotection and discuss in detail the intrinsic biological properties that may contribute to their cytoprotective effects and their usefulness as a broad-acting class of neuroprotective drugs.

The impact of postsynaptic density 95 blocking peptide (Tat-NR2B9c) and an iNOS inhibitor (1400W) on proteomic profile of the hippocampus in C57BL/6J mouse model of kainate-induced epileptogenesis

Antiepileptogenic agents that prevent the development of epilepsy following a brain insult remain the holy grail of epilepsy therapeutics. We have employed a label-free proteomic approach that allows quantification of large numbers of brain-expressed proteins in a single analysis in the mouse (male C57BL/6J) kainate (KA) model of epileptogenesis. In addition, we have incorporated two putative antiepileptogenic drugs, postsynaptic density protein-95 blocking peptide (PSD95BP or Tat-NR2B9c) and a highly selective inducible nitric oxide synthase inhibitor, 1400W, to give an insight into how such agents might ameliorate epileptogenesis. The test drugs were administered after the induction of status epilepticus (SE) and the animals were euthanized at 7 days, their hippocampi removed, and subjected to LC-MS/MS analysis. A total of 2,579 proteins were identified; their normalized abundance was compared between treatment groups using ANOVA, with correction for multiple testing by false discovery rate. Significantly altered proteins were subjected to gene ontology and KEGG pathway enrichment analyses. KA-induced SE was most robustly associated with an alteration in the abundance of proteins involved in neuroinflammation, including heat shock protein beta-1 (HSP27), glial fibrillary acidic protein, and CD44 antigen. Treatment with PSD95BP or 1400W moderated the abundance of several of these proteins plus that of secretogranin and Src substrate cortactin. Pathway analysis identified the glutamatergic synapse as a key target for both drugs. Our observations require validation in a larger-scale investigation, with candidate proteins explored in more detail. Nevertheless, this study has identified several mechanisms by which epilepsy might develop and several targets for novel drug development. OPEN PRACTICES: This article has been awarded Open Data. All materials and data are publicly accessible as supporting information. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

Discovery and development of NA-1 for the treatment of acute ischemic stroke

Stroke creates a complex interplay of multiple signaing pathways including excitotoxicity, ionic imbalance, inflammation, oxidative stress and apoptosis. There are very few treatments that have been shown to be beneficial in acute stroke. Recent findings have provided insights into the pathophysiology and mechanisms of ischemic stroke, complementing the traditional glutamate hypothesis: the molecular interaction between PSD95 and GluN2B has been identified as a culprit in stroke-mediated excitotoxicity, leading to the discovery of NA-1, a peptide that disrupts that interaction, as a potent neuroprotective agent for the treatment of acute stroke. In this review we describe its signaling cascade, the target of its therapeutic intervention and its translation from bench to clinical trial.

Progranulin and Its Related MicroRNAs after Status Epilepticus: Possible Mechanisms of Neuroprotection

The current knowledge about neuroprotective mechanisms in humans after status epilepticus is scarce. One reason is the difficulty to measure possible mediators of these neuroprotective mechanisms. The dawn of microRNA detection in the cerebrospinal fluid (CSF) and the recent advancements in measuring proteins in the CSF such as progranulin, which is, e.g., responsible for neurite outgrowth and limiting exceeding neuroinflammatory responses, have given us new insights into putative neuroprotective mechanisms following status epilepticus. This should complement the animal data. In this review, we cover what is known about the role of progranulin as well as the links between microRNA changes and the progranulin pathway following status epilepticus in humans and animals hypothesizing neuroprotective and neurorehabilitative effects. Progranulin has also been found to feature prominently in the neuroprotective processes under hypoxic conditions and initiating neurorehabilitative processes. These properties may be used therapeutically, e.g., through drugs that raise the progranulin levels and therefore the cerebral progranulin levels as well with the goal of improving the outcome after status epilepticus.

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.

Neuroprotective peptides fused to arginine-rich cell penetrating peptides: Neuroprotective mechanism likely mediated by peptide endocytic properties

Several recent studies have demonstrated that TAT and other arginine-rich cell penetrating peptides (CPPs) have intrinsic neuroprotective properties in their own right. Examples, we have demonstrated that in addition to TAT, poly-arginine peptides (R8 to R18; containing 8-18 arginine residues) as well as some other arginine-rich peptides are neuroprotective in vitro (in neurons exposed to glutamic acid excitotoxicity and oxygen glucose deprivation) and in the case of R9 in vivo (after permanent middle cerebral artery occlusion in the rat). Based on several lines of evidence, we propose that this neuroprotection is related to the peptide's endocytosis-inducing properties, with peptide charge and arginine residues being critical factors. Specifically, we propose that during peptide endocytosis neuronal cell surface structures such as ion channels and transporters are internalised, thereby reducing calcium influx associated with excitotoxicity and other receptor-mediated neurodamaging signalling pathways. We also hypothesise that a peptide cargo can act synergistically with TAT and other arginine-rich CPPs due to potentiation of the CPPs endocytic traits rather than by the cargo-peptide acting directly on its supposedly intended intracellular target. In this review, we systematically consider a number of studies that have used CPPs to deliver neuroprotective peptides to the central nervous system (CNS) following stroke and other neurological disorders. Consequently, we critically review evidence that supports our hypothesis that neuroprotection is mediated by carrier peptide endocytosis. In conclusion, we believe that there are strong grounds to regard arginine-rich peptides as a new class of neuroprotective molecules for the treatment of a range of neurological disorders.

Progressive brain damage, synaptic reorganization and NMDA activation in a model of epileptogenic cortical dysplasia

Whether severe epilepsy could be a progressive disorder remains as yet unresolved. We previously demonstrated in a rat model of acquired focal cortical dysplasia, the methylazoxymethanol/pilocarpine - MAM/pilocarpine - rats, that the occurrence of status epilepticus (SE) and subsequent seizures fostered a pathologic process capable of modifying the morphology of cortical pyramidal neurons and NMDA receptor expression/localization. We have here extended our analysis by evaluating neocortical and hippocampal changes in MAM/pilocarpine rats at different epilepsy stages, from few days after onset up to six months of chronic epilepsy. Our findings indicate that the process triggered by SE and subsequent seizures in the malformed brain i) is steadily progressive, deeply altering neocortical and hippocampal morphology, with atrophy of neocortex and CA regions and progressive increase of granule cell layer dispersion; ii) changes dramatically the fine morphology of neurons in neocortex and hippocampus, by increasing cell size and decreasing both dendrite arborization and spine density; iii) induces reorganization of glutamatergic and GABAergic networks in both neocortex and hippocampus, favoring excitatory vs inhibitory input; iv) activates NMDA regulatory subunits. Taken together, our data indicate that, at least in experimental models of brain malformations, severe seizure activity, i.e., SE plus recurrent seizures, may lead to a widespread, steadily progressive architectural, neuronal and synaptic reorganization in the brain. They also suggest the mechanistic relevance of glutamate/NMDA hyper-activation in the seizure-related brain pathologic plasticity.

Proteomic analysis of the effect of acupuncture on the suppression of kainic Acid-induced neuronal destruction in mouse hippocampus

Kainic acid (KA) is a neurotoxin that induces epileptic seizures and excitotoxicity in the hippocampus. Acupuncture is frequently used as an alternative therapy for epilepsy, and it has been known to protect hippocampal neurons against KA toxicity. Using proteomic analysis, we investigated protein expression changes in the hippocampus following acupuncture stimulation at HT8. Eight-week-old male C57BL/6 mice (20-25 g) received acupuncture treatment at HT8 acupoint bilaterally once a day for 3 days and were then administered KA (30 mg/kg) intraperitoneally. Twenty-four hours after KA injection, neuronal survival and astrocyte activation in the hippocampus were measured, and protein expression in the hippocampus was identified by 2-dimensional electrophoresis. Acupuncture stimulation at HT8 suppressed KA-induced neuronal death and astrocyte activation in the hippocampus. We identified the changes in the expression of 11 proteins by KA or acupuncture stimulation at HT8 and found that acupuncture stimulation at HT8 normalized the expression of dihydropyrimidinase-related protein 2 and upregulated the expression of transcriptional activator protein pur-alpha, serine/threonine-protein phosphatase 5, and T-complex protein 1 subunit alpha, which are related to the survival of neurons. These results suggest that acupuncture stimulation at HT8 changes protein expression profiles in the hippocampus in favor of neuronal survival in KA-treated mice.

Dantrolene inhibits the calcium plateau and prevents the development of spontaneous recurrent epileptiform discharges following in vitro status epilepticus

Status epilepticus is a clinical emergency that can lead to the development of acquired epilepsy following neuronal injury. Understanding the pathophysiological changes that occur between the injury itself and the expression of epilepsy is important in the development of new therapeutics to prevent epileptogenesis. Currently, no anti-epileptogenic agents exist; thus, the ability to treat an individual immediately after status epilepticus to prevent the ultimate development of epilepsy remains an important clinical challenge. In the Sprague-Dawley rat pilocarpine model of status epilepticus-induced acquired epilepsy, intracellular calcium has been shown to increase in hippocampal neurons during status epilepticus and remain elevated well past the duration of the injury in those animals that develop epilepsy. This study aimed to determine if such changes in calcium dynamics exist in the hippocampal culture model of status epilepticus-induced acquired epilepsy and, if so, to study whether manipulating the calcium plateau after status epilepticus would prevent epileptogenesis. The in vitro status epilepticus model resembled the in vivo model in terms of elevations in neuronal calcium concentrations that were maintained well past the duration of the injury. When used following in vitro status epilepticus, dantrolene, a ryanodine receptor inhibitor, but not the N-methyl-D-aspartic acid channel blocker MK-801 inhibited the elevations in intracellular calcium, decreased neuronal death and prevented the expression of spontaneous recurrent epileptiform discharges, the in vitro correlate of epilepsy. These findings offer potential for a novel treatment to prevent the development of epileptiform discharges following brain injuries.

Cell Permeable Peptides: A Promising Tool to Deliver Neuroprotective Agents in the Brain

The inability of most drugs to cross the blood-brain barrier and/or plasma membrane limits their use for biomedical applications in the brain. Cell Permeable Peptides (CPPs) overcome this problem and are effective in vivo, crossing the plasma membrane and the blood-brain barrier. CPPs deliver a wide variety of compounds intracellularly in an active form. In fact, many bioactive cargoes have neuroprotective properties, and due to their ability to block protein-protein interactions, offer exciting perspectives in the clinical setting. In this review we give an overview of the Cell Permeable Peptides strategy to deliver neuroprotectants against neurodegeneration in the CNS.