tat-nr2b9c and Disease-Models--Animal

Excitotoxicity mediated by the N-methyl-D-aspartate receptor (NMDAR) is believed to be a primary mechanism of neuronal injury following stroke. Thus, many drugs and therapeutic peptides were developed to inhibit either the NMDAR at the cell surface or its downstream intracellular death-signaling cascades. Nevertheless, the majority of focal ischemia studies concerning NMDAR antagonism were performed using the intraluminal suture-induced middle cerebral arterial occlusion (MCAO) model, which produces a large cortical and subcortical infarct leading to hypothalamic damage and fever in experimental animals. Here, we investigated whether NMDAR antagonism by drugs and therapeutic peptides was neuroprotective in a mouse model of distal MCAO (dMCAO), which produces a small cortical infarct sparing the hypothalamus and other subcortical structures. For establishment of this model, mice were subjected to dMCAO under normothermic conditions or body-temperature manipulations, and in the former case, their brains were collected at 3-72 h post-ischemia to follow the infarct development. These mice developed cortical infarction 6 h post-ischemia, which matured by 24-48 h post-ischemia. Consistent with the hypothesis that the delayed infarction in this model can be alleviated by neuroprotective interventions, hypothermia strongly protected the mouse brain against cerebral infarction in this model. To evaluate the therapeutic efficacy of NMDAR antagonism in this model, we treated the mice with MK801, Tat-NR2B9c, and L-JNKI-1 at doses that were neuroprotective in the MCAO model, and 30 min later, they were subjected to 120 min of dMCAO either in the awake state or under anesthesia with normothermic controls. Nevertheless, NMDAR antagonism, despite exerting pharmacological effects on mouse behavior, repeatedly failed to show neuroprotection against cerebral infarction in this model. The lack of efficacy of these treatments is reminiscent of the recurrent failure of NMDAR antagonism in clinical trials. While our data do not exclude the possibility that these treatments could be effective at a different dose or treatment regimen, they emphasize the need to test drug efficacy in different stroke models before optimal doses and treatment regimens can be selected for clinical trials.

Topics: Animals; Cerebral Infarction; Disease Models, Animal; Dizocilpine Maleate; Hypothermia, Induced; Infarction, Middle Cerebral Artery; Male; Mice; Neuroprotective Agents; Peptides; Receptors, N-Methyl-D-Aspartate; Treatment Outcome

Topics: Animals; Brain Injuries, Traumatic; Cell Line, Tumor; Disease Models, Animal; Disks Large Homolog 4 Protein; Drug Carriers; Humans; Male; Mice, Inbred C57BL; Nanoparticles; Peptides; Rotarod Performance Test; Thrombin

Following positive results with the poly-arginine peptide R18 when administered intravenously 30 or 60min after permanent and/or transient middle cerebral artery occlusion (MCAO; 90min) in the rat, we examined the effectiveness of the peptide when administered 2h after MCAO. R18 was administered intravenously (1000nmol/kg via jugular vein) after permanent MCAO or a transient 3-h MCAO or when administered intra-arterially (100nmol/kg via internal carotid artery) immediately after reperfusion following a transient 2-h MCAO. In the transient MCAO studies, the neuroprotective NA-1 peptide was used as a positive control. Infarct volume, cerebral edema and functional outcomes were measured 24h after MCAO. Following permanent or transient MCAO, neither R18 nor NA-1 significantly reduced infarct volume. However, following permanent MCAO, R18 appeared to reduce cerebral edema (p=0.006), whereas following a transient 3-h MCAO, R18 improved the time to remove adhesive tape (p=0.04) without significantly affecting cerebral edema. There was also a trend (p=0.07) towards improved rota-rod performance with R18 in both permanent and transient 3-h MCAO. Following a transient 2-h MCAO, R18 had no significant effects on cerebral edema or neurological score but did lessen the extent of weight loss. Overall, while R18 had no effect on infarct volume, the peptide reduced cerebral edema after permanent MCAO, and improved some functional outcomes after transient MCAO.

Topics: Animals; Brain Edema; Brain Ischemia; Carotid Artery Injuries; Carotid Artery, Internal; Cerebral Arteries; Cerebrovascular Disorders; Disease Models, Animal; Infarction, Middle Cerebral Artery; Intracellular Signaling Peptides and Proteins; Ischemic Attack, Transient; Male; Neuroprotective Agents; Peptides; Rats; Reperfusion; Stroke

We examined the efficacy of R18 in a transient MCAO model and compared its effectiveness to the well-characterized neuroprotective NA-1 peptide. R18 and NA-1 peptides were administered intravenously (30, 100, 300, 1000nmol/kg), 60min after the onset of 90min of MCAO. Infarct volume, cerebral swelling and functional outcomes (neurological score, adhesive tape and rota-rod) were measured 24h after MCAO. R18 reduced total infarct volume by 35.1% (p=0.008), 24.8% (p=0.059), 12.2% and 9.6% for the respective 1000 to 30nmol/kg doses, while the corresponding doses of NA-1 reduced lesion volume by 26.1% (p=0.047), 16.6%, 16.5% and 7%, respectively. R18 also reduced hemisphere swelling by between 46.1% (1000 and 300nmol/kg; p=0.009) and 24.4% (100nmol/kg; p=0.066), while NA-1 reduced swelling by 25.7% (1000nmol/kg; p=0.054). In addition, several R18 and NA-1 treatment groups displayed a significant improvement in at least one parameter of the adhesive tape test. These results confirm the neuroprotective properties of R18, and suggest that the peptide is a more effective neuroprotective agent than NA-1. This provides strong justification for the continuing development of R18 as a neuroprotective treatment for stroke.

Topics: Animals; Brain Edema; Brain Infarction; Disease Models, Animal; Dose-Response Relationship, Drug; Infarction, Middle Cerebral Artery; Movement; Nervous System Diseases; Neuroprotective Agents; Peptides; Psychomotor Performance; Rats; Statistics, Nonparametric; Treatment Outcome

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.

Topics: Animals; Brain; Disease Models, Animal; Dose-Response Relationship, Drug; Infarction, Middle Cerebral Artery; Male; Mice; Mice, Inbred C57BL; Neuroprotective Agents; Peptides; Rats; Species Specificity

Huntington disease (HD) is a dominantly inherited neurodegenerative disease caused by a polyglutamine (polyQ) expansion in the protein huntingtin (htt). Previous studies have shown enhanced N-methyl-d-aspartate (NMDA)-induced excitotoxicity in neuronal models of HD, mediated in part by increased NMDA receptor (NMDAR) GluN2B subunit binding with the postsynaptic density protein-95 (PSD-95). In cultured hippocampal neurons, the NMDAR-activated p38 Mitogen-activated Protein Kinase (MAPK) death pathway is disrupted by a peptide (Tat-NR2B9c) that uncouples GluN2B from PSD-95, whereas NMDAR-mediated activation of c-Jun N-terminal Kinase (JNK) MAPK is PSD-95-independent. To investigate the mechanism by which Tat-NR2B9c protects striatal medium spiny neurons (MSNs) from mutant htt (mhtt)-enhanced NMDAR toxicity, we compared striatal tissue and cultured MSNs from presymptomatic yeast artificial chromosome (YAC) mice expressing htt with 128 polyQ (YAC128) to those from YAC18 and/or WT mice as controls. Similar to the previously published shift of GluN2B-containing NMDARs to extrasynaptic sites, we found increased PSD-95 localization as well as elevated PSD-95-GluN2B interactions in the striatal non-PSD (extrasynaptic) fraction from YAC128 mice. Notably, basal levels of both activated p38 and JNK MAPKs were elevated in the YAC128 striatum. NMDA stimulation of acute slices increased activation of p38 and JNK in WT and YAC128 striatum, but Tat-NR2B9c pretreatment reduced only the p38 activation in YAC128. In cultured MSNs, p38 MAPK inhibition reduced YAC128 NMDAR-mediated cell death to WT levels, and occluded the Tat-NR2B9c peptide protective effect; in contrast, inhibition of JNK had a similar protective effect in cultured MSNs from both WT and YAC128 mice. Our results suggest that altered activation of p38 MAPK contributes to mhtt enhancement of GluN2B/PSD-95 toxic signaling.

Topics: Analysis of Variance; Animals; Animals, Newborn; Apoptosis; Bacterial Proteins; Cerebral Cortex; Chromosomes, Artificial, Yeast; Coculture Techniques; Corpus Striatum; Disease Models, Animal; Disks Large Homolog 4 Protein; Embryo, Mammalian; Enzyme Inhibitors; Gene Expression Regulation; Guanylate Kinases; Humans; Huntingtin Protein; Huntington Disease; Immunoprecipitation; In Situ Nick-End Labeling; Luminescent Proteins; Membrane Proteins; Mice; Mice, Transgenic; N-Methylaspartate; Nerve Tissue Proteins; Neurons; Nuclear Proteins; p38 Mitogen-Activated Protein Kinases; Peptides; Receptors, N-Methyl-D-Aspartate; Subcellular Fractions

Over decades, all attempts to translate acute stroke neuroprotectants from discovery in lower-order species to human clinical use have failed. This raised concerns about the predictive validity of preclinical studies in animals for outcomes in human stroke trials. To bridge this translational gap, we used high-order gyrencephalic nonhuman primates subjected to an experimental protocol that mimicked that of a corresponding, separately reported, clinical trial in which the human subjects underwent endovascular cerebral aneurysm repair. Both placebo-controlled studies tested neuroprotection by Tat-NR2B9c, a prospective therapeutic compound, in anesthetized subjects. Embolic strokes were produced by small intra-arterial emboli caused by the endovascular procedure. We show that primates treated with Tat-NR2B9c after the onset of embolic strokes exhibited significantly reduced numbers and volumes of strokes, as visualized by diffusion- and T2-weighted magnetic resonance imaging. These results correctly anticipated the outcome of the corresponding human trial, thus validating this study design as a predictor of neuroprotective efficacy in humans. This strategy may facilitate the evaluation of promising neuroprotectants before undertaking similar studies in human subjects.

Topics: Animals; Disease Models, Animal; Magnetic Resonance Imaging; Neuroprotective Agents; Peptides; Primates; Stroke