Neuroprotective effects of the N-terminal tripeptide of insulin-like growth factor-1, glycine-proline-glutamate (GPE) following intravenous infusion in hypoxic-ischemic adult rats

Reduction in Hippocampal Amyloid-β Peptide (Aβ) Content during Glycine-Proline-Glutamate (Gly-Pro-Glu) Co-Administration Is Associated with Changes in Inflammation and Insulin-like Growth Factor (IGF)-I Signaling

Alzheimer's disease (AD) is characterized by the deposition in the brain of senile plaques composed of amyloid-β peptides (Aβs) that increase inflammation. An endogenous peptide derived from the insulin-like growth factor (IGF)-I, glycine-proline-glutamate (GPE), has IGF-I-sensitizing and neuroprotective actions. Here, we examined the effects of GPE on Aβ levels and hippocampal inflammation generated by the intracerebroventricular infusion of Aβ25-35 for 2 weeks (300 pmol/day) in ovariectomized rats and the signaling-related pathways and levels of Aβ-degrading enzymes associated with these GPE-related effects. GPE prevented the Aβ-induced increase in the phosphorylation of p38 mitogen-activated protein kinase and the reduction in activation of signal transducer and activator of transcription 3, insulin receptor substrate-1, and Akt, as well as on interleukin (IL)-2 and IL-13 levels in the hippocampus. The functionality of somatostatin, measured as the percentage of inhibition of adenylate cyclase activity and the levels of insulin-degrading enzyme, was also preserved by GPE co-treatment. These findings indicate that GPE co-administration may protect from Aβ insult by changing hippocampal cytokine content and somatostatin functionality through regulation of leptin- and IGF-I-signaling pathways that could influence the reduction in Aβ levels through modulation of levels and/or activity of Aβ proteases.

Poly(N-acryloylglycine-acrylamide) Hydrogel Mimics the Cellular Microenvironment and Promotes Neurite Growth with Protection from Oxidative Stress

In this work, the glycine-based acryloyl monomer is polymerized to obtain a neurogenic polymeric hydrogel for regenerative applications. The synthesized poly(N-acryloylglycine-acrylamide) [poly(NAG-b-A)] nanohydrogel exhibits high swelling (∼1500%) and is mechanically very stable, biocompatible, and proliferative in nature. The poly(NAG-b-A) nanohydrogel provides a stable 3D extracellular mimetic environment and promotes healthy neurite growth for primary cortical neurons by facilitating cellular adhesion, proliferation, actin filament stabilization, and neuronal differentiation. Furthermore, the protective role of the poly(NAG-b-A) hydrogel for the neurons in oxidative stress conditions is revealed and it is found that it is a clinically relevant material for neuronal regenerative applications, such as for promoting nerve regeneration via GSK3β inhibition. This hydrogel additionally plays an important role in modulating the biological microenvironment, either as an agonist and antagonist or as an antioxidant. Furthermore, it favors the physiological responses and eases the neurite growth efficiency. Additionally, we found out that the conversion of glycine-based acryloyl monomers into their corresponding polymer modulates the mechanical performance, mimics the cellular microenvironment, and accelerates the self-healing capability due to the responsive behavior towards reactive oxygen species (ROS). Thus, the p(NAG-b-A) hydrogel could be a potential candidate to induce neuronal regeneration since it provides a physical cue and significantly boosts neurite outgrowth and also maintains the microtubule integrity in neuronal cells.

Concise Overview of Glypromate Neuropeptide Research: From Chemistry to Pharmacological Applications in Neurosciences

Neurodegenerative diseases of the central nervous system (CNS) pose a serious health concern worldwide, with a particular incidence in developed countries as a result of life expectancy increase and the absence of restorative treatments. Presently, treatments for these neurological conditions are focused on managing the symptoms and/or slowing down their progression. As so, the research on novel neuroprotective drugs is of high interest. Glypromate (glycyl-l-prolyl-l-glutamic acid, also known as GPE), an endogenous small peptide widespread in the brain, holds great promise to tackle neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington's, s well as other CNS-related disorders like Rett and Down's syndromes. However, the limited pharmacokinetic properties of Glypromate hinder its clinical application. As such, intense research has been devoted to leveraging the pharmacokinetic profile of this neuropeptide. This review aims to offer an updated perspective on Glypromate research by exploring the vast array of chemical derivatizations of more than 100 analogs described in the literature over the past two decades. The collection and discussion of the most relevant structure-activity relationships will hopefully guide the discovery of new Glypromate-based neuroprotective drugs.

Cyclic Glycine-Proline (cGP) Normalises Insulin-Like Growth Factor-1 (IGF-1) Function: Clinical Significance in the Ageing Brain and in Age-Related Neurological Conditions

Insulin-like growth factor-1 (IGF-1) function declines with age and is associated with brain ageing and the progression of age-related neurological conditions. The reversible binding of IGF-1 to IGF binding protein (IGFBP)-3 regulates the amount of bioavailable, functional IGF-1 in circulation. Cyclic glycine-proline (cGP), a metabolite from the binding site of IGF-1, retains its affinity for IGFBP-3 and competes against IGF-1 for IGFBP-3 binding. Thus, cGP and IGFBP-3 collectively regulate the bioavailability of IGF-1. The molar ratio of cGP/IGF-1 represents the amount of bioavailable and functional IGF-1 in circulation. The cGP/IGF-1 molar ratio is low in patients with age-related conditions, including hypertension, stroke, and neurological disorders with cognitive impairment. Stroke patients with a higher cGP/IGF-1 molar ratio have more favourable clinical outcomes. The elderly with more cGP have better memory retention. An increase in the cGP/IGF-1 molar ratio with age is associated with normal cognition, whereas a decrease in this ratio with age is associated with dementia in Parkinson disease. In addition, cGP administration reduces systolic blood pressure, improves memory, and aids in stroke recovery. These clinical and experimental observations demonstrate the role of cGP in regulating IGF-1 function and its potential clinical applications in age-related brain diseases as a plasma biomarker for-and an intervention to improve-IGF-1 function.

Mechanism of evodiamine blocking Nrf2/MAPK pathway to inhibit apoptosis of grass carp hepatocytes induced by DEHP

Di (2-ethylhexyl) phthalate (DEHP) is often used as a plasticizer for plastic products, and its excessive use can cause irreversible damage to aquatic animals and humans. Evodiamine (EVO) is an alkaloid component in the fruit of Evodia rutaecarpa, which has antioxidant and detoxification functions. To investigate the toxic mechanism of DEHP on grass carp (Ctenopharyngodon idellus) hepatocyte cell line (L8824) and the therapeutic effect of evodiamine, an experimental model of L8824 cells exposed to 800 μM DEHP and/or 10 μM EVO for 24 h was established. Flow cytometry, AO/EB fluorescence staining, real-time quantitative PCR, and western blot were used to detect the degree of cell injury, oxidative stress level, MAPK signaling pathway relative genes, and the expression of apoptosis-related molecules. The results showed that DEHP exposure could significantly increase the level of reactive oxygen species (ROS), inhibit the activities of antioxidant enzymes (CAT, SOD, GSH-Px), and cause the accumulation of MDA. DEHP also activated MAPK signaling pathway-related molecules (JNK, ERK, P38 MAPK), and then up-regulated the expression of pro-apoptotic factors Bcl-2-Associated X (Bax) and caspase 3, while inhibiting the anti-apoptotic factor B-cell lymphoma-2 (Bcl-2). In addition, EVO can also promote the dissociation of nuclear factor-E2-related factor 2 (Nrf2) into the nucleus, reduce the level of ROS and the occurrence of oxidative stress in grass carp hepatocytes, down-regulate the MAPK pathway, alleviate DEHP-induced apoptosis, and restore the expression of antioxidant genes. These results indicated that evodiamine could block Nrf2/MAPK pathway to inhibit DEHP-induced apoptosis of grass carp hepatocytes.

Toxicity of Glycyl-l-Prolyl-l-Glutamate Pseudotripeptides: Cytotoxic, Oxidative, Genotoxic, and Embryotoxic Perspectives

The tripeptide H-Gly-Pro-Glu-OH (GPE) and its analogs began to take much interest from scientists for developing effective novel molecules in the treatment of several disorders including Alzheimer’s disease, Parkinson’s disease, and stroke. The peptidomimetics of GPEs exerted significant biological properties involving anti-inflammatory, antiapoptotic, and anticancer properties. The assessments of their hematological toxicity potentials are critically required for their possible usage in further preclinical and clinical trials against a wide range of pathological conditions. However, there is so limited information on the safety profiling of GPE and its analogs on human blood tissue from cytotoxic, oxidative, and genotoxic perspectives. And, their embryotoxicity potentials were not investigated yet. Therefore, in this study, measurements of mitochondrial viability (using MTT assay) and lactate dehydrogenase (LDH) release as well as total antioxidant capacity (TAC) assays were performed on cultured human whole blood cells after treatment with GPE and its three novel peptidomimetics for 72 h. Sister chromatid exchange (SCE), micronucleus (MN), and 8-oxo-2-deoxyguanosine (8-OH-dG) assays were performed for determining the genotoxic damage potentials. In addition, the nuclear division index (NDI) was figured out for revealing their cytostatic potentials. Embryotoxicity assessments were performed on cultured human pluripotent NT2 embryonal carcinoma cells by MTT and LDH assays. The present results from cytotoxicity, oxidative, genotoxicity, and embryotoxicity testing clearly propounded that GPEs had good biosafety profiles and were trouble-free from the toxicological point of view. Noncytotoxic, antioxidative, nongenotoxic, noncytostatic, and nonembryotoxic features of GPE analogs are worthwhile exploring further and may exert high potentials for improving the development of novel disease-modifying agents.

Neuroinflammation in Cerebral Ischemia and Ischemia/Reperfusion Injuries: From Pathophysiology to Therapeutic Strategies

Its increasing incidence has led stroke to be the second leading cause of death worldwide. Despite significant advances in recanalization strategies, patients are still at risk for ischemia/reperfusion injuries in this pathophysiology, in which neuroinflammation is significantly involved. Research has shown that in the acute phase, neuroinflammatory cascades lead to apoptosis, disruption of the blood-brain barrier, cerebral edema, and hemorrhagic transformation, while in later stages, these pathways support tissue repair and functional recovery. The present review discusses the various cell types and the mechanisms through which neuroinflammation contributes to parenchymal injury and tissue repair, as well as therapeutic attempts made in vitro, in animal experiments, and in clinical trials which target neuroinflammation, highlighting future therapeutic perspectives.

Fragile X Syndrome: Lessons Learned and What New Treatment Avenues Are on the Horizon

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and the leading single-gene form of autism spectrum disorder, encompassing cognitive, behavioral, and physical forms of clinical involvement. FXS is caused by large expansions of a noncoding CGG repeat (>200 repeats) in the FMR1 gene, at which point the gene is generally silenced. Absence of FMR1 protein (FMRP), important for synaptic development and maintenance, gives rise to the neurodevelopmental disorder. There is, at present, no therapeutic approach that directly reverses the loss of FMRP; however, there is an increasing number of potential treatments that target the pathways dysregulated in FXS, including those that address the enhanced activity of the mGluR5 pathway and deficits in GABA pathways. Based on studies of targeted therapeutics to date, the prospects are good for one or more effective therapies for FXS in the near future. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Neuroprotective Effects of Tripeptides-Epigenetic Regulators in Mouse Model of Alzheimer's Disease

KED and EDR peptides prevent dendritic spines loss in amyloid synaptotoxicity in in vitro model of Alzheimer’s disease (AD). The objective of this paper was to study epigenetic mechanisms of EDR and KED peptides’ neuroprotective effects on neuroplasticity and dendritic spine morphology in an AD mouse model. Daily intraperitoneal administration of the KED peptide in 5xFAD mice from 2 to 4 months of age at a concentration of 400 μg/kg tended to increase neuroplasticity. KED and EDR peptides prevented dendritic spine loss in 5xFAD-M mice. Their action’s possible molecular mechanisms were investigated by molecular modeling and docking of peptides in dsDNA, containing all possible combinations of hexanucleotide sequences. Similar DNA sequences were found in the lowest-energy complexes of the studied peptides with DNA in the classical B-form. EDR peptide has binding sites in the promoter region of CASP3, NES, GAP43, APOE, SOD2, PPARA, PPARG, GDX1 genes. Protein products of these genes are involved in AD pathogenesis. The neuroprotective effect of EDR and KED peptides in AD can be defined by their ability to prevent dendritic spine elimination and neuroplasticity impairments at the molecular epigenetic level.

Glycyl-L-Prolyl-L-Glutamate Pseudotripeptides for Treatment of Alzheimer's Disease

So far, there is no effective disease-modifying therapies for Alzheimer’s Disease (AD) in clinical practice. In this context, glycine-L-proline-L-glutamate (GPE) and its analogs may open the way for developing a novel molecule for treating neurodegenerative disorders, including AD. In turn, this study was aimed to investigate the neuroprotective potentials exerted by three novel GPE peptidomimetics (GPE1, GPE2, and GPE3) using an in vitro AD model. Anti-Alzheimer potentials were determined using a wide array of techniques, such as measurements of mitochondrial viability (MTT) and lactate dehydrogenase (LDH) release assays, determination of acetylcholinesterase (AChE), α-secretase and β-secretase activities, comparisons of total antioxidant capacity (TAC) and total oxidative status (TOS) levels, flow cytometric and microscopic detection of apoptotic and necrotic neuronal death, and investigating gene expression responses via PCR arrays involving 64 critical genes related to 10 different pathways. Our analysis showed that GPE peptidomimetics modulate oxidative stress, ACh depletion, α-secretase inactivation, apoptotic, and necrotic cell death. In vitro results suggested that treatments with novel GPE analogs might be promising therapeutic agents for treatment and/or or prevention of AD.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Improvement in inflammation is associated with the protective effect of Gly-Pro-Glu and cycloprolylglycine against Aβ-induced depletion of the hippocampal somatostatinergic system

Glycine-proline-glutamate (GPE) is a cleaved tripeptide of IGF-I that can be processed to cycloprolylglycine (cPG) in the brain. IGF-I protects the hippocampal somatostatinergic system from β-amyloid (Aβ) insult and although neither IGF-I-derived peptides bind to IGF-I receptors, they exert protective actions in several neurological disorders. As their effects on the hippocampal somatostatinergic system remain unknown, the objective of this study was to evaluate if cPG and/or GPE prevent the deleterious effects of Aβ_25-35 infusion on this system and whether changes in intracellular-related signaling and interleukin (IL) content are involved in their protective effect. We also determined the effect of cPG or GPE co-administration with Aβ_25-35 on IL secretion in glial cultures and the influence of these ILs on signaling activation and somatostatin synthesis in neuronal cultures. cPG or GPE co-administration reduced Aβ-induced cell death and pro-inflammatory ILs, increased IL-4 and partially avoided the reduction of components of the somatostatinergic system affected by Aβ_25-35. GPE increased activation of Akt and CREB and reduced GSK3β activation and astrogliosis, whereas cPG increased phosphorylation of extracellular signal-regulated kinases. Both peptides converged in the activation of mTOR and S6 kinase. Co-administration of these peptides with Aβ_25-35 to glial cultures increased IL-4 and reduced IL-1β; this release of IL-4 could be responsible for activation of Akt and increased somatostatin in neuronal cultures. Our findings suggest that cPG and GPE exert protective effects against Aβ on the somatostatinergic system by a reduction of the inflammatory environment that may activate different pro-survival pathways in these neurons.

Synthesis and biological evaluation of novel analogues of Gly-l-Pro-l-Glu (GPE) as neuroprotective agents

This study investigated the anti-inflammatory effects of novel pseudotripeptides (GPE 1-3) as potential candidates to counteract neuroinflammation processes in Alzheimer's disease. GPE 1-3 pseudotripeptides are synthetic derivatives of Gly-l-Pro-l-Glu (GPE), the N-terminal tripeptide of IGF-1, obtained through the introduction of isosteres of the amidic bond (aminomethylene unit) to increase the metabolic stability of the native tripeptide. The results showed that all synthetic derivatives possessed higher half-lives (t_1/2 > 4 h) than GPE (t_1/2 = 30 min) in human plasma and had good water solubility. The biological results demonstrated that GPE 1-3 had protective properties in several experimental models of treated THP-1 cells. Notably, the novel pseudotripeptides influenced inflammatory cytokine expression (IL-1β, IL-18, and TNF-α) in Aβ_25-35-, PMA-, and LPS-treated THP-1 cells. In PMA-differentiated THP-1 macrophages, both GPE 1 and GPE 3 reduced the expression levels of all selected cyto-chemokines, even though GPE 3 showed the best neuroprotective properties.

(R)-α-Lipoyl-Gly-l-Pro-l-Glu dimethyl ester as dual acting agent for the treatment of Alzheimer's disease

In this study, effects of LA-GPE (R-α-Lipoyl-Gly-l-Pro-l-Glu dimethyl ester) and GPE (Gly-L-Pro-L-Glu) on the cytotoxic action of Aβ_1-42 were tested with differentiated human neuroblastoma SH-SY5Y cells as cellular Alzheimer model via measurements of mitochondrial viability (MTT assay) and lactate dehydrogenase release (LDH assay). Effects of LA-GPE and GPE on acetylcholinesterase (AChE) activity, total antioxidant capacity (TAC) and total oxidative status (TOS) levels, and neural cell apoptosis and necrosis were also determined. In addition, biological safety of these novel formulations was evaluated in human blood cells using different cytotoxicity and genotoxicity assays. Our results indicated that both compounds could block Aβ_1-42 induced cell death. LA-GPE reduced Aβ-induced AChE activity and oxidative stress, suggesting it as a multifunctional compound potentially valuable for the treatment of Alzheimer's disease (AD).

GPE Promotes the Proliferation and Migration of Mouse Embryonic Neural Stem Cells and Their Progeny In Vitro

This study was designed to investigate a possible role of the N-terminal tripeptide of insulin-like growth factor-1 (IGF-I), Gly-Pro-Glu (GPE), physiologically generated in neurons following IGF-I-specific cleavage, in promoting neural regeneration after an injury. Primary cultures of mouse neural stem cells (NSCs), obtained from 13.5 Days post-conception (dpc) mouse embryos, were challenged with either GPE, growth hormone (GH), or GPE + GH and the effects on cell proliferation, migration, and survival were evaluated both under basal conditions and in response to a wound healing assay. The cellular pathways activated by GPE were also investigated by using specific chemical inhibitors. The results of the study indicate that GPE treatment promotes the proliferation and the migration of neural stem cells in vitro through a mechanism that involves the activation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase PI3K-Akt pathways. Intriguingly, both GPE effects and the signaling pathways activated were similar to those observed after GH treatment. Based upon the results obtained from this study, GPE, as well as GH, may be useful in promoting neural protection and/or regeneration after an injury.

Improving Treatment Trial Outcomes for Rett Syndrome: The Development of Rett-specific Anchors for the Clinical Global Impression Scale

Rett syndrome is a genetically based neurodevelopmental disorder. Although the clinical consequences of Rett syndrome are profound and lifelong, currently no approved drug treatments are available specifically targeted to Rett symptoms. High quality outcome measures, specific to the core symptoms of a disorder are a critical component of well-designed clinical trials for individuals with neurodevelopmental disorders. The Clinical Global Impression Scale is a measure of global clinical change with strong face validity that has been widely used as an outcome measure in clinical trials of central nervous system disorders. Despite its favorable assay sensitivity in clinical trials, as a global measure, the Clinical Global Impression Scale is not specific to the signs and symptoms of the disorder under study. Development of key anchors for the scale, specific to the disorder being assessed, holds promise for enhancing the validity and reliability of the measure for disorders such as Rett syndrome.

Combination Therapies for Traumatic Brain Injury: Retrospective Considerations

Patients enrolled in clinical trials for traumatic brain injury (TBI) may present with heterogeneous features over a range of injury severity, such as diffuse axonal injury, ischemia, edema, hemorrhage, oxidative damage, mitochondrial and metabolic dysfunction, excitotoxicity, inflammation, and other pathophysiological processes. To determine whether combination therapies might be more effective than monotherapy at attenuating moderate TBI or promoting recovery, the National Institutes of Health funded six preclinical studies in adult and immature male rats to evaluate promising acute treatments alone and in combination. Each of the studies had a solid rationale for its approach based on previous research, but only one reported significant improvements in long-term outcomes across a battery of behavioral tests. Four studies had equivocal results because of a lack of sensitivity of the outcome assessments. One study demonstrated worse results with the combination in comparison with monotherapies. While specific research findings are reported elsewhere, this article provides an overview of the study designs, insights, and recommendations for future research aimed at therapy development for TBI.

Phelan-McDermid Syndrome and SHANK3: Implications for Treatment

Phelan-McDermid syndrome (PMS), also called 22q13.3 deletion syndrome, is a neurodevelopmental disorder characterized by global developmental delay, intellectual disability, severe speech delays, poor motor tone and function, and autism spectrum disorder (ASD). Although the overall prevalence of PMS is unknown, there have been at least 1200 cases reported worldwide, according to the Phelan-McDermid Syndrome Foundation. PMS is now considered to be a relatively common cause of ASD and intellectual disability, accounting for between 0.5% and 2.0% of cases. The cause of PMS has been isolated to loss of function of one copy of SHANK3, which codes for a master scaffolding protein found in the postsynaptic density of excitatory synapses. Reduced expression of SH3 and multiple ankyrin repeat domains 3 (SHANK3) leads to reduced numbers of dendrites, and impaired synaptic transmission and plasticity. Recent mouse and human neuronal models of PMS have led to important opportunities to develop novel therapeutics, and at least 2 clinical trials are underway, one in the USA, and one in the Netherlands. The SHANK3 pathway may also be relevant to other forms of ASD, and many of the single-gene causes of ASD identified to date appear to converge on several common molecular pathways that underlie synaptic neurotransmission. As a result, treatments developed for PMS may also affect other forms of ASD.

The role for IGF-1-derived small neuropeptides as a therapeutic target for neurological disorders

INTRODUCTION

Exogenous IGF-1 protects the brain from ischemic injury and improves function. However, its clinical application to neurological disorders is limited by its large molecular size, poor central uptake and mitogenic potential.

AREAS COVERED

In this review, the authors have discussed the efficacy, pharmacokinetics and mechanisms of IGF-1 derivatives on protecting acute brain injury, preventing memory impairment and improving recovery from neurological degenerative conditions evaluated in various animal models. We have included natural metabolites of IGF-1, glycine-proline-glutamate (GPE), cleaved from N-terminal IGF-1 and cyclic glycine-proline (cGP) as well as the structural analogues of GPE and cGP, glycine-2-methyl-proline-glutamate and cyclo-l-glycyl-l-2-allylproline, respectively. In addition, the regulatory role for cGP in bioavailability of IGF-1 has also been discussed.

EXPERT OPINION

These small neuropeptides provide effective neuroprotection by offering an improved pharmacokinetic profile and more practical route of administration compared with IGF-1 administration. Developing modified neuropeptides to overcome the limitations of their endogenous counterparts represents a novel strategy of pharmaceutical discovery for neurological disorders. The mechanism of action may involve a regulation of IGF-1 bioavailability.

The IGF-derived tripeptide Gly-Pro-Glu is a weak NMDA receptor agonist

Glutamate acts as the universal agonist at ionotropic glutamate receptors in part because of its high degree of conformational flexibility. Other amino acids and small peptides, however, can activate N-methyl-d-aspartate (NMDA) receptors, albeit usually with lower affinity and efficacy. Here, we examined the action of glycine-proline-glutamate (GPE), a naturally occurring tripeptide formed in the brain following cleavage of IGF-I. GPE is thought to have biological activity in the brain, but its mechanism of action remains unclear. With its flanking glutamate and glycine residues, GPE could bind to either the agonist or coagonist sites on NMDA receptors, however, this has not been directly tested. Using whole cell patch-clamp recordings in combination with rapid solution exchange, we examined both steady-state currents induced by GPE as well as the effects of GPE on synaptically evoked currents. High concentrations of GPE evoked inward currents, which were blocked either by NMDA receptor competitive antagonists or the voltage-dependent channel blocker Mg(2+). GPE also produced a slight attenuation in the NMDA- and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-mediated excitatory postsynaptic currents without altering the paired-pulse ratio. Our results suggest that GPE can activate NMDA receptors but at concentrations well above the expected concentration of GPE in the brain. Therefore, it is unlikely that endogenous GPE interacts with glutamate receptors under normal conditions.

Cyclic glycine-proline regulates IGF-1 homeostasis by altering the binding of IGFBP-3 to IGF-1

The homeostasis of insulin-like growth factor-1 (IGF-1) is essential for metabolism, development and survival. Insufficient IGF-1 is associated with poor recovery from wounds whereas excessive IGF-1 contributes to growth of tumours. We have shown that cyclic glycine-proline (cGP), a metabolite of IGF-1, can normalise IGF-1 function by showing its efficacy in improving the recovery from ischemic brain injury in rats and inhibiting the growth of lymphomic tumours in mice. Further investigation in cell culture suggested that cGP promoted the activity of IGF-1 when it was insufficient, but inhibited the activity of IGF-1 when it was excessive. Mathematical modelling revealed that the efficacy of cGP was a modulated IGF-1 effect via changing the binding of IGF-1 to its binding proteins, which dynamically regulates the balance between bioavailable and non-bioavailable IGF-1. Our data reveal a novel mechanism of auto-regulation of IGF-1, which has physiological and pathophysiological consequences and potential pharmacological utility.

Optimization of hydrolysis conditions, isolation, and identification of neuroprotective peptides derived from seahorse Hippocampus trimaculatus

Hippocampus trimaculatus is one of the most heavily traded seahorse species for traditional medicine purposes in many countries. In the present study, we showed neuroprotective effects of peptide derived from H. trimaculatus against amyloid-β42 (Aβ42) toxicity which are central to the pathogenesis of Alzheimer's diseases (AD). Firstly, H. trimaculatus was separately hydrolyzed by four different enzymes and tested for their protective effect on Aβ42-induced neurotoxicity in differentiated PC12 cells. Pronase E hydrolysate exerted highest protection with cell viability value of 88.33 ± 3.33 %. Furthermore, we used response surface methodology to optimize pronase E hydrolysis conditions and found that temperature at 36.69 °C with the hydrolysis time 20.01 h, enzyme to substrate (E/S) ratio of 2.02 % and pH 7.34 were the most optimum conditions. Following several purification steps, H. trimaculatus-derived neuroprotective peptides (HTP-1) sequence was identified as Gly-Thr-Glu-Asp-Glu-Leu-Asp-Lys (906.4 Da). HTP-1 protected PC12 cells from Aβ42-induced neuronal death with the cell viability value of 85.52 ± 2.22 % and up-regulated pro-survival gene (Bcl-2) expressions. These results suggest that HTP-1 has the potential to be used in treatment of neurodegenerative diseases, particularly AD. Identification, characterization, and synthesis of bioactive components derived from H. trimaculatus have the potential to replace or at least complement the use of seahorse as traditional medicine, which further may become an approach to minimize seahorse exploitation in traditional medicine.

Window of opportunity for neuroprotection with an antioxidant, allene oxide synthase, after hypoxia-ischemia in adult male rats

AIMS

Oxidative stress is an early event in the cascade leading in neuronal damage after hypoxic-ischemic (HI) brain injury. In the present study, we examined the dose response and window of opportunity for neuroprotection after HI injury with Allene Oxide Synthase (AOS), an anti-oxidative enzyme of the member of cytochrome P450 family.

METHODS

Adult male rats received intra-cerebro-ventricular infusions of either saline (vehicle) or AOS (1 μg or 10 μg or 100 μg per rat, intracerebroventricular n = 16 all groups) either 45 min or 3 h after unilateral HI brain injury. Brains were collected 5 days later. The extent of brain damage, neuronal survival, apoptosis, and glial reactions were assessed in the striatum, hippocampus, and cortex.

RESULTS

Allene Oxide Synthase was associated with reduced neuronal damage scores when given 45 min, but not 3 h, after HI injury (P < 0.0001) in all brain regions. AOS treatment (10 μg) improved neuronal survival in the striatum, cortex, and hippocampus (P < 0.05, P < 0.001) and reduced the microglia reaction (P < 0.05) and numbers of caspase-3-positive cells in the hippocampus (P < 0.01).

CONCLUSIONS

Early blockade of oxidative stress after HI injury reduces inflammatory response, neuronal necrosis, and apoptosis. The neuroprotective effects of AOS were time of administration-dependent suggesting a relatively restricted window of opportunity for acute brain injury.

Molecular mechanism underlying the cerebral effect of Gly-Pro-Glu tripeptide bound to L-dopa in a Parkinson's animal model

Oxidative stress is a critical contributing factor to neurodegenerative disorders. Therefore, the inhibition of ROS formation, responsible for chronic detrimental neuroinflammation, is an important strategy for preventing the neurodegenerative disease and for neuroprotective therapy. Gly-Pro-Glu (GPE) is the N-terminal tripeptide of insulin-like growth factor-I, which is naturally cleaved in the plasma and brain tissues. GPE has neuroprotective effects since it crosses the blood-CSF and the functional CSF-brain barriers and binds to glial cells. It has been shown that GPE improves motor behaviour in rats after 6-OHDA lesion, although it does not rescue dopaminergic neurons. Thus, we hypothesized that the GPE therapeutic efficacy in a Parkinson model might be improved by combining GPE to L: -dopa. Here, we used an animal model that represents a progressive chronic Parkinson's disease (PD) model, characterized by high levels of oxidative stress and inflammation. We showed that the co-drug, in which L: -dopa is covalently linked to the GPE tripeptide, by down-regulating the expression of inflammatory genes, decreases the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced inflammatory response and, by up-regulating tyrosine hydroxylase, reduces MPTP-induced neurotoxicity. Furthermore, by determining the nuclear translocation/activation of Nrf2 and NF-κB, we showed that systemic administration of the co-drug activates Nrf2-induced antioxidant response while suppressing NF-κB inflammatory pathway. Data suggest that the binding of L: -dopa to GPE tripeptide might represent a promising strategy to supply L: -dopa to parkinsonian patients.

Insulin-like growth factor-I peptides act centrally to decrease depression-like behavior of mice treated intraperitoneally with lipopolysaccharide

Centrally administered insulin-like growth factor (IGF)-I has anti-depressant activity in several rodent models, including lipopolysaccharide (LPS)-induced depression. In this study we tested the ability of IGF-I and GPE (the N-terminal tri-peptide derived from IGF-I) to alter depression-like behavior induced by intraperitoneal (i.p.) administration of LPS in a preventive and curative manner. In the first case, IGF-I (1 μg) or GPE (5 μg) was administered i.c.v. to CD-1 mice followed 30 min later by 330 μg/kg body weight i.p. LPS. In the second case, 830 μg/kg body weight LPS was given 24 h prior to either IGF-I or GPE. When administered i.p., LPS induced full-blown sickness assessed as a loss of body weight, decrease in food intake and sickness behavior. None of these indices were affected by IGF-I or GPE. LPS also induced depression-like behavior; assessed as an increased duration of immobility in the tail suspension and forced swim tests. When administered before or after LPS, IGF-I and GPE abrogated the LPS response; attenuating induction of depression-like behaviors and blocking preexistent depression-like behaviors. Similar to previous work with IGF-I, GPE decreased brain expression of cytokines in response to LPS although unlike IGF-I, GPE did not induce the expression of brain-derived neurotrophic factor (BDNF). LPS induced expression of tryptophan dioxygenases, IDO1, IDO2 and TDO2, but expression of these enzymes was not altered by GPE. Thus, both IGF-I and GPE elicit specific improvement in depression-like behavior independent of sickness, an action that could be due to their anti-inflammatory properties.

Reprint of "The developing oligodendrocyte: key cellular target in brain injury in the premature infant"

Brain injury in the premature infant, a problem of enormous importance, is associated with a high risk of neurodevelopmental disability. The major type of injury involves cerebral white matter and the principal cellular target is the developing oligodendrocyte. The specific phase of the oligodendroglial lineage affected has been defined from study of both human brain and experimental models. This premyelinating cell (pre-OL) is vulnerable because of a series of maturation-dependent events. The pathogenesis of pre-OL injury relates to operation of two upstream mechanisms, hypoxia-ischemia and systemic infection/inflammation, both of which are common occurrences in premature infants. The focus of this review and of our research over the past 15-20 years has been the cellular and molecular bases for the maturation-dependent vulnerability of the pre-OL to the action of the two upstream mechanisms. Three downstream mechanisms have been identified, i.e., microglial activation, excitotoxicity and free radical attack. The work in both experimental models and human brain has identified a remarkable confluence of maturation-dependent factors that render the pre-OL so exquisitely vulnerable to these downstream mechanisms. Most importantly, elucidation of these factors has led to delineation of a series of potential therapeutic interventions, which in experimental models show marked protective properties. The critical next step, i.e., clinical trials in the living infant, is now on the horizon.

The developing oligodendrocyte: key cellular target in brain injury in the premature infant

Brain injury in the premature infant, a problem of enormous importance, is associated with a high risk of neurodevelopmental disability. The major type of injury involves cerebral white matter and the principal cellular target is the developing oligodendrocyte. The specific phase of the oligodendroglial lineage affected has been defined from study of both human brain and experimental models. This premyelinating cell (pre-OL) is vulnerable because of a series of maturation-dependent events. The pathogenesis of pre-OL injury relates to operation of two upstream mechanisms, hypoxia-ischemia and systemic infection/inflammation, both of which are common occurrences in premature infants. The focus of this review and of our research over the past 15-20 years has been the cellular and molecular bases for the maturation-dependent vulnerability of the pre-OL to the action of the two upstream mechanisms. Three downstream mechanisms have been identified, i.e., microglial activation, excitotoxicity and free radical attack. The work in both experimental models and human brain has identified a remarkable confluence of maturation-dependent factors that render the pre-OL so exquisitely vulnerable to these downstream mechanisms. Most importantly, elucidation of these factors has led to delineation of a series of potential therapeutic interventions, which in experimental models show marked protective properties. The critical next step, i.e., clinical trials in the living infant, is now on the horizon.

Insulin-like growth factor-1 regulates neurite outgrowth and neuronal migration from organotypic cultured dorsal root ganglion

ABSTRACT Insulin-like growth factor-1 (IGF-1) is a neurotrophic factor and plays an important role in promoting axonal growth from neurons. Whether IGF-1 could promote neurite outgrowth and neuronal migration of dorsal root ganglion (DRG) explants in vitro remains unknown. In the present study, organotypic rat DRG explant culture model was established. Using this unique culture system, outgrowth of neurites from the peripheral nerve attached to DRG explant and migration of neurons from DRG explant to the peripheral area were quantified in the presence (5 nmol/L, 10 nmol/L, 20 nmol/L) or absence of IGF-1. The number of nerve fiber bundles extended from DRG explant increased significantly in the presence of IGF-1 (5 nmol/L, 19.25 ± 3.11, p < .05; 10 nmol/L, 20.92 ± 2.31, p < .01; 20 nmol/L, 23.00 ± 4.09, p < .001) as compared with that in the absence of IGF-1 (16.58 ± 2.94). The number of neurons migrated from DRG explant increased significantly in the presence of IGF-1 (5 nmol/L, 104.08 ± 16.70, p < .05; 10 nmol/L, 115.25 ± 13.68, p < .001; 20 nmol/L, 138.75 ± 18.05, p < .001) as compared with that in the absence of IGF-1 (90.25 ± 8.53). These data implicated that IGF-1 could promote neurite outgrowth and neuronal migration from DRG explants in vitro.

The effect of sevoflurane anesthesia on cognitive function and the expression of Insulin-like Growth Factor-1 in CA1 region of hippocampus in old rats

To investigate the effects of sevoflurane on cognitive function in old Sprague-Dawley (SD) rats and the expression of insulin-like growth factor-1 (IGF-1) in CA1 region of hippocampus. Forty Sprague-Dawley rats of 12 months old were randomly divided into five groups: the normal control group; 1.5% sevoflurane I group (be tested after received 1.5% sevoflurane for 1 day); 1.5% sevoflurane II group (be tested after received 1.5% sevoflurane for 7 day); 3.0% sevoflurane I group (be tested after received 3.0% sevoflurane for 1 day) and 3.0% sevoflurane II group (be tested after received 3.0% sevoflurane for 7 day). All SD rats were received 1.5 or 3.0% sevoflurane in a special glass anesthesia box for 2 h respectively, except for the normal control group. Y-maze was used to test the ability of learning and memory after being received sevoflurane for 1 or 7 days at the same moment portion. The altered expression level of IGF-1 in the hippocampus was tested to compare its transcripts by RT-PCR analysis. The results showed that 3% sevoflurane induced the decline of cognitive function and significantly deceased the IGF-1 expression at mRNA levels at 1 day in the 3.0% sevoflurane I group when compared with the normal control group. However, there were no significant difference among the other groups when compared with normal control group. Therefore, administration of sevoflurane might temporally affect the ability of cognitive function of rats through suppressing the IGF-1 expression at mRNA levels in hippocampus.

Regulatory effects of insulin-like growth factor-1 on the expression of sensory neuropeptide mRNAs in cultured dorsal root ganglion neurons with excitotoxicity induced by glutamate

OBJECTIVE

To determine the effects of insulin-like growth factor-1 (IGF-1) on the expression of preprotachykinin (PPT) mRNA encoding substance P (SP) and calcitonin gene-related peptide (CGRP) mRNA in cultured dorsal root ganglion (DRG) neurons with excitotoxicity induced by glutamate (Glu).

METHODS

DRGs were dissected from embryonic day 15 Wistar rats. DRG neurons were dissociated and cultured for 48 h and then exposed to Glu (0.2 mmol/L) or Glu (0.2 mmol/L) plus IGF-1 (5 nmol/L, 10 nmol/L and 20 nmol/L) for 12 h. The DRG neurons in control group were exposed to only growth media throughout the experiment. After that, the living DRG neurons were observed under inverted phase contrast microscope and microphotographs were taken. The expression levels of PPT and CGRP mRNAs were detected by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

IGF-1 could inhibit Glu-induced shortening of neurite. Besides, IGF-1 could significantly increase the levels of PPT mRNA and CGRP mRNA in primary cultured DRG neurons with Glu-induced excitotoxicity, in a dose-dependent manner.

CONCLUSION

IGF-1 may exert neuroprotective effects on DRG neurons against Glu-induced excitotoxicity, probably through regulating the expression levels of PPT and CGRP mRNAs.

Insulin-like growth factor -1 (IGF-1) derived neuropeptides, a novel strategy for the development of pharmaceuticals for managing ischemic brain injury

Insulin-Like Growth Factor-1 (IGF-1) is neuroprotective and improves long-term function after brain injury. However, its clinical application to neurological disorders is limited by its large molecular size, poor central uptake, and mitogenic potential. Glycine-proline-glutamate (GPE) is naturally cleaved from the IGF-1 N-terminal and is also neuroprotective after ischemic injury, thus providing a potential novel strategy of drug discovery for management of neurological disorders. GPE is not enzymatically stable, thus intravenous infusion of GPE becomes necessary for stable and potent neuroprotection. The broad effective dose range and treatment window of 3-7 h after the lesion suggest its potential for treating acute brain injuries. The neuroprotective action of GPE is not age selective, is not dependent on cerebral reperfusion, plasma glucose concentrations, and core body temperature. G-2mPE, a GPE analogue designed to be more resistant to enzymatic activity, has a prolonged plasma half-life and is more potent in neuroprotection. Neuroprotection by GPE and its analogue may be involved in modulation of inflammation, promotion of astrocytosis, inhibition of apoptosis, and in vascular remodeling. Small neuropeptides have advantages over growth factors in the treatment of brain injury, and modified neuropeptides, designed to overcome the limitations of their endogenous counterparts, represent a novel strategy of pharmaceutical discovery for neurological disorders.

NNZ-2566, a glypromate analog, attenuates brain ischemia-induced non-convulsive seizures in rats

Ischemic and traumatic brain injuries often induce non-convulsive seizures (NCSs), which likely contribute to the worsening of neurological outcomes. Here, we evaluated the effect of glycyl-L-methylprolyl-L-glutamic acid (NNZ-2566) to lessen the severity of NCSs caused by permanent middle cerebral artery occlusion (pMCAo). Continuous electroencephalographic recordings were performed in rats during pMCAo. Glycyl-L-methylprolyl-L-glutamic acid (3, 10, or 100 mg/kg bolus followed by an infusion of a fixed dose of 3 mg/kg per hour for 12 h) was delivered at 20 mins after pMCAo (before the first NCS event) or delayed until immediately after the first NCS event occurred. Control rats received pMCAo and saline treatment. The results revealed that 91% of the saline-treated animals had NCSs (23 episodes per rat and 1238 secs per rat) with an onset latency of 35 mins after injury. When NNZ-2566 was administered before the NCS events, it dose-dependently reduced the NCS incidence to 36%-80%, decreased NCS frequency to 5-16 episodes per rat, and shortened the total duration of NCS to 251-706 secs per rat. The two high doses significantly reduced the infarct volume by 28%-30%. Delayed treatment also attenuated NCS duration but had no effect on the infarct volume. Results indicate that NNZ-2566 possesses a unique therapeutic potential as a safe prophylactic agent that synergistically provides neuroprotection and reduces injury-induced seizures.

NNZ-2566, a glypromate analog, improves functional recovery and attenuates apoptosis and inflammation in a rat model of penetrating ballistic-type brain injury

Glycine-proline-glutamate (GPE) is an N-terminal tripeptide endogenously cleaved from insulin-like growth factor-1 in the brain and is neuroprotective against hypoxic-ischemic brain injury and neurodegeneration. NNZ-2566 is an analog of GPE designed to have improved bioavailability. In this study, we tested NNZ-2566 in a rat model of penetrating ballistic-type brain injury (PBBI) and assessed its effects on injury-induced histopathology, behavioral deficits, and molecular and cellular events associated with inflammation and apoptosis. In the initial dose-response experiments, NNZ-2566 (0.01-3 mg/kg/h x 12 h intravenous infusion) was given at 30 min post-injury and the therapeutic time window was established by delaying treatments 2-4 h post-injury, but with the addition of a 10- or 30-mg/kg bolus dose. All animals survived 72 h. Neuroprotection was evaluated by balance beam testing and histopathology. The effects of NNZ-2566 on injury-induced changes in Bax and Bcl-2 proteins, activated microgliosis, neutrophil infiltration, and astrocyte reactivity were also examined. Behavioral results demonstrated that NNZ-2566 dose-dependently reduced foot faults by 19-66% after acute treatments, and 35-55% after delayed treatments. Although gross lesion volume was not affected, NNZ-2566 treatment significantly attenuated neutrophil infiltration and reduced the number of activated microglial cells in the peri-lesion regions of the PBBI. PBBI induced a significant upregulation in Bax expression (36%) and a concomitant downregulation in Bcl-2 expression (33%), both of which were significantly reversed by NNZ-2566. Collectively, these results demonstrated that NNZ-2566 treatment promoted functional recovery following PBBI, an effect related to the modulation of injury-induced neural inflammatory and apoptotic mechanisms.

NNZ-2566 treatment inhibits neuroinflammation and pro-inflammatory cytokine expression induced by experimental penetrating ballistic-like brain injury in rats

Background

Inflammatory cytokines play a crucial role in the pathophysiology of traumatic brain injury (TBI), exerting either deleterious effects on the progression of tissue damage or beneficial roles during recovery and repair. NNZ-2566, a synthetic analogue of the neuroprotective tripeptide Glypromate^®, has been shown to be neuroprotective in animal models of brain injury. The goal of this study was to determine the effects of NNZ-2566 on inflammatory cytokine expression and neuroinflammation induced by penetrating ballistic-like brain injury (PBBI) in rats.

Methods

NNZ-2566 or vehicle (saline) was administered intravenously as a bolus injection (10 mg/kg) at 30 min post-injury, immediately followed by a continuous infusion of NNZ-2566 (3 mg/kg/h), or equal volume of vehicle, for various durations. Inflammatory cytokine gene expression from the brain tissue of rats exposed to PBBI was evaluated using microarray, quantitative real time PCR (QRT-PCR), and enzyme-linked immunosorbent assay (ELISA) array. Histopathology of the injured brains was examined using hematoxylin and eosin (H&E) and immunocytochemistry of inflammatory cytokine IL-1β.

Results

NNZ-2566 treatment significantly reduced injury-mediated up-regulation of IL-1β, TNF-α, E-selectin and IL-6 mRNA during the acute injury phase. ELISA cytokine array showed that NZ-2566 treatment significantly reduced levels of the pro-inflammatory cytokines IL-1β, TNF-α and IFN-γ in the injured brain, but did not affect anti-inflammatory cytokine IL-6 levels.

Conclusion

Collectively, these results suggest that the neuroprotective effects of NNZ-2566 may, in part, be functionally attributed to the compound's ability to modulate expression of multiple neuroinflammatory mediators in the injured brain.

Adult neural stem/progenitor cells reduce NMDA-induced excitotoxicity via the novel neuroprotective peptide pentinin

Although the potential of adult neural stem cells to repair damage via cell replacement has been widely reported, the ability of endogenous stem cells to positively modulate damage is less well studied. We investigated whether medium conditioned by adult hippocampal stem/progenitor cells altered the extent of excitotoxic cell death in hippocampal slice cultures. Conditioned medium significantly reduced cell death following 24 h of exposure to 10 microM NMDA. Neuroprotection was greater in the dentate gyrus, a region neighboring the subgranular zone where stem/progenitor cells reside compared with pyramidal cells of the cornis ammonis. Using mass spectrometric analysis of the conditioned medium, we identified a pentameric peptide fragment that corresponded to residues 26-30 of the insulin B chain which we termed 'pentinin'. The peptide is a putative breakdown product of insulin, a constituent of the culture medium, and may be produced by insulin-degrading enzyme, an enzyme expressed by the stem/progenitor cells. In the presence of 100 pM of synthetic pentinin, the number of mature and immature neurons killed by NMDA-induced toxicity was significantly reduced in the dentate gyrus. These data suggest that progenitors in the subgranular zone may convert exogenous insulin into a peptide capable of protecting neighboring neurons from excitotoxic injury.

IGF-1 derived small neuropeptides and analogues: a novel strategy for the development of pharmaceuticals for neurological conditions

Insulin-like growth factor-1 (IGF-1) is neuroprotective and improves long-term function after brain injury. However, its clinical application to neurological disorders is limited by its large molecular size, poor central uptake and mitogenic potential. Glycine-proline-glutamate (GPE) is naturally cleaved from the IGF-1 N-terminal and it is also neuroprotective after ischemic injury, which provided a novel strategy of drug discovery for neurological disorders. GPE is not enzymatically stable, thus intravenous infusion of GPE becomes necessary for stable and potent neuroprotection. The broad effective dose range and treatment window of 3-7 h after the lesion suggest its potential for treating acute brain injuries. G-2meth-PE, a GPE analogue designed to be more enzymatic resistant, has a prolonged plasma half-life and is more potent in neuroprotection. Neuroprotection by GPE and its analogue may involve modulation of inflammation, promotion of astrocytosis, inhibition of apoptosis and vascular remodelling. Acute administration of GPE also prevents 6-OHDA-induced nigrostrial dopamine depletion. Delayed treatment with GPE does not prevent dopamine loss, but improves long-term function. Cyclo-glycyl-proline (cyclic Gly-Pro) is an endogenous DKP that may be derived from GPE. Cyclic Gly-Pro and its analogue cyclo-L-glycyl-L-2-allylproline (NNZ 2591) are both neuroprotective after ischaemic injury. NNZ2591 is highly enzymatic resistant and centrally accessible. Its peripheral administration improves somatosensory-motor function and long-term histological outcome after brain injury. Our research suggests that small neuropeptides have advantages over growth factors in the treatment of brain injury, and that modified neuropeptides designed to overcome the limitations of their endogenous counterparts represent a novel strategy of pharmaceutical discovery for neurological disorders.

Partial reversal of Rett Syndrome-like symptoms in MeCP2 mutant mice

Rett Syndrome (RTT) is a severe form of X-linked mental retardation caused by mutations in the gene coding for methyl CpG-binding protein 2 (MECP2). Mice deficient in MeCP2 have a range of physiological and neurological abnormalities that mimic the human syndrome. Here we show that systemic treatment of MeCP2 mutant mice with an active peptide fragment of Insulin-like Growth Factor 1 (IGF-1) extends the life span of the mice, improves locomotor function, ameliorates breathing patterns, and reduces irregularity in heart rate. In addition, treatment with IGF-1 peptide increases brain weight of the mutant mice. Multiple measurements support the hypothesis that RTT results from a deficit in synaptic maturation in the brain: MeCP2 mutant mice have sparse dendritic spines and reduced PSD-95 in motor cortex pyramidal neurons, reduced synaptic amplitude in the same neurons, and protracted cortical plasticity in vivo. Treatment with IGF-1 peptide partially restores spine density and synaptic amplitude, increases PSD-95, and stabilizes cortical plasticity to wild-type levels. Our results thus strongly suggest IGF-1 as a candidate for pharmacological treatment of RTT and potentially of other CNS disorders caused by delayed synapse maturation.

Delayed peripheral administration of the N-terminal tripeptide of IGF-1 (GPE) reduces brain damage following microsphere induced embolic damage in young adult and aged rats

We have previously reported that peripheral administration of GPE prevents neuronal injury after ischemic reperfusion injury in young adult rats. This study examined the ameliorating effects of GPE-treatment after embolic injury induced by microsphere injection in young adult and aged male rats. Unilateral injury was induced by injecting microspheres into the right internal carotid artery in both young adult (3-4 months) and aged (16-17 months) male rats. Either GPE (12mg/kg) or the vehicle was infused intravenously over 1h starting 3h after embolic injury and the degree of brain injury, astrocytosis and vascular remodeling were examined using histological and immunohistochemical analysis 8 days later. Changes in core temperature, blood glucose concentration, oxygen saturation and heart rate were monitored. Microsphere injection induced multiple sites of focal damage in the ipsilateral subcortical regions. Massive numbers of microglia accumulated within the core of the tissue damage whereas astrocytes were located in the penumbra. There was no difference in the degree of brain injury between the young and aged control rats. However the aged rats showed less injury-induced astrocytosis and greater vascular remodeling. Intravenous infusion of GPE 3h after the injury reduced overall damage scores in both young (p<0.01) and aged rats (p<0.05). GPE-treatment reduced astrocytosis in young, but not aged animals and did not significantly alter the vascular remodeling in either age group. The data suggested that the neuroprotection of the tripeptide is independent of cerebral reperfusion and is not age selective.

A novel diketopiperazine improves functional recovery given after the onset of 6-OHDA-induced motor deficit in rats

BACKGROUND AND PURPOSE

Cyclo-L-glycyl-L-2-allylproline (NNZ-2591), a modified diketopiperazine, is neuroprotective and improves long-term function after hypoxic-ischaemic brain injury in rats. The present studies were designed to examine both the neuroprotective and neurotrophic actions of NNZ-2591 on neurochemical and behavioural changes in a rat model of Parkinson's disease.

EXPERIMENTAL APPROACH

To examine its protective effect, either NNZ-2591 (20 ng.day(-1)) or saline was given intracerebroventricularly for 3 days starting 2 h after 6-hydroxydopamine (6-OHDA) induced unilateral striatal lesion. In a subsequent experiment either NNZ-2591 (0.2, 1 and 5 mg.day(-1), s.c.) or saline was administered daily for 14 days starting 2 weeks after the lesion. Behavioural and neurochemical outcomes were examined using the adjusting step test and immunohistochemical staining.

KEY RESULTS

Cyclo-L-glycyl-L-2-allylproline given 2 h after the lesion reduced the degree of motor deficit compared with the saline-treated group. Delayed treatment with NNZ-2591, initiated after the onset of motor deficit, significantly improved motor function from week 7 onwards compared with the saline-treated group. Neither treatment regime altered nigrostriatal dopamine depletion. NNZ-2591 significantly enhanced the expression of doublecortin-positive neuroblasts in the sub-ventricular zone.

CONCLUSIONS AND IMPLICATIONS

These studies reveal that early treatment with NNZ-2591 protects against the motor deficit induced by 6-OHDA and that treatment initiated after the establishment of motor impairment significantly improves long-term motor function. These effects of NNZ-2591 on functional recovery were independent of dopamine depletion and also appeared not to be symptomatic as the improved motor function was long-lasting. NNZ-2591 has potential as a therapeutic agent for neurodegenerative disorders.

Neuroprotection during cardiac surgery

Cardiac surgery continues to be associated with significant adverse cerebral outcomes, ranging from stroke to cognitive decline. The underlying mechanism of the associated cerebral injury is incompletely understood but is believed to be primarily caused by cerebral embolism and hypoperfusion, exacerbated by ischemia/reperfusion injury. Extensive research has been undertaken in an attempt to minimize the incidence of perioperative cerebral injury, and both pharmacological and nonpharmacological strategies have been investigated. Although many agents demonstrated promise in preclinical studies, there is currently insufficient evidence from clinical trials to recommend the routine administration of any pharmacological agents for neuroprotection during cardiac surgery. The nonpharmacological strategies that can be recommended on the basis of evidence include transesophageal echocardiography and epiaortic ultrasound-guided assessment of the atheromatous ascending aorta with appropriate modification of cannulation, clamping or anastomotic technique and optimal temperature management. Large-scale randomized controlled trials are still required to address further the issues of optimal pH management, glycemic control, blood pressure management and hematocrit during cardiopulmonary bypass. Past, present and future directions in the field of neuroprotection in cardiac surgery will be discussed.