Delayed peripheral administration of a GPE analogue induces astrogliosis and angiogenesis and reduces inflammation and brain injury following hypoxia-ischemia in the neonatal rat

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.

Midkine: The Who, What, Where, and When of a Promising Neurotrophic Therapy for Perinatal Brain Injury

Midkine (MK) is a small secreted heparin-binding protein highly expressed during embryonic/fetal development which, through interactions with multiple cell surface receptors promotes growth through effects on cell proliferation, migration, and differentiation. MK is upregulated in the adult central nervous system (CNS) after multiple types of experimental injury and has neuroprotective and neuroregenerative properties. The potential for MK as a therapy for developmental brain injury is largely unknown. This review discusses what is known of MK's expression and actions in the developing brain, areas for future research, and the potential for using MK as a therapeutic agent to ameliorate the effects of brain damage caused by insults such as birth-related hypoxia and inflammation.

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.

Attenuation of Retinal Vascular Development in Neonatal Mice Subjected to Hypoxic-Ischemic Encephalopathy

A significant proportion of children that survive hypoxic-ischemic encephalopathy (HIE) develop visual impairment. These visual deficits are generally attributed to injuries that occur in the primary visual cortex and other visual processing systems. Recent studies suggested that neuronal damage might also occur in the retina. An important structure affecting the viability of retinal neurons is the vasculature. However, the effects of HIE on the retinal neurovasculature have not been systemically evaluated. Here we investigated whether exposure of postnatal day 9 (P9) neonatal mice to HIE is sufficient to induce neurovascular damage in the retina. We demonstrate that the blood vessels on the surface of the retina, from mice subjected to HIE, were abnormally enlarged with signs of degeneration. The intermediate and deep vascular layers in these retinas failed to form normally, particularly in the periphery. All the vascular damages observed here were irreversible in nature up to 100 days post HIE. We also observed loss of retinal neurons, together with changes in both astrocytes and Müller cells mainly in the inner retina at the periphery. Collectively, our findings suggest that HIE results in profound alterations in the retinal vasculature, indicating the importance of developing therapeutic strategies to protect neurovascular dysfunction not only in the brain but also in the retina for infants exposed to HIE.

Systemic infusions of anti-interleukin-1β neutralizing antibodies reduce short-term brain injury after cerebral ischemia in the ovine fetus

Perinatal hypoxic-ischemic reperfusion (I/R)-related brain injury is a leading cause of neurologic morbidity and life-long disability in children. Infants exposed to I/R brain injury develop long-term cognitive and behavioral deficits, placing a large burden on parents and society. Therapeutic strategies are currently not available for infants with I/R brain damage, except for hypothermia, which can only be used in full term infants with hypoxic-ischemic encephalopathy (HIE). Moreover, hypothermia is only partially protective. Pro-inflammatory cytokines are key contributors to the pathogenesis of perinatal I/R brain injury. Interleukin-1β (IL-1β) is a critical pro-inflammatory cytokine, which has been shown to predict the severity of HIE in infants. We have previously shown that systemic infusions of mouse anti-ovine IL-1β monoclonal antibody (mAb) into fetal sheep resulted in anti-IL-1β mAb penetration into brain, reduced I/R-related increases in IL-1β expression and blood-brain barrier (BBB) dysfunction in fetal brain. The purpose of the current study was to examine the effects of systemic infusions of anti-IL-1β mAb on short-term I/R-related parenchymal brain injury in the fetus by examining: 1) histopathological changes, 2) apoptosis and caspase-3 activity, 3) neuronal degeneration 4) reactive gliosis and 5) myelin basic protein (MBP) immunohistochemical staining. The study groups included non-ischemic controls, placebo-treated ischemic, and anti-IL-1β mAb treated ischemic fetal sheep at 127days of gestation. The systemic intravenous infusions of anti-IL-1β mAb were administered at fifteen minutes and four hours after in utero brain ischemia. The duration of each infusion was two hours. Parenchymal brain injury was evaluated by determining pathological injury scores, ApopTag® positive cells/mm², caspase-3 activity, Fluoro-Jade B positive cells/mm², glial fibrillary acidic protein (GFAP) and MBP staining in the brains of fetal sheep 24h after 30min of ischemia. Treatment with anti-IL-1β mAb reduced (P<0.05) the global pathological injury scores, number of apoptotic positive cells/mm², and caspase-3 activity after ischemia in fetal sheep. The regional pathological scores and Fluoro-Jade B positive cells/mm² did not differ between the placebo- and anti-IL-1β mAb treated ischemic fetal sheep. The percent of the cortical area stained for GFAP was lower (P<0.05) in the placebo ischemic treated than in the non-ischemic group, but did not differ between the placebo- and anti-IL-1β mAb treated ischemic groups. MBP immunohistochemical expression did not differ among the groups. In conclusion, infusions of anti-IL-1β mAb attenuate short-term I/R-related histopathological tissue injury, apoptosis, and reduce I/R-related increases in caspase-3 activity in ovine fetal brain. Therefore, systemic infusions of anti-IL-1β mAb attenuate short-term I/R-related parenchymal brain injury in the fetus.

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.

Anticonvulsant effect of neural regeneration peptide 2945 on pentylenetetrazol-induced seizures in rats

Neuron regeneration peptides (NRPs) are small synthetic peptides that stimulate neural proliferation, migration, and differentiation with no apparent toxicity and high target specificity in CNS. The aim of this study was to investigate the effect of NRP2945 on seizure activity induced by pentylenetetrazol (PTZ) in rats. Using behavioural assessment and electrocorticographical recordings, the effects of different doses of NRP2945 (5-20 µg/kg) were tested on seizure attacks induced by PTZ injection. In addition, the effect of NRP2945 was evaluated on the production of dark neurons and expression of GABAA receptor α and β subunits and GAD-65 in the hippocampus and somatosensory cortex of the rat brain. Intraperitoneal injection of NRP2945 at 20 µg/kg prevented seizure attacks after PTZ injection. NRP2945 at doses of 5 and 10 µg/kg significantly decreased the total duration of seizure attacks and reduced the amplitude, duration and latency of epileptiform burst discharges induced by PTZ. In addition, the peptide significantly inhibited the production of dark neurons in the hippocampus and somatosensory cortex of epileptic rats. NRP2945 also significantly increased the expression of GABAA receptor α and β subunits and GAD-65 in the hippocampus and somatosensory cortex compared with PTZ treated rats. This study indicates that NRP2945 is able to prevent the seizure attacks and neuronal injuries induced by PTZ, likely by stimulating GABAA and GAD-65 protein expression and/or protecting these components of GABAergic signalling from PTZ-induced alteration. Further studies are needed to elucidate the potential role of NRP2945 as an antiepileptic drug.

Estrogen-IGF-1 interactions in neuroprotection: ischemic stroke as a case study

The steroid hormone 17b-estradiol and the peptide hormone insulin-like growth factor (IGF)-1 independently exert neuroprotective actions in neurologic diseases such as stroke. Only a few studies have directly addressed the interaction between the two hormone systems, however, there is a large literature that indicates potentially greater interactions between the 17b-estradiol and IGF-1 systems. The present review focuses on key issues related to this interaction including IGF-1 and sex differences and common activation of second messenger systems. Using ischemic stroke as a case study, this review also focuses on independent and cooperative actions of estrogen and IGF-1 on neuroprotection, blood brain barrier integrity, angiogenesis, inflammation and post-stroke epilepsy. Finally, the review also focuses on the astrocyte, a key mediator of post stroke repair, as a local source of 17b-estradiol and IGF-1. This review thus highlights areas where significant new research is needed to clarify the interactions between these two neuroprotectants.

Acute and chronic vascular responses to experimental focal arterial stroke in the neonate rat

The presence of active developmental angiogenesis and vascular outgrowth in the postnatal brain may differentially affect vascular responses to stroke in newborns and adults, but very little is known about the dynamics of vascular injury and re-growth after stroke during the neonatal period. In this study we used a clinically relevant animal model of ischemic arterial stroke in neonate rats, a transient middle cerebral artery occlusion (MCAO) in postnatal day 7 (P7), to characterize the effects of injury on vascular density and angiogenesis from acute through the chronic phase. A marked vessel degeneration and suppressed endothelial cell proliferation occur in the ischemic regions early after neonatal stroke. In contrast to what has been described in adult animals, endothelial cell proliferation and vascular density are not increased in the peri-ischemic regions during the first week after MCAO in neonates. By two weeks after injury, endothelial cell proliferation is increased in the cortical peri-ischemic region but these changes are not accompanied by an increased vascular density. Suppressed angiogenesis in injured postnatal brain that we report may limit recovery after neonatal stroke. Thus, enhancement of angiogenesis after neonatal stroke may be a promising strategy for the long-term recovery of the affected newborns.

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.

Supplementation of complex milk lipid concentrate (CMLc) improved the memory of aged rats

OBJECTIVES

The socio-economic impact from age-related mental decline is escalating. Supplementation of functional foods for sustaining mental health is desirable. We examined the effect of long-term supplementation of complex milk lipid concentrate (CMLc), mixed dairy phospholipids, on memory and associated vascular and neuronal changes in aged rats.

METHODS

Fisher/Norway Brown rats were used. Two groups of aged rats (24 months) were fed with either gelatin-formulated CMLc or blank gelatin as the control, for 4 months. To determine age-related changes, a young group (5 months) was also fed with blank gelatin. Morris water maze tests were carried out after the supplementation and brain tissues were collected for biological analysis.

RESULTS

The aged control rats learnt to locate the platform slower than the young control rats during acquisition trials (*P < 0.05), and made fewer entries to and more initial heading errors from the platform zone during testing trials (*P < 0.05). The CMLc supplementation improved memory by showing the reduced initial heading errors in a delayed probe trial ((#)P < 0.05). We also found that the aged rats with CMLc supplementation improved vascular density, dopamine output, and neuroplasticity ((#)P < 0.05) in the brain regions involved in memory compared with that of the aged control rats.

DISCUSSION

The data suggested that the supplementation of CMLc during the early stage of brain aging may prevent memory decline possibly through improving vascular and neuronal function.

Intranasal delivery of cell-penetrating anti-NF-κB peptides (Tat-NBD) alleviates infection-sensitized hypoxic-ischemic brain injury

Perinatal infection aggravates neonatal hypoxic-ischemic (HI) brain injury and may interfere with therapeutic hypothermia. While the NF-κB signaling pathway has been implicated in microglia activation in infection-sensitized HI, the current therapeutic strategies rely on systemic intervention, which could impair neonatal immunity and increase the risk of severe infection. To devise a brain-targeted anti-NF-κB strategy, we examined the effects of intranasal delivery of tat-NBD peptides in two animal models of neonatal infection-sensitized HI. Kinetic experiments showed that tat-NBD peptides entered the olfactory bulbs rapidly (10-30 min) and peaked in the cerebral cortex around 60 min after intranasal application in P7 rats. Further, intranasal delivery of 1.4 mg/kg tat-NBD, which is only 7% of the intravenous dose in past studies, markedly attenuated NF-κB signaling, microglia activation, and brain damage triggered by HI with 4 or 72 h pre-exposure to the bacterial endotoxin lipopolysaccharide (LPS). In contrast, intranasal delivery of mutant tat-NBD peptides or systemic application of minocycline failed to block LPS-sensitized HI injury. Yet, intranasal delivery of up to 5.6 mg/kg tat-NBD peptides immediately after pure-HI insult showed little protection, likely due to its rapid clearance from the brain and inability to inhibit parenchymal plasminogen activators. Together, these results suggest a novel therapy of infection-sensitized HI brain injury in newborns.

Age-related memory decline is associated with vascular and microglial degeneration in aged rats

The hippocampus processes memory is an early target of aging-related biological and structural lesions, leading to memory decline. With absent neurodegeneration in the hippocampus, which identified in rodent model of normal aging the pathology underlying age-related memory impairment is not complete. The effective glial-vascular networks are the key for maintaining neuronal functions. The changes of glial cells and cerebral capillaries with age may contribute to memory decline. Thus we examined age associated changes in neurons, glial phenotypes and microvasculature in the hippocampus of aged rats with memory decline. Young adult (6 months) and aged (35 months) male rats (Fisher/Norway-Brown) were used. To evaluate memory, four days of acquisition phase of Morris water maze tasks were carried out in both age groups and followed by a probe trial 2 h after the acquisition. The brains were then collected for analysis using immunochemistry. The aged rats showed a delayed latency (p<0.001) and longer swimming path (p<0.001) to locate a hidden platform. They also spent less time in and made delayed and fewer entries into the correct quadrant during the probe trial. Without seen neuronal degeneration, the aged rats with memory impairments have displayed dopamine depletion, profound vascular and microglial degeneration with reduced vascular endothelial growth factor and elevated GFAP expression in the hippocampus. The data indicate the memory decline with age is associated with neuronal dysfunction, possibly due to impaired glial-vascular-neuronal networks, but not neuronal degeneration. Glial and vascular degeneration found in aged rats may represent early event of aging pathology prior to neuronal degeneration.

The evolving landscape of neuroinflammation after neonatal hypoxia-ischemia

Hypoxic-ischemic brain injury remains a leading cause of mortality and morbidity in neonates. The inflammatory response, which is characterized in part by activation of local immune cells, has been implicated as a core component for the progression of damage to the immature brain following hypoxia-ischemia (HI). However, mounting evidence implicates circulating immune cells recruited to the site of damage as orchestrators of neuron-glial interactions and perpetuators of secondary brain injury. This suggests that re-directing our attention from the local inflammatory response toward the molecular mediators believed to link brain-immune cell interactions may be a more effective approach to mitigating the inflammatory sequelae of perinatal HI. In this review, we focus our attention on cyclooxygenase-2, a mediator by which peripheral immune cells may modulate signaling pathways in the brain that lead to a worsened outcome. Additionally, we present an overview of emerging therapeutic modalities that target mechanisms of neuroinflammation in the hypoxic-ischemic neonate.

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.

Hypoxic-ischemic encephalopathy in the term infant

Hypoxia-ischemia in the perinatal period is an important cause of cerebral palsy and associated disabilities in children. There has been significant research progress in hypoxic-ischemic encephalopathy over the last 2 decades, and many new molecular mechanisms have been identified. Despite all these advances, therapeutic interventions are still limited. In this article the authors discuss several molecular pathways involved in hypoxia-ischemia, and potential therapeutic targets.

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.

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.

Prenatal to early postnatal nicotine exposure impairs central chemoreception and modifies breathing pattern in mouse neonates: a probable link to sudden infant death syndrome

Nicotine is a neuroteratogen and is the likely link between maternal cigarette smoking during pregnancy and sudden infant death syndrome (SIDS). Osmotic minipumps were implanted in 5-7 d CF1 pregnant mice to deliver nicotine bitartrate (60 mg Kg(-1) day(-1)) or saline (control) solutions for up to 28 d. Prenatal to early postnatal nicotine exposure did not modify the number of newborns per litter or their postnatal growth; however, nicotine-exposed neonates hypoventilated and had reduced responses to hypercarbia (inhalation of air enriched with 10% CO(2) for 20 min) and hypoxia (inhalation of 100% N(2) for 20 s) at postnatal days 0-3 (P0-P3). In contrast, at postnatal day 8, nicotine-exposed neonates were indistinguishable from controls. Isolated brainstem-spinal cord preparations obtained from P0 to P3 nicotine-exposed neonates showed fictive respiration with respiratory cycles longer and more irregular than those of controls, as indicated by high short- and long-term variability in Poincaré plots. In addition, their responses to acidification were reduced, indicating compromise of central chemoreception. Furthermore, the cholinergic contribution to central chemosensory responses switched from muscarinic receptor to nicotinic receptor-based mechanisms. No significant astrogliosis was detectable in the ventral respiratory group of neurons with glial fibrillary acidic protein immunohistochemistry. These results indicate that nicotine exposure affects the respiratory rhythm pattern generator and causes a decline in central chemoreception during early postnatal life. Consequently, breathing would become highly vulnerable, failing to respond to chemosensory demands. Such impairment could be related to the ventilatory abnormalities observed in SIDS.

Cytokines and perinatal brain damage

Perinatal brain damage has been implicated in the pathogenesis of neurodevelopmental impairments and psychiatric illnesses. This article reviews evidence that infection outside of the brain can damage the brain, and discusses specific cytokines and pathomechanisms that probably mediate the putative effect of remote infection on the developing brain. Events associated with increased circulating inflammatory cytokines, chemokines, and immune cells are described. Finally, studies of genetic variation in susceptibility to cytokine-related brain damage are reviewed.

High-content analysis in neuroscience

High-content analysis (HCA) combines automated microscopy and automated image analysis to quantify complex cellular anatomy and biochemistry objectively, accurately and quickly. High-content assays that are applicable to neuroscience include those that can quantify various aspects of dendritic trees, protein aggregation, transcription factor translocation, neurotransmitter receptor internalization, neuron and synapse number, cell migration, proliferation and apoptosis. The data that are generated by HCA are rich and multiplexed. HCA thus provides a powerful high-throughput tool for neuroscientists.