glycyl-prolyl-glutamic-acid and Brain-Ischemia

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.

Topics: Animals; Brain Ischemia; Drug Discovery; Humans; Insulin-Like Growth Factor I; Nervous System Diseases; Neuropeptides; Neuroprotective Agents; Oligopeptides; Peptide Fragments; Rats

Brain ischemia induces the IGF-1 system in damaged regions, and exogenous administration of IGF-1 after injury is neuroprotective and improves long-term neurological function. The short treatment window can be extended by mild hypothermia, probably due to delayed apoptosis. Nevertheless, the poor central uptake of IGF-1 and its mitogenic potential preclude clinical application. The N-terminal tripeptide of IGF-1 (glycine-proline-glutamate, GPE) is neuroprotective after central administration. Central uptake of GPE is injury dependent, and it is rapidly degraded in the plasma. Intravenous infusion of GPE prevents brain injury and improves long-term functional recovery, with a broad effective dose range and a 3-7 hour therapeutic window. GPE does not interact with IGF receptors. G-2meth-PE, a GPE analogue with improved stability, has a prolonged plasma half life and is neuroprotective after ischemic injury. Neuroprotection by GPE and its analogue may involve modulating inflammation, promoting astrocytosis and inhibiting apoptosis, and the analogue may have a vascular effect. Cyclo-glycyl-proline (cGP) is an endogenous diketopiperazine possibly derived from GPE. Cyclic GP and its analogue cyclo-L-glycyl-L-2-allylproline (cG-2allylP) are neuroprotective after ischemic injury. cG-2allylP crosses the BBB independent of injury and remains detectable several hours after a single administration. Repeated peripheral administration of cG-2allyP improves somatosensory-motor function and long-term histological outcome.

Topics: Animals; Brain Injuries; Brain Ischemia; Disease Models, Animal; Humans; Insulin-Like Growth Factor I; Oligopeptides; Peptide Fragments

Following global cerebral ischaemia due to cardiac arrest (CA), selective neuronal vulnerability and delayed neuronal death with distinct signs of apoptosis could be observed in certain areas of the brain. Growth hormones like the insulin-like growth factor 1 (IGF-1) and the bioactive N-terminal tripeptide of IGF-1, glycine-proline-glutamate (GPE), exhibit strong protective properties in focal ischaemia in vivo and in vitro. To examine these promising effects on neuronal survival and cerebral recovery after experimental cardiopulmonary resuscitation, the most vulnerable hippocampal CA-1 sector was investigated.. After 6 min of CA, 54 male Wistar rats were resuscitated and were randomly assigned to 3 groups (IGF-1, GPE vs. placebo; n=6 per group) and 3 different reperfusion periods. Intracerebroventricular application of IGF-1 (1.25 μgh(-1)), GPE (50 ngh(-1)) and placebo was performed using osmotic minipumps up to day 7 following reperfusion. After 3, 7 and 14 days, coronal brain sections were analysed by counting Nissl-positive (i.e. viable) neurons and TUNEL-positive (i.e., apoptotic) cells. All experiments were performed in a randomised and blinded setting.. In all groups in the hippocampal CA-1 sector typical delayed neurodegeneration from day 3 to day 14 after CA could be found. No significant increase of the number of Nissl-positive neurons after IGF-1-treatment (p=0.18) as well as after GPE-treatment (p=0.14) could be observed. The number of TUNEL-positive cells could not be reduced significantly in the IGF-1 group (p=0.13), whereas GPE treatment revealed significant less TUNEL-positive cells (p=0.02). This was primarily an effect in the early phase (day 3: p=0.02) of reperfusion and was no more detectable 7 days (p=0.69) and 14 days after ROSC (p=0.30).. Despite the well known neuroprotective properties of IGF-1 and GPE in ischaemic induced neuronal degeneration, this model could only reveal a short-term beneficial effect of GPE after experimental cardiac arrest in rats. (Institutional protocol number: 35-9185.81/43/00.).

Topics: Animals; Apoptosis; Brain Ischemia; Cardiopulmonary Resuscitation; Heart Arrest; Hippocampus; In Situ Nick-End Labeling; Injections, Intraventricular; Insulin-Like Growth Factor I; Male; Neurons; Neuroprotective Agents; Oligopeptides; Rats; Rats, Wistar

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.

Topics: Animals; Brain Infarction; Brain Ischemia; Electroencephalography; Male; Neuroprotective Agents; Oligopeptides; Rats; Rats, Sprague-Dawley; Seizures

Insulin-like growth factor-1 has pleiotropic effects in the central nervous system and can act both as a survival and a differentiation factor. Insulin-like growth factor-1 can be proteolytically cleaved into des-N-(1-3)-insulin-like growth factor-1 and a N-terminal tripeptide fragment, glycine-proline-glutamate. Both insulin-like growth factor-1 and des-N-(1-3)-insulin-like growth factor-1 can improve neuronal survival after hypoxic-ischemic brain injury in vivo. The present study investigates the effects of glycine-proline-glutamate on different brain regions and neuronal populations after hypoxic-ischemic injury. Unilateral hypoxic-ischemic injury was induced in adult rats. Glycine-proline-glutamate (3 microg) was administered centrally 2 h after the injury and the extent of brain damage determined five days later. In a separate trial immunohistochemical techniques were used to determine the effects of glycine-proline-glutamate on specific populations of neurons in the striatum after the injury. Compared to the vehicle treatment, glycine-proline-glutamate (n=19) treatment reduced the extent of cortical damage and neuronal loss in the CA1-2 subregions of the hippocampus (P<0.05). In the striatum, there was a trend towards a reduction in neuronal loss after glycine-proline-glutamate treatment (P=0.053) compared to the vehicle (n=21)-treated animals. In a separate study, glycine-proline-glutamate (n=8) treatment prevented the loss of choline acetyltransferase (P<0.05), glutamate acid decarboxylase (P<0.05) and somatostatin (P<0.05) containing neurons in the ipsilateral striatum following hypoxic-ischemic brain injury and also increased the numbers of neuronal nitric oxide synthase (P<0.05) containing neurons in the contralateral side. These studies suggest that in addition to neuroprotective effects, glycine-proline-glutamate can influence neuronal activity after hypoxic-ischemic injury.

Topics: Animals; Brain Damage, Chronic; Brain Ischemia; Choline O-Acetyltransferase; Corpus Striatum; Drug Evaluation, Preclinical; Glutamate Decarboxylase; Hippocampus; Hypoxia, Brain; Insulin-Like Growth Factor I; Male; Nerve Tissue Proteins; Neurons; Oligopeptides; Rats; Somatostatin