The window of opportunity for neuronal rescue with insulin-like growth factor-1 after hypoxia-ischemia in rats is critically modulated by cerebral temperature during recovery

Traditional Pediatric Massage Enhanced Hippocampal GR, BDNF and IGF-1 Expressions and Exerted an Anti-depressant Effect in an Adolescent Rat Model of CUMS-induced Depression

This study aimed to investigate the anti-depressant effect of traditional pediatric massage (TPM) in adolescent rats and its possible mechanism. The adolescent depression model in rats was established by using chronic unpredictable mild stress (CUMS). All rats were randomly divided into five groups (seven per group), including the groups of control (CON), CUMS, CUMS with TPM, CUMS with back stroking massage (BSM) and CUMS with fluoxetine (FLX). The tests of sucrose preference, Morris water maze and elevated plus maze were used to evaluate depression-related behaviors. Plasma corticosterone (CORT) level was measured by ELISA. The gene and protein expressions of glucocorticoid receptor (GR), brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1) were measured by RT-qPCR and IHC respectively. The results showed that CUMS induced depression-related behaviors in the adolescent rats, along with decreased weight gain and reduced hippocampal expressions of GR, IGF-1 and BDNF. TPM could effectively prevent depression-related behaviors in CUMS-exposed adolescent rats, manifested as increasing weight gain, sucrose consumption, ratio of open-arm entry, times of crossing the specific quadrant and shortening escape latency. TPM also decreased CORT level in plasma, together with enhancing expressions of GR, IGF-1 and BDNF in the hippocampus. These results may support the clinical application of TPM to prevent and treat adolescent depression.

Update on mechanisms of the pathophysiology of neonatal encephalopathy

Therapeutic hypothermia is now well established to significantly improve survival without disability after neonatal encephalopathy (NE). To further improve outcomes, we need to better understand the mechanisms of brain injury. The central finding, which offers the potential for neuroprotective and neurorestorative interventions, is that brain damage after perinatal hypoxia-ischemia evolves slowly over time. Although brain cells may die during profound hypoxia-ischemia, even after surprisingly severe insults many cells show transient recovery of oxidative metabolism during a "latent" phase characterized by actively suppressed neural metabolism and activity. Critically, after moderate to severe hypoxia-ischemia, this transient recovery is followed after ~6 h by a phase of secondary deterioration, with delayed seizures, failure of mitochondrial function, cytotoxic edema, and cell death over ~72 h. This is followed by a tertiary phase of remodeling and recovery. This review discusses the mechanisms of injury that occur during the primary, latent, secondary and tertiary phases of injury and potential treatments that target one or more of these phases. By analogy with therapeutic hypothermia, treatment as early as possible in the latent phase is likely to have the greatest potential to prevent injury ("neuroprotection"). In the secondary phase of injury, anticonvulsants can attenuate seizures, but show limited neuroprotection. Encouragingly, there is now increasing preclinical evidence that late, neurorestorative interventions have potential to improve long-term outcomes.

Recombinant erythropoietin does not augment hypothermic white matter protection after global cerebral ischaemia in near-term fetal sheep

Therapeutic hypothermia for hypoxic-ischaemic encephalopathy provides partial white matter protection. Recombinant erythropoietin reduces demyelination after hypoxia-ischaemia, but it is unclear whether adjunct erythropoietin treatment can further improve outcomes after therapeutic hypothermia. Term-equivalent fetal sheep received sham-ischaemia (n = 9) or cerebral ischaemia for 30 min (ischaemia-vehicle, n = 8), followed by intravenous infusion of recombinant erythropoietin (ischaemia-Epo, n = 8; 5000 IU/kg bolus dose, then 833.3 IU/kg/h), cerebral hypothermia (ischaemia-hypothermia, n = 8), or recombinant erythropoietin plus hypothermia (ischaemia-Epo-hypothermia, n = 8), from 3 to 72 h post-ischaemia. Foetal brains were harvested at 7 days after cerebral ischaemia. Ischaemia was associated with marked loss of total Olig2-positive oligodendrocytes with reduced density of myelin and linearity of the white matter tracts (P < 0.01), and microglial induction and increased caspase-3-positive apoptosis. Cerebral hypothermia improved the total number of oligodendrocytes and restored myelin basic protein (P < 0.01), whereas recombinant erythropoietin partially improved myelin basic protein density and tract linearity. Both interventions suppressed microgliosis and caspase-3 (P < 0.05). Co-treatment improved 2′,3′-cyclic-nucleotide 3′-phosphodiesterase-myelin density compared to hypothermia, but had no other additive effect. These findings suggest that although hypothermia and recombinant erythropoietin independently protect white matter after severe hypoxia-ischaemia, they have partially overlapping anti-inflammatory and anti-apoptotic effects, with little additive benefit of combination therapy.

Role of Regular Physical Activity in Neuroprotection against Acute Ischemia

One of the major obstacles that prevents an effective therapeutic intervention against ischemic stroke is the lack of neuroprotective agents able to reduce neuronal damage; this results in frequent evolution towards a long-term disability with limited alternatives available to aid in recovery. Nevertheless, various treatment options have shown clinical efficacy. Neurotrophins such as brain-derived neurotrophic factor (BDNF), widely produced throughout the brain, but also in distant tissues such as the muscle, have demonstrated regenerative properties with the potential to restore damaged neural tissue. Neurotrophins play a significant role in both protection and recovery of function following neurological diseases such as ischemic stroke or traumatic brain injury. Unfortunately, the efficacy of exogenous administration of these neurotrophins is limited by rapid degradation with subsequent poor half-life and a lack of blood-brain-barrier permeability. Regular exercise seems to be a therapeutic approach able to induce the activation of several pathways related to the neurotrophins release. Exercise, furthermore, reduces the infarct volume in the ischemic brain and ameliorates motor function in animal models increasing astrocyte proliferation, inducing angiogenesis and reducing neuronal apoptosis and oxidative stress. One of the most critical issues is to identify the relationship between neurotrophins and myokines, newly discovered skeletal muscle-derived factors released during and after exercise able to exert several biological functions. Various myokines (e.g., Insulin-Like Growth Factor 1, Irisin) have recently shown their ability to protects against neuronal injury in cerebral ischemia models, suggesting that these substances may influence the degree of neuronal damage in part via inhibiting inflammatory signaling pathways. The aim of this narrative review is to examine the main experimental data available to date on the neuroprotective and anti-ischemic role of regular exercise, analyzing also the possible role played by neurotrophins and myokines.

Plasma cyclic glycine proline/IGF-1 ratio predicts clinical outcome and recovery in stroke patients

Objective

Many stroke patients make a partial recovery in function during the first 3 months, partially through promoting insulin‐like growth factor‐1 (IGF‐1) function. A prognostic biomarker that associates with IGF‐1 function may predict clinical outcome and recovery of stroke. This study evaluated plasma concentrations of IGF‐1, IGF binding protein (IGFBP)‐3 and cyclic‐glycine‐proline (cGP) and their associations with clinical outcome in stroke patients.

Methods

Thirty‐four patients were recruited within 3 days of stroke. Clinical assessments included the National Institutes of Health Stroke Scale (NIHSS) within 3 days (baseline), and at days 7 and 90; the modified Rankin Scale (mRS) and Fugl‐Meyer Upper‐Limb Assessment Scale (FM‐UL) at days 7 and 90. Plasma samples were collected from the patients at the baseline, days 7 and 90. Fifty age‐matched control participants with no history of stroke were also recruited and provided plasma samples. IGF‐1, IGFBP‐3, and cGP concentrations were analyzed using ELISA or HPLC‐MS.

Results

Baseline concentrations of IGFBP‐3, cGP, and cGP/IGF‐1 ratio were lower in stroke patients than the control group. The neurological scores of stroke patients were improved and plasma cGP and cGP/IGF‐1 ratio increased over time. Baseline cGP/IGF‐1 ratio was correlated with the NIHSS scores at day 90 and the changes in NIHSS scores from the baseline to 90 days.

Interpretation

Low cGP concentrations and cGP/IGF‐1 ratio in stroke patients suggest an impaired IGF‐1 function. The cGP/IGF‐1 ratio at admission maybe further developed as a prognostic biomarker for stroke recovery.

The Neuroprotective Effects of Exercise: Maintaining a Healthy Brain Throughout Aging

Physical activity plays an essential role in maintaining a healthy body, yet it also provides unique benefits for the vascular and cellular systems that sustain a healthy brain. While the benefit of exercise has been observed in humans of all ages, the availability of preclinical models has permitted systematic investigations into the mechanisms by which exercise supports and protects the brain. Over the past twenty-five years, rodent models have shown that increased physical activity elevates neurotrophic factors in the hippocampal and cortical areas, facilitating neurotransmission throughout the brain. Increased physical activity (such as by the voluntary use of a running wheel or regular, timed sessions on a treadmill) also promotes proliferation, maturation and survival of cells in the dentate gyrus, contributing to the process of adult hippocampal neurogenesis. In this way, rodent studies have tremendous value as they demonstrate that an 'active lifestyle' has the capacity to ameliorate a number of age-related changes in the brain, including the decline in adult neurogenesis. Moreover, these studies have shown that greater physical activity may protect the brain health into advanced age through a number of complimentary mechanisms: in addition to upregulating factors in pro-survival neurotrophic pathways and enhancing synaptic plasticity, increased physical activity promotes brain health by supporting the cerebrovasculature, sustaining the integrity of the blood-brain barrier, increasing glymphatic clearance and proteolytic degradation of amyloid beta species, and regulating microglia activation. Collectively, preclinical studies demonstrate that exercise initiates diverse and powerful neuroprotective pathways that may converge to promote continued brain health into old age. This review will draw on both seminal and current literature that highlights mechanisms by which exercise supports the functioning of the brain, and aids in its protection.

Hypothermia broadens the therapeutic time window of mesenchymal stem cell transplantation for severe neonatal hypoxic ischemic encephalopathy

Recently, we have demonstrated that concurrent hypothermia and mesenchymal stem cells (MSCs) transplantation synergistically improved severe neonatal hypoxic ischemic encephalopathy (HIE). The current study was designed to determine whether hypothermia could extend the therapeutic time window of MSC transplantation for severe neonatal HIE. To induce HIE, newborn rat pups were exposed to 8% oxygen for 2 h following unilateral carotid artery ligation on postnatal day (P) 7. After approving severe HIE involving >50% of the ipsilateral hemisphere volume, hypothermia (32 °C) for 2 days was started. MSCs were transplanted 2 days after HIE modeling. Follow-up brain MRI, sensorimotor function tests, assessment of inflammatory cytokines in the cerebrospinal fluid (CSF), and histological evaluation of peri-infarction area were performed. HIE induced progressively increasing brain infarction area over time, increased cell death, reactive gliosis and brain inflammation, and impaired sensorimotor function. All these damages observed in severe HIE showed better, robust improvement with a combination treatment of hypothermia and delayed MSC transplantation than with either stand-alone therapy. Hypothermia itself did not significantly reduce brain injury, but broadened the therapeutic time window of MSC transplantation for severe newborn HIE.

Tanshinone I alleviates motor and cognitive impairments via suppressing oxidative stress in the neonatal rats after hypoxic-ischemic brain damage

Neonatal hypoxia-ischemia is one of the main reasons that cause neuronal damage and neonatal death. Several studies have shown that tanshinone I (TsI), one of the major ingredients of Danshen, exerts potential neuroprotective effect in adult mice exposed to permanent left cerebral ischemia. However, it is unclear whether administration of TsI has neuroprotective effect on neonatal hypoxic-ischemic brain damage (HIBD), and if so, the potential mechanisms also remain unclear. Here, we reported that treatment with TsI (5 mg/kg, i.p.) significantly alleviated the deficits of myodynamia and motor functions as well as the spatial learning and memory in the rat model of HIBD. These behavioral changes were accompanied by a significant decrease in the number of neuronal loss in the CA1 area of hippocampus. Moreover, ELISA assay showed that TsI significantly increased the production of antioxidants including total antioxidant capacity (T-AOC), glutathione (GSH), total superoxide dismutase (T-SOD) and catalase (CAT), and reduced the production of pro-oxidants including hydrogen peroxide (H₂O₂), total nitric oxide synthase (T-NOS) and inducible nitric oxide synthase (iNOS). Taken together, these results indicate that TsI presents potential neuroprotection against neuronal damage via exerting significantly antioxidative activity and against pro-oxidant challenge, thereby ameliorating hypoxia-ischemia-induced motor and cognitive impairments in the neonatal rats, suggesting that TsI may be a potential therapeutic agent against HIBD.

Daucosterol protects neurons against oxygen-glucose deprivation/reperfusion-mediated injury by activating IGF1 signaling pathway

We previously reported that daucosterol (a sterolin) up-regulates the expression of insulin-like growth factor I (IGF1)(1) protein in neural stem cells. In this study, we investigated the effects of daucosterol on the survival of cultured cortical neurons after neurons were subjected to oxygen and glucose deprivation and simulated reperfusion (OGD/R)(2), and determined the corresponding molecular mechanism. The results showed that post-treatment of daucosterol significantly reduced neuronal loss, as well as apoptotic rate and caspase-3 activity, displaying the neuroprotective activity. We also found that daucosterol increased the expression level of IGF1 protein, diminished the down-regulation of p-AKT(3) and p-GSK-3β(4), thus activating the AKT(5) signal pathway. Additionally, it diminished the down-regulation of the anti-apoptotic proteins Mcl-1(6) and Bcl-2(7), and decreased the expression level of the pro-apoptotic protein Bax(8), thus raising the ratio of Bcl-2/Bax. The neuroprotective effect of daucosterol was inhibited in the presence of picropodophyllin (PPP)(9), the inhibitor of insulin-like growth factor I receptors (IGF1R)(10). Our study provided information about daucosterol as an efficient and inexpensive neuroprotectants, to which the IGF1-like activity of daucosterol contributes. Daucosterol could be potentially developed as a medicine for ischemic stroke treatment.

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.

Endothelin-1-induced focal cerebral ischemia in the growth hormone/IGF-1 deficient Lewis Dwarf rat

Aging is a major risk factor for cerebrovascular disease. Growth hormone (GH) and its anabolic mediator, insulin-like growth factor (IGF)-1, decrease with advancing age and this decline has been shown to promote vascular dysfunction. In addition, lower GH/IGF-1 levels are associated with higher stroke mortality in humans. These results suggest that decreased GH/IGF-1 level is an important factor in increased risk of cerebrovascular diseases. This study was designed to assess whether GH/IGF-1-deficiency influences the outcome of cerebral ischemia. We found that endothelin-1-induced middle cerebral artery occlusion resulted in a modest but nonsignificant decrease in cerebral infarct size in GH/IGF-1 deficient dw/dw rats compared with control heterozygous littermates and dw/dw rats with early-life GH treatment. Expression of endothelin receptors and endothelin-1-induced constriction of the middle cerebral arteries were similar in the three experimental groups. Interestingly, dw/dw rats exhibited reduced brain edema and less astrocytic infiltration compared with their heterozygous littermates and this effect was reversed by GH-treatment. Because reactive astrocytes are critical for the regulation of poststroke inflammatory processes, maintenance of the blood-brain barrier and neural repair, further studies are warranted to determine the long-term functional consequences of decreased astrocytic activation in GH/IGF-1 deficient animals after cerebral ischemia.

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.

Hypothermia and erythropoietin for neuroprotection after neonatal brain damage

BACKGROUND

Both hypothermia and erythropoietin (EPO) are reported to have neuroprotective effects after perinatal hypoxia-ischemia (HI). We investigated a possible additive effect of the use of a combination of hypothermia-EPO in a rat model of neonatal HI.

METHODS

At postnatal day 7, rats were subjected to HI and then randomized to 3 h of hypothermia, EPO, or both. Sensorimotor function was assessed by the cylinder-rearing test (CRT) at 2 and 5 wk after HI. Brain lesion volume and white matter loss were determined by hematoxylin-eosin and luxol fast blue staining, respectively.

RESULTS

Multivariable analysis using general linear modeling showed that hypothermia, EPO, and the interaction hypothermia × gender were determinants of sensorimotor function, both at 2 and 5 wk after HI. Neuroprotective effects of hypothermia at 5 wk were more pronounced in females, showing 52% improvement in the CRT. Maximal improvement in males was 26% after combined treatment with hypothermia and EPO. Histological outcome was improved by hypothermia only with no additional effect of EPO or gender.

CONCLUSION

Hypothermia after HI improved sensorimotor function in females more than in males. There was a borderline additive effect of EPO when combined with hypothermia. Histology of brain lesion volume and white matter damage was improved only by hypothermia.

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.

Polymorphisms of IGFI contribute to the development of ischemic stroke

Insulin-like growth factor 1 (IFG1) is neuroprotective in animal models of focal brain ischemia and correlates with ischemic stroke (IS) outcome in the elderly. In this study, we investigated whether single nucleotide polymorphisms (SNPs) of the IFG1 gene are associated with the development and clinical features of IS in a Korean population. A total of 119 patients with IS and 289 control subjects were recruited. Stroke patients were classified into subgroups according to the scores of the National Institutes of Health Stroke Survey (NIHSS; <6 and ≥6) and the Modified Barthel Index (MBI; <60 and ≥60). Among the SNPs of the IFG1 gene, five SNPs were selected and analyzed by direct sequencing: rs2162679 (intron), rs2195239 (intron), rs978458 (intron), rs1520220 (intron) and rs6214 (3' untranslated region; 3'UTR). Multiple logistic regression models were conducted to analyze genetic data. SNPStats, SNPAnalyzer Pro and Helixtree programs were used to calculate odds ratios (ORs), 95% confidence intervals (CIs) and p-values. Two SNPs, rs2162679 and rs6214, were associated with the development of IS. After Bonferroni correction (p(c)), the A and G alleles of rs2162679 and rs6214 had significant differences between patients with IS and the controls [rs2162679, OR (95% CI) = 1.64 (1.17-2.31), p=0.004, p(c)=0.02; rs6214, OR (95% CI) = 1.52 (1.12-2.07), p=0.007, p(c)=0.035], respectively. However, the five selected SNPs were not related to the NIHSS and MBI scores. These results suggest that IGF1 may be associated with the development of IS.

Intranasal administration of insulin-like growth factor-1 protects against lipopolysaccharide-induced injury in the developing rat brain

Our previous studies show that insulin-like growth factor-1 (IGF-1) can either protect against or increase lipopolysaccharide (LPS)-induced damage in the developing brain, depending on the dose, when it is co-administered with LPS through intracerebral injection. To further explore effects of IGF-1 on central inflammation associated brain injury, IGF-1 was administered through intranasal infusion in the current study. Postnatal day 5 (P5) rats were exposed to LPS at a dose of 1 μg/g body weight or sterile saline through intracerebral injection. Recombinant human insulin-like growth factor-1 (rhIGF-1) at a dose of 50 μg/pup or vehicle was administered intranasally 1 or 2 h after the LPS injection. Neonatal LPS exposure resulted in oligodendrocyte (OL) and white matter injury in the P6 or P21 rat brain. The damages include dilatation of lateral ventricles, pyknotic cell death, loss of OL progenitor cells and mature OLs in the cingulum area, and impairment of myelination at the corpus callosum area. Neurological dysfunctions were observed in juvenile rats with neonatal LPS exposure. Intranasal IGF-1 treatment at either 1 or 2 h after LPS exposure significantly attenuated LPS-induced brain injury and improved some behavioral deficits. Intranasal IGF-1 treatment also reduced infiltration of polymorphonuclear (PMN) leukocytes and activation of microglia in the rat brain 24 h after LPS exposure, but it did not prevent the elevation in concentrations of interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNFα) in the LPS-exposed rat brain during the first 24 h. This is an indication that direct anti-inflammation might not be the primary mechanism for the protection of IGF-1, and other mechanisms, such as anti-apoptotic effects, are likely involved in its protective effects.

Pharmacological neuroprotection after perinatal hypoxic-ischemic brain injury

Perinatal hypoxia-ischemia (HI) is an important cause of neonatal brain injury. Recent progress in the search for neuroprotective compounds has provided us with several promising drugs to reduce perinatal HI-induced brain injury. In the early stage (first 6 hours after birth) therapies are concentrated on prevention of the production of reactive oxygen species or free radicals (xanthine-oxidase-, nitric oxide synthase-, and prostaglandin inhibition), anti-inflammatory effects (erythropoietin, melatonin, Xenon) and anti-apoptotic interventions (nuclear factor kappa B- and c-jun N-terminal kinase inhibition); in a later stage stimulation of neurotrophic properties in the neonatal brain (erythropoietin, growth factors) can be targeted to promote neuronal and oligodendrocyte regeneration. Combination of pharmacological means of treatment with moderate hypothermia, which is accepted now as a meaningful therapy, is probably the next step in clinical treatment to fight post-asphyxial brain damage. Further studies should be directed at a more rational use of therapies by determining the optimal time and dose to inhibit the different potentially destructive molecular pathways or to enhance endogenous repair while at the same time avoiding adverse effects of the drugs used.

Whole body hypothermia broadens the therapeutic window of intranasally administered IGF-1 in a neonatal rat model of cerebral hypoxia-ischemia

To investigate whether whole body hypothermia after neonatal cerebral hypoxia-ischemia (HI) could broaden the therapeutic window of intranasal treatment of IGF-1 (iN-IGF-1), postnatal day 7 rat pups were subjected to right common carotid artery ligation, followed by 8% oxygen inhalation for 2h. After HI, one group of pups were returned to their dams and kept at room temperature (24.5±0.2°C). A second group of pups were subjected to whole body hypothermia in a cool environment (21.5±0.3°C) for 2 or 4h before being returned to their dams. Two doses of 50 μg recombinant human IGF-1 were administered intranasally at a 1h interval starting at 0, 2 or 4h after hypothermia. Hypothermia decreased the rectal temperature of pups by 4.5°C as compared to those kept at room temperature. While hypothermia or iN-IGF-1 administered 2h after HI alone did not provide neuroprotection, the combined treatment of hypothermia with iN-IGF-1 significantly protected the neonatal rat brain from HI injury. Hypothermia treatment extended the therapeutic window of IGF-1 to 6h after HI. The extended IGF-1 therapeutic window by hypothermia was associated with decreases in infiltration of polymorphonuclear leukocytes and activation of microglia/macrophages and with attenuation of NF-κB activation in the ipsilateral hemisphere following HI.

Filling the evidence gap: how can we improve the outcome of neonatal encephalopathy in the next 10 years?

Neonatal encephalopathy associated with perinatal hypoxia-ischaemia is one of the most common causes of death and permanent disability worldwide. However, of a wide range of "experimentally neuroprotective treatments" invented so far, only therapeutic hypothermia has been promoted into a standard clinical practice. Such a wide gap in the efficacy of neuroprotective treatments between the experimental setting and clinical practice may be attributed to the strategic flaw in translating basic knowledge into clinical care. When previous clinical studies are carefully reviewed, one may notice that few therapeutic options were chosen based on their track records in experimental studies; protective effects of some drugs had been assumed only based on their pharmacokinetics in adult species; several therapies were chosen merely because clinicians were familiar to these treatments for other purpose; some other therapies were imported too preliminarily from laboratory to clinical practice, potentially ignoring the difference in physiological and pathological backgrounds between rodent models and human patients. When further clinical trials are planned, it is important to ask whether (i) the treatment is supported by pharmacokinetics specific to immature brain, and (ii) the neuroprotective effect of the treatment has consistently been demonstrated using clinically relevant models and study designs. The use of translational large animal models allows the practical simulation and fine-tuning of clinical protocols, which may further assist successful translation of basic knowledge. In addition to the effort to develop alternative therapeutic options, it is important to maximise the effect of the current only neuroprotective option, or therapeutic hypothermia. Independent variables which influence the efficacy of hypothermia have to be elucidated to improve its therapeutic protocol, and to increase the number of patients who will benefit from this treatment.

Insulinlike growth factor-1, insulinlike growth factor binding protein-1, and cognitive function in older men and women

OBJECTIVES

To assess the association between insulinlike growth factor (IGF)-1 and IGF binding protein (IGFBP)-1 with three cognitive function tests in a healthy elderly population.

DESIGN

Cross-sectional analyses from the Rancho Bernardo Cohort Study.

SETTING

Southern California community of Rancho Bernardo.

PARTICIPANTS

Men (n=636) and women (n=899) from the Rancho Bernardo study (median age 74) were assessed between 1988 and 1992 for cognitive function using the Mini-Mental State Examination (MMSE), Verbal Fluency (VF) test, and Trail-Making Test Part B (Trails B). Blood samples were obtained at the same time for IGF-1 and IGFBP-1 levels. The association between biomarkers and cognitive function tests was assessed by dichotomizing tests at the clinically relevant cutoff using logistic regression and according to tertiles and continuous IGF-1 and IGFBP-1 levels using multivariate linear regression analyses.

RESULTS

The mean MMSE, VF and Trails B scores indicated better cognitive function with higher IGF-1 tertile. Multivariate analyses showed that VF and MMSE were each significantly associated with IGF-1 in a dose-response manner for men (P for trend=.001), but no cognitive function tests were related to IGF-1 in women. For men, the highest IGFBP-1 tertile was inversely and significantly different from the lowest tertile for the MMSE test only (P for trend=.02).

CONCLUSION

IGF-1 was independently and positively related to MMSE and VF in men, and IGFBP-1 was inversely associated with MMSE in men. Sex differences in the association should be further investigated.

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.

Intranasal administration of IGF-1 attenuates hypoxic-ischemic brain injury in neonatal rats

To determine whether intranasal administration (iN) of recombinant human insulin-like growth factor-1 (rhIGF-1) provides neuroprotection to the neonatal rat brain following cerebral hypoxia-ischemia (HI), two doses of rhIGF-1 (50 microg at a 1 h interval) were infused into the right naris of postnatal day 7 (P7) rat pups with or without a prior HI insult (right common carotid artery ligation, followed by an exposure to 8% oxygen for 2 h). Our result showed that rhIGF-1 administered via iN was successfully delivered into the brain 30 min after the second dose. In the following studies rhIGF-1 was administered to P7 rat pups at 0, 1 or 2 h after HI at the dose described above. Pups in the control group received cerebral HI and vehicle treatment. Pups that underwent sham operation and vehicle treatment served as the sham group. Brain pathological changes were evaluated 2 and 15 days after HI. Our results showed that rhIGF-1 treatment up to 1 h after cerebral HI effectively reduced brain injury as compared to that in the vehicle-treated rats. Moreover, rhIGF-1 treatment improved neurobehavioral performance (tested on P5-P21) in juvenile rats subjected to HI. Our results further showed that rhIGF-1 inhibited apoptotic cell death, possibly through activating the Akt signal transduction pathway. rhIGF-1 enhanced proliferation of neuronal and oligodendroglial progenitors after cerebral HI as well. These data suggest that iN administration of IGF-1 has the potential to be used for clinical treatment.

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.

Insulin-like growth factor I: a potential neuroprotective compound for the treatment of acute ischemic stroke?

BACKGROUND AND PURPOSE

Insulin-like growth factor I (IGF-I) exerts neuroprotective effects in both white and gray matter under different detrimental conditions. The purpose of this review is to collect the evidence whether IGF-I is a candidate neuroprotective drug in patients with acute ischemic stroke.

RESULTS

IGF-I was found to be neuroprotective in animal models of focal brain ischemia when given >or=2 hours after the insult. Different routes of administration (eg, cerebroventricular, intravenous, and intranasal) were found to be effective. In addition to inhibition of apoptosis and reduction of the infarct volume, IGF-I also improved neurological outcome. Furthermore, there are strong indications that IGF-I can also stimulate the regeneration of neural tissue.

CONCLUSIONS

Additional studies are required to reveal the neuroprotective mechanisms of IGF-I in detail and to elucidate the role of IGF-binding proteins. Preclinical studies in relevant animal models for studying stroke (ie, hypertensive, diabetic, or aged animals) should be done testing different doses and routes of IGF-I administration and different combinations of IGF-I and IGF-binding proteins.

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

Glycine 2-methyl proline glutamate (G-2mPE) is a proline-modified analogue to the naturally existing N-terminal tripeptide glycine-proline-glutamate that is a cleaved product from insulin-like growth factor-1. G-2mPE is designed to be more enzymatically resistant than glycine-proline-glutamate and to increase its bioavailability. The current study has investigated the protective effects of G-2mPE following hypoxic-ischemic brain injury in the neonatal brain. On postnatal day 7, Wistar rats were exposed to hypoxia-ischemia (HI). HI was induced by unilateral ligation of the left carotid artery followed by hypoxia (7.7% O2, 36 degrees C) for 60 min. The drug treatment started 2 h after the insult, and the pups were given either 1.2 mg/kg (bolus), 1.2 mg/ml once a day for 7 days, or vehicle. The degree of brain damage was determined histochemically by thionin/acid fuchsin staining. G-2mPE's anti-inflammatory properties were investigated by IL-1beta, IL-6, and IL-18 ELISA, and effects on apoptosis by caspase 3 activity. Vascularization was determined immunohistochemically by the total length of isolectin-positive blood vessels. Effect on astrocytosis was also determined in the hippocampus. Animals treated with multiple doses of G-2mPE demonstrated reduced overall brain injury 7 days after HI, particularly in the hippocampus and thalamus compared to vehicle-treated rats. The expression of IL-6 was decreased in G-2mPE-treated animals compared to vehicle-treated pups, and both the capillary length and astrogliosis were increased in the drug-treated animals. There was no effect on caspase 3 activity. This study indicates that peripheral administration of G-2mPE, starting 2 h after a hypoxic-ischemic insult, reduces the degree of brain injury in the immature rat brain. The normalization of IL-6 levels and the promotion of both neovascularization and reactive astrocytosis may be potential mechanisms that underlie its protective effects.

Peripheral administration of a novel diketopiperazine, NNZ 2591, prevents brain injury and improves somatosensory-motor function following hypoxia-ischemia in adult rats

The current study describes the neuroprotective effects of an endogenous diketopiperazine, cyclo-glycyl-proline (cyclic GP), in rats with hypoxic-ischemic brain injury and the pre-clinical development of an analogue, cyclo-L-glycyl-L-2-allylproline (NNZ 2591), modified for improved bioavailability. The compounds were given either intracerebroventricularly or subcutaneously 2h after hypoxia-ischemia. Histology, immunohistochemistry and behavior were used to evaluate treatment effects. The central uptake of NNZ 2591 was also examined in normal and hypoxic-ischemic injured rats by HPLC-mass spectrometry. Central administration of cyclic GP or NNZ 2591 reduced the extent of brain damage in the lateral cortex, the hippocampus and the striatum (p<0.001), with NNZ 2591 being more potent. NNZ 2591 was stable in the plasma and crossed the blood-brain barrier independent of hypoxic-ischemic injury. The level of NNZ 2591 in the CSF was maintained for 2 h after a single subcutaneous dose, and modest neuroprotection was seen after a bolus subcutaneous administration (overall p<0.001). Treatment with NNZ 2591 for 5 d subcutaneously improved somatosensory-motor function (p<0.05) and long-term histological outcome (overall p<0.0001). NNZ 2591 treatment not only reduced both caspase-3 mediated apoptosis and microglial activation but also enhanced astrocytic reactivity, which may mediate its protective effect. The pharmacokinetic profile and potent long-term protective effects of NNZ 2591 suggests its utility for the treatment of ischemic brain injury and other neurological conditions requiring chronic intervention.

"Therapeutic time window" duration decreases with increasing severity of cerebral hypoxia-ischaemia under normothermia and delayed hypothermia in newborn piglets

OBJECTIVE

For optimal neuroprotection following transient perinatal hypoxia-ischaemia (HI), therapy should start before overt secondary energy failure and its irreversible neurotoxic cascade. Hypothermia is a promising neuroprotective intervention that also prolongs the therapeutic time window ("latent-phase"; the period between re-establishment of apparently normal cerebral metabolism after HI, and the start of secondary energy failure). The influences of HI severity on latent-phase duration and regional neuroprotection are unclear. Under normothermia and delayed whole-body cooling to 35 and 33 degrees C we aimed to assess relationships between HI severity and: (i) latent-phase duration; (ii) secondary-energy-failure severity; and (iii) neuronal injury 48 h following HI.

METHODS

Newborn piglets were randomized to: (i) HI-normothermia (n=12), (ii) HI-35 degrees C (n=7), and (iii) HI-33 degrees C (n=10). HI-35 degrees C and HI-33 degrees C piglets were cooled between 2 and 26 h after HI. Insult and secondary-energy-failure severity and latent-phase duration were evaluated using phosphorus magnetic resonance spectroscopy and compared with neuronal death in cortical-grey and deep-grey matter.

RESULTS

More severe HI was associated with shorter latent-phase (p=0.002), worse secondary energy failure (p=0.023) and more cortical-grey-matter neuronal death (p=0.016).

CONCLUSIONS

Latent-phase duration is inversely related to insult severity; latent-phase brevity may explain the apparently less effective neuroprotection following severe cerebral HI.

Insulin-like growth factor-1 is an endogenous mediator of focal ischemia-induced neural progenitor proliferation

The adult mammalian brain contains resident neural progenitors in the subgranular zone of the dentate gyrus (DG) and the subventricular zone (SVZ) of the lateral ventricles. The proliferation of neural progenitors increases after focal cerebral ischemia in both of these regions, but the mechanisms that promote ischemia-induced neural progenitor proliferation are not yet understood. We hypothesize that diffusible factors from the ischemic area play a role in this process as the DG is remote from the area of infarction. In this study, we observed that the peak of neural progenitor proliferation in the ipsilateral DG was between day 2 and day 4 of reperfusion after transient middle cerebral artery occlusion in adult spontaneously hypertensive rats. GeneChip and real-time PCR analysis showed a three- to 102-fold increase in the expression of 15 diffusible, mitogenic factors in the ischemic cortex at 3 days of reperfusion. Of these, insulin-like growth factor-1 (IGF-1) showed increased protein expression in the activated astrocytes in the ischemic penumbra. In addition, the progenitors in both the SVZ and DG showed IGF-1 receptor expression. Inhibiting IGF-1 activity by introcerebroventricular infusion of IGF-1 antibody significantly prevented the ischemia-induced neural progenitor proliferation. These results indicate that IGF-1 formed in the ischemic penumbra might be one of the diffusible factors that mediate post-ischemic neural progenitor proliferation.

Alteration of Insulin-like Growth Factor-1 Expression After Middle Cerebral Artery Occlusion in Monkeys and Rats: Complementary DNA Microarray, Immunohistochemistry, and In Situ Hybridization Studies

It is well established that insulin-like growth factor (IGF)-1 has potent neuroprotective effects on cerebral ischemia in the rat and sheep model. In order to investigate whether it has neuroprotective effects on brain insult in human stroke, as one part of serial subhuman primate stroke research, the present study was designed to observe whether IGF-1 messenger RNA (mRNA) and protein is expressed in middle cerebral artery occlusion in monkeys and rats. A total of 12,800 dots complementary DNA microarray, in situ hybridization, and immunohistochemistry were used. Complementary DNA microarray showed that among the nearly 8000 genes, approximately 8% of the total number of genes examined was affected after ischemia/reperfusion injury especially in the growth factor family including IGF-1 in the ischemic region. The decreased IGF-1 mRNA and protein expression was found in the insular striatum, but there was an increased mRNA expression and unchanged protein expression in the hippocampus 24 hours after ischemia. The results suggested that IGF-1 might contribute to the neuroprotective pathway in a pattern different from that of rats, and it might play a role in protection of ischemic injured neuronal cells after monkey focal cerebral ischemia.

Hypothermic neuroprotection

The possibility that hypothermia during or after resuscitation from asphyxia at birth, or cardiac arrest in adults, might reduce evolving damage has tantalized clinicians for a very long time. It is now known that severe hypoxia-ischemia may not necessarily cause immediate cell death, but can precipitate a complex biochemical cascade leading to the delayed neuronal loss. Clinically and experimentally, the key phases of injury include a latent phase after reperfusion, with initial recovery of cerebral energy metabolism but EEG suppression, followed by a secondary phase characterized by accumulation of cytotoxins, seizures, cytotoxic edema, and failure of cerebral oxidative metabolism starting 6 to 15 h post insult. Although many of the secondary processes can be injurious, they appear to be primarily epiphenomena of the 'execution' phase of cell death. Studies designed around this conceptual framework have shown that moderate cerebral hypothermia initiated as early as possible before the onset of secondary deterioration, and continued for a sufficient duration in relation to the severity of the cerebral injury, has been associated with potent, long-lasting neuroprotection in both adult and perinatal species. Two large controlled trials, one of head cooling with mild hypothermia, and one of moderate whole body cooling have demonstrated that post resuscitation cooling is generally safe in intensive care, and reduces death or disability at 18 months of age after neonatal encephalopathy. These studies, however, show that only a subset of babies seemed to benefit. The challenge for the future is to find ways of improving the effectiveness of treatment.

Delayed whole-body cooling to 33 or 35 degrees C and the development of impaired energy generation consequential to transient cerebral hypoxia-ischemia in the newborn piglet

OBJECTIVES

Fundamental questions remain about the precise temperature providing optimal neuroprotection after perinatal hypoxia-ischemia (HI). Furthermore, if hypothermia delays the onset of the neurotoxic cascade and the secondary impairment in cerebral energy generation, the "latent phase" may be prolonged, thus extending the period when additional treatments may be effective. The aims of this study were to investigate the effects of delayed systemic cooling at either 33 degrees C or 35 degrees C on the following: (1) latent-phase duration, and (2) cerebral metabolism during secondary energy failure itself, in the 48-hour period after transient HI.

METHODS

Piglets were randomly assigned to the following: (1) HI-normothermic (HI-n) rectal temperature (Trectal; n = 12), (2) HI-Trectal 35 degrees C (HI-35; n = 7), and (3) HI-Trectal 33 degrees C (HI-33; n = 10). Groups were cooled to the target Trectal between 2 and 26 hours after HI. Serial magnetic resonance spectroscopy was performed over 48 hours. The effect of cooling on secondary energy failure severity (indexed by the nucleotide triphosphate/exchangeable phosphate pool [NTP/EPP] and phosphocreatine/inorganic phosphate [PCr/Pi] ratios) was assessed.

RESULTS

Compared with HI-n, HI-35 and HI-33 had a longer NTP/EPP latent phase and during the entire study duration had higher mean NTP/EPP and PCr/Pi. The latent phase (both PCr/Pi and NTP/EPP) and the whole-brain cerebral energetics were similar for HI-35 and HI-33. During the hypothermic period, compared with HI-n, PCr/Pi was preserved in the cooled groups, but this advantage was not maintained after rewarming. Compared with HI-n, HI-35 and HI-33 had higher NTP/EPP after rewarming.

CONCLUSIONS

Whole-body hypothermia for 24 hours at either 35 or 33 degrees C, commenced 2 hours after resuscitation, prolonged the NTP/EPP latent phase and reduced the overall secondary falls in mean PCr/Pi and NTP/EPP during 48 hours after HI. Reducing the temperature from 35 to 33 degrees C neither increased mean PCr/Pi and NTP/EPP nor further lengthened the latent phase.

A strong neuroprotective effect of the autonomous C‐terminal peptide of IGF‐1 Ec (MGF) in brain ischemia

The ischemic stroke is the third leading cause of death in developed countries. The C-terminal peptide of mechano-growth factor (MGF), an alternatively spliced variant of insulin-like growth factor 1 (IGF-1), was found to function independently from the rest of the molecule and showed a neuroprotective effect in vivo and in vitro. In vivo, in a gerbil model of transient brain ischemia, treatment with the synthetic MGF C-terminal peptide provided very significant protection to the vulnerable neurons. In the same model, ischemia evoked increased expression of endogenous MGF in the ischemia-resistant hippocampal neurons, suggesting that the endogenous MGF might have an important neuroprotective function. In an in vitro organotypic hippocampal culture model of neurodegeneration, the synthetic peptide was as potent as the full-length IGF-1 while its effect lasted significantly longer than that of recombinant IGF-1. While two peptides showed an additive effect, the neuroprotective action of the C-terminal MGF was independent from the IGF-1 receptor, indicating a new mode of action for this molecule. Although MGF is known for its regenerative capability in skeletal muscle, our findings demonstrate for the first time a neuroprotective role against ischemia for this specific IGF-1 isoform. Therefore, the C-terminal MGF peptide has a potential to be developed into a therapeutic modality for the prevention of neuronal damage.

Molecular mediators of hypoxic-ischemic injury and implications for epilepsy in the developing brain

Perinatal hypoxia-ischemia (HI) is the most common cause of cerebral palsy, and an important consequence of perinatal HI is epilepsy. Epilepsy is a disorder in which the balance between cerebral excitability and inhibition is tipped toward uncontrolled excitability. Selected neuronal circuits as well as certain populations of glial cells die from the excitotoxicity triggered by HI. Excitotoxicity, a term referring to cell death caused by overstimulation of the excitatory glutamate neurotransmitter receptors, plays a critical role in brain injury caused by perinatal HI. Ample evidence suggests distinct differences between the immature and mature brain with respect to the pathology and consequences of hypoxic-ischemic brain injury. Thus, the intrinsic vulnerability of specific cell types and systems in the developing brain is particularly important in determining the final pattern of damage and functional disability caused by perinatal HI. These patterns of neuronal vulnerability are associated with clinical syndromes of neurologic disorders such as cerebral palsy, epilepsy, and seizures. Recent studies have uncovered important molecular and cellular aspects of hypoxic-ischemic brain injury. The cascade of biochemical and histopathological events initiated by HI can extend for days to weeks after the insult is triggered, which may provide a "therapeutic window" for intervening in the pathogenesis in the developing brain. Activation of apoptotic programs accounts for the majority of HI-induced pathophysiology in neonatal brain disorders. New experimental approaches to protecting brain tissue from the effects of neonatal HI include administration of neuronal growth factors and effective inhibition of the death effector pathways, such as caspase cascade, and their downstream targets, which execute apoptosis and/or induction of their regulatory cellular proteins. Our recent findings that a novel neuronal protein, neuronal pentraxin 1 (NP1), is induced following HI in neonatal brain and that NP1 gene silencing is neuroprotective suggest that NP1 could be a new molecular target in the central neurons for preventing HI injury in developing brain. Most importantly, the specific interactions between NP1 and the excitatory glutamate receptors and their colocalization further implicate a role for this novel neuronal protein in the excitotoxic cascade. Recent experimental work suggests that these approaches may be effective during a longer therapeutic window after the insult, as they are acting on events that are relatively delayed, creating the potential for therapeutic interventions for these lifelong neurological disabilities.

In normal rat, intraventricularly administered insulin-like growth factor-1 is rapidly cleared from CSF with limited distribution into brain

Background

Putatively active drugs are often intraventricularly administered to gain direct access to brain and circumvent the blood-brain barrier. A few studies on the normal central nervous system (CNS) have shown, however, that the distribution of materials after intraventricular injections is much more limited than presumed and their exit from cerebrospinal fluid (CSF) is more rapid than generally believed. In this study, we report the intracranial distribution and the clearance from CSF and adjacent CNS tissue of radiolabeled insulin-like growth factor-1 after injection into one lateral ventricle of the normal rat brain.

Methods

Under barbiturate anesthesia, ¹²⁵I-labeled insulin-like growth factor-1 (IGF-1) was injected into one lateral ventricle of normal Sprague-Dawley rats. The subsequent distribution of IGF-1 through the cerebrospinal fluid (CSF) system and into brain, cerebral blood vessels, and systemic blood was measured over time by gamma counting and quantitative autoradiography (QAR).

Results

Within 5 min of infusion, IGF-1 had spread from the infused lateral ventricle into and through the third and fourth ventricles. At this time, 25% of the infused IGF-1 had disappeared from the CSF-brain-meningeal system; the half time of this loss was 12 min. The plasma concentration of cleared IGF-1 was, however, very low from 2 to 9 min and only began to rise markedly after 20 min. This delay between loss and gain plus the lack of radiotracer in the cortical subarachnoid space suggested that much of the IGF-1 was cleared into blood via the cranial and/or spinal nerve roots and their associated lymphatic systems rather than periventricular tissue and arachnoid villi. Less than 10% of the injected radioactivity remained in the CSF-brain system after 180 min. The CSF and arteries and arterioles within the subarachnoid cisterns were labeled with IGF-1 within 10 min. Between 60 and 180 min, most of the radioactivity within the cranium was retained within and around these blood vessels and by periaqueductal gray matter. Tissue profiles at two sites next to ventricular CSF showed that IGF-1 penetrated less than 1.25 mm into brain tissue and appreciable ¹²⁵I-activity remained at the tissue-ventricular CSF interface after 180 min.

Conclusion

Our findings suggest that entry of IGF-1 into normal brain parenchyma after lateral ventricle administration is limited by rapid clearance from CSF and brain and slow movement, apparently by diffusion, into the periventricular tissue. Various growth factors and other neuroactive agents have been reported to be neuroprotective within the injured brain after intraventricular administration. It is postulated that the delivery of such factors to neurons and glia in the injured brain may be facilitated by abnormal CSF flow. These several observations suggest that the flow of CSF and entrained solutes may differ considerably between normal and abnormal brain and even among various neuropathologies.

Growth hormone and insulin-like growth factor-1 (IGF-1) and their influence on cognitive aging

The concept that growth hormone and IGF-1 are required for normal development of the mammalian body and, more recently the brain, is supported by a vast experimental literature. IGF-1 crosses the blood-brain barrier and in recent years, much attention has focused on age-related decreases in serum growth hormone and IGF-1 as potential mechanisms that may influence cognitive function in the elderly. However, interventional studies are needed to establish a definite link between these hormones and function of the aging brain. In rodents, long-term growth hormone/IGF-1 replacement improves learning and memory in aged rats. While the exact mechanism underlying these cognitive improvements is unknown, growth hormone and IGF-1 replacement to aged animals increases neurogenesis, vascular density, and glucose utilization, and alters NMDA receptor subunit composition in brain areas that are implicated in learning and memory. While these observations offer valuable insight into the influence of growth hormone and IGF-1 on neuronal events in the aged mammal, additional functional studies are required to link these changes to cognitive improvements.

Genes and outcome after aneurysmal subarachnoid haemorrhage

OBJECTIVES

Initial and secondary ischaemia are important determinants of outcome after subarachnoid haemorrhage (SAH). Cerebral ischaemia is a potent stimulus for expression of genes that may influence recovery.We investigated whether functional polymorphisms in the apolipoprotein E (APOE), insulin-like growth factor-1 (IGF-1), tumor necrosis factor-A (TNF-A), interleukin-1A (IL-1A), interleukin-1B (IL-1B), and interleukin-6 (IL-6) genes are related with outcome after aneurysmal SAH.

METHODS

Genotyping of the polymorphisms was performed in a consecutive series of 167 patients with aneurysmal SAH. The risk of a poor outcome was analysed with logistic regression with adjustment for prognostic factors for outcome after SAH, using the homozygotes for the wild type alleles as a reference.

RESULTS

Patients carrying any IGF-1 non-wild type allele had a lower risk of a poor outcome (OR 0.4, 95% CI 0.2-1.0), while carriers of the TNF-A non-wild type allele had a higher risk (OR 2.3, 95% CI 1.0-5.4). We could not demonstrate an association with outcome for APOE (APOE epsilon4 OR 0.4, 95% CI 0.1-1.2; APOE epsilon2 OR 0.7, 95% CI 0.2-2.4), IL-1A (OR 1.8, 95% CI 0.8-4.0), IL-1B (OR 0.7, 95% CI 0.3-1.5) and IL-6 (OR 0.7, 95% CI 0.3-1.8) polymorphisms.

CONCLUSIONS

Variation in some genes that are expressed after cerebral ischaemia may partly explain the large differences in outcome between patients with aneurysmal SAH. SAH patients homozygote for the IGF-1 wild type allele or carriers of the TNF-A non-wild type allele have a higher risk of poor outcome. Additional studies in other populations are needed to assess the generalisability of our results.

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

The N-terminal tripeptide of insulin-like growth factor-1, GPE is neuroprotective when given intracerebroventricularly 2 h after hypoxic-ischemic (HI) brain injury in rats. We have now examined whether GPE can cross the blood-brain barrier and exert neuroprotective actions following intravenous administration. Following a single bolus intravenous injection, GPE was rapidly metabolized and cleared from the circulation. The short half-life (<2 min) in blood was subsequently associated with modest and inconsistent neuroprotection. In contrast, potent neuroprotection of GPE was consistently observed in all brain regions examined following 4 h intravenous infusion (12 mg/kg). The neuroprotective effects of GPE after infusion showed a broad effective dose range (1.2-120 mg/kg) and an extended window of treatment to 7-11 h after injury. The central penetration of GPE after intravenous infusion was injury-dependent. GPE also improved long-term somatofunction with a comparable neuronal outcome. GPE reduced both caspase-3-dependent and -independent apoptosis in the hippocampus. Treatment with GPE also inhibited microglial proliferation and prevented the injury-induced loss of astrocytes. In conclusion, the neuroprotective actions of GPE infusion were global, robust and displayed a broad effective dose range and treatment window. GPE's activity included the prevention of neuronal apoptosis, promotion of astrocyte survival and inhibition of microglial proliferation. With injury specific central penetration, GPE has considerable promise as a systemic neuroprotective treatment after acute encephalopathies.

Time for a cool head-neuroprotection becomes a reality

Studies in encephalopathic infants have demonstrated a brief phase of normal cerebral energetics following hypoxia-ischaemia prior to development of delayed energy failure. In experimental models, mild hypothermia has shown a consistent neuroprotective action, although its efficacy is critically dependent on the severity of the primary insult, the delay in initiating cooling, and the duration and depth of hypothermia. Early electroencephalographic assessment of encephalopathic infants has the potential to provide objective information about the preceding insult, aiding the selection of infants for enrollment to clinical trials. Preliminary results from a large randomised trial of selective head cooling suggest that early intervention can lead to significantly improved outcome in a subgroup of encephalopathic infants with intermediate electroencephalographic abnormalities. Further research in established experimental models is essential to improve the identification of suitable infants for treatment, to investigate the importance of variations in regional brain temperature, and to examine the therapeutic potential of hypothermia combined with other neuroprotective agents.

Insulin-like growth factor 1 as a predictor of ischemic stroke outcome in the elderly

PURPOSE

To examine whether serum insulin-like growth factor 1 (IGF-1) and IGF binding protein 3 (IGFBP-3) concentrations, determined early after the onset of stroke, are predictive of clinical outcome in elderly patients.

METHODS

The sample comprised 85 patients (mean [+/- SD] age, 83 +/- 7.4 years; range, 67 to 99 years; 34% male) who were admitted with acute stroke to a geriatric ward between January 1998 and June 2000, and 88 control patients who were similar in age and sex. Clinical and laboratory assessments, computed tomographic scan of the head, carotid ultrasonography, and electrocardiography were employed to define the clinical and etiologic stroke subtype. Fasting blood samples were collected within 24 hours of admission for IGF-I and IGFBP-3 measurement. Univariate and multiple logistic regression analyses, with adjustment for other related clinical covariates, were used to assess the relation of IGF-I and IGFBP-3 to poor outcome, defined as severe disability (Barthel index <60/100) or death, at 1 month (or at discharge), 3 months, and 6 months.

RESULTS

Mean (+/- SD) IGF-1 levels were lower in patients with stroke than in controls (69 +/- 45 ng/mL vs. 102 +/- 67 ng/mL, P adjusted for age = 0.001). The mean IGF-1/IGFBP-3 molar ratio was also lower in stroke patients (0.12 +/- 0.07 vs. 0.19 +/- 0.09, P adjusted for age <0.0001). However, there was no relation of hormone levels to either the clinical subtype of stroke or the extent of neurologic impairment. IGF-1 levels were inversely related to poor outcome (mainly death) at 3 and 6 months, independent of other clinical covariates that were highly predictive of outcome, such as age and stroke scale score on admission (hazard ratio for death at 6 months for each 20-ng/mL increase = 0.7; 95% confidence interval: 0.5 to 0.9). An independent association of the molar ratio with death at 3 and 6 months was also found.

CONCLUSION

Low levels of circulating IGF-1 may predict the clinical outcome of stroke in elderly patients.

Window of opportunity of cerebral hypothermia for postischemic white matter injury in the near-term fetal sheep

Postresuscitation cerebral hypothermia is consistently neuroprotective in experimental preparations; however, its effects on white matter injury are poorly understood. Using a model of reversible cerebral ischemia in unanesthetized near-term fetal sheep, we examined the effects of cerebral hypothermia (fetal extradural temperature reduced from 39.4 +/- 0.1 degrees C to between 30 and 33 degrees C), induced at different times after reperfusion and continued for 72 hours after ischemia, on injury in the parasagittal white matter 5 days after ischemia. Cooling started within 90 minutes of reperfusion was associated with a significant increase in bioactive oligodendrocytes in the intragyral white matter compared with sham cooling (41 +/- 20 vs 18 +/- 11 per field, P < 0.05), increased myelin basic protein density and reduced expression of activated caspase-3 (14 +/- 12 vs 91 +/- 51, P < 0.05). Reactive microglia were profoundly suppressed compared with sham cooling (4 +/- 6 vs 38 +/- 18 per field, P < 0.05) with no effect on numbers of astrocytes. When cooling was delayed until 5.5 hours after reperfusion there was no significant effect on loss of oligodendrocytes (24 +/- 12 per field). In conclusion, hypothermia can effectively protect white matter after ischemia, but only if initiated early after the insult. Protection was closely associated with reduced expression of both activated caspase-3 and of reactive microglia.

The window of opportunity for treatment of focal cerebral ischemic damage with noninvasive intranasal insulin-like growth factor-I in rats

Intracerebroventricular injection of insulin-like growth factor (IGF)-I has been shown to protect against stroke in rats. This method of delivery is not practical in human beings, as it requires an operation with risk of infection and other complications. Intranasal (i.n.) delivery offers a noninvasive method of bypassing the blood-brain barrier to deliver IGF-I to the brain. This study delineates the window of opportunity for treatment of focal cerebral ischemic damage using i.n. IGF-I after middle cerebral artery occlusion (MCAO). Rats were allowed to survive 7 days after 2 hours of MCAO. Infarct volume, apoptosis after 7 days, and neurologic deficit scores from the postural reflex and adhesive tape tests assessing motor-sensory and somatosensory functions, respectively, at 1 to 7 days were used to evaluate the efficacy of i.n. IGF-I (150 microg) administered at different times after MCAO. I.n. IGF-I significantly reduced infarct volume by 54%; and 39%; versus control when administered at 2 or 4 hours, respectively, after the onset of MCAO (P < .05) and improved motor-sensory and somatosensory functions (P < .05) when administered 2 hours after the onset of MCAO. In addition, treatment with i.n. IGF-I at 2, 4, or 6 hours after MCAO decreased apoptotic cell counts by more than 90%; in the hemisphere ipsilateral to the occlusion. I.n. IGF-I is a promising treatment for stroke with a therapeutic window of opportunity for up to 6 hours after the onset of ischemia. This noninvasive method provides a simpler, safer, and potentially more cost-effective method of delivery than other methods currently in use.

Neuroprotective effects of insulin-like growth factor-binding protein ligand inhibitors in vitro and in vivo

The role of brain insulin-like growth factors (IGFs) and IGF binding proteins (IGFBPs) in neuroprotection was further investigated using in vitro and in vivo models of cerebral ischemia by assessing the effects of IGF-I, IGF-II, and high affinity IGFBP ligand inhibitors (the peptide [Leu24, 59, 60, Ala31]hIGF-I (IGFBP-LI) and the small molecule NBI-31772 (1-(3,4-dihydroxybenzoyl)-3-hydroxycarbonyl-6, 7-dihydroxyisoquinoline), which pharmacologically displace and elevate endogenous, bioactive IGFs from IGFBPs. Treatment with IGF-I, IGF-II, or IGFBP-LI (2 microg/mL) significantly (P < 0.05) reduced CA1 damage in organotypic hippocampal cultures resulting from 35 minutes of oxygen and glucose deprivation by 71%, 60%, and 40%, respectively. In the subtemporal middle cerebral artery occlusion (MCAO) model of focal ischemia, intracerebroventricular (icv) administration of IGF-I and IGF-II at the time of artery occlusion reduced ischemic brain damage in a dose-dependent manner, with maximum reductions in total infarct size of 37% (P < 0.01) and 38% (P < 0.01), respectively. In this model of MCAO, i.c.v. administration of NBI-31772 at the time of ischemia onset also dose-dependently reduced infarct size, and the highest dose (100 microg) significantly reduced both total (by 40%, P < 0.01) and cortical (by 43%, P < 0.05) infarct volume. In the intraluminal suture MCAO model, administration of NBI-31772 (50 microg i.c.v.) at the time of artery occlusion reduced both cortical infarct volume (by 40%, P < 0.01) and brain swelling (by 24%, P < 0.05), and it was still effective when treatment was delayed up to 3 hours after the induction of ischemia. These results further define the neuroprotective properties of IGFs and IGFBP ligand inhibitors in experimental models of cerebral ischemia.

Insulin-like growth factor-1 and post-ischemic brain injury

Insulin-like growth factor-1 (IGF-1) is a naturally occurring neurotrophic factor that plays an important role in promoting cell proliferation and differentiation during normal brain development and maturation. The present review examines recent evidence that endogenous IGF-1 also plays a significant role in recovery from insults such as hypoxia-ischemia and that giving additional exogenous IGF-1 can actively ameliorate damage. It is now well established that neurons and other cell types die many hours or even days after initial injury due to activation of programmed cell death pathways. IGF-1 and its binding proteins and receptors are intensely induced within damaged brain regions following brain injury, suggesting a possible a role for IGF-1 in brain recovery. Exogenous administration of IGF-1 within a few hours after brain injury is now known to be protective in both gray and white matter and leads to improved somatic function. In contrast, pre-treatment is ineffective, likely reflecting limited intracerebral penetration of IGF-1 into the uninjured brain. The neuroprotective effects of IGF-1 are mediated by IGF-1 receptors and its binding proteins and are specific to particular cellular phenotypes and brain regions. The window of opportunity for treatment with IGF-1 is limited to a few hours after normothermic brain injury, reflecting its specific actions on early, intracellular events in the apoptotic cascade. However, injury-associated mild post-hypoxic hypothermia, which delays the development of cell death, can shift and dramatically extend the window of opportunity for delayed treatment with IGF-1. Such a combined approach is likely to be essential for any clinical treatment.

Insulin-like growth factor (IGF)-1 suppresses oligodendrocyte caspase-3 activation and increases glial proliferation after ischemia in near-term fetal sheep

Insulin-like growth factor (IGF-1) markedly increases myelination and glial numbers in white matter after ischemia in near-term fetal sheep; however, it is unclear whether this is due to reduced cell loss or increased secondary proliferation. Brain injury was induced in near-term fetal sheep by 30 minutes of bilateral carotid artery occlusion. Ninety minutes after the occlusion, fetuses were given, intracerebroventricularly, either a single dose of IGF-1 (either 3 or 30 micro g), or 3 micro g followed by 3 micro g over 24 hours (3 + 3 micro g). White matter was assessed 4 days after reperfusion. Three micrograms, but not 30 micro g of IGF-1 prevented loss of oligodendrocytes and myelin basic protein density (P < 0.001) compared to the vehicle-treated ischemia controls. No additional effect was observed in the 3 + 3 micro g group. IGF-1 treatment was associated with reduced caspase-3 activation and increased glial proliferation in a similar dose-dependent manner. Caspase-3 was only expressed in oligodendrocytes that showed apoptotic morphology. Proliferating cell nuclear antigen co-localized with both oligodendrocytes and astrocytes and microglia. Thus, increased oligodendrocyte numbers after IGF-1 treatment is partly due to suppression of apoptosis, and partly to increased proliferation. In contrast, the increase in reactive glia was related only to proliferation. Speculatively, reactive glia may partly mediate IGF-1 white matter protection.

The emerging role of induced hypothermia in the management of acute stroke

Current treatment of acute stroke remains unsatisfactory. This review presents experimental and clinical data which suggest that mild induced hypothermia could be a potent and practicable neuroprotective treatment of acute ischaemic stroke and intracerebral haemorrhage. Hypothermia, if proven to be safe, effective and widely practicable in patients with acute stroke, could have an enormous positive impact on reducing the burden of stroke worldwide. Critical issues that will need to be considered in a well designed randomised controlled trial of induced hypothermia in acute stroke patients are discussed.

Moderate hypothermia alters interleukin-6 and interleukin-1alpha reactions in ischemic brain in mice

Female C57BL/6 mice were decapitated and their brains were removed and cultured at either 37 or 33 degrees C for 48 h to investigate whether or not moderate hypothermia alters the cytokine reactions in the ischemic brain. The interleukin-6 and interleukin-1alpha levels in the culture media were significantly elevated in a time-dependent manner. The interleukin-6 levels after the incubation at 33 degrees C were significantly lower than those at 37 degrees C. The interleukin-1alpha levels at 33 degrees C were significantly higher than those at 37 degrees C. The interleukin-1alpha levels incubated with interleukin-6 antibody were significantly higher than those without IL-6 antibody. At 37 degrees C, the mRNA expression of interleukin-6 was observed from 2 to 48 h after incubation, but the same expression of interleukin-1alpha was only detected until 12 h. Accordingly, the ischemic brain incubated at 33 degrees C showed a decreased interleukin-6 production in comparison with that at 37 degrees C and the level of interleukin-6 showed negative feedback for the production of interleukin-1alpha. The temperature should, therefore, be carefully considered when evaluating the cytokine reaction for cerebral ischemia.

Insulin-like growth factor-1 improves somatosensory function and reduces the extent of cortical infarction and ongoing neuronal loss after hypoxia-ischemia in rats

Treatment with insulin-like growth factor-1 has been demonstrated to reduce the extent of cortical infarction 5 days after hypoxic-ischemic brain injury. As neuronal death can be progressive and long lasting after initial injury, the present study examined the long-term effects of insulin-like growth factor-1 on late neuronal loss 20 days after hypoxic-ischemic injury, together with evaluating neurobehavioral outcome as assumed by somatosensory function. Unilateral brain injury was induced in adult rats by carotid artery ligation followed by 10 min of hypoxia (6% O2). A single dose of insulin-like growth factor-1 (50 microg) was administered intracerebroventricularly via a stereotaxically pre-fixed cannula 2 h after injury. A bilateral tactile stimulation test was used to examine the degree of somatosensory function at 3, 5, 10 and 20 days after the hypoxia in both insulin-like growth factor-1- (n=12) and its vehicle- (n=12) treated rats, along with sham-operated rats (n=9). Cortical infarction and percentage of selective neuronal loss in the cerebral cortex were examined 20 days after the hypoxic-ischemic injury in both treatment groups. Hypoxic-ischemic injury resulted in a significant delay in the time taken to contact the patch over the period examined (left/right ratio 5.1+/-0.79), particularly at 3 days (7.0+/-2.8) after the hypoxia, compared to sham-operated rats (1.1+/-0.9, P<0.05). The overall effect of insulin-like growth factor-1 in reducing the time taken to contact the patch was significant (P=0.03, 2.6+/-0.79) compared to the vehicle group. There was a trend towards a reduction of cortical infarction after insulin-like growth factor-1 treatment (P=0.058), however insulin-like growth factor-1 significantly reduced the percentage of selective neuronal loss (P=0.027) 20 days following the hypoxia. From these data we suggest that insulin-like growth factor-1 improves somatosensory function by reducing both the extent of cortical infarction and ongoing progressive neuronal death during brain recovery from hypoxic-ischemic injury.

Insulin and insulin-like growth factors in human development: implications for the perinatal period

The physiologic and cellular mechanisms regulating fetal growth cannot be adequately described by regulatory mechanisms important postnatally. This review summarizes recent advances in clinical medicine, cell and molecular biology, and physiology showing the central and essential roles of insulin and the insulin-like growth factor family of peptides in regulating fetal growth. Moreover, the importance of insulin-like growth factors in tissue-specific growth regulation during critical periods of development suggest that these mechanisms may also be relevant to the pathogenesis of tissue injury in the preterm infant, and may offer therapeutic strategies aimed at reducing morbidity associated with prematurity. Illustrations of how the insulin-like growth factor axis may represent potential therapeutic targets for specific clinical problems facing the newborn are briefly discussed.

Interactions of estrogens and insulin-like growth factor-I in the brain: implications for neuroprotection

Data from epidemiological studies suggest that the decline in estrogen following menopause could increase the risk of neurodegenerative diseases. Furthermore, experimental studies on different animal models have shown that estrogen is neuroprotective. The mechanisms involved in the neuroprotective effects of estrogen are still unclear. Anti-oxidant effects, activation of different membrane-associated intracellular signaling pathways, and activation of classical nuclear estrogen receptors (ERs) could contribute to neuroprotection. Interactions with neurotrophins and other growth factors may also be important for the neuroprotective effects of estradiol. In this review we focus on the interaction between insulin-like growth factor-I (IGF-I) and estrogen signaling in the brain and on the implications of this interaction for neuroprotection. During the development of the nervous system, IGF-I promotes the differentiation and survival of specific neuronal populations. In the adult brain, IGF-I is a neuromodulator, regulates synaptic plasticity, is involved in the response of neural tissue to injury and protects neurons against different neurodegenerative stimuli. As an endocrine signal, IGF-I represents a link between the growth and reproductive axes and the interaction between estradiol and IGF-I is of particular physiological relevance for the regulation of growth, sexual maturation and adult neuroendocrine function. There are several potential points of convergence between estradiol and IGF-I receptor (IGF-IR) signaling in the brain. Estrogen activates the mitogen-activated protein kinase (MAPK) pathway and has a synergistic effect with IGF-I on the activation of Akt, a kinase downstream of phosphoinositol-3 kinase. In addition, IGF-IR is necessary for the estradiol induced expression of the anti-apoptotic molecule Bcl-2 in hypothalamic neurons. The interaction of ERs and IGF-IR in the brain may depend on interactions between neural cells expressing ERs with neural cells expressing IGF-IR, or on direct interactions of the signaling pathways of alpha and beta ERs and IGF-IR in the same cell, since most neurons expressing IGF-IR also express at least one of the ER subtypes. In addition, studies on adult ovariectomized rats given intracerebroventricular (i.c.v.) infusions with antagonists for ERs or IGF-IR or with IGF-I have shown that there is a cross-regulation of the expression of ERs and IGF-IR in the brain. The interaction of estradiol and IGF-I and their receptors may be involved in different neural events. In the developing brain, ERs and IGF-IR are interdependent in the promotion of neuronal differentiation. In the adult, ERs and IGF-IR interact in the induction of synaptic plasticity. Furthermore, both in vitro and in vivo studies have shown that there is an interaction between ERs and IGF-IR in the promotion of neuronal survival and in the response of neural tissue to injury, suggesting that a parallel activation or co-activation of ERs and IGF-IR mediates neuroprotection.