Systemic application of granulocyte-colony stimulating factor and stem cell factor exacerbates excitotoxic brain injury in newborn mice

A further examination of growth factors, T helper 1 polarization, and the gut microbiome in major depression: Associations with reoccurrence of illness, cognitive functions, suicidal behaviors, and quality of life

Growth factors, T helper (Th)1 polarization, and the microbiome are involved in the pathophysiology of major depression (MDD). It remains unclear whether the combination of these three pathways could enhance the accuracy of predicting the features of MDD, including recurrence of illness (ROI), suicidal behaviors and the phenome. We measured serum stem cell factor (SCF), stem cell growth factor (SCGF), stromal cell-derived factor-1 (SDF-1), platelet-derived growth factor (PDGF), hepatocyte growth factor (HGF), macrophage-colony stimulating factor (M-CSF) and vascular endothelial growth factor (VEGF), the ratio of serum Th1/Th2 cytokines (zTh1-zTh2), and the abundances of gut microbiome taxa by analyzing stool samples using 16S rDNA sequencing from 32 MDD patients and 37 healthy controls. The results show that serum SCF is significantly lower and VEGF increased in MDD. Adverse childhood experiences (ACE) and ROI are significantly associated with lowered SCF and increasing VEGF. Lifetime and current suicidal behaviors are strongly predicted (63.5%) by an increased VEGF/SCF ratio, Th1 polarization, a gut microbiome enterotype indicating gut dysbiosis, and lowered abundance of Dorea and Faecalobacterium. Around 80.5% of the variance in the phenome's severity is explained by ROI, ACEs, and lowered Parabacteroides distasonis and Clostridium IV abundances. A large part of the variance in health-related quality of life (54.1%) is explained by the VEGF/SCF ratio, Th1 polarization, ACE, and male sex. In conclusion, key features of MDD are largely predicted by the cumulative effects of ACE, Th1 polarization, aberrations in growth factors and the gut microbiome with increased pathobionts but lowered beneficial symbionts.

The role of G-CSF neuroprotective effects in neonatal hypoxic-ischemic encephalopathy (HIE): current status

Hypoxic-ischemic encephalopathy (HIE) is an important cause of permanent damage to central nervous system (CNS) that may result in neonatal death or manifest later as mental retardation, epilepsy, cerebral palsy, or developmental delay. The primary cause of this condition is systemic hypoxemia and/or reduced cerebral blood flow with long-lasting neurological disabilities and neurodevelopmental impairment in neonates. About 20 to 25% of infants with HIE die in the neonatal period, and 25-30% of survivors are left with permanent neurodevelopmental abnormalities. The mechanisms of hypoxia-ischemia (HI) include activation and/or stimulation of myriad of cascades such as increased excitotoxicity, oxidative stress, N-methyl-D-aspartic acid (NMDA) receptor hyperexcitability, mitochondrial collapse, inflammation, cell swelling, impaired maturation, and loss of trophic support. Different therapeutic modalities have been implicated in managing neonatal HIE, though translation of most of these regimens into clinical practices is still limited. Therapeutic hypothermia, for instance, is the most widely used standard treatment in neonates with HIE as studies have shown that it can inhibit many steps in the excito-oxidative cascade including secondary energy failure, increases in brain lactic acid, glutamate, and nitric oxide concentration. Granulocyte-colony stimulating factor (G-CSF) is a glycoprotein that has been implicated in stimulation of cell survival, proliferation, and function of neutrophil precursors and mature neutrophils. Extensive studies both in vivo and ex vivo have shown the neuroprotective effect of G-CSF in neurodegenerative diseases and neonatal brain damage via inhibition of apoptosis and inflammation. Yet, there are still few experimentation models of neonatal HIE and G-CSF's effectiveness, and extrapolation of adult stroke models is challenging because of the evolving brain. Here, we review current studies and/or researches of G-CSF's crucial role in regulating these cytokines and apoptotic mediators triggered following neonatal brain injury, as well as driving neurogenesis and angiogenesis post-HI insults.

The impact of trophic and immunomodulatory factors on oligodendrocyte maturation: Potential treatments for encephalopathy of prematurity

Encephalopathy of prematurity (EoP) is a major cause of morbidity in preterm neonates, causing neurodevelopmental adversities that can lead to lifelong impairments. Preterm birth-related insults, such as cerebral oxygen fluctuations and perinatal inflammation, are believed to negatively impact brain development, leading to a range of brain abnormalities. Diffuse white matter injury is a major hallmark of EoP and characterized by widespread hypomyelination, the result of disturbances in oligodendrocyte lineage development. At present, there are no treatment options available, despite the enormous burden of EoP on patients, their families, and society. Over the years, research in the field of neonatal brain injury and other white matter pathologies has led to the identification of several promising trophic factors and cytokines that contribute to the survival and maturation of oligodendrocytes, and/or dampening neuroinflammation. In this review, we discuss the current literature on selected factors and their therapeutic potential to combat EoP, covering a wide range of in vitro, preclinical and clinical studies. Furthermore, we offer a future perspective on the translatability of these factors into clinical practice.

Short-, Mid-, and Long-Term Effect of Granulocyte Colony-Stimulating Factor/Stem Cell Factor and Fms-Related Tyrosine Kinase 3 Ligand Evaluated in an In Vivo Model of Hypoxic-Hyperoxic Ischemic Neonatal Brain Injury

Hematopoietic growth factors are considered to bear neuroprotective potential. We have previously shown that delayed treatment with granulocyte colony-stimulating factor (G-CSF)/stem cell factor (SCF) and Fms-related tyrosine kinase 3 ligand (FL) ameliorates excitotoxic neonatal brain injury. The effect of these substances in combined-stressor neonatal brain injury models more closely mimicking clinical conditions has not been investigated. The aim of this study was to assess the short-, mid-, and long-term neuroprotective potential of G-CSF/SCF and FL in a neonatal model of hypoxic-hyperoxic ischemic brain injury. Five-day-old (P5) CD-1 mice were subjected to unilateral common carotid artery ligation and subsequent alternating periods of hypoxia and hyperoxia for 65 minutes. Sixty hours after injury, pups were randomly assigned to intraperitoneal treatment with (i) G-CSF (200 μg/kg)/SCF (50 μg/kg), (ii) FL (100 μg/kg), or (iii) vehicle every 24 hours for three or five consecutive days. Histopathological and functional outcomes were evaluated on P10, P18, and P90. Baseline outcome parameters were established in sham-treated and healthy control animals. Gross brain injury did not significantly differ between treatment groups at any time point. On P10, caspase-3 activation and caspase-independent apoptosis were similar between treatment groups; cell proliferation and the number of BrdU-positive vessels did not differ on P18 or P90. Neurobehavioral assessment did not reveal significant differences between treatment groups in accelerod performance, open field behavior, or novel object recognition capacity on P90. Turning behavior was more frequently observed in G-CSF/SCF- and FL-treated animals. No sex-specific differences were detected in any outcome parameter evaluated. In hypoxic-hyperoxic ischemic neonatal brain injury, G-CSF/SCF and FL treatment does not convey neuroprotection. Prior to potential clinical use, meticulous assessment of these hematopoietic growth factors is mandated.

Emergent Prophylactic, Reparative and Restorative Brain Interventions for Infants Born Preterm With Cerebral Palsy

Worldwide, an estimated 15 million babies are born preterm (<37 weeks' gestation) every year. Despite significant improvements in survival rates, preterm infants often face a lifetime of neurodevelopmental disability including cognitive, behavioral, and motor impairments. Indeed, prematurity remains the largest risk factor for the development of cerebral palsy. The developing brain of the preterm infant is particularly fragile; preterm babies exhibit varying severities of cerebral palsy arising from reductions in both cerebral white and gray matter volumes, as well as altered brain microstructure and connectivity. Current intensive care therapies aim to optimize cardiovascular and respiratory function to protect the brain from injury by preserving oxygenation and blood flow. If a brain injury does occur, definitive diagnosis of cerebral palsy in the first few hours and weeks of life is difficult, especially when the lesions are subtle and not apparent on cranial ultrasound. However, early diagnosis of mildly affected infants is critical, because these are the patients most likely to respond to emergent treatments inducing neuroplasticity via high-intensity motor training programs and regenerative therapies involving stem cells. A current controversy is whether to test universal treatment in all infants at risk of brain injury, accepting that some patients never required treatment, because the perceived potential benefits outweigh the risk of harm. Versus, waiting for a diagnosis before commencing targeted treatment for infants with a brain injury, and potentially missing the therapeutic window. In this review, we discuss the emerging prophylactic, reparative, and restorative brain interventions for infants born preterm, who are at high risk of developing cerebral palsy. We examine the current evidence, considering the timing of the intervention with relation to the proposed mechanism/s of action. Finally, we consider the development of novel markers of preterm brain injury, which will undoubtedly lead to improved diagnostic and prognostic capability, and more accurate instruments to assess the efficacy of emerging interventions for this most vulnerable group of infants.

Delayed application of the haematopoietic growth factors G-CSF/SCF and FL reduces neonatal excitotoxic brain injury

BACKGROUND

Developmental brain injury results in cognitive and motor deficits in the preterm infant. Enhanced glutamate release and subsequent receptor activation are major pathogenetic factors. The effect of haematopoietic growth factors, such as granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF) and flt-3 ligand (FL) on neonatal brain injury is controversially discussed. Timing of treatment is known to be a crucial factor. Based on the hypothesis that an exacerbation of injury is caused by administration of substances in the acute phase, the objective of this study was to evaluate the effect of delayed administration of G-CSF/SCF and FL to protect against excitotoxic brain injury in vivo.

METHODS

In an established neonatal mouse model of excitotoxic brain injury, we evaluated the effect of daily intraperitoneal doses of G-CSF/SCF or FL, starting 60 h after the excitotoxic insult.

RESULTS

Intraperitoneal injections of G-CSF/SCF and FL, given 60 h after the excitotoxic insult, significantly reduced lesion size at postnatal days 10, 18 and 90. G-CSF/SCF treatment resulted in a decrease in apoptotic cell death indicated by reduced caspase-3 activation. G-CSF/SCF and FL treatment did not affect apoptosis-inducing factor-dependent apoptosis or cell proliferation.

CONCLUSION

We show that delayed systemic treatment with the haematopoietic growth factors G-CSF/SCF and FL protects against N-methyl-D-aspartate receptor-mediated developmental excitotoxic brain damage. Our results suggest that neuroprotective effects in this neonatal animal model of excitotoxic brain injury depend on the timing of drug administration after the insult.

NMDA receptor blockade in the developing cortex induces autophagy-mediated death of immature cortical GABAergic interneurons: An ex vivo and in vivo study in Gad67-GFP mice

In neonates, excitotoxicity is a major process involved in hypoxic-ischemic brain lesions, and several research groups have suggested the use of NMDA antagonists for neuroprotection. However, despite their clinical interest, there is more and more evidence suggesting that, in the immature brain, these molecules exert deleterious actions on migrating GABAergic interneurons by suppressing glutamatergic trophic inputs. Consequently, preventing the side effects of NMDA antagonists would be therapeutically useful. Because macroautophagy is involved in the adaptive response to trophic deprivation, the aim of the present study was to investigate the impact of autophagy modulators on the MK801-induced death of immature GABAergic interneurons and to characterize the crosstalk between autophagic and apoptotic mechanisms in this cell type. Ex vivo, using cortical slices from NMRI and Gad67-GFP mice, we show that blockade of the NMDA receptor results in an accumulation of autophagosomes due to the disruption of the autophagic flux. This effect precedes the activation of the mitochondrial apoptotic pathway, and the degeneration of immature GABAergic neurons present in developing cortical layers II-IV and is prevented by 3-MA, an autophagy inhibitor. In contrast, modulators of autophagy (3-MA, rapamycin) do not interfere with the anti-excitotoxic and neuroprotective effect of MK801 observed in deep layers V and VI. In vivo, 3-MA blocks the rapid increase in caspase-3 cleavage induced by the blockade of NMDA receptors and prevents the resulting long-term decrease in Gad67-GFP neurons in layers II-IV. Together, these data suggest that, in the developing cortex, the suppression of glutamatergic inputs through NMDA receptor inhibition results in the impairment of the autophagic flux and the subsequent switch to apoptotic death of immature GABAergic interneurons. The concomitant inhibition of autophagy prevents this pro-apoptotic action of the NMDA blocker and favors the long-term rescue of GABAergic interneurons without interfering with its neuroprotective actions. The use of autophagy modulators in the developing brain would create new opportunities to prevent the side effects of NMDA antagonists used for neuroprotection or anesthesia.

Systemic G-CSF attenuates cerebral inflammation and hypomyelination but does not reduce seizure burden in preterm sheep exposed to global hypoxia-ischemia

Hypoxic-ischemic encephalopathy (HIE) is common in preterm infants, but currently no curative therapy is available. Cell-based therapy has a great potential in the treatment of hypoxic-ischemic preterm brain injury. Granulocyte-colony stimulating factor (G-CSF) is known to mobilize endogenous hematopoietic stem cells (HSC) and promotes proliferation of endogenous neural stem cells. On these grounds, we hypothesized that systemic G-CSF would be neuroprotective in a large translational animal model of hypoxic-ischemic injury in the preterm brain. Global hypoxia-ischemia (HI) was induced by transient umbilical cord occlusion in instrumented preterm sheep. G-CSF treatment (100μg/kg intravenously, during five consecutive days) was started one day before the global HI insult to ascertain mobilization of endogenous stem cells within the acute phase after global HI. Mobilization of HSC and neutrophils was studied by flow cytometry. Brain sections were stained for microglia (IBA-1), myelin basic protein (MBP) and myeloperoxidase (MPO) to study microglial proliferation, white matter injury and neutrophil invasion respectively. Electrographic seizure activity was analyzed using amplitude-integrated electroencephalogram (aEEG). G-CSF effectively mobilized CD34-positive HSC in the preterm sheep. In addition, G-CSF caused marked mobilization of neutrophils, but did not influence enhanced invasion of neutrophils into the preterm brain after global HI. Microglial proliferation and hypomyelination following global HI were reduced as a result of G-CSF treatment. G-CSF did not cause a reduction of the electrographic seizure activity after global HI. In conclusion, G-CSF induced mobilization of endogenous stem cells which was associated with modulation of the cerebral inflammatory response and reduced white matter injury in an ovine model of preterm brain injury after global HI. G-CSF treatment did not improve neuronal function as shown by seizure analysis. Our study shows that G-CSF treatment has neuroprotective potential following hypoxic-ischemic injury in the preterm brain.

Flt3 ligand synergizes with granulocyte-colony-stimulating factor in bone marrow mobilization to improve functional outcome after spinal cord injury in the rat

BACKGROUND AIMS

The effect of granulocyte-colony-stimulating factor (G-CSF) and/or the cytokine fms-like thyrosin kinase 3 (Flt3) ligand on functional outcome and tissue regeneration was studied in a rat model of spinal cord injury (SCI).

METHODS

Rats with a balloon-induced compression lesion were injected with G-CSF and/or Flt3 ligand to mobilize bone marrow cells. Behavioral tests (Basso-Beattie-Bresnahan and plantar test), blood counts, morphometric evaluation of the white and gray matter, and histology were performed 5 weeks after SCI.

RESULTS

The mobilization of bone marrow cells by G-CSF, Flt3 ligand and their combination improved the motor and sensory performance of rats with SCI, reduced glial scarring, increased axonal sprouting and spared white and gray matter in the lesion. The best results were obtained with a combination of G-CSF and Flt3. G-CSF alone or in combination with Flt3 ligand significantly increased the number of white blood cells, but not red blood cells or hemoglobin content, during and after the time-course of bone marrow stimulation. The combination of factors led to infiltration of the lesion by CD11b(+) cells.

CONCLUSIONS

The observed improvement in behavioral and morphologic parameters and tissue regeneration in animals with SCI treated with a combination of both factors could be associated with a prolonged time-course of mobilization of bone marrow cells. The intravenous administration of G-CSF and/or Flt3 ligand represents a safe and effective treatment modality for SCI.

Systemic G-CSF treatment does not improve long-term outcomes after neonatal hypoxic-ischaemic brain injury

Hypoxia-ischaemia (HI) is a major factor in the pathogenesis of developmental brain injury, leading to cognitive deficits and motor disabilities in preterm infants. The haematopoietic growth factor granulocyte colony-stimulating factor (G-CSF) has been shown to exert a neuroprotective activity in rodent models of ischaemic stroke and is currently subject to phase I/II clinical trials in adults. Results of studies examining the effect of G-CSF in perinatal brain damage have been contradictory. We have previously shown that G-CSF increases NMDAR-mediated excitotoxic brain injury in the neonatal mouse brain. In this study, we evaluated the effect of G-CSF on long-term outcomes after HI. On postnatal day 5, mice pubs were first randomly assigned to a sham operation or HI and then divided into four treatment groups: i) G-CSF; ii) phosphate buffered saline (PBS) 1h after injury; iii) G-CSF and iv) PBS 60 h after injury. G-CSF (200 μg/kg BW) was administered five times within a 24h interval. Neuromotor and cognitive outcomes were assessed by open-field, novel object recognition tests and rotarod tests starting on P90, with subsequent histological analyses of brain injury. G-CSF treatment did not improve either neurobehavioural outcomes or brain injuries. Interestingly, the application of PBS and G-CSF in the acute phase increased brain damage in the hippocampus. We could not confirm the neuroprotective properties of G-CSF in neonatal HI brain damage. The exacerbation of injury by the administration of substances in the acute phase might indicate a heightened state of neurological sensitivity that is specific to mechanisms of secondary neurodegeneration and influenced by unidentified external factors possibly associated with the treatment protocol during the acute phase. This article is part of a Special Issue entitled "Interaction between repair, disease, & inflammation."

Neuroprotective strategies in excitotoxic brain injury: potential applications to the preterm brain

Neuronal and oligodendroglial cell death owing to increased glutamate levels plays an important role in the pathophysiology of hypoxic-, ischemic- and inflammation-mediated brain injury as well as in disorders such as epilepsy, Alzheimer’s, Parkinson’s or Huntington’s disease. In addition, excitotoxic brain injury is known to be a major contributing factor to brain injury in preterm infants. Excitotoxicity is characterized as excessive glutamatergic activation of postsynaptic receptors that consequently leads to cell injury and cell death. The major excitatory amino acid neurotransmitter is glutamate. Glutamate plays a key role in brain development, affecting progenitor cell differentiation, proliferation, migration and survival. In physiological conditions the presence of glutamate in the synapse is regulated by ATP-dependent glutamate transporters in neurons and glial cells, with astrocytes being responsible for a major part of glutamate uptake in the brain. In pathologic circumstances the function of the transporters is impaired, leading to glutamate accumulation in the synaptic cleft and in turn excessive activation of postsynaptic glutamate receptors with subsequent massive Ca2+ influx, activation of neuronal nitric oxide synthase, translocation of proapoptotic genes to the mitochondria, mitochondrial dysfunction, release of cytochrome C into the cytosol, activation of caspases and subsequent cell death. Based on the pathogenic concept of an overactivation of the excitatory pathways, glutamate receptors have been a longstanding therapeutic target for rational drug design. This article reviews the pathophysiology of excitotoxic brain injury in the example of preterm brain injury, as well as current research on therapeutic antiexcitotoxic strategies.

Granulocyte stimulating factor attenuates hypoxic-ischemic brain injury by inhibiting apoptosis in neonatal rats

PURPOSE

This study was undertaken to determine the neuroprotective effect of granulocyte stimulating factor (G-CSF) on neonatal hypoxic-ischemic brain injury.

MATERIALS AND METHODS

Seven-day-old male newborn rat pups were subjected to 110 minutes of 8% oxygen following a unilateral carotid artery ligation. Apoptosis was identified by performing terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining and flow cytometry with a combination of fluorescinated annexin V and propidium iodide (PI) and JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'- tetraethylbenzimidazolyl-carbocyanine iodide). The extent of cerebral infarction was evaluated at 2 weeks after recovery.

RESULTS

With a single dose (50microg/kg) of G-CSF treatment immediately after hypoxic-ischemic insult, hypoxia-ischemia induced increase in TUNEL-positive cells, annexinV+/PI- and JC-1 positive apoptotic cells in the ipsilateral cerebral cortex was significantly reduced at 24 hours, measured by flow cytometry, and the extent of cerebral infarction at 2 weeks after recovery was also significantly attenuated compared to the hypoxia-ischemia control group.

CONCLUSION

Our data suggest that G-CSF is neuroprotective by inhibiting apoptosis, thereby reducing the ensuing cerebral infarction in a newborn rat pup model of cerebral hypoxia-ischemia (HI).

Anti-inflammatory and immunomodulatory strategies to protect the perinatal brain

Infection and inflammation contribute to perinatal brain damage, particularly to the white matter. Although combating perinatal inflammation can be dangerous, because inflammation might have beneficial effects for mother and fetus, it is worthwhile reviewing potential anti-inflammatory neuroprotective compounds, along with their potential adverse effects. Further research on the possible neuroprotective roles of existing medications and substances is necessary.

Epo and other hematopoietic factors

The growth factors erythropoietin and granulocyte-colony stimulating factor have hematopoietic and non-hematopoietic functions. Both are used clinically in their recombinant forms. Both also have interesting tissue-protective effects in other organs, which are unrelated to their hematopoietic functions. They have clinical hematopoietic uses in neonatal populations and in experimental non-hematopoietic research, and clinical potential as neuroprotective or tissue-protective agents.

T3 replacement does not prevent excitotoxic cell death but reduces developmental neuronal apoptosis in newborn mice

BACKGROUND

Periventricular leukomalacia (PVL) is a major cause of neurological handicap in pre-term infants. At present, there are no effective or causal therapies available. Thyroid hormones play an essential role in brain development and are reported to be decreased in pre-terms and following brain injury in adults.

HYPOTHESIS

Excitotoxic brain damage of newborn mice decreases thyroid hormone concentrations. Exogenous T3 administration restores thyroid hormone levels and reduces perinatal brain damage in an animal model of PVL.

DESIGN AND METHOD

To create white and gray matter (WM/GM) lesion mimicking several key aspects of PVL, we injected ibotenic acid (Ibo), a glutamate analog, into the right hemisphere (intracranially (i.c.)) of 5-day-old mice. T3 (10 microg/kg body weight (bw)) was injected intraperitoneally (i.p.) 1 h or repeatedly 1/24/48/72/96 h post-insult. We determined lesion size, number of apoptotic cells in WM/GM and serum T3/T4 concentration at 24 and 120 h after injury. Serum T3/T4 concentration was also determined before and 1 and 2h after T3 administration.

RESULTS

Excitotoxic brain damage did not alter serum T3/T4 concentrations within 120 h of injury. Serum T3 levels were distinctly elevated within 1 h of T3 injection; however, this elevation was relatively short-lived (half-life estimated to be less than 12 h). Neither single nor repetitive T3 treatment regimen reduced excitotoxic lesion size, but it did reduce apoptosis.

CONCLUSIONS

T3 replacement does not prevent excitotoxic cell death, but it does reduce developmental neuronal apoptosis, which could participate to the beneficial neuropsychological effects of hormone therapy. Further study is therefore warranted.

Granulocyte-colony stimulating factor inhibits apoptotic neuron loss after neonatal hypoxia-ischemia in rats

Neonatal hypoxia-ischemia (HI) is an important clinical problem with few effective treatments. Granulocyte-colony stimulating factor (G-CSF) is an endogenous peptide hormone of the hematopoietic system that has been shown to be neuroprotective in focal ischemia in vivo and is currently in phase I/II clinical trials for ischemic stroke in humans. We tested G-CSF in a rat model of neonatal hypoxia-ischemia in postnatal day 7 unsexed rat pups. Three groups of animals were used: hypoxia-ischemia (HI, n=67), hypoxia-ischemia with G-CSF treatment (HI+G, n=65), and healthy control (C, n=53). G-CSF (50 microg/kg, subcutaneous) was administered 1 h after HI and given on four subsequent days (five total injections). Animals were euthanized 24 h, 1, 2, and 3 weeks after HI. Assessment included brain weight, histology, immunohistochemistry, and Western blotting. G-CSF treatment was associated with improved quantitative brain weight and qualitative Nissl histology after hypoxia-ischemia. TUNEL demonstrated reduced apoptosis in group HI+G. Western blot demonstrated decreased expression of Bax and cleaved caspase-3 in group HI+G. G-CSF treatment was also associated with increased expression of STAT3, Bcl-2, and Pim-1, all of which may have participated in the anti-apoptotic effect of the drug. We conclude that G-CSF ameliorates hypoxic-ischemic brain injury and that this may occur in part by an inhibition of apoptotic cell death.

The effect of granulocyte-colony stimulating factor in global cerebral ischemia in rats

Granulocyte-colony stimulating factor (G-CSF) is an endogenous peptide hormone of the hematopoietic system that has entered Phase I/II clinical trials for treatment of ischemic stroke. Severe intraoperative hypotension can lead to global cerebral ischemia and apoptotic neuron loss within the hippocampus. We tested G-CSF in a rat model of global cerebral ischemia. Global cerebral ischemia was induced in male Sprague-Dawley rats (280-330 g) with the 2-vessel occlusion model (hemorrhagic hypotension to a mean arterial pressure of 30-35 mm Hg and bilateral common carotid artery occlusion for 8 min). Three groups of animals were used: global ischemia without treatment (GI, n=49), global ischemia with G-CSF treatment (GI+G-CSF, n=42), and sham surgery (Sham, n=26). Rats in the treatment group received G-CSF (50 mug/kg, subcutaneously) 12 h before surgery, on the day of surgery, and on postoperative Day 1 and were euthanized on Days 2, 3, and 14. Mild hyperglycemia was observed in all groups. T-maze testing for spontaneous alternation demonstrated initial improvement in the G-CSF treatment group but no long-term benefit. Measurement of daily body weight demonstrated an initial trend toward improvement in the G-CSF group. Quantitative Nissl histology of the hippocampus demonstrated equivalent outcomes on Days 3 and 14, which was supported by quantitative TUNEL stain. Immunohistochemistry and Western blot demonstrated an initial increase in phosphorylated-AKT in the GI+G-CSF group on Day 2. We conclude that G-CSF treatment is associated with transient early improvement in neurobehavioral outcomes after global ischemia complicated by mild hyperglycemia, but no long-term protection.

Erythropoietin is neuroprotective against NMDA-receptor-mediated excitotoxic brain injury in newborn mice

Using an established mouse model of human periventricular leukomalacia, we investigated whether EPO could reduce excitotoxic damage. When administered 1 h following intracerebral injection of 10 microg ibotenic acid at day 5 of life, both a single injection of EPO (5000 IU/kg bw) and repetitive administrations of EPO reduced white and gray matter lesion size. The therapeutic window for protection was small as the protective effect of EPO was lost when EPO administration was delayed to 4 h post-insult. EPO-mediated upregulation of EPO-R, but not EPO, mRNA was observed within 4 h of the excitotoxic insult. The EPO effect was gender independent. Minor hematopoetic effects were observed following EPO treatment. We conclude that a single dose of EPO is sufficient to reduce excitotoxic brain injury and may therefore possess therapeutic relevance in the clinical setting.