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

The effect of intra-nasal co-treatment with insulin and growth factor-rich serum on behavioral defects, hippocampal oxidative-nitrosative stress, and histological changes induced by icv-STZ in a rat model

Impaired insulin and growth factor functions are thought to drive many alterations in neurodegenerative diseases like dementia and seem to contribute to oxidative stress and inflammatory responses. Recent studies revealed that nasal growth factor therapy could induce neuronal and oligodendroglia protection in rodent brain damage induction models. Impairment of several growth factors signaling was reported in neurodegenerative diseases. So, in the present study, we examined the effects of intranasal co-treatment of insulin and a pool of growth factor-rich serum (GFRS) which separated from activated platelets on memory, and behavioral defects induced by intracerebroventricular streptozotocin (icv-STZ) rat model also investigated changes in the hippocampal oxidative-nitrosative state and histology. We found that icv-STZ injection (3 mg/kg bilaterally) impairs spatial learning and memory in Morris Water Maze, leads to anxiogenic-like behavior in the open field arena, and induces oxidative-nitrosative stress, neuroinflammation, and neuronal/oligodendroglia death in the hippocampus. GFRS (1µl/kg, each other day, 9 doses) and regular insulin (4 U/40 µl, daily, 18 doses) treatments improved learning, memory, and anxiogenic behaviors. The present study showed that co-treatment (GFRS + insulin with respective dose) has more robust protection against hippocampal oxidative-nitrosative stress, neuroinflammation, and neuronal/oligodendroglia survival in comparison with the single therapy. Memory and behavioral improvements in the co-treatment of insulin and GFRS could be attributed to their effects on neuronal/oligodendroglia survival and reduction of neuroinflammation in the hippocampus.

Insulin-like growth factor 1 supplementation supports motor coordination and affects myelination in preterm pigs

Introduction

Preterm infants have increased risk of impaired neurodevelopment to which reduced systemic levels of insulin-like growth factor 1 (IGF-1) in the weeks after birth may play a role. Hence, we hypothesized that postnatal IGF-1 supplementation would improve brain development in preterm pigs, used as a model for preterm infants.

Methods

Preterm pigs delivered by cesarean section received recombinant human IGF-1/IGF binding protein-3 complex (rhIGF-1/rhIGFBP-3, 2.25 mg/kg/day) or vehicle from birth to postnatal day 19. Motor function and cognition were assessed by monitoring of in-cage and open field activities, balance beam test, gait parameters, novel object recognition and operant conditioning tests. Collected brains were subject to magnetic resonance imaging (MRI), immunohistochemistry, gene expression analyses and protein synthesis measurements.

Results

The IGF-1 treatment increased cerebellar protein synthesis rates (both in vivo and ex vivo). Performance in the balance beam test was improved by IGF-1 but not in other neurofunctional tests. The treatment decreased total and relative caudate nucleus weights, without any effects to total brain weight or grey/white matter volumes. Supplementation with IGF-1 reduced myelination in caudate nucleus, cerebellum, and white matter regions and decreased hilar synapse formation, without effects to oligodendrocyte maturation or neuron differentiation. Gene expression analyses indicated enhanced maturation of the GABAergic system in the caudate nucleus (decreased NKCC1:KCC2 ratio) with limited effects in cerebellum or hippocampus.

Conclusion

Supplemental IGF-1 during the first three weeks after preterm birth may support motor function by enhancing GABAergic maturation in the caudate nucleus, despite reduced myelination. Supplemental IGF-1 may support postnatal brain development in preterm infants, but more studies are required to identify optimal treatment regimens for subgroups of very or extremely preterm infants.

Neuronal and Astrocyte Insulin-like Growth Factor-1 Signaling Differentially Modulates Ischemic Stroke Damage

Ischemic stroke is a leading cause of death and disability, as therapeutic options for mitigating the long-term deficits precipitated by the event remain limited. Acute administration of the neuroendocrine modulator insulin-like growth factor-1 (IGF-1) attenuates ischemic stroke damage in preclinical models, and clinical studies suggest IGF-1 can reduce the risk of stroke and improve overall outcomes. The cellular mechanism by which IGF-1 exerts this protection is poorly defined, as all cells within the neurovascular unit express the IGF-1 receptor. We hypothesize that the functional regulation of both neurons and astrocytes by IGF-1 is critical in minimizing damage in ischemic stroke. To test this, we utilized inducible astrocyte-specific or neuron-specific transgenic mouse models to selectively reduce IGF-1R in the adult mouse brain prior to photothrombotic stroke. Acute changes in blood brain barrier permeability, microglial activation, systemic inflammation, and biochemical composition of the brain were assessed 3 hours following photothrombosis, and significant protection was observed in mice deficient in neuronal and astrocytic IGF-1R. When the extent of tissue damage and sensorimotor dysfunction was assessed for 3 days following stroke, only the neurological deficit score continued to show improvements, and the extent of improvement was enhanced with additional IGF-1 supplementation. Overall, results indicate that neuronal and astrocytic IGF-1 signaling influences stroke damage but IGF-1 signaling within these individual cell types is not required for minimizing tissue damage or behavioral outcome.

Hot Spots for the Use of Intranasal Insulin: Cerebral Ischemia, Brain Injury, Diabetes Mellitus, Endocrine Disorders and Postoperative Delirium

A decrease in the activity of the insulin signaling system of the brain, due to both central insulin resistance and insulin deficiency, leads to neurodegeneration and impaired regulation of appetite, metabolism, endocrine functions. This is due to the neuroprotective properties of brain insulin and its leading role in maintaining glucose homeostasis in the brain, as well as in the regulation of the brain signaling network responsible for the functioning of the nervous, endocrine, and other systems. One of the approaches to restore the activity of the insulin system of the brain is the use of intranasally administered insulin (INI). Currently, INI is being considered as a promising drug to treat Alzheimer's disease and mild cognitive impairment. The clinical application of INI is being developed for the treatment of other neurodegenerative diseases and improve cognitive abilities in stress, overwork, and depression. At the same time, much attention has recently been paid to the prospects of using INI for the treatment of cerebral ischemia, traumatic brain injuries, and postoperative delirium (after anesthesia), as well as diabetes mellitus and its complications, including dysfunctions in the gonadal and thyroid axes. This review is devoted to the prospects and current trends in the use of INI for the treatment of these diseases, which, although differing in etiology and pathogenesis, are characterized by impaired insulin signaling in the brain.

Postnatal serum IGF-1 levels associate with brain volumes at term in extremely preterm infants

BACKGROUND

Growth factors important for normal brain development are low in preterm infants. This study investigated the link between growth factors and preterm brain volumes at term.

MATERIAL/METHODS

Infants born <28 weeks gestational age (GA) were included. Endogenous levels of insulin-like growth factor (IGF)-1, brain-derived growth factor, vascular endothelial growth factor, and platelet-derived growth factor (expressed as area under the curve [AUC] for serum samples from postnatal days 1, 7, 14, and 28) were utilized in a multivariable linear regression model. Brain volumes were determined by magnetic resonance imaging (MRI) at term equivalent age.

RESULTS

In total, 49 infants (median [range] GA 25.4 [22.9-27.9] weeks) were included following MRI segmentation quality assessment and AUC calculation. IGF-1 levels were independently positively associated with the total brain (p < 0.001, β = 0.90), white matter (p = 0.007, β = 0.33), cortical gray matter (p = 0.002, β = 0.43), deep gray matter (p = 0.008, β = 0.05), and cerebellar (p = 0.006, β = 0.08) volume adjusted for GA at birth and postmenstrual age at MRI. No associations were seen for other growth factors.

CONCLUSIONS

Endogenous exposure to IGF-1 during the first 4 weeks of life was associated with total and regional brain volumes at term. Optimizing levels of IGF-1 might improve brain growth in extremely preterm infants.

IMPACT

High serum levels of insulin-like growth factor (IGF)-1 during the first month of life were independently associated with increased total brain volume, white matter, gray matter, and cerebellar volume at term equivalent age in extremely preterm infants. IGF-1 is a critical regulator of neurodevelopment and postnatal levels are low in preterm infants. The effects of IGF-1 levels on brain development in extremely preterm infants are not fully understood. Optimizing levels of IGF-1 may benefit early brain growth in extremely preterm infants. The effects of systemically administered IGF-1/IGFBP3 in extremely preterm infants are now being investigated in a randomized controlled trial (Clinicaltrials.gov: NCT03253263).

Pharmacological Neuroprotection of the Preterm Brain: Current Evidence and Perspectives

Despite improvements in viability, the long-term neurodevelopmental outcomes of preterm babies remain serious concern as a significant percentage of these infants develop neurological and/or intellectual impairment, and they are also at increased risk of psychiatric illnesses later in life. The current challenge is to develop neuroprotective approaches to improve adverse outcomes in preterm survivors. The purpose of this review was to provide an overview of the current evidence on pharmacological agents targeting the neuroprotection of the preterm brain. Among them, magnesium sulfate, given antenatally to pregnant women with imminent preterm birth before 30 to 34 weeks of gestation, as well as caffeine administered to preterm infants after birth, exhibited neuroprotective effects for human preterm brain. Erythropoietin treatment of preterm infants did not result in neuroprotection at 2 years of age in two out of three published large randomized controlled trials; however, long-term follow-up of these infants is needed to come to definite conclusions. Further studies are also required to assess whether melatonin, neurosteroids, inhaled nitric oxide, allopurinol, or dietary supplements (omega-3 fatty acids, choline, curcumin, etc.) could be implemented as neuroprotectants in clinical practice. Furthermore, other pharmacological agents showing promising signs of neuroprotective efficacy in preclinical studies (growth factors, hyaluronidase inhibitors or treatment, antidiabetic drugs, cannabidiol, histamine-H3 receptor antagonists, etc.), as well as stem cell- or exosomal-based therapies and nanomedicine, may prove useful in the future as potential neuroprotective approaches for human preterm brain. KEY POINTS: · Magnesium and caffeine have neuroprotective effects for the preterm brain.. · Follow-up of infants treated with erythropoietin is needed.. · Neuroprotective efficacy of several drugs in animals needs to be shown in humans..

Emerging neuroprotective interventions in periventricular leukomalacia: A systematic review of preclinical studies

INTRODUCTION

Periventricular leukomalacia (PVL) is a result of various antenatal, intrapartum, or postnatal insults to the developing brain and is an important harbinger of cerebral palsy in preterm neonates. There is no proven therapy for PVL. This calls for appraisal of targeted therapies that have been investigated in animal models to evaluate their relevance in clinical research context.

AREAS COVERED

This systematic review identifies interventions that were evaluated in preclinical studies for neuroprotective efficacy against PVL. We identified 142 studies evaluating various interventions in PVL animal models. (Search method is detailed in section 2).

EXPERT OPINION

Interventions that have yielded significant results in preclinical research, and that have been evaluated in a limited number of clinical trials include stem cells, erythropoietin, and melatonin. Many other therapeutic modalities evaluated in preclinical studies have been identified, but more data on their neuroprotective potential in PVL must be garnered before they can be considered for clinical trials. Because most of the tested interventions had only a partial efficacy, a combination of interventions that could be synergistic should be investigated in future preclinical studies. Furthermore, since the nature and pattern of perinatal insults to preterm brain predisposing it to PVL are substantially variable, individualised approaches for the choice of appropriate neuroprotective interventions tailored to different sub-groups of preterm neonates should be explored.

Oligodendrocyte Development and Implication in Perinatal White Matter Injury

Perinatal white matter injury (WMI) is the most common brain injury in premature infants and can lead to life-long neurological deficits such as cerebral palsy. Preterm birth is typically accompanied by inflammation and hypoxic-ischemic events. Such perinatal insults negatively impact maturation of oligodendrocytes (OLs) and cause myelination failure. At present, no treatment options are clinically available to prevent or cure WMI. Given that arrested OL maturation plays a central role in the etiology of perinatal WMI, an increased interest has emerged regarding the functional restoration of these cells as potential therapeutic strategy. Cell transplantation and promoting endogenous oligodendrocyte function are two potential options to address this major unmet need. In this review, we highlight the underlying pathophysiology of WMI with a specific focus on OL biology and their implication for the development of new therapeutic targets.

Transplanted Oligodendrocyte Progenitor Cells Survive in the Brain of a Rat Neonatal White Matter Injury Model but Less Mature in Comparison with the Normal Brain

Preterm infants have a high risk of neonatal white matter injury (WMI) caused by hypoxia-ischemia. Cell-based therapies are promising strategies for neonatal WMI by providing trophic substances and replacing lost cells. Using a rat model of neonatal WMI in which oligodendrocyte progenitors (OPCs) are predominantly damaged, we investigated whether insulin-like growth factor 2 (IGF2) has trophic effects on OPCs in vitro and whether OPC transplantation has potential as a cell replacement therapy. Enhanced expression of Igf2 mRNA was first confirmed in the brain of P5 model rats by real-time polymerase chain reaction. Immunostaining for IGF2 and its receptor IGF2 R revealed that both proteins were co-expressed in OLIG2-positive and GFAP-positive cells in the corpus callosum (CC), indicating autocrine and paracrine effects of IGF2. To investigate the in vitro effect of IGF2 on OPCs, IGF2 (100 ng/ml) was added to the differentiation medium containing ciliary neurotrophic factor (10 ng/ml) and triiodothyronine (20 ng/ml), and IGF2 promoted the differentiation of OPCs into mature oligodendrocytes. We next transplanted rat-derived OPCs that express green fluorescent protein into the CC of neonatal WMI model rats without immunosuppression and investigated the survival of grafted cells for 8 weeks. Although many OPCs survived for at least 8 weeks, the number of mature oligodendrocytes was unexpectedly small in the CC of the model compared with that in the sham-operated control. These findings suggest that the mechanism in the brain that inhibits differentiation should be solved in cell replacement therapy for neonatal WMI as same as trophic support from IGF2.

Hippocampal epigenetic and insulin-like growth factor alterations in noninvasive versus invasive mechanical ventilation in preterm lambs

BACKGROUND

The brain of chronically ventilated preterm human infants is vulnerable to collateral damage during invasive mechanical ventilation (IMV). Damage is manifest, in part, by learning and memory impairments, which are hippocampal functions. A molecular regulator of hippocampal development is insulin-like growth factor 1 (IGF1). A gentler ventilation strategy is noninvasive respiratory support (NRS). We tested the hypotheses that NRS leads to greater levels of IGF1 messenger RNA (mRNA) variants and distinct epigenetic profile along the IGF1 gene locus in the hippocampus compared to IMV.

METHODS

Preterm lambs were managed by NRS or IMV for 3 or 21 days. Isolated hippocampi were analyzed for IGF1 mRNA levels and splice variants for promoter 1 (P1), P2, and IGF1A and 1B, DNA methylation in P1 region, and histone covalent modifications along the gene locus.

RESULTS

NRS had significantly greater levels of IGF1 P1 (predominant transcript), and 1A and 1B mRNA variants compared to IMV at 3 or 21 days. NRS also led to more DNA methylation and greater occupancy of activating mark H3K4 trimethylation (H3K4me³), repressive mark H3K27me³, and elongation mark H3K36me³ compared to IMV.

CONCLUSIONS

NRS leads to distinct IGF1 mRNA variant levels and epigenetic profile in the hippocampus compared to IMV.

IMPACT

Our study shows that 3 or 21 days of NRS of preterm lambs leads to distinct IGF1 mRNA variant levels and epigenetic profile in the hippocampus compared to IMV. Preterm infant studies suggest that NRS leads to better neurodevelopmental outcomes later in life versus IMV. Also, duration of IMV is directly related to hippocampal damage; however, molecular players remain unknown. NRS, as a gentler mode of respiratory management of preterm neonates, may reduce damage to the immature hippocampus through an epigenetic mechanism.

Regenerative Therapies to Restore Interneuron Disturbances in Experimental Models of Encephalopathy of Prematurity

Encephalopathy of Prematurity (EoP) is a major cause of morbidity in (extreme) preterm neonates. Though the majority of EoP research has focused on failure of oligodendrocyte maturation as an underlying pathophysiological mechanism, recent pioneer work has identified developmental disturbances in inhibitory interneurons to contribute to EoP. Here we investigated interneuron abnormalities in two experimental models of EoP and explored the potential of two promising treatment strategies, namely intranasal mesenchymal stem cells (MSCs) or insulin-like growth factor I (IGF1), to restore interneuron development. In rats, fetal inflammation and postnatal hypoxia led to a transient increase in total cortical interneuron numbers, with a layer-specific deficit in parvalbumin (PV)+ interneurons. Additionally, a transient excess of total cortical cell density was observed, including excitatory neuron numbers. In the hippocampal cornu ammonis (CA) 1 region, long-term deficits in total interneuron numbers and PV+ subtype were observed. In mice subjected to postnatal hypoxia/ischemia and systemic inflammation, total numbers of cortical interneurons remained unaffected; however, subtype analysis revealed a global, transient reduction in PV+ cells and a long-lasting layer-specific increase in vasoactive intestinal polypeptide (VIP)+ cells. In the dentate gyrus, a long-lasting deficit of somatostatin (SST)+ cells was observed. Both intranasal MSC and IGF1 therapy restored the majority of interneuron abnormalities in EoP mice. In line with the histological findings, EoP mice displayed impaired social behavior, which was partly restored by the therapies. In conclusion, induction of experimental EoP is associated with model-specific disturbances in interneuron development. In addition, intranasal MSCs and IGF1 are promising therapeutic strategies to aid interneuron development after EoP.

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.

Intranasal Delivery: Effects on the Neuroimmune Axes and Treatment of Neuroinflammation

This review highlights the pre-clinical and clinical work performed to use intranasal delivery of various compounds from growth factors to stem cells to reduce neuroimmune interactions. We introduce the concept of intranasal (IN) delivery and the variations of this delivery method based on the model used (i.e., rodents, non-human primates, and humans). We summarize the literature available on IN delivery of growth factors, vitamins and metabolites, cytokines, immunosuppressants, exosomes, and lastly stem cells. We focus on the improvement of neuroimmune interactions, such as the activation of resident central nervous system (CNS) immune cells, expression or release of cytokines, and detrimental effects of signaling processes. We highlight common diseases that are linked to dysregulations in neuroimmune interactions, such as Alzheimer's disease, Parkinson's disease, stroke, multiple sclerosis, and traumatic brain injury.

Structural and biochemical imaging reveals systemic LPS-induced changes in the rat brain

Despite mounting evidence for the role of inflammation in Major Depressive Disorder (MDD), in vivo preclinical investigations of inflammation-induced negative affect using whole brain imaging modalities are scarce, precluding a valid model within which to evaluate pharmacological interventions. Here we used an E. coli lipopolysaccharide (LPS)-based model of inflammation-induced depressive signs in rats to explore brain changes using multimodal neuroimaging methods. During the acute phase of the LPS response (2 h post injection), prior to the emergence of a task-quantifiable depressive phenotype, striatal glutamine levels and splenial, retrosplenial, and peri-callosal hippocampal cortex volumes were greater than at baseline. LPS-induced depressive behaviors observed at 24 h, however, occurred concurrently with lower than control levels of striatal glutamine and a reversibility of volume expansion (i.e., shrinkage of splenial, retrosplenial, and peri-callosal hippocampal cortex to baseline volumes). In both striatum and hippocampus at 24 h, mRNA expression in LPS relative to control animals demonstrated alterations in enzymes and transporters regulating glutamine homeostasis. Collectively, the observed behavioral, in vivo structural and metabolic, and mRNA expression alterations suggest a critical role for astrocytic regulation of inflammation-induced depressive behaviors.

Central IGF-1 protects against features of cognitive and sensorimotor decline with aging in male mice

Disruptions in growth hormone/insulin-like growth factor-1 (GH/IGF-1) signaling have been linked to improved longevity in mice and humans. Nevertheless, while IGF-1 levels are associated with increased cancer risk, they have been paradoxically implicated with protection from other age-related conditions, particularly in the brain, suggesting that strategies aimed at selectively increasing central IGF-1 action may have favorable effects on aging. To test this hypothesis, we generated inducible, brain-specific (TRE-IGF-1 × Camk2a-tTA) IGF-1 (bIGF-1) overexpression mice and studied effects on healthspan. Doxycycline was removed from the diet at 12 weeks old to permit post-development brain IGF-1 overexpression, and animals were monitored up to 24 months. Brain IGF-1 levels were increased approximately twofold in bIGF-1 mice, along with greater brain weights, volume, and myelin density (P < 0.05). Age-related changes in rotarod performance, exercise capacity, depressive-like behavior, and hippocampal gliosis were all attenuated specifically in bIGF-1 male mice (P < 0.05). However, chronic brain IGF-1 failed to prevent declines in cognitive function or neurovascular coupling. Therefore, we performed a short-term intranasal (IN) treatment of either IGF-1 or saline in 24-month-old male C57BL/6 mice and found that IN IGF-1 treatment tended to reduce depressive (P = 0.09) and anxiety-like behavior (P = 0.08) and improve motor coordination (P = 0.07) and unlike transgenic mice improved motor learning (P < 0.05) and visuospatial and working memory (P < 0.05). These data highlight important sex differences in how brain IGF-1 action impacts healthspan and suggest that translational approaches that target IGF-1 centrally can restore cognitive function, a possibility that should be explored as a strategy to combat age-related cognitive decline.

Hormonal Changes Associated With Intra-Uterine Growth Restriction: Impact on the Developing Brain and Future Neurodevelopment

The environment in which a fetus develops is not only important for its growth and maturation but also for its long-term postnatal health and neurodevelopment. Several hormones including glucocorticosteroids, estrogens and progesterone, insulin growth factor and thyroid hormones, carefully regulate the growth of the fetus and its metabolism during pregnancy by controlling the supply of nutrients crossing the placenta. In addition to fetal synthesis, hormones regulating fetal growth are also expressed and regulated in the placenta, and they play a key role in the vulnerability of the developing brain and its maturation. This review summarizes the current understanding and evidence regarding the involvement of hormonal dysregulation associated with intra-uterine growth restriction and its consequences on brain development.

rhIGF-1 reduces the permeability of the blood-brain barrier following intracerebral hemorrhage in mice

Disruption of the blood-brain barrier results in the formation of edema and contributes to the loss of neurological function following intracerebral hemorrhage (ICH). This study examined insulin-like growth factor-1 (IGF-1) as a treatment and its mechanism of action for protecting the blood-brain barrier after ICH in mice. 171 Male CD-1 mice were subjected to ICH via collagenase or autologous blood. A dose study for recombinant human IGF-1 (rhIGF-1) was performed. Brain water content and behavioral deficits were evaluated at 24 and 72 h after the surgery, and Evans blue extravasation and hemoglobin assay were conducted at 24 h. Western blotting was performed for the mechanism study and interventions were used targeting the IGF-1R/GSK3β/MEKK1 pathway. rhIGF-1 reduced edema and blood-brain barrier permeability, and improved neurobehavior outcomes. Western blots showed that rhIGF-1 reduced p-GSK3β and MEKK1 expression, thereby increasing occludin and claudin-5 expression. Inhibition and knockdown of IGF-1R reversed the therapeutic benefits of rhIGF-1. The findings within suggest that stimulation of the IGF-1R is a therapeutic target for ICH which may lead to improved neurofunctional and blood-brain barrier protection.

The role of inflammation in subventricular zone cancer

The adult subventricular zone (SVZ) stem cell niche has proven vital for discovering neurodevelopmental mechanisms and holds great potential in medicine for neurodegenerative diseases. Yet the SVZ holds a dark side - it can become tumorigenic. Glioblastomas can arise from the SVZ via cancer stem cells (CSCs). Glioblastoma and other brain cancers often have dismal prognoses since they are resistant to treatment. In this review we argue that the SVZ is susceptible to cancer because it contains stem cells, migratory progenitors and unusual inflammation. Theoretically, SVZ stem cells can convert to CSCs more readily than can postmitotic neural cells. Additionally, the robust long-distance migration of SVZ progenitors can be subverted upon tumorigenesis to an infiltrative phenotype. There is evidence that the SVZ, even in health, exhibits chronic low-grade cellular and molecular inflammation. Its inflammatory response to brain injuries and disease differs from that of other brain regions. We hypothesize that the SVZ inflammatory environment can predispose cells to novel mutations and exacerbate cancer phenotypes. This can be studied in animal models in which human mutations related to cancer are knocked into the SVZ to induce tumorigenesis and the CSC immune interactions that precede full-blown cancer. Importantly inflammation can be pharmacologically modulated providing an avenue to brain cancer management and treatment. The SVZ is accessible by virtue of its location surrounding the lateral ventricles and CSCs in the SVZ can be targeted with a variety of pharmacotherapies. Thus, the SVZ can yield aggressive tumors but can be targeted via several strategies.

Nutrient Sensing, Signaling and Ageing: The Role of IGF-1 and mTOR in Ageing and Age-Related Disease

Nutrient signaling through insulin/IGF-1 was the first pathway demonstrated to regulate ageing and age-related disease in model organisms. Pharmacological or dietary interventions targeting nutrient signaling pathways have been shown to robustly attenuate ageing in many organisms. Caloric restriction, the most widely studied longevity promoting intervention, works through multiple nutrient signaling pathways, while inhibition of mTOR through treatment with rapamycin reproducibly delays ageing and disease through specific inhibition of the mTOR complexes. Although the benefits of reduced insulin/IGF-1 in lifespan and health are well documented in model organisms, defining the precise role of the IGF-1 in human ageing and age-related disease has proven more difficult. Association studies provide some insight but also reveal paradoxes. Low serum IGF-1 predicts longevity, but IGF-1 decreases with age and IGF-1 therapy benefits some of age-related pathologies. Circulating IGF-1 has been associated both positively and negatively with risk of age-related diseases in humans, and in some cases both activation and inhibition of IGF-1 signaling have provided benefit in animal models of the same diseases. Interventions designed modulate the nutrient sensing signaling pathways positively or negatively are already available for clinical use, highlighting the need for a clear understanding of the role of nutrient signaling in ageing and age-related disease. This chapter examines data from model organisms and human genetic association studies, with a special emphasis on IGF-1 and mTOR, and discusses potential models for resolving the paradoxes surrounding IGF-1 data.

Origin and dynamics of oligodendrocytes in the developing brain: Implications for perinatal white matter injury

Infants born prematurely are at high risk to develop white matter injury (WMI), due to exposure to hypoxic and/or inflammatory insults. Such perinatal insults negatively impact the maturation of oligodendrocytes (OLs), thereby causing deficits in myelination. To elucidate the precise pathophysiology underlying perinatal WMI, it is essential to fully understand the cellular mechanisms contributing to healthy/normal white matter development. OLs are responsible for myelination of axons. During brain development, OLs are generally derived from neuroepithelial zones, where neural stem cells committed to the OL lineage differentiate into OL precursor cells (OPCs). OPCs, in turn, develop into premyelinating OLs and finally mature into myelinating OLs. Recent studies revealed that OPCs develop in multiple waves and form potentially heterogeneous populations. Furthermore, it has been shown that myelination is a dynamic and plastic process with an excess of OPCs being generated and then abolished if not integrated into neural circuits. Myelination patterns between rodents and humans show high spatial and temporal similarity. Therefore, experimental studies on OL biology may provide novel insights into the pathophysiology of WMI in the preterm infant and offers new perspectives on potential treatments for these patients.

Nose-to-brain peptide delivery - The potential of nanotechnology

Nose-to-brain (N-to-B) delivery offers to protein and peptide drugs the possibility to reach the brain in a non-invasive way. This article is a comprehensive review of the state-of-the-art of this emerging peptide delivery route, as well as of the challenges associated to it. Emphasis is given on the potential of nanosized drug delivery carriers to enhance the direct N-to-B transport of protein or peptide drugs. In particular, polymer- and lipid- based nanocarriers are comparatively analyzed in terms of the influence of their physicochemical characteristics and composition on their in vivo fate and efficacy. The use of biorecognitive ligands and permeation enhancers in order to enhance their brain targeting efficiency is also discussed. The article concludes highlighting the early stage of this research field and its still unveiled potential. The final message is that more explicatory PK/PD studies are required in order to achieve the translation from preclinical to the clinical development phase.

Neuroprotective Effects of Intranasal IGF-1 against Neonatal Lipopolysaccharide-Induced Neurobehavioral Deficits and Neuronal Inflammation in the Substantia Nigra and Locus Coeruleus of Juvenile Rats

Neonatal lipopolysaccharide (LPS) exposure-induced brain inflammation resulted in motor dysfunction and brain dopaminergic neuronal injury, and increased the risks of neurodegenerative disorders in adult rats. Our previous studies showed that intranasal administration of insulin-like growth factor-1 (IGF-1) protects against LPS-induced white matter injury in the developing rat brain. To further examine whether IGF-1 protects against LPS-induced brain neuronal injury and neurobehavioral dysfunction, recombinant human IGF-1 (rhIGF-1) at a dose of 50 µg/pup was administered intranasally 1 h following intracerebral injection of LPS (1 mg/kg) in postnatal day 5 (P5) Sprague-Dawley rat pups. Neurobehavioral tests were carried out from P7 to P21, and brain neuronal injury was examined at P21. Our results showed that LPS exposure resulted in disturbances of motor behaviors in juvenile rats. Moreover, LPS exposure caused injury to central catecholaminergic neurons, as indicated by a reduction of tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra (SN), ventral tegmental area (VTA) and olfactory bulb (OB), and brain noradrenergic neurons, as indicated by a reduction of TH immunoreactivity in the locus coeruleus (LC) of the P21 rat brain. The LPS-induced reduction of TH+ cells was observed at a greater degree in the SN and LC of the P21 rat brain. Intranasal rhIGF-1 treatment attenuated LPS-induced central catecholaminergic neuronal injury and motor behavioral disturbances, including locomotion, beam walking test and gait analysis. Intranasal rhIGF-1 administration also attenuated LPS-induced elevation of IL-1β levels and numbers of activated microglia, and cyclooxygenase-2+ cells, which were double labeled with TH+ cells in the SN, VTA, OB and LC of the P21 rat brain. These results suggest that IGF-1 may provide protection against neonatal LPS exposure-induced central catecholaminergic neuronal injury and motor behavioral disturbances, and that the protective effects are associated with the inhibition of microglia activation and the reduction of neuronal oxidative stress by the suppression of the neuronal cyclooxygenase-2 expression.

Intranasal surfactant protein D as neuroprotective rescue in a neonatal rat model of periventricular leukomalacia

BACKGROUND

Periventricular leukomalacia (PVL) is the leading cause of neurocognitive deficits in children with prematurity. We previously hypothesized that surfactant protein D (SPD) with its ability to bind toll-like receptors may have a possible ameliorating effect in PVL.

METHODS

Three groups were defined as: LPS-administered and postnatal intranasal saline administered group, LPS-administered and postnatal intranasal SPD-treated group, and control group. Twenty-eight offspring rats were reared with their dams until their sacrifice for histological evaluation on day 7.

RESULTS

A significant loss of brain weight occurred in the LPS group compared with controls. The postnatal intranasal SPD treatment significantly reduced the number of TUNEL-positive cells in the periventricular white matter as compared with the LPS-treated group. Compared with the control group, LPS injection in the rat brain significantly reduced the MBP-positive staining. Postnatal SPD treatment greatly prevented LPS-stimulated loss of MBP staining.

CONCLUSIONS

Present study demonstrated a neuroprotective effect of SPD in a rat model of PVL. Our results offer future implications towards increasing our understanding about multifactorial mechanisms underlying periventricular leukomalacia and developing plausible therapeutic strategies in order to prevent neurocognitive deficits in preterm infants.

Effect of insulin-like growth factor-I during the early postnatal period in intrauterine growth-restricted rats

BACKGROUND

Insulin-like growth factor-I (IGF-I) is essential for perinatal growth and development; low serum IGF-I has been observed during intrauterine growth restriction (IUGR). We investigated the effects of recombinant human (rh) IGF-I in IUGR rats during the early postnatal period.

METHODS

Intrauterine growth restriction was induced by bilateral uterine artery ligation in pregnant rats. IUGR pups were divided into two groups injected daily with rhIGF-I (2 mg/kg; IUGR/IGF-I, n = 16) or saline (IUGR/physiologic saline solution (PSS), n = 16) from postnatal day (PND) 7 to 13. Maternal sham-operated pups injected with saline were used as controls (control, n = 16). Serum IGF-I and IGF binding proteins (IGFBP) 3 and 5 were measured on PND25. The expression of Igf-i, IGF-I receptor (Igf-ir), Igfbp3, and 5 mRNA in the liver and brain was measured using real-time polymerase chain reaction on PND25. Immunohistochemical staining of the liver for IGF expression was performed.

RESULTS

Mean bodyweight on PND3 and PND25 in the IUGR pups (IUGR/IGF-I and IUGR/PSS) was significantly lower than that of the control pups. Serum IGF-I and hepatic Igf-ir mRNA in the IUGR pups were significantly lower than those in the control pups. In the IUGR/IGF-I group, hepatic Igfbp3 mRNA and liver immunohistochemical staining were increased. In the IUGR/PSS and control pups, there were no significant differences between these two groups in serum IGFBP3 and IGFBP5, hepatic Igf-i and Igfbp-5 mRNA, or brain Igf mRNA.

CONCLUSIONS

No benefits on body and brain weight gain but an effective increase in hepatic IGFBP-3 was observed after treatment with 2 mg/kg rhIGF-I during the early postnatal period.

Inhibition of microRNA-210 provides neuroprotection in hypoxic-ischemic brain injury in neonatal rats

Perinatal hypoxic-ischemic encephalopathy (HIE) is associated with high neonatal mortality and severe long-term neurologic morbidity. Yet the mechanisms of brain injury in infants with HIE remain largely elusive. The present study determined a novel mechanism of microRNA-210 (miR-210) in silencing endogenous neuroprotection and increasing hypoxic-ischemic brain injury in neonatal rats. The study further revealed a potential therapeutic effect of miR-210 inhibition using complementary locked nucleic acid oligonucleotides (miR-210-LNA) in 10-day-old neonatal rats in the Rice-Vannucci model. The underlying mechanisms were investigated with intracerebroventricular injection (i.c.v) of miR-210 mimic, miR-210-LNA, glucocorticoid receptor (GR) agonist and antagonist. Luciferase reporter gene assay was conducted for identification of miR-210 targeting GR 3'untranslated region. The results showed that the HI treatment significantly increased miR-210 levels in the brain, and miR-210 mimic significantly decreased GR protein abundance and exacerbated HI brain injury in the pups. MiR-210-LNA administration via i.c.v. 4h after the HI insult significantly decreased brain miR-210 levels, increased GR protein abundance, reduced HI-induced neuronal death and brain infarct size, and improved long-term neurological function recovery. Of importance, the intranasal delivery of miR-210-LNA 4h after the HI insult produced similar effects in decreasing HI-induced neonatal brain injury and improving neurological function later in life. Altogether, the present study provides evidence of a novel mechanism of miR-210 in a neonatal HI brain injury model, and suggests a potential therapeutic approach of miR-210 inhibition in the treatment of neonatal HIE.

Central insulin-like growth factor-1 (IGF-1) restores whole-body insulin action in a model of age-related insulin resistance and IGF-1 decline

Low insulin‐like growth factor‐1 (IGF‐1) signaling is associated with improved longevity, but is paradoxically linked with several age‐related diseases in humans. Insulin‐like growth factor‐1 has proven to be particularly beneficial to the brain, where it confers protection against features of neuronal and cognitive decline. While aging is characterized by central insulin resistance in the face of hyperinsulinemia, the somatotropic axis markedly declines in older humans. Thus, we hypothesized that increasing IGF‐1 in the brain may prove to be a novel therapeutic alternative to overcome central insulin resistance and restore whole‐body insulin action in aging. Utilizing hyperinsulinemic‐euglycemic clamps, we show that old insulin‐resistant rats with age‐related declines in IGF‐1 level demonstrate markedly improved whole‐body insulin action, when treated with central IGF‐1, as compared to central vehicle or insulin (P < 0.05). Furthermore, central IGF‐1, but not insulin, suppressed hepatic glucose production and increased glucose disposal rates in aging rats (P < 0.05). Taken together, IGF‐1 action in the brain and periphery provides a ‘balance’ between its beneficial and detrimental actions. Therefore, we propose that strategies aimed at ‘tipping the balance’ of IGF‐1 action centrally are the optimal approach to achieve healthy aging and longevity in humans.

Intranasal insulin protects against substantia nigra dopaminergic neuronal loss and alleviates motor deficits induced by 6-OHDA in rats

Protection of substantia nigra (SN) dopaminergic (DA) neurons by neurotrophic factors (NTFs) is one of the promising strategies in Parkinson's disease (PD) therapy. A major clinical challenge for NTF-based therapy is that NTFs need to be delivered into the brain via invasive means, which often shows limited delivery efficiency. The nose to brain pathway is a non-invasive brain drug delivery approach developed in recent years. Of particular interest is the finding that intranasal insulin improves cognitive functions in Alzheimer's patients. In vitro, insulin has been shown to protect neurons against various insults. Therefore, the current study was designed to test whether intranasal insulin could afford neuroprotection in the 6-hydroxydopamine (6-OHDA)-based rat PD model. 6-OHDA was injected into the right side of striatum to induce a progressive DA neuronal lesion in the ipsilateral SN pars compact (SNc). Recombinant human insulin was applied intranasally to rats starting from 24h post lesion, once per day, for 2 weeks. A battery of motor behavioral tests was conducted on day 8 and 15. The number of DA neurons in the SNc was estimated by stereological counting. Our results showed that 6-OHDA injection led to significant motor deficits and 53% of DA neuron loss in the ipsilateral side of injection. Treatment with insulin significantly ameliorated 6-OHDA-induced motor impairments, as shown by improved locomotor activity, tapered/ledged beam-walking performance, vibrissa-elicited forelimb-placing, initial steps, as well as methamphetamine-induced rotational behavior. Consistent with behavioral improvements, insulin treatment provided a potent protection of DA neurons in the SNc against 6-OHDA neurotoxicity, as shown by a 74.8% increase in tyrosine hydroxylase (TH)-positive neurons compared to the vehicle group. Intranasal insulin treatment did not affect body weight and blood glucose levels. In conclusion, our study showed that intranasal insulin provided strong neuroprotection in the 6-OHDA rat PD model, suggesting that insulin signaling may be a novel therapeutic target in broad neurodegenerative disorders.

Impaired oligodendrocyte maturation in preterm infants: Potential therapeutic targets

Preterm birth is an evolving challenge in neonatal health care. Despite declining mortality rates among extremely premature neonates, morbidity rates remain very high. Currently, perinatal diffuse white matter injury (WMI) is the most commonly observed type of brain injury in preterm infants and has become an important research area. Diffuse WMI is associated with impaired cognitive, sensory and psychological functioning and is increasingly being recognized as a risk factor for autism-spectrum disorders, ADHD, and other psychological disturbances. No treatment options are currently available for diffuse WMI and the underlying pathophysiological mechanisms are far from being completely understood. Preterm birth is associated with maternal inflammation, perinatal infections and disrupted oxygen supply which can affect the cerebral microenvironment by causing activation of microglia, astrogliosis, excitotoxicity, and oxidative stress. This intricate interplay of events negatively influences oligodendrocyte development, causing arrested oligodendrocyte maturation or oligodendrocyte cell death, which ultimately results in myelination failure in the developing white matter. This review discusses the current state in perinatal WMI research, ranging from a clinical perspective to basic molecular pathophysiology. The complex regulation of oligodendrocyte development in healthy and pathological conditions is described, with a specific focus on signaling cascades that may play a role in WMI. Furthermore, emerging concepts in the field of WMI and issues regarding currently available animal models are put forward. Novel insights into the molecular mechanisms underlying impeded oligodendrocyte maturation in diffuse WMI may aid the development of novel treatment options which are desperately needed to improve the quality-of-life of preterm neonates.

Intranasal gene delivery for treating Parkinson's disease: overcoming the blood-brain barrier

INTRODUCTION

Developing a disease-modifying gene therapy for Parkinson's disease (PD) has been a high priority for over a decade. However, due to the inability of large biomolecules to cross the blood-brain barrier (BBB), the only means of delivery to the brain has been intracerebral infusion. Intranasal administration offers a non-surgical means of bypassing the BBB to deliver neurotrophic factors, and the genes encoding them, directly to the brain.

AREAS COVERED

This review summarizes: i) evidence demonstrating intranasal delivery to the brain of a number of biomolecules having therapeutic potential for various CNS disorders; and ii) evidence demonstrating neuroprotective efficacy of a subset of biomolecules specifically for PD. The intersection of these two spheres represents the area of opportunity for development of new intranasal gene therapies for PD. To that end, our laboratory showed that intranasal administration of glial cell line-derived neurotrophic factor (GDNF), or plasmid DNA nanoparticles encoding GDNF, provides neuroprotection in a rat model of PD, and that the cells transfected by the nanoparticle vector are likely to be pericytes.

EXPERT OPINION

A number of genes encoding neurotrophic factors have therapeutic potential for PD, but few have been tested by the intranasal route and shown to be neuroprotective in a model of PD. Intranasal delivery provides a largely unexplored, promising approach for development of a non-invasive gene therapy for PD.

Enhanced memory consolidation in mice lacking the circadian modulators Sharp1 and -2 caused by elevated Igf2 signaling in the cortex

The bHLH transcription factors SHARP1 and SHARP2 are partially redundant modulators of the circadian system. SHARP1/DEC2 has been shown to control sleep length in humans and sleep architecture is also altered in double mutant mice (S1/2(-/-)). Because of the importance of sleep for memory consolidation, we investigated the role of SHARP1 and SHARP2 in cognitive processing. S1/2(-/-) mice show enhanced cortex (Cx)-dependent remote fear memory formation as well as improved reversal learning, but do not display alterations in hippocampus (Hi)-dependent recent fear memory formation. SHARP1 and SHARP2 single null mutants do not display any cognitive phenotype supporting functional redundancy of both factors. Molecular and biochemical analyses revealed elevated insulin-related growth factor 2 (IGF2) signaling and increased phosphorylation of MAPK and S6 in the Cx but not the Hi of S1/2(-/-) mice. No changes were detected in single mutants. Moreover, adeno-associated virus type 2-mediated IGF2 overexpression in the anterior cingulate cortex enhanced remote fear memory formation and the analysis of forebrain-specific double null mutants of the Insulin and IGF1 receptors revealed their essential function for memory formation. Impaired fear memory formation in aged S1/2(-/-) mice indicates that elevated IGF2 signaling in the long term, however, has a negative impact on cognitive processing. In summary, we conclude that the bHLH transcription factors SHARP1 and SHARP2 are involved in cognitive processing by controlling Igf2 expression and associated signaling cascades. Our analyses provide evidence that the control of sleep and memory consolidation may share common molecular mechanisms.

Neonatal manipulation of oxytocin prevents lipopolysaccharide-induced decrease in gene expression of growth factors in two developmental stages of the female rat

Oxytocin production and secretion is important for early development of the brain. Long-term consequences of manipulation of oxytocin system might include changes in markers of brain plasticity - cytoskeletal proteins and neurotrophins. The aim of the present study was (1) to determine whether neonatal oxytocin administration affects gene expression of nestin, microtubule-associated protein-2 (MAP-2), brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the brain of two developmental stages of rat and (2) to evaluate whether neonatal oxytocin administration protects against lipopolysaccharide (LPS) induced inflammation. Neonatal oxytocin did not prevent a decrease of body weight in the LPS treated animals. Oxytocin significantly increased gene expression of BDNF in the right hippocampus in 21-day and 2-month old rats of both sexes. Gene expression of NGF and MAP-2 significantly increased in males treated with oxytocin. Both, growth factors and intermediate filament-nestin mRNA levels, were reduced in females exposed to LPS. Oxytocin treatment prevented a decrease in the gene expression of only growth factors. In conclusion, neonatal manipulation of oxytocin has developmental and sex-dependent effect on markers of brain plasticity. These results also indicate, that oxytocin may be protective against inflammation particularly in females.

The challenge of understanding cerebral white matter injury in the premature infant

White matter injury in the premature infant leads to motor and more commonly behavioral and cognitive problems that are a tremendous burden to society. While there has been much progress in understanding unique vulnerabilities of developing oligodendrocytes over the past 30years, there remain no proven therapies for the premature infant beyond supportive care. The lack of translational progress may be partially explained by the challenge of developing relevant animal models when the etiology remains unclear, as is the case in this disorder. There has been an emphasis on hypoxia-ischemia and infection/inflammation as upstream etiologies, but less consideration of other contributory factors. This review highlights the evolution of white matter pathology in the premature infant, discusses the prevailing proposed etiologies, critically analyzes a sampling of common animal models and provides detailed support for our hypothesis that nutritional and hormonal deprivation may be additional factors playing critical and overlooked roles in white matter pathology in the premature infant.

Interleukin-1 receptor blockade in perinatal brain injury

Interleukin-1 (IL-1) is a potent inflammatory cytokine that can be produced by a variety of cell types throughout the body. While IL-1 is a central mediator of inflammation and response to infection, the role of IL-1 signaling in adult and pediatric brain injury is becoming increasingly clear. Although the mechanisms of IL-1 expression are largely understood, the downstream effects and contributions to excitotoxicity and oxidative stress are poorly defined. Here, we present a review of mechanisms of IL-1 signaling with a focus on the role of IL-1 in perinatal brain injury. We highlight research models of perinatal brain injury and the use of interleukin-1 receptor antagonist (IL-1RA) as an agent of therapeutic potential in preventing perinatal brain injury due to exposure to inflammation.

IGF-1 intranasal administration rescues Huntington's disease phenotypes in YAC128 mice

Huntington's disease (HD) is an autosomal dominant disease caused by an expansion of CAG repeats in the gene encoding for huntingtin. Brain metabolic dysfunction and altered Akt signaling pathways have been associated with disease progression. Nevertheless, conflicting results persist regarding the role of insulin-like growth factor-1 (IGF-1)/Akt pathway in HD. While high plasma levels of IGF-1 correlated with cognitive decline in HD patients, other data showed protective effects of IGF-1 in HD striatal neurons and R6/2 mice. Thus, in the present study, we investigated motor phenotype, peripheral and central metabolic profile, and striatal and cortical signaling pathways in YAC128 mice subjected to intranasal administration of recombinant human IGF-1 (rhIGF-1) for 2 weeks, in order to promote IGF-1 delivery to the brain. We show that IGF-1 supplementation enhances IGF-1 cortical levels and improves motor activity and both peripheral and central metabolic abnormalities in YAC128 mice. Moreover, decreased Akt activation in HD mice brain was ameliorated following IGF-1 administration. Upregulation of Akt following rhIGF-1 treatment occurred concomitantly with increased phosphorylation of mutant huntingtin on Ser421. These data suggest that intranasal administration of rhIGF-1 ameliorates HD-associated glucose metabolic brain abnormalities and mice phenotype.

Circulatory insulin-like growth factor-I and brain volumes in relation to neurodevelopmental outcome in very preterm infants

BACKGROUND

To evaluate the relationships between postnatal change in circulatory insulin-like growth factor-I (IGF-I) concentrations, brain volumes, and developmental outcome at 2 y of age in very preterm infants.

METHODS

IGF-I was measured weekly, and nutritional intake was calculated daily from birth until a postmenstrual age (PMA) of 35 wk. Individual β coefficients for IGF-I, IGF-I(B), representing the rate of increase in IGF-I from birth until a PMA of 35 wk were calculated. Brain magnetic resonance imaging was performed at term age, with segmentation into total brain, cerebellar, gray matter, and unmyelinated white matter volume (UWMV). Developmental outcome was evaluated using Bayley Scales of Infant Development-II.

RESULTS

Forty-nine infants, with mean gestational age (GA) of 26.0 wk, were evaluated at mean 24.6 mo corrected age. Higher IGF-I(B), UWMV, and cerebellar volume were associated with a decreased risk for a Mental Developmental Index (MDI) < 85 (odds ratio (95% confidence interval): 0.6 (0.4-0.9), 0.96 (0.94-0.99), and 0.78 (0.6-0.96), respectively). In multivariate analysis, higher IGF-I(B) and higher UWMV combined with female gender constituted the two models with the highest predictive value for MDI > 85.

CONCLUSION

A higher rate of increase in circulating IGF-I is associated with a decreased risk for subnormal MDI at 2 y of corrected age. This relationship is in part dependent on brain volume at term age.

Oligodendroglial alterations and the role of microglia in white matter injury: relevance to schizophrenia

Schizophrenia is a chronic and debilitating mental illness characterized by a broad range of abnormal behaviors, including delusions and hallucinations, impaired cognitive function, as well as mood disturbances and social withdrawal. Due to the heterogeneous nature of the disease, the causes of schizophrenia are very complex; its etiology is believed to involve multiple brain regions and the connections between them, and includes alterations in both gray and white matter regions. The onset of symptoms varies with age and severity, and there is some debate over a degenerative or developmental etiology. Longitudinal magnetic resonance imaging studies have detected progressive gray matter loss in the first years of disease, suggesting neurodegeneration; but there is also increasing recognition of a temporal association between clinical complications at birth and disease onset that supports a neurodevelopmental origin. Presently, neuronal abnormalities in schizophrenia are better understood than alterations in myelin-producing cells of the brain, the oligodendrocytes, which are the predominant constituents of white matter structures. Proper white matter development and its structural integrity critically impacts brain connectivity, which affects sensorimotor coordination and cognitive ability. Evidence of defective white matter growth and compromised white matter integrity has been found in individuals at high risk of psychosis, and decreased numbers of mature oligodendrocytes are detected in schizophrenia patients. Inflammatory markers, including proinflammatory cytokines and chemokines, are also associated with psychosis. A relationship between risk of psychosis, white matter defects and prenatal inflammation is being established. Animal models of perinatal brain injury are successful in producing white matter damage in the brain, typified by hypomyelination and/or dysmyelination, impaired motor coordination and prepulse inhibition of the acoustic startle reflex, recapitulating structural and functional characteristics observed in schizophrenia. In addition, elevated expression of inflammation-related genes in brain tissue and increased production of cytokines by blood cells from patients with schizophrenia indicate immunological dysfunction and abnormal inflammatory responses, which are also important underlying features in experimental models. Microglia, resident immune defenders of the central nervous system, play important roles in the development and protection of neural cells, but can contribute to injury under pathological conditions. This article discusses oligodendroglial changes in schizophrenia and focuses on microglial activity in the context of the disease, in neonatal brain injury and in various experimental models of white matter damage. These include disorders associated with premature birth, and animal models of perinatal bacterial and viral infection, oxygen deprivation (hypoxia) and excess (hyperoxia), and elevated systemic proinflammatory cytokine levels. We briefly review the effects of treatment with antipsychotic and anti-inflammatory agents in models of perinatal brain injury, and comment on the therapeutic potential of these strategies. By understanding the neurobiological basis of oligodendroglial abnormalities in schizophrenia, it is hoped that patients will benefit from the availability of targeted and more efficacious treatment options.

One-pot three-component synthesis of novel heterocyclic steroids as a central antioxidant and anti-inflammatory agents

Oxidative stress and inflammation have been implicated in several neurodegenerative and developmental brain disorders. The present work was devoted to the design and synthesis of novel steroid derivatives bearing promising heterocyclic moiety that would act to reduce neuro-inflammation and oxidative stress in brain. The novel heterocyclic steroids were synthesized and their chemical structures were confirmed by studying their analytical and spectral data. The tested compounds were assayed in the model of neuro-inflammation produced in rats by cerebral lipopolysaccharide injection. The intracerebral administration of bacterial endotoxin resulted in cerebral inflammatory state evidenced by increased malondialdehyde (MDA), decreased reduced glutathione (GSH) level, increased nitric oxide as well as increased acetylcholinesterase (AChE) activity in the brain. Compounds 6, 10, 8b and 13a markedly increased reduced glutathione. Malondialadehyde and nitric oxide levels were reduced to normal values after treatment with all tested compounds. AChE activity was normalized by compound 8b and reduced to below normal values by compounds 10 and 14a. These results are exciting in that these agents might be useful candidates in treatment of cerebral inflammation.

Traumatic brain injury increased IGF-1B mRNA and altered IGF-1 exon 5 and promoter region epigenetic characteristics in the rat pup hippocampus

Traumatic brain injury (TBI) is a major cause of acquired cognitive disability in childhood. Such disability may be blunted by enhancing the brain's endogenous neuroprotective response. An important endogenous neuroprotective response is the insulin-like growth factor-1 (IGF-1) mRNA variant, IGF-1B. IGF-1B mRNA, characterized by exon 5 inclusion, encodes the IGF-1 and Eb peptides. IGF-1A mRNA excludes exon 5 and encodes the IGF-1 and Ea peptides. A region in the human IGF-1B homologue acts as an exon-splicing enhancer (ESE) to increase IGF-1B mRNA. It is not known if TBI is associated with increased brain IGF-1B mRNA. Epigenetic modifications may underlie altered gene expression in the brain after TBI. We hypothesized that TBI would increase hippocampal IGF-1B mRNA in 17-day-old rats, associated with DNA methylation and/or histone modifications at the promoter site 1 (P1) or exon 5/ESE region. Hippocampi from rat pups after controlled cortical impact (CCI) were used to measure IGF-1B mRNA, DNA methylation, and histone modifications at the P1, P2, and exon5/ESE regions. In CCI hippocampi, IGF-1B mRNA peaked at post-injury day (PID) 2 (1700±320% sham), but normalized by PID 14. IGF-1A peaked at PID 3 (280±52% sham), and remained elevated at PID 14. Increased IGF-1B mRNA was associated with increased methylation at P1, and increased histone modifications associated with gene activation at P2 and exon5/ESE, together with differential methylation in the exon 5/ESE regions. We report for the first time that hippocampal IGF-1B mRNA increased after developmental TBI. We speculate that epigenetic modifications at the P2 and exon 5/ESE regions are important in the regulation of IGF-1B mRNA expression. The exon 5/ESE region may present a means for future therapies to target IGF-1B transcription after TBI.

Cuprizone-induced demyelination in the rat cerebral cortex and thyroid hormone effects on cortical remyelination

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the Central Nervous System which is characterized by multifocal demyelinated lesions dispersed throughout the brain. Although white matter lesions have been the most extensively studied, cortical demyelinaton lesions are also detected in MS brains. Cuprizone (CPZ)-induced demyelination in rodents has been widely used as a model for MS. Most of these studies focus on oligodendrocyte-rich structures, such as the corpus callosum (CC) and the cerebellar peduncles. However, it has been recently described that CPZ administration in mice also produces cortical demyelination, resembling some of the lesions found in MS patients. In this work we used CPZ-demyelinating model in Wistar rats to study demyelination in cortical forebrain areas. At the ultrastructural level, demyelination in the cortex was observed before detectable myelin loss in the subcortical white matter. During the course of CPZ intoxication Myelin Basic Protein immunodetection was decreased in cortical layers I-III due to a reduction in the number of cortical oligodendrocytes (OL). Oligodendroglial loss in CPZ-intoxicated rats correlated with an increase in the number of Glial Fibrillary Acidic Protein positive astrocytes and a shift in the location of Carbonic Anhydrase II from OL to astrocytes. After removal of CPZ from the diet, we evaluate intranasal Thyroid hormone (TH) effects on the progression of cortical lesions. As previously reported in the CC, TH treatment also accelerates remyelination rate in the cortex compared to rats undergoing spontaneous remyelination. Our results suggest that manipulation of TH levels could be considered as a strategy to promote remyelination process in the cortex and to prevent neuronal irreversible damage in patients suffering from MS.