Cytokines which signal through the LIF receptor and their actions in the nervous system

Arbovirus infection increases the risk for the development of neurodegenerative disease pathology in the murine model

Alzheimer's disease is classified as a progressive disorder resulting from protein misfolding, also known as proteinopathies. Proteinopathies include synucleinopathies triggered by misfolded amyloid α-synuclein, tauopathies triggered by misfolded tau, and amyloidopathies triggered by misfolded amyloid of which Alzheimer's disease (β-amyloid) is most prevalent. Most neurodegenerative diseases (>90%) are not due to dominantly inherited genetic causes. Instead, it is thought that the risk for disease is a complicated interaction between inherited and environmental risk factors that, with age, drive pathology that ultimately results in neurodegeneration and disease onset. Since it is increasingly appreciated that encephalitic viral infections can have profoundly detrimental neurological consequences long after the acute infection has resolved, we tested the hypothesis that viral encephalitis exacerbates the pathological profile of protein-misfolding diseases. Using a robust, reproducible, and well-characterized mouse model for β-amyloidosis, Tg2576, we studied the contribution of alphavirus-induced encephalitis (TC-83 strain of VEEV to model alphavirus encephalitis viruses) on the progression of neurodegenerative pathology. We longitudinally evaluated neurological, neurobehavioral, and cognitive levels, followed by a post-mortem analysis of brain pathology focusing on neuroinflammation. We found more severe cognitive deficits and brain pathology in Tg2576 mice inoculated with TC-83 than in their mock controls. These data set the groundwork to investigate sporadic Alzheimer's disease and treatment interventions for this infectious disease risk factor.

Out of Line or Altered States? Neural Progenitors as a Target in a Polygenic Neurodevelopmental Disorder

The genesis of a mature complement of neurons is thought to require, at least in part, precursor cell lineages in which neural progenitors have distinct identities recognized by exclusive expression of one or a few molecular markers. Nevertheless, limited progenitor types distinguished by specific markers and lineal progression through such subclasses cannot easily yield the magnitude of neuronal diversity in most regions of the nervous system. The late Verne Caviness, to whom this edition of Developmental Neuroscience is dedicated, recognized this mismatch. In his pioneering work on the histogenesis of the cerebral cortex, he acknowledged the additional flexibility required to generate multiple classes of cortical projection and interneurons. This flexibility may be accomplished by establishing cell states in which levels rather than binary expression or repression of individual genes vary across each progenitor's shared transcriptome. Such states may reflect local, stochastic signaling via soluble factors or coincidence of cell surface ligand/receptor pairs in subsets of neighboring progenitors. This probabilistic, rather than determined, signaling could modify transcription levels via multiple pathways within an apparently uniform population of progenitors. Progenitor states, therefore, rather than lineal relationships between types may underlie the generation of neuronal diversity in most regions of the nervous system. Moreover, mechanisms that influence variation required for flexible progenitor states may be targets for pathological changes in a broad range of neurodevelopmental disorders, especially those with polygenic origins.

Myelin in Alzheimer's disease: culprit or bystander?

Alzheimer's disease (AD) is a neurodegenerative disorder with neuronal and synaptic losses due to the accumulation of toxic amyloid β (Αβ) peptide oligomers, plaques, and tangles containing tau (tubulin-associated unit) protein. While familial AD is caused by specific mutations, the sporadic disease is more common and appears to result from a complex chronic brain neuroinflammation with mitochondriopathies, inducing free radicals' accumulation. In aged brain, mutations in DNA and several unfolded proteins participate in a chronic amyloidosis response with a toxic effect on myelin sheath and axons, leading to cognitive deficits and dementia. Αβ peptides are the most frequent form of toxic amyloid oligomers. Accumulations of misfolded proteins during several years alters different metabolic mechanisms, induce chronic inflammatory and immune responses with toxic consequences on neuronal cells. Myelin composition and architecture may appear to be an early target for the toxic activity of Aβ peptides and others hydrophobic misfolded proteins. In this work, we describe the possible role of early myelin alterations in the genesis of neuronal alterations and the onset of symptomatology. We propose that some pathophysiological and clinical forms of the disease may arise from structural and metabolic disorders in the processes of myelination/demyelination of brain regions where the accumulation of non-functional toxic proteins is important. In these forms, the primacy of the deleterious role of amyloid peptides would be a matter of questioning and the initiating role of neuropathology would be primarily the fact of dysmyelination.

Leukemia Inhibitory Factor: An Important Cytokine in Pathologies and Cancer

Leukemia Inhibitory Factor (LIF) is a member of the IL-6 cytokine family and is expressed in almost every tissue type within the body. Although LIF was named for its ability to induce differentiation of myeloid leukemia cells, studies of LIF in additional diseases and solid tumor types have shown that it has the potential to contribute to many other pathologies. Exploring the roles of LIF in normal physiology and non-cancer pathologies can give important insights into how it may be dysregulated within cancers, and the possible effects of this dysregulation. Within various cancer types, LIF expression has been linked to hallmarks of cancer, such as proliferation, metastasis, and chemoresistance, as well as overall patient survival. The mechanisms behind these effects of LIF are not well understood and can differ between different tissue types. In fact, research has shown that while LIF may promote malignancy progression in some solid tumors, it can have anti-neoplastic effects in others. This review will summarize current knowledge of how LIF expression impacts cellular function and dysfunction to help reveal new adjuvant treatment options for cancer patients, while also revealing potential adverse effects of treatments targeting LIF signaling.

Leukemia inhibitory factor regulates Schwann cell proliferation and migration and affects peripheral nerve regeneration

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine that stimulates neuronal development and survival. Our previous study has demonstrated that LIF mRNA is dysregulated in the peripheral nerve segments after nerve injury. Here, we show that LIF protein is abundantly expressed in Schwann cells after rat sciatic nerve injury. Functionally, suppressed or elevated LIF increases or decreases the proliferation rate and migration ability of Schwann cells, respectively. Morphological observations demonstrate that in vivo application of siRNA against LIF after peripheral nerve injury promotes Schwann cell migration and proliferation, axon elongation, and myelin formation. Electrophysiological and behavior assessments disclose that knockdown of LIF benefits the function recovery of injured peripheral nerves. Differentially expressed LIF affects the metabolism of Schwann cells and negatively regulates ERFE (Erythroferrone). Collectively, our observations reveal the essential roles for LIF in regulating the proliferation and migration of Schwann cells and the regeneration of injured peripheral nerves, discover ERFE as a downstream effector of LIF, and extend our understanding of the molecular mechanisms underlying peripheral nerve regeneration.

Spatiotemporal expression of leukemia inhibitory factor receptor protein during neural tube development in embryos with neural tube defects

Leukemia inhibitory factor receptor (LIFR), as a neuroregulatory cytokine receptor, generally shows a neuroprotective effect in central nervous system injuries. In this study, to understand the effect of LIFR on pathogenesis of neural tube defects, we explored spatiotemporal expression of LIFR at different stages of fetal development in normal and neural tube defect embryos. Spina bifida aperta was induced with all-trans retinoic acid on embryonic day 10 in rats, and the spatiotemporal expression of LIFR was investigated in spina bifida aperta rats and healthy rats from embryonic day 11 to 17. Real time-polymerase chain reaction and western blot assay were used to examine mRNA and protein expression of LIFR in healthy control and neural tube defect embryos. Results of the animal experiment demonstrated that expression of LIFR protein and mRNA in the spinal cords of normal rat embryos increased with embryonic development. LIFR was significantly downregulated in the spinal cords of spina bifida aperta rats compared with healthy rats from embryonic days 11 to 17. Immunohistochemical staining showed that the expression of LIFR in placenta and spinal cord in spina bifida aperta rat embryos was decreased compared with that in control embryos at embryonic day 15. Results from human embryo specimens showed that LIFR mRNA expression was significantly down-regulated in spinal cords of human fetuses with neural tube defects compared with normal controls at a gestational age of 24 to 33 weeks. The results were consistent with the down-regulation of LIFR in the animal experiments. Our study revealed spatiotemporal changes in expression of LIFR during embryonic neurulation. Thus, LIFR might play a specific role in neural tube development. All animal and human experimental procedures were approved by the Medical Ethics Committee of Shengjing Hospital of China Medical University, China (approval No. 2016PS106K) on February 25, 2016.

Potential skin involvement in ALS: revisiting Charcot's observation - a review of skin abnormalities in ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting motor neurons of the brain and spinal cord, leading to progressive paralysis and death. Interestingly, many skin changes have been reported in ALS patients, but never as yet fully explained. These observations could be due to the common embryonic origin of the skin and neural tissue known as the ectodermal germ layer. Following the first observation in ALS patients' skin by Dr Charcot in the 19th century, in the absence of bedsores unlike other bedridden patients, other morphological and molecular changes have been observed. Thus, the skin could be of interest in the study of ALS and other neurodegenerative diseases. This review summarizes skin changes reported in the literature over the years and discusses about a novel in vitro ALS tissue-engineered skin model, derived from patients, for the study of ALS.

Insulin-Like Growth Factor-II/Cation-Independent Mannose 6-Phosphate Receptor in Neurodegenerative Diseases

The insulin-like growth factor II/mannose 6-phosphate (IGF-II/M6P) receptor is a multifunctional single transmembrane glycoprotein. Recent studies have advanced our understanding of the structure, ligand-binding properties, and trafficking of the IGF-II/M6P receptor. This receptor has been implicated in a variety of important cellular processes including growth and development, clearance of IGF-II, proteolytic activation of enzymes, and growth factor precursors, in addition to its well-known role in the delivery of lysosomal enzymes. The IGF-II/M6P receptor, distributed widely in the central nervous system, has additional roles in mediating neurotransmitter release and memory enhancement/consolidation, possibly through activating IGF-II-related intracellular signaling pathways. Recent studies suggest that overexpression of the IGF-II/M6P receptor may have an important role in regulating the levels of transcripts and proteins involved in the development of Alzheimer's disease (AD)-the prevalent cause of dementia affecting the elderly population in our society. It is reported that IGF-II/M6P receptor overexpression can increase the levels/processing of amyloid precursor protein leading to the generation of β-amyloid peptide, which is associated with degeneration of neurons and subsequent development of AD pathology. Given the significance of the receptor in mediating the transport and functioning of the lysosomal enzymes, it is being considered for therapeutic delivery of enzymes to the lysosomes to treat lysosomal storage disorders. Notwithstanding these results, additional studies are required to validate and fully characterize the function of the IGF-II/M6P receptor in the normal brain and its involvement in various neurodegenerative disorders including AD. It is also critical to understand the interaction between the IGF-II/M6P receptor and lysosomal enzymes in neurodegenerative processes, which may shed some light on developing approaches to detect and prevent neurodegeneration through the dysfunction of the receptor and the endosomal-lysosomal system.

Glucocorticoids: Protectors of the Brain during Innate Immune Responses

The innate immune response is a coordinated set of reactions involving cells of myeloid lineage and a network of signaling molecules. Such a response takes place in the CNS during trauma, stroke, spinal cord injury, and neurodegenerative diseases, suggesting that macrophages/microglia are the cells that perpetuate the progressive neuronal damage. However, there is accumulating evidence that these cells and their secreted proinflammatory molecules have more beneficial effects than detrimental consequences for the neuronal elements. Indeed, a timely controlled innate immune response may limit toxicity in swiftly eliminating foreign materials and debris that are known to interfere with recovery and regeneration. Each step of the immune cascade is under the tight control of stimulatory and inhibitory signals. Glucocorticoids (GCs) act as the critical negative feedback on all myeloid cells, including those present within the brain parenchyma. Because too little is like too much, both an inappropriate feedback of GCs on microglia and high circulating GC levels in stressed individuals have been associated with deleterious consequences for the brain. In this review, the authors discuss both sides of the story with a particular emphasis on the neuro-protective role of endogenous GCs during immune challenges and the problems in determining whether GCs can be a good therapy for the treatment of neuropathological conditions.

Leukemia inhibitory factor (LIF)

Leukemia inhibitory factor (LIF) is the most pleiotropic member of the interleukin-6 family of cytokines. It utilises a receptor that consists of the LIF receptor β and gp130 and this receptor complex is also used by ciliary neurotrophic growth factor (CNTF), oncostatin M, cardiotrophin1 (CT1) and cardiotrophin-like cytokine (CLC). Despite common signal transduction mechanisms (JAK/STAT, MAPK and PI3K) LIF can have paradoxically opposite effects in different cell types including stimulating or inhibiting each of cell proliferation, differentiation and survival. While LIF can act on a wide range of cell types, LIF knockout mice have revealed that many of these actions are not apparent during ordinary development and that they may be the result of induced LIF expression during tissue damage or injury. Nevertheless LIF does appear to have non-redundant actions in maternal receptivity to blastocyst implantation, placental formation and in the development of the nervous system. LIF has also found practical use in the maintenance of self-renewal and totipotency of embryonic stem cells and induced pluripotent stem cells.

CARM1 regulates astroglial lineage through transcriptional regulation of Nanog and posttranscriptional regulation by miR92a

Coactivator-associated arginine methyltransferase (CARM1/PRMT4)-mediated transcriptional coactivation and arginine methylation is known to regulate various tissue-specific differentiation events. Although CARM1 is expressed in the neural crest region in early development, coinciding with early neuronal progenitor specification, the role of CARM1 in any neuronal developmental pathways has been unexplored. Using a specific small-molecule inhibitor of CARM1-mediated H3R17 methylation in human embryonic stem cell line, we find that H3R17 methylation contributes to the maintenance of the astroglial cell population. A network of regulation was observed on the miR92a promoter by which H3R17-responsive Nanog bound to the miR92a promoter decreased upon inhibition, resulting in an abnormal gene expression program influencing the glial lineage. This was also true in zebrafish, in which, with the help of CARM1 inhibitor and CARM1 morpholinos, we show that inhibition of H3R17 methylation results in defective glial cell morphology and a sensory defect in a subpopulation. A gain-of-function strategy in which mCARM1 was introduced in the morpholino-treated embryos exhibited recovery of the sensory defect phenotype. This study thus establishes the functional cooperation between arginine methylation and microRNA expression in the neuronal developmental process, with potential implications in sensory development pathways.

Deletion of interleukin-6 signal transducer gp130 in small sensory neurons attenuates mechanonociception and down-regulates TRPA1 expression

Glycoprotein 130 (gp130) is the signal transducing receptor subunit for cytokines of the interleukin-6 (IL-6) family, and it is expressed in a multitude of cell types of the immune and nervous system. IL-6-like cytokines are not only key regulators of innate immunity and inflammation but are also essential factors for the differentiation and development of the somatosensory system. Mice with a null mutation of gp130 in primary nociceptive afferents (SNS-gp130(-/-)) are largely protected from hypersensitivity to mechanical stimuli in mouse models of pathological pain. Therefore, we set out to investigate how neuronal gp130 regulates mechanonociception. SNS-gp130(-/-) mice revealed reduced mechanosensitivity to high mechanical forces in the von Frey assay in vivo, and this was associated with a reduced sensitivity of nociceptive primary afferents in vitro. Together with these findings, transient receptor potential ankyrin 1 (TRPA1) mRNA expression was significantly reduced in DRG from SNS-gp130(-/-) mice. This was also reflected by a reduced number of neurons responding with calcium transients to TRPA1 agonists in primary DRG cultures. Downregulation of Trpa1 expression was predominantly discovered in nonpeptidergic neurons, with the deficit becoming evident during stages of early postnatal development. Regulation of Trpa1 mRNA expression levels downstream of gp130 involved the classical Janus kinase family-signal transducer and activator of transcription pathway. Our results closely link proinflammatory cytokines to the expression of TRPA1, both of which have been shown to contribute to hypersensitive pain states. We suggest that gp130 has an essential role in mechanonociception and in the regulation of TRPA1 expression.

Role of cytokine signaling during nervous system development

Cytokines are signaling proteins that were first characterized as components of the immune response, but have been found to have pleiotropic effects in diverse aspects of body function in health and disease. They are secreted by numerous cells and are used extensively in intercellular communications to produce different activities, including intricate processes engaged in the ontogenetic development of the brain. This review discusses factors involved in brain growth regulation and recent findings exploring cytokine signaling pathways during development of the central nervous system. In view of existing data suggesting roles for neurotropic cytokines in promoting brain growth and repair, these molecules and their signaling pathways might become targets for therapeutic intervention in neurodegenerative processes due to diseases, toxicity, or trauma.

Fingolimod: direct CNS effects of sphingosine 1-phosphate (S1P) receptor modulation and implications in multiple sclerosis therapy

Fingolimod is the first oral disease-modifying therapy approved for relapsing forms of multiple sclerosis (MS). Following phosphorylation in vivo, the active agent, fingolimod phosphate (fingolimod-P), acts as a sphingosine 1-phosphate (S1P) receptor modulator, binding with high affinity to four of the five known S1P receptors (S1P1, S1P3, S1P4 and S1P5). The mechanism of action of fingolimod in MS has primarily been considered as immunomodulatory, whereby fingolimod-P modulates S1P1 on lymphocytes, selectively retaining autoreactive lymphocytes in lymph nodes to reduce damaging infiltration into the central nervous system (CNS). However, emerging evidence indicates that fingolimod has direct effects in the CNS in MS. For example, in the MS animal model of experimental autoimmune encephalomyelitis (EAE), fingolimod is highly efficacious in both a prophylactic and therapeutic setting, yet becomes ineffective in animals selectively deficient for S1P1 on astrocytes, despite maintained normal immunologic receptor expression and functions, and S1P-mediated immune activities. Here we review S1P signaling effects relevant to MS in neural cell types expressing S1P receptors, including astrocytes, oligodendrocytes, neurons, microglia and dendritic cells. The direct effects of fingolimod on these CNS cells observed in preclinical studies are discussed in view of the functional consequences of reducing neurodegenerative processes and promoting myelin preservation and repair. The therapeutic implications of S1P modulation in the CNS are considered in terms of the clinical outcomes of MS, such as reducing MS-related brain atrophy, and other CNS disorders. Additionally, we briefly outline other existing and investigational MS therapies that may also have effects in the CNS.

Leukaemia inhibitory factor stimulates proliferation of olfactory neuronal progenitors via inducible nitric oxide synthase

Neurogenesis continues in the adult brain and in the adult olfactory epithelium. The cytokine, leukaemia inhibitory factor and nitric oxide are both known to stimulate neuronal progenitor cell proliferation in the olfactory epithelium after injury. Our aim here was to determine whether these observations are independent, specifically, whether leukaemia inhibitory factor triggers neural precursor proliferation via the inducible nitric oxide synthase pathway. We evaluated the effects of leukaemia inhibitory factor on inducible form of nitric oxide synthase (iNOS) expression, and cell proliferation in olfactory epithelial cell cultures and olfactory neurosphere-derived cells. Leukaemia inhibitory factor induced expression of iNOS and increased cell proliferation. An iNOS inhibitor and an anti-leukaemia inhibitory factor receptor blocking antibody inhibited leukaemia inhibitory factor-induced cell proliferation, an effect that was reversed by a NO donor. Altogether, the results strongly suggest that leukaemia inhibitory factor induces iNOS expression, increasing nitric oxide levels, to stimulate proliferation of olfactory neural precursor cells. This finding sheds light on neuronal regeneration occurring after injury of the olfactory epithelium.

The reactivity, distribution and abundance of Non-astrocytic Inner Retinal Glial (NIRG) cells are regulated by microglia, acute damage, and IGF1

Recent studies have described a novel type of glial cell that is scattered across the inner layers of the avian retina and possibly the retinas of primates. These cells have been termed Non-astrocytic Inner Retinal Glial (NIRG) cells. These cells are stimulated by insulin-like growth factor 1 (IGF1) to proliferate, migrate distally into the retina, and become reactive. These changes in glial activity correlate with increased susceptibility of retinal neurons and Müller glia to excitotoxic damage. The purpose of this study was to further study the NIRG cells in retinas treated with IGF1 or acute damage. In response to IGF1, the reactivity, proliferation and migration of NIRG cells persists through 3 days after treatment. At 7 days after treatment, the numbers and distribution of NIRG cells returns to normal, suggesting that homeostatic mechanisms are in place within the retina to maintain the numbers and distribution of these glial cells. By comparison, IGF1-induced microglial reactivity persists for at least 7 days after treatment. In damaged retinas, we find a transient accumulation of NIRG cells, which parallels the accumulation of reactive microglia, suggesting that the reactivity of NIRG cells and microglia are linked. When the microglia are selectively ablated by the combination of interleukin 6 and clodronate-liposomes, the NIRG cells down-regulate transitin and perish within the following week, suggesting that the survival and phenotype of NIRG cells are somehow linked to the microglia. We conclude that the abundance, reactivity and retinal distribution of NIRG cells can be dynamic, are regulated by homoestatic mechanisms and are tethered to the microglia.

Neuroplastic changes in depression: a role for the immune system

Accumulating evidence suggests that there is a rich cross-talk between the neuroimmune system and neuroplasticity mechanisms under both physiological conditions and pathophysiological conditions in depression. Anti-neuroplastic changes which occur in depression include a decrease in proliferation of neural stem cells (NSCs), decreased survival of neuroblasts and immature neurons, impaired neurocircuitry (cortical-striatal-limbic circuits), reduced levels of neurotrophins, reduced spine density and dendritic retraction. Since both humoral and cellular immune factors have been implicated in neuroplastic processes, in this review we present a model suggesting that neuroplastic processes in depression are mediated through various neuroimmune mechanisms. The review puts forward a model in that both humoral and cellular neuroimmune factors are involved with impairing neuroplasticity under pathophysiological conditions such as depression. Specifically, neuroimmune factors including interleukin (IL)-1, IL-6, tumour necrosis factor (TNF)-α, CD4⁺CD25⁺T regulatory cells (T reg), self-specific CD4⁺T cells, monocyte-derived macrophages, microglia and astrocytes are shown to be vital to processes of neuroplasticity such as long-term potentiation (LTP), NSC survival, synaptic branching, neurotrophin regulation and neurogenesis. In rodent models of depression, IL-1, IL-6 and TNF are associated with reduced hippocampal neurogenesis; mechanisms which are associated with this include the stress-activated protein kinase (SAPK)/Janus Kinase (JNK) pathway, hypoxia-inducible factors (HIF)-1α, JAK-Signal Transducer and Activator of Transcription (STAT) pathway, mitogen-activated protein kinase (MAPK)/cAMP responsive element binding protein (CREB) pathway, Ras-MAPK, PI-3 kinase, IKK/nuclear factor (NF)-κB and TGFβ activated kinase-1 (TAK-1). Neuroimmunological mechanisms have an active role in the neuroplastic changes associated with depression. Since therapies in depression, including antidepressants (AD), omega-3 polyunsaturated fatty acids (PUFAs) and physical activity exert neuroplasticity-enhancing effects potentially mediated by neuroimmune mechanisms, the immune system might serve as a promising target for interventions in depression.

Astrocytes and disease: a neurodevelopmental perspective

Astrocytes are no longer seen as a homogenous population of cells. In fact, recent studies indicate that astrocytes are morphologically and functionally diverse and play critical roles in neurodevelopmental diseases such as Rett syndrome and fragile X mental retardation. This review summarizes recent advances in astrocyte development, including the role of neural tube patterning in specification and developmental functions of astrocytes during synaptogenesis. We propose here that a precise understanding of astrocyte development is critical to defining heterogeneity and could lead advances in understanding and treating a variety of neuropsychiatric diseases.

Interleukin-6 gene (IL-6): a possible role in brain morphology in the healthy adult brain

Background

Cytokines such as interleukin 6 (IL-6) have been implicated in dual functions in neuropsychiatric disorders. Little is known about the genetic predisposition to neurodegenerative and neuroproliferative properties of cytokine genes. In this study the potential dual role of several IL-6 polymorphisms in brain morphology is investigated.

Methodology

In a large sample of healthy individuals (N = 303), associations between genetic variants of IL-6 (rs1800795; rs1800796, rs2069833, rs2069840) and brain volume (gray matter volume) were analyzed using voxel-based morphometry (VBM). Selection of single nucleotide polymorphisms (SNPs) followed a tagging SNP approach (e.g., Stampa algorigthm), yielding a capture 97.08% of the variation in the IL-6 gene using four tagging SNPs.

Principal findings/results

In a whole-brain analysis, the polymorphism rs1800795 (−174 C/G) showed a strong main effect of genotype (43 CC vs. 150 CG vs. 100 GG; x = 24, y = −10, z = −15; F(2,286) = 8.54, p_uncorrected = 0.0002; p_{AlphaSim-corrected} = 0.002; cluster size k = 577) within the right hippocampus head. Homozygous carriers of the G-allele had significantly larger hippocampus gray matter volumes compared to heterozygous subjects. None of the other investigated SNPs showed a significant association with grey matter volume in whole-brain analyses.

Conclusions/significance

These findings suggest a possible neuroprotective role of the G-allele of the SNP rs1800795 on hippocampal volumes. Studies on the role of this SNP in psychiatric populations and especially in those with an affected hippocampus (e.g., by maltreatment, stress) are warranted.

Vascular effects of glycoprotein130 ligands--part II: biomarkers and therapeutic targets

Glycoprotein130 (gp130) ligands are defined by the use of the common receptor subunit gp130 and comprise interleukin (IL)-6, oncostatin M (OSM), IL-11, leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), cardiotrophin-like cytokine (CLC), ciliary neurotrophic factor (CNTF), IL-27 and neuropoietin (NP). In part I of this review we addressed the pathophysiological functions of gp130 ligands with respect to the vascular wall. In part II of this review on the vascular effects of gp130 ligands we will discuss data about possible use of these molecules as biomarkers to predict development or progression of cardiovascular diseases. Furthermore, the possibility to modulate circulating levels of gp130 ligands or their tissue expression by specific antibodies, soluble gp130 protein, renin-angiotensin-aldosterone system (RASS) inhibitors, statins, agonists of peroxisome proliferator-activated receptors (PPAR), hormone replacement therapy, nonsteroidal anti-inflammatory drugs (NSAID) or lifestyle modulating strategies are presented. Recent knowledge about the application of recombinant cytokines from the gp130 cytokine family as therapeutic agents in obesity or atherosclerosis is also summarized. Thus the purpose of this review is to cover a possible usefulness of gp130 ligands as biomarkers and targets for therapy in cardiovascular pathologies.

CNTF and retina

Ciliary neurotrophic factor (CNTF) is one of the most studied neurotrophic factors for neuroprotection of the retina. A large body of evidence demonstrates that CNTF promotes rod photoreceptor survival in almost all animal models. Recent studies indicate that CNTF also promotes cone photoreceptor survival and cone outer segment regeneration in the degenerating retina and improves cone function in dogs with congenital achromotopsia. In addition, CNTF is a neuroprotective factor and an axogenesis factor for retinal ganglion cells (RGCs). This review focuses on the effects of exogenous CNTF on photoreceptors and RGCs in the mammalian retina and the potential clinical application of CNTF for retinal degenerative diseases.

Wallerian degeneration: the innate-immune response to traumatic nerve injury

Traumatic injury to peripheral nerves results in the loss of neural functions. Recovery by regeneration depends on the cellular and molecular events of Wallerian degeneration that injury induces distal to the lesion site, the domain through which severed axons regenerate back to their target tissues. Innate-immunity is central to Wallerian degeneration since innate-immune cells, functions and molecules that are produced by immune and non-immune cells are involved. The innate-immune response helps to turn the peripheral nerve tissue into an environment that supports regeneration by removing inhibitory myelin and by upregulating neurotrophic properties. The characteristics of an efficient innate-immune response are rapid onset and conclusion, and the orchestrated interplay between Schwann cells, fibroblasts, macrophages, endothelial cells, and molecules they produce. Wallerian degeneration serves as a prelude for successful repair when these requirements are met. In contrast, functional recovery is poor when injury fails to produce the efficient innate-immune response of Wallerian degeneration.

Oncostatin M is a novel glucocorticoid-dependent neuroinflammatory factor that enhances oligodendrocyte precursor cell activity in demyelinated sites

The innate immune reaction to tissue injury is a natural process, which can have detrimental effects in the absence of negative feedbacks by glucocorticoids (GCs). Although acute lipopolysaccharide (LPS) challenge is relatively harmless to the brain parenchyma of adult animals, the endotoxin is highly neurotoxic in animals that are treated with the GC receptor antagonist RU486. This study investigated the role of cytokines of the gp130-related family in these effects, because they are essential components of the inflammatory process that provide survival signals to neurons. Intracerebral LPS injection stimulated expression of several members of this family of cytokines, but oncostatin M (Osm) was the unique ligand to be completely inhibited by the RU486 treatment. OSM receptor (Osmr) is expressed mainly in astrocytes and endothelial cells following LPS administration and GCs are directly responsible for its transcriptional activation in the presence of the endotoxin. In a mouse model of demyelination, exogenous OSM significantly modulated the expression of genes involved in the mobilization of oligodendrocyte precursor cells (OPCs), differentiation of oligodendrocyte, and production of myelin. In conclusion, the activation of OSM signaling is a mechanism activated by TLR4 in the presence of negative feedback by GCs on the innate immune system of the brain. OSM absence is associated with detrimental effects of LPS, whereas exogenous OSM favors repair response to demyelinated regions.

Mending the broken brain: neuroimmune interactions in neurogenesis

Neuroimmune networks and the brain endocannabinoid system contribute to the maintenance of neurogenesis. Cytokines and chemokines are important neuroinflammatory mediators that are involved in the pathological processes resulting from brain trauma, ischemia and chronic neurodegenerative diseases. However, they are also involved in brain repair and recovery. Compelling evidence obtained, in vivo and in vitro, establish a dynamic interplay between the endocannabinoid system, the immune system and neural stem/progenitor cells (NSC) in order to promote brain self-repair. Cross-talk between inflammatory mediators and NSC might have important consequences for neural development and brain repair. In addition, brain immune cells (microglia) support NSC renewal, migration and lineage specification. The proliferation and differentiation of multipotent NSC must be precisely controlled during the development of the CNS, as well as for adult brain repair. Although signalling through neuroimmune networks has been implicated in many aspects of neural development, how it affects NSC remains unclear. However, recent findings have clearly demonstrated that there is bi-directional cross-talk between NSC, and the neuroimmune network to control the signals involved in self-renewal and differentiation of NSC. Specifically, there is evidence emerging that neuroimmune interactions control the generation of new functional neurones from adult NSC. Here, we review the evidence that neuroimmune networks contribute to neurogenesis, focusing on the regulatory mechanisms that favour the immune system (immune cells and immune molecules) as a novel element in the coordination of the self-renewal, migration and differentiation of NSC in the CNS. In conjunction, these data suggest a novel mode of action for the immune system in neurogenesis that may be of therapeutic interest in the emerging field of brain repair.

Astrogliosis in CNS pathologies: is there a role for microglia?

Astrogliosis, a cellular reaction with specific structural and functional characteristics, represents a remarkably homotypic response of astrocytes to all kinds of central nervous system (CNS) pathologies. Astrocytes play diverse functions in the brain, both harmful and beneficial. Mounting evidence indicates that astrogliosis is an underlying component of a diverse range of diseases and associated neuropathologies. The mechanisms that lead to astrogliosis are not fully understood, nevertheless, damaged neurons have long been reported to induce astrogliosis and astrogliosis has been used as an index for underlying neuronal damage. As the predominant source of proinflammatory factors in the CNS, microglia are readily activated under certain pathological conditions. An increasing body of evidence suggests that release of cytokines and other soluble products by activated microglia can significantly influence the subsequent development of astrogliosis and scar formation in CNS. It is well known that damaged neurons activate microglia very quickly, therefore, it is possible that activated microglia contribute factors/mediators through which damaged neuron induce astrogliosis. The hypothesis that activated microglia initiate and maintain astrogliosis suggests that suppression of microglial overactivation might effectively attenuate reactive astrogliosis. Development of targeted anti-microglial activation therapies might slow or halt the progression of astrogliosis and, therefore, help achieve a more beneficial environment in various CNS pathologies.

Recent advances in amyotrophic lateral sclerosis research: perspectives for personalized clinical application

Treatment of amyotrophic lateral sclerosis (ALS) has been fueled, in part, by frustration over the shortcomings of the symptomatic drugs available, since these do not impede the progression of this disease. Currently, over 150 different potential therapeutic agents or strategies have been tested in preclinical models of ALS. Unfortunately, therapeutic modifiers of murine ALS have failed to be successfully translated into strategies for patients, probably because of differences in pharmacokinetics of the therapeutic agents, route of delivery, inefficiency of the agents to affect the distinct pathologies of the disease or inherent limitations of the available animal models. Given the multiplicity of the pathological mechanisms implicated in ALS, new therapies should consider the simultaneous manipulation of multiple targets. Additionally, a better management of ALS therapy should include understanding the interactions between potential risk factors, biomarkers and heterogeneous clinical features of the patients, aiming to manage their adverse events or personalize the safety profile of these agents. This review will discuss novel pharmacological approaches concerning adjusted therapy for ALS patients: iron-binding brain permeable multimodal compounds, genetic manipulation and cell-based treatment.

CNS-targeted LIF expression improves therapeutic efficacy and limits autoimmune-mediated demyelination in a model of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) with an inflammatory and a neurodegenerative component. The neuropoietic cytokine leukemia inhibitory factor (LIF) is expressed in MS lesions, but its effect on lesion development is far from understood. LIF is an interesting candidate for MS therapy, as it has neuroprotective properties and may also promote the survival of myelinating oligodendrocytes (OLGs). However, therapeutic administration of LIF is complicated by its limited ability to cross the blood-brain barrier and its pleiotropic actions outside the CNS. In this study, lentiviral vectors (LVs) were used to achieve stable expression and secretion of LIF in the CNS of adult mice. CNS-targeted expression of LIF significantly reduced demyelination in a murine model of MS. In addition, local expression of LIF ameliorated clinical symptoms with enhanced efficacy compared to systemic treatment with recombinant protein. These findings demonstrate that gene therapeutic administration of LIF is a promising approach to limit lesion burden and clinical symptoms in neuroinflammatory disease.

Expression of LIF and LIF receptor beta in Alzheimer's and Parkinson's diseases

BACKGROUND

Signaling through the leukemia inhibitory factor (LIF) receptor (LIFR) is crucial for nervous system development. There are few studies concerning the expression of LIF and LIFR in normal and degenerating adult human brain.

OBJECTIVES

To study the expression of LIF and LIFR in Alzheimer's disease (AD), Parkinson's disease (PD), and control brains.

PATIENTS AND METHODS

LIF and LIFR mRNA copy numbers were determined by quantitative real-time RT-PCR from four brain regions of 34 patients with AD, 40 patients with PD, and 40 controls. Immunohistochemistry was performed in seven PD and in four AD patients and in seven normal controls.

RESULTS

In general, the LIF copy numbers were 1 log higher than the LIFR copy numbers. In the AD brains, LIF expression was higher than in the controls in the hippocampus and in the temporal cortex, and in the PD brains in the hippocampus and in the anterior cingulated cortex. Expressions of LIF and LIFR in different brain regions were opposite except for the AD hippocampus and PD anterior cingulated cortex, where the expression patterns were parallel.

CONCLUSIONS

Co-operative expression of LIF and LIFR in AD hippocampus and PD anterior cingulated cortex may indicate a role for LIF in neuronal damage or repair in these sites.

TNF reduces LIF endocytosis despite increasing NFkappaB-mediated gp130 expression

To examine how the proinflammatory cytokine tumor necrosis factor alpha (TNF) modulates the response of cerebral microvessels to other cytokines, we used rat cerebral microvessel endothelial RBE4 cells to simulate the in vitro blood-brain barrier (BBB). The gp130 receptor, which is shared by the interleukin (IL)-6 family of cytokines, showed specific upregulation by TNF. TNF treatment (5 ng/ml for 30 min to 24 h) increased gp130 at both the levels of transcription and protein expression. The stability of gp130 protein was mediated by NFkappaB activity, as the inhibitors quinazoline and MG132 not only blocked the increase induced by 6 h of TNF treatment, but also reduced its basal level of expression. By contrast, the lysosomal inhibitor chloroquine and the extracellular regulated kinase inhibitor U0126 showed no effect. Despite the increase of gp130, TNF caused a significant reduction in the cell binding and endocytosis of leukemia inhibitory factor (LIF), another proinflammatory cytokine that binds to the gp130 co-receptor and its unique gp190 receptor. This is consistent with our previous findings that TNF reduces gp190 expression and Stat3 activation. Thus, TNF stimulation results in decreased responsiveness of RBE4 cells to LIF, indicating complex regulatory interactions of cytokines at the BBB.

Analysis of leukemia inhibitory factor and leukemia inhibitory factor receptor in embryonic and adult zebrafish (Danio rerio)

Leukemia inhibitory factor (LIF) is a member of the IL-6 cytokine family that functions in the survival, repair and formation of neurons as well as in the maintenance of neural and embryonic stem cells. The functions of LIF have been well documented in mammals, however until recently, the presence of IL-6 family cytokines in ectothermic vertebrates has only been speculated. We report on the identification of lif and lifr transcripts in the zebrafish and document the expression of these molecules in the developing embryos and tissues of adult zebrafish. We also examined the phylogenetic relationship between these molecules and other IL-6 cytokine family members known in mammals. In adult zebrafish, lif is expressed in the kidney and brain while lifr is expressed in the kidney, gill, brain, spleen and liver. During zebrafish embryogenesis, lif and lifr are both expressed as early as 12 hours postfertilization (hpf). In developing zebrafish, lif is expressed in the otic vesicle, retina and cranial sensory ganglia, and lifr is strongly expressed in the notochord, forebrain, otic vesicle, cranial ganglia and the retina. Morpholino knockdown of Lif and Lifr in developing embryos suggests that Lifr, but not Lif is required for proper neural development. lifr morpholino-injected embryos exhibit defects in the trigeminal, facial and vagal branchiomotor neurons, and improper axonal development as measured by acetylated tubulin staining. These embryos also display severe hydrocephaly by 48 hpf. This suggests that Lifrs are involved in proper neural development in zebrafish. This is the first evidence of the expression and role of an LIFR-like molecule in developing fish.

Interactions of interleukin-1 with neurotrophic factors in the central nervous system: beneficial or detrimental?

Interleukin (IL)-1 is a multifunctional cytokine that plays a key role in mediating inflammation in the brain. Many different cell types in the brain express the IL-1 receptor and respond to this cytokine by activating cell-type-specific signaling pathways leading to distinct functional responses, which collectively comprise the inflammatory response in the brain. One key effect of IL-1 in the brain is the induction of trophic factor production by glial cells, which has traditionally been considered a neuroprotective response to injury or disease. However, recent studies have shown that nerve growth factor, which is regulated by IL-1, can induce neuronal survival or apoptosis via different receptors. This article examines the interaction of IL-1 with different trophic factors in the brain.

Culture conditions determine the prevalence of bipolar and monopolar neurons in cultures of dissociated spiral ganglion

To gain insight into the mechanisms that control the generation or maintenance of the characteristic bipolar morphology of cochlear spiral ganglion neurons, we have taken advantage of our recently developed procedure for culture of dissociated newborn mouse spiral ganglion. In these cultures, inclusion of the cytokine leukemia inhibitory factor (LIF) in the medium increases neuronal survival and the number of bipolar neurons. Here we tested effects of two other LIF-type cytokines (ciliary neurotrophic factor, CNTF; and human recombinant oncostatin M, hOSM) and of bone morphogenetic protein 4 (BMP4) on survival, morphology and neurite lengths of neurons in cultures of dissociated spiral ganglion. Like LIF, CNTF and hOSM increased neuronal survival and the number of surviving bipolar neurons. BMP4 also increased neuronal survival, but unlike LIF, CNTF and hOSM, increased the number of monopolar neurons and neurons with no neurites. In addition, population histograms demonstrate that the population lengths of the longer and shorter neurites of bipolar neurons were shorter in BMP4 containing cultures than in control or LIF cultures. When LIF and BMP4 were simultaneously added to the cultures, the BMP4 effects predominated. These experiments demonstrate that exposure to different environmental conditions can result in different morphologies in the surviving population of spiral ganglion neurons in culture.

Cardiotrophin-1 induces interleukin-6 synthesis in human umbilical vein endothelial cells

In patients with chronic heart failure (CHF) increased plasma concentrations of proinflammatory cytokines are found. For example, the plasma interleukin-6 (IL-6) concentration correlates with disease severity. Beside IL-6 cardiotrophin-1 (CT-1), a member of the IL-6 superfamily, is also increased in CHF. We examined whether CT-1 is able to induce IL-6 in human umbilical vein endothelial cells (HUVEC) and characterised the underlying pathway. IL-6 mRNA was determined by real-time PCR and by RT-PCR in HUVEC which were stimulated with different CT-1 concentrations and for different time periods. IL-6 concentration in the supernatant was determined by ELISA. For the pathway determination following inhibitors were used: piceatannol (signal transducer and activation of transcription (STAT)3 phosphorylation), wortmannin (phosphatiylinositol 3-kinase (PI3K)), SB203580 (p38 mitogen-activated protein kinase (MAPK)), AG490 (Janus kinase (JAK)2), PD98059 (mitogen-activated protein kinase kinase (MEK) 1/2), parthenolide (nuclear factor kappaB) and cycloheximide (protein biosynthesis). CT-1 caused a concentration- and time-dependent increase in IL-6 mRNA in HUVEC with a maximal induction seen after 6 h (2-fold compared to control) with 100 ng/ml CT-1. In the supernatant of HUVEC a concentration- and time-dependent increase of IL-6 protein was found. A maximum effect with 100 ng/ml CT-1 was found after 24 h (11-fold compared to control). AG490, SB203580, piceatannol, parthenolide and cycloheximide inhibit CT-1 induced IL-6 mRNA and protein expression whereas wortmannin and PD98059 did not inhibit IL-6 expression. CT-1 induced both IL-6 mRNA and protein in a concentration- and time-dependent manner in HUVEC. The underlying pathway includes activation of JAK2, STAT3, p38 and NFkappaB. CT-1 induced IL-6 expression and requires protein synthesis and IL-6 is not stored intracellularly. We speculate that in CHF CT-1 might be in part responsible for increased IL-6 plasma concentrations. Modulation of the CT-1 pathway may be a further strategy in CHF treatment.

Neuronal survival depends on EGFR signaling in cortical but not midbrain astrocytes

Mice lacking epidermal growth factor receptor (EGFR) develop a neurodegeneration of unknown etiology affecting exclusively the frontal cortex and olfactory bulbs. Here, we show that EGFR signaling controls cortical degeneration by regulating cortical astrocyte apoptosis. Whereas EGFR(-/-) midbrain astrocytes are unaffected, mutant cortical astrocytes display increased apoptosis mediated by an Akt-caspase-dependent mechanism and are unable to support neuronal survival. The expression of many neurotrophic factors is unaltered in EGFR(-/-) cortical astrocytes suggesting that neuronal loss occurs as a consequence of increased astrocyte apoptosis rather than impaired secretion of trophic factors. Neuron-specific expression of activated Ras can compensate for the deficiency of EGFR(-/-) cortical astrocytes and prevent neuronal death. These results identify two functionally distinct astrocyte populations, which differentially depend on EGFR signaling for their survival and also for their ability to support neuronal survival. These spatial differences in astrocyte composition provide a mechanism for the region-specific neurodegeneration in EGFR(-/-) mice.

Leukemia inhibitory factor is a key regulator of astrocytic, microglial and neuronal responses in a low-dose pilocarpine injury model

Insult to the central nervous system (CNS) induces many changes, including altered neurotransmitter expression, activation of astrocytes and microglia, neurogenesis and cell death. Cytokines and growth factors are candidates to be involved in astrocyte and microglial activation, and the up-regulation of glial fibrillary acidic protein (GFAP) is associated with brain damage. One of these candidates is leukemia inhibitory factor (LIF), a pro-inflammatory cytokine that is induced in astrocytes by brain damage or seizure. LIF also regulates expression of both neuropeptide Y (NPY) and galanin following peripheral nerve injury. To test the hypothesis that LIF regulates astrocyte, microglial and neuropeptide responses to a mild insult, we used a low-dose pilocarpine model to induce a brief seizure in LIF knock-out (KO) mice. Compared to wild type mice, the LIF KO mouse displays reduced astrocyte and microglial activation in the hippocampus. In addition, LIF KO mice display dramatically altered NPY, but not galanin, expression in response to injury. Thus, LIF is required for normal glial responses to brain damage, and, as in the periphery, LIF regulates NPY expression in the CNS.

Survival and morphology of auditory neurons in dissociated cultures of newborn mouse spiral ganglion

We have systematically characterized neuronal survival and growth in cultures derived from newborn/postnatal day 1 mouse cochlea. Dissociated cultures of the cochlear spiral ganglion provide an experimental environment in which to examine molecular mechanisms of survival, development and physiology of auditory neurons. To relate survival to the total number of neurons present in the source tissue, three cochleas from different newborn CD-1 mice were embedded in Araldite resin and serially sectioned at 5 mum thickness. All neurons were counted. To avoid overcounting, each section served as a lookup section for the next, giving 8240+/-423 (S.D.) neurons per ganglion. Cultures maintained in the presence of adjacent non-neural tissue, brain-derived neurotrophic factor, neurotrophin 3, leukemia inhibitory factor (LIF) and 10% fetal bovine serum returned the best overall survival (30%) at 42 h post-plating. Best overall survival required the continuous presence of a serum component(s) larger than 100,000 MW. Plating efficiency (number of neurons that attach to the well after 4 h) was similar in the presence or absence of LIF. Inclusion of LIF maintained 100% survival of plated neurons over 42 h of culture; without LIF, a large fraction of the neurons did not survive. LIF appeared to maintain survival by preferentially preserving a population of bipolar neurons, while having little effect on the number of monopolar neurons. This work provides quantitative measures of survival and morphology of auditory neurons in vitro. The results support the idea that survival of spiral ganglion neurons in vivo may depend on interactions with adjacent, non-neural tissue and raise the possibility that maintenance of bipolar morphology after hair cell damage may require biochemical mechanisms in addition to those induced by neurotrophins.

Challenges in the study of neuronal differentiation: a view from the embryonic eye

Progress in the study of the molecular mechanisms that regulate neuronal differentiation has been quite impressive in recent years, and promises to continue to an equally fast pace. This should not lead us into a sense of complacency, however, because there are still significant barriers that cannot be overcome by simply conducting the same type of experiments that we have been performing thus far. This article will describe some of these challenges, while highlighting the conceptual and methodological breakthroughs that will be necessary to overcome them.

Therapeutic potential of neurotrophic factors in neurodegenerative diseases

There is a vast amount of evidence indicating that neurotrophic factors play a major role in the development, maintenance, and survival of neurons and neuron-supporting cells such as glia and oligodendrocytes. In addition, it is well known that alterations in levels of neurotrophic factors or their receptors can lead to neuronal death and contribute to the pathogenesis of neurodegenerative diseases such as Parkinson disease, Alzheimer disease, Huntington disease, amyotrophic lateral sclerosis, and also aging. Although various treatments alleviate the symptoms of neurodegenerative diseases, none of them prevent or halt the neurodegenerative process. The high potency of neurotrophic factors, as shown by many experimental studies, makes them a rational candidate co-therapeutic agent in neurodegenerative disease. However, in practice, their clinical use is limited because of difficulties in protein delivery and pharmacokinetics in the central nervous system. To overcome these disadvantages and to facilitate the development of drugs with improved pharmacotherapeutic profiles, research is underway on neurotrophic factors and their receptors, and the molecular mechanisms by which they work, together with the development of new technologies for their delivery into the brain.

Leukemia inhibitory factor promotes oligodendrocyte survival after spinal cord injury

Injury to the mammalian spinal cord is accompanied by a delayed, secondary wave of oligodendrocyte apoptosis that arises several days after the initial injury. A strong candidate to support oligodendrocyte survival after spinal cord injury is the pleiotropic cytokine, leukemia inhibitory factor (LIF). In vitro, LIF potentiates the differentiation and survival of oligodendrocyte precursors. LIF can also prevent oligodendrocyte apoptosis in response to either growth factor removal or cytotoxic challenge. More recently, in vivo studies have demonstrated that LIF is effective in preventing oligodendrocyte death in a mouse model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). We therefore asked whether systemic delivery of LIF could ameliorate oligodendrocyte death in a mouse model of spinal cord injury. We have found that daily administration of LIF (25 microg/kg/day) promotes oligodendrocyte survival after spinal cord injury. Interestingly however, this effect does not appear to be mediated by a direct action of LIF on the oligodendrocyte but rather via an ancillary cell type, which results in augmented expression of another trophic factor capable of supporting oligodendrocyte survival, insulin-like growth factor 1 (IGF-1).

Leukemia inhibitory factor is a proliferative factor for olfactory sensory neurons

Neuropoietic cytokines are known to play crucial roles in neuronal development. Among them, leukemia inhibitory factor (LIF) has been implicated in various processes of neuronal development, such as neuronal differentiation, survival and neurogenesis. Moreover, LIF is highly expressed in regions of the central nervous system where adult neurogenesis occurs. LIF was tested for its efficacy in promoting postnatal neurogenesis using LIF-null mice and dissociated cultures of early postnatal rat olfactory sensory neurons. Our results indicate that LIF promoted proliferation of olfactory sensory neuron precursors both in vivo and in vitro. In addition, LIF did not affect proliferation of non-neuronal cells. LIF may therefore be useful when developing stem cell therapy to replace damaged olfactory sensory neurons as well as a therapeutic agent to treat some anosmic symptoms.

CNTF/LIF/gp130 receptor complex signaling maintains a VZ precursor differentiation gradient in the developing ventral forebrain

The extrinsic signaling pathways responsible for the formation and maintenance of the unique laminar organization of the forebrain germinal zones are largely unknown. In the present study, we asked whether ciliary neurotrophic factor (CNTF)/leukemia inhibitory factor (LIF)/gp130 signaling plays a role in the development of the germinal layers in the lateral ganglionic eminence. We found that CNTF/LIF/gp130 receptor signaling promotes the self-renewal/expansion of a subpopulation of fibroblast growth factor-responsive ventricular zone (VZ) precursors in the ventral forebrain. Analysis of Lifr-/- mice suggests that CNTF/LIF/gp130 signaling maintains a subpopulation of GSH2+ VZ precursors, which are necessary for normal growth of the early ventral forebrain and for maintaining a gradient of VZ precursor differentiation in the lateral ganglionic eminence, as defined by GSH2, MASH1 and DLX2 expression. Furthermore, addition of exogenous CNTF to embryonic forebrain explant cultures deprived of choroid plexus-derived CNTF, was sufficient to promote a VZ differentiation gradient. In contrast to the forebrain, CNTF/LIF/gp130 signaling reduced, rather than enhanced, precursor self-renewal/expansion in the spinal cord. These results demonstrate a novel region-specific role for CNTF/LIF/gp130 signaling in the development of the germinal layers of the embryonic telencephalon.

Comparative studies of oncostatin M expression in the tissues of adult rodents

Oncostatin M (OSM), a member of the interleukin-6 family of cytokines, is thought to be expressed mostly by activated T-lymphocytes and monocytes in adult animals. However, here we report specific constitutive tissue expression of OSM in the pancreas, kidney, testes, spleen, stomach, and brain, but not liver or lung, of three adult rodent species.

Potent pro-inflammatory actions of leukemia inhibitory factor in the spinal cord of the adult mouse

Injury in the peripheral or central nervous systems causes a significant rise in the levels of the pleiotropic cytokine leukemia inhibitory factor (LIF). This increase influences cell survival, reactive gliosis and inflammatory responses. Since prior work has focused primarily on peripheral nerve and brain, little is known about the role of LIF in the spinal cord injury response. We address this issue by examining the effects of injury in the LIF knockout (KO) mouse, as well as using an adenoviral vector to over-express LIF in the spinal cord of adult mice. We find that LIF over-expression results in a dramatic rise in cell proliferation, primarily in microglia/macrophages. Astrocytes are not stimulated to proliferate but are activated by the elevated LIF. LIF over-expression also causes the development of severe hindlimb motor dysfunction, an effect mediated by the enhanced activation of microglia/macrophages, as inhibiting microglial activation with minocycline attenuates these motor deficits. Conversely, proliferation is significantly diminished and the microglial/macrophage response to spinal cord injury is much less in the LIF KO compared to wild type (WT). Thus, LIF is a potent pro-inflammatory factor in the adult spinal cord and represents a potential target for the manipulation of inflammatory reactions after spinal cord injury.

Cardiotrophin-1: expression in experimental myocardial infarction and potential role in post-MI wound healing

Cardiotrophin-1 (CT-1), a member of the IL-6 family of cytokines, has been shown to be elevated in the serum of patients with ischemic heart disease and valvular heart disease, and induces cardiomyocyte hypertrophy in vitro. We investigated expression of CT-1 in post-MI rat heart and the effect of CT-1 on cultured primary adult rat cardiac fibroblasts. Elevated CT-1 expression was observed in the infarct zone at 24 h and continued through 2, 4 and 8 weeks post-MI, compared to sham-operated animals. CT-1 induced rapid phosphorylation of Jak, Jak2, STAT1, STAT3, p42/44 MAPK and Akt in cultured adult cardiac fibroblasts. CT-1 induced cardiac fibroblast protein synthesis and proliferation. Protein and DNA synthesis were dependent on activation of Jak/STAT, MEK1/2, PI3K and Src pathways as evidenced by decreased 3H-leucine and 3H-thymidine incorporation after pretreatment with AG490, PD98059, LY294002 and genistein respectively. Furthermore, CT-1 treatment increased procollagen-1-carboxypropeptide (PICP) synthesis, a marker of mature collagen synthesis. CT-1 induced cell migration of rat cardiac fibroblasts. Our results suggest that CT-1, as expressed in post-MI heart, may play an important role in infarct scar formation and ongoing remodeling of the scar. CT-1 was able to initiate each of the processes considered important in the formation of infarct scar including cardiac fibroblast migration as well as fibroblast proliferation and collagen synthesis. Further work is required to determine factors that induce CT-1 expression and interplay with other mediators of cardiac infarct wound healing in the setting of acute cardiac ischemia and chronic post-MI heart failure.