Essential roles of heparin-binding epidermal growth factor-like growth factor in the brain

Impacts of SARS-CoV-2 on brain renin angiotensin system related signaling and its subsequent complications on brain: A theoretical perspective

Cellular ACE2 (cACE2), a vital component of the renin-angiotensin system (RAS), possesses catalytic activity to maintain AngII and Ang 1-7 balance, which is necessary to prevent harmful effects of AngII/AT2R and promote protective pathways of Ang (1-7)/MasR and Ang (1-7)/AT2R. Hemostasis of the brain-RAS is essential for maintaining normal central nervous system (CNS) function. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a viral disease that causes multi-organ dysfunction. SARS-CoV-2 mainly uses cACE2 to enter the cells and cause its downregulation. This, in turn, prevents the conversion of Ang II to Ang (1-7) and disrupts the normal balance of brain-RAS. Brain-RAS disturbances give rise to one of the pathological pathways in which SARS-CoV-2 suppresses neuroprotective pathways and induces inflammatory cytokines and reactive oxygen species. Finally, these impairments lead to neuroinflammation, neuronal injury, and neurological complications. In conclusion, the influence of RAS on various processes within the brain has significant implications for the neurological manifestations associated with COVID-19. These effects include sensory disturbances, such as olfactory and gustatory dysfunctions, as well as cerebrovascular and brain stem-related disorders, all of which are intertwined with disruptions in the RAS homeostasis of the brain.

Cytokine polarized, alternatively activated bone marrow neutrophils drive axon regeneration

The adult central nervous system (CNS) possesses a limited capacity for self-repair. Severed CNS axons typically fail to regrow. There is an unmet need for treatments designed to enhance neuronal viability, facilitate axon regeneration and ultimately restore lost neurological functions to individuals affected by traumatic CNS injury, multiple sclerosis, stroke and other neurological disorders. Here we demonstrate that both mouse and human bone marrow neutrophils, when polarized with a combination of recombinant interleukin-4 (IL-4) and granulocyte colony-stimulating factor (G-CSF), upregulate alternative activation markers and produce an array of growth factors, thereby gaining the capacity to promote neurite outgrowth. Moreover, adoptive transfer of IL-4/G-CSF-polarized bone marrow neutrophils into experimental models of CNS injury triggered substantial axon regeneration within the optic nerve and spinal cord. These findings have far-reaching implications for the future development of autologous myeloid cell-based therapies that may bring us closer to effective solutions for reversing CNS damage.

HB-EGF promotes progenitor cell proliferation and sensory neuron regeneration in the zebrafish olfactory epithelium

Maintenance and regeneration of the zebrafish olfactory epithelium (OE) are supported by two distinct progenitor cell populations that occupy spatially discrete stem cell niches and respond to different tissue conditions. Globose basal cells (GBCs) reside at the inner and peripheral margins of the sensory OE and are constitutively active to replace sporadically dying olfactory sensory neurons (OSNs). In contrast, horizontal basal cells (HBCs) are uniformly distributed across the sensory tissue and are selectively activated by acute injury conditions. Here we show that expression of the heparin-binding epidermal growth factor-like growth factor (HB-EGF) is strongly and transiently upregulated in response to OE injury and signals through the EGF receptor (EGFR), which is expressed by HBCs. Exogenous stimulation of the OE with recombinant HB-EGF promotes HBC expansion and OSN neurogenesis in a pattern that resembles the tissue response to injury. In contrast, pharmacological inhibition of HB-EGF membrane shedding, HB-EGF availability, and EGFR signaling strongly attenuate or delay injury-induced HBC activity and OSN restoration without affecting maintenance neurogenesis by GBCs. Thus, HB-EGF/EGFR signaling appears to be a critical component of the signaling network that controls HBC activity and, consequently, repair neurogenesis in the zebrafish OE.

Genetic overlap between Alzheimer's disease and immune-mediated diseases: an atlas of shared genetic determinants and biological convergence

The occurrence of immune disease comorbidities in Alzheimer's disease (AD) has been observed in both epidemiological and molecular studies, suggesting a neuroinflammatory basis in AD. However, their shared genetic components have not been systematically studied. Here, we composed an atlas of the shared genetic associations between 11 immune-mediated diseases and AD by analyzing genome-wide association studies (GWAS) summary statistics. Our results unveiled a significant genetic overlap between AD and 11 individual immune-mediated diseases despite negligible genetic correlations, suggesting a complex shared genetic architecture distributed across the genome. The shared loci between AD and immune-mediated diseases implicated several genes, including GRAMD1B, FUT2, ADAMTS4, HBEGF, WNT3, TSPAN14, DHODH, ABCB9, and TNIP1, all of which are protein-coding genes and thus potential drug targets. Top biological pathways enriched with these identified shared genes were related to the immune system and cell adhesion. In addition, in silico single-cell analyses showed enrichment of immune and brain cells, including neurons and microglia. In summary, our results suggest a genetic relationship between AD and the 11 immune-mediated diseases, pinpointing the existence of a shared however non-causal genetic basis. These identified protein-coding genes have the potential to serve as a novel path to therapeutic interventions for both AD and immune-mediated diseases and their comorbidities.

Role of an interdependent Wnt, GSK3-β/β-catenin and HB-EGF/EGFR mechanism in arsenic-induced hippocampal neurotoxicity in adult mice

We previously reported the neurotoxic effects of arsenic in the hippocampus. Here, we explored the involvement of Wnt pathway, which contributes to neuronal functions. Administering environmentally relevant arsenic concentrations to postnatal day-60 (PND60) mice demonstrated a dose-dependent increase in hippocampal Wnt3a and its components, Frizzled, phospho-LRP6, Dishevelled and Axin1 at PND90 and PND120. However, p-GSK3-β(Ser9) and β-catenin levels although elevated at PND90, decreased at PND120. Additionally, treatment with Wnt-inhibitor, rDkk1, reduced p-GSK3-β(Ser9) and β-catenin at PND90, but failed to affect their levels at PND120, indicating a time-dependent link with Wnt. To explore other underlying factors, we assessed epidermal growth factor receptor (EGFR) pathway, which interacts with GSK3-β and appears relevant to neuronal functions. We primarily found that arsenic reduced hippocampal phosphorylated-EGFR and its ligand, Heparin-binding EGF-like growth factor (HB-EGF), at both PND90 and PND120. Moreover, treatment with HB-EGF rescued p-GSK3-β(Ser9) and β-catenin levels at PND120, suggesting their HB-EGF/EGFR-dependent regulation at this time point. Additionally, rDkk1, LiCl (GSK3-β-activity inhibitor), or β-catenin protein treatments induced a time-dependent recovery in HB-EGF, indicating potential inter-dependent mechanism between hippocampal Wnt/β-catenin and HB-EGF/EGFR following arsenic exposure. Fluorescence immunolabeling then validated these findings in hippocampal neurons. Further exploration of hippocampal neuronal survival and apoptosis demonstrated that treatment with rDkk1, LiCl, β-catenin and HB-EGF improved Nissl staining and NeuN levels, and reduced cleaved-caspase-3 levels in arsenic-treated mice. Supportively, we detected improved Y-Maze and Passive Avoidance performances for learning-memory functions in these mice. Overall, our study provides novel insights into Wnt/β-catenin and HB-EGF/EGFR pathway interaction in arsenic-induced hippocampal neurotoxicity.

MicroRNA-194-5p/Heparin-binding EGF-like growth factor signaling mediates dexamethasone-induced activation of pseudorabies virus in rat pheochromocytoma cells

Pseudorabies virus (PRV) is a neurotropic virus, which infects a wide range of mammals. The activity of PRV is gradually suppressed in hosts that have tolerated the primary infection. Increased glucocorticoid levels resulting from stressful stimuli overcome repression of PRV activity. However, the host cell mechanism involved in the activation processes under stressful conditions remains unclear. In this study, infection of rat PC-12 pheochromocytoma cells with neuronal properties using PRV at a multiplicity of infection (MOI) = 1 for 24 h made the activity of PRV be the relatively repressed state, and then incubation with 0.5 μM of the corticosteroid dexamethasone (DEX) for 4 h overcomes the relative repression of PRV activity. RNA-seq deep sequencing and bioinformatics analyses revealed different microRNA and mRNA profiles of PC-12 cells with/without PRV and/or DEX treatment. qRT-PCR and western blot analyses confirmed the negative regulatory relationship of miRNA-194-5p and its target heparin-binding EGF-like growth factor (Hbegf); a dual-luciferase reporter assay revealed that Hbegf is directly targeted by miRNA-194-5p. Further, miRNA-194-5p mock transfection contributed to PRV activation, Hbegf was downregulated in DEX-treated PRV infection cells, and Hbegf overexpression contributed to returning activated PRV to the repression state. Moreover, miRNA-194-5p overexpression resulted in reduced levels of HBEGF, c-JUN, and p-EGFR, whereas Hbegf overexpression suppressed the reduction caused by miRNA-194-5p overexpression. Overall, this study is the first to report that changes in the miR-194-5p-HBEGF/EGFR pathway in neurons are involved in DEX-induced activation of PRV, laying a foundation for the clinical prevention of stress-induced PRV activation.

Sarcosine May Induce EGF Production or Inhibit the Decline in EGF Concentrations in Patients with Chronic Schizophrenia (Results of the PULSAR Study)

Sarcosine (N-methylglycine), a glutamatergic modulator, reduces the primary negative symptoms of schizophrenia. These beneficial changes might be mediated by trophic factors such as epidermal growth factor (EGF). We assessed associations between initial serum EGF levels or changes in serum EGF levels and symptom severity during the addition of sarcosine to stable antipsychotic treatment and thereby evaluated the associations between glutamatergic modulation, clinical changes and peripheral EGF concentrations. Fifty-eight subjects with a diagnosis of chronic schizophrenia with dominant negative symptoms, stably treated with antipsychotics, completed a prospective 6-month, randomized, double-blind, placebo-controlled study. Subjects received orally 2 g of sarcosine (n = 28) or placebo (n = 30) daily. Serum EGF levels and symptom severity (using the Positive and Negative Syndrome Scale (PANSS) and the Calgary Depression Scale for Schizophrenia (CDSS)) were assessed at baseline, 6-week and 6-month follow-up. Augmentation antipsychotic treatment with sarcosine had no effect on EGF serum levels at any time points. Only the sarcosine group showed a significant improvement in negative symptoms, general psychopathology subscales and the overall PANSS score. We found a reduction in serum EGF levels in the placebo group, but levels in the sarcosine remained stable during the study. Our data indicate that improvement in negative symptoms due to sarcosine augmentation is not directly mediated by EGF, but effective treatment may induce the production or block the decrease in EGF concentrations, which indicates the neuroprotective effect of treatment and confirms the relationship between neuroprotection and EGF levels.

Cytokine polarized, alternatively activated bone marrow neutrophils drive axon regeneration

The adult central nervous system (CNS) possesses a limited capacity for self-repair. Severed CNS axons typically fail to regrow. There is an unmet need for treatments designed to enhance neuronal viability, facilitate axon regeneration, and ultimately restore lost neurological functions to individuals affected by traumatic CNS injury, multiple sclerosis, stroke, and other neurological disorders. Here we demonstrate that both mouse and human bone marrow (BM) neutrophils, when polarized with a combination of recombinant interleukin (IL)-4 and granulocyte-colony stimulating factor (G-CSF), upregulate alternative activation markers and produce an array of growth factors, thereby gaining the capacity to promote neurite outgrowth. Moreover, adoptive transfer of IL-4/G-CSF polarized BM neutrophils into experimental models of CNS injury triggered substantial axon regeneration within the optic nerve and spinal cord. These findings have far-reaching implications for the future development of autologous myeloid cell-based therapies that may bring us closer to effective solutions for reversing CNS damage.

Genetic overlap between Alzheimer's disease and immune-mediated diseases: An atlas of shared genetic determinants and biological convergence

The occurrence of immune disease comorbidities in Alzheimer's disease (AD) has been observed in both epidemiological and molecular studies, suggesting a neuroinflammatory basis in AD. However, their shared genetic components have not been systematically studied. Here, we composed an atlas of the shared genetic associations between 11 immune-mediated diseases and AD by analyzing genome-wide association studies (GWAS) summary statistics. Our results unveiled a significant genetic overlap between AD and 11 individual immune-mediated diseases despite negligible genetic correlations, suggesting a complex shared genetic architecture distributed across the genome. The shared loci between AD and immune-mediated diseases implicated several genes, including GRAMD1B, FUT2, ADAMTS4, HBEGF, WNT3, TSPAN14, DHODH, ABCB9 and TNIP1, all of which are protein-coding genes and thus potential drug targets. Top biological pathways enriched with these identified shared genes were related to the immune system and cell adhesion. In addition, in silico single-cell analyses showed enrichment of immune and brain cells, including neurons and microglia. In summary, our results suggest a genetic relationship between AD and the 11 immune-mediated diseases, pinpointing the existence of a shared however non-causal genetic basis. These identified protein-coding genes have the potential to serve as a novel path to therapeutic interventions for both AD and immune-mediated diseases and their comorbidities.

A 4D transcriptomic map for the evolution of multiple sclerosis-like lesions in the marmoset brain

Single-time-point histopathological studies on postmortem multiple sclerosis (MS) tissue fail to capture lesion evolution dynamics, posing challenges for therapy development targeting development and repair of focal inflammatory demyelination. To close this gap, we studied experimental autoimmune encephalitis (EAE) in the common marmoset, the most faithful animal model of these processes. Using MRI-informed RNA profiling, we analyzed ~600,000 single-nucleus and ~55,000 spatial transcriptomes, comparing them against EAE inoculation status, longitudinal radiological signals, and histopathological features. We categorized 5 groups of microenvironments pertinent to neural function, immune and glial responses, tissue destruction and repair, and regulatory network at brain borders. Exploring perilesional microenvironment diversity, we uncovered central roles of EAE-associated astrocytes, oligodendrocyte precursor cells, and ependyma in lesion formation and resolution. We pinpointed imaging and molecular features capturing the pathological trajectory of WM, offering potential for assessing treatment outcomes using marmoset as a platform.

Serum Growth Factors in Schizophrenia Patients

Some hypotheses include schizophrenia as a neurodevelopmental disorder, which indicates a special role in growth factors and neuroglia in the development of schizophrenia symptoms. Growth factors are cytokine molecules that play an important role in the regulation of tissue nucleation, cell development, survival, and migration of all tissues in organisms, including the brain and nervous system. The aim of the study was to determine the serum concentration of six growth factors (EGF, VEGF, FGF-2, TGF-α, PDGF-AA, PDGF-AB/BB) in schizophrenia patients and to identify the correlations with clinical characteristics. After signing an informed consent form, 236 schizophrenia patients (F20 according to the ICD-10) and 102 healthy people were recruited in the study. In patients with schizophrenia, we observed a significant elevation in the TGF-α and PDGF-AA serum levels. The duration of schizophrenia was significantly positively correlated with the FGF-2 level. The PANSS total score had a positive correlation with the FGF-2 level and a negative correlation with the TGF-α level. Our results and literature indicate the involvement of growth factors in the mechanisms of development of schizophrenia. Combined biomarker screening seems to be necessary to improve diagnosis and clinical follow-up of patients with severe mental illnesses.

Up-Regulation of Hsa-miR-11181 in Glioblastoma Multiforme as A Regulator of AKT2 and TGFBR1 Signalling

Objective

MicroRNAs (miRNAs) are short non-coding RNAs that play a role in post-transcriptional regulation of gene expression. Hsa-miR-11181 was originally introduced as a regulator of genes involved in some brain tumours. Due to the high expression of Hsa-miR-11181 in limited glioblastoma brain tumours, in this study we intend to assess the expressions of Hsa-miR-11181 and Has-miR11181-3p in brain tumour tissues and attribute new target genes to these miRNAs.

Materials and Methods

In this experimental study, total RNA from brain tissue samples was extracted for real-time quantitative polymerase chain reaction (RT-qPCR) analysis after cDNA synthesis. In order to confirm a direct interaction of Hsa-miR-11181 with two target genes, the 3ˊ UTR of AKT2 and transforming growth factor-beta receptor 1 (TGFBR1) were cloned separately for assessment by the dual luciferase assay.

Results

RT-qPCR analysis indicated that both Hsa-miR-11181-5p and Hsa-miR-11181-3p specifically up-regulated in higher grades of glioma tumours versus other brain tumour types. Consistently, lower expression levels of AKT2 and TGFBR1 were detected in higher grade gliomas compared to other types of brain tumours, which was inverse to the level of expression detected for the heparin-binding EGF-like growth factor (HBEGF) gene. The results of the dual luciferase assay supported a direct interaction of Hsa-miR-11181 with the 3ˊ UTR sequences of the AKT2 and TGFBR1 genes.

Conclusion

Overall, our data suggest that miR-1118 is a potential molecular biomarker for discrimination of glioma brain tumours from other brain tumour types.

Elevated HB-EGF expression in neural stem cells causes middle age obesity by suppressing Hypocretin/Orexin expression

Obesity is common in the middle aged population and it increases the risks of diabetes, cardiovascular diseases, certain cancers, and dementia. Yet, its etiology remains incompletely understood. Here, we show that ectopic expression of HB-EGF, an important regulator of neurogenesis, in Nestin⁺ neuroepithelial progenitors with the Cre-LoxP system leads to development of spontaneous middle age obesity in male mice accompanied by hyperglycemia and insulin resistance. The Nestin-HB-EGF mice show decreases in food uptake, energy expenditure, and physical activity, suggesting that reduced energy expenditure underlies the pathogenesis of this obesity model. However, HB-EGF expression in appetite-controlling POMC or AgRP neurons or adipocytes fails to induce obesity. Mechanistically, HB-EGF suppresses expression of Hypocretin/Orexin, an orexigenic neuropeptide hormone, in the hypothalamus of middle aged Nestin-HB-EGF mice. Hypothalamus Orexin administration alleviates the obese and hyperglycemic phenotypes in Nestin-HB-EGF mice. This study uncovers an important role for HB-EGF in regulating Orexin expression and energy expenditure and establishes a midlife obesity model whose pathogenesis involves age-dependent changes in hypothalamus neurons.

Genetic Variability in Molecular Pathways Implicated in Alzheimer's Disease: A Comprehensive Review

Alzheimer's disease (AD) is a complex neurodegenerative disease, affecting a significant part of the population. The majority of AD cases occur in the elderly with a typical age of onset of the disease above 65 years. AD presents a major burden for the healthcare system and since population is rapidly aging, the burden of the disease will increase in the future. However, no effective drug treatment for a full-blown disease has been developed to date. The genetic background of AD is extensively studied; numerous genome-wide association studies (GWAS) identified significant genes associated with increased risk of AD development. This review summarizes more than 100 risk loci. Many of them may serve as biomarkers of AD progression, even in the preclinical stage of the disease. Furthermore, we used GWAS data to identify key pathways of AD pathogenesis: cellular processes, metabolic processes, biological regulation, localization, transport, regulation of cellular processes, and neurological system processes. Gene clustering into molecular pathways can provide background for identification of novel molecular targets and may support the development of tailored and personalized treatment of AD.

Glycosaminoglycan-Protein Interactions and Their Roles in Human Disease

Glycosaminoglycans (GAGs) are a family of linear and negatively charged polysaccharides that exist ubiquitously on the human cell surface as well as in the extracellular matrix. GAGs interact with a wide range of proteins, including proteases, growth factors, cytokines, chemokines and adhesion molecules, enabling them to mediate many physiological processes, such as protein function, cellular adhesion and signaling. GAG-protein interactions participate in and intervene in a variety of human diseases, including cardiovascular disease, infectious disease, neurodegenerative diseases and tumors. The breakthrough in analytical tools and approaches during the last two decades has facilitated a greater understanding of the importance of GAG-protein interactions and their roles in human diseases. This review focuses on aspects of the molecular basis and mechanisms of GAG-protein interactions involved in human disease. The most recent advances in analytical tools, especially mass spectrometry-based GAG sequencing and binding motif characterization methods, are introduced. An update of selected families of GAG binding proteins is presented. Perspectives on development of novel therapeutics targeting specific GAG-protein interactions are also covered in this review.

APP Binds to the EGFR Ligands HB-EGF and EGF, Acting Synergistically with EGF to Promote ERK Signaling and Neuritogenesis

The amyloid precursor protein (APP) is a transmembrane glycoprotein central to Alzheimer's disease (AD) with functions in brain development and plasticity, including in neurogenesis and neurite outgrowth. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor (HB-EGF) are well-described neurotrophic and neuromodulator EGFR ligands, both implicated in neurological disorders, including AD. Pro-HB-EGF arose as a putative novel APP interactor in a human brain cDNA library yeast two-hybrid screen. Based on their structural and functional similarities, we first aimed to verify if APP could bind to (HB-)EGF proforms. Here, we show that APP interacts with these two EGFR ligands, and further characterized the effects of APP-EGF interaction in ERK activation and neuritogenesis. Yeast co-transformation and co-immunoprecipitation assays confirmed APP interaction with HB-EGF. Co-immunoprecipitation also revealed that APP binds to cellular pro-EGF. Overexpression of HB-EGF in HeLa cells, or exposure of SH-SY5Y cells to EGF, both resulted in increased APP protein levels. EGF and APP were observed to synergistically activate the ERK pathway, crucial for neuronal differentiation. Immunofluorescence analysis of cellular neuritogenesis in APP overexpression and EGF exposure conditions confirmed a synergistic effect in promoting the number and the mean length of neurite-like processes. Synergistic ERK activation and neuritogenic effects were completely blocked by the EGFR inhibitor PD 168393, implying APP/EGF-induced activation of EGFR as part of the mechanism. This work shows novel APP protein interactors and provides a major insight into the APP/EGF-driven mechanisms underlying neurite outgrowth and neuronal differentiation, with potential relevance for AD and for adult neuroregeneration.

Lentivirus-Mediated Expression of Human Secreted Amyloid Precursor Protein-Alpha Promotes Long-Term Induction of Neuroprotective Genes and Pathways in a Mouse Model of Alzheimer's Disease

BACKGROUND

Secreted amyloid precursor protein-alpha (sAPPα) can enhance memory and is neurotrophic and neuroprotective across a range of disease-associated insults, including amyloid-β toxicity. In a significant step toward validating sAPPα as a therapeutic for Alzheimer's disease (AD), we demonstrated that long-term overexpression of human sAPPα (for 8 months) in a mouse model of amyloidosis (APP/PS1) could prevent the behavioral and electrophysiological deficits that develop in these mice.

OBJECTIVE

To explore the underlying molecular mechanisms responsible for the significant physiological and behavioral improvements observed in sAPPα-treated APP/PS1 mice.

METHODS

We assessed the long-term effects on the hippocampal transcriptome following continuous lentiviral delivery of sAPPα or empty-vector to male APP/PS1 mice and wild-type controls using Affymetrix Mouse Transcriptome Assays. Data analysis was carried out within the Affymetrix Transcriptome Analysis Console and an integrated analysis of the resulting transcriptomic data was performed with Ingenuity Pathway analysis (IPA).

RESULTS

Mouse transcriptome assays revealed expected AD-associated gene expression changes in empty-vector APP/PS1 mice, providing validation of the assays used for the analysis. By contrast, there were specific sAPPα-associated gene expression profiles which included increases in key neuroprotective genes such as Decorin, betaine-GABA transporter and protocadherin beta-5, subsequently validated by qRT-PCR. An integrated biological pathways analysis highlighted regulation of GABA receptor signaling, cell survival and inflammatory responses. Furthermore, upstream gene regulatory analysis implicated sAPPα activation of Interleukin-4, which can counteract inflammatory changes in AD.

CONCLUSION

This study identified key molecular processes that likely underpin the long-term neuroprotective and therapeutic effects of increasing sAPPα levels in vivo.

Exploiting the diphtheria toxin internalization receptor enhances delivery of proteins to lysosomes for enzyme replacement therapy

Enzyme replacement therapy, in which a functional copy of an enzyme is injected either systemically or directly into the brain of affected individuals, has proven to be an effective strategy for treating certain lysosomal storage diseases. The inefficient uptake of recombinant enzymes via the mannose-6-phosphate receptor, however, prohibits the broad utility of replacement therapy. Here, to improve the efficiency and efficacy of lysosomal enzyme uptake, we exploited the strategy used by diphtheria toxin to enter into the endolysosomal network of cells by creating a chimera between the receptor-binding fragment of diphtheria toxin and the lysosomal hydrolase TPP1. We show that chimeric TPP1 binds with high affinity to target cells and is efficiently delivered into lysosomes. Further, we show superior uptake of chimeric TPP1 over TPP1 alone in brain tissue following intracerebroventricular injection in mice lacking TPP1, demonstrating the potential of this strategy for enhancing lysosomal storage disease therapy.

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.

Plasma dilution improves cognition and attenuates neuroinflammation in old mice

Our recent study has established that young blood factors are not causal, nor necessary, for the systemic rejuvenation of mammalian tissues. Instead, a procedure referred to as neutral blood exchange (NBE) that resets signaling milieu to a pro-regenerative state through dilution of old plasma, enhanced the health and repair of the muscle and liver, and promoted better hippocampal neurogenesis in 2-year-old mice (Mehdipour et al., Aging 12:8790–8819, 2020). Here we expand the rejuvenative phenotypes of NBE, focusing on the brain. Namely, our results demonstrate that old mice perform much better in novel object and novel texture (whisker discrimination) tests after a single NBE, which is accompanied by reduced neuroinflammation (less-activated CD68⁺ microglia). Evidence against attenuation/dilution of peripheral senescence-associated secretory phenotype (SASP) as the main mechanism behind NBE was that the senolytic ABT 263 had limited effects on neuroinflammation and did not enhance hippocampal neurogenesis in the old mice. Interestingly, peripherally acting ABT 263 and NBE both diminished SA-βGal signal in the old brain, demonstrating that peripheral senescence propagates to the brain, but NBE was more robustly rejuvenative than ABT 263, suggesting that rejuvenation was not simply by reducing senescence. Explaining the mechanism of the positive effects of NBE on the brain, our comparative proteomics analysis demonstrated that dilution of old blood plasma yields an increase in the determinants of brain maintenance and repair in mice and in people. These findings confirm the paradigm of rejuvenation through dilution of age-elevated systemic factors and extrapolate it to brain health and function.

Involvement of HB-EGF/Ascl1/Lin28a Genes in Dedifferentiation of Adult Mammalian Müller Glia

Previous studies from this lab have determined that dedifferentiation of Müller glia occurs after eye drop application of an α7 nicotinic acetylcholine receptor (nAChR) agonist, PNU-282987, to the adult rodent eye. PNU-282987 acts on α7 nAChRs on retinal pigment epithelial cells to stimulate production of Müller-derived progenitor cells (MDPCs) and ultimately lead to neurogenesis. This current study was designed to test the hypothesis that the activation of genes involved in the HB-EGF/Ascl1/Lin28a signaling pathway in Müller glia leads to the genesis of MDPCs. RNA-seq was performed on a Müller glial cell line (rMC-1) following contact with supernatant collected from a retinal pigment epithelial (RPE) cell line treated with PNU-282987. Differentially regulated genes were compared with published literature of Müller glia dedifferentiation that occurs in lower vertebrate regeneration and early mammalian development. HB-EGF was significantly up-regulated by 8 h and expression increased through 12 h. By 48 h, up-regulation of Ascl1 and Lin28a was observed, two genes known to be rapidly induced in dedifferentiating zebrafish Müller glia. Up-regulation of other genes known to be involved in mammalian development and zebrafish regeneration were also observed, as well as down-regulation of some factors necessary for Müller glia cell identity. RNA-seq results were verified using qRT-PCR. Using immunocytochemistry, the presence of markers associated with MDCP identity, Otx2, Nestin, and Vsx2, were found to be expressed in the 48 h treatment group cultures. This study is novel in its demonstration that Müller glia in adult rodents can be induced into regenerative activity by stimulating genes involved in the HB-EGF/Ascl1/Lin28a pathway that leads to MDPCs after introducing conditioned media from PNU-282987 treated RPE. This study furthers our understanding of the mechanism by which Müller glia dedifferentiate in response to PNU-282987 in the adult mammalian retina.

From putative brain tumor marker to high cognitive abilities: Emerging roles of a disintegrin and metalloprotease (ADAM) 12 in the brain

ADAM (a disintergin and metalloprotease) 12 is a member of the large family of multidomain metalloprotease-disintegrins, which possess cell-binding and metalloprotease properties. The enzyme is responsible for the shedding of a number of membrane-bound proteins (heparin-binding-EGF, insulin-like growth factor 2-binding proteins 3 and 5, oxytocinase, glycoprotein non-metastatic melanoma protein B and basigin). In rat and human CNS, ADAM12 is predominantly localized in white and gray matter oligodendrocytes. In addition it can be detected in astrocytes, neurons and endothelial cells. Its function in healthy brain is not well established yet, but prominent roles in CNS development, myelination and high cognitive abilities are discussed. There is increasing evidence that ADAM12 is involved in numerous major diseases of the CNS, which are summarized in the present review (brain tumors, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer´s disease, stroke, schizophrenia, autism and bipolar disorder).

Post-pubertal Difference in Nigral Dopaminergic Cells Firing in the Schizophrenia Model Prepared by Perinatal Challenges of a Cytokine, EGF

Schizophrenia in humans typically develops during and after adolescence; however, the biological underpinning for the specificity of this onset time window remains to be determined. In the present study, we investigated this knowledge gap using our own animal model for schizophrenia. Rodents and monkeys challenged with a cytokine, epidermal growth factor (EGF), as neonates are known to exhibit various behavioral and cognitive abnormalities at the post-pubertal stage. We used the EGF-challenged mice as an animal model for schizophrenia to evaluate the electrophysiological impact of this modeling on nigral dopamine neurons before and after puberty. In vivo single unit recording revealed that the burst firing of putative dopamine neurons in substantia nigra pars compacta was significantly higher in the post-pubertal stage of the EGF model than in that of control mice; in contrast, this difference was not observed in the pre-pubertal stage. The increase in burst firing was accompanied by a decline in Ca²⁺-activated K⁺ (I_SK) currents, which influence the firing pattern of dopamine neurons. In vivo local application of the SK channel blocker apamin (80 μM) to the substantia nigra was less effective at increasing burst firing in the EGF model than in control mice, suggesting the pathologic role of the I_SK decrease in this model. Thus, these results suggest that the aberrant post-pubertal hyperactivity of midbrain dopaminergic neurons is associated with the temporal specificity of the behavioral deficit of this model, and support the hypothesis that this dopaminergic aberration could be implicated in the adolescent onset of schizophrenia.

Attenuated diphtheria toxin mediates siRNA delivery

Toxins efficiently deliver cargo to cells by binding to cell surface ligands, initiating endocytosis, and escaping the endolysosomal pathway into the cytoplasm. We took advantage of this delivery pathway by conjugating an attenuated diphtheria toxin to siRNA, thereby achieving gene downregulation in patient-derived glioblastoma cells. We delivered siRNA against integrin-β1 (ITGB1)-a gene that promotes invasion and metastasis-and siRNA against eukaryotic translation initiation factor 3 subunit b (eIF-3b)-a survival gene. We demonstrated mRNA downregulation of both genes and the corresponding functional outcomes: knockdown of ITGB1 led to a significant inhibition of invasion, shown with an innovative 3D hydrogel model; and knockdown of eIF-3b resulted in significant cell death. This is the first example of diphtheria toxin being used to deliver siRNAs, and the first time a toxin-based siRNA delivery strategy has been shown to induce relevant genotypic and phenotypic effects in cancer cells.

Role of Heparin-Binding Epidermal Growth Factor-Like Growth Factor in Oxidative Stress-Associated Metabolic Diseases

Heparin-binding EGF-like growth factor (HB-EGF) is an EGF family member that interacts with epidermal growth factor receptor (EGFR) and ERBB4. Since HB-EGF was first identified as a novel growth factor secreted from a human macrophage cell line, numerous pathological and physiological functions related to cell proliferation, migration, and inflammation have been reported. Notably, the expression of HB-EGF is sensitively upregulated by oxidative stress in the endothelial cells and functions for auto- and paracrine-EGFR signaling. Overnutrition and obesity cause elevation of HB-EGF expression and EGFR signaling in the hepatic and vascular systems. Modulations of HB-EGF signaling showed a series of protections against phenotypes related to metabolic syndrome and advanced metabolic diseases, suggesting HB-EGF as a potential target against metabolic diseases.

Soluble Heparin Binding Epidermal Growth Factor-Like Growth Factor Is a Regulator of GALGT2 Expression and GALGT2-Dependent Muscle and Neuromuscular Phenotypes

GALGT2 (also B4GALNT2) encodes a glycosyltransferase that is normally confined to the neuromuscular and myotendinous junction in adult skeletal muscle. GALGT2 overexpression in muscle can inhibit muscular dystrophy in mouse models of the disease by inducing the overexpression of surrogate muscle proteins, including utrophin, agrin, laminins, and integrins. Despite its well-documented biological properties, little is known about the endogenous regulation of muscle GALGT2 expression. Here, we demonstrate that epidermal growth factor receptor (EGFR) ligands can activate the human GALGT2 promoter. Overexpression of one such ligand, soluble heparin-binding EGF-like growth factor (sHB-EGF), also stimulated mouse muscle Galgt2 gene expression and expression of GALGT2-inducible surrogate muscle genes. Deletion analysis of the GALGT2 promoter identified a 45-bp region containing a TFAP4-binding site that was required for sHB-EGF activation. sHB-EGF increased TFAP4 binding to this site in muscle cells and increased endogenous Tfap4 gene expression. sHB-EGF also increased muscle EGFR protein expression and activated EGFR-Akt signaling. sHB-EGF expression was concentrated at the neuromuscular junction, and Hbegf deletion reduced Galgt2-dependent synaptic glycosylation. Hbegf deletion also mimicked Galgt2-dependent neuromuscular and muscular dystrophy phenotypes. These data demonstrate that sHB-EGF is an endogenous regulator of muscle Galgt2 gene expression and can mimic Galgt2-dependent muscle phenotypes.

Chi3l3 induces oligodendrogenesis in an experimental model of autoimmune neuroinflammation

In demyelinating diseases including multiple sclerosis (MS), neural stem cells (NSCs) can replace damaged oligodendrocytes if the local microenvironment supports the required differentiation process. Although chitinase-like proteins (CLPs) form part of this microenvironment, their function in this differentiation process is unknown. Here, we demonstrate that murine Chitinase 3-like-3 (Chi3l3/Ym1), human Chi3L1 and Chit1 induce oligodendrogenesis. In mice, Chi3l3 is highly expressed in the subventricular zone, a stem cell niche of the adult brain, and in inflammatory brain lesions during experimental autoimmune encephalomyelitis (EAE). We find that silencing Chi3l3 increases severity of EAE. We present evidence that in NSCs Chi3l3 activates the epidermal growth factor receptor (EGFR), thereby inducing Pyk2-and Erk1/2- dependent expression of a pro-oligodendrogenic transcription factor signature. Our results implicate CLP-EGFR-Pyk2-MEK-ERK as a key intrinsic pathway controlling oligodendrogenesis.

Glycosaminoglycans from Alzheimer's disease hippocampus have altered capacities to bind and regulate growth factors activities and to bind tau

Glycosaminoglycans (GAGs), including heparan sulfates and chondroitin sulfates, are major components of the extracellular matrix. Upon interacting with heparin binding growth factors (HBGF), GAGs participate to the maintaintenance of tissue homeostasis and contribute to self-healing. Although several processes regulated by HBGF are altered in Alzheimer’s disease, it is unknown whether the brain GAG capacities to bind and regulate the function of HBGF or of other heparin binding proteins, as tau, are modified in this disease. Here, we show that total sulfated GAGs from hippocampus of Alzheimer’s disease have altered capacities to bind and potentiate the activities of growth factors including FGF-2, VEGF, and BDNF while their capacity to bind to tau is remarkable increased. Alterations of GAG structures and capacities to interact with and regulate the activity of heparin binding proteins might contribute to impaired tissue homeostasis in the Alzheimer’s disease brain.

Immune dysregulation in offspring of a bipolar parent. Altered serum levels of immune growth factors at adolescent age

Immune dysregulation plays a role in the vulnerability for mood disorders. Immune growth factors, such as Stem Cell Factor (SCF), Insulin-like Growth Factor-Binding Protein-2 (IGF-BP2), Epidermal Growth Factor (EGF), IL-7 and sCD25 have repeatedly been reported altered in patients with mood disorders. The aim of this study was to investigate levels of these factors in serum of adolescent bipolar offspring, who have a heightened risk for mood disorder development and to also analyze the data combined with previously published data. Growth factors were assessed by CBA/ELISA in adolescent bipolar offspring (n=96, mean age=16years) and in age- and gender-matched healthy controls (n=50). EGF belonged to a mutually correlating cluster of mainly neurotrophic compounds including S100B and BDNF, which were in general decreased in serum. IL-7, SCF, IGF-BP2 and sCD25, belonged to a different mutually correlating cluster of immune growth factors, which were in general increased: IGF-BP2 significantly in serum of offspring without a mood disorder, IL-7 and SCF in serum of offspring who had experienced a mood episode. This pattern of de- and increases was not different between bipolar offspring that developed or did not develop a mood disorder over time, apart from the IGF-BP2 level, which was near significantly higher in offspring later developing a mood disorder. Correlations with the previously published immune-cellular abnormalities were not found. In conclusion non-affected adolescents at familial mood disorder development risk were characterized by a distinct pattern of a series of compounds operating in a network of hematopoiesis, neurogenesis and inflammation.

Epidermal growth factor signals attenuate phenotypic and functional development of neocortical GABA neurons

Phenotypic development of neocortical GABA neurons is highly plastic and promoted by various neurotrophic factors such as neuregulin-1. A subpopulation of GABA neurons expresses not only neuregulin receptor (ErbB4) but also epidermal growth factor (EGF) receptor (ErbB1) during development, but the neurobiological action of EGF on this cell population is less understood than that of neuregulin-1. Here, we examined the effects of exogenous EGF on immature GABA neurons both in culture and in vivo and also explored physiological consequences in adults. We prepared low density cultures from the neocortex of rat embryos and treated neocortical neurons with EGF. EGF decreased protein levels of glutamic acid decarboxylases (GAD65 and GAD67), and EGF influences on neuronal survival and glial proliferation were negligible or limited. The EGF treatment also diminished the frequency of miniature inhibitory postsynaptic currents (mIPSCs). In vivo administration of EGF to mouse pups reproduced the above GABAergic phenomena in neocortical culture. In EGF-injected postnatal mice, GAD- and parvalbumin-immunoreactivities were reduced in the frontal cortex. In addition, postnatal EGF treatment decreased mIPSC frequency in, and the density of, GABAergic terminals on pyramidal cells. Although these phenotypic influences on GABA neurons became less marked during development, it later resulted in the reduced β- and γ-powers of sound-evoked electroencephalogram in adults, which is regulated by parvalbumin-positive GABA neurons and implicated in the schizophrenia pathophysiology. These findings suggest that, in contrast to the ErbB4 ligand of neuregulin-1, the ErbB1 ligand of EGF exerts unique maturation-attenuating influences on developing cortical GABAergic neurons.

Integrative Single-Cell Transcriptomics Reveals Molecular Networks Defining Neuronal Maturation During Postnatal Neurogenesis

In mammalian hippocampus, new neurons are continuously produced from neural stem cells throughout life. This postnatal neurogenesis may contribute to information processing critical for cognition, adaptation, learning, and memory, and is implicated in numerous neurological disorders. During neurogenesis, the immature neuron stage defined by doublecortin (DCX) expression is the most sensitive to regulation by extrinsic factors. However, little is known about the dynamic biology within this critical interval that drives maturation and confers susceptibility to regulatory signals. This study aims to test the hypothesis that DCX-expressing immature neurons progress through developmental stages via activity of specific transcriptional networks. Using single-cell RNA-seq combined with a novel integrative bioinformatics approach, we discovered that individual immature neurons can be classified into distinct developmental subgroups based on characteristic gene expression profiles and subgroup-specific markers. Comparisons between immature and more mature subgroups revealed novel pathways involved in neuronal maturation. Genes enriched in less mature cells shared significant overlap with genes implicated in neurodegenerative diseases, while genes positively associated with neuronal maturation were enriched for autism-related gene sets. Our study thus discovers molecular signatures of individual immature neurons and unveils potential novel targets for therapeutic approaches to treat neurodevelopmental and neurological diseases.

Role for Egr1 in the Transcriptional Program Associated with Neuronal Differentiation of PC12 Cells

PC12 cells are a well-established model to study how differences in signal transduction duration can elicit distinct cell behaviors. Epidermal growth factor (EGF) activates transient ERK signaling in PC12 cells that lasts 30–60 min, which in turn promotes proliferation; nerve growth factor (NGF) activates more sustained ERK signaling that lasts 4–6 h, which in turns induces neuronal differentiation. Data presented here extend a previous study by Mullenbrock et al. (2011) that demonstrated that sustained ERK signaling in response to NGF induces preferential expression of a 69-member gene set compared to transient ERK signaling in response to EGF and that the transcription factors AP-1 and CREB play a major role in the preferential expression of several genes within the set. Here, we examined whether the Egr family of transcription factors also contributes to the preferential expression of the gene set in response to NGF. Our data demonstrate that NGF causes transient induction of all Egr family member transcripts, but a corresponding induction of protein was detected for only Egr1 and 2. Chromatin immunoprecipitation experiments provided clearest evidence that, after induction, Egr1 binds 12 of the 69 genes that are preferentially expressed during sustained ERK signaling. In addition, Egr1 expression and binding upstream of its target genes were both sustained in response to NGF versus EGF within the same timeframe that its targets are preferentially expressed. These data thus provide evidence that Egr1 contributes to the transcriptional program activated by sustained ERK signaling in response to NGF, specifically by contributing to the preferential expression of its target genes identified here.

Growth factors as clinical biomarkers of prognosis and diagnosis in psychiatric disorders

The psychiatric disorders are one of the most disabling illnesses in the world and represent a major problem for public health. These disorders are characterized by neuroanatomical or biochemical changes and it has been suggested that such changes may be due to inadequate neurodevelopment. Diverse alterations in the gene expression and/or serum level of specific growth factors have been implicated in the etiology, symptoms and progression of some psychiatric disorders. Herein, we summarize the latest information regarding the role of brain-derived neurotrophic factor (BDNF), epidermal growth factor (EGF), fibroblast growth factor (FGF), Insulin-like growth factor (IGF-1), neuroregulin-1 (NGR-1), erythropoietin (EPO), vascular growth factor (VEGF), transforming growth factor beta (TGF-β), nerve growth factor (NGF) and others cytokines in the pathogenesis of schizophrenia, depression, bipolar and anxiety disorders. Focusing on the role of these growth factors and their relationship with the main impairments (cognitive, emotional and social) of these pathologies. Some of these signaling molecules may be suitable biological markers for diagnosis and prognosis in cognitive, mood and social disabilities across different mental disorders.

The Role of Stem Cells in the Treatment of Cerebral Palsy: a Review

Cerebral palsy (CP) is a neuromuscular disease due to injury in the infant's brain. The CP disorder causes many neurologic dysfunctions in the patient. Various treatment methods have been used for the management of CP disorder. However, there has been no absolute cure for this condition. Furthermore, some of the procedures which are currently used for relief of symptoms in CP cause discomfort or side effects in the patient. Recently, stem cell therapy has attracted a huge interest as a new therapeutic method for treatment of CP. Several investigations in animal and human with CP have demonstrated positive potential of stem cell transplantation for the treatment of CP disorder. The ultimate goal of this therapeutic method is to harness the regenerative capacity of the stem cells causing a formation of new tissues to replace the damaged tissue. During the recent years, there have been many investigations on stem cell therapy. However, there are still many unclear issues regarding this method and high effort is needed to create a technology as a perfect treatment. This review will discuss the scientific background of stem cell therapy for cerebral palsy including evidences from current clinical trials.

Cypermethrin Stimulates GSK3β-Dependent Aβ and p-tau Proteins and Cognitive Loss in Young Rats: Reduced HB-EGF Signaling and Downstream Neuroinflammation as Critical Regulators

Pesticide exposure is recognized as a risk factor for Alzheimer's disease (AD). We investigated early signs of AD-like pathology upon exposure to a pyrethroid pesticide, cypermethrin, reported to impair neurodevelopment. We treated weanling rats with cypermethrin (10 and 25 mg/kg) and detected dose-dependent increase in the key proteins of AD, amyloid beta (Aβ), and phospho-tau, in frontal cortex and hippocampus as early as postnatal day 45. Upregulation of Aβ pathway involved an increase in amyloid precursor protein (APP) and its pro-amyloidogenic processing through beta-secretase (BACE) and gamma-secretase. Tau pathway entailed elevation in tau and glycogen-synthase kinase-3-beta (GSK3β)-dependent, phospho-tau. GSK3β emerged as a molecular link between the two pathways, evident from reduction in phospho-tau as well as BACE upon treating GSK3β inhibitor, lithium chloride. Exploring the mechanism revealed an attenuated heparin-binding epidermal growth factor (HB-EGF) signaling and downstream astrogliosis-mediated neuroinflammation to be responsible for inducing Aβ and phospho-tau. Cypermethrin caused a proximal reduction in HB-EGF, which promoted astrocytic nuclear factor kappa B signaling and astroglial activation close to Aβ and phospho-tau. Glial activation stimulated generation of interleukin-1 (IL-1), which upregulated GSK3β, and APP and tau as well, resulting in co-localization of Aβ and phospho-tau with IL-1 receptor. Intracerebral insertion of exogenous HB-EGF restored its own signaling and suppressed neuroinflammation and thereby Aβ and phospho-tau in cypermethrin-exposed rats, proving a central role of reduced HB-EGF signaling in cypermethrin-mediated neurodegeneration. Furthermore, cypermethrin stimulated cognitive impairments, which could be prevented by exogenous HB-EGF. Our data demonstrate that cypermethrin induces premature upregulation of GSK3β-dependent Aβ and tau pathways, where HB-EGF signaling and neuroinflammation serve as essential regulators.

Whole-scale neurobehavioral assessments of photothrombotic ischemia in freely moving mice

BACKGROUND

Neurobehavioral assessments have been considered as an essential component of preclinical research in ischemic stroke. However, real-time neurobehavioral evaluation is seldom applied during ischemia induction as it is usually accompanied with anesthesia.

NEW METHOD

We induced photothrombosis in freely moving mice after one-week recovery from cannula implantation surgeries. After rose bengal (RB) injection (100 mg/kg, i.p.), photothrombosis was induced in freely moving mice by 473 nm laser irradiation through the cannulas implanted into unilateral primary motor cortex beforehand. Mice received nimodipine (15 mg/kg, i.p.), a widely used anti-ischemic agent, or vehicle before irradiation. Motor coordination and equilibrium were evaluated by rotarod and rung walk tests throughout the whole process of ischemia. Endurance capacity was assessed by treadmill at 1 day and 7 days after irradiation. Mice were decapitated at different time points post irradiation for TTC (2,3,5-triphenyltetrazolium chloride) staining.

RESULTS

Consistent with the results of TTC staining, motor deficits firstly occurred at 15-min post irradiation and aggravated 1-day later, while the capacity improved 3-days later and partially recovered 7-days post irradiation. And, the recovery process was accelerated by nimodipine application.

COMPARISON WITH EXISTING METHODS

This method established a precise linkage between focal brain ischemia development and neurobehavioral deficits throughout a full scale of photothrombosis, which avoided the confounding factors of anesthetics and surgeries on neurobehavioral assessments, as infarct was induced in freely moving mice.

CONCLUSIONS

This method with high temporal and spatial resolution will be an optimal model for neurobehavioral evaluation in preclinical anti-ischemic drug screening.