Lymphotoxin β receptor-mediated NFκB signaling promotes glial lineage differentiation and inhibits neuronal lineage differentiation in mouse brain neural stem/progenitor cells

Abstract

BackgroundLymphotoxin (LT) is a lymphokine mainly expressed in lymphocytes. LTα binds one or two membrane-associated LTβ to form LTα2β1 or LTα1β2 heterotrimers. The predominant LTα1β2 binds to LTβ receptor (LTβR) primarily expressed in epithelial and stromal cells. Most studies on LTβR signaling have focused on the organization, development, and maintenance of lymphoid tissues. However, the roles of LTβR signaling in the nervous system, particularly in neurogenesis, remain unknown. Here, we investigated the role of LTβR-mediated NFκB signaling in regulating neural lineage differentiation.MethodsThe C57BL/6J wild-type and GFAP-dnIκBα transgenic mice were used. Serum-free embryoid bodies were cultured from mouse embryonic stem cells and further induced into neural stem/progenitor cells (NSCs/NPCs). Primary neurospheres were cultured from embryonic and adult mouse brains followed by monolayer culture for amplification/passage. NFκB activation was determined by adenovirus-mediated NFκB-firefly-luciferase reporter assay and p65/RelB/p52 nuclear translocation assay. LTβR mRNA expression was evaluated by quantitative RT-PCR and LTβR protein expression was determined by immunohistochemistry and Western blot analysis. Multilabeled immunocytochemistry or immunohistochemistry followed by fluorescent confocal microscopy and quantitative analysis of neural lineage differentiation were performed. Graphing and statistical analysis were performed with GraphPad Prism software.ResultsIn cultured NSCs/NPCs, LTα1β2 stimulation induced an activation of classical and non-classical NFκB signaling. The expression of LTβR-like immunoreactivity in GFAP+/Sox2+ NSCs was identified in well-established neurogenic zones of adult mouse brain. Quantitative RT-PCR and Western blot analysis validated the expression of LTβR in cultured NSCs/NPCs and brain neurogenic regions. LTβR expression was significantly increased during neural induction. LTα1β2 stimulation in cultured NSCs/NPCs promoted astroglial and oligodendrocytic lineage differentiation, but inhibited neuronal lineage differentiation. Astroglial NFκB inactivation in GFAP-dnIκBα transgenic mice rescued LTβR-mediated abnormal phenotypes of cultured NSCs/NPCs.ConclusionThis study provides the first evidence for the expression and function of LTβR signaling in NSCs/NPCs. Activation of LTβR signaling promotes glial lineage differentiation. Our results suggest that neurogenesis is regulated by the adaptive immunity and inflammatory responses.Electronic supplementary materialThe online version of this article (10.1186/s12974-018-1074-z) contains supplementary material, which is available to authorized users.

The Nuclear Protein HOXB13 Enhances Methylmercury Toxicity by Inducing Oncostatin M and Promoting Its Binding to TNFR3 in Cultured Cells

“…Recently, the adverse effects of methylmercury on fetuses, due to pregnant women eating a diet high in fish, are becoming a global concern. As described above, TNFR3 is expressed in neural stem cells of the brain, and HOXB13 is known to be highly expressed during the developmental stages of the mouse [34]. Therefore, our finding that methylmercury toxicity is enhanced by the activation of the OSM/TNFR3 pathway via HOXB13 may be important for methylmercury toxicity during fetal development and could benefit future research into its prevention.…”

“…Thus, HOXB13 is, at least, expressed in the adult mouse brain and could be associated with central nervous system injury caused by methylmercury. In contrast, OSM has been reported to be expressed in microglia and astrocytes [32,33], whereas TNFR3 is expressed in neural stem cells of the brain [34]. In our study, HEK293 and mouse neuronal stem cells (C17.2) were used as simple models to show that methylmercury induces OSM expression via HOXB13 and causes cell death through TNFR3 in an autocrine manner.…”

Cellular Specificity of NF-κB Function in the Nervous System

“…As in neurons, the predominant activated form of NF-κB in mature glial cells appears to contain the RelA/p65 subunit, rather than utilizing non-cannonical signaling mediated by RelB:p52 heterodimers. However, evidence for the involvement of p52 and RelB has been reported in neural stem cells from the adult mouse nervous system following lymphotoxin β receptor-mediated signaling (52). RelB and p52 are also reported to function in driving tumor progression in glioma cell lines and is correlated with invasive potential (53).…”

“…For example, a transgenic mouse line expressing the DN-IκB under control of the GFAP promoter, displays expression in precursor cells and a deficit in adult neurogenesis (68), as well as expression in adult astroglial cells which complicates determining the origins of observed learning and memory deficits (69). GFAP-promoter driven expression of DN-IκB in cultured neural stem cells is reported to promote glial lineage differentiation at the expense of neuronal lineage differentiation (52). Recently a new astrocyte-selective marker has been identified, Aldh1I1, which is reported to show little or no detection in neuronal populations or precursors (67).…”

Role of CGRP in Neuroimmune Interaction via NF-κB Signaling Genes in Glial Cells of Trigeminal Ganglia

“…Activation of Ltbr signaling promotes astroglia and oligodendrocytic, but inhibits neuronal, lineage differentiation. Astroglial inactivation of NF-κB signaling compromises astroglial, but promotes neuronal, lineage differentiation [ 67 ]. There are no research reporting the connection between the upregulation of Ltbr and Minocycline’s anti-apoptotic, neuroprotective, or anti-inflammatory profile through glial inactivation or inhibition.…”