A Preliminary Study of Mild Heat Stress on Inflammasome Activation in Murine Macrophages.

Inflammation and mitochondrial-dependent oxidative stress are interrelated processes implicated in multiple neuroinflammatory disorders, including Alzheimer's disease (AD) and depression. Exposure to elevated temperature (hyperthermia) is proposed as a non-pharmacological, anti-inflammatory treatment for these disorders; however, the underlying mechanisms are not fully understood. Here we asked if the inflammasome, a protein complex essential for orchestrating the inflammatory response and linked to mitochondrial stress, might be modulated by elevated temperatures. To test this, in preliminary studies, immortalized bone-marrow-derived murine macrophages (iBMM) were primed with inflammatory stimuli, exposed to a range of temperatures (37-41.5 °C), and examined for markers of inflammasome and mitochondrial activity. We found that exposure to mild heat stress (39 °C for 15 min) rapidly inhibited iBMM inflammasome activity. Furthermore, heat exposure led to decreased ASC speck formation and increased numbers of polarized mitochondria. These results suggest that mild hyperthermia inhibits inflammasome activity in the iBMM, limiting potentially harmful inflammation and mitigating mitochondrial stress. Our findings suggest an additional potential mechanism by which hyperthermia may exert its beneficial effects on inflammatory diseases.

Nociceptor neurons affect cancer immunosurveillance.

Solid tumours are innervated by nerve fibres that arise from the autonomic and sensory peripheral nervous systems1-5. Whether the neo-innervation of tumours by pain-initiating sensory neurons affects cancer immunosurveillance remains unclear. Here we show that melanoma cells interact with nociceptor neurons, leading to increases in their neurite outgrowth, responsiveness to noxious ligands and neuropeptide release. Calcitonin gene-related peptide (CGRP)-one such nociceptor-produced neuropeptide-directly increases the exhaustion of cytotoxic CD8+ T cells, which limits their capacity to eliminate melanoma. Genetic ablation of the TRPV1 lineage, local pharmacological silencing of nociceptors and antagonism of the CGRP receptor RAMP1 all reduced the exhaustion of tumour-infiltrating leukocytes and decreased the growth of tumours, nearly tripling the survival rate of mice that were inoculated with B16F10 melanoma cells. Conversely, CD8+ T cell exhaustion was rescued in sensory-neuron-depleted mice that were treated with local recombinant CGRP. As compared with wild-type CD8+ T cells, Ramp1-/- CD8+ T cells were protected against exhaustion when co-transplanted into tumour-bearing Rag1-deficient mice. Single-cell RNA sequencing of biopsies from patients with melanoma revealed that intratumoral RAMP1-expressing CD8+ T cells were more exhausted than their RAMP1-negative counterparts, whereas overexpression of RAMP1 correlated with a poorer clinical prognosis. Overall, our results suggest that reducing the release of CGRP from tumour-innervating nociceptors could be a strategy to improve anti-tumour immunity by eliminating the immunomodulatory effects of CGRP on cytotoxic CD8+ T cells.

Nociceptor neurons promote IgE class switch in B cells.

Nociceptors, the high-threshold primary sensory neurons that trigger pain, interact with immune cells in the periphery to modulate innate immune responses. Whether they also participate in adaptive and humoral immunity is, however, not known. In this study, we probed if nociceptors have a role in distinct airway and skin models of allergic inflammation. In both models, the genetic ablation and pharmacological silencing of nociceptors substantially reduced inflammatory cell infiltration to the affected tissue. Moreover, we also found a profound and specific deficit in IgE production in these models of allergic inflammation. Mechanistically, we discovered that the nociceptor-released neuropeptide substance P helped trigger the formation of antibody-secreting cells and their release of IgE. Our findings suggest that nociceptors, in addition to their contributions to innate immunity, play a key role in modulating the adaptive immune response, particularly B cell antibody class switching to IgE.

FcεR1-expressing nociceptors trigger allergic airway inflammation.

BACKGROUND: Lung nociceptor neurons amplify immune cell activity and mucus metaplasia in response to an inhaled allergen challenge in sensitized mice. OBJECTIVE: We sought to identify the cellular mechanisms by which these sensory neurons are activated subsequent to allergen exposure. METHODS: We used calcium microscopy and electrophysiologic recording to assess whether vagal neurons directly respond to the model allergen ovalbumin (OVA). Next, we generated the first nociceptor-specific FcεR1γ knockdown (TRPV1Cre::FcεR1γfl/fl) mice to assess whether this targeted invalidation would affect the severity of allergic inflammation in response to allergen challenges. RESULTS: Lung-innervating jugular nodose complex ganglion neurons express the high-affinity IgE receptor FcεR1, the levels of which increase in OVA-sensitized mice. FcεR1γ-expressing vagal nociceptor neurons respond directly to OVA complexed with IgE with depolarization, action potential firing, calcium influx, and neuropeptide release. Activation of vagal neurons by IgE-allergen immune complexes, through the release of substance P from their peripheral terminals, directly amplifies TH2 cell influx and polarization in the airways. Allergic airway inflammation is decreased in TRPV1Cre::FcεR1γfl/fl mice and in FcεR1α-/- mice into which bone marrow has been transplanted. Finally, increased in vivo circulating levels of IgE following allergen sensitization enhances the responsiveness of FcεR1 to immune complexes in both mouse jugular nodose complex ganglion neurons and human induced pluripotent stem cell-derived nociceptors. CONCLUSIONS: Allergen sensitization triggers a feedforward inflammatory loop between IgE-producing plasma cells, FcεR1-expressing vagal sensory neurons, and TH2 cells, which helps to both initiate and amplify allergic airway inflammation. These data highlight a novel target for reducing allergy, namely, FcεR1γ expressed by nociceptors.

Epineural optogenetic activation of nociceptors initiates and amplifies inflammation.

Activation of nociceptor sensory neurons by noxious stimuli both triggers pain and increases capillary permeability and blood flow to produce neurogenic inflammation1,2, but whether nociceptors also interact with the immune system remains poorly understood. Here we report a neurotechnology for selective epineural optogenetic neuromodulation of nociceptors and demonstrate that nociceptor activation drives both protective pain behavior and inflammation. The wireless optoelectronic system consists of sub-millimeter-scale light-emitting diodes embedded in a soft, circumneural sciatic nerve implant, powered and driven by a miniaturized head-mounted control unit. Photostimulation of axons in freely moving mice that express channelrhodopsin only in nociceptors resulted in behaviors characteristic of pain, reflecting orthodromic input to the spinal cord. It also led to immune reactions in the skin in the absence of inflammation and potentiation of established inflammation, a consequence of the antidromic activation of nociceptor peripheral terminals. These results reveal a link between nociceptors and immune cells, which might have implications for the treatment of inflammation.

Publisher Correction: The metabolite BH4 controls T cell proliferation in autoimmunity and cancer.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.

The metabolite BH4 controls T cell proliferation in autoimmunity and cancer.

Genetic regulators and environmental stimuli modulate T cell activation in autoimmunity and cancer. The enzyme co-factor tetrahydrobiopterin (BH4) is involved in the production of monoamine neurotransmitters, the generation of nitric oxide, and pain1,2. Here we uncover a link between these processes, identifying a fundamental role for BH4 in T cell biology. We find that genetic inactivation of GTP cyclohydrolase 1 (GCH1, the rate-limiting enzyme in the synthesis of BH4) and inhibition of sepiapterin reductase (the terminal enzyme in the synthetic pathway for BH4) severely impair the proliferation of mature mouse and human T cells. BH4 production in activated T cells is linked to alterations in iron metabolism and mitochondrial bioenergetics. In vivo blockade of BH4 synthesis abrogates T-cell-mediated autoimmunity and allergic inflammation, and enhancing BH4 levels through GCH1 overexpression augments responses by CD4- and CD8-expressing T cells, increasing their antitumour activity in vivo. Administration of BH4 to mice markedly reduces tumour growth and expands the population of intratumoral effector T cells. Kynurenine-a tryptophan metabolite that blocks antitumour immunity-inhibits T cell proliferation in a manner that can be rescued by BH4. Finally, we report the development of a potent SPR antagonist for possible clinical use. Our data uncover GCH1, SPR and their downstream metabolite BH4 as critical regulators of T cell biology that can be readily manipulated to either block autoimmunity or enhance anticancer immunity.

Bibliometric analysis of recent sodium channel research.

Although sodium channels have been a hot multidisciplinary focus for decades and most of nerve system drugs worked on alerting sodium channel function, the trends and future directions of sodium channel studies have not been comprehensive analyzed bibliometrically. Herein, we collected the scientific publications of sodium channels research and constructed a model to evaluate the current trend systematically. Publications were selected from the Web of Science Core Collection (WoSCC) database from 2013 to 2017. Microsoft Excel 2016, Prism 6, and CiteSpace V software were used to analyze publication outputs, journal sources, countries, territories, institutions, authors, and research areas. A total of 4,275 publications on sodium channel research were identified. PLoS ONE ranked top for publishing 170 papers. The United States of America had the largest number of publications (1,595), citation frequency (19,490), and H-index (53). S. G. Waxman (62 publications) and W. A. Catterall (585 citations) were the most productive authors and had the greatest co-citation counts. This is the first report that shows the trends and future development in sodium channel publications, and our study provides a clear profile for the contribution to this field by countries, authors, keywords, and institutions.

Mechanistic Differences in Neuropathic Pain Modalities Revealed by Correlating Behavior with Global Expression Profiling.

Chronic neuropathic pain is a major morbidity of neural injury, yet its mechanisms are incompletely understood. Hypersensitivity to previously non-noxious stimuli (allodynia) is a common symptom. Here, we demonstrate that the onset of cold hypersensitivity precedes tactile allodynia in a model of partial nerve injury, and this temporal divergence was associated with major differences in global gene expression in innervating dorsal root ganglia. Transcripts whose expression change correlates with the onset of cold allodynia were nociceptor related, whereas those correlating with tactile hypersensitivity were immune cell centric. Ablation of TrpV1 lineage nociceptors resulted in mice that did not acquire cold allodynia but developed normal tactile hypersensitivity, whereas depletion of macrophages or T cells reduced neuropathic tactile allodynia but not cold hypersensitivity. We conclude that neuropathic pain incorporates reactive processes of sensory neurons and immune cells, each leading to distinct forms of hypersensitivity, potentially allowing drug development targeted to each pain type.

Alternative activation generates IL-10 producing type 2 innate lymphoid cells.

Type 2 innate lymphoid cells (ILC2) share cytokine and transcription factor expression with CD4+ Th2 cells, but functional diversity of the ILC2 lineage has yet to be fully explored. Here, we show induction of a molecularly distinct subset of activated lung ILC2, termed ILC210. These cells produce IL-10 and downregulate some pro-inflammatory genes. Signals that generate ILC210 are distinct from those that induce IL-13 production, and gene expression data indicate that an alternative activation pathway leads to the generation of ILC210. In vivo, IL-2 enhances ILC210 generation and is associated with decreased eosinophil recruitment to the lung. Unlike most activated ILC2, the ILC210 population contracts after cessation of stimulation in vivo, with maintenance of a subset that can be recalled by restimulation, analogous to T-cell effector cell and memory cell generation. These data demonstrate the generation of a previously unappreciated IL-10 producing ILC2 effector cell population.

Sense and Immunity: Context-Dependent Neuro-Immune Interplay.

The sensory nervous and immune systems, historically considered autonomous, actually work in concert to promote host defense and tissue homeostasis. These systems interact with each other through a common language of cell surface G protein-coupled receptors and receptor tyrosine kinases as well as cytokines, growth factors, and neuropeptides. While this bidirectional communication is adaptive in many settings, helping protect from danger, it can also become maladaptive and contribute to disease pathophysiology. The fundamental logic of how, where, and when sensory neurons and immune cells contribute to either health or disease remains, however, unclear. Our lab and others' have begun to explore how this neuro-immune reciprocal dialog contributes to physiological and pathological immune responses and sensory disorders. The cumulative results collected so far indicate that there is an important role for nociceptors (noxious stimulus detecting sensory neurons) in driving immune responses, but that this is highly context dependent. To illustrate this concept, we present our findings in a model of airway inflammation, in which nociceptors seem to have major involvement in type 2 but not type 1 adaptive immunity.

In vitro Differentiation of Murine Innate Lymphoid Cells from Common Lymphoid Progenitor Cells.

Subtypes of innate lymphoid cells (ILC), defined based on their cytokine secretion profiles and transcription factor expression, are important for host protection from pathogens and maintaining tissue homeostasis. ILCs develop from common lymphoid progenitors (CLP) in the bone marrow. Using the methods described here, we have previously shown that loss of the transcriptional regulator TOX (Thymocyte-selection associated HMG-box protein) leads to specific changes in ILC development and differentiation. Here, we describe how to obtain ILCs from in vivo isolated CLP grown in vitro.

The Role of TOX in the Development of Innate Lymphoid Cells.

TOX, an evolutionarily conserved member of the HMG-box family of proteins, is essential for the development of various cells of both the innate and adaptive immune system. TOX is required for the development of CD4(+) T lineage cells in the thymus, including natural killer T and T regulatory cells, as well as development of natural killer cells and fetal lymphoid tissue inducer cells, the latter required for lymph node organogenesis. Recently, we have identified a broader role for TOX in the innate immune system, demonstrating that this nuclear protein is required for generation of bone marrow progenitors that have potential to give rise to all innate lymphoid cells. Innate lymphoid cells, classified according to transcription factor expression and cytokine secretion profiles, derive from common lymphoid progenitors in the bone marrow and require Notch signals for their development. We discuss here the role of TOX in specifying CLP toward an innate lymphoid cell fate and hypothesize a possible role for TOX in regulating Notch gene targets during innate lymphoid cell development.

The development of innate lymphoid cells requires TOX-dependent generation of a common innate lymphoid cell progenitor.

Diverse innate lymphoid cell (ILC) subtypes have been defined on the basis of effector function and transcription factor expression. ILCs derive from common lymphoid progenitors, although the transcriptional pathways that lead to ILC-lineage specification remain poorly characterized. Here we found that the transcriptional regulator TOX was required for the in vivo differentiation of common lymphoid progenitors into ILC lineage-restricted cells. In vitro modeling demonstrated that TOX deficiency resulted in early defects in the survival or proliferation of progenitor cells, as well as ILC differentiation at a later stage. In addition, comparative transcriptome analysis of bone marrow progenitors revealed that TOX-deficient cells failed to upregulate many genes of the ILC program, including genes that are targets of Notch, which indicated that TOX is a key determinant of early specification to the ILC lineage.

Lentiviral vector-mediated genetic modification of human neural progenitor cells for ex vivo gene therapy.

Human neural progenitor cells (hNPC) hold great potential as an ex vivo system for delivery of therapeutic proteins to the central nervous system. When cultured as aggregates, termed neurospheres, hNPC are capable of significant in vitro expansion. In the current study, we present a robust method for lentiviral vector-mediated gene delivery into hNPC that maintains the differentiation and proliferative properties of neurosphere cultures while minimizing the amount of viral vector used and controlling the number of insertion sites per population. This method results in long-term, stable expression even after differentiation of the hNPC to neurons and astrocytes and allows for generation of equivalent transgenic populations of hNPC. In addition, the in vitro analysis presented predicts the behavior of transgenic lines in vivo when transplanted into a rodent model of Parkinson's disease. The methods presented provide a powerful tool for assessing the impact of factors such as promoter systems or different transgenes on the therapeutic utility of these cells.

Over-expression of alpha-synuclein in human neural progenitors leads to specific changes in fate and differentiation.

Missense mutations and extra copies of the alpha-Synuclein gene result in Parkinson disease (PD). Human stem and progenitor cells can be expanded from embryonic tissues and provide a source of non-transformed neural cells to explore the effects of these pathogenic mutations specifically in human nervous tissue. We over-expressed the wild type, A53T and A30P forms of alpha-synuclein in expanded populations of progenitors derived from the human fetal cortex. The protein localized in the nucleus and around microvesicles. Only the A53T form was acutely toxic, suggesting a unique vulnerability of these progenitors to this mutation. Interestingly, constitutive over-expression of wild-type alpha-synuclein progressively impaired the innate ability of progenitors to switch toward gliogenesis at later passages. To explore the effect of alpha-synuclein on neuronal subtypes selectively affected in PD, such as dopaminergic neurons, alpha-synuclein and its mutations were also over-expressed in terminally differentiating neuroectodermal cultures derived from human embryonic stem cells (hESC). Alpha-synuclein induced acute cytotoxicity and reduced the number of neurons expressing either tyrosine hydroxylase or gamma-aminobutyric acid over time. Consistent with the selective vulnerability of ventral midbrain dopaminergic neurons, alpha-synuclein cytotoxicity appeared most pronounced following FGF8/SHH specification and was decreased by inhibition of dopamine synthesis. Together, these data show that alpha-synuclein over-expressed in human neural embryonic cells results in patterns of degeneration that in some cases match features of Parkinson Disease. Thus, neural cells derived from hESC provide a useful model system to understand the development of alpha-synuclein-related pathologies and allow therapeutic drug screening.