Takuto Ohki

A pain-mediated neural signal induces relapse in murine autoimmune encephalomyelitis, a multiple sclerosis model

Although pain is a common symptom of various diseases and disorders, its contribution to disease pathogenesis is not well understood. Here we show using murine experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS), that pain induces EAE relapse. Mechanistic analysis showed that pain induction activates a sensory-sympathetic signal followed by a chemokine-mediated accumulation of MHC class II+CD11b+ cells that showed antigen-presentation activity at specific ventral vessels in the fifth lumbar cord of EAE-recovered mice. Following this accumulation, various immune cells including pathogenic CD4+ T cells recruited in the spinal cord in a manner dependent on a local chemokine inducer in endothelial cells, resulting in EAE relapse. Our results demonstrate that a pain-mediated neural signal can be transformed into an inflammation reaction at specific vessels to induce disease relapse, thus making this signal a potential therapeutic target. DOI: http://dx.doi.org/10.7554/eLife.08733.001

Brain micro-inflammation at specific vessels dysregulates organ-homeostasis via the activation of a new neural circuit.

Impact of stress on diseases including gastrointestinal failure is well-known, but molecular mechanism is not understood. Here we show underlying molecular mechanism using EAE mice. Under stress conditions, EAE caused severe gastrointestinal failure with high-mortality. Mechanistically, autoreactive-pathogenic CD4+ T cells accumulated at specific vessels of boundary area of third-ventricle, thalamus, and dentate-gyrus to establish brain micro-inflammation via stress-gateway reflex. Importantly, induction of brain micro-inflammation at specific vessels by cytokine injection was sufficient to establish fatal gastrointestinal failure. Resulting micro-inflammation activated new neural pathway including neurons in paraventricular-nucleus, dorsomedial-nucleus-of-hypothalamus, and also vagal neurons to cause fatal gastrointestinal failure. Suppression of the brain micro-inflammation or blockage of these neural pathways inhibited the gastrointestinal failure. These results demonstrate direct link between brain micro-inflammation and fatal gastrointestinal disease via establishment of a new neural pathway under stress. They further suggest that brain micro-inflammation around specific vessels could be switch to activate new neural pathway(s) to regulate organ homeostasis. DOI: http://dx.doi.org/10.7554/eLife.25517.001

Gateway reflexes: A new paradigm of neuroimmune interactions

The immune system is affected considerably by the physical environment. The molecular mechanisms that regulate this connection are not well understood. Because neural activities sense the environment, it has been hypothesized that neural signals transduce environmental stimulations into immune responses. Recently, we discovered that regional neural activations change the dynamics of immune cell migration through the activity of endothelial cells by using a multiple sclerosis model, experimental autoimmune encephalomyelitis. More specifically, we identified the dorsal vessels of the fifth lumbar (L5) spinal cord as the initial entry site of pathogenic T cells. This entry site was defined by the activation of sensory neurons innervating from the soleus muscles, which are the main antigravity muscles. The resulting sensory neural activation created a gateway through the activation of regional sympathetic pathways to increase the expression of chemokines at the dorsal vessels of the L5 spinal cord, attracting autoreactive pathogenic T cells. In other experiments, we activated different regional neurons by electric pulses or pain sensation and discovered that gateways for immune cells, including autoreactive pathogenic T cells, are dependent on the site of the regional neural activation, particularly the sensory–sympathetic crosstalk. We termed these neuroimmune interactions as “gateway reflexes.” In the present review, we discuss details of the gateway reflex.

Rbm10 regulates inflammation development via alternative splicing of Dnmt3b

RNA-binding motif 10 (Rbm10) is an RNA-binding protein that regulates alternative splicing, but its role in inflammation is not well defined. Here, we show that Rbm10 controls appropriate splicing of DNA (cytosine-5)-methyltransferase 3b (Dnmt3b), a DNA methyltransferase, to regulate the activity of NF-κB-responsive promoters and consequently inflammation development. Rbm10 deficiency suppressed NF-κB-mediated responses in vivo and in vitro. Mechanistic analysis showed that Rbm10 deficiency decreased promoter recruitment of NF-κB, with increased DNA methylation of the promoter regions in NF-κB-responsive genes. Consistently, Rbm10 deficiency increased the expression level of Dnmt3b2, which has enzyme activity, while it decreased the splicing isoform Dnmt3b3, which does not. These two isoforms associated with NF-κB efficiently, and overexpression of enzymatically active Dnmt3b2 suppressed the expression of NF-κB targets, indicating that Rbm10-mediated Dnmt3b2 regulation is important for the induction of NF-κB-mediated transcription. Therefore, Rbm10-dependent Dnmt3b regulation is a possible therapeutic target for various inflammatory diseases.

Gateway reflex: neural activation-mediated immune cell gateways in the central nervous system

The neural regulation of organs can be categorized as systemic or local. Whereas systemic regulation by the hypothalamus-pituitary-adrenal gland-mediated release of steroid hormones has been well studied, the mechanisms for local regulation have only recently emerged. Two types of local neural regulation are known, the gateway reflex and the inflammatory reflex. The gateway reflex describes a mechanism that converts regional neural stimulations into inflammatory outputs by changing the state of specific blood vessels. Molecularly, the enhancement of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) activity in endothelial cells by neurotransmitters, such as noradrenaline and ATP, induces an enhanced production of pro-inflammatory mediators, including chemokines, which form immune cell gateways at specific vessels. Several types of gateway reflex have been identified, and each regulates distinct organs by creating gateways for autoreactive T cells that induce local inflammation. On the other hand, the inflammatory reflex elicits an anti-inflammatory response through vagal nerves. Here, we summarize recent works on these two local neuro-immune interactions, giving special focus to the gateway reflex.

The Gateway Reflex, a Novel Neuro‐immune Interaction, is Critical for the Development of Mouse Multiple Sclerosis (MS) Models

The central nervous system (CNS) is an immune‐privileged tissue protected by the brain– blood barrier (BBB), which limits the absorption of substances and cells from blood flow. In the case of inflammatory diseases in the CNS, such as multiple sclerosis (MS), however, autoreactive T cells that attack brain autoantigens, including myelin proteins, circum‐ vent the BBB. Despite the wide distribution of brain autoantigens, demyelination often occurs as discrete foci. This fact suggests that there might be a certain cue that guides autoreactive T cells to particular site(s) in the CNS. In other words, there exists a mechanism that facilitates a site‐specific accumulation of autoreactive T cells in the CNS. Using a murine model of MS, experimental autoimmune encephalomyelitis (EAE), we identi‐ fied dorsal vessels of the fifth lumbar (L5) spinal cord as the initial entry site of immune cells. The formation of a gateway for immune cells is defined by local neural stimula‐ tions. For example, neural stimulation by gravity creates this gateway by increasing the expression of chemokines that attract autoreactive T cells. Regional neural activation by the other stimuli, such as electric pulses or pain sensation, also induces gateway formation, but at different blood vessels via chemokine expression. These neuro‐immune interac‐ tions are examples of the gateway reflex and are extensively reviewed in this chapter.

Pain is an inducer for relapse in multiple sclerosis models through a regional neural signal

Pain is a common symptom in many diseases including multiple sclerosis (MS), and chronic pain greatly reduces the patient’s quality of life. Pain is often considered a by-product of disease, with little consideration given to whether pain directly worsens disease progression or symptoms. We previously reported the gateway reflex, a phenomenon in which a regional neural signal, caused by gravitymediated stimulation of the soleus muscles, induces the expression of a neurotransmitter at the dorsal blood vessels of the fifth lumbar (L5) cord. This expression in turn causes the expression of various chemokines leading to local inflammation and eventually pathogenesis in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). Our current study focused on how a pain-mediated neural signal affects disease symptoms including EAE relapses. Our results show that if pain is experimentally induced at the onset of EAE, the symptoms worsen; and conversely, if analgesics are administered, symptoms improve. These results show that pain induction directly contributes to the progress of disease in EAE through a regional neural signal. Because a large proportion of patients with MS experience remission and relapse during the course of disease progression with the frequent association of pain, we considered whether pain induces the relapse. Therefore, we carried out pain induction in the remission phase of EAE. We found that pain induction during this phase could cause the relapse of EAE symptoms (Fig. 1), suggesting that pain itself could trigger the relapse of MS. Furthermore, we found that the gateway reflex is involved. After pain induction in mice, the excitation of sensory neurons at the anterior cingulate cortex, which is the brain region that governs pain sensation, was detected, and in turn activated sympathetic neurons that specifically control the ventral blood vessels of the whole spinal cord. The activation of sympathetic neurons caused the release of norepinephrine just around the ventral blood vessels, which was followed by the expression of the chemokine, CX3CL1, from astrocytes and activated monocytes. Because activated monocytes, which were abundant in the L5 spinal cord of EAE-recovered mice, express CX3CL1 after norepinephrine stimulation, there is a positive feedback loop of activated monocyte

Gateway reflex: Local neuroimmune interactions that regulate blood vessels

Neuroimmunology is a research field that intersects neuroscience and immunology, with the larger aim of gaining significant insights into the pathophysiology of chronic inflammatory diseases such as multiple sclerosis. Conventional studies in this field have so far mainly dealt with immune responses in the nervous system (i.e. neuroinflammation) or systemic immune regulation by the release of glucocorticoids. On the other hand, recently accumulating evidence has indicated bidirectional interactions between specific neural activations and local immune responses. Here we discuss one such local neuroimmune interaction, the gateway reflex. The gateway reflex represents a mechanism that translates specific neural stimulations into local inflammatory outcomes by changing the state of specific blood vessels to allow immune cells to extravasate, thus forming the gateway. Several types of gateway reflex have been identified, and each regulates distinct blood vessels to create gateways for immune cells that induce local inflammation. The gateway reflex represents a novel therapeutic strategy for neuroinflammation and is potentially applicable to other inflammatory diseases in peripheral organs.

Bmi1 Regulates IκBα Degradation via Association with the SCF Complex

Bmi1 is a polycomb group protein and regulator that stabilizes the ubiquitination complex PRC1 in the nucleus with no evidently direct link to the NF-κB pathway. In this study, we report a novel function of Bmi1: its regulation of IκBα ubiquitination in the cytoplasm. A deficiency of Bmi1 inhibited NF-κB–mediated gene expression in vitro and a NF-κB–mediated mouse model of arthritis in vivo. Mechanistic analysis showed that Bmi1 associated with the SCF ubiquitination complex via its N terminus and with phosphorylation by an IKKα/β-dependent pathway, leading to the ubiquitination of IκBα. These effects on NF-κB–related inflammation suggest Bmi1 in the SCF complex is a potential therapeutic target for various diseases and disorders, including autoimmune diseases.

Gateway Reflexes Are Stimulated by Neural Activations and Promote the Pathogenesis of Multiple Sclerosis Models

Abstract The central nervous system (CNS) is tightly regulated by the blood–brain barrier. This regulation is compromised in patients with neuroinflammatory diseases such as multiple sclerosis (MS), which allows immune cells to infiltrate the CNS. We identified a gateway, dorsal vessels of the fifth lumbar (L5) cord, for this infiltration using MS mouse models. The gateway is regulated by local neural activation. Sensory neurons activated by gravity induce local norepinephrine production via sympathetic nerve activations, which increases the expression of chemokines to attract autoreactive CD4+ T cells at L5 dorsal vessels. Neural activation caused by other stimulations, such as electric pulses and pain sensation, also results in gateways. This chapter focuses on these gateway reflexes, which are critical for immune reactions in the CNS.