The Gut-CNS Axis in Multiple Sclerosis.

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the CNS driven by the inflammatory activity of peripheral immune cells recruited to the CNS and by CNS-resident glial cells. MS pathogenesis has been linked to both genetic and environmental factors. In addition, the commensal flora have been shown to modulate immune processes relevant to MS pathogenesis. We discuss the effects of the gut microbiota on T cells and glial cells, and their relevance for the control of inflammation and neurodegeneration in MS. A better understanding of the gut-CNS axis will shed new light on the mechanisms of disease pathogenesis, and may help to guide the development of efficacious therapies for MS.

Gut microbiota-dependent CCR9+CD4+ T cells are altered in secondary progressive multiple sclerosis.

The mechanism underlying the progression of relapsing-remitting multiple sclerosis to secondary progressive multiple sclerosis (SPMS), characterized by accumulating fixed disability, is yet to be fully understood. Although alterations in the gut microbiota have recently been highlighted in multiple sclerosis pathogenesis, the mechanism linking the altered gut environment with the remote CNS pathology remains unclear. Here, we analyse human CD4+ memory T cells expressing the gut-homing chemokine receptor CCR9 and found a reduced frequency of CCR9+ memory T cells in the peripheral blood of patients with SPMS relative to healthy controls. The reduction in the proportion of CCR9+ cells among CD4+ memory T cells (%CCR9) in SPMS did not correlate with age, disease duration or expanded disability status scale score, although %CCR9 decreased linearly with age in healthy controls. During the clinical relapse of both, relapsing-remitting multiple sclerosis and neuromyelitis optica, a high proportion of cells expressing the lymphocyte activating 3 gene (LAG3) was detected among CCR9+ memory T cells isolated from the CSF, similar to that observed for mouse regulatory intraepithelial lymphocytes. In healthy individuals, CCR9+ memory T cells expressed higher levels of CCR6, a CNS-homing chemokine receptor, and exhibited a regulatory profile characterized by both the expression of C-MAF and the production of IL-4 and IL-10. However, in CCR9+ memory T cells, the expression of RORγt was specifically upregulated, and the production of IL-17A and IFNγ was high in patients with SPMS, indicating a loss of regulatory function. The evaluation of other cytokines supported the finding that CCR9+ memory T cells acquire a more inflammatory profile in SPMS, reporting similar aspects to CCR9+ memory T cells of the elderly healthy controls. CCR9+ memory T cell frequency decreased in germ-free mice, whereas antibiotic treatment increased their number in specific pathogen-free conditions. Here, we also demonstrate that CCR9+ memory T cells preferentially infiltrate into the inflamed CNS resulting from the initial phase and that they express LAG3 in the late phase in the experimental autoimmune encephalomyelitis mouse model of multiple sclerosis. Antibiotic treatment reduced experimental autoimmune encephalomyelitis symptoms and was accompanied by an increase in CCR9+ memory T cells in the peripheral blood. Antibodies against mucosal vascular addressin cell adhesion molecule 1 (MADCAM1), which is capable of blocking cell migration to the gut, also ameliorated experimental autoimmune encephalomyelitis. Overall, we postulate that the alterations in CCR9+ memory T cells observed, caused by either the gut microbiota changes or ageing, may lead to the development of SPMS.

Identification of a vesicular ATP release inhibitor for the treatment of neuropathic and inflammatory pain.

Despite the high incidence of neuropathic and inflammatory pain worldwide, effective drugs with few side effects are currently unavailable for the treatment of chronic pain. Recently, researchers have proposed that inhibitors of purinergic chemical transmission, which plays a key role in the pathological pain response, may allow for targeted treatment of pathological neuropathic and inflammatory pain. However, such therapeutic analgesic agents have yet to be developed. In the present study, we demonstrated that clodronate, a first-generation bisphosphonate with comparatively fewer side effects than traditional treatments, significantly attenuates neuropathic and inflammatory pain unrelated to bone abnormalities via inhibition of vesicular nucleotide transporter (VNUT), a key molecule for the initiation of purinergic chemical transmission. In vitro analyses indicated that clodronate inhibits VNUT at a half-maximal inhibitory concentration of 15.6 nM without affecting other vesicular neurotransmitter transporters, acting as an allosteric modulator through competition with Cl- A low concentration of clodronate impaired vesicular ATP release from neurons, microglia, and immune cells. In vivo analyses revealed that clodronate is more effective than other therapeutic agents in attenuating neuropathic and inflammatory pain, as well as the accompanying inflammation, in wild-type but not VNUT -/- mice, without affecting basal nociception. These findings indicate that clodronate may represent a unique treatment strategy for chronic neuropathic and inflammatory pain via inhibition of vesicular ATP release.

Neuronal inhibition and seizure suppression by acetoacetate and its analog, 2-phenylbutyrate.

OBJECTIVE: The ketogenic diet is clinically used to treat drug-resistant epilepsy. The diet treatment markedly increases ketone bodies (acetoacetate and ß-hydroxybutyrate), which work as energy metabolites in the brain. Here, we investigated effects of acetoacetate on voltage-dependent Ca2+ channels (VDCCs) in pyramidal cells of the hippocampus. We further explored an acetoacetate analog that inhibited VDCCs in pyramidal cells, reduced excitatory postsynaptic currents (EPSCs), and suppressed seizures in vivo. METHODS: The effects of acetoacetate and its analogs on VDCCs and EPSCs were evaluated using patch-clamp recordings from CA1 pyramidal cells of mouse hippocampal slices. The in vivo effects of these reagents were also evaluated using a chronic seizure model induced by intrahippocampal injection of kainate. RESULTS: Acetoacetate inhibited VDCCs in pyramidal cells of hippocampal slices, and reduced EPSCs in slices exhibiting epileptiform activity. More potent EPSC inhibitors were then explored by modifying the chemical structure of acetoacetate, and 2-phenylbutyrate was identified as an acetoacetate analog that inhibited VDCCs and EPSCs more potently. Although acetoacetate is known to inhibit vesicular glutamate transporters (VGLUTs), 2-phenylbutyrate did not inhibit VGLUTs, showing that 2-phenylbutyrate is an acetoacetate analog that preferably inhibits VDCCs. In addition, 2-phenylbutyrate markedly reduced EPSCs in slices exhibiting epileptiform activity, and suppressed hippocampal seizures in vivo in a mouse model of epilepsy. The in vivo antiseizure effects of 2-phenylbutyrate were more potent than those of acetoacetate. Finally, intraperitoneal 2-phenylbutyrate was delivered to the brain, and its brain concentration reached the level enough to reduce EPSCs. SIGNIFICANCE: These results demonstrate that 2-phenylbutyrate is an acetoacetate analog that inhibits VDCCs and EPSCs in pyramidal cells, suppresses hippocampal seizures in vivo, and has brain penetration ability. Thus 2-phenylbutyrate provides a useful chemical structure as a lead compound to develop new antiseizure drugs originating from ketone bodies.

Gut environment-induced intraepithelial autoreactive CD4(+) T cells suppress central nervous system autoimmunity via LAG-3.

The gut environment has been found to significantly influence autoimmune diseases such as multiple sclerosis; however, immune cell mechanisms are unclear. Here we show that the gut epithelium of myelin oligodendrocyte glycoprotein(35-55)-specific T-cell receptor transgenic mice contains environmental stimuli-induced intraepithelial lymphocytes (IELs) that inhibit experimental autoimmune encephalomyelitis on transfer. These cells express surface markers phenotypical of 'induced' IELs, have a TH17-like profile and infiltrate the central nervous system (CNS). They constitutively express Ctla4 and Tgfb1 and markedly upregulate Lag3 expression in the CNS, thereby inhibiting inflammation. We also demonstrate the suppressive capability of CD4(+) IELs with alternative antigen specificities, their proliferation in response to gut-derived antigens and contribution of the microbiota and dietary aryl hydrocarbon receptor ligands to their induction. Thus, the gut environment favours the generation of autoreactive CD4(+) T cells with unique regulatory functions, potentially important for preventing CNS autoimmunity.

Temperature sensitization of liposomes by use of N-isopropylacrylamide copolymers with varying transition endotherms.

Three kinds of copolymers of N-isopropylacrylamide (NIPAM) with the same conformational transition temperature and varying transition endotherms were synthesized with N-acryloylpyrrolidine (APr), N,N-dimethylacrylamide (DMAM), and N-isopropylmethacrylamide (NIPMAM) as the comonomers. Two dodecyl groups were incorporated into the termini of these copolymers as an anchor for the fixation to a liposomal membrane. Egg yolk phosphatidylcholine liposomes having these copolymers were prepared and their temperature-sensitive contents release and association properties were investigated. While these copolymer exhibited a conformational transition at ca. 40 degrees C, DeltaH for the transition increased in the order of poly(APr-co-NIPAM) < poly(DMAM-co-NIPAM) < poly(NIPMAM-co-NIPAM). The liposomes containing poly(NIPMAM-co-NIPAM) showed a drastic release enhancement of entrapped calcein above the transition temperature, whereas the liposomes with poly(DMAM-co-NIPAM) and those with poly(APr-co-NIPAM) exhibited moderate and slight enhancement of calcein release above that temperature, respectively. On the contrary, the liposomes containing poly(APr-co-NIPAM) showed significant aggregation above the transition temperature, but the aggregation was hardly observed for the liposomes having poly(NIPMAM-co-NIPAM), indicating that poly(APr-co-NIPAM) more efficiently made the liposome surface hydrophobic. Thus, we concluded that the copolymer with a large DeltaH is suitable for obtaining functional liposomes with a temperature-sensitive contents release property, whereas the copolymer with a small DeltaH is appropriate for preparing functional liposomes with a temperature-sensitive surface property.