myelin-oligodendrocyte-glycoprotein-(35-55) and Neuralgia

Central neuropathic pain is a common untreated symptom in progressive multiple sclerosis (PMS) and is associated with poor quality of life and interference with patients' daily activities. The neuroinflammation process and mitochondrial dysfunction in the PMS lesions generate reactive species. The transient potential receptor ankyrin 1 (TRPA1) has been identified as one of the major mechanisms that contribute to neuropathic pain signaling and can be activated by reactive compounds. Thus, the goal of our study was to evaluate the role of spinal TRPA1 in the central neuropathic pain observed in a PMS model in mice. We used C57BL/6 female mice (20-30 g), and the PMS model was induced by the experimental autoimmune encephalomyelitis (EAE) using mouse myelin oligodendrocyte glycoprotein (MOG

Topics: Acetanilides; Acetophenones; Analgesics; Animals; Antipyrine; Dipyrone; Encephalomyelitis, Autoimmune, Experimental; Female; Hyperalgesia; Mice; Mice, Inbred C57BL; Myelin-Oligodendrocyte Glycoprotein; NADPH Oxidases; Nerve Tissue Proteins; Neuralgia; Nociception; Oligonucleotides, Antisense; Oxidative Stress; Oximes; Peptide Fragments; Pregabalin; Purines; Spinal Cord; Thioctic Acid; TRPA1 Cation Channel; Up-Regulation

Pain is a frequent and disabling symptom in patients with multiple sclerosis (MS); however, the underlying mechanisms of MS-related pain are not fully understood. Here, we demonstrated that cathepsin E (CatE) in neutrophils contributes to the generation of mechanical allodynia in experimental autoimmune encephalomyelitis, an animal model of MS. We showed that CatE-deficient (CatE) mice were highly resistant to myelin oligodendrocyte glycoprotein (MOG35-55)-induced mechanical allodynia. After MOG35-55 immunization, neutrophils immediately accumulated in the dorsal root ganglion (DRG). Adoptive transfer of MOG35-55-stimulated wild-type neutrophils into the dorsal root ganglion induced mechanical allodynia in the recipient C57BL/6 mice. However, the pain threshold did not change when MOG35-55-stimulated CatE neutrophils were transferred into the recipient C57BL/6 mice. MOG35-55 stimulation caused CatE-dependent secretion of elastase in neutrophils. Behavioral analyses revealed that sivelestat, a selective neutrophil elastase inhibitor, suppressed mechanical allodynia induced by adoptively transferred MOG35-55-stimulated neutrophils. MOG35-55 directly bound to toll-like receptor 4, which led to increased production of CatE in neutrophils. Our findings suggest that inhibition of CatE-dependent elastase production in neutrophil might be a potential therapeutic target for pain in patients with MS.

Topics: Animals; Cathepsin E; Encephalomyelitis, Autoimmune, Experimental; Female; Mice; Mice, Inbred C57BL; Mice, Transgenic; Myelin-Oligodendrocyte Glycoprotein; Neuralgia; Neutrophils; Peptide Fragments

Multiple sclerosis (MS) is an autoimmune-inflammatory neurodegenerative disease that is often accompanied by a debilitating neuropathic pain. Disease-modifying agents slow down the progression of multiple sclerosis and prevent relapses, yet it remains unclear if they yield analgesia. We explored the analgesic potential of fingolimod (FTY720), an agonist and/or functional antagonist at the sphingosine-1-phosphate receptor 1 (S1PR1), because it reduces hyperalgesia in models of peripheral inflammatory and neuropathic pain. We used a myelin oligodendrocyte glycoprotein 35 to 55 (MOG35-55) mouse model of experimental autoimmune encephalomyelitis, modified to avoid frank paralysis, and thus, allow for assessment of withdrawal behaviors to somatosensory stimuli. Daily intraperitoneal fingolimod reduced behavioral signs of central neuropathic pain (mechanical and cold hypersensitivity) in a dose-dependent and reversible manner. Both autoimmune encephalomyelitis and fingolimod changed hyperalgesia before modifying motor function, suggesting that pain-related effects and clinical neurological deficits were modulated independently. Fingolimod also reduced cellular markers of central sensitization of neurons in the dorsal horn of the spinal cord: glutamate-evoked Ca signaling and stimulus-evoked phospho-extracellular signal-related kinase ERK (pERK) expression, as well as upregulation of astrocytes (GFAP) and macrophage/microglia (Iba1) immunoreactivity. The antihyperalgesic effects of fingolimod were prevented or reversed by the S1PR1 antagonist W146 (1 mg/kg daily, i.p.) and could be mimicked by either repeated or single injection of the S1PR1-selective agonist SEW2871. Fingolimod did not change spinal membrane S1PR1 content, arguing against a functional antagonist mechanism. We conclude that fingolimod behaves as an S1PR1 agonist to reduce pain in multiple sclerosis by reversing central sensitization of spinal nociceptive neurons.

Topics: Anilides; Animals; Central Nervous System Sensitization; Disease Models, Animal; eIF-2 Kinase; Female; Fingolimod Hydrochloride; Immunosuppressive Agents; Male; Mice; Mice, Inbred C57BL; Motor Activity; Multiple Sclerosis; Myelin-Oligodendrocyte Glycoprotein; Neuralgia; Organophosphonates; Oxadiazoles; Pain Threshold; Peptide Fragments; Receptors, Lysosphingolipid; Sphingosine-1-Phosphate Receptors; Spinal Cord; Spinal Nerve Roots; Subcellular Fractions; Thiophenes

Several types of myeloid cell are resident in the CNS. In the steady state, microglia are present in the CNS parenchyma, whereas macrophages reside in boundary regions of the CNS, such as perivascular spaces, the meninges and choroid plexus. In addition, monocytes infiltrate into the CNS parenchyma from circulation upon blood-brain barrier breakdown after CNS injury and inflammation. Although several markers, such as CD11b and ionized calcium-binding adapter molecule 1 (Iba1), are frequently used as microglial markers, they are also expressed by other types of myeloid cell and microglia-specific markers were not defined until recently. Previous transcriptome analyses of isolated microglia identified a transmembrane lectin, sialic acid-binding immunoglobulin-like lectin H (Siglec-H), as a molecular signature for microglia; however, this was not confirmed by histological studies in the nervous system and the reliability of Siglec-H as a microglial marker remained unclear. Here, we demonstrate that Siglec-H is an authentic marker for microglia in mice by immunohistochemistry using a Siglec-H-specific antibody. Siglec-H was expressed by parenchymal microglia from developmental stages to adulthood, and the expression was maintained in activated microglia under injury or inflammatory condition. However, Siglec-H expression was absent from CNS-associated macrophages and CNS-infiltrating monocytes, except for a minor subset of cells. We also show that the Siglech gene locus is a feasible site for specific targeting of microglia in the nervous system. In conclusion, Siglec-H is a reliable marker for microglia that will allow histological identification of microglia and microglia-specific gene manipulation in the nervous system.

Topics: Animals; Animals, Newborn; Central Nervous System; Disease Models, Animal; Embryo, Mammalian; Encephalomyelitis, Autoimmune, Experimental; Gene Expression Regulation; Lectins; Macrophages; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microglia; Myelin-Oligodendrocyte Glycoprotein; Myeloid Cells; Neuralgia; Neutrophil Infiltration; Peptide Fragments; Pertussis Toxin; Receptors, CCR2; Receptors, Cell Surface

Patients with multiple sclerosis (MS) often complain of neuropathic pain. According to the Gate Control Theory of Pain, spinal networks of GABAergic inhibitory interneurons are important in modulating nociceptive inputs from the periphery. Na+-K+-2Cl- co-transporter 1 (NKCC1) and K+-Cl- co-transporter 2 (KCC2) generally dictate the tone of GABA/glycine inhibition by regulating intracellular chloride concentrations. In this study, we investigated the role of NKCC1 and KCC2 in neuropathic pain observed in the animal model, experimental autoimmune encephalomyelitis (EAE), a commonly used model to study the pathophysiology of MS. Quantitative real-time polymerase chain reactions (qRT-PCR) analysis revealed no change in NKCC1 mRNA transcripts in dorsal root ganglia throughout EAE disease course. However, NKCC1 and KCC2 mRNA levels in the dorsal spinal cord were significantly reduced at disease onset and peak only to recover by the chronic time point. Similarly, Western blot data revealed a significant downregulation of NKCC1 and KCC2 in the dorsal spinal cord at disease onset but an upregulation of NKCC1 protein in the dorsal root ganglia at this time point. Treatment with bumetanide, an NKCC inhibitor, had no effect on mechanical hypersensitivity seen in mice with EAE even though it reversed the changes in the levels of NKCC1 and KCC2. We noted that bumetanide treatment, while effective at reversing the changes in monomeric KCC2 levels was ineffective at reversing the changes in oligomeric KCC2 which remained repressed. These results indicate that mechanical hypersensitivity in EAE is not mediated by altered levels of NKCC1.

Topics: Animals; Bumetanide; Disease Progression; Encephalomyelitis, Autoimmune, Experimental; Female; Ganglia, Spinal; Gene Expression; Hyperalgesia; K Cl- Cotransporters; Mice, Inbred C57BL; Myelin-Oligodendrocyte Glycoprotein; Neuralgia; Peptide Fragments; RNA, Messenger; Sodium Potassium Chloride Symporter Inhibitors; Solute Carrier Family 12, Member 2; Spinal Cord; Symporters

Chronic neuropathic pain is a common symptom of multiple sclerosis (MS). MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) has been used as an animal model to investigate the mechanisms of pain in MS. Previous studies have implicated sensitization of spinal nociceptive networks in the pathogenesis of pain in EAE. However, the involvement of supraspinal sites of nociceptive integration, such as the primary somatosensory cortex (S1), has not been defined. We therefore examined functional, structural, and immunological alterations in S1 during the early stages of EAE, when pain behaviors first appear. We also assessed the effects of the antidepressant phenelzine (PLZ) on S1 alterations and nociceptive (mechanical) sensitivity in early EAE. PLZ has been shown to restore central nervous system (CNS) tissue concentrations of GABA and the monoamines (5-HT, NA) in EAE. We hypothesized that PLZ treatment would also normalize nociceptive sensitivity in EAE by restoring the balance of excitation and inhibition (E-I) in the CNS.. We used in vivo flavoprotein autofluorescence imaging (FAI) to assess neural ensemble responses in S1 to vibrotactile stimulation of the limbs in early EAE. We also used immunohistochemistry (IHC), and Golgi-Cox staining, to examine synaptic changes and neuroinflammation in S1. Mechanical sensitivity was assessed at the clinical onset of EAE with Von Frey hairs.. Mice with early EAE exhibited significantly intensified and expanded FAI responses in S1 compared to controls. IHC revealed increased vesicular glutamate transporter (VGLUT1) expression and disrupted parvalbumin+ (PV+) interneuron connectivity in S1 of EAE mice. Furthermore, peri-neuronal nets (PNNs) were significantly reduced in S1. Morphological analysis of excitatory neurons in S1 revealed increased dendritic spine densities. Iba-1+ cortical microglia were significantly elevated early in the disease. Chronic PLZ treatment was found to normalize mechanical thresholds in EAE. PLZ also normalized S1 FAI responses, neuronal morphologies, and cortical microglia numbers and attenuated VGLUT1 reactivity-but did not significantly attenuate the loss of PNNs.. These findings implicate a pro-excitatory shift in the E-I balance of the somatosensory CNS, arising early in the pathogenesis EAE and leading to large-scale functional and structural plasticity in S1. They also suggest a novel antinociceptive effect of PLZ treatment.

Topics: Animals; Antidepressive Agents; Calcium-Binding Proteins; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental; Female; Freund's Adjuvant; Hyperalgesia; Mice; Mice, Inbred C57BL; Microfilament Proteins; Myelin-Oligodendrocyte Glycoprotein; Neuralgia; Neurons; Pain Measurement; Pain Threshold; Parvalbumins; Peptide Fragments; Phenelzine; Plant Lectins; Receptors, N-Acetylglucosamine; Somatosensory Cortex; Synapses

Multiple sclerosis (MS) is classically defined by motor deficits, but it is also associated with the secondary symptoms of pain, depression, and anxiety. Up to this point modifying these secondary symptoms has been difficult. There is evidence that both MS and the animal model experimental autoimmune encephalomyelitis (EAE), commonly used to study the pathophysiology of the disease, can be modulated by exercise. To examine whether limited voluntary wheel running could modulate EAE disease progression and the co-morbid symptoms of pain, mice with EAE were allowed access to running wheels for 1h every day. Allowing only 1h every day of voluntary running led to a significant delay in the onset of clinical signs of the disease. The development of mechanical allodynia was assessed using Von Frey hairs and indicated that wheel running had a modest positive effect on the pain hypersensitivity associated with EAE. These behavioral changes were associated with reduced numbers of cFOS and phosphorylated NR1 positive cells in the dorsal horn of the spinal cord compared to no-run EAE controls. In addition, within the dorsal horn, voluntary wheel running reduced the number of infiltrating CD3(+) T-cells and reduced the overall levels of Iba1 immunoreactivity. Using high performance liquid chromatography (HPLC), we observed that wheel-running lead to significant changes in the spinal cord levels of the antioxidant glutathione. Oxidative stress has separately been shown to contribute to EAE disease progression and neuropathic pain. Together these results indicate that in mice with EAE, voluntary motor activity can delay the onset of clinical signs and reduce pain symptoms associated with the disease.

Topics: Animals; Antigens, CD; Calcium-Binding Proteins; Electron Transport Complex IV; Exercise Therapy; Female; Hyperalgesia; Mice; Mice, Inbred C57BL; Microfilament Proteins; Motor Activity; Myelin-Oligodendrocyte Glycoprotein; Nerve Tissue Proteins; Neuralgia; Neuritis, Autoimmune, Experimental; Nitric Oxide Synthase Type II; Pain Threshold; Peptide Fragments; Proto-Oncogene Proteins c-fos; Receptors, N-Methyl-D-Aspartate; Running; Statistics, Nonparametric

Current treatments used in Multiple Sclerosis (MS) are partly effective in the early stages of the disease but display very limited benefits in patients affected by progressive MS. One possible explanation is that these therapies are unable to target the inflammatory component most active during the progressive phase of the disease, and compartmentalized behind the blood-brain barrier. Our findings show that Rapamycin ameliorates clinical and histological signs of chronic EAE when administered during ongoing disease. Moreover, Rapamycin significantly reduced the hyperalgesia observed before clinical development of EAE which, in turn, is completely abolished by the administration of the drug.

Topics: Analysis of Variance; Animals; Cytokines; Disease Models, Animal; Encephalomyelitis, Autoimmune, Experimental; Female; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Glycoproteins; Hyperalgesia; Immunosuppressive Agents; Mice; Mice, Inbred C57BL; Myelin Basic Protein; Myelin Sheath; Myelin-Oligodendrocyte Glycoprotein; Neuralgia; Pain Threshold; Peptide Fragments; Pertussis Toxin; RNA, Messenger; Sirolimus; T-Lymphocytes; Time Factors

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). While the primary symptoms of MS are losses of sensory and motor functions, it is now recognized that chronic pain is also a major concern affecting between 50% and 80% of MS patients. To date, however, few studies have examined the underlying mechanisms of chronic pain in MS or in the animal model, experimental autoimmune encephalomyelitis (EAE), which shares many features of MS pathology. We, therefore, set out to characterize the changes in pain sensitivity that arises in a chronic-relapsing model of EAE. We show here that female C57BL/6 mice immunized with myelin oligodendrocyte glycoprotein (MOG(35-55)) develop a robust allodynia to both cold and tactile stimuli. Allodynia emerges early in the disease process, often before any signs of neurological deficit and is independent of the overall symptom severity in these mice. "Classical" cellular substrates for neuropathic pain and allodynia such as altered expression of sensory neuropeptides in the dorsal horn of the spinal do not appear to underlie these changes in sensory function. There is, however, a significant influx of CD3+ T cells and increased astrocyte and microglia/macrophage reactivity in the superficial dorsal horn of mice with MOG(35-55) EAE. This suggests that inflammation and reactive gliosis may be key mediators of allodynia in MOG(35-55) EAE similar to peripheral nerve and spinal cord injury models. Taken together, our results show that the MOG(35-55) EAE model is a useful tool to study neuropathic pain in MS.

Topics: Analysis of Variance; Animals; Antigens, CD; Antigens, Differentiation; Calcitonin Gene-Related Peptide; Disease Models, Animal; Disease Progression; Encephalomyelitis, Autoimmune, Experimental; Female; Gliosis; Glycoproteins; Hyperalgesia; Mice; Mice, Inbred C57BL; Motor Activity; Myelin-Oligodendrocyte Glycoprotein; Neuralgia; Pain Threshold; Peptide Fragments; Reaction Time; Spinal Cord