Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0014070 (encephalomyelitis)
 13,017 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myelinated fibres are characterized by the aggregation of Nav1.6 sodium channels within the axon membrane at nodes of Ranvier, where their presence supports saltatory conduction. In this study, we used immunocytochemical methods to study the organization of sodium channels along axons in experimental allergic encephalomyelitis (EAE), a model of multiple sclerosis. We studied axons within the optic nerve, a CNS tract commonly affected in multiple sclerosis, and their cell bodies of origin (retinal ganglion cells), using subtype-specific antibodies generated against sodium channel subtypes Nav1.1, Nav1.2, Nav1.3 and Nav1.6, which previously have been shown to be expressed by retinal ganglion cells. We demonstrate a significant switch from Nav1.6 to Nav1.2 expression in the optic nerve in EAE; there was a reduction in frequency of Nav1.6-positive nodes (84.5% Nav1.6-immunopositive nodes in control versus 32.9% in EAE) and increased frequency of Nav1.2-positive nodes (11.8% Nav1.2 immunopositive nodes in control versus 74.9% in EAE). Moreover, we observed a significant increase in the number of linear (presumably demyelinated) axonal profiles demonstrating extended diffuse immunostaining for Nav1.2 in EAE versus control optic nerves. These changes within the optic nerve are paralleled by decreased levels of Nav1.6 and increased Nav1.2 protein, together with increased levels of Nav1.2 mRNA, within retinal ganglion cells in EAE. Our findings of a loss of Nav1.6 and increased expression of Nav1.2 suggest that electrogenesis in EAE may revert to a stage similar to that observed in immature retinal ganglion cells in which Nav1.2 channels support conduction of action potentials along axons.
 ...
PMID:Abnormal sodium channel distribution in optic nerve axons in a model of inflammatory demyelination. 1280 13

Axonal degeneration within the spinal cord contributes substantially to neurological disability in multiple sclerosis (MS). Thus neuroprotective therapies that preserve axons, so that they maintain their integrity and continue to function, might be expected to result in improved neurological outcome. Sodium channels are known to provide a route for sodium influx that can drive calcium influx, via reverse operation of the Na+/Ca2+ exchanger, after injury to axons within the CNS, and sodium channel blockers have been shown to protect CNS axons from degeneration after experimental anoxic, traumatic, and nitric oxide (NO)-induced injury. In this study, we asked whether phenytoin, which is known to block sodium channels, can protect spinal cord axons from degeneration in mice with experimental allergic encephalomyelitis (EAE), which display substantial axonal degeneration and clinical paralysis. We demonstrate that the loss of dorsal corticospinal tract (63%) and dorsal column (cuneate fasciculus; 43%) axons in EAE is significantly ameliorated (corticospinal tract: 28%; cuneate fasciculus: 17%) by treatment with phenytoin. Spinal cord compound action potentials (CAP) were significantly attenuated in untreated EAE, whereas spinal cords from phenytoin-treated EAE had robust CAPs, similar to those from phenytoin-treated control mice. Clinical scores in phenytoin-treated EAE at 28 days were significantly improved (1.5, i.e., minor righting reflex abnormalities) compared with untreated EAE (3.8, i.e., near-complete hindlimb paralysis). Our results demonstrate that phenytoin has a protective effect in vivo on spinal cord axons, preventing their degeneration, maintaining their ability to conduct action potentials, and improving clinical status in a model of neuroinflammation.
 ...
PMID:Phenytoin protects spinal cord axons and preserves axonal conduction and neurological function in a model of neuroinflammation in vivo. 1290 34

Multiple sclerosis (MS) is recognized to involve demyelination and axonal atrophy but accumulating evidence suggests that dysregulated sodium channel expression may also contribute to its pathophysiology. Recent studies have demonstrated that the expression of Na(v)1.8 voltage-gated sodium channels, which are normally undetectable within the CNS, is upregulated in cerebellar Purkinje cells in experimental allergic encephalomyelitis (EAE) and MS, and suggest that the aberrant expression of these channels contributes to clinical dysfunction by distorting the firing pattern of these neurons. In this study we examined the temporal pattern of upregulation for Na(v)1.8 mRNA and protein in chronic relapsing EAE by in situ hybridization and immunocytochemistry, respectively. Our results demonstrate a positive correlation between disease duration and degree of upregulation of Na(v)1.8 mRNA and protein in Purkinje neurons in chronic-relapsing EAE. The progressive deterioration in clinical baseline scores (i.e. in clinical scores during remissions) is paralleled by a continued increase in Na(v)1.8 mRNA and protein expression, but temporary worsening during relapses is not associated with transient changes in Na(v)1.8 expression. These results provide evidence that the expression of sodium channel Na(v)1.8 contributes to the development of clinical deficits in an in vivo model of neuroinflammatory disease.
 ...
PMID:Temporal course of upregulation of Na(v)1.8 in Purkinje neurons parallels the progression of clinical deficit in experimental allergic encephalomyelitis. 1453 85

A sugar acid, 2-B4O, has been found to increase from 3.5 to 13 microM in rat serum at 36 h after food deprivation. Injections of 2-B4O (2.5 microM) into the rat III cerebral ventricle (III ICV) suppress food intake and single neuronal activity in the lateral hypothalamic area (LHA). 2-B4O is effective even in 72 h food-deprived rats. 2-B4O hyperpolarizes glucose-sensitive neurons in the LHA via Na+-K+ pump activation, but depolarizes glucoreceptor neurons in the ventromedial nucleus (VMH) via closure of ATP-sensitive K channels. The plasma levels of glucose, corticosterone, and catecholamines, and the firing rate in both parvocellular neurons in the paraventricular nucleus (PVN) and sympathetic efferent nerves, all increase 2-B4O intravenous (iv) injection, indicating activation of the hypothalamo-pituitary-adrenal axis. A 2-B4O iv injection facilitates emotional and spatial learning and memory, and pretreatment with anti-acidic fibroblast growth factor (aFGF) antibody ICV eliminates these effects. aFGF is released from ependymal cells in the III cerebral ventricle in response to the glucose increase in CSF induced by 2-B4O iv injection. 2-B4O also suppresses the clinical symptoms of experimental allergic encephalomyelitis (EAE) in Lewis rats [induced by immunization with a myelin basic protein (MBP)], a model for human multiple sclerosis. After immunization with MBP, the delayed-type hypersensitivity response to MBP is also reduced in 2-B4O-treated rats. 2-B4O thus suppresses autoimmune responses. These results indicate that 2-B4O is not only a powerful satiety substance, but also effective as an activator of the hypothalamo-pituitary-adrenal axis and sympathetic efferent outflow, and as a memory facilitation and a modulator of immune functions.
 ...
PMID:Physiological significance of 2-buten-4-olide (2-B4O), an endogenous satiety substance increased in the fasted state. 1461 Feb 53

Axonal degeneration contributes to the development of non-remitting neurological deficits and disability in multiple sclerosis, but the molecular mechanisms that underlie axonal loss in multiple sclerosis are not clearly understood. Studies of white matter axonal injury have demonstrated that voltage-gated sodium channels can provide a route for sodium influx into axons that triggers reverse operation of the Na(+)/Ca(2+) exchanger (NCX) and subsequent influx of damaging levels of intra-axonal calcium. The molecular identities of the involved sodium channels have, however, not been determined. We have previously demonstrated extensive regions of diffuse expression of Na(v)1.6 and Na(v)1.2 sodium channels along demyelinated axons in experimental allergic encephalomyelitis (EAE). Based on the hypothesis that the co-localization of Na(v)1.6 and NCX along extensive regions of demyelinated axons may predispose these axons to injury, we examined the expression of myelin basic protein, Na(v)1.2, Na(v)1.6, NCX and beta-amyloid precursor protein (beta-APP), a marker of axonal injury, in the spinal cord dorsal columns of mice with EAE. We demonstrate a significant increase in the number of demyelinated axons demonstrating diffuse Na(v)1.6 and Na(v)1.2 sodium channel immunoreactivity in EAE (92.2 +/- 2.1% of beta-APP positive axons were Na(v)1.6-positive). Only 38.0 +/- 2.9% of beta-APP positive axons were Na(v)1.2 positive, and 95% of these co-expressed Na(v)1.6 together with Na(v)1.2. Using triple-labelled fluorescent immunohistochemistry, we demonstrate that 73.5 +/- 4.3% of beta-APP positive axons co-express Na(v)1.6 and NCX, compared with 4.4 +/- 1.0% in beta-APP negative axons. Our results indicate that co-expression of Na(v)1.6 and NCX is associated with axonal injury in the spinal cord in EAE.
 ...
PMID:Co-localization of sodium channel Nav1.6 and the sodium-calcium exchanger at sites of axonal injury in the spinal cord in EAE. 1466 15

We studied the effects of oral administration of sodium salicylate on the expression of the pro-inflammatory mediators, nitric oxide synthase (iNOS) and cyclooxygenase- (COX-) 1 and 2, in rats with experimental autoimmune encephalomyelitis (EAE). Sodium salicylate (200 mg/kg) was administered orally for 13 days after the induction of EAE by immunization with guinea pig myelin basic protein and complete Freund's adjuvant. The onset (P<0.0001) and severity (P<0.05) of EAE paralysis in salicylate-treated animals were delayed and suppressed significantly compared with vehicle-treated controls. Western blot analysis showed that expression of COX-2 and iNOS, but not COX-1, decreased significantly in the spinal cords of salicylate-treated rats compared with vehicle-treated controls (P<0.05) and this finding was paralleled by immunohistochemical observations. These results suggest that the amelioration by salicylate of paralysis in rats with EAE is mediated in part by the suppression of COX and iNOS.
 ...
PMID:Sodium salicylate-induced amelioration of experimental autoimmune encephalomyelitis in Lewis rats is associated with the suppression of inducible nitric oxide synthase and cyclooxygenases. 1474 79

Bruton tyrosine kinase (Btk), a non-receptor-associated tyrosine kinase of the Tec family, appears to participate in many myeloid cell functions. We show that macrophages from X-linked immunodeficient (XID) mice lacking functional Btk cannot generate efficient bursts of reactive oxygen intermediates (ROIs). The induction of apoptotic cell death by inflammatory stimuli is also enhanced in XID macrophages. Phagocytosis of bacterial particles is only marginally affected in them. In vivo, XID mice show reduced severity of inflammatory diseases in models of experimental autoimmune encephalomyelitis (EAE), dextran sulfate sodium (DSS)-induced colitis, and carrageenan-induced acute edema. Also, polymorphonuclear neutrophil granulocytes (PMNs) in XID mice show poor ROI and nitric oxide (NO) induction, along with a reduction in PMN recruitment to peritoneal inflammation. XID mice show reduction in PMN numbers in peripheral blood, and their bone marrow shows a reduction in the numbers of both monocytic and granulocytic lineages, extending to the earliest progenitor populations. Thus, Btk is likely to play a significant role at multiple points during the development and functioning of the myeloid lineages, affecting the outcome of many infectious as well as noninfectious inflammatory events in vivo.
 ...
PMID:Pleiotropic consequences of Bruton tyrosine kinase deficiency in myeloid lineages lead to poor inflammatory responses. 1511 62

Loss of axons is a major contributor to nonremitting deficits in the inflammatory demyelinating disease multiple sclerosis (MS). Based on biophysical studies showing that activity of axonal sodium channels can trigger axonal degeneration, recent studies have tested sodium channel-blocking drugs in experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and have demonstrated a protective effect on axons. However, it is possible that, in addition to a direct effect on axons, sodium channel blockers may also interfere with inflammatory mechanisms. We therefore examined the novel hypothesis that sodium channels contribute to activation of microglia and macrophages in EAE and acute MS lesions. In this study, we demonstrate a robust increase of sodium channel Nav1.6 expression in activated microglia and macrophages in EAE and MS. We further demonstrate that treatment with the sodium channel blocker phenytoin ameliorates the inflammatory cell infiltrate in EAE by 75%. Supporting a role for sodium channels in microglial activation, we show that tetrodotoxin, a specific sodium channel blocker, reduces the phagocytic function of activated rat microglia by 40%. To further confirm a role of Nav1.6 in microglial activation, we examined the phagocytic capacity of microglia from med mice, which lack Nav1.6 channels, and show a 65% reduction in phagocytic capacity compared with microglia from wildtype mice. Our findings indicate that sodium channels are important for activation and phagocytosis of microglia and macrophages in EAE and MS and suggest that, in addition to a direct neuroprotective effect on axons, sodium channel blockade may ameliorate neuroinflammatory disorders via anti-inflammatory mechanisms.
 ...
PMID:Sodium channels contribute to microglia/macrophage activation and function in EAE and MS. 1539 90

Cerebellar dysfunction in multiple sclerosis (MS) is a significant contributor to disability, is relatively refractory to symptomatic therapy, and often progresses despite treatment with disease-modifying agents. Thus, there is a need for better understanding of its pathophysiology. This chapter reviews a growing body of evidence which suggests that mis-tuning of Purkinje cells, due to expression of an abnormal repertoire of sodium channels, contributes to cerebellar deficits in MS. Within the normal nervous system, sodium channel Na(v)1.8 is expressed in a highly specific manner within spinal sensory and trigeminal neurons, and is not present within Purkinje cells, Na(v)1.8 mRNA and protein are, however, expressed within Purkinje cells both in models of MS (experimenal autoimmume encephalomyelitis; EAE), and in postmortem tissue from humans with MS. Expression of Na(v)1.8 within Purkinje cells in vitro alters electrogenesis in these cells in several ways: first, by increasing duration and amplitude of action potentials; second, by decreasing the proportion of action potentials that are conglomerate and the number of spikes per conglomerate action potential; and third, by supporting sustained, pacemaker-like impulse trains in response to depolarization, which are not seen in the absence of Na(v)1.8. Similar changes are observed in recordings from Purkinje cells in vivo from mice with EAE. Taken together, these results suggest that expression of Na(v)1.8 within Purkinje cells distorts their pattern of firing in MS.
 ...
PMID:Cerebellar dysfunction in multiple sclerosis: evidence for an acquired channelopathy. 1566 Dec 3

Axonal degeneration is a major contributor to non-remitting deficits in multiple sclerosis, and there is thus considerable current interest in the development of strategies that might prevent axonal loss in neuroinflammatory disease. Dysregulation of sodium ion homeostasis has been implicated in mechanisms leading to axonal degeneration, and several studies have shown that blockade of sodium channels can ameliorate axon damage following anoxic, traumatic and nitric oxide-induced CNS injury. Two sodium channel blockers, phenytoin and flecainide, have been reported to protect axons in experimental autoimmune encephalomyelitis (EAE) for 30 days, but long-term protective effects have not been studied. We demonstrate here that oral administration of phenytoin provides long-term (up to 180 days) protection for spinal cord corticospinal tract (CST) and dorsal column (DC) axons in both monophasic (C57/BL6 mice) and chronic-relapsing (Biozzi mice) murine EAE. Untreated C57/BL6 mice exhibit a 40-50% loss of CST and DF axons at 90 and 180 days post-EAE induction via myelin-oligodendrocyte glycoprotein (MOG) injection. In contrast, only 4% of DF axons are lost at 90 days, and only 8% are lost at 180 days in phenytoin-treated C57/BL6 mice with EAE; only 21-29% of CST axons are lost at 90 and 180 days in phenytoin-treated C57/BL6 mice with EAE. Attenuation of dorsal column compound action potentials was ameliorated and clinical status was also significantly enhanced with phenytoin treatment at 90 and 180 days in this model. In addition, inflammatory cell infiltration into the dorsal columns was reduced in phenytoin-treated mice with EAE compared with untreated mice with EAE. Similar results were obtained in Biozzi mice with chronic-relapsing EAE followed for 120 days post-injection. These observations demonstrate that phenytoin provides long-term protection of CNS axons and improves clinical status in both monophasic and chronic-relapsing models of neuroinflammation.
 ...
PMID:Long-term protection of central axons with phenytoin in monophasic and chronic-relapsing EAE. 1713 43


<< Previous 1 2 3 4 5 6 7 8 9 Next >>