Pertussis toxin-induced hyperacute autoimmune encephalomyelitis in Lewis rats is correlated with increased expression of inducible nitric oxide synthase and tumor necrosis factor alpha

Pertussis Toxin Inhibits Encephalitogenic T-Cell Infiltration and Promotes a B-Cell-Driven Disease during Th17-EAE

Pertussis toxin (PTX) is a required co-adjuvant for experimental autoimmune encephalomyelitis (EAE) induced by immunization with myelin antigen. However, PTX’s effects on EAE induced by the transfer of myelin-specific T helper cells is not known. Therefore, we investigated how PTX affects the Th17 transfer EAE model (Th17-EAE). We found that PTX significantly reduced Th17-EAE by inhibiting chemokine-receptor-dependent trafficking of Th17 cells. Strikingly, PTX also promoted the accumulation of B cells in the CNS, suggesting that PTX alters the disease toward a B-cell-dependent pathology. To determine the role of B cells, we compared the effects of PTX on Th17-EAE in wild-type (WT) and B-cell-deficient (µMT) mice. Without PTX treatment, disease severity was equivalent between WT and µMT mice. In contrast, with PTX treatment, the µMT mice had significantly less disease and a reduction in pathogenic Th17 cells in the CNS compared to the WT mice. In conclusion, this study shows that PTX inhibits the migration of pathogenic Th17 cells, while promoting the accumulation of pathogenic B cells in the CNS during Th17-EAE. These data provide useful methodological information for adoptive-transfer Th17-EAE and, furthermore, describe another important experimental system to study the pathogenic mechanisms of B cells in multiple sclerosis.

Amelioration of experimental autoimmune encephalomyelitis by Ishige okamurae

Experimental autoimmune encephalomyelitis (EAE) is a T-cell-mediated autoimmune central nervous system disease characterized by inflammation with oxidative stress. The aim of this study was to evaluate an anti-inflammatory effect of Ishige okamurae on EAE-induced paralysis in rats. An ethanolic extract of I. okamurae significantly delayed the first onset and reduced the duration and severity of hind-limb paralysis. The neuropathological and immunohistochemical findings in the spinal cord were in agreement with these clinical results. T-cell proliferation assay revealed that the ethyl-acetate fraction of I. okamurae suppressed the proliferation of myelin basic protein reactive T cells from EAE affected rats. Flow cytometric analysis showed TCRαβ⁺ T cells was significantly reduced in the spleen of EAE rats with I. okamurae treatment with concurrent decrease of inflammatory mediators including tumor necrosis factor-α and cyclooxygenase-2. Collectively, it is postulated that I. okamurae ameliorates EAE paralysis with suppression of T-cell proliferation as well as decrease of pro-inflammatory mediators as far as rat EAE is concerned.

Cytapheresis with a filter for selective removal of CD4+ T cells in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a major animal model of human multiple sclerosis (MS). CD4+ T cells are thought to play a pivotal role in the patho genesis of EAE and MS. In order to investigate the depletio n of CD4+ T cells from the systemic circulation as an effective strategy for the treatment of MS, we performed extracorporeal CD4+ T cell adsorption, using a filter to which anti-CD4+ antibody is immobilized as a ligand, in adoptively transferred EAE. Rats treated with CD4+ T cell removal filter (C D4RF) exhibited milder clinical signs of EAE and earlier recovery than those receiving sham treatment. Moreover, the thymic cells from EAE rats treated with C D4RF exhibited a suppressed proliferative response and IFN-g production to myelin basic protein. These results suggest that depletion of CD4+ T cells from the systemic circulation by extracorporeal treatment is a potentially useful strategy for treatment of acute phase and relapsing MS.

Nitric oxide inhibits CXCL12 expression in neuroinflammation

Chemokine CXCL12 (C-X-C motif chemokine ligand 12) restricts immune cell invasion of the central nervous system (CNS) and limits neuroinflammation in experimental autoimmune encephalomyelitis (EAE), an animal model of inflammatory and demyelinating disease of the CNS, multiple sclerosis (MS). Nitric oxide (NO), by contrast, predominantly contributes to CNS tissue destruction in MS and EAE. Thus, the influence of NO on CXCL12 in the inflamed CNS was investigated. Excess expression of inducible NO synthase was inversely correlated to CXCL12 gene expression in spinal cord homogenates of rats immunized to develop EAE. NO inhibited gene expression of CXCL12 in astrocytes and endothelial cells in vitro. The inhibition was paralleled with reduction of p38 mitogen-activated protein kinase (MAPK) phosphorylation and it was mimicked with inhibitors of p38 MAPK activation in astrocytes. In vivo suppression of nitric generation recovered CXCL12 expression in the CNS and attenuated EAE in Dark Agouti rats. On the contrary, in vivo NO donation decreased CXCL12 expression in the CNS of EAE-resistant Albino Oxford (AO) rats. However, the effect was not paralleled with induction of EAE in AO rats. It is suggested that NO acting through suppression of p38 MAPK inhibits CXCL12 expression in neuroinflammation. These results imply that downregulation of NO release and protection of CXCL12 expression within the CNS might present the potential approaches in MS therapy.

Mechanism of experimental autoimmune encephalomyelitis in Lewis rats: recent insights from macrophages

Experimental autoimmune encephalomyelitis (EAE) in Lewis rats is an acute monophasic paralytic central nervous system disease, in which most rats spontaneously recover from paralysis. EAE in Lewis rats is induced by encephalitogenic antigens, including myelin basic protein. EAE is mediated by CD4⁺ Th1 cells, which secrete pro-inflammatory mediators, and spontaneous recovery is mediated by regulatory T cells. Recently, it was established that classically activated macrophages (M1 phenotype) play an important role in the initiation of EAE, while alternatively activated macrophages (M2 phenotype) contribute to spontaneous recovery from rat EAE. This review will summarize the neuroimmunological aspects of active monophasic EAE, which manifests as neuroinflammation followed by neuroimmunomodulation and/or neuroprotection, with a focus on the role of alternatively activated macrophages.

Immunohistochemical study of arginase-1 in the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis

Arginase-1, a marker for M2 phenotype alternatively activated macrophages, inhibits inflammation and is associated with phagocytosis of cell debris and apoptotic cells. We analyzed the expression of arginase-1, a competitive enzyme of inducible nitric oxide synthase (iNOS), in the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis (EAE). Western blot analysis showed that both arginase-1 and iNOS significantly increased in the spinal cords of rats at the peak stage of EAE compared with the expression level in control animals (p<0.05) and declined thereafter. Immunofluorescent staining demonstrated that increased expression of arginase-1 in EAE spinal cords was confirmed in macrophages as well as in some neurons and astrocytes that were constitutively positive for arginase-1 in normal spinal cords. A semiquantitative analysis by immunofluorescence showed that in EAE lesions, an increased level of arginase-1 immunoreactivity was matched with ED1-positive macrophages, which were also positive for activin A, a marker for the M2 phenotype. Taking all of these findings into consideration, we postulate that the increased level of arginase-1, which is partly from M2 macrophages, contributes to the modulation of neuroinflammation in EAE lesions, possibly through the reduction of nitric oxide in the lesion via competition with iNOS for the use of L-arginine.

High dose combination pertussis toxin induces autoimmune inner ear disease in Sprague-Dawley rats

CONCLUSION

A better animal model of autoimmune inner ear disease (AIED) in Sprague-Dawley rats has been developed by combination with high dose of pertussis toxin. This study also indicated that inner ear-specific antigens can be involved in autoimmune reactions. Cell-mediated immune injury can play an important role in the induction of AIED, at least in the earlier stage.

OBJECTIVES

The purpose of this study was to develop a more suitable rat model that demonstrated closer resemblance to the pathophysiological process in AIED.

METHODS

Ninety-six female Sprague-Dawley rats were divided into four groups. They were subcutaneously immunized with crude inner ear antigen/complete Freund's adjuvant (CIEAg/CFA), or intraperitoneal injection of 500 ng pertussis toxin (PT), or injection of CIEAg/CFA+PT, or phosphate-buffered saline (PBS) alone. The auditory function, histopathology of the inner ear, and autoantibodies were examined.

RESULTS

Significant differences in the time course of auditory brainstem response (ABR) threshold and mean score of cellular infiltration were demonstrated in the CIEAg/CFA+PT group of animals. Missing hair cells, degeneration of the spiral ganglion cells, endolymphatic hydrops, and autoantibodies were all noted after immunization. There were no significant differences in ABR threshold or histopathology in any other group of animals.

Centrally administered pertussis toxin inhibits microglia migration to the spinal cord and prevents dissemination of disease in an EAE mouse model

Background

Experimental autoimmune encephalomyelitis (EAE) models are important vehicles for studying the effect of infectious elements such as Pertussis toxin (PTx) on disease processes related to acute demyelinating encephalomyelitis (ADEM) or multiple sclerosis (MS). PTx has pleotropic effects on the immune system. This study was designed to investigate the effects of PTx administered intracerebroventricularly (icv) in preventing downstream immune cell infiltration and demyelination of the spinal cord.

Methods and Findings

EAE was induced in C57BL/6 mice with MOG_35–55. PTx icv at seven days post MOG immunization resulted in mitigation of clinical motor symptoms, minimal T cell infiltration, and the marked absence of axonal loss and demyelination of the spinal cord. Integrity of the blood brain barrier was compromised in the brain whereas spinal cord BBB integrity remained intact. PTx icv markedly increased microglia numbers in the brain preventing their migration to the spinal cord. An in vitro transwell study demonstrated that PTx inhibited migration of microglia.

Conclusion

Centrally administered PTx abrogated migration of microglia in EAE mice, limiting the inflammatory cytokine milieu to the brain and prevented dissemination of demyelination. The effects of PTx icv warrants further investigation and provides an attractive template for further study regarding the pleotropic effects of infectious elements such as PTx in the pathogenesis of autoimmune disorders.

Amelioration of experimental autoimmune encephalomyelitis in Lewis rats treated with fucoidan

We examined whether fucoidan affected the clinical symptoms of experimental autoimmune encephalomyelitis (EAE) in rats. EAE was induced in Lewis rats that were immunized with guinea-pig myelin basic protein (MBP) and complete Freund's adjuvant. Fucoidan (50 mg/kg, daily) was administered to rats with EAE intraperitoneally, either in the EAE induction phase from either 1 day before immunization to day 7 post-immunization (PI), or the effector phase from day 8 to 14 PI, to test which phase of rat EAE is affected by fucoidan treatment.The onset, severity and duration of EAE paralysis in the fucoidan-treated group in the days 8-14 PI-treated rats, but not in days -1-7 PI-treated rats, were significantly delayed, suppressed and reduced, respectively, compared with the vehicle-treated controls. Treatment with fucoidan reduced the encephalitogenic response and TNF-alpha production during EAE. Moreover, the clinical amelioration coincided with decreased infiltration of inflammatory cells in the EAE-affected spinal cord. The ameliorative effect of fucoidan on clinical paralysis in EAE-affected rats may be mediated, in part, by the suppression of the autoreactive T cell response and inflammatory cytokine production.

Therapeutic DNA vaccination as a repair strategy following spinal cord injury

Myelin-derived proteins, such as tenascin-R (TN-R), myelin associate glycoprotein (MAG), oligodendrocyte-myelin glycoprotein (OMgp), and Nogo-A, inhibit the central nervous system regeneration. In this study, the DNA vaccine encoding for oligodendrocyte and myelin-related antigens was employed to attenuate the axonal growth inhibitory properties of myelin in the setting of spinal cord injury. Using a rat spinal cord dorsal hemisection model, the vaccine directed against the inhibitory epitopes of Nogo-A, MAG, OMgp, and TN-R was administered intramuscularly once a week following spinal cord injury, supplemented with local application of specific anti-sera against the four antigens. Anterograde labeling of dorsal column fibers showed active axonal regeneration through the lesion site at the eighth week following the treatment in experimental group but not in control groups. Light microscopic and ultrastructural analysis revealed that vaccination with these myelin-related antigens did not lead to demyelinating disease. OMgp and TN-R levels were down-regulated at the lesion site together with a parallel increase in growth-associated protein 43 levels in the treatment groups. This study reveals the effective approach of a DNA vaccine strategy by attaining the special antibody to direct neutralization of the myelin inhibitors during spinal cord injury.

Nitric oxide and TNFalpha effects in experimental autoimmune encephalomyelitis demyelination

The involvement of inducible nitric oxide synthase (iNOS), which plays various roles in the progression of autoimmune diseases, was studied in iNOS knockout (KO) mice and wild-type (WT) controls with respect to experimental autoimmune encephalomyelitis (EAE). The iNOS (KO) mice presented a less severe form of the disease than the WT control mice. Although the levels of TNFalpha decreased in the periphery in both groups, an increase in the number of TNFalpha-positive cells was detected in the central nervous system during the acute phase of EAE in the WT mice, but not in the KO mice. These findings suggest that NO and TNFalpha contribute to the pathogenesis of acute EAE.

Bone marrow-derived versus parenchymal sources of inducible nitric oxide synthase in experimental autoimmune encephalomyelitis

The role of nitric oxide (NO) in central nervous system (CNS) inflammation is uncertain. Whereas experimental autoimmune encephalomyelitis (EAE) is exacerbated in mice deficient in inducible nitric oxide synthase (iNOS), inhibitor studies have suggested a pro-inflammatory role for NO. These discrepancies may reflect balance between immunoregulatory and neurocytopathologic roles for NO. We investigated selective effects of bone marrow-derived versus CNS parenchymal sources of iNOS in EAE in chimeric mice. Chimeras that selectively expressed or ablated iNOS in leukocytes both showed significant delay in disease onset, with no difference in disease severity. We conclude that bone marrow-derived and CNS parenchymal sources of iNOS-derived NO both play a regulatory role in EAE.

Expression of constitutive endothelial and inducible nitric oxide synthase in the sciatic nerve of Lewis rats with experimental autoimmune neuritis

This study examined the expression of constitutive endothelial nitric oxide synthase (eNOS) and inducible NOS (iNOS) in the sciatic nerve of Lewis rats with experimental autoimmune neuritis (EAN). Western blot analysis showed that both eNOS and iNOS expressions in the sciatic nerves of rats increased significantly during the peak stage of EAN, but declined thereafter. Only minimal amounts of these enzymes were identified in normal rat sciatic nerves. Immunohistochemical studies showed that eNOS was increased in vascular endothelial cells and Schwann cells, but not in inflammatory cells, during the peak stage of EAN. However, iNOS was found mainly in inflammatory macrophages in sciatic nerve EAN lesions.These findings suggest that, depending on the stage of peripheral nervous system autoimmune disease, the increased expressions of both eNOS and iNOS might be involved in either the production of detrimental effects during the induction stage of EAN or in the recovery from EAN paralysis.