Mice overexpressing Bcl-2 in their neurons are resistant to myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE)

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) characterized by destruction of myelin. Recent studies have indicated that axonal damage is involved in the pathogenesis of the progressive disability of this disease. To study the role of axonal damage in the pathogenesis of MS-like disease induced by myelin oligodendrocyte glycoprotein (MOG), we compared experimental autoimmune encephalomyelitis (EAE) in wild-type (WT) and transgenic mice expressing the human bcl-2 gene exclusively in neurons under the control of the neuron-specific enolase (NSE) promoter. Our study shows that, following EAE induction with pMOG 35-55, the WT mice developed significant clinical manifestations with complete hind-limb paralysis. In contrast, most of the NSE-bcl-2 mice (16/27) were completely resistant, whereas the others showed only mild clinical signs. Histological examination of CNS tissue sections showed multifocal areas of perivascular lymphohistiocytic inflammation with loss of myelin and axons in the WT mice, whereas only focal inflammation and minimal axonal damage were demonstrated in NSE-bcl-2 mice. No difference could be detected in the immune potency as indicated by delayed-type hypersensitivity (DTH) and T-cell proliferative responses to MOG. We also demonstrated that purified synaptosomes from the NSE-bcl-2 mice produce significantly lower level of reactive oxygen species (ROS) following exposure to H₂0₂ and nitric oxide (NO) than WT mice. In conclusion, we demonstrated that the expression of the antiapoptotic gene, bcl-2, reduces axonal damage and attenuates the severity of MOG-induced EAE. Our results emphasize the importance of developing neuroprotective therapies, in addition to immune-specific approaches, for treatment of MS. D.O. and J.F.K. contributed equally.     

Analysis of gene expression in MOG-induced experimental autoimmune encephalomyelitis after treatment with a novel brain-penetrating antioxidant

Accumulating data from experimental studies indicate that oxidative stress has a major role in the pathogenesis of multiple sclerosis (MS). It has been suggested that local production of reactive oxygen species, probably by macrophages, mediates axonal damage in both MS patients and the mouse model experimental autoimmune encephalomyelitis (EAE). We have shown previously that our novel brain-penetrating antioxidant, N-acetylcysteine amide (AD4), reduces the clinical and pathological symptoms, including inflammation and axonal damage in myelin oligodendrocyte glycoprotein (MOG)-induced chronic EAE in mice. The aim of this study was to examine the molecular mechanism by which AD4 exerts protection in MOG-induced EAE mice. Therefore, we analyzed gene-expression profile in the spinal cords of MOG-induced chronic EAE mice and compared them with MOG-induced mice treated with AD4, using a cDNA microarray. We found that MOG treatment up-regulated genes encoding growth factors, cytokines, death receptors, proteases, and myelin structure proteins, whereas MOG- and AD4-treated mice demonstrated gene expression profiles similar to that seen in naive healthy mice. In conclusion, our study shows that chronic AD4 administration suppresses the induction of various pathological pathways that play a role in EAE and probably in MS.     

Intravenous immunoglobulin therapy prevents development of autoimmune encephalomyelitis and suppresses activation of matrix metalloproteinases

Although intravenous immunoglobulin (IVIG) has been reported to improve the status of expanded disability status scale (EDSS) of multiple sclerosis (MS) patients and reduce the annual relapse rate, some studies did not find its beneficial effects. In the present study, using an animal model for MS, we found that prophylactic, but not therapeutic, treatment successfully suppressed the disease development. During the search for factors involved in the disease suppression by IVIG, we obtained evidence suggesting that IVIG exerts its function, at least in part, by suppressing activation of matrix metalloproteinases (MMP)‐2 and ‐9. Gelatin zymography revealed that gelatinase activities were suppressed by IVIG treatment in the spinal cord, but not in plasma. This finding raises the possibility that IVIG blocks MMP activities at the interface between the blood stream and CNS. With in situ zymography, we also observed that gelatinase activities were expressed mainly in astrocytes in the inflamed spinal cord of control rats and that this expression was attenuated by the treatment. These findings provide useful information to set optimal conditions for IVIG treatment of MS and to obtain more beneficial effects.     

实验性自身免疫性脑脊髓炎动物模型的比较

目的 比较两种不同品系大鼠及不同免疫原诱发的EAE模型特点。方法 应用MOG35-55、同种脊髓匀浆（DA-SCH）、MBP68-86、豚鼠-MBP为免疫原．分别免疫DA大鼠或Lewis大鼠制备EAE动物模型。观察比较大鼠发病过程、临床评分及病理变化。结果 应用MOG35-55或DA-SCH为免疫原致敏的DA大鼠病程呈现缓解-复发的双相病程．应用MBP68-86、豚鼠-MBP致敏Lewis大鼠而诱发的EAE模型为急性单相病程。豚鼠-MBP诱发的EAE模型发病时间匀齐、发病率最高、病情也最重．应用DA-SCH诱发的EAE模型病情其次重但发病时间不匀齐．MOG及MBP肽段引发的病情相对较轻。各实验组在发病高峰期组织病理变化以炎症反应为主。DA大鼠两个实验组第二次发病期炎症反应相对较轻而脱髓鞘较明显。结论 不同免疫原制备的EAE模型具有不同的特点．可根据研究目的不同选取所需模型。     

Oligoclonal IgG bands synthesized in the central nervous system are present in rats with experimental autoimmune encephalomyelitis

OBJECTIVE: Oligoclonal bands (OBs) in electrophoresis of cerebrospinal fluid (CSF) are present in multiple sclerosis and here is investigated whether these also occur in experimental autoimmune encephalomyelitis (EAE). MATERIAL AND METHODS: Experimental autoimmune encephalomyelitis was induced in 42 DA rats after immunization with rat spinal chord homogenate and the occurrence of OBs were detected by electrophoresis of both sera and CSF. The relationship between disease symptoms, antibody response against myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) and appearance of OBs was studied. RESULTS: Development of CSF-specific OB was found to occur, 6 weeks after immunization, in seven of 42 rats. OB was detected in rats with an antibody response against MBP, whereas as a role no such bands were present in rats with an antibody response against MOG. Initially severe disease symptoms were correlated to a concomitant intense oligoclonal antibody response. CONCLUSION: Cerebrospinal fluid-specific OB occurs in EAE. It is present in rats with an anti-MBP, but not in rats with an anti-MOG antibody response. A severe disease results in an intense oligoclonal antibody response, which might have an anti-inflammatory effect.     

Depletion of autoreactive B-lymphocytes by a recombinant myelin oligodendrocyte glycoprotein-based immunotoxin

We report the construction of a fusion protein comprising the extracellular domain of myelin oligodendrocyte glycoprotein (MOG) and a truncated version of Pseudomonas aeruginosa exotoxin A (ETA′). The chimeric immunotoxin targeted MOG-reactive B-lymphocytes by binding selectively to the appropriate receptors, leading to internalization and apoptosis of the target cells. The functionality of the immunotoxin was tested on a MOG-sensitive murine hybridoma cell line and ex vivo on freshly isolated splenocytes from transgenic IgH_MOG mice. These data demonstrate, for the first time, the specific cytotoxicity of a MOG-containing recombinant immunotoxin expressed in bacteria towards MOG-reactive B-lymphocytes.     

Chronic mechanical hypersensitivity in experimental autoimmune encephalomyelitis is regulated by disease severity and neuroinflammation

Chronic pain severely affects quality of life in more than half of people living with multiple sclerosis (MS). A commonly-used model of MS, experimental autoimmune encephalomyelitis (EAE), typically presents with hindlimb paralysis, neuroinflammation and neurodegeneration. However, this paralysis may hinder the use of pain behavior tests, with no apparent hypersensitivity observed post-peak disease. We sought to adapt the classic actively-induced EAE model to optimize its pain phenotype. EAE was induced with MOG_35-55/CFA and 100–600 ng pertussis toxin (PTX), and mice were assessed for mechanical, cold and thermal sensitivity over a 28-day period. Spinal cord tissue was collected at 14 and 28 days post-injection to assess demyelination and neuroinflammation. Only mice treated with 100 ng PTX exhibited mechanical hypersensitivity. Hallmarks of disease pathology, including demyelination, immune cell recruitment, cytokine expression, glial activation, and neuronal damage were higher in EAE mice induced with moderate (200 ng) doses of pertussis toxin, compared to those treated with low (100 ng) levels. Immunostaining demonstrated activated astrocytes and myeloid/microglial cells in both EAE groups. These results indicate that a lower severity of EAE disease may allow for the study of pain behaviors while still presenting with disease pathology. By using this modified model, researchers may better study the mechanisms underlying pain.     

Variation in experimental autoimmune encephalomyelitis scores in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is a common demyelinating central nervous system disease associated with progressive physical impairment. To study the mechanism underlying disease pathogenesis and develop potential treatments, experimental autoimmune encephalomyelitis (EAE) is often used as an animal model. EAE can be induced in various species by introducing specific antigens, which ultimately result in motor dysfunction. Although the severity of the paralysis is indicated using the EAE score, there is no standard scoring system for EAE signs, and there is variability between research groups with regard to the exact EAE scoring system utilized. Here, we describe the criteria used for EAE scoring systems in various laboratories and suggest combining EAE score with another quantitative index to evaluate paralysis, such as the traveled distance, with the goal of facilitating the study of the mechanisms and treatment of MS.     

Myelin oligodendrocyte glycoprotein (MOG) gene polymorphisms and multiple sclerosis: no evidence of disease association with MOG

The region surrounding the myelin oligodendrocyte glycoprotein (MOG) gene, located telomeric to the major histocompatibility complex on chromosome 6, was shown to contain three highly informative microsatellites. To examine the potential role of variants of the MOG gene in susceptibility to multiple sclerosis, these CA-repeat polymorphic markers were characterized on a sample of 169 multiple sclerosis patients and 173 healthy unrelated individuals by a method combining fluorescence labelling of PCR products and use of an automated DNA sequencer. Both patients and controls lived in the southwest of France (in the Pyrénées-Atlantiques) and had similar ethnic background. The distribution of the MOG haplotypes was not significantly different in the two groups (P = 0.38). This is not in favour of the implication of the MOG gene in the genetic component of multiple sclerosis, unless different independent mutations have occurred within this gene.     

FK506 and a nonimmunosuppressant derivative reduce axonal and myelin damage in experimental autoimmune encephalomyelitis: neuroimmunophilin ligand-mediated neuroprotection in a model of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) in which demyelination and axonal loss result in permanent neurologic disability. We examined the neuroprotective property of the immunosuppressant FK506 (tacrolimus), FK1706 (a nonimmunosuppressant FK506 derivative) and cyclosporin A (CsA) in a chronic relapsing experimental autoimmune encephalomyelitis (EAE) model of MS. Female SJL/J mice were immunized by subcutaneous (s.c.) injection with proteolipid protein 139-151 peptide in complete Freund's adjuvant. At the onset of paralysis, 12-14 days after immunization, mice received daily s.c. injections of FK506 (0.2, 1, and 5 mg/kg), FK1706 (5 mg/kg), CsA (2, 10, and 50 mg/kg), saline or vehicle (30% dimethylsulfoxide) for 30 days. FK506 (at a dose of 5 mg/kg) reduced the severity of the initial disease and suppressed relapses. FK1706 did not significantly alter the clinical course and CsA (at a dose of 50 mg/kg) lessened the severity of the initial episode of EAE but did not alter relapses. In the thoracic spinal cord, FK506 (5 mg/kg), FK1706 (5 mg/kg), and CsA (50 mg/kg) significantly (P < 0.001) reduced the extent of damage in the dorsal, lateral, and ventral white matter by a mean of up to 95, 68, and 30%, respectively. A nonimmunosuppressant dose of FK506 (0.2 mg/kg) also significantly (P < 0.001) reduced the extent of damage in the spinal cord by a mean of up to 45%. Other dosages of these compounds were ineffective. FK506 markedly protects against demyelination and axonal loss in this MS model through immunosuppression and neuroprotection.     

Activation of mitogen-activated protein kinases in experimental autoimmune encephalomyelitis

The expression of mitogen-activated protein (MAP) kinases, including extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal protein kinase (JNK), and p38, was analyzed in experimental autoimmune encephalomyelitis (EAE) in rats.

Western blot analysis showed that the three MAP kinases (phosphorylated ERK (p-ERK), p-JNK, and p-p38) were increased significantly in the spinal cords of rats with EAE at the peak stage as compared with the levels in controls (p<0.05), and both p-ERK and p-JNK declined slightly in the recovery stage of EAE. Immunohistochemistry showed that p-ERK was constitutively expressed in brain cells, including astroglial cells, and showed enhanced immunoreactivity in those cells in EAE, while some T cells and macrophages were weakly immunopositive for p-ERK in EAE lesions. Both p-JNK and p-p38 were intensely immunostained in T cells in EAE lesions, while a few glial cells and astrocytes were weakly positive for both.

Taking all these facts into consideration, we postulate that increased expression of the phosphorylated form of each MAP kinase plays an important role in the initiation of acute monophasic EAE. Differential expression of three MAP kinases was discerned in an animal model of human autoimmune central nervous system diseases, including multiple sclerosis.     

实验性自身免疫性脑脊髓炎大鼠模型脑组织硫化氢的变化

目的 观察实验性自身免疫性脑脊髓炎(EAE)模型大鼠脑组织中硫化氢(H2S)动态变化,探讨H2S与多发性硬化(MS)的关系. 方法 按随机区组设计方法将SD大鼠分成对照组及模型组,每组78只.模型组制备EAE模型,对照组用生理盐水代替诱导乳剂,余措施相同.采用HE染色、尼氏染色观察2组大鼠脑组织病理变化;比较不同时间点(建模后5、10、15、20、25、30、35、40、45、50、55、60 d和65 d)2组大鼠平均临床评分;采用比色法检测各时间点H2S和丙二醛(MDA)水平. 结果 (1)HE和尼氏染色显示模型组中可见明显的炎性细胞浸润现象及血管袖套形成,对照组未发现明显改变.(2)模型组于建模后第20天及第50天出现2次发病高峰,临床评分分别为(4.0±0.55)分和(3.5±0.25)分;对照组的评分为0分.(3)模型组大鼠各时间点脑组织中H2S表达量随着发病呈逐渐下降趋势,从第10天开始低于对照组,差异有统计学意义(P＜0.05).相反,模型组大鼠各时间点脑组织中MDA呈逐渐增加趋势,从第10天开始高于对照组,差异有统计学意义(P＜0.05).对照组大鼠H2S和MDA水平无明显变化.(4)模型组大鼠脑组织中H2S水平的变化与临床评分、MDA水平呈负相关(r=0.960,P=0.000;r=-0.920,P=0.000);临床症状评分和MDA水平呈正相关(r=0.910,P=0.000). 结论 H2S在EAE模型中表达明显降低,在MS中的作用机制有待进一步研究.     

基质金属蛋白酶9在实验性自身免疫性脑脊髓炎大鼠发病过程中的动态表达

目的通过检测基质金属蛋白酶-9(MMP-9)在EAE大鼠发病过程中不同阶段外周血和中枢神经系统中的表达水平及动态变化,以探讨其在多发性硬化发病过程中的作用及机制。方法 Wistar雌性大鼠80只,分为模型组(EAE组)、完全福氏佐剂组(CFA组),分别于免疫后6天、8天、10天、12天、14天、16天、18天及20天取视交叉处脑组织和脊髓腰膨大段行HE染色观察炎性细胞的浸润状况;免疫组化法检测脑和脊髓组织中MMP-9的表达,酶联免疫吸附实验测定血清中MMP-9的含量。结果 EAE组大鼠脊髓和脑组织中MMP-9阳性细胞数及血清中MMP-9水平均显著高于同期CFA组(P<0.05);EAE 10天组与EAE 6天、14天、18天及20天组比较,大鼠脊髓腰膨大处MMP-9阳性细胞数较多(P<0.05);EAE 12天组与EAE 6天组、8天组、14天组、16天组、18天组及20天组比较,大鼠脑组织视交叉处MMP-9阳性细胞数较多(P<0.05);EAE 12天组与EAE 6天组、8天组、10天组、14天组、16天组、18天组及20天组相比较,大鼠血清中MMP-9含量较高(P<0.05)。结论在EAE大鼠发病前期即有中枢组织内MMP-9的高表达,且EAE大鼠脊髓中MMP-9的高表达要早于脑组织和外周血,但MMP-9表达的高峰在第12天与病理变化和疾病进展是同步的。     

MOG35-55诱发C57BL/6小鼠实验性自身免疫性脑脊髓炎模型轴索损害可能并非继发于炎性脱髓鞘

采用MOG35-55加完全弗氏佐剂诱发实验性自身免疫性脑脊髓炎C57BL/6小鼠模型,其发病潜伏期约12 d,发病率100%,呈慢性非复发性病程经过。其神经组织病理改变表现为：光镜下见小血管周围炎细胞浸润,呈袖套状改变;Luxol-fast-blue染色可见髓鞘脱失;TUNEL染色和Bielshowsky银染法发现神经元变性和轴索损害;电镜下可见线粒体肿胀,细胞器消失,髓鞘结构松散、断裂或融合, 并可见不同程度的髓鞘重建。且轴索损害与髓鞘脱失的分布并不一致,轴索损伤的程度与髓鞘脱失亦不成比例,部分甚至与脱髓鞘无关。提示实验性自身免疫性脑脊髓炎的轴索损害并非继发于炎性脱髓鞘。     

Validation of a novel biomarker for acute axonal injury in experimental autoimmune encephalomyelitis

In multiple sclerosis, inflammatory axonal injury is a key pathological mechanism responsible for the development of progressive neurological dysfunction. The injured axon represents a therapeutic target in this disease; however, therapeutic trials of neuroprotective candidates will initially require preclinical testing in an animal model of inflammatory axonal injury and subsequently the development of a reliable paraclinical measure of axonal degeneration in humans. In the present study, we demonstrate the validity of serum phosphorylated neurofilament H (pNF-H) as a marker of axonal injury in murine experimental autoimmune encephalomyelitis (EAE). At the time of maximum disease severity (EAE day 22), the average serum pNF-H level reached 5.7 ng/ml, correlating significantly with the EAE paraplegia score (r = 0.75, P < 0.001). On average, 40% of axons in the spinal cord were lost in EAE, and serum pNF-H levels were highly correlated with axon loss (r = 0.8, P < 0.001). Axonal injury was a severe and acute event, insofar as serum pNF-H levels were not significantly elevated at early (EAE day 12) or late (EAE days 35 and 50) disease time points. Our results demonstrate that acute inflammatory axonal injury is a pathological feature of murine MOG(35-55) EAE, indicating that this model may mirror the acute pathological events in active multiple sclerosis lesions. Furthermore, we have validated the serum pNF-H assay as an unbiased measurement of axonal injury in EAE, facilitating rapid screening of potential neuroprotective therapies in this model.     

Expression of citrullinated proteins in murine experimental autoimmune encephalomyelitis

In this study, we demonstrate for the first time the immunohistochemical expression of citrullinated proteins in the central nervous system (CNS) of mice with myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). By using an established monoclonal antibody (F95) against natural and synthetic citrullinated proteins (Nicholas and Whitaker [2002] Glia 37:328-336), numerous, small, previously unrecognized "patches" of citrullinated proteins were discovered throughout EAE brains, whereas EAE spinal cords showed similar but much larger lesions. On dual color immunofluorescence, these lesions were found to contain citrullinated myelin basic protein (MBP) and were surrounded by astrocytes immunoreactive for both glial fibrillary acidic protein (GFAP) and F95. These lesions became evident about the time when EAE mice became symptomatic and increased in size and number with increasing disease severity. In some sections of spinal cord but not brains of severely debilitated EAE mice, a widespread gliotic response was seen, with astrocytes containing citrullinated GFAP spread throughout the gray and white matter. Western blot analysis of acidic proteins from the brains and spinal cords of EAE mice had higher levels of multiple citrullinated GFAP isoforms compared with controls, with more F95-positive bands in the EAE brains vs. spinal cords. These results raise the possibility that citrullination of both GFAP and MBP may contribute to the pathophysiology of EAE and that the brains of EAE mice may contain more pathology than previously realized.     

Recent advances in the immunopathology of experimental autoimmune encephalomyelitis: With special reference to cytokine production in the central nervous system

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease that can be induced by immunization with encephalitogenic antigens such as myelin basic protein. Recent in vitro studies have demonstrated that cytokines play an important role in immune reactions in the central nervous system (CNS), suggesting that cytokines released by infiltrating cells and glial cells may contribute to the pathogenesis of EAE. In this review, we focus on the interactions between infiltrating cells and brain cells during the inflammatory process in EAE and discuss the roles of cytokines in the CNS. After immunization with proper myelin antigens, encephalitogenic T cells increase in number and infiltrate the CNS parenchyma via the subarachnoid space or the blood vessels. Once inflammatory cells infiltrate the CNS, microglia and astrocytes are activated, and some of these cells proliferate in response to cytokines released by infiltrating cells. Following this, activated microglia present antigens to induce T cell proliferation and cytokine production. In contrast, astrocytes induce T cell unresponsiveness, probably due to a lack of costimulatory signals. Furthermore, infiltrating T cells are the main producers of Th1 cytokines and are involved in T cell-brain cell interactions. This cascade of events indicates that immune reactions take place in the CNS, although the CNS has previously been considered to be an immunologically privileged site. Based on these findings, we also discuss the feasibility of using various cytokines to stimulate the immunomodulation of brain inflammation as a treatment for autoimmune demyelinating diseases.     

Time course and distribution of inflammatory and neurodegenerative events suggest structural bases for the pathogenesis of experimental autoimmune encephalomyelitis

Murine models of experimental autoimmune encephalomyelitis (EAE) are important vehicles for studying the effects of genetic manipulation on disease processes related to multiple sclerosis (MS). Currently, a comprehensive assessment of EAE pathogenesis with respect to inflammatory and degenerating neuronal elements is lacking. By using Fluoro-jade histochemistry to mark neurodegeneration and dual immunostaining to follow T-cell, microglial, and vascular responses, the time course and distribution of pathological events in EAE was surveyed. C57BL/6J mice were killed at 7, 10, 14, 21 or 35 days after vaccination with the myelin oligodendrocyte glycoprotein peptide MOG(35-55). Disease onset occurred at day 14 and peaked at day 21. Early T-cell infiltration and microglial activation in periventricular and superficial white matter structures adjacent to meninges suggested initial recruitment of effector T cells via the cerebrospinal fluid and choroid plexus. This was associated with microglial activation at distal sites along the same white matter tracts, with subsequent vascular recruitment of T cells associated with further injury. Systematic examination of the entire CNS supported this two-step model of EAE pathogenesis, with inflammation and neurodegeneration commencing at similar times and affecting multiple levels of predominantly sensory central pathways, including their terminal fields. This included aspects of the visual, auditory/vestibular, somatosensory (lemniscal), and proprioceptive (spinocerebellar) systems. The early targeting of visual and periventricular structures followed by more widespread CNS involvement is consistent with common presenting signs in human MS patients and suggestive of a similar basis in neuropathology.     

Restoration of conduction in the spinal roots correlates with clinical recovery from experimental autoimmune encephalomyelitis

In the Lewis rat, acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants is characterized by tail and hindlimb weakness that resolves spontaneously after several days. In rats with neurological signs of this form of EAE (MBP-EAE) we have previously demonstrated demyelination and nerve conduction block in the proximal peripheral nervous system (PNS) and in the central nervous system (CNS). The present study was performed to assess conduction in the PNS and CNS, after recovery from acute MBP-EAE, using direct recordings from surgically exposed spinal roots and spinal cord dorsal columns. The study revealed that 1–2 weeks after clinical recovery from tail paralysis there was almost complete restoration of conduction in the sacral spinal roots but persistent severe conduction abnormalities in the dorsal columns. Significant restoration of conduction through the dorsal columns occurred over the following 2 weeks. These findings indicate that PNS conduction block due to a demyelinating polyradiculitis is a major cause of the neurological signs of acute MBP-EAE in the Lewis rat.© 1995 John Wiley & Sons, Inc.