Oligodendrocyte/myelin injury and repair as a function of the central nervous system environment

Nerve growth factor is elevated in the CSF of patients with multiple sclerosis and central neuropathic pain

Central neuropathic pain (CNP) is common and disabling among patients with multiple sclerosis (MS). The pathological mechanisms underlying CNP in MS are not well understood. We explored whether NGF is implicated in the pathogenesis of CNP in MS. We measured NGF concentration in the CSF of 73 patients affected by MS, 15 with and 58 without CNP and 14 controls. We found increased levels of NGF in the CSF of patients with CNP compared to patients without and to controls. This finding supports the hypothesis that NGF plays a role in MS related CNP.

Increased neutralization capacity of TNF-α in sera of relapsing remitting multiple sclerosis patients is not related to soluble TNF-α receptors or anti-TNF-α autoantibody levels

The increased TNF-α levels in active lesions and CSF of multiple sclerosis (MS) patients and the beneficial effect of TNF-α blockade in animal models of MS led to the therapeutic usage of TNF-α antagonists. However, systemic TNF-α blockade exacerbated MS activity and was associated with new-onset MS when implemented for treating other autoimmune disorders. We employed a TNF-α neutralization bioassay and demonstrated that the capacity of sera from untreated and IFN-β-treated relapsing remitting MS patients to neutralize TNF-α is significantly higher than that of matched healthy controls. This finding was not related to sTNFRI, sTNFRII, or anti-TNF-α Abs levels.

Multiple sclerosis: autoimmune disease or autoimmune reaction?

Multiple sclerosis (MS) is traditionally considered an autoimmune inflammatory demyelinating disease of the central nervous system (CNS) with much knowledge available to support this view. However, this characterization implies that the primary event is an aberrant immune response directed at CNS antigens, promoting inflammation and later driving progressive axo-glial degeneration. Trials with potent anti-inflammatory agents and detailed neuropathological studies raise questions about this sequence of events. This hypothetical paper argues that MS may be primarily a "cytodegenerative" disease, possibly first involving the oligodendrocyte/myelin unit. Liberation of autoantigens secondarily recruits an immune response, the force of which heavily depends on the host's immune predisposition. Thus, the spectrum of MS from highly aggressive Marburg type, to primary progressive disease with little inflammatory burden, is governed by a "convolution" between the underlying cytodegeneration and the host's immune predilection. Clinical heterogeneity may be a reflection of a variable immune response, whereas in reality, the "real MS" may be a homogeneous degenerative process analogous to well known primary neurodegenerative diseases.

LINGO-1 antagonists as therapy for multiple sclerosis: in vitro and in vivo evidence

BACKGROUND

Multiple sclerosis (MS) is an inflammatory disease of the CNS that causes progressive neurological disability in most patients. Certain alleles of immunity-associated genes increase risk of MS, confirming a role for autoimmune mechanisms in pathogenesis. Activated mononuclear cells infiltrate the CNS and trigger an inflammatory cascade, resulting in demyelination and axonal injury. Non-inflammatory mechanisms also appear to be involved in axonal degeneration but are not fully elucidated. Current therapies are anti-inflammatory, and no available therapy is known to promote myelin repair or maintenance. Leucine-rich repeats and Ig domain-containing, neurite outgrowth inhibitor (Nogo) receptor-interacting protein-1 (LINGO-1) is a potent negative regulator of axonal myelination.

OBJECTIVE/METHODS

This article provides an overview of the available data on the effects of LINGO-1 antagonists on oligodendrocyte differentiation and remyelination.

RESULTS/CONCLUSION

LINGO-1 is a potential target for neuroprotective therapy in that antagonists may promote remyelination in diseases such as MS.

Neuroinflammation and Peripheral Immune Infiltration in Parkinson's Disease: An Autoimmune Hypothesis

Despite decades of research and the development of a large group of animal models, our understanding of the mechanisms responsible for the progressive loss of dopamine neurons in Parkinson's disease (PD) is unknown. So-called neuroprotective studies demonstrate that a vast group of molecules readily attenuate the dopamine (DA) neuron loss produced by DA neurotoxin insult. Despite these successes, these neuroprotective strategies have been surprisingly ineffective in patients. This may reflect the fact that the initial pathogenic event and the subsequent disease progression is a consequence of different mechanisms. As we began to think about this disconnect, we discovered that animals exposed to DA neurotoxins exhibited blood–brain barrier (BBB) dysfunction. If the BBB in PD patients is disrupted, then the barrier that normally segregates peripheral vascular factors from brain parenchyma is no longer present. Immune cells could then enter brain and produce a self-perpetuating (progressive) degenerative process. In this review, we propose that peripheral immunity contributes to the degenerative process of PD and may be responsible for the progressive nature of the disease. This hypothesis is supported by a broad and diverse literature that is just beginning to come together to suggest that PD is, in part, an autoimmune disease. In order to understand this hypothesis, the reader must question the conventional wisdom that the BBB is intact in PD, the brain is an immune privileged area, and that pathogenic insult and disease progression may reflect different mechanisms.

Effects of acute and repeated exposure to lipopolysaccharide on cytokine and corticosterone production during remyelination

Chronic exposure to the copper-chelating agent, cuprizone (CPZ), is an increasingly popular model for producing demyelination. More importantly, cessation of cuprizone exposure allows for full remyelination, which represents a window of opportunity for determining the influence of environmental factors on regenerative processes. In the present study, CPZ-treated animals were assessed for functional status of systemic and central cytokine responsiveness to LPS, as well as assessment for signs of body weight changes. Exposure of male C57BL/6J mice to 5 weeks of 0.2% CPZ in the diet was optimal in producing demyelination and microglial activation, as measured by myelin basic protein, CD11b, and CD45 immunohistochemistry. Acute challenge with LPS at the end of 5 weeks CPZ treatment did not alter IL-1beta, IL-6, nor TNFalpha responses in the spleen and corpus callosum. Similarly, repeated exposure to LPS during the remyelination phase (CPZ removal) did not influence these measures to LPS. Plasma corticosterone was unaffected following acute challenge of CPZ-pretreated animals, but after repeated LPS treatment, there was a significant augmentation of the corticosterone response in CPZ-pretreated mice. Interestingly, the basal concentration of IL-1beta in the corpus callosum of CPZ treated animals was significantly increased, which was in keeping with the increase in activated microglial cells. In conclusion, the cuprizone model of demyelination and remyelination does not appear to influence the systemic nor central IL-1, IL-6, and TNF responses to acute nor repeated LPS. This opens up the possibility for studying the contribution of systemic inflammatory processes on remyelination after cessation of CPZ treatment.

The natural history of relapses in multiple sclerosis

Relapses are a defining feature of multiple sclerosis (MS), serving as the basis for categorizing the different phases of the disease, and providing a means of measuring treatment success, following disease activity, and defining prognostic features. While the dissociation between relapses and disease progression indicates the boundaries of relapse history in determining disease course over time, it also highlights the importance of relapses to overall disease evolution. A broad understanding of relapse definition and dynamics is important to promote accurate diagnosis, patient management, and treatment decisions. In an attempt to describe the underlying etiology and clinical impact of relapses in MS, this review will examine relapse findings from natural history studies, the utility of relapse as a predictor of disease course, the factors that may contribute to relapse, and data on relapse resolution. The relationship of clinical relapses to MRI disease activity and to the onset of progressive disease will also be addressed.