An electrophysiological and histological study of trypsin induced demyelination

Nerve conductions studies in experimental models of autoimmune neuritis: A meta-analysis and guideline

Nerve conduction studies (NCS) are essential to assess peripheral nerve fiber function in research models of immune-mediated neuritis. However, the current lack of standard protocols and reference values impedes data comparability across models and studies. We performed a systematic review and subsequent meta-analysis of the last 30 years of NCS of immune-mediated neuritis in Lewis-rats. Twenty-six papers met the inclusion criteria for meta-analysis. Extracted data showed considerable heterogeneity of recorded nerve conduction velocity (NCV) and compound muscle action potential (CMAP). Studies also significantly differed in terms of technical, methodical, and data reporting issues. The heterogeneity of the underlying studies emphasizes the need for standardization when conducting and reporting NCS in rats. We provide normative values for NCS of the sciatic nerve of Lewis rats and propose seven items that should be addressed when NCS are performed when studying immune paradigms in Lewis rats.

Significant Contribution of Mouse Mast Cell Protease 4 in Early Phases of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a mouse model that reproduces cardinal signs of clinical, histopathological, and immunological features found in Multiple Sclerosis (MS). Mast cells are suggested to be involved in the main inflammatory phases occurring during EAE development, possibly by secreting several autacoids and proteases. Among the latter, the chymase mouse mast cell protease 4 (mMCP-4) can contribute to the inflammatory response by producing endothelin-1 (ET-1). The aim of this study was to determine the impact of mMCP-4 on acute inflammatory stages in EAE. C57BL/6 wild type (WT) or mMCP-4 knockout (KO) mice were immunized with MOG_35–55 plus complete Freund's adjuvant followed by pertussis toxin. Immunized WT mice presented an initial acute phase characterized by progressive increases in clinical score, which were significantly reduced in mMCP-4 KO mice. In addition, higher levels of spinal myelin were found in mMCP-4 KO as compared with WT mice. Finally, whereas EAE triggered significant increases in brain levels of mMCP-4 mRNA and immunoreactive ET-1 in WT mice, the latter peptide was reduced to basal levels in mMCP-4 KO congeners. Together, the present study supports a role for mMCP-4 in the early inflammatory phases of the disease in a mouse model of MS.

Mast cells are essential for early onset and severe disease in a murine model of multiple sclerosis

In addition to their well characterized role in allergic inflammation, recent data confirm that mast cells play a more extensive role in a variety of immune responses. However, their contribution to autoimmune and neurologic disease processes has not been investigated. Experimental allergic encephalomyelitis (EAE) and its human disease counterpart, multiple sclerosis, are considered to be CD4(+) T cell-mediated autoimmune diseases affecting the central nervous system. Several lines of indirect evidence suggest that mast cells could also play a role in the pathogenesis of both the human and murine disease. Using a myelin oligodendrocyte glycoprotein (MOG)-induced model of acute EAE, we show that mast cell-deficient W/W(v) mice exhibit significantly reduced disease incidence, delayed disease onset, and decreased mean clinical scores when compared with their wild-type congenic littermates. No differences were observed in MOG-specific T and B cell responses between the two groups, indicating that a global T or B cell defect is not present in W/W(v) animals. Reconstitution of the mast cell population in W/W(v) mice restores induction of early and severe disease to wild-type levels, suggesting that mast cells are critical for the full manifestation of disease. These data provide a new mechanism for immune destruction in EAE and indicate that mast cells play a broader role in neurologic inflammation.

Pathogenesis of Guillain-Barré syndrome

Recent neurophysiological and pathological studies have led to a reclassification of the diseases that underlie Guillain-Barré syndrome (GBS) into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor and sensory axonal neuropathy (AMSAN) and acute motor axonal neuropathy (AMAN). The Fisher syndrome of ophthalmoplegia, ataxia and areflexia is the most striking of several related conditions. Significant antecedent events include Campylobacter jejuni (4-66%), cytomegalovirus (5-15%), Epstein-Barr virus (2-10%), and Mycoplasma pneumoniae (1-5%) infections. These infections are not uniquely associated with any clinical subtype but severe axonal degeneration is more common following C. jejuni and severe sensory impairment following cytomegalovirus. Strong evidence supports an important role for antibodies to gangliosides in pathogenesis. In particular antibodies to ganglioside GM1 are present in 14-50% of patients with GBS, and are more common in cases with severe axonal degeneration associated with any subtype. Antibodies to ganglioside GQ1b are very closely associated with Fisher syndrome, its formes frustes and related syndromes. Ganglioside-like epitopes exist in the bacterial wall of C. jejuni. Infection by this and other organisms triggers an antibody response in patients with GBS but not in those with uncomplicated enteritis. The development of GBS is likely to be a consequence of special properties of the infecting organism, since some strains such as Penner 0:19 and 0:41 are particularly associated with GBS but not with enteritis. It is also likely to be a consequence of the immunogenetic background of the patient since few patients develop GBS after infection even with one of these strains. Attempts to match the subtypes of GBS to the fine specificity of anti-ganglioside antibodies and to functional effects in experimental models continue but have not yet fully explained the pathogenesis. T cells are also involved in the pathogenesis of most or perhaps all forms of GBS. T cell responses to any of three myelin proteins, P2, PO and PMP22, are sufficient to induce experimental autoimmune neuritis. Activated T cells are present in the circulation in the acute stage, up-regulate matrix metalloproteinases, cross the blood-nerve barrier and encounter their cognate antigens. Identification of the specificity of these T cell responses is still at a preliminary stage. The invasion of intact myelin sheaths by activated macrophages is difficult to explain according to a purely T cell mediated mechanism. The different patterns of GBS are probably due to the diverse interplay between antibodies and T cells of differing specificities.

Local effects of recombinant rat interleukin-6 on the peripheral nervous system

Interleukin-6 (IL-6) is a multifunctional cytokine with a broad range of activities and can affect a variety of target cells or systems in multiple ways. However, there is currently no consensus on how IL-6 directly affects the peripheral nervous tissue. We performed histopathological and immunohistochemical analyses to investigate the direct effects of recombinant rat IL-6 (rrIL-6) following its intraneural injection into the sciatic nerve of adult Lewis rats. One day after injection, a large number of macrophages, major histocompatibility complex (MHC) class II positive cells, and CD4+ and CD8+ T cells appeared within the perineurium and endoneurium. From day 4 to day 7 after injection, we observed a gradual increase of inflammation and demyelination. On day 7, demyelination affected more than 80% of nerve fibres. In contrast, in the sterile phosphate-buffered saline (PBS)-injected control group, lower inflammation and fewer demyelinating nerve fibres were observed on days 4 and 7. Thus, intraneural injection of rrIL-6 into the sciatic nerve induces high inflammation and severe demyelination. This study improves our understanding of the effector mechanisms underlying inflammation and demyelination and identifies IL-6 as an essential mediator of inflammation and demyelination in the peripheral nervous system after local administration.