Recent studies on the roles of antiglycosphingolipids in the pathogenesis of neurological disorders

Evidence is mounting to suggest a causal role of humoral immunity arising from antiglycosphingolipid (GSL) antibodies in a variety of neurological disorders. These disorders include the demyelinating and axonal forms of Guillain-Barre syndrome, multifocal motor neuropathy, chronic inflammatory demyelinating polyradiculoneuropathy, and IgM paraproteinemia. Many claims have been made regarding other neurological disorders, which should be carefully scrutinized for their validity, based on several criteria proposed in this review. These criteria include 1) characterization of the causative antigens and immunoglobulins, 2) correlation of the pathological lesions and clinical manifestation of the antigens, 3) establishment of animal models using pure GSLs as the antigens, 4) immunopathogenic mechanisms of the neurodenerative process, 5) mechanisms for the malfunctioning of blood-nerve barrier and the ensuing leakage of circulating antibodies into peripheral nerve parenchyma, and 6) the roles of anti-GSL antibodies that may cause humorally mediated nerve dysfunction and injury as well as interference with ion channel function at the node of Ranvier, where carbohydrate epitopes are located. Finally, the origin of the anti-GSL antibodies is discussed in light of the recent circumstantial evidence pointing to a molecular mimicry mechanism with infectious agents. With a better understanding of the immunopathogenic mechanisms, it will then be possible to devise rational and effective diagnostic and therapeutic strategies for the treatment of these neurological disorders.

Parameters for monitoring treatment effects in CIDP with anti-MAG/SGPG IgM antibody

We used cycles of plasma exchange and intravenous cyclophosphamide to treat a patient who had chronic inflammatory demyelinating polyneuropathy with anti-myelin-associated glycoprotein/sulfoglucuronylparagloboside IgM antibody. After treatment, serum anti-sulfoglucuronylparagloboside IgM antibody titers were reduced significantly, and clear symptomatic improvement followed. The percentage of CD57-positive lymphocytes and natural killer cell activity had also returned to normal. Our findings indicate that serial measurements of these parameters are useful for monitoring treatment effect in this disease.

The demonstration by transplantation of the very restricted remyelinating potential of post-mitotic oligodendrocytes

To examine the remyelinating ability of post-mitotic oligodendrocytes, we subjected cell preparations derived from neonatal and adult rats to 40 Grays of X-irradiation to remove mitotically active cells and injected them into areas of demyelination in which the inherent ability to generate remyelinating cells had been inhibited. The extensive remyelination seen following implantation of non-irradiated neonatal and adult cells was almost completely abolished when the transplanted cell suspension was exposed to 40 Grays of X-irradiation, demonstrating that effective remyelination requires the generation of cells by mitosis. Radiation-resistant and therefore non-dividing oligodendrocytes were detected in areas of demyelination following transplantation of neonatal cultures and oligodendrocyte preparations derived from the adult nervous system. However, the pattern of myelin formation associated with the radiation-resistant oligodendrocytes from the two sources was different. Following implantation of X-irradiated neonatal cultures, a small number of oligodendrocytes could be found within the area of demyelination, and although these cells formed sheets of myelin membrane, they did not form myelin sheaths. After implantation of X-irradiated adult cells, in addition to the aberrant myelin formation seen with the neonatal cells, some myelin sheaths were observed. Our findings confirm that effective remyelination requires cell division and suggest that there may be diverse populations of radiation-resistant oligodendrocytes in the adult nervous system, some of which can form myelin sheaths and others of which can only make myelin sheets. Important for the interpretation of our previous studies is the demonstration here that 40 Grays of X-irradiation per se does not inhibit oligodendrocytes from remyelinating axons.

A practical approach to the use of intravenous immunoglobulin in neurological disease

Intravenous immunoglobulin is now used in a wide range of neurological conditions. However, side effects are relatively common, treatment is expensive and sustained benefit unusual without repeated administration. This article aims to provide clinicians with an overview of the potential benefits and drawbacks of intravenous immunoglobulin in neurological practice and concludes with suggested guidelines for its use in adults.

Reemergence of sucrose nephropathy: acute renal failure caused by high-dose intravenous immune globulin therapy

Sucrose nephropathy was first described more than 50 years ago. The disorder is characterized by acute renal failure caused by the uptake of sucrose by renal proximal tubule cells with subsequent cellular swelling and occlusion of the tubule lumen. Approximately 114 cases of renal failure have been associated with high-dose intravenous immune globulin (IVIG) therapy. Almost all cases were caused by preparations containing large amounts of sucrose. Clinicians should consider using IVIG preparations containing no sucrose in patients who are at high risk for renal failure. Risk factors include older age, baseline renal failure, and volume contraction.

Areas of demyelination do not attract significant numbers of schwann cells transplanted into normal white matter

If Schwann cell transplantation is to be used as a therapy for demyelinating disease, it is important to know if the number of transplanted cells and their transplantation site affects the extent of remyelination. Primary Schwann cell cultures were obtained from neonatal rat sciatic nerve, purified, and expanded using bovine pituitary extract and forskolin. Areas of persistent demyelination were created in the dorsal funiculus of the thoracolumbar spinal cord of rats by injecting ethidium bromide into white matter exposed to 40 Gy of X-irradiation, and a high and low number of Schwann cells were transplanted, into either the area of demyelination or the dorsal funiculus cranial to the area of demyelination. Animals were perfused 4 weeks after transplantation. After injection of 4 x 10(4) cells into the area of demyelination, the area of Schwann cell remyelination was 0.88 +/- 0.16 mm(2), while following the injection of 3 x 10(3) cells it was significantly smaller, 0.29 +/- 0.09 mm(2). After implantation of Schwann cells 1-3 mm (mean 2.5 mm) cranial to the area of demyelination, only one of the eight animals (a high-dose animal) showed extensive Schwann cell remyelination. In this animal, the cells were transplanted within 1 mm of the area of demyelination, well within the length of tissue over which cells are passively spread by the injection procedure (1-3 mm). Our results show that significant numbers of transplanted Schwann cells are not attracted through normal tissue to areas of demyelination and when transplanted into areas of demyelination the extent of myelination is related to the number of Schwann cells transplanted.

High-dose mouse immunoglobulin G administration suppresses Theiler's murine encephalomyelitis virus-induced demyelinating disease

We studied the effect of high-dose mouse IgG on TMEV-induced demyelinating disease (TMEV-IDD). We injected TMEV intracerebrally into susceptible SJL/J mice and induced TMEV-IDD. Mouse IgG were injected intraperitonealy, and clinical course and various immunological indicators were studied. The results show that TMEV-IDD was significantly suppressed both clinically and histologically (P<0.01) when IgG were administered in the effector phase. The delayed type hypersensitivity and T cell proliferative response specific for TMEV were decreased by this treatment. In an ELISPOT assay, the number of TNF-alpha producing lymphocytes in the spinal cords was low in high-dose IgG treated mice compared with PBS treated control mice. These data suggest that administration of IgG suppresses TMEV-IDD and may be promising treatment to prevent exacerbation of human multiple sclerosis.

[Oligodendrocytes have a key role in the development of CNS function and in myelin related diseases]

Oligodendrocytes provide CNS axons with myelin sheaths through processes of various lengths. The lipid-rich myelin insulates axons electrically, which increases conduction velocity. In addition, oligodendrocytes have trophic effects on axons. During development immature oligodendrocytes undergo controlled migration, proliferation and differentiation, influenced by various growth factors and axons. A number of genetically manipulated animal models have provided insights regarding myelination and the function of myelin components. Current research on myelin related diseases, i.e. multiple sclerosis, focus on novel strategies for remyelination through transplantation of myelinating cells or stimulation of endogenous oligodendrocytes.

Schwann cell remyelination is restricted to astrocyte-deficient areas after transplantation into demyelinated adult rat brain

The ability to generate large numbers of Schwann cells from a peripheral nerve biopsy makes them potential candidates for the clinical application of cell transplantation to enhance remyelination in human demyelinating disease. Transplant-derived Schwann cell remyelination has previously been demonstrated in the spinal cord but not for demyelinated axons in the brain, a more likely site for initial clinical intervention. We have transplanted Schwann cells from male neonatal rat sciatic nerves into ethidium bromide-induced areas of demyelination in the deep cerebellar white matter of adult female rats. The extent of Schwann cell remyelination 28 days after transplantation was significantly increased in lesions that received direct injections of Schwann cells compared with non-transplanted lesions. Using in situ hybridisation to identify the rat Y chromosome, transplanted male cells were found to co-localise with the P0 immunoreactive area of Schwann cell remyelination. Combined immunohistochemistry and in situ hybridisation confirmed that many remyelinating Schwann cells were transplant-derived. P0 immunoreactivity and transplanted male cells were found in GFAP-negative, astrocyte-free areas. Transplanted Schwann cells were not identified outside of transplanted lesions, nor did they did not contribute to remyelination of a lesion at a distance from the site of transplantation. Our findings indicate that demyelinated axons in the adult brain can be remyelinated by transplanted Schwann cells but that migration and remyelination are restricted to areas from which astrocytes are absent.

[Treatment of chronic immune-mediated polyneuropathies. State of the art and perspectives]

Chronic immune-mediated polyneuropathies encompass chronic inflammatory demyelinating polyneuropathies, polyneuropathies associated with monoclonal gammopathy and multifocal motor neuropathy with persistent conduction blocks. Their diagnosis is made on clinical, electrophysiological and sometimes immunochemical and pathological criteria. The efficacy of short-term treatments (corticosteroids, plasma exchanges, intravenous immunoglobulins) depends on the type of the polyneuropathy, but these treatments may sometimes lead to prolonged improvement. The efficacy of long-term treatments needs further evaluation.

[Acquired demyelinating neuropathies]

The acquired demyelinating polyneuropathies with either acute or chronic clinical presentation are considered autoimmune disorders. The Guillain-Barré syndrome is viewed as an acutely reactive and self-limited autoimmune disease, triggered by preceding bacterial or viral infections. There is a particularly strong association with the gastroenteric pathogen, Campylobacter jejuni, and with Cytomegalovirus and Epstein-Barr virus. It is likely that immune response directed towards the infecting organisms are involved in the pathogenesis of Guillain-Barré syndrome by cross-reaction with neural tissues. In the susceptible individual, the infecting organism induces humoral and cellular immune responses that, because of the sharing of homologous epitopes (molecular mimicry), cross-react with ganglioside surface components of peripheral nerve. Immune reactions against target epitopes in the Schwann cell surface membrane or myelin result in acute inflammatory demyelinating neuropathy (90% of cases); reactions against epitopes contained in the axonal membrane cause the acute axonal forms of Guillain-Barré syndrome. Immunomodulation with infusions of IgG or plasma exchange treatments effectively foreshorten the disease course. The immunopathogenesis of the chronic disease forms, chronic inflammatory demyelinating peripheral neuropathy and multifocal motor neuropathy are less well-known. Immunomodulatory treatments with corticosteroid or cytotoxic drug treatments, infusion of Ig or therapeutic plasma exchanges are variably effective. The article outlines the principles and practices of an individualized approach to therapy.

Investigating demyelination in the brain in a canine model of globoid cell leukodystrophy (Krabbe disease) using magnetization transfer contrast: preliminary results

PURPOSE

This study was designed to examine the use of quantitative magnetization transfer imaging (MTI) in naturally occurring globoid cell leukodystrophy (GLD) in the Cairn terrier.

METHOD

A model of GLD was established via a breeding colony, and a total of seven animals were studied with MTI, including two dogs with GLD, one of which underwent whole-body irradiation (725 cGy) and bone marrow transplantation from a genotypically normal littermate. The remaining dogs served as untreated, irradiated, and unirradiated controls.

RESULTS

Region-of-interest (ROI) analysis of the MTI showed a decrease in MT ratio (MTR) in the internal capsule of the untreated/affected dog compared with age-matched controls but revealed similar results in the two other study animals. On MT contour plotting, inside-to-out gradients of MTR mimicked the demyelination pathology of the disease in the untreated/affected dog.

CONCLUSION

MT contour plotting demonstrated patterns of MT abnormality in the untreated/affected dog that were consistent with histopathology, establishing a clear relationship between pathology-proven demyelination and MTR as well as a striking contrast to the patterns of radiation damage.

Impact of plasma exchange on indices of demyelination in chronic inflammatory demyelinating polyradiculoneuropathy

We studied the impact of plasma exchange (PE) on indices of primary demyelination in patients of the Canadian multicenter trial of PE in chronic inflammatory demyelinating polyneuropathy (CIDP). Individual motor nerves (median, ulnar, peroneal, tibial) were studied: distal motor latencies (DMLs), proximal and distal compound muscle action potential (M-wave) amplitudes, negative peak areas and durations, and motor conduction velocities (CVs). Proximal M-wave amplitudes in individual motor territories, particularly in the ulnar nerve (from below elbow, above elbow, and axillary stimulating sites) demonstrated significant improvement with PE, but not sham exchange. Proximal ulnar M-wave areas also had significant improvement with PE. Trends toward improvement of individual nerve motor CVs, M-wave durations, and DMLs did not achieve statistical significance. Proximal M-wave amplitudes, particularly in the ulnar motor territory, and proximal M-wave areas (providing a measure of conduction block) were the most sensitive indices of improvement conferred by PE in CIDP. In individual patients, these indices may help judge the efficacy of therapy.

Chronic demyelinating hypertrophic brachial plexus neuropathy

A patient with unilateral, painless, chronic progressive upper limb sensorimotor deficit showed electrophysiological evidence of a focal demyelinating neuropathy with almost complete conduction block across the brachial plexus. Magnetic resonance imaging disclosed marked brachial plexus hypertrophy. Intravenous immunoglobulin led to fast and complete recovery, maintained by intermittent perfusions. Hypertrophic brachial plexus neuropathy can be a presentation of focal chronic inflammatory demyelinating polyradiculoneuropathy. Objective and quantitative assessment of hand function is useful to evaluate treatment results and to optimize treatment regimens.

Influence of diabetes mellitus on chronic inflammatory demyelinating polyneuropathy

Patients with diabetes occasionally develop clinical and electrodiagnostic features suggestive of chronic inflammatory demyelinating polyneuropathy (CIDP). To clarify the role of diabetes in patients with a CIDP-like syndrome, we compared the clinical, pathological, and electrodiagnostic features of 14 patients (10 men, 4 women) with diabetes and CIDP (DM-CIDP) to 60 patients with idiopathic CIDP (I-CIDP). The average duration of diabetes was 9 years. The patients with DM-CIDP were older and more often complained of imbalance compared to the idiopathic group, but the frequency of other symptoms and neurologic findings were similar. The mean amplitude of the ulnar compound muscle action potential in the DM-CIDP group was comparatively reduced, the sural sensory nerve action potential was more often absent, and axonal loss was more commonly observed on nerve biopsy. The response rate to treatment was similar, but the magnitude of functional recovery was greater in patients with I-CIDP. Thus, our patients with diabetes and CIDP had clinical features similar to those with idiopathic CIDP, but their nerve conduction studies and nerve biopsies showed more severe axonal loss and the degree of improvement following treatment was less favorable. These differences most likely reflect the additive effects of superimposed diabetic axonal polyneuropathy in patients who develop CIDP.

Response of patients with IgM and IgA-associated peripheral polyneuropathies to "off-line" immunoadsorption treatment using the Prosorba protein A column

Sensory or sensorimotor demyelinating polyneuropathies may be associated with monoclonal immunoglobulins (paraproteins). Our prior experience suggests that "off-line" Prosorba(R) column treatments may be effective therapy for patients with polyneuropathies associated with paraproteins of the IgG class. We report herein the treatment, using Prosorba(R), of 2 patients with peripheral neuropathies and paraproteins of the IgM class and 1 patient with peripheral neuropathy whose paraprotein was of the IgA class. All three patients were treated "off-line" with Prosorba(R) six times in a 2-week period. Each time they were phlebotomized 1 U of whole blood. The plasma and red cells were separated in the blood bank. The plasma was passed over the column while the red blood cells were returned to the patient through a heparin lock. Then the treated plasma was returned separately. There were no adverse effects of treatment, and, in one patient with an IgM paraprotein and one with an IgA paraprotein, neurological symptoms and signs improved over the subsequent 2 weeks. Prosorba(R) appears effective for predominantly sensory demyelinating polyneuropathies associated with M-components of all major immunoglobulin classes. Our current experience further suggests that the mechanism of action of Prosorba(R) may not depend on removal of small amounts of IgG-containing immune complexes from patients' plasma. A proper large-scale clinical trial is warranted.

Neurotransplantation of magnetically labeled oligodendrocyte progenitors: magnetic resonance tracking of cell migration and myelination

Demyelination is a common pathological finding in human neurological diseases and frequently persists as a result of failure of endogenous repair. Transplanted oligodendrocytes and their precursor cells can (re)myelinate axons, raising the possibility of therapeutic intervention. The migratory capacity of transplanted cells is of key importance in determining the extent of (re)myelination and can, at present, be evaluated only by using invasive and irreversible procedures. We have exploited the transferrin receptor as an efficient intracellular delivery device for magnetic nanoparticles, and transplanted tagged oligodendrocyte progenitor cells into the spinal cord of myelin-deficient rats. Cell migration could be easily detected by using three-dimensional magnetic resonance microscopy, with a close correlation between the areas of contrast enhancement and the achieved extent of myelination. The present results demonstrate that magnetic resonance tracking of transplanted oligodendrocyte progenitors is feasible; this technique has the potential to be easily extended to other neurotransplantation studies involving different precursor cell types.