Morphological and molecular response of the MOCH-1 oligodendrocyte cell line to serum and interferon-gamma: possible implications for demyelinating disorders

Mechanisms of damage to myelin and oligodendrocytes and their relevance to disease

Oligodendrocytes synthesize and maintain myelin in the central nervous system (CNS). Damage may occur to these cells in a number of conditions, including infections, exposure to toxins, injury, degeneration, or autoimmune disease, arising both in the course of human disease and in experimental animal models of demyelination and dysmyelination; multiple sclerosis is the commonest human demyelinating disorder. Conventional classical accounts of the pathology of this and other myelin diseases have given great insights into their core features, but there remain considerable uncertainties concerning the timing, means and cause(s) of oligodendrocyte and myelin damage. At present, therapeutic efforts largely concentrate on immune manipulation and damage limitation, an approach that has produced only modest effects in multiple sclerosis. One reason for this must be the limited understanding of the mechanisms underlying cell damage - clearly, successful therapeutic strategies for preserving the oligodendrocyte-myelin unit must depend on knowledge of how oligodendrocyte damage and death occurs. In this review, mechanisms of oligodendrocyte and myelin damage are considered, and attempts made to relate them to disease processes, clinical and experimental. The hallmarks of different cell death processes are described, and oligodendrocyte-myelin injury by cellular and soluble mediators is discussed, both in vitro and invivo. Recent developments concerning the pathological involvement of oligodendrocytes in neurodegenerative disease are summarized. Finally, these neuropathological and applied neurobiological observations are drawn together in the context of multiple sclerosis.

Oligodendroglial response to the immune cytokine interferon gamma

In the human demyelinating disorder multiple sclerosis, and its animal model experimental allergic encephalomyelitis, there is a breakdown of the blood-brain barrier and an infiltration of immune cells into the CNS. Infiltrating T lymphocytes and macrophages are believed to be key mediators of the disease process. Considerable circumstantial and experimental evidence has suggested that the pleiotropic cytokine interferon gamma (IFN-gamma), which is exclusively expressed by T cells and natural killer cells, is a deleterious component of the immune response in these disorders. When experimentally introduced into the CNS IFN-gamma promotes many of the pathological changes that occur in immune-mediated demyelinating disorders. In vitro, this cytokine elicits a number of effects on oligodendrocytes, including cell death. The harmful actions of IFN-gamma on CNS myelin are likely mediated through direct effects on the myelinating cells, as well as through the activation of macrophages and microglia. In this review we summarize relevant studies concerning the action of IFN-gamma in demyelinating disorders and discuss possible mechanisms for the observed effects.

Two proteins bind to a novel motif in the promoter of the myelin basic protein gene from mouse

The box 1 and 2 motif of the myelin basic protein (MBP) promoter is a potential regulatory sequence of the MBP transcription unit. A DNA fragment that contained the sequence of the box 1 and 2 motif from mouse was synthesized, and its protein binding properties were examined by gel-shift assays. The box 1 and 2 probe and nuclear extracts from mouse brain generated a pattern of six major DNA-protein complexes (a, b, c, d, e, and f). The box 1 and 2 probe and nuclear extracts from oligodendrocyte-like glioma cells 1C10 generated a pattern of DNA-protein complexes that exhibited only complexes a, b, e, and f. Complex b generated by extracts from 1C10 cells, however, was very intense compared to any of the other complexes. It was determined that dephosphorylation of the proteins in nuclear extracts from 1C10 cells with acid phosphatase significantly altered their DNA binding properties. Two proteins of minimum M, approximately 32 and approximately 38 kDa (MBP32 and MBP38) that bind to the box 1 and 2 motif were identified in these nuclear extracts by using a UV crosslinking method. MBP32 and MBP38 are found in cell types and tissues known to express the golli transcription unit of the golli-MBP gene complex and may be involved in the modulation of the MBP unit in those cells.

The effects of interferon-gamma on the central nervous system

Interferon-gamma (IFN-gamma) is a pleotropic cytokine released by T-lymphocytes and natural killer cells. Normally, these cells do not traverse the blood-brain barrier at appreciable levels and, as such, IFN-gamma is generally undetectable within the central nervous system (CNS). Nevertheless, in response to CNS infections, as well as during certain disorders in which the CNS is affected, T-cell traffic across the blood-brain barrier increases considerably, thereby exposing neuronal and glial cells to the potent effects of IFN-gamma. A larger portion of this article is devoted to the substantial circumstantial and experimental evidence that suggests that IFN-gamma plays an important role in the pathogenesis of the demyelinating disorder multiple sclerosis (MS) and its animal model experimental allergic encephalomyelitis (EAE). Moreover, the biochemical and physiological effects of IFN-gamma are discussed in the context of the potential consequences of such activities on the developing and mature nervous systems.

Glycolipids and myelin proteins in human oligodendrogliomas

We studied myelin proteins and glycolipids in 24 human oligodendrogliomas (16 pure, eight mixed), including two grade I, 13 grade II, five grade III, and four grade IV. Tumours with a 1b ganglioside content (GD1b, GT1b and GQ1b) over 30% of total gangliosides occur more frequently in the WHO grade I and II (47%) and grade III (40%) than in the grade IV (25%) group; there was no difference in the amounts of total ganglioside or individual gangliosides between pure and mixed oligodendrogliomas. The presence of 6'-LM1 correlated with higher grades of tumours (chi 2 P approximately 0.02); however, 3'-LM1 and total neolacto-series gangliosides did not correlated with grade. Immunohistochemical studies of oligodendrocyte and myelin markers (GalCer, sulfatide, 2',3' -cyclic nucleotide phosphodiesterase, myelin basic protein and proteolipid protein) using specific antibodies showed only a very small proportion of tumour cells staining. These data do not support the hypothesis that tumours classified as oligodendrogliomas are derived from mature oligodendrocytes.

Inflammation in EAE: role of chemokine/cytokine expression by resident and infiltrating cells

Experimental allergic encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system (CNS) which has many clinical and pathological features in common with multiple sclerosis (MS). Comparison of the histopathology of EAE and MS reveals a close similarity suggesting that these two diseases share common pathogenetic mechanisms. Immunologic processes are widely accepted to contribute to the initiation and continuation of the diseases and recent studies have indicated that microglia, astrocytes and the infiltrating immune cells have separate roles in the pathogenesis of the MS lesion. The role of cytokines as important regulatory elements in these immune processes has been well established in EAE and the presence of cytokines in cells at the edge of MS lesions has also been observed. However, the role of chemokines in the initial inflammatory process as well as in the unique demyelinating event associated with MS and EAE has only recently been examined. A few studies have detected the transient presence of selected chemokines at the earliest sign of leukocyte infiltration of CNS tissue and have suggested astrocytes as their cellular source. Based on these studies, chemokines have been postulated as a promising target for future therapy of CNS inflammation. This review summarized the events that occur during the inflammatory process in EAE and discusses the roles of cytokine and chemokine expression by the resident and infiltrating cells participating in the process.