Increased c-Jun expression in neurons affected by lysolecithin-induced demyelination in rats

Alterations in neuronal gene expression profiles in response to experimental demyelination and axonal transection

The main pathological features of multiple sclerosis, demyelination and axonal transection, are considered to cause reversible and irreversible neurological deficits, respectively. This study aimed to separately analyze the effects of these pathological hallmarks on neuronal gene expression in experimental paradigms. The pontocerebellar pathway was targeted with either lysolecithin-induced chemical demyelination or a complete pathway transection (axonal transection) in rats. Transcriptional changes in the pontocerebellar neurons were investigated with microarrays at days 4, 10 and 37 post-intervention, which was confirmed by immunohistochemistry on protein level. A common as well as unique set of injury-response genes was identified. The increased expression of activating transcription factor 3 (Atf3) and thyrotropin-releasing hormone (Trh) in both injury paradigms was validated by immunohistochemistry. The expression of Atf3 in a patient with Marburg's variant of multiple sclerosis was also detected, also confirming the activation of the Atf3 pathway in a human disease sample. It was concluded that this experimental approach may be useful for the identification of pathways that could be targeted for remyelinative or neuroprotective drug development.

Modulation of inflammation in brain: a matter of fat

Neuroinflammation is a host defense mechanism associated with neutralization of an insult and restoration of normal structure and function of brain. Neuroinflammation is a hallmark of all major CNS diseases. The main mediators of neuroinflammation are microglial cells. These cells are activated during a CNS injury. Microglial cells initiate a rapid response that involves cell migration, proliferation, release of cytokines/chemokines and trophic and/or toxic effects. Cytokines/chemokines stimulate phospholipases A2 and cyclooxygenases. This results in breakdown of membrane glycerophospholipids with the release of arachidonic acid (AA) and docosahexaenoic acid (DHA). Oxidation of AA produces pro-inflammatory prostaglandins, leukotrienes, and thromboxanes. One of the lyso-glycerophospholipids, the other products of reactions catalyzed by phospholipase A2, is used for the synthesis of pro-inflammatory platelet-activating factor. These pro-inflammatory mediators intensify neuroinflammation. Lipoxin, an oxidized product of AA through 5-lipoxygenase, is involved in the resolution of inflammation and is anti-inflammatory. Docosahexaenoic acid is metabolized to resolvins and neuroprotectins. These lipid mediators inhibit the generation of prostaglandins, leukotrienes, and thromboxanes. Levels of prostaglandins, leukotrienes, and thromboxanes are markedly increased in acute neural trauma and neurodegenerative diseases. Docosahexaenoic acid and its lipid mediators prevent neuroinflammation by inhibiting transcription factor NFkappaB, preventing cytokine secretion, blocking the synthesis of prostaglandins, leukotrienes, and thromboxanes, and modulating leukocyte trafficking. Depending on its timing and magnitude in brain tissue, inflammation serves multiple purposes. It is involved in the protection of uninjured neurons and removal of degenerating neuronal debris and also in assisting repair and recovery processes. The dietary ratio of AA to DHA may affect neurodegeneration associated with acute neural trauma and neurodegenerative diseases. The dietary intake of docosahexaenoic acid offers the possibility of counter-balancing the harmful effects of high levels of AA-derived pro-inflammatory lipid mediators.

Cerebrospinal fluid analysis in multiple sclerosis

Although the diagnosis of multiple sclerosis (MS) may be clinically suspect and the magnetic resonance imaging findings compatible, cerebrospinal fluid (CSF) analysis remains mandatory in order to support the diagnosis. This is especially important since our understanding of the defining disease pathogenesis remains incomplete. However, there is no specifically diagnostic CSF test. And until recently, laboratory techniques for CSF analysis had not been rigorously standardized. Unconcentrated CSF without fixative should be used for the determinations of cell count and differential, protein and glucose, lactate, myelin basic protein, and the CSF/serum albumin ratio which is an indicator of blood-CSF barrier disruption. Additionally, CSF immunoglobulin-gamma (IgG) determinations are of major importance and are now included in the MS diagnostic criteria. Testing for oligoclonal IgG bands utilizing isoelectric focusing with IgG immunoblotting, the IgG synthesis rate, and the IgG index should be included. CSF analysis for kappa light chains and IGM may be diagnostically helpful. The search for biomarkers including those possibly present in the CSF which could predict and assess the course as well as response to treatment in a particular MS patient has not yet been successful. CSF immunoglobulin and T-cell/B-cell patterns, soluble HLA class I and II antigens, nitrous oxide metabolites, neurofilament and microtubule components and antibodies, tau protein, 14-3-3-protein, neuronal cell and intercellular adhesion molecules, and chemokines are actively being investigated as MS biomarkers.