myelin-basic-protein and Ischemia

Demyelination is one of the most important pathological factors of spinal cord injury. Oligodendrocyte apoptosis is involved in triggering demyelination. However, fewer reports on pathological changes and mechanism of demyelination have been presented from compressed spinal cord injury (CSCI). The relative effect of oligodendrocyte apoptosis on CSCI-induced demyelination and the mechanism of apoptosis remain unclear.. In this study, a custom-designed model of CSCI was used to determine whether or not demyelination and oligodendrocyte apoptosis occur after CSCI. The pathological changes in axonal myelinated fibers were investigated by osmic acid staining and transmission electron microscopy. Myelin basic protein (MBP), which is used in myelin formation in the central nervous system, was detected by immunofluorescence and Western blot assays. Oligodendrocyte apoptosis was revealed by in situ terminal-deoxytransferase-mediated dUTP nick-end labeling. To analyze the mechanism of oligodendrocyte apoptosis, we detected caspase-12 [a representative of endoplasmic reticulum (ER) stress], cytochrome c (an apoptotic factor and hallmark of mitochondria), and inhibitor of DNA binding 2 (Id2, an oligodendrocyte lineage gene) by immunofluorescence and Western blot assays.. The custom-designed model of CSCI was successfully established. The rats were spastic, paralyzed, and incontinent. The Basso, Beattie, and Bresnahan (BBB) locomotor rating scale scores were decreased as time passed. The compressed spinal cord slices were ischemic. Myelin sheaths became swollen and degenerative; these sheaths were broken down as time passed after CSCI. MBP expression was downregulated after CSCI and consistent with the degree of demyelination. Oligodendrocyte apoptosis occurred at 1 day after CSCI and increased as caspase-12 expression was enhanced and cytochrome c was released. Id2 was distributed widely in the white matter. Id2 expression increased with time after CSCI.. Demyelination occurred after CSCI and might be partly caused by oligodendrocyte apoptosis, which was positively correlated with ER-mitochondria interactions and enhanced Id2 expression after CSCI in rats.

Topics: Animals; Apoptosis; Axons; Blotting, Western; Caspase 12; Cytochromes c; Demyelinating Diseases; Endoplasmic Reticulum; Fluorescent Antibody Technique; In Situ Nick-End Labeling; Inhibitor of Differentiation Protein 2; Ischemia; Lumbar Vertebrae; Microscopy, Electron, Transmission; Mitochondria; Myelin Basic Protein; Oligodendroglia; Organelles; Rats; Rats, Sprague-Dawley; Spinal Cord Compression

A pronounced hippocampal expression of the Protease-activated Receptor 4 (PAR4) has recently been shown. In the current study the authors define the PAR4-associated sub-cellular structures and the influence of global ischaemia on the expression of PAR4. For that purpose the authors performed double labelling with fluorescence immunohistochemistry on tissue from naïve and post-ischaemic rats. In naïve animals - apart from the expression in granular and pyramidal neurons - there was an intensive lamellar expression of PAR4 in the CA4 region. Further analysis revealed that PAR4 was localised exclusively on mossy fibre axons in CA4 as detected by double-labelling with calbindin D-28k, but there was no overlap with markers of the neuronal cell body, interneurons, and post-synaptic, pre-synaptic and dendritic structures. Three and 14 days post ischaemia, CA1 neurons were degenerated and, consequently, there was no PAR4 signal in the CA1 band. In most other hippocampal structures no change in the PAR4 expression was detectable, with the exception of the CA3 region. Here, the fibre-associated PAR4 signal was diminished and disintegrated post ischaemia. Additionally, a redistribution from the membrane-bound neuronal localisation of PAR4 in control animals to a diffuse localisation all over the cell soma was revealed in the CA3 area 14 days post ischaemia. In conclusion, the current study proves for the first time that PAR4 is localised in mossy fibre axons. The altered expression in CA3 neurons after ischaemia indicates that PAR4 may be involved in post-ischaemic adaptive mechanisms.

Topics: Adaptor Proteins, Signal Transducing; Animals; Calbindins; Disease Models, Animal; Gene Expression Regulation; Hippocampus; Ischemia; Microtubule-Associated Proteins; Myelin Basic Protein; Nerve Tissue Proteins; Phosphopyruvate Hydratase; Rats; Receptors, Thrombin; S100 Calcium Binding Protein G; Subcellular Fractions; Synaptophysin; Time Factors

This study examines cell death and proliferation in the white matter after neonatal stroke. In postnatal day 7 injured rat, there was a marked reduction in myelin basic protein (MBP) immunostaining mainly corresponding to numerous pyknotic immature oligodendrocytes and TUNEL-positive astrocytes in the ipsilateral external capsule. In contrast, a substantial restoration of MBP, as indicated by the MBP ratio of left-to-right, occurred in the cingulum at 48 (1.27 +/- 0.12) and 72 (1.30 +/- 0.18, P < 0.05) h of recovery as compared to age-matched controls (1.03 +/- 0.14). Ki-67 immunostaining revealed a first peak of newly generated cells in the dorsolateral hippocampal subventricular zone and cingulum at 72 h after reperfusion. Double immunofluorescence revealed that most of the Ki-67-positive cells were astrocytes at 48 h and NG2 pre-oligodendrocytes at 72 h of recovery. Microglia infiltration occurs over several days in the cingulum, and a huge quantity of macrophages reached the subcortical white matter where they engulfed immature oligodendrocytes. The overall results suggest that the persistent activation of microglia involves a chronic component of immunoinflammation, which overwhelms repair processes and contributes to cystic growth in the developing brain.

Topics: Animals; Animals, Newborn; Antigens; Brain; Brain Infarction; Cell Count; Female; Fluorescent Antibody Technique; Functional Laterality; Glial Fibrillary Acidic Protein; In Situ Nick-End Labeling; Ischemia; Ki-67 Antigen; Male; Myelin Basic Protein; Neuroglia; Proteoglycans; Rats; Statistics, Nonparametric; Time Factors

The extracellular signal-regulated kinases (ERK) participate in numerous signaling pathways and are abundantly expressed in the CNS. It has been proposed that ERK activation promotes survival in models of neuronal injury. Inhibition of MEK, the upstream kinase that activates ERK, however, leads to neuroprotection in models of cerebral ischemia and trauma, suggesting that in this context ERK activation contributes to cellular damage. The effect of ischemia and reperfusion on activity and expression of ERK was investigated using a reversible model of rabbit spinal cord ischemia. Active ERK was observed in nai;ve animals, which decreased during 15 to 60 min of ischemia. Upon reperfusion, a robust activation of ERK was observed in animals occluded for 60 min that remained permanently paraplegic. Immunohistochemical analyses revealed increased staining of phosphorylated ERK (pERK) in glial cells and faint nuclear staining in motor neurons of animals occluded for 60 min and reperfused for 18 h. In contrast ERK activity did not increase in animals occluded for 15 min that regained motor function. No evidence of increased pERK immunoreactivity in motor neurons or nuclear translocation was noted in these animals. ERK1 was demonstrated to be identical to a p46 c-Jun/ATF-2 kinase previously shown to be activated by reperfusion after a 60-min occlusion. The results suggest that activation of ERK during reperfusion of ischemic spinal cord participates in the cellular pathways leading to neuronal damage.

Topics: Activating Transcription Factor 2; Animals; Cell Line; Cyclic AMP Response Element-Binding Protein; Enzyme Activation; Hippocampus; Immunoblotting; Immunohistochemistry; Ischemia; JNK Mitogen-Activated Protein Kinases; Male; MAP Kinase Kinase 4; Mice; Mitogen-Activated Protein Kinase Kinases; Mitogen-Activated Protein Kinases; Myelin Basic Protein; Phosphorylation; Precipitin Tests; Protein Kinases; Rabbits; Reperfusion; Spinal Cord Diseases; Subcellular Fractions; Time Factors; Transcription Factors

Both axon and myelin degeneration have significant impact on the long-term disability of patients with white matter disorder. However, the clinical manifestations of the neurological dysfunction caused by white matter disorders are not sufficient to determine the origin of neurological deficits. A noninvasive biological marker capable of detecting and differentiating axon and myelin degeneration would be a significant addition to currently available tools. Directional diffusivities derived from diffusion tensor imaging (DTI) have been previously proposed by this group as potential biological markers to detect and differentiate axon and myelin degeneration. To further test the hypothesis that axial (lambdaparallel) and radial (lambdaperpendicular) diffusivities reflect axon and myelin pathologies, respectively, the optic nerve was examined serially using DTI in a mouse model of retinal ischemia. A significant decrease of lambdaparallel, the putative DTI axonal marker, was observed 3 days after ischemia without concurrently detectable changes in lambdaperpendicular, the putative myelin marker. This result is consistent with histological findings of significant axonal degeneration with no detectable demyelination at 3 days after ischemia. The elevation of lambdaperpendicular observed 5 days after ischemia is consistent with histological findings of myelin degeneration at this time. These results support the hypothesis that lambdaparallel and lambdaperpendicular hold promise as specific markers of axonal and myelin injury, respectively, and, further, that the coexistence of axonal and myelin degeneration does not confound this utility.

Topics: Animals; Axons; Diffusion Magnetic Resonance Imaging; Immunohistochemistry; Ischemia; Mice; Models, Neurological; Myelin Basic Protein; Myelin Sheath; Nerve Degeneration; Neurofilament Proteins; Optic Nerve; Retinal Degeneration; Retinal Vessels; Wallerian Degeneration

Three aspects of the pathophysiology of experimental autoimmune encephalomyelitis (EAE) are discussed: firstly, the possible electrophysiological effects in the CNS of myelin basic protein, which is released during demyelination; secondly, the partial degeneration of monoaminergic and glutamatergic neurons which occurs during an attack of EAE in addition to demyelination; thirdly, the importance of ischemic events, accompanied by free radical release, in EAE. Especially the third aspect could have therapeutic implications. Treatment with radical scavengers, N-methyl-D-aspartate receptor blockers, or calcium blockers (as suggested for ischemia) might prove effective for EAE. Our present aim is to investigate whether these results are also relevant for MS, for which EAE is an animal model.

Topics: Animals; Autoimmune Diseases; Brain; Encephalomyelitis, Autoimmune, Experimental; Free Radicals; Ischemia; Myelin Basic Protein; Nerve Degeneration; Neurotransmitter Agents; Rats; Synaptic Transmission