Basal magnocellular and pontine cholinergic neurons coexpress FGF receptor mRNA

Pathological changes in mice with long term cuprizone administration

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). In MS, a long disease duration is known to be a strong risk factor for converting the clinical course of the disease from relapse remitting MS to secondary progressing MS. There is a hypothesis that long sustained demyelination may exhaust neurons, however, pathological changes induced in neurons following demyelination remain unknown. Cuprizone administration can induce and sustain demyelination in the mouse CNS. We examined pathological changes in mice following long sustained demyelination caused by up to 34-week cuprizone administration. Twelve-week cuprizone administration induced severe demyelination in the cerebral cortex, corpus callosum and deep cerebellar nuclei. Demyelination persisted up to 34 weeks, as shown by myelin basic protein immunohistochemistry. In contrast, cuprizone administration developed demyelination in the striatum by week 34. In these demyelinated regions, no neuronal loss was observed. However, in the striatum and deep cerebellar nuclei, cuprizone-induced demyelination changed the intracellular distribution of parvalbumin (PV). Furthermore, in the striatum, there was an increase in PV in the demyelinated axons and most PV immunoreactivity did not co-localize with SMI32 immunoreactivity in mice with 34-week cuprizone administration. Further, mice with 34-week cuprizone administration showed motor coordination dysfunction in the balance beam test. However, 12-week withdrawal from the cuprizone diet induced remyelination in the regions and motor coordination dysfunction recovered. These results indicate that 34-week cuprizone administration induces and sustains demyelination and results in reversible motor coordination dysfunction. The change of intracellular PV distribution suggests that PV may protect demyelinated axons by Ca²⁺ buffering. This model may be useful to investigate pathological and behavioral changes following demyelination in the CNS.

Neuropsin promotes oligodendrocyte death, demyelination and axonal degeneration after spinal cord injury

Previous studies indicated that the expression of neuropsin, a serine protease, is induced in mature oligodendrocytes after injury to the CNS. The pathophysiology of spinal cord injury (SCI) involves primary and secondary mechanisms, the latter contributing further to permanent losses of function. To explore the role of neuropsin after SCI, histochemical and behavioral analyses were performed in wild-type (WT) and neuropsin-deficient (neuropsin(-/-)) mice using a crush injury model, a well-characterized and consistently reproducible model of SCI. In situ hybridization revealed that neuropsin mRNA expression was induced in the spinal cord white matter from WT mice after crush SCI, peaking at day 4. Neuropsin(-/-) mice showed attenuated demyelination, oligodendrocyte death, and axonal damage after SCI. Although axonal degeneration in the corticospinal tract was obvious caudal to the lesion site in both strains of mice after SCI, the number of surviving nerve fibers caudal to the lesion was significantly larger in neuropsin(-/-) mice than WT mice. Behavioral analysis revealed that the recovery at days 10-42 was significantly improved in neuropsin(-/-) mice compared with WT mice in spite of the severe initial hindlimb impairments due to SCI in both strains. These observations suggest that neuropsin is involved in the secondary phase of the pathogenesis of SCI mediated by demyelination, oligodendrocyte death, and axonal degeneration.

Nerve injury induces the expression of EXT2, a glycosyltransferase required for heparan sulfate synthesis

Heparan sulfate proteoglycans, which bear long chains of heparan sulfate glycosaminoglycan, play significant roles during embryogenesis, including the formation of the CNS. However, their involvement in nerve regeneration has not yet been clarified. Here, we found that the mRNA expression of EXT2, one of the crucial enzymes for heparan sulfate-glycosaminoglycan synthesis, was markedly up-regulated in injured hypoglossal motor neurons after axotomy. In addition, immunohistochemical staining with an antibody specific for heparan sulfate-glycosaminoglycan chains demonstrated increased expression of heparan sulfate-glycosaminoglycan chains in the injured nucleus. Furthermore, the mRNA expressions of glypican-1 and syndecan-1, which are both well-known heparan sulfate proteoglycans, were prominently up-regulated in injured motor neurons. These results suggest that the biosynthesis of heparan sulfate chains promoted by EXT2 is activated in injured motor neurons, and that glypican-1 and syndecan-1 are potent candidates for heparan sulfate proteoglycans involved in peripheral nerve regeneration.

Involvement of neuropsin in the pathogenesis of experimental autoimmune encephalomyelitis

Inflammation, demyelination, and axonal damage of the central nervous system (CNS) are major pathological features of multiple sclerosis (MS). Proteolytic digestion of the blood-brain barrier and myelin protein by serine proteases is known to contribute to the development and progression of MS. Neuropsin, a serine protease, has a role in neuronal plasticity, and its expression has been shown to be upregulated in response to injury to the CNS. To determine the possible involvement of neuropsin in demyelinating diseases of the CNS, we examined its expression in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a recognized animal model for MS. Neuropsin mRNA expression was induced in the spinal cord white matter of mice with EAE. Combined in situ hybridization and immunohistochemistry demonstrated that most of the cells expressing neuropsin mRNA showed immunoreactivity for CNPase, a cell-specific marker for oligodendrocytes. Mice lacking neuropsin (neuropsin-/-) exhibited an altered EAE progression characterized by delayed onset and progression of clinical symptoms as compared to wild-type mice. Neuropsin-/- mice also showed attenuated demyelination and delayed oligodendroglial death early during the course of EAE. These observations suggest that neuropsin is involved in the pathogenesis of EAE mediated by demyelination and oligodendroglial death.

Differential expression of protease M/neurosin in oligodendrocytes and their progenitors in an animal model of multiple sclerosis

To determine the possible involvement of protease M/neurosin in demyelinating diseases of the CNS, we examined its expression in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a recognized animal model of multiple sclerosis (MS). In situ hybridization, immunohistochemistry and quantitative real-time polymerase chain reaction (PCR) demonstrated that EAE caused an increase in the expression of protease M/neurosin mRNA and its protein product throughout the white and gray matter surrounding demyelinating lesions. Combined in situ hybridization and immunohistochemistry demonstrated that most of the cells expressing protease M/neurosin mRNA within control spinal cord showed immunoreactivity for CNPase or NG2, cell-specific markers for oligodendrocytes and their progenitors, respectively. In the spinal cord from mice with EAE, the expression of protease M/neurosin mRNA in CNPase-positive cells appeared to be increased while double-labeled cells positive for protease M/neurosin mRNA and NG2 were rarely found in areas associated with demyelinating lesions. Although a prominent accumulation of inflammatory cells including T-cells was observed in the vicinity of demyelinated lesions, these cells were not associated with protease M/neurosin mRNA expression. The levels of protease M/neurosin mRNA expression were unchanged in the spleen and even decreased in the thymus during the course of EAE. These observations suggest that the differential expression of protease M/neurosin in mature oligodendrocytes and their progenitors is involved in the pathogenesis of MS and EAE.

Differential expression of neuropsin and protease M/neurosin in oligodendrocytes after injury to the spinal cord

Neuropsin and protease M/neurosin are serine proteases expressed by neurons and glial cells, and serve a variety of functions in the central nervous system (CNS). The current study demonstrates changes in the expression of these proteases following hemisection of the mouse spinal cord. Within unlesioned spinal cord, neuropsin mRNA expression was occasionally observed in the gray but not white matter, while the level of protease M/neurosin mRNA was higher in the white matter. After injury to the spinal cord, neuropsin mRNA expression was induced in the white matter in the area immediately adjacent to the lesion, peaking at 4 days post-injury and disappearing by 14 days. Enhanced expression of protease M/neurosin mRNA was observed throughout the white and gray matter surrounding the lesion, peaking at 4 days and persisting for 14 days. Neuropsin mRNA was expressed predominantly by CNPase-positive oligodendrocytes. Furthermore, most of these cells were also associated with immunoreactivity for protease M/neurosin protein. Within unlesioned spinal cord, most protease M/neurosin mRNA-expressing cells were CNPase-positive oligodendrocytes, and a substantial fraction of these cells also showed immunoreactivity for NG2, a marker for oligodendrocyte progenitors. After injury, protease M/neurosin mRNA expression within NG2-positive cells was significantly decreased, while the constitutive expression in CNPase-positive oligodendrocytes appeared to be preserved. These findings suggest that each subpopulation of oligodendrocytes based on the expression of neuropsin and protease M/neurosin has different roles in the response of the spinal cord to injury as well as in normal homeostasis.

Expression of membrane-bound and soluble guanylyl cyclase mRNAs in embryonic and adult retina of the medaka fish Oryzias latipes

Localization of mRNAs for four membrane-bound guanylyl cyclases (membrane GCs; OlGC3, OlGC4, OlGC5, and OlGC-R2), three soluble guanylyl cyclase subunits (soluble GC; OlGCS-alpha(1), OlGCS-alpha(2), and OlGCS-beta(1)), neuronal nitric oxide synthase (nNOS), and cGMP-dependent protein kinase I (cGK I) was examined in the embryonic and adult retinas of the medaka fish Oryzias latipes by in situ hybridization. All of the membrane GC mRNAs were detected in the photoreceptor cells of the adult and embryonic retinas, but in different parts; the OlGC3 and OlGC5 mRNAs were expressed in the proximal part and the OlGC4 and OlGC-R2 mRNAs were expressed in the outer nuclear layer. The mRNA for nNOS was expressed in a scattered fashion on the inner side of the inner nuclear layer in the adult and embryonic retinas. The mRNAs (OlGCS-alpha(2) and OlGCS- beta(1)) of two soluble GC subunits (alpha(2) and beta(1)) were expressed mainly in the inner nuclear layer and the ganglion cell layer of the embryonic retina while the mRNAs of the soluble GC alpha(1) subunit and cGK I were not detected in either the adult or embryonic retina. These results suggest that NO itself and/or the cGMP generated by soluble GC (alpha(2)/beta(1) heterodimer) play a novel role in the neuronal signaling and neuronal development in the medaka fish embryonic retina in addition to the role played by phototransduction through membrane GCs in the adult and embryonic retinas.

Decidualization induces the expression and activation of an extracellular protease neuropsin in mouse uterus

Uterine decidualization is accompanied by the remodeling of the cell-matrix and cell-cell interactions around the endometrial stromal cells to allow an appropriate invasion of trophoblasts. This remodeling is thought to require the proteolysis of extracellular matrix proteins or cell adhesion molecules; however, the molecular mechanism remains poorly understood. In this study, decidualization induced the expression and activation of an extracellular serine protease neuropsin in the mouse uterus. Although nonpregnant uteri contained little neuropsin, the protein content and enzymatic activity increased markedly and peaked at the midgestational period in pregnant uteri. Neuropsin expression and activity was also upregulated in artificially induced deciduomata but not in nondecidualized pseudopregnant uteri. Neuropsin is the first extracellular protease to show the evident induction of expression and activity by decidualization and might contribute to the remodeling of extracellular components after decidualization.

Acidic fibroblast growth factor (FGF-1) in the anterior horn cells of ALS and control cases

The expression and localization of acidic fibroblast growth factor (aFGF; FGF-1) were examined in the spinal cord of patients with amyotrophic lateral sclerosis (ALS) and controls by reverse transcription-polymerase chain reaction (RT-PCR) method and immunohistochemistry. The RT-PCR experiments demonstrated that aFGF amplification products were clearly detected in all control cases but could be scarcely seen in ALS patients. aFGF immunoreactivity was detected in the anterior horn cells of the spinal cord. Double immunostaining for aFGF and choline acetyltransferase revealed that the majority (95.9%) of cholinergic neurons expressed aFGF. In ALS cases, the number and the staining intensity of aFGF-positive neurons were markedly decreased. These results suggest that aFGF is involved in ALS pathology.

Expression of neuropsin in oligodendrocytes after injury to the CNS

Proteases are involved in a variety of processes including demyelination after injury to the central nervous system. Neuropsin is a serine protease, which is constitutively expressed in the neurons of the limbic system. In the present study, intrahippocampal kainate injection and enucleation were performed on adult mice. Neuropsin mRNA and protein expression was detected by in situ hybridization and immunohistochemistry. Double in situ hybridization confirmed that the mRNA expression was induced in oligodendrocytes. One day after kainate injection to the hippocampus, neuropsin mRNA was expressed, peaking 4-8 days postoperatively and disappearing at 14 days. Immunohistochemistry and immunoelectron microscopy revealed that neuropsin was expressed in the cell body of oligodendrocytes and myelin. To see if neuropsin degrades myelin protein, purified myelin was incubated with recombinant neuropsin. A decrease in the intensity of the bands of myelin basic protein was observed. These results indicate that neuropsin is involved in demyelination.

The ascending reticular activating system--from aminergic neurons to nitric oxide

The cholinergic neurons of the laterodorsal and pedunculopontine tegmental neurons are thought to comprise an important portion of the ascending reticular activating system. More recent work has demonstrated that the neurons of this cell group also released a number of neruoactive peptides and can produce nitric oxide in response to increases in intracellular calcium. The release of NO from the nerve terminals of these cells within the thalamus varies with behavioural state, being much lower during slow wave sleep than during wake and paradoxical sleep states. The NO release in the thalamus appears to act via the type II cGMP-dependent protein kinase present at high levels in the thalamic neurons. Thus the NO-cGMP signal transduction system can play an important role in regulating thalamic activity across behavioural states.

Localization of huntingtin-interacting protein-2 (Hip-2) mRNA in the developing mouse brain

Huntingtin-interacting protein-2 (Hip-2) was identified as a human protein specifically associated with huntingtin in vitro, a gene product affected in patients with Huntington disease (HD). It is a ubiquitin-conjugating enzyme identical to the previously characterized bovine E2-25k. We identified the mouse Hip-2 homologue (mHip-2) and examined its distribution patterns in the developing mouse brain in order to gain an insight into the functional significance of the Hip-2 protein in the normal brain as well as in the pathogenesis of HD. As reported with huntingtin, the mHip-2 mRNA expression developed in parallel with neuronal maturation and became distributed widely in the postnatal mouse brain. This spatiotemporal pattern of mHip-2 mRNA expression resembled that of huntingtin. We further demonstrated that mHip-2 mRNA was colocalized with huntingtin-like immunoreactivity in a single neuron. These findings suggested that the Hip-2 interacted with huntingtin in vivo and played an important role in HD pathogenesis.

Protease M/neurosin mRNA is expressed in mature oligodendrocytes

No proteases have been identified to be oligodendrocyte-specific though there are phenomena in which proteases may be committed. We have cloned a cDNA for mouse homologue of protease M/neurosin, serine protease, and localized its mRNA in the mouse brain. The cDNA and the deduced amino acid sequences were 66% identical to those of human protease M/neurosin. In situ hybridization histochemistry revealed that the mRNA was localized in the mature oligodendrocytes which expressed proteolipid protein mRNA. Developmentally, protease M/neurosin mRNA was expressed by oligodendrocytes 2 to 7 days after the maturation. Thus, protease M/neurosin may be important to the processes occurring after the maturation of oligodendrocytes such as myelination or turnover of the proteins in the myelin.

Injury induces neuropsin mRNA in the central nervous system

We have shown that neuropsin is expressed in the neurons of the limbic system in the adult mouse. After the central nervous system was injured by incision or intraperitoneal kainate injection, neuropsin mRNA was induced in the peri-lesioned region. The cells in which neuropsin mRNA was induced were localized mainly in axon fiber pathways and closely associated to proteolipid protein (PLP) mRNA expressing oligodendrocytes.

Discriminable excitotoxic effects of ibotenic acid, AMPA, NMDA and quinolinic acid in the rat laterodorsal tegmental nucleus

Excitotoxins are valuable tools in neuroscience research as they can help us to discover the extent to which certain neurones are necessary for different types of behaviour. They have distinctive neurotoxic effects depending on where they are infused, and this study was conducted to delineate the neurotoxic profiles of excitotoxins in the laterodorsal tegmental nucleus (LDTg). Two 0.1 microl infusions of 0.1 M ibotenate, 0.1 M quinolinate, 0.04-0.1 M NMDA, or 0.05-0.015 M AMPA, were made unilaterally into the LDTg under either pentobarbitone or Avertin anaesthesia. The injection needle was oriented at an angle of 24 degrees from vertical in the mediolateral plane. After 23-27 days, sections through the mesopontine tegmentum were processed using standard histological procedures for NADPH-diaphorase histochemistry, tyrosine hydroxylase or 5-hydroxytryptamine immunohistochemistry, and Cresyl violet. Lesions were assessed in terms of the size of the damaged area (identified by reactive gliosis), the extent of cholinergic cell loss in the mesopontine tegmentum (by counting NADPH-diaphorase-positive neurones), and neuronal loss induced in the locus coeruleus and dorsal raphe nucleus. Ibotenate induced compact lesions in the LDTg (more than 80% cholinergic loss) and did little damage to the locus coeruleus and dorsal raphe nucleus. Quinolinate and low doses of AMPA and NMDA made very small lesions with less than 35% cholinergic loss, while at higher doses, AMPA and NMDA induced large areas of reactive gliosis but killed only a proportion of the cholinergic neurones. AMPA appeared to have a particular affinity for noradrenergic neurones in the locus coeruleus, with the 0.015 M dose injected into the LDTg typically destroying the majority of these neurones. The results are discussed in the context of what is known about the mechanisms of excitotoxins and the glutamate receptor profile of mesopontine neurones.

Acidic fibroblast growth factor mRNA is expressed by basal forebrain and striatal cholinergic neurons

Evidence for the importance of the basal forebrain cholinergic system in the maintenance of cognitive function has stimulated efforts to identify trophic mechanisms that protect this cell population from atrophy and dysfunction associated with aging and disease. Acidic fibroblast growth factor (aFGF) has been reported to support cholinergic neuronal survival and has been localized in basal forebrain with the use of immunohistochemical techniques. Although these data indicate that aFGF is present in regions containing cholinergic cell bodies, the actual site of synthesis of this factor has yet to be determined. In the present study, in situ hybridization techniques were used to evaluate the distribution and possible colocalization of mRNAs for aFGF and the cholinergic neuron marker choline acetyltransferase (ChAT) in basal forebrain and striatum. In single-labeling preparations, aFGF mRNA-containing neurons were found to be codistributed with ChAT mRNA+ cells throughout all fields of basal forebrain, including the medial septum/diagonal band complex and striatum. By using a double-labeling (colormetric and isotopic) technique, high levels of colocalization (over 85%) of aFGF and ChAT mRNAs were observed in the medial septum, the diagonal bands of Broca, the magnocellular preoptic area, and the nucleus basalis of Meynert. The degree of colocalization was lower in the striatum, with 64% of the cholinergic cells in the caudate and 33% in the ventral striatum and olfactory tubercle labeled by the aFGF cRNA. These data demonstrate substantial regionally specific patterns of colocalization and support the hypothesis that, via an autocrine mechanism, aFGF provides local trophic support for cholinergic neurons in the basal forebrain and the striatum.