2 ␤) is considered to play a role in signal transduction and maintenance of homeostasis or remodeling of membrane phospholipids. A role of iPLA 2 ␤ has been suggested in various physiological and pathological processes, including immunity, chemotaxis, and cell death, but the details remain unclear. Accordingly, we investigated mice with targeted disruption of the iPLA 2 ␤ gene. iPLA 2 ␤ Ϫ/Ϫ mice developed normally and grew to maturity, but all showed evidence of severe motor dysfunction, including a hindlimb clasping reflex during tail suspension, abnormal gait, and poor performance in the hanging wire grip test. Neuropathological examination of the nervous system revealed widespread degeneration of axons and/or synapses, accompanied by the presence of numerous spheroids (swollen axons) and vacuoles. These findings provide evidence that impairment of iPLA 2 ␤ causes neuroaxonal degeneration, and indicate that the iPLA 2 ␤ Ϫ/Ϫ mouse is an appropriate animal model of human neurodegenerative diseases associated with mutations of the iPLA 2 ␤ gene, such as infantile neuroaxonal dystrophy and neurodegeneration with brain iron accumulation.

Valproic acid (VPA) has long been used as an antiepileptic drug and recently as a mood stabilizer, and evidence is increasing that VPA exerts neuroprotective effects through changes in a variety of intracellular signalling pathways including upregulation of Bcl-2 protein with an antiapoptotic property and inhibiting glycogen synthase kinase 3-beta, which is considered to promote cell survival. Although the neuroprotective effects of VPA have been demonstrated in a murine model of human immunodeficiency virus-1 encephalitis, there have been no reports on the effect of VPA in chronic progressing neurodegenerative disease models including amyotrophic lateral sclerosis (ALS). ALS is a devastating disease selectively affecting motoneurons, and its disease model mice bear a close resemblance to ALS symptomatically and pathologically. First, we used an organotypic slice culture using mouse spinal cord, and showed that VPA protected spinal motoneurons against death from glutamate toxicity in vitro. Then, we treated ALS model mice with VPA at the dose effective level for epileptic model mice after 45 days of age (pre-onset treatment) or the day of the disease onset (post-onset treatment). We found a significant prolongation of the disease duration in ALS model mice in both methods of treatment. Considering the long usage of VPA for epileptic patients with good tolerance and safety, these data strongly support the clinical application of VPA for ALS treatment.

Lewy bodies (LBs), which mainly consist of α-synuclein (α-syn), are neuropathological hallmarks of patients with Parkinson’s disease (PD). The fine structure of LBs is unknown, and LBs cannot be made artificially. Nevertheless, many studies have described fibrillisation using recombinant α-syn purified from E. coli. An extremely fundamental problem is whether the structure of LBs is the same as that of recombinant amyloid fibrils. Thus, we used synchrotron Fourier transform infrared micro-spectroscopy (FTIRM) to analyse the fine structure of LBs in the brain of PD patients. Our results showed a shift in the infrared spectrum that indicates abundance of a β-sheet-rich structure in LBs. Also, 2D infrared mapping of LBs revealed that the content of the β-sheet structure is higher in the halo than in the core, and the core contains a large amount of proteins and lipids.

Hepatoma-derived growth factor (HDGF) is a heparinbinding proliferating factor originally isolated from conditioned medium of the hepatoma-derived cell line HuH-7. HDGF has greatest homology in an amino acid sequence with high mobility group 1 (HMG1), which has been characterized as a DNA-binding, inflammatory, and potent neurite outgrowth molecule. HDGF is reported to be widely expressed and act as a growth factor in many kinds of cells. However, it has not been investigated in the nervous system. Here, we show by Western blot analysis that HDGF is present in the mouse brain from the embryonic period until adulthood. In situ hybridization and immunohistochemical analyses revealed that HDGF was expressed mainly in neurons, and HDGF protein was localized to the nucleus. HDGF and high mobility group 1 were secreted under physiological conditions and released extracellularly in necrotic conditions. Furthermore, we showed that exogenously supplied HDGF had a neurotrophic effect and was able to partially prevent the cell death of neurons in which endogenous HDGF was suppressed. Therefore, we propose that HDGF is a novel type of neurotrophic factor, on account of its localization in the nucleus and its potential to function in an autocrine manner under both physiological and pathological conditions throughout life.

We previously reported that abnormal copper release from mutated Cu, Zn-superoxide dismutase (SOD1) proteins might be a common toxic gain-of-function in the pathogenesis of familial amyotrophic lateral sclerosis (FALS) [Ogawa et al. (1997) Biochem. Biophys. Res. Commun., 241, 251-257.]. In the present study, we first examined metallothioneins (MTs), known to bind copper ions and decrease oxidative toxicity, and found a twofold increase in MTs in the spinal cord of the SOD1 transgenic mice with a FALS-linked mutation (G93A), but not in the spinal cord of wild-type SOD1 transgenic mice. We then investigated whether the clinical course of FALS mice could be modified by the reduced expression of MTs, by crossing the FALS mice with MT-I- and MT-II-deficient mice. FALS mice clearly reached the onset of clinical signs and death significantly earlier in response to the reduction of protein expression. These results indicated that the copper-mediated free radical generation derived from mutant SOD1 might be related to the degeneration of motor neurons in FALS and that MTs might play a protective role against the expression of the disease.

A glial reaction associated with up-regulation of inflammatory molecules has been suggested to play an important role in dopaminergic neuron loss in Parkinson's disease (PD). Among inflammatory molecules, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) have been focused upon as key factors in the pathogenesis. However, the mechanism of how these molecules are induced in PD brains is not clearly understood. We focused on CD 40, which is expressed on neural cells and could be implicated in the neuroinflammation by inducing inflammatory molecules. We showed that both iNOS and COX-2 were up-regulated in microglia and astrocytes by CD 40 stimulation in association with a low dose of interferon-gamma (IFN-gamma) in vitro. Selective loss of dopaminergic neurons was induced by costimulation with CD 40 and IFN-gamma in mesencephalic cultures, which was protected by selective inhibitors of iNOS and/or COX-2. We also found in CD 40-stimulated astrocytes an increase of a low-affinity IgE receptor CD 23, which is known to induce iNOS expression. Together these data suggest that up-regulated iNOS and COX-2 via the CD 40 pathway may lead to dopaminergic neuron loss and may participate in the neuroinflammaory pathway of PD.

TAR DNA binding protein 43 (TDP-43) has been considered a signature protein in frontotemporal dementia and amyotrophic lateral sclerosis (ALS), but not in ALS associated with the superoxide dismutase 1 (SOD1) gene mutations (ALS1). To clarify how TDP may be involved in ALS pathogenesis, clinical and pathological features in cases of sporadic ALS ([SALS] n = 18) and ALS1 (n = 6) were analyzed. In SALS patients with rapid clinical courses, TDP mislocalization (i.e. cytoplasmic staining and TDP-positive cytoplasmic inclusions) in anterior horn cells was frequent. In SALS patients with slow clinical courses, TDP-43 mislocalization was rare. In an ALS1 patient with the SOD1 gene mutation C111Y, there were numerous TDP-positive inclusions and colocalization of SOD1 and TDP. In mutant SOD1 transgenic (G93A) mice at the end stage (median, 256 days), TDP-positive inclusions and TDP colocalization with SOD1 were also observed; nuclear TDP-43 immunoreactivity was highly correlated with life span in these mice. In both humans and mice, nuclei that stained strongly for TDP were large and circular; weakly stained nuclei were atrophic or deformed. In conclusion, low levels of TDP expression in the nucleus cor relate with a rapid clinical course in SALS and in ALS1 model mice, suggesting that nuclear TDP may play a protective role against motor neuron death resulting from different underlying etiologies.

In our previous study, we found that CD36-deficient mice showed significant delays in peripheral nerve remyelination after sciatic nerve crush injury and suggested that CD36 played an important role in the restoration of injured peripheral nerves. The aim of this study was to investigate whether CD36 upregulation can promote peripheral nerve remyelination. We made crush injury that caused demyelination and mild axonal degeneration to sciatic nerves and investigated the effect of pioglitazone (PIO) on the remyelination post-injury in C57Bl/6 wild-type and CD36-deficient mice. The immunohistochemistry with anti-CD36 antibody showed that CD36 was upregulated in macrophages infiltrating peripheral nerves from the wild-type mice by PIO administration at 1 week post-injury. The lectin histochemistry represented that infiltrating macrophages lessened in the wild-type mice at 3 weeks post-injury by PIO administration. General histopathology and morphometry indicated that thinly myelinated fibers and naked axons diminished in PIO-treated wild-type mice compared with non-treated wild-type mice at 3 weeks post-injury. No significant differences were observed in remyelination and number of infiltrating macrophages between PIO-treated and non-treated CD36-deficient mice. These results indicate that PIO promotes peripheral nerve remyelination possibly through CD36. It may be possible to apply PIO to the remedy against demyelinating neuropathies.