Fujiya Gomi

Growth Inhibitory Factor Prevents Neurite Extension and the Death of Cortical Neurons Caused by High Oxygen Exposure through Hydroxyl Radical Scavenging

Growth inhibitory factor (GIF), a brain-specific member of the metallothionein family (MT-III), has been characterized as a inhibitory substance for neurotrophic factors in Alzheimers disease brains. However, the function of GIF, other than the inhibition of neurotrophic factors, remains unknown. We demonstrate here that exogenous GIF prevents neurite extension of cortical neurons in the early period of differentiation and the death of differentiated neurons caused by high oxygen exposure. Down-regulation of GIF in cortical neurons with antisense S-oligonucleotides promoted neuronal death under high oxygen conditions. ESR spin-trapping studies demonstrated that GIF at 2–6 μm scavenged hydroxyl radicals generated by a Fenton-type reaction or the photolysis of hydrogen peroxide much more effectively than the same concentration of metallothionein I+II. GIF did not scavenge either superoxide produced by the xanthine/xanthine oxidase reaction or NO generated from 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene. Moreover, GIF at 40–80 μm inhibited tyrosine nitration by peroxynitrite as efficiently as metallothionein I+II at the same concentration. These results indicate that GIF prevents neurite extension of neurons in the early period of differentiation and supports the survival of differentiated neurons by scavenging hydroxyl radicals.

Differential Regulation of Basic Helix-Loop-Helix Factors Mash1 and Olig2 by β-Amyloid Accelerates Both Differentiation and Death of Cultured Neural Stem/Progenitor Cells

Despite increased neurogenic differentiation markers in the hippocampal CA1 in Alzheimer disease, neurons are not replaced in CA1 and the neocortex in the disease. β-Amyloid (Aβ) might cause deterioration of the brain microenvironment supporting neurogenesis and the survival of immature neurons. To test this possibility, we examined whether Aβ alters the expression of cell fate determinants in cerebral cortical cultures and in an Alzheimer disease mouse model (PrP-APPSW). Up-regulation of Mash1 and down-regulation of Olig2 were found in cerebral cortical cultures treated with Aβ-(1-42). Mash1 was expressed in nestin-positive immature cells. The majority of Mash1-positive cells in untreated cortical culture co-expressed Olig2. Aβ increased the proportion of Olig2-negative/Mash1-positive cells. A decrease in Olig2+ cells was also observed in the cerebral cortex of adult PrP-APPSW mice. Cotransfection experiments with Mash1 cDNA and Olig2 siRNA revealed that overexpression of Mash1 in neurosphere cells retaining Olig2 expression enhanced neural differentiation but accelerated death of Olig2-depleted cells. Growth factor deprivation, which down-regulated Olig2, accelerated death of Mash1-overexpressing neurosphere cells. We conclude that cooperation between Mash1 and Olig2 is necessary for neural stem/progenitor cells to develop into fully mature neurons and that down-regulation of Olig2 by Aβ in Mash1-overexpressing cells switches the cell fate to death. Maintaining Olig2 expression in differentiating cells could have therapeutic potential.

Differential regulation of bHLH factors mash1 and olig2 by β-amyloid accelerates both differentiation and the death of cultured neural stem/progenitor cells

Despite increased neurogenic differentiation markers in the hippocampal CA1 in Alzheimer disease, neurons are not replaced in CA1 and the neocortex in the disease. β-Amyloid (Aβ) might cause deterioration of the brain microenvironment supporting neurogenesis and the survival of immature neurons. To test this possibility, we examined whether Aβ alters the expression of cell fate determinants in cerebral cortical cultures and in an Alzheimer disease mouse model (PrP-APPSW). Up-regulation of Mash1 and down-regulation of Olig2 were found in cerebral cortical cultures treated with Aβ-(1-42). Mash1 was expressed in nestin-positive immature cells. The majority of Mash1-positive cells in untreated cortical culture co-expressed Olig2. Aβ increased the proportion of Olig2-negative/Mash1-positive cells. A decrease in Olig2+ cells was also observed in the cerebral cortex of adult PrP-APPSW mice. Cotransfection experiments with Mash1 cDNA and Olig2 siRNA revealed that overexpression of Mash1 in neurosphere cells retaining Olig2 expression enhanced neural differentiation but accelerated death of Olig2-depleted cells. Growth factor deprivation, which down-regulated Olig2, accelerated death of Mash1-overexpressing neurosphere cells. We conclude that cooperation between Mash1 and Olig2 is necessary for neural stem/progenitor cells to develop into fully mature neurons and that down-regulation of Olig2 by Aβ in Mash1-overexpressing cells switches the cell fate to death. Maintaining Olig2 expression in differentiating cells could have therapeutic potential.

MAP1B 1–126 interacts with tubulin isoforms and induces neurite outgrowth and neuronal death of cultured cortical neurons

Previously we reported that overexpression of MAP1B containing N-terminal 126 amino acids promoted neuronal death. Here, we identified α-, β-, and βIII-tubulins as proteins interacting with MAP1B 1-126 by two-hybrid and pull-down assays. Transfection experiments indicated that MAP1B 1-126 interacts with microtubules, but to a much lesser extent than two previously reported microtubule-binding domains. Overexpression of MAP1B 1-126 induced both neurite extension and neuronal death, suggesting that MAP1B 1-126 could be involved in neuronal degeneration and aberrant sprouting.

Up-regulation of calsyntenin-3 by β-amyloid increases vulnerability of cortical neurons

β‐Amyloid (Aβ) may play an important role in the pathogenesis of Alzheimers disease. However, a causal relationship between Aβ oligomers and layer‐specific neurodegeneration has not been clarified. Here we show up‐regulation of calsyntenin (Cst)‐3 in cultured neurons treated with Aβ oligomers and in Tg2576 mice. Cst‐3 is distributed in large neurons in layers 2–3 and 5 of the cerebral cortex, and accumulated in dystrophic neurites surrounding Aβ‐plaques. Overexpression of Cst‐3 accelerates neuronal death. These results indicate that up‐regulation of Cst‐3 in cortical neurons in layers 2–3 and 5 by Aβ oligomers may lead to increase in vulnerability of neurons.

Tolerance of aged rat brains to mild hyperoxia: possible involvement of higher GIF content.

We investigate the aging effects of the hyperoxia-mediated induction of two antioxidants and three antioxidant enzymes in the rat brain. All of these genes responded to hyperoxia in young but not aged brains. Despite the partial inactivation of CuZn SOD and glutathione peroxidase by hyperoxia in aged rat brains, lipid peroxidation did not increase. The higher growth inhibitory factor (GIF) content in aged rat brains may be utilized as an antioxidant during hyperoxia.

The role of calsyntenin-3 in dystrophic neurite formation in Alzheimer's disease brain

β‐Amyloid (Aβ) oligomers may play an important role in the early pathogenesis of Alzheimers disease: cognitive impairment caused by synaptic dysfunction. Dystrophic neurites surrounding Aβ plaques, another pathological feature of Alzheimers disease, are plaque‐associated neuritic alterations preceding the appearance of synaptic loss. In the present review, we focus on the mechanism of dystrophic neurite formation by Aß oligomers, and discuss the neurotoxic role of Aβ‐induced calsyntenin‐3 in mediating dystrophic neurite formation. Geriatr Gerontol Int 2016; 16 (Suppl. 1): 43–50.

Up-regulation of NSP3 by Oligomeric Aβ Accelerates Neuronal Death Through Cas-independent Rap1A Activation

β-Amyloid (Aβ) plays an important role in the early pathogenesis of Alzheimers disease (AD). In vitro studies have demonstrated that Aβ oligomers induce hippocampal and neocortical neuronal death. However the neurotoxic mechanisms by which soluble Aβ oligomers cause neuronal damage and death remain to be fully elucidated. To this end, we analyzed the gene expression profile of rat cerebral cortical neurons treated with Aβ oligomers in vitro. Aβ treatment induced the expression of novel SH2-containing protein 3 (NSP3), an adaptor molecule interacting with Cas family proteins. NSP3 expression was upregulated not only in oligomeric-Aβ-treated cultured neurons but also in the neocortex of aged Tg2576 mice. NSP3 overexpression in cultured cortical neurons accelerated neuronal death. The C-terminal region of NSP3 unbound to a Cas protein was necessary for the NSP3-induced acceleration of neuronal death, as was Cas-independent Rap1A activation downstream of NSP3. Moreover, NSP3 RNAi knockdown partially rescued Aβ-oligomer-treated neurons. These results indicate that NSP3 upregulation by soluble Aβ oligomers may accelerate neuronal death via Cas-independent Rap1A activation, implicating NSP3 in the pathogenesis of AD.

Kinesin light chain-1 isoform E does not interact with calsyntenin-1.

&bgr;-Amyloid is generated by the sequential cleavage of amyloid precursor protein. Calsyntenin-1 and kinesin light chain-1 splice variant E (KLC1-E) have been proposed to regulate &bgr;-amyloid production from amyloid precursor protein. Vesicles containing calsyntenin-1 are transported from the Golgi apparatus to axons by interaction between calsyntenin-1 and KLC1 in their C-terminal regions. However, it is unclear whether KLC1 isoform E influences the interaction between KLC1 and calsyntenin-1, resulting in the impaired axonal transport of calsyntenin-1 vesicles. Here, we show that KLC1-E does not interact with calsyntenin-1 using a pull-down assay, coimmunoprecipitation, and immunocytochemistry. These findings suggest that KLC1-E enrichment may impair the axonal transport of calsyntenin-1 vesicles.

The cleavage of C-terminal fragment of calsyntenin-3 by γ-secretase prevents death of calsyntenin-3-overexpressing neurons

transplanted NSCs into the damaged hippocampal CA1 region to address how NSCs form synaptic connections and contribute to the cognitive recovery. We found that NSCs survived for at least 2 weeks, which received synaptic connections from CA3 neurons by using of lentiviral vectors expressing rabies viral membrane proteins and td-Tomato as a retrograde trans-synaptic tracer. Moreover transplantation of NSCs most significantly improved spatial memory of mice during 6 weeks after transplantation. These results suggested that the transplanted NSCs could have therapeutic value in diseases and conditions that result in spatial memory loss. Research fund: Presto.