Takao Satou

Up-regulation of Bcl-2 is associated with neuronal DNA damage in Alzheimer's disease

Cell death and neurofibrillary tangle formation are prominent features of Alzheimers disease (AD). It has been suggested that DNA damage may reflect neuronal vulnerability. In this context, the Ced homologue Bcl-2 is able to repress a number of cell death programs. Recently we found both numerous nuclei exhibiting DNA damage within neurons in the AD brain and increases in Bcl-2 immunoreactivity. In this study, we examined the relationship between Bcl-2 expression and nuclear DNA damage or tangle formation. Nuclei exhibiting DNA damage were associated with an up-regulation of Bcl-2 expression, whereas tangle-bearing neurons were associated with a down-regulation of Bcl-2 expression.

The relationship between SDF-1α/CXCR4 and neural stem cells appearing in damaged area after traumatic brain injury in rats

Abstract Objective: The actual relationship between neural stem cells and SDF-1α/CXCR4 after brain injury has not yet been elucidated, although recent studies have speculated that stromal cell-derived factor-1α (SDF-1α) and its receptor, CXCR4, could contribute to neural stem cells migration after brain injury. In the present study, the temporal relationship between neural stem cells (NSCs) and SDF-1α/CXCR4 around a damaged area was investigated using a rat traumatic brain injury (TBI) model. Methods: We used molecular biology techniques and immunohistochemistry to investigate the relationship between SDF-1α/CXCR4 expression and NSCs existence around a damaged area after TBI in the rat brain. Results: SDF-1α mRNA expression and SDF-1α protein synthesis did not increase after TBI. However, SDF-1α leaked from the injured area and diffused into the cortex 1–3 days after TBI. Subsequently, the levels of CXCR4 mRNA expression and CXCR4 protein synthesis increased significantly. Many small cells with a nestin-positive cytoplasm and fibers also showed immunopositivity for both CXCR4 and SOX-2, but not for GFAP, 3–7 days after TBI. Moreover, a proportion of the CXCR4-positive cells and fibers also showed immunostaining for neurofilaments. Discussion: These results suggest that the leaked SDF-1α attracted CXCR4-positive NSCs as well as elongated nerve fibers. It is considered that the SDF-1α/CXCR4 system in the brain contributes to neural stem cells appearance and maturation after TBI. Therefore, exploitation of the SDF-1α/CXCR4 system around a damaged area may improve the brain dysfunction after TBI.

Reduction of lung metastasis, cell invasion, and adhesion in mouse melanoma by statin-induced blockade of the Rho/Rho-associated coiled-coil- containing protein kinase pathway

BackgroundMelanomas are highly malignant and have high metastatic potential; hence, there is a need for new therapeutic strategies to prevent cell metastasis. In the present study, we investigated whether statins inhibit tumor cell migration, invasion, adhesion, and metastasis in the B16BL6 mouse melanoma cell line.MethodsThe cytotoxicity of statins toward the B16BL6 cells were evaluated using a cell viability assay. As an experimental model, B16BL6 cells were intravenously injected into C57BL/6 mice. Cell migration and invasion were assessed using Boyden chamber assays. Cell adhesion analysis was performed using type I collagen-, type IV collagen-, fibronectin-, and laminin-coated plates. The mRNA levels, enzyme activities and protein levels of matrix metalloproteinases (MMPs) were determined using RT-PCR, activity assay kits, and Western blot analysis, respectively; the mRNA and protein levels of vary late antigens (VLAs) were also determined. The effects of statins on signal transduction molecules were determined by western blot analyses.ResultsWe found that statins significantly inhibited lung metastasis, cell migration, invasion, and adhesion at concentrations that did not have cytotoxic effects on B16BL6 cells. Statins also inhibited the mRNA expressions and enzymatic activities of matrix metalloproteinases (MMPs). Moreover, they suppressed the mRNA and protein expressions of integrin α2, integrin α4, and integrin α5 and decreased the membrane localization of Rho, and phosphorylated LIM kinase (LIMK) and myosin light chain (MLC).ConclusionsThe results indicated that statins suppressed the Rho/Rho-associated coiled-coil-containing protein kinase (ROCK) pathways, thereby inhibiting B16BL6 cell migration, invasion, adhesion, and metastasis. Furthermore, they markedly inhibited clinically evident metastasis. Thus, these findings suggest that statins have potential clinical applications for the treatment of tumor cell metastasis.

Expression of amyloid precursor protein after rat traumatic brain injury.

Abstract Objective: Previous reports have demonstrated that some focal brain injuries increase amyloid precursor protein (APP) immunoreactivity in the region surrounding the injury in the cerebral cortex. However, the chronologic changes in APP expression have not been evaluated after traumatic brain injury (TBI). Methods: In this study, we immunohistochemically and biologically investigated chronologic changes in cellular sources and levels of APP production after rat TBI. Results: In the present report, we show that traumatic brain injury increased the expression of APP in the neuronal perikarya and in damaged dystrophic neurites from 1 to 90 days after injury. Moreover, 7 days after injury, some macrophages/microglia also were co-localized with APP, which was overproduced by the neuronal perikarya and APP-positive dystrophic neurites after injury and then APP were phagocytosed by macrophages/microglia during this phase. However, astroglia did not express APP immunopositivity after brain injury. Discussion: These results suggested that long-term overexpression of APP was confirmed by immunohistochemical and biologic technique after TBI. This may be related to the induction of Alzheimer type dementia and it is a very important risk factor for this disease.

A MORPHOLOGICAL STUDY ON THE EFFECTS OF COLLAGEN GEL MATRIX ON REGENERATION OF SEVERED RAT SCIATIC NERVE IN SILICONE TUBES

The present study is a chronological morphological examination on the effects of collagen gel matrix on regeneration of severed sciatic nerves. The nerves (5 mm length) were resected, and both the distal and proximal stumps were inserted into a silicone tube with 5 mm gap in between. In the test side, the gap in the tube was then injected with liquid collagen which gells in the tissue when reconstructed with a certain buffer solution. The gap space in the tube of the control side was left empty. In a chronological examination of the tissue in the tube, considerably more rapid growth of sprouting axons toward the distal stump in the test side was revealed in comparison with the control side. The cells, including both fibroblasts and larger Schwann cells, were less in number. More orderly directions were observed in the collagen matrix than in the control tube. The result indicates that regeneration of the peripheral nerves in the silicone tube can be improved, by using appropriate exogenous fine materials, collagen matrix.

Tamoxifen inhibits tumor cell invasion and metastasis in mouse melanoma through suppression of PKC/MEK/ERK and PKC/PI3K/Akt pathways.

In melanoma, several signaling pathways are constitutively activated. Among these, the protein kinase C (PKC) signaling pathways are activated through multiple signal transduction molecules and appear to play major roles in melanoma progression. Recently, it has been reported that tamoxifen, an anti-estrogen reagent, inhibits PKC signaling in estrogen-negative and estrogen-independent cancer cell lines. Thus, we investigated whether tamoxifen inhibited tumor cell invasion and metastasis in mouse melanoma cell line B16BL6. Tamoxifen significantly inhibited lung metastasis, cell migration, and invasion at concentrations that did not show anti-proliferative effects on B16BL6 cells. Tamoxifen also inhibited the mRNA expressions and protein activities of matrix metalloproteinases (MMPs). Furthermore, tamoxifen suppressed phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt through the inhibition of PKCalpha and PKCdelta phosphorylation. However, other signal transduction factor, such as p38 mitogen-activated protein kinase (p38MAPK) was unaffected. The results indicate that tamoxifen suppresses the PKC/mitogen-activated protein kinase kinase (MEK)/ERK and PKC/phosphatidylinositol-3 kinase (PI3K)/Akt pathways, thereby inhibiting B16BL6 cell migration, invasion, and metastasis. Moreover, tamoxifen markedly inhibited not only developing but also clinically evident metastasis. These findings suggest that tamoxifen has potential clinical applications for the treatment of tumor cell metastasis.

Statin-induced apoptosis via the suppression of ERK1/2 and Akt activation by inhibition of the geranylgeranyl-pyrophosphate biosynthesis in glioblastoma

BackgroundStatins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, the rate-limiting enzyme in cholesterol synthesis. The inhibition of this key enzyme in the mevalonate pathway leads to suppression of cell proliferation and induction of apoptosis. However, the molecular mechanism of apoptosis induction by statins is not well understood in glioblastoma. In the present study, we attempted to elucidate the mechanism by which statins induce apoptosis in C6 glioma cells.MethodsThe cytotoxicity of statins toward the C6 glioma cells were evaluated using a cell viability assay. The enzyme activity of caspase-3 was determined using activity assay kits. The effects of statins on signal transduction molecules were determined by western blot analyses.ResultsWe found that statins inhibited cell proliferation and induced apoptosis in these cells. We also observed an increase in caspase-3 activity. The apoptosis induced by statins was not inhibited by the addition of farnesyl pyrophosphate, squalene, ubiquinone, and isopentenyladenine, but by geranylgeranyl-pyrophosphate (GGPP). Furthermore, statins decreased the levels of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt.ConclusionsThese results suggest that statins induce apoptosis when GGPP biosynthesis is inhibited and consequently decreases the level of phosphorylated ERK1/2 and Akt. The results of this study also indicate that statins could be used as anticancer agents in glioblastoma.

Activation of NF-κB by the RANKL/RANK system up-regulates snail and twist expressions and induces epithelial-to-mesenchymal transition in mammary tumor cell lines

BackgroundIncreased motility and invasiveness of cancer cells are reminiscent of the epithelial-mesenchymal transition (EMT), which occurs during cancer progression and metastasis. Recent studies have indicated the expression of receptor activator of nuclear factor-κB (RANK) in various solid tumors, including breast cancer. Although activation of the RANK ligand (RANKL)/RANK system promotes cell migration, metastasis, and anchorage-independent growth of tumor-initiating cells, it remains to be investigated if RANKL induces EMT in breast cancer cells. In this study, we investigated whether RANKL induces EMT in normal breast mammary epithelial cells and breast cancer cells, and the mechanism underlying such induction.MethodsExpression levels of vimentin, N-cadherin, E-cadherin, Snail, Slug, and Twist were examined by real-time polymerase chain reaction. Cell migration and invasion were assessed using Boyden chamber and invasion assays, respectively. The effects of RANKL on signal transduction molecules were determined by western blot analyses.ResultsWe found that stimulation by RANKL altered the cell morphology to the mesenchymal phenotype in normal breast epithelial and breast cancer cells. In addition, RANKL increased the expression levels of vimentin, N-cadherin, Snail, and Twist and decreased the expression of E-cadherin. We also found that RANKL activated nuclear factor-κB (NF-κB), but not extracellular signal-regulated kinase 1/2, Akt, mammalian target of rapamycin, c-Jun N-terminal kinase, and signal transducer and activator of transcription 3. Moreover, dimethyl fumarate, a NF-κB inhibitor, inhibited RANKL-induced EMT, cell migration, and invasion, and upregulated the expressions of Snail, Twist, vimentin, and N-cadherin.ConclusionsThe results indicate that RANKL induces EMT by activating the NF-κB pathway and enhancing Snail and Twist expression. These findings suggest that the RANKL/RANK system promotes tumor cell migration, invasion, and metastasis via the induction of EMT.

Immature and mature neurons coexist among glial scars after rat traumatic brain injury

Abstract Objectives: Glial scars around a damaged area after brain injury inhibit neurite elongation from surviving neurons and axonal plasticity, and thus prevent neural network regeneration. However, the generation, differentiation and maturation of neural stem cells (NSCs) among glial scars after brain injury have not yet been reported. Methods: In the present study, we investigated the chronological relationship between gliosis and maturation of new neurons around a damaged area using a rat traumatic brain injury (TBI) model. Results: Between 1 and 7 days after injury, many nestin-positive cells were observed around the damaged area. Three days after injury, many small nestin-positive cells showed an astrocytic morphology. Between 1 and 30 days after injury, doublecortin (DCX)-positive cells were present around the damaged area. Three and 7 days after injury, a small number of nestin-positive cells were immunopositive for glial fibrillary acidic protein (GFAP). Seven days after injury, there were DCX-positive cells in the gliosis occurring in the lesion. Thirty days after injury, DCX-positive cells were observed near and among the glial scars and a small number of these cells were immunopositive for NeuN. Discussion: These results suggest that DCX-positive cells were present near and among the glial scars after brain injury, and that these cells changed from immature to mature neurons. It is considered that promotion of the maturation and differentiation of newly formed immature neurons near and among glial scars after injury may improve the brain dysfunction induced by glial scars after brain injury.

Reduction of metastasis, cell invasion, and adhesion in mouse osteosarcoma by YM529/ONO-5920-induced blockade of the Ras/MEK/ERK and Ras/PI3K/Akt pathway

Osteosarcoma is one of the most common primary malignant bone tumors in children and adolescents. Some patients continue to have a poor prognosis, because of the metastatic disease. YM529/ONO-5920 is a nitrogen-containing bisphosphonate that has been used for the treatment of osteoporosis. YM529/ONO-5920 has recently been reported to induce apoptosis in various tumors including osteosarcoma. However, the mode of metastasis suppression in osteosarcoma by YM529/ONO-5920 is unclear. In the present study, we investigated whether YM529/ONO-5920 inhibited tumor cell migration, invasion, adhesion, or metastasis in the LM8 mouse osteosarcoma cell line. We found that YM529/ONO-5920 significantly inhibited metastasis, cell migration, invasion, and adhesion at concentrations that did not have antiproliferative effects on LM8 cells. YM529/ONO-5920 also inhibited the mRNA expression and protein activities of matrix metalloproteinases (MMPs). In addition, YM529/ONO-5920 suppressed phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and the serine/threonine protein kinase B (Akt) by the inhibition of Ras prenylation. Moreover, U0126, a mitogen-activated protein kinase kinase (MEK) 1/2 inhibitor, and LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, also inhibited LM8 cell migration, invasion, adhesion, and metastasis, as well as the mRNA expression and protein activities of MMP-1, MMP-2, MMP-9, and MT1-MMP. The results indicated that YM529/ONO-5920 suppressed the Ras/MEK/ERK and Ras/PI3K/Akt pathways, thereby inhibiting LM8 cell migration, invasion, adhesion, and metastasis. These findings suggest that YM529/ONO-5920 has potential clinical applications for the treatment of tumor cell metastasis in osteosarcoma.