Biomedical subjects

Eiko Takada

Publications and source records attributed to Eiko Takada.

7 recordsLinked to original sources

PubMed2006

Requirement for JNK-dependent upregulation of BimL in anti-IgM-induced apoptosis in murine B lymphoma cell lines WEHI-231 and CH31.

The cross-linking of B cell receptor (BCR) undergoes growth arrest, accompanied by apoptosis, in the CH31 and WEHI-231 B lymphoma cells, a model representing primary immature B cells. We have previously demonstrated that sustained activation of c-Jun N-terminal kinase (JNK) is required for BCR-mediated apoptosis. In the present study, we examined how the anti-IgM-induced prolonged activation of JNK results in apoptosis. Anti-IgM upregulated the expression levels of three isoforms of Bim protein, especially BimL, which appeared to be dependent on JNK activation. In contrast to protein expression, BimL mRNA levels were down-regulated upon anti-IgM stimulation, suggesting that anti-IgM-induced upregulation of BimL is regulated through post-transcriptional control. Upon JNK activation, phosphorylated form of JNK, together with Bax migrated from cytosol to mitochondria. In unstimulated cells, BimL protein was complexed with Bcl-x(L) and changed the partner to associate with Bax on the mitochondrial membrane after ligation of BCR, leading to initiation of apoptotic processes. Retroviral transduction of BimL into WEHI-231 cells overexpressing dominant-negative form of JNK1 (dnJNK1) resulted in a comparable level of apoptotic cells to control cells, whereas the BimL-mediated apoptosis was partially prevented by Bcl-x(L). Taken together, engagement of BCR with anti-IgM results in association of Bax-alpha with BimL in the mitochondria, at least in part, through a sustained activation of JNK.

Animals↗

PubMed2004

Interferon-beta-induced activation of c-Jun NH2-terminal kinase mediates apoptosis through up-regulation of CD95 in CH31 B lymphoma cells.

Type I interferon (IFN)-induced antitumor action is due in part to apoptosis, but the molecular mechanisms underlying IFN-induced apoptosis remain largely unresolved. In the present study, we demonstrate that IFN-beta induced apoptosis and the loss of mitochondrial membrane potential (delta psi m) in the murine CH31 B lymphoma cell line, and this was accompanied by the up-regulation of CD95, but not CD95-ligand (CD95-L), tumor necrosis factor (TNF), or TNF-related apoptosis-inducing ligand (TRAIL). Pretreatment with anti-CD95-L mAb partially prevented the IFN-beta-induced loss of delta psi m, suggesting that the interaction of IFN-beta-up-regulated CD95 with CD95-L plays a crucial role in the induction of fratricide. IFN-beta induced a sustained activation of c-Jun NH2-terminal kinase 1 (JNK1), but not extracellular signal-regulated kinases (ERKs). The IFN-beta-induced apoptosis and loss of delta psi m were substantially compromised in cells overexpressing a dominant-negative form of JNK1 (dnJNK1), and it was slightly enhanced in cells carrying a constitutively active JNK construct, MKK7-JNK1 fusion protein. The IFN-beta-induced up-regulation of CD95 together with caspase-8 activation was also abrogated in the dnJNK1 cells while it was further enhanced in the MKK7-JNK1 cells. The levels of cellular FLIP (c-FLIP), competitively interacting with caspase-8, were down-regulated by stimulation with IFN-beta but were reversed by the proteasome inhibitor lactacystin. Collectively, the IFN-beta-induced sustained activation of JNK mediates apoptosis, at least in part, through up-regulation of CD95 protein in combination with down-regulation of c-FLIP protein.

Animals↗

PubMed2003

Modulation of mThy28 nuclear protein expression during thymocyte development.

We have recently shown that down-regulation of mouse Thy28 (mThy28) protein expression appears to be accompanied by apoptotic processes. Thymocytes from mice contain moderate amounts of mThy28 protein and undergo proliferation, differentiation, or apoptosis during murine thymic maturation. As a first step to examine the potential role of the mThy28 protein in the thymocyte development, such as positive-negative selection, the expression of mThy28 protein in the thymocyte subsets was examined. Thymocytes are separated into four subpopulations by the expression levels of CD4 and CD8: CD4-CD8- (DN), CD4+CD8+ (DP), and CD4+CD8- or CD4-CD8+ (SP). Flow cytometry analysis using three-color staining demonstrated that the mThy28 expression in immature DP cells is lower than that in DN and SP cells. The down-regulation of the mThy28 expression in the DP stage was also detected by Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). The immunostaining method also showed that mThy28 protein was expressed in the medulla containing mature thymocytes, but not the cortex having immature thymocytes. The mThy28 protein in the thymocytes was mainly localized in the nucleus, as recently demonstrated in lymphoma cells, indicating that the mThy28 protein resides in the nucleus, irrespective of the cyclic or resting stage of the cell cycle. Together, the observation that mThy28 expression is down-modulated during the DP stage suggests that mThy28 protein might play some role in the positive-negative selection step in thymic maturation.

Animals↗

PubMed2003

Chemotherapeutic agents sensitize sarcoma cell lines to tumor necrosis factor-related apoptosis-inducing ligand-induced caspase-8 activation, apoptosis and loss of mitochondrial membrane potential.

Chemotherapeutic agents have been used for the treatment of patients with osteosarcoma (OS). However, inherent or acquired resistance to these agents is a serious problem in the management of OS patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered to induce apoptosis in a variety of cancer cells but not normal cells. In the present study, we examined whether chemotherapeutic agents enhance TRAIL-induced apoptosis in the sarcoma cell lines MG-63 and SaOS-2. Pretreatment with sub-toxic or slightly toxic concentrations of chemotherapeutic agents (cis-diammine dichloroplatinum, CDDP and doxorubicin, DXR) sensitized both cell lines to TRAIL-induced apoptosis, as assessed by the propidium iodide or Annexin V-Cy5 staining method. These cell lines expressed death receptors TRAIL-receptor 1 (TRAIL-R1) and TRAIL-R2, which were unaltered by treatment with CDDP, as assessed by flow cytometry. The decoy receptors TRAIL-R3 and -R4 were barely detected in both cell lines. CDDP down-regulated c-FLIP, tending to lower the activation threshold required for TRAIL-induced caspase-8 activation. The CDDP-pretreated cells indeed demonstrated more increased TRAIL-mediated caspase-8 activation, loss of mitochondrial membrane potential (DeltaPsi(m)), and apoptosis than untreated cells. Consequently, the activated caspase-8 might lead to either activation of effector caspases such as caspase-3 or loss in DeltaPsi(m). Both the increased caspase activation and mitochondrial dysfunction induced by combination of CDDP and TRAIL would contribute to enhanced apoptotic cell death. The results of the present study would be valuable for the design of novel treatment modalities for patients with OS.

Antineoplastic Agents↗

PubMed2002

Thiamine-responsive pyruvate dehydrogenase deficiency in two patients caused by a point mutation (F205L and L216F) within the thiamine pyrophosphate binding region.

The human pyruvate dehydrogenase complex (PDHC) catalyzes the thiamine-dependent decarboxylation of pyruvate. Thiamine treatment is very effective for some patients with PDHC deficiency. Among these patients, five mutations of the pyruvate dehydrogenase (E1)alpha subunit have been reported previously: H44R, R88S, G89S, R263G, and V389fs. All five mutations are in a region outside the thiamine pyrophosphate (TPP)-binding region of the E1alpha subunit. We report the biochemical and molecular analysis of two patients with clinically thiamine-responsive lactic acidemia. The PDHC activity was assayed using two different concentrations of TPP. These two patients displayed very low PDHC activity in the presence of a low (1 x 10(-4) mM) TPP concentration, but their PDHC activity significantly increased at a high (0.4 mM) TPP concentration. Therefore, the PDHC deficiency in these two patients was due to a decreased affinity of PDHC for TPP. Treatment of both patients with thiamine resulted in a reduction in the serum lactate concentration and clinical improvement, suggesting that these two patients have a thiamine-responsive PDHC deficiency. The DNA sequence of these two male patients' X-linked E1alpha subunit revealed a point mutation (F205L and L216F) within the TPP-binding region in exon 7.

Binding Sites↗

PubMed2002

Requirement of c-Jun N terminal kinase and P38 mitogen-activated protein kinase for anti-IgM-induced reduction in mitochondrial membrane potential in CH31 B lymphoma cells.

CH31 cells have been used for analysis of B cell tolerance, since engagement of membrane immunoglobulin (mIg) results in loss in mitochondrial membrane potential (DeltaPsim), followed by cell death. We have reported that the dominant-negative (dn) form of c-Jun N-terminal kinase (JNK) substantially prevented a loss of DeltaPsim at 24 h, with partial protection around 48 h after anti-IgM stimulation. In this study, we demonstrate that anti-IgM induced a sustained activation of p38 mitogen-activated protein (MAP) kinase. The p38MAP kinase inhibitor SB203580 substantially prevented loss of DeltaPsim at 14 h, with partial prevention (18-24 h) after anti-IgM stimulation. The dnJNK1-mediated prevention of anti-IgM-induced mitochondrial dissipation was enhanced by SB203580 at 42 h, but not 24 h, after stimulation, suggesting that activation of either p38 MAP kinase or JNK may be sufficient for the initiation of early phase of anti-IgM-induced loss of DeltaPsim while both may be necessary in the late phase.

Amino Acid Chloromethyl Ketones↗

PubMed2002

Oral administration of interferon-beta suppresses experimental autoimmune uveoretinitis.

BACKGROUND: The oral administration of type I interferons (IFNs) have been reported to reduce severity of inflammation in several animal models of autoimmune disease. This study examined whether oral administration of IFN-beta is capable of modulating inflammation in experimental autoimmune uveoretinitis (EAU). METHODS: EAU was induced in rats by immunization with interphotoreceptor retinoid-binding protein (IRBP) emulsified in complete Freund's adjuvant. Rats were treated with either varying doses (10(2), 10(3), 10(4) or 10(5)IU) of mouse recombinant IFN-beta or phosphate-buffered saline for control, via direct oropharyngeal application once a day for 28 days starting 7 days before IRBP immunization. Intraocular inflammation was assessed by slit-lamp biomicroscopy and histopathological examination. Spleen cell proliferation response and cytokine production under IRBP stimulation were assessed. Spleen cell subpopulations were also measured. RESULTS: IFN-beta at doses of either 10(4) or 10(5) IU significantly reduced both the clinical and histopathological severity of EAU. Spleen cell proliferation and IFN-gamma production from rats treated with 10(4) IU IFN-beta were significantly decreased compared with controls. Furthermore, the proportion of both NK cells and NKT cells in the spleen of rats treated with IFN-beta was increased compared with controls. CONCLUSION: These results suggest that the oral administration of IFN-beta reduces inflammation in IRBP-mediated EAU and that the mechanism of this action may involve NK cells and NKT cells.

Administration, Oral↗