Biomedical subjects

N Tanuma

Publications and source records attributed to N Tanuma.

At least 19 recordsLinked to original sources

PubMed2001

Protein tyrosine phosphatase epsilonC selectively inhibits interleukin-6- and interleukin- 10-induced JAK-STAT signaling.

Protein tyrosine phosphatase (PTP) epsilon (PTPepsilon) exists as 2 forms generated by alternative promoter usage. It has recently been reported that a cytosolic isoform of PTPepsilon (PTPepsilonC) when over-expressed in murine M1 myeloid cells inhibits interleukin-6 (IL-6)- and leukemia inhibitory factor-induced activation of Janus kinases (JAKs), thereby suppressing STAT3 tyrosine phosphorylation and STAT3 signaling. This study characterizes an inhibitory action of PTPepsilonC on IL-6 signaling and also reveals that PTPepsilonC inhibitory activity is independent of other potential negative regulators, such as SHP-2 and SOCS family proteins. Furthermore, it analyzes the selectivity of PTPepsilonC action toward several cytokines. On IL-6 stimulation, expression of PTPepsilonC-DA, a catalytically inactive mutant of PTPepsilonC, results in an earlier onset of STAT3 tyrosine phosphorylation, suggesting different modes of action between PTPepsilonC and other negative regulators. In addition, the study shows PTPepsilonC-DA enhances activation of STAT1 by IL-6 as well. In terms of specificity to cytokines, over-expressed PTPepsilonC also inhibits IL-10-induced tyrosine phosphorylation of STAT3 in M1 cells, whereas PTPepsilonC does not affect either interferon-beta- and interferon-gamma-induced tyrosine phosphorylation of STATs or expression of STAT transcriptional targets. Among cytokines tested, the inhibitory effect of PTPepsilonC is selective to IL-6- and IL-10-induced JAK-STAT signaling.

3T3 Cells↗

PubMed2001

Intrathecal administration of endothelin-1 receptor antagonist ameliorates autoimmune encephalomyelitis in Lewis rats.

The role of endothelin-1 (ET-1) in the development of experimental autoimmune encephalomyelitis (EAE) was studied by the blocking the action of ET-1 with a receptor antagonist, BQ-123. Intrathecal administration of BQ-123 significantly ameliorated EAE progression at the peak stage of EAE (p<0.05). By immunohistochemistry, ED-1-positive macrophages in EAE lesions were identified as major producers of ET-1, whereas the immunoreactivity of ET-1 on brain cells, such as astrocytes, was dramatically increased in accordance with the progression of EAE. This study points to a putative pro-1nflammatory role for ET-1 in the pathogenesis of EAE. One possible application for the ET-1 receptor antagonist might be helpful in the therapy of autoimmune neurological disorders.

Animals↗

PubMed2001

STAT expression and localization in the central nervous system during autoimmune encephalomyelitis in Lewis rats.

Autoimmune inflammation in the central nervous system (CNS) is maintained by secretion of a large number of cytokines. To elucidate its molecular mechanisms, we examined the expression and localization of STAT1, STAT3, STAT4 and STAT6 molecules, which are the downstream molecules of the cytokine signal transduction pathway, in the CNS during acute experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats. Western blot analysis demonstrated that STAT1 protein increased gradually till the recovery stage, whereas STAT4 protein showed abrupt increase at the early stage followed by gradual decrease. STAT3 and STAT6 showed stable expression throughout the course of the disease. The kinetics of the phosphorylated form of STAT1 and STAT4 roughly paralleled that of the total protein although the peak of STAT3 phosphorylation was recognized at the preclinical stage. Immunohistochemical examinations revealed that STAT3 and STAT4, but not STAT1 and STAT6, immunoreactivities were mainly expressed in astrocytes and microglia, respectively, and were closely associated with inflammatory lesions. Taken together, these findings suggest that STAT3 and STAT4 play an important role in the formation of, and recovery from, autoimmune inflammation in the CNS.

Animals↗

PubMed2001

Immune responses against the myelin/oligodendrocyte glycoprotein in experimental autoimmune demyelination.

Myelin/oligodendrocyte glycoprotein (MOG) is a surface-exposed antigen of myelin and an important target for autoimmune responses which mediate inflammatory demyelination in the central nervous system. Experimentally, MOG induces strong pathogenic T cell responses in many strains of laboratory animals. Immunological studies in humans also identify MOG as a surprisingly prevalent antigenic molecule among the myelin proteins. In addition, the encephalitogenic properties of MOG are linked to the induction of antibody responses which have been demonstrated to directly promote central nervous system demyelination, a hallmark neuropathological feature in disorders such as human multiple sclerosis. Factors responsible for autoimmunity to MOG likely include genetic influences as well as other mechanisms, which are the subject of intense investigation. This article reviews experimental data currently available on specificity and pathogenic roles of T cell and antibody responses against MOG, which have implications relevant to multiple sclerosis and related disorders.

Amino Acid Sequence↗

PubMed2000

Up-regulation of I-2(PP2A)/SET gene expression in rat primary hepatomas and regenerating livers.

I-2(PP2A)/SET, an inhibitor of protein phosphatase 2A, is supposed to be one of the oncoproteins associated with human myeloid leukemia. The I-2(PP2A)/SET gene expression was observed ubiquitously among all the rat tissues examined, but low in liver. Of interest is that the expression in the rat primary hepatomas and hyperplastic nodules was significantly elevated. The experiments using regenerating livers after partial hepatectomy showed that the expression of I-2(PP2A)/SET mRNA was low at the quiescent hepatocytes, but up-regulated at 12-24 h after partial hepatectomy, which corresponds to the mid G1 to S transition in the cell cycle. These results suggested the importance of I-2(PP2A)/SET in the hepatocarcinogenesis and hepatic cell proliferation.

Amino Acid Sequence↗

PubMed2000

Protein-tyrosine phosphatase PTPepsilon C inhibits Jak-STAT signaling and differentiation induced by interleukin-6 and leukemia inhibitory factor in M1 leukemia cells.

We engineered and expressed both a wild-type and mutant cytosolic isoform of PTPepsilon (PTPepsilonC) in murine M1 leukemic cells, which can be induced to growth arrest and monocytic differentiation by interleukin (IL)-6 and leukemia inhibitory factor (LIF). Forced expression of PTPepsilonC inhibited IL-6- and LIF-induced monocytic differentiation and apoptosis in M1 cells, whereas expression of PTPepsilonM, a transmembrane isoform of PTPepsilon, did not. PTPepsilonC expression resulted in lower levels of IL-6-induced tyrosine phosphorylation of Jak1, Tyk2, gp130, and Stat3 compared with parent cells. In M1 transfectants expressing an inactive mutant of PTPepsilonC, both tyrosine phosphorylation and apoptosis induced by IL-6 and LIF were potentiated rather than inhibited. These results suggest an important role for PTPepsilonC in negative regulation of IL-6- and LIF-induced Jak-STAT signaling.

Animals↗

PubMed2000

Characterization of acute versus chronic relapsing autoimmune encephalomyelitis in DA rats.

This study was undertaken to better understand the role of cytokines in the pathogenesis, especially in the mechanisms of relapse, of experimental autoimmune encephalomyelitis (EAE). For this purpose, we induced acute and chronic relapsing (CR) EAE in DA rats and determined several immunological parameters in rats at various stages of two types of EAE. Histopathological analysis revealed that there was no significant difference in the severity of inflammation in the spinal cord lesions between the two groups. However, demyelination was observed only in rats with CR EAE. Cytokine analysis by competitive PCR demonstrated that levels of TNF-alpha, IL-6 and IL-12 p40 mRNA in the spinal cord at the first attack of CR EAE were significantly higher than those at the peak stage of acute EAE. The mRNA expression of anti-inflammatory cytokines, IL-10 and TGF-beta1, was generally low in both acute EAE and the first attack of CR EAE and upregulated at later stages of CR EAE. These findings suggest that persistent high-level expression of pro-inflammatory cytokines is closely associated with demyelination and relapse of EAE. In contrast, anti-inflammatory cytokines play only a minor role in the relapse.

Acute Disease↗

PubMed2000

Increased expression of p53 and Bax in the spinal cords of rats with experimental autoimmune encephalomyelitis.

The expression of pro-apoptotic molecules p53 and Bax in the spinal cord of rats with experimental autoimmune encephalomyelitis (EAE) was examined. Apoptosis was confirmed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method. TUNEL (+) apoptotic cells were mainly either ED1 (+) macrophages or T-cells in the parenchyma of EAE. Western blot analysis showed that both p53 and Bax expression significantly (P<0. 01) increased in the spinal cords of EAE rats at the peak stage, and thereafter declined. An immunohistochemical study showed that inflammatory cells (notably T cells) in the parenchyma express p53 and Bax, while brain cells, including neurons and glia, were devoid of nuclear staining for these molecules. The nuclear expression of p53 largely matches apoptotic cells in the parenchyma of EAE. These findings suggest that the pro-apoptotic molecules p53 and Bax may play an important role in eliminating T cells in the parenchyma in EAE.

Animals↗

PubMed2000

Analysis of experimental autoimmune encephalomyelitis induced in F344 rats by pertussis toxin administration.

To elucidate the factor(s) accelerating the autoimmune disease processes, we induced two types of experimental autoimmune encephalomyelitis (EAE), severe and very mild, in F344 rats by immunization with myelin basic protein (MBP) plus pertussis toxin (PT) (PT+) or with MBP alone (PT-) and compared the differences between the two. Immunohistochemical examinations showed that although the nature of inflammation was essentially the same between the two groups, the proportion of Vbeta8.2(+) T cells in the CNS lesion of PT (+) rats was larger than that of PT (-) rats. Cytokine analysis by competitive PCR revealed that IL-10 mRNA in the lymphoid organ was significantly suppressed in the PT(+) group, whereas levels of IFN-gamma,TNF-alpha and TGF-beta mRNA were insignificantly different after PT administration. In addition, T cells taken from PT (+) rats proliferated well in response to MBP, while those from PT (-) rats showed a marginal response to the same antigen. However, this finding does not indicate the switching of non-encephalitogenic to encephalitogenic T cells upon PT administration because PT (-) rats contained encephalitogenic T cells and/or their precursor cells as revealed by adoptive transfer experiments. Taken together, these findings suggest that suppression of IL-10 by PT administration is the major factor contributing to the exacerbation of EAE in PT(+) rats.

Animals↗

PubMed2000

Characterization of T cell receptor associated with the development of P2 peptide-induced autoimmune neuritis.

To characterize experimental autoimmune neuritis (EAN)-inducing T cells in more detail, we performed CDR3 spectratyping analysis and found oligoclonal expansion of several Vbeta spectratypes in nerve-infiltrating T cells. Vbeta5 expansion was observed all the stages examined, whereas Vbeta8.2 and Vbeta17 expansion was mainly found at the peak and preclinical stages, respectively. Since Vbeta5 expansion persists throughout the course of the disease, Vbeta5+ T cells are judged to be the main effector cells. Vbeta8.2+ and Vbeta17+ T cells may also be pathogenic but are not the main effectors because expansion of these spectratypes was found at a limited period of time. Sequence analysis revealed that Vbeta5, Vbeta8.2 and Vbeta17 spectratype-derived TCR clones possess their own dominant sequences in the CDR3 region with no homology among the clones. These findings suggest that polyclonally activated T cells are involved in the formation of the nerve lesion. Furthermore, vaccination with Vbeta5 DNA, but not with Vbeta10 DNA, suppressed the development of EAN significantly. Collectively, these findings indicate that determination of autoimmune disease-associated TCR by CDR3 spectratyping provides useful information for designing TCR-based immunotherapy for the disease.

Amino Acid Sequence↗

PubMed2000

Fine T cell receptor repertoire analysis of spinal cord T cells responding to the major and minor epitopes of myelin basic protein during rat autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis is a disease induced by neuroantigen-reactive T cells bearing particular types of T cell receptor (TCR). Although the nature of TCRs of encephalitogenic T cells has been partially delineated using encephalitogenic T cell clones established in vitro, the entire TCR repertoire formed in situ after immunization with neuroantigen remains unclear. In the present study, we immunized Lewis rats with myelin basic protein (MBP) and its fragment peptides and determined the TCR repertoire of spinal cord T cells formed after the immunization by CDR3 spectra-typing. It was revealed that the oligoclonal expansion of Vbeta2, Vbeta8.2, and Vbeta17 spectratypes was detectable after immunization with guinea pig MBP and its immunodominant epitope, the 68-88 sequence, whereas immunization with a peptide containing a minor epitope induced Vbeta10 expansion. Immunization with rat MBP induced much broader TCR Vbeta expansion (all of the above Vbetas plus Vbeta3). These findings suggest that TCRs activated by immunization with guinea pig MBP used as heteroclitic immunogen recognize autoantigen, rat MBP. Furthermore, the strategy used in this study gives insight into the pathogenesis of autoimmune disease and provides useful information for designing TCR-based immunotherapy.

Animals↗

PubMed2000

ACTH activates rapid eye movement-related phasic inhibition during REM sleep in patients with infantile spasms.

OBJECTIVES: Phasic inhibition index (PII) is the rate of the simultaneous occurrence of phasic chin muscle activity (PCMA) and rapid eye movement bursts during rapid-eye-movement sleep (REMS). In naive patients with infantile spasms (IS), the PII value was found to reflect their prognosis. We studied the effects of adrenocorticotropic hormone (ACTH) on REMS components including PII in IS. METHODS: REMS parameters were examined in 18 IS patients before and after ACTH treatment. The effects of corticosteroids (CSs) were examined in 3 patients with congenital adrenal hyperplasia (CAH) and 3 with nephrotic syndrome (NS). RESULTS: ACTH decreased PII and PCMA in IS patients. In CAH patients, physiological doses of CSs corrected the increased intrinsic ACTH level and increased PII. In NS patients, therapeutic doses of CSs suppressed PCMA without affecting PII. CONCLUSION: ACTH suppressed PCMA through CSs, and reduced PII directly. ACTH was hypothesized to eliminate IS through these dual modes of action.

Adolescent↗

PubMed2000

Immunohistochemical analysis of brainstem lesions in infantile spasms.

Whether the cerebral or subcortical lesions are involved in the pathogenesis in infantile spasms (IS) remains to be determined. To investigate the functional lesions of the subcortical structures in IS, the brainstem expression of neurotransmitters, neuropeptides and calcium-binding proteins in IS autopsy cases of lissencephaly and of perinatal hypoxic ischemic encephalopathy (HIE/IS) was investigated. The IS patients consisted of four subjects each of lissencephaly and HIE. They suffered from both West and Lennox-Gastaut syndromes. The healthy and disease controls were composed of four subjects without neuromuscular disorders and six cases of HIE (HIE/C), neither of whom had the epileptic syndrome. In these subjects the expressions of tryptophan hydroxylase (TrH), tyrosine hydroxylase (TH), parvalbumin (PV), methionine-enkephalin (ME) and substance P (SP) were immunohistochemically determined in serial sections of the midbrain, pons and medulla oblongata. The immunoreactivity of neurons and neuronal processes for TH was altered in the mesencephalic periaqueductal gray matter, locus ceruleus, and dorsal vagal nucleus in the patients. The HIE/IS cases showed reduced TrH-immunoreactivity in the medullary raphe nuclei. The brainstem auditory tract was poorly discernible on anti-PV immunostaining in the IS patients. The immunoreactivity for ME in the spinal trigeminal nucleus was severely affected in the IS patients, while that for SP was comparatively well preserved. It is suggested that the presence of common brainstem lesions in IS is irrespective of etiologies. It is intriguing that some of the changes seemed to be interrelated with the neurophysiological abnormalities being reported in IS patients.

Adolescent↗

PubMed2000

[Clinical symptoms and characteristic MR spectroscopic findings in Pelizaeus-Merzbacher disease].

Clinical symptoms and MR spectroscopic findings were studied on 4 cases of Pelizaeus-Merzbacher disease including 1 autopsy case. Common symptoms were severe mental retardation and spastic tetraplegia. These cases had nystagmus, and one had involuntary athetotic movement. Genetical diagnosis revealed in 2 cases, duplication of proteolipid protein (PLP) and deletion in 1, whereas one case had no abnormality of PLP gene. MRI indicated the reversal of signal intensities on T1- and T2-weighed images, a characteristic finding of PMD MR spectroscopy demonstrated a pattern of NAA in 3 cases. This was specific to PMD because other white matter diseases show a decrease in NAA. In conclusion, MRS was useful to differentiate PMD from other white matter diseases.

Adult↗

PubMed2000

Enhanced expression of constitutive and inducible forms of nitric oxide synthase in autoimmune encephalomyelitis.

To elucidate the role of nitric oxide synthase (NOS) in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), we analyzed the expression of constitutive neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS) in the spinal cords of rats with EAE. We further examined the structural interaction between apoptotic cells and spinal cord cells including neurons and astrocytes, which are potent cell types of nitric oxide (NO) production in the brain. Western blot analysis showed that three forms of NOS significantly increased in the spinal cords of rats at the peak stage of EAE, while small amounts of these enzymes were identified in the spinal cords of rats without EAE. Immunohistochemical study showed that the expression of either nNOS or eNOS increased in the brain cells including neurons and astrocytes during the peak and recovery stages of EAE, while the expression of iNOS was found mainly in the inflammatory macrophages in the perivascular EAE lesions. Double labeling showed that apoptotic cells had intimate contacts with either neurons or astrocytes, which are major cell types to express nNOS and eNOS constitutively. Our results suggest that the three NOS may play an important role in the recovery of EAE.

Animals↗

PubMed1999

Stage-dependent usage of TCR alpha chains with different CDR3 motifs by spinal cord T cells in autoimmune encephalomyelitis.

To characterize the nature of the alpha chain of TCR associated with the development of experimental autoimmune encephalomyelitis (EAE), spinal cord T cells isolated from individual rats with preclinical and clinical EAE were investigated by CDR3 spectratyping and subsequently, the amino acid sequences of the CDR3 region of oligoclonally expanded TCR determined. In contrast to the beta chain repertoire in which Vbeta8.2 with the shortest CDR3 is the predominant population throughout the course, multiple oligoclonal expansion was observed at all time points examined. Characteristically, Valpha1 and Valpha2 expansion was observed at preclinical and early stages, whereas that of Valpha8, Valpha13 and Valpha23 was detected at early and peak stages. Sequence analysis of the CDR3 region revealed that the former group possessed an asparagine repeat in the middle portion, whereas the latter group had the KLTF motif in the C terminal region of CDR3. These findings suggest that Valpha usage by EAE-associated T cells is stage-dependent and that EAE is induced by polyclonally activated T cells which switch TCR alpha chain, but not beta chain, phenotype as the disease progresses.

Amino Acid Sequence↗

PubMed1999

Differential role of TNF-alpha and IFN-gamma in the brain of rats with chronic relapsing autoimmune encephalomyelitis.

To elucidate the mechanisms of relapses of the clinical signs in experimental autoimmune encephalomyelitis (EAE), the cytokine profile of chronic relapsing EAE (CR-EAE) in rats was determined by competitive polymerase chain reaction (PCR). By immunization with guinea pig spinal cord homogenate and treatment with low-dose cyclosporin A (CsA), rats developed two attacks of EAE with remission in between. Cytokine analysis revealed that the level of TNF-alpha mRNA increased at the first and second attacks with transient disappearance at the remission phase. In contrast, the level of IFN-gamma mRNA was suppressed at the first attack by CsA and peaked at the second attack. Intraventricular administration of IFN-gamma prior to onset of disease signs induced more relapses, or a severe lethal form. In addition, the intraventricular injection of TNF-alpha caused the persistence of the clinical signs. These findings suggest that TNF-alpha contributes to the first and second attacks of CR-EAE, while IFN-gamma is not required for the first attack but is closely related to the relapse of the disease. With regard to anti-inflammatory cytokines, the levels of both TGF-beta1 and IL-10 mRNA at the second attack were higher than those at the first attack. Taken together, differential involvement of TNF-alpha and IFN-gamma is closely associated with the clinical features of CR-EAE.

Animals↗

PubMed1999

Distinct promoters control transmembrane and cytosolic protein tyrosine phosphatase epsilon expression during macrophage differentiation.

We have recently isolated two cDNAs encoding two forms of transmembrane and cytosolic protein tyrosine phosphatase epsilon (PTPepsilon). In this study, the 5' end of the rat PTPepsilon gene was isolated and characterized. Transmembrane PTPepsilon (PTPepsilonM) and cytosolic PTPepsilon (PTPepsilonC) were encoded by a single gene. 5' RACE analysis and RNase protection assay showed that the mRNA of each PTPepsilon isoform was transcribed from different promoters. The putative promoter regions of two alternative first exons lacked a TATA box, but contained potential recognition sites for several transcription factors. Reverse transcription PCR analysis revealed that PTPepsilonC mRNA was up-regulated during interleukin 6-induced differentiation of murine leukemia M1 cells, whereas PTPepsilonM mRNA was down-regulated. With the use of luciferase as a reporter gene, the promoter activities of the 5'-flanking regions were examined during phorbol myristate acetate-induced differentiation of HL-60 cells. In the differentiated HL-60 cells, the activity of the PTPepsilonC promoter, but not that of PTPepsilonM, was dramatically elevated. Furthermore, we found that PTPepsilonC mRNA is highly expressed in mouse peritoneal macrophages and enhanced during activation by lipopolysaccharide. These results suggest that the different promoters control expression of PTPepsilon isoforms during the differentiation and/or activation of macrophages.

Amino Acid Sequence↗