Yoshinobu Okuda

Expression of the inducible isoform of nitric oxide synthase in the central nervous system of mice correlates with the severity of actively induced experimental allergic encephalomyelitis.

A cytokine-mediated excessive increase in nitric oxide (NO) by macrophages or glial cells via an inducible isoform of NO synthase (iNOS) has been proposed to play an important role in demyelinating diseases. To further investigate the role of iNOS in demyelination, experimental allergic encephalomyelitis (EAE), a known animal model of multiple sclerosis (MS) in mice, was chosen in this study. A semiquantitative reverse transcriptase-polymerase chain reaction (RT/PCR) analysis revealed an increase in the mRNA levels of iNOS and cytokines known to induce iNOS or inflammatory cytokines (interleukin (IL)-1 alpha, IL-1 beta, IL-2, IL-6, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and TNF-beta) in the spinal cord corresponding to the severity of the disease without significant change in the mRNA levels of immunoregulatory cytokines (IL-4, IL-10 and transforming growth factor (TGF)-beta) during the course of EAE. An immunohistochemical examination of the spinal cord using an iNOS-specific antibody showed iNOS-positive cells to be mainly inflammatory cells with a higher frequency of iNOS-positive cells at the peak of EAE than in the early phase. These iNOS-positive cells at the peak appeared to be composed of infiltrating macrophages and most of them were located in the necrotic area. These results suggested that cytokine-induced excessive NO via iNOS by macrophages caused tissue damage in the central nervous system in EAE.

IL-6 plays a crucial role in the induction phase of myelin oligodendrocyte glycoprotein 35–55 induced experimental autoimmune encephalomyelitis

We investigated the role of IL-6 in myelin oligodendrocyte glycoprotein (MOG) peptide induced experimental autoimmune encephalomyelitis (EAE) using IL-6-deficient mice and found that IL-6-deficient mice were resistant to active induction of EAE, but that the treatment of those mice with IL-6 during the preclinical phase caused typical EAE. We also found that both wild-type and IL-6-deficient mice were resistant to passive transfer of EAE by lymphocytes from IL-6-deficient mice, but that passive transfer of lymphocytes from wild-type mice induced typical EAE in IL-6-deficient mice. Histological abnormalities of the central nervous system (CNS) in those IL-6-deficient mice with EAE were similar to those in wild-type mice with EAE. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed no difference in the production of inflammatory cytokines such as IL-1beta, IL-2, TNF-alpha, and IFN-gamma in the CNS of IL-6-deficient mice with EAE as compared to the CNS of wild-type mice with EAE. These results indicated that IL-6 might be an important factor in the induction phase, but might have little influence on the effector phase of EAE. We further estimated the production of cytokines in MOG-stimulated lymph node (LN) cells by enzyme-linked immunosorbent assay. Increased IL-4 and IL-10 production and reduced IL-2 and IFN-gamma production were observed in LN cells from IL-6-deficient mice as compared to LN cells from wild-type mice. These results suggested that a shift of T cell responses from Thl to Th2 might explain the resistance of IL-6-deficient mice to EAE. Taken together, IL-6 may play a crucial role in the induction phase of EAE by modulating Th1/Th2 balance.

Nitric oxide via an inducible isoform of nitric oxide synthase is a possible factor to eliminate inflammatory cells from the central nervous system of mice with experimental allergic encephalomyelitis

We recently identified the inducible isoform of nitric oxide synthase (iNOS) in inflammatory lesions of the central nervous system (CNS) in mice with experimental allergic encephalomyelitis (EAE), a known animal model of multiple sclerosis (MS). In the present study, the role of excessive nitric oxide (NO) production via iNOS was investigated in mice with EAE using immunohistochemistry with antibodies to nitrotyrosine and iNOS, NADPH-diaphorase histochemistry, and the in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) method to detect cell death, presumably through an apoptotic mechanism. NADPH-diaphorase histochemistry and immunohistochemistry for iNOS revealed an elevation of nitric oxide synthase (NOS) activity during the course of EAE, which came from iNOS. Nitrotyrosine was detected in infiltrated cells and some glial cells in the spinal cord lesions, where iNOS-positive inflammatory cells were present at the peak of EAE. The findings implied the generation of NO and peroxynitrite in the EAE lesions, which might damage structural and functional proteins. The TUNEL positive cells were mainly inflammatory ones, and most of them were located in close proximity to iNOS-positive cells, while some of them were iNOS-positive themselves. These results suggested that excessive NO via iNOS played an important role to eliminate inflammatory cells in the CNS of mice with EAE, possibly through an apoptotic mechanism.

Gender does not influence the susceptibility of C57BL/6 mice to develop chronic experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein.

Multiple sclerosis (MS), an inflammatory demyelinating disease of the central nervous system (CNS), is more prevalent in females than males. It is well documented that a significant gender difference exits in the susceptibility of mice to develop experimental autoimmune encephalomyelitis (EAE), a model of MS, induced by myelin basic protein or proteolipid protein. In contrast, we report here that no significant difference between female mice and male mice with myelin oligodendrocyte glycoprotein (MOG)-induced EAE was observed in the incidence of disease, clinical course, histological findings in the CNS, T cell response and cytokine production of spleen cells to MOG, and anti-MOG IgG level in serum. These results suggest that gender-related difference in EAE depends on the encephalitogen and/or the strain of animals used. Given that MOG is a putative pathogenic myelin antigen in MS, the present findings may have implications for the pathogenesis of this disease.

Aminoguanidine, a selective inhibitor of the inducible nitric oxide synthase, has different effects on experimental allergic encephalomyelitis in the induction and progression phase

To elucidate the role of excessive nitric oxide (NO) via the inducible nitric oxide synthase (iNOS) in experimental allergic encephalomyelitis (EAE), the effect of a selective iNOS inhibitor, aminoguanidine, was investigated using mice with actively induced EAE. Administration of aminoguanidine by intraperitoneal or intracisternal injection from day 2 to day 12 after immunization produced a significant delay in the onset of EAE. On the other hand, administration of aminoguanidine by intraperitoneal or intracisternal injection for 10 days after the onset of EAE enhanced the clinical severity and mortality rate and hastened the onset of relapse significantly. The histological study at day 11 after the onset revealed that more inflammatory cells were present in the central nervous system of mice treated with aminoguanidine as compared with mice without aminoguanidine treatment. These results suggested that NO via iNOS was a pathogenetic factor in the induction phase of EAE, but had an inhibitory role in the progression phase of EAE. Although the effect of NO synthase inhibitors on EAE has been controversial, the present study suggested that the timing of administration might be an important consideration and might explain the previous contradictory reports.

NITRIC OXIDE INDUCES APOPTOSIS IN MOUSE SPLENIC T LYMPHOCYTES

The cytotoxic effect of nitric oxide (NO) on mouse T lymphocytes was investigated. Freshly isolated T lymphocytes from mouse spleen were incubated with NOR, a novel NO releasing agent, at different doses. After incubation for 4 h, apoptotic cell death was observed in both NOR-treated T lymphocytes and controls as judged by the appearance of DNA laddering in agarose gel electrophoresis, but a quantitative analysis by flow cytometry indicated that the high level of exogenous NO (500 micrograms ml of NOR) could promote apoptosis in T lymphocytes as compared with controls (30% vs. 8%). After 8 h, NO promoted apoptosis of T lymphocytes in a dose-dependent manner. This study indicated that NO might be one of the factors which regulate this life of T lymphocytes in vivo.

Regulatory role of p53 in experimental autoimmune encephalomyelitis

The role of p53, a pro-apoptotic protein, in experimental autoimmune encephalomyelitis (EAE) was investigated using p53-deficient C57BL/6J mice. p53-deficient mice immunised with myelin oligodendrocyte glycoprotein (MOG) exhibited a more severe clinical course of EAE with more severe inflammation in the central nervous system (CNS) compared to wild-type littermates. While T and B cell responses of p53-deficient mice to MOG were comparable to those of wild-type littermates, significantly higher production of IL-6, granulocyte macrophage colony-stimulating factor and IL-10 was observed in lymphocytes exposed to MOG from p53-deficient mice than those from wild-type littermates. Furthermore, a flow cytometric analysis of Annexin V staining showed that apoptosis of CNS-infiltrating cells was less in p53-deficient mice with EAE compared to wild-type littermates. These results suggest that p53 may be involved in the regulatory process of EAE through the control of cytokine production and/or the apoptotic elimination of inflammatory cells.

Fas has a crucial role in the progression of experimental autoimmune encephalomyelitis

To investigate the role of Fas in experimental autoimmune encephalomyelitis (EAE) in mice, we examined the susceptibility of EAE in C57BL/6 (B6).lpr mice lacking Fas. The frequency of myelin oligodendrocyte glycoprotein (MOG)-induced EAE in B6.lpr mice was significantly lower than that in B6 mice (19% vs 94%). However, no significant difference was observed between them in either the lymphocyte proliferation response or antibody reactivity to MOG. In addition, the histological examination and semiquantitative reverse transcriptase polymerase chain reaction analysis revealed that the infiltration of inflammatory cells and the up-regulation of gene expression for inflammatory cytokines occurred in the central nervous system (CNS) of B6.lpr mice immunized with MOG, even if they showed no clinical sign. These results indicate that Fas may contribute to the pathogenesis of EAE and may play a crucial role in the expansion of inflammation and/or myelin destruction in the CNS rather than in the activation of encephalitogenic T cells in the periphery and/or the breakdown of blood brain barrier.

The expression of ion channel mRNAs in skeletal muscles from patients with myotonic muscular dystrophy

We investigated gene expression patterns of ion channels including the apamin-sensitive small-conductance Ca(2+)-activated K(+) (SK3) channel, the adult isoform of the skeletal muscle Na(+) channel (SkM1), the fetal isoform of skeletal muscle Na(+) channel (H1), and the Cl(-) channel (ClC-1) by using the semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) for muscle samples from patients with adult onset myotonic dystrophy (DM), amyotrophic lateral sclerosis, and polymyositis. Patients with DM showed a significant increase in SK3 mRNA but not in mRNAs for other ion channels. The increased expression of SK3 gene in DM did not correlate with H1, the marker of muscle denervation, or the percentage of type 2C fiber, the marker of muscle regeneration.

The pattern of cytokine gene expression in lymphoid organs and peripheral blood mononuclear cells of mice with experimental allergic encephalomyelitis

We previously observed Th1-dominated response in the central nervous system (CNS) of mice during the course of experimental allergic encephalomyelitis (EAE) with a semiquantitative reverse transcriptase-polymerase chain reaction (RT/PCR) analysis. We report here that mRNA levels for both inflammatory cytokines including interleukin (IL)-1beta, IL-2, IL-6, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and TNF-beta and immunoregulatory cytokines including IL-4, IL-10 and transforming growth factor (TGF)-beta were up-regulated in the preclinical and/or acute phase but down-regulated in the recovery phase of EAE in lymph node (LN) of mice. Similar profiles for cytokine mRNA levels were also observed in spleen and peripheral blood mononuclear cells (PBMC). The present study also showed that a significant down-regulation of the mRNA level for IL-6 in the acute phase as compared with the preclinical phase, and a significant reduction of the mRNA level for TGF-beta in the preclinical and acute phase as compared with the corresponding mRNA levels in the control mice treated with complete Freunds adjuvant alone were characteristic in peripheral immune organs of mice with EAE. These results indicate that no particular bias in cytokine production occurred in peripheral immune organs of mice with actively induced relapsing EAE, and that the relative reduction in production of TGF-beta or IL-6 in peripheral circulation might participate in the induction or remission of EAE, respectively. Our results using the animal model of multiple sclerosis (MS) suggested that the mRNA levels for IL-6 and TGF-beta in PBMC from patients with MS may be a good indicator to assess the disease activity or to predict relapse.