Tomoko Suzuki

Dehydroepiandrosterone enhances IL2 production and cytotoxic effector function of human T cells

Dehydroepiandrosterone (DHEA) is the most abundant adrenal steroid hormone in humans. Although it is well established that DHEA serves as an intermediate in sex steroid synthesis, recent studies in mice suggest that DHEA may also be a physiologic regulator of IL2 secretion. To explore the effect of DHEA on the human immune system, T lymphocytes from healthy adults were exposed to DHEA followed by stimulation with mitogens or antigen. Upon activation with a variety of stimuli, T cells pretreated with 10(-8) to 10(-11) M DHEA produced significantly greater amounts of IL2 and mediated more potent cytotoxicity than T cells activated in the absence of this steroid hormone. The peak effect of DHEA was observed at 10(-9) M, the concentration of hormone present in the blood of normal adults. In contrast to its effect on murine T cells, the IL2 enhancing effect of DHEA on human lymphocytes was limited to fresh CD4+ T cells and CD4+ clones; neither fresh CD8+ cells nor CD8+ clones were directly affected by DHEA treatment, although CD8+ cells stimulated in the presence of CD4+ cells and DHEA demonstrated enhanced cytotoxicity. The enhancing effect of DHEA was also detected at the level of IL2 mRNA, suggesting that DHEA may act as a transcriptional enhancer of the IL2 gene in CD4+ T cells. These results corroborate and extend earlier studies in mice and suggest a physiologic role for DHEA in regulating the human immune response.

Low serum levels of dehydroepiandrosterone may cause deficient IL-2 production by lymphocytes in patients with systemic lupus erythematosus (SLE)

The principal cause of IL‐2 deficiency, a common feature of both murine lupus and human SLE, remains obscure. Recent studies of our own as well as others have shown that dehydroepiandrosterone (DHEA), an intermediate compound in testosterone synthesis, significantly up‐regulates IL‐2 production of T cells, and that administration of exogenous DHEA or IL‐2 via a vaccinia construct to murine lupus dramatically reverses their clinical autoimmune diseases. Thus, we have examined serum levels of DHEA in patients with SLE to test whether abnormal DHEA activity is associated with IL‐2 deficiency of the patients. We found that nearly all of the patients examined have very low levels of serum DHEA. The decreased DHEA levels were not simply a reflection of a long term corticosteroid treatment which may cause adrenal atrophy, since serum samples drawn at the onset of disease, which are devoid of corticosteroid treatment, also contained low levels of DHEA. In addition, exogenous DHEA restored impaired IL‐2 production of T cells from patients with SLE in vitro. These results indicate that defects of IL‐2 synthesis of patients with SLE are at least in part due to the low DHEA activity in the serum.

Excessive CD4+ T cells co-expressing interleukin-17 and interferon-γ in patients with Behçet's disease.

Excessive T helper type 1 (Th1) cell activity has been reported in Behçets disease (BD). Recently, association of Th17 cells with certain autoimmune diseases was reported, and we thus investigated circulating Th17 cells in BD. CD4+CD45RO– (naive) T cells were cultured with Th0‐, Th1‐, Th2‐ and Th17‐related cytokines and antibodies, and their mRNA was studied by real‐time polymerase chain reaction (PCR). When naive CD4+ T cells were cultured with Th1‐ and Th17‐related cytokines, interferon (IFN)‐γ mRNA and interleukin (IL)‐17 mRNA were up‐regulated, respectively, in BD patients. Naive CD4+ T cells cultured in a Th17 cell‐inducing condition expressed IL‐23 receptor (IL‐23R) mRNA excessively. IL‐17 mRNA expression was induced only when naive CD4+T cells were cultured in the presence of IL‐23. CD4+ T cells cultured with Th17 cytokines expressed excessive RAR‐related orphan receptor C (RORC) mRNA. Using intracellular cytokine staining, we found that CD45RO+(memory) CD4+ T cells producing IL‐17 and IFN‐γ simultaneously were increased significantly. Memory CD4+ T cells producing IFN‐γ but not IL‐17 decreased profoundly in BD patients. CD4+ T cells producing IL‐17 and IFN‐γ simultaneously were found in BD skin lesions. Collectively, we found excessive CD4+ T cells producing IL‐17 and IFN‐γ (Th1/Th17) cells in patients with BD, and possible involvement of IL‐23/IL‐23R pathway for the appearance of excessive Th1/Th17 cells.

Restoration of spatial memory dysfunction of human APP transgenic mice by transplantation of neuronal precursors derived from human iPS cells.

PDGF promoter driven amyloid precursor protein (PDAPP) transgenic mice were accompanied by age dependent amyloid β deposition and progressive spatial memory dysfunction which emerges within a few months of age. We conducted transplantation of neuronal precursors of cholinergic neuron phenotype which were derived from human iPS (hiPS) cells into bilateral hippocampus of PDAPP mice. We first generated neuronal precursors with cholinergic neuron phenotype from hiPS cells by culturing them with retinoic acid (RA), sonic hedgehog (SHH) and noggin-Fc (NOG). Spatial memory function of PDAPP mice was significantly impaired compared to that of nontransgenic littermates at age 8 weeks. After neuronal precursor transplantation, subsequent memory dysfunction of PDAPP mice was significantly improved, compared to that of vehicle injected PDAPP mice. We observed choline acetyltransferase (ChAT) positive cholinergic human neurons and vesicle GABA transporter (VGAT) positive GABAergic human neurons in PDAPP mouse hippocampus 45 days after the transplantation. Neuronal precursors with cholinergic neuron phenotype derived from hiPS cells survived in PDAPP mouse hippocampus and their spatial memory loss was improved. hiPS cells may become applicable for the treatment of patients with dementia.

Bifidobacteria Abundance-Featured Gut Microbiota Compositional Change in Patients with Behcet’s Disease

Gut microbiota compositional alteration may have an association with immune dysfunction in patients with Behcet’s disease (BD). We conducted a fecal metagenomic analysis of BD patients. We analyzed fecal microbiota obtained from 12 patients with BD and 12 normal individuals by sequencing of 16S ribosomal RNA gene. We compared the relative abundance of bacterial taxa. Direct comparison of the relative abundance of bacterial taxa demonstrated that the genera Bifidobacterium and Eggerthella increased significantly and the genera Megamonas and Prevotella decreased significantly in BD patients compared with normal individuals. A linear discriminant analysis of bacterial taxa showed that the phylum Actinobacteria, including Bifidobacterium, and the family Lactobacillaceae exhibited larger positive effect sizes than other bacteria in patients with BD. The phylum Firmicutes and the class Clostridia had large effect sizes in normal individuals. There was no significant difference in annotated species numbers (as numbers of operational taxonomic unit; OTU) and bacterial diversity of each sample (alpha diversity) between BD patients and normal individuals. We next assigned each sample to a position using three axes by principal coordinates analysis of the OTU table. The two groups had a significant distance as beta diversity in the 3-axis space. Fecal sIgA concentrations increased significantly in BD patients but did not correlate with any bacterial taxonomic abundance. These data suggest that the compositional changes of gut microbes may be one type of dysbiosis (unfavorable microbiota alteration) in patients with BD. The dysbiosis may have an association with the pathophysiology of BD.

Role of SDF1/CXCR4 Interaction in Experimental Hemiplegic Models with Neural Cell Transplantation

Much attention has been focused on neural cell transplantation because of its promising clinical applications. We have reported that embryonic stem (ES) cell derived neural stem/progenitor cell transplantation significantly improved motor functions in a hemiplegic mouse model. It is important to understand the molecular mechanisms governing neural regeneration of the damaged motor cortex after the transplantation. Recent investigations disclosed that chemokines participated in the regulation of migration and maturation of neural cell grafts. In this review, we summarize the involvement of inflammatory chemokines including stromal cell derived factor 1 (SDF1) in neural regeneration after ES cell derived neural stem/progenitor cell transplantation in mouse stroke models.

Cellular and molecular mechanisms of the restoration of human APP transgenic mouse cognitive dysfunction after transplant of human iPS cell-derived neural cells

Cholinergic neuronal loss is a common finding in patients with Alzheimers disease (AD) and AD model mice. We previously transplanted neurons derived from human induced pluripotent stem (iPS) cells into the hippocampus of human amyloid precursor protein transgenic AD model mice. In the present study, we examined the cellular and molecular mechanisms involved in the alleviation of cognitive dysfunction in transplanted mice. After transplant, mice showed improvement in cognitive function, confirming our previous findings. Human choline acetyltransferase (ChAT)-positive cholinergic neurons were distributed throughout the cortex of the grafted mice. Human and mouse ChAT-positive neurons and alpha7 nicotinic acetylcholine receptor (α7nAChR)-positive neurons were significantly increased in the cortex and hippocampus of the grafted mice compared with the vehicle-injected mice. In addition, human and mouse vesicular GABA transporter (VGAT)-positive neurons were located mainly in the hippocampus and, though the number was small, human VGAT-positive neurons were observed in the cortex. In the grafted mouse cortex, the number of GABA receptor (GABAR)-positive neurons of both human origin and mouse origin were significantly increased compared with those in the vehicle-injected mouse cortex. The α7nAChR-positive and GABAR-positive neurons expressed phosphorylated Akt and c-fos in the cortex, suggesting that these receptor-expressing neurons were possibly activated by the neurotransmitters secreted from the grafted neurons. Collectively, the grafted and host neurons may form positive feedback loops via neurotransmitter secretion in both the cerebral cortex and hippocampus, leading to alleviation of cognitive dysfunction in dementia model mice.

Establishment of retinal progenitor cell clones by transfection with Pax6 gene of mouse induced pluripotent stem (iPS) cells.

We previously reported that transfection of Pax6 gene which regulated early events in eye development into mouse ES cells brought about their differentiation into retinal progenitors. Here, we attempted to establish cloned retinal progenitors which had ability to further differentiate into photoreceptor like cells by transfecting mouse induced pluripotent stem (iPS) cells with Pax6 gene. Undifferentiated iPS cells were transfected with Pax6 cDNA, followed by selection with G418. After limiting dilution culture, we selected cloned Pax6-transfected cells, which simultaneously expressed mRNAs of Nestin, Musashi1, Six3 and Chx10 for further characterization. We obtained totally 8 clonally expanding Pax6-transfected cells. They started to express mRNAs of Brn3b, Cone-rod homeobox (Crx), pkc, CD73, rhodopsin and the γ-subunit of rod cGMP phosphodiesterase (PDEγ). Flow cytometric analysis revealed that almost half of the cells were CD73+, a marker of photoreceptor precursors. Western blotting confirmed cytoplasmic protein expression of rhodopsin. High KCl stimulation increased free Ca influx into the cells on Ca(2+) imaging. iPS cells transfected with Pax6 gene, followed by subsequent limiting dilution culture became retinal progenitors including photoreceptor like cells. The cloned cell lines may be useful for analyzing differentiation requirement of retinal progenitors.

Human iPS cell derived neural cell sheets exhibit mature neural and extendable scaffold functions and promote recovery in injured mouse spinal cords

We developed neural cell sheets being positive for mature motoneuron markers, such as βIII tubulin, islet1 and HB9, from human induced pluripotent stem (hiPS) cells after embryoid body formation. We transplanted the neural cell sheets into the complete transection sites of spinal cord injury (SCI) model mice. We assessed functional and histological analyses of the SCI mice and compared the data with those of hiPS cell derived neural stem/progenitor (NSP) cell transplanted SCI mice. Neurofilament medium (NFM), βIII tubulin, and HB9 positive cells were significantly increased in vitro in neural cell sheets compared with those in NSP cells. The neural cell sheets expressed remarkably high mRNA of NFM and islet 1 compared with NSP cells. After transplantation, the neural cell sheets elongated human neural cell adhesion molecule (hNCAM) positive axons over the L1 spinal level and carried a neuron tracer cholera toxin β subunit (CTβ) to downstream region. The sheet transplantation showed significantly better locomotor recovery of SCI mice until day 65 than NSP cell transplantation. The sheet transplantation tended to improve spinal cord atrophy in caudal part of injured/grafted site to the same extent as NSP cell transplantation. We suggest that the neural cell sheets derived from hiPS cells may be one of the most effective treatment for SCI, through the mature neural and extendable scaffold functions. Correspondence to: Noboru Suzuki MD, Ph.D, Department of Immunology and Medicine, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamaeku, Kawasaki, Kanagawa 216-8511, Japan, Tel: +81-44-977-8111 (ex 3547), Fax: +81-44-976-3315, E-mail: n3suzuki@marianna-u.ac.jp

Propionate-producing bacteria in the intestine may associate with skewed responses of IL10-producing regulatory T cells in patients with relapsing polychondritis

Relapsing polychondritis (RP) is an inflammatory disease of unknown causes, characterized by recurrent inflammation in cartilaginous tissues of the whole body. Recently, researchers have reported that, in mouse experiments, altered gut microbe-dependent T cell differentiation occurred in gut associated lymphoid tissues. Here, we investigated whether gut microbe alteration existed, and if so, the alteration affected peripheral T cell differentiation in patients with RP. In an analysis of gut microbiota, we found increased annotated species numbers in RP patients compared with normal individuals. In the RP gut microbiota, we observed several predominant species, namely Veillonella parvula, Bacteroides eggerthii, Bacteroides fragilis, Ruminococcus bromii, and Eubacterium dolichum, all species of which were reported to associate with propionate production in human intestine. Propionate is a short-chain fatty acid and is suggested to associate with interleukin (IL)10-producing regulatory T (Treg) cell differentiation in gut associated lymphoid tissues. IL10 gene expressions were moderately higher in freshly isolated peripheral blood mononuclear cells (PBMC) of RP patients than those of normal individuals. Six hours after the initiation of the cell culture, regardless of the presence and absence of mitogen stimulation, IL10 gene expressions were significantly lower in RP patients than those in normal individuals. It is well known that PBMC of patients with autoimmune and inflammatory diseases show hyporesponsiveness to mitogen stimulation. We suggest that, in RP patients, continuous stimulation of intestinal T cells by excessive propionate leads to the spontaneous IL10 production and a subsequent refractory period of T cells in patients with RP. The hyporesponsiveness of Treg cells upon activation may associate with inflammatory cytokine production of PBMC and subsequently relate to chondritis in RP patients.