Taketo Yamada

Innate production of TH2 cytokines by adipose tissue-associated c-Kit+Sca-1+ lymphoid cells

Innate immune responses are important in combating various microbes during the early phases of infection. Natural killer (NK) cells are innate lymphocytes that, unlike T and B lymphocytes, do not express antigen receptors but rapidly exhibit cytotoxic activities against virus-infected cells and produce various cytokines. Here we report a new type of innate lymphocyte present in a novel lymphoid structure associated with adipose tissues in the peritoneal cavity. These cells do not express lineage (Lin) markers but do express c-Kit, Sca-1 (also known as Ly6a), IL7R and IL33R. Similar lymphoid clusters were found in both human and mouse mesentery and we term this tissue ‘FALC’ (fat-associated lymphoid cluster). FALC Lin-c-Kit+Sca-1+ cells are distinct from lymphoid progenitors and lymphoid tissue inducer cells. These cells proliferate in response to IL2 and produce large amounts of TH2 cytokines such as IL5, IL6 and IL13. IL5 and IL6 regulate B-cell antibody production and self-renewal of B1 cells. Indeed, FALC Lin-c-Kit+Sca-1+ cells support the self-renewal of B1 cells and enhance IgA production. IL5 and IL13 mediate allergic inflammation and protection against helminth infection. After helminth infection and in response to IL33, FALC Lin-c-Kit+Sca-1+ cells produce large amounts of IL13, which leads to goblet cell hyperplasia—a critical step for helminth expulsion. In mice devoid of FALC Lin-c-Kit+Sca-1+ cells, such goblet cell hyperplasia was not induced. Thus, FALC Lin-c-Kit+Sca-1+ cells are TH2-type innate lymphocytes, and we propose that these cells be called ‘natural helper cells’.

Induction of Apoptosis in Leukemic Cells by Homovanillic Acid Derivative, Capsaicin, through Oxidative Stress Implication of Phosphorylation of p53 at Ser-15 Residue by Reactive Oxygen Species

Capsaicin (N-vanillyl-8-methyl-1-nonenamide) is a homovanillic acid derivative found in pungent fruits. Several investigators have reported the ability of capsaicin to inhibit events associated with the promotion of cancer. However, the effects of capsaicin on human leukemic cells have never been investigated. We investigated the effects of capsaicin on leukemic cells in vitro and in vivo and further examined the molecular mechanisms of capsaicin-induced apoptosis in myeloid leukemic cells. Capsaicin suppressed the growth of leukemic cells, but not normal bone marrow mononuclear cells, via induction of G0-G1 phase cell cycle arrest and apoptosis. Capsaicin-induced apoptosis was in association with the elevation of intracellular reactive oxygen species production. Interestingly, capsaicin-sensitive leukemic cells were possessed of wild-type p53, resulting in the phosphorylation of p53 at the Ser-15 residue by the treatment of capsaicin. Abrogation of p53 expression by the antisense oligonucleotides significantly attenuated capsaicin-induced cell cycle arrest and apoptosis. Pretreatment with the antioxidant N-acetyl-l-cystein and catalase, but not superoxide dismutase, completely inhibited capsaicin-induced apoptosis by inhibiting phosphorylation of Ser-15 residue of p53. Moreover, capsaicin effectively inhibited tumor growth and induced apoptosis in vivo using NOD/SCID mice with no toxic effects. We conclude that capsaicin has potential as a novel therapeutic agent for the treatment of leukemia.

Hypoplasia of pancreatic islets in transgenic mice expressing activin receptor mutants.

Activin, a member of the TGF-beta superfamily, regulates the growth and differentiation of a variety of cell types. Based on the expression of activin in pancreatic rudiments of rat embryos and stimulation of insulin secretion from adult rat pancreatic islets by activin, activin is implicated in the development and function of islets. To examine the significance of activin signaling in the fetal and postnatal development of islets, transgenic mice expressing a dominant negative form of activin receptor (dn-ActR) or a constitutively active form of activin receptor (ActR-T206D) in islets were generated together with the transgenic mice expressing intact activin receptor (intact ActR) as a negative control. Transgenic mice with both dn-ActR and ActR-T206D showed lower survival rates, smaller islet area, and lower insulin content in the whole pancreas with impaired glucose tolerance when compared with transgenic mice with intact ActR or littermates, but they showed the same alpha cell/beta cell ratios as their littermates. In addition to islet hypoplasia, the insulin response to glucose was severely impaired in dn-ActR transgenic mice. It is suggested that a precisely regulated intensity of activin signaling is necessary for the normal development of islets at the stage before differentiation into alpha and beta cells, and that activin plays a role in the postnatal functional maturation of islet beta cells.

PI3K-Akt-mTORC1-S6K1/2 Axis Controls Th17 Differentiation by Regulating Gfi1 Expression and Nuclear Translocation of RORγ

The PI3K-Akt-mTORC1 axis contributes to the activation, survival, and proliferation of CD4(+) T cells upon stimulation through TCR and CD28. Here, we demonstrate that the suppression of this axis by deletion of p85α or PI3K/mTORC1 inhibitors as well as T cell-specific deletion of raptor, an essential component of mTORC1, impairs Th17 differentiation in vitro and in vivo in a S6K1/2-dependent fashion. Inhibition of PI3K-Akt-mTORC1-S6K1 axis impairs the downregulation of Gfi1, a negative regulator of Th17 differentiation. Furthermore, we demonstrate that S6K2, a nuclear counterpart of S6K1, is induced by the PI3K-Akt-mTORC1 axis, binds RORγ, and carries RORγ to the nucleus. These results point toward a pivotal role of PI3K-Akt-mTORC1-S6K1/2 axis in Th17 differentiation.

Prorenin Receptor Is Essential for Normal Podocyte Structure and Function

The prorenin receptor is an accessory subunit of the vacuolar H(+)-ATPase, suggesting that it has fundamental functions beyond activation of the local renin-angiotensin system. Podocytes express the prorenin receptor, but its function in these cells is unknown. Here, podocyte-specific, conditional, prorenin receptor-knockout mice died of kidney failure and severe proteinuria within 4 weeks of birth. The podocytes of these mice exhibited foot process effacement with reduced and altered localization of the slit-diaphragm proteins nephrin and podocin. Furthermore, the podocytes contained numerous autophagic vacuoles, confirmed by enhanced accumulation of microtubule-associated protein 1 light chain 3-positive intracellular vesicles. Ablation of the prorenin receptor selectively suppressed expression of the V(0) c-subunit of the vacuolar H(+)-ATPase in podocytes, resulting in deacidification of intracellular vesicles. In conclusion, the prorenin receptor is important for the maintenance of normal podocyte structure and function.

G-Protein-Coupled Receptor GPR49 is Up-regulated in Basal Cell Carcinoma and Promotes Cell Proliferation and Tumor Formation

The significance of Hedgehog (HH) signaling in the development of basal cell carcinoma (BCC) has been established. Although several target genes of HH signaling have been described previously, their precise role in tumorigenesis and cell proliferation is not yet known. To identify genes responsible for tumor formation in BCC, we screened a DNA microarray database of human BCC cases; the orphan G-protein-coupled receptor GPR49 was found to be up-regulated in all cases. GPR49 is a novel gene reported to be a marker of follicular and other tissue stem cells. Using real-time quantitative RT-PCR analysis, significant expression of GPR49 mRNA was observed in 19 of 20 BCC cases (95%) compared with controls. Up-regulation of GPR49 was confirmed by in situ hybridization. Moreover, knockdown of mouse Gpr49 showed suppression of cell proliferation in a mouse BCC cell line, and overexpression of GPR49 in human immortalized keratinocyte HaCaT cells induced proliferation. Furthermore, HaCaT cells overexpressing GPR49 showed tumor formation when transplanted into immunodeficient mice. In addition, inhibition of the HH signaling pathway in a mouse BCC cell line down-regulated endogenous Gpr49, whereas activation of HH signaling in mouse NIH3T3 cells up-regulated endogenous GPR49. These results suggest that GPR49 is expressed downstream of HH signaling and promotes cell proliferation and tumor formation in cases of BCC.

Overexpression of leucine-rich repeat-containing G protein-coupled receptor 5 in colorectal cancer

Leucine‐rich repeat‐containing G protein‐coupled receptor 5 (LGR5) is a 7‐transmembrane receptor reportedly expressed in stem cells of the intestinal crypts and hair follicles of mice. Overexpression of LGR5 is observed in some types of cancer; however, there has been no specific assessment in colorectal tumorigenesis. We performed quantitative RT‐PCR for LGR5 expression in 37 representative cancer cell lines, and showed that LGR5 mRNA was frequently overexpressed in colon cancer cell lines. Moreover, LGR5 expression was higher in colon cancer cell lines derived from metastatic tumors compared with those from primary tumors. In clinical specimens, there was significant overexpression of LGR5 in 35 of 50 colorectal cancers (CRCs), and in seven of seven sporadic colonic adenomas, compared with matched normal mucosa. This suggests up‐regulation of LGR5 from the early stage of colorectal tumorigenesis. LGR5 expression showed marked variation among CRC cases and correlated significantly with lymphatic invasion, vascular invasion, tumor depth, lymph node metastasis, and tumor stage (IIIC vs. IIIB). In addition to cancer cells, crypt base columnar cells of the small intestine and colon were shown by in situ hybridization to express LGR5. This is the first report suggesting the involvement of LGR5, not only in early events but also in late events in colorectal tumorigenesis. (Cancer Sci 2010)

Role of Peyer's patches in the induction of Helicobacter pylori-induced gastritis

Helicobacter pylori is a Gram-negative spiral bacterium that causes gastritis and peptic ulcer and has been implicated in the pathogenesis of gastric adenocarcinoma and mucosa-associated lymphoid tissue lymphoma. Although Th1 immunity is involved in gastritis and the accumulation of H. pylori-specific CD4+ T cells in the H. pylori-infected gastric mucosa in human patients, how T cells are primed with H. pylori antigens is unknown because no apparent lymphoid tissues are present in the stomach. We demonstrate here that Peyers patches (PPs) in the small intestine play critical roles in H. pylori-induced gastritis; no gastritis is induced in H. pylori-infected mice lacking PPs. We also observed that the coccoid form of H. pylori is phagocytosed by dendritic cells in PPs. We propose that H. pylori converts to the coccoid form in the anaerobic small intestine and stimulates the host immune system through PPs.

Histopathological features and prognostic significance of the micropapillary pattern in lung adenocarcinoma

The micropapillary pattern is characterized by small papillary tufts with no fibrovascular core lying in spaces and has been reported as an aggressive variant of carcinoma in several organs. We investigated the histopathobiological properties of the micropapillary pattern with immunohistochemistry, serial sections, and electron microscopy in lung adenocarcinoma. We further analyzed its clinicopathological character and prognosis. The subjects included 383 adenocarcinoma cases, of which 184 (48%) were micropapillary pattern-positive and 199 (52%) were micropapillary pattern-negative. On histology, micropapillary tufts seemed to float in the alveolar space or spaces encased by connective tissues, whereas serial sections revealed that most tufts had continuity with other tufts and even with the main tumor. Positive staining for the adhesion molecules E-cadherin and β-catenin suggested the preservation of tight adhesion, and electron microscopy showed the existence of intercellular junctions. Negative staining for laminin and loss of basement membrane as determined by electron microscopy suggest a loss of cell–matrix contact. Positive staining for Ki-67 indicates that cells constituting micropapillary tufts retained their proliferation potency. There were no CD34-positive cells in micropapillary tufts, and the loss of the vascular core was confirmed. In micropapillary pattern-positive cases, lymphatic invasion was identified significantly more frequently than in micropapillary pattern-negative cases (P<0.001), even at stageIA (without lymph node metastasis, N=197) (P<0.001). The 5-year and 10-year overall survival rates of the micropapillary pattern-positive stageIA group were 77.6 and 67.6%, respectively, which were significantly less than those of the micropapillary pattern-negative stageIA group (98.1 and 98.1%) (P=0.001). In conclusion, cells constituting the micropapillary pattern are likely to have acquired anchorage-independent growth and a potential for high malignancy.

Acute onset of diabetic pathological changes in transgenic mice with human aldose reductase cDNA

SummaryTo investigate the role of human aldose reductase (hAR) in the pathogenesis of diabetic complications, we generated transgenic mice carrying hAR cDNA driven by the murine MHC class I molecule promoter (hAR-Tg). Northern and Western blot analyses and immunoassay of hAR revealed that both hAR mRNA and the protein were expressed in all tissues tested. Thrombosis in renal vessels and fibrinous deposits in Bowmans capsule were observed in 6-week-old hAR-Tg mice fed a normal diet. Ingestion of a 30% glucose diet for 5 days caused sorbitol concentrations in the liver, kidney, and muscle of hAR-Tg mice to be elevated significantly. Seven-week-old hAR-Tg mice fed a 20% galactose diet for 7 days developed cataracts and occlusion of the retinochoroidal vessels, in addition to pathological changes in the kidney. Despite an elevated aldose reductase level in hAR-Tg mice and their intake of an aldose diet, no histopathological changes were found in other tissues, including the brain, lungs, heart, thymus, spleen, intestine, liver, muscle, spinal cord, or sciatic nerve. Results suggest that target organs of diabetic complications, such as the kidney, lens, and retina are sensitive to damage associated with a high level of AR expression, but other organs are not; the susceptibility of each organ to diabetic complications is determined by not only hAR but also other factors.