3-OH Phloretin Inhibits High-Fat Diet-Induced Obesity and Obesity-Induced Inflammation by Reducing Macrophage Infiltration into White Adipose Tissue.

Phloretin and its glycoside phlorizin have been reported to prevent obesity induced by high-fat diet (HFD), but the effect of 3-OH phloretin, a catechol metabolite of phloretin, has not been investigated. In this study, we investigated the anti-obesity effects of phloretin and 3-OH phloretin in HFD-fed mice. The body weight gain induced by HFD was more inhibited by administration of 3-OH phloretin than by phloretin. The increases in fat mass, white adipose tissue (WAT) weight, adipocyte size, and lipid accumulation by HFD were also remarkably inhibited by 3-OH phloretin and, to a lesser extent, by phloretin. The HFD-induced upregulation of chemokines and pro-inflammatory cytokines was suppressed by 3-OH phloretin, preventing M1 macrophages from infiltrating into WAT and thereby reducing WAT inflammation. 3-OH phloretin also showed a more potent effect than phloretin on suppressing the expression of adipogenesis regulator genes, such as PPARγ2, C/EBPα, FAS, and CD36. Fasting blood glucose and insulin levels increased by HFD were diminished by the administration of 3-OH phloretin, suggesting that 3-OH phloretin may alleviate obesity-induced insulin resistance. These findings suggested that 3-OH phloretin has the potential to be a natural bioactive compound that can be used in the prevention or treatment of obesity and insulin resistance.

Cyclophilin A is an endogenous ligand for the triggering receptor expressed on myeloid cells-2 (TREM2).

Triggering receptor expressed on myeloid cells 2 (TREM2) is a cell surface receptor expressed on macrophages, microglial cells, and pre-osteoclasts, and that participates in diverse cellular function, including inflammation, bone homeostasis, neurological development, and coagulation. In spite of the indispensable role of the TREM2 protein in the maintenance of immune homeostasis and osteoclast differentiation, the exact ligand for TREM2 has not yet been identified. Here, we report a putative TREM2 ligand which is secreted from MC38 cells and identified as a cyclophilin A (CypA). A specific interaction between CypA and TREM2 was shown at both protein and cellular levels. Exogenous CypA specifically interacted and co-localized with TREM2 in RAW264.7 cells, and the physical interactions were shown to regulate TREM2 signaling transduction. The Pro144 residue in the extracellular domain of TREM2 was found to be the specific binding site of CypA. When considered together, this provides evidence that CypA interacts specifically with TREM2 as a potent ligand.

TREM2 promotes natural killer cell development in CD3-CD122+NK1.1+ pNK cells.

BACKGROUND: Triggering receptor expressed on myeloid cells 2 (TREM2) signaling is considered to regulate anti-inflammatory responses in macrophages, dendritic cell maturation, osteoclast development, induction of obesity, and Alzheimer's disease pathogenesis. However, little is known regarding the effect of TREM2 on natural killer (NK) cells. RESULTS: Here, we demonstrated for the first time that CD3-CD122+NK1.1+ precursor NK (pNK) cells expressed TREM2 and their population increased in TREM2-overexpressing transgenic (TREM2-TG) mice compared with that in female C57BL/6 J wild type (WT) mice. Both NK cell-activating receptors and NK cell-associated genes were expressed at higher levels in various tissues of TREM2-TG mice than in WT mice. In addition, bone marrow-derived hematopoietic stem cells (HSCs) of TREM2-TG mice (TG-HSCs) successfully differentiated into NK cells in vitro, with a higher yield from TG-HSCs than from WT-HSCs. In contrast, TREM2 signaling inhibition by TREM2-Ig or a phosphatidylinositol 3-kinase (PI3K) inhibitor affected the expression of the NK cell receptor repertoire and decreased the expression levels of NK cell-associated genes, resulting in significant impairment of NK cell differentiation. Moreover, in melanoma-bearing WT mice, injection of bone marrow cells from TREM2-TG mice exerted greater antitumor effects than that with cells from WT control mice. CONCLUSIONS: Collectively, our data clearly showed that TREM2 promoted NK cell development and tumor regression, suggesting TREM2 as a new candidate for cancer immunotherapy.

Axl is a key regulator of intestinal γδ T-cell homeostasis.

Gut-homing γδ T cells are induced by chemokines and cell adhesion molecules and play a critical role in homeostasis and mucosal immunity; however, little is known regarding their upstream regulators. We investigated the role of Axl as a specific regulator of chemokines and cell adhesion molecule in the distribution of intestinal γδ T cells. The population of γδ T-cell receptor-positive cells including Vγ1 and Vγ7 subsets was remarkably increased in the intraepithelial lymphocytes of Axl-/- mice compared with those of wild-type (WT) mice. An increased number of migrated γδ T cells were observed in the coculture with intraepithelial cells from Axl-/- mice. The mRNA expression level of chemokine (C-C motif) ligand (CCL) 25 was specifically higher in the small intestine of Axl-/- mice than in WT mice. In adoptive transfer, the migration of both thymic and extrathymic γδ T cells was increased in Axl-/- mice. The activation of Axl signaling down-regulated CCL25 expression via ERK signaling pathway and reduced the population of γδ T cells. Systemic dissemination was suppressed in Axl-/- mice infected with Salmonella typhimurium. Thus, our findings suggest that Axl plays a critical role in regulating the migration of γδ T cells for the maintenance of homeostasis and bacterial resistance.-Kim, S.-M., Park, M., Yee, S.-M., Ji, K.-Y., Lee, E.-H., Nguyen, T.-V., Nguyen, T. H.-L., Jang, J., Kim, E.-M., Choi, H.-R., Yun, C.-H., Kang, H.-S. Axl is a key regulator of intestinal γδ T-cell homeostasis.

Evaluating lead-free alternatives for radiation shielding in diagnostic radiology: a case study from a tertiary general hospital in Korea.

With the continued increase in the number of pieces of diagnostic medical radiography equipment being used, radiation shielding in radiology departments is becoming increasingly important. Lead is the most commonly used material for radiation protection; however, there are numerous disadvantages associated with the use of lead, including environmental hazards and harm to the human body. Alternative shielding materials that can be used as replacements include barium sulfate, tungsten, or bismuth. Among alternative materials, barium sulfate appears to be the most cost-effective and easiest to process. In the present study, before constructing shielding barriers, a barrier thickness program for lead-free barrier materials based on National Council on Radiation Protection and Measurements (NCRP) Report No. 147 was used to determine the appropriate barrier thickness. The required thickness for lead-free boards for each type of diagnostic radiography room was calculated based on a tertiary general hospital in the Republic of Korea.

Axl alleviates DSS-induced colitis by preventing dysbiosis of gut microbiota.

Axl is a tyrosine kinase receptor, a negative regulator for innate immune responses and inflammatory bowel disease (IBD). The gut microbiota regulates intestinal immune homeostasis, but the role of Axl in the pathogenesis of IBD through the regulation of gut microbiota composition remains unresolved. In this study, mice with DSS-induced colitis showed increased Axl expression, which was almost entirely suppressed by depleting the gut microbiota with antibiotics. Axl-/- mice without DSS administration exhibited increased bacterial loads, especially the Proteobacteria abundant in patients with IBD, significantly consistent with DSS-induced colitis mice. Axl-/- mice also had an inflammatory intestinal microenvironment with reduced antimicrobial peptides and overexpression of inflammatory cytokines. The onset of DSS-induced colitis occurred faster with an abnormal expansion of Proteobacteria in Axl-/- mice than in WT mice. These findings suggest that a lack of Axl signaling exacerbates colitis by inducing aberrant compositions of the gut microbiota in conjunction with an inflammatory gut microenvironment. In conclusion, the data demonstrated that Axl signaling could ameliorate the pathogenesis of colitis by preventing dysbiosis of gut microbiota. Therefore, Axl may act as a potential novel biomarker for IBD and can be a potential candidate for the prophylactic or therapeutic target of diverse microbiota dysbiosis-related diseases.

Interleukin-24 attenuates ß-glycerophosphate-induced calcification of vascular smooth muscle cells by inhibiting apoptosis, the expression of calcification and osteoblastic markers, and the Wnt/ß-catenin pathway.

Vascular calcification is a hallmark of cardiovascular disease. Interleukin-24 (IL-24) has been known to suppress tumor progression in a variety of human cancers. However, the role of IL-24 in the pathophysiology of diseases other than cancer is unclear. We investigated the role of IL-24 in vascular calcification. IL-24 was applied to a ß-glycerophosphate (ß-GP)-induced rat vascular smooth muscle cell (VSMC) calcification model. In this study, IL-24 significantly inhibited ß-GP-induced VSMC calcification, as determined by von Kossa staining and calcium content. The inhibitory effect of IL-24 on VSMC calcification was due to the suppression of ß-GP-induced apoptosis and expression of calcification and osteoblastic markers. In addition, IL-24 abrogated ß-GP-induced activation of the Wnt/ß-catenin pathway, which plays a key role in the pathogenesis of vascular calcification. The specificity of IL-24 for the inhibition of VSMC calcification was confirmed by using a neutralizing antibody to IL-24. Our results suggest that IL-24 inhibits ß-GP-induced VSMC calcification by inhibiting apoptosis, the expression of calcification and osteoblastic markers, and the Wnt/ ß-catenin pathway. Our study may provide a novel mechanism of action of IL-24 in cardiovascular disease and indicates that IL-24 is a potential therapeutic agent in VSMC calcification.

TREM2 Acts as a Tumor Suppressor in Colorectal Carcinoma through Wnt1/ß-catenin and Erk Signaling.

TREM2 (triggering receptor expressed on myeloid cells) is involved in the development of malignancies. However, the function of TREM2 in colorectal cancer has not been clearly elucidated. Here, we investigated TREM2 function for the first time in colorectal epithelial cancer cells and demonstrated that TREM2 is a novel tumor suppressor in colorectal carcinoma. Blockade of TREM2 significantly promoted the proliferation of HT29 colorectal carcinoma cells by regulating cell cycle-related factors, such as p53 phosphorylation and p21 and cyclin D1 protein levels. HT29 cell migration was also increased by TREM2 inhibition via MMP9 (matrix metalloproteinase 9) expression upregulation. Furthermore, we found that the tumor suppressor effects of TREM2 were associated with Wnt/ß-catenin and extracellular signal-regulated kinase (ERK) signaling. Importantly, the effect of TREM2 in the suppression of tumor development was demonstrated by in vivo and in vitro assays, as well as in human colon cancer patient tissue arrays. Overall, our results identify TREM2 as a potential prognostic biomarker and therapeutic target for colorectal cancer.

Daucosterol suppresses dextran sulfate sodium (DSS)-induced colitis in mice.

The effects of daucosterol have been identified in cancer therapy and neuronal diseases. However, the regulatory function of daucosterol in DSS-induced colitis has not yet been investigated. In this study, we evaluated the immunological and therapeutic effects of daucosterol in a mouse model of dextran sulfate sodium (DSS)-induced colitis. Unlike vehicle mice, mice pre- or post-treated with daucosterol showed inhibition of body weight loss and the decrease in the disease activity index (DAI). In addition, daucosterol treatment rescued the DSS-induced decrease in colon length and disruption of the epithelial lining. Furthermore, it reduced DSS-induced production of reactive oxygen species (ROS), infiltration of macrophages, and expression of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1ß. Mice with colitis showed a decreased population of Foxp3+ cells, which was upregulated by daucosterol treatment. Furthermore, daucosterol increased natural killer (NK) cell activity and inhibited excessive IgA levels in mice with DSS-induced colitis. Collectively, our findings demonstrated that daucosterol significantly alleviated DSS-induced colitis, indicating the possibility of daucosterol as a therapeutic option for colitis.

Axl signaling induces development of natural killer cells in vitro and in vivo.

Natural killer (NK) cells have been well known to play a critical role in innate immunity, but they are also capable of regulating adaptive immunity through the induction of T cell-mediated memory response and B cell-mediated autoimmune response. NK cells are differentiated from hematopoietic stem cells (HSCs) in the bone marrow (BM), and a series of surface molecules are expressed on NK cells in a differentiation stage-specific manner. Axl receptor tyrosine kinase is originally identified as homeostatic regulators for antigen-presenting cells, and its ligand, growth-arrest-specific gene 6 (Gas6), has been reported to promote cell survival, proliferation, and migration, but their regulatory role in the development and effector function of NK cells is not yet fully understood. In this study, to investigate whether Axl is required for the regulation of NK cell development, the expression of mature NK (mNK) cell-specific receptors and NK cell-associated genes was analyzed in the differentiated HSCs-derived NK cells in vitro and the NK cells harvested from Axl-/- mice. We found that agonistic anti-Axl antibody or recombinant Gas6 specifically upregulated the expression of mNK cell-specific receptors, such as LY49A, Ly49G2, Ly49C/F/I, NKG2A/C/E (1.5- to 3.5-fold increase), and NK cell-associated genes, such as IL-2Rß (2.3- or 2.4-fold increase), Perforin (4.1- or 2.1-fold increase), IL-15Rα (2.14- or 2.04-fold increase), and IFN-γ (3.3- or 2.8-fold increase) compared to each isotype control, whereas it was abrogated by treatment of Axl-Ig. Anti-Axl antibody or rGas6 also induced a 2.5- or 1.9-fold increase in the proliferation of developing NK cells compared to each control, respectively. mNK cell populations expressing mNK cell-specific receptors were reduced about twofold in NK cells differentiated from HSCs of Axl-/- mice compared with those of wild-type mice. Furthermore, the triggering of Axl signaling by agonistic anti-Axl antibody promoted the cytolytic activity (1.5- to 1.9-fold increase) against target tumor cells. In B16F10 melanoma-bearing mice, the number of metastatic colonies was decreased by 83 % by the administration of mNK cells treated with anti-Axl antibody compared to control Ig. These data suggest that Axl plays an essential role in the regulation of NK cell development as well as NK effector function.

Blockade of Axl signaling ameliorates HPV16E6-mediated tumorigenecity of cervical cancer.

Axl receptor tyrosine kinase is involved in the tumorigenesis and metastasis of many cancers. Axl expression was markedly higher in human papilloma virus type 16E6 (HPV16E6)-overexpressing HeLa (HE6F) cells and lower in HPV16E6-suppressing CaSki (CE6R) cells than in the controls. SiRNA-mediated knockdown of E6 expression led to increased phosphatase and tensin homolog (PTEN) phosphorylation at Ser380 and attenuated AKT phosphorylation. Expression of membrane-associated guanylate kinase inverted-2 (MAGI-2), an E6-induced degradation target, was induced in E6-siRNA-transfected cells. Moreover, myeloid zinc finger protein 1 (MZF1) binds directly to the Axl promoter in HE6F cells. Axl expression was regulated by HPV16E6-mediated PTEN/AKT signalling pathway, and Axl promoter activity was regulated through MZF1 activation in cervical cancer, which promoted malignancy. Axl silencing suppressed the metastasis of Caski cells and enhanced the susceptibility to NK cell-mediated killing of HE6F cells. In addition, the expression of Axl and MZF1 was highly correlated with clinical stage of cervical cancer and HPV16/18 infection. Taken together, Axl expression was induced by HPV16E6 in cervical cancer cells, suggesting that blockade of Axl signalling might be an effective way to reduce the progression of cervical cancer.

Axl acts as a tumor suppressor by regulating LIGHT expression in T lymphoma.

Axl is an oncogenic receptor tyrosine kinase that plays a role in many cancers. LIGHT (Lymphotoxin-related inducible ligand that competes for glycoprotein D binding to herpesvirus entry mediator on T cells) is a ligand that induces robust anti-tumor immunity by enhancing the recruitment and activation of effector immune cells at tumor sites. We observed that mouse EL4 and human Jurkat T lymphoma cells that stably overexpressed Axl also showed high expression of LIGHT. When Jurkat-Axl cells were treated with Gas6, a ligand for Axl, LIGHT expression was upregulated through activation of the PI3K/AKT signaling pathway and transcriptional induction by Sp1. The lytic activity of cytotoxic T lymphocytes and natural killer cells was enhanced by EL4-Axl cells. In addition, tumor volume and growth were markedly reduced due to enhanced apoptotic cell death in EL4-Axl tumor-bearing mice as compared to control mice. We also observed upregulated expression of CCL5 and its receptor, CCR5, and enhanced intratumoral infiltration of cytotoxic T lymphocytes and natural killer cells in EL4-Axl-bearing mice as compared to mock controls. These data strongly suggested that Axl exerts novel tumor suppressor effects by inducing upregulation of LIGHT in the tumor microenvironment of T lymphoma.

TREM2 promotes Aß phagocytosis by upregulating C/EBPα-dependent CD36 expression in microglia.

TREM2 plays a critical role in the alleviation of Alzheimer's disease by promoting Aß phagocytosis by microglia, but the detailed molecular mechanism underlying TREM2-induced direct phagocytic activity of Aß remains to be revealed. We found that learning and memory functions were improved in aged TREM2 TG mice, with the opposite effects in KO mice. The amount of phagocytosed Aß was significantly reduced in the primary microglia of KO mice. CD36 expression in primary microglia was greater in TG than in WT mice but was substantially decreased in KO mice. The expression of C/EBPα, an upstream transcriptional activator of CD36, was also elevated in primary microglia of TG mice but decreased in KO mice. The transcription of CD36 was markedly increased by TREM2 overexpression, and this effect was suppressed by a mutation of the C/EBPα binding site on the CD36 promoter. The TREM2-induced expression of CD36 and C/EBPα was inhibited by treatment with PI3K/AKT signaling blockers, and phosphorylation of AKT was elevated in TREM2-overexpressing BV2 cells. The present study provides evidence that TREM2 is required for preventing loss of memory and learning in Alzheimer's disease by regulating C/EBPα-dependent CD36 expression and the consequent Aß phagocytosis.

Bacterial ß-(1,3)-glucan prevents DSS-induced IBD by restoring the reduced population of regulatory T cells.

Bacterial ß-(1,3)-glucan has more advantages in terms of cost, yield and efficiency than that derived from mushrooms, plants, yeasts and fungi. We have previously developed a novel and high-yield ß-(1,3)-glucan produced by Agrobacterium sp. R259. This study aimed to elucidate the functional mechanism and therapeutic efficacy of bacterial ß-(1,3)-glucan in dextran sulfate sodium (DSS)-induced inflammatory bowel disease (IBD).Mice were orally pretreated with bacterial ß-(1,3)-glucan at daily doses of 2.5 or 5mg/kg for 2 weeks. After 6 days of DSS treatment, clinical assessment of IBD severity and expression of pro-inflammatory cytokines were evaluated. In vivo cell proliferation was examined by immunohistochemistry using Ki-67 and ER-TR7 antibodies. The frequency of regulatory T cells (Tregs) was analyzed by flow cytometry. Natural killer (NK) activity and IgA level were evaluated using NK cytotoxicity assay and ELISA.The deterioration of body weight gain, colonic architecture, disease score and histological score was recovered in DSS-induced IBD mice when pretreated with bacterial ß-(1,3)-glucan. The recruitment of macrophages and the gene expression of proinflammatory cytokines, such as IL-1ß, IL-6 and IL-17A/F, were markedly decreased in the colon of ß-(1,3)-glucan-pretreated mice. ß-(1,3)-Glucan induced the recovery of Tregs in terms of their frequency in DSS-induced IBD mice. Intriguingly, ß-(1,3)-glucan reversed the functional defects of NK cells and excessive IgA production in DSS-induced IBD mice.We conclude that bacterial ß-(1,3)-glucan prevented the progression of DSS-induced IBD by recovering the reduction of Tregs, functional defect of NK cells and excessive IgA production.

Differential gene expression profiles in spontaneously hypertensive rats induced by administration of enalapril and nifedipine.

Enalapril and nifedipine are used as antihypertensive drugs; however, the therapeutic target molecules regulated by enalapril and nifedipine have yet to be fully identified. The aim of this study was to identify novel target genes that are specifically regulated by enalapril and nifedipine in tissues from spontaneously hypertensive rats (SHR) using DNA microarray analysis. We found that administration of SHR with enalapril and nifedipine differentially regulated 33 genes involved in the pathogenesis of cardiovascular diseases. Furthermore, we identified 16 genes that have not previously been implicated in cardiovascular diseases, including interleukin-24 (IL-24). Among them, exogenous administration of IL-24 attenuated the expression of vascular inflammation and hypertension-related genes induced by H2O2 treatment in mouse vascular smooth muscle (MOVAS) cells. This study provides valuable information for the development of novel antihypertensive drugs. In addition, the genes identified may be of use as biomarkers and therapeutic targets for cardiovascular diseases, including hypertension.