Yong Hyun Jeon

Regulation of systemic energy homeostasis by serotonin in adipose tissues

Central serotonin (5-HT) is an anorexigenic neurotransmitter in the brain. However, accumulating evidence suggests peripheral 5-HT may affect organismal energy homeostasis. Here we show 5-HT regulates white and brown adipose tissue function. Pharmacological inhibition of 5-HT synthesis leads to inhibition of lipogenesis in epididymal white adipose tissue (WAT), induction of browning in inguinal WAT and activation of adaptive thermogenesis in brown adipose tissue (BAT). Mice with inducible Tph1 KO in adipose tissues exhibit a similar phenotype as mice in which 5-HT synthesis is inhibited pharmacologically, suggesting 5-HT has localized effects on adipose tissues. In addition, Htr3a KO mice exhibit increased energy expenditure and reduced weight gain when fed a high-fat diet. Treatment with an Htr2a antagonist reduces lipid accumulation in 3T3-L1 adipocytes. These data suggest important roles for adipocyte-derived 5-HT in controlling energy homeostasis.

Trafficking Macrophage Migration Using Reporter Gene Imaging with Human Sodium Iodide Symporter in Animal Models of Inflammation

The aim of this study was to investigate the feasibility of nuclear molecular imaging using the human sodium iodide symporter (hNIS) as a reporter gene to monitor macrophage migration toward the inflammatory foci. Methods: A stable macrophage cell line coexpressing hNIS and green fluorescent protein (GFP) genes (RAW264.7/hNIS-GFP and RNIS cell) was established from an immortalized macrophage cell line (RAW264.7 cells). 125I uptake was determined (for hNIS protein functional activity), and flow cytometry analysis (to examine GFP gene expression), a cell proliferation assay, a cytokine assay, and a phagocytic activity assay were performed. 99mTc-pertechnetate images were acquired at 1 d after subcutaneous inoculation of RNIS cells in nude mice. Chemical inflammation was induced for in vivo imaging in the thigh of nude mice by turpentine oil injection. Small-animal PET with 18F-FDG and 124I was performed with an intravenous administration of RAW264.7 or RNIS cells in inflammation-induced animals. Results: The expression of hNIS and GFP genes was confirmed in RNIS cells by flow cytometry and immunofluorescent staining. 125I uptake was about 67 times higher in RNIS cells than in RAW264.7 cells. No significant difference was observed in cell proliferation, cytokine production, and phagocytic activity between RAW264.7 and RNIS cells. 99mTc-pertechnetate imaging revealed increased tracer uptake at the inoculation site. PET with 124I demonstrated a donut-shaped uptake, correlating with uptake shown by the 18F-FDG PET images, at the inflammation site of mice administered RNIS cells. 124I uptake (percentage injected dose per gram) was about 2.12 times higher at the inflammation site in the RNIS mice than in RAW264.7 mice. By immunohistochemistry, the migration of macrophages was further confirmed by positive staining for GFP and hNIS at the inflammation site of RNIS mice. Conclusion: These data support the feasibility of hNIS reporter gene imaging to monitor the macrophage migration toward an inflammatory lesion. Macrophages expressing hNIS may provide a new strategy to investigate the cellular behavior seen with inflammatory response in a preclinical model.

Fibroblast growth factor 21 analogue LY2405319 lowers blood glucose in streptozotocin-induced insulin-deficient diabetic mice by restoring brown adipose tissue function.

To investigate the effects of LY2405319, an analogue of fibroblast growth factor 21 (FGF21), on glucose homeostasis in streptozotocin (STZ)‐induced insulin‐deficient mice (STZ mice).

Suppression of tumorigenesis in mitochondrial NADP(+)-dependent isocitrate dehydrogenase knock-out mice.

The tumor host microenvironment is increasingly viewed as an important contributor to tumor growth and suppression. Cellular oxidative stress resulting from high levels of reactive oxygen species (ROS) contributes to various processes involved in the development and progress of malignant tumors including carcinogenesis, aberrant growth, metastasis, and angiogenesis. In this regard, the stroma induces oxidative stress in adjacent tumor cells, and this in turn causes several changes in tumor cells including modulation of the redox status, inhibition of cell proliferation, and induction of apoptotic or necrotic cell death. Because the levels of ROS are determined by a balance between ROS generation and ROS detoxification, disruption of this system will result in increased or decreased ROS level. Recently, we demonstrated that the control of mitochondrial redox balance and cellular defense against oxidative damage is one of the primary functions of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDH2) that supplies NADPH for antioxidant systems. To explore the interactions between tumor cells and the host, we evaluated tumorigenesis between IDH2-deficient (knock-out) and wild-type mice in which B16F10 melanoma cells had been implanted. Suppression of B16F10 cell tumorigenesis was reproducibly observed in the IDH2-deficient mice along with significant elevation of oxidative stress in both the tumor and the stroma. In addition, the expression of angiogenesis markers was significantly down-regulated in both the tumor and the stroma of the IDH2-deficient mice. These results support the hypothesis that redox status-associated changes in the host environment of tumor-bearing mice may contribute to cancer progression.

Combined Positron Emission Tomography and Cerenkov Luminescence Imaging of Sentinel Lymph Nodes Using PEGylated Radionuclide-Embedded Gold Nanoparticles.

New imaging probes with high sensitivity and stability are urgently needed to accurately detect sentinel lymph nodes (SLNs) for successful cancer diagnosis. Herein, the use of highly sensitive and stable PEGylated radionuclide-embedded gold nanoparticles (PEG-RIe-AuNPs) is reported for the detection of SLNs by combined positron emission tomography and Cerenkov luminescence imaging (PET/CLI). PEG-RIe-AuNPs show high sensitivity and stability both in vitro and in vivo, and are not toxic to normal ovarian and immune cells. In vivo PET/CLI imaging clearly reveals SLNs as early as 1 h post PEG-RIe-AuNP-injection, with peak signals achieved at 6 h postinjection, which is consistent with the biodistribution results. Taken together, the data provide strong evidence that PEG-RIe-AuNPs are promising as potential lymphatic tracers in biomedical imaging for pre and intraoperative surgical guidance.

Retinoic acid‐related orphan receptor alpha reprograms glucose metabolism in glutamine‐deficient hepatoma cells

The metabolism of glutamine and glucose is recognized as a promising therapeutic target for the treatment of cancer; however, targeted molecules that mediate glutamine and glucose metabolism in cancer cells have not been addressed. Here, we show that restricting the supply of glutamine in hepatoma cells, including HepG2 and Hep3B cells, markedly increased the expression of retinoic acid‐related orphan receptor alpha (RORα). Up‐regulation of RORα in glutamine‐deficient hepatoma cells resulted from an increase in the level of cellular reactive oxygen species and in the nicotinamide adenine dinucleotide phosphate/nicotinamide adenine dinucleotide phosphate reduced (NADP+/NADPH) ratio, which was consistent with a reduction in the glutathione/glutathione disulfide (GSH/GSSG) ratio. Adenovirus (Ad)‐mediated overexpression of RORα (Ad‐RORα) or treatment with the RORα activator, SR1078, reduced aerobic glycolysis and down‐regulated biosynthetic pathways in hepatoma cells. Ad‐RORα and SR1078 reduced the expression of pyruvate dehydrogenase kinase 2 (PDK2) and inhibited the phosphorylation of pyruvate dehydrogenase and subsequently shifted pyruvate to complete oxidation. The RORα‐mediated decrease in PDK2 levels was caused by up‐regulation of p21, rather than p53. Furthermore, RORα inhibited hepatoma growth both in vitro and in a xenograft model in vivo. We also found that suppression of PDK2 inhibited hepatoma growth in a xenograft model. These findings mimic the altered glucose utilization and hepatoma growth caused by glutamine deprivation. Finally, tumor tissue from 187 hepatocellular carcinoma patients expressed lower levels of RORα than adjacent nontumor tissue, supporting a potential beneficial effect of RORα activation in the treatment of liver cancer. Conclusion: RORα mediates reprogramming of glucose metabolism in hepatoma cells in response to glutamine deficiency. The relationships established here between glutamine metabolism, RORα expression and signaling, and aerobic glycolysis have implications for therapeutic targeting of liver cancer metabolism. (Hepatology 2015;61:953–964)

Enhancement of Natural Killer Cell Cytotoxicity by Sodium/Iodide Symporter Gene-Mediated Radioiodine Pretreatment in Breast Cancer Cells

A phase II study of NK cell therapy in treatment of patients with recurrent breast cancer has recently been reported. However, because of the complexities of tumor microenvironments, effective therapeutic effects have not been achieved in NK cell therapy. Radioiodine (I-131) therapy inhibits cancer growth by inducing the apoptosis and necrosis of cancer cells. Furthermore, it can modify cancer cell phenotypes and enhance the effect of immunotherapy against cancer cells. The present study showed that I-131 therapy can modulate microenvironment of breast cancer and improve the therapeutic effect by enhancing NK cell cytotoxicity to the tumor cells. The susceptibility of breast cancer cells to NK cell was increased by precedent I-131 treatment in vitro. Tumor burden in mice treated with I-131 plus NK cell was significantly lower than that in mice treated with NK cell or I-131 alone. The up-regulation of Fas, DR5 and MIC A/B on irradiated tumor cells could be the explanation for the enhancement of NK cell cytotoxicity to tumor cells. It can be applied to breast cancer patients with iodine avid metastatic lesions that are non-responsive to conventional treatments.

In Vivo Tracking of Chemokine Receptor CXCR4-Engineered Mesenchymal Stem Cell Migration by Optical Molecular Imaging

CXCR4, the stromal cell-derived factor-1 receptor, plays an important role in the migration of hematopoietic progenitor/stem cells to injured and inflamed areas. Noninvasive cell tracking methods could be useful for monitoring cell fate. Therefore, in this study, we evaluated the efficacy of an intravenous infusion of genetically engineered mesenchymal stem cells (MSCs) overexpressing CXC chemokine receptor 4 (CXCR4) to home to the tumor, by optical imaging. We constructed a retroviral vector containing CXCR with dual reporter genes, eGFP and Fluc2, under the control of an EF1α promoter (pBABE-EF1α-CXCR4-eGFP-IRES-Fluc2). We also developed an eGFP-Fluc2 construct in the Retro-X retroviral vector (Retro-X-eGFP-Fluc2). MSCs were transduced with retroviruses to generate CXCR4-overexpressing MSCs (MSC-CXCR4/Fluc2) and MSCs (MSC/Fluc2). CXCR4 mRNA and protein expression was confirmed by RT-PCR and Western blotting, respectively, and it was higher in MSC-CXCR4/Fluc2 than in naive MSCs. eGFP expression was confirmed by confocal microscopy. The transfected MSC-CXCR4/Fluc2 cells showed higher migratory capacity than naive MSCs observed in Transwell migration assay. The in vivo migration of CXCR4-overexpressing MSCs to MDAMB231/Rluc tumor model by BLI imaging was also confirmed. Intravenous delivery of genetically modified MSCs overexpressing CXCR4 with a Fluc2 reporter gene may be a useful, noninvasive BLI imaging tool for tracking cell fate.

Combined E7-Dendritic Cell-Based Immunotherapy and Human Sodium/Iodide Symporter Radioiodine Gene Therapy with Monitoring of Antitumor Effects by Bioluminescent Imaging in a Mouse Model of Uterine Cervical Cancer

Using a uterine cervical cancer cell line expressing human papillomavirus (HPV) 16 E7 antigen and bioluminescent imaging (BLI), we evaluated the therapeutic potential of combined immunotherapy using transfected dendritic cells (DC-E7) and human sodium/iodide symporter (hNIS) radioiodine gene therapy in a xenograft animal cancer model. Dendritic cells expressing either E7 antigen (DC-E7) or no-insert (DC-no insert) were made for immunization materials, and murine uterine cervical cancer cell line coexpressing E7, firefly luciferase, hNIS, and EGFP genes (TC-1/FNG) were prepared for the animal tumor model. C57BL/6 mice were divided into five therapy groups (phosphate-buffered saline [PBS], DC-no insert, DC-E7, I-131, and DC-E7+I-131 groups). Single therapy with either DC-E7 or I-131 induced greater retardation in tumor growth compared with PBS or DC-no insert groups, and it resulted in some tumor-free mice (DC-E7 and I-131 groups, 40% and 20%, respectively). Combination therapy with DC-E7 and I-131 dramatically inhibited tumor growth, thus causing complete disappearance of tumors in all mice, and these effects were further confirmed by BLI in vivo. In conclusion, complete disappearance of the tumor was achieved with combined DC-E7 vaccination and hNIS radioiodine gene therapy in a mouse model with E7-expressing uterine cervical cancer, and serial BLIs successfully demonstrated antitumor effects in vivo.

Visualization of Macrophage Recruitment to Inflammation Lesions using Highly Sensitive and Stable Radionuclide-Embedded Gold Nanoparticles as a Nuclear Bio-Imaging Platform

Reliable and sensitive imaging tools are required to track macrophage migration and provide a better understating of their biological roles in various diseases. Here, we demonstrate the possibility of radioactive iodide-embedded gold nanoparticles (RIe-AuNPs) as a cell tracker for nuclear medicine imaging. To demonstrate this utility, we monitored macrophage migration to carrageenan-induced sites of acute inflammation in living subjects and visualized the effects of anti-inflammatory agents on this process. Macrophage labeling with RIe-AuNPs did not alter their biological functions such as cell proliferation, phenotype marker expression, or phagocytic activity. In vivo imaging with positron-emission tomography revealed the migration of labeled macrophages to carrageenan-induced inflammation lesions 3 h after transfer, with highest recruitment at 6 h and a slight decline of radioactive signal at 24 h; these findings were highly consistent with the data of a bio-distribution study. Treatment with dexamethasone (an anti-inflammation drug) or GSK5182 (an ERRγ inverse agonist) hindered macrophage recruitment to the inflamed sites. Our findings suggest that a cell tracking strategy utilizing RIe-AuNPs will likely be highly useful in research related to macrophage-related disease and cell-based therapies.