Yoo Jin Choi

Identification of Arabidopsis rat mutants

Limited knowledge currently exists regarding the roles of plant genes and proteins in the Agrobacterium tumefaciens-mediated transformation process. To understand the host contribution to transformation, we carried out root-based transformation assays to identify Arabidopsis mutants that are resistant to Agrobacterium transformation (rat mutants). To date, we have identified 126 rat mutants by screening libraries of T-DNA insertion mutants and by using various “reverse genetic” approaches. These mutants disrupt expression of genes of numerous categories, including chromatin structural and remodeling genes, and genes encoding proteins implicated in nuclear targeting, cell wall structure and metabolism, cytoskeleton structure and function, and signal transduction. Here, we present an update on the identification and characterization of these rat mutants.

Resveratrol analog, HS-1793 enhance anti-tumor immunity by reducing the CD4+CD25 + regulatory T cells in FM3A tumor bearing mice

Natural agents with the immunomodulating property have been gaining traction to be employed in the complementary therapy of cancer because the ineffectiveness of numerous therapeutic strategies may be related in part to the tumor-induced immunosuppressive phenotypes, especially regulatory T (Treg) cells found in the tumor microenvironment. The present study was undertaken to examine whether HS-1793, synthetic resvertrol analog free from the restriction of metabolic instability and high dose requirement of resveratrol, induces an in vivo anti-tumor effect in FM3A tumor bearing mice through the suppression of Treg cells, which contribute to an increase in tumor specific cytotoxic T cell responses. Intraperitoneal injections of HS-1793 showed not only therapeutic benefits on established tumors, but also preventive anti-tumor effects. Treg cells (CD4+CD25+Foxp3+ cells) were significantly reduced in the total splenocytes as well as tumor tissues from HS-1793-administered mice, and the production of TGF-β inducing Treg showed a similar pattern. On the contrary, the administration of HS-1793 increased IFN-γ-expressing CD8+ T cells, upregulated IFN-γ production, and enhanced the cytotoxicity of splenocytes against FM3A tumor cells both in therapeutic and preventive experimental animals. These results demonstrated the suppressive role of HS-1793 on the function of Treg cells contributing to tumor specific cytotoxic T lymphocyte responses in tumor-bearing mice, which explained the underlying mechanism of the anti-tumor immunity of HS-1793.

The Anti-inflammatory Effects of Water Extract from Cordyceps militaris in Murine Macrophage

Abstract The aim of this study was to determine the in vitro anti-inflammatory effect of hot water extract from Cordyceps militaris fruiting bodies (CMWE) on lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) release in RAW 264.7 cells. The treatment of macrophages with various concentrations of hot CMWE significantly reduced LPS-induced production as well as NO, TNF-α and IL-6 secretion in a concentration-dependent manner. These results suggest that CMWE have potent inhibitory effects on the production of these inflammatory mediators.

Effect of Microalgal Extracts of Tetraselmis suecica against UVB-Induced Photoaging in Human Skin Fibroblasts

Exposure of cells to ultraviolet B (UVB) radiation can induce production of free radicals and reactive oxygen species (ROS), which damage cellular components. In addition, these agents can stimulate the expression of matrix metalloproteinase (MMP) and decrease collagen synthesis in human skin cells. In this study, we examined the anti-photoaging effects of extracts of Tetraselmis suecica (W-TS). W-TS showed the strongest scavenging activity against 2,2-difenyl-1-picrylhydrazyl (DPPH) and peroxyl radicals, followed by superoxide anions from the xanthine/xanthine oxidase system. We observed that the levels of both intracellular ROS and lipid peroxidation significantly increased in UVB-irradiated human skin fibroblast cells. Furthermore, the activities of enzymatic antioxidants (e.g., superoxide dismutase) and the levels of non-enzymatic antioxidants (e.g., glutathione) significantly decreased in cells. However, W-TS pretreatment, at the maximum tested concentration, significantly decreased intracellular ROS and malondialdehyde (MDA) levels, and increased superoxide dismutase and glutathione levels in the cells. At this same concentration, W-TS did not show cytotoxicity. Type 1 procollagen and MMP-1 released were quantified using RT-PCR techniques. The results showed that W-TS protected type 1 procollagen against UVBinduced depletion in fibroblast cells in a dose-dependent manner via inhibition of UVB-induced MMP-1. Taken together, the results of the study suggest that W-TS effectively inhibits UVB-induced photoaging in skin fibroblasts by its strong anti-oxidant ability.

Methanolic Extract of Asterina pectinifera inhibits LPS-Induced Inflammatory Mediators in Murine Macrophage

This study aimed to elucidate anti-inflammatory activities from extracts of Asterina pectinifera on nitric oxide (NO) production, TNF-α and IL-6 release in lipopolysaccharide (LPS) -stimulated murine macrophage cell, RAW264.7. We prepared the methanolic extracts (60-MAP, 70-MAP, 80-MAP and 90-MAP) , aqueous extract (W-AP) and functional bioactive compound fraction (He-AP and EA-AP) from Asterina pectinifera according to extract method. The 60-MAP, 70-MAP, 80-MAP, 90-MAP and W-AP were significantly suppressed LPS-induced production NO, TNF-α and IL-6 secretion in a concentration-dependent manner (P < 0.05) . Especially, 80-MAP by extracted 80% methanol had the strongest activity in reduction of inflammatory mediators among these extracts. Indeed, to identify active fraction, which contained potential bioactive compounds, from 80-MAP of Asterina pectinifera, we tested anti-inflammatory activity of the He-AP or the EA-AP. The He-AP was next extracted from 80-MAP and the EA-AP were extracted from the other methanol layer except the He-AP. The EA-AP demonstrated a strong anti-inflammatory effect through its ability to reduce NO production and it also inhibited the production of proinflammatory cytokines such as IL-6 and TNF-α at low concentration. These results suggested that the methanolic extract from Asterina pectinifera had the potential inhibitory effects on the production of these inflammatory mediators.

In Vitro Genotoxicity Assessment of a Novel Resveratrol Analogue, HS-1793.

Resveratrol has received considerable attention as a polyphenol with various biological effects such as anti-inflammatory, anti-oxidant, anti-mutagenic, anti-carcinogenic, and cardioprotective properties. As part of the overall safety assessment of HS-1793, a novel resveratrol analogue free from the restriction of metabolic instability and the high dose requirement of resveratrol, we assessed genotoxicity in three in vitro assays: a bacterial mutation assay, a comet assay, and a chromosomal aberration assay. In the bacterial reverse mutation assay, HS-1793 did not increase revertant colony numbers in S. typhimurium strains (TA98, TA100, TA1535 and TA1537) or an E. coli strain (WP2 uvrA) regardless of metabolic activation. HS-1793 showed no evidence of genotoxic activity such as DNA damage on L5178Y Tk+/− mouse lymphoma cells with or without the S9 mix in the in vitro comet assay. No statistically significant differences in the incidence of chromosomal aberrations following HS-1793 treatment was observed on Chinese hamster lung cells exposed with or without the S9 mix. These results provide additional evidence that HS-1793 is non-genotoxic at the dose tested in three standard tests and further supports the generally recognized as safe determination of HS-1793 during early drug development.

EpCAM peptide-primed dendritic cell vaccination confers significant anti-tumor immunity in hepatocellular carcinoma cells

Cancer stem-like cells (CSCs) may play a key role in tumor initiation, self-renewal, differentiation, and resistance to current treatments. Dendritic cells (DCs) play a vital role in host immune reactions as well as antigen presentation. In this study, we explored the suitability of using CSC peptides as antigen sources for DC vaccination against human breast cancer and hepatocellular carcinoma (HCC) with the aim of achieving CSC targeting and enhancing anti-tumor immunity. CD44 is used as a CSC marker for breast cancer and EpCAM is used as a CSC marker for HCC. We selected CD44 and EpCAM peptides that bind to HLA-A2 molecules on the basis of their binding affinity, as determined by a peptide-T2 binding assay. Our data showed that CSCs express high levels of tumor-associated antigens (TAAs) as well as major histocompatibility complex (MHC) molecules. Pulsing DCs with CD44 and EpCAM peptides resulted in the efficient generation of mature DCs (mDCs), thus enhancing T cell stimulation and generating potent cytotoxic T lymphocytes (CTLs). The activation of CSC peptide-specific immune responses by the DC vaccine in combination with standard chemotherapy may provide better clinical outcomes in advanced carcinomas.

In vitro and in vivo anti-inflammatory effects of pegmatite

Pegmatite is a coarse-grained intrusive igneous rock rich in rare elements such as uranium, tungsten, and tantalum with Ca, K, Mg, Fe, Se, Ge, and Ho. We tested in vitro and in vivo assays for the anti-inflammatory activity of pegmatites. We firstly evaluated the suppressive effects of pegmatite on macrophage cell line RAW 264.7 cells stimulated with proinflammatory stimuli lipopolysaccharide (LPS) to determine nitric oxide (NO) production and TNF-α and IL-6 release. The IC50 values of pegmatite exceeded 5,000 μg/mL. Treatment of RAW 264.7 cells with pegmatite significantly inhibited LPS-stimulated NO production and proinflammatory cytokines such as TNF-α and IL-6 secretion in a dose-dependent manner (P<0.05). In vivo studies were tested with two animal models of arachidonic acid-induced mouse ear edema and an acetic acid-induced increase in capillary permeability. The pegmatite significantly attenuated ear edema induced by arachidonic acid and reduced the acetic acid-induced increase in capillary permeability in mice (P<0.05) when the pegmatite was administered topically (10 mg per ear) for 24 h. Therefore, pegmatite potentially shows an anti-inflammatory activity in the in vitro and in vivo mice and in the development of newer anti-inflammatory agents as mineral materials.

Radical Scavenging Activities of Phellinus pini

The concentration of phenolics in Phellinus pini (CY001) extracts, expressed as mg of GAEs per g of P. pini fractions, and the EtOAc fraction (436.5 ㎎ GAEs/g) of P. pini had a higher phenolic content than other fractions. Several biochemical assays were used to screen antioxidant properties such as reducing power, 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, NBT/XO superoxide system and inhibition of DCF/AAPH peroxyl radicals. Among the six mushroom extracts, the EtOAc fraction from P. pini (CY001) showed the most potent DPPH radical, superoxide radical, and peroxyl radical scavenging activities, with IC 50 values of 11.49 ㎍/ml, 8.32 ㎍/㎖, and 1.91 μg/㎖, respectively. The EtOAc fraction of P. pini (CY001) significantly inhibited enzymatic lipid peroxidation and effectively attenuated LPS-induced NO production of RAW 264.7 cells without cytotoxicity. We also found that the EtOAc fraction had a significant hepato-protectant effect on tacrine-induced cytotoxicity in HepG2 cells. These findings suggest that P. pini (CY001) may have potential as a natural antioxidant, which contains compound(s) with radical scavenging activity.