Seok Joo Kwon

Bio: Seok Joo Kwon is an academic researcher from Rutgers University. The author has contributed to research in topics: Prostate cancer & Bone morphogenetic protein. The author has an hindex of 12, co-authored 20 publications receiving 706 citations. Previous affiliations of Seok Joo Kwon include National Institutes of Health.

Peracetylation as a means of enhancing in vitro bioactivity and bioavailability of epigallocatechin-3-gallate.

Abstract: (-)-Epigallocatechin-3-gallate (EGCG) is the widely studied catechin in green tea (Camellia sinensis). Previously, we have reported the low bioavailability of EGCG in rats and mice. As a means of improving the bioavailability of EGCG, we have prepared a peracetylated EGCG derivative (AcEGCG) and herein report its growth inhibitory activity and cellular uptake in vitro, as well as bioavailability in mice. AcEGCG exhibited enhanced growth inhibitory activity relative to EGCG in both KYSE150 human esophageal (IC50 = 10 versus 20 microM) and HCT116 human colon cancer cells (IC50 = 32 versus 45 microM). AcEGCG was rapidly converted to EGCG by HCT116 cells, and treatment of cells with AcEGCG resulted in a 2.8- to 30-fold greater intracellular concentration of EGCG as compared with treatment with EGCG. AcEGCG was also more potent than EGCG at inhibiting nitric oxide production (4.4-fold) and arachidonic acid release (2.0-fold) from lipopolysaccharide-stimulated RAW264.7 murine macrophages. Intragastric administration of AcEGCG to CF-1 mice resulted in higher bioavailability compared with administration of equimolar doses of EGCG. The plasma area under the curve from 0 to infinity (AUC0-->infinity) of total EGCG was 465.0 and 194.6 [(microg/ml) . min] from the administration of AcEGCG and EGCG, respectively. The t1/2 of EGCG was also increased following administration of AcEGCG compared with EGCG (441.0 versus 200.3 min). The AUC0-->infinity and t1/2 were also increased in small intestinal (2.8- and 4.3-fold, respectively) and colonic tissues (2.4- and 6.0-fold, respectively). These data suggest that acetylation represents a means of increasing the biological potency in vitro, increasing the bioavailability of EGCG in vivo, and may improve cancer-preventive activity.

Modulation of arachidonic acid metabolism and nitric oxide synthesis by garcinol and its derivatives

Abstract: Garcinol, a polyisoprenylated benzophenone, from the fruit rind of Garcinia spp., has been shown to have anti-inflammatory and anticarcinogenic activities. To study its mechanism of action, we analyzed the effects of garcinol and its derivatives, including cambogin, garcim-1 and garcim-2, on arachidonic acid metabolism and nitric oxide (NO) synthesis in lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages as well as in three intestinal cell lines. We also examined the effect of garcinol on cytosolic phospholipase A2 (cPLA2), cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), and related upstream signaling. At 1 microM, garcinol and its derivatives, added 1 h after LPS stimulation, significantly inhibited the release of arachidonic acid and its metabolites in macrophages; garcinol was the most effective, showing >50% inhibition. Similar inhibitory activity was also observed in intestinal cells, HT-29, HCT-116 and IEC-6 cells, showing 40-50% inhibition by 1 microM garcinol. In LPS-stimulated macrophages, garcinol inhibited the phosphorylation of cPLA2 without altering its protein level, and the effect was related to the inhibition of ERK1/2 phosphorylation. Garcinol inhibited NFkappaB activation and COX-2 expression only when it was added to the cells before LPS stimulation. Garcinol (1 microM) also significantly decreased iNOS expression and NO release from LPS-stimulated macrophages; this is probably due to the inhibition of the signal transducer and activator of transcription-1 (STAT-1), an upstream event in the activation of iNOS synthesis. The results suggest that garcinol modulates arachidonic acid metabolism by blocking the phosphorylation of cPLA2 and decreases iNOS protein level by inhibiting STAT-1 activation. These activities may contribute to the anti-inflammatory and anticarcinogenic actions of garcinol and its derivatives.

Effect of bone morphogenetic protein‐6 on macrophages

Abstract: Bone morphogenetic proteins (BMPs) are members of the transforming growth factor (TGF)-beta superfamily which regulates bone formation, haematopoiesis and development. While TGF-beta is known to be a negative regulator of the immune system, the effect of BMPs on the immune system is largely unknown. Herein, the effect of BMP-6 on the innate immune system was investigated using the murine macrophage cell line RAW 264.7. BMP-6 altered cellular morphology, inhibited cellular proliferation, increased the fraction of subG(1) phase cells, and decreased the fraction of cells in the S and G(2)M phases, without changing the percentage of apoptotic cells. In addition, BMP-6 induced expression of pro-inflammatory inducible nitric oxide synthase (iNOS) and the cytokine tumour necrosis factor (TNF)-alpha. Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated the expression of all three known type II BMP receptors [BMP-RII, activin (Act)-RIIA and Act-RIIB] and two of the three known type I receptors [activin receptor-like kinase 2 (ALK2) and ALK3]. Over-expression as well as knock-down studies using short hairpin RNA (shRNA) demonstrated that BMP-RII, ALK2 and ALK3 are the functional BMP-6 receptors in macrophages. Finally, the effect of BMP-6 was confirmed in murine peritoneal macrophages and the THP-1 human monocyte cell line. Taken together, these results demonstrate that BMP-6 regulates the proliferation and gene expression profile of macrophages.

BMP-6 in Renal Cell Carcinoma Promotes Tumor Proliferation through IL-10–Dependent M2 Polarization of Tumor-Associated Macrophages

Abstract: Dysregulated bone morphogenetic proteins (BMP) may contribute to the development and progression of renal cell carcinoma (RCC). Herein, we report that BMP-6 promotes the growth of RCC by interleukin (IL)-10-mediated M2 polarization of tumor-associated macrophages (TAM). BMP-6-mediated IL-10 expression in macrophages required Smad5 and STAT3. In human RCC specimens, the three-marker signature BMP-6/IL-10/CD68 was associated with a poor prognosis. Furthermore, patients with elevated IL-10 serum levels had worse outcome after surgery. Together, our results suggest that BMP-6/macrophage/IL-10 regulates M2 polarization of TAMs in RCC.

Exogenous antioxidants--Double-edged swords in cellular redox state: Health beneficial effects at physiologic doses versus deleterious effects at high doses.

Abstract: The balance between oxidation and antioxidation is believed to be critical in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system including e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and others, allows the elimination of excess reactive oxygen species (ROS) including, among others superoxide anions (O2(·-)), hydroxyl radicals (OH·), alkoxyl radicals (RO·) and peroxyradicals (ROO·). However, our endogenous antioxidant defense systems are incomplete without exogenous originating reducing compounds such as vitamin C, vitamin E, carotenoids and polyphenols, playing an essential role in many antioxidant mechanisms in living organisms. Therefore, there is continuous demand for exogenous antioxidants in order to prevent oxidative stress, representing a disequilibrium redox state in favor of oxidation. However, high doses of isolated compounds may be toxic, owing to prooxidative effects at high concentrations or their potential to react with beneficial concentrations of ROS normally present at physiological conditions that are required for optimal cellular functioning. This review aims to examine the double-edged effects of dietary originating antioxidants with a focus on the most abundant compounds, especially polyphenols, vitamin C, vitamin E and carotenoids. Different approaches to enrich our body with exogenous antioxidants such as via synthetic antioxidants, diets rich in fruits and vegetables and taking supplements will be reviewed and experimental and epidemiological evidences discussed, highlighting that antioxidants at physiological doses are generally safe, exhibiting interesting health beneficial effects.

Role of tumor associated macrophages in tumor angiogenesis and lymphangiogenesis.

Abstract: Tumor angiogenesis is an essential process for supplying rapidly growing malignant tissues with essential nutrients and oxygen. An angiogenic switch allows tumor cells to survive and grow, and provides them access to vasculature resulting in metastatic disease. Monocyte-derived macrophages recruited and reprogrammed by tumor cells serve as a major source of angiogenic factors boosting the angiogenic switch. Tumor endothelium releases angiopoietin-2 and further facilitates recruitment of TIE2 receptor expressing monocytes (TEM) into tumor sites. Tumor-associated macrophages (TAM) sense hypoxia in avascular areas of tumors, and react by production of angiogenic factors such as VEGFA. VEGFA stimulates chemotaxis of endothelial cells (EC) and macrophages. In some tumors, TAM appeared to be a major source of MMP9. Elevated expression of MMP9 by TAM mediates extracellular matrix (ECM) degradation and the release of bioactive VEGFA. Other angiogenic factors released by TAM include basic fibroblast growth factor (bFGF), thymidine phosphorylase (TP), urokinase-type plasminogen activator (uPA), and adrenomedullin (ADM). The same factors used by macrophages for the induction of angiogenesis [like vascular endothelial growth factor A (VEGF-A) and MMP9] support lymphangiogenesis. TAM can express LYVE-1, one of the established markers of lymphatic endothelium. TAM support tumor lymphangiogenesis not only by secretion of pro-lymphangiogenic factors but also by trans-differentiation into lymphatic EC. New pro-angiogenic factor YKL-40 belongs to a family of mammalian chitinase-like proteins (CLP) that act as cytokines or growth factors. Human CLP family comprises YKL-40, YKL-39, and SI-CLP. Production of all three CLP in macrophages is antagonistically regulated by cytokines. It was recently established that YKL-40 induces angiogenesis in vitro and in animal tumor models. YKL-40-neutralizing monoclonal antibody blocks tumor angiogenesis and progression. The role of YKL-39 and SI-CLP in tumor angiogenesis and lymphangiogenesis remains to be investigated.

Anti-infective properties of epigallocatechin-3-gallate (EGCG), a component of green tea.

Abstract: The consumption of green tea (Camellia sinensis) has been shown to have many physiological and pharmacological health benefits. In the past two decades several studies have reported that epigallocatechin-3-gallate (EGCG), the main constituent of green tea, has anti-infective properties. Antiviral activities of EGCG with different modes of action have been demonstrated on diverse families of viruses, such as Retroviridae, Orthomyxoviridae and Flaviviridae and include important human pathogens like human immunodeficiency virus, influenza A virus and the hepatitis C virus. Furthermore, the molecule interferes with the replication cycle of DNA viruses like hepatitis B virus, herpes simplex virus and adenovirus. Most of these studies demonstrated antiviral properties within physiological concentrations of EGCG in vitro. In contrast, the minimum inhibitory concentrations against bacteria were 10–100-fold higher. Nevertheless, the antibacterial effects of EGCG alone and in combination with different antibiotics have been intensively analysed against a number of bacteria including multidrug-resistant strains such as methicillin-resistant Staphylococcus aureus or Stenotrophomonas maltophilia. Furthermore, the catechin EGCG has antifungal activity against human-pathogenic yeasts like Candida albicans. Although the mechanistic effects of EGCG are not fully understood, there are results indicating that EGCG binds to lipid membranes and affects the folic acid metabolism of bacteria and fungi by inhibiting the cytoplasmic enzyme dihydrofolate reductase. This review summarizes the current knowledge and future perspectives on the antibacterial, antifungal and antiviral effects of the green tea constituent EGCG.