Chul-Hoon Lee

Suppression of Inflammatory Responses by Surfactin, a Selective Inhibitor of Platelet Cytosolic Phospholipase A2

Surfactin inhibits platelet and spleen cytosolic 100 kDa phospholipase A2 (PLA2). In contrast, this same compound enhances rat platelet group II PLA2 activity by approximately 2-fold and slightly increases group I PLA2 activity from porcine pancreas and Naja naja venom in vitro. Surfactin does not affect a Ca2+ -independent PLA2 partially purified from bovine brain. Thus, this compound inhibits selectively the cytosolic form of PLA2. Based on in vitro studies utilizing preincubation of surfactin with the enzyme, dialysis, and increased concentrations of substrates, the inhibitory effect of surfactin appears to be due to a direct interaction with the enzyme. Linear regression analysis of the linear portion of a concentration-response curve reveals an IC50 of 8.5 microM. To further determine the inhibitory pattern, a Dixon plot was constructed to show that the inhibition by surfactin is competitive, but not uncompetitive, with an inhibition constant of Ki = 4.7 microM in 50 mM Tris-HCl buffer, pH 8.0, at 37 degrees. Surfactin blocked non-stimulated and calcium ionophore A23187-stimulated release of arachidonic acid from monkey kidney CV-1 cells, which contain a cytosolic 100 kDa PLA2 as the major activity, as shown in an anionic exchange DEAE-5PW high performance liquid chromatography profile and western blotting analysis. Surfactin ameliorated inflammation induced by several chemicals. That is, it exhibited in vivo anti-inflammatory activity in several tested inflammatory reactions including 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema, carrageenan-induced rat paw edema, and acetic acid-induced mouse writhing. These results demonstrate that surfactin is a selective inhibitor for cytosolic PLA2 and a putative anti-inflammatory agent through the inhibitory effect produced by direct interaction with cytosolic PLA2, and that inhibition of cytosolic PLA2 activity may suppress inflammatory responses.

Mitogen-activated protein kinase and activator protein-1 dependent signals are essential for Bacteroides fragilis enterotoxin-induced enteritis.

The approximately 20‐kDa heat‐labile toxin produced by enterotoxigenic Bacteroides fragilis is known to be associated with the development of enteritis. However, the molecular mechanism involved is not yet fully understood. In this study, we assessed whether B. fragilis enterotoxin (BFT)‐induced enteritis is related to mitogen‐activated protein kinase (MAPK) signaling pathways. In human colon epithelial cells, BFT activated three major MAPK cascades. The activation of p38 was sustained for a relatively long period, while the stimulation of extracellular signal‐regulated kinases (ERK) and c‐Jun N‐terminal kinase (JNK) was transient. BFT stimulation also activated AP‐1 signals composed of c‐Jun/c‐Fos heterodimers. The p38 inhibitor SB203580 and the ERK inhibitor U0126 reduced not only AP‐1 activity, but also decreased IL‐8 and MCP‐1 expression. In addition, the overexpression of superrepressors for c‐Jun and Ras induced by BFT stimulation decreased the levels of IL‐8 and MCP‐1 production. Furthermore, SB203580 prevented BFT‐induced colitis in the mouse ileum, as evidenced by significant decreases in villous destruction, neutrophil infiltration, and mucosal congestion. These results suggest that a pathway, including Ras, MAPK, and subsequent AP‐1 activation, is required for IL‐8 and MCP‐1 expression in intestinal epithelial cells exposed to BFT, and can be involved in the development of enteritis.

Localized mucosal involvement and severe pulmonary involvement in a young patient with paraneoplastic pemphigus associated with Castleman's tumour

We describe a 19‐year‐old female patient who developed recurrent ulcerations limited to the orogenital mucosa for the last 3 years. She also developed dyspnoea 5 months after the onset of the orogenital lesions. Castlemans tumour of the retroperitoneum was found incidentally during routine physical examination. The diagnosis of paraneoplastic pemphigus (PNP) was made by pathological and immunological studies. The orogenital ulceration responded well to corticosteroid therapy, but severe bronchiolitis obliterans progressed despite intensive care. The patient eventually died from respiratory failure. This case demonstrates the diversity of clinical features of paraneoplastic pemphigus.

Anti-allergic and anti-inflammatory effects of butanol extract from Arctium Lappa L

BackgroundAtopic dermatitis is a chronic, allergic inflammatory skin disease that is accompanied by markedly increased levels of inflammatory cells, including eosinophils, mast cells, and T cells. Arctium lappa L. is a traditional medicine in Asia. This study examined whether a butanol extract of A. lappa (ALBE) had previously unreported anti-allergic or anti-inflammatory effects.MethodsThis study examined the effect of ALBE on the release of β-hexosaminidase in antigen-stimulated-RBL-2H3 cells. We also evaluated the ConA-induced expression of IL-4, IL-5, mitogen-activated protein kinases (MAPKs), and nuclear factor (NF)-κB using RT-PCR, Western blotting, and ELISA in mouse splenocytes after ALBE treatment.ResultsWe observed significant inhibition of β-hexosaminidase release in RBL-2H3 cells and suppressed mRNA expression and protein secretion of IL-4 and IL-5 induced by ConA-treated primary murine splenocytes after ALBE treatment. Additionally, ALBE (100 μg/mL) suppressed not only the transcriptional activation of NF-κB, but also the phosphorylation of MAPKs in ConA-treated primary splenocytes.ConclusionsThese results suggest that ALBE inhibits the expression of IL-4 and IL-5 by downregulating MAPKs and NF-κB activation in ConA-treated splenocytes and supports the hypothesis that ALBE may have beneficial effects in the treatment of allergic diseases, including atopic dermatitis.

Effects of Korean Red Ginseng Extract for the Treatment of Atopic Dermatitis-Like Skin Lesions in Mice

Atopic dermatitis (AD) is an allergic, inflammatory skin disease characterized by chronic eczema and mechanical injury to the skin, caused by scratching. Korean red ginseng (RG) has diverse biological activities, but the molecular effects of RG on allergic diseases, like AD, are unclear. The present study was designed to investigate whether RG inhibits 1-chloro-2,4-dinitrobenzene (DNCB)-induced AD in a mouse model. DNCB was applied topically on the dorsal surface of Balb/c mice to induce AD-like skin lesions. We observed the scratching behavior and examined the serum IgE level and interleukin (IL)-4 and IL-10 in splenocytes compared with dexamethasone. We also evaluated the DNCB-induced mitogen-activated protein kinases (MAPKs), NF-κB, and Ikaros activities after RG treatment using reverse transcriptase-polymerase chain reaction, Western blotting, and ELISA. Our data showed that the topical application of RG significantly improved the AD-like skin lesions and scratching behavior. RG decreased not only the mRNA expression of IL-4 and IL-10, but also the secretion of IL-4 protein and serum IgE in mice. Additionally, RG treatment decreased the DNCB-induced MAPKs activity and subsequent Ikaros translocation irrespective of NF-κB. We suggest that RG may be useful as a therapeutic nutrition for the treatment of AD.

Cell cycle arrest and apoptotic induction in LNCaP cells by MCS-C2, novel cyclin-dependent kinase inhibitor, through p53/p21WAF1/CIP1 pathway

The purpose of the present study was to investigate the mechanisms involved in the antiproliferative and apoptotic effects of MCS‐C2, a novel analog of the pyrrolo[2,3‐d]pyrimidine nucleoside toyocamycin and sangivamycin, in human prostate cancer LNCaP cells. MCS‐C2, a selective inhibitor of cyclin‐dependent kinase, was found to inhibit cell growth in a time‐ and dose‐dependent manner, and inhibit cell cycle progression by inducing the arrest of the G1 phase and apoptosis in LNCaP cells. When treated with 3 µM MCS‐C2, inhibited proliferation associated with apoptotic induction was found in the LNCaP cells in a concentration and time‐dependent manner, and nuclear DAPI staining revealed the typical nuclear features of apoptosis. Furthermore, MCS‐C2 induced cell cycle arrest in the G1 phase through the upregulated phosphorylation of the p53 protein at Ser‐15 and activation of its downstream target gene p21WAF1/CIP1. Accordingly, these results suggest that MCS‐C2 inhibits the proliferation of LNCaP cells by way of G1‐phase arrest and apoptosis in association with the regulation of multiple molecules in the cell cycle progression. (Cancer Sci 2006; 97: 430 –436)

Novel anticancer agent, benzyldihydroxyoctenone, isolated from Streptomyces sp. causes G1 cell cycle arrest and induces apoptosis of HeLa cells

In the course of screening for anticancer agents, a novel active compound, F3‐2‐5, was isolated from culture broth of Streptomyces sp., KACC91015. Its structure was identified using nuclear magnetic resonance, mass spectrometry, and molecular modeling experiments, and confirmed by total synthesis. The growth of various human cancer cell lines was inhibited in a dose‐dependent manner by 0.06–0.48 mM F3‐2‐5 over 24 h. Its IC50 values were estimated at 37 µM on HeLa, 72 µM on A549, and 190 µM on HT‐29 cells. However, F3‐2‐5 had no antiproliferative effect on normal lymphocytes and normal fibroblasts used as controls. Moreover, it affected cell cycle regulation and caused apoptosis of the HeLa cells; chromatin condensation and DNA fragmentation were observed in cells exposed to 80 µM F3‐2‐5. Western blot analysis revealed that F3‐2‐5 inhibited phosphorylation of retinoblastoma protein (pRb) and reduced expression of cyclin‐dependent kinase‐4 and ‐6, and cyclin D1 and E, while levels of p53 and p21WAF1/CIP1 increased. Taken together, these findings show that F3‐2‐5 inhibits proliferation of HeLa cells by inducing G1 phase arrest as a consequence of inhibition of pRb phosphorylation following up‐regulation of p21WAF1/CIP1 and p53. Furthermore, apoptosis in HeLa cells treated with F3‐2‐5 was associated with an increase in Bax and p53, leading to release of cytochrome c, activation of caspase‐3, and ‐8, and cleavage of poly (ADP‐ribose) polymerase. (Cancer Sci 2007; 98: 795–802)

Identification and characterization of wblA-dependent tmcT regulation during tautomycetin biosynthesis in Streptomyces sp. CK4412.

Tautomycetin (TMC) is an unusual linear polyketide compound esterified with a cyclic anhydride. It exhibits novel activated T cell-specific immunosuppressant as well as anti-cancer activities. Previously, we isolated and characterized the entire TMC biosynthetic gene cluster from Streptomyces sp. CK4412, including a TMC pathway-specific gene, tmcN, the over-expression of which led to a significant increase in TMC productivity. In addition, we also reported that WblA acts as a global down-regulator of antibiotic biosynthesis through pathway-specific regulation in Streptomyces species. Here, we confirm that TmcT acts as another TMC pathway-specific regulator within the TMC biosynthetic cluster. Specifically, tmcT deletion resulted in the complete loss of TMC production, whereas complementation with a tmcT-carrying integrative plasmid significantly restored TMC biosynthesis. We also identified a 0.39kb wblA ortholog (named wblA(tmc)) from Streptomyces sp. CK4412 via genomic DNA library screening that showed 96% amino acid identity compared to a previously-known S. coelicolor wblA. Targeted gene disruption of wblA(tmc) in Streptomyces sp. CK4412 exhibited approximately 3-fold higher TMC productivity than that in the wild-type strain. Moreover, transcription analyses of the TMC biosynthetic and regulatory genes revealed that the expression of tmcT was strongly down-regulated by wblA(tmc). These results imply that the TMC biosynthetic regulation network is controlled by two pathway-specific positive regulator, WblA(tmc)-dependent TmcT as well as WblA(tmc)-independent TmcN in Streptomyces sp. CK4412.

HLA class II allele associations in Korean patients with pemphigus.

Background: Studies at the population level have demonstrated associations between pemphigus (pemphigus vulgaris, PV, and pemphigus foliaceus, PF) and particular HLA haplotypes, which suggests that there may be a genetic predisposition for the disease. Objective/Methods: The aim of the present study was to examine the distribution/frequency pattern of HLA class II alleles (DRB1, DQA1 and DQB1) from a group of 30 Korean patients with pemphigus (15 PV and 15 PF) by PCR amplification with sequence-specific primers. Results: In PV, the frequency of DRB1*01 allele was found to be significantly high (pc = 0.0014); in PF, DRB1*01, DQA1*0302 and DQB1*0603 alleles showed positive associations with statistical significances (pc = 0.0002, 0.0007 and 0.0067, respectively), when compared with those found in Korean controls. Conclusions: In this small-sample study, findings of allelic frequencies among Korean patients with pemphigus are somewhat different from those found in other populations.

Tat-enhanced delivery of metallothionein can partially prevent the development of diabetes.

Metallothioneins (MTs) are intracellular low-molecular-weight, cysteine-rich proteins with potent metal-binding and redox functions, but with limited membrane permeativity. The aim of this study was to investigate whether we could enhance delivery of MT-1 to pancreatic islets or β cells in vitro and in vivo. The second goal was to determine whether increased MT-1 could prevent cellular toxicity induced by high glucose and free fatty acids in vitro (glucolipotoxicity) and ameliorate the development of diabetes induced by streptozotocin in mice or delay the development of diabetes by improving insulin secretion and resistance in the OLETF rat model of type 2 diabetes. Expression of HIV-1 Tat-MT-1 enabled efficient delivery of MT into both INS-1 cells and rat islets. Intracellular MT activity increased in parallel with the amount of protein delivered to cells. The formation of reactive oxygen species, glucolipotoxicity, and DNA fragmentation due to streptozotocin decreased after treating pancreatic β cells with Tat-MT in vitro. Importantly, in vivo, intraperitoneal injection resulted in delivery of the Tat-MT protein to the pancreas as well as liver, muscle, and white adipose tissues. Multiple injections increased radical-scavenging activity, decreased apoptosis, and reduced endoplasmic reticulum stress in the pancreas. Treatment with Tat-MT fusion protein delayed the development of diabetes in streptozotocin-induced mice and improved insulin secretion and resistance in OLETF rats. These results suggest that in vivo transduction of Tat-MT may offer a new strategy to protect pancreatic β cells from glucolipotoxicity, may improve insulin resistance in type 2 diabetes, and may have a protective effect in preventing islet destruction in type 1 diabetes.