Seung Namkoong

Prostaglandin E2 stimulates angiogenesis by activating the nitric oxide/cGMP pathway in human umbilical vein endothelial cells.

Prostaglandin E2(PGE2), a major product of cyclooxygenase, has been implicated in modulating angiogenesis, vascular function, and inflammatory processes, but the underlying mechanism is not clearly elucidated. We here investigated the molecular mechanism by which PGE 2 regulates angiogenesis. Treatment of human umbilical vein endothelial cells (HUVEC) with PGE 2 increased angiogenesis. PGE 2 increased phosphorylation of Akt and endothelial nitric oxide synthase (eNOS), eNOS activity, and nitric oxide (NO) production by the activation of cAMP-dependent protein kinase (PKA) and phosphatidylinositol 3-kinase (PI3K). Dibutyryl cAMP (DB-cAMP) mimicked the role of PGE 2 in angiogenesis and the signaling pathway, suggesting that cAMP is a down-stream mediator of PGE 2. Furthermore, PGE 2 increased endothelial cell sprouting from normal murine aortic segments, but not from eNOS-deficient ones, on Matrigel. The angiogenic effects of PGE 2 were inhibited by the inhibitors of PKA, PI3K, eNOS, and soluble guanylate cyclase, but not by phospholipase C inhibitor. These results clearly show that PGE 2 increased angiogenesis by activating the NO/cGMP signaling pathway through PKA/PI3K/Akt-dependent increase in eNOS activity.

Serum bioactive lysophospholipids prevent TRAIL-induced apoptosis via PI3K/Akt-dependent cFLIP expression and Bad phosphorylation

AbstractSerum contains a variety of biomolecules, which play an important role in cell proliferation and survival. We sought to identify the serum factor responsible for mitigating tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis and to investigate its molecular mechanism. TRAIL induced effective apoptosis without serum, whereas bovine serum decreased apoptosis by suppressing cytochrome c release and caspase activation. Indeed, albumin-bound lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) inhibited TRAIL-induced apoptosis by suppressing caspase activation and cytochrome c release. LPA increased phosphatidylinositol 3-kinase (PI3K)-dependent Akt activation, cellular FLICE-inhibitory protein (cFLIP) expression, and Bad phosphorylation, resulting in inhibition of caspase-8 activation and Bad translocation to mitochondria. The antiapoptotic effect of LPA was abrogated by PI3K inhibitor, transfection with dominant-negative Akt, and specific downregulation of cFLIP expression using siRNA and further increased by siRNA-mediated suppression of Bad expression. Moreover, sera from ovarian cancer patients showed more protective effect against TRAIL-induced apoptosis than those from healthy donors, and this protection was suppressed by PI3K inhibitor. Our results indicate that albumin-bound LPA and S1P prevent TRAIL-induced apoptosis by upregulation of cFLIP expression and in part by Bad phosphorylation, through the activation of PI3K/Akt pathway.

Dexamethasone protects primary cultured hepatocytes from death receptor-mediated apoptosis by upregulation of cFLIP

Dexamethasone (DEX) pretreatment protected hepatocytes from TNF-α plus actinomycin D (ActD)-induced apoptosis by suppressing caspase-8 activation and the mitochondria-dependent apoptosis pathway. DEX treatment upregulated cellular FLICE inhibitory protein (cFLIP) expression, but did not alter the protein levels of Bcl-2, Bcl-xL, Mcl-1, and cIAP as well as Akt activation. The increased cFLIP mRNA level by DEX was inhibited by ActD, indicating that DEX upregulates cFLIP expression at the transcriptional step. DEX also inhibited Jo2-mediated hepatocyte apoptosis by blocking the formation of the death-inducing signaling complex and caspase-8 activation. Specific downregulation of cFLIP expression using siRNA reversed the antiapoptotic effect of DEX by increasing caspase-8 activation. Moreover, DEX administration into mice increased cFLIP expression in the liver and prevented Jo2-induced hepatic injury by inhibiting caspase-8 and -3 activities. Our results indicate that DEX exerts a protective role in death receptor-induced in vitro and in vivo hepatocyte apoptosis by upregulating cFLIP expression.

The analgesic and anti-inflammatory effects of Litsea japonica fruit are mediated via suppression of NF-κB and JNK/p38 MAPK activation.

Fruits of the Litsea family of trees and shrubs contain biologically active compounds, some of which have been used as natural nutrients and flavoring agents in food. In this study, we identified novel anti-nociceptive effects of the 30% ethanol extract, the CH(2)Cl(2) fraction and the associated active components (Hamabiwalactone A and B) from Litsea japonica fruit by using in vivo peripheral and central nervous pain models. In addition, we compared the anti-inflammatory effects of several fractions from L. japonica fruit extracts using lipopolysaccharide (LPS)-stimulated Raw264.7 cells. The CH(2)Cl(2) fraction of L. japonica fruit (LJM) had an optimal combination of anti-inflammatory effects and low cytotoxicity. Dose response studies were performed to determine the inhibitory effects of LJM on the pro-inflammatory enzymes, COX-2/PGE(2) and NO/iNOS, and pro-inflammatory cytokines, IL-1β, IL-6, and TNF-α. Molecular profiling revealed that LJM exerts anti-inflammatory effects through inhibition of NF-κB and JNK/p38 MAPK signaling in LPS-induced macrophages. This study suggests that CH2Cl2 fraction of L. japonica fruit and its bioactive components are potential candidates as anti-inflammatory and analgesic agents (painkillers) for the treatment of inflammatory diseases.

Differential regulation of apoptosis by caspase-mediated cleavage of phospholipase D isozymes.

Phospholipase D (PLD) has been implicated in survival and anti-apoptosis, but the molecular mechanism by which it responds to apoptotic stimuli is poorly unknown. Here, we demonstrate that cleavage of PLD isozymes as specific substrates of caspase differentially regulates apoptosis. PLD1 is cleaved at one internal site (DDVD(545)S) and PLD2 is cleaved at two or three sites (PTGD(13)ELD(16)S and DEVD(28)T) in the front of N-terminus. Cleavage of PLD was endogenously detected in post-mortem Alzheimer brain together with activated caspase-3, suggesting the physiological relevance. The cleavage of PLD1 but not PLD2 might act as an inactivating process since PLD1 but not PLD2 activity is significantly decreased during apoptosis, suggesting that differential cleavage of PLD isozymes could affect its enzymatic activity. Moreover, caspase-resistant mutant of PLD1 showed more potent anti-apoptotic capacity than that of wild type PLD1, whereas PLD2 maintained anti-apoptotic potency in spite of its cleavage during apoptosis. Moreover, PLD2 showed more potent anti-apoptotic effect than that of PLD1 in overexpression and knockdown experiments, suggesting that difference in anti-apoptotic potency between PLD1 and PLD2 might be due to its intrinsic protein property. Taken together, our results demonstrate that differential cleavage pattern of PLD isozymes by caspase might affect its enzymatic activity and anti-apoptotic function.

Fucoidan from Fucus vesiculosus Protects against Alcohol-Induced Liver Damage by Modulating Inflammatory Mediators in Mice and HepG2 Cells

Fucoidan is an l-fucose-enriched sulfated polysaccharide isolated from brown algae and marine invertebrates. In this study, we investigated the protective effect of fucoidan from Fucus vesiculosus on alcohol-induced murine liver damage. Liver injury was induced by oral administration of 25% alcohol with or without fucoidan (30 mg/kg or 60 mg/kg) for seven days. Alcohol administration increased serum aspartate aminotransferase and alanine aminotransferase levels, but these increases were suppressed by the treatment of fucoidan. Transforming growth factor beta 1 (TGF-β1), a liver fibrosis-inducing factor, was highly expressed in the alcohol-fed group and human hepatoma HepG2 cell; however, the increase in TGF-β1 expression was reduced following fucoidan administration. Treatment with fucoidan was also found to significantly reduce the production of inflammation-promoting cyclooygenase-2 and nitric oxide, while markedly increasing the expression of the hepatoprotective enzyme, hemeoxygenase-1, on murine liver and HepG2 cells. Taken together, the antifibrotic and anti-inflammatory effects of fucoidan on alcohol-induced liver damage may provide valuable insights into developing new therapeutics or interventions.

Effect of the combinatory mixture of Rubus coreanus Miquel and Astragalus membranaceus Bunge extracts on ovariectomy-induced osteoporosis in mice and anti-RANK signaling effect

ETHNOPHARMACOLOGICAL RELEVANCE Postmenopausal osteoporosis is one of the most common disorders in women after menopause, which is linked to an estrogen deficiency and characterized by an excessive loss of trabecular bone. Rubus coreanus and Astragalus membranaceus have been used for their various pharmacological properties in Asia as a traditional medicine. The present study evaluated the anti-osteoporotic effects of the optimal combination of Rubus coreanus and Astragalus membranaceus in 7:3 mixture (RAM) in ovariectomized (OVX) mice by investigating bone biomechanical properties and the serum levels of TNF-α, osteocalcin, RANKL, OPG, and RANK-RANKL signal-related osteoclast differentiation markers. MATERIALS AND METHODS A total of 36 mature female outbred ICR (Institute of cancer research) strain mice (7 weeks) were divided into 6 groups with 7 mice in each group as follows: (1) Sham-operated control mice (Sham) received daily oral phosphate-buffered-saline (PBS) of equal volumes through gavage. (2) OVX mice received a daily oral gavage of PBS (OVX). (3) OVX mice were treated daily with 50mg/kgb.w./day of RAM (4) with 100mg/kgb.w./day of RAM or (5) with 200mg/kgb.w./day of RAM via oral gavage. (6) OVX mice received i.p. injections of 17β-estradiol (E2) (0.1mg/kgb.w./day) three times per week for 12 weeks. RESULTS Micro-CT images showed that oral administration of RAM to OVX mice prevented tibial bone loss, preserved trabecular bone microarchitecture, and improved bone biomechanical properties. RAM administration also showed recovery effects on the levels of TNF-α, OPG and RANKL concentration in OVX-states. Additionally, we found that the mechanism by which RAM elicited anti-osteoporotic effects was by down-regulating the expression of TRAF6 and NFATc1 in RANKL-RANK pathway, a route of osteoclast differentiation, followed by reducing the production of osteoclast differentiation factors, calcitonin receptors and cathepsin K. CONCLUSIONS Our research strongly suggests that RAM can be clinically used in the prevention and treatment of postmenopausal osteoporosis.

Microscopic technique for the detection of nitric oxide-dependent angiogenesis in an animal model.

Nitric oxide (NO) plays an important role in maintaining vascular homeostasis. The importance of NO in the vasculature is demonstrated by several experimental conditions, such as vascular endothelial growth factor (VEGF)-induced angiogenesis. Thus, the NO metabolic pathway in endothelial cells could be one of the main contributing factors for angiogenesis. Although several methods have been used for measuring in vitro angiogenesis, a proper technique has not been developed for identifying in vivo NO-dependent angiogenesis. This chapter provides a new intravital microscopic method for detecting and measuring NO-dependent angiogenesis in a mouse model. This technique showed strong abdominal neovascularization in wild-type mice, but not eNOS knockout mice, locally injected with VEGF, as well as stimulation of angiogenesis in NO donor-injected mice. This technique also revealed the inhibitory effect of the NOS inhibitor N(G)-iminoethyl-L-ornithine in VEGF-mediated in vivo angiogenesis. This chapter describes intravital microscopy as a new imaging technique for detecting NO-dependent angiogenesis in an animal model.

Effects of red ginseng on the regulation of cyclooxygenase-2 of spleen cells in whole-body gamma irradiated mice

Exposure to gamma radiation causes a wide range of biological damage and alterations, including oxidative stress, inflammation and cancer. This study aimed to identify the radioprotective effect of Korean red ginseng extract (RG) against whole-body gamma-irradiation (γIR) in mice and the regulatory mechanisms of the radiosensitive gene in spleen, cyclooxygenase-2 (COX-2). RG was administered intraperitoneally (i.p.) or orally (p.o.) to C57BL/6 mice for five days, which were then exposed to 6.5 Gy of (137)Cs-γIR. Thymus and spleen were harvested after three days, and organ size and COX-2 expression of the spleen using Western blotting, were examined. γIR shrank both organs and RG recovered the size of thymus but not spleen. RG also significantly inhibited the increased expression of COX-2 induced by γIR. These results were similar following both routes of RG administration, however i.p. RG administration was more effective, thus it was used in progressive studies. In terms of COX-2 expression related intracellular factors, we found here that γIR activated the p38 MAPK, PI3K/Akt and HO-1 but not NF-κB or Nrf2. Activated p38 MAPK, PI3K/Akt and HO-1 were down-regulated by RG while the RG-induced COX-2 expression was only related to HO-1 activation. These results suggest that RG supplementation provides protective effects against radiation-induced inflammation and cancer, and its potential to be utilized in clinical trials and functional foods.

Analysis of the risk factors of musculoskeletal disease among dentists induced by work posture.

[Purpose] The purpose of this study was to ergonomically evaluate the work posture of dentists to examine their subsequent risk of developing musculoskeletal diseases. [Subjects and Methods] Scenes in which the three dentists performed procedures at their dental clinics were videotaped. The videotapes of the dentists’ work postures were evaluated and analyzed by using the Rapid Upper Limb Assessment (RULA) and Quick Exposure Check (QEC). [Results] The RULA analysis of the dentists’ work posture indicated, “improvement required” in the posture used to treat the anterior and “instant improvement required” in the posture used to treat the maxillary second molar. Of all the work postures studied, the risk was considered particularly high in the lower back and neck, implying prominent problems in these body parts. The QEC analysis showed that the worst work posture was that required to treat the maxillary second molar, which led to a high risk of neck problems and vibrations. [Conclusion] The neck area has the highest risk of developing musculoskeletal disease. Hence, regular rests and the provision of information regarding muscle strengthening exercise for the neck are necessary.