Misung Kwon

Anti-inflammatory Activities of an Ethanol Extract of Ecklonia stolonifera in Lipopolysaccharide-Stimulated RAW 264.7 Murine Macrophage Cells

Ecklonia stolonifera is a brown alga that was shown to have antioxidant, anti-inflammatory, tyrosinase inhibitory, and chemopreventive activities. However, the molecular mechanisms underlying its anti-inflammatory activity remain unclear. In this study, we investigated the molecular mechanism of the anti-inflammatory action of E. stolonifera ethanolic extracts (ESE) using lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. ESE inhibited LPS-induced nitric oxide (IC(50) = 72 ± 1.9 μg/mL) and prostaglandin E(2) (IC(50) = 98 ± 5.3 μg/mL) production in a dose-dependent manner and suppressed the expression of inducible nitric oxide synthase and cyclooxygenase-2 in RAW 264.7 cells. ESE also reduced the production of pro-inflammatory cytokines in LPS-stimulated RAW 264.7 cells. LPS-induced nuclear factor-κB (NF-κB) transcriptional activity and NF-κB translocation into the nucleus were significantly inhibited by ESE treatment through the prevention of the degradation of inhibitor κB-α. Moreover, ESE inhibited the activation of Akt, ERK, JNK1/2, and p38 MAPK in LPS-stimulated RAW 264.7 cells. The main components with anti-inflammatory activity in ESE were identified as phlorofucofuroeckol A and B based on the inhibition of NO production. Our results indicate that ESE can be considered as a potential source of therapeutic agents for inflammatory diseases.

Phlorofucofuroeckol B suppresses inflammatory responses by down-regulating nuclear factor κB activation via Akt, ERK, and JNK in LPS-stimulated microglial cells

Microglial activation has been implicated in many neurological disorders for its inflammatory and neurotrophic effects. In this study, we investigated the effects of phlorofucofuroeckol B (PFF-B) isolated from Ecklonia stolonifera, on the production of inflammatory mediators in lipopolysaccharide (LPS)-stimulated microglia. PFF-B decreased secretion of pro-inflammatory cytokines including tumor necrosis factor α, interleukin (IL)-1β, and IL-6 and the expression of pro-inflammatory proteins such as cyclooxygenase-2 and inducible nitric oxide synthase in LPS-stimulated BV-2 cells. Profoundly, PFF-B inhibited activation of nuclear factor kappaB (NF-κB) by preventing the degradation of inhibitor κB-α (IκB-α), which led to prevent the nuclear translocation of p65 NF-κB subunit. Moreover, PFF-B inhibited the phosphorylation of Akt, ERK, and JNK. These results indicate that the anti-inflammatory effect of PFF-B on LPS-stimulated microglial cells is mainly regulated by the inhibition of IκB-α/NF-κB and Akt/ERK/JNK pathways. Our study suggests that PFF-B can be considered as a therapeutic agent against neuroinflammation by inhibiting microglial activation.

Sargachromenol protects against vascular inflammation by preventing TNF-α-induced monocyte adhesion to primary endothelial cells via inhibition of NF-κB activation

Abstract Vascular inflammation is a key factor in the pathogenesis of atherosclerosis. The purpose of this study was to investigate the protective effects of sargachromenol (SCM) against tumor necrosis factor (TNF)‐&agr;‐induced vascular inflammation. SCM decreased the expression of cell adhesion molecules, including intracellular adhesion molecule‐1 and vascular cell adhesion molecule‐1, in TNF‐&agr;‐stimulated human umbilical vein endothelial cells (HUVECs), resulted in reduced adhesion of monocytes to HUVECs. SCM also decreased the production of monocyte chemoattractant protein‐1 and matrix metalloproteinase‐9 in TNF‐&agr;‐induced HUVECs. Additionally, SCM inhibited activation of nuclear factor kappa B (NF‐&kgr;B) induced by TNF‐&agr; through preventing the degradation of inhibitor kappa B. Moreover, SCM reduced the production of reactive oxygen species in TNF‐&agr;‐treated HUVECs. Overall, SCM alleviated vascular inflammation through the regulation of NF‐&kgr;B activation and through its intrinsic antioxidant activity in TNF‐&agr;‐induced HUVECs. These results indicate that SCM may have potential application as a therapeutic agent against vascular inflammation. HighlightsSargachromenol (SCM) was isolated from Sargassum serratifolium.SCM inhibited the adhesion of THP‐1 to TNF‐&agr;‐stimulated endothelium.SCM inhibited the expression of ICAM‐1, VCAM‐1, and MCP‐1 via NF‐&kgr;B pathway.SCM could be a novel therapeutic agent to treat vascular inflammatory diseases.

Kaempferol Isolated from Nelumbo nucifera Inhibits Lipid Accumulation and Increases Fatty Acid Oxidation Signaling in Adipocytes

Stamens of Nelumbo nucifera Gaertn have been used as a Chinese medicine due to its antioxidant, hypoglycemic, and antiatherogenic activity. However, the effects of kaempferol, a main component of N. nucifera, on obesity are not fully understood. We examined the effect of kaempferol on adipogenesis and fatty acid oxidation signaling pathways in 3T3-L1 adipocytes. Kaempferol reduced cytoplasmic triglyceride (TG) accumulation in dose and time-dependent manners during adipocyte differentiation. Accumulation of TG was rapidly reversed by retrieving kaempferol treatment. Kaempferol broadly decreased mRNA or protein levels of adipogenic transcription factors and their target genes related to lipid accumulation. Kaempferol also suppressed glucose uptake and glucose transporter GLUT4 mRNA expression in adipocytes. Furthermore, protein docking simulation suggests that Kaempferol can directly bind to and activate peroxisome proliferator-activated receptor (PPAR)-α by forming hydrophobic interactions with VAL324, THR279, and LEU321 residues of PPARα. The binding affinity was higher than a well-known PPARα agonist fenofibrate. Consistently, mRNA expression levels of PPARα target genes were increased. Our study indicates while kaempferol inhibits lipogenic transcription factors and lipid accumulation, it may bind to PPARα and stimulate fatty acid oxidation signaling in adipocytes.

Ethanolic extract of Sargassum serratifolium inhibits adipogenesis in 3T3-L1 preadipocytes by cell cycle arrest

The brown alga, Sargassum serratifolium C. Agardh, has been reported to have high levels of meroterpenoids having anti-inflammatory, antioxidant, and anti-diabetic activities. This study investigated the effect of ethanolic extract of S. serratifolium (ESS) on the inhibition of adipogenesis and lipid accumulation in 3T3-L1 preadipocytes. ESS suppressed the accumulation of lipid droplets and triglycerides (TG), while enhancing the lipolysis of intracellular TG. We found that ESS induced cell cycle arrest at the G1/S phase via suppressing protein expression of cyclin-dependent kinases (CDK) 2, CDK4, CDK6, and cyclin E. Moreover, ESS reduced the expression of CCAAT/enhancer-binding protein (C/EBP) β during the early stage of adipogenesis, leading to suppressed expression of both messenger RNA (mRNA) and protein of C/EBPα and peroxisome proliferator-activated receptor γ. As a result, ESS reduced mRNA and protein levels of lipogenic transcription factors such as retinoid X receptor, and sterol regulatory element-binding protein 1c and their target genes, such as fatty acid synthase and stearoyl-CoA desaturase (SCD) 1. Overall, ESS inhibited adipocyte differentiation in early stage and lipid accumulation during adipogenesis through downregulation of adipogenic and lipogenic transcription factors, providing the anti-obesity mechanism of ESS.

Meroterpenoid-Rich Fraction of the Ethanolic Extract from Sargassum serratifolium Suppressed Oxidative Stress Induced by Tert-Butyl Hydroperoxide in HepG2 Cells

Sargassum species have been reported to be a source of phytochemicals, with a wide range of biological activities. In this study, we evaluated the hepatoprotective effect of a meroterpenoid-rich fraction of the ethanolic extract from Sargassum serratifolium (MES) against tert-butyl hydroperoxide (t-BHP)-treated HepG2 cells. Treatment with MES recovered the cell viability from the t-BHP-induced oxidative damage in a dose-dependent manner. It suppressed the reactive oxygen species production, lipid peroxidation, and glutathione depletion in the t-BHP-treated HepG2 cells. The activity of the antioxidants induced by t-BHP, including superoxide dismutase (SOD) and catalase, was reduced by the MES treatment. Moreover, it increased the nuclear translocation of nuclear factor erythroid 2-related factor 2, leading to the enhanced activity of glutathione S transferase, and the increased production of heme oxygenase-1 and NAD(P)H:quinine oxidoreductase 1 in t-BHP-treated HepG2 cells. These results demonstrate that the antioxidant activity of MES substituted the activity of the SOD and catalase, and induced the production of detoxifying enzymes, indicating that MES might be used as a hepatoprotectant against t-BHP-induced oxidative stress.

Sargaquinoic acid ameliorates hyperpigmentation through cAMP and ERK-mediated downregulation of MITF in α-MSH-stimulated B16F10 cells

Hyperpigmentation disorders of the skin adversely influence the quality of life. We previously demonstrated the hypopigmenting properties of the ethanolic extract from Sargassum serratifolium and identified sargaquinoic acid (SQA) as an active component. The current study aims to investigate the hypopigmenting action of SQA in α-melanocyte stimulating hormone (α-MSH)-stimulated B16F10 cells. SQA attenuated cellular melanin synthesis by inhibiting the expression of the melanogenic enzymes, including tyrosinase (TYR), tyrosinase-related protein 1 (TRP1), and TRP2. SQA also inhibited cellular TYR activity in a dose-dependent manner. Reduced intracellular cAMP accumulation by SQA treatment resulted in the suppressed phosphorylation of cAMP-responsive element-binding protein (CREB), leading to the downregulation of microphthalmia-associated transcription factor (MITF) in α-MSH-stimulated B16F10 cells. SQA increased the phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and MITF (Ser73), inducing proteasomal degradation of MITF. SQA showed high binding affinity to the cAMP binding domain of PKA; the direct binding of SQA to PKA may exert an additional inhibitory effect on the PKA-dependent CREB activation. Our data demonstrated that SQA suppressed melanin production through the cAMP/CREB- and ERK1/2-mediated downregulation of MITF in α-MSH-stimulated B16F10 cells and SQA has a potential therapeutic agent for the treatment of skin hyperpigmentation disorders.