Mi Hyun Nam

Monocyte-endothelium-smooth muscle cell interaction in co-culture: proliferation and cytokine productions in response to advanced glycation end products.

BACKGROUNDnDuring hyperglycemia, reducing sugars react with the amino groups to form Amadori products which then form advanced glycation end-products (AGEs). Studies have shown that the AGEs and the receptor binding generated reactive oxygen species, and triggered secretion of cytokines contributing to the local regulations of proliferation and inflammation in cells. Interaction of vessel wall cells and monocytes may trigger the processes leading to atherosclerosis. We evaluated the effects of AGEs on smooth muscle cell (SMC) proliferation and cytokine synthesis in co-cultures of human monocytes (THP-1), endothelial cells (HUVEC) and aortic vascular smooth muscle cell (SMC) to clarify the effects of AGEs on vascular cells and to investigate the mechanisms of arteriosclerosis.nnnMETHODSnGlycolaldehyde-induced AGEs (glycol-AGEs) was prepared. The THP-1 and HUVEC were cultured with SMC in transwell plates with 100 μg/ml of glycol-AGEs for 24 to 48 h.nnnRESULTSnThe proliferation of SMC was induced by glycol-AGEs in the co-culture system. Moreover, SMC treated with glycol-AGEs also expressed interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), and the level of cytokines expression was significantly elevated in the co-culture system of HUVEC and THP-1 when treated with glycol-AGEs.nnnCONCLUSIONnThese results suggest that employing a co-culture system is necessary to investigate the synergistic effects of AGEs on intercellular cellular interactions and it creates a more in vivo-like environment for AGEs implicated atherosclerosis research.nnnGENERAL SIGNIFICANCEnAll three cell types are required to be investigated together to understand the effects of AGEs on intercellular interactions occurring among these cells.

Antioxidant Effects and Physiological Activities of Pumpkin (Cucurbita moschata Duch.) Extract from Different Aerial Parts

This study investigated the antioxidant effects and physiological activities of extract from various parts of pumpkin (Cucurbita moschata Duch.) such as leaf, flesh, skin and seed. Different dried parts of C. moschata were boiled in ethanol for three hours, evaporated, and lyophilized with a freeze-dryer. Total polyphenol contents were the highest in leaf (29.62±0.88 mg GAE/g DM). The same result was observed in the measurement of the flavonoid content. The leaf extract of C. moschata had stronger DPPH radical-scavenging activities and ABTS-radical scavenging activities than any other part. Leaf extract of C. moschata was found to have the highest ferric-reducing antioxidant power (FRAP) value. Meanwhile, at 0.1 mg/mL of all extracts higher degree of tyrosinase inhibitory effects than kojic acid was observed (leaf; 49.58%, flesh; 40.20%, skin; 41.30%, seed; 36.79% and kojic acid; 20.70%). The glycation inhibitory activity decreased in the order leaf>skin>flesh>seed. The α-glucosidase inhibitory activity of seed extract was the highest with a value of 63.58% at the concentration of 1 mg/mL.This study investigated the antioxidant effects and physiological activities of extract from various parts of pumpkin (Cucurbita moschata Duch.) such as leaf, flesh, skin and seed. Different dried parts of C. moschata were boiled in ethanol for three hours, evaporated, and lyophilized with a freeze-dryer. Total polyphenol contents were the highest in leaf (29.62±0.88 mg GAE/g DM). The same result was observed in the measurement of the flavonoid content. The leaf extract of C. moschata had stronger DPPH radical-scavenging activities and ABTS-radical scavenging activities than any other part. Leaf extract of C. moschata was found to have the highest ferric-reducing antioxidant power (FRAP) value. Meanwhile, at 0.1 mg/mL of all extracts higher degree of tyrosinase inhibitory effects than kojic acid was observed (leaf; 49.58%, flesh; 40.20%, skin; 41.30%, seed; 36.79% and kojic acid; 20.70%). The glycation inhibitory activity decreased in the order leaf>skin>flesh>seed. The α-glucosidase inhibitory activity of seed extract was the highest with a value of 63.58% at the concentration of 1 mg/mL.

Chebulic acid prevents hepatic fibrosis induced by advanced glycation end-products in LX-2 cell by modulating Nrf2 translocation via ERK pathway

Advanced glycation end-products (AGEs) are formed during normal aging, and at an accelerated rate in metabolic syndrome patients. Nonalcoholic steatohepatitis (NASH) can be caused by the AGEs in plasma, while glyceraldehyde-derived AGEs (glycer-AGEs) are significantly higher in the serum of NASH patients. In this study, we investigated the molecular mechanisms of chebulic acid, isolated from Terminalia chebula Retz., in the inhibition of glycer-AGEs induced production of reactive oxygen species (ROS) and collagen accumulation using the LX-2 cell line. Chebulic acid significantly inhibited the induction of ROS and accumulation of collagen proteins by glycer-AGEs. ERK phosphorylation and total nuclear factor E2-related factor 2 (Nrf2) protein expression were induced by chebulic acid in a dose-dependent manner. Chebulic acid was also found to induce translocation of Nrf2 into the nucleus, which was attenuated by inhibition of ERK phosphorylation through treatment with PD98059. Following translocation of Nrf2, chebulic acid induced the protein expressions of catalytic subunit of γ-glutamylcysteine synthetase and glutathione synthesis. Collagen accumulation was also significantly reduced by chebulic acid treatment. The observed effects of chebulic acid were all inhibited by PD98059 treatment. Taken together, these results suggest that chebulic acid prevents the glycer-AGEs-induced ROS formation of LX-2 cells and collagen accumulation by ERK-phosphorylation-mediated Nrf2 nuclear translocation, which causes upregulation of antioxidant protein production.

Inhibitory effects of Terminalia chebula extract on glycation and endothelial cell adhesion.

Terminalia chebula Retz. has been used in India for a long time to treat many diseases, and its extract was reported to have antidiabetic activity in vivo. In this study, T. chebula methanolic extract (TCE) containing 2.7 % chebulic acid was evaluated for its preventive effects against the formation of advanced glycation end products (AGEs) and endothelial cell dysfunction. When the effects of TCE on AGE formation and on protein crossing-linking by glycation with D-threose and lens crystallines were examined, TCE showed inhibitory activity in a dose-dependent manner, and the concentration of 1000 µg/mL presented an activity similar to that of 5 mM aminoguanidine as a positive control. Upon investigating the protective activity of TCE against AGE-induced vascular endothelium dysfunction, human umbilical vein endothelial cells (HUVEC) incubated with 100 µg/mL of AGEs had significantly enhanced reactive oxygen species (ROS) formation, whereas the treatment of T. chebula reduced AGE-induced ROS generation. The incubation of HUVEC with 100 µg/mL of AGEs caused a considerable increase in THP-1 monocytic cell adhesion, but this adhesion was reduced by the treatment of TCE. These results suggest that TCE is a potential agent for alleviating diabetic complications.

Plantamajoside Inhibits UVB and Advanced Glycation End Products-Induced MMP-1 Expression by Suppressing the MAPK and NF-κB Pathways in HaCaT Cells.

Photoaging and glycation stress are major causes of skin deterioration. Oxidative stress caused by ultraviolet B (UVB) irradiation can upregulate matrix metalloprotease 1 (MMP‐1), a major enzyme responsible for collagen damage in the skin. Advanced glycation end products (AGEs) accumulate via gradual formation from skin proteins, especially from long‐lived proteins such as dermal elastin and collagen. Plantamajoside (PM), isolated from Plantago asiatica, has various biological effects including anti‐inflammatory and antioxidant effects. In this study, we assessed the protective effects of PM on a human keratinocyte cell line (HaCaT) and primary human dermal fibroblasts (HDF) against stress caused by glyceraldehyde‐induced AGEs (glycer‐AGEs) with UVB irradiation. We found that PM attenuated UVB‐ and‐glycer‐AGEs‐induced MMP‐1 expression in HaCaT and HDF cells and proinflammatory cytokines expression by inhibiting the phosphorylation of mitogen‐activated protein kinases (MAPKs) activated by reactive oxygen species. Specific inhibitors of NF‐κB and MAPKs attenuated the induced expression of MMP‐1. PM also inhibited the phosphorylation of IκBα, and reduced nuclear translocation of NF‐κB in these cells. Furthermore, PM attenuated the upregulation of receptor for AGEs (RAGE) by glycer‐AGEs with UVB irradiation. Therefore, our findings strongly suggest that PM is a promising inhibitor of skin photoaging.

Caffeic Acid Inhibits the Uptake of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by Inducing the Efflux Transporters Expression in Caco-2 Cells

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is formed as a by-product of the Maillard reaction during cooking and frying of protein-rich foods at high temperatures. PhIP is metabolized in the liver by cytochrome P450 1A1/2 to carcinogenic metabolite N-hydroxy PhIP, which can form DNA adduct. The ATP binding cassette (ABC) transporters, P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP) are capable of transporting the food-borne procarcinogen PhIP back to the intestinal lumen. In the present study, the uptake and efflux of PhIP were assessed by determining apparent bidirectional permeability coefficients and efflux ratio. The efflux ratio of PhIP with 10 µM caffeic acid was significantly increased compared with control. The mRNA levels of efflux transporters were measured to evaluate the effect of caffeic acid in the presence of PhIP on efflux-mediated transport of PhIP. Caco-2 cells exposed to 10 µM caffeic acid for 3 and 6 h also exhibited higher mRNA levels of P-gp and BCRP than those of control. In contrast, the mRNA level of MRP2 was only slightly induced after 3 h and 6 h. Therefore, caffeic acid at low concentration is expected to be used not only as an antioxidant, but also as an inhibitor of the absorption of food borne carcinogen heterocyclic amines. However, further studies, especially in vivo studies, are required to confirm these results.

In vivo study of the renal protective effects of Capsosiphon fulvescens against streptozotocin-induced oxidative stress

Mi-Hyun Nam, Yun-Chang Koo, Chung-Oui Hong, Sung-Yong Yang, Se-Wook Kim, Hye-Lim Jung, Hwa Lee, Ji-Yeon Kim, Ah-Ram Han, Won-rak Son, Min-Cheol Pyo, and Kwang-Won Lee*Division of Food Bioscience and Technology, College of Life Science & Biotechnology, Korea UniversityAbstract In this study, we evaluated the effect of Capsosiphon fulvescens extract (CFE) and its active compound,pheophorbide A (PhA), on diabetic kidney failure. Diabetes mellitus (DM) was induced by a single intraperitoneal injectionof streptozotocin (STZ; 40 mg/kg body weight (BW)). After a week, the rats were orally administered CFE (4 and 20 mg/kg BW) or PhA (0.2 mg/kg BW) once a day for 9 weeks. After scarification, renal tissue samples were collected forbiochemical and histochemical analyses. Our study showed that the treatment with CFE and PhA significantly decreasedlipid peroxidation level and the activities of glutathione peroxidase and glutathione-S-transferase (p<0.05), but it increasedglutathione level and the activities of glutathione reductase, superoxide dismutase, and catalase in the renal tissues(p<0.05). The CFE- and PhA-treated rats with DM showed improved histochemical appearance and decreased abnormalglycogen accumulation. Therefore, we suggest that PhA-containing CFE could exert renal protective effects against STZ-induced oxidative stress.Keywords: Capsosiphon fulvescens , streptozotocin, diabetic rats, oxidative stress, antioxidant enzyme, renal protective effects

Inhibitory Effect of Yellow Myrobalan (Terminalia chebula) Extract on Fibrosis Induced by Carbon Tetrachloride in Rat Liver

Ethyl acetate layer of methanol extract (TCE) of yellow myrobalan (Terminalia chebula) contains 2.4% of chebulic acid, a standard compound in TCE, which have a strong anti-oxidative effect and was reported in our previous study. Thirty-one male SD rats were randomly divided into 5 groups (normal control, CCl4 control, TCE control, CCl4+high dose TCE, and low dose TCE). Liver fibrosis was induced by i.p. injection of CCl4 and TCE were orally administrated. TCE decreased the up-regulated malondealdehyde value and increased the down-regulated ratio of GSH/GSSG content and activities of GRd, GPx, and GST compared to the CCl4 control group. Decreased dysfunction and inflammatory reaction in liver was confirmed by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, relative liver weight and infiltration of neutrophils. Also, TCE inhibited phenotype change of hepatic stellate cells (HSC) by reducing α-smooth muscle actin (α-SMA) gene expression and protein production. Inhibition of collagen 1A1 gene expression and protein production were also confirmed. From these results, TCE may be a useful material for preventing liver fibrosis.

Effect of Diet Containing Whole Wheat Bread with Capsosiphon fulvescens and Lindera obtusiloba Ethanol Extracts on Plasma Glucose and Lipid Levels in Rats

The present study was conducted to investigate the effect of whole wheat bread with added Lindera obtusiloba (LO) and Capsosiphon fulvescens (CF) ethanol extracts on serum glucose and lipid levels in Sprague Dawley rats. Rats were divided into five groups depending on the diet administered: normal bread (NC), whole wheat bread (W), whole wheat bread with LO leaves extract (WL), whole wheat bread with CF extract (WC), and whole wheat bread with freeze-drying CF (WDC). After 4 weeks of consuming the experimental diet, the blood glucose level and hemoglobin A1c contents were found to be significantly lower in the W, WL, WC, and WDC groups than in the NC group. The high-density lipoprotein-cholesterol levels increased in the WL group when compared to those in the NC group and triglycerides levels decreased in all wheat groups compared to those in the NC group. These results suggest that wheat breads containing LO and CF extracts are effective for preventing hypercholesterolemia and obesity.

Pheophorbide a from Capsosiphon fulvescens Inhibits Advanced Glycation End Products Mediated Endothelial Dysfunction

During hyperglycemia, the first step toward the formation of advanced glycation end products is the nonenzymatic glycation between the carbonyl group of a sugar and the primary amino group of a protein. Advanced glycation end products are then produced through more complex reactions. Reactive oxygen species derived from advanced glycation end products may play a key role in inflammation of the endothelium, leading to the complications seen in diabetes. Glycolaldehyde-induced advanced glycation end products have been reported to express proinflammatory cytokines, such as tumor necrosis factor-α and interleukin-1β. This study focused on Capsosiphon fulvescens, a Capsosiphonaceae type of green algae that has shown potential as a functional food material. Pheophorbide a, an anti-glycation compound, was isolated from C. fulvescens by extraction using a mixture of ethanol and water, followed by column fractionation of the resulting extract. The compound separated from C. fulvescens was identified by means of high-performance liquid chromatography combined with mass spectrometry. Pheophorbide a showed scavenging activity of the intracellular reactive oxygen species as well as monocyte adhesiveness inhibitory activity on the human myelomonocytic cell line (THP-1) and human umbilical vein endothelial cells cocultivation system. The mRNA levels of inflammation-related genes such as monocyte chemoattractant protein-1 and interleukin-6 were significantly decreased by pheophorbide a, and advanced glycation end products-stimulated tumor necrosis factor-α and interleukin-1β were downregulated as well. These results indicate that pheophorbide a has significant reactive oxygen species-scavenging activity, monocyte adhesive inhibitory activity, and downregulatory activity of cytokines related to inflammation affecting the endothelium. Pheophorbide a could therefore be a promising candidate for modulating endothelial cell dysfunction.