Chul Woong Oh

Dieckol enhances the expression of antioxidant and detoxifying enzymes by the activation of Nrf2–MAPK signalling pathway in HepG2 cells

Dieckol was previously reported to exhibit antioxidant and anticancer activities in vitro studies. In this study, we characterised the mechanism underlying the dieckol-mediated expression of antioxidant and detoxifying enzymes. Dieckol suppressed the production of intracellular reactive oxygen species in the presence or absence of H2O2 and increased glutathione level in HepG2 cells. Dieckol enhanced the activities of antioxidant enzymes, and the expression of detoxifying enzymes including heme oxygenase-1 (HO-1), NAD(P)H:quinine oxidoreductase 1 (NQO1), and glutathione S-transferase (GST) in HepG2 cells. Enhanced expression of antioxidant and detoxifying enzymes by dieckol was presumed to be the activation of the nuclear factor erythroid-derived 2-like 2 (Nrf2) demonstrated by its nuclear translocation and transcriptional activity via activation of mitogen-activated protein kinases in HepG2 cells. Furthermore, we demonstrated dieckol induced the expression of HO-1 in mouse liver. These results demonstrate that the dieckol-mediated cytoprotection in HepG2 cells is mediated through a ROS-independent up-regulation of antioxidant and detoxifying enzymes via Nrf2 activation as well as its intrinsic antioxidant activity, suggesting that dieckol may be used as a natural cytoprotective agent.

Sargaquinoic acid attenuates inflammatory responses by regulating NF-κB and Nrf2 pathways in lipopolysaccharide-stimulated RAW 264.7 cells

Myagropsis myagroides, a brown alga, showed strong anti-inflammatory activities in the previous studies. In this study, we isolated a strong anti-inflammatory compound, sargaquinoic acid (SQA), from M. myagroides and investigated the anti-inflammatory action using lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. SQA suppressed the production of inducible nitric oxide synthase and cyclooxygenase-2 in LPS-stimulated cells as well as that of reactive oxygen species. As a result, SQA inhibited the production of NO, prostaglandin E2, and pro-inflammatory cytokines. LPS-induced transcriptional activation of nuclear factor-κB (NF-κB) was remarkably inhibited by SQA treatment through the prevention of inhibitor κB-α degradation. The regulation of NF-κB activation was also mediated by the phosphorylation of ERK and Akt in LPS-stimulated RAW 264.7 cells. Moreover, SQA induced the production of heme oxygenase 1 via activation of transcription factor Nrf2. These results indicate that SQA inhibits the LPS-induced expression of inflammatory mediators via suppression of ERK and Akt-mediated NF-κB pathway as well as up-regulation of Nrf2/HO-1 pathway, indicating that SQA has a potential therapeutic and preventive application in various inflammatory diseases.

Age and Growth of the Mudskipper, Scartelaos gigas (Perciformes, Gobiidae) from Korea

Abstract Age and growth of the mudskipper, Scartelaos gigas were investigated using the second actinost bone of the pectoral girdle, based on an analysis of 560 individuals collected from the mud flats in south west Korea. Specimens were collected semimonthly from March to September of 2003. Actinost and ring radii of each ring group showed a direct one‐to‐one relationship, with ring radius increasing in tandem with actinost radius. Monthly change in the marginal indices showed that ring formation occurred between May and July (mainly June), being supported by the monthly change in the gonadosomatic (highest in June) and hepatosomatic (lowest in July) indices. Because the species has not been found since November, when air temperature was less than about 10°C, it is thought to enter to hibernation. Therefore, it was suggested that the two new actinost rings may appear a year: one during the spawning season (May‐July) and another during hibernation (since November). Although the growth of S. gigas must be limited to short periods each year from March to April and from August to October, its growth rate was considerably fast. The von Bertalanffy growth parameters of S. gigas were TL8= 179.36 mm, K=0.78 year-1, t0=-0.7762, and age‐length key were TL1 = 134.3 mm, TL2=158.6 mm, TL3=169.1 mm, TL4= 175.0 mm.

Toxic effects of juvenile sablefish, Anoplopoma fimbria by ammonia exposure at different water temperature

Juvenile sablefish, Anoplopoma fimbria (mean length 17.1±2.4cm, and mean weight 75.6±5.7g) were used to evaluate toxic effects on antioxidant systems, immune responses, and stress indicators by ammonia exposure (0, 0.25, 0.75, and 1.25mg/L) at different water temperature (12 and 17°C) in 1 and 2 months. In antioxidant responses, superoxide dismutase (SOD) and catalase (CAT) were significantly increased by ammonia exposure, whereas glutathione (GSH) was decreased. In immune responses, lysozyme and phagocytosis activity were significantly increased by ammonia exposure. In stress indicators, plasma glucose, heat shock protein 70 (HSP 70), and cortisol were significantly increased. At high water temperature (17°C), alterations by ammonia exposure were more distinctly. The results of this study indicated that ammonia exposure can induce toxic effects in the sablefish, and high water temperature can affect the ammonia exposure toxicity.

Antioxidant Responses, Neurotoxicity, and Metallothionein Gene Expression in Juvenile Korean Rockfish Sebastes schlegelii under Dietary Lead Exposure

This study was conducted to assess toxic effects of dietary lead (Pb) exposure on Korean Rockfish Sebastes schlegelii. Juvenile rockfish were used to evaluate the oxidative stress, neurotoxicity, and metallothionein (MT) gene expression after dietary exposure to lead (as Pb2+; 0, 30, 60, 120 and 240 mg/kg). Superoxide dismutase (SOD) activity, a measure of oxidative stress, was substantially elevated in the livers and gills of fish given dietary Pb greater than 60 mg/kg. Glutathione S-transferase (GST) activity in the liver and gill was significantly increased by dietary Pb > 60 mg/kg. A significant decrease in glutathione (GSH) level was observed in fish liver after exposure to dietary Pb > 30 mg/kg and in the gill after treatment with dietary Pb > 120 mg/kg. Acecyltholinesterase (AChE) was noticeably decreased in the brain by dietary Pb > 120 mg/kg and in the muscle by dietary Pb > 60 mg/kg. Metallothionein gene expression in the liver was stimulated significantly by the Pb exposure. Because dietary Pb exposure had a toxic effect on antioxidant responses, a neurotransmitter, and a specific immune expression in rockfish, the results of this study can be used to determine potential useful markers of Pb toxicity. Received June 11, 2016; accepted March 10, 2017.

Reproductive traits of the lake prawn Palaemon paucidens De Haan, 1844 (Decapoda, Palaemonidae), from Goesan Lake, South Korea

The reproductive biology of Palaemon paucidens De Haan, 1844, from Goesan Lake, Korea, was investigated during the period May 2010-October 2011. The proportion of females was significantly greater than that of males (female : male ratio, 1 : 0.7). The gonadosomatic index (GSI) varied monthly, reaching a maximum in May and a minimum in September. Monthly variations in the proportions of ovigerous females showed peaks in April and May. The highest values of the GSI coincided with the breeding period of P. paucidens (April-August). There was no significant difference between the mean GSI of females with non-eyed and eyed eggs, indicating that P. paucidens is a non-consecutive breeder. There was a significant correlation between the number of eggs and the carapace length at early egg stages. There was no significant difference in the intercepts of the regressions of the number of eggs versus carapace length between females carrying non-eyed and eyed egg stages, indicating that there was no brood loss during the incubation period. Egg volume increased significantly (by 75.6%) as eggs developed from the non-eyed to the eyed stage. Reproductive output was 0.20 ± 0.04, based on dry weights in early egg stages. The results were compared with other studies of P. paucidens in Sukdang Lake and other species of palaemonids in different habitats. This comparison reveals intra- and inter-specific variations in reproductive traits of palaemonid shrimp. The phenomenon is suggested to be a result of adaptations to different environmental conditions. Variation in reproductive traits within the same species reflects a different life strategy adaptation in species that will require a different approach in fisheries management. Information on intra- and inter-specific variation in reproductive traits is important to be used as one basic issue of biological information to support an effective fisheries management of P. paucidens, which has been locally exploited in Korea and Japan.

First Record of the Hermit Crab Catapaguroides fragilis (Decapoda: Anomura: Paguridae) in the Korean Waters

A pagurid hermit crab Catapaguroides fragilis was collected in Jeju Island, and described as new to the Korean fauna. It is the first member of the genus Catapaguroides known from Korea. Morphological descriptions of C. fragilis are presented with illustrations.

Age and Growth of Barbel Steed Hemibarbus labeo in Goe-san Lake in Korea

Age and growth of Hemibarbus labeo caught from Goe-san Lake in South Korea from March to November, 2011, were studied. A total of 201 specimens was collected, ranging from 110 to 580 mm in total length (TL). Males and females made up 47.9% and 52.1% of the sample, respectively. Marginal increment analyses showed that vertebral increments, each composed of one opaque and one hyaline zone, were deposited annually. Opaque edges were prevalent from June to July. The relationship between TL and vertebral radius was linear, with equations of R = 0.008TL - 0.208 (male) and R = 0.009TL - 0.272 (female). Regression equations between TL and total weight (TW) were TW = 9×10 -6