Jae-Sung Rhee

Age-dependent antioxidant responses to the bioconcentration of microcystin-LR in the mysid crustacean, Neomysis awatschensis

Microcystins (MCs) are naturally occurring algal toxins in the aquatic environment and pose a serious threat to the ecosystem. In general, aquatic populations are structured by organisms of different ages, with varying degrees of biochemical and physiological responses. In this study, juvenile and adult marine mysids (Neomysis awatschensis) were exposed to MC-Leucine Arginine (MC-LR) (0.1, 1, and 10xa0μgxa0L-1) for 7 days, and the bioconcentration dynamics and responses of antioxidant defense system were measured during the exposure and additional depuration periods (7 days). MC-LR bioconcentrated in a dose-dependent manner, from a threshold concentration of 1xa0μgxa0L-1 in both stages, and the levels reduced gradually during the depuration phase. Bioconcentration patterns of MC-LR were highly age-specific, as juvenile mysids showed peaks during the exposure period, whereas adults exhibited a peak on the first day of depuration. After exposure to 10xa0μgxa0L-1 concentration, elevated levels of malondialdehyde (MDA) and glutathione (GSH) were observed during the late (days 5 and 7) exposure and early (days 1 and 3) depuration periods in juvenile mysids, while adult mysids showed a peak on day 7 of the exposure period. Age-specific responses were also observed in the enzymatic activities of glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR). Juvenile mysids showed a significant elevation in all enzymatic activities during the exposure and/or depuration phase upon exposure to 10xa0μgxa0L-1 MC-LR, but only CAT and SOD enzymes showed significant changes during the exposure and/or depuration periods in adults. Overall, our results indicate the bioconcentration potential of MC-LR and its threshold in the marine mysid, in addition to age-specific MC-LR dynamics and subsequent biochemical responses.

Transcriptome profiles of Daphnia magna across to the different water chemistry of surface water of the Korean Demilitarized Zone

The Korean Demilitarized Zone (DMZ) has almost completely protected surface water conditions. Despite the water conditions of DMZ are excellent clear, downstream of river or natural irrigation ponds near the region are recently developed by human activities such as agriculture, ginseng fields or ecotourism. To understand the potential effect of physico-chemical characteristics of the DMZ water, the freshwater model Daphnia magna was exposed to water samples that were collected from four sites near the DMZ. RNA-seq identified some differentially expressed transcripts which are sensitive to small differences of water chemistry. Particularly transcripts coding for the stress responsive heat shock protein (Hsp) superfamily and innate immune system were significantly increased in response to the water samples of irrigation ponds and downstream of Seweol river where are analyzed to have low pH and high levels of chemical fertilizer nutrients such as nitrogen (N) and phosphorus (P). These water samples decreased mRNA expressions of crucial members which are involved in crustacean morphogenesis and reproduction metabolism (e.g. cuticle protein family, ecdysteroid metabolism, vitellogenesis). Evidence on the high transcriptional sensitivity of the aquatic model D. magna against small differences of water chemistry will be a useful strength for further applications in environmental and ecotoxicological genomics.

Sublethal concentrations of atrazine promote molecular and biochemical changes in the digestive gland of the Pacific oyster Crassostrea gigas

Atrazine is an herbicide used to control pre- and post-emergence broadleaf weeds and grasses. To understand the acute effects of atrazine on oyster digestive gland, a series of molecular and biochemical responsive parameters were analyzed in the Pacific oyster Crassostrea gigas after exposure to different concentrations (1, 10, and 50 μg L-1) for 96 h. Intracellular malondialdehyde (MDA) level was significantly increased in the 50 μg L-1 exposed oysters, while no significant modulation was observed in glutathione (GSH) level. Of antioxidant defense system, enzymatic activities of catalase (CAT) and superoxide dismutase (SOD) were significantly higher at 50 μg L-1 compared to the control or DMSO treated groups. Regarding their transcriptional levels, two glutathione S-transferases (GSTs) GSTO and GSTP, CuZnSOD, MnSOD, and CAT were significantly upregulated at 10 and/or 50 μg L-1 in the oyster digestive gland. Atrazine exposure reduced both enzymatic activity and mRNA expression of Na+/K+-ATPase and acetylcholinesterase (AChE) at 50 μg L-1. In addition, acute exposure of 10 and/or 50 μg L-1 atrazine significantly increased transcriptional expression of Hsp superfamily with strong induction of hsp70 and hsp90 family. These results suggest that atrazine has detrimental effects on the digestive gland of C. gigas by modulating important molecular and biochemical parameters within relatively short time period.

Bisphenol A causes mortality and reduced hatching success through increase of cell damage and dysfunction of antioxidant defense system in marine medaka embryo

In this study, marine medaka embryos were continuously exposed to different concentrations of bisphenol A (BPA; 200-1000 μg/L) during post fertilization. Mortality, hatching rate, and cellular death in marine medaka embryos were detected. In addition, survival rate of hatched larvae was measured to analyze whether BPA has persistent effects from BPA-exposed embryos to post-hatching period. Our results clearly showed that the hatching rate was decreased in a dose-dependent manner, while the mortality was increased with induction of cellular death and dysfunction of antioxidant defense system in marine medaka embryos. Of hatched larvae, the survival rate was decreased as the exposure concentrations increasing. Thus, our data suggested that early exposure of BPA caused embryonic toxicity, resulted in persistent effects on larval survival in marine medaka.

Dose- and age-specific antioxidant responses of the mysid crustacean Neomysis awatschensis to metal exposure

Waterborne metals can adversely affect an organisms innate defenses through oxidative stress. In the present study, the marine mysid Neomysis awatchensis was exposed to sublethal concentrations (1/10 and 1/5 of the median LC50s) of As, Cd, Cu, Pb, and Zn for 48 or 96u202fh at the juvenile and adult developmental stages, and the dose- and age-specific antioxidant defense system responses were characterized. Metal accumulation and modulation of four key antioxidant biomarkers, malondialdehyde (MDA), glutathione (GSH), superoxide dismutase, and catalase, were measured in juvenile and adult mysids. Based on LC50, level of metal toxicity was dependent on metal concentration, developmental stage, and the exposure duration. Intracellular MDA content was increased in the As-, Cu-, Pb-, and Zn-exposed juvenile mysids after exposure for 48 and/or 96u202fh, while increases in MDA content were observed in adult mysids following Cu and Zn exposure. Interestingly, GSH content was differentially modulated, where intracellular GSH levels decreased in juvenile mysids following Cd, Cu, Pb, and Zn exposure, but significantly increased in metal-exposed adult mysids, except for Pb exposure. The catalase and superoxide dismutase activities displayed similar stage-specific increases or decreases as also observed for the different GSH levels, suggesting that the susceptibility to and defense against metal-induced oxidative stress differed based on stage. Modulations in MDA and GSH content and enzymatic activity of the antioxidant defense system indicate that mysid antioxidant defense system factors are intimately connected during control of oxidative imbalances with different capacities at different developmental stages.

Non-target effects of antifouling agents on mortality, hatching success, and acetylcholinesterase activity in the brine shrimp Artemia salina

Many commercial shipping, leisure crafts, and aquaculture facilities employ antifouling agents to control biofouling/biocorrosion by keeping their metallic hulls clear, but most agents have been known to cause negative effects such as pollution in coastal marine ecosystem. In this study, we measured the deleterious effects of three antifouling agents (i.e. tributyltin; TBT, diuron, irgarol 1051) on nauplii mortality, acetylcholinesterase (AChE, EC3.1.1.7) activity, and hatching success of cysts in the brine shrimp Artemia salina. Lethal concentration 50 (LC50) was measured using A. salina nauplii in time-course (i.e. 24, 48, and 72 h) to select proper concentrations for the suite of AChE assays. The 24 h-LC50 toxicities of three antifouling agents ranged for mortality were as follows: TBT 0.208 μg/L, diuron 10261 μg/L, and irgarol 1051 982 μg/L. Selected doses within the LC50 value of each antifouling agent significantly inhibited AChE activity for 24 h, and newly hatched nauplii were more sensitive than 48 h old nauplii. Furthermore, the exposure conditions dose-dependently reduced the hatching rate of A. salina cysts. We conclude that three antifouling agents tested in this study may have a toxic cholinergic effect on nauplii through AChE inhibition, in addition to ecotoxicity on cyst hatching.

Waterborne Phenanthrene Modulates Immune, Biochemical, and Antioxidant Parameters in the Bloods of Juvenile Olive Flounder

ObjectiveThe current study aimed to evaluate potential effect of waterborne phenanthrene (Phe) on immune, biochemical, and antioxidant parameters in the blood of juvenile olive flounder (Paralichthys olivaceus).MethodsJuvenile olive flounder were exposed to different concentrations (control, 0.1, 0.5, and 1.0 μg L-1) of Phe for 14 days and bloods were sampled at day 7 and 14. Hematological (alternative complement activity, ACH50; lysozyme; total immunoglobulin, Ig; cortisol; Hemoglobin, Hb; red blood cell, RBC; white blood cell, WBC), biochemical (glucose; albumin; alanine aminotransferase, ALT; aspartate aminotransferase, AST; alkaline aminotransferase, ALP), lipid peroxidation marker malondialdehyde (MDA), and antioxidant (glutathione, GSH; catalase, CAT; superoxide dismutase, SOD) parameters were evaluated in the blood samples.ResultsACH50, lysozyme, Ig, and WBC values were significantly decreased by 1.0 μg L-1 of Phe at day 14, while cortisol level was significantly increased by 0.5 and 1 μg L-1 of Phe at day 14. Total protein concentration was significantly decreased in the 1.0 μg L-1 Phe-exposed blood sample at day 7 and 14. Values for ALT, AST, and ALP were significantly increased in response to 0.5 and 1.0 μg L-1 of Phe at day 14. There was no significant change in Hb, RBC, albumin, and glucose upon Phe. MDA content was significantly increased by 1.0 μg L-1 of Phe at day 14. GSH content was significantly elevated upon 1.0 μg L-1 of Phe at day 7, while the content was significantly depleted at day 14. The enzymatic activities of CAT and SOD were significantly increased by 0.5 and 1.0 μg L-1 of Phe at day 14.ConclusionThe results indicate significant modulatory effects of waterborne Phe on immune, biochemical, and antioxidant parameters in the economically important fish. The modulations can be used as potential biomarkers in Phe-contaminated aquatic environment.

Exposure to sublethal concentrations of tributyltin reduced survival, growth, and 20-hydroxyecdysone levels in a marine mysid

Tributyltin (TBT) is as an antifouling organotin compound used in boat paints. Although organotin-based antifouling agents have been banned on a global scale, the mode of action of TBT has been studied in numerous aquatic species because of its toxicity, persistence, bioaccumulation potential, and endocrine-disrupting characteristics. In this study, we conducted 96-h acute toxicity tests wherein we exposed juvenile and adult marine mysids to waterborne TBT. Over 4 weeks of exposure, mortality was dose-dependently increased in juveniles and adult mysids. To test sublethal effects of TBT on juvenile development, newborn juvenile mysids were exposed to 1, 5, or 10u202fngu202fL-1u202fTBT for 4 weeks. Subsequently, we measured morphological growth parameters and quantified the hormone ecdysterone (20-hydroxyecdysone: 20E), which controls molting in mysids. The lengths of the whole body, antennal scale, exopod, endopod, and telson were significantly smaller in the 5 and/or 10u202fngu202fL-1 TBT-exposed juvenile mysids than in control and DMSO-exposed groups. Levels of 20E were significantly lower at 5 and 10u202fngu202fL-1u202fTBT exposures. Additionally, the number of newly hatched juveniles was significantly lower from females previously exposed to 10u202fngu202fL-1u202fTBT. Our results indicate sublethal concentrations of TBT have inhibitory effects on the survival, growth, and production of juveniles. The lower 20E levels could be strongly associated with TBT-triggered inhibition.

Comparative Toxicokinetics and Antioxidant Response in the Microcystin-LR-Exposed Gill of Two Marine Bivalves, Crassostrea gigas and Mytilus edulis

ABSTRACT n Microcystins (MC) produced by several cyanobacteria are potent hepatotoxins, whereas the toxicokinetics and subsequent detrimental effects ofMCare not fully understood in marine bivalves. In this study, the accumulation and depuration pattern of MC-Leucine-Arginine (MC-LR) along with the antioxidant response were investigated in the gill tissue of Pacific oyster Crassostrea gigas and blue mussel Mytilus edulis exposed to 0.1, 1, 10, and 20 µg L-1 MC-LR for 7 days. Time- and concentration-dependent accumulation and depuration of MC-LR were observed in the gill tissue during the exposure and depuration phases. The values for maximum accumulation of MC-LR and malondialdehyde content were statistically significant (P < 0.05) at the end of exposure (day 7) to 20 µg L-1 MC-LR for both the bivalves, and at the beginning of the depuration period when M. edulis and C. gigas were exposed to 10 and 20 µg L-1, respectively. A significant level of glutathione (GSH) was detected in M. edulis in response to 20 µg L-1 MC-LR during the exposure and depuration periods, whereas no significant levels of GSH were detected in C. gigas. The MC-LR accumulation induced oxidative stress in the gill tissue through modulation of the activities of antioxidant enzymes, the antioxidant response being more significant in the mussel than in the oyster. The enzymatic activities of glutathione S-transferase, superoxide dismutase (SOD), glutathione peroxidase, and glutathione reductase (GR) increased significantly in M. edulis, whereas in C. gigas, significant increase in the activities of SOD, catalase, and GR were observed at the end of exposure (day 7) to 20 µg L-1 MC-LR. Similarly, during the depuration period, significant increases in the antioxidant activities were observed in M. edulis mostly at the beginning (day 1 and day 5) of exposure compared with the levels in C. gigas. The results obtained in this study will be useful in the understanding of MC-LR accumulation in bivalve gill tissues and the subsequent antioxidant defense response.

Plasma biomarkers in juvenile marine fish provide evidence for endocrine modulation potential of organotin compounds

Organotin compounds, such as tributyltin (TBT) and triphenyltin (TPT), have been widely used to control marine fouling. Here, we show that organotin stimulation reduces the hormone levels in the plasma of two economically important aquaculture fish. Blood plasma samples were collected from juvenile red seabream and black rockfish exposed to environmentally realistic concentrations of TBT and TPT for 14u202fdays. The levels of two plasma biomarkers, namely the yolk protein precursor vitellogenin (VTG) and the sex steroid 17β-estradiol (E2), were measured to determine the endocrine disrupting potential of the organotin compounds. Both organotin compounds were dose-dependently accumulated in the blood of two fish. Exposure to waterborne TBT and TBT significantly decreased the plasma VTG levels in both the juvenile fish in a dose-dependent manner. In contrast, the treatment with E2, a well-known VTG inducer, significantly increased the plasma VTG levels in both the fish. In addition, the mRNA levels of vtg were also downregulated in the liver tissues of both the fish at 100 and/or 1000u202fngu202fL-1 of TBT or TPT exposure. The plasma E2 titers were significantly suppressed at 100 and/or 1000u202fngu202fL-1 of TBT or TPT exposure for 14u202fdays compared to their titer in the control. Since estrogen directly regulates vtg gene expression and VTG synthesis, our results reveal the endocrine disrupting potential of organotin compounds, and subsequently the endocrine modulation at early stage of fish can trigger further fluctuations in sexual differentiation, maturation, sex ration or egg production. In addition, the results demonstrate their effects on non-target organisms, particularly on animals reared in aquaculture and fisheries.