Oxidative Stress and DNA Damage in Pagrus major by the Dinoflagellate Karenia mikimotoi

Karenia mikimotoi is a common species of red tide dinoflagellate that causes the mass mortality of marine fauna in coastal waters of Republic of Korea. Despite continuous studies on the ecophysiology and toxicity of K. mikimotoi, the underlying molecular mechanisms remain poorly understood. Red sea bream, Pagrus major, is a high-value aquaculture fish species, and the coastal aquaculture industry of red sea bream has been increasingly affected by red tides. To investigate the potential oxidative effects of K. mikimotoi on P. major and the molecular mechanisms involved, we exposed the fish to varying concentrations of K. mikimotoi and evaluated its toxicity. Our results showed that exposure to K. mikimotoi led to an accumulation of reactive oxygen species (ROS) and oxidative DNA damage in the gill tissue of P. major. Furthermore, we found that K. mikimotoi induced the activation of antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, in the gill tissue of P. major, with a significant increase in activity at concentrations above 5000 cells/mL. However, the activity of glutathione S-transferase did not significantly increase at the equivalent concentration. Our study confirms that oxidative stress and DNA damage is induced by acute exposure to K. mikimotoi, as it produces ROS and hypoxic conditions in P. major. In addition, it was confirmed that gill and blood samples can be used as biomarkers to detect the degree of oxidative stress in fish. These findings have important implications for the aquaculture of red sea bream, particularly in the face of red tide disasters.

Thrap3 promotes nonalcoholic fatty liver disease by suppressing AMPK-mediated autophagy

Autophagy functions in cellular quality control and metabolic regulation. Dysregulation of autophagy is one of the major pathogenic factors contributing to the progression of nonalcoholic fatty liver disease (NAFLD). Autophagy is involved in the breakdown of intracellular lipids and the maintenance of healthy mitochondria in NAFLD. However, the mechanisms underlying autophagy dysregulation in NAFLD remain unclear. Here, we demonstrate that the hepatic expression level of Thrap3 was significantly increased in NAFLD conditions. Liver-specific Thrap3 knockout improved lipid accumulation and metabolic properties in a high-fat diet (HFD)-induced NAFLD model. Furthermore, Thrap3 deficiency enhanced autophagy and mitochondrial function. Interestingly, Thrap3 knockout increased the cytosolic translocation of AMPK from the nucleus and enhanced its activation through physical interaction. The translocation of AMPK was regulated by direct binding with AMPK and the C-terminal domain of Thrap3. Our results indicate a role for Thrap3 in NAFLD progression and suggest that Thrap3 is a potential target for NAFLD treatment.

Complete mitochondrial genome of the sea-pen, Cavernularia obesa (Valenciennes, 1850) (Octocorallia: Veretillidae)

Here, we sequenced and annotated the complete mitochondrial genome for the sea-pen, Cavernularia obesa (Valenciennes, 1850). The complete mitogenome of C. obesa is 18,641 bp, with 34.7% of GC ratio. The mitogenome comprises 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a non-coding region. Phylogenomic analysis based on 19 in-group taxa belonging to the orders Alcyonacea and Pennatulacea has congruent with published phylogenetic relationship for Octocorallia, which C. obesa was grouped to members of the Pennatulacea. This mitogenome resource will be useful for future phylogenetic studies of water fleas.

Characterization and phylogenetic analysis of the complete mitochondrial genome of the rainbow krib, Pelvicachromis pulcher (Perciformes: Cichlidae)

We report the complete mitochondrial genome information of the rainbow krib, Pelvicachromis pulcher (Boulenger 1901). Illumina HiSeq genome sequencing allowed the assembly of a circular mitogenome of 17,196 base pairs (bp) from P. pulcher consisting of 47% GC nucleotides, 13 protein-coding genes (PCGs), 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a putative control region in the typical teleost gene composition. The gene order of the P. pulcher mitogenome was identical to that of other cichlid species. A maximum likelihood phylogenetic tree based on mitochondrial PCGs showed a relationship of P. pulcher with a cichlid Tylochromis polylepis (Boulenger 1900), suggesting that more complete mitogenomes are needed to explore mitogenome evolution in West African tribes and riverine cichlids, as this genomic information is the first complete mitogenome in the tribe Chromidotilapiini.

Reductive Transformation of Hexavalent Chromium in Ice Decreases Chromium Toxicity in Aquatic Animals

In this study, the toxicity of hexavalent chromium [Cr(VI)] reduced by citric acid in ice was measured using representative aquatic model invertebrates (i.e., rotifer, water flea, amphipod, and polychaete) and a vertebrate (zebrafish) by analyzing short- and/or long-term endpoints that are frequently applied to each animal. Cr(VI) reduction in the presence of citric acid was markedly enhanced in the ice phase compared to that in an aqueous solution through the freeze concentration effect. The highly concentrated Cr(VI) and citric acid in ice grain boundaries were also confirmed using in situ cryogenic confocal Raman spectroscopy. Overall, exposure to Cr(VI) resulted in higher acute and/or chronic effects on aquatic animals, such as drastic mortality, growth inhibition, and decrease in offspring number, whereas the animals were increasingly tolerant to Cr(VI) that was reduced in the ice phase. Sublethal concentrations of Cr(VI) significantly decreased the antioxidant capacity in the aquatic animals. However, when the same concentrations of Cr(VI) were reduced in ice, these treatments showed no modulation or increase in the antioxidant defense system. Taken together, our results suggest that Cr(VI) reduction into Cr(III) was successfully achieved in ice and that this methodology can decrease the actual toxicity of Cr(VI) in aquatic animals.

Effects of extremely high concentrations of polystyrene microplastics on asexual reproduction and nematocyst discharge in the jellyfish Sanderia malayensis

Numerous studies have assessed the detrimental effects of microplastics (MPs) on aquatic invertebrates due to their ubiquitous and persistent nature. In this study, the toxic effects of MPs were examined on the polyp and ephyrae of the marine hydrozoan Sanderia malayensis. The jellyfish were exposed to different sizes (1-6 μm) of non-functionalized polystyrene microbeads at a concentration of 1 × 10⁴ particles mL^-1. The MPs randomly attached to the external and internal parts of the jellyfish body, and the longest MP attachment was 52 days during the depuration after initial exposure (for 24 h). Consistent seventeen-day exposure to MPs significantly reduced the asexual reproduction of the S. malayensis polyps. To assess if the MPs can stimulate nematocyst discharge in polyp and ephyrae stages via direct contact, they were exposed to particle sizes up to 430 μm. None of the MPs or their aggregates, including the 430 μm particles, induced nematocyst discharge. These results suggest that prolonged exposure to relatively high MP concentrations affects the early stages of jellies and provides evidence for the no effect on nematocyst discharge.

Complete mitochondrial genome of the six-line wrasse Pseudocheilinus hexataenia (Labriformes, Labridae)

Here, we report the complete mitogenome information of the six-line wrasse Pseudocheilinus hexataenia (Bleeker, 1857). Genome sequencing using the Illumina HiSeq platform allowed the assembly of a circular mitochondrial genome of 17,111 bp from P. hexataenia, consisting of 54% AT nucleotides, 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a putative control region in the typical Labriformes gene composition. The gene order of the P. hexataenia mitochondrion was identical to that of the Labridae mitogenomes. Phylogenetic reconstruction places P. hexataenia with a close relationship with the mitogenome of the goldsinny wrasse, Ctenolabrus rupestris.

Hepatic MIR20B promotes nonalcoholic fatty liver disease by suppressing PPARA

Background

Non-alcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation and imbalances in lipid metabolism in the liver. Although nuclear receptors (NRs) play a crucial role in hepatic lipid metabolism, the underlying mechanisms of NR regulation in NAFLD remain largely unclear.

Methods

Using network analysis and RNA-seq to determine the correlation between NRs and microRNA in human NAFLD patients, we revealed that MIR20B specifically targets PPARA. MIR20B mimic and anti-MIR20B were administered to human HepG2 and Huh-7 cells and mouse primary hepatocytes as well as high fat diet (HFD)- or methionine-deficient diet (MCD)-fed mice to verify the specific function of MIR20B in NAFLD. We tested the inhibition of the therapeutic effect of a PPARα agonist, fenofibrate, by Mir20b and the synergic effect of combination of fenofibrate with anti-Mir20b in NAFLD mouse model.

Results

We revealed that MIR20B specifically targets PPARA through miRNA regulatory network analysis of nuclear receptor genes in NAFLD. The expression of MIR20B was upregulated in free fatty acid (FA)-treated hepatocytes and the livers of both obesity-induced mice and NAFLD patients. Overexpression of MIR20B significantly increased hepatic lipid accumulation and triglyceride levels. Furthermore, MIR20B significantly reduced FA oxidation and mitochondrial biogenesis by targeting PPARA. In Mir20b-introduced mice, the effect of fenofibrate to ameliorate hepatic steatosis was significantly suppressed. Finally, inhibition of Mir20b significantly increased FA oxidation and uptake, resulting in improved insulin sensitivity and a decrease in NAFLD progression. Moreover, combination of fenofibrate and anti-Mir20b exhibited the synergic effect on improvement of NAFLD in MCD-fed mice.

Conclusions

Taken together, our results demonstrate that the novel MIR20B targets PPARA, plays a significant role in hepatic lipid metabolism, and present an opportunity for the development of novel therapeutics for NAFLD.

Funding

This research was funded by Korea Mouse Phenotyping Project (2016M3A9D5A01952411), the National Research Foundation of Korea (NRF) grant funded by the Korea government (2020R1F1A1061267, 2018R1A5A1024340, NRF-2021R1I1A2041463, 2020R1I1A1A01074940), and the Future-leading Project Research Fund (1.210034.01) of UNIST.

The complete mitochondrial genome of Lamprologus signatus (Perciformes: Cichlidae)

In this study, the complete 16,583 bp mitochondrial genome of Lamprologus signatus (Poll, 1952) was determined from a specimen sourced from Lake Tanganyika. The mitogenome contains 37 genes [13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, and 22 transfer RNA (tRNA) genes] and a putative control region, which consists of 27.1% A, 27.0% T, 29.9% C, and 16.0% G, with a total G + C content of 45.9%. A maximum likelihood phylogenetic tree based on mitochondrial PCGs suggested that L. signatus is clustered with members of the tribes Haplochromini and Tropheini. As this is the first report of the entire mitogenome in the tribe Lamprologini, the complete mitochondrial sequence information of L. sigantus will be useful in determining phylogenetic relationships of Pseudocrenilabrinae tribes.

Exposure to metals premixed with microplastics increases toxicity through bioconcentration and impairs antioxidant defense and cholinergic response in a marine mysid

Coexistence of metals and microplastics (MPs) in aquatic environments represents a growing concern; however, little is known regarding the risks associated with their combined effects. Here, the effects of five metals (As, Cd, Cu, Pb, and Zn), alone or combined with MPs for various premixing durations (30 and 60 days), on the juvenile and adult stages of the marine mysid Neomysis awatschensis were evaluated. The toxicity (50% lethal concentration for 96 h) and bioconcentration of metals premixed with MPs were measured, and their effects on the antioxidant defense and cholinergic systems were examined. Metal toxicity increased with increasing premixing period with MPs, and juveniles were more sensitive to exposure to metals premixed with MPs than adults. Metal bioconcentration in the mysid body increased following co-exposure with MPs. Metals premixed with MPs significantly increased intracellular malondialdehyde content at both stages but decreased glutathione content in juveniles. At both stages, catalase and superoxide dismutase activity was suppressed following co-exposure to metals and MPs, except under the Cu treatment. Moreover, co-exposure inhibited acetylcholinesterase activity at both stages, suggesting cholinergic impairment. Taken together, metals and MPs produce synergistic detrimental effects on marine mysids in a stage-specific manner. Further studies are warranted to elucidate the role of MPs as a vector for contaminants and stimulator of toxicity in aquatic organisms.

Exposure to sublethal concentrations of zinc pyrithione inhibits growth and survival of marine polychaete through induction of oxidative stress and DNA damage

Effects of zinc pyrithione (ZnPT) and inorganic Zn (ZnCl₂) were evaluated on a marine polychaete at sublethal concentrations for 14 days. ZnPT decreased the burrowing activity and AChE activity with higher acute toxicities, implying its cholinergic effect. Both ZnPT and ZnCl₂ increased MDA levels at higher concentrations, suggesting lipid peroxidation and oxidative stress. In the ZnPT-treated polychaete, enzymatic activities of CAT and SOD were elevated with an increase in DNA damage, whereas the levels of GSH, GPx, GR, and GST were decreased. However, in the ZnCl₂-treated polychaete, the level of GSH and enzymatic activities of CAT, SOD, GPx, GR, and GST were significantly elevated to resist cellular damage. During 97 days depuration experiment, significant mortality and growth retardation were observed in the ZnPT-exposed polychaete. Overall, ZnPT was found to be more toxic than ZnCl₂ with the harmful impact on antioxidant defense system and DNA stability in marine polychaete.

PPM1A Controls Diabetic Gene Programming through Directly Dephosphorylating PPARγ at Ser273

Peroxisome proliferator-activated receptor γ (PPARγ) is a master regulator of adipose tissue biology. In obesity, phosphorylation of PPARγ at Ser273 (pSer273) by cyclin-dependent kinase 5 (CDK5)/extracellular signal-regulated kinase (ERK) orchestrates diabetic gene reprogramming via dysregulation of specific gene expression. Although many recent studies have focused on the development of non-classical agonist drugs that inhibit the phosphorylation of PPARγ at Ser273, the molecular mechanism of PPARγ dephosphorylation at Ser273 is not well characterized. Here, we report that protein phosphatase Mg²⁺/Mn²⁺-dependent 1A (PPM1A) is a novel PPARγ phosphatase that directly dephosphorylates Ser273 and restores diabetic gene expression which is dysregulated by pSer273. The expression of PPM1A significantly decreases in two models of insulin resistance: diet-induced obese (DIO) mice and db/db mice, in which it negatively correlates with pSer273. Transcriptomic analysis using microarray and genotype-tissue expression (GTEx) data in humans shows positive correlations between PPM1A and most of the genes that are dysregulated by pSer273. These findings suggest that PPM1A dephosphorylates PPARγ at Ser273 and represents a potential target for the treatment of obesity-linked metabolic disorders.

Waterborne zinc pyrithione modulates immunity, biochemical, and antioxidant parameters in the blood of olive flounder

In this study, potential immunological and hematological effects of different concentrations (0, 1, 10, and 50 μg L^-l) of waterborne zinc pyrithione (ZnPT) were studied in the blood of the olive flounder Paralichthys olivaceus over 30 days. Reduced alternative complement activity (ACH50) and lysozyme activity were measured in fish exposed to 10 and/or 50 μg L^-l of ZnPT for 20 days. Decreased levels of total Ig were also observed in response to 10 and/or 50 μg L^-l ZnPT during the exposure period. Levels of cortisol, a marker of stress, were significantly increased by 10 and 50 μg L^-l ZnPT from day 10, and by 1 μg L^-l exposure on day 30. The levels of red blood cells (RBCs) and white blood cells (WBCs) decreased following exposure to 10 and/or 50 μg L^-l ZnPT, while no significant change was observed in hemoglobin level. Concentrations of total protein and albumin were significantly reduced with 50 μg L^-l ZnPT at day 20. Alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activities were significantly increased following exposure to 10 and/or 50 μg L^-l ZnPT. Lipid peroxidation was induced by ZnPT, and higher concentrations (10 and 50 μg L^-l) significantly increased intracellular malondialdehyde levels during exposure. Regarding the subsequent antioxidant response, intracellular glutathione levels increased significantly in response to 10 and 50 μg L^-l ZnPT on days 20 and 30. Similarly, catalase and superoxide dismutase activity was significantly increased in response to 10 and 50 μg L^-l ZnPT after day 10. Taken together, changes in the studied parameters suggested the immunotoxicity of ZnPT, with modulations observed in hematological homeostasis and oxidative stress induction in the blood of olive flounder.

Effects of sublethal concentrations of the antifouling biocide Sea-Nine on biochemical parameters of the marine polychaete Perinereis aibuhitensis

Sea-Nine™ 211 is an emerging biocide that has an adverse impact on aquatic environments. In this study, the marine polychaete Perinereis aibuhitensis was exposed to Sea-Nine (0.1, 1, and 10 μg L^-1), and acute toxicity and biochemical responses such as changes in the intracellular contents of malondialdehyde (MDA) and glutathione (GSH) and enzymatic activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and acetylcholinesterase (AChE) were evaluated over a period of 14 d. Determined median lethal doses, LC50 were 268 μg L^-1, 142 μg L^-1, and 55 μg L^-1 at 24 h, 96 h, and 14 d, respectively. The MDA content increased significantly in a dose- and time-dependent manner, indicative of lipid peroxidation-related oxidative damage. Significantly higher intracellular GSH levels and antioxidant defense-related enzyme (CAT, SOD, GPx, GR, and GST) activities were observed after exposure to 10 μg L^-1 Sea-Nine. In contrast, Sea-Nine treatment significantly reduced AChE activity at the highest concentration of Sea-Nine used (10 μg L^-1). Taken together, these results indicate that sublethal concentrations of Sea-Nine are toxic to marine polychaetes through potential lipid peroxidation, induction of oxidative stress, and modulation of the cholinergic system. Our results can contribute to biomonitoring of aquatic environments and ecotoxicological research through the measurements of polychaete cellular defenses against waterborne biocides.

Chlorothalonil induces oxidative stress and reduces enzymatic activities of Na+/K+-ATPase and acetylcholinesterase in gill tissues of marine bivalves

Chlorothalonil is a thiol-reactive antifoulant that disperses widely and has been found in the marine environment. However, there is limited information on the deleterious effects of chlorothalonil in marine mollusks. In this study, we evaluated the effects of chlorothalonil on the gill tissues of the Pacific oyster, Crassostrea gigas and the blue mussel, Mytilus edulis after exposure to different concentrations of chlorothalonil (0.1, 1, and 10 μg L⁻¹) for 96 h. Following exposure to 1 and/or 10 μg L⁻¹ of chlorothalonil, malondialdehyde (MDA) levels significantly increased in the gill tissues of C. gigas and M. edulis compared to that in the control group at 96 h. Similarly, glutathione (GSH) levels were significantly affected in both bivalves after chlorothalonil exposure. The chlorothalonil treatment caused a significant time- and concentration-dependent increase in the activity of enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR), in the antioxidant defense system. Furthermore, 10 μg L⁻¹ of chlorothalonil resulted in significant inhibitions in the enzymatic activity of Na⁺/K⁺-ATPase and acetylcholinesterase (AChE). These results suggest that chlorothalonil induces potential oxidative stress and changes in osmoregulation and the cholinergic system in bivalve gill tissues. This information will be a useful reference for the potential toxicity of chlorothalonil in marine bivalves.

Long-term exposure to waterborne nonylphenol alters reproductive physiological parameters in economically important marine fish

Low concentrations of nonylphenol (NP) in aquatic environment can induce drastic effects on the endocrine system in animals. In this study, we examined the modulatory effects of NP on reproductive and physiological parameters in juveniles of the red seabream and black rockfish following waterborne NP exposure (0, 1, 10, and 50 μg L^-1) for 60 days. In red seabream exposed to 50 μg L^-1 NP, plasma levels of 17β-estradiol (E2) and 11-ketotestosterone (11-KT) were significantly lower at 30 and 60 days, while E2 levels were slightly higher in 10 μg L^-1-exposed individuals at day 30. Similarly, significantly lower levels of E2 and 11-KT were observed in 10 and 50 μg L^-1-exposed black rockfish at 60 days, whereas the E2 level was higher in 1 μg L^-1-exposed individuals at day 30. After exposure to NP, plasma and mRNA levels of vitellogenin (VTG) were significantly higher in both species at 30 and 60 days, similar to the inducible effects from synthetic estrogen. Plasma cortisol levels were significantly elevated by relatively higher concentrations of NP (10 and 50 μg L^-1) at 30 and 60 days. Finally, 60 days of exposure of 50 μg L^-1 NP significantly decreased the gonadosomatic index (GSI) and increased the hepatosomatic index (HSI) in both species. The results obtained from this study provide an evidence of the endocrine disrupting potential of waterborne NP on early stages of economically important marine fish. The NP-triggered endocrine modulation can induce effects on the development of reproductive and metabolic organs in fish species.

Rigorous formulation for electromagnetic plane-wave scattering from a general-shaped groove in a perfectly conducting plane

Scattering of an obliquely incident plane wave by a general-shaped groove engraved on a perfectly conducting plane is rigorously solved. The scattered field is represented by a Fourier-integral representation. To analytically represent the fields in a general-shaped groove, the groove is divided into L number of layers. Fields are then expressed in each layer as summations of 2D spatial harmonic fields with unknown coefficients. Matching the boundary conditions between layers provides a linear set of equations connecting all the unknown harmonic coefficients. Judicious use of Fourier transform on the equations resulting from matching boundary conditions at the groove aperture provides a series representation of the scattered field in the spectral domain with unknown harmonic coefficients of the first layer in the groove. A stable solution is obtained by solving the complete system of equations with an adaptive choice for the number of modes in each layer.

Acoustic scattering from two circular apertures in a thick hard plane

A problem of acoustic wave scattering from two circular apertures in a thick hard plane is solved. The Hankel transform and mode matching is used to represent the scattered field in rapidly convergent series. The reflection coefficient, transmission coefficient, and far-zone field are rigorously derived and presented in numerically efficient forms. Numerical computations are performed to illustrate scattering behaviors in terms of aperture geometry.

Acoustic hybrid junction in a rectangular waveguide

Acoustic scattering from a hybrid junction in a rectangular waveguide is studied. The Fourier transform and mode matching is used to represent the scattered wave and the simultaneous equations for the modal coefficients are formulated. A residue calculus is utilized to obtain a solution to the simultaneous equations in fast-converging series. Numerical computations are performed to show the behavior of transmission in terms of junction geometry and operating frequency. The utility of acoustic hybrid junction is discussed in terms of its decoupling characteristics.

Examination of the factorial validity of the Group Environment Questionnaire

The purpose of this study was to test the hypothesized factor structure of the Group Environment Questionnaire (GEQ) with confirmatory factor analysis and to ascertain the degree of factorial invariance across gender and across type of sport (team, individual). Additionally, the underlying theoretical structure on which the GEQ was developed was examined by fitting the data to alternative hierarchical factor structures. These models were tested with GEQ data collected on 740 high school varsity athletes (426 males, 314 females). It was shown that the males and females had different factor structures and that neither group exhibited the hypothesized structure. Attempts to fit the data to a two-factor and a second-order hierarchical factor model were unsuccessful. Finally, exploratory factor analysis did not produce a satisfactory four-factor solution. It was concluded that the data from this sample do not support the hypothesized four-factor structure of the GEQ and that further examination of the factor structure of this instrument is required.