Immunostaining of UVA-induced DNA damage in erythrocytes of medaka (Oryzias latipes)

Regulation of Biomineralization and Autophagy by the Stress-Sensing Transcription Factor CgRunx1 in Crassostrea gigas Under Daylight Ultraviolet B Radiation

As human activities increase and environmental changes persist, increased ultraviolet B (UVB) radiation in aquatic ecosystems poses significant threats to aquatic life. This study, through transcriptomic analysis of the mantle tissue of Crassostrea gigas following UVB radiation exposure, identified and validated two key transcription factors, CgRunx1 and CgCBFβ. The highest expression levels of CgRunx1 and CgCBFβ in the mantle suggest their pivotal roles in this tissue. Co-immunoprecipitation experiments revealed that CgRunx1 and CgCBFβ could form heterodimers and interact with each other. Furthermore, this study assessed the impact of UVB radiation on the levels of reactive oxygen species of the C. gigas, speculating that CgRunx1, as a potential redox-sensitive transcription factor, might be regulated by intracellular ROS. Through screening and binding site prediction analysis of target genes, coupled with dual-luciferase reporter assays, we verified that CgRunx1 might participate in regulating the biomineralization and autophagy processes in C. gigas by activating the transcriptional expression of target genes Transport and Golgi organization 1 and V-type proton ATPase catalytic subunit A. These findings provide new insights into the molecular response mechanisms of the C. gigas to UVB radiation and lay an important foundation for studying the adaptive evolution of bivalves to environmental stress.

In vitro photoprotective potential of aryl-sandwiched (thio)semicarbazones against UVA mediated cellular and DNA damage

The most prevalent solar ultraviolet radiation is ultraviolet-A (UVA) radiation. It is the inducer of reactive oxygen species (ROS), a potent mediator of inflammation and photocarcinogenesis. Regular application of sunscreens containing UVA filters is an effective preventive measure in mitigating the risk associated with the formation of dermal carcinoma. Therefore, the development of new photoprotective agents is of great need. The current work examined the in vitro photoprotection of the aryl-linked (thio)semicarbazone derivatives against UVA-mediated DNA damage, inflammation, reactive nitrogen species (RNS), and ROS. Except for the inflammatory cytokine assay, which was carried out on the human monocytic leukemia (THP-1) cell line, all tests were conducted on the human dermal fibroblast (BJ) cell line. In comparison to benzophenone (reference compound), the compound (2Z, 2'Z)-2,2'-(1,3-Phenylenebis (methanylylidene)) bis (hydrazine-1-carbothioamide) (DD-21) demonstrated considerable protection against UVA-induced damage. Compared to the UVA-irradiated control, DD-21 significantly decreased the levels of nitric oxide (NO) and ROS (p < 0.001). In the presence of DD-21, the release of UVA-induced pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), was also significantly reduced (p < 0.05). Moreover, it was observed that DD-21 protected the cells from UVA-mediated DNA strand breaks and also inhibited the formation of cyclobutane pyrimidine dimers (CPDs) upon comparison to the UVA-exposed control cells (p < 0.001). In conclusion, the findings of this study revealed that DD-21 exhibits remarkable photoprotective properties, thus demonstrating its potential as a candidate UVA filter.

Inactivation of antibiotic resistant bacteria from stormwater runoff using UVA/LED and its potential risks

Recently, increasing attention has been paid to antibiotic resistance in stormwater runoff. However, there is no available literature about the control of antibiotic resistant bacteria (ARB) through 365 nm ultraviolet light-emitting diode (UVA/LED). In this study, batch experiments were conducted to investigate ARB inactivation kinetics, effects of light intensity and water matrix (including suspended solid (SS) concentration, initial pH and bacteria concentration), and potential transmission risks after UVA/LED irradiation. Results showed that ARB inactivation efficiencies reached 6.31 log reduction at 8 mW/cm² (86 J/cm²) of UVA/LED for 180 min. ARB inactivation efficiencies increased with the increase of light intensity, and showed a linear relationship. ARB inactivation decreased with increasing SS levels, and the largest inactivation efficiencies was 3.56 log reduction at 50 mg/L of SS. Initial pH had slight effect on ARB inactivation through UVA/LED irradiation. A low initial bacteria concentration (10⁵ CFU/mL) was not necessarily associated with good ARB inactivation (3.59 log reduction). After UVA/LED irradiation, ARB was hardly detected during 12 hr of dark repair, and the transfer frequency of kanamycin resistance gene was increased to 5.43 × 10^-4. These suggested that the application of UVA/LED to inactivate ARB in stormwater runoff was feasible and desirable in this study.

Reproductive Toxicity and Recovery Associated With 4-Non-ylphenol Exposure in Juvenile African Catfish (Clarias garepinus)

Although, the effects of 4-non-ylphenol (4-NP) on fish's reproductive hormones were assessed in several studies using adult models, however, the effect of this endocrine disruptor on immature fish's reproductive hormones was not addressed commonly. We aimed to study the apoptosis induction, hematotoxicity, reproductive toxicity, and the recovery associated with 4-NP exposure in juvenile African catfish [Clarias garepinus) using some hormones [17β-estradiol (E2), testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH)] and gonad histology as biomarkers. The toxic effects of 4-NP have been studied in many animal models, but there is still limited knowledge about the dose-dependent damage caused by 4-NP exposure in juvenile Clarias gariepinus. A healthy juvenile C. gariepinus was categorized into four groups (n = 3/group; three replicates in each group). The first group was the control, and the other three groups were subjected to 4-NP concentrations as 0.1, 0.2, and 0.3 mg/L for 15 days; they were left for a recovery period of another 15 days. The reproductive hormones of C. gariepinus exposed to 4-NP for 15 days exhibited significant variations between the treatment groups and the control (P < 0.05), which were evident in E2 and T-values, whereas FSH, LH, total protein, and lipid peroxidation values showed non-significant differences among all groups at P < 0.05. Such a situation referred to the fact that the 15-day recovery period was insufficient to remove the impacts of 4-NP doses in concern. The trend of dose-dependent increase/decrease was recorded for T, E2, FSH, and LH. The histopathological alterations of 4-NP treated in gonad tissues were recorded in juvenile C. gariepinus, reflecting their sensitivity to 4-NP estrogenic-like effects. Overall, our results investigate that recovery has improved the reproductive toxicity caused by 4-NP in juvenile C. garepinus. Significant variations between the treated groups and the control group (P < 0.05) were evident in hematological parameters except for hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). The parameters exhibiting significance decreased with such increased doses [red blood cells (RBCs), hematocrit (Hct), and white blood cells (WBCs)]. Similar patterns of significant variations toward the increase or decrease were recorded following the 15-day recovery period. Apoptotic frequency in erythrocytes and brain cells has increased significantly with increased 4-NP exposure, indicating that 4-NP caused cytotoxic effects, such as apoptosis in a dose-dependent manner. However, these cellular alterations greatly decreased after the 15-day recovery period.

Cytotoxic and genotoxic effects of arsenic on erythrocytes of Oryzias latipes: Bioremediation using Spirulina platensis

BACKGROUND

Exposure to the environmental pollutants poses a serious threat to aquatic organism. The arsenic exposure in fish increases the risk of developing serious alterations from embryo to adult.

OBJECTIVES

The present investigation was done to study the toxic effects of heavy metal arsenic [As(III)] on medaka (Oryzias latipes). Morphological alterations, apoptosis, nuclear abnormalities, and genotoxic biomarkers in erythrocytes were used to determine the stress caused by arsenic (As) exposure.

METHODS

Medaka was exposed to As for 15 days at two toxic sublethal concentrations (7 ppm and 10 ppm) in combination with Spirulina platensis (SP) treatment as antioxidant algae at 200 mg/L.

RESULTS

Results were consistent with a previous study results on tilapia. Exposure of medaka to As resulted in a dose-dependent increase in most the biomarkers used in the current study. Fish exposed to10 ppm As showed highest level of DNA damage. For the first time to our knowledge, using SP to counter the As toxicity in medaka, DNA damage restored to control levels.

CONCLUSION

Accordingly, those results suggests that SP can protect medaka in aquaculture against As-induced damage by its ability as reactive oxygen species (ROS) reducer, antioxidant role, and DNA damage scavenger.

Ameliorative effect of Spirulina platensis against lead nitrate-induced cytotoxicity and genotoxicity in catfish Clarias gariepinus

The present study was designed to investigate the protective role of dietary supplementation of Spirulina platensis (SP) against cytotoxic and genotoxic effects of lead nitrate in Clarias gariepinus. Four groups of fishes were used: first group as control which fed on basal diet, second group fed on basal diet and exposed to (1 mg/L of lead nitrate), third group fed on diet containing 0.25% SP and exposed to (1 mg/L of lead nitrate), and fourth group fed on diet containing 0.5%SP and exposed to (1 mg/L of lead nitrate). Fish samples were taken at 2nd and 4th week of exposure. The hematological indices of lead nitrate-exposed group were decreased significantly compared to the control group at 2nd and 4th week of exposure. Lead nitrate caused a significant increase in the percentage of poikilocytosis, micronuclei, and apoptotic cells as well as comet tail length and olive tail moment compared with the control group at 2nd and 4th week of exposure. The highest level of damage was found on 4th week of exposure with all parameters. Dietary inclusion of SP ameliorated these cytotoxic and genetic changes, as well as this amelioration was concentration and time dependent. Consequently, the present study proposed that the addition of SP to the fish diet can be used as a promising protective agent to oppose cytotoxic and genotoxic effects of lead nitrate in aquaculture. Graphical abstract.

Protective role of Spirulina platensis against UVA-induced haemato-biochemical and cellular alterations in Clarias gariepinus

Recently, it has become widely recognized that ultraviolet A (UVA) exposure is harmful for both aquatic and terrestrial organisms. Many studies have reported the effects of UVA on aquatic animals, especially fish, but little is known about the antioxidant role of microalgae in ameliorating the negative effects of UVA exposure. Recently, there has been great interest in using Spirulina platensis (SP) as a dietary antioxidant agent. Therefore, this study aimed to investigate the protective role of SP against UVA-induced effects by analysing haemato-biochemical alterations and erythrocyte cytotoxic and genotoxic biomarkers in African catfish (Clarias gariepinus). Fish were exposed to UVA, UVA + 100 mg/L SP extract, UVA + 200 mg/L SP extract for 3 days (UVA exposure: 1 h/day), and were not subjected to treatment (control group). The results showed the presence of some morphological malformations in red blood cells (RBCs) after UVA exposure. Additionally, nuclear abnormalities, including micronuclei, were observed. UVA induced alterations in most of the haemato-biochemical indices. Adding SP to the fish aquaria restored the haemato-biochemical parameters to their control values. In addition, SP repaired cellular damage in a dose-dependent manner. We conclude that SP plays a modulatory role in preventing and/or repairing the haemotoxic effects induced by UVA.

UVA-induced neurotoxicity in Japanese medaka (Oryzias latipes)

Ultraviolet radiation-induced neurodegeneration has been studied in the early stages of development in fish, but not extensively in the adult stage. The present study aimed at investigating the effects of ultraviolet radiation-A (UVA) in adult Japanese medaka (Oryzias latipes). The brain, spinal cord, and retina were examined histopathologically as nervous system target organs. Japanese medaka fish were exposed to 15, 30, and 60 min day^-1 UVA for 3 days, and samples were obtained 24 h and 14 days after UVA exposure. Neurohistopathological alterations in brain tissue included vacuoles, blood congestion, degeneration of neuropils, and pyknotic nuclei in neurons. Alterations in the spinal cord included neuronal cell degeneration, reduction in the spinal cord area, and degeneration of Mauthner cells. Retinal tissue showed vacuolation in the nerve fiber layer (NFL), pyknotic nuclei in the ganglion cell layer (GCL), and decreased cell populations particularly in the inner nuclear layer (INL) and GCL. The degree of degeneration was dependent on the duration of UVA exposure. The signs of degeneration decreased gradually and disappeared completely after the 14-day recovery period. In addition, p53-deficient medaka fish were more tolerant than were wild-type (Hd-rR) Japanese medaka. In conclusion, UV radiation induced neurodegeneration in the brain, spinal cord, and retina of adult Japanese medaka (Oryzias latipes) but their normal histological architecture reappeared in these tissues after 14 days.

Uptake, depuration, dose estimation and effects in zebrafish exposed to Am-241 via dietary route

Zebrafish were chronically exposed to Am-241, an alpha-emitting radionuclide via daily consumption of an enriched artificial diet. Am-241 uptake was quantified in Danio rerio after 5 and 21 days of exposure via daily Am-spiked food ingestion and after 21 days of exposure followed by 5 days of depuration. Americium accumulates mostly in digestive tract, muscle, rest of the body but the accumulation levels and trophic transfer rate (0.033-0.013%) were low. Corresponding cumulative doses were calculated for the whole body (9 mGy) and for the digestive tract (42 mGy) with internal alpha radiation contributing to more than 99% of the total dose. Genotoxic effects (gamma-H2AX assay) and differential gene expressions of main biological functions were examined. Although fish were exposed to a low dose rate of 13 μGy h^-1, DNA integrity and gene expression linked to oxidative stress, hormonal signaling and spermatogenesis were altered after 21 days of Am-241 exposure. These results underline the higher toxicity of alpha emitter Am-241, as compared to other studies on gamma radiation exposure.

SDS-PAGE technique as biomarker for fish toxicological studies

Although many studies on the hematological and biochemical parameters in fishes have been done, still there are some shortage in the estimation and evaluation of the baseline's values of marine and freshwater fishes. Recently, the use of hematology and biochemistry of fishes in toxicology, aquaculture, environmental pollution, feeding, and antioxidants studies has been increased. In this study we introduced the importance of those parameters and their importance as biomarkers in fish toxicology from previous literature and as new findings. Hemato-biochemical parameters were widely used in fish toxicological studies. Many researches have used the protein electrophoresis as a valid tool to determining intra and inter-specific variation among species. Protein profile was extensively used in determining the health of fish, as indicators of anemia or other diseases provide information about the existence of the disease, and in the diagnosis of disease. So, to carry out the aim of this study, we reported one of the more advanced techniques used SDS-PAGE as molecular biomarker for protein profile analysis in fish with shedding the light on the importance of hematological and biochemical parameters in fish toxicological studies.

Oocyte atresia in WT (HdrR) and P53 (-/-) medaka (Oryzias latipes) exposed to UVA

The negative effects of ambient ultraviolet (UVA) on the water environment have been recently highlighted; UVA can create deleterious effects by stimulating stress on pelagic organisms. Little is known about UVA effects on oocyte characteristics of female fish. In the present study we explored the effects of exposure to ecologically relevant levels of simulated UVA radiation on ovaries of two major strains WT (HdrR) and P53 (-/-) of medaka (Oryzias latipes) mature female. Fish were assigned to control and three UVA-exposed groups as (15 min, 30 min, and 60 min/day) for three days and sample selection was 24 h and 14 days after exposure. Histological alterations and oocyte atresia percentage were analyzed in the UVA-exposed fish compared to control. Alteration comprised hyperthrophied follicular cells with increased thickness, breakdown of egg chorion (zona radiata), damage of cortical alveoli, and distorted nucleus and cytoplasm. The atresia percentages significantly increased with higher UVA exposure dose and time for both the wild type and the p53 deficient fish. The wild type displayed significantly higher oocyte atresia percentage than the p53 mutant. These results suggested that UVA exposure provoked histological alterations in both p53 and WT medaka oocytes leading to follicular atresia, which reduce female reproductive ability and larval production. UVA oocyte response showed p53 dependent and independent histological alteration, however, the p53 mutant was less sensitive to UVA than the wild type in medaka fish.

UVA-Induced DNA Damage and Apoptosis in Red Blood Cells of the African Catfish Clarias gariepinus

Ultraviolet-A light (UVA)-induced DNA damage and repair in red blood cells to investigate the sensitivity of African catfish to UVA exposure is reported. Fishes were irradiated with various doses of UVA light (15, 30, and 60 min day^-1 for 3 days). Morphological and nuclear abnormalities in red blood cells were observed in the fish exposed to UVA compared with controls. Morphological alterations such as acanthocytes, crenated cells, swollen cells, teardrop-like cells, hemolyzed cells, and sickle cells were observed. Those alterations were increased after 24 h exposure to UVA light and decreased at 14 days after exposure. The percentage of apoptosis was higher in red blood cells exposed to higher doses of UVA light. No micronuclei were detected, but small nuclear abnormalities such as deformed and eccentric nuclei were observed in some groups. We concluded that exposure to UVA light induced DNA damage, apoptosis, and morphological alterations in red blood cells in catfish; however, catfish were found to be less sensitive to UVA light than wild-type medaka.