Cadmium triggers kidney cell apoptosis of purse red common carp (Cyprinus carpio) without caspase-8 activation

Seasonal changes in hepatic lipid metabolism and apoptosis in Chinese soft-shelled turtle (Pelodiscus sinensis)

Chinese soft-shelled turtle (Pelodiscus sinensis) hibernates without eating and drinking when the ambient temperature is very low. To better understand the characteristics of energy utilization during hibernation, the turtles in the physiological phases of summer active (SA), Pre-Hibernation (Pre-H), Mid-Hibernation (Mid-H) and early arousal (EA) were sampled. The results showed that the levels of serum triglyceride and hepatic lipid droplet were markedly increased in Pre-H and decreased in Mid-H compared with that in SA, indicating that P. sinensis experiences lipid accumulation in Pre-H and lipid is the predominant energy reserve during hibernation. The mRNA expression levels of genes (FABP and CPT-2) involved in lipolysis and lipid oxidation were up-regulated in Mid-H, while the genes related to lipid synthesis (FAS, ACSL-1, ACC, elovl5, and SCD1) were inhibited in Mid-H. Meanwhile, the mRNA expression levels of endoplasmic reticulum stress marker gene Bip and key genes (ATF4, ATF6, and IRE1α) involving the unfolded protein response were significantly increased in Mid-H and EA. Also, the expression levels of genes (ASK1, JNK1, and Bax) associated with cell apoptosis increased in Mid-H and EA, however, the expression of Bcl2 was inhibited in Mid-H. Therefore, hibernation can cause endoplasmic reticulum stress and apoptosis. The findings will provide a theoretical framework for an animal's cold adaptation and offer insights into preventing and managing metabolic syndrome.

n-3 polyunsaturated fatty acids alleviate the progression of obesity-related osteoarthritis and protect cartilage through inhibiting the HMGB1-RAGE/TLR4 signaling pathway

Osteoarthritis (OA) is a common joint degenerative disease. There is currently no cure for OA. Dietary fatty acids have potential value in the prevention and treatment of OA. n-3 polyunsaturated fatty acids (PUFAs) have anti-inflammatory effects, but their anti-OA mechanism remains unclear. High-mobility group box 1 (HMGB1) promotes inflammation and participates the pathogenesis of OA. The purpose of this study was to investigate the protective effect of n-3 PUFAs on cartilage and whether n-3 PUFAs could exert an anti-OA effect through inhibiting HMGB1-RAGE/TLR4 signaling pathway. We established an obesity-related post-traumatic OA mice model and an in vitro study was conducted to explore the regulatory mechanism of n-3 PUFAs on HMGB1 and its signal pathway against OA. We found that diet rich in n-3 PUFAs alleviated OA-like lesions of articular cartilage with the decrease of HMGB1-RAGE/TLR4 signaling protein in mice. In SW1353 cells, DHA significantly reduced the expression of HMGB1-RAGE/TLR4 signaling protein which was up-regulated by IL-1β stimulation. HMGB1 overexpression reversed the inhibitory effect of DHA on HMGB1-RAGE/TLR4 signaling pathway. The activation of SIRT1 may participate the inhibitory effect of DHA on HMGB1-RAGE/TLR4 signaling pathway. In conclusion, n-3 PUFAs could attenuate the progression of obesity-related OA and exert protective effect on cartilage by inhibiting HMGB1-RAGE/TLR4 signaling pathway, which may be associated with the activation of SIRT1. Dietary n-3 PUFAs supplements can be considered as a potential therapeutic substance for OA.

Cadmium induced time-dependent kidney injury in common carp via mitochondrial pathway: Impaired mitochondrial energy metabolism and mitochondrion-dependent apoptosis

Toxic effect of heavy metal cadmium (Cd) on fish kidneys had been reported. Mitochondrion is an important organelle for maintaining kidney function, while its role in Cd-induced kidney injury in common carp remained unclarified. In this experiment, we established a poisoning model of common carp with Cd exposure (0.26 mg/L) for 15, 30, and 45 days. Serum biochemistry determination, histological observation, TUNEL assay, qRT-PCR, Western blot, and integrated biomarker response (IBR) were applied to assess the nephrotoxicity of Cd to common carp. Our results displayed that Cd exposure increased the levels of serum biochemical indexes (UREA, CRE, and UA), indicating kidney injury. We further revealed via histological observation that Cd damaged structural integrity of kidneys, as evidenced by renal glomerulus and renal tubular injury, hallmark phenotypes of apoptosis, and mitochondrial damage, suggesting that mitochondria damage and apoptosis were involved in Cd-induced kidney injury. Moreover, Cd exposure decreased ATPase (Na⁺/K⁺-ATPase, Ca²⁺-ATPase, Mg²⁺-ATPase, and Ca²⁺Mg²⁺-ATPase) activities as well as PGC-1a and Mfn2 levels, while increased Drp1 and PINK1 levels as well as LC3-II/LC3-I ratio, which indicated that Cd-impaired renal energy metabolism was related to mitochondrial dysfunction. Additionally, we found that Cd induced oxidative stress (abnormal levels of SOD, CAT, GPX, MDA, and H₂O₂) in kidneys, which was involved in triggering mitochondrial dysfunction and further impairing mitochondrial energy metabolism. Moreover, the occurrence of mitochondria-dependent apoptosis was found after Cd-exposure in common carp kidneys, as indicated by enhanced levels of Bax, CytC, APAF1, Caspase-9, and Caspase-3, while declined level of Bcl-2. Subsequently, we confirmed a time-dependent nephrotoxicity of Cd to common carp via IBR assessment. In conclusion, Cd induced time-dependent nephrotoxicity in common carp via mitochondrial pathway. This mitochondria-oriented study shed light on underlying mechanisms of Cd-induced renal pathologies and provided a theoretical basis for evaluating Cd toxicity to aquatic organisms.

Toxicity of single and combined 4-epianhydrotetracycline and cadmium at environmentally relevant concentrations on the zebrafish embryos (Danio rerio)

The combined pollution of antibiotics and heavy metals has attracted a worldwide attention in the recent years. 4-epianhydrotetracycline (EATC) is the major degradation product of tetracycline (TC), which has been detected frequently in environment and its concentration is even higher than TC under some circumstances. Cadmium (Cd) is a common heavy metal contaminant and has highly toxic to organisms, plants and humans even at low doses. In the present study, zebrafish (Danio rerio) embryo toxicity test was performed to investigate the single and combined effects of EATC and Cd on aquatic organisms. Exposure to EATC and Cd at environmentally relevant concentrations had a series of hazardous impacts on the embryonic development, including lethality, hatching rate, heart rate and teratogenic effects. Compared to the contaminant existed alone, combined pollution produced stronger toxicity, which appeared as the decreasing of heart rate and hatching rate, and the increasing of malformation of zebrafish embryos. After 96 h exposure, the reactive oxygen species (ROS) levels in zebrafish embryos were increased significantly, revealing that EATC-Cd co-exposure resulted in potential oxidative stress-induced damage. Acridine orange (AO) staining showed that combined exposure resulted in stronger cell apoptosis. The potential health risks of the combined pollution of EATC and Cd should be paid more attention to higher level vertebrates and humans.

iTRAQ-based quantitative proteomic analysis in liver of Pomacea canaliculata induced by oleanolic acid stress

BACKGROUND

Triterpene acid is one of the typical active constituents of Eucalyptus bark, which is the main by-product of the Eucalyptus wood industry. Our studies have demonstrated that triterpene acid stress could inhibit climbing and increase mortality in Pomacea canaliculata (Lamarck). However, limited attention has been paid to the proteomic responses of this snail under triterpene acid stress.

RESULT

Using iTRAQ-based quantitative proteomics, we elucidated the regulatory mechanism in the livers of P. canaliculata held in chlorine-free water and exposed to 100 mg L^-1 oleanolic acid (OA) for 24 h. A total of 4308 proteins were identified, of which 274 were differentially expressed proteins (DEPs) including 168 (61.31%) differentially upregulated proteins and 106 (38.69%) differentially downregulated proteins. Bioinformatics analysis revealed that P. canaliculata responses to OA stress are mainly involved in glucose metabolism, energy synthesis, immune response, stress response, protein synthesis, and apoptosis. According to KEGG analysis, the 274 DEPs were mapped to 168 KEGG pathways and 10 KEGG pathways were significantly enriched (P < 0.05). Furthermore, qRT-PCR was performed for histone H4, catalase, isocitrate dehydrogenase, superoxide dismutase, ferritin, lipase, and tropomyosin to validate the iTRAQ results.

CONCLUSION

Proteomic analysis suggested that OA stress led to the disruption of glucose metabolism, energy synthesis, and protein synthesis, and triggered a series of molecular pathways containing many key proteins involved in the immune process, thereby helping P. canaliculata resist OA stress. © 2022 Society of Chemical Industry.

Molecular Mechanism Based on Histopathology, Antioxidant System and Transcriptomic Profiles in Heat Stress Response in the Gills of Japanese Flounder

As an economically important flatfish in Asia, Japanese flounder is threatened by continuously rising temperatures due to global warming. To understand the molecular responses of this species to temperature stress, adult Japanese flounder individuals were treated with two kinds of heat stress—a gradual temperature rise (GTR) and an abrupt temperature rise (ATR)—in aquaria under experimental conditions. Changes in histopathology, programmed cell death levels and the oxidative stress status of gills were investigated. Histopathology showed that the damage caused by ATR stress was more serious. TUNEL signals confirmed this result, showing more programmed cell death in the ATR group. In addition, reactive oxygen species (ROS) levels and the 8-O-hDG contents of both the GTR and ATR groups increased significantly, and the total superoxide dismutase (T-SOD) activities and total antioxidant capacity (T-AOC) levels decreased in the two stressed groups, which showed damage to antioxidant systems. Meanwhile, RNA-seq was utilized to illustrate the molecular mechanisms underyling gill damage. Compared to the control group of 18 °C, 507 differentially expressed genes (DEGs) were screened in the GTR group; 341 were up-regulated and 166 were down-regulated, and pathway enrichment analysis indicated that they were involved in regulation and adaptation, including chaperone and folding catalyst pathways, the mitogen-activated protein kinase signaling (MAPK) pathway and DNA replication protein pathways. After ATR stress, 1070 DEGs were identified, 627 were up-regulated and 423 were down-regulated, and most DEGs were involved in chaperone and folding catalyst and DNA-related pathways, such as DNA replication proteins and nucleotide excision repair. The annotation of DEGs showed the great importance of heat shock proteins (HSPs) in protecting Japanese flounder from heat stress injury; 12 hsp genes were found after GTR, while 5 hsp genes were found after ATR. In summary, our study records gill dysfunction after heat stress, with different response patterns observed in the two experimental designs; chaperones were activated to defend heat stress after GTR, while replication was almost abandoned due to the severe damage consequent on ATR stress.

Effects of dietary xylooligosaccharide prebiotic supplementation on growth, antioxidant and intestinal immune-related genes expression in common carp Cyprinus carpio fed a high-fat diet

This study investigated the effects of xylooligosaccharide (XOS) supplementation on growth, intestinal enzyme, antioxidant and immune-related genes in common carp Cyprinus carpio fed a high-fat diet (HFD). One hundred and ninety two fish with an initial weight of 19.61 ± 0.96 g were allocated into 24 tanks (eight fish per tank in four replicate) and were fed the control diet, HFD, HFD with 0.5%, 1%, 2% and 3% XOS supplementation. From the result, fish offered HFD with 1% XOS supplementation significantly obtained a higher body mass index and feed efficiency ratio, whereas condition factor was higher in fish fed HFD supplemented with 2% XOS but no difference was attributed to other supplemented group compared to control group. Also, fish fed HFD supplemented with 1%-2% XOS significantly improved protease, lipase, creatine kinase and sodium/potassium ATPase activities compared to other groups. Fish offered HFD were significantly lower in superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), myeloperoxidase, acid phosphatase, lysozyme activities and immunoglobulin content, but the opposite result was found for aspartate transaminase, alanine transaminase activities, malondialdehyde, protein carbonyl and cortisol content as compared with the control. However, this effect was reversed with HFD supplemented with XOS. Also, interleukin 1β, interleukin 8, tumour necrosis factors, interferons, caspase-3 and caspase-9 in the intestine were all up-regulated in the HFD group, while the reverse pattern was found in SOD, GPX, lysozyme-C, complement 3 and mucin 5b (muc5b), than the control group. These effects were all enhanced by feeding the XOS diet, especially those fed 1%-3% supplementation. In conclusion, XOS inclusion can improve the growth, digestive enzymes, antioxidants and immune response of common carp fed HFD.

Environmentally relevant concentrations of arsenic induces apoptosis in the early life stage of zebrafish

Arsenic (As) in the aquatic environment is a considerable environmental issue, previous studies have reported the toxic effects of low concentrations (≤ 150 μg/L) of As on fish. However, limited information is available regarding the impact of low levels of As on apoptosis. To evaluate this, zebrafish embryos were exposed to different concentrations (0, 25, 50, 75, and 150 μg/L) of As (arsenite [AsIII] and arsenate [AsV]) for 120 h. Our results indicated that low concentrations of AsIII exposure significantly inhibited the survival of zebrafish larvae, and significantly increased the transcription of Caspase-9 and Caspase-3, the ratio of Bax/Bcl-2 transcription, and protein levels of Caspase-3. In contrast, AsV decreased the ratios of Bax/Bcl-2 transcription and protein levels, as well as protein levels of Caspase-3. Our data demonstrated that AsIII and AsV exert different toxic effects, AsIII induced apoptosis via the mitochondrial pathway and the extrinsic pathway, while AsV induced apoptosis only via the mitochondrial pathway.

Transcriptome profiling reveals differential expression of immune-related genes in gills of hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂) under hypoxic stress: Potential NLR-mediated immune response

Fish gills are the primary organ that respond to sudden changes in the dissolved oxygen (DO) level in the aquatic environment. Hypoxic stress impairs the normal function of gill tissues. However, little is known about the mechanisms of the response of yellow catfish gills to hypoxic stress. In this study, we compared transcriptomic and physiological changes in gill tissues of hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂) between a hypoxia-treated group (DO: 1.5 mg/L) and a control group (DO: 6.5 mg/L). In fish in the hypoxia-treated group, gill filaments underwent adaptive changes, and the number of vacuoles in gill tissues increased. Exposure to hypoxic conditions for 96 h resulted in increased anaerobic metabolism and decreased antioxidant and immune capacity in gill tissues. Transcriptome analyses revealed 1556 differentially expressed genes, including 316 up-regulated and 1240 down-regulated genes, between fish in the hypoxia-treated and control groups. Functional analyses indicated that the main pathway enriched with differentially expressed genes was immune response, followed by energy metabolism and signal transduction. Under hypoxic stress, the transcript levels of genes involved in the NOD-like receptor signaling pathway initially increased rapidly but then decreased over time, suggesting that the NOD-like receptor-mediated immune response plays an essential role in hypoxia tolerance and resistance in hybrid yellow catfish. Our results provide novel insights into which immune-related genes and pathways are activated under hypoxic stress, and reveal details of early adaptation of the immune response and defense mechanisms under hypoxic stress.

Effects of 4-epianhydrotetracycline on oxidative stress in zebrafish (Danio rerio) embryos

4-Epianhydrotetracycline (4-EATC) is a major intermediate product of tetracycline during its degradation progress in the natural environment, which is frequently detected in aquatic environments and poses a potential threat to aquatic organisms. In the present study, the ecotoxicity of 4-EATC have been studied from the perspective of oxidative stress by using zebrafish embryos. After 96 h exposure, the reactive oxygen species (ROS) levels, malondialdehyde (MDA) concentrations and protein carbonyl (PC) contents in zebrafish embryos in the lower-concentration 4-EATC treatment groups (1.25 mg/L and 2.50 mg/L) showed no significant differences compared with the negative control group. However, the total superoxide dismutase (SOD) activity was increased significantly. After exposed to the higher-concentration of 4-EATC (5.00, 10.0 and 20.0 mg/L) resulted in a significant increase in ROS levels, MDA concentrations and PC contents, in contrast, a significant decrease in SOD activities. The results indicate that exposure to high concentrations of 4-EATC (5.00, 10.0 and 20.0 mg/L) could disrupt the redox equilibrium in zebrafish embryos, leading to the occurrence of oxidative damage. Apoptosis of the embryonic cells could be induced by 4-EATC exposure at different concentration and the rate of apoptosis enhanced with the increase of 4-EATC concentration. The pericardium was the most frequent site of apoptosis. The present study points out that more attention should be paid to the potential ecological risks of antibiotic degradation products.

Ammonia exposure induces endoplasmic reticulum stress and apoptosis in Chinese striped-necked turtle (Mauremys sinensis)

Ammonia is a major pollutant in the water environment, which could cause severe harm to aquatic organisms. To explore the pathological and physiological effects of ammonia in Chinese striped-necked turtles (Mauremys sinensis), the individuals (body mass: 218.26 ± 12.65 g) were divided into two groups: control group and ammonia exposed group (6.25 mM total ammonia), then the expression levels of signaling factors involved in the endoplasmic reticulum stress and apoptotic pathways were determined. The results showed that ammonia exposure up-regulated the transcriptional and protein levels of endoplasmic reticulum stress marker gene Bip. Meanwhile, the relative mRNA levels of key genes (PERK, ATF6, eIF2α, ATF4, IRE1α and XBP1) involved in unfolded protein response up-regulated, and the phosphorylation levels of PERK, eIF2α and IRE1α increased correspondingly. In addition, the protein and transcriptional levels of CHOP and JNK related to apoptotic pathway induced by unfolded protein reaction increased under ammonia exposure. Moreover, Bcl-2 mRNA expression levels and protein levels decreased, whereas BAX and caspase-3 showed an opposite trend, and the cleaved protein of caspase-3 appeared when the turtles in the elevated ammonia. Furthermore, the apoptotic cells in liver increased after ammonia exposure. These results suggested ammonia exposure induced endoplasmic reticulum stress, then activated unfolded protein response, followed by apoptosis in M. sinensis. The results will contribute to a better understanding of the toxicity mechanism of ammonia to aquatic turtles.

Assessment spermatogenic cell apoptosis and the transcript levels of metallothionein and p53 in Meretrix meretrix induced by cadmium

Cadmium (Cd) has been widely used in industry and can accumulate in the water, soil, and food. Meretrix meretrix is one of the marine shellfishes cultivated for economic purpose in China. The increasing Cd levels in coastal marine water could adversely affect the economic benefits of shellfish cultivation. In the present study, M. meretrix were exposed to different Cd²⁺ concentrations (0, 1.5, 3, 6, and 12 mg L^-1) for 5 d to evaluate the effects of Cd on spermatogenic cell. The Cd accumulation, survival rate and the indices of oxidative stress and apoptosis were determined in the spermatogenic cells of M. meretrix. The expression levels of p53 and metallothionein (MT) mRNA were also measured in the spermatogenic cells. Cd accumulation and the mortality rate of spermatogenic cells were found to increase in a dose-response manner with Cd²⁺ concentrations. Histopathology changes, especially the damage of membranous structure, were more severe as the Cd²⁺ levels in the testis became higher. The indexes of oxidative stress, including reactive oxygen species, malondialdehyde, protein carbonyl derivates and DNA-protein crosslinks all increased after exposure to Cd²⁺. However, the total antioxidant capacity gradually decreased with the increasing Cd²⁺ concentration. In addition, exposure to Cd²⁺ increased the apoptotic rate and caspase-3 and 9 activities but decreased the level of mitochondrial membrane potential and cytochrome C oxidase in the spermatogenic cells. MT mRNA expression increased in lower Cd²⁺ concentration treated groups whereas decreased in higher groups, while the p53 mRNA expression increased in a dose-response manner with Cd²⁺ and was positively correlated with the oxidative damage indices. These results indicated that Cd²⁺ caused oxidative stress and p53 induced apoptosis in the spermatogenic cells, and thus decreased the survival rate of sperm cells. This finding highlights that Cd can reduce the reproductive capacity of M. meretrix, thus threatening to wild shellfish populations and reducing the efficiency of shellfish farming.

Neurotoxic responses of rainbow trout (Oncorhynchus mykiss) exposed to fipronil: multi-biomarker approach to illuminate the mechanism in brain

Insecticides have potential to non-target organisms, disrupting the healthy functioning of the aquatic environment as they are the ultimate receptor of the aquatic ecosystem. Insecticides, which are widely used in agriculture, have high neurotoxicity on aquatic organisms. In this study, the acute alterations [catalase (CAT), arylesterase (ARE), malondialdehyde (MDA), myeleperoxidase (MPO), paraoxonase (PON), glutathione peroxidase (GPX), superoxide dismutase (SOD), 8-hydroxy-2-deoxyguanosine (8-OHdG) level, caspase-3 activity, and Acetylcholinesterase (AChE) enzyme activity] caused by the different concentrations of Fipronil (FP) insecticide (0.05, 0.1, and 0.2 mg/L) on rainbow trout (Oncorhynchus mykiss) brain tissue were investigated. It has been determined that superoxide dismutase -catalase - glutathione peroxidase - paraoxonase and arylesterase enzyme activities were inhibited but MDA and MPO induced depending on the concentration in brain tissue. When compared with the control group, the changes between the pesticide exposed groups were found statistically significant (p < 0.05). In brain tissue, while AChE enzyme activity was decreased depending on concentration, caspase-3 activity increased with 8-OHdG level. As a result, it has been determined that FP is a dangerous environmental pollutant for aquatic organisms, even at low concentrations, inducing oxidative stress, damaging the brain tissue of fish and stimulating apoptosis.

Differential regulation of endoplasmic reticulum stress-induced autophagy and apoptosis in two strains of gibel carp (Carassius gibelio) exposed to acute waterborne cadmium

Previous studies illustrated that gibel carp F strain displays better lipid mobilization and antioxidant ability and compared to the A strain. We therefore hypothesized that the F strain would exhibit superior defense to cadmium exposure. Comparative studies were conducted between A and F strains using plasma stress biomarkers, histological observations, and analysis of hepatic molecular events to examine exposure to waterborne Cd (11.9 mg L^-1) for 48 h and 96 h. Waterborne Cd exposure stimulated stress response and hepatic metallothionein mRNA induction in both gibel carp strains confirming exposure. Antioxidant responses were stimulated to counteract Cd toxicity, suggested by the upregulation of mRNA levels of genes associated with nuclear factor erythroid 2-related factor 2 (nrf2) signaling. Cd exposure induced endoplasmic reticulum (ER) stress, meanwhile, branches of genes in unfolded protein response (UPR) were activated. Slight time-dependent effects were implied by greater ER stress, UPR, and apoptosis signals with the duration of Cd exposure. Genotype-specific effects were identified, revealing that the F strain showed greater stress at 96 h exposure and higher antioxidant response compared to the A strain, as indicated by the mRNA levels of genes in nrf2 signaling. ER stress and UPR were also stronger in the F strain after Cd exposure. In contrast, the A strain showed higher autophagy and apoptosis response compared to the F strain. Collectively, combined autophagy and apoptosis were triggered under ER stress, which might serve as defense strategies in both gibel carp strains. The F strain showed greater antioxidant detoxification response and UPR to mitigate Cd toxicity, whereas excessive ER stress contributed to higher autophagy and apoptosis in the A strain. The present study uncovered the differential regulation and defense strategies in fish strains exposed to metal exposure.

iTRAQ and PRM-based comparative proteomic profiling in gills of white shrimp Litopenaeus vannamei under copper stress

Crustaceans are particularly sensitive to heavy metal pollution. Copper (Cu) is one of typical heavy metal pollutants in aquatic ecosystems. However, limited attention has been paid on the proteomic responses of shrimp under Cu stress. White shrimp Litopenaeus vannamei held in 5‰ seawater were exposed to 5 mg L^-1 Cu for 3 h, and the regulatory mechanism in the gills was elucidated using iTRAQ-based quantitative proteomics. The results showed that a total of 5034 proteins were identified, 385 differentially expressed proteins (DEPs), including 147 differentially up-regulated proteins (DUPs) and 238 differentially down-regulated proteins (DDPs) were found. Bioinformatics analysis indicated the DEPs responding to Cu stress mainly involved in cytoskeleton, immune response, stress response, protein synthesis, detoxification, ion homeostasis and apoptosis. Furthermore, we still performed PRM analysis on sarcoplasmic calcium binding protein (SCP), serine proteinase inhibitor B3 (SPIB3), C-type lectin 4 (CTL4), cathepsin L (CATHL), JHE-like carboxylesterase 1 (CXE1) and paramyosin (PMY), and biochemical analysis on Cu/Zn-superoxide dismutase (Cu/Zn-SOD) to validate the iTRAQ results, respectively. The present proteome analysis revealed that Cu stress disrupted the ion homeostasis and protein synthesis, and L.vannamei mainly regulates a series of molecular pathways which contained many key proteins involved in the immune process to protect the organism from Cu stress. Our data provides more insight about the underlying mechanisms that related to the stress response of Cu exposure in crustacean.

Kidney developmental effects of metal-herbicide mixtures: Implications for chronic kidney disease of unknown etiology

Chronic kidney disease of unknown etiology (CKDu) is an emerging global concern affecting several agricultural communities in the Americas and South Asia. Environmental contaminants such as heavy metals (e.g., Cd, As, Pb, and V) and organic pesticides (e.g., glyphosate) in the drinking water have been hypothesized to play a role in childhood onset and progression of this disease. However, a comprehensive analysis of chemical contaminants in the drinking water and effects of these compounds and their mixtures on kidney development and function remains unknown. Here, we conducted targeted and non-targeted chemical analyses of sediment and drinking water in CKDu affected regions in Sri Lanka, one of the most affected countries. Using zebrafish Danio rerio, a toxicology and kidney disease model, we then examined kidney developmental effects of exposure to (i) environmentally derived samples from CKDu endemic and non-endemic regions and (ii) Cd, As, V, Pb, and glyphosate as individual compounds and in mixtures. We found that drinking water is contaminated with various organic chemicals including nephrotoxic compounds as well as heavy metals, but at levels considered safe for drinking. Histological studies and gene expression analyses examining markers of kidney development (pax2a) and kidney injury (kim1) showed novel metal and glyphosate-metal mixture specific effects on kidney development. Mitochondrial dysfunction is directly linked to kidney failure, and examination of mixture specific mitochondrial toxicity showed altered mitochondrial function following treatment with environmental samples from endemic regions. Collectively, we show that metals in drinking water, even at safe levels, can impede kidney development at an early age, potentiating increased susceptibility to other agrochemicals such as glyphosate. Drinking water contaminant effects on mitochondria can further contribute to progression of kidney dysfunction and our mitochondrial assay may help identify regions at risk of CKDu.

Effects of thermal stress-induced lead (Pb) toxicity on apoptotic cell death, inflammatory response, oxidative defense, and DNA methylation in zebrafish (Danio rerio) embryos

Lead (Pb) is a toxic environmental pollutant that is frequently present in effluents from urban, mining, and industrial sources. The combinatorial effects of heavy metal exposure and temperature in aquatic organisms have received considerable attention as heat stress occurs simultaneously in conjunction with several contaminants in a natural environment. In this study, we examined the potential effects of Pb exposure in conditions of thermal stress (34 °C) in zebrafish (Danio rerio) embryos. Thermal stress at 34 °C induced a dramatic decrease in the survival rate, although exposure to Pb at 26 °C decreased the survival rate of the embryos. Malformations, such as the curved body shape, were increased in response to exposure to a combination of Pb and heat stress. The combination of Pb and heat stress also caused a decrease in the heart rate. Moreover, Pb and high-temperature exposure induced the upregulation of SOD, CAT, TNF-α, IL-1β, p53, and BAX transcripts, and downregulation of Dnmt1 and Dnmt3b transcripts. Thermal stress enhanced transcriptional responses of eight indicator genes following Pb toxicity. The induction of cell death in response to combined exposures was also confirmed in the body of zebrafish by fluorescence intensity image analysis. These data indicated that thermal stress enhanced the poisonous effects of Pb exposure on antioxidant defense, inflammation, and apoptotic mechanisms. Transcriptional inhibition of DNA methylation-related genes might serve as a crucial factor contributing to the possibility of epigenetic adaptation by altering combined stress. We suggest that a careful evaluation of the potential effects of climate change (especially temperature) should be considered when investigating the toxic levels of metal pollution, such as Pb, in an aquatic environment.

Effects of combined stressors to cadmium and high temperature on antioxidant defense, apoptotic cell death, and DNA methylation in zebrafish (Danio rerio) embryos

Fish are frequently affected by environmental stressors, such as temperature changes and heavy metal exposure, in aquatic ecosystems. In this study, we evaluated the combined effects of cadmium (Cd) toxicity and temperature (rearing temperature of 26 °C and heat stress at 34 °C) on zebrafish (Danio rerio) embryos. The survival and heart rates of zebrafish embryos decreased at relatively high Cd concentrations of 0.07 and 0.1 mg L^-1. Abnormal morphology was induced by exposure to a combination of Cd toxicity and heat stress. The yolk sac edema size was not significantly different between the control- and Cd-treated groups. Cd exposure induced reactive oxygen species (ROS) production and cell death in the live zebrafish. High temperature (34 °C) triggered Cd-induced cell death and intracellular ROS production to a greater extent than the rearing temperature of 26 °C. Transcriptional levels of six genes-CAT, SOD, p53, BAX, Dnmt1, and Dnmt3b-were investigated. The mRNA expression of CAT and SOD, molecular indicators of oxidative stress, was increased significantly at 34 °C after Cd exposure. The mRNA expression of CAT was more sensitive to temperature than that of SOD in Cd-treated zebrafish. p53 and BAX, apoptosis-related genes, were upregulated upon combined exposure to high temperature and Cd. In addition, at 34 °C, the expression of Dnmt1 and Dnmt3b transcripts, markers of DNA methylation, was increased upon exposure of zebrafish to all concentrations of Cd. Overall, these results suggest that high temperature facilitates the potential role of Cd toxicity in the transcriptional regulation of genes involved in the antioxidant system, apoptosis, and DNA methylation.

Interactive effect of thermal and hypoxia on largemouth bass (Micropterus salmoides) gill and liver: Aggravation of oxidative stress, inhibition of immunity and promotion of cell apoptosis

High temperatures and low oxygen in aquatic environments, such as intensive aquaculture or in natural watersheds, inevitably cause stress in fish. Fish are exposed to high temperatures during the summer, which exacerbates hypoxia. Hypoxia (1.2 ± 0.2 mg/L) under 20 °C (20 HG) and 26 °C (26 HG) was simulated to induce stress in largemouth bass (Micropterus salmoides). Related enzymes and genes involved in antioxidant, immune, and apoptotic responses were selected to explore the interactive effects of temperature and hypoxia on largemouth bass. The results showed that malondialdehyde (MDA) levels in plasma, gill, and liver increased in the 26 HG (p < 0.05). Liver superoxide dismutase (SOD) activity increased in the 26 HG. Peak SOD (SOD1, SOD2, SOD3a, and SOD3b), CAT, and GSH-Px mRNA levels in the gill and liver were observed at 12-24 h of stress. The levels of gill and liver total antioxidant capacity, catalase (CAT), glutathione peroxidase (GSH-Px) activities and other enzyme activities and genes in the 26 HG were higher than those in the 20 HG (p < 0.05). The gill and liver acid phosphatase and alkaline phosphatase activities increased with time in the 26 HG (p < 0.05), while gill and liver lysozyme activities in the 26 HG were lower than those in the 20 HG (p < 0.05). Tumor necrosis factor-α mRNA level was upregulated in the gill and downregulated in the liver at 24 h in the 26 HG. Interleukin (IL)-1β and IL-8 mRNA levels were upregulated in the gill and liver in the 26 HG at 24 h, whereas IL-15 mRNA level was downregulated in the 26 HG at 12 h. Transforming growth factor-β1 mRNA level was upregulated in the gill in the 20 HG at 24 h, but downregulated in gill and liver in the 26 HG at 24 h. Similarly, IL-10, Hepcidin-1, and Hepcidin-2 showed lower expression levels in the 26 HG. Gill and liver caspase-3 activities were higher in the 26 HG (p < 0.05), and gill caspase-3 activity was higher than that in the liver. The mRNA levels of proapoptotic genes (caspase-3, caspase-8, and caspase-9) were higher in the 26 HG. The present study demonstrates the interactive effects of temperature and hypoxia on stress in largemouth bass gill and liver. These results will be helpful to understand the mechanisms of stress induced by temperature and hypoxia in fish and provide a theoretical basis for aquaculture management.

Involvement of Nrf2 and mitochondrial apoptotic signaling in trehalose protection against cadmium-induced kidney injury

Cadmium (Cd) poisoning is characterized by multiple organ dysfunction in organisms, and the kidney is the main target organ of Cd toxicity. Trehalose (Tr), a multifunctional bioactive disaccharide, possesses potential kidney protective properties. Nevertheless, the specific biological function of Tr in antagonizing kidney injury induced by Cd remains to be elucidated. Herein, an in vivo model of Tr antagonizing Cd nephrotoxicity was established and the indictors related to kidney function, oxidative stress, and apoptosis were detected to investigate the molecular mechanism underlying the Tr-protection against Cd-induced kidney injury of rats. Firstly, Tr significantly declined the levels of blood urea nitrogen (BUN) and serum creatinine, and partially restored renal pathological changes caused by Cd. Secondly, Cd exposure significantly increased the malondialdehyde (MDA) content, and decreased the levels of total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and glutathione (GSH) in serum. However, Tr significantly ameliorated these abnormal alterations. Moreover, Tr regulated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway to suppress the Cd-induced nuclear translocation of Nrf2 and the up-regulation of heme oxygenase-1 (HO-1) and NAD (P) H quinone reductase-1 (NQO1). Meanwhile, Tr significantly reversed the increased Sequestosome-1(SQSTM1/p62) and decreased Kelch-like ECH associated protein-1 (Keap1) protein levels induced by Cd. Thirdly, further mechanistic exploration suggested that Tr inhibited the mitochondrial apoptotic signaling pathway induced by Cd. Collectively, the results indicated that Tr exerts antioxidant and anti-apoptosis functions involving the Nrf2 and mitochondrial apoptotic signaling pathways to protect against Cd-induced kidney injury in rats.

Effect of acute exposure of triazophos on histological structure and apoptosis of the brain and liver of zebrafish (Danio rerio)

Triazophos (TAP) has become a part of widespread pollutant of the aquatic environment due to its residue. Current study was designed to investigate the toxic effect of TAP at different doses (0.06, 0.3 and 1.5 mg/L) to the model organism of zebrafish (Danio rerio) by using multi-endpoint analysis in a 96 h acute exposure test. The direct observation that histological and ultrastructural alteration of zebrafish brain and liver were carried out via paraffin section in hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM), respectively. In addition, a series of methods were applied for exploring the physiological parameters related to cellular apoptosis. Results indicated that vacuolar structure after 96 h treatment with TAP were appeared in the molecular and granular layers of cerebellum. A large number of nuclear retraction, tissues vacuolation and cytoplasmic loss were observed in liver at histological level. From the fine structural level, the mitochondrial vacuolation and membrane damage of brain cells were found and the cristae of mitochondria disintegrated partly in hepatocytes. Onset of such histological structure alterations were one of the most intuitive reflection to TAP exposure, which needs to analyze biochemical alterations for further study. The mitochondrial membrane potential (MMP) showed a downward trend in the brain and liver of zebrafish. Simultaneously, the activity of caspase-3 and caspase-9 increased after 96 h exposure with a concentration-dependent manner, which could be served as a suitable indicator of cellular apoptosis. Furthermore, apoptosis-related genes (Apaf-1, p53, Bax, Bcl-2, caspase-3 and caspase-9) transcription showed different alterations in response to the TAP treatment. These results indicated that TAP exposure led to apoptosis in zebrafish brain and liver and it was speculated that the apoptosis may occur through mitochondrial pathway. The present study demonstrated that the exposure of zebrafish to the insecticide TAP led to observe its effects at both histological structure and apoptosis level in liver and brain.

Bioaccumulation and physiological responses in juvenile Marsupenaeus japonicus exposed to cadmium

The heavy metal cadmium readily accumulates in organisms, causing damage. In this study, juvenile marine shrimp Marsupenaeus japonicus were exposed to cadmium (Cd²⁺; 5, 50 and 500 μg L^-1). Cd accumulation and antioxidant-related indices were determined, and damage to biomolecules was assessed, after 24, 48 and 96 h. Cd bioaccumulation in M. japonicus increased with exposure time and concentration, which reached the highest value at 96 h. The data showed that 5, 50 and 500 μg L^-1 Cd increased glutathione (GSH) content and the activities of superoxide dismutase (SOD) and glutathione S-transferase (GST) in a Cd-dose-dependent manner, but 5 and 50 μg L^-1 Cd had no effect on caspase-3 activity. The expression levels of SOD, GST, heat shock protein 70 (HSP70), metallothionein (MT), p53 and caspase-3 genes were rapidly increased after 50 and 500 μg L^-1 Cd exposure, and remained at a significantly higher level than in the control after 96 h of exposure. After exposure to 5, 50 and 500 μg L^-1 Cd, F-value (the ratio between double-stranded DNA and total DNA) remained high at 24 h, however, as the exposure time increased, the F-value decreased in a dose-dependent manner. An increase in malondialdehyde content was also observed following exposure to 50 and 500 μg L^-1 Cd. Our data suggest that Cd induces oxidative stress, molecular damage and apoptosis in juvenile M. japonicus in a concentration- and time-dependent manner.

Methylmercury, cadmium and arsenic(III)-induced toxicity, oxidative stress and apoptosis in Pacific red snapper leukocytes

Methylmercury (MeHg), cadmium (Cd) and arsenic (As(III)) are among the most toxic metals in aquatic systems that have been associated with multiple animal and human health problems. This study investigated cytotoxic, oxidative stress, and apoptosis effects on fish leukocytes following their exposure to metals. A preliminary study indicated that leukocytes exposed to MeHg at a concentration of 0.01 mM, Cd at 0.05 mM, and As(III) at 2 mM showed a time-dependent cell viability reduction (around 40%), so they were selected for further experiments. To evaluate the effect of MeHg, Cd and As(III) on Pacific red snapper Lutjanus peru, we measured cytotoxicity, reactive oxygen species, antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT)), nitric oxide production, apoptosis-related and immune-related genes on head-kidney and spleen leukocytes following exposure to MeHg (0.01 mM), Cd (0.05 mM) and As(III) (2 mM) for 30 min and 2 h. Reactive oxygen species (ROS) generation highly increased in time-dependent doses in head-kidney leukocytes compared with the control group. Regarding antioxidant activity, SOD increased significantly in leukocytes exposed to any heavy metals after two h. Expressly, CAT activity decreased in those leukocytes exposed to Cd and As(III). Apoptotic function genes (Casp-2, Casp-3, and Casp-7) strongly up-regulated after heavy metal exposure, but Cd was more toxic. Finally, granzyme A and perforin 1 strongly up-regulated in leukocytes exposed to MeHg and As(III) compared with the control group. Our data showed that MeHg, Cd, and As(III) might have been cytotoxic and induced oxidative stress and apoptosis with possible biological consequences in fish.

Molecular characterization of caspase-8-like and its expression induced by microcystin-LR in grass carp (Ctenopharygodon idella)

Caspase-8, an initiator caspase, plays a vital role in apoptosis. In this study, caspase-8-like (named as Cicaspase-8-like), a homologue of caspase-8, was identified in grass carp (Ctenopharygodon idella). The full-length cDNA sequence of CiCaspase-8-like was 1409 bp and contained a 162 bp 5'-UTR, a 239 bp 3'-UTR and a 1008 bp coding sequence. The putative amino acids sequence was 335 residues long, including a large subunit (P20) and a small subunit (P10), but lacking conserved death effector domains. A histidine active site DHSQMDAFVCCVLSHG and a cysteine active-site motif KPKLFFIQACQG were found in P20. Phylogenetic analysis showed that Cicaspase-8-like clustered with the caspase-8 and caspase-8-like of other fish and grouped closely with Carassius auratus caspase-8-like. Quantitative real-time PCR revealed that the Cicaspase-8-like mRNA were expressed constitutively in all tested tissues from healthy grass carp, with high expression level in the blood, spleen, liver and gill, indicating its role in immune reaction. The expression of Cicaspase-8-like mRNA was decreased significantly in the liver because of the stress caused by microcystin-LR (MC-LR) (75 and 100 μg MC-LR/kg BW) at 24 h and 96 h post injection (P < 0.05), but it was increased significantly in grass carp treated with 25 μg MC-LR/kg BW at 24 h (P < 0.05) post injection. Cleaved fragments of Cicaspase-8-like were observed using western blot analysis, and the expression of Cicaspase-8-like protein was increased after MC-LR treatments. Moreover, the expression of both caspase-9 and caspase-3 mRNA increased significantly after treatment with the three doses of MC-LR. TUNEL assay results showed remarkable changes in apoptosis after the MC-LR treatment. These results suggest that Cicaspase-8-like is an important caspase and plays an essential role in MC-LR-induced apoptosis.

Limited oxidative stress in common carp (Cyprinus carpio, L., 1758) exposed to a sublethal tertiary (Cu, Cd and Zn) metal mixture

Analyzing effects of metal mixtures is important to obtain a realistic understanding of the impact of mixed stress in natural ecosystems. The impact of a one-week exposure to a sublethal metal mixture containing copper (4.8 μg/L), cadmium (2.9 μg/L) and zinc (206.8 μg/L) was evaluated in the common carp (Cyprinus carpio). To explore whether this exposure induced oxidative stress or whether defense mechanisms were sufficiently fitting to prevent oxidative stress, indicators of apoptosis (expression of caspase 9 [CASP] gene) and of oxidative stress (malondialdehyde [MDA] level and xanthine oxidase [XO] activity) were measured in liver and gills, as well as activities and gene expression of enzymes involved in antioxidant defense (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx], glutathione reductase [GR] and glutathione-S-transferase [GST]). The total antioxidative capacity (T-AOC) was also quantified. No proof of oxidative stress was found in either tissue but there was indication of apoptosis in the liver. CAT, GPx, GR and GST total activities were reduced after 7 days, suggesting a potential decrease of glutathione levels and risk of increased free radicals if the exposure would have lasted longer. There were no major changes in the total activities of antioxidant enzymes in the gills, but the relative expression of the genes coding for CAT and GR were triggered, suggesting a response at the transcription level. These results indicate that C. carpio is well equipped to handle these levels of metal pollution, at least during short term exposure.

Environmental pollution and toxic substances: Cellular apoptosis as a key parameter in a sensible model like fish

The industrial wastes, sewage effluents, agricultural run-off and decomposition of biological waste may cause high environmental concentration of chemicals that can interfere with the cell cycle activating the programmed process of cells death (apoptosis). In order to provide a detailed understanding of environmental pollutants-induced apoptosis, here we reviewed the current knowledge on the interactions of environmental chemicals and programmed cell death. Metals (aluminum, arsenic, cadmium, chromium, cobalt, zinc, copper, mercury and silver) as well as other chemicals including bleached kraft pulp mill effluent (BKME), persistent organic pollutants (POPs), and pesticides (organo-phosphated, organo-chlorinated, carbamates, phyretroids and biopesticides) were evaluated in relation to apoptotic pathways, heat shock proteins and metallothioneins. Although research performed over the past decades has improved our understanding of processes involved in apoptosis in fish, yet there is lack of knowledge on associations between environmental pollutants and apoptosis. Thus, this review could be useful tool to study the cytotoxic/apoptotic effects of different pollutants in fish species.

Effects of high temperature on biochemical parameters, oxidative stress, DNA damage and apoptosis of pufferfish (Takifugu obscurus)

Water temperature is an important environmental factor that affects physiology and biochemical activities of fish. In this study, we investigated of high temperature on biochemical parameters, oxidative stress, DNA damage and apoptosis of pufferfish. Thermal stress could significantly increase the levels of AST, ALT, LDH, GLU and TG, whereas the levels of ALP and TP decrease significantly. In addition, thermal stress also decreased total blood cell count, inhibited cell viability, and subsequently lead to DNA damage and apoptosis. The mRNA levels of p53, caspase-9 and caspase-3 were up-regulated under thermal stress. These results suggested that caspase-dependent and p53 signaling pathways could play important roles in thermal stress-induced apoptosis in fish. Furthermore, the gene expression of SOD, CAT, HSP90 and C3 were induced by thermal stress. This study provides new insights into the mechanism whereby thermal stress affects physiological responses and apoptosis in pufferfish.

Molecular characterization of caspase members and expression response to Nervous Necrosis Virus outbreak in Pacific cod

Multiple functions of caspases include normal cell turnover, proper development and function of the immune system, hormone-dependent atrophy, embryonic development and chemical-induced cell injury. During artificial propagation of Pacific cod, Gadus macrocephalus, high mortality occurred during early development stages. Here, we performed various analyses on the cDNA and protein sequences of six different G. macrocephalus caspases namely GmCasp3, 6, 7, 8, 9 and 10, and tried to investigate the contributions of caspase family to the development and Nervous Necrosis Virus (NNV) resistance. Sequence analysis of GmCaspase proteins showed that each caspase shared conserved domains like "HG", "QACXG (X for R, G or Q)" and "GSWF" except GmCasp10. Sequence alignment and phylogenetic tree showed that GmCasp8 and GmCasp10 were quite different from those of other fishes. 3-D models indicated that structure of GmCasp3 is very conservative, but GmCasp6, 7, 8, 9 and 10 are less conservative. Tissue distribution analysis showed that six Gmcaspases mRNA transcripts were detected in tissues of intestine, gill, thymus, head-kidney and spleen with different abundance, but Gmcasp7 were not detected in the brain. GmCasp3 transcript was kept at very low level in the early development stages, while the expression levels of GmCasp6, 7, 8, 10 were different at various development stages. GmCasp8 level seemed to be much higher than other caspases in the heads of 65dph and 75dph juveniles. To understand the role of caspases during NNV outbreak, modulation in expression of each Gmcaspases were investigated. The results showed that GmCasp3 transcript level increased significantly when NNV broke out, while GmCasp7, 8, 9 and 10 in cod heads decreased obviously at 69dph and 77dph. The results suggest that caspases in Pacific cod should be diverse in their structure and function, and their unique features and response to NNV outbreak add more evidences for the specificity of immune system in Pacific cod.

DNA damage and cytotoxicity induced on common carp by pollutants in water from an urban reservoir. Madín reservoir, a case study

Madín Reservoir provides a substantial amount of drinking water to two municipalities close to Mexico City metropolitan area. However, it receives untreated wastewater discharges from domestic sources in the towns of Nuevo Madín and others, as well as diverse pollutants which are hauled by the Río Tlalnepantla from its upper reaches, so that the xenobiotics in the reservoir are highly diverse in terms of type and quantity. Previous studies showed that MR is contaminated with xenobiotics such as Al, Hg and Fe, as well as NSAIDs, at concentrations exceeding the limits established for aquatic life protection. These pollutants have been shown to induce oxidative stress on Cyprinus carpio and may therefore also damage the genetic material of exposed organisms, eliciting cytotoxicity as well. The present study aimed to determine the genotoxicity and cytotoxicity induced on blood, liver and gill of C. carpio by the pollutants present in MR water. Specimens were exposed to water from five sampling sites and the following biomarkers were evaluated: DNA damage by comet assay, frequency of micronuclei, apoptosis by TUNEL assay and caspase-3 activity. Significant increases relative to the control group (P < 0.05) were found with all biomarkers in all tissues evaluated, with the level of damage differing between sampling sites. In conclusion, pollutants present in MR water are genotoxic and cytotoxic to C. carpio, and this sentinel species, coupled with the biomarkers evaluated herein, is a reliable tool for assessing the health risk to wildlife posed by exposure to pollutants in freshwater bodies.

Identification of apoptosis-related genes Bcl2 and Bax from yellow catfish Pelteobagrus fulvidraco and their transcriptional responses to waterborne and dietborne zinc exposure

Apoptosis plays a key role in the physiology of multicellular organisms, and has been well studied in mammals, but not in teleosts. Zinc (Zn) has been shown to be an important regulator of apoptosis and apoptosis involves in the regulation of lipid metabolism. Moreover, our recent study indicated that waterborne and dietborne Zn exposure differently influenced lipid metabolism in Pelteobagrus fulvidraco, but further mechanism remained unknown. The hypothesis of the present study is that apoptosis mediated the Zn-induced changes of lipid metabolism of P. fulvidraco subjected to different exposure pathways. To this end, we cloned full-length cDNA sequences of Bcl2 and three Bax subtypes involved in apoptosis in P. fulvidraco, explored their mRNA expressions in responses to different Zn exposure pathways. Bcl2 and three Bax subtypes shared similar domain structure as typical pro- and anti-apoptotic Bcl2 family members. Their mRNAs were widely expressed among various tissues, but at variable levels. Waterborne Zn exposure down-regulated mRNA levels of Baxg and ratios of Baxa/Bcl2, and Baxg/Bcl2, but showed no significant effects on mRNA abundances of Bcl2, Baxa and Baxb, and the ratio of Baxb/Bcl2. In contrast, dietborne Zn exposure up-regulated mRNA levels of Bcl2, Baxa, Baxb and Baxg, but reduced the ratios of Baxa/Bcl2, Baxb/Bcl2, and Baxg/Bcl2. Considering their important roles of these genes in apoptosis induced by Zn, apoptosis may mediate the Zn-induced changes of hepatic lipid metabolism of Pelteobagrus fulvidraco under different Zn exposure pathways. For the first time, we characterized the full-length cDNA sequences of Bcl2 and three Bax subtypes, determined their expression profiles and transcriptional responses to different Zn exposure pathways, which would contribute to our understanding of the molecular basis of apoptosis, and also provide new insights into physiological responses to different Zn exposure pathways.

Cypermethrin toxication leads to histopathological lesions and induces inflammation and apoptosis in common carp (Cyprinus carpio L.)

Cypermethrin (Cyp), a known neurotoxic pesticide, is widely used in agricultural applications. In the present study, the aim was to determine the histopathological effects of Cyp toxication and evaluate the activation of inducible nitric oxide synthetase (iNOS) and 8-hydroxy-2-deoxyguanosine (8-OHdG) using an immunofluorescence assay. Thereafter, we identified the expressions of caspase 3, capsase 8, iNOS, and metallothionein 1 (MT1) genes in common carp using quantitative reverse transcription polymerase chain reaction (qRT-PCR). High and low doses of Cyp were administered to experimental groups for 24, 48, 72, and 96 h. As a result, necrotic neurons in different stages and desquamation of ependymal cells due to necrosis were detected in the brain. Histopathological changes, including hyperplasia of lamellar cells, telangiectasia of lamellae and thickening due to cellular infiltration in gills, hemorrhage, diffuse hydropic degeneration, and focal necrosis in the liver were observed in the experimental groups. Immunopositive reactions of 8-OHdG were clearly observed in the nuclei and cytoplasm of neurons, and positive reactions for iNOS were detected in the cytoplasm of neurons and in the glial cells of the experimental groups. Furthermore, we found that caspase 3, capsase 8, iNOS, and MT1 genes were up-regulated in the brain when exposed to both high and low doses of Cyp. In conclusion, our findings revealed that Cyp toxication harms the organs of common carp, particularly the brain, and also gives rise to inflammation, DNA damage, and apoptosis. Therefore, the use of Cyp should be restricted to protect the health of aquatic animals.

Vitamin E deficiency depressed fish growth, disease resistance, and the immunity and structural integrity of immune organs in grass carp (Ctenopharyngodon idella): Referring to NF-κB, TOR and Nrf2 signaling

This study investigated the effects of dietary vitamin E on growth, disease resistance and the immunity and structural integrity of head kidney, spleen and skin in grass carp (Ctenopharyngodon idella). The fish were fed six diets containing graded levels of vitamin E (0, 45, 90, 135, 180 and 225 mg/kg diet) for 10 weeks. Subsequently, a challenge test was conducted by injection of Aeromonas hydrophila. The results showed that compared with optimal vitamin E supplementation, vitamin E deficiency caused depressed growth, poor survival rates and increased skin lesion morbidity in grass carp. Meanwhile, vitamin E deficiency decreased lysozyme and acid phosphatase activities, complement component 3 and complement component 4 contents in the head kidney, spleen and skin of grass carp (P < 0.05). Moreover, vitamin E deficiency down-regulated antimicrobial peptides (Hepcidin, liver-expressed antimicrobial peptide-2A, -2B, β-defensin), IL-10, TGFβ1, IκBα, TOR and S6K1 mRNA levels (P < 0.05) and up-regulated IL-1β, IL-6, IL-8, IFN-γ2 and TNFα, NF-κB p65, IKKα, IKKβ and 4EBP1 (not in the head kidney) mRNA levels (P < 0.05). In addition, vitamin E deficiency caused oxidative damage, decreased superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione reductase (GR) activities, and down-regulated the mRNA levels of antioxidant enzymes and signaling molecules Nrf2 (P < 0.05). Vitamin E deficiency also induced apoptosis by up-regulating capase-2, -3, -7, and -8 mRNA levels in the head kidney, spleen and skin of grass carp. In conclusion, this study indicated that dietary vitamin E deficiency depressed fish growth, impaired the immune function and disturbed the structural integrity of the head kidney, spleen and skin in grass carp, but optimal vitamin E supplementation can reverse those negative effects in fish. The optimal vitamin E requirements for young grass carp (266.39-1026.63 g) to achieve optimal growth performance and disease resistance based on the percent weight gain (PWG) and skin lesion morbidity were estimated to be 116.2 and 130.9 mg/kg diet, respectively. Meanwhile, based on immune indicator (LA activity in the head kidney) and antioxidant indicator (protection of spleen against MDA), the optimal vitamin E requirements for young grass carp were estimated to be 123.8 and 136.4 mg/kg diet, respectively.

Treatment of cadmium-induced renal oxidative damage in rats by administration of alpha-lipoic acid

Cadmium (Cd) is a toxic heavy metal that is widespread and nephrotoxic, but the mechanism of its toxicity is not well understood. Alpha-lipoic acid (α-LA) has a protective effect on Cd-induced oxidative stress, but the underlying mechanism is also not clear. This study aimed to confirm that Cd causes renal damage and to explore the potential underlying mechanism of α-LA to the kidney. Rats were randomly divided into four groups: control group, Cd group (50 mg/L CdAc₂), Cd+α-LA group (50 mg/L CdAc₂ + 50 mg/kg body wt/day α-LA), and α-LA group (50 mg/kg body wt/day). The rats were exposed to Cd via drinking water and α-LA in the form of gavage at the same time every day. After 12 weeks, the activity of antioxidant enzymes and the level of Cd in the kidney were analyzed. Renal damage was evaluated based on histopathological and ultrastructure examinations. The apoptosis index was determined based on the results of western blotting and qRT-PCR. Our results indicate that accumulation of Cd causes serious kidney damage and α-LA has a protective effect against Cd-induced oxidative stress and apoptosis. Further, the findings indicate that the antioxidant, Cd chelation, and antiapoptotic activities of α-LA are the key factors that alleviate nephrotoxicity.

Molecular and functional characterization of caspase-8 from the big-belly seahorse (Hippocampus abdominalis)

Apoptosis is a physiological process that can also participate in host immune defense mechanisms, including tumor growth suppression along with homeostasis and maturation of immune cells. Caspases are known to be involved in cellular apoptotic signaling; among them, caspase-8 plays an important role in the initiation phase of the apoptotic death cascade. In the current study, we molecularly characterized a caspase-8 homolog (designated as HaCasp-8) from Hippocampus abdominalis. The HaCasp-8 gene harbors a 1476 bp open reading frame (ORF) that codes for a protein of 492 amino acids (aa) with a predicted molecular mass of 55 kDa. HaCasp-8 houses the typical domain architecture of known initiator caspases, including the death effector domain and the carboxyl-terminal catalytic domain. As expected, phylogenetic analysis reflected a closer evolutionary relationship of HaCasp-8 with its teleostean similitudes. The results of our qPCR assays confirmed the ubiquitous expression of HaCasp-8 in physiologically important tissues examined, with pronounced expression levels in ovary tissues, followed by blood cells. HaCasp-8 expression at the mRNA level was found to be significantly modulated by lipopolysaccharide, polyinosinic:polycytidylic acid, Streptococcus iniae, and Edwardsiella tarda injection. Overexpression of HaCasp-8 could trigger a significant level of cell death in HEK293T cells, suggesting its putative role in cell death. Taken together, our findings suggest that HaCasp-8 is an important component in the caspase cascade, and its expression can be significantly modulated under pathogen stress conditions in the big-belly seahorse.

Molecular cloning and characterization of four caspases members in Apostichopus japonicus

The caspase family representing aspartate-specific cysteine proteases have been demonstrated to possess key roles in apoptosis and immune response. We previously demonstrated that LPS challenged Apostichopus japonicus coelomocyte could significantly induced apoptosis in vitro. However, apoptosis related molecules were scarcely investigated in this economic species. In the present work, we cloned and characterized four members caspase family from A. japonicus (designated as Ajcaspase-2, Ajcaspase-3, Ajcaspase-6, and Ajcaspase-8, respectively) by RACE. Multiple sequence alignment and structural analysis revealed that all Ajcaspases contained the conservative CASC domain at C terminal, in which some unique features for each Ajcaspase made them different from each other. These specific domains together with phylogenetic analysis supported that all these four identified proteins belonged to novel members of apoptotic signaling pathway in sea cucumber. Tissue distribution analysis revealed that four Ajcaspase genes were constitutively expressed in all examined tissues. The expression of Ajcaspase-2 was tightly correlated with that of Ajcaspase-8 in each detected tissues. Ajcaspase-3 and Ajcaspase-6 transcripts were both highly expressed in immune tissue of coelomocytes. Furthermore, the Vibrio splendidus challenged sea cucumber coelomocytes could significantly up-regulate the mRNA expressions of four genes. The expression levels of Ajcaspase-2 and Ajcaspase-8 were relative earlier than those of Ajcaspase-6 and Ajcaspase-3, respectively, which could be inferred that Ajcapase-2 might directly modulate Ajcaspase-6, and Ajcaspase-8 initiate the expression of Ajcaspase-3. The induce expressions differed among each Ajcaspase depending upon their roles such as initiator or effector caspase. All our results demonstrated that four Ajcaspases present diversified functions in apoptotic cascade signaling pathway of sea cucumber under immune response.

Endoplasmic reticulum stress eIF2α-ATF4 pathway-mediated cyclooxygenase-2 induction regulates cadmium-induced autophagy in kidney

The heavy metal cadmium (Cd) is nephrotoxic. Recent studies show that autophagy plays an essential role in Cd-induced kidney injury. However, the mechanisms of Cd-induced kidney injury accompanied by autophagy are still obscure. In the present study, we first confirmed that Cd induced kidney damage and dysfunction, along with autophagy, both in vivo and in vitro. Then, we observed that cyclooxygenase-2 (COX-2) and the eIF2α-ATF4 pathway of endoplasmic reticulum (ER) stress were induced by Cd in both kidney tissues and cultured cells. Further studies showed that inhibition of COX-2 with celecoxib or RNA interference (RNAi) inhibited the Cd-induced autophagy in kidney cells. In addition, blocking ER stress with 4-phenylbutyrate or RNAi partially counteracted COX-2 overexpression and autophagy induced by Cd, which suggested that ER stress was required for Cd-induced kidney autophagy. Significantly, our results showed that Cd activated ATF4 and induced its translocation to the nucleus. Knockdown of ATF4 inhibited Cd-induced COX-2 overexpression. While COX-2 overexpression is involved in renal dysfunction, there is no prior report on the role of COX-2 in autophagy regulation. The results of the current study suggest a novel molecular mechanism that the ER stress eIF2α-ATF4 pathway-mediated COX-2 overexpression contributes to Cd-induced kidney autophagy and injury. The present study implies that COX-2 may be a potential target for therapy against Cd-induced nephrotoxicity.

Multifunctional murrel caspase 1, 2, 3, 8 and 9: Conservation, uniqueness and their pathogen-induced expression pattern

Caspases are evolutionarily conserved proteases which play fundamental role in apoptosis. Invasion of pathogen triggers the activation of caspases-mediated pro-inflammatory and pro-apoptotic pathways, where multifunctional caspases are involved. In striped murrel Channa striatus, epizootic ulcerative syndrome (EUS) causes endemics resulting in huge economic loss. Aphanomyces invadans, an oomycete is the primary causative agent of EUS which further induces secondary bacterial infections especially Aeromonas hydrophila. In order to get insights into the caspase gene family in C. striatus during EUS infection, we performed various physicochemical and structural analyses on the cDNA and protein sequences of five different murrel caspases namely CsCasp 1, 2, 3, 8 and 9. Sequence analysis of murrel caspase proteins showed that in spite of the conserved CASC domain, each caspase embraces some unique features which made them functionally different. Tissue distribution analysis showed that all the murrel caspases are highly expressed in one of the immune organs such as liver, kidney, spleen and blood cells. Further, to understand the role of caspase during EUS infection, modulation in expression of each caspase gene was analysed after inducing fungal and bacterial infection in C. striatus. Pathogen-induced gene expression pattern revealed an interesting fact that the expression of all the caspase genes reached a maximum level at 24 h post-infection (p.i) in case of bacteria, whereas it was 48 h in fungus. However, the initiation of elevated expression differed between each caspase based on their role such as pro-inflammatory, initiator and executioner caspase. Overall, the results suggested that the caspases in murrel are diverse in their structure and function. Here, we discuss the similarities and differences of five different murrel caspases.

Deficient and excess dietary selenium levels affect growth performance, blood cells apoptosis and liver HSP70 expression in juvenile yellow catfish Pelteobagrus fulvidraco

We investigated the effects of deficient and excess dietary selenium (Se) on growth, blood cells apoptosis and liver heat shock protein 70 (HSP70) expression in juvenile yellow catfish (Pelteobagrus fulvidraco). After 8 weeks, yellow catfish (initial weight: 2.12 ± 0.01 g) fed isonitrogenous and isolipid diets containing <0.05 (deficient dietary Se) or 6.5 (excess dietary Se) mg Se/kg displayed a significantly lower weight gain ratio (WGR) than those fed a diet containing 0.23 (normal dietary Se) mg Se/kg. As dietary Se levels increased, liver Se concentration, glutathione peroxidase activity and the hepatosomatic index increased significantly. Plasma glucose concentration was highest in the normal treatment compared with the excess dietary Se treatment. Both deficient and excess dietary Se lead to increased reactive oxygen species (ROS) production and apoptosis ratio in blood cells, whereas only excess dietary Se increased their cytoplasmic free-Ca(2+) (CF-Ca(2+)) concentration. Excess dietary Se also resulted in the highest level of HSP70 expression, thereby possibly providing a protective mechanism against oxidative stress. These results indicate that both deficient and excess dietary Se restrained the growth of juvenile yellow catfish and caused oxidative stress. The overproduction of ROS may act as a signal molecule mediate apoptosis when dietary Se deficiency. Both ROS and CF-Ca(2+) were recorded when dietary Se excess, suggesting that Ca(2+) may be activated by Se and play a major role during Se-induced oxidative stress and cell apoptosis.

Molecular cloning, immunohistochemical localization, characterization and expression analysis of caspase-8 from the blunt snout bream (Megalobrama amblycephala) exposed to ammonia

Caspase-8 is an initiator caspase that plays a crucial role in some cases of apoptosis by extrinsic and intrinsic pathways. Caspase-8 structure and function have been extensively studied in mammals, but in fish the characterization of that initiator caspase is still scarce. In this study, we isolated the caspase-8 gene from Megalobrama amblycephala, one of the most important industrial aquatic animals in China using rapid amplification of cDNA ends (RACE). The 2034 bp full-length M. amblycephala caspase-8 cDNA sequence contained an ORF of 1467 bp encoding a polypeptide of 489 amino acid residues, a 5'-UTR of 102 bp and a 3'-UTR of 462 bp. The caspase-8 amino acid sequences contained two highly conservative death effector domains (DEDs) at N-terminal, the caspase family domains P20 and P10, caspase-8 active-site pentapeptide and potential aspartic acid cleavage sites. Phylogenetic analysis revealed that M. amblycephala caspase-8 were clustered with the caspase-8 from other vertebrate. Real-time quantitative PCR analysis revealed that caspase-8 transcripts were detected in liver after exposure to ammonia. Meanwhile using Western blot analysis, caspase-8 cleaved fragment was detected and significant alteration of procaspase-8 level was found with the same ammonia treatment condition. Furthermore, the result of immunohistochemical detection showed that remarkable changes of immunopositive staining were observed after ammonia treatment. Accordingly, the results signify that caspase-8 of fish may play an essential role in ammonia induced apoptosis.

Short-term cadmium exposure induces stress responses in frog (Pelophylax bergeri) skin organ culture

There have been a few studies on the negative effects of pollutants on amphibian skin, the first structural barrier that interacts with the environment and its potential contaminants. In this study an ex vivo skin organ culture from the amphibian Pelophylax bergeri was used to evaluate cell stress responses induced by short-term exposure to cadmium (Cd), a toxic heavy metal known to be an environmental hazard to both humans and wildlife. Histopathological studies were carried out on skin explants using light microscopy and changes in the expression of stress proteins, such as Metallothionein (MT) and Heat shock proteins (HSPs), were investigated by Real-time RT-PCR. Results revealed that amphibian skin reacts to Cd-induced stress by activating biological responses such as morphological alterations and dose- and time-dependent induction of Mt and Hsp70 mRNA expression, suggesting their potential role as biomarkers of exposure to Cd. This work provides a basis for a better understanding of the tissue-specific responses of amphibian skin as a target organ to Cd exposure and its in vitro use for testing potentially harmful substances present in the environment.

Changes in barrier health status of the gill for grass carp (Ctenopharyngodon idella) during valine deficiency: Regulation of tight junction protein transcript, antioxidant status and apoptosis-related gene expression

This study investigated the effects of dietary valine on tight junction protein transcription, antioxidant status and apoptosis on grass carp gills (Ctenopharyngodon idella). Fish were fed six different experimental diets containing graded levels of valine (4.3, 8.0, 10.6, 13.1, 16.7, 19.1 g/kg). The results indicated that valine deficiency decreased Claudin b, Claudin 3, Occludin and ZO-1 transcription and increased Claudin 15 expression in the fish gill (P < 0.05). These effects were partly due to the down-regulation of interleukin 10 (IL-10), transforming growth factor β1 (TGF-β1) and IκB α and the up-regulation of relative mRNA expression of interleukin 1β (IL-1β), interleukin 8 (IL-8), tumor necrosis factor-α (TNF-α) and nuclear factor κB P65 (NF-κB P65) (P < 0.05). However, valine deficiency and valine supplementation did not have a significant effect on Claudin c and Claudin 12 expression in grass carp gills (P > 0.05). Valine deficiency also disrupted antioxidant status in the gill by decreasing anti-superoxide radicals and hydroxyl radical capacity, glutathione contents and the activities and mRNA levels of Cu/Zn superoxide dismutase (SOD1), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) (P < 0.05). These results may be ascribed to the down-regulation of NF-E2-related factor 2 (Nrf2), target of rapamycin (TOR) and ribosomal protein S6 kinase 1 (S6K1) and the up-regulation of Kelch-like-ECH-associated protein 1 (Keap1) (P < 0.05). Additionally, valine deficiency induced DNA fragmentation via the up-regulation of Caspase 3, Caspase 8 and Caspase 9 expressions (P < 0.05). These results may be ascribed to the improvement in ROS levels in the fish gill (P < 0.05). Taken together, the results showed that valine deficiency impaired the structural integrity of fish gill by disrupted fish antioxidant defenses and regulating the expression of tight junction protein, cytokines, antioxidant enzymes, NF-κB p65, IκBα, TOR, Nrf2, Keap1 and apoptosis-related genes in the fish gill.

Effects of ammonia exposure on apoptosis, oxidative stress and immune response in pufferfish (Takifugu obscurus)

Ammonia is one of major environmental pollutants in the freshwater aquatic system that affects the survival and growth of organisms. In the present study, we investigated the effects of ammonia exposure on apoptosis, oxidative stress and immune response in pufferfish (Takifugu obscurus). Fish were exposed to various concentrations of ammonia (0, 1.43, 3.57, 7.14mM) for 72h. The date showed that ammonia exposure could induce intracellular reactive oxygen species (ROS), interrupt intracellular Ca(2+) (cf-Ca(2+)) homeostasis, and subsequently lead to DNA damage and cell apoptosis. To test the apoptotic pathway, the expression patterns of some key apoptotic related genes including P53, Bax Bcl2, Caspase 9, Caspase 8 and Caspase 3 in the liver were examined. The results showed that ammonia stress could change these genes transcription, associated with increasing of cell apoptosis, suggesting that the P53-Bax-Bcl2 pathway and caspase-dependent apoptotic pathway could be involved in cell apoptosis induced by ammonia stress. In addition, ammonia stress could induced up-regulation of inflammatory cytokines (BAFF, TNF-α, IL-6 and IL-12) transcription, indicating that innate immune system play important roles in ammonia-induced toxicity in fish. Furthermore, the gene expressions of antioxidant enzymes (Mn-SOD, CAT, GPx, and GR) and heat shock proteins (HSP90 and HSP70) in the liver were induced by ammonia stress, suggesting that antioxidant system and heat shock proteins tried to protect cells from oxidative stress and apoptosis induced by ammonia stress. Our results will be helpful to understand the mechanism of aquatic toxicology induced by ammonia in fish.

Effects of tetracycline on developmental toxicity and molecular responses in zebrafish (Danio rerio) embryos

The extensive use of pharmaceuticals has resulted in the intensive contamination of water bodies. Tetracycline is a type of antibiotic and its potential toxicity is causing environmental concern. The effects of developmental toxicity and the mechanisms of tetracycline on fish embryos are not well understood. Zebrafish embryos are used in this study to investigate the developmental toxicity of this compound. Four hour post-fertilization (hpf) zebrafish embryos are exposed to different concentrations of tetracycline until 96 hpf. The larvae display developmental delay phenotypes, including hatching delay, shorter body length, increased yolk sac area and uninflated swim bladder upon exposure to tetracycline. Delayed yolk sac absorption and swim bladder deficiency at 96 hpf are observed in the zebrafish larvae upon exposure to 20 μg/L of tetracycline. To test whether tetracycline causes oxidative damage and the resulting oxidative stress-induced apoptosis, the generation of reactive oxygen species (ROS), Acridine Orange staining and real time polymerase chain reaction have been performed in this study. The results indicate that tetracycline exposure results in significant increases in ROS production and cell apoptosis, mainly in the tail areas at 96 hpf. The gene expression pattern demonstrates that tetracycline induces ROS which causes apoptosis in the zebrafish larvae, and the results also indicate that caspase-dependent apoptotic pathways may greatly contribute to tetracycline-induced apoptosis in the early-life stages of the zebrafish. In addition, we have investigated the effects of tetracycline on marker genes related to resistance mechanisms and gene regulating drug biotransformation. The results of these gene expression studies indicate that tetracycline could induce zebrafish to resist pharmaceuticals and Cytochrome P450s that are involved in the biotransformation of tetracycline in zebrafish larvae. The overall results indicate that tetracycline can produce oxidative stress and induce apoptosis, which brings about significant developmental delay in zebrafish embryos.

Gene networks and toxicity pathways induced by acute cadmium exposure in adult largemouth bass (Micropterus salmoides)

Cadmium is a heavy metal that can accumulate to toxic levels in the environment leading to detrimental effects in animals and humans including kidney, liver and lung injuries. Using a transcriptomics approach, genes and cellular pathways affected by a low dose of cadmium were investigated. Adult largemouth bass were intraperitoneally injected with 20μg/kg of cadmium chloride (mean exposure level - 2.6μg of cadmium per fish) and microarray analyses were conducted in the liver and testis 48h after injection. Transcriptomic profiles identified in response to cadmium exposure were tissue-specific with the most differential expression changes found in the liver tissues, which also contained much higher levels of cadmium than the testis. Acute exposure to a low dose of cadmium induced oxidative stress response and oxidative damage pathways in the liver. The mRNA levels of antioxidants such as catalase increased and numerous transcripts related to DNA damage and DNA repair were significantly altered. Hepatic mRNA levels of metallothionein, a molecular marker of metal exposure, did not increase significantly after 48h exposure. Carbohydrate metabolic pathways were also disrupted with hepatic transcripts such as UDP-glucose, pyrophosphorylase 2, and sorbitol dehydrogenase highly induced. Both tissues exhibited a disruption of steroid signaling pathways. In the testis, estrogen receptor beta and transcripts linked to cholesterol metabolism were suppressed. On the contrary, genes involved in cholesterol metabolism were highly increased in the liver including genes encoding for the rate limiting steroidogenic acute regulatory protein and the catalytic enzyme 7-dehydrocholesterol reductase. Integration of the transcriptomic data using functional enrichment analyses revealed a number of enriched gene networks associated with previously reported adverse outcomes of cadmium exposure such as liver toxicity and impaired reproduction.

The role of apoptosis in MCLR-induced developmental toxicity in zebrafish embryos

We previously demonstrated that cyanobacteria-derived microcystin-leucine-arginine (MCLR) is able to induce developing toxicity, such as malformation, growth delay and also decreased heart rates in zebrafish embryos. However, the molecular mechanisms by which MCLR induces its toxicity during the development of zebrafish remain largely unknown. Here, we evaluate the role of apoptosis in MCLR-induced developmental toxicity. Zebrafish embryos were exposed to various concentrations of MCLR (0, 0.2, 0.5, 2, and 5.0 mg L(-1)) for 96 h, at which time reactive oxygen species (ROS) was significantly induced in the 2 and 5.0 mg L(-1) MCLR exposure groups. Acridine orange (AO) staining and terminal deoxynucleotide transferase-mediated deoxy-UTP nick end labelling (TUNEL) assay showed that MCLR exposure resulted in cell apoptosis. To test the apoptotic pathway, the expression pattern of several apoptotic-related genes was examined for the level of enzyme activity, gene and protein expression, respectively. The overall results demonstrate that MCLR induced ROS which consequently triggered apoptosis in the heart of developing zebrafish embryos. Our results also indicate that the p53-Bax-Bcl-2 pathway and the caspase-dependent apoptotic pathway play major roles in MCLR-induced apoptosis in the developing embryos.

Ultrasound microbubble-mediated delivery of integrin-linked kinase gene improves endothelial progenitor cells dysfunction in pre-eclampsia

Pre-eclampsia (PE) is a specific vascular complication in pregnancy whose precise mechanism is still unclear. We hypothesized that endothelial progenitor cells (EPCs), the precursor of endothelial cells, might be impaired in patients with PE and hold a great promise for the treatment of PE. In the present study, we analyzed the EPCs number and expression of integrin-linked kinase (ILK) in PE patients. We confirmed that both EPCs number and ILK expression were diminished in PE patients. Next, we transfected EPCs with ILK gene using ultrasonic microbubble technique (UMT) for the first time, as UMT is a novel type of gene transfer technology showing promising applications in stem cells apart from EPCs. To further investigate the transfection efficiency of UMT, RT-PCR analysis and western blot were used to examine the messenger RNA (mRNA) and protein level of ILK. After transfection of the ILK gene, EPCs function was tested to illustrate the role of ILK in cell proliferation, apoptosis, migration, and secretion. The results of the in vitro study suggested that UMT, a novel gene delivery system, could be considered a potent physical method for EPCs transfection. Moreover, the growth and angiogenetic properties of EPCs are enhanced by introducing ILK. This study may afford a new trend for EPCs transfection and gene therapy in PE.

Cadmium induces liver cell apoptosis through caspase-3A activation in purse red common carp (Cyprinus carpio)

Caspase-3, the essential effector caspase, plays a pivotal role during caspase-dependent apoptosis. In this study, we isolated and characterized caspase-3A gene from common carp. The common carp caspase-3A comprising 273 amino acids showed 71.8% sequence similarity and 59.3% sequence identity to human caspase-3. It exhibited an evolutionarily conserved structure of mammalian caspase-3 genes, including a pro-domain, a large subunit, a small subunit and other motifs such as the pentapeptide active-site motif (QACRG) and the putative cleavage sites at the aspartic acids. Phylogenetic analysis demonstrated that common carp caspase-3A formed a clade with cyprinid fish caspase-3. To assess whether caspase-3A is involved in cadmium (Cd)-induced cell apoptosis in common carp, a Cd exposure experiment was performed. TUNEL analysis showed that Cd triggered liver cell apoptosis; caspase-3A activity was markedly increased; its proenzyme level was significantly decreased, and the levels of its cleaved forms were markedly increased. However, real-time quantitative PCR analysis revealed that the mRNA transcript level of caspase-3A was not significantly elevated. Immunoreactivities were observed in the cytoplasm of hepatocytes by immunohistochemical detection. The findings indicates that Cd can trigger liver cell apoptosis through the activation of caspase-3A. Caspase-3A may play an essential role in Cd-induced apoptosis.