Stress In Gills Research Articles

Assessing the Effects of a Diet of BPA Analogue-Exposed Microalgae in the Clam Ruditapes philippinarum.

In our previous study, we demonstrated that the microalgae Phaeodactylum tricornutum can bioaccumulate bisphenol A analogues. Since this microalgae species is part of the diet of marine filter-feeding organisms, such as bivalves, in this study we tested the hypothesis that a diet based on exposed microalgae can exert negative effects on the clam Ruditapes philippinarum. Microalgae were exposed for 7 days to 300 ng/L of bisphenol AF (BPAF), bisphenol F (BPF), and bisphenol S (BPS), alone or as a mixture (MIX), to allow bioaccumulation. Microalgae were then supplied as food to bivalves. After 7 and 14 days of diet, the effects of exposed microalgae were evaluated on a battery of biomarkers measured in haemolymph/haemocytes, gills and digestive glands of clams. In addition, bioaccumulation of the three bisphenols was investigated in clams by UHPLC-HRMS. The results obtained demonstrated that total haemocyte count (THC) increased in clams following ingestion for 7 days of BPAF- and BPF-exposed microalgae, while BPS-exposed microalgae significantly reduced THC after 14 days of diet. MIX- and BPS-exposed microalgae increased haemocyte proliferation. The diet of exposed microalgae affected acid and alkaline phosphatase activity in clams, with an opposite response between haemolymph and haemocytes. Regarding antioxidants, an increase in catalase activity was observed in clams after ingestion of BPA analogue-exposed microalgae. The results also demonstrated marked oxidative stress in gills, the first tissue playing an important role in the feeding process. Oxidative damage was recorded in both the gills and digestive glands of clams fed BPA analogue-exposed microalgae. Alterations in epigenetic-involved enzyme activity were also found, demonstrating for the first time that BPA analogue-exposed food can alter epigenetic mechanisms in marine invertebrates. No bioaccumulation of BPA analogues was detected in clam soft tissues. Overall, this study demonstrated that a diet of BPA analogue-exposed microalgae can induce significant alterations of some important biological responses of R. philippinarum. To our knowledge, this is the first study demonstrating the effects of ingestion of BPA analogue-exposed microalgae in the clam R. philippinarum, suggesting a potential ecotoxicological risk for the marine food chain, at least at the first levels.

Hypoxia leads to gill endoplasmic reticulum stress and disruption of mitochondrial homeostasis in grass carp (Ctenopharyngodon idella): Mitigation effect of thiamine

Hypoxia in water environment is one of the important problems faced by intensive aquaculture. Under hypoxia stress, the effects of dietary thiamine were investigated on grass carp gill tissue damage and their mechanisms. Six thiamine diets with different thiamine levels (0.22, 0.43, 0.73, 1.03, 1.33 and 1.63 mg/kg) were fed grass carp (Ctenopharyngodon idella) for 63 days. Then, 96-hour hypoxia stress test was conducted. This study described that thiamine enhanced the growth performance of adult grass carp and ameliorated nutritional status of thiamine (pyruvic acid, glucose, lactic acid and transketolase). Additionally, thiamine alleviated the deterioration of blood parameters [glutamic oxalacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), glucose, cortisol, lactic dehydrogenase (LDH), erythrocyte fragility, and red blood cell count (RBC count)] caused by hypoxia stress, and reduced reactive oxygen species (ROS) content and oxidative damage to the gills. In addition, thiamine alleviated endoplasmic reticulum stress in the gills, which may be related to its inhibition of RNA-dependent protein kinase-like ER kinase (PERK)/eukaryotic translation initiation factor-2α (eIF2α)/activating transcription factor4 (ATF4), inositol-requiring enzyme 1 (IRE1)/X-Box binding protein 1 (XBP1) and activating transcription factor 6 (ATF6) pathways. Furthermore, thiamine maintaining mitochondrial dynamics balance was probably related to promoting mitochondrial fusion and inhibiting mitochondrial fission, and inhibiting mitophagy may involve PTEN induced putative kinase 1 (PINK1)/Parkin-dependent pathway and hypoxia-inducible factor (HIF)-Bcl-2 adenovirus E1B 19 kDa interacting protein 3 (BNIP3) pathway. In summary, thiamine alleviated hypoxia stress in fish gills, which may be related to reducing endoplasmic reticulum stress, regulating mitochondrial dynamics balance and reducing mitophagy. The thiamine requirement for optimum growth [percent weight gain (PWG)] of adult grass carp was estimated to be 0.81 mg/kg diet. Based on the index of anti-hypoxia stress (ROS content in gill), the thiamine requirement for adult grass carp was estimated to be 1.32 mg/kg diet.

Gills de novo assembly reveals oxidative stress, unfolded protein, and immune response on red cusk-eel (Genypterus chilensis) under thermal stress

The heat waves on the South Pacific coast could lead to thermal stress in native fish. The red cusk-eel (Genypterus chilensis) is relevant for Chilean artisanal fisheries and aquaculture diversification. This study examined the effect of high-temperature stress in the gills of G. chilensis in control (14 °C) and high-temperature stress (19 °C) conditions. High-temperature stress induces a significant increase in gills cortisol levels. Additionally, oxidative damage was observed in gills (protein carbonylation and lipoperoxidation). RNA-seq data was used to build the first transcriptome assembly of gills in this species (23,656 annotated transcripts). A total of 1138 down-regulated and 1531 up-regulated transcripts were observed in response to high-temperature stress in gills. The enrichment analysis showed immune response and replication enriched processes (on down-regulated transcripts), and processes related to the folding of proteins, endoplasmic reticulum, and transporter activity (on up-regulated transcripts). The present study showed how gills could be affected by high-temperature stress.

Phthalate induced hormetic effect reveals susceptibility of gill compared to muscle tissue after depuration in commercially important fish (Etroplus suratensis)

Effect of Bis-2ethylhexyl phthalate (DEHP) on commercially important tropical fish pearl spot has not been demonstrated at environmental concentrations along with depuration. The species is estuarine, juvenile and difficult to maintain but widely consumed and well distributed in tropical estuaries. Antioxidant activity of SOD, CAT and GPx was enhanced on all exposure days for gill and muscle suggesting high oxidative stress, except on day 5. Detoxifying enzyme-GST behaved differentially in gill and muscle tissue after depuration, depicting inhibited activity of GST in gill leading to lipid peroxidation. However, the muscle tissue was able to recover from stress after 7 days of depuration with the help of detoxifying enzymes. Overcompensation of antioxidant activity was observed over disruption of homeostasis defining hormesis effect. Integrated biomarker (IBR) index depicted high toxicity during entire exposure time, but after depuration, gill could not mediate LPO at lowest concentration (10 μg/l) while muscle tissue recovered, suggesting persistence of stress in gill.

Interplay of gene expression and regulators under salinity stress in gill of Labeo rohita

BackgroundLabeo rohita is the most preferred freshwater carp species in India. The concern of increasing salinity concentration in freshwater bodies due to climate change may greatly impact the aquatic environment. Gills are one of the important osmoregulatory organs and have direct contact with external environment. Hence, the current study is conducted to understand the gill transcriptomic response of L. rohita under hypersalinity environment.ResultsComprehensive analysis of differentially expressed long non-coding RNAs (lncRNAs), microRNAs (miRNAs) and mRNAs was performed in gills of L. rohita treated with 2, 4, 6 and 8ppt salinity concentrations. Networks of lncRNA-miRNA-mRNA revealed involvement of 20, 33, 52 and 61 differentially expressed lncRNAs, 11, 13, 26 and 21 differentially expressed miRNAs in 2, 4, 6 and 8ppt groups between control and treatment respectively. These lncRNA-miRNA pairs were regulating 87, 214, 499 and 435 differentially expressed mRNAs (DE mRNAs) in 2, 4, 6 and 8ppt treatments respectively. Functional analysis of these genes showed enrichment in pathways related to ion transportation and osmolyte production to cope with induced osmotic pressure due to high salt concentration. Pathways related to signal transduction (MAPK, FOXO and phosphatidylinositol signaling), and environmental information processing were also upregulated under hypersalinity. Energy metabolism and innate immune response pathways also appear to be regulated. Protein turnover was high at 8ppt as evidenced by enrichment of the proteasome and aminoacyl tRNA synthesis pathways, along with other enriched KEGG terms such as apoptosis, cellular senescence and cell cycle.ConclusionAltogether, the RNA-seq analysis provided valuable insights into competitive endogenous (lncRNA-miRNA-mRNA) regulatory network of L. rohita under salinity stress. L. rohita is adapting to the salinity stress by means of upregulating protein turnover, osmolyte production and removing the damaged cells using apoptotic pathway and regulating the cell growth and hence diverting the essential energy for coping with salinity stress.

The IL17 signaling pathway: A potential signaling pathway mediating gill hyperplasia and inflammation under ammonia nitrogen stress was identified by multi-omics analysis

Ammonia nitrogen is extremely toxic to aquatic animals, and is also the most common pollutant in the aquatic environment. In order to investigate the effect of high concentration of ambient ammonia nitrogen on fish gills, two groups, including a high ammonia group (T group: TAN = 2.5 mg/L, 10 % 96 h LC50) and a control group (Z group: total ammonia nitrogen (TAN) = 0 mg/L) were set up in this study. The effects of chronic ammonia stress on the gills of Pelteobagrus fulvidraco were investigated by histopathological, enzymatic, transcriptomic and proteomic analyses after 28 d of stress at different ammonia nitrogen concentrations. Histopathological observations revealed significant inflammatory cell infiltration, necrotic and abscission at the base of the gill filaments, and massive proliferation of cells at the base of the gill lamellae. Ammonia nitrogen stress led to increased reactive oxygen species (ROS) content and decreased catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX) activities in gills, indicating significant oxidative stress in gills. And further transcriptomic analysis revealed that 807 differential expression genes (DEGs) were generated in the gills, of which 587 DEGs were up-regulated and 220 DEGs were down-regulated. In addition, proteomics analysis identified 1073 differential expression proteins (DEPs) in gills, including 983 up- and 90 down-regulated DEPs. Pathway enrichment analysis of the DEGs and DEPs revealed that multiple inflammation-related signaling pathways were activated in the gill, including the significantly enriched IL17 signaling pathway. This suggests that IL17 signaling pathway might have a significant impact during signaling transduction. Further analysis of network regulation by mapping DEGs and DEPs to KEGG pathway revealed that IL17 signaling pathway mediated inflammation and cell proliferation in gills under ammonia stress. The results of this study provided new insights into the response of fish gills to ammonia nitrogen stress, and the IL17 signaling pathway may be a potential therapeutic target for reducing ammonia nitrogen gill toxicity.

Azoxystrobin-induced Oxidative Stress in Gills, Hematological Biomarkers and Histopathological Ailments in Fresh Water Fish

Azoxystrobin-induced Oxidative Stress in Gills, Hematological Biomarkers and Histopathological Ailments in Fresh Water Fish

Adaptive potential of the Mediterranean mussel Mytilus galloprovincialis to short-term environmental hypoxia

Environmental hypoxia naturally occurs in coastal ecosystems and bivalve mollusks have to frequently face fluctuations of dissolved oxygen concentrations. Exposure to hypoxia is often associated with the change of the antioxidant and functional status in bivalves, and restoration of the normal oxygen supply is considered to induce oxidative stress in tissues of mollusks. The study investigates changes in the activity of two antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD), as well as the expression level of SOD and CAT genes in gills of the Mediterranean mussel, Mytilus galloprovincialis, under exposure to low dissolved oxygen concentration (2.2 mg L−1) for 24 h and 72 h, and 24 h reoxygenation period. We also evaluated the intracellular level of reactive oxygen species (ROS), mortality and changes in mitochondrial membrane potential in hemocytes following hypoxia-reoxygenation cycle. 24 h exposure to hypoxia significantly decreased activity of both enzymes, which then recovered up to control levels at the end of 72 h experimental period for SOD and after reoxygenation for CAT. Expression of antioxidant enzyme genes was up-regulated following the 72 h hypoxic exposure period and returned to the basal normoxic level after 24 h reoxygenation. Hypoxia demonstrated a time-dependent effect on the functional state of hemocytes. The 24 h exposure period did not influence aerobic respiration of hemocytes, but prolonged hypoxia (72 h) was associated with a substantial decrease in mitochondrial membrane potential of hemocytes. The intracellular ROS level and mortality of hemocytes did not change under hypoxia. Reoxygenation period was accompanied with a significant decrease of intracellular ROS level. This study indicated that hypoxia did not induce the pronounced oxidative stress in gills and the changes in the antioxidant status were reversible within 24 h of reoxygenation. Hemolymph demonstrated a stable functional state indicating the tolerance of mussels to short-time hypoxia.

Multi-omics profiling and biochemical assays reveal the acute toxicity of environmental related concentrations of Di-(2-ethylhexyl) phthalate (DEHP) on the gill of crucian carp (Carassius auratus)

Di-(2-ethylhexyl) phthalate (DEHP) is one of the most extensively utilized plasticizers in the plastic manufacturing process. It is widely used in various fields due to its low cost and excellent effect. Although there is evidence that DEHP is harmful to animal and human health, DEHP-induced gill toxicity in aquatic organisms is inconclusive, and its mechanism has not been fully elucidated. Here, we investigated the effects of DEHP acute exposure on crucian carp gills at environmentally relevant concentrations of 20, 100, and 500 μg/L. Multi-omics profiling and biochemical assays were employed to characterize the potential toxicological mechanisms. The results showed that acute exposure to 100 and 500 μg/L of DEHP leads to oxidative stress in gills, as evidenced by overproduction of reactive oxygen species (ROS), increased antioxidant enzyme activity, and the transformation of glutathione from reduced to oxidized form, resulting in lipid peroxidation. Integrative analysis of transcriptomics and metabolomics indicated that increased purine metabolism was the potential source of increased ROS. Moreover, lipid metabolism disorder, including arachidonic acid metabolism, induces inflammation. Further, DEHP causes the imbalance of the CYP enzyme system in the gill, and DEHP-induced gill toxicity in crucian carp was associated with interference with CYP450 homeostasis. Taken together, this study broadens the molecular understanding of the DEHP-induced gill toxicity in aquatic organisms and provides novel perspectives for assessing the effects of DEHP on target and non-target aquatic organisms in the environment.

The roles of calcium and salinity in protecting against physiological symptoms of waterborne zinc toxicity in the euryhaline killifish (Fundulus heteroclitus)

In fresh water, environmental Ca ameliorates Zn toxicity because Ca2+ and Zn2+ compete for uptake at the gills. Zn toxicity is also lower in sea water, but it is unclear whether this is due to increased Ca2+ concentration, and/or to the other ions present at higher salinity. Using the euryhaline killifish, we evaluated the relative roles of Ca2+ (as CaNO3) versus the other ions contributing to salinity in protecting against physiological symptoms of Zn2+ toxicity. Killifish were exposed to a sublethal level of Zn (500 μg/L, as ZnSO4) for 96 h in either fresh water (0 % salinity) at low (1 mmol/L) and High Ca (10 mmol/L) or 35 ppt sea water (100 % salinity) at low (1 mmol/L) and High Ca (10 mmol/L). At 0 % salinity, High Ca partly or completely protected against the following effects of Zn seen at Low Ca: elevated plasma Zn, hypocalcaemia, inhibited unidirectional Ca2+ influx, inhibited branchial Na+/K+ATPase and Ca2+ATPase activities, and oxidative stress in gills, liver, intestine, and muscle. At 100 % salinity, in the presence of 1 mmol/L (Low Ca), Zn caused no disturbances in most of these same parameters, showing that the “non-Ca” components of sea water alone provided complete protection. However, for a few endpoints (inhibited intestinal Ca2+ATPase activity, oxidative stress in gill and liver), High Ca (10 mmol/L) was needed to provide full protection against Zn in 100 % salinity. There was no instance where the combination of 100 % salinity and High Ca failed to provide complete protection against Zn-induced disturbances in sea water.

The physiological, biochemical and transcriptional responses to sulfamethoxazole in the Asian clam, Corbicula fluminea (O. F. Müller, 1774)

Sulfamethoxazole (SMX), a broad-spectrum antibiotic, has been widely used in the treatment and prevention of infection caused by bacteria in recent years. The present study was aimed to evaluate the response mechanisms to SMX stress in gills and digestive gland of Corbicula fluminea (O. F. Müller, 1774). To this end, clams were exposed to environmentally relevant concentrations of SMX (0, 1, 10 and 100 μg/L) for 7 and 28 days, and siphon behavior, tissue-specific enzymatic and transcriptional changes were assayed. Our results showed that exposure to SMX significantly suppressed filtration rate and acetylcholinesterase (AChE) activity, activated antioxidant defense system and elevated transcription of several genes related to cell apoptosis in gills and digestive gland of clams. In general, SMX at environmentally relevant concentrations exhibited a negative impact on siphon behavior and induced neurotoxicology, oxidative stress and cell apoptosis in C. fluminea. The current study will help broaden our understanding of the ecotoxicity of SMX on freshwater bivalves.

Protection of teprenone against anesthetic stress in gills and liver of spotted seabass Lateolabrax maculatus

Teprenone is a terpene ketone in which a (9E,13E)-geranylgernayl group is bonded to one of the alpha-methyls of acetone. It has a role as an anti-ulcer drug, a multiple organ protective agent, and a HSP70 inducer. In this study, we evaluated the protective efficiency of teprenone to the damage of two types of anesthetics, tricaine methanesulfonate (MS-222) and eugenol, in the liver and gills of spotted seabass Lateolabrax maculatus. Fish (mean ± SD, 98.6 ± 7.6 g) were exposed to MS-222 (60 mg/L), eugenol (12 mg/L) and anesthetic-free water (control) after being fed diets containing different levels of teprenone: 0 mg/kg (control), 200 mg/kg, 400 mg/kg, and 800 mg/kg for 3 days. Compared with the control group, dietary teprenone significantly decreased cytochrome C concentration, and cysteine-aspartic proteases-3 and cysteine-aspartic proteases-9 activities in the liver and gills. The activities of aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase decreased in the serum. The gills morphology was improved, and the heat shock protein 70 concentration and NA+-K+-ATPase activity were significantly increased in gills with admistration of teprenone in the diet. These results reveal that the admisstraiton of teprenone at 400 mg/kg in the diet for three days could reduce the anesthesic damages in L. maculatus by inducing HSP70 and decreasing apoptosis.

Effects of salinity on haemolymph osmolality, gill Na+/K+ ATPase and antioxidant enzyme activities in the male mud crab Scylla olivacea (Herbst, 1796)

ABSTRACT The mud crab Scylla olivacea is a well-known commercially and ecologically important species that inhabits intertidal mangroves. These mud crabs spend juvenile and adult stages in mangroves where they can experience daily fluctuations in salinity. They are almost certainly adapted to deal with salinity challenges. Although S. olivacea has a wide salinity tolerance, there is a lack of studies on its osmoregulatory responses. Antioxidant enzymes play crucial roles to counteract oxidative stress in various tissues of aquatic animals. However, salinity changes affecting antioxidant responses are not well studied in tropical decapod crustaceans. Therefore, this study aims to characterize the osmoregulatory and antioxidant responses of the male S. olivacea when exposed to salinity changes. Haemolymph osmolality, Na+/K+ ATPase and antioxidant enzyme activities in gills were analysed after they were exposed to various salinities. The results showed that S. olivacea is a hyper-hypoosmoregulator. The salinity had greater effects on Na+/K+ ATPase and antioxidant enzyme activities in the posterior gills than the anterior gills. Notably, the modifications of gill SOD activity were detected only in the posterior gills, which function highly in active ion uptake. These findings may imply some associations between osmoregulatory and antioxidant responses during salinity challenges. The increase in gill SOD activities be a response for coping with elevated ROS levels due to high metabolic demands for osmoregulation under salinity stress. Moreover, the crabs exhibited some modified activities of gill CAT in several salinity levels. Overall, the results demonstrated that S. olivacea were well-adapted to the salinity changes based on their osmoregulatory and antioxidant responses. These physiological adaptations may allow these crabs to disperse in some areas of mangroves. The salinity range of 15–25 psu would likely be the recommended optimal range for adult S. olivacea, which may enhance growth and minimize oxidative stress in gills of crabs, especially in aquaculture conditions.

Differential responses in the biotransformation systems of the oyster Crassostrea gigas (Thunberg, 1789) elicited by pyrene and fluorene: Molecular, biochemical and histological approach – Part II

Pyrene (PYR) and fluorene (FLU) are among the sixteen priority Polycyclic Aromatic Hydrocarbons (PAH) of the United States Environmental Protection Agency and are both frequently detected in contaminated sites. Due to the importance of bivalve mollusks in biomonitoring programs and the scarce information on the biotransformation system in these organisms, the aim of this study was to investigate the effect of PYR and FLU at the transcriptional level and the enzymatic activities of some biotransformation systems in the Pacific oyster Crassostrea gigas, and to evaluate the histological effects in their soft tissues. Oysters C. gigas were exposed for 24 h and 96 h to PYR (0.25 and 0.5 μM) and FLU (0.6 and 1.2 μM). After exposure, transcript levels of cytochrome P450 coding genes (CYP1-like, CYP2-like, CYP2AU2, CYP356A1, CYP17α-like), glutathione S tranferase genes (omega GSTO-like and microsomal, MGST-like) and sulfotransferase gene (SULT-like), and the activity of ethoxyresorufin O-deethylase (EROD), Glutathione S-transferase (GST) and microssomal GST (MGST) were evaluated in gills. Histologic changes were also evaluated after the exposure period. PYR and FLU bioconcentrated in oyster soft tissues. The half-life time of PYR in water was lower than fluorene, which is in accordance to the higher lipophilicity and bioconcentration of the former. EROD activity was below the limit of detection in all oysters exposed for 96 h to PYR and FLU. The reproductive stage of the oysters exposed to PYR was post-spawn. Exposure to PYR caused tubular atrophy in digestive diverticula, but had no effect on transcript levels of biotransformation genes. However, the organisms exposed for 96 h to PYR 0.5 μM showed higher MGST activity, suggesting a protective role against oxidative stress in gills of oysters under higher levels of PYR in the tissues. Increased number of mucous cells in mantle were observed in oysters exposed to the higher FLU concentration, suggesting a defense mechanisms. Oysters exposed for 24 h to FLU 1.2 μM were in the ripe stage of gonadal development and showed higher transcript levels of CYP2AU2, GSTO-like and SULT-like genes, suggesting a role in the FLU biotransformation. In addition, after 96 h of exposure to FLU there was a significant increase of mucous cells in the mantle of oysters but no effect was observed on the EROD, total GST and MGST activities. These results suggest that PAH have different effects on transcript levels of biotransformation genes and enzyme activities, however these differences could also be related to the reproductive stage.

Impact of different crystalline forms of nTiO2 on metabolism and arsenic toxicity in Limnoperna fortunei

Arsenic (As) is a ubiquitous contaminant in the environment and it is known to induce oxidative stress in aquatic organisms. In an attempt to remove As from water, some studies have suggested the titanium dioxide nanomaterial (nTiO2) as a promising alternative. However, it has been observed that nTiO2 can induce toxicity alone or in combination with metals, and this toxicity is dependent on its crystalline form of nanomaterial (mainly rutile as nTiO2R and anatase as nTiO2A, respectively). Considering that both (nTiO2 and As) can occur together, the objective of this study was to evaluate if co-exposure to rutile and anatase may influence accumulation, metabolisation, and toxicity of arsenite (As+3) in the golden mussel Limnoperna fortunei after 48 h of co-exposure to nTiO2 (1 mg/L) and As (50 μg/L). Accumulation and chemical speciation of As in organisms were determined. Also, biochemical analyses, such as the activity of the enzymes glutathione S-transferase omega (GSTΩ), catalase (CAT) and glutathione S-transferase (GST), as well as lipid peroxidation (LPO) were investigated. Results showed that co-exposure to nTiO2A + As changed accumulation pattern of metalloid in gills and digestive gland. Both crystalline forms of nTiO2 affected the metabolisation capacity favoring the accumulation of more toxic As compounds and nTiO2A alone or in combination with As showed induce oxidative stress in gills of L. fortunei. In this way, it has a high potential risk of the co-exposure of these contaminants to aquatic organisms, and it also needs to consider the nanomaterial (nTiO2) properties and their application in the environmental remediation, carefully and judiciously.

Single and Combined Effects of Cadmium and Aroclor 1254 on Oxidative Stress in Gills of Mytilus coruscus

Both polychlorinated biphenyls (PCBs) and cadmium (Cd) can be frequently found in marine ecosystems and have detrimental effects on marine organisms, especially on filter-feeding marine mussels. Although biological responses to single metal or PCB exposure in mussels have been well-studied, information about oxidative stress is still limited, especially in different tissues in mussels. Considering the variety of contaminants existing in the actual marine environment, the exposures of the marine mussel Mytilus coruscus to Cd2+ alone (0.194, 0.388, and 0.775 mg/L) and Aroclor 1254 alone (0.005, 0.010, and 0.050 mg/L) and the co-exposures of the marine mussel Mytilus coruscus to Cd2+ (0.194 and 0.388 mg/L) and Aroclor 1254 (0.005 and 0.010 mg/L) were tested in an 8-day exposure experiment followed by a 7-day acclimation experiment. The alterations in superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde levels in the gills of the mussels were assessed. The effects of the depressed antioxidant were induced by the exposures of Cd2+ and Aroclor 1254 and their co-exposures. All exposures resulted in an initial increase and then a reduction in antioxidant enzyme activities. The range and rate of the antioxidant enzyme activities were positively correlated with stress duration and the concentration of the stress material. The effect of combined stress was stronger than that of each individual stressor. The valuable information for future investigations of stress response mechanisms, especially in relation to tissue functions in marine organisms, has been provided by the results and experimental model. The study of combined pollution effects has more scientific significance for marine pollution monitoring.

Oxidative stress, histopathological alterations and anti-oxidant capacity in different tissues of largemouth bass (Micropterus salmoides) exposed to a newly developed sodium carbonate peroxyhydrate granular algaecide formulated with hydrogen peroxide

Various strategies exist to control noxious cyanobacterial populations, although the application of a newly developed granular compound (sodium carbonate peroxyhydrate ‘SCP’, trade name ‘PAK® 27’ algaecide) containing hydrogen peroxide (H2O2) as the active ingredient, has been recently proven as an effective and ecofriendly treatment. However, in aquaculture settings the application of SCP to treat cynobacterial blooms may affect non-targeted biota, such as fish due to H2O2 being known to elicit toxic oxidative stress. Consequently, a better understanding of the side effects as a function of dosing concentrations would help to improve treatment efficacy and fish welfare. Thus, the aim of the current study is to assess the potential risks of SCP to largemouth bass (Micropterus salmoides), a high priced fish in the U.S. To this end, fish were exposed to two recommended doses of SCP corresponding to either 2.5 or 4.0 mg/L H2O2 for 6 days, with a control group in parallel. After 6 days, the effect of SCP exposure on oxidative stress, histopathological changes and anti-oxidant potential in the brain, liver, gills and muscle were investigated. Results show that exposure to 4.0 mg/L H2O2 -SCP incited oxidative damage, evidenced by an over-accumulation of H2O2 and malondialdehyde (MDA) in the brain and liver, which were accompanied by an increment in xanthine oxidase activity. Unlike 4.0 mg/L H2O2, these oxidative stress biomarkers in the brain and liver tissue of 2.5 mg/L H2O2-SCP exposed fish were restrained within control levels and concomitant with an increase in superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione-s-transferase (GST) activity. In contrast, many of these anti-oxidants sentinels in the 4.0 mg/L H2O2 exposed fish were either unaffected or significantly inhibited, which resulted in over-accumulation of H2O2 and MDA. In addition, a series of histopathological alterations were observed, and the most severe brain injuries and liver inflammation were recorded in 4.0 mg/L H2O2-SCP exposed fish. Based on oxidative parameters, both SCP doses resulted in a relatively mild oxidative stress in gills but no effect in muscle, probably explaining the modest anti-oxidative responses in the former and almost complete lack of anti-oxidative responses in the latter. Overall, our findings suggests that the application of SCP at 4.0 mg/L H2O2 to control cyanobacterial blooms in aquaculture settings can possess potential risks to the farmed fish.

Perkinsus mediterraneus infection induces oxidative stress in the mollusc Mimachlamys varia.

Perkinsus mediterraneus is a protozoan parasite that can cause marine mollusc diseases known as perkinsosis being a serious threat for clam cultures worldwide. The aim of the present study was first to determine the Perkinsus species infecting the variegated scallop Mimachlamys varia and then to evaluate the existence of oxidative stress in gills of M.varia according to different degrees of infection. DNA sequencing confirmed that P.mediterraneus was the species infecting M.varia. ROS production was progressively increasing with the degree of infection although the differences were only significant in the high-infected group. Low degree of infection significantly increased superoxide dismutase (SOD) and glutathione S-transferase (GST) activities and nitrite levels with respect to the control group. In the high-infected group, a significant increase was evidenced in all analysed enzymes, catalase, SOD, glutathione reductase and GST. Non-significant differences in MDA levels were observed between the control and low-infected groups; however, a significant increase in MDA levels was observed in the high-infected group. In conclusion, the infection by Perkinsus mediterraneus in M.varia induces oxidative stress and an antioxidant response directly related to the infection degree that can contribute to the pathogenicity of the infection.

Microcystin – LR exposure causes cardiorespiratory impairments and tissue oxidative damage in trahira, Hoplias malabaricus

This study investigated the effect of microcystin-LR (MC-LR) on in vivo cardiorespiratory function and on tissue biomarkers of oxidative stress in gills and liver of the trahira, a neotropical freshwater fish. Trahira were treated with an intraperitoneal injection of 100 µg MC-LR.kg−1 body mass or a saline, with the toxic effects of MC-LR then evaluated after 48 h. Rates of oxygen uptake (V̇O2) did not differ significantly between Control and the exposed group (Mcys), but exposure to MC-LR significantly reduced O2 extraction in the Mcys group at all O2 tensions. This was associated with higher gill ventilation volume (V̇G) in the Mcys group at all O2 tensions except 140 and 120 mmHg, and a higher tidal volume (VT) of the Mcys group at all tensions except 140 mmHg. Heart rate was also higher in the Mcys group, significantly so at an O2 tension of 40 mmHg. In the liver of trahira, exposure to MC-LR has significant effects on antioxidant defense systems, inducing a significant increase in the activity of the (GPx) glutathione peroxidase enzyme (100%) and in the reduced glutathione (GSH) content (70%) compared to the control group, but no effects on superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) enzymes. The liver showed no oxidative damage, when measured as lipid peroxidation (LPO) levels and protein carbonyl (PC) content. In the gills SOD and GPx enzyme activity increased significantly in the Mcys group (98% and 73% respectively) compared to the controls, although GSH, CAT and GST did not differ between groups. There was also no significant difference in GSH in this tissue. Levels of lipid peroxidation in the gills were 53% higher in the Mcys group, although carbonyl protein levels did not differ. In conclusion, these data show that MC-LR leads to development of hyperventilation and increased activity of the detoxification system and that this species was able to compensate the deleterious effects of microcystin on its vital functions. The antioxidant defense in the liver was able to contain the propagation of LPO and prevent the oxidation of proteins, although the gills of the fishes exposed to MC-LR were not able to contain the formation of reactive oxygen species and LPO, which led to the establishment of oxidative stress which impaired gill function.

Effect of Lead Graded Doses in <i>Mactra Corallina</i> Gills: Antioxidants Status, Cholinergic Function and Histopathological Studies

Lead is non-essential toxic metal used in the industrial process causes severe risk to aquatic organisms. This study aimed (aims) to evaluate the effect of Pb on oxidative stress in gills of <i>Mactra corallina</i>. During the experiment, bivalves were randomly divided into four groups, control served as control and D1, D2 and D3 groups were exposed to Pb graded doses (1mg/L, 2.5mg/L and 5mg/L) during 5 days, respectively. Pb accumulation was significantly increased in all treated gills with doses dependent manner. The exposure of M. corallina to PbCl₂ promoted oxidative stress in gills with an increase in malondialdehyde (MDA) and in metallothionein (MTs) levels. Moreover, a decline in glutathione (GSH), non-protein–SH (NPSH) and ascorbic acid (Vit C) levels were detected in all treated groups. Thus, alterations of enzymatic antioxidants systems were confirmed by a significant increase of catalase (CAT) and decreases of glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities in doses dependent manner. The cholinergic function was confirmed by a significant decrease of acetylcholinesterase (AChE) activity in the highest exposure dose. The impairment of the gill function was confirmed by the histological study.