Impact of acute Cd²⁺ exposure on the antioxidant defence systems in the skin and red blood cells of common carp (Cyprinus carpio)

Imidacloprid exposure cause the histopathological changes, activation of TNF-α, iNOS, 8-OHdG biomarkers, and alteration of caspase 3, iNOS, CYP1A, MT1 gene expression levels in common carp (Cyprinus carpio L.)

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IMI toxication was evaluated with three different methods.

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Pathological lesions were observed after IMI exposure in gills, liver and brain.

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IMI exposure induced iNOS, 8-OHdG and TNF-α activation in gills, liver and brain.

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IMI exposure caused upregulation iNOS, caspase 3 and MT1 expressions in brain.

Imidacloprid (IMI) is a neonicotinoid that is widely used for the protection of crops and carnivores from insects and parasites, respectively. It is well known that imidacloprid exposure has a harmful effect on several organisms. However, there is little information about imidacloprid toxicity in aquatic animals, particularly fish. Thus, in the current study, we assessed the histopathological changes; activation of iNOS, 8-OHdG and TNF-α; and expression levels of caspase 3, iNOS, CYP1A and MT1 genes in the common carp exposed to imidacloprid. For this purpose, fish were exposed to either a low dose (140 mg/L) or a high dose (280 mg/L) of imidacloprid for 24 h, 48 h, 72 h and 96 h. After IMI exposure, we detected hyperplasia of secondary lamellar cells and mucous cell hyperplasia in the gills, as well as hydropic degeneration in hepatocytes and necrosis in the liver. Moreover, 8-OHdG, iNOS and TNF-α activation was found particularly in the gills and liver but also moderately in the brain. Transcriptional analysis showed that caspase 3 expression was altered low dose and high doses of IMI for 72 h and 96 h exposure (p < 0.05), iNOS expression was up-regulated with both low and high doses of IMI and in a time-dependent manner (p < 0.05, p < 0.01, p < 0.001), CYP1A expression was not significantly changed regardless of the dose of IMI and exposure time (p > 0.05) except with low and high doses of IMI for 96 h (p < 0.05), and lastly, MT1 gene expression was up-regulated only in the brain with low doses of IMI for 96 h and high doses of IMI for 48 h, 72 h and 96 h exposure (p < 0.05, p < 0.01). Our results indicated that acute IMI exposure moderately induce apoptosis in the brain but caused severe histopathological lesions, inflammation, and oxidative stress in the gills, liver, and brain of the common carp.

Histopathological effects, responses of oxidative stress, inflammation, apoptosis biomarkers and alteration of gene expressions related to apoptosis, oxidative stress, and reproductive system in chlorpyrifos-exposed common carp (Cyprinus carpio L.)

In this study, we aimed to identify the toxic effects of chlorpyrifos exposure on the tissues of common carp. For this purpose, we evaluated histopathological changes in the brain, gills, liver, kidney, testis, and ovaries after 21 days of chlorpyrifos exposure. Activation of 8-OHdG, cleaved caspase-3, and iNOS were assesed by immunofluorescence assay in chlorpyrifos-exposed brain and liver tissue. Additionally, we measured the expression levels of caspase-3, caspase-8, iNOS, MT1, CYP1A, and CYP3A genes in chlorpyrifos-exposed brain tissue, as well as the expression levels of FSH and LH genes in chlorpyrifos-exposed ovaries, using qRT-PCR. We observed severe histopathological lesions, including inflammation, degeneration, necrosis, and hemorrhage, in the evaluated tissues of common carp after both high and low levels of exposure to chlorpyrifos. We detected strong and diffuse signs of immunofluorescence reaction for 8-OHdG, iNOS, and cleaved caspase-3 in the chlorpyrifos-exposed brain and liver tissues. Furthermore, we found that chlorpyrifos exposure significantly upregulated the expressions of caspase-3, caspase-8, iNOS, and MT1, and also moderately upregulated CYP1A and CYP3A in the brain tissue of exposed carp. We also noted downregulation of FSH and LH gene expressions in chlorpyrifos-exposed ovary tissues. Based on our results, chlorpyrifos toxication caused crucial histopathological lesions in vital organs, induced oxidative stress, inflammation, and apoptosis in liver and brain tissues, and triggered reproductive sterility in common carp. Therefore, we can propose that chlorpyrifos toxication is highly dangerous to the health of common carp. Moreover, chlorpyrifos pollution in the water could threaten the common carp population. Use of chlorpyrifos should be restricted, and aquatic systems should be monitored for chlorpyrifos pollution.

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.

Cytotoxicity and alterations at transcriptional level caused by metals on fish erythrocytes in vitro

The in vitro use of fish erythrocytes to test the toxicity of aquatic pollutants could be a valuable alternative to fish bioassays but has received little attention. In this study, erythrocytes from marine gilthead sea bream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.) specimens were exposed for 24 h to Cd, Hg, Pb and As and the resulting cytotoxicity was evaluated. Exposure to metals produced a dose-dependent reduction in the viability, and mercury showed the highest toxicity followed by MeHg, Cd, As and Pb. Moreover, fish erythrocytes incubated with each one of the metals exhibited alteration in gene expression profile of metallothionein, superoxide dismutase, catalase, peroxiredoxin, glutathione reductase, heat shock proteins 70 and 90, Bcl2-associated X protein and calpain1 indicating cellular protection, stress and apoptosis death as well as oxidative stress. This study points to the benefits for evaluating the toxicological mechanisms of marine pollution using fish erythrocytes in vitro.

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.