Antioxidant status and Na(+), K (+)-ATPase activity in freshwater fish Carassius auratus exposed to different combustion products of Nafion 117 membrane: an integrated biomarker approach

Life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) causes alterations in antioxidative status, ion regulation and histology of zebrafish gills

Tris (2-chloroethyl) phosphate (TCEP) has been receiving great concerns owing to its ubiquitous occurrence in various environmental compartments and potential risks to wildlife and humans. Gill is structural basis for ion regulation and homeostasis in fish and susceptible to xenobiotics. However, current knowledge on the impacts of long-term exposure to TCEP on the structure and physiological function of fish gills are insufficient. In this work, zebrafish were exposed to environmental realistic concentrations (0.8, 4, 20 and 100 μg/L) of TCEP from 3 h post ferterlization (hpf) till 120 days post ferterlization (dpf). Our results demonstrated that life-cycle exposure to TCEP significantly decreased the activity of glutathione S-transferase (GST), but elevated the activities of antioxidative enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and increased malondialdehyde (MDA) content in zebrafish gills. Gene transcription analysis implied that the mRNA expressions of antioxidant-related genes (nrf2, cat and nqo1) were induced, while the transcription of gstα1, hmox1, keap1 were down-regulated, indicating that Nrf2-Keap1 pathway might be activated to defend the oxidative stress induced by TCEP. Additionally, the ion homeostasis was disrupted by TCEP exposure, evidenced by reduced activities of Na+/K+-ATPase (NKA), Ca2+-ATPase and Mg2+-ATPase and downregulated transcription levels of ncc, nkcc, cftr and clc-3. Besides, whole-life exposure to TCEP resulted in a series of structural damages to gills, including epithelial lifting, epithelial rupture, telangiectasis, vacuolation, edema and shortened gill lamellae. Overall, our results demonstrated that long-term TCEP exposure could induce oxidative stress, affect ion regulation and cause histological changes in zebrafish gills.

Transformation pathways of chlorinated paraffins relevant for remediation: a mini-review

In the past decades, the environmental presence and ecological risks of chlorinated paraffins (CPs), an emerging class of organic halogen compounds, have been receiving increasing attention worldwide. Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) constitute the important CPs of considerable concern. In this review article, the state-of-the-art research status on the environmental transformation of CPs, including thermal decomposition, photolytic and photocatalytic degradation, biological metabolism, and atmospheric transformation, was summarized and integrated in detail. The degradation efficiency and transformation products of CPs in these environmental processes were evaluated, in which dechlorination was considered as the major reaction pathway. Notably, waste incineration of CPs has been demonstrated to generate a variety of persistent chlorinated aromatic hydrocarbons such as polychlorinated biphenyls and polychlorinated naphthalenes, which have more significant environmental impacts. Additionally, photodegradation and photocatalysis are suggested as the feasible techniques for efficient removal of SCCPs from water matrices. Overall, the current transformation studies of CPs could facilitate the comprehensive understanding of their environmental behaviors and fate as well as the development of promising remediation strategies for pollution control.

Monobutyl phthalate (MBP) can dysregulate the antioxidant system and induce apoptosis of zebrafish liver

In this paper, the acute toxicity of monobutyl phthalate (MBP), the main hydrolysis product of dibutyl phthalate, on adult zebrafish liver antioxidant system was studied. Compared the toxicity effect of MBP and DBP by histopathology and apoptosis experiments, we speculated that the toxic effects of DBP on animals may be caused by its metabolite MBP. The results indicated that the antioxidant Nrf2-Keap1 pathway was insufficient to resist MBP-induced hepatotoxicity and led to an imbalance of membrane ion homeostasis and liver damage. Decreased cell viability, significant tissue lesions and early hepatocyte apoptosis were observed in the zebrafish liver in MBP exposure at high concentration (10 mg/L). The activities of antioxidant enzymes and ATPases in zebrafish liver were inhibited with increased malondialdehyde (MDA) content and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Integrated biomarker response (IBR) calculation results indicated that MBP mainly inhibited catalase (CAT) activity. Simultaneously, the expression of antioxidant-related genes (SOD, CAT, GPx, Nrf2, HO-1) was down-regulated, while apoptosis-related genes (p53, bax, cas3) were significantly up-regulated.

A novel mechanism underlies atrazine toxicity in quails (Coturnix Coturnix coturnix): triggering ionic disorder via disruption of ATPases

The widely used atrazine has been reported to exhibit extensive ecological hazards. Due to the biological accumulation, atrazine elicits widespread toxic effects on different organisms. However, true proof for the mechanism of atrazine-induced toxicity is lacking. To determine the potential mechanism by which atrazine exerted toxic effects, quails were treated with atrazine (0, 50, 250 and 500 mg/kg) by gavage administration for 45 days. Atrazine significantly increased the histological alterations and serum creatine kinase, lactate dehydrogenase and choline esterase levels. A marked disorder in ionic (Na+, K+, Ca2+ and Mg2+)contents and the decrease of ATPases (Na+-K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and Ca2+-Mg2+-ATPase) activities were observed in the heart and liver of atrazine-exposed quails. Of note, it was also observed that atrazine suppressed the transcription of Na+, K+ transfer associated genes (Na+-K+-ATPase subunits) and Ca2+ transfer associated genes (Ca2+-ATPase subunits, solute carriers) in heart and liver. In conclusion, atrazine induced cardiac and hepatic damage via causing the ionic disorder, triggering the transcription of the ion transporters and leading the histopathological and functional alternations in the heart and liver of quails. This study demonstrated atrazine significantly induced the ionic disorder via decreasing the ATPases activities and disturbing the transcription of the ion transporters.