In recent years, the cardiovascular toxicity of urban fine particulate matter (PM₂.₅) has sparked significant alarm. Mitochondria produce 90% of ATP and make up 30% of the volume of cardiomyocytes. Thus knowledge of myocardial mitochondrial dysfunction due to PM₂.₅ exposure is essential for further cardiotoxic effects. Here, the mechanism of PM₂.₅-induced cardiac hypertrophy through calcium overload and mitochondrial dysfunction was investigated in vivo and in vitro. Male and female BALB/c mice were given 1.28, 5.5, and 11 mg PM₂.₅/kg bodyweight weekly through oropharyngeal inhalation for four weeks and were assigned to low, medium, and high dose groups, respectively. PM₂.₅-induced myocardial edema and cardiac hypertrophy were detected in the high-dose group. Mitochondria were scattered and ruptured with abnormal ultrastructural morphology. In vitro experiments on human cardiomyocyte AC16 showed that exposure to PM₂.₅ for 24 h caused opened mitochondrial permeability transition pore --leading to excessive calcium production, decreased mitochondrial membrane potential, weakened mitochondrial respiratory metabolism capacity, and decreased ATP production. Nevertheless, the administration of calcium chelator ameliorated the mitochondrial damage in the PM₂.₅-treated group. Our in vivo and in vitro results confirmed that calcium overload under PM₂.₅ exposure triggered mTOR/AKT/GSK-3β activation, leading to mitochondrial bioenergetics dysfunction and cardiac hypertrophy.

Evaluation of the toxicity of pesticide residues on non-target organisms in the ecosystem is an important part of pesticide environmental risk assessment. Flupyradifurone is a new type of butenolide insecticide produced by Bayer, who claims it to be “low toxic” to non-target organisms in the environment. However, there is little evidence in the literature to show how flupyradifurone affects aquatic organism development. In the current study, zebrafish embryos were treated with 0.1, 0.15, and 0.2 mg/mL of flupyradifurone within 6.0–72 h past fertilization (hpf). We found that the half-lethal concentration (LC₅₀) of flupyradifurone for zebrafish embryos at 96 hpf was 0.21 mg/mL. Flupyradifurone decreases the heart rate, survival rate, and body length of zebrafish embryos. The flupyradifurone treatment also led to the failure of heart looping, and pericardial edema. Moreover, flupyradifurone increased the level of reactive oxygen species (ROS) and decreased the enzymatic catalysis of catalase (CAT) and superoxide dismutase (SOD). Alterations were induced in the transcription of apoptosis-related genes (bcl-2, bax, bax/bcl-2, p53 and caspase-9) and the heart development-related genes (gata4, myh6, nkx2.5, nppa, tbx2b, tbx5 and vmhc). In the current study, new evidences have been provided regarding the toxic effects of flupyradifurone and the risk of its residues in agricultural products and the environment.

In toxicology, standard sigmoidal concentration-response curves are used to predict effects concentrations and set chemical regulations. However, current literature also establishes the existence of complex, bimodal concentration-response curves, as is the case for arsenic toxicity. This bimodal response has been observed at the molecular level, but not characterized at the whole organism level. This study investigated the effect of arsenic (sodium arsenite) on post-gastrulated zebrafish embryos and elucidated effects of bimodal concentration-responses on different phenotypic perturbations.Six hour post fertilized (hpf) zebrafish embryos were exposed to arsenic to 96 hpf. Hatching success, mortality, and morphometric endpoints were evaluated both in embryos with chorions and dechorionated embryos. Zebrafish embryos exhibited a bimodal response to arsenic exposure. Concentration-response curves for exposed embryos with intact chorions had an initial peak in mortality (88%) at 1.33 mM arsenic, followed by a decrease in toxicity (~20% mortality) at 1.75 mM, and subsequently peaked to 100% mortality at higher concentrations. To account for the bimodal response, two distinct concentration-response curves were generated with estimated LC10 values (and 95% CI) of 0.462 (0.415, 0.508) mM and 1.69 (1.58, 1.78) mM for the ‘low concentration’ and ‘high concentration’ peaks, respectively. Other phenotypic analyses, including embryo length, yolk and pericardial edema all produced similar concentration-response patterns. Tests with dechorionated embryos also resulted in a bimodal toxicity response but with lower LC10 values of 0.170 (0.120, 0.220) mM and 0.800 (0.60, 0842) mM, respectively. Similarities in bimodal concentration-responses between with-chorion and dechorionated embryos indicate that the observed effect was not caused by the chorion limiting arsenic availability, thus lending support to other studies such as those that hypothesized a conserved bimodal mechanism of arsenic interference with nuclear receptor activation.

Azoxystrobin (AZ) and pyraclostrobin (PY) are strobilurin fungicides that inhibit fungal mitochondrial respiration. In this study, a representative model, zebrafish (Danio rerio), was used as a test species for acute and developmental toxicity. Survival and malformation rates were observed only PY-treated embryos, with an LC₅₀ value of 77.75 ppb accompanied by a dramatic decrease in hatching rate, while AZ did not show great mortality. Morphological changes were observed in PY-treated embryos with the occurrence of pericadial edema at 25 ppb. A delay in growth was observed after treatment with pyraclostrobin at 50 ppb. Use of genetically engineered Tg(cmlc:EGFP) allowed fluorescence observation during heart development. PY interfered with normal heart development via upregulation of the nppa gene responsible for the expression of natriuretic peptides. Heart function was dramatically reduced as indicated by reduced heart rates. Increased expression of the nppa gene was also seen in AZ-treated embryos. The expression level of cyp24a1 was also up-regulated, while ugt1a1 and sult1st6 were down-regulated after treatment of zebrafish embryos with AZ or PY. Overall, strobilurin fungicides might inhibit normal heart formation and function within the range of concentrations tested.

The potential risks of phthalates affecting human and animal health as well as the environment are emerging as serious concerns worldwide. However, the mechanism by which phthalates induce developmental effects is under debate. Herein, we found that embryonic exposure of zebrafish to di-(2-ethylhexyl) phthalate (DEHP) and di-butyl phthalate (DBP) increased the rate of heart defects including abnormal heart rate and pericardial edema. Changes in the transcriptional profile demonstrated that genes involved in the development of the heart, such as tbx5b, nppa, ctnt, my17, cmlc1, were significantly altered by DEHP and DBP at 50 μg/L, which agreed with the abnormal cardiac outcomes. Methylated DNA immunoprecipitation sequencing (MeDIP-Seq) further showed that significant hypomethylation of nppa and ctnt was identified after DEHP and DBP exposure, which was consistent with the up-regulation of these genes. Notably, hypermethylation on the promoter region (<1 kb) of tbx5b was found after DEHP and DBP exposure, which might be responsible for its decrease in transcription. In conclusion, phthalates have the potential to induce cardiac birth defects, which might be associated with the transcriptional regulation of the involved developmental factors such as tbx5b. These findings would contribute to understand the molecular pathways that mediated the cardiac defects caused by phthalates.

Spirocyclic tetramic acids are widely used in controlling phytophagous mite species throughout the world. the data set is incomplete and provides insufficient evidence for drawing the same conclusion for fish. To fill the gap whether these acaricides alter lipid metabolism on vertebrates, zebrafish embryos exposed to a series concentration of pesticides, the developmental effects, enzyme activities and levels of gene expression were assessed, battery of biomarker utilized by the integrated biomarker response (IBRv2) model. The 96 h-LC₅₀ of spirodiclofen, spiromesifen and spirotetramat were 0.14, 0.12 and 5.94 mg/L, respectively. Yolk sac deformity, pericardial edema, spinal curvature and tail malformation were observed. Three spirocyclic acids were unfavouring the lipid accumulation of by inhibited the acetyl-CoA carboxylase (ACC), fatty acid synthesis (FAS), fatty acid binding proteins (FABP2) and lipoprotein lipase (LPL) activity. The total cholesterol (TCHO) level significantly decreased in the 0.072 mg/L spirodiclofen group and 0.015 and 0.030 mg/L in the spiromesifen groups. No expected change in spirotetramat group on the TCHO and triglycerides (TGs) levels for any of the treatments. The mRNA levels of the genes related to lipid metabolism also significantly altered. In both spirodiclofen and spiromesifen, ACC achieved the highest scores among a battery of biomarkers using integrated biomarker response (IBRv2). The results suggest that spiromesifen was the most toxic for embryos development and spirodiclofen was the most toxic for lipid metabolism in embryos. The 0.07 mg/L of spirodiclofen, 0.05 mg/L of spiromesifen and 2.00 mg/L would cause malformation on zebrafish embryos. This study will provide new insight that fatty acid metabolism may be a suitable biomarker for the spirocyclic tetramic acids in fish species.

The potential leakage from marine CO2 storage sites is of increasing concern, but few studies have evaluated the probable adverse effects on marine organisms. Fish, one of the top predators in marine environments, should be an essential representative species used for water column toxicity testing in response to waterborne CO2 exposure. In the present study, we conducted fish life cycle toxicity tests to fully elucidate CO2 toxicity mechanism effects. We tested sub-lethal and lethal toxicities of elevated CO2 concentrations on marine medaka (Oryzias melastigma) at different developmental stages. At each developmental stage, the test species was exposed to varying concentrations of gaseous CO2 (control air, 5%, 10%, 20%, and 30%), with 96 h of exposure at 0–4 d (early stage), 4–8 d (middle stage), and 8–12 d (late stage). Sub-lethal and lethal effects, including early developmental delays, cardiac edema, tail abnormalities, abnormal pigmentation, and mortality were monitored daily during the 14 d exposure period. At the embryonic stage, significant sub-lethal and lethal effects were observed at pH < 6.30. Hypercapnia can cause long-term and/or delayed developmental embryonic problems, even after transfer back to clean seawater. At fish juvenile and adult stages, significant mortality was observed at pH < 5.70, indicating elevated CO2 exposure might cause various adverse effects, even during short-term exposure periods. It should be noted the early embryonic stage was found more sensitive to CO2 exposure than other developmental stages of the fish life cycle. Overall, the present study provided baseline information for potential adverse effects of high CO2 concentration exposure on fish developmental processes at different life cycle stages in marine ecosystems.

Due to the activities inherent to medical care units, the hospital effluent released contains diverse contaminants such as tensoactives, disinfectants, metals, pharmaceutical products and chemical reagents, which are potentially toxic to the environment since they receive no treatment or are not effectively removed by such treatment before entering the drain. They are incorporated into municipal wastewater, eventually entering water bodies where they can have harmful effects on organisms and can result in ecological damage. To determine the toxicological risk induced by this type of eflluents, eight metals and 11 pharmaceuticals were quantified, in effluent from a hospital. Developmental effects, teratogenesis and oxidative stress induction were evaluated in two bioindicator species: Xenopus laevis and Lithobates catesbeianus. FETAX (frog embryo teratogenesis assay–Xenopus) was used to obtain the median lethal concentration (LC50), effective concentration inducing 50% malformation (EC50), teratogenic index (TI), minimum concentration to inhibit growth (MCIG), and the types of malformation induced. Twenty oocytes in midblastula transition were exposed to six concentrations of effluent (0.1, 0.3, 0.5, 0.7, 0.9, 1%) and negative and positive (6-aminonicotinamide) controls. After 96 h of exposure, diverse biomarkers of oxidative damage were evaluated: hydroperoxide content, lipid peroxidation, protein carbonyl content, and the antioxidant enzymes superoxide dismutase and catalase. TI was 3.8 in X. laevis and 4.0 in L. catesbeianus, both exceed the value in the FETAX protocol (1.2), indicating that this effluent is teratogenic to both species. Growth inhibition was induced as well as diverse malformation including microcephaly, cardiac and facial edema, eye malformations, and notochord, tail, fin and gut damage. Significant differences relative to the control group were observed in both species with all biomarkers. This hospital effluent contains contaminants which represents a toxic risk, since these substances are teratogenic to the bioindicators used. The mechanism of damage induction may be associated with oxidative stress.

Hydraulic fracturing to extract oil and natural gas reserves is an increasing practice in many international energy sectors. Hydraulic fracturing flowback and produced water (FPW) is a hyper saline wastewater returned to the surface from a fractured well containing chemical species present in the initial fracturing fluid, geogenic contaminants, and potentially newly synthesized chemicals formed in the fracturing well environment. However, information on FPW toxicological mechanisms of action remain largely unknown. Both cardiotoxic and respirometric responses were explored in zebrafish (Danio rerio) embryos after either an acute sediment-free (FPW-SF) or raw/sediment containing (FPW-S) fraction exposure of 24 and 48 h at 2.5% and 5% dilutions. A 48 h exposure to either FPW fraction in 24–72 h post fertilization zebrafish embryos significantly increased occurrences of pericardial edema, yolk-sac edema, and tail/spine curvature. In contrast, larval heart rates significantly decreased after FPW fraction exposures. FPW-S, but not FPW-SF, at 2.5% doses significantly reduced embryonic respiration/metabolic rates (MO2), while for 5% FPW, both fractions reduced MO2. Expression of select cardiac genes were also significantly altered in each FPW exposure group, implicating a cardiovascular system compromise as the potential cause for reduced embryonic MO2. Collectively, these results support our hypothesis that organics are major contributors to cardiac and respiratory responses to FPW exposure in zebrafish embryos. Our study is the first to investigate cardiac and respiratory sub-lethal effects of FPW exposure, demonstrating that FPW effects extend beyond initial osmotic stressors and verifies the use of respirometry as a potential marker for FPW exposure.

During hydraulic fracturing, wastewaters - termed flowback and produced water (FPW) - are created as a by-product during hydrocarbon extraction. Given the large volumes of FPW that a single well can produce, and the history of FPW release to surface water bodies, it is imperative to understand the hazards that hydraulic fracturing and FPW pose to aquatic biota. Using rainbow trout embryos as model organisms, we investigated impacts to cardio-respiratory system development and function following acute (48 h) and sub-chronic (28-day) FPW exposure by examining occurrences of developmental deformities, rates of embryonic respiration (MO₂), and changes in expression of critical cardiac-specific genes. FPW-exposed embryos had significantly increased rates of pericardial edema, yolk-sac edema, and tail/trunk curvatures at hatch. Furthermore, when exposed at three days post-fertilization (dpf), acute 5% FPW exposures significantly increased embryonic MO₂ through development until 15 dpf, where a switch to significantly reduced MO₂ rates was subsequently recorded. A similar trend was observed during sub-chronic 1% FPW exposures. Interestingly, at certain specific developmental timepoints, previous salinity exposure seemed to affect embryonic MO₂; a result not previously observed. Following acute FPW exposures, embryonic genes for cardiac development and function were significantly altered, although at termination of sub-chronic exposures, significant changes to these same genes were not found. Together, our evidence of induced developmental deformities, modified embryonic MO₂, and altered cardiac transcript expression suggest that cardio-respiratory tissues are toxicologically targeted following FPW exposure in developing rainbow trout. These results may be helpful to regulatory bodies when developing hazard identification and risk management protocols concerning hydraulic fracturing activities.