Ability of the Hershberger assay protocol to detect thyroid function modulators

Bromuconazole exposure induces cardiotoxicity and lipid transport disorder in larval zebrafish

Bromuconazole (BRO), as one of the typical triazole fungicides, has not been reported on its effects on aquatic organisms. In this study, zebrafish embryos were used as experimental objects to evaluate the toxicity of BRO. In the acute embryo toxicity test, it was observed that the heart rate and growing development were affected by BRO in a concentration-dependent manner, and the half-lethal concentration (LC50) of BRO at 96 h post-fertilization (hpf) was about 11.83 mg/L. Then, low concentrations of BRO (50 ng/L, 0.075 mg/L, 0.3 mg/L, 1.2 mg/L), which were set according to the LC50 and environmental related concentrations, were used to analyze the toxic effects on the different endpoints in larval zebrafish. Interestingly, the transcriptomic analysis found that most different expressed genes (DEGs) could be focused on the pathways of lipid metabolism, myocardial function, glycometabolism, indicating that heart function and lipid metabolism in larval zebrafish were disrupted by BRO. For supporting this idea, we re-exposed the transgenic zebrafish and WT zebrafish embryos, proved that BRO caused damage to heart development and lipid transport on morphological and genetic level, which was consistent with transcriptomic results. In addition, BRO exposure caused oxidative damage in the larvae. Taken together, BRO exposure could affect the myocardial contraction function and lipid transport in larval zebrafish, accompanied by disturbances in the level of oxidative stress, which was of great significance for improving the biotoxicological information of BRO.

Bromuconazole caused genotoxicity and hepatic and renal damage via oxidative stress process in Wistar rats

Bromuconazole is a triazole pesticide used to protect vegetables and fruits against diverse fungi pathologies. However, its utilization may be accompanied by diverse tissue injuries. In this study, we evaluated the biochemical and histopathological modifications, and we analyzed genotoxic and oxidative stress, in the aim to examine bromuconazole effects in the liver and kidney. We subdivided animals into four groups, each one contains six adult male Wistar rats. Untreated rats received daily a corn oil (vehicle) orally. Three oral bromuconazole doses were tested (1, 5, and 10 % of LD50) daily for 28 days. Bromuconazole increased the plasma activities of alkaline phosphatase, lactate dehydrogenase, and transaminases. It also increased the plasma levels of creatinine and uric acid. Histopathological check showed that bromuconazole caused organ damage. This study makes known that bromuconazole caused conspicuous DNA damage either in hepatic or kidney tissues, with a significant increase in the levels of malondialdehyde and protein carbonyl followed by an enhancement in catalase and superoxide dismutase enzymatic activities, and these increases are in a dose-dependent manner. In other side, we found that Glutathione-S-transferase and peroxidase activities raised. Our outcomes highlight that bromuconazole exposure induced genotoxic damage and organ damage which may be caused by the disturbances of oxidative stress statue in the liver and kidney.

Specific alteration of gene expression profile in rats by treatment with thyroid toxicants that inhibit thyroid hormone synthesis

Transcriptomics technologies have been used for risk assessment of chemicals, mainly to predict the modes of action (MOAs) of chemicals or identify biomarkers. Transcriptomics data may also be helpful to understand MOAs of chemicals at the molecular level in more detail. As an example of the known MOAs, there are two MOAs of thyroid toxicity: inhibition of thyroid hormone synthesis ("direct" effect) and hypermetabolism of thyroid hormone by enzyme induction in liver ("indirect" effect). In the present study, global profiles of gene expression were analyzed in rats treated with chemicals acting directly on the thyroid (thyroid peroxidase inhibitors such as propylthiouracil and methimazole) and chemicals acting indirectly on the thyroid (hepatic enzyme inducers such as phenobarbital and pregnenolone-16α-carbonitrile) using microarrays. Using a subtraction method between these two types of chemicals, we identified characteristic gene expression changes on the thyroid hormone synthesis pathway by direct-acting chemicals. Based on the functions of these genes, alterations of their expression seem to indicate the results of thyroid peroxidase inhibition, and might be helpful in more accurate evaluation of MOAs for thyroid toxicity.