Sun YongXue

Evaluation of glutathione s‐transferase as toxicity indicator for roxarsone and arsanilic acid in Eisenia fetida

Different compounds can induce stress response by targeting specific genes. Studies related to elucidating the detoxification and adaptive responses of proteins like glutathione‐s‐transferase (GST) can be helpful in better understanding toxicity. Roxarsone and arsanilic acid, which have been exhaustively used as animal and poultry feed additives, pose a threat to the environment and human health. GST enzyme bioassay revealed fluctuations in response to different concentrations of roxarsone and arsanilic acid at different time intervals. The highest GST enzyme activity (40.51%) was observed on day 15 of treatment with roxarsone. On the other hand, arsanilic acid caused the maximum enzyme activity (52.11%) on day 10 of treatment. During this study, the full‐length gene sequence of GST, having the size 984 bp (Genbankno. HQ693699), was achieved from Eisenia fetida and established as a biomarker to assess the toxicity of roxarsone and arsanilic acid. The deduced protein has a computed molecular mass of 23.56 kDa and a predicted isoelectric point of 9.92. Quantitative real‐time PCR revealed significant differential gene expression in response to roxarsone and arsanilic acid treatment as compared with control treatment. Roxarsone caused the highest gene expression of 7.0‐fold increase over control on day 15 of treatment, whereas arsanilic acid resulted in the highest gene expression reaching to 14.56‐fold as compared with control. This study is helpful in understanding the role of GST as a potential biomarker for chemicals like roxarsone and arsanilic acid, which can pollute the food chain. Copyright

Stress-responsive genes (hsp70 and mt) and genotoxicity elicited by roxarsone exposure in Carassius auratus

In this study, comet assay (single-cell gel electrophoresis), real-time quantitative PCR (qPCR) and proteomics approach were used to comprehensively assess toxicity elicited by roxarsone exposure in C. auratus at 50, 150 and 300 μg/L for 7, 14 and 21 days. Results of comet assay showed that DNA were seriously damaged under the pressure of roxarsone, especially the concentration of 50 μg/L that always maintained a sustained and increased damage effect to fish liver cell during the 21 days experiment. The expressions of biomarker genes showed that hsp70 gene expressions raised significantly and the group of 50 μg/L also showed a continued increased response effect, whereas mt gene was only slightly increased. Results of proteomics for the concentration of 300 μg/L found that thirty six significantly changed proteins were identified by MALDI-TOF/TOF-MS. They are involved in many important processes including energy producing, cytoskeleton stabilization, substance metabolism and stress response. Among these metabolites, carbohydrate metabolism (mainly occurred during day 1-14) and cytoskeleton proteins (mainly occurred during day 14-21) were the most identified proteins. These results revealed that the low levels of 50 μg/L probably led to a continuous damage than the higher groups during the experiment time. Furthermore, proteomics results might implied that though cell system expected to mobilize almost all the functional proteins to quickly establish a new homeostasis together when facing the roxarsone at first, but in the end the destroyed cell cytoskeleton structure might burst the bubble.