Chronic toxicity of arsenic during Rhinella arenarum embryonic and larval development: Potential biomarkers of oxidative stress and antioxidant response

Abstract

The Argentinean autochthonous toad Rhinella arenarum was selected to study the chronic toxicity of arsenic (As) and the biochemical responses elicited by exposure to As in water during embryonic and larval development. Significant decreases in the total reactive antioxidant potential and in catalase activity were observed in individuals exposed chronically to sublethal concentrations of As, which is indicative of an oxidative stress situation. However, an antioxidant response was elicited during chronic exposure to As, as evidenced by the increase in endogenous reduced glutathione content and glutathione-related enzymatic activities such as glutathione S-transferase (GST) and glutathione reductase. This protective response might prevent a deeper decline in the antioxidant system and further oxidative damage. Alternatively, it might be linked to As conjugation with reduced glutathione for its excretion. Considering the sustained increase in GST activity and the decrease in the total antioxidant reactive potential observed, the authors propose them as good candidates to be used as biomarkers during As exposure. Interestingly, glutathione reductase activity was inhibited at a very low concentration of As considered safe for aquatic life. Environ Toxicol Chem 2017;36:1614-1621. © 2016 SETAC.

mRNA Transcript Analysis of Hypothesis-driven Pathways as Known Responders to Organophosphate Exposure: Rhinella Arenarum Larvae Transcriptome Study

“…In our experience, the antioxidant enzymatic activity response varies greatly in R. arenarum embryos and larvae exposed to OP pesticides, showing cycles of induction followed by inhibition attributed to catalytic site inactivation due to ROS attack 8, 24,35,41,43 . In the response of R. arenarum larvae to arsenic-induced oxidative stress, we observed an increase in Cu/Zn SOD protein, followed by a decrease together with a decrease in CAT protein, with similar enzymatic activity patterns 11,44 .…”

“…Finally, remarking on the complexity of the responses and crosstalk between pathways, we have reported for different developmental states in R. arenarum and cell cultures exposed to CPF, other OP pesticides or arsenic, an increase in MEK1/2 and ERK1/2 proteins, their translocation to the nucleus, and ERK phosphorylation, considering that the MAP kinase pathway regulates the Nrf2-mediated response. Additionally, cFOS and cJUN proteins are increased after oxidative stress in R. arenarum embryos and larvae 43,44,54 .…”

Hypothesis-driven dragging of transcriptomic data to analyze proven targeted pathways in Rhinella arenarum larvae exposed to organophosphorus pesticides

“…The enhanced translocation of Mek to the nucleus due to CPF exposure might be a stress response downregulating the pathway. Furthermore, cFos and cJun proteins are increased after oxidative stress in R. arenarum embryos and larvae 12 , 47 , 52 . The complex nature of the regulatory crosstalk leading to the prevailing downregulation of biochemical responses in R. arenarum larvae exposed to OP, is depicted in Fig.…”

Evaluation of the Acute Effects of Arsenic on Adults of the Neotropical Native Fish Cnesterodon decemmaculatus Using a Set of Biomarkers

“…Generally, the activity of these enzymes is increased after acute exposure to low As concentrations, whereas it is decreased under chronic exposure (Flora, 2011). Several studies have reported As‐induced antioxidant imbalance in freshwater animals (Allen & Rana, 2004; Mardirosian et al, 2016; Sarkar et al, 2014; Tuulaikhuu et al, 2015). These studies demonstrated that some enzymatic and non‐enzymatic factors help in protecting cells by scavenging and clearing ROS.…”

“…Gambusia holbrooki chronically exposed to 120 µg/L of As showed increase in the activity of SOD and GR after 9 days and of GST after 55 days of exposure (Tuulaikhuu et al, 2015). In Rhinella arenarun tadpoles, As induced an increase in oxidative stress enzymes, mainly GST, and in gene expression and transcription factors (Mardirosian et al, 2016).…”