Linking biochemical and individual-level effects of chlorpyrifos, triphenyl phosphate, and bisphenol A on sea urchin (Paracentrotus lividus) larvae

Abstract

The effects of three relevant organic pollutants: chlorpyrifos (CPF), a widely used insecticide, triphenyl phosphate (TPHP), employed as flame retardant and as plastic additive, and bisphenol A (BPA), used primarily as plastic additive, on sea urchin (Paracentrotus lividus) larvae, were investigated. Experiments consisted of exposing sea urchin fertilized eggs throughout their development to the 4-arm pluteus larval stage. The antioxidant enzymes glutathione reductase (GR) and catalase (CAT), the phase II detoxification enzyme glutathione S-transferase (GST), and the neurotransmitter catabolism enzyme acetylcholinesterase (AChE) were assessed in combination with responses at the individual level (larval growth). CPF was the most toxic compound with 10 and 50% effective concentrations (EC₁₀ and EC₅₀) values of 60 and 279 μg/l (0.17 and 0.80 μM), followed by TPHP with EC₁₀ and EC₅₀ values of 224 and 1213 μg/l (0.68 and 3.7 μM), and by BPA with EC₁₀ and EC₅₀ values of 885 and 1549 μg/l (3.9 and 6.8 μM). The toxicity of the three compounds was attributed to oxidative stress, to the modulation of the AChE response, and/or to the reduction of the detoxification efficacy. Increasing trends in CAT activity were observed for BPA and, to a lower extent, for CPF. GR activity showed a bell-shaped response in larvae exposed to CPF, whereas BPA caused an increasing trend in GR. GST also displayed a bell-shaped response to CPF exposure and a decreasing trend was observed for TPHP. An inhibition pattern in AChE activity was observed at increasing BPA concentrations. A potential role of the GST in the metabolism of CPF was proposed, but not for TPHP or BPA, and a significant increase of AChE activity associated with oxidative stress was observed in TPHP-exposed larvae. Among the biochemical responses, the GR activity was found to be a reliable biomarker of exposure for sea urchin early-life stages, providing a first sign of damage. These results show that the integration of responses at the biochemical level with fitness-related responses (e.g., growth) may help to improve knowledge about the impact of toxic substances on marine ecosystems.

Keywords: Acetylcholinesterase; Antioxidant enzymes; Biomarkers; Embryo-larval bioassay; Glutathione S-transferase; Sea urchin.

Fig. 1

Inhibition of sea urchin larval growth by chlorpyrifos (left), triphenyl phosphate (center), and bisphenol A (right). Square: exposure experiments carried out to define the toxicity of each substance. Circle: exposure experiments for biomarker analysis. Lines represent the fittings of experimental data to Eq. 1 for the square. Bars represent standard errors

Fig. 2

Catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), and acetylcholinesterase (AChE) activities in sea urchin larvae exposed to chlorpyrifos (left), triphenyl phosphate (center), and bisphenol A (right). “0”: DMSO controls (< 0.01 % v/v). Data were analyzed by one-way ANOVA, followed by post hoc Student-Newman-Keuls test at a significance level of p < 0.05. Bars represent standard errors

Fig. 3

Glutathione S-transferase (GST, up) and glutathione reductase (GR, down) activities in sea urchin larva exposed to chlorpyrifos. Lines represent the predictions of the model described by Eq. 2. Bars represent standard errors

Fig. 4

Pearson correlation coefficients between enzymatic activities, larval growth, and CPF (A), BPA (B), and TPHP (C) concentrations

Fig. 5

Two-dimensional plot of the principal component analysis for the biomarker responses (gray arrows), showing the different CPF (square), TPHP (diamond), and BPA (circle) treatments. Open symbols represent controls