Oxidative Stress Biomarkers in Erythrocytes of Captive Pre-Juvenile Loggerhead Turtles Following Acute Exposure to Methylmercury

Javier Hernández-Fernández,Andrés Pinzón-Velasco,Pilar Rodríguez-Becerra,Leonardo Mariño-Ramírez,Ellie Anne López-Barrera

doi:10.3390/app10103602

Abstract

This study describes the use of erythrocytes (RBCs) of loggerhead turtles as in vitro models for evaluating their toxicity to methylmercury. Blood samples of loggerhead turtles that were born in the Colombian Caribbean were used. The LC50 of RBCs to methylmercury was determined at 96 h using methylmercury concentrations of 0.5–100 mg L−1. Next, the viability of the RBCs and the activity of the enzymes superoxide dismutase (SOD), glutathione S-transferase (GST), and lipid peroxidation by malondialdehyde (MDA) at 6 and 12 h of exposure to acute concentrations of 0, 1, and 5 mg L−1 were evaluated. The LC50 for loggerhead turtle RBCs was 8.32 mg L−1. The cell viability bioassay of RBCs exposed for 12 h only showed 100% cell viability. Increasing in vitro MeHg concentrations caused a corresponding increase in MDA concentration as well as decreases in the activities of SOD and GST. The RBCs represent an excellent model for ecotoxicological studies and SOD, GST, and MDA are biomarkers of environmental pollution and oxidative stress in loggerhead turtles. This was the first study conducted on loggerhead turtle where the response of RBCs to MeHg-induced oxidative stress is evaluated.

Highlights

The loggerhead turtle (Caretta caretta) is a marine reptile that is distributed throughout the world; its population is in decline and in danger of extinction due to anthropic and environmental causes
The present study aims to evaluate the use of erythrocytes (RBCs) of captive loggerhead turtles as a predictive in vitro model of oxidative stress that is produced by acute exposure to different
Studies in mice that were exposed to Hg and MeHg have shown that doses of these compounds reduce glutation and superoxide dismutase (SOD) levels, respectively, in liver and brain tissues [80,81]. These experimental results agree with the results shown in this study, and they would indicate that loggerhead turtle RBCs are as susceptible to oxidative stress that is caused by MeHg exposure as the brain cells of the fish [76], mouse, and insect neuronal and liver cells [79], since these same trends were observed for the activity of the SOD and GST enzymes, and lipid peroxidation

Summary

Introduction

The loggerhead turtle (Caretta caretta) is a marine reptile that is distributed throughout the world; its population is in decline and in danger of extinction due to anthropic and environmental causes. The loggerhead turtle is considered to be a sentinel species of environmental pollution due to its longevity and high rate of biomagnification of contaminants [1]. These conditions allow for loggerhead turtles to be used as monitoring units for environmental pollutants. In Colombia, the loggerhead turtle is distributed in the departments of Atlántico, San Andrés Archipelago, Providencia and Santa Catalina, La Guajira, Magdalena, and Sucre.

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