The long-term transport of Potamotrygon wallacei increases lactate levels and triggers oxidative stress in its brain: The protective role of recovery and the essential oil of Lippia alba

Abstract

This study aimed to determine whether the long-term transport model of cururu stingray (Potamotrygon wallacei) could disturb the brain redox status and brain functions, including antioxidant defenses, signaling pathways activated by oxidative stress, and the physiological responses to transport-induced stress upon arrival and after its recovery; and also to identify how the addition of essential oil of Lippia alba (EOLA) in the water transport could influence on these changes. For this reason, the cururu stingrays were anesthetized with 200 mg/L eugenol and sampled by sectioning of the spinal cord before transport (n = 5), after 32 h-transport in the absence (n = 5) and presence of 10 μL/L of the EOLA (n = 5); and after recovery for 24 h and 48 h post-transport without and with EOLA (n = 5, each group) for blood and brain removal, totalizing 35 animals (four replicates). Transport triggered a rise in the levels of lactate in plasma and brain of cururu stingray on arrival. Besides, it increased the superoxide anion (O2•-) and hydrogen peroxide (H2O2) levels, and decreased the superoxide dismutase (SOD) 1 and 2, catalase, glutathione peroxidase (GPx) 1, and glutathione reductase (GR) activities, activated nuclear factor κB (NF-κB), led to glutathione oxidation, lipid peroxidation (measured through the thiobarbituric acid reactive substances (TBARS)), and elevated heat shock protein 70 (HSP70) levels in the cururu stingray brain. The addition of the EOLA to water protected brain against stress and oxidative stress on arrival, speeding up a process that could take until 48 h to occur in the absence of this additive. To reach this response, the EOLA decreased lactate levels in plasma and brain of cururu stingray, and also reduced O2•- and H2O2 levels, and NF-κB activation, increased SOD2, catalase, GPx1 and GR activities, decreased the ratio between oxidized and reduced glutathione, avoiding the increase in the TBARS levels in the brain tissue, and regulated the physiological responses to stress, as illustrated by low HSP70 levels found in it. These data make the addition of EOLA to the water even more recommended for long-term transport of cururu stingrays.