β‐Naphthoflavone induces oxidative stress in the intertidal copepod, Tigriopus japonicus

Abstract

ABSTRACTβ‐Naphtoflavone (β‐NF) is a flavonoid and enhances oxidative stress in vertebrates with little information from aquatic invertebrates as yet. In this study, we investigated the effects of β‐NF on the antioxidant defense systems of the intertidal copepod Tigriopus japonicus. To measure the β‐NF‐triggered changes in oxidative stress markers, such as intracellular reactive oxygen species (ROS), glutathione (GSH) concentration, residual glutathione S‐transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), and superoxide dismutase (SOD) activity, T. japonicus were exposed to β‐NF (0.5 and 1 mg/L) for 72 h. Significant (P < 0.05) induction of the intracellular ROS content (%) was observed in 1 mg/L of β‐NF exposed T. japonicus, compared to the negative control and H2O2‐exposed group. The GSH levels were significantly increased in the 0.5 mg/L of β‐NF‐exposed group for 12 h and 1 mg/L of β‐NF‐exposed groups for 12–24 h. GPx, GST, and GR activities showed a significant increase in the 1 mg/L β‐NF‐exposed group, indicating that β‐NF induces oxidative stress in T. japonicus. To understand the effects of β‐NF at the level of transcript expression, a 6K microarray analysis was employed. Transcript profiles of selected antioxidant‐related genes were modulated after 72 h exposure to 1 mg/L of β‐NF. From microarray data, 10 GST isoforms, GR, GPx, PH‐GPx, and Se‐GPx were chosen for a time‐course test by real‐time RT‐PCR. T. japonicus GST‐S, GST‐O, GST‐M, and GST‐D1 were significantly increased in a 1 mg/L β‐NF‐exposed group. T. japonicus GPx, GR, and Se‐GPx mRNA levels were also significantly increased at both concentrations. Our results revealed that oxidative stress was induced by β‐NF exposure in T. japonicus. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 332–342, 2015.