Naphthenic Acid-Induced ROS Emissions by Rainbow Trout Mitochondria

Area of Science:

• Environmental Toxicology
• Mitochondrial Biochemistry
• Aquatic Toxicology

Background:

• Naphthenic acid fraction compounds (NAFCs) are common in petrochemical wastewater.
• NAFCs can induce reactive oxygen species (ROS) in isolated mitochondria.

Purpose of the Study:

• To investigate the effect of 3,5-dimethyladamantane-1-acetic acid, a NAFC, on mitochondrial ROS production and consumption.
• To determine the specific mitochondrial sites responsible for NAFC-induced ROS generation.

Main Methods:

• Isolated rainbow trout liver mitochondria were exposed to 3,5-dimethyladamantane-1-acetic acid.
• ROS emission was measured during different respiratory states using fluorometry.
• ROS production from specific mitochondrial complexes was quantified using the Amplex UltraRed-horseradish peroxidase system.

Main Results:

• 3,5-dimethyladamantane-1-acetic acid increased ROS emission in a dose-dependent manner at mitochondrial complex II (II_F) (EC50 = 0.2 mM).
• Complex II (II_F) was identified as the predominant site of NAFC-stimulated ROS production.
• Malonate, an inhibitor of succinate dehydrogenase, abolished ROS production.

Conclusions:

• Mitochondrial complex II (II_F) is the primary source of ROS induced by adamantane-type NAFCs.
• NAFCs impair mitochondrial redox balance in fish by stimulating ROS production at complex II.