Reactive oxygen species and other biochemical and morphological biomarkers in the gills and kidneys of the Neotropical freshwater fish, Prochilodus lineatus, exposed to titanium dioxide (TiO2) nanoparticles

Abstract

This study investigated the action of titanium dioxide nanoparticles (TiO-NPs), on the gills and kidneys of Neotropical freshwater fish, Prochilodus lineatus, with emphasis on reactive oxygen species (ROS) production, antioxidant responses, and morphological changes. Fish were exposed to 1, 5, 10, and 50 mg L nominal TiO-NPs suspended into water for 2 or 14 days. In gills, ROS decreased and glutathione (GSH) increased after 2 days, while ROS and GSH increased and superoxide dismutase activity decreased after 14 days. In kidneys, GSH and lipoperoxidation increased after 2 days and catalase activity decreased after 14 days. Common histopathologies in gills were epithelium hyperplasia, cellular hypertrophy, proliferation of mitochondria-rich cells (MRC), and lamellar stasis; in kidneys, there were cellular and nuclear hypertrophy, focal tubule degeneration, necrosis, and melanomacrophage (MM) proliferation. Although environmentally unlikely, high-dose exposures clarified biological effects of TiO-NPs, such as ROS formation and MRC responses in the gills, which may impair ionic balance. It was also found that MM are likely responsible for eliminating NPs in the kidney. These findings will help to regulate TiO-NP disposal, but longer-term studies are still needed.

Overview of the toxic effects of titanium dioxide nanoparticles in blood, liver, muscles, and brain of a Neotropical detritivorous fish

“…High concentrations of TiO 2 ‐NP suspended in water were not lethal for P. lineatus , as no fish died during the experiments. Although most of the TiO 2 ‐NP have quickly deposited on the aquariums' bottom due to their instability in water, some amount remained in suspension on the water column as reported in a previous study. Low concentrations of TiO 2 ‐NP suspended in the water column in anthropic polluted environment (receiving river streams) were also reported to cause TiO 2 ‐NP accumulation in liver, brain, and muscle of crucian carp.…”

“…Previous tests were done to describe the behavior of TiO 2 ‐NP in the water used in this study . Samples of aquarium water were taken in the middle of the water column immediately after TiO 2 ‐NP dilution and again 24 hours later.…”

“…Biomarkers were quantified as described in Carmo et al ROS (relative fluorescence U 10 6 ) was quantified according to the Viarengo et al method by quantifying the conversion of dichlorofluorescein‐2,7‐diacetate into 2,7‐dichlorofluorescein (excitation/emission: 370/445 nm) in the same day the samples were collected. Superoxide dismutase (SOD) activity (U SOD min −1 mg pt −1 ) was determined following the inhibition of cytochrome C reduction rate by superoxide radical at λ = 550 nm.…”

“…TiO 2 ‐NP may cross cell membranes by processes such as diffusion (adhesion interactions), endocytosis, or through binding to cellular receptors . In freshwater Teleostei, TiO 2 ‐NP are likely absorbed through the gills during the respiratory process and/or through the intestine via diet, and from these organs, they may reach the blood stream. Once in the blood, TiO 2 ‐NP may cause genotoxic damage to erythrocytes (formation of micronuclei and nuclear abnormalities) as it was found in marine fish .…”

“…In freshwater fish, a reduction of red blood cells, hemoglobin content, and white blood cells were found after TiO 2 ‐NP exposure . In addition to their effect on blood cells, TiO 2 ‐NP may also be distributed by the blood stream to several organs, thus modifying their cellular metabolism and potentially leading to the physiological dysfunction of these affected organs …”