Abstract
Neurotoxic effects of aluminum chloride in higher than usual environment concentration (10 mg/L) were studied in brains of fishes from various pelagic areas, especially in sunfish (Lepomis macrochirus Rafinesque, 1819), roach (Rutilus rutilus Linnaeus, 1758), crucian carp (Carasius carasius Linnaeus, 1758), goby (Neogobius fluviatilis Pallas, 1811). The intensity of oxidative stress and the content of both cytoskeleton protein GFAP and cytosol Ca-binding protein S100β were determined. The differences in oxidative stress data were observed in the liver and brain of fish during 45 days of treatment with aluminum chloride. The data indicated that in the modeling of aluminum intoxication in mature adult fishes the level of oxidative stress was noticeably higher in the brain than in the liver. This index was lower by1.5–2.0 times on average in the liver cells than in the brain. The obtained data evidently demonstrate high sensitivity to aluminum ions in neural tissue cells of fish from various pelagic areas. Chronic intoxication with aluminum ions induced intense astrogliosis in the fish brain. Astrogliosis was determined as result of overexpression of both cytoskeleton and cytosole markers of astrocytes – GFAP and protein S100β (on 75–112% and 67–105% accordingly). Moreover, it was shown that the neurotixic effect of aluminum ions is closely related to metabolism of astroglial intermediate filaments. The results of western blotting showed a considerable increase in the content of the lysis protein products of GFAP with a range of molecular weight from 40–49 kDa. A similar metabolic disturbance was determined for the upregulation protein S100β expression and particularly in the increase in the content of polypeptide fragments of this protein with molecular weight 24–37 kDa. Thus, the obtained results allow one to presume that aluminum ions activate in the fish brain intracellular proteases which have a capacity to destroy the proteins of intermediate filaments. The data presented display the pronounced neurotoxic effect of mobile forms of aluminum on both expression level and the metabolism of molecular markers of astrocytes GFAP and protein S100β. Aluminum ions induce integrated changes, the more important of which are a significant increase in final LPO products, an increase in antioxidant enzyme activity, a reactivation of glial cells in the brain. Integrated determination of the content and polypeptide fragments of specific astrocyte proteins in fishes brains coupled with oxidative stress data may be used as valid biomarkers of toxic pollutant effects in aquatic environments.
Highlights
Aluminum is the most common metal in nature
Despite the fact that the anatomical and morphological analysis of the experimental and control groups of fish showed no abnormalities and deviations from healthy growth, while studying the intensity of oxidative stress in the liver and brain of gobies, crucian carp and roach from the experimental groups, it was established that the content of TBA-reactive products significantly increased
The number of TBA active products in the liver of individuals of the experimental groups was higher by 22–69% as compared with the groups of fish kept in the purified tap water (Table 1)
Summary
Aluminum is the most common metal in nature. The number of minerals which consist of aluminum is more than 250, including aluminum silicates – compounds that make up about 82% of the earth’s crust. Being one of the most common elements in the Earth’s crust, aluminum is found in almost all natural water resources (Gostomski, 1990). Established criteria recommend that the one-hour average concentration of aluminum should not exceed 750 μg/l and four-day average concentration should not exceed 87 μg/l These criteria were developed by an acute toxicity study for 20 species of freshwater aquatic organisms. Biological effects of aluminum are determined for a number of water quality characteristics, especially pH, content of organic carbon and hardness (Trenfield et al, 2012; Cardwell et al, 2017)
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