Haemato-biochemical, mutagenic, and histopathological changes in Oreochromis niloticus exposed to BTX

Abstract

The study of the DNA damage response in erythrocytes after exposure to volatile organic compounds (VOCs) can present evidence for its potential effect as genotoxic- biomarkers for environmental pollution. Although VOCs are dangerous pollutants, still little is known about hemotoxic, cytotoxic, and genotoxic effects of such pollutants on fish. We optimized an assay method for apoptosis and DNA damage in erythrocytes of adult tilapia fish after 15 days exposure to benzene (0.762 ng/L), toluene (26.614 ng/L), and xylene (89.403 ng/L). The highest level of apoptosis and DNA damage were recorded in benzene-exposed fish, as was the highest level of histopathological alterations in gills, liver, and kidney. The imbalance of the antioxidants profile explained the stress-case reported in exposed fish. These results suggest that hemotoxic, cytotoxic, genotoxic, and tissue damage were recorded after exposure to BTX in Oreochromis niloticus.

Keywords: Acridine orange; BTX; DNA damage; Erythrocytes; Fish.

Fig. 1

Apoptosis detection and DNA damage in erythrocytes Nile tilapia exposed to BTX for 7 days. Cells appeared light green were apoptotic. Cells stained with ethidium bromide were considered to have DNA damage. (Scale bar = 50 μm)

Fig. 2

The mean tail moment score in erythrocytes of Nile tilapia exposed to BTX

Fig. 3

Photomicrograph of Nile tilapia gills, H&E-stained Showing, a- edema and congestion of gill arch (double arrow), b- Dilatation and congestion of blood vessels of primary lamellae (star) and secondary lamellae, fusion on the tips of gill filament (arrow) C- epithelial hyperplasia (EH) of primary lamellae which lead to fusion of secondary lamellae d- epithelial detachment (lifting)of the secondary gill lamellae (arrow). e, f- lamellar telangictasis (circle)

Fig. 4

Photomicrograph of Nile tilapia liver, H&E-stained Showing, a- vacuolar degeneration (VD) with fat degeneration (FD), b- congested central vein (arrow) and dilated sinusoids (DS) after toluene exposure. After benzene exposure, c- Melanomacrophages aggregation (arrow) and d- Hepatocellular necrosis (circle). After xylene exposure, e- Congestion of hepatopancrease (star) and sinusoids (arrow) and f- Thrombus inside central vein (star)

Fig. 5

Photomicrograph of Nile tilapia kidney, H&E-stained Showing, a- melanomacrophages aggregation (arrow) with glomerular swelling (star). b, c- interstitial inflammatory cell infiltration (arrow), necrosis and vacuolar degeneration of renal tubular epithelium (circle), congestion of blood vessels (yellow star) d- diffuse Interstitial hemorrhages (circle) Separation of tubular epithelium from basement (arrow). e- necrosis of blood vessels wall (arrow). f- degeneration of blood vessels wall (double arrow) hypercellularity of glomeruli (star)