Evaluation of intestinal histological damage in zebrafish exposed to environmentally relevant concentrations of manganese

Abstract

Manganese is an essential element for many physiological processes. However, in prolonged exposures or at high concentrations it may present toxicity to several organs, which has made it an object of study in pharmacological, behavioral, neurological and environmental research in different organisms. Thus, it was aimed to evaluate the damage caused by acute and chronic exposures to this element, through the histopathological analysis of the zebrafish (Danio rerio) intestine. Samples were embedded in paraffin for further processing in rotating microtome, and the slides were stained with Alcian Blue and hematoxylin for observation and analysis under light microscopy. The results demonstrated the potential of the metal to cause histological changes in this organ, such as fusion of villi (in 0.5 and 4.0 mg L-1), and to increase by more than 50% the number of goblet cells (in 8.0 and 16 mg L-1) in the region analyzed, mainly in the highest concentrations of Manganese Chloride and in chronic exposures, characterizing a possible inflammation of the intestinal epithelium. Thus, the histological analysis of intestines demonstrated to be a reliable alternative for the toxicological evaluation. It is important to monitor the concentrations of this and other metals in the water bodies, given their toxicity.

Fish Diseases Analysis Used as Bioindicators for Water Quality and its Importance for Environmental Monitoring

“…According to Authman et al (2015), heavy metals such as mercury, cadmium, copper, lead and zinc are of the most important pollutants which affect aquatic environment and fish. Rodrigues et al (2018) did not observe significant histopathological changes in the intestine of the species Danio rerio in the acute experiment, however, there was a tendency for increased histological changes as MnCl2 concentrations increased. Lamas et al (2007) reported several specific advantages in describing the natural characteristics of aquatic systems and in assessing changes to habitats.…”

What is the relationship between hypoxia, water chemistry and otolith manganese content?

“…Lastly, MnCl 2 used to create elevated water Mn might have impacts on fish physiology. Studies have revealed changes in intestinal epithelium (Rodrigues et al ., 2018) and a 10 times higher activity of peroxidase, which is usually used due to the toxicity‐generated reactive oxygen species, in fish brain (Altaf et al ., 2016). Nonetheless, both studies involved high treatments of Mn of approximately 7 mg l −1 or 70 mg l −1 compared to 0.55 mg l −1 in this study, suggesting the impacts of MnCl 2 in this study might be weak.…”

Titanium dioxide nanoparticles promote histopathological and genotoxic effects in Danio rerio after acute and chronic exposures

“…Regarding the intestine analysis, 5 fields per animal were analyzed by evaluating the percentage of altered villi in each field (2 villi per field). The increase in the thickness of intestinal villi, leukocyte infiltration, and presence/absence of eosinophils were registered according to the classification used by Rodrigues et al (2018). The percentage of cellular alterations was calculated, and the number of intestinal goblet cells was also counted.…”