Investigating the effect of probiotic feeding and experimental poisoning with naproxen on the histopathology of zebrafish (Danio rerio)

The pollution of waters with low concentrations of environmental pollutants has attracted the scientific community's attention for several decades. It has become a significant challenge that addresses whether ecological concentrations of such compounds can disrupt the physiological function of organisms in aquatic ecosystems. In this regard, the present study evaluated the effect of feeding with Lactobacillus roteri and long-term exposure to naproxen on histopathology changes in zebrafish. In this study, the fish were fed with essential diet (TN, C) and probiotic (TP, TPN) (with a concentration of 1.5 × 108 CFU/ml) for 60 days, and at the same time, they were exposed to naproxen with a concentration of 100 μg/L (TN, TPN). Sampling was done to check intestinal morphology and histopathological changes of intestinal, liver, and kidney tissues on the 30th and 60th days of the test. The results showed a significant increase in the length and width of the villi and the number of goblet cells in the intestine in fish fed with probiotics. Also, due to exposure to naproxen, histopathological lesions such as villus corruption, vacuolization, necrosis, and hyperemia were reported in fish intestines. In the liver, the observed tissue complications included atrophy, fatty change, necrosis, thinning of the sinusoid, dark granules, blood occlusion, bleeding, and edema. Tubular necrosis, glomerular necrosis, hyperemia, infiltration of edematous cells, expansion of Bowman's space, and nephrocalcinosis were observed in kidney tissue. The remarkable thing was that in all three studied tissues, the destructive effect of the complications was reduced in the fish fed with probiotics. According to the results obtained in this study and the continuous increase in the consumption and release of drugs in aquatic environments, using Lactobacillus roteri probiotic supplement in aquaculture farms that use polluted water is recommended to improve fish health. As observed in this study, long-term exposure to low drug concentrations also causes tissue damage, resulting in significant economic losses.