Possible beneficial effects of nano chitosan against doxycycline toxicity in Nile tilapia (Oreochromis niloticus)

In aquaculture, improper and illogical antibiotic use could yield negative outcomes. Therefore, this study investigates the ameliorative effects of chitosan (CS) and chitosan nanoparticles (CSNPs) against the toxicity of the antibiotic doxycycline in Nile tilapia fish. The fish were divided into four distinct categories: the first group served as the control, the second group was subjected to doxycycline (40 mg/L), the third group experienced doxycycline (40 mg/L) and CS (0.5% in fish diet), and the fourth group was exposed to doxycycline (40 mg/L) with CSNPs (0.5% in fish diet) for 15 days. Levels of creatinine, uric acid, and aspartate aminotransferase activities notably elevated (p < 0.05) in the doxycycline-treated group when compared with the control group. Meanwhile, fish in the doxycycline-exposed group demonstrated significantly lower (p < 0.05) levels of red blood cells, hemoglobin, packed cell volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and neutrophils. Conversely, mean corpuscular volume, platelets, white blood cells, and lymphocytes exhibited notably higher (p < 0.05) levels in the doxycycline group. Other hematological indicators, including monocytes and eosinophils, showed no notable variances (p > 0.05) among the studied groups. Fish treated with doxycycline exhibited notably higher (p < 0.05) interleukin-1β and interleukin-6 activity in comparison to the control group. Additionally, histopathological changes were detected in the gills, liver, and kidney tissues of doxycycline-exposed fish when contrasted with the control group. Co-exposure of CS and CSNPs significantly restored most hematological, biochemical, and immunological parameters, as well as histopathological indices, in the fish, aligning these values closer to those observed in the control group in comparison to the fish treated solely with doxycycline. In conclusion, both CS and CSNPs played an important role in moderating the negative effects of doxycycline on fish, through improving hematological indices, reductions in creatinine, uric acid, and aspartate aminotransferase activity, as well as anti-inflammatory action through reductions in interleukin-1β and interleukin-6 activity.