The role of garlic oil in the amelioration of oxidative stress and tissue damage in rohu Labeo rohita treated with silver nanoparticles

Aquatic contamination with silver nanoparticles (Ag-NPs) can cause toxicity in target organisms that are directly exposed to them. Oxidative stress and tissue alterations are potential endpoints of Ag-NPs toxicity. We determined whether garlic oil can ameliorate the effects of toxicity induced by amine-coated and spherical Ag-NPs in 100 +/- 5 g freshwater rohu Labeo rohita. The stock fish were placed in tanks with continuous water supply. There were three treatments and a control group, each with three replicates comprising five fish each. The treatments were: garlic only, Ag-NPs only, and garlic plus Ag-NPs. The Ag-NPs (30 mg/L) was supplied in water, whereas garlic oil (50 mu l/kg) was given to the fish through a prepared feed. The treatment duration was 28 days. In the control and garlic oil treatment there were no observed alterations in fish. The Ag-NP treatment initiated inflammation and necrosis in hepatic parenchyma, which resulted in venous congestion. Garlic oil treatment reduced vascular congestion in hepatic tissues. Ag-NPs also induced cellular vacuolization and the build-up of a yellow pigment. Inflammatory gill filament cartilage and lamellae were observed, as were swelling and collapse of lamellae, accumulation of macrophages, and necrosis and fusion of secondary lamellae in gill sections of Ag-NP-treated fish. Garlic oil ameliorated these changes, although some alterations like fused secondary lamellae, separation between the epithelium and lamellae, and accumulation of macrophages were still recorded in gill sections of garlic-treated fish. Garlic oil increased the activity of antioxidants (superoxide dismutase, catalase, glutathione S-transferase and glutathione) and caused a reduction in lipid peroxidation and/or MDA content. Furthermore, garlic oil treatment also improved measured hematologic parameters. This study confirms the role of garlic as a natural antioxidant for the amelioration of oxidative stress and histological and hemotologic changes in fish exposed to Ag-NPs.