Nigella sativa oil ameliorates malathion-ınduced toxicity in Nile tilapia: a multi-systemic and molecular evaluation

This study investigated the protective effects of dietary supplementation with 2% black cumin (Nigella sativa) oil (BCO) against malathion-induced toxicity in Nile tilapia (Oreochromis niloticus). Over a 72-day feeding trial, fish were divided into four groups: control, 2% BCO, malathion (LC₅₀/20), and malathion + 2% BCO. The results demonstrated that sublethal malathion exposure significantly impaired growth performance including final weight, weight gain, and specific growth rate and worsening the feed conversion ratio. Hematological analysis revealed a severe anemic response, marked by significant reductions in red blood cell (RBC) counts, hemoglobin (Hb), and hematocrit (Hct) levels. Furthermore, malathion induced profound hepatic and metabolic dysfunction, evidenced by elevated serum AST, ALT, ALP, glucose, and cholesterol levels. Oxidative stress was prominent in the malathion-exposed group, characterized by suppressed antioxidant enzyme activities (SOD, CAT, GPx) and a severe increase in lipid peroxidation (MDA). Molecular assessments of brain tissue showed a marked upregulation of pro-inflammatory (il-1β, tnf-α) and apoptotic (caspase-3) genes, indicating neuroinflammation. Histopathological examinations confirmed severe multi-organ damage, including branchial lamellar fusion, hepatic necrosis, renal tubular degeneration, and brain hyperemia. Conversely, dietary supplementation with 2% BCO significantly ameliorated these toxic effects. Notably, BCO supplementation effectively restored growth parameters and FCR to levels statistically comparable to the control group, normalized hematological and biochemical profiles, bolstered antioxidant defenses, and significantly downregulated neuroinflammatory and apoptotic gene expressions, thereby preserving overall tissue architecture. In conclusion, this study demonstrates that dietary Nigella sativa oil effectively mitigates malathion-induced toxic effects. Rather than presenting individual components as entirely novel, the true strength and novelty of this approach lie in the multi-systemic integration of tissue histopathology with underlying neuroinflammatory and apoptotic gene expressions in the brain, offering a comprehensive insight into the protective mechanisms of black cumin oil in aquaculture.