Fish and their ectoparasites serve as model organisms for evaluating aquatic ecosystem health and can thus function as bioindicators of environmental pollution. This study, therefore, investigates the gene expression of biomarkers of effect in Clarias gariepinus inhabiting a polluted drain called the Kitchener Drain and the Nile River (a reference habitat). Ectoparasites and metacercariae of digenean endoparasites on the collected fish were examined to further clarify the impact of pollution. Compared with the Nile River, the Kitchener Drain contained significantly elevated concentrations of heavy metals, bicarbonates, sulfates, and minerals. Interestingly, the prevalence, mean intensity, and abundance of ectoparasitic monogeneans from C. gariepinus collected from the Nile River were higher compared with those from the Kitchener Drain, whereas the drain had higher levels of metacercaria of the digenean endoparasite Centrocestus formosanus. Fish from the Kitchener Drain had significantly elevated hepatic expressions of genes related to metal toxicity, oxidative stress, inflammation, heat shock response, and xenobiotic metabolism. The results indicate that C. gariepinus exposed to metals and other pollutants triggers an adaptive response involving multiple stress-response pathways. The findings also highlight the impact of pollution on parasitic infestation in this fish population. The study supports the utilization of molecular biomarkers and ectoparasitic infestation as early warning signals for water pollution.

Background/Objectives: Nickel exposure is a significant environmental and occupational risk factor associated with the onset and progression of chronic liver diseases due to its capacity to induce persistent oxidative stress, inflammation, and hepatocellular injury. This study aimed to evaluate the enhanced hepatoprotective and antioxidant/anti-inflammatory effects of naringin-loaded nanoliposomes (NRG-NLPs), a novel nanoformulation designed to improve the bioavailability of naringin, a citrus-derived flavonoid phytochemical, against nickel sulfate (NiSO₄)-induced hepatotoxicity in male Wistar rats. Methods: Ninety rats were allocated into six groups (n = 15 each): control, NRG, NRG-NLPs, NiSO₄, NiSO₄ + NRG, and NiSO₄ + NRG-NLPs. Treatments consisted of oral administration of NRG or NRG-NLPs (80 mg/kg/day) and intraperitoneal injections of NiSO₄ (20 mg/kg/day) for three weeks. Endpoints included assessment of growth performance, serum biochemistry, hepatic antioxidant status, inflammatory mediators, apoptotic gene expression, nickel tissue accumulation, and histopathological and ultrastructural liver changes. Results: NiSO₄ exposure induced marked hepatic injury, evidenced by reduced body weight, adverse serum biochemical profiles, increased hepatic enzymes and bilirubin, elevated oxidative damage markers (MDA, protein carbonyls), increased proinflammatory cytokines, and upregulation of HMGB1, PI3K, mTOR, JAK/STAT, and proapoptotic genes, accompanied by aberrant nickel accumulation and severe histopathological alterations. Co-treatment with NRG-NLPs significantly ameliorated biochemical and histological disturbances, restored antioxidant defense systems (SOD, CAT, GPx, GSH, Nrf2, HO-1), and modulated key pathways of inflammation (NF-κB, TNF-α, IL-6), fibrosis (TGF-β), cell survival, and apoptosis more effectively than crude naringin. NRG-NLPs also substantially reduced hepatic nickel deposition and preserved near-normal liver architecture. Conclusions: These findings demonstrate that nanoformulated naringin confers superior hepatoprotective benefits against nickel-induced liver injury through enhanced bioavailability and multi-pathway modulation, supporting its translational potential as a citrus-derived medicinal phytochemical and dietary bioactive for the prevention and therapeutic intervention of oxidative and inflammatory chronic liver disease.

The invasion of fish by heavy metals is a recognized environmental problem. Heavy metals, after leaking into the water, penetrate fish directly through the gill and later the skin. Fish develops protective defense mechanisms against the damaging effects of heavy metals. This study was aimed to investigate the concentrations of certain metals (cadmium, iron, manganese, cobalt, and lead) in the muscle tissues of the Nile tilapia (Oreochromis niloticus) and their possible impact on its histological, nanomechanical, and biochemical biomarkers. The results showed that fish muscle from the polluted site contained high levels of heavy metals compared to the reference site. Biochemical profile of the Nile tilapia showed that serum glucose, total proteins, uric acid, creatinine, bilirubin, superoxide dismutase, and malondialdehyde were elevated in exposed tilapia compared to their corresponding reference. Histological examination of the liver showed severe alterations in the liver tissue. Nanomechanical properties (roughness and stiffness) confirmed the damaging effect of metals on the liver tissue. These findings provide a rational application of histological, nanomechanical and biochemical parameters to be used as indicators of metal stress. Integrated biomarker response is a comprehensive index of all biomarkers and a good indicator of the health status of aquatic ecosystem.