ABSTRACT
In the present study, we explored the capability of manganese nanoparticles (Mn-NPs) to alleviate the toxicity induced by lead (Pb) and ammonia (NH3) toxicity in Oreochromis niloticus (GIFT strain). The experiment followed a completely randomized design, including a control group (Mn-NPs-0 mg kg-1 diet) and groups exposed to Pb and NH3 alongwith Mn-NPs at 2 and 3 mg kg-1. Cortisol levels were significantly elevated in Pb + NH3 group whereas reduced by Mn-NPs diets. Gene expressions of HSP 70, iNOS, CYP 450, and Cas 3a were notably upregulated by Pb + NH3 group and downregulated by Mn-NPs diets. The cellular metabolic enzymes were affected by Pb + NH3 exposure and mitigated by Mn-NPs diets. The liver and kidney exhibited reduced activities of catalase, superoxide dismutase, and glutathione-s-transferase with Mn-NPs diets. Concurrently, immune-related genes such as total immunoglobulin (Ig) and tumor necrosis factor (TNFα) were upregulated in the Mn-NPs-fed groups. Growth performance indicators, including weight gain %, feed conversion ratio, specific growth rate, protein efficiency ratio, and relative feed intake were adversely affected by Pb + NH3 stress but improvement with Mn-NPs diets. Genes associated with growth performance, such as growth hormone (GH), growth hormone regulatory (GHR1), and myostatin, exhibited enhancements in response to Mn-NPs diets. Digestive enzymes, including protease and amylase were also enhanced by Mn-NPs diets. Additionally, Mn-NPs diets led to a reduction in the bioaccumulation of lead. This study aims to investigate the role of Mn-NPs in mitigating the effects of lead and ammonia toxicity on fish by examining various biochemical and gene regulatory factors to enhance fish wellbeing.