Rahman_2025_Vet.Res.Commun_50_79

Waterborne trace elements (TE), such as mercury (Hg) and zinc (Zn), are environmental contaminants that often co-occur in aquatic ecosystems. Cucurbita pepo (pumpkin peel; PP) is a medicinal plant with diverse pharmacological properties. Accordingly, this innovative trial looked at the efficacy of PP, administered as powder (12.00 g/kg diet), in mitigating the toxicological effects of a mixture of trace elements (MTE) containing Hg (0.05 mg/L) and Zn (7.00 mg/L) in Oreochromis niloticus. A total of 160 fingerlings (28.50 +/- 1.33 g) were randomly assigned to four groups, with four replicates per group: control, PP, MTE, and PP + MTE. The experiment was conducted over two months. The findings disclosed a reduced fish survival rate (72.50%) and a pronounced neuro-stress response following MTE exposure, as indicated by elevated cortisol, norepinephrine, and glucose concentrations, along with decreased acetylcholinesterase activity. The MTE exposure also induced oxidative stress in gills, evidenced by increased malondialdehyde concentration and diminished glutathione peroxidase activity, and reduced glutathione content. Additionally, MTE caused extensive histopathological alterations in both brain and gill tissues. Furthermore, MTE exposure induced endoplasmic reticulum stress and activated apoptotic pathways, as evidenced by the significant upregulation of cysteine-aspartic acid protease-3 (casp-3), eukaryotic translation initiation factor 2 A (eif-2a), C/EBP homologous protein (chop), and X-box binding protein 1(xbp-1) and inositol-requiring enzyme 1 alpha (ire-1alpha), activating transcription factor 6 (atf-6), and glucose-regulated protein 78 (grp-78) genes in both the brain and gills. Remarkably, dietary supplementation with PP improved these parameters and restored normal tissue histology. These findings suggest that PP can be effectively incorporated into the diet of O. niloticus to mitigate the toxic effects of MTE exposure.