Dietary lemon essential oil mitigates metalaxyl-induced oxidative stress, hematological disruptions, and immunotoxicity in Nile tilapia (Oreochromis niloticus) with associated changes in splenic MAPK-and caspase-related gene expression

Journal Article

2026

Published in: https://doi.org/10.1016/j.rvsc.2026.106307

Antioxidant defense Citrus essential oil Fish nutrition Immunotoxicity Metalaxyl Nile tilapia

The agricultural accumulation of the phenylamide fungicide metalaxyl (MXL) poses an increasing threat to
aquatic organisms. Natural compounds, such as Citrus limon peel essential oil (CLPO), offer antioxidant and
immunostimulant properties that may counteract these toxic effects. This study evaluated the protective effects
of a CLPO-enriched diet against MXL-induced toxicity in Oreochromis niloticus. For 12 weeks, fingerlings (33.46
± 0.28 g; n = 50 per group) were assigned to four treatments: Control, CLPO (1 g/kg diet), MXL (12.34 mg/L),
and CLPO+MXL. MXL exposure reduced survival to 78%, disrupted hematological parameters (decreased white
and red blood cells, hemoglobin, and hematocrit), and elevated glucose and cortisol levels. Immune dysfunction
was evidenced by reductions in complement 3, lysozyme, nitric oxide, and myeloperoxidase. Furthermore, MXL
triggered oxidative stress, marked by diminished antioxidant enzyme activities and increased malondialdehyde
levels. At the molecular level, MXL exposure upregulated the stress-signaling transcripts (mapk1 and mapk14)
and pro-apoptotic genes (casp-3 and casp-8), while concurrently suppressing the anti-inflammatory cytokine il-
10. These physiological changes correlated with splenic depletion and enlarged melanomacrophage centers.
Conversely, dietary CLPO enhanced immune-antioxidant function, restored hematological profiles, mitigated
gene expression disturbances, and preserved splenic structure. Overall, dietary CLPO supplementation significantly
attenuated several adverse effects under the present experimental conditions, highlighting its potential as
a protective additive in aquafeeds

• Publication Work Type: Article
• Publisher Name: Elsevier
• Publishing City: Riyadh
• Volume Number: 210
• Issue Number: 106307
• Magazine \ Newspaper: Research in Veterinary Science
• Pages: 1-13