Palliative effects of vanillin against pymetrozine toxicity in Clarias gariepinus: Modulation of growth, antioxidant-immune capacity, ER-stress signaling, autophagy, and apoptosis

Globally, inappropriate and excessive use of pesticides compromises aquatic ecosystems involving fish. Consequently, this perspective investigates the consequences of the long-term exposure to a novel insecticide (pymetrozine; PYM) on growth, immune-antioxidant response, and the respective target gene pathways of inflammation, endoplasmic reticulum (ER) stress, autophagy, and apoptosis in African catfish (Clarias gariepinus). As well, the potential ameliorative role of dietary vanillin (VN; 10 mg/kg diet), a phenolic aldehyde, against PYM toxicity is assessed. For 60 days, one hundred and sixty fish of 81.17 ± 3.17 g were haphazardly distributed into four sets [control, VN, PYM (0.065 mg/L), and VN+PYM]. The findings highlighted a reduced survival (62.50 %) and impaired growth (weight gain rate and specific growth rate) following PYM exposure. First, PYM exposure induced immune impairment, as evidenced by decreased lysozyme activity and complement 3 levels, accompanied by an inflammatory response reflected by elevated C-reactive protein. Additionally, oxidative damage was observed, indicated by reduced glutathione peroxidase and superoxide dismutase activities and increased malondialdehyde levels. Moreover, PYM exposure caused marked histological alterations in splenic tissue, including depletion of white pulp and apoptosis of lymphoid elements, along with downregulation of beclin-1 (an autophagy regulatory gene). Furthermore, PYM toxicity significantly upregulated target genes related to pro-inflammatory cytokines (tumor necrosis factor-α and interleukin-6), ER stress (binding immunoglobulin protein, activating transcription factor-6, and X-box-binding protein-1), autophagy inhibition (mechanistic target of rapamycin kinase and transformation-related protein-53), and apoptosis (Bcl-2-associated X-protein and cysteine-aspartic acid protease-10). Feeding on the VN-supplemented diet improved the survival (87.50 %), immune-antioxidant capacity, and ameliorated genetic disruptions, while preserving the histological structure of the spleen in the PYM group. In conclusion, this viewpoint suggests that dietary VN may alleviate the deleterious impacts of PYM toxicity in African catfish, with potential implications for PYM-exposed African catfish farming.