Diverse alterations and correlations in antioxidant gene expression in honeybee (Apis mellifera) hemocytes interacting with microbial pathogen-associated molecular patterns and pesticide cocktails

Abstract

Imidacloprid and amitraz, two common pesticides, affect honeybee health, behavior, and pathogen resistance. Understanding multi-risk exposures is vital to explaining their role in hive performance decline and colony health. This study assessed antioxidant system genes to evaluate pesticide impacts on immune response and enzymes responsible for hydrogen peroxide (H₂O₂) production. Honeybee hemocytes were exposed to imidacloprid and amitraz at various concentrations, alongside pathogen-associated molecular patterns (PAMPs) like zymosan A (ZYM), lipopolysaccharide (LPS), and peptidoglycan (PGN). Imidacloprid primarily affects mitochondrial components like mitochondrial superoxide dismutase (MnSOD), while amitraz decreases the expression of both mitochondrial and cytosolic genes (MnSOD, DUOX, and CuZnSOD). PAMPs modulate antioxidant responses, with LPS showing the strongest impact. DUOX and the phenoloxidase system are consistently linked. While AmPPO (prophenoloxidase) involved in melanization is less affected, pesticides significantly disrupt H₂O₂ production and antioxidant defenses, complicating risk assessment robustness.