Insights into developmental impairment, oxidative stress, and immune-metabolic dysregulation induced by lead exposure in honeybee larvae (Apis mellifera)

Heavy metal pollution is a growing global environmental concern, and its potential risks to pollinating insects are receiving increasing attention. Previous research has mainly focused on toxic hazards occurring during the adult developmental stage of bees. However, the toxic effects of lead (Pb) on honeybee larvae and their underlying mechanisms remain insufficiently understood. This study systematically evaluates the multidimensional impacts of Pb exposure on the growth and development, immune metabolism, and molecular responses of honeybee larvae (Apis mellifera). Following exposure to sublethal Pb concentrations of 1.7 and 8.5 mg/kg for 72 h, larval survival, growth and development were significantly reduced. It also leads to significant decreases in morphological indicators of newly emerged adult bees. Pb exposure induced pronounced oxidative stress, characterized by a decrease in antioxidant and immune enzyme activities and total antioxidant capacity, accompanied by the accumulation of lipid peroxidation products (MDA and 4-HNE) and DNA oxidative damage markers (8-OHDG). At the molecular level, high-concentration Pb exposure suppressed pathways related to cytochrome P450-mediated xenobiotic metabolism and amino acid metabolism. At the metabolic level, the arachidonic acid metabolism pathway was significantly activated, with key inflammatory mediators, such as leukotrienes and prostaglandins, showing marked accumulation, thereby exacerbating toxic damage through interactive inflammatory and oxidative pathways. This study provides insights into understanding the toxic effects of the heavy metal Pb on bee larvae. It emphasizes the importance of the larval developmental stage in colony health risk assessment and offers an important basis for deepening the understanding of sublethal effects and ecological risks of heavy metals on pollinators.