Nano-La2O3 undermines honeybee cognition by invading the brain and accelerating neuronal apoptosis

Abstract

The widespread application of nanoparticles in agriculture poses threats to pollinators like honeybees, but the mechanisms of nanoparticle effects on honeybee cognitive behaviours remain poorly understood. To begin to address this knowledge gap, we examined the cognitive and physiological implications of lanthanum oxide nanoparticles (nano-La₂O₃) on honeybees (Apis mellifera L.). Our findings revealed that exposure to nano-La₂O₃ (e.g., >10 mg L⁻¹) significantly impaired olfactory associative learning and memory of honeybees (p < 0.05) in a dose-dependent fashion, attributable to the increased apoptosis of neural cells and the downregulation of genes related to cognitive functions (cAMP-dependent protein kinase (pka), cAMP-responsive element binding protein (creb), n-methyl-D-aspartate receptor 1 (nmdar1)) due to the invasion of nano-La₂O₃ into brains. This further led to decreased sucrose consumption and reduced survival rates among exposed honeybees. Our research documents the first evidence of nano-La₂O₃ accumulation in honeybee brains and provides insights into the mechanisms through which nanoparticles negatively affect the cognitive behaviour of honeybees, highlighting new potential ecological risks posed by nanomaterials.