Sessions

The western honey bee (Apis mellifera) is of outstanding economic importance not only for the production of apicultural products but also as an indispensable cornerstone of global food security and terrestrial biodiversity through the pollination of flowering plants. The colony losses observed in recent decades may be driven by the synergistic interaction of multiple factors, including biotic stressors, pesticides, and climate change. These impacts deplete the energy reserves of worker bees and can induce oxidative stress. The aim of this TDK study was to investigate the pro-oxidative effects of zymosan along the gut–brain axis - which mimics a fungal-derived immune stimulus - as well as the protective potential of the antioxidant capacity-supporting glycine and N-acetylcysteine combination (GlyNAC) in the central nervous system of bees.

For the study, Apis mellifera workers were collected from a clinically healthy and treatment-free colony located in Veszprém County. Following a 36-hour laboratory acclimatization period, the bees were assigned to six experimental groups, with 40 individuals per cage and three replicates per group. During the 48-hour per os exposure, bees were treated with a zymosan-containing nutrient solution (0.01%), and their diet was supplemented with GlyNAC at two different doses (low dose: 0.1% glycine + 0.05% N-acetylcysteine; high dose: 1% glycine + 0.5% N-acetylcysteine). Following termination, oxidative stress biomarkers and the activities of antioxidant enzymes were determined from the prepared brain homogenates.

Based on our results, orally administered zymosan significantly increased the concentration of malondialdehyde (MDA) as well as the level of hydrogen peroxide (H₂O₂). In parallel, the activities of catalase, superoxide dismutase, and glucose-6-phosphate dehydrogenase also increased. The co-administration of high-dose GlyNAC with zymosan significantly decreased H₂O₂ concentrations compared to the group treated with zymosan alone.

Our findings indicate that orally administered zymosan induced oxidative stress and enhanced lipid peroxidation in the central nervous system of honey bees, while also triggering the activation of their antioxidant defense systems. However, the upregulation of the antioxidant response was insufficient to fully prevent oxidative damage. High-dose GlyNAC mitigated certain components of the oxidative burden induced by zymosan but did not provide complete protection against oxidative damage. Our study contributes to a more precise understanding of the link between gut-derived immune stimulation and redox processes within the central nervous system of honey bees, and may serve as a basis for further investigations into targeted dietary interventions for pollinator health protection.