Pyriproxyfen disrupts liver development in Gallus domesticus embryos at environmentally relevant concentrations

Introduction

Extensively used in vector-control programs across public health and agriculture, pyriproxyfen (PPF) is an insect growth regulator considered to pose minimal risk to non-target organisms. However, growing evidence indicates that it can cross biological barriers and interfere with conserved molecular pathways. Although its neurotoxicity in vertebrates has been described, their hepatotoxic potential during embryogenesis remains poorly understood. Thus, the aim of this study was to investigate the PPF effects on liver development of Gallus domesticus.

Methods

Fertilized eggs were exposed at embryonic day 1 (E1) to vehicle control (1% DMSO), the WHO-recommended PPF concentration (0.01 mg/L), or a worst-case scenario concentration (10 mg/L). Embryos were incubated until E10, when liver were collected for biometric, histological, histochemical, and cellular analyses. All experimental procedures were approved by the Animal Use Ethics Committee of the Federal University of Santa Catarina (5843231018).

Results/Discussion

Embryos exposed to PPF exhibited increased hepatosomatic index along with marked histoarchitectural disruption, including reduced hepatocyte density and increased vacuolization at both PPF concentrations. The combined histopathological index was significantly elevated in PPF-exposed groups. Histochemical analyses further demonstrated metabolic impairment, whereas toluidine blue O reaction showed increased metachromasia at both PPF concentrations, suggesting accumulation of acidic components associated with cellular stress. Conversely, Periodic Acid–Schiff reaction revealed reduced neutral polysaccharides only at 10 mg/L, suggesting glycogen depletion. Reduced Coomassie Brilliant Blue reaction suggested loss of protein integrity or synthesis. Moreover, cellular markers confirmed disrupted hepatic development, in which proliferation (PHH3) was significantly reduced, while apoptosis (cleaved caspase-3) increased even at PPF environmentally relevant concentration (0.01 mg/L).

Conclusion

Together, these results demonstrate that PPF compromises liver homeostasis, metabolism, and cellular turnover during early development, establishing its potential as an embryonic hepatotoxicant. These findings underscore the need for ecotoxicological monitoring and stricter evaluation of PPF use in environments shared with non-target vertebrates.