Synergistic Cytotoxicity of Permethrin and N,N-Diethyl-Meta-Toluamide on Sinonasal Epithelial Cells

N,N-Diethyl-meta-toluamide (DEET) and permethrin are pesticides commonly used in combination due to their synergistic insecticidal and repellent properties. This study investigates whether simultaneous exposure to these compounds elicits synergistic cytotoxicity in sinonasal epithelial cells (SNECs). Ethmoid sinus mucosal specimens were procured from eight patients during endoscopic sinus surgery. SNECs were expanded on culture plates and exposed to various concentrations of DEET and permethrin (0-5 mM), individually and concurrently, for up to 156 hours. Experiments were replicated in triplets, and cell viability was recorded every 2 hours using Incucyte real-time cell imaging system. Synergy score was calculated on the basis of the Loewe additivity synergy model. DEET and permethrin exhibited synergistic cytotoxicity across all eight tissues, albeit with variations in onset and magnitude. In conclusion, the concurrent exposure of DEET and permethrin can lead to synergistic cytotoxicity in sinonasal epithelia.