Mechanisms of Antimicrobial Agent Cetylpyridinium Chloride Mitochondrial Toxicity in Rodent and Primary Human Cells: Super-resolution Microscopy Reveals Nanostructural Disruption

People are exposed to high concentrations of antibacterial agent cetylpyridinium chloride (CPC) via personal care and food products, despite little information regarding CPC effects on eukaryotes. CPC is used as an antibacterial agent via a detergent mechanism when above [~]600- 900 M. While three previous studies suggested CPC mitochondrial toxicity, this phenomenon is not well-studied. Here, we show that low-micromolar CPC inhibits mitochondrial ATP production in primary human keratinocytes, mouse NIH-3T3 fibroblasts, and rat RBL-2H3 immune mast cells, in galactose media, which causes cells to produce ATP via mitochondria. ATP inhibition via CPC (EC50 1.7LJ{micro}M) is nearly as potent as that caused by canonical mitotoxicant CCCP (EC50 1.2LJ{micro}M). CPC inhibition of oxygen consumption rate (OCR) tracks with that of ATP: OCR is halved due to 1.75 M CPC in RBL-2H3 cells and 1.25 M in primary human keratinocytes. Here we demonstrate that CPC is more potent as a mitotoxicant than as an immune mast cell signaling inhibitor, an effect published previously. Mitochondrial [Ca2+] changes can cause mitochondrial dysfunction. Here we show, using a novel plate reader assay with reporter CEPIA2mt, that CPC causes mitochondrial Ca2+ efflux from mast cells via an ATP-inhibition mechanism. Using super-resolution microscopy (fluorescence photoactivation localization) in live cells, we have discovered that CPC causes mitochondrial nanostructural defects in fibroblasts, including the formation of spherical structures with donut-like cross section, as quantified by novel Fourier transform analysis. This work reveals CPC as a mitotoxicant despite widespread use, highlighting the importance of further research into its toxicological safety.