Mechanism of cytotoxic action of perfluorinated acids.: I. Alteration in plasma membrane potential and intracellular pH level

Perfluorinated (aliphatic) acids (PFAs) and congeners have many applications in various industrial fields and household for decades. Years later they have been detected in wildlife and this has spurred interest in environmental occurrence as well as influencing living organisms. PFAs were established as peroxisome proliferators and hepatocarcinogens. Amphipatic structure suggests that they may alter cell membrane potential (mbΔΨ) and/or induce changes in cytosolic pH (pHi). The aim of this study was to examine the correlation between changes of above parameters and PFAs structure (CF₆-CF₁₂) in human colon carcinoma HCT116 cells.mbΔΨ and pHi were measured by flow cytometry using fluorescence polarization of the plasma membrane probe 3,3′-dipentyloxacarbocyanine (DiOC₅(3)) and fluorescein diacetate (FDA), respectively. Dose- and time-dependent manner analysis revealed relatively fast depolarization of plasma membrane and acidification of cytosol both positively correlated with fluorocarbon chain length. mbΔΨ depletion after 4 h of incubation reached 8.01% and 30.08% for 50 μM PFOA and 50 μM PFDoDA, respectively. Prolonged treatment (72 h) led to dramatic dissipation of membrane potential up to 21.65% and 51.29% and strong acidification to pHi level at 6.92 and 6.03 at the presence of above compounds, respectively.The data demonstrate that PFAs can alter plasma membrane protonotrophy with the mode dependent on the compound hydrophobicity.