Phosphine-Induced Oxidative Stress in Hepa 1c1c7 Cells

Phosphine (PH₃), from hydrolysis of metal phosphides, is animportant insecticide (aluminum phosphide) and rodenticide (zincphosphide) and is considered genotoxic and cytotoxic in mammals.This study tests the hypothesis that PH₃-induced genotoxicityand cytotoxicity are associated with oxidative stress by examiningliver (Hepa 1c1c7) cells for possible relationships among celldeath, increases in reactive oxygen species (ROS) and lipidperoxidation, and elevated 8-hydroxyguanine (8-OH-Gua) in DNA.PH₃ was generated from 0.5 mM magnesium phosphide (Mg₃P₂ togive 1 mM PH₃ as the nominal and maximal concentration. Thislevel causes 31% cell death at 6 h, measured by lactate dehydrogenaseleakage, with appropriate dependence on concentration and time.The intracellular ROS level is elevated within 0.5 h followingexposure to PH₃, peaking at 235% of the control by about 1 h.Lipid peroxidation (measured as malondialdehyde plus 4-hydroxyalkenals)is increased up to 504% by PH₃ at 6 h in a time-dependent manner.The level of 8-OH-Gua in DNA, a biomarker of mutagenic oxidativeDNA damage analyzed by GC/MS, increases to 259% at 6 h afterPH₃ treatment. Antioxidants significantly attenuate the PH₃-inducedROS formation, lipid peroxidation, 8-OH-Gua formation in DNA,and cell death, with the general order for effectiveness ofGSH (5 mM) and D-mannitol (10 mM) (hydroxyl radical scavengers),then Tempol (2.5 mM) and sodium azide (3 mM) (superoxide anionand singlet oxygen scavengers, respectively). These studiessupport the hypothesis that PH₃-induced mutagenic and cytotoxiceffects are due to increased ROS levels, probably hydroxyl radicals,initiating Oxidative damage.