Influence of platinum, palladium and rhodium as compared with cadmium, nickel and chromium on cell viability and oxidative stress in human bronchial epithelial cells

The platinum group elements (PGE) Pt, Pd and Rh are increasingly emitted into the environment by automobile catalytic converters. Whereas the biological availability of PGE to plants and animals has been demonstrated, only few studies concentrate on the influence of PGE on a cellular level. The effects of Pt, Pd and Rh compared with Cd, Ni and Cr on cell viability and oxidative stress response using soluble metal salts were studied in the human bronchial epithelial cell line BEAS-2B. Whilst Rh(III) showed little influence, both Pt(II) and Pt(IV) as well as Pd(II) had significant effects on cell viability at levels comparable to Cd(II) and Cr(VI). Arranging metal species in order of increasing toxicity as determined by LC50 yields: Rh(III) = 1.2 mmol/L < Ni(II) = 0.8 mmol/L < Pt(II) = Pd(II) = 0.4 mmol/L < Pt(IV) = 0.05 mmol/L < Cr(VI) = 0.02 mmol/L < Cd(II) = 0.005 mmol/L. ROS induction can be used as a biomarker for oxidative cell stress. The maximum relative increase in ROS production for Pt(IV) (1134%) was more than twice as high as for Cr(VI) (560%), with Pt(II) still resulting in an increase of 238%. These findings underline the strong effects of PGE on cell metabolism and emphasize the need for further studies of their toxic properties.