Study of cytotoxicity mechanisms of silver nitrate in human dermal fibroblasts.

Certain concentrations of the antiseptic AgNO3, a potent broad-spectrum antimicrobial agent, exert cytotoxic effects on fibroblasts and endothelial cells which are directly related to the wound-healing process. In vitro assessment of human fibroblast cytotoxicity has proved to be a useful method for characterizing cell toxicity mechanisms of topically-applied antiseptics. In the present study human dermal fibroblasts were exposed to AgNO3 at concentrations of 4.12-82.4 microM for 8 and 24 h. Silver ions greatly inhibited fibroblast proliferation and prolonged AgNO3 exposure produced Ag-dependent cell loss. In the sequence of events occurring during our in vitro experimental model, the inhibitory action on DNA synthesis was the primary event in AgNO3 cytotoxicity, associated with significant loss of cell protein. Both parameters decreased as the content of fetal calf serum (FCS) in the exposure medium was gradually reduced from 10 to 2%. The parallel study of DNA synthesis and cell protein content suggests that the toxic damage produced by silver in different phases of the cell cycle may lead to destruction of the entire cell population and therefore hinder the tissue regeneration process. A concentration- and time-dependent depletion of intracellular ATP content is also caused by ionic silver, thereby compromising the cell energy charge which precedes human dermal fibroblast death. Concomitant incorporation of FCS to the medium always attenuated Ag+ cytotoxicity curves in a concentration-dependent fashion and maximum protection was observed at 10% in situations closely resembling physiological conditions.