Growth-altering effects of sodium hypochlorite in cultured human dermal fibroblasts

Sodium hypochlorite, the most widely used antimicrobial active chlorine com pound in chemical disinfection, is little used as an antiseptic in clinical practice. This study aimed to assess the capacity of hypochlorite to alter human dermal fibroblast growth in vitro in relation to the concentration a nd exposure time. Effects of decreasing concentrations of hypochlorite (0.5 %-0.00025%) on fibroblast adherence capacity and proliferation, according t o varying exposure times and fetal calf serum (FCS) concentrations were inv estigated combining XTT assay, which provides cytochemical quantification o f metabolically-active cell number, and total cell protein content, an indi rect method for assessing substrate-adhered cell number. Initial cytotoxici ty was produced at 0.0075% hypochlorite within contact time of two hours, p rovoking concentration-dependent cell detachment. From 0.1% upwards, NaOCl exerted a profound cytotoxic effect on fibroblasts. At later stages (4 h) a nd concentrations greater than or equal to 0.01% hypochlorite produced dose -dependent mitochondrial dysfunction: cell survival progressively diminishe d from 71% to 10%. Cytotoxic effects were not significantly affected by exp osure-time periods, probably because maximum chlorine is released within th e first four hours. Hypochlorite concentrations from 0.005% to 0.00025% wer e found to have no inhibitory effects on cell growth; in fact, they appear to exhibit the opposite effect. Increments in protein content found after 2 4 h exposure ranged from 30% to 120% above control values. Hypochlorite is highly cytotoxic for fibroblasts at concentrations greater than or equal to 0.01% provoking concentration-dependent loss of cell adherence capacity an d mitochondrial dysfunction. In contrast, a mitogenic effect was observed w ith concentrations less than or equal to 0.005% which supports NaOCl as a s ource growth-promoting activity in cultured human fibroblasts. Hypochlorite proved to be a highly reactive molecule which inhibits or stimulates cell division according to the concentration. (C) 2000 Elsevier Science Inc. All rights reserved.