Objective: To explore mechanism of dermal toxicity of trichloroethylene(TCE).
Methods: Normal human keratinocytes (KC) were isolated from foreskins of healthy donors undergoing circumcision by two-step trypsin digestion and cultured in serum-free medium. Cells were treated with medium, 1% acetone (volume fraction) 0.125, 0.500 or 2.000 mmol/L TCE for different time (4, 8, 12 or 24) hours. After treatment, MTT assay and ATPase activity detected, inhibition ratio of mitochondrial enzyme was calculated according to optical density (A) value of MTT assay. Mitochondrial membrane potential (MMP) was detected by flow cytometry FCM after being stained with Rhodamine123 (Rh123). Morphological changes were also observed through transmission electron microscope (TEM).
Results: Cellular viability and ATPase activity declined with dose of TCE, while inhibition ratio of mitochondrial enzyme increased with dose of TCE. FCM results showed that after treatment with 2.000 mmol/L TCE, fluorescence density of Rh123 decreased quickly from 18.73 +/- 0.45(0 h) to 8.20 +/- 0.66(8 h) (P < 0.01). After 8 h, fluorescence density maintained at the level equal to that of 8 h (fluorescence density of Rh123 were 8.20 +/- 0.36 and 8.20 +/- 0.40 for 12 and 24 h respectively, compared with that for 8 h group, P > 0.05). The results also showed that MMP diminished with dose of TCE. Under TEM, mitochondria in TCE-treated group appeared extensive swelling and vacuolar degeneration with less matrix and obscure or vanished mitochondria cristae but in control group, mitochondrial structure was integrated, with uniform matrix and visible mitochondria cristae.
Conclusions: TCE could inhibit mitochondrial metabolic enzyme, reduce ATP production, diminish MMP, and destroy ultrastructure of mitochondria in KC, all these contributing to the cytotoxicity of TCE.