Combination Toxicity Of Benzene, Toluene, Xylene And Formaldehyde On Human Embryo Lung Cell And The Related Mechanism

Objective: observe the cytotoxicity of formaldehyde and BTX on human embryo lung cell in vitro, investigate the joint effects of formaldehyde and BTX, explore its toxic mechanism, to provide with the experimental base for defining formaldehyde and BTX environmental sanitation standardization.Methods: 1.study the joint effect of formaldehyde and BTX on human embryo lung cell: Human fetal lung cells exposed to different concentrations of toxicants and their mixtures. Use MTT assay measured the survival rate. Find median lethal concentration (OLC₅₀) of each toxicants and their mixtures according to the linear regression method. Predicted lethal concentration(PLC₅₀) of the toxic mixtures derived by finney law. Judge the joint effects of these toxic mixtures depending on the Q value (PLC₅₀/OLC₅₀). 2. Study the damage of formaldehyde and BTX on human embryo lung cell and the Related Mechanism: cells divided into DMSO control group and mixture of formaldehyde and BTX damage group(final concentration are 0.1mmol/L, 0.2mmol/L, 0.3mmol/L, 0.4mmol/L), exposed to mixture for 24 hours. The concentrations of malondialdehyde (MDA) were determined by thiobarbiturif acid reactive substance method. The activity of super oxide dismutase (SOD) was determined by xianthine-xanthine oxidase method. Intracellular reduced glutathione(GSH) level were measured to evaluate the oxidative damage degree. The activation of nuclear factor-κB3 was investigated by immunocytochemistry (SP kit); To determine time-dependent effect, cells were exposed to 0.3mmol/L mixture of formaldehyde and BTX for 0h, 6h, 12h, 24h, 48h, detect each index.Results: 1. Four compounds on human embryonic lung cells LC₅₀ were respectively: formaldehyde: 0.234×10^-3mmol/mL, benzene: 0.079mmol/mL, toluene: 0.215mmol/mL, xylene: 0.209mmol/mL. Q value exposed to formaldehyde and benzene\toluene\xylene were between 0.5 to 2.6, Q value exposed to benzene andtoluene\xylene were less than 0.5 and Q value exposed to xylene and toluene was beyond 2.6; 2. Mixture of formaldehyde and BTX can restrain the activity of SOD, decrease the content of GSH and increase the lever of MDA in culture fluid in concentration and time dependent; 3. The activity of NF-kB in mixture of formaldehyde and BTX damage group was higher than that in the control group, the change has concentration and time dependent.Conclusion: 1. The lung cell toxicity sequence of these four kinds of compounds is formaldehyde＞the benzene＞the xylene＞the toluene, they basically consistent with the order of their vitro toxicity. The joint effects between formaldehyde and benzene\toluene\xylene maybe additional action. The joint effects between benzene and toluene or xylene maybe antagonistic action. The joint effects between toluene and xylene maybe synergistic action. When four compounds are mixed together, its joint effects maybe synergistic action.2. The damage induced by formaldehyde and BTX on Human Embryo Lung Cell is related to lipid peroxidation. Formaldehyde and BTX may aggravate cell oxidative stress harm by activating NF-kB express, starting or accommodating Primary-response gene's transcription.