Chlorophenols and chlorocatechols induce apoptosis in human lymphocytes (in vitro)

In this work the effect of 2,4,5-trichlorophenol (2,4,5-TCP), pentachlorophenol (PCP), 4,6-dichloroguaiacol (4,6-DCG), tetrachloroguaiacol (TeCG), 4,5-dichlorocatechol (4,5-DCC) and tetrachlorocatechol (TeCC) on the induction of apoptosis in human peripheral blood lymphocytes was examined. The analysis of the changes in mitochondrial transmembrane potential (ΔΨm) was performed using JC-9 fluorescent probe. It was noted that all the compounds studied (excluding 4,6-DCG) in a dose-dependent manner (0.2-25 ppm) increased the number of cells, which were characterized by the ΔΨm reduction, with the strongest effect observed for TeCG and TeCC. Moreover, fluorimetric assay of the caspase-3 activity revealed that 2,4,5-TCP, chlorocatechols and TeCG in the range of the concentrations of 1-50 ppm increased the caspase-3 expression, whereas PCP in its highest concentration of 50 ppm decreased the activity of this enzyme. It was also noted that the caspase-3 activity was the most strongly induced by tetrachlorocatechols, particularly by TeCC. The analysis of YO-PRO-1 iodide/propidum iodide staining revealed that TeCC, the most strongly increased the number of apoptotic cells at 5 and 25 ppm, whereas at a dose of 100 ppm the strongest effect on apoptosis induction was observed for 2,4,5-TCP.