Low-Dose Responses to 2,3,7,8-Tetrachlorodibenzo-<i>p</i>-dioxin in Single Living Human Cells Measured by Synchrotron Infrared Spectromicroscopy

Abstract

Synchrotron radiation (SR)-based Fourier transform infrared (FTIR) spectromicroscopy measurements are presented of HepG2 cells exposed to an environmental contaminant that is a known ligand for the aryl hydrocarbon (Ah) receptor. Measurements were made on cells treated with an Ah receptor-binding model compound 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Compared to untreated control cells, treated cells displayed unique spectral changes with TCDD concentrations of 0.01−10.0 nM. Key spectral changes involved PO, C−O, and C−H stretching bands. The first changes are related to the environment of the phosphate backbone of nucleic acids. The C−H stretching bands data show a relative increase in the number of methyl to methylene groups. An excellent correlation was found between spectral changes and an increase in CYP1A1 expression measured by the reverse transcriptase polymerase chain reaction (RT-PCR) technique demonstrating that the SR−FTIR method is observing cellular biochemical changes related to this gene expression pathway. Finally, the potential use of SR−FTIR spectromicroscopy is discussed as a diagnostic tool for monitoring cellular exposure and early molecular responses to environmental pollutants.