Using fluorescence analysis and chemiluminescence to determine the causes of increased sensitivity of cancer cells to blue light

Abstract

The studies carried out in this work showed the important role of endogenous porphyrins (free-base and their zinc complexes) in the generation of reactive oxygen species in cells (and, above all, singlet oxygen), which are capable of influencing, by changing the redox state of cells upon absorption of blue light, the metabolic processes occurring in them. It has been shown that the decisive role of porphyrins in the effects of cell sensitization occurs despite higher, at least two orders of magnitude, concentrations of flavins (riboflavin, FMN, FAD) in cells.
The manifestation of the sensitizing properties of porphyrins in cells is facilitated by: a) higher efficacy of formation of singlet oxygen sensitized by them and higher values of their molar extinction coefficients compared to flavins; b) localization of porphyrins in mitochondria, while a significant proportion of flavins are localized in the cytosol; c) binding of flavins to proteins that perform a protective function against flavin-sensitized damage to cellular structures; d) pronounced antioxidant properties of flavins, which contributes to the quenching of ROS generated by them during photoexcitation.
The leading role of porphyrins, and not flavins, in the photobiological processes that determine cell metabolism when exposed to blue light is confirmed by a higher rate of inhibition of cell metabolic activity and higher levels of ROS formation, recorded using the chemiluminescence assay, when a cell suspension is exposed to radiation with 405 nm compared to 445 nm. In this case, radiation with a wavelength of 405 nm corresponds to the maximum of the absorption spectrum of protoporphyrin IX and the local minimum of the absorption spectrum of flavins, and radiation with 445 nm corresponds to the maximum of the absorption spectrum of flavins and the region of local minimum of the absorption spectrum of porphyrins.
For the first time, it has been shown that one of the reasons for the increased sensitivity of cancer cells compared to normal cells to the blue light is the higher concentration of endogenous porphyrin sensitizers, which is confirmed by fluorescent analysis methods. The determining role of porphyrins in the difference in the reactions of cancer and normal cells to the blue light on their suspension is also evidenced by higher levels of ROS formation and a higher rate of light-induced inhibition of the metabolic activity of HeLa cancer cells compared to normal BGM cells.

Speaker

Vitaly Yu. Plavskii
B.I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, Minsk, Belarus
Belarus

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