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1The 30th International Conference on Advanced Laser Technologies B-I-8
ALT'23
Factors determining the increased sensitivity of cancer cells to the action of laser radiation in the blue region of the spectrum
V. Plavskii, L. Plavskaya, O. Dudinova, A. Sobchuk, A. Svechko, R. Nahorny, A. Tretyakova, A. Mikulich, T. Ananich, S. Yakimchuk, I. Leusenko
B.I.Stepanov Institute of Physics of the National Academy of Sciences of Belarus, Minsk, Belarus
The objective of this work is comparative studies of the effectiveness of radiation of various wavelengths of the blue spectral region on cancer and untransformed cells in vitro, comparing the level of concentrations of endogenous photosensitizers and reactive oxygen species (ROS) in cells of these types, elucidation of the mechanism of antitumor activity of blue light and the reasons determining the higher sensitivity of cancer cells to the action of blue light.
The performed studies have shown the ability of radiation from laser and LED sources with a wavelength in the range of X = 405-465 nm, in the range of energy doses of 1-15 J/cm2 to influence the metabolic activity of cancer cells (epithelioid carcinoma of the cervix HeLa) and normal untransformed cells (African green monkey kidney cells BGM). Comparative studies performed using semiconductor lasers and LEDs with a wavelength of 405 and 445 nm revealed the absence of fundamental differences in the biological effect of monochromatic radiation from laser sources and quasi-monochromatic radiation from LEDs. The most pronounced effect on the metabolic activity of cells is exerted by radiation with X = 405 nm. The photobio-logical effect initiated by exposure to radiation with X = 445 nm is significantly lower; radiation with X = 465 nm has the least pronounced effect. Depending on the intensity of radiation and the energy dose, the light of the blue region of the spectrum can both stimulate the metabolic activity of cells (which is observed in a fairly narrow range of energy doses) and inhibit it. Moreover, the inhibitory effect increases with an increase in the energy dose of light exposure. At low energy doses of light exposure, the decrease in the metabolic activity of cells is not explained by their death, but is due to a change in the duration of individual phases of the cell cycle. However, at high energy doses, cell death, realized by the mechanism of necrosis and apoptosis, makes a significant contribution to the decrease in metabolic activity.
The main conclusion that follows from the performed studies is that at the same energy dose, the inhibitory effect of blue light is significantly more pronounced in relation to tumor cells than in relation to normal untransformed ones. It has been established that the biological effect of blue light is caused by reactions initiated by ROS due to the excitation of endogenous photosensitizers. The addition of ROS quenchers to the nutrient medium of cells before their irradiation can block the photobiological effect. It was shown for the first time that the contribution of various types of ROS (singlet oxygen, hydrogen peroxide, etc.) to the effects of cell inactivation depends on the time after the cessation of irradiation, which is associated with the launch of a wave of massive secondary ROS production in cells, and, above all, hydrogen peroxide. If, immediately after the cessation of exposure, the main intermediate determining the course of photobiological reactions in cells is singlet oxygen, then a day after the cessation of irradiation - hydrogen peroxide.
Using stationary and kinetic spectrofluorimetry methods, porphyrin components were registered for the first time in the fluorescence spectra of a suspension of living cells along with the flavin component. It has been shown that the level of porphyrin photosensitizers is approximately 2.5 times higher in tumor cells than in untransformed ones. The higher concentration of endogenous photosensitizers in cancer cells is the reason for the higher rate of their inactivation compared to normal cells. Based on a comparison of the absorption characteristics of flavin and porphyrin sensitizers, as well as data from chemiluminescence analysis and the biological effects of radiation with X = 405 and 445 nm, it is concluded that the determining contribution to the formation of singlet oxygen in cells when exposed to radiation with X = 405 nm is made by endogenous porphyrins, characterized by the most intense absorption in this area. The contribution of flavins is more pronounced under the action of radiation with X = 445 nm, corresponding to the maximum in their absorption spectrum and the minimum absorption of endogenous porphyrins.
