Mitochondrial dependent oxidative stress in cell culture induced by laser radiation at 1265 nm

Abstract

Photodynamic therapy is the main technique applied for surface carcinoma treatment. This technique employs singlet oxygen generated via a laser excited photosensitizer as a main damaging agent. However, prolonged sensitivity to intensive light, relatively low tissue penetration by activating light the cost of photosensitizer (PS) administration can limit photodynamic therapy applications. Early was reported singlet oxygen generation without photosensitizer induced by a laser irradiation at the wavelength of 1250-1270 nm. Here, we study the dynamics of oxidative stress, DNA damage, changes of mitochondrial potential, and mitochondrial mass induced by a laser at 1265 nm have been studied in HCT-116 and CHO-K cells. Laser irradiation of HCT-116 and CHO-K cells has induced a dose-dependent cell death via increasing intracellular reactive oxygen species (ROS) concentration, increase of DNA damage, decrease of mitochondrial potential, and reduced glutathione. It has been shown that, along with singlet oxygen generation, the increase of the intracellular ROS concentration induced by mitochondrial damage contributes to the damaging effect of the laser irradiation at 1265 nm.

Direct 1O2 optical excitation: A tool for redox biology

“…This is a very interesting topic, with far-reaching consequences and will be further discussed in Section 5.2. Further experiments employing a 1265 nm cw excitation have been done by Kurkov et al ., where oxidative stress and regression was induced in experimental animal tumors [26], and oxidative mitochondrial and overall cell disruption was recently obtained in cell cultures [28]. As mentioned in relation with some of the experimental results presented, the main concern using this band is its photothermal potential due to IR water absorption [121].…”

“…Direct excitation of 1 O 2 can be employed to induce cellular redox eustress (stimulation [5]) [33], [180], redox distress (stress response and damage [5]) [28], [33], [119], [120], cell death [24], [27], [32], [33], [116], and, seemingly, it can be put to clinical use, at least for some kind of tumors [108], [189]. A puzzling aspect of 1 O 2 action at all this levels is the apparent high biological susceptibility to small 1 O 2 amounts: given the very small absorption coefficient of 3 O 2 and its low concentration in cells and tissues, it is not easy to understand how relatively short irradiations can have such a biological impact.…”

“…That an initial “oxidative spark” by optically excited 1 O 2 can reach the threshold for significant local structural/functional modifications, that subsequently lead to an increased ROS production, seems feasible in view our current knowledge of the cell physiology and RIRR. Putative ROS sources for such an 1 O 2 -driven RIRR can be the mitochondria [28], [193], the family of NAD(P)H Oxidases (NOX) [41], [194], the lipoxygenases [195] or, most probably, a mixture of all of them. The ROS interconversion process is surely playing a role in this 1 O 2 susceptibility, as it can transform a short-lived ROS like 1 O 2 into longer lived species like H 2 O 2 .…”

“…Many different laser types have been employed to directly pump monomol and dimol O 2 bands: Nd:YAG and Nd-based [29], [30], [122], [123], [124], [125], [126], [127], [128], [135], [136], [137], [138], [139], [140], [141], [142], [143], [144], Yb-based [31], He-Ne [29], [99], [108], [123], [141], [143], [144], [177], [178], [179], [180], [181], semiconductor (diode) [27], [108], [109], [114], [119], [120], [137], [146], [148], [149], [150], [151], [152], [153], [154], [168], Raman-shifted [23], [24], [25], [26], [28], [115], dye-based [174], [185], alexandrite (Cr:BeAl 2 O 4 ) [108], and forsterite (Cr:Mg 2 SiO 4 ) [109] to name the most common ones (more examples can be found in each wavelength subsection above). Visible excitation of O 2 has the drawback of overlapping with endogenous cellular chromophores, like cytochromes, porphyrins, certain cofactors (like flavin- and nicotinamide-containing metabolites), etc [170].…”

“…Recently, however several groups have re-sparked interest on the possibility to directly excite the oxygen molecule with light at certain wavelengths, for biological research or clinical applications [22]. Some successful light wavelengths employed towards this end have been 1270 nm [23], [24], [25], [26], [27], [28], 1065 nm [29], [30], [31] and 760 nm [32], [33], [34], to name a few. However, it must be mentioned (see details in Section 4) that research on the direct optical excitation of O 2 predates by several decades these studies.…”