An experimental study of light-oxygen and photodynamic effects at histamine induced skin inflammatory reactions

Purpose. To compare light-oxygen and photodynamic effects at the development of inflammatory reactions caused by histamine so as to study mechanisms of the singlet oxygen effect at biological objects and to optimize their application in clinical practice. Materials and methods. A domestic diode laser ‘Super Sab’ with λ ≈ 1265 nm (produced by New Surgical Technologies LLC, Moscow, Russia) was used as a source of laser light. 10 female rats of Wistar population weighing 250–300 g were taken in the study. Power density of laser irradiation was 0.25 W/cm 2 (exposure dose – 30 J/cm 2 ). Not irradiated scarification sites were used as controls. Histamine concentration in the solution after its irradiation with the same laser was studied by the immunoenzymatic analysis. Photodynamic effect was studied in 12 volunteers; scarification samples with histamine and preliminary applied gel photosensitizer ‘Photoditazine’ were put to them, and the subsequent irradiation with laser light generated by device ‘Atkus-2’ (produced by CJSC ‘Semiconductor Devices, St. Petersburg) having λ ≈ 662 nm, power density 0.3 W/cm 2 and exposure dose 50 J/cm 2 was made. Scarifications without irradiation were used as controls. Results. Reliable results ( p ≤ 0.01) obtained in the experimental animals revealed the decrease of inflammatory reactions at the irradiated scarification sites with histamine application compared to the controls. While examining the histamine solution irradiated in vitro , no decrease in the histamine concentration was found under different irradiation doses. Histamine tests in volunteers also revealed reliable results ( p ≤ 0.05) when the decrease of inflammatory reactions was seen in them after photosensitiser application compared to the controls. Conclusion. The newly obtained data may clarify some mechanisms of light-oxygen and photodynamic therapy (LOT and PDT); they may also expand indications for clinical application of the discussed therapy and serve as a starting point for future in-depth trials in this direction. One of them, in particular, may be revealing changes in the chemical structure of some important biologically active substances under the impact of LOT and PDT.