Mechanistic approaches to the light-induced neural cell differentiation: Photobiomodulation vs Low-Dose Photodynamic Therapy.

BACKGROUND: Neurodegenerative diseases are the result of irreversible damage in the neuronal cells by effecting vital functions temporarily or even permanently. The use of light for the treatment of these diseases is an emerging promising innovative method. Photobiomodulation (PBM) and Photodynamic Therapy (PDT) are the modalities that have a wide range of use in medicine and have opposite purposes, biostimulation and cell death respectively. METHODS: In this study, we aimed to compare these two modalities (PDT and PBM) at low-level intensities and create a stimulatory effect on the differentiation of PC12 cells. Three different energy densities (1, 3, and 5 J/cm2) were used in PBM and Chlorin e6-mediated PDT applications upon irradiation with 655-nm laser light. The light-induced differentiation profile of PC12 cells was analyzed by morphological examinations, qRT-PCR, cell viability assay, and some mechanistic approaches such as; the analysis of intracellular ROS production, NO release, and mitochondrial membrane potential change. RESULTS: It has been observed that both of these modalities were successful at neural cell differentiation. PBM at 1 J/cm2 and low-dose PDT at 3 J/cm2 energy densities provided the best differentiation profiles which were proved by the over-expressions of SYN-1 and GAP43 genes. It was also observed that intracellular ROS production and NO release had pivotal roles in these mechanisms with more cell differentiation obtained especially in low-dose PDT application. CONCLUSION: It can be concluded that light-induced mechanisms with properly optimized light parameters have the capacity for neural cell regeneration and thus, can be a successful treatment for incurable neurodegenerative diseases.

Induced photo-cytotoxicity on prostate cancer cells with the photodynamic action of toluidine Blue ortho.

BACKGROUND: Photodynamic therapy (PDT) has become an advantageous therapeutic approach for the treatment of select cancers and microbial infections. PDT generates toxic reactive oxygen species as an end product of the interaction between the photosensitizer and light with an appropriate wavelength. Toluidine blue ortho is a photosensitizer that is commonly used in the photodynamic treatment of bacterial infection and a promising photosensitizer for cancer treatment. This study aims to evaluate the potential photo-cytotoxicity of toluidine blue ortho-mediated photodynamic therapy on PC-3 prostate cancer cells. METHODS: In this study toluidine blue ortho-mediated photodynamic therapy was assessed on PC-3 cancer cells with various photosensitizer concentrations and light energy densities of the 655-nm diode laser. MTT analysis was used for the determination of the cytotoxicity on the cells and viability/cytotoxicity assay was used for live/dead cell staining after the applications. The mechanism of this application was further analyzed with the determination of intracellular reactive oxygen species and nitric oxide release. RESULTS: The light applications and the photosensitizer alone did not inhibit the cell viability of PC-3 cells. 20 J/cm2 laser energy density together with 100 µM photosensitizer concentration resulted in maximum cancer cell death with a rate of approximately 89 %. The level of intracellular reactive oxygen species increased with the increasing parameters of the applications that resulted in more cell death. CONCLUSION: This study showed the successful anticancer activity of toluidine blue ortho upon irradiation with 655 nm of laser light against PC-3 cancer cells and it was mediated with the production of reactive oxygen species.