Cellular and Molecular Mechanisms of Photobiomodulation (Low-Power Laser Therapy)

Monochromatic (laser) and quasimonochromatic (LED) radiation in the red-to-near infrared optical region both in CW and pulsed modes is used to treat in a nondestructive fashion various soft-tissue and neurologic conditions. Cytochrome c oxidase, the terminal enzyme of mitochondrial respiratory chain, is considered as the photoacceptor. The mechanisms of photobiomodulation on cellular level are based on the electronic excitation of CuA and CuB chromophores in cytochrome c oxidase molecule. As the result, the redox status of cytochrome c oxidase molecule as well as its functional activity is modulated. The primary reactions in mitochondria switch on a set of secondary biochemical reactions (light-sensitive retrograde mitochondrial signaling) with endpoint as gene expression in the nucleus. Also, two specific topics are discussed and reviewed: patch-clamp studies in connection with optical stimulation of nerves and differences in CW and pulsed light action mechanisms when biological objects are irradiated.