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. Themechanisms of photobiomodulation on cellular level are based on the electronic excitation of Cu-A and Cu-B 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.