Cellular mechanisms of low power laser therapy

Cytochrome c oxidase is discussed as a possible photoacceptor when cells are irradiated with monochromatic red to near-IR radiation. Five primary action mechanisms are reviewed: changes in the redox properties of the respiratory chain components following photoexcitation of their electronic states, generation of singlet oxygen, localized transient heating of absorbing chromophores, NO release from catalytic center of cytochrome c oxidase, and increased superoxide anion production with subsequent increase in concentration of the product of its dismutation, H₂O₂. A cascade of reactions connected with alteration in cellular homeostasis parameters (pH_i, [Ca_i], cAMP, E_h, [ATP] and as well as NF - κB, AP-1) is considered as a photosignal transduction and amplification chain in a cell (secondary mechanisms).