Photobiomodulation therapy is defined as the utilization of non-ionizing electromagnetic energy to trigger photochemical changes within cellular structures that are receptive to photons. Mitochondria is particularly receptive to this process. At the cellular level, visible red and near infrared light (NIR) energy are absorbed by mitochondria, which perform the function of producing cellular energy called “ATP”. The key to this entire process is a mitochondrial enzyme called cytochrome oxidase c, a chromophore, which accepts photonic energy of specific wavelengths when functioning below par.
Photobiology is the study of the effects of non-ionizing radiation on biological systems. The biological effect varies with the wavelength region of the radiation. The radiation is absorbed by molecules in skin such as DNA, protein or certain drugs. The molecules are changed chemically into products that initiate biochemical responses in the cells.
The current and widely accepted proposal is that low level visible red to near infrared light (NIR) energy is absorbed by mitochondria and converted into ATP for cellular use. In addition, the process creates mild oxidants (ROS), which leads to gene transcription and then to cellular repair and healing. The process also unclogs the chain that has been clogged by nitric oxide (NO). The nitric oxide is then released back into the system. Nitric oxide is a molecule that our body produces to help its 50 trillion cells communicate with each other. This communication happens by transmission of signals throughout the entire body. Additionally, nitric oxide helps to dilate the blood vessels and improve blood circulation.
“Low-energy photon irradiation in the near-IR spectral range with low-energy lasers or LEDs positively modulates various important biological processes in cell culture and animal models. Photobiomodulation is applied clinically in the treatment of soft tissue injuries and accelerated wound healing. The mechanism of photobiomodulation by red to near-IR light at the cellular level has been ascribed by research institutions to the activation of cellular mitochondrial respiratory chain components, resulting in a signaling cascade that promotes cellular proliferation and cytoprotection.
Research indicates that cytochrome c oxidase is a key photo-acceptor of irradiation in the far-red to near-IR spectral range. Cytochrome c oxidase is an integral membrane protein that contains multiple redox active metal centers. Additionally, it has a strong absorbency in the far-red to near-IR spectral range detectable in-vivo by near-IR spectroscopy.
Additionally, photobiomodulation increases the rate of electron transfer in purified cytochrome oxidase, increasing mitochondrial respiration and ATP synthesis in isolated mitochondria, and up-regulating cytochrome oxidase activity in cultured neuronal cells – leading to neuroprotective effects and neuronal function.
In addition to increased oxidative metabolism, red to near-IR light stimulation of mitochondrial electron transfer is known to increase the generation of reactive oxygen species (ROS). ROS functions as signaling molecules, providing communication between mitochondria and the nucleus.”
 – Proc Natl Acad Sci U S A. 2003 Mar 18; 100(6): 3439–3444.