The primary target of laser therapy and photobiomodulation is the cytochrome C complex which is found within the mitochondria. Cytochrome C is a vital component of the electron transport chain that drives cellular metabolism. As light is absorbed, cytochrome C is stimulated leading to increased production of ATP. ATP is the molecule that facilitates energy transfer within the cell thus leading to cellular healing through increased protein synthesis and cellular proliferation.
In addition to ATP, laser therapy or photobiomodulation also produces free nitric oxide and reactive oxygen species. Nitric oxide is a powerful vasodilator and an important cellular signaling molecule involved in many beneficial physiological processes. Reactive oxygen species have been shown to affect many important physiological signaling pathways including the inflammatory response.
Together, the production of these signaling molecules has have been shown to induce growth factor production, to increase cellular proliferation and motility, and to promote extracellular matrix deposition and pro-survival pathways. Outside of the cell, nitric oxide signaling drives vasodilation which improves microcirculation in the damaged tissues thus delivering oxygen, vital sugars, proteins, and salts while removing cellular by-products and waste. As a result, increased cellular healing is observed, as well as a reduction in pain.
The recent development of higher power, Class 4 lasers, allows the us, the veterinarian, the ability to more efficiently deliver adequate therapeutic doses of photons deep into tissues to reduce pain, reduce inflammation, and accelerate healing (Class 3 and 4 lasers carry FDA approval for these three uses).