Photobiomodulation Therapy (PBMT)

Photobiomodulation (PBM) therapy, also known as low-level laser therapy (LLLT), is a non-invasive healing light therapy that uses red and near infrared light to treat pain, reduce inflammation, and improve tissue repair. A lot of biological mechanisms has been proposed that are associated with promoting physiological change through PBMT. Near-infrared light in the 650-1000 nm wavelength range with a sufficient power density has been largely associated with PBMT. According to the first law of photobiology, for any photochemical reaction to take place within a biological tissue, the absorption bands of the chromophores present within the tissue must be able to absorb photons.

Cytochrome C oxidase (CCO) is the terminal enzyme (unit IV) in the electron transport chain situated in the outer mitochondrial membrane. During PBM, the mitochondrial chromophore CCO increases ROS generation, which in turn activates the PI3K/Akt pathway, while the effector enzyme, adenylyl cyclase, converts ATP to cyclic AMP (cAMP). cAMP could either activate pKA and RAS which further leads SIRT and ERK signaling to promote cell survival, inhibit inflammatory processes, and apoptosis. In the damaged cells, CCO, the protein that serves the purpose of end-point electron acceptor, becomes inhibited by non- covalent binding of nitric oxide (NO). When damaged cells are irradiated with low level NIR light, the photons in it will be absorbed by CCO leading to an increase in mitochondrial adenosine tri-phosphate (ATP) and release the nitric oxide which diffuses into the blood, increasing local blood flow and vasodilation.

An increase in mitochondrial membrane potential (MMP), ATP, cyclic adenosine monophosphate (cAMP), and NO is necessary for PBM to exert its effects. This is because CCO is activated in this process thereby catalyzing the reduction of oxygen to water. The activation of specific cellular networks requires NO as a signaling agent. PBM boosts NO production by cleaving metal compounds in cytochrome c and/or increasing cytochrome c levels. It is thought that PBM stimulates mitochondria-mediated cellular processes in damaged or dysfunctional tissue, leading to a broad variety of therapeutic effects.

Through continuous exposure of photons for a reasonable amount of time, a brief burst of reactive oxygen species (ROS) occurs in the mitochondria and activation of redox-sensitive genes, and related transcription factors including NF-κβ happens. The PBMT stimulates gene expression for cellular proliferation, migration, and the production of anti-inflammatory cytokines and growth factors. The role PBM plays in the mitochondria has brought it to the forefront as a potential therapeutic candidate in the treatment of neurodegenerative diseases, which are currently incurable due to their complex and multifaceted nature. Studies have also demonstrated the neuroprotective efficacy of PBM in several models of neurodegenerative diseases.

The application of laser therapy favors angiogenesis, collagen synthesis, mitochondrial ATP production, cytokines and growth factors synthesis, in addition to inducing cell proliferation and differentiation. PBMT on diabetic wound healing using 810 nm (IR) wavelength and 650 nm (Red) light with a fluency of 60 J/cm2 could lead to a significant increase in fibro blast proliferation and collagen synthesis. Additionally, PBMT has anti-inflammatory, analgesic and bio-stimulating effects, acting mainly in the initial stages of tissue healing.

Photobiomodulation Therapy (PBMT): What is it, how does it work and what can it do for you? By Juanita J. Anders, Ph.D., Professor of Anatomy, Physiology, and Genetics and Professor of Neuroscience at Uniformed Services University.