Photobiomodulation

The light energy used in PBMT is absorbed by cells, triggering a series of biochemical reactions that improve cellular function and tissue healing. For this reason, it can be applied to various tissues in the body, including the skin, muscles, joints and organs, to reduce inflammation, promote tissue repair and alleviate pain; consequently, it is used in a variety of medical applications. Current research is actively focusing on PBMT to better understand its potential in the treatment of various incurable diseases; research has shown that PBMT has promising therapeutic effects in combination therapy.

The concept of pulsation and continuity in light sources:

Most light sources (such as the light bulbs in your home and the screen on which you are reading this post) emit continuous-wave light, i.e. at a constant intensity, which appears unchanging to the naked eye.

Pulsed emission, on the other hand, involves the light source switching on and off many times per second, giving it its characteristic ‘flickering’.

A primary advantage of pulsing is improved heat management. Essentially, the ‘off’ period during pulsing allows the laser to cool down and, compared to a continuous laser, generates less heat at a given intensity level.

With pulsed light, it is possible to safely deliver incredible amounts of energy. In one study, for example, researchers shone light on the heads of rats using both continuous and pulsed light at a peak intensity of 750 mW/cm² – over 100 times the intensity of commonly used devices on the market. The brains of the rats exposed to continuous light were fried by the heat and exhibited severe neurological deficits. In contrast, no neurological or other tissue damage was found in the rats exposed to pulsed light.

Of course, this is an extreme example: both continuous and pulsed LLLT have repeatedly been shown to be 100% safe, as they utilise only a fraction of the energy used in this study, meaning that any heat-related adverse effects are limited to mild discomfort. However, the principle remains: pulsed light can be used to deliver greater amounts of energy, deeper into the tissues, with greater comfort for patients.

A brief history of PBM

The history of using light to treat diseases dates back over 100 years. Electric light therapy, heliotherapy and low-level laser therapy have led to what we now call photobiomodulation therapy (PBM). PBM has traditionally been used for

wound healing, pain and inflammation. However, in recent years, interest has grown in applying this method to the treatment of brain disorders. PBM uses red or near-infrared (NIR) light (600–1100 nm) from lasers or light-emitting diodes to stimulate healing, protect tissues from cell death, enhance mitochondrial function, improve blood flow and tissue oxygenation, and stimulate stem cells. Progress has been made in identifying chromophores and cellular photoreceptors, including mitochondria and, specifically, mitochondrial respiratory proteins and TRP ion channels. Results from studies in small animal models, other animals, and human trials demonstrate that PBM can also act to reduce swelling, redness and erythema, increase intrinsic cellular antioxidants, decrease inflammation, protect cells from apoptosis, and modulate the state of microglial activation. The administration of PBM to the head is beneficial in cases of both acute and chronic traumatic brain injury. Furthermore, PBM has been shown to be

effective in the complementary treatment of neurodegenerative diseases (Alzheimer’s and Parkinson’s) and psychiatric disorders (depression, anxiety and opioid dependence). Another application is cognitive enhancement in healthy individuals.

The mechanism of photobiomodulation (PBM) at the cellular level has been attributed to the activation of components of the mitochondrial respiratory chain, resulting in the stabilisation of metabolic function and the initiation of a signalling cascade that promotes cell proliferation and cytoprotection.

PBM acts through the absorption of photons by photoacceptors in the target tissue. Once absorbed, secondary cellular effects include increased energy production and changes in signalling pathways such as reactive oxygen species, nitric oxide and intracellular calcium.  Cellular changes occur through the activation of transcription factors, leading to the modulation of protein synthesis, proliferation and, ultimately, improved cell survival.

Recent scientific publications have demonstrated the benefits of PBM on the gene expression of CCO (cytochrome c oxidase) in injured, diabetic and ischaemic cells, highlighting a significant stimulation of the transcription of genes involved in the electron transport chain, a critical mitochondrial pathway used to convert glucose and oxygen (O2) into energy. Adenosine triphosphate (ATP) is one of the main forms of stored energy produced in cells. PBM triggers the activation of various genes involved in energy metabolism and oxidative phosphorylation, thereby stimulating increased ATP production, which regulates other cellular processes, leading to the normalisation of cellular functions.

Further scientific studies:

…have revealed that in studies involving metabolically highly active cells such as nerve tissue, unfavourable results were more commonly attributed to excessive dosage rather than insufficient dosage. In the current research, nerve recovery was significantly accelerated using an energy density of 6 J/cm². This finding supports the notion of a ‘biphasic dose-response effect’ in PBMT, in which positive biostimulation responses are activated at doses below 10 J/cm², whilst inhibitory responses are prominent at doses above 20 J/cm². However, the concept of a ‘window effect’ has been extensively examined in the existing literature, and the results align well with established data in this field.

The results obtained demonstrated elevated concentrations of nerve growth factor (NGF) in rats undergoing PBMT treatment, compared to the control group that did not receive PBMT. This increase in NGF levels corresponded to a more rapid restoration of neurosensory function. Similarly, a multitude of other studies, including both controlled and uncontrolled trials, have highlighted the favourable subjective improvements attributed to PBMT in various clinical contexts, such as perioral lesions, recovery following musculoskeletal surgery, and the promotion of osteogenic differentiation. In summary, PBMT has a positive influence on various systems, specifically the nervous, musculoskeletal and epithelial systems.

Photobiomodulation (PBM) involves the use of low-power-density red and/or near-infrared light to produce a beneficial effect on cells and tissues. PBM therapy is used to reduce pain, inflammation and oedema, and to regenerate damaged tissues such as wounds, bones and tendons. The primary site of light absorption in mammalian cells has been identified as the mitochondria and, more specifically, cytochrome c oxidase (CCO). It is hypothesised that inhibitory nitric oxide may be dissociated from CCO, thereby restoring electron transport and increasing the mitochondrial membrane potential. Another mechanism involves the activation of light-sensitive or thermoregulated ion channels.