- ROS are chemically active molecules (e.g., superoxide and hydrogen peroxide)
that are involved in cell signaling, regulation of cell cycle progression, the
activation of enzymes, and the synthesis of nucleic acid and protein. - ATP is stored in the cytoplasm and nucleoplasm of every cell, and directly
supplies the energy for the operation of essentially all physiological
mechanisms. - NO is a biological agent that dilates blood vessels. The NO molecules prevent
the muscles in artery walls from tightening, thereby preventing the walls from
narrowing. As a result, bloodflows more easily through the arteries, so that
blood pressure is reduced and the heart does not have to pump as hard.
The results of these processes are cell proliferation, growth factor production,
and an enhancement of cell motility (which describes the movement and energy
consumption of cells).
Among the clinical applications that have been examined for photobiomodula-
tion are the following [ 32 – 38 ]: - Physiotherapy and rehabilitation clinics: alleviate acute or chronic pain, reduce
neck and lower-back pain, improve mobility - Dermatology: treat edema (swelling of body tissues), promote burn healing, and
treat dermatitis - Surgery: promote wound and tissue healing, alleviate post-operative pain
- Neurology: treat conditions related to stroke, traumatic brain injury, degenera-
tive brain disease, spinal cord injury, and nerve conditions - Rheumatology: treat arthritis and other rheumatic diseases
- Dentistry: treat inflamed oral tissues, promote ulceration healing, improve bone
formation and healing - Sports medicine: treat sports injuries such as sprains and strains, muscle sore-
ness and fatigue, and tendon injuries - Veterinary medicine (e.g., dogs and racehorses): reduce swelling, increase
mobility after leg injuries, promote wound and tissue healing.
6.5.2 Photochemical Interaction
Whereas photobiomodulation processes are based on a photochemical effect that
uses low irradiances to promote tissue healing and cell growth, an increase in the
irradiance results in a different photochemical light-tissue interaction methodology
that is used to destroy unwanted, cancerous, or diseased cells. For example, in
processes such asphotodynamic therapy(PDT) the interaction of light with pho-
tosensitive drugs produces reactive oxygen species that cause necrosis (cell death)
or apoptosis (programmed cell death). PDT is a treatment modality for a wide range
of diseases and skin conditions that involve fast-growing or pathological cells or
6.5 Light-Tissue Interaction Mechanisms 177