Photorelaxation or photo-vasorelaxation, is described as the relaxation of
blood vessels in response to light. This has been reported for around sixty years, it was never described, pursued or explained. It was serendipitously rediscovered by Dr. Gautam Sikka and his mentor Dr. Dan Berkowitz at
Johns Hopkins University in
Baltimore
Baltimore ( , locally: or ) is the most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic, and the 30th most populous city in the United States with a population of 585,708 in 2020. Baltimore was d ...
, USA, and along with his team he not only elucidated the mechanism but is trying to harness light for treatment of
cardiovascular disease
Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
.
The research by Sikka ''et al'' concluded that there light-sensing receptors,
melanopsin
Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene ''Opn4''. In the mammalian retina, there are two additional categories of opsins, both involved in the for ...
receptors, are present in blood vessels and mediate wavelength specific, light-dependent vascular relaxation. This photorelaxation signal transduction involves
cyclic guanosine monophosphate (cGMP) and
phosphodiesterase type 6, but not cGMP-dependent protein
kinase
In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule don ...
or Protein Kinase G (PKG). Furthermore, it is regulated by Beta adrenergic receptor kinase type 1 (βARK or BARK) also called G protein coupled receptor kinase 2 (GRK2), and involves vascular hyperpolarization, and this receptor pathway could be targeted for wavelength-specific light-based therapy in the treatment of diseases that involve altered vasoreactivity.
References
{{Reflist
Angiology
G protein-coupled receptors