A Novel Mitochondrial Signaling Pathway Activated by Visible-to-near Infrared Radiation is one of Tiina Karu's big papers, which basically outlines the effect that laser irradiation has on cellular metobolism. I quote her: "The comparative analysis of action spectra allows the conclusions that first, CuA and CuB chromophores of cytochrome c oxidase could be involved as photoacceptors and second, various signaling pathways (reaction channels) between cytochrome c oxidase and cell attachment regulation are at work."
Absorption Measurements of Cell Monolayers Relevant to Mechanisms of Laser Phototherapy: Reduction or Oxidation of Cytochrome c Oxidase Under Laser Radiation at 632.8 nm is Tiina Karu's BIG DOG paper. I quote her again: irradiation "causes either a (transient) relative reduction of the photoacceptor, putatively cytochrome c oxidase, or its (transient) relative oxidation, depending on the initial redox status of the photoacceptor." This is exactly the back-and-forth handshaking mechanism addressed in the my literature. Basically, cytochrome c oxidase undergoes a cyclic process of oxidation and reduction, and the absorption by a photon can stimulate the progression of this cycle. In this particular study she used a HeNe laser at 632.8 nm on cell monolayers, but most of her literature (including the references above) concludes that there are several peaks in absorption of this enzyme, most of which is in the NIR.
Characterization of the near infrared absorption spectra of cytochrome aa 3 and haemoglobin for the non-invasive monitoring of cerebral oxygenation is the reference from which I extracted the data for our absorption chart for cytochrome and hemoglobin. This paper does not address the mechanisms of action of laser therapy and so is not skewed by its practitioners. Instead, this gives a good historical reference on how people, specifically neurologists and neurosurgeons, started to use NIR radiation, as well as clean, unbiased data about in vivo absorption of the principal chromophores in the body.
Mechanisms of Low Level Light Therapy is Michael Hamblin's (Harvard) paper. This is probably the most accurate and detailed review of the mechanisms of laser therapy. Most of the points addressed above, as well as many others are covered in this paper. It is important to note that the term "Low Level" is a relative term, originally devised to delineate therapeutic from surgical devices. Class III laser companies tend to skew this definition to exclude Class IV modalities, but even in Dr. Hamblin's suggested dose parameters he defines a relevant therapeutic dose on the order of 10-50 Joules/cm2, which is exactly the range of doses that our protocols have been designed to deliver AT THE DEPTH OF THE AILMENT INSIDE THE PATIENT.
Near-Infrared Time-Resolved Optical Absorption Studies of the Reaction of Fully Reduced Cytochrome c Oxidase with Dioxygen shows more data on the absorption spectrum of the different oxidation states of cytochrome c oxidase. Remember that the reduction of dioxygen (O-2) to water, the process that is fully measured and documented in this study, is exactly the process that creates ATP, chemical energy.
Targeted Increase in Cerebral Blood Flow by Transcranial Near-Infrared Laser Irradiation
supports the first mechanism we maintain, which is the increase of local circulation from laser irradiation. They showed that with an 808 nm beam, you can get significant increases in cerebral blood flow in vivo. Notice they used up to 3.2 Watts/cm2 on mice to penetrate the skull. This also supports the use of Class IV lasers on the basis of penetration, since being larger creatures, humans will require higher power for irradiation to penetrate in useful treatment times. Again, this is unbiased research where no mention of brand name is made.
