Hello, and welcome to episode three of the Focal Allied Health Practitioner Podcast. In this episode what we’re going to be doing is we’re going to dive into a thing which I’ve been doing quite a bit of reading about recently, and that is photobiomodulation. Now this used to be referred to as a thing called low level laser therapy, and then as things developed a little bit and became alternatives out there apart from using lasers, the term low level light therapy then started to be used. And so you may actually see it referred to as LLLT, the abbreviation shorting for low level laser therapy or low level light therapy. And what we’re going to do is we’re going to actually discuss photobiomodulation, we’re going to look at what it is and how it works, and just going to dive into that a little bit more and pull it apart and hopefully give you guys some good understanding of the mechanisms behind PBM, as I’ll refer to it as we move forward.
Okay, so like I said, it used to be referred to as low level light therapy, and then the term photobiomodulation started to become used because of the wide number of activations, or sorry, applications that PBM has been found to have. Now when I was at university I really didn’t think much of laser therapies, but that was about 25 years ago, and the technology wasn’t anything like what it is today. These days it’s become extremely widespread and there’s many, many options available, there’s very high tech laser units which will cost many tens of thousands of dollars, and you can also get things off eBay which use LEDs of certain wavelengths, and so forth, and it’s entirely possible that they all have potential therapeutic effects.
Traditionally things such as lasers were what were used, and lasers are quite unique, obviously, in that the light wave are very coherent, and as a consequence they can deliver quite a degree of energy into the tissues. However, non-coherent light sources, such as LEDs, have been found to also have an effect as well. It may well be that because they’re of a slightly lower energy they may actually be slower to have their effects, which if you’re running a busy clinic may well be a bit of an issue, and so therefore you want to get through your patient visits as quickly as you possibly can for the most effective use of your time, in which case using LED sources may not be the ideal way to do it and you may decide that lasers are more appropriate. But there certainly is quite a lot of variety that is available there these days.
Now, PBM has been used for a wide variety of conditions, people use it for tendinopathies, they use it for scar tissue. I’m personally very interested in it for its effects on brain function, like I said, but however, it can be used on many other tissues. Now it’s thought that the light with PBM can penetrate several centimetres depending upon the tissue that is being irradiated and the intensity of the light. Now interestingly wavelengths in the 600 to 700 nanometre bandwidth seem to be better for superficial tissue, and this is in the visible light spectrum, so this will be a dark, deep red sort of colour in that 600 to 700 nanometre wavelength.
Whereas your 780 to 950 nanometre wavelengths, they penetrate better into deeper tissues, and they’re getting into the near infrared spectrum. So when you actually look at those LEDs, or lasers, or whatever, not that you should look directly into a laser, because it can damage your eyes, but even so, with very intense LEDs as well, but those near infrared wavelengths, they’re obviously getting outside the visible spectrum, so you may well want to educate your patients about the fact that you’re shining this light on them and they can’t actually see anything, as to what’s actually going on there.
Now there’s a number of proposed mechanisms behind PBM, and the exact effects are going to depend upon the wavelength of light that are used. Now we’re going to focus on the red and near infrared effects of them, so that fits in with those wavelengths bands that I was talking about earlier, but I believe some people are using things like blue light for skin conditions, and so on, that’s not really something that I’ve investigated a great deal, but if that’s something that fits in with you, then do some further reading on that, I’m sure you’ll find plenty of material out there. Certainly the material seems to be increasing dramatically, and there’s a number of good systematic reviews that you can look at in that way, and even narrative reviews are out there as well.
Now let’s dive into the mechanism. So one of the primary mechanisms appears to be due to the activation of cytochrome c oxidase in the mitochondria of the cells. Now cytochrome c oxidase is part of the respiratory chain in mitochondria, and hence it’s used for energy production within the cell. Now cytochrome oxidase, cytochrome c, beg your pardon, oxidase can be reversibly deactivated by nitric oxide, and when it’s deactivated it inhibits energy production. Now when you’re looking at nitric oxide, that’s a very interesting chemical. In the mitochondria what it will do is it will actually bind to the cytochrome c oxidase, and like I said, will block the energy production, but there can be a number of ways that nitric oxide is produced.
So there’s a couple of very short term enzymes that tend to be reversible in their function, and so on, that will produce a nitric oxide, but when tissues are damaged, so when you’ve got inflammation going on, you get a more persistent form of the enzymes which produce nitric oxide, and so they can have the effect of dampening down energy production within the cell. And so it’s quite possible that some of the reparative effects of photobiomodulation, particularly in acute trauma, may actually be due to the decoupling of the produced nitric oxide, and thereby allowing energy production to resume, or a higher level of energy production to resume, within the cell, which surely is going to be a better thing when you’ve got aerobic metabolism, good support of energy metabolism within the cell, that’s generally a better outcome for cellular structures. Interestingly, the released nitric oxide also causes vasodilation and improves lymphatic flow, so it dilates the lymphatic structures as well, so you’re going to get better tissue perfusion and better lymphatic drainage from the release of nitric oxide by photobiomodulation. So that’s pretty interesting stuff, I reckon, that’s pretty great.
Now there’s also an increase in reactive oxygen species, and that is basically molecules, so these are things like free radical molecules, basically. Now your initial thought might be, well, hang on, why do we actually want to be increasing the number of free radicals within the tissue and potentially causing tissue damage and so forth? What happens is that the short term increase in free radicals actually provokes cytoprotective antioxidant and anti-apoptotic mechanisms within the cell. The consequence of this is that you actually improve the cell’s ability to deal with reactive oxygen species and free radicals, et cetera, and as a consequence you actually improve the stability of the cell.
Now, interestingly, some people find that if they use PBM too long it can actually irritate tissues and can make them worse, and I wonder whether some of the irritant type effects of photobiomodulation is actually due to increased production of these reactive oxygen species over a prolonged period of time, which actually ends up having a damaging effect, or a more marked damaging effect on the cell, and as a consequence I reckon that may well be one of the underlying mechanisms. Just my guess, but it would certainly make sense to me if that was the case.
Now other wavelengths are also effective, suggesting that there are other mechanisms at play, such as light sensitive calcium channels as well. So the mechanisms that we’ve been talking about here with the cytochrome oxidase c and the nitric oxide, and so forth, are more associated with the 600 to 700 nanometre and the 760 to 940 nanometre wavelengths, and wavelengths outside of those bandwidths don’t tend to have the same effects in releasing those nitric oxide molecules. But as we said, other wavelengths are effective, so that suggests there are other mechanisms, and these light sensitive calcium channels may well be one of them. We know that increasing calcium levels within the cell tends to lead to stimulation of gene factors, so the transduction of genes, increased protein synthesis, et cetera, so that would potentially be another mechanism that could be going on there.
Now there’s also lasting effects, which is probably due to activation of signalling and transcription factors within the cell ending up resulting in changes in protein expressions, so you’re going to get more long lasting effects, or some long lasting effects with the photobiomodulation. So you can see that it has a number of potential mechanisms that could be underlying the effects that this modality is having upon the tissues.
Now, in terms of penetration into the tissues, in this brain the skull is clearly a barrier to the penetration there, and studies vary in their theorised penetration. Some people have been saying that it goes several centimetres into brain tissue, some people are saying, well it can’t really get through the skull at all, what are you talking about? But interestingly, some of the effects that people might be seeing with, in particular, brain function may actually be due to irradiation of the bone marrow, as they’ve found that actually irradiating the long bones can have similar effects in mice. So if they radiate the mice tibia with the photobiomodulation device, it can have similar effects to irradiating the brain on brain function, which is pretty amazing, really. So it may actually be due to not so much direct irradiation of the rain, but actually these effects that are mediated via bone marrow, and so forth, as well, so that’s rather interesting stuff, I reckon.
Now in our practises we’re using photobiomodulation for the treatment of traumatic brain injury, so concussion patients, and we’re also looking at cognitive disorders like Parkinson’s and Alzheimer’s disease. Now this doesn’t work for everybody, but the early research is very promising for these conditions, and this is particularly the case given the poor prognosis of things like Parkinson’s disease and Alzheimer’s, the good safety profile of photobiomodulation, and the distinct lack of alternative effective therapies of Parkinson’s disease and Alzheimer’s. So it may well be something that we’re going to see more and more of, and I know there are some people out there that are actually using homemade light hats in effect, in things like Parkinson’s disease and Alzheimer’s, and there’s anecdotal reports of improved function as a consequence of using these light hats. So watch this space, I’m sure we’re going to see increasing research and increasing products available around this type of thing.
Now with respect to dosage, there appears to be a dose response curve. So basically you will, with this dose response curve, it’s a bit of a bell curve in effect, where you increase the level of exposure and that then tends to lead to improving effects, but then you’ll reach a peak where further irradiation doesn’t lead to further improvements, but actually tends lead to a decreasing effectiveness with continued dosing. So you do need to be aware of that When you’re actually irradiating your patients with the, it sounds rather dangerous when you say irradiating, but when you’re shining the light on your patients you’re actually going to have this dose response curve.
And very interestingly as well, the tissues with higher number of mitochondria actually need a lower dose to produce effects. Now you could theorise that that may actually be due to the fact that there’s a certain number of photons that are going to go into the tissue, and if there’s not many mitochondria in there, you’re actually going to find that most of those photons are probably going to bounce around and they’re not really going to have a great deal of effect, and only a certain number of those photons are actually going to connect with cytochrome c oxidase within the mitochondria and therefore produce an effect.
Whereas if you have increased density of mitochondria you’ve got more mitochondria for the photons to run into, so therefore you may be actually producing an effect faster as a consequence of the higher number of mitochondria, so things like bone or muscle tissues, et cetera, where there’s high numbers of mitochondria, are going to need lower doses in order to produce an effect. Simply, I suppose, because if you continue to irradiate the high number of mitochondria, you’re going to release more of these reactive oxygen species, and therefore you’re probably more likely to end up producing detrimental effects, and so forth.
Okay, now unfortunately there’s a certain amount of trial and error in dosage, and it’s very difficult for me to give recommendations here, and so I’m not even going to try, because it’s going to vary considerably based upon your equipment. Some equipment, if you are using very high tech lasers, and so forth, you may actually not need a very long dose at all, whereas if you’re using a light pad that you bought off eBay for $30, or $100, or whatever, you may actually find that you need to be irradiating the tissues for 5, 10, 15 minutes, et cetera. It’s just going to vary depending upon the device that you’re using. And so there’s a certain amount of trial and error in dose, and if the manufacturers of the device can’t give you specific advice, then you’re going to need to just “experiment” and find out what works best with the particular device that you’ve got for particular conditions, and so forth.
So I’m going to wind up this podcast there, hopefully you found this one to be interesting. I’m hoping to potentially revisit this topic further down the track when we’ve looked into it even more, and maybe we’ve got even more clinical experience, we can talk in depth more about some of these interventions, and some of the conditions that we’re using it on, and so forth. In the next podcast I’m hoping to look at stress responses and how they actually will work with musculoskeletal conditions in particular, but other types of conditions as well, and there’s some really interesting research around that, and I’m really quite keen to dive into that a little bit more.
If there’s something in particular you’d like me to discuss, then feel free to pop it in the comments. I can’t promise that I’ll be able to do everything, there’s certain limits to my time and my expertise, but I’ll try and do that, and we can start discussing some of the stuff that you guys are particularly interested in. So thanks for your attention, and I will see you again soon.
Image credit: Ron Brown https://www.science.org/content/article/trials-begin-new-weapon-against-parkinson-s-light