Investigation: How Phototherapy Combats Neuropathic Pain

Investigation: How Phototherapy Combats Neuropathic Pain

Researchers have been looking more closely at the non-invasive and effective use of low-level laser therapy to treat neuropathic pain, particularly in people with diabetes.  They found that as diabetes progressed, the structure of the sciatic nerve’s myelin sheath changed.  And, after four sessions of laser treatment  the myelin had almost completely recovered.

Recent studies performed at the University of São Paulo’s Biomedical Science Institute (ICB-USP) in Brazil helped elucidate the mechanisms behind the effect of low-level laser therapy.

“We tested laser therapy in different rat neuropathy models, and behavioral responses improved in all of them,” said Professor Marucia Chacur, the principal investigator. “One of the beneficial effects observed was myelin sheath recovery. The myelin sheath is a lipid layer that covers the axon and acts as electrical insulation to assist nerve impulse propagation.”

The following details were made in a press release from the ICB-USP:

The treatment in a model of diabetic neuropathy, one of the most common chronic and incapacitating complications of diabetes was tested. The problem occurs when the disease is not properly controlled and excessive amounts of blood sugar cause oxidation of the myelin sheath, damaging the structure of peripheral nerves. As well as causing pain, this degenerative process impairs communication among neurons and can even lead to amputation of the lower limbs.

To induce a condition similar to type 1 diabetes, the researchers injected the rats with streptozotocin (STZ), a chemical that destroys the insulin-producing beta cells of the pancreas. In this model, the animals became diabetic approximately one week later.

“We began the treatment after 45 days, when the neuropathic condition was well-established and had become chronic,” Chacur said. “We used a 904-nanometer laser, which can penetrate deep into tissue.”

The degree of pain was evaluated before and after the start of treatment by behavioral tests such as the von Frey hair test, in which nylon filaments of different thicknesses are pressed against the rat’s paw. Each filament represents a force in grams and indicates the pressure tolerated without signs of discomfort. There are similar tests that use thermal and mechanical stimulation.

“We plan to apply the technique to humans, so we used similar therapeutic protocols,” Chacur said. “We initially scheduled ten sessions of phototherapy applied to the thigh every ten days, each lasting one minute, but we observed an improvement shortly after the fourth session and sacrificed the rats to analyze their sciatic nerves.”

With the aid of a transmission electron microscope, the researchers found that as diabetes progressed, the structure of the sciatic nerve’s myelin sheath changed. After four sessions of the treatment, however, the myelin had almost completely recovered.

“The condition of the nerve practically returned to baseline levels after treatment. We’re now continuing the study by analyzing protein expression and the release of inflammatory cytokines to understand exactly what’s happening,” Chacur said.

In another study, treatment again focused on the sciatic nerve, but the injury was induced by compression to simulate what happens in patients with spinal stenosis or disc herniation.

“The nerve was ligated and kept compressed for two weeks until the injury became chronic. Phototherapy began on the 14th day,” Chacur explained. “Shortly after the second session, we observed a behavioral improvement, which persisted until the end of the treatment.”

After the tenth session of phototherapy, the animals were sacrificed for analysis of the dorsal root ganglion, a cluster of nerve cell bodies located in the posterior region of the vertebrae along the spinal cord and conveying sensory and motor information.

The researchers used immunoblotting to scan the dorsal root ganglion for the presence of astrocytes, star-shaped cells that play an active role in brain function and inflammatory responses.

“Astrocytes are the first type of cell to migrate to the site of a nerve injury or inflammatory process,” Chacur said. “They’re like a sort of macrophage for the central nervous system, the first line of defense.”

The analysis showed smaller numbers of astrocytes in rats treated with laser therapy than in untreated rats.

“These cells release several inflammatory mediators, including interleukin-1 (IL1), tumor necrosis factor alpha (TNF-α) and glutamate. These mediators in turn trigger the release of other inflammatory substances. We believe the laser curtails this chain reaction as if it were anti-inflammatory medication, by reducing the migration of astrocytes to the site of the injury,” Chacur said.

The next step is to measure the concentration of each inflammatory substance separately, she added. The third model used to test low-level laser therapy focused on orofacial pain. In this model, a lesion was induced by crushing the inferior alveolar nerve, one of the branches of the trigeminal nerve responsible for innervating the face.

“This type of injury can occur during extraction of a wisdom tooth, for example. Many dentists are using low-level laser therapy for patient pain relief,” Chacur said.

Phototherapy began two days after the nerve was injured. An improvement in pain-related behavior was observed after two sessions and persisted throughout the treatment, which comprised ten sessions (one every two days).

The animals were sacrificed, and then Western blotting was used to analyze the treated tissue for the presence of certain proteins.

“We set out to understand the mechanisms and mediators involved because we believed phototherapy could be used in association with pharmacological treatment because it acts via a different pathway. In this way, it may be possible to reduce the drug dose and mitigate the systemic effects of the treatment,” Chacur said.

The results suggest that all three models of neuropathic pain studied share a common mechanism involving myelin sheath regeneration and reduced astrocyte migration to the site of the lesion, she added.

“Evidence in the literature also suggests an effect on mitochondria. The laser apparently facilitates the flow of calcium in these organelles, boosting production of ATP [adenosine triphosphate, the body’s cellular fuel] and leading to enhanced healing as well as the release of mediators that assist remodeling. In future studies, we plan to investigate this effect on mitochondria more thoroughly,” Chacur concluded.

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Jean Price

Some laser treatments are already available now, and widely used for professional athletes! Yet the the treatment is not covered by insurance. And I’m not sure of the potency of the lasers now used. It would be interesting to see how effective this type of treatment is for those with long standing nerve damage and multiple muscle and myofscial issues from years of pain. It makes me wonder if there is a point of no return for these therapies to be able to help…since two week old damage has to be a lot different to work with than damage that has occurred years ago and even still continues to progress. The body’s responses are complex, and each person is different…it seems it will take a thorough understanding of what lasers do for pain for this to be accepted as a mainstream therapy…and used! Right now, as far as I know, only chiropractors use them and also those who provide concentrated sports medicine for professional athletes!

I’m guessing we will have the same issues here as we have now for other adjunct therapies, IF it does become available to us humans…expense, availability, insurance coverage, the effectiveness of helping many types of pain, and also if there is a point when the benefit actually will plateau or be “too late” to affect relief. A lot to consider…especially when so many are hurting NOW!!

Eve Rios

Maybe this treatment could help CRPS?

Kathy C

This is really interesting. These Lazer treatments, at the very least feel really good. They have made claims before about long term benefits, though it is hard to tell if that was anything more than advertising. Unlike a lot of other “treatments” Red Light Lazers feel good and are very soothing. So even if they have no long term benefits, the short term, benefits are worth it. Unfortunately Insurance does not cover these treatments, and they apparently have to be done by someone trained to do them. This Article appears to be Scientific, they looked at the Myelelin Sheaths on the nerves. These are a measurable Indicator, unlike many of those “Studies” that get reprinted by Corporate Media. So many of these Articles contain, Biased unscientific “Conclusions” that are overstated in the Title. In this case they used something measurable, the Myelin Sheathing. So many of these “Articles” are based on Non Scientific, overstated Observations where a Biased “Researcher” Makes claims that can not be determined from their limited Study on rats. They claim they can tell if a rat is in pain, perhaps, but drawing a conclusion, and then having that “Study” go viral because it has an Appealing Conclusion, is unscientific and creates confusion. So many of these Studies are done in other Countries, which should have us asking why not the U.S. That is the elephant in the room. The US spends more on Research, and every aspect of healthcare, with the worst outcomes of any developed nation. Pain and “Back Pain” are big parts of our spending on Healthcare, after Heart Disease and Diabetes. Our “Research” has fallen behind, and when we look at certain topics, like “Pain” there is a pattern. The Pattern is virtually no “research.” The Research has been directed to obfuscate pain. Even some phrases like “Failed Back Surgery” have been removed from the language. They keep repeating useless “Studies” about the “Mind Body Connection,” even after these have been repeated, and show no meaningful connection, they repeat them. These Studies were very helpful for the Industries. the Other “Studies” they do in various areas of Healthcare, are the ones that try to prove a a Product offers more than a Placebo effect on various Conditions. Our Research is Directed by the Industries that profit from them. We are now in the Fact Free Era. If the Research was directed at the most debilitating conditions, or the most expensive, there would be a lot more research on Pain. The “Research” has been directed towards finding ways to deny that pain exists. Virtually every Article that has been pickled up my Corporate Media either reiterates the “Mind Body Connection”, were they try to have the observations of Biased Observer, a Psychologist who is already invested in the Outcome, deny the existence of pain or mislead us into the false assumption that we can ignore pain, and attribute it to “other factors.” Physicians and their employers, seeking to avoid liability and gain more deniability… Read more »

gittel nadel

is there research being done or is there laser therapy for spinal injuries in use?

i have several severe pain issues and medical marijuana isn’t the answer in the long run nor effective enough. opioids are not a life either.