Types of Hair Loss and Treatment Options, Including the Novel Low-level Light Therapy and its Proposed Mechanism

Mahyar Ghanaat, MD


South Med J. 2010;103(9):917-921. 

In This Article

The Mechanism of LLLT

There are several theories that explain the mechanisms of LLLT: cytochrome c oxidase-mediated increase in adenosine triphosphate (ATP) production, the singlet oxygen hypothesis, the redox properties alteration hypothesis, and nitrous oxide (NO) hypothesis.[26] Cytochrome c oxidase is part of the respiratory chain that ultimately results in ATP production. It is hypothesized that the light absorbed by this moiety may ultimately result in increased ATP production, which may alter cell metabolism.[26] This is a concept similar to photosynthesis in plants. Singlet oxygen hypothesis stems from the fact that radiation used in high doses to kill cancer cells causes a paradoxical cell proliferation in low doses.[26] The redox properties alteration hypothesis proposes that enzymes other than cytochrome c are induced to produce superoxide anion.[26] The NO hypothesis proposes that LLLT may uninhibit the effect of NO on cytochrome c.[26]

There have been several studies to evaluate the effects of LLLT. Increase in ATP synthesis, proton electrochemical potential, and oxygen uptake have all been shown in rat liver mitochondria.[26,29,30] LLLT has been shown to increase procollagen synthesis in fibroblasts.[25,26] However, numerous human and animal studies have shown inconsistent results, mainly due to lack of coherence in protocols.[25] Some also relate the variability in results across studies to the fact that the effect of LLLT depends on the physiologic state of cells.[31] One study reported a failure in treatment of AA.[32] However, the researchers used a small dose (630 nm at 37 J/cm2 for 7.5 min) only once a month.[32] In addition, they reported successful treatment in beard AA after only three sessions in three patients.[32] Sobanko and Alster[25] propose that better understanding of the mechanisms of LLLT will help resolve some of these questions. Some negative results are also attributed to poor design and use of very low doses.[33] Unresolved questions regarding the properties of light being used include: wavelength, laser vs noncoherent, dose, pulsed vs continuous wave (CW), and polarization status.[26] All of these conditions and cell culture condition will determine the effect of LLLT.[33] Usually wavelengths in the 600-1000 nm range and powers from 5–500 mW are used.[25] Evans and Abrahamse[33] studied the effect of light with wavelengths of 638.2, 830, and 1064 nm at 5, 10, and 16 J/cm2 intensities to compare control vs wounded fibroblasts. They found the most stimulatory effect on wounded fibroblasts using 5 J/cm2 of 632.8 nm light.[33] They also found the dose of 16 J/cm2 to cause DNA damage and reversible cell damage (in most instances).[33] Similarly, in assessing free radical formation, Haywood et al[34] found no detectable free radicals after exposure of human skin biopsy to 694 nm light at 11–14 J/cm2 in 0.9 ms pulses using electron spin resonance spectroscopy.


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