LLLT - an overview

LLLT can include light emitting diodes (LED), lamps and fluorescent tube devices. This form of therapy appears to help the inflammation of rosacea. LED is one example of a gentle form of light which can be used. There are also infra-red and near infra-red forms of light therapy being reported as effective. Drop by here to find out the latest about this emerging treatment area.

LLLT - an overview

Postby Twickle Purple » Mon Mar 10, 2008 4:36 am


Research indicates that many acute and chronic conditions can be improved or eliminated through phototherapy, including:

* Arthritis
* Migraine Headaches
* Lower Back Pain
* Repetitive Injuries (RSI)
* Carpal Tunnel Syndrome (CTS)
* Tendonitis
* Fibromyalgia
* Sprains and Strains
* Post-Operative Pain
* Tennis and Golfer's Elbow
* Temperomandibular Joint ( TMJ )
* Musculoskeletal Conditions and Pain Management
* Injury and Soft Tissue Healing
* Postoperative Wounds
* Soft Tissue Swelling
* Burns
* Pressure Ulcers
* Herpes Simplex
* Acne
* Inflammatory Skin Conditions
* Rosacea
* Non-healing Wounds
* Hematomas

Light therapy has been shown in over 40 years of independent research worldwide to deliver powerful therapeutic benefits to living tissues and organisms. Both visible red and infrared light have been shown to effect at least 24 different positive changes at a cellular level.

Visible red light, at a wavelength of 660 nanometers (nm – 1 nanometer is equal to one billionth of a meter), penetrates tissue to a depth of about 8-10 mm. It is very beneficial in treating problems close to the surface such as wounds, cuts, scars, trigger and acupuncture points and is particularly effective in treating infections. Infrared light (904nm) penetrates to a depth of about 30-40 mm which makes it more effective for bones, joints, deep muscle, etc.

The diverse tissue and cell types in the body all have their own unique light absorption characteristics; that is, they will only absorb light at specific wavelengths and not at others. For example, skin layers, because of their high blood and water content, absorb red light very readily, while calcium and phosphorus absorb light of a different wavelength.

Although both red and infrared wavelengths penetrate to different depths and affect tissues differently, their therapeutic effects are similar. Depth of penetration is defined as the depth at which 60% of the light is absorbed by the tissue, while 40% of the light will continue to be absorbed in a manner that is less fully understood.

Treating points with Light can have a dramatic effect on remote and internal areas of the body through the stimulation of nerves, acupuncture and trigger points that perform a function not unlike transmission cables.At this time, research has shown no side effects from this form of therapy.

    Occasionally, one may experience an increase in pain or discomfort for a short period of time after treating chronic conditions. This occurs as the body reestablishes new equilibrium points following treatment. It is a phenomenon that may occur as part of the normal process of recovery.

Light therapy has also been given the name " phototherapy". A study done by the Mayo Clinic in 1989 suggests that the results of light therapy are a direct effect of light itself, generated at specific wavelengths, and are not necessarily a function of the characteristics of coherency and polarization associated with lasers.

In a study entitled Low-Energy Laser Therapy: Controversies and New Research Findings, Jeffrey R. Basford, M.D. of the Mayo Clinic’s Department of Physical Medicine and Rehabilitation, suggests that the coherent aspect of laser may not be the source of its therapeutic effect. He states "firstly, the stimulating effects (from therapeutic light) are reported following irradiation with non-laser sources and secondly, tissue scattering, as well as fiber optic delivery systems used in many experiments rapidly degrade coherency . . .

Thus any effects produced by low-energy lasers may be due to the effects of light in general and not to the unique properties of lasers. This view is not difficult to accept when it is remembered that wave-length dependent photobiochemical reactions occur throughout nature and are involved in such things as vision, photosynthesis, tanning and Vitamin D metabolism.

In this view, laser therapy is really a form of light therapy, and lasers are important in that they are convenient sources of intense light at wavelengths that stimulate specific physiological functions (Lasers in Surgery and Medicine 9:1-5, Mayo Clinic, Rochester, Minnesota, 1989).

LED’s and LASERS are no more than convenient devices for producing electromagnetic radiation at specific wavelengths, and in addition to the one already cited, several other studies establish that it is the light itself at specific wavelengths that is therapeutic in nature and not the machine which produced it.

For example, Kendric C. Smith at the Department of Radiation Oncology, Stanford University School of Medicine, concludes in an important article entitled The Photobiological Effect of Low Level Laser Radiation Therapy (Laser Therapy, Vol. 3, No. 1, Jan - Mar 1991) that:

1. Lasers are just convenient machines that produce radiation.
2. It is the radiation that produces the photobiological and/or photophysical effects and therapeutic gains, not the machines.
3. Radiation must be absorbed to produce a chemical or physical change, which results in a biological response."The equation between the machine and the biological response is a common error often made by those who wish to promote the commercial interests of low-energy laser technology. Light radiation must be absorbed to produce a biological response. All biological systems have a unique absorption spectrum which determines what wavelengths of radiation will be absorbed to produce a given therapeutic effect. The visible red and infrared portions of the spectrum have been shown to have highly absorbent and unique therapeutic effects in living tissues.

The following are definitions of commonly used terms used in connection with the use of therapeutic light devices:

1. Visible Light: light that is within the visible spectrum, 400nm(violet) to 700nm(red)
2. Infrared Light: light in the invisible spectrum below red, from 700nm to 2,000nm
3. Frequency: number of cycles per second measured in Hertz
4. Coherency: wavelengths of light traveling in phase with one another
5. Monochromaticity: light that is of one color, or one wavelength
6. Collimation: light focused in a beam, maintaining a constant diameter regardless of its distance from the object or surface at which it is directed
7. Nanometer (nm): a unit of measure of wavelength of light (one billionth of a meter)
8. Nanosecond: one billionth of a second
9. Joule (J): unit used to measure the energy delivered
10. Watts (w) and milliwatts (mw, 1/ 1000th of a watt): units used to measure the power capability
11. Peak power output: the maximum output of power, measured in milliwatts and watts
12. Average power: amount of power actually delivered in a given period of time
13. Duty cycle: the amount of time the light is actually on during a given period of time

Lasers are of two principal types, "hot" and "cold", and they are distinguished by the amount of peak power they deliver.

"Hot" lasers deliver power up to thousands of watts. They are used in surgery because they can make an incision that is very clean with little or no bleeding and because the laser cauterizes the incision as it cuts. They are also used in surgery that requires the removal of unhealthy tissue without damaging the healthy tissue that surrounds it.

"Cold" lasers produce a lower average power of 100 milliwatts or less. This is the type of laser that is used for therapeutic purposes and it is typically, although not always, pulsed. The light is actually on for only a fraction of a second because it is pulsed (turned on and off) at so many pulses per second.

Pulsation results in an average power output that is very low compared to the maximum or peak output. Hence, most therapeutic lasers produce a high peak but low average power output.

Therapeutic laser light is generally either visible (red, in most cases) or invisible (infrared). However, most therapeutic lasers operate at 904 nm which is an infrared light.

What is the Difference between LED’s and LASERS?

Light Emitting Diodes (LEDs) are another form of light therapy that is a relatively recent development of the laser industry. LEDs are similar to lasers inasmuch as they have the same healing effects but differ in the way that the light energy is delivered.

A significant difference between lasers and LEDs is the power output. The peak power output of LEDs is measured in milliwatts, while that of lasers is measured in watts. However, this difference when considered alone is misleading, since the most critical factor that determines the amount of energy delivered is the duty cycle of the device.

LED devices usually have a 50% duty cycle. That is, the LED pulse is "on" for 0.5 seconds and "off" for 0.5 seconds versus the 2 ten-millionths of a second burst from laser at 1 cycle per second (1 hertz). Moreover, LED is "on" 50% of the time and "off" 50% of the time regardless of what frequency setting (pulses per second) is used.

In the majority of lasers on the market, the energy output varies with the frequency setting: the lower the frequency, the lower the output. In the Lumen™ system on the contrary, the output is constant regardless of frequency. Even in the case of lasers that claim a peak output of 10 watts, because of the very short duty cycle, the average output at the highest frequencies is of the order of about 10 milliwatts.

At the lower frequencies, however, the average output plummets into the range of microwatts (1 microwatt = 1000th of 1 milliwatt).LEDs do not deliver enough power to damage the tissue, but they do deliver enough energy to stimulate a response from the body to heal itself. With a low peak power output but high duty cycle, the LEDs provide a much gentler delivery of the same healing wavelengths of light as does the laser but at a substantially greater energy output.

For this reason, LEDs do not have the same risk of accidental eye damage that lasers do. Moreover, LEDs are neither coherent nor collimated and they generate a broader band of wavelengths than do the single-wavelength laser.

Non-collimation and the wide-angle diffusion of the LED confers upon it a greater ease of application, since light emissions are thereby able to penetrate a broader surface area. Moreover, the multiplicity of wavelengths in the LED, contrary to the single-wavelength laser, may enable it to affect a broader range of tissue types and produce a wider range of photochemical reactions in the tissue.If LED disperses over a greater surface area, this results in a faster treatment time for a given area than laser.

The primary reason that Lumen chose the LEDs over lasers is that LEDs are safer, more cost effective, provide a gentle but effective delivery of light and a greater energy output per unit of surface area in a given time duration. They are offered in combinations of visible red light at 660nm and infrared light at from 830nm to 930nm, with 880nm as their average.

The Photobiological Basis of Low Level Laser Radiation Therapy, Kendric C. Smith; Stanford University School of Medicine; Laser Therapy, Vol. 3, No. 1, Jan - Mar 1991.
Low-Energy Laser Therapy: Controversies & Research Findings, Jeffrey R. Basford MD; Mayo Clinic; Lasers in Surgery and Medicine 9, pp. 1-5 (1989).
New Biological Phenomena Associated with Laser Radiation , M.I. Belkin & U. Schwartz; Tel-Aviv University; Health Physics, Vol. 56, No. 5, May 1989; pp. 687-690.
Macrophage Responsiveness to Light Therapy, S Young PhD, P Bolton BSc, U Dyson PhD, W Harvey PhD, & C Diamantopoulos BSc; London: Lasers in Surgery and Medicine, 9; pp. 497-505 (1989).
Photobiology of Low-Power Laser Effects, Tina Karu PhD; Laser Technology Centre of Russia; Health Physics, Vol. 56, No. 5. May 89, pp. 691-704.
A Review of Low Level Laser Therapy, S Kitchen MSCMCSP & C Partridge PhD; Centre for Physiotherapy Research, King's College London Physiotherapy, Vol. 77, No. 3, March 1991.
Systemic Effects of Low-Power Laser Irradiation on the Peripherial & Central Nervous System, Cutaneous Wounds & Burns, S Rochkind MD, M Rousso MD, M Nissan PhD, M Villarreal MD, L Barr-Nea PhD. & DG Rees PhD, Lasers in Surgery and Medicine, 9; pp. 174-182 (1989).
Use of Laser Light to Treat Certain Lesions in Standardbreds, L.S McKibbin DVM, & D Paraschak BSc., MA; Mod Veterinary Practice, March 1984, Sec. 3, p. 13.
Low Level Laser Therapy: Current Clinical Practice In Northern Ireland, GD Baxter BSc, AJ Bet, MA,,JM AtienPhD, J Ravey PhD; Blamed Research Centre University Ulster Physiotherapy, Vol. 77, No. 3, March 1991.
The Effects of Low Energy Laser on Soft Tissue in Veterinary Medicine, LS McKibbin & R Downie; The Acupuncture Institute, Ontario Canada; J. Wiley & Sons.
A Study of the Effects or Lasering of Chronic Bowed Tendons, Wheatley, LS McKibbin DVM, and DM Paraschak Bsc MA; Lasers in Surg & Medicine, Vol. pp. 55-59 (1983).
Scc 3 Lasers and Wound Healing, Albert J. Nemeth, MD; Laser and Dermatology Center, Clearwater FL, Dermatologic Clinics, Vol.. 11 #4, 1993.
Low Level Laser Therapy: A Practical Introduction, T. Ohshiro & RG Caiderhead, Wiley and Sons.
Low Reactive-Level Laser Therapy: A Practical Application, T. Ohshiro;Book:Wiley and Sons.
Laser Biostimulation of Healing Wounds: Specific Effects and Mechanisms of Action, Chukuka S Enwemeka, PhD; Assistant Professor of Physical Therapy - U. of Texas, Health Science Center, San Antonio, TX; The Journal of Orthopaedic & Sports Physical Therapy, Vol. 9. No.10, 1988.
Effect of Helium-Neon and Infrared Laser Irradiation on Wound Healing in Rabbits,B Braverman, PhD; R McCarthy. Pharmd, A Lyankovich, MD; D Forde, BS, M Overfield, BS and M Bapna, PhD; Rush- Presbyterian-St. Luke's Medical Center; University of Illinois, Lasers in Surgery and Medicine 9:50-58 (1989).
Bone Fracture Consolidates Faster With Low-Power Laser, MA Trelles, MD and E Mayayo, MD, Barcelona, Spain; Lasers in Surgery & Med. 7:36-45 (1987).
Wound Management with Whirlpool and Infrared Cold Laser Treatment, P Gogia; B Hurt and T Zim; AMI-Park Plaza Hospital, Houston TX, Physical Therapy, Vol. 68, No. 8, August 1988.
Effects of Low-Level Energy Lasers on the Healing of Full-Thickness Skin Defects, J Surinchak. MA; M Alago, BS,, R Bellamy, MD; B Stuck, MS and M Belkin, MD; Lettennan Army Institute of Research. Presido of San Fransico, CA; Lasers in Surgery & Medicine, 2:267-274 (1983).
Biostimulation of Wound Healing by Lasers: Experimental Approaches in Animal Models and in Fibroblast Cultures, RP Abergel, MD; R Lyons. MD; J Castel, MS, R Dwyer. MD and i Uitlo. MD, PhD; Harbor UCLA Medical Center. CA: J Dennatol. Surgery Oncol., 13:2 Feb. 1987.
Effects of Low Energy Laser on Wound Healing In a Porcine Model, J Hunter, MD; L Leonard, MD; R Wilsom MD; G Snider, MD and J DLxon, MD; Department of Surgery, University of Utah Medical Center, Salt Lake City UT, Lasers in Surgery & Med. 3:285-290, 84.
Effect of Laser Rays on Wound Healing, E Mester, MD; T Spiry, MD; B Szende. MD and J Tola; Semmelweis Medical Univ. Budapes, The American Journal of Surgery. Vol 122, Oct 1971.
Low Level Laser Therapy in the United Kingdom, Kevin C Moore, MD; The Royal Oldham Hospital, Oldhant, UK.
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Re: LLLT - an overview

Postby Quiller » Mon Mar 10, 2008 5:50 am

An excellent overview of the biochemical effects of LLLT can be found here (link is to PDF).

For the visual learners (like me), here's a succinct illustration:


Interesting paragraph from the above link:

Normal human fibroblasts were exposed for 3 days to 0.88J/cm2 of 628 nm light from light emitting diode. Gene expression profiles upon irradiation were examined using a cDNA microarray containing 9982 human genes. 111 genes were found to be affected by light. All genes from antioxidant related category and genes related to energy metabolism and respiratory chain were upregulated. Most of the genes related to cell proliferation were upregulated too.
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Re: LLLT - an overview

Postby Aurelia » Mon Mar 10, 2008 12:31 pm


When I was first trying to find out about RLT, there was hardly any info around. Now there's so much material, it's hard for newbies to know where to start, so it's great to have such clear and well-presented info going into the LLLT section.

Kind regards,

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Re: LLLT - an overview

Postby David Pascoe » Tue Mar 11, 2008 1:34 am

Thanks TP and Quiller for your info - some nice ways to ease into understanding LLLT.
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Re: LLLT - an overview

Postby Twickle Purple » Tue May 20, 2008 3:53 am

Here's a more indepth article, with reknowned expert, Dr. Tiina Karu.
I dug this up 2 years ago, the format may not be as tidy as I'd like, but here it is:

Prof. Tiina Karu's
Cellular Mechanisms of Low-Power Laser Therapy


1. What is photobiomodulation (low-power laser therapy?)

More than 30 year ago the first publications about low-power laser therapy or
photobiomodulation (at that time called laser biostimulation) appeared. Since then
approximately 2000 studies have been published on this topic (analysis of these publications
can be found in [1]). Medical treatment with coherent light sources (lasers) or noncoherent
light (Light Emitting Diodes, LED's) has passed through its childhood and early maturity.

Photobiomodulation is being used by physiotherapists (to treat a wide variety of acute and
chronic muscosceletal aches and pains), dentists (to treat inflamed oral tissues, and to heal
diverse ulcerations), dermatologists (to treat oedema, indolent ulcers, burns, dermatitis),
rheumatologists (relief of pain, treatment of chronic inflammations and autoimmune diseases),
and by other specialists (e.g., for treatment of middle and inner ear diseases, nerve
regeneration). Photobiomodulation is also used in veterinary medicine (especially in
racehorse training centers) and in sports medicine and rehabilitation clinics (to reduce swelling
and hematoma, relief of pain and improvement of mobility and for treatment of acute soft
tissue injuries). Lasers and LED's are applied directly to respective areas (e.g., wounds, sites
of injuries) or to various points on the body (acupuncture points, muscle trigger points). For
details of clinical applications and techniques used, the books [ 1-3] are recommended.

2. What light sources (lasers, LED's) can be used?

The field of photobiomodulation is characterized by variety of methodologies and use of
various light sources (lasers, LED's) with different parameters (wavelength, output power,
continuous wave or pulsed operation modes, pulse parameters). These parameters are
usually given in manufacturers manuals.

The GaAlAs diodes are used both in diode lasers and LED's, the difference is whether the
device contains the resonator (as the laser does) or not (LED). In latter years, longer
wavelengths (-800-900 nm) and higher output powers (to 100 mW) are preferred in
therapeutic devices.

Should a medical doctor use a laser or a diode? The answer is - it depends on what one
irradiates, in other words, how deep tissue layers must be irradiated. By light interaction with a
biotissue, coherent properties of laser light are not manifested at the molecular level. The
absorption of low-intensity laser light by biological systems is of a purely noncoherent (i.e.,
photobiological) nature. On the cellular level, the biological responses are determined by
absorption of light with photoacceptor molecules (see the section 3 below). Coherent
properties of laser light are not important when cellular monolayers, thin layers of cell
suspension as well as thin layers of tissue surface are irradiated (Fig. 1). In these cases, the
coherent and noncoherent light (i.e., both lasers and LED's) with the same wavelength,
intensity and dose provides the same biological response.
Some additional (therapeutical)
effects from the coherent and polarized radiation (lasers) can occur in deeper layers of bulk
tissue only and they are connected with random interference of light waves. An interested
reader is guided to the ref. [4] for more details. Here we illustrate this situation by Fig. 1.
Large volumes of tissue can be irradiated by laser sources only because the length of
longitudinal coherence Lcoh is too small for noncoherent radiation sources [4].

3. Enhancement of cellular metabolism via activation of respiratory chain: a universal
photobiological action mechanism

A photobiological reaction involves the absorption of a specific wavelength of light by the
functioning photoacceptor molecule. The photobiological nature of photobiomodulation
means that some molecule (photoacceptor) must first absorb the light used for the irradiation.
After promotion of electronically excited states, primary molecular processes from these states
can lead to a measurable biological effect (via secondary biochemical reaction, or
photosignal transduction cascade, or cellular signaling) at the cellular level. The question
is, which molecule is the photoacceptor.


Fig. 1. Depth (On in which the beam coherency is manifested, and coherence length Lcoh in
various irradiated systems: (A) monolayer of cells, (B) optically thin suspension of cells, (C)
surface layer of tissue and bulk tissue. Lcoh, - length of temporal (longitudinal) coherence of
laser light, hw) marks the radiation.

When considering the cellular effects, this question can be answered by action spectra. Any
graph representing a photoresponse as a function of wavelength, wave number, frequency,
or photon energy, is called action spectrum. Action spectra have a highest importance for
identifying the photoacceptor inasmuch as the action spectrum of a biological response
resembles the absorption spectrum of the photoacceptor molecule. Existence of a structured
action spectrum is strong evidence that the phenomenon under study is a photobiological
one (i.e., primary photoacceptors and cellular signaling pathways exist). Fig. 2 represents
some examples of action spectra for eukaryotic cells: two of them (A, B) consider the
processes occurring in cell nucleus, and one spectrum (C) is for cell membrane. Fig. 2D shows
the absorption spectrum of the monolayer of the same cells.


Fig. 2. Action spectra of: (A) DNA and (B) RNA synthesis rate in HeLa cells; (C) plasma
membrane adhesion of HeLa cells for red-to-near IR radiation; (D) absorption spectrum of air-
dried monolayer of HeLa cells for the same spectral region. Original data can be found in ref. [5].

The spectra in Fig. 2 represent the red-to-near infrared (IR) region only, i.e. the region that is
most important for photobiomodulation. The action spectra for full visibleto-near IR region can
be found in [5]. In [5] one can find action spectra for various cellular responses for other
eukaryotic and prokaryotic cells as well.

Two conclusions can be drawn from action spectra in Fig. 2. First, the similarity of the action
spectra for different cellular responses suggests that the primary photoacceptor is the same
for all these responses. Second, the existence of the action spectra for biochemical
processes occurring in various cellular organelles (nucleus, Fig. 2A, B and plasma membrane,
Fig. 2C) assume the existence of cellular signaling pathways inside of a cell between the
photoacceptor and the nucleus as well as between the photoacceptor and cell membrane.

Action spectra also indicate, which wavelengths are the best for irradiation: maximal biological
responses are occurring when irradiated at 620, 680, 760 and 820-830 nm (maxima of the
spectra in Fig. 2). Skipping over the story of identifying the photoacceptor (described in [5])
let us conclude that photoacceptor for eukaryotic cells in red-to-near IR region is believed to
be the terminal enzyme of the respiratory chain cytochrome c oxidase (located in cell
mitochondrion). To be more exact, it is a mixed valence (partially reduced) form of this
enzyme, which has not yet been identified. In the violet-to-blue spectral region, flavoproteins
(e.g., NADHdehydrogenase in the beginning of the respiratory chain) are also among the
photoacceptors as well terminal oxidases.

An important point has to be emphasized. When the excitable cells (e.g., neurons,
cardiomyocites) are irradiated with monochromatic visible light, the photoacceptors are also
believed to be components of respiratory chain. Some of the experimental evidence
concerning excitable cells is shortly summarized in Fig. 3. It is quite clear from experimental
data (reviewed in [4]) that irradiation can cause physiological and morphological changes in
nonpigmental excitable cells via absorption in mitochondria. Later, similar irradiation
experiments were performed with neurons in connection with low-power laser therapy. It was
shown in 80's that He-Ne laser radiation alters the firing pattern of nerves; it was also found
that transcutaneous irradiation with HeNe laser mimicked the effect of peripheral stimulation
of a behavioral reflex. These findings were found to be connected with pain therapy (review [4])


So, what happens when the molecule of photoacceptor absorbs photons?

Answer - electronic excitation followed by photochemical reactions occurring from lower excitation
states (first singlet and triplet). It is also known that electronic excitation of absorbing centers
alters their redox properties. Until yet, five primary reactions have been discussed in literature
(Fig. 4). Two of them are connected with alteration of redox properties and two mechanisms
involve generation of reactive oxygen species (ROE). Also, induction of local transient (very
short time) heating of absorbing chromophors is possible. Details of these mechanisms can
be found in [4, 5].

There is no ground to believe that only one of the reactions shown in Fig. 4 occurs when a
cell is irradiated and excited electronic states are promoted. The question is, which
mechanism is decisive. It is not excluded that all mechanisms shown in Fig. 4 lead to a similar
result, to a modulation of redox state of the mitochondria (a shift to more oxidized direction).
However, depending on the light dose and intensity used, some mechanism(s) can prevail
significantly [5].


The next question is, the following if photoacceptors are located in the mitochondria, then
how the primary reactions occurring under irradiation in the respiratory chain (Fig. 4) are
connected with DNA and RNA synthesis in the nucleus (the action spectra in Fig. 2A, B) or
with changes in plasma membrane (Fig. 2C)? The principal answer is that between these
events there are secondary (dark) reactions (cellular signaling cascades or photosignal
transduction and amplification, Fig. 5).

Three regulation pathways are suggested in Fig. 4. The first one is the control of
photoacceptor over the level of intracellular ATP. It is known tat even small changes in ATP
level can alter cellular metabolism significantly. This regulation way is especially important by
irradiation of hypoxic, starving or otherways stressed cells. However, in many cases the
regulative role of redox homeostasis is proved to be more important than that of ATP. For
example, it is known that the susceptibility of cells to hypoxic injury depends more on the
capacity of cells to maintain the redox homeostasis and less on their capacity to maintain the
energy status.


The second and third regulation pathways are mediated through the cellular redox state (Eh;
Fig. 4). This way involve redox-sensitive transcription factors (NF-KB and AP1, Fig. 4) or
cellular signaling homeostatic cascades from cytoplasma via cells membrane to the nucleus
(Fig. 4). As a whole, the scheme in Fig. 4 suggests a shift in overcell redox potential into more
oxidized direction. Modulation of cellular redox state affects gene expression namely via
transcription factors. It is important that in spite of some similar or even identical steps in
cellular signaling, the final cellular responses to the irradiation differ due to existence of
different modes of regulation of transcription factors. The mechanisms of regulation are not
understood well yet.

    The magnitude of cellular responses depends on cellular redox potential (and its
    physiological status, respectively) at the moment of irradiation. The cellular response is
    stronger when the redox potential of the target cell is initially shifted to a more reduced state
    (and intracellular pH, pH;, is lowered, as usually happens in injured cells). This explains why
    the degrees of cellular responses can differ markedly in different experiments or in different
    clinical cases, and why the effects are sometimes nonexistent.

One should emphasize that some biological limitations exist for photobiomodulation effects.
These are discussed in [5].

4. Enhancement of cellular metabolism via activation of nonmitochondrial
photoacceptors. Indirect activation/suppression

The redox regulation mechanism cannot occur solely via respiratory chain (Section 3). Other
redox chains containing molecules, which absorb light in visible-to-near IR radiation, and are
some key structures that can regulate a metabolic pathway, can be photoacceptors for
photobiomodulation as well. One such example is NADPH-oxidase of phagocytic cells, which
is responsible for nonmitochondrial respiratory burst. This multicomponent enzyme system
located in the plasma membrane is a redox chain that generates reactive oxygen species
(ROS) as a response to the microbicidal or other types of activation. Irradiation with He-Ne
laser and diode lasers and LED's can activate this chain in various phagocytic cells. Many
worked examples can be found in [5]. In phagocytes, the activation of respiratory chains in
mitochondria occurs as well, as NADHP-oxidase activation, but the latter is much stronger.
ROS, burst of which is induced by direct irradiation of phagocytes, can activate or inactivate
other cells, which were not irradiated directly. In this way, indirect activation or suppression of
metabolic pathways in non-irradiated cells occurs. Also, lymphokines and cytokines produced
by irradiated lymphocytes can influence metabolism of other cells. This situation is common by
irradiation on tissues.

5. Concluding Remarks

The photobiological action mechanism via activation of respiratory chain is a universal working
mechanism for various cells. Crucial events of this type of cell metabolism activation are
occurring due to a shift of cellular redox potential into more oxidized direction as well as due
to ATP extrasynthesis. Susceptibility to irradiation and capability for activation depend on
physiological status of irradiated cells: the cells, which overall redox potential is shifted to
more reduced state (example: some pathological conditions) are more sensitive to the
irradiation. The specificity of final photobiological response is determined not at the level of
primary reactions in the respiratory chain but at the transcription level during cellular signaling
cascades. In some cells, only partial activation of cell metabolism happens by this mechanism
(example: redox priming of lymphocytes).

    All light-induced biological effects depend on the parameters of the irradiation (wavelength,
    dose, intensity, irradiation time, and continuous wave or pulsed mode, pulse parameters).
    According to action spectra, optimal wavelengths are 820-830, 760, 680, and 620 nn. Large
    volumes and deeper layers of tissues can successfully irradiated by laser only (e.g. inner and
    middle ear diseases, injured siatic or optical nerves, deep inflammations etc.). The LED's are
    excellent for irradiation of surface injuries.

Cited Literature
1. Tuner, J. and Hode, L. (1999). Low Level Laser Therapy. Clinical Practice and Scientific Background. Prima Books, Grangesberg (Sweden).
2. Baxter, G.D. (1994). Therapeutic Lasers. Theory and Practice. Churchill Livingstone, London.
3. Simunovic, Z., editor (2000). Lasers in Medicine and Dentistry, vol. I. Vitgraf, Rijeka (Croatia).
4. Karu, T.I. (2002). Low power laser therapy. In: CRC Biomedical Photonics Handbook, T.
Vo-Dinh, Editor- in-Chief, CRC Press, Boca Raton (USA).
5. Karu, T.I. (1998). The Science of Low Power Laser Therapy. Gordon and Breach Sci.
Publ., London.
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Re: LLLT - an overview

Postby deegirl » Wed May 21, 2008 12:17 am

I know volumes have been written on the subject but I'm considering getting an red light unit. I'm curious if it's okay to use while taking oracea. I'm also wondering what a good inexpensive unit is because cost is a big factor for me. Any help would be appreciated.
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Re: LLLT - an overview

Postby David Pascoe » Wed May 21, 2008 3:24 am

Thanks heaps for keeping us up to date and informed TP, we appreciate it !
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Joined: Sat Jul 07, 2007 3:17 pm
Location: Perth, Western Australia.

Re: LLLT - an overview

Postby Twickle Purple » Wed May 21, 2008 4:10 am

Hi Deegirl,

Could you start up a thread asking for this input? I'll dig up what I can for you and post it there. That would make it easy for folks to find when they are looking for the same info you're looking for.

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Twickle Purple
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Location: Vancouver Island, BC

Re: LLLT - an overview

Postby Twickle Purple » Wed May 21, 2008 4:21 am

Always a pleasure David. (hug2) I know you have a ton of excellent info in the Articles Section and I am glad I can contribute in any way. Your site has been a huge source of information, inspiration and support for me, and many others. Thank you David!!
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Twickle Purple
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Re: LLLT - an overview

Postby Aurelia » Thu May 22, 2008 2:19 pm

Thanks, Corinna.

I see from the home page that it's just five months short of a decade since David set up the world's first rosacea internet group. That represents an incredible amount of dedication, considering that apart from very rare holidays, he is online for hours every single day making sure it's all working properly and that messages are in line with his "friendship-promoting" rules, as well as answering questions and doing much of the moderating. We're lucky he is so selfless, and that his very lovely Julia doesn't begrudge us that time. A lot of wives would.

Kind regards,

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