Photobiomodulation and reactive oxygen species (ROS)
To Understand It Fully: The Paradox of Beneficial Stress
What are ROS?
Reactive oxygen species (ROS) are highly reactive molecules produced by our cells. In excess, they can damage DNA or proteins. But in small amounts, they are essential: they act as chemical messengers that trigger beneficial reactions.
Light stimulates moderate production
When photobiomodulation is used, light activates the mitochondria. This triggers a small amount of ROS production. This stimulation is not dangerous: it acts as a gentle alarm that tells the cell, “Repair yourself, strengthen yourself, reactivate yourself.”
Result: improved cellular function
This well-balanced production makes it possible to:
- faster repairs,
- activation of protective genes,
- better protection against aging or inflammation.
Further Reading: The Biochemical Role of ROS
The Origin of ROS in Photobiomodulation
When mitochondria are activated by red or infrared light, an electron leak in the respiratory chain (complexes I through IV) generates:
- superoxide (O₂•⁻),
- hydrogen peroxide (H₂O₂),
- hydroxyl groups (•OH).
These ROS are produced in low doses, on a transient basis, and play a role in redox signaling.
Triggered cellular signaling
ROS play a key role in activating signaling pathways:
- Nrf2: stimulates antioxidantenzymes (SOD, catalase, glutathione),
- NF-κB: regulates inflammation,
- MAPK, PI3K/Akt: trigger cell repair, proliferation, and migration.
This is known as ROS-dependent signaling, triggered by light.
Biphasic Effect and Safety
- At low doses, ROS activate repair mechanisms.
- In excessive amounts, they can cause harmful oxidative stress.
👉 This is why it is important to adhere to the specified dose, fluence, frequency, and power settings in photobiomodulation.
Therapeutic Applications of Controlled ROS
- Tissue regeneration (skin, muscles, nerves)
- Gentle immune stimulation
- Reduction of Chronic Inflammation
- Prevention of Cellular Aging
Clinical protocols are designed to stimulate these effects without causing harmful oxidative stress.
LED Photobiomodulation and Management of Oxidative Stress
The LED light used in PBM allows for:
- precise control of the intensity,
- a uniform distribution of energy,
- a reduced risk of overstimulation compared to other, more focused sources (such as a poorly calibrated laser).
This is why the biphasic curve (too little = effective / too much = inhibition) fully applies to ROS.
Frequently Asked Questions
What are ROS in the context of photobiomodulation?
ROS (reactive oxygen species) are unstable molecules produced by cells, particularly in response to red or infrared light. At low doses, they play a beneficial role in cellular regulation, repair, and signaling.
Is ROS production beneficial or harmful?
It depends on the dose. At low concentrations, ROS stimulate protective and antioxidant mechanisms. In excess, they can cause oxidative stress and damage DNA, cell membranes, and proteins.
How does photobiomodulation modulate ROS?
PBM temporarily raises ROS levels, which activates the cell's natural antioxidant defenses. This process is beneficial if the dose is properly adjusted: this is the very principle behind the biphasic curve.
Scientific sources cited
- Huang Y.Y. et al. (2009). Biphasic dose response in low-level light therapy.
Link to the study
→ Shows that photobiomodulation stimulates ROS at low doses to trigger an adaptive response, but can lead to their overproduction at high doses. - Rhee S.G. (2006). Cell signaling: H₂O₂, a necessary evil for cell signaling.
Link to the study
→ Shows that ROS, and in particular hydrogen peroxide (H₂O₂), play a crucial role in cell signaling. - Hamblin, M.R. (2017). Mechanisms and doses for photobiomodulation therapy.
Link to the study
→ Explains how controlled ROS production helps stimulate natural antioxidant mechanisms. - Cadet J. et al. (2003). Oxidative DNA damage: mechanisms, mutation, and disease.
Link to the study
→ Highlights the risks associated with excessive ROS and the importance of maintaining a physiological balance.
See also
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