A GEM-like model of light-tissue interactions.

The Body’s GEM: High Sensitivity Processes for High Gain in Light-Tissue Interactions.

As always, this is not medical advice, and reading this does not form a client relationship with me - your health is your responsibility. I’ll add more in the future.

Gaseous Electron Multipliers

In physics, we use different detectors to understand experiments. One detector is the Gaseous Electron Multiplier (GEM).  GEMs are used in particle physics, astrophysics and cosmology, medical imaging, material science, etc. GEMs allow for high sensitivity and high gain - detect and amplify weak signals.

A simplified view of how they work is a charged particle enters a chamber filled with gas that has a high electric field across it. The particle interacts with the gas, which becomes ionized leading to free electrons and positive ions. The high electric field then causes these free electrons to accelerate so they collide with more gas molecules creating an avalanche of electrons, known as amplification/ a signal cascade. These electrons then interact with an electrode leading to the signal. Absorption of various wavelengths of light also leads to an amplification/ signal cascade internally.

Infrared (IR) light (heat)

The depth at which light is absorbed depends on its wavelength (indirectly proportional to frequency). Longer, long-waveIR, wavelengths (~3,000nm-10,000nm) can penetrate several centimeters - hypodermis/ subcutaneous tissue. Where shorter, NearIR (700nm-1,100nm), is mostly absorbed by the dermis. There is always some level of transmission, absorption, and reflection.

Back to the idea of a GEM-like model, IR photon absorption leads to the following - this is not an exhaustive list:

1. Stimulates cytochrome c oxidase (complex IV of the electron transport chain) by increasing electron transfer. The exact mechanism as to how this occurs is not fully known.  Everyone points to IR dissociating NO attached to complex IV (photodissociation). However, it arguably also has to do with:

• IR increases water structure, the ETC, including its “transmembrane” proteins, are surrounded by water.

• Vibrational resonance

• Conformational change

This leads to increased mitochondrial respiration - more ATP, CO2, and H2O production.

2. IR activates TRPV1 receptors causing a signaling cascade via calcium ion influx leading to:

• neurotransmitter release - mood modulation via serotonin:dopamine:glutamine

• pain relief - substance P and calcitonin gene-related peptide activate endogenous pain-inhibitory pathways

• vasodilation

• neuroprotection

3. Direct activation of heat shock proteins (e.g., HSP70 and 90). These have roles in protein folding, repair, and degradation. The HSPs stabilize proteins to prevent them from being denatured due to heat stress. Light bulbs should be going off in those who do not tolerate higher temperatures. Elevated HSPs are seen in cancer, autoimmune diseases, and neurodegenerative conditions like Alzheimers and Parkinsons - but again, cause or symptom?

4. Increased nitric oxide production - yes, CO2 should be acting as our main vasodilator. But I see CO2 like CA’s power grid. It’s providing the baseline. However, sometimes there are surges in demand on the grid, just like the body, that’s where NO comes in.

• IR increases intracellular Ca activating the NOS isoforms.

• via HSPs.

• IR activates protein kinase C and B (Akt) which can activate NOS.

5. Stimulates collagen synthesis - hello to my fellow hEDS, EDS, Marfans, HSDs, etc. This might not be beneficial given these conditions seem to have faulty collagen properties/ laying down. Stimulating collagen recycling and production could lead to further tissue fragility and instability. Also, IR-stimulated fibroblast activity could perpetuate the overproduction of defective collagen.

6. And others:

• modulation of inflammation via suppressing pro-inflammatory cytokines and promoting anti-inflammatory cytokines

• modulation of immune cell migration, activation, and proliferation; etc.

The above are examples of how IR light is like a GEM in that there is IR photon absorption, signal amplification (usually via Ca), a cellular response, followed by cascade propagation via cellular light emission, NTs, hormones, etc.

Visible light

Yes, what we can see - 400-700nm, so not much of the light spectrum. White light is all the colors together - use a prism to see the colors via refraction. Dark is an absence of light. Oh! And the color you see is because that is the wavelength(s) being reflected back to you. The others are either absorbed or transmitted. So is it really that color? 🤔

Visible light is absorbed in the epidermis and dermis by porphyrins - chlorophyll and heme are porphyrins! Bilirubin is as well.

The absorbed light is primarily absorbed by the conjugated double bonds in the porphyrin ring. This causes electrons to be excited so they jump up an energy level - remember, we are talking about quantized, so discrete vs. continuous. The electrons are not ionized - we will get there with UV, as there is something called the photoelectric effect stopping potential. The electrons then relax to their lower energy state releasing heat or light - this light will be a longer wavelength than what was originally absorbed. Yes, cells emit light - it’s most likely part of the communication, etc. of the body. See the book “Light in Shaping Life” for more. Fluorescence is not the same as phosphorescence which emits light for a longer duration. Scattered sunlight can also reach the organs and deeper tissues.

This process is important for oxygen transport to and from the lungs and other tissues. The heme in hemoglobin absorbs specific wavelengths of light in the red and blue (yes blue, blue is needed!) regions of the visible spectrum. This mechanism could be used in areas of low oxygen partial pressure to make sure the cells receive sufficient oxygen - which happens naturally at altitude. But it can also be leveraged for those in pseudo-hypoxia-like states!

Blue light

1. Activates enzymes in the pentose phosphate pathway to make more NADPH - antioxidant cascade, cholesterol synthesis, pharmaceutical/ herb metabolism, DNA repair, cell signaling via PI3K/ Akt and AMPK, etc.

2. Decreases DNA methylation via promoting demethylation and inhibiting DNMTs.

3. Decreases urea cycle activity - might lead to ammonia buildup.

4. Decreases GSH synthesis and reduction of GSSG to GSH.

5. Decreases heme and hemoglobin synthesis. Too much could lead to a buildup of toxic intermediates in the heme pathway.

6. Suppresses melatonin production.

7. Can suppress anabolic and non-catabolic hormones.

8. Can increase catabolic hormones.

9. Mostly absorbed by the dermal layer.

Red light

1. Stimulates NNT activity to generate NADPH from NADH.

2. Increases DNA methylation via DNMTs.

3. Enhances enzymes in methylation like methionine synthase.

4. Increases urea cycle enzyme activity.

5. Increases GSH synthesis and reduction of GSSG to GSH.

6. Promotes Fe regulation.

7. Supports RBC maturation.

8. Increases heme and hemoglobin synthesis.

9. Does not suppress melatonin production.

10. Supports regulation of HPA, etc. axes.

11. Mostly absorbed by the subcutaneous tissue.

Our visible light receptors are:

1. Rods (low light conditions, peripheral and night vision) and cones in the retina (color and bright light conditions, central and color perception).

2. ipRGCs - blue light.

3. Melanopsin - blue light.

4. L-opsin - red light.

UVA light

UVA reaches the hypodermis (subcutaneous tissue) layer. 

UVA is absorbed by:

1. DNA. When DNA absorbs UVA, electrons in the DNA are excited leading to a signal. This signal is then amplified via chemical reactions leading to turning on repair pathways, gene expression, and other signaling cascades.

2. Melanin - pigment and some think a form of human photosynthetic properties. The indole or phenolic groups that make up conjugated rings in melanin act as its chromophore (the part that absorbs the UVA). The light causes ROS generation that melanin primarily seems to quench with its conjugated ring groups. This, along with the antioxidant cascade (vit E, vit C, etc.) protects the skin and eyes from damage caused by UV. This is because UVA is a higher energy photon which overcomes melanin’s stopping potential. This means the energy from UVA is high enough r remove an electron from melanin - more electrons = reductive state that turns into ROS.

3. Proteins - e.g., tryptophan (e.g., serotonin and melatonin) and tyrosine (thyroid hormones, dopamine, etc.). This can lead to oxidative stress and inflammation via protein damage and denaturation, etc.

4. Unsaturated fats and cholesterol - leading to peroxidation, fragmentation, disruption of cell surface activity and structure, etc. causing inflammation, apoptosis, etc.

5. Porphyrins - oxidation, fragmentation, etc. this can cause lipofuscin depending on Fe dynamics.

6. Flavins e.g., FAD and FMN - smaller doses UVA beneficially activates flavin dependent enzymes (e.g., complex II, PDH, MAO, etc.) and electron carriers.

7. NADH and NADPH - in vitro photoxidation to NAD+ and NADP+! In vivo this is not as probable due to depth of absorption.

8. Carotenoids, polyphenols, and other compounds.

There are no direct photopigments or receptors that detect UVA. UVA plays a role in activating ligands for the following receptors:

1. Vit D, VDRs - Ca homeostasis, modulates immune system response, etc.

2. Retinoic acid, RARs - cell growth, differentiation, apoptosis, etc.

3. Aryl Hydrocarbon, AhRs - detoxification, glucose and lipid metabolism, etc.

4. Peroxisome proliferator-activated, PPARs - glucose and lipid metabolism, fat storage, etc.

UVB Light

UVB is mostly absorbed in the epidermis (outermost skin layer) but some makes it to the dermis.

The dermis layer includes:

1. The extracellular matrix - collagen, elastin, GAGs, etc.

2. Lymphatic vessels.

3. Sensory and motor nerve fibers.

4. Blood vessels.

5. Hair follicles.

6. Sweat and sebaceous glands, etc.

There are also no known direct photopigments or receptors that detect UVB. Research continues to look for UVA- and UVB- like “opsins.” UVB is also “detected” much like UVA via DNA damage sensors, TRP channels, etc - UVB works primarily through ROS, inflammation, and DNA damage. UVB leads to the following conversions from 7-dehydrocholesterol:

1. pre-vitamin D3.

2. lumisterol

3. tachysterol

The following are resistant to UV radiation (e.g., they have a higher stopping potential):

1. DNA

2. RNA

3. Aromatic amino acids like tryptophan and tyrosine.

4. Antioxidants like glutathione and ubiquionone.

During solar noon, UVA and UVB are typically at their max, accounting for 4-6% and 1-2% of the light from the sun respectively. Infrared as mostly IR-A (nearIR, 25-30%), IR-B (short-wave IR, 10-15%), and IR-C (long-wave IR, 10-12%). And lastly visible 42-45%. Away from solar noon, UVA and UVB drop off until the UV index is zero.

IR-A, B, and C, UV-A and B, and visible light all reflect off various sources so you are still receiving them in the shade. The amount of each you receive is dependent on the angle of incidence, how far you are from the reflecting surface, the reflectivity of the surface, atmospheric conditions, etc.

Windows absorb approximately 5-10% visible, ~90+% UV, and 20-50% IR. The rest is transmitted or reflected. Many modern windows have coatings to increase their light absorption. Window screens absorb 5-15% visible, negligible IR, and up to 50+% UV. Spectacles absorb 1-5% visible, negligible IR, and a significant amount of UV depending on the lens and coating. The rest is transmitted or reflected.

The moon reflects some visible, nearIR, and short-waveIR. The amount of each depends on its phase. Everything that has interacted with the sunlight throughout the day also can emit some light at night - e.g., a house that is warm (IR) well into the night.

To summarize, simplistically, the light signal is predominantly amplified via the calcium cascade and ROS.

This is all incredibly interesting, but I hope the important thing you take away from this is there are positives and negatives to each wavelength of light and its actions - the full spectrum in its solar ratios balances each other and allows for cycling anabolism and catabolism. I recommend leveraging shade and not getting a sunburn.

Biochemistry 🤝 Biophysics