Infrared radiation (IR) is well known for its therapeutic use, in night vision devices, telescopes, or even in security cameras. But it is surprising to imagine that 53% of solar energy is composed of IR waves and that one-third of the solar energy that daily reaches our skin comes from a type of infrared radiation called short waves (IR) ranging from 760 to 1440 nm, which are further divided into IRA, IRB, and IRC.
Compared to the action of UV radiation, IRA has the ability to penetrate more deeply into human skin. Recently, it was discovered that in addition to simply penetrating the skin and reaching the dermal compartment, IRA radiation affects fibroblasts and induces them to increase the expression of the enzyme that degrades collagen, called metalloproteinase (MMP). Since collagen is one of the main fibers involved in the integrity and firmness of the skin, the biological effects of IRA irradiation may favor the appearance of wrinkles in the skin.
If we recall the previous discussion, it was presented that UV light, like visible light, is also capable of inducing the expression of MMP-1; however, the mechanisms by which this pathway is activated are distinct as they use different chromophores (molecules that absorb electromagnetic waves and have excitable electrons at a certain wavelength). For example, for UVB radiation, we can cite a nuclear molecule, while for UVA, a molecule in the structure of the lipid membrane. For IR, the radiation is absorbed by proteins in the mitochondria (the cellular organelle responsible for cellular respiration).
The effect of IR radiation increasing the expression of MMP-1 in the dermal compartment has even been directly verified in the skin of healthy volunteers, in vivo. Furthermore, it has been suggested that this effect is mediated by a response to oxidative stress, as the level of antioxidants in the skin declined after short periods of exposure to IR (Schroeder, P. et al, 2008).
However, the intracellular signaling mechanisms responsible for these modifications are not yet fully elucidated. It is believed that IR radiation is absorbed by the complex of molecules (cytochromes) of the respiratory chain within the mitochondria, with the subsequent formation of reactive oxygen species that will alter calcium levels in the cytoplasm of the cell until modifying the expression of the MMP-1 gene via activation of other proteins within the same cell (Krutmann et al, 2012).
Calles and collaborators (2010) aimed to better understand the impact of this IR radiation by studying the transcriptome of fibroblasts (skin cells) exposed to such radiation. It is worth noting that the transcriptome is a technology that studies the RNAs of cells, that is, the molecules that contain the genetic information that will be translated into proteins. Therefore, this technique uses large-scale analysis methods, as it simultaneously studies all the coders present in the cells in question at a given moment.
The microarray analysis revealed a modulation of approximately 600 transcripts categorized basically into 4 major groups according to their activity: extracellular matrix metabolism, calcium ion flow homeostasis, cellular stress signaling, and apoptosis regulation. The authors emphasize that the observations regarding the modulations of intracellular signaling pathways and the biological effect caused by IR radiation differ from those induced by UVA and UVB radiation, suggesting once again the opportunity to develop new and specific technological strategies for treating the effects caused by IR.
Meanwhile, in Europe, there is already a movement for the development of this technology, which is even appearing in some cosmetics.
All these discoveries are recent and show how much we still have to study to uncover the results of the human-environment interaction that occurs daily from the astronomical level to the cellular level.
Bibliographic References
Calles C, Schneider M, Macaluso F, Benesova T, Krutmann J, Schroeder P. Infrared A radiation influences the skin fibroblast transcriptome: mechanisms and consequences. J Invest Dermatol. 2010 Jun;130(6):1524-36. Epub 2010 Feb 4.
Julia Menegola, Kelen Arroteia, Virginie Brumenil, Michel Salmon (2012). Development of cell-based in vitro models for infrared radiation A (IRA) and thermal exposure. J Invest Dermatol, May 12, 132 Suppl 1 page S115.
Krutmann J, Morita A, Chung JH. Sun exposure: what molecular photodermatology tells us about its good and bad sides. J Invest Dermatol. 2012 Mar;132(3 Pt 2):976-84. doi: 10.1038/jid.2011.394. Epub 2011 Dec 15.
Schroeder P, Lademann J, Darvin ME, Stege H, Marks C, Bruhnke S, Krutmann J. Infrared radiation-induced matrix metalloproteinase in human skin: implications for protection. J Invest Dermatol. 2008 Oct;128(10):2491-7. Epub 2008 May 1
