Both UV and IR Induce Skin Damage but in Different Ways
Like UV, IRA radiation generates an important quantity of ROS (such as singlet oxygen and superoxide anion) in the skin and this leads to:
-the upregulation of MMP-1, which is an enzyme that destroys the fibers of collagen type 1 (the most abundant collagen in the human body)
-the downregulation of collagen type 1**.
This means that existing collagen is damaged and not sufficiently replaced as the production of new collagen is reduced. Therefore, IRA is an important contributor to the photo-aging process which accelerates the appearance of wrinkles, age spots and discoloration and makes the skin lose its firmness and elasticity.
However, the underlying mechanism of IRA differs from that of UV: UV generates ROS directly in the cell membrane while IRA induces their formation mainly in the mitochondria. Indeed, IRA is absorbed by the electron transport chain (ETC) in the mitochondria and this leads to the formation of ROS in these organelles. These ROS will ultimately leak into the cytoplasm and induce a signaling cascade ending in the nucleus that will result in an increased synthesis of MMP-1 and a reduced sythesis of collagen-1.
IRA Disturbs the Entire Cell by Impacting Mitochondria
The disturbance of the ETC by the ROS in the mitochondria also affects the performance of this organelle. As a result, this ´´powerhouse´´produces less ATP (energy) and this has an impact on the function of cells and tissues.
Therefore, whilst mitochondria are the main target of IRA, the damages it induces (destruction of collagen and reduced energy production) affect the entire cell and tissue.
Source: Mibelle Biochemistry