Multifaceted pathways protect human skin from UV radiation

Oxidative stress plays an important role in skin aging and skin damage, with its main feature being increased intracellular ROS.

“Oxidative stress plays an important role in skin aging and skin damage processes, and its main feature is increased intracellular ROS.”

Accumulation of ROS causes DNA damage, induces skin inflammatory response, reduces antioxidant enzymes, activates NF-kB and AP-1 to inhibit collagen production, and increases matrix metalloproteinases to decompose collagen and binding proteins in the dermis, eventually leading to skin aging.

“The accumulation of ROS causes DNA damage, induces skin inflammatory response, reduces antioxidant enzymes, activates nuclear factor kappa B (NF-kB) and activator protein1 (AP–1) to inhibit collagen production, and increases matrix metalloproteinases to decompose collagen and binding proteins in the dermis, which eventually leads to skin aging [30,31,32,33].”

Oxidative stress is a major source of skin aging.

“Additionally, it is well known that oxidative stress is a major source of skin aging, and the mechanisms by which it occurs have been reviewed [2,13,14].”

UVA penetrates deeper into dermis to degrade collagen and elastin fibers via oxidative stress mechanisms that activate MMPs and damage mitochondrial structure/function, leading to extrinsic skin photoaging.

“UVA (320-400 nm) at a higher wavelength range represents 95-98% of the total UV radiation reaching the Earth's surface can damage the epidermis and penetrates deeper into the dermis to degrade collagen and elastin fibers via oxidative stress mechanisms that in turn activate matrix metalloproteinases (MMPs) and damage mitochondrial structure/function that leads to extrinsic skin photoaging [2,13,14”

Most UV-induced oxidative stress is generated by UVA, which is more cytotoxic to human skin compared to UVB; UVB are mostly mutagenic; both stimulate generation of ROS.

“Thus, most UV-induced oxidative stress is generated by UVA, which is more cytotoxic to human skin compared to UVB; whereas UVB are mostly mutagenic, both are known to stimulate the generation of ROS, [2,13,14,25]”

Photoaging or extrinsic aging due to UV light and environmental pollutants trigger oxidative stress and formation of ROS that damages DNA, mitochondrial function, protein, lipids, and results in declination of antioxidant levels.

“photoaging or extrinsic aging due to exposure to UV light along with assaults from environmental pollutants (such as particles, wind or cold) trigger oxidative stress and the formation of ROS that damages DNA, mitochondrial function, protein, lipids, and results in the declination of antioxidant levels [2,13,14].”

The formation of ROS is a widely accepted pivotal mechanism leading to skin aging.

“The formation of ROS is a widely accepted pivotal mechanism leading to skin aging (see Figure 6) [2,13,14].”