Mechanism of Skin aging
Skin aging is a cumulative & multi-factorial process caused by a combination of the effects of time and environmental factors such as UV radiation and environmental pollutants. Since much of the progressive damage to collagen, elastin & hyaluronic acid components of the skin is due to accumulation of ROS & inflammation which are caused by both aging and environmental factors, let’s review how these factors end up damaging your skin.
ROS are constantly generated by several metabolic pathways in almost all cells in our body. The ROS are particularly harmful because they damage DNA and promote chain reactions which leads to collagen breakdown and decreased collagen production. Fortunately our skin has a natural anti-oxidative system which is responsible to combat these produced ROS; however, the problem arises when the balance between the ROS production and their neutralization by our skin’s natural antioxidant systems is impaired! There are 3 reasons that can cause this imbalance:
1. Aging: as we age the function of this protective antioxidant system declines.
2. Environmental damages: factors such as UV rays and pollution significantly increase the amount of ROS in the skin and decrease ongoing collagen synthesis.
3. Inflammation: will talk about this one soon…
Another very important factor contributing to skin aging is inflammation. Inflammation is the immune system’s protective response to an infection, damaged tissue or UV radiation. During inflammation cells release a large amount of oxidants and enzymes to cope with the inflammation. The problem arises when there is an excessive response by the immune system which could result in ROS generation.
It should be noted that while inflammation causes ROS production, at the same time, overproduction of ROS results in cell and tissue injury, production of pro-inflammatory cytokines & contribute to inflammation! Inflammation also plays a key role in acne vulgaris.
Skin hydration is defined as the water content of both epidermis and dermis. GAGS such as Hyaluronic Acid are natural components of the skin and hydrate the skin via retaining water molecules. Similar to collagen & elastin, HA is also produced by fibroblast in dermis and the HA content of epidermis is supplied from the dermis as well. So what causes dehydration?
1. Aging: as we age the amount of naturally occurring GAGs (HA) in the skin continuously decreases, which results in decreased tissue elasticity and hydration, and contributes to the formation of wrinkles.
2. Environmental damage: factors such as UV rays significantly increase the amount of ROS in the skin which not only cause collagen & elastin breakdown, it also promotes the cleavage of hyaluronic acid & cause HA molecules to clump and deposit abnormally in dermis! ROS also destroys lipids of the skin and damages the brick and mortar structure of the outermost layer causing transepidermal water loss, when the water content of the outermost layer is lost more quickly than that which is received from the lower layers of the skin it results in dehydration.