Can antioxidants enhance the protective effect of melanin when we are exposed to sunlight?
Ultraviolet radiation (UVR) plays an important a role in melanogenesis, by stimulating melanin synthesis in melanocytes. The enzyme tyrosinase plays a major role in melanin synthesis, and individuals with higher levels in their skin are less sensitive to UVR than those who have lower levels.
Apart from stimulating melanin synthesis UVR also can cause DNA mutations, protein and lipid damage, which can over time can result in melanoma formation. UVB directly causes DNA mutations, while UVA does so by generating reactive oxygen species (ROS). The addition of exogenous antioxidants, such as vitamin C or E, could protect melanocytes against UV-induced ROS, thereby reducing the rates of melanomagenesis.
The UVR component of sunlight plays an important role in the formation of vitamin D, which is necessary for human health. However, extreme exposure to UVR can cause sunburn, accelerated skin ageing and skin cancer (basal cell carcinoma, squamous cell carcinoma and melanoma). In Australia, over 434,000 people were diagnosed with one or more non-melanoma skin cancers as well as 11,000 with melanoma in 2010 (1). In order to decrease the harmful effects of UVR on the skin and to prevent skin cancer formation, it is essential to understand the role UV plays in tumorigenesis and of the protective effect antioxidants may play in this process, by reducing the deleterious effects caused by ROS.
The skin is exposed to oxidative stress from numerous sources, such as smoking, chemical air pollutants, and UVR (2). UVR is a part of the electromagnetic spectrum emitted by the sun and can be divided into three main groups: UVC (100-280 nm), UVB (280-320 nm) and UVA (320-400 nm). The ozone layer blocks UVC, while only 5% of UVB and 95% of UVA radiation emitted by the sun reaches the Earth's surface (3).