UV got sun cream on, right?

By Lauren Hoskin

With an ever-increasing number of pasty Brits working 360 days in the office, only to fly out for five days of sun in the Costa del Sol, it is no wonder that UV-induced diseases are on the up.

Ultraviolet (UV) radiation is part of the electromagnetic spectrum from the sun. Since its wavelengths are shorter than normally visible, we cannot actually see it. Yet it still penetrates human skin and can cause a number of diseases.

One of these diseases, melanoma, has more than doubled in the past 25 years and shows no signs of stopping. Melanoma is a malignant tumour of melanocytes, which are the cells that produce the skin’s natural pigmentation, melanin.

Melanin’s role in the skin is to protect our DNA from harmful UV. Granules of melanin gather above the nucleus inside cells of the epidermis, where they act as a parasol for the DNA. Hence, the more melanin in the skin, the better protected your DNA is.

Unfortunately, this also works in the converse. As a consequence, fair-skinned people in hot countries make ideal targets for malicious rays of UV. With a lack of protection from melanin, UV radiation can cause radical and irreparable DNA damage.

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This damage can then be replicated into the next cell and the next and so on. This often isn’t a problem since much of our DNA will be damaged over a lifetime. However, if the damaged DNA codes for a gene that ordinarily regulates cell growth and division, cell replication may spiral out of control.

These important regulatory genes are called proto-oncogenes and tumour-suppressor genes. It is thought that UV rays are able to initiate melanoma through damage of two different genes that both encode tumour suppressor proteins; TP53 and CDKN2A. If a tumour suppressor gene is damaged, then so may be the tumour-suppressing abilities of the protein it encodes.

So how does sun cream help to reduce damage from DNA?

Sun creams contain both chemical and physical filters. The chemical filters are organic compounds that absorb UV rays and reduce the light into heat so that it cannot harm DNA. The physical filters, which are metal oxides such as TiO2 and ZnO, block UV by reflecting and scattering the light. This provides the Sun Protection Factor (SPF) that many of us need.

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