Colored sunscreen protects skin from damage caused by visible light

December 05, 2017

There is something wrong with people's exposure to sunlight. Despite rising worldwide consumption of sunscreens, the number of cases of skin cancer continues to grow. One of the reasons may be the action of visible light, which is also harmful to skin and is not blocked by conventional sunscreens.

This is the conclusion drawn by a team at the Center for Research on Redox Processes in Biomedicine (Redoxome), one of the Research, Innovation and Dissemination Centers (RIDCs) funded by the São Paulo Research Foundation - FAPESP. In an article published in the Journal of Investigative Dermatology, the researchers describe the combined damaging effects of UVA (long-wavelength ultraviolet radiation) and visible light on the cells that produce keratin.

"We knew visible light could damage the skin, but we've gained a deeper understanding of the mechanisms by showing that UVA stimulates accumulation of a pigment called lipofuscin, which later acts as a photosensitizer to visible light in the epidermis," said Maurício Baptista, a professor at the University of São Paulo's Chemistry Institute (IQ-USP), in Brazil, and a member of Redoxome.

"Basically, UVA damages the skin, and visible light augments the damage," he said.

A physical barrier such as cloth or apparel, or else a colored sunscreen, is needed to protect the skin from the adverse effects of visible light. "A colored sunscreen shouldn't be just any color," Baptista said. "It should be the same hue as the individual's own skin tone. We've developed a product that protects the skin against UVA, UVB and visible light. It uses nanoparticles coated with a fine film of melanin. This invention is patented [by the University of São Paulo, with FAPESP's support], and we're looking for partners to produce it."

Lack of strategy for protection against visible light

Baptista adverts about the way we protect our skin against sunlight: not only it is wrong, but it is also exaggerated. "Vitamin D levels are steadily falling in the Brazilian population because we hardly expose ourselves to the sun at all without sunscreen. However, we don't avoid visible light, which also damages the epidermis and isn't blocked by sunscreen."

The mechanism by which visible light and UVA damage the skin is the same. Both act on the cells of the epidermis by means of photoexcitation.

UVA radiation penetrates deeper into the epidermis and causes another kind of damage, which is perceptible in the long run. "We believe the types of skin cancer characterized by exposure to UVA must also be due in large measure to the action of visible light, which has never been taken into account," Baptista said. "UVA and visible light cause similar lesions. They act together. Both the oxidative damage done by UVA and the effect of visible light cause DNA oxidation."

This is completely different from the way UVB (shortwave ultraviolet) damages the skin. UVB radiation is directly absorbed by epidermal cell DNA. The response is much faster, consisting initially of redness for people who produce less melanin, and the skin is more severely damaged. Infrared radiation heats the blood vessels and causes inflammation.

Protection against UVB is also essential. "It would be quite wrong to interpret the study as saying we don't need to use sunscreen. That's not the point at all. UVB is far more toxic than UVA and visible light, but the number of cases of severe skin cancer is rising largely because people have been protecting themselves from UVB for at least 40 years, yet for a long time, there were no products to block UVA. There aren't any visible light blockers even now," he said.

Damage to keratinocytes

In a 2014 study, the Redoxome team focused on finding out how melanocytes, cells that produce melanin, respond to visible light. The new study goes further by analyzing how keratinocytes, which correspond to most epidermal cells, are damaged by visible light.

According to Baptista, keratinocytes are the first victims of the damage done by UVA, which makes these cells produce lipofuscin, which acts as a visible light photosensitizer, generating reactive oxygen species and mediating light-induced damage. "We found that not just melanocytes but also keratinocytes are damaged by visible light," he said.

Visible light has fewer damaging effects on the skin than other kinds of solar radiation, but the response in the epidermis is augmented when the skin is no longer healthy owing to damage by UVA. Moreover, visible light accounts for 45% of the solar radiation that reaches the skin, while UV accounts for only 5%.
About São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. For more information:

Fundação de Amparo à Pesquisa do Estado de São Paulo

Related Solar Radiation Articles from Brightsurf:

Sheer protection from electromagnetic radiation
A printable ink that is both conductive and transparent can also block radio waves.

What membrane can do in dealing with radiation
USTC recently found that polymethylmethacrylate (PMMA) and polyvinyl chloride (PVC) can release acidic substance under γ radiation, whose amount is proportional to the radiation intensity.

First measurements of radiation levels on the moon
In the current issue (25 September) of the prestigious journal Science Advances, Chinese and German scientists report for the first time on time-resolved measurements of the radiation on the moon.

Merging solar cell and liquid battery produces long-lasting solar storage
Combining liquid chemical battery technology with perovskite solar cells has led to a new record in solar energy conversion within a single device.

Merging solar cell and liquid battery produces efficient, long-lasting solar storage
Chemists at the University of Wisconsin-Madison and their collaborators have created a highly efficient and long-lasting solar flow battery, a way to generate, store and redeliver renewable electricity from the sun in one device.

New biomaterial could shield against harmful radiation
Northwestern University researchers have synthesized a new form of melanin enriched with selenium.

The effectiveness of a heating system is validated, heating air from solar radiation
The device, which takes advantage of heat generated on the outer layer of building facades, could cover the heating required to ventilate a building for up to 75% of the days in a cold season.

Solar wind samples suggest new physics of massive solar ejections
A new study led by the University of Hawai'i (UH) at Mānoa has helped refine understanding of the amount of hydrogen, helium and other elements present in violent outbursts from the Sun, and other types of solar 'wind,' a stream of ionized atoms ejected from the Sun.

Nimotuzumab-cisplatin-radiation versus cisplatin-radiation in HPV negative oropharyngeal cancer
Oncotarget Volume 11, Issue 4: In this study, locally advanced head and neck cancer patients undergoing definitive chemoradiation were randomly allocated to weekly cisplatin - radiation {CRT arm} or nimotuzumab -weekly cisplatin -radiation {NCRT arm}.

Breaking up amino acids with radiation
A new experimental and theoretical study published in EPJ D has shown how the ions formed when electrons collide with one amino acid, glutamine, differ according to the energy of the colliding electrons.

Read More: Solar Radiation News and Solar Radiation Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to