Levels of a protein called lamin B1 could be used to measure how sun exposure accelerates skin aging.
Lamins are components of the nuclear lamina, a fibrous layer on the nucleoplasmic side of the inner nuclear membrane, which is thought to provide a framework for the nuclear envelope and may also interact with chromatin. Researchers from A*STAR and their colleagues were studying the cells of patients with progeria, a genetic disorder that causes them to age and die prematurely, when they realized that these patients’ senescent cells — those that have stopped growing and dividing — showed very low levels of lamin B1.
“Lamin B1 is expressed in every cell type of the human body, so if this protein disappears when cells age, it could be a useful new marker to identify aging cells,” says Oliver Dreesen, from the A*STAR Institute of Medical Biology.
Researchers decided to use this knowledge to look at the effects of ultraviolet light on skin cell aging. To begin with, they exposed human skin cells in a petri dish to the same amount of ultraviolet B light that might be experienced by someone spending around 18 minutes in the Singaporean sun in the middle of the day.
They found that in the UVB-exposed cells, the levels of lamin B1 dropped, while in cells that were protected with SPF50 sunscreen, the levels remained the same, suggesting that the UVB exposure was leading to cell senescence.
The researchers also wanted to know how UVB exposure affected cells in different skin layers, so, in collaboration with Carlos Clavel, also from the Institute of Medical Biology, they looked at lamin B1 levels in mice whose skin was treated with UVB light daily for ten days.
“In our experiment, UVB light only affected the epidermis, the top layer of the skin, and it didn’t seem to affect the dermis, which is the lower part,” Dreesen says.
The researchers also noticed that once the mice’s skin recovered from the UVB exposure and the skin regenerated, the levels of lamin B1 returned to normal.
As well as providing a way to measure sun damage of skin cells, lamin B1 levels could also help in the study of age-related skin problems such as actinic keratosis, which is caused by sun exposure. It could also help explore the impact of other environmental conditions, such as pollution, on skin aging.
“The long-term goal is to set up a toolkit that allows us to systematically look at how senescent cells contribute to pathological and cosmetic changes that occur in aging skin,” Dreesen says.