Ultraviolet rays on your skin may exacerbate your brain function

SEOUL, South Korea, Nov. 27, 2017 /PRNewswire/ -- A research team led by Professor Jin Ho Chung of the Department of Dermatology (Mira Han, Qing-Ling Quan, and Jae-Jun Ban) at Seoul National University Hospital (SNUH) has discovered that ultraviolet light (UV) makes stress hormone in the skin, and subsequently affects the brain function. The research team observed that UV-exposed mice show reduced neurogenesis in the hippocampus of the brain, which plays important roles in regulating memory and cognitive functions.

The research team analyzed neurogenesis as well as the changes in synaptic proteins that connect neurons to neurons in the hippocampus of the brain after irradiating the mouse skin with UV for a total of 6 times over 2 weeks. The hippocampus is an important part of the brain, which is responsible for memory and cognitive functions, and new neurons are continuously created in the hippocampus.

The research team found that, the neurogenesis and synaptic protein (NMDAR2A, PSD-95) were significantly reduced in mice exposed to UV, compared to normal mice. Brain-derived neurotrophic factor (BDNF), a major neurogenic factor, was also decreased in the hippocampus.

In addition, the experiment showed that the amount of corticosterone in the blood of the mouse that received ultraviolet light increased. The research team said that corticosterone is a stress hormone that acts on the brain through blood, and leads to impairment in the function of the hippocampus. In other words, just like a stressful condition, UV irradiation to the skin can cause memory loss and cognitive impairment. The longer the exposure to UV, the greater the effect.

UV is known to cause skin cancer and aggravate skin aging, however, this study by the Seoul National University Hospital is the world's first research to reveal that UV affects the hippocampus.

Professor Jin Ho Chung, said, "When we are going outdoors, we should always wear sunglasses and long-sleeved clothes to minimize damage to the brain caused by UV, and to maintain our memory and cognitive functions at the best conditions."

"Among the various causes of memory and cognitive decline, unintentionally received UV throughout life may be the important factor. Efforts to avoid ultraviolet rays all the time, maybe a way to maintain a memory like a young person, even if you are older."

The findings were published in the internationally renowned scientific journal, Scientific Reports.

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SOURCE Seoul National University Hospital