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A study looking at how Tibetan frogs living at high altitude have evolved to better protect themselves from ultraviolet radiation could help scientists better understand human diseases such as skin cancer, according to researchers involved in the project.
The team from the Chinese Academy of Sciences discovered a number of genetic and molecular mechanisms that give the frogs better protections than similar species living at lower altitude.
Su Bing, a researcher with the academy’s Kunming Institute of Zoology, said the mechanisms that help frogs adapt to UV may be useful in understanding similar processes in humans.
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“The skin structure of frogs and human beings are different so their mechanisms, including genes involved in resistance to UV radiation, may be different but the pigment formation may be similar,” said Su, who was not involved in the study.
Overexposure to UV radiation can damage the eyes and skin, as well as causing serious illnesses such as melanoma and other types of skin cancer.
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Species at high altitudes tend to have a higher capability to block UV radiation, and the differences can be reflected at the molecular level, according to the study, which was published in the peer-reviewed Proceedings of the National Academy of Sciences on Tuesday.
Most recent molecular studies on this issue have been carried out on mice or human cells in the lab. They identified specific genes that could prevent or reduce UV-induced damage, but a comprehensive understanding of UV defence mechanisms in a living organism was lacking, the authors wrote.
They compared one Tibetan frog species – Nanorana parkeri, also known as the High Himalaya frog – that lives at an altitude of 4,500 metres (14,760ft) with two other species living at lower altitudes to see how the genes of the Tibetan frog have evolved to adapt to high UV radiation.
They found that the high-altitude frogs had a different skin structure that made them more resistant to UV radiation.
“Here, we used N. parkeri to systematically demonstrate how various defence genes ... have evolved to work together in an organism to protect its skin from UV damage,” the study said.
“The mechanisms and pathways that we have identified may also be useful to understand the regulatory mechanisms underlying skin physiology and complex diseases, such as melanoma.”
The researchers exposed the three frog species to UV radiation and collected at least 54 images from each species to check their skin structures and degrees of skin damage.
After UV exposure, the researchers found that compared with the other species, the High Himalaya frog had less skin damage and exhibited greater antioxidant activity, which helps boost UV resistance.
They also produced more neurotransmitters related to anti-inflammation and wound repair compared with the unexposed frogs.
“The combined production of these compounds resulted in highly efficient antioxidant activity accompanied by immune modulation and anti-inflammatory effects, which together increase UV resistance in N. parkeri,” the study said.
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They concluded that its defences against UV were not determined by a single gene “but by a suite of genetic adaptations acting in concert”.
They also found that genes associated with defence against UV damage were activated at specific times during the exposure.
The frog’s immune system and moisturisation were activated in the early phase of UV exposure to form a protective screen for the skin, which was followed by a response from its antioxidation system.
The researchers also identified some new systems – including a heat stress response – that helps the frogs defend themselves against UV.
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