The researchers built a mechanized rodent tanning salon and exposed mice engineered to lack the enzyme and normal mice to UV light three times a week for 20 weeks, enough to cause redness, but not to burn. At the end of the experiment, the engineered mice still had smooth, unblemished skin, while the normal mice were deeply wrinkled.
Granzyme B breaks down proteins and interferes with the organization and the integrity of collagen, dismantling the scaffolding — or extra-cellular matrix — that cells bind to. This causes structural weakness, leading to wrinkles. Sunlight appears to increase levels of the enzyme and accelerate its damaging effects.