22275
The effects of BAE and AE on UVB - induced photoaging were tested by measuring the levels of reactive oxygen species , MMP - 1 , MMP - 3 , IL - 6 , type I procollagen , and TGF - beta 1 after UVB irradiation .
 oxygen
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 oxygen