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Pretreatment of the A549 cells with N - acetyl - cysteine ( NAC ) , an antioxidant , decreased the effects of AgNPs on the reduced cell viability , change in the MMP and proportion of cells in the sub - G1population , but had no effect on the AgNP - mediated S phase arrest or down - regulation of PCNA .
 Chemical: N - acetyl - cysteine; Chemical: NAC
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: N - acetyl - cysteine; Chemical: NAC