In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Prolonged CsA exposure aggravated renal damage , without clear changes on the traditional markers , but with changes in serums TGF - b and IL - 7 , TBARs clearance , and kidney TGF - b and mTOR .
### Output Text:
Prolonged <span class="chemical">CsA</span> exposure aggravated renal damage , without clear changes on the traditional markers , but with changes in serums TGF - b and IL - 7 , TBARs clearance , and kidney TGF - b and mTOR . 