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: CAA reduced hRPTEC cell number and protein , induced a loss in free intracellular thiols and an increase in necrosis markers .
### Output Text:
<span class="chemical">CAA</span> reduced hRPTEC cell number and protein , induced a loss in free intracellular <span class="chemical">thiols</span> and an increase in necrosis markers . 