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: This was associated with elevated renal mPGES - 1 protein expression and increased urine PGE ( 2 ) excretion .
### Output Text:
This was associated with elevated renal mPGES - 1 protein expression and increased urine <span class="chemical">PGE ( 2 )</span> excretion . 