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 is , in part , due to ROS - mediated NO inactivation , lead - associated inhibition of NOS activity , and perhaps stimulatory actions of increased shear stress associated with hypertension .
### Output Text:
This is , in part , due to ROS - mediated <span class="chemical">NO</span> inactivation , <span class="chemical">lead</span> - associated inhibition of NOS activity , and perhaps stimulatory actions of increased shear stress associated with hypertension . 