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: We concluded a critical time window for systemic lipopolysaccharide pretreatment in exerting effective protection against methamphetamine - induced nigrostriatal dopamine neurotoxicity .
### Output Text:
We concluded a critical time window for systemic <span class="chemical">lipopolysaccharide</span> pretreatment in exerting effective protection against <span class="chemical">methamphetamine</span> - induced nigrostriatal <span class="chemical">dopamine</span> neurotoxicity . 