HMOX1 and brain inflammatory disease: Similarly, 6–10 weeks of exposure to PM ranging from nanoscale to PM2, 5 in C57BL/6 mice and Wistar rats resulted in increased IL-1α, IL-1β, TNFα, heme oxygenase-1 (HO-1), GFAP, CD14, and CD68 mRNA, which together confirm increased brain inflammation (Guerra et al., 2013; Cheng et al., 2016).