HMOX1 and COVID-19: Therefore, in a recent publication, we evaluated in an in vivo model whether RAS could be the trait d’union between air pollution and COVID-19 by assessing the ACE2 and ACE expression levels, as well as those of inflammatory markers (cyclooxygenase 2, COX-2) and oxidative stress markers (heme oxygenase-1, HO-1, and inducible nitric oxide synthase, iNOS), following exposure to PM2.5 [34].