ACE2 and COVID-19: In conclusion, ACE2 is important because (a) it activates the Nrf2 (anti-inflammatory) pathway and instead turns off NFKB (inflammatory) to avoid a dysregulated inflammation response; (b) COVID-19, by binding to ACE2, alters this mechanism; and (c) ACE2 is over-expressed following exposure to PM2.5, and thus it may be plausible that it could increase the probability of COVID-19 infection, with ACE2 being the entry key for the virus.