HMOX1 and infection: Infection with K. pneumoniae decreased protein expression of Keap1 and HO-1 in bMECs compared to the Control group at 6 or 9 hours post infection (hpi) (P < 0.05, Fig. 3C–E); however, pre-treatment with EVs prior to infection with K. pneumoniae increased Keap1 and HO-1 protein expression in bMECs as compared to the K. pneumoniae infection group at 6 or 9 hpi (P < 0.05, Fig. 3C–E).