Peptide MSI‐1 inhibited MCR‐1 and regulated outer membrane vesicles to combat immune evasion of Escherichia coli

Polymyxin resistance is conferred by MCR‐1 (mobile colistin resistance 1)‐induced lipopolysaccharide (LPS) modification of G(−) bacteria. However, the peptide MSI‐1 exerts potent antimicrobial activity against mcr‐1‐carrying bacteria. To further investigate the potential role of MCR‐1 in improving bacterial virulence and facilitating immune evasion, and the immunomodulatory effect of peptide MSI‐1, we first explored outer membrane vesicle (OMV) alterations of mcr‐1‐carrying bacteria in the presence and absence of sub‐MIC MSI‐1, and host immune activation during bacterial infection and OMV stimulation. Our results demonstrated that LPS remodelling induced by MCR‐1 negatively affected OMV formation and protein cargo by E. coli. In addition, MCR‐1 diminished LPS‐stimulated pyroptosis but facilitated mitochondrial dysfunction, further aggravating apoptosis in macrophages induced by OMVs of E. coli. Similarly, TLR4‐mediated NF‐κB activation was markedly alleviated once LPS was modified by MCR‐1. However, peptide MSI‐1 at the sub‐MIC level inhibited the expression of MCR‐1, further partly rescuing OMV alteration and attenuation of immune responses in the presence of MCR‐1 during both infection and OMV stimulation, which can be exploited for anti‐infective therapy.