Antisense Growth Inhibition of Methicillin-Resistant Staphylococcus aureus by Locked Nucleic Acid Conjugated with Cell-Penetrating Peptide as a Novel FtsZ Inhibitor

Methicillin-resistant Staphylococcus aureus (MRSA) infections are becoming increasingly difficult to treat, owing to acquired antibiotic resistance. The emergence and spread of MRSA limit therapeutic options and require new therapeutic strategies, including novel MRSA-active antibiotics. Filamentous temperature-sensitive protein Z (FtsZ) is a highly conserved bacterial tubulin homologue that is essential for controlling the bacterial cell division process in different species of S. aureus. We conjugated a locked nucleic acid (LNA) that targeted ftsZ mRNA with the peptide (KFF)3K, to generate peptide-LNA (PLNA). The present study aimed to investigate whether PLNA could be used as a novel antibacterial agent. PLNA787, the most active agent synthesized, exhibited promising inhibitory effects on four pathogenic S. aureus strains in vitro. PLNA787 inhibited bacterial growth and resolved lethal Mu50 infections in epithelial cell cultures. PLNA787 also improved the survival rates of Mu50-infected mice and was associated with reductions of bacterial titers in several tissue types. The inhibitory effects on ftsZ mRNA and FtsZ protein expression and inhibition of the bacterial cell division process are considered to be the major mechanisms of PLNA. PLNA787 demonstrated activity against MRSA infections in vitro and in vivo. Our findings suggest that ftsZ mRNA is a promising new target for developing novel antisense antibiotics.