Abstract
Although CD14 has been implicated in the initiation of multiple TLR-mediated inflammatory responses to sepsis and sepsis-related acute lung injury (ALI), an inhibitor of CD14, except for neutralizing Abs, has not been developed. A partial peptide, microglial healing peptide 1 with N-terminal acetylation and C-terminal amidation (MHP1-AcN), derived from the receptor activator of the NF-кB ligand, was recently found to inhibit multiple TLR signaling in the macrophages. Therefore, we hypothesized that the inhibitory effect of MHP1-AcN might be through the inhibition of CD14, a common coreceptor for multiple TLRs. In cultured mouse macrophages, MHP1-AcN was shown to bind to CD14 and compete with LPS for competitive inhibition of CD14, resulting in inhibition of TLR4 signaling, including NF-кB and IFN regulatory factor 3 activation and nuclear translocation. In addition to TLR2, TLR4, and TLR7, MHP1-AcN also inhibited TLR3 signaling and Escherichia coli DNA-induced, CD14-dependent TLR9 signals; however, CpG oligodeoxynucleotide-induced, CD14-independent TLR9 signals were not inhibited in the mouse macrophages. In sepsis-induced ALI mouse model, MHP1-AcN treatment showed the reduction in the expression of IL-6 and CCL2 in both the serum and lung tissues. IL-6 levels in the bronchoalveolar lavage fluid and pathological score were also decreased by MHP1-AcN. Thus, MHP1-AcN, a novel CD14 inhibitor, could be a promising agent for treating sepsis-induced ALI.