Nano-Antagonist Alleviates Inflammation and Allows for MRI of Atherosclerosis

Specific targeting of inflammation remains a challenge in many pathologies, because of the necessary balance between host tolerance and efficacious inflammation resolution. Here, we discovered a short, 4-mer peptide which possesses antagonist properties towards CC chemokine receptor 2 (CCR2), but only when displayed on the surface of lipid nanoparticles. According to BLAST analysis, this peptide motif is a common repeating fragment in a number of proteins of the CC chemokine family, which are key players in the inflammatory response. In this study, self-assembled, peptide-conjugated nanoparticles (CCTV) exhibited typical properties of CCR2 antagonism, including affinity to the CCR2 receptor, inhibition of chemotactic migration of primary monocytes, and prevention from CC chemokine ligand 2 (CCL2)-induced actin polymerization. Furthermore, CCTV ameliorated NFkB activation and downregulated the secondary, but not the primary, inflammatory response in cultured macrophages. When conjugated with gadolinium or europium cryptates, CCTV enabled targeted imaging (via magnetic resonance imaging and time-resolved fluorescence) of atherosclerosis, a chronic inflammatory condition in which the CCL2/CCR2 axis is highly dysfunctional. CCTV targeted CCR2(hi)Ly6C(hi) inflammatory monocytes in blood and the atherosclerotic plaque, resulting in cell-specific transcriptional downregulation of key inflammatory genes. Finally, CCTV generated pronounced inflammasome inactivation, likely mediated through reactive oxygen species scavenging and downregulation of NLRP3. In summary, our work demonstrates for the first time that a short peptide fragment presented on a nanoparticle surface exhibit potent receptor-targeted antagonist effects, which are not seen with the peptide alone. Unlike commonly used cargo-carrying, vector-directed drug delivery vehicles, CCTV nanoparticles may act as therapeutics/theranostics themselves, particularly in inflammatory conditions with CCL2/CCR2 pathogenesis, including cardiovascular disease and cancer.