An engineered cyclic peptide alleviates symptoms of inflammation in a murine model of inflammatory bowel disease

Abstract

Edited by Wolfgang PetiInflammatory bowel diseases (IBDs) are a set of complex and debilitating diseases for which there is no satisfactory treatment. Recent studies have shown that small peptides show promise for reducing inflammation in models of IBD. However, these small peptides are likely to be unstable and rapidly cleared from the circulation, and therefore, if not modified for better stability, represent non-viable drug leads. We hypothesized that improving the stability of these peptides by grafting them into a stable cyclic peptide scaffold may enhance their therapeutic potential. Using this approach, we have designed a novel cyclic peptide that comprises a small bioactive peptide from the annexin A1 protein grafted into a sunflower trypsin inhibitor cyclic scaffold. We used native chemical ligation to synthesize the grafted cyclic peptide. This engineered cyclic peptide maintained the overall fold of the naturally occurring cyclic peptide, was more effective at reducing inflammation in a mouse model of acute colitis than the bioactive peptide alone, and showed enhanced stability in human serum. Our findings suggest that the use of cyclic peptides as structural backbones offers a promising approach for the treatment of IBD and potentially other chronic inflammatory conditions. Inflammatory bowel diseases (IBDs)3 are a set of chronic inflammatory disorders of the gastrointestinal tract; the two major forms are ulcerative colitis and Crohn's disease (1). Although there are several medications on the market for IBD, they generally only provide temporary relief, and 70% of IBD patients require surgical intervention (2). Because the current treatments are not satisfactory, new drug leads are being sought from a range of sources, including small molecules from plants and bioactive regions of larger proteins (3-6).Intriguingly, several small peptides, some comprising only three residues, have been shown to be effective in the treatment of experimental colitis in mice (7-11). One example is a tripeptide (MC-12) derived from annexin A1, a calcium-dependent phospholipid-binding, anti-inflammatory protein (12). Annexin A1 mediates expression of cytokines such as TNF-␣, IL-6, and IL-10. It is required for the inhibition of NF-B activity by anti-inflammatory drugs (13) and has recently been shown to be a potential biomarker of therapeutic efficacy for IBD (14). The N-terminal region of annexin A1 comprising residues 2-26 (Ac2-26) has been well studied (15, 16) and appears to have the same biological effects as the full-length protein (17). Analysis of a series of peptides based on the N-terminal sequence of annexin A1 showed that MC-12 (Ac-Gln-Ala-Trp) was the most potent inhibitor of NF-B activity in SW480 cells (13).Small peptides such as MC-12 are likely to be unstable and not viable drug leads, supported by the finding that high doses (25 mg/kg) of MC-12 were required to elicit an in vivo response in mouse colitis models, and it was more effective when injected compared with oral administration (18). Improving t...

Designing macrocyclic disulfide-rich peptides for biotechnological applications

“…However, we know very little about why these peptides are orally active as well asor about their pharmacodynamics and pharmacokinetic properties. For now, it might be worthwhile to focus on therapeutic applications that side-step the delivery hurdle and thus allow for fast-tracking of translation 64 . For example, grafted peptides that have been developed into imaging agents with in vivo selectivity 63 could be administered intravenously.…”

Peptides as Therapeutic Agents for Inflammatory-Related Diseases

“…With the aim to identify the minimum active sequence of the N-term domain, starting from the Ac2–26 sequence, different short peptides, reported in Figure 4 , were investigated. Their action was tested in SW480 cells; only three of six peptides inhibited NF-κB activity, but the most active compound was the tripeptide named MC-12 (Ac-QAW-COOH) including fragment 10–12 ( Figure 4 ) [ 20 , 75 ].…”

Using backbone-cyclized Cys-rich polypeptides as molecular scaffolds to target protein–protein interactions

“…The SFTI-1 molecular framework was recently employed to produce a cyclic peptide for for reducing inflammation in models of inflammatory bowel diseases (IBDs) (105). In this work, the authors grafted a small bioactive peptide from the annexin A1 protein into trypsin binding loop of SFTI-1.…”