Synthetic Modification within the “RPRL” Region of Apelin Peptides: Impact on Cardiovascular Activity and Stability to Neprilysin and Plasma Degradation

Abstract

Apelin is an important mammalian peptide hormone with a range of physiological roles, especially in the cardiovascular system. The apelinergic system is a promising target for treatment of disease, but this remains to be realized due to rapid proteolysis of apelin-derived peptides by proteases, including neprilysin (NEP). The synthetic analogues modified within the NEP degradation site ("RPRL" motif) showed improved in vitro proteolytic stability while maintaining receptor-binding affinities, with three candidate peptides retaining full cardiovascular activities for potential therapeutic application. Many such analogues proved physiologically inactive even with relatively conservative modifications, highlighting the importance of this region for full agonist activity of this peptide hormone.

Apelin directs endothelial cell differentiation and vascular repair following immune-mediated injury

“…Apelin-17 treatment blocks progression of transplant vasculopathy. To determine whether an apelin receptor agonist treatment could modify graft coronary arterial injury, we treated recipient mice daily with the synthetic apelin receptor agonist apelin-17 peptide, which is resistant to degradation by endogenous plasma proteinases (30). Treatment was begun at 2 weeks after transplantation to model the clinical scenario of treatment of early, established injury.…”

Apelins, ELABELA, and their derivatives: Peptidic regulators of the cardiovascular system and beyond

“…In the same group, McKinnie et al recently reported previously unidentified proteolytic cleavage sites between the Arg4‐Leu5 and Leu5‐Ser6 residues of apelin‐13, −17, and −36 by the metalloprotease neprilysin (NEP) . Subsequently, they introduced N ‐Methyl‐, α‐Methyl‐, aza ‐Arg, and ‐Leu residues to replace Arg4 and Leu5 in apelin‐13 (in combination with the above Pro12Aib and Phe13(4‐Br)Phe substitutions aimed to reduce proteolysis by NEP; Table ) . The resulting compounds bearing several modifications displayed high affinity (0.10‐1.0 nM), showing that these replacements did not harm receptor interaction.…”

“…To reduce proteolysis mediated by NEP, McKinnie et al reported a series of analogues where Arg8 and Leu9 of a C ‐terminal derivative of apelin‐17 were substituted by unnatural residues (Table ) . Compared to the parent peptide 34 ( K i 0.19 nM), compounds 35–40 exhibited similar binding affinities ( K i 0.13 nM – 0.45 nM).…”

“…Most significantly, following administration to mice, compounds 36 , 38 , and 40 induced a drop in MABP comparable or superior to that of the parent peptide 34 . In ex vivo Langendorff isolated heart experiments, 38 and 40 tended to improve the heart ability to recover from ischemia‐reperfusion injury compared to 34 , as shown by physiological measurements of cardiac performance parameters such as left ventricular developed pressure (LVDP) and rate‐pressure product (RPR) . Protamine, a 5–10 kDa protein originally isolated from salmon sperm, was shown to bind the apelin receptor with an affinity of 390 nM and behave as an antagonist with respect to G‐protein and β‐arrestin‐dependent signaling pathways.…”

Conformational properties, membrane interaction, and antibacterial activity of the peptaibiotic chalciporin A: Multitechnique spectroscopic and biophysical investigations on the natural compound and labeled analogs

“…Peptaibiotics are constituents of a family of naturally occurring, linear peptides , 4‐ to 21‐amino acid residue long, with membrane and antibiotic activities, characterized by a very high percentage of the effective helix‐supporting, C α ‐tetrasubstituted Aib (α‐aminoisobutyric acid) residue . Their well‐known, relevant peculiarity for drug development (peptide bond stability in the presence of plasma enzymes) is strictly related to the multiple presence of this sterically highly hindered, quaternary amino acid in the primary structure. Further stability to peptidase attack is provided by their acylated N‐terminus and amidated C‐terminus.…”