Received for publication September 22, 2008.
Revised November 26, 2008.
Accepted for publication November 26, 2008.

Angiotensin-(1-7) with thioether-bridge: an ACE-resistant, potent Ang-(1-7) analogue

Abstract

The in vivo efficacy of many therapeutic peptides is hampered by their rapid proteolytic degradation. Cyclization of these therapeutic peptides is an excellent way to render them more resistance against breakdown. Here we describe the enzymatic introduction of a thioether ring in angiotensin (Ang)-(1-7), a heptapeptide that plays a pivotal role in the renin-angiotensin system and possesses important therapeutic activities. The lactic acid bacterium Lactococcus lactis equipped with the plasmid-based nisin modification machinery was used to produce thioether bridged Ang-(1-7). The resulting cyclized Ang-(1-7) is fully resistant against purified angiotensin-converting enzyme, has significantly increased stability in homogenates of different organs and in plasma derived from pig, and displays a strongly (34-fold) enhanced survival in Sprague Dawley (SD) rats, in vivo. With respect to functional activity, cyclized Ang-(1-7) induces relaxation of precontracted SD rat aorta rings, in vitro. The magnitude of this effect is two-fold larger than that obtained for natural Ang-(1-7). The Ang-(1-7) receptor antagonist D-Pro⁷-Ang-(1-7) which completely inhibits the activity of natural Ang-(1-7) also abolishes the vasodilation by cyclized Ang-(1-7), providing evidence that also cyclized Ang-(1-7) interacts with the Ang-(1-7) receptor. Taken together, applying a highly innovative enzymatic peptide stabilization method we generated a stable Ang-(1-7) analogue with strongly enhanced therapeutic potential.

Key words: ACE, angiotensin-(1-7) analogue, cyclization, proteolytic resistance, thioether bridge, vasodilation