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Stimulation of the angiotensin II type 2 receptor (AT 2 R) evokes protective effects in various cardiovascular diseases. Thus, this study aimed to investigate the effects of AT 2 R stimulation, with or without AT 1 R blockade, in a model of hypertension with concomitant type 1 diabetes mellitus (T1DM). Spontaneously hypertensive rats (SHRs) were given either citrate or a single dose of streptozotocin (STZ; 55 mg/kg, i.p.) to induce diabetes. After 4 weeks of diabetes, animals were administered either a vehicle (saline), AT 2 R agonist, β-Pro 7 Ang III (0.1 mg/kg/day via osmotic mini-pump), AT 1 R blocker, candesartan (2 mg/kg/day via drinking water), or a combination of both for a further 8 weeks. β-Pro 7 Ang III treatment had no effect on blood pressure, but attenuated the significant increase in cardiac interstitial collagen and protein expression of fibrotic and inflammatory markers, and superoxide levels that was evident in diabetic SHRs. These effects were not observed with candesartan, despite its blood pressure lowering effects. Although β-Pro 7 Ang III had no effect on aortic fibrosis, it significantly attenuated MCP-1 protein expression and superoxide levels when compared to both the non-diabetic and diabetic SHRs, to a similar extent as candesartan. In both the heart and vasculature, the effects of β-Pro 7 Ang III in combination with candesartan were similar to those of β-Pro 7 Ang III alone, and superior to candesartan alone. It was concluded that in hypertension with concomitant diabetes, AT 2 R stimulation with a novel ligand alone, or in combination with AT 1 R blockade, improved the cardiac and vascular structural changes that were strongly associated with inflammation and oxidative stress, independent of blood pressure regulation., Competing Interests: Declaration of Competing Interest Please declare any financial or personal interests that might be potentially viewed to influence the work presented. Interests could include consultancies, honoraria, patent ownership or other. If there are none state ‘there are none’., (Copyright © 2023. Published by Elsevier Masson SAS.)

Background and Purpose: This study investigated the reno-protective effects of a highly selective AT 2 R agonist peptide, β-Pro 7 Ang III in a mouse model of acute kidney injury (AKI)., Methods: C57BL/6 J mice underwent either sham surgery or unilateral kidney ischemia-reperfusion injury (IRI) for 40 min. IRI mice were treated with either β-Pro 7 Ang III or perindopril and at 7 days post-surgery the kidneys analysed for histopathology and the development of fibrosis and matrix metalloproteinase (MMP)-2 and -9 activity. The association of the therapeutic effects of β-Pro 7 Ang III with macrophage number and phenotype was determined in vivo and in vitro., Key Results: Decreased kidney tubular injury, interstitial matrix expansion and reduced interstitial immune cell infiltration in IRI mice receiving β-Pro 7 Ang III treatment was observed at day 7, compared to IRI mice without treatment. This correlated to reduced collagen accumulation and MMP-2 activity in IRI mice following β-Pro 7 Ang III treatment. FACS analysis showed a reduced number and proportion of CD45 + CD11b + F4/80 + macrophages in IRI kidneys in response to β-Pro 7 Ang III, correlating with a significant increase in M2 macrophage markers and decreased M1 markers at day 3 and 7 post-IR injury, respectively. In vitro analysis of cultured THP-1 cells showed that β-Pro 7 Ang III attenuated lipopolysaccharide (LPS)-induced tumour necrosis factor-α (TNF-α) and interleukin (IL)- 6 production but increased IL-10 secretion, compared to LPS alone., Conclusion: Administration of β-Pro 7 Ang III via mini-pump improved kidney structure and reduced interstitial collagen accumulation, in parallel with an alteration of macrophage phenotype and anti-inflammatory cytokine release, therefore mitigating the downstream progression of ischemic AKI., Competing Interests: Conflict of interest statement The authors declare that there are no conflicts of interests., (Copyright © 2023. Published by Elsevier Masson SAS.)

A high salt (HS) diet is associated with an increased risk for cardiovascular diseases (CVDs) and fibrosis is a key contributor to the organ dysfunction involved in CVDs. The activation of the renin angiotensin type 2 receptor (AT 2 R) has been considered as organ protective in many CVDs. However, there are limited AT 2 R-selective agonists available. Our first reported β-substituted angiotensin III peptide, β-Pro 7 -AngIII, showed high selectivity for the AT 2 R. In the current study, we examine the potential anti-fibrotic and anti-inflammatory effects of this novel AT 2 R-selective peptide on HS-induced organ damage. FVB/N mice fed with a 5% HS diet for 8 weeks developed cardiac and renal fibrosis and inflammation, which were associated with increased TGF-β1 levels in heart, kidney and plasma. Four weeks' treatment (from weeks 5-8) with β-Pro 7 -AngIII inhibited the HS-induced cardiac and renal fibrosis and inflammation. These protective effects were accompanied by reduced local and systemic TGF-β1 as well as reduced cardiac myofibroblast differentiation. Importantly, the anti-fibrotic and anti-inflammatory effects caused by β-Pro 7 -AngIII were attenuated by the AT 2 R antagonist PD123319. These results demonstrate, for the first time, the cardio- and reno-protective roles of the AT 2 R-selective β-Pro 7 -AngIII, highlighting it as an important therapeutic that can target the AT 2 R to treat end-organ damage.

The Renin-Angiotensin System (RAS) plays a crucial role in numerous pathological conditions. Two of the critical RAS players, the angiotensin receptors AT1R and AT2R, possess differential functional profiles, although they share high sequence similarity. Although the main focus has been placed on AT1R, several epidemiological studies have evidenced that activation of AT2R could operate as a multimodal therapeutic target for different diseases. Thus, the development of selective AT2R ligands could have a high clinical potential for different therapeutic directions. Furthermore, they could serve as a powerful tool to interrogate the molecular mechanisms that are mediated by AT2R. Based on our recently established high affinity and AT2R selective compound [Y] 6 -AII we developed several analogues through modifying aminoacids located at positions 6 and 7 with various conformationally constrained analogues to enhance both the selectivity and stability. We report the development of high-affinity AT2R binders, which displayed high selectivity for AT2R versus AT1R. Furthermore, all analogues presented enhanced stability in human plasma with respect to the parent hormone Angiotensin II as also [Y] 6 -AII., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Peptide self-assembly has been exploited to generate a multitude of biomaterials that exhibit biocompatibility due to their similarity to naturally occurring proteins. Previously, we have shown that β-tripeptides self-assemble despite containing sterically bulky, functional sidechains. Herein, we describe the synthesis of a novel β-amino acid to allow for the synthesis of a trifunctional β-tripeptide that remarkably maintains self-assembly and acts as a bioactive neuronal scaffold. These scaffolds show promise for studies involving neuronal cell growth and development.

Mutating the side-chains of amino acids in a peptide ligand, with unnatural amino acids, aiming to mitigate its short half-life is an established approach. However, it is hypothesized that mutating specific backbone peptide bonds with bioisosters can be exploited not only to enhance the proteolytic stability of parent peptides, but also to tune its receptor subtype selectivity. Towards this end, four [Y] 6 -Angiotensin II analogues are synthesized where amide bonds have been replaced by 1,4-disubstituted 1,2,3-triazole isosteres in four different backbone locations. All the analogues possessed enhanced stability in human plasma in comparison with the parent peptide, whereas only two of them achieved enhanced AT 2 R/AT 1 R subtype selectivity. This diversification has been studied through 2D NMR spectroscopy and unveiled a putative more structured microenvironment for the two selective ligands accompanied with increased number of NOE cross-peaks. The most potent analogue, compound 2, has been explored regarding its neurotrophic potential and resulted in an enhanced neurite growth with respect to the established agent C21., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

There are a number of therapeutic targets to treat organ fibrosis that are under investigation in preclinical models. There is increasing evidence that stimulation of the angiotensin II type 2 receptor (AT 2 R) is a novel anti-fibrotic strategy and we have reviewed the published in vivo preclinical data relating to the effects of compound 21 (C21), which is the only nonpeptide AT 2 R agonist that is currently available for use in chronic preclinical studies. In particular, the differential influence of AT 2 R on extracellular matrix status in various preclinical fibrotic models is discussed. Collectively, these studies demonstrate that pharmacological AT 2 R stimulation using C21 decreases organ fibrosis, which has been most studied in the setting of cardiovascular and renal disease. In addition, AT 2 R-mediated anti-inflammatory effects may contribute to the beneficial AT 2 R-mediated anti-fibrotic effects seen in preclinical models.

β(3)-amino acid based polypeptides offer a unique starting material for the design of self-assembled nanostructures such as fibres and hierarchical dendritic assemblies, due to their well-defined helical geometry in which the peptide side chains align at 120° due to the 3.0-3.1 residue pitch of the helix. In a previous work we have described the head-to-tail self-assembly of N-terminal acetylated β(3)-peptides into infinite helical nanorods that was achieved by designing a bioinspired supramolecular self-assembly motif. Here we describe the effect of consecutively more polar side chains on the self-assembly characteristics of β(3)-tetrapeptides Ac-β (3)Ala-β(3)Leu-β(3)Ile-β(3)Ala (Ac-β(3)[ALIA]), Ac-β(3)Ser-β(3)Leu-β(3)Ile-β(3)Ala (Ac-β(3)[SLIA]) and Ac-β (3)Lys-β (3)Leu-β(3)Ile-β (3)Glu (Ac-β(3)[KLIE]). β(3)-tetrapeptides complete 1 1/3 turns of the helix: thus in the oligomeric form the side chain positions shift 120° with each added monomer, forming a regular periodic pattern along the nanorod. Dynamic light scattering (DLS) measurements confirmed that these peptides self-assemble even in highly polar solvents such as water and DMSO, while diffusion-ordered NMR spectroscopy revealed the presence of a substantial monomeric population. Temperature dependence of the size distribution in DLS measurements suggests a dynamic equilibrium between monomers and oligomers. Solution casting produced distinct fibrillar deposits after evaporating the solvent. In the case of the apolar Ac-β(3)[ALIA] the longitudinal helix morphology gives rise to geometrically defined (∼70°) junctions between fibres, forming a mesh that opens up possibilities for applications e.g. in tissue scaffolding. The deposits of polar Ac-β(3)[SLIA] and Ac-β(3)[KLIE] exhibit fibres in regular parallel alignment over surface areas in the order of 10 μm.

We have previously shown that individual β-amino acid substitution in angiotensin (Ang) II reduced Ang II type 1 receptor (AT1R) but not Ang II type 2 receptor (AT2R)-binding and that the heptapeptide Ang III exhibited greater AT2R:AT1R selectivity than Ang II. Therefore, we hypothesized that β-amino-acid-substituted Ang III peptide analogues would yield highly selective AT2R ligands, which we have tested in binding and functional vascular assays. In competition binding experiments using either AT1R- or AT2R-transfected human embryonic kidney (HEK)-293 cells, novel β-substituted Ang III analogues lacked appreciable AT1R affinity, whereas most compounds could fully displace (125)I-Sar(1)Ile(8) Ang II from AT2R. The rank order of affinity at AT2R was CGP42112 > Ang III > β-Pro(7) Ang III=Ang II > β-Tyr(4) Ang III ≥ PD123319 >> β-Phe(8) Ang III >> β Arg(2) Ang III=β-Val(3) Ang III >> β-Ile(5) Ang III. The novel analogue β-Pro(7) Ang III was the most selective AT2R ligand tested, which was >20,000-fold more selective for AT2R than AT1R. IC50 values at AT2R from binding studies correlated with maximum vasorelaxation in mouse aortic rings. Given that β-Pro(7) Ang III was an AT2R agonist, we compared β-Pro(7) Ang III and native Ang III for their ability to reduce blood pressure in separate groups of conscious spontaneously hypertensive rats. Whereas Ang III alone increased mean arterial pressure (MAP), β-Pro(7) Ang III had no effect. During low-level AT1R blockade, both Ang III and β-Pro(7) Ang III, but not Ang II, lowered MAP (by ∼30 mmHg) at equimolar infusions (150 pmol/kg/min for 4 h) and these depressor effects were abolished by the co-administration of the AT2R antagonist PD123319. Thus, β-Pro(7) Ang III has remarkable AT2R selectivity determined in binding and functional studies and will be a valuable research tool for insight into AT2R function and for future drug development., (© 2015 Authors; published by Portland Press Limited.)

Endomorphin 1 (Endo-1=Tyr-Pro-Trp-Phe-NH(2)), an endogenous opioid with high affinity and selectivity for mu-opioid receptors, mediates acute and neuropathic pain in rodents. To overcome metabolic instability and poor membrane permeability, the N- and C-termini of Endo-1 were modified by lipoamino acids (Laa) and/or sugars, and 2',6'-dimethyltyrosine (Dmt) replacement of Tyr. Analogues were assessed for mu-opioid receptor affinity, inhibition of cAMP accumulation, enzymatic stability, and permeability across Caco-2 cell monolayers. C-terminus modification decreased receptor affinity, while N-terminus C8-Laa improved stability and permeability with slight change in receptor affinity. Dmt provided a promising lead compound: [C8Laa-Dmt[1]]-Endo-1 is nine times more stable (t(1/2)=43.5min), >8-fold more permeable in Caco-2 cell monolayers, and exhibits 140-fold greater mu-opioid receptor affinity (K(imu)=0.08nM).