ACE2 abrogates tumor resistance to VEGFR inhibitors suggesting angiotensin-(1-7) as a therapy for clear cell renal cell carcinoma.

Angiotensin converting enzyme 2 (ACE2) is an enzyme that belongs to the renin-angiotensin system (RAS) and antagonizes the classical angiotensin (Ang) II/angiotensin II receptor type 1 (AT1) receptor pathway. Here, we report that higher ACE2 expression correlates with better overall survival in patients with clear cell renal cell carcinoma (ccRCC). Moreover, ACE2 has inhibitory effects on tumor proliferation in ccRCC in vitro and in preclinical animal models of ccRCC. We further show that Ang-(1-7), a heptapeptide generated by ACE2, is the likely mediator of this effect. Vascular endothelial growth factor receptor-tyrosine kinase inhibitor (VEGFR-TKI) treatment of ccRCC xenografts decreased ACE2 expression, and combination treatment with VEGFR-TKI and Ang-(1-7) generated additive suppression of tumor growth and improved survival outcomes. Last, the addition of Ang-(1-7) to programmed death-ligand 1 (PD-L1) pathway inhibitor and VEGFR-TKI showed further growth suppression in an immunocompetent RCC model. Together, these results suggest that targeting the ACE2/Ang-(1-7) axis is a promising therapeutic strategy against ccRCC.

Neprilysin degrades murine Amyloid-ß (Aß) more efficiently than human Aß: Further implication for species-specific amyloid accumulation.

For over a century, aggregated forms of amyloid-ß protein (Aß) have been viewed as a key hallmark of brains affected by Alzheimer's disease (AD). Today, it remains unknown whether Aß aggregates (oligomers, fibrils or plaques) originate from increased production or decreased catabolism of Aß. Neprilysin (NEP, neutral endopeptidase) is a ubiquitously distributed peptidase, known to degrade Aß, amongst other peptides. In this study, we identified differences in NEP-mediated catabolism of murine and human forms of Aß, using recombinant human NEP, membrane-bound NEP from cells overexpressing the murine peptidase or from human organ preparations with high NEP activity, and purified soluble bovine NEP. NEP degraded murine Aß (mAß) faster than human Aß (hAß). These findings were observed with full-length Aß containing 40 or 42 amino acids (Aß1-40 and Aß1-42) and a truncated form (Aß4-15), which (i) contains one of the main NEP cleavage sites for Aß (between positions 9 and 10), (ii) harbours all three amino acid differences between murine and human Aß sequences, and (iii) is less prone to aggregation and thus might be a simpler model to investigate Aß biochemistry. While it has previously been shown that mAß has a far lower propensity to aggregate than hAß, evidence from this study suggests that a faster NEP-mediated turnover of mAß may provide additional protection against Aß aggregation in murine species.

Decarboxylation of Ang-(1-7) to Ala1-Ang-(1-7) leads to significant changes in pharmacodynamics.

The heptapeptide angiotensin (Ang)-(1-7) is part of the beneficial arm of the renin-angiotensin system. Ang-(1-7) has cardiovascular protective effects, stimulates regeneration, and opposes the often detrimental effects of AngII. We recently identified the G protein-coupled receptors Mas and MrgD as receptors for the heptapeptide. Ala1-Ang-(1-7) (Alamandine), a decarboxylated form of Ang-(1-7), has similar vasorelaxant effects, but has been described as only stimulating MrgD. Therefore, this study aimed to characterise the consequences of the lack of the carboxyl group in amino acid 1 on intracellular signalling and to identify the receptor fingerprint for Ala1-Ang-(1-7). In primary endothelial and mesangial cells, Ala1-Ang-(1-7) elevated cAMP concentration. Dose response curves generated with Ang-(1-7) and Ala1-Ang-(1-7) significantly differed from each other, with a much lower EC50 and a bell-shape curve for Ala1-Ang-(1-7). We provided pharmacological proof that both, Mas and MrgD, are functional receptors for Ala1-Ang-(1-7). Consequently, in primary mesangial cells with genetic deficiency in both receptors, the heptapeptide failed to increase cAMP concentration. As we previously described for Ang-(1-7), the Ala1-Ang-(1-7)-mediated cAMP increase in Mas/MrgD-transfected HEK293 cells and primary cells was blocked by the AT2 receptor blocker, PD123319. The very distinct dose-response curves for both heptapeptides could be explained by in silico modelling, electrostatic potential calculations, and an involvement of Galpha i for higher concentrations of Ala1-Ang-(1-7). Our results identify Ala1-Ang-(1-7) as a peptide with specific pharmacodynamic properties and builds the basis for the design of more potent and efficient Ang-(1-7) analogues for therapeutic intervention in a rapidly growing number of diseases.