#5797 aminopeptidase a regulates acute angiotensin dependent hypertension

Abstract Background and Aims Aminopeptidase A (APA) is an enzyme that cleaves a single aspartate residue from the amino-terminus of several renin-angiotensin systems (RAS) peptides. We have shown that genetic deficiency of APA was associated with increased blood pressure and ultrastructural glomerular pathology in mice. Here we studied the effect of this Aminopeptidase on different peptides of the RAS and its effect on acute hypertension. Method We developed an in vitro assay based on Aspartate formation by APA to detect which Angiotensin (Ang) peptides are the substrate of this enzyme. The identified Ang peptides were injected to determine their relative effects on systolic blood pressure (SBP) in anesthetized WT mice. The effect of recombinant Aminopeptidase A on Ang I, Ang II and Ang 1-12 mediated SBP increase was further assessed in APA deficiency using global knockout mice (KO), and after systemic injection of recombinant APA. Results In the in vitro assay, the rAPA showed significant cleavage activities for Ang II (22427±3353, n = 12), Ang I (21883±1692, n = 3), Ang1-7 (15833±3395, n = 3), Ang1-9 (15773±3395, n = 3) and Ang1-12 (13170±220, n = 3) as evidenced by the formation of aspartate measured as a readout of enzymatic cleavage. When the five angiotensin peptides were injected into WT mice, only Ang I, Ang II and Ang 1-12 caused a substantial increase in SBP (Figure 1, left). In APA KO mice the bolus administration of Ang II showed an exaggerated increase in SBP compared to WT mice (Figure 1, right). The effect of Ang I and Ang 1-12 in APA KO appeared similar (not shown). When Ang I, Ang II and Ang 1-12 were administrated in WT mice preinjected with APA the increase in SBP was markedly reduced (p<0,001, p = 0,0024 and p = 0,0063, respectively). Conclusion Aminopeptidase A can cleave the N-terminal aspartate from Ang II as well as from other RAS peptides upstream [Ang 1-12, Ang I (1-10) and Ang 1-9] and downstream of Ang II (Ang 1-7). Aminopeptidase A deficiency is associated with exaggerated SBP response to Ang I, Ang II and Ang 1-12 whereas the recombinant enzyme restores the effect on acute hypertension caused by infusion of these peptides. This suggests that APA could be used to treat hypertension due to RAS overactivity.