Identification of Novel Protein Kinase G I alpha Interacting Proteins as Potential Targets To Prevent Cardiac Remodeling

Introduction: The cardiorenal protective actions of B-type natriuretic peptide (BNP) are mediated through guanylyl cyclase A (GC-A) activation and its second messenger cGMP, while the protective actions of Angiotensin 1-7 (Ang1-7) are mediated by the Mas receptor (MasR) and its second messenger cAMP. We synthesized a chimeric peptide of human BNP (hBNP) and substituted its N-terminus with Ang1-7, to create ANG1-7/BNP. Our aim was to engineer a peptide that would activate both GC-A and MasR, with the potential to limit development of cardiorenal disease by natriuretic, antiproliferative and RAAS suppressing actions. Hypothesis: We hypothesized that ANG1-7/BNP would stimulate the GC-A and MasR in vitro, and that it would be biologically active in vivo.Methods: HEK cells expressing either GC-A or MasR were stimulated with ANG1-7/BNP. Three groups (n54) of normal dogs received 45 minutes infusions of equimolar doses of Ang1-7, hBNP or ANG1-7/BNP and hemodynamic, renal and neurohumoral functions were assessed during infusion and two hours thereafter. Results: In vitro GC-A stimulation by ANG1-7/BNP resulted in cGMP production at 10-10M, 10-8 M and 10-6 M concentrations (p!0.05). MasR stimulation by ANG1-7/BNP resulted in cAMP release at 10-6 M and 10-5 M concentrations (p!0.05). Only ANG1-7/BNP reduced SVR while both hBNP and ANG1-7/BNP lowered MAP compared to Ang1-7 with a more sustained effect by ANG1-7/BNP. Only ANG1-7/BNP reduced PCWP. ANG1-7/BNP resulted in persistent increase in RBF. HR increased in the ANG1-7/BNP group in association with the greatest decline in MAP and PCWP, however change in HR was not different from the other groups (p5ns). ANG1-7/BNP mediated a natriuretic and diuretic effect similar to hBNP, and higher than Ang1-7 (p!0.05). Plasma and urine cGMP was higher in the ANG1-7/BNP dogs compared to hBNP dogs during infusion (p!0.05). Plasma cAMP was suppressed by hBNP and ANG1-7/BNP, however, urine excretion of cAMP was equal in all groups. Conclusion: The new chimeric peptide ANG1-7/ BNP is a first in class dual activator of GC-A/MasR in vitro. ANG1-7/BNP is biologically active when infused in a large animal, with systemic and renal cGMP activation, reduction in SVR and PCWP, as well as natriuretic and diuretic properties. Through the separate signaling pathways of Ang1-7 and BNP, ANG1-7/BNP may represent a new and innovative therapy with the potential of treating acute syndromes like heart failure, and chronically in preventing progression of cardiorenal disease.