Abstract 11349: The Natriuretic Peptide Prohormones are Processed into Active Peptides in the Normal Human Circulation and the Processing is Preserved in Heart Failure
Introduction: We have reported that proBNP1-108 circulates in normal humans and is processed to mature BNP1-32 in human blood thus advancing the novel paradigm that proBNP1-108 is a circulating hormone. To date it remains unclear if proANP1-127 and proCNP1-103 also are processed in the circulation. We thought to determine if pre/proNP is processed in circulation and the processed forms can activate cGMP production, the second messenger of the natriuretic peptide receptors GC-A and GC-B. Since BNP1-32 is deficient and most abundant circulating BNP molecular form is proBNP1-108 in heart failure (HF), we hypothesize that each pro-or preproNPs is processed into active forms in normals but may not be in HF patients ex vivo.
Methods: Fresh serum or EDTA plasma was obtained from normal volunteers (n=11) and patients with HF (n=12). Samples were incubated with or without exogenous pro- or preproNP tagged with 6 Histidines in the C-terminal end to facilitate isolation of mature processed forms. The processed peptides were isolated by immunoprecipitation and detected by Western Blot, and then sequenced. GC-A or GC-B expressing HEK293 cells were treated with or without the isolated peptides for 10 min and cGMP activity was measured.
Results: All three precursor pre/pro NPs were processed in normal human serum. Specifically, proBNP1-108 was processed into BNP1-32*, preproANP1-151 was processed into ANP1-28* and preproCNP1-126 was processed into CNP1-53* in normal human serum (*confirmed by sequence analysis). Processed forms from each pre/proNPs were significantly increased at 5 min and persisted for 15 min, with no significant difference between normals and HF patients. Isolated processed peptides from preproANP and proBNP significantly stimulated cGMP production in GC-A cells, and those from preproCNP significantly stimulated cGMP production in GC-B cells in a pattern similar to mature ANP, BNP, and CNP.
Conclusions: All three pre/proNPs are processed in both normal and HF circulation and all processed NPs are biologically active cGMP-activating molecular forms. There is no impaired processing of exogenous non-glycosylated pre/proNPs in HF, suggesting the emerging new concept about the processing of proNPs in the circulation of both normal and disease states.
- © 2012 by American Heart Association, Inc.