The anti-fibrotic effect of atrial natriuretic peptide depends on myocardial accumulation of the peptide in rat heart

Abstract Background The atrial natriuretic peptide (ANP) has an anti-fibrotic function for the heart. However, during heart failure (HF), which is characterized by marked myocardial fibrosis, ANP has a time-limited effect due to the rapid peptide degradation. Angiotensin-receptor-neprilysin inhibitors are a new class of drug that inhibits ANP degradation and improves cardiac performance, raising the question of the impact of increased ANP bioavailability on this pharmacological effect. Purpose We aim to assess the impact of intracardiac accumulation of ANP on cardiac function and myocardial fibrosis. An original strategy consisted of using a mutated ANP, MANP, also known as fsANP (frameshift), which is highly resistant to enzymatic degradation. Methods Type 2 diabetes was induced in adult male rats by a high fat diet coupled to low dose streptozotocin injections (25 mg/kg). MANP and ANP were administered each at a dose of 2 pmol/kg/min by subcutaneous osmotic minipumps. Sacubitril was given orally at a dose of 18 mg/kg. The protocol duration was 42 days. Cardiac fibrosis and cultured cardiac fibroblasts (CFs) were evaluated in the presence or absence of ANP, MANP, and angiotensin-receptor-neprilysin inhibitors; sacubitril. In addition to classical immunohistological and biochemical approaches, cGMP production was measured by real-time imaging in live cultured CFs (n=477). Results: MANP and sacubitril preserved cardiac performance more efficiently than ANP (p<0.05). Moreover, MANP, as well as sacubitril attenuated myocardial, epicardial, and perivascular fibrosis were more efficient than ANP (p<0.05). There was an increase in the bioavailability of MANP compared to ANP in cardiac tissue (p<0.05). Furthermore, a high-level expression of protein kinase G, and inhibition of the SMADs signaling pathway were identified in CFs. Moreover, cGMP bio-sensing in CFs, showed that similarly to ANP, MANP enhances cGMP production and activates PKG signaling, resulting in similar SMADs pathway inhibition (p<0.05). These results indicate similar biological efficiency as ANP and MANP. Conclusion MANP and sacubitril are more efficient than ANP to improve cardiac function and to reduce myocardial fibrosis in HF. Both molecules increase ANP bioavailability. This study proves that tissue accumulation of ANP is an important therapeutic target during HF.