Iyer, Seethalakshmi

Abstract Background/Introduction MANP is a novel atrial natriuretic peptide (ANP) analog bioengineered as a particulate guanylyl cyclase A receptor (GC-A) activator with superior receptor binding, resistance to neprilysin degradation, natriuretic, aldosterone suppressing and blood pressure (BP) lowering properties than native ANP. MANP is now under clinical development for resistant hypertension (RH). The rationale for its design was the fundamental role of the ANP/GC-A system in BP homeostasis through which GC-A activation with MANP leads to BP reduction through renal, vascular, and hormonal mechanisms mediated by the second messenger cGMP. Purpose We investigated the safety, tolerability, cGMP activation and BP reductions of MANP compared to placebo in subjects with RH. Methods We performed a double-blind, placebo controlled randomized trial in 36 RH patients comprised of approximately 50% non-African Americans (NAA) and 50% AA. MANP was administered in 6 cohorts receiving ascending subcutaneous (SQ) doses of MANP once daily from 3 ug/kg to a maximal dose of 7 ug/kg or placebo for 5 days and then followed for 21 days after dosing. Endpoints included safety, cGMP activation and changes in systolic BP (SBP), aldosterone (Aldo) levels and glomerular filtration rate (GFR). Results MANP was safe and well tolerated. One patient in the 7 ug/kg cohort was discontinued due to symptomatic hypotension. Compared to baseline, plasma cGMP increased in all MANP groups on Day 1 and Day 5 with no change in the placebo group. The maximal SBP reduction in the MANP group on Days 1 (D1) and 5 (D5) was -17.5 (D1) and -16 mmHg (D5) with 3 ug/kg (lowest dose) and -39.5 (D1) and -36.3 mmHg (D5) with 7 ug/kg (highest dose); Changes in the Placebo group were -6.3 (D1) and -16.7 mmHg (D5). Notably, the SBP reductions in AA were greater than NAA in the 4 and 7 ug/kg cohorts. After the 1-hour timepoint on both the first and fifth days, Aldo and percentage of Aldo reduction generally remained suppressed compared to baseline. Twenty-one days after MANP dosing, SBP remained lower in three groups receiving SQ MANP (4, 4.5 and 7 ug/kg) compared to placebo in association with a preservation of GFR. There were no reported drug related serious adverse events. Conclusions This clinical trial demonstrates that once a day SQ administration of MANP in RH subjects activates cGMP, without attenuation over 5 days, and reduces SBP and preserves GFR. At higher doses of MANP, SBP reductions were greater in AA compared to NAA. MANP also demonstrated Aldo inhibiting actions compared to placebo. Importantly, MANP was overall safe and well-tolerated. Our findings support the continued clinical development of MANP as a novel GC-A activating peptide for the treatment of RH.

Abstract Background/Introduction Hypertension (HTN) and metabolic syndrome (MetS) are both leading risk factors for major cardiovascular diseases, which frequently coexist as a complicated cardiometabolic disorder. The cardiac hormone atrial natriuretic peptide (ANP) plays a key role in both blood pressure and metabolic regulation through activation of the guanylyl cyclase-A receptor (GC-A) and the second messenger 3’,5’ cyclic guanosine monophosphate (cGMP). Indeed, ANP decreases blood pressure, induces lipolysis by increasing plasma levels of non-esterified fatty acids (NEFA) and improves insulin-sensitivity. MANP is a new Mayo Clinic designed natriuretic peptide consisting of the native ANP with a 12-amino-acid C-terminus extension and its biological actions are mediated by the GC-A/cGMP pathway. MANP is less susceptible to neprilysin degradation and exert more sustained cGMP dependent biological actions than ANP. Purpose In a proof-of-principle human study, for the first time we aimed to determine the cardiovascular and metabolic properties of MANP, a novel ANP analog, in the clinical setting of HTN with MetS. Methods We conducted a double-blind, placebo-controlled trial in 22 patients (17 receiving MANP) with HTN and MetS involving single subcutaneous injection of MANP (2.5 µg/kg) or placebo (NCT03781739). Blood pressure (BP) and circulating cGMP were monitored for 24 hours post treatment. Circulating metabolic parameters including insulin, glucose, non-esterified fatty acids (NEFA) and insulin resistance (HOMA-IR) and insulin sensitivity (HOMA-IS) indexes were assessed for the first 4 hours post treatment. Results Compared to baseline, MANP increased plasma cGMP at 30 minutes (delta: 4.8 ± 2.0 pmol/mL, P = 0.02) and 1 hour (delta: 2.9 ± 1.3 pmol/mL, P = 0.03) post injection. At 6 hours, systolic BP decreased by 5.7 ± 2.9 mmHg (P = 0.06) in the MANP group, whereas no reduction in BP was observed in placebo group. Among the 17 subjects receiving MANP, lower baseline cGMP levels were associated with greater mean reductions in systolic BP (ρ = 0.66, P = 0.005). After MANP injection, glucose levels decreased at 2 (delta: -4.7 ± 2.1 mg/mL, P = 0.04) and 4 hours (delta: -13.1 ± 3.9 mg/mL, P = 0.003) compared to baseline while insulin levels remained stable. During the first 4 hours post injection, we also observed a trend of increase in insulin sensitivity index (HOMA2-IS) and decrease in insulin resistance index (HOMA2-IR) with MANP, both were opposite to the trends in placebo. At 1 hour post MANP administration, NEFA increased by 108.2 ± 37.4 µM compared to baseline (P = 0.01). Conclusion(s) Our findings support the favorable cardiovascular and metabolic actions of MANP as a potential therapeutic strategy for HTN with MetS.

Males are characterized by lower ANP and BNP with greater prevalence of cardiometabolic disease. The ANP genetic variant rs5068 was associated with less metabolic dysfunction in males, whereas no metabolic profile was related to the BNP genetic variant rs198389 in the general population. ANP may play a more biological role in metabolic homeostasis compared with BNP in the general population with greater physiological metabolic actions in males compared with females.

Introduction: Previously, miR-425 have been implicated in the inhibition of the cardiac natriuretic peptide (NP) ANP gene expression with their role on BNP undefined. The mechanism by which miR-425 modulates NP expression remains to be explored. In heart failure (HF), adrenergic and neurohormone pathways are aberrantly activated. Our goal was to investigate the role of miR-425 and its downstream target Cofilin 2 (CFL2) on ANP and BNP expression in human CV disease (CVD). Hypothesis: We hypothesized miR-425, via CFL2, supresses NPs expression in vitro. MiR-425, CFL2 and NP levels were also determined in CVD patients. Methods: In vitro, human cardiomyocytes (HCM) were treated with vehicle (Veh), catecholamine isoproterenol (ISO) and cytokine endothelin (ET), miR-425 mimic. Cells were transfected with CFL2 plasmid or CFL2 siRNA. Normal (NM, n=100), Hypertension (HTN, n=30) and Acute HF (AHF, n=74) cohorts were studied. A confirmatory cohort was recruited. Plasma NT-proBNP, miR-425 were measured. In left ventricles (LV) from NM or HF (n=5 each), NP, CFL2 and miR-425 expression were assessed. Data expressed as means±SEM. * p<0.05 vs NM or Veh. Results: In vitro in HCM, treatment with ISO or ET in HCM reduced miR-425 and elevated NP mRNA levels. Furthermore, miR-425 mimic reduced Nppa (Veh: 1.0±0.03, mimic: 0.7±0.02*) and Nppb levels (Veh: 1.0±0.03, mimic: 0.5±0.01*). We showed that a top predicted target of miR-425, CFL2, was also reduced by the mimic. Further, NP mRNA was elevated by CFL2 overexpression and reduced by the knockdown of CFL2. In humans, MiR-425 was lower in HTN and AHF patients (NM: 0.15±0.03, HTN: 0.03±0.005*, HF: 0.01±0.003*) than NM. MiR-425 negatively correlates with NT-proBNP in NM and AHF cohorts. Downregulation of miR-425 was validated in a second AHF cohort. Similarly, in HF LV tissues, miR-425 (NM: 2.5±0.5, HF: 1.0±0.5*) was lower than NM group, while CFL2 and NP gene and protein expression were increased. Conclusion: In vitro, cardiac stress hormones downregulate miR-425 and increase NP gene expression, potentially through a novel target, CFL2. In CVD patients, miR-425 is lower, accompanied by an elevation of CFL2 and NP. Our findings implicate the pathway of stress hormones/miR-425/CFL2/NP production in CVD.

The natriuretic peptide system (NPS) and renin-angiotensin-aldosterone system (RAAS) function oppositely at multiple levels. While it has long been suspected that angiotensin II (ANGII) may directly suppress NPS activity, no clear evidence to date supports this notion. This study was designed to systematically investigate ANGII–NPS interaction in humans, in vivo, and in vitro. Circulating atrial, b-type, and c-type natriuretic peptides (ANP, BNP, CNP), cyclic guanosine monophosphate (cGMP), and ANGII were simultaneously investigated in 128 human subjects. Prompted hypothesis was validated in vivo to determine the influence of ANGII on ANP actions. The underlying mechanisms were further explored via in vitro approaches. In humans, ANGII demonstrated an inverse relationship with ANP, BNP, and cGMP. In regression models predicting cGMP, adding ANGII levels and the interaction term between ANGII and natriuretic peptides increased the predictive accuracy of the base models constructed with either ANP or BNP, but not CNP. Importantly, stratified correlation analysis further revealed a positive association between cGMP and ANP or BNP only in subjects with low, but not high, ANGII levels. In rats, co-infusion of ANGII even at a physiological dose attenuated cGMP generation mediated by ANP infusion. In vitro, we found the suppressive effect of ANGII on ANP-stimulated cGMP requires the presence of ANGII type-1 (AT1) receptor and mechanistically involves protein kinase C (PKC), as this suppression can be substantially rescued by either valsartan (AT1 blocker) or Go6983 (PKC inhibitor). Using surface plasmon resonance (SPR), we showed ANGII has low binding affinity to the guanylyl cyclase A (GC-A) receptor compared to ANP or BNP. Our study reveals ANGII is a natural suppressor for the cGMP-generating action of GC-A via AT1/PKC dependent manner and highlights the importance of dual-targeting RAAS and NPS in maximizing beneficial properties of natriuretic peptides in cardiovascular protection.

Background: Aldosterone is a critical pathological driver for cardiac and renal diseases. We recently discovered that mutant atrial natriuretic peptide (MANP), a novel atrial natriuretic peptide (ANP) analog, possessed more potent aldosterone inhibitory action than ANP in vivo. MANP and natriuretic peptide (NP)-augmenting therapy sacubitril/valsartan are under investigations for human hypertension treatment. Understanding the elusive mechanism of aldosterone inhibition by NPs remains to be a priority. Conflicting results were reported on the roles of the pGC-A (particulate guanylyl cyclase A receptor) and NP clearance receptor in aldosterone inhibition. Furthermore, the function of PKG (protein kinase G) and PDEs (phosphodiesterases) on aldosterone regulation are not clear. Methods: In the present study, we investigated the molecular mechanism of aldosterone regulation in a human adrenocortical cell line H295R and in mice. Results: We first provided evidence to show that pGC-A, not NP clearance receptor, mediates aldosterone inhibition. Next, we confirmed that MANP inhibits aldosterone via PDE2 (phosphodiesterase 2) not PKG, with specific agonists, antagonists, siRNA silencing, and fluorescence resonance energy transfer experiments. Further, the inhibitory effect is mediated by a reduction of intracellular Ca2+ levels. We then illustrated that MANP directly reduces aldosterone synthase CYP11B2 (cytochrome p450 family 11 subfamily b member 2) expression via PDE2. Last, in PDE2 knockout mice, consistent with in vitro findings, embryonic adrenal CYP11B2 is markedly increased. Conclusions: Our results innovatively explore and expand the NP/pGC-A/3',5', cyclic guanosine monophosphate (cGMP)/PDE2 pathway for aldosterone inhibition by MANP in vitro and in vivo. In addition, our data also support the development of MANP as a novel ANP analog drug for aldosterone excess treatment.

Introduction: Therapeutic strategies dual-targeting renin-angiotensin system (RAS) and natriuretic peptide system (NPS), such as Sacubitril/Valsartan, have been proven promising in treating cardiorenal disease (CRD). However, mechanisms behind the crosstalk between RAS and NPS remain to be fully elucidated. While angiotensin II (ANGII), the central RAS hormone, is thought to interact with NPS at multiple levels, whether and how it may influence the actions of particulate guanylyl cyclase A (pGC-A), the receptor activated by ANP and BNP to increase its second messenger cGMP, has not been investigated. Hypothesis: We hypothesize ANGII naturally suppresses pGC-A activity and inhibition of this ANGII mediated action can be a new strategy to combat CRD. Methods: Studies consist of biomarker analyses in plasma from healthy humans, drug infusions in normal rats, molecular characterization in human HEK293 cells, and in vitro assessment of CRRL290, an innovative dual-functional peptide designed to activate pGC-A and inhibit protein kinase C (PKC). Results: In 128 healthy humans, plasma cGMP was positively associated with ANP or BNP in low (≤ 4.5 pg/mL) but not those with high (> 4.5 pg/mL) ANGII levels. Infusion of ANP (300 pmol/kg/min) in normal rats increased plasma and urinary cGMP, however ANP mediated cGMP generation was reduced in the presence of ANGII. Interestingly, suppression effect of ANGII on pGC-A was only recapitulated in HEK293 cell overexpressing both pGC-A and AT1R, but not in HEK293 cell overexpressing pGC-A alone. We also found PKC, a known downstream target of AT1R, was a key mediator as the suppression effect of ANGII was largely ablated by Go6983, a pan PKC inhibitor. Accordingly, we designed and synthesized CRRL290. Notably, CRRL290 had superior potency in cGMP generation compared to the currently best-in-class ANP-analog, MANP, in HEK293 cells. Conclusions: We demonstrate that ANGII is a natural suppressor of pGC-A via AT1R and PKC signaling. We also report for the first time that CRRL290, a novel bioengineered peptide that activates pGC-A receptor while inhibiting PKC signaling, potently generates cGMP. Our study provides new insights into the RAS-NPS interaction, and highlights a novel and mechanism-based therapeutic avenue for treating CRD.