The aging heart, myocardial fibrosis, and its relationship to circulating C-type natriuretic Peptide

Myocardial aging is characterized by left ventricular (LV) fibrosis leading to diastolic and systolic dysfunction. Studies have established the potent antifibrotic and antiproliferative properties of C-type natriuretic peptide (CNP); however, the relationship between circulating CNP, LV fibrosis, and associated changes in LV function with natural aging are undefined. Accordingly, we characterized the relationship of plasma CNP with LV fibrosis and function in 2-, 11-, and 20-month-old male Fischer rats. Further in vitro, we established the antiproliferative actions of CNP and the participation of the clearance receptor using adult human cardiac fibroblasts. Here we establish for the first time that a progressive decline in circulating CNP characterizes natural aging and is strongly associated with a reciprocal increase in LV fibrosis that precedes impairment of diastolic and systolic function. Additionally, we demonstrate in cultured adult human cardiac fibroblasts that the direct antiproliferative actions of high-dose CNP may involve a non-cGMP pathway via the clearance receptor. Together, these studies provide new insights into myocardial aging and the relationship to the antifibrotic and antiproliferative peptide CNP.     

Surveillance mammography after treatment for male breast cancer

Breast Cancer Research and Treatment - To identify the practice patterns related to use of surveillance mammography in male breast cancer (MaBC) survivors. Using administrative claims data from...     

Factors Associated with Emergency Department Utilization and Admission in Patients with Colorectal Cancer

Purpose

We assessed emergency department (ED) utilization in patients with colorectal cancer to identify factors associated with ED visits and subsequent admission, as well as identify a high-risk subset of patients that could be targeted to reduce ED visits.

Methods

Data from Optum Labs Data Warehouse, a national administrative claims database, was retrospectively analyzed to identify patients with colorectal cancer from 2008 to 2014. Multivariable logistic regression was used to identify factors associated with ED visits and ED “super-users” (3+ visits). Repeated measures analysis was used to model ED visits resulting in hospitalization as a logistic regression based on treatments 30 days prior to ED visit.

Results

Of 13,466 patients with colorectal cancer, 7440 (55.2%) had at least one ED visit within 12 months of diagnosis. Factors associated with having an ED visit included non-white race, advancing age, increased comorbidities, and receipt of chemotherapy or radiation. 69.2% of patients who visited the ED were admitted to the hospital. A group of 1834 “super-users” comprised 13.6% of our population yet accounted for 52.1% of the total number of ED visits and 32.3% of admissions.

Conclusions

Over half of privately insured patients undergoing treatment for colorectal cancer will visit the ED within 12 months of diagnosis. Within this group, we identify common factors for a high-risk subset of patients with three or more ED visits who account for over half of all ED visits and a third of all admissions. These patients could potentially be targeted with alternative management strategies in the outpatient setting.

     

Estrogen protects against the development of salt-induced cardiac hypertrophy in heterozygous proANP gene-disrupted mice

Cardiovascular disease is the leading cause of morbidity and mortality in both men and women, but the incidence for women rises sharply after menopause. This has been mainly attributed in the reduction of the female sex hormone estrogen during menopause, suggesting that estrogen may have cardioprotective effects, although how estrogen exerts its cardioprotective effects is not fully understood. Moreover, the beneficial effect of estrogen on end-organ damage such as cardiac hypertrophy (CH) remains unclear. The aim of the present study was to examine the interaction between estrogen and the natriuretic peptide system (NPS) and their possible roles during the development of CH by using the proANP heterozygous atrial natriuretic peptide (ANP +/-) mouse as a model of salt-sensitive CH. Male, female ANP +/- mice, and also ovariectomized (Ovx) female ANP +/- mice treated with oil or estrogen were fed either a normal or high salt (HS) diet. After a 5-week treatment period, marked CH was noted in the male and oil-injected Ovx female ANP +/- mice treated with HS. The cardiac NPS, i.e. ANP, B-type natriuretic peptide, and natriuretic peptide receptor-A, was activated in these ANP +/- mice. Interestingly, the female and estrogen-injected Ovx female ANP +/- mice did not exhibit CH, and the cardiac NPS remained unchanged. Collectively, we provide direct evidence that estrogen has the ability to resist the induction of salt-induced CH in ANP +/- mice. Furthermore, the development of hypertrophy may be activating the cardiac NPS in an attempt to blunt these structural changes.     

Discovery of small molecule guanylyl cyclase A receptor positive allosteric modulators

The particulate guanylyl cyclase A receptor (GC-A), via activation by its endogenous ligands atrial natriuretic peptide (ANP) and b-type natriuretic peptide (BNP), possesses beneficial biological properties such as blood pressure regulation, natriuresis, suppression of adverse remodeling, inhibition of the renin-angiotensin-aldosterone system, and favorable metabolic actions through the generation of its second messenger cyclic guanosine monophosphate (cGMP). Thus, the GC-A represents an important molecular therapeutic target for cardiovascular disease and its associated risk factors. However, a small molecule that is orally bioavailable and directly targets the GC-A to potentiate cGMP has yet to be discovered. Here, we performed a cell-based high-throughput screening campaign of the NIH Molecular Libraries Small Molecule Repository, and we successfully identified small molecule GC-A positive allosteric modulator (PAM) scaffolds. Further medicinal chemistry structure–activity relationship efforts of the lead scaffold resulted in the development of a GC-A PAM, MCUF-651, which enhanced ANP-mediated cGMP generation in human cardiac, renal, and fat cells and inhibited cardiomyocyte hypertrophy in vitro. Further, binding analysis confirmed MCUF-651 binds to GC-A and selectively enhances the binding of ANP to GC-A. Moreover, MCUF-651 is orally bioavailable in mice and enhances the ability of endogenous ANP and BNP, found in the plasma of normal subjects and patients with hypertension or heart failure, to generate GC-A–mediated cGMP ex vivo. In this work, we report the discovery and development of an oral, small molecule GC-A PAM that holds great potential as a therapeutic for cardiovascular, renal, and metabolic diseases.

The global burden of cardiovascular diseases (CVDs) and its associated risk factors of hypertension, obesity, and renal dysfunction, all of which are major drivers for premature mortality, are rapidly growing worldwide (1, 2). While drug discovery continues in this area, there remains a high unmet need for novel therapies, especially with innovative molecular targets. Employing native and designer peptides, we and others have established the favorable pleiotropic properties of the particulate guanylyl cyclase A receptor (GC-A) through the generation of its second messenger 3′, 5′ cyclic guanosine monophosphate (cGMP) (3–6). In response to GC-A activation by the native cardiac hormones atrial natriuretic peptides (ANP) and b-type natriuretic peptides (BNP), such beneficial biological properties include the reduction in blood pressure (BP), natriuresis, suppression of adverse cardiorenal and CV remodeling, inhibition of the renin-angiotensin-aldosterone system (RAAS), and favorable metabolic properties (4–6). Most recently, studies from the PROVE-HF trial have reported that ANP is the predominant natriuretic peptide (NP) increased by sacubitril/valsartan (S/V) and is closely correlated with S/V mediated reverse remodeling, thus supporting a key role for GC-A activation in the actions of S/V (7). Taken together, these biological properties render the GC-A/cGMP pathway an unprecedented molecular target for CV therapeutics.Historically, GC-A therapeutics have been dependent on use of synthetic or recombinant peptides forms of ANP and BNP. Specifically, ANP and BNP are both approved for the treatment of acute heart failure (HF) via intravenous (IV) infusion in Japan and the United States, respectively (8, 9). Beyond the need for IV infusion, these ligands have short circulating half-lives due to their rapid enzymatic degradation by neprilysin (NEP) and receptor-mediated clearance through the NP clearance receptor, NPR-C (10). Thus, the development of designer NPs has evolved in an effort to overcome these therapeutic challenges related to short bioavailability and delivery. Indeed, MANP is a novel ANP analog that possesses greater resistance to NEP degradation compared to ANP and is in clinical trials for resistant hypertension (11, 12). However, as a peptide, MANP must be administered as an injection, similar to that of insulin in diabetes. Hence, the discovery of small molecules, which are noted for favorable oral bioavailability, would represent a major breakthrough in GC-A therapeutics.Allosteric ligands bind to sites on the receptor that are separate from the orthosteric binding site to which the endogenous ligands, such as ANP and BNP, bind (13). Positive allosteric modulators (PAMs) lack actions when binding to the receptor in the absence of the specific endogenous receptor ligand(s). As such, studies suggest that PAMs have high specificity to receptors (14). Furthermore, in animal models and humans, PAMs operate to physiological and pathophysiological variations in their endogenous ligand hormones and therefore are self-titrating to maximize cell signaling and avoid drug tolerance. To date, no such small molecules have been reported to target the GC-A receptor and to enhance its cGMP-mediated biological effects.The goal of the current study was to pursue a cell-based high-throughput screening (HTS) campaign to identify small molecule GC-A PAMs using the NIH Molecular Libraries Small Molecule Repository (MLSMR). Here, we report the discovery of small molecule GC-A PAM scaffolds and the identification of a lead molecule, MCUF-651. Moreover, we also designed the following studies to determine the ability of MCUF-651 to 1) augment cGMP in HEK293 cells overexpressing either GC-A or the alternative GC-B receptor so as to establish potency with the endogenous ligands for each receptor and selectivity for GC-A; 2) potentiate cGMP levels, in the presence of ANP, in primary cells naturally expressing GC-A including human renal proximal tubular cells (HRPTCs), human adipocytes (HAs), and human cardiomyocytes (HCM); 3) enhance ANP-mediated anti-hypertrophic actions in HCM; 4) assess the binding of MCUF-651 alone or in the presence of increasing concentrations of ANP/BNP or C-type natriuretic peptide (CNP) to human GC-A and GC-B, respectively; 5) determine the pharmacokinetics (PK) and oral bioavailability in mice; and 6) augment cGMP in a human plasma from normal subjects and patients with hypertension and HF using an ex vivo potency assay.