Contemporary outpatient management of patients with worsening heart failure with reduced ejection fraction: Rationale and design of the CHART-HF study.

Background: Patients with heart failure with reduced ejection fraction (HFrEF) and worsening HF events (WHFE) represent a distinct subset of patients with a substantial comorbidity burden, greater potential for intolerance to medical therapy, and high risk of subsequent death, hospitalization and excessive healthcare costs. Although multiple therapies have been shown to be efficacious and safe in this high-risk population, there are limited real-world data regarding factors that impact clinical decision-making when initiating or modifying therapy. Likewise, prior analyses of US clinical practice support major gaps in medical therapy for HFrEF and few medication changes during longitudinal follow-up, yet granular data on reasons why clinicians do not initiate or up-titrate guideline-directed medication are lacking.

Chronic Inhibition of Renal Outer Medullary Potassium Channel Not Only Prevented but Also Reversed Development of Hypertension and End-Organ Damage in Dahl Salt-Sensitive Rats.

The renal outer medullary potassium (ROMK) channel mediates potassium recycling and facilitates sodium reabsorption through the Na/K/2Cl cotransporter in the loop of Henle and potassium secretion at the cortical collecting duct. Evidence from the phenotype of humans and rodents with functional ROMK deficiency supports the contention that selective ROMK inhibitors (ROMKi) will represent a novel diuretic with potential of therapeutic benefit for hypertension. ROMKi have recently been synthesized by Merck & Co, Inc.

Discovery of Vibegron: A Potent and Selective β3 Adrenergic Receptor Agonist for the Treatment of Overactive Bladder.

The discovery of vibegron, a potent and selective human β3-AR agonist for the treatment of overactive bladder (OAB), is described. An early-generation clinical β3-AR agonist MK-0634 (3) exhibited efficacy in humans for the treatment of OAB, but development was discontinued due to unacceptable structure-based toxicity in preclinical species. Optimization of a series of second-generation pyrrolidine-derived β3-AR agonists included reducing the risk for phospholipidosis, the risk of formation of disproportionate human metabolites, and the risk of formation of high levels of circulating metabolites in preclinical species.

Design, synthesis, and evaluation of conformationally restricted acetanilides as potent and selective β3 adrenergic receptor agonists for the treatment of overactive bladder.

A series of conformationally restricted acetanilides were synthesized and evaluated as β3-adrenergic receptor agonists (β3-AR) for the treatment of overactive bladder (OAB). Optimization studies identified a five-membered ring as the preferred conformational lock of the acetanilide. Further optimization of both the aromatic and thiazole regions led to compounds such as 19 and 29, which have a good balance of potency and selectivity.

Agonist-induced Ca2+ sensitization in smooth muscle: redundancy of Rho guanine nucleotide exchange factors (RhoGEFs) and response kinetics, a caged compound study.

Many agonists, acting through G-protein-coupled receptors and Gα subunits of the heterotrimeric G-proteins, induce contraction of smooth muscle through an increase of [Ca(2+)]i as well as activation of the RhoA/RhoA-activated kinase pathway that amplifies the contractile force, a phenomenon known as Ca(2+) sensitization. Gα12/13 subunits are known to activate the regulator of G-protein signaling-like family of guanine nucleotide exchange factors (RhoGEFs), which includes PDZ-RhoGEF (PRG) and leukemia-associated RhoGEF (LARG). However, their contributions to Ca(2+)-sensitized force are not well understood.

Selective, direct activation of high-conductance, calcium-activated potassium channels causes smooth muscle relaxation.

High-conductance calcium-activated potassium (Maxi-K) channels are present in smooth muscle where they regulate tone. Activation of Maxi-K channels causes smooth muscle hyperpolarization and shortening of action-potential duration, which would limit calcium entry through voltage-dependent calcium channels leading to relaxation. Although Maxi-K channels appear to indirectly mediate the relaxant effects of a number of agents, activators that bind directly to the channel with appropriate potency and pharmacological properties useful for proof-of-concept studies are not available.

The cAMP-responsive Rap1 guanine nucleotide exchange factor, Epac, induces smooth muscle relaxation by down-regulation of RhoA activity.

Agonist activation of the small GTPase, RhoA, and its effector Rho kinase leads to down-regulation of smooth muscle (SM) myosin light chain phosphatase activity, an increase in myosin light chain (RLC(20)) phosphorylation and force. Cyclic nucleotides can reverse this process. We report a new mechanism of cAMP-mediated relaxation through Epac, a GTP exchange factor for the small GTPase Rap1 resulting in an increase in Rap1 activity and suppression of RhoA activity.

Discovery of a highly potent, selective, and bioavailable soluble epoxide hydrolase inhibitor with excellent ex vivo target engagement.

4-Substituted piperidine-derived trisubstituted ureas are reported as highly potent and selective inhibitors for sEH. The SAR outlines approaches to improve activity against sEH and reduce ion channel and CYP liability. With minimal off-target activity and a good PK profile, the benchmark 2d exhibited remarkable in vitro and ex vivo target engagement.

Phosphorylation-dependent autoinhibition of myosin light chain phosphatase accounts for Ca2+ sensitization force of smooth muscle contraction.

The reversible regulation of myosin light chain phosphatase (MLCP) in response to agonist stimulation and cAMP/cGMP signals plays an important role in the regulation of smooth muscle (SM) tone. Here, we investigated the mechanism underlying the inhibition of MLCP induced by the phosphorylation of myosin phosphatase targeting subunit (MYPT1), a regulatory subunit of MLCP, at Thr-696 and Thr-853 using glutathione S-transferase (GST)-MYPT1 fragments having the inhibitory phosphorylation sites. GST-MYPT1 fragments, including only Thr-696 and only Thr-853, inhibited purified MLCP (IC(50) = 1.

Uncoupling of GPCR and RhoA-induced Ca2+-sensitization of chicken amnion smooth muscle lacking CPI-17.

Ca2+-sensitization of smooth muscle occurs through inhibition of myosin light chain phosphatase (MLCP) leading to an increase in the MLCK:MLCP activity ratio. MLCP is inhibited through phosphorylation of its regulatory subunit (MYPT-1) following activation of the RhoA/Rho kinase (ROK) pathway or through phosphorylation of the PP1c inhibitory protein, CPI-17, by PKC delta or ROK. Here, we explore the crosstalk between these two modes of MLCP inhibition in a smooth muscle of a natural CPI-17 knockout, chicken amnion.

The crystal structure of RhoA in complex with the DH/PH fragment of PDZRhoGEF, an activator of the Ca(2+) sensitization pathway in smooth muscle.

Calcium sensitization in smooth muscle is mediated by the RhoA GTPase, activated by hitherto unspecified nucleotide exchange factors (GEFs) acting downstream of Galphaq/Galpha(12/13) trimeric G proteins. Here, we show that at least one potential GEF, the PDZRhoGEF, is present in smooth muscle, and its isolated DH/PH fragment induces calcium sensitization in the absence of agonist-mediated signaling. In vitro, the fragment shows high selectivity for the RhoA GTPase.

Constitutively elevated nuclear export activity opposes Ca2+-dependent NFATc3 nuclear accumulation in vascular smooth muscle: role of JNK2 and Crm-1.

The transcription factor NFAT (nuclear factor of activated T-cells) is a cytosolic phosphoprotein that accumulates in the nucleus following dephosphorylation by the calcium (Ca2+)/calmodulin-dependent phosphatase, calcineurin. A defining feature of stimuli that induce NFAT nuclear accumulation/activation is a sustained increase in global intracellular Ca2+. Contrary to expectations, we have found that a sustained elevation of intracellular Ca2+, induced by membrane potential depolarization and mediated by voltage-dependent Ca2+ channels, does not result in nuclear localization of the NFATc3 isoform in smooth muscle.

NFAT regulation in smooth muscle.

First identified in activated T cells, the calcium (Ca2+)-dependent transcription factor, nuclear factor of activated T cells (NFAT), has since been shown to play a role in nonimmune cells, including cells of the cardiovascular system. In arterial smooth muscle, the diverse array of calcium-signaling modalities, the functional interplay between smooth muscle and endothelial cells, and the influence of intravascular pressure on calcium and other signaling pathways creates a calcium-regulatory environment that is arguably unique. This review focuses on mechanisms that control the initial Ca2+/calcineurin-dependent events in NFAT activation, with a particular emphasis on NFAT regulation in native vascular smooth muscle.

Opposing actions of inositol 1,4,5-trisphosphate and ryanodine receptors on nuclear factor of activated T-cells regulation in smooth muscle.

The nuclear factor of activated T-cells (NFAT), originally identified in T-cells, has since been shown to play a role in mediating Ca(2+)-dependent gene transcription in diverse cell types outside of the immune system. We have previously shown that nuclear accumulation of NFATc3 is induced in ileal smooth muscle by platelet-derived growth factor in a manner that depends on Ca(2+) influx through L-type, voltage-dependent Ca(2+) channels. Here we show that NFATc3 is also the predominant NFAT isoform expressed in cerebral artery smooth muscle and is induced to accumulate in the nucleus by UTP and other G(q/11)-coupled receptor agonists.