Relationship Between Focal and Diffuse Fibrosis Assessed by CMR and Clinical Outcomes in Heart Failure With Preserved Ejection Fraction

ObjectivesThis study sought to assess the presence and extent of focal and diffuse fibrosis in heart failure in patients with preserved ejection fraction (HFpEF) compared to asymptomatic control subjects, and the relationship of fibrosis to clinical outcome.BackgroundMyocardial fibrosis has been implicated in the pathophysiology of HFpEF.MethodsIn this prospective, observational study, 140 subjects of similar age and sex (HFpEF: n = 96; control subjects: n = 44; 73 ± 8 years of age; 49% males) underwent cardiac magnetic resonance imaging. Late gadolinium-enhanced (LGE) imaging and T1 mapping to calculate myocardial extracellular volume indexed to body surface area (iECV) were used to assess fibrosis.ResultsPatients with HFpEF had more concentric remodeling and worse diastolic function. Focal fibrosis was more frequent in HFpEF subjects (overall: n = 49; infarction: n = 17; nonischemic cases: n = 36; mixed patterns: n = 4) than in control subjects (overall: n = 3). Diffuse fibrosis was also greater in HFpEF subjects than control subjects (iECV: 13.7 ± 4.4 ml/m² versus 10.9 ± 2.8 ml/m²; p < 0.0001). During median follow-up (1,429 days), there were 42 composite events (14 deaths; 28 heart failure hospitalizations) in cases of HFpEF. Myocardial infarction revealed on LGE imaging was a predictor of outcomes on univariate analysis only. With multivariate analysis, iECV (hazard ratio [HR]: 1.689; 95% confidence interval [CI]: 1.141 to 2.501; p = 0.009) was an independent predictor of outcome along with mitral peak velocity of early filling (E)-to-early diastolic mitral annular velocity (E′) (E/E′) ratio (HR: 1.716; 95% CI: 1.191 to 2.472; p = 0.004) and prior HF hospitalization (HR: 2.537; 95% CI: 1.090 to 5.902; p = 0.031). iECV was also significantly associated with ventricular/left atrial remodeling and renal dysfunction: right ventricular end-diastolic volume indexed (r = 0.456; p < 0.0001), left ventricular mass/volume (r = 0.348; p = 0.001), maximal left atrial volume indexed (r = 0. 269; p = 0.009), and creatinine (r = 0.271; p = 0.009).ConclusionsBoth focal and diffuse myocardial fibrosis are more prevalent in HFpEF subjects than in control subjects of similar age and sex. iECV significantly correlates with indices of ventricular/left atrial remodeling and renal dysfunction and is an independent predictor of adverse outcome in HFpEF. (Developing Imaging And plasMa biOmarkers iN Describing Heart Failure With Preserved Ejection Fraction [DIAMONDHFpEF]; NCT03050593)     

Discovery of Potent Selective Nonzinc Binding Autotaxin Inhibitor BIO-32546

Autotaxin (ATX) is a lysophospholipase D that is the main enzyme responsible for generating LPA in body fluids. Although ATX was isolated from a conditioned medium of melanoma cells, later it was discovered to play a critical role in vascular and neuronal development. ATX has also been implicated in primary brain tumor, fibrosis, and rheumatoid arthritis, as well as neurological diseases such as multiple sclerosis, Alzheimer’s disease, and neuropathic pain. As ATX and LPA levels are increased upon neuronal injury, a selective ATX inhibitor could provide a new approach to treat neuropathic pain. Herein we describe the discovery of a novel series of nonzinc binding reversible ATX inhibitors, particularly a potent, selective, orally bioavailable, brain-penetrable tool compound BIO-32546, as well as its synthesis, X-ray cocrystal structure, pharmacokinetics, and in vivo efficacy.     

Susceptibility of nanoparticle-encapsulated paclitaxel to P-glycoprotein-mediated drug efflux

Overexpression of P-glycoprotein (P-gp) is a key factor contributing to the development of multidrug resistance (MDR) in cancer cells. The objective of the study is to investigate whether a P-gp substrate, paclitaxel, delivered to MDR tumor cells in poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles is susceptible to P-gp – mediated drug efflux. Paclitaxel-loaded nanoparticles were formulated by emulsion-solvent evaporation technique. Nanoparticles had a mean hydrodynamic diameter of about 195 nm, and demonstrated sustained release of paclitaxel. In vitro cell culture studies indicated that paclitaxel nanoparticles result in sustained, dose-dependent and significant cytotoxicity in drug-sensitive MCF-7 tumor cells but not in drug-resistant NCI-ADR/RES cells. Resistance to nanoparticle-encapsulated paclitaxel was reversed by verapamil, a P-gp inhibitor. Further, sustained inhibition of P-gp was necessary for sustaining the cytotoxicity of nanoparticle-encapsulated paclitaxel in drug-resistant cells. Inhibition of P-gp by verapamil did not significantly affect the uptake or retention of nanoparticles in drug-resistant cells. In conclusion, our studies suggest that P-gp substrates, such as paclitaxel, delivered to MDR cells by PLGA nanoparticles, are susceptible to efflux by P-gp. Inhibition of P-gp restores sensitivity to paclitaxel; however, sustained inhibition of P-gp is required for sustained therapeutic efficacy of nanoparticle-encapsulated drug.     

Geometry and symmetry presculpt the free-energy landscape of proteins

We present a simple physical model that demonstrates that the native-state folds of proteins can emerge on the basis of considerations of geometry and symmetry. We show that the inherent anisotropy of a chain molecule, the geometrical and energetic constraints placed by the hydrogen bonds and sterics, and hydrophobicity are sufficient to yield a free-energy landscape with broad minima even for a homopolymer. These minima correspond to marginally compact structures comprising the menu of folds that proteins choose from to house their native states in. Our results provide a general framework for understanding the common characteristics of globular proteins.     

Thrombotic occlusion of a drug-eluting stent - is IVUS mandatory

Acute stent thrombosis is a rare but serious complication of stent implantation. Although anecdotal reports suggest that the use of drug-eluting stents (DES) may increase the risk of stent thrombosis, this has not been borne out in randomized, controlled trials. We report a case of acute stent thrombosis following implantation of a DES, with review of the literature. Despite the initial favorable procedural result, the patient developed stent thrombosis 7 days later; intravascular ultrasound (IVUS) demonstrated incomplete deployment of the stent. We recommend the use of IVUS in the management of acute stent thrombosis in order to exclude incomplete stent expansion which may underlie acute thrombotic occlusion.     

Common attributes of native-state structures of proteins, disordered proteins, and amyloid

We show that a framework derived from the common character of globular proteins can be used to understand the design of protein sequences, the behavior of intrinsically unstructured proteins, and the formation of amyloid fibrils in a unified manner. Our studies provide compelling support for the idea that protein native-state structures, the structures adopted by intrinsically unstructured proteins on binding as well as those of amyloid aggregates, all reside in a physical state of matter in which the free energy landscape is sculpted not by the specific sequence of amino acids, but rather by considerations of geometry and symmetry. We elucidate the key role played by sequence design in selecting the structure of choice from the predetermined menu of putative native-state structures.     

South Indian men with reduced CAG repeat length in the androgen receptor gene have an increased risk of prostate cancer

The androgen receptor (AR) gene possesses polymorphic CAG tandem repeats and the repeat length has been inversely related to the risk of prostate cancer (PCa). The distinct ethnic variation in the CAG repeat length may be correlated to differences in PCa risk in different populations. To evaluate the CAG repeat length in the AR gene and the implications for PCa, we screened 87 PCa patients and 120 control subjects from South India. The mean CAG repeat length in PCa patients was significantly smaller than that of controls (17.0 vs 20.7; P<0.001). Men with 19 CAG repeats had a significantly increased risk of cancer compared to those with >19 CAG repeats (age-adjusted OR=7.01; 95% CI=3.52–13.94; P<0.001). However, no significant association was observed between CAG repeats and age of onset or prostate-specific antigen levels. Although there was a trend towards shorter CAG repeat length in high grades of cancer, it was not significant (P=0.085). Thus, our results suggest an association between short CAG repeats in the AR gene and PCa risk in South Indian men. Further, we propose that CAG repeats could be used as a prognostic marker for PCa diagnosis.     

A backbone-based theory of protein folding

Under physiological conditions, a protein undergoes a spontaneous disorder order transition called "folding." The protein polymer is highly flexible when unfolded but adopts its unique native, three-dimensional structure when folded. Current experimental knowledge comes primarily from thermodynamic measurements in solution or the structures of individual molecules, elucidated by either x-ray crystallography or NMR spectroscopy. From the former, we know the enthalpy, entropy, and free energy differences between the folded and unfolded forms of hundreds of proteins under a variety of solvent/cosolvent conditions. From the latter, we know the structures of approximately 35,000 proteins, which are built on scaffolds of hydrogen-bonded structural elements, alpha-helix and beta-sheet. Anfinsen showed that the amino acid sequence alone is sufficient to determine a protein's structure, but the molecular mechanism responsible for self-assembly remains an open question, probably the most fundamental open question in biochemistry. This perspective is a hybrid: partly review, partly proposal. First, we summarize key ideas regarding protein folding developed over the past half-century and culminating in the current mindset. In this view, the energetics of side-chain interactions dominate the folding process, driving the chain to self-organize under folding conditions. Next, having taken stock, we propose an alternative model that inverts the prevailing side-chain/backbone paradigm. Here, the energetics of backbone hydrogen bonds dominate the folding process, with preorganization in the unfolded state. Then, under folding conditions, the resultant fold is selected from a limited repertoire of structural possibilities, each corresponding to a distinct hydrogen-bonded arrangement of alpha-helices and/or strands of beta-sheet.     

Pharmacological inhibition of the ClpXP protease increases bacterial susceptibility to host cathelicidin antimicrobial peptides and cell envelope-active antibiotics

The ClpXP protease is a critical bacterial intracellular protease that regulates protein turnover in many bacterial species. Here we identified a pharmacological inhibitor of the ClpXP protease, F2, and evaluated its action in Bacillus anthracis and Staphylococcus aureus. We found that F2 exhibited synergistic antimicrobial activity with cathelicidin antimicrobial peptides and antibiotics that target the cell well and/or cell membrane, such as penicillin and daptomycin, in B. anthracis and drug-resistant strains of S. aureus. ClpXP inhibition represents a novel therapeutic strategy to simultaneously sensitize pathogenic bacteria to host defenses and pharmaceutical antibiotics.