Cardioprotection by aldosterone receptor antagonism in heart failure. Part I. The role of aldosterone in heart failure

In recent years understanding of the role of aldosterone has expanded beyond the known classic effects of promoting renal sodium retention and potassium and magnesium loss. It is now well documented that aldosterone causes myocardial and perivascular fibrosis, blocks the myocardial uptake of norepinephrine, and increases plasminogen activator inhibitor levels. In conjunction with angiotensin II, aldosterone causes vascular damage, endothelial dysfunction, and decreased vascular compliance. Therefore, the renin-angiotensin-aldosterone system (RAAS) plays a major role in the development of both hypertension and heart failure and is therefore, a key target for therapeutic interventions. Commonly prescribed medications for control of hypertension and congestive heart failure are inhibitors of the RAAS, including angiotensin converting enzyme inhibitors (ACE-I) and Angiotensin II (A-II) receptor antagonists. There is a well-documented increase in aldosterone levels that occurs over several months during chronic treatment with an ACE-I or A-II receptor antagonist. Such suppression of circulating aldosterone however, is transient, as exemplified by the term "escape" used to describe the phenomenon. This rebound of aldosterone even occurs when patients receive both an ACE-I and A-II receptor antagonist. In addition, ACE-I and A-II receptor antagonists are less effective in controlling BP in the estimated 60% of hypertensive patients who are salt (volume) sensitive and more prone to hypertension-associated morbidity such as black patients and type 2 diabetics. Thus chronic and complete blockade of aldosterone action requires an aldosterone receptor antagonist. The "Randomized Aldactone Evaluation Study" (RALES) trial results in patients with severe heart failure NYHA class III or IV and a left ventricular ejection fraction of no more than 35 percent showed that administration of a sub-hemodynamic dose of spironolactone (25 mg a day) as an add on therapy to ACE-I plus standard treatment resulted in a significant mortality reduction due both to decreased death from progressive heart failure and sudden cardiac death. These findings support the pivotal role of aldosterone in the pathophysiology of progressive heart failure. Although it is an effective antialdosterone agent, widespread use of spironolactone in humans is limited by its tendency to produce undesirable sexual side effects. At standard doses, impotence and gynaecomastia can be induced in men, whereas pre-menopausal women may experience menstrual disturbances. Data on a selective aldosterone receptor antagonist, eplerenone, appear promising for the effective blockade of aldosterone and its harmful effects without the sexual disturbances of spironolactone. Recently Eplerenone was successfully introduced for the treatment of hypertension and heart failure. Growing number of experimental studies are finding a broader role for Aldosterone in driving the pathophysiology of both heart failure and hypertension. When added to conventional therapy aldosterone receptor blockers show benefits which are in addition to those conferred by ACE-I and/or AII receptor blockers.     

Hybrid xerogel films as novel coatings for antifouling and fouling release

Hybrid sol-gel-derived xerogel films prepared from 45/55 (mol ratio) n-propyltrimethoxysilane (C3-TMOS)/tetramethylorthosilane (TMOS), 2/98 (mol ratio) bis[3-(trimethoxysilyl)propyl]-ethylenediamine (enTMOS)/tetraethylorthosilane (TEOS), 50/50 (mol ratio) n-octyltriethoxysilane (C8-TEOS)/TMOS, and 50/50 (mol ratio) 3,3,3-trifluoropropyltrimethoxysilane (TFP-TMOS)/TMOS were found to inhibit settlement of zoospores of the marine fouling alga Ulva (syn. Enteromorpha) relative to settlement on acid-washed glass and give greater release of settled zoospores relative to glass upon exposure to pressure from a water jet. The more hydrophobic 50/50 C8-TEOS/TMOS xerogel films had the lowest critical surface tension by comprehensive contact angle analysis and gave significantly greater release of 8-day Ulva sporeling biomass after exposure to turbulent flow generated by a flow channel than the other xerogel surfaces or glass. The 50/50 C8-TEOS/TMOS xerogel was also a fouling release surface for juveniles of the tropical barnacle Balanus amphitrite. X-ray photon electron data indicated that the alkylsilyl residues of the C3-TMOS-, C8-TEOS-, and TFP-TMOS-containing xerogels were located on the surface of the xerogel films (in a vacuum), which contributes to the film hydrophobicity. Similarly, the amine-containing silyl residues of the enTMOS/TEOS films were located at the surface of the xerogel films, which contributes to the more hydrophilic character and increased critical surface tension of these films.     

Canonical Wnt signaling: high-throughput RNAi widens the path

The canonical Wnt signaling pathway is highly conserved in evolution, widely used throughout animal development, and frequently hyperactive in cancer. Although Wnt signaling has been the subject of extensive genetic analysis in the past, some 200 genes have now been identified as candidate modulators of this pathway by a recent study using high-throughput RNAi screening.     

Metabolic effect of telmisartan and losartan in hypertensive patients with metabolic syndrome

Background

Metabolic syndrome is a cluster of common cardiovascular risk factors that includes hypertension and insulin resistance. Hypertension and diabetes mellitus are frequent comorbidities and, like metabolic syndrome, increase the risk of cardiovascular events. Telmisartan, an antihypertensive agent with evidence of partial peroxisome proliferator-activated receptor activity-gamma (PPARγ) activity, may improve insulin sensitivity and lipid profile in patients with metabolic syndrome.

Methods

In a double-blind, parallel-group, randomized study, patients with World Health Organization criteria for metabolic syndrome received once-daily doses of telmisartan (80 mg, n = 20) or losartan (50 mg, n = 20) for 3 months. At baseline and end of treatment, fasting and postprandial plasma glucose, insulin sensitivity, glycosylated haemoglobin (HBA_1c) and 24-hour mean systolic and diastolic blood pressures were determined.

Results

Telmisartan, but not losartan, significantly (p < 0.05) reduced free plasma glucose, free plasma insulin, homeostasis model assessment of insulin resistance and HbA_ic. Following treatment, plasma glucose and insulin were reduced during the oral glucose tolerance test by telmisartan, but not by losartan. Telmisartan also significantly reduced 24-hour mean systolic blood pressure (p < 0.05) and diastolic blood pressure (p < 0.05) compared with losartan.

Conclusion

As well as providing superior 24-hour blood pressure control, telmisartan, unlike losartan, displayed insulin-sensitizing activity, which may be explained by its partial PPARγ activity.     

The transmembrane helix of the Escherichia coli division protein FtsI localizes to the septal ring

FtsI (also called PBP3) of Escherichia coli is a transpeptidase required for synthesis of peptidoglycan in the division septum and is one of about a dozen division proteins that localize to the septal ring. FtsI comprises a short amino-terminal cytoplasmic domain, a single transmembrane helix (TMH), and a large periplasmic domain that encodes the catalytic (transpeptidase) activity. We show here that a 26-amino-acid fragment of FtsI is sufficient to direct green fluorescent protein to the septal ring in cells depleted of wild-type FtsI. This fragment extends from W22 to V47 and corresponds to the TMH. This is a remarkable finding because it is unusual [corrected] for a TMH to target a protein to a site more specific than the membrane. Alanine-scanning mutagenesis of the TMH identified several residues important for septal localization. These residues cluster on one side of an alpha-helix, which we propose interacts directly with another division protein to recruit FtsI to the septal ring.     

Using latent effects to determine the ecological importance of dissolved organic matter to marine invertebrates

The uptake and utilization of dissolved organic matter (DOM)by marine invertebrates is a field that has received significantattention over the past 100 years. Although it is well establishedthat DOM is taken up by marine invertebrates, the extent towhich it contributes to an animal's survival, growth, and reproduction(that is, the ecological benefits) remains largely unknown.Previous work seeking to demonstrate the putative ecologicalbenefits of DOM uptake have examined them within a single lifestage of an animal. Moreover, most of the benefits are demonstratedthrough indirect approaches by examining (1) mass balance, or(2) making comparisons of oxyenthalpic conversions of transportrates to metabolic rate as judged by oxygen consumption. Wesuggest that directly examining delayed metamorphosis or thelatent effects associated with nutritional stress of larvaeis a better model for investigating the ecological importanceof DOM to marine invertebrates. We also provide direct evidencethat availability of DOM enhances survival and growth of thebryozoan Bugula neritina. That DOM offsets latent effects inB. neritina suggests that the underlying mechanisms are at leastin part energetic.     

Influence of Heparin Mimetics on Assembly of the FGF·FGFR4 Signaling Complex

Fibroblast growth factor (FGF) signaling regulates mammalian development and metabolism, and its dysregulation is implicated in many inherited and acquired diseases, including cancer. Heparan sulfate glycosaminoglycans (HSGAGs) are essential for FGF signaling as they promote FGF·FGF receptor (FGFR) binding and dimerization. Using novel organic synthesis protocols to prepare homogeneously sulfated heparin mimetics (HM), including hexasaccharide (HM₆), octasaccharide (HM₈), and decasaccharide (HM₁₀), we tested the ability of these HM to support FGF1 and FGF2 signaling through FGFR4. Biological assays show that both HM₈ and HM₁₀ are significantly more potent than HM₆ in promoting FGF2-mediated FGFR4 signaling. In contrast, all three HM have comparable activity in promoting FGF1·FGFR4 signaling. To understand the molecular basis for these differential activities in FGF1/2·FGFR4 signaling, we used NMR spectroscopy, isothermal titration calorimetry, and size-exclusion chromatography to characterize binding interactions of FGF1/2 with the isolated Ig-domain 2 (D2) of FGFR4 in the presence of HM, and binary interactions of FGFs and D2 with HM. Our data confirm the existence of both a secondary FGF1·FGFR4 interaction site and a direct FGFR4·FGFR4 interaction site thus supporting the formation of the symmetric mode of FGF·FGFR dimerization in solution. Moreover, our results show that the observed higher activity of HM₈ relative to HM₆ in stimulating FGF2·FGFR4 signaling correlates with the higher affinity of HM₈ to bind and dimerize FGF2. Notably FGF2·HM₈ exhibits pronounced positive binding cooperativity. Based on our findings we propose a refined symmetric FGF·FGFR dimerization model, which incorporates the differential ability of HM to dimerize FGFs.     

Comparison of the established standard complement-dependent cytotoxicity and flow cytometric crossmatch assays with a novel ELISA-based HLA crossmatch procedure

The detection of donor-specific anti-HLA antibodies by standard procedures such as complement-dependent cytotoxicity assay (CDC) or flow cytometric (FACS) analysis is limited by its low sensitivity and the quality of the donor cells. Therefore, an ELISA-based technique was employed using solid phase-immobilized monoclonal antibodies to capture HLA class I or class II molecules of the donor, respectively. In this HLA class I and class II antibody monitoring system (AMS) the donor-specific anti-HLA antibodies from the sera of recipients bind to the HLA molecules of the donor which have been immobilized by monoclonal antibodies (mAb) recognizing non-polymorphic epitopes. Upon binding of donor-specific anti-HLA antibodies they are recognized by secondary enzyme-conjugated anti-human immunoglobulin (Ig) antibodies. A newly established modification of the standard protocol allows the differentiation between bound antibodies of the IgG and IgM isotype. Furthermore, this assay was adapted for investigating small amounts of solid tissue of donors from whom no other cells (e.g. from blood) were available. We here provide an overview of the classical crossmatch methods with their advantages and limits. In addition, the design of the novel AMS-ELISA is described in terms of quality and sensitivity of the approach using exemplary cases of different application. The selected cases show that the AMS-ELISA represents a valuable tool for the post-transplantation monitoring of donor-specific anti-HLA antibodies during reaction crisis, after transfusion reactions and in particular cases of tissue transplantations lacking single cells.