BACE-1 inhibitors part 3: identification of hydroxy ethylamines (HEAs) with nanomolar potency in cells

This article is focusing on further optimization of previously described hydroxy ethylamine (HEA) BACE-1 inhibitors obtained from a focused library with the support of X-ray crystallography. Optimization of the non-prime side of our inhibitors and introduction of a 6-membered sultam substituent binding to Asn-294 as well as a fluorine in the C-2 position led to derivatives with nanomolar potency in cell-based assays.     

Discovery of GSK345931A: An EP1 receptor antagonist with efficacy in preclinical models of inflammatory pain

Herein we describe the medicinal chemistry programme to identify a potential back-up compound to the EP₁ receptor antagonist GW848687X. This work started with the lipophilic 1,2-biaryl benzene derivative 4 which displayed molecular weight of 414.9 g/mol and poor in vivo metabolic stability in the rat and resulted in the identification of compound 7i (GSK345931A) which demonstrated good metabolic stability in the rat and lower molecular weight (381.9 g/mol). In addition, 7i (GSK345931A) showed measurable CNS penetration in the mouse and rat and potent analgesic efficacy in acute and sub-chronic models of inflammatory pain.     

Colonisation and mass rearing: learning from others

Mosquitoes, just as other insects produced for the sterile insect technique (SIT), are subjected to several unnatural processes including laboratory colonisation and large-scale factory production. After these processes, sterile male mosquitoes must perform the natural task of locating and mating with wild females. Therefore, the colonisation and production processes must preserve characters necessary for these functions. Fortunately, in contrast to natural selection which favours a suite of characteristics that improve overall fitness, colonisation and production practices for SIT strive to maximize only the few qualities that are necessary to effectively control populations.However, there is considerable uncertainty about some of the appropriate characteristics due to the lack of data. Development of biological products for other applications suggest that it is possible to identify and modify competitiveness characteristics in order to produce competitive mass produced sterile mosquitoes. This goal has been pursued - and sometimes achieved - by mosquito colonisation, production, and studies that have linked these characteristics to field performance. Parallels are drawn to studies in other insect SIT programmes and aquaculture which serve as vital technical reference points for mass-production of mosquitoes, most of whose development occurs - and characteristics of which are determined - in an aquatic environment. Poorly understood areas that require further study are numerous: diet, mass handling and genetic and physiological factors that influence mating competitiveness. Compromises in such traits due to demands to increase numbers or reduce costs, should be carefully considered in light of the desired field performance.     

Repeated increases in blood flow, independent of exercise, enhance conduit artery vasodilator function in humans

This study aimed to determine the importance of repeated increases in blood flow to conduit artery adaptation, using an exercise-independent repeated episodic stimulus. Recent studies suggest that exercise training improves vasodilator function of conduit arteries via shear stress-mediated mechanisms. However, exercise is a complex stimulus that may induce shear-independent adaptations. Nine healthy men immersed their forearms in water at 42°C for three 30-min sessions/wk across 8 wk. During each session, a pneumatic pressure cuff was inflated around one forearm to unilaterally modulate heating-induced increases in shear. Forearm heating was associated with an increase in brachial artery blood flow (P<0.001) and shear rate (P<0.001) in the uncuffed forearm; this response was attenuated in the cuffed limb (P<0.005). Repeated episodic exposure to bilateral heating induced an increase in endothelium-dependent vasodilation in response to 5-min ischemic (P<0.05) and ischemic handgrip exercise (P<0.005) stimuli in the uncuffed forearm, whereas the 8-wk heating intervention did not influence dilation to either stimulus in the cuffed limb. Endothelium-independent glyceryl trinitrate responses were not altered in either limb. Repeated heating increases blood flow to levels that enhance endothelium-mediated vasodilator function in humans. These findings reinforce the importance of the direct impacts of shear stress on the vascular endothelium in humans.     

Amino Acid and protein metabolism in bermuda grass during water stress

The ability of Arizona Common and Coastal Bermuda grass [Cynodon dactylon (L.) Pers.] to synthesize amino acids and proteins during water stress was investigated. Amino acids were continually synthesized during the water stress treatments, but protein synthesis was inhibited and protein levels decreased.     

Structural and mechanical functions of integrins

Integrins are ubiquitously expressed cell surface receptors that play a critical role in regulating the interaction between a cell and its microenvironment to control cell fate. These molecules are regulated either via their expression on the cell surface or through a unique bidirectional signalling mechanism. However, integrins are just the tip of the adhesome iceberg, initiating the assembly of a large range of adaptor and signalling proteins that mediate the structural and signalling functions of integrin. In this review, we summarise the structure of integrins and mechanisms by which integrin activation is controlled. The different adhesion structures formed by integrins are discussed, as well as the mechanical and structural roles integrins play during cell migration. As the function of integrin signalling can be quite varied based on cell type and context, an in depth understanding of these processes will aid our understanding of aberrant adhesion and migration, which is often associated with human pathologies such as cancer.     

AB5 toxins: structures and inhibitor design

High-resolution crystal structures of AB₅ toxins in their native form or in complex with a variety of ligands have led to the structure-based design and discovery of inhibitors targeting different areas of the toxins. The most significant progress is the development of highly potent multivalent ligands that block binding of the toxins to their receptors.     

Identification of residues critical for toxicity in Clostridium perfringens phospholipase C, the key toxin in gas gangrene.

Clostridium perfringens phospholipase C (PLC), also called alpha-toxin, is the major virulence factor in the pathogenesis of gas gangrene. The toxic activities of genetically engineered alpha-toxin variants harboring single amino-acid substitutions in three loops of its C-terminal domain were studied. The substitutions were made in aspartic acid residues which bind calcium, and tyrosine residues of the putative membrane-interacting region. The variants D269N and D336N had less than 20% of the hemolytic activity and displayed a cytotoxic potency 103-fold lower than that of the wild-type toxin. The variants in which Tyr275, Tyr307, and Tyr331 were substituted by Asn, Phe, or Leu had 11-73% of the hemolytic activity and exhibited a cytotoxic potency 102- to 105-fold lower than that of the wild-type toxin. The results demonstrated that the sphingomyelinase activity and the C-terminal domain are required for myotoxicity in vivo and that the variants D269N, D336N, Y275N, Y307F, and Y331L had less than 12% of the myotoxic activity displayed by the wild-type toxin. This work therefore identifies residues critical for the toxic activities of C. perfringens PLC and provides new insights toward understanding the mechanism of action of this toxin at a molecular level.     

Time to treatment with thrombolytic therapy: determinants and effect on short-term nonfatal outcomes of acute myocardial infarction

OBJECTIVES: To characterize the extent of delay in administration of thrombolytic therapy to patients with acute myocardial infarction (AMI) in Canada, to examine patient-specific predictors of such delay and to measure the effect of delay on short-term nonfatal cardiac outcomes. DESIGN: Secondary cohort analysis of data from the first international Global Utilization of Streptokinase and tPA for Occluded Coronary Arteries (GUSTO-I) trial. SETTING: Sixty-three acute care hospitals across Canada. SUBJECTS: All 2898 Canadian patients with an AMI enrolled in GUSTO-I. MAIN OUTCOMES: Time before arrival at a hospital ("symptom-to-door" time) and time from arrival to administration of therapy ("door-to-needle" time) for patients who had an AMI outside of a hospital, in clinically relevant categories; proportions of patients with nonfatal, serious cardiac events, including shock, sustained ventricular tachycardia, ventricular fibrillation and asystole. RESULTS: Of the total number of patients enrolled, records were complete for 2708; 2542 of these patients (93.9%) had an AMI outside of a hospital. These 2542 patients presented a median 81 (interquartile range 50 to 130) minutes after the onset of symptoms, and the median time to treatment in hospital was 85 (interquartile range 61 to 115) minutes. Whereas a greater proportion of Canadian patients than of patients enrolled in GUSTO-I in other countries reached hospital within 2 hours of symptom onset (71.5% v. 61.2%, p < 0.001), a greater proportion of Canadian patients experienced in-hospital treatment delays of more than 1 hour (75.3% v. 57.1%, p < 0.001). In an analysis of all 2708 patients with complete records, both the unadjusted and adjusted odds of nonfatal cardiac events for those treated 4 to 6 hours after symptom onset were significantly higher than for those treated within 2 hours (odds ratio 1.60, 95% confidence interval 1.09 to 2.37). CONCLUSION: After arrival at a hospital, Canadian patients enrolled in GUSTO-I received thrombolytic therapy more slowly than trial enrollees in other countries. Such delays are already known to decrease the rate of short-term survival after AMI. The findings further show that long time to treatment also increases the odds of nonfatal, serious cardiac events. Hospitals and physicians caring for patients with AMI should routinely assess whether and how they can improve door-to-needle times.