Inflammation Drives Stiffness Mediated Uptake of Lipoproteins in Primary Human Macrophages and Foam Cell Proliferation.

Macrophage to foam cell transition and their accumulation in the arterial intima are the key events that trigger atherosclerosis, a multifactorial inflammatory disease. Previous studies have linked arterial stiffness and cardiovascular disease and have highlighted the use of arterial stiffness as a potential early-stage marker. Yet the relationship between arterial stiffness and atherosclerosis in terms of macrophage function is poorly understood. Thus, it is pertinent to understand the mechanobiology of macrophages to clarify their role in plaque advancement. We explore how substrate stiffness affects proliferation of macrophages and foam cells, traction forces exerted by macrophages and uptake of native and oxidized low-density lipoproteins. We demonstrate that stiffness influences foam cell proliferation under both naïve and inflammatory conditions. Naïve foam cells proliferated faster on the 4 kPa polyacrylamide gel and glass whereas under inflammatory conditions, maximum proliferation was recorded on glass. Macrophage and foam cell traction forces were positively correlated to the substrate stiffness. Furthermore, the influence of stiffness was demonstrated on the uptake of lipoproteins on macrophages treated with lipopolysaccharide + interferon gamma. Cells on softer 1 kPa substrates had a significantly higher uptake of low-density lipoproteins and oxidized low-density lipoproteins compared to stiffer substrates. The results herein indicate that macrophage function is modulated by stiffness and help better understand ways in which macrophages and foam cells could contribute to the development and progression of atherosclerotic plaque.

Pathological polyQ expansion does not alter the conformation of the Huntingtin-HAP40 complex.

The abnormal amplification of a CAG repeat in the gene coding for huntingtin (HTT) leads to Huntington's disease (HD). At the protein level, this translates into the expansion of a polyglutamine (polyQ) stretch located at the HTT N terminus, which renders HTT aggregation prone by unknown mechanisms. Here we investigated the effects of polyQ expansion on HTT in a complex with its stabilizing interaction partner huntingtin-associated protein 40 (HAP40). Surprisingly, our comprehensive biophysical, crosslinking mass spectrometry and cryo-EM experiments revealed no major differences in the conformation of HTT-HAP40 complexes of various polyQ length, including 17QHTT-HAP40 (wild type), 46QHTT-HAP40 (typical polyQ length in HD patients), and 128QHTT-HAP40 (extreme polyQ length). Thus, HTT polyQ expansion does not alter the global conformation of HTT when associated with HAP40.

The Driving Force: Nuclear Mechanotransduction in Cellular Function, Fate, and Disease.

Cellular behavior is continuously affected by microenvironmental forces through the process of mechanotransduction, in which mechanical stimuli are rapidly converted to biochemical responses. Mounting evidence suggests that the nucleus itself is a mechanoresponsive element, reacting to cytoskeletal forces and mediating downstream biochemical responses. The nucleus responds through a host of mechanisms, including partial unfolding, conformational changes, and phosphorylation of nuclear envelope proteins; modulation of nuclear import/export; and altered chromatin organization, resulting in transcriptional changes. It is unclear which of these events present direct mechanotransduction processes and which are downstream of other mechanotransduction pathways. We critically review and discuss the current evidence for nuclear mechanotransduction, particularly in the context of stem cell fate, a largely unexplored topic, and in disease, where an improved understanding of nuclear mechanotransduction is beginning to open new treatment avenues. Finally, we discuss innovative technological developments that will allow outstanding questions in the rapidly growing field of nuclear mechanotransduction to be answered.

Cross-Isotopic Bioorthogonal Tools as Molecular Twins for Radiotheranostic Applications.

Radiotheranostics are designed by labeling targeting (bio)molecules with radionuclides for diagnostic or therapeutic application. Because the pharmacokinetics of therapeutic compounds play a pivotal role, chemically closely related imaging agents are used to evaluate the overall feasibility of the therapeutic approach. "Theranostic relatives" that utilize different elements are frequently used in clinical practice. However, variations in pharmacokinetics, biodistribution, and target affinity due to different chemical properties of the radioisotopes remain as hurdles to the design of optimized clinical tools. Herein, the design and synthesis of structurally identical compounds, either for diagnostic (18 F and a stable metal isotope) or therapeutic application (radiometal and stable 19 F), are reported. Such "molecular twins" have been prepared by applying a modular strategy based on click chemistry that enables efficient radiolabeling of compounds containing a metal complex and a tetrazine moiety. This additional bioorthogonal functionality can be used for subsequent radiolabeling of (bio)molecules or pretargeting approaches, which is demonstrated in vitro.

The cryo-electron microscopy structure of huntingtin.

Huntingtin (HTT) is a large (348 kDa) protein that is essential for embryonic development and is involved in diverse cellular activities such as vesicular transport, endocytosis, autophagy and the regulation of transcription. Although an integrative understanding of the biological functions of HTT is lacking, the large number of identified HTT interactors suggests that it serves as a protein-protein interaction hub. Furthermore, Huntington's disease is caused by a mutation in the HTT gene, resulting in a pathogenic expansion of a polyglutamine repeat at the amino terminus of HTT. However, only limited structural information regarding HTT is currently available. Here we use cryo-electron microscopy to determine the structure of full-length human HTT in a complex with HTT-associated protein 40 (HAP40; encoded by three F8A genes in humans) to an overall resolution of 4 Å. HTT is largely α-helical and consists of three major domains. The amino- and carboxy-terminal domains contain multiple HEAT (huntingtin, elongation factor 3, protein phosphatase 2A and lipid kinase TOR) repeats arranged in a solenoid fashion. These domains are connected by a smaller bridge domain containing different types of tandem repeats. HAP40 is also largely α-helical and has a tetratricopeptide repeat-like organization. HAP40 binds in a cleft and contacts the three HTT domains by hydrophobic and electrostatic interactions, thereby stabilizing the conformation of HTT. These data rationalize previous biochemical results and pave the way for improved understanding of the diverse cellular functions of HTT.

Synthetic ozonide drug candidate OZ439 offers new hope for a single-dose cure of uncomplicated malaria.

Ozonide OZ439 is a synthetic peroxide antimalarial drug candidate designed to provide a single-dose oral cure in humans. OZ439 has successfully completed Phase I clinical trials, where it was shown to be safe at doses up to 1,600 mg and is currently undergoing Phase IIa trials in malaria patients. Herein, we describe the discovery of OZ439 and the exceptional antimalarial and pharmacokinetic properties that led to its selection as a clinical drug development candidate. In vitro, OZ439 is fast-acting against all asexual erythrocytic Plasmodium falciparum stages with IC(50) values comparable to those for the clinically used artemisinin derivatives. Unlike all other synthetic peroxides and semisynthetic artemisinin derivatives, OZ439 completely cures Plasmodium berghei-infected mice with a single oral dose of 20 mg/kg and exhibits prophylactic activity superior to that of the benchmark chemoprophylactic agent, mefloquine. Compared with other peroxide-containing antimalarial agents, such as the artemisinin derivatives and the first-generation ozonide OZ277, OZ439 exhibits a substantial increase in the pharmacokinetic half-life and blood concentration versus time profile in three preclinical species. The outstanding efficacy and prolonged blood concentrations of OZ439 are the result of a design strategy that stabilizes the intrinsically unstable pharmacophoric peroxide bond, thereby reducing clearance yet maintaining the necessary Fe(II)-reactivity to elicit parasite death.

Patches of bare ground as a staple commodity for declining ground-foraging insectivorous farmland birds.

Conceived to combat widescale biodiversity erosion in farmland, agri-environment schemes have largely failed to deliver their promises despite massive financial support. While several common species have shown to react positively to existing measures, rare species have continued to decline in most European countries. Of particular concern is the status of insectivorous farmland birds that forage on the ground. We modelled the foraging habitat preferences of four declining insectivorous bird species (hoopoe, wryneck, woodlark, common redstart) inhabiting fruit tree plantations, orchards and vineyards. All species preferred foraging in habitat mosaics consisting of patches of grass and bare ground, with an optimal, species-specific bare ground coverage of 30-70% at the foraging patch scale. In the study areas, birds thrived in intensively cultivated farmland where such ground vegetation mosaics existed. Not promoted by conventional agri-environment schemes until now, patches of bare ground should be implemented throughout grassland in order to prevent further decline of insectivorous farmland birds.