The role of zinc, an essential element for normal brain function, in the pathology of Alzheimer's disease (AD) is poorly understood. On one hand, physiological and genetic evidence from transgenic mouse models supports its pathogenic role in promoting the deposition of the amyloid beta-protein (Abeta) in senile plaques. On the other hand, levels of extracellular ("free") zinc in the brain, as inferred by the levels of zinc in cerebrospinal fluid, were found to be too low for inducing Abeta aggregation. Remarkably, the release of transient high local concentrations of zinc during rapid synaptic events was reported. The role of such free zinc pulses in promoting Abeta aggregation has never been established. Using a range of time-resolved structural and spectroscopic techniques, we found that zinc, when introduced in millisecond pulses of micromolar concentrations, immediately interacts with Abeta 1-40 and promotes its aggregation. These interactions specifically stabilize non-fibrillar pathogenic related aggregate forms and prevent the formation of Abeta fibrils (more benign species) presumably by interfering with the self-assembly process of Abeta. These in vitro results strongly suggest a significant role for zinc pulses in Abeta pathology. We further propose that by interfering with Abeta self-assembly, which leads to insoluble, non-pathological fibrillar forms, zinc stabilizes transient, harmful amyloid forms. This report argues that zinc represents a class of molecular pathogens that effectively perturb the self-assembly of benign Abeta fibrils, and stabilize harmful non-fibrillar forms.

The morphology of micrometer-sized beta-hematin crystals (synthetic malaria pigment) was determined by TEM images and diffraction, and by grazing incidence synchrotron X-ray diffraction at the air-water interface. The needle-like crystals are bounded by sharp {100} and {010} side faces, and capped by {011} and, to a lesser extent, by {001} end faces, in agreement with hemozoin (malaria pigment) crystals. The beta-hematin crystals grown in the presence of 10% chloroquine or quinine took appreciably longer to precipitate and tended to be symmetrically tapered toward both ends of the needle, due to stereoselective additive binding to {001} or {011} ledges. Evidence, but marginal, is presented that additives reduce crystal mosaic domain size along the needle axis, based on X-ray powder diffraction data. Coherent grazing exit X-ray diffraction suggests that the mosaic domains are smaller and less structurally stable than in pure crystals. IR-ATR and Raman spectra indicate molecular based differences due to a modification of surface and bulk propionic acid groups, following additive binding and a molecular rearrangement in the environment of the bulk sites poisoned by occluded quinoline. These results provided incentive to examine computationally whether hemozoin may be a target of antimalarial drugs diethylamino-alkoxyxanthones and artemisinin. A variation in activity of the former as a function of the alkoxy chain length is correlated with computed binding energy to {001} and {011} faces of beta-hematin. A model is proposed for artemisinin activity involving hemozoin nucleation inhibition via artemisinin-beta-hematin adducts bound to the principal crystal faces. Regarding nucleation of hemozoin inside the digestive vacuole of the malaria parasite, nucleation via the vacuole's membranous surface is proposed, based on a reported hemozoin alignment. As a test, a dibehenoyl-phosphatidylcholine monolayer transferred onto OTS-Si wafer nucleated far more beta-hematin crystals, albeit randomly oriented, than a reference OTS-Si.

Crystalline nucleation of cholesterol at the air-water interface has been studied via grazing incidence x-ray diffraction using synchrotron radiation. The various stages of cholesterol molecular assembly from monolayer to three bilayers incorporating interleaving hydrogen-bonded water layers in a monoclinic cholesterol.H(2)O phase, has been monitored and their structures characterized to near atomic resolution. Crystallographic evidence is presented that this multilayer phase is similar to that of a reported metastable cholesterol phase of undetermined structure obtained from bile before transformation to the triclinic phase of cholesterol.H(2)O, the thermodynamically stable macroscopic form. According to grazing incidence x-ray diffraction measurements and crystallographic data, a transformation from the monoclinic film structure to a multilayer of the stable monohydrate phase involves, at least initially, an intralayer cholesterol rearrangement in a single-crystal-to-single-crystal transition. The preferred nucleation of the monoclinic phase of cholesterol.H(2)O followed by transformation to the stable monohydrate phase may be associated with an energetically more stable cholesterol bilayer arrangement of the former and a more favorable hydrogen-bonding arrangement of the latter. The relevance of this nucleation process of cholesterol monohydrate to pathological crystallization of cholesterol from cell biomembranes is discussed.

No abstract

Mounting an effective immune response, while also protecting tissue integrity, is critical for host survival. We used a combined genomic and proteomic approach to investigate the role of extracellular matrix (ECM) proteolysis in achieving this balance in the lung during influenza virus infection. We identified the membrane-tethered matrix metalloprotease MT1-MMP as a prominent host-ECM-remodeling collagenase in influenza infection. Selective inhibition of MT1-MMP protected the tissue from infection-related structural and compositional tissue damage. MT1-MMP inhibition did not significantly alter the immune response or cytokine expression. The available flu therapeutic Oseltamivir did not prevent lung ECM damage and was less effective than anti-MT1-MMP in influenza virus Streptococcus pneumoniae coinfection paradigms. Combination therapy of Oseltamivir with anti-MT1-MMP showed a strong synergistic effect and resulted in complete recovery of infected mice. This study highlights the importance of tissue resilience in surviving infection and the potential of such host-pathogen therapy combinations for respiratory infections.

Abnormal architectures of collagen fibers in the extracellular matrix (ECM) are hallmarks of many invasive diseases, including cancer. Targeting specific stages of collagen assembly in vivo presents a great challenge due to the involvement of various crosslinking enzymes in the multistep, hierarchical process of ECM build-up. Using advanced microscopic tools, we monitored stages of fibrillary collagen assembly in a native fibroblast-derived 3D matrix system and identified anti-lysyl oxidase-like 2 (LOXL2) antibodies that alter the natural alignment and width of endogenic fibrillary collagens without affecting ECM composition. The disrupted collagen morphologies interfered with the adhesion and invasion properties of human breast cancer cells. Treatment of mice bearing breast cancer xenografts with the inhibitory antibodies resulted in disruption of the tumorigenic collagen superstructure and in reduction of primary tumor growth. Our approach could serve as a general methodology to identify novel therapeutics targeting fibrillary protein organization to treat ECMassociated pathologies.

The matrix metalloproteinases (MMPs) play a crucial role in irreversible remodeling of the extracellular matrix (ECM) in normal homeostasis and pathological states. Accumulating data from various studies strongly suggest that MMPs are tightly regulated, starting from the level of gene expression all the way to zymogen activation and endogenous inhibition, with each level controlled by multiple factors. Recent in vivo findings indicate that cell-ECM and cell-cell interactions, as well as ECM bio-active products, contribute an additional layer of regulation at all levels, indicating that individual MMP expression and activity in vivo are highly coordinated and tissue specific processes.

The extracellular matrix (ECM) is a key noncellular component in all organs and tissues. It is composed of a large number of proteins including collagens, glycoproteins (GP), and ECM-associated proteins, which show diversity of biochemical and biophysical functions. The ECM is dynamic both in normal physiology of tissues and under pathological conditions. One cellular phenomenon associated with changes in both ECM components expression and in ECM remodeling enzymes secretion is cellular senescence. It represents a stable state form of cell cycle arrest induced in proliferating cells by various forms of stress. Short-term induction of senescence is essential for tumor suppression and tissue repair. However, longterm presence of senescent cells in tissues may have a detrimental role in promoting tissue damage and aging. Up to date, there is insufficient knowledge about the interplay between the ECM and senescence cells. Since changes in the ECM occur in many physiological and pathological conditions in which senescent cells are present, a better understanding of ECMsenescence interactions is necessary. Here, we will review the functions of the different ECM components and will discuss the current knowledge about their regulation in senescent cells and their influence on the senescence state.