Human carotid plaque phosphatidylcholine specifically interacts with paraoxonase 1, increases its activity,and enhances its uptake by macrophage at the expense of its binding to HDL

Human carotid atherosclerotic plaque is in direct contact with circulatory blood components. Thus, plaque and blood components may affect each other. The current study presents the effects of plaque chloroform:methanol (C:M) extract on the HDL-associated enzyme paraoxnase 1 (PON1). This study is part of our investigation on the mutual effects of the interactions between atherosclerotic lesions and blood components. Recombinant PON1 (rePON1) was incubated with the human carotid plaques C:M extract and PON1 activities were analyzed. Lactonase and paraoxonase activities were elevated due to C:M treatment, by 140 and by 69%, respectively. Analytical chemistry analyses revealed specific phosphatidylcholines (PCs) as the plaque active components. Tryptophan fluorescence quenching assay, together with molecular docking, shows that PON1 activity is enhanced in correlation with the level of PC affinity to PON1. Molecular docking revealed that PCs interact specifically with H2-PON1 α-helix, which together with H1 enzyme α-helix links the protein to the HDL surface. These findings are supported by additional results from the PON1 ∆20 mutant that lack its H1-α-helix. Incubation of this mutant with the plaque C:M extract increased PON1 activity by only 20%, much less than the wild-type PON1 that elevated PON1 activity at the same concentration by as much as 95%. Furthermore, as much as the affinity of the enzyme to the PC was augmented, the ability of PON1 to bind to the HDL particle decreased. Finally, PON1 interaction with PC enhance its uptake into the macrophage cytoplasm. In conclusions, Specific lesion phosphatidylcholines (PCs) present in the human carotid plaque significantly enhance PON1 catalytic activities due to their interaction with the enzyme. Such a lesion׳s PC–PON1 interaction, in turn, competes with HDL PCs and enhances PON1 uptake by macrophage at the expense of PON1 binding to the HDL.     

Gallyas-Schiff Stain for Senile Plaques

Gallyas technique was modified by a direct application of Schiff's reagent after physical development, resulting in distinctive staining of amyloid deposits in argyrophilic structures. With this modified method, senile plaques in Alzheimer's disease are clearer. This method is easy to perform and suitable for routine neuropathol-ogical examination.     

A fluorescence lifetime spectroscopy study of matrix metalloproteinases‐2 and ‐9 in human atherosclerotic plaque

Matrix metalloproteinase (MMP)‐2 and ‐9 play important roles in the progression of atherosclerosis. This study aims to determine whether MMP‐2 and ‐9 content in the fibrotic caps of atherosclerotic plaque is correlated with plaque autofluorescence. A time‐resolved laser‐induced fluorescence spectroscopy (TR‐LIFS) system was used to measure the autofluorescence and assess the biochemical composition of human plaques obtained from carotid endarterectomy. Results presented here demonstrate for the first time the ability to characterize the biochemical composition as it relates to MMP‐2 and ‐9 content in the atherosclerotic plaque cap using a label‐free imaging technique implemented with a fiberoptic TR‐LIFS system. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)