Although cholesterol has been involved in the pathophysiology of Alzheimer disease (AD), its distribution in the cerebral cortex over the course of AD is unknown. We describe an original method to quantify cholesterol distribution using time-of-flight secondary ion mass spectrometry imaging. Cholesterol was unevenly distributed along the cortical thickness, being more abundant close to the white matter, in both control and AD cases. However, the mean cholesterol signal was significantly higher in the lower half of the cortex in AD samples compared to controls. This increase, when converted into cortical layers, was statistically significant for layers III and IV and did not reach significance in layers V + VI, the variability being too high at the interface between grey and white matter. The density of neurofibrillary tangles and of senile plaques was not statistically linked to the abundance of cholesterol. Cholesterol overload thus appears a new and independent alteration of AD cerebral cortex. The structure in which cholesterol accumulates and the mechanism of this accumulation remain to be elucidated.

Mass spectrometry and spectroscopy-based approaches can provide an overview of the chemical composition of a tissue sample. This opens up the possibility to investigate in depth the subtle biochemical changes associated with pathological tissues. In this study, time-of-flight secondary ion mass spectrometry (TOF-SIMS) and synchrotron-FT-IR and -UV imaging were applied to the same tissue section by using the same sample holder. The tested sample involved liver cirrhosis, which is characterized by regeneration nodules surrounded by annular fibrosis. A tissue section from a cirrhotic liver was deposited on a gold coated glass slide and was initially analyzed by FT-IR microspectroscopy in order to image the distribution of lipids, proteins, sugars, and nucleic acids. This technique has identified collagen enrichment in fibrosis whereas esters were mostly distributed into the cirrhotic nodules. The exact same section was investigated using TOF-SIMS demonstrating that some molecular lipid species were differentially distributed into the fibrosis areas or cirrhotic nodules. Spectra of UV microspectroscopy obtained from the same section allowed visualizing high autofluorescence from fibrous septa confirming the presence of collagen. Altogether, these results demonstrated that TOF-SIMS and FT-IR/UV microspectroscopy analyses can be successfully performed on the same tissue section.

Mass spectrometry imaging of lipids using MALDI-TOF/TOF mass spectrometers is of growing interest for chemical mapping of organic compounds at the surface of tissue sections. Many efforts have been devoted to the best matrix choice and deposition technique. Nevertheless, the identification of lipid species desorbed from tissue sections remains problematic. It is now well-known that protonated, sodium- and potassium-cationized lipids are detected from biological samples, thus complicating the data analysis. A new sample preparation method is proposed, involving the use of lithium salts in the matrix solution in order to simplify the mass spectra with only lithium-cationized molecules instead of a mixture of various cationized species. Five different lithium salts were tested. Among them, lithium trifluoroacetate and lithium iodide merged the different lipid adducts into one single lithium-cationized species. An optimized sample preparation protocol demonstrated that the lithium trifluoroacetate salt slightly increased desorption of phosphatidylcholines. Mass spectrometry images acquired on rat brain tissue sections by adding lithium trifluoroacetate showed the best results in terms of image contrast. Moreover, more structurally relevant fragments were generated by tandem mass spectrometry when analyzing lithium-cationized species.

Microcins are a peculiar class of gene-encoded low-molecular-mass antibacterial peptides secreted by enterobacteria. They contribute to the regulation of microbial competitions within the intestinal microbiota. The genetic systems involved in microcin biosynthesis share a conserved organization. Similar to bacteriocins of Gram-positive bacteria, microcins exert potent antibacterial activity directed against phylogenetically-related bacterial strains, with minimal inhibitory concentrations in the nanomolar range. In contrast to bacteriocins, they display a great structural diversity among the few representatives well characterized until now, that makes difficult the description of microcin subclasses. This review focuses on three microcins, MccE492m that carries a C-terminal posttranslational modification containing a catechol-type siderophore, MccJ25, a cyclic peptide with a unique ‘lasso-type’ structure and MccC7 or C51, with a common N-formylated heptapeptide-nucleotide structure. We show these microcins exhibit ‘Trojan horse’ mechanisms of antibacterial activity: either (i) the microcin structure is a mime of an essential element, permitting its recognition by outer membrane receptors used for vital functions in bacteria and further translocation into the periplasmic space, or (ii) it is secreted as a harmless molecule and further processed in susceptible bacteria to form the toxic entity. When inside target bacteria, microcins bind essential enzymes or interact with the inner membrane to form a bacterial killing structure.

Despite its importance during viral or bacterial infections, transcriptional regulation of the interferon-β gene (Ifnb1) in activated macrophages is only partially understood. Here we report that TRIM33 deficiency results in high, sustained expression of Ifnb1 at late stages of toll-like receptor-mediated activation in macrophages but not in fibroblasts. In macrophages, TRIM33 is recruited by PU.1 to a conserved region, the Ifnb1 Control Element (ICE), located 15 kb upstream of the Ifnb1 transcription start site. ICE constitutively interacts with Ifnb1 through a TRIM33-independent chromatin loop. At late phases of lipopolysaccharide activation of macrophages, TRIM33 is bound to ICE, regulates Ifnb1 enhanceosome loading, controls Ifnb1 chromatin structure and represses Ifnb1 gene transcription by preventing recruitment of CBP/p300. These results characterize a previously unknown mechanism of macrophage-specific regulation of Ifnb1 transcription whereby TRIM33 is critical for Ifnb1 gene transcription shutdown.

The histidine-rich antimicrobial peptide PvHCt derived from shrimp hemocyanin is a strictly antifungal peptide, which adopts an amphipathic α-helical structure, and selectively binds to and permeabilizes fungal cells.

The tripartite motif (TRIM) family of proteins plays important roles in innate immunity and antimicrobial infection. None of these proteins has been shown to directly regulate transcription of genes in monocyte/macrophage except TRIM33 that we have recently shown to be a macrophage specific transcriptional inhibitor of Ifnb1. Using ChIP-seq analyses, we now report that TRIM33 is bound to two fold more genes in immature than in mature myeloid cell lines. When located near the same genes, TRIM33 is bound to different sequences in the two cell lines suggesting a role of TRIM33 in both immature and mature myeloid cells. Accordingly, expression of TRIM33 in immature myeloid cells is necessary for efficient production of small peritoneal macrophages, monocytes and bone marrow derived macrophage (BMDM) and TRIM33 targets a subset of genes involved in the inflammatory response only in mature myeloid cells. Functionally, this targeting is associated with impaired repression of pathways regulating the late phases of lipopolysaccharide (LPS) activation of BMDM and a high sensitivity to LPS in vivo when the trim33 gene is inactivated in mature myeloid cells. These findings pinpoint TRIM33 as an important transcriptional actor of monocyte/macrophage mediated inflammation.

Divercin V41 (DvnV41) is a class IIa bacteriocin with potent antilisterial activity isolated from Carnobacterium divergens V41. Previously, we expressed from a synthetic gene, in Escherichia coli Origami, a recombinant DvnV41 designated DvnRV41, which possesses four additional amino acids (AMDP) in the N-terminal region that result from enzymatic cleavage and retains the initial DvnV41 activity. To unravel the relationship between the structure of DvnRV41 and its particularly elevated activity, we produced by site-directed mutagenesis eight variants in which a single amino acid replacement was specifically introduced into the sequence. The point mutations were designed to change either conserved residues in class IIa bacteriocins or residues specific to DvnV41 located mainly in the C-terminal region. The fusion proteins were purified from the cytosoluble fractions by immobilized affinity chromatography. DvnRV41 and its variants were released from the fusion proteins by enzymatic cleavage, using enterokinase. The purity of DvnRV41 and of the variants was checked by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, high-performance liquid chromatography, and mass spectrometry. The antibacterial activity of DvnRV41 and its variants was assessed using different indicator strains, including Listeria monocytogenes EGDe and Enterococcus faecalis JH2-2. The activity of all of the variants appeared to be less than the activity of DvnRV41. The decrease in activity did not appear to be related to a global conformational change, as determined by circular dichroism. Overall, the variants of DvnRV41 produced in the present study provide interesting insights into structure-activity relationships of class IIa bacteriocins.Lactic acid bacterium (LAB) bacteriocins are ribosomally synthesized antimicrobial peptides that could be useful as natural and nontoxic food preservatives. Most bacteriocins produced by LAB are known to be active only against grampositive bacteria. A few exceptions to this general rule, including bacteriocins from Lactobacillus species (5, 31, 35, 49, 52), AS-48 from Enterococcus faecalis (1), enterocin E50-52 from Enterococcus faecium (50), and thermophylin produced by Streptococcus thermophilus (26), have been described; these bacteriocins exhibit various degrees of activity against gram-negative bacteria.A classification of bacteriocins produced by LAB was first proposed by Klaenhammer (30) and then was modified by Nes and Holo (39) and further updated by Cotter et al. (9). Class I and class II bacteriocins are the most abundant and thoroughly studied bacteriocins. Class I bacteriocins, namely lantibiotics, have been widely studied, and one of them, nisin, is routinely used by the food industry as a preservative due to its high level of inhibitory activity against a wide range of bacterial pathogens. These bacteriocins are characterized by the presence in their primary structure of posttranslationally modified amino acid residues (lanthionine and methylanthionine). Bacteriocin class II is composed...