Vγ9/Vδ2 T cell activation induced by bacterial low molecular mass compounds depends on the 1-deoxy-d-xylulose 5-phosphate pathway of isoprenoid biosynthesis

Isopentenyl diphosphate (IPP), an important precursor of isoprenoid biosynthesis in prokaryotic and eukaryotic organisms, has been shown to activate Vgamma9/Vdelta2 T cells, the major subset of human gammadelta T cells. The biosynthesis of IPP has been first described as the acetate/mevalonate pathway. Recently, 1-deoxy-D-xylulose 5-phosphate (DOXP) and 2-C-methyl-D-erythritol 4-phosphate have been shown to be key metabolites in the DOXP pathway also leading to the formation of IPP in some eubacteria such as Escherichia coli. Here we report that the low molecular mass fraction of extracts from bacteria using the DOXP pathway induces Vgamma9/Vdelta2 T cell activation, while analogous preparations from bacteria using the classical mevalonate pathway fail to do so. Addition of 1-deoxy-D-xylulose potentiates the ability of E. coli extracts to activate Vgamma9/Vdelta2 T cells. As the amounts of IPP present in the bacterial preparations are not sufficient to induce significant Vgamma9/Vdelta2 T cell activation, our data suggest that compounds other than IPP associated with the DOXP pathway are responsible for Vgamma9/Vdelta2 T cell activation.     

Expression and characterization of a human BMP-7 variant with improved biochemical properties

Bone morphogenetic protein-7 (BMP-7, OP-1) is a secreted growth factor that is predominantly known for its osteoinductive properties, though it has also been implicated as having a role in mammalian kidney development. Clinical efficacy of recombinant BMP-7 has been demonstrated in the treatment of orthopedic injuries through topical application. However, the pharmaceutical development of recombinant BMP-7 for systemic delivery has presented many challenges. Specifically, the expression level of recombinant mature BMP-7 protein in mammalian cells is very low, the molecule has poor solubility at neutral pH, and intracellular proteolytic processing events result in a secreted BMP-7 having multiple amino-termini, creating a heterogeneous mixture of proteins. Utilizing structural information, we have designed and generated a number of rational BMP-7 mutations that improved both expression levels in mammalian cells and solubility at neutral pH, while limiting the amino-terminal heterogeneity of the mature protein. Introduction of these mutations did not compromise BMP-7 in vitro bioactivity. This improved BMP-7 molecule is better suited for pharmaceutical development and clinical advancement for indications where systemic delivery may be required.     

Effects of arsenic (As) exposure on the antioxidant status of gills of the zebrafish Danio rerio (Cyprinidae)

In fishes, arsenic (As) is absorbed via the gills and is capable of causing disturbance to the antioxidant system. The objective of present study was to evaluate antioxidant responses after As exposure in gills of zebrafish (Danio rerio, Cyprinidae). Fish were exposed for 48 h to three concentration of As, including the highest As concentration allowed by current Brazilian legislation (10 μg As/L). A control group was exposed to tap water (pH 8.0; 26 °C; 7.20 mg O₂/L). As exposure resulted in (1) an increase (p < 0.05) of glutathione (GSH) levels after exposure to 10 and 100 μg As/L, (2) an increase of the glutamate cysteine ligase (GCL) activity in the same concentrations (p < 0.05), (3) no significant differences in terms of glutathione reductase, glutathione-S-transferase and catalase activities; (4) a significantly lower (p < 0.05) oxygen consumption after exposure to 100 μg As/L; (4) no differences in terms of oxygen reactive species generation and lipid peroxidation content (p > 0,05). In the gills, only inorganic As was detected. Overall, it can be concluded that As affected the antioxidant responses increasing GCL activity and GSH levels, even at concentration considered safe by Brazilian legislation.     

Staphylococcus aureus α-Hemolysin Activates the NLRP3-Inflammasome in Human and Mouse Monocytic Cells

Community Acquired Methicillin Resistant Staphylococcus aureus (CA-MRSA) causes severe necrotizing infections of the skin, soft tissues, and lungs. Staphylococcal α-hemolysin is an essential virulence factor in mouse models of CA-MRSA necrotizing pneumonia. S. aureus α-hemolysin has long been known to induce inflammatory signaling and cell death in host organisms, however the mechanism underlying these signaling events were not well understood. Using highly purified recombinant α-hemolysin, we now demonstrate that α-hemolysin activates the Nucleotide-binding domain and leucine-rich repeat containing gene family, pyrin domain containing 3 protein (NLRP3)-inflammasome, a host inflammatory signaling complex involved in responses to pathogens and endogenous danger signals. Non-cytolytic mutant α-hemolysin molecules fail to elicit NLRP3-inflammasome signaling, demonstrating that the responses are not due to non-specific activation of this innate immune signaling system by bacterially derived proteins. In monocyte-derived cells from humans and mice, inflammasome assembly in response to α-hemolysin results in activation of the cysteine proteinase, caspase-1. We also show that inflammasome activation by α-hemolysin works in conjunction with signaling by other CA-MRSA-derived Pathogen Associated Molecular Patterns (PAMPs) to induce secretion of pro-inflammatory cytokines IL-1β and IL-18. Additionally, α-hemolysin induces cell death in these cells through an NLRP3-dependent program of cellular necrosis, resulting in the release of endogenous pro-inflammatory molecules, like the chromatin-associated protein, High-mobility group box 1 (HMGB1). These studies link the activity of a major S. aureus virulence factor to a specific host signaling pathway. The cellular events linked to inflammasome activity have clear relevance to the disease processes associated with CA-MRSA including tissue necrosis and inflammation.