The CD8-Derived Chemokine XCL1/Lymphotactin Is a Conformation-Dependent,Broad-Spectrum Inhibitor of HIV-1

CD8+ T cells play a key role in the in vivo control of HIV-1 replication via their cytolytic activity as well as their ability to secrete non-lytic soluble suppressive factors. Although the chemokines that naturally bind CCR5 (CCL3/MIP-1α, CCL4/MIP- 1β, CCL5/RANTES) are major components of the CD8-derived anti-HIV activity, evidence indicates the existence of additional, still undefined, CD8-derived HIV-suppressive factors. Here, we report the characterization of a novel anti-HIV chemokine, XCL1/lymphotactin, a member of the C-chemokine family that is produced primarily by activated CD8+ T cells and behaves as a metamorphic protein, interconverting between two structurally distinct conformations (classic and alternative). We found that XCL1 inhibits a broad spectrum of HIV-1 isolates, irrespective of their coreceptor-usage phenotype. Experiments with stabilized variants of XCL1 demonstrated that HIV-1 inhibition requires access to the alternative, all-β conformation, which interacts with proteoglycans but does not bind/activate the specific XCR1 receptor, while the classic XCL1 conformation is inactive. HIV-1 inhibition by XCL1 was shown to occur at an early stage of infection, via blockade of viral attachment and entry into host cells. Analogous to the recently described anti-HIV effect of the CXC chemokine CXCL4/PF4, XCL1-mediated inhibition is associated with direct interaction of the chemokine with the HIV-1 envelope. These results may open new perspectives for understanding the mechanisms of HIV-1 control and reveal new molecular targets for the design of effective therapeutic and preventive strategies against HIV-1.     

Neu1 sialidase and matrix metalloproteinase-9 cross-talk is essential for Toll-like receptor activation and cellular signaling

The signaling pathways of mammalian Toll-like receptors (TLRs) are well characterized, but the precise mechanism(s) by which TLRs are activated upon ligand binding remains poorly defined. Recently, we reported a novel membrane sialidase-controlling mechanism that depends on ligand binding to its TLR to induce mammalian neuraminidase-1 (Neu1) activity, to influence receptor desialylation, and subsequently to induce TLR receptor activation and the production of nitric oxide and proinflammatory cytokines in dendritic and macrophage cells. The α-2,3-sialyl residue of TLR was identified as the specific target for hydrolysis by Neu1. Here, we report a membrane signaling paradigm initiated by endotoxin lipopolysaccharide (LPS) binding to TLR4 to potentiate G protein-coupled receptor (GPCR) signaling via membrane Gα(i) subunit proteins and matrix metalloproteinase-9 (MMP9) activation to induce Neu1. Central to this process is that a Neu1-MMP9 complex is bound to TLR4 on the cell surface of naive macrophage cells. Specific inhibition of MMP9 and GPCR Gα(i)-signaling proteins blocks LPS-induced Neu1 activity and NFκB activation. Silencing MMP9 mRNA using lentivirus MMP9 shRNA transduction or siRNA transfection of macrophage cells and MMP9 knock-out primary macrophage cells significantly reduced Neu1 activity and NFκB activation associated with LPS-treated cells. These findings uncover a molecular organizational signaling platform of a novel Neu1 and MMP9 cross-talk in alliance with TLR4 on the cell surface that is essential for ligand activation of TLRs and subsequent cellular signaling.     

Design,synthesis, and SAR of N-((1-(4-(propylsulfonyl)piperazin-1-yl)cycloalkyl)methyl)benzamide inhibitors of glycine transporter-1

The design, synthesis, and structure–activity relationships (SAR) of a series of N-((1-(4-(propylsulfonyl)piperazin-1-yl)cycloalkyl)methyl)benzamide inhibitors of glycine transporter-1 (GlyT-1) are described. Optimization of the benzamide and central ring components of the core scaffold led to the identification of a GlyT-1 inhibitor that demonstrated in vivo activity in a rodent cerebral spinal fluid (CSF) glycine model.     

Molecular characterisation of the gene encoding an esterase from Bacillus licheniformis sharing significant similarities with lipases

An esterase gene from the moderate thermophilic strain Bacillus licheniformis LCB40 was cloned and expressed in Escherichia coli. Comparison of the amino acid sequence of the esterase with those of known lipases and esterases showed the presence of the well-conserved Gly-X-Ser-X-Gly pentapeptide, with an alanine replacing the first glycine. This substitution has never been reported for an esterase but it is present in the lipases from Bacillus subtilis, Bacillus pumilus and Galactomyces candidum. The amino acid sequence showed similarities with lipases and with mammalian lecithin-cholesterol acyltranferases and no similarities with esterases. The enzyme activity of a crude extract from a recombinant Escherichia coli strain showed hydrolysis of p-nitrophenyl caprylate (pNPC8) as for esterases, but not of p-nitrophenyl palmitate (pNPC16) or olive oil such as for lipases. Thus, the enzyme displays the original property of associating the activity of an esterase with a primary sequence showing high similarity with lipases.     

Rate of cirrhosis progression reduced in HIV/HCV co-infected non-responders to anti-HCV therapy

This is a retrospective longitudinal follow-up study of 25 HIV/HCV positive cirrhotic patients not responding to peg-IFN plus ribavirin, and 25 untreated controls matched for age (+/-5 years), gender and Child-Pugh score. The primary endpoint of the study was the incidence of cirrhosis progression (CP) defined as the occurrence of at least one of the following events: death, ascites, jaundice, encephalopathy, gastrointestinal bleeding and hepatocellular carcinoma (HCC). During the median follow-up of 54 months (34-89), four treated (16%) and 13 untreated patients (52%) experienced CP (p = 0.02). Poisson's regression model showed that the independent predictors of CP were Peg-IFN therapy (p = 0.016), positive HIV-RNA (p = 0.024), and altered ALP values (p = 0.012). Peg-IFN therapy seems to slow down the rate of cirrhosis progression also in HIV/HCV co-infected patients nonresponders to anti-HCV therapy, in comparison with untreated patients.     

Examination of the Cytotoxic and Embryotoxic Potential and Underlying Mechanisms of Next-Generation Synthetic Trioxolane and Tetraoxane Antimalarials

Semisynthetic artemisinin-based therapies are the first-line treatment for P. falciparum malaria, but next-generation synthetic drug candidates are urgently required to improve availability and respond to the emergence of artemisinin-resistant parasites. Artemisinins are embryotoxic in animal models and induce apoptosis in sensitive mammalian cells. Understanding the cytotoxic propensities of antimalarial drug candidates is crucial to their successful development and utilization. Here, we demonstrate that, similarly to the model artemisinin artesunate (ARS), a synthetic tetraoxane drug candidate (RKA182) and a trioxolane equivalent (FBEG100) induce embryotoxicity and depletion of primitive erythroblasts in a rodent model. We also show that RKA182, FBEG100 and ARS are cytotoxic toward a panel of established and primary human cell lines, with caspase-dependent apoptosis and caspase-independent necrosis underlying the induction of cell death. Although the toxic effects of RKA182 and FBEG100 proceed more rapidly and are relatively less cell-selective than that of ARS, all three compounds are shown to be dependent upon heme, iron and oxidative stress for their ability to induce cell death. However, in contrast to previously studied artemisinins, the toxicity of RKA182 and FBEG100 is shown to be independent of general chemical decomposition. Although tetraoxanes and trioxolanes have shown promise as next-generation antimalarials, the data described here indicate that adverse effects associated with artemisinins, including embryotoxicity, cannot be ruled out with these novel compounds, and a full understanding of their toxicological actions will be central to the continuing design and development of safe and effective drug candidates which could prove important in the fight against malaria.