Chalcones identify cTXNPx as a potential antileishmanial drug target

With current drug treatments failing due to toxicity, low efficacy and resistance; leishmaniasis is a major global health challenge that desperately needs new validated drug targets. Inspired by activity of the natural chalcone 2’,6’-dihydroxy-4’-methoxychalcone (DMC), the nitro-analogue, 3-nitro-2’,4’,6’- trimethoxychalcone (NAT22, 1c) was identified as potent broad spectrum antileishmanial drug lead. Structural modification provided an alkyne containing chemical probe that labelled a protein within the parasite that was confirmed as cytosolic tryparedoxin peroxidase (cTXNPx). Crucially, labelling is observed in both promastigote and intramacrophage amastigote life forms, with no evidence of host macrophage toxicity. Incubation of the chalcone in the parasite leads to ROS accumulation and parasite death. Deletion of cTXNPx, by CRISPR-Cas9, dramatically impacts upon the parasite phenotype and reduces the antileishmanial activity of the chalcone analogue. Molecular docking studies with a homology model of in-silico cTXNPx suggest that the chalcone is able to bind in the putative active site hindering access to the crucial cysteine residue. Collectively, this work identifies cTXNPx as an important target for antileishmanial chalcones.     

Structural basis for the interaction of the free SH2 domain EAT-2 with SLAM receptors in hematopoietic cells.

The T and natural killer (NK) cell-specific gene SAP (SH2D1A) encodes a 'free SH2 domain' that binds a specific tyrosine motif in the cytoplasmic tail of SLAM (CD150) and related cell surface proteins. Mutations in SH2D1A cause the X-linked lymphoproliferative disease, a primary immunodeficiency. Here we report that a second gene encoding a free SH2 domain, EAT-2, is expressed in macrophages and B lympho cytes. The EAT-2 structure in complex with a phosphotyrosine peptide containing a sequence motif with Tyr281 of the cytoplasmic tail of CD150 is very similar to the structure of SH2D1A complexed with the same peptide. This explains the high affinity of EAT-2 for the pTyr motif in the cytoplasmic tail of CD150 but, unlike SH2D1A, EAT-2 does not bind to non-phosphorylated CD150. EAT-2 binds to the phosphorylated receptors CD84, CD150, CD229 and CD244, and acts as a natural inhibitor, which interferes with the recruitment of the tyrosine phosphatase SHP-2. We conclude that EAT-2 plays a role in controlling signal transduction through at least four receptors expressed on the surface of professional antigen-presenting cells.     

An AIF orthologue regulates apoptosis in yeast

Apoptosis-inducing factor (AIF), a key regulator of cell death, is essential for normal mammalian development and participates in pathological apoptosis. The proapoptotic nature of AIF and its mode of action are controversial. Here, we show that the yeast AIF homologue Ynr074cp controls yeast apoptosis. Similar to mammalian AIF, Ynr074cp is located in mitochondria and translocates to the nucleus of yeast cells in response to apoptotic stimuli. Purified Ynr074cp degrades yeast nuclei and plasmid DNA. YNR074C disruption rescues yeast cells from oxygen stress and delays age-induced apoptosis. Conversely, overexpression of Ynr074cp strongly stimulates apoptotic cell death induced by hydrogen peroxide and this effect is attenuated by disruption of cyclophilin A or the yeast caspase YCA1. We conclude that Ynr074cp is a cell death effector in yeast and rename it AIF-1 (Aif1p, gene AIF1).     

Optimization of the auxiliary ligand shell of Cobalt(III)(8-hydroxyquinoline) complexes as model hypoxia-selective radiation-activated prodrugs

A potential approach for activating prodrugs in hypoxic regions of tumors is to use ionizing radiation, rather than bioreductive enzymes, to effect reduction. This study investigates radiolytic release of 8-hydroxyquinoline (8-HQ), as a model for hydroxyaza-chloromethylbenzindoline DNA minor groove alkylators, from Co(III) complexes under hypoxia. 8-HQ release, measured by HPLC, showed higher efficiency (one-electron stoichiometry) when the auxiliary ligand was a tetraazamacrocycle [e.g. 1,4,7,10-tetraazacyclododecane (cyclen)] rather than a triazamacrocycle [1,4,7-triazacyclononane (TACN)]. These complexes differ from the bioreductive cobalt complex SN 24771 in that their reduction provides stable cobalt-containing products rather than free (aquated) Co(2+). Radiolytic release of 8-HQ from Co(cyclen)(8-HQ) and Co(TACN)(CN)(8-HQ) was also demonstrated in deoxygenated human plasma, selectively in the absence of oxygen, again with higher efficiency for the cyclen system. The cobalt complexes were >1000-fold less potent than free 8-HQ as inhibitors of cell proliferation and were metabolically stable in aerobic and hypoxic cell cultures. Investigation of cell uptake of total cobalt, by inductively coupled plasma mass spectrometry, showed that these complexes enter cells but do not accumulate to the high concentrations seen with SN 24771. The results demonstrate the feasibility of masking the cytotoxicity of hydroxyquinoline-based cytotoxins as Co(III) complexes and demonstrate the utility of cyclen-based auxiliary ligands for optimizing radiolytic activation of these novel prodrugs under hypoxia.     

Efficacy of preoperative decontamination of the oral cavity

This two-part study consisted of: (1) a survey to assess current practice patterns, and (2) an experiment designed to assess the results of varying intraoral preparations. A 48 percent response rate was obtained from the survey of the 318 active members of the American Society of Maxillofacial Surgeons. This survey demonstrated that significant controversy continues regarding the efficacy of preoperative decontamination of the oral cavity. This prospective, randomized experimental study of 30 patients (saline, 10; povidone-iodine, 10; no preparation, 10) demonstrates a significant and sustained reduction of both anaerobic and aerobic bacteria after intraoral preparation with povidone-iodine solution but not saline. The patient's age, use of preoperative intravenous cephalosporin, and type and length of procedure did not influence the postoperative bacterial counts. Although none of the patients in this study developed an infection, recommendations are provided for standardized preoperative treatment of the oral cavity.     

DNA targeted platinum complexes: synthesis, cytotoxicity and DNA interactions of cis-dichloroplatinum(II) complexes tethered to phenazine-1-carboxamides

A series of intercalator-tethered platinum(II) complexes PtLCl2 have been prepared, where L are the diamine ligands N-[2-[(aminoethyl)amino]ethyl]-phenazine-1-carboxamide, N-[3-[(2-aminoethyl)amino]propyl]-phenazine-1-carboxamide, N-[4-[(2-aminoethyl)amino]butyl]-phenazine-1-carboxamide and N-[5-[(aminoethyl)amino]pentyl]-phenazine-1-carboxamide. Measurements of the time-course of unwinding of supercoiled pUC19 plasmid DNA by the phenazine complexes PtLCl2 reveal that the presence of the intercalator leads to enhanced rates of DNA platination when compared with the complex Pt(en)Cl2. The platinum(II) complexes where the polymethylene linker chain contains three, four or five carbon atoms are considerably more cytotoxic against murine P388/W than either cisplatin, Pt(en)Cl2, or the metal-free ligands themselves.     

Evidence that Ralstonia eutropha (Alcaligenes eutrophus) contains a functional homologue of the Ralstonia solanacearum Phc cell density sensing system

In the phytopathogen Ralstonia (Pseudomonas) solanacearum, control of many virulence genes is partly mediated by the Phc cell density sensing system. Phc uses a novel self-produced signal molecule [3-hydroxypalmitic acid methyl ester (3-OH PAME)], an atypical two-component system (PhcS/PhcR), and a LysR-type activator (PhcA) to regulate a reversible switching between two different physiological states. While Phc is present in most R. solanacearum strains, it is apparently absent from other pseudomonad plant pathogens and prokaryotic genomes that have been sequenced. Here, we report discovery of a phcA orthologue in the non-pathogenic, facultative chemolithoautotroph Ralstonia eutropha (Alcaligenes eutrophus) that fully complements R. solanacearum phcA mutants. We also demonstrate that some R. eutropha produce an extracellular factor that complements R. solanacearum mutants deficient in production of the 3-OH PAME signal molecule that controls phcA. Additionally, Southern blot hybridization analysis suggested that R. eutropha harbours other Phc components, such as PhcB (a biosynthetic enzyme for 3-OH PAME) and PhcS (a 3-OH PAME-responsive sensor kinase). Analysis of a phcA-null mutant of R. eutropha showed that phcA (and probably Phc) positively activates motility, in contrast to R. solanacearum where it represses motility. Similarly, the R. eutropha phcA mutant was unaffected in siderophore production, whereas inactivation of phcA in R. solanacearum increases siderophore production. Although our data strongly suggest that R. eutropha has a functional Phc-like system and support the phylogeny of Ralstonia, it implies that Phc may have a different physiological and ecological function in R. eutropha.     

Synthesis of substituted indeno[1,2-b]quinoline-6-carboxamides, [1]benzothieno[3,2-b]quinoline-4-carboxamides and 10H-quindoline-4-carboxamides: evaluation of structure-activity relationships for cytotoxicity

New substituted indeno[1,2-b]quinoline-6-carboxamides, [1]benzothieno[3,2-b]quinoline-4-carboxamides and 10H-quindoline-4-carboxamides were prepared from methyl 2-amino-3-formylbenzoate by a new Friedlander synthesis. Evaluation of these carboxamides for cytotoxicity in a panel of cell lines showed that small lipophilic substituents in the non-carboxamide ring, in a pseudo-peri position to the side chain, significantly increased cytotoxic potency while retaining a pattern of cytotoxicity consistent with a non-topo II mode of action. The methyl-substituted indeno[1,2-b]quinoline-6-carboxamide demonstrated substantial effectiveness (20-day growth delays) in a sub-cutaneous colon 38 in vivo tumor model. This is comparable to that reported for the dual topo I/II inhibitor DACA that is in clinical trial.     

Reduction of infarct size and postischemic inflammation from ATL-146e, a highly selective adenosine A2A receptor agonist, in reperfused canine myocardium

Adenosine and adenosine A(2A) receptor agonists have been shown to limit myocardial infarct size when given at vasodilatory doses during reperfusion. This beneficial effect is thought to be due, in part, to stimulation of adenosine A(2A) receptors on inflammatory cells. The specific aims of this study were to determine whether the anti-inflammatory and cardioprotective properties of a novel adenosine A(2A) receptor agonist, ATL-146e (ATL), alone or in combination with the phosphodiesterase IV inhibitor rolipram would occur using very low, nonvasodilating doses. In a canine model of reperfused myocardial infarction, low-dose ATL given alone reduced infarct size by 45% (P < 0.05 vs. control). When ATL was combined with a very low dose of rolipram (0.001 microg.kg(-1).min(-1)), a marked reduction in P-selectin expression and neutrophil infiltration (51% lower; P < 0.001 vs. control) was seen and the infarct size reduction (58% lower; P < 0.01 vs. control) was greater than observed with ATL (45% lower; P < 0.05) or rolipram (33% lower; P < 0.05) alone. In conclusion, a low, nonvasodilating dose of ATL, a highly selective adenosine A(2A) receptor agonist, reduced infarct size after reperfusion. Furthermore, combining ATL and the phosphodiesterase IV inhibitor rolipram reduced infarct size even more than either agent alone. Such combination therapy may be beneficial clinically by potentiating cardioprotection after coronary reperfusion at doses far below those producing vasodilatation or side effects.     

Similar protective effects of BQ-123 and erythropoietin on survival of neural cells and generation of neurons upon hypoxic injury

Our recent study [Danielyan et al., 2005. Eur. J. Cell Biol. 84, 567-579] showed an additive protective effect of endothelin (ET) receptor A (ETA-R) blockade and erythropoietin (EPO) on the survival and rejuvenation of rat astroglial cells exposed to hypoxia. Whether the effects observed with rodent astroglial cells can be reproduced in human astrocytes and whether these effects of ETA-R blockade and EPO on astrocytes are associated with neuronal survival remained open. Therefore, in the present study, the effects of the ETA-R antagonist BQ-123 and EPO on the maintenance of the neuronal population and survival of the human fetal astroglial cell line (SV-FHAS) under normoxic and hypoxic conditions (NC and HC, respectively) were investigated. Rat brain primary cultures exposed to BQ-123 and/or EPO revealed an increase in the number of beta-III tubulin-positive neurons under NC. The hypoxia-caused loss of neurons was abolished by administration of BQ-123 or EPO. Simultaneous application of EPO and BQ-123 led to an additive protective effect on the generation of neurons under NC only. By contrast, BQ-788, the selective ETB-R antagonist, diminished the neuronal population both in NC and HC. Both under NC and HC the number of non-differentiated nestin+/GFAP- neural cells increased upon application of EPO or BQ-123. SV-FHAS responded to BQ-123 or EPO by a decrease in LDH activity in the culture medium under NC (35%) and HC (26% LDH decrease). Concomitant effects of EPO and BQ-123 were illustrated in an additional increase in the survival of human astrocytes (33% under NC and 17% under HC). These data hint at a neuroprotective therapeutic potency of ETA-R blockade, which either alone or in combination with EPO may improve the survival of astroglial and neuronal cells upon hypoxic injury.