CD40 engagement on dendritic cells, but not on B or T cells, is required for long-term control of murine gammaherpesvirus 68

CD4 T cells are not essential for primary clearance of replicating murine gammaherpesvirus 68 (MHV-68) but are required for effective long-term control. The virus reactivates in the lungs of major histocompatibility complex class II-deficient (CII-/-) mice that lack functional CD4 T cells. CD40 ligand (CD40L) is upregulated on activated CD4 T cells, and it is thought that CD40-CD40L interactions are an important component of CD4 T-cell help. Our previous studies have shown that agonistic antibodies to CD40 can substitute for CD4 T-cell function in the long-term control of MHV-68. In the present study, we sought to identify the CD40-positive cell type mediating this effect. To address this question, we adoptively transferred MHV-68 peptide-pulsed CII(-/-) dendritic cells (DC) that had been treated with an agonistic antibody to CD40 into MHV-68-infected CII(-/-) recipients. Viral reactivation was significantly lower in mice injected with anti-CD40-treated DC than in those injected with control DC or in mice that did not receive any DC. However, in similar experiments with B cells, anti-CD40 treatment had no effect. We also investigated the requirement for CD40 expression on T cells by adoptive transfer of T cells from CD40(+/+) or CD40(-/-) mice into T-cell-deficient recipients that were subsequently infected with MHV-68. The results showed that CD40 expression on T cells is not necessary for preventing viral reactivation. Taken together, our data suggest that CD40 engagement on DC, but not on T or B cells, is essential for effective long-term control of MHV-68.     

Inhibition of apoptosome formation by suppression of Hsp90beta phosphorylation in tyrosine kinase-induced leukemias

Constitutively active tyrosine kinases promote leukemogenesis by increasing cell proliferation and inhibiting apoptosis. However, mechanisms underlying apoptotic inhibition have not been fully elucidated. In many settings, apoptosis occurs by mitochondrial cytochrome c release, which nucleates the Apaf-1/caspase-9 apoptosome. Here we report that the leukemogenic kinases, Bcr-Abl, FLT3/D835Y, and Tel-PDGFRβ, all can inhibit apoptosome function. In cells expressing these kinases, the previously reported apoptosome inhibitor, Hsp90β, bound strongly to Apaf-1, preventing cytochrome c-induced Apaf-1 oligomerization and caspase-9 recruitment. Hsp90β interacted weakly with the apoptosome in untransformed cells. While Hsp90β was phosphorylated at Ser 226/Ser 255 in untransformed cells, phosphorylation was absent in leukemic cells. Expression of mutant Hsp90β (S226A/S255A), which mimics the hypophosphorylated form in leukemic cells, conferred resistance to cytochrome c-induced apoptosome activation in normal cells, reflecting enhanced binding of nonphosphorylatable Hsp90β to Apaf-1. In Bcr-Abl-positive mouse bone marrow cells, nonphosphorylatable Hsp90β expression conferred imatinib (Gleevec) resistance. These data provide an explanation for apoptosome inhibition by activated leukemogenic tyrosine kinases and suggest that alterations in Hsp90β-apoptosome interactions may contribute to chemoresistance in leukemias.     

The effects of diabetes and aminoguanidine treatment on endothelial function in a primate model of type 1 diabetes

Abnormalities of endothelial function have been demonstrated in diabetes and are thought to play a role in the pathogenesis of diabetic complications. The aims of this study were to determine whether aminoguanidine, an inhibitor of glycation, can prevent endothelial and microcirculation abnormalities in a primate model of type 1 diabetes. Male baboons (Papio hamadryas) were assigned to one of the four groups: control, diabetes, control treated with aminoguanidine or diabetes treated with aminoguanidine. Diabetes was induced by streptozocin (60 mg/kg) and treated with once daily injection of insulin. Aminoguanidine was given subcutaneously (10 mg/kg), once a day. Diabetic animals had a mean duration of diabetes of 8.9 +/- 3.4 years and HbA1c of 8.9 +/- 1.1%. Microvascular function was measured by laser Doppler velocimetry, with examination of endothelium-dependent increase in skin blood flow (SkBF) following iontophoresis of acetylcholine (ACh) and endothelium-independent increase in SkBF in response to the nitric oxide (NO) donor sodium nitroprusside (SNP). Multiple regression analysis identified diabetes (P = 0.049) and aminioguanidine treatment (P = 0.026) as significant determinants of ACh response. The diabetic baboons treated with aminoguanidine had less Ach-mediated SkBF response compared with controls (1.39 +/- 0.32 vs. 2.26 +/- 0.61, F = 3.3, P = 0.04), but there was no difference between groups in SkBF response to SNP. We conclude that endothelial dysfunction can be demonstrated in this primate model of type 1 diabetes at a stage when overt diabetic complications are not present. This occurred in the absence of insulin resistance or significant hypercholesterolemia. Administration of aminoguanidine from the onset of diabetes was not able to prevent this abnormality and in fact aggravated the endothelial response. Effects of aminoguanidine on NO synthase may contribute to this phenomenon.     

Complete genome sequence of Nitrobacter hamburgensis X14 and comparative genomic analysis of species within the genus Nitrobacter

The alphaproteobacterium Nitrobacter hamburgensis X14 is a gram-negative facultative chemolithoautotroph that conserves energy from the oxidation of nitrite to nitrate. Sequencing and analysis of the Nitrobacter hamburgensis X14 genome revealed four replicons comprised of one chromosome (4.4 Mbp) and three plasmids (294, 188, and 121 kbp). Over 20% of the genome is composed of pseudogenes and paralogs. Whole-genome comparisons were conducted between N. hamburgensis and the finished and draft genome sequences of Nitrobacter winogradskyi and Nitrobacter sp. strain Nb-311A, respectively. Most of the plasmid-borne genes were unique to N. hamburgensis and encode a variety of functions (central metabolism, energy conservation, conjugation, and heavy metal resistance), yet approximately 21 kb of a approximately 28-kb "autotrophic" island on the largest plasmid was conserved in the chromosomes of Nitrobacter winogradskyi Nb-255 and Nitrobacter sp. strain Nb-311A. The N. hamburgensis chromosome also harbors many unique genes, including those for heme-copper oxidases, cytochrome b(561), and putative pathways for the catabolism of aromatic, organic, and one-carbon compounds, which help verify and extend its mixotrophic potential. A Nitrobacter "subcore" genome was also constructed by removing homologs found in strains of the closest evolutionary relatives, Bradyrhizobium japonicum and Rhodopseudomonas palustris. Among the Nitrobacter subcore inventory (116 genes), copies of genes or gene clusters for nitrite oxidoreductase (NXR), cytochromes associated with a dissimilatory nitrite reductase (NirK), PII-like regulators, and polysaccharide formation were identified. Many of the subcore genes have diverged significantly from, or have origins outside, the alphaproteobacterial lineage and may indicate some of the unique genetic requirements for nitrite oxidation in Nitrobacter.     

Simvastatin attenuates release of neutrophilic and remodeling factors from primary bronchial epithelial cells derived from stable lung transplant recipients

Obliterative bronchiolitis (OB), the major cause of chronic lung allograft dysfunction, is characterized by airway neutrophilia, inflammation, and remodeling, with progressive fibroproliferation and obliteration of small airways that ultimately leads to patient death. Statins have potential anti-inflammatory effects and have been demonstrated to confer a survival advantage in lung transplant patients. We postulated that the beneficial effects of simvastatin in lung transplantation are in part due to inhibition of the epithelial production of key mediators of neutrophil chemotaxis, inflammation, and airway remodeling. Our objective was to assess the effect of simvastatin on a unique population of primary bronchial epithelial cells (PBECs) derived from stable lung allografts, with specific reference to airway neutrophilia and remodeling. PBEC cultures were stimulated with IL-17 or transforming growth factor (TGF)-beta, with and without simvastatin. Supernatant levels of factors critical to driving airway neutrophilia and remodeling were measured. IL-17 upregulated IL-8, IL-6, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor (GM-CSF), and VEGF, whereas TGF-beta increased IL-6, GM-CSF, matrix metalloproteinase (MMP)-2, and MMP-9. Simvastatin attenuated effects of both IL-17 and TGF-beta. We have demonstrated the ability of simvastatin to attenuate release of airway neutrophilic and remodeling mediators and to inhibit their upregulation by TGF-beta and IL-17. These data illustrate the potential of simvastatin to alleviate neutrophilic airway inflammation and remodeling in the transplanted lung and may have additional relevance to other neutrophilic airway conditions, such as chronic obstructive pulmonary disease.     

Quantitative determination of besifloxacin, a novel fluoroquinolone antimicrobial agent, in human tears by liquid chromatography-tandem mass spectrometry

A rapid and sensitive method was developed using high-performance liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) for the quantification of besifloxacin in human tears using sparfloxacin as the internal standard (IS). Besifloxacin was extracted from human tear samples using an ammonium formate buffer at pH 3.25. The method was validated over a concentration range of 2-2000 ng/mL, with a total run time of less than 4 min. The overall intra- and inter-day precision for this method was less than 6%. The method was used to measure besifloxacin concentrations in tear samples collected after topical ocular administration to humans; besifloxacin concentrations were 610+/-540 microg/g (15 min) and 1.60+/-2.28 microg/g (24h).