A Legionella pneumophila Kinase Phosphorylates the Hsp70 Chaperone Family to Inhibit Eukaryotic Protein Synthesis

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The Association between Body Mass Index and Mortality in Incident Dialysis Patients

Objectives

To study the body mass index (BMI) trajectory in patients with incident end-stage kidney disease and its association with all-cause mortality.

Methods

This longitudinal cohort study included 17022 adult patients commencing hemodialysis [HD] (n = 10860) or peritoneal dialysis [PD] (n = 6162) between 2001 and 2008 and had ≥6-month follow-up and ≥2 weight measurements, using the Australia and New Zealand Dialysis and Transplant Registry data. The association of time-varying BMI with all-cause mortality was explored using multivariate Cox regression models.

Results

The median follow-up was 2.3 years. There was a non-linear change in the mean BMI (kg/m²) over time, with an initial decrease from 27.6 (95% confidence interval [CI]: 27.5, 27.7) to 26.7 (95% CI: 26.6, 26.9) at 3-month, followed by increments to 27.1 (95% CI: 27, 27.2) at 1-year and 27.2 (95% CI: 26.8, 27.1) at 3-year, and a gradual decrease subsequently. The BMI trajectory was significantly lower in HD patients who died than those who survived, although this pattern was not observed in PD patients. Compared to the reference time-varying BMI category of 25.1–28 kg/m², the mortality risks of both HD and PD patients were greater in all categories of time-varying BMI <25 kg/m². The mortality risks were significantly lower in all categories of time-varying BMI >28.1 kg/m² among HD patients, but only in the category 28.1–31 kg/m² among PD patients.

Conclusions

BMI changed over time in a non-linear fashion in incident dialysis patients. Time-varying measures of BMI were significantly associated with mortality risk in both HD and PD patients.     

DNBS/TNBS Colitis Models: Providing Insights Into Inflammatory Bowel Disease and Effects of Dietary Fat

Inflammatory Bowel Diseases (IBD), including Crohn''s Disease and Ulcerative Colitis, have long been associated with a genetic basis, and more recently host immune responses to microbial and environmental agents. Dinitrobenzene sulfonic acid (DNBS)-induced colitis allows one to study the pathogenesis of IBD associated environmental triggers such as stress and diet, the effects of potential therapies, and the mechanisms underlying intestinal inflammation and mucosal injury. In this paper, we investigated the effects of dietary n-3 and n-6 fatty acids on the colonic mucosal inflammatory response to DNBS-induced colitis in rats. All rats were fed identical diets with the exception of different types of fatty acids [safflower oil (SO), canola oil (CO), or fish oil (FO)] for three weeks prior to exposure to intrarectal DNBS. Control rats given intrarectal ethanol continued gaining weight over the 5 day study, whereas, DNBS-treated rats fed lipid diets all lost weight with FO and CO fed rats demonstrating significant weight loss by 48 hr and rats fed SO by 72 hr. Weight gain resumed after 72 hr post DNBS, and by 5 days post DNBS, the FO group had a higher body weight than SO or CO groups. Colonic sections collected 5 days post DNBS-treatment showed focal ulceration, crypt destruction, goblet cell depletion, and mucosal infiltration of both acute and chronic inflammatory cells that differed in severity among diet groups. The SO fed group showed the most severe damage followed by the CO, and FO fed groups that showed the mildest degree of tissue injury. Similarly, colonic myeloperoxidase (MPO) activity, a marker of neutrophil activity was significantly higher in SO followed by CO fed rats, with FO fed rats having significantly lower MPO activity. These results demonstrate the use of DNBS-induced colitis, as outlined in this protocol, to determine the impact of diet in the pathogenesis of IBD.     

Fasting increases microbiome-based colonization resistance and reduces host inflammatory responses during an enteric bacterial infection

Reducing food intake is a common host response to infection, yet it remains unclear whether fasting is detrimental or beneficial to an infected host. Despite the gastrointestinal tract being the primary site of nutrient uptake and a common route for infection, studies have yet to examine how fasting alters the host’s response to an enteric infection. To test this, mice were fasted before and during oral infection with the invasive bacterium Salmonella enterica serovar Typhimurium. Fasting dramatically interrupted infection and subsequent gastroenteritis by suppressing Salmonella’s SPI-1 virulence program, preventing invasion of the gut epithelium. Virulence suppression depended on the gut microbiota, as Salmonella’s invasion of the epithelium proceeded in fasting gnotobiotic mice. Despite Salmonella’s restored virulence within the intestines of gnotobiotic mice, fasting downregulated pro-inflammatory signaling, greatly reducing intestinal pathology. Our study highlights how food intake controls the complex relationship between host, pathogen and gut microbiota during an enteric infection.     

Chemical genetic blockade of transformation reveals dependence on aberrant oncogenic signaling

BACKGROUND: Our understanding of protein kinase inhibition in the treatment of cancer is clearly limited by the lack of inhibitors that selectively block a single kinase implicated in neoplastic transformation. One approach to developing specific inhibitors is to engineer in protein kinases silent mutations that allow selective inhibition while retaining kinase activity. Because it is implicated in a large number of malignancies, EGFR provides an attractive target for such selective kinase inhibition.RESULTS: We generated an inhibitor-sensitized allele of the transforming receptor tyrosine kinase v-erbB. Transformation of immortalized rodent fibroblasts by sensitized versions of v-erbB (v-erbB-as1) was blocked by 1-napthyl PP1 (NaPP1), a cell-permeable ATP-competitive inhibitor. NaPP1 also reversed morphological transformation by v-erbB-as1. Signaling through MAP kinase and PI(3) kinase was initially blocked by inhibitor treatment and then recovered to levels comparable to those in nontransformed cells. Surprisingly, NaPP1-treated v-erbB-as1 cells failed to re-enter the cell cycle, showed decreased levels of D- and A-type cyclins, and showed increased levels of p27. To extend this result, we showed that NaPP1 treatment of v-Src-as1 cells also led to cell cycle arrest. Arrested cells could be rescued with a conditional allele of Raf or by transduction of a constitutive allele of cyclin D1.CONCLUSIONS: These data suggest that mammalian cells can become dependent on aberrant oncogenic signaling; this dependency renders them incapable of returning to a normal, proliferative phenotype.     

RAGE ligation affects T cell activation and controls T cell differentiation

The pattern recognition receptor, RAGE, has been shown to be involved in adaptive immune responses but its role on the components of these responses is not well understood. We have studied the effects of a small molecule inhibitor of RAGE and the deletion of the receptor (RAGE-/- mice) on T cell responses involved in autoimmunity and allograft rejection. Syngeneic islet graft and islet allograft rejection was reduced in NOD and B6 mice treated with TTP488, a small molecule RAGE inhibitor (p < 0.001). RAGE-/- mice with streptozotocin-induced diabetes showed delayed rejection of islet allografts compared with wild type (WT) mice (p < 0.02). This response in vivo correlated with reduced proliferative responses of RAGE-/- T cells in MLRs and in WT T cells cultured with TTP488. Overall T cell proliferation following activation with anti-CD3 and anti-CD28 mAbs were similar in RAGE-/- and WT cells, but RAGE-/- T cells did not respond to costimulation with anti-CD28 mAb. Furthermore, culture supernatants from cultures with anti-CD3 and anti-CD28 mAbs showed higher levels of IL-10, IL-5, and TNF-alpha with RAGE-/- compared with WT T cells, and WT T cells showed reduced production of IFN-gamma in the presence of TTP488, suggesting that RAGE may be important in the differentiation of T cell subjects. Indeed, by real-time PCR, we found higher levels of RAGE mRNA expression on clonal T cells activated under Th1 differentiating conditions. We conclude that activation of RAGE on T cells is involved in early events that lead to differentiation of Th1(+) T cells.     

Human carbonyl reductase 1 is an S-nitrosoglutathione reductase

Human carbonyl reductase 1 (hCBR1) is an NADPH-dependent short chain dehydrogenase/reductase with broad substrate specificity and is thought to be responsible for the in vivo reduction of quinones, prostaglandins, and other carbonyl-containing compounds including xenobiotics. In addition, hCBR1 possesses a glutathione binding site that allows for increased affinity toward GSH-conjugated molecules. It has been suggested that the GSH-binding site is near the active site; however, no structures with GSH or GSH conjugates have been reported. We have solved the x-ray crystal structures of hCBR1 and a substrate mimic in complex with GSH and the catalytically inert GSH conjugate hydroxymethylglutathione (HMGSH). The structures reveal the GSH-binding site and provide insight into the affinity determinants for GSH-conjugated substrates. We further demonstrate that the structural isostere of HMGSH, S-nitrosoglutathione, is an ideal hCBR1 substrate (Km = 30 microm, kcat = 450 min(-1)) with kinetic constants comparable with the best known hCBR1 substrates. Furthermore, we demonstrate that hCBR1 dependent GSNO reduction occurs in A549 lung adenocarcinoma cell lysates and suggest that hCBR1 may be involved in regulation of tissue levels of GSNO.     

Artificial covering on trap nests improves the colonization of trap-nesting wasps

To evaluate the role that a trap‐nest cover might have on sampling methodologies, the abundance of each species of trap‐nesting Hymenoptera and the parasitism rate in a Canadian forest were compared between artificially covered and uncovered traps. Of trap tubes exposed at eight forest sites in six trap‐nest boxes, 531 trap tubes were occupied and 1216 individuals of 12 wasp species of four predatory families, Vespidae (Eumeninae), Crabronidae, Sphecidae and Pompilidae emerged over 2 years, and no bee species were found. Results indicated that artificial covering led to a significant increase in the number of nested tubes of Ancistrocerus adiabatus, Ancistrocerus antilope, Ancistrocerus campestris and Auplopus mellipes, and significant effects of covering were not found for the other species. No significant difference in the overall parasitism rate between covered and uncovered traps was noted. These suggested that the covering technique could provide more opportunities for some wasp species to colonize trap nests.     

A Mathematical Model of Forager Loss in Honeybee Colonies Infested with <Emphasis Type="Italic">Varroa destructor</Emphasis> and the Acute Bee Paralysis Virus

We incorporate a mathematical model of Varroa destructor and the Acute Bee Paralysis Virus with an existing model for a honeybee colony, in which the bee population is divided into hive bees and forager bees based on tasks performed in the colony. The model is a system of five ordinary differential equations with dependent variables: uninfected hive bees, uninfected forager bees, infected hive bees, virus-free mites and virus-carrying mites. The interplay between forager loss and disease infestation is studied. We study the stability of the disease-free equilibrium of the bee-mite-virus model and observe that the disease cannot be fought off in the absence of varroacide treatment. However, the disease-free equilibrium can be stable if the treatment is strong enough and also if the virus-carrying mites become virus-free at a rate faster than the mite birth rate. The critical forager loss due to homing failure, above which the colony fails, is calculated using simulation experiments for disease-free, treated and untreated mite-infested, and treated virus-infested colonies. A virus-infested colony without varroacide treatment fails regardless of the forager mortality rate.