Stress Resistance and Longevity Are Not Directly Linked to Levels of Enzymatic Antioxidants in the Ponerine Ant Harpegnathos saltator

BACKGROUND: The molecular mechanisms of variations in individual longevity are not well understood, even though longevity can be increased substantially by means of diverse experimental manipulations. One of the factors supposed to be involved in the increase of longevity is a higher stress resistance. To test this hypothesis in a natural system, eusocial insects such as bees or ants are ideally suited. In contrast to most other eusocial insects, ponerine ants show a peculiar life history that comprises the possibility to switch during adult life from a normal worker to a reproductive gamergate, therewith increasing their life expectancy significantly. RESULTS: We show that increased resistance against major stressors, such as reactive oxygen species and infection accompanies the switch from a life-history trait with normal lifespan to one with a longer life expectancy. A short period of social isolation was sufficient to enhance stress resistance of workers from the ponerine ant species Harpegnathos saltator significantly. All ant groups with increased stress resistances (reproducing gamergates and socially isolated workers) have lower catalase activities and glutathione levels than normal workers. Therewith, these ants resemble the characteristics of the youngest ants in the colony. CONCLUSIONS: Social insects with their specific life history including a switch from normal workers to reproducing gamergates during adult life are well suited for ageing research. The regulation of stress resistance in gamergates seemed to be modified compared to foraging workers in an economic way. Interestingly, a switch towards more stress resistant animals can also be induced by a brief period of social isolation, which may already be associated with a shift to a reproductive trajectory. In Harpegnathos saltator, stress resistances are differently and potentially more economically regulated in reproductive individuals, highlighting the significance of reproduction for an increase in longevity in social insects. As already shown for other organisms with a long lifespan, this trait is not directly coupled to higher levels of enzymatic and non-enzymatic antioxidants

DNA methylation partially mediates antidiabetic effects of metformin on HbA1c levels in individuals with type 2 diabetes

Aims: Despite metformin being used as first-line pharmacological therapy for type 2 diabetes, its underlying mechanisms remain unclear. We aimed to determine whether metformin altered DNA methylation in newlydiagnosed individuals with type 2 diabetes. Methods and Results: We found that metformin therapy is associated with altered methylation of 26 sites in blood from Scandinavian discovery and replication cohorts (FDR < 0.05), using MethylationEPIC arrays. The majority (88%) of these 26 sites were hypermethylated in patients taking metformin for ~ 3 months compared to controls, who had diabetes but had not taken any diabetes medication. Two of these blood-based methylation markers mirrored the epigenetic pattern in muscle and adipose tissue (FDR < 0.05). Four type 2 diabetes-associated SNPs were annotated to genes with differential methylation between metformin cases and controls, e.g., GRB10, RPTOR, SLC22A18AS and TH2LCRR. Methylation correlated with expression in human islets for two of these genes. Three metformin-associated methylation sites (PKNOX2, WDTC1 and MICB) partially mediate effects of metformin on follow-up HbA1c levels. When combining methylation of these three sites into a score, which was used in a causal mediation analysis, methylation was suggested to mediate up to 32% of metformin’s effects on HbA1c. Conclusion: Metformin-associated alterations in DNA methylation partially mediates metformin’s antidiabetic effects on HbA1c in newly-diagnosed individuals with type 2 diabetes

JAM-A is highly expressed on human hematopoietic repopulating cells and associates with the key hematopoietic chemokine receptor CXCR4

Hematopoietic stem/progenitor cells (HSPCs) reside in specialized bone marrow microenvironmental niches, with vascular elements (endothelial/mesenchymal stromal cells) and CXCR4-CXCL12 interactions playing particularly important roles for HSPC entry, retention and maintenance. The functional effects of CXCL12 are dependent on its local concentration and rely on complex HSPC-niche interactions. Two Junctional Adhesion Molecule family proteins, JAM-B and JAM-C, are reported to mediate HSPC-stromal cell interactions, which in turn regulate CXCL12 production by mesenchymal stromal cells (MSCs). Here, we demonstrate that another JAM family member, JAM-A, is most highly expressed on human hematopoietic stem cells with in vivo repopulating activity (p&lt;0.01 for JAM-Ahigh compared to JAM-AInt or Low cord blood CD34+ cells). JAM-A blockade, silencing and overexpression show that JAM-A contributes significantly (p&lt;0.05) to the adhesion of human HSPCs to IL-1β activated human bone marrow sinusoidal endothelium. Further studies highlight a novel association of JAM-A with CXCR4, with these molecules moving to the leading edge of the cell upon presentation with CXCL12 (p&lt;0.05 compared to no CXCL12). Therefore, we hypothesize that JAM family members differentially regulate CXCR4 function and CXCL12 secretion in the bone marrow niche.</p

Labeled EF-Tus for rapid kinetic studies of pretranslocation complex formation

The universally conserved translation elongation factor EF-Tu delivers aminoacyl(aa)-tRNA in the form of an aa-tRNA·EF-Tu·GTP ternary complex (TC) to the ribosome where it binds to the cognate mRNA codon within the ribosomal A-site, leading to formation of a pretranslocation (PRE) complex. Here we describe preparation of QSY9 and Cy5 derivatives of the variant E348C-EF-Tu that are functional in translation elongation. Together with fluorophore derivatives of aa-tRNA and of ribosomal protein L11, located within the GTPase associated center (GAC), these labeled EF-Tus allow development of two new FRET assays that permit the dynamics of distance changes between EF-Tu and both L11 (Tu-L11 assay) and aa-tRNA (Tu-tRNA assay) to be determined during the decoding process. We use these assays to examine: (i) the relative rates of EF-Tu movement away from the GAC and from aa-tRNA during decoding, (ii) the effects of the misreading-inducing antibiotics streptomycin and paromomycin on tRNA selection at the A-site, and (iii) how strengthening the binding of aa-tRNA to EF-Tu affects the rate of EF-Tu movement away from L11 on the ribosome. These FRET assays have the potential to be adapted for high throughput screening of ribosomal antibiotics

Ascorbic acid partly antagonizes resveratrol mediated heme oxygenase-1 but not paraoxonase-1 induction in cultured hepatocytes - role of the redox-regulated transcription factor Nrf2

<p>Abstract</p> <p>Background</p> <p>Both resveratrol and vitamin C (ascorbic acid) are frequently used in complementary and alternative medicine. However, little is known about the underlying mechanisms for potential health benefits of resveratrol and its interactions with ascorbic acid.</p> <p>Methods</p> <p>The antioxidant enzymes heme oxygenase-1 and paraoxonase-1 were analysed for their mRNA and protein levels in HUH7 liver cells treated with 10 and 25 μmol/l resveratrol in the absence and presence of 100 and 1000 μmol/l ascorbic acid. Additionally the transactivation of the transcription factor Nrf2 and paraoxonase-1 were determined by reporter gene assays.</p> <p>Results</p> <p>Here, we demonstrate that resveratrol induces the antioxidant enzymes heme oxygenase-1 and paraoxonase-1 in cultured hepatocytes. Heme oxygenase-1 induction by resveratrol was accompanied by an increase in Nrf2 transactivation. Resveratrol mediated Nrf2 transactivation as well as heme oxygenase-1 induction were partly antagonized by 1000 μmol/l ascorbic acid.</p> <p>Conclusions</p> <p>Unlike heme oxygenase-1 (which is highly regulated by Nrf2) paraoxonase-1 (which exhibits fewer ARE/Nrf2 binding sites in its promoter) induction by resveratrol was not counteracted by ascorbic acid. Addition of resveratrol to the cell culture medium produced relatively low levels of hydrogen peroxide which may be a positive hormetic redox-signal for Nrf2 dependent gene expression thereby driving heme oxygenase-1 induction. However, high concentrations of ascorbic acid manifold increased hydrogen peroxide production in the cell culture medium which may be a stress signal thereby disrupting the Nrf2 signalling pathway.</p

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

Analysis of torque and force with differently tapered rotary endodontic instruments in vitro.

The aim of this study was to compare torques and forces developed by two sequences of nickel-titanium rotary instruments, using only .04 taper instruments or a combination of .04 and .06 tapers, respectively. Curved canals in plastic blocks were shaped in a torque-testing device; torque, force, contact areas and numbers of working rotations were determined. Analysis of variance and Pearson correlation coefficients were used to compare the two sequences. Mean torque ranged from 0.2 +/- 0.03 to 3.19 +/- 0.28 Ncm and was higher for instrument sizes 25 to 45 in group A. Mean vertical forces ranged from 1.49 +/- 0.54 to 12.0 +/- 3.5 N; there were significant correlations between torque and force as well as between torque and contact areas. Numbers of rotations were lower in the combined .04 and .06 sequence. An instrumentation sequence encompassing various tapers seems to be safer regarding torsional and fatigue failure compared to a sequence that used one single taper. However, the former sequence requires the use of more instruments

Analysis of torque and force with differently tapered rotary endodontic instruments in vitro.

The aim of this study was to compare torques and forces developed by two sequences of nickel-titanium rotary instruments, using only .04 taper instruments or a combination of .04 and .06 tapers, respectively. Curved canals in plastic blocks were shaped in a torque-testing device; torque, force, contact areas and numbers of working rotations were determined. Analysis of variance and Pearson correlation coefficients were used to compare the two sequences. Mean torque ranged from 0.2 +/- 0.03 to 3.19 +/- 0.28 Ncm and was higher for instrument sizes 25 to 45 in group A. Mean vertical forces ranged from 1.49 +/- 0.54 to 12.0 +/- 3.5 N; there were significant correlations between torque and force as well as between torque and contact areas. Numbers of rotations were lower in the combined .04 and .06 sequence. An instrumentation sequence encompassing various tapers seems to be safer regarding torsional and fatigue failure compared to a sequence that used one single taper. However, the former sequence requires the use of more instruments