DNA bending by the human damage recognition complex XPC-HR23B

Genome integrity is maintained, despite constant assault on DNA, due to the action of a variety of DNA repair pathways. Nucleotide excision repair (NER) protects the genome from the deleterious effects of UV irradiation as well as other agents that induce chemical changes in DNA bases. The mechanistic steps required for eukaryotic NER involve the concerted action of at least six proteins or protein complexes. The specificity to incise only the DNA strand including the damage at defined positions is determined by the coordinated assembly of active protein complexes onto damaged DNA. In order to understand the molecular mechanism of the NER reactions and the origin of this specificity and control we analyzed the architecture of functional NER complexes at nanometer resolution by scanning force microscopy (SFM). In the initial step of damage recognition by XPC-HR23B we observe a protein induced change in DNA conformation. XPC-HR23B induces a bend in DNA upon binding and this is stabilized at the site of damage. We discuss the importance of the XPC-HR23B-induced distortion as an architectural feature that can be exploited for subsequent assembly of an active NER complex.     

Comparison of assays for Cryptosporidium parvum oocysts viability after chemical disinfection

Abstract In vitro excystation, vital dyes (4', 6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI)), and infeictivity in neonatal CD-1 mice were used to assess the viability of Cryptosporidium parvum oocysts after chemical disinfection. In vitro excystation and DAPI/PI staining provided similar estimates of viability in bench-scale experiments, but both of these methods significantly overestimated the viability when compared with infectivity (Pr ≤ 0.01). Infectivity was the most reliable measure of the viability of C. parvum oocysts following chemical disinfection.     

Size-Dependent Effects of Gold Nanoparticles Uptake on Maturation and Antitumor Functions of Human Dendritic Cells In Vitro

Gold nanoparticles (GNPs) are claimed as outstanding biomedical tools for cancer diagnostics and photo-thermal therapy, but without enough evidence on their potentially adverse immunological effects. Using a model of human dendritic cells (DCs), we showed that 10 nm- and 50 nm-sized GNPs (GNP₁₀ and GNP₅₀, respectively) were internalized predominantly via dynamin-dependent mechanisms, and they both impaired LPS-induced maturation and allostimulatory capacity of DCs, although the effect of GNP₁₀ was more prominent. However, GNP₁₀ inhibited LPS-induced production of IL-12p70 by DCs, and potentiated their Th2 polarization capacity, while GNP₅₀ promoted Th17 polarization. Such effects of GNP₁₀ correlated with a stronger inhibition of LPS-induced changes in Ca²⁺ oscillations, their higher number per DC, and more frequent extra-endosomal localization, as judged by live-cell imaging, proton, and electron microscopy, respectively. Even when released from heat-killed necrotic HEp-2 cells, GNP₁₀ inhibited the necrotic tumor cell-induced maturation and functions of DCs, potentiated their Th2/Th17 polarization capacity, and thus, impaired the DCs'' capacity to induce T cell-mediated anti-tumor cytotoxicity in vitro. Therefore, GNP₁₀ could potentially induce more adverse DC-mediated immunological effects, compared to GNP₅₀.     

The preoperative activity of Th1 and Th17 cytokine axes in prediction of sepsis after radical cystectomy

The aim of the study was to correlate the preoperative activity of Th1 and Th17 cytokine axes with the development of sepsis after radical cystectomy. The study involved twenty patients with the infiltrative transitional cell carcinoma of the urinary bladder without previous radiotherapy/chemotherapy, who underwent open radical cystectomy with urinary diversion. Preoperative plasma concentrations of Th1 cytokines interleukin 12 (IL-12) and interferon gamma (IFN-γ), and Th17 cytokines IL-23 and IL-17, were measured using ELISA. Preoperative expression of mRNA for IL-12p35, IFN-γ, IL-23p19 and IL-17 was quantified by real-time RT-PCR using mRNA extracted from peripheral blood mononuclear cells. Eight patients developed postoperative sepsis, diagnosed within two weeks post-operation as systemic inflammatory response syndrome in the presence of local or systemic infection. The preoperative basal plasma concentrations of Th1 and Th17 cytokines were slightly above the detection limits, with a tendency toward lower concentrations in patients who developed sepsis, but the difference was not significant (p>0.05). The preoperative expression of mRNA encoding IL-12p35 and IL-17 was significantly lower in patients who developed sepsis (p=0.003 and p=0.028, respectively). The similar trend was observed for IL-23p19 and IFN-γ, but the differences did not reach the statistical significance (p=0.051 and p=0.172, respectively). These data suggest that determination of preoperative Th1 and Th17 cytokine mRNA levels might be useful in predicting sepsis development after radical cystectomy.     

Signaling through Toll-like receptor 3 and Dectin-1 potentiates the capability of human monocyte-derived dendritic cells to promote T-helper 1 and T-helper 17 immune responses

Background aimsRecent studies have shown that the ligation of Toll-like receptor 3 (TLR3) or Dectin-1 on human monocyte-derived dendritic cells (MoDC) elicits their maturation, but with a different outcome on immunomodulation. Therefore the aim of this work was to study the response of MoDC to the combined effect of polyinosinic:polycytydilic acid [Poly (I:C)] and curdlan, selective TLR3 and Dectin-1 agonists, respectively.MethodsImmature MoDC, generated from human monocytes, were treated with Poly (I:C), curdlan or their combination for 2 days. Phenotypic characteristics of MoDC were determined by flow cytometry, and cytokine production was measured by enzyme-linked immunosorbent assay (ELISA) and FlowCytomix, while the stimulatory capability of MoDC was tested using a mixed leukocyte reaction assay.ResultsThe combination of Poly (I:C) and curdlan induced phenotypic maturation of MoDC with the capability to stimulate an alloreactive response. Such treated MoDC up-regulated the production of interleukin (IL)-12, IL-23 and IL-10, compared with the effect of Poly (I:C) alone. Curdlan-treated MoDC stimulated the production of IL-17 by alloreactive CD4 + T cells more strongly than Poly (I:C)-treated MoDC. The opposite effect was observed for interferon(IFN)-γ production. When combined, these agonists primed MoDC to increase further the production of IFN-γ by CD4 + T cells in co-culture, especially those of naive (CD45RA ⁺) phenotype, and IL-17 by memory (CD45RO +) CD4 + T cells.ConclusionsLigation of TLR3 and Dectin-1 receptor up-regulates T-helper (Th) 1 and Th17 immune responses compared with single agonists. These findings may have therapeutic implications for the use of MoDC in immunotherapy.     

Effect of dietary zinc on the levels and distribution of fatty acids and vitamin A in blood plasma chylomicrons

The aim of this work was to explore the effects of a low- and high-zinc diet and vitamin Aon the distribution of fatty acids in chylomicrons. Mongolian Gerbils were fed a basal diet (for 3 wk) containing 8 or 38 mg zinc/kg of feed (low-zinc group [termed LZ group] and saturated zinc group [termed SZ group], respectively). The following day, the animals were given sunflower oil containing 50 nmol vitamin A. The results showed that the concentration of zinc in blood plasma was similar in both groups. The amount of plasma chylomicrons was lower in the LZ group than in the SZ group (p < 0.001). The concentration of retinol in blood plasma was lower in the LZ group than in the SZ group (p < 0.01). However, the results demonstrated an increase in the blood plasma retinol concentration in the LZ group compared to the SZ group when calculated per milligram of plasma chylomicrons (p < 0.01). In plasma chylomicrons, fatty acids corresponding to 16:0, 16:1, 17:0, 17:1, 18:0, 18:1, 18:2, 18:3, 20:0, 21:0, and 20:4 were detected. The fatty acid distribution was similar in both groups. There was no major difference in the concentration of fatty acids in plasma chylomicrons between both experimental groups, except for 20:4 (a lower amount was found in the SZ group). Our results show that dietary zinc influences both the amount of chylomicrons in blood plasma and the concentrations of retinol and arachidonic acid in chylomicrons.