Incorporation of collagen into Pseudomonas aeruginosa and Staphylococcus aureus biofilms impedes phagocytosis by neutrophils.

Biofilms are communities of microbes embedded in a matrix of extracellular polymeric substances (EPS). Matrix components can be produced by biofilm organisms and can also originate from the environment and then be incorporated into the biofilm. For example, we have recently shown that collagen, a host-produced protein that is abundant in many different infection sites, can be taken up into the biofilm matrix, altering biofilm mechanics. The biofilm matrix protects bacteria from clearance by the immune system, and some of that protection likely arises from the mechanical properties of the biofilm. Pseudomonas aeruginosa and Staphylococcus aureus are common human pathogens notable for forming biofilm infections in anatomical sites rich in collagen. Here, we show that the incorporation of Type I collagen into P. aeruginosa and S. aureus biofilms significantly hinders phagocytosis of biofilm bacteria by human neutrophils. However, enzymatic treatment with collagenase, which breaks down collagen, can partly or entirely negate the protective effect of collagen and restore the ability of neutrophils to engulf biofilm bacteria. From these findings, we suggest that enzymatic degradation of host materials may be a potential way to compromise biofilm infections and enhance the efficacy of the host immune response without promoting antibiotic resistance. Such an approach might be beneficial both in cases where the infecting species is known and also in cases wherein biofilm components are not readily known, such as multispecies infections or infections by unknown species.

Kindlin-2 promotes rear focal adhesion disassembly and directional persistence during cell migration.

Cell migration involves front-to-rear asymmetric focal adhesion (FA) dynamics, which facilitates trailing edge detachment and directional persistence. Here, we show that kindlin-2 is crucial for FA sliding and disassembly in migrating cells. Loss of kindlin-2 markedly reduced FA number and selectively impaired rear FA sliding and disassembly, resulting in defective rear retraction and reduced directional persistence during cell migration. Kindlin-2-deficient cells failed to develop serum-induced actomyosin-dependent tension at FAs. At the molecular level, kindlin-2 directly interacted with myosin light chain kinase (MYLK, hereafter referred to as MLCK), which was enhanced in response to serum stimulation. Serum deprivation inhibited rear FA disassembly, which was released in response to serum stimulation. Overexpression of the MLCK-binding kindlin-2 F0F1 fragment (amino acid residues 1-167), which inhibits the interaction of endogenous kindlin-2 with MLCK, phenocopied kindlin-2 deficiency-induced migration defects. Inhibition of MLCK, like loss of kindlin-2, also impaired trailing-edge detachment, rear FA disassembly and directional persistence. These results suggest a role of kindlin-2 in promoting actomyosin contractility at FAs, leading to increased rear FA sliding and disassembly, and directional persistence during cell migration.

Pure Acetylene Semihydrogenation over Ni-Cu Bimetallic Catalysts: Effect of the Cu/Ni Ratio on Catalytic Performance.

Ethylene is an important chemical raw material and with the increasing consumption of petroleum resources, the production of ethylene through the calcium carbide acetylene route has important research significance. In this work, a series of bimetallic catalysts with different Cu/Ni molar ratios are prepared by co-impregnation method for the hydrogenation of calcium carbide acetylene to ethylene. The introduction of an appropriate amount of Cu effectively inhibits not only the formation of ethane and green oil, thus increasing the selectivity of ethylene, but also the formation of carbon deposits, which improves the stability of the catalyst. The ethylene selectivity of the Ni-Cu bimetallic catalyst increases from 45% to 63% compared with the Ni monometallic counterpart and the acetylene conversion still can reach 100% at the optimal conditions of 250 °C, 8000 mL·g-1·h-1 and V(H2)/V(C2H2) = 3. X-ray diffraction and transmission electron microscopy confirmed that the metal particles were highly dispersed on the support, High-resolution transmission electron microscopy and H2-Temperature programmed reduction proved that there was an interaction between Ni and Cu, combined with X-ray photoelectron spectroscopy and density functional theory calculations results, Cu transferred electrons to Ni changed the Ni electron cloud density in NiCux catalysts, thus reducing the adsorption of acetylene and ethylene, which is favorable to ethylene selectivity.

[Blockade of TLR4/NF-κB pathway promotes the inflammation of Acinetobacter baumannii-infected rats].

Objective To explore the effects of TLR4 on Acinetobacter baumannii (A. baumannii) infection in a rat model. Methods Healthy male SD rats were divided into normal control group, TAK-242 treated group, A. baumannii treated group, TAK-242 and A. baumannii combined treatment group. Rats of TAK-242-treated group were prepared by caudal vein injection of TAK-242 (1 mg/kg). A. baumannii were isolated from intensive care unit (ICU) and the freshly grown bacteria (1×108 CFU/mL) were prepared. Each normal or TAK-242-treated rat was inoculated with 50 µL A. baumannii through trachea. The bronchoalveolar lavage fluid (BALF) and blood were collected at 72 hours after inoculation. The histopathology of lung was evaluated by HE staining. TNF-α and IL-6 were detected by ELISA. The level of phosphorylated NF-κBp65 (p-NF-κBp65) in peripheral blood mononuclear cells (PBMCs) was detected by Western blot analysis. Results A. baumannii were eliminated within 72 hours in normal rats, whereas bacteria continued to replicate rapidly in the lungs of TAK-242 A. baumannii treated group. The pulmonary inflammatory was more severe than the normal rats. The levels of TNF-α and IL-6 increased markedly after the infection. However, the levels of TNF-α and IL-6 in the TAK-242 combined with A. baumannii treated group were lower than those in the A. baumannii treated group. The level of p-NF-κBp65 increased significantly in the PBMCs of the normal rats 72 hours after infected with A. baumannii, but increased slightly in the TAK-242 combined with A. baumannii treated group. Conclusion TLR4/NF-κB pathway plays an important role in the process of A. baumannii infection, and TLR4 can be used as a target molecule in the treatment of A. baumannii infection.

[Activation of platelet activating factor receptor by Acinetobacter baumannii results in oxidative stress and apoptosis in human bronchial epithelial cells].

Objective To investigate the effect of platelet activating factor receptor (PAFR) on human bronchial epithelial (HBE) cells infected by Acinetobacter baumannii (A. baumannii). Methods HBE cells were divided into control group, ginkgolide B (GB) group, A. baumannii infected group, A. baumannii infection and inhibitor group. HBE cells were infected with low dose (1×103 CFU/mL), medium dose (1×105 CFU/mL) and high dose (1×107 CFU/mL) A. baumannii separated from clinical samples. The PAFR activity was blocked by the 10 µmol/L GB. The expression of PAFR was detected using Western blotting in HBE cells. The proliferation ability of HBE cells was detected using CCK-8 assay. The oxidative stress level was evaluated by superoxide dismutase (SOD) and malondialdehyde(MDA) kits. Apoptosis of HBE cells was observed by annexin V-FITC-V/PI staining. The phosphorylation level of PAFR and its downstream molecule JAK1/STAT1 in HBE cells were examined by Western blot analysis. Results Compared with the control group, the expression of PAFR increased significantly in A. baumannii infected group. A. baumannii infection could decrease cell vitality, but increase intracellular oxidative stress, apoptosis, and JAK1/STAT1 phosphorylation. Conclusion PAFR is an important mediator molecule for A. baumannii infection in HBE cells, and PAFR/JAK1/STAT1 signaling pathway plays an important role in the pulmonary infection of A. baumannii.

[Establishment of Acinetobacter baumannii-induced pneumonia model in mice].

Objective To establish Acinetobacter baumannii (A. baumannii)-induced pneumonia models in C57BL/6 mice, and study the molecule mechanism of A. baumannii infection. Methods Eighty C57BL/6 mice were divided into normal control group, cyclophosphamide-treated group, A. baumannii infection group, and cyclophosphamide-pretreated A. baumannii infection group. Immunodeficient mice were prepared by injecting cyclophosphamide intraperitoneally. A. baumannii was isolated from intensive care unit (ICU) and fresh bacteria (1×108 CFU/mL) were prepared. Each normal or immunodeficient mouse was inoculated with 50 µL A. baumannii through trachea. The lung, bronchoalveolar lavage fluid (BALF) and blood were collected at 6, 24 and 72 hours after inoculation. The numbers of white blood cells (WBCs) and neutrophils were detected by cell counting. The histopathology of the lung was evaluated by HE staining. Cytokines such as granulocyte macrophage colony-stimulating factor (GM-CSF), interferon γ (IFN-γ), interleukin 1ß (IL-1ß), IL-2, IL-4, IL-5, IL-6, IL-10, IL-12, tumor necrosis factor α (TNF-α) were detected by ELISA. Results A. baumannii was eliminated within 72 hours after infection in normal mice, whereas the bacteria continued to replicate rapidly in the lungs and blood in the immunodeficient mice. The numbers of WBCs and neutrophils were elevated markedly 6 hours post infection, and return to the normal within 72 hours. However, the numbers of WBCs and neutrophils continuously increased in cyclophosphamide-pretreated A. baumannii infection group, and the pulmonary inflammatory was more severe than that in the normal mice. The cytokines of blood increased markedly 6 hours post infection, and then decreased until 72 hours. However, the cytokines continuously increased in cyclophosphamide-pretreated A. baumannii infection group. Conclusion A. baumannii-induced pneumonia models in C57BL/6 mice were established successfully.

[Caspase-1 inhibitor AC-YVAD-CMK blocks IL-1ß secretion of bone marrow-derived macrophages induced by Acinetobacter baumannii].

Objective To explore the effect of caspase-1 selective inhibitor AC-YVAD-CMK on IL-1ß secretion of bone marrow-derived macrophages (BMDMs) induced by Acinetobacter baumannii (A. baumannii). Methods Macrophages were separated from C57BL/6 mice which were stimulated using different concentrations of A. baumannii. The level of IL-1ß in the culture supernatant was detected by ELISA. The expression of pro-IL-1ß mRNA and protein were detected using the real-time quantitative PCR and Western blot analysis, respectively. The role of caspase-1 in the secretion of IL-1ß was tested by AC-YVAD-CMK treatment to block caspase-1. Pneumonia models in C57BL/6 mice were prepared by A. baumannii inoculation. The level of IL-1ß in bronchoalveolar lavage fluid (BALF) and the morphology of lung were detected by ELISA or HE staining, respectively. Results IL-1ß level in the culture supernatant was up-reregulated by A. baumannii stimulation in a dose-dependent manner. The expression of pro-IL-1ß mRNA and protein were not significantly changed with A. baumannii stimulation. Mature IL-1ß secretion was blocked by AC-YVAD-CMK either in vitro or in vivo. The damage of lung induced by A. baumannii infection in mice was ameliorated by AC-YVAD-CMK. Conclusion AC-YVAD-CMK alleviates pulmonary pathological damage by reducing the caspase-1-mediated IL-1ß secretion.

Assessment of heavy metals contamination in sediments from three adjacent regions of the Yellow River using metal chemical fractions and multivariate analysis techniques.

Metal chemical fractions obtained by optimized BCR three-stage extraction procedure and multivariate analysis techniques were exploited for assessing 7 heavy metals (Cr, Pb, Cd, Co, Cu, Zn and Ni) in sediments from Gansu province, Ningxia and Inner Mongolia Autonomous Regions of the Yellow River in Northern China. The results indicated that higher susceptibility and bioavailability of Cr and Cd with a strong anthropogenic source were due to their higher availability in the exchangeable fraction. A portion of Pb, Cd, Co, Zn, and Ni in reducible fraction may be due to the fact that they can form stable complexes with Fe and Mn oxides. Substantial amount of Pb, Co, Ni and Cu was observed as oxidizable fraction because of their strong affinity to the organic matters so that they can complex with humic substances in sediments. The high geo-accumulation indexes (I(geo)) for Cr and Cd showed their higher environmental risk to the aquatic biota. Principal component analysis (PCA) revealed that high toxic Cr and Cd in polluted sites (Cd in S10, S11 and Cr in S13) may be contributed to anthropogenic sources, it was consistent with the results of dual hierarchical clustering analysis (DHCA), which could give more details about contributing sources.