Dual antibacterial activities of a chitosan-modified upconversion photodynamic therapy system against drug-resistant bacteria in deep tissue

Photodynamic therapy (PDT) has recently been proposed as an innovative approach to combat multi-drug resistant (MDR) bacteria. To improve the penetration depth of current PDT, a core-shell upconversion nanoparticle (UCNP) based PDT system, composed of a cationic N-octyl chitosan (OC) coated UCNP loaded with the photosensitizer zinc phthalocyanine (OC-UCNP-ZnPc), was constructed to enhance the antibacterial efficacy against MDR bacteria in deep tissue. The core-shell UCNPs displayed a higher upconversion fluorescence efficiency compared to the inner UCNP core. Dual antibacterial activities induced by chitosan and PDT-induced ROS were demonstrated, independent of the bacterial species. In particular, these nanoconstructs exhibited excellent antibacterial effects on the MDR bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and β-lactamase-producing Escherichia coli. In vivo antibacterial therapy for murine MRSA-infected abscesses in the deep tissue (1 cm) strongly confirmed the outstanding anti-MRSA efficacy of OC-UCNP-ZnPc. Our results indicated that the OC-UCNP-ZnPc based PDT system triggered by deep-penetrating NIR light has a prominent antibacterial effect on MDR bacteria, which could be a promising strategy for deep-tissue infections.

Bulk Fermi Surface of Charge-Neutral Excitations in SmB_{6} or Not: A Heat-Transport Study

Recently, there have been increasingly hot debates on whether a bulk Fermi surface of charge-neutral excitations exists in the topological Kondo insulator SmB_{6}. To unambiguously resolve this issue, we perform the low-temperature thermal conductivity measurements of a high-quality SmB_{6} single crystal down to 0.1 K and up to 14.5 T. Our experiments show that the residual linear term of thermal conductivity at the zero field is zero, within the experimental accuracy. Furthermore, the thermal conductivity is insensitive to the magnetic field up to 14.5 T. These results demonstrate the absence of fermionic charge-neutral excitations in bulk SmB_{6}, such as scalar Majorana fermions or spinons and, thus, exclude the existence of a bulk Fermi surface suggested by a recent quantum oscillation study of SmB_{6}. This puts a strong constraint on the explanation of the quantum oscillations observed in SmB_{6}.

Current advances in the novel functions of hypoxia-inducible factor and prolyl hydroxylase in invertebrates

Oxygen is essential for aerobic life, and hypoxia has very severe consequences. Organisms need to overcome low oxygen levels to maintain biological functions during normal development and in disease states. The mechanism underlying the hypoxic response has been widely investigated in model animals such as Drosophila melanogaster and Caenorhabditis elegans. Hypoxia-inducible factor (HIF), a key gene product in the response to oxygen deprivation, is primarily regulated by prolyl hydroxylase domain enzymes (PHDs). However, recent findings have uncovered novel HIF-independent functions of PHDs. This review provides an overview of how invertebrates are able to sustain hypoxic damages, and highlights some recent discoveries in the regulation of cellular signalling by PHDs. Given that some core genes and major pathways are evolutionarily conserved, these research findings could provide insight into oxygen-sensitive signalling in mammals, and have biomedical implications for human diseases.

Ultrasensitive UPLC-MS/MS method for analysis of etheno-DNA adducts in human white blood cells

Etheno-DNA adducts are generated by interaction of cellular DNA with exogenous environmental carcinogens and end products of lipid peroxidation. It has been determined that 1,N(6)-etheno-2'-deoxyadenosine (εdA) and 3,N(4)-etheno-2'-deoxycytidine (εdC) adducts formed in human white blood cells can be used to serve as biomarkers of genetic damage mediated by oxidative stress. In this study, we developed an ultrasensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method used to detect and quantify εdA and dC adducts in human white blood cells. The percent recoveries of εdA and dC adducts were found to be 88.9% ± 2.8 and 95.7% ± 3.7, respectively. The detection limits were ∼ 1.45 fmol for εdA and ∼ 1.27 fmol for εdC in 20 μg of human white blood cell DNA samples, both εdA and εdC adducts could be detected using only ∼ 5 μg of DNA per sample. For validation of the method, 34 human blood cell DNA samples were assayed and the results revealed a significant difference (P < 0.01) between levels (fmol/μg DNA) of 0.82 ± 0.83 (standard deviation [SD]) (range: 0.15-3.11) for εdA, 3.28 ± 3.15 (SD) (range: 0.05-9.6) for εdC in benzene-exposed workers; and 0.04 ± 0.08 (SD) (range: 0.0-0.27) for εdA and 0.77 ± 1.02 (SD) (range: 0.10-4.11) for εdC in non-benzene-exposed workers. Our method shows a high sensitivity and specificity when applied to small amounts of human white blood cell DNA samples; background levels of εdA and εdC could be reproducibly detected. The ultrasensitive and simple detection method is thus suitable for applications in human biomonitoring and molecular epidemiology studies.

Clinical Safety and Preliminary Efficacy of Plasmid pUDK-HGF Expressing Human Hepatocyte Growth Factor (HGF) in Patients with Critical Limb Ischemia

OBJECTIVE

Critical limb ischemia (CLI) is the most severe form of peripheral arterial disease and a major unmet public health care need. This phase I clinical study was performed to assess the safety and preliminary efficacy of naked plasmid DNA (pUDK-HGF) expressing human hepatocyte growth factor (HGF) in patients with critical limb ischemia (CLI).

DESIGN

Twenty-one patients with CLI were enrolled and randomly divided into four dose groups (4-16 mg) to receive local injection of pUDK-HGF into ischemic calf and/or thigh muscles twice on days 1 and 15. Safety, including adverse events and physiological parameters, and preliminary efficacy, including pain severity score (VAS), ulcer size, transcutaneous oxygen pressure (TcPO2), and ankle brachial index (ABI), were evaluated throughout a 3 month follow up period.

RESULTS

All doses of pUDK-HGF were well tolerated by the patients. None of the adverse effects was considered to be related to pUDK-HGF injection. Two significant clinical results were observed after pUDK-HGF administration. The mean VAS value of all patients decreased from 4.52 at baseline to 0.30 (p < .01), and pain had disappeared in 14 out of 17 evaluable patients by day 91. Two of four ulcers had completely healed, with the other two patients having more than 25% ulcer size reduction in the long axis diameter. Of five patients with gangrene, one gangrenous wound had healed completely and two patients showed marked size reduction by day 91. The mean hemodynamic parameters (ABI, TcPO2) were also improved.

CONCLUSION

Intramuscular injection of pUDK-HGF is safe, and may provide symptomatic relief for CLI patients. A larger, randomized, double blinded phase II trial will provide more information on safety and efficacy.

Galactose as Broad Ligand for Multiple Tumor Imaging and Therapy

Galactose residues could be specifically recognized by the asialoglycoprotein receptor (ASGPR) which is highly exhibited on liver tissues. However, ASGPR has not been widely investigated on different tumor cell lines except for hepatoma carcinoma cells, which motivates us to investigate the possibility of galactose serving as a board tumor ligand.

In this study, a galactose (Gal)-based probe conjugated with fluorescence dye MPA (Gal-MPA) was constructed for the evaluation of tumor affinities/targeted ability on different tumor cell lines. In the vitro cell study, it was indicated that the fluorescence probe Gal-MPA displayed higher cell affinity to tumor cells (HepG2, MCF-7 and A549) than that of the normal liver cells l02. In the vivo dynamic study of Gal-MPA in tumor-bearing mice (HepG2, MCF-7, A549, HCT116, U87, MDA-MB-231 and S180), it was shown that its high tumor targeted ability with the maximal tumor/normal tissue ratio reached up to 6.8. Meanwhile, the fast tumor-targeted ability within 2 hours and long retention on tumor site up to 120 hours were observed. Our results demonstrated that galactose should be a promising broad ligand for multiple tumor imaging and targeted therapy.

Subsequently, Gal was covalently conjugated to doxorubicin (DOX) to form prodrug Gal-DOX for tumor targeted therapy. The therapeutic results of Gal-DOX than DOX being better suggested that galactosylated prodrugs might have the prospective potential in tumor targeted therapy.

The cultivation of bone marrow mesenchymal stem cells derived from patients with high altitude polycythemia

The aim of this study was to isolate and culture bone marrow mesenchymal stem cells (MSCs) from patients with high altitude polycythemia (HAPC) in order to provide a foundation for further exploration of their biological characteristics. MSCs were isolated and cultured from 10 HAPC patients and 10 healthy controls by using a density gradient centrifugation and an adherent screening method. The morphous of MSCs were observed under an inverted microscope, and its surface antigens were determined using flow cytometry. The growth of the MSCs was also detected to evaluate its proliferation. Bone marrow mononuclear cells were isolated from the bone marrow using a density gradient centrifugation, and they were cultured in vitro. The bone marrow MSCs were successfully isolated and cultured, which presented as fusiform and adherent cells. The MSCs in both groups expressed CD90,CD44,CD29,CD105, CD106, CD146, CD166,Stro&mdash;1 and CD13, but they did not express CD45, CD4,CD8,CD19,CD20,CD80,CD14,CD3,CD34 or HLA&mdash;DR (P>0.05). The bone marrow MSCs from HAPC patients had a higher proliferation than the bone marrow MSCs from the healthy controls (P&lt;0.01). The bone marrow MSCs from HAPC patients can be effectively cultured in vitro.

Folic acid inhibits tau phosphorylation through regulation of PP2A methylation in SH-SY5Y cells

OBJECTIVES

Neurofibrillary tangles (NFTs), which are composed of intracellular filamentous aggregates of hyperphosphorylated tau protein, are one of the pathological hallmarks of Alzheimer's disease (AD). Because tau phosphorylation is regulated by phosphatases, abnormal metabolism of protein phosphatase 2A (PP2A) has been proposed to be a contributing factor to the disease process.

RESULTS

To determine the function of folic acid on tau phosphorylation, an in vitro model of human neuroblastoma cells (SH-SY5Y) were exposed to folic acid (0-40 μmol/L) for 96 h, in the presence or absence of the phosphoesterase inhibitor okadaic acid (OA) (10 nmol/L) for 9 h. The data of western blot showed tau phosphorylation at the Ser396 site in OA-incubated SH-SY5Y cells was inhibited by folic acid in a concentration-dependent manner, with the folic acid concentration of 40 μmol/L providing maximal inhibition. Folic acid can downregulate tau protein phosphorylation by inhibiting the demethylation reactions of PP2A. High folic acid concentrations (20 and 40 μmol/L) increased SAM:SAH ratios and cell viability.

CONCLUSION

Therefore, we can speculate that folate deficiency may be a cause of PP2A deregulation, which can in turn lead to expression of the abnormal hyperphosphorylated form of tau.

Oxytocin-induced membrane hyperpolarization in pain-sensitive dorsal root ganglia neurons mediated by Ca(2+)/nNOS/NO/KATP pathway

Oxytocin (OT) plays an important role in pain modulation and antinociception in the central nervous system. However, little is known about its peripheral effects. This study was conducted to investigate the effect of OT on the electrical properties of neurons in the dorsal root ganglia (DRG) and the underlying mechanisms. DRG neurons from adult rats were acutely dissociated and cultured. Intracellular Ca(2+) was determined by fluorescent microscopy using an indicator dye. The electrical properties of DRG neurons were tested by patch-clamp recording. The oxytocin receptor (OTR) and neuronal nitric oxide synthase (nNOS) on DRG neurons were assessed with immunofluorescence assays. OTR co-localized with nNOS in most of Isolectin B4 (IB4)-binding cultured DRG neurons in rats. OT decreased the excitability, increased the outward current, and evoked the membrane hyperpolarization in cultured DRG neurons. Sodium nitroprusside (SNP), the donor of nitric oxide (NO), exerted similar effects as OT on the membrane potential of cultured DRG neurons. OT increased the production of NO in DRGs and cultured DRG neurons. Pre-treatment of the OTR antagonist atosiban or the selective nNOS inhibitor N-Propyl-l-arginine (NPLA) significantly attenuated the hyperpolarization effect evoked by OT. OT produced a concentration-dependent increase in intracellular Ca(2+) in DRG neurons that responds to capsaicin, which can be attenuated by atosiban, but not by NPLA. OT-evoked membrane hyperpolarization and increase of outward current were distinctly attenuated by glibenclamide, a blocker of ATP-sensitive K(+) (KATP) channel. OT might be an endogenous antinociceptive agent and the peripheral antinociceptive effects of OT are mediated by activation of the Ca(2+)/nNOS/NO/KATP pathway in DRG neurons.