Biomedical subjects

Bin Qiao

Publications and source records attributed to Bin Qiao.

8 recordsLinked to original sources

PubMed2006

All-trans retinoic acid negatively regulates cytotoxic activities of nature killer cell line 92.

NK cells are key components of innate immune systems and their activities are regulated by cytokines and hormones. All-trans retinoic acid (ATRA), as a metabolite of vitamin A and an immunomodulatory hormone, plays an important role in regulating immune responses. In the present study, we investigated the effect of ATRA on human NK cell line NK92. We found that ATRA dose-dependently suppressed cytotoxic activities of NK92 cells without affecting their proliferation. To explore the mechanisms underlying the ATRA influence on NK92 cells, we examined the production of cytokines (TNF-alpha, IFN-gamma), gene expression of cytotoxic-associated molecules (perforin, granzyme B, nature killer receptors (NCRs), and NKG2D), and the activation of NF-kappaB pathways related with immune response. Our results demonstrated that ATRA suppressed NF-kappaB activity and prevented IkappaBalpha degradation in a dose-dependent way, inhibited IFN-gamma production and gene expression of granzyme B and NKp46. Our findings suggest that ATRA is a negative regulator of NK92 cell activation and may act as a potential regulator of anti-inflammatory functions in vivo.

Cell Line↗

PubMed2006

Differential analysis of secondary metabolites by LC-MS following strain improvement of Streptomyces lydicus AS 4.2501.

Metabolite variations in a high-yielding mutant and its parent strain were studied by comparative LC-MS analysis after strain improvement. Streptomyces lydicus AS 4.2501-P28, a propionate-resistant mutant isolated by the high-frequency screening method using the principle of eliminating precursor inhibition effects, showed an increase of 267% in streptolydigin titre over the starting strain. Culture extracts of this mutant and its parent strain were analysed in parallel by an LC-MS technique, including full scan and extracted-ion scan, ESI-MS (electrospray-ionization MS) detection, DAD (diode-array detection) and MS2 (tandem MS) measurement. The main metabolic variations were obviously found in intermediates, metabolites and biosynthetic pathways: two unknown metabolites with the molecular [M-H]- ions at m/z 423.3 and 687.2, corresponding to two branch pathways, were blocked in the mutant, and the accumulation of a significant intermediate at m/z 363.1 [M-H]- decreased dramatically in the mutant cultures, resulting in the overproduction of streptolydigin (an antibiotic that inhibits prokaryotic RNA polymerase) in the mutant. Ion fragmentations of the tandem-MS spectra provided experimental evidence for the structural characterization of the three compounds obtained. In comparison with the traditional methods, comparative LC-MS analysis was rapid, sensitive and suitable for characterizing intermediates, metabolites and pathways for elucidation of the metabolic alterations after the isolation of improved strains.

Aminoglycosides↗

PubMed2006

Autoantibodies closely relate to the elevation level of in vivo hydrogen peroxide and tissue damage in systemic lupus erythematosus.

Recent studies have shown that antibodies efficiently catalyze the conversion of molecular singlet oxygen (1O2) plus water to hydrogen peroxide (H2O2). H2O2 is toxic to cells and is a cause of further free radical generation that are implicated in the pathogenesis of a variety of diseases. Systemic lupus erythematosus (SLE) is one of the most serious autoimmune diseases which are characterized by the production of various autoantibodies and subsequent tissue damage. However, the correlation of autoantibodies, H2O2, and tissue lesion in SLE has not been yet investigated. To address this issue, in the present study, we induced autoantibodies and kidney tissue damage by using SLE animal model as described previously. We detected the level of H2O2 in SLE mice and found the increase of in vivo H2O2 was accompanied and closely correlated with the production of anti-dsDNA and antihistone antibodies. Importantly, there was onefold increase of H2O2 in the mice kidneys with apparent glomerulonephritis and IgG deposits. These results suggest that the induced autoantibodies possess catalytic activity. The produced autoantibodies lead to the production and elevation of H2O2, which results in subsequent renal damage and the pathogenesis of SLE. Our findings provide an insight into the understanding of SLE mechanism and provide a potential approach for therapeutic intervention of SLE.

Animals↗

PubMed2006

Multi-stage collisionally-activated decomposition in an ion trap for identification of sequences, structures and bn --> bn-1 fragmentation pathways of protonated cyclic peptides.

Cyclic penta-, hexa- and heptapeptides have been designed, synthesized and their fragmentations induced by multistage tandem mass spectrometry have been studied. Under low-energy collisionally activated decomposition (CAD), the protonated cyclic peptides mainly dissociate via ring opening pathways and the corresponding bn --> bn-1 pathways to form several sets of b ions as oxazolone rings (and b1 ions as aziridinone rings). Through repeated observation of these b ions in multistep CAD experiments, accurate sequencing and head-to-tail ring structure of cyclic peptides can be determined. The mistaken assignments of these b ions can be avoided by this sequencing method. Semiempirical molecular orbital calculations have been utilized to provide insight into the proposed dissociation mechanism. In addition, for cyclic peptides that include an Asn residue, the nitrogen of the Asn side chain is observed to be preferentially protonated, which can induce a unique ring-opening pathway with a loss of ammonia that competes with the conventional ring opening pathway.

Indicators and Reagents↗

PubMed2006

Functional analysis of type II thioesterase of Streptomyces lydicus AS 4.2501.

Constructing a mutant strain of single gene disruption is the basis for the study of gene function and metabolomics. Systematic and complete genome sequencing is the basis of genetic manipulation. In the case of a little knowledge about the Streptomyces lydicus genome and the speculation that polyketide synthases (type I) might be responsible for the polyketide side chain biosynthesis of streptolydigin, a 588-bp fragment was amplified by polymerase chain reaction (PCR) according to the homology existing in the same functional genes among Streptomyces. A mutant strain of this gene was constructed by single crossover homologous recombination. The results of sequence analysis as well as the metabolite analysis of the mutant and the original strain by liquid chromatography/mass spectroscopy indicated that this fragment was part of type II thioesterase (TE) gene, which was required for streptolydigin biosynthesis like other type II TEs function in related antibiotics biosynthesis. Furthermore, targeted gene manipulation based on PCR was a powerful tool for studying gene function and metabolomics, especially when little was known about the genomic sequence of streptomyces.

Amino Acid Sequence↗

PubMed2005

Amplification loop cascade for increasing caspase activity induced by docetaxel.

The hierarchy of events accompanying induction of apoptosis by the microtubule inhibitor docetaxel was investigated in HL-60 human leukemia cells. Treatment of HL-60 cells with docetaxel resulted in the production of reactive oxygen species (ROS), activation of caspase-3 (-like) protease, c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) activation, bcl-2 phosphorylation and apoptosis. Docetaxel elicited ROS production from NADPH oxidase as demonstrated by specific oxidase inhibitor diphenylene iodonium (DPI). ROS mediated the caspase-3 activation and apoptosis in HL-60 cells. The caspase inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) effectively inhibited JNK/SAPK activation, bcl-2 phosphorylation and partially attenuated the ROS production induced by docetaxel. Docetaxel-induced bcl-2 phosphorylation was completely blocked by expression of dominant negative JNK or the JNK/SAPK inhibitor SP600125. Overexpression of bcl-2 partially prevented docetaxel-mediated ROS production and subsequent caspase-3 activation, thereby inhibiting apoptotic cell death. It is thus conferred that such sequent events as ROS production, caspase activation, JNK/SAPK activation, bcl-2 phosphorylation and the further generation of ROS should be parts of an amplification loop to increase caspase activity, thereby facilitating the apoptotic cell death process.

Apoptosis↗

PubMed2005

Specific siRNA downregulated TLR9 and altered cytokine expression pattern in macrophage after CpG DNA stimulation.

Bacterial CpG DNA or synthetic oligonucleotides (ODNs) that contain unmethylated CpG motifs (CpG ODN) can directly activate antigen-presenting cells (APCs) to secrete various cytokines through the intracellular receptor TLR9. Cytokine profiles elicited by the actions of stimulatory CpG DNA on TLR9 expressed APCs are crucial to the subsequent immune responses. To date, cytokine profiles in APCs upon CpG ODN stimulation in vitro are not fully investigated. In the present study, vector-based siRNA was used to downregulate TLR9 expression. Cytokine profiles were observed in murine macrophage cell line RAW264.7 transfected with TLR9-siRNA plasmid upon CpG ODN stimulation. We found that not all the cytokine expressions by the macrophage were decreased while TLR9 was downregulated. IL-12, TNF-alpha, IFN-gamma and IL-1beta expressions were significantly decreased, but IL-6, IFN-beta and IL-10 expressions were not affected. Interestingly, the level of IFN-alpha was even increased. This alteration of cytokines produced by TLR9-downregulated APCs upon CpG ODN stimulation might indicate that the role of CpG DNA is more complicated in the pathogenesis and prevention of diseases.

Animals↗

PubMed2004

Comparison of burst of reactive oxygen species and activation of caspase-3 in apoptosis of K562 and HL-60 cells induced by docetaxel.

Apoptosis-resistant K562 cells and apoptosis-proficient HL-60 acute myelomonocytic leukemia cells were selected to study the cell-type-specific characteristics of docetaxel. The kinetics of cytotoxicity of docetaxel showed a delayed response of K562 cells compared to HL-60 cells. After treatment with 10(-8)M docetaxel, DNA fragmentation and sub-G0/G1 cells were evident in HL-60 cells in less than 6 h, while K562 cells gradually arrested in G2/M phase of the cell cycle and appeared normal for 24 h before developing similar apoptotic changes. The delayed apoptotic changes in K562 cells were accompanied by delayed activation of caspase-3. Additionally, NADPH oxidase inhibition with diphenylene iodonium showed that reactive oxygen species (ROS) burst mediated critically in the caspase-3 activation and apoptosis in HL-60 cells but was only partially involved in those events of K562 cells. These results suggested that docetaxel exposure triggered the delayed apoptosis in K562 cells and the different ROS-dependent or independent signal pathways might account for this phenomenon. Docetaxel elicited ROS production from NADPH oxidase, which in turn triggered activation of caspase-3, leading to apoptosis in HL-60 cells. While in K562 cells, docetaxel induced apoptosis after G2/M accumulation through ROS-independent or partially dependent pathways.

Antineoplastic Agents, Phytogenic↗