Aiguo Zeng

SIRT1 Regulates CD40 Expression Induced by TNF-α via NF-ĸB Pathway in Endothelial Cells

Background: Compelling evidence suggests that SIRT1, NAD+-dependent class III protein deacetylase, plays an important role in the prevention and treatment of atherosclerosis by counteracting inflammation. Cluster of differentiation 40 (CD40), as a pro-inflammatory cytokine, has been shown to participate in the pathophysiology of atherosclerosis. The relationship between SIRT1 and CD40, however, remained elusive. The present study was thus designed to explore the potential effect of SIRT1 on CD40 expression induced by tumor necrosis factor-α (TNF-α) and to disclose the underlying mechanism in CRL-1730 endothelial cells. Methods: mRNA and protein expressions were identified by quantitative real-time PCR and Western blot respectively. Subcellular localization of SIRT1 was detected by immunofluorescence analysis. SIRT1 small-interfering RNA (siRNA) was carried out for mechanism study. Results: TNF-α reduced SIRT1 expression and induced CD40 expression in CRL-1730 endothelial cells in a time- and concentration- dependent manner. Pretreatment with resveratrol (a potent SIRT1 activator) inhibited TNF-α-induced CD40 expression, while pretreatment with nicotinamide (class b HDACs inhibitor nicotinamide) or sirtinol (a known SIRT1 inhibitor), especially SIRT1 siRNA significantly augmented TNF-α-induced CD40 expression. The frther sudy idicated that PDTC (NF-ĸB inhibitor) pretreatment attenuated TNF-α-induced CD40 expression, and SIRT1 siRNA significantly augmented TNF-α-induced acetylated-NF-ĸB p65 (Lys310) expression. Conclusion: The present study provides the direct evidence that SIRT1 can inhibit TNF-α- induced CD40 expression in CRL-1730 endothelial cells by deacetylating the RelA/p65 subunit of NF-ĸB at lysine 310, which provides new insights into understanding of the anti-inflammatory and anti-athroscerotic actions of SIRT1.

Frontal analysis of cell-membrane chromatography for determination of drug-α1D adrenergic receptor affinity

The aim of the present study was to determine drug-alpha(1D) adrenergic receptor (AR) affinity by frontal analysis of cell-membrane chromatography (CMC). The cell-membrane stationary phase (CMSP) was prepared by immobilizing rat aorta cell membranes on porous silica, and the resulting CMSP was used to determine drug binding affinity to alpha(1D)-AR by frontal analysis. The CMSP of rat aorta was stable and reproducible. Relative binding affinities (dissociation constant, K(d)) were determined by frontal chromatography for prazosin (166.13+/-18.36 nmol), BMY7378 (537.40+/-30.84 nmol), phentolamine (646.92+/-23.17 nmol), 5-methylurapidil (725.66+/-25.48 nmol), oxymetazoline (910.56+/-40.62 nmol) and methoxamine (1299.27+/-51.73 nmol). These results were consistent with the affinity rank order and showed a good correlation with the affinity of the same compounds for the cloned alpha(1D)-AR subtype obtained from radioligand-binding assay. The study demonstrates that frontal analysis of CMC may be used for direct determination of drug-receptor binding interactions, and that CMC is an alternative reliable method to quantitatively study ligand-receptor interactions.

Simultaneous analysis and retention behavior of major isoflavonoids in Radix Puerariae lobatae and Radix Puerariae thomsonii by high performance liquid chromatography with cyclodextrins as a mobile phase modifier

In order to differentiate two species of Radix Puerariae (Radix Puerariae lobatae and Radix Puerariae thomsonii) and to determine major isoflavonoids (puerarin, daidzin, daidzein and genistein) in the samples, a simple high performance liquid chromatography (HPLC) method with isocratic elution employing cyclodextrins (CDs) as mobile phase additives was developed. Various factors affecting the retention of isoflavonoids in the C(18) reversed-phase column, such as the nature of CDs, the concentration of hydroxypropyl-β-cyclodextrin (HP-β-CD) and the methanol percentage in the mobile phase, were studied. Experimental results confirmed that HP-β-CD, as a very effective mobile phase additive, could markedly reduce the retention of isoflavonoids, especially daidzein and genistein. The elution of four isoflavonoids could be achieved on a Kromasil(®) C(18) column within 56 min by using the methanol-water contained 5 mM HP-β-CD (25/75, v/v) mixture as the mobile phase. The formation of the inclusion complexes between isoflavonoids and HP-β-CD explained the modification of the retention of analytes. The apparent formation constants determined by HPLC confirmed that the stoichiometry of HP-β-CD-isoflavonoid complexes was 1:1, and the stability of the complexes depended on the size and property of isoflavonoids. The optimized method was successfully applied for the simultaneous determination of major isoflavonoids in P. lobatae and P. thomsonii samples. This work provides a useful method for the analysis of traditional Chinese herbs.

Synthesis and α-glucosidase inhibitory activity evaluation of N-substituted aminomethyl-β-d-glucopyranosides

A series of N-substituted 1-aminomethyl-β-d-glucopyranoside derivatives was prepared. These novel synthetic compounds were assessed in vitro for inhibitory activity against yeast α-glucosidase and both rat intestinal α-glucosidases maltase and sucrase. Most of the compounds displayed α-glucosidase inhibitory activity, with IC50 values covering the wide range from 2.3μM to 2.0mM. Compounds 19a (IC50=2.3μM) and 19b (IC50=5.6μM) were identified as the most potent inhibitors for yeast α-glucosidase, while compounds 16 (IC50=7.7 and 15.6μM) and 19e (IC50=5.1 and 10.4μM) were the strongest inhibitors of rat intestinal maltase and sucrase. Analysis of the kinetics of enzyme inhibition indicated that 19e inhibited maltase and sucrase in a competitive manner. The results suggest that the aminomethyl-β-d-glucopyranoside moiety can mimic the substrates of α-glucosidase in the enzyme catalytic site, leading to competitive enzyme inhibition. Moreover, the nature of the N-substituent has considerable influence on inhibitory potency.

Development of molecularly imprinted column-on line-two dimensional liquid chromatography for rapidly and selectively monitoring estradiol in cosmetics.

Nowadays, the illegal use of estradiol in cosmetics has caused a series of events which endangering public health seriously. Therefore, it is imperative to establish a simple, fast and specific method for monitoring the illegal use of estradiol in cosmetics. In current study, we developed a molecular imprinted monolithic column two dimensional liquid chromatography method (MIMC-2D-LC) for rapid and selective determination of estradiol in various cosmetic samples. The best polymerization, morphology, structure property, surface groups, and the adsorption performance of the prepared material were investigated. The MIMC-2D-LC was validated and successfully used for detecting estradiol in cosmetic samples with good selectivity, sensitivity, efficiency and reproducibility. The linear range of the MIMC-2D-LC for estradiol was 0.5-50μgg-1 with the limit of detection of 0.08μgg-1. Finally, six batches of cosmetic samples obtained from local markets were tested by the proposed method. The test results showed that the illegal use of estradiol still existed in the commercially available samples.

A novel surface molecularly imprinted polymer as the solid-phase extraction adsorbent for the selective determination of ampicillin sodium in milk and blood samples☆

Surface molecularly imprinted polymers (SMIPs) for selective adsorption of ampicillin sodium were synthesized using surface molecular imprinting technique with silica gel as a support. The physical and morphological characteristics of the polymers were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), elemental analysis and nitrogen adsorption–desorption test. The obtained results showed that the SMIPs displayed great adsorption capacity (13.5 μg/mg), high recognition ability (the imprinted factor is 3.2) and good binding kinetics for ampicillin sodium. Finally, as solid phase extraction adsorbents, the SMIPs coupled with HPLC method were validated and applied for the enrichment, purification and determination of ampicillin sodium in real milk and blood samples. The averages of spiked accuracy ranged from 92.1% to 107.6%. The relative standard deviations of intra- and inter-day precisions were less than 4.6%. This study provides a new and promising method for enriching, extracting and determining ampicillin sodium in complex biological samples.

Fluorescence spectroscopy of osthole binding to human serum albumin

The interaction of human serum albumin (HSA) with osthole was investigated by fluorescence spectroscopy. Osthole can quench the fluorescence of HSA and the quenching mechanism is a static process. The binding site number n and apparent binding constant K were measured at different temperatures. The thermodynamic parameters ΔH0, ΔG0 and ΔS0 were calculated at different temperatures. The results indicated that electrostatic forces played a major role in the interaction of osthole with HSA. Results of osthole synchronous fluorescence and UV absorption spectra showed that the microenvironment and conformation of HSA were changed.

Influence of sodium dodecyl sulfate on swelling, erosion and release behavior of HPMC matrix tablets containing a poorly water-soluble drug

The effect of sodium dodecyl sulfate (SDS) on the swelling, erosion and release behavior of HPMC matrix tablets was examined. Swelling and erosion of HPMC matrix tablets were determined by measuring the wet and subsequent dry weights of matrices. The rate of uptake of the dissolution medium by the matrix was quantified using a square root relationship whilst the erosion of the polymer was described using the cube root law. The extent of swelling decreased with increasing SDS concentrations in the dissolution medium but the rate of erosion was found to follow a reverse trend. Such phenomena might have been caused by the attractive hydrophobic interaction between HPMC and SDS as demonstrated by the cloud points of the solutions containing both the surfactant and polymer. Release profiles of nimodipine from HPMC tablets in aqueous media containing different concentrations of SDS were finally studied. Increasing SDS concentrations in the medium was shown to accelerate the release of nimodipine from the tablets, possibly due to increasing nimodipine solubility and increasing rate of erosion by increasing SDS concentrations in the dissolution medium.

Enrichment of total steroidal saponins from the extracts of Trillium tschonoskii Maxim by macroporous resin and the simultaneous determination of eight steroidal saponins in the final product by HPLC

An effective and simple method was established for the separation and enrichment of steroidal saponins from Trillium tschonoskii Maxim. The adsorption and desorption properties of seven macroporous resins were investigated. Among the tested resins, AB-8 resin showed the best adsorption and desorption capacities. The adsorption of steroidal saponins on AB-8 at 25°C was quite consistent with both the Freundlich isotherm model and the pseudo-second-order kinetics model. By optimizing the dynamic adsorption and desorption parameters, the content of steroidal saponins increased from 5.20% in the crude extracts to 51.93% in the final product, with a recovery yield of 86.67%. Furthermore, by scale-up separation, the concentration and recovery of total steroidal saponins were 43.8 and 85.5%, respectively, which suggested that AB-8 resin had great industrial and pharmaceutical potential because of its high efficiency and cost-effectiveness. In addition, a high-performance liquid chromatography method for the simultaneous determination of eight steroidal saponins was established for the first time, which was employed to qualitatively and quantitatively analyze the final product. Based on the methodological validation results, the high-performance liquid chromatography method can be widely applied to the quality control of steroidal saponins from Trillium tschonoskii Maxim due to its excellent accuracy, stability, and repeatability.

Preparation and evaluation of a molecularly imprinted sol–gel material as the solid‐phase extraction adsorbents for the specific recognition of cloxacilloic acid in cloxacillin

Highly selective molecularly imprinted polymers on the surface of silica gels were prepared by a sol-gel process and used as solid-phase extraction adsorbents for the specific recognition, enrichment and detection of cloxacilloic acid in cloxacillin. The obtained polymers were characterized by scanning electron microscopy, FTIR spectroscopy, nitrogen adsorption and desorption, elemental analysis and thermogravimetric analysis. The imprinted polymers not only possessed high adsorption capacity (6.5 μg/mg), but also exhibited fast adsorption kinetics (they adsorb 80% of the maximum amount within 20 min) and excellent selectivity (the imprinted factor was 3.6). A method using the imprinted polymers as solid-phase extraction adsorbents coupled with high-performance liquid chromatography was established with good specificity, linearity (r = 0.9962), precision (ranging from 0.5 to 6.7%), accuracy (ranging from 93.9 to 97.7%) and extraction recoveries (ranging from 78.8 to 89.8%). The limits of detection and quantification were 0.07 and 0.25 mg/g, respectively. This work could provide a promising method in the enrichment, extraction and detection of allergenic impurities in the manufacture, storage and application of cloxacillin.