Mei-Li Wu

National Pingtung University of Science and Technology, Pingtung, Taiwan, Taiwan

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Publications (12)28.05 Total impact

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    ABSTRACT: Cinnamaldehyde has been demonstrated to stimulate glutathione production and the expression of phase II detoxifying enzymes in HepG2 cells. The mechanism underlying this cinnamaldehyde-mediated gene expression relies on Nrf2 transcriptional activity. Therefore, the molecular signaling events in cinnamaldehyde-mediated detoxifying enzyme expression were further investigated in this study. Cinnamaldehyde activated ERK1/2, Akt, and JNK signaling pathways, but not the p38 MAP kinase pathway, subsequently leading to Nrf2 nuclear translocation and eventually increasing phase II enzyme expression. In contrast, inhibition of ERK1/2, Akt, or JNK pathways attenuated Nrf2 nuclear translocation and phase II enzyme expression. Depletion of Nrf2 by small RNA interference (si-RNA) showed that the protein levels of phase II enzymes were no longer induced by cinnamaldehyde. A luciferase reporter assay and an electrophoretic mobility shift assay (EMSA) also demonstrated that cinnamaldehyde-activated signaling resulted in the increased transcriptional activity of Nrf2 through binding to the ARE4 enhancer sequence. Altogether, these data suggest that ERK1/2, Akt, and JNK pathways activated by cinnamaldehyde collectively control Nrf2 nuclear translocation and transcriptional activity, leading to the increase of phase II enzyme expression. Application of an appropriate chemopreventive agent such as cinnamaldehyde could potentially be an alternative strategy for cancer chemoprevention.
    Journal of Agricultural and Food Chemistry 04/2011; 59(9):5164-71. · 2.91 Impact Factor
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    ABSTRACT: Dectin-1, a specific pattern recognition receptor for β-1,3/β-1,6-glucans, is expressed mainly on phagocytes. Human dectin-1 (hDectin-1) and mouse dectin-1 (mDectin-1) were separately expressed on HEK293 cell surfaces for examination of the binding abilities of a synthetic particulate β-glucan (pβG), a product extracted from Saccharomyces cerevisiae, in this study. The binding of zymosan-FITC to hDectin-1 and mDectin-1 was inhibited by pβG at similar concentrations for 50% inhibition of binding (IC₅₀). However, the kinetics of the time course and dose response to zymosan stimulation observed for U937 and J774A.1 differed. Superoxide anion production was increased in U937 but reduced in J774A.1 when cells were treated with pβG, zymosan, or laminarin, whereas ovalbumin endocytosis was enhanced in U937 and J774A.1 treated either with pβG, zymosan, laminarin, or barley-glucan. These results indicate that the binding affinity of pβG to hDectin-1 is similar to the binding affinity to mDectin-1, and that stimulation by pβG as well as various forms of β-1,3-glucans on U937 and J774A.1 resulted in upregulation of cell activity and ovalbumin endocytosis. Additionally, other coreceptors on U937 and J774A.1 may be involved in directing different responses to superoxide anion production in these two types of cells. These results will likely contribute to further investigations on identifying the biological forms of β-glucans capable of binding its specific receptor as the effective immunomodulators.
    Biotechnology Progress 09/2010; 26(5):1391-9. · 1.85 Impact Factor
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    ABSTRACT: The process of applying salt-stressed baker’s yeast during southern style Chinese steamed bread dough preparation was examined. Baker’s yeast was stressed in 7% salt solution then mixed into dough, which was then evaluated for dough fermentation producing gas, dough expansion, texture profile analysis (TPA), colour, specific volume, spread ratio and sensory analysis. The results of this study pointed out salt-stressed baker’s yeast produced significant amount of gas and dough expansion, particularly after 40 min of salt stressing. The texture of steamed bread was softer (463.08 g) than control (541.35 g) (P < 0.05), greater in specific volume (3.15 cm3 g−1) than control (2.89 cm3 g−1) (P < 0.05), had a lower spread ratio (1.45) than control (1.74) (P < 0.05) and a significantly improved sensory properties for taste (90.6) than control (81.6) (P < 0.05) were obtained.
    International Journal of Food Science & Technology 11/2009; 44(12):2637 - 2643. · 1.24 Impact Factor
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    ABSTRACT: Interleukin-18 (IL-18) can induce interferon-gamma (IFN-gamma) production and promote Th1 immunity, and hence, it modulates immune functions. In the present study, the in vitro and in vivo immunomodulatory activities of full length or mature chicken IL-18 expressed in a prokaryotic expression system (pCHIL18-F and pCHIL18-M, respectively) and chicken IL-18 expressed in a eukaryotic expression system (euCHIL18) were examined. Results showed that pCHIL18-F, pCHIL18-M and euCHIL18 significantly enhanced IFN-gamma mRNA expression in chicken splenocytes, which successfully increased IFN-gamma-induced nitric oxide (NO) synthesis by macrophages. Vaccination with cell-cultured Newcastle disease vaccine (NDTC) co-administrated with pCHIL18-F, pCHIL18-M or euCHIL18 resulted in significant increments of hemagglutination inhibition (HI) titers, cell proliferation of peripheral blood mononuclear cells (PBMC), and ratios of CD8(+) to CD4(+) in chickens compared with inoculation of PBS or NDTC alone. Thus, full length and mature chicken IL-18 expressed using a prokaryotic system and using a eukaryotic system showed equivalent in vitro and in vivo biological activities, and all forms effectively enhanced cell-mediated and humoral immunity, suggesting possible future use as a potential adjuvant in chicken NDTC vaccine production.
    Vaccine 11/2009; 28(5):1148-55. · 3.77 Impact Factor
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    ABSTRACT: 2-Acetyl-1-pyrroline (2-AP) was identified as an important aroma compound of aromatic vegetable soybean. The level of 2-AP in 6 aromatic vegetable soybean lines was found to be positively correlated with popcorn-like aroma score. Comparison between aromatic and nonaromatic vegetable soybeans found that aromatic vegetable soybean contains higher concentration of methylglyoxal (MG) and Delta(1)-pyrroline-5-carboxylate (P5C) than a nonaromatic one. For MG formation-related genes, GapC was down-regulated and TPI was up-regulated in aromatic cultivar (Aromatic 7) as compared to nonaromatic control, which may contribute to the increase of MG level. Based on the data presented, a formation mechanism for 2-AP via interaction between MG and P5C in aromatic vegetable soybean was proposed.
    Journal of Food Science 07/2009; 74(5):S192-7. · 1.78 Impact Factor
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    ABSTRACT: The immunopharmacological activities of beta-glucans with a backbone of beta-1,3/beta-1,6-linkages associated with anti-tumor, anti-viral, bacterial and fungal infections have been well documented. Dectin-1, a specific pattern recognition receptor for beta-1,3/beta-1,6-glucans, is expressed mainly on phagocytes, especially macrophages and dendritic cells (DCs). In this study, the encoding nucleotide for the carbohydrate-recognition domain (CRD) of porcine dectin-1 was sequenced for the first time, and the immunomodulatory functions of a synthetic particulate beta-glucan (p-beta-glucan) were examined. Results showed that p-beta-glucan significantly enhanced cell activity and phagocytosis in porcine alveolar macrophages (AMs), immature DCs (imDCs) and mature DCs (mDCs), in a similar way to zymosan. Zymosan enhanced dectin-1/TLR2/TLR4 expression and TNF-alpha/IL-10 production in all of three types of cell, whereas p-beta-glucan increased dectin-1/TLR4 and TNF-alpha/IL-12 production in AMs but inhibited IL-10 in mDCs. These results indicate that the complex collaborating interactions between dectin-1 and TLRs in the recognition of beta-1,3/beta-1,6-glucans with different structural features may direct different cellular responses.
    Veterinary Immunology and Immunopathology 05/2009; 131(3-4):147-57. · 1.88 Impact Factor
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    ABSTRACT: 2-Acetyl-1-pyrroline (2-AP) was identified as the major flavor compound in aromatic rice varieties Tainung 71 and 72. In order to understand the mechanism of 2-AP biosynthesis in aromatic rice, we studied the formation of putative precursors, Delta(1)-pyrroline-5-carboxylic acid and methylglyoxal. The endogenous Delta(1)-pyrroline-5-carboxylic acid contents of Tainung 71 and 72 calli reached 191 to 276%, compared to nonaromatic rice Tainung 67. In addition, calli of Tainung 71 and 72 contained 1.30- and 1.36-fold, respectively, higher methylglyoxal levels than that of Tainung 67. Specific enzyme activities of Delta(1)-pyrroline-5-carboxylic acid-synthetic enzyme including Delta(1)-pyrolline-5-carboxylic acid synthetase (P5CS) and ornithine aminotransferase (OAT) increased significantly in aromatic rice varieties. The expression levels of P5CS1 and P5CS2 genes were found to be significantly higher in aromatic rice than nonaromatic rice. Results of a tracer experiment with (15)N-labeled glutamic acid revealed that the nitrogen atom of 2-acetyl-1-pyrroline was derived from glutamic acid. Upregulation of P5CS in aromatic rice Tainung 72 may contribute to the increase of Delta(1)-pyrroline-5-carboxylic acid level and thus leads to the accumulation of an extra amount of 2-acetyl-1-pyrroline.
    Journal of Agricultural and Food Chemistry 09/2008; 56(16):7399-404. · 2.91 Impact Factor
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    ABSTRACT: This study demonstrated that ergocalciferol was able to inhibit leukemia cell growth in a concentration-dependent manner. Exploration of the acting mechanisms involved this event revealed that ergocalciferol induced DNA fragmentation and increased sub-G1 DNA contents in HL-60 cells, both of which are hallmarks of apoptosis. Analysis of the integrity of mitochondria demonstrated that ergocalciferol caused loss of mitochondrial membrane potential with release cytochrome c to cytosol, generation of reactive oxygen species (ROS), and depletion of glutathione (GSH), suggesting that ergocalciferol may induce apoptosis in HL-60 cells through a ROS-dependent pathway. Further results show that caspases-2, -3, -6, and -9 were all activated by ergocalciferol, together with cleavage of the downstream caspase-3 targets, DNA fragmentation factor (DFF-45), and poly(ADP-ribose) polymerase. In addition, ergocalciferol led to the increase in pro-apoptotic factor Bax accompanied with the decrease in anti-apoptotic member Mcl-1, and the reduced Mcl-1 to Bax ratio may be a critical event concerning mitochondrial decay by ergocalciferol. Furthermore, ergocalciferol also led to induction of Fas death receptor closely linked to caspase-2 activation, suggesting the involvement of a Fas-mediated pathway in ergocalciferol-induced apoptosis. Totally, these findings suggest that ergocalciferol causes HL-60 apoptosis via a modulation of mitochondria involving ROS production, GSH depletion, caspase activation, and Fas induction. On the basis of anticancer activity of ergocalciferol, it may be feasible to develop chemopreventive agents from edible mushrooms or hop.
    Journal of Agricultural and Food Chemistry 06/2008; 56(9):2996-3005. · 2.91 Impact Factor
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    ABSTRACT: The expression level of phase I (CYP1A1 and CYP1A2) and phase II (GST, and UGT) enzyme-coded genes were measured in liver microsomes of 30 Sprague-Dawley rats fed sea weed (Monostroma nitidum). Quantitative and qualitative analysis of the detoxifying enzymes were investigated using reverse transcription polymerase reaction (RT-PCR) and real time polymerase reaction (Real-time PCR) techniques. The antioxidative properties of seaweed were screened and investigated for its hepatoprotective activity in rat. There was no significant induction of GSTYa1, GSTYa2, and CYP1A2. However, an M. nitidum diet was found to significantly increase UGT1A1 and UGT1A6 mRNA levels and to decrease CYP1A1 mRNA levels in rat liver. Structural studies confirmed the presence of sulfated polysaccharides in the seaweed samples. The results demonstrate the potential of seaweed as a natural source of sulfated polysaccharide substances with potential use in chemoprevention medicine.
    Food and Chemical Toxicology 01/2008; 45(12):2390-6. · 3.01 Impact Factor
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    ABSTRACT: Proline dehydrogenase (PRODH) catalyzes the biosynthesis of Delta1-pyrroline-5-carboxylic acid (P5C). The Bacillus subtilis subsp. natto gene for the proline dehydrogenase (BnPRODH) was cloned and expressed in Escherichia coli. Nucleotide sequence analysis of the clone revealed an open-reading frame that encodes 302 amino acid polypeptide with a calculated molecular mass of 34.5 kDa. The deduced amino acid sequence showed sequence similarity to bacterial PRODH and PutA of E. coli. The BnPRODH gene was cloned into pET21b and was expressed at a high level in E. coli BL21(DE3). The expressed protein was purified by using nickel ion affinity column chromatography to homogeneity before characterization. The purified recombinant BnPRODH was used to produce P5C. Model system composed of P5C and methylglyoxal was set up to study the formation of 2-acetyl-1-pyrroline. Our data showed that P5C, derived from the conversion of l-proline by the purified recombinant PRODH, might react directly with methylglyoxal to form 2-AP. P5C/methylglyoxal pathway represents the first report of a biological mechanism by which 2-AP may be synthesized in vitro by PRODH.
    Journal of Agricultural and Food Chemistry 07/2007; 55(13):5097-102. · 2.91 Impact Factor
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    ABSTRACT: The gene (lat) encoding L-lysine epsilon-aminotransferase (LAT) in Streptomyces clavuligerus was cloned and expressed in Escherichia coli. Nucleotide sequence analysis of lat predicted a single open reading frame (ORF) of 1371 bp, encoding a polypeptide of 457 amino acids with calculated molecular mass of 49.89 kDa. S. clavuligerus LAT was grouped into aminotransferase subfamily II of alpha family on the basis of sequence homology. A model system composed of the recombinant LAT in phosphate buffer was set up to study the biosynthesis of 2-acetyltetrahydropyridine. Lysine was found to be transformed to 1-piperideine-6-carboxylic acid. 2-Acetyltetrahydropyridine was characterized from the mixture of 1-piperideine-6-carboxylic acid and methylglyoxal. For the first time, we demonstrated that the L-lysine epsilon-aminotransferase is responsible for the formation of 1-piperideine-6-carboxylic acid, which may react with methylglyoxal to generate the acylated N-heterocyclic odorant 2-acetyltetrahydropyridine.
    Journal of Agricultural and Food Chemistry 04/2007; 55(5):1767-72. · 2.91 Impact Factor
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