Meng-Hwan Lee

Ligustilide prevents LPS-induced iNOS expression in RAW 264.7 macrophages by preventing ROS production and down-regulating the MAPK, NF-κB and AP-1 signaling pathways.

Angelica sinensis (AS), an herb used in traditional Chinese medicine, is thought to have anti-inflammatory activities. Ligustilide is its most abundant ingredient. This study sought to determine ligustilides effects on lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 macrophages. Ligustilide significantly suppressed the production of nitric oxide (NO), prostaglandin E(2) (PGE(2)) and tumor necrosis factor-α (TNF-α). The inhibition of NO was concomitant with a decrease in the protein and mRNA levels of LPS-induced nitric oxide synthase (iNOS). Furthermore, activation of activator protein-1 (AP-1) and nuclear factor κB (NF-κB) in the nucleus and the cytosolic degradation of IκBα were abrogated by ligustilide. Ligustilide also inhibited the phosphorylation of IκB kinase (IKK) and mitogen-activated protein kinases (MAPKs), including p38 MAPK, extracellular signal-regulated kinase (ERK1/2) and c-Jun N-terminal kinase (JNK). The intracellular reactive oxygen species (iROS) level was also significantly decreased. These results suggest that ligustilide exhibits anti-inflammatory activities by blocking the activation of MAPKs/IKK and the downstream transcription factors AP-1 and NF-κB, which may result from ligustilides down-regulation of iROS production.

Crystal structure of glucooligosaccharide oxidase from Acremonium strictum: a novel flavinylation of 6-S-cysteinyl, 8alpha-N1-histidyl FAD

Glucooligosaccharide oxidase from Acremonium strictum has been screened for potential applications in oligosaccharide acid production and alternative carbohydrate detection, because it catalyzes the oxidation of glucose, maltose, lactose, cellobiose and cello- and maltooligosaccharides. We report the crystal structures of the enzyme and of its complex with an inhibitor, 5-amino-5-deoxy- cellobiono-1,5-lactam at 1.55- and 1.98-Å resolution, respectively. Unexpectedly, the protein structure demonstrates the first known double attachment flavinylation, 6-S-cysteinyl, 8α-N1-histidyl FAD. The FAD cofactor is cross-linked to the enzyme via the C6 atom and the 8α-methyl group of the isoalloxazine ring with Cys130 and His70, respectively. This sugar oxidase possesses an open carbohydrate-binding groove, allowing the accommodation of higher oligosaccharides. The complex structure suggests that this enzyme may prefer a β-d-glucosyl residue at the reducing end with the conserved Tyr429 acting as a general base to abstract the OH1 proton in concert with the H1 hydride transfer to the flavin N5. Finally, a detailed comparison illustrates the structural conservation as well as the divergence between this protein and its related flavoenzymes.

Inhibitory Effects of Citronellol and Geraniol on Nitric Oxide and Prostaglandin E2 Production in Macrophages

Geranium oil has been used traditionally for diarrhea, dermatitis, and intestinal inflammation in East Asia. The aim of this study was to determine the effects of geranium oils characteristic components, citronellol and geraniol, on lipopolysaccharide (LPS)-induced nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production in RAW 264.7 macrophages. Citronellol and geraniol suppressed NO and PGE(2) production in a dose-dependent manner. The inhibitory efficacy of geraniol was concomitant with decreases in protein and mRNA expression levels of inducible nitric oxide synthase (iNOS), whereas citronellol inhibited only iNOS enzymatic activity. By adding citronellol and geraniol, the LPS-induced cyclooxygenase-2 (COX-2) protein and mRNA expression levels were significantly attenuated, whereas cytosolic degradation of I κB α and upregulation of NF-κB p65 in the nucleus were reversed. These results suggested that citronellol and geraniol exhibit anti-inflammatory activities, supporting their common use and demonstrating their therapeutic potential for inflammation-associated disorders.

The inhibitory activity of linalool against the filamentous growth and biofilm formation in Candida albicans

Candida spp. are part of the natural human microbiota, but they also represent important opportunistic human pathogens. Biofilm-associated Candida albicans infections are clinically relevant due to their high levels of resistance to traditional antifungal agents. In this study, we investigated the ability of linalool to inhibit the formation of C. albicans biofilms and reduce existing C. albicans biofilms. Linalool exhibited antifungal activity against C. albicans ATCC 14053, with a minimum inhibitory concentration (MIC) of 8 mM. Sub-MIC concentrations of linalool also inhibited the formation of germ tubes and biofilms in that strain. The defective architecture composition of C. albicans biofilms exposed to linalool was characterized by scanning electron microscopy. The expression levels of the adhesin genes HWP1 and ALS3 were downregulated by linalool, as assessed by real-time RT-PCR. The expression levels of CYR1 and CPH1, which encode components of the cAMP-PKA and MAPK hyphal formation regulatory pathways, respectively, were also suppressed by linalool, as was the gene encoding their upstream regulator, Ras1. The expression levels of long-term hyphae maintenance associated genes, including UME6, HGC1, and EED1, were all suppressed by linalool. These results indicate that linalool may have therapeutic potential in the treatment of candidiasis associated with medical devices because it interferes with the morphological switch and biofilm formation of C. albicans.

Structural Characterization of Glucooligosaccharide Oxidase from Acremonium strictum

ABSTRACT Glucooligosaccharide oxidase from Acremonium strictum was screened for potential applications in oligosaccharide acid production and carbohydrate detection. This protein is a unique covalent flavoenzyme which catalyzes the oxidation of a variety of carbohydrates with high selectivity for cello- and maltooligosaccharides. Kinetic measurements suggested that this enzyme possesses an open carbohydrate-binding groove, which is mainly composed of two glucosyl-binding subsites. The encoding gene was subsequently cloned, and one intron was detected in the genomic DNA. Large amounts of active enzymes were expressed in Pichia pastoris, with a yield of 300 mg per liter medium. The protein was predicted to share structural homology with plant cytokinin dehydrogenase and related flavoproteins that share a conserved flavin adenine dinucleotide (FAD)-binding domain. The closest sequence matches are those of plant berberine bridge enzyme-like proteins, particularly the characteristic flavinylation site. Unexpectedly, mutation of the putative FAD-attaching residue, H70, to alanine, serine, cysteine, and tyrosine did not abolish the covalent FAD linkage and had little effect on the Km. Instead, the variants displayed kcat values that were 50- to 600-fold lower, indicating that H70 is crucial for efficient redox catalysis, perhaps through modulation of the oxidative power of the flavin.

Methyl cinnamate inhibits adipocyte differentiation via activation of the CaMKK2-AMPK pathway in 3T3-L1 preadipocytes.

Methyl cinnamate, an active component of Zanthoxylum armatum , is a widely used natural flavor compound with antimicrobial and tyrosinase inhibitor activities. However, the underlying bioactivity and molecular mechanisms of methyl cinnamate on adipocyte function and metabolism remain unclear. The aim of this study was to investigate the inhibitory effect of methyl cinnamate on adipogenesis in 3T3-L1 preadipocytes. Methyl cinnamate markedly suppressed triglyceride accumulation associated with down-regulation of adipogenic transcription factor expression, including sterol regulatory element binding protein-1 (SREBP-1), peroxisome proliferator-activated receptor γ (PPARγ), and CCAAT/enhancer-binding protein α (C/EBPα). Additionally, methyl cinnamate-inhibited PPARγ activity and adipocyte differentiation were partially reversed by the PPARγ agonist troglitazone. Furthermore, methyl cinnamate stimulated Ca(2+)/calmodulin-dependent protein kinase kinase 2 (CaMKK2) and phospho-AMP-activated protein kinase (AMPK) expression during adipogenesis. This study first revealed methyl cinnamate has antiadipogenic activity through mechanisms mediated, in part, by the CaMKK2-AMPK signaling pathway in 3T3-L1 cells.

Effect of Lactobacillus plantarum Strain K21 on High-Fat Diet-Fed Obese Mice

Recent studies have demonstrated beneficial effects of specific probiotics on alleviating obesity-related disorders. Here we aimed to identify probiotics with potential antiobesity activity among 88 lactic acid bacterial strains via in vitro screening assays, and a Lactobacillus plantarum strain K21 was found to harbor abilities required for hydrolyzing bile salt, reducing cholesterol, and inhibiting the accumulation of lipid in 3T3-L1 preadipocytes. Furthermore, effects of K21 on diet-induced obese (DIO) mice were examined. Male C57Bl/6J mice received a normal diet, high-fat diet (HFD), or HFD with K21 administration (109 CFU in 0.2 mL PBS/day) for eight weeks. Supplementation of K21, but not placebo, appeared to alleviate body weight gain and epididymal fat mass accumulation, reduce plasma leptin levels, decrease cholesterol and triglyceride levels, and mitigate liver damage in DIO mice. Moreover, the hepatic expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) related to adipogenesis was significantly downregulated in DIO mice by K21 intervention. We also found that K21 supplementation strengthens intestinal permeability and modulates the amount of Lactobacillus spp., Bifidobacterium spp., and Clostridium perfringens in the cecal contents of DIO mice. In conclusion, our results suggest that dietary intake of K21 protects against the onset of HFD-induced obesity through multiple mechanisms of action.

Inhibitory effect of Lactobacillus salivarius on Streptococcus mutans biofilm formation.

Dental caries arises from an imbalance of metabolic activities in dental biofilms developed primarily by Streptococcus mutans. This study was conducted to isolate potential oral probiotics with antagonistic activities against S. mutans biofilm formation from Lactobacillus salivarius, frequently found in human saliva. We analysed 64 L. salivarius strains and found that two, K35 and K43, significantly inhibited S. mutans biofilm formation with inhibitory activities more pronounced than those of Lactobacillus rhamnosus GG (LGG), a prototypical probiotic that shows anti-caries activity. Scanning electron microscopy showed that co-culture of S. mutans with K35 or K43 resulted in significantly reduced amounts of attached bacteria and network-like structures, typically comprising exopolysaccharides. Spot assay for S. mutans indicated that K35 and K43 strains possessed a stronger bactericidal activity against S. mutans than LGG. Moreover, quantitative real-time polymerase chain reaction showed that the expression of genes encoding glucosyltransferases, gtfB, gtfC, and gtfD was reduced when S. mutans were co-cultured with K35 or K43. However, LGG activated the expression of gtfB and gtfC, but did not influence the expression of gtfD in the co-culture. A transwell-based biofilm assay indicated that these lactobacilli inhibited S. mutans biofilm formation in a contact-independent manner. In conclusion, we identified two L. salivarius strains with inhibitory activities on the growth and expression of S. mutans virulence genes to reduce its biofilm formation. This is not a general characteristic of the species, so presents a potential strategy for in vivo alteration of plaque biofilm and caries.

Inhibition of Herpes Simplex Virus Type 1 by Thymol-Related Monoterpenoids

This study examined the anti-herpes simplex virus type I activity of the major constituents of several essential oils. Plaque reduction assays were performed to evaluate anti-herpes simplex virus type I activity. Thymol and carvacrol both possessed significant antiviral activity with an IC₅₀ of 7  µM, and herpes simplex virus type I was 90 % inactivated within 1 hr. The mode of antiviral action was shown to affect the virion directly. Evidence was also observed by electron microscopy. Evaluation of the structural requirements for antiviral activity of thymol-related monoterpenoids revealed that aliphatic side chains had a minor effect, while a hydrophilic group on the benzene ring was sufficient for activity. Our results suggest that thymol and carvacrol are potential candidates for topical therapeutic application to reduce herpes simplex virus transmission.

Characterization of a Novel PepF-Like Oligopeptidase Secreted by Bacillus amyloliquefaciens 23-7A†

ABSTRACT An oligopeptidase from Bacillus amyloliquefaciens 23-7A was characterized along with its biochemical activities and structural gene. The proteins amino acid sequence and enzymatic activities were similar to those of other bacterial PepFs, which belong to metallopeptidase family M3. While most bacterial PepFs are cytoplasmic endopeptidases, the identified PepFBa oligopeptidase is a secreted protein and may facilitate the process of sporulation.