Byeoung-Soo Park

Natural derivatives of curcumin attenuate the Wnt/β-catenin pathway through down-regulation of the transcriptional coactivator p300

Curcumin, a component of turmeric (Curcuma longa), has been reported to suppress beta-catenin response transcription (CRT), which is aberrantly activated in colorectal cancer. However, the effects of its natural analogs (demethoxycurcumin [DMC] and bisdemethoxycurcumin [BDMC]) and metabolite (tetrahydrocurcumin [THC]) on the Wnt/beta-catenin pathway have not been investigated. Here, we show that DMC and BDMC suppressed CRT that was activated by Wnt3a conditioned-medium (Wnt3a-CM) without altering the level of intracellular beta-catenin, and inhibited the growth of various colon cancer cells, with comparable potency to curcumin. Additionally, DMC and BDMC down-regulated p300, which is a positive regulator of the Wnt/beta-catenin pathway. Notably, THC also inhibited CRT and cell proliferation, but to a much lesser degree than curcumin, DMC, or BDMC, indicating that the conjugated bonds in the central seven-carbon chain of curcuminoids are essential for the inhibition of Wnt/beta-catenin pathway and the anti-proliferative activity of curcuminoids. Thus, our findings suggest that curcumin derivatives inhibit the Wnt/beta-catenin pathway by decreasing the amount of the transcriptional coactivator p300.

MONOTERPENES FROM THYME (THYMUS VULGARIS) AS POTENTIAL MOSQUITO REPELLENTS

ABSTRACT Five monoterpenes (carvacrol, p-cymene, linalool, α-terpinene, and thymol) derived from the essential oil of thyme (Thymus vulgaris) were examined for their repellency against the mosquito Culex pipiens pallens. All 5 monoterpenes effectively repelled mosquitoes based on a human forearm bioassay. α-Terpinene and carvacrol showed significantly greater repellency than a commercial formulation, N,N-diethyl-m-methylben-zamide (deet), whereas thymol showed similar repellency to that of deet. The duration of repellency after application for all these monoterpenes was equal to or higher than that of deet. These findings indicate that a spray-type solution containing 2% α-terpinene may serve as an alternative mosquito repellent.

STEREOSELECTIVE METABOLISM OF ENDOSULFAN BY HUMAN LIVER MICROSOMES AND HUMAN CYTOCHROME P450 ISOFORMS

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo(e)dioxathiepin-3-oxide) is a broad-spectrum chlorinated cyclodiene insecticide. This study was performed to elucidate the stereoselective metabolism of endosulfan in human liver microsomes and to characterize the cytochrome P450 (P450) enzymes that are involved in the metabolism of endosulfan. Human liver microsomal incubation of endosulfan in the presence of NADPH resulted in the formation of the toxic metabolite, endosulfan sulfate. The intrinsic clearances (CLint) of endosulfan sulfate from β-endosulfan were 3.5-fold higher than those from α-endosulfan, suggesting that β-endosulfan would be cleared more rapidly than α-endosulfan. Correlation analysis between the known P450 enzyme activities and the rate of the formation of endosulfan sulfate in the 14 human liver microsomes showed that α-endosulfan metabolism is significantly correlated with CYP2B6-mediated bupropion hydroxylation and CYP3A-mediated midazolam hydroxylation, and that β-endosulfan metabolism is correlated with CYP3A activity. The P450 isoform-selective inhibition study in human liver microsomes and the incubation study of cDNA-expressed enzymes also demonstrated that the stereoselective endosulfan sulfate formation from α-endosulfan is mediated by CYP2B6, CYP3A4, and CYP3A5, and that from β-endosulfan is mediated by CYP3A4 and CYP3A5. The total CLint values of endosulfan sulfate formation catalyzed by CYP3A4 and CYP3A5 were consistently higher for β-endosulfan than for the α-form (CLint of 0.67 versus 10.46 μl/min/pmol P450, respectively). CYP2B6 stereoselectively metabolizes α-endosulfan, but not β-endosulfan. These findings suggest that the CYP2B6 and CYP3A enzymes are major enzymes contributing to the stereoselective disposition of endosulfan.

Fumigant Toxicity of Essential Oils and Monoterpenes Against the Red Flour Beetle, Tribolium castaneum Herbst

Abstract Toxicity of various essential oils and their volatile components against the red flour beetle, Tribolium castaneum (Herbst) was determined. The most potent fumigant toxicity was found in essential oil from rosemary (LD 50 = 7.8 μl/l air) followed by the oils of lemon (LD 50 = 16.2 μl/l air), basil (LD 50 = 17.8 μl/l air), lime (LD 50 = 17.9 μl/l air), and peppermint (LD 50 = 25.8 μl/l air). 1,8-Cineole was the most toxic fumigant compound found in rosemary essential oil (LD 50 = 7.4 μl/l air) followed by menthone (LD 50 = 8.5 μl/l air) and p -cymene (LD 50 = 11.4 μl/l air). 1,8-Cineole exhibited similar fumigant toxicity against a PH3-resistant T. castaneum relative to the susceptible insects. Therefore, 1,8-cineole and rosemary essential oil could be a safer fumigant to control stored-product insect pests than those currently used.

Suppression of ochratoxin biosynthesis by naturally occurring alkaloids

The effects of four alkaloids on the biosynthesis of ochratoxin A (OTA), ochratoxin B (OTB) and citrinin were examined on four OTA-producing aspergilli: Aspergillus auricomus, A. sclerotiorum and two isolates of A. alliaceus. Piperine and piperlongumine, natural alkaloids of Piper longum, significantly inhibited OTA production at 0.001% (w/v) for all aspergilli examined. Piperine and piperlongumine affected the polyketide synthesis step of OTA production and inhibited production of citrinin. Curcumin, a constituent of tumeric, completely inhibited mycelial growth of A. alliaceus isolate 791 at 0.1% (w/v) and decreased OTA production by ∼70% at 0.01% (w/v). Sesamin, a constituent of sesame oil, inhibited OTA and OTB production by 60 and 45%, respectively, at 0.1% (w/v), showing its effect was on chloroperoxidase and polyketide synthase activity. The potential advantage of these natural products to reduce ochratoxin contamination of agricultural commodities is discussed.

Identification and characterization of potent CYP2B6 inhibitors in Woohwangcheongsimwon suspension, an herbal preparation used in the treatment and prevention of apoplexy in Korea and China

Woohwangcheongsimwon is a traditional medicine for treating hypertension, arteriosclerosis, coma, and stroke in China and Korea. To assess potential interactions of herb and drug metabolism, commercially available Woohwangcheongsimwon suspensions were examined for their potential to inhibit the activity of nine human cytochrome P450 enzymes. The Woohwangcheongsimwon suspensions showed strong inhibition of CYP2B6 activity. To identify individual constituents with inhibitory activity, the suspension was partitioned using hexane, ethyl acetate, and dichloromethane, and each fraction was tested for its inhibitory effect on CYP2B6-catalyzed bupropion hydroxylation. The hexane fraction possessed inhibitory activity, and gas chromatography/mass spectrometry analysis identified borneol and isoborneol as major constituents of the hexane fraction. These two terpenoids moderately inhibited CYP2B6-catalyzed bupropion hydroxylase activity in a competitive manner, with Ki values of 9.5 and 5.9 μM, respectively, as well as efavirenz 8-hydroxylase activity, with Ki values of 22 and 26 μM, respectively. Additionally, reconstituted mixtures of borneol and isoborneol, at the same concentrations as in the Woohwangcheongsimwon suspension, had comparable potency in inhibiting bupropion hydroxylation. These in vitro data indicate that Woohwangcheongsimwon preparations contain constituents that can potently inhibit the activity of CYP2B6 and suggest that these preparations should be examined for potential pharmacokinetic drug interactions in vivo.

Deposition of Ti–B–N films by ICP assisted sputtering

Abstract Ti–B–N coatings were prepared by inductively coupled plasma assisted DC magnetron sputtering using a TiB 2 target and a gas mixture of N 2 and Ar at 200 °C and a pressure of 60 mTorr. In addition to ICP, the effect of the substrate bias voltage on the structure and properties of the coating was investigated. By applying ICP the hardness of the TiB 2 coating was increased by more than 60 GPa, as a result of enhanced ionization in the plasma. By adding N 2 into the TiB 2 coating, the hardness decreased as reported previously. However, the hardness could be increased up to 76 GPa by applying ICP and a bias voltage to the substrate. The Ti–B–N coating, which had the highest hardness, showed the best surface uniformity and a very dense structure with a grain size of 3 nm. This sample also showed a high crystallinity compared to the coating prepared using other deposition parameters.

Isodihydrocapsiate stimulates plasma glucose uptake by activation of AMP-activated protein kinase.

AMP-activated protein kinase (AMPK) is an energy-sensing enzyme that is implicated as a key factor in controlling whole body homeostasis, including fatty acid oxidation and glucose uptake. We report that a synthetic structural isomer of dihydrocapsiate, isodihydrocapsiate (8-methylnonanoic acid 3-hydroxy-4-methoxy benzyl ester) improves type 2 diabetes by activating AMPK through the LKB1 pathway. In L6 myotube cells, phosphorylation of AMPK and acetyl-CoA carboxylase (ACC) and glucose uptake were significantly increased, whereas these effects were attenuated by an AMPK inhibitor, compound C. In addition, increased phosphorylation of AMPK and ACC by isodihydrocapsiate was significantly reduced by radicicol, an LKB1 destabilizer, suggesting that increased glucose uptake in L6 cells with isodihydrocapsiate treatment is predominantly accomplished by a LKB1-mediated AMPK activation pathway. Oral administration of isodihydrocapsiate to diabetic (db/db) mice reduced blood glucose levels by 40% after a 4-week treatment period. Our results support the development of isodihydrocapsiate as a potential therapeutic agent to target AMPK in type 2 diabetes.

Comparative Nutritional Analysis for Genetically Modified Rice, Iksan483 and Milyang204, and Nontransgenic Counterparts

Recently, two glufosinate-tolerant rice varieties, Iksan483 and Milyang204, were developed in Korea generated by adding bar gene to genomes of the conventional rice varieties. Comparative assessment of nutritional composition was conducted with genetically modified rice grains and its conventional counterparts for substantial equivalence. Nutrients including proximates, fatty acids, amino acids, minerals, vitamins, and antinutrients were investigated using several statistical comparisons. The results showed that, except for small differences in a few fatty acids, minerals, and trypsin inhibitor, there was no significant difference between genetically modified rice and conventional counterpart variety with respect to their nutrient composition. Most of measured levels of nutrients were in good compliance with the literature ranges, showing substantial equivalency. The results of principle component analysis demonstrated that the environment affects the nutritional composition and that all differences between the genetically modified and conventional rice varieties are within the range as the differences observed among conventional varieties grown in different years. Therefore, the insertion of bar gene did not change the nutritional composition of genetically modified rice grains.

Proteomic evaluation of adults of Rhyzopertha dominica resistant to phosphine

A proteomic study using a PH(3)-susceptible (RD2) and -resistant strain (CRD343) of Rhyzopertha dominica was undertaken to validate the relation between change of proteins and PH(3) resistance. Protein expression levels were compared using PD-Quest program after two-dimensional polyacrylamide gel-electrophoresis. Comparing the intensity of proteins, 15 proteins decreased and 6 proteins were newly expressed in CRD343. After MALDI-TOF and LC-MS/MS analyses, the decreased proteins were identified as arginine kinases, dihydrolipoamide dehydrogenase, Hsp60, reverse transcriptase, glyceraldehydes-3-phosphate dehydrogenase, triosephosphate isomerase and hypothetical proteins. Dihydrolipoamide dehydrogenase is involved in the Krebs cycle and glyceraldehydes-3-phosphate dehydrogenase and triosephosphate isomerase are involved in the glycolysis pathway. Among up-regulated proteins, sodium channel, glutamate racemase, enolase and vitellogenin were identified. Taken together, PH(3) affected glycolysis as well as Krebs cycle and the induction of enolase might recover this dysfunction.