Mingyue Song

Identification of pinostilbene as a major colonic metabolite of pterostilbene and its inhibitory effects on colon cancer cells

SCOPE Pterostilbene (PTE) is a resveratrol derivative mainly found in blueberries, and it has been shown to inhibit colon carcinogenesis in multiple animal models. To shed light on the mechanism of PTE in inhibiting colon carcinogenesis, we investigated the PTE metabolites in the mouse colon and in the human colon cancer cells. METHODS AND RESULTS CD-1 mice were fed PTE-containing diet for 3 weeks, and colonic content and colonic mucosa were collected and subjected to LC-MS analysis. Pinostilbene (PIN) was identified as a major metabolite of PTE in the mouse colon. Importantly, the level of PIN was found to be approximately equivalent to that of PTE in the colonic mucosa. PIN significantly inhibited the growth of human colon cancer cells, i.e., HCT116 and HT29. These inhibitory effects were similar to those produced by PTE. Moreover, under physiologically relevant conditions, 20 and 40 μM of PIN caused cell cycle arrest at S phase and induced apoptosis in colon cancer cells. These effects were associated with profound modulation of signaling proteins related with cell proliferation and programmed cell death. CONCLUSION Our results demonstrated that PIN is a major metabolite of PTE in the colon of mice fed with PTE, and PIN may play important roles in the anti-colon cancer effects elicited by orally administered PTE.

Enhanced Anti-Inflammatory Activities by the Combination of Luteolin and Tangeretin

Dietary components in combination may act synergistically and produce enhanced biological activities. Herein, we investigated the anti-inflammatory effects of 2 flavonoids, that is luteolin (LUT) and tangeretin (TAN) in combination. Lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages were treated with noncytotoxic concentrations of LUT, TAN, and their combinations. The results showed that LUT/TAN in combination produced synergistic inhibitory effects on LPS-stimulated production of nitric oxide (NO). ELISA results demonstrated that LUT/TAN in combination caused stronger suppression on the LPS-induced overexpression of proinflammatory mediators, such as prostaglandin E2 (PGE2 ), interleukin (IL)-1β, and IL-6 than LUT or TAN alone. Immunoblotting and Real-Time PCR analyses showed that LUT/TAN combination significantly decreased LPS-induced protein and mRNA expression of inducible nitric oxide synthase and cyclooxygenase-2. These inhibitory effects of the combination treatment were stronger than those produced by LUT or TAN alone. Overall, our results demonstrated for the first time that combination of LUT and TAN produced synergistic anti-inflammatory effects in LPS-stimulated RAW 264.7 macrophages.

Nobiletin and its colonic metabolites suppress colitis-associated colon carcinogenesis by down-regulating iNOS, inducing antioxidative enzymes and arresting cell cycle progression

Nobiletin (NOB) is a major citrus polymethoxyflavone (PMF) with various beneficial biological activities. We reported previously that dietary NOB significantly inhibited colitis-associated colon carcinogenesis in azoxymethane (AOM)/dextran sulfate sodium (DSS)-treated mice, and the chemopreventive effects were associated with NOB metabolites found in the mouse colonic tissues. In this study, to better understand the role of colonic metabolites of NOB, we determined the anti-inflammation and anticancer effects of a mixture of NOB and its major metabolites (NOB-Met) at the concentrations equivalent to those found in colonic tissues of NOB-fed mice. The results demonstrated that NOB-Met effectively decreased the expression level of inducible nitric oxide synthase (iNOS), increased the level of heme oxygenase-1 (HO-1) and NADH quinone oxidoreductase 1 (NQO1) and up-regulated nuclear factor erythroid 2-related factor (Nrf2) signaling pathway in lipopolysaccharide (LPS)-stimulated macrophages. NOB-Met also caused a significant cell cycle arrest in human colon cancer cells. Validation study confirmed that dietary NOB led to the effects similar to those described above in the colon of AOM/DSS-treated mice. Specifically, dietary NOB significantly reduced the level of iNOS, up-regulated Nrf2-dependent enzymes and profoundly modulated key signaling proteins resulting in decreased cell cycle progression in the colonic tissue of AOM/DSS-treated mice. Overall, our findings demonstrated that dietary NOB led to the presence of NOB and its metabolites in the colonic tissue, which suppressed colitis-associated colon carcinogenesis via down-regulating iNOS, inducing antioxidative enzymes and arresting cell cycle progression.

Analysis of 10 metabolites of polymethoxyflavones with high sensitivity by electrochemical detection in high-performance liquid chromatography.

Polymethoxyflavones (PMFs) have been known as a type of bioactive flavones that possess various beneficial biological functions. Accumulating evidence demonstrated that the metabolites of PMFs, that is, hydroxyl PMFs (OH-PMFs), had more potent beneficial biological effects than their corresponding parent PMFs. To facilitate the further identification and quantification of OH-PMFs in biological samples, the aim of this study was to develop a methodology for the simultaneous determination of 10 OH-PMFs using high-performance liquid chromatography (HPLC) coupled with electrochemistry detection. The HPLC profiles of these 10 OH-PMFs affected by different chromatographic parameters (different organic composition in mobile phases, the concentration of trifluoroacetic acid, and the concentration of ammonium acetate) are fully discussed in this study. The optimal condition was selected for the following validation studies. The linearity of calibration curves, accuracy, and precision (intra- and interday) at three concentration levels (low, middle, and high concentration range) were verified. The regression equations were linear (r > 0.9992) over the range of 0.005-10 μM. The limit of detection for 10 OH-PMFs was in the range of 0.8-3.7 ng/mL (S/N = 3, 10 μL injection). The recovery rates ranged from 86.6 to 108.7%. The precisions of intraday and interday analyses were less than 7.37 and 8.63% for relative standard deviation, respectively. This validated method was applied for the analysis of a variety of samples containing OH-PMFs. This paper also gives an example of analyzing the metabolites of nobiletin in mouse urine using the developed method. The transformation from nobiletin to traces of 5-hydroxyl metabolites has been discovered by this effective method, and this is the first paper to report such an association.

Structure–Activity Relationship of Curcumin: Role of the Methoxy Group in Anti-inflammatory and Anticolitis Effects of Curcumin

Curcumin, a dietary compound from turmeric, has beneficial effects on inflammatory diseases such as inflammatory bowel disease. Most previous studies have focused on the structure-activity relationship of the thiol-reactive α,β-unsaturated carbonyl groups of curcumin, so little is known about the roles of methoxy groups in biological activities of curcumin. Here we synthesized a series of curcumin analogues with different substitution groups (R = H-, Br-, Cl-, F-, NO2-, CH3-, and OH-) to replace the methoxy group and evaluated their biological effects in vitro and in vivo. Curcumin, Cur-OH, and Cur-Br (25 μM) suppressed 74.91 ± 0.88, 77.75 ± 0.89, and 71.75 ± 0.90% of LPS-induced NO production, respectively (P < 0.05). Similarly, these compounds also decreased iNOS expression, COX-2 expression, and NF-κB signaling in RAW 264.7 macrophage cells (P < 0.05). However, other analogues, especially Cur-NO2, were inactive (P > 0.05). In the dextran sulfate sodium (DSS)-induced colitis mouse model, the Cur-Br analogue also showed a beneficial effect the same as curcumin (P < 0.05), whereas the Cur-NO2 analogue had no effect in the animal model (P > 0.05). Together, the analogues have dramatically different effects on inflammation, supporting that the substitution group on the methoxy position plays an important role in the anti-inflammatory effects of curcumin. The methoxy group is a potential structural candidate for modification to design curcumin-based drugs for inflammatory diseases.

Synergistic chemopreventive effects of nobiletin and atorvastatin on colon carcinogenesis

Different cancer chemopreventive agents may act synergistically and their combination may produce enhanced protective effects against carcinogenesis than each individual agent alone. Herein, we investigated the chemopreventive effects of nobiletin (NBT, a citrus polymethoxyflavone) and atorvastatin (ATST, a lipid-lowering drug) in colon cancer cells/macrophages and an azoxymethane (AOM)-induced colon carcinogenesis rat model. The results demonstrated that co-treatments of NBT/ATST produced enhanced growth inhibitory and anti-inflammatory effects on the colon cancer cells and macrophages, respectively. Isobologram analysis confirmed that these interactions between NBT and ATST were synergistic. NBT/ATST co-treatment also synergistically induced extensive cell cycle arrest and apoptosis in colon cancer cells. Oral administration of NBT (0.1%, w/w in diet) or ATST (0.04%, w/w in diet) significantly decreased colonic tumor incidence and multiplicity in AOM-treated rats. Most importantly, co-treatment of NBT/ATST at their half doses (0.05% NBT + 0.02% ATST, w/w in diet) resulted in even stronger inhibitory effects on colonic tumor incidence and multiplicity than did NBT or ATST alone at higher doses. Statistical analysis confirmed that the enhanced chemopreventive activities against colon carcinogenesis in rats by the NBT/ATST combination were highly synergistic. Our results further demonstrated that NBT/ATST co-treatment profoundly modulated key cellular signaling regulators associated with inflammation, cell proliferation, cell cycle progression, apoptosis, angiogenesis and metastasis in the colon of AOM-treated rats. In conclusion, for the first time, our results demonstrated a strong synergy in inhibiting colon carcinogenesis produced by the co-treatment of NBT and ATST, which provided a scientific basis for using NBT in combination with ATST for colon cancer chemoprevention in humans.

Novel ent-Kaurane Diterpenoid from Rubus corchorifolius L. f. Inhibits Human Colon Cancer Cell Growth via Inducing Cell Cycle Arrest and Apoptosis

The tender leaves of Rubus corchorifolius L. f. have been consumed as tea for drinking in China since ancient times. In this study, a novel ent-kaurane diterpenoid was isolated and identified from R. corchorifolius L. f. leaves as ent-kaur-2-one-16β,17-dihydroxy-acetone-ketal (DEK). DEK suppressed the growth of HCT116 human colon cancer cells with an IC50 value of 40 ± 0.21 μM, while it did not cause significant growth inhibition on CCD-18Co human colonic myofibroblasts at up to100 μM. Moreover, DEK induced extensive apoptosis and S phase cell cycle arrest in the colon cancer cells. Accordingly, DEK caused profound effects on multiple signaling proteins associated with cell proliferation, cell death, and inflammation. DEK significantly upregulated the expression levels of pro-apoptotic proteins such as cleaved caspase-3, cleaved caspase-9, cleaved PARP, p53, Bax, and tumor suppressor p21Cip1/Waf1, downregulated the levels of cell cycle regulating proteins such as cyclinD1, CDK2, and CDK4 and carcinogenic proteins such as EGFR and COX-2, and suppressed the activation of Akt. Overall, our results provide a basis for using DEK as a potential chemopreventive agent against colon carcinogenesis.

Potential impact of biopolymers (ε-polylysine and/or pectin) on gastrointestinal fate of foods: In vitro study

Food-grade biopolymers, such as proteins and polysaccharides, may impact the gastrointestinal fate of foods through various mechanisms. In this study, we examined the influence of ε-polylysine (an antimicrobial) and pectin (a thickening agent) on the behavior of a standard rodent diet (full-fat and fat-free) in a simulated gastrointestinal tract that included mouth, stomach, and small intestine phases. Powdered biopolymers were incorporated into the standard diet in either individual or complexed form. The presence of the biopolymers altered the microstructure and charge characteristics of the gastrointestinal contents. In particular, the presence of pectin appeared to increase the rate and extent of lipid digestion, which may have been due to its ability to inhibit protein aggregation. Our results do not support the hypothesis that polylysine inhibits lipid digestion, as has been reported previously. Overall, the results of this study may be useful for interpreting animal feeding studies of the influence of biopolymers on the gastrointestinal fate of foods.

A common antimicrobial additive increases colonic inflammation and colitis-associated colon tumorigenesis in mice

The commonly used antimicrobial compound triclosan increases colonic inflammation and colon cancer in mice. Triclosan triggers inflammation Antimicrobials are ubiquitous in manufactured products beyond hand soap and exist in the environment as pollutants. Triclosan exposure is practically unavoidable in the United States, but little is known how ingestion may affect our health. Yang and colleagues used mouse models of colitis and colon cancer to see how brief exposures of triclosan could affect inflammation. They observed that triclosan altered mouse gut microbiota and increased inflammation in a TLR4-dependent manner. Triclosan increased the severity of colitis symptoms and spurred colitis-associated colon cancer cell growth. Although the study is limited to mouse models, this work suggests that the effects of triclosan on human health should be examined more closely. Triclosan (TCS) is a high-volume chemical used as an antimicrobial ingredient in more than 2000 consumer products, such as toothpaste, cosmetics, kitchenware, and toys. We report that brief exposure to TCS, at relatively low doses, causes low-grade colonic inflammation, increases colitis, and exacerbates colitis-associated colon cancer in mice. Exposure to TCS alters gut microbiota in mice, and its proinflammatory effect is attenuated in germ-free mice. In addition, TCS treatment increases activation of Toll-like receptor 4 (TLR4) signaling in vivo and fails to promote colitis in Tlr4−/− mice. Together, our results demonstrate that this widely used antimicrobial ingredient could have adverse effects on colonic inflammation and associated colon tumorigenesis through modulation of the gut microbiota and TLR4 signaling. Together, these results highlight the need to reassess the effects of TCS on human health and potentially update policies regulating the use of this widely used antimicrobial.

Chemopreventive Effects of Whole Cranberry (Vaccinium macrocarpon) on Colitis-associated Colon Tumorigenesis

SCOPE There are growing interests in using a whole-food-based approach to prevent chronic diseases due to potential synergistic interactions among different bioactive components within the whole foods. North American cranberry (Vaccinium macrocarpon), a polyphenol-rich fruit, has been shown to exert multiple beneficial health effects. METHODS AND RESULTS For the first time, the protective effects of whole cranberry powder (WCP) are determined against colitis-associated mouse colon tumorigenesis induced by azoxymethane (AOM) and dextran sulfate sodium (DSS). The results show that dietary administration of WCP (1.5%, w/w in the diet) significantly suppresses colon tumorigenesis as indicated by the reduced tumor incidence, multiplicity, burden, and average tumor size in WCP-fed mice compared to the positive control mice. Both gene and protein expression levels of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α are markedly attenuated by WCP treatment in the colon of AOM/DSS-treated mice. Moreover, WCP profoundly modulates multiple signaling pathways/proteins related to inflammation, cell proliferation, apoptosis, angiogenesis, and metastasis in the colon, which is closely associated with the inhibitory effects of WCP on colon tumorigenesis. CONCLUSION Overall, the results demonstrate chemopreventive effects of WCP on colon tumorigenesis in mice, providing a scientific basis for using the whole cranberry as a functional food to promote colon health in humans.