Research
Phase 2 Starch Blocker
Altern Med Rev. 1998 Jun;3(3):187-98
Use of transgenic and mutant animal models in the study of heterocyclic amine-induced mutagenesis and carcinogenesis.
Heterocyclic amines (HCAs) are potent mutagens generated during the cooking of meat and fish, and several of these compounds produce tumors in conventional experimental animals. During the past 5 years or so, HCAs have been tested in a number of novel in vivo murine models, including the following: lacZ, lacI, cII, c-myc/lacZ, rpsL, and gptDelta. transgenics, XPA-/-, XPC-/-, Msh2+/-, Msh2-/- and p53+/- knock-outs, Apc mutant mice (ApcDelta716, Apc1638N, Apcmin), and A33DeltaNbeta-cat knock-in mice. Several of these models have provided insights into the mutation spectra induced in vivo by HCAs in target and non-target organs for tumorigenesis, as well as demonstrating enhanced susceptibility to HCA-induced tumors and preneoplastic lesions. This review describes several of the more recent reports in which novel animal models were used to examine HCA-induced mutagenesis and carcinogenesis in vivo, including a number of studies which assessed the inhibitory activities of chemopreventive agents such as 1,2-dithiole-3-thione, conjugated linoleic acids, tea, curcumin, chlorophyllin-chitosan, and sulindac.
J Biochem Mol Biol. 2003 Jan 31;36(1):35-42
Dietary supplementation of curcumin enhances antioxidant and phase II metabolizing enzymes in ddY male mice: possible role in protection against chemical carcinogenesis and toxicity.
Dietary antioxidants protect laboratory animals against the induction of tumours by a variety of chemical carcinogens. Among possible mechanism of protection against chemical carcinogenesis could be mediated via-antioxidant-dependent induction of detoxifying enzymes. Curcumin, a yellow pigment from Curcuma longa, is a major component of turmeric and is commonly used as a spice and food colouring material and exhibits antiinflammatory antitumour, and antioxidant properties. In this study we therefore investigated the effect of dietary supplementation of curcumin on the activities of antioxidant and phase II-metabolizing enzymes involved in detoxification, and production of reactive oxygen species were quantified in ddY male mice. Dietary supplementation of curcumin (2%, w/v) to male ddY mice for 30 days significantly increased the activities of glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and catalase to 189%, 179%, 189%, and 181% in liver and 143%, 134%, 167% and 115% in kidney respectively as compared with corresponding normal diet fed control (P<0.05-0.001). Parallel to these changes, curcumin feeding to mice also resulted in a considerable enhancement in the activity of phase II-metabolizing enzymes viz. glutathione S-transferase and quinone reductase to 1.7 and 1.8 times in liver and 1.1 and 1.3 times in kidney respectively as compared with corresponding normal diet fed control (P<0.05-0.01). In general, the increase in activities of antioxidant and phase II-metabolizing enzymes was more pronounced in liver as compared to kidney. The induction of such detoxifying enzymes by curcumin suggest the potential value of this compound as protective agent against chemical carcinogenesis and other forms of electrophilic toxicity. The significance of these results can be implicated in relation to cancer chemopreventive effects of curcumin against the induction of tumours in various target organs.
Pharmacol Toxicol. 2003 Jan;92(1):33-8
Inhibition of carcinogen induced c-Ha-ras and c-fos proto-oncogenes expression by dietary curcumin.
BACKGROUND: We investigated the chemopreventive action of dietary curcumin on 7,12-dimethylbenz(a)anthracene (DMBA)-initiated and 12,0-tetradecanoylphorbol-13-acetate (TPA)-promoted skin tumor formation in Swiss albino mice. Curcumin, a yellow coloring matter isolated from roots of Curcuma longa Linn, is a phenolic compound possessing antioxidant, free radical scavenger, and antiinflammatory properties. It has been shown by previously reported work that TPA-induced skin tumors were inhibited by topical application of curcumin, and curcumin has been shown to inhibit a variety of biological activities of TPA. Topical application of curcumin was reported to inhibit TPA-induced c-fos, c-jun and c-myc gene expression in mouse skin. This paper reports the effects of orally administered curcumin, which was consumed as a dietary component at concentrations of 0.2 % or 1 %, in ad libitum feeding. RESULTS: Animals in which tumors had been initiated with DMBA and promoted with TPA experienced significantly fewer tumors and less tumor volume if they ingested either 0.2% or 1% curcumin diets. Also, the dietary consumption of curcumin resulted in a significantly decreased expression of ras and fos proto-oncogenes in the tumorous skin, as measured by enhanced chemiluminesence Western blotting detection system (Amersham). CONCLUSIONS: Whereas earlier work demonstrated that topical application of curcumin to mouse skin inhibited TPA-induced expression of c-fos, c-jun and c-myc oncogenes, our results are the first to show that orally consumed curcumin significantly inhibited DMBA- and TPA-induced ras and fos gene expression in mouse skin.
Anticancer Drugs. 1997 Jun;8(5):470-81
Potent induction of phase 2 enzymes in human prostate cells by sulforaphane.
Two population-based, case-control studies have documented reduced risk of prostate cancer in men who consume cruciferous vegetables. Cruciferae contain high levels of the isothiocyanate sulforaphane. Sulforaphane is known to bolster the defenses of cells against carcinogens through up-regulation of enzymes of carcinogen defense (phase 2 enzymes). Prostate cancer is characterized by an early and near universal loss of expression of the phase 2 enzyme glutathione S-transferase (GST)-pi. We tested whether sulforaphane may act in prostatic cells by increasing phase 2 enzyme expression. The human prostate cancer cell lines LNCaP, MDA PCa 2a, MDA PCa 2b, PC-3, and TSU-Pr1 were treated with 0.1-15 microM sulforaphane in vitro. LNCaP was also treated with an aqueous extract of broccoli sprouts. Quinone reductase enzymatic activity, a surrogate of global phase 2 enzyme activity, was assayed by the menadione-coupled reduction of tetrazolium dye. Expression of NQO-1, GST-alpha, gamma-glutamylcysteine synthetase-heavy and -light chains, and microsomal GST was assessed by Northern blot analysis. Sulforaphane and broccoli sprout extract potently induce quinone reductase activity in cultured prostate cells, and this induction appears to be mediated by increased transcription of the NQO-1 gene. Sulforaphane also induces expression of gamma-glutamylcysteine synthetase light subunit but not the heavy subunit, and this induction is associated with moderate increases in intracellular glutathione levels. Microsomal and alpha-class glutathione transferases were also induced transcriptionally. Sulforaphane induces phase 2 enzyme expression and activity significantly in human prostatic cells. This induction is accompanied by, but not because of, increased intracellular glutathione synthesis. Our findings may help explain the observed inverse correlation between consumption of cruciferae and prostate cancer risk.
Cancer Epidemiol Biomarkers Prev. 2001 Sep;10(9):949-54
Chemoprotective glucosinolates and isothiocyanates of broccoli sprouts: metabolism and excretion in humans.
Broccoli sprouts are a rich source of glucosinolates and isothiocyanates that induce phase 2 detoxication enzymes, boost antioxidant status, and protect animals against chemically induced cancer. Glucosinolates are hydrolyzed by myrosinase (an enzyme found in plants and bowel microflora) to form isothiocyanates. In vivo, isothiocyanates are conjugated with glutathione and then sequentially metabolized to mercapturic acids. These metabolites are collectively designated dithiocarbamates. We studied the disposition of broccoli sprout glucosinolates and isothiocyanates in healthy volunteers. Broccoli sprouts were grown, processed, and analyzed for (a) inducer potency; (b) glucosinolate and isothiocyanate concentrations; (c) glucosinolate profiles; and (d) myrosinase activity. Dosing preparations included uncooked fresh sprouts (with active myrosinase) as well as homogenates of boiled sprouts that were devoid of myrosinase activity and contained either glucosinolates only or isothiocyanates only. In a crossover study, urinary dithiocarbamate excretion increased sharply after administration of broccoli sprout glucosinolates or isothiocyanates. Cumulative excretion of dithiocarbamates following 111-micromol doses of isothiocyanates was greater than that after glucosinolates (88.9 +/- 5.5 and 13.1 +/- 1.9 micromol, respectively; P < 0.0003). In subjects fed four repeated 50-micromol doses of isothiocyanates, the intra- and intersubject variation in dithiocarbamate excretion was very small (coefficient of variation, 9%), and after escalating doses, excretion was linear over a 25- to 200-micromol dose range. Dithiocarbamate excretion was higher when intact sprouts were chewed thoroughly rather than swallowed whole (42.4 +/- 7.5 and 28.8 +/- 2.6 micromol; P = 0.049). These studies indicate that isothiocyanates are about six times more bioavailable than glucosinolates, which must first be hydrolyzed. Thorough chewing of fresh sprouts exposes the glucosinolates to plant myrosinase and significantly increases dithiocarbamate excretion. These findings will assist in the design of dosing regimens for clinical studies of broccoli sprout efficacy.
Therapeutic potential of dietary phase 2 enzyme inducers in ameliorating diseases that have an underlying inflammatory component.
Can J Physiol Pharmacol. 2001; 79(3):266-82 (ISSN: 0008-4212)
Juurlink BH
Department of Anatomy & Cell Biology, The Cameco Multiple Sclerosis and Neuroscience Research Centre, College of Medicine, University of Saskatchewan, Saskatoon, Canada. juurlink@duke.usask.ca
Many diseases associated with ageing have an underlying oxidative stress and accompanying inflammatory component, for example, Alzheimer''s disease or atherosclerosis. Reviewed in this manuscript are: the role of oxidative stress in activating the transcription factor nuclear factor kappa B (NFkappaB), the role of NFkappaB in activating proinflammatory gene transcription, strong oxidants produced by cells, anti-oxidant defense systems, the central role of phase 2 enzymes in the anti-oxidant defense, dietary phase 2 enzyme inducers and evidence that dietary phase 2 enzymes decrease oxidative stress. It is likely that a diet containing phase 2 enzyme inducers may ameliorate or even prevent diseases that have a prominent inflammatory component to them. Research should be directed into the potential therapeutic effects of dietary phase 2 enzyme inducers in ameliorating diseases with an underlying oxidative stress and inflammatory component to them.
Phytochemicals May Protect Cartilage, Prevent Pain in Joints
arthritissupport.com
10-24-2005
Source: Johns Hopkins University
Phase 2 enzyme inducers appear to stop harmful inflammation
Johns Hopkins researchers have discovered that plant-derived compounds known for their ability to protect tissue also appear to block the activity of an enzyme that triggers inflammation in joints. Their findings, based on experiments with human cells in a lab, could lead to new arthritis treatments and better methods of making artificial cartilage.
The discovery was detailed in a paper published in the Sept. 27 edition of Proceedings of the National Academy of Sciences.
The findings came to light while the researchers were studying the wildly different ways in which cells in human blood vessels and joints respond to pressure gradients generated from liquid moving along their surface, a force called shear stress.
In cells that line blood vessels, the reaction to shear stress is beneficial: the boosting of phase 2 enzymes that may protect the cells from cancer-causing chemicals and other toxic agents. Yet in joints, the response to high shear stress is potentially harmful: an increase in the levels of COX-2 enzyme, which triggers inflammation and pain, and suppresses the activity of phase 2 enzymes, ultimately causing the death of chondrocytic cells. Healthy chondrocytes are responsible for the smooth functioning of joints. When chondrocytes stop functioning properly, the result can be arthritis.
The divergent responses to shear stress prompted a series of experiments in a Johns Hopkins lab supervised by Konstantinos Konstantopoulos, associate professor of chemical and biomolecular engineering and Agarwal-Masson Faculty Scholar. His team knew that strenuous exercise or heavy exertion of muscles can cause joints to increase the levels of harmful COX-2 enzyme. What would happen, the researchers wondered, if the vulnerable chondrocyte cells in human joints were first exposed to the beneficial phase 2 enzymes?
To find out, the researchers obtained compounds that boost the activity of helpful phase 2 enzymes. They added these phase 2 inducers to a dish containing the chondrocyte cells that are crucial to maintaining healthy joints. After 24 hours, the cells were subjected to a stress test designed to mimic aspects of strenuous exercise on a joint as well as the hydrodynamic environment in a bioreactor designed to generate artificial cartilage.
The results were surprising. "The beneficial phase 2 enzymes somehow seemed to prevent the activation of the inflammatory COX-2 enzyme," said Zachary R. Healy, a doctoral student in Konstantopoulos'' lab and lead author of the journal paper. "The phase 2 enzymes inhibited the inflammation and the apoptosis -- the cellular suicide we''d observed."
Some prescription drugs like Vioxx keep COX-2 enzyme at bay by temporarily blocking its ability to send the biochemical signals that set off pain and inflammation. When the medication is stopped, however, the stockpiled COX-2 enzyme can resume its damaging ways. Unlike these traditional pain killers, Healy said, the phase 2 enzyme inducers seemed to stop the increasing activity of COX-2 enzyme.
"That means these compounds could be useful as a preventive measure, perhaps before strenuous exercise," Healy said. "This has the potential for stopping pain and inflammation before they start."
Although these experiments appeared to be the first to determine how phase 2 enzyme inducers affect chondrocytes, these compounds have been studied extensively by researchers at the Johns Hopkins School of Medicine. Paul Talalay, the medical school''s John Jacob Abel Distinguished Service Professor of Pharmacology, has shown that phase 2 enzymes can detoxify certain cancer-causing agents and damaging free radicals in tissue, including cells that line blood vessels. He has isolated compounds in edible plants that boost production of phase 2 enzymes. These phytochemicals can be found in cruciferous plants, including broccoli.
Talalay provided one of the phase 2 inducers used in Healy''s experiments. "This was the first work done in applying these phytochemicals to chondrocytes, which are constantly under the influence of forces because of the way we move our joints," Talalay said. "The phase 2 inducers seemed to counteract the effects of that stress by inhibiting the expression of COX-2 enzyme. It''s interesting to think that people may be able to obtain this benefit through dietary components."
By showing a way to ward off inflammation and by providing insights into the effects of shear stress, the new chondrocyte research may also aid tissue engineers who are trying to grow artificial cartilage or seeking to revitalize human cartilage in the lab. This is important because human bodies cannot make new cartilage to replace tissue that''s lost to injury or disease.
"More research is needed," said Konstantopoulos, who directed and supervised the experiments. "But these discoveries could provide guidelines for designing an ideal hydrodynamic environment in bioreactors for generating functional cartilage as well as for the treatment of osteoarthritis."
Funding for the research was provided by a DuPont Young Professor Award, a National Science Foundation Graduate Research Fellowship and an Achievement Reward for College Students Fellowship. Healy''s co-authors on the PNAS paper were Talalay, Konstantopoulos, Norman H. Lee of the Institute for Genomic Research, Xiangqun Gao of the Department of Pharmacology and Molecular Sciences at the Johns Hopkins School of Medicine, Mary B. Goldring of the Harvard Institutes of Medicine, and Thomas W. Kensler of the Department of Environmental Health Sciences in the Johns Hopkins Bloomberg School of Public Health.
