DNC News

 

Cox-2 inhibitors

 

Subject: the Cox-2 gene plays a role in inflammation and cancer development. Natural extracts affect cancer and inflammation in a way which differs from prescription drugs

 

The Cyclo-oxygenase type 2 (COX-2) gene was discovered 13 years ago. It plays an important role in chronic inflammation and the development of certain types of cancer. Blocking the action of the COX-2 gene decreases inflammation and many scientists think doing so will help protect against colon, breast and other cancers.

 

There have been a number of news stories in recent months about prescription drugs which block COX-2. Vioxx, Celebrex and other anti inflammatory drugs, which work so well for arthritis, are being pulled off the market because the relief they provide isn't worth the increased risk they cause for heart disease and stroke. This story will continue as lawyers and regulators attempt to determine who knew what when, so as to place blame and demand restitution. Let's back up for a moment though and see if I can explain a little of this chemistry and what is going on.

 

This began with prostaglandins. Prostaglandins are a group of hormone-like chemicals which in tiny amounts have profound effects in stimulating and regulating physical processes in the body. The first of these chemicals discovered was isolated from the prostate gland, thus the name. We now know they are made throughout the body and different prostaglandins have different actions. The one we are interested in for this discussion is prostaglandin E2 (PGE2). We are interested in PGE2 because it causes inflammation; intense hot swelling of any tissue that gets even a whiff of it. PGE-2 is made from a fatty acid called arachidonic acid. Arachidonic acid is found primarily in meats. This is the basis of the proscription to reduce meat consumption for people with chronic inflammatory conditions. The less meat consumed, the less arachidonic acid available and the less PGE-2 synthesized to promote inflammation.

 

Arachidonic acid is converted into PGE-2 by an enzyme called cyclo-oxygenase, abbreviated as COX. Blocking the COX enzyme decreases PGE-2 production.

 

There are two forms or subtypes of cyclo-oxygenase which are named simply Cox-1 and Cox-2. Cox-1 is produced throughout the body and regulates blood flow in the kidneys, supports normal platelet function and maintains the stomach lining. The body produces a steady supply of COX-1 to these areas which require it to function normally. Cox-2 is activated and made only under certain conditions. Stressors will stimulate production of PGE-2 in inflamed tissue. When activated COX-2 produces those hormone like prostaglandins, PGE-2 which are associated with inflammation and tumor development.

 

Bayer began selling aspirin in 1899 but it wasn't until 1971, when an estimated 10-20 thousand tons of aspirin were consumed annually in the United States , that it was understood why it worked. Aspirin, ibuprofen, and other common pain relievers known as nonsteroidal anti inflammatory drugs (NSAIDs) are COX inhibitors. They stop the Cyclo-oxygenase enzymes from working, but they stop the both COX-1 and COX-2. This dual effect causes problems. Blocking COX-1 can lead to stomach problems, especially bleeding ulcers.

Once this chemistry was understood, drug companies developed medications which only block COX-2 in order to minimize the stomach side effects. These selective COX-2 inhibitors were very successful at treating pain and inflammation, especially arthritis and osteoarthritis.

 

Unfortunately these selective COX-2 inhibitors also suppress another prostaglandin called Prostaglandin I(2). This prostaglandin has an anti-thrombotic effect on the blood; it prevents formation of blood clots. Thus these drugs, Vioxx, Celebrex, Valdecoxib and others by accidentally suppressing the formation of prostaglandin I(2), promote heart attacks and strokes. Up until September 30 when Merck withdrew Vioxx from the market the drug was bringing in 2.5 billion dollars a year. Recalling Vioxx cost Merck $27 billion and that doesn't including what is expected to be a flood of class action law suits.

 

The first suspicious data came to light in 2000 with the Vioxx Gastrointestinal Outcomes Research (VIGOR) study. Prior studies hade seen no difference between cardiovascular problems between Vioxx and NSAIDs. The VIGOR study compared Vioxx with Naproxen without a placebo arm to the study. The study showed a 400% increase in heart attacks in patients on Vioxx versus naproxen but without a placebo group, Merck claims they didn't know whether Vioxx was the problem or naproxen was protective and producing less heart attacks in users.

 

The convincing data came with the Adematous Polyp Prevention on Vioxx (APPROVe) study last fall. APPROVe showed patients taking Vioxx had double the heart attacks and strokes of people taking a placebo after just 18 months of use.

 

 

There are a number of herbal extracts which we have used for years to treat inflammation and which have an effect at suppressing COX-2. Now we are trying to figure out which of these mimic the dangerous side effects of the pharmaceutical COX-2 inhibitors and which don't.

 

Which finally brings me back to the topic of this newsletter. Andrew Dannenberg and his colleagues have tested over 800 natural extracts for their ability to inhibit COX-2.

They report that Carnosol [i] a chemical extracted from rosemary, curcumin, a chemical extracted from the turmeric root [ii] , and Resveratrol [iii] extracted from red wine, all inhibit COX-2 activity but work by a different mechanism than the drugs. The COX-2 inhibitory drugs target the enzyme itself and stop it from working. These natural substances target the gene that codes for the enzyme cyclo-oxygenase; they prevent the COX-2 enzyme from being made. Though they tend to be slower acting than the drugs, in the long run they will be more specific and safer. These extracts have a long history of use as anti-inflammatories and a growing body of research suggesting that they are cancer preventive. Until someone figures a way to patent them, it is unlikely that we will see research studies and promotion to rival Vioxx and its relatives of the drug world.

 

 

  My desk is piled with advertisements promoting natural anti inflammatory extracts: ginger [iv] , turmeric, rosemary, green tea [v] , oregano, skullcap [vi] , hops [vii] and Boswellia [viii] . All have some anti-inflammatory effect. Most of these act by down regulating the COX-2 gene so it produces fewer enzymes and slowing the production of PGE-2. Although some of them also down regulate COX-1, some such as rosemary and hops have been shown to only affect COX-2. The research is skimpy as far as measuring these effects. I will assume that things such as ginger, Boswellia and turmeric which have a long history of use in treating stomach problems do not inhibit COX-1 significantly; if so they would cause stomach ulcers and probably not be effective at treating stomach problems. Little has been written about prostaglandin (I)2. Until recently no one considered it an issue. Would we have noticed if these herbs increased cardiovascular events? Perhaps not.

 

This story is far from over. The drug companies have too much invested in this research to let these products disappear. Yet the risk now associated with COX-2 inhibitors will push many people to seek natural treatments for chronic inflammation. This will no doubt spur the development, research and understanding of both our existing products and new natural extracts as well.

 

References:

 

[i] Cancer Res. 2002 May 1;62(9):2522-30.

Retinoids and carnosol suppress cyclooxygenase-2 transcription by CREB-binding protein/p300-dependent and -independent mechanisms.

 

Subbaramaiah K, Cole PA, Dannenberg AJ.

 

Department of Medicine, New York Presbyterian Hospital-Cornell and Strang Cancer Prevention Center , New York , New York 10021, USA . ksubba@med.cornell.edu

 

Treatment with retinoic acid (RA) or carnosol, two structurally unrelated compounds with anticancer properties, inhibited phorbol ester (PMA)-mediated induction of activator protein-1 (AP-1) activity and cyclooxygenase-2 (COX-2) expression in human mammary epithelial cells. The induction of COX-2 transcription by PMA was mediated by increased binding of AP-1 to the cyclic AMP response element (CRE) of the COX-2 promoter. Inhibition of the histone acetyltransferase activity of CREB- binding protein (CBP)/p300 blocked the induction of COX-2 by PMA. Treatment with carnosol but not RA blocked increased binding of AP-1 to the COX-2 promoter. Because AP-1 binding was unaffected by RA, we investigated whether RA inhibited COX-2 transcription via effects on the coactivator CBP/p300. Treatment with RA stimulated an interaction between RA receptor-alpha and CBP/p300; a corresponding decrease in the interaction between CBP/p300 and c-Jun was observed. Importantly, overexpressing CBP/p300 or dominant-negative RA receptor-alpha relieved the suppressive effect of RA on PMA-mediated stimulation of the COX-2 promoter. To elucidate the mechanism by which carnosol inhibited COX-2 transcription, its effects on protein kinase C (PKC) signaling were determined. Carnosol but not RA inhibited the activation of PKC, ERK1/2, p38, and c-Jun NH2-terminal kinase mitogen-activated protein kinase. Overexpressing c-Jun but not CBP/p300 reversed the suppressive effect of carnosol on PMA-mediated stimulation of COX-2 promoter activity. Thus, RA acted by a receptor-dependent mechanism to limit the amount of CBP/p300 that was available for AP-1-mediated induction of COX-2. By contrast, carnosol inhibited the induction of COX-2 by blocking PKC signaling and thereby the binding of AP-1 to the CRE of the COX-2 promoter. Taken together, these results show that small molecules can block the activation of COX-2 transcription by distinct mechanisms.

 

PMID: 11980644 [PubMed - indexed for MEDLINE]

 

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[ii] Carcinogenesis. 1999 Mar;20(3):445-51.

 

Curcumin inhibits cyclooxygenase-2 transcription in bile acid- and phorbol ester-treated human gastrointestinal epithelial cells.

 

Zhang F, Altorki NK, Mestre JR, Subbaramaiah K, Dannenberg AJ.

 

Department of Cardiothoracic Surgery, New York Presbyterian Hospital and Weill Medical College of Cornell University, NY 10021, USA.

 

We investigated whether curcumin, a chemopreventive agent, inhibited chenodeoxycholate (CD)- or phorbol ester (PMA)-mediated induction of cyclooxygenase-2 (COX-2) in several gastrointestinal cell lines (SK-GT-4, SCC450, IEC-18 and HCA-7). Treatment with curcumin suppressed CD- and PMA-mediated induction of COX-2 protein and synthesis of prostaglandin E2. Curcumin also suppressed the induction of COX-2 mRNA by CD and PMA. Nuclear run-offs revealed increased rates of COX-2 transcription after treatment with CD or PMA and these effects were inhibited by curcumin. Treatment with CD or PMA increased binding of AP-1 to DNA. This effect was also blocked by curcumin. In addition to the above effects on gene expression, we found that curcumin directly inhibited the activity of COX-2. These data provide new insights into the anticancer properties of curcumin.

 

PMID: 10190560 [PubMed - indexed for MEDLINE]

 

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[iii] Adv Exp Med Biol. 2001;492:147-57.

Resveratrol inhibits the expression of cyclooxygenase-2 in mammary epithelial cells.

Subbaramaiah K, Dannenberg AJ.

 

Department of Medicine, New York Presbyterian Hospital, Cornell, New York 10021, USA.

 

PMID: 11480663 [PubMed - indexed for MEDLINE]

 

Ann N Y Acad Sci. 1999;889:214-23.

 

Resveratrol inhibits cyclooxygenase-2 transcription in human mammary epithelial cells.

 

Subbaramaiah K, Michaluart P, Chung WJ, Tanabe T, Telang N, Dannenberg AJ.

 

Department of Medicine, New York Presbyterian Hospital-Cornell, New York 10021, USA. ksubba@mail.med.cornell.edu

 

A large body of evidence suggests that inhibiting cyclooxygenase-2 (COX-2), the inducible form of COX, will be an important strategy for preventing cancer. In this study, we investigated whether resveratrol, a chemopreventive agent found in grapes, could suppress phorbol ester (PMA)-mediated induction of COX-2 in human mammary and oral epithelial cells. Treatment of cells with PMA induced COX-2 mRNA, COX-2 protein, and prostaglandin synthesis. These effects were inhibited by resveratrol. Nuclear runoffs revealed increased rates of COX-2 transcription after treatment with PMA, an effect that was inhibited by resveratrol. Resveratrol inhibited PMA-mediated activation of protein kinase C and the induction of COX-2 promoter activity by c-Jun. Phorbol ester-mediated induction of AP-1 activity was blocked by resveratrol. These data are likely to be important for understanding the anticancer and anti-inflammatory properties of resveratrol.

 

PMID: 10668496 [PubMed - indexed for MEDLINE]

 

J Biol Chem. 1998 Aug 21;273(34):21875-82.

 

Resveratrol inhibits cyclooxygenase-2 transcription and activity in phorbol ester-treated human mammary epithelial cells.

 

Subbaramaiah K, Chung WJ, Michaluart P, Telang N, Tanabe T, Inoue H, Jang M, Pezzuto JM, Dannenberg AJ.

 

Department of Medicine, Department of Surgery, at Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.

 

We determined whether resveratrol, a phenolic antioxidant found in grapes and other food products, inhibited phorbol ester (PMA)-mediated induction of COX-2 in human mammary and oral epithelial cells. Treatment of cells with PMA induces COX-2 and causes a marked increase in the production of prostaglandin E2. These effects were inhibited by resveratrol. Resveratrol suppressed PMA-mediated increases in COX-2 mRNA and protein. Nuclear run-offs revealed increased rates of COX-2 transcription after treatment with PMA, an effect that was inhibited by resveratrol. PMA caused about a 6-fold increase in COX-2 promoter activity, which was suppressed by resveratrol. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs, in which specific enhancer elements were mutagenized, indicated that the effects of PMA and resveratrol were mediated via a cyclic AMP response element. Resveratrol inhibited PMA-mediated activation of protein kinase C. Overexpressing protein kinase C-alpha, ERK1, and c-Jun led to 4.7-, 5.1-, and 4-fold increases in COX-2 promoter activity, respectively. These effects also were inhibited by resveratrol. Resveratrol blocked PMA-dependent activation of AP-1-mediated gene expression. In addition to the above effects on gene expression, we found that resveratrol also directly inhibited the activity of COX-2. These data are likely to be important for understanding the anti-cancer and anti-inflammatory properties of resveratrol.

 

PMID: 9705326 [PubMed - indexed for MEDLINE]

 

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[iv] Bioorg Chem. 2001 Jun;29(3):156-63.

 

Effect of ginger constituents and synthetic analogues on cyclooxygenase-2 enzyme in intact cells.

 

Tjendraputra E, Tran VH, Liu-Brennan D, Roufogalis BD, Duke CC.

 

Herbal Medicines Research and Education Centre, University of Sydney, NSW 2006, Australia.

 

Seventeen pungent oleoresin principles of ginger (Zingiber officinale, Roscoe) and synthetic analogues were evaluated for inhibition of cyclooxygenase-2 (COX-2) enzyme activity in the intact cell. These compounds exhibited a concentration and structure dependent inhibition of the enzyme, with IC(50) values in the range of 1-25 microM. Ginger constituents, [8]-paradol and [8]-shogaol, as well as two synthetic analogues, 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)decane and 5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)dodecane, showed strong inhibitory effects on COX-2 enzyme activity. The SAR analysis of these phenolic compounds revealed three important structural features that affect COX-2 inhibition: (i) lipophilicity of the alkyl side chain, (ii) substitution pattern of hydroxy and carbonyl groups on the side chain, and (iii) substitution pattern of hydroxy and methoxy groups on the aromatic moiety. Copyright 2001 Academic Press.

 

PMID: 11437391 [PubMed - indexed for MEDLINE]

 

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[v] Int J Cancer. 2005 Feb 10;113(4):660-9.

 

Green tea constituent epigallocatechin-3-gallate selectively inhibits COX-2 without affecting COX-1 expression in human prostate carcinoma cells.

 

Hussain T, Gupta S, Adhami VM, Mukhtar H.

 

University of Wisconsin, Department of Dermatology, 1300 University Ave., Madison, WI 53706, USA.

 

Overexpression of cyclooxygenase (COX)-2 has been implicated in many pathologic conditions, including cancer. One practical inference of this finding is that sustained inhibition of COX-2 could serve as a promising target for prevention or therapy of cancer. Conventional nonsteroidal antiinflammatory drugs (NSAIDs) and recently developed COX-2-specific inhibitors have shown considerable promise in prevention of some forms of human cancer; however, its application is limited due to severe toxic side effects on normal cells. Therefore, there is a need to define novel, nontoxic dietary constituents with proven chemopreventive effects through other pathways that also possess COX-2 but not COX-1 inhibitory activity. Recent studies on green tea and its major polyphenolic constituent (-)epigallocatechin-3-gallate (EGCG) have established its remarkable cancer preventive and some cancer therapeutic effects. Here, we show that EGCG inhibits COX-2 without affecting COX-1 expression at both the mRNA and protein levels, in androgen-sensitive LNCaP and androgen-insensitive PC-3 human prostate carcinoma cells. Based on our study, it is tempting to suggest that a combination of EGCG with chemotherapeutic drugs could be an improved strategy for prevention and treatment of prostate cancer.

 

PMID: 15455372 [PubMed - in process]

[vi] Cancer Res. 2003 Jul 15;63(14):4037-43.

 

Inhibition of cancer cell proliferation and prostaglandin E2 synthesis by Scutellaria baicalensis.

 

Zhang DY, Wu J, Ye F, Xue L, Jiang S, Yi J, Zhang W, Wei H, Sung M, Wang W, Li X.

 

Department of Pathology, Mount Sinai School of Medicine, New York University, New York, New York 10029, USA. David.Zhang@mssm.edu

 

Scutellaria baicalensis is a widely used Chinese herbal medicine that has been used historically in anti-inflammatory and anticancer therapy. The purpose of this study is to verify its anticancer activity on head and neck squamous cell carcinoma (HNSCC) in vitro and in vivo and to investigate its effect on cyclooxygenase-2 (COX-2), which converts arachidonic acid to prostaglandin E(2) (PGE(2)) and is highly expressed in HNSCC. Two human HNSCC cell lines (SCC-25 and KB) and a nontumorigenic cell line (HaCaT) were tested in vitro for growth inhibition, proliferation cell nuclear antigen expression, and COX-2 activity and expression after treatment with Scutellaria baicalensis extract. Its effects were compared with those of baicalein (a flavonoid isolated from Scutellaria baicalensis), indomethacin (a nonselective COX inhibitor), and celecoxib (a selective COX-2 inhibitor). Four nude mice with s.c. inoculation of KB cells were tested for its anticancer activity in vivo by oral administration of Scutellaria baicalensis at a dose of 1.5 mg/mouse (75 mg/kg), five times/week for 7 weeks. Scutellaria baicalensis and other agents demonstrated a strong growth inhibition in both tested human HNSCC cell lines. No growth inhibition of HaCaT cells was observed with Scutellaria baicalensis. The IC(50)s were 150 micro g/ml for Scutellaria baicalensis, 25 micro M for celecoxib, and 75 micro M for baicalein and indomethacin. Scutellaria baicalensis, as well as celecoxib and indomethacin, but not baicalein, suppressed proliferation cell nuclear antigen expression and PGE(2) synthesis in both cell types. Scutellaria baicalensis inhibited COX-2 expression, whereas celecoxib inhibited COX-2 activity directly. A 66% reduction in tumor mass was observed in the nude mice. Scutellaria baicalensis selectively and effectively inhibits cancer cell growth in vitro and in vivo and can be an effective chemotherapeutic agent for HNSCC. Inhibition of PGE(2) synthesis via suppression of COX-2 expression may be responsible for its anticancer activity. Differences in biological effects of Scutellaria baicalensis compared with baicalein suggest the synergistic effects among components in Scutellaria baicalensis.

 

PMID: 12874003 [PubMed - indexed for MEDLINE]

 

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[vii] Asia Pac J Clin Nutr. 2004;13(Suppl):S110.

 

 

In vitro and ex vivo cyclooxygenase inhibition by a hops extract.

 

Lemay M, Murray MA, Davies A, Roh-Schmidt H, Randolph RK.

 

Access Business Group LLC, California, USA.

 

While there has been much research on botanical materials as potential pain-relieving Cox inhibitors, it has not yet been demonstrated that oral consumption of botanical agents can inhibit Cox-2 activity in humans. In particular it would be of interest to determine whether any botanical anti-inflammatory has Cox-1-sparing activity, in order to reduce the risk of gastrointestinal side effects. This two-stage study was designed to first screen a variety of botanicals in vitro, and then to select one or more promising agents to test in human volunteers. Method: Seventeen botanical agents, putative anti-inflammatories or pain-relievers all, were evaluated in vitro for Cox-1 and -2 inhibitory potency and selectivity using a caco-2 cell line with ibuprofen as an active control. A promising compound, a hops extract high in alpha acids, showed a Cox-2/Cox-1 IC50 selectivity ratio of 0.06, compared to 4.2 for ibuprofen. Two different formulations of a standardized hops extract (resin and powder) were compared with ibuprofen in a double-blind, randomized, ex vivo study. Subjects consumed hops powder extract, hops resin extract, or ibuprofen, and provided blood samples before and at intervals for 9 h following the first dose. Plasma was extracted and analyzed in a validated Cox-1 and -2 inhibition assay. Results: There were no differences between active treatments or ibuprofen control in Cox-2 inhibitory action, as indicated by 9-hour Cox-2 Area over the Inhibition Curve (AOC); however, hops powder or hops resin extract produced a 9-hour Cox-1 / Cox-2 AOC ratio of about 0.4 (i.e., some degree of Cox-1 sparing), compared to 1.5 for ibuprofen (i.e. no Cox-1 sparing). Conclusion: Hops exhibited Cox-2 inhibition over 9 hours equivalent to ibuprofen 400 mg but had significant Cox-1 sparing activity relative to ibuprofen. Hops extracts may represent a safe alternative to ibuprofen for non-prescription anti-inflammation.

 

PMID: 15294636 [PubMed - in process]

 

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[viii] Integr Cancer Ther. 2002 Mar;1(1):7-37; discussion 37.

 

Nutritional and botanical modulation of the inflammatory cascade--eicosanoids, cyclooxygenases, and lipoxygenases--as an adjunct in cancer therapy.

 

Wallace JM.

 

Nutritional Solutions, Inc., 2935 North, 1000 East, North Logan, UT 84341, USA. BTnutrition@aol.com

 

Emerging on the horizon in cancer therapy is an expansion of the scope of treatment beyond cytotoxic approaches to include molecular management of cancer physiopathology. The goal in these integrative approaches, which extends beyond eradicating the affected cells, is to control the cancer phenotype. One key new approach appears to be modulation of the inflammatory cascade, as research is expanding that links cancer initiation, promotion, progression, angiogenesis, and metastasis to inflammatory events. This article presents a literature review of the emerging relationship between neoplasia and inflammatory eicosanoids (PGE2 and related prostaglandins), with a focus on how inhibition of their synthesizing oxidases, particularly cyclooxygenase (COX), offers anticancer actions in vitro and in vivo. Although a majority of this research emphasizes the pharmaceutical applications of nonsteroidal anti-inflammatory drugs and selective COX-2 inhibitors, these agents fail to address alternate pathways available for the synthesis of proinflammatory eicosanoids. Evidence is presented that suggests the inhibition of lipoxygenase and its by-products-LTB4, 5-HETE, and 12-HETE-represents an overlooked but crucial component in complementary cancer therapies. Based on the hypothesis that natural agents capable of modulating both lipoxygenase and COX may advance the efficacy of cancer therapy, an overview and discussion is presented of dietary modifications and selected nutritional and botanical agents (notably, omega-3 fatty acids, antioxidants, boswellia, bromelain, curcumin, and quercetin) that favorably influence eicosanoid production.

 

Publication Types:

Review

 

PMID: 14664746 [PubMed - indexed for MEDLINE]

 

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