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Yin K, Smith AG. Nuclear receptor function in skin health and disease: therapeutic opportunities in the orphan and adopted receptor classes. Cell Mol Life Sci 2016; 73:3789-800. [PMID: 27544210 PMCID: PMC11108460 DOI: 10.1007/s00018-016-2329-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 08/04/2016] [Indexed: 12/12/2022]
Abstract
The skin forms a vital barrier between an organism's external environment, providing protection from pathogens and numerous physical and chemical threats. Moreover, the intact barrier is essential to prevent water and electrolyte loss without which terrestrial life could not be maintained. Accordingly, acute disruption of the skin through physical or chemical trauma needs to be repaired timely and efficiently as sustained skin pathologies ranging from mild irritations and inflammation through to malignancy impact considerably on morbidity and mortality. The Nuclear Hormone Receptor Family of transcriptional regulators has proven to be highly valuable targets for addressing a range of pathologies, including metabolic syndrome and cancer. Indeed members of the classic endocrine sub-group, such as the glucocorticoid, retinoid, and Vitamin D receptors, represent mainstay treatment strategies for numerous inflammatory skin disorders, though side effects from prolonged use are common. Emerging evidence has now highlighted important functional roles for nuclear receptors belonging to the adopted and orphan subgroups in skin physiology and patho-physiology. This review will focus on these subgroups and explore the current evidence that suggests these nuclear receptor hold great promise as future stand-alone or complementary drug targets in treating common skin diseases and maintaining skin homeostasis.
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Affiliation(s)
- Kelvin Yin
- School of Biomedical Sciences, University of Queensland, Brisbane, QLD, 4072, Australia
| | - Aaron G Smith
- Dermatology Research Centre, School of Medicine, University of Queensland, Brisbane, QLD, 4072, Australia.
- School of Biomedical Science, Institute of Health and Biomedical Innovation at the Translational Research Institute, Queensland University of Technology, Woolloongabba, QLD, 4102, Australia.
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2
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Nagayama K, Morino K, Sekine O, Nakagawa F, Ishikado A, Iwasaki H, Okada T, Tawa M, Sato D, Imamura T, Nishio Y, Ugi S, Kashiwagi A, Okamura T, Maegawa H. Duality of n-3 Polyunsaturated Fatty Acids on Mcp-1 Expression in Vascular Smooth Muscle: A Potential Role of 4-Hydroxy Hexenal. Nutrients 2015; 7:8112-26. [PMID: 26402697 PMCID: PMC4586576 DOI: 10.3390/nu7095381] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 08/24/2015] [Accepted: 08/31/2015] [Indexed: 01/12/2023] Open
Abstract
N-3 polyunsaturated fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have protective effects against atherosclerosis. Monocyte chemotactic protein (MCP)-1 is a major inflammatory mediator in the progression of atherosclerosis. However, little is known about the regulation of MCP-1 by DHA and EPA in vessels and vascular smooth muscle cells (VSMCs). In this study, we compared the effect of DHA and EPA on the expression of Mcp-1 in rat arterial strips and rat VSMCs. DHA, but not EPA, suppressed Mcp-1 expression in arterial strips. Furthermore, DHA generated 4-hydroxy hexenal (4-HHE), an end product of n-3 polyunsaturated fatty acids (PUFAs), in arterial strips as measured by liquid chromatography-tandem mass spectrometry. In addition, 4-HHE treatment suppressed Mcp-1 expression in arterial strips, suggesting 4-HHE derived from DHA may be involved in the mechanism of this phenomenon. In contrast, Mcp-1 expression was stimulated by DHA, EPA and 4-HHE through p38 kinase and the Keap1-Nuclear factor erythroid-derived 2-like 2 (Nrf2) pathway in VSMCs. In conclusion, there is a dual effect of n-3 PUFAs on the regulation of Mcp-1 expression. Further study is necessary to elucidate the pathological role of this phenomenon.
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MESH Headings
- Aldehydes/metabolism
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/metabolism
- Cells, Cultured
- Chemokine CCL2/genetics
- Chemokine CCL2/metabolism
- Chromatography, Liquid
- Docosahexaenoic Acids/pharmacology
- Dose-Response Relationship, Drug
- Down-Regulation
- Eicosapentaenoic Acid/pharmacology
- In Vitro Techniques
- Male
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- NF-E2-Related Factor 2/metabolism
- RNA Interference
- Rats, Sprague-Dawley
- Signal Transduction/drug effects
- Tandem Mass Spectrometry
- Time Factors
- Transfection
- p38 Mitogen-Activated Protein Kinases/metabolism
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Affiliation(s)
- Kohji Nagayama
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Katsutaro Morino
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Osamu Sekine
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Fumiyuki Nakagawa
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
- Osaka Laboratory, JCL Bioassay Corporation, 5-16-26, Minamisuita, Suita-shi, Osaka 564-0043, Japan.
| | - Atsushi Ishikado
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
- Sunstar Inc., 3-1 Asahi-machi, Takatsuki, Osaka 569-1195, Japan.
- Joslin Diabetes Centre, Harvard Medical School, MA 02115, USA.
| | - Hirotaka Iwasaki
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
- Department of Pharmacology, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Takashi Okada
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Masashi Tawa
- Department of Pharmacology, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Daisuke Sato
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Takeshi Imamura
- Department of Pharmacology, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Yoshihiko Nishio
- Department of Diabetes and Endocrine Medicine, Kagoshima University, Kagoshima 890-8580, Japan.
| | - Satoshi Ugi
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Atsunori Kashiwagi
- Kusatsu General Hospital, 1660, Yabase-cho, Kusatsu, Shiga 525-8585, Japan.
| | - Tomio Okamura
- Department of Pharmacology, Shiga University of Medical Science, Shiga 520-2192, Japan.
| | - Hiroshi Maegawa
- Department of Medicine, Shiga University of Medical Science, Shiga 520-2192, Japan.
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3
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Jing K, Shin S, Jeong S, Kim S, Song KS, Park JH, Heo JY, Seo KS, Park SK, Kweon GR, Wu T, Park JI, Lim K. Docosahexaenoic acid induces the degradation of HPV E6/E7 oncoproteins by activating the ubiquitin-proteasome system. Cell Death Dis 2014; 5:e1524. [PMID: 25393480 PMCID: PMC4260735 DOI: 10.1038/cddis.2014.477] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 09/20/2014] [Accepted: 10/06/2014] [Indexed: 01/24/2023]
Abstract
The oncogenic human papillomavirus (HPV) E6/E7 proteins are essential for the onset and maintenance of HPV-associated malignancies. Here, we report that activation of the cellular ubiquitin–proteasome system (UPS) by the omega-3 fatty acid, docosahexaenoic acid (DHA), leads to proteasome-mediated degradation of E6/E7 viral proteins and the induction of apoptosis in HPV-infected cancer cells. The increases in UPS activity and degradation of E6/E7 oncoproteins were associated with DHA-induced overproduction of mitochondrial reactive oxygen species (ROS). Exogenous oxidative stress and pharmacological induction of mitochondrial ROS showed effects similar to those of DHA, and inhibition of ROS production abolished UPS activation, E6/E7 viral protein destabilization, and apoptosis. These findings identify a novel role for DHA in the regulation of UPS and viral proteins, and provide evidence for the use of DHA as a mechanistically unique anticancer agent for the chemoprevention and treatment of HPV-associated tumors.
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Affiliation(s)
- K Jing
- 1] Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea [2] Infection Signaling Network Research Center, Chungnam National University, Daejeon, Korea [3] Stem Cell Research and Cellular Therapy Center, Affiliated Hospital of Guangdong Medical College, Zhanjiang, China
| | - S Shin
- 1] Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea [2] Infection Signaling Network Research Center, Chungnam National University, Daejeon, Korea
| | - S Jeong
- 1] Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea [2] Infection Signaling Network Research Center, Chungnam National University, Daejeon, Korea
| | - S Kim
- 1] Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea [2] Infection Signaling Network Research Center, Chungnam National University, Daejeon, Korea
| | - K-S Song
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - J-H Park
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - J-Y Heo
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - K-S Seo
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - S-K Park
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - G-R Kweon
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - T Wu
- Department of Pathology and Laboratory Medicine, Tulane University School of Medicine, New Orleans, LA, USA
| | - J-I Park
- Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea
| | - K Lim
- 1] Department of Biochemistry, School of Medicine, Chungnam National University, Daejeon, Korea [2] Infection Signaling Network Research Center, Chungnam National University, Daejeon, Korea [3] Cancer Research Institute, Chungnam National University, Daejeon, Korea
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4
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Wang C, Xia W, Jiang Q, Xu Y, Yu P. Differential effects of lipid fractions from silver carp brain on human cervical carcinoma cells in vitro. Food Funct 2014; 5:2194-201. [PMID: 25047635 DOI: 10.1039/c4fo00168k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Previous research has revealed that n3 polyunsaturated fatty acids (PUFAs) exhibit anticancer activities. Lipids from a fish brain contain substantial n3 PUFAs. However, no research has been conducted on the action and mechanism of their potent anticancer activities. In this study, total lipids (TLs) from silver carp brain were isolated into polar lipids (PLs) and neutral lipids (NLs), and the anticancer potential of the lipid fractions (LFs) was investigated using the human cervical carcinoma HeLa cell line. LFs effectively inhibited the cell proliferation of HeLa cells in a time- and dose-dependent manner by cell cycle arrest at the S stage and by inducing apoptosis. Further analyses indicated that the loss of mitochondrial membrane potential could be one of mechanisms of apoptosis induced by LFs. Among the TLs, PLs have proven to be more effective in inducing cervical carcinoma cell death than NLs. This work will play a role in promoting lipids from silver carp brain as a potential preventive and therapeutic agent against human cervical carcinoma.
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Affiliation(s)
- Caixia Wang
- State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
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5
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Zulfakar MH, Ong CM, Heard CM. The effects of betamethasone dipropionate and fish oil on HaCaT proliferation and apoptosis. Int J Pharm 2012; 434:399-405. [DOI: 10.1016/j.ijpharm.2012.06.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 05/31/2012] [Accepted: 06/03/2012] [Indexed: 12/28/2022]
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6
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Antiproliferative effect of docosahexaenoic acid on adult human keratinocytes in vitro / Antiproliferativni efekat dokosaheksanoične kiseline na adultne humane keratinocite in vitro. SERBIAN JOURNAL OF DERMATOLOGY AND VENEREOLOGY 2009. [DOI: 10.2478/v10249-011-0005-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Abstract
Numerous clinical studies demonstrate benefits of dietary supplementation with fish oils in autoimmune diseases and other inflammatory diseases such as psoriasis, multiple sclerosis, systemic lupus erythematodes and so on. Docosahexaenoic acid (DHA) is an omega-3 fatty acid which is abundantly found in fish oil. In the present study we investigated effects of DHA on proliferation of human keratinocytes established from skin of seven adult donors, cultivated in growth medium that allows optimal cell proliferation. We found a dose-dependent inhibition of cell proliferation when keratinocytes were incubated with 6.25, 12.5 and 25 -μM of DHA. Inhibition of proliferative capacity considerably varied in keratinocyte cultures derived from different donors, particularly when incubated with the lowest concentration of the assessed substance. Lactate dehydrogenase-release assay excluded necrosis of cultivated keratinocytes as a cause of decreased proliferation. Our results suggest that DHA may potentially be used as a routine adjuvant therapy, with classical therapy of inflammatory hyperproliferative skin diseases.
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7
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Schmuth M, Jiang YJ, Dubrac S, Elias PM, Feingold KR. Thematic review series: skin lipids. Peroxisome proliferator-activated receptors and liver X receptors in epidermal biology. J Lipid Res 2008; 49:499-509. [PMID: 18182682 DOI: 10.1194/jlr.r800001-jlr200] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The epidermis is a very active site of lipid metabolism, and all peroxisome proliferator-activated receptor (PPAR) and liver X receptor (LXR) isoforms are expressed in the epidermis. Activation of PPARalpha, -beta/delta, or -gamma or LXRs stimulates keratinocyte differentiation. Additionally, activation of these receptors also improves permeability barrier homeostasis by a number of mechanisms, including stimulating epidermal lipid synthesis, increasing lamellar body formation and secretion, and increasing the activity of enzymes required for the extracellular processing of lipids in the stratum corneum, leading to the formation of lamellar membranes that mediate permeability barrier function. The stimulation of keratinocyte differentiation and permeability barrier formation also occurs during fetal development, resulting in accelerated epidermal development. PPAR and LXR activation regulates keratinocyte proliferation and apoptosis, and studies have shown that these receptors play a role in cutaneous carcinogenesis. Lastly, PPAR and LXR activation is anti-inflammatory, reducing inflammation in animal models of allergic and irritant contact dermatitis. Because of their broad profile of beneficial effects on skin homeostasis, PPAR and LXR have great potential to serve as drug targets for common skin diseases such as psoriasis, atopic dermatitis, and skin cancer.
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Affiliation(s)
- Matthias Schmuth
- Department of Dermatology, University of California, San Francisco, CA, USA.
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8
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Auborn KJ. Can indole-3-carbinol-induced changes in cervical intraepithelial neoplasia be extrapolated to other food components? J Nutr 2006; 136:2676S-8S. [PMID: 16988146 DOI: 10.1093/jn/136.10.2676s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Karen J Auborn
- North Shore LIJ Institute for Medical Research, Manhasset, NY 11030, USA.
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9
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Abstract
PURPOSE OF REVIEW This review discusses recent advances in delineating basic mechanisms underlying the beneficial effects of omega-3 fatty acids on health and on disease. RECENT FINDINGS While a substantial number of studies have delineated many differences between the biological effects of saturated versus polyunsaturated fatty acids, less is known about the long-chain omega-3 fatty acids commonly present in certain fish oils. In this review, we focus on recent studies relating to basic mechanisms whereby omega-3 fatty acids modulate cellular pathways to exert beneficial effects on promoting health and decreasing risks of certain diseases. We will use, as examples, conditions of the cardiovascular, neurological, and immunological systems as well as diabetes and cancer, and then discuss basic regulatory pathways. SUMMARY Omega-3 fatty acids are major regulators of multiple molecular pathways, altering many areas of cellular and organ function, metabolism and gene expression. Generally, these regulatory events lead to "positive" endpoints relating to health and disease.
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Affiliation(s)
- Toru Seo
- Department of Pediatrics, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University, 630 W. 168th Street, New York, NY 10032, USA
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10
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Siddiqui RA, Jenski LJ, Wiesehan JD, Hunter MV, Kovacs RJ, Stillwell W. Prevention of docosahexaenoic acid-induced cytotoxicity by phosphatidic acid in Jurkat leukemic cells: the role of protein phosphatase-1. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1541:188-200. [PMID: 11755213 DOI: 10.1016/s0167-4889(01)00143-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The present investigation explores the role of phosphatidic acid (PA), a specific protein phosphatase-1 (PP1) inhibitor, in cytotoxicity induced by docosahexaenoic acid (DHA). The cytotoxicity of DHA was assayed by quantifying cell survival using the trypan blue exclusion method. A dose-response effect demonstrated that 5 or 10 microM DHA has no effect on Jurkat cell survival; however, 15 microM DHA rapidly decreased cell survival to 40% within 2 h of treatment. Cytotoxicity of 15 microM DHA was prevented by PA. Structurally similar phospholipids (lysophosphatidic acid, sphingosine 1-phosphate, sphingosine, and sphingosine phosphocholine) or metabolites of PA (lyso-PA and diacylglycerol) did not prevent DHA-induced cytotoxicity. PA did not produce micelles alone or in combination with DHA as examined spectrophotometrically, indicating that PA did not entrap DHA and therefore did not affect the amount of DHA available to the cells. Supporting this observation, the uptake or incorporation of [1-14C]DHA in Jurkat cells was not affected by the presence of PA. However, PA treatment reduced the amount of DHA-induced inorganic phosphate released from Jurkat leukemic cells and also inhibited DHA-induced dephosphorylation of cellular proteins. These observations indicate that PA has exerted its anti-cytotoxic effects by causing inhibition of protein phosphatase activities. Cytotoxicity of DHA on Jurkat cells was also blocked by the use of a highly specific caspase-3 inhibitor (N-acetyl-ala-ala-val-ala-leu-leu-pro-ala-val-leu-leu-ala-leu-leu-ala-pro-asp-glu-val-asp-CHO), indicating that the cytotoxic effects of DHA were due to the induction of apoptosis though activation of caspase-3. Consistent with these data, proteolytic activation of procaspase-3 was also evident when examined by immunoblotting. PA prevented procaspase-3 degradation in DHA-treated cells, indicating that PA causes inhibition of DHA-induced apoptosis in Jurkat leukemic cells. Since DHA-induced apoptosis can be inhibited by PA, we conclude that the process is mediated through activation of PP1.
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Affiliation(s)
- R A Siddiqui
- Cellular Biochemistry Laboratory, Methodist Research Institute at Clarian Health, Indianapolis, IN 46202, USA.
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11
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Chen DZ, Qi M, Auborn KJ, Carter TH. Indole-3-carbinol and diindolylmethane induce apoptosis of human cervical cancer cells and in murine HPV16-transgenic preneoplastic cervical epithelium. J Nutr 2001; 131:3294-302. [PMID: 11739883 DOI: 10.1093/jn/131.12.3294] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Dietary indole-3-carbinol (I3C) has clinical benefits for both cervical cancer and laryngeal papillomatosis, and causes apoptosis of breast cancer cells in vitro. We asked whether I3C and its major acid-catalyzed condensation product diindolylmethane (DIM), which is produced in the stomach after consumption of cruciferous vegetables, could induce apoptosis of cervical cancer cell lines. We also asked whether this effect could be observed in vivo. In vitro, both I3C and DIM caused accumulation of DNA strand breaks in three cervical cancer cell lines. Induction of apoptosis was confirmed by nuclear morphology, nucleosome leakage, altered cytoplasmic membrane permeability and caspase 3 activation. Neither I3C nor DIM caused apoptotic changes in normal human keratinocytes. In C33A cervical cancer cells, DIM was more potent than I3C [dose at which the number of viable cells was 50% of that in untreated cultures (LD(50)) = 50-60 micromol/L for DIM and 200 micromol/L for I3C in a mitochondrial function assay] and faster acting. Furthermore, I3C reduced Bcl-2 protein in a time- and dose-dependent manner. In HPV16-transgenic mice, which develop cervical cancer after chronic estradiol exposure, apoptotic cells were detected in cervical epithelium by TdT-mediated dUTP nick-end labeling staining and by immunohistochemical staining of active caspase 3 only in mice exposed to 17beta-estradiol (E2) and fed I3C. Rare apoptotic cells were also observed by hematoxylin and eosin staining in the spinous layer of the cervical epithelium in both control and transgenic mice. Estradiol reduced the percentage of these late-stage apoptotic cells in the cervical epithelium of transgenic, E2-treated mice, but this reduction was prevented by I3C. These data confirm the proapoptotic action of I3C on transformed cells in vitro, extend the observations to cervical cancer cells and to DIM and show for the first time that dietary I3C results in increased apoptosis in target tissues in vivo.
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Affiliation(s)
- D Z Chen
- North Shore-Long Island Jewish Research Institute, Manhasset, NY 11030, USA
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12
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Siddiqui RA, Jenski LJ, Neff K, Harvey K, Kovacs RJ, Stillwell W. Docosahexaenoic acid induces apoptosis in Jurkat cells by a protein phosphatase-mediated process. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1499:265-75. [PMID: 11341974 DOI: 10.1016/s0167-4889(00)00128-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Docosahexaenoic acid (DHA) is an omega-3 fatty acid under intense investigation for its ability to modulate cancer cell growth and survival. This research was performed to study the cellular and molecular effects of DHA. Our experiments indicated that the treatment of Jurkat cells with DHA inhibited their survival, whereas similar concentrations (60 and 90 microM) of arachidonic acid and oleic acid had little effect. To explore the mechanism of inhibition, we used several measures of apoptosis to determine whether this process was involved in DHA-induced cell death in Jurkat cells. Caspase-3, an important cytosolic downstream regulator of apoptosis, is activated by death signals through proteolytic cleavage. Incubation of Jurkat cells with 60 and 90 microM DHA caused proteolysis of caspase-3 within 48 and 24 h, respectively. DHA treatment also caused the degradation of poly-ADP-ribose polymerase and DNA fragmentation as assayed by flow cytometric TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay. These results indicate that DHA induces apoptosis in Jurkat leukemic cells. DHA-induced apoptosis was effectively inhibited by tautomycin and cypermethrin at concentrations that affect protein phosphatase 1 (PP1) and protein phosphatase 2B (PP2B) activities, respectively, implying a role for these phosphatases in the apoptotic pathway. Okadaic acid, an inhibitor of protein phosphatase 2A, had no effect on DHA-induced apoptosis. These results suggest that one mechanism through which DHA may control cancer cell growth is through apoptosis involving PP1/PP2B protein phosphatase activities.
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Affiliation(s)
- R A Siddiqui
- Cellular Biochemistry Laboratory, Methodist Research Institute at Clarian Health, Indianapolis, IN 46202, USA.
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