51
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Tayem Y, Green CJ, Motterlini R, Foresti R. Isothiocyanate–cysteine conjugates protect renal tissue against cisplatin-induced apoptosis via induction of heme oxygenase-1. Pharmacol Res 2014; 81:1-9. [DOI: 10.1016/j.phrs.2014.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 01/02/2014] [Accepted: 01/03/2014] [Indexed: 12/27/2022]
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52
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Sikalidis AK, Mazor KM, Lee JI, Roman HB, Hirschberger LL, Stipanuk MH. Upregulation of capacity for glutathione synthesis in response to amino acid deprivation: regulation of glutamate-cysteine ligase subunits. Amino Acids 2014; 46:1285-96. [PMID: 24557597 DOI: 10.1007/s00726-014-1687-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 01/29/2014] [Indexed: 12/22/2022]
Abstract
Using HepG2/C3A cells and MEFs, we investigated whether induction of GSH synthesis in response to sulfur amino acid deficiency is mediated by the decrease in cysteine levels or whether it requires a decrease in GSH levels per se. Both the glutamate-cysteine ligase catalytic (GCLC) and modifier (GCLM) subunit mRNA levels were upregulated in response to a lack of cysteine or other essential amino acids, independent of GSH levels. This upregulation did not occur in MEFs lacking GCN2 (general control non-derepressible 2, also known as eIF2α kinase 4) or in cells expressing mutant eIF2α lacking the eIF2α kinase Ser(51) phosphorylation site, indicating that expression of both GCLC and GCLM was mediated by the GCN2/ATF4 stress response pathway. Only the increase in GCLM mRNA level, however, was accompanied by a parallel increase in protein expression, suggesting that the enhanced capacity for GSH synthesis depended largely on increased association of GCLC with its regulatory subunit. Upregulation of both GCLC and GLCM mRNA levels in response to cysteine deprivation was dependent on new protein synthesis, which is consistent with expression of GCLC and GCLM being mediated by proteins whose synthesis depends on activation of the GCN2/ATF4 pathway. Our data suggest that the regulation of GCLC expression may be mediated by changes in the abundance of transcriptional regulators, whereas the regulation of GCLM expression may be mediated by changes in the abundance of mRNA stabilizing or destabilizing proteins. Upregulation of GCLM levels in response to low cysteine levels may serve to protect the cell in the face of a future stress requiring GSH as an antioxidant or conjugating/detoxifying agent.
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Affiliation(s)
- Angelos K Sikalidis
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
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Sulforaphane as a potential protective phytochemical against neurodegenerative diseases. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2013; 2013:415078. [PMID: 23983898 PMCID: PMC3745957 DOI: 10.1155/2013/415078] [Citation(s) in RCA: 189] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/28/2013] [Accepted: 07/03/2013] [Indexed: 12/30/2022]
Abstract
A wide variety of acute and chronic neurodegenerative diseases, including ischemic/traumatic brain injury, Alzheimer's disease, and Parkinson's disease, share common characteristics such as oxidative stress, misfolded proteins, excitotoxicity, inflammation, and neuronal loss.
As no drugs are available to prevent the progression of these neurological disorders, intervention strategies using phytochemicals have been proposed as an alternative form of treatment. Among phytochemicals, isothiocyanate sulforaphane, derived from the hydrolysis of the glucosinolate glucoraphanin mainly present in Brassica vegetables, has demonstrated neuroprotective effects in several in vitro and in vivo studies. In particular, evidence suggests that sulforaphane beneficial effects could be mainly ascribed to its peculiar ability to activate the Nrf2/ARE pathway. Therefore, sulforaphane appears to be a promising compound with neuroprotective properties that may play an important role in preventing neurodegeneration.
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Morroni F, Tarozzi A, Sita G, Bolondi C, Zolezzi Moraga JM, Cantelli-Forti G, Hrelia P. Neuroprotective effect of sulforaphane in 6-hydroxydopamine-lesioned mouse model of Parkinson's disease. Neurotoxicology 2013; 36:63-71. [PMID: 23518299 DOI: 10.1016/j.neuro.2013.03.004] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 03/04/2013] [Accepted: 03/11/2013] [Indexed: 12/18/2022]
Abstract
Parkinson's disease (PD) is characterized by the selective loss of dopaminergic nigrostriatal neurons, which leads to disabling motor disturbances. Sulforaphane (SFN), found in cruciferous vegetables, is a potent indirect antioxidant and recent advances have shown its neuroprotective activity in various experimental models of neurodegeneration. This study was undertaken to examine the effects of SFN on behavioral changes and dopaminergic neurotoxicity in mice exposed to 6-hydroxydopamine (6-OHDA). For this purpose, mice were treated with SFN (5mg/kg twice a week) for four weeks after the unilateral intrastriatal injection of 6-OHDA. The increase in 6-OHDA-induced rotations and deficits in motor coordination were ameliorated significantly by SFN treatment. In addition, SFN protected 6-OHDA-induced apoptosis via blocking DNA fragmentation and caspase-3 activation. These results were further supported by immunohistochemical findings in the substantia nigra that showed that SFN protected neurons from neurotoxic effects of 6-OHDA. The neuroprotective effect of SFN may be attributed to its ability to enhance glutathione levels and its dependent enzymes (glutathione-S-transferase and glutathione reductase) and to modulate neuronal survival pathways, such as ERK1/2, in the brain of mice. These results suggest that SFN may potentially be effective in slowing down the progression of idiopathic PD by the modulation of oxidative stress and apoptotic machinery.
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Affiliation(s)
- Fabiana Morroni
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Bologna, Italy.
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55
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Gillespie S, Gavins FNE. Phytochemicals: countering risk factors and pathological responses associated with ischaemia reperfusion injury. Pharmacol Ther 2012; 138:38-45. [PMID: 23269179 DOI: 10.1016/j.pharmthera.2012.12.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 11/19/2012] [Indexed: 01/20/2023]
Abstract
Plant derived non-nutritive molecules, known as phytochemicals, have been investigated for their ability to provide protection against inflammation. Emerging studies of several vasculopathies (e.g. atherosclerosis, hypertension) provide novel data to support these anti-inflammatory effects and offer evidence for involvement of host pathways. Fundamental mechanisms of action are common amongst these compounds, and furthermore, the administration of these phytochemicals activates host defence pathways innately present to protect cells from oxidative stress. This review will elucidate the real benefit of therapeutic intervention with these phytochemicals for vasculopathies, and associated ischaemia reperfusion injury in both the heart and brain.
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56
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Mastaloudis A, Wood SM. Age-related changes in cellular protection, purification, and inflammation-related gene expression: role of dietary phytonutrients. Ann N Y Acad Sci 2012; 1259:112-20. [PMID: 22758643 DOI: 10.1111/j.1749-6632.2012.06610.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Oxidative injury and inflammation are intimately involved in the aging process and the development of age-related diseases. To date, most nutritional antiaging strategies have focused solely on the delivery of exogenous antioxidants to combat the negative effects of aging. A promising new strategy is to identify nutrients and phytochemicals that can directly target intrinsic cytoprotective mechanisms, including modulation of the expression of (1) genes involved in the detoxification of xenobiotics, (2) genes involved in the synthesis and regulation of intrinsic antioxidants and antioxidant enzymes, (3) genes involved in the regulation of inflammation, and (4) vitagenes. The purpose of this review is to provide an overview of the age-related changes in gene expression related to oxidative stress, detoxification, and inflammatory processes, and to discuss natural compounds with the potential to oppose age-related changes in gene expression related to these processes, which therefore may be suitable for use in human antiaging research.
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57
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Genetic evidence of an evolutionarily conserved role for Nrf2 in the protection against oxidative stress. Mol Cell Biol 2012; 32:4455-61. [PMID: 22949501 DOI: 10.1128/mcb.00481-12] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Transcription factor Nrf2 is considered a master regulator of antioxidant defense in mammals. However, it is unclear whether this concept is applicable to nonmammalian vertebrates, because no animal model other than Nrf2 knockout mice has been generated to examine the effects of Nrf2 deficiency. Here, we characterized a recessive loss-of-function mutant of Nrf2 (nrf2(fh318)) in a lower vertebrate, the zebrafish (Danio rerio). In keeping with the findings in the mouse model, nrf2(fh318) mutants exhibited reduced induction of the Nrf2 target genes in response to oxidative stress and electrophiles but were viable and fertile, and their embryos developed normally. The nrf2(fh318) larvae displayed enhanced sensitivity to oxidative stress and electrophiles, especially peroxides, and pretreatment with an Nrf2-activating compound, sulforaphane, decreased peroxide-induced lethality in the wild type but not nrf2(fh318) mutants, indicating that resistance to oxidative stress is highly dependent on Nrf2 functions. These results reveal an evolutionarily conserved role of vertebrate Nrf2 in protection against oxidative stress. Interestingly, there were no significant differences between wild-type and nrf2(fh318) larvae with regard to their sensitivity to superoxide and singlet oxygen generators, suggesting that the importance of Nrf2 in oxidative stress protection varies based on the type of reactive oxygen species (ROS).
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58
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Tarozzi A, Morroni F, Bolondi C, Sita G, Hrelia P, Djemil A, Cantelli-Forti G. Neuroprotective effects of erucin against 6-hydroxydopamine-induced oxidative damage in a dopaminergic-like neuroblastoma cell line. Int J Mol Sci 2012; 13:10899-10910. [PMID: 23109827 PMCID: PMC3472719 DOI: 10.3390/ijms130910899] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 08/20/2012] [Accepted: 08/22/2012] [Indexed: 11/16/2022] Open
Abstract
Oxidative stress (OS) contributes to the cascade leading to the dysfunction or death of dopaminergic neurons during Parkinson’s disease (PD). A strategy to prevent the OS of dopaminergic neurons may be the use of phytochemicals as inducers of endogenous antioxidants and phase 2 enzymes. In this study, we demonstrated that treatment of the dopaminergic-like neuroblastoma SH-SY5Y cell line with isothiocyanate erucin (ER), a compound of cruciferous vegetables, resulted in significant increases of both total glutathione (GSH) levels and total antioxidant capacity at the cytosolic level. The increase of GSH levels was associated with an increase in the resistance of SH-SY5Y cells to neuronal death, in terms of apoptosis, induced by 6-hydroxydopamine (6-OHDA). The pretreatment of SH-SY5Y cells with ER was also shown to prevent the redox status impairment, in terms of intracellular ROS and O2•− formation, and loss of mitochondrial membrane potential, early events that are initiators of the apoptotic process, induced by 6-OHDA. Last, the antiapoptotic and antioxidant effects of ER were abolished by buthionine sulfoximine, supporting the main role of GSH in the neuroprotective effects recorded by ER. These results suggest that ER may prevent the oxidative damage induced by 6-OHDA.
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Affiliation(s)
- Andrea Tarozzi
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +39-51-2091810; Fax: +39-51-248862
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59
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Wright KE, MacRobert AJ, Phillips JB. Inhibition of Specific Cellular Antioxidant Pathways Increases the Sensitivity of Neurons to Meta-tetrahydroxyphenyl Chlorin-Mediated Photodynamic Therapy in a 3D Co-culture Model. Photochem Photobiol 2012; 88:1539-45. [DOI: 10.1111/j.1751-1097.2012.01185.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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60
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Kachadourian R, Day BJ, Pugazhenti S, Franklin CC, Genoux-Bastide E, Mahaffey G, Gauthier C, Di Pietro A, Boumendjel A. A synthetic chalcone as a potent inducer of glutathione biosynthesis. J Med Chem 2012; 55:1382-8. [PMID: 22239485 DOI: 10.1021/jm2016073] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chalcones continue to attract considerable interest due to their anti-inflammatory and antiangiogenic properties. We recently reported the ability of 2',5'-dihydroxychalcone (2',5'-DHC) to induce both breast cancer resistance protein-mediated export of glutathione (GSH) and c-Jun N-terminal kinase-mediated increased intracellular GSH levels. Herein, we report a structure-activity relationship study of a series of 30 synthetic chalcone derivatives with hydroxyl, methoxyl, and halogen (F and Cl) substituents and their ability to increase intracellular GSH levels. This effect was drastically improved with one or two electrowithdrawing groups on phenyl ring B and up to three methoxyl and/or hydroxyl groups on phenyl ring A. The optimal structure, 2-chloro-4',6'-dimethoxy-2'-hydroxychalcone, induced both a potent NF-E2-related factor 2-mediated transcriptional response and an increased formation of glutamate cysteine ligase holoenzyme, as shown using a human breast cancer cell line stably expressing a luciferase reporter gene driven by antioxidant response elements.
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Affiliation(s)
- Remy Kachadourian
- Department of Medicine, National Jewish Health, Denver, Colorado 80206, United States.
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61
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Taka E, Mazzio E, Soliman KFA, Renee Reams R. Microarray genomic profile of mitochondrial and oxidant response in manganese chloride treated PC12 cells. Neurotoxicology 2012; 33:162-8. [PMID: 22281203 DOI: 10.1016/j.neuro.2012.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 01/04/2012] [Accepted: 01/06/2012] [Indexed: 11/28/2022]
Abstract
Environmental or occupational exposure to high levels of manganese (Mn) can lead to manganism, a symptomatic neuro-degenerative disorder similar to idiopathic Parkinson's disease. The underlying mechanism of Mn neurotoxicity remains unclear. In this study, we evaluate the primary toxicological events associated with MnCl(2) toxicity in rat PC12 cells using whole genome cDNA microarray, RT-PCR, Western blot and functional studies. The results show that a sub-lethal dose range (38-300 μM MnCl(2)) initiated slight metabolic stress evidenced by heightened glycolytic rate and induction of enolase/aldolase - gene expression. The largest shift observed in the transcriptome was MnCl(2) induction of heme-oxygenase 1 (HO-1) [7.7 fold, p<0.001], which was further corroborated by RT-PCR and Western blot studies. Concentrations in excess of 300 μM corresponded to dose dependent loss of cell viability which was associated with enhanced production of H(2)O(2) concomitant to elevation of gene expression for diverse antioxidant enzymes; biliverdin reductase, arsenite inducible RNA associated protein, dithiolethione-inducible gene-1 (DIG-1) and thioredoxin reductase 1. Moreover, Mn initiated significant reduction of gene expression of mitochondrial glutaryl-coenzyme A dehydrogenase (GCDH), an enzyme involved with glutaric acidemia, oxidative stress, lipid peroxidation and striatal degeneration observed in association with severe dystonic-dyskinetic movement disorder. Future research will be required to elucidate a defined role for HO-1 and GCDH in Mn toxicity.
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Affiliation(s)
- Equar Taka
- College of Pharmacy and Pharmaceutical Sciences, Florida A & M University, Tallahassee, FL 32307, USA
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62
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Xu LW, Kluwe L, Zhang TT, Li SN, Mou YY, Sang Z, Ma J, Lu X, Sun ZJ. Chinese herb mix Tiáo-Gēng-Tāng possesses antiaging and antioxidative effects and upregulates expression of estrogen receptors alpha and beta in ovariectomized rats. Altern Ther Health Med 2011; 11:137. [PMID: 22206438 PMCID: PMC3286390 DOI: 10.1186/1472-6882-11-137] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 12/30/2011] [Indexed: 11/30/2022]
Abstract
Background Herb mixtures are widely used as an alternative to hormonal therapy in China for treatment of the menopausal syndrome. However, composition of these herb mixtures are complex and their working mechanism is often unknown. This study investigated the effect of Tiáo-Gēng-Tāng (TG-decoction), a Chinese herbal mixture extract, in balancing female hormones, regulating expression of estrogen receptors (ERs), and preventing aging-related tissue damage. Methods Ovariectomized 5-month-old female rats were used to model menopause and treated with either TG-decoction or conjugated estrogen for 8 weeks. Estradiol (E2), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured in serum and in the hypothalamus. Hypothalamic expression of estrogen receptor (ER) alpha and beta were studied by real-time PCR and western blotting. Total antioxidant capacity (T-AOC), oxidation indicator superoxide dismutase (SOD) activity and tissue damage parameter malondialdehyde (MDA) were measured using standard assays. Aging-related ultrastructural alterations in mitochondria were studied in all animals by transmission electron microscopy. Results TG-decoction-treatment elevated E2 and lowered FSH in serum of ovariectomized rats. The potency and efficacy of TG-decoction on the hypothalamus was generally weaker than that of conjugated estrogens. However, TG-decoction was superior in upregulating expression of ERα and β. TG-decoction increased hypothalamic SOD and T-AOC levels and decreased MDAlevels and mitochondrial damage in hypothalamic neurons. Conclusions TG-decoction balances female hormones similarly to conjugated estrogens but less effectively. However, it is superior in up regulating ERα and β and exhibits antioxidative antiaging activities. Whilst it shares similar effects with estrogen, TG-decoction also seems to have distinctive and more complex functions and activities.
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Fimognari C, Turrini E, Ferruzzi L, Lenzi M, Hrelia P. Natural isothiocyanates: genotoxic potential versus chemoprevention. Mutat Res 2011; 750:107-131. [PMID: 22178957 DOI: 10.1016/j.mrrev.2011.12.001] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 12/01/2011] [Accepted: 12/02/2011] [Indexed: 12/12/2022]
Abstract
Isothiocyanates, occurring in many dietary cruciferous vegetables, show interesting chemopreventive activities against several chronic-degenerative diseases, including cancer, cardiovascular diseases, neurodegeneration, diabetes. The electrophilic carbon residue in the isothiocyanate moiety reacts with biological nucleophiles and modification of proteins is recognized as a key mechanism underlying the biological activity of isothiocyanates. The nuclear factor-erythroid-2-related factor 2 system, which orchestrates the expression of a wide array of antioxidant genes, plays a role in the protective effect of isothiocyanates against almost all the pathological conditions reported above. Recent emerging findings suggest a further common mechanism. Chronic inflammation plays a central role in many human diseases and isothiocyanates inhibit the activity of many inflammation components, suppress cyclooxygenase 2, and irreversibly inactivate the macrophage migration inhibitory factor. Due to their electrophilic reactivity, some isothiocyanates are able to form adducts with DNA and induce gene mutations and chromosomal aberrations. DNA damage has been demonstrated to be involved in the pathogenesis of various chronic-degenerative diseases of epidemiological relevance. Thus, the genotoxicity of the isothiocyanates should be carefully considered. In addition, the dose-response relationship for genotoxic compounds does not suggest evidence of a threshold. Thus, chemicals that are genotoxic pose a greater potential risk to humans than non-genotoxic compounds. Dietary consumption levels of isothiocyanates appear to be several orders of magnitude lower than the doses used in the genotoxicity studies and thus it is highly unlikely that such toxicities would occur in humans. However, the beneficial properties of isothiocyanates stimulated an increase of dietary supplements and functional foods with highly enriched isothiocyanate concentrations on the market. Whether such concentrations may exert a potential health risk cannot be excluded with certainty and an accurate evaluation of the toxicological profile of isothiocyanates should be prompted before any major increase in their consumption be recommended or their clinical use suggested.
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Affiliation(s)
- Carmela Fimognari
- Department of Pharmacology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy.
| | - Eleonora Turrini
- Department of Pharmacology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy
| | - Lorenzo Ferruzzi
- Department of Pharmacology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy
| | - Monia Lenzi
- Department of Pharmacology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy
| | - Patrizia Hrelia
- Department of Pharmacology, University of Bologna, via Irnerio 48, 40126 Bologna, Italy
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Pan MH, Lai CS, Tsai ML, Wu JC, Ho CT. Molecular mechanisms for anti-aging by natural dietary compounds. Mol Nutr Food Res 2011; 56:88-115. [PMID: 22083941 DOI: 10.1002/mnfr.201100509] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 08/20/2011] [Accepted: 09/02/2011] [Indexed: 12/11/2022]
Abstract
Aging is defined as a normal decline in survival with advancing age; however, the recent researches have showed that physiological functions of the body change during the aging process. Majority of the changes are often subject to a higher risk of developing diseases, such as cardiovascular disease, type II diabetes, Alzheimer's disease, Parkinson's disease, as well as the dysregulated immune and inflammatory disorders. Aging process is controlled by a complicated and precise signaling network that involved in energy homeostasis, cellular metabolism and stress resistance. Over the past few decades, research in natural dietary compounds by various organism and animal models provides a new strategy for anti-aging. Natural dietary compounds act through a variety mechanisms to extend lifespan and prevent age-related diseases. This review summarizes the current understanding on signaling pathways of aging and knowledge and underlying mechanism of natural dietary compounds that provide potential application on anti-aging and improve heath in human.
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Affiliation(s)
- Min-Hsiung Pan
- Department of Seafood Science, National Kaohsiung Marine University, Kaohsiung, Taiwan.
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Blum NM, Mueller K, Hirche F, Lippmann D, Most E, Pallauf J, Linn T, Mueller AS. Glucoraphanin does not reduce plasma homocysteine in rats with sufficient Se supply via the induction of liver ARE-regulated glutathione biosynthesis enzymes. Food Funct 2011; 2:654-64. [PMID: 21959850 DOI: 10.1039/c1fo10122f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Data from human and animal trials have revealed contradictory results regarding the influence of selenium (Se) status on homocysteine (HCys) metabolism. It was hypothesised that sufficient Se reduces the flux of HCys through the transsulphuration pathway by decreasing the expression of glutathione (GSH) synthesising enzymes. Glucoraphanin (GRA) is a potent inducer of genes regulated via an antioxidant response element (ARE), including those of GSH biosynthesis. We tested the hypothesis that GRA supplementation to rat diets lowers plasma HCys levels by increasing GSH synthesis. Therefore 96 weaned albino rats were assigned to 8 groups of 12 and fed diets containing four different Se levels (15, 50, 150 and 450 μg kg(diet)(-1)), either without GRA (groups: C15, C50, C150 and C450) or in combination with 700 μmol GRA kg(diet)(-1) (groups G15, G50, G150 and G450). Rats fed the low Se diets C15 and G15 showed an impressive decrease of plasma HCys. Se supplementation increased plasma HCys and lowered GSH significantly by reducing the expression of GSH biosynthesis enzymes. As new molecular targets explaining these results, we found a significant down-regulation of the hepatic GSH exporter MRP4 and an up-regulation of the HCys exporter Slco1a4. In contrast to our hypothesis, GRA feeding did not reduce plasma HCys levels in Se supplemented rats (G50, G150 and 450) through inducing GSH biosynthesis enzymes and MRP4, but reduced their mRNA in some cases to a higher extent than Se alone. We conclude: 1. That the long-term supplementation of moderate GRA doses reduces ARE-driven gene expression in the liver by increasing the intestinal barrier against oxidative stress. 2. That the up-regulation of ARE-regulated genes in the liver largely depends on GRA cleavage to free sulforaphane and glucose by plant-derived myrosinase or bacterial β-glucosidases. As a consequence, higher dietary GRA concentrations should be used in future experiments to test if GRA or sulforaphane can be established as HCys lowering compounds.
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Affiliation(s)
- Nicole M Blum
- Institute of Agricultural and Nutritional Sciences, Preventive Nutrition Group, Martin Luther University Halle Wittenberg, Von Danckelmann Platz 2, D-06120, Halle (Saale), Germany
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