Helmut Sies | Heinrich Heine University Düsseldorf (original) (raw)
Papers by Helmut Sies
Free Radical Biology and Medicine, 2000
A large body of experimental research indicates that oxidative stress contributes to the processe... more A large body of experimental research indicates that oxidative stress contributes to the processes related to aging and to the pathogenesis of several age-related diseases. Vitamins and antioxidant enzymes have a fundamental role in defending the organism from oxidative stress. To better understand the role of antioxidants in human aging, we measured plasma levels of vitamin C (ascorbic acid), uric acid, vitamin E (␣-tocopherol), vitamin A (retinol), carotenoids, total thiol groups, and the activity of plasma superoxide dismutase (SOD) and glutathione peroxidase (GPX) as well as the activity of red blood cell (RBC) SOD in 32 healthy centenarians-17 elderly subjects aged 80 -99 years, 34 elderly subjects aged 60 -79 years, and 24 adults aged less than 60 years. Considering the "noncentenarians" only, we observed a consistent behavior in the antioxidant pattern, with a decrease of the nonenzymatic antioxidants and an increase of the enzymatic antioxidant activities relative to age. Remarkably, centenarians were characterized as having the highest levels of vitamins A and E, whereas the activities of both plasma and RBC SOD, which increase with age, decreased in centenarians. From these results, it is evident that healthy centenarians show a particular profile in which high levels of vitamin A and vitamin E seem to be important in guaranteeing their extreme longevity.
Analytical Proceedings, 1990
GBM Annual Fall meeting Berlin/Potsdam 2005, 2005
Diabetologie und Stoffwechsel, 2010
![Research paper thumbnail of Combining benzo[d]isoselenazol-3-ones with sterically hindered alicyclic amines and nitroxides: enhanced activity as glutathione peroxidase mimics](https://attachments.academia-assets.com/45692264/thumbnails/1.jpg)
](Organic & biomolecular chemistry, Jan 7, 2005
Benzo[d]isoselenazol-3-ones N-substituted with sterically hindered diamagnetic and paramagnetic f... more Benzo[d]isoselenazol-3-ones N-substituted with sterically hindered diamagnetic and paramagnetic five- or six-membered nitroxides or their precursors, including ring-opened diselenides, exhibit synergism in glutathione peroxidase (GPx) activity.
Nutrition Reviews, 2009
The theme of this year's special conference was "State-of-the-Science on Dietary Flavonoids." The... more The theme of this year's special conference was "State-of-the-Science on Dietary Flavonoids." The conference began with a general introduction and overview of flavonoids and their presence in the diet as well as the estimated intake levels in the US population. Subsequent presentations addressed issues pertaining to study design and interpretation, mechanisms of action, and the potential health impacts related to inflammation, the vasculature, and the brain. The present summary of the current science indicates that dietary flavonoids, particularly flavanols, show promising potential for reducing cardiovascular disease risk via reduction of inflammation and improvement in vascular function. However, the existing data must be interpreted cautiously, with consideration given to the compound tested (i.e., parent or metabolite), the use of controls, and the practicality of the concentrations used. While more data are needed on the long-term health impacts of dietary flavonoids in humans, including the efficacious dose, current data indicate it may soon be possible to develop public health messages about flavonoid-rich foods.n ure_257 736..743 The literature on flavonoids and health has expanded considerably over the last 2 decades, with a quarter of the papers on vitamin/flavonoids and health published in 2008 being on flavonoids, compared to only 5% in 1988. This is coupled with increasing consumer interest in food and in government-led campaigns encouraging the consumption of five portions of fruits or vegetables per day. Unfortunately, there is also a considerable amount of false or misleading information in the press and on the Internet, which threatens to undermine the serious scientific advances that have been made in this area. Painstaking Affiliations: G Williamson is with the University of Leeds, Leeds, UK. H Sies is with the Heinrich-
Journal of Molecular Medicine, 2007
The impact of nutrients on gene expression can be mediated by the availability of amino acids. Th... more The impact of nutrients on gene expression can be mediated by the availability of amino acids. The aim of this study is to examine the effect of limited availability of L-arginine on the DNA-binding activity of NF-κB, a dominant transcription factor in inflammation, and the consequence for the expression pattern of inducible nitric oxide synthase (iNOS) in murine keratinocytes. Low availability of L-arginine leads to activation and increased DNA-binding activity of NF-κB and induction of iNOS messenger RNA (mRNA) in the absence of cytokines, but not to translation into iNOS protein. Cytokine challenge at low L-arginine also enhances iNOS mRNA expression, but translation into iNOS protein is diminished, leading to lowered nitric oxide production. The decrease in iNOS protein expression is mediated by the phosphorylation of the translation initiation factor eIF2α subunit, a key regulator of cellular translation. In contrast, the mRNA expression of the NF-κB-dependent genes IL-1α and cationic amino acid transporter-2 (CAT-2) are not affected by the availability of L-arginine. These results demonstrate that the availability of L-arginine can play a role in the control of gene expression by augmenting the DNAbinding activity of NF-κB, which can affect the initiation and progression of dermal inflammation. Abbreviations iNOS inducible nitric oxide synthase NIO L-N[22]-(1-imino-ethyl)ornithine eIF2α eukaryotic Initiation Factor 2 subunit α NF-κB nuclear transcription factor-kappa B DETA/ NO ((Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino] diazen-1-ium-1,2-diolate) RPMI Roswell Park Memorial Institute MAEC murine aorta endothelial cells J Mol Med (2007) 85:723-732
Journal of Investigative Dermatology, 2002
Abbreviations: AP-1, activator protein 1; ERK, extracellular signal-regulated kinase; Hsp, heat s... more Abbreviations: AP-1, activator protein 1; ERK, extracellular signal-regulated kinase; Hsp, heat shock protein; IR, infrared radiation; MAPK, mitogen-activated protein kinase; MEK, MAPK/ERK kinase; MMP-1, matrix metalloproteinase 1; MTT, 3 -(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2Htetrazolium bromide; TIMP, tissue inhibitor of matrix metalloproteinases.
Journal of Experimental Medicine, 1997
Ultraviolet A (UVA) irradiation is effectively used to treat patients with atopic dermatitis and ... more Ultraviolet A (UVA) irradiation is effectively used to treat patients with atopic dermatitis and other T cell mediated, inflammatory skin diseases. In the present study, successful phototherapy of atopic dermatitis was found to result from UVA radiation-induced apoptosis in skin-infiltrating T helper cells, leading to T cell depletion from eczematous skin. In vitro, UVA radiationinduced human T helper cell apoptosis was mediated through the FAS/FAS-ligand system, which was activated in irradiated T cells as a consequence of singlet oxygen generation. These studies demonstrate that singlet oxygen is a potent trigger for the induction of human T cell apoptosis. They also identify singlet oxygen generation as a fundamental mechanism of action operative in phototherapy.
Free Radical Research, 1993
The activities of reactive oxygen species scavenging enzymes, superoxide dismutases (SODs) and ca... more The activities of reactive oxygen species scavenging enzymes, superoxide dismutases (SODs) and catalase (in cells of two melanomas (mouse B16 and human SK23) and in Chinese hamster ovary (CHO) cells were examined. Melanoma cells are relatively depleted in activities of superoxide dismutases and catalase as compared to CHO cells. Short equitoxic (500 microM for CHO and B16 cells and 5 microM for SK23 cells) paraquat treatment (15 min before the X-irradiation, 45 min in postirradiation period--the total time of treatment was 1 h) caused an increase in radiation resistance, measured as colony forming ability, in two of the three lines examined. It is proposed that PQ may exert its radioprotective effect by induction of antioxidant enzymes.
Free Radical Research, 1993
The effects of hydrogen peroxide on cell viability and, in particular, on lysosomal integrity wer... more The effects of hydrogen peroxide on cell viability and, in particular, on lysosomal integrity were investigated in a model system of cultured, established, macrophage-like J-774 cells. The cells were found to rapidly degrade added hydrogen peroxide, withstanding concentrations < or = 250 microM without cell death; however, all tested concentrations (100-500 microM) substantially decreased cellular ATP to approximately the same degree. Concentrations of hydrogen peroxide > or = 500 microM resulted in a pronounced and rapid decrease in cell viability preceded by the loss of lysosomal integrity, as judged by the relocalization of acridine orange, a lysosomotropic weak base, in pre-labelled cells. Hydrogen peroxide-induced relocalization of acridine orange and cell death were either enhanced or much prevented, according to if the cells were initially allowed to endocytose ferric iron or the specific iron-chelator deferoxamine, respectively. Depletion of ATP, however, was not associated with the loss of lysosomal integrity and viability regardless of iron or deferoxamine pretreatment. Pre-exposure to E-64, an inhibitor of lysosomal thiol proteases, resulted in the reduction of both lysosomal membrane damage and cell death. The results are interpreted as indicating (i) generation of hydroxyl radicals within the secondary lysosomal compartment due to the occurrence of reactive ferrous iron, leading to (ii) peroxidative alterations of the lysosomal membrane resulting in (iii) loss of lysosomal membrane integrity with dissipation of the proton gradient and leakage of lysosomal contents, including hydrolytic enzymes, into the cell sap.
Clinical Nutrition, 1997
The authors are aware that there is still a need for much research to elucidate the possible prev... more The authors are aware that there is still a need for much research to elucidate the possible preventive effects of antioxidant vitamins with regard to degenerative and neoplastic diseases. There must also be vigorous examination of the evidence that antioxidant vitamins can play a crucial part in a large number of other disorders (Alzheimer's disease, Parkinson's disease, diabetes, chronic and acute inflammations, airway disorders, reperfusion syndrome). The aim of prevention-oriented medical research must be to develop suitable measures able to make a considerable contribution to the overall prevention policy. Although there is still uncertainty about the mode of action and the optimal dosage of antioxidant nutrients and dietary constituents, particularly because of the safety when the dosage is correct, more information must be provided about early prevention of an inappropriate, low antioxidant intake; intake in the diet should definitely be preferred to supplementation because of the other beneficial effects of the recommended foodstuffs.
Carcinogenesis, 2003
is a characteristic of cancer cells. Since a coordinated interaction of epithelial tumor cells wi... more is a characteristic of cancer cells. Since a coordinated interaction of epithelial tumor cells with stromal cells is a prerequisite for tumor invasion and metastasis, the present study was designed to test the hypothesis that skin-derived tumor cells may modulate homologous and heterologous GJIC. While homologous GJIC of human dermal fibroblasts as well as epidermal keratinocytes was detected, no communication was measured between SCL-1 cells derived from squamous cell carcinoma of human skin. Interestingly, co-cultures of dermal fibroblasts and SCL-1 tumor cells in serum-containing medium resulted in a 52±70% lowering of the number of communicating fibroblasts. Furthermore, incubation of confluent fibroblast cultures with serum-free supernatant fractions (20±30 kDa) from tumor cells, termed the 20/30 fraction, lowered the homologous gap junction communication of fibroblasts by 490%. This novel aspect of down-regulated homologous GJIC of dermal fibroblasts, which is reversible, was neither mediated by alteration of the expression of con-nexin43, the major gap junctional protein of dermal fibroblasts, nor by aberrant localization of connexin43 in the plasma membrane. Furthermore, post-translational modifications of connexins, such as phosphorylation, was not measured by mobility shift studies. Tumor cell-mediated GJIC down-regulation between fibroblasts was suppressed using EGTA-containing serum-free tumor cell-derived supernatants suggesting that calcium ions (Ca 2 ) might mediate the transduction of this effect. The involvement of Ca 2 in down-regulation of homologous GJIC of fibroblasts was supported by an increase in fluorescence intensity of the intracellular calcium-sensitive indicator Fura-2 upon treatment of fibroblasts with the active 20/30 fraction. In conclusion, these data establish homologous GJIC of (stromal) fibroblasts as a parameter modulated by a paracrine acting factor(s) of epithelial tumor cells during tumor±stroma interaction of skin cells.
Archives of Biochemistry and Biophysics, 1999
Apo-carotenoids with different numbers of conjugated double bonds are formed upon excentric cleav... more Apo-carotenoids with different numbers of conjugated double bonds are formed upon excentric cleavage of carotenoids. These compounds may exhibit biological activities similar to those of the parent carotenoids or their central cleavage products, the retinoids. 11-Apo-canthaxanthin-11-oic acid, 13-apocanthaxanthin-13-oic acid, and 14-apo-canthaxanthin-14-oic acid, carrying 2, 3, or 5 conjugated double bonds in the polyene chain, respectively, were tested for their effects on gap junctional communication (GJC), on stabilization of connexin43 mRNA, and on the activation of the retinoic acid-2 receptor (RAR-2 receptor); the effects were compared to those of retinoic acid and 4-oxo-retinoic acid, known to stimulate GJC and to activate the RAR-2 receptor. The effects of 4-oxo-retinoic acid were comparable to those of retinoic acid. 4-Oxo-retinoic acid, like retinoic acid, influences the stability of connexin 43 mRNA via elements located in the 3-UTR. No effects were observed with the short-chain apo-canthaxanthinoic acids. A small but statistically significant induction of GJC and transactivation activity towards the RAR2 was found with 14-apo-canthaxanthin-14-oic acid. This might be due to biological effects of the compound itself or to biologically active breakdown products. The data suggest that the major biological effects of canthaxanthin on retinoid signaling pathways are related to activities mediated by the products of the central cleavage.
Proceedings of the …, Jan 1, 2000
peroxynitrite (ONOO ؊ ) decomposes after protonation to singlet oxygen ( 1 ⌬gO2) and singlet oxon... more peroxynitrite (ONOO ؊ ) decomposes after protonation to singlet oxygen ( 1 ⌬gO2) and singlet oxonitrate (nitroxyl, 1 NO ؊ ) in high yield. They claimed to have observed nitrosyl hemoglobin from the reaction of NO ؊ with methemoglobin; however, contamination with hydrogen peroxide gave rise to ferryl hemoglobin, the spectrum of which was mistakenly assigned to nitrosyl hemoglobin. We have carried out UV-visible and EPR experiments with methemoglobin and hydrogen peroxide-free peroxynitrite and find that no NO ؊ is formed. With this peroxynitrite preparation, no light emission from singlet oxygen at 1270 nm is observed, nor is singlet oxygen chemically trapped; however, singlet oxygen was trapped when hydrogen peroxide was also present, as previously described [Di Mascio, P., Bechara, E. J. H., Medeiros, M. H. G., Briviba, K. & Sies, H. (1994) FEBS Lett. 355, 287-289]. Quantum mechanical and thermodynamic calculations show that formation of the postulated intermediate, a cyclic form of peroxynitrous acid (trioxazetidine), and the products 1 NO ؊ and 1 ⌬gO2 requires Gibbs energies of ca. ؉415 kJ⅐mol ؊1 and ca. ؉180 kJ⅐mol ؊1 , respectively. Our results show that the results of Khan et al. are best explained by interference from contaminating hydrogen peroxide left from the synthesis of peroxynitrite.
Toxicology, 2001
S-Nitrosothiols are formed in vivo and are involved in NO signaling. We investigated the sulfur-t... more S-Nitrosothiols are formed in vivo and are involved in NO signaling. We investigated the sulfur-to-nitrogen transnitrosation activity of S-nitrosocysteine, S-nitrosoglutathione, S-nitrosohomocysteine, S-nitrosocysteinylglycine and S-nitroso-N-acetylcysteine in their reaction with the secondary amine diethanolamine in vitro. The resulting N-nitrosodiethanolamine, a strong carcinogen, was formed in yields of up to 11% from S-nitrosocysteine and S-nitrosocysteinylglycine, whereas the transnitrosation activity of the other S-nitroso compounds was weak. However, the addition of L-cysteine to a solution of S-nitrosohomocysteine and diethanolamine accelerated the decomposition of S-nitrosohomocysteine and resulted in a significant formation of N-nitrosodiethanolamine accompanied by the intermediate generation of S-nitrosocysteine. Thus, reactive nitrosothiols can be formed from less reactive analogs via sulfur-to-sulfur transnitrosation. We suggest that this affects regulation of NO trafficking in vivo. The reaction provides an alternative mechanism for the generation of carcinogenic N-nitroso derivatives.
Biological Chemistry, 2000
Recently, gamma-glutamyl transpeptidase, which initiates cleavage of extracellular glutathione, h... more Recently, gamma-glutamyl transpeptidase, which initiates cleavage of extracellular glutathione, has been shown to promote oxidative damage to cells. Here we examined a murine disease model of glomerulosclerosis, involving loss of the Mpv17 gene coding for a peroxisomal protein. In Mpv17-/- cells, enzyme activity and mRNA expression (examined by quantitative RT-PCR) of membrane-bound gamma-glutamyl transpeptidase were increased, while plasma glutathione peroxidase and superoxide dismutase levels were lowered. Superoxide anion production in these cells was increased as documented by electron spin resonance spectroscopy. In the presence of Mn(III)tetrakis(4-benzoic acid)porphyrin, the activities of gamma-glutamyl transpeptidase and plasma glutathione peroxidase were unchanged, suggesting a relationship between enzyme expression and the amount of reactive oxygen species. Inhibition of gamma-glutamyl transpeptidase by acivicin reverted the lowered plasma glutathione peroxidase and superoxide dismutase activities, indicating reciprocal control of gene expression for these enzymes.
Free Radical Biology and Medicine, 2000
A large body of experimental research indicates that oxidative stress contributes to the processe... more A large body of experimental research indicates that oxidative stress contributes to the processes related to aging and to the pathogenesis of several age-related diseases. Vitamins and antioxidant enzymes have a fundamental role in defending the organism from oxidative stress. To better understand the role of antioxidants in human aging, we measured plasma levels of vitamin C (ascorbic acid), uric acid, vitamin E (␣-tocopherol), vitamin A (retinol), carotenoids, total thiol groups, and the activity of plasma superoxide dismutase (SOD) and glutathione peroxidase (GPX) as well as the activity of red blood cell (RBC) SOD in 32 healthy centenarians-17 elderly subjects aged 80 -99 years, 34 elderly subjects aged 60 -79 years, and 24 adults aged less than 60 years. Considering the "noncentenarians" only, we observed a consistent behavior in the antioxidant pattern, with a decrease of the nonenzymatic antioxidants and an increase of the enzymatic antioxidant activities relative to age. Remarkably, centenarians were characterized as having the highest levels of vitamins A and E, whereas the activities of both plasma and RBC SOD, which increase with age, decreased in centenarians. From these results, it is evident that healthy centenarians show a particular profile in which high levels of vitamin A and vitamin E seem to be important in guaranteeing their extreme longevity.
Analytical Proceedings, 1990
GBM Annual Fall meeting Berlin/Potsdam 2005, 2005
Diabetologie und Stoffwechsel, 2010
Organic & biomolecular chemistry, Jan 7, 2005
Benzo[d]isoselenazol-3-ones N-substituted with sterically hindered diamagnetic and paramagnetic f... more Benzo[d]isoselenazol-3-ones N-substituted with sterically hindered diamagnetic and paramagnetic five- or six-membered nitroxides or their precursors, including ring-opened diselenides, exhibit synergism in glutathione peroxidase (GPx) activity.
Nutrition Reviews, 2009
The theme of this year's special conference was "State-of-the-Science on Dietary Flavonoids." The... more The theme of this year's special conference was "State-of-the-Science on Dietary Flavonoids." The conference began with a general introduction and overview of flavonoids and their presence in the diet as well as the estimated intake levels in the US population. Subsequent presentations addressed issues pertaining to study design and interpretation, mechanisms of action, and the potential health impacts related to inflammation, the vasculature, and the brain. The present summary of the current science indicates that dietary flavonoids, particularly flavanols, show promising potential for reducing cardiovascular disease risk via reduction of inflammation and improvement in vascular function. However, the existing data must be interpreted cautiously, with consideration given to the compound tested (i.e., parent or metabolite), the use of controls, and the practicality of the concentrations used. While more data are needed on the long-term health impacts of dietary flavonoids in humans, including the efficacious dose, current data indicate it may soon be possible to develop public health messages about flavonoid-rich foods.n ure_257 736..743 The literature on flavonoids and health has expanded considerably over the last 2 decades, with a quarter of the papers on vitamin/flavonoids and health published in 2008 being on flavonoids, compared to only 5% in 1988. This is coupled with increasing consumer interest in food and in government-led campaigns encouraging the consumption of five portions of fruits or vegetables per day. Unfortunately, there is also a considerable amount of false or misleading information in the press and on the Internet, which threatens to undermine the serious scientific advances that have been made in this area. Painstaking Affiliations: G Williamson is with the University of Leeds, Leeds, UK. H Sies is with the Heinrich-
Journal of Molecular Medicine, 2007
The impact of nutrients on gene expression can be mediated by the availability of amino acids. Th... more The impact of nutrients on gene expression can be mediated by the availability of amino acids. The aim of this study is to examine the effect of limited availability of L-arginine on the DNA-binding activity of NF-κB, a dominant transcription factor in inflammation, and the consequence for the expression pattern of inducible nitric oxide synthase (iNOS) in murine keratinocytes. Low availability of L-arginine leads to activation and increased DNA-binding activity of NF-κB and induction of iNOS messenger RNA (mRNA) in the absence of cytokines, but not to translation into iNOS protein. Cytokine challenge at low L-arginine also enhances iNOS mRNA expression, but translation into iNOS protein is diminished, leading to lowered nitric oxide production. The decrease in iNOS protein expression is mediated by the phosphorylation of the translation initiation factor eIF2α subunit, a key regulator of cellular translation. In contrast, the mRNA expression of the NF-κB-dependent genes IL-1α and cationic amino acid transporter-2 (CAT-2) are not affected by the availability of L-arginine. These results demonstrate that the availability of L-arginine can play a role in the control of gene expression by augmenting the DNAbinding activity of NF-κB, which can affect the initiation and progression of dermal inflammation. Abbreviations iNOS inducible nitric oxide synthase NIO L-N[22]-(1-imino-ethyl)ornithine eIF2α eukaryotic Initiation Factor 2 subunit α NF-κB nuclear transcription factor-kappa B DETA/ NO ((Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino] diazen-1-ium-1,2-diolate) RPMI Roswell Park Memorial Institute MAEC murine aorta endothelial cells J Mol Med (2007) 85:723-732
Journal of Investigative Dermatology, 2002
Abbreviations: AP-1, activator protein 1; ERK, extracellular signal-regulated kinase; Hsp, heat s... more Abbreviations: AP-1, activator protein 1; ERK, extracellular signal-regulated kinase; Hsp, heat shock protein; IR, infrared radiation; MAPK, mitogen-activated protein kinase; MEK, MAPK/ERK kinase; MMP-1, matrix metalloproteinase 1; MTT, 3 -(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2Htetrazolium bromide; TIMP, tissue inhibitor of matrix metalloproteinases.
Journal of Experimental Medicine, 1997
Ultraviolet A (UVA) irradiation is effectively used to treat patients with atopic dermatitis and ... more Ultraviolet A (UVA) irradiation is effectively used to treat patients with atopic dermatitis and other T cell mediated, inflammatory skin diseases. In the present study, successful phototherapy of atopic dermatitis was found to result from UVA radiation-induced apoptosis in skin-infiltrating T helper cells, leading to T cell depletion from eczematous skin. In vitro, UVA radiationinduced human T helper cell apoptosis was mediated through the FAS/FAS-ligand system, which was activated in irradiated T cells as a consequence of singlet oxygen generation. These studies demonstrate that singlet oxygen is a potent trigger for the induction of human T cell apoptosis. They also identify singlet oxygen generation as a fundamental mechanism of action operative in phototherapy.
Free Radical Research, 1993
The activities of reactive oxygen species scavenging enzymes, superoxide dismutases (SODs) and ca... more The activities of reactive oxygen species scavenging enzymes, superoxide dismutases (SODs) and catalase (in cells of two melanomas (mouse B16 and human SK23) and in Chinese hamster ovary (CHO) cells were examined. Melanoma cells are relatively depleted in activities of superoxide dismutases and catalase as compared to CHO cells. Short equitoxic (500 microM for CHO and B16 cells and 5 microM for SK23 cells) paraquat treatment (15 min before the X-irradiation, 45 min in postirradiation period--the total time of treatment was 1 h) caused an increase in radiation resistance, measured as colony forming ability, in two of the three lines examined. It is proposed that PQ may exert its radioprotective effect by induction of antioxidant enzymes.
Free Radical Research, 1993
The effects of hydrogen peroxide on cell viability and, in particular, on lysosomal integrity wer... more The effects of hydrogen peroxide on cell viability and, in particular, on lysosomal integrity were investigated in a model system of cultured, established, macrophage-like J-774 cells. The cells were found to rapidly degrade added hydrogen peroxide, withstanding concentrations < or = 250 microM without cell death; however, all tested concentrations (100-500 microM) substantially decreased cellular ATP to approximately the same degree. Concentrations of hydrogen peroxide > or = 500 microM resulted in a pronounced and rapid decrease in cell viability preceded by the loss of lysosomal integrity, as judged by the relocalization of acridine orange, a lysosomotropic weak base, in pre-labelled cells. Hydrogen peroxide-induced relocalization of acridine orange and cell death were either enhanced or much prevented, according to if the cells were initially allowed to endocytose ferric iron or the specific iron-chelator deferoxamine, respectively. Depletion of ATP, however, was not associated with the loss of lysosomal integrity and viability regardless of iron or deferoxamine pretreatment. Pre-exposure to E-64, an inhibitor of lysosomal thiol proteases, resulted in the reduction of both lysosomal membrane damage and cell death. The results are interpreted as indicating (i) generation of hydroxyl radicals within the secondary lysosomal compartment due to the occurrence of reactive ferrous iron, leading to (ii) peroxidative alterations of the lysosomal membrane resulting in (iii) loss of lysosomal membrane integrity with dissipation of the proton gradient and leakage of lysosomal contents, including hydrolytic enzymes, into the cell sap.
Clinical Nutrition, 1997
The authors are aware that there is still a need for much research to elucidate the possible prev... more The authors are aware that there is still a need for much research to elucidate the possible preventive effects of antioxidant vitamins with regard to degenerative and neoplastic diseases. There must also be vigorous examination of the evidence that antioxidant vitamins can play a crucial part in a large number of other disorders (Alzheimer's disease, Parkinson's disease, diabetes, chronic and acute inflammations, airway disorders, reperfusion syndrome). The aim of prevention-oriented medical research must be to develop suitable measures able to make a considerable contribution to the overall prevention policy. Although there is still uncertainty about the mode of action and the optimal dosage of antioxidant nutrients and dietary constituents, particularly because of the safety when the dosage is correct, more information must be provided about early prevention of an inappropriate, low antioxidant intake; intake in the diet should definitely be preferred to supplementation because of the other beneficial effects of the recommended foodstuffs.
Carcinogenesis, 2003
is a characteristic of cancer cells. Since a coordinated interaction of epithelial tumor cells wi... more is a characteristic of cancer cells. Since a coordinated interaction of epithelial tumor cells with stromal cells is a prerequisite for tumor invasion and metastasis, the present study was designed to test the hypothesis that skin-derived tumor cells may modulate homologous and heterologous GJIC. While homologous GJIC of human dermal fibroblasts as well as epidermal keratinocytes was detected, no communication was measured between SCL-1 cells derived from squamous cell carcinoma of human skin. Interestingly, co-cultures of dermal fibroblasts and SCL-1 tumor cells in serum-containing medium resulted in a 52±70% lowering of the number of communicating fibroblasts. Furthermore, incubation of confluent fibroblast cultures with serum-free supernatant fractions (20±30 kDa) from tumor cells, termed the 20/30 fraction, lowered the homologous gap junction communication of fibroblasts by 490%. This novel aspect of down-regulated homologous GJIC of dermal fibroblasts, which is reversible, was neither mediated by alteration of the expression of con-nexin43, the major gap junctional protein of dermal fibroblasts, nor by aberrant localization of connexin43 in the plasma membrane. Furthermore, post-translational modifications of connexins, such as phosphorylation, was not measured by mobility shift studies. Tumor cell-mediated GJIC down-regulation between fibroblasts was suppressed using EGTA-containing serum-free tumor cell-derived supernatants suggesting that calcium ions (Ca 2 ) might mediate the transduction of this effect. The involvement of Ca 2 in down-regulation of homologous GJIC of fibroblasts was supported by an increase in fluorescence intensity of the intracellular calcium-sensitive indicator Fura-2 upon treatment of fibroblasts with the active 20/30 fraction. In conclusion, these data establish homologous GJIC of (stromal) fibroblasts as a parameter modulated by a paracrine acting factor(s) of epithelial tumor cells during tumor±stroma interaction of skin cells.
Archives of Biochemistry and Biophysics, 1999
Apo-carotenoids with different numbers of conjugated double bonds are formed upon excentric cleav... more Apo-carotenoids with different numbers of conjugated double bonds are formed upon excentric cleavage of carotenoids. These compounds may exhibit biological activities similar to those of the parent carotenoids or their central cleavage products, the retinoids. 11-Apo-canthaxanthin-11-oic acid, 13-apocanthaxanthin-13-oic acid, and 14-apo-canthaxanthin-14-oic acid, carrying 2, 3, or 5 conjugated double bonds in the polyene chain, respectively, were tested for their effects on gap junctional communication (GJC), on stabilization of connexin43 mRNA, and on the activation of the retinoic acid-2 receptor (RAR-2 receptor); the effects were compared to those of retinoic acid and 4-oxo-retinoic acid, known to stimulate GJC and to activate the RAR-2 receptor. The effects of 4-oxo-retinoic acid were comparable to those of retinoic acid. 4-Oxo-retinoic acid, like retinoic acid, influences the stability of connexin 43 mRNA via elements located in the 3-UTR. No effects were observed with the short-chain apo-canthaxanthinoic acids. A small but statistically significant induction of GJC and transactivation activity towards the RAR2 was found with 14-apo-canthaxanthin-14-oic acid. This might be due to biological effects of the compound itself or to biologically active breakdown products. The data suggest that the major biological effects of canthaxanthin on retinoid signaling pathways are related to activities mediated by the products of the central cleavage.
Proceedings of the …, Jan 1, 2000
peroxynitrite (ONOO ؊ ) decomposes after protonation to singlet oxygen ( 1 ⌬gO2) and singlet oxon... more peroxynitrite (ONOO ؊ ) decomposes after protonation to singlet oxygen ( 1 ⌬gO2) and singlet oxonitrate (nitroxyl, 1 NO ؊ ) in high yield. They claimed to have observed nitrosyl hemoglobin from the reaction of NO ؊ with methemoglobin; however, contamination with hydrogen peroxide gave rise to ferryl hemoglobin, the spectrum of which was mistakenly assigned to nitrosyl hemoglobin. We have carried out UV-visible and EPR experiments with methemoglobin and hydrogen peroxide-free peroxynitrite and find that no NO ؊ is formed. With this peroxynitrite preparation, no light emission from singlet oxygen at 1270 nm is observed, nor is singlet oxygen chemically trapped; however, singlet oxygen was trapped when hydrogen peroxide was also present, as previously described [Di Mascio, P., Bechara, E. J. H., Medeiros, M. H. G., Briviba, K. & Sies, H. (1994) FEBS Lett. 355, 287-289]. Quantum mechanical and thermodynamic calculations show that formation of the postulated intermediate, a cyclic form of peroxynitrous acid (trioxazetidine), and the products 1 NO ؊ and 1 ⌬gO2 requires Gibbs energies of ca. ؉415 kJ⅐mol ؊1 and ca. ؉180 kJ⅐mol ؊1 , respectively. Our results show that the results of Khan et al. are best explained by interference from contaminating hydrogen peroxide left from the synthesis of peroxynitrite.
Toxicology, 2001
S-Nitrosothiols are formed in vivo and are involved in NO signaling. We investigated the sulfur-t... more S-Nitrosothiols are formed in vivo and are involved in NO signaling. We investigated the sulfur-to-nitrogen transnitrosation activity of S-nitrosocysteine, S-nitrosoglutathione, S-nitrosohomocysteine, S-nitrosocysteinylglycine and S-nitroso-N-acetylcysteine in their reaction with the secondary amine diethanolamine in vitro. The resulting N-nitrosodiethanolamine, a strong carcinogen, was formed in yields of up to 11% from S-nitrosocysteine and S-nitrosocysteinylglycine, whereas the transnitrosation activity of the other S-nitroso compounds was weak. However, the addition of L-cysteine to a solution of S-nitrosohomocysteine and diethanolamine accelerated the decomposition of S-nitrosohomocysteine and resulted in a significant formation of N-nitrosodiethanolamine accompanied by the intermediate generation of S-nitrosocysteine. Thus, reactive nitrosothiols can be formed from less reactive analogs via sulfur-to-sulfur transnitrosation. We suggest that this affects regulation of NO trafficking in vivo. The reaction provides an alternative mechanism for the generation of carcinogenic N-nitroso derivatives.
Biological Chemistry, 2000
Recently, gamma-glutamyl transpeptidase, which initiates cleavage of extracellular glutathione, h... more Recently, gamma-glutamyl transpeptidase, which initiates cleavage of extracellular glutathione, has been shown to promote oxidative damage to cells. Here we examined a murine disease model of glomerulosclerosis, involving loss of the Mpv17 gene coding for a peroxisomal protein. In Mpv17-/- cells, enzyme activity and mRNA expression (examined by quantitative RT-PCR) of membrane-bound gamma-glutamyl transpeptidase were increased, while plasma glutathione peroxidase and superoxide dismutase levels were lowered. Superoxide anion production in these cells was increased as documented by electron spin resonance spectroscopy. In the presence of Mn(III)tetrakis(4-benzoic acid)porphyrin, the activities of gamma-glutamyl transpeptidase and plasma glutathione peroxidase were unchanged, suggesting a relationship between enzyme expression and the amount of reactive oxygen species. Inhibition of gamma-glutamyl transpeptidase by acivicin reverted the lowered plasma glutathione peroxidase and superoxide dismutase activities, indicating reciprocal control of gene expression for these enzymes.