The effects of antioxidants on radiation-induced apoptosis pathways in TK6 cells

Effects of antioxidant capacity on micronucleus induction by cigarette smoke in mammalian cells

We have compared micronucleus (MN) induction by cigarette smoke in the L5178Y, TK6, and CHL/IU cell lines. The test sample was total particulate matter of 3R4F reference cigarette smoke, suspended in DMSO. After 3-h treatment, with or without a rat liver S9 metabolic activation system, followed by 24-h recovery, dose-dependent MN increases were seen in all cell lines. However, CHL/IU and TK6 cells were more resistant than L5178Y cells (comparison by Benchmark Doses with PROAST software). 3R4F smoke generates reactive oxygen species (ROS). Therefore, we explored the relationship between the sensitivities to 3R4F smoke and the antioxidant capacities of the cell lines. While the total antioxidant capacities were not significantly different among the cell lines, cellular glutathione (GSH) was higher in CHL/IU cells than in L5178Y cells. Pretreatment of CHL/IU cells with a GSH precursor, N-acetylcysteine (NAC), reduced the genotoxicity/cytotoxicity of 3R4F, whereas an inhibitor of GSH biosynthesis, buthionine sulfoximine (BSO), enhanced it. The effects of NAC and BSO were also seen after treatment with allyl isothiocyanate, a ROS-generating chemical, but not with mitomycin C, a ROS-independent genotoxicant. Pretreatment with NAC increased cellular thiol levels. From the present results, the genotoxicity and cytotoxicity of cigarette smoke differs among these cell lines in a manner that may be related to their antioxidant thiol levels.

N-Acetyl-L-cysteine protects thyroid cells against DNA damage induced by external and internal irradiation

We evaluated the effect of the antioxidant N-acetyl-L-cysteine (NAC) on the levels of reactive oxygen species (ROS), DNA double strand breaks (DSB) and micronuclei (MN) induced by internal and external irradiation using a rat thyroid cell line PCCL3. In internal irradiation experiments, ROS and DSB levels increased immediately after ¹³¹I addition and then gradually declined, resulting in very high levels of MN at 24 and 48 h. NAC administration both pre- and also post-¹³¹I addition suppressed ROS, DSB and MN. In external irradiation experiments with a low dose (0.5 Gy), ROS and DSB increased shortly and could be prevented by NAC administration pre-, but not post-irradiation. In contrast, external irradiation with a high dose (5 Gy) increased ROS and DSB in a bimodal way: ROS and DSB levels increased immediately after irradiation, quickly returned to the basal levels and gradually rose again after >24 h. The second phase was in parallel with an increase in 4-hydroxy-2-nonenal. The number of MN induced by the second wave of ROS/DSB elevations was much higher than that by the first peak. In this situation, NAC administered pre- and post-irradiation comparably suppressed MN induced by a delayed ROS elevation. In conclusion, a prolonged ROS increase during internal irradiation and a delayed ROS increase after external irradiation with a high dose caused serious DNA damage, which were efficiently prevented by NAC. Thus, NAC administration even both after internal or external irradiation prevents ROS increase and eventual DNA damage.

Radio-protective effect and mechanism of 4-Acetamido-2,2,6,6- tetramethylpiperidin-1-oxyl in HUVEC cells

OBJECTIVES

To search for more effective radiation protectors with minimal toxicity, a water-soluble nitroxides Acetamido-Tempol (AA-Tempol) was evaluated for potential radioprotective properties in HUVEC cells (Human Umbilical Vein Endothelial cell line).

METHODS

To study the anti-radiation effect of AA-Tempol in cell culture, the viability of irradiated HUVEC cells using a clonogenic survival assay was examined. The anti-apoptosis effects of AA-Tempol using Annexin V/propidium iodide staining in a flow cytometry assay was also evaluated. To elucidate the molecular mechanism of the anti-apoptosis effect of AA-Tempol against X-radiation induced HUVEC cell apoptosis, the expression of Bax, Bcl-2 and p53 and caspase-3 were examined. The changes in the level of malondialdehyde (MDA) and glutathione (GSH) in HUVEC cells after X-radiation were also investigated.

RESULTS

Pretreatment of the HUVEC cells colony with AA-Tempol 1 h before X-radiation significantly increased the colony survival (p < 0.05) compared with the cells without pretreatment. This demonstrates that AA-Tempol provides an effective radiation protection in the irradiated HUVEC cells, thus reducing apoptosis from 20.1 ± 1.3% in 8 Gy X-radiated cells to 12.2 ± 0.9% (1.0 mmol/L-1 AA-Tempol) in AA-Tempo pretreated HUVEC cells. This implies that 1.0 mM AA-Tempol treatment significantly block the increase of caspase-3 activity in radiated HUVEC cells (P < 0.01), causing down-regulation in expressions of Bax and P53 and up-regulation in the expression of Bcl-2. Pretreatment with AA-Tempol also decreased the MDA activities (P < 0.01) and increase the GSH level (P < 0.05) in HUVEC cells compared to the 8Gy X-radiated cells without pretreatment.

CONCLUSIONS

These observations indicate that AA-Tempol is a potential therapeutic agent against the radiation damage.

Theranostic TEMPO-functionalized Ru(ii) complexes as photosensitizers and oxidative stress indicators

New TEMPO-functionalized Ru(ii) polypyridyl complexes displayed greatly improved PDT efficacy, capable of simultaneously monitoring cellular oxidative stress during photodynamic therapy.

Differences in quantification of DNA double-strand breaks assessed by 53BP1/γH2AX focus formation assays and the comet assay in mammalian cells treated with irradiation and N-acetyl-L-cysteine

The biological effect of ionizing radiation (IR) on genomic DNA is thought to be either direct or indirect; the latter is mediated by IR induction of free radicals and reactive oxygen species (ROS). This study was designed to evaluate the effect of N-acetyl-L-cysteine (NAC), a well-known ROS-scavenging antioxidant, on IR induction of genotoxicity, cytotoxicity and ROS production in mammalian cells, and aimed to clarify the conflicting data in previous publications. Although we clearly demonstrate the beneficial effect of NAC on IR-induced genotoxicity and cytotoxicity (determined using the micronucleus assay and cell viability/clonogenic assays), the data on NAC's effect on DNA double-strand break (DSB) formation were inconsistent in different assays. Specifically, mitigation of IR-induced DSBs by NAC was readily detected by the neutral comet assay, but not by the γH2AX or 53BP1 focus assays. NAC is a glutathione precursor and exerts its effect after conversion to glutathione, and presumably it has its own biological activity. Assuming that the focus assay reflects the biological responses to DSBs (detection and repair), while the comet assay reflects the physical status of genomic DNA, our results indicate that the comet assay could readily detect the antioxidant effect of NAC on DSB formation. However, NAC's biological effect might affect the detection of DSB repair by the focus assays. Our data illustrate that multiple parameters should be carefully used to analyze DNA damage when studying potential candidates for radioprotective compounds.

Quinestrol induces spermatogenic apoptosis in vivo via increasing pro-apoptotic proteins in adult male mice

The effects of quinestrol on spermatogenesis were investigated in adult male mice by daily intragastric administration of quinestrol with various doses of 5, 10, 50 and 100mg/kg body weight for 10 days. The sperm counts declined while the number of abnormal spermatozoa went up in mice treated with quinestrol. The testicular weight and seminiferous tubular area gradually declined with increasing dosages of quinestrol to 50 and 100mg/kg. Rarefied germ cells showed irregular distributions in the seminiferous tubules of mice treated with 50 and 100mg/kg quinestrol. Apoptosis was highly pronounced in spermatogonia, spermatocytes, spermatids and Leydig cells. Antioxidant enzyme activities - superoxide dismutase and glutathione peroxidase - as well as total antioxidant capacity significantly reduced, while malondialdehyde contents increased. The number of germ cells expressing caspase-3, p53, Bax and FasL significantly increased whereas cells expressing Bcl-2 significantly decreased in groups treated with 50 and 100mg/kg quinestrol compared with the control. The concentration of nitrogen monoxidum also increased significantly under these dosages. The results suggest that quinestrol stimulates oxidative stress to induce apoptosis in spermatogenic cells through the mitochondrial and death receptor pathways in adult male mice.

The chemistry and biological activities of N-acetylcysteine

BACKGROUND

N-acetylcysteine (NAC) has been in clinical practice for several decades. It has been used as a mucolytic agent and for the treatment of numerous disorders including paracetamol intoxication, doxorubicin cardiotoxicity, ischemia-reperfusion cardiac injury, acute respiratory distress syndrome, bronchitis, chemotherapy-induced toxicity, HIV/AIDS, heavy metal toxicity and psychiatric disorders.

SCOPE OF REVIEW

The mechanisms underlying the therapeutic and clinical applications of NAC are complex and still unclear. The present review is focused on the chemistry of NAC and its interactions and functions at the organ, tissue and cellular levels in an attempt to bridge the gap between its recognized biological activities and chemistry.

MAJOR CONCLUSIONS

The antioxidative activity of NAC as of other thiols can be attributed to its fast reactions with OH, NO2, CO3(-) and thiyl radicals as well as to restitution of impaired targets in vital cellular components. NAC reacts relatively slowly with superoxide, hydrogen-peroxide and peroxynitrite, which cast some doubt on the importance of these reactions under physiological conditions. The uniqueness of NAC is most probably due to efficient reduction of disulfide bonds in proteins thus altering their structures and disrupting their ligand bonding, competition with larger reducing molecules in sterically less accessible spaces, and serving as a precursor of cysteine for GSH synthesis.

GENERAL SIGNIFICANCE

The outlined reactions only partially explain the diverse biological effects of NAC, and further studies are required for determining its ability to cross the cell membrane and the blood-brain barrier as well as elucidating its reactions with components of cell signaling pathways.

Two-photon fluorescence microscopy imaging of cellular oxidative stress using profluorescent nitroxides

A range of varying chromophore nitroxide free radicals and their nonradical methoxyamine analogues were synthesized and their linear photophysical properties examined. The presence of the proximate free radical masks the chromophore's usual fluorescence emission, and these species are described as profluorescent. Two nitroxides incorporating anthracene and fluorescein chromophores (compounds 7 and 19, respectively) exhibited two-photon absorption (2PA) cross sections of approximately 400 G.M. when excited at wavelengths greater than 800 nm. Both of these profluorescent nitroxides demonstrated low cytotoxicity toward Chinese hamster ovary (CHO) cells. Imaging colocalization experiments with the commercially available CellROX Deep Red oxidative stress monitor demonstrated good cellular uptake of the nitroxide probes. Sensitivity of the nitroxide probes to H(2)O(2)-induced damage was also demonstrated by both one- and two-photon fluorescence microscopy. These profluorescent nitroxide probes are potentially powerful tools for imaging oxidative stress in biological systems, and they essentially "light up" in the presence of certain species generated from oxidative stress. The high ratio of the fluorescence quantum yield between the profluorescent nitroxide species and their nonradical adducts provides the sensitivity required for measuring a range of cellular redox environments. Furthermore, their reasonable 2PA cross sections provide for the option of using two-photon fluorescence microscopy, which circumvents commonly encountered disadvantages associated with one-photon imaging such as photobleaching and poor tissue penetration.

Beta-carotene antioxidant use during radiation therapy and prostate cancer outcome in the Physicians' Health Study

PURPOSE

The safety of antioxidant supplementation during radiation therapy (RT) for cancer is controversial. Antioxidants could potentially counteract the pro-oxidant effects of RT and compromise therapeutic efficacy. We performed a prospective study nested within the Physicians' Health Study (PHS) randomized trial to determine if supplemental antioxidant use during RT for prostate cancer is associated with an increased risk of prostate cancer death or metastases.

METHODS AND MATERIALS

PHS participants (383) received RT for prostate cancer while randomized to receive beta-carotene (50 mg on alternate days) or placebo. The primary endpoint was time from RT to lethal prostate cancer, defined as prostate cancer death or bone metastases. The Kaplan-Meier method was used to estimate survival probabilities and the log-rank test to compare groups. Cox proportional hazards regression was used to estimate the effect of beta-carotene compared with that of placebo during RT.

RESULTS

With a median follow-up of 10.5 years, there was no significant difference between risk of lethal prostate cancer with the use of beta-carotene during RT compared with that of placebo (hazard ratio = 0.72; 95% confidence interval [CI], 0.42-1.24; p = 0.24). After we adjusted for age at RT, prostate-specific antigen serum level, Gleason score, and clinical stage, the difference remained nonsignificant. The 10-year freedom from lethal prostate cancer was 92% (95% CI, 87-95%) in the beta-carotene group and 89% (95% CI, 84-93%) in the placebo group.

CONCLUSION

The use of supplemental antioxidant beta-carotene during RT was not associated with an increased risk of prostate cancer death or metastases. This study suggests a lack of harm from supplemental beta-carotene during RT for prostate cancer.

Adult exposure to sasanguasaponin induces spermatogenic cell apoptosis in vivo through increased oxidative stress in male mice

Effects of sasanguasaponin (SGS), a compound from defatted seeds of Camellia oleifera, on abnormal spermatogenesis were studied in adult male mice using daily intragastric administration of 100, 200 and 400 mg/kg body weight (BW) for 6 weeks. The sperm counts decreased and the number of abnormal spermatozoa increased in mice treated with SGS at 400 mg/kg dose level. Testicular weight and seminiferous tubular area gradually decreased as dosage increased to 400 mg/kg SGS. Germ cells were rarefied and showed irregular distribution in seminiferous tubules (STs). Apoptosis was pronounced among spermatocytes and spermatids at the 400 mg/kg dose level. Antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and total antioxide capacity (T-AOC) markedly decreased and malondialdehyde (MDA) concentration increased in the testes. These results suggest that adult exposure to SGS (400 mg/kg) induces spermatogenic apoptosis through increased oxidative stress in male mice.

N-acetyl cysteine protects against ionizing radiation-induced DNA damage but not against cell killing in yeast and mammals

Ionizing radiation (IR) induces DNA strand breaks leading to cell death or deleterious genome rearrangements. In the present study, we examined the role of N-acetyl-L-cysteine (NAC), a clinically proven safe agent, for it's ability to protect against gamma-ray-induced DNA strand breaks and/or DNA deletions in yeast and mammals. In the yeast Saccharomyces cerevisiae, DNA deletions were scored by reversion to histidine prototrophy. Human lymphoblastoid cells were examined for the frequency of gamma-H2AX foci formation, indicative of DNA double strand break formation. DNA strand breaks were also measured in mouse peripheral blood by the alkaline comet assay. In yeast, NAC reduced the frequency of IR-induced DNA deletions. However, NAC did not protect against cell death. NAC also reduced gamma-H2AX foci formation in human lymphoblastoid cells but had no protective effect in the colony survival assay. NAC administration via drinking water fully protected against DNA strand breaks in mice whole-body irradiated with 1Gy but not with 4Gy. NAC treatment in the absence of irradiation was not genotoxic. These data suggest that, given the safety and efficacy of NAC in humans, NAC may be useful in radiation therapy to prevent radiation-mediated genotoxicity, but does not interfere with efficient cancer cell killing.

Hypotaurine and sulfhydryl-containing antioxidants reduce H2S toxicity in erythrocytes from a marine invertebrate

Hypotaurine (HT) has been proposed to reduce sulfide toxicity in some deep-sea invertebrates by scavenging free radicals produced from sulfide oxidation or by scavenging sulfide via the reaction of HT with sulfide, forming thiotaurine (ThT). We tested whether HT or several antioxidants could reduce the total dissolved sulfide concentration in buffered seawater exposed to H2S, and whether HT, ThT or antioxidants could increase the viability of Glycera dibranchiataerythrocytes exposed to H2S in vitro. We found that 5 and 50 mmol l–1 HT reduced the dissolved sulfide in cell-free buffer exposed to H2S by up to 80% whereas the antioxidants glutathione ethyl ester (GEE), N-acetylcysteine (NAC), l-ascorbic acid (ASC), Tempol and Trolox had no consistent effect. Exposure of erythrocytes to 0.10%–3.2% H2S (producing 0.18–4.8 mmol l–1 sulfide) decreased the fraction of viable cells, as evidenced by loss of plasma membrane integrity, with virtually no cells remaining viable at 1.0% or more H2S. Addition of HT (0.5–50 mmol l–1) significantly increased the fraction of viable cells (e.g. from 0.01 to 0.84 at 0.32% H2S) whereas ThT (0.5 and 5 mmol l–1) decreased cell viability. GEE (0.03–3 mmol l–1) and NAC (0.001–1 mmol l–1), which contain sulfhydryl groups, increased cell viability during H2S exposure but to a lesser extent than HT whereas ASC, Tempol and Trolox, which do not contain sulfhydryl groups, decreased viability or had no effect. These data show that HT can protect cells from sulfide in vitro and suggest that sulfide scavenging, rather than free radical scavenging, is the most important mechanism of protection.

Effects of N-acetylcysteine amide (NACA), a thiol antioxidant on radiation-induced cytotoxicity in Chinese hamster ovary cells

Ionizing radiation is known to cause tissue damage in biological systems, mainly due to its ability to produce reactive oxygen species (ROS) in cells. Many thiol antioxidants have been used previously as radioprotectors, but their application has been limited by their toxicity. In this investigation, we have explored the possible radioprotective effects of a newly synthesized thiol antioxidant, N-acetylcysteine amide (NACA), in comparison with N-acetylcysteine (NAC), a commonly used antioxidant. Protective effects of NACA and NAC were assessed using Chinese hamster ovary (CHO) cells, irradiated with 6 gray (Gy) radiation. Oxidative stress parameters, including levels of reduced glutathione (GSH), cysteine, malondialdehyde (MDA), and activities of antioxidant enzymes like glutathione peroxidase, glutathione reductase, and catalase, were measured. Results indicate that NACA was capable of restoring GSH levels in irradiated cells in a dose dependent manner. In addition, NACA prevented radiation-induced loss in cell viability. NACA further restored levels of malondialdehyde, caspase-3 activity, and antioxidant enzyme activities to control levels. Although NAC affected cells in a similar manner to NACA, its effects were not as significant. Further, NAC was also found to be cytotoxic to cells at higher concentrations, whereas NACA was non-toxic at similar concentrations. These results suggest that NACA may be able to attenuate radiation-induced cytotoxicity, possibly by its ability to provide thiols to cells.

Therapeutic and clinical applications of nitroxide compounds

Nitroxide compounds have been used for many years as biophysical tools, but only during the past 15-20 years have the many interesting biochemical interactions been discovered and harnessed for therapeutic applications. By modifying oxidative stress and altering the redox status of tissues, nitroxides have the ability to interact with and alter many metabolic processes. This interaction can be exploited for therapeutic and research use, including protection against ionizing radiation, as probes in functional magnetic resonance imaging, cancer prevention and treatment, control of hypertension and weight, and protection from damage resulting from ischemia/reperfusion injury. Although much remains to be done, many applications have been well studied, and some are presently being tested in clinical trials. The therapeutic and research uses of nitroxides are reviewed here, with a focus on the progress from initial development to modern, state-of-the art trials.

Relationship between phosphorylated histone H2AX formation and cell survival in human microvascular endothelial cells (HMEC) as a function of ionizing radiation exposure in the presence or absence of thiol-containing drugs

Human microvascular endothelial cells (HMEC) were exposed to ionizing radiation at doses ranging from 0 to 16 Gy in either the presence or absence of the active thiol forms of amifostine (WR1065), phosphonol (WR255591), N-acetyl-l-cysteine (NAC), captopril or mesna. Each of these clinically relevant thiols, administered to HMEC at a dose of 4 mM for 30 min prior to irradiation, is known to exhibit antioxidant properties. The purpose of this investigation was to determine the relationship(s), if any, between the frequency of radiation-induced histone H2AX phosphorylation at serine 139 (gamma-H2AX) in cells and subsequent survival, as assessed by colony-forming ability, in exposed cell populations as a function of the presence or absence of each of the five thiol compounds during irradiation. gamma-H2AX formation in irradiated cells, as a function of relative DNA content, was quantified by bivariant flow cytometry analysis with FITC-conjugated gamma-H2AX antibody and nuclear DAPI staining. gamma-H2AX formation in cells was measured as the relative fold increase as a function of the treatment conditions. The frequency of gamma-H2AX-positive cells increased with increasing dose of radiation followed by a dose- and time-dependent decay. The most robust response for gamma-H2AX formation occurred 1 h after irradiation with their relative frequencies decreasing as a function of time 4 and 24 h later. To assess the effects of the various thiols on gamma-H2AX formation, all measurements were made 1 h after irradiation. WR1065 was not only effective in protecting HMEC against gamma-H2AX formation across the entire dose range of radiation exposures used, but it was also significantly more cytoprotective than either its prodrug (WR2721) or disulfide (WR33278) analogue. WR1065 had no significant effect on gamma-H2AX formation when administered immediately or up to 30 min after radiation exposure. An inhibitory effect against gamma-H2AX formation induced by 8 Gy of radiation was expressed by each of the thiols tested. NAC, captopril and mesna were equally effective in reducing the frequency of gamma-H2AX formation, with both WR1065 and WR255591 exhibiting a slightly more robust protective effect. Each of the five thiols was effective in reducing the frequency of gamma-H2AX-positive cells across all phases of the cell cycle. In contrast to the relative ability of each of these thiols to inhibit gamma-H2AX formation after irradiation, NAC, captopril and mesna afforded no protection to HMEC as determined using a colony-forming survival assay. Only WR1065 and WR255591 were effective in reducing the frequencies of radiation-induced gamma-H2AX-positive cells as well as protecting against cell death. These results suggest that the use of gamma-H2AX as a biomarker for screening the efficacy of novel antioxidant radioprotective compounds is highly problematic since their formation and disappearance may be linked to processes beyond simply the formation and repair of radiation-induced DSBs.

The chemistry and biology of nitroxide compounds

Cyclic nitroxides are a diverse group range of stable free radicals that have unique antioxidant properties. Because of their ability to interact with free radicals, they have been used for many years as biophysical tools. During the past 15-20 years, however, many interesting biochemical interactions have been discovered and harnessed for therapeutic applications. Biologically relevant effects of nitroxides have been described, including their ability to degrade superoxide and peroxide, inhibit Fenton reactions, and undergo radical-radical recombination. Cellular studies defined the activity of nitroxides in vitro. By modifying oxidative stress and altering the redox status of tissues, nitroxides have been found to interact with and alter many metabolic processes. These interactions can be exploited for therapeutic and research use, including protection against ionizing radiation, as probes in functional magnetic resonance imaging, cancer prevention and treatment, control of hypertension and weight, and protection from damage resulting from ischemia/reperfusion injury. Although much remains to be done, many applications have been well studied and some are currently being tested in clinical trials. The therapeutic and research uses of nitroxide compounds are reviewed here with a focus on the progress from initial development to modern trials.

Eradication of p53-mutated head and neck squamous cell carcinoma xenografts using nonviral p53 gene therapy and photochemical internalization

Photochemical internalization (PCI) technology has been used for PEI-mediated p53 gene transfer in mice bearing head and neck squamous cell carcinoma (HNSCC) xenografts. Using luciferase as a reporter gene, PCI led to a 20-fold increase in transgene expression 48 h after transfection and sustained transgene expression for 7 days. Therefore, iterative p53 gene transfer was performed by means of a weekly single injection of PEIGlu4/p53 complexes alone or with PCI for 5 (group A) or 7 (group B) weeks. The efficiency of p53 gene therapy was evaluated by following tumor growth and expression of P53-related downstream proteins (P21, MDM2, Bcl2, Bax). Apoptosis induction was evidenced through caspase-3 activation and PARP cleavage. Using PCI, tumor growth inhibition was observed in all transfected animals. Further, successful tumor cure was achieved in 17% (group A) and 83% (group B) of animals. PCI-mediated p53 gene transfer led to higher P53 protein expression that was correlated with induction of Bax and P21 proapoptotic proteins, repression of Bcl2 as well as activation of caspase-3, and cleavage of PARP. The present study demonstrates that PCI enhances the in vivo efficiency of PEI-mediated p53 gene transfer and can be proposed for p53 gene therapy in HNSCC.

Mitochondrial targeting of selective electron scavengers: synthesis and biological analysis of hemigramicidin-TEMPO conjugates

Synthetic hemigramicidin S-peptidyl TEMPO conjugates are effectively delivered into cells and mitochondria, where they act as electron scavengers and exert protection against apoptosis. Our delivery approach is based on the use of specific structural signaling features recognizable by cells as mitochondria targeting sequences and offers considerable therapeutic anti-apoptotic potential.

Oxidative Stress Promotes Endothelial Cell Apoptosis and Loss of Microvessels in the Spontaneously Hypertensive Rats

OBJECTIVE

Endothelial cell apoptosis caused by oxidative stress may lead to the loss of microvessels (rarefaction) in hypertension. We examine here the effects of antioxidants on cell apoptosis and rarefaction.

METHODS AND RESULTS

The juvenile spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were treated with superoxide scavengers, Tempol or Tiron, during growth. After the treatment, oxidative stress status, endothelial cell apoptosis rate, and microvessel length density in skeletal muscle and mesentery were evaluated in comparison with age-matched controls. Untreated 16-week-old SHR had higher oxidative stress (P<0.01) and cell apoptosis rate (P<0.05) and lower microvessel length density (371+/-17 mm/mm3 [P<0.01]) compared with age-matched WKY rats (435+/-15 mm/mm3). In the SHR, but not in WKY rats, systemically applied antioxidants attenuated oxidative stress and cell apoptosis rate (P<0.05 versus untreated controls) and prevented the loss of microvessels (411+/-15 mm/mm3 for Tempol [P<0.01 versus untreated control] and 399+/-17 mm/mm3 for Tiron [P<0.05]).

CONCLUSIONS

Antioxidant treatment with cell-permeable superoxide scavengers inhibits endothelial cell apoptosis and prevents microvessel rarefaction in the SHR during growth.

Water-soluble polysaccharides from Angelica sinensis (Oliv.) Diels: Preparation, characterization and bioactivity

Crude water-soluble polysaccharides (ASP) were separated from Angelica sinensis (Oliv.) Diels by hot water extraction. They were fractionated into neutral and acidic polysaccharides by anion-exchange chromatography. The neutral polysaccharide (ASP1) was rich in glucose, galactose, and arabinose suggesting a mixture of glucan and arabinogalactan. The acidic polysaccharide (ASP2, ASP3) consisted mainly of galacturonic acid along with rhamnose, arabinose, and galactose indicating a pectic polysaccharide. The degree of esterification of ASP and ASP3 were 54.06% and 47.14% for the crude and purified sample, respectively. ASP3, with a molecular weight of 3.4x10(4)Da determined by high-performance size-exclusion chromatography (HPSEC), was the major constituent for the crude extracts. The radioprotective effect of the pectic polysaccharide ASP3 was studied in murine models. ASP3 pretreated mice exhibited a significant decrease of apoptosis (P<0.05, dosage of 200 mg/kgd body weight) in peripheral lymphocytes compared to the irradiated control. The results showed that ASP3 can protect leucocytes and lymphocytes of mice against radiation induced damage, which has potential radioprotective effect on acute radiation injured mice.

REDOX REGULATION BY INTRINSIC SPECIES AND EXTRINSIC NUTRIENTS IN NORMAL AND CANCER CELLS

Cells in multicellular organisms are exposed to both endogenous oxidative stresses generated metabolically and to oxidative stresses that originate from neighboring cells and from other tissues. To protect themselves from oxidative stress, cells are equipped with reducing buffer systems (glutathione/GSH and thioredoxin/thioredoxin reductase) and have developed several enzymatic mechanisms against oxidants that include catalase, superoxide dismutase, and glutathione peroxidase. Other major extrinsic defenses (from the diet) include ascorbic acid, beta-carotene and other carotenoids, and selenium. Recent evidence indicates that in addition to their antioxidant function, several of these redox species and systems are involved in regulation of biological processes, including cellular signaling, transcription factor activity, and apoptosis in normal and cancer cells. The survival and overall well-being of the cell is dependent upon the balance between the activity and the intracellular levels of these antioxidants as well as their interaction with various regulatory factors, including Ref-1, nuclear factor-kappaB, and activating protein-1.