[Viral pathogenic spectrum analysis of severe acute respiratory infection cases in Luohe City, Henan province from 2017 to 2019]

Objective: The purpose of this study was to investigate the characteristics of viral pathogen spectrum and the epidemiological characteristics of each viral pathogen in hospitalized cases associated with severe acute respiratory infection (SARI) in Luohe City, Henan Province from 2017 to 2019. Methods: Based the SARI Case Surveillance Platform, SARI cases were collected in Central Hospital of Luohe City, Henan Province from November 2017 to February 2019. In the end, 783 SARI cases were included, whose throat swabs were taken within 24 h of admission, as well as their demographic characteristics, onset time, clinical characteristics and other information recorded. At the same time, viral identification was performed, and the age and time distribution of each virus were analyzed. Results: The age of 783 SARI cases shown as M (P₂₅, P₇₅) was 3 (1, 5) years old, ranging from 1 month to 95 years old. Children under 5 years old were the majority (71.01%). The males (61.81%) were more than females (38.18%). Among the 783 SARI cases, a total of 9 kind of viruses were identified with 64.88% (508/783) of the throat swabs tested positive for at least one virus. The positive rate of influenza virus and human respiratory syncytial virus were both 20.18% (158 cases), which was the highest among all the detected respiratory virus. The co-infection rate was 15.84% (124/783), among which double infection was the most common, accounting for 85.48% (106/124) of the co-infected cases. And human respiratory syncytial virus, human rhinovirus and influenza virus were the most common pathogen in co-infection cases. Moreover, the viral positive rate was 68.71% in children aged 5 years and 63.27% in people aged 60-95 years. Influenza and human respiratory syncytial virus dominated in winter and spring, while human parainfluenza virus was the main infection in summer. Conclusion: Influenza virus and human respiratory syncytial virus were the main viruses in throat swabs of SARI cases from 2017 to 2019 in Luohe City, Henan Province. There were differences in the age and seasonal epidemiological characteristics of each virus.

[Relationships between serum cystatin C, chemerin levels and subclinical atherosclerosis in type 2 diabetes mellitus patients]

Objective: To investigate the relationships between serum cystatin C (Cys C), chemerin levels and subclinical atherosclerosis in type 2 diabetes mellitus (T2DM) patients. Methods: A cross-sectional study was carried out between January 2016 and January 2018, and T2DM patients with carotid intima-media thickness (IMT) less than 1.1 mm were selected as subjects (100 males and 80 females, aged 40-60 years). The brachial-ankle pulse wave velocity (baPWV) ≥ 1 700 cm/s was set as the observation group (subclinical atherosclerosis) and baPWV<1 700 cm/s as the control group (non-subclinical atherosclerosis). Physical and blood examination were performed in both groups. Serum Cys C and chemerin levels were measured and their relationship with subclinical atherosclerosis was analyzed. Results: There was a statistically significant correlation between serum creatinine (r=0.167, P=0.011) and baPWV in the observation group, but not in the control group (r=0.105, P=0.070). Multiple linear regression analysis showed that age, duration of diabetes, serum creatinine, estimated glomerular filtration rate (eGFR), Cys C and chemerin were independently associated with baPWV, while high sensitive C reactive protein (hsCRP) and glycosylated hemoglobin (HbA1c) were not associated with baPWV. The elevation of serum Cys C (β'=0.393, P=0.003) and chemokine (β'=0.340, P=0.007) were correlative factors for atherosclerosis. Conclusion: The level of serum Cys C and chemerin is possibly related to the occurrence and development of subclinical atherosclerosis in T2DM patients.

Activated natural killer cells accelerate liver damage in patients with chronic hepatitis B virus infection

Emerging evidence indicates that natural killer (NK) cells may contribute to liver injury in patients with hepatitis B virus (HBV) infection. Because HBV infection progresses through various disease phases, the cytolytic profiles of peripheral and intrahepatic NK cells in HBV-infected patients remain to be defined. In this study, we comprehensively characterized intrahepatic and peripheral NK cells in a cohort of HBV-infected individuals, and investigated their impact on liver pathogenesis during chronic HBV infection. The study population included 34 immune-clearance (IC) patients, 36 immune-tolerant (IT) carriers and 10 healthy subjects. We found that the activity of peripheral NK cells from IC patients was functionally elevated compared to IT carriers and controls, and NK cell activation was indicated by an increased expression of CD69, CD107a, interferon (IFN)-γ and tumour necrosis factor (TNF)-α. Further analysis showed that the increased activity of both peripheral and hepatic NK cells was correlated positively with liver injury, which was assessed by serum alanine aminotransferase levels (ALT) and the liver histological activity index (HAI). Interestingly, the frequency of peripheral NK cells was reduced in IC patients (especially those with higher HAI scores of 3-4), but there was a concomitant increase in hepatic NK cells. The functionally activated NK cells are enriched preferentially in the livers of IC patients and skew towards cytolytic activity that accelerates liver injury in chronic hepatitis B (CHB) patients.

Zoledronate inhibits phosphate and bone morphogenetic protein 2-induced extracellular calcification of vascular smooth muscle cells in vitro

The aim of this study was to explore the effects of the bisphosphonate zoledronate on calcification induced by inorganic phosphate (Pi) and/or bone morphogenetic protein 2 (BMP-2) and the underlying mechanisms. Primary vascular smooth muscle cells (VSMCs) from rats were treated with 3 mM Pi or 3 mM Pi/BMP-2, with and without addition of zoledronate; 1.4 mM Pi served as a control. Calcium deposits, expression of core binding factor α-1 (Cbfa-1), osteopontin (OPN), parathyroid pituitary-specific transcription factor (Pit)-1 and Pit-2, and Pi uptake of VSMCs was determined. The calcification of VSMCs induced by elevated Pi or Pi/BMP-2 was significantly inhibited by zoledronate. The expression of Cbfa-1, OPN and Pit-1 was increased significantly after treatment with an elevated level of Pi or Pi/BMP-2, and this expression was significantly suppressed by addition of zoledronate. Pi uptake of VSMCs increased following treatment with elevated Pi and significantly decreased by addition of zoledronate. These results indicated that zoledronate effectively inhibited calcification induced by Pi/BMP-2, and this may have been achieved by means of the downregulation of expression of calcification-related proteins and uptake of Pi.

Induction of oxidative DNA damage in human foreskin fibroblast Hs68 cells by oxidized beta-Carotene and lycopene

Two recent clinical trials suggest that beta-carotene may be harmful to smokers. In this study we examined the hypothesis that beta-carotene may become toxic when degradation occurs. beta-Carotene (BC) and lycopene (LP) with or without prior heat treatment (60 degrees C for 1 h in open air) were incubated at 20 and 40 microM with calf thymus DNA or human fibroblasts Hs68 cells. The heat treatment resulted in ca. 80% and 35% bleaching of BC and LP, respectively. When Hs68 cells were incubated with the oxidized beta-carotene (OBC) or oxidized lycopene (OLP) at 37 degrees C for 20 h, cell viability was significantly and dose-dependently decreased whereas cell viability was not affected by BC or LP. Cell death, which was already evident at 4 h after incubation with OBC or OLP, was possibly attributable to apoptosis, as shown by the increased histone-associated DNA fragmentation. However, cell lysis, measured as release of lactate dehydrogenase, also occurred at 4 h after incubation with OBC and OLP, although the extent was relatively small and was greater for OLP than for OBC. When calf thymus DNA was incubated with OBC or OLP at 37 degrees C for 20 h, the 8-hydroxy-2-deoxyguanosine (8-OH-dG) level was significantly and dose-dependently increased by OLP whereas the increase by OBC was only significant at 40 microM. When Hs68 cells were incubated with OBC and OLP for 20 h, both compounds increased the 8-OH-dG level, but the effect was only significant for 40 microM OLP. Comet (single-cell gel electrophoresis) assay of DNA damage in Hs68 cells was determined at 2 h after incubation with OBC or OLP because of its high sensitivity. Both OBC and OLP significantly and dose-dependently increased DNA breakage while BC and LP had no effect. Inclusion of BHT during incubation of cells with 40 microM OBC or OLP partially inhibited (ca. 40%, p < .05) the extent of comet formation. Intriguingly, OBC and OLP neither induce lipid peroxidation in Hs68 cells (measured as thiobarbituric acid-reactive substances released into the medium) nor increased the intracellular level of reactive oxygen species. Although it is presently unclear about what degradation products are formed, this study has demonstrated that, when oxidized, BC and LP lead to oxidative damage to both purified DNA and cellular DNA. The results suggest that such damage may contribute to the adverse effects of beta-carotene reported in recent clinical studies and caution that it is important to prevent oxidation of BC and LP for human uses such as in supplemental studies.

DHEA inhibits cell growth and induces apoptosis in BV-2 cells and the effects are inversely associated with glucose concentration in the medium

Dehydroepiandrosterone (DHEA), a major steroid secreted by the adrenal gland which decreases with age after adolescence, is available as a nutritional supplement. DHEA is known to have antiproliferative effects but the mechanism is unclear. In this study using BV-2 cells, a murine microglial cell line, we investigated the effect of DHEA on cell viability and the interaction between DHEA and glucose concentrations in the medium. We showed that DHEA inhibited cell viability and G6PD activity in a dose-dependent manner and that the effect of DHEA on cell viability was inversely associated with glucose concentrations in the medium, i.e. lowered glucose strongly enhanced the inhibition of cell viability by DHEA. DHEA inhibited cell growth by causing cell cycle arrest primarily in the G0--G1 phase, and the effect was more pronounced at zero glucose (no glucose added, G0) than high glucose (4.5 mg/ml of the medium, G4.5). Glucose deprivation also enhanced apoptosis induced by DHEA. At G4.5, DHEA did not induce formation of DNA ladder until it reached 200 microM. However, at G0, 100 microM DHEA was able to induce apoptosis, as evidenced by the formation of DNA ladder, elevation of histone-associated DNA fragmentation and increase in cells positively stained with annexin V-FITC and annexin V-FITC/propidium iodide. The interactions between DHEA and glucose support the contention that DHEA exerts its antiproliferative effects through alteration of glucose metabolism, possibly by inhibition of G6PD activity leading to decreased supply of ribose-5-phosphate for synthesis of DNA and RNA. Although DHEA is only antiproliferative at pharmacological levels, our results indicate that its antiproliferative effect can be enhanced by limiting the supply of glucose such as by energy restriction. In addition, the present study shows that glucose concentration is an important factor to consider when studying the antiproliferative and toxicological effects of DHEA.

Total plasma malondialdehyde levels in 16 Taiwanese college students determined by various thiobarbituric acid tests and an improved high-performance liquid chromatography-based method

OBJECTIVES

In determining the plasma malondialdehyde MDA levels in some Taiwanese college students, we found rather different results by using different thiobarbituric acid TBA tests, even by the high-performance liquid chromatography HPLC-based methods. Here, we re-evaluated four commonly used TBA tests and improved the HPLC-based test.

DESIGN AND METHODS

We used the blood plasma of 16 college volunteers to determine plasma MDA by using four methods: a spectrophotometric measurement of thiobarbituric acid-reactive substances (TBARS) in the TCA-supernatant of plasma (Method A); a fluorescence measurement of plasma lipid peroxides (Method B); and two different HPLC-based measurements of MDA with either 532-nm measurement (Method C, HPLC/532 nm) or fluorescence measurement (Method D, HPLC/fluor.).

RESULTS

The levels of MDA or TBA reactive substances obtained from the four methods differed substantially (0.39 +/- 0.15; 2.14 +/- 0.73; 0.75 +/- 0.22; and 0.38 +/- 0.15 microM for Methods A, B, C, and D, respectively). The results were positively correlated between Methods A and B (r = 0.740, p < 0.02) and between Methods C and D (r = 0.516, p < 0.05). However, results were negatively correlated between Methods B and D (r = -0.548, p < 0.05). Because most plasma MDA is bound to proteins, we modified the HPLC-based methods (C and D) by adding an alkaline hydrolysis step, and the plasma TBA-MDA adduct detected by HPLC/532 nm was referred to as total MDA. RESULTS show that alkaline hydrolysis was a critical step for measurement of total MDA in plasma because this treatment led to release of MDA from plasma proteins. We also adapted the potassium iodide (KI) treatment of plasma from Method D to reduce lipid hydroperoxides. Our modified method gave a total MDA level in the 16 volunteers of approximately 1.5 microM, which was equal to protein-bound MDA plus free MDA. This total MDA level was positively (p < 0.05) correlated with the level of TBA reactive substances obtained from Methods C (r = 0.63, p < 0.05) and D (r = 0.48, p < 0.07), but was not correlated with those from Methods A and B. The recovery (84 approximately 105%), precision (within-assay coefficient of variation: 2.4%, between-assay coefficient of variation: 4 approximately 8%) and sensitivity of the modified procedure were comparable to other HPLC-based methods.

CONCLUSION

By using a validated modification of HPLC-based TBA method, the total plasma MDA in 16 Taiwanese college students was found to be 1.54 microM, which was relatively high compared to those obtained by other HPLC-based method, primarily due to the release of protein-bound MDA by alkaline hydrolysis. This level equaled the sum of protein-bound MDA and free MDA in plasma, confirming that this level represents total plasma MDA.

Use of rat liver slices for the study of oxidative DNA damage in comparison with isolated rat liver nuclei and HepG2 human hepatoma cells

Tissue slices are a useful biological system for lipid peroxidation studies but their use for DNA damage studies is not well characterized. Hence, the present study investigates DNA damage in rat liver slices, in comparison with isolated rat liver nuclei and HepG2 human hepatoma cells, incubated with ferric nitrilotriacetate (Fe(III)-NTA), bromotrichloromethane (BrCCl(3)), bromobenzene (BrB) or 2-nitropropane (2-NP) at 37 degrees C for 2 hr. DNA damage was measured in slices, cells or nuclei after centrifugation as formation of as 8-hydroxy-2'-deoxyguanosine (8-OH-dGu) and loss of double-stranded (dsDNA) due to strand breakage using a fluorometric analysis of DNA unwinding (FADU). Lipid peroxidation was measured as thiobarbituric acid-reactive substances (TBARS) released into the medium. The results show that in liver slices and isolated nuclei, Fe/NTA (1 mM/4 mM) induced high levels of TBARS but low levels of 8-OH-dGu, whereas the oxidant induced low levels of TBARS and no formation of 8-OH-dGu in HepG2 cells. In all three systems, inclusion of ascorbate caused dose-dependent formation of 8-OH-dGu, and the levels were similar between liver slices and HepG2 cells but were far higher in isolated nuclei. In liver slices the FADU assay was not applicable due to limited solubilization of DNA from the slice, whereas the assay detected significant loss of dsDNA in HepG2 cells and slight loss in isolated nuclei induced by Fe/NTA with or without ascorbate. Liver slices incubated with 1 mm BrCCl(3), BrB or 2-NP had elevated TBARS but had little or no formation of 8-OH-dGu; none of these oxidants induced lipid peroxidation or DNA damage in HepG2 cells. When liver slices obtained from rats injected with diethylmaleate (to deplete GSH) were incubated with BrCCl(3), BrB or 2-NP, levels of TBARS and 8-OH-dGu increased markedly. Similarly, HepG2 cells with decreased GSH showed marked elevation of TBARS and loss of dsDNA induced by these oxidants, although no formation of 8-OH-dGu was detected. The present study demonstrates the usefulness and limitations of liver slices for DNA damage studies and the importance of cellular GSH in the protection of DNA against environmental toxicants.

Toxicological and antioxidant effects of short-term dehydroepiandrosterone injection in young rats fed diets deficient or adequate in vitamin E

This study examined the in vivo antioxidant and/or prooxidant effect of short-term dehydroepiandrosterone (DHEA) injection and the effect of dietary vitamin E. Male Sprague-Dawley rats (4 wk old) were fed vitamin E-deficient or vitamin E-adequate (30 mg DL-alpha-tocopheryl acetate/kg) diet for 4 weeks followed by intraperitoneal injection of DHEA for 1 week. The results showed that DHEA injection caused a dose-dependent decrease in body weight, and this effect was more pronounced in vitamin E-deficient rats. In contrast, DHEA injection significantly increased liver, kidney and adrenal weights. Hepatic vitamin E content was significantly lowered by vitamin E deficiency, which led to significantly increased ex vivo and iron-induced lipid peroxidation. DHEA injection did not affect hepatic vitamin E content but significantly decreased ex vivo and iron-induced lipid peroxidation in vitamin E-deficient rats. Hepatic total sulfhydryl (SH) groups and non-protein SH contents were not affected by vitamin E but were significantly increased by DHEA injection, which at 100 mg/kg was not more effective than at 50 mg/kg. Hepatic glutathione S-transferase (GST) activity was significantly decreased by DHEA, but vitamin E alleviated such a decrease. DHEA injection significantly increased hepatic glucose 6-phosphate dehydrogenase (G6PD) activity, and the effect was dose dependent in vitamin E-deficient rats. Thus, DHEA may compensate for vitamin E deficiency in vivo, and this effect is masked when dietary vitamin E is adequate. The antioxidant effect of DHEA is accompanied by decreased body weights, enlarged (fat-laden) tissues and altered activities of hepatic GST and G6PD.

Elevated lipid peroxidation and disturbed antioxidant enzyme activities in plasma and erythrocytes of patients with uterine cervicitis and myoma

OBJECTIVES

We investigated whether oxidative stress is associated with human uterine cervicitis and uterine myoma.

DESIGN AND METHODS

We measured lipid peroxidation and antioxidant enzymes in plasma and erythrocytes of cervicitis patients and myoma patients in comparison with matched controls. Thiobarbituric acid-reactive substances (TBARS), a measure of lipid peroxidation, were determined in plasma; glutathione peroxidase (GSHPx) and catalase in erythrocytes; and superoxide dismutase (SOD) in both plasma and erythrocytes.

RESULTS

We showed that plasma TBARS were significantly higher (p < 0.05) in both cervicitis patients and myoma patients than in controls. Plasma TBARS were significantly (and negatively) correlated with plasma and erythrocyte T-SOD activities in cervicitis patients only. Plasma T-SOD activity was significantly lower in both groups of patients than in controls whereas erythrocyte T-SOD activity was only significantly lower in myoma patients. The lowered plasma T-SOD activity in the cervicitis patients was attributed to decreased Mn-SOD activity whereas the lowered plasma T-SOD activity in myoma patients was attributed to decreased activities of both Cu,Zn-SOD and Mn-SOD. Erythrocyte GSHPx activity was 14% higher (p < 0.05) in cervicitis patients and 11% lower (p > 0.05) in myoma patients than in controls; catalase activity was 10% higher (p > 0.05) in cervicitis patients and 13% lower (p > 0.05) in myoma patients than in controls. Neither erythrocyte GSHPx nor catalase activity was significantly correlated with plasma TBARS.

CONCLUSIONS

The elevated lipid peroxidation and disturbed antioxidant enzyme activities demonstrate the potential of oxidative injury in patients with uterine cervicitis and myoma.

UVA-induced oxidative damage to rat liver nuclei: reduction of iron ions and the relationship between lipid peroxidation and DNA damage

Lipid peroxidation and DNA damage and the relationship between the two events were studied in rat liver nuclei irradiated with low dose UVA. Lipid peroxidation was measured as thiobarbituric acid-reactive substances (TBARS) by spectrophotometric method and as malondialdehyde-TBA adduct by HPLC, and DNA damage was measured as 8-hydroxy-deoxyguanosine (8-OH-dGu) and strand breakage (or loss of double-stranded DNA) by a fluorometric analysis of alkaline DNA unwinding method. The results show that UVA irradiation by itself increased nuclear lipid peroxidation but caused little or no DNA strand breakage or 8-OH-dGu. When 0.5 mM ferric (Fe+3) or ferrous (Fe+2) ions were added to the nuclei during UVA irradiation, lipid peroxidation and DNA damage, measured both as 8-OH-dGu and loss of double-stranded DNA, were strongly enhanced. Lipid peroxidation occurred concurrently with the appearance of 8-OH-dGu. Fe3+ ions were reduced to Fe2+ in this UVA/Fe2+/nuclei system. Lipid peroxidation and DNA damage were neither inhibited by scavengers of hydroxyl radical and singlet oxygen nor inhibited by superoxide dismutase and catalase. Inclusion of EDTA or chain-breaking antioxidants, butylated hydroxytoluene (BHT) and diphenylamine (an alkoxy radical scavenger), inhibited lipid peroxidation but not the level of 8-OH-dGu. BHT also did not inhibit the loss of double-stranded DNA in this system. This study demonstrates the reduction of exogenous Fe+3 by UVA when added to rat liver nuclei, and, as a result, oxidative damage is strongly enhanced. In addition, the results show that DNA damage is not a result of lipid peroxidation in this UVA/Fe2+/nuclei system.

Reaction of cyclohexylamine with hypochlorite and enhancement of oxidation of plasma sulfhydryl groups by hypochlorite in vitro

In this study we investigated the reaction of cyclamate and its major metabolite, cyclohexylamine (CyhNH2), with NaOCl. NaOCl at 100 microM was allowed to react with various concentrations of cyclamate and CyhNH2, and the reactivity was compared with those of reduced glutathione (GSH) and ascorbic acid. The results showed that CyhNH2 was less reactive with NaOCl than GSH but was slightly more reactive than ascorbic acid at concentrations below 50 microM. CyhNH2 at 75 and 100 microM did not further decrease NaOCl. Cyclamate was much less reactive than CyhNH2, with only 43% loss in NaOCl at 100 microM cyclamate. When human blood plasma was incubated with 0.75 microM NaOCl, inclusion of CyhNH2 enhanced oxidation of sulfhydryl groups in a concentration-dependent manner, with complete oxidation of SH groups at 7.5 mM CyhNH2. Cyclamate had no effect. This enhancement by CyhNH2 suggests the formation of reactive products from the reaction of CyhNH2 with NaOCl. Absorption spectra demonstrated that reaction of CyhNH2 with NaOCl at pH 7.4 produced N-monochloramine, as evidenced by the appearance of a new peak at 245 nm and by the disappearance of the 292-nm peak of NaOCl. Cyclamate, which contains a sulfamic acid instead of a primary amine, also reacted with NaOCl at pH 7.4, but the reaction was much less pronounced and the product was probably not monochloramine since the peak was at 270 nm rather than at 245 nm. Because cyclamate is an important sweetener in many countries for people with diabetes mellitus, the possibility exists that CyhNH2 may enhance oxidation of important proteins by HOCl/OCl-.

Plasma levels of antioxidant vitamins, selenium, total sulfhydryl groups and oxidative products in ischemic-stroke patients as compared to matched controls in Taiwan

The possible involvement of oxidative damage and antioxidant protection has been suggested in the pathogenesis of stroke which is the second-leading cause of death in Taiwan. In this study we investigated the relationship between ischemic stroke and plasma status of antioxidants and oxidative products. Plasma levels of vitamin A, alpha-tocopherol, carotenoids, selenium (Se), total SH groups (T-SH), thiobarbituric acid-reactive substances (TBARS) and protein carbonyl, a marker of protein damage, were determined in ischemic-stroke patients (n = 36, blood sampled within 24 hrs after the clinical event) in comparison with 21 matched controls. The cholesterol-adjusted carotenoids and vitamin E were significantly lower (P < 0.05) in the plasma of ischemic-stroke patients than those of the controls. TBARS were higher (P < 0.05) in the patients than in the controls but Se, T-SH and protein carbonyls were not significantly different between the two groups. Separation of the patients into small-artery ischemic stroke (SAIS, n = 17) and large-artery ischemic stroke (LAIS, n = 19) groups revealed that both carotenoids/cholesterol and vitamin E/cholesterol ratios were significantly lower in both LAIS and SAIS groups than the controls (n = 21) while vitamin A/cholesterol was not different among the three groups. TBARS were only significantly higher in the LAIS group. The results demonstrated that, within 24 hrs after the clinical event, the acute-ischemic stroke patients had lowered levels of cholesterol-adjusted carotenoids and alpha-tocopherol but elevated levels of TBARS in the plasma as compared to the matched controls. It remains to be resolved as to whether enhanced lipid peroxidation is a cause or a result of lowered antioxidants in ischemic stroke.

Hemolytic effects of dehydroepiandrosterone in vitro

Dehydroepiandrosterone (DHEA), a major steroid secreted by the adrenal gland which decreases with age after adolescence, is available as a over-the-counter product. This study demonstrates that DHEA induced lysis of human red blood cells (RBCs) in a concentration-dependent manner, with ca. 70% hemolysis at 2 mM DHEA at 37 degrees C for 1 hr. Hemolysis induced by 2 mM DHEA was rapid and involved neither hemoglobin oxidation nor lipid peroxidation. The hemolysis was also not inhibited by addition of EDTA, catalase, superoxide dismutase, glucose or a radical scavenger including mannitol, dimethylsulfoxide and alpha-tocopherol, indicating a non-oxidative mechanism. RBCs stored overnight before incubation with DHEA were hemolyzed to a lesser extent than the freshly prepared RBCs. Light microscopy of the fresh RBCs following 1-h incubation with 2 mM DHEA revealed thickened and cup-shaped deformity of the membranes, suggesting a change in the membrane structure possibly due to the intercalation of the steroid into the membranes.

Ascorbic acid inhibits lipid peroxidation but enhances DNA damage in rat liver nuclei incubated with iron ions

In this report we studied DNA damage and lipid peroxidation in rat liver nuclei incubated with iron ions for up to 2 hrs in order to examine whether nuclear DNA damage was dependent on membrane lipid peroxidation. Lipid peroxidation was measured as thiobarbituric acid-reactive substances (TBARS) and DNA damage was measured as 8-OH-deoxyguanosine (8-OH-dG). We showed that Fe(II) induced nuclear lipid peroxidation dose-dependently but only the highest concentration (1.0 mM) used induced appreciable 8-OH-dG. Fe(III) up to 1 mM induced minimal lipid peroxidation and negligible amounts of 8-OH-dG. Ascorbic acid enhanced Fe(II)-induced lipid peroxidation at a ratio to Fe(II) of 1:1 but strongly inhibited peroxidation at ratios of 2.5:1 and 5:1. By contrast, ascorbate markedly enhanced DNA damage at all ratios tested and in a concentration-dependent manner. The nuclear DNA damage induced by 1 mM FeSO4/5 mM ascorbic acid was largely inhibited by iron chelators and by dimethylsulphoxide and mannitol, indicating the involvement of OH. Hydrogen peroxide and superoxide anions were also involved, as DNA damage was partially inhibited by catalase and, to a lesser extent, by superoxide dismutase. The chain-breaking antioxidants butylated hydroxytoluene and diphenylamine (an alkoxyl radical scavenger) did not inhibit DNA damage. Hence, this study demonstrated that ascorbic acid enhanced Fe(II)-induced DNA base modification which was not dependent on lipid peroxidation in rat liver nuclei.

Nutritional evaluation of women in urban areas in continental China

In 1993-1995, a nutritional survey was conducted in China, in which 50 women each in three cities of Beijing, Shanghai and Nanning (thus 150 in total) volunteered to offer 24-hr total food duplicates and peripheral blood samples. People daily took 1,776 kcal (7,431 kJ) energy, 57 g protein, 75 g lipid, 218 g carbohydrate, 439 mg calcium, 24 mg iron, 3,398 mg sodium and 1,521 mg potassium. When compared with the recommended dietary allowance for Chinese, intakes of energy, iron and possibly vitamin C were sufficient in a majority of the participants, but not so in cases of calcium, and several vitamins. The lipid energy ratio was 38% on an average and was higher than 30% in a majority (73%) of the people. BMI, but not the lipid energy ratio, correlated with the serum triglyceride level. In accordance with high iron intake, the prevalence of anemia was low. Inter-city differences were evident in nutrient sources. Thus, Beijing people took more amounts of protein and lipid from meats (including eggs and milk), whereas plant-based foods were important sources of lipid in Shanghai and that of protein in Nanning. Furthermore, consumption of rice was significantly lower in Beijing than in Shanghai and Nanning, whereas wheat consumption was higher in Beijing than in Shanghai and Nanning.

UVA-potentiated damage to calf thymus DNA by Fenton reaction system and protection by para-aminobenzoic acid

Calf thymus DNA was irradiated with low-intensity UVA (main output at 365 nm, 2 mW cm-2 or 36 kJ m-2 for 30 min), and the role of metal ions, hydrogen peroxide and reactive oxygen species (ROS) was examined. DNA damage was measured as thiobarbituric acid-reactive substances (possibly from degradation of deoxyribose) and as changes in ethidium bromide-DNA fluorescence due to unwinding from strand breaks. Under the present experimental conditions, UVA alone or in the presence of H2O2 had no effect on DNA but slightly enhanced the damage by iron/EDTA. Ultraviolet A strongly enhanced DNA damage (ca four- to five-fold) by the Fenton reaction system (50 microM Fe2+/100 microM EDTA + 0.5 mM H2O2). The results suggest that the Fenton reaction system was "photosensitized" to damage DNA by low-intensity UVA radiation. The enhanced damage by UVA was attributed in part to the reduction of Fe3+ to Fe2+. Ultraviolet A had no effect when iron (ferric or ferrous) ions were replaced by Cu2+, Zn2+, Mn2+ or Cd2+. The ROS involved in the UVA-enhanced damage to DNA by the Fenton reagents were OH and, to a lesser extent, superoxide anions. The UVA-potentiated DNA damage by the Fenton reaction system was then used to examine the protective effect of para-aminobenzoate (PABA), a UVB-absorbing sunscreen that protects against photocarcinogenesis in hairless mice. The results show that PABA and mannitol dose-dependently inhibited the damage with concentrations required for 50% inhibition at 0.1 mM and 3 mM, respectively. The protection by PABA was attributed to its radical-scavenging ability because PABA does not absorb light in the UVA region. These findings may be relevant to the biological damage by UVA and suggest that PABA is useful in protection against photocarcinogenesis by wide-range UV radiation.

The antioxidant and prooxidant activity of some B vitamins and vitamin-like compounds

The antioxidant and prooxidant properties of some B vitamins (BVIT) and vitamin-like compounds (VLC) that are commonly included in multivitamin preparations were investigated. Microsomal lipid peroxidation induced by FeCl3 and ascorbate was dose-dependently inhibited by pyridoxal and pantothenate but was stimulated by thiamin, pyridoxine and carnitine. Among the compounds tested, only pyridoxine and pyridoxal reacted, but rather poorly, with superoxide anions. All test compounds reacted with .OH with second-order rate constants comparable or higher than that for mannitol, as assayed using deoxyribose oxidation by a system containing EDTA-chelated Fe(III), H2O2 and ascorbate. When assayed in the absence of EDTA, pyridoxal showed increased inhibition of deoxyribose oxidation over that in the presence of EDTA, suggesting a potent ability of pyridoxal to bind and deactivate iron. Pantothenate, pyridoxine and myo-inositol appeared to equally inhibit deoxyribose oxidation both in the presence and absence of EDTA. The lack of inhibition on deoxyribose oxidation in the absence of EDTA by thiamin, carnitine and choline may suggest that the .OH-scavenging ability is equalled by the ability of the scavenger-iron complexes to form .OH or other redox active species. However, stimulation of lipid peroxidation by pyridoxine was unexplained and the effect was not attributed to reduction of Fe(III) to Fe(II). This study shows that the radical-scavenging ability of BVIT and VLC did not correlate with their effects on microsomal lipid peroxidation. Moreover, the stimulation of lipid peroxidation by thiamin, pyridoxine and carnitine suggests that supplementation of large amounts of these compounds may not be desirable.

Some similarities in vascular effects of oleic acid and oxidized low-density lipoproteins on rabbit aorta

In the present study oxidized low-density lipoproteins (ox-LDL) was prepared by a new simple method: oxidizing LDL by electrolysis-generated free radicals. In endothelium-intact norepinephrine(NE)-precontracted rabbit aortic rings, ox-LDL (2 mg protein/ml)-incubation for 30 min or 3 mM oleic acid for 10 min, significantly attenuated the acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR) (both P < 0.01 v control). Such attenuated EDR were sustained after washout. The oleic acid-induced endothelial dysfunction was associated with concomitant reduction of cGMP level in aortic rings. Preincubation of aortic rings with 500 microM L-arginine or 100 u/ml superoxide dismutase for 10 min partly prevented the oleic acid-induced attenuation of EDR and reduction of cGMP, indicating that oleic acid may impair the L-arginine-nitric acid pathway and/or inactivate the nitric oxide. Both ox-LDL and oleic acid potentiated NE-induced aortic ring contraction (both P < 0.01 v control). Such potentiating effects were abolished by preincubation with 1 microM verapamil, indicating the possible involvement of calcium influx in vascular smooth muscle cells during the enhanced contraction. Gas-chromatographic analysis showed that oleic acid content is the highest among all free fatty acids in ox-LDL. In conclusion, we found that oleic acid possesses certain similar vascular effects as ox-LDL in inducing endothelial dysfunction and in enhancing NE-induced vasocontraction in rabbit aortic ring. We proposed that the vasoactive effects of ox-LDL may be resulted partly from the activation or release of active oleic acid molecule during oxidative modification of LDL.

Potentiation of oxidative damage to rat red blood cells by the concurrent presence of t-butyl hydroperoxide and bromotrichloromethane

Recently potentiation of oxidative damage in rat red blood cells (rRBC) incubated with t-butylhydroperoxide (BHP) in combination with bromotrichloromethane (BrCCI3) was demonstrated. The mechanism by which this combination (BrCCI3/BHP) potentiates the oxidative damage to rRBC was investigated in this study. When rRBC were incubated with 0.1 mM BHP, 0.5 mM BrCCI3, or the two combined, BrCCI3/BHP-potentiated lipid peroxidation and hemolysis were further enhanced under anaerobic conditions. However, the potentiation of lipid peroxidation was abolished by heating or trypsin digestion of rRBC. Electron spin resonance (ESR) studies demonstrated an increase of alkoyl radical induced by BrCCI3/BHP in rRBC, and this increase was abolished by heating or predigestion of hemolysates with trypsin. The inhibition of lipid peroxidation by diphenylamine (which reacts with alkoxyl radicals but not peroxyl radicals) suggests an important role of alkoxyl radicals. Overall, the present findings demonstrate that the increase in radical-related oxidative damage, possibly mediated by proteinlike materials, may be at least partially responsible for the potentiation of damage to rRBC induced by BrCCI3/BHP, and perhaps by BrCCI3. Although the in vivo significance of these results remains to be investigated, it seems likely that halocarbon toxicity may be amplified by elevated levels of lipid peroxide in blood.

Interactions of human blood plasma with hydrogen peroxide and hypochlorous acid

Activated neutrophils produce both hydrogen peroxide (H2O2) and hypochlorous acid (HOCl). Previous work has shown that HOCl depletes antioxidants, modifies proteins, and forms fatty acid chlorohydrins but does not cause significant lipid peroxidation in human plasma. Because activated phagocytes have been claimed to stimulate lipid peroxidation in plasma, we examined the effects of H2O2 and HOCl alone and in combination on plasma constituents. Hydrogen peroxide at concentrations below 0.5 mmol/L had little effect, but 1 to 2 mmol/L H2O2 caused loss of ascorbic acid and protein thiol groups, an effect potentiated by preincubation of the plasma with sodium azide to inhibit catalase. H2O2 caused no detectable lipid peroxidation or loss of alpha-tocopherol in plasma, but some depletion of ubiquinol occurred. The combination of HOCl and H2O2 caused more lipid peroxidation than either agent alone. Peroxidation was not inhibited by the metal chelators ethylenediaminetetraacetic acid and deferoxamine or by the singlet O2/hydroxyl radical scavenger histidine. We hypothesize that the phagocyte-derived H2O2 and HOCl could interact in the microenvironment of the activated leukocyte to induce lipid peroxidation of plasma lipoproteins or cell membranes (or both).

Oxidation of biologic molecules by ozone: the effect of pH

Ozone (O3) is a powerfully oxidizing pollutant gas. Its toxic effects to animals appear to be worsened by coexposures to acid-generating compounds such as oxides of nitrogen and sulfur. Ozone (16 ppm) oxidizes ascorbic acid and uric acid (two important antioxidants in lung lining fluids) at equal rates at pH 5.0 or pH 7.4. Loss of intrinsic fluorescence and formation of carbonyls in albumin exposed to O3 are similar at both pH values. However, albumin-SH groups are lost much faster on exposure to O3 at pH 7.4 than at acidic pH values. A similar slower rate of -SH group disappearance at acidic pH is seen when cysteine or reduced glutathione are exposed to O3. We suggest that the ability of reduced glutathione, albumin, and other proteins containing -SH groups to scavenge O3 in the respiratory tract is impaired at low pH and that this effect could contribute to the aggravation of O3 toxicity.

Cigarette smoke oxidation of human plasma constituents

In vitro exposure of fresh human plasma to cigarette smoke (CS) was used as a model for reactions that could be occurring in CS-exposed respiratory tract lining fluids (RTLFs) and lung parenchyma. The central focus of this model was to characterize the consumption of endogenous plasma antioxidants in relationship to the appearance of oxidized proteins and lipids as a consequence of exposure to CS, or to aldehydes present in CS. The amelioration of CS-induced protein and lipid oxidation in plasma by the addition of selective exogenous antioxidants was also assessed. We found that: (i) exposure of human plasma to gas phase CS causes both lipid peroxidation and protein oxidation, and endogenous ascorbic acid protects against lipid, but not protein, oxidation; (ii) whole CS causes protein oxidation, but does not induce lipid peroxidation; (iii) addition to plasma of aldehydes known to be present in CS causes protein damage, but does not induce either lipid peroxidation or oxidation of ascorbic acid; and (iv) exogenously added dihydrolipoic acid (DHLA) preserves ascorbic acid levels in plasma exposed to the gas phase of CS, and protects, to some extent, against lipid peroxidation; DHLA also protects against protein oxidation, whereas added glutathione (GSH) only protects against protein, but not lipid, oxidation.

Cigarette smoke oxidation of human plasma constituents

In vitro exposure of fresh human plasma to cigarette smoke (CS) was used as a model for reactions that could be occurring in CS-exposed respiratory tract lining fluids (RTLFs) and lung parenchyma. The central focus of this model was to characterize the consumption of endogenous plasma antioxidants in relationship to the appearance of oxidized proteins and lipids as a consequence of exposure to CS, or to aldehydes present in CS. The amelioration of CS-induced protein and lipid oxidation in plasma by the addition of selective exogenous antioxidants was also assessed. We found that: (i) exposure of human plasma to gas phase CS causes both lipid peroxidation and protein oxidation, and endogenous ascorbic acid protects against lipid, but not protein, oxidation; (ii) whole CS causes protein oxidation, but does not induce lipid peroxidation; (iii) addition to plasma of aldehydes known to be present in CS causes protein damage, but does not induce either lipid peroxidation or oxidation of ascorbic acid; and (iv) exogenously added dihydrolipoic acid (DHLA) preserves ascorbic acid levels in plasma exposed to the gas phase of CS, and protects, to some extent, against lipid peroxidation; DHLA also protects against protein oxidation, whereas added glutathione (GSH) only protects against protein, but not lipid, oxidation.

Antioxidant protection against hypochlorous acid in human plasma

Hypochlorous acid (HOCI) is a powerful oxidizing and chlorinating agent produced by the neutrophil enzyme myeloperoxidase. The antioxidant defenses of freshly prepared human plasma against HOCI/OCI- were explored. Addition of HOCI/OCI- to plasma caused rapid oxidation of ascorbic acid and thiol (-SH) groups but not of uric acid. Plasma -SH groups (which are known to be largely located on albumin) were quantitatively the most important scavenger of HOCI/OCI-, but adding extra ascorbate to plasma caused this molecule to have a more important scavenging role against HOCI/OCI-. Added HOCI/OCI- produced no detectable lipid peroxidation in plasma or depletion of lipid-soluble antioxidants (alpha-tocopherol or ubiquinol-10). No evidence of oxidative damage to protein amino acid residues (other than -SH) was detected by the carbonyl assay. It seems that -SH groups are a major target of attack by HOCI/OCI- in vivo, and plasma albumin may be an important protective antioxidant. Ascorbic acid might also play a protective role, especially in individuals supplemented with this vitamin. Ascorbate might also be important in extracellular fluids with low albumin concentrations such as synovial, respiratory tract lining, and cerebrospinal fluids.

No detrimental effects in delaying initiation of gonadotropin administration after pituitary desensitization with gonadotropin-releasing hormone agonist

OBJECTIVE

To determine if delaying initiation of exogenous gonadotropin administration after pituitary desensitization with gonadotropin-releasing hormone agonist (GnRH-a) is a realistic option to avoid scheduling clinical and laboratory work on weekends/holidays.

DESIGN, PATIENTS

A review of 57 in vitro fertilization (IVF) cycles in which, after pituitary desensitization with GnRH-a, initiation of gonadotropin administration were delayed in an attempt to avoid off-hour work. Thirty-eight IVF cohort cycles served as control.

SETTING

Tertiary medical center.

RESULTS

There were no statistically significant differences in ovarian response, dose of gonadotropin required, oocytes and embryos obtained, pregnancy rates, and abortion rates between groups. Eighty-three percent of the delayed cycles had clinical and laboratory work that fell within weekdays.

CONCLUSION

Delaying initiation of exogenous gonadotropin administration after pituitary desensitization had no detrimental effects on IVF outcomes. It may be used to avoid scheduling work on weekends/holidays.

Interaction of nitrogen dioxide with human plasma. Antioxidant depletion and oxidative damage

Nitrogen dioxide (NO2.) is often present in inhaled air and may be generated in vivo from nitric oxide. Exposure of human blood plasma to NO2. caused rapid losses of ascorbic acid, uric acid and protein thiol groups, as well as lipid peroxidation and depletions of alpha-tocopherol, bilirubin and ubiquinol-10. No increase in protein carbonyls was detected. Supplementation of plasma with ascorbate decreased the rates of lipid peroxidation, alpha-tocopherol depletion and loss of uric acid. Uric acid supplementation decreased rates of lipid peroxidation but not the loss of alpha-tocopherol. We conclude that ascorbic acid, protein -SH groups, uric acid and alpha-tocopherol may be important agents protecting against NO2. in vivo. If these antioxidants are depleted, peroxidation of lipids occurs and might contribute to the toxicity of NO2..

Modification of plasma proteins by cigarette smoke as measured by protein carbonyl formation

Exposure of human plasma to gas-phase (but not to whole) cigarette smoke (CS) produces oxidative damage to lipids [Frei, Forte, Ames & Cross (1991) Biochem. J. 277, 133-138], which is prevented by ascorbic acid. The ability of CS to induce protein damage was measured by the carbonyl assay and by loss of enzyme activity and protein -SH groups. Both whole and gas-phase CS caused formation of carbonyls in human plasma, which was partially inhibited by GSH but not by ascorbic acid or metal-ion-chelating agents. Isolated albumin exposed to CS showed much faster carbonyl formation (per unit protein) than did whole plasma; damage to isolated albumin was partially prevented by chelating agents. Isolated creatine kinase (CK) lost activity upon exposure to CS much faster than did CK in plasma. Direct addition to plasma of mixtures of some or all of the aldehydes reported to be present in CS caused protein carbonyl formation and inactivation of CK, but neither occurred to the extent produced by CS exposure.

Potentiation of oxidative damage to proteins by ultraviolet-A and protection by antioxidants

We have studied the damage of alcohol dehydrogenase (ADH) and glyceraldehyde 3-phosphate dehydrogenase (GAPD) induced by Fe++/EDTA + H2O2 in combination with UV-A (main output at 365 nm). Enzyme inactivation, formation of hydroxyl radicals (measured in the absence of enzymes), increase in protein carbonyls, oxidation of sulfhydryl (SH) groups, loss of native protein fluorescence, and enhanced protease degradation were used to determine protein damage. Hydroxyl radical production was greatly enhanced by the combination of UV-A with Fe++/EDTA + H2O2. The combined treatment increased protein carbonyls but decreased native protein fluorescence and SH groups. The combined treatment caused turbidity in GAPD but not in ADH, whereas trypsin susceptibility was increased more in ADH than in GAPD. These measurements of protein oxidation correlated well with enzyme activities. Glyceraldehyde 3-phosphate dehydrogenase and dithiothreitol were most protective against such damage, while hydroxyl radical and singlet oxygen scavengers were partially effective. Superoxide dismutase had no effect. Thus, UV-A potentiation of protein damage induced by FE++/EDTA + H2O2 appeared to involve hydroxyl radicals and perhaps singlet oxygen but not superoxide radicals. The damage to proteins induced by combination of UV-A with physiological oxidants, iron ions and H2O2 may be relevant to UV-A-induced skin and tissue damage.

Glutathione and antioxidants protect microsomes against lipid peroxidation and enzyme inactivation

The study investigated the relationship between lipid peroxidation and enzyme inactivation in rat hepatic microsomes and whether prior inactivation of aldehyde dehydrogenase (ALDH) exacerbated inactivation of other enzymes. In microsomes incubated with 2.5 microM iron as ferric sulfate and 50 microM ascorbate, ALDH, glucose-6-phosphatase (G6Pase) and cytochrome P450 (Cyt-P450) levels decreased rapidly and concurrently with increased levels of thiobarbituric acid-reactive substances. Microsomal glutathione S-transferase and nicotinamide adenine dinucleotide phosphate-cytochrome c reductase were little affected during 1 hr of incubation. Addition of reduced glutathione partially protected and N,N'-diphenyl-p-phenylenediamine and butylated hydroxytoluene completely protected microsomes against inactivation of ALDH, G6Pase and Cyt-P450, as well as lipid peroxidation induced by iron and ascorbate. ALDH was more susceptible than G6Pase to inactivation by iron and ascorbate, and was thus an excellent marker for oxidative stress. Inhibition of ALDH by cyanamide injection of rats exacerbated the inactivation of G6Pase in microsomes incubated with 0.1 mM, but not 25 microM 4-hydroxynonenal (4-HN). 4-HN did not stimulate lipid peroxidation. Thus, 4-HN may play a minor role in microsomal enzyme inactivation. In contrast, lipid peroxyl radicals play an important role in microsomal enzyme inactivation, as evidenced by the prevention of both lipid peroxidation and enzyme inactivation by chain-breaking antioxidants.

Vitamin E, diethylmaleate and bromotrichloromethane interactions in oxidative damage in vivo

In vivo interactions of vitamin E with diethylmaleate (DEM) and bromotrichloromethane (CBrCl3) were examined in rats fed a diet either without vitamin E or supplemented with 30 IU dl-alpha-tocopheryl acetate/kg. Groups of rats within each dietary group were given two injections 30 min apart. One group received two injections of the mineral oil carrier. The other groups were injected with either DEM and mineral oil, mineral oil and CBrCl3, or DEM and CBrCl3. The rats were killed 10 min after the second injection. Measurements were made of hepatic GSH, thiobarbituric acid-reactive substances (TBARS) as a lipid peroxidation index, and 11 enzymes as potential markers of oxidant damage. Special focus was placed on reactive cysteine-containing aldehyde dehydrogenase (ALDH). Although dietary vitamin E protected ALDH, the enzyme was highly susceptible to oxidant damage. ALDH activity was correlated with GSH (r = 0.83, p less than 0.001) and there was an inverse relationship between the logarithmic values of ALDH activity and TBARS (r = 0.78, p less than 0.001). Similar results were observed for a number of other enzymes when GSH depletion preceded oxidant treatment. Two-way analysis of variance revealed significant effects of vitamin E and of injection treatments on hepatic GSH. There was a significant interaction between vitamin E and the injection treatments on the activities of five enzymes. The results suggested that vitamin E and GSH functioned together to protect sensitive enzymes against oxidant stress. The sensitive enzymes may be useful markers of hepatic damage in vivo.

Effect of dietary menhaden oil and vitamin E on in vivo lipid peroxidation induced by iron

Weanling rats were fed diets containing 10% menhaden oil (MO) or 10% corn oil-lard (1:1, COL) with low (less than or equal to 5 IU/kg) or supplementary (35 IU/kg) vitamin E for six weeks. The rats were killed 30 min after injection with 24 mg iron/kg as ferrous chloride because thiobarbituric acid-reactive substances (TBARS) in liver homogenates were highest at 30 min after injection of iron into rats fed a standard diet. Tissue homogenates were used either without incubation (zero-time) or after incubation at 37 degrees C for 1 hr. In addition to TBARS and conjugated dienes, headspace hexanal and total volatiles (TOV) determined by capillary gas chromatography were useful indices of lipid peroxidation since they were decreased by vitamin E supplementation and were increased with increasing iron dose. Regardless of the dietary lipid used, vitamin E supplementation decreased headspace hexanal, TOV, TBARS and conjugated dienes in both zero-time and incubated homogenates of liver and kidney. Dietary MO increased TBARS in both zero-time and incubated homogenates of tissue from rats injected with iron. In contrast, dietary MO decreased hexanal and TOV in incubated tissue homogenates. The study demonstrated the usefulness and limitations of using hexanal and TOV as indices of lipid peroxidation.

Lipid peroxidation in rat tissue slices: effect of dietary vitamin E, corn oil-lard and menhaden oil

Rats were fed for 5 weeks either 10% (w/w) menhaden oil (MO) or a 10% corn oil-lard (COL) mixture (1:1) in diets with less than or equal to 5 IU or less than or equal to 2 IU/kg vitamin E, respectively, or the same diets supplemented with d-alpha-tocopheryl succinate to a total of 35 and 180 IU vitamin E/kg, respectively. Slices of liver and heart from these rats were used to study lipid peroxidation in vitro. Thiobarbituric acid-reactive substances (TBARS) were measured in the medium after incubation of the slices at 37 degrees C for 1 hr in the absence (uninduced) and presence of 0.5 mM tert-butyl hydroperoxide (induced). The release of TBARS from slices of heart and liver from rats fed either lipid decreased with increasing levels of dietary vitamin E. At the same level of dietary vitamin E, TBARS release was greater for slices of liver and heart from the MO-fed rats than from the COL-fed rats. Application of the TBARS data to a model simulating the experimental conditions showed a good correlation (r = 0.95, p less than 0.001) between experimental and simulated values. Of the 16:0-22:6 fatty acids measured in liver from MO-fed rats, 15.4% was n-6 fatty acids and 29.9% was n-3 fatty acids; in liver from COL-fed rats, the respective values were 37.4% and 3.7%. Liver and kidney vitamin E levels were unaffected by the dietary lipid.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary supplements of vitamin E, beta-carotene, coenzyme Q10 and selenium protect tissues against lipid peroxidation in rat tissue slices

A tissue slice model was employed to assess the effects of dietary antioxidant supplements on lipid peroxidation. In one experiment, rats were fed diets containing, either alone or in combination, vitamin E, selenium, beta-carotene or coenzyme Q10 for 42 d, and the extent of spontaneous and induced lipid peroxidation was determined by release of thiobarbituric acid-reactive substances (TBARS) into the medium. Vitamin E exhibited the greatest protection against lipid peroxidation in liver, heart and spleen; in kidney, selenium was most protective. Coenzyme Q10 was active against lipid peroxidation induced by tertbutyl hydroperoxide (t-BHP). In a second experiment, rats were fed diets containing varying amounts of vitamin E, selenium, beta-carotene and coenzyme Q10 for 30 d. Spontaneous lipid peroxidation in liver, kidney and heart decreased with increasing levels of dietary antioxidants. With increasing amounts of antioxidants, there was a diminution in TBARS released by liver and kidney slices incubated with t-BHP; in heart, only the highest levels of antioxidants significantly decreased production of TBARS. Inverse correlations between dietary vitamin E and TBARS, tissue vitamin E and TBARS, and tissue selenium-glutathione peroxidase and TBARS were highly significant. The procedure used here can evaluate dietary supplements that may find practical applications in decreasing the oxidant radical portion of disease processes.

Oxidant stress inhibits the endogenous production of lipoxygenase metabolites in rat lungs and fish gills

Hydroperoxides are potent initiators of lipid peroxidation in vivo. Acyl hydroperoxides may also regulate various aspects of lipid metabolism. In this study we investigated the regulation of the endogenous 12 lipoxygenase in trout gill and rat lung, a prominent acyl hydroperoxide catalyst in these tissues. Initial experiments revealed that the enzyme from trout gill was activated by hydroperoxides at low levels and inactivated by the same hydroperoxides at high levels. Homogenization of these tissues resulted in the production of a predominant metabolite class from released endogenous polyunsaturated fatty acids, the 12 lipoxygenase products. In rat lung, arachidonic acid was the major polyunsaturated fatty acid released and 12 (S) HETE was the major metabolite. In trout gill 20:4, 20:5 n3, and 22:6 n3 were released and the 12(S), 12, and 14 hydroxy derivatives the corresponding metabolites. Computer simulations of the sensitivity of these enzymes to hydroperoxides predicted that exogenous oxidant stress would reduce significantly the production of HETEs. Tertiary butyl hydroperoxide was added to tissue homogenates and resulted in elimination of greater than 95% of the lipoxygenase activity. These results suggest that the lipoxygenase enzyme in lung and gill tissue is a major potential source for acyl hydroperoxides in vivo, but is also very sensitive to oxidant stresses including the acyl hydroperoxides themselves. This enzyme could thus be an important focus for oxidant injury in lungs.

Rapid headspace gas chromatography of hexanal as a measure of lipid peroxidation in biological samples

A rapid, sensitive and convenient capillary gas chromatographic-headspace method was developed to determine hexanal as an important volatile decomposition product of hydroperoxides formed from n-6 polyunsaturated fatty acids in rat liver samples. Total volatiles were also determined as a measure of overall lipid peroxidation. Samples of headspace taken from sealed serum bottles incubated at 37 degrees C were injected into a gas chromatograph. It was possible to make 15 determinations per hour. This method is convenient because no special sample manipulations are necessary. The addition of 0.5 mM ascorbic acid prior to gas chromatographic analysis significantly increased hexanal production. The applicability of the method was demonstrated in studies of the effect of iron in the presence or absence of hydroperoxides of methyl linoleate and methyl linolenate and tert-butyl hydroperoxide on rat liver homogenates, slices and microsomes. A rapid silica cartridge chromatographic procedure was used to purify hydroperoxides from autoxidized methyl linoleate and methyl linolenate, and hydroperoxy epidioxides (cyclic peroxides) from autoxidized methyl linolenate in 20-40 mg quantities. The hydroperoxides and hydroperoxy epidioxides of methyl linolenate were effective inducers of n-6 polyunsaturated fatty acid peroxidation in liver homogenates. Hexanal and thiobarbituric acid-reacting substances were significantly correlated in liver homogenates and microsomes but not in slices. This specific method for hexanal, a known product of peroxidation of n-6 polyunsaturated fatty acids, can be used as a good measure of lipid peroxidation.

Effect of dietary lipids and vitamin E on in vitro lipid peroxidation in rat liver and kidney homogenates

Rats were fed for 5 wk 10% (wt/wt) menhaden oil (MO) or a 10% corn oil-lard (COL) mixture (1:1) in diets with a low vitamin E content (less than or equal to 5 mg/kg) or supplemented with d-alpha-tocopheryl succinate to a total of 30 or 150 mg per kg. Thiobarbituric acid-reactive substances (TBARS), conjugated dienes (CD), hexanal and total volatiles (TOV) were measured in tissue homogenates incubated at 37 degrees C for 1 h in the absence (uninduced) and presence of 15 microM ferrous sulfate (induced). The fatty acid composition of liver and kidney reflected that of dietary lipids. For uninduced peroxidation, there was in general a significant inverse correlation of TBARS, CD and TOV with the log of dietary vitamin E content for liver and kidney from rats fed either lipid. For induced peroxidation, the inverse correlation was significant for liver, but not for kidney, from rats fed either lipid. The correlation was generally higher for liver and kidney from rats fed COL than for tissues from rats fed MO. Vitamin E was thus a more effective antioxidant for liver than for kidney regardless of the dietary lipid, and for liver and kidney from rats fed COL than from rats fed MO. Dietary MO enhanced tissue susceptibility to both peroxidation systems. A simulation model developed to mimic the experiments showed good correlations between experimental data and simulated values.

In vivo effects of aurothioglucose and sodium thioglucose on rat tissue sulfhydryl levels and plasma sulfhydryl reactivity

The active component of aurothioglucose (ATG) in effecting changes in plasma sulfhydryl (SH) levels and plasma SH reactivity with 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) was determined. These two measurements are applied clinically to rheumatoid arthritis patients undergoing chrysotherapy. Normal rats were injected intramuscularly daily for seven days with 30 mumol of either ATG or sodium thioglucose (STG)/kg body wt or with an equivalent volume of the carrier, 0.05% benzyl alcohol. ATG but not STG significantly increased total SH levels in plasma, liver, and kidney. The seven-day treatment with ATG significantly increased glutathione levels in kidney but not in liver or plasma. Thus, gold(I) rather than thioglucose was the active moiety that affected SH levels in ATG-injected rats. In vivo, gold(I) was also the active moiety that stimulated plasma SH reactions with DTNB at pH 7.4, since injection of ATG but not STG stimulated the SH reactivity in fresh plasma. In vitro, ATG increased the rate of plasma reaction with DTNB at pH 7.4, thus, gold(I) ions acted as a catalyst in the SH-disulfide exchange reaction. This study demonstrates that gold(I) but not its thiol ligand strongly interacts with protein SH groups in the rat tissues. Such an interaction may play an important role in the biological actions of gold.

Effect of chronic aurothioglucose treatment of rats on kidney catalase and cytochromes

Catalase activity and cytochrome content were measured in kidneys of Fisher 344 rats injected with aurothioglucose (ATG) either daily for 3 days or 5 days a week for up to 8 wk. Catalase activity was decreased 39%, 59%, and 48% (all p less than 0.001) after 3 days, 2 wk, and 8 wk, respectively. Microsomal cytochrome P-450 levels decreased 71%, 86%, and 80% (all p less than 0.001) after 3 days, 2 wk, and 8 wk, respectively. In contrast, cytochrome b5 was significantly increased at 3 days and 2 wk, but not at 8 wk. Microsomal heme contents decreased 44% (p less than 0.001), 34% (p less than 0.001), and 22% (p greater than 0.05) at 3 days, 2 wk, and 8 wk, respectively. The content of mitochondrial cytochromes aa3, b, c1, and c were not affected after 8 wk of ATG treatment. In vitro inhibition of the heme-containing enzyme delta-aminolevulinic acid dehydratase by ATG was reversible in the presence of physiological concentrations of small thiols. Although the activity of this enzyme in kidneys of ATG-treated rats was not measured, its significant inhibition in vivo by ATG appears unlikely. This study demonstrates that there were differential effects of gold on the various cytochromes and that changes in catalase activity paralleled changes in cytochrome P-450 and heme contents in the kidneys of ATG-treated rats. The findings are relevant to nephrotoxicity during chrysotherapy.

Interactions of gold with cytosolic selenium-containing proteins in rat kidney and liver

Rats injected with aurothioglucose (ATG) for 5 days were subsequently injected with [75Se]selenious acid and killed after 3 days. Kidney and liver cytosols were chromatographed on Sephadex G-150. 75Se in kidney was associated with high molecular weight (HMW), 85,000 Mr, 26,000 Mr, and 10,000 Mr proteins and with a nonprotein fraction. The elution profile of liver cytosol was similar to that of kidney, but without a 26,000 Mr protein. ATG injection increased the association of 75Se with all fractions of kidney cytosol except the 85,000 Mr fractions, which contained Se-glutathione peroxidase (SeGSHPx) activity; 75Se in liver was increased only in HMW fractions. Unfractionated kidney cytosolic SeGSHPx activity was decreased 14% by ATG injection, but liver enzyme activity was not changed. However, Sephadex G-150 chromatography showed that total and specific activities, respectively, were decreased 28 and 23% in kidney and 25 and 16% in liver. Au coeluted with HMW and 10,000 Mr 73Se-containing kidney proteins; the latter contained 50% of the Au eluted from the column. DEAE Sephacel chromatography of the 10,000 Mr kidney protein showed that both Au and 75Se were tightly associated with metallothionein-like proteins. This study demonstrates the interaction of Au with rat liver and kidney 75Se-containing proteins.

Aurothioglucose effect on sulfhydryls and glutathione-metabolizing enzymes: in vivo inhibition of selenium-dependent glutathione peroxidase

Fisher 344 rats injected with a total of 20.8 +/- 1.5 mg of gold (Au) as aurothioglucose over an 8-wk period were used to study the effect of long-term Au treatment on selenium-dependent glutathione peroxidase (SeGSHPx), other enzymes related to GSH metabolism, GSH, nonprotein sulfhydryls, and total sulfhydryls (SH) in various tissues. The indirect coupled assay for SeGSHPx revealed decreased activity in platelets of Au-treated rats but not in other tissues. Inhibition of SeGSHPx by Au is reversible upon dilution. A direct assay of GSH consumption by concentrated tissue cytosols that was developed to minimize enzyme dilution provided evidence of in vivo inhibition of SeGSHPx in kidney and liver from Au-injected rats. Kidneys of these rats had decreased (P less than 0.05) activities of GSSG reductase (36%), gamma-glutamylcysteine synthetase (19%), and gamma-glutamyl transpeptidase (26%), and increased (P less than 0.05) activities of glucose 6-phosphate dehydrogenase (90%) and GSH S-transferase (130%). The reactivity of fresh plasma SH groups with 5,5'-dithiobis-(2-nitrobenzoic acid) increased as a function of injection time. Enhanced SH reactivity suggests that Au may react with protein GSH-disulfides to release GSH. New findings were (i) decreased platelet SeGSHPx and kidney GSSG reductase in aurothioglucose-injected rats, (ii) direct in vivo inhibition of kidney and liver SeGSHPx in aurothioglucose-injected rats, and (iii) no significant correlation between the activity of GSH-metabolizing enzymes and levels of tissue GSH.

Selenium as a sulfhydryl redox catalyst and survey of potential selenium-dependent enzymes

The ability of selenium (Se) to act as a redox catalyst is an important factor in understanding the biological function of selenoproteins in addition to that of GSH peroxidase. Selenocystine at micromolar levels exhibited pseudothiotransferase activity by enhancing the reduction of 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB) by thiols. In contrast, selenite inhibited the reduction of DTNB by thiols. Selenite was more catalytic than selenocystine in the reduction of cytochrome c by GSH, whereas GSH peroxidase was a weak catalyst. Tissues from Se-deficient and Se-supplemented rats were assayed for activities of GSH-thiotransferase, NADPH cytochrome c reductase, formaldehyde dehydrogenase, and a hypothesized GSH cytochrome c reductase. GSH-thiotransferase activity was significantly increased in the liver of Se-deficient rats. No appreciable activity of this enzyme was found in the kidney of rats from either dietary group. No enzymatic activity for cytochrome c reduction by GSH was detected in cytosols, mitochondria, or microsomes from liver and kidney of Se-deficient or Se-supplemented rats. Formaldehyde dehydrogenase was significantly higher in liver cytosols from Se-supplemented rats than from Se-deficient rats. The higher activity was not attributed to Se-containing proteins, but to an unknown small molecular-weight factor. This study did not support the hypothesis that physiological levels of Se may be involved in sulfhydryl-disulfide exchange reactions in vivo, or that selenium may enhance cytochrome c reduction by GSH in vivo.

Effect of aurothioglucose on glutathione and glutathione-metabolizing and related enzymes in rat liver and kidney

The antirheumatic drug aurothioglucose is an inhibitor of the selenoenzyme GSH peroxidase. During chrysotherapy, the decreased levels of erythrocyte GSH and serum sulfhydryls of rheumatoid arthritis patients are normalized concomitant with clinical efficacy. This investigation examined the in vivo and in vitro effect of gold(I) as aurothioglucose on enzymes related to the GSH redox cycle or metabolism. The enzymes measured were GSH peroxidase, GSSG reductase, gamma-glutamyl transpeptidase, gamma-glutamylcysteine synthetase, GSH S-transferase, GSH thiotransferase, glucose-6-phosphate dehydrogenase, superoxide dismutase and catalase. Rats were injected with 30 mumol aurothioglucose/kg body wt. daily for 7 days by intramuscular injection. GSH levels in aurothioglucose-treated rats were 68% higher in erythrocytes (P less than 0.005) and 45% higher in kidney (P less than 0.001) than in control rats. Treatment with aurothioglucose did not elevate plasma or liver GSH. The enzyme activities that were changed by aurothioglucose treatment were GSH peroxidase in kidney (41% decreased, P = 0.005) and liver (13% decreased, P less than 0.05), gamma-glutamyl transpeptidase in kidney (15% decreased, P less than 0.05), and catalase in kidney (58% decreased, P less than 0.001). Kidney glucose-6-phosphate dehydrogenase activity was increased 50% (P less than 0.005) and GSH S-transferase was increased 72% (P less than 0.001). In vitro the only liver enzymes inhibited more than 50% by concentrations of less than 50 microM aurothioglucose were GSH peroxidase (50% inhibited by 25 microM aurothioglucose) and GSH thiotransferase (50% inhibited by 5 microM aurothioglucose). Studies of in vitro enzyme inhibition by aurothioglucose could not be used to predict decreased enzyme activities in vivo. Although decreased activities of two major enzymes that utilize GSH, GSH peroxidase and gamma-glutamyl transpeptidase, coincided with elevated GSH in kidneys of aurothioglucose-treated rats, a direct cause and effect relationship remains speculative.

Dietary selenium and aniline-induced methemoglobinemia in rats

Depletion of selenium from rats for 8 weeks decreased blood glutathione peroxidase activity to 5.7% of that in selenium-supplemented (0.5 ppm selenium as Na2SeO3) rats. Aniline (60 mg/kg, i.p.) resulted in no significant difference in methemoglobin and blood reduced glutathione (GSH) levels between Se-deficient and Se-supplemented rats. A lowered aniline dose (36 mg/kg, i.p.) also resulted in no difference in methemoglobin levels. The selenium-deficient rat was able to reduce methemoglobin induced by aniline as efficiently as the selenium-sufficient rat.