Effects of alpha-tocopherol on thiobarbituric acid reactive substances in serum and hepatic subcellular organelles and lipid metabolism

Physiological and molecular responses to heavy metal stresses suggest different detoxification mechanism of Populus deltoides and P. x canadensis

Plants have divergent defense mechanisms against the harmful effects of heavy metals present in excess in soils and groundwaters. Poplars (Populus spp.) are widely cultivated because of their rapid growth and high biomass production, and members of the genus are increasingly used as experimental model organisms of trees and for phytoremediation purposes. Our aim was to investigate the copper and zinc stress responses of three outstanding biomass producer bred poplar lines to identify such transcripts of genes involved in the detoxification mechanisms, which can play an important role in the protection against heavy metals. Poplar cuttings were grown hydroponically and subjected to short-term (one week) mild and sublethal copper and zinc stresses. We evaluated the effects of the applied heavy metals and the responses of plants by detecting the changes of multiple physiological and biochemical parameters. The most severe cellular oxidative damage was caused by 30μM copper treatment, while zinc was less harmful. Analysis of stress-related transcripts revealed genotype-specific differences that are likely related to alterations in heavy metal tolerance. P. deltoides clones B-229 and PE 19/66 clones were clearly more effective at inducing the expression of various genes implicated in the detoxification process, such as the glutathione transferases, metallothioneins, ABC transporters, (namely PtGSTU51, PxMT1, PdABCC2,3), while the P. canadensis line M-1 accumulated more metal, resulting in greater cellular oxidative damage. Our results show that all three poplar clones are efficient in stress acclimatization, but with different molecular bases.

Effects of low-dose X-ray irradiation on biomembrane in brain cortex of aged rats

We previously found that low-dose X-ray irradiation or radon (weak alpha-ray) inhalation increases SOD activities and reduces lipid peroxide levels in various organs of 7-week-old rats or rabbits. In this study, we examined how the changes of SOD activity, lipid peroxide level, and membrane fluidity of the cerebral cortex in aged male Wistar rats (65 and 91 weeks old) were affected by low-dose X-ray irradiation (100 cGy or under) compared with those in 7-week-old rats, to elucidate the mechanism of aging inhibition. The following results were obtained: Although radiation sensitivity was observed to decreases with age, low-dose irradiation changed the Mn-SOD activity, lipid peroxide level, and membrane protein fluidity parameter of the cerebral cortex in the age rats to be closer to those in the youth. These findings suggest that the increased SOD activity induced by low-dose irradiation enhances biomembrane functions, and that the decrease of lipid peroxide level enhances the membrane protein fluidity.

Age-related change of free radical generation in liver and sex glands of rats

Many investigations have been made on age-related changes of lipid peroxidation in tissue homogenates and subcellular fractions. However, to date there are few reports on the age-related change of free radicals in living organs during aging. In our study, we investigated free radical concentration in liver and sex glands of different aged rats by using electron spin resonance (ESR) technique. A significant reduction of free radicals in liver and sex glands of old aged rats was observed when compared with those of young or middle-aged ones. The decrease of free radical generation during aging is discussed.

No relationship between the age-related decrease in prostacyclin production and the level of intracellular lipid peroxidation in human umbilical vein endothelial cells in culture

Some investigators have speculated that a decrease in prostacyclin production observed during ageing of endothelial cells is caused by an increase in intracellular lipid peroxide. We checked this speculation using an in vitro model to study the ageing of human vascular endothelial cells. For this purpose we determined the levels of intracellular lipid peroxide of endothelial cells at various culture ages, and found that the level of intracellular lipid peroxidation did not increase during in vitro ageing. Amounts of intracellular lipid peroxide also differed depending on the growth phase, the addition of heparin and the strain of endothelial cells, but the cells producing prostacyclin at a low level did not necessarily contain larger amounts of intracellular lipid peroxide. Therefore, we postulate that the age-related decrease in prostacyclin production is not due to an increase in the amount of intracellular lipid peroxide as a function of age.

Increased hepatic lipid peroxidation in aged mice

In recent years, the free radical theory of aging has attained great interest. Many studies on aging using tissue homogenates and subcellular fractions have provided evidence for the occurrence of lipid peroxidation. However, there are studies which report decrease or no significant change in parameters of lipid peroxidation. In our study, we investigated whether hepatic lipid peroxidation levels in male Swiss-Albino mice change with age. Three groups of animals, 3, 6 and 18 months old, were used. The diene conjugate and malondialdehyde levels of liver homogenates, mitochondria and microsomes were measured. Significant increases in both diene conjugate and malondialdehyde levels of liver homogenates and mitochondria have been observed in 18-month-old mice when compared with those aged 3 and 6 months. As for microsomes, only malondialdehyde levels were elevated in the old group when compared with young and adult groups. Both parameters were significantly increased in aged mice which indicate that lipid peroxidation is important in advancing age in mice.

Serum lipid peroxide assayed by a new colorimetric method

Serum lipid peroxide (LPO) in 72 healthy male subjects was studied using a newly developed assay method based on the reaction of LPO with methylene blue derivative (MCDP; 10-N-Methylcarbamoyl-3,7-dimethylamino-10 H-phenothiazine). This method is specific for lipid hydroperoxide and the relation is equimolar. The value obtained was 7.63 +/- 2.78 nmol/ml. Positive correlations were observed between LPO and height (r = 0.290), body weight (r = 0.244) and hemoglobin (r = 0.248). However, no significant correlation was observed between serum LPO level and other clinical data, including age. In addition, serum LPO value measured by this method did not show significant correlation with that measured by the thiobarbituric acid method in rat serum. This discrepancy might be due to the differences in substrates measured by each method.

Senescence-associated decrease of NADPH-induced lipid peroxidation in rat liver microsomes

Senescence is associated with decrease in the NADPH-induced lipid peroxidation in liver homogenate as well as rough and smooth microsomes of female rats. In the microsomal fractions, sensitivity to NADPH-induced lipid peroxidation is high in young adults (3-month-old), decreases in middle aged (12-month-old) and reaches lowest levels in senescent (30-month-old) rats. Increasing the concentration of co-factors or time of incubation does not alter this resistance observed in the senescent rats. Major factors responsible for this resistance in senescent rats seem to be low levels of substrate in the c reductase, cytochrome P-450 and high cholesterol:phospholipid ratios besides enhanced levels of superoxide dismutase, alpha-tocopherol and reduced glutathione.

Lipid peroxidation in liver, plasma, and erythrocytes of rats chronically treated with ethanol

The effect of ingestion of water containing 20% ethanol for 1-2 months on lipid peroxide levels of liver, plasma, and erythrocyte was investigated in rats. Our results show that elevated plasma lipid peroxide levels and erythrocyte susceptibility to lipid peroxidation may reflect stimulated lipid peroxidation in rat liver following chronic ethanol ingestion.

Long term treatment with theophylline increases malonyl dialdehyde plasma concentrations

As theophylline is known to stimulate lipolysis and lipid mobilisation, plasma concentrations of malonyl dialdehyde were studied in asthmatic patients being treated with sustained release theophylline. Malonyl dialdehyde was assessed as malonyl dialdehyde like material (MDA-LM) by the thiobarbituric acid assay. In a kinetic study (eight patients) plasma MDA-LM concentrations were found to be significantly higher after 30 than after eight days' treatment or before treatment, but not significantly different after 90 than after 30 days. In a comparative study (29 patients and 29 healthy volunteers) the mean plasma MDA-LM concentration was shown to be very significantly higher in the asthmatic group. The results are probably explained by an effect of theophylline on lipid peroxidation, and the effect of long term treatment on plasma MDA-LM merits further investigation.

Serum lipid peroxide in cerebrovascular disorders determined by a new colorimetric method

A new colorimetric method for quantitative analysis of serum lipid peroxide, free of interference from sialic acids, has been developed. We have used the thiobarbituric acid dissolved in sodium sulfate solution and both liberation of lipid peroxide and color reaction have been performed simultaneously by heating serum protein precipitate with this reagent in a weak acid solution. The new method is specific and facilitates the precise measurements of serum lipid peroxide. The average values determined by the new method increased slightly with age in healthy subjects. In patients with sequelae of cerebrovascular disorders, serum lipid peroxide values were higher than in healthy controls. These results may demonstrate the important role of lipid peroxide in aging and cerebrovascular disorders.