Protective effect of ascorbic acid against lipid peroxidation and oxidative damage in cardiac microsomes

Combined effects of treatment with vitamin C, vitamin E and selenium on the skin of diabetic rats

The aim of this study was to investigate the effects of vitamin C, vitamin E and selenium (Se) on the skin tissue of streptozotocin-induced diabetic rats. Swiss albino rats were divided into four groups: control, control + antioxidants, diabetic, diabetic + antioxidants groups. Diabetes was induced by intraperitoneal injection of 65 mg/kg streptozotocin. Vitamin C (250 mg/kg), vitamin E (250 mg/kg) and Se (0.2 mg/kg) were given by gavage technique to rats of one diabetic and one control group for 30 days. In the diabetic group, the levels of serum urea and creatinine, skin lipid peroxidation and nonenzymatic glycosylation levels increased, but skin glutathione levels decreased. Treatment with vitamin C, vitamin E and Se reversed these effects. The present study showed that vitamin C, vitamin E and Se exerted antioxidant effects and consequently may prevent skin damage caused by streptozotocin-induced diabetes.

Age related modifications of soluble proteins in various organs of male garden lizard, Calotes versicolor

The oxidative modification of proteins measured as carbonyl derivatives increased with advancing age in the liver of male garden lizard. The same parameter did not show a significant change in other organs (brain, heart and kidney). Based on the observations in both homeotherms (mammals) and poikilotherms (insect and reptile), the in vivo oxidative modification of cellular proteins appears to be the most common mechanism leading to accumulation of altered proteins during aging. However, the degree of modifications may vary among the tissues/organs of a species. On the other hand the variations may also account for the role of modification of proteins in the pattern of aging in different species.

Status of antioxidant defense system in chromium-induced Swiss mice tissues

Based on epidemiological studies, chromium(VI) compounds are considered as more toxic and carcinogenic than chromium(III) compounds. The deleterious effects of chromium(VI) compounds are diversified affecting almost all the organ systems in a wide variety of animals. The present study, describes the cytotoxic effects of chromium trioxide, a well-known chromium(VI) compound in three tissues (liver, kidney, lungs) of male Swiss mice during post-treatment phase (5th-8th week after treatment). Lipid peroxidation, an index of oxidative stress, was determined as thiobarbituric acid-reactive substances (TBA-Rs) in mice tissues dosed with a single intraperitoneal injection of chromium trioxide (1mg/kg body weight). Tissue specific and statistically significant increases in TBA-Rs was observed in chromium-treated mice groups compared to controls in all the weeks of post-treatment. Endogenous ascorbic acid (vit-C) content of tissues which happens to be one of the stable antioxidants, declined significantly due to chromium-induction. Activity of antioxidative enzymes like superoxide dismutase (SOD), catalase (CT) and peroxidase (PD) was significantly inhibited among chromium-injected mice groups compared to respective controls. Protective role of ascorbic acid and the antioxidative enzymes in chromium-induced cytotoxicity in mice is discussed.

Potential role of vitamins in chromium induced spermatogenesis in Swiss mice

Chromium (Cr) (VI) compounds are known carcinogens and mutagens. The mechanism of carcinogenicity and mutagenicity caused by chromium(VI) compounds remained unclear for several years. However, in the recent past chromium-induced carcinogenicity and/or mutagenicity was known to happen due to the generation of reactive oxygen species (ROS). In the present context, chromic acid (CrO(3)), a potential Cr(VI) compound could be able to generate reactive oxygen radicals in the testes of Swiss mice as evidenced from significantly higher lipid peroxidation compared to untreated controls. The cytotoxic effects of the compound on the testes are depicted in terms of significantly reduced sperm count level accompanied with increased abnormal sperm population in treated mice. Supplementation of vitamins like Vitamin C and Vitamin E (Vit C and Vit E) to CrO(3) injected mice groups could partially prevent the incidence of abnormal sperm population and increased the sperm count. Of the two vitamins, taken for the study, Vit C happens to be more effective in ameliorating germ cells from degeneration and from mutation to abnormal sperm. Possible antioxidative role of both the vitamins have been studied for significant decrease in lipid peroxidation associated with marked elevation in sperm count level and significant decrease in the percentage of abnormal sperm formation in CrO(3)-treated mice.

Effect of age on lipid peroxides, lipofuscin and ascorbic acid contents of the lungs of male garden lizard

Oxidative damage was assessed through the estimation of lipid peroxides (LP) in the lungs of an ageing short-lived species of reptile, Calotes versicolor, commonly known as the garden lizard. Attempts were also made to trace its relationship with the age pigment, lipofuscin and the antioxidant ascorbic acid. While LP increased with advancing age the contents of both lipofuscin and ascorbic acid did not show appreciable change during maturation ( < 1-1 year old) but declined during senescence phase (1 to 2-4 year old). While the pattern of age associated changes in LP and ascorbic acid indicate similarity with the pattern observed in most of the mammals, the reduction of lipofuscin in older lizards is a significant departure from the common trend.

Reduction of lipid peroxidation in different brain regions by a combination of alpha-tocopherol and ascorbic acid

Lipid peroxidation an outcome of free radicals activity has been hypothesized as one of the possible factor involved in the pathogenesis of neuronal damage. We investigated the effects of free radical scavengers, alpha-tocopherol (T) and ascorbic acid (A) combination (TA-combination) to attenuate tert-butyl hydroperoxide (t-BuOOH)-induced lipid peroxidation in different regions of mice brain. Examinations of effect of three regimens (100, 200, 300 mg/kg body weight) of t-BuOOH on mid brain, cerebellum, striatum, cortex and hippocampus revealed dose and time dependent increase in lipid peroxidation. We observed that prior supplementation of TA-combination reduced lipid peroxidation induced by t-BuOOH in every brain region. These findings suggest that TA-combination may play a vital role in protecting the brain tissue against free radicals.

Biochemistry and pathology of radical-mediated protein oxidation

Radical-mediated damage to proteins may be initiated by electron leakage, metal-ion-dependent reactions and autoxidation of lipids and sugars. The consequent protein oxidation is O2-dependent, and involves several propagating radicals, notably alkoxyl radicals. Its products include several categories of reactive species, and a range of stable products whose chemistry is currently being elucidated. Among the reactive products, protein hydroperoxides can generate further radical fluxes on reaction with transition-metal ions; protein-bound reductants (notably dopa) can reduce transition-metal ions and thereby facilitate their reaction with hydroperoxides; and aldehydes may participate in Schiff-base formation and other reactions. Cells can detoxify some of the reactive species, e.g. by reducing protein hydroperoxides to unreactive hydroxides. Oxidized proteins are often functionally inactive and their unfolding is associated with enhanced susceptibility to proteinases. Thus cells can generally remove oxidized proteins by proteolysis. However, certain oxidized proteins are poorly handled by cells, and together with possible alterations in the rate of production of oxidized proteins, this may contribute to the observed accumulation and damaging actions of oxidized proteins during aging and in pathologies such as diabetes, atherosclerosis and neurodegenerative diseases. Protein oxidation may also sometimes play controlling roles in cellular remodelling and cell growth. Proteins are also key targets in defensive cytolysis and in inflammatory self-damage. The possibility of selective protection against protein oxidation (antioxidation) is raised.

In vitro influence of ascorbate on lipid peroxidation in rat testis and heart microsomes

Lipid peroxidation (LPO) in rat testis and heart microsomes was compared using the ADP/Fe2+ as initiator with and without ascorbate at different concentrations. The extent of LPO was estimated by the levels of TBARS and PUFA. Without ascorbate, LPO was higher in heart than in testis despite elevated levels of catalase in heart. With increased ascorbate concentrations, a biphasic effect of LPO was observed. For a concentration < or = 0.2 mM, ascorbate acted as pro-oxidant and increased TBARS correlated with decreased PUFA were observed both in testis and heart. Above 0.2 mM, ascorbate acts as antioxidant but differences in the rate of LPO were observed. In heart decreased TBARS correlated with increased PUFA whereas in testis TBARS only decreased, PUFA were not significantly modified. These results suggest different mechanisms in LPO initiation in the two organs. Increasing concentrations of H2O2 produced directly elevated TBARS levels in testis while a lag phase was observed in heart before the increase, suggesting that H2O2 was the essential ROS produced by ascorbate-ADP/Fe2+. The effects of scavengers such as catalase and ethanol showed an inhibitory effect on TBARS production only in testis, suggesting the role of H2O2/OH. as an initiator of LPO. In heart, catalase produced a slight increase in TBARS levels whereas no modification was observed with ethanol, suggesting a possible direct activation by ADP/Fe2+ through a metal-oxo intermediate.

NADPH-initiated cytochrome P450-dependent free iron-independent microsomal lipid peroxidation: specific prevention by ascorbic acid

In this paper we demonstrate that ascorbic acid specifically prevents NADPH-initiated cytochrome P450 (P450)-mediated microsomal lipid peroxidation in the absence of free iron. Lipid peroxidation has been evidenced by the formations of conjugated dienes, lipid hydroperoxide and malondialdehyde. Other scavengers of reactive oxygen species including superoxide dismutase, catalase, glutathione, alpha-tocopherol, uric acid, thiourea, mannitol, histidine, beta-carotene and probucol are ineffective to prevent the NADPH-initiated P450-mediated free iron-independent microsomal lipid peroxidation. Using a reconstituted system comprised of purified NADPH-P450 reductase, P450 and isolated microsomal lipid or pure L-alpha-phosphatidylcholine diarachidoyl, a mechanism has been proposed for the iron-independent microsomal lipid peroxidation and its prevention by ascorbic acid. It is proposed that the perferryl moiety P450 Fe3+.O2.- initiates lipid peroxidation by abstracting methylene hydrogen from polyunsaturated lipid to form lipid radical, which then combines with oxygen to produce the chain propagating peroxyl radical for subsequent formation of lipid peroxides. Apparently, ascorbic acid prevents initiation of lipid peroxidation by interacting with P450 Fe3+.O2.-.

Ascorbic acid prevents lipid peroxidation and oxidative damage of proteins in guinea pig extrahepatic tissue microsomes

It has recently been indicated that in the absence of free iron, NADPH initiates oxidative damage of proteins in guinea pig liver microsomes and also lipid peroxidation and protein damage in cardiac microsomes and that ascorbic acid specifically inhibits both the lipid peroxidation and protein damage [Mukhopadhyay CK, Chatterjee IB: J Biol Chem 269: 13390-13397, 1994; Mukhopadhyay M et al.: Mol Cell Biochem 126: 69-75, 1993]. In this paper we demonstrate that Fe(III)-independent NADPH-initiated lipid peroxidation and oxidative damage of proteins occur in the microsomes of all the extrahepatic tissues including lung, kidney, adrenal gland and brain and that both the lipid peroxidation and protein damage are specifically prevented by ascorbic acid. We further demonstrate that when NADPH is replaced by O2 as the electron donor, the O2-initiated lipid peroxidation and protein damage are also inhibited by ascorbic acid.