Ocimum sanctum aqueous leaf extract provides protection against mercury induced toxicity in Swiss albino mice

HgCl2 (5.0 mg/kg body weight) induced toxicity led to significant elevation of lipid peroxidation (LPO) level but decline in the glutathione content in liver of Swiss albino mice. In serum of HgCl2 treated mice there was significant elevation in serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) activities but significant decline in the alkaline phosphatase activity. Animals treated with O. sanctum extract (10 mg/kg body weight, po) before and after mercury intoxication showed a significant decrease in LPO level, SGOT and SGPT activities and increase in serum alkaline phosphatase activity and glutathione (GSH) content. Ocimum treatment alone did not alter SGOT, SGPT and alkaline phosphatase activities but significantly enhanced reduced glutathione. The results suggest that oral administration of Ocimum extract provides protection against HgCl2 induced toxicity in Swiss albino mice.     

Antidiabetic, antihypercholesterolaemic and antioxidant effect of Ocimum sanctum (Linn) seed oil

Antihyperlipidaemic and antioxidant effect of Ocimum sanctum Linn. seed oil (OSSO) was investigated in rabbits. Administration of OSSO (0.8 g/kg body weight/day) for four weeks, in cholesterol (100 mg/kg body weight/day) fed rabbits significantly decreased serum cholesterol, triacylglycerol and LDL-+VLDL-cholesterol as compared to untreated cholesterol fed group. There was significant fall in atherogenic index in OSSO treated group. In addition, treatment with OSSO decreased lipid peroxidation and increased reduced glutathione content in blood. Antidiabetic effect of O. sanctum seed oil was evaluated in alloxan diabetic rabbits. Two weeks treatment of diabetic rabbits with OSSO (0.8 gm/kg/day) showed no significant hypoglycaemic effect. Results of the present study show that OSSO has hypocholesterolaemic and antioxidant effects but it does not have antidiabetic effect.     

Modulation of heme oxygenase in tissue injury and its implication in protection against gastrointestinal diseases.

Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme, followed by production of biliverdin, free iron and carbon monoxide (CO). There are three isoforms of HO: HO-1 is highly inducible, whereas HO-2 and HO-3 are constitutively expressed. In addition to heme, a variety of nonheme compounds, including heavy metals, cytokines, endotoxins and heat shock stress are strong inducers of HO-1 expression. Many studies indicated that induction of HO-1 is associated with a protective response due to the removal of free heme, which is shown to be toxic. However, recent studies demonstrated that the expression of HO-1 in response to different inflammatory mediators could contribute in part to the resolution of inflammation and have protective effects on brain, liver, kidney and lung against injuries. These beneficial effects seem to be due to the production of bile pigment biliverdin and bilirubin that is a potent antioxidant, as well as the release of iron and CO. However, there are few studies concerning the relationship between HO-1 and inflammation as well as injury in the gut. Interestingly, a preliminary study implicated that induction of HO-1 expression in a colonic damage model induced by trinitrobenzene sulfonic acid played a critical protective role, indicating that activation of HO-1 could act as a natural defensive mechanism to alleviate inflammation and tissue injury in the gastrointestinal tract.     

Synthesis and role of glutathione in protection against oxidative stress in yeast

Summary

Glutathione (GSH) is an abundant and ubiquitous low-molecular-mass thiol with proposed roles in many cellular processes including amino acid transport, synthesis of proteins and nucleic acids, modulation of enzyme activity and metabolism of xenobiotics, carcinogens and reactive oxygen species. This review describes recent findings in the lower eukaryote Saccharomyces cerevisiae that are leading to a better understanding of the role of this peptide in eukaryotic cell metabolism. In particular, two gene products involved in maintaining the levels of reduced GSH have been studied; namely, GSH1 encoding γ-glutamylcysteine synthetase, the first step in the biosynthesis of GSH, and glutathione reductase, which recycles glutathione to its reduced form. These studies indicate that GSH is an essential metabolite in yeast, and that it is required for protection against oxidative stress produced by mitochondrial metabolism and exogenous reactive oxygen species. These findings are discussed in the light of analogous observations made in higher eukaryotes.     

Roles of glutathione and glutathione peroxidase in the protection against endothelial cell injury induced by 15-hydroperoxyeicosatetraenoic acid.

We investigated the role of the glutathione redox cycle in endothelial cell injury induced by 15(S)-hydroperoxyeicosatetraenoic acid (15-HPETE), an arachidonate lipoxygenase product. Pretreatment of endothelial monolayers with reduced glutathione (GSH) markedly suppressed 15-HPETE-induced cellular injury, which was determined by the 51Cr-release assay. 15-HPETE-induced cytotoxicity was modified by several GSH-modulating agents such as buthionine sulfoximine and 2-oxothiazolidine-4-carboxylate, indicating that this cyto-protective action of GSH was correlated with the intracellular GSH level. These GSH-modulating agents also modified the conversion of 15-HPETE to 15(S)-hydroxyeicosatetraenoic acid by endothelial cells. On the other hand, the exposure of endothelial cell monolayers to 15-HPETE did not deplete intracellular GSH levels but decreased GSH peroxidase activity. In addition, sodium selenite and ebselen, a stimulator and mimic of GSH peroxidase activity, respectively, displayed remarkable protective effects against 15-HPETE-induced cytotoxicity. These results suggest that intracellular GSH plays a pivotal role in the protection against 15-HPETE-induced endothelial cell injury, and that the decreased activity of GSH peroxidase activity is involved in 15-HPETE-induced cytotoxicity.     

A role of vitamin E in protection against cell injury. Maintenance of intracellular glutathione precursors and biosynthesis

The depletion of cell calcium from isolated rat hepatocytes results in stimulated lipid peroxidation, loss of intracellular and mitochondrial GSH (reduced glutathione), and enhancement of both efflux and oxidation of GSH. These events are followed by cell injury and enhance the susceptibility of the cells to toxic chemicals. It is shown herein that an initial event in the generation of such injury is the depletion of cellular alpha-tocopherol. alpha-Tocopheryl succinate addition (25 microM) to the calcium-depleted cells markedly elevated the alpha-tocopherol content of the cells, inhibited the associated lipid peroxidation, and maintained intracellular GSH levels without affecting its efflux or redox status. This resulted in an enhanced formation of total glutathione after a 5-h incubation, which correlated with the alpha-tocopherol content of the cells, and was greater than that expected by a direct sparing action of vitamin E. Inhibition of hepatocyte glutathione biosynthesis by buthionine sulfoximine (0.5 mM) eliminated the enhancement of GSH formation by vitamin E. Analysis of endogenous and 35S-labelled precursors of glutathione biosynthesis by high-performance liquid chromatography demonstrated that the depletion of cellular alpha-tocopherol resulted in the efflux of glutathione precursors. It is concluded that cell injury associated with alpha-tocopherol depletion is partly the result of the efflux of glutathione precursors, and hence diminished biosynthesis and intracellular levels of GSH. These losses and resultant cell injury are preventable by maintenance of cellular alpha-tocopherol levels.     

Anticonvulsant potential of holy basil, Ocimum sanctum Linn., and its cultures

Callus cultures from stem of O. sanctum were induced on slightly modified Murashige and Skoog's (MS) medium and supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D, 1-2 ppm) and kinetin (kn, 1 ppm). Different extractives of stem, leaf and stem callus of O. sanctum were tested for anticonvulsant activity against standard drug phenytoin using maximal electroshock (MES) model. Ethanol and chloroform extractives of stem, leaf and stem calli were effective in preventing tonic convulsions induced by transcorneal electroshock.     

Azadirachta indica and Ocimum sanctum leaf extracts alleviate arsenic toxicity by reducing arsenic uptake and improving antioxidant system in rice seedlings

In the present study the potentials of aqueous extracts of the two plants, neem (Azadirachta indica) and Tulsi (Ocimum sanctum) were examined in alleviating arsenic toxicity in rice (Oryza sativa L.) plants grown in hydroponics. Seedlings of rice grown for 8 days in nutrient solution containing 50 μM sodium arsenite showed decline in growth, reduced biomass, altered membrane permeability and increased production of superoxide anion (O2·−), H2O2 and hydroxyl radicals (·OH). Increased lipid peroxidation marked by elevated TBARS (thiobarbituric acid reactive substances) level, increased protein carbonylation, alterated levels of ascorbate, glutathione and increased activities of enzymes SOD (superoxide dismutase), CAT (catalase), APX (ascorbate peroxidase) and GPX (glutathione peroxidase) were noted in the seedlings on As treatment. Exogenously added leaf aqueous extracts of Azadirachta indica (0.75 mg mL−1, w/v) and Ocimum sanctum (0.87 mg mL−1, w/v) in the growth medium considerably alleviated As toxicity effects in the seedlings, marked by reduced As uptake, restoration of membrane integrity, reduced production of ROS, lowering oxidative damage and restoring the levels of ascorbate, glutathione and activity levels of antioxidative enzymes. Arsenic uptake in the seedlings declined by 72.5% in roots and 72.8% in shoots, when A. indica extract was present in the As treatment medium whereas with O. sanctum extract, the uptake declined by 67.2% in roots and 70.01% in shoots. Results suggest that both A. indica and O. sanctum aqueous extracts have potentials to alleviate arsenic toxicity in rice plants and that A. indica can serve as better As toxicity alleviator compared to O. sanctum.     

Modulation of rat erythrocyte antioxidant defense system by buthionine sulfoximine and its reversal by glutathione monoester therapy

The protective effects of glutathione monoester (GME) on buthionine sulfoximine (BSO)-induced glutathione (GSH) depletion and its sequel were evaluated in rat erythrocyte/erythrocyte membrane. Animals were divided into three groups (n=6 in each): control, BSO and BSO+GME group. Administration of BSO, at a concentration of 4 mmol/kg bw, to the albino rats resulted in depletion of blood GSH level to about 59%. GSH was elevated several folds in the GME group as compared to the control (P<0.05) and BSO (P<0.001) groups. Decreased concentration of vitamin E was found in the erythrocyte membrane isolated from BSO-administered animals. Antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) were also found to be altered due to BSO-induced GSH depletion in blood erythrocytes. The SOD and CAT activities in BSO group were significantly lower (P<0.001) than the other groups. Lipid peroxidation index and malondialdehyde (MDA) levels in erythrocytes and their membranes were increased to about 45% and 40%, respectively. The activities of Ca2+ ATPase, Mg2+ ATPase and Na+K+ ATPase were lower than those of control group (P<0.05), whereas the activities of these enzymes were found to be restored to normal followed by GME therapy (P<0.05). Cholesterol, phospholipid and C/P ratio and some of the phospholipid classes like phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin were significantly (P<0.05) altered in the erythrocyte membranes of BSO-administered rats compared with those of control group. These parameters were restored to control group levels in GME-treated group. Oxidative stress may play a major role in the BSO-mediated gamma glutamyl cysteine synthetase (gamma-GCS) inhibition and hence the depletion of GSH. In conclusion, our findings have shown that antioxidant status decreased and lipid peroxidation increased in BSO-treated rats. GME potentiates the RBC and blood antioxidant defense mechanisms and decreases lipid peroxidation.     

Modulation of glutathione synthetic enzymes by acidic fibroblast growth factor

Increasing evidence suggests that glutathione (GSH) synthesis is a regulated process. Documented increases in gamma-glutamylcysteine synthetase (GCS) occur in response to oxidants, in tumors, on plating cells at a low cell density, and with nerve growth factor stimulation, suggesting that GSH synthesis may be related to the cell growth and transformation. Previously, extracellular acidic fibroblast growth factor (FGF-1) has been demonstrated to cause transformation and aggressive cell growth in murine embryonic fibroblasts. In the present investigation, we sought to determine whether FGF-1, with its growth inducing properties, resulted in the modulation of GSH biosynthetic enzymes, GCS and GSH synthetase. Murine fibroblasts transduced with (hst/KS)FGF-1, a chimeric human FGF-1 gene containing a signal peptide sequence for secretion, displayed elevated gene expression of both heavy and light subunits of GCS. Activity of GSH synthetase was also elevated in these cells compared with control cells. Nonetheless, GSH was decreased in the FGF-1-transduced cells along with high energy phosphates, adenine nucleotides, NADH, and the redox poise. However, GSSG was not elevated in these cells. Fibroblasts stably expressing human immunodeficiency virus type 1 Tat, which induces intrinsic FGF-1 secretion, resulted in similar changes in GCS, GS, and GSH. The results suggest that although increases in the enzymes of GSH synthesis are a common response to growth factors, an increase in GSH content per se is not required for altered cell growth.     

Antioxidant and radioprotective properties of an Ocimum sanctum polysaccharide

The antioxidant activity of two polysaccharides isolated from the Indian medicinal plants, Ocimum sanctum and Tinospora malabarica, was studied. Only the O. sanctum polysaccharide (OSP) showed significant activity. OSP could prevent oxidative damage to liposomal lipids and plasmid DNA induced by various oxidants such as iron, AAPH and gamma-radiation, besides scavenging important ROS such as the superoxide radical and hydrogen peroxide and inhibiting xanthine oxidase. In addition, OSP could prevent gamma-radiation-mediated cell deaths in mouse splenocytes.     

Probucol promotes endogenous antioxidant reserve and confers protection against reperfusion injury

The present study examines whether a subchronic probucol treatment of rats offers protection against ischemia-reperfusion (IR) injury in isolated perfused hearts. Sprague-Dawley rats were treated every second day per week with probucol (cumulative dose 120 mg/kg body mass, i.p.) for 4 weeks. In the probucol group, baseline myocardial antioxidant enzyme, glutathione peroxidase (GSHPx), activity was increased (p<0.05), whereas superoxide dismutase (SOD) and catalase (CAT) activities were not changed. Baseline oxidative stress, as indicated by the myocardial lipid peroxidation, was less (p<0.05) in the probucol group. Isolated hearts were subjected to 60 min global I and 20 min R. Recovery of the contractile function in globally ischemic hearts upon reperfusion was 36% in untreated group and 74% in the probucol group. After IR, GSHPx and CAT activities were significantly (p<0.05) higher in the probucol group compared with the control group, whereas SOD did not change. Lipid peroxidation owing to IR was significantly less in the probocol group. These data suggest that probucol treatment improves endogenous antioxidant reserve and protects against increased oxidative stress following IR injury.     

Evaluation of nootropic potential of Ocimum sanctum Linn. in mice

Dementia is one of the age related mental problems and a characteristic symptom of various neurodegenerative disorders including Alzheimer's disease. Certain drugs like diazepam, barbiturates and alcohol disrupt learning and memory in animals and man. However, a new class of drugs known as nootropic agents is now used in situations where there is organic disorder in learning abilities. The present work was undertaken to assess the potential of O. sanctum extract as a nootropic and anti-amnesic agent in mice. Aqueous extract of dried whole plant of O. sanctum ameliorated the amnesic effect of scopolamine (0.4 mg/kg), diazepam (1 mg/kg) and aging induced memory deficits in mice. Elevated plus maze and passive avoidance paradigm served as the exteroceptive behavioral models. O. sanctum extract decreased transfer latency and increased step down latency, when compared to control (piracetam treated), scopolamine and aged groups of mice significantly. O. sanctum preparations could of beneficial in the treatment of cognitive disorders such as dementia and Alzheimer's disease.     

Modulation of endoperoxide product levels and cyclophosphamide-induced injury by glutathione repletion

Glutathione is a tripeptide important in a number of diverse cellular functions including enzymatic reactions involved in prostaglandin endoperoxide metabolism. We have previously reported that cyclophosphamide administration to rats results in acute lung injury manifested by increased bronchoalveolar lavage albumin concentrations. In the current study we examine whether cyclophosphamide treatment affects pulmonary glutathione stores or bronchoalveolar endoperoxide metabolic product levels and whether these effects may be related to acute lung injury caused by the drug. We show that cyclophosphamide treatment causes a dose-dependent reduction in pulmonary glutathione stores 4 h after drug administration. In addition, acute lung injury as the result of cyclophosphamide can be abrogated by coadministration of oxothiazolidine carboxylate, an intracellular cysteine delivery system that also reverses pulmonary glutathione depletion induced by cyclophosphamide in our study. Finally, cyclophosphamide treatment reduces prostaglandin E2 concentrations in bronchoalveolar lavage and alveolar macrophage culture supernatant in a dose-dependent fashion and increases bronchoalveolar thromboxane concentrations in low dose-treated animals. These effects are reversed to a variable degree by coadministration of oxothiazolidine carboxylate. Our study suggests in vivo pulmonary arachidonic acid metabolism and cyclophosphamide-induced acute lung injury are modulated by cellular glutathione stores. These findings may have important implications for the treatment of acute lung injury.     

Renal antioxidant enzymes and glutathione redox status in leptin-induced hypertension

Previously, we have demonstrated that leptin increases blood pressure (BP) in the rats through two oxidative stress-dependent mechanisms: stimulation of extracellular signal-regulated kinases (ERK) by H(2)O(2) and scavenging of nitric oxide (NO) by superoxide (O(2-.)). Herein, we examined if renal glutathione system and antioxidant enzymes determine the mechanism of prohypertensive effect of leptin. Leptin administered at 0.5 mg/kg/day for 4 or 8 days increased BP and renal Na(+),K(+)-ATPase activity and reduced fractional sodium excretion; these effects were prevented by NADPH oxidase inhibitor, apocynin. Superoxide scavenger, tempol, abolished the effect of leptin on BP and renal Na(+) pump in rats receiving leptin for 8 days, whereas ERK inhibitor, PD98059, was effective in animals treated with leptin for 4 days. Leptin administered for 4 days decreased glutathione (GSH) and increased glutathione disulfide (GSSG) in the kidney. In animals receiving leptin for 8 days GSH returned to normal level, which was accompanied by up-regulation of gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of the GSH biosynthetic pathway. In addition, superoxide dismutase (SOD) activity was decreased, whereas glutathione peroxidase (GPx) was increased in rats receiving leptin for 8 days. Cotreatment with gamma-GCS inhibitor, buthionine sulfoximine (BSO), accelerated, whereas GSH precursor, N-acetylcysteine (NAC), attenuated leptin-induced changes in gamma-GCS, SOD, and GPx. In addition, coadministration of BSO changed the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent in animals receiving leptin for 4 days, whereas NAC had the opposite effect in rats treated with leptin for 8 days. These results suggest that initial change in GSH redox status induces decrease in SOD/GPx ratio, which results in greater amount of (O)2-.)) versus H(2)O(2) in later phase of leptin treatment, thus shifting the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent.     

Involvement of glutathione and glutathione-related enzymes in the protection of normal and trisomic human fibroblasts against daunorubicin

We measured the glutathione content, and the activity of glutathione-related enzymes and DT-diaphorase in cultured normal (cell line: S-126) and trisomic (cell lines: S-158, S-240) human fibroblasts exposed to daunorubicin (DNR). Determination of reduced and total glutathione levels, and measurement of the activity of glutathione peroxidase, glutathione reductase, glutathione-S-transferase and DT-diaphorase were performed spectrophotometrically. Human fibroblasts were exposed to 4 microm DNR for 2 h, and the cells placed in drug-free medium for 6, 12, 24, 48, and 72 h. Cellular levels of GSH and total glutathione decreased following exposure to DNR. However, the ratio of GSH to total glutathione returned to control levels only in trisomic cells. These changes were concomitant with increasing glutathione-S-transferase and glutathione reductase activities. DNR also significantly increased the activity of Se-independent peroxidase and DT-diaphorase in trisomic fibroblasts. Marked increases in the activity of Se-dependent peroxidase and DT-diaphorase alone were seen in normal cells. The results provide the first evidence that DNR can induce alterations in the level of glutathione and glutathione-dependent enzymes in trisomic fibroblasts as compared to normal cells, which may provide additional protection against daunorubicin-induced oxidative stress in trisomic fibroblasts.     

Protective effect of glutathione and selenium against alloxan induced lipid peroxidation and loss of antioxidant enzymes in erythrocytes

Alloxan is a diabetogenic drug and is known to induce diabetes through generation of free radicals. The toxic oxygen species can be detoxified by antioxidant enzyme system and thus reduce the deleterious effect of lipid peroxidation. Erythrocytes exposed to alloxan induced lipid peroxidationin vivo as well asin vitro. Although alloxan treatment produced a deleterious effect on antioxidant enzymes, pretreatment with glutathione and selenium led to a recovery of the activities of superoxide dismutase and glutathione peroxidase. However, catalase activity increased on alloxan treatment. Alloxan reduced blood glucose level significantly within 60 min but thereafter a slow and steady rise was observed.