Counterpoint,patronage and professionalism

Abstract

Several studies have shown the role of thiol-rich proteins especially metallothionein (MT) in the therapeutic interventions against oxidative damage. Previously, we have provided strong evidence for the involvement of ROS in iron nitrilotriacetate (Fe-NTA)-induced renal toxicity, which may have relevance to its carcinogenicity. The purpose of this study was to evaluate the role of zinc metallothionein (Zn-MT) on the protection against Fe-NTA-induced renal oxidative damage. The results demonstrate that Zn-MT pretreatment provided protection against Fe-NTA-induced mortality in mice (40% protection). Similarly, Zn-MT pretreatment also provided protection against Fe-NTA-induced lipid peroxidation (26% inhibition, P < 0.001). It is proposed that Zn-MT protects kidney tissue against the noxious effect of Fe-NTA primarily by interference with lipid peroxides. It is concluded that Zn-MT may serve as an excellent physiological antioxidant against Fe-NTA-mediated renal oxidative damage.     

Nitroglycerin, a nitric oxide generator attenuates ferric nitrilotriacetate-induced renal oxidative stress, hyperproliferative response and necrosis in ddY mice

Nitric oxide (NO) is a short lived, readily diffusible intracellular messenger molecule associated with multiple organ-specific regulatory functions. In this communication, we elucidate the effect of exogenous NO administration, using nitroglycerin (GTN), on ferric nitrilotriacetate (Fe-NTA)-induced renal oxidative stress, hyperproliferative response and necrosis in ddY mice. Fe-NTA is a known complete renal carcinogen as well as renal and hepatic tumor promoter, which act by generating oxidative stress in the tissues. GTN treatment to ddY mice prior to Fe-NTA administration resulted in a highly significant protection against Fe-NTA-induced renal oxidative stress, hyperproliferative response and necrosis. In oxidative stress protection studies, the decrease in the level of renal glutathione and antioxidant enzyme activities induced by Fe-NTA were significantly reversed by GTN pretreatment in a dose-dependent manner (12-46% recovery, P<0.05-0.001). GTN pretreatment also resulted in a dose-dependent inhibition (24-39% inhibition, P<0.05-0.001) of Fe-NTA-induced lipid peroxidation as measured by TBARS formation in renal tissues. Similarly, in hyperproliferation protection studies, GTN pretreatment showed a strong inhibition of Fe-NTA-induced renal ornithine decarboxylase (ODC) activity (51-57% inhibition, P<0.001) and [3H]thymidine incorporation (43-58% inhibition, P<0.001) into renal DNA. GTN pretreatment almost completely prevented kidney biomolecules from oxidative damage and protected the tissue against the observed histopathological alterations. From this data, it can be concluded that exogenously produced NO from GTN might scavenge reactive oxygen species (ROS) and decreases toxic metabolites of Fe-NTA and thereby inhibiting renal oxidative stress. In addition, exogenously produced NO can also inhibit Fe-NTA-induced hyperproliferative response by down-regulating the activity of ODC and the rate of [3H]thymidine incorporation into renal DNA and could be suggested as another possible clinical application for this NO-donor (GTN, traditionally used as a vasodilator) in oncological medicine.     

Vitamin E inhibits hepatic oxidative stress, toxicity and hyperproliferation in rats treated with the renal carcinogen ferric nitrilotriacetate

Ferric nitrilotriacetate (Fe-NTA) is a potent renal and hepatic tumor promoter, which acts through a mechanism involving oxidative stress. Fe-NTA when injected intraperitoneally into rats induces hepatic ornithine decarboxylase activity as well as hepatic DNA synthesis. Vitamin E is a well-known, lipid-soluble and chain-breaking antioxidant which protects cell membranes from peroxidative damage. In this study, we investigated the protective effect of vitamin E, a major fat-soluble antioxidant, against Fe-NTA-mediated hepatic oxidative stress, toxicity and hyperproliferation in Wistar rats. Animals were treated with two different doses of vitamin E for 1 week prior to Fe-NTA treatment. Vitamin E at a higher dose of 2.0 mg/animal/day showed significant reduction in Fe-NTA-induced hepatic ornithine decarboxylase activity, DNA synthesis, microsomal lipid peroxidation and hydrogen peroxide generation. Fe-NTA treatment alone caused depletion of glutathione, glutathione metabolizing and antioxidant enzymes in rat liver, whereas pretreatment of animals with vitamin E reversed these changes in a dose-dependent manner. Taken together, our results suggest that vitamin E may afford substantial protection against the damage caused by Fe-NTA exposure and can serve as a potent preventive agent to suppress oxidant-induced tissue injury.     

Glyceryl trinitrate,a nitric oxide donor,abrogates ferric nitrilotriacetate-induced oxidative stress and renal damage

Ferric nitrilotriacetate (Fe-NTA), a common water pollutant and a known renal carcinogen, acts through the generation of oxidative stress and hyperproliferative response. In the present study, we show that the nitric oxide (NO) generated by the administration of glyceryl trinitrate (GTN) affords protection against Fe-NTA-induced oxidative stress and proliferative response. Administration of Fe-NTA resulted in a significant (P<0.001) depletion of renal glutathione (GSH) content with concomitant increase in lipid peroxidation and elevated tissue damage marker release in serum. Parallel to these changes, Fe-NTA also caused down-regulation of GSH metabolizing enzymes including glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase and several fold induction in ornithine decarboxylase (ODC) activity and rate of DNA synthesis. Subsequent exogenous administration of GTN at doses of 3 and 6mg/kg body weight resulted in significant (P<0.001) recovery of GSH metabolizing enzymes and amelioration of tissue GSH content, in a dose-dependent manner. GTN administration also inhibited malondialdehyde (MDA) formation, induction of ODC activity, enhanced rate of DNA synthesis, and pathological deterioration in a dose-dependent fashion. Further, administration of NO inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), exacerbated Fe-NTA-induced oxidative tissue injury, hyperproliferative response, and pathological damage. Overall, the study suggests that NO administration subsequent to Fe-NTA affords protection against ROS-mediated damage induced by Fe-NTA.     

Vitamin E inhibits hepatic oxidative stress,toxicity and hyperproliferation in rats treated with the renal carcinogen ferric nitrilotriacetate

Abstract

Ferric nitrilotriacetate (Fe-NTA) is a potent renal and hepatic tumor promoter, which acts through a mechanism involving oxidative stress. Fe-NTA when injected intraperitoneally into rats induces hepatic ornithine decarboxylase activity as well as hepatic DNA synthesis. Vitamin E is a well-known, lipid-soluble and chain-breaking antioxidant which protects cell membranes from peroxidative damage. In this study, we investigated the protective effect of vitamin E, a major fat-soluble antioxidant, against Fe-NTA-mediated hepatic oxidative stress, toxicity and hyperproliferation in Wistar rats. Animals were treated with two different doses of vitamin E for 1 week prior to Fe-NTA treatment. Vitamin E at a higher dose of 2.0 mg/animal/day showed significant reduction in Fe-NTA-induced hepatic ornithine decarboxylase activity, DNA synthesis, microsomal lipid peroxidation and hydrogen peroxide generation. Fe-NTA treatment alone caused depletion of glutathione, glutathione metabolizing and antioxidant enzymes in rat liver, whereas pretreatment of animals with vitamin E reversed these changes in a dose-dependent manner. Taken together, our results suggest that vitamin E may afford substantial protection against the damage caused by Fe-NTA exposure and can serve as a potent preventive agent to suppress oxidant-induced tissue injury.     

Chemomodulatory effect of Ficus racemosa extract against chemically induced renal carcinogenesis and oxidative damage response in Wistar rats

Ferric nitrilotriacetate (Fe-NTA) is a well-known renal carcinogen. In this communication, we show the chemopreventive effect of Ficus racemosa extract against Fe-NTA-induced renal oxidative stress, hyperproliferative response and renal carcinogenesis in rats. Fe-NTA (9 mg Fe/kg body weight, intraperitoneally) enhances renal lipid peroxidation, xanthine oxidase, gamma-glutamyl transpeptidase and hydrogen peroxide (H(2)O(2)) generation with reduction in renal glutathione content, antioxidant enzymes, viz., glutathione peroxidase, glutathione reductase, catalase, glucose-6-phosphate dehydrogenase and phase-II metabolising enzymes such as glutathione-S-transferase and quinone reductase. It also enhances blood urea nitrogen, serum creatinine, ornithine decarboxylase (ODC) activity and thymidine [(3)H] incorporation into renal DNA. It also enhances DEN (N-diethylnitrosamine) initiated renal carcinogenesis by increasing the percentage incidence of tumors. Treatment of rats orally with F. racemosa extract (200 and 400 mg/kg body weight) resulted in significant decrease in gamma-glutamyl transpeptidase, lipid peroxidation, xanthine oxidase, H(2)O(2) generation, blood urea nitrogen, serum creatinine, renal ODC activity, DNA synthesis (P<0.001) and incidence of tumors. Renal glutathione content (P<0.01), glutathione metabolizing enzymes (P<0.001) and antioxidant enzymes were also recovered to significant level (P<0.001). Thus, our data suggests that F. racemosa extract is a potent chemopreventive agent and suppresses Fe-NTA-induced renal carcinogenesis and oxidative damage response in Wistar rats.     

Attenuation of oxidative stress, inflammation and early markers of tumor promotion by caffeic acid in Fe-NTA exposed kidneys of Wistar rats

Iron nitrilotriacetate (Fe-NTA), a chief environmental pollutant, is known for its extensive toxic manifestations on renal system. In the present study, caffeic acid, one of the most frequently occurring phenolic acids in fruits, grains, and dietary supplements was evaluated for its shielding effect against the Fe-NTA-induced oxidative, inflammatory, and pathological damage in kidney. Fe-NTA was administered (9 mg Fe/kg body weight) intraperitoneally to the Wistar male rats on 20th day while caffeic acid was administered orally (20 and 40 mg/kg body weight) before administration of Fe-NTA. The intraperitoneal administration of Fe-NTA-enhanced lipid peroxidation, xanthine oxidase, and hydrogen peroxide generation with reduction in renal glutathione content, antioxidant enzymes, viz., catalase, glutathione peroxidase, and glutathione reductase. A sharp elevation in the levels of myloperoxidase, blood urea nitrogen (BUN), and serum creatinine has also been observed. Tumor promotion markers viz., ornithine decarboxylase (ODC) and [(3)H] thymidine incorporation into renal DNA were also significantly increased. Treatment of rats orally with caffeic acid (20 and 40 mg/kg body weight) resulted in a significant decrease in xanthine oxidase (P < 0.001), lipid peroxidation (P < 0.001), γ-glutamyl transpeptidase (P < 0.01), and H(2)O(2) (P < 0.01). There was significant recovery of renal glutathione content (P < 0.001) and antioxidant enzymes (P < 0.001). There was also a reversal in the enhancement of renal ODC activity, DNA synthesis, BUN, and serum creatinine (P < 0.001). All these changes were supported by histological observations. The results indicate that caffeic acid may be beneficial in ameliorating the Fe-NTA-induced oxidative damage and tumor promotion in the kidney of rats.     

Chemopreventive effect of <Emphasis Type="BoldItalic">Padina boergesenii</Emphasis> extracts on ferric nitrilotriacetate (Fe-NTA)-induced oxidative damage in Wistar rats

The present study was designed to investigate the prophylactic effect of extracts of the brown alga Padina boergesenii against potent nephrotoxic agent ferric nitrilotriacetate (Fe-NTA), in blood circulation of rats. Administration of Fe-NTA for seven consecutive days significantly enhanced lipid peroxidation accompanied with reduction in glutathione content. Together with this, the level of antioxidant enzymes, glutathione peroxidase, superoxide dismutase, and catalase was significantly (P < 0.05) diminished. Pretreatment of rats with P. boergesenii (150 mg kg⁻¹ body weight) reversed Fe-NTA-induced oxidative damage in lipid peroxidation and glutathione content significantly (P < 0.05). Further, the activity of antioxidant enzymes was also restored significantly. In order to assess the role of polyphenolic components in the relevant activity, phenolic contents of the extract was found to be 1.78 ± 0.02% in the methanol extract and 1.30 ± 0.30% in the diethyl ether extract. Hence, the present results confirm that the brown alga P. boergesenii preclude its role in Fe-NTA-induced oxidative damage and hyperproliferative response in circulation.     

Probucol modulates iron nitrilotriacetate (Fe-NTA)-dependent renal carcinogenesis and hyperproliferative response: diminution of oxidative stress

Probucol is a clinically used cholesterol-lowering drug, with pronounced antioxidant properties. We have reported previously, that dietary supplementation of probucol enhances NAD(P)H:quinone reductase (Iqbal M, Okada S (2003) Pharmacol Toxicol 93:259–263) and inhibits Fe-NTA induced lipid peroxidation and DNA damage in vitro (Iqbal M, Sharma SD, Oakada (2004) Redox Rep 9:167–172). Further to this, in the present study, we evaluated the modulatory effect of probucol on iron nitrilotriacetae (Fe-NTA) dependent renal carcinogenesis, hyperproliferative response and oxidative stress. In Fe-NTA alone treated group, a 20% renal cell tumor incidence was recorded whereas, in N-diethylnitrosamine (DEN)-initiated and Fe-NTA promoted animals, the percentage tumor incidence was increased to 70% as compared with untreated controls. No tumor incidence was recorded in DEN-initiated, nonpromoted group. Diet supplemented with 1.0% probucol fed prior to, during and after Fe-NTA treatment in DEN-initiated animals afforded >65% protection in renal cell tumor incidence. Probucol fed diet pretreatment also resulted a significant and dose dependent inhibition of Fe-NTA induced renal ornithine decarboxylase (ODC) activity. In oxidative stress studies, Fe-NTA alone treatment enhanced lipid peroxidation, accompanied by a decrease in the level of GSH, activities of antioxidants and phase II metabolizing enzymes in kidney concomitant with histolopathological changes. These changes were significantly and dose-dependently alleviated by probucol fed diet. From this data, it can be concluded that probucol can modulates toxic and tumor promoting effects of Fe-NTA and can serve as a potent chemopreventive agent to suppress oxidant induced tissue injury and carcinogenesis, in addition to being a cholesterol lowering and anti-atherogenic drug.     

Probucol as a potent inhibitor of oxygen radical-induced lipid peroxidation and DNA damage: in vitro studies

Probucol, a clinically used cholesterol lowering and antioxidant drug, was investigated for possible protection against lipid peroxidation and DNA damage induced by iron nitrilotriacetate (Fe-NTA) plus hydrogen peroxide (H2O2). Fe-NTA is a potent nephrotoxic agent and induces acute and subacute renal proximal tubular necrosis by catalyzing the decomposition of H2O2-derived production of hydroxyl radicals, which are known to cause lipid peroxidation and DNA damage. Fe-NTA is associated with a high incidence of renal adenocarcinoma in rodents. Lipid peroxidation and DNA damage are the principal manifestation of Fe-NTA induced toxicity, which could be mitigated by probucol. Incubation of renal microsomal membrane and/or calf thymus DNA with H2O2 (40 mM) in the presence of Fe-NTA (0.1 mM) induces renal microsomal lipid peroxidation and DNA damage to about 2.4-fold and 5.9-fold, respectively, as compared to control (P < 0.05). Induction of renal microsomal lipid peroxidation and DNA damage was inhibited by probucol in a concentration-dependent manner. In lipid peroxidation protection studies, probucol treatment showed a concentration-dependent inhibition (10-34% inhibition; P < 0.05) of Fe-NTA plus H2O2-induced lipid peroxidation as measured by thiobarbituric acid reacting species' (TBARS) formation in renal microsomes. Similarly, in DNA damage protection studies, probucol treatment also showed a concentration-dependent strong inhibition (36-71% inhibition; P < 0.05) of DNA damage. From these studies, it was concluded that probucol inhibits peroxidation of microsomal membrane lipids and DNA damage induced by Fe-NTA plus H2O2. However, because the lipid peroxidation and DNA damage studied here are regarded as early markers of carcinogenesis, we suggest that probucol may be developed as a cancer chemopreventive agent against renal carcinogenesis and other adverse effects of Fe-NTA exposure in experimental animals, in addition to being a cholesterol-lowering drug, useful for the control of hypercholestrolemia.     

Protective effect of Didymocarpus pedicellata on ferric nitrilotriacetate (Fe-NTA) induced renal oxidative stress and hyperproliferative response

Didymocarpus pedicellata R. Br. (Gesneriaceae) is widely used in traditional Indian medicines against renal afflictions. In the present study, we have revealed ethanolic extract of aerial parts of D. pedicellata to possess significant antioxidant activity and protect against ferric nitrilotriacetate (Fe-NTA) mediated renal oxidative stress, nephrotoxicity and tumor promotion response. D. pedicellata extract was found to possess a high content of total polyphenolics, exhibit potent reducing power and significantly scavenge free radicals including several reactive oxygen species (ROS) and reactive nitrogen species (RNS). The extract also significantly and dose-dependently protected against Fe-NTA plus H(2)O(2)-mediated damage to lipids and DNA. Protective efficacy of the extract was also tested in vivo against Fe-NTA mediated nephrotoxicity and tumor promotion response. Administration of Fe-NTA (9 mg/kg body weight, i.p.) to Swiss albino mice depleted renal glutathione content and activities of antioxidant and phase II metabolizing enzymes with concomitant induction of oxidative damage. Fe-NTA also incited hyperproliferation response elevating ornithine decarboxylase activity and [(3)H]-thymidine incorporation into DNA. Elevation in serum creatinine (SCr) and blood urea nitrogen (BUN), and histopathological changes were also evident and suggested Fe-NTA to afflict damage to kidney. Pretreatment of mice with D. pedicellata extract (100-200 mg/kg body weight) for 7 days not only restored antioxidant armory near normal values but also significantly protected against renal oxidative stress and damage restoring normal renal architecture and levels of renal damage markers, viz., BUN and SCr. The results of the present study indicate D. pedicellata to possess potent antioxidant and free radical scavenging activities and preclude oxidative damage and hyperproliferation in renal tissues.     

Localization of 4-hydroxy-2-nonenal-modified proteins in kidney following iron overload.

Intraperitoneal (IP) injection of ferric nitrilotriacetate (Fe-NTA) to rats and mice results in iron-induced free radical injury and cancer in kidneys. We sought to clarify the exact localization of acute oxidative damage in Fe-NTA-induced nephrotoxicity by performing immunogold light and electron microscopic (EM) techniques using an antibody against 4-hydroxy-2-nonenal (HNE)-modified proteins. Biochemical assays were done to provide complementary quantitative data. Renal accumulation of lipid peroxidation-derived aldehydes, such as malondialdehyde (MDA) and 4-hydroxy-2-alkenals (4-HDA), increased in parallel with protein carbonyl content, an indicator of protein oxidation, 30 min after administration of Fe-NTA. Immunogold light microscopy showed that HNE-modified proteins increased at 30 min with positivity localized to proximal tubular cells. Immunogold EM demonstrated that HNE-modified proteins were mainly in the mitochondria and nuclei of the proximal tubular epithelium. The intensity of labeling at both the light and EM levels increased together with levels of biochemically measured lipid peroxidation products and protein carbonyl content. Our data suggest that the mechanism of acute nephrotoxicity of Fe-NTA involves mitochondrial and nuclear oxidative damage, findings that may help to define the mechanisms of iron-induced cell injury.     

Experimental approaches to free radicals and ageing

Abstract

Probucol, a clinically used cholesterol lowering and antioxidant drug, was investigated for possible protection against lipid peroxidation and DNA damage induced by iron nitrilotriacetate (Fe-NTA) plus hydrogen peroxide (H₂O₂). Fe-NTA is a potent nephrotoxic agent and induces acute and subacute renal proximal tubular necrosis by catalyzing the decomposition of H₂O₂-derived production of hydroxyl radicals, which are known to cause lipid peroxidation and DNA damage. Fe-NTA is associated with a high incidence of renal adenocarcinoma in rodents. Lipid peroxidation and DNA damage are the principal manifestation of Fe-NTA induced toxicity, which could be mitigated by probucol. Incubation of renal microsomal membrane and/or calf thymus DNA with H₂O₂ (40 mM) in the presence of Fe-NTA (0.1 mM) induces renal microsomal lipid peroxidation and DNA damage to about 2.4-fold and 5.9-fold, respectively, as compared to control (P < 0.05). Induction of renal microsomal lipid peroxidation and DNA damage was inhibited by probucol in a concentration-dependent manner. In lipid peroxidation protection studies, probucol treatment showed a concentration-dependent inhibition (10–34% inhibition; P <0.05) of Fe-NTA plus H₂O₂-induced lipid peroxidation as measured by thiobarbituric acid reacting species' (TBARS) formation in renal microsomes. Similarly, in DNA damage protection studies, probucol treatment also showed a concentration-dependent strong inhibition (36–71% inhibition; P < 0.05) of DNA damage. From these studies, it was concluded that probucol inhibits peroxidation of microsomal membrane lipids and DNA damage induced by Fe-NTA plus H₂O₂. However, because the lipid peroxidation and DNA damage studied here are regarded as early markers of carcinogenesis, we suggest that probucol may be developed as a cancer chemopreventive agent against renal carcinogenesis and other adverse effects of Fe-NTA exposure in experimental animals, in addition to being a cholesterol-lowering drug, useful for the control of hypercholestrolemia.     

Lycopene inhibits DNA damage and liver necrosis in rats treated with ferric nitrilotriacetate.

Experimental and epidemiological evidence suggests that lycopene, a carotenoid present in tomatoes, tomato products, and several fruits and vegetables, may play a role in preventing certain cancers in humans. We have investigated the effect of lycopene pretreatment on lipid peroxidation, oxidative damage to DNA, and histopathological changes in liver of animals subjected to intraperitoneal (ip) ferric nitrilotriacetate (Fe-NTA) administration. Compared with control rats, liver of Fe-NTA-treated animals showed a significant increase in the 8-oxo-7,8-dihydro-2'-deoxyguanosine level and a 75% increase in malondialdehyde accumulation concomitant with histopathological changes. Five days of lycopene pretreatment (10 mg/kg body weight, ip) almost completely prevented liver biomolecule oxidative damage and protected the tissue against the observed histological alterations.     

Strobilanthes crispus attenuates renal carcinogen, iron nitrilotriacetate (Fe-NTA)-mediated oxidative damage of lipids and DNA

This study was aimed to evaluate the effect of Strobilanthes crispus extract for possible protection against lipid peroxidation and DNA damage induced by iron nitrilotriacetate (Fe-NTA) and hydrogen peroxide (H₂O₂). Fe-NTA is a potent nephrotoxic agent and induces acute and subacute renal proximal tubular necrosis by catalyzing the decomposition of H₂O₂-derived production of hydroxyl radicals, which are known to cause lipid peroxidation and DNA damage. Incubation of postmitochondrial supernatant and/or calf thymus DNA with H₂O₂ (40 mM) in the presence of Fe-NTA (0.1 mM) induces lipid peroxidation and DNA damage to about 2.3-fold and 2.9-fold, respectively, as compared to control (P < 0.05). In lipid peroxidation protection studies, S. crispus treatment showed a dose-dependent inhibition (45–53% inhibition, P < 0.05) of Fe-NTA and H₂O₂ induced lipid peroxidation. Similarly, in DNA damage protection studies, S. crispus treatment also showed a dose-dependent inhibition (18–30% inhibition, P < 0.05) of DNA damage. In addition, the protection was closely related to the content of phenolic compounds as evident by S. crispus extract showing the value of 124.48 mg/g total phenolics expressed as gallic acid equivalent (GAE, mg/g of extract). From these studies, it is concluded that S. crispus inhibits peroxidation of membrane lipids and DNA damage induced by Fe-NTA and H₂O₂ and possesses the potential to be used to treat or prevent degenerative diseases where oxidative stress is implicated.     

Modulatory Effects of Shape Pluchea Lanceolata Against Chemically Induced Oxidative Damage, Hyperproliferation And Two-Stage Renal Carcinogenesis in Wistar Rats

Ferric nitrilotriacetate (Fe-NTA) is a well-established renal carcinogen. Here, we have shown that Pluchea lanceolata (PL) belonging to the family Asteraceae. PL attenuates Fe-NTA induced renal oxidative stress, hyperproliferative response and renal carcinogenesis in rats. It promoted DEN (N-diethyl nitrosamine) initiated renal carcinogenesis by increasing the percentage incidence of tumors and induces early tumor markers viz. ornithine decarboxylase (ODC) and renal DNA synthesis. Fe-NTA (9 mg Fe/kg body weight, intraperitoneally) also enhances renal lipid peroxidation (LPO), xanthine oxidase (XO) and hydrogen peroxide (H₂O₂) generation with reduction in renal glutathione content (GSH), antioxidant enzymes, viz., glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), glucose-6-phosphate dehydrogenase and phase-II metabolizing enzymes such as glutathione-S-transferase and quinone reductase (QR). It also enhances blood urea nitrogen (BUN) and serum creatinine. Oral treatment of rats with PL extract (100 and 200 mg/kg body weight) resulted in significant decrease in lipid peroxidation (LPO), xanthine oxidase (XO), H₂O₂ generation, blood urea nitrogen (BUN), serum creatinine, renal ODC activity, DNA synthesis (p < 0.001) and incidence of tumors. Renal glutathione content (p < 0.01), its metabolizing enzymes (p < 0.001) and antioxidant enzymes were also recovered to significant level (p < 0.001). Thus, present study supports PL as a potent chemopreventive agent and suppresses Fe-NTA-induced renal carcinogenesis and oxidative damage response in Wistar rat.     

Zinc resistance impairs sensitivity to oxidative stress in HeLa cells: protection through metallothioneins expression.

To analyze the effects of high concentrations of zinc ions on oxidative stress protection, we developed an original model of zinc-resistant HeLa cells (HZR), by using a 200 microM zinc sulfate-supplemented medium. Resistant cells specifically accumulate high zinc levels in intracellular vesicles. These resistant cells also exhibit high expression of metallothioneins (MT), mainly located in the cytoplasm. Exposure of HZR to Zn-depleted medium for 3 or 7 d decreases the intracellular zinc content, but only slightly reduces MT levels of resistant cells. No changes of the intracellular redox status were detected, but zinc resistance enhanced H2O2-mediated cytotoxicity. Conversely, zinc-depleted resistant cells were protected against H2O2-induced cell death. Basal- and oxidant-induced DNA damage was increased in zinc resistant cells. Moreover, measurement of DNA damage on zinc-depleted resistant cells suggests that cytoplasmic metal-free MT ensures an efficient protection against oxidative DNA damage, while Zn-MT does not. This newly developed Zn-resistant HeLa model demonstrates that high intracellular concentrations of zinc enhance oxidative DNA damage and subsequent cell death. Effective protection against oxidative damage is provided by metallothionein under nonsaturating zinc conditions. Thus, induction of MT by zinc may mediate the main cellular protective effect of zinc against oxidative injury.     

Curcumin attenuates oxidative damage in animals treated with a renal carcinogen, ferric nitrilotriacetate (Fe-NTA): implications for cancer prevention

Curcumin (diferuloylmethane), a biologically active ingredient derived from rhizome of the plant Curcuma longa, has potent anticancer properties as demonstrated in a plethora of human cancer cell lines/animal carcinogenesis model and also acts as a biological response modifier in various disorders. We have reported previously that dietary supplementation of curcumin suppresses renal ornithine decarboxylase (Okazaki et al. Biochim Biophys Acta 1740:357–366, 2005) and enhances activities of antioxidant and phase II metabolizing enzymes in mice (Iqbal et al. Pharmacol Toxicol 92:33–38, 2003) and also inhibits Fe-NTA-induced oxidative injury of lipids and DNA in vitro (Iqbal et al. Teratog Carcinog Mutagen 1:151–160, 2003). This study was designed to examine whether curcumin possess the potential to suppress the oxidative damage caused by kidney-specific carcinogen, Fe-NTA, in animals. In accord with previous report, at 1 h after Fe-NTA treatment (9.0 mg Fe/kg body weight intraperitoneally), a substantial increased formation of 4-hydroxy-2-nonenal (HNE)-modified protein adducts in renal proximal tubules of animals was observed. Likewise, the levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and protein reactive carbonyl, an indicator of protein oxidation, were also increased at 1 h after Fe-NTA treatment in the kidneys of animals. The prophylactic feeding of animals with 1.0% curcumin in diet for 4 weeks completely abolished the formation of (i) HNE-modified protein adducts, (ii) 8-OHdG, and (iii) protein reactive carbonyl in the kidneys of Fe-NTA-treated animals. Taken together, our results suggest that curcumin may afford substantial protection against oxidative damage caused by Fe-NTA, and these protective effects may be mediated via its antioxidant properties. These properties of curcumin strongly suggest that it could be used as a cancer chemopreventive agent.     

Protective effect of lycopene on lipid peroxidation and oxidative DNA damage in cell culture

A high incidence of cancer has been correlated with chronic iron overload, and carotenoids are of interest as possible anticarcinogens. We have investigated the effect of lycopene on lipid peroxidation and on the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in CV1-P monkey cells exposed to ferric nitrilotriacetate (Fe-NTA) plus ascorbate. Cells supplemented with lycopene (20 pmol/10(6) cells) showed a reduction of 86% in Fe-NTA/ascorbate-induced lipid peroxidation (TBARS). Levels of 8-oxodGuo rose from 1.59+/-0.09 residues/10(6) dGuo in the control cells to 14.02+/-0.41 residues/10(6) dGuo after incubation with (1:4 mM) Fe-NTA/ascorbate (40 microM). Lycopene supplementation decreased in 77% the 8-oxodGuo levels in Fe-NTA/ascorbate-treated cells. These results indicate that lycopene can protect mammalian cells against membrane and DNA damage and possibly play a protective role against tumor promotion associated with oxidative damage.     

Induction of renal oxidative stress and cell proliferation response by ferric nitrilotriacetate (Fe-NTA): diminution by soy isoflavones

Ferric nitrilotriacetate (Fe-NTA) is a known potent nephrotoxic agent. In this communication, we report the chemopreventive effect of soy isoflavones on renal oxidative stress, toxicity and cell proliferation response in Wistar rats. Fe-NTA (9 mg Fe/kg body weight, intraperitoneally) enhances gamma-glutamyl transpeptidase, renal lipid peroxidation, xanthine oxidase and hydrogen peroxide (H2O2) generation with reduction in renal glutathione content, antioxidant enzymes, viz., glutathione peroxidase, glutathione reductase, catalase, glucose-6-phosphate dehydrogenase and phase-II metabolising enzymes such as glutathione-S-transferase and quinone reductase. Fe-NTA treatment also induced tumor promotion markers, viz., ornithine decarboxylase (ODC) activity and thymidine [3H] incorporation into renal DNA. A sharp elevation in the levels of blood urea nitrogen and serum creatinine has also been observed. Treatment of rats orally with soy isoflavones (5 mg/kg body weight and 10 mg/kg body weight) resulted in significant decreases in gamma-glutamyl transpeptidase, lipid peroxidation, xanthine oxidase, H2O2 generation, blood urea nitrogen, serum creatinine, renal ODC activity and DNA synthesis (P < 0.001). Renal glutathione content (P < 0.01), glutathione metabolizing enzymes (P < 0.001) and antioxidant enzymes were also returned to normal levels (P < 0.001). Thus, our data suggest that soy isoflavones may be used as an effective chemopreventive agent against Fe-NTA-mediated renal oxidative stress, toxicity and cell proliferation response in Wistar rats.