Bisphenol A promotes hyperuricemia via activating xanthine oxidase.

The prevalence of hyperuricemia has increased rapidly over the past decades. Bisphenol A (BPA) is an environmental endocrine disruptor. We investigated the effects of BPA on uric acid metabolism and its potential mechanisms. Experiments were performed in different animal models, cell cultures, and humans. In 3 different animal models, BPA exposure increased serum and hepatic uric acid with enhanced activity of xanthine oxidase (XO) in liver, whereas the excretion of uric acid was unchanged. Both in vivo and in vitro, BPA-induced uric acid production was decreased after treatment with allopurinol, which is a XO inhibitor. XO led to the accumulation of uric acid after xanthine was added, with the enzyme-catalyzed reaction, which was enhanced by BPA. Altered secondary structures of XO were found by circular dichroism analysis in the conditions of different BPA concentrations. Molecular docking portrayed Asp360 and Lys422 of XO to be the preferred binding sites for BPA. Mutation of both sites significantly blocked the effect of BPA on XO activity. In humans, patients with hyperuricemia exhibited higher levels of serum BPA than subjects without hyperuricemia. These findings demonstrate BPA promotes hyperuricemia by increasing hepatic uric acid synthesis via the activation of XO, probably through direct binding.-Ma, L., Hu, J., Li, J., Yang, Y., Zhang, L., Zou, L., Gao, R., Peng, C., Wang, Y., Luo, T., Xiang, X., Qing, H., Xiao, X., Wu, C., Wang, Z., He, J. C., Li, Q., Yang, S. Bisphenol A promotes hyperuricemia via activating xanthine oxidase.

Nicorandil, a K(atp) channel opener, alleviates chronic renal injury by targeting podocytes and macrophages.

Nicorandil exhibits a protective effect in the vascular system, which is thought to be due to vasodilatation from opening ATP-dependent potassium channels and donation of nitric oxide. Recently, nicorandil was shown to be renoprotective in models of acute kidney injury and glomerulonephritis. However, the specific mechanisms of renoprotection are unclear. We evaluated the effect of nicorandil on the rat remnant kidney model of chronic kidney disease. Blood pressure was unchanged by a 10-wk course of nicorandil, while albuminuria was significantly reduced. Glomerular injury and tubulointerstitial injury were also ameliorated by nicorandil. Oxidative stress, as noted by renal nitrotyrosine level and urine 8-hydroxy-2'-deoxyguanosine, were elevated in this model and was significantly reduced by nicorandil treatment. Treatment was associated with maintenance of the mitochondrial antioxidant, manganese SOD, in podocytes and with suppression of xanthine oxidase expression in infiltrating macrophages. Interestingly, these two cell types express sulfonylurea receptor 2 (SUR2), a binding site of nicorandil in the ATP-dependent K channel. Consistently, we found that stimulating SUR2 with nicorandil prevented angiotensin II-mediated upregulation of xanthine oxidase in the cultured macrophage, while xanthine oxidase expression was rather induced by blocking SUR2 with glibenclamide. In conclusion, nicorandil reduces albuminuria and ameliorates renal injury by blocking oxidative stress in chronic kidney disease.

In Silico and 3D QSAR Studies of Natural Based Derivatives as Xanthine Oxidase Inhibitors.

BACKGROUND: A large number of disorders and their symptoms emerge from deficiency or overproduction of specific metabolites has drawn the attention for the discovery of new therapeutic agents for the treatment of disorders. Various approaches such as computational drug design have provided the new methodology for the selection and evaluation of target protein and the lead compound mechanistically. For instance, the overproduction of xanthine oxidase causes the accumulation of uric acid which can prompt gout. OBJECTIVE: In the present study we critically discussed the various techniques such as 3-D QSAR and molecular docking for the study of the natural based xanthine oxidase inhibitors with their mechanistic insight into the interaction of xanthine oxidase and various natural leads. CONCLUSION: The computational studies of deferent natural compounds were discussed as a result the flavonoids, anthraquinones, xanthones shown the remarkable inhibitory potential for xanthine oxidase inhibition moreover the flavonoids such as hesperidin and rutin were found as promising candidates for further exploration.

New evidence for the role of TNF-alpha in liver ischaemic/reperfusion injury.

BACKGROUND: Tumour necrosis factor-alpha (TNF-alpha) plays a key role in causing ischaemia/reperfusion (I/R) injury. I/R also causes activation of xanthine oxidase and dehydrogenase (XDH + XO) system that, via generated free radicals, causes organ damage. We investigated the effect of ischaemia, reperfusion and non-ischaemic prolonged perfusion (NIP) on TNF-alpha and XDH + XO production in an isolated perfused rat liver model. MATERIALS AND METHODS: Rat livers underwent 150 min NIP (control group) or two hours of ischaemia followed by reperfusion (I/R group). TNF-alpha (TNF-alpha mRNA and protein level), XDH + XO production and bile secretion were determined in tissue and effluent at baseline, at 120 min of ischaemia, after 30 min of reperfusion (I/R group) and after 120 and 150 min of prolonged perfusion (control). RESULTS: Unexpectedly, neither ischaemia nor reperfusion had any effect on TNF-alpha production. TNF-alpha in effluent was 11 +/- 4.8 pg mL(-1) at baseline, 7 +/- 3.2 pg mL(-1) at the end of ischaemia, and 13 +/- 5.3 pg mL(-1) after 30 min of reperfusion. NIP, however, caused a significant increase of TNF-alpha synthesis and release. TNF-alpha effluent level after 120 and 150 min of perfusion was 392 +/- 78.7 pg mL(-1) and 408 +/- 64.3 pg mL(-1), respectively. TNF-alpha mRNA in tissue was also significantly elevated compared to baseline levels (1.31 +/- 0.2 P < 0.001 and 1.38 P < 0.002, respectively). Decrease of liver function (expressed by bile secretion) during I/R and NIP was accompanied by significant XDH + XO elevation. CONCLUSION: This is the first evidence that NIP, and not I/R, is the decisive trigger for TNF-alpha production. This study leads to a better understanding of pathogenesis of liver I/R and perfusion damage.

Conversion of xanthine dehydrogenase to oxidase in ischemic rat tissues.

In response to global ischemia, tissue xanthine dehydrogenase was converted to xanthine oxidase in all tissues with half-times of conversion at 37 degrees C of approximately 3.6, 6, 7, and 14 h for the liver, kidney, heart, and lung, respectively. The time course of enzyme conversion at 4 degrees C was greatly extended with half-conversion times of 6, 5, 5, and 6 d for the respective tissues. Increases in xanthine oxidase activity were accompanied by the appearance of a distinct new protein species with greater electrophoretic mobility. The oxidase from ischemic rat liver was purified 781-fold and found to migrate with a higher mobility on native gels than the purified native dehydrogenase. Sodium dodecyl sulfate profiles revealed the presence of a single major band of 137 kD for the native dehydrogenase, whereas the oxidase had been partially cleaved generating polypeptides of 127, 91, and 57 kD. Polypeptide patterns for the oxidase resemble those seen following limited in vitro proteolysis of the native dehydrogenase supporting a proteolytic mechanism for the conversion of xanthine dehydrogenase to oxidase in ischemic rat liver.

12-O-tetradecanoylphorbol-13-acetate-dependent induction of xanthine dehydrogenase and conversion to xanthine oxidase in murine epidermis.

Both xanthine dehydrogenase (XD) and xanthine oxidase (XO) catalyze the conversion of hypoxanthine to xanthine, and xanthine to uric acid. Topical application of a promoting dose of 12-O-tetradecanoylphorbol-13-acetate (TPA) to the dorsal skin of female SENCAR mice resulted in a 3.0-3.5-fold elevation of epidermal XO specific activity. Epidermal XO specific activity was maximally elevated 48-96 h after TPA treatment, and required 11 days to return to control levels. Although TPA increased the XO/(XD + XO) ratio from 0.45 to 0.7, the conversion of preexisting XD to XO could not solely account for the TPA-dependent elevation in XO specific activity since control XD plus XO activity was less than just the XO activity in TPA-treated epidermis. Topical application of cycloheximide simultaneously with, or 12 h after, TPA treatment inhibited the TPA-dependent increases in the XO/(XD + XO) ratio and XO specific activities. Collectively, these results suggest that the increased XO activity detected following TPA treatment is the consequence of TPA-induced XD synthesis, and a conversion of existing and newly synthesized XD to XO. In addition, the in vivo promoting activities of analogues of TPA could be correlated with their abilities to elevate XO activity (TPA greater than phorbol-12,13-dibenzoate much greater than 4-O-methyl-TPA = phorbol).

Nitroreductases and glutathione transferases that act on 4-nitroquinoline 1-oxide and their differential induction by butylated hydroxyanisole in mice.

These studies concern the initial steps in 4-nitroquinoline 1-oxide (4NQO) metabolism in relation to mechanisms of anticarcinogenesis. Butylated hydroxyanisole (BHA) administration by a protocol known to inhibit the pulmonary tumorigenicity of 4NQO in A/HeJ mice enhanced hepatic and pulmonary activities for 4NQO metabolism by two major pathways, conjugative detoxification and nitroreductive activation. High-performance liquid chromatography analysis showed approximate doubling of two types of glutathione transferase subunits with 4NQO-conjugating activity in livers of BHA-treated mice. Similar increases were observed in hepatic 4NQO-conjugating activity and in Vmax, while Km for 4NQO was 39 to 43 microM. Pulmonary 4NQO-glutathione transferase activity increased 24 to 29%. DT diaphorase activity toward 4NQO was elevated 3.3-fold in livers and 2.7-fold in lungs of BHA-treated mice. However, the predominant 4NQO reductase of liver and lung was dicumarol resistant, had a strong preference for NADH, and showed little if any response to BHA. This Mr 200,000 enzyme, partially purified from livers of Swiss mice, exhibited the stoichiometry of 2-NADH/4NQO expected for reduction of 4NQO to 4-hydroxyaminoquinoline 1-oxide. Its high affinity for 4NQO (Km, 15 microM) signified a much greater influence on 4NQO metabolism than DT diaphorase (Km, 208 microM). The dicumarol-resistant 4NQO reductase differed from several known cytosolic nitroreductases. The results suggest that protection by BHA may result from alteration of the balance between 4NQO activation and conjugation.

Role of xanthine oxidase in the interferon-mediated depression of the hepatic cytochrome P-450 system in mice.

Interferon, interferon inducers, and a variety of other immunomodulators are known to depress the hepatic cytochrome P-450 drug-metabolizing system. Two concepts have been proposed to explain this phenomenon. (a) The steady-state of cytochrome P-450 is altered through decreased synthesis and increased degradation of cytochrome P-450 apoprotein. (b) Interferon induces xanthine oxidase; superoxide generated by interferon-induced xanthine oxidase destroys cytochrome P-450. The current study investigated the second concept. Administered polyribonucleotides [polyriboinosinic acid.polyribocytidylic acid (poly IC), polyriboinosinic acid.polycytidylic acid, polylysine and carboxymethylcellulose, mismatched poly IC], recombinant murine gamma-interferon, and a natural murine alpha/beta-interferon were shown to depress hepatic cytochrome P-450 and selected microsomal cytochrome P-450-dependent monooxygenase reactions and to induce hepatic xanthine oxidase activity. The feeding of tungstate in the drinking water largely depleted xanthine oxidase in mice; cytochrome P-450 levels and monooxygenase activities were not affected by tungstate treatment. Tungstate rendered the level of xanthine oxidase much below that in mice that had not received tungstate regardless of whether or not they had received poly IC or interferon; nevertheless, poly IC and interferon produced losses of cytochrome P-450 and monooxygenase activities in these tungstate-treated mice equivalent to those observed in mice that had not received tungstate. The administration of N-acetylcysteine did not prevent the loss of cytochrome P-450 induced by poly IC, as has been reported, nor did the incubation of microsomal cytochrome P-450 with buttermilk xanthine oxidase and hypoxanthine cause a loss of cytochrome P-450, which has also been reported. It is concluded from these studies that the induction of xanthine oxidase and the loss of cytochrome P-450 generated by interferon are coincidental rather than causally related phenomena.

Effect of interferon-gamma on purine catabolic and salvage enzyme activities in rats.

To determine whether interferon-gamma affects rat purine catabolic and salvage enzyme activities, rats were injected with interferon-gamma (600000 U/kg, i.p.) and, similarly to a vehicle-injected control group, killed before or after injection at 6, 12, and 24 h. Organ homogenates were prepared and enzymatic reactions with substrates were carried out, after which the products were measured either chromatographically or spectrophotometrically. Western and Northern blotting also were performed. In contrast to the vehicle-injected rats, interferon-gamma-injected rats showed a significant rise in xanthine oxidoreductase activity in the liver, while enzyme activity was unchanged in the spleen, kidney, and lung. Western analysis of hepatic xanthine oxidoreductase showed an increased concentration of this protein 12 and 24 h after interferon-gamma injection. Northern analysis disclosed an enhanced mRNA expression coding for this enzyme, peaking 12 h after injection. Contrastingly, the activities of adenosine deaminase, purine nucleoside phosphorylase, hypoxanthine guanine phosphoribosyltransferase, and adenine phosphoribosyltransferase were not affected by interferon-gamma in any organ tested. While interferon-gamma causes an increased hepatic biosynthesis of xanthine oxidoreductase, the physiologic role of this enzyme induction remains undetermined.

Xanthine oxidase-derived reactive oxygen metabolites contribute to liver necrosis: protection by 4-hydroxypyrazolo[3,4-d]pyrimidine.

Xanthine oxidase (XO) generates reactive oxygen metabolites (ROM) as a by-product while catalyzing their reaction. The present study implicates these ROM in the pathogenesis of liver necrosis produced in rats by the intraperitoneal administration of thioacetamide (TAA; 400 mg/kg b.wt.). After 16 h of TAA administration, the activity of rat liver XO increased significantly compared to that of the control group. At the same time, the level of serum marker enzymes of liver necrosis (aminotransferases and alkaline phosphatase) and tissue malondialdehyde content also increased in TAA treated rats. Tissue malondialdehyde concentration is an indicator of lipid peroxidation and acts as a useful marker of oxidative damage. Pretreatment of rats with XO inhibitor (4-hydroxypyrazolo[3,4-d]pyrimidine; allopurinol (AP)) followed by TAA could lower the hepatotoxin-mediated rise in malondialdehyde level as well as the level of marker enzymes associated with liver necrosis. The survival rate also increased in rats given AP followed by the lethal dose of TAA. In either case, the effect of AP was dose-dependent. Results presented in the paper indicate that increased production of XO-derived ROM contributes to liver necrosis, which can be protected by AP.

Gene conversion and transfer of genetic information within the inverted region of inversion heterozygotes.

Prior studies of recombination which monitor exchange events in exceedingly short intervals (i.e., separable sites within a cistron) reveal that the basic event in recombination involves a non-reciprocal transfer of information, termed conversion. As a logical consequence of the model suggested by the work in Drosophila, the present investigation examined recombination between rosy mutant alleles (ry:3-52.0) in Drosophila melanogaster in a paracentric inversion (In(3R)P(18)) heterozygote, which placed the rosy region approximately at the center of the inverted region. Comparison of the results of this study with experiments carried out in standard chromosome homozygotes reveals a dramatic suppression of classical crossovers between the rosy mutant alleles in the inversion heterozygote. However, conversions continue to occur for all rosy mutant alleles in all heterozygous combinations in the inversion heterozygote. Moreover, the order of magnitude of conversion frequencies seen in the inversion heterozygote does not change from that seen in the standard chromosome homozygote study. The significance of these observations with reference to the role of rearrangements as barriers of information transfer is discussed. Particular attention is directed to the elaborate inversion polymorphisms seen in natural populations, and to notions concerning their role in the evolution of adaptive gene complexes.

Conversion of xanthine dehydrogenase to xanthine oxidase occurs during keratinocyte differentiation: modulation by 12-O-tetradecanoylphorbol-13-acetate.

The distributions of xanthine dehydrogenase (XD) and xanthine oxidase (XO) in subpopulations of murine keratinocytes differing in their stages of terminal differentiation were determined by enzymatic analyses. Keratinocytes were isolated from the skins of female SENCAR mice that had been treated 72 h earlier with either acetone or 12-O-tetradecanoylphorbol-13-acetate (TPA). The ratio of XO/(XD + XO) specific activities was used as an index of the XD to XO conversion. The XO/(XD + XO) ratios for basal cell, suprabasal cell, granular cell plus squamae, and horny sheet preparations isolated from acetone- or TPA-treated mice were 0.35, 0.35, 0.45, 0.75 and 0.28, 0.29, 0.58, and 1.0, respectively. Total XD + XO and XO specific activities in each subpopulation derived from TPA-treated mice were approximately twice the values measured in their control counterparts. Suspension culturing of basal cell keratinocytes in methylcellulose induced terminal differentiation and a conversion of XD to XO. The kinetics of keratin disulfide crosslinking and the XD to XO conversion were similar and preceded cornification. Collectively, these studies demonstrate that the conversion of XD to XO occurs primarily during the later stages of keratinocyte terminal differentiation. Furthermore, the increases in XO activity measured in epidermal homogenates after TPA treatment are due to TPA-dependent increases in 1) the relative proportions of keratinocytes undergoing differentiation, 2) tissue XD content, and 3) increased conversion of XD to XO.

Diurnal variation and melatonin induction of hepatic molybdenum hydroxylase activity in the guinea-pig.

The activities of the xenobiotic metabolizing enzymes, aldehyde oxidase and xanthine oxidase, were determined in partially purified fractions of adult guinea-pig liver at given times in the day or night. A marked circadian variation in aldehyde oxidase activity was observed with several substrates (phthalazine, phenanthridine, N-phenylquinolinium and 3,4-dihydro-4-hydroxy-3-methyl-2-quinazolinone). The main peak occurred at 0300 hr with minimum activity from 1200 to 1800 hr, the differences between rhythmic extremes being statistically significant (P less than 0.005). Xanthine oxidase activity also exhibited a daily rhythm but with a lower amplitude. Guinea-pig serum melatonin showed a synchronous circadian fluctuation with peak values at 0300 hr falling throughout the day to a minimum at 1800 hr. Exogenously administered melatonin caused a significant increase in aldehyde oxidase activity at 0900 and 1200 hr and in xanthine oxidase activity at 0900 hr. It was concluded that melatonin concentrations may be related to the circadian variation in liver molybdenum hydroxylase activity.

Elevation of molybdenum hydroxylase levels in rabbit liver after ingestion of phthalazine or its hydroxylated metabolite.

Oral administration of phthalazine (50 mg/kg/day) or 1-hydroxyphthalazine (10 mg/kg/day) to female rabbits caused an increase in the specific activity of the hepatic molybdenum hydroxylases aldehyde oxidase and xanthine oxidase, whereas no effect on microsomal cytochrome P-450 activity was observed. The rise in the specific activity of purified aldehyde oxidase fractions was accompanied by a similar increase in molybdenum content. A significant lowering of the Km value for phthalazine was demonstrated with enzyme from treated rabbits whereas Km values for structurally similar substrates such as isoquinoline were unchanged from control values. Iso-electric focusing of DEAE-cellulose fractions showed the presence of an additional band of activity indicating that genuine induction of aldehyde oxidase had occurred in rabbits treated with phthalazine or 1-hydroxyphthalazine.

Dissociation of xanthine oxidase induction and cytochrome P450 depression during interferon induction in the rat.

Interferon (IFN) and IFN inducers down-regulate hepatic cytochrome P450 (P450) through a pretranslational mechanism involving depression of P450 mRNA levels and a subsequent decrease in P450 synthesis. Current evidence suggests that interferon induces the synthesis of a protein which subsequently mediates the down-regulation of P450. Xanthine oxidase (XO) activity is induced by interferons in rodents, and the XO inhibitor allopurinol (AP) inhibits the down-regulation of P450 by interferons in the mouse and hamster so it has been proposed as the putative intermediate protein. In studies undertaken in rats to further characterize the molecular basis of the protective effect of AP, we observed that AP (20 and 50 mg/kg) did not protect against down-regulation of P450 by the interferon inducer polyinosinic-polycytidylic acid (10 mg/kg). In fact, at 50 mg/kg AP had an additive effect on the depression of CYP2E1. Total XO induction in the rat was only 30-50% compared with 100-500% in mice and hamsters, and this induction was inhibited completely by AP. Therefore, XO does not mediate the down-regulation of hepatic cytochrome P450 by interferons in the rat.

Inducible nitric oxide synthase, but not xanthine oxidase, is highly expressed in interstitial pneumonias and granulomatous diseases of human lung.

We assessed the distribution and expression of inducible nitric oxide synthase (i-NOS), endothelial nitric oxide synthase (e-NOS), and xanthine oxidase (XAO) in usual interstitial pneumonia, desquamative interstitial pneumonia, and granulomatous diseases. The material consisted of biopsy specimens from 5 healthy subjects (nonsmokers), 9 patients with usual interstitial pneumonia, 11 with desquamative interstitial pneumonia, 14 with sarcoidosis, and 8 with extrinsic allergic alveolitis. i-NOS was expressed intensively in inflammatory but not infibrotic lesions. It was expressed most prominently in alveolar macrophages and alveolar epithelium of all disorders and in the granulomas of sarcoidosis and extrinsic allergic alveolitis. In contrast with i-NOS, e-NOS was expressed prominently in control lung tissue samples but also in granulomas of sarcoidosis and extrinsic allergic alveolitis. Reverse transcription-polymerase chain reaction performed on bronchoalveolar lavage fluid samples from patients with sarcoidosis or usual interstitial pneumonia andfrom healthy subjects indicated positivity for XAO, but immunohistochemical analysis in samples from healthy lung and all parenchymal lung disorders showed no immunoreactivity for XAO. i-NOS has an important role in the pathogenesis of interstitial lung diseases, being up-regulated during the inflammatory but not during the fibrotic disease stage.

Purification and characterization of multiple forms of rat liver xanthine oxidoreductase expressed in baculovirus-insect cell system.

cDNA of rat liver xanthine oxidoreductase (XOR), a molybdenum-containing iron-sulfur flavoprotein, was expressed in a baculovirus-insect cell system. The expressed XOR consisted of a heterogeneous mixture of native dimeric, demolybdo-dimeric, and monomeric forms, each of which was separated and purified to homogeneity. All the expressed forms contained flavin, of which the semiquinone form was stable during dithionite titration after dithiothreitol treatment, indicating that the flavin domains of all the expressed molecules have the intact conformations interconvertible between NAD(+)-dependent dehydrogenase (XDH) and O(2)-dependent oxidase (XO) types. The absorption spectrum and metal analyses showed that the monomeric form lacks not only molybdopterin but also one of the iron-sulfur centers. The reductive titration of the monomer with dithionite showed that the monomeric form required only three electrons for complete reduction, and the redox potential of the iron-sulfur center in the monomeric form is a lower value than that of FAD. In contrast to native or demolybdo-dimeric XDHs, the monomer showed a very slow reductive process with NADH under anaerobic conditions, although the conformation around FAD is a dehydrogenase form, suggesting the important role of the iron-sulfur center in the reductive process of FAD with the reduced pyridine nucleotide.

Xanthine oxidoreductase and xanthine oxidase in human cornea.

Xanthine oxidoreductase (xanthine dehydrogenase + xanthine oxidase) is a complex enzyme that catalyzes the oxidation of hypoxanthine to xanthine, subsequently producing uric acid. The enzyme complex exists in separate but interconvertible forms, xanthine dehydrogenase and xanthine oxidase, which generate reactive oxygen species (ROS), a well known causative factor in ischemia/reperfusion injury and also in some other pathological states and diseases. Because the enzymes had not been localized in human corneas until now, the aim of this study was to detect xanthine oxidoreductase and xanthine oxidase in the corneas of normal post-mortem human eyes using histochemical and immunohistochemical methods. Xanthine oxidoreductase activity was demonstrated by the tetrazolium salt reduction method and xanthine oxidase activity was detected by methods based on cerium ion capture of hydrogen peroxide. For immunohistochemical studies. we used rabbit antibovine xanthine oxidase antibody, rabbit antihuman xanthine oxidase antibody and monoclonal mouse antihuman xanthine oxidase/xanthine dehydrogenase/aldehyde oxidase antibody. The results show that the enzymes are present in the corneal epithelium and endothelium. The activity of xanthine oxidoreductase is higher than that of xanthine oxidase, as clearly seen in the epithelium. Further studies are necessary to elucidate the role of these enzymes in the diseased human cornea. Based on the findings obtained in this study (xanthine oxidoreductase/xanthine oxidase activities are present in normal human corneas), we hypothesize that during various pathological states, xanthine oxidase-generated ROS might be involved in oxidative eye injury.

Asafoetida inhibits early events of carcinogenesis: a chemopreventive study.

Ferula (a genus of many species) commonly known as asafoetida is used as a flavoring agent in food and is used as a traditional medicine for many diseases in many parts of world. In the current investigation, we report the antioxidant and anticarcinogenic potential of asafoetida (Ferula narthex) in swiss albino mice. A single dose of TPA (20 nmol/0.2 ml acetone/animal), a known tumor promoter decreased the cellular antioxidant level significantly (p<0.01) when applied topically to mice skin. It also induced the ODC activity, rate of DNA synthesis, hydrogen peroxide level, xanthine oxidase activity and protein carbonyl content in mice skin significantly (p<0.01). These events are early biomarkers of carcinogenesis. However, the pretreatment of animals with asafoetida (300, 400 and 500 microg/200 microl acetone/animal) caused the reversal of all events significantly (p<0.01). The pretreament of animals with asafoetida recovered the antioxidant level and reversed the induced ODC activity and DNA synthesis significantly (p<0.01). We conclude that asafoetida is a potent antioxidant and can afford protection against free radical mediated diseases such as carcinogenesis.

Salix caprea inhibits skin carcinogenesis in murine skin: inhibition of oxidative stress, ornithine decarboxylase activity and DNA synthesis.

Chemoprevention of free radical-mediated diseases including cancer by natural products is an emerging discipline due to its wider applicability and acceptance. The present study deals with the chemopreventive effect of Salix caprea against phorbol ester-induced oxidative stress and tumor promotion in murine skin. In the present investigation, it was observed that a single application of 12-O-tetradecanoyl-13-phorbol acetate (TPA) (20 nmol/0.2 ml acetone/animal) caused a significant (P < 0.05) depletion of cutaneous antioxidants viz., glutathione, glutathione reductase, glutathione peroxidase, catalase and phase II drug metabolizing enzymes viz., glutathione-S-transferase, quinone reductase. An increase in the hydrogen peroxide generation and protein oxidation (measured in terms of protein carbonyl content) was also observed with a single application of TPA. However, the pretreatment of animals with different doses of Salix caprea (0.5, 1.0 and 1.5 mg/kg/0.2 ml acetone) caused a significant recovery in the TPA-mediated depletion in antioxidant levels. The pretreatment of animals with Salix caprea was observed to inhibit the TPA-mediated depletion in phase II enzymes. It was also observed that Salix caprea reversed the TPA-mediated depletion in the activity of phase II enzymes that is an important characteristic of cancer chemopreventive agents. Phorbol esters are known to induce the tumor promotion by increasing rate of DNA synthesis, ornithine decarboxylase activity (ODC), and xanthine oxidase activity. In the present investigation, it was observed that the pretreatment of animals with Salix caprea caused a significant (P < 0.05) depletion in the TPA-induced DNA synthesis, ODC and xanthine oxidase activity in mice skin. Salix caprea significantly reduced the tumor promotion in mice skin when tested in two-stage chemical carcinogenesis model. It was observed to inhibit significantly P < 0.05) the 7,12-dimethyl benz[a] anthracene (DMBA)-initiated phorbol ester promoted skin carcinogenesis. It was concluded from the results that Salix caprea is an effective antioxidant and chemopreventive agent against phorbol ester-induced tumor promotion.