VITAMIN E MODULATION OF DIELDRIN-INDUCED HEPATIC FOCAL LESION GROWTH IN MICE

The effect of vitamin E on dieldrin-induced hepatic focal lesion growth in male B6C3F1 mice previously treated with diethylnitrosamine (DEN) was investigated. After hepatic focal lesions were formed, mice were placed into one of the following treatment groups: Group 1, 50 mg vitamin E/kg diet (control NIH-07 diet); Group 2, 10 mg dieldrin/ kg NIH-07 diet; Group 3, 10 mg dieldrin and 450 mg vitamin E/ kg NIH-07 diet; and Group 4, 450 mg vitamin E/kg NIH-07 diet. Mice were killed and necropsied after 30 and 60 d of dietary treatment. The effect of treatment on lesion growth was examined by measuring the number of focal lesions per liver and the relative hepatic focal lesion volume. In addition, the possible cellular mechanism of focal hepatocyte growth was investigated by examining both focal DNA synthesis and apoptosis. Dieldrin treatment alone (Group 2) increased the focal lesion volume, focal lesion number, and focal lesion labeling index. Supplementation with vitamin E (Group 3) blocked this effect. Vitamin E supplementation to the diet alone (Group 4) also enhanced focal lesion growth and increased the number of lesions per liver, the relative focal volume, and the labeling index in hepatic focal lesions. Interestingly, vitamin E supplementation inhibited apoptosis in normal liver but did not produce an observable decrease in apoptosis in hepatic focal lesions. The present study showed that dieldrin (Group 2) or vitamin E supplementation alone (Group 4) promoted the growth of hepatic focal lesions in mice. However, when vitamin E is supplemented to dieldrin-fed mice (Group 3), there is an inhibition of hepatic focal lesion growth.     

Effect of supplementation of n-3 polyunsaturated fatty acids on oxidative stress-induced DNA damage of rat hepatocytes

The effect of supplementation of n-3 polyunsaturated fatty acids (PUFA) on oxidative stress-induced DNA damage of rat hepatocytes was examined. Male Wistar rats were fed a diet containing safflower oil (control n-6 PUFA diet) or fish oil (n-3 PUFA diet) in 50 g/kg of dried diet and an equal amount of vitamin E in 59 mg/kg of dried diet for 6 weeks. The liver of rats fed safflower oil was rich in n-6 PUFA, whereas that of rats fed fish oil was rich in n-3 PUFA. Isolated hepatocytes were treated in vitro with ADP/Fe (II) ion or hydrogen peroxide at 37 degrees C for 30 min to induce oxidative stress. The degree of lipid peroxidation was assessed by the levels of phospholipid hydroperoxides and thiobarbituric acid-reactive substances. The degree of oxidative DNA damage was assessed based on comet-type characterization in alkaline single-cell gel electrophoresis and 8-hydroxy-deoxyguanosine levels. In both ADP/Fe(II) ion and hydrogen peroxide oxidation, the degree of lipid peroxidation of hepatocytes increased in both diet groups, and the level of increase in the fish oil diet group was slightly higher than that in the safflower oil diet group. In ADP/Fe(II) ion oxidation, the degree of DNA damage increased in both diet groups, but there were no significant differences in the level of increase. In contrast, in hydrogen peroxide oxidation, the degree of DNA damage increased in both diet, and the increase in the fish oil diet group was significantly lower than that in the safflower oil diet group. It is unlikely that an n-3 PUFA-rich diet enhances oxidative stress-induced hepatocyte DNA damage as compared with the control n-6 PUFA-rich diet.     

Effect of dietary fat-soluble vitamins A and E and proanthocyanidin-rich extract from grape seeds on oxidative DNA damage in rats.

This study reports the effect of the fat-soluble vitamin A or vitamin E and grape seed proanthocyanidin extract (GSPE) on oxidative DNA damage estimated by 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG) contents in urine and leukocyte of rats. Little is known about the antioxidant potency of dietary anthocyanidins and consequently, the aim of this study was to establish whether anthocyanidins could act as putative antioxidant micronutrients. Seven groups of male Sprague-Dawley rats were fed during 47 days with the following diets: a basic diet, two deficient vitamin A or E diets, two supplemented vitamin A or E diets and two supplemented diets enriched with two doses of grape seed proanthocyanidin extract. At the end of the diet intervention period, 24h, urine and blood were collected. The levels of 8-oxodG in leukocytes rats were significantly lower in the supplemented vitamin A, E and GSPE diet groups with respect to the control group. However, consumption of alpha-tocopherol, vitamin A or GSPE had no effect on the excretion of the oxidised nucleoside 8-oxodG. These results suggest that a vitamin E and A and GSPE enriched-diets have a protective effect on oxidative DNA damage limited to rat leukocytes.     

Antitumor effects by low dose total body irradiation

Total-body irradiation (TBI) with 0.02-0.25 Gy has been reported to have antitumor effects. In mice, low-dose TBI induces tumor growth delay, antimetastatic effects, suppressive effects on the incidence of spontaneous thymiclymphoma, sensitization of tumor to ionizing radiation, and decrease in TD50 value. In artificial metastasis, 0.20 Gy TBI suppressed lung metastasis when it was conducted between 3 h before and 3 h after tumor cell injection into a tail vein. In spontaneous metastasis, 0.15-0.20 Gy TBI suppressed lung metastasis. Irradiation with 0.15 Gy twice a week from 11 weeks of age for 40 weeks significantly suppressed the incidence of spontaneous thymic lymphoma in AKR/J mice, which caused prolonged life span. Low-dose TBI has been used in the clinical treatment of lymphomatous malignancies including chronic lymphocytic leukaemia (CLL) and non-Hodgkin's lymphoma (NHL). The usual practice was to give 0.1 Gy TBI three times a week or 0.15 Gy TBI two times a week to a total dose of 1.5 Gy. Despite this low total dose, low-dose fractionated TBI could induce long-term remissions and was as effective as the chemotherapy to which it was compared. Experimental data suggest that the antitumor effects of low-dose TBI could be explained by immune enhancement, induction of apoptosis, and intrinsic hypersensitivity to low-dose irradiation. Possible mechanisms of immune enhancement are elimination of the T-suppressor subset of lymphocytes and augmentation of the immune response including alteration of cytokine release and enhanced proliferative activity of lymphocytes to mitogenic stimuli.     

Effects of chronic vitamin E deficiency and a high polyunsaturated fatty acid diet on rat mesenteric arterial function.

1. Male rats were deprived as weanlings of dietary vitamin E and fed on a high polyunsaturated fatty acid (PUFA) diet for 6 months. Rats fed on a high PUFA or on an untreated diet served as controls. Mesenteric arterial beds were isolated and perfused at a constant flow rate (5 ml min-1) and the function of sympathetic nerves, smooth muscle and endothelium was assessed. 2. Electrical field stimulation (4-32 Hz, 90 V, 1 ms, for 30 s) elicited frequency-dependent vasoconstriction of the mesenteric arterial preparations. Response curves were similar between untreated control and PUFA-fed control groups. Maximum vasoconstrictor responses (at 24 and 32 Hz) were significantly attenuated in rats deprived of vitamin E and on a high PUFA diet compared to the PUFA-fed controls (P < 0.05). 3. Exogenous noradrenaline (NA; 0.15-500 nmol) elicited dose-dependent constriction of the mesenteric arterial beds. Preparations from rats fed on a high PUFA diet elicited significantly smaller responses compared to the control group. There was no significant difference in constrictor responses of PUFA rats deprived of vitamin E compared to the PUFA controls. Vasoconstrictor responses to doses of adenosine 5'-triphosphate (ATP) (5-5000 nmol) were significantly impaired in vitamin E-deficiency with a high PUFA diet compared to a high PUFA diet alone (P < < 0.001). Constrictor responses to potassium chloride (0.15 mmol) were significantly impaired in vitamin E-deficient PUFA rats compared to the PUFA-fed control group (P < 0.05). 4. Vasodilator responses were assessed in preparations in which tone was raised by continuous perfusion with methoxamine (4-25 microM). Mesenteric arterial beds from PUFA-fed rats deprived of vitamin E acquired significantly less tone, 59.8 +/- 4.6 mmHg (n = 7), than PUFA-fed controls 116.9 +/- 7.6 mmHg (n = 7) (P < 0.001) and were refractory to further increases in tone with further additions of methoxamine. Methoxamine-induced tone of PUFA-fed controls was greater than in P that in the untreated controls (83.9 +/- 7.4 mmHg; n = 5) (P < 0.05). Responses to the endothelium-dependent vasodilators acetylcholine (ACh) and ATP were significantly reduced in preparations from rats fed on the vitamin E-deficient high-PUFA diet compared to PUFA controls. Vasodilator responses to ACh were greater in PUFA controls than in untreated controls and this reached statistical significance at 5 nmol ACh. 5. Vasodilator responses to sodium nitroprusside, which acts directly on the vascular smooth muscle, were similar in untreated control and PUFA control groups. Responses were significantly attenuated in vitamin E-deficient PUFA rats compared to the PUFA control group (P < < 0.001). 6. These results indicate that a combination of a high PUFA diet and vitamin E deficiency impairs mesenteric arterial function at the level of the vascular smooth muscle. A high PUFA diet alone attenuates responses to NA and augments endothelium-dependent vasodilation. The detrimental effects of loss of antioxidant activity due to vitamin E-deficiency on vascular function may be exacerbated by a high PUFA diet.     

Effect of dietary vitamin E on nitrite-treated rats

The effect of dietary vitamin E on cellular responses to nitrite was studied in rats. One-month-old male Sprague-Dawley rats were fed a basal vitamin E-deficient diet with or without 100 ppm vitamin E and 1000 ppm sodium nitrite (NaNO₂) for 9 weeks. In addition to a high mortality rate, nitrite-fed rats maintained on a vitamin E-deficient diet exhibited a marked increase in liver necrosis, tubular nephrosis and myodegeneration, as well as greater biochemical and hematological alterations when compared to the control animals. No animal mortality or histopathologic lesions in any tissues were observed in rats receiving a vitamin E-supplemented diet with or without nitrite. The results suggest that depletion of vitamin E renders rats more susceptible to the adverse effect of nitrite, and that nitrite administration potentiates deficiency of vitamin E in rats.     

Enhanced oxidative stress in the skin of vitamin E deficient mice exposed to semisynthetic metal working fluids

Metal working fluids (MWFs) are widely used in industry for metal cutting, drilling, shaping, lubricating, and milling. Many occupational health concerns have arisen for workers exposed to MWFs. It has been reported earlier that occupational exposure to MWFs causes allergic and irritant contact dermatitis. Previously, we have shown that dermal exposure of female and male B6C3F1 mice to 5% MWFs for 3 months resulted in accumulation of mast cells and elevation of histamine in the skin. Topical exposure to MWFs also resulted in elevated oxidative stress in the liver of both sexes and the testes in males. The goal of this study was to evaluate whether preexisting oxidative stress in the skin exacerbated mast cell influx after MWFs treatment. Oxidative stress in the skin of B6C3F1 mice was generated by dietary vitamin E deprivation. Mice were given vitamin E deficient (5-10 i.v./kg of vitamin E) or basal (50 i.v./kg of vitamin E) diets for 34 weeks. Topical treatment with MWFs (100 microl, 30%) started after 18 weeks of alimentary vitamin E deprivation. Histology of the skin after 16 weeks of exposure to MWFs revealed a 53% increase in mast cell accumulation in vitamin E deficient diets compared to mice given a vitamin E sufficient diet. Total antioxidant reserve in skin of vitamin E deprived mice treated with MWFs was decreased by 66% as compared to those mice given a vitamin E sufficient diet. GSH and protein thiols in the dermis of vitamin E deprived mice exposed to MWFs were also decreased 39 and 42%, respectively, as compared to mice given basal diet. This study clearly delineates the role of oxidative stress in enhancing mast cell accumulation caused by topical exposure to MWFs.     

Effect of dietary treatment with n-propyl gallate or vitamin E on the survival of mice exposed to phosgene

Phosgene, widely used in industrial processes, can cause life-threatening pulmonary edema and acute lung injury. One mechanism of protection against phosgene-induced lung injury may involve the use of antioxidants. The present study focused on dietary supplementation in mice using n-propyl gallate (nPG)--a gallate acid ester compound used in food preservation--and vitamin E. Five groups of male mice were studied: group 1, control-fed with Purina rodent chow 5002; group 2, fed 0.75% nPG (w/w) in 5002; group 3, fed 1.5% nPG (w/w) in 5002; group 4 fed 1% (w/w) vitamin E in 5002; and group 5, fed 2% (w/w) vitamin E also in 5002. Mice were fed for 23 days. On day 23 mice were exposed to 32 mg m-3 (8 ppm) phosgene for 20 min (640 mg. min m-3) in a whole-body exposure chamber. Survival rates were determined at 12 and 24 h. In mice that died within 12 h, the lungs were removed and lung wet weights, dry weights, wet/dry weight ratios, lipid peroxidation (thiobarbituric acid reactive substances, TBARS) and glutathione (GSH) were assessed. Vitamin E had no positive effect on any outcome measured. There was no significant difference between 1.5% nPG and any parameter measured or survival rate compared with 5002 + phosgene. However, dietary treatment with 0.75% nPG significantly increased survival rate (P 相似文献   

Alteration of convulsive threshold and conditioned avoidance response in mice fed diets containing contraceptive steroids

Female CD1 mice given the contraceptive steroids mestranol and norethynodrel (1:10) in the diet (0.0033%) for 4 months had a growth reduction of 20% when compared with mice fed a normal diet, and had lower convulsive thresholds when tested with the vitamin B6 antagonists 2,4-dimethyl-5-methyl-hydroxypyrimidine and thiosemicarbazide. In conditioned avoidance response (CAR) tests, mice fed the steroid-containing diets showed a decreased acquisition performance during all six sessions; however, mice fed the same diet supplemented with vitamin B6 (0.04%) performed as well during the last three sessions of the CAR tests as mice fed the normal diet.     

Nitrofurantoin-Induced Hepatic and Pulmonary Biochemical Changes in Mice Fed Different Vitamin E Doses

Abstract: The hepatic and pulmonary effects of nitrofurantoin (40 mg/kg, intraperitoneally) were determined at 4 and 24 hr following its administration in mice fed for 10 weeks with a vitamin E sufficient, deficient or enriched diet. Liver glutathione (GSH) was reduced by nitrofurantoin at 4 hr but was unchanged 20 hr later. Nitrofurantoin did not affect liver glutathione peroxidase, glutathione reductase or superoxide dismutase activities. Liver catalase activities were decreased by nitrofurantoin at 4 hr. Lung GSH levels were increased whilst glutathione peroxidase activity was decreased at 4 and 24 hr. Lung glutathione reductase activity was reduced in certain groups. Nitrofurantoin did not affect lung superoxide dismutase, but catalase was decreased at 24 hr. Liver malondialdehyde levels were increased by nitrofurantoin in the vitamin E deficient group whilst lung malondialdehyde levels remained unchanged. Both liver and lung malondialdehyde levels were unaffected by vitamin E supplementation when compared to the vitamin E-sufficient group. These results suggest that nitrofurantoin (40 mg/kg) was deleterious to the liver and lung. Nitrofurantoin-induced lipid peroxidation was seen in vitamin E deficiency but an increase in dietary vitamin E content did not provide additional protection compared to the recommended daily allowance. The antioxidant acitivities of α-tocopherol and γ-enriched tocotrienol were similar.     

Exosomes are involved in total body irradiation-induced intestinal injury in mice

Ionizing radiation-induced intestinal injury is a catastrophic complication in patients receiving radiotherapy. Circulating exosomes from patients undergoing radiotherapy can mediate communication between cells and facilitate a variety of pathological processes in vivo, but its effects on ionizing radiation-induced intestinal damage are undetermined. In this study we investigated the roles of exosomes during total body irradiation (TBI)-induced intestinal injury in vivo and in vitro. We isolated exosomes from serum of donor mice 24 h after lethal dose (9 Gy) TBI (Exo-IR-24h), then intravenously injected the exosomes into receipt mice, and found that Exo-IR-24h injection not only exacerbated 9 Gy TBI-induced lethality and weight loss, but also promoted crypt-villus structural and functional injury of the small intestine in receipt mice. Moreover, Exo-IR-24h injection significantly enhanced the apoptosis and DNA damage of small intestine in receipt mice following TBI exposure. In murine intestinal epithelial MODE-K cells, treatment with Exo-IR-24h significantly promoted 4 Gy ionizing radiation-induced apoptosis, resulting in decreased cell vitality. We further demonstrated that Exo-IR-24h promoted the IR-induced injury in receipt mice partially through its DNA damage-promoting effects and attenuating Nrf2 antioxidant response in irradiated MODE-K cells. In addition, TBI-related miRNAs and their targets in the exosomes of mice were enriched functionally using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Finally, injection of GW4869 (an inhibitor of exosome biogenesis and release, 1.25 mg·kg⁻¹·d⁻¹, ip, for 5 consecutive days starting 3 days before radiation exposure) was able to rescue mice against 9 Gy TBI-induced lethality and intestinal damage. Collectively, this study reveals that exosomes are involved in TBI-induced intestinal injury in mice and provides a new target to protect patients against irradiation-induced intestinal injury during radiotherapy.     

Altered serum immunoglobulin response to model intestinal antigens during dietary exposure to vomitoxin (deoxynivalenol)

The effect of dietary vomitoxin on the serum IgA and IgG responses to two model intestinal antigens, casein and cholera toxin (CT), were assessed in 4 experimental groups: (1) mice fed casein-based diet, (2) mice fed casein-based diet containing 25 ppm vomitoxin, (3) mice fed casein-based diet and immunized with CT, and (4) mice fed casein-based diet containing 25 ppm vomitoxin and immunized with CT. Unimmunized and CT-immunized mice that were fed vomitoxin exhibited increased levels of total serum IgA relative to matched control animals fed the standard diet. Relative concentrations of casein-specific IgA were greater in both unimmunized mice and CT-immunized mice fed standard diet with vomitoxin than in matched controls fed standard diet only. CT-specific serum IgA in CT-immunized mice was not affected by vomitoxin feeding, but relative levels of CT-specific IgA were higher in unimmunized mice fed vomitoxin than in unimmunized mice fed standard diet. Both casein- and CT-specific serum IgG were depressed in mice fed vomitoxin. Significant differences in total, casein-specific and CT-specific IgA within the intestinal contents were not observed between CT-immunized mice fed vomitoxin and those fed the control diet. The results suggest that vomitoxin altered regulation of the normal immunoglobulin response to intestinal antigens and that this was manifested in the systemic compartment.     

Cell proliferation and apoptosis are altered in mice deficient in the NF-kappaB p50 subunit after treatment with the peroxisome proliferator ciprofibrate.

We previously showed that the peroxisome proliferator ciprofibrate increases hepatic NF-kappaB DNA binding activity in rats, mice, and hepatoma cell lines. Here, we analyzed the response to ciprofibrate in mice that lack the NF-kappaB p50 gene (p50-/-). Wild-type and p50-/- mice were fed a diet with or without 0.01% ciprofibrate for 10 days. NF-kappaB DNA binding activity was present and increased after ciprofibrate treatment in wild-type mice, but was not detected in p50-/- mice. The untreated p50-/- mice had a higher level of hepatic cell proliferation, as measured by BrdU labeling, than did untreated wild-type mice. However, the increase in proliferation was greater in ciprofibrate-fed wild-type mice than in ciprofibrate-fed p50-/- mice. The apoptotic index was low in wild-type mice in the presence or absence of ciprofibrate. Apoptosis was increased in untreated p50-/- mice compared to wild-type mice; apoptosis was reduced in p50-/- mice after ciprofibrate feeding. The c-Jun and JunB mRNA levels were higher in untreated p50-/- mice than in untreated control mice; c-Jun mRNA levels increased, whereas JunB mRNA levels decreased in both groups after ciprofibrate treatment. The c-Jun and JunB protein levels were the same in untreated wild-type and p50-/- mice and increased in both groups after ciprofibrate treatment. Several apoptosis-related mRNAs were higher in untreated p50-/- mice compared to untreated control mice; expression of these genes increased in both groups after ciprofibrate treatment. These data indicate that NF-kappaB contributes to the proliferative and apoptotic changes that occur in the liver in response to ciprofibrate.     

Effect of vitamin E on carbon tetrachloride-induced lipid peroxidation as demonstrated by in vivo pentane production

Pentane production by rats fed a stock diet exhibited a dose-dependent relationship with carbon tetrachloride (CCl₄) administered intraperitoneally. Total pentane produced during a 2-h test period following administration of a single dose of 30 μl CCl₄/100 g body wt. was greater by rats fed a vitamin Edeficient diet than by rats fed a diet supplemented with vitamin E. Vitamin Esupplemented rats pretreated with 30 μl CCl₄ daily for 4 days produced less pentane following administration of 60 μl CCl₄ on day 5 than did rats not pretreated with CCl₄; conversely, rats fed a vitamin E-deficient diet and similarly treated produced more pentane than did non-pretreated rats. This study confirmed that CCl₄ toxicity involves lipid peroxidation and that protection is provided by vitamin E. The usefulness in toxicological studies of monitoring pentane as an index of lipid peroxidation in vivo was shown.     

Quercetin and vitamin E attenuate Bonny Light crude oil-induced alterations in testicular apoptosis,stress proteins and steroidogenic acute regulatory protein in Wistar rats

Studies have shown the reproductive effects of Bonny Light crude oil (BLCO) via the mechanism of oxidative stress and testicular apoptosis. We investigated the protective role of quercetin and vitamin E on BLCO-induced testicular apoptosis. Experimental rats were divided into four groups of four each. Animals were orally administered 2?ml/kg corn oil (control: group 1), BLCO-800?mg/kg body weight?+?10?mg/kg quercetin (group 2), BLCO-800?mg/kg body weight?+?50?mg/kg vitamin E (group 3) and BLCO-800?mg/kg body weight only (group 4) for 7 d. Protein levels of caspase 3, FasL, NF-kB, steroidogenic acute regulatory protein and stress response proteins were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunofluorescence staining was used to quantify the expression of caspase 3, FasL and NF-kB. Apoptosis was quantified by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay. Administration of BLCO resulted in a significant increase in the levels of stress response proteins and apoptosis-related proteins by 50% and above after 7 d following BLCO exposure and a concomitant increase in expression of caspase 3, FasL and NF-kB expression by immunofluorescence staining. Apoptosis showed a significant increase in TUNEL positive cells. Co-administration with quercetin or vitamin E reversed BLCO-induced apoptosis and levels of stress protein, relative to control. These findings suggest that quercetin and vitamin E may confer protection against BLCO-induced testicular oxidative stress-related apoptosis.     

Increased radiation-induced apoptosis in mouse thymus in the absence of metallothionein.

Metallothionein (MT) has been shown to protect cells from free radical induced DNA damage after exposure to copper, hydrogen peroxide and also radiation. In order to study the role of MT in radiation induced apoptosis, age-matched male control mice (C57BL/6J), MT-I overexpressing (MT-I*) and MT-null transgenic mice were exposed to whole body cobalt 60 gamma-irradiation at 0, 5, or 10 Gy, and their thymus were removed 24 h later. The basal levels of MT and zinc concentrations in the thymus were measured by 109Cadmium-heme assay and atomic absorption spectrophotometry, respectively. The MT expression after radiation was determined by immunohistochemical staining using a polyclonal antibody to MT. The extent of apoptosis in thymocytes was determined by histology (H&E stain). DNA was isolated from the thymus, and DNA fragmentation was determined by agarose gel electrophoresis. The results showed that the basal level of MT protein in MT-I* thymus was 2.4-fold higher than control mice, and that MT was inducible in both MT-I* and control C57BL6 thymus after radiation exposure. Minimal MT protein was detected in MT-null mice thymus before or after radiation, while, a significantly higher number of apoptotic cells and DNA fragmentation were found in MT-null thymus after whole body irradiation. These data demonstrated a protective role for MT in radiation-induced apoptosis in mouse thymus.     

Alteration of Convulsive Threshold and Conditioned Avoidance Response in Mice Fed Diets Containing Contraceptive Steroids

ABSTRACT

Female CD₁ mice given the contraceptive steroids mestranol and norethynodrel (1:10) in the diet (0.0033%) for 4 months had a growth reduction of 20% when compared with mice fed a normal diet, and had lower convulsive thresholds when tested with the vitamin B₆ antagonists 2, 4-dimethyl-5-methyl-hydroxypyrimidine and thiosemicarbazide. In conditioned avoidance response (CAR) tests, mice fed the steroid-containing diets showed a decreased acquisition performance during all six sessions; however, mice fed the same diet supplemented with vitamin B₆ (0.04%) performed as well during the last three sessions of the CAR tests as mice fed the normal diet.     

Low iron diet retards 12-<Emphasis Type="Italic">O</Emphasis>-tetradecanoyl phorbol-13-acetate-mediated tumor promotion in murine skin

Recently, we have shown that low iron state reduces benzoyl peroxide-mediated tumor promotion in murine skin. To further test the dependence of iron on skin tumor development, we assessed the effect of a low iron diet on 12-O-tetradecanoyl phorbol-13-acetate (TPA)-mediated tumor promotion in murine skin. Female Swiss albino mice were fed on a low iron diet and initiated with a single dose of 7,12-dimethylbenz[a]anthracene (DMBA, 40 µg as150 µl per mouse) and promoted with TPA (2.5 µg as 200 µl per mouse, twice-weekly application for 20 weeks). The appearance of the first papilloma and the number of tumors (papillomas and carcinomas) per mouse were recorded weekly. We observed a decrease in tumor incidence (papillomas and carcinomas) and number of tumors per mouse in TPA-promoted mice fed on low iron diet (0.23 mg Fe/kg diet) compared to normal mice fed on balanced mouse chow (1.70 mg Fe/kg diet). The total iron consumption per day by mice being fed on balanced mouse chow was 340–400 µg Fe/kg body weight, and the total iron consumption per day by mice being fed on low iron diet was 45–55 µg Fe/kg body weight. The number of papillomas per mouse was 45% lower and the conversion of papillomas to carcinomas was about 20% lower in mice fed a low iron diet. The tumor size was also smaller in mice being fed on low iron diet. TPA treatment resulted in decreases in the activities of antioxidant enzymes and depletion in the level of epidermal reduced glutathione (GSH). Feeding mice on low iron diet along with TPA treatment resulted in ~50–75% recovery of the depleted levels of GSH and antioxidant enzymes. In addition, TPA-mediated induction of biological markers of tumor promotion, viz. ornithine decarboxylase activity and [³H]thymidine incorporation into cutaneous DNA, was about 60% lower in TPA-treated mice fed on low iron diet than in normal mice treated with TPA. Cutaneous iron levels were also lower in mice fed on low iron diet than in mice fed on normal diet. Histopathological sections of the skin portion adjoining tumors showed a lower degree of epidermal hyperplasia and lesser infiltration of inflammatory cells in the dermis, and absence of hyperkeratosis in mice fed on low iron diet. Thus, in this study we observe that the tumor promoting potential of TPA is reduced in mice fed on low iron diet, which is also accompanied by lesser inflammatory changes in the skin of tumor-bearing mice fed on low iron diet.