Protection of salvia miltiorrhiza against aflatoxin-B1-induced hepatocarcinogenesis in Fischer 344 rats dual mechanisms involved

Extract of Salvia Miltiorrhiza (SM) has been widely used in traditional Chinese medicine for treating liver diseases. Recent experimental evidence indicates that it has anti-tumor potential. In this study, the effect of SM on alfatoxin B1 (AFB1)-induced hepatocarcinogenesis was investigated in male Fischer 344 rats. AFB1 (40 microg/100 g body wt, by gavage) was administered once a week for 24 weeks. In SM treatment group, rats were given SM (0.25g/100g body wt, 5 days/week by gavage) for a total of 28 weeks, including 4 weeks before and 24 weeks during AFB1 exposure. Results showed that the elevation of serum alanine aminotransferase and aspartate aminotransferase activities due to AFB1 dosing was almost completely abolished by the treatment of SM, indicating that SM could prevent AFB1-induced liver cell injury. It was further observed that SM substantially reduced glutathione S-transferase placenta form (GST-P) positive foci formation and GST-P mRNA expression caused by AFB1, which clearly suggests that SM is effective in preventing AFB1-induced hepatocarcinogenesis. Furthermore, the inhibition on AFB1 hepatocarcinigenesis was associated with a corresponding decrease in AFB1-DNA adducts formation as well as AFB1-induced oxidative DNA damage (8-hydroxydeoxyguanosine) in rat liver. Our results also indicate that the protective effect of SM might be mediated through dual mechanisms: (i) the enhancement of AFB1 detoxification pathway, especially the induction of GST-Yc2 mRNA expression, and (ii) the antioxidant property of SM.

Study on mechanism of multistep hepatotumorigenesis in rat: development of hepatotumorigenesis

With the aim of establishing bio-indices for the development of multistep hepatotumorigenesis, rats were fed water containing 0.01% diethylnitrosamine (DEN) ad libitum for 13 weeks. This treatment with DEN only made it possible to induce hepatic tumors in 100%. After the DEN administration, several clinical symptoms were observed including minor behavioral changes, brittleness of hair and a decrease in water and food intake. The concentration of total serum protein and albumin in all treated groups was significantly lower than in non-treated controls (P<0.05). Increase of specific enzyme (AST, ALT and GGT) activity (P<0.05), variable tumor size and hepatomegaly of the liver was observed in all rats treated with DEN for 10 weeks. Both hepatocellular carcinoma and cholangiocarcinoma were found in the same livers at the same time, and were prominently developed after 12 weeks. In case of carcinoma, some of the livers showed more or less advanced states over the 12-15 weeks period. In the present study, hepatocellular carcinoma was developed by treating DEN in only the drinking water, without any other carcinogens or without partial hepatectomy. These results indicate that DEN is a new carcinogen that acts directly on it the liver, moreover, it might be very useful for investigating hepatotumorigenesis.

Mechanism for the antitumor and anticachectic effects of n-3 fatty acids

Dietary intake of the n-6 fatty acid (FA) linoleic acid (LA) has a strong growth-promoting effect on many rodent tumors and human tumor xenografts grown in immunodeficient rodents. n-3 FAs such as alpha-linolenic and eicosapentaenoic acids (EPAs), which differ from LA and arachidonic acid, respectively, by only a single double bond in the n-3 position, are recognized cancer chemopreventive and anticachectic agents. Understanding how this seemingly small structural difference leads to such remarkable functional differences has been a challenge. In a previous study, we showed that LA uptake, [3H]thymidine incorporation into DNA, and total DNA content were decreased in tissue-isolated hepatoma 7288CTC perfused in situ with arterial blood containing alpha-linolenic acid, EPA, or docosahexaenoic acids. The Ki for the inhibition of LA uptake and [3H]thymidine incorporation by alpha-linolenic acid was 0.18 and 0.25 mM, respectively. Here we show that the addition of alpha-linolenic acid or EPA to arterial blood inhibits tumor FA uptake, including LA, and the subsequent conversion of LA to the mitogen 13-hydroxyoctadecadienoic acid (13-HODE) in vivo and during perfusion in situ. [3H]Thymidine incorporation during perfusion in situ was also inhibited. Addition of 13-HODE to the arterial blood reversed the inhibition of [3H]thymidine incorporation but had no effect on FA uptake. These two n-3 FAs also inhibited FA transport in inguinal fat pads in vivo and during perfusion in situ in fed (FA uptake) and fasted (FA release) rats. The effects of EPA and talinolenic acid on transport of saturated, monounsaturated, and n-6 polyunsaturated FAs in hepatoma 7288CTC and inguinal fat pads during perfusion in situ were reversed by the addition of forskolin (1 microM), pertussis toxin (0.5 microg/ml), or 8-bromo-cyclic AMP (10 microM) to the arterial blood. We conclude that the antitumor and anticachectic effects of n-3 FAs on hepatoma 7288CTC and inguinal fat pads in vivo result from an inhibition of FA transport. These inhibitions are mediated by a putative n-3 FA receptor via a Gi protein-coupled signal transduction pathway that decreases intracellular cyclic AMP. A specific decrease in LA uptake and its conversion to the mitogen 13-HODE causes the tumor growth inhibition.

Changes in tumor oxygenation/perfusion induced by the no donor, isosorbide dinitrate, in comparison with carbogen: monitoring by EPR and MRI

PURPOSE

In an effort to improve radiotherapy treatments, methods aimed at increasing the quantity of oxygen delivered to tumors were investigated. The aim of this study was to evaluate the effect of one nitric oxide (NO) donor (isosorbide dinitrate) on pO(2) and blood flow in a murine tumor model. The effect was compared to carbogen, used as a reference treatment.

METHODS AND MATERIALS

Thirty-six liver tumors implanted in mouse thighs were imaged using magnetic resonance imaging (MRI) at 4.7 Tesla with dynamic Gd-DTPA and blood oxygen level-dependent (BOLD) contrast-enhanced imaging after administration of isosorbide dinitrate or carbogen. The effect on the pO(2) was also tested by EPR oximetry (1.1 GHz) on 52 mice.

RESULTS

A significant increase in MRI intensity was observed for both treatments in comparison with the control group. EPR oximetry showed a dose-dependant increase in tumor pO(2) for isosorbide dinitrate (by 5.9 mmHg at 0.2 mg/kg) and a substantially greater change for carbogen breathing (by 23 mmHg).

CONCLUSION

Both tumor blood flow and pO(2) were increased by isosorbide dinitrate and carbogen. Carbogen is more efficient than isosorbide dinitrate in increasing the BOLD image intensity, as well as the tumor pO(2), but as efficient as isosorbide dinitrate in the Gd-DTPA contrast-enhanced imaging. We conclude that the effects of carbogen on improving tumor pO(2) involve both improved blood flow and improved hemoglobin oxygenation, whereas the effects of isosorbide dinitrate are predominantly mediated by improved blood flow alone.

Effects of glutamine on tumor growth and apoptosis of hepatoma cells

AIM

To explore the effects of glutamine on growth and apoptosis of hepatoma cells.

METHODS

Mice inoculated with hepatoma cell (H22) suspension subcutaneously at right axilla were orally administered with glutamine (GLN) solution. Human hepatoma cell culture (SMMC-7721) was treated with different concentrations of GLN solution. The content of malondialdehyde (MDA) and nitric oxide (NO) was detected in mice plasma and cell culture, and that of glutathione (GSH) was decected in cells. The inoculated tumor's growth in the mice and hepatoma cells' proliferation and apoptosis were observed.

RESULTS

When mice were administered orally with GLN solution (300 mg/kg), the growth of inoculated hepatoma was suppressed in the mice. When different concentrations of GLN solution were added in human hepatoma cell culture, the hepatoma cells' proliferation was inhibited and cells were induced to apoptosis, which was dependent on GLN concentration; meanwhile the contents of NO rose both in mice plasma and in cell culture, however MDA contents were slightly lowered in both, and the activity of GSH increased in the cells which had been ultrasonically shattered.

CONCLUSION

Hepatoma cell apoptosis and tumor growth inhibition by GLN may be associated with its antioxidative activity and its intervention in hepatoma cell proliferation, and simultaneous release of NO.

Effect of normal and tumor factors on different phases of cell populations cycle

In the present experiments we studied the effect of extracts from intact liver (LE), ES2 tumor extract (TE), plasmas from intact mice (PI), and from tumor bearing animals (PT) on different phases of hepatocytes and renocytes cell cycles. C3HS 28-day-old male mice, standardized for periodicity analysis, were injected at 16:00 hours and killed every 4 hours during a circadian cycle at 20:00/04; 00:00/08; 04:00/12; 08:00/16; 12:00/20 and 16:00/24 (time of day/hours post treatment). Colchicine (2 microg/g) was injected 4 hours before killing them. Samples of livers and kidneys were processed for histology and mitotic index determinations. The results were expressed as colchicine arrested metaphases per 1000 nuclei. The TE, LE and PI had a promoting effect on the mitotic activity of hepatocytes during the first 12 hours post treatment. During the subsequent 12 hours, not only these treatments but also the PI had an inhibiting effect on the mitotic activity of the same cell population. Also the TE and the PT had a promoting effect on the mitotic activity of the renocytes during the first 12 hours while the effect of all treatments showed a clear inhibition of the mitotic activity studied during the last 12 hours. Taking into account the time elapsed between the injections and the measurements made in these light-dark synchronized animals, we conclude that the increase in mitotic index observed in those tissues stemmed from a reinitiation of cell-cycle traverse in a subpopulation of G2-arrested, noncycling cells.

[Generation of reactive forms of oxygen by polymorphonuclear leukocytes during hepatoma growth in the peritoneal cavity of animals]

In the present work, an attempt was made to analyse generation of reactive oxygen species (ROS) by polymorphonuclear leucocytes (PMN) in the course of tumour growth, using chemiluminescence (CL). A multiple increase in the capacity of polymorphonuclear leucocytes of generating active forms of oxygen in the course of tumor growth was discovered. Two causes of this process were found. 1) the increase in specific activity of leucocytes; 2) the increase in the total quantity of PMN circulating in the blood. Leucocytes were also found in the ascite liquid. PMN leucocytes were shown to participate in the antitumor defence of the organism.

Carcinoembryonic antigen-related cell-cell adhesion molecule C-CAM is greatly increased in serum and urine of rats with liver diseases

C-CAM (rat cell CAM/human CD66a) is ubiquitous and multifunctional. It is involved in intercellular adhesion, signal transduction and cell growth inhibition. Structurally, it is related to the carcinoembryonic antigen. In the present study serum, bile and urine of rats with liver diseases were analyzed for the presence of cell CAM. After bile duct ligation and during galactosamine (GalN) hepatitis we found that large amounts of liver membrane-bound C-CAM are secreted or shed into blood. The serum level of another liver membrane-bound protein, LI-cadherin, is not increased. It was shown that C-CAM is also present in bile fluid, and for the first time that C-CAM is present in the urine of rats with liver diseases. A particularly high concentration was measured in the urine of rats suffering from GalN hepatitis.

Hypercoagulable state and disseminated intravascular coagulation following an effective chemotherapy in tumor-bearing rats

OBJECTIVE

To detect the changes in blood coagulation system and clarify the related mechanisms of chemotherapy-induced disseminated intravascular coagulation.

METHODS

Changes in blood coagulation system and immunohistochemistry for fibrinogen were investigated in six groups of rats designed for different purposes.

RESULTS

Decreased platelet count, prolonged prothrombin time and active partial thromboplastin time, elevated fibrinogen level, and decreased antithrombin were observed in the rats receiving a newly developed chemotherapy (NDC group), in which mitomycin C was administered intravenously together with angiotensin. Accumulation of fibrinogen and microthrombi in the blood vessels of multiple organs were also found in the NDC group by immunohistochemistry and histopathological examination.

CONCLUSIONS

Rapid reduction of tumor mass induced by an effective chemotherapy could cause hypercoagulable state and disseminated intravascular coagulation.

The effect of experimental neoplastic disease on malondialdehyde level and glutathione status in erythrocytes of rats

The level of lipid peroxidation products and the content of glutathione in erythrocytes of rats with Morris 5123 hepatoma at different stages of tumor development were examined. The content of endogenous malondialdehyde (MDA) was increased throughout all periods of tumor development as compared to the results for healthy rats. From the extent of MDA generation under oxidative stress we concluded that erythrocytes of Morris 5123 hepatoma bearing rats were more susceptible to autoxidation than those from control rats. The content of reduced glutathione (GSH) and oxidized glutathione (GSSG) was increased at the early stage of tumor growth. At the advanced stage of the disease both the content of GSH and the GSH/GSSG ratio were decreased while the content of GSSG remained at the elevated level.

Suppression of hypercholesterolemia in hepatoma-bearing rats by cabbage extract and its component, S-methyl-L-cysteine sulfoxide

The effect of cabbage extract on cholesterol metabolism was studied in Donryu rats subcutaneously implanted with an ascites hepatoma cell line (AH109A). The hepatoma-bearing rats exhibited hypercholesterolemia induced by increasing cholesterogenesis in the host liver and decreasing steroid excretion into feces. The cabbage extract intake or administration reduced serum cholesterol level and enhanced fecal bile acid excretion and cholesterol 7alpha-hydroxylase activity, the rate-limiting enzyme of bile acid biosynthesis, in the microsomal fraction of the liver. Furthermore, S-methyl-L-cysteine sulfoxide, a component of cabbage, could mimic the effect of cabbage extract when orally administered. These results suggest that cabbage suppresses hypercholesterolemia responding to hepatoma growth by upregulating cholesterol catabolism and that S-methyl-L-cysteine sulfoxide in cabbage is one of the factors suppressing hypercholesterolemia in the hepatoma-bearing rats.

[Study on inhibition and prevention of tumor and antioxidative effects of lithium carbonate in tumor bearing mice]

Two Kinds of tumor-bearing mice (hepatoma H22 and sarcoma S180) were administered with lithium carbonate (Li2CO3) for 17 or 10 days (advanced and simultaneous administration), in order to observe the effects of prevention and treatment of Li2CO3 on malignant tumor, as well as the relationship between Li2CO3 and lipid peroxidation in tumor-bearing mice. Meanwhile, we compared the toxic and side effects of cyclophosphamide (CP) with that of Li2CO3. The results showed that Li2CO3 had no significant toxic or side effects with the suggested doses. In the tests of inhibition and prevention of tumor, Li2CO3 could significantly inhibit the grouth of the two kinds of tumor, and increase the activity of superoxide dismutage (SOD) and decrease the contents of Malonyldialdehyde (MDA). In addition, Li2CO3 had no effect on the white blood cells (WBC) and decreased the micronucleus frequency (MNF) in bone marrow polychromatic erythrocytes (PCE), while CP had definite effect of decreasing the WBC and increasing the MNF in the tumor-bearing mice.

In vivo tumor necrosis factor-alpha induction following chlorin e6-photodynamic therapy in Buffalo rats

Photodynamic therapy may induce in the in vivo conditions the cytokine tumor necrosis factor-alpha in Buffalo rats. The sensitizer, i.e. chlorin e6, in the doses 2.5, 5.0 and 7.5 mg/kg of body weight followed by light treatment with total doses 50, 100, 150, 200 and 250 J/cm2 resulted in the increase of serum levels of the cytokine. The levels of tumor necrosis factor-alpha have been determined at different time points using enzyme-linked immunosorbent assay (ELISA). In control animals these levels did not exceed the mean value of 189 pg/ml, whereas in photodynamically treated rats the levels were almost 3-4 times higher. The entire experiment has been carried out on healthy animals; control, tumor-bearing rats have also been included to the present experiment.

Light contamination during the dark phase in "photoperiodically controlled" animal rooms: effect on tumor growth and metabolism in rats

Enhanced neoplastic growth and metabolism have been reported in animals maintained in a constant light (24L:0D) environment. Results from this laboratory indicate that tumor growth is directly dependent upon increased ambient blood concentrations of arachidonic and linoleic acids, particularly linoleic acid. Tumor linoleic acid utilization and production if its putative mitogenic metabolite, 13-hydroxyoctadecadienoic acid (13-HODE), are suppressed by the circadian neurohormone melatonin, the production of which is itself regulated by light in all mammals. This study was performed to determine whether minimal light contamination (0.2 lux) in an animal room during an otherwise normal dark phase may disrupt normal circadian production of melatonin and affect tumor growth and metabolism. Animals of groups I (12L:12D), II (12L:12-h light-contaminated dark phase), and III (24L:0D) had plasma total fatty acid (TFA), linoleic acid (LA), and melatonin concentrations measured prior to tumor implantation; groups I and II had daily cycles in plasma TFA and LA values, whereas group III had constant values throughout the day. The integrated mean TFA and LA values for the entire day were similar in all groups. Although group-I animals had a normal nocturnal surge of melatonin (127.0 pg/ml) at 2400 h, the nocturnal amplitude was suppressed in group-II animals (16.0 pg/ml); circadian variation in melatonin concentration was not seen in group-III animals (7.4 pg/ml). At 12 weeks of age, rats had the Morris hepatoma 7288CTC implanted as "tissue-isolated" tumors grown subcutaneously. Latency to onset of palpable tumor mass for groups I, II, and III was 11, 9, and 5 days respectively. Tumor growth rates were 0.72 +/- 0.09, 1.30 +/- 0.15, and 1.48 +/- 0.17 g/d (mean +/- SD, n = 6/group) in groups I, II, and III respectively. Arteriovenous difference measurements for TFA and LA across the tumors were 4.22 +/- 0.89 and 0.83 +/- 0.18 (group I), 8.26 +/- 0.66 and 1.64 +/- 0.13 (group II), and 7.10 +/- 0.78 and 1.50 +/- 0.16 (group III)/min/g, and groups II and III were significantly different from group I (P < 0.05). Tumor TFA and LA contents were 14.3 +/- 1.7 and 1.8 +/- 0.3 (group I), 52.9 +/- 5.5 and 7.9 +/- 0.8 (group II), and 106.0 +/- 12.0 and 18.5 +/- 2.4 (group III) micrograms/g and were significantly different from each other (P < 0.001). Production of 13-HODE by the hepatomas in groups I, II, and III was 35.5 +/- 6.3, 109.6 +/- 10.6, and 196.2 +/- 34.9 ng/min/g respectively, values which also were significantly different among groups (P < 0.001). The results indicate that minimal light contamination of only 0.2 lux during an otherwise normal dark phase inhibits host melatonin secretion and increases the rate of tumor growth and lipid uptake and metabolism. These data suggest that great care must be taken to prevent "light-leaks" in animal rooms during the dark phase of a diurnal cycle because such contamination may adversely affect the outcome of tumor growth investigations.

Correlation of repressed transcription of alpha-tocopherol transfer protein with serum alpha-tocopherol during hepatocarcinogenesis

Using a subtraction-enhanced display technique, we identified a rodent alpha-tocopherol transfer protein (alpha-TTP) cDNA which exhibited markedly lower messenger RNA (mRNA) amounts in rat hepatocellular carcinoma (HCC) than in healthy controls. Several lines of evidence have substantiated that abnormal alpha-TTP results in isolated vitamin E deficiency. In this study, we investigated the hepatic mRNA amounts of alpha-TTP during rat hepatic carcinogenesis and liver regeneration on Northern blot, localization of alpha-TTP mRNA in HCC of rats and humans by in situ hybridization, and we analyzed the correlation between alpha-TTP mRNA and alpha-tocopherol. alpha-TTP mRNA concentrations of the rats were decreased at the early stage of hepatic carcinogenesis, and remained 3-5-fold reduced as the tumor progressed. In parallel, serum alpha-tocopherol concentrations were significantly decreased to 40% of those in the controls at the early stages of rat hepatic carcinogenesis (p < 0.01). The 2 data sets were strongly correlated (r = 0.834, p < 0.001). In situ hybridization revealed that a decrease of alpha-TTP mRNA was preferentially localized in the tumor nodules of rats and humans with HCC. Our data suggest that repressed transcription of alpha-TTP is associated with a decrease of serum alpha-tocopherol and with hepatic carcinogenesis.

Ascorbic acid protects guinea pigs from acute aflatoxin toxicity

These studies were conducted to investigate whether ascorbic acid protected guinea pigs from aflatoxin B1 (AFB1) toxicity. Young guinea pigs, fed either 0 (AA) or 25 mg (25 AA) or gavaged 300 mg ascorbic acid (300 AA) per day for 21 days, were gavaged with the LD50 dose of AFB1 on the 22nd day. Seven out of 10 animals in the AA group died within 72 hr of AFB1 administration. The livers of the animals showed regional massive necrosis and multilobular degeneration. There was no mortality in the 25 AA group. Their livers, however, showed changes similar to those seen in AA group. Serum alanine amino transferase (ALAT) and aspartate amino transferase (ASAT) levels were elevated. There was neither mortality nor pathological changes in livers in the 300 AA group. Their ALAT and ASAT levels were unaffected. In vitro production of AFM1 by liver microsomes tended to be higher than that in the other two groups. Three animals saved from the 300 AA group and continued with their supplementation were administered a second, intraperitoneal (ip) LD50 dose of AFB1 1 month after the first AFB1 dose. One animal died. Livers of the animals showed centrilobular degeneration and moderate necrosis in scattered hepatocytes. Liver microsomal cytochrome P450 and cytosolic glutathione S-transferase (GST) levels and AFM1 production were drastically reduced. ALAT and ASAT activities were raised. The results indicated that intake of 300 mg of ascorbic acid almost protected the animals from acute toxicity of AFB1 when given by gavage, but not when administered as a second dose ip.

Vanadium-mediated chemoprotection against chemical hepatocarcinogenesis in rats: haematological and histological characteristics

The trace element vanadium was investigated for its anti-neoplastic role in relation to haematological status, hepatic histopathology and histochemical analysis of glycogen in liver. Its impact on the survival of male Sprague-Dawley rats subjected to a two-stage hepatocarcinogenesis regimen was also assessed. Initiation was performed using a single intraperitoneal injection of diethylnitrosamine (DENA) (200 mg/kg) followed by promotion with phenobarbital (0.05%) in a basal diet. Vanadium supplementation as ammonium monovanadate at 0.5 ppm vanadium in drinking water was given ad libitum throughout the experiment (20 weeks), before the initiation (4 weeks), or during the promotional period (14 weeks). At the end of the study, there was a significant decrease in red blood cell count, haemoglobin content, haematocrit value, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, plasma volume change and total white cell count, with a concurrent alteration in lymphoid:myeloid ratio in DENA control animals compared with their normal counterparts. Vanadium supplementation throughout the study or before the initiation significantly reversed the DENA-induced alterations in most of the haematological indices. A single intraperitoneal injection of DENA also depleted the plasma albumin concentration, raised the plasma globulin content, and decreased the ratio of albumin to globulin. These altered features began to return to normal following vanadium supplementation. Supplementary vanadium also elicited substantial protection against DENA-mediated rat liver carcinogenesis. This was fairly evident from hepatic histology and evaluation of glycogen accumulation by periodic acid-Schiff reaction. The survival of DENA-treated animals was considerably increased in the presence of vanadium. The critical involvement of vanadium in modulating several factors associated with erythropoiesis under carcinogenic challenge may thus have a possible impact on the eventual increased survival of the host.

Comparison of the enhancing effects of dehydroepiandrosterone with the structural analog 16 alpha-fluoro-5-androsten-17-one on aflatoxin B1 hepatocarcinogenesis in rainbow trout

Dehydroepiandrosterone (DHEA) is an adrenal steroid with chemoprotective effects against a wide variety of conditions including cancer, obesity, diabetes, and cardiovascular disease. However, DHEA is also a carcinogen in laboratory animals, possibly through its function as a precursor of sex steroids or peroxisome proliferation. The structural analog 16 alpha-fluoro-5-androsten-17-one (8354) has been reported to have enhanced chemopreventive activity without the steroid precursor and peroxisome proliferating effects of DHEA. This study compares DHEA and 8354 in rainbow trout, a species that is resistant to peroxisome proliferation but is highly susceptible to the carcinogenic and tumor enhancing effects of DHEA. Trout were exposed as fry to aflatoxin B1 (AFB1) or given a sham exposure, then were fed diets containing 444 ppm DHEA or 8354 for 6 months. Postinitiation treatment with DHEA significantly increased liver tumor incidence, multiplicity, and size compared to initiated controls. The analog 8354 slightly increased tumor incidence (p = 0.06) but had no effect on multiplicity or size. Six percent of trout treated with DHEA alone developed tumors, whereas no tumors occurred in noninitiated trout fed control or 8354-containing diets. Serum levels of androstenedione were elevated by DHEA (48-fold) or 8354 (6-fold) treatment. Serum beta-estradiol titers were increased in DHEA- but not 8354-treated trout. Vitellogenin was induced significantly by either DHEA (434-fold) or 8354 (21-fold). Peroxisomal beta-oxidation was not increased by either compound and catalase activity was decreased in DHEA-treated animals. Both steroids were potent inhibitors in vitro of trout liver glucose-6-phosphate dehydrogenase with IC50s of 24 and 0.5 microM for DHEA and 8354, respectively. This research suggests that in trout the tumor enhancing effects of DHEA may be due to its function as a sex steroid precursor and are unrelated to peroxisome proliferation. These carcinogenic properties are reduced in the analog 8354 which has been advocated as an alternative to DHEA for chemoprevention.

Responses of serum lipids and adipose tissue lipases to lipopolysaccharide administration in normal and hepatoma-bearing rats

The effects of in vivo lipopolysaccharide administration on serum lipid metabolism were studied in normal and hepatoma-bearing rats. Changes in serum lipid levels and adipose tissue lipase (lipoprotein lipase and hormone-sensitive lipase) activities following injection of lipopolysaccharide into normal rats resembled those in hepatoma-bearing rats. These results suggest the presence of some common factor(s) involved in the incidence of abnormal lipid metabolism upon lipopolysaccharide injection and hepatoma transplantation.

Deoxycholic acid as an endogenous risk factor for hepatocarcinogenesis and effects of gomisin A, a lignan component of Schizandra fruits

Although hepatocarcinogensis has been reported to be promoted by exogenous administration of bile acids, the relation of endogenous bile acids to hepatocarcinogenesis is not completely understood. This study investigates the relationship between serum concentration of bile acids, the appearance of preneoplastic change, glutathione S-transferase placental form (GST-P)-positive foci in the liver of male Donryu rats which had been fed 0.06% 3'-methyl-4-dimethylamino-azobenzene (3'-MeDAB), and the effects of gomisin A, previously reported to inhibit the tumor promotion process. During the feeding of 3'-MeDAB for 5 weeks, the concentrations of serum bile acids were found to have increased significantly to several times the levels found at the start of the experiment. The increase of serum bile acids, especially deoxycholic acid (DCA), and the appearance of preneoplastic lesions, the number and area of GST-P-positive foci in the liver, were significantly inhibited by simultaneous oral administration of gomisin A (30 mg/kg). When DCA (100 mg/kg) was orally administered after an initiation by 3'-MeDAB, serum bile acids and preneoplastic changes were significantly increased, these increases were inhibited by combined feeding of 0.03% gomisin A in the diet. There were good correlations between the serum concentration of DCA and the number of GST-P-positive foci in the liver in both experimental protocols. These results confirm that DCA is an endogenous risk factor for hepatocarcinogenesis and suggest that anti-promoter effect of gomisin A is based on improving metabolism of bile acids, including DCA.

Pharmacokinetics and antitumor effects of mitoxantrone after intratumoral or intraarterial hepatic administration in rabbits

The intratumoral (i.t.) delivery of anticancer drugs aims at controlling tumor growth and thereby provides palliative treatment for liver neoplasms. Mitoxantrone is a good candidate for local or regional administration because (1) its metabolism is mainly hepatic, (2) it has a steep dose-response curve for multiple solid tumors, and (3) its fixation in tissues is sustained without vesicant effects after extravasation. We compared the tolerance, pharmacokinetics, and antitumor effects of mitoxantrone on hepatic VX2 tumors in rabbits treated with i.t. intraarterial hepatic (i.a.h.) or i.v. mitoxantrone, i.t. ethanol; or i.t. 0.9% NaCl and in control animals. Tumor growth rates (TGRs) were evaluated at 9 days after treatment. Myelosuppression was the limiting toxicity of i.v. mitoxantrone at 1.5 mg/kg (maximal tolerated dose, MTD), but neither i.t. nor i.a.h. administration led to hematologic toxicity at the same dose. The mitoxantrone retained in tumors after i.t. administration was seen as blue-stained areas of complete necrosis according to histologic analysis. Pharmacokinetic parameters showed a significantly decreased systemic exposure to the drug after both regional treatments, although the i.a.h. route appeared to have an edge over the i.t. route. TGRs were significantly reduced after i.t. mitoxantrone (81 +/- 62%), i.a.h. mitoxantrone (337 +/- 110%), and i.t. ethanol treatments (287 +/- 117%) as compared with control values (886 +/- 223%; p < 0.01). Treatment with i.v. mitoxantrone (816 +/- 132%) had no antitumor effect, nor did NaCl injections (868 +/- 116%). Mitoxantrone given i.t. induced the highest antitumor effects, resulting in a 3.5-fold reduction in TGRs as compared with i.a.h. mitoxantrone and i.t. ethanol treatments (p < 0.02). Treatment with i.t. mitoxantrone provided efficient antitumor therapy without producing major side effects. This method should be considered as palliative treatment for nonresectable liver tumors and other localized malignancies.

Prevention of experimental hepatic metastasis with thromboxane synthase inhibitor

To investigate the effectiveness of thromboxane (Tx) synthase inhibitor in the prevention of experimental hepatic metastasis, an in vivo study was designed. Hepatic metastasis was brought about by injection of 1 x 10(5) cells of colon 38 tumor into the portal vein of C57 B1/65 mice. Seven groups (n = 16 in each group) received different treatments: with TxA2 synthase inhibitor (sodium ozagrel), 5, 10 or 15 mg/kg BW before tumor inoculation, and daily for the following 3 days, (groups A, B and C, respectively); with acetyl salicylic acid (aspirin), 1.0, 1.5 or 2.0 mg/kg BW (groups C, D, and E, respectively); a control group, inoculated with vehicle only. Serum TxB2, a stable metabolite of TxA2, and prostaglandin F1 alpha were measured. Labeling index for tumor proliferation by bromodeoxy-uridine radioimmuno-assay was also studied. Incidence of metastasis in groups A (60.5%), B (49.5%), C (43.0%), D (80.5%), E (66.0%) and F (58.4%) was less than that in the control group (100%). Tumor size, number of labeling index did not differ among the groups. Serum TxB2 (pg/ml) levels were significantly lower in all of the groups than in the control. Serum PGF1 alpha levels in the groups with aspirin were lower than those in sodium ozagrel. Tx synthase inhibitor is effective in the prevention of experimental hepatic metastasis when it is given before and immediately after tumor inoculation. As Tx synthase inhibitor leaves metabolic pathway to PGI2 production intact, it is more effective in the prevention of metastasis than aspirin since aspirin inhibits both thromboxane and PGI2.

Beta-carotene prevents lipid peroxidation and red blood cell membrane protein damage in experimental hepatocarcinogenesis

The anti-cancer efficacy of dietary beta-carotene (BC, 120 mg/kg diet, daily) was evaluated during diethylnitrosamine (DEN, 200 mg/kg body weight)-induced hepatocarcinogenesis in male Sprague-Dawley rats. BC treatment was carried out throughout the study, before initiation or selection/promotion phase of hepatocarcinogenesis in a defined experimental protocol. In red blood cells (RBC) and microsomal fractions from hepatic nodular and non-nodular surrounding parenchyma, the enzymatic lipid peroxidation increased significantly by more than 3-fold, 9- to 10-fold and 4- to 7-fold respectively 18 weeks following initiation by DEN as compared to normal control animals. RBC membrane protein damage was estimated by alanine release and was found to increase more than 5-fold in the same time period in DEN control rats. A decrease in hepatic cytosolic and microsomal glucose-6-phosphatase activities was observed, whereas the activities of the oxygen-derived free-radical scavenger enzymes, like cytosolic catalase and superoxide dismutase, were shown to increase significantly at the same time point. However, BC exposure in the different phases to hepatocarcinogenesis substantially changed all the above parameters in limiting the action of DEN. Results showed that the most significant beneficial effect of BC during hepatocarcinogenesis was exerted mainly in long term continuous and/or the initiation phase of carcinogenicity, rather than in the selection/promotion phase. Moreover, the volumetric and numerical densities of the preneoplastic lesions were all appreciably reduced by exposure to BC. We conclude that long term intake of BC could reduce cancer risk by preventing hepatic lipid peroxidation and RBC membrane protein damage due to its antioxidant actions.

Effects of gomisin A on the promotor action and serum bile acid concentration in hepatocarcinogenesis induced by 3'-methyl-4-dimethylamino-azobenzene

The effects of gomisin A, a lignan component of Schizandra fruits, on the promotion stage of hepatocarcinogenesis initiated by 3'-methyl-4-dimethylamino-azobenzene (3'-MeDAB) in male Donryu rats were investigated. When different types of tumor promotors, phenobarbital (PB) and deoxycholic acid (DCA), were administered for 5 weeks after initiation by 3'-MeDAB, preneoplastic alterations in the liver, determined by glutathione S-transferase placental form (GST-P), were markedly increased. Gomisin A significantly inhibited the increase in number and size of GST-P positive foci, regardless of the promotor. This lignan inhibited the increase in serum bile acid concentration by administration of DCA, but hardly influenced the serum bile acids in the PB-combined group. These results suggest that the inhibitory effect of gomisin A on the promotive action of DCA is based on improving bile acid metabolism, but regarding the action of PB, the effect could not be elucidated from the metabolism of bile acids.