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F Horio

Publications and source records attributed to F Horio.

At least 37 records · Page 2Linked to original sources

Bilirubin oxidation provoked by endotoxin treatment is suppressed by feeding ascorbic acid in a rat mutant unable to synthesize ascorbic acid.

We examined the possibility that bilirubin oxidation is provoked in vivo by using scurvy-prone ODS-od/od rats treated with endotoxin (lipopolysaccharide). Recently, bilirubin oxidative metabolites were isolated from human urine and named biotripyrrin-a and biotripyrrin-b. In ODS-od/od rats fed an ascorbic-acid-free diet, the concentration of bilirubin metabolites in urine was increased 7.0-fold at 3 h after injection of lipopolysaccharide and 4.4-fold at 10 h compared to the control rats injected with saline. The dietary supplement of ascorbic acid, the physiological antioxidant, suppressed the increase in bilirubin metabolites in urine after lipopolysaccharide injection: concentrations of biotripyrrin-a and biotripyrrin-b in urine collected 6.5-10 h after the injection were lower in rats fed an ascorbic-acid-supplemented diet than in rats fed an ascorbic-acid-free diet. Moreover, feeding of ascorbic acid suppressed the hepatic mRNA level of heme oxygenase-1, the rate-limiting enzyme of bilirubin biosynthesis, in rats injected with lipopolysaccharide. These findings indicate that bilirubin oxidation is markedly stimulated in lipopolysaccharide-treated rats and suggest that bilirubin and ascorbic acid have physiologically protective effects against oxidative stress.

Animals↗

Ascorbic acid deficiency decreases the renal level of kidney fatty acid-binding protein by lowering the alpha2u-globulin gene expression in liver in scurvy-prone ODS rats.

The evidence for the role of ascorbic acid in gene expression or protein synthesis in vivo is limited. To investigate this role of ascorbic acid, we surveyed proteins whose tissue levels are changed by ascorbic acid deficiency by using ODS rats with a hereditary defect in ascorbic acid biosynthesis. Male ODS rats (7 wk old, body weight approximately 130 g) were fed a basal diet containing ascorbic acid (300 mg/kg diet) or an ascorbic acid-free diet for 14 d. Ascorbic acid deficiency decreased a renal protein with an apparent molecular mass of 17 kDa. The amino-terminal amino acid sequence of 16 residues of this 17-kDa protein was identical to a kidney fatty acid-binding protein known to be generated by proteolytic degradation of alpha2u-globulin, a major urinary protein of adult male rats. alpha2u-Globulin is synthesized in liver, secreted into blood and excreted into urine, but partially reabsorbed by renal proximal tubules. It exists in kidney in a proteolytically modified form. Ascorbic acid deficiency lowered the renal level of kidney fatty acid-binding protein to 53% (P < 0.05) and lowered the serum level of alpha2u-globulin to 52% (P < 0.05) of the level of the control group, but did not affect the amount of alpha2u-globulin excreted into urine. The hepatic level of alpha2u-globulin mRNA of the ascorbic acid-deficient rats was significantly lower (30%) than that of the control rats. These results suggest that in male ODS rats, ascorbic acid deficiency decreases the renal level of kidney fatty acid-binding protein by lowering alpha2u-globulin gene expression in liver.

Alpha-Globulins↗

The role of microsomal beta-glucuronidase in ascorbic acid biosynthesis stimulated by xenobiotics in rats.

We (Horio et al., 1993) have reported that the stimulation of the expression of the UDPglucuronosyltransferase (UDPGT) gene played a key role in the ascorbic acid biosynthesis induced by xenobiotics, such as 3-methylcholanthrene (3MC) and phenobarbital (PB). beta-Glucuronidase catalyzes the hydrolysis of glucuronide formed by UDPGT. The role of microsomal beta-glucuronidase in ascorbic acid biosynthesis induced by xenobiotics was investigated using homozygous and heterozygous EHBRs (Eisai hyperbilirubinuria rats) which are deficient in microsomal beta-glucuronidase. Homozygous EHBRs, heterozygous EHBRs, and Sprague Dawley (SD) rats were injected intraperitoneally once with 3MC (20 mg/kg body weight), or once a day for 2 d with PB (100 mg/day kg body weight). In these three strains of rats, the hepatic level of xenobiotics-inducible UDPGT mRNA was elevated similarly by the treatment with xenobiotics. The increases of the hepatic concentration of ascorbic acid and the urinary excretion of ascorbic acid by the treatment with 3MC or PB were markedly suppressed in both EHBRs compared with those in the control SD rats. These results indicate that the microsomal beta-glucuronidase has an important role in the hepatic ascorbic acid biosynthesis induced by xenobiotics.

Animals↗

Role of bilirubin as an antioxidant in an ischemia-reperfusion of rat liver and induction of heme oxygenase.

The anti-oxidative effect of bilirubin was investigated in an ischemia-reperfusion model of rat liver. The rat portal vessel and liver artery were ligated with a vascular clip, and after reperfusion the urine was collected at intervals. The amount of biopyrrins, the oxidative metabolites of bilirubin, in rat urine reached a maximum 4 hours after reperfusion. Biotripyrrin-a and -b which are biopyrrins isolated from human urine were included in urinary bilirubin oxidative metabolites of rats after reperfusion. The hepatic mRNA level of heme oxygenase-1 (HO-1), the rate limiting enzyme of bilirubin biosynthesis, reached a maximum after 4 hours. Furthermore, the hepatic activity of HO began to rise 4 hours after treatment and remained high until 24 hours posttreatment. These findings suggest that bilirubin acts as a physiological antioxidant in vivo in ischemia-reperfusion and that bilirubin biosynthesis is evoked by oxidative stress.

Animals↗

Ascorbic acid deficiency reduces hepatic apolipoprotein A-I mRNA in scurvy-prone ODS rats.

Using the ODS rat (genotype od/od) as a model, we investigated the effect of ascorbic acid deficiency on the expression of the apolipoprotein A-I gene. Male ODS rats (7 wk old, body weight approximately 140 g) were fed a basal diet containing ascorbic acid (300 mg/kg) or a diet without ascorbic acid for 14 d. Ascorbic acid deficiency lowered the serum apolipoprotein A-I concentration. The apolipoprotein A-I mRNA level in the liver of ascorbic acid-deficient rats was lowered to about 40% (P < 0.05) of that of control rats fed sufficient ascorbic acid. The mRNA level in jejunum was not affected by ascorbic acid deficiency. Ascorbic acid deficiency did not change the transcriptional rate of the hepatic apolipoprotein A-I gene, suggesting that post-transcriptional regulation was involved in lowering the mRNA level. The low level of hepatic apolipoprotein A-I mRNA was restored to the control level within 3 d after the administration of sufficient ascorbic acid. These data indicate that ascorbic acid deficiency lowers serum apolipoprotein A-I concentration through lowering its mRNA level and subsequent depression of its synthesis in liver.

Animals↗

Bilirubin is oxidized in rats treated with endotoxin and acts as a physiological antioxidant synergistically with ascorbic acid in vivo.

We examined the possibility that bilirubin physiologically acts as an antioxidant by using scurvy-prone ODS-od/od rats treated with endotoxin (lipopolysaccharide: LPS). Recently, bilirubin oxidative metabolites were isolated from human urine and named biotripyrrin-a and biotripyrrin-b. The LPS injection markedly increased bilirubin oxidative metabolites in urine of rats fed an ascorbic acid-free diet. This increase was supressed by feeding an adequate amount of ascorbic acid, a physiological antioxidant. the concentrations of biotripyrrin-a and -b in urine collected 6.5-10 h after the LPS injection were lower in rats fed an ascorbic acid-supplemented diet than in rats fed an ascorbic acid-free diet. Moreover, feeding with ascorbic acid suppressed the elevation of hepatic mRNA level of heme oxygenase-1, the rate-limiting enzyme of bilirubin biosynthesis, in rats injected with LPS. These findings suggest that bilirubin is oxidized in rats treated with LPS and acts as a physiological antioxidant synergistically with ascorbic acid in vivo.

Animals↗

Acute nephrotoxicity of a carcinogenic iron chelate. Selective inhibition of a proteolytic conversion of alpha 2U-globulin to the kidney fatty acid-binding protein.

The mechanism of acute nephrotoxicity of an iron chelate in vivo has been investigated. Administration of a renal carcinogen ferric nitrilotriacetate (Fe-NTA) (15 mg Fe/kg body weight, intraperitoneally) led to selective loss of a renal protein with an apparent molecular mass of 17 kDa. Analysis of the 17 kDa protein by NH2-terminal sequence demonstrated its identity over 16 NH2-terminal residues as a kidney fatty acid-binding protein (k-FABP) that is a proteolytically modified form of alpha 2U-globulin, a major urinary protein of adult male rats. An immunochemical study using anti-alpha 2U-globulin polyclonal antibodies confirmed that a single injection of Fe-NTA led to a decrease in k-FABP levels. However, a 19-kDa protein identical to the alpha 2U-globulin progressively appeared in the kidney, suggesting that the proteolytic processing of alpha 2U-globulin in the renal proximal tubules was suppressed by the treatment with Fe-NTA. By monitoring k-FABP and its precursor alpha 2U-globulin, it was determined that repeated exposure to Fe-NTA caused suppression of both proteolytic and endocytotic activity of the kidney. The implications of these data in relation to the nephrotoxicity of Fe-NTA are discussed.

Alpha-Globulins↗

A low protein diet increases 4-nitrophenol-UDPglucuronosyltransferase but decreases chloramphenicol-UDPglucuronosyltransferase activity and mRNA level in livers of rats treated with polychorinated biphenyls.

We have examined the effects of dietary level of protein (5% or 30% in casein) on enzyme activities and mRNA levels of two xenobiotic-inducible UDPglucuronosyltransferase (UDPGT) enzymes, such as chloramphenicol-UDPGT (CP-UDPGT) and 4-nitrophenol-UDPGT (4NP-UDPGT), in the livers of rats treated or not treated with polychlorinated biphenyls (PCB). In animals fed 5% casein and not treated with PCB, CP-UDPGT activity tended to be lower than in rats fed 30% casein. In contrast, 4NP-UDPGT activity was higher in rats fed 5% casein. In rats treated with PCB, the activities of both enzymes were increased. CP-UDPGT mRNA level was higher (1.4-fold) in rats fed 30% dietary casein than in those fed 5% casein. In contrast, 4NP-UDPGT mRNA level was higher (2.8-fold) in rats fed 5% casein than in those fed 30% casein. These changes in mRNA levels paralleled those in the activities of the two enzymes. The data indicate that the dietary protein is an important factor controlling the expression of hepatic xenobiotic-inducible UDPGT genes and modulates the capacity of the liver to metabolize foreign compounds.

Animals↗

Reactive oxygen intermediates in autoimmune islet cell destruction of the NOD mouse induced by peritoneal exudate cells (rich in macrophages) but not T cells.

The non-obese diabetic (NOD) mouse spontaneously develops autoimmune Type 1 (insulin-dependent) diabetes mellitus. NOD mice exhibit massive infiltrates of T cells and macrophages into pancreatic islets (insulitis) prior to diabetes. The contribution of oxygen free radicals to the development of insulitis in NOD mice was examined by administration of its scavengers, such as superoxide dismutase and catalase. Bovine superoxide dismutase and catalase were each coupled to polyethylene glycol. The treatment with superoxide dismutase-polyethylene glycol reduced the number of islets with insulitis and increased the undamaged islet tissue, as compared with the control group. The treatment with catalase-polyethylene glycol showed a similar tendency which did not reach significance. Using a flow cytometric assay of the oxidation of 2', 7'-dichlorofluorescein, the content of reactive oxygen intermediates in islet cells in the culture system was measured and the effect of peritoneal exudate cells and T cells on their production examined. Peritoneal exudate cells, but not T cells, from NOD mice increased the content of reactive oxygen intermediates in islet cells of either the NOD mouse or the ILI mouse (MHC-identical to NOD); the addition of superoxide dismutase to the culture medium suppressed this increase in NOD or ILI islet cells. The present data support the concept that production of oxygen free radicals mediated by macrophages can damage islet beta cells, directly resulting in autoimmune Type 1 diabetes in NOD mice.

Animals↗

UDP glucuronosyltransferase gene expression is involved in the stimulation of ascorbic acid biosynthesis by xenobiotics in rats.

Wistar-Shi (genotype +/+), heterozygous Gunn (j/+) and homozygous Gunn (j/j) rats was injected intraperitoneally with 3-methylcholanthrene (3MC) dissolved in corn oil. In rats of all genotypes the hepatic concentration of UDP glucuronosyltransferase (UDPGT) mRNA was increased at 48 and 96 h after the treatment with 3MC. Hepatic activity of 4-nitrophenol UDPGT was increased by 3MC in Wistar-Shi rats and heterozygous Gunn rats but not in homozygous Gunn rats. Urinary ascorbic acid excretion increased 72 and 96 h after the injection with 3MC in Wistar-Shi and heterozygous Gunn rats but not in homozygous Gunn rats. Ninety-six hours after the injection with 3MC, the hepatic concentration of ascorbic acid in Wistar-Shi rats was 90% higher than that in the corresponding control group, whereas in heterozygous and homozygous Gunn rats the increases were 70 and 30%, respectively. Wistar-Shi rats and homozygous Gunn rats were also injected daily for 3 d with sodium phenobarbital. In rats of both genotypes, the activity and hepatic concentration of chloramphenicol-UDPGT mRNA and liver and urine ascorbic acid concentration were increased by sodium phenobarbital. The data indicate that the stimulation of the expression of both the 4-nitrophenol and chloramphenicol UDPGT genes plays a key role in the ascorbic acid biosynthesis induced by 3MC and sodium phenobarbital.

Analysis of Variance↗

L-gulono-gamma-lactone oxidase is not induced in rats by xenobiotics stimulating L-ascorbic acid biosynthesis.

L-Ascorbic acid (AsA) is synthesized from D-glucose in rats; the terminal step of this synthetic pathway is catalyzed by L-gulono-gamma-lactone oxidase (GLO). In this study, we examined the effects of phenobarbital (PB) and 3-methylcholanthrene (MC), both of which are known to stimulate AsA biosynthesis in rats, on the hepatic levels of GLO activity, GLO mRNA, and AsA. Firstly, the existence of GLO mRNA was examined in the liver, kidney, lung, small intestine, spleen, testis, and prostate from a male rat; and GLO mRNA was found to be present only in the liver, in which GLO activity was also detected. The intraperitoneal injection with PB (100 mg/day/kg body weight, once a day for 2 days) or MC (20 mg/day/kg body weight, once) significantly elevated the hepatic level of AsA and the urinary excretion of AsA in rats (5-week-old males). The hepatic levels of cytochrome P-450IIB1 mRNA and cytochrome P-450IIB2 mRNA and those of cytochrome P-450IA1 mRNA and cytochrome P-450IA2 mRNA were also elevated in the rats treated with PB and MC, respectively, indicating a normal response of these animals to these compounds. However, the level of GLO mRNA and the activity of GLO in the liver tended to be slightly decreased by the administration of PB or MC, though the differences were not significant. Thus it is clear that the treatment with PB or MC stimulates the biosynthesis of AsA by increasing the activity of some enzyme(s) participating in the synthesis prior to GLO.

Animals↗

Ascorbic acid deficiency reduces the level of mRNA for cytochrome P-450 on the induction by polychlorinated biphenyls.

Ascorbic acid (AsA) deficiency causes a decrease in hepatic concentration of cytochrome P-450 and a decrease in hepatic activity of drug-metabolizing enzymes in rats unable to synthesize AsA (ODS rats). To study the mechanism of the decrease in hepatic concentration of cytochrome P-450 isozymes by AsA deficiency, we chose the xenobiotics-inducible cytochrome P-450 and performed the experiments indicated below. AsA-deficient rats were fed polychlorinated biphenyls (PCB) which markedly induce both CYP1A subfamily and several isozymes in CYP2B subfamily. First, we assayed the activities of two drug-metabolizing enzymes so that one could be functionally distinguished from another. AsA deficiency significantly reduced the hepatic activity of aminopyrine-N-demethylase in ODS rats with and without dietary PCB, but had no effect on benzo(a)pyrene hydroxylase activity. Secondly, quantitative immunoblot analyses demonstrated that the levels of CYP2B1/2B2 and CYP1A1 in the AsA-deficiency rats fed PCB were approximately 60 and 80% lower than those found in rats fed AsA-supplemented diet. The degree of reduction in CYP2B1/2B2 was greater than CYP1A1. Thirdly, AsA deficiency caused a decrease in hepatic abundance of CYP2B1/2B2 mRNA, whereas it had no effect on the levels of CYP1A1 and 1A2 mRNA. These results indicated that dietary AsA selectively affects the levels of CYP2B1/2B2 mRNA among cytochrome P-450 induced by PCB and plays important roles for optimum induction of drug-inducible cytochrome P-450. We concluded that AsA deficiency decreases specific froms of drug-inducible cytochrome P-450, especially CYP2B1/2B2 and that the reduction of CYP2B1/2B2 mRNA level in AsA-deficient rats caused a decrease in cytochrome P-450 concentration and hepatic activity of drug-metabolizing enzymes.

Aminopyrine N-Demethylase↗

Thermogenesis, low-protein diets, and decreased development of AFB1-induced preneoplastic foci in rat liver.

The development of hepatocellular, putatively preneoplastic, gamma-glutamyl transpeptidase positive (GGT+) foci and tumors induced by aflatoxin B1 (AFB1) has been shown to be reduced in male F344 rats fed a diet containing 6% protein (as casein). This reduction occurs despite increased energy intake, when compared with animals fed a diet containing 22% protein. Among its many effects, low protein intake is known to increase the proportion of energy intake expended in the form of heat (thermogenesis); thus, this investigation examined the association between the development of GGT+ foci and alterations in indices of thermogenesis induced by feeding varying levels of dietary protein. Five days following the completion of AFB1 dosing, animals were assigned to groups fed 4%, 8%, 12%, 16%, or 22% dietary protein for 6 weeks. Foci development (% liver volume occupied) was markedly reduced in animals fed the low-protein diet (4%, 8%), yet calorie consumption per 100 g body wt was greater. A modest negative linear trend was observed in oxygen consumption with increasing levels of dietary protein intake. Urinary norepinephrine levels were elevated in the groups fed 4% and 8% protein; urinary dopamine and norepinephrine turnover rates in brown adipose tissue were highest in animals fed 4% protein. These results suggest that GGT+ foci development occurs when a "critical level" (approx 12%) of dietary protein intake is reached. Inhibition of foci development at lower levels of protein intake is associated with several indicators of increased thermogenesis.

Aflatoxin B1↗

Ascorbic acid deficiency elevates serum level of LDL-cholesterol in a rat mutant unable to synthesize ascorbic acid.

The effect of ascorbic acid deficiency on serum levels of high density lipoprotein- (HDL-), low density lipoprotein- (LDL-), very low density lipoprotein- (VLDL-) and chylomicron-cholesterol was examined in ODS-od/od rat (ODS rat), that is a rat mutant unable to synthesize ascorbic acid. Male ODS rats were fed an ascrobic acid-free diet for 20 days. In another two groups, the diet supplemented with 300 mg ascorbic acid/kg diet was fed either ad libitum (ad libitum control) or in pair-feeding (pair-fed control). Pair-fed rats received the same amount of diet as rats fed the ascorbic acid-free diet. Serum level of total cholesterol in the ad libitum control rats, ascorbic acid-deficient rats, and the pair-fed control rats were 100.1 +/- 8.4 mg/dl, 92.8 +/- 6.2 mg/dl and 72.2 +/- 4.8 mg/dl, respectively. The level of LDL-cholesterol in ascorbic acid-deficient rats was significantly higher than that in the ad libitum control or that in the pair-fed control. The level of HDL-cholesterol in ascorbic acid-deficient rats was lower than that in the ad libitum control, but was not changed as compared with that in the pair-fed control. Ascorbic acid deficiency did not affect serum level of VLDL-cholesterol or chylomicron-cholesterol as compared with those in the controls. These results demonstrate that ascorbic acid deficiency causes the elevation of serum level of LDL-cholesterol both in ad libitum feeding condition and pair feeding condition.

Animals↗

Effect of dietary ascorbic acid, cholesterol and PCB on cholesterol and bile acid metabolism in a rat mutant unable to synthesize ascorbic acid.

The effect of acute or chronic ascorbic acid deficiency on the activity of hepatic cholesterol 7 alpha-hydroxylase and fecal excretion of bile acids was investigated in ODS-od/od (OD) rats (a rat mutant unable to synthesize ascorbic acid) fed a purified basal diet or purified diets containing either cholesterol (2%) or polychlorinated biphenyl (PCB) (200 mg/kg). In OD rats, the dietary requirement of ascorbic acid to maintain normal growth and normal levels of cholesterol in serum and liver is about 300 mg of ascorbic acid/kg diet. In OD rats fed the basal diet, acute or chronic ascorbic acid deficiency did not affect the activity of hepatic cholesterol 7 alpha-hydroxylase and fecal excretion of bile acids. However, in OD rats fed diets containing either cholesterol or PCB, acute ascorbic acid deficiency caused a higher level of serum cholesterol, a lower activity of hepatic cholesterol 7 alpha-hydroxylase and a lower excretion of fecal bile acids than in OD rats fed a basal diet containing an adequate level of ascrobic acid. It is concluded that acute ascorbic acid deficiency causes a hypercholesterolemia due to the depression of bile acid synthesis in OD rats fed a purified diet with cholesterol or PCB.

Animals↗

Effect of dietary ascorbic acid, cholesterol and PCB on cholesterol concentrations in serum and liver in a rat mutant unable to synthesize ascorbic acid.

The effect of ascorbic acid deficiency and excessive ascorbic acid intake on serum and liver levels of cholesterol and lipids was investigated in ODS-od/od (OD) rats fed a normal diet, a cholesterol-containing diet or a polychlorinated biphenyl (PCB)-containing diet. The OD rat is a rat mutant unable to synthesize ascorbic acid. In OD rats, the dietary requirement of ascorbic acid to maintain normal growth and normal levels of cholesterol in serum and liver is about 300 mg of ascorbic acid/kg diet. In control (ODS-+/+) rats that can synthesize ascorbic acid, dietary addition of 0.5% cholesterol and 0.25% cholic acid caused elevation of cholesterol concentrations in serum and liver, elevation of total lipids in liver and reduction of the ratio of high density lipoprotein (HDL) cholesterol to total cholesterol in serum. Dietary addition of PCB (200 mg/kg diet) caused elevation of serum concentration of cholesterol and of the ratio of HDL-cholesterol to total cholesterol in serum. In OD rats fed a normal diet, ascorbic acid deficiency slightly elevated serum concentration of cholesterol, elevated liver concentration of cholesterol and reduced the ratio of HDL-cholesterol to total cholesterol in serum; and ascorbic acid excess did not affect serum and liver concentrations of cholesterol and the ratio of HDL-cholesterol to total cholesterol in serum. In OD rats fed a cholesterol-containing diet, ascorbic acid deficiency elevated serum and liver concentrations of cholesterol, and did not affect the ratio of HDL-cholesterol to total cholesterol in serum; and ascorbic acid excess did not affect serum and liver concentrations of cholesterol and the ratio of HDL-cholesterol to total cholesterol in serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Long-term effects of dietary polychlorinated biphenyl and high level of vitamin E on ascorbic acid and lipid metabolism in rats.

Long-term feeding of purified diets containing (per kg diet) 100 mg of polychlorinated biphenyl (PCB) and 1000 mg of vitamin E (RRR-alpha-tocopheryl acetate) to male Wistar rats was carried out. Rats fed a diet containing PCB rapidly became hypercholesterolemic and maintained high cholesterol levels throughout the 240 d of the experiment. Rats fed a high dietary level of vitamin E plus PCB had higher serum cholesterol and lower liver cholesterol than rats fed a lower level of vitamin E plus PCB. In rats fed PCB, urinary excretion of ascorbic acid was higher than in rats not fed PCB. Urinary ascorbic acid was lower in rats fed high levels of vitamin E plus PCB than in those fed the normal levels of vitamin E plus PCB. Rats fed PCB had lower liver vitamin A storage and higher vitamin A in kidney than rats not fed PCB. This implies that a redistribution of vitamin A occurred in rats fed PCB. Histological observations revealed that central halves of the hepatic lobules of rats fed PCB showed distinct changes consisting of hypertrophy of hepatocytes in the perivenous region and accumulation of vacuoles (lipid droplets) in the cells in the remaining affected portion. Administration of a high dose of vitamin E could not ameliorate this lesion while the treatment depressed effectively the lipid peroxidation. This suggests that the lipid peroxidation was not responsible for the hepatic damage induced by PCB.

Animals↗