Effect of carbon tetrachloride on polyamine metabolism in rodent liver

Elevation of N1-acetylspermidine and putrescine in hepatic tissues of patients with fulminant hepatitis and liver cirrhosis

Hepatic polyamines were assayed in 15 patients with liver diseases, 5 with fulminant hepatitis (FH); 3 with exacerbated liver cirrhosis (ELC); and 7 with liver cirrhosis (LC). Hepatic putrescine and N1-acetylspermidine as percentages of total polyamines, were elevated and spermine was decreased in all 15 patients. The increase in hepatic N1-acetylspermidine levels appeared to be greater in patients with FH and ELC than in those with LC. These results suggest that the production of N1-acetylspermidine in human liver is closely associated with the induction of spermidine/spermine N1-acetyltransferase activity in liver diseases.

Persistent decrease in spermidine/spermine N1-acetyltransferase activity in 'post-regeneration' rat liver

The activity of cytosolic spermidine/spermine N1-acetyltransferase and polyamine levels were measured in livers of rats killed at different times after partial hepatectomy. The enzyme activity, which showed an early increase a few hours after the operation, had significantly and persistently decreased by the time the liver mass had been regained (10 days) compared to intact rats or sham-operated rats, and up to 30 days after partial hepatectomy, compared to intact rats of the same age. The early induction of spermidine/spermine N1-acetyltransferase activity was also confirmed by the high level of N1-acetylspermidine, which normally is undetectable, and by a dramatic increase in putrescine content. Spermidine levels were increased during the first 10 days after partial hepatectomy, i.e., when the liver had regained its mass, and progressively decreased after this time until 30 days after the operation. The changes in spermine content were similar but not as marked as the changes in spermidine content at the different observation times.

Insulin and glucagon therapy of acute hepatic failure

When insulin and glucagon are administered to rats with severe liver injury, survival is enhanced with an attenuation of the liver injury compared to that of untreated controls. In rats with acute liver injury both hormones produce a rapid normalization of hepatic protein content following initiation of DNA synthesis. When rats receive both hormones after partial hepatectomy, the first burst of DNA synthesis reaches a maximum earlier than that seen in controls. Both hormones enhance the increment of hepatic putrescine essential for DNA synthesis through activation of ornithine decaroxylase and/or spermidine-N1-acetyltransferase. The enhancement of putrescine content by each hormone is additive. Putrescine supplementation promotes hepatic DNA synthesis after hepatectomy. Based on these data, we conclude that a combination of insulin and glucagon is effective in the therapy of acute hepatic failure in rats. The restoration of liver function as well as the stimulation of liver cell proliferation via putrescine production may contribute to this effect.

Perturbations in polyamines and related enzymes following chlordecone-potentiated bromotrichloromethane hepatotoxicity

The mechanism by which chlordecone (CD) amplifies the hepatotoxicity of halomethanes such as CCl4, CHCl3, and BrCCl3 has been a subject of intense study. Recent work has shown that suppression of hepatocellular regeneration leads to accelerated progression of liver injury leading to complete hepatic failure due to an unusual interaction between individually nontoxic low-dose combination of CD and CCl4. Since polyamines are involved in cell division, their levels reflect the extent to which there is suppression of hepatocellular regeneration during CD and CCl4 interaction. The present studies were designed to investigate the polyamine levels and associated enzymes in livers of rats treated with BrCCl3 alone or CD and BrCCl3 low-dose combination in order to confirm whether the sequence of events of hepatotoxicity is similar to that seen in CCl4 toxicity or that seen during CD and CCl4 interaction. The extent of liver toxicity in rats fed 10 ppm chlordecone (CD) for 15 days prior to the injection of a single low dose of BrCCl3 (15 microL/kg body weight) or after exposure to a high dose of BrCCl3 (80 microL/kg body weight) without CD pretreatment, was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was also an increase in transaminase levels, in rats exposed to a single low dose of BrCCl3 alone (15 microL/kg body weight) but this increase was far below the high-dose exposure alone or the combination treatment. Hepatic levels of ornithine decarboxylase, S-adenosylmethionine decarboxylase, N1-acetylputrescine, N1-acetylspermidine, putrescine, spermidine, and spermine at the end of 24 hr increased after exposure to a low dose of BrCCl3 alone as compared to exposure to a high dose alone or the low-dose combination of CD and BrCCl3. Liver spermidine N1-acetyltransferase was elevated at 2, 6, and 24 hr after exposure to a high dose of BrCCl3 alone as compared to treatment with a low-dose combination of CD and BrCCl3 suggesting decreased synthesis of this enzyme, in spite of a greater need as seen from liver transaminase levels. In general, it was observed that there is significant elevation in some polyamines and related enzymes during toxicity of a low dose of BrCCl3 which seemed to stabilize within 24 hr. This was not observed with the other two groups of rats exposed either to BrCCl3 high dose alone or the low-dose combination of CD and BrCCl3.(ABSTRACT TRUNCATED AT 400 WORDS)

Protective role of fructose 1,6-bisphosphate during CCl4 hepatotoxicity in rats

Rats were injected intraperitoneally with CCl4 (2.5 ml/kg body wt.) and the hepatotoxicity was compared with that of rats receiving the same dose of CCl4 and an intraperitoneal injection of fructose 1,6-bisphosphate (2 g/kg body wt.). A 50-70% decrease in plasma aspartate aminotransferase and alanine aminotransferase activities was observed in the latter treatment, indicating a protective role of the sugar bisphosphate in CCl4 hepatotoxicity. The protection was accompanied by elevated hepatic activities of ornithine decarboxylase at 2, 6 and 24 h, S-adenosylmethionine decarboxylase at 6 h, and spermidine N1-acetyltransferase at 2 h. The increase in the enzymes involved in polyamine metabolism was shown in our previous work [Rao, Young & Mehendale (1989) J. Biochem. Toxicol. 4, 55-63] to correlate with increased polyamine synthesis or interconversion, which was related to the extent of hepatocellular regeneration. The hepatic contents of fructose 1,6-bisphosphate and ATP significantly decreased after CCl4 treatment, and administration of the sugar bisphosphate increased hepatic ATP. Fructose 1,6-bisphosphate, an intermediary metabolite of the glycolytic pathway, may decrease CCl4 toxicity by increasing the ATP in the hepatocytes. The ATP generated is useful for hepatocellular regeneration and tissue repair, events which enable the liver to overcome CCl4 injury.

Changes in polyamine-oxidizing capacity of peroxisomes under various physiological conditions in rats

Rat liver peroxisomal polyamine oxidase activity was determined under various physiological conditions by using the peroxidase method with phenol and 4-aminoantipyrine. N1-Acetylpolyamines such as N1-acetylspermine and N1-acetylspermidine were better substrates than the free polyamines. The polyamine oxidase activity in rat peroxisomes increased significantly when cell proliferation was high. The activity began to appear in fetal liver at the 16th approximately 18th day of pregnancy and peaked in neonatal liver on the first day (approx. 1.7-times higher than in adult liver). In regenerating rat liver, only polyamine oxidase activity among the peroxisomal enzymes tested was increased considerably 12 h after partial hepatectomy (approx. 2.8-fold over the control liver). Finally, the enzyme activity was significantly increased by administration of clofibrate, a peroxisome proliferator, which also causes hepatomegaly. In all cases, the increase in polyamine oxidase activity was not more than 3-fold. Since the level of polyamine oxidase activity in the normal liver is more than adequate in relation to the level of the substrates, the slight but significant increase under conditions of cell proliferation may have a role in modulating levels of polyamines in the proliferating liver tissue.

Hepatic polyamines and related enzymes following chlordecone-potentiated carbon tetrachloride toxicity in rats

Chlordecone potentiation of the hepatotoxic and lethal effects of CCL4 has been well established. Recent studies have shown that the suppression of hepatocellular regeneration results in an accelerated progression of liver injury leading to complete hepatic failure. Since polyamines are involved in cell division, these studies were designed to investigate the polyamine levels and associated enzymes in the livers of rats treated with a low-dose combination of CD and CCl4. For comparison, a large toxic dose of CCl4 was also employed. The extent of liver toxicity in rats fed 10 parts per million chlordecone (CD) for 15 days and subsequently injected with a single dose of CCl4 (100 microL/kg body weight) or a high dose of CCL4 alone (2.5 mL/kg body weight) was similar 6 and 24 hr later as assessed by plasma transaminase levels. There was significant elevation in liver ornithine decarboxylase, S-adenosylmethionine decarboxylase, and putrescine at 24 hr and spermidine N1-acetyltransferase, N1-acetylputrescine, putreanine, putrescine, and N1-acetylspermidine at 6 hr in rats treated with the high dose of CCl4 alone compared to the combination treatment. Spermidine levels decreased up to 6 hr and then increased up to 24 hr for both treatments. Spermine continuously decreased up to 24 hr for the CD and CCl4 low-dose combination treatment compared to rats treated with a high dose of CCl4 alone. Spermidine levels were lower than in controls and rose towards control value between 6 and 24 hr after the combination treatment and the high dose of CCl4. Results indicate that the CD and CCl4 low-dose combination treatment increased liver toxicity, resulting in compromised polyamine metabolism that is coincidental with suppressed hepatocellular regeneration, which leads to an accelerated progressive phase of liver injury and culminates in complete hepatic failure.

Polyamine metabolism in reversible cerebral ischemia: effect of alpha-difluoromethylornithine

Severe forebrain ischemia was produced in rats by occluding both carotid and vertebral arteries. Following 30 min ischemia brains were recirculated for 8 or 24 h. Twelve animals subjected to 8 or 24 h recirculation (n = 6, each group) were given alpha-difluoromethylornithine (DFMO; injected intraperitoneally) immediately before recirculation. At the end of the experiments brains were frozen and samples were taken from the cerebellum, cortex, caudatoputamen and hippocampus. Samples from the left hemisphere were used for measuring ornithine decarboxylase (ODC) activity, and those from the right hemisphere for determining putrescine profiles. During recirculation ODC activity increased markedly in all brain structures, the most pronounced change being in the caudatoputamen after 8 h recirculation. Putrescine increased drastically after 8 h and even more after 24 h recirculation. DFMO-treatment significantly reduced ODC activity after 8 h recirculation and following 24 h recirculation. Putrescine, however, was significantly reduced following 24 h but not after 8 h recirculation. The discrepancy between reduction in ODC activity and putrescine levels in DFMO-treated animals was most prominent in the hippocampus after 8 h recirculation: here DFMO reduced ODC activity to control values without affecting putrescine levels. The results suggest that the observed overshoot in putrescine formation following ischemia is only partly caused by activation of ODC.

Elevation of acetylpolyamine levels in mouse tissues, serum and urine after treatment with radical-producing drugs and lipopolysaccharide

Polyamines and acetylpolyamines were analyzed in the liver, spleen, lung, kidney, serum and urine by high-performance liquid chromatography on a column of cation-exchange resin after administering various cytotoxic substances to male mice. All of the compounds tested more or less affected the tissue levels of polyamines, including putrescine, spermidine, spermine and acetylpolyamines (N1-acetylspermidine and N1-acetylspermine). It was found that they were classified into two groups of substances: one group (including radical-producing drugs and lipopolysaccharide) which elevated the tissue levels of N1-acetylspermidine, especially in the liver, while another group of drugs (such as D-galactosamine and DL-ethionine) had little effect on the acetylpolyamine levels. When the acetylpolyamine levels rose, the levels of spermidine and spermine declined, and then putrescine levels were elevated. N1-Acetylspermine was detected only when N1-acetylspermidine levels were very high after treatment with radical-producing drugs and lipopolysaccharide. Halogenated carbon, such as carbon tetrachloride and halothane, elevated the levels of acetylpolyamines especially in the liver, while paraquat elevated them in all tissues examined.

Regional profile of polyamines in reversible cerebral ischemia of Mongolian gerbils

Reversible cerebral ischemia was produced in Mongolian gerbils (Meriones unguiculatus) by occluding both common carotid arteries. After 5 min ischemia brains were recirculated for 8, 24, 48, 72, or 96 h. An additional 6 animals were subjected to 10 min ischemia and 24 h recirculation. Sham-operated animals served as controls. At the end of the experiments, brains were frozen in situ and cut in a cryostat. Coronal sections, 10 micron thick, were taken for histological staining. In addition, tissue samples (2-4 mg each) were taken from the cortex, lateral caudoputamen, CA1-layer of the hippocampus, and thalamus. Polyamines (spermidine, spermine, and the precursor putrescine) were measured in these samples using reverse-phase HPLC and fluorescence detection after extraction and precolumn derivatization. Five-minute cerebral ischemia had no effect on the levels of putrescine, spermidine, or spermine. However, following recirculation, putrescine increased markedly with time, being most pronounced in the CA1-subfield of the hippocampus, less so in the cortex, and even less so in the thalamus. After prolonged recirculation, severe neuronal necroses could be observed only in regions exhibiting high putrescine levels. Spermidine or spermine did not change during recirculation, except in severely damaged regions: Here, spermine levels were markedly reduced following prolonged recirculation. The post-ischemic increase in putrescine is discussed in respect to the known multiple activities of putrescine.

Malondialdehyde production from spermine by homogenates of normal and transformed cells

The oxidation of spermine in vitro by a mixture of polyamine oxidase and diamine oxidase from pig kidney gives rise to malondialdehyde via 3-aminopropanol as the intermediate. Conversely, with spermidine, under similar experimental conditions, no evidence could be obtained for malondialdehyde formation within the limits of sensitivity of the assay (2.0 nmol). The activities of both these enzymes show about a 2-fold increase in normal rat kidney cells (LA31 NRK) transformed by the temperature sensitive mutant of Rous sarcoma virus (LA31) and incubated at the non permissive temperature (39 degrees C) compared to the activities in LA31 NRK at the permissive temperature (33 degrees C). These same enzymatic activities show no temperature dependent changes in normal rat kidney cells (NRK) or in these same cells infected by the wild type virus (NRK B77). In extracts derived from Friend erythroleukemic cells induced to differentiate by dimethyl sulfoxide or hexamethylene bis acetamide, spermine oxidation takes place more efficiently than in non induced cells. A rise in diamine oxidase activity is seen in LA31 NRK (39 degrees C) 12 h after the temperature shift, whereas morphological manifestations of normalcy are seen only at 48 h. The Km of diamine oxidase is 10(-6) M for putrescine and 10(-3) M for 3-aminopropanol. A possible mechanism involving the well documented acetylation of putrescine [23,26] is proposed for diverting intracellular putrescine away from cytosolic diamine oxidase and towards intramitochondrial monoamine oxidase.

Ornithine decarboxylase and spermidine/spermine N1-acetyltransferase are induced in K562 cells by S-adenosylmethionine decarboxylase inhibitor methylglyoxal bis(guanylhydrazone) but not by analogous methylglyoxal bis(butylamidinohydrazone)

The activities of ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SAT) were increased by the addition of S-adenosylmethionine decarboxylase (AdoMetDC) inhibitor methylglyoxal bis(guanylhydrazone) (MGBG) in cultured human erythroid leukemia K 562 cells. ODC activity began to increase 4 hr after the addition of the drug and attained a maximum at 12 hr. The increase of SAT activity lagged behind that of ODC activity. The increases of both ODC and SAT activities produced by MGBG were blocked by treatment with cycloheximide, suggesting that the increase of enzyme activity resulted from the synthesis of new enzyme proteins. The putrescine content in cells treated with MGBG increased markedly, whereas the levels of spermidine and spermine were depressed lower. On the other hand, methylglyoxal bis(butylamidinohydrazone) (MGBB), a derivative of MGBG inhibiting AdoMetDC effectively, did not induce ODC or SAT activities.

Induction of spermidine/spermine N1-acetyltransferase in rat tissues by polyamines

Treatment of rats with spermidine, spermine or sym-norspermidine led to a substantial induction of spermidine/spermine N1-acetyltransferase activity in liver, kidney and lung. The increase in this enzyme, which was determined independently of other acetylases by using a specific antiserum, accounted for all of the increased acetylase activity in extracts from rats treated with these polyamines. Spermine was the most active inducer, and the greatest effect was seen in liver. Liver spermidine/spermine N1-acetyltransferase activity was increased about 300-fold within 6 h of treatment with 0.3 mmol/kg doses of spermine; activity in kidney increased 30-fold and activity in the lung 15-fold under these conditions. The increased spermidine/spermine N1-acetyltransferase activity led to a large increase in the liver putrescine content and a decline in spermidine. These changes are due to the oxidation by polyamine oxidase of the N1-acetylspermidine formed by the acetyltransferase. Our results indicated that spermidine was the preferred substrate in vivo of the acetylase/oxidase pathway for the conversion of the higher polyamines into putrescine. The induction of the spermidine/spermine N1-acetyltransferase by polyamines may provide a mechanism by which excess polyamines can be removed.

Stabilization of ornithine decarboxylase and N1-spermidine acetyltransferase in rat liver by methylglyoxal bis(guanylhydrazone)

The activities of ornithine decarboxylase and spermidine N1-acetyltransferase started to rise in normal rat liver 4 h after the intraperitoneal injection of methylglyoxal bis(guanylhydrazone) (MGBG; 80 mg/kg). Ornithine decarboxylase had its greatest activity 24 h after a single injection of MGBG and the acetyltransferase peaked 8 h after the injection. Measurement of the apparent half-life of ornithine decarboxylase after MGBG treatment revealed a clear decrease in the decay rate of the enzyme in both normal and regenerating rat liver. MGBG slowed the decay of the transferase also in normal rat liver, as well as inhibiting its activity in vitro. The stabilization by MGBG of these two short-lived proteins involved in metabolism of polyamines should lead to their accumulation in liver, thus explaining their increased activities. In the case of ornithine decarboxylase, studies with a specific antibody against mouse kidney ornithine decarboxylase showed that the rise in ornithine decarboxylase activity after MGBG application was not due to the appearance of an immunologically different isozyme.

Effect of chloroform on hepatic and renal DNA synthesis and ornithine decarboxylase activity in mice and rats

Chloroform administered intraperitoneally (i.p.) to male mice and rats resulted in a dose-dependent increase in hepatic ornithine decarboxylase (ODC) activity. Maximal induction of the enzyme in mice was 10-fold and occurred at 375 mg/kg chloroform; in rats it was 52-fold and occurred at 750 mg/kg chloroform. Chloroform increased in mice and decreased in rats the rate of hepatic and renal DNA synthesis. Therefore, the induction of ODC activity in rat liver was not followed with an increase in DNA synthesis. The implications of these results to the proposed nongenetic mechanism of chloroform induction of hepatocellular carcinoma in mice and renal tumors in rats are discussed.

Comparison of 3-isobutyl-1-methylxanthine-induced accumulation of putrescine in rat pancreas and liver

3-Isobutylmethylxanthine (IBMX), a potent phosphodiesterase inhibitor, causes accumulation of putrescine of same magnitude in rat pancreas and liver. IBMX produces increases of acetyl CoA: polyamine N'-acetyltransferase (PAT) and of ornithine decarboxylase (ODC) activities in both organs. However ODC activity is 300 times higher in liver than in pancreas. In the latter organ, there is a transient increase of N1-acetylspermidine, followed by a decrease of spermidine, alpha-Difluoromethylornithine (DFMO), a potent ODC inhibitor, impairs the accumulation of putrescine in liver but not in pancreas. These results suggest that in pancreas the accumulated putrescine is essentially formed from spermidine, via N1-acetylation and oxidation, while in liver it is formed from decarboxylation of ornithine. A possible involvement of cAMP in the stimulation of the polyamine interconversion pathway is discussed.

Studies of the specificity and kinetics of rat liver spermidine/spermine N1-acetyltransferase

The substrate specificity and kinetic mechanism of spermidine N1-acetyltransferase from rat liver was investigated using a highly purified (18 000-fold) preparation from the livers of rats in which the enzyme was induced by treatment with carbon tetrachloride (1.5 ml/kg body wt. 6h before death). The enzyme catalysed the acetylation of spermidine, spermine, sym-norspermidine, sym-norspermine, N-(3-aminopropyl)-cadaverine, N1-acetylspermine, 3,3'-diamino-N-methyldipropylamine and 1,3-diaminopropane, but was inactive with putrescine, cadaverine, sym-homospermidine and N1-acetylspermidine. These results suggest that the enzyme is highly specific for the acetylation of a primary amino group that is separated by a three-carbon aliphatic chain from another nitrogen atom (i.e. the substrates are of the type H2N[CH2]3NHR). The maximal rates of acetylation of 1,3-diaminopropane and 3,3'-diamino-N-methyldipropylamine were much lower than the maximal rates with spermidine or sym-norspermidine as substrates, suggesting a preference for a secondary amino group bearing the aminopropyl group that is acetylated. The best substrates for acetylation were sym-norspermidine and sym-norspermine, which had Km values of about 10 micrograms and Vmax. values of about 2 mumol of product/min per mg of enzyme compared with Km of 130 microM and Vmax. of 1.3 mumol/min per mg for spermidine. N1-Acetylspermidine (the product of the reaction) and N8-acetylspermidine were weak inhibitors and were competitive with spermidine, having Ki values of about 6.6 mM and 0.4 mM respectively. N1-Acetylspermidine was a non-competitive inhibitor with respect to acetyl-CoA. CoA was also inhibitory to the reaction, showing non-competitive kinetics when either [acetyl-CoA] or [spermidine] was varied. These results suggest that the reaction occurs via an ordered Bi Bi mechanism in which spermidine binds first and N1-acetyl-spermidine is the final product to be released.