Cellular thiol status-dependent inhibition of tumor cell growth via modulation of p27kip1 translocation and retinoblastoma protein phosphorylation by 1′-acetoxychavicol acetate

1'-Acetoxychavicol acetate (ACA) has been shown to inhibit tumor cell growth, but there is limited information on its effects on cell signaling and the cell cycle control pathway. In this study, we sought to determine how ACA alters cell cycle and its related control factors in its growth inhibitory effect in Ehrlich ascites tumor cells (EATC). ACA caused an accumulation of cells in the G1 phase and an inhibition of DNA synthesis, which were reversed by supplementation with N-acetylcysteine (NAC) or glutathione ethyl ester (GEE). Furthermore, ACA decreased hyperphosphorylated Rb levels and increased hypophosphorylated Rb levels. NAC and GEE also abolished the decease in Rb phosphorylation by ACA. As Rb phosphorylation is regulated by G1 cyclin dependent kinase and CDK inhibitor p27(kip1), which is an important regulator of the mammalian cell cycle, we estimated the amount of p27(kip1) levels by western blotting. Treatment with ACA had virtually no effect on the amount of p27(kip1) levels, but caused a decrease in phosphorylated p27(kip1) and an increase in unphosphorylated p27(kip1) as well as an increase in the nuclear localization of p27(kip1). These events were abolished in the presence of NAC or GEE. These results suggest that in EATC, cell growth inhibition elicited by ACA involves decreases in Rb and p27(kip1) phosphorylation and an increase in nuclear localization of p27(kip1), and these events are dependent on the cellular thiol status.

Protective effect of gamma-aminobutyric acid (GABA) against cytotoxicity of ethanol in isolated rat hepatocytes involves modulations in cellular polyamine levels

Gamma-aminobutyric acid (GABA) is considered to be a multifunctional molecule with various physiological effects throughout the body. It is also evident that the liver contains GABA and its transporter. However, the functions of GABA in liver have not been well documented. In this study, the cytoprotective effect of GABA against ethanol-induced hepatotoxicity was evaluated in primary cultured rat hepatocytes. Addition of ethanol induced decrease of cell viability in a dose-dependent manner. However, treatment with GABA resulted in a dose-dependent recovery from ethanol (150 mM)-induced cytotoxicity.GABA reversed the ethanol-induced decrease in intracellular polyamine levels. Furthermore, the addition of polyamines also reversed the ethanol-induced decrease of cell viability. These results suggest that GABA is protective against the cytotoxicity of ethanol in isolated rat hepatocytes and this effect may be modulated by the maintenance of intracellular polyamine levels.

Involvement of polyamines in evening primrose extract-induced apoptosis in Ehrlich ascites tumor cells

We previously demonstrated that evening primrose extract (EPE) induced apoptosis and inhibited the DNA synthesis in Ehrlich ascites tumor cells (EATC) and suggested that EPE-induced inhibition of the growth of EATC are via at least two pathway differentially modulated by reactive oxygen species, notably intracellular peroxides. These are (a) the EPE-induced apoptosis pathway which is dependent on increases in hydrogen peroxide and (b) the EPE-induced inhibition of cell proliferation which is hydrogen peroxide independent. In this study, EPE brought about a significant decrease in intracellular polyamine levels. Furthermore, the addition of polyamines reversed the EPE-induced decrease in cell viability and suppressed the EPE-induced increase in intracellular hydrogen peroxides. However, the addition of polyamines did not reverse EPE-induced decrease in DNA synthesis and phosphorylation of Rb protein, and EPE-induced translocation of AIF. These results suggest the involvement of polyamines in the EPE-induced apoptosis pathway which is dependent on increase in hydrogen peroxide.

Growth inhibitory effect of green tea extract in Ehrlich ascites tumor cells involves cytochrome c release and caspase activation

We reported previously that the mechanism by which Green tea extract (GTE) elicited growth-inhibitory effects in Ehrlich ascites tumor cells involved a decrease in ornithine decarboxylase (ODC) activity and in cell viability. Decrease in ODC activity has been associated with apoptotic cell death and we therefore studied changes in cytochrome c release and caspase activation, which characterize apoptosis. GTE caused a dose- and time-dependent increase in caspase-3-like protease activation, preceded by a release of cytochrome c from the mitochondria. Inhibiting the activation of caspase-3 with acetyl-Asp-Glu-Val-Asp-alpha-aldehyde (caspase inhibitor) caused a reversal in the effect on cell viability.

Growth inhibitory effect of green tea extract and (-)-epigallocatechin in Ehrlich ascites tumor cells involves a cellular thiol-dependent activation of mitogenic-activated protein kinases

The effect of green tea extract (GTE) in Ehrlich ascites tumor cells (EATC) was studied with respect to changes in the intracellular kinase system involving mitogen-activated protein kinases (MAPKs) and cellular thiol. We have previously shown a reduction in viability of EATC and tyrosine phosphorylation of 42 and 45 kDa proteins by GTE and its polyphenolic component, Epigallocatechin (EGC) (D.O. Kennedy, S. Nishimura, T. Hasuma, Y. Yoshihisa, S. Otani, I. Matsui-Yuasa, Involvement of protein tyrosine phosphorylation in the effect of green tea polyphenols on Ehrlich ascites tumor cells in vitro, Chem. Biol. Interact. 110 (1998) 159-172). Furthermore, GTE and EGC significantly decreased both cellular non-protein and protein sulfhydryl levels in EATC, but replenishing thiol stores with N-acetylcysteine (NAC) caused a recovery in cell viability, and therefore SH groups were identified as a novel target of green tea cytotoxicity (D.O. Kennedy, M. Matsumoto, A. Kojima, I. Matsui-Yuasa, Cellular thiol status and cell death in the effect of green tea polyphenols in Ehrlich ascites tumor cells, Chem. Biol. Interact. 122 (1999) 59-71). In this study, we have observed the stimulation of three forms of MAPK, namely ERK1/2, JNK/SAPK and p38, by EGC, which were dose and time-dependent. These MAPK stimulations were found to be cellular thiol status-dependent events as NAC reversed these stimulations. Furthermore, inhibition of the p38 MAPK pathway using the p38 inhibitor SB203580 caused a marked dose-dependent reduction in the decrease in cell viability caused by EGC treatment. Inhibiting the Erk1/2 MAPK pathway using the MEK inhibitor PD098059 caused a slight change in the decrease in cell viability by EGC. These may suggest that the cytotoxicity associated with EGC was more associated with the other MAPKs than with ERK1/2. This may be the first study of its kind providing a novel evidence of a role for different forms of MAPKs in the antitumor effect of green tea polyphenols, especially EGC, in Ehrlich ascites tumor cells.

Induction of apoptosis in CTLL-2 cells by protocatechualdehyde

The purpose of this study was to investigate the possible molecular mechanisms of the antiproliferative effect induced by protocatechualdehyde (PA, a dihydroxybenzene derivative). The viability of cytotoxic T cells (CfLL-2) stimulated by IL2 was significantly inhibited at 0.12 mM PA. This inhibitory effect was associated with the induction of apoptosis detected by DNA fragmentation assay. DNA ladder appeared at 0.12 mM PA and the intensity of DNA ladder was visible at 0.3 mM PA. PA inhibited the Ib2-dependent tyrosine phosphorylation of 91, 80 and 55 KDa proteins, but did not affect IL2-dependent serine/threonine phosphorylation of proteins. The levels of bcl-2 protein and mRNA were suppressed by PA. An alteration in bax protein expression on the apoptosis process in CTLL-2 cells was not observed. However, caspase-3 activity was increased by PA. Our results demonstrate that PA inhibited cell proliferation and induced apoptosis in CTLL-2 cells. It is concluded that PA is a potent anti-proliferative agent and is expected to be a promising candidate for novel therapeutics.

Polyamines and thiols in the cytoprotective effect of L-cysteine and L-methionine on carbon tetrachloride-induced hepatotoxicity

The relationship between cellular glutathione (GSH), protein-SH levels, and lactate dehydrogenase (LDH), with respect to the effect of polyamines on the cytoprotective ability of L-cysteine and L-methionine, the most important components in the sulfur amino acid metabolic pathway, in carbon tetrachloride (CCl4)-induced toxicity in isolated rat hepatocytes was studied. CCl4 induced a LDH release and decreased cellular thiols and polyamines levels but treatment with L-cysteine and L-methionine reversed these decreases. Treating with methylglyoxal bis-(guanylhydrazone), MGBG, an irreversible inhibitor of S-adenosylmethionine decarboxylase, which is a key enzyme in spermidine and spermine biosynthesis, and therefore used to deplete cellular polyamines, prevented the protective effect of L-cysteine and L-methionine, but the addition of exogenous polyamines inhibited the influence of MGBG. These results suggest that the cytoprotective effect of L-cysteine and L-methionine in CCl4-induced toxicity were via maintenance of cellular polyamines, GSH and protein-SH concentrations and prevention of LDH leakage.

Apoptosis induced by 1'-acetoxychavicol acetate in Ehrlich ascites tumor cells is associated with modulation of polyamine metabolism and caspase-3 activation

The efficacy of the antitumor activity of 1'-acetoxychavicol acetate (ACA), reported to be a suppressor of chemically induced carcinogenesis, was evaluated in Ehrlich ascites tumor cells. ACA treatment resulted in changes in morphology and a dose-dependent suppression of cell viability. Apoptosis, characterized by nuclear condensation, membrane blebbing, cell shrinkage and a significant induction of caspase-3-like protease activity at 8 h in a time-course study were observed. Formation of apoptotic bodies was preceded by lowering of intracellular polyamines, particularly putrescine, and both dose- and time-dependent inhibitory and activation effect by ACA on ornithine decarboxylase (ODC) and spermidine/spermine N(1)-acetyltransferase (SSAT), respectively. Administration of exogenous polyamines prevented ACA-induced apoptosis represented by a reduction in the number of apoptotic bodies and also caused reduction in the induced caspase-3-like protease activity at 8 h. These findings suggest that the anticarcinogenic effects of ACA might be partly due to perturbation of the polyamine metabolic pathway and triggering of caspase-3-like activity, which result in apoptosis.

Thiols and polyamines in the cytoprotective effect of taurine on carbon tetrachloride-induced hepatotoxicity

The mechanism by which taurine (2-aminoethanesulfonic acid) protects hepatocytes injury induced by carbon tetrachloride (CCl4) is not fully understood. In a previous study, we reported that cellular polyamines play an important role in this mechanism. The relationship between cellular glutathione (GSH), protein-SH levels, and lactate dehydrogenase (LDH), with respect to the effect of polyamine on the cytoprotective ability of taurine in CCl4-induced toxicity in isolated rat hepatocytes, was examined. CCl4 induced a LDH release and decreased cellular thiols and polyamine levels. Treating with taurine reversed these depletions. The effect of CCl4 was also reversed by the addition of exogenous polyamines. Pretreating with alpha-difluoromethylornithine, an irreversible inhibitor of ornithine decarboxylase, which is a key enzyme in polyamine biosynthesis and therefore used to deplete cellular polyamine, prevented the protective effect of taurine. Adding diethyl maleate, a cellular glutathione-depleting agent, reduced the effect of exogenous polyamines. The role of polyamine in the cytoprotective effect of taurine in CCl4-induced toxicity may therefore be by preventing, among others, GSH and protein-SH depletions.

Interleukin-1beta induces elevation of spermidine/spermine N1-acetyltransferase activity and an increase in the amount of putrescine in synovial adherent cells from patients with rheumatoid arthritis

OBJECTIVE

To investigate polyamine metabolism in rheumatoid synovial adherent cells stimulated by interleukin- 1beta (IL-1beta).

METHODS

Synovial adherent cells obtained from patients with rheumatoid arthritis (RA) were cultured and incubated in the presence or absence of human recombinant IL-1beta at a concentration of 10 ng/ml for 24 h. The cellular contents of polyamines as well as the activities of spermidine/spermine N1-acetyltransferase (SAT) and ornithine decarboxylase (ODC) were measured.

RESULTS

Polyamines in synovial adherent cells decreased significantly after 24 h incubation in the absence of IL-1beta. However, in the presence of IL-Ibeta, putrescine and N'-acetylspermidine increased significantly. No significant difference was observed between the amount of spermidine in synovial adherent cells incubated with and without IL-1beta. Spermine and N8-acetylspermidine in synovial adherent cells incubated with IL-1beta decreased significantly more than in synovial adherent cells incubated without. SAT activity reached a peak 12 h after the addition of IL-1beta and then decreased, while the ODC activity did not increase. SAT activity was elevated by the addition of IL-1beta in a dose dependent manner.

CONCLUSION

An increase in the putrescine level in rheumatoid synovial adherent cells as a result of the elevation of SAT activity induced by IL-1beta may play a role in RA.

Apoptosis induced by chelation of intracellular zinc is associated with depletion of cellular reduced glutathione level in rat hepatocytes

Zn(2+) has multiple implications in cellular metabolism, including free radicals metabolism and cell death by apoptosis. In the present study, we examined the role of Zn(2+) in the regulation of apoptosis in cultured rat hepatocytes. The chelation of Zn(2+) by a membrane permeable metal ion chelator, N, N, N', N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), induced apoptosis. Addition of ZnSO(4) prevented TPEN-induced apoptosis. Unlike the effect of TPEN, a membrane impermeable metal ion chelator, diethylenetriamine pentaacetic acid (DTPA), did not induce apoptosis, indicating that chelation of intracellular Zn(2+) was required to trigger apoptosis. Caspase-3-like proteolytic activity, a general biochemical mediator of apoptosis in a variety of cells and tissues, was also activated with the treatment of TPEN but not DTPA. TPEN treatment, but not DTPA, also resulted in the depletion of intracellular reduced glutathione (GSH) but addition of Zn(2+) recovered the GSH level. N-acetyl-L-cysteine (NAC), a thiol antioxidant, prevented TPEN-induced apoptosis. These results taken together suggest that intracellular Zn(2+) interfere with the apoptosis process, possibly through the regulation of cellular redox potential involving GSH.

Cellular thiols status and cell death in the effect of green tea polyphenols in Ehrlich ascites tumor cells

Epidemiological studies suggest that the consumption of green tea may help prevent cancers in humans, and also breast and prostate cancers in animal models are reduced by green tea, and several mechanisms have been proposed for these effects. In this study the relationship between cellular sulfhydryl (SH) groups and the cytotoxicity of green tea polyphenols in Ehrlich ascites tumor cells was examined. It was found that in the presence of green tea extract (GTE) (100 microg/ml) and one of its polyphenolic components, epigallocatechin (EGC; 100 microM), both cellular non-protein (GSH) and protein-sulfhydryl (PSH) levels were significantly decreased and this was associated with a decrease in cell viability. Replenishing the thiol levels by using N-acetylcysteine (NAC) caused a recovery in cell viability, but this recovery was dependent on the time of thiol replenishment in the presence of EGC (initial 15 min). These results identify SH groups as a novel target of green tea polyphenols cytotoxicity in tumor cells, and a regulatory role for green tea in terms of reducing sulfhydryls in tumor inhibition.

Induction of smooth muscle cells in the fibrous capsule of human hepatocellular carcinoma but not in the septa of hepatic cirrhosis

We examined the expression of smooth muscle cytoskeleton in spindle-shaped cells in the capsule of hepatocellular carcinoma (HCC) and the septa of liver cirrhosis (LC). Serial sections of livers resected from 11 patients were stained with monoclonal antibodies against vimentin, desmin, smooth muscle actin (1A4, HHF35, CGA7) and smooth muscle myosin heavy chain isoforms (SM1, SM2). Capsular spindle-shaped cells exhibited a cytoskeletal feature indicative of intermediately differentiated smooth muscle cells. Computer-assisted morphometry revealed that the proportions of 1A4-, HHF35-, CGA7- and SM1- positive areas to vimentin-positive area were 88.0+/-11.0%, 50.8+/-17.4%, 25.3+/-16.4% and 19.4+/-12.4% (n=11) in main tumours and 86.6+/-9.4%, 50.9+/-18.7%, 21.1+/-12.3% and 17.6+/-9.7% (n=12) in daughter tumours, indicating that spindle-shaped cells are heterogeneous in cytoskeletal expression. Septal spindle-shaped cells in LC lacked the cytoskeletal proteins specific to differentiated smooth muscle cells (CGA7, SM1, SM2 and desmin). Electron microscopically, capsular spindle-shaped cells contained more microfilaments and less rough endoplasmic reticulum than do septal cells. Intermediately differentiated smooth muscle cells are induced in the capsule of HCC but not in the septa of LC, suggesting a role for stromal interaction by tumour cells in the induction of smooth muscle cells.

The role of polyamines in growth factor induced DNA synthesis in cultured rat hepatocytes

BACKGROUND/AIMS

Hepatocyte growth factor and transforming growth factor-alpha are growth factors with important roles in hepatocyte proliferation. The polyamines, putrescine, spermidine, and spermine are widely distributed in many different cells and play an essential role in cell growth and differentiation. The present study examined the role of polyamine in this growth promoting factor-induced hepatocyte proliferation, in primary cultured rat hepatocytes.

METHODOLOGY

Hepatocytes were isolated from rats by the collagenase perfusion method. Ornithine decarboxylase and S-adenosylmethionine decarboxylase activities were measured as the release of 14CO2 from L-[-14C]ornithine and S-adenosyl-L-[carboxyl14C]methionine, respectively. The concentration of polyamine was analyzed by high performance liquid chromatography.

RESULTS

When transforming growth factor-alpha and hepatocyte growth factor were added to the hepatocyte culture simultaneously, ornithine decarboxylase activity, S-adenosylmethionine decarboxylase activity, polyamine concentration and DNA synthesis increased additively. The increase in DNA synthesis caused by transforming growth factor-alpha, hepatocyte growth factor, or both was completely inhibited by alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone). The inhibition was reversed by exogenous spermidine or spermine, but not by putrescine.

CONCLUSIONS

Increased spermidine or spermine levels are essential for hepatocyte proliferation in cultured rat hepatocytes.

Involvement of polyamines in retinoblastoma protein phosphorylation

Hepatocyte growth factor (HGF) increased both levels of phosphorylated and non-phosphorylated forms of retinoblastoma protein (RB) in primary cultured rat hepatocytes. Combined treatment of HGF and a specific inhibitor of ornithine decarboxylase (ODC), alpha-difluoromethylornithine (DFMO), reduced the levels of hyper-phosphorylated and hypo-phosphorylated forms of RB and increased the levels of the non-phosphorylated form, compared to HGF alone, but did not affect the total level of RB. Polyamines added exogenously overcame the effects of DFMO; they increased hyper- and hypo-phosphorylated forms and decreased non-phosphorylated RB. TGF-beta1 inhibited the increases in ODC activity, RB phosphorylation, and DNA synthesis induced by HGF. However, polyamines added exogenously could not overcome the inhibition by RB phosphorylation and DNA synthesis by TGF-beta1. These results suggest that polyamines are involved in the phosphorylation of RB, but the inhibition of polyamine biosynthesis by TGF-beta1 did not result in the inhibition of RB phosphorylation and DNA synthesis.

Involvement of protein tyrosine phosphorylation in the effect of green tea polyphenols on Ehrlich ascites tumor cells in vitro

Green tea extract and its polyphenolic components have been found to possess anticarcinogenic, antimutagenic, antihypertensive and antihepatotoxic effects, and several mechanisms have been proposed for these effects. In this study, the effects of five tea polyphenols, (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (-) epicatechin-3-gallate (ECG), ( -) epicatechin (EC) and (+)-catechin (C), were examined on the viability of Ehrlich ascites tumor cells in vitro and a possible relationship with tyrosine phosphorylation was determined. Proteins extracted from the cells treated with the tea polyphenols were separated by SDS-PAGE, and tyrosine-phosphorylated proteins were detected by immunoblotting with anti-phosphotyrosine antibody and the extent of phosphorylation determined. EGC (100 microM) caused a significant decrease in cell viability to 4.1 +/- 0.2% of the control value, and this correlated with a stimulation of protein tyrosine kinase (PTK) activity. EGCG (100 microM) also caused a slight decrease in cell viability (approximately 70% of the control value) but this and the other polyphenols, which had no effect on cell viability likewise, had no effect on tyrosine phosphorylation. Tyrosine phosphorylations of 42 and 45 kDa proteins were also observed for EGC. Further evaluation of the effect of EGC showed that the activity of ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis in cells, decreased significantly as well. A significant correlation has therefore been observed between a cellular event, namely, a reduction in the viability of Ehrlich ascites tumor cells and an association with a tyrosine phosphorylation of 42 and 45 kDa proteins by the polyphenol EGC.

Restricted Zn2+ availability affects the antizyme-dependent ornithine decarboxylase degradation pathway in isolated primary cultured rat hepatocytes

We previously reported that lack of Zn2+ decreased ornithine decarboxylase (ODC) activity without any change in ODC messenger RNA levels and the half-life of ODC activity being about 2-fold more rapid in primary cultured adult rat hepatocytes, suggesting that lack of Zn2+ decreased ODC activity mainly by degrading the enzyme. The present investigations showed that the chelator, diethylenetriamine penta-acetic acid (DTPA), increased the ratio of ODC-antizyme complex to total ODC (about 2-fold) and caused a decrease in antizyme inhibitor, a protein inhibitor of ODC antizyme (about 50%). These results indicate that a restricted Zn2+ availability affects the antizyme-dependent ODC degradation pathway and consequently decreases ODC activity in primary cultured rat hepatocytes.

Polyamine metabolism of rat gastric mucosa after oral administration of hypertonic sodium chloride solution

Oral administration of 1 ml of 3.42 M NaCl solution to rats induced spermidine/spermine N1-acetyltransferase (SSAT) activity in gastric mucosa as well as ornithine decarboxylase (ODC) activity. SSAT activity increased and peaked at 5 h and again at 7 h, whereas ODC activity peaked at 6 h. SSAT mRNA also increased after 3.42 M NaCl administration to an extent similar to the increase in SSAT activity at 5 h. Intracellular putrescine level and DNA synthesis were increased by NaCl administration. A polyamine oxidase inhibitor, N,N'-bis(2,3-butadienyl)-1,4-butanediamine (MDL-72527), but not an ODC inhibitor, alpha-difluoromethylornithine (DFMO), inhibited the increases in putrescine level and DNA synthesis at 5 h. The inhibition of DNA synthesis by MDL-72527 was reversed by putrescine administration. In contrast, both MDL-72527 and DFMO inhibited the increase in putrescine level and DNA synthesis at 16.5 h. These findings suggest that putrescine produced from preexistent spermidine by SSAT is responsible for the initial DNA synthesis after mucosal injury induced by NaCl and that both SSAT and ODC are involved in formation of putrescine, which is required for subsequent DNA synthesis.

Protective effect of green tea extract and tea polyphenols against the cytotoxicity of 1,4-naphthoquinone in isolated rat hepatocytes

The cytoprotective effect of green tea extract and its phenolic compounds against 1,4-naphthoquinone-induced hepatotoxicity was evaluated in primary cultured rat hepatocytes. After exposure to 1,4-naphthoquinone, lactate dehydrogenase (LDH) leakage and cell viability were both improved by the presence of the tea extract and tea polyphenols. This cytoprotective effect was related to the structure of tea polyphenols, the galloyl group of (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate being particularly effective. The production of liquid peroxidation by 1,4-naphthoquinone was not inhibited by the tea extract nor by tea polyphenol addition. After 2 h of incubation, the protein thiol concentration was reduced by 1,4-naphthoquinone, but this reduction was prevented by the tea extract and tea polyphenols. The reduction in protein thiol content of the cells closely paralleled the LDH leakage and loss of cell viability. These results suggest that the mechanism of protection by tea polyphenols against 1,4-naphthoquinone-induced toxicity to rat hepatocytes was due to the maintenance of protein thiol levels.

Possible carcinogenic potential of dimethylarsinic acid as assessed in rat in vivo models: a review

The modifying effects of dimethylarsinic acid (DMA), the major metabolite of ingested arsenicals in most mammals, on chemical carcinogenesis were investigated using rat in vivo models and reviewed here. In a multi-organ bioassay, rats pretreated with 5 carcinogens were administered DMA at various concentrations in their drinking water. Significantly increased tumor induction due to DMA was observed in the urinary bladder, kidney, liver, and thyroid gland. This was associated with significantly elevated ornithine decarboxylase activity in the kidneys of DMA-treated animals. To estimate the hazard levels of its promoting influence, further examinations were carried out concerned with urinary bladder and liver carcinogenesis. Doses of 25 and 50 ppm, respectively, of DMA were found capable of enhancing lesion development in the two organs. In conclusion, our data indicate that DMA is a carcinogen or promoter in the urinary bladder, liver, kidney and thyroid gland, in line with previous epidemiological findings.

Cytotoxicity of cholestane 3 beta,5 alpha,6 beta-triol on cultured intestinal epithelial crypt cells (IEC-6)

The effects of cholestane 3 beta,5 alpha,6 beta-triol on intestinal epithelial crypt cells were investigated using the IEC-6 cell line. Cholestane 3 beta,5 alpha,6 beta-triol decreased SH groups (glutathione and protein SH) in the cell, and showed cytotoxicity in a time-dependent manner. Although the concentration of cholestane 3 beta,5 alpha,6 beta-triol used in this study (100 microM) was very high compared with that in plasma of experimental animals, cholestane 3 beta,5 alpha,6 beta-triol did not show any cytotoxicity on IEC-6 cells without fetal calf serum (FCS). The level of cytotoxicity was dependent upon the concentration of FCS in the culture medium. Unknown components in FSC (not VLDL or LDL) were suggested to be associated with the cytotoxicity of cholestane 3 beta,5 alpha,6 beta-triol. Moreover, the fact that even heat-treated FCS (100 degrees C for 30 min) still mediated the cytotoxicity suggested the participation of non-protein components.

Involvement of polyamines in the protection of taurine against the cytotoxicity of hydrazine or carbon tetrachloride in isolated rat hepatocytes

Taurine (2-aminoethanesulfonic acid) is known to protect hepatocyte injury induced by hydrazine or carbon tetrachloride. We investigated whether cellular polyamines are involved in the protective mechanism of taurine in the hepatocyte injury caused by hydrazine or carbon tetrachloride. The agents decreased cellular polyamine concentrations, but the treatment with taurine prevented this decrease. The protection of taurine against hepatic injury was not observed in hepatocytes treated with alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase which is a key enzyme in polyamine biosynthesis. The protection of taurine was recovered by the addition of polyamines to DFMO-treated hepatocytes. These results suggest that cellular polyamines play an important role in the protection of taurine in hydrazine or carbon tetrachloride-induced hepatocyte injury.

Cytotoxicity of 7-ketocholesterol toward cultured rat hepatocytes and the effect of vitamin E

The effects of 7-ketocholesterol on rat hepatocytes prepared by collagenase perfusion were examined. The viability of cells incubated with 100 microM 7-ketocholesterol was significantly lower than those with cholesterol, although the LDH activity in the cultured medium remained unchanged during the incubation. Hepatocytes treated with 7-ketocholesterol produced large amounts of .NO and O2- in the early stage of incubation. Treatment of the hepatocytes with Carboxy-PTIO, which selectively scavenged .NO, or with L-NMMA, an inhibitor of .NO synthase, increased the cell viability. The addition of 7-ketocholesterol to the culture medium tended to increase the ratio of total sterol to phospholipid of the hepatocytes in a time-dependent manner without changing the content of phospholipid. No lipid peroxidation or oxidation of the cellular SH groups, protein SH and glutathione, was apparent. Vitamin E added 1 h before the addition of 7-ketocholesterol prevented the hepatocytes from cell death by suppressing the incorporation of 7-ketocholesterol into the hepatocytes and by scavenging O2-.

Highly hydrogenated dietary soybean oil modifies the responses to polychlorinated biphenyls in rats

The effects of dietary highly hydrogenated soybean oil (HSO) upon the changes caused by dietary polychlorinated biphenyls (PCBs) were examined in rats. Six groups of rats were fed the following diets for 30 d: a 20% soybean oil-containing diet (control diet), a diet in which a half of soybean oil was substituted with HSO (HSO-A diet), a diet in which cellulose powder was replaced with HSO (HSO-B diet) and these diets supplemented with 100 ppm PCBs (control + PCBs, HSO-A + PCBs and HSO-B + PCBs diets). Hepatic concentration of PCBs and relative liver weight were markedly decreased in rats fed with the HSO-A + PCBs diet compared with those fed with the other diets containing PCBs. Liver lipids and liver cholesterol were considerably decreased with a reciprocal increase in fecal sterol excretion by rats fed the HSO-A + PCBs and the HSO-B + PCBs diets compared with those fed with the control + PCBs diet. The fatty acid composition in hepatic phospholipids showed an independent increase of the saturated fatty acid content induced by dietary HSO and PCBs. Dietary PCBs also caused decreases in the amounts of monounsaturated and n-3 polyunsaturated fatty acids. These results suggest that dietary HSO prevents accumulation of PCBs in the liver and promotes the excretion of lipids stimulated by PCBs, accompanied by a change in fatty acid metabolism.

Promotive action of acylated ascorbate on cellular DNA synthesis and growth at low doses in contrast to inhibitory action at high doses or upon combination with hyperthermia

Effects of 6-O-palmitoyl ascorbate (ascorbate) developed to increase the antitumour activity of ascorbic acid on DNA synthesis and proliferation of Ehrlich ascites tumour cells were investigated. Treatment of the cells with the acylated ascorbate at 25-50 microM for 1 h resulted in no effect on DNA synthesis, assayed by pulse incorporation of [3H]thymidine after a culture period of 20 h, but led to 49%-87% enhanced DNA synthesis after 4 days, suggesting that long-term culture is required for promotion by ascorbate to occur. At a dose as high as 75 microM acylated ascorbate, however, cellular DNA synthesis was 64% inhibited after 20 h and 99% after 4 days. The results suggest that acylated ascorbate exhibits a dual action on DNA synthesis: promotion at low doses and inhibition at high doses, both of which are potentiated in a time-dependent manner. In contrast to the above-mentioned results at 37 degrees C, acylated ascorbate at 25-75 microM inhibited but did not promote DNA synthesis at 42 degrees C whatever the culture period. Similar results were exhibited when proliferation of cells cultured for a long period was investigated. At 37 degrees C, 50 microM acylated ascorbate increased the number of the cells to 3.6 times the control values after 8 days and to 1.9 times after 11 days; in contrast, a 75-microM dose decreased the cell number considerably. Combination with hyperthermia (42 degrees C) suppressed the increase and cell growth was completely inhibited at 75 microM.

Overexpression of c-myc messenger RNA in primary and metastatic lesions of carcinoma of the stomach

BACKGROUND

Although c-myc expression in carcinoma of the stomach has been reported to be involved in progression of the disease, little is known about the mechanism or significance of its expression.

STUDY DESIGN

We measured c-myc messenger RNA (mRNA) levels by Northern blot hybridization in 51 primary gastric carcinoma lesions and 15 metastatic lesions accompanied by normal mucosal tissues from the same patients. The extent of c-myc mRNA expression in malignant lesions was determined and compared with that in normal mucosal tissues. The clinical and pathologic significance of c-myc mRNA expression was investigated.

RESULTS

In 35 (68.6 percent) of 51 primary gastric carcinomas c-myc mRNA was overexpressed. Expression was found to be more frequent and stronger in early lesions than in advanced lesions (90 percent, 6.15-fold compared with 54.8 percent, 2.42-fold, p < 0.05). However, c-myc mRNA expression in the primary lesions showed little influence on either the histologic features or the disease progression. C-myc mRNA levels were higher in every metastatic lesion than in the primary lesions (9.89-fold compared with 3.04-fold, p < 0.05).

CONCLUSIONS

These observations suggest that c-myc mRNA overexpression may play a role in the early development of primary lesions as well as in the formation of metastatic lesions of carcinomas of the stomach.

Regulation of apoptosis of interleukin 2-dependent mouse T-cell line by protein tyrosine phosphorylation and polyamines

We examined the effect of inhibitors of tyrosine kinase and tyrosine phosphatase on DNA fragmentation, protein tyrosine phosphorylation, and polyamine metabolism in the murine T-cell line CTLL-2. When cells were exposed to herbimycin A, a specific inhibitor of tyrosine kinase (Uehara et al., 1989, Biochem. Biophys. Res. Commun., 163:803-809), in the presence of interleukin 2 (IL-2), DNA was degraded into oligonucleosomal fragments in a dose-dependent fashion. Genistein, another inhibitor of tyrosine kinase (Akiyama et al., 1987, J. Biol. Chem., 262:5592-5596), had similar effects. Exposure of CTLL-2 cells to vanadate, a tyrosine phosphatase inhibitor, blocked with the DNA fragmentation induced by herbimycin A. Tyrosine phosphorylation of 55 Kd protein was inhibited by herbimycin A, and the inhibition was reduced by vanadate. Ornithine decarboxylase (ODC) activity decreased rapidly after herbimycin A was added to CTLL-2 cell cultures, while vanadate increased ODC activity. The exogenous addition of putrescine or spermine, but not that of spermidine, attenuated herbimycin A-induced DNA fragmentation. These findings suggest that phosphorylation of tyrosine residues of 55 Kd protein prevents DNA fragmentation and that polyamines are involved in regulation of apoptosis.

Polyamine metabolism in the rat liver after orthotopic liver transplantation

We examined the polyamine metabolism in liver transplanted after cold ischemia and effects of putrescine administration on liver injury, liver regeneration, and survival rate after orthotopic liver transplantation in the rat. Male Wistar rats were used as donors and recipients. Grafts were stored in Euro-Collins solution for 6 h at 4 degrees C. Orthotopic liver transplantation was performed by the three cuff technique. The activities of aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase elevated and peaked 4 h after liver transplantation. Hepatic ornithine decarboxylase and spermidine/spermine N1-acetyltransferase activities were also elevated and peaked 8 h after the operation. In agreement with the increases in ornithine decarboxylase and spermidine/spermine N1-acetyltransferase activities, the putrescine content increased and spermidine content decreased in the transplanted liver. Putrescine administrated intraperitoneally improved the survival rate, decreased serum transaminase level and increased the [3H]thymidine incorporation into the liver DNA. These findings suggest that both biosynthetic and biodegradative pathways are stimulated in liver transplantation, resulting in the increase in the formation of putrescine from ornithine and from spermidine, and that putrescine administration improve the survival rate by protecting the damaged graft after cold ischemia and reperfusion and by stimulating liver regeneration.

Effects of highly hydrogenated soybean oil and cholesterol on plasma, liver cholesterol, and fecal steroids in rats

We investigated the relationship between dietary highly hydrogenated soybean oil (HSO) and cholesterol transport in rats. In the first study, to examine the effects on cholesterol transport of different concentrations of HSO in dietary oil, rats were given one of the three diets containing 0, 25, or 50% HSO in dietary oil with cholesterol (5 g/kg diet) or a diet without HSO and cholesterol for 22 d. Feeding the high concentration of HSO prevented the increase in plasma total cholesterol, hepatic total lipids, and cholesterol and the decrease in high-density lipoprotein-cholesterol, which were caused by dietary cholesterol. Moreover, HSO increased the fecal excretion, fecal lipids, and steroids in a dose-dependent manner. In the second study, to examine the effects on cholesterol transport of redistribution of steric acid in the triacylglycerol species contained in HSO, rats were given one of the six diets containing HSO (distearoylmonoacylglycerol and tristearoylglycerol)-rich, monostearoylglycerol-rich, or palmitic acid-rich oil with/without cholesterol (5 g/kg diet), for 30 d. Whereas the accumulation of cholesterol in the body was reduced, cholesterol excretion was enhanced effectively in rats given the HSO-rich diet compared with rats given the monostearoylglycerol-rich diet. These results suggested that not only the high concentration of stearic acid but also its uneven distribution in HSO-triacylglycerol contributed to the reduction in intestinal cholesterol absorption in rats.

Cancer induction by an organic arsenic compound, dimethylarsinic acid (cacodylic acid), in F344/DuCrj rats after pretreatment with five carcinogens

Arsenic (As) is environmentally ubiquitous and an epidemiologically significant chemical related to certain human cancers. Dimethylarsinic acid (cacodylic acid; DMA) is one of the major methylated metabolites of ingested arsenicals in most mammals. To evaluate the effects of DMA on chemical carcinogenesis, we conducted a multiorgan bioassay in rats given various doses of DMA. One-hundred twenty-four male F344/DuCrj rats were divided randomly into 7 groups (20 rats each for groups 1-5; 12 rats each for groups 6 and 7). To initiate multiple organs and tissues, animals in groups 1-5 were treated sequentially with diethylnitrosamine (100 mg/kg body weight, i.p., single dose at the commencement) and N-methyl-N-nitrosourea (20 mg/kg body weight, i.p., 4 times, on days 5, 8, 11, and 14). Thereafter, rats received 1,2-dimethylhydrazine (40 mg/kg body weight, s.c., 4 times, on days 18, 22, 26, and 30). During the same period, the animals were sequentially administered N-butyl-N-(4-hydroxybutyl)nitrosamine (0.05% in the drinking water, during weeks 1 and 2) and N-bis(2-hydroxypropyl)nitrosamine (0.1% in the drinking water, during weeks 3 and 4; DMBDD treatment). After a 2-week interval, groups 2-5 were given 50, 100, 200, or 400 ppm DMA, respectively, in the drinking water. Groups 6 and 7, which were not given DMBDD treatment, received 100 and 400 ppm DMA during weeks 6-30. All rats were killed at the end of week 30. In the initiated groups (groups 1-5), DMA significantly enhanced the tumor induction in the urinary bladder, kidney, liver, and thyroid gland, with respective incidences in group 5 (400 ppm DMA) being 80, 65, 65, and 45%. Induction of preneoplastic lesions (glutathione S-transferase placental form-positive foci in the liver and atypical tubules in the kidney) was also significantly increased in DMA-treated groups. Ornithine decarboxylase activity in the kidneys of rats treated with 100 ppm DMA was significantly increased compared with control values (P < 0.001). In conclusion, DMA is acting as a promoter of urinary bladder, kidney, liver, and thyroid gland carcinogenesis in rats, and we speculate that this may be related to cancer induction by As in humans.

Enhanced inhibitory effects of hyperthermia combined with ascorbic acid on DNA synthesis in Ehrlich ascites tumor cells grown at a low cell density

Effects of hyperthermia and cell densities on inhibitory activity of ascorbic acid on DNA synthesis in Ehrlich ascites tumor cells were studied. When cells at a low density of 5 x 10(3)/ml were treated with 75 microM ascorbic acid for 1 h, DNA synthesis was inhibited after treatment at 37 degrees C and the inhibition was significantly enhanced at 42 degrees C. At a cell density as high as 1 x 10(5)/ml, however, inhibition did not occur at 37 degrees C or 42 degrees C. In contrast, dehydroascorbic acid was inactive even at a low cell density under similar conditions. Inhibitory effects of ascorbic acid on DNA synthesis were also markedly enhanced by treatment at 40 degrees C. DNA synthesis was not inhibited in the absence of the drug. Furthermore, mice transplanted with cells treated with a combination of 75 microM ascorbic acid and hyperthermia at 42 degrees C, considerably prolonged their survival time in comparison with untreated cells. Addition of ascorbic acid to hyperthermia is suggested to be an advantageous treatment for cancer.

Effect of sucrose monostearate, an emulsifier, on polyamine metabolism and phosphatidylinositol turnover in Ehrlich ascites tumor cells

Sucrose esters of fatty acids have antitumor activity. We studied the effect of sucrose monostearate (SS), an emulsifier, on polyamine metabolism and phosphatidylinositol turnover in Ehrlich ascites tumor cells. The activity of ornithine decarboxylase (ODC) was increased in the cells by changing the medium. This increase in the activity was inhibited by adding sucrose stearate, but not sucrose or stearate to the medium. The activity of spermidine/spermine N1-acetyltransferase (SAT), a rate-limiting enzyme of polyamine biodegradation, was enhanced with the addition of SS in a time- and dose-dependent manner. The elevation of SAT activity was completely prevented when cycloheximide was added to the culture simultaneously. In in vitro studies, SS at various concentrations up to 1 mM hardly affected the activities of ODC or SAT. The incorporation of [3H]inositol into both fractions of inositolphospholipid and inositol phosphates was inhibited by SS. These results suggest that the perturbation of polyamine metabolism and phosphatidylinositol turnover is involved in the mechanism of antitumor activity of SS in Ehrlich ascites tumor cells.

DNA synthesis inhibition and transmembrane permeation into tumor cells by various dialkyl phthalates upon hyperthermia

Diisobutyl-, dibutyl-, and dioctyl phthalates, at a concentration of 50 microM, markedly inhibited the incorporation of [3H]thymidine into DNA in tumor cells and also cell proliferation. The inhibitions were synergistically enhanced by hyperthermia at 42 degrees C for 1 h. In contrast, dimethyl-, and diethyl phthalates induced almost no inhibition. The effective phthalates were detected in the cells by gas-liquid chromatography, whereas the non-effective drugs were not or were little detected, suggesting involvement of permeability through cell membrane in cytotoxic effects. Combination of the cytotoxic phthalic acid esters and hyperthermia is suggested to be an advantageous treatment for cancer.

Increased spermidine or spermine level is essential for hepatocyte growth factor-induced DNA synthesis in cultured rat hepatocytes

BACKGROUND/AIMS

Hepatocyte growth factor is a potent mitogen for mature hepatocytes and seems to act as a trigger for liver regeneration. Hepatocyte growth factor was first purified from human and rabbit plasma and rat platelets. Additionally, putrescine, spermidine, and spermine are widely distributed in many different cells; intracellular concentrations of these polyamines are closely related to cell proliferation. The present study examined whether polyamine metabolism is involved in hepatocyte growth factor-induced DNA synthesis in primary cultured rat hepatocytes.

METHODS

Hepatocytes were isolated from rats by the collagenase perfusion method. Ornithine decarboxylase and S-adenosylmethionine decarboxylase activities were measured as the release of 14CO2 from L-[1-14C]ornithine and S-adenosyl-L-[carboxyl-14C]methionine, respectively.

RESULTS

alpha-Difluoromethylornithine inhibited hepatocyte growth factor-induced DNA synthesis by only 21%. On the other hand, methylglyoxal bis(guanylhydrazone) completely inhibited hepatocyte growth factor-induced DNA synthesis to nontreated control level. The inhibitory effect of methylglyoxal bis(guanylhydrazone) on hepatocyte growth factor-induced DNA synthesis was reversed by exogenously added spermidine or spermine.

CONCLUSIONS

Spermidine or spermine is essential for hepatocyte growth factor-induced DNA synthesis in primary cultured rat hepatocytes.

The involvement of polyamines in the activation of vitamin D receptor from porcine intestinal mucosa

In the intracellular process of the action of calcitriol, vitamin D receptor is thought to undergo some kind of physiochemical change, called activation, before the receptor binds to the vitamin D response element of the gene. In this paper, the effects of polyamines and their analogues on the sedimentation properties of vitamin D receptor prepared from porcine intestinal mucosa, and on DNA binding activity of the receptor, were studied. In sucrose density gradient analysis, polyamines decreased the sedimentation coefficient of vitamin D receptor in a dose-dependent fashion. Polyamines increased DNA binding activity of vitamin D receptor dose-dependently. These findings show that polyamines can activate vitamin D receptor in vitro. Among naturally existing polyamines, spermidine and spermine, but not putrescine, were effective within their physiological intracellular concentrations, suggesting that both spermidine and spermine can activate vitamin D receptor in vivo as well. Sucrose density gradient analysis using various kinds of polyamine analogues having various numbers of cations showed that the number of cation of polyamines is important for the efficiency to change the sedimentation coefficient of vitamin D receptor, and that the distance between two cationic charges does not play an important role.

Severity of promotion by sodium salts of succinic acid in rat urinary bladder carcinogenesis correlates with sodium ion concentration under conditions of equal urinary pH

Elevation of urinary pH and Na ion concentration induced by feeding high doses of sodium salts plays a crucial role in promotion of urinary bladder carcinogenesis in male rats initially treated with N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). In the present study, urinary bladder carcinogenesis in male F344 rats was promoted by feeding the mono- and di-sodium salts of succinic acid, and the activity was enhanced by varying urinary sodium ion concentration under conditions of equally high pH. In Experiment 1, the rats were given 0.05% BBN in their drinking water for 4 weeks and then fed basal diet containing 5% succinic acid, 5% sodium succinate (Na-Suc) or 5% di-sodium succinate (2Na-Suc) for 32 weeks. The development of carcinomas in the urinary bladder was enhanced by treatment with Na-Suc and with 2Na-Suc. 2Na-Suc induced larger urinary bladder tumors than the Na-Suc. In Experiment 2, 5% Na-Suc and/or 5% 2Na-Suc were fed to the rats for 8 weeks without prior BBN treatment. Induction of simple hyperplasia as observed by light microscopy, was greater in rats fed 2Na-Suc than Na-Suc. Increased 5-bromo-2'-deoxyuridine labeling index and alterations of the urothelial surface observed by scanning electron microscopy of the urinary bladder were similarly greater in rats fed 2Na-Suc compared to Na-Suc. In addition, there was a tendency toward increased spermidine/spermine N1-acetyltransferase activity in the urinary bladder epithelium of rats fed 5% 2Na-Suc. The results of Experiment 2 corresponded to differences in promoting activity for the different chemicals in Experiment 1. Thus, tumor growth was associated with sodium ion concentration level under conditions of equal increase of urinary pH.

Levels of urinary polyamines in patients with rheumatoid arthritis

OBJECTIVE

To compare urinary polyamine levels in patients with rheumatoid arthritis (RA), with osteoarthritis (OA), and in healthy controls and examine the relationship between urinary polyamine levels and several disease variables in patients with RA.

METHODS

We determined the concentrations of urinary polyamines in 33 patients with RA, 24 with OA, and 20 healthy controls, using the enzymatic assay method. For patients with RA relevant clinical and laboratory variables were obtained and functional and radiologic scores determined for the joints.

RESULTS

Urinary polyamine levels were significantly higher in patients with RA versus those with OA and healthy controls. In patients with RA the levels of urinary polyamines correlated significantly with the concentrations of serum C-reactive protein (CRP); there was also a statistically significant negative correlation between their urinary polyamine levels and average grip strength in either hand. Moreover, the levels of urinary polyamines in patients with RA showed an increase in proportion to the degree of joint functional damage and radiologic progression.

CONCLUSION

Our results confirm our previous report of an increase in the amount of free putrescine in synovial fluids and a significant correlation between the putrescine contents of synovial tissues and the serum CRP concentrations in patients with RA; they also suggest that urinary polyamine levels may be related to the activity and progression of RA, indicating that polyamine may play an important role in RA.

The effect of hepatic ischemia-reperfusion on polyamine metabolism in some organs of the rat

Hepatic ischemia was produced by clamping the portal venous and hepatic arterial blood supply to the left lateral and median lobes of the rat liver. Hepatic ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SAT) activities in ischemic and nonischemic regions were increased and, respectively, peaked by 6 hr and 3 hr after 1 hr of hepatic ischemia. Hepatic putrescine contents in ischemic and nonischemic regions were increased and peaked by 6 hr. However, hepatic spermidine and spermine were not increased. an increase in ODC activity was also observed in the spleen and the kidney after 1 hr of hepatic ischemia. [3H]thymidine incorporation into DNA was observed in the liver and the spleen--however it was not observed in the kidney--after hepatic ischemia.

Increase in ornithine decarboxylase activity caused by hepatocyte growth factor in primary cultured adult rat hepatocytes

The effect of hepatocyte growth factor on ornithine decarboxylase activity was studied in primary cultured adult rat hepatocytes. Ornithine decarboxylase activity was increased 3 hr after the addition of hepatocyte growth factor and remained at a high level until 12 hr; thereafter it decreased, and it returned to the control level by 24 hr. Enzyme activity began to increase with 1 ng/ml hepatocyte growth factor and reached its maximum with 5 ng/ml hepatocyte growth factor. When insulin or epidermal growth factor was added with hepatocyte growth factor, enzyme activity was further stimulated. The level of ornithine decarboxylase messenger RNA did not increase with addition of hepatocyte growth factor. The half-time of ornithine decarboxylase activity was prolonged about twofold by hepatocyte growth factor treatment. These results suggest that hepatocyte growth factor treatment of cells enhanced ornithine decarboxylase activity posttranslationally.

Spermidine/spermine N1-acetyltransferase, a new biochemical marker for epithelial proliferation in rat bladder

We examined the activity of spermidine/spermine N1-acetyltransferase (SAT), a rate-limiting enzyme of the biodegradation of polyamines, in N-butyl-N-(4-hydroxybutyl)nitrosamine-induced transitional cell carcinoma (TCC) and melamine-induced papillomatosis of rat bladder, and compared the activity to that of ornithine decarboxylase (ODC). Both activities were higher in both lesions than in control rats. The difference between SAT and ODC activities in cancerous tissue and papillomatosis was not significant. Cells stained for proliferating cell nuclear antigen (PCNA) were abundant in papillomatosis. TCC had areas with much PCNA. The results indicated that an elevation of SAT activity occurs in both reversible and irreversible proliferation of bladder epithelium and could be important in bladder carcinogenesis.

Effect of hyperthermia and protein kinase C inhibitors on DNA synthesis and cell proliferation on Ehrlich ascites tumour cells in vitro

Effect of hyperthermia and/or protein kinase inhibitors on DNA synthesis and cell proliferation was investigated in Ehrlich ascites tumour cells in vitro. Both H-7 and H-8, potent inhibitors of protein kinase C, suppressed DNA synthesis significantly, but HA1004, an inhibitor of cAMP- and cGMP-dependent protein kinase, did not. Hyperthermia increased greatly the suppressive activity of H-7 and H-8 but not that of HA1004. H-7 also inhibited cell growth. These results suggest that the inhibition of protein kinase C enhances the suppression of DNA synthesis and the proliferation of tumour cells by hyperthermia.

Polyamine metabolism in colonic mucosa from patients with ulcerative colitis

Polyamine metabolism in mucosa both from patients in the active or remission stage of ulcerative colitis (UC) and from healthy controls was studied. In the active stage of UC, mucosal spermidine concentration was higher than in remission or in the controls, but the activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase, rate-limiting enzymes of polyamine biosynthesis, were lower. In the active stage of UC, the mucosal level of mRNA coding for ornithine decarboxylase was lower than in the remission stage of UC or in the controls. The activity of spermidine/spermine N1-acetyltransferase, the rate-limiting enzyme of polyamine degradation, was higher in the active stage of UC than in the remission stage of UC or in the controls. However, it seemed that this activity did not reflect the increase in the spermidine concentration. The results showed that the spermidine increase in the active stage of UC was not due to changes in the synthesis or degradation of polyamines; the increase may have been due to increased exogenous spermidine uptake.

Posttranslational regulation of spermidine/spermine N1-acetyltransferase with stress

The effect of stress on the activity and level of mRNA of spermidine/spermine N1-acetyltransferase (SAT), a polyamine degradation rate-limiting enzyme, was studied in Ehrlich ascites tumor cells. When the cells were treated with sodium arsenite or ethanol for 1 h at 37 degrees C, the activity of SAT increased time- and dose-dependently. Total RNA was isolated from cells treated with stress, and the relative abundance of the SAT mRNA was measured by Northern blot analysis. The amount was comparable to those in control cells. In stress-treated cells, the biological half-life of the enzyme was 48-55 min, but 27-30 min in control cells. When cells were treated with arsenite in the presence of cycloheximide, enzyme activity did not increase. In those cells, half-life of the enzyme was shorter than in the cells treated with arsenite alone. This suggests that stress-treatment of cells enhanced SAT activity posttranslationally and that some factor(s) which was synthesized de novo during the treatment of arsenite is involved in the stabilization of the enzyme.

Polyamine levels in synovial tissues and synovial fluids of patients with rheumatoid arthritis

We determined the polyamine contents of the synovial tissues from 11 patients with rheumatoid arthritis (RA), and the free putrescine levels in the synovial fluids (SF) from 10 patients with RA, 7 with osteoarthritis (OA), 5 with posttraumatic arthritis, and 3 with infectious arthritis. Putrescine levels in the synovial tissues correlated with serum C reactive protein concentration in patients with RA. Free putrescine levels in SF were significantly elevated in patients with infectious arthritis, compared with those found in RA, OA, and posttraumatic arthritis. Free putrescine levels in SF from patients with RA were significantly higher than in those with OA. Our findings suggest that polyamines may play an important role in RA.

Enhancement of spermidine/spermine N1-acetyltransferase activity by treatment with lithium chloride in Ehrlich ascites tumor cells

The activity of spermidine/spermine N1-acetyltransferase (SAT) was enhanced in Ehrlich ascites tumor cells by the addition of lithium chloride. Na+ did not affect the enzyme activity. Total RNA was isolated from cells treated with LiCl and the relative abundance of the SAT mRNA was measured by Northern blot analysis. The levels in cells treated with LiCl were comparable to those in control cells. In the treated cells, the biological half-life of SAT was approximately 20 min, which was the same as for control cells. When LiCl and H-7, a protein kinase inhibitor, were added simultaneously to culture, the elevation caused by LiCl of SAT activity was reduced. LiCl did not cause maximum enhancement of the enzyme in cells treated beforehand with a higher concentration of TPA. These results suggest that treatment of Ehrlich ascites tumor cells with LiCl enhanced SAT activity during translation, not during transcription or after translation and that the enhancement of SAT by LiCl is probably mediated by protein kinase C.

Effects of single ethanol administration on hepatic ornithine decarboxylase induction and polyamine metabolism

The effects of a single ethanol administration on ornithine decarboxylase induction, polyamine metabolism and DNA synthesis in rat liver after partial hepatectomy were studied. Ethanol given 1 hr before partial hepatectomy at the dose of 2, 3 or 5 gm/kg body wt inhibited the increase in ornithine decarboxylase activity and that in the putrescine level in the liver 4 hr after partial hepatectomy. The hepatectomy increased the amount of ornithine decarboxylase messenger RNA expressed, and this amount was unaffected by ethanol administration. Further, ethanol did not accelerate the degradation of ornithine decarboxylase 4 hr after partial hepatectomy, indicating that the inhibition of ornithine decarboxylase activity caused by ethanol was not caused by a decrease in the ornithine decarboxylase messenger RNA level or by the acceleration of ODC degradation. The single dose of ethanol inhibited [3H]thymidine incorporation into the hepatic DNA 24 hr after partial hepatectomy. The suppression of [3H]thymidine incorporation was partially reversed by the administration of putrescine. These results suggested that ethanol inhibits the increase in ornithine decarboxylase activity after transcription, suppressing the accumulation of putrescine, which prevents DNA synthesis in response to hepatectomy.

Reduction by interferon-alpha of levels of c-myc protein and DNA synthesis in a human hepatoma cell line mediated by inhibition of putrescine synthesis

Interferon-alpha inhibited increases in ornithine decarboxylase, intracellular putrescine, and DNA synthesis as human hepatoma cells were stimulated to grow. Interferon-alpha inhibited the increase in the c-myc protein level, but not its mRNA level. Added putrescine abrogated the effects on c-myc protein and DNA synthesis. Interferon-alpha seemed to inhibit the increase in the c-myc protein level post-transcriptionally by reducing the putrescine level, inhibiting DNA synthesis.

Differential effects of cyclosporine A on ornithine decarboxylase activity induced by ultraviolet-B and PUVA in mouse skin

The inhibitory effect of cyclosporine A (CsA) on the activity of ornithine decarboxylase (ODC) induced by phorbol ester tumor promoter has been reported. In the present study, the effects of CsA on ODC activity induced by ultraviolet-B (UV-B) and PUVA in the skin of the SKH/hr 1 hairless mouse were investigated. Topical application of CsA (1.7 mumol) to the dorsal skin irradiated with 50 mJ/cm2 UV-B did not remarkably change ODC activity. On the other hand, if CsA was applied simultaneously with 3 J/cm2 UV-A 1 h after treatment with 0.3% 8-methoxypsoralen, PUVA-induced ODC activity was suppressed by about 60% at 12 and 24 h after UV-A irradiation. In the dot blotting analysis of ODC-specific mRNA level, a significant but slight decrease in ODC mRNA level (about 20% inhibition) was observed in the PUVA-treated group compared with the control group (vehicle and UV-A). The inhibition of PUVA-induced ODC activity by CsA may have been caused in part by the decrease in ODC mRNA level and in part by a post-transcriptional regulation mechanism.

Effects of parathyroid hormone on ornithine decarboxylase activity in human osteosarcoma cells

Ornithine decarboxylase (ODC) is a rate-limiting enzyme of the biosynthesis of polyamines, which are important in cell growth and differentiation. Here, we studied whether parathyroid hormone (PTH) affects the induction of ODC and the proliferation of the human osteoblast-like cell line SaOS2, which is sensitive to PTH. In confluent cells, ODC activity was not detected, but activity was significantly induced by fresh medium, with maximum activity 6 h after the change. PTH potentiated this enzyme induction in a dose-dependent manner at 10(-9) and 10(-8) M at which range the intracellular cAMP level also rose. Dibutyryl cAMP, cholera toxin, and 3-isobutyl-1-methylxanthine each caused an increase in ODC activity similar to that with PTH. The half-life of enzyme activity was about 30 min and was not changed by the addition of PTH. mRNA coding for ODC was detected in the confluent cells and its concentration was increased two- to threefold by the fresh medium. No further increase in mRNA occurred when PTH was added. At 48 h after the change of medium, PTH inhibited the DNA synthesis induced by fresh medium. These results suggest that the increase in ODC activity caused by PTH was caused by enhancement of cAMP synthesis, and that this augmentation involves post-transcriptional regulation.

Role of putrescine in interleukin 1 beta production in human histiocytic lymphoma cell line U937

Treatment with 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and incubation with lipopolysaccharide (LPS) induces interleukin 1 beta (IL-1 beta) production in the histiocytic lymphoma cell line U937. Here we investigated the effect of treatment with both TPA and 1 alpha, 25-dihydroxyvitamin D3 (1,25(OH)2D3) on LPS-induced IL-1 beta production in U937 cells. To clarify the mechanism of IL-1 beta production, the possible role of polyamines in this process was examined. Combined treatment with TPA and 1,25(OH)2D3 for 72 h followed by incubation with LPS for 24 h caused synergistic induction of both IL-1 beta release and mRNA expression. On the other hand, TPA increased the numbers of vitamin D3 receptors, which may be one mechanism of this synergistic induction. Ornithine decarboxylase (ODC), a rate-limiting enzyme for polyamine biosynthesis, was also induced by these compounds biphasically: the first peak of ODC activity was observed at 4 h of the incubation with the two compounds and the second peak was at 4 h after the addition of LPS. To find whether these peaks were related to IL-1 beta production, DL-alpha-difluoromethylornithine (DFMO), a specific irreversible inhibitor of ODC, was added together with TPA and 1,25(OH)2D3. DFMO decreased the cellular levels of putrescine and spermidine and suppressed IL-1 beta release and IL-1 beta mRNA expression by 65%. Exogenous putrescine, but not spermidine, abrogated these kinds of inhibition. Similar results were obtained with DFMO and the polyamines during the differentiation of the cells up to the monocyte or macrophage stage. These results thus suggest that changes in either of these intracellular polyamines, especially putrescine, help to regulate the differentiation of U937 cells, resulting in partial control of the regulation of IL-1 beta production.