Ornithine Decarboxylase mRNA Levels Research Articles

Polyamine- and insulin-like growth factor-I-mediated proliferation of porcine uterine endometrial cells: a potential role for spermidine/spermine N(1)-acetyltransferase during peri-implantation.

Insulin-like growth factor-I (IGF-I) and the polyamine catabolic enzyme spermidine/spermine N(1)-acetyltransferase (SSAT) are progesterone-regulated genes with maximal expression at peri-implantation in the porcine uterine endometrium. However, while IGF-I stimulates cell proliferation, SSAT, by acetylating the naturally occurring polyamines (PA) spermine (SPM) and spermidine (SPD), typically functions as a cell growth inhibitor. The present study examined the functional relationships of IGF-I, SSAT, and PA in the control of endometrial cell proliferation. Northern blot analysis indicated that SSAT mRNA levels change with distinct pregnancy stages, in contrast to those for the PA biosynthetic enzyme ornithine decarboxylase (ODC). Primary cultures of luminal and glandular epithelial (LE, GE) and stromal (ST) cells isolated from Day 12 pregnant pig endometrium had IGF-I mRNA levels for ST > LE > GE cells. The mRNA levels for SSAT and ODC were transiently diminished by IGF-I treatment, but only in GE cells. By contrast, SPM and SPD increased SSAT mRNA levels in GE and ST cells, but increased ODC mRNA levels only in GE cells. IGF-I, putrescine (PUT), and SPM individually increased cellular DNA synthesis as measured by tritiated thymidine incorporation in GE and ST cells, while SPD had an effect only in ST cells. IGF-I enhanced the proliferative effect of each PA in GE cells, but only of SPD in ST cells. The mitogen-activated protein kinase inhibitor, PD98059, inhibited the induction by SPM of GE cell DNA synthesis but not that of IGF-I. Wortmannin, a phosphatidylinositol-3-kinase inhibitor had no effect on either IGF-I or SPM induction of GE cell DNA synthesis. The relative concentrations of SPM, SPD, and PUT in uterine luminal fluids differed, with the levels for each PA higher at pregnancy Day 12 than at 11.5. These results suggest that IGF-I and PA act through distinct signaling pathways to mediate cell-type-specific growth of early pregnancy pig uterine endometrium. Further, SSAT, through its control of intracellular PA levels, likely plays a modulatory role in the establishment of an optimal uterine environment for successful embryo attachment.

The suppression of ornithine decarboxylase expression and cell proliferation at the promotion stage of lung tumorigenesis in mice by α-tocopheryloxybutyric acid

It is known that vitamin E inhibits tumor cell growth in vitro irrespective of its antioxidative effect. However, it is unclear whether the effect in vitro can be applied to the in vivo situation. In order to address this question, we estimated if α-tocopheryloxybutyric acid (TSE), a non-antioxidative vitamin E derivative in vivo, could inhibit cell proliferation during the tumorigenic process of lung in mice treated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), the most potent carcinogen among tobacco-specific nitrosamines. TSE administration suppressed the labeling index of the proliferating cell nuclear antigen, a marker of cell proliferation at a promotion phase of NNK-induced lung tumorigenesis in mice. Similarly, TSE administration inhibited the elevation of ornithine decarboxylase (ODC) activity and its mRNA at the promotion phase. Of four transcription factors contributing to ODC induction, the change in the level of the c-Myc/Max–consensus oligonucleotide complex was only proportional to the change in ODC mRNA level. These results suggest that vitamin E can inhibit cell proliferation linked with ODC induction at the promotion phase of lung tumorigenesis irrespective of its antioxidative effect and that modulation of the transactivation of the c-Myc/Max complex for the ODC gene by TSE in part contributes to the suppression of ODC induction.

Cross-talk between steroid-receptor-mediated and cell-membrane-receptor-mediated signalling pathways results in the in vivo modulation of c-Met and ornithine decarboxylase gene expression in mouse kidney.

The cross-talk in vivo between two signalling pathways activated by testosterone via intracellular androgen receptor, and induced by damage to renal tubules evoked by anti-folate [N(10)-propargyl-5,8-dideazafolic acid (CB 3717)] or folate is reported. We show that CB 3717/folate induces the expression of the hepatocyte growth factor (HGF)/c-Met signalling system in injured kidneys in which a significant, but transient, elevation of the HGF mRNA level occurs. It is followed by a severalfold increase in the c-Met transmembrane receptor message that persists for up to 24 h. The c-Met expression is also positively controlled by testosterone, which induces a significant increase in its mRNA level that is abolished by an anti-androgen, casodex. However, when testosterone and anti-folate/folate are administered sequentially, a substantial (3.5-4.0-fold) decrease in the increase of c-Met expression caused by CB 3717/folate alone occurs. Similarly, testosterone-induced ornithine decarboxylase (ODC) mRNA level and activity are decreased 2.8-7.7-fold when the androgen is applied together with CB 3717. Antagonism between these pathways is also visible under physiological conditions in the kidneys of male mice in which, owing to elevated endogenous testosterone levels, neither the ODC activity nor the mRNA level is induced by anti-folate/folate, whereas the c-Met message response to these drugs is significantly decreased. Our results document a substantial negative regulation of c-Met and ODC gene expression as a result of the cross-talk between testosterone-activated and HGF-activated pathways and suggest a sex-differentiated response to injury of mouse kidneys.

Cross-talk between steroid-receptor-mediated and cell-membrane-receptor-mediated signalling pathways results in the in vivo modulation of c-Met and ornithine decarboxylase gene expression in mouse kidney

The cross-talk in vivo between two signalling pathways activated by testosterone via intracellular androgen receptor, and induced by damage to renal tubules evoked by anti-folate [N10-propargyl-5,8-dideazafolic acid (CB 3717)] or folate is reported. We show that CB 3717/folate induces the expression of the hepatocyte growth factor (HGF)/c-Met signalling system in injured kidneys in which a significant, but transient, elevation of the HGF mRNA level occurs. It is followed by a severalfold increase in the c-Met transmembrane receptor message that persists for up to 24h. The c-Met expression is also positively controlled by testosterone, which induces a significant increase in its mRNA level that is abolished by an anti-androgen, casodex. However, when testosterone and anti-folate/folate are administered sequentially, a substantial (3.5Ő4.0-fold) decrease in the increase of c-Met expression caused by CB 3717/folate alone occurs. Similarly, testosterone-induced ornithine decarboxylase (ODC) mRNA level and activity are decreased 2.8Ő7.7-fold when the androgen is applied together with CB 3717. Antagonism between these pathways is also visible under physiological conditions in the kidneys of male mice in which, owing to elevated endogenous testosterone levels, neither the ODC activity nor the mRNA level is induced by anti-folate/folate, whereas the c-Met message response to these drugs is significantly decreased. Our results document a substantial negative regulation of c-Met and ODC gene expression as a result of the cross-talk between testosterone-activated and HGF-activated pathways and suggest a sex-differentiated response to injury of mouse kidneys.

ODC mRNA as a prognostic factor for predicting recurrence in meningiomas.

In proliferating neoplastic cells, activity of the enzyme ornithine decarboxylase (ODC) increases. Among other brain tumors, ODC activation could also be observed in meningiomas. In the present study, we have investigated ODC gene expression in primary and recurrent meningiomas at the transcriptional level. ODC mRNA (messenger ribonucleic acid), ODC activity, number of mitoses, and Ki-67 index as a marker for nuclear proliferation were quantified in three different groups of meningiomas: tumors without recurrence in a 8.4 years median follow-up period, tumors with recurrence within a median follow-up of 3.0 years, and their corresponding recurrent tumors. ODC mRNA level was significantly higher in meningiomas with later recurrence as compared to meningiomas without recurrence (p < or = 0.01), whereas it declined in the recurrences of the second group (p < or = 0.001). In contrast, ODC activity showed no difference between the two groups of primary tumors, but a significant increase of enzyme activity could be observed in the recurrences as compared to the correponding primary tumors (p < or = 0.001). Likewise, an increase of the Ki-67 index could be detected in the recurrent group (p < or = 0.001). These results suggest that ODC mRNA may represent a prognostic factor for predicting recurrence in meningiomas.

Ornithine decarboxylase activity and its gene expression are increased in benign hyperplastic prostate.

Ornithine decarboxylase (ODC) is the first key enzyme in the polyamine biosynthesis pathway. Polyamine is believed to participate in cellular proliferation and differentiation. To study the relationship between ODC and the pathogenesis of benign prostatic hyperplasia (BPH), the polyamine levels, ODC activities, and expression of ODC mRNA in benign hyperplastic and normal human prostates were assayed. Polyamine contents and ODC activities in tissue extracts were determined by reverse-phase high-performance liquid chromatography and spectrophotometric procedures, respectively. The ODC mRNA levels were assayed by Northern blot analysis. The contents of putrescine, spermidine, and spermine in BPH tissues were 2.2, 3.4, and 6.0 times higher than those in normal tissues, respectively; the ODC activity of BPH tissue was about 3.2 times higher than in normal tissue; the expression level of ODC mRNA in the BPH tissues was greater than that of normal tissues. The findings imply that 1) the increased ODC activity and polyamine content in prostatic tissue may correlate with the pathogenesis of BPH, and 2) the high level of ODC activity is induced by the overexpression of ODC mRNA.

Dietary induction of ornithine decarboxylase in male mouse kidney

In male mouse kidney, ornithine decarboxylase (ODC) is induced after feeding, and the induction depends on dietary protein content. 24 h after feeding with 50% casein-containing meal, ODC activity and amount of immunoreactive ODC protein increased more than 10-fold, ODC mRNA level increased 2-fold, and the ODC half-life extended 7-fold. The renal ODC induction after feeding is, therefore, due mainly to stabilization of ODC protein. Urinary excretion of putrescine increased in response to the ODC induction, but the renal polyamine contents scarcely changed. Consistently, the level of antizyme, a polyamine-inducible protein, determined as the ODC–antizyme complex level, scarcely changed after feeding, and the antizyme/ODC ratio in the kidney largely decreased, resulting in the stabilization of ODC protein. The present results suggest that the strong excretion system of the kidney for newly synthesized polyamines enables renal ODC escape from antizyme-mediated feedback regulation.

Antiproliferative Effect of IL-1 Is Mediated by p38 Mitogen-Activated Protein Kinase in Human Melanoma Cell A375

The role of p38 mitogen-activated protein kinase (MAPK) in IL-1-induced growth inhibition was investigated using IL-1-sensitive human melanoma A375-C2-1 cells and IL-1-resistant A375-R8 cells. In both cells, p38 MAPK was activated by IL-1. A selective inhibitor for p38 MAPK, SB203580, almost completely recovered the IL-1-induced growth inhibition in A375-C2-1 cells. IL-1-induced IL-6 production was also suppressed by SB203580. However, the reversal effect of SB203580 was not due to the suppression of IL-6 production because the SB203580 effect was still observed in the presence of exogenous IL-6. Down-regulation of ornithine decarboxylase (ODC) activity as well as its protein level has been shown to be essential for IL-1-induced growth inhibition. SB203580 also reversed the IL-1-induced down-regulation of ODC activity and intracellular polyamine levels without affecting ODC mRNA levels in A375-C2-1 cells. In IL-1-resistant R8 cells, however, IL-1 only slightly suppressed ODC activity. In A375-C2-1 cells, the mRNA expression level of antizyme (AZ), a regulatory factor of ODC activity, has been shown to be up-regulated by IL-1. IL-1-induced up-regulation of AZ mRNA level was not affected by SB203580. These findings demonstrate that p38 MAPK plays an important role in IL-1-induced growth inhibition in A375 cells through down-regulating ODC activity without affecting the level of ODC mRNA and AZ mRNA. In IL-1-resistant A375-R8 cells, IL-1 signaling pathway is deficient between p38 MAPK activation and down-regulation of ODC activity.

Early alterations of polyamine metabolism induced after acute administration of clenbuterol in mouse heart

An acute treatment of mice with clenbuterol, a β-adrenergic agonist, produced a marked increase of polyamines levels in heart, particularly during the early phase of administration of the drug. A single dose of 1.5 mg/kg caused as much as a 10 fold induction in activity of ornithine decarboxylase (ODC) and 3 to 4 fold increase in levels of putrescine, spermidine and spermine in mouse heart. Maximum changes were observed 3 to 4 hours post-administration of clenbuterol. This treatment did not produce any change in S-adenosylmethionine decarboxylase activity. The induction of cardiac ODC by clenbuterol was also dose dependent with a peak at about 5 μmol/kg. Co-administration of difluoromethylornithine, an irreversible inhibitor of ODC, or propranolol, a nonspecific β-antagonist, with clenbuterol completely prevented the induction of ODC activity as well as the increase in polyamine levels in heart. However, pretreatment with alprenolol or metoprolol, the specific β 1 and β 2-antagonists, respectively, produced only partial prevention. The cardiac ODC from controls as well as clenbuterol treated mice exhibited similar affinity (Km) for its substrate, ornithine, while maximum enzyme activity (Vmax) was about 14 fold higher in clenbuterol treated mouse heart than in the control. Clenbuterol produced no change in the level of specific ODC mRNA or the protein, but the enzyme from the drug-treated mouse heart was considerably more stable than the control. Pretreatment of mice with either cycloheximide or actinomycin D followed by administration of clenbuterol could not prevent the induction in ODC activity suggesting that de novo biosynthesis of the enzyme protein or ODC mRNA was not responsible for induction of ODC activity. Post-translational changes in ODC may be responsible for an early increase of ODC activity due to clenbuterol treatment.

Ornithine Decarboxylase Is a Transcriptional Target of Tumor Suppressor WT1

The product of the Wilm's tumor suppressor gene, WT1, is a zinc-finger DNA-binding protein, which is thought to be a transcription factor. Two genes, those encoding epidermal growth factor receptor and syndecan-1, are known to be endogenous targets of WT1. Previous studies had identified binding sites for WT1 in the promoter of the ornithine decarboxylase (ODC) gene. In this paper, we tested whether the endogenous ODC gene might be a target of WT1 by establishing lines of baby hamster kidney (BHK) cells that expressed WT1 isoform A under control of a tetracycline-regulated expression system. When expression of WT1 was activated in BHK cells, the cellular level of ODC mRNA declined, with kinetics that correlated with the increase in WT1 level, demonstrating that the endogenous ODC gene was indeed responsive to cellular level of WT1. WT1 isoforms A and B inhibited the activity of the ODC promoter by approximately fivefold in transiently transfected BHK cells, while isoforms C and D, which have altered DNA binding domains, had no significant effect. The sequence CTCCCCCGC, located at nucleotides −106 to −98 relative to the site of transcriptional initiation in the ODC gene, interacted with the zinc-finger domain of isoforms A and B of WT1 with high affinity and specificity. A mutation in the binding site that disrupted this interaction partially removed the inhibition of ODC promoter activity by WT1, as did mutation of the two E-box sequences in intron I of the ODC gene. Simultaneous mutation of the WT1-binding motif and the two E-boxes completely abolished inhibition by WT1 of ODC promoter activity. These results, taken together, implicate the ODC gene as a downstream target of the tumor suppressor WT1.

Synergistic induction of ornithine decarboxylase by asparagine and gut peptides in intestinal crypt cells.

The objective of this study was to determine whether the amino acid asparagine stimulated the activity of ornithine decarboxylase (ODC) synergistically with epidermal growth factor (EGF) or gastrin in IEC-6 cells, a line of normal rat small intestinal crypt cells. Cells were grown in DMEM containing 5% dialyzed fetal bovine serum, and serum was deprived for 24 h before experiments. Exposure to EGF or gastrin alone increased ODC activity 4.5- to 6-fold. Asparagine alone increased the enzyme activity 10- to 13-fold in IEC-6 cells. Simultaneous addition of asparagine and EGF or gastrin, however, increased ODC activity more than 40-fold. In contrast, there was no synergistic induction of ODC activity when gastrin and EGF were added together. Increased ODC activity in cells treated with asparagine and EGF or gastrin was associated with an increase in ODC mRNA and protein levels. The rate of transcription of the ODC gene was significantly increased by exposure to EGF or gastrin. Asparagine alone had little or no effect on the rate of transcription of the ODC gene. When given together with EGF or gastrin, asparagine also had no additional effect on the transcription rate of the ODC gene. The half-life of mRNA for ODC in unstimulated IEC-6 cells was approximately 30 min and increased to more than 2 h in cells exposed to asparagine, although neither gastrin nor EGF prolonged the stability of ODC mRNA. The half-life of mRNA for ODC after combined addition of asparagine and EGF or gastrin was extended to approximately 2 h, similar to asparagine alone. Combined addition of asparagine and EGF or gastrin also significantly increased DNA synthesis compared with cells exposed to each of the three agents alone. In conclusion, 1) simultaneous addition of asparagine and EGF or gastrin increases ODC activity in a synergistic manner and 2) asparagine increases ODC mRNA levels through completely distinct mechanisms from EGF or gastrin. EGF or gastrin specifically stimulates transcription of the ODC gene, whereas asparagine affects a posttranscriptional process.

Differences in transglutaminase mRNA after polyamine depletion in two cell lines.

Polyamines serve as natural substrates for the transglutaminase that catalyzes covalent cross-linking of proteins and is involved in cellular adhesion and proliferation. This study tests the hypothesis that intracellular polyamines play a role in the regulation of transglutaminase expression in rat small intestinal crypt cells (IEC-6 cell line) and human colon carcinoma cells (Caco-2 cell line). Treatment with alpha-difluoromethylornithine (DFMO; a specific inhibitor of polyamine synthesis) significantly depleted the cellular polyamines putrescine, spermidine, and spermine in both cell lines. In IEC-6 cells, polyamine depletion was associated with a decrease in the levels of transglutaminase mRNA. In Caco-2 cells, however, polyamine depletion significantly increased the levels of transglutaminase mRNA and enzyme activity. In both cell lines, ornithine decarboxylase mRNA levels increased and protooncogene c-myc mRNA decreased in the presence of DFMO. Addition of polyamines to cells treated with DFMO reversed the effect of DFMO on the levels of mRNA for these genes in both lines. There was no significant change in the stability of transglutaminase mRNA between control and DFMO-treated IEC-6 cells. In contrast, the half-life of mRNA for transglutaminase in Caco-2 cells was dramatically increased after polyamine depletion. Spermidine, when given together with DFMO, completely prevented increased half-life of transglutaminase mRNA in Caco-2 cells. These results indicate that 1) expression of transglutaminase requires polyamines in IEC-6 cells but is inhibited by these agents in Caco-2 cells, 2) polyamines modulate transglutaminase expression at the level of mRNA through different pathways in these two cell lines, and 3) posttranscriptional regulation plays a major role in the induction of transglutaminase mRNA in polyamine-deficient Caco-2 cells.

Modulation of the induction of ornithine decarboxylase by some opioid receptor agonists in immune cells and cardiomyocytes.

The ability of natural and synthetic opioids to modulate the induction of ornithine decarboxylase (ODC) was investigated in immune cells and cardiomyocytes in culture. In particular, Leu-enkephalin, which shows preference for delta-receptors, enhanced ODC activity in both thymocytes and cardiomyocytes, whereas the effect of U-50488H, a synthetic kappa-selective agonist, was cell-specific. In thymocytes, U-50488H markedly inhibited the induction of the enzyme elicited by the mitogen concanavalin A (Con A) or by a combined treatment with PMA and A23187, and also reduced basal ODC activity. However the drug did not affect ODC induced by other stimuli. The inhibition of the induction of ODC activity was accompanied by a reduction of ODC mRNA level and an acceleration of ODC turnover. The action of U-50488H in thymocytes does not appear to be mediated by kappa or other classical opioid receptors lacking both stereospecificity and antagonist sensitivity, but may involve a pertussis toxin-sensitive G protein. Splenocytes also showed the ODC inhibiting effect of U-50488H, although they were less sensitive compared to thymocytes. In contrast, U-50488H enhanced ODC activity in cardiomyocytes and this effect was blocked by a specific kappa-antagonist. In conclusion, these results indicate that some opioid agonists can modulate ODC expression in non neural cells. In particular, kappa-opioid receptors may be involved in the U-50488H action in cardiomyocytes, and a distinct site, linked to inhibition of cell proliferation, may operate in immune cells.

Anti-IgM-Induced Growth Inhibition and Apoptosis Are Independent of Ornithine Decarboxylase in Ramos Cells

Ornithine decarboxylase (ODC) is a key enzyme involved in polyamine production and is thought to regulate growth and apoptosis in multiple cell systems. A potential link between ODC and growth may involve the action of an oncogene c-mycwhich is thought to transcriptionally regulate ODC. We have examined the involvement of ODC in anti-IgM-induced growth inhibition and apoptosis in Burkitt's lymphoma cells. Inhibitors of ODC such as difluoromethylornithine (DFMO) completely blocked ODC activity, resulting in growth inhibition but not apoptosis. Addition of putrescine, the product of ODC enzymatic action, to Ramos cells had only a minor effect on growth, did not cause apoptosis, did not augment or block anti-IgM-mediated growth inhibition and apoptosis, but did reverse DFMO-mediated growth inhibition. Anti-IgM treatment of Ramos cells, which markedly decreased c-mycmRNA and protein, caused a paradoxical increase in ODC mRNA level as well as ODC enzymatic activity and increased cellular levels of putrescine. DFMO and putrescine did not alter c-mycmRNA levels directly, nor did they have any affects on anti-IgM-mediated down-regulation of c-mycmRNA. TNF-α, which inhibited anti-IgM-mediated apoptosis, did not inhibit either anti-IgM or DFMO-mediated inhibition of growth. These agents were without effect on ODC activity itself or on the anti-IgM-mediated increase in ODC activity. From these studies we conclude that ODC inhibition affects growth but is unrelated to the induction of apoptosis. Both anti-IgM-mediated inhibition of growth and induction of apoptosis are independent of ODC. Thus two distinct pathways for growth regulation are present: one in which ODC and polyamines are important and the other cell surface receptor-mediated (sIg) which is independent of ODC and polyamines.

Effects of Ethanol on Rat Sertoli Cell Function: Studies In Vitro and In Vivo

Chronic alcohol administration to male animals is associated with testicular atrophy and gonadal failure. The Sertoli cell seems to be the first testicular cell injured as a result of alcohol exposure. To investigate the adverse effects of ethanol on testicular and particularly Sertoli cell function, the consequences of in vivo and in vitro ethanol exposure on rat Sertoli cell mRNA and protein levels of transferrin and ornithine decarboxylase were investigated. In vivo, ethanol exposure enhanced the levels of both hepatic and testicular (Sertoli cell) transferrin protein and mRNA. Ethanol exposure also enhanced testicular, but not hepatic, levels of ornithine decarboxylase protein and mRNA. These in vivo findings were confirmed when isolated Sertoli cells were studied in vitro. Specifically, ethanol exposure increased Sertoli cell transferrin protein and mRNA levels. Ethanol exposure increased Sertoli cell ornithine decarboxylase mRNA and protein when cultured in serum-free media, but not when cultured in the presence of serum. These studies demonstrate that ethanol exposure of rat Sertoli cells is associated with alterations in the levels of mRNA and protein that are known to be important in the process of spermatogenesis. These findings add to the body of evidence that suggests that, within the testes, the Sertoli cell may be an important target for ethanol-induced gonadal injury.

Phosphatidylinositol 3-Kinase Is Required for the Induction of Ornithine Decarboxylase in Leukemia Cells Stimulated to Growth

The involvement of phosphatidylinositol 3-kinase (PI3K) in the induction of ornithine decarboxylase (ODC) was investigated by using specific PI3K inhibitors. In difluoromethylornithine-resistant L1210 cells stimulated to growth from quiescence, treatment with LY294002 inhibited cell growth and provoked a complete block of the induction of ODC activity (IC50∼2 μM) and ODC protein. Some reduction in the accumulation of ODC mRNA was also observed, whereas ODC turnover was not affected significantly. Wortmannin, another specific inhibitor of PI3K, structurally unrelated to LY294002, also inhibited ODC induction with an IC50of about 10 nM. These results indicate that PI3K activity is required for the induction of ODC, possibly affecting both ODC mRNA level and translation. Since p70 S6 kinase (p70S6K) is considered an important mediator of PI3K action in several experimental systems, the effect of rapamycin, which can lead to selective inhibition of p70S6K, was also investigated. Rapamycin inhibited p70S6Kactivity and produced ODC inhibiting effects similar to those elicited by LY294002. However, LY294002 and wortmannin at concentrations which inhibited almost completely PI3K activity did not decrease p70S6Kactivity, suggesting that p70S6Kdoes not mediate the PI3K effects on ODC, but may lie on a separate pathway in this experimental model.

Effects of eicosanoids on lipopolysaccharide-induced ornithine decarboxylase activity and polyamine metabolism in the mouse liver

Background/Aims: During endotoxic shock, arachidonic acid is released from the inflammatory cell membranes and is metabolized to form eicosanoids, which modify the deleterious effects of lipopolysaccharide (LPS) on liver function, However, it is not known which protaglandins (PGs) or leukotrienes (LTs) are produced or how they affect the LPS-treated liver. As LPS treatment elevates hepatic ornithine decarboxylase (ODC) activity and affects the polyamine levels of the mouse liver, this study was carried out to examine the effects of eicosanoids and their inhibitors on the induction of ODC activity and polyamine levels in the LPS-treated mouse liver.Methods: LPS in the presence or absence of other drugs was intraperitoneally administered to 6-week-old mice and the livers were then removed. The hepatic ODC activity, polyamine levels, and level of ODC mRNA were determined.Results: The levels of LPS-induced ODC activity, the putrescine (PUT) and N1-acetylspermidine (A-SPD) were reduced by the administration of PGE1. ODC activity was enhanced by the administration of corticosteron, AA-2414 (an antagonist of thromboxane (TX) A2) and TXB2, whereas the A-SPD level was reduced by corticosterone and AA-2414 treatment. The level of ODC mRNA changed in parallel with the change in OdC activity.Conclusions: PGE1 may reduce the LPS-induced production of inflammation-accelerating cytokines and reduce the level of ODC activation. Corticosterone and AA-2414 treatment may attenuate the LPS-induced production of eicosanoids, and enhance the LPS-induced ODC activation. It is possible that the eicosanoids produced by LPS treatment inhibit ODC activation during endotoxic shock.

Central administration of morphine inhibits brain and liver ornithine decarboxylase activity in neonatal rats: Involvement of transcription- and non-transcription-dependent mechanisms

This study examined whether the developmental deficits usually observed in infants born to opiate addicted mothers could involve effects on ornithine decarboxylase, a growth-controlling enzyme. Intracerebroventricular (i.c.v.) injection of a single dose of morphine (2 μg) to 6-day-old rats markedly decreased basal brain and liver ornithine decarboxylase activity as well as the increases in hepatic ornithine decarboxylase activity produced by subcutaneously (s.c.) administered insulin, an important trophic hormone. Centrally applied morphine acts supraspinally to downregulate peripheral ornithine decarboxylase activity, since s.c. administration of the same dose as used i.c.v. decreased neither basal liver ornithine decarboxylase levels nor tissue responsiveness to insulin. This does not imply that the opiate is unable to affect ornithine decarboxylase when applied systemically. In fact, a robust inhibition of both basal and induced liver ornithine decarboxylase activity was obtained in rat pups given 20 μg of morphine s.c. This larger dose is able to trigger the hepatic ornithine decarboxylase effects presumably by stimulating opiate receptors located at central sites after crossing the blood–brain barrier and penetrating into the brain. Concomitant administration of naloxone plus morphine i.c.v. prevented morphine from downregulating ornithine decarboxylase activity, confirming the participation of supraspinal opioid receptors in morphine ornithine decarboxylase actions. Finally, as was the case for insulin induced stimulation of ornithine decarboxylase activity, i.c.v. injection of morphine markedly diminished insulin induced stimulation of hepatic ornithine decarboxylase mRNA accumulation. In turn, contrary to the inhibition of basal ornithine decarboxylase activity, morphine did not lower basal hepatic ornithine decarboxylase mRNA levels when given alone. Thus, CNS morphine can apparently suppress tissue ornithine decarboxylase expression through both transcriptional and posttranscriptional mechanisms. The evidence obtained suggest that postnatal exposure to opiate drugs might detrimentally affect development by altering normal tissue ornithine decarboxylase ontogeny.

Catecholamines are required for androgen-induced ODC expression but not for hypertrophy of mouse kidney

Catecholamine depletion, evoked by reserpine, dramatically impaired (5-fold) the testosterone-induced increase of ornithine decarboxylase (ODC) activity in female mouse kidney. However, reserpine did not prevent kidney hypertrophy evoked by testosterone. This is evidenced by the activity of sensitive, biochemical markers of renal hypertrophy, namely arginase and ornithine aminotransferase (OAT), that responded with the increase and decrease of activities to testosterone treatment, respectively [1]. Arginine and ornithine, substrates and/or products of marker enzymes, showed a striking homeostasis as their level was not affected by testosterone and reserpine, and only slightly by DFMO. Northern blot analysis revealed that the ODC mRNA level, that was increased 10-fold by testosterone, was decreased 2-fold in catecholamine-depleted hypertrophic kidney. Thus, ODC transcript level, lowered by reserpine, correlated partially with an attenuated response of ODC activity to testosterone. This was in contrast to DFMO, which inhibited ODC activity, but significantly increased its mRNA content. It is concluded that catecholamines could be involved together with testosterone in regulation of the ODC gene expression in mouse kidney. © 1997 Elsevier Science B.V. All rights reserved.

Interleukin-1-induced Growth Inhibition of Human Melanoma Cells: INTERLEUKIN-1-INDUCED ANTIZYME EXPRESSION IS RESPONSIBLE FOR ORNITHINE DECARBOXYLASE ACTIVITY DOWN-REGULATION

Interleukin (IL)-1 is a multi-functional cytokine and regulates cell growth either positively or negatively. Previous studies have shown that IL-1-induced ornithine decarboxylase (ODC) activity down-regulation is involved in the anti-proliferative effect of IL-1 on human A375 melanoma cells. In this study, we examined the IL-1alpha-induced molecular events resulting in ODC activity down-regulation in C2-1, a A375 cell line stably transfected with human type I IL-1 receptor. Recombinant human (rh) IL-1alpha inhibited the growth and down-regulated the ODC activity of C2-1 cells in a dose-dependent manner. Kinetics studies showed that both the DNA synthesis and ODC activity of C2-1 cells progressively decreased from 12 h after IL-1 addition. Northern hybridization showed that IL-1 had no influence on ODC mRNA level. However, rhIL-1 induced both a decrease of ODC protein and an ODC-inhibiting activity in IL-1-treated C2-1 cells. IL-1 specifically up-modulated the mRNA level of antizyme, a protein essential for ODC regulation, but had little effect on its stability. IL-1-induced antizyme up-modulation preceded IL-1-induced down-regulation of ODC protein, ODC activity, and DNA synthesis in C2-1 cells. Run-on transcription analysis confirmed that the increased antizyme mRNA expression was due to elevated antizyme gene transcription. Furthermore, the action of IL-1 to inhibit the ODC activity and growth of C2-1 cells was blocked by expressing the antisense RNA of human antizyme in C2-1 cells. These results suggest that IL-1-induced antizyme expression is responsible for IL-1-induced ODC activity down-regulation in human melanoma cells.