Reduction Of Ornithine Decarboxylase Activity Research Articles

Changes in amino acid decarboxylation in maize (Zea mays; Poaceae) tissues in response to bird cherry-oat aphid (Rhopalosiphum padi; Aphididae) infestation

The study was focused on changes in the activities of ornithine decarboxylase (ODC), lysine decarboxylase (LDC) and tyrosine decarboxylase (TyDC) in maize seedlings infested by bird cherry-oat aphid (Rhopalosiphum padi L.).Obtained results showed that the aphid infestation induced LDC activity strongly within tissues of less aphid-settled maize (Waza cv.) during the first week of the infestation in comparison to the control plants and the activity was suppressed after two weeks. However, TyDC activity fluctuated under the aphid infestation. In relation to the control, the enzyme activity was inhibited on the first day, activated after the first week and reduced again two weeks into the experiment. A significant reduction in ODC activity was also observed in seedlings of aphid-infested maize Waza cv. during the first week. In a more susceptible maize cv. (Złota Karłowa), an increase in LDC and TyDC activities in relation to the control and a simultaneous decrease in ODC activity were noted after the first day of the infestation. After one week of aphid attack, TyDC activity was induced and ODC was inhibited, whereas after two weeks ODC activity was decreased with a simultaneous increase in LDC activity in the Złota Karłowa seedlings.

Developmental and polyamine metabolism alterations in Rhinella arenarum embryos exposed to the organophosphate chlorpyrifos

Organophosphorus pesticides (OPs) are widely applied in the Alto Valle of Río Negro and Neuquén, Argentina, due to intensive fruit growing. Amphibians are particularly sensitive to environmental pollution, and OPs may transiently accumulate in ponds and channels of the region during their reproductive season. Organophosphorus pesticide exposure may alter amphibian embryonic development and the reproductive success of autochthonous species. In the present study, embryos of the common toad Rhinella arenarum were employed to assess developmental alterations and to study polyamine metabolism, which is essential to normal growth, as a possible target underlying the effects of the OP chlorpyrifos. As the duration of chlorpyrifos exposure increased and embryonic development progressed, the median lethal concentration (LC50) values decreased, and the percentage of malformed embryos increased. Developmental arrest was also observed and several morphological alterations were recorded, such as incomplete and abnormal closure of the neural tube, dorsal curvature of the caudal fin, reduction of body size and caudal fin length, atrophy, and edema. An early decrease in ornithine decarboxylase (ODC) activity and polyamine levels was also observed in embryos exposed to chlorpyrifos. The decrease in polyamine contents in tail bud embryos might be a consequence of the reduction in ODC activity. The alteration of polyamine metabolism occurred before embryonic growth was interrupted and embryonic malformations were observed and may be useful as a biomarker in environmental studies.

Chemopreventive effects of pomegranate seed oil on skin tumor development in CD1 mice.

Pomegranate seed oil was investigated for possible skin cancer chemopreventive efficacy in mice. In the main experiment, two groups consisting each of 30, 4-5-week-old, female CD(1) mice were used. Both groups had skin cancer initiated with an initial topical exposure of 7,12-dimethylbenzanthracene and with biweekly promotion using 12-O-tetradecanoylphorbol 13-acetate (TPA). The experimental group was pretreated with 5% pomegranate seed oil prior to each TPA application. Tumor incidence, the number of mice containing at least one tumor, was 100% and 93%, and multiplicity, the average number of tumors per mouse, was 20.8 and 16.3 per mouse after 20 weeks of promotion in the control and pomegranate seed oil-treated groups, respectively (P <.05). In a second experiment, two groups each consisting of three CD(1) mice were used to assess the effect of pomegranate seed oil on TPA-stimulated ornithine decarboxylase (ODC) activity, an important event in skin cancer promotion. Each group received a single topical application of TPA, with the experimental group receiving a topical treatment 1 h prior with 5% pomegranate seed oil. The mice were killed 5 h later, and ODC activity was assessed by radiometric method. The experimental group showed a 17% reduction in ODC activity. Pomegranate seed oil (5%) significantly decreased (P <.05) tumor incidence, multiplicity, and TPA-induced ODC activity. Overall, the results highlight the potential of pomegranate seed oil as a safe and effective chemopreventive agent against skin cancer.

Regulation of ornithine decarboxylase and polyamine import by hypoxia in pulmonary artery endothelial cells.

In rat lung and cultured lung vascular cells, hypoxia decreases ornithine decarboxylase (ODC) activity and increases polyamine import. In this study, we used rat cultured pulmonary artery endothelial cells to explore the mechanism of hypoxia-induced reduction in ODC activity and determined whether this event was functionally related to the increase in polyamine import. Two strategies known to suppress proteasome-mediated ODC degradation, lactacystin treatment and use of cells expressing a truncated ODC incapable of interacting with the proteasome, prevented the hypoxia-induced decrease in ODC activity. Interestingly, though, cellular abundance of the 24-kDa antizyme, a known physiological accelerator of ODC degradation, was not increased by hypoxia. These observations suggest that an antizyme-independent ODC degradation pathway contributes to hypoxia-induced reductions of ODC activity. When reductions in ODC activity in hypoxia were prevented by the proteasome inhibitor strategies, hypoxia failed to increase polyamine transport. The induction of polyamine transport in hypoxic pulmonary artery endothelial cells thus seems to require decreased ODC activity as an initiating event.

Cigarette smoke extracts delay wound healing in the stomach: involvement of polyamine synthesis.

The association between cigarette smoking and peptic ulcer diseases has been well established. Ornithine decarboxylase (ODC) is crucial for the gastroprotective and mucosal growth promoting effects in gastric ulcer healing. The aim of this study is to elucidate the possible mechanism of how inhibition of ODC activity is involved in the delay of ulcer healing, if any, by cigarette smoke extracts (CSE). CSE were fractionated into chloroform extract (CE) and ethanol extract (EE). In in vivo study, rats with acetic acid-induced ulcers were given CE or EE intragastrically (2.5 or 5 mg/kg) once daily for 3 days. Ulcer sizes were significantly larger after CE or EE administration, followed by an increase in myeloperoxidase activity and a reduction in cell proliferation. However, both CSE stimulated the number of microvessels following the increase of basic fibroblast growth factor. In in vitro studies, the effect of CE or EE (10, 40, or 100 microg/ml) on cell migration and cell proliferation were measured using an in vitro wound model and [(3)H]-thymidine incorporation assay, respectively. Both CSE delayed cell migration and decreased cell proliferation, which were accompanied with a reduction in ODC activity. Exogenous spermidine (5 or 10 microM) could reverse the inhibitory action on cell proliferation and ODC activity induced by CSE. In conclusion, both CSE significantly delayed ulcer healing as a result of reduction in cell proliferation and cell migration. All these effects are, in part, related to the reduction of polyamine synthesis.

PPAR-γ ligands inhibit growth of human esophageal adenocarcinoma cells through induction of apoptosis, cell cycle arrest and reduction of ornithine decarboxylase activity

Peroxisome proliferator-activated receptor gamma (PPAR-gamma), a member of the nuclear hormone receptor superfamily, is involved in suppression of growth of several types of tumors such as liposarcoma, breast cancer, prostate cancer, and colon cancer, possibly through induction of cell cycle arrest and/or apoptosis. In this study, we demonstrated expression of PPAR-gamma mRNA and protein in human esophageal carcinoma cells. Expression of PPAR-gamma protein was higher in an adenocarcinoma cell line (TE-7 cells) than in a squamous cell carcinoma cell line (TE-1 cells). PPAR-gamma ligands such as 15-deoxy-Delta12,14-prostaglandin J2 and troglitazone significantly inhibited the growth of TE-7 cells but had less or no effect on growth of TE-1 cells. 15d-PGJ2 and troglitazone induced apoptosis in TE-7 cells but not in TE-1 cells. Troglitazone caused G1 cell cycle arrest and reduced ornithine decarboxylase activity (ODC) in TE-7 cells but not in TE-1 cells. Inhibition by PPAR-gamma ligands of growth of esophageal adenocarcinoma cells may thus be due to induction of apoptosis, G1 cell cycle arrest and reduction of ODC activity.

Polyamines regulate gap junction communication in connexin 43-expressing cells

The control of cell–cell communication through gap junctions is thought to be crucial in normal tissue function and during various stages of tumorigenesis. However, few natural regulators of gap junctions have been found. We show here that increasing the activity of ornithine decarboxylase, or adding polyamines to the outside of cells, increases the level of gap junction communication between various epithelial cells. Conversely, reduction of ornithine decarboxylase activity decreases the level of gap junction communication. This regulation is dependent upon the expression of connexin 43 (Cx43 or Cxα1), which is a major connexin expressed in many different cell types, and involves an increase in Cx43 and its cellular re-distribution.

Polyamines regulate gap junction communication in connexin 43-expressing cells.

The control of cell-cell communication through gap junctions is thought to be crucial in normal tissue function and during various stages of tumorigenesis. However, few natural regulators of gap junctions have been found. We show here that increasing the activity of ornithine decarboxylase, or adding polyamines to the outside of cells, increases the level of gap junction communication between various epithelial cells. Conversely, reduction of ornithine decarboxylase activity decreases the level of gap junction communication. This regulation is dependent upon the expression of connexin 43 (Cx43 or Cxalpha1), which is a major connexin expressed in many different cell types, and involves an increase in Cx43 and its cellular re-distribution.

The role of polyamines in gastric mucus synthesis inhibited by cigarette smoke or its extract

BACKGROUNDCigarette smoking was shown to delay gastric ulcer healing and reduce synthesis of mucus, which is important for gastric ulcer protection and healing. Polyamines are important in these processes.AIMSTo study...

Ornithine decarboxylase activity in muscle, liver, and intestinal tissue of turkeys during a short-term feed withdrawal and following refeeding

The activity of ornithine decarboxylase (ODC), an enzyme associated with cellular growth and protein synthesis, was examined in breast muscle, liver, and intestinal tissues of turkeys during a short-term period of feed withdrawal (FW) and following refeeding. Turkeys from a randombred control line were reared under standard management practices to 3 wk of age in battery brooders. Feed was then withdrawn from FW birds for a 48-h period, after which feed was consumed ad libitum. Control birds consumed feed ad libitum throughout the test period. Tissues were collected from 12 birds per treatment following 24 and 48 h of FW and at 6, 12, 24, and 48 h following refeeding for later determination of tissue ODC activity. Activity of ODC was greater in tissue from the small intestine than in liver tissue and both had greater activity than that exhibited by breast muscle. Short-term FW and refeeding produced differential responses in ODC activity of the three tissues examined. Feed withdrawal resulted in a reduction of ODC activity in intestinal tissue, whereas activity was unaffected for liver or breast muscle tissues. Compensatory increases in ODC activity were observed in liver and intestinal tissues; however, the increase was both more rapid and transitory in small intestine than in liver tissue. The ODC activity in breast muscle was largely unaffected by short-term FW and refeeding. Patterns of ODC activity in liver during FW and refeeding closely resembled patterns observed for absolute and relative liver weight. Thus, the results of the present experiment demonstrate that short-term FW and refeeding influence underlying growth mechanisms of supply organs, such as hepatic and intestinal tissue, in addition to affecting overall growth and muscle development.

Regulation of ornithine decarboxylase by hypoxia in pulmonary artery smooth muscle cells.

The polyamines are a family of low-molecular-weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Elevations in cellular polyamine contents necessary for most physiological and pathological events in the lung appear to be driven by increase de novo synthesis. In contrast, increases in lung cell polyamines required for hypoxic pulmonary vascular disease can be attributed to augmented transmembrane polyamine transport which may, in turn, be the result of hypoxia-related decreases in the activity of the initial and generally rate-limiting enzyme in de novo polyamine synthesis, ornithine decarboxylase (ODC). To begin to define the unusual mechanism whereby hypoxia governs polyamine regulatory pathways, the present study examined the impact of varying severity and durations of hypoxic exposure on ODC activity and mRNA content in cultured bovine main pulmonary artery smooth muscle cells (PASMC). The effect of hypoxia on the activity of another rate-limiting enzyme in polyamine synthesis, S-adenosylmethionine decarboxylase (AdoMet-DC), also was examined. Hypoxia caused time-dependent decreases in ODC and AdoMet-DC activities that were related to the severity of hypoxic exposure. Similarly, ODC mRNA content also was depressed by hypoxic exposure. The relationship between the decline in ODC activity and mRNA content was roughly linear. To determine whether hypoxia impairs ODC mRNA stability, two different inhibitors of transcription and Northern analyses were used to follow the decay in ODC mRNA abundance in hypoxic and normoxic PASMC. Densitometric scanning of Northern analysis indicated that ODC mRNA stability did not differ between hypoxic and normoxic PASMC. These results suggest that the reduction in ODC activity provoked by hypoxia in cultured bovine PASMC can be ascribed in part to a diminished transcriptional rate rather than to alterations in mRNA stability.

Rat Antizyme Inhibits the Activity but Does Not Promote the Degradation of Mouse Ornithine Decarboxylase in Trypanosoma brucei

Ornithine decarboxylase (ODC) of African trypanosomes is an important target for anti-trypanosomal chemotherapy because of its remarkable stability in vivo. The in vivo activity and stability of mammalian ODC are regulated by polyamines. Polyamines induce antizyme, which inactivates ODC by tight association and promotes degradation of ODC by the mammalian 26 S proteasome. Here we found, in contrast to mammalian cells, that polyamines caused no reduction of ODC activity in Trypanosoma brucei. Mouse ODC expressed in T. brucei was also unaffected by exogenous polyamines, suggesting that a mammalian antizyme equivalent may be absent in T. brucei. The rat antizyme expressed in T. brucei was found capable of inhibiting mouse ODC activity by the formation of rat antizyme-mouse ODC complex. However, complex formation did not lead to degradation of mouse ODC in T. brucei. Further in vitro experiments suggested the presence of an inhibitory factor(s) in trypanosome, which interferes with the degradation of mouse ODC. We also demonstrated the presence of proteasomes in T. brucei. But the mobility of the trypanosomal proteasome on native gel is different from that of the mammalian proteasome. Thus, the absence of antizyme, the presence of inhibitory factor(s), and the differences between trypanosomal and mammalian proteasome may account for the stability of mouse ODC in T. brucei cells.

Inhibition of Ornithine Decarboxylase Activity and Cell Proliferation by Ultraviolet B Radiation in EGF-Stimulated Cultured Human Epidermal Keratinocytes

Irradiation of EGF-stimulated human keratinocytes in vitro with ultraviolet B (UVB) radiation inhibited both ornithine decarboxylase (ODC) activity and cellular proliferation. A dose-dependent reduction in ODC activity occurred in primary cultures of adult facial keratinocytes and neonatal foreskin keratinocytes, and in an SV40-transformed keratinocyte cell line derived from neonatal foreskin. When SV40-transformed keratinocytes were treated with epidermal growth factor (EGF), ODC activity was induced up to 21 times in the absence of ultraviolet radiation. However, pre-treatment with UVB significantly reduced the EGF induction of ODC. For example, 85% less ODC activity was observed in cultures treated with EGF (10 ng/ml) plus 2.5 mJ/cm2 of UVB than cultures treated with EGF alone. To assess the effect of UVB on cell proliferation, normal human epidermal keratinocytes grown in medium containing EGF were irradiated with 5 and 10 mJ/cm2 UVB. At days 3 and 5 post-irradiation a significant (up to 78%) decrease in proliferation was observed. Nevertheless, the mean proportion of viable to dead cells remained similar in both UVB-treated and non-irradiated cell cultures. Northern blot analysis of total RNA isolated from irradiated and sham-irradiated cultures showed that UVB caused approximately a one third reduction in steady-state ODC mRNA levels in EGF-stimulated keratinocyte cultures. Because ODC is an enzyme required for cell proliferation, we propose that the UVB-induced decrease in cell proliferation may result at least in part from UVB inhibition of ODC mRNA accumulation and reduced enzyme activity.

Evaluation of ornithine decarboxylase activity as a marker for tumor growth rate in malignant tumors

Ornithine decarboxylase (ODC) is a rate-limiting enzyme in the synthesis of polyamines. Polyamines regulate DNA synthesis by a mechanism that is not fully understood. High levels of polyamines and ODC activity are associated with rapid cell growth, particularly in tumor tissues. The aim of this study was to determine whether ODC activity as a marker for rapid alterations in tumor growth could be used to investigate whether nutritional support in cancer patients stimulates tumor cell proliferation. Weight-losing head and neck cancer patients and tumor-bearing mice (MCG 101, C57/BL) were studied during different feeding regimens. The ODC activity in tumor tissue was investigated in relation to the following variables: (1) histopathologic differentiation; (2) DNA content; and (3) bromodeoxyuridine (BrdUrd) incorporation into DNA. After the animals were starved for 24 hours, a significant reduction of tumor growth was demonstrated in the experimental tumor along with a reduction of ODC activity, an accumulation of cells in the G 0G 1 phase, and a reduction of cells incorporating BrdUrd into DNA. Refeeding after 24 hours generated a response by all variables. Tumor biopsy specimens from patients with head and neck cancer malignancies demonstrated aneuploidy in the cells of 70% of the patients. High ODC activity in tumor tissue was demonstrated mainly among poorly differentiated tumors, and ODC activity was correlated with the compartment size of aneuploidic cells in the tumor. High ODC activity indicated a poor short-term survival (1 year). It was concluded that experimental tumor growth is highly dependent on host feeding. However, there was no evidence supporting the claim that nutritional support to cancer patients stimulates tumor cell proliferation. Determination of ODC activity may be used to monitor rapid changes in DNA synthesis and may have prognostic significance for survival.

Effects of central administration of beta-endorphin on brain and liver DNA synthesis in preweanling rats

We have previously shown that central administration of beta-endorphin results in a reduction of ornithine decarboxylase activity. Ornithine decarboxylase catalyses the rate-limiting step in the biosynthesis of the polyamines putrescine, spermidine and spermine, thought to modulate nucleic acid synthesis. The present study examines the effects of intracisternal injection of beta-endorphin on brain and liver DNA synthesis in preweanling rats. In six-day-old rats, beta-endorphin (0.75 μg/g brain wt) produced approximately a 70% inhibition in brain and liver DNA synthesis 1h after injection, and values were still subnormal in both tissues 10 h later. Subcutaneous administration of beta-endorphin did not alter liver DNA synthesis. Thus, it is most likely that the suppressed liver DNA synthesis observed in animals given beta-endorphin intracisternally is mediated by central mechanisms. Co-administration of naloxone plus beta-endorphin intracisternally prevented the response, indicating an opioid receptormediated phenomenon. Naloxone alone caused small but significant increases in brain and liver DNA synthesis, suggesting a tonic influence on tissue DNA by endogenous opioids in the CNS. Acute inhibition of ornithine decarboxylase activity by alpha-difluoromethylornithine did not alter DNA synthesis, indicating that the decreases in DNA synthesis induced by beta-endorphin are unrelated to the ornithine decarboxylase/polyamine system. The effect appears to be restricted to early development as no significant changes in DNA synthesis were obtained in 20-day-old animals. The results from these studies indicate that CNS beta-endorphin has the ability to influence DNA synthesis in central as well as in peripheral tissues. Since changes in DNA biosynthetic rates reflect alterations in cell replication, perturbations in CNS beta-endorphin levels during early postnatal life could result in significant deficits in development.

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

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

Effect of removal of glutamine and addition of dexamethasone on the activities of glutamine synthetase, ornithine decarboxylase and lactate dehydrogenase in primary cultures of forebrain and cerebellar astrocytes

The regulation of glutamine synthetase (GS) and ornithine decarboxylase (ODC) was studied in primary cultures of two types of astrocytes derived from either newborn forebrain or 8-day-old cerebellum of the rat. In the 14-day-old cultures the specific activities of both these enzymes were about twice as great in forebrain astrocytes as in cerebellar astrocytes. Treatment with dexamethasone or removal of glutamine from the culture medium caused a marked increase in the specific activity of GS. The glutamine-mediated relative increase in GS activity was similar in both types of astrocytes. Removal of glutamine caused a transient reduction in ODC activity in the forebrain astrocytes, while in cerebellar astrocytes the activity remained markedly decreased throughout the period of glutamine deprivation. The severe reduction in ODC activity had relatively little effect on the cell numbers or protein content of the astrocyte cultures. The increase in GS activities, involving protein synthesis de novo, caused by removal of glutamine and by addition of dexamethasone, were additive and therefore probably mediated by different mechanisms. The induction of GS after glutamine removal was blocked by cycloheximide but not by α-amanitin, suggesting regulation at the post-transcriptional level. In contrast, the dexamethasone-mediated induction of GS appeared to be regulated at the transcriptional level, as it was markedly reduced by α-amanitin. None of these conditions had any effect on lactate dehydrogenase activity. Treatment with α-amanitin resulted in a complete suppression of the activity of ODC (a protein with a very short half life), in both the control and dexamethasone treated cultures. However, this enzyme activity was reduced only partially in astrocytes cultured in glutamine deficient medium, suggesting that under these experimental conditions the mRNA may be markedly stabilized in astroglial cells.

Participation of Ornithine Decarboxylase in Early Stages of Tomato Fruit Development

The apparent association of ornithine decarboxylase (ODC) with rapid cell proliferation in developing tomato (Lycopersicon esculentum Mill. cv. Pearson ms-35) fruits has been previously described. Further evidence is provided by the use of two ODC inhibitors, alpha-difluoromethylornithine (alpha-DFMO) and alpha-methylornithine (alpha-MO). Fruit development was inhibited by these inhibitors if applied during the period of intensive cell division. When applied in vitro, the two inhibitors were shown to inhibit the activity of ODC but not that of arginine decarboxylase (ADC). When applied in vivo, alpha-DFMO, a catalytic irreversible inhibitor, caused 97.1% reduction of ODC activity in the dialyzed extract from the treated ovaries, while it had no effect on ADC. On the other hand, alpha-MO, a reversible inhibitor, did not reduce the activity of these two enzymes in the dialyzed extracts when applied in vivo. The dialysis procedure probably removed alpha-MO from the enzyme fraction. Putrescine, the product of both ODC and ADC, alleviated the inhibition of fruit development but did not restore ODC activity to the control level. These results suggest that in the young developing tomato fruit, ODC is the enzyme responsible for the synthesis of putrescine, which is essential for the early stages of fruit development. The reduced activity of ODC elicited by putrescine suggests a mechanism of feedback regulation by enzyme repression or release of an ODC anti-enzyme.

Maternal Behavior as a Regulator of Polyamine Biosynthesis in Brain and Heart of the Developing Rat Pup

Rat pups removed from the mother and placed in a warm incubator for 1 hour or more show a 50 percent reduction in ornithine decarboxylase activity in the brain and heart. The decline is not caused by lack of nutrition. Instead, these studies suggest that active maternal behavior is necessary to maintain normal polyamine metabolism in brain and heart of the pup during development.