Ornithine Decarboxylase Gene Expression Research Articles

Co-functioning of 2AP precursor amino acids enhances 2-acetyl-1-pyrroline under salt stress in aromatic rice (Oryza sativa L.) cultivars

Aromatic rice (Oryza sativa) fetches a premium price due to the pleasant aroma. The major aroma compound 2-acetyl-1-pyrroline (2AP) has been found to be enhanced under stress. This condition can be considered to study the genes, precursors, enzymes, and metabolites involved in elevated levels of 2AP biosynthesis. In the present study, 100 mM salt treatment was given to two aromatic rice cultivars Ambemohar-157 (A-157) and Basmati-370 (B-370) at the vegetative stage (VS3). After salt treatment, in the leaves, 2AP contents were elevated by 2.2 and 1.8 fold in A-157 and B-370, respectively. Under these elevated 2AP conditions, the precursor amino acids (glutamate, putrescine, ornithine, and proline), their related genes, enzymes, and metabolites (methylglyoxal and γ-aminobutyric acid (GABA) related to 2AP biosynthesis were analyzed. In addition, agronomic characters were also studied. It was observed that the proline content was enhanced in both the cultivars by 29% (A-157) and 40% (B-370) as compared to control. The Δ1-pyrroline-5-carboxylate synthetase (P5CS) enzyme activity was increased in salt-treated plants leaf tissue by 31% (A-157) and 40% (B-370) compared to control. The P5CS gene expression was enhanced by A-157 (1.8 fold) and B-370 (2.2 fold) compared to control, putrescine content in A-157 and B-370 decreased by 2.5 and 2.7 fold respectively as compared to control. The ornithine decarboxylase (ODC) activity was enhanced in A-157 (12%) and B-370 (35%) over control. Further, ODC gene expression was enhanced in both the cultivars A-157 (1.5 fold) and B-370 (1.3 fold). The diamino oxidase (DAO) enzyme activity was increased by 28% (A-157) and 35% (B-370) respectively over control. The GABA content marginally increased over control in both the cultivars namely, A-157 (1.9%) and B-370 (9.5%). The methylglyoxal levels were enhanced by 1.4 fold in A-157 and 1.6 fold in B-370. Interestingly, the enhancement in 2AP in the vegetative stage also helped to accumulate it in mature grains (twofold in A-157 and 1.5 fold in B-370) without test weight penalty. The study indicated that the ornithine and proline together along with methylglyoxal contribute towards the enhancement of 2AP under salt stress.

Putrescine biosynthetic pathways modulate root growth differently in tomato seedlings grown under different N sources

The biosynthesis of putrescine is mainly driven by arginine decarboxylase (ADC) and ornithine decarboxylase (ODC). Hence, in this study, we generated independent ADC and ODC transgenic silenced tomato lines (SilADC and SilODC, respectively) to test the effect of defective ADC and ODC gene expression on root development under nitrate (NN) or ammonium (NA) conditions. The results showed that SilODC seedlings displayed an increase in ADC expression that led to polyamine accumulation, suggesting a compensatory effect of ADC. However, this effect was not observed in SilADC seedlings. These pathways are involved in different growth processes. The SilADC seedlings showed an increase in fresh weight, shoot length, lateral root number and shoot:root ratio under the NN source and an enhancement in fresh weight, and shoot and root length under NA conditions. However, SilODC seedlings displayed greater weight and shoot length under the NN source, whereas a decrease in lateral root density was found under NA conditions. Moreover, two overexpressed ODC lines were generated to check the relevance of the compensatory effect of the ADC pathway when ODC was silenced. These overexpressed lines showed not only an enhancement of almost all the studied growth parameters under both N sources but also an amelioration of ammonium syndrome under NA conditions. Together, these results reflect the importance of both pathways in plant growth, particularly ODC silencing, which requires compensation by ADC induction.

<p class="Default"><strong>Changes in expression of polyamines and ethylene biosynthesis genes in groundnut (<em>Arachis hypogaea </em>L.) genotypes during <em>Sclerotium rolfsii</em> infection</strong></p>

Stem rot disease caused by fungal pathogen, Sclerotium rolfsii Sacc., is potential threat to groundnut production in warm and humid condition. After host-pathogen interaction, a multitude of plant resistance associated reactions are initiated. In the present investigation we studied the role of polyamines and ethylene during host-pathogen interaction in stem rot tolerant (CS319, GG17 and GG31) and susceptible (TG37A) groundnut genotypes at 24, 48 and 72 h after infection. Stem rot tolerant genotypes showed higher expression of polyamine biosynthesis genes ornithine decarboxylase (Ordec), spermine synthase (Sms) and lipoxygenase1 (LOX1) gene at 72 h after infection than that of susceptible genotype TG37A. The expression analysis of ethylene biosynthesis genes (1-aminocyclopropane-1-carboxylate oxidase: ACCO and (ACCS) showed up regulation in stem rot susceptible genotype TG37A than that of tolerant genotypes after infection at all stages (24, 48 and 72 h after infection). The expression of amine oxidase (AMO) gene was observed highest in stem rot susceptible genotype TG37A while minimum in GJG31. Expression of this gene was remarkably induced in TG37A which may leads to higher accumulation of H2O2. Higher content of a polyamine, putrescine was found in the leaves of stem rot tolerant genotypes at 48 and 72 h after infection. These results implied that tolerant genotypes induced higher polyamine biosynthesis which may involve in plant defense and impart tolerance/ resistance. While, susceptible genotype (TG37A), utilized higher flux of S-Adenosyl methionine (SAM) for ethylene biosynthesis which may leads to necrosis of plants. Thus, stem rot resistant genotypes may be developed through genetic manipulation of polyamine biosynthesis pathway.

Silencing of the Ornithine Decarboxylase Gene of Fusarium oxysporum f. sp. lycopersici by Host-Induced RNAi Confers Resistance to Fusarium Wilt in Tomato

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici, a hemibiotrophic filamentous fungal pathogen is one of the important diseases of tomato. Recently, RNA interference (RNAi) has emerged as a novel alternative strategy for the control of plant diseases caused by fungal pathogens. Therefore, we tested the potential of RNAi for the control of Fusarium wilt in tomato by targeting a key polyamine (PA) biosynthesis gene, ornithine decarboxylase (ODC) of the pathogen as PAs (putrescine, spermidine, and spermine) are absolutely essential for normal growth and development. The target fungal ODC gene fragment was cloned in a hairpin RNA construct, which was used to develop several transgenic tomato plants. These RNAi transgenic lines expressed the intended small interfering RNAs (siRNAs) and exhibited moderate to high resistance when challenged with the spores of F. oxysporum. Interestingly, the silencing effect was confined only to the fungal pathogen and had no influence on the plant ODC gene expression, polyamine levels, and morphology. These results confirm that the ODC gene is vital for fungal growth and is a suitable target for disease control through host-induced gene silencing (HIGS) and also implicates the transfer of dsRNA/siRNAs from host plant cells to the fungal cells. To further validate the uptake of plant-derived siRNAs by fungal cells in a visual manner, silencing of the GFP transgene was observed in F. oxysporum GFP transformants upon infecting the dsGFP-expressing transgenic tomato plants. These experiments demonstrate the applicability of RNAi-based approach for crop protection from the filamentous fungal pathogens.

Influence of arginine on enzymes related to arginine metabolism in bovine mammary epithelial cells in vitro

Bovine mammary epithelial cells were used to evaluate the effects of different levels of Arginine (Arg) on enzymes related to Arg metabolism. A series of seven Arg concentrations in the medium as treatments were T0 (0.00 mg L−1) as control group, and T0.25 (69.50 mg L−1), T0.5 (139.00 mg L−1), T1 (278.00 mg L−1), T2 (556.00 mg L−1), T4 (1112.00 mg L−1), and T8 (2224.00 mg L−1) as experiment groups, respectively. The quantitative polymerase chain reaction and enzyme-linked immunosorbent assay analysis showed that the nitric oxide concentration, the expressions of endothelial nitric oxide synthase in mRNA, and enzyme level were all increased in response to enhanced Arg doses such that the T8 was the greatest group (P < 0.05). Four-fold Arg concentration improved gene expression and synthesis of arginase which then deceased when excessive Arg was supplied (P < 0.05). The expressions of ornithine aminotransferase mRNA and enzyme in T1 and T2 groups were significantly greater than that in the other groups (P < 0.05). Two-fold Arg was the optimum level for ornithine decarboxylase gene expression and enzyme synthesis among all seven treatments (P < 0.05). These somewhat various effects of Arg concentrations on four kinds of enzymes in different Arg metabolic pathways suggest that Arg might participate in regulating bovine mammary physiological function with an optimum concentration by influencing the enzymes in related metabolic pathways.

Urtica dioica inhibits cell growth and induces apoptosis by targeting Ornithine decarboxylase and Adenosine deaminase as key regulatory enzymes in adenosine and polyamines homeostasis in human breast cancer cell lines

Breast cancer is a heterogeneous and multifactorial disease with variable disease progression risk, and treatment response. Urtica dioica is a traditional herb used as an adjuvant therapeutic agent in cancer. In the present study, we have evaluated the effects of the aqueous extract of Urtica dioica on Adenosine deaminase (ADA) and Ornithine decarboxylase (ODC1) gene expression in MCF-7, MDA-MB-231, two breast cancer cell lines being estrogen receptor positive and estrogen receptor negative, respectively. Cell lines were cultured in suitable media. After 24 h, different concentrations of the extract were added and after 72 h, ADA and ODC1 gene expression as well as BCL2 and BAX apoptotic genes were assessed by Taqman real time PCR assay. Cells viability was assessed by MTT assay, and apoptosis was also evaluated at cellular level. The intra and extracellular levels of ODC1 and ADA enzymes were evaluated by ELISA. Results showed differential expression of ADA and ODC1 genes in cancer cell lines. In MCF-7 cell line, the expression level of ADA was upregulated in a dose-dependent manner but its expression did not change in MDA-MB cell line. ODC1 expression was increased in both examined cell lines. Also, increased level of the apoptotic BAX/BCL-2 ratio was detected in MCF-7 cells. These results demonstrated that Urtica dioica induces apoptosis in breast cancer cells by influencing ODC1 and ADA genes expression, and estrogen receptors. The different responses observed with these cell lines could be due to the interaction of Urtica dioica as a phytoestrogen with the estrogen receptor.

Ornithine decarboxylase gene expression and activity in lung cancer

Lung cancer is the malignant tumor of highest mortality rate in men worldwide, and its rate is increasing in women. Ornithine decarboxylase (ODC) is the first enzyme in the pathway of polyamines synthesis and its expression was found increased in many types of tumor tissues. This investigation aimed at measuring ODC activity and gene expression in patients with non-small cell lung cancer (NSCLC). 3 different histopathologic types were included; adenocarcinoma (AC), squamous lung carcinoma (SCC) and large cell lung carcinoma (LCC). The patients were at stages I or II and undergone curative tumor resection. The study revealed that, ODC gene expression and activity were significantly elevated in tumor tissue compared to benign tissue (P<0.0001). In tumor tissues from patients with adenocarcinoma and large cell carcinoma ODC had a higher genetic expression level and activity than in tumor tissues from patients with squamous cell carcinoma (P<0.05). We concluded that ODC may have a clinical and prognostic significance regarding the type and severity of tumor in patients with NSCLC.

ORNITHINE DECARBOXYLASE GENE EXPRESSION IN HUMAN LUNG ADENOCARCINOMA CELL (A549) TREATED WITH POMEGRANATE JUICE

The polyamine biosynthesis pathway plays a significant role in cell growth, both normal and malignant. As polyamines are crucial in cellular growth and differentiation, they are linked to the development of cancer, with higher polyamine level observed in cancerous cells than in healthy cells. Accordingly, suppressing the polyamine pathway has been found to disrupt tumour development. Chemoprevention is considered a more feasible option in cancer management than chemotherapy, with a focus on natural chemopreventive agent. Pomegranate is known to inhibit several progression of lung cancer, although prior studies on the chemopreventive effect of pomegranate on lung cancer did not explore into polyamine pathway. Hence, this study investigated the effect of pomegranate juice on the polyamine pathway, by focusing on the biosynthesis involving ornithine decarboxylase (ODC), the rate limiting enzyme in the pathway. Quantitative polymerase chain reaction (qPCR) was applied to quantify the changes in ODC gene expression in A549 cells treated with pomegranate. The inhibition of growth was determined using Trypan Blue exclusion and the changes in intracellular polyamine in pomegranate treated cells was observed using High Performance Liquid Chromatography (HPLC). It was found that there was inhibition of A549 cell growth and reduced in intracellular polyamine content in pomegranate treated cells. The ODC expression was significantly inhibited compared to untreated cells, with a 48-fold difference. While this finding supports the hypothesis, there is much yet to be elucidated regarding its exact mechanism.

Chemical hypoxia-induced stimulation of polyamine biosynthesis and ornithine decarboxylase gene transcription in C6 glioma cells

Polyamines, aliphatic polycationic compounds distributed ubiquitously in the living organisms, are considered to be implicated in various cellular processes, and furthermore speculated to play a possible pathophysiological role in physical and mental disorders. In particular, the regulation of polyamine metabolism in damaged glial cells seems interesting and important to understand a possible connection of polyamines with the brain functions. On the other hand, previous studies have shown that ornithine decarboxylase (ODC), the enzyme catalyzing the rate-limiting step of polyamine biosynthesis, can be activated during the period of recovery from various damage in the brain, but little is known about the effects of toxic insults on the expression of ODC gene in neuronal and glial cells. Based on the hypothesis that noxious impacts on the brain might be able to increase polyamine production in glial cells to protect the neuronal cell functions against toxic injuries, the effects of chemical hypoxia on polyamine production and the transcription of ODC gene in C6 glioma cells were investigated using a HPLC assay method and a one-step RT-PCR analysis. In consequence, both cobalt and azide were shown to increase the cellular polyamine contents through elevating ODC mRNA levels under the conditions in which hypoxia-inducible factor-1 (Hif-1) gene was expressed. Thus, chemical hypoxia is speculated to induce ODC gene transcription, thus resulting in the increment of polyamine contents in glial cells, thereby contributing to the recovery of brain function from hypoxic injury.

DNA-protection by Polyamines in Lactobacillus sakei No.2

In a previous study we showed that we had isolated Lactic Acid Bacteria (LAB) that produce high amounts of the polyamines found in fermented food that function as antioxidants . In this study, we concentrated on another function by investigating polyamines in relation to anti-cancer effects. Although a QR (Quinone Reductase) test showed no anti-cancer effect, good results were obtained for DNA protection and we compared polyamine production and growth of No.2 strain using a RT-PCR machine. This DNA protection may be related to an anti-cancer effect. After suggesting that polyamines had the ability to protect DNA, we collected polyamines of LAB (Lactobacillus sp. No.2) by HPLC with a fraction collector. Next, Ornithine Decarboxylase (ODC), which is considered as a polyamine producing enzyme, was detected in Lactobacillus sp. No.2 using Western blot and RT-PCR analyses. The results of RT-PCR showed that polyamine production from No.2 strain was related to growth time and especially that culture for 36 hours provided the best conditions for polyamine production. In summary this means that ODC gene expression is related to polyamine production and hence DNA protection.

Modulation of intestinal epithelial cell proliferation, migration, and differentiation in vitro by Astragalus polysaccharides.

Previous studies have shown that Astragalus polysaccharides (APS) can be used to treat general gastrointestinal disturbances including intestinal mucosal injury. However, the mechanism by which APS mediate this effect is unclear. In the present study, the effects of APS on proliferation, migration, and differentiation of intestinal epithelial cells (IEC-6) were assessed using an in vitro wounding model and colorimetric thiazolyl blue (MTT) assays. The effect of APS on IEC-6 cell differentiation was observed using a light microscope and scanning electron microscope, and the expression of differentiation-specific markers of IEC-6 cells, such as cytokeratin 18 (CK18), alkaline phosphatase (ALP), tight junction protein ZO-2, and sucrase-isomaltase (SI), was determined by immunofluorescence assay (IFA) and real-time PCR. In addition, APS-induced signaling pathways in IEC-6 cells were characterized. Our results indicated that APS significantly enhance migration and proliferation of IEC-6 cells in vitro. APS-treated IEC-6 cells have numerous microvilli on their apical surface and also highly express CK18, ALP, ZO-2, and SI. Moreover, APS-treated IEC-6 cells, in which the activity and expression level of ornithine decarboxylase (ODC) were significantly elevated, also exhibited an increase in cellular putrescine, whereas no significant increase in TGF-β levels was observed. These findings suggest that APS may enhance intestinal epithelial cell proliferation, migration, and differentiation in vitro by stimulating ODC gene expression and activity and putrescine production, independent of TGF-β. Exogenous administration of APS may provide a new approach for modulating intestinal epithelial wound restitution in vivo.

Inhibitory effects of Momordica grosvenori Swingle extracts on 12-O-tetradecanoylphorbol 13-acetate-induced skin inflammation and tumor promotion in mouse skin

Our previous data showed that the Momordica grosvenori Swingle extract (MSE) exhibited the anti-inflammatory effect through markedly suppressed LPS-induced up-regulation of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2) and ODC (ornithine decarboxylase) gene expression in RAW 264.7 cells. Regarding the link between inflammation and carcinogenesis, we further investigated the bio-molecular mechanisms of both anti-inflammatory and anti-tumor activities in vivo using a TPA (12-O-tetradecanoyl phorbol 13-acetate)-stimulated mouse skin model. Pretreatment with MSE in mouse skin has led to the reduction of TPA-induced nuclear translocation of the nuclear factor-κB (NFκB) subunits as well as phosphorylation of IκBα and p65 subsequent reduction of IκBα degradation. In addition, the MSE inhibitory effect on upstream of NFκB was found to involve the transcriptional effects of MAPK signaling as indicated by strong suppression on TPA-induced activation of extracellular signal regulate kinase (ERK)1/2, p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK)1/2, phosphatidylinositol 3-kinase (PI3K) and Akt. Moreover, MSE significantly inhibited 7,12-dimethylbenz[a]anthracene (DMBA)-TPA-induced skin tumor formation in mice measured by the tumor multiplicity of papillomas at 20 weeks. The results suggested that MSE contained promising functional ingredients capable of preventing inflammation-associated tumorigenesis.

Hexahydro-β-Acids Potently Inhibit 12-O-Tetradecanoylphorbol 13-Acetate-Induced Skin Inflammation and Tumor Promotion in Mice

We previously reported that hexahydro-beta-acids (HBAs), reduced derivatives of beta-acids (BA) from hop (Humulus lupulus L.), displayed more potent anti-inflammatory activity than BA in lipopolysaccharide-stimulated murine macrophages. In this study, we investigated the effects and underlying molecular mechanisms of hexahydro-β-acids (HBAs) on 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated mouse skin inflammation and in the two-stage carcinogenesis model. Female ICR mice pretreated with HBA at 1 and 10 μg significantly reduced ear edema, epidermal hyperplasia, and infiltration of inflammatory cells caused by TPA. Molecular analysis exhibited that HBA suppressed iNOS, COX-2, and ornithine decarboxylase (ODC) protein and gene expression through interfering with mitogen-activated protein kinases (MAPKs) and phosphatidylinositiol 3-kinase (PI3K)/Akt signaling as well as the activation of transcription factor NF-κB. Furthermore, application of HBA (1 and 10 μg) prior to each TPA treatment (17.2 ± 0.9 tumors/mouse) resulted in the significant reduction of tumor multiplicity (5.1 ± 1.2, P < 0.01 and 2.3 ± 1.2, P < 0.001, respectively) in 7,12-dimethyl-benzanthracene (DMBA)-initiated mouse skin. The tumor incidence was significantly lowered to 75% (P < 0.05) and 58.7% (P < 0.01) by HBA pretreatment, respectively, and significantly reduced the tumor weight (0.34 ± 0.14 g, P < 0.01 and 0.09 ± 0.10 g, P < 0.001, respectively) as compared to DMBA/TPA-induced tumors (0.76 ± 0.04 g).

Effects of Ganoderma lucidum polysaccharides on IEC-6 cell proliferation, migration and morphology of differentiation benefiting intestinal epithelium healing in vitro

Restoration of epithelial continuity in the intestinal surface after extensive destruction is important since intestinal epithelial cells stand as a boundary between the body's internal and external environment. Polysaccharides from Ganoderma lucidum (Gl-PS) may benefit intestinal epithelial wound healing in different aspects, which awaits clarification. To identify potential effects, a non-transformed small-intestinal epithelial cell line, IEC-6 cells, was used. Effects on epithelial cell proliferation, migration, morphology of differentiation and transforming growth factor beta (TGF-β) protein expression, as well as the cellular ornithine decarboxylase (ODC) mRNA and c-Myc mRNA expression, were assessed, respectively, by MTT assay, wound model in vitro, observation under a microscope after hematoxylin and eosin staining, enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction assays. It was shown that Gl-PS stimulated IEC-6 cell proliferation and migration significantly in a dose-dependent manner; 10 µg/ml Gl-PS improved the morphology of differentiation in IEC-6 cells. Inefficacy in expression of TGF-β in IEC-6 cells indicated a possible TGF-β independent action of Gl-PS. However, Gl-PS increased ODC mRNA and c-Myc mRNA expression in a dose-dependent manner, indicating, at least partially possible involvement of ODC and c-Myc gene expression in improvement of intestinal wound healing. These results suggest the potential usefulness of Gl-PS to cure intestinal disorders characterized by injury and ineffective repair of the intestinal mucosa.

Downregulation of ornithine decarboxylase by pcDNA-ODCr inhibits gastric cancer cell growth in vitro

Ornithine decarboxylase (ODC), the first rate-limiting enzyme of polyamine biosynthesis, was found to be associated with cell growth, proliferation and transformation. ODC gene expression in gastric cancer was increased and its level was positively correlated with the degree of malignity of gastric mucosa and development of gastric lesions. In order to evaluate the therapeutic effects of antisense RNA of ODC on gastric cancer, an antisense RNA of ODC expressing plasmid pcDNA-ODCr which delivered a 120 bp fragment complementary to the initiation codon of ODC gene was constructed and transfected to gastric cancer cells SGC7901 and MGC803. Expression of ODC in gastric cancer cells was determined by western blot. Cell proliferation was assessed by MTS assay. Cell cycle was analyzed by flow cytometry and Matrigel assay was performed to assess the ability of gastric cancer cell invasiveness. The results showed that the ODC gene expression in gastric cancer cells transfected with the pcDNA-ODCr was downregulated efficiently. Tumor cell proliferation was suppressed significantly, and cell cycle was arrested at G1 phase. Gastric cancer cells had reduced invasiveness after gene transfer. Our study suggested that antisense RNA of ODC expressing plasmid pcDNA-ODCr had antitumor activity by inhibiting the expression of ODC, and downregulation of ODC expression using a gene therapy approach might be a novel therapeutic strategy for gastric cancer.

Anti-inflammatory and antitumor promotional effects of a novel urinary metabolite, 3',4'-didemethylnobiletin, derived from nobiletin

We reported previously that 3',4'-didemethylnobiletin (DDMN) is the major metabolite of nobiletin in mouse urine. In this study, we examined DDMN's molecular mechanism of action and its anti-inflammatory and antitumor properties. We demonstrated that topical application of DDMN effectively inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated transcription of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 and ornithine decarboxylase (ODC) messenger RNA and protein expression in mouse skin. Pretreatment with DDMN has resulted in the reduction of TPA-induced nuclear translocation of the nuclear factor-kappa B (NF-kappaB) subunit. DDMN also reduced DNA binding by blocking phosphorylation of inhibitor kappaB (IkappaB) alpha and p65 and caused subsequent degradation of IkappaBalpha. DDMN inhibited TPA-induced phosphorylation and nuclear translocation of the signal transducer and activator of transcription 3. Moreover, DDMN suppressed TPA-induced activation of extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, phosphatidylinositol 3-kinase/Akt and protein kinase C that are upstream of NF-kappaB and activator protien-1. We also found that DDMN significantly inhibited TPA-induced mouse skin inflammation by decreasing inflammatory parameters. Furthermore, DDMN significantly inhibited 7,12-dimethylbenz[a]anthracene/TPA-induced skin tumor formation measured by the tumor multiplicity of papillomas at 20 weeks. Presented data for the first time reveal that DDMN is an effective antitumor agent that functions by downregulating inflammatory iNOS, COX-2 and ODC gene expression in mouse skin. It is suggested that DDMN is a novel functional agent capable of preventing inflammation-associated tumorigenesis.

Regulatory effects of corticosterone on ornithine decarboxylase activity during liver regeneration in rats

The regulation of ornithine decarboxylase (ODC) gene expression and enzyme activity by corticosterone during rat liver regeneration induced by partial hepatectomy (PH) was evaluated. Bilateral adrenalectomies were performed on ether-anesthetized rats 3 days before PH. Corticosterone in sesame oil was injected subcutaneously to adrenalectomized rats. ODC mRNA, ODC protein and enzyme activity were detected by in situ hybridization, Western blot and high performance liquid chromatography (HPLC), respectively. The ODC mRNA levels, protein accumulation and enzyme activity were lower in the intact liver compared to the regenerating liver. After PH, mRNA levels were remarkably enhanced in all groups and peaked at 5 h post-PH, and presented a persistent increase only in adrenalectomy rats during the regeneration process. Corticosterone treatment resulted in a dose-dependent decrease in ODC mRNA content after 5 h post-PH. ODC protein accumulation in adrenalectomy rats was higher than that in sham-adrenalectomy rats, but it decreased in corticosterone-treated (10 mg/kg) rats until 24 h post-PH, with a strong decline seen in 40 mg/kg corticosterone-treated rats. ODC activity was rapidly promoted, and the highest levels were observed at 6 h after PH in all groups. After corticosterone treatment, the activities declined significantly at 6 h post-PH, with the lowest value found in the 40 mg/kg group. Corticosterone treatment results in dose-dependent decreases in ODC mRNA and enzyme protein both in the intact liver and the regenerating liver. The change in ODC activity is partially related to alterations of ODC mRNA and protein accumulation.

Androgen receptor and c-Myc transcription factors as putative partners in the in vivo cross-talk between androgen receptor-mediated and c-Met-mediated signalling pathways.

Cross-talk between two signal transduction pathways leads to a negative regulation of androgen-induced ornithine decarboxylase (ODC) gene expression in the mouse kidney. One pathway is triggered by testosterone via the intracellular androgen receptor, AR, and the other is induced by antifolate CB 3717 or folate via hepatocyte growth factor and its cell membrane receptor c-Met. Here we report the studies of the expression of AR and c-Myc transcription factors involved in ODC transactivation. Administration of CB 3717 or folate decreased the expression of AR. In contrast, testosterone did not modify AR mRNA content but augmented the AR protein. Furthermore, we demonstrate that administration of folate, but not testosterone, increases c-Myc transcript and protein level. We also document that activation of both examined pathways does not decrease the testosterone-induced AR protein level, but markedly increases c-Myc protein which is nearly 2-fold up-regulated compared to its level evoked solely by testosterone. We suspect that this pronounced increase of c-Myc protein might have functional consequences mirrored by down-regulated expression of AR target genes, among them ODC.

The effects of genetic manipulation of putrescine biosynthesis on transcription and activities of the other polyamine biosynthetic enzymes1

We have studied the effects of overproduction of putrescine (Put) via transgenic expression of a mouse ornithine decarboxylase (ODC) gene on the expression of native genes for four enzymes involved in polyamine biosynthesis in hybrid poplar (Populus nigra×maximowiczii) cells. An examination of the transcript levels of arginine decarboxylase (ADC), ODC, S‐adenosylmethionine decarboxylase (SAMDC) and spermidine synthase (SPDS), as well as their enzyme activities (except SPDS), showed that the expression of different members of the SAMDC and SPDS gene families was affected differently in response to alteration of the cellular Put content. It was further observed that there was a strong correlation between transcript levels and the activity of the respective enzyme in the cells. Moreover, there was no feedback inhibition of the expression of the native ODC or the ADC genes or their enzyme activities by increased Put in the cells.

Consistency of polyamine profiles and expression of arginine decarboxylase in mitosis during zygotic embryogenesis of Scots pine.

In this study, we show that both arginine decarboxylase (ADC) protein and mRNA transcript are present at different phases of mitosis in Scots pine (Pinus sylvestris) zygotic embryogenesis. We also examined the consistency of polyamine (PA) profiles with the effective temperature sum, the latter indicating the developmental stage of the embryos. PA metabolism was analyzed by fitting statistical regression models to the data of free and soluble conjugated PAs, to the enzyme activities of ADC and ornithine decarboxylase (ODC), as well as to the gene expression of ADC. According to the fitted models, PAs typically had the tendency to increase at the early stages but decrease at the late stages of embryogenesis. Only the free putrescine fraction remained stable during embryo development. The PA biosynthesis strongly preferred the ADC pathway. Both ADC gene expression and ADC enzyme activity were substantially higher than putative ODC gene expression or ODC enzyme activity, respectively. ADC gene expression and enzyme activity increased during embryogenesis, which suggests the involvement of transcriptional regulation in the expression of ADC. Both ADC mRNA and ADC protein localized in dividing cells of embryo meristems and more specifically within the mitotic spindle apparatus and close to the chromosomes, respectively. The results suggest the essential role of ADC in the mitosis of plant cells.