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Northern analysis of non-transgenic () and SSAT transgenic () mouse tissues for SSAT mRNAs. The upper panel is the autoradiogram of the Northern blot whereas the lower panel is the ethidium bromide-stained gel prior to blotting. Sizes of mRNAs are indicated to the right.
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Overexpression of SSAT (polyamine catabolic enzyme) in female mice results in impaired ovarian folliculogenesis and uterine hypoplasia. To identify the molecular basis for this, the gene expression profiles in uterus and ovary and for comparison, liver and kidney, from non-transgenic (NT) and SSAT transgenic (ST) mice were compared. The mRNA abunda...
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... Similarly, E2 treatment significantly increased IGFBP-2 mRNA levels also in uteri of ovariectomized rats (39). A robust increase of IGFBP-2 gene expression was further found in uteri from mice characterized by transgenic spermidine/spermine N1-acetyltransferase (SSAT) expression (26). Steroid control of IGFBP-2 is also observed in non-mammalian species as gonadotropin, E2, and P4 were able to increase expression of IGFBP-2 mRNA in de-yolked follicles from the rainbow trout (32) whereas E2 decreased IGFBP-2 mRNA expression in the orange-spotted grouper (36). ...
IGFBP-2 (1) has been described as a brain tumor oncogene (2) and is widely expressed in cancers from different origins (3–8). IGFBP-2 alone cannot cause malignant transformation, yet progression of brain tumors to higher grade (9) and also has been provided as a protective element in earlier stages of multistage colon carcinogenesis (10). Therefore, it is crucial to understand the factors that determine expression patterns of IGFBP-2 under normal and malignant conditions. The present review provides a comprehensive update of known factors that have an impact on expression of IGFBP-2.
... The spermine/spermidine ratios were found to increase slightly at day 2, and then decreased at day 4 after the treatment with the mixture of the inducers (Fig. 1a). To test whether the polyamine metabolism could be involved in the changes in cellular polyamine ratios after stimulation, spermidine/spermine-N 1 -acetyltransferase (SSAT) activity, which is one of major polyamine metabolic enzymes, inducible in many normal and disease processes (Min et al. 2002), was measured during 3T3-L1 adipogenesis. The activity of SSAT in stimulated cells taken as a control was found to be significantly higher than that in unstimulated cells taken as a blank. ...
Polyamines spermidine and spermine are known to be required for mammalian cell proliferation and for embryonic development. Alpha-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase (ODC) a limiting enzyme of polyamine biosynthesis, depleted the cellular polyamines and prevented triglyceride accumulation and differentiation in 3T3-L1 cells. In this study, to explore the function of polyamines in adipogenesis, we examined the effect of polyamine biosynthesis inhibitors on adipocyte differentiation and lipid accumulation of 3T3-L1 cells. The spermidine synthase inhibitor trans-4-methylcyclohexylamine (MCHA) increased spermine/spermidine ratios, whereas the spermine synthase inhibitor N-(3-aminopropyl)-cyclohexylamine (APCHA) decreased the ratios in the cells. MCHA was found to decrease lipid accumulation and GPDH activity during differentiation, while APCHA increased lipid accumulation and GPDH activity indicating the enhancement of differentiation. The polyamine-acetylating enzyme, spermidine/spermine N
1-acetyltransferase (SSAT) activity was increased within a few hours after stimulus for differentiation, and was found to be elevated by APCHA. In mature adipocytes APCHA decreased lipid accumulation while MCHA had the opposite effect. An acetylpolyamine oxidase and spermine oxidase inhibitor MDL72527 or an antioxidant N-acetylcysteine prevented the promoting effect of APCHA on adipogenesis. These results suggest that not only spermine/spermidine ratios but also polyamine catabolic enzyme activity may contribute to adipogenesis.
... Significant phenotypic changes were found in these mice, such as substantial alterations in the polyamine pool, early and permanent hair loss, female infertility, weight loss, and lack of subcutaneous fat.[39] Sat1 overexpression also led to the disappearance of visceral fat depots and general lipoatrophy.[4041] ...
Genetics and diet are both considered important risk determinants for colorectal cancer, a leading cause of death in the US and worldwide. Genetically engineered mouse (GEM) models have made a significant contribution to the characterization of colorectal cancer risk factors. Reliable, reproducible, and clinically relevant animal models help in the identification of the molecular events associated with disease progression and in the development of effictive treatment strategies. This review is focused on the use of mouse models for studying the role of polyamines in colon carcinogenesis. We describe how the available mouse models of colon cancer such as the multiple intestinal neoplasia (Min) mice and knockout genetic models facilitate understanding of the role of polyamines in colon carcinogenesis and help in the development of a rational strategy for colon cancer chemoprevention.
... For example, SSAT transgenic animals show anomalous changes in the skin and reproductive tract. SSAT overexpression also leads to the onset of acute pancreatitis and impaired hepatic regeneration (1)(2)(3)22). In addition, SSAT transgenic mice demonstrate a complete loss of white adipose tissue and decreases in lipogenesis by the loss of acetyl-and malonyl-CoA pools (15,25). ...
The expression of catabolic enzymes spermidine/spermine N(1)-acetyltransferase (SSAT) and spermine oxidase (SMO) increases after ischemic reperfusion injury. We hypothesized that polyamine catabolism is upregulated and that this increase in catabolic response contributes to tissue damage in endotoxin-induced acute kidney injury (AKI). SSAT mRNA expression peaked at threefold 24 h following LPS injection and returned to background levels by 48 h. The activity of SSAT correlated with its mRNA levels. The expression of SMO also increased in the kidney after LPS administration. Serum creatinine levels increased significantly at approximately 15 h, peaking by 24 h, and returned to background levels by 72 h. To test the role of SSAT in endotoxin-induced AKI, we injected wild-type (SSAT-wt) and SSAT-deficient (SSAT-ko) mice with LPS. Compared with SSAT-wt mice, the SSAT-ko mice subjected to endotoxic-AKI had less severe kidney damage as indicated by better preservation of kidney function. The role of polyamine oxidation in the mediation of kidney injury was examined by comparing the severity of renal damage in SSAT-wt mice treated with MDL72527, an inhibitor of both polyamine oxidase and SMO. Animals treated with MDL72527 showed significant protection against endotoxin-induced AKI. We conclude that increased polyamine catabolism through generation of by-products of polyamine oxidation contributes to kidney damage and that modulation of polyamine catabolism may be a viable approach for the treatment of endotoxin-induced AKI.
... In contrast, the SSAT-overexpressing females developed ovarian hypofunction and uterine hypoplasia leading to infertility at a very young fertile age [4]. Interestingly, the expression levels of numerous genes were different in the uterus and ovary of transgenic females when compared with those in their non-transgenic littermates [39]. The exact roles of the differentially expressed genes in the observed phenotypic changes have not been clarifi ed, but the fi ndings tend to indicate that polyamines play an important role in controlling molecular mechanisms of reproductive tract development and function. ...
Cloning of genes related to polyamine metabolism has enabled the generation of genetically modified mice and rats overproducing or devoid of proteins encoded by these genes. Our first transgenic mice overexpressing ODC (ornithine decarboxylase) were generated in 1991 and, thereafter, most genes involved in polyamine metabolism have been used for overproduction of the respective proteins, either ubiquitously or in a tissue-specific fashion in transgenic animals. Phenotypic characterization of these animals has revealed a multitude of changes, many of which could not have been predicted based on the previous knowledge of the polyamine requirements and functions. Animals that overexpress the genes encoding the inducible key enzymes of biosynthesis and catabolism, ODC and SSAT (spermidine/spermine N1-acetyltransferase) respectively, appear to possess the most pleiotropic phenotypes. Mice overexpressing ODC have particularly been used as cancer research models. Transgenic mice and rats with enhanced polyamine catabolism have revealed an association of rapidly depleted polyamine pools and accelerated metabolic cycle with development of acute pancreatitis and a fatless phenotype respectively. The latter phenotype with improved glucose tolerance and insulin sensitivity is useful in uncovering the mechanisms that lead to the opposite phenotype in humans, Type 2 diabetes. Disruption of the ODC or AdoMetDC [AdoMet (S-adenosylmethionine) decarboxylase] gene is not compatible with mouse embryogenesis, whereas mice with a disrupted SSAT gene are viable and show no harmful phenotypic changes, except insulin resistance at a late age. Ultimately, the mice with genetically altered polyamine metabolism can be used to develop targeted means to treat human disease conditions that they relevantly model.
... The role of SSAT in this regard is supported by in vivo and in vitro evidence showing that its expression leads to oxidative stress and that it is detrimental to the integrity of tissues and organs (1-3, 28 -30, 34, 36, 37). Studies examining the effect of transgenic expression of SSAT in mice indicate that it adversely effects the integrity and function of various tissues (28,30,34). These results are complemented by in vitro observations indicating that SSAT expression leads to alterations in cell physiology, cell cycle arrest, and apoptosis (36,37). ...
Expression of spermine/spermidine-N1-acetyltransferase (SSAT), the rate-limiting enzyme of polyamine backconversion cascade, increases after ischemia-reperfusion injuries (IRI). We hypothesized that SSAT plays an important role in the mediation of IRI. To test our hypothesis, wild-type (SSAT-wt) and SSAT-deficient (SSAT-ko) mice were subjected to liver or kidney IRI by ligation of hepatic or renal arteries. The liver and kidney content of putrescine (Put), a downstream by-product of SSAT activity, increased in SSAT-wt animals but not in SSAT-ko animals after IRI, indicating that polyamine backconversion is not functional in SSAT-deficient mice. When subjected to hepatic IRI, SSAT-ko mice were significantly protected against liver damage compared with SSAT-wt mice. Similarly, SSAT-ko animals subjected to renal IRI showed significantly greater protection against damage to kidney tubules than SSAT-wt mice. These studies indicate that SSAT-deficient animals are protected against IRI and suggest that SSAT is an important mediator of the tissue damage in IRI.
... It is interesting that the polyamine pathway may be the converging pathway in GBM tumors because insulin-like growth factor activation has been shown to lead to an increase in SSAT (49,50), suggesting an elevation of natural polyamine levels in cells. A possible scenario is that oncogenic alterations such as insulin-like growth factor receptor and phosphatidylinositol 3-kinase/akt activation increase the metabolism of cancer cells, leading to a high demand for polyamines. ...
Glioblastoma multiforme (GBM) is one of the most therapeutically refractory human cancers. Elevated cellular polyamine levels are a common feature of cancer cells, including GBM cells, and the polyamine pathway has been explored as a potential therapeutic target to inhibit polyamine biosynthesis or activate polyamine catabolism. In this study, we investigated the effect of N1,N11-diethyl-norspermine (DENSPM), a spermine analog that activates polyamine catabolism, in GBM cells. The in vitro cell culture experiments showed that DENSPM increased the sub-G1 apoptotic cell population in GBM cell lines but caused minimal cytotoxicity in normal astrocytes. Prior to apoptosis induction, DENSPM caused the elevation of spermidine/spermine N1-acetyltransferase (SSAT) expression accompanied by a decrease in polyamine levels and an increase of acetylated polyamine levels, which temporally coincided with the onset of hydrogen peroxide (H2O2) induction in the cells. The cytotoxic effects of DENSPM in the GBM cells could be partially attenuated by either turning down SSAT mRNA with small interference RNA or inhibiting H2O2 production with N1-acetylpolymine oxidase (APAO)/spermine oxidase (SMO) inhibitor. Though mitochondrial damage was induced, neither activation of the caspase cascade nor cytochrome c redistribution between the mitochondria and cytoplasm was observed. Systemic DENSPM treatment of mice with intracerebral GBM led to longer survival. Taken together, our studies indicate that DENSPM kills GBM cells through induction of SSAT coupled with H2O2 production, which is a potential target for GBM therapy.
... The female members of the SSAT overexpressing mice are infertile due to uterine hypoplasia and lack of corpora lutea (9). Although female reproductive organs of the SSAT mice show some differences in gene expression pattern in comparison with wild-type mice (22), the contribution of these changes to the infertility remains to be elucidated. ...
Activation of polyamine catabolism through the overexpression of spermidine/spermine N1-acetyltransferase (SSAT) in transgenic rodents does not only lead to distorted tissue polyamine homeostasis, manifested as striking accumulation of putrescine, appearance N1-acetylspermidine and reduction of tissue spermidine and/or spermine pools, but likewise creates striking phenotypic changes. The latter include loss of hair, lipoatrophy and female infertility. Forced expression of SSAT modulates skin, prostate and intestinal carcinogenesis, induces acute pancreatitis and blocks early liver regeneration. Although many of these features are directly attributable to altered tissue polyamine pools, some of them are more likely related to the greatly accelerated flux of the polyamines caused by activated catabolism and compensatorily enhanced biosynthesis.
... Gene expression analyses in transgenic uterus and ovary revealed several differentially expressed genes. The expression of lipoprotein lipase, glyceraldehydes-3-phosphate dehydrogenase and insulin-like growth factor binding protein-2 was enhanced in the transgenic females while that of insulin-like growth factor binding protein-3 was reduced in transgenic uterus [52]. The possible contribution of these changes to the observed uterine hypoplasia and ovarian hypofunction is not known. ...
The polyamines putrescine, spermidine and spermine are natural components of all living cells. Although their exact cellular functions are still largely unknown, a constant supply of these compounds is required for mammalian cell proliferation to occur. Studies with animals displaying genetically altered polyamine metabolism have shown that polyamines are intimately involved in the development of diverse tumors, putrescine apparently has specific role in skin physiology and neuroprotection and the higher polyamines spermidine and spermine are required for the maintenance of pancreatic integrity and liver regeneration. In the absence of ongoing polyamine biosynthesis, murine embryogenesis does not proceed beyond the blastocyst stage. The last years have also witnessed the appearance of the first reports linking genetically altered polyamine metabolism to human diseases.
... Polyamines have also been implicated in the development and function of both male 97 and female reproductive organs 98,99 . Aberrant expression of spermidine/spermine N 1 -acetyltransferase influences specific gene expression controlling reproductive-tract tissue growth and function 100 . ...
The amino-acid-derived polyamines have long been associated with cell growth and cancer, and specific oncogenes and tumour-suppressor genes regulate polyamine metabolism. Inhibition of polyamine synthesis has proven to be generally ineffective as an anticancer strategy in clinical trials, but it is a potent cancer chemoprevention strategy in preclinical studies. Clinical trials, with well-defined goals, are now underway to evaluate the chemopreventive efficacy of inhibitors of polyamine synthesis in a range of tissues.
