Effect of polyamine depletion on caspase activation: a study with spermine synthase-deficient cells

Modulation of Fatty Acid-Related Genes in the Response of H9c2 Cardiac Cells to Palmitate and n-3 Polyunsaturated Fatty Acids

While high levels of saturated fatty acids are associated with impairment of cardiovascular functions, n-3 polyunsaturated fatty acids (PUFAs) have been shown to exert protective effects. However the molecular mechanisms underlying this evidence are not completely understood. In the present study we have used rat H9c2 ventricular cardiomyoblasts as a cellular model of lipotoxicity to highlight the effects of palmitate, a saturated fatty acid, on genetic and epigenetic modulation of fatty acid metabolism and fate, and the ability of PUFAs, eicosapentaenoic acid, and docosahexaenoic acid, to contrast the actions that may contribute to cardiac dysfunction and remodeling. Treatment with a high dose of palmitate provoked mitochondrial depolarization, apoptosis, and hypertrophy of cardiomyoblasts. Palmitate also enhanced the mRNA levels of sterol regulatory element-binding proteins (SREBPs), a family of master transcription factors for lipogenesis, and it favored the expression of genes encoding key enzymes that metabolically activate palmitate and commit it to biosynthetic pathways. Moreover, miR-33a, a highly conserved microRNA embedded in an intronic sequence of the SREBP2 gene, was co-expressed with the SREBP2 messenger, while its target carnitine palmitoyltransferase-1b was down-regulated. Manipulation of the levels of miR-33a and SREBPs allowed us to understand their involvement in cell death and hypertrophy. The simultaneous addition of PUFAs prevented the effects of palmitate and protected H9c2 cells. These results may have implications for the control of cardiac metabolism and dysfunction, particularly in relation to dietary habits and the quality of fatty acid intake.

Polyamine supplementation reduces DNA damage in adipose stem cells cultured in 3-D

According to previous research, natural polyamines exert a role in regulating cell committment and differentiation from stemness during skeletal development. In order to assess whether distinct polyamine patterns are associated with different skeletal cell types, primary cultures of stem cells, chondrocytes or osteoblasts were dedicated for HPLC analysis of intracellular polyamines. Spermine (SPM) and Spermidine (SPD) levels were higher in adipose derived stem cells (ASC) compared to mature skeletal cells, i.e. chondrocytes and osteoblasts, confirming the connection of polyamine content with stemness. To establish whether polyamines can protect ASC against oxidative DNA damage in a 3-D differentiation model, the level of γH2AX was measured by western blot, and found to correlate with age and BMI of patients. Addition of either polyamine to ASC was able to hinder DNA damage in the low micromolecular range, with marked reduction of γH2AX level at 10 µM SPM and 5 µM SPD. Molecular analysis of the mechanisms that might underlie the protective effect of polyamine supplementation evidences a possible involvement of autophagy. Altogether, these results support the idea that polyamines are able to manage both stem cell differentiation and cell oxidative damage, and therefore represent appealing tools for regenerative and cell based applications.

Polyamine delivery as a tool to modulate stem cell differentiation in skeletal tissue engineering

The first step in skeleton development is the condensation of mesenchymal precursors followed by any of two different types of ossification, depending on the type of bone segment: in intramembranous ossification, the bone is deposed directly in the mesenchymal anlagen, whereas in endochondral ossification, the bone is deposed onto a template of cartilage that is subsequently substituted by bone. Polyamines and polyamine-related enzymes have been implicated in bone development as global regulators of the transcriptional and translational activity of stem cells and pivotal transcription factors. Therefore, it is tempting to investigate their use as a tool to improve regenerative medicine strategies in orthopedics. Growing evidence in vitro suggests a role for polyamines in enhancing differentiation in both adult stem cells and differentiated chondrocytes. Adipose-derived stem cells have recently proved to be a convenient alternative to bone marrow stromal cells, due to their easy accessibility and the high frequency of stem cell precursors per volume unit. State-of-the-art "prolotherapy" approaches for skeleton regeneration include the use of adipose-derived stem cells and platelet concentrates, such as platelet-rich plasma (PRP). Besides several growth factors, PRP also contains polyamines in the micromolar range, which may also exert an anti-apoptotic effect, thus helping to explain the efficacy of PRP in enhancing osteogenesis in vitro and in vivo. On the other hand, spermidine and spermine are both able to enhance hypertrophy and terminal differentiation of chondrocytes and therefore appear to be inducers of endochondral ossification. Finally, the peculiar activity of spermidine as an inducer of autophagy suggests the possibility of exploiting its use to enhance this cytoprotective mechanism to counteract the degenerative changes underlying either the aging or degenerative diseases that affect bone or cartilage.

Antiapoptotic and antiautophagic effects of eicosapentaenoic acid in cardiac myoblasts exposed to palmitic acid

Apoptosis is a programmed cell death that plays a critical role in cell homeostasis. In particular, apoptosis in cardiomyocytes is involved in several cardiovascular diseases including heart failure. Recently autophagy has emerged as an important modulator of programmed cell death pathway. Recent evidence indicates that saturated fatty acids induce cell death through apoptosis and this effect is specific for palmitate. On the other hand, n-3 polyunsaturated fatty acids (PUFAs) have been implicated in the protection against cardiovascular diseases, cardiac ischemic damage and myocardial dysfunction. In the present study we show that n-3 PUFA eicosapentaenoic acid (EPA) treatment to culture medium of H9c2 rat cardiomyoblasts protects cells against palmitate-induced apoptosis, as well as counteracts palmitate-mediated increase of autophagy. Further investigation is required to establish whether the antiautophagic effect of EPA may be involved in its cytoprotective outcome and to explore the underlying biochemical mechanisms through which palmitate and EPA control the fate of cardiac cells.

Role of polyamines in hypertrophy and terminal differentiation of osteoarthritic chondrocytes

Polyamines are naturally occurring, positively charged polycations which are able to control several cellular processes in different cell types, by interacting with negatively charged compounds and structures within the living cell. Functional genomics in rodents targeting key biosynthetic or catabolic enzymes have revealed a series of phenotypic changes, many of them related to human diseases. Several pieces of evidence from the literature point at a role of polyamines in promoting chondrocyte differentiation, a process which is physiological in growth plate maturation or fracture healing, but has pathological consequences in articular chondrocytes, programmed to keep a maturational arrested state. Inappropriate differentiation of articular chondrocytes results in osteoarthritis. Thus, we have studied the effects of exogenously added spermine or spermidine in chondrocyte maturation recapitulated in 3D cultures, to tease out the effects on gene and protein expression of key chondrogenesis regulatory transcription factors, markers and effectors, as well as their posttranscriptional regulation. The results indicate that both polyamines are able to increase the rate and the extent of chondrogenesis, with enhanced collagen 2 deposition and remodeling with downstream generation of collagen 2 bioactive peptides. These were able to promote nuclear localization of RUNX-2, the pivotal transcription factor in chondrocyte hypertrophy and osteoblast generation. Indeed, samples stimulated with polyamines showed an enhanced mineralization, along with increased caspase activity, indicating increased chondrocyte terminal differentiation. In conclusion these results indicate that the polyamine pathway can represent a potential target to control and correct chondrocyte inappropriate maturation in osteoarthritis.

Codonopsis lanceolata extract induces G0/G1 arrest and apoptosis in human colon tumor HT-29 cells--involvement of ROS generation and polyamine depletion

Codonopsis lanceolata (Campanulasea) is widely distributed and grown in Asia and has been in use as traditional medicine for long time. The n-butanol fraction (BF) of C. lanceolata significantly inhibited human colon cancer HT-29 cell growth in a dose- and time-dependent manner by inducing G0/G1 phase arrest and apoptosis. The inhibition was associated with intracellular ROS generation and polyamine depletion as evidenced by HPLC quantitatively. Additionally, semi-quantitative RT-PCR revealed enhanced expression of caspase-3, p53, and the Bax/Bcl-2 ratio and reduced expression of survivin in HT-29 cells treated with BF. Furthermore, western blot analysis of p53, JNK, and caspase-3 showed that ROS generation was accompanied by JNK activation. Increase of the Bax/Bcl-2 ratio and activation of caspase-3 might be due to intracellular polyamine depletion. Conclusively, the findings of this study imply a critical role of ROS and polyamine depletion in the anticancer effects of C. lanceolata root extract.

Amine oxidases in apoptosis and cancer

Amine oxidases, the major enzymes of biogenic amines metabolism, are considered to be biological regulators, especially for cell growth and differentiation. A primary involvement of amine oxidases in cancer growth inhibition and progression, especially by means of aldehydes, H(2)O(2) and other reactive oxygen species, the amine oxidase-mediated products of biogenic amines oxidation, has been demonstrated. Amine oxidases are involved in cancer growth inhibition because of the higher content in tumour cells of biogenic amines in comparison to normal cells. The cytotoxic effect can be explained by a damage to cell membranes and/or nuclei or, indirectly, through modulation of membrane permeability transition and therefore apoptosis. The oxidation products of biogenic amines appears to be also carcinogenic, while acrolein, produced from the oxidation of spermine and spermidine, should be a key compound both carcinogenic and cytotoxic. The cancer inhibition/promotion effect of amine oxidases could be explained by taking into consideration the full pattern of the enzyme content of the cell. The balance of amine oxidases and antioxidant enzymes appear to be a crucial point for cancer inhibition or progression. A long lasting imbalance of these enzymes appears to be carcinogenic, while, for a short time, amine oxidases are cytotoxic for cancer cells.

Modulation of apoptosis by cancer chemopreventive agents

A review of almost 2000 studies showed that the large majority of 39 putative cancer chemopreventive agents induced "spontaneous" apoptosis. Inhibition of the programmed cell death triggered by a variety of stimuli was consistently reported only with ascorbic acid, alpha-tocopherol, and N-acetylcysteine (NAC). We performed experimental studies in rodents exposed to cigarette smoke, either mainstream (MCS) or environmental (ECS), and UV-A/B-containing light. The nonsteroidal anti-inflammatory drug sulindac did not affect the apoptotic process in the skin of light-exposed mice and in the lungs of ECS-exposed mice. Likewise, 5,6-benzoflavone, indole-3-carbinol, 1,2-dithiole-3-thione and oltipraz failed to modulate apoptosis in the respiratory tract of ECS-exposed rats. Phenethyl isothiocyanate further enhanced the frequency of apoptosis in pulmonary alveolar macrophages and bronchial epithelial cells, and upregulated several genes in the lung of ECS-exposed rats. Both individually and in combination with oltipraz, NAC inhibited apoptosis in the respiratory tract of rats exposed either to MCS or ECS. Moreover, NAC attenuated the ECS-related overexpression of proapoptotic genes and normalized the levels of proapoptotic proteins in rat lung. The transplacental administration of NAC to mice considerably attenuated gene overexpression in the liver of fetuses exposed to ECS throughout pregnancy. Inhibition of apoptosis by chemopreventive agents reflects their ability to counteract certain upstream signals, such as genotoxic damage, redox imbalances, and other forms of cellular stress that trigger apoptosis. On the other hand, enhancement of apoptosis is a double-edged sword, since it represents a protective mechanism in carcinogenesis but may contribute to the pathogenesis of other degenerative diseases. We suggest that stimulation of apoptosis by so many chemopreventive agents, as reported in the literature, may often reflect the occurrence of toxic effects at high doses.

Polyamines and apoptosis

The natural polyamines putrescine, spermidine and spermine are in multiple ways involved in cell growth and the maintenance of cell viability. In the course of the last 15 years more and more evidence hinted also at roles in gene regulation. It is therefore not surprising that the polyamines are involved in events inherent to genetically programmed cell death. Following inhibition of ornithine decarboxylase, a key step in polyamine biosynthesis, numerous links have been identified between the polyamines and apoptotic pathways. Examples of activation and prevention of apoptosis due to polyamine depletion are known for several cell lines. Elevation of polyamine concentrations may lead to apoptosis or to malignant transformation. These observations are discussed in the present review, together with possible mechanisms of action of the polyamines. Contradictory results and incomplete information blur the picture and complicate interpretation. Since, however, much interest is focussed at present on all aspects of programmed cell death, a considerable progress in the elucidation of polyamine functions in apoptotic signalling pathways is expected, even though enormous difficulties oppose pinpointing specific interactions of the polyamines with pro- and anti-apoptotic factors. Such situation is quite common in polyamine research.

Polyamine depletion inhibits NF-kappaB binding to DNA and interleukin-8 production in human chondrocytes stimulated by tumor necrosis factor-alpha

The activation of the NF-kappaB pathway by pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNFalpha), can be an important contributor for the re-programming of chondrocyte gene expression, thereby making it a therapeutic target in articular diseases. To search for new approaches to limit cartilage damage, we investigated the requirement of polyamines for NF-kappaB activation by TNFalpha in human C-28/I2 chondrocytes, using alpha-difluoromethylornithine (DFMO), a specific polyamine biosynthesis inhibitor. The NF-kappaB pathway was dissected by using pharmacological inhibitors or by expressing a transdominant IkappaBalpha super repressor. Treatment of C-28/I2 chondrocytes with TNFalpha resulted in a rapid enhancement of nuclear localization and DNA binding activity of the p65 NF-kappaB subunit. TNFalpha also increased the level and extracellular release of interleukin-8 (IL-8), a CXC chemokine that can have a role in arthritis, in an NF-kappaB-dependent manner. Pre-treatment of chondrocytes with DFMO, while causing polyamine depletion, significantly reduced NF-kappaB DNA binding activity. Moreover, DFMO also decreased IL-8 production without affecting cellular viability. Restoration of polyamine levels by the co-addition of putrescine circumvented the inhibitory effects of DFMO. Our results show that the intracellular depletion of polyamines inhibits the response of chondrocytes to TNFalpha by interfering with the DNA binding activity of NF-kappaB. This suggests that a pharmacological and/or genetic approach to deplete the polyamine pool in chondrocytes may represent a useful way to reduce NF-kappaB activation by inflammatory cytokines in arthritis without provoking chondrocyte apoptosis.

Effect of spermine synthase on the sensitivity of cells to anti-tumour agents

The role of spermine in the sensitivity of cells to various established and experimental anti-tumour agents was examined, using paired cell lines that possess or lack spermine synthase. All spermine-synthase-deficient cells had no detectable spermine, and elevated spermidine, content. Spermine content did not alter the cell growth rate. There was little or no difference in sensitivity of immortalized mouse embryonic fibroblasts to doxorubicin, etoposide, cisplatin, methylglyoxal bis(guanylhydrazone) or H(2)O(2) and only a slight increase in sensitivity to vinblastine and nocodazole. However, the absence of spermine clearly increased the sensitivity to 1,3-bis(2-chloroethyl)- N -nitrosourea, suggesting that depletion of spermine may be a useful way to increase the anti-neoplastic effects of anti-tumour agents that form chloroethyl-mediated interstrand DNA cross-links. The effects of spermine on the response to polyamine analogues (which have been proposed to be useful anti-neoplastic agents) were complex, and depended on the compound examined and on the cells tested. Sensitivity to CHENSpm ( N (1)-ethyl- N (11)-[(cycloheptyl)methyl]-4,8-diazaundecane) was substantially greater in immortalized fibroblasts that lack spermine. In contrast, BE-3-4-3 [ N (1), N (12)-bis(ethyl)spermine] and BE-3-3-3 [ N (1), N (11)-bis(ethyl)norspermine] were more active against cells that contained spermine. The presence of spermine correlated with a greater induction of spermidine/spermine- N (1)-acetyltransferase by BE-3-3-3, which is consistent with suggestions that this induction is important for the response to this drug. These findings support the concepts that different polyamine analogues have different sites of action and that CHENSpm has a different site of action from BE-3-3-3.

Resistance to plant pathogens: possible roles for free polyamines and polyamine catabolism

Although most work on polyamines in incompatible interactions between plants and pathogens has focussed on polyamines conjugated to phenolic compounds (hydroxycinnamic acid amides), changes in free polyamines and their catabolism have been shown to occur in such interactions. A common feature of these interactions is an increase in diamine oxidase (DAO) activity and, in some interactions, of polyamine oxidase (PAO). The activities of these two enzymes produces hydrogen peroxide (H₂ O₂ ), which may act in structural defense, as a signal molecule, or as an antimicrobial compound in host resistance. There are several possible roles for polyamines and polyamine catabolism in plant resistance to pathogen infection; H₂ O₂ produced might trigger the hypersensitive response (HR), thought to be a form of programmed cell death (PCD), the polyamine spermine might act as an inducer of PR proteins, and as a trigger for caspase activity and hence HR. There is, however, a need for more precise information on the timing and location of changes in polyamine metabolism in the development of resistance. Only with this information can a case be made for the involvement of polyamines and polyamine catabolism in plant defense.

Correlation between polyamines and apoptosis among Egyptian breast cancer patients

OBJECTIVES

The polyamines putrescine, spermidine, and spermine, play an important role in cell proliferation, differentiation, and transformation. The aim of this study is to correlate the polyamines with apoptosis and clinico-pathologic events in Egyptian breast cancer patients.

METHODS

PUT, SPD, and SPN were investigated using thin layer chromatography (TLC) and apoptosis in fresh frozen tissue specimens obtained from 40 patients suffering from breast cancer, as well as 20 patients with benign breast lesions.

RESULTS

The levels of PUT, SPD, and SPN were higher in breast cancer tissues than in benign breast lesions (p < 0.001). Polyamines were correlated well with apoptosis. Moreover, PUT was an independent prognostic factor for relapse. Also, SPD and SPN correlated significantly with early tumor grades. ROC curves were used to choose the best cut-off values for polyamines (70, 135, and 290 mmol/g tissue) for PUT, SPD, and SPN, respectively. At these cut-off values, the sensitivities were (75%, 60%, and 70%), and the specificities were (80%, 95%, and 95%) for PUT, SPD, and SPN, respectively.

CONCLUSION

Polyamines may be used as additional markers for detection of malignant transformation in breast tissue. Moreover, because of their ability to induce apoptosis in malignant tissues, polyamines are suitable targets for therapeutic intervention that is specifically directed to induce apoptosis.