Sodium butyrate induces apoptosis and accumulation of ubiquitinated proteins in human breast carcinoma cells.
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To investigate the possible relationship between apoptosis and the ubiquitin pathway we examined the patterns of ubiquitinated proteins in the human breast carcinoma MCF-7 cell line following induction of apoptotic death by sodium butyrate. Apoptosis in these cells was associated with internucleosomal DNA fragmentation and proteolytic cleavage of poly(ADP-ribose) polymerase. By dual in situ antiubiquitin immunofluorescence and chromatin DNA staining, we demonstrated that ubiquitin fluorescence was increased specifically in cells that underwent sodium butyrate-mediated apoptosis. The extent of ubiquitin incorporation into protein conjugates was examined in both adherent (not yet apoptotic) and floating (apoptotic) cell populations. We found that apoptotic cells exhibited enhanced intensity of ubiquitin-immunoreactive conjugates, whereas adherent cells did not. In addition, two-dimensional immunoblot analysis of proteins from apoptotic cells identified a set of isomeric ubiquitinated conjugates located at a pI range of 4. 2 - 4.6 and a Mr approximately of 30 kDa. These data indicate that the ubiquitin pathway may play a role in the sodium butyrate-induced apoptotic program in breast carcinoma cells. (+info)
Cancer cell sensitization to fas-mediated apoptosis by sodium butyrate.
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Cancer cells often resist Fas-mediated apoptosis even when the Fas receptor is expressed at the cell surface. We show here that human and rat colon cancer cells undergo massive apoptosis when they are exposed to soluble Fas ligand in the presence of sodium butyrate, an agent that induces by itself only a low rate of apoptosis. Sodium butyrate potentiates Fas-dependent apoptosis in seven out of eight colon cancer cell lines. Sodium butyrate does not increase Fas receptor cell surface expression and does not modify cell levels of Bcl-2, Bcl-xL, Bcl-xS and Bax. Sodium butyrate also induces tumor cell sensitization to the apoptotic effect of the combination of TNF-alpha and IFN-gamma, but it does not modify the level of the FADD/Mort1 adaptator molecule, at the connection between Fas- and TNF-dependent apoptosis pathways. Because the clinical toxicity of butyrate is low, its ability to enhance Fas-signal delivery in cancer cells could be of therapeutic interest. (+info)
Pharmacological activities of TEI-8362, a novel inhibitor of human neutrophil elastase.
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1. TEI-8362, 4-(N-(3-((3-carboxypropyl)amino)-8-methyl-1-oxo-4-azaisochromen-6- yl)carbamoyl)-4-((phenylmethoxy)carbonylamino)butanoic acid (C26H28N4O9) is a novel inhibitor of human neutrophil elastase (HNE). We evaluated its pharmacological profile in vitro and in vivo. 2. TEI-8362 demonstrated potent inhibition of HNE with a Ki value of 1.38 x 10(-9) M. Its selectivity for HNE among a variety of proteases ranged from 163 fold to 68,000 fold in favour of HNE. 3. The pulmonary haemorrhage that occurred after i.t. instillation of HNE to hamsters was inhibited by either i.t., i.v., or inhalant administration of TEI-8362. 4. Intratracheal administration of lipopolysaccharide induced pulmonary neutrophilia. Twenty-four hours after lipopolysaccharide administration, the additional treatment with formyl-methionyl-leucyl-phenylalanine resulted in a specific neutrophil-dependent acute lung injury. In this model, lung injury was significantly attenuated by i.t., i.v., or inhalant administration of TEI-8362. 5. These pharmacological actions of TEI-8362 suggest that this drug has therapeutic value in the treatment of destructive lung diseases due to neutrophils. (+info)
Interleukin-2 overexpresses c-myc and down-regulates cytochrome P-450 in rat hepatocytes.
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The interaction of interleukin-2 (IL-2) with its receptor (IL-2R) decreases cytochrome P-450 (CYP) expression in rat hepatocytes. Because IL-2 increases c-Myc in lymphocytes and because c-myc overexpression represses several genes, we postulated that the IL-2/IL-2R interaction may increase c-Myc and thereby down-regulate CYP in hepatocytes. Cultured rat hepatocytes were exposed for 24 h to IL-2 (350 U/ml) and other agents. IL-2 increased c-myc mRNA and protein but decreased total CYP and the mRNAs and proteins of CYP2C11 and CYP3A. The IL-2-mediated c-myc overexpression and CYP down-regulation were prevented by 1) genistein (a tyrosine kinase inhibitor that blocks the initial transduction of the IL-2R signal), 2) retinoic acid, butyric acid, or dimethyl sulfoxide (three agents that block c-myc transcription), or 3) an antisense c-myc oligonucleotide (which may cause rapid degradation of the c-myc transcript). It is concluded that IL-2 causes the overexpression of c-myc and the down-regulation of CYPs in rat hepatocytes. Block of c-myc overexpression, at three different levels with five different agents, prevents CYP down-regulation, suggesting that c-myc overexpression may directly or indirectly repress CYP in hepatocytes. (+info)
Quantitative analysis of histone H1 degrees protein synthesis in HTC cells.
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H1 degrees, a member of histone H1 family associated with cell growth arrest and differentiation, is barely expressed in most mammalian cells in culture. Depending on the cell type, serum deprivation or drugs, such as sodium butyrate, significantly increase H1 degrees mRNA level and H1 degrees protein accumulates. However, probably because of a lack of a simple quantitative procedure, little is known about the relationship between H1 degrees mRNA content and its effective translation rate. Using a rat hepatoma cell line and sodium butyrate as a model system, we attempted to evaluate this in different cellular conditions by measuring H1 degrees synthesis with a rapid quantitative procedure we described previously. We found that although the amount of H1 degrees mRNA rapidly increased and then stabilized under sodium butyrate treatment, its transcription was delayed and H1 degrees protein was synthesized in a progressive wave. Butyrate removal from cell culture confirmed that mRNA level and protein synthesis were independently regulated, and provided evidence that sodium butyrate would not directly target the translation apparatus. In contrast, during the S phase of the cell cycle, H1 degrees gene transcription and protein synthesis were concomitantly activated. Taken together these data provide evidence that H1 degrees accumulation results from an increase of its synthesis and that, depending on conditions, a cell exhibits a H1 degrees translation efficiency which may or may not reflect the mRNA level. (+info)
Short-chain fatty acids suppress cholesterol synthesis in rat liver and intestine.
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We previously showed that plasma cholesterol levels decreased following ingestion of a short-chain fatty acid (SCFA) mixture composed of sodium salts of acetic, propionic, and butyric acids simulating cecal fermentation products of sugar-beet fiber (SBF). In the present study, we investigated whether hepatic and small intestinal cholesterol synthesis is involved in the cholesterol-lowering effects of SCFA and SBF. In vitro (expt. 1) and in vivo (expt. 2) cholesterol synthesis rates and the diurnal pattern of SCFA concentrations in portal plasma (expt. 3) were studied in three separate experiments in rats fed diets containing the SCFA mixture, SBF (100 g/kg diet), or the fiber-free control diet. Cholesterol synthesis was measured using 3H2O as a tracer. The in vitro rate of cholesterol synthesis, measured using liver slices, was greater in the SBF group, but not in the SCFA group, than in the fiber-free control group. In contrast, the hepatic cholesterol synthesis rate in vivo was lower in the SCFA group, but not in the SBF group, than in the control group. The mucosal cholesterol synthesis rate for the whole small intestine was <50% of the hepatic rate. The rate in the proximal region was slightly but significantly lower in the SCFA group, and was significantly higher in the SBF group than in the fiber-free group. The rate in the distal small intestines was also significantly greater in the SBF group than in the fiber-free group. Plasma total cholesterol concentrations were lower in the SCFA and SBF groups than in the fiber-free group in both experiments 2 and 3. Diurnal changes in portal SCFA and cholesterol levels were studied in the experiment 3. SCFA concentrations increased rapidly after the start of feeding the SCFA diet, and changes in plasma cholesterol were the reciprocal of those observed in SCFA. These results show that a decrease in hepatic cholesterol synthesis rate mainly contributes to the lowering of plasma cholesterol in rats fed the SCFA mixture diet. Changes in portal SCFA and cholesterol concentrations support this conclusion. In SBF-fed rats, SCFA produced by cecal fermentation are possibly involved in lowering plasma cholesterol levels by negating the counteractive induction of hepatic cholesterol synthesis caused by an increase in bile acid excretion. (+info)
Sodium butyrate enhances STAT 1 expression in PLC/PRF/5 hepatoma cells and augments their responsiveness to interferon-alpha.
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Although interferon-alpha (IFN-alpha) has shown great promise in the treatment of chronic viral hepatitis, the anti-tumour effect of this agent in the therapy of liver cancer is unclear. Recent studies have demonstrated that differentiation-inducing agents could modulate the responsiveness of cancer cells to IFN-alpha by regulating the expression of signal transducers and activators of transcription (STAT) proteins, a group of transcription factors which play important roles in the IFN signalling pathway. We have reported that sodium butyrate is a potent differentiation inducer for human hepatoma cells. In this study, we investigated whether this drug could regulate the expression of STAT proteins and enhance the anti-tumour effect of IFN-alpha in hepatoma cells. We found that sodium butyrate specifically activated STAT1 gene expression and enhanced IFN-alpha-induced phosphorylation and activation of STAT1 proteins. Co-treatment with these two drugs led to G1 growth arrest, accompanied by down-regulation of cyclin D1 and up-regulation of p21WAF-1, and accumulation of hypophosphorylated retinoblastoma protein in hepatoma cells. Additionally, internucleosomal DNA fragmentation, a biological hallmark of apoptosis, was detected in hepatoma cells after continuous incubation with a combination of these two drugs for 72 h. Our results show that sodium butyrate potently enhances the anti-tumour effect of IFN-alpha in vitro and suggest that a rational combination of these two drugs may be useful for the treatment of liver cancer. (+info)
Expression and up-regulation of interleukin-6 in oesophageal carcinoma cells by n-sodium butyrate.
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Recently, the serum level of interleukin (IL)-6 has been shown to correlate with disease progression and prognosis of cancer patients. However, the available information about the source and the pathophysiological regulation of IL-6 in cancer cells is limited. Thus, in this study, we tried to identify the source and the clinical roles of serum IL-6 in patients with oesophageal squamous cell carcinoma (ESCC), and then further to characterize the biological regulation of IL-6 in ESCC cell lines. Sera and tissue specimens from 80 consecutive patients with ESCC were collected between 1993 and 1997. Additionally, three ESCC cell lines were used for in vitro study. The concentration of serum IL-6 was measured by enzyme-linked immunosorbent assay (ELISA), and correlated the survival time with measured IL-6 level. Expressions of IL-6, IL-6R alpha (IL-6 receptor alpha) and gp130 in pathological sections and cell lines were characterized by immunological staining. Detection of IL-6 mRNA was determined by in situ hybridization (ISH) and reverse transcription-polymerase chain reaction (RT-PCR). Up-regulation of IL-6 by n-sodium butyrate (n-BT) was studied in ESCC cell lines. The levels of serum IL-6 in patients with ESCC were significantly higher than those in the healthy controls. Serum levels of IL-6 were also shown to correlate with disease progression and survival. However, sCD8 levels and lymphocyte counts in the peripheral blood were not parallel to the changed pattern of serum IL-6. In pathological sections and ESCC cell lines, message of IL-6 was identified by ISH in cancer cells. Expression of IL-6 mRNA was further confirmed with RT-PCR in ESCC cell lines. Although IL-6 was detected in some ESCC cell lines, IL-6 gene expression and protein production could be induced or enhanced by n-BT treatment in all three cell lines. The serum levels of IL-6 are frequently elevated at diagnosis of ESCC, and are associated with poor prognosis. IL-6 that could be produced by cancer cells is up-regulated by n-BT. (+info)