Sodium butyrate modulates cell cycle-related proteins in HT29 human colonic adenocarcinoma cells

Mucosal Microbiome in Patients with Early Bowel Polyps: Inferences from Short-Read and Long-Read 16S rRNA Sequencing

Numerous studies have correlated dysbiosis in stool microbiota with colorectal cancer (CRC); however, fewer studies have investigated the mucosal microbiome in pre-cancerous bowel polyps. The short-read sequencing of variable regions in the 16S rRNA gene has commonly been used to infer bacterial taxonomy, and this has led, in part, to inconsistent findings between studies. Here, we examined mucosal microbiota from patients who presented with one or more polyps, compared to patients with no polyps, at the time of colonoscopy. We evaluated the results obtained using both short-read and PacBio long-read 16S rRNA sequencing. Neither sequencing technology identified significant differences in microbial diversity measures between patients with or without bowel polyps. Differential abundance measures showed that amplicon sequence variants (ASVs) associated with Ruminococcus gnavus and Escherichia coli were elevated in mucosa from polyp patients, while ASVs associated with Parabacteroides merdae, Veillonella nakazawae, and Sutterella wadsworthensis were relatively decreased. Only R. gnavus was consistently identified using both sequencing technologies as being altered between patients with polyps compared to patients without polyps, suggesting differences in technologies and bioinformatics processing impact study findings. Several of the differentially abundant bacteria identified using either sequencing technology are associated with inflammatory bowel diseases despite these patients being excluded from the current study, which suggests that early bowel neoplasia may be associated with a local inflammatory niche.

Potential Role of ROS in Butyrate- and Dietary Fiber-Mediated Growth Inhibition and Modulation of Cell Cycle-, Apoptosis- and Antioxidant-Relevant Proteins in LT97 Colon Adenoma and HT29 Colon Carcinoma Cells

The aim of the present study was to examine whether reactive oxygen species (ROS) contribute to chemopreventive effects of fermentation supernatants (FS) of different dietary fibers (Synergy1^®, oat-, barley-, yeast β-glucan, Curdlan) and butyrate as a fermentation metabolite. LT97 and HT29 cells were treated with butyrate and FS alone or with N-acetyl-cysteine (NAC) and their impact on ROS formation, cell growth, and protein expression (Cyclin D2, p21, PARP, Bid, GPx2) was investigated. Butyrate and FS significantly decreased cell growth. ROS levels were significantly increased, particularly in LT97 cells, while co-treatment with NAC decreased ROS formation and growth inhibitory effects in both cell lines. After treatment with butyrate and FS, Cyclin D2 expression was reduced in LT97 cells and p21 expression was increased in both cell lines. Levels of full-length PARP and Bid were decreased, while levels of cleaved PARP were enhanced. GPx2 expression was significantly reduced by fiber FS in HT29 cells. A notable effect of NAC on butyrate- and FS-modulated protein expression was observed exclusively for PARP and Bid in HT29 cells. From the present results, a contribution of ROS to growth inhibitory and apoptotic effects of butyrate and FS on LT97 and HT29 cells cannot be excluded.

Dietary supplements for intestinal inflammation

Intestinal inflammation leads to various chronic diseases, collectively known as inflammatory bowel disease (IBD). IBD mainly affects the large intestine, but it can also affect the gastrointestinal tract as a whole. Its major symptoms are pain, diarrhea, and weight loss, and it is usually associated with deficiencies of both macro- and micronutrients. Unluckily, after some time the body develops resistance against the already available drugs: thus, many patients fail to maintain remission, which is achieved in less than 50% of cases. Diet is a major determinant of gut inflammation. An unbalanced diet can affect the gut microbiota and cause dysbiosis, which is related to a dysregulated host immune response. The Mediterranean Diet its renowned for its anti-inflammatory effects and for preventing dysbiosis. In order to improve management and treatment of intestinal inflammatory diseases, it should become common practice to integrate the patient's diet with dietary supplements with anti-inflammatory effects (probiotics, butyrate, phosphatidylcholine, lactoferrin, palmitoylethanolamide, silymarin, and omega 3), which maintain the stability of the intestinal microbial cohort and strengthen the mucosal barrier, thus preventing or soothing IBD symptoms. Dietary supplements may help fight the high costs, the adverse side effects, and the recurrent relapses typical of drug use.

Luminescent properties of chameleon-like metal-organic framework between zinc(II) dichloride and two quinoline-N-oxide molecules

Zinc compounds in the form of inorganic/organic hybrids containing both zinc halides and heterocyclic ligands show various interesting optical and physicochemical properties. Due to these properties, there is a potential for development of various innovative technologies and applications within the life sciences. In this study, experimental and theoretical results on the absorption and emission (steady state and time-resolved) properties of the hybrid ZnCl₂(QO)₂ complex formed between ZnCl₂ and quinoline N-oxide, have been reported. Single crystal X-ray analysis revealed the tetragonal cell (Z = 4) with P4₁2₁2 space group and a slight crystal distortion. Interestingly, experiments in aprotic solvents show that both absorption and emission spectra peak in the ultraviolet (UV) region suggesting a weak CT character of the emissive S₁ state, confirmed by a middle Stokes shift values. The results of the nanosecond time-resolved emission spectroscopy suggest two different structures of the complex described by the two different lifetimes and variable amplitudes dependent on the polarity of the medium. In the solid state, a relatively strong, bright blue luminescence appears at 413 nm (τ = 2.26 ns). Theoretical calculations (DFT and TD DFT) confirm experimental studies and reveal the solvent-dependent chameleon properties of ZnCl₂(QO)₂ by two different structures in two solvents of a contrast polarity. In apolar cyclohexane (CHX, μ = 5.612 D), the planes of both lateral quinoline N-oxide (QO) rings show to be nearly parallel each to another, resembling the crystal structure, while in a strongly polar acetonitrile (AN, μ = 9.328 D) they are nearly perpendicular. Such parallel arrangement of quinoline rings of ZnCl₂(QO)₂ complex in weakly polar methylcyclohexane can hinder the process of Photoinduced Electron Transfer, resulting in a stronger emission and significant quantum yield in comparison to more polar media.

Role of thalidomide, senicapoc, and sodium butyrate in choroidal neovascularization

Choroidal neovascularization (CNV) is the hallmark of wet age-related macular degeneration (AMD), a leading cause of irreversible blindness in the modern world. The objective for this study was to investigate the therapeutic potential of known antiangiogenic agents: thalidomide, senicapoc, and sodium butyrate. Dose-dependent effect of the agents on growth of ARPE-19 cells and human umbilical vein endothelial cells (HUVECs) was investigated with cell counting assays. Half-maximal inhibitory concentrations of thalidomide (765 μM and 1520 μM), senicapoc (50 μM and 79 μM), and sodium butyrate (933 μM and 557 μM) were determined for HUVECs and ARPE-19 cells, respectively. Immunofluorescence analysis showed decrease of VEGFA expression in both ARPE-19 cells and HUVECs after treatment only with thalidomide but not with senicapoc or sodium butyrate. Efficacy of the agents was studied in vivo with laser-induced CNV in C57BL/6 mice. Thalidomide (24 μg), senicapoc (4 μg), or sodium butyrate (100 μg) was intravitreally injected the day after CNV induction. Thalidomide, senicapoc, and sodium butyrate inhibited CNV size by 56%, 24%, and 21% respectively on day 7 post-laser. Thalidomide also reduced cobalt chloride induced increase of VEGFA mRNA in ARPE-19 (-33%) and protein in culture medium (-20%). Our results suggest that thalidomide may have more therapeutic potential than senicapoc or sodium butyrate for treatment of CNV or wet AMD.

Sodium Butyrate Selectively Kills Cancer Cells and Inhibits Migration in Colorectal Cancer by Targeting Thioredoxin-1

Background

Sodium butyrate (NaB) is a short-chain fatty acid which is produced by bacterial fermentation of nondigestible dietary fiber and has been reported to exert anti-tumor effects in many tumors including colorectal cancer (CRC). However, the role of thioredoxin-1 (Trx-1) in NaB-induced anti-tumor effect has not been completely clarified.

Materials and Methods

Effects of NaB on the growth of CRC cell lines HT29 and SW480 were detected by the Cell Counting Kit-8 (CCK-8) and colony formation assays. The apoptotic cells were determined by flow cytometry, and cell migration was assessed by a Transwell assay. Western blot analysis was used to test the Trx-1 and epithelial-to-mesenchymal transition (EMT)-related proteins level. Reactive oxygen species (ROS) level was determined and N-acetylcysteine (NAC) recovery experiment was performed in CRC cells. In addition, mice xenograft model was established to test the effect of NaB on CRC growth in vivo. Further, the effects of NaB on CRC cells with overexpression or knockdown were tested by the CCK-8 and Transwell assays.

Results

NaB treatment significantly inhibited cell growth and decreased Trx-1 protein expression in CRC cells but not in normal colon epithelial cells. NaB also induced apoptosis, inhibited colony formation, migration and EMT in CRC cells. Besides, NaB increased ROS level in CRC cells and NAC reversed NaB-induced inhibition of cell proliferation. Moreover, downregulation of Trx-1 significantly enhanced NaB-induced inhibitory effects on cell growth and migration, whereas overexpression of Trx-1 attenuated NaB-induced inhibitory effects on growth and migration in CRC cells.

Conclusion

These findings indicate that the NaB-mediated anti-tumor effects on CRC cells are related to downregulation of Trx-1.

Exacerbation of Chikungunya Virus Rheumatic Immunopathology by a High Fiber Diet and Butyrate

Chikungunya virus (CHIKV) is a mosquito transmitted alphavirus associated with a robust systemic infection and an acute inflammatory rheumatic disease. A high fiber diet has been widely promoted for its ability to ameliorate inflammatory diseases. Fiber is fermented in the gut into short chain fatty acids such as acetate, propionate, and butyrate, which enter the circulation providing systemic anti-inflammatory activities. Herein we show that mice fed a high fiber diet show a clear exacerbation of CHIKV arthropathy, with increased edema and neutrophil infiltrates. RNA-Seq analyses illustrated that a high fiber diet, in this setting, promoted a range of pro-neutrophil responses including Th17/IL-17. Gene Set Enrichment Analyses demonstrated significant similarities with mouse models of inflammatory psoriasis and significant depression of macrophage resolution phase signatures in the CHIKV arthritic lesions from mice fed a high fiber diet. Supplementation of the drinking water with butyrate also increased edema after CHIKV infection. However, the mechanisms involved were different, with modulation of AP-1 and NF-κB responses identified, potentially implicating deoptimization of endothelial barrier repair. Thus, neither fiber nor short chain fatty acids provided benefits in this acute infectious disease setting, which is characterized by widespread viral cytopathic effects and a need for tissue repair.

Butyrate enhances mitochondrial function during oxidative stress in cell lines from boys with autism

Butyrate (BT) is a ubiquitous short-chain fatty acid (SCFA) principally derived from the enteric microbiome. BT positively modulates mitochondrial function, including enhancing oxidative phosphorylation and beta-oxidation and has been proposed as a neuroprotectant. BT and other SCFAs have also been associated with autism spectrum disorders (ASD), a condition associated with mitochondrial dysfunction. We have developed a lymphoblastoid cell line (LCL) model of ASD, with a subset of LCLs demonstrating mitochondrial dysfunction (AD-A) and another subset of LCLs demonstrating normal mitochondrial function (AD-N). Given the positive modulation of BT on mitochondrial function, we hypothesized that BT would have a preferential positive effect on AD-A LCLs. To this end, we measured mitochondrial function in ASD and age-matched control (CNT) LCLs, all derived from boys, following 24 and 48 h exposure to BT (0, 0.1, 0.5, and 1 mM) both with and without an in vitro increase in reactive oxygen species (ROS). We also examined the expression of key genes involved in cellular and mitochondrial response to stress. In CNT LCLs, respiratory parameters linked to adenosine triphosphate (ATP) production were attenuated by 1 mM BT. In contrast, BT significantly increased respiratory parameters linked to ATP production in AD-A LCLs but not in AD-N LCLs. In the context of ROS exposure, BT increased respiratory parameters linked to ATP production for all groups. BT was found to modulate individual LCL mitochondrial respiration to a common set-point, with this set-point slightly higher for the AD-A LCLs as compared to the other groups. The highest concentration of BT (1 mM) increased the expression of genes involved in mitochondrial fission (PINK1, DRP1, FIS1) and physiological stress (UCP2, mTOR, HIF1α, PGC1α) as well as genes thought to be linked to cognition and behavior (CREB1, CamKinase II). These data show that the enteric microbiome-derived SCFA BT modulates mitochondrial activity, with this modulation dependent on concentration, microenvironment redox state, and the underlying mitochondrial function of the cell. In general, these data suggest that BT can enhance mitochondrial function in the context of physiological stress and/or mitochondrial dysfunction, and may be an important metabolite that can help rescue energy metabolism during disease states. Thus, insight into this metabolic modulator may have wide applications for both health and disease since BT has been implicated in a wide variety of conditions including ASD. However, future clinical studies in humans are needed to help define the practical implications of these physiological findings.

Konjac glucomannan, a promising polysaccharide of Amorphophallus konjac K. Koch in health care

In recent year, konjac glucomannan (KGM) has attracted more attention due to its non-harmful and non-toxic properties, good biocompatibility, biodegradability and hydrophilic ability. Moreover, KGM and their derivatives have several importances in the multidirectional research areas such as nutritional, biotechnological and fine chemical fields. In the previous article, we have reviewed the nutritional aspects of KGM covering the various aspects of functional foods, food additives and their derivatives. This review aims at highlighting the diverse biomedical research conducted on KGM in the past ten years, covering therapies for anti-obesity, regulation in lipid metabolism, laxative effect, anti-diabetic, anti-inflammatory, prebiotic to wound dressing applications. Moreover, this review deals with global health aspects of KGM and the disparate health related factors associated with diseases and their control measures.

Review: The potential of the common bean (Phaseolus vulgaris) as a vehicle for iron biofortification

Common beans are a staple food and the major source of iron for populations in Eastern Africa and Latin America. Bean iron concentration is high and can be further increased by biofortification. A major constraint to bean iron biofortification is low iron absorption, attributed to inhibitory compounds such as phytic acid (PA) and polyphenol(s) (PP). We have evaluated the usefulness of the common bean as a vehicle for iron biofortification. High iron concentrations and wide genetic variability have enabled plant breeders to develop high iron bean varieties (up to 10 mg/100 g). PA concentrations in beans are high and tend to increase with iron biofortification. Short-term human isotope studies indicate that iron absorption from beans is low, PA is the major inhibitor, and bean PP play a minor role. Multiple composite meal studies indicate that decreasing the PA level in the biofortified varieties substantially increases iron absorption. Fractional iron absorption from composite meals was 4%–7% in iron deficient women; thus the consumption of 100 g biofortified beans/day would provide about 30%–50% of their daily iron requirement. Beans are a good vehicle for iron biofortification, and regular high consumption would be expected to help combat iron deficiency (ID).

Butyrate regulates leptin expression through different signaling pathways in adipocytes

Leptin is an adipocytokine that regulates body weight, and maintains energy homeostasis by promoting reduced food intake and increasing energy expenditure. Leptin expression and secretion is regulated by various factors including hormones and fatty acids. Butyrate is a short-chain fatty acid that acts as source of energy in humans. We determined whether this fatty acid can play a role in leptin expression in fully differentiated human adipocytes. Mature differentiated adipocytes were incubated with or without increasing concentrations of butyrate. RNA was extracted and leptin mRNA expression was examined by Northern blot analysis. Moreover, the cells were incubated with regulators that may affect signals which may alter leptin expression and analyzed with Northern blotting. Butyrate stimulated leptin expression, and stimulated mitogen activated protein kinase (MAPK) and phospho-CREB signaling in a time-dependent manner. Prior treatment of the cells with signal transduction inhibitors as pertusis toxin, G(i) protein antagonist, PD98059 (a MAPK inhibitor), and wortmannin (a PI3K inhibitor) abolished leptin mRNA expression. These results suggest that butyrate can regulate leptin expression in humans at the transcriptional level. This is accomplished by: 1) G(i) protein-coupled receptors specific for short-chain fatty acids, and 2) MAPK and phosphatidylinositol-3-kinase (PI3K) signaling pathways.

The inhibitory effects and mechanisms of rhamnogalacturonan I pectin from potato on HT-29 colon cancer cell proliferation and cell cycle progression

Pectin is an important dietary component of all fruits and vegetables. Some pectins have been shown to inhibit cancer cell growth, but the effective structures and mechanisms have remained unclear. In this study, we investigated the effects of four structurally distinct pectins on human colon cancer HT-29 cells and the possible mechanisms accounting for the actions. The proliferation inhibitory effect was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometry was used to visualize the cell cycle distribution. An reverse transcription polymerase chain reaction (RT-PCR)-based assay was utilized to detect mRNA levels of the proteins related to cell cycle arrest. The data showed that the rhamnogalacturonan I domain-rich pectin from potato inhibited the proliferation of HT-29 cells and induced significant G2/M cell cycle arrest. This inhibitory effect was due to the down-regulation of cyclin B1 and cyclin-dependent kinase 1 expression, but not p21(WAF1/CIP1) expression. The results suggested that the rhamnogalacturonan I domain might relate to the anticancer activity of pectin.

Zinc sensing receptor signaling, mediated by GPR39, reduces butyrate-induced cell death in HT29 colonocytes via upregulation of clusterin

Zinc enhances epithelial proliferation, protects the digestive epithelial layer and has profound antiulcerative and antidiarrheal roles in the colon. Despite the clinical significance of this ion, the mechanisms linking zinc to these cellular processes are poorly understood. We have previously identified an extracellular Zn²⁺ sensing G-protein coupled receptor (ZnR) that activates Ca²⁺ signaling in colonocytes, but its molecular identity as well as its effects on colonocytes' survival remained elusive. Here, we show that Zn²⁺, by activation of the ZnR, protects HT29 colonocytes from butyrate induced cell death. Silencing of the G-protein coupled receptor GPR39 expression abolished ZnR-dependent Ca²⁺ release and Zn²⁺-dependent survival of butyrate-treated colonocytes. Importantly, GPR39 also mediated ZnR-dependent upregulation of Na⁺/H⁺ exchange activity as this activity was found in native colon tissue but not in tissue obtained from GPR39 knock-out mice. Although ZnR-dependent upregulation of Na⁺/H⁺ exchange reduced the cellular acid load induced by butyrate, it did not rescue HT29 cells from butyrate induced cell death. ZnR/GPR39 activation however, increased the expression of the anti-apoptotic protein clusterin in butyrate-treated cells. Furthermore, silencing of clusterin abolished the Zn²⁺-dependent survival of HT29 cells. Altogether, our results demonstrate that extracellular Zn²⁺, acting through ZnR, regulates intracellular pH and clusterin expression thereby enhancing survival of HT29 colonocytes. Moreover, we identify GPR39 as the molecular moiety of ZnR in HT29 and native colonocytes.

Milk fermented by Propionibacterium freudenreichii induces apoptosis of HGT-1 human gastric cancer cells

Background

Gastric cancer is one of the most common cancers in the world. The “economically developed countries” life style, including diet, constitutes a risk factor favoring this cancer. Diet modulation may lower digestive cancer incidence. Among promising food components, dairy propionibacteria were shown to trigger apoptosis of human colon cancer cells, via the release of short-chain fatty acids acetate and propionate.

Methodology/Principal Findings

A fermented milk, exclusively fermented by P. freudenreichii, was recently designed. In this work, the pro-apoptotic potential of this new fermented milk was demonstrated on HGT-1 human gastric cancer cells. Fermented milk supernatant induced typical features of apoptosis including chromatin condensation, formation of apoptotic bodies, DNA laddering, cell cycle arrest and emergence of a subG1 population, phosphatidylserine exposure at the plasma membrane outer leaflet, reactive oxygen species accumulation, mitochondrial transmembrane potential disruption, caspase activation and cytochrome c release. Remarkably, this new fermented milk containing P. freudenreichii enhanced the cytotoxicity of camptothecin, a drug used in gastric cancer chemotherapy.

Conclusions/Significance

Such new probiotic fermented milk may thus be useful as part of a preventive diet designed to prevent gastric cancer and/or as a food supplement to potentiate cancer therapeutic treatments.

Association between low colonic short-chain fatty acids and high bile acids in high colon cancer risk populations

We propose that the influence of diet on colon cancer risk is mediated by the microbiota. To investigate how dietary fat influences risk, we compared the colonic contents of 12 adult high-risk African Americans (AAs) and 10 Caucasian Americans (CAs) who consumed a high-fat diet (123 ± 11 g/d and 129 ± 17 g/d, respectively) to 13 native Africans (NAs) who subsisted on a low-fat (38 ± 3.0 g/d) diet, all aged 50-60 yr. The colonic bile acids were measured by LC-MS and the short-chain fatty acids (SCFAs) by GC. The chief secondary colonic bile acids, deoxycholic acid and lithocholic acid, were correlated with fat intake and similar between AAs and CAs, but 3-4 times higher than in AAs (p < 0.05). The major SCFAs were lower in AAs (p < 0.001) and CAs (p < 0.001) compared to AAs, but conversely, the branched chain fatty acids (BFCA) were higher. Our results suggest that the higher risk of colon cancer in Americans may be partly explained by their high-fat and high-protein, low complex carbohydrate diet, which produces colonic residues that promote microbes to produce potentially carcinogenic secondary bile acids and less antineoplastic SCFAs. The role of BCFA in colonic carcinogenesis deserves further study.

Association between low colonic short-chain fatty acids and high bile acids in high colon cancer risk populations

We propose that the influence of diet on colon cancer risk is mediated by the microbiota. To investigate how dietary fat influences risk, we compared the colonic contents of 12 adult high-risk African Americans (AAs) and 10 Caucasian Americans (CAs) who consumed a high-fat diet (123 ± 11 g/d and 129 ± 17 g/d, respectively) to 13 native Africans (NAs) who subsisted on a low-fat (38 ± 3.0 g/d) diet, all aged 50-60 yr. The colonic bile acids were measured by LC-MS and the short-chain fatty acids (SCFAs) by GC. The chief secondary colonic bile acids, deoxycholic acid and lithocholic acid, were correlated with fat intake and similar between AAs and CAs, but 3-4 times higher than in AAs (p < 0.05). The major SCFAs were lower in AAs (p < 0.001) and CAs (p < 0.001) compared to AAs, but conversely, the branched chain fatty acids (BFCA) were higher. Our results suggest that the higher risk of colon cancer in Americans may be partly explained by their high-fat and high-protein, low complex carbohydrate diet, which produces colonic residues that promote microbes to produce potentially carcinogenic secondary bile acids and less antineoplastic SCFAs. The role of BCFA in colonic carcinogenesis deserves further study.

Dietary fiber enhances TGF-β signaling and growth inhibition in the gut

Dietary fiber intake links to decreased risk of colorectal cancers. The underlying mechanisms remain unclear. Recently, we found that butyrate, a short-chain fatty acid produced in gut by bacterial fermentation of dietary fiber, enhances TGF-β signaling in rat intestinal epithelial cells (RIE-1). Furthermore, TGF-β represses inhibitors of differentiation (Ids), leading to apoptosis. We hypothesized that dietary fiber enhances TGF-β's growth inhibitory effects on gut epithelium via inhibition of Id2. In this study, Balb/c and DBA/2N mice were fed with a regular rodent chow or supplemented with a dietary fiber (20% pectin) and Smad3 level in gut epithelium was measured. In vitro, RIE-1 cells were treated with butyrate and TGF-β(1), and cell functions were evaluated. Furthermore, the role of Ids in butyrate- and TGF-β-induced growth inhibition was investigated. We found that pectin feeding increased Smad3 protein levels in the jejunum (1.47 ± 0.26-fold, P = 0.045, in Balb/c mice; 1.49 ± 0.19-fold, P = 0.016, in DBA/2N mice), and phospho-Smad3 levels (1.92 ± 0.27-fold, P = 0.009, in Balb/c mice; 1.83 ± 0.28-fold, P = 0.022, in DBA/2N mice). Butyrate or TGF-β alone inhibited cell growth and induced cell cycle arrest. The combined treatment of butyrate and TGF-β synergistically induced cell cycle arrest and apoptosis in RIE-1 cells and repressed Id2 and Id3 levels. Furthermore, knockdown of Id2 gene expression by use of small interfering RNA caused cell cycle arrest and apoptosis. We conclude that dietary fiber pectin enhanced Smad3 expression and activation in the gut. Butyrate and TGF-β induced cell cycle arrest and apoptosis, which may be mediated by repression of Id2. Our results implicate a novel mechanism of dietary fiber in reducing the risk of colorectal cancer development.

Effects of konjac glucomannan on putative risk factors for colon carcinogenesis in rats fed a high-fat diet

The aim of this study was to determine effects of konjac glucomannan (KGM) in a high fat corn oil diet on risk factors of colon carcinogenesis, that is, fecal β-glucuronidase, mucinase, and bile acids, and on preventive factors, that is, fecal microflora and cecal short-chain fatty acids (SCFAs). Sprague-Dawley rats (n = 8 animals per group) were fed a normal-fat fiber-free (5% corn oil, w/w) or high-fat (25% corn oil, w/w) diet containing no fiber, KGM (5%, w/w), or inulin (5%, w/w, as a prebiotic control) for 4 weeks. Results indicated that the high-fat fiber-free diet significantly elevated the fecal β-glucuronidase and mucinase activities and total bile acid concentration and decreased cecal SCFA contents, as compared with its normal-fat counterpart. The incorporation of KGM, as well as inulin, into the high-fat fiber-free diet beneficially reduced the fecal β-glucuronidase and mucinase activities and lithocholic acid (secondary bile acid) concentration. Although KGM elevated the daily fecal total bile acid excretion, the change was due to the primary, instead of the secondary, bile acids. In addition, KGM beneficially promoted the daily fecal excretion of bifidobacteria and lactobacilli and cecal SCFA contents, as compared with the high-fat fiber-free diet. Therefore, the present study suggests that KGM potentially attenuated the high fat-induced risk in colon carcinogenesis.

Oral administration of sodium butyrate reduces chemically-induced preneoplastic lesions in experimental carcinogenesis

OBJECTIVE: The objective was to assess the effects of oral administration of sodium butyrate on colon carcinogenesis. METHODS: Carcinogenesis in adult male Wistar rats was induced with 1.2-dimethylhydrazine injections at a dose of 40mg/kg of body weight. A solution of sodium butyrate (3.4%) was given ad libitum for 4 weeks (butyrate group, n=16) instead of water (control group, n=9). Rats were killed 17 weeks after 1.2-dimethylhydrazine administration. Aberrant crypt foci and expression of the messenger ribonucleic acid (mRNA) of cyclins D1 and E were quantified in the colon. Alterations in the fatty acid profile of the colon, liver, intra-abdominal fat and feces were also analyzed. RESULTS: A significant decrease in aberrant crypt foci was found in the group taking butyrate. No differences were found between the groups in the mRNA expression of cyclins D1 and E. Nevertheless, butyrate intake decreased the content of stearic and oleic acids in the intra-abdominal fat and docosahexaenoic acid in the liver. Moreover, these rats presented higher percentages of linoleic acid in the intra-abdominal fat than control rats. CONCLUSION: The data indicate that butyrate use in rats reduced preneoplastic lesions and changes in the intra-abdominal fat and fatty acid profile of the liver, commonly found in colon carcinogenesis.

Sodium butyrate induces human colon carcinoma HT-29 cell apoptosis through a mitochondrial pathway

Some tumours respond favourably to tumour necrosis factor-alpha (TNF-alpha). Despite this preferential sensitivity, resistance to TNF-alpha remains a clinical problem and more interest is now being focused on finding compounds that induce apoptosis through other pathways. Sodium butyrate (NaBt) has anti-tumour effects on colon cancer cells, inhibiting cell growth and promoting differentiation and apoptosis. In this study we investigated whether NaBt induced apoptosis in the human colon cancer cell line HT-29 and examined the intracellular mechanisms involved. Pre-incubation of cells with NaBt significantly increased apoptosis as measured by fluorescence activated cell sorter analysis and mitochondrial membrane potential determination. This effect could be blocked with the caspase inhibitors, z-VAD-fmk (pan-caspase inhibitor), z-DEVD-fmk (caspase-3 inhibitor) and z-LEHD-fmk (caspase-9 inhibitor), but not with z-IETD-fmk (caspase-8 inhibitor). Enhancement of caspase-3 and caspase-9 activities suggests that NaBt induces apoptosis via mitochondrial pathways not involving TNF-alpha.

Fermented wheat aleurone inhibits growth and induces apoptosis in human HT29 colon adenocarcinoma cells

Fermentation of dietary fibre by the gut microflora may enhance levels of SCFA, which are potentially chemoprotective against colon cancer. Functional food containing wheat aleurone may prevent cancer by influencing cell cycle and cell death. We investigated effects of fermented wheat aleurone on growth and apoptosis of HT29 cells. Wheat aleurone, flour and bran were digested and fermentedin vitro. The resulting fermentation supernatants (fs) were analysed for their major metabolites (SCFA, bile acids and ammonia). HT29 cells were treated for 24–72 h with the fs or synthetic mixtures mimicking the fs in SCFA, butyrate or deoxycholic acid (DCA) contents, and the influence on cell growth was determined. Fs aleurone was used to investigate the modulation of apoptosis and cell cycle. The fermented wheat samples contained two- to threefold higher amounts of SCFA than the faeces control (blank), but reduced levels of bile acids and increased concentrations of ammonia. Fs aleurone and flour equally reduced cell growth of HT29 more effectively than the corresponding blank and the SCFA mixtures. The EC50(48 h) ranged from 10 % (flour) to 19 % (blank). Markedly after 48 h, fs aleurone (10 %) significantly induced apoptosis and inhibited cell proliferation by arresting the cell cycle in the G0/G1 phase. In conclusion, fermentation of wheat aleurone results in a reduced level of tumour-promoting DCA, but higher levels of potentially chemopreventive SCFA. Fermented wheat aleurone is able to induce apoptosis and to block cell cycle – two essential markers of secondary chemoprevention.

Epigenetic silencing of the tumor suppressor microRNA Hsa-miR-124a regulates CDK6 expression and confers a poor prognosis in acute lymphoblastic leukemia

Whereas transcriptional silencing of genes due to epigenetic mechanisms is one of the most important alterations in acute lymphoblastic leukemia (ALL), some recent studies indicate that DNA methylation contributes to down-regulation of miRNAs during tumorigenesis. To explore the epigenetic alterations of miRNAs in ALL, we analyzed the methylation and chromatin status of the miR-124a loci in ALL. Expression of miR-124a was down-regulated in ALL by hypermethylation of the promoter and histone modifications including decreased levels of 3mk4H3 and AcH3 and increased levels of 2mK9H3, 3mK9H3, and 3mK27H3. Epigenetic down-regulation of miR-124a induced an up-regulation of its target, CDK6, and phosphorylation of retinoblastoma (Rb) and contributed to the abnormal proliferation of ALL cells both in vitro and in vivo. Cyclin-dependent kinase 6 (CDK6) inhibition by sodium butyrate or PD-0332991 decreased ALL cell growth in vitro, whereas overexpression of pre-miR124a led to decreased tumorigenicity in a xenogeneic in vivo Rag2(-/-)gammac(-/-) mouse model. The clinical implications of these findings were analyzed in a group of 353 patients diagnosed with ALL. Methylation of hsa-miR-124a was observed in 59% of the patients, which correlated with down-regulation of miR-124a (P < 0.001). Furthermore, hypermethylation of hsa-miR-124a was associated with higher relapse rate (P = 0.001) and mortality rate (P < 0.001), being an independent prognostic factor for disease-free survival (P < 0.001) and overall survival (P = 0.005) in the multivariate analysis. These results provide the grounds for new therapeutic strategies in ALL either targeting the epigenetic regulation of microRNAs and/or directly targeting the CDK6-Rb pathway.

Butyrate-induced apoptosis and cell cycle arrest in bovine kidney epithelial cells: involvement of caspase and proteasome pathways

Beyond their nutritional effect, short-chain fatty acids, especially butyrate, modulate cell differentiation, proliferation, motility, and in particular, they induce cell cycle arrest and apoptosis. A bovine kidney epithelial cell line (Madin-Darby bovine kidney; MDBK) was used to investigate the cell cycle regulatory and apoptotic effects of butyrate. Butyrate not only induced apoptosis but also induced cell cycle arrest at the G1/S boundary and M/G2 in MDBK cells (P < 0.01). The cell responses were concentration-dependent (r(2) = 0.9482, P <0.001). In examining possible mechanisms for the apoptosis and cell cycle arrest induced by butyrate, the results showed that butyrate treatment activates caspase-3 activities and induces accumulation of acetylated histone. At least two proteins, cdc6 and cdk1, become targeted for destruction on butyrate treatment. These two proteins are downregulated (P < 0.01 and P < 0.05, respectively) by proteolytic pathways. Moreover, the proteasome inhibitor MG-132 (carbobenzoxy-L-leucyl-L-leucyl-L-leucinal) reverses the cell cycle arrest induced by butyrate, indicating a multiprotein crosstalk wherein the ubiquitination/ proteasome pathway interacted with the caspase-signaling pathway. Because the proteasome inhibitor MG-132 blocked activation of caspase-3, these results functionally locate the proteasome pathway upstream of the caspase pathway. All these results indicate that butyrate functions as both a nutrient and signaling molecule regulating cell growth and proliferation.

The zinc sensing receptor, a link between zinc and cell signaling

Zinc is essential for cell growth. For many years it has been used to treat various epithelial disorders, ranging from wound healing to diarrhea and ulcerative colon disease. The physiological/molecular mechanisms linking zinc and cell growth, however, are not well understood. In recent years, Zn2+ has emerged as an important signaling molecule, activating intracellular pathways and regulating cell fate. We have functionally identified an extracellular zinc sensing receptor, called zinc sensing receptor (ZnR), that is specifically activated by extracellular Zn2+ at physiological concentrations. The putative ZnR is pharmacologically coupled to a Gq-protein which triggers release of Ca2+ from intracellular stores via the Inositol 1,4,5-trisphosphate (IP3) pathway. This, in turn results in downstream signaling via the MAP and phosphatidylinositol 3-kinase (PI3 kinase) pathways that are linked to cell proliferation. In some cell types, e.g., colonocytes, ZnR activity also upregulates Na+/H+ exchange, mediated by Na+/H+ exchanger isoform 1 (NHE1), which is involved in cellular ion homeostasis in addition to cell proliferation. Our overall hypothesis, as discussed below, is that a ZnR, found in organs where dynamic zinc homeostasis is observed, enables extracellular Zn2+ to trigger intracellular signaling pathways regulating key cell functions. These include cell proliferation and survival, vectorial ion transport and hormone secretion. Finally, we suggest that ZnR activity found in colonocytes is well positioned to attenuate erosion of the epithelial lining of the colon, thereby preventing or ameliorating diarrhea, but, by signaling through the same pathways, a ZnR may enhance tumor progression in neoplastic disease.

A new oral formulation for the release of sodium butyrate in the ileo-cecal region and colon

AIM: To develop a new formulation with hydroxy propyl methyl cellulose and Shellac coating for extended and selective delivery of butyrate in the ileo-caecal region and colon.

METHODS: One-gram sodium butyrate coated tablets containing ¹³C-butyrate were orally administered to 12 healthy subjects and 12 Crohn’s disease patients and the rate of ¹³C-butyrate absorption was evaluated by ¹³CO₂ breath test analysis for eight hours. Tauroursodeoxycholic acid (500 mg) was co-administered as a biomarker of oro-ileal transit time to determine also the site of release and absorption of butyrate by the time of its serum maximum concentration.

RESULTS: The coated formulation delayed the ¹³C-butyrate release by 2-3 h with respect to the uncoated tablets. Sodium butyrate was delivered in the intestine of all subjects and a more variable transit time was found in Crohn’s disease patients than in healthy subjects. The variability of the peak ¹³CO₂ in the kinetic release of butyrate was explained by the inter-subject variability in transit time. However, the coating chosen ensured an efficient release of the active compound even in patients with a short transit time.

CONCLUSION: Simultaneous evaluation of breath ¹³CO₂ and tauroursodeoxycholic acid concentration-time curves has shown that the new oral formulation consistently releases sodium butyrate in the ileo-cecal region and colon both in healthy subjects and Crohn’s disease patients with variable intestinal transit time. This formulation may be of therapeutic value in inflammatory bowel disease patients due to the appropriate release of the active compound.

Characterization of the effects of butyric acid on cell proliferation, cell cycle distribution and apoptosis

We examined concentration-dependent changes in cell cycle distribution and cell cycle-related proteins induced by butyric acid. Butyric acid enhanced or suppressed the proliferation of Jurkat human T lymphocytes depending on concentration. A low concentration of butyric acid induced a massive increase in the number of cells in S and G2/M phases, whereas a high concentration significantly increased the accumulation of cells in G2/M phase, suppressed the accumulation of cells in G0/G1 and S phases, and induced apoptosis that cell cycle-related protein expression in Jurkat cells treated with high levels of butyric acid caused a marked decrease in cyclin A, cyclin E, cyclin-dependent kinase 2 (CDK2), CDK4 and CDK6 protein levels in G0/G1 and S phases, with apoptosis induction, and a decrease in cyclin B, Cdc25c and p27KIP1 protein levels, as well as an increase in p21CIP1/WAF1 protein level, in the G2/M phase. Taken together, our results indicate that butyric acid has bimodal effects on cell proliferation and survival. The inhibition of cell growth followed by the increase in apoptosis induced by high levels of butyric acid were related to an increase in cell death in G0/G1 and S phases, as well as G2/M arrest of cells. Finally, these results were further substantiated by the expression profile of butyric acid-treated Jurkat cells obtained by means of cDNA array.

Augmentation of sodium butyrate-induced apoptosis by phosphatidylinositol 3-kinase inhibition in the human cervical cancer cell-line

PURPOSE

Sodium butyrate (NaBT) is principally a histone deacetylase (HDAC) inhibitor, and it has the potential to arrest HPV-positive carcinoma cells at the G1 to S phase transition of the cell cycle. The aim of study was to determine whether phosphatidylinositol 3-kinase (PI3K) inhibition can enhance the inhibitory effect of NaBT on a human cervical cancer cell line (HeLa).

MATERIALS AND METHODS

Cervical cancer cells (HeLa) were treated with NaBT alone or in combination with the PI3K inhibitors wortmannin or LY294002. Cell viability analysis and FACS analysis were carried out. The expressions of the cell cycle related proteins were evaluated by Western-blot analysis.

RESULTS

Inhibition of PI3K enhanced NaBT-mediated apoptosis and this decreased the HeLa cell viability. Either wortmannin or LY294002, combined with NaBT, enhanced the activation of caspase 3 and caspase 9, and this enhanced the subsequent cleavage of poly (ADP-ribose) polymerase (PARP). Cervical cancer cells were arrested in the subG1 and G2/M phase, as was detected by FACS analysis. NaBT treatment in combination with PI3K inhibitors showed the increased expression of the CDK inhibitors p21(Cip1/Waf1) and p27(Kip1), in a p53 dependent manner, and also the increased dephosphorylation of Rb whereas there was a reduction in the expression levels of cyclin A, cyclin D1 and cyclin B1.

CONCLUSION

The results demonstrate that inhibition of PI3K enhances NaBT-mediated cervical cancer cell apoptosis through the activation of the caspase pathway. Moreover, these findings will support future investigation using the PI3K inhibitors in combination with adjuvant treatment for treating carcinoma of the cervix.

Both wheat (Triticum aestivum) bran arabinoxylans and gut flora-mediated fermentation products protect human colon cells from genotoxic activities of 4-hydroxynonenal and hydrogen peroxide

Dietary fibers are fermented by the gut flora to yield short chain fatty acids (SCFAs), which inhibit the growth of tumor cells, induce glutathione S-transferases (GSTs), and protect cells from the genotoxic activity of 4-hydroxynonenal (HNE). Here, we investigated effects of wheat bran-derived arabinoxylans and fermentation products on these parameters of chemoprevention. Newly isolated water extractable (WeAx) and alkali extractable arabinoxylans (AeAx) were fermented under anaerobic conditions with human feces. Resulting fermentation supernatants (FSs) were analyzed for SCFAs and used to treat HT29 colon cancer cells. Cell growth, cytotoxicity, antigenotoxicity against hydrogen peroxide (H2O2) or HNE, and GST activity were determined. Nonfermented WeAx decreased H2O2-induced DNA damage by 64%, thus demonstrating chemoprotective properties by this nonfermented wheat bran fiber. The fermentation of WeAx and AeAx resulted in 3-fold increases of SCFA, but all FSs (including the control without arabinoxylans) inhibited the growth of the HT29 cells, reduced the genotoxicity of HNE, and enhanced the activity of GSTs (FS WeAx, 2-fold; FS AeAx, 1.7-fold; and control FS, 1.4-fold), which detoxify HNE. Thus, increases in SCFAs were not reflected by enhanced functional effects. The conclusion is that fermentation mixtures contain modulatory compounds that arise from the feces and might add to the effectiveness of SCFAs.

A novel retinoic/butyric hyaluronan ester for the treatment of acute promyelocytic leukemia: preliminary preclinical results

All-trans retinoic acid (ATRA) represents the therapy of choice for patients with acute promyelocytic leukemia (APL). However, patients often relapse due to ATRA-resistance. The molecular basis of APL alterations indicates that addition of a histone deacetylase inhibitor to ATRA may restore the sensitivity to retinoids. We explored the in vitro and in vivo effects of a novel retinoic/butyric hyaluronan ester (HBR) on a retinoic acid (RA)-sensitive human myeloid cell line, NB4, and on its RA-resistant subclone, NB4.007/6. In vitro, HBR induced growth arrest and terminal differentiation in RA-sensitive NB4 cells (as confirmed by an increased expression of CD11 family members and nitroblue tetrazolium assay), whereas it inhibited the growth of RA-resistant cells by apoptosis, paralleled by an increase in the levels of caspase 3 and 7. In vivo, HBR treatment of NB4-inoculated severe combined immunodeficient mice resulted in a statistically significant increase in survival time (P<0.0001), comparable to that induced by a maximum tolerated dose of RA alone. Also on P388-inoculated mice, HBR was active in contrast to RA that was completely ineffective. Present findings suggest that, owing to the simultaneous presence of RA and an histone deacetylases inhibitor, HBR might be useful in controlling the proliferation of RA-resistant cells and the differentiation of RA-sensitive cells.

Src family kinase members have a common response to histone deacetylase inhibitors in human colon cancer cells

Histone deacetylase inhibitors (HDIs) induce cell cycle arrest, differentiation and/or apoptosis in numerous cancer cell types and have shown promise in clinical trials. These agents are particularly novel, given their ability to selectively influence gene expression. Previously, we demonstrated that the HDIs butyrate and trichostatin A (TSA) directly repress c-Src proto-oncogene expression in many cancer cell lines. Activation and/or overexpression of c-Src have been frequently observed in numerous malignancies, especially of the colon. Therefore, our observation was particularly interesting since butyrate is a naturally abundant component of the large intestine and has been suggested to be a cancer-preventive agent. However, c-Src is not the only Src family kinase (SFK) member to be implicated in the development of human cancers, including those of the colon. Therefore, the relative expression levels of known SFKs were examined in a panel of human colon cancer cell lines. We found a surprisingly diverse expression pattern but noted that most cell lines expressed relatively high levels of at least 2 SFKs. When the effects of butyrate and TSA were examined in representative cell lines, the expression of all SFKs was repressed in a dose- and time-dependent manner. Further, detailed examination of Lck, Yes and Lyn demonstrated that this repression had a direct effect on transcription and was independent of new protein synthesis. These results mirror our earlier data obtained with c-Src and suggest that SFKs are a major target of HDIs and likely account in part for the anticancer effects of these promising new drugs.

The anti-cancer effects of poi (Colocasia esculenta) on colonic adenocarcinoma cells In vitro

Hawaiians tend to have lower incidence rates of colorectal cancer and it was hypothesized that this may be due to ethnic differences in diet, specifically, their consumption of poi, a starchy paste made from the taro (Colocasia esulenta L.) plant corm. Soluble extracts of poi were incubated at 100 mg/mL in vitro for antiproliferative activity against the rat YYT colon cancer cell line. (3)H-thymidine incorporation studies were conducted to demonstrate that the poi inhibited the proliferation of these cancer cells in a dose-dependent manner. The greatest suppression of YYT colon cancer growth occurred when 25% concentration was used. When poi was incubated with the YYT cells after 2 days, the YYT cells underwent apoptotic changes as evidenced by a positive terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) stain. Poi enhanced the proliferation of normal mouse splenocyte control cells, suggesting that poi is not simply toxic to all cells but even has a positive immunostimulatory role. By flow cytometry, T cells (CD4+ and CD8+) were predominantly activated by the poi. Although numerous factors can contribute to the risk of colon cancer, perhaps poi consumption may contribute to the lower colon cancer rates among Hawaiians by two distinct mechanisms. First, by inducing apoptosis within colon cancer cells; second, by non-specifically activating lymphocytes, which in turn can lyse cancerous cells. Our results suggest for the first time that poi may have novel tumor specific anti-cancer activities and future research is suggested with animal studies and human clinical trials.

Increase in Ara-C cytotoxicity in the presence of valproate, a histone deacetylase inhibitor, is associated with the concurrent expression of cyclin D1 and p27Kip1 in acute myeloblastic leukemia cells

The effects of valproate and butyrate were investigated in an acute myeloblastic cell line (OCI/AML-2) on cytotoxicity, cell cycle profile and expression of cell cycle regulating proteins in the presence of cytarabine (Ara-C) and etoposide. As a single agent valproate and butyrate inhibited AML cell growth but did not significantly induce cell death. A dramatic increase in cytotoxicity was observed when combining valproate or butyrate with Ara-C, whereas, co-addition of them with etoposide had much smaller effect on cell death. Valproate induced a clear G1 phase arrest and up-regulated cyclin D1 expression in the presence of Ara-C and etoposide. In addition, valporate was able to block the Ara-C-induced down-regulation of p27(Kip1) expression but not that induced by etoposide.

Tangutorine induces p21 expression and abnormal mitosis in human colon cancer HT-29 cells

A novel beta-carboline alkaloid, tangutorine (benz[f]indolo[2,3-a]quinolizidine) was isolated from the leaves of Nitraria tangutorum L. [Duan JA, Williams ID, Che CT, Zhou RH, Zhao RH, Tangutorine: a novel beta-carboline alkaloid from Nitraria tangutorum. Tetrahedron Lett 1999;40:2593-6], and its unique structural characters led us to initiate a study of its potential anti-proliferation activity. The in vitro treatment with low doses of tangutorine slightly stimulated the proliferation of human colon cancer HT29 cells until at concentrations higher than 6.25 microg/ml when the cell numbers, cellular MTT reduction, and cell proliferation by 3H-thymidine incorporation decreased in a dose-dependent manner (IC50=15 microg/ml=48 microM). Morphological studies of cells by fluorescence and electron microscopy did not show features for apoptosis but only large vacuoles, swollen mitochondria and dense cytoskeletal filaments bunching in the cytoplasm. Immunoblotting analysis revealed a dramatic induction of cyclin kinase inhibitor p21 as well as an inhibition of topoisomerase II expression at 25 microg/ml tangutorine, thereby impeding cell progression from S to G2/M phase. Cells accumulated at G1 phase of the cell cycle at concentrations > or =50 microg/ml tangutorine. Interestingly, some cells escaped from prolonged growth arrest without cell division and resulted in binucleated and polyploid G1 cells. Taken all results together, tangutorine induced a p21 suppression of all cyclins and their associated kinases, such as the topoisomerase II, and thus inhibited normal DNA replication and mitosis.

Hyaluronic acid butyric esters in cancer therapy

In this review we focus on a promising novel histone deacetylase (HDAC) inhibitor (HA-But) obtained by the esterification of butyric acid (BA), the smallest HDAC inhibitor, with hyaluronic acid (HA), the main constituent of the extracellular matrix which selectively recognizes a transmembrane receptor (CD44) overexpressed in most primary cancers and associated with tumor progression. In vitro, HA-But has proved to be 10-fold more effective than BA in inhibiting the proliferation of a panel of human cancer cell lines, representative of the most common human cancers, and, similar to BA, to regulate the expression of some cell cycle-related proteins, to induce growth arrest in the G1/G0 phase of the cell cycle and to increase histone acetylation. In vivo, HA-But treatment has demonstrated a marked potency in inhibiting primary tumor growth and lung metastases formation from murine Lewis lung carcinoma (LL3) as well as liver metastases formation from intrasplenic implantation of LL3 or B16-F10 murine melanoma cells. In particular, the effect of s.c. and i.p. treatment with HA-But on liver metastases resulted, respectively, in 87 and 100% metastases-free animals, and in a significant prolongation of the survival time compared to the control groups. The results suggest that the presence of the HA backbone does not interfere with the biological activity of butyric residues and that HA-But could represent a promising cell-targetable antineoplastic agent for the treatment of primary and metastatic tumors.

Differentiation of human colon adenocarcinoma cells alters the expression and intracellular localization of annexins A1, A2, and A5

Butyrate induces differentiation and alters cell proliferation in intestinal-epithelial cells by modulation of the expression of several genes. Annexins are a superfamily of ubiquitous proteins characterized by their calcium-dependent ability to bind to biological membranes; their involvement in several physiological processes, such as membrane trafficking, calcium signaling, cell motility, proliferation, and differentiation has been proposed. Thus, we have analyzed changes in annexin A1 (AnxA1), annexin A2 (AnxA2), and annexin A5 (AnxA5) levels and localization in human colon adenocarcinoma cells differentiated by butyrate treatment or by culture in glucose-free inosine-containing medium. The acquired differentiated phenotype increased dipeptidyl peptidase-IV (DPP-IV) expression and alkaline phosphatase (ALP) activity, two well known brush border markers. Butyrate induces cell differentiation and growth arrest in BCS-TC2, BCS-TC2.2, HT-29, and Caco-2 cells, increasing the levels of AnxA1 and AnxA5, whereas AnxA2 decreases except in Caco-2 cells. Inosine-differentiated cells present increased amounts of the three studied annexins, as occurs in spontaneously differentiated Caco-2 cells. AnxA2 down-regulation is not due to proteasome activation and seems to be related to the butyrate-induced cell proliferation arrest; AnxA1 and AnxA5 expression is growth-state independent. AnxA1 and AnxA5 are mainly found in the cytoplasm while AnxA2 is localized underneath the plasma membrane in cell-to-cell contacts. Butyrate induces changes in subcellular localization towards a vesicle-associated pattern. Human colon adenocarcinoma cell differentiation is associated with an up-regulation of AnxA1, AnxA2, and AnxA5 and with a subcellular relocation of these proteins. No correlation between annexin levels and tumorigenicity was found. Up-regulation of AnxA1 could contribute to the reported anti-inflammatory effects of butyrate in colon inflammatory diseases.

Acid sphingomyelinase is induced by butyrate but does not initiate the anticancer effect of butyrate in HT29 and HepG2 cells

Butyric acid and sphingomyelin (SM) affect colonic tumorigenesis. We examined the potential link between butyrate stimulation and SM metabolism in colonic and hepatic cancer cell lines. After incubating HT29 and HepG2 cells with butyrate and other short-chain fatty acids, we found that butyrate increased acid but not neutral or alkaline sphingomyelinase (SMase) activity by 10- to 20-fold. The effects occurred after 16 h of incubation and were associated with reduced SM and phosphatidylcholine contents and increased ceramide levels. Northern blotting showed increased acid SMase mRNA levels in these cells after butyrate stimulation. Propionate was less potent, and acetate had no effect. No similar changes of acid phosphatase could be identified. At concentrations that increased acid SMase expression, butyrate inhibited cell proliferation, activated caspase 3, and induced apoptosis. However, the antiproliferative and apoptotic effects of butyrate preceded the changes of acid SMase and were not affected by knocking down acid SMase expression by small, interfering RNA. In addition, butyrate-induced acid SMase expression was not affected by blocking the caspase pathway. In conclusion, butyrate regulates SM metabolism by stimulating acid SMase expression in colon and liver cancer cells, but the increased acid SMase is not a critical mechanism for initiating the anticancer effects of butyrate.

Bile acid deoxycholate induces differential subcellular localisation of the PKC isoenzymes beta 1, epsilon and delta in colonic epithelial cells in a sodium butyrate insensitive manner

Elevated levels of bile acids have been implicated in the abnormal morphogenesis of the colonic epithelium thus contributing to colorectal cancer (CRC). Alternatively sodium butyrate (NaB) produced by anaerobic fermentation of dietary fibre is regarded as being protective against colon cancer. Bile acids such as deoxycholic acid (DCA) are thought to mediate some of their actions by differentially activating protein kinase C (PKC). We examined the effects of DCA on the subcellular localisation of PKC-beta(1), -epsilon and -delta and whether these responses could be modulated by NaB. HCT116 cells endogenously express PKC-epsilon and -delta but not PKC-beta. DCA treatment results in endogenous PKC-epsilon translocation but not PKC-delta after 1 hr. To study the subcellular localisation of PKC isoforms in response to DCA in real time, PKC-beta(1), PKC-epsilon and PKC-delta functionally intact green fluorescent protein (GFP) fusion constructs were used. Stimulation with 300 microM DCA induces rapid translocation of PKC-beta(1)-GFP and PKC-epsilon-GFP but not PKC-delta-GFP from the cytosol to the plasma membrane in 15 min. Interestingly, pretreatment with 4mM NaB does not modify the response of the PKC isoenzymes to DCA as PKC-beta(1)-GFP and PKC-epsilon-GFP translocates to the plasma membrane in 15 min whereas PKC-delta-GFP localisation remains unaltered. Immunofluorescence shows that PKC-beta(1)-GFP and PKC-epsilon-GFP cells treated with DCA colocalise with the cytoskeletal elements actin and tubulin adjacent to the plasma membrane. Our findings demonstrate that the differential activation of the PKC isoenzymes by DCA may be of critical importance for the functional responses of colonic epithelial cells. Supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.

The role of intracellularly released formaldehyde and butyric acid in the anticancer activity of acyloxyalkyl esters

Previous studies described a family of anticancer histone deacetylase inhibitor prodrugs of formula Me(CH(2))(2)COOCH(R)OR(1), which upon intracellular hydrolysis release acids and aldehydes. This study examines the mechanisms by which the prodrugs affect tumor cells and the contribution of the released aldehyde (formaldehyde or acetaldehyde) and acids to their anticancer activity. Type I prodrugs release 2 equiv of a carboxylic acid and 1 equiv of an aldehyde, and of Type II release 2 equiv of acids and 2 equiv of an aldehyde. SAR studied inhibition of proliferation, induction of differentiation and apoptosis, histone acetylation, and gene expression. Formaldehyde, measured intracellularly, was the dominant factor affecting proliferation and cell death. Among the released acids, butyric acid elicited the greatest antiproliferative activity, but the nature of the acid had minor impact on proliferation. In HL-60 cells, formaldehyde-releasing prodrugs significantly increased apoptosis. The prodrugs affected to a similar extent the wild-type HL-60 and MES-SA cell lines and their multidrug-resistant HL-60/MX2 and MES-Dx5 subclones. In a cell-free histone deacetylase (HDAC) inhibition-assay only butyric acid inhibited HDAC activity. The butyric acid and formaldehyde induced cell differentiation and increased p53 and p21 levels, suggesting that both affect cancer cells, the acid by inhibiting HDAC and the aldehyde by an as yet unknown mechanism.

The human colonic monocarboxylate transporter Isoform 1: its potential importance to colonic tissue homeostasis

BACKGROUND & AIMS

Butyrate serves as the major source of energy for colonic epithelial cells, and has profound effects on their proliferation, differentiation, and apoptosis. Transport of butyrate across the colonocyte luminal membrane is mediated by the monocarboxylate transporter, MCT1; the expression of which is down-regulated dramatically during colon carcinogenesis. We have proposed that the decline in MCT1 expression during colon carcinogenesis may reduce the intracellular availability of butyrate required to regulate expression of genes associated with the processes maintaining tissue homeostasis within the colonic mucosa.

METHODS

To test this hypothesis we used the technique of RNA interference to inhibit MCT1 expression specifically, and determined the consequences of this inhibition on the ability of butyrate to exert its recognized effects in vitro using flow cytometry, immunofluorescence, Northern analysis, and Western analysis.

RESULTS

We show that inhibition of MCT1 expression, and hence butyrate uptake, has profound inhibitory effects on the ability of butyrate to regulate expression of key target genes: p21waf1/cip1 (p21), intestinal alkaline phosphatase (IAP), and cyclin D1, and their associated processes of proliferation and differentiation. In contrast, inhibition of MCT1 expression had no effect on the ability of butyrate to modulate expression of either bcl-XL or bak, and this was reflected in a corresponding lack of effect on butyrate induction of apoptosis.

CONCLUSIONS

Collectively, these results show the importance of MCT1 to the ability of butyrate to induce cell-cycle arrest and differentiation, and suggest fundamental differences in the mechanisms by which butyrate modulates specific aspects of cell function.

Cholesteryl butyrate solid lipid nanoparticles as a butyric acid pro-drug: effects on cell proliferation, cell-cycle distribution and c-myc expression in human leukemic cells

Cholesteryl butyrate solid lipid nanoparticles (chol-but SLN) have been proposed as a pro-drug to deliver butyric acid. We compared the effects on cell growth, cell-cycle distribution and c-myc expression of chol-but SLN and sodium butyrate (Na-but) in the human leukemic cell lines Jurkat, U937 and HL-60. In all the cell lines 0.5 and 1.0 mM chol-but SLN provoked a complete block of cell growth. Cell-cycle analysis demonstrated in Jurkat cells that 0.25 mM chol-but SLN caused a pronounced increase of G2/M cells and a decrease of G0/G1 cells, whereas in U937 and HL-60 cells chol-but SLN led to a dose-dependent increase of G0/G1 cells, with a decrease of G2/M cells. In Jurkat and HL-60 cells 0.5 mM chol-but SLN induced a significant increase of sub-G0/G1 apoptotic cells. Cell growth and cell-cycle distribution were unaffected by the same concentrations of Na-but. A concentration of 0.25 mM chol-but SLN was able to cause a rapid and transient down-regulation of c-myc expression in all the cell lines, whereas 1 mM Na-but caused a slight reduction of c-myc expression only in U937 cells. The results show how chol-but SLN affects the proliferation pattern of both myeloid and lymphoid cells to an extent greater than the natural butyrate.

Hyaluronic-acid butyric esters as promising antineoplastic agents in human lung carcinoma: a preclinical study

New promising compounds, derived from the esterification of hyaluronic acid with butyric acid, were investigated in vitro on a non-small cell lung carcinoma cell line (NCI-H460) and an its metastatic subclone (NCI-H460M). All new compounds exerted a dose-dependent inhibitory effect on both cell lines, which expressed CD44, the specific surface receptor for hyaluronic acid, in a very high percentage of cells (90%). HE1, the most effective of these compounds, was 10-fold more effective than sodium butyrate (NaB) in inhibiting cell proliferation. Similarly to NaB, after 24 hours of treatment, HE1 affected the expression of three cell cycle-related proteins (p27(kip1), p53 and p21(waf1)) responsible for growth arrest, indicating that the presence of the hyaluronic acid backbone does not interfere with the biologic activity. Intratumoral treatment with HE1 demonstrated a marked efficacy on primary tumor growth and on lung metastases formation of the murine Lewis Lung Carcinoma model. Altogether, present findings suggest a possible clinical application of these novel butyric pro-drugs in primary and metastatic lung cancer.

Conjugated Docosahexaenoic Acid Is a Potent Inducer of Cell Cycle Arrest and Apoptosis and Inhibits Growth of Colo 201 Human Colon Cancer Cells

The effect of conjugated docosahexaenoic acid (CDHA) on the inhibition of colon cancer cell growth was examined in the colo 201 human colon cancer cell line, and the effect was compared with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). CDHA was a more potent tumor cell growth inhibitor than DHA and EPA by colorimetric 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay (IC50 for 72 h: 31.6 microM, 46.8 microM, and 56.6 microM, respectively). CDHA inhibited cell cycle progression, due to accumulation of cells in G1 phase, which involved increased p21Cip1/Waf1 and decreased cyclin D1, cyclin E, and proliferating cell nuclear antigen expression; the p53 and cyclin A levels were unchanged. Induction of apoptosis was confirmed by the appearance of sub-G1 populations, and apoptosis cascade involved upregulation of the apoptosis-enhancing proteins (Bak and Bcl-xS) and downregulation of the apoptosis-suppressing proteins (Bcl-xL and Bcl-2). CDHA modulated cell cycle regulatory proteins and apoptosis-related proteins, similar to the effects of DHA. CDHA at a dietary dose of 1.0% significantly inhibited growth of colo 201 cells transplanted in nude mice.

Leptin counteracts sodium butyrate-induced apoptosis in human colon cancer HT-29 cells via NF-kappaB signaling

This study shows that leptin induced a rapid phosphorylation of p42/44 mitogen-activated protein kinase, an enhancement of both NF-kappaB DNA binding and transcriptional activities, and a concentration-dependent increase of HT-29 cell proliferation. These effects are consistent with the presence of leptin receptors on cell membranes. The leptin induction of cell growth was associated with an increase of cell population in S and G2/M phase compared with control cells found in G0/G1 phase of the cell cycle. Moreover, cyclin D1 immunoreactivity was enhanced in leptin-treated HT-29 cells and this increase was essentially associated with cell population in G0/G1 phase. On the other hand, we observed that sodium butyrate inhibited cell proliferation by blocking HT-29 cells in G0/G1 phase of the cell cycle. Interestingly, at physiological concentration, leptin prevented sodium butyrate-induced morphological nucleus changes, DNA laddering and suppressed butyrate-induced cell cycle arrest. This anti-apoptotic effect of leptin was associated with HT-29 cell proliferation and activation NF-kappaB pathways. However, the phosphorylation of p42/44 MAP kinase in response to leptin was reduced in butyrate-treated cells. These data demonstrated that leptin is a potent mitogenic factor for intestinal epithelial cells through the MAP kinase and NF-kappaB pathways. They also showed, for the first time, that leptin promotes colon cancer HT-29 cell survival upon butyrate challenge by counteracting the apoptotic programs initiated by this short chain fatty acid probably through the NF-kappaB pathways. Although further studies are required to unravel the precise mechanism, these data may have significance in the pathogenesis of colorectal cancer and ulcerative colitis diseases.

Sodium Butyrate Inhibits Cell Growth and Stimulates p21WAF1/CIP1 Protein in Human Colonic Adenocarcinoma Cells Independently of p53 Status

Butyric acid, one of the short-chain fatty acids produced by microbial fermentation in the colon, exhibits antiproliferative activities in various cancer cell lines. The initial objective of the study was to assess whether the effect of sodium butyrate (NaB) on cell growth differed by p53 status of the cells. Four human colorectal adenocarcinoma cell lines were used: HT29 (p53 point mutation), Caco2 (p53 truncation), LS513 (p53 wild type), and Lovo (p53 wild type). NaB significantly inhibited cell growth in all four cell lines. NaB arrested HT29 and LS513 cells in G0/G1 and Caco2 and Lovo in G2-phase. A second objective was to determine whether NaB similarly affected the cyclin-dependent kinase inhibitor, p21WAF1/CIP1. In all cell lines, p21 mRNA levels were immediately elevated after NaB exposure, and p21 protein levels were increased within 6 h. NaB increased p21 promoter activity in both Caco2 and Lovo, suggesting p53 independence. NaB did not influence p21 mRNA stability. Although three DNase I hypersensitivity sites were identified in the region of the p21 gene, induction of p21 mRNA by NaB was not accompanied by relaxation of the chromatin in the region of the p21 gene.

Trichostatin A suppresses transformation by the v-myb oncogene in BM2 cells

BM2 cells are chicken monoblasts transformed by the v-myb oncogene of avian myeloblastosis virus. The constitutively high v-myb expression interferes with the terminal differentiation of BM2 cells, but these cells can be induced to differentiate into macrophage-like cells by phorbol esters. Histone acetylation plays an important role in regulation of transcription and is particularly relevant to the regulation and pathology of hematopoiesis. In the present study, we examined the contribution of elevated histone acetylation to the differentiation of BM2 cells. Inhibition of the activity of endogenous histone deacetylases by trichostatin A (TSA) resulted in histone hyperacetylation causing cell cycle arrest and differentiation of BM2 cells into macrophage polykaryons. TSA did not affect the level of v-Myb protein in BM2 cells, but it downregulated its transcription activation capability. This suggests that chromatin remodeling can be significantly engaged in regulation of proliferation and differentiation of leukemic cells.

Novel mode of interference with nuclear factor of activated T-cells regulation in T-cells by the bacterial metabolite n-butyrate

The transcription factor nuclear factor of activated T-cells (NF-AT) plays an essential role in the activation of many early immune response genes. A dynamic equilibrium between calcineurin and cellular kinases controls its phosphorylation and thus regulates its activity by determining its subcellular localization. Here, we demonstrate that T-cell activation in the presence of the bacterial metabolite n-butyrate, which leads to inhibition of interleukin-2 transcription, is characterized by the maintenance of the activity of counter-regulatory kinases glycogen synthase kinase 3 and protein kinase A as well as persistence of intracellular cAMP levels, whereas calcium response and mitogen-activated protein kinase activation were indistinguishable from cells stimulated in the absence of n-butyrate. Nuclear binding of NF-AT was decreased but other transcription factors implicated in interleukin-2 expression such as AP1 and nuclear factor kappaB were unaffected. The effect on NF-AT binding appeared to be the result of increased nuclear export because the export inhibitor leptomycin B completely restored nuclear binding of NF-AT. We, therefore, provide first evidence for interference with NF-AT regulation alternative to the currently understood inhibition of nuclear import. This mechanism might represent a bacterial strategy to subvert host defense, which could be of particular clinical importance in the gastrointestinal tract where high amounts of n-butyrate are physiologically present.

Mechanisms of growth inhibition in keratinocytes by mercurio-substituted 4',5'-dihydropsoralens

Psoralens, together with ultraviolet light A (PUVA), are used in the treatment of epidermal proliferative disorders. Although these compounds can enter cells and photo cross-link DNA, lipids and proteins, including a specific membrane receptor, are also potential targets for the psoralens. To better elucidate the site of action of the psoralens, we have synthesized a family of 5'-mercurio-substituted derivatives of 4',5'-dihydropsoralen. These compounds are identified by their heavy metal content and can be used as a model to deliver thiol reactive psoralen derivatives into keratinocytes. The 5'-mercuriopsoralen derivatives were found to be effective inhibitors of keratinocyte growth without photoactivation. The most active compound, 4,8-dimethyl-5'-iodomercuriomethyl-4',5'-dihydropsoralen (IC50=10 microM), was also a potent photosensitizer (IC50=0.3 microM). Depletion of keratinocyte GSH with buthionine sulfoximine markedly increased their sensitivity to this analog, both with and without UVA light. In contrast, N-acetyl-L-cysteine partially protected the cells from growth inhibition, indicating that a sulfhydryl-sensitive site is growth limiting and that this target can be photoactivated. Iodomercurio-4',5'-dihydropsoralen was found to form adducts with GSH and cysteine, which were not active without UVA light. Thus, these adducts may also contribute to the photosensitization reactions of the parent compound. Using plasmid DNA unwinding assays, iodomercurio-4',5'-dihydropsoralen was also found to modify DNA, an activity that increased following UVA light treatment. This suggests that DNA damage may contribute to the actions of these psoralens. Taken together, our data demonstrate that there are multiple sites of action for mercuriopsoralens. These compounds may prove useful for understanding the mechanisms of psoralen-induced growth inhibition in the skin.

In vitro effects of cholesteryl butyrate solid lipid nanospheres as a butyric acid pro-drug on melanoma cells: evaluation of antiproliferative activity and apoptosis induction

Literature data show that butyric acid derivatives bear a dose-dependent differentiative anti-proliferative activity on cancer cell lines and that apoptosis induction may play a major role. Although it was recently shown that solid lipid nanospheres (SLNs) are a suitable tool for several in vivo drug administration routes, there is little available information on melanoma cell lines. This study was aimed at evaluating the anti-proliferative and apoptotic in vitro effects of cholesteryl butyrate (chol-but) SLNs on melanoma cells. Increasing concentrations of chol-but SLNs were used to test two melanoma cell lines. Both cell lines were treated with Na-butyrate (Na-but) and chol-but SLNs for viability. Those tested with chol-but SLNs were more effective than Na-butirate (3 to 72 h). The apoptotic effects of chol-but SLNs were evaluated between 3 and 72 h by annexin-V (ANX-V)/propidium iodide (PI) staining and the antiproliferative effect by PI staining. Apoptosis anti-proliferative-regulatory proteins as bcl-2, Fas/APO1 (CD95) and PCNA (PC10) were also investigated. Flow cytometric analyses evidenced a G(0/1)-S transition block and a 'sub-G(0/1)' apoptotic peak from 0.5 to 1.0 mM butyric acid. In ANX-V/PI flow cytometric staining, a dose- and time-dependent increase in the apoptotic cell percentage (ANX-V+) coupled with a down-regulation of PC10 and bcl-2 and a parallel up-regulation of Fas/APO1 (CD95) were found in both lines started after 3 to 24 h of chol-but SLNs treatment. Results show that chol-but SLNs exerts a dose/time-dependent effect in melanoma cell apoptosis induction between 3 and 24 h and a dose but not time-dependent effect after 24 h of treatment.