Toxic and metabolic effect of sodium butyrate on SAS tongue cancer cells: role of cell cycle deregulation and redox changes

Butyrate is a metabolite produced by oral and colonic microorganism. Butyrate has been shown to reduce colon cancer, whereas its role in oral carcinogenesis is not clear. Butyrate concentration in dental plaque and saliva ranged from 0.2 to 16 mM. In this study, we found that sodium butyrate inhibited the growth of SAS tongue cancer cells by 32% and 53% at concentrations of 1 and 2mM, respectively. Low concentrations of sodium butyrate (1-8mM) induced G0/G1 cell cycle arrest of SAS cells, whereas concentrations of 4-16 mM elicited G2/M arrest and a slight increase in apoptotic cell populations. These events were concomitant with induction of intracellular reactive oxygen species (ROS) production. An elevation in p21 mRNA and protein level was noted in SAS cells by sodium butyrate. On the contrary, a decline of cyclin Bl, cdc2 and cdc25C mRNA and protein expression in SAS cells was found after exposure to sodium butyrate. In addition, no evident increase in cdc2 inhibitory phosphorylation was found in sodium butyrate-treated SAS cancer cells. Inclusion of N-acetyl-l-cysteine (NAC) (3mM), catalase (1000 U/ml) and dimethylthiourea (DMT, 5mM), and also SOD (500 U/ml) attenuated the sodium butyrate-induced ROS production in SAS cells. However, they were not able to prevent the cell cycle arrest, apoptosis and growth inhibition in SAS cells induced by 1, 2 and 16 mM of sodium butyrate. These results indicate that sodium butyrate is toxic and inhibits the tongue cancer cell growth via induction of cell cycle arrest and apoptosis. Sodium butyrate mediates these events by mechanisms additional to ROS production.     

丁酸钠和曲古抑菌素A促进K562细胞分化机制的研究及其对比

目的　探讨丁酸钠与曲古抑菌素A(TSA)促进K5 6 2细胞分化的机制 ,并对比二者的异同。方法　台盼蓝拒染实验观察药物对细胞生长曲线的影响 ;四氮唑盐还原试验和细胞表面分化抗原检测观察药物对细胞的分化作用 ;流式细胞仪分析细胞周期 ;RT PCR和WesternBlot分别检察细胞周期蛋白在mRNA和蛋白质水平的表达。结果　丁酸钠和TSA分别将细胞主要阻滞于G0 /G1期和G2 期 ;丁酸钠下调cyclinD1mRNA的水平基本上不影响其蛋白质的表达 ,上调cyclinD3蛋白质表达水平基本上不影响其mRNA的水平 ;TSA与丁酸钠的作用相同 ;二者均可以在mRNA和蛋白质水平刺激K5 6 2细胞 p2 1的表达。 结论　丁酸钠和TSA促进K5 6 2的分化是通过诱导 p2 1和cyclinD3蛋白质的表达而完成的 ,丁酸钠和TSA均有望成为治疗慢性髓系白血病的药物。     

原花青素对Aβ_(25-35)诱导PC12细胞凋亡的影响及其机制的研究

目的　探讨原花青素(Procyanidins,PC)对β淀粉样肽25~35(βamyloidpeptide25 -35, Aβ25-35 )诱导PC12细胞凋亡的影响及其机制。方法　采用MTT比色法分析细胞存活率, Hoechst33258 PI荧光染色法检测凋亡, RT PCR检测P53和bcl 2基因mRNA表达,Westernblot检测P53和Bcl 2蛋白表达。结果　不同剂量PC预处理PC12细胞 1h可剂量依赖性对抗Aβ25-35引起的凋亡,提高细胞的存活率,减少Aβ25-35引起的核固缩,凝聚和碎裂,降低P53mRNA表达以及P53蛋白表达,增加bcl 2mRNA表达以及Bcl 2蛋白表达。结论　PC可剂量依赖性对抗Aβ25-35对PC12细胞的毒性作用,其机制可能与下调凋亡基因P53和上调抗凋亡基因bcl 2表达有关。     

丁酸钠诱导结肠癌HT-29细胞凋亡的信号通路及对AQP3基因表达影响的研究

目的：探讨丁酸钠诱导结肠癌HT-29细胞凋亡过程的分子机理及其对水通道蛋白AQP3基因表达的影响。方法：MTT法检测不同浓度的丁酸钠对结肠癌HT-29细胞生长的影响;RT-PCR检测不同浓度的丁酸钠对细胞周期蛋白Cyclin D1、CDK4、p16和AQP3的基因表达水平,同时使用流式细胞仪检测细胞周期。结果：加入浓度超过2.5mmol/L的丁酸钠后,结肠癌HT-29细胞生长受到抑制,Cyclin D1、CDK4和AQP3的表达水平下降,p16的表达水平上调,细胞阻滞于G1/S期。结论：浓度超过2.5mmol/L的丁酸钠可以诱导结肠癌HT-29细胞凋亡,使其细胞周期阻滞于G1/S期,且这种诱导作用是剂量依赖型的,其分子通路可能是通过p16-Cyclin D1/CDK4这条信号途径,在此过程中,伴随着AQP3的基因表达水平降低。     

The effect of sulphasalazine and its metabolites on the colonic epithelial Caco-2 cells

Sulphaselazine (SAS) is a drug commonly used to treat patients suffering from chronic inflammatory states such as inflammatory bowel diseases. It was shown that besides bacteriostatic, antiinflammatory and immunosuppressive activity of this drug, the risk of neoplastic changes in the colon and rectum was substantially diminished during ulcerative colitis therapy with SAS. In the present study the effects of SAS and its main metabolites--sulphapyridine (SP) and 5-aminosalicylic acid (5-ASA) on colon adenocarcinoma Caco-2 cells viability and proliferation was evaluated. Significant inhibitory impact of SAS was observed already at 1 mM concentration whereas 5-ASA and SP impaired cellular growth when used at 5 mM concentration. 5 mM SAS exerted a strong cytotoxic effect on Caco-2 cells resulting in their necrotic death. The inhibition of cellular proliferation and the cytotoxic effects of SAS and its metabolites (5-ASA and SP) on the colonic carcinoma cells (Caco-2) confirm the suggestions that these compounds at appropriate concentrations may reduce the risk of neoplastic changes frequently initiated by prolonged inflammatory states.     

Induction of cytotoxicity and ssDNA breaks by 9-bromo-5-morpholino-tetrazolo[1,5-c]quinazoline in tumor cells cultured in vitro.

9-Bromo-5-morpholino-tetrazolo[1,5-c]quinazoline (BMTQ) acted cytotoxically on murine leukemia cell line L1210 and human colon carcinoma cells Caco-2. We found the two highest concentrations of BMTQ (149.2 and 74.6 microM) induced an acute cytotoxic effect, however other tested concentrations (<74.6 microM) manifested a concentration/dependent and time/dependent cytotoxic effect. The sensitivity of murine leukemia cells L1210 and human colon carcinoma cells Caco-2 was expressed in the same order. The cytotoxicity of BMTQ was not accompanied by changes of the cell cycle profile. Following the cytotoxicity-related effects of BMTQ we observed the induction of ssDNA breaks after BMTQ treatment. All the concentrations of BMTQ increased the level of ssDNA breaks 1.3-2.9 times (after 2 h of treatment) and 1.6-2.8 times (after 4 h of treatment) in Caco-2 cells compared to the control. No apoptotic DNA fragmentation induced by BMTQ in Caco-2 cells was recorded.     

Regulation of beta-adrenoceptor number and subtype in 3T3-L1 preadipocytes by sodium butyrate

In mouse 3T3-L1 preadipocytes, the glucocorticoid dexamethasone has been shown to promote a switch in beta-adrenoceptor subtype expression from beta 1 to beta 2 and to increase the total number of beta-adrenoceptors. The present study demonstrates that sodium butyrate also modulates beta-adrenoceptor expression in these cells. Incubation of preadipocytes with 2-10 mM butyrate for 24-48 h promoted a dose- and time-dependent switch in beta-adrenoceptor subtype from a near equal mixture of beta 1 and beta 2 to greater than 85% beta 2 and caused an approximate doubling of the receptor number. beta-Adrenoceptors were assayed in membranes prepared from 3T3-L1 cells using the radiolabeled antagonist [125I]iodocyanopindolol and the beta 2-selective antagonist ICI 118.551. Other short chain acids were not as effective as butyrate in promoting changes in beta-adrenoceptor expression. Cycloheximide (1.0 microgram/ml) inhibited the effects of butyrate on both beta-adrenoceptor subtype and number. Alterations in beta-adrenoceptor phenotype promoted by either butyrate or dexamethasone were functionally correlated with cAMP accumulation in these cells. Comparison of the effects of butyrate and dexamethasone on beta-adrenoceptor expression suggests that these two agents regulate beta-adrenoceptors by different mechanisms.     

Genotoxicity of 4-hydroxy-2-nonenal in human colon tumor cells is associated with cellular levels of glutathione and the modulation of glutathione S-transferase A4 expression by butyrate.

The cellular production of 4-hydroxy-2-nonenal (HNE), a product of endogenous lipid peroxidation, constitutes a genotoxic risk factor for carcinogenesis. Our previous studies have shown that human HT29 colon cells developed resistance toward HNE injury after treatment with butyrate, a diet-associated gut fermentation product. This resistance was attributed to the induction of certain glutathione S-transferases (hGSTP1-1, hGSTM2-2, and hGSTA1-1) and also for the tripeptide glutathione (GSH) synthesizing enzymes. In the present study, we have investigated in HT29 cells whether hGSTA4-4, which has a high substrate specificity for HNE, was also inducible by butyrate and, thus, could contribute to the previously observed chemoresistance. In addition, we investigated if cellular depletion of GSH by L-buthionine-S,R-sulfoximine (BSO) enhances chemosensitivity to HNE injury in HT29 cells. Incubation of HT29 cells with butyrate (2-4 mM) significantly elicited a 1.8 to 3-fold upregulation of steady state hGSTA4 mRNA over 8-24 h after treatment. Moreover, 4 mM butyrate tended to increase hGSTA4-4 protein concentrations. Incubation with 100 microM BSO decreased cellular GSH levels by 77% without significant changes in cell viability. Associated with this was a 2-fold higher level of HNE-induced DNA damage as measured by the comet assay. Collectively, the results of this study and our previous work indicate that the genotoxicity of HNE is highly dependent on cellular GSH status and those GSTs that contribute toward HNE conjugation, including hGSTA4-4. Since HNE contributes to colon carcinogenesis, the favorable modulation of the GSH/GST system by butyrate may contribute to chemoprevention and reduction of the risks.     

Effects of budesonide on P-glycoprotein expression in intestinal cell lines

BACKGROUND AND PURPOSE: P-glycoprotein (P-gp) is an important efflux transporter that supports the barrier function of the gut against invading antigens and against administered drugs. Since glucocorticoids, such as budesonide, are frequently used during inflammatory bowel disease we investigated how budesonide influences P-gp expression in different intestinal cell lines. EXPERIMENTAL APPROACH: LS180 and Caco-2 cells were incubated with budesonide and changes in P-gp expression were determined on mRNA, protein and functional level. The mRNA expression levels of glucocorticoid receptor (GR) and pregnane X receptor (PXR) were determined in these cell lines. PXR receptor was transiently transfected into Caco-2 cells. KEY RESULTS: Budesonide showed an induction of P-gp in LS180 cells and a down-regulation in Caco-2 cells. Expression levels of nuclear receptors revealed high expression of PXR only in LS180 cells and exclusive expression of GR in Caco-2 cells. Mifepristone, an anti-glucocorticoid, could not reverse the down-regulation of P-gp by budesonide in Caco-2 cells. In PXR-transfected Caco-2 cells the budesonide-mediated down-regulation of P-gp was abolished. Furthermore the expression of cytochrome P450 3A4 (CYP3A4), another PXR target gene, was induced in PXR-transfected Caco-2 cells after budesonide treatment. CONCLUSIONS AND IMPLICATIONS: Budesonide has the potential to influence MDR1 expression in vitro. In LS180 cells, the induction of MDR1 by budesonide probably is mediated via PXR. The mechanism of the down-regulation in Caco-2 cells still remains unclear, but GR does not seem to be involved. Further studies are required to evaluate how budesonide alters P-gp expression in vivo.     

Glutathione S-transferase expression and isoenzyme composition during cell differentiation of Caco-2 cells

The human colon adenocarcinoma cell line Caco-2 is frequently used to study human intestinal metabolism and transport of xenobiotica. Previous studies have shown that both Caco-2 cells and human colon cells constitutively express the multigene family of detoxifying enzymes glutathione S-transferases (GSTs), particularly GST alpha and GST pi. GSTs may play a fundamental role in the molecular interplay between phase I, II enzymes and ABC-transporters. The gut fermentation product, butyrate, can modulate the potential for detoxification. The aim of this study was to investigate the basal expression of further cytosolic GSTs in Caco-2 cells during cell differentiation. In addition, a comparison was made with expression levels in MCF-7 and HepG2, two other cell types with barrier functions. Finally, the butyrate-mediated modulation of gene and protein expression was determined by real time PCR and western blot analysis.     

The effect of five artificial sweeteners on Caco-2, HT-29 and HEK-293 cells

Context: Artificial sweeteners (AS) have been associated with tumor development (including colon cancer) in both animals and humans although evidence has been conflicting. Objectives: Additional research was thus conducted by studying the effects of 5 AS on the morphology, cell proliferation and DNA in cells by utilizing Caco-2, HT-29 (colon) and HEK-293 (kidney) cell lines. Materials and methods: Cells were exposed to sodium cyclamate, sodium saccharin, sucralose and acesulfame-K (0–50?mM) and aspartame (0–35?mM) over 24, 48 and 72 hours. Morphological changes were presented photographically and % cell viability was determined by using the MTT cell viability assay. Possible DNA damage (comet assay) induced by the AS (0.1, 1 and 10?mM, treated for 24, 48 and 72 hours) was studied. The appearance of “comets” was scored from no damage to severe damage (0–4). Results: Cells became flatter and less well defined at higher AS concentrations (>10?mM). At concentrations >10?mM, decreased cell viability was noted with both increasing concentration and increasing incubation time for all cell lines tested. In general, HEK-293 cells seemed to be less affected then the colon cancer cells. Sucralose and sodium saccharin seemed to elicit the greatest degree of DNA fragmentation of all the sweeteners tested in all the cell lines used. Discussion: Morphological cell alterations, cell viability and DNA fragmentation seemed to be more in the colon cancer cells. Conclusions: Further studies have to be performed to clarify mechanisms involved causing these alterations in mammalian cells.     

Distribution of breast cancer resistance protein (BCRP/ABCG2) mRNA expression along the human GI tract

Human breast cancer resistance protein (BCRP/ABCG2) is an ABC-transporter that is present on the luminal membrane of intestinal epithelial cells and restricts absorption of anticancer drugs such as methotrexate, topotecan, mitoxantrone, and doxorubicin. The exact anatomic distribution of BCRP along the gastrointestinal (GI) tract, however, has not been determined before. The aim of this study was, therefore to investigate BCRP mRNA expression pattern along the GI tract in 14 healthy subjects. Furthermore, BCRP duodenal mRNA expression was compared with MDR1/ABCB1 mRNA. Additionally, BCRP mRNA expression was investigated in two human intestinal cell lines (Caco-2 and LS180). Since previous animal studies have suggested sex specific differences in BCRP expression, we analyzed intestinal BCRP expression with respect to sex. Biopsies were taken from different gut segments (duodenum, terminal ileum and ascending, transverse, descending and sigmoid colon). Gene expression was assessed by quantitative real-time PCR (Taqman). BCRP mRNA expression was maximal in the duodenum and decreased continuously down to the rectum (terminal ileum 93.7%, ascending colon 75.8%, transverse colon 66.6%, descending colon 62.8%, and sigmoid colon 50.1% compared to duodenum, respectively). BCRP expression in the duodenum was comparable to MDR1/ABCB1 gene expression. Caco-2 cells showed a comparable expression of BCRP as human duodenal tissue. Gender specific differences in BCRP expression were not observed. These findings represent the first systematic site-specific analysis of BCRP expression along the GI tract. This information might be helpful to develop target strategies for orally administered anticancer drugs.     

Regulation of microglial inflammatory response by sodium butyrate and short-chain fatty acids

1. Recent studies have shown that sodium butyrate and other short-chain fatty acids (SCFAs) can prevent inflammation in colon diseases. Our aim was to elucidate whether sodium butyrate and SCFAs regulate the inflammatory responses in different neural inflammation models in cell cultures. 2. Inflammatory responses to LPS-induced microglial activation were recorded by the secretion of nitric oxide (NO) and cytokines IL-6 and TNF-alpha and related to the changes in the DNA-binding activities of NF-kappaB complex. 3. We observed that sodium butyrate is strongly anti-inflammatory against LPS-induced responses in rat primary microglia as well as in hippocampal slice cultures and in neural cocultures of microglial cells, astrocytes and cerebellar granule neurons. 4. In murine N9 microglial cell line, instead, sodium butyrate and other SCFAs (propionate, valerate and caproate) enhanced the LPS-induced inflammatory response. 5. The pretreatment with butyrate before LPS exposure induced an equal or more enhanced response than simultaneous exposure with butyrate and LPS. This indicates that butyrate induces an adaptative response against microglial activation. 6. We also observed that butyrate treatment both in transformed N9 cells and in hippocampal slice cultures downregulates the NF-kappaB-binding capacity induced by LPS stimulation. 7. Our results show that butyrate is anti-inflammatory in primary, brain-derived microglial cells, as observed recently in colon diseases, but proinflammatory in transformed, proliferating N9 microglial cells, which may be related to the anticancer properties of butyrate observed in tumor cells.