Dietary polyphenols are considered beneficial because of their potential protective role in the pathogenesis of chronic diseases associated to oxidative stress. However, many of these effects may depend on the concentration of the antioxidants used. The aim of the study was to evaluate the effect of quercetin, chlorogenic acid and epigallocatechin on proliferation of human colon adenocarcinoma cells Caco-2. Caco-2 cells were treated with different concentrations (25, 50, 100, 200, and 400 μM in DMSO) of antioxidants and the proliferation was assayed by MTT method. The results of the study indicated that chlorogenic acid and quercetin enhanced Caco-2 cells proliferation in time- and concentration-dependent manner. In contrary, epigallocatechin exhibit inhibitory influence, particularly significant at concentration ≥ 200 μM.
3
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Physiological process of cell death, apoptosis, plays a beneficial role in organism survival, but in some pathologies, like gastric Helicobacter pylori (Hp) infection, this process may turn against the host organism causing tissue damage. Knowledge of the mechanisms controlling apoptosis may have potential significance in treatment of these pathologic states. Therefore, we sought to determine whether apoptosis induced in the gastric epithelial cells exposed to live Hp involves the alteration in heat shock protein 70 (HSP70) expression and activation of caspase-3 in peroxisome proliferator-activated receptors (PPARg dependent manner). Experiments were performed with KATO III, gastric epithelial cells, exposed to CagA and Vac A positive live Hp , water Hp extracts or Hp culture supernatant over different time periods. Total cellular RNA and proteins were isolated for PCR, western-blot and EMSA studies. Genomic DNA was isolated to analyze apoptosis status. We propose new model of Hp induced HSP70 dependent, caspase-3 executed apoptosis in human gastric epithelium. KATO III cells exposed to Hp , showed an increase in caspase-3 activity accompanied and preceeded by activation of nuclear translocation of PPAR peaking at 48 h of culture. Moreover, heat shock factor 1 (HSF-1) bound up with phosphorylated STAT-3 was unable to activate HSP70 protein synthesis in KATO III exposed to Hp . Lack of protective effect of HSP70, activation of caspase-3 - dependent apoptosis pathway caused by Hp and alteration of the bax/bcl-2 cellular equilibrium led to gastric epithelial cell death. The observed phenomenon might be helpful in understanding of the mechanism of Hp related gastrointestinal tract diseasess, especially gastric cancer.
There are numerous studies suggesting that inflammation of the oral cavity caused by bacteria or fungi is accompanied by gastric inflammation. This is particularly relevant in patients using complete dentures. Since the presence of H. pylori in the oral cavity can be easily discovered by bacteria culture and that in the stomach by 13C urea breath test (UBT) and histology of gastric endoscopic biopsy samples it is reasonably to state that the majority of the patients show the presence of bacterium in oral cavity and active gastric H. pylori infection. When comparing, however, the bacteria culture originating from the oral mucosa to those from the gastric mucosa, employing molecular biology examination, such as polymerase chain reaction (PCR), we found that the oral bacteria and those originating from stomach are completely different, suggesting that H. pylori may be present only transiently in oral cavity and does not play major role in gastric H. pylori infection. Thus, oral cavity does not serve as bacterial reservoir to infect gastric mucosa. Most important finding of our study is that patients with recognized inflammation in the oral cavity in the form of stomatitis prothetica hyperplasica both fibrosa as well as papillaris showed in nearly 100% gastric H. pylori infection, usually without the presence of the same bacterium in the oral cavity, suggesting that gastric H. pylori infection affects oral mucosa at distance by some, as yet, unknown mechanism.
The involvement of peroxisome proliferator-activated receptors (PPARs) in the cancer cell elimination through apoptosis is a generally accepted fact. However, some reports indicate that the activation of PPAR is directly responsible for carcinogenesis. Caco-2 cells, a human adenocarcinoma cells, were used as a model of colon cancer. Cell cultures (5x106 cell per dish) were pretreated for 24h with PPARagonists ciglitazone (CI, 1x10-6M) and retinoic acid (RA, 1x10-6M) and part of the cultures were subsequently subjected to -radiation (photons) with therapeutic dose of 2,5 Gy. Total cellular RNA and proteins (cytoplasmic and nuclear) were isolated 24h after cultures irradiation or 48h after stimulation in the non irradiated part of experiment to preserve the equal growth time for all samples. -Irradiation of the cells abolished nuclear translocation of PPARunder its agonists treatment and preserved PPARin the cytoplasmic pool. But it did not affect the HSP 70 expression in response to ciglitazone and retinoic acid. Moreover, combined -irradiation and CI/RA treatment of the cells changed the equilibrium between Bax and Bcl-2 mRNA to anti apoptotic state with increased expression of Bcl-2 and almost abolished expression of Bax. In conclusion, this paper provides an evidence for the anti-apoptotic action of PPARagonists used along with the -radiation. Moreover, it shows that the up-regulated HSP70, in response to PPARagonists in -irradiated cultures promotes cell survival.
Heat shock proteins (HSP) are crucial for the maintenance of cell integrity under normal cell growth and at pathophysiological conditions such as colonization of gastric mucosa by Helicobacter pylori (Hp). The effect of Hp on mRNA expression for HSP70 in the gastric epithelial cells in vitro has been little studied and remains inconclusive. In this study we attempted to determine the alterations in gene expression for HSP70 induced by two live strains of Hp in the epithelial MKN7 cells. The following Hp strains were employed; 1) Hp strain expressing cagA and vacA, and 2) cagA and vacA negative Hp strain without or with addition of exogenous recombinant protein CagA. MKN7 cells were incubated in a standard medium RPMI 1640 supplemented with 10% fetal bovine serum at 37°C with 5% CO2 and humidified atmosphere under basal condition or in a presence of Hp (1x109 CFU per dish) without or with the recombinant CagA (10 µg/ml of RPMI 1640 medium). After 3h, 24h and 48 h of incubation with Hp and in some experiments with the prolonged incubation time up to 72 h, the cells were harvested, the total cellular RNA was isolated and the expression of mRNA for HSP70 was determined by RT-PCR. The incubation of the MKN cells with CagA protein alone failed to affect significantly the expression of HSP70. In contrast, the strain Hp (cagA+, vacA+) inhibited in time-dependent manner the expression of mRNA for HSP70. When the MKN7 cells were coincubated with Hp (cagA+, vacA+) and exogenous CagA, the significant inhibition of the signal intensity for HSP70 mRNA was observed at 3 h and 24 h of incubation and these effects were followed by complete disappearance of the signal for HSP70 mRNA at 48 h. The incubation of MKN7 with Hp (cagA-, vacA-) also significantly attenuated the expression of HSP70 mRNA with the most pronounced inhibitory effect observed at 72 h of incubation with this Hp strain. Addition of the recombinant CagA to Hp (cagA-, vacA-) completely suppressed the expression of HSP70 at 48 h and 72 h after the end of incubation periods. We conclude that 1) both, Hp (cagA+, vacA+) and Hp (cagA-, vacA-) inhibit expression of HSP70 in MKN7 human gastric epithelial cells independently of the presence or absence of cagA gene, and that 2) recombinant CagA protein may exert biological activity in vitro via acceleration of inhibitory effect of Hp negative for Cag A and VacA on HSP70 expression in epithelial cells infected with this bacteria.
10
Dostęp do pełnego tekstu na zewnętrznej witrynie WWW
Aim of study was to verify whether pulsating electromagnetic field (PEMF) can affect cancer cells proliferation and death. U937 human lymphoid cell line at densities starting from 1x106 cells/ml to 0.0625x106 cells/ml, were exposed to a pulsating magnetic field 50Hz, 45±5 mT three times for 3 h per each stimulation with 24 h intervals. Proliferation has been studied by counting number of cells stimulated and non-stimulated by PEMF during four days of cultivation. viability of cells was analyzed by APC labeled Annexin V and 7-AAD (7-amino-actinomycin D) dye binding and flow cytometry. Growing densities of cells increase cell death in cultures of U937 cells. PEMF exposition decreased amount of cells only in higher densities. Measurement of Annexin V binding and 7-AAD dye incorporation has shown that density-induced cell death corresponds with decrease of proliferation activity. PEMF potentiated density-induced death both apoptosis and necrosis. The strongest influence of PEMF has been found for 1x106cells/ml and 0.5x106 cells/ml density. To eliminate density effect on cell death, for further studies density 0.25x106 cells/ml was chosen. Puromycin, a telomerase inhibitor, was used as a cell death inducer at concentration 100 µg/ml. Combined interaction of three doses of puromycin and three fold PEMF interaction resulted in a reduced of apoptosis by 24,7% and necrosis by 13%. PEMF protects U937 cells against puromycin- induced cell death. PEMF effects on the human lymphoid cell line depends upon cell density. Increased density induced cells death and on the other hand prevented cells death induced by puromycin.