Effects of Lactobacillus casei 01 and its exopolysaccharide on 1,2-dimethylhydrazine induced colon precancerous lesions in F344 rats
Date Issued
2010
Date
2010
Author(s)
Liu, Chu-Ting
Abstract
Colorectal cancer is a major cause of death in Taiwan. Approximately 70% of colorectal cancer is related to diets. Lactic acid bacteria might be used for cancer chemoprevention due to their putative anticarcinogenic and antitumor activities. The benefit effects on human health of lactic acid bacteria might be attributable to positive physiological effect of exopolysaccharides (EPS). In the present study, we employ the Lactobacillus casei 01 and EPS as materials.
The cell fractions (heat-treated cells, crude cell walls and intracellular extracts) and EPS of L. casei 01 were studied for their effects on the growth of human intestinal epithelial cells, intestine 407 and the proliferation of human colon cancer cell, HT-29. The results showed that EPS exhibited the most antiproliferation activity on HT-29 cell. The viability of intestine 407 cells was not affected by EPS. EPS was further used to study the prevention of 4-Nitroquinoline N-oxide (4NQO)-induced DNA damage on intestine 407 cells. The results showed that 50-100 μg/mL of L. casei 01 EPS had antiproliferation on HT-29, and low concentration (5-50 μg/mL) of EPS will not affect the growth of intestine 407 cells. Furthermore, possible anticytotoxic mechanisms of EPS were investigated by section-preincubation test and comet assay to explore the effects of EPS against 4NQO-induced DNA damage on intestine 407. The results indicated that low concentrations (10 and 50 μg/mL) of EPS markedly raised the cell viability of intestine 407, besides, 50 μg/mL of EPS significantly reduced the genetoxicity of 4NQO-induced DNA damage on intestine 407 cells (p < 0.05). These findings suggest that EPS had bioanticytotoxic effects, and the blocking effect was the main mechanism of anticytotoxicity for EPS against 4NQO.
Secondly, the effects of L. casei 01 and EPS on alteration of fecal microflora, serum lipid levels, antioxidant enzymes of blood, and tissue lipid peroxidation, such as tissue thiobarbituricacid substances (TBARS) as well as their inhibitory effect on precancerous colon lesions in male F344 rats were determined. Rats were divided into four groups. Group 1 served as control, group 2, 3 and 4 were given weekly subcutaneous injections of 1,2-dimethylhydrazine (DMH) at a dose of 20 mg/kg body weight for 12 weeks. Besides, group 3 and 4 were given a treatment of L. casei 01 (1010 cfu/10 mL/kg bw/2 d, 12 weeks) and EPS (100 mg/10 mL/kg bw/2 d, 12 weeks) orally, respectively. Animals were sacrificed at the end of 12 weeks. It was found that L. casei 01 treatment decreased serum alanine aminotransferase (ALT) activity and triglycerides concentration. However, these rats treated with L. casei 01 enhanced activity of superoxide dismutase (SOD), and reduced the concentrations of glutathione reductase (GRd), and glutathione peroxidase (GPx) when compared with those DMH-treated rats. There was a decrease in the population of staphylococci, Escherichia coli, and total coliforms in the feces of L. casei 01-treated rats compared with the control. Both EPS and L. casei 01 markedly increased the cell numbers of lactobacilli and bifidobacteria for F344 rats treated with DMH. Moreover, the amount of TBARS in serum and tissues were significantly raised in DMH-treated rats, while they were significantly diminished in rats received L. casei 01- or EPS-treatment simultaneously. Histopathological changes in the colon of L. casei 01- and EPS-treated rats showed reduced DMH-induced focal slight cryptic necrosis in the mucosal layer.
Finally, the effects of L. casei 01 and EPS on the gene expression profiles of DMH-induced experimental colon precancerous lesions in rats were investigated. For gene expression analysis, the RNA of DMH-, DMH+EPS-, and DMH+L. casei 01-treated group were hybridized with that of the control on 4×44K whole rat genome oligo microarray and selected genes were validated by quantitative RT-PCR. Microarray gene expression analysis showed complex gene expression alterations in DMH-, DMH+EPS-, and DMH+L. casei 01-treated group, while compared with the control encompassing many biological pathways. Functional analysis showed that pathways controlling response to chemical stimulus, transcription, inflammatory response, immune system response, cell process, and apoptosis. SGK1 expression favors the development of intestinal tumors, but the SGK1 expressions in DMH-, DMH+EPS-, and DMH+L. casei 01-treated group were down-regulated. The gene expression alteration analysis showed that EPS and L. casei 01 may raise the tumor-suppressor gene expression and supper the oncogene expression of DMH-treated rats. These findings suggest that SGK1-dependent colorectal cancer pathway may be accomplished by the other SGK isoforms.
Subjects
exopolysaccharide
4-Nitroquinoline N-oxide, 1
2-dimethylhydrazine
gene expression
microarray
SDGs
Type
thesis
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