Selection of a galactose-positive mutant strain of Streptococcus thermophilus and its optimized production as a high-vitality starter culture

Streptococcus thermophilus (S. thermophilus) is a common starter in yogurt production and plays an important role in the dairy industry. In this study, a galactose-positive (Gal+) mutant strain, IMAU20246Y, was produced using the chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine (NTG) from wild type S. thermophilus IMAU20246 which was known to have good fermentation characteristics. The sugar content of milk fermented by either the mutant or the wild type was determined using high performance liquid chromatography (HPLC); metabolism of lactose and galactose was significantly increased in the mutant strain. In addition, we used the response surface methodology to optimize components of the basic medium M17 for survival ratio of the mutant strain. Under these optimal conditions, the viable counts of mutant S. thermophilus IMAU20246Y reached 4.15 × 108 cfu/mL and following freeze drying in the medium retained cell viability of up to 67.42%. The above results are conducive to production of a high vitality starter culture and development of 'low sugar, high sweetness' dairy products.

Effects of Granule Dendrobii on chronic atrophic gastritis induced by N-methyl-N'-nitro-N-nitrosoguanidine in rats

BACKGROUND

Dendrobium officinale is an herb of Traditional Chinese Medicine (TCM) commonly used for treating stomach diseases. One formula of Granule Dendrobii (GD) consists of Dendrobium officinale and American Ginseng (Radix Panacis quinquefolii), and is a potent TCM product in China. Whether treatment with GD can promote gastric acid secretion and alleviate gastric gland atrophy in chronic atrophic gastritis (CAG) requires verification.

AIM

To determine the effect of GD treatment on CAG and its potential cellular mechanism.

METHODS

A CAG model was induced by feeding rats N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for 12 wk. After oral administration of low, moderate, and high doses of GD in CAG rats for 8 wk, its effects on body weight, gastric mucosa histology, mucosal atrophy, intestinal metaplasia, immunohistochemical staining of proliferating cell nuclear antigen (PCNA) and B-cell lymphoma-2, and hemoglobin and red blood cells were examined.

RESULTS

The body weights of MNNG-induced CAG model rats before treatment (143.5 ± 14.26 g) were significantly lower than that of healthy rats (220.2 ± 31.20 g, P < 0.01). At the 8^th week of treatment, the body weights of rats in the low-, moderate-, and high-dose groups of GD (220.1 ± 36.62 g) were significantly higher than those in the untreated group (173.3 ± 28.09 g, all P < 0.01). The level of inflammation in gastric tissue of the high-dose group (1.68 ± 0.54) was significantly reduced (P < 0.01) compared with that of the untreated group (3.00 ± 0.00, P < 0.05). The number and thickness of gastric glands in the high-dose group (31.50 ± 6.07/mm, 306.4 ± 49.32 µm) were significantly higher than those in the untreated group (26.86 ± 6.41/mm, 244.3 ± 51.82 µm, respectively, P < 0.01 and P < 0.05), indicating improved atrophy of gastric mucosa. The areas of intestinal metaplasia were significantly lower in the high-dose group (1.74% ± 1.13%), medium-dose group (1.81% ± 0.66%) and low-dose group (2.36% ± 1.08%) than in the untreated group (3.91% ± 0.96%, all P < 0.01). The expression of PCNA in high-dose group was significantly reduced compared with that in untreated group (P < 0.01). Hemoglobin level in the high-dose group (145.3 ± 5.90 g/L), medium-dose group (139.3 ± 5.71 g/L) and low-dose group (137.5 ± 7.56 g/L) was markedly increased compared with the untreated group (132.1 ± 7.76 g/L; P < 0.01 or P < 0.05).

CONCLUSION

Treatment with GD for 8 wk demonstrate that GD is effective in the treatment of CAG in the MNNG model by improving the histopathology of gastric mucosa, reversing gastric atrophy and intestinal metaplasia, and alleviating gastric inflammation.

Proteomics analyses of Xiaopi granules in MNNG-induced gastric epithelial dysplasia rat model by LC-MS

OBJECTIVE

Xiaopi granules have been shown to ameliorate gastric epithelial dysplasia in patients. However, the therapeutic mechanism is unclear. Herein, the proteomics method was applied to identify the differentially expressed proteins and related pathways.

METHODS

Sixty male Sprague-Dawley (SD) rats were randomly divided into four groups: control (C group, n=10), model (M group), Xiaopi granules (X group), and vitacoenzyme (V group). The rat gastric epithelial dysplasia model was established by intragastrically administering N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and ranitidine, and drinking 0.05% ammonia solution. After 12 weeks, the stomach tissue was analyzed by H&E staining and proteomics analyses. Western blot analysis was applied to further validate the proteomics results.

RESULTS

Compared to the M group, levels of 326 and 350 proteins were altered significantly in the X and V groups (1.5-fold, P<0.05), which were significantly enriched in digestion, metabolism, coagulation, and cell apoptosis. CELA2A, GHRL, NDUFB9, and PGC were significantly upregulated (P<0.0001), while CLCA1, PLG, and DAC2 were downregulated (P<0.001 or P<0.0001) in the M group vs. the C group. The change in the above proteins could be reversed after the treatment of Xiaopi granules or vitacoenzyme tablets.

CONCLUSION

Xiaopi granules improve ameliorated gastric epithelial dysplasia by intervening in digestion, metabolism, blood coagulation, cell apoptosis, and other related pathways.

Therapeutic effects and potential mechanism of dehydroevodiamine on N-methyl-N'-nitro-N-nitrosoguanidine-induced chronic atrophic gastritis

BACKGROUNDS

Dehydroevodiamine (DHE) is a quinazoline alkaloid isolated from a Chinese herbal medicine, named Euodiae Fructus (Wu-Zhu-Yu in Chinese). This study aimed to investigate the therapeutic effects and potential mechanism of DHE on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced chronic atrophic gastritis (CAG) based on integrated approaches.

METHODS

Therapeutic effects of DHE on serum biochemical indices and histopathology of gastric tissue in MNNG-induced CAG rats were analyzed. MNNG-induced GES-1 human gastric epithelial cell injury model was established. Cell viability and proliferation was quantified by a cell counting kit-8 assay. Cell morphology and mitochondrial membrane potential (MMP) were detected by a high content screening (HCS) assay. Cell migration and invasion were detected by a Transwell chamber. Moreover, UHPLC-Q-TOF/MS was performed to investigate the potential metabolites and signaling pathway affecting the protective effects of DHE on MNNG-induced cell migration and invasion of GES-1. Furthermore, in view of the key role of angiogenesis in the transformation of inflammation and cancer, this study explored relative mRNA and protein expression levels of HIF-1α-mediated VEGF pathway in vivo and in vitro by RT-PCR and Western Blotting, respectively.

RESULTS

The results showed that the therapeutic effects of DHE on CAG rats were presented in down-regulation serum biochemical indices and alleviating histological damage of gastric tissue. Besides, DHE has an effect on increasing cell proliferation of GES-1 cells, ameliorating MNNG-induced gastric epithelial cell damage and mitochondrial dysfunction. In addition, DHE could inhibit MNNG induced migration and invasion of GES-1 cells. Cell metabolomics analyses showed that the protective effect of DHE on GES-1 cells is mainly associated with the regulation of inflammation metabolites and energy metabolism related pathways. It was found that DHE has a regulating effect on tumor angiogenesis and can inhibit the relative gene and protein expression of HIF-1α-mediated VEGF signaling pathway.

CONCLUSIONS

The present work highlighted the role of DHE ameliorated gastric injury in MNNG-induced CAG rats in vivo and GES-1 cell migration in vitro by inhibiting HIF-1α/VEGF angiogenesis pathway. These results suggest that DHE may be the effective components of Euodiae Fructus, which provides a new agent for the treatment of CAG.

Demethylation of the hTERT promoter in normal human gastric mucosal epithelial cells following N-methyl-N'-nitro-N-nitrosoguanidine exposure

N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) is an alkylating agent that can induce gastric carcinoma. As a well-known human carcinogen, MNNG has been universally recognized as a methylating agent and is believed to act through methylation mechanism. In the present study, the epigenetic status of the human telomerase reverse transcriptase (hTERT) promoter was investigated in MNNG-treated normal human gastric mucosal epithelial cells. After 4 h exposure to MNNG at different concentrations, 6.8 and 68 µM, bisulfite sequencing polymerase chain reaction showed that five methylated cytosines outside the CpG dinucleotides in the 290-bp fragment from the hTERT promoter were demethylated and all the methylated cytosines in CpG dinucleotides remained intact. Furthermore, the epigenetic status of the target region following MNNG exposure was extremely similar to those of the BGC-823, SGC-7901 and MKN-28 lines; the three cell lines from human gastric adenocarcinoma. The result indicates that MNNG-induced demethylation in cytosines outside the CpG dinucleotides may be an early molecular lesion with the potential for impacting malignant transformation and a possible underlying carcinogenic mechanism of MNNG. Thus, it may provide another insight into the mechanisms of MNNG carcinogenesis.

Effects of Antimutagens on the Teratogenicity of N-Methyl-N'-Nitro-N-Nitrosoguanidine in Mice

We examined whether vanillin (VA) and CoCl₂ ∙6H₂ O(CoCl₂ ), antimutagens, which have mutation suppressing effect, i.e., promotion of cellular repair function in vitro, can modify the teratogenicity in mice caused by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a direct-acting monofunctional alkylating agent. ICR mice were treated with MNNG alone (single IP dose of 40 or 60 mg/kg) or in combination with the antimutagen on day 11 of gestation. Embryotoxicity and teratogenicity were examined at term. The incidence of MNNG-induced syndactyly in the fore- and hindlimbs was significantly decreased by VA (50 mg/kg, IP) or CoCl₂ (10 mg/kg, IV) and a tendency to decrease in the incidence of oligodactyly was noted as well. On the other hand, the incidence of MNNG-induced brachydactyly was increased by VA or CoCl₂ . Though the mechanism of the modifying effects of both VA and CoCl₂ on MNNG-induced malformations could not be delineated in the present study, the results indicate that the antimutagens which stimulate DNA recombination repair in vitro modify the manifestation of malformations caused by teratogens that attack the fetal DNA in the initial teratogenic mechanism.