Effects of 17β-estradiol on colorectal cancer development after azoxymethane/dextran sulfate sodium treatment of ovariectomized mice

Estrogen is known to have a protective effect in colorectal cancer (CRC) development. Previously, we reported the anti-inflammatory and antitumorigenic effects of 17β-estradiol (E2) in azoxymethane (AOM)/dextran sulfate sodium (DSS)-treated male mice. The aim of this study was to investigate whether ovariectomy in a female AOM/DSS mouse model increases colorectal tumorigenesis and whether tumorigenesis is reduced by estrogen supplementation after ovariectomy. Clinical symptoms and histological severity of colitis and the levels of inflammatory mediators were evaluated in the colon of AOM/DSS-treated ovariectomized (OVX) mice. The levels of E2, myeloperoxidase (MPO), and NF-κB-dependent cytokines (interleukin (IL)-1β and IL-6) were measured by ELISA. Furthermore, quantitative real-time (qRT) PCR and Western blot analysis were performed. Ovariectomy did not aggravate AOM/DSS-induced colitis at 2 weeks. At weeks 10 and 16, ovariectomy significantly increased tumor number and incidence rate in only the proximal colon after AOM/DSS treatment (F_AOM/DSS vs OVX_AOM/DSS), and these increases were significantly reduced by E2 supplementation (OVX_AOM/DSS vs OVX_AOM/DSS/E2). However, ovariectomy did not affect CRC development in the distal colon (F_AOM/DSS vs OVX_AOM/DSS). At week 2, E2 administration to AOM/DSS-treated OVX mice attenuated the histological severity of colitis by decreasing the protein and/or mRNA levels of estrogen receptor alpha (ERα) and NF-κB-related mediators (i.e., COX-2, TNF-α, and IL-6) and by enhancing estrogen receptor beta (ERβ) and nuclear Nrf2 protein expression and the mRNA expression of related antioxidant enzyme genes (i.e., HO-1, GCLC, GCLM, and NQO1). Endogenous estrogen in females protects against the development of proximal colon cancer, and exogenous E2 replacement in OVX female mice showed protective effects against AOM/DSS-induced colitis and carcinogenesis. The mechanism could involve modulating ERs-, NF-κB- and Nrf2-mediated pathways.

Risk factors of rescue bismuth quadruple therapy failure for Helicobacter pylori eradication

BACKGROUND AND AIM

Failure of bismuth quadruple therapy for Helicobacter pylori eradication is frequently observed. To increase the eradication rate, comprehensive analyses need to be performed regarding risk factors of bismuth quadruple therapy failure based on complete standard culture and antimicrobial susceptibility testing results.

METHODS

Patients with history of failed first therapy who had H. pylori colonies isolated from culture and successful minimum inhibitory concentration (MIC) test were enrolled. Esomeprazole, bismuth, metronidazole, and tetracycline (quadruple) therapies for 7 or 14 days were given. Eradication rate, treatment compliance, adverse events, and risk factors for the failure of bismuth quadruple therapy were analyzed.

RESULTS

A total 54 patients were enrolled. Overall eradication rate in the present study was 88.8%. The eradication rate for cases with metronidazole resistance such as MIC 8-16 μg/mL or 16-32 μg/mL was 92.8% (13/14). For cases with high level metronidazole resistance (MIC > 32 μg/mL), the eradication rate was only 60% (6/10). Multivariate analysis regarding compliance, treatment duration, age > 60, three kinds of metronidazole MICs, tetracycline MIC > 4 μg/mL, adverse events and any other parameters, "metronidazole resistance, high level (MIC > 32 μg/mL)" was the only independent risk factor for eradication failure (P = 0.007).

CONCLUSION

For cases with metronidazole resistance at MIC > 32 μg/mL, rescue therapy other than bismuth-containing quadruple therapy is needed.

Rat Intestinal Acetic Acid and Butyric acid and Effects of Age, Sex, and High-fat Diet on the Intestinal Levels in Rats

Background

High-fat diet is known to be implicated in the pathogenesis of various metabolic disorders related to an inflammatory response. The aim of this study was to investigate the influence of high-fat diet for intestinal acetic acid and butyric acid concentrations which are related to inflammation-associated colon cancer risk.

Methods

Both male and female rats of 6, 31, 74 and 104-week of age were fed chow diet or high-fat diet for 8 weeks. Body weight and food intake were measured weekly during the feeding period. Intestinal acetic acid and butyric acid levels were measured by high-performance liquid chromatography from luminal contents of ileum and cecum.

Results

Male rats showed greater weight change than female rats in every age. Calorie-adjusted food intake was also higher in male rats compared to female rats. Male rats showed similar intake of food in every age while 31-week old female rats showed increased intake, which was decreased at 74-week and 104-week of age. The ileal acetic acid concentration was increased in male rats fed high-fat diet, while female rats fed high-fat diet showed no significant change in the ileal acetic acid level. On the other hand, butyric acid almost disappeared in high-fat diet fed rats regardless of sex.

Conclusions

High-fat diet increases the intestinal acetic acid concentration while reducing the butyric acid concentration which may account for increased risk of inflammation-associated colon cancer.

Effects of 17β-Estradiol on Colonic Permeability and Inflammation in an Azoxymethane/Dextran Sulfate Sodium-Induced Colitis Mouse Model

Background/Aims

Intestinal barrier dysfunction is a hallmark of inflammatory bowel diseases (IBDs) such as ulcerative colitis. This dysfunction is caused by increased permeability and the loss of tight junctions in intestinal epithelial cells. The aim of this study was to investigate whether estradiol treatment reduces colonic permeability, tight junction disruption, and inflammation in an azoxymethane (AOM)/dextran sodium sulfate (DSS) colon cancer mouse model.

Methods

The effects of 17β-estradiol (E2) were evaluated in ICR male mice 4 weeks after AOM/DSS treatment. Histological damage was scored by hematoxylin and eosin staining and the levels of the colonic mucosal cytokine myeloperoxidase (MPO) were assessed by enzyme-linked immunosorbent assay (ELISA). To evaluate the effects of E2 on intestinal permeability, tight junctions, and inflammation, we performed quantitative real-time polymerase chain reaction and Western blot analysis. Furthermore, the expression levels of mucin 2 (MUC2) and mucin 4 (MUC4) were measured as target genes for intestinal permeability, whereas zonula occludens 1 (ZO-1), occludin (OCLN), and claudin 4 (CLDN4) served as target genes for the tight junctions.

Results

The colitis-mediated induced damage score and MPO activity were reduced by E2 treatment (p<0.05). In addition, the mRNA expression levels of intestinal barrier-related molecules (i.e., MUC2, ZO-1, OCLN, and CLDN4) were decreased by AOM/DSS-treatment; furthermore, this inhibition was rescued by E2 supplementation. The mRNA and protein expression of inflammation-related genes (i.e., KLF4, NF-κB, iNOS, and COX-2) was increased by AOM/DSS-treatment and ameliorated by E2.

Conclusions

E2 acts through the estrogen receptor β signaling pathway to elicit anti-inflammatory effects on intestinal barrier by inducing the expression of MUC2 and tight junction molecules and inhibiting pro-inflammatory cytokines.

Microbial Changes and Host Response in F344 Rat Colon Depending on Sex and Age Following a High-Fat Diet

Gut microbiota, an important component that affects host health, change rapidly and directly in response to altered diet composition. Recently, the role of diet–microbiome interaction on the development of colon cancer has been the focus of interest. Colon cancer occurs more frequently in an aged population, and in males. However, the effect of dietary changes on the gut microbiome has been studied mainly in young males, even though it may vary with age and sex. The aim of this study was to investigate microbial changes and host response in the colons of male and female 6-week-old (young) and 2-year-old (old) Fisher-344 rats exposed to a high-fat diet (HFD). Our results showed that exposure to HFD for 8 weeks decreased the species richness of microbiota (Chao1) and increased Firmicutes/Bacteroidetes ratio only in aged rats, and not in young rats. Sex differences underlying the alteration by HFD in the gut microbiome were observed in the microbiome of aged rats. For instance, the abundance ratio of Akkermansia muciniphila and Desulfovibrio spp. increased in response to HFD in young rats and female aged rats, but not in male aged rats. Histological inflammation and cell proliferation of colon mucosa (indexed by Ki67) were significantly increased by HFD even in young rats; aged rats showed significantly higher cell proliferation in the HFD group than in the control. The HFD-induced decrease of species richness and the increase in specific species (Desulfovibrio spp. and Clostridium lavalense), which produce carcinogenic compounds such as H₂S and N-nitroso compounds, were significantly correlated with Ki67 index. In colon mucosa, the concentration of myeloperoxidase was increased by HFD only in males, and not in females. In conclusion, the results suggest a link between HFD-induced gut dysbiosis (particularly the low species richness and high abundance ratios of Desulfovibrio spp. and C. lavalense) and cell proliferation of colon mucosa (indicated by Ki67 IHC). In addition, sex differences influence the response of gut microbiome to HFD particularly in old age. Such sex differences in the gut microbiota might be related to sex differences in inflammation in the colon mucosa.

Effect of Estradiol in an Azoxymethane/Dextran Sulfate Sodium-Treated Mouse Model of Colorectal Cancer: Implication for Sex Difference in Colorectal Cancer Development

Purpose

This study demonstrates that estradiol downregulates inflammation and inhibits colorectal cancer (CRC) development in azoxymethane/dextran sulfate sodium (AOM/DSS) mouse model.

Materials and Methods

AOM/DSS-treated male and female mice were sacrificed at weeks 2, 10, and 16, to assess estrogen effects on colitis and carcinogenesis. Macroscopic and histologic severity of colitis and Western blot and quantitative real-time polymerase chain reaction were evaluated, to measure inflammatory mediators and cytokines.

Results

Compared with AOM/DSS-treated male mice (M-AOM/DSS group), AOM/DSS-treated male mice with estradiol administration (M-AOM/DSS+estr group) displayed at week 2 significantly decreased severity of colitis. At weeks 10 and 16, AOM/DSS-treated female mice (F-AOM/DSS group) and the M-AOM/DSS+estr group showed significantly lower tumor multiplicity compared with the M-AOM/DSS group. At week 2, F-AOM/DSS group had a lower level of nuclear factor-κB (NF-κB) expression and higher level of nuclear factor erythroid 2-related factor 2 (Nrf2) expression, compared to the M-AOM/DSS group. At week 2, expression levels of NF-κB and its related mediators decreased in the M-AOM/DSS+estr group, while levels of Nrf2 and Nrf2-related anti-oxidant enzymes increased. In addition, estradiol significantly increased Nod-like receptor protein 3 (NLRP3) inflammasome expressions in AOM/DSS-treated male mice. In contrast, at weeks 10 and 16, Nrf2 and its-related anti-oxidant enzymes and NLRP3 inflammasome were highly expressed in M-AOM/DSS group and in F-AOM/DSS group, who developed cancer.

Conclusion

The data suggest that estradiol inhibits the initiation of CRC by regulating Nrf2-related pathways. Moreover, these imply the dual role of Nrf2 and NLRP3 inflammasome, including promotion of tumor progression upon tumor initiation.

Comparative Analysis of Ileal and Cecal Microbiota in Aged Rats

Background

Gut microbiota contributes to intestinal and immune homeostasis through host-microbiota interactions. Distribution of the gut microbiota differs according to the location in the gastrointestinal tract. Although the microbiota properties change with age, evidence for the regional difference of gut microbiota has been restricted to the young. The aim of this study is to compare the gut microbiota between terminal ileum and cecum of old rats.

Methods

We analyzed gut microbiome of luminal contents from ileum and cecum of 74-week-old and 2-year-old rats (corresponding to 60-year and 80-year-old of human age) by metagenome sequencing of 16S rRNA.

Results

Inter-individual variation (beta diversity) of microbiota was higher in ileum than in cecum. Conversely, alpha diversity of microbiota composition was higher in cecum than in ileum. Lactobacillaceae were more abundant in ileum compared to cecum while Ruminococcaceae and Lachnospiraceae were more enriched in cecum. The proportions of Deltaproteobacteria were increased in cecal microbiota of 2-year-old rats compared to 74-week-old rats.

Conclusions

Major regional distinctions of microbiota between ileum and cecum of old rats appear consistent with those of young rats. Age-related alterations of gut microbiota in old rats seem to occur in minor compositions.

Pantoprazole Does Not Reduce the Antiplatelet Effect of Clopidogrel: A Randomized Controlled Trial in Korea

Background/Aims

Concerns that proton pump inhibitors (PPIs) diminish the efficacy of clopidogrel could hamper the appropriate prescription of PPIs. We evaluated the influence of pantoprazole on the antiplatelet effect of clopidogrel compared with ranitidine, which is regarded as safe, after stratification of the population according to the presence of a cytochrome (CYP) 2C19 polymorphism in Korea.

Methods

Forty patients who underwent dual antiplatelet therapy were randomized to receive pantoprazole (n=20) or ranitidine (n=20). Platelet aggregation was evaluated by impedance aggregometry at baseline (D0) and 8 days after acid-lowering treatments (D9). CYP2C19 was genotyped by polymerase chain reaction restriction fragment length polymorphism.

Results

After co-treatment, the percentage of clopidogrel low-response was 11.1% (2/18) in the pantoprazole group and 10.5% (2/19) in the ranitidine group (p=0.954). The impedance values with adenosine diphosphate stimulus after acid-lowering treatments did not significantly differ between the two groups. In a multiple regression analysis, only ST-elevation myocardial infarction was marginally associated with a reduced antiplatelet effect (odds ratio, 12.07; 95% confidence interval, 0.84 to 173.78). However, pantoprazole use did not affect the antiplatelet effect after correction for the CYP2C19 polymorphism.

Conclusions

This study showed that pantoprazole does not increase platelet aggregation in patients receiving dual antiplatelet therapy (ClinicalTrials.gov number: NCT02733640).

rdxA, frxA, and efflux pump in metronidazole-resistant Helicobacter pylori: Their relation to clinical outcomes

BACKGROUND AND AIM

rdxA and frxA mutations and enhancement of efflux pump have been suggested as the cause of metronidazole resistance in Helicobacter pylori. This study was performed to investigate the resistance mechanisms related to clinical eradication outcome, and to examine direct involvement of hefA in metronidazole-resistant isolates with intact rdxA and frxA.

METHODS

A total of 53 H. pylori-positive patients who were treated with metronidazole-containing sequential or quadruple therapy from 2011 to 2015 were enrolled. The metronidazole susceptibility of H. pylori isolates was examined by agar dilution test. Mutations in rdxA and frxA, were analyzed with DNA sequencing, and impact of hefA on metronidazole resistance was examined with quantitative real-time reverse transcription polymerase chain reaction, knockout and genetic complementation test for hefA.

RESULTS

Seven mutation types of rdxA and/or frxA were found in H. pylori isolated from non-eradicated subjects. rdxA mutation was associated with eradication failure (P = 0.002), and nonsense mutation in rdxA reduced eradication efficacy (P = 0.009). hefA expression was significantly higher in resistant isolates (P < 0.001), especially in rdxA(-)frxA(-) as compared to rdxA(+)frxA(+) (P = 0.027). Resistant isolates with no mutation in rdxA and frxA became susceptible after hefA knockout. Genetic complementation for hefA recovered metronidazole resistance in all of three hefA knockout mutants.

CONCLUSIONS

These results suggest that rdxA mutations play a critical role in metronidazole resistance as well as the outcomes of eradication therapy. In addition, hefA seems to be directly involved in metronidazole resistance, which explains the resistance in clinical isolates with intact rdxA and frxA.

Specific mutations of penicillin-binding protein 1A in 77 clinically acquired amoxicillin-resistant Helicobacter pylori strains in comparison with 77 amoxicillin-susceptible strains

BACKGROUND

Amoxicillin (Amx) is one of the most important antibiotics for eradication of Helicobacter pylori (H. pylori). Main determinants of genetically stable Amx resistance are mutations in the C-terminus of penicillin-binding protein 1A (pbp1A). However, contribution of individual mutation remains unclear.

METHODS

77 Amx-resistant (Amx^R ) and 77 Amx-susceptible (Amx^S ) H. pylori strains were isolated from gastric tissues, and DNA sequencing was performed to compare C-terminus sequences of pbp1A gene between Amx^R and Amx^S strains. Natural transformation of these mutated genes into amoxicillin-susceptible strains was performed.

RESULTS

Among many mutations in pbp1A, D479E (OR: 37.4, 95% CI: 5.53-252.49, P < .001), and T593 mutation (OR: 32.0, 95% CI: 4.04-252.86, P < .001) independently contributed to Amx resistance in H. pylori strains. In the transformation experiment, T593 mutations were identified in their transformants showing Amx resistance. However, PCR product of D479E was not inserted into recipient (ATCC 43504) resulting in transformation failure.

CONCLUSION

Amx resistance is associated with various substitutions in pbp1A and T593 mutation contributes to Amx resistance of H. pylori.

Changes in the interstitial cells of Cajal and neuronal nitric oxide synthase positive neuronal cells with aging in the esophagus of F344 rats

The aging-associated cellular and molecular changes in esophagus have not been established, yet. Thus we evaluated histological structure, interstitial cells of Cajal (ICCs), neuronal nitric oxide synthase (nNOS)-positive cells, and contractility in the esophagus of Fischer 344 rat at different ages (6-, 31-, 74-weeks, and 2-years). The lamina propria thickness and endomysial area were calculated. The immunoreactivity of c-Kit, nNOS and protein gene product (PGP) 9.5 was counted after immunohistochemistry. Expression of c-Kit, stem cell factor (SCF), nNOS and PGP 9.5 mRNA was measured by real-time PCR, and expression of c-Kit and nNOS protein was detected by Western blot. Isovolumetric contractile force measurement and electrical field stimulation (EFS) were conducted. The lamina propria thickness increased (6 week vs 2 year, P = 0.005) and the endomysial area of longitudinal muscle decreased with aging (6 week vs 2 year, P<0.001), while endomysial area of circular muscle did not significantly decrease. The proportions of NOS-immunoreactive cells and c-Kit-immunoreactive areas declined with aging (6 week vs 2 year; P<0.001 and P = 0.004, respectively), but there was no significant change of PGP 9.5-immunopositiviy. The expressions of nNOS, c-Kit and SCF mRNA also reduced with aging (6 week vs 2 year; P = 0.006, P = 0.001 and P = 0.006, respectively), while the change of PGP 9.5 mRNA expression was not significant. Western blot showed the significant decreases of nNOS and c-Kit protein expression with aging (6 week vs 2 year; P = 0.008 and P = 0.012, respectively). The EFS-induced esophageal contractions significantly decreased in 2-yr-old rat compared with 6-wk-old rats, however, L-NG-Nitroarginine methylester did not significantly increase the spontaneous and EFS-induced contractions in the 6-wk- and 2-yr-old rat esophagus. In conclusion, an increase of lamina propria thickness, a decrease of endomysial area, c-Kit, SCF and NOS expression with preserved total enteric neurons, and contractility in aged rat esophagus may explain the aging-associated esophageal dysmotility.

Comparison of Changes in the Interstitial Cells of Cajal and Neuronal Nitric Oxide Synthase-positive Neuronal Cells With Aging Between the Ascending and Descending Colon of F344 Rats

Background/Aims

Neuronal degeneration and changes in interstitial cells of Cajal (ICCs) are important mechanisms of age-related constipation. This study aims to compare the distribution of ICCs and neuronal nitric oxide synthase (nNOS) with regard to age-related changes between the ascending colon (AC) and descending colon (DC) in 6-, 31-, and 74-week old and 2-year old male Fischer-344 rats.

Methods

The amount of fecal pellet and the bead expulsion times were measured. Fat proportion in the muscle layer of the colon was analyzed by hematoxylin and eosin staining. Proto-oncogene receptor tyrosine kinase (KIT) and neuronal nitric oxide synthase (nNOS) expression were analyzed with Western blotting and immunohistochemistry. Isovolumetric contractile measurements and electrical field stimulation were used to assess smooth muscle contractility.

Results

Colon transit and bead expulsion slowed with senescence. Fat in the muscle layer accumulated with age in the AC, but not in the DC. The proportion of KIT-immunoreactive ICCs in the submucosal and myenteric plexus was higher in the DC than in the AC, and it declined with age, especially in the AC. In contrast, the proportion of NOS-immunoreactive neurons in the myenteric plexus was higher in the AC than in the DC, and both decreased in older rats. Nitric oxide levels declined with age in the DC. Muscle strip experiments showed that the inhibitory response mediated by nitric oxide in the circular direction of the DC was reduced in 2-year old rats.

Conclusion

The AC and DC differ in their distribution of ICCs and nNOS, and age-related loss of nitrergic neurons more severely affects the DC than the AC.

Açaí Berries Inhibit Colon Tumorigenesis in Azoxymethane/Dextran Sulfate Sodium-Treated Mice

Background/Aims

The aim of this study was to investigate the protective effect of açaí against azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colorectal cancer development.

Methods

The effect of açaí on tumorigenesis was assessed by evaluating tumor incidence, multiplicity and invasiveness in the mouse colon. The levels of myeloperoxidase (MPO) and proinflammatory cytokines (tumor necrosis factor α [TNF-α], interleukin [IL]-1β, and IL-6) were measured via enzyme-linked immunosorbent assay. Protein levels of cyclooxygenase 2 (COX-2), proliferating cell nuclear antigen (PCNA), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated death promoter (Bad) and cleaved-caspase-3 were assessed by immunoblotting.

Results

Administration of pellets containing 5% açaí powder reduced the incidences of both colonic adenoma and cancer (adenoma, 23.1% vs 76.9%, respectively, p=0.006; cancer, 15.4% vs 76.9%, respectively, p=0.002). In the açaí-treated mice, the MPO, TNF-α, IL-1β and IL-6 levels in the colon were significantly down-regulated. Açaí inhibited PCNA and Bcl-2 expression and increased Bad and cleaved-caspase-3 expression. In vitro studies demonstrated that açaí treatment reduced lipopolysaccharide-induced expression of TNF-α, IL-1β, IL-6 and COX-2 in murine macrophage RAW 264.7 cells.

Conclusions

Açaí demonstrated protective effects against AOM/DSS-induced colon carcinogenesis, which suggests that the intake of açaí may be beneficial for the prevention of human colon cancer.

Impact of Long-Term Proton Pump Inhibitor Therapy on Gut Microbiota in F344 Rats: Pilot Study

Background/Aims

To evaluate changes in gut microbiota composition following long-term proton pump inhibitor (PPI) treatment.

Methods

Twenty-four-week-old F344 rats were fed diets with (n=6) or without (n=5) lansoprazole for 50 weeks. Profiles of luminal microbiota in the terminal ileum were then analyzed. Pyrosequencing of the 16S rRNA gene was performed using an FLX genome sequencer (454 Life Sciences/Roche).

Results

Rats treated with lansoprazole showed significantly reduced body weights compared to controls (lansoprazole-treated rats and controls, 322.3±15.3 g vs 403.2±5.2 g, respectively, p<0.001). However, stool frequencies and consistencies did not differ between the two groups. The composition of the gut microbiota in lansoprazole-treated rats was quite different from that of the controls. In the controls, the microbiota profiles obtained from the terminal ileum showed a predominance of Proteobacteria (93.9%) due to the abundance of Escherichia and Pasteurella genera. Conversely, lansoprazole-treated rats showed an elevated population of Firmicutes (66.9%), which was attributed to an increased ratio of Clostridium g4 to Lactobacillus genera.

Conclusions

This preliminary study suggests that long-term administration of PPI may cause weight loss and changes to the microbiota in the terminal ileum.

PMK-S005 Alleviates Age-Related Gastric Acid Secretion, Inflammation, and Oxidative Status in the Rat Stomach

Background/Aims

The aim of this study was to evaluate the effect of the synthetic S-allyl-l-cysteine (SAC) PMK-S005 on gastric acid secretion, inflammation, and antioxidant enzymes in aging rats.

Methods

The rats were divided into four groups at 31 weeks of age and were continuously fed a diet containing a vehicle control, PMK-S005 (5 or 10 mg/kg), or lansoprazole (5 mg/kg). Gastric acid secretion and connective tissue thickness of the lamina propria were evaluated at 74 weeks and 2 years of age. Tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and COX-2 levels were measured by using enzyme-linked immunosorbent assays (ELISAs) or Western blot assays. Levels of antioxidant enzymes, including heme oxyganase 1 (HO-1) and NAD(P)H:quinone oxidoreductase 1 (NQO-1), were also measured.

Results

As the rats aged, gastric acid secretion significantly decreased, and the connective tissue of the lamina propria increased. However, 74-week-old rats in the PMK-S005 group exhibited greater levels of gastric acid secretion than those of the control and lansoprazole groups. The increase of TNF-α, IL-1β, and COX-2 expression in 74-week and 2-year-old control rats were inhibited by PMK-S005. In addition, the decrease in HO-1 and NQO-1 protein expression that occurred with aging was inhibited by PMK-S005 in the 74-week-old rats.

Conclusions

These results suggest that PMK-S005 has therapeutic potential as an antiaging agent to ameliorate age-related gastric acid secretion, inflammation, and oxidative stress in the stomach.

Analysis of Gastric Body Microbiota by Pyrosequencing: Possible Role of Bacteria Other Than Helicobacter pylori in the Gastric Carcinogenesis

Background

Gastric microbiota along with Helicobacter pylori (HP) plays a key role in gastric disease. The aim of our study is to investigate the difference of human gastric microbiota between antrum and body according to disease (control vs. gastric cancer) and HP status.

Methods

Each antrum and body biopsy was collected from 12 subjects at Seoul National University Bundang Hospital. Gastric microbiota was analyzed by bar-coded 454 pyrosequencing of the 16S rRNA gene. Twelve subjects consisted of HP-negative control (n = 2), HP-negative cancer (n = 2), HP-positive control (n = 3), and HP-positive cancer (n = 5). The analysis was focused on non-HP urease-producing bacteria (UB) and non-HP nitrosating or nitroreducing bacteria (NB) between antrum and body.

Results

Gastric body samples showed higher diversity compared to gastric antrum mucosa samples but there was no significant difference. The mean of operational taxonomic units was higher in HP(−) cancer than HP(+) cancer (antrum, 273.5 vs. 228.2, P = 0.439; body, 585.5 vs. 183.2, P = 0.053). The number of non-HP UB and non-HP NB was higher in HP(−) cancer groups than the others. These differences were more pronounced in the body (P = 0.051 and P = 0.081, respectively). Analysis of overlap of non-HP UB and non-HP NB revealed the higher composition of Streptococcus pseudopneumoniae, S. parasanguinis, and S. oralis in HP(−) cancer groups than the others, only in the body (P = 0.030) but not in the antrum (P = 0.123).

Conclusions

Higher diversity and higher composition of S. pseudopneumoniae, S. parasanguinis, and S. oralis in HP(−) cancer group than the other groups in the body suggest that analysis of microbiota from body mucosa could be beneficial to identify a role of non-HP bacteria in the gastric carcinogenesis.

Gastroprotective Effects of PMK-S005 against Ethanol-Induced Acute Gastric Damage in Rats

Background/Aims

This study aimed to examine the gastroprotective effects of PMK-S005, which is a synthetic S-allyl-l-cysteine (SAC; a sulfur-containing amino acid), against acute ethanol-induced gastric damage in rats.

Methods

Sprague-Dawley rats were divided into six groups, including a nonethanol group, groups treated with absolute ethanol 1 hour after pretreatment with various doses of PMK-S005 (1, 5, and 10 mg/kg) or rebamipide (50 mg/kg), and an absolute ethanol-only group. Ethanol-induced gross ulcer and mucus levels were measured. Myeloperoxidase, tumor necrosis factor α, interleukin 1β, PGE₂, LTB₄, cPLA₂, COX-1, and COX-2 levels were estimated by enzyme-linked immunosorbent assay or Western blot analysis. Furthermore, the protein expression levels of antioxidant enzymes, including heme oxygenase-1 (HO-1), NAD(P)H:quinine oxidoreductase 1 (NQO-1), GCLC, and GCLM, were assessed.

Results

PMK-S005 significantly attenuated the ethanol-induced gastric damage; it reduced mucosal inflammatory cytokine production and increased mucus levels. The expression levels of cPLA₂, COX-1, and COX-2 were decreased by PMK-S005. PMK-S005 did not affect PGE₂ synthesis, but LTB₄ production was significantly suppressed. In addition, long-term administration of PMK-S005 significantly increased the expression of HO-1, NQO-1, GCLC, and GCLM.

Conclusions

These results strongly suggest that PMK-S005 prevents gastric mucosal damage and that these gastroprotective activities are due to anti-inflammatory effects and enhancement of the gastric defense system, including antioxidant enzymes.

The Effect of Sex on the Azoxymethane/Dextran Sulfate Sodium-treated Mice Model of Colon Cancer

Background

The colitis-associated cancer exhibits different characteristics according to sex in the initiation and progression of the tumors. The aim of this study was to investigate the sex-associated difference in the azoxymethane/dextran sulfate sodium (AOM/DSS)-induced colitis-associated cancer model.

Methods

The AOM/DSS ICR mouse model was established to compare male with female, and then the severity of colitis-associated carcinogenesis was examined macroscopically and histologically regarding the number, size, and location of tumors. Subsequently, levels of colonic mucosal cytokine, interleukin (IL)-1β and myeloperoxidase (MPO) were assessed.

Results

At the 16th week, the tumor multiplicity and the pro-inflammatory factors differed according to sex. The total tumor number was significantly higher in male (P = 0.020) and the number of large tumors (diameter > 2 mm) was higher in male (P = 0.026). In male, the tumors located more in distal colon (P = 0.001). MPO was significantly higher in AOM/DSS-treated male mice compared to the control group (P = 0.003), whereas the corresponding female group showed no significant change (P = 0.086). Colonic IL-1β level significantly increased in AOM/DSS groups compared to control groups both in male and female (male, P = 0.014; female, P = 0.005). It was higher in male group; however, there was no statistical significance (P = 0.226).

Conclusions

In AOM/DSS murine model, colitis-associated colon tumorigenesis are induced more severely in male mice than female probably by way of inflammatory mediators such as IL-1β and MPO. The sex-related differences at the animal model of colon cancer suggest the importance of approach to disease with sex-specific medicine in human.

Repeated Water Avoidance Stress Alters Mucosal Mast Cell Counts, Interleukin-1β Levels with Sex Differences in the Distal Colon of Wistar Rats

Background/Aims

This study was aimed at evaluating differences in the effects of repeated water avoidance stress (rWAS) on colonic movement, mucosal mast cell counts, cytokine levels, and visceromotor response (VMR) to colorectal distension (CRD) in rats of both sexes.

Methods

Wistar rats were divided into stress and no-stress groups. Rats in the stress group were exposed to rWAS (1 hr/day) for 10 days. Mucosal mast cells were immunohistochemically stained with anti-mast cell tryptase antibody and counted. The colonic mucosal cytokine levels were measured with enzyme-linked immunosorbent assay. The VMR to CRD (visceral analgesia) was assessed by using a barostat and noninvasive manometry.

Results

The mean number of fecal pellets in the rWAS group increased significantly as compared with that in the no-stress group in both sexes. After adjustment for body weight, the female rats had a significantly higher pellet output than the male rats. The mucosal mast cell count of the female rWAS group was higher than that of the male rWAS group (13.0 ± 0.9 vs 8.8 ± 0.6; P < 0.001). The colonic mucosal interleukin-1β level was also higher only in the female rats of the rWAS group than in those of the no-stress group. On days 10 and 11, a decrease in VMR to CRD was observed at 40 and 60 mmHg in both sexes of the rWAS group, without a sex-based difference.

Conclusions

The colonic response to stress appeared to be more sensitive in the female rats than in the male rats. However, stress-induced visceral analgesia had no sex-related difference and the underlying mechanism needs to be further evaluated.

Analysis of Gastric Microbiota by Pyrosequencing: Minor Role of Bacteria Other Than Helicobacter pylori in the Gastric Carcinogenesis

BACKGROUND

Little is known about the role of gastric microbiota except for Helicobacter pylori (HP) in human health and disease. We compared the differences of human gastric microbiota according to gastric cancer or control and HP infection status and assessed the role of bacteria other than HP.

METHODS

Gastric microbiota of 63 antral mucosal and 18 corpus mucosal samples were analyzed by bar-coded 454 pyrosequencing of the 16S rRNA gene. Antral samples were divided into four subgroups based on HP positivity in pyrosequencing and the presence of cancer. The analysis was focused on bacteria other than HP, especially nitrosating or nitrate-reducing bacteria (NB). The changes of NB in antral mucosa of 16 subjects were followed up.

RESULTS

The number of NB other than HP (non-HP-NB) was two times higher in the cancer groups than in the control groups, but it did not reach statistical significance. The number of non-HP-NB tends to increase over time, but this phenomenon was prevented by HP eradication in the HP-positive control group, but not in the HP-positive cancer group.

CONCLUSION

We could not find the significant role of bacteria other than HP in the gastric carcinogenesis.

Effect of N-Methyl-N-Nitrosourea on Helicobacter-induced Gastric Carcinogenesis in C57BL/6 Mice

BACKGROUND

The aim of this study was to investigate the effect of N-methyl-N-nitrosourea (MNU) treatment followed by chronic Helicobacter pylori SS1 and H. felis colonization on the stomachs of C57BL/6 mice. The role of MNU and Helicobacter species in gastric carcinogenesis was also elucidated.

METHODS

A total of 69 C57BL/6 mice at 4 weeks of age were divided into 6 groups according to MNU treatment and H. pylori SS1 or H. felis infection. The mice were sacrificed at 21 and 50 weeks. The degree of inflammation was determined by histopathology. The levels of gastric mucosal myeloperoxidase, TNF-α, and interleukin-1β (IL-1β) were measured by ELISA.

RESULTS

In the H. felis groups with or without MNU, the incidence of gastric tumors was 21.1% and 35.0% at 21 and 50 weeks, respectively. No gastric tumors were observed in all control mice. At 50 weeks, 37.5% of gastric adenoma cases were observed in the H. felis alone and MNU + H. felis groups. Furthermore, 12.5% of gastric adenocarcinoma cases were observed in the MNU alone and MNU + H. felis groups. The gastric mucosal IL-1β level was significantly higher in the MNU + H. felis group at 21 weeks and H. felis group at 50 weeks, respectively, than that for control mice (P < 0.05). However, the effect of MNU on H. pylori SS1-induced gastric carcinogenesis was low compared to that on H. felis.

CONCLUSIONS

Administration of MNU before H. felis infection provokes severe inflammation through IL-1β, and eventually induces gastric cancer. However, the role of MNU in H. pylori SS1-induced gastric carcinogenesis model is minor.

Difficult establishment of a chronic nonsteroidal anti-inflammatory drugs induced gastric inflammation rat model due to gastric adaptation and small bowel damage

BACKGROUND/AIMS

The prevalence of peptic ulcer disease has not decreased mainly due to an increase in the use of NSAIDs. This study was conducted in order to determine whether a chronic NSAID-induced gastric inflammation model could be established by repeated administration of NSAID.

METHODS

Indomethacin (10 mg/kg) was administered once per week for six weeks in 8- and 26-week rats and animals were sacrificed every week after administration. Gross ulcer index, histologic damage index, myeloperoxidase (MPO) activity, and mucus (glucosamine) levels were measured. Small bowel damage was also evaluated.

RESULTS

Gross gastric damage index showed a peak level at three weeks and then decreased slowly in the 26-week indomethacin group. Gastric mucosal glucosamine level increased in both the 8-week (p=0.038) and 26-week groups (p=0.007). In addition, gastric mucosal MPO level decreased in the 8-week group (p=0.018) but did not show a decrease in the 26-week group. Small bowel damage began to occur at three weeks during the schedule and eight of 36 rats (22.2%) died due to perforation or peritonitis of the small bowel in the 8- and 26-week indomethacin groups, respectively.

CONCLUSIONS

Due to gastric adaptation and small bowel damage, repeated administration of NSAID to experimental animals may not be an adequate method for establishment of the chronic gastric inflammation model.

Comparison of Gastric Microbiota Between Gastric Juice and Mucosa by Next Generation Sequencing Method

Background:

Not much is known about the role of gastric microbiota except for Helicobacter pylori in human health and disease. In this study, we aimed to detect human gastric microbiota in both gastric mucosa and gastric juice by barcoded 454-pyrosequencing of the 16S rRNA gene and to compare the results from mucosa and juice.

Methods:

Gastric biopsies and stomach juices were collected from 4 subjects who underwent standard endoscopy at Seoul National University Bundang Hospital. Gastric microbiota of antral mucosa, corpus mucosa samples, and gastric fluids were analyzed by barcoded 454-pyrosequencing of the 16S rRNA gene. The analysis focused on bacteria, such as H. pylori and nitrosating or nitrate-reducing bacteria.

Results:

Gastric fluid samples showed higher diversity compared to that of gastric mucosa samples. The mean of operational taxonomic units was higher in gastric fluid than in gastric mucosa. The samples of gastric fluid and gastric mucosa showed different composition of phyla. The composition of H. pylori and Proteobacteria was higher in mucosa samples compared to gastric fluid samples (H. pylori, 66.5% vs. 3.3%, P = 0.033; Proteobacteria, 75.4% vs. 26.3%, P = 0.041), while Actinobacteria, Bacteroidetes, and Firmicutes were proportioned relatively less in mucosa samples than gastric fluid. However there was no significant difference. (Actinobacteria, 3.5% vs. 20.2%, P = 0.312; Bacteroidetes, 6.0% vs. 14.8%, P = 0.329; Firmicutes, 12.8% vs. 33.4%, P = 0.246).

Conclusions:

Even though these samples were small, gastric mucosa could be more effective than gastric fluid in the detection of meaningful gastric microbiota by pyrosequencing.