Effects of quercetin and beta-carotene supplementation on azoxymethane-induced colon carcinogenesis and inflammatory responses in rats fed with high-fat diet rich in omega-6 fatty acids

Chronic inflammation in gastrointestinal tract has been suggested as a risk factor for tumor formation. The effect of dietary supplementation of quercetin or beta-carotene on colon carcinogenesis and inflammatory response in rats fed with high-fat diet rich in omega-6 fatty acids was assessed. Animals were exposed to two weekly subcutaneous injections of AOM (azoxymethane) at a single dose of 15 mg/kg body weight. A portion of rats from each group was sacrificed at 8 weeks after the last AOM treatment to determine ACF (aberrant crypt foci) formation. Colonic mucosa expression of iNOS (inducible nitric oxide) and COX-2 (cyclooxygenase-2) protein, and blood PGE2 (prostaglandin E2) level were measured. The remaining groups of animals were sacrificed at 33 weeks after the last AOM treatment to examine colon tumor formation. Rats on high-fat diet developed more aberrant crypt foci (P<0.05) compared with those of rats on regular diet. In the same vein, but in contrast to the effect seen with regular diet, the high-fat diet induced a significant up-regulation of iNOS expression. There was no significant change in the extent of COX-2 expression or in the PGE2 levels. Quercetin or beta-carotene supplementation reduced the number of ACF only in animals fed high-fat diet (p<0.05), however, no significant difference in tumor incidence was found. At week 33, the expression of iNOS was reduced by quercetin without a statistical significance, and COX-2 expression was slightly reduced in rats on beta-carotene supplementation. No change in PGE2 levels was observed. Whilst dietary antioxidants are considered as effective suppressors for precancerous lesion formation in colons exposed to high-risk diet, it is clear that elucidating the role of individual antioxidants in colon tumor formation coupled with an understanding of the molecular mechanisms involved would benefit colon cancer prevention strategies.     

Effects of Treadmill Exercise on Neural Stem Cells, Cell Proliferation, and Neuroblast Differentiation in the Subgranular Zone of the Dentate Gyrus in Cyclooxygenase-2 Knockout Mice

Cyclooxygenase-2 (COX-2) function has been implicated in a number of physiological processes, including inflammatory responses, synaptic transmission, and synaptic plasticity in the brain. However, the specific role of COX-2 in exercise-induced neurogenesis is still debatable. Here, we assessed the role of COX-2 in exercise-induced plasticity by comparing COX-2 knockout mice to wild-type control littermates. We investigated the number of neural stem cells, and the degree of cell proliferation and neuronal differentiation in COX-2 knockout and its wild-type mice that either exercised or remained inactive. Wild-type and COX-2 knockout mice were put on a treadmill and were either sedentary or were forced to run 1 h/day for five consecutive days at a pace of 10–12 m/min for 5 weeks. Loss of COX-2 expression in the knockout mice was confirmed with two measures: (1) COX immunolabeling in the hippocampus, and (2) the identification of abnormal kidney development using hematoxylin and eosin staining, including subcapsular glomerular hypoplasia and hypertrophy of the deeper cortical glomeruli. Compared to wild-type mice, COX-2 knockout mice exhibited a significant reduction in the neural stem cells (nestin-positive cells), cell proliferation (Ki67-positive cells), and neuroblast differentiation (doublecortin-positive cells). In contrast, exercise significantly increased the neural stem cells, cell proliferation, and neuroblast differentiation in both the wild-type and COX-2 knockout mice although the NeuN-immunoreactive neurons were similar in all groups. Expression of phosphorylated cAMP-response element binding protein was decreased in knockout mice. Exercise increased its expression in the subgranular zone of the dentate gyrus in both wild-type and knockout mice. These results suggest that the COX-2 pathway is one of important factors on neural stem cells, cell proliferation and neuroblast differentiation in sedentary mice. The ability of exercise to increase these types of neural plasticity, regardless of COX-2 signaling, suggests that the effects of exercise on neural stem cells, cell proliferation, and neuroblast differentiation are induced via a pathway that is independent of COX-2.     

COX-2 and iNOS, good targets for chemoprevention of colon cancer

Cyclooxygenase (COX)-2 has been suggested to play an important role in colon carcinogenesis. We found that the COX-2 selective inhibitor, nimesulide, reduces azoxymethane (AOM)-induced aberrant crypt foci (ACF) in rats and colon carcinogenesis in mice, as well as formation of intestinal polyps in Min mice. Thus, selective inhibitors of COX-2, which catalyzes the synthesis of prostanoids, could be good candidates as chemopreventive agents against colon cancer. Examination of the effect of prostanoid receptor deficiency and a selective antagonist of prostanoid receptor on the development of AOM-induced ACF in mice revealed the involvement of the EP1 receptor. Moreover, a selective EP1 antagonist reduced the number of intestinal polyps in Min mice. These results suggest that PGE2 contributes to colon carcinogenesis through binding to the EP1 receptor. Nitric oxide synthase (NOS) is known to be overexpressed in colon cancers of humans and rats, and a NOS inhibitor, L-NG-nitroarginine methyl ester, was found to inhibit the development of AOM-induced ACF in rats. Thus, NOS including iNOS could also be a good target for chemoprevention of colon cancer, as in the COX-2 case.     

Suppressive effect of an inducible nitric oxide inhibitor, ONO-1714, on AOM-induced rat colon carcinogenesis.

The expression of inducible nitric oxide synthase (iNOS) is markedly elevated in rat colon cancers induced by azoxymethane (AOM). In addition, iNOS can be detected in most adenomas and dysplastic aberrant crypt foci (ACF), suggesting that iNOS plays an important role in colon carcinogenesis. In the present study, the effect of an iNOS inhibitor, ONO-1714 ((1S,5S,6R,7R)-7-chloro-3-imino-5-methyl-2-azabicyclo[4.1.0] heptane hydrochloride), on AOM-induced rat colon carcinogenesis was investigated. Male F344 rats were treated with 15 mg/kg body weight of AOM once a week, for 2 weeks. ONO-1714 was given to the rats at doses of 10, 20, 50, and 100 ppm in diet for 4 weeks from the day before the first carcinogen treatment. The number of AOM-induced ACF in the rats receiving 10, 20, 50 and 100 ppm ONO-1714 were 94, 73 (P < 0.05), 71 (P < 0.005), and 53% (P < 0.0005), respectively, of the control value. Moreover, the mean number of aberrant crypts per focus was significantly lowered in 100 ppm ONO-1714 group (P < 0.05). Then, the effects of long-term treatment (32 weeks) with 50 and 100 ppm ONO-1714 on AOM-induced colorectal tumor development were examined. Although incidences and multiplicities of colon tumors did not significantly differ among the groups, number of tumors developing in the middle part of colon were reduced with both 50 and 100 ppm doses (P < 0.05). Furthermore, colon tumor volume tended to be decreased by ONO-1714 treatment, and the number of colon tumors more than 3mm in diameter was significantly lowered in the 100 ppm ONO-1714 group (P < 0.01). These results suggest that iNOS plays roles in both early and late stages of colon carcinogenesis.     

Genome-wide association and fine mapping of genetic loci predisposing to colon carcinogenesis in mice

To identify the genetic determinants of colon tumorigenesis, 268 male mice from 33 inbred strains derived from different genealogies were treated with azoxymethane (AOM; 10 mg/kg) once a week for six weeks to induce colon tumors. Tumors were localized exclusively within the distal colon in each of the strains examined. Inbred mouse strains exhibit a large variability in genetic susceptibility to AOM-induced colon tumorigenesis. The mean colon tumor multiplicity ranged from 0 to 38.6 (mean = 6.5 ± 8.6) and tumor volume ranged from 0 to 706.5 mm(3) (mean = 87.4 ± 181.9) at 24 weeks after the first dose of AOM. AOM-induced colon tumor phenotypes are highly heritable in inbred mice, and 68.8% and 71.3% of total phenotypic variation in colon tumor multiplicity and tumor volume, respectively, are attributable to strain-dependent genetic background. Using 97,854 single-nucleotide polymorphisms, we carried out a genome-wide association study (GWAS) of AOM-induced colon tumorigenesis and identified a novel susceptibility locus on chromosome 15 (rs32359607, P = 6.31 × 10(-6)). Subsequent fine mapping confirmed five (Scc3, Scc2, Scc12, Scc8, and Ccs1) of 16 linkage regions previously found to be associated with colon tumor susceptibility. These five loci were refined to less than 1 Mb genomic regions of interest. Major candidates in these loci are Sema5a, Fmn2, Grem2, Fap, Gsg1l, Xpo6, Rabep2, Eif3c, Unc5d, and Gpr65. In particular, the refined Scc3 locus shows high concordance with the human GWAS locus that underlies hereditary mixed polyposis syndrome. These findings increase our understanding of the complex genetics of colon tumorigenesis, and provide important insights into the pathways of colorectal cancer development and might ultimately lead to more effective individually targeted cancer prevention strategies.     

Nobiletin and its colonic metabolites suppress colitis-associated colon carcinogenesis by down-regulating iNOS,inducing antioxidative enzymes and arresting cell cycle progression

Nobiletin (NOB) is a major citrus polymethoxyflavone (PMF) with various beneficial biological activities. We reported previously that dietary NOB significantly inhibited colitis-associated colon carcinogenesis in azoxymethane (AOM)/dextran sulfate sodium (DSS)-treated mice, and the chemopreventive effects were associated with NOB metabolites found in the mouse colonic tissues. In this study, to better understand the role of colonic metabolites of NOB, we determined the anti-inflammation and anticancer effects of a mixture of NOB and its major metabolites (NOB-Met) at the concentrations equivalent to those found in colonic tissues of NOB-fed mice. The results demonstrated that NOB-Met effectively decreased the expression level of inducible nitric oxide synthase (iNOS), increased the level of heme oxygenase-1 (HO-1) and NADH quinone oxidoreductase 1 (NQO1) and up-regulated nuclear factor erythroid 2-related factor (Nrf2) signaling pathway in lipopolysaccharide (LPS)-stimulated macrophages. NOB-Met also caused a significant cell cycle arrest in human colon cancer cells. Validation study confirmed that dietary NOB led to the effects similar to those described above in the colon of AOM/DSS-treated mice. Specifically, dietary NOB significantly reduced the level of iNOS, up-regulated Nrf2-dependent enzymes and profoundly modulated key signaling proteins resulting in decreased cell cycle progression in the colonic tissue of AOM/DSS-treated mice. Overall, our findings demonstrated that dietary NOB led to the presence of NOB and its metabolites in the colonic tissue, which suppressed colitis-associated colon carcinogenesis via down-regulating iNOS, inducing antioxidative enzymes and arresting cell cycle progression.     

The Effect of Diet and Exercise on Intestinal Integrity and Microbial Diversity in Mice

Background

The gut microbiota is now known to play an important role contributing to inflammatory-based chronic diseases. This study examined intestinal integrity/inflammation and the gut microbial communities in sedentary and exercising mice presented with a normal or high-fat diet.

Methods

Thirty-six, 6-week old C57BL/6NTac male mice were fed a normal or high-fat diet for 12-weeks and randomly assigned to exercise or sedentary groups. After 12 weeks animals were sacrificed and duodenum/ileum tissues were fixed for immunohistochemistry for occludin, E-cadherin, and cyclooxygenase-2 (COX-2). The bacterial communities were assayed in fecal samples using terminal restriction fragment length polymorphism (TRFLP) analysis and pyrosequencing of 16S rRNA gene amplicons.

Results

Lean sedentary (LS) mice presented normal histologic villi while obese sedentary (OS) mice had similar villi height with more than twice the width of the LS animals. Both lean (LX) and obese exercise (OX) mice duodenum and ileum were histologically normal. COX-2 expression was the greatest in the OS group, followed by LS, LX and OX. The TRFLP and pyrosequencing indicated that members of the Clostridiales order were predominant in all diet groups. Specific phylotypes were observed with exercise, including Faecalibacterium prausnitzi, Clostridium spp., and Allobaculum spp.

Conclusion

These data suggest that exercise has a strong influence on gut integrity and host microbiome which points to the necessity for more mechanistic studies of the interactions between specific bacteria in the gut and its host.     

Regular exercise prevents high-sucrose diet-induced fatty liver via improvement of hepatic lipid metabolism

Fatty liver is known as the initial stage in nonalcoholic fatty liver disease. Epidemiological studies have shown that regular exercise prevents accumulation of hepatic lipids, although the underlying mechanism is unclear. The purpose of this study was to investigate the effect of exercise on fatty liver associated with hepatic lipid metabolism. KK/Ta mice (6 weeks old) were divided into sedentary and exercise groups and compared with sedentary Balb/c mice. All the mice were fed a high-sucrose diet for 12 weeks. The KK/Ta mice in the exercise group performed a treadmill running exercise at 20 m/min for 30 min (3 times per week). Twelve weeks of regular exercise suppressed the accumulation of lipid in the liver, along with reduction in the level of lipid in the plasma. The levels of carnitine palmitoyl transferase II, acyl-coenzyme A dehydrogenase, and trifunctional enzyme, which are rate-limiting enzymes in fatty acid oxidation in the liver, were elevated by exercise. In addition, the expression of fatty acid synthase, a key lipogenetic enzyme, was reduced by exercise. Furthermore, regular exercise decreased the expression of heat shock protein 47, a marker of hepatic fibrosis, in the liver. Our results suggest that regular exercise prevents fatty liver via improvement of hepatic lipid metabolism.     

EFFECT OF EXERCISE TRAINING OF DIFFERENT INTENSITIES ON ANTI-INFLAMMATORY REACTION IN STREPTOZOTOCIN-INDUCED DIABETIC RATS

The study investigated the effect of high- and low-intensity exercise training on inflammatory reaction of blood and skeletal muscle in streptozotocin (STZ)-induced diabetic male Sprague-Dawley rats (243 ± 7 g, 8 weeks). The rats completed treadmill running in either high-intensity exercise (6 weeks of exercise training, acute bouts of exercise) or low-intensity exercise (6 weeks of exercise training). Non-running, sedentary rats served as controls. To induce diabetes mellitus, rats received a peritoneal injection of STZ (50 mg · kg⁻¹). Rats were sacrificed immediately after an acute bout of exercise and 6 weeks of exercise training. Inflammatory factors were analyzed by ELISA and by immune blotting from the soleus and extensor digitorum longus muscles. In the serum, inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-4) and reactive oxygen species (ROS) (nitric oxide and malondialdehyde) increased in diabetic rats. However, all exercise training groups displayed reduced inflammatory cytokines and reactive oxygen species. In skeletal muscles, low-intensity exercise training, but not high intensity exercise, reduced the levels of COX-2, iNOS, and MMP-2, which were otherwise markedly elevated in the presence of STZ. Moreover, the levels of GLUT-4 and MyoD were effectively increased by different exercise intensity and exercise duration. Low-intensity exercise training appeared most effective to reduce diabetes-related inflammation. However, high-intensity training also reduced inflammatory factors in tissue-specific muscles. The data implicate regular exercise in protecting against chronic inflammatory diseases, such as diabetes.     

The Synergic Effect of Regular Exercise and Resveratrol on Kainate-Induced Oxidative Stress and Seizure Activity in Mice

The synergic effect of regular exercise and resveratrol, a polyphenolic compound with potent antioxidant activity, was investigated against kainate-induced seizures and oxidative stress in mice. After 6 weeks of swimming training, the total body weight decreased and the blood concentration of lactate stabilized statistically in comparison with the sedentary mice, indicate that the training program increased the aerobic resistance of mice. Kainate (30 mg/kg) evoked seizure activity 5 min after injection, and seizure activity was measured seizure rating scores every 5 min up to 2 h. As previously well known experiments, regular exercise and resveratrol (40 mg/kg, daily supplementation for 6 weeks) have an inhibitory effect on kainate-induced seizure activity and oxidative stress. In particularly, a synergistic cooperation of regular exercise and resveratrol was observed in seizure activity, mortality and oxidative stress especially in SOD activity. These results suggest that regular exercise along with an anti-convulsant agent such as resveratrol could be a more efficient method for the prevention of seizure development than exercise alone.     

COX-2 mediates morphine-induced delayed cardioprotection via an iNOS-dependent mechanism

Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) have been shown to be mediators of cardioprotection induced by ischemic preconditioning and opioids. However, it is not known whether COX-2 is involved in morphine-induced cardioprotection accompanied with iNOS. Therefore, we investigated the role of COX-2 in morphine-induced cardioprotection and the effect of iNOS on COX-2. Myocardial ischemia was induced by a 45-min coronary artery occlusion in mice. Infarct size (IS) as a percentage of the area at risk (AAR) was determined by triphenyltetrazolium chloride staining. The COX-2-selective inhibitor NS-398 was used to investigate the role of COX-2. Expression of COX-2 was assessed by Western blotting, and the myocardial prostaglandin (PG)E2 and 6-keto-PGF(1alpha) contents were measured using enzyme immunoassays. The iNOS-selective inhibitor SMT and iNOS gene-knockout mice were used to investigate the effect of iNOS on COX-2. IS/AAR was reduced significantly 1 and 24 h after morphine preconditioning. The infarct-sparing effect 24 h after morphine administration, but not the cardioprotection 1 h later, was completely abolished by NS-398. Marked enhancement of myocardial COX-2 expression was measured 24 h after morphine preconditioning associated with up-regulation of myocardial contents of PGE2 and 6-keto-PGF(1alpha). Neither the level of COX-2 nor the contents of PGE2 and 6-keto-PGF(1alpha) were enhanced 1 h later. Administration of SMT and targeted abrogation of iNOS gene blocked the enhancement of myocardial PGE2 and 6-keto-PGF(1alpha) 24 h after morphine administration but did not inhibit the up-regulation of COX-2 expression. We concluded that COX-2 mediates morphine-induced delayed cardioprotection via an iNOS-dependent pathway.     

Antitumor effect of vitamin B6 and its mechanisms

Epidemiological studies have reported an inverse association between vitamin B(6) intake and colon cancer risk. Our recent study has been conducted to examine the effect of dietary vitamin B(6) on colon tumorigenesis in mice. Mice were fed diets containing 1, 7, 14 or 36 mg/kg pyridoxine for 22 weeks, and given a weekly injection of azoxymethane (AOM) for the initial 10 weeks. Compared with the 1 mg/kg pyridoxine diet, 7, 14 and 35 mg/kg pyridoxine diets significantly suppressed the incidence and number of colon tumors, colon cell proliferation and expressions of c-myc and c-fos proteins. Supplemental vitamin B(6) lowered the levels of colonic 8-hydroxyguanosine (8-OHdG), 4-hydroxy-2-nonenal (4-HNE, oxidative stress markers) and inducible nitric oxide (NO) synthase protein. In an ex vivo serum-free matrix culture model using rat aortic ring, supplemental pyridoxine and pyridoxal 5'-phosphate (PLP) had antiangiogenic effect. The results suggest that dietary vitamin B(6) suppresses colon tumorigenesis by reducing cell proliferation, oxidative stress, NO production and angiogenesis.     

Anti-inflammatory actions of plant-derived multiple monoclonal antibody CO17-1A × BR55 related with anti-cancer effects in AOM/DSS-induced colorectal cancer mouse via down-regulating of ERK1/2

Plant-derived multiple monoclonal antibody (mAb) CO17-1A?×?BR55 (mAb^P CO17-1A?×?BR55) produced in transgenic tobacco plants were cross-pollinated with mAb CO17-1A and mAb BR55. Human anti-colorectal cancer multiple mAb CO17-1A?×?BR55 was cloned using pBI121 vector. Mice were given a single intraperitoneal injection of azoxymethane (AOM) with 10?mg/kg body weight. Starting 1 week after the injection, mice received 2% dextran sulfate sodium (DSS) in the drinking water for 1 week. In addition, the mice were injected intraperitoneal with mAbs dissolved in phosphate buffered saline (100?μg/mouse) twice per week for 4 weeks. Apoptotic cell death, expression of pro-apoptotic proteins, activity of inflammatory cytokines and ERK pathway phosphorylation were assayed by Western blot and TUNEL kit. mAb^P CO17-1A?×?BR55 meaningfully and efficiently suppressed the development of AOM/DSS-induced colorectal inflammation and colorectal tumors, as determined by a reduced activation of inflammatory cytokines, number of colorectal tumor-induced mouse, number of tumor per mouse colon than other mAbs. Cell death by apoptosis was much increased in the mAb^P CO17-1A?×?BR55-treated tumor compared with negative control. Apoptotic cell death and expression of pro-apoptotic proteins including Bax and cleaved caspase-3 were highest in treatment with mAb^P CO17-1A?×?BR55. In addition, mAbP CO17-1A?×?BR55 was meaningfully decreased the expression of inflammatory cytokines, including COX-2, iNOS, p50 and p65, but the expression of PPARγ was significantly increased compared with AOM/DSS-induced carcinogenesis negative control. Moreover, mAb^P CO17-1A?×?BR55 meaningfully repressed the ERK1/2 phosphorylation in AOM/DSS-induced colorectal tumors. Therefore, our results suggest that multiple mAb^P CO17-1A?×?BR55 have meaningful effects of anti-inflammation related with the anti-carcinogenesis in AOM/DSS-induced colorectal tumor by inhibition of ERK1/2 phosphorylation.     

白藜芦醇抑制肠癌细胞焦亡的作用*

目的: 研究白藜芦醇(Res)对肠癌细胞焦亡的影响。方法: ①葡聚糖硫酸钠(DSS)诱发小鼠结肠癌(CRC)实验:30只C57BL/6小鼠随机分为正常对照组(Contro组),氧化偶氮甲烷(AOM)组,AOM/DSS组,AOM/DSS+Res组和Res组,每组6只,造模周期共70 d。第1周第1日对AOM组、AOM/DSS组和AOM/DSS+Res组小鼠AOM(10 mg/kg)腹腔注射一次,无菌水饮水,1% DSS水供AOM/DSS组和AOM/DSS+Res组饮用,对AOM/DSS+Res组和Res组小鼠灌胃给予Res(50 mg/kg),造模结束后,取小鼠结肠组织固定、包埋、切片; IHC和Western blot检测小鼠结肠组织NLRP3、Caspase-1、IL-18蛋白表达情况。②离体实验:HCT 116细胞给予Res(2.4 μg/L)以及转染miR-31,加Res实验分为4组,分别标记0 h、12 h、24 h、48 h组;细胞转染分组为5组,即control组、miR-31 mimic组、miR-31 mimic+Res组、miR-31inhibitor组、miR-31inhibitor+Res组,48 h后收集细胞,每组设置三个复孔,并通过Western blot检测细胞NLRP3、Caspase-1、GSDMD-N、IL-18和IL-1β蛋白表达情况。结果: 动物实验:与control组相比较,AOM/DSS组NLRP3、Caspase-1、IL-18蛋白表达显著升高(P<0.01),AOM/DSS+Res组NLRP3、Caspase-1、IL-18蛋白表达水平相较于AOM/DSS组有显著下降(P<0.01);细胞实验:与control组相比,miR-31 mimic组NLRP3(P<0.01)、GSDMD-N(P<0.05)、IL-18(P<0.01)蛋白表达显著升高, miR-31 inhibitor组NLRP3、GSDMD-N、IL-18蛋白表达显著降低(P<0.05)。结论: Res可通过细胞焦亡抑制结肠癌。     

Melatonin suppresses AOM/DSS-induced large bowel oncogenesis in rats

The inhibitory effects of exogenous melatonin (MEL) on colon oncogenesis were investigated using an azoxymethane (AOM)/dextran sodium sulfate (DSS) rat model. Male F344 rats initiated with a single intraperitoneal injection of AOM (20 mg/kg bw) were promoted by 1% (w/v) DSS in drinking water for 7 days. They were then given 0.4, 2 or 10 ppm MEL in drinking water for 17 weeks. At week 20, the development of colonic adenocarcinoma was significantly inhibited by the administration with MEL dose-dependently. MEL exposure modulated the mitotic and apoptotic indices in the colonic adenocarcinomas that developed and lowered the immunohistochemical expression of nuclear factor kappa B, tumor necrosis factor α, interleukin-1β and STAT3 in the epithelial malignancies. These results may indicate the beneficial effects of MEL on colitis-related colon carcinogenesis and a potential application for inhibiting colorectal cancer development in the inflamed colon.     

Is the tissue persistence of O(6)-methyl-2'-deoxyguanosine an indicator of tumour formation in the gastrointestinal tract?

Azoxymethane (AOM) is a methylating agent capable of inducing mutations in DNA by forming adducts with DNA bases. It has been used to understand the mechanisms involved in colon carcinogenesis. Of the adducts formed in response to AOM, O(6)-methyl-2'-deoxy-guanosine (O(6)-mdGua) is the most mutagenic. Based on studies in rodents of the abundance and persistence of DNA adducts in various tissues after treatment with alkylating agents, previous results suggest, as a generalization, that the longer O(6)-mdGua adducts remain unrepaired in the cells of a tissue, the greater the risk for tumorigenesis. To test this hypothesis, we have built on these studies, expanding the number of tissues in which O(6)-mdGua abundance and persistence were examined and correlating these data with tumour distribution and abundance in rats maintained for 26 weeks after the treatment with AOM. Our study revealed firstly the existence of groups of tissues that developed relatively large amounts (proximal and distal colon, proximal small intestine (SI), liver and kidney) and relatively low levels (stomach, distal SI, bladder, spleen, blood and lung) of O(6)-mdGua after AOM exposure. Secondly, while all tissues showed an increase in adduct levels at 6h after mutagen treatment and most showed a significant drop in adduct levels between 6h and 48h (stomach, proximal and distal SI, liver, spleen, blood and lung), one group of tissues displayed O(6)-mdGua levels that did not decrease at 48h (proximal and distal colon, kidney and bladder). Predictably, the colon displayed tumours 26 weeks after treatment. Interestingly, however, the proximal SI also displayed significant tumour formation at that time. Our findings demonstrate (1) a direct association between exposure to O(6)-mdGua and tumours of the distal colon and (2) a dissociation of the relationship between adduct clearance and tumorigenesis in the SI. This diversity of response in the gastrointestinal tract warrants further analysis.     

Comparison of effects on colitis-associated tumorigenesis and gut microbiota in mice between Ophiocordyceps sinensis and Cordyceps militaris

Background: Gut microbiota plays an indispensable role in the treatment of inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). As traditional medicinal fungi, previous studies have shown that Ophiocordyceps sinensis could better maintain intestinal health via promoting the growth of probiotics in vitro compared with Cordyceps militaris. However, the detailed pharmacological activities and clinical efficacy of O. sinensis and C. militaris are still elusive.Purpose: We aimed to evaluate the different actions of O. sinensis and C. militaris on colitis-associated tumorigenesis in Azoxymethane (AOM)/Dextran Sulfate Sodium (DSS)-treated mice and explore the potential gut microbiota-dependent mechanisms.Methods: C57BL/6 mice (Male, 4 weeks old) were used to construct the AOM/DSS-induced CAC mice model. The mice were administered with 0.6 mg/g/d O. sinensis or C. militaris for 12 weeks. It's worth noting that fecal microbiota transplantation (FMT) and antibiotic treatment were used to investigated the complex interactions between the medicinal fungi, gut microbiota and colonic tumorigenesis.Results: O. sinensis treatment significantly increased the body weight and survival rate, reduced the number of colon tumors, improved the damage of colon epithelial tissue, restored the crypt structure and alleviate the colonic inflammation in AOM/DSS-treated mice. RT-qPCR results indicated that O. sinensis partly regulated the Wnt/β-catenin signaling via alleviating the overexpression of β-catenin, TCF4 and c-Myc genes in adjacent noncancerous tissues. Compared with C. militaris, O. sinensis showed better anti-tumor activity. Gut microbiota analysis revealed that O. sinensis reversed the decline of gut microbiota diversity and the structural disorder induced by AOM/DSS. Spearman's correlation analysis showed that O. sinensis promoted the growth of Parabacteroides goldsteinii and Bifidobacterium pseudolongum PV8-2, which were positively correlated with the anti-tumor activity and the production of SCFAs. FMT combined with antibiotic treatment showed that horizontal fecal transfer derived from O. sinensis-treated mice improved the intestinal inflammation and alleviated the colitis-associated tumorigenesis, which was consistent with the direct ingestion of O. sinensis.Conclusion: O. sinensis could better attenuate colitis-associated tumorigenesis compared with C. militaris. These effects might be at least partially due to the increased abundance of probiotics, especially P. goldsteinii and B. pseudolongum PV8-2.     

Intestinal inflammatory cytokine response in relation to tumorigenesis in the Apc(Min/+) mouse

The etiology of colon cancer is a complex phenomenon that involves both genetic and environmental factors. However, only about 20% have a familial basis with the largest fraction being attributed to environmental causes that can lead to chronic inflammation. While the link between inflammation and colon cancer is well established, the temporal sequence of the inflammatory response in relation to tumorigenesis has not been characterized. We examined the timing and magnitude of the intestinal inflammatory cytokine response in relation to tumorigenesis in the Apc^Min/+ mouse. Apc^Min/+ mice and wildtype mice were sacrificed at one of 4 time-points: 8, 12, 16, and 20 weeks of age. Intestinal tissue was analyzed for polyp burden (sections 1, 4 and 5) and mRNA expression and protein concentration of MCP-1, IL-1β, IL-6 and TNF-α (sections 2 and 3). The results show that polyp burden was increased at 12, 16 and 20 weeks compared to 8 weeks (P < 0.05). Gene expression (mRNA) of MCP-1, IL-1β, IL-6 and TNF-α was increased in sections 2 and 3 starting at week 12 (P < 0.05), with further increases in MCP-1, IL-1β and IL-6 at 16 weeks (P < 0.05). Protein concentration for these cytokines followed a similar pattern in section 3. Similarly, circulating MCP-1 was increased at 12 weeks (P < 0.05) and then again at 20 weeks (P < 0.05). In general, overall polyp number and abundance of large polyps were significantly correlated with the inflammatory cytokine response providing further support for a relationship between polyp progression and these markers. These data confirm the association between intestinal cytokines and tumorigenesis in the Apc^Min/+ mouse and provide new information on the timing and magnitude of this response in relation to polyp development. These findings may lead to the development of inflammatory mediators as important biomarkers for colon cancer progression. Further, these data may be relevant in the design of future investigations of therapeutic interventions to effectively target inflammatory processes in rodent models.     

Involvement of the atrial natriuretic peptide in the reduction of arterial pressure induced by swimming but not by running training in hypertensive rats

The aim of this study was to compare, under resting conditions, the influence of chronic training in swimming or running on mean arterial pressure (MAP) and the involvement of the natriuretic peptide system in this response. Two-month-old male spontaneously hypertensive rats (SHR) were divided into three groups—sedentary (SD), swimming (SW) and running (RN)—and were trained for eight weeks under regimens of similar intensities. Atria tissue and plasma atrial natriuretic peptide (ANP) concentrations were measured by radioimmunoassay. ANP mRNA levels in the right and left atria as well as the natriuretic peptide receptors (NPR), NPR-A and NPR-C, mRNA levels in the kidney were determined by real-time PCR. Autoradiography was used to quantify NPR-A and NPR-C in mesenteric adipose tissue. Both training modalities, swimming and running, reduced the mean arterial pressure (MAP) of SHR. Swimming, but not running, training increased plasma levels of ANP compared to the sedentary group (P < 0.05). Expression of ANP mRNA in the left atrium was reduced in the RN compared to the SD group (P < 0.05). Expression of NPR-A and NPR-C in the kidneys of the SW group decreased significantly (P < 0.05) compared to the SD group. Although swimming increased ¹²⁵I-ANP binding to mesenteric adipose tissue, displacement by c-ANF was reduced, indicating a reduction of NPR-C. These results suggest that the MAP reduction induced by exercise in SHR differs in its mechanisms between the training modalities, as evidenced by the finding that increased levels of ANP were only observed after the swimming regimen.     

Short-chain fatty acids administration is protective in colitis-associated colorectal cancer development

Reduced short-chain fatty acids (SCFAs) have been reported in patients with ulcerative colitis, and increased intake of dietary fiber has shown to be clinically beneficial for colitis. Whether SCFAs suppress tumorigenesis in colitis-associated colorectal cancer remains unknown. The chemopreventive effect of SCFAs in colitis-associated colorectal cancer was evaluated in this study. Model of colitis-associated colorectal cancer in male BALB/c mice was induced by azoxymethane (AOM) and dextran sodium sulfate (DSS). SCFAs mix (67.5 mM acetate, 40 mM butyrate, 25.9 mM propionate) was administered in drink water during the study period. Macroscopic and histological studies were performed to examine the colorectal inflammation and tumorigenesis in AOM/DSS-induced mice treated with or without SCFA mix. The effects of SCFAs mix on colonic epithelial cellular proliferation were also assessed using Ki67 immunohistochemistry and TUNEL staining. The administration of SCFAs mix significantly reduced the tumor incidence and size in mice with AOM/DSS-induced colitis associated colorectal cancer. SCFAs mix protected from AOM/DSS-induced colorectal cancer by improving colon inflammation and disease activity index score as well as suppressing the expression of proinflammatory cytokines including IL-6, TNF-α and IL-17. A decrease in cell proliferation markers and an increase in TUNEL-positive tumor epithelial cells were also demonstrated in AOM/DSS mice treated with SCFAs mix. SCFAs mix administration prevented development of tumor and attenuated the colonic inflammation in a mouse model of colitis-associated colorectal cancer. SCFAs mix may be a potential agent in the prevention and treatment of colitis-associated colorectal cancer.