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.     

Protein kinase C betaII and TGFbetaRII in omega-3 fatty acid-mediated inhibition of colon carcinogenesis

Increasing evidence demonstrates that protein kinase C betaII (PKCbetaII) promotes colon carcinogenesis. We previously reported that colonic PKCbetaII is induced during colon carcinogenesis in rodents and humans, and that elevated expression of PKCbetaII in the colon of transgenic mice enhances colon carcinogenesis. Here, we demonstrate that PKCbetaII represses transforming growth factor beta receptor type II (TGFbetaRII) expression and reduces sensitivity to TGF-beta-mediated growth inhibition in intestinal epithelial cells. Transgenic PKCbetaII mice exhibit hyperproliferation, enhanced colon carcinogenesis, and marked repression of TGFbetaRII expression. Chemopreventive dietary omega-3 fatty acids inhibit colonic PKCbetaII activity in vivo and block PKCbetaII-mediated hyperproliferation, enhanced carcinogenesis, and repression of TGFbetaRII expression in the colonic epithelium of transgenic PKCbetaII mice. These data indicate that dietary omega-3 fatty acids prevent colon cancer, at least in part, through inhibition of colonic PKCbetaII signaling and restoration of TGF-beta responsiveness.     

Dose-dependent promoting effect of dextran sodium sulfate on mouse colon carcinogenesis initiated with azoxymethane

We previously reported a powerful tumor-promoting ability of dextran sodium sulfate (DSS) in a novel mouse model for colitis-related colon carcinogenesis initiated with azoxymethane (AOM). To determine the dose-dependent influence of DSS in our animal model, male ICR mice were given a single intraperitoneal injection of AOM (10 mg/kg body weight), followed by DSS at dose levels of 2, 1, 0.5, 0.25, and 0.1% (w/v) in drinking water for 1 week. All animals were sacrificed at week 14 and histological alterations in their colon and nitrotyrosine immunohistochemistry were examined to evaluate the nitrosative stress. In the mice which received AOM and 2% DSS, the incidences (multiplicity) of colonic tubular adenoma and adenocarcinoma were 75% (1.25+/-1.26/mouse) and 100% (2.75+/-2.22/mouse), respectively. Mice given AOM and 1% DSS had 80% incidence of adenoma (1.00+/-0.71/mouse) and 60% incidence of adenocarcinoma (1.40+/-2.07/mouse) in the colon. In a mouse treated with AOM and 0.5% DSS, only one colonic adenoma (20% incidence with 0.20+/-0.45 multiplicity) developed. Higher frequency of high-grade colonic dysplasia was noted in mice given AOM and 2% or 1% DSS when compared with mice treated with AOM and lower doses of DSS. Also, scoring of inflammation and nitrotyrosine immunoreactivity suggested that severe inflammation and nitrosation stress caused by high-doses (2% and 1%) of DSS contribute its tumor-promoting effects in mouse colon carcinogenesis initiated with a low dose of AOM. Thus, our findings indicate that a tumor-promoting effect of DSS was dose-dependent (1% or more) and the effect might occur under the condition of inflammation and nitrosation stress.     

Expression of N-myristoyltransferase inhibitor protein and its relationship to c-Src levels in human colon cancer cell lines

Earlier, we have reported that N-myristoyltransferase (NMT) activity is higher in colonic epithelial neoplasms than in normal appearing colonic tissue and that increase in NMT activity appears at an early stage in colonic carcinogenesis [Magnuson, B., Raju, R. V. S., Moyana, T. N., and Sharma, R. K. (1995) J. Natl. Cancer Inst. 87, 1630-1635]. In this study, we demonstrate increased NMT mRNA in well-differentiated adenocarcinomas. NMT and c-Src mRNA levels were generally elevated in a subset of human colon cancer cell lines. Western blotting analysis employing N-myristoyltransferase inhibitory protein (NIP(71)) antibody demonstrated low levels of NIP(71) in high-expressing c-Src cell lines and high levels of NIP(71) in low-expressing c-Src cell lines. Interestingly, down regulation of c-Src by antisense expression in the HT-29 cell line resulted in increased expression of NIP(71), suggesting c-Src may negatively regulate NIP(71) expression. Furthermore, this is the first study demonstrating the expression of NIP(71) in human colon cancer cell lines and a possible relationship to colon carcinogenesis.     

Antioxidant effects of dehydroepiandrosterone and 7alpha-hydroxy-dehydroepiandrosterone in the rat colon, intestine and liver

This study examined in healthy male Wistar rats the in vivo antioxidant effect of dehydroepiandrosterone (DHEA) and 7alpha-hydroxy-DHEA administered by intraperitoneal injections (50 mg/kg body weight) for 2 or 7 days. Markers of oxidative damage to lipids (thiobarbituric acid-reacting substances, TBARS) and to proteins (protein carbonyls) were assessed in colon, small intestine, and liver homogenates. DHEA and 7alpha-hydroxy-DHEA caused a decrease in body weight. DHEA treatment significantly increased liver, colon, and small intestine cell weights. After 7 days, DHEA exerted an antioxidant effect in all organs studied. In the colon, oxidative damage protection was accompanied by a goblet cell proliferation and increase in acidic mucus production. After 2 days, the antioxidant effect of 7alpha-hydroxy-DHEA was mainly observed in the liver. Nonprotein sulfhydryl groups (mostly glutathione levels) were altered by DHEA in the liver whereas they remained unchanged after 7alpha-hydroxy-DHEA treatment. The results indicate that in healthy animals, DHEA exerts a protective effect, particularly in the colon, by reducing the tissue susceptibility to oxidation of both lipids and proteins. This effect was not limited to a specific tissue, whereas the metabolite 7alpha-hydroxy-DHEA exerted its antioxidant effect towards the two markers of oxidative damage earlier than DHEA, and mainly in the liver.     

Elevated lipopolysaccharide in the colon evokes intestinal inflammation, aggravated in immune modulator-impaired mice

Frequency of gram-negative bacteria is markedly enhanced in inflamed gut, leading to augmented LPS in the intestine. Although LPS in the intestine is considered harmless and, rather, provides protective effects against epithelial injury, it has been suggested that LPS causes intestinal inflammation, such as necrotizing enterocolitis. Therefore, direct effects of LPS in the intestine remain to be studied. In this study, we examine the effect of LPS in the colon of mice instilled with LPS by rectal enema. We found that augmented LPS on the luminal side of the colon elicited inflammation in the small intestine remotely, not in the colon; this inflammation was characterized by body weight loss, increased fluid secretion, enhanced inflammatory cytokine production, and epithelial damage. In contrast to the inflamed small intestine induced by colonic LPS, the colonic epithelium did not exhibit histological tissue damage or inflammatory lesions, although intracolonic LPS treatment elicited inflammatory cytokine gene expression in the colon tissues. Moreover, we found that intracolonic LPS treatment substantially decreased the frequency of immune-suppressive regulatory T cells (CD4(+)/CD25(+) and CD4(+)/Foxp3(+)). We were intrigued to find that LPS-promoted intestinal inflammation is exacerbated in immune modulator-impaired IL-10(-/-) and Rag-1(-/-) mice. In conclusion, our results provide evidence that elevated LPS in the colon is able to cause intestinal inflammation and, therefore, suggest a physiological explanation for the importance of maintaining the balance between gram-negative and gram-positive bacteria in the intestine to maintain homeostasis in the gut.     

Triple therapy with octreotide,galanin and serotonin induces necrosis and increases apoptosis of a rat colon carcinoma

A rat colonic adenocarcinoma was implanted subcutaneously (s.c.) in nude mice. After 7 days, the animals were divided into different groups. Two groups received subcutaneous injections twice daily with 3 or 6 micro g/kg body weight octreotide, galanin and serotonin. Three groups were respectively treated with 20, 30, and 40 micro g/kg body weight of the previously mentioned bioactive substances. Control group received only saline solution in the same fashion as treated animals. The treatment lasted for 5 days. The tumour volume and weight, the relative density of blood vessels, of tumour necrotic tissue, of apoptotic nuclei and of proliferating nuclei were measured. Apoptosis was detected by in situ labelling of nuclear DNA fragmentation according to TUNEL method, and proliferation by immunocytochemistry. Morphometry was done with the classical stereological point-counting method. Food consumption, animal weight, faeces weight and its water content were measured for 3 days before and after treatment. Triple therapy with 3 and 6 micro g/kg body weight had no effect on any of the parameters measured, except in reducing the relative volume density of tumour blood vessels. Treatment with 20, 30 and 40 micro g/kg body weight of the previously mentioned bioactive substances reduced the tumour volume, the relative volume density of blood vessels and increased the relative volume density of necrotic tissue and of apoptotic nuclei (in the 20 micro g group). However, there was no difference between treated mice and controls regarding the relative volume density of proliferating nuclei. There was no statistical difference between treated animals regarding food consumption, body weight, faeces weight and its water content before and during treatment. The present study confirms that triple therapy with octreotide, galanin and serotonin causes regression of a rat colon carcinoma. It further showed that optimum treatment dose is 20 micro g/kg body weight of each bioactive substance. Moreover, this therapy regime does not show apparent side effects in the experiments carried out on mice.     

Cholecystokinin stimulates neuronal receptors to produce contraction of the canine colon

The motor effects of cholecystokinin 26-33-amide (CCK octapeptide; CCK-OP) and several purported CCK receptor antagonists on canine colonic circular muscle were determined in pentobarbital anesthetized dogs. Intravenous injections of CCK-OP had no effect on colonic motility at doses that contracted the gallbladder, stomach and duodenum. CCK-OP delivered by intraarterial injection to a small segment of the proximal colon produced a dose related increase in colonic motility with one-half maximum response at 12 ng/Kg and maximum response at 50 ng/Kg. The effects of intraarterial injections of several established CCK-receptor antagonists on proximal colonic responses to intraarterial injections of CCK-OP were determined. Proglumide, 10 mg/Kg, did not produce colonic contractions itself, but antagonized CCK-OP-induced responses. Carbobenzyloxy (CBZ)-CCK27-32-amide antagonized CCK-OP-induced colonic responses and also had no effect on basal colonic motility (0.1-1 and 5 micrograms/Kg). Neither compound antagonized acetylcholine- induced colonic responses. Butoxycarbonyl (BOC)-CCK31-33-amide increased basal colonic motility, but did not alter CCK-OP-induced responses at doses of 0.1 and 0.2 mg/Kg. Dibutyryl-cGMP at a dose of 0.1 mg/Kg did not affect basal motility or CCK-OP-induced contractions. At a dose of 1.0 mg/kg it increased basal colonic motility but did not affect CCK-OP-induced contractions. Pentagastrin increased colonic motor activity only at a dose of 5 micrograms/Kg, i.a., a much higher dose than effective doses of CCK-OP. The mechanism of CCK-OP-induced colonic motor effects also was determined. Atropine sulfate, 100 micrograms/Kg, i.v. significantly reduced both intraarterial acetylcholine-and CCK-OP-induced maximum colonic contractions. Tetrodotoxin, at intravenous doses that completely block neuronal activity, did not affect maximum acetylcholine-induced contractions but practically eliminated maximum CCK-OP-induced maximum colonic responses. In conclusion, intraarterial CCK-OP produces circular muscle contraction of the canine proximal colon that is mediated by stimulation of specific CCK receptors which produce the release of acetylcholine from cholinergic enteric neurons. Proglumide and CBZ-CCK27-32-amide are effective CCK receptor antagonists at these colonic neuronal receptors.     

Modulatory efficacy of hesperetin (citrus flavanone) on xenobiotic-metabolizing enzymes during 1,2-dimethylhydrazine-induced colon carcinogenesis

Colorectal cancer is the second leading cause of cancer death worldwide with diet playing a prominent role in disease initiation and progression. Diet and nutrition play an important role during this multistep colon carcinogenic process. We have investigated the modulatory efficacy of hesperetin on aberrant crypt foci (ACF) and xenobiotic-metabolizing enzymes on 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis. Male albino Wistar rats were randomly divided into six groups. Group 1 served as control, received modified pellet diet and group 2 rats received 20 mg/kg body weight of hesperetin p.o. every day. Groups 3-6 rats were given subcutaneous injections of 1,2-dimethylhydrazine (20 mg/kg body weight) once a week for 15 weeks to induce ACF in the colon. In addition, rats in group 4 received hesperetin as in group 2 orally for the first 15 weeks (initiation), group 5 rats received hesperetin as in group 2 after the last injection of DMH and continued till the end of the experimental period (post-initiation). Group 6 received hesperetin as in group 2 throughout the entire period of 32 weeks. DMH exposure showed high incidence (90%) of ACF (280 ± 24.5 aberrant crypt/colon) and dysplastic ACF, elevated activities of phase I enzymes and reduced the activities of phase II enzymes in the liver and colonic mucosa of colon cancer bearing rats. Hesperetin supplementation significantly reversed these effects, the effect being more pronounced in group 6 rats (hesperetin supplemented throughout the study period).These findings suggest that hesperetin can significantly reduce the formation of preneoplastic lesions and effectively modulate the xenobiotic-metabolizing enzymes in rats.     

Mitochondrial lipid peroxidation is influenced by dietary factors in early colon carcinogenesis

Oxidative damage to mitochondrial proteins, lipids, and DNA seem to influence the promotion and progression of tumors. High-fat diets and diets high in iron decrease manganese superoxide dismutase activity, a mitochondrial antioxidant, in colon mucosa. Lipid peroxidation products are low in microsomal preparations from colonic mucosa even under peroxide-inducing conditions. However, damage specific to mitochondrial membranes is unknown. This study was designed to investigate dietary lipid and iron effects on fatty acid incorporation and lipid peroxide formation in mitochondrial membranes of colonic mucosa. Male Fischer rats were fed high-fat diets containing either corn oil or menhaden oil with an iron level of either 35 or 535 mg/kg diet. Animals were given two injections of the colon carcinogen, azoxymethane, or saline. Colon tissue was collected 1 and 6 weeks after injections. Mitochondrial and microsomal fractions were prepared for fatty acid analysis and quantitation of lipid peroxidation products. Results showed that lipid composition of both subcellular fractions were influenced by diet. Fatty acid composition of mitochondria differed from microsomes, but overall saturation remained constant. Peroxidation products in mitochondrial membranes were significantly greater than in microsomal membranes. Dietary treatment significantly affected mitochondrial peroxidation in carcinogen-treated animals. Therefore, mitochondria from colon mucosa are more susceptible to peroxidation than are microsomes, dietary factors influence the degree of peroxidation, and the resulting damage may be important in early colon carcinogenesis.     

Chemopreventive efficacy of green tea drinking against 1,2‐dimethyl hydrazine‐induced rat colon carcinogenesis

Colorectal cancer is one of the leading causes of tumour‐related deaths. In the present study, the chemopreventive effect of green tea on 1,2‐dimethylhydrazine (DMH)‐induced colon carcinogenesis was studied in male Wistar rats. The DMH group received subcutaneous injections of DMH (30 mg kg^?1 body weight) once a week for 30 weeks, the normal group received the vehicle of DMH, and the DMH + green tea group received DMH simultaneously with 1% green tea as their sole source of drinking fluid throughout the experimental period. In the DMH group treated with green tea, significant reductions in gene overexpressions of colonic nuclear factor κB (NF‐κB), tumour necrosis factor α, inducible nitric oxide synthase and cyclooxygenase 2, and NF‐κB immunostaining indicates the anti‐inflammatory effect of green tea in attenuating colon cancer. Moreover, the anti‐angiogenic and anti‐invasiveness effects of green tea were revealed as reductions of both vascular endothelial growth factor and matrix metalloproteinase‐7 mRNA expression levels. These effects were confirmed by the significant reduction of serum tumour necrosis factor α, C‐reactive protein levels, inhibition of tumour incidence, and nearly normal survival rate and colonic architecture. It can be concluded that green tea exerts a potent chemopreventive effect on colon carcinogenesis possibly due to the inhibition of NF‐κB. Copyright © 2012 John Wiley & Sons, Ltd.     

Dietary astaxanthin inhibits colitis and colitis-associated colon carcinogenesis in mice via modulation of the inflammatory cytokines

Astaxanthin (AX) is one of the marine carotenoid pigments, which possess powerful biological antioxidant, anti-inflammatory and anti-cancer properties. The purpose of this study is to investigate possible inhibitory effect of AX against inflammation-related mouse colon carcinogenesis and dextran sulfate sodium (DSS)-induced colitis in male ICR mice. We conducted two different experiments. In the first experiment, we evaluated the effects of AX at three dose levels, 50, 100 and 200 ppm in diet, on colitis-associated colon carcinogenesis induced by azoxymethane (AOM)/DSS in mice. In the second, the effects of the AX (100 and 200 ppm) in diet on DSS-induced colitis were determined. We found that dietary AX significantly inhibited the occurrence of colonic mucosal ulcers, dysplastic crypts, and colonic adenocarcinoma at week 20. AX-feeding suppressed expression of inflammatory cytokines, including nuclear factor (NF)-κB, tumor necrosis factor (TNF)-α and interleukin (IL)-1β, inhibited proliferation, and induced apoptosis in the colonic adenocarcinomas. Feeding with 200 ppm AX, but not 100 ppm, significantly inhibited the development of DSS-induced colitis. AX feeding (200 ppm in diet) also lowered the protein expression of NF-κB, and the mRNA expression of inflammatory cytokines, including IL-1β, IL-6, and cyclooxygenase (COX)-2. Our results suggest that the dietary AX suppresses the colitis and colitis-related colon carcinogenesis in mice, partly through inhibition of the expression of inflammatory cytokine and proliferation. Our findings suggest that AX is one of the candidates for prevention of colitis and inflammation-associated colon carcinogenesis in humans.     

Chemoprevention of benzo(a)pyrene-induced colon polyps in ApcMin mice by resveratrol

Human dietary exposure to benzo(a)pyrene (BaP) has generated interest with regard to the association of BaP with gastrointestinal carcinogenesis. Since colon cancer ranks third among cancer-related mortalities, it is necessary to evaluate the effect of phytochemicals on colon cancer initiation and progression. In this study, we investigated the preventive effects of resveratrol (RVT) on BaP-induced colon carcinogenesis in Apc^Min mouse model. For the first group of mice, 100 μg BaP/kg body weight was administered to mice in peanut oil via oral gavage over a 60-day period. For the second group, RVT was coadministered with BaP at a dose of 45 μg/kg. For the third group, RVT was administered for 1 week prior to BaP exposure for 60 days. Jejunum, colon and liver were collected at 60 days post BaP and RVT exposure; adenomas in jejunum and colon were counted and subjected to histopathology. RVT reduced the number of colon adenomas in BaP+RVT-treated mice significantly compared to that in mice that received BaP alone. While dysplasia of varying degrees was noted in colon of BaP-treated mice, the dysplasias were of limited occurrence in RVT-treated mice. To ascertain whether the tumor inhibition is a result of altered BaP-induced toxicity of tumor cells, growth, apoptosis and proliferation of adenocarcinoma cells were assessed posttreatment with RVT and BaP. Cotreatment with RVT increased apoptosis and decreased cell proliferation to a greater extent than with BaP alone. Overall, our observations reveal that RVT inhibits colon tumorigenesis when given together with BaP and holds promise as a therapeutic agent.     

Effect of estrogen on cell proliferation in colonic mucosa of the mouse

The effect of estrogen on cell proliferation in the descending colon of the mouse as an example of a non-target organ was investigated. Ovariectomized mice were given single or multiple injections of 10 ng/g body weight of 17 beta-estradiol and were killed 1 h after 3H-thymidine injection. Estrogen treatments decreased incorporation of 3H-thymidine into the DNA of colonic mucosa most markedly at 4 h after the single or the last of multiple injections. The inhibitory effect of estrogen on 3H-thymidine incorporation was greater and lasted longer after a single injection than after multiple ones. A similar inhibitory effect was observed in the colonic mucosa of male mice as well as in the mucosa of mice in which colonic epithelial cell proliferation was enhanced by refeeding after 48 h of fasting. However, the colonic mucosa of mice treated with estrogen implants for up to 4 days was not affected. Estrogen treatments caused no significant change in the DNA, RNA and protein contents of the colonic mucosa. The efficacy of estrogen treatments was verified by an increase in both the wet and dry weights of the uterine horns of ovariectomized mice.     

The antiapoptotic role of pregnane X receptor in human colon cancer cells

The orphan nuclear receptor pregnane X receptor (PXR) plays an important role in the detoxification of foreign and endogenous chemicals, including bile acids. PXR promotes bile acid elimination by activating bile acid-detoxifying enzymes and transporters. Certain bile acids are known to promote colonic carcinogenesis by inducing colon cancer cell apoptosis. However, whether and how PXR plays a role in colon cancer apoptosis has not been reported. In this study, we showed that activation of PXR by genetic (using a constitutively activated PXR) or pharmacological (using PXR agonist rifampicin) means protected the PXR-overexpressing colon cancer HCT116 cells from deoxycholic acid-induced apoptosis. Interestingly, activation of PXR also protected HCT116 cells from adriamycin-induced cell death, suggesting that the antiapoptotic effect of PXR was not bile acid specific. Moreover, the antiapoptotic effect of PXR in HCT116 cells appeared to be independent of xenobiotic enzyme regulation, because these cells had little basal and inducible expression of bile acid-detoxifying enzymes. Instead, SuperArray analysis showed that PXR-mediated deoxycholic acid resistance was associated with up-regulation of multiple antiapoptotic genes, including BAG3, BIRC2, and MCL-1, and down-regulation of proapoptotic genes, such as BAK1 and TP53/p53. Treatment with rifampicin in colon cancer LS180 cells, a cell line known to express endogenous PXR, also inhibited apoptosis. Activation of PXR in transgenic mice inhibited bile acid-induced colonic epithelial apoptosis and sensitized mice to dimethylhydrazine-induced colonic carcinogenesis, suggesting that the antiapoptotic effect of PXR is conserved in normal colon epithelium. In summary, our results have established the antiapoptotic role of PXR in both human colon cancer cells and normal mouse colon epithelium.     

Amelioration of dextran sulfate sodium-induced colitis in mice by oral administration of beta-caryophyllene, a sesquiterpene

beta-Caryophyllene (BCP), a naturally occurring plant sesquiterpene, was examined for anti-inflammatory activity in a mouse model of experimental colitis induced by dextran sulfate sodium (DSS). Colitis was induced by exposing male BALB/c mice to 5% DSS in drinking water for 7 days. BCP in doses of 30 and 300 mg/kg was administered orally once a day, beginning concurrently with exposure to DSS. The body weight and colon length were measured, and histological damage and myeloperoxidase (MPO) activity as well as inflammatory cytokines were assessed in both serum and colonic tissue after 7 days of treatment with DSS. The DSS treatment damaged the colonic tissue, increased MPO activity and inflammatory cytokines, lowered the body weight, and shortened the length of the colon. Oral administration of BCP at 300 mg/kg significantly suppressed the shortening of colon length and slightly offset the loss of body weight. BCP treatment (300 mg/kg) also significantly reduced the inflammation of colon and reversed the increase in MPO activity that had been induced by exposure to DSS. Further, BCP significantly suppressed the serum level of IL-6 protein (a 55% reduction) as well as the level of IL-6 mRNA in the tissue. These results demonstrate that BCP ameliorates DSS-induced experimental colitis, and may be useful in the prevention and treatment of colitis.     

Chemopreventive potential of luteolin during colon carcinogenesis induced by 1,2-dimethylhydrazine

We investigated the chemopreventive potential of luteolin on hepatic and circulatory lipid peroxidation and antioxidant status during 1,2-dimethylhydrazine induced colon carcinogenesis in rats. Rats were given a weekly subcutaneous injection of DMH at a dose of 20 mg/kg body weight for 15 weeks. Luteolin (0.2 mg/kg body weight/everyday p.o.) was given at the initiation and also at the postinitiation stages of carcinogenesis to DMH treated rats. The animals were sacrificed at the end of 30 weeks. Enhanced lipid peroxidation in the liver and circulation of tumor bearing rats was accompanied by a significant decrease in the levels of plasma and hepatic reduced glutathione (GSH), glutathione peroxidase (GPx), glutathione-S-transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), vitamin C, vitamin E and beta-carotene in DMH treated rats as compared to the control rats. Intragastric administration of luteolin (0.2mg/kg body weight) to DMH-treated rats significantly reduced the incidence and size of tumor in the colon, reduced lipid peroxidation levels and enhanced the plasma and hepatic activities of GSH, GPx, GST, GR, SOD, CAT, vitamin C, vitamin E and beta-carotene. Thus the chemopreventive efficacy of luteolin against colon carcinogenesis is evidenced by our preliminary studies which showed decreased incidence of tumors and the antiperoxidative and antioxidant effect of luteolin. Further study on the exact mechanism of action of luteolin in preventing colon carcinogenesis is yet to be elucidated.     

Polyamines and colon cancer

In colon cancer, the activities of polyamine-synthesizing enzymes and polyamine content are increased 3-4-fold over that found in the equivalent normal colonic mucosa, and polyamines have even been attributed as markers of neoplastic proliferation in the colon. Furthermore, and in contrast with all other cell systems in the body, normal and neoplastic cells in the colon are exposed to high concentrations of putrescine from the lumen, synthesized by colonic microflora. While such a high polyamine supply may be of benefit in non-neoplastic colonic mucosal growth, the role of luminal polyamines in colon cancer is a clear concern. Luminal polyamines are readily taken up by neoplastic colonocytes, they are utilized in full to support neoplastic growth, and their uptake is strongly up-regulated by the mitogens known to play an important role in colonic carcinogenesis. Inhibition of polyamine synthesis and their uptake, impaired utilization of exogenous polyamines, and enhanced catabolism of polyamines in neoplastic colonocytes are therefore logical approaches in the chemoprevention of colorectal cancer.     

cis-Urocanic acid attenuates acute dextran sodium sulphate-induced intestinal inflammation

On exposure to sunlight, urocanic acid (UCA) in the skin is converted from trans to the cis form and distributed systemically where it confers systemic immunosuppression. The aim of this study was to determine if administration of cis-UCA would be effective in attenuating colitis and the possible role of IL-10. Colitis was induced in 129/SvEv mice by administering 5% dextran sodium sulfate (DSS) for 7 days in drinking water. During this period mice received daily subcutaneously injections of cis-UCA or vehicle. To examine a role for IL-10, 129/SvEv IL-10(-/-) mice were injected for 24 days with cis-UCA or vehicle. Clinical disease was assessed by measurement of body weight, stool consistency, and presence of blood. At sacrifice, colonic tissue was collected for histology and measurement of myeloperoxidase and cytokines. Splenocytes were analyzed for CD4+CD25+FoxP3+ T-regulatory cells via flow cytometry. Murine bone-marrow derived antigen-presenting cells were treated with lipopolysaccharide (LPS) ± UCA and cytokine secretion measured. Our results demonstrated that cis-UCA at a dose of 50 μg was effective in ameliorating DSS-induced colitis as evidenced by reduced weight loss and attenuated changes in colon weight/length. This protection was associated with reduced colonic expression of CXCL1, an increased expression of IL-17A and a significant preservation of splenic CD4+CD25+FoxP3+ T-regulatory cells. cis-UCA decreased LPS induced CXCL1, but not TNFα secretion, from antigen-presenting cells in vitro. UCA reduced colonic levels of IFNγ in IL-10(-/-) mice but did not attenuate colitis. In conclusion, this study demonstrates that cis-urocanic acid is effective in reducing the severity of colitis in a chemically-induced mouse model, indicating that pathways induced by ultraviolet radiation to the skin can influence distal sites of inflammation. This provides further evidence for a possible role for sunlight exposure in modulating inflammatory disorders.     

Zinc mediated normalization of histoarchitecture and antioxidant status offers protection against initiation of experimental carcinogenesis

The present study evaluated the inhibitory effects of zinc on colonic antioxidant defense system and histoarchitecture during 1,2 dimethylhydrazine (DMH) induced colon carcinogenesis in male Sparque Dawley rats. The rats were segregated into four groups viz., normal control, DMH treated, zinc treated, DMH + zinc treated. Colon carcinogenesis was induced through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 8 weeks. Zinc (in the form of zinc sulphate) was supplemented to rats at a dose level of 227 mg/l in drinking water, ad libitum for the entire duration of the study. Increased lipid peroxidation was accompanied by a decrease in reduced glutathione (GSH), glutathione reductase (GR), glutathione-s-transferase (GST), superoxide dismutase (SOD), and catalase. Administration of zinc to DMH treated rats significantly decreased the lipid peroxidation levels with simultaneous enhancement of GSH, GR, GST, SOD, and Catalase. Histopathological studies from DMH treated rats revealed disorganization of colonic histoarchitecture. However, zinc treatment to DMH treated rats greatly restored normalcy in the colonic histoarchitecture, with no apparent signs of abnormality. Energy Dispersive X-Ray Fluorescence (EDXRF) studies revealed a significant decrease in tissue concentrations of zinc in the colon following DMH treatment, which upon zinc supplementation were recovered to near normal levels. In conclusion, the results of this study suggest that zinc has a beneficial effect during the initiation of key events leading to the development of experimentally induced carcinogenesis.