A86 CANNABIS USE IN PATIENTS WITH INFLAMMATORY BOWEL DISEASE IS HIGHER FOLLOWING LEGALIZATION OF CANNABIS IN CANADA AND IS ASSOCIATED WITH LOWER QUALITY OF LIFE

Background

Patients with inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), often experience fluctuating and unpredictable symptoms. Most individuals require chronic therapy with immunomodulators or novel biologics to maintain disease remission. In addition to conventional medical therapy, many patients also seek out alternative therapies such as cannabis. Reports in the USA suggest that cannabis is used by ~12% of UC and ~16% of CD patients, despite it being legally prohibited.

Purpose

The aim of our study is to evaluate the use of cannabis in a cohort of patients with IBD following its legalization in Canada, and to assess its effects on IBD disease severity.

Method

We conducted a prospective cohort study of adult IBD patients seen in clinic at a tertiary care center in London, ON. Patients completed an online 40-question survey that collected data on demographics, IBD disease history, cannabis use, and included the Short Inflammatory Bowel Disease Questionnaire (SIBDQ). The survey was distributed and collected by the REDCap platform maintained by Western University. The study was approved by the Western University Ethics Committee.

Result(s)

Completed surveys were obtained from 254 individuals (148 individuals with CD, 90 with UC and 16 with indeterminate colitis). Over half of participants were between 35-64 years of age and female. Fifty-three percent of participants reported life-time cannabis use and 51% of users started using cannabis only in the preceding 3 years. Individuals with CD had higher rates of recent use, defined as use within the past 6 months, when compared with UC (41% vs 31%). Cannabis was taken multiple times per week by 57% of users. Cannabis was used to treat GI symptoms by 30% of users, as well as to help with sleep (26%) and for recreation (27%). Despite side effects such as dry mouth, anxiety and concentration issues, 79% of users felt the benefits of cannabis outweighed its harms. Interestingly, only 46% of cannabis users discussed their use with their family physician or gastroenterologist. Recent cannabis users did not differ in the use of IBD medication or self-reported rates of GI symptoms. Furthermore, recent users did not differ in the rates of surgical procedures for IBD (recent 35% vs non-recent 32%). Recent cannabis users did have a significantly lower quality of life as indicated by SIBDQ scores when compared to non-recent users (recent use 37 vs non-recent use 40).

Conclusion(s)

Cannabis use among patients with IBD after its legalization is more than double the rate previously reported in the literature. Importantly, physicians are likely to be unaware of its prevalence in their practice. Cannabis was used by patients to treat GI and non-GI symptoms, and it was associated with lower SIBDQ scores. Our results suggest that physicians should inquire about Cannabis use amongst their patients with IBD, and that further studies are required to determine its effects on disease severity.

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CIHR

Disclosure of Interest

None Declared

A222 EFFECT OF CLINICAL FACTORS ON IBD TREATMENT RESPONSE: FINDINGS FROM A NOVEL SINGLE CENTER PATIENT REGISTRY

Background

Inflammatory bowel disease (IBD), comprising both Crohn’s disease as well as ulcerative colitis, has shown heterogenous response to therapy. Over the past decades, targeted biologic therapies have become the mainstay of treatment. Even with the rapid pace of progress in this field, roughly a third of patients do not show an initial response to these treatments. The ability to accurately predict treatment response to therapy would both improve patient safety and satisfaction as well as decrease costs from ineffective therapies.

Purpose

The primary aim of this project is to identify clinical factors predictive of disease response to induction biologic therapy in inflammatory bowel disease through the creation of a novel single center patient registry.

Method

Initially, a single center tissue biopsy registry of IBD patients receiving colonoscopy was created. Retrospective clinical data was subsequently collected on patients identified to have initiated or changed biologic therapy after entry into the registry. Clinical data regarding age, sex, comorbidities, lifestyle factors, time since initial diagnosis, extra intestinal manifestations, serum markers, prior IBD treatments, planned treatment, clinical response, as well as endoscopic response were collected. A Pilot study of the first 30 patients identified was undertaken. Individual clinical factors were compared between patients with a documented clinical response to biologic therapy and non-responders at the group level as well as by biologic therapy initiated.

Result(s)

No statistically significant differences in collected clinical data parameters were observed between treatment responders and non responders in aggregate as well as when sub selected by individual biologic therapy initiated, bio-naive status, and steroid dependence.

Conclusion(s)

This project has demonstrated that clinical factors alone do not adequately predict disease response in inflammatory bowel disease. Future work will expand this data registry to further clinical factors and continue patient enrolment. Next steps also include the addition of tissue level data, in particular tissue level RNA data. It is hoped that these parameters, either individually or in combination, will provide a robust and accessible predictor of response to biologic therapy in inflammatory bowel disease.

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Other

Please indicate your source of funding below:

Western University Department of Medicine

Disclosure of Interest

None Declared

A27 DNA HYPOMETHYLATION INDUCED BY 5-AZA-CDR OR LOSS OF DNMT1 INHIBITS COLITIS-ASSOCIATED COLORECTAL CANCER

Background

Colorectal cancer is the second leading cause of cancer death in Canada. A major risk factor for the development of colorectal cancer is chronic inflammation leading to colitis-associated cancer (CAC). We previously described a CAC mouse model in which tumors arise from DCLK1+ tuft cells following loss of the tumor suppressor adenomatous polyposis coli (APC) and induction of colitis. Interestingly, both colitis and CAC display epigenetic changes that modulate gene expression. However, the impact of DNA methylation changes on colonic tumorigenesis is not known. Thus, we hypothesize that inhibition of DNA methylation in DCLK1+ tuft cells reduces colonic tumorigenesis.

Purpose

In this study, we aim to investigate the role of DNA methylation in CAC by inhibiting DNA methylation using genetic and pharmacologic means.

Method

Using a publicly available dataset (GSE75214) of gene expression data analyzed by microarray from colonic biopsies of patients with ulcerative colitis and Crohn’s Disease with active disease, we examined the expression of DNA methyltransferases (DNMTs). Expression of DNMTs in mice with colitis was additionally examined by RT-qPCR and global DNA methylation levels measured by 5-mC ELISA. In separate experiments, Dclk1-CreERT2/Apc^f/f mice were crossed to DNMT1^f/f mice to knock-out the DNA methyltransferase DNMT1 in DCLK1+ tuft cells. Dclk1/Apc^f/f and Dclk1/Apc^f/f/DNMT1^f/f mice were then administered three doses of tamoxifen followed by 2.5% dextran sodium sulfate (DSS) for five days to induce colitis. Fourteen weeks later, we assessed colonic tumor number and size. In a separate cohort of Dclk1/Apc^f/f mice, we induced colitis and treated the mice with six doses of the DNA de-methylating drug 5-AZA-2’-deoxycytidine (5-AZA) or vehicle, and assessed colonic tumor number. To examine DNA methylation changes, we then treated WT mice with 5-AZA and DSS and isolated intestinal epithelial cells. From the intestinal epithelial cell, we isolated DNA and ran the Infinium MouseMethylation BeadChip Array.

Result(s)

Patients with IBD were found to have increased expression of DNMT1 compared to healthy controls. Mice treated with DSS similarly had increased DNMT1 expression, as well as, global methylation levels compared to controls. Deletion of DNMT1 in DCLK1+ cells significantly inhibited the number and size of colonic tumors. Treatment of mice with 5-AZA decreased global and gene specific DNA methylation levels, and significantly reduced both the number of mice with tumors, and the average colonic tumor number and size per mouse.

Conclusion(s)

Our findings demonstrate that colitis in both patients and mice is associated with DNA methylation. Furthermore, DNA hypomethylation by 5-AZA treatment or loss of DNMT1 reduces CAC formation suggesting that altered DNA methylation plays a critical role in colonic tumorigenesis.

Disclosure of Interest

None Declared

A35 DNA HYPOMETHYLATION INHIBITS TUFT CELL-DERIVED COLITIS-ASSOCIATED CANCER

Background

Colorectal cancer is the second leading cause of cancer death in Canada. A major risk factor for the development of colorectal cancer is chronic inflammation leading to colitis-associated cancer (CAC). We previously described a CAC mouse mode in which tumors arise from DCLK1+ tuft cells following loss of the tumor suppressor adenomatous polyposis coli (APC) and induction of colitis. Interestingly, both colitis and CAC display epigenetic changes that modulate gene expression. Specifically, DNA methylation is altered in colitis, but its role in colonic tumorigenesis is not known. We hypothesize that inhibition of DNA methylation in DCLK1+ tuft cells reduces colonic tumorigenesis.

Aims

In this study, we aim to investigate the role of DNA methylation in CAC by inhibiting DNA methylation by genetic and pharmacologic means.

Methods

We crossed our Dclk1-CreERT2/Apc^f/f mice to DNMT1^f/f mice to delete the DNA methyltransferase DNMT1 in DCLK1+ tuft cells. We induced CAC in Dclk1/Apc^f/f and Dclk1/Apc^f/f/DNMT1^f/f mice by administering three doses of tamoxifen followed by 2.5% dextran sodium sulfate (DSS) for five days. Fourteen weeks later we assessed colonic tumor number and size. Lineage tracing of Dclk1+ cells was also examined in colonic tissues from all mice. In a separate cohort of Dclk1/Apc^f/f mice, we induced colitis and treated the mice with six doses of the DNA de-methylating drug 5-AZA-2’-deoxycytidine (5-AZA) or vehicle. Ki67 immunostaining was additionally performed to assess cellular proliferation in the colon.

Results

Deletion of DNMT1 in DCLK1+ cells significantly inhibited the number and size of colonic tumors. Treatment of mice with 5-AZA similarly reduced the overall number of mice with tumors, as well as, the number and size of tumors per mouse. Interestingly, 5-AZA treatment was associated with reduced colonic proliferation as assessed by fewer Ki67+ cells, and quiescent DCLK1+ cells that did not lineage trace. Furthermore, deletion of DNMT1 or treatment with 5-AZA reduced the number of lineage tracing events detected upon exposure to low DSS.

Conclusions

Our findings demonstrate that loss of Dnmt1 or 5-AZA treatment reduces CAC formation. Furthermore, 5-AZA appears to exert its anti-tumor effects by reducing proliferation and preventing tuft cell stemness. Our data demonstrates that altering DNA methylation plays an important role in CAC.

Funding Agencies

CIHR

A166 CANNABIS USE IN CANADIAN INDIVIDUALS WITH INFLAMMATORY BOWEL DISEASE FOLLOWING LEGALIZATION OF CANNABIS

Background

Inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), are characterized by remitting and relapsing symptoms of abdominal pain, diarrhea, nausea, fatigue, and poor sleep. Most patients with IBD require chronic immunosuppressive therapy to maintain their disease in remission. Due to their disease chronicity, individuals often seek additional complementary or alternative medicines such as cannabis to treat their symptoms. Reports from the US show cannabis use in 12% of UC and 16% of CD patients. However, these numbers are likely underestimates given that cannabis remains illegal in many states.

Aims

The aim of our study is to evaluate the use of cannabis in a cohort of patients with IBD and to assess its association with IBD disease severity.

Methods

We conducted a prospective cohort survey of adult patients with IBD seen in tertiary care in London Health Sciences Centre. A 40-question online survey was completed by consenting patients and collected data on demographics, IBD disease history, cannabis use, and included the Short Inflammatory Bowel Disease Questionnaire (SIBDQ) as a measure of disease severity. The study was approved by the Western University Ethics Committee. Statistical analyses was performed using a Chi squared test for categorical data, and a two-tailed t-test for continuous data.

Results

Completed surveys were obtained from 210 individuals (135 individuals with CD and 75 with UC) and demographics were similar between the CD and UC cohort. Fifty-six percent of participants reported cannabis use at least once in their lifetime, with 38% of participants reporting cannabis use in the preceding 6 months. Interestingly, 46 percent of life-time cannabis users did not divulge their cannabis use to their physicians. In patients with UC, those who actively used cannabis were less likely to be on 5-ASA therapy (9 active users vs 22 non-users, p<0.05). Medical therapy was otherwise similar between cannabis users and non-users. Surgical rates were similar between cannabis users and non-users amongst both IBD subtypes. With respect to the burden of disease, patients with CD reported higher rates of abdominal pain if they were active users, however, overall SIBDQ scores were not altered by cannabis use (21 user vs 20 non-user). Similarly, SIBDQ scores were similar amongst patients with UC who were cannabis users and non-users (20 user vs 16 non-user).

Conclusions

Cannabis use in patients with IBD is very common and much higher than previously reported prior to the legalization in Canada, but its use is not associated with lower disease severity based on patient reported outcomes. Our study also reveals that patients often do not report this use to their doctors so physicians must be aware of its prevalence amongst their IBD patient population.

Funding Agencies

None

A1 F4/80+LY6CHI MACROPHAGES ARE KEY TO CANCER INITIATION IN COLITIS

Background

Colorectal cancer (CRC) is the third leading cause of cancer death, with a major risk factor being chronic inflammation. Thus, patients with inflammatory bowel disease (IBD) are at an increased risk of CRC. Despite the clear association between inflammation and cancer, the mechanism by which colitis leads to CRC is still not well understood.

Aims

In this study, we aim to explore the mechanism by which inflammation contributes to the initiation of colitis-associated cancer (CAC). We hypothesize that dextran sodium sulfate (DSS)-induced colitis leads to the infiltration of a specific immune cell type associated with tumorigenesis.

Methods

Following an injection of azoxymethane (AOM), mice were treated with the colitis-inducing agents DSS, trinitrobenzene sulfonic acid (TNBS), oxazolone (oxa), Citrobacter rodentium, or Doxorubicin (Doxo). The tumor studies were repeated using our published Cre-dependent murine model of CAC. To generate tamoxifen-inducible Cre transgenic mice that allow for Dclk1+ cell lineage tracing and cell-specific knock-out of the tumor suppressor adenomatous polyposis coli (APC), we crossed our Dclk1CreERT2 mice to both ROSA26tdTomato and APCfl/fl mice (Dclk1/APCfl/fl).

Results

Treatment with DSS, TNBS, oxa, C. rodentium, or Doxo induced colonic inflammation as detected by increased myeloperoxidase (MPO) activity and histologic analysis. DSS administration led to colonic tumors, whereas TNBS, oxa, C. rodentium, or Doxo did not lead to tumorigenesis up to 52 weeks following colitis induction. Upon flow cytometric analysis of several types of immune cells in the colonic tissue, we observed no difference in the number of T and B cells between mice treated with various colitis inducing agents. We did, however, detect significantly increased levels of Ly6G+ neutrophils and F4/80+Ly6Chi macrophages in the DSS-treated mice when compared to mice in the other models of colitis. mRNA and protein array analyses of the colonic tissue, as well as analysis of the RNA-seq data from 206 UC patients (GSE109142), revealed upregulated expression of genes associated with macrophages and neutrophils. Addition of macrophage-produced cytokines, such as IL-1β, TNF-α, or IL-6, induced lineage tracing of Dclk1+ tuft cells in intestinal organoids. Clodronate liposome-mediated depletion of F4/80+Ly6Chi macrophages significantly reduced the number of colonic tumors but did not affect tumor size in Dclk1/APCfl/fl mice.

Conclusions

Our data suggest that infiltration of F4/80+Ly6Chi macrophages, unique to DSS-induced colitis, leads to colonic tumor formation. This demonstrates that specific immune cell types, rather than the presence of colonic inflammation, plays an important role in the initiation of CAC.

Funding Agencies

CAG, CIHR

A29 HOPX LABELS A COLONIC STEM CELL THAT CONTRIBUTES TO COLONIC REGENERATION BUT NOT COLONIC TUMORS

Background

Colorectal cancer is the 2nd leading cause of cancer death in Canada. In rapidly dividing tissues such as the intestine or colon, only long-lived, multipotent, self-renewing tissue stem cells have longevity to accumulate mutations and serve as the cellular origin of cancer. In the small intestine, genetic fate mapping studies have demonstrated that there are at least two principal stem cell pools: actively cycling, crypt base cells expressing Lgr5, and quiescent cells situated above the crypt base. Clevers and colleagues have previously shown that Lgr5-expressing cells can give rise to cancer upon mutation. Interestingly, when Lgr5+ stem cells are selectively “killed”, intestinal integrity remains intact and other stem cells restore homeostasis. To determine whether another stem cell population can give rise to cancer in the colon, we examined whether the atypical homeobox protein Hopx, marks stem cells in the colon and whether these cells can give rise to colon cancer.

Aims

In the present study, we aim to determine whether Hopx-expressing cells are colonic stem cells that contribute to gut healing and can give rise to colonic tumours following the loss of APC.

Methods

To determine whether Hopx expressing cells show stemness, we crossed Hopx-CreERT mice to R26-TdTomato reporter mice. We then conducted genetic lineage tracing studies in the colon during homeostasis and following dextran sodium sulphate (DSS)-induced colitis. To test the function of Hopx expressing cells, Hopx-CreERT mice were also crossed to R26DTR mice and treated with diphtheria toxin (DT) following tamoxifen. These mice were then exposed to either normal drinking water or DSS to determine the role of Hopx+ cells in colonic regeneration. To test whether Hopx expressing cells can serve as a cellular origin for colon cancer, Hopx-CreERT mice were crossed to Apcf/f (floxed) mice.

Results

Consistent with the labeling of a stem cell, following tamoxifen, Hopx+ cells expressing tdTomato expanded to lineage trace full colonic crypts within 7 days, and labelling was persistent for greater than 6 months. Interestingly, ablation of Hopx+ cells with DT did not alter weight, histological damage or survival during normal homeostasis, however, Hopx+ cell ablation in mice treated with DSS resulted in increased histological damage. Surprisingly, loss of APC in Hopx-expressing cells did not induce colonic adenomas even after 8 months following tamoxifen administration.

Conclusions

These findings prove that Hopx expressing cells identify a novel colonic stem cell pool that is redundant in homeostasis, but in the context of injury, are essential for epithelial regeneration. Interestingly, Hopx+ cells do not have the capacity to give rise to colorectal adenomas upon loss of the APC gene.

Funding Agencies

CIHR

A30 INHIBITION OF NF-KB SIGNALING IN DCLK1+ CELLS PROMOTES COLONIC INFLAMMATION AND COLITIS-ASSOCIATED CANCER

Background

Colorectal cancer (CRC) is the 2nd leading cause of cancer death in Canada. A major risk factor for this disease is chronic inflammation. Despite the clear link between inflammation and cancer, the exact mechanism by which colitis leads to cancer is unknown. Our group has previously shown that a rare cell type in the gut marked by the expression of doublecortin-like kinase-1 (Dclk1) and known as a tuft cell, is quiescent, long-lived, and resistant to proliferation even upon mutation of the tumor suppressor APC. Interestingly, in the setting of colitis, these APC-mutated tuft cells become powerful cancer-initiating cells, but the mechanism by which this occurs is not known. NF-kB signaling is a major inflammatory pathway active in colitis and that has been linked to colorectal cancer. Inhibition of the NF-kB pathway in intestinal epithelial cells has also been shown to inhibit tumor initiation in a mouse model of colitis-associated cancer (Greten et al., 2004).

Aims

In the present study, we aim to examine the effect of NF-kB inhibition in tuft cells on colitis-associated cancer.

Methods

Dclk1CreERT2/APCf/f mice were crossed to IKK-β f/f mice and administered tamoxifen to conditionally knockout the function of both APC and IKK-β in tuft cells. Mice were then exposed to the colitis-inducing agent dextran sodium sulfate (DSS) to induce tumorigenesis. Approximately 16 weeks post-tamoxifen, colonic tumor number and size were analyzed to determine the effect of NF-kB pathway inhibition on tumor initiation and growth, respectively. Extent of inflammation was assessed by myeloperoxidase (MPO) activity and histological damage, and colonic tissue was collected for measurement of inflammatory mediators by qRT-PCR at both acute and long-term time points.

Results

Interestingly, at baseline we detected increased MPO activity in Dclk1CreERT2/APCf/f/IKK-β f/f mice compared to control mice, suggesting that inhibition of NF-kB in Dclk1+ cells may increase basal colonic inflammation. Consistent with this observation, inhibition of the NF-kB pathway also resulted in an increased number of tuft cell-derived tumors, with no observed change in tumor size. Acutely, we also observed an exacerbation of DSS-colitis in Dclk1CreERT2/APCf/f/IKK-β f/f mice, as detected by elevated MPO activity, increased histological damage, and reduced colon length compared to wildtype (IKK-β +/+) controls.

Conclusions

These data suggest that Dclk1+ cell-specific NF-kB signaling plays a key protective role against colitis and colitis-associated tumorigenesis. Targeting the NF-kB pathway may reduce the severity of colitis and the incidence of colitis-associated cancer.

Funding Agencies

CIHR

A16 ROLE OF MYELOID CELLS IN THE INITIATION OF COLITIS-ASSOCIATED COLON CANCER

Background

Colorectal cancer (CRC) is the second leading cause of cancer death, with a major risk factor being chronic inflammation. Despite the clear association between inflammation and cancer, the mechanism by which colitis leads to CRC is not well understood. We recently showed that the presence of inflammation does not always correlate with colonic tumorigenesis, as the type of colitis (i.e. colitis-inducing agent) appears to be important for tumor initiation.

Aims

In this study, we aim to explore the mechanism by which inflammation contributes to the initiation of colitis-associated cancer. We hypothesized that dextran sodium sulfate (DSS)-induced colitis leads to the infiltration of a specific immune cell type that is associated with colonic tumorigenesis.

Methods

To generate tamoxifen-inducible Cre transgenic mice that allow for Dclk1+ cell lineage tracing and cell-specific knock-out of the tumor suppressor adenomatous polyposis coli (APC), we first crossed our transgenic Dclk1CreERT2 mice to both ROSA26tdTomato and APCfl/fl mice (Dclk1/APCfl/fl). Following Tamoxifen induction, mice were treated with the colitis-inducing agents DSS, trinitrobenzene sulfonic acid (TNBS), oxazolone, or Citrobacter rodentium. The tumor studies were repeated using azoxymethane (AOM)-DSS induced colitis-associated cancer model.

Results

Treatment with any of the four colitis-inducing agents (DSS, TNBS, oxazolone, or C. rodentium) induced colonic inflammation as detected by increased myeloperoxidase (MPO) activity and histologic analysis. Interestingly, DSS administration led to colonic tumors, whereas TNBS, oxazolone, or C. rodentium did not, even up to 52 weeks following colitis induction. FACS analysis of immune cells in the colon revealed no difference in the number of T or B cells in mice treated with any of the colitis-inducing agents. We did, however, detect significantly increased levels of Ly6G+ neutrophils and F4/80+ macrophages in DSS-treated mice compared to mice in any of the other three models of colitis. Consistent with this myeloid cell infiltration, significantly upregulated protein levels of G-CSF, IL-6, TNF-α, and CXCL1 were detected in DSS-treated mice compared to the other three models of colitis. IL-1α, IL-1β, IL-4, IL-10, and TGF-β levels were unchanged.

Conclusions

Our data suggest that infiltration of Ly6G+ neutrophils and pro-inflammatory F4/80+ macrophages, unique to DSS-induced colitis, contributes to colonic tumor formation. These data demonstrate that specific immune cell types, rather than the presence of colonic inflammation, play a critical role in the initiation of colitis-associated CRC.

Funding Agencies

CAG, CIHR

Protease-activated receptor-4: a novel mechanism of inflammatory pain modulation

BACKGROUND AND PURPOSE

Protease-activated receptor-4 (PAR(4)), the most recently discovered member of the PARs family, is activated by thrombin, trypsin and cathepsin G, but can also be selectively activated by small synthetic peptides (PAR(4)-activating peptide, PAR(4)-AP). PAR(4) is considered a potent mediator of platelet activation and inflammation. As both PAR(1) and PAR(2) have been implicated in the modulation of nociceptive mechanisms, we investigated the expression of PAR(4) in sensory neurons and the effects of its selective activation on nociception.

EXPERIMENTAL APPROACH AND KEY RESULTS

We demonstrated the expression of PAR(4) in sensory neurons isolated from rat dorsal root ganglia by reverse transcription-polymerase chain reaction and immunofluorescence. We found that PAR(4) colocalized with calcitonin gene-related peptide and substance P. We also showed that a selective PAR(4)-AP was able to inhibit calcium mobilization evoked by KCl and capsaicin in rat sensory neurons. Moreover, the intraplantar injection of a PAR(4)-AP significantly increased nociceptive threshold in response to thermal and mechanical noxious stimuli, while a PAR(4) inactive control peptide had no effect. The anti-nociceptive effects of the PAR(4)-AP were dose-dependent and occurred at doses below the threshold needed to cause inflammation. Finally, co-injection of the PAR(4)-AP with carrageenan significantly reduced the carrageenan-induced inflammatory hyperalgesia and allodynia, but had no effect on inflammatory parameters such as oedema and granulocyte infiltration.

CONCLUSIONS AND IMPLICATIONS

Taken together, these results identified PAR(4) as a novel potential endogenous analgesic factor, which can modulate nociceptive responses in normal and inflammatory conditions.

Persistent epithelial dysfunction and bacterial translocation after resolution of intestinal inflammation

Epithelial secretion may play an important role in reducing bacterial colonization and translocation in intestine. If so, secretory dysfunction could result in increased susceptibility to infection and inflammation. We investigated whether long-term colonic secretory dysfunction occurs after a bout of colitis and if this is accompanied by an increase in bacterial colonization and translocation. Rats were studied 6 wk after induction of colitis with trinitrobenzene sulfonic acid when inflammation had completely resolved, and epithelial permeability was normal. Intestinal loops were stimulated with either Clostridium difficile toxin A or a phosphodiesterase inhibitor. In vitro, colonic tissue from previously sensitized rats was exposed to antigen (ovalbumin). Secretory responses to all three stimuli were suppressed in rats that had previously had colitis. These rats exhibited increased (16-fold) numbers of colonic aerobic bacteria and increased (>3-fold) bacterial translocation, similar to results in rats studied after resolution of enteritis. Postcolitis bacterial translocation was prevented by daily treatment with an inhibitor of inducible nitric oxide synthase. This study demonstrates that intestinal inflammation results in prolonged impairment of colonic epithelial secretion, which may contribute to increases in bacterial load and bacterial translocation. Epithelial dysfunction of this type could underlie an increased propensity for further bouts of inflammation, a hallmark of diseases such as inflammatory bowel disease.

Enhanced anti-inflammatory effects of a nitric oxide-releasing derivative of mesalamine in rats

BACKGROUND & AIMS

Nitric oxide (NO)-releasing derivatives of cyclooxygenase inhibitors exhibit enhanced anti-inflammatory activity and greatly reduced gastrointestinal toxicity. We evaluated whether a similar derivatization of mesalamine (5-aminosalicylic acid) would improve its anti-inflammatory activity.

METHODS

Effects of an NO-releasing derivative of mesalamine (NCX-456; NO-mesalamine) were compared with those of mesalamine itself and 2 other NO donors in a rat model of colitis. These drugs were compared for their ability to inhibit leukocyte adherence to the vascular endothelium in vivo, interleukin (IL)-1beta and interferon (IFN)-gamma release in vitro (splenocytes and colon), and messenger RNA expression in the inflamed colon.

RESULTS

NO-mesalamine was significantly more effective than mesalamine in reducing the severity of colitis (damage and granulocyte infiltration). Unlike mesalamine, NO-mesalamine significantly suppressed leukocyte adherence to the vascular endothelium in vivo. NO-mesalamine inhibited IL-1beta and IFN-gamma release and caspase 1 activity in splenocytes; such effects were not found in the inflamed colon.

CONCLUSIONS

These studies show that an NO-releasing derivative of mesalamine has significantly enhanced anti-inflammatory activity, including improved efficacy in a rat model of colitis. The improved efficacy of this derivative is most likely caused by its enhanced ability to suppress leukocyte infiltration and possibly to scavenge peroxynitrite.

Prolonged colonic epithelial hyporesponsiveness after colitis: role of inducible nitric oxide synthase

Colonic epithelial secretion is an important host defense mechanism. We examined whether a bout of colitis would produce long-lasting changes in epithelial function that persisted after resolution of mucosal inflammation. Colitis was induced in rats with intracolonic trinitrobenzenesulfonic acid. Six weeks later, colonic damage and inducible nitric oxide synthase (iNOS) mRNA expression and activity were measured. Segments of distal colon were mounted in Ussing chambers for measurement of permeability and responsiveness to secretory stimuli. Basal electrolyte transport parameters and permeability were not different from untreated controls. Despite normal macroscopic and histological appearance, secretory responses to electrical field stimulation (EFS), isobutylmethylxanthine (IBMX), and carbachol were significantly depressed (by 60-70%) relative to controls. iNOS mRNA expression and enzyme activity were significantly elevated. Dexamethasone reversed epithelial hyporesponsiveness and significantly reduced iNOS mRNA expression. A selective iNOS inhibitor normalized the secretory responses to EFS and IBMX but not to carbachol. These data suggest that ongoing synthesis of nitric oxide by iNOS contributes to chronic suppression of epithelial secretory function after episodes of colitis.

Cyclooxygenase 1 contributes to inflammatory responses in rats and mice: implications for gastrointestinal toxicity

BACKGROUND & AIMS

Selective inhibitors of cyclooxygenase (COX)-2 are being developed as gastrointestinal-sparing anti-inflammatory drugs based on the premise that this isoform is solely responsible for prostaglandin synthesis at sites of inflammation, whereas COX-1 produces prostaglandins important for maintenance of mucosal integrity. We investigated the relationship between suppression of inflammation by COX-2 inhibitors (NS-398, nimesulide, DuP697, and etodolac) and their effects on gastric prostaglandin synthesis.

METHODS

Effects of pretreatment of rats with drugs with a range of in vitro selectivity for COX-2 vs. COX-1 on carrageenan-induced paw inflammation were assessed, along with extent of suppression of COX-1 and COX-2. The role of COX-1 in inflammation was also assessed in COX-2-deficient mice.

RESULTS

Significant anti-inflammatory effects were only observed at doses of the drugs that inhibited COX-1. At these doses, the drugs also significantly suppressed gastric prostaglandin synthesis and elicited gastric mucosal erosions. The degree of suppression of prostaglandin synthesis at the site of inflammation correlated significantly with inhibition of COX-1 but not COX-2.

CONCLUSIONS

COX-1 makes an important contribution to inflammatory responses. To achieve desirable anti-inflammatory effects, COX-2 inhibitors needed to be given at doses in which selectivity was lost, leading to suppression of gastric prostaglandin synthesis and to mucosal injury.

Reduction of acute and reactivated colitis in rats by an inhibitor of neutrophil activation

Neutrophils have been implicated as major contributors to tissue injury in inflammatory bowel disease. In this study, we have assessed the effects of an inhibitor of neutrophil activation and adherence, NPC-18915 (4-¿2-[2-(2-benzofuranyl)phenyl]-(E)-ethenyl¿benzoic acid sodium salt), in models of both acute and reactivated colitis. Acute colitis was induced by intracolonic administration of a hapten. In other rats, colitis was reactivated 6 wk after a bout of acute colitis by subcutaneous administration of the hapten. NPC-18915 given during the first 4 days after induction of acute colitis significantly reduced tissue injury and the incidence of diarrhea and adhesions. When treatment of NPC-18915 was initiated after colitis was firmly established (48 h posthapten), it did not produce a significant effect. NPC-18915 was effective at significantly reducing colonic injury and granulocyte infiltration in the reactivated colitis model, and a similar effect could be observed in rats treated with antineutrophil serum. These results demonstrate that an inhibitor of neutrophil activation is effective in both acute and reactivated colitis, although in the former case, effectiveness is only seen when the drug is given before full establishment of colitis. These results also suggest that neutrophils, are a critical effector cell of hapten-induced colitis in the rat, particularly in the case of reactivated colitis.

Aspirin causes rapid up-regulation of cyclo-oxygenase-2 expression in the stomach of rats

BACKGROUND

Cyclo-oxygenase-1 (COX-1) is believed to produce prostaglandins vital to mucosal defence, whereas cyclo-oxygenase-2 (COX-2) is induced at sites of inflammation. Little is known about the regulation of COX-2 in the stomach, particularly during the period following mucosal injury. In this study, we examined COX-1 and COX-2 expression shortly after administration of NSAIDs or ethanol.

METHODS

Fasted rats were given aspirin, salicylate, indomethacin or ethanol (20% or 40%) orally. Three hours later the stomach was excised, the severity of damage scored and samples taken for RT-PCR of COX-1 and COX-2 mRNA and immunohistochemistry. Nitric oxide synthase mRNA (iNOS and eNOS) and activity were also measured.

RESULTS

Aspirin, indomethacin and the higher concentration of ethanol produced widespread mucosal damage, whereas salicylate and 20% ethanol caused only superficial epithelial damage. Aspirin caused a significant increase in COX-2 mRNA expression and a marked increase in COX-2 immunoreactivity, particularly in the superficial mucosa. Expression of COX-1 (mRNA and protein) was unaffected by aspirin, as were NOS mRNA expression and enzyme activity. Pre-treatment with prostaglandin E2 prevented the induction of COX-2 by aspirin. Salicylate and indomethacin caused modest increases in COX-2 immunoreactivity but no change in COX-2 mRNA. Neither concentration of ethanol affected COX-2 mRNA or protein expression, suggesting that this was a specific response to the aspirin, rather than to injury.

CONCLUSIONS

These results demonstrate a rapid up-regulation of COX-2 expression in response to aspirin, possibly representing a compensatory response to inhibition of gastric prostaglandin synthesis.

Induction of cyclooxygenase 1 and 2 in the rat stomach during endotoxemia: role in resistance to damage

BACKGROUND & AIMS

Prostaglandins and nitric oxide are key mediators of gastric mucosal defense. Endotoxemia alters gastric resistance to damage, but little is known of the effects of chronic endotoxemia on the expression of prostaglandin and nitric oxide synthases (NOSs). The effects of short- vs. long-term administration of endotoxin on gastric resistance to damage and on expression of NOS and prostaglandin synthesis were compared.

METHODS

Rats were treated with short- or long-term bacterial endotoxin, after which susceptibility to ethanol-induced damage was assessed. The effects of various inhibitors of prostaglandin and NOS were examined. Expression of gastric NOS and cyclooxygenase (COX) messenger RNA (mRNA) were examined.

RESULTS

Repeated administration of endotoxin increased gastric resistance to ethanol- but not indomethacin-induced injury. Indomethacin, but not a highly selective COX-2 inhibitor or an inducible NOS inhibitor, abolished long-term endotoxin-induced gastric resistance to injury. Expression of mRNA for both COX-1 and -2, but not for endothelial or inducible NOS, were significantly increased after long-term endotoxin administration.

CONCLUSIONS

Repeated exposure to endotoxin resulted in increased resistance of the gastric mucosa to injury through a prostaglandin-dependent pathway. These prostaglandins were produced via COX-1, which like COX-2, is induced by endotoxin administration.

Exacerbation of inflammation-associated colonic injury in rat through inhibition of cyclooxygenase-2

Cyclooxygenase type 1 is constitutively expressed and accounts for synthesis of prostaglandins in the normal gastrointestinal tract. Cyclooxygenase-2 is expressed at sites of inflammation. Selective inhibitors of cyclooxygenase-2 have been suggested to spare gastrointestinal prostaglandin synthesis, and therefore lack the ulcerogenic effects associated with standard nonsteroidal antiinflammatory drugs. However, the effects of cyclooxygenase-2 inhibitors on inflamed gastrointestinal mucosa have not been examined. We examined cyclooxygenase-2 mRNA and protein expression before and after induction of colitis in the rat, the contribution of cyclooxygenase-2 to colonic prostaglandin synthesis during colitis and the effects of selective inhibitors of cyclooxygenase-2 on colonic injury in this model. Cyclooxygenase-2 mRNA expression increased three to sixfold during the period 24 h to 1 wk after induction of colitis, with marked increases in cyclooxygenase-2 protein expression in the lamina propria and muscularis of the colon during colitis. Cyclooxygenase-1 expression (mRNA and protein) was not affected by the induction of colitis. The prostaglandins produced during colitis were largely derived from cyclooxygenase-2. Treatment with selective cyclooxygenase-2 inhibitors resulted in exacerbation of colitis, with perforation occurring when the compounds were administered for a week. These studies demonstrate that suppression of cyclooxygenase-2 can result in exacerbation of inflammation-associated colonic injury.