Maria T. Abreu

TLR4 and MD-2 Expression Is Regulated by Immune-mediated Signals in Human Intestinal Epithelial Cells

The normal intestinal epithelium is not inflamed despite contact with a high density of commensal bacteria. Intestinal epithelial cells (IEC) express low levels of TLR4 and MD-2 and are lipopolysaccharide (LPS)-unresponsive. We hypothesized that immune-mediated signals regulate the expression of TLR4 and MD-2 in IEC. Expression of TLR4 and MD-2 was examined in normal colonic epithelial cells or intestinal epithelial cell lines. The effect of the cytokines interferon (IFN)-γ, IFN-α, and tumor necrosis factor-α (TNF-α) on TLR4 and MD-2 expression was examined by reverse transcription-PCR and Western blot. NF-κB transcriptional activation and interleukin-8 secretion were used as measures of LPS responsiveness. Native colonic epithelial cells and IEC lines express a low level of TLR4 and MD-2 mRNA. IFN-γ regulates MD-2 expression in both IEC lines, whereas IFN-γ and TNF-α regulate TLR4 mRNA expression in IEC lines. Pre-incubation with IFN-γ and/or TNF-α sensitizes IEC to LPS-dependent interleukin-8 secretion. To examine MD-2 transcriptional regulation, we cloned a 1-kb sequence proximal to the MD-2 gene translational start site. This promoter directed expression of a reporter gene in endothelial cells and IEC. IFN-γ positively regulated MD-2 promoter activity in IEC. Co-expression of a STAT inhibitor, SOCS3, blocked IFN-γ-mediated MD-2 promoter activation. T cell-derived cytokines lead to increased expression of TLR4 and MD-2 and LPS-dependent pro-inflammatory cytokine secretion in IEC. IFN-γ regulates expression of the critical TLR4 co-receptor MD-2 through the Janus tyrosine kinase-STAT pathway. Th1 cytokines may initiate or perpetuate intestinal inflammation by altering toll-like receptor expression and bacterial reactivity.

6-thioguanine can cause serious liver injury in inflammatory bowel disease patients

BACKGROUND & AIMS Thioguanine (6-TG) has been studied as an alternative thiopurine in inflammatory bowel disease (IBD). Short-term safety and efficacy data were favorable. Experience with 6-TG in patients with acute lymphoblastic leukemia raised long-term safety concerns when implicated in nodular regenerative hyperplasia (NRH) of the liver and portal hypertension. The aim of this study was to describe the association between 6-TG and NRH in IBD. METHODS Liver chemistries and complete blood counts were monitored, and patients were encouraged to undergo liver biopsy. Clinical data were collected by chart review, and associations were tested by univariate and multivariable analyses. Patients were classified based on the presence (group 1) or absence (group 2) of laboratory abnormalities. RESULTS Laboratory abnormalities occurred in 29 of 111 patients (26%). Elevations of liver enzymes and a decrease in platelet counts (<200,000) were most commonly observed. Male gender (odds ratio, 2.9; 95% CI, 1.1-7.3; P < 0.03) and preferential 6-methylmercaptopurine production on 6-mercaptopurine/azathioprine (odds ratio, 3.0; 95% CI, 1.2-7.4; P < 0.04) were independently associated with laboratory abnormalities. No association was seen with duration of 6-TG treatment, cumulative dose, or 6-TG nucleotide levels. The median increase in alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels was 39, 30, and 75 U/L, respectively, in group 1, and the median decrease in platelet count was 115,000 in group 1 versus 7000 in group 2 (P < 0.001). NRH occurred in 76% of patients undergoing biopsy in group 1 and 33% in group 2. CONCLUSIONS NRH is a common finding in 6-TG-treated patients with IBD. The progression or reversibility of NRH remains unknown. Our findings suggest that 6-TG should not be considered as therapy for patients with IBD.

Outcome of cytomegalovirus infections in patients with inflammatory bowel disease

OBJECTIVE: The aim of this study was to determine the outcome of cytomegalovirus (CMV) infections complicating the course of inflammatory bowel disease (IBD). METHODS: The records and clinical courses were reviewed for all IBD patients who were evaluated at the IBD Center of the Cedars-Sinai Medical Center and who developed CMV infection. RESULTS: Ten patients with severe, medically refractory IBD (five ulcerative colitis, three Crohn’s colitis, and two indeterminate colitis) developed CMV infection. All but two were hospitalized with exacerbation of their underlying disease and were receiving immunosuppressive treatment with steroids, thiopurines, and/or cyclosporine at the time CMV infection was recognized. Eight patients had documented colonic CMV (one had concurrent upper GI tract involvement), one developed interstitial CMV and Pneumocystis carinii pneumonia, and one developed primary CMV mononucleosis. Prompt treatment with ganciclovir and withdrawal of immunosuppressive treatment resulted in gradual improvement and induction of remission of the underlying IBD in five patients. The patient with concomitant CMV and P. carinii pneumonitis died. In two patients, treatment with ganciclovir did not alter the clinical course of their IBD, and one of them underwent colectomy. In one patient CMV was found on the resected colonic specimen. One patient with primary CMV infection responded also to ganciclovir treatment. CONCLUSIONS: CMV infection may aggravate the course of seemingly refractory IBD in patients who either fail to respond or experience worsening of symptoms despite immunosuppressive therapy. Expedient evaluation, prompt treatment intervention with ganciclovir, and withdrawal of immunosuppressive treatment may avoid complications and mortality. This regimen leads to improvement of the underlying IBD in most patients.

Measurement of vitamin D levels in inflammatory bowel disease patients reveals a subset of Crohn’s disease patients with elevated 1,25-dihydroxyvitamin D and low bone mineral density

Objectives: Many patients with Crohn’s disease (CD) have low bone mineral density (BMD) that may not be solely attributable to glucocorticoid use. We hypothesised that low BMD in patients with CD is associated with elevated circulating levels of the active form of vitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D). We further hypothesised that this was secondary to increased synthesis of 1,25(OH)2D by inflammatory cells in the intestine. The aim of this study was to examine the relationship between 1,25(OH)2D levels and BMD in patients with CD. Methods: An IRB approved retrospective review of medical records from patients with CD (n = 138) or ulcerative colitis (UC, n = 29). Measurements of vitamin D metabolites and immunoreactive parathyroid hormone (iPTH) were carried out. BMD results were available for 88 CD and 20 UC patients. Immunohistochemistry or real time reverse transcription-polymerase chain reaction (RT-PCR) for the enzyme 1α-hydroxylase was performed on colonic biopsies from patients with CD (14) or UC (12) and normal colons (4). Results: Inappropriately high levels of serum 1,25(OH)2D (>60 pg/ml) were observed in 42% of patients with CD compared with only 7% in UC, despite no differences in mean iPTH. Serum 1,25(OH)2D levels were higher in CD (57 pg/ml) versus UC (41 pg/ml) (p = 0.0001). In patients with CD, there was a negative correlation between 1,25(OH)2D levels and lumbar BMD (r = −0.301, p = 0.005) independent of therapeutic glucocorticoid use. 1,25(OH)2D levels also correlated with CD activity. Lastly, immunohistochemistry and RT-PCR demonstrated increased expression of intestinal 1α-hydroxylase in patients with CD. Conclusions: These data demonstrate that elevated 1,25(OH)2D is more common in CD than previously appreciated and is independently associated with low bone mineral density. The source of the active vitamin D may be the inflamed intestine. Treatment of the underlying inflammation may improve metabolic bone disease in this subgroup of patients.

An open-label pilot study using thioguanine as a therapeutic alternative in Crohn's disease patients resistant to 6-mercaptopurine therapy

Background and AimsA substantial number of patients with inflammatory bowel disease (IBD) fail to achieve a complete clinical response with 6-mercaptopurine (6-MP) and azathioprine (AZA). Inability to achieve therapeutic 6-thioguanine nucleotide (6-TGN) levels due to the preferential overproduction of 6-methylmercaptopurine ribonucleotides (6-MMPR) upon dose escalation characterizes a newly described subgroup of IBD patients resistant to 6-MP/AZA therapy. Treatment with 6-thioguanine (6-TG), a related thiopurine, which forms 6-TGNs more directly may be beneficial in such patients. This pilot study evaluated the safety, tolerance, and efficacy of 6-TG in the subgroup of Crohns disease (CD) patients failing to attain adequate disease control with traditional 6-MP/AZA therapy. MethodsTen CD patients with preferential 6-MMPR production upon 6-MP/AZA dose escalation were enrolled in an open-label pilot study. Seven of 10 patients had experienced dose-related 6-MP toxicities. ResultsSeventy percent of the patients (7 of 10) responded or were in remission at week 16. Clinical response was evident by week 4 in most. 6-TGN levels were nine-fold higher with 6-TG treatment than with 6-MP, whereas 6-MMPR levels were undetectable. No patient developed a recurrence of hepatic or hematological toxicity. Conclusions6-TG was a safer and more efficacious thiopurine in this subgroup of IBD patients resistant to 6-MP therapy. Larger controlled trials are warranted to further evaluate both the short-and long-term safety and efficacy in this subgroup of patients as well as a broader spectrum of IBD patients.

Thioguanine: a potential alternate thiopurine for IBD patients allergic to 6-mercaptopurine or azathioprine.

OBJECTIVE:Approximately 10% of inflammatory bowel disease (IBD) patients receiving 6-mercaptopurine (6-MP) or azathioprine (AZA) develop drug hypersensitivity reactions necessitating early discontinuation of these traditional thiopurines. These allergic reactions typically reoccur upon rechallenge. Our recently published pilot study suggested that thioguanine (6-TG), a closely related thiopurine, was efficacious and well tolerated in IBD patients resistant to 6-MP/AZA. The aim of this study was to determine if hypersensitivity reactions to 6-MP/AZA reoccur with 6-TG therapy.METHODS:IBD patients allergic to 6-MP and/or AZA were treated with 6-TG as an alternate thiopurine. Hypersensitivity reactions to 6-MP/AZA must have been documented within 6 wk of 6-MP/AZA initiation.RESULTS:6-TG was initiated in 21 IBD patients at a median (range) dose of 20 (10–40) mg/day. 6-TG hypersensitivity reaction occurred in only four of 21 (19%) patients after a median time interval of 9 days. Pancreatitis did not reoccur with 6-TG. Eighty-two percent of 6-TG tolerant patients were assessed as improved at last follow-up.CONCLUSIONS:These results suggest that 6-TG may be considered as a possible alternate thiopurine in patients allergic to traditional 6-MP/AZA. Despite these favorable results, candidates for 6-TG should be selected with caution, and its use should be reserved for IBD patients well informed about potential toxicities.

TLR signaling at the intestinal epithelial interface.

The intestinal epithelium provides a critical interface between lumenal bacteria and the mucosal immune system. Whereas normal commensal flora do not trigger acute inflammation, pathogenic bacteria trigger a potent inflammatory response. Our studies emanate from the hypothesis that the intestinal epithelium is normally hyporesponsive to commensal pathogen-associated molecular patterns (PAMPs) such as LPS. Our data demonstrate that normal human colonic epithelial cells and lamina propria cells express low levels of TLR4 and its co-receptor MD-2. This expression pattern is mirrored by intestinal epithelial cell (IEC) lines. Co-expression of TLR4 and MD-2 is necessary and sufficient for LPS responsiveness in IEC. Moreover, LPS sensing occurs along the basolateral membrane of polarized IEC in culture. Expression of MD-2 is regulated by IFN-gamma. Cloning of the MD-2 promoter demonstrates that promoter activity is increased by IFN-gamma and blocked by the STAT inhibitor SOCS3. We conclude from our studies that the intestinal epithelium down-regulates expression of TLR4 and MD-2 and is LPS unresponsive. The Th1 cytokine IFN-gamma up-regulates expression of MD-2 in a STAT-dependent fashion. The results of our studies have important implications for understanding human inflammatory bowel diseases.

Outcome measurement in clinical trials for Ulcerative Colitis: towards standardisation

Clinical trials on novel drug therapies require clear criteria for patient selection and agreed definitions of disease remission. This principle has been successfully applied in the field of rheumatology where agreed disease scoring systems have allowed multi-centre collaborations and facilitated audit across treatment centres. Unfortunately in ulcerative colitis this consensus is lacking. Thirteen scoring systems have been developed but none have been properly validated. Most trials choose different endpoints and activity indices, making comparison of results from different trials extremely difficult. International consensus on endoscopic, clinical and histological scoring systems is essential as these are the key components used to determine entry criteria and outcome measurements in clinical trials on ulcerative colitis. With multiple new therapies under development, there is a pressing need for consensus to be reached.

The spectrum of gastrointestinal toxicity and effect on disease activity of selective cyclooxygenase-2 inhibitors in patients with inflammatory bowel disease

The safety and toxicity associated with the use of selective cyclooxygenase-2 (COX-2) inhibitors in patients with inflammatory bowel disease (IBD) has not been extensively studied. Thirty-three patients with IBD who were prescribed celecoxib or rofecoxib were identified from questionnaire during their clinic visit at the Cedars-Sinai IBD Center between 1999 and 2002. Twenty-six had Crohns disease (CD), 6 had ulcerative colitis (UC), and 1 had indeterminate colitis (IC). Twenty-one received rofecoxib, 10 celecoxib, and 2 received both medications at different time points. Overall, 13 (39%) patients experienced disease exacerbation, 7 of which had received celecoxib and six rofecoxib. IBD exacerbation associated with COX-2 treatment did not correlate with age, disease activity, or use of immunosuppressive medications. All patients experienced flare-up of their underlying IBD within 6 weeks of initiating COX-2 therapy. Five of 13 (38%) patients had resolution of their symptoms after discontinuing the COX-2 inhibitor, but the remaining patients required additional medical therapy to control their disease. Six other patients (18%) experienced GI side effects not associated with their underlying IBD. Five developed abdominal pain, and one developed a duodenal ulcer and a circumferential ileo-colonic ulceration with GI bleeding. Treatment with COX-2 inhibitors is associated with a high incidence of exacerbation of the underlying IBD and GI-related complications.

Early hepatic nodular hyperplasia and submicroscopic fibrosis associated with 6-thioguanine therapy in inflammatory bowel disease

Background6-Thioguanine (6-TG) has been used as an alternative thiopurine for inflammatory bowel disease (IBD) patients not responsive to or intolerant of azathioprine (AZA) and 6-mercaptopurine (6-MP). 6-TG-related hepatotoxicity, including liver biochemistry value elevations, sinusoidal collagen deposition on electron microscopy, and veno-occlusive disease, have been described related to its use as therapy for neoplastic disease. MethodsWe studied 38 liver biopsies from patients treated with 6-TG, almost all of whom (n = 125) received 6-TG for 1 to 3 years at the Inflammatory Bowel Disease Center at Cedars-Sinai Medical Center. All biopsies were fixed in 4% buffered formalin and prepared in the usual manner. Hematoxylin and eosin, Masson’s trichrome (trichrome), and reticulin silver impregnation (reticulin) stained slides were studied. In 23 cases, tissue was also prospectively fixed in glutaraldehyde and processed for electron microscopy. ResultsIn 20 of the 37 patients studied (53%), nodular regeneration of varying degree was seen with reticulin. In only 4 of these 20 instances (11% of the total) were the changes seen with hematoxylin and eosin and in 3 of the 4, only in retrospect after studying the reticulin preparation. Minimal fibrosis was seen with trichrome in only 13 biopsies (34%), but sinusoidal collagen deposition was observed in 14 of the 23 cases studied with electron microscopy (60%). The biopsy from the 1 patient with nodular hyperplasia obvious with hematoxylin and eosin also demonstrated changes of venous outflow obstruction. Conclusions6-TG-treated IBD patients are at significant risk for nodular hyperplasia, early fibrosis and, less often, venous outflow disease (Budd-Chiari). The natural history of these changes is unknown and follow-up biopsies are needed to determine histologic and clinical sequela. Patients not demonstrating nodular hyperplasia or fibrosis who continue with 6-TG because there are no better therapeutic choices should be periodically rebiopsied.