Faculty Bibliography

COX-2 and 5-lipoxygenase (5-LO) use arachidonic acid for the synthesis of eicosanoids that have been implicated in carcinogenesis and cardiovascular disease. The ability of celecoxib, a selective COX-2 inhibitor, to redirect arachidonic acid into the 5-LO pathway can potentially reduce its efficacy as a chemopreventive agent and increase the risk of cardiovascular complications. Levels of urinary prostaglandin E metabolite (PGE-M) and leukotriene E4 (LTE4), biomarkers of the COX and 5-LO pathways, are elevated in smokers. Here, we investigated the effects of zileuton, a 5-LO inhibitor, versus zileuton and celecoxib for 6 +/- 1 days on urinary PGE-M and LTE4 levels in smokers. Treatment with zileuton led to an 18% decrease in PGE-M levels (P = 0.03); the combination of zileuton and celecoxib led to a 62% reduction in PGE-M levels (P < 0.001). Levels of LTE4 decreased by 61% in subjects treated with zileuton alone (P < 0.001) and were unaffected by the addition of celecoxib. Although zileuton use was associated with a small overall decrease in PGE-M levels, increased PGE-M levels were found in a subset (19 of 52) of subjects. Notably, the addition of celecoxib to the 5-LO inhibitor protected against the increase in urinary PGE-M levels (P = 0.03). In conclusion, zileuton was an effective inhibitor of 5-LO activity resulting in marked suppression of urinary LTE4 levels and possible redirection of arachidonic acid into the COX-2 pathway in a subset of subjects. Combining celecoxib and zileuton was associated with inhibition of both the COX-2 and 5-LO pathways manifested as reduced levels of urinary PGE-M and LTE4.

OBJECTIVES: Two prior studies suggested that coeliac disease (CD) has a higher prevalence rate (8%) in SSc than in the general population (1%), but these studies were limited by small numbers and the use of traditional coeliac screening antibody tests, where newer ones with improved accuracy have since emerged. Our aim was to determine the prevalence of CD in a larger SSc population using a more modern serological approach to coeliac testing and to correlate coeliac antibody status with gastrointestinal symptoms. METHODS: Stored sera from 72 SSc patients in the Scleroderma Registry at the Hospital for Special Surgery were tested for anti-tissue transglutaminase (traditional) and anti-deamidated gliadin peptide (novel) antibodies. If any of these antibodies were positive, anti-endomysial antibodies were tested and confirmatory small-bowel endoscopy and biopsy were obtained. Registry clinical data were used to determine whether antibody status correlated with gastrointestinal symptoms. RESULTS: The prevalence of coeliac antibodies in our SSc population was 3/72 (4%). No significant differences with respect to gastrointestinal symptoms were seen in the coeliac antibody-positive compared with -negative SSc patients. No cases of confirmed CD were seen in our cohort. CONCLUSION: Contrary to the only two previously published studies, the low prevalence of CD that we found does not suggest that concurrent CD is a common cause of gastrointestinal complaints in SSc patients.

Signaling through sphingosine-1-phosphate receptor(1) (S1P(1)) promotes blood vessel barrier function. Degradation of S1P(1) results in increased vascular permeability in the lung and may explain side effects associated with administration of FTY720, a functional antagonist of the S1P(1) receptor that is currently used to treat multiple sclerosis. Ulcerative colitis (UC) is characterized by an increased density of abnormal vessels. The expression or role of S1P(1) in blood vessels in the colon has not been investigated. In the present study, we show that S1P(1) is overexpressed in the colonic mucosa of UC patients. This increase in S1P(1) levels reflects increased vascular density in the inflamed mucosa. Genetic deletion of S1pr1 in mice increases colonic vascular permeability under basal conditions and increases bleeding in experimental colitis. In contrast, neither FTY720 nor AUY954, two S1P receptor-targeting agents, increases bleeding in experimental colitis. Taken together, our findings demonstrate that S1P(1) is critical to maintaining colonic vascular integrity and may play a role in UC pathogenesis.

Escherichia coli is implicated in the pathogenesis of inflammatory bowel disease (IBD). Rifaximin, a nonabsorbable derivative of rifampin effective against E. coli, improves symptoms in mild-to-moderate IBD. However, rifaximin resistance can develop in a single step in vitro. We examined the prevalence and mechanisms of rifaximin resistance in 62 strains of E. coli isolated from the ileal mucosa of 50 patients (19 with ileal Crohn's disease [L1+L3], 6 with colonic Crohn's disease [L2], 13 with ulcerative colitis [UC], 4 with symptomatic non-IBD diagnoses [NI], and 8 healthy [H]). Resistance (MIC > 1,024 mg/liter) was present in 12/48 IBD-associated ileal E. coli strains. Resistance correlated with prior rifaximin treatment (P < 0.00000001) but not with the presence of ileal inflammation (P = 0.73) or E. coli phylogroup. Mutations in a 1,057-bp region of rpoB, which encodes the bacterial target of rifaximin, were identified in 10/12 resistant strains versus 0/50 sensitive strains (P < 0.000000001) and consisted of seven amino acid substitutions. The efflux pump inhibitor Phe-Arg-beta-naphthylamide (PAbetaN) lowered the MIC of 9/12 resistant strains 8- to 128-fold. Resistance was stable in the absence of rifaximin in 10/12 resistant strains after 30 passages. We conclude that IBD-associated ileal E. coli frequently manifest resistance to rifaximin that correlates with prior rifaximin use, amino acid substitutions in rpoB, and activity of PAbetaN-inhibitable efflux pumps, but not with the presence of ileal inflammation or E. coli phylogroup. These findings have significant implications for treatment trials targeting IBD-associated E. coli.

BACKGROUND: Escherichia coli is increasingly implicated in the pathogenesis of ileal Crohn's disease (ICD), offering a potential therapeutic target for disease management. Empirical antimicrobial targeting of ileal E. coli has advantages of economy and speed of implementation, but relies on uniform susceptibility of E. coli to routinely selected antimicrobials to avoid apparent treatment failure. Therefore, we examined the susceptibility of ileal E. coli to such antimicrobials. METHODS: E. coli from 32 patients with ICD and 28 with normal ileum (NI) were characterized by phylogroup, pathotype, antimicrobial susceptibility, and presence of antimicrobial resistance genes. RESULTS: In all, 17/32 ICD and 12/28 NI patients harbored >/= 1 E. coli strain; 10/24 E. coli strains from ICD and 2/14 from NI were nonsuscepti-ble to >/= 1 antimicrobial in >/= 3 categories (multidrug-resistant). Resistance to amoxicillin/clavulanic-acid, cefoxitin, chloramphenicol, ciprofloxa-cin, gentamicin, and rifaximin was restricted to ICD, with 10/24 strains from 8/17 patients resistant to ciprofloxacin or rifaximin (P < 0.01). Adherent-invasive E. coli (AIEC) were isolated from 8/32 ICD and 5/28 NI, and accounted for 54% and 43% of E. coli strains in these groups. In all, 8/13 AIEC strains from ICD (6/8 patients) versus 2/6 NI (2/5 patients) showed resistance to the macrophage-penetrating antimicrobials ciprofloxacin, clarithromycin, rifampicin, tetracycline, and trimethoprim/sulfamethoxazole. Resistance was associated with tetA, tetB, tetC, bla-(TEM), bla(oxa)-1, sulI, sulII, dhfrI, dhfrVII, ant(3'')-Ia, and catI genes and prior use of rifaximin (P < 0.01). CONCLUSIONS: ICD-associated E. coli frequently manifest resistance to commonly used antimicrobials. Clinical trials of antimicrobials against E. coli in ICD that are informed by susceptibility testing, rather than empirical selection, are more likely to demonstrate valid outcomes of such therapy.