guanosine-diphosphate and Crohn-Disease

In inflammatory bowel disease (IBD), large areas of apparently healthy mucosa lie adjacent to ulcerated intestine. Knowledge of the mechanisms that maintain remission in an otherwise inflamed intestine could provide important clues to the pathogenesis of this disease and provide rationale for clinical treatment strategies. We used kinome profiling to generate comprehensive descriptions of signal transduction pathways in inflamed and noninflamed colonic mucosa in a cohort of IBD patients, and compared the results to non-IBD controls. We observed that p21Rac1 guanosine triphosphatase (GTPase) signaling was strongly suppressed in noninflamed colonic mucosa in IBD. This suppression was due to both reduced guanine nucleotide exchange factor activity and increased intrinsic GTPase activity. Pharmacological p21Rac1 inhibition correlated with clinical improvement in IBD, and mechanistically unrelated pharmacological p21Rac1 inhibitors increased innate immune functions such as phagocytosis, bacterial killing, and interleukin-8 production in healthy controls and patients. Thus, suppression of p21Rac activity assists innate immunity in bactericidal activity and may induce remission in IBD.

Topics: Animals; Biopsy; Crohn Disease; Cyclin-Dependent Kinase Inhibitor p21; Down-Regulation; Enzyme Inhibitors; GTPase-Activating Proteins; Guanine Nucleotide Exchange Factors; Guanosine Diphosphate; Guanosine Triphosphate; Humans; Hydrolysis; Immunity, Innate; Inflammation; Intestinal Mucosa; Protein Kinases; rac1 GTP-Binding Protein; Remission Induction; Signal Transduction; Thioguanine

Azathioprine is the gold standard for immunosuppressive therapy in Crohn's disease (CD) and its molecular mechanism of action is caused by the metabolite 6-thioguanosine triphosphate (TGTP). In this study we assessed the impact of TGTP levels for monitoring of azathioprine therapy.. A novel, highly sensitive assay was established to measure levels of TGTP and its precursors 6-thioguanosine monophosphates and 6-thioguanosine diphosphates (TGDP) in red blood cells from 50 CD patients. The results were correlated with clinical outcome.. TGTP levels could be quantified in 47 patients and a subgroup of these patients showed significantly high levels of TGDP. 6-thioguanine nucleotide (6-TGN) levels showed a significant correlation with TGDP plus TGTP concentrations, suggesting that active TGTP and its inactive precursor TGDP are the main metabolites within 6-TGN. Patients with 6-TGN levels higher than 100 pmol/8x10(8) red blood cells showed better response rates, on average, than patients with lower 6-TGN levels. The subgroup of patients with higher 6-TGN and increased TGDP levels showed a worse outcome with lower response rates, more flares, and higher infliximab demand than patients with high 6-TGN, low TGDP, and predominantly detectable TGTP levels.. This study shows that quantification of TGTP levels can be used to monitor azathioprine therapy in inflammatory bowel disease patients. Furthermore, the data suggest that TGDP levels of more than 15% of total 6-TGN levels may be a useful surrogate parameter to predict poor response in a subgroup of azathioprine-treated patients.

Topics: Adult; Antibodies, Monoclonal; Azathioprine; Biomarkers; Crohn Disease; Erythrocytes; Guanine Nucleotides; Guanosine Diphosphate; Humans; Immunosuppressive Agents; Infliximab; Thionucleotides