Novel endoscopic scoring system for immune mediated colitis: A Multicenter Retrospective Study of 674 Patients.

BACKGROUND & AIMS: No endoscopic scoring system has been established for immune-mediated colitis (IMC). This study aimed to establish such a system for IMC and explore its utility in guiding future selective immunosuppressive therapy (SIT) use compared to clinical symptoms. METHODS: This retrospective international 14-center study included 674 patients who developed IMC after immunotherapy and underwent endoscopic evaluation. Ten endoscopic features were selected by group consensus and assigned one point each to calculate an IMC endoscopic score (IMCES). IMCES cutoffs were chosen to maximize specificity for SIT use. This specificity was compared between IMCES, and clinical symptoms graded according to a standardized instrument. RESULTS: A total of 309 (45.8%) patients received SIT. IMCES specificity for SIT use was 82.8% with a cutoff of 4 . The inclusion of ulceration as a mandatory criterion resulted in higher specificity (85.0% for a cutoff of 4). In comparison, the specificity of a Mayo Endoscopy Score (MES) of 3 was 74.6% while specificity of clinical symptom grading was much lower at 27.4% and 12.3% respectively. Early endoscopy was associated with timely SIT use (p<0.001, r=0.4084). CONCLUSIONS: This is the largest, multi-center study to devise an endoscopic scoring system to guide IMC management. An IMCES cutoff 4 has a higher specificity for SIT use than clinical symptoms, supporting early endoscopic evaluation for IMC.

Gain-of-function mutations identify amino acids within transmembrane domains of the yeast vacuolar transporter Zrc1 that determine metal specificity.

Cation diffusion facilitator transporters are found in all three Kingdoms of life and are involved in transporting transition metals out of the cytosol. The metals they transport include Zn2+, Co2+, Fe2+, Cd2+, Ni2+ and Mn2+; however, no single transporter transports all metals. Previously we showed that a single amino acid mutation in the yeast vacuolar zinc transporter Zrc1 changed its substrate specificity from Zn2+ to Fe2+ and Mn2+ [Lin, Kumanovics, Nelson, Warner, Ward and Kaplan (2008) J. Biol. Chem. 283, 33865-33873]. Mutant Zrc1 that gained iron transport activity could protect cells with a deletion in the vacuolar iron transporter (CCC1) from high iron toxicity. Utilizing suppression of high iron toxicity and PCR mutagenesis of ZRC1, we identified other amino acid substitutions within ZRC1 that changed its metal specificity. All Zrc1 mutants that transported Fe2+ could also transport Mn2+. Some Zrc1 mutants lost the ability to transport Zn2+, but others retained the ability to transport Zn2+. All of the amino acid substitutions that resulted in a gain in Fe2+ transport activity were found in transmembrane domains. In addition to alteration of residues adjacent to the putative metal- binding site in two transmembrane domains, alteration of residues distant from the binding site affected substrate specificity. These results suggest that substrate selection involves co-operativity between transmembrane domains.

A single amino acid change in the yeast vacuolar metal transporters ZRC1 and COT1 alters their substrate specificity.

Iron is an essential nutrient but in excess may damage cells by generating reactive oxygen species due to Fenton reaction or by substituting for other transition metals in essential proteins. The budding yeast Saccharomyces cerevisiae detoxifies cytosolic iron by storage in the vacuole. Deletion of CCC1, which encodes the vacuolar iron importer, results in high iron sensitivity due to increased cytosolic iron. We selected mutants that permitted Deltaccc1 cells to grow under high iron conditions by UV mutagenesis. We identified a mutation (N44I) in the vacuolar zinc transporter ZRC1 that changed the substrate specificity of the transporter from zinc to iron. COT1, a vacuolar zinc and cobalt transporter, is a homologue of ZRC1 and both are members of the cation diffusion facilitator family. Mutation of the homologous amino acid (N45I) in COT1 results in an increased ability to transport iron and decreased ability to transport cobalt. These mutations are within the second hydrophobic domain of the transporters and show the essential nature of this domain in the specificity of metal transport.