Tissue nitrosothiol levels in acute ulcerative colitis A step in disease induction?

Copyright © 2008 Published by Elsevier Inc.Background and aims: Production of luminal nitric oxide (NO) in the colon is significantly increased in ulcerative colitis (UC) due to bacterial metabolism or activated immune cells. The effect on tissues of prolonged elevation of nitric oxide is unknown. Formation of nitrosothiols has been discounted as these occur under acidic conditions which nevertheless may prevail in acute colitis. The aim was to measure nitrosothiol formation in colonocytes in acute colitis as well as to assess nitrosation of CoA in vitro. Materials and methods: Fresh rectal biopsies obtained at colonoscopies of cases with acute colitis, newly diagnosed or after recurrent attacks, were analysed. Exposure to glutaraldehyde/formaldehyde was avoided and samples stored in the dark at −80 °C. After mechanical homogenization nitrosothiols were measured with the Saville-Griess reaction with and without exposure to mercuric chloride. The reaction with sulphanilamide was measured at 540 nm after azo dye coupling. By calibration curves with GSNO and tissue protein measurement (Bradford reaction) results were expressed as nmoles/mg protein. Purified samples of CoA were obtained for UV spectroscopic analysis after exposure to nitrite or sodium sulphide. Results: Nitrosothiols were not measureable in tissues exposed to formaldehyde. Nitrosothiol levels were 129.3 ± 25.6 (n = 6) in acute UC compared with healthy controls of 53.2 ± 13.8 (n = 6) (p < 0.02). Nitrosothiols of CoA were measureable at acidic pH (2.0) and increased by the presence of sodium sulphide (0.5 mM). Nitroso-CoA formation to a lesser degree occurred at higher pH (6.9) but amplification with sulphide was not clearly identified. Conclusions: Elevated tissue nitrosothiols are found in association with acute colitis. As both CoA and glutathione are known to be depleted in UC, results suggest that these agents could be diminished by nitrosothiol formation