Electron Paramagnetic Resonance (EPR) Spectroscopy to Measure Oxidative Stress (OS) in Ulcerative Colitis Mouse

Abstract

Background: Inflammatory bowel disease (IBD) refers to a group of chronic, complex, relapsing and remitting inflammatory disorders that affect the gastrointestinal (GI) tract. Crohn’s disease (CD) and ulcerative colitis (UC) are the two commonly diagnosed forms of IBD that affect over 3 million Americans, or 1.3% of the US population. In CD, patchy inflammation penetrating through multiple epithelial layers is present in any part of the GI tract, whereas UC is characterized by uniform inflammation restricted to the colon and rectum. Studies have shown increased oxidative stress (OS) as one of the major mechanisms involved in the pathogenesis of UC. Increased OS has thus far been measured using Biochemical assay-kits. In recent studies, electron paramagnetic resonance (EPR) spectroscopy has been extensively used to quantitatively characterize OS level in various tissues. Hypothesis: We hypothesize that EPR technique could be used to characterize OS in epithelia of colon. Aim: We aimed to develop EPR spectroscopy technique to quantify the level of OS in epithelia of normal and UC mouse colon. Methods: Normal mice (C57BL/6 male; 6 – 7 weeks old; Charles River, Wilmington, MA) were given regular water, while acute UC mice were given 5% Dextran-Sulfate-Sodium (DSS) water ad libitum for 7-days. EPR spectroscopy measurements were performed using the redox sensitive hydroxylamine spin probe, 1-hydroxy-3-carboxymethyl-2,2,5,5-tetramethyl-pyrrolidine (CMH; EPR silent). CMH is oxidized by reactive species/oxidants to 3-carboxymethyl-2,2,5,5- tetramethyl-pyrrolidinyloxy radical (CM•; EPR active). We used EPR detected CM• level as a quantitative marker of OS level. OS levels were measured both in serum and distal colon collected from euthanized mice. OS levels were presented as arbitrary units of EPR intensity. Results: OS levels were increased by 41% in serum from UC mice (normal vs UC: 33.6 ± 2.2 vs 47.0 ± 2.0 units; p < 0.011). OS levels were also significantly (60%) increased in UC mice colon compared to normal colon (normal vs UC: 3.5 ± 0.1 vs 5.6 ± 0.7 EPR units; p < 0.02). OS levels were approximately 9-fold higher in serum compared to colon in both normal and UC mice (normal: 3.5 ± 0.1 vs 33.6 ± 2.2; UC: 5.6 ± 0.7 vs 47.0 ± 2.0 EPR signals). Conclusions: We conclude that: 1) EPR spectroscopy technique could successfully be used for the precise measurement of OS levels in serum and colon; 2) OS levels were significantly increased in both serum and colon of UC mice; and 3) increased tissue oxidants were continuously released into the blood. Speculation: Increased serum oxidants may eventually affect other tissues in the body. This study was supported by the West Virginia Clinical and Translational Science Institute (WVCTSI) pilot grant (JTK), and Transition Grant Support, Offce of Research and Graduate Education, WVU Health Sciences Center (VMR). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.