The nitroxide 4-methoxy-tempo inhibits the pathogenesis of dextran sodium sulfate-stimulated experimental colitis

Abstract

Inflammatory bowel disease (IBD) is a chronic condition characterised by leukocyte recruitment to the gut mucosa. Leukocyte myeloperoxidase (MPO) produces the two-electron oxidant hypochlorous acid (HOCl), damaging tissue and playing a role in cellular recruitment, thereby exacerbating gut injury. We tested whether the MPO-inhibitor, 4-Methoxy-TEMPO (MetT), ameliorates experimental IBD. Colitis was induced in C57BL/6 mice by 3% w/v dextran-sodium-sulfate (DSS) in drinking water ad libitum over 9-days with MetT (15 mg/kg; via i. p. injection) or vehicle control (10% v/v DMSO+90% v/v phosphate buffered saline) administered twice daily during DSS challenge. MetT attenuated body-weight loss (50%, p < 0.05, n = 6), improved clinical score (53%, p < 0.05, n = 6) and inhibited serum lipid peroxidation. Histopathological damage decreased markedly in MetT-treated mice, as judged by maintenance of crypt integrity, goblet cell density and decreased cellular infiltrate. Colonic Ly6C+, MPO-labelled cells and 3-chlorotyrosine (3-Cl-Tyr) decreased in MetT-treated mice, although biomarkers for nitrosative stress (3-nitro-tyrosine-tyrosine; 3-NO2-Tyr) and low-molecular weight thiol damage (assessed as glutathione sulfonamide; GSA) were unchanged. Interestingly, MetT did not significantly impact colonic IL-10 and IL-6 levels, suggesting a non-immunomodulatory pathway. Overall, MetT ameliorated the severity of experimental IBD, likely via a mechanism involving the modulation of MPO-mediated damage.

The Synthetic Myeloperoxidase Inhibitor AZD3241 Ameliorates Dextran Sodium Sulfate Stimulated Experimental Colitis

“…We propose AZD3241 might offer therapeutic potential through mitigating MPO-HOCl production during colon inflammation, thereby preserving in situ antioxidant capacity and inhibiting oxidative tissue damage that contributes to the progression of this acute pathology. Thus, AZD3241 significantly improves body weight and clinical score when compared to the absence of drug supplementation by inhibiting MPO-halogenating activity and oxidative damage that contribute to colon inflammation and suppressing neutrophil activation (judged by assessing calprotectin) (Chami et al, 2020). It is notable that neutrophils are the predominant cell type that are recruited early during acute inflammation and calprotectin represents~60% of all soluble cytosolic proteins in these cells.…”

“…As a consequence of the relatively acute nature of disease development in this model, disease progression and severity were monitored and recorded daily after commencement of treatment through the assessment of four gross observational measures, enumerated to give a combined clinical scoring as we and others have described earlier (Kim et al, 2012;Chami et al, 2020). The combined score for each mouse displaying these criteria in each group was then averaged across the entire group to ascertain the impact of DSS +/-intervention.…”

“…Assessment of 3-Chloro-tyrosine (3-Chlor-Tyr) a biomarker of MPO activity was determined as previously published (Chami et al, 2020). Briefly, colon tissue homogenates were delipidated and precipitated by the addition of 25 µl of 0.3% w/v deoxycholic acid and 50 µl of 50% w/v trichloroacetic acid (TCA) over incubation for 5 min.…”

GPA peptide enhances Nur77 expression in intestinal epithelial cells to exert a protective effect against DSS‐induced colitis

“…Acute colitis was induced by feeding the mice with 3% (w/v) DSS dissolved in drinking water continuously for 7 days. 24,25 The experiment was randomly divided into five groups: control group, DSS group, and GPA (50, 100, or 150 mg/ kg) + DSS groups. GPA (50, 100, or 150 mg/kg) was administered for 7 days before and during DSS treatment via oral gavage once per day.…”

The Role of Thiocyanate in Modulating Myeloperoxidase Activity during Disease

“…Moreover, neutrophil depletion in rodents ameliorates experimental colitis [ 125 , 126 ]. Further, we earlier demonstrated a role for neutrophil-derived MPO in murine experimental colitis, with significant attenuation of disease via pharmacological inhibition of MPO [ 127 ].…”