Decreased Mucosal Sulfide Detoxification Capacity in Patients With Crohnʼs Disease

Abstract

To the Editor: The possible importance of H2S as a causative factor in the genesis or maintenance of ulcerative colitis (UC) is evident from studies reporting higher H2S levels and higher counts of sulfate-reducing bacteria in feces from patients with UC and from the role for H2S in impaired colonic butyrate oxidation.1 To prevent the deleterious effect of sulfide on the colonic epithelium, the large intestine disposes of 2 enzymes, thiol S-methyltransferase and thiosulfate sulfurtransferase (TST), responsible for the clearance of H2S.2,3 Recently, we showed that the mucosal detoxification of sulfides is impaired in patients with UC. This deficiency is initiated at the gene expression level, and it is the result of a decreased expression of TST and is clearly associated with inflammation.4 In Crohn's disease (CD), the mucosal enzymatic detoxification capacity by TST has only been investigated in 1 other study, but no data are available on the TST gene expression in CD. Picton et al5 found no statistical evidence of a decreased TST enzyme activity in the mucosa of patients with CD and did not observe a correlation with disease activity. However, only 7 patients were included in this study. In the present study, we evaluated whether a deficient sulfide detoxification capacity is also present at the TST gene expression level in the colonic mucosa of patients with CD. Therefore, measurements were performed in endoscopic-derived colonic mucosal biopsies from 18 CDpatients with active colitis before and 4 to 6 weeks after their first anti–tumor necrosis factor-α therapy with infliximab and from 20 normal control subjects. The response to infliximab in CD was defined as a complete endoscopic mucosal healing with a decrease of at least 3 points on the histologic score for CD.6 Patients who did not achieve this healing were considered nonresponders, although some of them presented endoscopic and histologic improvement. Of the 18 patients with CD, we identified 11 responders and 7 nonresponders. The gene expression levels of TST, interleukin-8 (IL-8), and β-actin were measured with quantitative reverse transcription PCR, as previously described.4 β-Actin was used as the endogenous reference gene, while IL-8 as marker for inflammatory activity. IL-8 is involved in a continued influx of inflammatory cells in inflammatory bowel disease and its expression is increased in colon inflamed as a result of inflammatory bowel disease.7 Similar to our results in UC,4TST expression was significantly decreased in active CD versus control subjects (Fig. 1A). After infliximab therapy, TST expression was significantly increased in CD responders when compared with their baseline samples (Fig. 1A). However, their expression levels remained significantly lower after the therapy when compared with the control subjects (Fig. 1A). In contrast, no effect of infliximab therapy was seen on the TST expression in CD nonresponders, and TST expression remained significantly decreased after the therapy in CD nonresponders versus control subjects (Fig. 1A). Furthermore, a significantly strong negative correlation between the expression levels of TST and the inflammatory marker IL-8 was found in CD and control samples (Fig. 1B), which suggests that the decreased expression of TST is the consequence of the mucosal inflammation. A, TST colonic gene expression in controls (n = 20), infliximab CD responders (n = 11), and infliximab CD nonresponders (n = 7). A line between 2 points represents the change in expression before and after infliximab therapy. *P < 0.001, Mann–Whitney U test; ^P < 0.05, Wilcoxon signed rank test. B, Scatter plot representing negative correlation between TST and IL-8 messenger RNA levels in CD and control samples (Spearman correlation coefficient, R = −0.828; P < 0.001). In conclusion, we provide evidence that the expression of the sulfide detoxification gene TST is not only downregulated in UC but also in CD. Inflammation is clearly associated with the observed deficiency in CD. An upregulation of the expression levels after anti-inflammatory therapy was observed in responders to infliximab therapy with complete mucosal healing suggesting that, similar to that in patients with UC, the effect is secondary to inflammation.