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Chie Kurihara, Toshihide Ohmori, Kenichi Inaba, Shunsuke Komoto, Kengo Tomita, Ryota Hokari Gastroenterology 2020 158 (6) Suppl.S-1046

Background: Granulocyte and monocyte adsorptive apheresis (GMA) is non-pharmacological therapy which selective depletion of activated granulocytes and monocytes/macrophages from peripheral blood, and it is used as induction therapy for IBD. However, its therapeutic mechanism has not been well characterized. Recently, it has been reported that Th17 releases chemokines which attract neutrophils, and some neutrophils produce IL17. We investigated that changes in mRNA expression levels of inflammation associated molecules such as cytokines, chemokines in colonic mucosa of ulcerative colitis (UC) patients before and after GMA treatment in order to obtain further understanding of GMA therapeutic mechanisms. Methods: Thirty-two active UC patients (Mayo score ≥ 5 and Mayo endoscopic score ≥ 2) and 10 non-IBD control subjects were enrolled in this study. All UC patients received 10 times of GMA, and colonoscopies were applied before the first GMA and after the last GMA. Control subjects underwent colonoscopies for screening of colon cancer. Assessment of GMA therapeutic efficacy was determined based on Mayo score. Inflammation-related molecules mRNA expressions were determined by quantitative RT-PCR using biopsy specimen of colonic mucosa. Results: GMA treatment efficacy is 11 patients (34.4%) achieved clinical remission, 17 patients (53.1%) were response and 4 patients (12.5%) were non-response. Baseline characteristics such as sex, location of disease, CRP, WBC and Mayo score were not significantly different according to GMA efficacy. In the remission group, mRNA levels in mucosal tissue of IL1β, IL6, IL17, IL23 and GM-CSF which are Th17-asociated cytokines significantly decreased after the last GMA compared to the baseline levels(P<0,05) in contrast, expression of these mRNA tended to increase following GMA treatment in the non-response group. On the other hand, IL12 and IFN- γ which are associated with Th1 did not significantly decrease in the remission group. mRNA levels of leukocyte trafficking associated molecules such as MAdCAM-1, ICAM-1, integrinβ7, IL8 and MIP-1β significantly decreased following GMA treatment in the remission group(P <0.05), whereas only IL8 mRNA expression in the non-response group tended to increase. IL1 β, IL6, GM-CSF which are Th17-asociated cytokines and IL8 mRNA expressions in post-GMA treatment were significantly higher in the non-response group compared to the remission group or control group(P <0.05). Conclusion: In UC patients who achieved clinical remission by GMA, Th17- associated cytokines and leukocyte trafficking associated molecules but not Th1-asociated cytokines decreased significantly. Furthermore, Th17-asociated cytokines increased in the non-responders. These results reaffirm the involvement of neutrophil in the pathophysiology of UC and could be helpful for characterizing of GMA therapeutic mechanism.

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