Seinen Margien L, van Nieuw Amerongen Geerten P, de Boer Nanne K H, Mulder Chris J J, van Bezu Jan, van Bodegraven Adriaan A
Departments of *Gastroenterology and Hepatology and †Physiology, VU University Medical Center, Amsterdam; and ‡Department of Gastroenterology, Geriatrics, Internal and Intensive Care Medicine (Co-MIK), Zuyderland Medical Center, Heerlen-Sittard-Geleen, the Netherlands.
Ther Drug Monit. 2016 Oct;38(5):621-7. doi: 10.1097/FTD.0000000000000326.
Azathioprine and mercaptopurine (MP) are effective in treating patients with inflammatory bowel disease (IBD). Immunosuppressive effects of thiopurines involve T-cell apoptosis after inhibition of GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1). This study aimed to assess whether expression and activity of Rac1 or phosphorylated ezrin-radixin-moesin (pERM) in patients with IBD could provide a useful biomarker for the pharmacodynamic thiopurine effect and might be related to clinical effectiveness.
This was a 2-stage study: stage 1 concerned a cross-sectional cohort of patients with IBD clinically in remission and treated with (n = 10) or without stable weight-based thiopurine therapy (n = 11) and healthy controls (n = 6); stage 2 concerned a prospective study regarding IBD patients with clinically active disease who initiated MP therapy (n = 11) compared with healthy controls (n = 11). Expression and activity of Rac1 and ERM and pERM were determined.
The median Rac1 expression was statistically significantly reduced by thiopurine maintenance therapy {0.54 [interquartile range (IQR) 0.47-0.88] versus 0.80 arbitrary units [IQR 0.64-1.46]} compared with patients without immunosuppressive therapy (P = 0.042), but not Rac1 activity and pERM. In responders to MP therapy (n = 6), both median active Rac1 [93 (IQR 81-151) to 76 ng Rac1/mg protein (IQR 62-98)] and Rac1 expression [16.2 (8.8-29.4) to 1.5 arbitrary units (0.9-5.3)] decreased (P = 0.028). In nonresponders (n = 3), Rac1 expression and activity increased.
IBD patients treated with thiopurines had a lower expression of Rac1 compared with those not treated with thiopurine. Effective MP therapy led to decreasing concentrations of Rac1-GTP and Rac1 expression. Therefore, Rac1-GTP and expression of Rac1, but not phosphorylation of ERM, form potentially pharmacodynamic markers of therapeutic thiopurine effectiveness in patients with IBD.
硫唑嘌呤和巯嘌呤（MP）在治疗炎症性肠病（IBD）患者方面有效。硫嘌呤类药物的免疫抑制作用涉及抑制鸟苷三磷酸酶Ras相关C3肉毒杆菌毒素底物1（Rac1）后T细胞凋亡。本研究旨在评估IBD患者中Rac1或磷酸化埃兹蛋白-根蛋白-膜突蛋白（pERM）的表达和活性是否可为硫嘌呤类药物的药效学作用提供有用的生物标志物，以及是否可能与临床疗效相关。
这是一项两阶段研究：第一阶段涉及一组横断面队列，包括临床缓解且接受（n = 10）或未接受基于体重的稳定硫嘌呤治疗（n = 11）的IBD患者以及健康对照（n = 6）；第二阶段涉及一项前瞻性研究，将开始接受MP治疗的临床活动期IBD患者（n = 11）与健康对照（n = 11）进行比较。测定Rac1、ERM和pERM的表达和活性。
与未接受免疫抑制治疗的患者相比，硫嘌呤维持治疗使Rac1表达中位数显著降低{0.54 [四分位间距（IQR）0.47 - 0.88] 对0.80任意单位 [IQR 0.64 - 1.46]}（P = 0.042），但Rac1活性和pERM未降低。在MP治疗的反应者（n = 6）中，活性Rac1中位数[93（IQR 81 - 151）降至76 ng Rac1/ mg蛋白（IQR 62 - 98）]和Rac1表达[16.2（8.8 - 29.4）降至1.5任意单位（0.9 - 5.3）]均降低（P = 0.028）。在无反应者（n = 3）中，Rac1表达和活性增加。
与未接受硫嘌呤治疗的IBD患者相比，接受硫嘌呤治疗的患者Rac1表达较低。有效的MP治疗导致Rac1 - GTP浓度和Rac1表达降低。因此，Rac1 - GTP和Rac1表达而非ERM磷酸化构成IBD患者治疗性硫嘌呤有效性的潜在药效学标志物。
