BackgroundDespite NUDT15 variants showing significant association with thiopurine-induced adverse events (AEs) in Asians, it remains unclear which variants of NUDT15 or whether additional genetic variants should be tested to predict AEs. To clarify the best pharmacogenetic test to be used clinically, we performed association studies of NUDT15 variants and haplotypes with AEs, genome-wide association study (GWAS) to discover additional variants, and ROC analysis to select the model to predict severe AEs.MethodsOverall, 2630 patients with inflammatory bowel disease (IBD) were enrolled and genotyped for NUDT15 codon 139; 1291 patients were treated with thiopurines. diplotypes were analyzed in 970 patients, and GWASs of AEs were performed with 1221 patients using population-optimized genotyping array and imputation.ResultsWe confirmed the association of NUDT15 p.Arg139Cys with leukopenia and alopecia (p = 2.20E−63, 1.32E−69, OR = 6.59, 12.1, respectively), and found a novel association with digestive symptoms (p = 6.39E−04, OR = 1.89). Time to leukopenia was significantly shorter, and when leukopenia was diagnosed, thiopurine doses were significantly lower in Arg/Cys and Cys/Cys than in Arg/Arg. In GWASs, no additional variants were found to be associated with thiopurine-induced AEs. Despite strong correlation of leukopenia frequency with estimated enzyme activities based on the diplotypes (r2 = 0.926, p = 0.0087), there were no significant differences in the AUCs of diplotypes from those of codon 139 to predict severe AEs (AUC = 0.916, 0.921, for acute severe leukopenia, AUC = 0.990, 0.991, for severe alopecia, respectively).ConclusionsGenotyping of NUDT15 codon 139 was sufficient to predict acute severe leukopenia and alopecia in Japanese patients with IBD.Electronic supplementary materialThe online version of this article (10.1007/s00535-018-1486-7) contains supplementary material, which is available to authorized users.

The gene region constitutes a high-risk genetic locus for the occurrence of both inflammatory bowel diseases (IBDs) and Parkinson's disease. We show that dendritic cells (DCs) from patients with Crohn's disease (CD) and lymphoblastoid cell lines derived from patients without CD but bearing a high-risk allele (rs11564258) at this locus as heterozygotes exhibited increased LRRK2 expression in vitro. To investigate the immunological consequences of this increased LRRK2 expression, we conducted studies in transgenic mice overexpressing and showed that these mice exhibited more severe colitis induced by dextran sodium sulfate (DSS) than did littermate control animals. This increase in colitis severity was associated with lamina propria DCs that showed increased Dectin-1-induced NF-κB activation and proinflammatory cytokine secretion. Colitis severity was driven by LRRK2 activation of NF-κB pathway components including the TAK1 complex and TRAF6. Next, we found that membrane-associated LRRK2 (in association with TAB2) caused inactivation of Beclin-1 and inhibition of autophagy. HCT116 colon epithelial cells lacking Beclin-1 exhibited increased LRRK2 expression compared to wild-type cells, suggesting that inhibition of autophagy potentially could augment LRRK2 proinflammatory signaling. We then showed that LRRK2 inhibitors decreased Dectin-1-induced TNF-α production by mouse DCs and ameliorated DSS-induced colitis, both in control and transgenic animals. Finally, we demonstrated that LRRK2 inhibitors blocked TNF-α production by cultured DCs from patients with CD. Our findings suggest that normalization of LRRK2 activation could be a therapeutic approach for treating IBD, regardless of whether a risk allele is involved.

Background Resolvin E1 (RvE1), an endogenous lipid mediator derived from eicosapentaenoic acid (EPA), has been identified in local inflammation during the healing stage. RvE1 reduces inflammation in several types of animal models including peritonitis and retinopathy, and blocks human neutrophil transendothelial cell migration. The RvE1 receptor ChemR23 is expressed on myeloid cells such as macrophages and dendritic cells. The aim of this study was to determine whether RvE1 regulates colonic inflammation when the innate immune response of macrophages plays a key role in the pathogenesis and tissue damage. Methods/Results RvE1 receptor, ChemR23, was expressed in mouse peritoneal macrophages as defined by flow cytometry. Peritoneal macrophages were pretreated with RvE1, followed by lipopolysaccharide (LPS) stimulation whereupon of the transcriptional levels of proinflammatory cytokines were analyzed. RvE1 treatment led to the inhibition of proinflammatory cytokines including TNF-α and IL-12p40. In HEK293 cells, pretreatment with RvE1 inhibited TNF-α-induced nuclear translocation of NF-κB in a ChemR23 dependent manner. These results suggested that RvE1 could regulate pro-inflammatory responses of macrophages expressing ChemR23. Therefore, we investigated the beneficial effects of RvE1 in dextran sulfate sodium (DSS) induced colitis. RvE1 treatment led to amelioration of colonic inflammation. Conclusions These results indicate that RvE1 suppresses pro-inflammatory responses of macrophages. RvE1 and its receptor may therefore be useful as therapeutic targets in the treatment of human inflammatory bowel disease (IBD) and other inflammatory disorders.