The risk of thiopurine-induced myelotoxicity markedly increases in patients treated with combined 5-ASA and 2 mg/kg/day AZA therapy, which may be correlated to the increase in 6-TGN. 50 mg daily AZA when concomitant 5-ASA might help maintain an effective 6-TGN level without increasing the risk of myelotoxicity.
High levels of HPRT activity could be a predictor of leukopenia and unsafe 6-TGN concentrations in patients undergoing AZA/6-MP therapy. This could partly explain the therapeutic response or toxicity that could not be adequately explained by the polymorphisms of TPMT.
Up to approximately 40% to 50% of patients discontinue thiopurine therapy during the course of inflammatory bowel disease (IBD). We investigated the role of the metabolite thiopurine in IBD treatment. This was a prospective study.IBD patients receiving azathioprine (AZA) were prospectively included. Thiopurine methyltransferase (TPMT) genotypes were examined before therapy, and thiopurine metabolite levels were examined at weeks 2, 4, 8, 12, 24, and 48. In total, 132 patients were included. The frequency of leucopenia increased at 6-thioguanine nucleotide (6-TGN) levels ≥420 pmol/8 × 108 RBC (odds ratio [OR] = 7.9; 95% confidence interval (95%CI): 3.5–18.0; P < 0.001) and increased more during the initial 12 weeks of thiopurine therapy (OR = 16.0; 95%CI: 5.7–44.9; P < 0.001). The patients with 6-TGN levels ≥420 pmol/8 × 108 RBC at weeks 4, 8, and 12 had an increased likelihood of leucopenia. Clinical response increased at 6-TGN levels ≥225 pmol/8 × 108 RBC (OR = 13.5; 95% CI: 3.7–48.9; P < 0.001) in Crohn disease (CD) patients. The CD patients with 6-TGN levels ≥225 pmol/8 × 108 RBC at weeks 8, 12, and 24 had an increased likelihood of successful clinical response. TPMT∗3C had a specificity of 100%, but a sensitivity of 8% for predicting leucopenia.A 6-TGN level between 225 and 420 pmol/8 × 108 RBC could be a therapeutic window in patients receiving AZA therapy, and it could likely predict leucopenia in the initial 12 weeks of AZA therapy and a reasonable chance of successful clinical response in CD patients. The value of TPMT genotyping before thiopurine therapy is limited in Chinese patients with IBD, considering the low sensitivity of predicting leucopenia.
Argonaute (AGO) proteins play a pivotal role in plant growth and development as the core components of RNA-induced silencing complex (RISC). However, no systematic characterization of AGO genes in wheat has been reported to date. In this study, a total number of 69 TaAGO genes in the hexaploid bread wheat (Triticum aestivum cv. Chinese Spring) genome, divided into 10 subfamilies, were identified. Compared to all wheat genes, TaAGOs showed a significantly lower evolutionary rate, which is consistent with their high conservation in eukaryotes. However, the homoeolog retention was remarkably higher than the average, implying the nonredundant biological importance of TaAGO genes in bread wheat. Further homoeologous gene expression bias analyses revealed that TaAGOs may have undergone neofunctionalization after polyploidization and duplication through the divergent expression of homoeologous gene copies, to provide new opportunities for the generation of adaptive traits. Moreover, quantitative real-time polymerase chain reaction (qRT-PCR) analyses indicated that TaAGO gene expression was involved in response to heat, drought, and salt stresses. Our results would provide a theoretical basis for future studies on the biological functions of TaAGO genes in wheat and other gramineous species.
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