Genotypic analysis of thiopurine S-methyltransferase in patients with Crohn's disease and severe myelosuppression during azathioprine therapy

BACKGROUND & AIMS: Myelosuppression in patients with Crohn's disease (CD) treated with azathioprine has been attributed to low activity of thiopurine S-methyltransferase (TPMT). Allelic variants of the TPMT gene responsible for changes in the enzyme activity have been characterized. We investigated the distribution of mutant alleles associated with TPMT deficiency in patients with CD and myelosuppression during azathioprine/6-mercaptopurine therapy. METHODS: Forty-one patients with CD were included. They developed leukopenia or thrombocytopenia during azathioprine or 6-mercaptopurine treatment. Polymerase chain reaction-based methods were used to search for mutations associated with TPMT deficiency. RESULTS: Four patients (10%) had 2 mutant alleles associated with TPMT deficiency, 7 (17%) had 1 mutant allele, and 30 (73%) had no known TPMT mutation. The delay between administration of the drug and occurrence of bone marrow toxicity was less than 1.5 months in the 4 patients with 2 mutant alleles, and ranged from 1 to 18 months in patients with 1 mutant allele and from 0.5 to 87 months in patients with normal genotype. CONCLUSIONS: Twenty-seven percent of patients with CD and myelosuppression during azathioprine therapy had mutant alleles of the TPMT gene associated with enzyme deficiency. Myelosuppression is more often caused by other factors. Continued monitoring of blood cell counts remains mandatory in patients treated with azathioprine.     

Choice of azathioprine or 6-mercaptopurine dose based on thiopurine methyltransferase (TPMT) activity to avoid myelosuppression. A prospective study

BACKGROUND/AIMS: To prospectively evaluate whether, in patients with inflammatory bowel disease, the choice of azathioprine (AZA) or 6-mercaptopurine (6-MP) dose based on thiopurine methyltransferase (TPMT) activity prevents myelotoxicity. METHODOLOGY: TPMT activity in red blood cells was measured in 99 patients with Crohn's disease and 32 with ulcerative colitis prior to initiating AZA/6-MP treatment. AZA/6-MP dose was chosen based on TPMT activity, which was again determined one month after starting therapy. Incidence of adverse effects was evaluated for at least 6 months of follow-up. RESULTS: Mean basal TPMT value was 21.6 +/- 5 U/mL. No patient had low levels (< 5 U/mL), 6.9% had intermediate levels (5-13.7 U/mL), and 93.1% had high levels (> 13.8 U/mL). In patients with Crohn's disease, mean TPMT activity significantly decreased after AZA/6-MP therapy, while in patients with ulcerative colitis this activity did not change. Among the 4 patients having myelotoxicity, one had intermediate basal TPMT levels, and 3 even had high levels, but no patient had low levels. CONCLUSIONS: In this prospective study we could not confirm that the choice of AZA/6-MP dose based on TPMT activity prevents myelotoxicity in patients with inflammatory bowel disease. Routine analytical controls should be performed in these patients independently of TPMT activity.     

Identification of thiopurine methyltransferase (TPMT) polymorphisms cannot predict myelosuppression in systemic lupus erythematosus patients taking azathioprine.

OBJECTIVE: To determine whether the presence of polymorphisms associated with reduced or absent activity of thiopurine methyltransferase (TPMT), an enzyme involved in azathioprine metabolism, can predict side-effects, particularly myelosuppression, in patients taking this drug. METHODS: The TPMT genotype was determined in 120 patients with systemic lupus erythematosus (SLE) together with 15 patients with inflammatory bowel disease (IBD) and correlated with the effects of clinical exposure to azathioprine. RESULTS: TPMT polymorphisms were detected in eight patients. Severe marrow toxicity occurred in the single homozygote identified. Azathioprine was generally well tolerated, but 11 drug-associated neutropenias were detected. In only one of the 11 cases was a TPMT polymorphism identified. CONCLUSION: Homozygous TPMT deficiency was associated with severe marrow suppression. In the majority of cases, however, TPMT genotyping prior to azathioprine therapy would not have predicted myelosuppressive events and may augment, but not replace, regular blood monitoring.     

Synovial fluid pyrophosphate and nucleoside triphosphate pyrophosphatase: comparison between normal and diseased and between inflamed and non-inflamed joints.

Deposition of intra-articular calcium pyrophosphate is associated with both aging and arthropathy; increased concentrations of free pyrophosphate (PPi) may contribute to such deposition. Free pyrophosphate and nucleoside triphosphate pyrophosphatase (NTPase) were estimated in synovial fluids from 50 subjects with normal knees and from 44 patients with rheumatoid arthritis, 61 with pyrophosphate arthropathy, and 59 with osteoarthritis. For arthropathic knees clinically assessed inflammation was classified as active or inactive using a summated score of six clinical features. The order of PPi (mumol/l) and NTPase (mumol PPi/30 min/mg protein) was pyrophosphate arthropathy greater than osteoarthritis greater than rheumatoid arthritis (median PPi, NTPase respectively: for pyrophosphate arthropathy 15.9, 0.45; for osteoarthritis 9.3, 0.25; for rheumatoid arthritis 4.4, 0.18), with significant differences between all groups. In pyrophosphate arthropathy both PPi (mumol/l) and NTPase (mumol PPi/30 min/mg protein) were higher than normal (15.9, 0.45 v 8.6, 0.2 respectively), but findings in osteoarthritis did not differ from normal. The inflammatory state of the knee had a distinct but variable effect on synovial fluid findings in rheumatoid arthritis and pyrophosphate arthropathy, but not in osteoarthritis. There was no correlation of either PPi or NTPase with age, or between PPi and NTPase in any group. This study provides in vivo data for synovial fluid PPi and NTPase. It suggests that factors other than PPi need to be considered in a study of crystal associated arthropathy. Clinical inflammation, as well as diagnosis, is important in synovial fluid studies.     

Adenosine triphosphate pyrophosphohydrolase and neutral inorganic pyrophosphatase in pathologic joint fluids. Elevated pyrophosphohydrolase in calcium pyrophosphate dihydrate crystal deposition disease

Adenosine triphosphate pyrophosphohydrolase (ATPPPH) and neutral inorganic pyrophosphatase activities were assayed in synovial fluids (SF) from 37 patients with a variety of arthropathies. ATPPPH activity was detected in all fluids, but was highest in patients with chronic chondrocalcinosis; its activity in patients with osteoarthritis was higher than that in patients with rheumatoid arthritis, gout, or pseudogout. ATPPPH activity correlated positively with SF pyrophosphate concentration and negatively with SF white blood cell count. Pyrophosphatase activity did not correlate with diagnosis, pyrophosphate level, or white blood cell count.     

High frequency of mutant thiopurine S-methyltransferase genotypes in Mexican patients with systemic lupus erythematosus and rheumatoid arthritis

Systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are treated with immunosuppressive purine analogs, 6-mercaptopurine/6-thioguanine/azathiopurine, which are inactivated by thiopurine S-methyltransferase (TPMT). Non-synonymous polymorphisms in TPMT are associated with increased risk of adverse effects in patients treated with thiopurines. This study aimed to determine the frequency of the most common mutant TPMT alleles in Mexican patients with SLE (a prototype autoimmune disease) and RA (one of the most common autoimmune diseases in Mexico). Five hundred fifty-three consecutive patients from Central Mexico with SLE (178) and RA (375) were included. Subjects were genotyped to identify TPMT*2 (rs1800462), TPMT*3A (rs1800460 and rs1142345), TPMT*3B (rs1800460), and TPMT*3C (rs1142345) mutant alleles. DNA samples were assayed with the 5′ exonuclease technique and TaqMan probes. Mutant alleles were detected in 6.2 and 5.2% of SLE and RA cases, respectively. Of note, 12.4% of SLE cases and 10.1% of RA cases carried mutant genotypes. Among those, the null genotype (TPMT*2/*3A, 0.3%) and the TPMT*3B (0.5%) and TPMT*3C (1.0%) alleles were found in RA, but not SLE cases. Mexican SLE cases displayed the highest frequency of mutant TPMT genotypes worldwide. TPMT genotyping should be performed for Mexican patients with SLE and RA before prescribing purine analogs.     

Monitoring of thiopurine methyltransferase and thiopurine metabolites to optimize azathioprine therapy in inflammatory bowel disease

Determination of the activity of thiopurine methyltransferase (TPMT) and of thiopurine metabolites (6-thioguanine and 6-methylmercaptopurine nucleotides) could be useful for individualized monitoring of azathioprine (AZA) and 6-mercaptopurine (6-MP) doses. TPMT activity in the general population follows a trimodal distribution, in which approximately 0.3% of the population is homozygotic for the low-activity allele. A notable correlation has been observed between the low TPMP activity genotype or phenotype and the risk of myelotoxicity. Patients with a high TPMT activity genotype or homozygous phenotype should receive immunosuppressive doses that have clearly been demonstrated to be effective. In contrast, in patients with a low TPMT activity genotype or homozygous phenotype, the use of AZA/6-MP should be contraindicated or only very small doses should be administered. Importantly, TPMP deficiency explains only some cases of myelotoxicity and consequently periodic laboratory testing should be performed in patients receiving AZA/6-MP, even though TPMP function may be normal. Currently, the utility of routine thiopurine metabolite determinations in patients undergoing AZA/6-MP therapy has not been established and this practice should be limited to specific situations such as lack of response to thiopurine therapy or the occurrence of thiopurine-related adverse effects. Randomized trials comparing the routine strategy of AZA/6-MP dosing (based exclusively on the patient's weight) versus individualized monitoring (based on quantification of TPMP activity and/or thiopurine metabolites) are required before definitive conclusions on the most effective alternative can be drawn.     

Thiopurine-methyltransferase and inosine triphosphate pyrophosphatase polymorphism in a liver transplant recipient developing nodular regenerative hyperplasia on low-dose azathioprine

The enzymes thiopurine-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) are involved in thiopurine metabolism. We describe a liver transplant recipient who presented with liver enzyme abnormalities after 78 months of low-dose azathioprine (AZA) therapy (less than 1 mg/kg). No underlying etiology of these abnormalities was identified after extensive analysis including repeated liver biopsy. Fifteen years after transplantation, the patient presented with variceal bleeding, liver biopsy showed nodular regenerative hyperplasia (NRH). TPMT*3C genotype was found in the patient's lymphocytes and heterozygous ITPA (94C>A) genotype was found in both patient and donor liver. These findings further emphasize the importance of pharmacogenetics in predicting NRH and other adverse events during AZA therapy. Furthermore, a high index of suspicion with early detection of NRH is crucial, as improvement seems only to occur in patients with compensated liver disease. Liver biopsy and discontinuation of AZA are recommended in case of liver enzyme abnormalities or signs of portal hypertension.     

Helicobacter pylori vacA genotypes and cagA status and their relationship to associated diseases

Helicobacter pylori (H. pylori ) is a major causativebacterium of chronic gastritis, peptic ulcer and mucosaassociated lymphoid tissue lymphoma in humans, and associated with an increased risk of gastric cancer[1 -8]. An important virulant factor of H. pylori is the vacuolating cytotoxin ( VacA ) encoded by vacA that induces cytoplasmic vacuolation in target cells both in vitro and in vivo[9-11]. VacA is produced as a 140 kDa precursor which contains an N-terminal signal peptide and an approximately 33 kDa C-terminal outer membrance exporter. The precursor is cleaved at both N-terminal and C-terminal and secreted into the extracellular milieu as a 95 kDa mature protein. The mature protein futher undergoes specific cleavage to yield 37 kDa and 58 kDa subunits[12-14] Although vacA is present in all H. pylori strains, only about 50% to 60% of strains can induce vacuolation of epithelial cells as assessed by the HeLa cell assay. vacA shows considerable genetic variation in H. pylori isolated from all over the world and contains at least two variable regions. The s region exists as sl or s2 allelic types. Among type sl strains, subtypes sla and slb have been identified. The m region occurs as ml or m2 allelic types. Specific vacA genotype of H. pylori strains are associated with the production of the cytotoxin in vitro, epithelial damage in vivo, and clinical consequences[15-27]. The other virulant factor is the cytotoxin-associated protein (CagA) encoded by the cytotoxin-associated gene (cagA). The cagA gene is present in about 60% to 70% of strains and all of these strains express the cagA. The presence of cagA is also associated with the production of the cytotoxin in vitro, and clinical outcome[24-30]. The aim of this study was (i) to identify vacA genotypes and cagA status of H. pylori isolated from Chinese patients; (ii) to evaluation the relatioship beween vacA genotypes, cagA status and related gastroenterological disorders.     

Dynamics of pyrimidine deoxynucleoside triphosphate pools in relationship to DNA synthesis in 3T6 mouse fibroblasts.

The 3H-labeled nucleosides cytidine, deoxycytidine, and thymidine are rapidly incorporated into DNA via dCTP or dTTP pools. Between 30 and 60 min after addition of tracer amounts of a labeled nucleoside to the medium of rapidly growing 3T6 cells, dNTP pools attained a constant specific activity resulting from a steady-state equilibrium between incorporation of nucleoside, de novo synthesis, and linear incorporation of isotope into DNA. Removal of labeled deoxycytidine or thymidine depleted the dNTP pools of isotope within a few minutes and incorporation into DNA stopped. When de novo synthesis of dTTP was blocked with amethopterin, the intracellular dTTP pool rapidly reached the specific activity of thymidine of the medium and isotope incorporation into DNA then measured absolute rates of DNA synthesis. In experiments with and without amethopterin, we found no kinetic evidence for the existence of more than one dTTP pool and the decay of the pool suggested that all dTTP served as precursor of DNA. In contrast, experiments with deoxycytidine and cytidine suggested the presence of separate dCTP pools with preferential DNA synthesis from the pool labeled from cytidine.     

耐多药及广泛耐药MTB菌株对SQ109的耐药性及其与北京基因型的关系

目的 评价耐多药(MDR)及广泛耐药(XDR)MTB菌株对抗结核新药乙胺丁醇(EMB)类似物SQ109的耐药性,为SQ109的临床应用提供依据。方法 收集首都医科大学附属北京胸科医院2014年7月至2016年12月临床分离培养阳性的MTB菌株,共计223株,包括MDR菌株109株,XDR菌株114株。采用微孔板阿尔玛蓝显色法检测SQ109对菌株的最低抑菌浓度(MIC),确定流行病学界值(ECOFF值);采用RD207基因作为北京基因型和非北京基因型的分离标准进行基因型鉴别,并比较不同基因型菌株耐药情况;根据临床药物敏感性试验(简称“药敏试验”)结果将菌株对EMB的耐药情况进行分类,并比较EMB耐药菌株和敏感菌株对SQ109耐药率的差异。结果 根据临床MTB菌株对于SQ109的MIC值频数分布情况,确定ECOFF值为1.000mg/L。XDR菌株耐药率为4.4%(5/114),MDR菌株中无耐药菌株,两者耐药率差异无统计学意义(Fisher精确概率法,P>0.05)。109株MDR菌株中有8株非北京基因型,114株XDR中有10株非北京基因型。北京基因型菌株对SQ109耐药率为2.4%(5/205),非北京基因型菌株中未发现耐药菌株,两者耐药率差异无统计学意义(Fisher精确概率法,P>0.05)。223株菌株中共有138株EMB敏感菌株和85株EMB耐药菌株。EMB敏感菌株对SQ109耐药菌株数为1株,耐药率为0.7%(1/138);EMB耐药菌株对SQ109耐药菌株数为4株,耐药率为4.7%(4/85),两者耐药率差异无统计学意义(Fisher精确概率法,P>0.05)。结论 SQ109在体外药敏试验中表现出对MDR-MTB和XDR-MTB菌株具有良好的抑菌效果。北京基因型菌株与SQ109耐药性无相关性。菌株对EMB的耐药性与对SQ109的耐药性无相关性。     

RFLP法检测PBMCs和血浆中HCV基因型的相关性与慢性化的关系

目的检测HCV感染者血浆和外周血单个核细胞(PBMCs)中HCV基因型的相关性,同时研究不同型的HCV与丙型肝炎复发及慢性化的关系。方法应用特异性限制性片段长度多态分析(RFLP)—酶切分型法进行基因分型。结果82例血浆HCVRNA阳性的病例中1b(Ⅱ)型为37例(45.1%),2a(Ⅲ)型为34例(41.5%),1b/2a(Ⅱ/Ⅲ)型为11例(13.4%)。PBMCs中HCVRNA阳性的为54例(65.85%),其中1b型为38例,2a型为12例,1b/2a型为4例。结论HCV感染人体后,不但在血浆中可以检测到HCVRNA,而且也可以在PBMCs中检测到HCVRNA。同时HCV1b型比2a型更易感染PBMCs,HCV1b型感染者易出现慢性持续性感染,以至于发展为肝硬化。     

Hepatitis C virus genotypes in France: relationship with epidemiology, pathogenicity and response to interferon therapy. The GEMHEP

The aim of this study was to investigate the following in a large population of French patients with chronic hepatitis C: the geographical distribution of hepatitis C virus (HCV) genotypes; the relationship between HCV genotypes and epidemiological characteristics; severity of the disease; and response to interferon (IFN) therapy. Data from 14 tertiary referral centres, corresponding to 1872 patients with chronic hepatitis C, were prospectively collected from 1989 to 1997. HCV genotyping was performed using the line probe assay (LiPA). HCV genotypes 1b, 3, 1a, 2, 4 and a mixed infection were found in 41%, 22%, 16%, 11%, 4% and 4% of our population, respectively. HCV genotype distribution was homogeneous, except for genotype 2 that was found more frequently in the southwest than in the other regions (21% vs 9.2%) ( P =0.001). HCV distribution was associated with gender, age, and source and duration of infection. In multivariate analysis, these correlations were related to the source of infection, which was the only independent factor significantly associated with genotype ( P =0.001). Genotype 1b was significantly more common in patients with cirrhosis, but in multivariate analysis cirrhosis was independently related to older age at exposure and longer duration of infection ( P =0.001). A sustained response to IFN therapy was observed in 11% of patients infected with genotypes 1a or 1b vs 32% of those infected with genotypes 2 or 3 ( P =0.001). This study shows that HCV genotype is mainly related to the source infection, but not to the intrinsic pathogenicity of HCV, and is a strong predictor of sustained response to therapy.     

Mechanism of azathioprine-induced injury to hepatocytes: roles of glutathione depletion and mitochondrial injury

BACKGROUND/AIMS: We sought evidence that azathioprine causes cell death through reduced glutathione (GSH) depletion and mitochondrial injury. METHODS: Studies were conducted in primary cultures of rat hepatocytes and cultured Hep G2 cells. RESULTS: Azathioprine toxicity to rat hepatocytes was preceded by depletion of GSH. Prior GSH depletion (by treatment with buthionine sulfoximine) enhanced toxicity whilst supplemental GSH or N-acetylcysteine was protective. In hepatocytes, GSH is consumed during metabolism of azathioprine to 6-mercaptopurine. 6-Mercaptopurine was not toxic to hepatocytes, suggesting that the later steps in azathioprine metabolism were not related to the pathogenic mechanism. In Hep G2 cells, azathioprine did not alter levels of GSH and was not toxic. Ultrastructural studies showed hepatocyte mitochondrial lesions after exposure to azathioprine, but no features of apoptosis. Azathioprine produced rapid and profound depletion of adenosine 5'-triphosphate (ATP). Cyclosporin A and glycine afforded protection against azathioprine toxicity, and Trolox and high-dose allopurinol also attenuated injury. CONCLUSIONS: The mechanism of azathioprine toxicity to hepatocytes involves depletion of GSH leading to mitochondrial injury with profound depletion of ATP and cell death by necrosis. Cell death was prevented by potent antioxidants, glycine and blocking the mitochondrial permeability transition pore.     

Detection of hepatitis C virus by polymerase chain reaction and response to interferon-alpha therapy: relationship to genotypes of hepatitis C virus.

To investigate the relationship between genotypes of hepatitis C virus and response to interferon-alpha therapy, hepatitis C virus RNA was assayed by polymerase chain reaction with three sets of primers and probes in 70 patients with non-A, non-B chronic hepatitis who received interferon-alpha. Twenty-four patients sustained long-term remissions (complete responders). Polymerase chain reaction for 5'-terminal noncoding region detected hepatitis C virus RNA in 94.3% (66 of 70) of the patients. Polymerase chain reaction for nonstructural region 3, in which primers and a probe were synthesized to be identical to hepatitis C virus-J, detected hepatitis C virus RNA in 40 patients. Polymerase chain reaction for nonstructural region 5-in which sequences of primers and a probe were derived from hepatitis C virus-K2, a genotype different from hepatitis C virus-J--detected hepatitis C virus RNA in 17 patients. Only one patient was positive on both nonstructural region 3 and nonstructural region 5 polymerase chain reaction. Nucleotide sequence of clones obtained from 5' terminal noncoding region polymerase chain reaction products of two patients positive on polymerase chain reaction for nonstructural region 3 and negative on polymerase chain reaction for nonstructural region 5 (group 1) corresponded to that of the hepatitis C virus-J group, and those of clones from two patients negative on polymerase chain reaction for nonstructural region 3 and positive on polymerase chain reaction for nonstructural region 5 (group 2) corresponded to that of hepatitis C virus-K2.(ABSTRACT TRUNCATED AT 250 WORDS)     

三磷酸腺苷对房室结前向传导的影响与房室结前传功能的相关性研究

目的　评价三磷酸腺苷 (ATP)对房室结前向传导的影响与房室结前传功能的相关性。方法　选择 19例预激综合征行射频消融术后且房室结前传文氏点等于或大于 15 0次/分的患者 ,测量房室结前传功能 (前传文氏点、2 :1点)和有效不应期 ,在心房起搏时静脉推注ATP,直至 0 .3 0mg/kg或出现房室前传阻断。结果　房室结前传文氏点平均为 (3 0 5 .79± 4 5 .0 1)ms,前传 2 :1点平均为(2 62 .63±2 4 .5 5 )ms,房室结前传有效不应期平均为(2 3 5 .78± 5 9.2 4 )ms,阻断房室结前传所需ATP平均剂量为(0 .16±0 .0 5 7)mg/kg,总量平均为 (11.4±4 .5 3 )mg。房室结前传文氏点、2 :1点 (ms)与阻断其前向传导所需ATP剂量呈负相关 (r=- 0 .797,P <0 .0 1;r=- 0 .699,P <0 .0 1)。房室结前传有效不应期与阻断其传导所需ATP剂量呈负相关(r=- 0 .4 65 ,P <0 .0 5 )。结论　阻断房室结前向传导所需ATP与房室结前传功能、房室结前传有效不应期有明显相关性 ,房室结前传功能越好 ,房室结前传有效不应期越短 ,阻断房室结前传所需ATP剂量越大。