Pharmacogenetic study of drug-metabolising enzyme polymorphisms on the risk of anti-tuberculosis drug-induced liver injury: a meta-analysis

Hepatotoxicity during Treatment for Tuberculosis in People Living with HIV/AIDS

Hepatotoxicity is frequently reported as an adverse reaction during the treatment of tuberculosis. The aim of this study was to determine the incidence of hepatotoxicity and to identify predictive factors for developing hepatotoxicity after people living with HIV/AIDS (PLWHA) start treatment for tuberculosis. This was a prospective cohort study with PLWHA who were monitored during the first 60 days of tuberculosis treatment in Pernambuco, Brazil. Hepatotoxicity was considered increased levels of aminotransferase, namely those that rose to three times higher than the level before initiating tuberculosis treatment, these levels being associated with symptoms of hepatitis. We conducted a multivariate logistic regression analysis and the magnitude of the associations was expressed by the odds ratio with a confidence interval of 95%. Hepatotoxicity was observed in 53 (30.6%) of the 173 patients who started tuberculosis treatment. The final multivariate logistic regression model demonstrated that the use of fluconazole, malnutrition and the subject being classified as a phenotypically slow acetylator increased the risk of hepatotoxicity significantly. The incidence of hepatotoxicity during treatment for tuberculosis in PLWHA was high. Those classified as phenotypically slow acetylators and as malnourished should be targeted for specific care to reduce the risk of hepatotoxicity during treatment for tuberculosis. The use of fluconazole should be avoided during tuberculosis treatment in PLWHA.

Genetic Polymorphisms of Glutathione S-Transferase P1 (GSTP1) and the Incidence of Anti-Tuberculosis Drug-Induced Hepatotoxicity

Background

Anti-tuberculosis drug-induced hepatotoxicity (ATDH) is one of the most common adverse effects associated with tuberculosis (TB) therapy. Animal studies have demonstrated important roles of glutathione S-transferases in the prevention of chemical-induced hepatotoxicity. The aim of this study was to investigate the relationship between single nucleotide polymorphisms (SNPs) of glutathione S-transferase P1 (GSTP1) and ATDH in TB patients.

Methods

We used two independent samples for this genetic association study. In the initial prospective study, 322 newly diagnosed TB patients were followed up for three months after initiating anti-TB therapy. In an independent retrospective study, 115 ATDH patients and 116 patients without ATDH were selected to verify the results of the prospective study. Tag-SNPs of GSTP1 were genotyped either with the MassARRAY platform or the improved multiple ligase detection reaction (iMLDR) method. The associations between SNPs and ATDH were analyzed by logistic regression analysis adjusting for confounding factors.

Results

Of the 322 patients recruited in the prospective cohort, 35 were excluded during the 3 months of follow-up, and 30 were diagnosed with ATDH and were considered as the ATDH group. The remaining 257 subjects without ATDH were considered as the non-ATDH group. After correction for potential confounding factors, significant differences were found for rs1695 (A>G) under an allelic model (OR = 3.876, 95%CI: 1.258011.905; P = 0.018). In the retrospective study, rs1695 allele A also had a higher risk of ATDH (OR = 2.10, 95%CI: 1.17–3.76; P = 0.012). We only found rs4147581AA genotype under a dominant model was related to ATDH in the prospective study (OR = 2.578, 95%CI: 1.076–6.173; P = 0.034).

Conclusions

This is the first study to suggest that GSTP1 genotyping can be an important tool for identifying patients who are susceptible to ATDH. This result should be verified in independent large sample studies and also in other ethnic populations.

Genotype and allele frequencies of isoniazid-metabolizing enzymes NAT2 and GSTM1 in Latvian tuberculosis patients

Pharmacogenomic testing of tuberculosis drug-metabolizing enzyme genes was proposed as a strategy to identify patients at risk for suboptimal responses to medications. However, variations of the genotype frequencies among ethnic groups exist and new alleles are been identified. The aim of this study was to identify polymorphisms of genes encoding metabolic enzymes NAT2 and GSTM1 in tuberculosis patients in Latvia and to estimate the frequency of NAT2 slow acetylator and GSTM1 null genotypes. In total, 85 DNA samples were genotyped, all individuals were Caucasian. An ethnic heterogeneity reflecting the multiethnic population of the country was observed. 49 patients were Latvians, 30 were Russians and 6 of other ethnicity. In total, 7 NAT2 alleles were identified: *4, *5, *6, *7, *11, *12, * and *13. The most frequent was the slow acetylation allele NAT2*6 (frequency 0.388) followed by the slow acetylation allele NAT2*5 and the rapid acetylation allele NAT2*4 (frequencies 0.306 and 0.194, respectively). The predominance of slow (51.8%) and intermediate (43.5%) acetylators compared with rapid acetylators (4.7%) was observed. The GSTM1 null genotype was detected in 48.2% of tuberculosis patients. When subgroup analysis was performed according to ethnicity, the results showed that neither NAT2 allele frequencies nor GSTM1 null genotype frequency did not differ significantly in TB patients of Latvian or Russian ethnicity. Overall, genotyping results were similar with previous reports of a NAT2 gene variation and GSTM1 null genotype frequency in Caucasians. Our findings have a contribution for the pharmacogenetics-based tuberculosis therapy in Latvia in future.

Update meta-analysis of the CYP2E1 RsaI/PstI and DraI polymorphisms and risk of antituberculosis drug-induced hepatotoxicity: evidence from 26 studies

WHAT IS KNOWN AND OBJECTIVE

Several studies have investigated the association of the CYP2E1 RsaI/PstI and/or DraI polymorphisms with susceptibility to antituberculosis drug-induced hepatotoxicity (ATDH), but the results have been inconsistent. Therefore, we performed a large meta-analysis to determine a more precise estimation of this relationship.

METHODS

The PubMed, EMBASE, China National Knowledge Infrastructure and Chinese Biomedical Literature databases were systematically searched to identify relevant studies. Meta-analyses based on the entire population and subgroups were performed to examine the association between CYP2E1 polymorphisms and susceptibility to ATDH. The odds ratio (OR) with 95% confidence interval (CI) was used to assess the strength of the associations.

RESULTS AND DISCUSSION

Twenty-six studies with a total of 7423 participants were analysed. The overall ORs of relevant studies demonstrated that the CYP2E1 RsaI/PstI C1/C1 genotype was associated with an elevated risk of ATDH (OR = 1·32, 95% CI 1·03-1·69, P = 0·027), but for the DraI polymorphism there was no increase in risk (OR = 1·05, 95% CI 0·80-1·37, P = 0·748). In subgroup analyses of the RsaI/PstI polymorphism, significant results were found in East Asians, patients who used isoniazid + rifampicin + pyrazinamide + ethambutol and patients with twice the upper limit of normal as the minimum standard for defining ATDH.

WHAT IS NEW AND CONCLUSION

This meta-analysis suggests that there is an increased risk of ATDH in individuals carrying the C1/C1 genotype of the CYP2E1 RsaI/PstI polymorphism. However, no association was found for the DraI polymorphism.

Susceptibility of N-acetyltransferase 2 slow acetylators to antituberculosis drug-induced liver injury: a meta-analysis

AIM

This study aimed to evaluate the association between N-acetyltransferase 2 (NAT2) gene polymorphisms and the risk of antituberculosis drug-induced liver injury (ATLI).

MATERIALS & METHODS

A meta-analysis was performed including 27 studies with 1289 cases and 5462 controls. Odds ratio with 95% CI was used to evaluate the strength of association.

RESULTS

Our meta-analysis found that NAT2 slow acetylators were associated with increased risk of ATLI compared with fast and intermediate acetylators when standard dose of isoniazid was administrated (odds ratio: 3.08; 95% CI: 2.29-4.15).

CONCLUSION

Individuals with NAT2 slow acetylators may have increased risk of ATLI when standard dose of isoniazid was used. Detection of NAT2 genotype may benefit to the prevention of ATLI.

Novel perspectives in the tuberculosis treatment: Administration of isoniazid through the skin

Despite its high efficacy in anti-tuberculosis therapy, the oral administration of isoniazid (INH) may lead to poor patient compliance due to hepatotoxicity events. In this context, the transdermal administration of INH was evaluated, for the first time, since this route avoids hepatic first pass effect. INH was applied to porcine skin in Franz diffusion chambers alone and with 5% menthol, limonene or Transcutol(®). Infrared and DSC analyses were selected for mechanistic studies. The transdermal absorption of INH was sufficient to ensure a systemic therapeutic effect. Menthol was not able to improve the absorption of INH, but it increased the drug accumulation in skin compared to the control (1.4-fold). Transcutol(®) reduced permeation flux of INH (2.2-fold) and also increased the amount of drug retained in skin (1.7-fold). Limonene was the most effective excipient since it increased permeation flux of INH (1.5-fold) and lag time was greatly shortened (2.8-fold). DSC and FTIR analyses of limonene-treated skin suggest higher degree of disorder in lipid bilayers. Transdermal delivery of INH was positively correlated with logP of chemical enhancers. INH can be efficiently delivered by skin route and specific excipients may be selected depending on intended use.

Pharmacogenomics of antimicrobial agents

Antimicrobial efficacy and toxicity varies between individuals owing to multiple factors. Genetic variants that affect drug-metabolizing enzymes may influence antimicrobial pharmacokinetics and pharmacodynamics, thereby determining efficacy and/or toxicity. In addition, many severe immune-mediated reactions have been associated with HLA class I and class II genes. In the last two decades, understanding of pharmacogenomic factors that influence antimicrobial efficacy and toxicity has rapidly evolved, leading to translational success such as the routine use of HLA-B*57:01 screening to prevent abacavir hypersensitivity reactions. This article examines recent advances in the field of antimicrobial pharmacogenomics that potentially affect treatment efficacy and toxicity, and challenges that exist between pharmacogenomic discovery and translation into clinical use.

Pharmaceutical care for patients with anti-tuberculosis drug induced liver injury

Drug induced liver injury is one of the most important and serious adverse effects of anti-tuberculosis drugs. The clinical features of anti-tuberculosis drug induced liver injury (ATLI) ranges from asymptomatic alanine aminotransferase (ALT) elevations to acute hepatitis symptoms, and the mortality cases associated with liver failure are not rare. ATLI diminishes the effectiveness of anti-tuberculosis treatment, as they may cause non-adherence, and further leads to treatment interruption, recurrence or the emergence of drug resistance. The aim of this paper is to discuss the clinical features, mechanisms, risk factors and treatment principles for ATLI. In addition, the reasonable adjustment of anti-tuberculosis treatment and implementation of pharmaceutical care are also reviewed so as to provide thoughts on the prevention, diagnosis and timely intervention of ATLI.

Pharmacogenetic testing in idiosyncratic drug-induced liver injury: current role in clinical practice

In contrast to the studies that have explored association of genetic variants with other complex traits, those investigating hepatotoxicity have identified risk alleles with substantially higher risk ratios for the susceptibility to drug-induced liver injury (DILI). In addition, a relatively small number of human leukocyte antigen (HLA) alleles have overlapping associations with a variety of adverse reactions including DILI, cutaneous hypersensitivity and drug-induced pancreatitis. However, if used as a test prior to prescription to prevent potential adverse reaction, genotyping would have a very high negative predictive value, yet a low positive predictive value based on the low incidence of DILI. One potential consideration is to treat all relevant HLA genotypes as one panel covering different forms of adverse drug reactions, thereby improving the positive predictive value of the panel and widen its application. The majority of HLA alleles associated with DILI have a very high negative predictive value; therefore, they can be used to rule out hepatotoxicity caused by particular drugs. A high negative predictive value of a genetic test can be used to identify the correct agent underlying DILI when the patient had been exposed to two concomitant medications with a potential to cause DILI. Inclusion of genetic tests in the causality assessment of an event, where DILI is suspected, may improve consistency and precision of causality assessment tools. A recent clinical trial used N-acetyltransferase 2 genotyping to determine the appropriate dose of isoniazid in an anti-tuberculosis therapeutic regimen and demonstrated that pharmacogenetic-based clinical algorithms have the potential to improve efficacy of a drug and to reduce DILI.

Meta-Analysis-Based Preliminary Exploration of the Connection between ATDILI and Schizophrenia by GSTM1/T1 Gene Polymorphisms

Anti-tuberculosis drugs have some adverse effects such as anti-tuberculosis drug-induced liver injury (ATDILI) and mental disorders. The involvement of glutathione S-transferase (GST) genes in pathogenesis of ATDILI or schizophrenia (SCZ) has been reported. Therefore, GST genes may exemplify molecular connectors between ATDILI and SCZ. However, association studies of GSTM1/T1 polymorphisms with these two diseases have yielded conflicting results. After searching case-control association studies in PubMed, ISI Web of Science, EMBASE, Chinese National Knowledge Infrastructure (CNKI), and Chinese BioMedical Literature Database, we performed meta-analyses across a total of 20 published association studies on 3146 subjects for the association of GSTM1 and ATDILI, 2587 for the GSTT1-ATDILI association, 2283 for GSTM1-SCZ and 1116 for GSTT1-SCZ to test the associations of GSTM1/T1 polymorphisms with ATDILI and SCZ. The GSTM1 present genotype was significantly associated with decreased risks of ATDILI (risk ratio(RR): 0.81, 95% confidence interval (CI): 0.75–0.88, P < 0.0001) and SCZ (RR: 0.88, 95%CI: 0.80–0.96, P = 0.004) according to the fixed-effect model, while the GSTT1 present genotype was significantly associated only with a high risk of SCZ (RR: 1.17, 95%CI: 1.04–1.32, P = 0.01) according to both the random- and fixed-effect models, but not with ATDILI (P = 0.82) according to the fixed-effect model. Moreover, these significant results were supported with moderate evidence according to the Venice criteria. These results indicate that GSTM1 represents a genetic connection between ATDILI and SCZ, and suggest that ATDILI and SCZ may be co-occurring for the subjects with GSTM1 null genotype.

Involvement of cytochrome P450 1A1 and glutathione S-transferase P1 polymorphisms and promoter hypermethylation in the progression of anti-tuberculosis drug-induced liver injury: a case-control study

Background

Anti-tuberculosis (anti-TB) drug-induced liver injury (ADLI) is one of the most common adverse effects associated with TB treatment. Cytochrome P450 (CYP) 1A1 and glutathione S-transferase (GST) P1 are important phase I/II metabolizing enzymes involved in drug metabolism and detoxification. Genetic polymorphism and CpG island methylation have been reported as factors influencing the expression of CYP1A1 and GSTP1.

Objective

This study aimed to determine the potential relationships of CYP1A1 and GSTP1 polymorphisms and CpG island methylation with ADLI risk.

Design

This was a population-based one-to-one matched case–control study.

Setting

The subjects were patients with TB receiving treatment in China from December 2010 to June 2013.

Patients

In total, 127 patients with TB and ADLI (case group) and 127 patients with TB but without liver injury (control group) were included in this study. Subjects were matched in terms of sex, age, and therapeutic regimen.

Methods

The general condition of each patient was assessed using questionnaires. The CYP1A1 MspI and GSTP1 Ile105Val polymorphisms as well as methylation status were detected by polymerase chain reaction (PCR)–restriction fragment length polymorphism and the methylation-specific PCR method.

Results

We found no significant difference in GSTP1 and CYP1A1 genotypes between the two groups, probably because the sample size was not large enough; however, patients with ADLI had significantly higher GSTP1 and CYP1A1 promoter methylation rates than control subjects [odds ratio (OR) = 2.467 and 2.000, respectively]. After adjusting for drinking, which significantly differed between the groups as per univariate analysis, we found that hypermethylation of GSTP1 and CYP1A1 promoters was associated with ADLI (OR = 2.645 and 2.090, respectively).

Conclusion

Hypermethylation of CpG islands of GSTP1 and CYP1A1 promoters may thus play important roles in the development of ADLI and provide evidence of being used as novel markers for ADLI risk prediction.

Key factors of susceptibility to anti-tuberculosis drug-induced hepatotoxicity

Anti-tuberculosis drug-induced hepatotoxicity (ATDH) is one of the leading adverse drug reactions during the course of tuberculosis treatment and poses a considerable challenge to clinicians and researchers. Previous studies have revealed the important contribution of drug metabolism and transporter enzymes to the complexity of ATDH. The emerging roles of immune response and oxidative stress resulting from reactive metabolite in the development of ATDH have also gained attention recently. Both non-genetic and genetic factors can have a significant impact on the susceptibility to ATDH, consequently altering the risk of hepatotoxicity in susceptible individuals. Non-genetic risk factors associated with ATDH include host factors, environment factors and drug-related factors. Genetic factors contributing to the susceptibility of ATDH involve genetic variations in bioactivation/toxification pathways via the cytochrome P450 enzymes (phase I), detoxification reactions by N-acetyl transferase 2, glutathione S-transferase and uridine diphosphate glucuronosyltransferase (phase II) and hepatic transport (phase III), together with immunological factors and antioxidant response. Better understanding of these factors may help to predict and prevent the occurrence of ATDH and develop more effective treatments. This review focuses on the mechanisms of ATDH and the key factors of susceptibility associated with drug metabolism, hepatic transport, immune response and oxidative stress.

Future of pharmacogenetics-based therapy for tuberculosis

Personalized medicine uses technology to enable a level of personalization not previously practical. Currently, tuberculosis (TB) therapy is not personalized. Previous reports have shown that a genetic polymorphism of NAT2 is associated with large interindividual and inter-racial differences in the toxicity and efficacy of isoniazid. Herein, we show the safety and efficacy of a pharmacogenetics-based standard TB therapy and also provide a schematic presentation that proposed therapeutic approaches for latent TB infection (LTBI) using NAT2 genotyping. Our data show that the pharmacogenetics-based TB therapy is safer and more efficacious than the standard therapy. Therefore, the therapy using NAT2 genotyping proposed for LTBI herein will be safer and more efficacious than the standard LTBI therapy. Introduction of this therapy with NAT2 genotyping will be one of the cornerstones of personalized medicine.

Pharmacogenetics of isoniazid-induced hepatotoxicity

Tuberculosis is still a major problem in some developed and developing countries. The poor compliance to the treatment of tuberculosis patients due to the adverse events was supposed to be an important factor contributing to the high prevalence. This review aims to clarify the role and the pharmacological mechanism of the genes involved in the isoniazid-induced hepatotoxicity. We selected English articles of studies in human from PubMed up to May 2014 with the keywords pharmacogenetic, isoniazid and hepatotoxicity, N-acetyl transferase 2 (NAT2), CYP2E1 and glutathione S transferase (GST). Polymorphisms of NAT2, CYP2E1 and GST1 could increase patients' susceptibility to isoniazid-induced hepatotoxicity. The rapid acetylators of NAT2 and rapid metabolizers of CYP2E1 showed increased concentrations of hepatotoxic metabolites. However, the rapid metabolizers of GST1 could decrease the concentration of hepatotoxic metabolites. Some studies of human leukocyte antigen (HLA), Uridine 5'-dipphospho (UDP) glucuronosyltransferase (UGT), nitric oxide synthase (NOS), Broad complex, Tramtrack, Bric-a-brac (BTB) and cap'n'collar type of basic region leucine zipper factor family (CNC) homolog (BACH) and Maf basic leucine zipper protein (MAFK) polymorphisms showed their roles in isoniazid-induced hepatotoxicity by modifying the expression of antioxidant enzymes. A better insight into the role of polymorphisms of HLA, UGT, NOS, BACH and MAFK in addition to NAT2, CYP2E1 and GST1 in the hepatotoxicity of isoniazid may support physicians in monitoring patients hepatotoxicity symptoms and laboratory data and optimizing pharmacotherapy. Future studies about the role of such polymorphisms in different ethnicities are suggested.

[Tuberculosis: relevance of isoniazid dosage in prevention of liver side effects]

OBJECTIVE

Several recent studies have established a correlation between NAT2 polymorphism and hepatotoxicity induced by isoniazid. The objective of this work was to assess the place of isoniazid dosage, marker of acetylation phenotype, in clinical practice in the department of Haute-Garonne.

METHODS

Data from reportable disease of tuberculosis and the results of isoniazid dosage performed at the pharmacokinetics and clinical toxicology laboratory were used during the period 2009-2012.

RESULTS

The current practice of dosage is far from being systematical: only 3.9% of patients who developed tuberculosis have benefited from isoniazid dosage. The isoniazid initial posology was adapted to the acetylation capacity for only 33.3% of patients.

CONCLUSION

A decision tree was realized and used to identify populations (low metabolism) liable to benefit from isoniazid dosage.

Association of the CYP2B6 gene with anti-tuberculosis drug-induced hepatotoxicity in a Brazilian Amazon population

OBJECTIVES

The treatment of tuberculosis (TB) remains a challenge owing to the high incidence of drug-induced hepatotoxicity. The aim of this study was to examine the effect of two gene polymorphisms, one in the CYP2B6 (rs3745274) gene and one in the CYP3A5 (rs776746) gene, on the development of hepatotoxicity in patients treated with anti-TB drugs in a Brazilian Amazon population.

METHODS

TB patients who were treated with anti-TB drugs were examined for hepatotoxicity, an adverse effect that is characterized by liver damage. The genotype frequencies of the CYP2B6 and CYP3A5 genes examined in this study were assessed using RT-PCR.

RESULTS

Thirty-one of the 220 subjects (14.1%) included in this study developed drug-induced hepatotoxicity. The result was significant when the TT homozygous mutant of the CYP2B6 gene was analyzed with additional key variables (p=0.046; odds ratio (OR) 0.063, 95% confidence interval (CI) 0.004-0.955), which may explain the hepatotoxicity results in this study. Using a univariate statistical model to associate the CYP3A5 gene A6986G polymorphism with the examined drugs, the results did not differ between samples from individuals with and without hepatotoxicity (p=0.176; OR 0.562, 95% CI 0.255-1.238).

CONCLUSIONS

The G516T polymorphism in the CYP2B6 gene is a key predictor of the therapeutic response to treatment in TB patients.

The association between HLA-DQB1 polymorphism and antituberculosis drug-induced liver injury: a Case-Control Study

WHAT IS KNOWN AND OBJECTIVE

Research on genetic factors associated with antitubercular drug-induced liver injuries (ATLI) has been reported. However, most of the research has focused on genetic polymorphisms of genes encoding metabolic enzymes, including NAT2, GST and CYP450. It is probable that the immune system also contributes to the onset of drug adverse effects. A few small studies have explored the possible association of HLA genes with drug-induced liver injuries (DILI), but more supportive evidence from larger studies or prospective cohort designs is needed. We aim to explore the possible association of HLA-DQB1 gene polymorphisms with ATLI in a case-control study.

METHODS

A case-control study design was used. ATLI was recorded in a prospectively followed-up cohort of patients receiving antituberculosis treatment. Identified cases were matched with control tuberculosis patients within the same cohort but with no adverse effects in 1 : 1 ratio. We used the sequence-based typing method to determine the HLA-DQB1 genotypes. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using conditional logistic regression.

RESULTS AND DISCUSSION

Eighty-nine cases were included in this case-control study. HLA-DQB1 typing was successful for 177 subjects. No association between frequency of HLA-DQB1 genotypes and ATLI was statistically significant in univariate analyses. Multivariate analysis using the conditional logistic regression model revealed that the individuals with two DQB1*05 alleles were at higher risk of ATLI than control subjects. The OR was 5.28 adjusted for use of liver protective drugs and weight (10/88 VS 2/88, 95% CI: 1.134-24.615, P = 0.034). Analysis according to the liver injury type showed that both mixed liver injury patients and cholestatic/mixed liver injury patients had higher proportions of DQB1*05 : 02 alleles (P values were 0.028 and 0.005, respectively).

WHAT IS NEW AND CONCLUSION

This study suggests that ATLI was more likely in subjects of HLA-DQB1*05/*05 genotype. Further studies are needed to verify this association.

Expression of NAT2 in immune system cells and the relation of NAT2 gene polymorphisms in the anti-tuberculosis therapy in Mexican mestizo population

Arylamine N-acetyltransferase 2 (NAT2) metabolizes isoniazid (INH) and Single Nucleotide Polymorphisms (SNP) responsible for its activity has been reported. The aim of this study in the Mexican mestizo population was to evaluate NAT2 expression at the protein level in immune cells, as well as the distribution and frequency of six NAT2 SNPs and their association with anti-TB therapy, by measuring the plasma levels of INH and Acetyl-INH (AcINH). We performed genotyping assays of NAT2 SNPs in 40 TB patients and 121 healthy volunteers by real-time PCR. A method for detecting NAT2 in immune cells using flow cytometry was developed. Plasma concentrations of INH and AcINH were obtained by HPLC in TB patients and the Metabolic Ratio (MR) was calculated. The phenotypes obtained in the healthy volunteers were as follows; 18.87 % of subjects had the rapid acetylator phenotype, 45.45 % had the intermediate phenotype and 39.66 % exhibited the slow acetylator phenotype. In the TB patient group, 35 % of patients had the rapid acetylator phenotype, 32.5 % were intermediate and 32.5 % showed the slow acetylator phenotype. A higher expression level of NAT2 in innate immune cells from TB patients compared to those from healthy volunteers was detected (P < 0.013). In TB patients the MR showed a bimodal distribution with an antimode of 0.7, which was used as a threshold value for acetylator classification. A high correspondence between the rapid and slow acetylator phenotype with MR was demonstrated. In conclusion, the 282C>T, 341T>C, 481C>T, 590G>A, 803A>G, 857G>A SNPs of NAT2 gene provides accurate for prediction of the acetylator phenotype in Mexican mestizo population. A statistical difference was found in frequency of rapid metabolizer phenotype, which was higher in TB patients. In addition, the expression of NAT2 protein in immune cells can lead to further studies related to its functional role in the innate immune response against M. tuberculosis and other xenobiotics metabolized by this enzyme.

Association of N-acetyltransferase 2 and cytochrome P450 2E1 gene polymorphisms with antituberculosis drug-induced hepatotoxicity in Western India

BACKGROUND AND AIM

Tuberculosis (TB) is a major public health problem in India. Despite the treatment availability and monitoring, drug-induced hepatotoxicity (DIH) is a serious concern and can lead to discontinuation of treatment. Anti-TB DIH is well known and can aggravate because of pharmacokinetic and pharmacodynamic interactions. Genetic polymorphism in the drug-metabolizing enzyme genes is an important factor that predisposes certain fraction of the population to drug-induced toxicity. The purpose of this study was to assess the association of N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) gene polymorphism with anti-TB DIH in Western Indian population.

METHODS

A prospective cohort study of 215 patients taking treatment against TB was performed. The NAT2 and CYP2E1 genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism methods. Logistic regression model was used to calculate odds ratio at 95% confidence interval and their respective P values.

RESULTS

The risk of anti-TB DIH was significantly higher in slow acetylator (SA) than in intermediate and rapid acetylator of NAT2 genotypes (odds ratio: 2.3, P = 0.01). We also observed the homozygous point mutation at position 481, associated with higher risk of hepatotoxicity (P < 0.01). The major haplotype NAT2*4 seems to provide protection in DIH compared with non-DIH TB patients (P = 0.04). However, we did not find a significant association between CYP2E1 genotypes and anti-TB DIH.

CONCLUSION

Increased susceptibility to isoniazid (INH)-induced hepatotoxicity due to presence of NAT2 SA polymorphism was demonstrated in Western Indian population. NAT2 genotyping can therefore serve as an important tool for identifying patients predisposed to anti-TB DIH.

Hepatocyte growth factor protects against isoniazid/rifampicin-induced oxidative liver damage

The worldwide increment of multidrug- and extensively drug-resistant tuberculosis has emphasized the importance of looking for new options in therapeutics. Long-time usage or higher doses of isoniazid and rifampicin have been considered for the treatment of multidrug-resistant tuberculosis; however, the risk of liver failure is proportionally increased. Hepatocyte growth factor (HGF) is a multitask growth factor that stimulates both antiapoptotic and antioxidant responses that counteract the toxic effects of drug metabolism in the liver. The present work was focused to address the antioxidant and antiapoptotic effects of HGF on isoniazid- and rifampicin-induced hepatotoxicity. BALB/c mice were subjected to rifampicin (150mg/kg, intragavage [ig]) plus isoniazid (75mg/kg, ig) for 7 days. Increments in alanine aminotransferase activity, steatosis, apoptosis, and oxidative stress markers were found in animals. Recombinant HGF (iv) prevented all the harmful effects by increasing the activation of Erk1/2 and PKCδ signaling pathways and glutathione (GSH) synthesis. Furthermore, inhibition of endogenous HGF with anti-HGF antibody (iv) enhanced the isoniazid- and rifampicin-induced oxidative stress damage and decreased the GSH content, aggravating liver damage. In conclusion, HGF demonstrated to be a good protective factor against antituberculosis drug-induced hepatotoxicity and could be considered a good adjuvant factor for the use of high doses of or the reintroduction of these antituberculosis drugs.

Pharmacogenomics of severe cutaneous adverse reactions and drug-induced liver injury

Rare but severe adverse drug reactions (ADRs) are an important issue in drug development and in the proper usage of drugs during the post-approval phase. The ability to predict patient susceptibility to severe ADRs would prevent drug administration to high-risk patients. This would save lives and ensure the quality of life for these patients, but occurrence of idiosyncratic severe ADRs had been very difficult to predict for a long time. However, in this decade, genetic markers have been found for several ADRs, especially for severe cutaneous adverse reactions (SCARs) and drug-induced liver injury (DILI). In this review, we summarize recent progress in identifying genetic markers for SCARS and DILI, and discuss issues that remain unresolved. As for SCARs, associations of HLA-B*15:02 or HLA-A*31:01 and HLA-B*58:01 have been revealed for carbamazepine- and allopurinol-related Stevens-Johnson syndrome and toxic epidermal neclolysis, respectively. HLA-B*57:01 is strongly associated with abacavir-induced hypersensitivity syndrome. Several HLA alleles also demonstrate drug-specific associations with DILI, such as HLA-A*33:03 for ticlopidine, HLA-B*57:01 for flucloxacillin and HLA-DQA1*02:01 for lapatinib. Efforts should be continued to find other genetic markers to achieve high predictability for ADRs, with the goal being development of genetic tests for use in clinical settings.

GSTM1 and GSTT1 genetic polymorphisms and risk of anti-tuberculosis drug-induced hepatotoxicity: an updated meta-analysis

The results of studies investigating the associations between GSTM1 and GSTT1 polymorphisms and anti-tuberculosis drug-induced hepatotoxicity (ADIH) risk exhibit much controversy. Therefore, a meta-analysis was performed in order to examine the associations between GST variants and ADIH risk. A total of 451 relevant studies were identified through the digital medical databases Medline, Embase, and CBM published up to October 2012. Thirteen individual case-control studies were eventually recruited for GSTM1 null polymorphism (including 951 ADIH cases, 1,922 controls) and 12 studies for GSTT1 null polymorphism (847 cases, 1,811 controls). Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were appropriately calculated from fixed-effects or random-effects models. Subgroup analyses were stratified by ethnicity and different treatment combinations. The overall ORs of relevant studies that exhibited elevated ADIH risk was significantly associated with GSTM1 null genotypes (OR = 1.36, 95% CI 1.04-1.79), but for the GSTT1 polymorphism, no difference was found (OR = 0.98, 95% CI 0.82-1.18). In the subgroup analyses, the pooled results showed that GSTM1 null allele carriers had a significant association with ADIH risk in East Asians and the patients who used isoniazid (INH) + rifampicin (RMP) + pyrazinamide (PZA) + ethambutol (EMB), or + streptomycin (SM) (HRZES), but the opposite result was observed for patients using HR. Moreover, the GSTT1 null genotype evaluated the susceptibility to ADIH for tuberculosis using HRZ. This meta-analysis provides evidence that there may be an increased risk of ADIH in individuals with null genotypes of GSTM1 in the total population, especially East Asians and patients receiving HRZE or HRZES. However, polymorphisms of the GSTT1 null genotype seem to have no association with susceptibility to ADIH, except for patients receiving HRZ.