Glutathione S transferase theta 1 gene (GSTT1) null genotype is associated with an increased risk for acquired aplastic anemia in children

Unbiased Single-Cell Sequencing of Hematopoietic and Immune Cells from Aplastic Anemia Reveals the Contributors of Hematopoiesis Failure and Dysfunctional Immune Regulation

Aplastic anemia (AA) is a bone marrow (BM) failure syndrome mediated by hyperactivated T-cells with heterogeneous pathogenic factors. The onset of BM failure cannot be accurately determined in humans; therefore, exact pathogenesis remains unclear. In this study, a cellular atlas and microenvironment interactions is established using unbiased single-cell RNA-seq, along with multi-omics analyses (mass cytometry, cytokine profiling, and oxidized fatty acid metabolomics). A new KIR+ CD8+ regulatory T cells (Treg) subset is identified in patients with AA that engages in immune homeostasis. Conventional CD4+ T-cells differentiate into highly differentiated T helper cells with type 2 cytokines (IL-4, IL-6, and IL-13), GM-SCF, and IL-1β. Immunosuppressive homeostasis is impaired by enhanced apoptosis of activated Treg cells. Pathological Vδ1 cells dominated the main fraction of γδ T-cells. The B/plasma, erythroid, and myeloid lineages also exhibit substantial pathological features. Interactions between TNFSF12-TNFRSF12A, TNF-TNFRSF1A, and granzyme-gasdermin are associated with the cell death of hematopoietic stem/progenitor (HSPCs), Treg, and early erythroid cells. Ferroptosis, a major driver of HSPCs destruction, is identified in patients with AA. Furthermore, a case of twins with AA is reported to enhance the persuasiveness of the analysis. These results collectively constitute the cellular atlas and microenvironment interactions in patients with AA and provide novel insights into the development of new therapeutic opportunities.

The relationship between interferon-gamma (INF-γ) single nucleotide polymorphism +874(T/A) and occurrence risk of aplastic anemia: a meta-analysis

Objective: This meta-analysis was designed to investigate the association between interferon-gamma (IFN-γ) polymorphisms and occurrence risk of aplastic anemia.Methods: Literature search was conducted in PubMed, Embase and Cochrane Library up to April 2018. The pooled odds ratios (ORs) and 95% confidence interval (CI) were calculated by R 3.12.Results: Total five studies with 304 aplastic anemia patients and 588 controls were included. The statistically significant results were found in the following models: allele genetic model (T vs A: OR = 2.1749, 95% CI = 1.6825-2.8114, P < 0.01), additive genetic model (TA vs AA: OR = 2.1071, 95% CI = 1.3962-3.1799, P < 0.01; TT vs AA: OR = 4.5788, 95% CI = 2.6606-7.8797, P < 0.01), recessive genetic model (TT vs AA + TA: OR = 2.5579, 95% = 1.6680-3.9226, P < 0.01), dominant genetic model (TT + TA vs AA: OR = 2.5599, 95% = 1.7424-3.7611, P < 0.01), the results suggested that the increased occurrence risk of aplastic anemia is significantly associated with the IFN-γ polymorphism.Conclusions: Patients with IFN-γ genotype carrying allele T have higher occurrence risk of aplastic anemia.

A hPSC-based platform to discover gene-environment interactions that impact human β-cell and dopamine neuron survival

Common disorders, including diabetes and Parkinson’s disease, are caused by a combination of environmental factors and genetic susceptibility. However, defining the mechanisms underlying gene-environment interactions has been challenging due to the lack of a suitable experimental platform. Using pancreatic β-like cells derived from human pluripotent stem cells (hPSCs), we discovered that a commonly used pesticide, propargite, induces pancreatic β-cell death, a pathological hallmark of diabetes. Screening a panel of diverse hPSC-derived cell types we extended this observation to a similar susceptibility in midbrain dopamine neurons, a cell type affected in Parkinson’s disease. We assessed gene-environment interactions using isogenic hPSC lines for genetic variants associated with diabetes and Parkinson’s disease. We found GSTT1^−/− pancreatic β-like cells and dopamine neurons were both hypersensitive to propargite-induced cell death. Our study identifies an environmental chemical that contributes to human β-cell and dopamine neuron loss and validates a novel hPSC-based platform for determining gene-environment interactions.

Diseases such as diabetes and Parkinson's manifest based on interactions between genes and environment. Here, the authors find among a panel of cell types that propargite, a common pesticide, induces pancreatic β-cell and dopamine neuron death and that loss of the gene GSTT1 confers hypersensitivity.

The clinical relevance and prognostic significance of microsomal epoxide hydrolase gene polymorphisms and their susceptibility to acquired aplastic anemia: an Egyptian study

BACKGROUND

Microsomal epoxide hydrolase enzyme (mEPHX) is involved in xenobiotics detoxification. Two variants of mEPHX, Tyr113His and His139Arg, have been described. Both may lead to acquired aplastic anemia (AA).

OBJECTIVES

Assessing mEPHX genetic polymorphisms and detecting their impact on susceptibility and prognosis in Egyptian AA patients.

PARTICIPANTS AND METHODS

mEPHX 113 and 139 genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 100 patients with AA and 100 control subjects.

RESULTS

Both mEPHX Tyr113His and His139Arg gene polymorphisms were associated with increased risk of developing AA, and have a significant impact of bad prognosis (p value < 0.01).

CONCLUSIONS

These mEPHX gene polymorphisms can be considered as risk factors and predictive molecular markers for prognosis in AA patients.

Association of GSTM1 and GSTT1 deletion polymorphisms with Pakistani aplastic anemia patients and controls and meta-analysis

Interaction of environmental and genetic elements plays a vital role in the pathogenesis of aplastic anemia (AA). Glutathione S-transferase (GST) is a key detoxifying enzyme. Absence or low levels of this enzyme may genetically predispose individuals to AA. GST genes GSTM1 and GSTT1 are polymorphic. The aim of this study was to screen Pakistani AA patients and controls for GSTM1 deletion GSTM0 and GSTT1 deletion GSTT0 and perform meta-analysis using our data and other published data regarding these polymorphisms. DNA samples from 137 patients and 220 controls were screened using multiplex polymerase chain reaction. GSTM0 emerged as susceptible genotype for AA in Pakistan with a percentage frequency of 49.6 % as compared to 30 % in controls with odds ratio (OR) of 2.25, 95 % confidence interval (CI) of 1.4-3.5 and corrected p = 0.006. The meta-analysis showed a significant association between the null genotype GSTT0 and AA in overall analysis with OR of 1.47, 95 % CI of 1.01-2.13 and p value of 0.04 in random effects model. Studies like these could play a role in understanding the underlying path in AA pathogenesis and therefore can help in designing means for prevention, diagnose and treatment.

Common polymorphic deletion of glutathione S-transferase theta predisposes to acquired aplastic anemia: Independent cohort and meta-analysis of 609 patients

Acquired aplastic anemia (AA) is a rare life-threatening bone marrow failure syndrome, caused by autoimmune destruction of hematopoietic stem and progenitor cells. Epidemiologic studies suggest that environmental exposures and metabolic gene polymorphisms contribute to disease pathogenesis. Several case-control studies linked homozygous deletion of the glutathione S-transferase theta (GSTT1) gene to AA; however, the role of GSTT1 deletion remains controversial as other studies failed to confirm the association. We asked whether a more precise relationship between the GSTT1 null polymorphism and aplastic anemia could be defined using a meta-analysis of 609 aplastic anemia patients, including an independent cohort of 67 patients from our institution. We searched PubMed, Embase, and the Cochrane Database for studies evaluating the association between GSTT1 null genotype and development of AA. Seven studies, involving a total of 609 patients and 3,914 controls, fulfilled the eligibility criteria. Meta-analysis revealed a significant association of GSTT1 null genotype and AA, with an OR = 1.74 (95% CI 1.31-2.31, P < 0.0001). The effect was not driven by any one individual result, nor was there evidence of significant publication bias. The association between AA and GSTT1 deletion suggests a role of glutathione-conjugation in AA, possibly through protecting the hematopoietic compartment from endogenous metabolites or environmental exposures. We propose a model whereby protein adducts generated by reactive metabolites serve as neo-epitopes to trigger autoimmunity in aplastic anemia.

Prevalence of glutathione S-transferase gene deletions and their effect on sickle cell patients

BACKGROUND

Glutathione S-transferase gene deletions are known detoxification agents and cause oxidative damage. Due to the different pathophysiology of anemia in thalassemia and sickle cell disease, there are significant differences in the pathophysiology of iron overload and iron-related complications in these disorders.

OBJECTIVE

The aim of this study was to estimate the frequency of the GSTM1 and GSTT1 genotypes in sickle cell disease patients and their effect on iron status.

METHODS

Forty sickle cell anemia and sixty sickle ß-thalassemia patients and 100 controls were evaluated to determine the frequency of GST gene deletions. Complete blood counts were performed by an automated cell analyzer. Hemoglobin F, hemoglobin A, hemoglobin A2 and hemoglobin S were measured and diagnosis of patients was achieved by high performance liquid chromatography with DNA extraction by the phenol-chloroform method. The GST null genotype was determined using multiplex polymerase chain reaction and serum ferritin was measured using an ELISA kit. Statistical analysis was by EpiInfo and GraphPad statistics software.

RESULTS

An increased frequency of the GSTT1 null genotype (p-value = 0.05) was seen in the patients. The mean serum ferritin level was higher in patients with the GST genotypes than in controls; this was statistically significant for all genotypes except GSTM1, however the higher levels of serum ferritin were due to blood transfusions in patients.

CONCLUSION

GST deletions do not play a direct role in iron overload of sickle cell patients.

Glutathione S-transferase gene deletions and their effect on iron status in HbE/beta thalassemia patients

Iron overload and oxidative stress are main pathophysiological features of HbE/beta thalassemia patients. Glutathione S-transferase genes (GSTT1 and GSTM1) are well known detoxification agents, and any mutation in the gene is known to cause oxidative damage. This study was aimed to compare the prevalence of GST deletions in 240 HbE/beta thalassemia patients with 100 controls and to determine role of deletions on iron overload. We observed significantly higher frequency of GSTT1 (P = 0.001) and GSTT1/GSTM1 (P = 0.03) in comparison to controls. Patients who had null genotype for both the alleles, i.e., GSTT1/GSTM1 had significantly higher levels of serum iron (P = 0.007) and serum ferritin (P = 0.001) than patients with normal genotype for GST deletions. This is the first study to prove the role of GST gene deletions with iron overload in HbE/beta thalassemia.

Reconstructing population exposures to environmental chemicals from biomarkers: challenges and opportunities

A conceptual/computational framework for exposure reconstruction from biomarker data combined with auxiliary exposure-related data is presented, evaluated with example applications, and examined in the context of future needs and opportunities. This framework employs physiologically based toxicokinetic (PBTK) modeling in conjunction with numerical "inversion" techniques. To quantify the value of different types of exposure data "accompanying" biomarker data, a study was conducted focusing on reconstructing exposures to chlorpyrifos, from measurements of its metabolite levels in urine. The study employed biomarker data as well as supporting exposure-related information from the National Human Exposure Assessment Survey (NHEXAS), Maryland, while the MENTOR-3P system (Modeling ENvironment for TOtal Risk with Physiologically based Pharmacokinetic modeling for Populations) was used for PBTK modeling. Recently proposed, simple numerical reconstruction methods were applied in this study, in conjunction with PBTK models. Two types of reconstructions were studied using (a) just the available biomarker and supporting exposure data and (b) synthetic data developed via augmenting available observations. Reconstruction using only available data resulted in a wide range of variation in estimated exposures. Reconstruction using synthetic data facilitated evaluation of numerical inversion methods and characterization of the value of additional information, such as study-specific data that can be collected in conjunction with the biomarker data. Although the NHEXAS data set provides a significant amount of supporting exposure-related information, especially when compared to national studies such as the National Health and Nutrition Examination Survey (NHANES), this information is still not adequate for detailed reconstruction of exposures under several conditions, as demonstrated here. The analysis presented here provides a starting point for introducing improved designs for future biomonitoring studies, from the perspective of exposure reconstruction; identifies specific limitations in existing exposure reconstruction methods that can be applied to population biomarker data; and suggests potential approaches for addressing exposure reconstruction from such data.

Association between GST genetic polymorphism and dose-related production of urinary benzene metabolite markers, trans, trans-muconic acid and S-phenylmercapturic acid

The urinary benzene metabolites, trans, trans-muconic acid (ttMA) and S-phenylmercapturic acid (SPMA), are widely used as benzene exposure biomarkers. The influence of the glutathione S-transferase (GST) genetic polymorphism on the excretion levels of urinary ttMA and/or SPMA has been investigated. The association between dose-related production of urinary benzene metabolites and benzene exposure level was also reported. However, the association between the dose-related productions of urinary benzene metabolites and GST genetic polymorphism was not described in the literature. The purpose of this study was to investigate the association between the GST genetic polymorphism and dose-related production of the two widely used biomarkers, urinary ttMA and SPMA. Seventy male workers in a chemical factory were measured for their benzene exposure levels and provided blood and urine specimens at the end of work-shift. The atmospheric benzene exposure levels of these workers were determined by passive samplers with gas chromatograph mass spectrometer. The urinary ttMA and SPMA levels were quantitated by an online dual-loop cleanup device with an electrospray ionization tandem mass spectrometer. The analyses of GST genotypes, including M(1), T(1), and P(1), were done using PCR. Mean (+/- SD) of benzene exposure levels in participants was 7.2 +/- 15 ppm. The ttMA and SPMA levels in the high benzene exposure group (> or =1 ppm) were higher than those in the low benzene exposure group (<1 ppm; P < 0.001). Among the GST genotypes investigated in this study, the results showed that only the GSTT1 genotype was related to the level and dose-related production of SPMA. Using SPMA for evaluating benzene exposure, the results suggest that the GSTT1 genetic polymorphism, especially in a comparison study between two populations with different GSTT1 genotype frequencies, should be considered. Additionally, the biological exposure index value of SPMA should be set based on the levels of subjects with GSTT1-deficient genotypes for protection of all subjects.

Study of genetic polymorphism of xenobiotic enzymes in acute leukemia

The work studied possible association between genetic polymorphisms of CYP2D6, GSTM1, GSTT1and NQO1 and altered susceptibility to leukaemia, correlating these genetic polymorphisms with clinical prognostic data, response to therapy and relapse. The study included 32 leukaemia patients, 19 with acute myeloid leukemia (AML) and 13 with acute lymphoid leukaemia (ALL), and 11 normal individuals (control group). Basic investigations for the diagnosis of AML and ALL were performed, including blood picture, bone marrow aspirate, cytochemistry and immunophenotyping for detection of subtypes. Detection of CYP2D6, NQO1, GSTM1 and GSTT1 genetic polymorphisms used a polymerase chain reaction-restriction fragment length polymorphism. A follow-up was made for association between the outcome of patients and different patterns of genetic polymorphisms. Results demonstrate a significant increase in the frequency of CYP2D6 wild-type and GSTM1 null genotypes in the acute leukaemia group compared with the control. Studying the relationship between polymorphisms of these genes and the outcome of our cases revealed the wild genotype of CYP2D6 significantly influenced the outcome of acute leukaemia particularly in AML cases, while GSTM1 null genotype was associated with bad prognosis among the ALL group. The study also revealed that patients with combined mutant CYP2D6/present GSTM1/present GSTT1 achieved the best prognosis, suggesting synergistic impact of these genetic polymorphisms on the outcome of acute leukaemia cases. This case-control study suggests a contribution of CYP2D6 and GSTM1 null variants in the development of acute leukaemia. In addition, GSTM1 and GSTT1 genotypes were apparently related to response, side effects and prognosis of patients with AML.

Genetic polymorphisms involved in toxicant-metabolizing enzymes and the risk of chronic benzene poisoning in Chinese occupationally exposed populations

Benzene is a recognized haematotoxin and leukaemogen, but its mechanism of action and the role of genetic susceptibility are still unclear. Cytochrome P450 2E1 (CYP2E1) and myeloperoxidase (MPO) are involved in benzene activation; and NAD (P)H:quinine oxidoreductase 1 (NQO1), glutathione S-transferase theta 1 (GSTT1) and glutathione S-transferase mu 1 (GSTM1) participate in benzene detoxification. The common, well-studied single-nucleotide polymorphisms (SNPs) were analysed in these genes drawn from the toxicant-metabolizing pathways. A total of 100 workers with chronic benzene poisoning (CBP) and 90 controls were enrolled in China. There was a 2.82-fold (95% CI = 1.42-5.58) increased risk of CBP in the subjects with the NQO1 609C > T mutation genotype (T/T) compared with those carrying heterozygous (C/T) and wild-type (C/C). The subjects with the GSTT1 null genotype had a 1.91-fold (95% CI = 1.05-3.45) increased risk of CBP compared with those with GSTT1 non-null genotype. There was no association of CYP2E1 and MPO genotype with CBP. A three genes' interaction showed that there was a 20.41-fold (95% CI = 3.79-111.11) increased risk of CBP in subjects with the NQO1 609C > T T/T genotype and with the GSTT1 null genotype and the GSTM1 null genotype compared with those carrying the NQO1 609C > T C/T and C/C genotype, GSTT1 non-null genotype, and GSTM1 non-null genotype. The study provides evidence of an association of a gene-gene interaction with the risk of CBP.

Differential expression of glutathione-S-transferase isoenzymes in various types of anemia in Taiwan

BACKGROUND

Published reports concerning the expression of GST in various anemias including aplastic, hemolytic, iron deficiency and thalassemia anemia has been insufficient. We improved the conventional GST assay by incorporating a chloroform treatment to remove the interference of hemoglobin and evaluated the altered expression of GSTs in various anemias in Taiwan.

METHODS

We incorporated a chloroform treatment to eliminate the interference of hemoglobin. Erythrocyte total GST and isoenzymes activities from 35 control subjects and 125 subjects of various anemias, including aplastic, hemolytic, iron deficiency and thalassemia anemias were measured spectrophotometrically.

RESULTS

Chloroform treatment did not significantly affect GST activities in erythrocytes of control subjects while the activities of erythrocyte total GST and alpha-GST were significantly increased in all anemic patients (P<0.001). The expression of mu-GST was significantly decreased, although at a less extent, in cases of aplastic, iron deficiency and thalassemia anemia (P<0.05), but pi-GST was not physiologically different in various types of anemia.

CONCLUSION

The determination of changes in erythrocyte GST activity is a promising indicator of oxidative stress conditions that occur in various types of anemia. Measurement of GST activity might be useful for the evaluation of prophylactic treatment in trials of antioxidant strategies.

EPHX1 polymorphisms and the risk of lung cancer: a HuGE review

BACKGROUND

Microsomal epoxide hydrolase 1 (EPHX1) plays an important role in both the activation and detoxification of tobacco-derived carcinogens. Polymorphisms at exons 3 and 4 of the EPHX1 gene have been reported to be associated with variations in EPHX1 activity. The aim of this study is to review and summarize the available molecular epidemiologic studies of lung cancer and EPHX1.

METHODS

We searched MEDLINE, Current Contents, and Web of Science databases for studies published before August 2004. We conducted a systematic review and meta-analysis of 13 case-control studies. Summary odds ratios and summary prevalence of the variant allele (genotype) of both polymorphisms in the EPHX1 gene were calculated using the DerSimonian and Laird method.

RESULTS

The low-activity (variant) genotype of EPHX1 polymorphism at exon 3 was associated with decreased risk of lung cancer (odds ratio = 0.65; 95% confidence interval = 0.44-0.96) in lung cancer risk among whites. In white populations, the high-activity (variant) genotype of EPHX1 polymorphism at exon 4 was associated with a modest increase in risk of lung cancer (1.22; 0.79-1.90) and the predicted low activity was associated with a modest decrease in risk (0.72; 0.43-1.22).

CONCLUSIONS

EPHX1 enzyme may act as a phase I enzyme in lung carcinogenesis. The low-activity genotype of EPHX1 gene is associated with decreased risk of lung cancer among whites.

Cytochrome P4501A1 and glutathione S transferase gene polymorphisms in patients with aplastic anemia in India

The etiology of acquired aplastic anemia (AA) in most patients remains unclear. It is believed that patients with a reduced ability to detoxify environmental toxins are at increased risk of developing AA. Cytochrome P450 (CYP450) and glutathione S transferase (GST) are the major phase I and phase II xenobiotic-metabolizing enzymes. We analyzed the impact of the polymorphisms in CYP4501A1 and GSTM1 and GSTT1 genes on the susceptibility and disease severity in 200 patients with AA and compared the frequency with the normal population. There was a significantly increased frequency of the CYP1A1m4 allele in AA patients compared with normal controls (odds ratio = 3.01; 95% confidence interval 1.76-5.17; p = 0.00001). None of the other CYP1A1 genotypes or the GST genotypes were significantly different between AA patients and controls. Altered metabolism of benzo(a)pyrene due to the polymorphism in the CYP1A1 gene might be an etiologic factor in the increased incidence of AA in these patients. The CYP1A1m4 allele may play a role in determining the risk of AA in India.

Work of breathing during nasal continuous positive airway pressure in preterm infants: a comparison of bubble vs variable-flow devices

OBJECTIVE

To compare work of breathing and breathing asynchrony during bubble nasal continuous positive airway pressure (NCPAP) vs variable-flow (VF)-NCPAP in premature infants.

STUDY DESIGN

We studied 18 premature infants of birth weight <1500 g who required NCPAP for mild respiratory distress. Each infant was studied on bubble and VF-NCPAP at 8, 6, 4, and 0 cm H2O. Tidal volumes were obtained by calibrated respiratory inductance plethysmography. Esophageal pressure estimated intrapleural pressure. Inspiratory and resistive work of breathing were calculated from pressure-volume data. Breathing asynchrony was assessed with phase angle. The results at all NCPAP levels were referenced to VF-NCPAP values at 8 cm H2O.

RESULTS

Provision of NCPAP with either device decreased inspiratory work of breathing, tidal volume, and minute ventilation relative to NCPAP of 0 cm H2O. Bubble NCPAP did not decrease resistive work of breathing relative to 0 cm H2O. Resistive work of breathing (p=0.01), respiratory rate (p<0.03), and phase angle (p=0.002) were all greater with bubble compared to VF-NCPAP.

CONCLUSION

The more labored and asynchronous breathing seen with bubble NCPAP may lead to higher failure rates over the long term than with VF-NCPAP.

Microsomal glutathione S-transferase 1 in the retinal pigment epithelium: protection against oxidative stress and a potential role in aging

High oxygen tension, exposure to light, and the biochemical events of vision generate significant oxidative stress in the retina and the retinal pigment epithelium (RPE). Understanding the mechanisms and basis of susceptibility to progressive retinal diseases involving oxidative damage such as age-related macular degeneration (AMD) remains a major challenge. Here microsomal glutathione S-transferase (MGST1) is shown to be a dominant, highly expressed enzyme in bovine and mouse RPE microsomes that displays significant reduction activity toward synthetic peroxides, oxidized RPE lipids, and oxidized retinoids. This enzymatic reduction activity (GPx) can be partially neutralized with a monoclonal anti-MGST1 antibody developed in this study. MGST1-transfected HEK293 cells exhibited greater viability (70 +/- 4% survival) compared with untransfected control cells (46 +/- 4% survival) when challenged with 20 microM H(2)O(2), and greater viability of MGST1-transfected cells following challenge with oxidized docosahexaenoic acid was also observed. Cultured ARPE19 cells transfected with silencing MGST1 siRNAs exhibited lower expression of MGST1 (12% and 26% of the controls) and significantly lower GPx activity (44 +/- 13%) and, thus, were more susceptible to oxidative damage. Immunoblotting revealed that the in vivo expression of MGST1 in mouse RPE decreases 3-4-fold with age, to trace levels in 18-month-old mice. GPx activity in the RPE was also found to be reduced in 12-month-old mice to approximately 67%. These results support an important protective function for MGST1 against oxidative insult in the RPE that decreases with age and suggest that this enzyme may play a role in the development of age-related diseases such as AMD.