Frequency Of Reticulocytes Research Articles

Vhl deletion in Dmp1-expressing cells alters MEP metabolism and promotes stress erythropoiesis

IntroductionErythropoiesis occurs in a specialized niche in the bone marrow and is regulated in part by oxygen-sensing signaling pathways. VHL is an E3 ubiquitin ligase that regulates the degradation of hypoxia-inducible factor (HIF) proteins under normoxic conditions. In hypoxia, VHL is inactivated resulting in enhancement of HIF signaling. Methods and resultsTo investigate the effects of HIF-activation in bone cells on erythropoiesis, we performed longitudinal analyses of conditional Vhl knockout mice (Dmp1-Cre;Vhlfl/fl; VhlcKO) mice, in which Vhl is deleted primarily in osteocytes but is retained in hematopoietic cells. VhlcKO mice display elevated red blood cell counts and erythropoietin levels starting at 10 weeks of age, resembling polycythemia. Using flow cytometry, we observed increased frequency of CD71loTER119hiFSClo orthochromatophilic erythroblasts and reticulocytes in 10- and 24-week-old VhlcKO bone marrow. Features of extramedullary hematopoiesis were observed in the spleen, including red pulp hyperplasia, the presence of megakaryocytes, and increased frequency of basophilic and polychromatophilic erythroblasts and of mature stress erythroid progenitors. To investigate the mechanisms that drive the accelerated erythropoiesis in the bone marrow, we enumerated myeloid progenitors and observed higher frequencies of megakaryocyte-erythroid progenitors (MEPs) at 6 and 10 weeks of age, but MEP frequency was similar to controls at 24 weeks. Despite this normalization in MEP frequencies, bulk RNA-Seq of MEPs at this age showed upregulation of Epas1 (Hif2a), consistent with a response to hypoxia, as well as genes involved in erythrocyte development. Surprisingly, genes involved in the response to glucose were also upregulated in VhlcKO MEPs. DiscussionOur studies implicate that HIF-driven alterations in skeletal homeostasis drive changes to the bone marrow microenvironment that influence erythroid cell development and MEP metabolism.

In Vivo Genotoxicity and Cytotoxicity Kinetics of Trimethoprim Sulfamethoxazole in Well-nourished and Undernourished Young Rats.

Undernutrition is a serious health problem prevalent in poor countries, affecting millions of people worldwide, especially young children, pregnant women, and sick elderly individuals. This condition increases vulnerability to infections, leading to widespread use of antibiotic treatments in undernourished populations. The objective of the present study was to determine the in vivo genotoxic and cytotoxic effects of trimethoprim-sulfamethoxazole (TMP-SMX) treatment according to nutritional conditions. The effects of TMP-SMX treatment were measured by analyzing the kinetics of micronucleated reticulocytes (MN-RET) induced in the peripheral blood of young, well-nourished (WN) and undernourished (UN) rats. In the WN group, two distinct peaks of MN-RET were observed, while the UN group had a significantly higher basal frequency of MN-RET compared to the WN group and only a later peak. Reticulocyte (RET) frequency slightly decreased in WN, indicating a poor cytotoxic effect. In contrast, in the UN, the treatment caused a significant increase in RET frequency. The results indicate that SMX's aromaticity index decreases when formed with TMP, suggesting potentially fewer toxic effects. In vivo TMP-SMX produces two MN-RET induction peaks in WN animals, indicating two DNA damage induction mechanisms and consequent micronucleus production. The UN rats did not display the two peaks, indicating that the first MN induction mechanism did not occur in UN, possibly due to pharmacokinetic effects, decreased metabolism or effects on cell proliferation. TMP-SMX has a slight cytotoxic effect on WN. In contrast, in the UN, the antibiotic treatment seems to favor early erythropoiesis.

Dose-response formation of N7-(3-benzo[1,3]dioxol-5-yl-2-hydroxypropyl)guanine in liver and urine correlates with micronucleated reticulocyte frequencies in mice administered safrole oxide

Safrole oxide (SAFO), a metabolite of naturally occurring hepatocarcinogen safrole, is implicated in causing DNA adduct formation. Our previous study first detected the most abundant SAFO-induced DNA adduct, N7-(3-benzo[1,3] dioxol-5-yl-2-hydroxypropyl)guanine (N7γ-SAFO-G), in mouse urine using a well-developed isotope-dilution high-performance liquid chromatography-electrospray ionization tandem mass spectrometry (ID-HPLC-ESI-MS/MS) method. This study further elucidated the genotoxic mode of action of SAFO in mice treated with SAFO 30, 60, 90, or 120 mg/kg for 28 days. The ID-HPLC-ESI-MS/MS method detected N7γ-SAFO-G with excellent sensitivity and specificity in mouse liver and urine of SAFO-treated mice. Our data provide the first direct evidence of SAFO-DNA adduct formation in rodent tissues. N7γ-SAFO-G levels in liver were significantly increased by SAFO 120 mg/kg compared with SAFO 30 mg/kg, suggesting rapid spontaneous or enzymatic depurination of N7γ-SAFO-G in tissue DNA. Urinary N7γ-SAFO-G exhibited a sublinear dose response. Moreover, the micronucleated peripheral reticulocyte frequencies increased dose-dependently and significantly correlated with N7γ-SAFO-G levels in liver (r = 0.8647; p < 0.0001) and urine (r = 0.846; p < 0.0001). Our study suggests that safrole-mediated genotoxicity may be caused partly by its metabolic activation to SAFO and that urinary N7γ-SAFO-G may serve as a chemically-specific cancer risk biomarker for safrole exposure.

Reticulocytes in donor blood units enhance red blood cell alloimmunization.

Although red blood cell (RBC) transfusions save lives, some patients develop clinically-significant alloantibodies against donor blood group antigens, which then have adverse effects in multiple clinical settings. Few effective measures exist to prevent RBC alloimmunization and/or eliminate alloantibodies in sensitized patients. Donor-related factors may influence alloimmunization; thus, there is an unmet clinical need to identify which RBC units are immunogenic. Repeat volunteer blood donors and donors on iron supplements have elevated reticulocyte counts compared to healthy non-donors. Early reticulocytes retain mitochondria and other components, which may act as danger signals in immune responses. Herein, we tested whether reticulocytes in donor RBC units could enhance RBC alloimmunization. Using a murine model, we demonstrate that transfusing donor RBC units with increased reticulocyte frequencies dose-dependently increased RBC alloimmunization rates and alloantibody levels. Transfusing reticulocyte-rich RBC units was associated with increased RBC clearance from the circulation and a robust proinflammatory cytokine response. As compared to previously reported post-transfusion RBC consumption patterns, erythrophagocytosis from reticulocyte-rich units was increasingly performed by splenic B cells. These data suggest that reticulocytes in a donated RBC unit impact the quality of blood transfused, are targeted to a distinct compartment, and may be an underappreciated risk factor for RBC alloimmunization.

IRE-dependent Regulation of Intestinal Dmt1 Prevails During Chronic Dietary Iron Deficiency but is Dispensable in Conditions of Acute Erythropoietic Stress.

IRE-dependent Regulation of Intestinal Dmt1 Prevails During Chronic Dietary Iron Deficiency but is Dispensable in Conditions of Acute Erythropoietic Stress.

Long‑term effects of COVID‑19 in sickle cell disease: A case report

Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection can generate a respiratory and systemic disease known as coronavirus disease 2019 (COVID‑19). To date, at least to the best of our knowledge, only a limited number of studies have identified SARS‑CoV‑2 infection in patients with sickle cell disease (SCD). Due to the lack of knowledge of the long‑term effects of COVID‑19, the present study presents the hematological alterations in a patient with SCD during hospitalization due to COVID‑19 and for up to 180 days following SARS‑CoV‑2 clearance and hospital discharge. The present study describes the case of a patient with SCD who was diagnosed with moderate COVID‑19 infection, without the need for invasive mechanical ventilation. Following SARS‑CoV‑2 clearance, long‑term (6 months) follow‑up identified an increase in the reticulocyte frequency, creatinine and D‑dimer levels. On the whole, the present study manuscript presents the case of a patient with moderate COVID‑19 infection with long‑term laboratory alterations at even 6 months following SARS‑CoV‑2 clearance. Further investigations are required however, to focus on the long‑term evaluations in patients who have recovered from COVID‑19, in order to fully determine the extension of possible sequelae.

Benchmark dose analysis of multiple genotoxicity endpoints in gpt delta mice exposed to aristolochic acid I.

As the carcinogenic risk of herbs containing aristolochic acids (AAs) is a global health issue, quantitative evaluation of toxicity is needed for the regulatory decision-making and risk assessment of AAs. In this study, we selected AA I (AAI), the most abundant and representative compound in AAs, to treat transgenic gpt delta mice at six gradient doses ranging from 0.125 to 4 mg/kg/day for 28 days. AAI-DNA adduct frequencies and gpt gene mutation frequencies (MFs) in the kidney, as well as Pig-a gene MFs and micronucleated reticulocytes (MN-RETs) frequencies in peripheral blood, were monitored. The dose-response (DR) relationship data for these in vivo genotoxicity endpoints were quantitatively evaluated using an advanced benchmark dose (BMD) approach with different critical effect sizes (CESs; i.e., BMD5, BMD10, BMD50 and BMD100). The results showed that the AAI-DNA adduct frequencies, gpt MFs and the MN-RETs presented good DR relationship to the administrated doses, and the corresponding BMDL100 (the lower 90% confidence interval of the BMD100) values were 0.017, 0.509 and 3.9 mg/kg/day, respectively. No positive responses were observed in the Pig-a MFs due to bone marrow suppression caused by AAI. Overall, we quantitatively evaluated the genotoxicity of AAI at low doses for multiple endpoints for the first time. Comparisons of BMD100 values across different endpoints provide a basis for the risk assessment and regulatory decision-making of AAs and are also valuable for understanding the genotoxicity mechanism of AAs.

Testing of acetaminophen in support of the international multilaboratory in vivo rat Pig-a assay validation trial.

Acetaminophen, a nonmutagenic compound as previously concluded from bacteria, in vitro mammalian cell, and in vivo transgenic rat assays, presented a good profile as a nonmutagenic reference compound for use in the international multilaboratory Pig‐a assay validation. Acetaminophen was administered at 250, 500, 1,000, and 2,000 mg·kg−1·day−1 to male Sprague Dawley rats once daily in 3 studies (3 days, 2 weeks, and 1 month with a 1‐month recovery group). The 3‐Day and 1‐Month Studies included assessments of the micronucleus endpoint in peripheral blood erythrocytes and the comet endpoint in liver cells and peripheral blood cells in addition to the Pig‐a assay; appropriate positive controls were included for each assay. Within these studies, potential toxicity of acetaminophen was evaluated and confirmed by inclusion of liver damage biomarkers and histopathology. Blood was sampled pre‐treatment and at multiple time points up to Day 57. Pig‐a mutant frequencies were determined in total red blood cells (RBCs) and reticulocytes (RETs) as CD59‐negative RBC and CD59‐negative RET frequencies, respectively. No increases in DNA damage as indicated through Pig‐a, micronucleus, or comet endpoints were seen in treated rats. All positive controls responded as appropriate. Data from this series of studies demonstrate that acetaminophen is not mutagenic in the rat Pig‐a model. These data are consistent with multiple studies in other nonclinical models, which have shown that acetaminophen is not mutagenic. At 1,000 mg·kg−1·day−1, Cmax values of acetaminophen on Day 28 were 153,600 ng/ml and 131,500 ng/ml after single and repeat dosing, respectively, which were multiples over that of clinical therapeutic exposures (2.6–6.1 fold for single doses of 4,000 mg and 1,000 mg, respectively, and 11.5 fold for multiple dose of 4,000 mg) (FDA 2002). Data generated were of high quality and valid for contribution to the international multilaboratory validation of the in vivo Rat Pig‐a Mutation Assay.

Dextran sulfate sodium mouse model of inflammatory bowel disease evaluated for systemic genotoxicity via blood micronucleus and Pig-a gene mutation assays

Inflammatory bowel disease (IBD) is an important risk factor for gastrointestinal cancers. Inflammation and other carcinogenesis-related effects at distal, tissue-specific sites require further study. In order to better understand if systemic genotoxicity is associated with IBD, we exposed mice to dextran sulfate sodium salt (DSS) and measured the incidence of micronucleated cells (MN) and Pig-a mutant phenotype cells in blood erythrocyte populations. In one study, 8-week-old male CD-1 mice were exposed to 0, 1, 2, 3 or 4% w/v DSS in drinking water. The 4-week in-life period was divided into four 1-week intervals-alternately on then off DSS treatment. Low volume blood samples were collected for MN analysis at the end of each week, and cardiac blood samples were collected at the end of the 4-week period for Pig-a analyses. The two highest doses of DSS were observed to induce significant increases in reticulocyte frequencies. Even so, no statistically significant treatment-related effects on the genotoxicity biomarkers were evident. While one high-dose mouse showed modestly elevated MN frequencies during the DSS treatment cycles, it also exhibited exceptionally high reticulocyte frequencies (e.g. 18.7% at the end of the second DSS cycle). In a second study, mice were treated with 0 or 4% DSS for 9-18 consecutive days. Exposure was continued until rectal bleeding or morbidity was evident, at which point the treatment was terminated and blood was collected for MN analysis. The Pig-a assay was conducted on samples collected 29 days after the start of treatment. The initial blood specimens showed highly elevated reticulocyte frequencies in DSS-exposed mice (mean ± SEM = 1.75 ± 0.10% vs. 13.04 ± 3.66% for 0 vs. 4% mice, respectively). Statistical analyses showed no treatment-related effect on MN or Pig-a mutant frequencies. Even so, the incidence of MN versus reticulocytes in the DSS-exposed mice were positively correlated (linear fit R2 = 0.657, P = 0.0044). Collectively, these results suggest that in the case of the DSS CD-1 mouse model, systemic effects include stress erythropoiesis but not remarkable genotoxicity. To the extent MN may have been slightly elevated in a minority of individual mice, these effects appear to be secondary, likely attributable to stimulated erythropoiesis.

Detection of Pig-a Mutant Erythrocytes in the Peripheral Blood of Rats and Mice.

The endogenous X-linked phosphatidyl inositol glycan class A gene (Pig-a) can be used as a reporter of in vivo somatic cell mutation in rats and mice. Pig-a mutant cells are deficient in specific protein surface markers and can be identified and quantified by immunofluorescent staining followed by high-throughput flow cytometry. Pig-a mutation detection is commonly performed with red blood cells (RBCs) because: (1) the low volumes of blood required for determining mutant frequencies in RBCs allow multiple samplings on small laboratory animals over extended periods of time; (2) the execution of the RBC assay is easy and the interpretation of the results is straightforward; and (3) RBC Pig-a mutant frequencies are known within hours of sample collection. Two endpoints are determined in the assay: the frequency of mutant total RBCs and the frequency of mutant reticulocytes. When Pig-a mutation is used to assess the in vivo mutagenic potential of suspect hazards, the frequency of mutant reticulocytes is an early indicator of mutagenic potential, while the mutant frequency in total RBCs can be measured more rapidly and with greater precision.

Integration of micronucleus, comet, and Pig-a gene mutation endpoints into rat 15-day repeat-treatment studies: Proof-of-principle with Auramine O

A series of genotoxicity assessments were conducted on male Sprague Dawley rats treated with Auramine O (AO) to establish a multiple-endpoint assay. The rat liver micronucleus assay, in combination with the comet assay, peripheral blood micronucleus assay, and erythrocyte Pig-a assay in the same experiment, comprehensively assess the genotoxicity of AO. Rats were orally exposed to 0, 100, 200, or 400 mg/kg/day AO for 15 consecutive days. The blood was sampled on Days -1 and 15 for the erythrocyte Pig-a assay and peripheral blood micronucleus assay. Livers were sampled on Day 15 for the liver micronucleus assay and comet assay. Based on the liver micronucleus assay and liver comet assay, AO induced a significant dose-related increase of micronucleated hepatocyte frequencies, and tail DNA percentages, respectively in the middle- and high-dose groups. On the blood micronucleus test and Pig-a assay, no significant increases were observed for the micronucleated reticulocyte frequencies, mutant erythrocyte frequencies (RBCCD59−) or mutant reticulocyte frequencies (RETCD59−) at any of the time points studied. In conclusion, using a multiple-endpoint genotoxicity assay method can reduce the number of experimental animals, boost the efficiency of the experiment, and improve the accuracy of investigations of genotoxicity.

2-Hydroxypyridine N-Oxide is not genotoxic in vivo.

2-Hydroxypyridine N-oxide (HOPO) is an important coupling reagent used in pharmaceutical synthesis. Our laboratory previously reported HOPO as equivocal in the Ames assay following extensive testing of multiple lots of material. Given the lack of reproducibility between lots of material and the weak increase in revertants observed, it was concluded that it would be highly unlikely that HOPO would pose a mutagenic risk in vivo. The purpose of the current investigation was to assess experimentally in rats the mutagenic (Pig-a mutation induction) and more broadly genotoxic (micronucleus and comet induction) potential of HOPO. Rats were administered HOPO (0, 50, 150, 300, and 500 mg/kg/day) by oral gavage for 28 days. At the end of study, the following parameters were assessed: frequency of Pig-a mutant red blood cells and reticulocytes, frequency of peripheral blood micronuclei, and the incidence of comet formation in liver. Toxicokinetic data collected on study Days 1 and 28 demonstrated systemic exposure to HOPO. Although there were no overt clinical signs, animals treated with HOPO showed a dose-related decrease in body weight gain. There were no increases observed in any of the genotoxicity endpoints assessed. The results from this study further support the conclusion that in the context of pharmaceutical synthesis, HOPO should not be considered a mutagenic impurity but rather controlled as a normal process-related impurity. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc.

Suitability of Long-Term Frozen Rat Blood Samples for the Interrogation of Pig-a Gene Mutation by Flow Cytometry.

The rodent blood Pig-a assay has been undergoing international validation for use as an in vivo hematopoietic cell gene mutation assay, and given the promising results an Organization for Economic Co-operation and Development (OECD) Test Guideline is currently under development. Enthusiasm for the assay stems in part from its alignment with 3Rs principles permitting combination with other genotoxicity endpoint(s) and integration into repeat-dose toxicology studies. One logistical requirement and experimental design limitation has been that blood samples required antibody labeling and flow cytometric analysis within one week of collection. In the current report, we describe the performance of freeze-thaw reagents that enable storage and subsequent labeling and analysis of rat blood samples for at least seven months. Data generated from three laboratories are presented that demonstrate rat erythrocyte recoveries in the range of 80-90%. Despite some loss of erythrocytes, Pearson coefficients and Bland-Altman analyses based on fresh blood vs. frozen/thawed matched pairs indicate that mutant cell and reticulocyte frequencies are not significantly affected, as the measurements are highly correlated and exhibit low bias. Collectively, these data support the effectiveness and suitability of a freeze-thaw procedure that endows the assay with several new advantageous characteristics that include: flexibility in scheduling personnel/instrumentation; reliability when shipping samples from in-life facilities to analytical sites; 3Rs-friendly, as blood from positive control animals can be stored frozen to serve as analytical controls; and ability to defer a decision to generate Pig-a data until more toxicological information becomes available on a test substance. Environ. Mol. Mutagen. 60:47-55, 2019. © 2018 Wiley Periodicals, Inc.

Attenuated Protein Synthesis Drives the Hematopoietic Defects in Shwachman-Diamond Syndrome

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterized by bone marrow failure and a striking propensity to develop poor prognosis myelodysplastic syndrome and acute myeloid leukemia. In 90 % of cases the disease is caused by biallelic mutations in the gene encoding SBDS. We have shown previously that SBDS is a cytoplasmic ribosome assembly factor that catalyzes the release of the eukaryotic initiation factor 6 (eIF6) from the subunit joining interface of 60S ribosomal subunit (Menne et al, 2007; Finch et al, 2011). Deficiency of SBDS therefore results in aberrant retention of eIF6 on the 60S subunits that in turn perturbs ribosomal subunit joining and the formation of translation-competent 80S ribosomes. However, the mechanism linking defective ribosome assembly to marrow failure and leukemia in SDS remain poorly understood.Lack of viable mouse models presents a barrier to progress in understanding SDS disease pathophysiology and to evaluate novel therapies. We hypothesized that induced overexpression of eIF6 would mimic the consequences of SBDS deficiency by reducing the cytoplasmic pool of free 60S subunits and impairing translation. To test this hypothesis we have generated a novel transgenic eIF6 mouse model for SDS using KH2 embryonic stem cells that constitutively express the M2-reverse tetracycline transactivator at the Rosa26 locus with the EIF6 gene targeted downstream of the Col1a1 locus. This strategy permits systemic doxycycline-inducible and graded overexpression of eIF6 through control of the transgene copy number.We have validated that eIF6 overexpression promotes an increase in eIF6-bound cytoplasmic 60S subunits with a concomitant reduction in 80S ribosomes and polysomes in c-kit+ hematopoietic progenitor cells isolated from the transgenic eIF6 mice, thereby recapitulating the ribosomal subunit joining defect observed in patients with SDS. In vitro, the hematopoietic progenitor cells exhibit a strict eIF6 dose-dependent expansion defect. In vivo, mice with graded eIF6 overexpression are viable but develop macrocytic anemia with reticulocytopenia, thrombocytosis and mild leukopenia. Bone marrow transfer experiments demonstrate that the phenotype is autonomous to the hematopoietic system. Longitudinal phenotypic analyses in primary and transplanted animals are ongoing. Flow cytometric analysis of the bone marrow from transgenic eIF6 mice reveals a significant increase in the frequencies of preCFU-E and CFU-E erythroid progenitor cells and erythroblasts, but a significant reduction in the frequency of reticulocytes. Furthermore, we observe a striking accumulation of abnormal orthochromatic erythroblast-like cells that appear to have failed to enucleate, comprising approximately 1.5 % of the total bone marrow cells. Amnis ImageStream analysis, which combines flow cytometry with fluorescent microscopy, reveals a significant decrease in the frequency of erythroblasts that are able to complete the enucleation process. To address the underlying mechanism, we hypothesized that by impairing the formation of translation-competent 80S ribosomes, eIF6 overexpression would reduce the global rate of protein synthesis. Indeed, O-propargyl-puromycin incorporation assays established that the erythroblasts from the transgenic eIF6 mice have an approximately 3-fold reduction in global protein synthesis rate. Furthermore, our preliminary data suggest that the erythroid phenotype is p53-independent. Finally, erythroblasts from the transgenic eIF6 mice show a significant increase in levels of reactive oxygen species, but the functional significance of this finding remains unclear.We conclude that reduced rates of global translation drive defective hematopoiesis in the transgenic eIF6 mice. Importantly, eIF6 overexpression in vivo phenocopies SBDS depletion in human CD34+ cells (Sen et al, 2011). Together with the recent discovery of DNAJC21 (the human homologue of the 60S ribosomal assembly factor JJJ1 in yeast) as an SDS disease gene, our data support the hypothesis that deregulated cytoplasmic 60S subunit maturation and reduced translation are the primary drivers of the hematopoietic defect in SDS. Our viable transgenic eIF6 mouse model provides a unique tool to further dissect the mechanisms that underlie bone marrow failure and malignant transformation in SDS and for the development of novel therapeutics. DisclosuresNo relevant conflicts of interest to declare.

A regenerative erythropoietic response does not increase the frequency of Pig-a mutant reticulocytes and erythrocytes in Sprague-Dawley rats.

The in vivo rodent Pig-a mutation assay is a sensitive test to identify exposure to mutagenic substances, and has been proposed as an assay for the identification of impurities for pharmaceuticals. Red blood cells (RBCs) and reticulocytes (RETs) are analyzed by flow cytometry after exposure to potentially mutagenic chemicals for cells deficient in the cell surface anchored protein CD59, representing mutation in the X-linked Pig-a gene. The full potential of the assay as well as its limitations are currently being explored. The current study investigated the effects of regenerative erythropoietic bone marrow responses on the frequency of Pig-a mutated reticulocytes (RETCD59- ) and erythrocytes (RBCCD59- ). We hypothesized that a robust regenerative erythropoietic response would not increase the basal frequency of RETCD59- or RBCCD59- cells. Two groups of six male Sprague-Dawley rats either had 2 mL of blood sampled each day via an indwelling catheter over a period of 5 days or were minimally sampled for hematology and used as controls. Blood was also then collected and evaluated 5, 18, and 49 days after the initial bleed period for the number of Pig-a mutant cells in either the RET or RBC population. Despite the expected decrease in hematocrit and the correlative increase in reticulocytes after bleeding, no increase in the number of Pig-a mutant cells was observed in male Sprague-Dawley rats that were bled for five consecutive days. These results indicate that changes in erythropoiesis and hematology parameters in rats appear to have no effect on the background levels of Pig-a mutated RETs and RBCs. Environ. Mol. Mutagen. 59:91-95, 2018. © 2017 Wiley Periodicals, Inc.

In vivo pig-a and micronucleus study of the prototypical aneugen vinblastine sulfate.

The Pig-a assay is being used in regulatory studies to evaluate the potential of agents to induce somatic cell gene mutations and an OECD test guideline is under development. A working group involved with establishing the guideline recently noted that representative aneugenic agents had not been evaluated, and to help fill this data gap Pig-a mutant phenotype and micronucleated reticulocyte frequencies were measured in an integrated study design to assess the mutagenic and cytogenetic damage responses to vinblastine sulfate exposure. Male Sprague Dawley rats were treated for twenty-eight consecutive days with vinblastine dose levels from 0.0156 to 0.125 mg/kg/day. Micronucleated reticulocyte frequencies in peripheral blood were determined at Days 4 and 29, and mutant cell frequencies were determined at Days -4, 15, 29, and 46. Vinblastine affected reticulocyte frequencies, with reductions noted during the treatment phase and increases observed following cessation of treatment. Micronucleated reticulocyte frequencies were significantly elevated at Day 4 in the high dose group. Although a statistically significant increase in mutant reticulocyte frequencies were found for one dose group at a single time point (Day 46), it was not deemed biologically relevant because there was no analogous finding in mutant RBCs, it occurred at the lowest dose tested, and only 1 rat exceeded an upper bound tolerance interval established with historical negative control rats. Therefore, whereas micronucleus induction reflects vinblastine's well-established aneugenic effect on hematopoietic cells, the lack of a Pig-a response indicates that this tubulin-binding agent does not cause appreciable mutagenicity in this same cell type. Environ. Mol. Mutagen. 59:30-37, 2018. © 2017 Wiley Periodicals, Inc.

Effects of sub-chronic exposure to terbuthylazine on DNA damage, oxidative stress and parent compound/metabolite levels in adult male rats

Terbuthylazine is a selective pre- and post-emergency chloro-triazine herbicide used for a broad spectrum of weed control. We evaluated the potential of low doses of terbuthylazine to induce oxidative stress and cytogenetic damage in peripheral blood samples of adult male Wistar rats. Following 28-day repeated oral exposure at 0.004 mg/kg b.w./day, 0.4 mg/kg b.w./day and 2.29 mg/kg b.w./day, parameters of lipid peroxidation, total antioxidant capacity, and activities of antioxidant enzymes were measured in blood samples. Alkaline comet assay on leukocytes and erythrocyte micronucleus assay were used to measure DNA damage. In addition, the concentration of terbuthylazine and its metabolite in urine and plasma were determined using high performance liquid chromatography with UV diode-array detector (HPLC-UV-DAD). The fraction of terbuthylazine excreted in urine was negligible and was not found in plasma. Deethylterbuthylazine was only compound detected in plasma samples. Exposure to terbuthylazine did not induce significant lipid peroxidation products. The significant changes in antioxidant enzyme activities and the elevated total antioxidant capacity indicated that terbuthylazine at experimental conditions applied has potential to disturb oxidative/antioxidant balance. Results regarding the alkaline comet assay as well as micronucleated reticulocyte frequency indicated that treatment led to low-level DNA instability. Our results call for further research using other sensitive biomarkers of effect, along with different exposure scenarios.

Monitoring genotoxicity in patients receiving chemotherapy for cancer: application of the PIG-A assay

The recently introduced Pig-a in vivo gene mutation assay measures endogeneous mutations of Pig-a (human, PIG-A), an X-linked gene that is conserved across species from rodents to humans. Flow cytometric analysis enables the enumeration of glycosylphosphatidylinositol (GPI) anchor-deficient erythrocytes, resulting from a mutation in Pig-a/PIG-A, in only a few microliters of peripheral blood. Pig-a/PIG-A mutations appear to function in a neutral manner, allowing evaluation of the accumulated genotoxic effects of repeated exposures. To date, most Pig-a studies have been conducted in rodents; only a few reports regarding human applications of the PIG-A assay have been published. We have conducted a PIG-A assay in the context of human genotoxicity monitoring. Peripheral blood was collected from healthy human donors and chemotherapy-treated cancer patients at Yamagata University Hospital. To investigate the PIG-A mutant frequency (MF) induced by chemotherapy, red blood cells were analyzed via flow cytometry following staining with allophycocyanin-conjugated anti-CD235ab (erythrocyte specific) and fluorescein isothiocyanate-conjugated anti-CD59 antibodies (GPI-anchored protein specific). Reticulocyte frequencies (%RET) were also analyzed using a phycoerythrin-conjugated anti-CD71 antibody to monitor bone marrow suppression and reticulocytosis. Two of 27 patients exhibited a significantly elevated frequency of PIG-A mutants. Although we observed either a reduced or an increased %RET in all patients, no association was observed between this factor and the PIG-A MF. Unfortunately, we could not analyze blood samples collected before treatment during therapeutic processes. Additionally, the sampling time point for some patients was too short to express the PIG-A mutant phenotypes. Therefore, the possibility of natively high PIG-A MFs prior to treatment must be considered. The human PIG-A assay shows promise as a human genotoxicity monitoring method.

IL-33 reflects dynamics of disease activity in patients with autoimmune hemolytic anemia by regulating autoantibody production.

Background Autoimmune hemolytic anemia (AIHA), a life-threatening anemia with rapid onset, is caused by autoantibody directed to self red blood cells (RBCs). Currently, mechanisms underlying AIHA pathogenesis are largely undefined. Here we explored the correlation of IL-33 with AIHA disease activity and evaluated IL-33 based therapeutics in AIHA treatment.Methods Thirty patients diagnosed with AIHA of warm-type autoantibodies without treatment were enrolled and followed up for 6 months. Levels of cytokines including IL-33, IL-4, IL-6 and IL-13 was determined with ELISA. AIHA disease activity was presented by levels of reticulocyte count, hemoglobin and lactate dehydrogenase. Serum RBC-bound IgG autoantibody was detected using anti-IgG antibody with flow cytometry. To evaluate the effect of IL-33 blockade on AIHA development, groups of B6 mice were immunized with rat RBCs plus recombinant IL-33 protein or IL-33 neutralizing antibody respectively and detected for levels of anti-RBC antibody, frequency of reticulocytes and destruction of transfused syngeneic mouse RBCs.ResultsSerum level of IL-33 was higher in AIHA patients compared with healthy individuals. Of interest, serum IL-33 was positively correlated with AIHA disease activity and sensitive to their changes in AIHA patients under clinical management. Mechanistically, IL-33 could promote the production of anti-RBC autoantibody. Serum IL-33 was closely associated with serum anti-RBC autoantibody and sensitive to their changes in AIHA patients. Accordingly, blockade of IL-33 interfered with AIHA incidence and ameliorated disease activity. Vice vasa, enforced IL-33 promoted AIHA incidence and disease activity.ConclusionsIL-33 was a potential biomarker for monitoring disease activity and therapeutic response in AIHA patients. Targeting IL-33 was a promising strategy for controlling autoantibody production in AIHA patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0745-0) contains supplementary material, which is available to authorized users.

Genotoxicity-suppressing effect of aqueous extract of Connarus ruber cortex on cigarette smoke-induced micronuclei in mouse peripheral erythrocytes.

IntroductionAccording to published information, it has not been determined whether the inhalation of cigarette smoke can induce chromosome aberrations and/or point mutations in mice, though cigarette smoke is clearly carcinogenic to mice. We tested clastogenicity of inhaled cigarette smoke in mouse by a micronucleus test using peripheral erythrocytes. Since it is important to determine the in vivo anti-genotoxic effect against inhaled cigarette smoke to reduce the risk of tobacco carcinogenesis, we also tested in vivo anti-gnotoxic effect against inhaled cigarette smoke of a Connarus extract whose in vitro anti-genotoxic effect was shown.ResultsMale ICR mice were exposed for 1 min to a 6-fold dilution of the smoke once a day for up to 14 consecutive days. Although the frequencies of reticulocytes with micronucleus (MNRETs) and erythrocytes with micronuclei (MN erythrocytes) did not increase within 72 h after a single inhalation of cigarette smoke, the frequency of MN erythrocytes increased significantly upon inhalation for 7 and 14 days. When the Connarus extract was fed to mice at >23.7 ppm during the inhalation period of 14 days, frequency of MN erythrocytes was significantly lower than that at 0 ppm. In vitro antioxidant activity of Connarus extract was almost same to that of vitamin C. The antioxidant activity of the Connarus extract might play an important role in its anti-genotoxic effect against cigarette smoke in vivo, like vitamins C.ConclusionsConsecutive inhalation of cigarette smoke is clastogenic to mouse bone marrow as shown by the increased frequency of MN erythrocytes. Also, it was shown the possibility that the Connarus extract reduces the risk of tobacco carcinogenesis.