FG-4592 protected haematopoietic system from ionising radiation in mice.

Ionising radiation exposure can lead to acute haematopoietic radiation syndrome. Despite significant advancements in the field of radioprotection, no drugs with high efficacy and low toxicity have yet been approved by the Food and Drug Administration. FG-4592, as a proline hydroxylase inhibitor, may play an important role in radioprotection of the haematopoietic system. Mice were peritoneal injected with FG-4592 or normal saline. After irradiation, the survival time, body weight, peripheral blood cell and bone marrow cell (BMC) count, cell apoptosis, pathology were analysed and RNA-sequence technique (RNA-Seq) was conducted to explore the mechanism of FG-4592 in the haematopoietic system. Our results indicated that FG-4592 improved the survival rate and weight of irradiated mice and protected the spleen, thymus and bone marrow from IR-induced injury. The number of BMCs was increased and protected against IR-induced apoptosis. FG-4592 also promoted the recovery of the blood system and erythroid differentiation. The results of RNA-Seq and Western blot showed that the NF-κB signalling pathway and hypoxia-inducible factor-1 (HIF-1) signalling pathway were upregulated by FG-4592. Meanwhile, RT-PCR results showed that FG-4592 could promote inflammatory response significantly. FG-4592 exhibited radioprotective effects in the haematopoietic system by promoting inflammatory response and targeting the NF-κB, HIF signalling pathway.

Novel chimeric TLR2/NOD2 agonist CL429 exhibited significant radioprotective effects in mice.

Severe ionizing radiation causes the acute lethal damage of haematopoietic system and gastrointestinal tract. Here, we found CL429, the novel chimeric TLR2/NOD2 agonist, exhibited significant radioprotective effects in mice. CL429 increased mice survival, protected mice against the lethal damage of haematopoietic system and gastrointestinal tract. CL429 was more effective than equivalent amounts of monospecific (TLR2 or NOD2) and combination (TLR2 + NOD2) of molecules in preventing radiation-induced death. The radioprotection of CL429 was mainly mediated by activating TLR2 and partially activating NOD2. CL429-induced radioprotection was largely dependent on the activation of TLR2-MyD88-NF-κB signalling pathway. In conclusion, the data suggested that the co-activation of TLR2 and NOD2 could induce significant synergistic radioprotective effects and CL429 might be a potential high-efficiency selective agent.

Improved nonclinical safety profile of a novel, highly selective inhibitor of the immunoproteasome subunit LMP7 (M3258).

M3258 is the first selective inhibitor of the immunoproteasome subunit LMP7 (Large multifunctional protease 7) in early clinical development with the potential to improve therapeutic utility in patients of multiple myeloma (MM) or other hematological malignancies. Safety pharmacology studies with M3258 did not reveal any functional impairments of the cardiovascular system in several in vitro tests employing human cardiomyocytes and cardiac ion channels (including hERG), guinea pig heart refractory period and force contraction, and rat aortic contraction as well as in cardiovascular function tests in dogs. Following single dose M3258 administration to rats, no changes were observed on respiratory function by using whole body plethysmography, nor did it change (neuro)behavioral parameters in a battery of tests. Based on pivotal 4-week toxicity studies with daily oral dosing of M3258, the identified key target organs of toxicity were limited to the lympho-hematopoietic system in rats and dogs, and to the intestine with its local lymphoid tissues in dogs only. Importantly, the stomach, nervous system, heart, lungs, and kidneys, that may be part of clinically relevant toxicities as reported for pan-proteasome inhibitors, were spared with M3258. Therefore, it is anticipated that by targeting highly selective and potent inhibition of LMP7, the resulting favorable safety profile of M3258 together with the maintained potent anti-tumor activity as previously reported in mouse MM xenograft models, may translate into an improved benefit-risk profile in MM patients.

Low hazard of silver nanoparticles and silver nitrate to the haematopoietic system of rainbow trout.

Silver nanoparticles (Ag NPs) are known for their antibacterial properties and are used in a growing number of nano-enabled products, with inevitable concerns for releases to the environment. Nanoparticles may also be antigenic and toxic to the haematopoietic system, but the immunotoxic effect of Ag NPs on non-target species such as fishes is poorly understood. This study aimed to assess the effect of Ag NP exposure via the water on the haematopoietic system of rainbow trout, Oncorhynchus mykiss, and to determine whether or not the hazard from Ag NPs was different from that of AgNO3. Fish were exposed for 7 days to a control (dechlorinated Plymouth freshwater), dispersant control, 1µgl-1 Ag as AgNO3 or 100µgl-1 Ag NPs. Animals were sampled on days 0, 4 and 7 for haematology, tissue trace metal concentration, biochemistry for evidence of oxidative stress/inflammation in the spleen and histopathology of the blood cells and spleen. The Ag NP treatment significantly increased the haematocrit, but the haematological changes were within the normal physiological range of the animal. Thrombocytes in spleen prints at day 4, and melanomacrophage deposits at day 7 in the spleen, of Ag NP exposed-fish displayed significant increases compared to all the other treatments within the time point. A dialysis experiment confirmed that dissolution rates were very low and any pathology observed is likely from the NP form rather than dissolved metal released from it. Overall, the data showed subtle differences in the effects of Ag NPs compared to AgNO3 on the haematopoietic system. The lack of pathology in the circulating blood cells and melanomacrophage deposits in the spleen suggests a compensatory physiological effort by the spleen to maintain normal circulating haematology during Ag NP exposure.

Protective Effects of 2-Amino-5,6-dihydro-4H-1,3-thiazine and Its Derivative against Radiation-Induced Hematopoietic and Intestinal Injury in Mice.

Ionizing radiation (IR) acts as an external stimulating factor, when it acts on the body, it will activate NF- κ B and cause the up-regulation of inducible nitric oxide synthase (iNOS) and induce a large amount of nitric oxide (NO) production. NO and other reactive nitrogen and oxygen species (RNS and ROS) can cause damage to biological molecules and affect their physiological functions. Our study investigated the protective role of 2-amino-5,6-dihydro-4H-1,3-thiazine hydrobromide (2-ADT) and 2-acetylamino-5,6-dihydro-4H-1,3-thiazine hydrobromide (2-AADT), two nitric oxide synthase inhibitors, against radiation-induced hematopoietic and intestinal injury in mice. Pretreatment with 2-ADT and 2-AADT improved the survival of mice exposed to a lethal dose of radiation, especially, the survival rate of the 2-ADT 20 mg/kg group was significantly higher than that of the vehicle group (p < 0.001). Our findings indicated that the radioprotective actions of 2-ADT and 2-AADT are achieved via accelerating hematopoietic system recovery, decreasing oxidative and nitrosative stress by enhancing the antioxidant defense system and reducing NO as well as peroxynitrite (ONOO − ) content, and mitigating the radiation-induced DNA damage evaluated by comet assay. These results suggest that 2-ADT and 2-AADT may have great application potential in ameliorating the damages of radiotherapy.

Zymosan-a Protects the Hematopoietic System from Radiation-Induced Damage by Targeting TLR2 Signaling Pathway.

BACKGROUND/AIMS: The hematopoietic system is vulnerable to ionizing radiation and is often severely damaged by radiation. Molecules affecting radioresistance include Toll-like receptor 2. We investigated whether Zymosan-A, a novel TLR2 agonist, can protect the hematopoietic system from radiation-induced damage after total body irradiation. METHODS: Mice were exposed to total body radiation after treatment with Zymosan-A or normal saline, and their survival was recorded. Tissue damage was evaluated by hematoxylin-eosin staining. The number of nucleated cells in bone marrow was determined by flow cytometry. Cell viability and apoptosis assay were determined by CCK-8 assay and flow cytometry assay. Enzyme-linked immunosorbent assay was used to detect the level of cytokines. RESULTS: Zymosan-A protected mice from radiation-induced death and prevented radiation-induced hematopoietic system damage. Zymosan-A also promoted cell viability and inhibited cell apoptosis caused by radiation, induced radioprotective effects via TLR2, upregulated IL-6, IL-11, IL-12, and TNF-α in vivo. CONCLUSION: Zymosan-A can provide protection against radiation-induced hematopoietic system damage by targeting the TLR2 signaling pathway. Thus, Zymosan-A can be potentially effective radioprotectant.

Bone Marrow Findings Secondary to Antineoplastic Compounds: Hematopoietic, Bone, and Cytokine Cross Talk.

New medullary bone formation has been observed in rats administered a variety of antineoplastic compounds. Similar effects reported in rats administered granulocyte colony-stimulating factor (G-CSF) were attributed to exaggerated pharmacology of G-CSF as a cytokine and growth factor, resulting in stromal proliferation in addition to the intended hematopoietic effects. Similar phenomena of marrow stromal change are reported among other species in association with various growth factors. Case study summaries of test item-related histopathologic changes in bone marrow, reflecting trabecular and/or endosteal new bone formation, are presented. In each of these cases, it was concluded that the new medullary bone and stromal proliferation did not reflect a primary target-related toxicity; rather, the mesenchymal changes were attributed to nonspecific, secondary effects of cytokines elaborated in response to primary cytotoxic effects on hematopoietic cells with subsequent impact on circulating blood cells. The common features associated with marrow stromal changes in the case studies, as well as with a variety of pharmacologic compounds across several species described in the literature, are hematologic effects and/or changes in growth factor levels and cytokine expression.

Environmentally induced tissue responses of hematopoietic system in abu mullet (Liza abu) and tiger tooth croaker (Otolithes ruber) from the Persian Gulf.

The present investigation aimed to assess the possibility of using plasma levels of erythropoietin (EPO) hormone and tissue changes of hematopoietic organs as biomarkers of environmental pollution in abu mullet (Liza abu) and tiger tooth croaker (Otolithes ruber) collected from Musa Creek (northwest of the Persian Gulf). 120 L. abu and O. ruber were collected from five stations at the Musa Creek: Petrochemical, Ghanam, Doragh, Zangi and Patil stations. Blood samples were obtained from the caudal vein. Tissue samples were also taken from the spleen and head kidney, and tissue sections were prepared according to routine histological methods. The concentrations of Hg, Pb, Zn, Cu, and Cd were also measured in the sediment samples. The minimum level of EPO and the most severe tissue changes were determined in fish collected near a Petrochemical station. This station is adjacent to the Imam Khomeini Petrochemical Complex and receives highly contaminated effluents from this complex. The highest degree of contamination (Cd) also belonged to this station. The fish collected from the Patil station represented the highest EPO level and the least tissue changes. This station exhibited a lesser degree of contamination. Based on the results, there was a significant correlation between the plasma level of EPO hormone and the degree of environmental contamination.

Pharmacological Modulation of Radiation Damage. Does It Exist a Chance for Other Substances than Hematopoietic Growth Factors and Cytokines?

In recent times, cytokines and hematopoietic growth factors have been at the center of attention for many researchers trying to establish pharmacological therapeutic procedures for the treatment of radiation accident victims. Two granulocyte colony-stimulating factor-based radiation countermeasures have been approved for the treatment of the hematopoietic acute radiation syndrome. However, at the same time, many different substances with varying effects have been tested in animal studies as potential radioprotectors and mitigators of radiation damage. A wide spectrum of these substances has been studied, comprising various immunomodulators, prostaglandins, inhibitors of prostaglandin synthesis, agonists of adenosine cell receptors, herbal extracts, flavonoids, vitamins, and others. These agents are often effective, relatively non-toxic, and cheap. This review summarizes the results of animal experiments, which show the potential for some of these untraditional or new radiation countermeasures to become a part of therapeutic procedures applicable in patients with the acute radiation syndrome. The authors consider ß-glucan, 5-AED (5-androstenediol), meloxicam, γ-tocotrienol, genistein, IB-MECA (N6-(3-iodobezyl)adenosine-5'-N-methyluronamide), Ex-RAD (4-carboxystyryl-4-chlorobenzylsulfone), and entolimod the most promising agents, with regards to their contingent use in clinical practice.

Hematopoiesis toxicity induced by 4-methylumbelliferon determined in an invertebrate model organism.

Umbelliferone has potential value as it has an inhibitory effect on tumor cells; however, its impact on an animal's circulatory system and hematopoietic function has not been reported. In this study, 4-methylumbelliferon (4-MU), an umbelliferone derivative, was used as a model drug, and its potential toxicity on hemocytes and hematopoietic organs (HOs) was investigated using an invertebrate animal model, the silkworm, Bombyx mori. The results showed that the level of reactive oxygen species in HOs increased when larvae (third day of the fifth instar) were orally exposed to 4 mM 4-MU for 8 min, followed by the induction of improved antioxidative metabolism of coenzymes in hemolymph. Exposure to 4-MU also significantly upregulated the expression levels of several genes in the hemolymph and fat body (a detoxification tissue similar to the liver in mammals) including antimicrobial peptide gene cecropinA and moricin, and a phagocytosis-related gene, tetraspanin E, suggesting an increased antioxidant level and antimicrobial ability of the circulatory system. However, the percentage of dead hemocytes increased and hematopoiesis significantly decreased in HOs, indicating the toxic effect of 4-MU on hemocytes and hematopoiesis, despite it inducing enhanced antioxidant and antimicrobial activity in the circulatory system.

Foxo-mediated Bim transcription is dispensable for the apoptosis of hematopoietic cells that is mediated by this BH3-only protein.

The BH3-only protein Bim is a critical initiator of apoptosis in hematopoietic cells. Bim is upregulated in response to growth factor withdrawal and in vitro studies have implicated the transcription factor Foxo3a as a critical inducer. To test the importance of this regulation in vivo, we generated mice with mutated Foxo-binding sites within the Bim promoters (Bim(ΔFoxo/ΔFoxo)). Contrary to Bim-deficient mice, Bim(ΔFoxo/ΔFoxo) mice had a normal hematopoietic system. Moreover, cytokine-dependent haematopoietic cells from Bim(ΔFoxo/ΔFoxo) and wt mice died at similar rates. These results indicate that regulation of Bim by Foxo transcription factors is not critical for the killing of hematopoietic cells.

FGF signaling facilitates postinjury recovery of mouse hematopoietic system.

Previous studies have shown that fibroblast growth factor (FGF) signaling promotes hematopoietic stem and progenitor cell (HSPC) expansion in vitro. However, it is unknown whether FGF promotes HSPC expansion in vivo. Here we examined FGF receptor 1 (FGFR1) expression and investigated its in vivo function in HSPCs. Conditional knockout (CKO) of Fgfr1 did not affect phenotypical number of HSPCs and homeostatic hematopoiesis, but led to a reduced engraftment only in the secondary transplantation. When treated with 5-fluorouracil (5FU), the Fgfr1 CKO mice showed defects in both proliferation and subsequent mobilization of HSPCs. We identified megakaryocytes (Mks) as a major resource for FGF production, and further discovered a novel mechanism by which Mks underwent FGF-FGFR signaling dependent expansion to accelerate rapid FGF production under stress. Within HSPCs, we observed an up-regulation of nuclear factor κB and CXCR4, a receptor for the chemoattractant SDF-1, in response to bone marrow damage only in control but not in Fgfr1 CKO model, accounting for the corresponding defects in proliferation and migration of HSPCs. This study provides the first in vivo evidence that FGF signaling facilitates postinjury recovery of the mouse hematopoietic system by promoting proliferation and facilitating mobilization of HSPCs.

Chronic exposure to low concentrations of strontium 90 affects bone physiology but not the hematopoietic system in mice.

The aim of this work was to delineate the effects of chronic ingestion of strontium 90 ((90) Sr) at low concentrations on the hematopoiesis and the bone physiology. A mouse model was used for that purpose. Parent animals ingested water containing 20 kBq l(-1) of (90) Sr two weeks before mating. Offspring were then continuously contaminated with (90) Sr through placental transfer during fetal life, through lactation after birth and through drinking water after weaning. At various ages between birth and 20 weeks, animals were tested for hematopoietic parameters such as blood cell counts, colony forming cells in spleen and bone marrow and cytokine concentrations in the plasma. However, we did not find any modification in (90) Sr ingesting animals as compared with control animals. By contrast, the analysis of bone physiology showed a modification of gene expression towards bone resorption. This was confirmed by an increase in C-telopeptide of collagen in the plasma of (90) Sr ingesting animals as compared with control animals. This modification in bone metabolism was not linked to a modification of the phosphocalcic homeostasis, as measured by calcium, phosphorus, vitamin D and parathyroid hormone in the blood. Overall these results suggest that the chronic ingestion of (90) Sr at low concentration in the long term may induce modifications in bone metabolism but not in hematopoiesis.

Study on the mechanism of mitigating radiation damage by improving the hematopoietic system and intestinal barrier with Tenebrio molitor peptides.

Research on plant and animal peptides has garnered significant attention, but there is a lack of studies on the functional properties of Tenebrio molitor peptides, particularly in relation to their potential mitigating effect on radiation damage and the underlying mechanisms. This study aims to explore the protective effects of Tenebrio molitor peptides against radiation-induced damage. Mice were divided into five groups: normal, radiation model, and low-, medium-, and high-dose Tenebrio molitor peptide (TMP) groups (0.15 g per kg BW, 0.30 g per kg BW, and 0.60 g per kg BW). Various parameters such as blood cell counts, bone marrow DNA content, immune organ indices, serum levels of D-lactic acid, diamine oxidase (DAO), endotoxin (LPS), and inflammatory factors were assessed at 3 and 15 days post gamma irradiation. Additionally, the intestinal tissue morphology was examined through H&E staining, RT-qPCR experiments were conducted to analyze the expression of inflammatory factors in the intestine, and immunohistochemistry was utilized to evaluate the expression of tight junction proteins ZO-1 and Occludin in the intestine. The findings revealed that high-dose TMP significantly enhanced the hematopoietic system function in mice post radiation exposure, leading to increased spleen index, thymus index, blood cell counts, and bone marrow DNA production (p < 0.05). Moreover, TMP improved the intestinal barrier integrity and reduced the intestinal permeability. Mechanistic insights suggested that these peptides may safeguard intestinal barrier function by downregulating the gene expression of inflammatory factors TNF-α, IL-1ß, and IL-6, while upregulating the expression of tight junction proteins ZO-1 and Occludin (p < 0.05). Overall, supplementation with TMP mitigates radiation-induced intestinal damage by enhancing the hematopoietic system and the intestinal barrier, offering valuable insights for further investigations into the mechanisms underlying the protective effects of these peptides against ionizing radiation.

Exploring the Potential of Metformin in Mitigating Radiation-induced Gastrointestinal and Hematopoietic System Injury in Rats After Whole-body X-ray Radiation: An Experimental Study.

BACKGROUND: The modern world faces a growing concern about the possibility of accidental radiation events. The Hematopoietic system is particularly vulnerable to radiationinduced apoptosis, which can lead to death. Metformin, a drug used to treat diabetes, has been shown to protect normal cells and tissues from the toxic effects of radiation. This study aimed to evaluate the effectiveness of metformin in mitigating radiation injury to the gastrointestinal and hematological systems of rats. MATERIALS AND METHODS: The study involved 73 male rats. After total body irradiation with 7.5 Gy of X-rays, rats were treated with metformin. Seven days later, the rats were sacrificed and blood samples were taken for evaluation. RESULTS: The study found that metformin was not effective in mitigating radiation injury. The histopathological assessment showed no significant changes in goblet cell injury, villi shortening, inflammation, or mucous layer thickness. In terms of biochemical evaluation, metformin did not significantly affect oxidative stress markers, but irradiation increased the mean MDA level in the radiation group. The complete blood count revealed a significant decrease in WBC and platelet, counts in the radiation group compared to the control group, but no significant difference was found between the radiation and radiation + metformin groups. CONCLUSION: In conclusion, metformin may not be a good option for reducing radiation toxicity after accidental exposure. Despite treatment, there was no improvement in platelet, white blood cell, and lymphocyte counts, nor was there any decrease in oxidative stress. Further research is needed to explore other potential treatments for radiation injury.

Micronucleus induction in the bone marrow of rats by pharmacological mechanisms. I: glucocorticoid receptor agonism.

A novel selective glucocorticoid receptor (GR) agonist, AZD2906, was found to increase the incidence of micronucleated immature erythrocytes (MIE) in the bone marrow of rats given two oral doses at the maximum tolerated level. Because GR agonists as a class are considered not to be genotoxic and AZD2906 showed no activity in the standard in vitro tests or in vivo in a rat liver comet assay, investigative studies were performed to compare AZD2906 with a reference traditional GR agonist, prednisolone. Emphasis was placed on blood and bone marrow parameters in these studies because GR activation has been reported to induce erythropoiesis which, in turn, is known to increase MIE in the bone marrow. Both compounds induced almost identical, small increases in micronucleus frequency at all doses tested. Directly comparable changes in haematological and bone marrow parameters were also seen with significant decreases in lymphoid cells in both compartments and significant increases in numbers of circulating neutrophils. Although no evidence of increased erythropoiesis was seen as increased immature erythrocyte numbers either in the blood or in the bone marrow, histopathological examination showed focal areas in the bone marrow where the erythroid population was enriched in association with an atrophic myeloid lineage. This could have been due to direct stimulation of the erythroid lineage or a secondary effect of myelosuppression inducing a rebound increase in erythropoiesis into the vacant haematopoietic cell compartment. It was concluded that the increased MIE frequencies induced by both AZD2906 and prednisolone are a consequence of their pharmacological effects on the bone marrow, either by directly inducing erythropoiesis or by some other unknown effect on cellular function, and do not indicate potential genotoxicity. This conclusion is supported by the lack of carcinogenic risk in man demonstrated by decades of clinical use of prednisolone and other GR agonists.

Effect of mycophenolate mofetil on hematological side effects incidence in renal transplant recipients.

Mycophenolate mofetil (MMF), an immunosuppressant administered after solid organ transplantation, is generally well tolerated; however, it frequently causes hematological toxicity. In this study, we aimed to assess the relation between the pharmacokinetic parameters of MMF metabolites (mycophenolic acid [MPA] and 7-O-MPA glucuronide [MPAG]) and the adverse effects on the hematopoietic system in renal transplant recipients. The four-h pharmacokinetic profiles of MPA and MPAG were determined using the HPLC method for MMF-treated patients (n = 61) among 106 renal transplant recipients (during the late post-transplant period) participating in the study. Anemia was more frequently observed in the study group compared with the control group (30.7% vs. 20.0%) and although the difference was insignificant, plasma iron concentrations were significantly higher in patients treated with MMF (32.9 ± 9.4 µmol/L vs. 28.7 ± 9.4 µmol/L; p = 0.032). Iron supplementation was more frequently applied to patients with anemia (48.2%) compared with patients with hemoglobin within the norm (20.3%; p = 0.005). As all MPAG pharmacokinetic parameters correlated negatively with hemoglobin and hematocrit, and MPAG pharmacokinetic parameters were higher in patients with anemia, MPAG may be the predicting factor of MMF side effects. In renal transplant recipients, especially with deteriorated renal function, extensive iron supplementation may be ineffective as anemia was associated with declined renal function and was not caused by low iron concentration.

Fancd2-/- mice have hematopoietic defects that can be partially corrected by resveratrol.

Progressive bone marrow failure is a major cause of morbidity and mortality in human Fanconi Anemia patients. In an effort to develop a Fanconi Anemia murine model to study bone marrow failure, we found that Fancd2(-/-) mice have readily measurable hematopoietic defects. Fancd2 deficiency was associated with a significant decline in the size of the c-Kit(+)Sca-1(+)Lineage(-) (KSL) pool and reduced stem cell repopulation and spleen colony-forming capacity. Fancd2(-/-) KSL cells showed an abnormal cell cycle status and loss of quiescence. In addition, the supportive function of the marrow microenvironment was compromised in Fancd2(-/-) mice. Treatment with Sirt1-mimetic and the antioxidant drug, resveratrol, maintained Fancd2(-/-) KSL cells in quiescence, improved the marrow microenvironment, partially corrected the abnormal cell cycle status, and significantly improved the spleen colony-forming capacity of Fancd2(-/-) bone marrow cells. We conclude that Fancd2(-/-) mice have readily quantifiable hematopoietic defects, and that this model is well suited for pharmacologic screening studies.

The ubiquitin-activating enzyme E1 as a therapeutic target for the treatment of leukemia and multiple myeloma.

The proteasomal pathway of protein degradation involves 2 discrete steps: ubiquitination and degradation. Here, we evaluated the effects of inhibiting the ubiquitination pathway at the level of the ubiquitin-activating enzyme UBA1 (E1). By immunoblotting, leukemia cell lines and primary patient samples had increased protein ubiquitination. Therefore, we examined the effects of genetic and chemical inhibition of the E1 enzyme. Knockdown of E1 decreased the abundance of ubiquitinated proteins in leukemia and myeloma cells and induced cell death. To further investigate effects of E1 inhibition in malignancy, we discovered a novel small molecule inhibitor, 3,5-dioxopyrazolidine compound, 1-(3-chloro-4-fluorophenyl)-4-[(5-nitro-2-furyl)methylene]-3,5-pyrazolidinedione (PYZD-4409). PYZD-4409 induced cell death in malignant cells and preferentially inhibited the clonogenic growth of primary acute myeloid leukemia cells compared with normal hematopoietic cells. Mechanistically, genetic or chemical inhibition of E1 increased expression of E1 stress markers. Moreover, BI-1 overexpression blocked cell death after E1 inhibition, suggesting ER stress is functionally important for cell death after E1 inhibition. Finally, in a mouse model of leukemia, intraperitoneal administration of PYZD-4409 decreased tumor weight and volume compared with control without untoward toxicity. Thus, our work highlights the E1 enzyme as a novel target for the treatment of hematologic malignancies.

United States Voluntary Children's Chemical Evaluation Program (VCCEP) risk assessment for children exposed to benzene.

As part of the Voluntary Children's Chemical Evaluation Program (VCCEP) program, a risk assessment was performed to evaluate the risks to children from environmental benzene exposures. This paper summarizes this risk assessment. Risk was characterized using two distinct methods: USEPA's default type of risk assessment, which used the Reference Dose (RfD) and Cancer Slope Factor (CSF) to characterize non-cancer and cancer risks, as well as a Margin of Safety (MOS) approach that utilized a point of departure (POD). The exposures for most scenarios evaluated in this VCCEP risk assessment are lower than both the cancer and non-cancer PODs by several orders of magnitude, indicating a large MOS and corresponding low potential for toxicity at these exposures. The highest benzene exposures likely experienced by children, associated with the lowest MOS, are from cigarette smoke. In addition, the potential for age-related differences in the sensitivity towards benzene-induced toxicity was investigated. In general, this risk assessment does not indicate that children are likely to be at a elevated risk of AML or hematopoietic toxicity associated with environmental exposures to benzene.