Cleaved Delta like 1 intracellular domain regulates neural development via Notch signal-dependent and -independent pathways.

Notch-Delta signaling regulates many developmental processes, including tissue homeostasis and maintenance of stem cells. Upon interaction of juxtaposed cells via Notch and Delta proteins, intracellular domains of both transmembrane proteins are cleaved and translocate to the nucleus. Notch intracellular domain activates target gene expression; however, the role of the Delta intracellular domain remains elusive. Here, we show the biological function of Delta like 1 intracellular domain (D1ICD) by modulating its production. We find that the sustained production of D1ICD abrogates cell proliferation but enhances neurogenesis in the developing dorsal root ganglia (DRG), whereas inhibition of D1ICD production promotes cell proliferation and gliogenesis. D1ICD acts as an integral component of lateral inhibition mechanism by inhibiting Notch activity. In addition, D1ICD promotes neurogenesis in a Notch signaling-independent manner. We show that D1ICD binds to Erk1/2 in neural crest stem cells and inhibits the phosphorylation of Erk1/2. In summary, our results indicate that D1ICD regulates DRG development by modulating not only Notch signaling but also the MAP kinase pathway.

Macrophage depletion using clodronate liposomes reveals latent dysfunction of the hematopoietic microenvironment associated with persistently imbalanced M1/M2 macrophage polarization in a mouse model of hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH), a hyperinflammatory syndrome, is caused by the incessant activation of lymphocytes and macrophages, resulting in damage to organs, including hematopoietic organs. Recently, we demonstrated that repeated lipopolysaccharide (LPS) treatment induces HLH-like features in senescence-accelerated (SAMP1/TA-1) mice but not in senescence-resistant control (SAMR1) mice. Hematopoietic failure in LPS-treated SAMP1/TA-1 mice was attributed to hematopoietic microenvironment dysfunction, concomitant with severely imbalanced M1 and M2 macrophage polarization. Macrophages are a major component of the bone marrow (BM) hematopoietic microenvironment. Clodronate liposomes are useful tools for in vivo macrophage depletion. In this study, we depleted macrophages using clodronate liposomes to determine their role in the hematopoietic microenvironment in SAMP1/TA-1 and SAMR1 mice. Under clodronate liposome treatment, the response between SAMR1 and SAMP1/TA-1 mice differed as follows: (1) increase in the number of activated M1 and M2 macrophages derived from newly generated macrophages and M2-dominant and imbalanced M1 and M2 macrophage polarization in the BM and spleen; (2) severe anemia and thrombocytopenia; (3) high mortality rate; (4) decrease in erythroid progenitors and B cell progenitors in the BM; and (5) decrease in the mRNA expression of erythroid-positive regulators such as erythropoietin and increase in that of erythroid- and B lymphoid-negative regulators such as interferon-γ in the BM. Depletion of residual macrophages in SAMP1/TA-1 mice impaired hematopoietic homeostasis, particularly erythropoiesis and B lymphopoiesis, owing to functional impairment of the hematopoietic microenvironment accompanied by persistently imbalanced M1/M2 polarization. Thus, macrophages play a vital role in regulating the hematopoietic microenvironment to maintain homeostasis.

International regulatory uses of acute systemic toxicity data and integration of new approach methodologies.

Chemical regulatory authorities around the world require systemic toxicity data from acute exposures via the oral, dermal, and inhalation routes for human health risk assessment. To identify opportunities for regulatory uses of non-animal replacements for these tests, we reviewed acute systemic toxicity testing requirements for jurisdictions that participate in the International Cooperation on Alternative Test Methods (ICATM): Brazil, Canada, China, the European Union, Japan, South Korea, Taiwan, and the USA. The chemical sectors included in our review of each jurisdiction were cosmetics, consumer products, industrial chemicals, pharmaceuticals, medical devices, and pesticides. We found acute systemic toxicity data were most often required for hazard assessment, classification, and labeling, and to a lesser extent quantitative risk assessment. Where animal methods were required, animal reduction methods were typically recommended. For many jurisdictions and chemical sectors, non-animal alternatives are not accepted, but several jurisdictions provide guidance to support the use of test waivers to reduce animal use for specific applications. An understanding of international regulatory requirements for acute systemic toxicity testing will inform ICATM's strategy for the development, acceptance, and implementation of non-animal alternatives to assess the health hazards and risks associated with acute toxicity.

Imbalanced M1 and M2 Macrophage Polarization in Bone Marrow Provokes Impairment of the Hematopoietic Microenvironment in a Mouse Model of Hemophagocytic Lymphohistiocytosis.

Lipopolysaccharide (LPS) treatment induced hemophagocytic lymphohistiocytosis in senescence-accelerated mice (SAMP1/TA-1), but not in senescence-resistant control mice (SAMR1). SAMP1/TA-1 treated with LPS exhibited functional impairment of the hematopoietic microenvironment, which disrupted the dynamics of hematopoiesis. Macrophages are a major component of the bone marrow (BM) hematopoietic microenvironment, which regulates hematopoiesis. Qualitative and quantitative changes in activated macrophages in LPS-treated SAMP1/TA-1 are thought to contribute to the functional deterioration of the hematopoietic microenvironment. Thus, we examined the polarization of pro-inflammatory (M1) and anti-inflammatory (M2) macrophages, and the dynamics of macrophage production in the BM of SAMP1/TA-1 and SAMR1 after LPS treatment. After LPS treatment, the proportions of M1 and M2 macrophages and the numbers of macrophage progenitor (CFU-M) cells increased in both SAMP1/TA-1 and SAMR1. However, compared to the SAMR1, the increase in the M1 macrophage proportion was prolonged, and the increase in the M2 macrophage proportion was delayed. The increase in the number of CFU-M cells was prolonged in SAMP1/TA-1 after LPS treatment. In addition, the levels of transcripts encoding an M1 macrophage-inducing cytokine (interferon-γ) and macrophage colony-stimulating factor were markedly increased, and the increases in the levels of transcripts encoding M2 macrophage-inducing cytokines (interleukin (IL)-4, IL-10, and IL-13) were delayed in SAMP1/TA-1 when compared to SAMR1. Our results suggest that LPS treatment led to the severely imbalanced polarization of activated M1/M2 macrophages accompanied by a prolonged increase in macrophage production in the BM of SAMP1/TA-1, which led to the impairment of the hematopoietic microenvironment, and disrupted the dynamics of hematopoiesis.

Dynamics of hematopoiesis is disrupted by impaired hematopoietic microenvironment in a mouse model of hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening systemic hyperinflammatory disorder. We found recently that repeated lipopolysaccharide (LPS) treatment induces HLH-like features in senescence-accelerated mice (SAMP1/TA-1) but not in senescence-resistant control mice (SAMR1). In this study, we analyzed the dynamics of hematopoiesis in this mouse model of HLH. When treated repeatedly with LPS, the numbers of myeloid progenitor cells (CFU-GM) and B-lymphoid progenitor cells (CFU-preB) in the bone marrow (BM) rapidly decreased after each treatment in both strains. The number of CFU-GM in SAMP1/TA-1 and SAMR1, and of CFU-preB in SAMR1, returned to pretreatment levels by 7 days after each treatment. However, the recovery in the number of CFU-preB in SAMP1/TA-1 was limited. In both strains, the BM expression of genes encoding positive regulators of myelopoiesis (granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), and interleukin (IL)-6), and negative regulators of B lymphopoiesis (tumor necrosis factor (TNF)-α) was increased. The expression of genes encoding positive regulators of B lymphopoiesis (stromal-cell derived factor (SDF)-1, IL-7, and stem cell factor (SCF)) was persistently decreased in SAMP1/TA-1 but not in SAMR1. Expression of the gene encoding p16INK4a and the proportion of ß-galactosidase-positive cells were increased in cultured stromal cells obtained from LPS-treated SAMP1/TA-1 but not in those from LPS-treated SAMR1. LPS treatment induced qualitative changes in stromal cells, which comprise the microenvironment supporting appropriate hematopoiesis, in SAMP1/TA-1; these stromal cell changes are inferred to disrupt the dynamics of hematopoiesis. Thus, hematopoietic tissue is one of the organs that suffer life-threatening damage in HLH.

Senescence-accelerated mice (SAMP1/TA-1) treated repeatedly with lipopolysaccharide develop a condition that resembles hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis is a life-threatening systemic hyperinflammatory disorder with primary and secondary forms. Primary hemophagocytic lymphohistiocytosis is associated with inherited defects in various genes that affect the immunological cytolytic pathway. Secondary hemophagocytic lymphohistiocytosis is not inherited, but complicates various medical conditions including infections, autoinflammatory/autoimmune diseases, and malignancies. When senescence-accelerated mice (SAMP1/TA-1) with latent deterioration of immunological function and senescence-resistant control mice (SAMR1) were treated repeatedly with lipopolysaccharide, SAMP1/TA-1 mice displayed the clinicopathological features of hemophagocytic lymphohistiocytosis such as hepatosplenomegaly, pancytopenia, hypofibrinogenemia, hyperferritinemia, and hemophagocytosis. SAMR1 mice showed no features of hemophagocytic lymphohistiocytosis. Lipopolysaccharide induced upregulation of proinflammatory cytokines such as interleukin-1ß, interleukin-6, tumor necrosis factor-α, and interferon-γ, and interferon-γ-inducible chemokines such as c-x-c motif chemokine ligands 9 and 10 in the liver and spleen in both SAMP1/TA-1 and SAMR1 mice. However, upregulation of proinflammatory cytokines and interferon-γ-inducible chemokines in the liver persisted for longer in SAMP1/TA-1 mice than in SAMR1 mice. In addition, the magnitude of upregulation of interferon-γ in the liver and spleen after lipopolysaccharide treatment was greater in SAMP1/TA-1 mice than in SAMR1 mice. Furthermore, lipopolysaccharide treatment led to a prolonged increase in the proportion of peritoneal M1 macrophages and simultaneously to a decrease in the proportion of M2 macrophages in SAMP1/TA-1 mice compared with SAMR1 mice. Lipopolysaccharide appeared to induce a hyperinflammatory reaction and prolonged inflammation in SAMP1/TA-1 mice, resulting in features of secondary hemophagocytic lymphohistiocytosis. Thus, SAMP1/TA-1 mice represent a useful mouse model to investigate the pathogenesis of bacterial infection-associated secondary hemophagocytic lymphohistiocytosis.

Thioredoxin-1 maintains mechanistic target of rapamycin (mTOR) function during oxidative stress in cardiomyocytes.

Thioredoxin 1 (Trx1) is a 12-kDa oxidoreductase that catalyzes thiol-disulfide exchange reactions to reduce proteins with disulfide bonds. As such, Trx1 helps protect the heart against stresses, such as ischemia and pressure overload. Mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that regulates cell growth, metabolism, and survival. We have shown previously that mTOR activity is increased in response to myocardial ischemia-reperfusion injury. However, whether Trx1 interacts with mTOR to preserve heart function remains unknown. Using a substrate-trapping mutant of Trx1 (Trx1C35S), we show here that mTOR is a direct interacting partner of Trx1 in the heart. In response to H2O2 treatment in cardiomyocytes, mTOR exhibited a high molecular weight shift in non-reducing SDS-PAGE in a 2-mercaptoethanol-sensitive manner, suggesting that mTOR is oxidized and forms disulfide bonds with itself or other proteins. The mTOR oxidation was accompanied by reduced phosphorylation of endogenous substrates, such as S6 kinase (S6K) and 4E-binding protein 1 (4E-BP1) in cardiomyocytes. Immune complex kinase assays disclosed that H2O2 treatment diminished mTOR kinase activity, indicating that mTOR is inhibited by oxidation. Of note, Trx1 overexpression attenuated both H2O2-mediated mTOR oxidation and inhibition, whereas Trx1 knockdown increased mTOR oxidation and inhibition. Moreover, Trx1 normalized H2O2-induced down-regulation of metabolic genes and stimulation of cell death, and an mTOR inhibitor abolished Trx1-mediated rescue of gene expression. H2O2-induced oxidation and inhibition of mTOR were attenuated when Cys-1483 of mTOR was mutated to phenylalanine. These results suggest that Trx1 protects cardiomyocytes against stress by reducing mTOR at Cys-1483, thereby preserving the activity of mTOR and inhibiting cell death.

Differential Regulation of Lympho-Myelopoiesis by Stromal Cells in the Early and Late Phases in BALB/c Mice Repeatedly Exposed to Lipopolysaccharide.

Chronic lipopolysaccharide (LPS) exposure to mice reduces the lymphoid compartment and skews the hematopoietic cell compartment toward myeloid-cells, which is considered to be a direct effect of LPS on hematopoietic stem cells. However, the effect of chronic LPS exposure on stromal-cells, which compose the hematopoietic microenvironment, has not been elucidated. Here, we investigated early- and late-phase effects of repeated LPS exposure on stromal-cells. During the early phase, when mice were treated with 5 or 25 µg LPS three times at weekly intervals, the numbers of myeloid-progenitor (colony forming unit-granulocyte macrophage (CFU-GM)) cells and B lymphoid-progenitor (CFU-preB) cells in the bone-marrow (BM) rapidly decreased after each treatment. The number of CFU-GM cells recovered from the initial decrease and then increased to levels higher than pretreatment levels, whereas the number of CFU-preB cells remained lower than pretreatment levels. In the BM, expression of genes for positive-regulators of myelopoiesis including granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), and interleukin (IL)-6 and negative-regulators of B lymphopoiesis including tumor necrosis factor (TNF)-α was up-regulated, whereas expression of positive-regulators of B lymphopoiesis including stromal cell-derived factor (SDF)-1, IL-7, and stem cell factor (SCF) was down-regulated. During the late phase, the number of CFU-preB cells remained lower than pretreatment levels 70 d after the first treatments with 5 and 25 µg LPS, whereas the number of CFU-GM cells returned to pretreatment levels. IL-7 gene expression in the BM remained down-regulated, whereas gene-expression levels of SDF-1 and SCF were restored. Thus, chronic LPS exposure may impair stromal-cell function, resulting in prolonged suppression of B lymphopoiesis, which may appear to be senescence similar to the hematological phenotype.

Experimentally induced, synergistic late effects of a single dose of radiation and aging: significance in LKS fraction as compared with mature blood cells.

The number of murine mature blood cells recovered within 6 weeks after 2-Gy whole-body irradiation at 6 weeks of age, whereas in the case of the undifferentiated hematopoietic stem/progenitor cell (HSC/HPC) compartment [cells in the lineage-negative, c-kit-positive and stem-cell-antigen-1-positive (LKS) fraction], the numerical differences between mice with and without irradiation remained more than a year, but conclusively the cells showed numerical recovery. When mice were exposed to radiation at 6 months of age, acute damages of mature blood cells were rather milder probably because of their maturation with age; but again, cells in the LKS fraction were specifically damaged, and their numerical recovery was significantly delayed probably as a result of LKS-specific cellular damages. Interestingly, in contrast to the recovery of the number of cells in the LKS fraction, their quality was not recovered, which was quantitatively assessed on the basis of oxidative-stress-related fluorescence intensity. To investigate why the recovery in the number of cells in the LKS fraction was delayed, expression levels of genes related to cellular proliferation and apoptosis of cells in the bone marrow and LKS fraction were analyzed by real-time polymerase chain reaction (RT-PCR). In the case of 21-month-old mice after radiation exposure, Ccnd1, PiK3r1 and Fyn were overexpressed solely in cells in the LKS fraction. Because Ccnd1and PiK3r1 upregulated by aging were further upregulated by radiation, single-dose radiation seemed to induce the acceleration of aging, which is related to the essential biological responses during aging based on a lifetime-dependent relationship between a living creature and xenobiotic materials.

[New Approach Method for drug discovery and development aimed at regulatory acceptance].

Recently, the importance of safety assessment based on mechanism of action for drug discovery has been emphasized, and international organizations are increasingly requesting safety assessment using non-animal test methods (Hereafter referred to as alternative method) that are not based on animal experiments using human-derived cells or tissues. However, it is clear that the variety of phenomena captured in animal studies cannot be covered by a stand-alone alternative method, as has been developed in the past, and there are some cases that are not intended to assess human toxicity based on comparison with the data of animal experiments. Expectations are therefore growing for the use of the New Approach Method (NAM) in drug discovery. In this article, we summarize the current status of alternative methods for reproductive toxicity testing and the regulatory acceptance of safety assessments by the Microphysiological system (MPS) as examples regarding NAM.

Mast cell development and biostresses: different stromal responses in bone marrow and spleen after treatment of myeloablater, 5-fluorouracil, and inflammatory stressor, lipopolysaccharide.

Mast-cell-development in the bone-marrow (BM) and the spleen is restrictedly controlled by stromal-cells which produce positive-regulators such as stem cell factor (SCF), and negative-regulators such as transforming growth factor-ß (TGF-ß). How the balance between positive- and negative-regulation is achieved or maintained by stromal-cells is not well understood. We intravenously injected 5-fluorouracil (5-FU) and lipopolysaccharide (LPS) into C3H/HeN mice to disrupt mast-cell-development in order to reveal mechanisms of mast-cell-regulation. 5-FU treatment induces a rapid decrease in the number of mast-cell-progenitor (colony-forming unit (CFU)-mast) cells in the BM and spleen, followed by rapid recovery of CFU-mast numbers. Expression of the SCF gene is one-fiftieth the level of that of TGF-ß during the steady-state in BM and spleen. After 5-FU treatment, SCF mRNA levels in the BM markedly increased, approaching TGF-ß mRNA levels, whereas SCF levels in the spleen showed limited oscillations whose increases paralleled those in TGF-ß levels. In contrast, LPS treatment induces a rapid decrease in CFU-mast number in the BM and a rapid increase in of CFU-mast number in the spleen. After LPS treatment, SCF mRNA levels in the BM markedly decreased, whereas SCF levels in the spleen remained unchanged. These results suggest that regulation of mast-cell-development is dominated by negative-signals in the BM and spleen during the steady-state, and, under biostress-conditions such as 5-FU and LPS treatment, the balance between positive- and negative-regulation can be changed in the BM but not in the spleen. The difference in the regulation of mast-cell-development in the BM versus the spleen probably reflects the different roles of tissue-specific stromal-cells.

The low-dose issue and stochastic responses to endocrine disruptors.

The impact of endocrine disruptors, and specifically the low-dose issue, involves interdisciplinary sciences. Thus, in the past these topics have been published widely in the toxicology area. Owing to recent developments in biology, including the whole-genome reading program, the mechanisms underlying the low-dose issue have been clarified. These mechanisms have been found to involve stochastic and probabilistic receptor-mediated adverse effects induced by endocrine disruptors. The effects thought to be induced by low doses of endocrine-disrupting chemicals remain disputed, and the underlying mechanisms remain poorly understood. Three independent factors, each only recently identified and never before encountered in the history of toxicological studies, are associated with what is termed the 'low-dose issue'. First, toxicological risk has been estimated only by extrapolation of adverse phenotypes from high-dose effects and thus provides no reliable information on low-dose effects observed at the right time under experimental paradigm with sufficient sensitivity. Second, toxicity is based on disturbances of homeostatic regulation, a largely unexplored area in toxicology. Third, toxicity is based on stochastic and probabilistic xenobiotic response, a new field of toxicology that is specifically linked to low-dose and less-frequent events. To resolve the low-dose issue whether it causes effects or whether effects observed at low-doses should be considered 'adverse'--or both, each of these factors needs to be addressed.

Age-related exacerbation of hematopoietic organ damage induced by systemic hyper-inflammation in senescence-accelerated mice.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening systemic hyper-inflammatory disorder. The mortality of HLH is higher in the elderly than in young adults. Senescence-accelerated mice (SAMP1/TA-1) exhibit characteristic accelerated aging after 30 weeks of age, and HLH-like features, including hematopoietic organ damage, are seen after lipopolysaccharide (LPS) treatment. Thus, SAMP1/TA-1 is a useful model of hematological pathophysiology in the elderly with HLH. In this study, dosing of SAMP1/TA-1 mice with LPS revealed that the suppression of myelopoiesis and B-lymphopoiesis was more severe in aged mice than in young mice. The bone marrow (BM) expression of genes encoding positive regulators of myelopoiesis (G-CSF, GM-CSF, and IL-6) and of those encoding negative regulators of B cell lymphopoiesis (TNF-α) increased in both groups, while the expression of genes encoding positive-regulators of B cell lymphopoiesis (IL-7, SDF-1, and SCF) decreased. The expression of the GM-CSF-encoding transcript was lower in aged mice than in young animals. The production of GM-CSF by cultured stromal cells after LPS treatment was also lower in aged mice than in young mice. The accumulation of the TNF-α-encoding transcript and the depletion of the IL-7-encoding transcript were prolonged in aged mice compared to young animals. LPS dosing led to a prolonged increase in the proportion of BM M1 macrophages in aged mice compared to young animals. The expression of the gene encoding p16INK4a and the proportion of ß-galactosidase- and phosphorylated ribosomal protein S6-positive cells were increased in cultured stromal cells from aged mice compared to those from young animals, while the proportion of Ki67-positive cells was decreased in stromal cells from aged mice. Thus, age-related deterioration of stromal cells probably causes the suppression of hematopoiesis in aged mice. This age-related latent organ dysfunction may be exacerbated in elderly people with HLH, resulting in poor prognosis.

Visualizing the spatial localization of ciclesonide and its metabolites in rat lungs after inhalation of 1-µm aerosol of ciclesonide by desorption electrospray ionization-time of flight mass spectrometry imaging.

Inhaled ciclesonide (CIC), a corticosteroid used to treat asthma that is also being investigated for the treatment of corona virus disease 2019, hydrolyzes to desisobutyryl-ciclesonide (des-CIC) followed by reversible esterification when exposed to fatty acids in lungs. While previous studies have described the distribution and metabolism of the compounds after inhalation, spatial localization in the lungs remains unclear. We visualized two-dimensional spatial localization of CIC and its metabolites in rat lungs after administration of a single dose of a CIC aerosol (with the mass median aerodynamic diameter of 0.918-1.168 µm) using desorption electrospray ionization-time of flight mass spectrometry imaging (DESI-MSI). In the analysis, CIC, des-CIC, and des-CIC-oleate were imaged in frozen lung sections at high spatial and mass resolutions in negative-ion mode. MSI revealed the coexistence of CIC, des-CIC, and des-CIC-oleate on the airway epithelium, and the distribution of des-CIC and des-CIC-oleate in peripheral lung regions. In addition, a part of CIC independently localized on the airway epithelium. These results suggest that distribution of CIC and its metabolites in lungs is related to both the intended delivery of aerosols to pulmonary alveoli and peripheral regions, and the potential deposition of CIC particles on the airway epithelium.

Considerations of the Japanese Research Working Group for the ICH S6 & Related Issues Regarding Nonclinical Safety Assessments of Oligonucleotide Therapeutics: Comparison with Those of Biopharmaceuticals.

This white paper summarizes the current consensus of the Japanese Research Working Group for the ICH S6 & Related Issues (WGS6) on strategies for the nonclinical safety assessment of oligonucleotide-based therapeutics (ONTs), specifically focused on the similarities and differences to biotechnology-derived pharmaceuticals (biopharmaceuticals). ONTs, like biopharmaceuticals, have high species and target specificities. However, ONTs have characteristic off-target effects that clearly differ from those of biopharmaceuticals. The product characteristics of ONTs necessitate specific considerations when planning nonclinical studies. Some ONTs have been approved for human use and many are currently undergoing nonclinical and/or clinical development. However, as ONTs are a rapidly evolving class of drugs, there is still much to learn to achieve optimal strategies for the development of ONTs. There are no formal specific guidelines, so safety assessments of ONTs are principally conducted by referring to published white papers and conventional guidelines for biopharmaceuticals and new chemical entities, and each ONT is assessed on a case-by-case basis. The WGS6 expects that this report will be useful in considering nonclinical safety assessments and developing appropriate guidelines specific for ONTs.

Novel hepatotoxicity biomarkers of extracellular vesicle (EV)-associated miRNAs induced by CCl4.

Recent findings have revealed that extracellular vesicles (EVs) are secreted from cells and circulate in the blood. EVs are classified as exosomes (40-100 nm), microvesicles (50-1,000 nm) or apoptotic bodies (500-2,000 nm). EVs contain mRNAs, microRNAs, and DNAs and have the ability to transfer them from cell to cell. Recently, especially in humans, the diagnostic accuracy of tumor cell type-specific EV-associated miRNAs as biomarkers has been found to be more than 90 %. In addition, microRNAs contained in EVs in blood are being identified as specific biomarkers of chemical-induced inflammation and organ damage. Therefore, microRNAs contained in the EVs released into the blood from tissues and organs in response to adverse events such as exposure to chemical substances and drugs are expected to be useful as novel biomarkers for toxicity assessment. In this study, C57BL/6 J male mice orally dosed with carbon tetrachloride (CCl4) were used as a hepatotoxicity animal model. Here, we report that not only the known hepatotoxicity biomarkers miR-122 and miR-192 but also 42 novel EV-associated biomarkers were upregulated in mice dosed with CCl4. Some of these novel biomarkers may be expected to be able to use for better understanding the mechanism of toxicity. These results suggest that our newly developed protocol using EV-associated miRNAs as a biomarker would accelerate the rapid evaluation of toxicity caused by chemical substances and/or drugs.

Thioredoxin-1 maintains mitochondrial function via mechanistic target of rapamycin signalling in the heart.

AIMS: Thioredoxin 1 (Trx1) is an evolutionarily conserved oxidoreductase that cleaves disulphide bonds in oxidized substrate proteins such as mechanistic target of rapamycin (mTOR) and maintains nuclear-encoded mitochondrial gene expression. The cardioprotective effect of Trx1 has been demonstrated via cardiac-specific overexpression of Trx1 and dominant negative Trx1. However, the pathophysiological role of endogenous Trx1 has not been defined with a loss-of-function model. To address this, we have generated cardiac-specific Trx1 knockout (Trx1cKO) mice. METHODS AND RESULTS: Trx1cKO mice were viable but died with a median survival age of 25.5 days. They developed heart failure, evidenced by contractile dysfunction, hypertrophy, and increased fibrosis and apoptotic cell death. Multiple markers consistently indicated increased oxidative stress and RNA-sequencing revealed downregulation of genes involved in energy production in Trx1cKO mice. Mitochondrial morphological abnormality was evident in these mice. Although heterozygous Trx1cKO mice did not show any significant baseline phenotype, pressure-overload-induced cardiac dysfunction, and downregulation of metabolic genes were exacerbated in these mice. mTOR was more oxidized and phosphorylation of mTOR substrates such as S6K and 4EBP1 was impaired in Trx1cKO mice. In cultured cardiomyocytes, Trx1 knockdown inhibited mitochondrial respiration and metabolic gene promoter activity, suggesting that Trx1 maintains mitochondrial function in a cell autonomous manner. Importantly, mTOR-C1483F, an oxidation-resistant mutation, prevented Trx1 knockdown-induced mTOR oxidation and inhibition and attenuated suppression of metabolic gene promoter activity. CONCLUSION: Endogenous Trx1 is essential for maintaining cardiac function and metabolism, partly through mTOR regulation via Cys1483.

Benzene activates caspase-4 and -12 at the transcription level, without an association with apoptosis, in mouse bone marrow cells lacking the p53 gene.

Benzene is a well-known environmental pollutant that can induce hematotoxicity, aplastic anemia, acute myelogenous leukemia, and lymphoma. However, although benzene metabolites are known to induce oxidative stress and disrupt the cell cycle, the mechanism underlying lympho/leukemogenicity is not fully understood. Caspase-4 (alias caspase-11) and -12 are inflammatory caspases implicated in inflammation and endoplasmic reticulum stress-induced apoptosis. The objectives of this study were to investigate the altered expression of caspase-4 and -12 in mouse bone marrow after benzene exposure and to determine whether their alterations are associated with benzene-induced bone marrow toxicity, especially cellular apoptosis. In addition, we evaluated whether the p53 gene is involved in regulating the mechanism, using both wild-type (WT) mice and mice lacking the p53 gene. For this study, 8-week-old C57BL/6 mice [WT and p53 knockout (KO)] were administered a benzene solution (150 mg/kg diluted in corn oil) via oral gavage once daily, 5 days/week, for 1 or 2 weeks. Blood and bone marrow cells were collected and cell counts were measured using a Coulter counter. Total mRNA and protein extracts were prepared from the harvested bone marrow cells. Then qRT-PCR and Western blotting were performed to detect changes in the caspases at the mRNA and protein level, respectively. A DNA fragmentation assay and Annexin-V staining were carried out on the bone marrow cells to detect apoptosis. Results indicated that when compared to the control, leukocyte number and bone marrow cellularity decreased significantly in WT mice. The expression of caspase-4 and -12 mRNA increased significantly after 12 days of benzene treatment in the bone marrow cells of benzene-exposed p53KO mice. However, apoptosis detection assays indicated no evidence of apoptosis in p53KO or WT mice. In addition, no changes of other apoptosis-related caspases, such as caspase-3 and -9, were found in WT or p53KO mice at the level of mRNA and proteins. These results indicated that upregulation of caspase-4 and -12 in mice lacking the p53 gene is not associated with cellular apoptosis. In conclusion, caspase-4 and -12 can be activated by benzene treatment without inducing cell apoptosis in mouse bone marrow, which are partly under the regulation of the p53 gene.