Nuclear translocation of an aminoacyl-tRNA synthetase may mediate a chronic "integrated stress response".

Various stress conditions are signaled through phosphorylation of translation initiation factor eukaryotic initiation factor 2α (eIF2α) to inhibit global translation while selectively activating transcription factor ATF4 to aid cell survival and recovery. However, this integrated stress response is acute and cannot resolve lasting stress. Here, we report that tyrosyl-tRNA synthetase (TyrRS), a member of the aminoacyl-tRNA synthetase family that responds to diverse stress conditions through cytosol-nucleus translocation to activate stress-response genes, also inhibits global translation. However, it occurs at a later stage than eIF2α/ATF4 and mammalian target of rapamycin (mTOR) responses. Excluding TyrRS from the nucleus over-activates translation and increases apoptosis in cells under prolonged oxidative stress. Nuclear TyrRS transcriptionally represses translation genes by recruiting TRIM28 and/or NuRD complex. We propose that TyrRS, possibly along with other family members, can sense a variety of stress signals through intrinsic properties of this enzyme and strategically located nuclear localization signal and integrate them by nucleus translocation to effect protective responses against chronic stress.

Mechanistic perspectives on anti-aminoacyl-tRNA synthetase syndrome.

Antisynthetase syndrome (ASSD) is an autoimmune disease characterized by circulating autoantibodies against one of eight aminoacyl-tRNA synthetases (aaRSs). Although these autoantibodies are believed to play critical roles in ASSD pathogenesis, the nature of their roles remains unclear. Here we describe ASSD pathogenesis and discuss ASSD-linked aaRSs - from the WHEP domain that may impart immunogenicity to the role of tRNA in eliciting the innate immune response and the secretion of aaRSs from cells. Through these explorations, we propose that ASSD pathogenesis involves the tissue-specific secretion of aaRSs and that extracellular tRNAs or tRNA fragments and their ability to engage Toll-like receptor signaling may be important disease factors.

Inflammatory platelet production stimulated by tyrosyl-tRNA synthetase mimicking viral infection.

Platelets play a role not only in hemostasis and thrombosis, but also in inflammation and innate immunity. We previously reported that an activated form of tyrosyl-tRNA synthetase (YRSACT) has an extratranslational activity that enhances megakaryopoiesis and platelet production in mice. Here, we report that YRSACT mimics inflammatory stress inducing a unique megakaryocyte (MK) population with stem cell (Sca1) and myeloid (F4/80) markers through a mechanism dependent on Toll-like receptor (TLR) activation and type I interferon (IFN-I) signaling. This mimicry of inflammatory stress by YRSACT was studied in mice infected by lymphocytic choriomeningitis virus (LCMV). Using Sca1/EGFP transgenic mice, we demonstrated that IFN-I induced by YRSACT or LCMV infection suppressed normal hematopoiesis while activating an alternative pathway of thrombopoiesis. Platelets of inflammatory origin (Sca1/EGFP+) were a relevant proportion of those circulating during recovery from thrombocytopenia. Analysis of these "inflammatory" MKs and platelets suggested their origin in myeloid/MK-biased hematopoietic stem cells (HSCs) that bypassed the classical MK-erythroid progenitor (MEP) pathway to replenish platelets and promote recovery from thrombocytopenia. Notably, inflammatory platelets displayed enhanced agonist-induced activation and procoagulant activities. Moreover, myeloid/MK-biased progenitors and MKs were mobilized from the bone marrow, as evidenced by their presence in the lung microvasculature within fibrin-containing microthrombi. Our results define the function of YRSACT in platelet generation and contribute to elucidate platelet alterations in number and function during viral infection.

The impact of aberrant von Willebrand factor-GPIbα interaction on megakaryopoiesis and platelets in humanized type 2B von Willebrand disease model mouse.

Type 2B von Willebrand disease (VWD) is caused by gain-of-function mutations in von Willebrand factor (VWF). Increased VWF affinity for GPIba results in loss of high molecular weight multimers and enhanced platelet clearance, both contributing to the bleeding phenotype. Severity of the symptoms vary among type 2B VWD patients, with some developing thrombocytopenia only under stress conditions. Efforts have been made to study underlying pathophysiology for platelet abnormalities, but animal studies have been limited because of species specificity in the VWF-GPIba interaction. Here, we generated a severe form of type 2B VWD (p.V1316M) knockin mice in the context of human VWF exon 28 (encoding A1 and A2 domains) and crossed them with human GPIba transgenic strain. Heterozygous mutant mice recapitulated the phenotype of type 2B VWD in autosomal dominant manner and presented severe macrothrombocytopenia. Of note, platelets remaining in the circulation had extracytoplasmic GPIba shed-off from the cell surface. Reciprocal bone marrow transplantation determined mutant VWF produced from endothelial cells as the major cause of the platelet phenotype in type 2B VWD mice. Moreover, altered megakaryocyte maturation in the bone marrow and enhanced extramedullary megakaryopoiesis in the spleen were observed. Interestingly, injection of anti-VWF A1 blocking antibody (NMC-4) not only ameliorated platelet count and GPIba expression, but also reversed MK ploidy shift. In conclusion, we present a type 2B VWD mouse model with humanized VWF-GPIba interaction which demonstrated direct influence of aberrant VWF-GPIba binding on megakaryocytes.

Repurposed drugs block toxin-driven platelet clearance by the hepatic Ashwell-Morell receptor to clear Staphylococcus aureus bacteremia.

Staphylococcus aureus (SA) bloodstream infections cause high morbidity and mortality (20 to 30%) despite modern supportive care. In a human bacteremia cohort, we found that development of thrombocytopenia was correlated to increased mortality and increased α-toxin expression by the pathogen. Platelet-derived antibacterial peptides are important in bloodstream defense against SA, but α-toxin decreased platelet viability, induced platelet sialidase to cause desialylation of platelet glycoproteins, and accelerated platelet clearance by the hepatic Ashwell-Morell receptor (AMR). Ticagrelor (Brilinta), a commonly prescribed P2Y12 receptor inhibitor used after myocardial infarction, blocked α-toxin-mediated platelet injury and resulting thrombocytopenia, thereby providing protection from lethal SA infection in a murine intravenous challenge model. Genetic deletion or pharmacological inhibition of AMR stabilized platelet counts and enhanced resistance to SA infection, and the anti-influenza sialidase inhibitor oseltamivir (Tamiflu) provided similar therapeutic benefit. Thus, a "toxin-platelet-AMR" regulatory pathway plays a critical role in the pathogenesis of SA bloodstream infection, and its elucidation provides proof of concept for repurposing two commonly prescribed drugs as adjunctive therapies to improve patient outcomes.

Extracellular tyrosyl-tRNA synthetase cleaved by plasma proteinases and stored in platelet α-granules: Potential role in monocyte activation.

BACKGROUND: Tyrosyl-tRNA synthetase (YRS) belongs to the family of enzymes that catalyzes the tRNA aminoacylation reaction for protein synthesis, and it has been recently shown to exert noncanonical functions. Although database results indicate extremely low levels of YRS mRNA in platelets, YRS protein is abundantly present. The source of YRS in platelets, as well as the physiological role of platelet-stored YRS, remains largely unknown. OBJECTIVES: To clarify how YRS accumulates in platelets and determine the potential role of platelet-stored YRS. METHODS: Recombinant YRS proteins with epitope tags were prepared and tested in vitro for proteolytic cleavage in human plasma. Fluorescent-labeled YRS was examined for uptake by platelets, as demonstrated by western blotting and confocal microscopy analysis. Using RAW-Dual reporter cells, Toll-like receptor and type I interferon activation pathways were analyzed after treatment with YRS. RESULTS: Full-length YRS was cleaved by both elastase and matrix metalloproteinases in the plasma. The cleaved, N-terminal YRS fragment corresponds to the endogenous YRS detected in platelet lysate by western blotting. Both full-length and cleaved forms of YRS were taken up by platelets in vitro and stored in the α-granules. The N-terminal YRS fragment generated by proteolytic cleavage had monocyte activation comparable to that of the constitutive-active mutant YRS (YRSY341A) previously reported. CONCLUSION: Platelets take up both full-length YRS and the active form of cleaved YRS fragment from the plasma. The cleaved, N-terminal YRS fragment stored in α-granules may have potential to activate monocytes.

LINE-1 Hypomethylation Is Associated With Malignant Traits and Cell Proliferation in Lung Adenocarcinoma.

BACKGROUND/AIM: Long interspersed nuclear element-1 (LINE-1) methylation status is a marker for global DNA methylation. However, the relationship between LINE-1 methylation and the biology of lung adenocarcinoma remains unclear. Here, we aimed to examine the role of LINE-1 in lung cancer. MATERIALS AND METHODS: LINE-1 methylation levels were quantified by bisulfite pyrosequencing of resected tumor specimens from 162 patients with lung adenocarcinoma. The relationships of LINE-1 methylation with clinicopathological factors, gene mutations, and Ki-67 immunoreactivity were investigated. RESULTS: LINE-1 hypomethylation was associated with tumor invasion and advanced stage. TP53 mutations were more frequently detected in the LINE-1 hypomethylation group than in the hypermethylation group. LINE-1 hypomethylation was associated with poor recurrence-free survival, high maximum standardized uptake value in positron-emission tomography, and high Ki-67 expression in tumors. CONCLUSION: LINE-1 hypomethylation was associated with high-grade malignancy and poor prognosis in lung adenocarcinoma, but was not related to driver mutations.

Mechanisms of anti-GPIbα antibody-induced thrombocytopenia in mice.

Immune thrombocytopenia (ITP) is an acquired bleeding disorder characterized by antibody-mediated platelet destruction. Different mechanisms have been suggested to explain accelerated platelet clearance and impaired thrombopoiesis, but the pathophysiology of ITP has yet to be fully delineated. In this study, we tested 2 mouse models of immune-mediated thrombocytopenia using the rat anti-mouse GPIbα monoclonal antibody 5A7, generated in our laboratory. After a single IV administration of high-dose (2 mg/kg) 5A7, opsonized platelets were rapidly cleared from the circulation into the spleen and liver; this was associated with rapid upregulation of thrombopoietin (TPO) messenger RNA. In contrast, subcutaneous administration of low-dose 5A7 (0.08-0.16 mg/kg) every 3 days gradually lowered the platelet count; in this case, opsonized platelets were observed only in the spleen, and TPO levels remained unaltered. Interestingly, in both models, the 5A7 antibody was found on the surface of, as well as internalized to, bone marrow megakaryocytes. Consequently, platelets generated in the chronic phase of repeated subcutaneous 5A7 administration model showed reduced GPIbα membrane expression on their surface. Our findings indicate that evaluation of platelet surface GPIbα relative to platelet size may be a useful marker to support the diagnosis of anti-GPIbα antibody-induced ITP.

Modified application of Kawamoto's film method for super-resolution imaging of megakaryocytes in undecalcified bone marrow.

BACKGROUND: Super-resolution microscopy has enabled high-resolution imaging of the actin cytoskeleton in megakaryocytes and platelets. These technologies have extended our knowledge of thrombopoiesis and platelet spreading using megakaryocytes and platelets cultured in vitro on matrix proteins. However, for better understanding of megakaryocytopoiesis and platelet production, high-resolution imaging of cells in an in vivo bone marrow microenvironment is required. Development of Kawamoto's film method greatly advanced the techniques of thin cryosectioning of hard tissues such as undecalcified bones. One obstacle that remains is the spherical aberration that occurs due to the difference in the refractive index for the light path, limiting the usage of Kawamoto's film method to lower magnification observation. OBJECTIVES: To overcome the weakness of the conventional Kawamoto's film method for higher magnification observation of undecalcified bone marrow. METHODS: We have modified the original method with a very simple method: flipping the film at the step of mounting the sections on the glass. RESULTS AND CONCLUSIONS: This new method successfully led to the adjustment of the refractive index and enabled super-resolution imaging of megakaryocytes in undecalcified mouse femurs. Our modified method will expand the application of Kawamoto's film method and enable precise analysis of megakaryocytopoiesis and platelet production in the bone marrow microenvironment under pathophysiological conditions.

TAFI deficiency causes maladaptive vascular remodeling after hemophilic joint bleeding.

Excessive vascular remodeling is characteristic of hemophilic arthropathy (HA) and may contribute to joint bleeding and the progression of HA. Mechanisms for pathological vascular remodeling after hemophilic joint bleeding are unknown. In hemophilia, activation of thrombin-activatable fibrinolysis inhibitor (TAFI) is impaired, which contributes to joint bleeding and may also underlie the aberrant vascular remodeling. Here, hemophilia A (factor VIII-deficient; FVIII-deficient) mice or TAFI-deficient mice with transient (antibody-induced) hemophilia A were used to determine the role of FVIII and TAFI in vascular remodeling after joint bleeding. Excessive vascular remodeling and vessel enlargement persisted in FVIII-deficient and TAFI-deficient mice, but not in transient hemophilia WT mice, after similar joint bleeding. TAFI-overexpression in FVIII-deficient mice prevented abnormal vessel enlargement and vascular leakage. Age-related vascular changes were observed with FVIII or TAFI deficiency and correlated positively with bleeding severity after injury, supporting increased vascularity as a major contributor to joint bleeding. Antibody-mediated inhibition of uPA also prevented abnormal vascular remodeling, suggesting that TAFI's protective effects include inhibition of uPA-mediated plasminogen activation. In conclusion, the functional TAFI deficiency in hemophilia drives maladaptive vascular remodeling in the joints after bleeding. These mechanistic insights allow targeted development of potentially new strategies to normalize vascularity and control rebleeding in HA.

Humanized GPIbα-von Willebrand factor interaction in the mouse.

The interaction of platelet glycoprotein Ibα (GPIbα) with von Willebrand factor (VWF) initiates hemostasis after vascular injury and also contributes to pathological thrombosis. GPIbα binding to the VWF A1 domain (VWFA1) is a target for antithrombotic intervention, but attempts to develop pharmacologic inhibitors have been hindered by the lack of animal models because of the species specificity of the interaction. To address this problem, we generated a knockin mouse with Vwf exon 28-encoding domains A1 and A2 replaced by the human homolog (VWFh28). VWFh28 mice (M1HA) were crossbred with a transgenic mouse strain expressing human GPIbα on platelets (mGPIbαnull;hGPIbαTg; H1MA) to generate a new strain (H1HA) with humanized GPIbα-VWFA1 binding. Plasma VWF levels in the latter 3 strains were similar to those of wild-type mice (M1MA). Compared with the strains that had homospecific GPIbα-VWF pairing (M1MA and H1HA), M1HA mice of those with heterospecific pairing had a markedly greater prolongation of tail bleeding time and attenuation of thrombogenesis after injury to the carotid artery than H1MA mice. Measurements of GPIbα-VWFA1 binding affinity by surface plasmon resonance agreed with the extent of observed functional defects. Ristocetin-induced platelet aggregation was similar in H1HA mouse and human platelet-rich plasma, and it was comparably inhibited by monoclonal antibody NMC-4, which is known to block human GPIbα-VWFA1 binding, which also inhibited FeCl3-induced mouse carotid artery thrombosis. Thus, the H1HA mouse strain is a fully humanized model of platelet GPIbα-VWFA1 binding that provides mechanistic and pharmacologic information relevant to human hemostatic and thrombotic disorders.

miR-3148 Is a Novel Onco-microRNA that Potentiates Tumor Growth In Vivo.

BACKGROUND/AIM: Alterations of microRNA expression in three-dimensional spheroids were examined to identify novel microRNAs that might be associated with tumorigenesis. MATERIALS AND METHODS: Using microRNA microarray analysis, we screened for microRNAs that were dramatically up-regulated inside three-dimensional spheroids in genetically-modified HCT116 human colon cancer cells expressing Copepoda Green Fluorescent Protein under hypoxia. RESULTS: miR-3148 was identified as a possible candidate onco-microRNA. A growth advantage of HCT116 cells stably expressing miR-3148 (HCT116-miR3148) was observed compared to parental cells in vivo, but not in vitro. Additionally, no change in growth under hypoxic or starvation conditions was seen in these cells cultured two-dimensionally; however, HCT116-miR3148 cells maintained as three-dimensional spheroids were highly resistant to hypoxic conditions. HCT116-miR3148 cells were more sensitive to mitogen-activated protein kinase (MAPK) kinase inhibitors and extracellular signal-regulated kinase (ERK) inhibitors. CONCLUSION: MiR-3148 may be a novel onco-microRNA that protects cancer cells from serious stress conditions through the MAPK/ERK pathway, especially in vivo.

Tyrosyl-tRNA synthetase stimulates thrombopoietin-independent hematopoiesis accelerating recovery from thrombocytopenia.

New mechanisms behind blood cell formation continue to be uncovered, with therapeutic approaches for hematological diseases being of great interest. Here we report an enzyme in protein synthesis, known for cell-based activities beyond translation, is a factor inducing megakaryocyte-biased hematopoiesis, most likely under stress conditions. We show an activated form of tyrosyl-tRNA synthetase (YRSACT), prepared either by rationally designed mutagenesis or alternative splicing, induces expansion of a previously unrecognized high-ploidy Sca-1+ megakaryocyte population capable of accelerating platelet replenishment after depletion. Moreover, YRSACT targets monocytic cells to induce secretion of transacting cytokines that enhance megakaryocyte expansion stimulating the Toll-like receptor/MyD88 pathway. Platelet replenishment by YRSACT is independent of thrombopoietin (TPO), as evidenced by expansion of the megakaryocytes from induced pluripotent stem cell-derived hematopoietic stem cells from a patient deficient in TPO signaling. We suggest megakaryocyte-biased hematopoiesis induced by YRSACT offers new approaches for treating thrombocytopenia, boosting yields from cell-culture production of platelet concentrates for transfusion, and bridging therapy for hematopoietic stem cell transplantation.

Correlation between CXCR4/CXCR7/CXCL12 chemokine axis expression and prognosis in lymph-node-positive lung cancer patients.

The CXCR4/CXCR7/CXCL12 chemokine axis plays important roles in the migration of tumor cells during cancer development by modulating site-specific distant metastasis including to regional lymph nodes. We investigated the correlation of these chemokine expressions to prognosis in lymph-node-positive non-small-cell lung cancer (NSCLC) patients. A total of 140 surgically resected specimens of primary site (PS) and metastatic lymph nodes (MLN) of NSCLC involving hilar and/or mediastinal lymph nodes (N1-2) were collected. CXCR4, CXCR7 and CXCL12 expressions were evaluated. Cox regression analysis was performed to determine whether these chemokines were independent prognostic factors in N1-2 NSCLC. High expression of CXCR4 in PS and CXCL12 in MLN was associated with poor overall survival (OS) (P = .025 and .033, respectively). Significant correlations between CXCR4 expression in PS and CXCL12 expression in MLN were observed (P = .040). There was significant difference in OS between 2 groups according to expressions of CXCR4 in PS and CXCL12 in MLN (P = .0033). Expression of CXCL12 in MLN was identified as an independent prognostic factor (HR 1.79, 95% CI 1.08-3.04, P = .023). CXCL12 in MLN was mainly expressed by tumor cells compared with stromal cells (56% vs 25%, respectively, P < .0001). CXCR4/CXCL12 may play roles in tumor progression in MLN and is associated with poor prognosis of lymph-node-positive NSCLC patients.

Monitoring trifluridine incorporation in the peripheral blood mononuclear cells of colorectal cancer patients under trifluridine/tipiracil medication.

Trifluridine/tipiracil (TFTD, TAS-102) is an orally administrated anti-cancer drug with efficacy validated for patients with metastatic colorectal cancer (mCRC). Trifluridine (FTD) is an active cytotoxic component of TFTD and mediates the anticancer effect via its incorporation into DNA. However, it has not been examined whether FTD is incorporated into the tissues of patients who received TFTD medication. By detecting FTD incorporation into DNA by a specific antibody, we successfully detected FTD in the bone marrow and spleen cells isolated from FTD-challenged mice as well as human peripheral blood mononuclear cells (PBMCs) activated with phytohemagglutinin-P and exposed to FTD in vitro. FTD was also detected in PBMCs isolated from mCRC patients who had administrated TFTD medication. Intriguingly, weekly evaluation of PBMCs from mCRC patients revealed the percentage of FTD-positive PBMCs increased and decreased in parallel with the administration and cessation of TFTD medication, respectively. To our knowledge, this is the first report to detect an active cytotoxic component of a chemotherapeutic drug in clinical specimens using a specific antibody. This technique may enable us to predict the clinical benefits or the adverse effects of TFTD in mCRC patients.

Clinical Significance of DNA Damage Response Factors and Chromosomal Instability in Primary Lung Adenocarcinoma.

AIM: The purpose of this study was to investigate the biological role of DNA damage-response genes and chromosomal instability in primary lung adenocarcinoma. MATERIALS AND METHODS: We investigated 60 surgically-resected lung adenocarcinomas. Levels of checkpoint kinase 2 gene (CHEK2) and breast cancer type 1 susceptibility protein gene (BRCA1) mRNA expression were evaluated by polymerase chain reaction (PCR). Epidermal growth factor receptor (EGFR) mutations (exon 19 deletion and exon 21 mutation) were detected by the PCR clamp method. Mutations in Kirsten rat sarcoma viral oncogene homolog gene (KRAS) and TP53 were examined by direct sequencing. Expression levels of p27 and p16 proteins were assessed by immunohistochemistry. Chromosomal aberrations (CA) were examined in 20 samples with single-nucleotide polymorphism-comparative genomic hybridization. RESULTS: CHEK2 mRNA levels were significantly increased in tumor tissues compared to normal tissues (p=0.0123, paired t-test), whereas BRCA mRNA levels were not increased. TP53 mutation positivity and BRCA1 mRNA expression were positively associated with CHEK2 mRNA expression status (p=0.022 and p=0.0008). High CHEK2 mRNA expression was associated with poor recurrence-free survival (p=0.028). CHEK2 mRNA levels were higher in samples with a high CA frequency than in those with a low CA frequency (averages: 0.326 vs. 0.185; p=0.0129). CONCLUSION: The CHEK2 mRNA expression level was found elevated in lung adenocarcinoma and was related to a poor prognostic outcome. The CHEK2 pathway may be important for the proliferation of lung adenocarcinoma, especially in tumors with chromosomal instability.

Underlying Problems in Surgical Treatment of cT1-2N1 Non-Small Cell Lung Cancer.

Background Obtaining an accurate preoperative diagnosis of N1 in non-small cell lung cancer (NSCLC) is a major difficulty. The aim of this retrospective study was to evaluate the pathological and long-term outcomes of NSCLC patients clinically staged with N1 disease, to aid in the search for better treatment strategies. Materials and Methods We retrospectively reviewed the clinical records of 1,180 consecutive patients with NSCLC who underwent surgery for curative intent from 1991 to 2011 in our department. Data on 96 (8.1%) patients who had cT1-2N1 disease and underwent lobectomy or more extensive surgery were available. Results Only 32% of patients (n = 31) were confirmed to have pathological N1 disease, and 34 and 33% of patients were proven to have pN0 and pN2 disease, respectively. Female gender, ≤ 30 pack-year tobacco smoking history, adenocarcinoma, and left-sided disease were significantly associated with pathological upstaging (χ2 test). Multivariate analysis using logistic regression revealed left-sided disease to be independently associated with upstaging (relative risk 4.00, p = 0.015). Left-sided disease was more likely to be underestimated by clinical N staging than right-sided disease (χ2 test, p = 0.0001). Univariate and multivariate survival analyses demonstrated that left-sided disease was an independent prognostic factor associated with poor outcomes (Cox proportional hazards regression: hazard ratio 2.27, p = 0.037). Conclusion The diagnostic accuracy of clinical N1 status was poor. Left-sided disease appeared to be understaged by the preoperative assessment of N status, and therefore, patients who might benefit from preoperative induction treatment would not receive it.