G-CSF induced reactive oxygen species involves Lyn-PI3-kinase-Akt and contributes to myeloid cell growth

The dualistic role of Lyn tyrosine kinase in immune cell signaling: implications for systemic lupus erythematosus

Systemic lupus erythematosus (SLE, lupus) is a debilitating, multisystem autoimmune disease that can affect any organ in the body. The disease is characterized by circulating autoantibodies that accumulate in organs and tissues, which triggers an inflammatory response that can cause permanent damage leading to significant morbidity and mortality. Lyn, a member of the Src family of non-receptor protein tyrosine kinases, is highly implicated in SLE as remarkably both mice lacking Lyn or expressing a gain-of-function mutation in Lyn develop spontaneous lupus-like disease due to altered signaling in B lymphocytes and myeloid cells, suggesting its expression or activation state plays a critical role in maintaining tolerance. The past 30 years of research has begun to elucidate the role of Lyn in a duplicitous signaling network of activating and inhibitory immunoreceptors and related targets, including interactions with the interferon regulatory factor family in the toll-like receptor pathway. Gain-of-function mutations in Lyn have now been identified in human cases and like mouse models, cause severe systemic autoinflammation. Studies of Lyn in SLE patients have presented mixed findings, which may reflect the heterogeneity of disease processes in SLE, with impairment or enhancement in Lyn function affecting subsets of SLE patients that may be a means of stratification. In this review, we present an overview of the phosphorylation and protein-binding targets of Lyn in B lymphocytes and myeloid cells, highlighting the structural domains of the protein that are involved in its function, and provide an update on studies of Lyn in SLE patients.

Biomaterials-Boosted Immunotherapy for Osteosarcoma

Osteosarcoma (OS) is a primary malignant bone tumor that emanates from mesenchymal cells, commonly found in the epiphyseal end of long bones. The highly recurrent and metastatic nature of OS poses significant challenges to the efficacy of treatment and negatively affects patient prognosis. Currently, available clinical treatment strategies primarily focus on maximizing tumor resection and reducing localized symptoms rather than the complete eradication of malignant tumor cells to achieve ideal outcomes. The biomaterials-boosted immunotherapy for OS is characterized by high effectiveness and a favorable safety profile. This therapeutic approach manipulates the tumor microenvironments at the cellular and molecular levels to impede tumor progression. This review delves into the mechanisms underlying the treatment of OS, emphasizing biomaterials-enhanced tumor immunity. Moreover, it summarizes the immune cell phenotype and tumor microenvironment regulation, along with the ability of immune checkpoint blockade to activate the autoimmune system. Gaining a profound comprehension of biomaterials-boosted OS immunotherapy is imperative to explore more efficacious immunotherapy protocols and treatment options in this setting.

BTK drives neutrophil activation for sterilizing antifungal immunity

We describe a previously-unappreciated role for Bruton's tyrosine kinase (BTK) in fungal immune surveillance against aspergillosis, an unforeseen complication of BTK inhibitors (BTKi) used for treating B-cell lymphoid malignancies. We studied BTK-dependent fungal responses in neutrophils from diverse populations, including healthy donors, BTKi-treated patients, and X-linked agammaglobulinemia patients. Upon fungal exposure, BTK was activated in human neutrophils in a TLR2-, Dectin-1-, and FcγR-dependent manner, triggering the oxidative burst. BTK inhibition selectively impeded neutrophil-mediated damage to Aspergillus hyphae, primary granule release, and the fungus-induced oxidative burst by abrogating NADPH oxidase subunit p40phox and GTPase RAC2 activation. Moreover, neutrophil-specific Btk deletion in mice enhanced aspergillosis susceptibility by impairing neutrophil function, not recruitment or lifespan. Conversely, GM-CSF partially mitigated these deficits by enhancing p47phox activation. Our findings underline the crucial role of BTK signaling in neutrophils for antifungal immunity and provide a rationale for GM-CSF use to offset these deficits in susceptible patients.

Hematopoietic colony-stimulating factors in head and neck cancers: Recent advances and therapeutic challenges

Colony-stimulating factors (CSFs) are key cytokines responsible for the production, maturation, and mobilization of the granulocytic and macrophage lineages from the bone marrow, which have been gaining attention for playing pro- and/or anti-tumorigenic roles in cancer. Head and neck cancers (HNCs) represent a group of heterogeneous neoplasms with high morbidity and mortality worldwide. Treatment for HNCs is still limited even with the advancements in cancer immunotherapy. Novel treatments for patients with recurrent and metastatic HNCs are urgently needed. This article provides an in-depth review of the role of hematopoietic cytokines such as granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), and interleukin-3 (IL-3; also known as multi-CSF) in the HNCs tumor microenvironment. We have reviewed current results from clinical trials using CSFs as adjuvant therapy to treat HNCs patients, and also clinical findings reported to date on the therapeutic application of CSFs toxicities arising from chemoradiotherapy.

Neutrophil-specific ORAI1 Calcium Channel Inhibition Reduces Pancreatitis-associated Acute Lung Injury

Acute pancreatitis is initiated within pancreatic exocrine cells and sustained by dysregulated systemic inflammatory responses mediated by neutrophils. Store-operated Ca2+ entry (SOCE) through ORAI1 channels in pancreatic acinar cells triggers acute pancreatitis, and ORAI1 inhibitors ameliorate experimental acute pancreatitis, but the role of ORAI1 in pancreatitis-associated acute lung injury has not been determined. Here, we showed mice with pancreas-specific deletion of Orai1 (Orai1ΔPdx1, ∼70% reduction in the expression of Orai1) are protected against pancreatic tissue damage and immune cell infiltration, but not pancreatitis-associated acute lung injury, suggesting the involvement of unknown cells that may cause such injury through SOCE via ORAI1. Genetic (Orai1ΔMRP8) or pharmacological inhibition of ORAI1 in murine and human neutrophils decreased Ca2+ influx and impaired chemotaxis, reactive oxygen species production, and neutrophil extracellular trap formation. Unlike pancreas-specific Orai1 deletion, mice with neutrophil-specific deletion of Orai1 (Orai1ΔMRP8) were protected against pancreatitis- and sepsis-associated lung cytokine release and injury, but not pancreatic injury in experimental acute pancreatitis. These results define critical differences between contributions from different cell types to either pancreatic or systemic organ injury in acute pancreatitis. Our findings suggest that any therapy for acute pancreatitis that targets multiple rather than single cell types is more likely to be effective.

Neutrophils in Cancer and Potential Therapeutic Strategies Using Neutrophil-Derived Exosomes

Neutrophils are the most abundant immune cells and make up about 70% of white blood cells in human blood and play a critical role as the first line of defense in the innate immune response. They also help regulate the inflammatory environment to promote tissue repair. However, in cancer, neutrophils can be manipulated by tumors to either promote or hinder tumor growth depending on the cytokine pool. Studies have shown that tumor-bearing mice have increased levels of neutrophils in peripheral circulation and that neutrophil-derived exosomes can deliver various cargos, including lncRNA and miRNA, which contribute to tumor growth and degradation of extracellular matrix. Exosomes derived from immune cells generally possess anti-tumor activities and induce tumor-cell apoptosis by delivering cytotoxic proteins, ROS generation, H2O2 or activation of Fas-mediated apoptosis in target cells. Engineered exosome-like nanovesicles have been developed to deliver chemotherapeutic drugs precisely to tumor cells. However, tumor-derived exosomes can aggravate cancer-associated thrombosis through the formation of neutrophil extracellular traps. Despite the advancements in neutrophil-related research, a detailed understanding of tumor-neutrophil crosstalk is still lacking and remains a major barrier in developing neutrophil-based or targeted therapy. This review will focus on the communication pathways between tumors and neutrophils, and the role of neutrophil-derived exosomes (NDEs) in tumor growth. Additionally, potential strategies to manipulate NDEs for therapeutic purposes will be discussed.

SIRT1-SIRT7 Expression in Patients with Lymphoproliferative Disorders Undergoing Hematopoietic Stem Cell Mobilization

Sirtuins are involved in the fate of hematopoietic stem cells (HSCs), including their metabolism, stress response, differentiation, migration, and apoptosis. The aim of this study was to explore SIRT1-7 expression during HSC mobilization. The study included 50 patients with lymphoproliferative disorders (39 multiple myeloma, 11 lymphoma). Samples were taken before mobilization (day 0) and on the day of first apheresis (day A). The sirtuin expression was evaluated by the Droplet Digital PCR (ddPCR) method. A significant increase of the SIRT1, SIRT2, SIRT3, SIRT5, SIRT6, and SIRT7 levels measured at day A as compared to baseline was observed. The study revealed a positive correlation between SIRT5, SIRT6, and SIRT7 expression and the CD34+ peak value in peripheral blood and the number of CD34+ cells collected on day A. Patients from the SIRT7 “high expressors” group collected more CD34+ cells on day A than “low expressors”. Upregulated expressions of SIRT3 and SIRT7 on the day of first apheresis were observed in patients in complete remission status (CR) as compared to the non-CR group. Our results suggest that the investigated sirtuins may influence the HSC migration and hematopoietic landscape during mobilization. SIRT5, SIRT6, and SIRT7 may be associated with the efficacy of HSC mobilization.

G-CSF, the guardian of granulopoiesis

A considerable amount of continuous proliferation and differentiation is required to produce daily a billion new neutrophils in an adult human. Of the few cytokines and factors known to control neutrophil production, G-CSF is the guardian of granulopoiesis. G-CSF/CSF3R signaling involves the recruitment of non-receptor protein tyrosine kinases and their dependent signaling pathways of serine/threonine kinases, tyrosine phosphatases, and lipid second messengers. These pathways converge to activate the families of STAT and C/EBP transcription factors. CSF3R mutations are associated with human disorders of neutrophil production, including severe congenital neutropenia, neutrophilia, and myeloid malignancies. More than three decades after their identification, cloning, and characterization of G-CSF and G-CSF receptor, fundamental questions remain about their physiology.

G-CSF - A double edge sword in neutrophil mediated immunity

Neutrophils are vital for the innate immune system's control of pathogens and neutrophil deficiency can render the host susceptible to life-threatening infections. Neutrophil responses must also be tightly regulated because excessive production, recruitment or activation of neutrophils can cause tissue damage in both acute and chronic inflammatory diseases. Granulocyte colony stimulating factor (G-CSF) is a key regulator of neutrophil biology, from production, differentiation, and release of neutrophil precursors in the bone marrow (BM) to modulating the function of mature neutrophils outside of the BM, particularly at sites of inflammation. G-CSF acts by binding to its cognate cell surface receptor on target cells, causing the activation of intracellular signalling pathways mediating the proliferation, differentiation, function, and survival of cells in the neutrophil lineage. Studies in humans and mice demonstrate that G-CSF contributes to protecting the host against infection, but conversely, it can play a deleterious role in inflammatory diseases. As such, neutrophils and the G-CSF pathway may provide novel therapeutic targets. This review will focus on understanding the role G-CSF plays in the balance between effective neutrophil mediated host defence versus neutrophil-mediated inflammation and tissue damage in various inflammatory and infectious diseases.

CD44 engagement enhances acute myeloid leukemia cell adhesion to the bone marrow microenvironment by increasing VLA-4 avidity

Adhesive properties of leukemia cells shape the degree of organ infiltration and the extent of leukocytosis. CD44 and the integrin VLA-4, a CD49d/CD29 heterodimer, are important factors in progenitor cell adhesion in bone marrow. Here, we report their cooperation in acute myeloid leukemia (AML) by a novel non-classical CD44-mediated way of inside-out VLA-4 activation. In primary AML bone marrow samples from patients and the OCI-AML3 cell line, CD44 engagement by hyaluronan induced inside-out activation of VLA-4 resulting in enhanced leukemia cell adhesion on VCAM-1. This was independent of VLA-4 affinity regulation but based on ligand-induced integrin clustering on the cell surface. CD44-induced VLA-4 activation could be inhibited by the Src family kinase inhibitor PP2 and the multikinase inhibitor midostaurin. As a further consequence, the increased adhesion on VCAM-1 allowed AML cells to bind stromal cells strongly. Thereby, the VLA-4/VCAM-1 interaction promoted activation of Akt, MAPK, NF-kB and mTOR signaling and decreased AML cell apoptosis. Collectively, our investigations provide a mechanistic description of an unusual CD44 function in regulating VLA-4 avidity in AML, enhancing AML cell retention in the supportive bone marrow microenvironment.

G-CSF in tumors: Aggressiveness, tumor microenvironment and immune cell regulation

Granulocyte colony-stimulating factor (G-CSF) is a cytokine most well-known for maturation and mobilization of bone marrow neutrophils. Although it is used therapeutically to treat chemotherapy induced neutropenia, it is also highly expressed in some tumors. Case reports suggest that tumors expressing high levels of G-CSF are aggressive, more difficult to treat, and present with poor prognosis and high mortality rates. Research on this topic suggests that G-CSF has tumor-promoting effects on both tumor cells and the tumor microenvironment. G-CSF has a direct effect on tumor cells to promote tumor stem cell longevity and overall tumor cell proliferation and migration. Additionally, it may promote pro-tumorigenic immune cell phenotypes such as M2 macrophages, myeloid-derived suppressor cells, and regulatory T cells. Overall, the literature suggests a plethora of pro-tumorigenic activity that should be balanced with the therapeutic use. In this review, we present an overview of the multiple complex roles of G-CSF and G-CSFR in tumors and their microenvironment and discuss how clinical advances and strategies may open new therapeutic avenues.

Neuroprotection through G-CSF: recent advances and future viewpoints

Granulocyte-colony stimulating factor (G-CSF), a member of the cytokine family of hematopoietic growth factors, is 19.6 kDa glycoprotein which is responsible for the proliferation, maturation, differentiation, and survival of neutrophilic granulocyte lineage. Apart from its proven clinical application to treat chemotherapy-associated neutropenia, recent pre-clinical studies have highlighted the neuroprotective roles of G-CSF i.e., mobilization of haemopoietic stem cells, anti-apoptotic, neuronal differentiation, angiogenesis and anti-inflammatory in animal models of neurological disorders. G-CSF is expressed by numerous cell types including neuronal, immune and endothelial cells. G-CSF is released in autocrine manner and binds to its receptor G-CSF-R which further activates numerous signaling transduction pathways including PI3K/AKT, JAK/STAT and MAP kinase, and thereby promote neuronal survival, proliferation, differentiation, mobilization of hematopoietic stem and progenitor cells. The expression of G-CSF receptors (G-CSF-R) in the different brain regions and their upregulation in response to neuronal insult indicates the autocrine protective signaling mechanism of G-CSF by inhibition of apoptosis, inflammation, and stimulation of neurogenesis. These observed neuroprotective effects of G-CSF makes it an attractive target to mitigate neurodegeneration associated with neurological disorders. The objective of the review is to highlight and summarize recent updates on G-CSF as a therapeutically versatile neuroprotective agent along with mechanisms of action as well as possible clinical applications in neurodegenerative disorders including AD, PD and HD.

Cyba-deficient mice display an increase in hematopoietic stem cells and an overproduction of immunoglobulins

The regulation of protein function by reversible oxidation is increasingly recognized as a key mechanism for the control of cellular signaling, modulating crucial biological processes such as cell differentiation. In this scenario, NADPH oxidases must occupy a prominent position. Our results show that hematopoietic stem and progenitor cells express three p22^phox -dependent NADPH oxidase members (NOX1, NOX2 and NOX4). By deleting the p22^phox coding gene (Cyba), here we have analyzed the importance of this family of enzymes during in vivo hematopoiesis. Cyba^-/- mice show a myeloid bias, and an enrichment of hematopoietic stem cell populations. By means of hematopoietic transplant experiments we have also tried to dissect the specific role of the NADPH oxidases. While the absence of NOX1 or NOX2 provides a higher level of reconstitution, a lack of NOX4 rendered the opposite result, suggesting a functional specificity among the different NADPH oxidases. Cyba^-/- cells showed a hampered activation of AKT1 and a sharp decrease in STAT5 protein. This is in line with the diminished response to IL-7 shown by our results, which could explain the overproduction of immunoglobulins observed in Cyba^-/- mice.

Effect of the unfolded protein response and oxidative stress on mutagenesis in CSF3R: a model for evolution of severe congenital neutropenia to myelodysplastic syndrome/acute myeloid leukemia

Severe congenital neutropenia (SCN) is a rare blood disorder characterised by abnormally low levels of circulating neutrophils. The most common recurrent mutations that cause SCN involve neutrophil elastase (ELANE). The treatment of choice for SCN is the administration of granulocyte-colony stimulating factor (G-CSF), which increases the neutrophil number and improves the survival and quality of life. Long-term survival is however linked to the development of myelodysplastic syndrome/acute myeloid leukemia (MDS/AML). About 70% of MDS/AML patients acquire nonsense mutations affecting the cytoplasmic domain of CSF3R (the G-CSF receptor). About 70% of SCN patients with AML harbour additional mutations in RUNX1. We hypothesised that this coding region of CSF3R constitutes a hotspot vulnerable to mutations resulting from excessive oxidative stress or endoplasmic reticulum (ER) stress. We used the murine Ba/F3 cell line to measure the effect of induced oxidative or ER stress on the mutation rate in our hypothesised hotspot of the exogenous human CSF3R, the corresponding region in the endogenous Csf3r, and Runx1. Ba/F3 cells transduced with the cDNA for partial C-terminal of CSF3R fused in-frame with a green fluorescent protein (GFP) tag were subjected to stress-inducing treatment for 30 days (~51 doubling times). The amplicon-based targeted deep sequencing data for days 15 and 30 samples show that although there was increased mutagenesis observed in all the three genes of interest (partial CSF3R, Csf3r and Runx1), there were more mutations in the GFP region compared with the partial CSF3R region. Our findings also indicate that there is no correlation between the stress-inducing chemical treatments and mutagenesis in Ba/F3 cells. Our data suggest that oxidative or ER stress induction does not promote genomic instability, affecting partial C-terminal of the transduced CSF3R, the endogenous Csf3R and the endogenous Runx1 in Ba/F3 cells that could account for these targets to being mutational hotspots. We conclude that other mechanisms to acquire mutations of CSF3R that help drive the evolution of SCN to MDS/AML.

Inhibition of Matrix Metalloproteinase with BB-94 Protects against Caerulein-Induced Pancreatitis via Modulating Neutrophil and Macrophage Activation

Methods

AP was induced in Balb/C mice by ten hourly intraperitoneal injections of caerulein (100 μg/kg) and LPS (5 mg/kg). The MMP inhibitor, BB-94 (20 mg/kg) was intraperitoneally administered 30 min before AP induction. Pancreatitis was confirmed by histology and serum amylase and lipase. Expression of pancreatic proinflammatory mediators and NF-κB activation were assessed. Bone marrow-derived neutrophils (BMDNs) and macrophages (BMDMs) were isolated. BMDNs were activated by phorbol 12-myristate 13-acetate (PMA, 50 ng/ml) and neutrophil reactive oxygen species (ROS) production was recorded. BMDMs were stimulated with 10 ng/ml IFN-γ and 100 ng/ml LPS to induce M1 macrophage polarization.

Results

Pancreatic MMP-9 was markedly upregulated and serum MMP-9 was increased in caerulein-induced pancreatitis. Inhibition of MMP with BB-94 ameliorated pancreatic tissue damage and decreased the expression of proinflammatory cytokines (TNFα and IL-6) or chemokines (CCL2 and CXCL2) and NF-κB activation. Furthermore, using isolated BMDNs and BMDMs, we found that inhibition of MMP with BB-94 markedly decreased neutrophil ROS production, inhibited inflammatory macrophage polarization and NF-κB activation.

Conclusions

Our results showed that inhibition of MMP with BB-94 protected against pancreatic inflammatory responses in caerulein-induced pancreatitis via modulating neutrophil and macrophage activation.

RUNX1 Mutations in the Leukemic Progression of Severe Congenital Neutropenia

Somatic RUNX1 mutations are found in approximately 10% of patients with de novo acute myeloid leukemia (AML), but are more common in secondary forms of myelodysplastic syndrome (MDS) or AML. Particularly, this applies to MDS/AML developing from certain types of leukemia-prone inherited bone marrow failure syndromes. How these RUNX1 mutations contribute to the pathobiology of secondary MDS/AML is still unknown. This mini-review focusses on the role of RUNX1 mutations as the most common secondary leukemogenic hit in MDS/AML evolving from severe congenital neutropenia (SCN).

Mechanisms of leukemic transformation in congenital neutropenia

PURPOSE OF REVIEW

The development of a myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) in patients with congenital neutropenia is now the major cause of mortality. Treatment options are limited and there are no effective prevention strategies. This review focuses on mechanisms of leukemic transformation in severe congenital neutropenia (SCN) and Shwachman-Diamond syndrome (SDS), the two most common types of congenital neutropenia.

RECENT FINDINGS

AML/MDS that develops in the setting of congenital neutropenia has distinct molecular features. Clonal hematopoiesis because of TP53 mutations is seen in nearly 50% of patients with SDS, but is not seen in patients with SCN. Accordingly, there is a very high frequency of TP53 mutations in AML/MDS arising in the setting of SDS but not SCN. The rate of mutation accumulation in hematopoietic stem cells (HSCs) from patients with congenital neutropenia is not increased.

SUMMARY

Both HSC cell-intrinsic and noncell-intrinsic changes contribute to the development of clonal hematopoiesis in congenital neutropenia and likely accounts for the high rate of leukemic transformation. In SCN, the persistently high levels of granulocyte colony-stimulating factor drive expansion of HSCs carrying truncation mutations of CSF3R. In SDS, impaired ribosome biogenesis induces p53-mediated growth inhibition and drives expansion of HSCs carrying TP53 mutations.

Upregulation of AKR1C1 in mesenchymal stromal cells promotes the survival of acute myeloid leukaemia cells

The leukaemic bone marrow microenvironment, comprising abnormal mesenchymal stromal cells (MSCs), is responsible for the poor prognosis of acute myeloid leukaemia (AML). Therefore, it is essential to determine the mechanisms underlying the supportive role of MSCs in the survival of leukaemia cells. Through in silico analyses, we identified a total of 271 aberrantly expressed genes in the MSCs derived from acute myeloid leukemia (AML) patients that were associated with adipogenic differentiation, of which aldo-keto reductase 1C1 (AKR1C1) was significantly upregulated in the AML-MSCs. Knockdown of AKR1C1 in the MSCs suppressed adipogenesis and promoted osteogenesis, and inhibited the growth of co-cultured AML cell lines compared to the situation in wild- type AML-derived MSCs. Introduction of recombinant human AKR1C1 in the MSCs partially alleviated the effects of AKR1C1 knockdown. In addition, the absence of AKR1C1 reduced secretion of cytokines such as MCP-1, IL-6 and G-CSF from the MSCs, along with inactivation of STAT3 and ERK1/2 in the co-cultured AML cells. AKR1C1 is an essential factor driving the adipogenic differentiation of leukaemic MSCs and mediates its pro-survival effects on AML cells by promoting cytokine secretion and activating the downstream pathways in the AML cells.

Vitamin D Deficiency: Effects on Oxidative Stress, Epigenetics, Gene Regulation, and Aging

Recent advances in vitamin D research indicate that this vitamin, a secosteroid hormone, has beneficial effects on several body systems other than the musculoskeletal system. Both 25 dihydroxy vitamin D [25(OH)₂D] and its active hormonal form, 1,25-dihydroxyvitamin D [1,25(OH)₂D] are essential for human physiological functions, including damping down inflammation and the excessive intracellular oxidative stresses. Vitamin D is one of the key controllers of systemic inflammation, oxidative stress and mitochondrial respiratory function, and thus, the aging process in humans. In turn, molecular and cellular actions form 1,25(OH)₂D slow down oxidative stress, cell and tissue damage, and the aging process. On the other hand, hypovitaminosis D impairs mitochondrial functions, and enhances oxidative stress and systemic inflammation. The interaction of 1,25(OH)₂D with its intracellular receptors modulates vitamin D–dependent gene transcription and activation of vitamin D-responsive elements, which triggers multiple second messenger systems. Thus, it is not surprising that hypovitaminosis D increases the incidence and severity of several age-related common diseases, such as metabolic disorders that are linked to oxidative stress. These include obesity, insulin resistance, type 2 diabetes, hypertension, pregnancy complications, memory disorders, osteoporosis, autoimmune diseases, certain cancers, and systemic inflammatory diseases. Vitamin D adequacy leads to less oxidative stress and improves mitochondrial and endocrine functions, reducing the risks of disorders, such as autoimmunity, infections, metabolic derangements, and impairment of DNA repair; all of this aids a healthy, graceful aging process. Vitamin D is also a potent anti-oxidant that facilitates balanced mitochondrial activities, preventing oxidative stress-related protein oxidation, lipid peroxidation, and DNA damage. New understandings of vitamin D-related advances in metabolomics, transcriptomics, epigenetics, in relation to its ability to control oxidative stress in conjunction with micronutrients, vitamins, and antioxidants, following normalization of serum 25(OH)D and tissue 1,25(OH)₂D concentrations, likely to promise cost-effective better clinical outcomes in humans.

Oxidant Signaling Mediated by Nox2 in Neutrophils Promotes Regenerative Myelopoiesis and Tissue Recovery following Ischemic Damage

Ischemic tissue damage activates hematopoietic stem and progenitor cells (HSPCs) in the bone marrow (BM)-generating myeloid cells, and persistent HSPC activity may drive chronic inflammation and impair tissue recovery. Although increased reactive oxygen species in the BM regulate HSPC functions, their roles in myelopoiesis of activated HSPCs and subsequent tissue recovery during ischemic damage are not well understood. In this paper, we report that deletion of Nox2 NADPH oxidase in mice results in persistent elevations in BM HSPC activity and levels of inflammatory monocytes/macrophages in BM and ischemic tissue in a model of hindlimb ischemia. Ischemic tissue damage induces oxidants in BM such as elevations of hydrogen peroxide and oxidized phospholipids, which activate redox-sensitive Lyn kinase in a Nox2-dependent manner. Moreover, during tissue recovery after ischemic injury, this Nox2-ROS-Lyn kinase axis is induced by Nox2 in neutrophils that home to the BM, which inhibits HSPC activity and inflammatory monocyte generation and promotes tissue regeneration after ischemic damage. Thus, oxidant signaling in the BM mediated by Nox2 in neutrophils regulates myelopoiesis of HSPCs to promote regeneration of damaged tissue.

Reactive oxygen species in haematopoiesis: leukaemic cells take a walk on the wild side

Oxidative stress is related to ageing and degenerative diseases, including cancer. However, a moderate amount of reactive oxygen species (ROS) is required for the regulation of cellular signalling and gene expression. A low level of ROS is important for maintaining quiescence and the differentiation potential of haematopoietic stem cells (HSCs), whereas the level of ROS increases during haematopoietic differentiation; thus, suggesting the importance of redox signalling in haematopoiesis. Here, we will analyse the importance of ROS for haematopoiesis and include evidence showing that cells from leukaemia patients live under oxidative stress. The potential sources of ROS will be described. Finally, the level of oxidative stress in leukaemic cells can also be harnessed for therapeutic purposes. In this regard, the reliance of front-line anti-leukaemia chemotherapeutics on increased levels of ROS for their mechanism of action, as well as the active search for novel compounds that modulate the redox state of leukaemic cells, will be analysed.

Expression and role of granulocyte macrophage colony-stimulating factor receptor (GM-CSFR) and granulocyte colony-stimulating factor receptor (G-CSFR) on Ph-positive acute B lymphoblastic leukemia

OBJECTIVE

We observed that ph + ALL patients administrated with recombinant human G-CSF (rhG-CSF) after intense chemotherapy have presented a trend of disease relapse. Thus, we aim to thoroughly investigate the expression and role of GM-CSFR and G-CSFR on ph + ALL patients.

METHOD

SUP-B15, BALL-1 and primary leukemia cells were used in this study. Transcript levels were analyzed by quantitative PCR while cell viability was measured using a CCK-8 assay. Flow cytometry was used to assess the different stages of cell cycle.

RESULTS

We found that the mRNA expression levels of GM-CSFR and G-CSFR were higher in patients with ph + ALL, as well as in SUP-B15 cells. rhG-CSF was also observed to promote the viability of SUP-B15 cells while inversely inhibiting BALL-1 cell viability. In addition, we also determined that rhG-CSF (100 ng/ml) decreased the sensitivity of SUP-B15 cells to imatinib and nilotinib, while the results were exactly the contrary for dasatinib.

CONCLUSION

We demonstrated high expression levels of GM-CSFR and G-CSFR, as well as their promotable role for viability in ph + ALL cells. We further found that rhG-CSF influenced the sensitivity of SUP-B15 cells to TKIs.

Severe congenital neutropenias

Severe congenital neutropenias are a heterogeneous group of rare haematological diseases characterized by impaired maturation of neutrophil granulocytes. Patients with severe congenital neutropenia are prone to recurrent, often life-threatening infections beginning in their first months of life. The most frequent pathogenic defects are autosomal dominant mutations in ELANE, which encodes neutrophil elastase, and autosomal recessive mutations in HAX1, whose product contributes to the activation of the granulocyte colony-stimulating factor (G-CSF) signalling pathway. The pathophysiological mechanisms of these conditions are the object of extensive research and are not fully understood. Furthermore, severe congenital neutropenias may predispose to myelodysplastic syndromes or acute myeloid leukaemia. Molecular events in the malignant progression include acquired mutations in CSF3R (encoding G-CSF receptor) and subsequently in other leukaemia-associated genes (such as RUNX1) in a majority of patients. Diagnosis is based on clinical manifestations, blood neutrophil count, bone marrow examination and genetic and immunological analyses. Daily subcutaneous G-CSF administration is the treatment of choice and leads to a substantial increase in blood neutrophil count, reduction of infections and drastic improvement of quality of life. Haematopoietic stem cell transplantation is the alternative treatment. Regular clinical assessments (including yearly bone marrow examinations) to monitor treatment course and detect chromosomal abnormalities (for example, monosomy 7 and trisomy 21) as well as somatic pre-leukaemic mutations are recommended.

Reactive Oxygen Species-Producing Myeloid Cells Act as a Bone Marrow Niche for Sterile Inflammation-Induced Reactive Granulopoiesis

Both microbial infection and sterile inflammation augment bone marrow (BM) neutrophil production, but whether the induced accelerated granulopoiesis is mediated by a common pathway and the nature of such a pathway are poorly defined. We recently established that BM myeloid cell-derived reactive oxygen species (ROS) externally regulate myeloid progenitor proliferation and differentiation in bacteria-elicited emergency granulopoiesis. In this article, we show that BM ROS levels are also elevated during sterile inflammation. Similar to in microbial infection, ROS were mainly generated by the phagocytic NADPH oxidase in Gr1⁺ myeloid cells. The myeloid cells and their ROS were uniformly distributed in the BM when visualized by multiphoton intravital microscopy, and ROS production was both required and sufficient for sterile inflammation-elicited reactive granulopoiesis. Elevated granulopoiesis was mediated by ROS-induced phosphatase and tensin homolog oxidation and deactivation, leading to upregulated PtdIns(3,4,5)P3 signaling and increased progenitor cell proliferation. Collectively, these results demonstrate that, although infection-induced emergency granulopoiesis and sterile inflammation-elicited reactive granulopoiesis are triggered by different stimuli and are mediated by distinct upstream signals, the pathways converge to NADPH oxidase-dependent ROS production by BM myeloid cells. Thus, BM Gr1⁺ myeloid cells represent a key hematopoietic niche that supports accelerated granulopoiesis in infective and sterile inflammation. This niche may be an excellent target in various immune-mediated pathologies or immune reconstitution after BM transplantation.

Granulocyte colony-stimulating factor receptor signaling in severe congenital neutropenia, chronic neutrophilic leukemia, and related malignancies

Granulocyte colony-stimulating factor is a hematopoietic cytokine that stimulates neutrophil production and hematopoietic stem cell mobilization by initiating the dimerization of homodimeric granulocyte colony-stimulating factor receptor. Different mutations of CSF3R have been linked to a unique spectrum of myeloid disorders and related malignancies. Myeloid disorders caused by the CSF3R mutations include severe congenital neutropenia, chronic neutrophilic leukemia, and atypical chronic myeloid leukemia. In this review, we provide an analysis of granulocyte colony-stimulating factor receptor, various mutations, and their roles in the severe congenital neutropenia, chronic neutrophilic leukemia, and malignant transformation, as well as the clinical implications and some perspective on approaches that could expand our knowledge with respect to the normal signaling mechanisms and those associated with mutations in the receptor.

Enhanced MAPK signaling is essential for CSF3R-induced leukemia

Both membrane-proximal and truncation mutations in CSF3R have recently been reported to drive the onset of chronic neutrophilic leukemia (CNL). Here we show that although truncation mutation alone can not induce leukemia, both proximal and compound mutations (proximal and truncation mutations on same allele) are leukemogenic with a disease latency of 90 and 23 days, respectively. Comparative whole-genome expression profiling and biochemical experiments revealed that induced expression of Mapk adaptor protein Ksr1 and enhanced Mapk signaling are crucial to leukemogenesis by CSF3R proximal and compound mutants. Moreover, inhibition of Mek1/2 by trametinib alone is sufficient to suppress leukemia induced by both CSF3R proximal and ruxolitinib-resistant compound mutations. Together, these findings elucidate a Mapk-dependent mechanism of CSF3R-induced pathogenesis, and they establish the rationale for clinical evaluation of MEK1/2 inhibition in CNL.

A ROS-Activatable Agent Elicits Homologous Recombination DNA Repair and Synergizes with Pathway Compounds

We designed ROS-activated cytotoxic agents (RACs) that are active against AML cancer cells. In this study, the mechanism of action and synergistic effects against cells coexpressing the AML oncogenes MLL-AF9 fusion and FLT3-ITD were investigated. One RAC (RAC1) had an IC50 value of 1.8±0.3 μm, with ninefold greater selectivity for transformed cells compared to untransformed cells. Treatment induced DNA strand breaks, apoptosis, and cell cycle arrest. Proteomics and transcriptomics revealed enhanced expression of the pentose phosphate pathway, DNA repair, and pathways common to cell stress. Western blotting confirmed repair by homologous recombination. Importantly, RAC1 treatment was synergistic in combination with multiple pathway-targeting therapies in AML cells but less so in untransformed cells. Together, these results demonstrate that RAC1 can selectively target poor prognosis AML and that it does so by creating DNA double-strand breaks that require homologous recombination.

GW5074 and PP2 kinase inhibitors implicate nontraditional c-Raf and Lyn function as drivers of retinoic acid-induced maturation

The multivariate nature of cancer necessitates multi-targeted therapy, and kinase inhibitors account for a vast majority of approved cancer therapeutics. While acute promyelocytic leukemia (APL) patients are highly responsive to retinoic acid (RA) therapy, kinase inhibitors have been gaining momentum as co-treatments with RA for non-APL acute myeloid leukemia (AML) differentiation therapies, especially as a means to treat relapsed or refractory AML patients. In this study GW5074 (a c-Raf inhibitor) and PP2 (a Src-family kinase inhibitor) enhanced RA-induced maturation of t(15;17)-negative myeloblastic leukemia cells and rescued response in RA-resistant cells. PD98059 (a MEK inhibitor) and Akti-1/2 (an Akt inhibitor) were less effective, but did tend to promote maturation-uncoupled G1/G0 arrest, while wortmannin (a PI3K inhibitor) did not enhance differentiation surface marker expression or growth arrest. PD98059 and Akti-1/2 did not enhance differentiation markers and have potential, antagonistic off-targets effects on the aryl hydrocarbon receptor (AhR), but neither could the AhR agonist 6-formylindolo(3,2-b)carbazole (FICZ) rescue differentiation events in the RA-resistant cells. GW5074 rescued early CD38 expression in RA-resistant cells exhibiting an early block in differentiation before CD38 expression, while for RA-resistant cells with differentiation blocked later, PP2 rescued the later differentiation marker CD11b; but surprisingly, the combination of the two was not synergistic. Kinases c-Raf, Src-family kinases Lyn and Fgr, and PI3K display highly correlated signaling changes during RA treatment, while activation of traditional downstream targets (Akt, MEK/ERK), and even the surface marker CD38, were poorly correlated with c-Raf or Lyn during differentiation. This suggests that an interrelated kinase module involving c-Raf, PI3K, Lyn and perhaps Fgr functions in a nontraditional way during RA-induced maturation or during rescue of RA induction therapy using inhibitor co-treatment in RA-resistant leukemia cells.

Regulation of Granulocyte Colony-Stimulating Factor and Its Receptor in Skeletal Muscle is Dependent Upon the Type of Inflammatory Stimulus

The cytokine granulocyte colony-stimulating factor (G-CSF) binds to its receptor (G-CSFR) to stimulate hematopoietic stem cell mobilization, myelopoiesis, and the production and activation of neutrophils. In response to exercise-induced muscle damage, G-CSF is increased in circulation and G-CSFR has recently been identified in skeletal muscle cells. While G-CSF/G-CSFR activation mediates pro- and anti-inflammatory responses, our understanding of the role and regulation in the muscle is limited. The aim of this study was to investigate, in vitro and in vivo, the role and regulation of G-CSF and G-CSFR in skeletal muscle under conditions of muscle inflammation and damage. First, C2C12 myotubes were treated with lipopolysaccharide (LPS) with and without G-CSF to determine if G-CSF modulates the inflammatory response. Second, the regulation of G-CSF and its receptor was measured following eccentric exercise-induced muscle damage and the expression levels we investigated for redox sensitivity by administering the antioxidant N-acetylcysteine (NAC). LPS stimulation of C2C12 myotubes resulted in increases in G-CSF, interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-α (TNFα) messenger RNA (mRNA) and an increase in G-CSF, IL-6, and MCP-1 release from C2C12 myotubes. The addition of G-CSF following LPS stimulation of C2C12 myotubes increased IL-6 mRNA and cytokine release into the media, however it did not affect MCP-1 or TNFα. Following eccentric exercise-induced muscle damage in humans, G-CSF levels were either marginally increased in circulation or remain unaltered in skeletal muscle. Similarly, G-CSFR levels remained unchanged in response to damaging exercise and G-CSF/G-CSFR did not change in response to NAC. Collectively, these findings suggest that G-CSF may cooperate with IL-6 and potentially promote muscle regeneration in vitro, whereas in vivo aseptic inflammation induced by exercise did not change G-CSF and G-CSFR responses. These observations suggest that different models of inflammation produce a different G-CSF response.

Myeloid-derived suppressor cells: their role in the pathophysiology of hematologic malignancies and potential as therapeutic targets

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells at various stages of differentiation/maturation that have a role in cancer induction and progression. They function as vasculogenic and immunosuppressive cells, utilizing multiple mechanisms to block both innate and adaptive anti-tumor immunity. Recently, their mechanism of action and clinical importance have been defined, and the cross-talk between myeloid cells and cancer cells has been shown to contribute to tumor induction, progression, metastasis and tolerance. In this review, we focus on the role of MDSCs in hematologic malignancies and the therapeutic approaches targeting MDSCs that are currently in clinical studies.

Myeloid cell-derived reactive oxygen species externally regulate the proliferation of myeloid progenitors in emergency granulopoiesis

The cellular mechanisms controlling infection-induced emergency granulopoiesis are poorly defined. Here we found that reactive oxygen species (ROS) concentrations in the bone marrow (BM) were elevated during acute infection in a phagocytic NADPH oxidase-dependent manner in myeloid cells. Gr1(+) myeloid cells were uniformly distributed in the BM, and all c-kit(+) progenitor cells were adjacent to Gr1(+) myeloid cells. Inflammation-induced ROS production in the BM played a critical role in myeloid progenitor expansion during emergency granulopoiesis. ROS elicited oxidation and deactivation of phosphatase and tensin homolog (PTEN), resulting in upregulation of PtdIns(3,4,5)P3 signaling in BM myeloid progenitors. We further revealed that BM myeloid cell-produced ROS stimulated proliferation of myeloid progenitors via a paracrine mechanism. Taken together, our results establish that phagocytic NADPH oxidase-mediated ROS production by BM myeloid cells plays a critical role in mediating emergency granulopoiesis during acute infection.

Game of clones: the genomic evolution of severe congenital neutropenia

Severe congenital neutropenia (SCN) is a genetically heterogeneous condition of bone marrow failure usually diagnosed in early childhood and characterized by a chronic and severe shortage of neutrophils. It is now well-established that mutations in HAX1 and ELANE (and more rarely in other genes) are the genetic cause of SCN. In contrast, it has remained unclear how these mutations affect neutrophil development. Innovative models based on induced pluripotent stem cell technology are being explored to address this issue. These days, most SCN patients receive life-long treatment with granulocyte colony-stimulating factor (G-CSF, CSF3). CSF3 therapy has greatly improved the life expectancy of SCN patients, but also unveiled a high frequency of progression toward myelodysplastic syndrome (MDS) and therapy refractory acute myeloid leukemia (AML). Expansion of hematopoietic clones with acquired mutations in the gene encoding the G-CSF receptor (CSF3R) is regularly seen in SCN patients and AML usually descends from one of these CSF3R mutant clones. These findings raised the questions how CSF3R mutations affect CSF3 responses of myeloid progenitors, how they contribute to the pre-leukemic state of SCN, and which additional events are responsible for progression to leukemia. The vast (sub)clonal heterogeneity of AML and the presence of AML-associated mutations in normally aged hematopoietic clones make it often difficult to determine which mutations are responsible for the leukemic process. Leukemia predisposition syndromes such as SCN are unique disease models to identify the sequential acquisition of these mutations and to interrogate how they contribute to clonal selection and leukemic evolution.

Nox family NADPH oxidases: Molecular mechanisms of activation

NADPH oxidases of the Nox family are important enzymatic sources of reactive oxygen species (ROS). Numerous homologue-specific mechanisms control the activity of this enzyme family involving calcium, free fatty acids, protein-protein interactions, intracellular trafficking, and posttranslational modifications such as phosphorylation, acetylation, or sumoylation. After a brief review on the classic pathways of Nox activation, this article will focus on novel mechanisms of homologue-specific activity control and on cell-specific aspects which govern Nox activity. From these findings of the recent years it must be concluded that the activity control of Nox enzymes is much more complex than anticipated. Moreover, depending on the cellular activity state, Nox enzymes are selectively activated or inactivated. The complex upstream signaling aspects of these events make the development of "intelligent" Nox inhibitors plausible, which selectively attenuate disease-related Nox-mediated ROS formation without altering physiological signaling ROS. This approach might be of relevance for Nox-mediated tissue injury in ischemia-reperfusion and inflammation and also for chronic Nox overactivation as present in cancer initiation and cardiovascular disease.

Granulocyte colony-stimulating factor receptor mutations in myeloid malignancy

Granulocyte colony-stimulating factor is a cytokine able to stimulate both myelopoiesis and hematopoietic stem cell mobilization, which has seen it used extensively in the clinic to aid hematopoietic recovery. It acts specifically via the homodimeric granulocyte colony-stimulating factor receptor (G-CSFR), which is principally expressed on the surface of myeloid and hematopoietic progenitor cells. A number of pathogenic mutations have now been identified in CSF3R, the gene encoding G-CSFR. These fall into distinct classes, each of which is associated with a particular spectrum of myeloid disorders, including malignancy. This review details the various CSF3R mutations, their mechanisms of action, and contribution to disease, as well as discussing the clinical implications of such mutations.

Stem cells, redox signaling, and stem cell aging

SIGNIFICANCE

Functional stem cell decline has been postulated to result in loss of maintenance of tissue homeostasis leading to organismal decline and diseases of aging.

RECENT ADVANCES

Recent findings implicate redox metabolism in the control of stem cell pool and stem cell aging. Although reactive oxygen species (ROS) are better known for their damaging properties to DNA, proteins and lipids, recent findings suggest that ROS may also be an integral physiological mediator of cellular signaling in primary cells.

CRITICAL ISSUES

Here we review recent published work on major signaling pathways and transcription factors that are regulated by ROS and mediate ROS regulation of stem cell fate. We will specifically focus on how alterations in this regulation may be implicated in disease and particularly in diseases of stem cell aging. In general, based on the work described here we propose a model in which ROS function as stem cell rheostat.

FUTURE DIRECTIONS

Future work in elucidating how ROS control stem cell cycling, apoptotic machinery, and lineage determination should shed light on mechanisms whereby ROS may control stem cell aging.

Prevalence and impact of colony stimulating factor 3 receptor (CSF3R) mutations among Egyptian acute myeloid leukemia patients

Granulocyte-colony stimulating factor receptor (G-CSFR) mutations have been implicated in the progression of severe congenital neutropenia (SCN) to leukemia. This study aimed to investigate the prevalence of colony stimulating factor 3 receptor (CSF3R) mutations among Egyptian acute myeloid leukemia and their clinic-pathological impact. The study was conducted on 179 adult patients (156 de novo AML and 23 secondary AML on top of SCN). CSF3R mutations were analyzed by sequencing of the PCR products. CSF3R mutations were detected in 2 cases out of 156 de novo AML patients (1.2%) and eighteen cases out of 23 secondary AML patients (78.2%). It was noticed that most of the mutant cases are of younger age, have a high white blood cells count, high bone marrow blasts, bad performance status, and absence of extra medullary disease and with low rate induction remission. Also the overall survival of AML patient's secondary to CSF3R mutations was shorter as compared to those with wild type AML cases. In conclusion the frequency of CSF3R mutations is highly prevalent among AML patients secondary to SCN compared to de novo AML.

Redox-mediated signal transduction by cardiovascular Nox NADPH oxidases

The only known function of the Nox family of NADPH oxidases is the production of reactive oxygen species (ROS). Some Nox enzymes show high tissue-specific expression and the ROS locally produced are required for synthesis of hormones or tissue components. In the cardiovascular system, Nox enzymes are low abundant and function as redox-modulators. By reacting with thiols, nitric oxide (NO) or trace metals, Nox-derived ROS elicit a plethora of cellular responses required for physiological growth factor signaling and the induction and adaptation to pathological processes. The interactions of Nox-derived ROS with signaling elements in the cardiovascular system are highly diverse and will be detailed in this article, which is part of a Special Issue entitled "Redox Signalling in the Cardiovascular System".

Reprint of Neutrophil cell surface receptors and their intracellular signal transduction pathways

Neutrophils play a critical role in the host defense against bacterial and fungal infections, but their inappropriate activation also contributes to tissue damage during autoimmune and inflammatory diseases. Neutrophils express a large number of cell surface receptors for the recognition of pathogen invasion and the inflammatory environment. Those include G-protein-coupled chemokine and chemoattractant receptors, Fc-receptors, adhesion receptors such as selectins/selectin ligands and integrins, various cytokine receptors, as well as innate immune receptors such as Toll-like receptors and C-type lectins. The various cell surface receptors trigger very diverse signal transduction pathways including activation of heterotrimeric and monomeric G-proteins, receptor-induced and store-operated Ca(2+) signals, protein and lipid kinases, adapter proteins and cytoskeletal rearrangement. Here we provide an overview of the receptors involved in neutrophil activation and the intracellular signal transduction processes they trigger. This knowledge is crucial for understanding how neutrophils participate in antimicrobial host defense and inflammatory tissue damage and may also point to possible future targets of the pharmacological therapy of neutrophil-mediated autoimmune or inflammatory diseases.

Overproduction of NOX-derived ROS in AML promotes proliferation and is associated with defective oxidative stress signaling

More than 60% of primary AML blasts constitutively produce high levels of NOX-derived reactive oxygen species (ROS), which drives AML proliferation. High ROS AMLs show depleted antioxidant defenses but evade the oxidative stress response through suppression of p38MAPK signaling.

Kinase AKT controls innate immune cell development and function

The critical roles of kinase AKT in tumour cell proliferation, apoptosis and protein synthesis have been widely recognized. But AKT also plays an important role in immune modulation. Recent studies have confirmed that kinase AKT can regulate the development and functions of innate immune cells (neutrophil, macrophage and dendritic cell). Studies have shown that different isoforms of kinase AKT have different effects in regulating immunity-related diseases, mainly through the mammalian target of rapamycin-dependent or -independent pathways. The purpose of this review is to illustrate the immune modulating effects of kinase AKT on innate immune cell development, survival and function.

Role for granulocyte colony stimulating factor in angiotensin II-induced neutrophil recruitment and cardiac fibrosis in mice

BACKGROUND

Granulocyte colony stimulating factor (G-CSF) is a key mediator of neutrophil infiltration and is profibrotic in the liver, lung, and infarcted heart, but its roles in angiotensin II (Ang II)-induced hypertension and cardiac remodeling have not been fully determined. Thus, we sought to investigate the causal relation of G-CSF to neutrophil recruitment and cardiac fibrosis in C57BL/6J mice.

METHODS

Hypertension and cardiac fibrosis were induced in wild-type (WT) mice receiving continuous infusion of Ang II (1,500ng/kg/min). After 7 days, heart sections were stained with hematoxylin and eosin, Masson's trichrome, and immunohistochemistry. The mRNA expression of cytokines was detected by real-time polymerase chain reaction analysis. The protein levels were measured by Western blot analysis.

RESULTS

After Ang II infusion, myocardial G-CSF expression was significantly elevated in the hearts. Moreover, WT mice exhibited increased blood pressure, marked neutrophil accumulation, proinflammatory cytokine expression, reactive oxygen species production, and cardiac fibrosis after 7 days of Ang II infusion. However, administration of anti-G-CSF neutralizing antibody, but not with control immunoglobulin G, significantly attenuated these effects. In addition, neutralizing G-CSF antibody reversed Ang II-induced activation of ERK1/2, STAT3, and AKT signaling pathways in the hearts.

CONCLUSIONS

This study demonstrates that G-CSF plays a critical role in hypertension and cardiac fibrosis and targeting this cytokine may be a novel therapeutic strategy to ameliorate hypertensive heart disease.

Neutrophil cell surface receptors and their intracellular signal transduction pathways

Neutrophils play a critical role in the host defense against bacterial and fungal infections, but their inappropriate activation also contributes to tissue damage during autoimmune and inflammatory diseases. Neutrophils express a large number of cell surface receptors for the recognition of pathogen invasion and the inflammatory environment. Those include G-protein-coupled chemokine and chemoattractant receptors, Fc-receptors, adhesion receptors such as selectins/selectin ligands and integrins, various cytokine receptors, as well as innate immune receptors such as Toll-like receptors and C-type lectins. The various cell surface receptors trigger very diverse signal transduction pathways including activation of heterotrimeric and monomeric G-proteins, receptor-induced and store-operated Ca^2 + signals, protein and lipid kinases, adapter proteins and cytoskeletal rearrangement. Here we provide an overview of the receptors involved in neutrophil activation and the intracellular signal transduction processes they trigger. This knowledge is crucial for understanding how neutrophils participate in antimicrobial host defense and inflammatory tissue damage and may also point to possible future targets of the pharmacological therapy of neutrophil-mediated autoimmune or inflammatory diseases.

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Neutrophils are crucial players in innate and adaptive immunity.

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Neutrophils also participate in autoimmune and inflammatory diseases.

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Various neutrophil receptors recognize pathogens and the inflammatory environment.

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The various cell surface receptors trigger diverse intracellular signaling.

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Neutrophil receptors and signaling are potential targets in inflammatory diseases.

Diacylglycerol kinases terminate diacylglycerol signaling during the respiratory burst leading to heterogeneous phagosomal NADPH oxidase activation

It is commonly assumed that all phagosomes have identical molecular composition. This assumption has remained largely unchallenged due to a paucity of methods to distinguish individual phagosomes. We devised an assay that extends the utility of nitro blue tetrazolium for detection and quantification of NAPDH oxidase (NOX) activity in individual phagosomes. Implementation of this assay revealed that in murine macrophages there is heterogeneity in the ability of individual phagosomes to generate superoxide, both between and within cells. To elucidate the molecular basis of the variability in NOX activation, we employed genetically encoded fluorescent biosensors to evaluate the uniformity in the distribution of phospholipid mediators of the oxidative response. Despite variability in superoxide generation, the distribution of phosphatidylinositol 3,4,5-trisphosphate, phosphatidylinositol 3-phosphate, and phosphatidic acid was nearly identical in all phagosomes. In contrast, diacylglycerol (DAG) was not generated uniformly across the phagosomal population, varying in a manner that directly mirrored superoxide production. Modulation of DAG levels suggested that NOX activation is precluded when phagosomes fail to reach a critical DAG concentration. In particular, forced expression of diacylglycerol kinase β abrogated DAG accumulation at the phagosome, leading to impaired respiratory burst. Conversely, pharmacological inhibition of DAG kinases or expression of an inactive diacylglycerol kinase β mutant increased the proportion of DAG-positive phagosomes, concomitantly potentiating phagosomal NOX activity. Our data suggest that diacylglycerol kinases limit the extent of NADPH oxidase activation, curtailing the production of potentially harmful reactive oxygen species. The resulting heterogeneity in phagosome responsiveness could enable the survival of a fraction of invading microorganisms.

Novel roles of reactive oxygen species in the pathogenesis of acute myeloid leukemia

It has become apparent that regulation of ROS is important in cell signaling and homeostasis. Accumulation of ROS triggers oxidative stress in various cell types and contributes to the development, progression, and persistence of cancer. Recent research has demonstrated that redox dysregulation caused by ROS promotes proliferation, differentiation, genomic, and epigenetic alterations; immune evasion; and survival in leukemic cells. ROS act as signaling molecules to regulate redox-sensitive transcriptional factors, enzymes, oncogenes, and other downstream effectors. Thus, a thorough understanding the role of ROS as key mediators in leukemogenesis is likely to provide opportunities for improved pharmacological intervention. In this review, we summarize the recent findings that support a role for ROS in the pathogenesis of AML and outline innovative approaches in the implementation of redox therapies for myeloid malignancies.

Effects of radiation on the maturation of megakaryocytes

Megakaryocytes are generated by the differentiation of megakaryocytic progenitors; however, little information has been reported regarding how ionizing radiation affects the differentiation pathway and cellular responses. Human leukemia K562 cells have been used as a model to study megakaryocytic differentiation. In the present study, to investigate the effects of radiation on phorbol 12-myristate 13-acetate (PMA)-induced megakaryocytic differentiation of K562 cells, the cellular processes responsible for the expression of CD41 antigen (GPIIb/IIIa), which is reported to be expressed early in megakaryocyte maturation, were analyzed. The expression of CD41 antigens was significantly increased 72 h after treatment with both 4 Gy X-irradiation and PMA. In this fraction, two populations, CD41(low) and CD41(high) cells, were detected by flow cytometry. The CD41(high) cells sustained intracellular ROS at the initial level for up to 72 h, but CD41(low) cells had reduced ROS by 48 h. The maximum suppressive effect on CD41 expression was observed when N-acetyl cysteine, which is known to act as a ROS scavenger, was administered 48 h after PMA stimulation. When K562 cells were pretreated with mitogen-activated protein kinase (MAPK) pathway inhibitors, an ERK1/2 inhibitor and a p38 MAPK inhibitor, followed by X-irradiation and PMA stimulation, the reactivity profiles of both inhibitors showed the involvement of MAPK pathway. There is a possibility that the K562 cell population contains at least two types of radiosensitive megakaryocytic progenitors with respect to ROS production mechanisms, and intracellular ROS levels determine the extent of CD41 expression.

Megakaryocytic differentiation in human chronic myelogenous leukemia K562 cells induced by ionizing radiation in combination with phorbol 12-myristate 13-acetate

Differentiation-induction therapy is an attractive approach in leukemia treatment. It has been suggested that the accumulation of intracellular reactive oxygen species (ROS) is involved in megakaryocytic differentiation induced by phorbol 12-myristate 13-acetate (PMA) in the K562 leukemia cell line. Therefore, a ROS-inducible technique could be a powerful method of differentiation induction. Accordingly, we hypothesized that ionizing radiation contributes to the acceleration of megakaryocytic differentiation through the accumulation of intracellular ROS in leukemia cells. In the present study, ionizing radiation was shown to promote PMA-induced megakaryocytic differentiation. Cells with high CD41 expression sustained intracellular ROS levels effectively. The enhancement of differentiation by ionizing radiation was found to be regulated through the mitogen-activated protein kinase (MAPK) pathway, involving both extracellular signal-regulated protein kinase 1/2 (ERK1/2) and p38 MAPK. Ionizing radiation also controlled mRNA expression of the oxidative stress response gene heme oxygenase-1 (HO1). Consequently, we concluded that intracellular ROS, increased by ionizing radiation, modulate megakaryocytic differentiation downstream of the MAPK pathway.

G-CSF activation of AKT is not sufficient to prolong neutrophil survival

Neutrophils play an important role in the innate immune response against bacterial and fungal infections. They have a short lifespan in circulation, and their survival can be modulated by several cytokines, including G-CSF. Previous studies have implicated AKT as a critical signaling intermediary in the regulation of neutrophil survival. Our results demonstrate that G-CSF activation of AKT is not sufficient to prolong neutrophil survival. Neutrophils treated with G-CSF undergo apoptosis, even in the presence of high levels of p-AKT. In addition, inhibitors of AKT and downstream targets failed to alter neutrophil survival. In contrast, neutrophil precursors appear to be dependent on AKT signaling pathways for survival, whereas high levels of p-AKT inhibit proliferation. Our data suggest that the AKT/mTOR pathway, although important in G-CSF-driven myeloid differentiation, proliferation, and survival of early hematopoietic progenitors, is less essential in G-CSF suppression of neutrophil apoptosis. Whereas basal AKT levels may be required for the brief life of neutrophils, further p-AKT expression is not able to extend the neutrophil lifespan in the presence of G-CSF.