Activation of SHIP by NADPH oxidase-stimulated Lyn leads to enhanced apoptosis in neutrophils

Neutrophils versus Protozoan Parasites: Plasmodium, Trichomonas, Leishmania, Trypanosoma, and Entameoba

Neutrophils are the most abundant polymorphonuclear granular leukocytes in human blood and are an essential part of the innate immune system. Neutrophils are efficient cells that eliminate pathogenic bacteria and fungi, but their role in dealing with protozoan parasitic infections remains controversial. At sites of protozoan parasite infections, a large number of infiltrating neutrophils is observed, suggesting that neutrophils are important cells for controlling the infection. Yet, in most cases, there is also a strong inflammatory response that can provoke tissue damage. Diseases like malaria, trichomoniasis, leishmaniasis, Chagas disease, and amoebiasis affect millions of people globally. In this review, we summarize these protozoan diseases and describe the novel view on how neutrophils are involved in protection from these parasites. Also, we present recent evidence that neutrophils play a double role in these infections participating both in control of the parasite and in the pathogenesis of the disease.

SHIP1 and its role for innate immune regulation-Novel targets for immunotherapy

Phosphoinositide-3-kinase/AKT (PI3K/AKT) signaling plays key roles in the regulation of cellular activity in both health and disease. In immune cells, this PI3K/AKT pathway is critically regulated by the phosphoinositide phosphatase SHIP1, which has been reported to modulate the function of most immune subsets. In this review, we summarize our current knowledge of SHIP1 with a focus on innate immune cells, where we reflect on the most pertinent aspects described in the current literature. We also present several small-molecule agonists and antagonists of SHIP1 developed over the last two decades, which have led to improved outcomes in several preclinical models of disease. We outline these promising findings and put them in relation to human diseases with unmet medical needs, where we discuss the most attractive targets for immune therapies based on SHIP1 modulation.

A heterophil/lymphocyte-selected population reveals the phosphatase PTPRJ is associated with immune defense in chickens

Quantification of leukocyte profiles is among the simplest measures of animal immune function. However, the relationship between H/L ratio and innate immunity and the measure's utility as an index for heterophil function remains to be analyzed. Variants associated with H/L ratio were fine-mapped based on the resequencing of 249 chickens of different generations and an F2 segregating population generated by crossing selection and control lines. H/L ratio in the selection line was associated with a selective sweep of mutations in protein tyrosine phosphatase, receptor type J (PTPRJ), which affects proliferation and differentiation of heterophils through its downstream regulatory genes. The SNP downstream of PTPRJ (rs736799474) have a universal effect on H/L, with CC homozygotes exhibiting improved heterophil function because of downregulated PTPRJ expression. In short, we systematically elucidated the genetic basis of the change in heterophil function resulting from H/L selection by identifying the regulatory gene (PTPRJ) and causative SNP.

Mulberry leaf meal: A potential feed supplement for juvenile Megalobrama amblycephala "Huahai No. 1"

This study was performed to evaluate the potential application of mulberry leaf meal (ML) and fermented mulberry leaf meal (FML) as feed supplements in aquatic animals for developing varieties of practical and economical feed ingredients. Juveniles Megalobrama amblycephala were fed a basal diet (35.7% crude protein, 10.4% crude lipid; control group) supplemented with 2.22% and 4.44% mulberry leaf meals (ML2, ML4) and fermented mulberry leaf meals (FML2, FML4) for 8 weeks. Generally, the two-way ANOVA showed the supplementation level exhibited a prominent effect on the growth performance and physiological status of fish. Furthermore, the two-way ANOVA showed the supplementary fermented mulberry leaf meal increased plasma complement 4 (C4) content (P < 0.05). The weight gain rate (WGR, 145.87%) and the specific growth rate (SGR, 1.63%) were significantly increased in FML2 group compared with the control group (P < 0.05). The muscle crude lipid content and hepatosomatic index (HSI) were higher in FML2 group than that in ML2 group (P < 0.05). The hepatic GSH content in ML4 group and CAT, T-SOD activities in FML4 group were significantly increased compared with the control group (P < 0.05). The hepatic MDA content in FML4 group was significantly decreased compared with the FML2 group (P < 0.05). Total cholesterol (TC) contents showed a significant decrease in ML4 and FML4 groups compared with the control group (P < 0.05). Regarding the gene expression, sirtiun 1 (Sirt1) gene expression was elevated in FML2 group compared with the ML2 group (P < 0.05). Compare to the control group, FML2 diet significantly increased the expression of i-kappa-B alpha (IKBα) gene in liver, and decreased the expression of forkhead box O1 α (FoxO1α), toll-like receptors 4 (TLR4) and nuclear factor-kappa B (NF-κB) genes (P < 0.05). In conclusion, 2.22% FML promoted the growth performance of M. amblycephala and enhanced the anti-inflammatory responses by inhibiting TLR4/NF-κB signaling pathway. On the other hand, 4.44% FML reduced plasma lipid content (hypolipedemic effect) and improved the hepatic antioxidant capacity of M. amblycephala.

The 5-Phosphatase SHIP2 Promotes Neutrophil Chemotaxis and Recruitment

Neutrophils, the most abundant circulating leukocytes in humans have key roles in host defense and in the inflammatory response. Agonist-activated phosphoinositide 3-kinases (PI3Ks) are important regulators of many facets of neutrophil biology. PIP3 is subject to dephosphorylation by several 5’ phosphatases, including SHIP family phosphatases, which convert the PI3K product and lipid second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP3) into PI(3,4)P2, a lipid second messenger in its own right. In addition to the leukocyte restricted SHIP1, neutrophils express the ubiquitous SHIP2. This study analyzed mice and isolated neutrophils carrying a catalytically inactive SHIP2, identifying an important regulatory function in neutrophil chemotaxis and directionality in vitro and in neutrophil recruitment to sites of sterile inflammation in vivo, in the absence of major defects of any other neutrophil functions analyzed, including, phagocytosis and the formation of reactive oxygen species. Mechanistically, this is explained by a subtle effect on global 3-phosphorylated phosphoinositide species. This work identifies a non-redundant role for the hitherto overlooked SHIP2 in the regulation of neutrophils, and specifically, neutrophil chemotaxis/trafficking. It completes an emerging wider understanding of the complexity of PI3K signaling in the neutrophil, and the roles played by individual kinases and phosphatases within.

The Role of SHIP1 on Apoptosis and Autophagy in the Adipose Tissue of Obese Mice

Obesity-induced adipocyte apoptosis promotes inflammation and insulin resistance. Src homology domain-containing inositol 5'-phosphatase 1 (SHIP1) is a key factor of apoptosis and inflammation. However, the role of SHIP1 in obesity-induced adipocyte apoptosis and autophagy is unclear. We found that diet-induced obesity (DIO) mice have significantly greater crown-like structures and terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL)-positive cells than ob/ob or control mice. Using RNA sequencing (RNA-seq) analysis, we identified that the apoptosis- and inflammation-related gene Ship1 is upregulated in DIO and ob/ob mice compared with control mice. In particular, DIO mice had more SHIP1-positive macrophages and lysosomal-associated membrane protein 1 (LAMP1) as well as a higher B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax)/Bcl-2 ratio compared with ob/ob or control mice. Furthermore, caloric restriction attenuated adipose tissue inflammation, apoptosis, and autophagy by reversing increases in SHIP1-associated macrophages, Bax/Bcl2-ratio, and autophagy in DIO and ob/ob mice. These results demonstrate that DIO, not ob/ob, aggravates adipocyte inflammation, apoptosis, and autophagy due to differential SHIP1 expression. The evidence of decreased SHIP1-mediated inflammation, apoptosis, and autophagy indicates new therapeutic approaches for obesity-induced chronic inflammatory diseases.

Modulation of phagocytosis-induced cell death of human neutrophils by Neisseria gonorrhoeae

Optimal innate immune response to infection includes eradication of potential pathogens, resolution of associated inflammation, and restitution of homeostasis. Phagocytosing human polymorphonuclear leukocytes (hPMN) undergo accelerated apoptosis, a process referred to as phagocytosis-induced cell death (PICD) and an early step in their clearance from inflammatory sites. Among human pathogens that modulate hPMN apoptosis, Neisseria gonorrhoeae delays PICD, which may contribute to the exuberant neutrophilic inflammation that characterizes gonorrhea. To elucidate the mechanisms underlying delayed PICD, we compared features of hPMN cell death that followed phagocytosis of N. gonorrhoeae FA1090 wild-type (GC) or serum-opsonized zymosan (OPZ), a prototypical stimulus of PICD. Phosphatidylserine externalization required NADPH oxidase activity after ingestion of GC or OPZ, and annexin V staining and DNA fragmentation were less after phagocytosis of GC compared to OPZ. Caspase 3/7 and caspase 9 activities after phagocytosis of GC were less than that seen after ingestion of OPZ, but caspase 8 activity was the same after ingestion of GC or OPZ. When hPMN sequentially ingested GC followed by OPZ, both caspase 3/7 and 9 activities were less than that seen after OPZ alone, and the inhibition was dose dependent for GC, suggesting that ingestion of GC actively inhibited PICD. Sequential phagocytosis did not block caspase 8 activity, mitochondrial depolarization, or annexin V/propidium iodide staining compared to responses of hPMN fed OPZ alone, despite inhibition of caspases 3/7 and 9. Taken together, these data suggest that active inhibition of the intrinsic pathway of apoptosis contributes to the delay in PICD after hPMN ingestion of N. gonorrhoeae.

Neutrophil interactions with the sexually transmitted parasite Trichomonas vaginalis: implications for immunity and pathogenesis

Trichomoniasis is the third most common sexually transmitted infection in humans and is caused by the protozoan parasite, Trichomonas vaginalis (Tv). Pathogenic outcomes are more common in women and generally include mild vaginitis or cervicitis. However, more serious effects associated with trichomoniasis include adverse reproductive outcomes. Like other infectious agents, pathogenesis from Tv infection is predicted to be the result of both parasite and host factors. At the site of infection, neutrophils are the most abundant immune cells present and probably play key roles in both parasite clearance and inflammatory pathology. Here, we discuss the evidence that neutrophils home to the site of Tv infection, kill the parasite, and that in some circumstances, parasites possibly evade neutrophil-directed killing. In vitro, the parasite is killed by neutrophils using a novel antimicrobial mechanism called trogocytosis, which probably involves both innate and adaptive immunity. While mechanisms of evasion are mostly conjecture at present, the persistence of Tv infections in patients argues strongly for their existence. Additionally, many strains of Tv harbour microbial symbionts Mycoplasma hominis or Trichomonasvirus, which are both predicted to impact neutrophil responses against the parasite. Novel research tools, especially animal models, will help to reveal the true outcomes of many factors involved in neutrophil-Tv interactions during trichomoniasis.

Neutrophils in innate immunity and systems biology-level approaches

The innate immune system is the first line of host defense against invading microorganisms. Polymorphonuclear leukocytes (PMNs or neutrophils) are the most abundant leukocyte in humans and essential to the innate immune response against invading pathogens. Compared to the acquired immune response, which requires time to develop and is dependent on previous interaction with specific microbes, the ability of neutrophils to kill microorganisms is immediate, nonspecific, and not dependent on previous exposure to microorganisms. Historically, studies of PMN-pathogen interaction focused on the events leading to killing of microorganisms, such as recruitment/chemotaxis, transmigration, phagocytosis, and activation, whereas postphagocytosis sequelae were infrequently considered. In addition, it was widely accepted that human neutrophils possessed limited capacity for new gene transcription and thus, relatively little biosynthetic capacity. This notion has changed dramatically within the past 20 years. Further, there is now more effort directed to understand the events occurring in PMNs after killing of microbes. Herein, we give an updated review of the systems biology-level approaches that have been used to gain an enhanced view of the role of neutrophils during host-pathogen interaction and neutrophil-mediated diseases. We anticipate that these and future systems-level studies will continue to provide information important for understanding, treatment, and control of diseases caused by pathogenic microorganisms. This article is categorized under: Physiology > Organismal Responses to Environment Physiology > Mammalian Physiology in Health and Disease Biological Mechanisms > Cell Fates.

Regulation of hematopoietic cell signaling by SHIP-1 inositol phosphatase: growth factors and beyond

SHIP-1 is a hematopoietic-specific inositol phosphatase activated downstream of a multitude of receptors including those for growth factors, cytokines, antigen, immunoglobulin and toll-like receptor agonists where it exerts inhibitory control. While it is constitutively expressed in all immune cells, SHIP-1 expression is negatively regulated by the inflammatory and oncogenic micro-RNA miR-155. Knockout mouse studies have shown the importance of SHIP-1 in various immune cell subsets and have revealed a range of immune-mediated pathologies that are engendered due to loss of SHIP-1's regulatory activity, impelling investigations into the role of SHIP-1 in human disease. In this review, we provide an overview of the literature relating to the role of SHIP-1 in hematopoietic cell signaling and function, we summarize recent reports that highlight the dysregulation of the SHIP-1 pathway in cancers, autoimmune disorders and inflammatory diseases, and lastly we discuss the importance of SHIP-1 in restraining myeloid growth factor signaling.

Transcriptional profile of breast muscle in heat stressed layers is similar to that of broiler chickens at control temperature

BACKGROUND

In recent years, the commercial importance of changes in muscle function of broiler chickens and of the corresponding effects on meat quality has increased. Furthermore, broilers are more sensitive to heat stress during transport and at high ambient temperatures than smaller egg-laying chickens. We hypothesised that heat stress would amplify muscle damage and expression of genes that are involved in such changes and, thus, lead to the identification of pathways and networks associated with broiler muscle and meat quality traits. Broiler and layer chickens were exposed to control or high ambient temperatures to characterise differences in gene expression between the two genotypes and the two environments.

RESULTS

Whole-genome expression studies in breast muscles of broiler and layer chickens were conducted before and after heat stress; 2213 differentially-expressed genes were detected based on a significant (P < 0.05) genotype × treatment interaction. This gene set was analysed with the BioLayout Express^3D and Ingenuity Pathway Analysis software and relevant biological pathways and networks were identified. Genes involved in functions related to inflammatory reactions, cell death, oxidative stress and tissue damage were upregulated in control broilers compared with control and heat-stressed layers. Expression of these genes was further increased in heat-stressed broilers.

CONCLUSIONS

Differences in gene expression between broiler and layer chickens under control and heat stress conditions suggest that damage of breast muscles in broilers at normal ambient temperatures is similar to that in heat-stressed layers and is amplified when broilers are exposed to heat stress. The patterns of gene expression of the two genotypes under heat stress were almost the polar opposite of each other, which is consistent with the conclusion that broiler chickens were not able to cope with heat stress by dissipating their body heat. The differentially expressed gene networks and pathways were consistent with the pathological changes that are observed in the breast muscle of heat-stressed broilers.

The effects of emodin on cell viability, respiratory burst and gene expression of Nrf2-Keap1 signaling molecules in the peripheral blood leukocytes of blunt snout bream (Megalobrama amblycephala)

We determined the effects of emodin on the cell viability, respiratory burst activity, mRNA levels of antioxidative enzymes (Cu-Zn SOD, CAT and NOX2), and gene expressions of the Nrf2-Keap1 signaling molecules in the peripheral blood leukocytes of blunt snout bream. Triplicate groups of cultured cells were treated with different concentrations of emodin (0.04-25 μg/ml) for 24 h. Results showed that the emodin caused a dramatic loss in cell viability, and occurred in a dose-dependent manner. Emodin exposure (1-25 μg/ml) were significantly induced the ROS generation compared to the control. The respiratory burst and NADPH oxidase activities were significantly induced at a concentration of 0.20 μg/ml, and inhibited at 25 μg/ml. Besides, mRNA levels of antioxidant enzyme genes were dramatically regulated by emodin exposure for 24 h. During low concentrations of exposure, mRNA levels of Cu-Zn SOD in the cells treated with 0.04, 0.20 μg/ml, CAT, NOX2 and Nrf2 in the cells treated with 1 μg/ml were sharply increased, respectively. Whereas, high concentrations were dramatically down-regulated the gene expressions of CAT in the cells treated with 5, 25 μg/ml and NOX2 in the cells treated with 25 μg/ml. Furthermore, sharp increase in Keap1and Bach1 expression levels were observed a dose-dependent manner. In conclusion, this study demonstrated that emodin could induce antioxidant defenses which were involved in cytotoxic activities, respiratory burst and the transcriptional regulation levels of antioxidant enzymes and Nrf2-Keap1 signaling molecules.

Tumor-associated neutrophils display a distinct N1 profile following TGFβ modulation: A transcriptomics analysis of pro- vs. antitumor TANs

It is becoming increasingly clear that tumor-associated neutrophils (TANs) play an important role in cancer biology, through direct impact on tumor growth and by recruitment of other cells types into the tumor. The function of neutrophils in cancer has been the subject of seemingly contradicting reports, pointing toward a dual role played by TANs in tumor progression. The existence of multiple neutrophil subsets, as well as phenotypic modulation of the neutrophils by various factors in the tumor microenvironment, has been shown. TGFβ plays a significant role in the determination of neutrophils' phenotype, by shifting the balance from an antitumor (N1) toward a more permissive (N2) phenotype. The full range of mechanisms responsible for the pro- vs. antitumor effects of TANs has not yet been elucidated. Therefore, the ability to identify the different neutrophil subpopulations in the tumor is critical in order to understand TANs evolution and contribution throughout tumor progression. Using a transcriptomic approach, we identified alternations in gene expression profile following TGFβ inhibition. We show that N1 and N2 TANs represent distinct subpopulations with different transcriptional signatures and both differ from naive bone marrow neutrophils. The analysis highlights a clear difference in pathways involved in neutrophil function such as cytoskeletal organization and antigen presentation, as well as alterations in chemokine profile, eventually affecting their effect on tumor cells and tumor growth. These data highlights several potential new pathways and mechanisms by which neutrophils can influence both the tumor cells and the adaptive immune system.

Nitric oxide-mediated apoptosis of neutrophils through caspase-8 and caspase-3-dependent mechanism

Neutrophils play an indispensable role in killing of invading pathogens by enhancing reactive oxygen species (ROS) and NO generation, and subsequently undergoing apoptosis. Unlike ROS/NOX2, role of NO/NOS still remains undefined in the apoptosis of neutrophils (PMNs) and the present study attempts to decipher the importance of NO/NOS in the neutrophil apoptosis. Prolonged treatment of human PMNs or mice bone marrow derived neutrophils (BMDN) with NO led to enhanced ROS generation, caspase-8/caspase-3 cleavage, reduced mitochondrial membrane potential and finally cellular apoptosis. NO-induced ROS generation led to caspase-8 deglutathionylation and activation, which subsequently activated mitochondrial death pathway via BID (Bcl-2 family protein) cleavage. NO-mediated augmentation of caspase-8 and BID cleavage was significantly prevented in BMDN from neutrophil cytosolic factor-1 (NCF-1) knockout (KO) mice, implying the involvement of NOX2 in NO-induced apoptosis of PMNs. Furthermore, ROS, NO generation and inducible nitric oxide synthase (iNOS) expression were enhanced in a time-dependent manner in human PMNs and mice BMDN undergoing spontaneous apoptosis. Pharmacological and genetic ablation of iNOS in human PMNs and mice BMDN significantly reduced the levels of apoptosis. Impaired apoptosis of BMDN from iNOS KO mice was due to reduced caspase-8 activity which subsequently prevented caspase-3 and -9 activation. Altogether, our results suggest a crucial role of NO/iNOS in neutrophil apoptosis via enhanced ROS generation and caspase-8 mediated activation of mitochondrial death pathway.

Molecular control of PtdIns(3,4,5)P3 signaling in neutrophils

Neutrophils play critical roles in innate immunity and host defense. However, excessive neutrophil accumulation or hyper-responsiveness of neutrophils can be detrimental to the host system. Thus, the response of neutrophils to inflammatory stimuli needs to be tightly controlled. Many cellular processes in neutrophils are mediated by localized formation of an inositol phospholipid, phosphatidylinositol (3,4,5)-trisphosphate (PtdIns(3,4,5)P3), at the plasma membrane. The PtdIns(3,4,5)P3 signaling pathway is negatively regulated by lipid phosphatases and inositol phosphates, which consequently play a critical role in controlling neutrophil function and would be expected to act as ideal therapeutic targets for enhancing or suppressing innate immune responses. Here, we comprehensively review current understanding about the action of lipid phosphatases and inositol phosphates in the control of neutrophil function in infection and inflammation.

Matrine inhibits the growth and induces apoptosis of osteosarcoma cells in vitro by inactivating the Akt pathway

Matrine, a natural product, has been demonstrated to be a promising chemotherapeutic drug for some cancers. Using flow cytometric analysis of the cell cycle and apoptosis, we found that matrine inhibited the proliferation and induced apoptosis in the human osteosarcoma (OS) cell lines MG63, HOS, U2OS, and SAOS2 in vitro in a dose-dependent manner. We therefore assessed the role of the serine/threonine kinase Akt in the regulation of matrine-mediated cell growth inhibition and apoptosis induction in human OS cell lines. After treatment for 48 h, matrine induced G0/G1-stage cell cycle arrest in MG63, U2OS, and SAOS2 cells associated with an increase in the expression of p27(Kip1) and a decrease in the expression of Akt, glycogen synthase kinase 3 (GSK3)-β (Ser9), and cyclin D1. Furthermore, the pro-apoptotic factor Bax was upregulated. Overall, our findings suggest that matrine may be an effective anti-osteosarcoma drug due to its ability to inhibit proliferation and induce apoptosis in OS cells, possibly through the involvement of Akt signaling.

The hepatitis B virus e antigen suppresses the respiratory burst and mobility of human monocytes and neutrophils

The Hepatitis B virus (HBV) e antigen (HBeAg) is a secretory, non-structural protein, and associated with persistent infection of HBV. Previous studies indicate that HBeAg is able to regulate T cell-mediated responses, however, the interaction between HBeAg and the innate immune system is poorly understood. In this study, we demonstrated that recombinant HBeAg (rHBe) bound to human peripheral blood monocytes, neutrophils, and B lymphocytes but not to T lymphocytes. We focused on investigating the effects of HBeAg on monocytes and neutrophils and found that rHBe decreased the respiratory burst in both types of cells. Furthermore, we observed that cell migration in monocytes and neutrophils was suppressed by rHBe in a transwell assay. The attenuation of rHBe was not caused by a general cytotoxic effect because rHBe treatment stimulated low levels of cytokine and chemokine production by monocytes and it promoted neutrophil survival. Since the recruitment of monocytes and neutrophils to the infected site is crucial for the initiation of inflammation, HBeAg may modulate innate immune responses by diminishing the respiratory burst and migration of monocytes and neutrophils, which might interfere with the subsequent innate and adaptive immune responses against HBV, leading to the establishment of chronic infection.

The human ΔNp53 isoform triggers metabolic and gene expression changes that activate mTOR and alter mitochondrial function

A naturally occurring p53 isoform that lacks 39 residues at the N-terminus (denoted ΔNp53), when expressed with wild-type p53 (WTp53), forms mixed ΔNp53:WTp53 tetramers and causes accelerated aging in mice. Cellular alterations specific to ΔNp53:WTp53 have been difficult to assess because ΔNp53 and WTp53 coexpression results in tetramer heterogeneity, including formation of contaminating WTp53 tetramers. Based on the p53 tetramer structure, we expressed ΔNp53 and WTp53 as a single transcript that maintained tetramer architecture, ensuring a 2:2 ΔNp53:WTp53 stoichiometry. As expected, ΔNp53:WTp53 tetramers were stable and transcriptionally active in vitro and in cells, largely mimicking the function of WTp53 tetramers. Microarray analyses, however, revealed about 80 genes whose expression was altered twofold or more in ΔNp53:WTp53 cells. Moreover, global metabolomic profiling quantitated hundreds of biochemicals across different experiments (WTp53, ΔNp53:WTp53, plus controls). When evaluated collectively, these data suggested altered mTOR signaling and mitochondrial function-each canonical regulators of longevity-in cells expressing ΔNp53:WTp53 vs. WTp53. Increased levels of free amino acids, increased expression of IRS-1, and decreased expression of INPP5D/SHIP-1 suggested activated mTOR signaling in ΔNp53:WTp53 cells; this was confirmed upon comparative analyses of several mTOR pathway intermediates. We also observed changes in mitochondrial function in ΔNp53:WTp53 cells, which correlated with increased MARS2 expression and increased levels of carnitine, acetyl CoA, ATP, and Krebs cycle intermediates. Finally, increased levels of succinate and 2-hydroxyglutarate indicate potential epigenetic means to propagate ΔNp53:WTp53-induced gene expression changes to cell progeny. This may be especially important for aging, as biological effects manifest over time.

Role of inositol poly-phosphatases and their targets in T cell biology

T lymphocytes play a critical role in host defense in all anatomical sites including mucosal surfaces. This not only includes the effector arm of the immune system, but also regulation of immune responses in order to prevent autoimmunity. Genetic targeting of PI3K isoforms suggests that generation of PI(3,4,5)P3 by PI3K plays a critical role in promoting effector T cell responses. Consequently, the 5'- and 3'-inositol poly-phosphatases SHIP1, SHIP2, and phosphatase and tensin homolog capable of targeting PI(3,4,5)P3 are potential genetic determinants of T cell effector functions in vivo. In addition, the 5'-inositol poly-phosphatases SHIP1 and 2 can shunt PI(3,4,5)P3 to the rare but potent signaling phosphoinositide species PI(3,4)P2 and thus these SHIP1/2, and the INPP4A/B enzymes that deplete PI(3,4)P2 may have precise roles in T cell biology to amplify or inhibit effectors of PI3K signaling that are selectively recruited to and activated by PI(3,4)P2. Here we summarize recent genetic and chemical evidence that indicates the inositol poly-phosphatases have important roles in both the effector and regulatory functions of the T cell compartment. In addition, we will discuss future genetic studies that might be undertaken to further elaborate the role of these enzymes in T cell biology as well as potential pharmaceutical manipulation of these enzymes for therapeutic purposes in disease settings where T cell function is a key in vivo target.

Modulation of Neutrophil Apoptosis and the Resolution of Inflammation through β2 Integrins

Precise control of the neutrophil death program provides a balance between their defense functions and safe clearance, whereas impaired regulation of neutrophil death is thought to contribute to a wide range of inflammatory pathologies. Apoptosis is essential for neutrophil functional shutdown, removal of emigrated neutrophils, and timely resolution of inflammation. Neutrophils receive survival and pro-apoptosis cues from the inflammatory microenvironment and integrate these signals through surface receptors and common downstream mechanisms. Among these receptors are the leukocyte-specific membrane receptors β2 integrins that are best known for regulating adhesion and phagocytosis. Accumulating evidence indicate that outside-in signaling through the β2 integrin Mac-1 can generate contrasting cues in neutrophils, leading to promotion of their survival or apoptosis. Binding of Mac-1 to its ligands ICAM-1, fibrinogen, or the azurophilic granule enzyme myeloperoxidase suppresses apoptosis, whereas Mac-1-mediated phagocytosis of bacteria evokes apoptotic cell death. Mac-1 signaling is also target for the anti-inflammatory, pro-resolving mediators, including lipoxin A4, aspirin-triggered lipoxin A4, and resolvin E1. This review focuses on molecular mechanisms underlying Mac-1 regulation of neutrophil apoptosis and highlights recent advances how hierarchy of survival and pro-apoptosis signals can be harnessed to facilitate neutrophil apoptosis and the resolution of inflammation.

Two SHIPs passing in the middle of the immune system

Immunity requires a complex, multiscale system of molecules, cells, and cytokines. In this issue of the European Journal of Immunology, Collazo et al. [Eur. J. Immunol. 2012. 42: 1785-1796] provide evidence that links the lipid phosphatase SHIP1 with the coordination of interactions between regulatory T (Treg) cells and myeloid-derived suppressor cells (MDSCs). Using conditional knockouts of SHIP1 in either the myeloid or T-cell-lineage of mice, the authors show that the regulated development of Treg cells is controlled directly by cell-intrinsic SHIP1, and indirectly by extrinsic SHIP1 control of an unknown myeloid cell. Regulation of MDSCs is also determined by SHIP1 in an extrinsic manner, again via an as-yet-unknown myeloid cell. Furthermore, this extrinsic control of Treg cells and MDSCs is mediated in part by increased production of G-CSF, a growth factor critical for the production of neutrophils, in SHIP1-deficient mice. Thus, a physiologically important implication of this report is the collaboration between the innate and adaptive immune systems in fine tuning of Treg cells as discussed in this commentary.

Sweet syndrome in an infant with chronic granulomatous disease

Sweet syndrome is characterized by painful, erythematous cutaneous lesions containing neutrophilic infiltrates. Although more commonly seen in adults, Sweet syndrome has also been recognized in several pediatric cases. Two previous cases of pediatric Sweet syndrome and 1 adult case have been described in chronic granulomatous disease (CGD) patients. We report the case of an infant with known CGD who was presented with methicillin-sensitive Staphylococcus aureus lymphadenitis and subsequently developed Sweet syndrome. CGD patients are prone to several disorders of inflammation. This case illustrates that Sweet syndrome may be part of the spectrum of inflammatory conditions to which CGD patients are predisposed.

Lucigenin- and luminol-dependent chemiluminescence of blood neutrophils in patients with renal cancer

High basal production of primary active oxygen forms was detected in the peripheral blood neutrophils of patients with renal cell cancer. In vitro stimulation of neutrophils led to more rapid release of superoxide radicals into extracellular space and to a reduction of cell capacity to more intense production of primary active oxygen forms.

Activity of the potent dual Abl/Src tyrosine kinase inhibitor FB2 against Bcr-Abl positive cell lines in vitro and in vivo

We have previously shown the inhibition of the small-molecule inhibitor FB2 on imatinib-sensitive and resistance CML cell lines with the wild-type Bcr-Abl fusion gene. Here we report the potent and selective antiproliferation on FB2 on transfected Ba/F3 p210 cell lines expressing various isoforms of Bcr-Abl (wild-type, Y253F, T315I). FB2 which orients Bcr-Abl and Src kinase activities, is shown to override imatinib-resistance CML involving Y253F mutation in the Abl kinase domain of the fusion protein except T315I in vivo and in vitro. Thus, we present FB2 that displays potency toward Bcr-Abl and Src as the molecular target, and which could potentially be used to override drug resistance in CML.

Tyrosine phosphorylation of SHIP promotes its proteasomal degradation

OBJECTIVE

The activity of the SH2-containing-phosphatidylinositol-5'-phosphatase (SHIP, also known as SHIP1), a critical hematopoietic-restricted negative regulator of the PI3 kinase (PI3K) pathway, is regulated in large part via its protein levels. We sought to determine the mechanism(s) involved in its downregulation by BCR-ABL and by interleukin (IL)-4.

MATERIALS AND METHODS

We used Ba/F3(p210-tetOFF) cells to study the downregulation of SHIP by BCR-ABL and bone marrow-derived macrophages to study SHIP's downregulation by IL-4.

RESULTS

We show herein that BCR-ABL downregulates SHIP, but not SHIP2 or PTEN, and this can be blocked with the Src kinase inhibitor PP2, which inhibits the tyrosine phosphorylation of SHIP, or with the proteasomal inhibitor MG-132. We also show, using anti-SHIP immunoprecipitates, that c-Cbl and Cbl-b are associated with SHIP and that BCR-ABL induces SHIP's polyubiquitination. This ubiquitination can be blocked with PP2, consistent with the tyrosine phosphorylation of SHIP acting as a signal for its ubiquitination. In bone marrow-derived macrophages, IL-4 also leads to the proteasomal degradation of SHIP but, unlike in Ba/F3(p210-tetOFF) cells, SHIP2 is also proteasomally degraded and the degradation of both inositol phosphatases can be prevented with PP2 or MG-132.

CONCLUSION

Our results suggest that SHIP protein levels can be reduced via BCR-ABL and/or Src family member-induced tyrosine phosphorylation of SHIP because this triggers its polyubiquitination and degradation within the proteasome.

Neutrophil spontaneous death is mediated by down-regulation of autocrine signaling through GPCR, PI3Kgamma, ROS, and actin

Neutrophil spontaneous apoptosis plays a crucial role in neutrophil homeostasis and the resolution of inflammation. We previously established Akt deactivation as a key mediator of this tightly regulated cellular death program. Nevertheless, the molecular mechanisms governing the diminished Akt activation were not characterized. Here, we report that Akt deactivation during the course of neutrophil spontaneous death was a result of reduced PtdIns(3,4,5)P3 level. The phosphatidylinositol lipid kinase activity of PI3Kgamma, but not class IA PI3Ks, was significantly reduced during neutrophil death. The production of PtdIns(3,4,5)P3 in apoptotic neutrophils was mainly maintained by autocrinely released chemokines that elicited PI3Kgamma activation via G protein-coupled receptors. Unlike in other cell types, serum-derived growth factors did not provide any survival advantage in neutrophils. PI3Kgamma, but not class IA PI3Ks, was negatively regulated by gradually accumulated ROS in apoptotic neutrophils, which suppressed PI3Kgamma activity by inhibiting an actin-mediated positive feedback loop. Taken together, these results provide insight into the mechanism of neutrophil spontaneous death and reveal a cellular pathway that regulates PtdIns(3,4,5)P3/Akt in neutrophils.

Role of neutrophils in innate immunity: a systems biology-level approach

The innate immune system is the first line of host defense against invading microorganisms. Polymorphonuclear leukocytes (PMNs or neutrophils) are the most abundant leukocyte in humans and essential to the innate immune response against invading pathogens. Compared with the acquired immune response, which requires time to develop and is dependent on previous interaction with specific microbes, the ability of neutrophils to kill microorganisms is immediate, non-specific, and not dependent on previous exposure to microorganisms. Historically, studies on PMN-pathogen interaction focused on the events leading to killing of microorganisms, such as recruitment/chemotaxis, transmigration, phagocytosis, and activation, whereas post-phagocytosis sequelae were infrequently considered. In addition, it was widely accepted that human neutrophils possessed limited capacity for new gene transcription and thus, relatively little biosynthetic capacity. This notion has changed dramatically within the past decade. Further, there is now more effort directed to understand the events occurring in PMNs after killing of microbes. Herein we review the systems biology-level approaches that have been used to gain an enhanced view of the role of neutrophils during host-pathogen interaction. We anticipate that these and future systems-level studies will ultimately provide information critical to our understanding, treatment, and control of diseases caused by pathogenic microorganisms.

SHIP1 is a repressor of mast cell hyperplasia, cytokine production, and allergic inflammation in vivo

SHIP1 inhibits immune receptor signaling through hydrolysis of the PI3K product phosphatidylinositol 3,4,5-trisphosphate, forming phosphatidylinositol 3,4-bisphosphate. In mast cells, SHIP1 represses FcepsilonRI- and cytokine-mediated activation in vitro, but little is known regarding the function of SHIP1 in mast cells in vivo or the susceptibility of Ship1(-/-) mice to mast cell-associated diseases. In this study, we found that Ship1(-/-) mice have systemic mast cell hyperplasia, increased serum levels of IL-6, TNF, and IL-5, and heightened anaphylactic response. Further, by reconstituting mast cell-deficient mice with Ship1(+/+) or Ship1(-/-) mast cells, we found that the above defects were due to loss of SHIP1 in mast cells. Additionally, we found that mice reconstituted with Ship1(-/-) mast cells suffered worse allergic asthma pathology than those reconstituted with Ship1(+/+) mast cells. In summary, our data show that SHIP1 represses allergic inflammation and mast cell hyperplasia in vivo and exerts these effects specifically in mast cells.

Lyn, PKC-delta, SHIP-1 interactions regulate GPVI-mediated platelet-dense granule secretion

Protein kinase C-delta (PKC-delta) is expressed in platelets and activated downstream of protease-activated receptors (PARs) and glycoprotein VI (GPVI) receptors. We have previously shown that PKC-delta positively regulates PAR-mediated dense granule secretion, whereas it negatively regulates GPVI-mediated dense granule secretion. We further investigated the mechanism of such differential regulation of dense granule release by PKC-delta in platelets. SH2 domain-containing inositol phosphatase-1 (SHIP-1) is phosphorylated on Y1020, a marker for its activation, upon stimulation of human platelets with PAR agonists SFLLRN and AYPGKF or GPVI agonist convulxin. GPVI-mediated SHIP-1 phosphorylation occurred rapidly at 15 seconds, whereas PAR-mediated phosphorylation was delayed, occurring at 1 minute. Lyn and SHIP-1, but not SHIP-2 or Shc, preferentially associated with PKC-delta on stimulation of platelets with a GPVI agonist, but not with a PAR agonist. In PKC-delta-null murine platelets, convulxin-induced SHIP-1 phosphorylation was inhibited. Furthermore, in Lyn null murine platelets, GPVI-mediated phosphorylations on Y-1020 of SHIP-1 and Y311 of PKC-delta were inhibited. In murine platelets lacking Lyn or SHIP-1, GPVI-mediated dense granule secretions are potentiated, whereas PAR-mediated dense granule secretions are inhibited. Therefore, we conclude that Lyn-mediated phosphorylations of PKC-delta and SHIP-1 and their associations negatively regulate GPVI-mediated dense granule secretion in platelets.

Neutrophil apoptosis and the resolution of infection

Polymorphonuclear leukocytes (PMNs) are the most abundant white cell in humans and an essential component of the innate immune system. PMNs are typically the first type of leukocyte recruited to sites of infection or areas of inflammation. Ingestion of microorganisms triggers production of reactive oxygen species and fusion of cytoplasmic granules with forming phagosomes, leading to effective killing of ingested microbes. Phagocytosis of bacteria typically accelerates neutrophil apoptosis, which ultimately promotes the resolution of infection. However, some bacterial pathogens alter PMN apoptosis to survive and thereby cause disease. Herein, we review PMN apoptosis and the ability of microorganisms to alter this important process.

Multiple roles of Lyn kinase in myeloid cell signaling and function

Lyn is an Src family kinase present in B lymphocytes and myeloid cells. In these cell types, Lyn establishes signaling thresholds by acting as both a positive and a negative modulator of a variety of signaling responses and effector functions. Lyn deficiency in mice results in the development of myeloproliferation and autoimmunity. The latter has been attributed to the hyper-reactivity of Lyn-deficient B cells due to the unique role of Lyn in downmodulating B-cell receptor activation, mainly through phosphorylation of inhibitory molecules and receptors. Myeloproliferation results, on the other hand, from the enhanced sensitivity of Lyn-deficient progenitors to a number of colony-stimulating factors (CSFs). The hyper-sensitivity to myeloid growth factors may also be secondary to poor inhibitory receptor phosphorylation, leading to impaired recruitment/activation of tyrosine phosphatases and reduced downmodulation of CSF signaling responses. Despite these observations, the overall role of Lyn in the modulation of myeloid cell effector functions is much less well understood, as often both positive and negative roles of this kinase have been reported. In this review, we discuss the current knowledge of the duplicitous nature of Lyn in the modulation of myeloid cell signaling and function.

Deficiency of nicotinamide adenine dinucleotide phosphate, reduced form oxidase enhances hepatocellular injury but attenuates fibrosis after chronic carbon tetrachloride administration

Reactive oxygen species (ROS) activate hepatic stellate cells and enhance fibrogenesis. This study determined the role of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase deficiency in the development of hepatocellular necrosis, inflammation, and apoptosis in relation to fibrosis produced by chronic carbon tetrachloride (CCl(4)) administration. Wild-type (WT) mice or mice with deficiency of the gp91(phox) subunit of NADPH complex (gp91(phox(-/-) )) were subjected to biweekly CCl(4) injections over 8 weeks, whereas controls were given isovolumetric injections of olive oil. Serum aspartate aminotransferase (AST) was higher after CCl(4) administration in gp91(phox(-/-) ) than in WT mice, correlating with increased necrosis on liver histology. By contrast, more hepatocyte apoptosis was found after CCl(4) in the WT than in the gp91(phox(-/-) ) mice, which was associated with changes in components of the mitochondrial pathway of apoptosis, namely, an increase in the pro-apoptotic BAX protein in the WT, but not in the gp91(phox(-/-) ) mice and also a lower cytosolic cytochrome c in the gp91(phox(-/-) ) mice. There were fewer stellate cells and less fibrosis after CCl(4) in the gp91(phox(-/-) ) as compared with the WT mice. The increase in alpha(1)(I) collagen messenger RNA (mRNA), however, was greater after CCl(4) in the gp91(phox(-/-) ) mice. Matrix metalloproteinase-2 (MMP-2) and MMP-9 mRNA increased more in the gp91(phox(-/-) ) than in WT mice after CCl(4.) Tissue inhibitor of metalloproteinase 1 (TIMP-1) and TIMP-2 increased after CCl(4) only in the gp91(phox(-/-) ) mice.

CONCLUSION

Decreased hepatic fibrosis after chronic CCl(4) administration in mice with NADPH oxidase deficiency occurs in the setting of greater necrosis and inflammation but decreased apoptosis.

Survival of monocytes and macrophages and their role in health and disease

Macrophages are versatile cells involved in health and disease. These cells act as scavengers to rid the body of apoptotic and senescent cells and debris through their phagocytic function. Although this is a primary function of these cells, macrophages play vital roles in inflammation and repair of damaged tissue. Macrophages secrete a large number of cytokines, chemokines and growth factors that recruit and activate a variety of cell types to inflamed tissue compartments. These cells are also critical in cell-mediated immunity and in the resolution of inflammation. Since macrophages, and their precursors, blood monocytes, are important in regulating and resolving inflammation, prolonged cellular survival in tissue compartments could be detrimental. Thus, factors that regulate the fate of monocyte and macrophage survival are important in cellular homeostasis. In this article, we will explore stimuli and the intracellular pathways important in regulating macrophage survival and implication in human disease.

Redox mechanisms in hepatic chronic wound healing and fibrogenesis

Reactive oxygen species (ROS) generated within cells or, more generally, in a tissue environment, may easily turn into a source of cell and tissue injury. Aerobic organisms have developed evolutionarily conserved mechanisms and strategies to carefully control the generation of ROS and other oxidative stress-related radical or non-radical reactive intermediates (that is, to maintain redox homeostasis), as well as to 'make use' of these molecules under physiological conditions as tools to modulate signal transduction, gene expression and cellular functional responses (that is, redox signalling). However, a derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, can play a significant role in the pathogenesis of major human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis. This review has been designed to first offer a critical introduction to current knowledge in the field of redox research in order to introduce readers to the complexity of redox signalling and redox homeostasis. This will include ready-to-use key information and concepts on ROS, free radicals and oxidative stress-related reactive intermediates and reactions, sources of ROS in mammalian cells and tissues, antioxidant defences, redox sensors and, more generally, the major principles of redox signalling and redox-dependent transcriptional regulation of mammalian cells. This information will serve as a basis of knowledge to introduce the role of ROS and other oxidative stress-related intermediates in contributing to essential events, such as the induction of cell death, the perpetuation of chronic inflammatory responses, fibrogenesis and much more, with a major focus on hepatic chronic wound healing and liver fibrogenesis.

ETosis: a novel cell death pathway

The formation of extracellular traps (ETs) by neutrophils and mast cells is an important mechanism in the innate immune response. These structures consist of a chromatin-DNA backbone with attached antimicrobial peptides and enzymes that trap and kill microbes. After stimulation of neutrophils and mast cells with phorbol esters, chemoattractant peptides, or chemokines, the generation of reactive oxygen species (ROS), such as hydrogen peroxide, by NAPDH [nicotinamide adenine dinucleotide phosphate (reduced form)] oxidase initiates a signaling cascade that leads to the disintegration of the nuclear and cellular membranes and the formation of ETs. This form of cell death is neither apoptotic nor necrotic, but whether it occurs because of the oxidation of phosphatases and kinases, as in other ROS-mediated signaling cascades, remains to be elucidated. These findings implicate "ETosis" as a novel cell death pathway in leukocytes.

Cholesterol-rich membrane rafts and Lyn are involved in phagocytosis during Pseudomonas aeruginosa infection

The mechanism of phagocytosis of pathogens remains to be fully characterized. We report a novel phagocytosis pathway for Pseudomonas aeruginosa, which is initiated by cholesterol-rich membrane rafts and is dependent on Lyn, primarily an immune regulator with both positive and negative roles. Blocking of Lyn or blocking of cholesterol synthesis significantly inhibited phagocytosis by alveolar macrophages. We found that Lyn, via Src homology 2 and 3 domains, bound to and then activated PI3K and Akt to regulate intracellular routing of the engulfed P. aeruginosa. Further analysis indicates that Lyn and raft components entered in phagosomes and late lysosomes. Finally, respiratory burst was dependent on Lyn and membrane rafts, as confirmed by small interfering RNA and dominant-negative strategies. Our investigations demonstrate that Lyn along with membrane rafts plays a fundamental role in phagocytosis by alveolar macrophages during infection.

Mechanisms of neutrophil death in human immunodeficiency virus-infected patients: role of reactive oxygen species, caspases and map kinase pathways

Neutrophils from human immunodeficiency virus-positive (HIV+) patients have an increased susceptibility to undergo programmed cell death (PCD), which could explain neutropenia during advanced disease. In this work, key steps of PCD have been evaluated in neutrophils from HIV+ patients. The role of caspase-3, caspase-8, mitogen activated protein kinase (MAPK) and reactive oxygen species (ROS) was analysed. Spontaneous neutrophil death is dependent upon caspase-3 but independent of caspase-8, suggesting that the intrinsic pathway is involved as a pathogenic mechanism of PCD. Inhibition of ROS decreased spontaneous PCD and caspase-3 hydrolysis, connecting oxidative stress and caspase-3 activation with neutrophil PCD in HIV-infected patients. Additionally, an increased neutrophil death was observed in HIV+ patients, following inhibition of p38 MAPK, suggesting a role for p38 MAPK in cell survival during the disease. We conclude that oxidative stress secondary to HIV infection can accelerate neutrophil death.

The role of SHIP1 in T-lymphocyte life and death

SHIP1 [SH2 (Src homology 2)-containing inositol phosphatase-1], an inositol 5-phosphatase expressed in haemopoietic cells, acts by hydrolysing the 5-phosphates from PtdIns(3,4,5)P(3) and Ins(1,3,4,5)P(4), thereby negatively regulating the PI3K (phosphoinositide 3-kinase) pathway. SHIP1 plays a major role in inhibiting proliferation of myeloid cells. As a result, SHIP1(-/-) mice have an increased number of neutrophils and monocytes/macrophages due to enhanced survival and proliferation of their progenitors. Although SHIP1 contributes to PtdIns(3,4,5)P(3) metabolism in T-lymphocytes, its exact role in this cell type is much less explored. Jurkat cells have recently emerged as an interesting tool to study SHIP1 function in T-cells because they do not express SHIP1 at the protein level, thereby allowing reintroduction experiments in a relatively easy-to-use system. Data obtained from SHIP1 reintroduction have revealed that SHIP1 not only acts as a negative player in T-cell lines proliferation, but also regulates critical pathways, such as NF-kappaB (nuclear factor kappaB) activation, and also appears to remarkably inhibit T-cell apoptosis. On the other hand, experiments using primary T-cells from SHIP1(-/-) mice have highlighted a new role for SHIP1 in regulatory T-cell development, but also emphasize that this protein is not required for T-cell proliferation. In support of these results, SHIP1(-/-) mice are lymphopenic, suggesting that SHIP1 function in T-cells differs from its role in the myeloid lineage.

Successful unrelated bone marrow transplantation in a child with chronic granulomatous disease complicated by pulmonary and cerebral granuloma formation

We report on a 6-year-old boy with chronic granulomatous disease (CGD) complicated by chronic inflammatory reactions with formation of large pulmonary granuloma as well as intracerebral lesions. Bone marrow transplantation (BMT) from an unrelated donor led to stable reconstitution, to rapid resolution of pulmonary granuloma, and to rapid resolution of intracerebral lesions.

Src kinase signaling in leukaemia

Role of Src kinases in acute lymphoblastic leukaemia has been recently demonstrated in leukaemia mouse model. Retained activation of Src kinases by the BCR-ABL oncoprotein in leukaemic cells following inhibition of BCR-ABL kinase activity by imatinib indicates that Src activation by BCR-ABL is independent of BCR-ABL kinase activity and provides an explanation for reduced effectiveness of the BCR-ABL kinase activity inhibitors in Philadelphia chromosome-positive acute lymphoblastic leukaemia. Simultaneous inhibition of kinase activity of both BCR-ABL and Src kinases results in long-term survival of mice with acute lymphoblastic leukaemia. Leukaemic stem cells exist in acute lymphoblastic leukaemia, and complete eradication of this group of cells would provide a curative therapy for this disease.

Reactive oxygen and nitrogen species as signaling molecules regulating neutrophil function

As a cornerstone of the innate immune response, neutrophils are the archetypical phagocytic cell; they actively seek out, ingest, and destroy pathogenic microorganisms. To achieve this essential role in host defense, neutrophils deploy a potent antimicrobial arsenal that includes oxidants, proteinases, and antimicrobial peptides. Importantly, oxidants produced by neutrophils, referred to in this article as reactive oxygen (ROS) and reactive nitrogen (RNS) species, have a dual function. On one hand they function as potent antimicrobial agents by virtue of their ability to kill microbial pathogens directly. On the other hand, they participate as signaling molecules that regulate diverse physiological signaling pathways in neutrophils. In the latter role, ROS and RNS serve as modulators of protein and lipid kinases and phosphatases, membrane receptors, ion channels, and transcription factors, including NF-kappaB. The latter regulates expression of key cytokines and chemokines that further modulate the inflammatory response. During the inflammatory response, ROS and RNS modulate phagocytosis, secretion, gene expression, and apoptosis. Under pathological circumstances such as acute lung injury and sepsis, excess production of ROS may influence vicinal cells such as endothelium or epithelium, contributing to inflammatory tissue injury. A better understanding of these pathways will help identify novel targets for amelioration of the untoward effects of inflammation.

Deactivation of phosphatidylinositol 3,4,5-trisphosphate/Akt signaling mediates neutrophil spontaneous death

Neutrophil spontaneous death plays essential roles in neutrophil homeostasis and resolution of inflammation, whereas the underlying molecular mechanisms are still ill-defined. Neutrophils die because of programmed cell death or apoptosis. However, treatment with inhibitor of caspases, which are responsible for the majority of apoptotic cell deaths, does not prevent the spontaneous death of neutrophils. PKB/Akt possesses prosurvival and antiapoptotic activities in a variety of cells. In this study, we show that Akt activity decreases dramatically during the course of neutrophil death. Both phosphatidylinositol 3-kinase and Akt inhibitors enhance neutrophil death. Conditions delaying neutrophil death, such as treatment with granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, or IFN-gamma, restore Akt activity. Finally, we demonstrate that neutrophils depleted of PTEN, a phosphatidylinositol 3'-phosphatase that negatively regulates Akt activity, live much longer than WT neutrophils. Thus, we establish Akt deactivation as a causal mediator of neutrophil spontaneous death.

The expanding role of NADPH oxidases in health and disease: no longer just agents of death and destruction

The NADPH oxidase was originally identified as a key component of human innate host defence. In phagocytes, this enzyme complex is activated to produce superoxide anion and other secondarily derived ROS (reactive oxygen species), which promote killing of invading micro-organisms. However, it is now well-established that NADPH oxidase and related enzymes also participate in important cellular processes not directly related to host defence, including signal transduction, cell proliferation and apoptosis. These enzymes are present in essentially every organ system in the body and contribute to a multitude of physiological events. Although essential for human health, excess NADPH-oxidase-generated ROS can promote numerous pathological conditions. Herein, we summarize our current understanding of NADPH oxidases and provide an overview of how they contribute to specific human diseases.

The duplicitous nature of the Lyn tyrosine kinase in growth factor signaling

The Lyn tyrosine kinase is a unique member of the Src family of non-receptor protein tyrosine kinases whose principal role is to regulate signals through inhibitory receptors thereby promoting signal attenuation. Lyn is renowned for its role in B cell antigen receptor and FcepsilonRI signaling; however, it is becoming increasingly apparent that Lyn also functions in signal transduction from growth factor receptors including the receptors for GM-CSF, IL-3, IL-5, SCF, erythropoietin, CSF-1, G-CSF, thrombopoietin and Flt3 ligand. Numerous studies have implicated Lyn in growth factor receptor signal amplification, while a number also suggest that Lyn participates in negative regulation of growth factor signaling. Indeed Lyn-deficient mice are hyper-responsive to myeloid growth factors and develop a myeloproliferative disorder that predisposes the mice to macrophage tumours, with loss of negative regulation through SHP-1 and SHIP-1 thought to be the major contributing factor to this phenotype. Developing a clear understanding of Lyn's role in establishing signaling thresholds in growth factor receptor signal amplification and signal inhibition may have important implications in the management of leukemias that may depend on Lyn activity.

Src kinases as targets for B cell acute lymphoblastic leukaemia therapy

The participation of Src kinases in the induction of BCR-ABL-induced B cell acute lymphoblastic leukaemia (B-ALL), but not chronic myeloid leukaemia (CML), demonstrates cell type-specific signalling in Philadelphia chromosome-positive (Ph+) leukaemias. Different therapeutic strategies are therefore needed for B-ALL and CML. Activation of Src kinases is independent of BCR-ABL kinase activity for activation. Thus, Src kinases provide a mechanism for resistance to the BCR-ABL kinase inhibitors and potential targets for B-ALL therapy. Simultaneous targeting of both BCR-ABL and Src kinases may benefit human B-ALL patients. Leukaemic stem cells may exist in Ph+ B-ALL, and eradication of this group of cells would provide a curative method for this disease.

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

Granulocyte colony-stimulating factor (G-CSF) drives the production, survival, differentiation, and inflammatory functions of granulocytes. Reactive oxygen species (ROSs) provide a major thrust of the inflammatory response, though excessive ROSs may be deleterious. G-CSF stimulation showed a time- and dose-dependent increase in ROS production, correlating with activation of Lyn and Akt. Inhibition of Lyn, PI3-kinase, and Akt abrogated G-CSF-induced ROS production. This was also blocked by DPI, a specific inhibitor of NADPH oxidase. Following G-CSF stimulation, neutrophils from Lyn-/- mice produced less ROSs than wild-type littermates. G-CSF induced both serine phosphorylation and membrane translocation of p47phox, a subunit of NADPH oxidase. Because patients with a truncated G-CSF receptor have a high risk of developing acute myeloid leukemia (AML), we hypothesized that dysregulation of ROSs contributes to leukemogenesis. Cells expressing the truncated G-CSF receptor produced more ROSs than those with the full-length receptor. G-CSF-induced ROS production was enhanced in bone marrow-derived neutrophils expressing G-CSFRdelta715, a truncated receptor. The antioxidant N-acetyl-L-cysteine diminished G-CSF-induced ROS production and cell proliferation by inhibiting Akt activation. These data suggest that the G-CSF-induced Lyn-PI3K-Akt pathway drives ROS production. One beneficial effect of therapeutic targeting of Lyn-PI3K-kinase-Akt cascade is abrogating ROS production.

Granulocyte apoptosis in the pathogenesis and resolution of lung disease

Apoptosis, programmed cell death, of neutrophil and eosinophil granulocytes is a potential control point in the physiological resolution of innate immune responses. There is also increasing evidence that cellular processes of apoptosis can be dysregulated by pathogens as a mechanism of immune evasion and that delayed apoptosis, resulting in prolonged inflammatory cell survival, is important in persistence of tissue inflammation. The identification of cell-type specific pathways to apoptosis may allow the design of novel anti-inflammatory therapies or agents to augment the innate immune responses to infection. This review will explore the physiological roles of granulocyte apoptosis and their importance in infectious and non-infectious lung disease.

Increased megakaryocytopoiesis in Lyn-deficient mice

Previous studies in cell lines have shown Lyn kinase to be a negative regulator of thrombopoietin (TPO)-induced proliferation. To further investigate the role of Lyn during megakaryocytopoiesis, Lyn-deficient mice (lyn(-/-)) were analyzed. We observed that lyn(-/-) mice have more bone marrow-derived GPIIB (CD41) and Mpl(+) cells when compared to their wild-type littermates. In addition, colony-forming unit-megakaryocytes (CFU-MK) are increased and TPO-induced expansion of primary marrow cells yielded a greater number of mature megakaryocytes (MKs) with increased nuclear ploidy. Histopathology of bone marrow and spleens from lyn(-/-) mice showed an increase in the number of MKs. Mechanistic studies revealed that TPO stimulation of MKs from lyn(-/-) mice did not affect phosphorylation of Janus kinase 2 (JAK2), signal transducer and activator of transcription (STAT) 3, STAT5, or MAP kinase kinase (MEK). Lyn-deficient MKs supported greater TPO-mediated phosphorylation and kinase activity of both Erk1/2 (mitogen-activated protein kinase, MAPK) and Akt. In contrast, there was a reduction of tyrosine phosphorylation of the inositol phosphatase, SHIP. This is the first direct evidence using primary MKs from Lyn-deficient mice that confirms our prior data from cell lines that Lyn kinase is a negative regulator of TPO signaling.