Granulocyte-macrophage colony-stimulating factor delays neutrophil constitutive apoptosis through phosphoinositide 3-kinase and extracellular signal-regulated kinase pathways

Induction of apoptosis and inhibition of migration of inflammatory and vascular wall cells by cerivastatin

Statins are thought to play a role in directly affecting immune and mesenchymal cells. Since cerivastatin's pleiotropic effects are poorly investigated, we were interested to find out whether this drug can modulate leukocyte and vessel wall cell functions. Leukocyte migration was tested in modified Boyden microchemotaxis chambers and oxygen radical production was measured fluorometrically. Transendothelial migration experiments were performed with human umbilical vein endothelial cells and neutrophils. Neutrophil, monocyte, and vascular smooth muscle cell caspase-3 activity and annexin-V binding were quantified by FIENA and FACS, respectively. Cerivastatin [10 pM to 100 microM] decreased leukocyte chemotaxis towards interleukin-8 or RANTES. Migration of cells was completely restored by addition of mevalonic acid. In neutrophils, cerivastatin [100 microM] reduced transendothelial migration, whereas treatment of endothelial cells failed to affect transmigration. Neutrophil respiratory burst activity was unaffected by cerivastatin. At concentrations of 10 nM or higher, cerivastatin increased the rate of apoptosis in phagocytes and smooth muscle cells. Results show that cerivastatin is able to inhibit leukocyte chemotaxis, and that cerivastatin induces neutrophil, monocyte, and smooth muscle cell apoptosis. The drug's impact on transendothelial migration is due to its effects on neutrophils. In addition to its lipid-lowering effects, pharmacological properties of cerivastatin may include modulatory actions in leukocytes and mesenchymal cells.

Correlating functional staging to effective treatment of acute surgical illness

BACKGROUND

Proinflammatory and anti-inflammatory events may eventually trigger host response, which acting via a broad spectrum of complex biological processes and molecular interactions may either enhance or resolve the symptoms of acute surgical illness (ASI). Staging the sequence of biological events that take place at the cellular level during the development of ASI may provide leads to effective stage-specific treatments. In line with the hypothesis that proper timing of therapeutic intervention may be crucial to the management of the disease, we have attempted in this review to correlate functional staging to effective treatment of ASI.

DATA SOURCE

The present report proposes a conceptual synthesis on the biogenesis and treatment of ASI that is based on known molecular and cellular aspects of human inflammatory sequence and patient data from clinical trials. It also introduces proper timing of therapeutic intervention as a potentially important determinant for the successful outcome of the disease process.

CONCLUSIONS

Progress in understanding the biogenesis of ASI did not result in successful therapeutic developments as yet. The challenge ahead should be a better understanding of the dynamics of the various processes and regulators in appropriate animal and clinical models of ASI, in order to properly intervene and direct effective therapies for the benefit of critically ill patients.

p90-RSK and Akt may promote rapid phosphorylation/inactivation of glycogen synthase kinase 3 in chemoattractant-stimulated neutrophils

Stimulation of neutrophils with the chemoattractant fMet-Leu-Phe (fMLP) triggers phosphorylation/inactivation of the a- and beta-isoforms of glycogen synthase kinase 3 (GSK-3) with phosphorylation of the alpha-isoform predominating. These reactions were monitored with a phosphospecific antibody that only recognized the alpha- or beta-isoforms of GSK-3 when these proteins were phosphorylated on serine residues 21 and 9, respectively. Inhibitor studies indicated that phosphorylation of GSK-3alpha may be catalyzed by the combined action of p90-RSK and Akt and may represent a new strategy by which G protein-coupled receptors inactivate GSK-3. Inactivation of GSK-3 may be one of the mechanisms that delay apoptosis in fMLP-stimulated neutrophils.

Nongenomic antiapoptotic signal transduction by estrogen in cultured cortical neurons

Estrogen replacement therapy in menopausal women has been suggested to be beneficial in preventing the progression of cognitive impairment in Alzheimer disease. We demonstrated previously that the phosphatidylinositol 3-kinase (PI3-K)/Akt signal transduction pathway plays a pivotal role on the neuroprotection provided by 17beta-estradiol against acute glutamate toxicity. In the present study, we investigated the mechanism of neuroprotection against apoptosis because acute glutamate toxicity predominantly induced necrosis. 17beta-estradiol provided neuroprotection against apoptosis induced by staurosporine. This neuroprotection was inhibited by pretreatment with a PI3-K inhibitor, LY294002. An estrogen receptor specific antagonist, ICI182780, also suppressed the neuroprotection provided by 17beta-estradiol. Western blotting analysis demonstrated that treatment with 17beta-estradiol induced the phosphorylation of Akt within 5 min, which was suppressed by pretreatment with LY294002 and ICI182780. Furthermore, 17beta-estradiol induced phosphorylation of the cAMP response element binding protein (CREB) at Ser(133) within 15 min and then upregulated Bcl-2 in a PI3-K/Akt-dependent manner. Because CREB is known to be a transcription factor for Bcl-2, these results suggest that 17beta-estradiol exerts its antiapoptotic effects by CREB phosphorylation and Bcl-2 upregulation via nongenomic activation of the PI3-K/Akt pathway in cultured cortical neurons.

Differentiation, apoptosis, and function of human immature and mature myeloid cells: intracellular signaling mechanism

Human myeloid cells include hematopoietic cells at various stages of differentiation, from immature myeloid cells to mature phagocytes. Normal immature myeloid cells undergo differentiation concomitantly with proliferation in response to hematopoietic growth factors, and terminally differentiated cells, ie, mature phagocytes, exert their effector functions and then die a natural death via apoptosis. However, leukemic myeloid cells are induced to differentiate with growth suppression by several inducers, such as retinoic acid. This review describes differentiation, apoptosis, and functionality of human myeloid cells. mainly focusing on the intracellular signaling mechanism. The signal transduction system for these biological events of the life cycle of myeloid cells has recently been studied, and several characteristics have been elucidated. First, the signaling pathway for myeloid differentiation is mainly focused in the mitogen-activated protein kinases, such as extracellular signal-regulated kinase and p38, and transcriptional factors such as the signal transducers and activators of transcription PU.1 and CCAAT enhancer binding protein. Second, the signaling mechanism for myeloid cell apoptosis is fundamentally identical to that found in other cells. Caspases, caspase-activated DNase, and mitochondrial molecules such as apoptosis-inducing factor have been reported to be important, and mitogen-activated protein kinases such as p38 appear to be less important. Finally, p38 and phosphatidylinositol 3-kinase play critical roles in the signaling cascade for functional activation of mature phagocytes. The reasons why the same signaling molecules play distinct roles according to the differentiation stage and biological event await future clarification.

Role of extracellular signal-regulated kinase and phosphatidylinositol-3 kinase in chemoattractant and LPS delay of constitutive neutrophil apoptosis

The present study examined the role of mitogen-activated protein kinases (MAPKs) and phosphatidylinositol-3 kinase-stimulated Akt (PI-3K/Akt) in the regulation of constitutive human neutrophil apoptosis by bacterial lipopolysaccharide (LPS) and two chemoattractants, fMLP and leukotriene B(4) (LTB(4)). LPS and LTB(4) inhibited apoptosis, while fMLP had no effect. Inhibition of extracellular signal-regulated kinase (ERK) with PD098059 significantly inhibited the anti-apoptotic effect of both LPS and LTB(4), while inhibition of p38 kinase with SB203580 had no effect. Inhibition of PI-3K with wortmannin and LY294002 significantly attenuated the anti-apoptotic effect of LTB(4), but not LPS. LPS, fMLP, and LTB(4) stimulated similar levels of ERK and Akt activation. LTB(4) and LPS inhibited neutrophil apoptosis when added simultaneously with fMLP, and LTB(4) and LPS demonstrated an additive effect. We conclude that the ERK and/or PI-3K/Akt pathways are necessary, but not sufficient, for LPS and LTB(4) to delay apoptosis, but other anti-apoptotic pathways remain to be identified.

Helicobacter pylori lipopolysaccharide hinders polymorphonuclear leucocyte apoptosis

A prominent histologic feature of Helicobacter pylori infection is a dense infiltration of polymorphonuclear leukocytes (PMNL) in gastric mucosa. H. pylori lipopolysaccharide (LPS) has been recognized as a primary virulence factor evoking acute mucosal inflammatory reaction. Previous works have shown that H. pylori LPS immunologic activities are lower than those of enterobacterial LPS. However, the effect of H. pylori LPS on spontaneous PMNL apoptosis, and mechanisms by which this H. pylori LPS may promote PMNL survival remain to be established. In this study, we investigated, by both morphologic and biochemical approaches, the action of H. pylori LPS on PMNL apoptosis in vitro, using broth culture filtrates (BCF) of H. pylori strains with different genotypes. We found that BCF from H. pylori caused a significant delay in spontaneous PMNL apoptosis and this delay was independent of the VacA, cag pathogenicity island and urease status. We demonstrated that LPS in BCF is responsible for this effect because it was abrogated by the LPS antagonist B287 (a synthetic analog of Rhodobactersphaeroides lipid A). Moreover, BCF from H. pylori induced P42/44MAP kinase activation in PMNL. Similar results were obtained with BCF of an Escherichia coli strain. Taken together these data suggest that longer survival of PMNL induced by H. pylori LPS may increase gastric epithelium injury in H. pylori-associated diseases.

p38 Kinase-dependent MAPKAPK-2 activation functions as 3-phosphoinositide-dependent kinase-2 for Akt in human neutrophils

Akt activation requires phosphorylation of Thr(308) and Ser(473) by 3-phosphoinositide-dependent kinase-1 and 2 (PDK1 and PDK2), respectively. While PDK1 has been cloned and sequenced, PDK2 has yet to be identified. The present study shows that phosphatidylinositol 3-kinase-dependent p38 kinase activation regulates Akt phosphorylation and activity in human neutrophils. Inhibition of p38 kinase activity with SB203580 inhibited Akt Ser(473) phosphorylation following neutrophil stimulation with formyl-methionyl-leucyl-phenylalanine, FcgammaR cross-linking, or phosphatidylinositol 3,4,5-trisphosphate. Concentration inhibition studies showed that Ser(473) phosphorylation was inhibited by 0.3 microm SB203580, while inhibition of Thr(308) phosphorylation required 10 microm SB203580. Transient transfection of HEK293 cells with adenoviruses containing constitutively active MKK3 or MKK6 resulted in activation of both p38 kinase and Akt. Immunoprecipitation and glutathione S-transferase (GST) pull-down studies showed that Akt was associated with p38 kinase, MK2, and Hsp27 in neutrophils, and Hsp27 dissociated from the complex upon activation. Active recombinant MK2 phosphorylated recombinant Akt and Akt in anti-Akt, anti-MK2, anti-p38, and anti-Hsp27 immunoprecipitates, and this was inhibited by an MK2 inhibitory peptide. We conclude that Akt exists in a signaling complex containing p38 kinase, MK2, and Hsp27 and that p38-dependent MK2 activation functions as PDK2 in human neutrophils.

Neutrophil activation and acute lung injury

Neutrophils are considered to be central to the pathogenesis of most forms of acute lung injury (ALI). For the sake of clarity, neutrophil involvement in ALI can be conceptualized as consisting of sequential stages, beginning with their sequestration in the pulmonary microvasculature, followed by adhesion and activation, and culminating in the production of a microbicidal or "effector" response, such as the generation of reactive oxygen species or release of proteolytic enzymes. Great strides have been made in elucidating these various stages of neutrophil involvement. Recent studies have focused on the intracellular signaling pathways that govern neutrophil activation and have elucidated complex cascades of kinases and other intracellular signaling molecules that allow for amplication of the neutrophil response, yet simultaneously confer specificity of a response. We believe that the inflammatory response in ALI may initially be adaptive, such as the pivotal role played by neutrophils in a bacterial or fungal infection. Ultimately, it is the persistence or the dysregulation of neutrophil activation that may lead to ALI. An increased understanding of how neutrophils function will facilitate the design of therapeutic strategies that retain the beneficial aspects of the inflammatory response, while avoiding unnecessary tissue damage.

Down-regulation of Pim-1 and Bcl-2 is accompanied with apoptosis of interleukin-6-depleted mouse B-cell hybridoma 7TD1 cells

Here we report, interleukin-6 (IL-6) dependent mouse B-cell hybridoma, 7TD1 cells underwent apoptotic cell death with the starvation of IL-6. First, 7TD1 cells cultured without IL-6 arrested at G0/G1 phase (maximum accumulation at 24 h ) of the cell cycle. After that, the parameters of apoptosis namely, decreased mitochondrial transmembrane potential (DeltaPsi(m)), activation of caspases, DNA fragmentation and morphological changes (condensed nucleus and formation of apoptotic bodies) were observed. As evidents by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analyses, down-regulation of Pim-1 (a serine/threonine kinase) and Bcl-2 was observed in the IL-6-depleted 7TD1 cells. There was no change in the expression of c-Myc, Bcl-xL and Mcl-1, even at 48 h of IL-6-depletion. Taken together, these results indicate that IL-6 withdrawn from the 7TD1 cells resulted in G0/G1 arrest and then caspase-dependent apoptosis via mitochondrial pathway by down-regulation of Pim-1 and Bcl-2, which may be essential for anti-apoptotic signals of IL-6.

Molecular control of neutrophil apoptosis

Human neutrophils constitutively undergo apoptosis and this process is critical for the resolution of inflammation. Whilst neutrophil apoptosis can be modulated by a wide variety of agents including GM-CSF, LPS and TNF-alpha, the molecular mechanisms underlying neutrophil death and survival remain largely undefined. Recent studies have shown the involvement of members of the Bcl-2 protein family (especially Mcl-1 and A1) and caspases in the regulation and execution of neutrophil apoptosis. Cell surface receptors and protein kinases, particularly mitogen-activated protein kinases, also play critical roles in transducing the signals that result in neutrophil apoptosis or extended survival. This review summarises current knowledge on the molecular mechanisms and components of neutrophil apoptosis.

Phosphoinositide 3-kinase: a critical signalling event in pulmonary cells

Phosphoinositide 3-kinases (PI-3Ks) are enzymes that generate lipid second messenger molecules, resulting in the activation of multiple intracellular signalling cascades. These events regulate a broad array of cellular responses including survival, activation, differentiation and proliferation and are now recognised to have a key role in a number of physiological and pathophysiological processes in the lung. PI-3Ks contribute to the pathogenesis of asthma by influencing the proliferation of airways smooth muscle and the recruitment of eosinophils, and affect the balance between the harmful and protective responses in pulmonary inflammation and infection by the modulation of granulocyte recruitment, activation and apoptosis. In addition they also seem to exert a critical influence on the malignant phenotype of small cell lung cancer. PI-3K isoforms and their downstream targets thus provide novel therapeutic targets for intervention in a broad spectrum of respiratory diseases.