Nuclear factor-kappaB activates dual inhibition sites in the regulation of tumor necrosis factor-alpha-induced neutrophil apoptosis

Cell Type-Specific Roles of NF-κB Linking Inflammation and Thrombosis

The transcription factor NF-κB is a central mediator of inflammation with multiple links to thrombotic processes. In this review, we focus on the role of NF-κB signaling in cell types within the vasculature and the circulation that are involved in thrombo-inflammatory processes. All these cells express NF-κB, which mediates important functions in cellular interactions, cell survival and differentiation, as well as expression of cytokines, chemokines, and coagulation factors. Even platelets, as anucleated cells, contain NF-κB family members and their corresponding signaling molecules, which are involved in platelet activation, as well as secondary feedback circuits. The response of endothelial cells to inflammation and NF-κB activation is characterized by the induction of adhesion molecules promoting binding and transmigration of leukocytes, while simultaneously increasing their thrombogenic potential. Paracrine signaling from endothelial cells activates NF-κB in vascular smooth muscle cells and causes a phenotypic switch to a “synthetic” state associated with a decrease in contractile proteins. Monocytes react to inflammatory situations with enforced expression of tissue factor and after differentiation to macrophages with altered polarization. Neutrophils respond with an extension of their life span—and upon full activation they can expel their DNA thereby forming so-called neutrophil extracellular traps (NETs), which exert antibacterial functions, but also induce a strong coagulatory response. This may cause formation of microthrombi that are important for the immobilization of pathogens, a process designated as immunothrombosis. However, deregulation of the complex cellular links between inflammation and thrombosis by unrestrained NET formation or the loss of the endothelial layer due to mechanical rupture or erosion can result in rapid activation and aggregation of platelets and the manifestation of thrombo-inflammatory diseases. Sepsis is an important example of such a disorder caused by a dysregulated host response to infection finally leading to severe coagulopathies. NF-κB is critically involved in these pathophysiological processes as it induces both inflammatory and thrombotic responses.

Diabetes Mellitus and Liver Surgery: The Effect of Diabetes on Oxidative Stress and Inflammation

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycaemia and high morbidity worldwide. The detrimental effects of hyperglycaemia include an increase in the oxidative stress (OS) response and an enhanced inflammatory response. DM compromises the ability of the liver to regenerate and is particularly associated with poor prognosis after ischaemia-reperfusion (I/R) injury. Considering the growing need for knowledge of the impact of DM on the liver following a surgical procedure, this review aims to present recent publications addressing the effects of DM (hyperglycaemia) on OS and the inflammatory process, which play an essential role in I/R injury and impaired hepatic regeneration after liver surgery.

Effects of gene polymorphisms in the endoplasmic reticulum stress pathway on clinical outcomes of chemoradiotherapy in Chinese patients with nasopharyngeal carcinoma

There is considerable inter-individual variabil¬ity in chemoradiotherapy responses in nasopharyngeal carcinoma (NPC) patients receiv¬ing the same or similar treatment protocols. In this study we evaluated the association between the gene polymorphisms in endoplasmic reticulum (ER) stress pathway and chemoradiation responses in Chinese NPC patients. A total of 150 patients with histopathologically conformed NPC and treated with concurrent chemoradiotherapy were enrolled. Genotypes in ER stress pathway genes, including VCP (valosin-containing protein) rs2074549, HSP90B1 rs17034943, CANX (calnexin) rs7566, HSPA5 [heat shock protein family A (Hsp70) member 5] rs430397, CALCR (calcitonin receptor) rs2528521, and XBP1 (X-box binding protein 1) rs2269577 were analyzed by Sequenom MassARRAY system. The short-term effects of primary tumor and lymph node after radiotherapy were assessed based on the Response Evaluation Criteria in Solid Tumors (RECIST) of WHO. And acute radiation-induced toxic reactions were evaluated according to the Radiation Therapy Oncology Group or European Organization for Research and Treatment of Cancer (RTOG/EORTC). The effects of gene polymorphisms on clinical outcomes of chemoradiotherapy were assessed by chi-square test, univariate and multivariate logistic regression analyses. We found that CT and CT+CC genotypes of CANX rs7566 was significantly correlated with primary tumor treatment efficacy at 3 months after chemoradiotherapy and with occurrence of radiation-induced myelosuppression in Chinese NPC patients. CT and CT+CC genotypes of CALCR rs2528521 were significantly correlated with cervical lymph node efficacy at 3 months after chemoradiotherapy. And CC and CT+CC genotypes of VCP rs2074549 were significantly associated with occurrence of myelosuppression. In conclusion, SNPs of VCP rs2074549, CANX rs7566 and CALCR rs2528521 in ER stress pathway genes may serve as predictors for clinical outcomes of chemoradiotherapy in Chinese NPC patients.

Hyperglycemia Aggravates Hepatic Ischemia Reperfusion Injury by Inducing Chronic Oxidative Stress and Inflammation

Aim. To investigate whether hyperglycemia will aggravate hepatic ischemia reperfusion injury (HIRI) and the underlying mechanisms. Methods. Control and streptozotocin-induced diabetic Sprague-Dawley rats were subjected to partial hepatic ischemia reperfusion. Liver histology, transferase, inflammatory cytokines, and oxidative stress were assessed accordingly. Similarly, BRL-3A hepatocytes were subjected to hypoxia/reoxygenation (H/R) after high (25 mM) or low (5.5 mM) glucose culture. Cell viability, reactive oxygen species (ROS), and activation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-κB) were determined. Results. Compared with control, diabetic rats presented more severe hepatic injury and increased hepatic inflammatory cytokines and oxidative stress. HIRI in diabetic rats could be ameliorated by pretreatment of N-acetyl-L-cysteine (NAC) or apocynin. Excessive ROS generation and consequent Nrf2 and NF-κB translocation were determined after high glucose exposure. NF-κB translocation and its downstream cytokines were further increased in high glucose cultured group after H/R. While proper regulation of Nrf2 to its downstream antioxidases was observed in low glucose cultured group, no further induction of Nrf2 pathway by H/R after high glucose culture was identified. Conclusion. Hyperglycemia aggravates HIRI, which might be attributed to chronic oxidative stress and inflammation and potential malfunction of antioxidative system.

VCP gene variation predicts outcome of advanced non-small-cell lung cancer platinum-based chemotherapy

Valosin-containing protein (VCP), or p97, is a member of the ATP-binding protein family, and is involved in numerous cellular events, such as, protein degradation, membrane fusion, and chaperone activity. VCP has been demonstrated playing a critical role in non-small-cell lung cancer (NSCLC) pathogenesis and progression recently. We investigated the association between VCP polymorphisms and clinical outcome in advanced NSCLC patients undergoing platinum-based chemotherapy. We recruited 663 Chinese advanced NSCLC patients who were treated with platinum-based regimens, and using their clinical data, we assessed the efficacy and side effects of their treatment. Three tag-single nucleotide polymorphisms (SNPs) of VCP were genotyped. SNP rs2074549 showed a significant association with severe neutropenia. Its G/G genotype increased the risk of grade 3 or 4 neutropenia compared with wild-type homozygotes A/A (P = .001, odds ratio = 2.975). Haplotype association analysis revealed that CGA was associated with the increased incidence of severe neutropenia (P = .041, odds ratio = 1.439). However, no significant relationship was found between the presence of VCP polymorphisms and treatment efficacy when objective response, progression-free survival, and overall survival (OS) were evaluated. Our study is the first to provide evidence that VCP polymorphisms are associated with a severe chemotherapy-related adverse outcome in platinum-treated advanced NSCLC patients.

Biological response of osteosarcoma cells to size-controlled nanostructured hydroxyapatite

Osteosarcoma is a primary malignant bone tumor, most prevalent in children and adolescents, and is usually highly aggressive and eventually lethal. Despite multimodal therapies, there is no effective approach to treat this malignant disease. In this study, we observed the biological response of osteosarcoma cells to two kinds of hydroxyapatite nanoparticles (Nano HA), NanoHA-S and NanoHA-L. These nanospheres have the same crystallinity (phase) and morphology, but they differ in size. Cells treated with two kinds of Nano HA were inhibited and mainly led to apoptotic cell death. Caspase-9-dependent intrinsic apoptotic pathway plays a role. It was interesting that the suppression and the apoptosis of osteosarcoma cells was directly related to the size of nanoparticles and that the larger-sized Nano HA exhibited more effectiveness than the smaller one. This in vitro study suggested the potential of size-controlled calcium phosphate nanoparticles for use in therapeutic replacement and reconstruction of bone merits after osteosarcoma extraction.

Lung inflammation and endothelial cell damage are decreased after treatment with phototherapy (PhT) in a model of acute lung injury induced by Escherichia coli lipopolysaccharide in the rat

Lipopolysaccharide (LPS) mimics the symptoms of acute lung injury (ALI), which is characterized by the accumulation in the lungs of neutrophils producing inflammatory mediators. Because of the lack of information about phototherapy (PhT) effects on ALI, we investigated whether PhT (685nm InGaAlP) attenuates LPS-induced ALI. PhT reduced lung edema, the accumulation of TNF-alpha in the lung, and myeloperoxidase (MPO) activity. However, PhT was not efficient in reducing of TNF-alpha concentration in both serum and neutrophils of blood after LPS. In another series of experiments, in vitro assays of the effects of PhT effect on mouse pulmonary arterial endothelium cells (MPAECs) after TNF-alpha showed that the laser restores the MPAECs damage induced at 6 or 24h after TNF-alpha. These results suggest the PhT effect on ALI is partly due to inhibition of TNF-alpha release from neutrophils and lung cells.

Effects of HMGB1 on PMN apoptosis during LPS-induced acute lung injury

OBJECTIVE

To observe the effects of intravenous injection of HMGB1 inhibitor sodium butyrate on changes in apoptosis of PMN during LPS-induced acute lung injury in rats and HMGB1 in vitro on human circulating PMN apoptosis, in order to clarify the role of HMGB1 in the pathogenesis of acute lung injury.

METHODS

(1) LPS-induced acute lung injury rat model was developed by LPS infusion. At different time-points after LPS challenge in the presence or absence of sodium butyrate (SB), the rat tissue sample, peripheral blood PMNs and BALF were collected. RT-PCR was applied to examining rat lung tissue HMGB1 mRNA expression level, and Western blotting analysis was adopted to determine expression of rat lung tissue HMGB1 protein. PMN apoptotic changes were determined by flow cytometric (FCM) analysis, Giemsa staining and TdT-mediated dUTP nick end labeling (TUNEL) method. (2) Separated and purified human circulating PMN were coincubated for 24 h with different doses of HMGB1 (0, 10, 100, 1000 ng/ml, respectively) at 37 degrees C in 5% CO(2). PMN apoptosis rate was determined by flow cytometric (FCM) analysis and by TdT-mediated dUTP nick end labeling (TUNEL) method.

RESULTS

(1) The percentage of apoptosis of PMN in rat model of LPS-induced ALI was gradually decreased as compared with that of normal control. The PMN apoptosis-initiation time and non-survival time in rat BALF prolonged significantly as compared with that of normal control. The injured rat lung tissue HMGB1 mRNA and protein expression was upregulated 6-24 h after LPS exposure; SB intervention significantly ameliorated the upregulation. In addition, the morphologic examination indicated that the edema severity and pathological changes of lung tissues were excessively aggravated in rats after LPS administration. By comparison, SB treatment diminished the severity of lung damage. Combined with lung HMGB1 expression level, the above changes indicate that the pathological changes of lung tissue were related to the injured lung HMGB1 expression, as well as apoptotic changes in PMN. (2) After coincubation of HMGB1 with human circulating PMNs, TUNEL and flow cytometry were performed. The study revealed that PMN apoptosis ratios was (40.53+/-4.12) % in control group (PMNs+RPMI 1640 medium), (19.05+/-2.44) % in LPS group (PMNs+RPMI 1640 medium+10 microg/ml LPS), (40.52+/-2.73) % in HMGB1-1 group (PMNs+RPMI 1640 medium+10 ng/ml HMGB1), (34.89+/-1.15) % in HMGB1-2 group (PMNs+RPMI 1640 medium+100 ng/ml HMGB1), and (18.77+/-3.02) % in HMGB1-3 group (PMNs+RPMI 1640 medium+1 000 ng/ml HMGB1). There was statistical significance. Meanwhile, PMN TUNEL positive rate was (31.42+/-4.40) %, (31.39+/-3.80) %, (25.62+/-2.46) %, and (17.98+/-3.20) % in control group, HMGB1-1 group, HMGB1-2 group and HMGB1-3 group, respectively. The inhibitory effect was HMGB1 dose-depended as compared with that of control group.

CONCLUSION

After LPS challenge, high expression of rats' lung HMGB1 mRNA occurs at a later phase, but keeps for a long time. Sodium butyrate (SB) treatment attenuated LPS-induced PMN apoptosis delay and inhibition, and down-regulated HMGB1 mRNA expression of injured lung. HMGB1 in vitro inhibited human circulating PMN apoptosis markedly, and the inhibitory effect was HMGB1 dose-depended. The results demonstrated that HMGB1 may play an important role as a modulator in apoptotic changes in PMN during LPS-induced ALI. It concludes that HMGB1 may contribute to the development of PMN apoptotic changes during LPS-induced acute lung injury.

Low level laser therapy (LLLT) decreases pulmonary microvascular leakage, neutrophil influx and IL-1beta levels in airway and lung from rat subjected to LPS-induced inflammation

BACKGROUND AND OBJECTIVE

Low level laser therapy (LLLT) is a known anti-inflammatory therapy. Herein we studied the effect of LLLT on lung permeability and the IL-1beta level in LPS-induced pulmonary inflammation. STUDY DESIGN/METHODOLOGY: Rats were divided into 12 groups (n = 7 for each group). Lung permeability was measured by quantifying extravasated albumin concentration in lung homogenate, inflammatory cells influx was determined by myeloperoxidase activity, IL-1beta in BAL was determined by ELISA and IL-1beta mRNA expression in trachea was evaluated by RT-PCR. The rats were irradiated on the skin over the upper bronchus at the site of tracheotomy after LPS.

RESULTS

LLLT attenuated lung permeability. In addition, there was reduced neutrophil influx, myeloperoxidase activity and both IL-1beta in BAL and IL-1beta mRNA expression in trachea obtained from animals subjected to LPS-induced inflammation.

CONCLUSION

LLLT reduced the lung permeability by a mechanism in which the IL-1beta seems to have an important role.

Low-level laser therapy decreases levels of lung neutrophils anti-apoptotic factors by a NF-kappaB dependent mechanism

BACKGROUND AND OBJECTIVE

Low-level laser therapy (LLLT) is a known modulator of inflammatory process. Herein we studied the effect of 660 nm diode laser on mRNA levels of neutrophils anti-apoptotic factors in lipopolysaccharide (LPS)-induced lung inflammation. STUDY DESIGN/METHODOLOGY: Mice were divided into 8 groups (n=7 for each group) and irradiated with energy dosage of 7.5 J/cm(2). The Bcl-xL and A1 mRNA levels in neutrophils were evaluated by Real Time-PCR (RT-PCR). The animals were irradiated after exposure time of LPS.

RESULTS

LLLT and an inhibitor of NF-kappaB nuclear translocation (BMS 205820) attenuated the mRNA levels of Bcl-xL and A1 mRNA in lung neutrophils obtained from mice subjected to LPS-induced inflammation.

CONCLUSION

LLLT reduced the levels of anti-apoptotic factors in LPS inflamed mice lung neutrophils by an action mechanism in which the NF-kappaB seems to be involved.

Norcantharidin preferentially induces apoptosis in human leukemic Jurkat cells without affecting viability of normal blood mononuclear cells

Norcantharidin (NCTD) is known to have anti-cancer potentials. The aim of this study was to assess the apoptosis-inducing effect of NCTD on human leukemic Jurkat cells. We found that NCTD preferentially inhibited the growth of Jurkat cells in a dose- and time-dependent manner, but not the growth of normal blood mononuclear cells (MNC). Pretreatment with agonistic (CH-11) and antagonistic (ZB4) Fas antibodies on Jurkat cells showed that NCTD-induced apoptosis might not involve Fas-FasL signaling. Flow cytometric assay of Jurkat cells treated with NCTD showed a markedly increased sub-G1 DNA phase and cell cycle arrest at S phase. Western blot analysis of NCTD-treated cells showed increased expressions of cytochrome c, active caspase-9 and -3, and cleavage of poly(ADP-ribose) polymerase (PARP), but the expressions of Bcl-2, Bax and apoptosis-inducing factor were not increased. The transcription factor STAT1 was translocated from cytosol to nucleus. Pancaspase inhibitor z-VAD-FMK not only limited the level of sub-G1 phase, but also prevented the degradation of PARP in NCTD-treated cells. The NCTD-induced cell cycle arrest and apoptosis were mediated through the regulation of ataxia-telangiectasia mutated (ATM), rather than P63 protein. The conditioned medium produced from human MNC (NCTD-MNC-CM) increased the percentage of apoptotic cells and the expression of PARP cleavage in Jurkat cells. Protein array assay of NCTD-MNC-CM showed 32.4- and 6.2-folds increases in TNF-alpha and GM-CSF, respectively, and the expression of MCP-1, GRO, RANTES and IL-10 was decreased. We conclude that NCTD can induce apoptosis in human leukemic Jurkat cells via a caspase-dependent pathway without affecting the viability of normal MNC, and that the apoptosis-inducing effect of NCTD can also be achieved by soluble cytokines produced from peripheral MNC.

In vitro effect of recombinant human tumor necrosis factor-alpha on canine neutrophil apoptosis

Neutrophils (polymorphonuclear leukocytes: PMNs) are essential for the host defense against various infections and are often injurious to the host, causing inflammatory diseases where tumor necrosis factor-alpha (TNF-alpha) is suggested to play an important role. Since an effect of TNF-alpha on canine PMN apoptosis has not been studied, canine PMNs were stimulated with recombinant human (rh)TNF-alpha in the present study to investigate the effect of TNF-alpha on canine PMN apoptosis. PMN apoptosis and function to produce ROS were assessed by flow cytometry. Delayed apoptosis was observed in the PMNs treated with rhTNF-alpha at 100 ng/ml, accompanied by retention of capability to produce ROS. However, PMN apoptosis was accelerated by rhTNF-alpha combined with cycloheximide. Therefore, it is indicated that TNF-alpha is able to activate anti- and pro-apoptotic pathways in PMNs and that the inhibition of PMN apoptosis by TNF-alpha requires protein synthesis in the PMNs.

The effect of fever‐like temperatures on neutrophil signaling

The effect of fever on neutrophils has not been explored. We tested the hypothesis that fever-like temperature spikes affect neutrophil signaling and function. Prior 60 min, 42 degrees C heat exposure inhibited p38 MAPK, ERK, PI3-Kinase/Akt, and NF-kappaB activation in TNF-alpha-challenged suspended neutrophils. Using pharmacological inhibitors and an inhibitory peptide transduced into neutrophils by a HIV-TAT sequence, we found that p38 MAPK and NF-kappaB mediate TNF-alpha-mediated delayed apoptosis in suspended neutrophils. Heat exposure (39-42 degrees C) did not affect constitutive apoptosis but abrogated TNF-alpha-delayed apoptosis in these suspended cells. In contrast, adhesion-dependent functions were not inhibited. Furthermore, we found that heat exposure neither blocked p38 MAPK, ERK, and NF-kappaB activation in neutrophils on fibronectin nor prevented delayed apoptosis by TNF-alpha when cells interacted with fibronectin. Above and beyond apoptosis, TNF-alpha initiated NF-kappaB-dependent gene transcription. Heat exposure blocked this effect in suspended neutrophils but not in neutrophils on fibronectin. Finally, we show that beta2-integrins, which are not necessary for TNF-alpha-induced NF-kappaB activation at 37 degrees C, transduce costimulatory signals allowing NF-kappaB activation after heat exposure. The effect could protect circulating neutrophils from TNF-alpha activation, while not interfering with activation of adherent neutrophils. Fever could make neutrophils more parsimonious.

Chlamydia pneumoniaeMultiply in Neutrophil Granulocytes and Delay Their Spontaneous Apoptosis

The obligate intracellular bacterial pathogen Chlamydia pneumoniae (Cp) is responsible for a range of human diseases, including acute respiratory infection. Although experimental intratracheal infection with Cp results in a massive recruitment of neutrophil granulocytes (polymorphonuclear neutrophils (PMN)), the role of these cells in the defense against Cp is unclear. In this study the interactions of PMN with Cp were investigated. In vitro coincubation experiments showed that human granulocytes were able to internalize Chlamydia in an opsonin-independent manner. Importantly, phagocytosed Cp were not killed; the ingested bacteria survived and multiplied within PMN. Although uninfected granulocytes became apoptotic within 10 h, infected PMN survived up to 90 h. Coincubation with Cp significantly decreased the ratio of apoptotic PMN, as detected by morphological analysis, annexin V, and TUNEL staining. The observed antiapoptotic effect was associated with a markedly lower level of procaspase-3 processing and, consequently, reduced caspase-3 activity in infected PMN. LPS was found as a major, but not exclusive, component responsible for the observed antiapoptotic effect. Chlamydia LPS affected PMN apoptosis both by acting directly on the cells and by inducing the autocrine production of the antiapoptotic cytokine IL-8. These data show that, in contrast to other microbial pathogens that drive phagocytes into apoptosis to escape killing, Cp can extend the life span of neutrophil granulocytes, making them suitable host cells for survival and multiplication within the first hours/days after infection.

Integrins and cytokines activate nuclear transcription factor-kappaB in human neutrophils

Neutrophil adhesion to extracellular matrix is necessary for an effective inflammatory response. Adhesion may accelerate neutrophil activation by affecting intracellular signaling pathways. The nuclear transcription factor kappaB (NF-kappaB) controls several cellular functions, including inflammation, proliferation, and cell survival. We explored the role of adhesion in NF-kappaB activation in human neutrophils. Cells were stimulated with tumor necrosis factor-alpha (TNF-alpha), granulocyte macrophage-colony-stimulating factor (GM-CSF), interleukin-8 (IL-8), and formyl-methionyl-leucyl-phenylalanine (fMLP). All four initiated neutrophil adherence to and spreading on fibronectin. GM-CSF and IL-8 did not activate NF-kappaB in suspended neutrophils but rapidly activated NF-kappaB under adherent conditions on matrix, as shown by IkappaB kinase activity assay, IkappaBalpha degradation, electromobility shift assay, and quantitative reverse transcriptase-PCR. In contrast, TNF-alpha activated NF-kappaB both in suspended cells and adherent cells. fMLP did not activate NF-kappaB in either suspended or adherent cells. Specific beta(2) integrin blockade prevented NF-kappaB activation by GM-CSF and IL-8 on fibronectin. Co-stimulating CD18 and CD11b with activating antibodies resulted in NF-kappaB activation by GM-CSF and IL-8 in suspended cells. We inhibited actin polymerization with cytochalasin and blocked the non-receptor kinase Syk with piceatannol. Both maneuvers prevented the co-stimulatory NF-kappaB-activating signal by beta(2) integrins. Thus, in addition to beta(2) integrin ligand binding, NF-kappaB activation depended on the formation of the receptor-associated intracellular focal adhesion complex. We conclude that beta(2) integrins may provide co-stimulatory signals allowing some soluble mediators to activate the NF-kappaB pathway even when they are not capable of doing so in suspension. This effect may become important when human neutrophils leave the circulating blood and migrate through extracellular matrix during inflammation.

Inhibition of NF-kappaB by a TAT-NEMO-binding domain peptide accelerates constitutive apoptosis and abrogates LPS-delayed neutrophil apoptosis

Delivery of biologically active peptides into human polymorphonuclear neutrophils (PMNs) has implications for studying cellular functions and may be therapeutically relevant. The transcription factor nuclear factor-kappaB (NF-kappaB) regulates the expression of multiple genes controlling inflammation, proliferation, and cell survival. PMNs play a crucial role in first-line defense. Targeting NF-kappaB in these cells may promote apoptosis and therefore facilitate resolution of inflammation. We used an 11-amino acid sequence NEMO-binding domain (NBD) that selectively inhibits the IKKgamma (NEMO)/IKKbeta interaction, preventing NF-kappaB activation. An HIV-TAT sequence served as a highly effective transducing shuttle. We show that lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor (GM-CSF), and dexamethasone (DEX) significantly reduced apoptosis after 20 hours. LPS, but not GM-CSF or DEX, activated NF-kappaB as shown by IkappaBalpha degradation, NF-kappaB DNA binding, and transcriptional activity. The TAT-NBD blocked LPS-induced NF-kappaB activation and NF-kappaB-dependent gene expression. TAT-NBD accelerated constitutive PMN apoptosis dose dependently and abrogated LPS-delayed apoptosis. These results provide a proof of principle for peptide delivery by TAT-derived protein transduction domains to specifically inhibit NF-kappaB activity in PMNs. This strategy may help in controlling various cellular functions even in short-lived, transfection-resistant primary human cells.

HIV-1 and IL-1 beta regulate Fas ligand expression in human astrocytes through the NF-kappa B pathway

Reactive astrogliosis is a prominent pathological feature of HIV-1-associated dementia (HAD). We hypothesized that in HAD, astrocytes activated with proinflammatory stimuli such as IL-1beta express Fas ligand (FasL), a death protein. IL-1beta and HIV-1-activated astrocytes expressed FasL mRNA and protein. Luciferase reporter constructs showed that IL-1beta and HIV-1 upregulated FasL promoter activity (p<0.001). The NF-kappaB pathway was involved as shown by inhibition with SN50 and dominant negative IkappaBalpha mutants. Brain extracts from HAD patients had significantly elevated FasL levels compared to HIV-seropositive (p<0.001) and seronegative individuals (p<0.01). We propose that astrocyte expression of FasL may participate in neuronal injury in HAD.

Involvement of p38 mitogen-activated protein kinase in heat shock protein 27 induction in human neutrophils

We investigated whether tumor necrosis factor-alpha (TNF-alpha) stimulates the induction of heat shock protein 27 (HSP27) in human neutrophils and the mechanism underlying this induction. In intact neutrophils, almost no HSP27 was detected. Stimulation of neutrophils by TNF-alpha increased the levels of HSP27 in the presence, but not in the absence, of cycloheximide. Reverse transcription-polymerase chain reaction (RT-PCR) experiments showed that TNF-alpha also induced HSP27 mRNA in the presence of cycloheximide. TNF-alpha induced the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase and p38 MAP kinase. The HSP27 accumulation induced by TNF-alpha was significantly suppressed by 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole (SB203580) or 4-(4-fluorophenyl)-2-(4-nitrophenyl)-5-(4-pyridyl)-1H-imidazole (PD169316); both are specific inhibitors of p38 MAP kinase, but not by 2'-amino-3'-methoxyflavone (PD098059, a specific inhibitor of the upstream kinase that activates p44/p42 MAP kinase). The accumulation of HSP27 induced by TNF-alpha plus cycloheximide was also suppressed by pretreatment with a specific protein kinase C (PKC) inhibitor. Furthermore, phorbol myristate acetate (PMA), a PKC stimulant, but not dibutyryl cyclic AMP, a protein kinase A stimulant, stimulated the accumulation of HSP27. Interestingly, SB203580 did not inhibit PMA-stimulated HSP27 induction. These results strongly suggest that TNF-alpha may act as the regulator of HSP27 induction in neutrophils. p38 MAP kinase (but not p44/p42 MAP kinase) and PKC take part in TNF-alpha-stimulated HSP27 induction in human neutrophils.

Involvement of a ferroprotein sensor in hypoxia-mediated inhibition of neutrophil apoptosis

Neutrophil apoptosis represents a major mechanism involved in the resolution of acute inflammation. In contrast to the effect of hypoxia observed in many other cell types, oxygen deprivation, as we have shown, causes a profound but reversible delay in the rate of constitutive apoptosis in human neutrophils when aged in vitro. This effect was mimicked by exposing cells to 2 structurally unrelated iron-chelating agents, desferrioxamine (DFO) and hydroxypyridines (CP-94), and it appeared specific for hypoxia in that no modulation of apoptosis was observed with mitochondrial electron transport inhibitors, glucose deprivation, or heat shock. The involvement of chelatable iron in the oxygen-sensing mechanism was confirmed by the abolition of the DFO and CP-94 survival effect by Fe(2+) ions. Although hypoxia inducible factor-1alpha (HIF-1alpha) mRNA was identified in freshly isolated neutrophils, HIF-1alpha protein was only detected in neutrophils incubated under hypoxic conditions or in the presence of DFO. Moreover, studies with cyclohexamide demonstrated that the survival effect of hypoxia was fully dependent on continuing protein synthesis. These results indicate that the neutrophil has a ferroprotein oxygen-sensing mechanism identical to that for erythropoietin regulation and results in HIF-1alpha up-regulation and profound but reversible inhibition of neutrophil apoptosis. This finding may have important implications for the resolution of granulocytic inflammation at sites of low-oxygen tension.

Inhibition of the spontaneous apoptosis of neutrophil granulocytes by the intracellular parasite Leishmania major

Macrophages are the major target cell population of the obligate intracellular parasites Leishmania. Although polymorphonuclear neutrophil granulocytes (PMN) are able to internalize Leishmania promastigotes, these cells have not been considered to date as host cells for the parasites, primarily due to their short life span. In vitro coincubation experiments were conducted to investigate whether Leishmania can modify the spontaneous apoptosis of human PMN. Coincubation of PMN with Leishmania major promastigotes resulted in a significant decrease in the ratio of apoptotic neutrophils as detected by morphological analysis of cell nuclei, TUNEL assay, gel electrophoresis of low m.w. DNA fragments, and annexin V staining. The observed antiapoptotic effect was found to be associated with a significant reduction of caspase-3 activity in PMN. The inhibition of PMN apoptosis depended on viable parasites because killed Leishmania or a lysate of the parasites did not have antiapoptotic effect. L. major did not block, but rather delayed the programmed cell death of neutrophils by approximately 24 h. The antiapoptotic effect of the parasites could not be transferred by the supernatants, despite secretion of IL-8 by PMN upon coculture with L. major. In vivo, intact parasites were found intracellularly in PMN collected from the skin of mice 3 days after s.c. infection. This finding strongly suggests that infection with Leishmania prolongs the survival time of neutrophils also in vivo. These data indicate that Leishmania induce an increased survival of neutrophil granulocytes both in vitro and in vivo.

Role of NF-kappaB in endotoxemia-induced alterations of lung neutrophil apoptosis

Acute lung injury is frequently associated with endotoxemia and is characterized by the accumulation in the lungs of large numbers of neutrophils activated to produce proinflammatory mediators. In the setting of acute lung injury, the percentage of apoptotic cells among lung neutrophils is decreased. The transcriptional regulatory factor NF-kappaB is activated in neutrophils and other pulmonary cell populations after endotoxemia and appears to play a central role in the development of the acute inflammatory process that leads to lung injury. Because NF-kappaB can modulate apoptosis through increasing expression of anti-apoptotic proteins, activation of NF-kappaB may contribute to the alterations in lung neutrophil apoptosis associated with acute lung injury. In the present experiments, endotoxemia resulted in decreased apoptosis and increased expression of anti-apoptotic mediators among lung neutrophils. Amounts of A1, A20, and Bcl-x(L), anti-apoptotic proteins whose transcription is dependent on NF-kappaB, were increased in lung neutrophils after endotoxemia. Inhibition of nuclear translocation of NF-kappaB increased the percentage of apoptotic lung neutrophils after endotoxemia, but not back to the levels found in unmanipulated animals. Although inhibition of nuclear translocation of NF-kappaB prevented endotoxemia-induced increases in Bcl-x(L), A1, and A20 in lung neutrophils, this intervention did not prevent endotoxemia-associated elevation of Mcl-1, an anti-apoptotic protein primarily under the transcriptional regulation of CREB. These results demonstrate that mechanisms independent of NF-kappaB activation play an important role in modulating lung neutrophil apoptosis after endotoxemia.

The loss of susceptibility to apoptosis in exudated tissue neutrophils is associated with their nuclear factor-kappa B activation

Tissue neutrophils, human salivary neutrophils donated from healthy subjects and synovial fluid neutrophils collected from patients with rheumatoid arthritis were compared with circulating blood neutrophils. Concomitant treatment of circulating blood neutrophils with tumor necrosis factor-alpha (TNF-alpha) and cycloheximide induced neutrophil apoptosis, whereas the same treatment failed to induce significant apoptosis in salivary and synovial fluid neutrophils. Caspase-3 activation by TNF-alpha was observed in these tissue neutrophils, although its activity was significantly weaker than that in circulating blood neutrophils. In circulating blood neutrophils, TNF-alpha induced activation of nuclear factor-kappa B (NF-kappa B), whereas, in tissue neutrophils, NF-kappa B had been already activated without any stimulation, and no further activation was induced by the treatment with TNF-alpha. Furthermore, while pretreatment of neutrophils with an NF-kappa B inhibitor produced typical apoptotic changes in circulating blood neutrophils, this inhibitor did not produce any morphological apoptotic changes induced by TNF-alpha in tissue neutrophils. These results indicate that neutrophils undergo marked functional changes such as altered sensitivity to apoptosis-inducing stimuli in association with their exudation from blood into tissue, and that NF-kappa B activation is involved in the acquisition of resistance to TNF-alpha-induced apoptosis.