Transepithelial migration of neutrophils in response to leukotriene B4 is mediated by a reactive oxygen species-extracellular signal-regulated kinase-linked cascade

Genetic and functional modulation by agonist MRS5698 and allosteric enhancer LUF6000 at the native A3 adenosine receptor in HL-60 cells

The A3 adenosine receptor (AR) is an important inflammatory and immunological target. However, the underlying mechanisms are not fully understood. Here, we report the gene regulation in HL-60 cells treated acutely with highly selective A3AR agonist MRS5698, positive allosteric modulator (PAM) LUF6000, or both. Both pro- and anti-inflammatory genes, such as IL-1a, IL-1β, and NFκBIZ, are significantly upregulated. During our observations, LUF6000 alone produced a lesser effect, while the MRS5698 + LUF6000 group demonstrated generally greater effects than MRS5698 alone, consistent with allosteric enhancement. The number of genes up- and down-regulated are similar. Pathway analysis highlighted the critical involvement of signaling molecules, including IL-6 and IL-17. Important upstream regulators include IL-1a, IL-1β, TNF-α, NF-κB, etc. PPAR, which modulates eicosanoid metabolism, was highly downregulated by the A3AR agonist. Considering previous pharmacological results and mathematical modeling, LUF6000's small enhancement of genetic upregulation suggested that MRS5698 is a nearly full agonist, which we demonstrated in both cAMP and calcium assays. The smaller effect of LUF6000 on MRS5698 in comparison to its effect on Cl-IB-MECA was shown in both HL-60 cells endogenously expressing the human (h) A3AR and in recombinant hA3AR-expressing CHO cells, consistent with its HL-60 cell genetic regulation patterns. In summary, by using both selective agonists and PAM, we identified genes that are closely relevant to immunity and inflammation to be regulated by A3AR in differentiated HL-60 cells, a cell model of neutrophil function. In addition, we demonstrated the previously uncharacterized allosteric signaling-enhancing effect of LUF6000 in cells endogenously expressing the hA3AR.

LIFR regulates cholesterol-driven bidirectional hepatocyte-neutrophil cross-talk to promote liver regeneration

Liver regeneration is under metabolic and immune regulation. Despite increasing recognition of the involvement of neutrophils in regeneration, it is unclear how the liver signals to the bone marrow to release neutrophils after injury and how reparative neutrophils signal to hepatocytes to reenter the cell cycle. Here we report that loss of the liver tumour suppressor Lifr in mouse hepatocytes impairs, whereas overexpression of leukaemia inhibitory factor receptor (LIFR) promotes liver repair and regeneration after partial hepatectomy or toxic injury. In response to physical or chemical damage to the liver, LIFR from hepatocytes promotes the secretion of cholesterol and CXCL1 in a STAT3-dependent manner, leading to the efflux of bone marrow neutrophils to the circulation and damaged liver. Cholesterol, via its receptor ERRα, stimulates neutrophils to secrete hepatocyte growth factor to accelerate hepatocyte proliferation. Altogether, our findings reveal a LIFR-STAT3-CXCL1-CXCR2 axis and a LIFR-STAT3-cholesterol-ERRα-hepatocyte growth factor axis that form bidirectional hepatocyte-neutrophil cross-talk to repair and regenerate the liver.

Granulocyte concentrate splitting does not affect phenotype and function

BACKGROUND

More granulocyte concentrates (GCs) could be produced for more patients from the same donor if apheresis bags were split and stored for longer periods of time. Hence, we tested the hypothesis that splitting and extension of storage of GCs do not impair granulocyte function or viability.

STUDY DESIGN AND METHODS

Granulocyte apheresis concentrates were produced using modified fluid gelatin as a separation enhancer, split into two portions, and stored for 24 and 48 h. Granulocyte function, represented by cell migration, reactive oxygen species (ROS) production, and neutrophil extracellular trap formation (NETosis), was measured by live-cell imaging. ROS production, adhesive surface protein expression, and viability were measured by flow cytometry.

RESULTS

Splitting had no effect on any of the tested parameters. After 24 h of storage, live-cell imaging showed no significant difference in migration, time to maximum ROS production, time to half-maximum NETosis, viability, or CD11b expression, but ROS production induced by phorbol 12-myristate 13-acetate (PMA) decreased from an initial median fluorescence intensity of 1775-590 artificial units. After 48 h, PMA-induced ROS production, viability, and migration declined, as reflected by decreases in median total distance (119 vs. 63.5 μm) and median Euclidean distance (30.75 vs. 14.3 μm).

CONCLUSION

Splitting GC products has no effect on granulocyte viability or function, but extended storage >24 h does compromise granulocyte function. The findings confirm that GCs should be transfused within 24 h of collection. Longer storage cannot be recommended.

Recent advances in function and structure of two leukotriene B4 receptors: BLT1 and BLT2

Leukotriene B₄ (LTB₄) is generated by the enzymatic oxidation of arachidonic acid, which is then released from the cell membrane and acts as a potent activator of leukocytes and other inflammatory cells. Numerous studies have demonstrated the physiological and pathophysiological significance of this lipid in various diseases. LTB₄ exerts its activities by binding to its specific G protein-coupled receptors (GPCRs): BLT1 and BLT2. In mouse disease models, treatment with BLT1 antagonists or BLT1 gene ablation attenuated various diseases, including bronchial asthma, arthritis, and psoriasis, whereas BLT2 deficiency exacerbated several diseases in the skin, cornea, and small intestine. Therefore, BLT1 inhibitors and BLT2 activators could be beneficial for the treatment of several inflammatory and immune disorders. As a result, attractive compounds targeting LTB₄ receptors have been developed by several pharmaceutical companies. This review aims to understand the potential of BLT1 and BLT2 as therapeutic targets for the treatment of various inflammatory diseases. In addition, recent topics are discussed with major focuses on the structure and post-translational modifications of BLT1 and BLT2. Collectively, current evidence on modulating LTB₄ receptor functions provides new strategies for the treatment of various diseases.

Temperature-sensitive migration dynamics in neutrophil-differentiated HL-60 cells

Cell migration plays an essential role in wound healing and inflammatory processes inside the human body. Peripheral blood neutrophils, a type of polymorphonuclear leukocyte (PMN), are the first cells to be activated during inflammation and subsequently migrate toward an injured tissue or infection site. This response is dependent on both biochemical signaling and the extracellular environment, one aspect of which includes increased temperature in the tissues surrounding the inflammation site. In our study, we analyzed temperature-dependent neutrophil migration using differentiated HL-60 cells. The migration speed of differentiated HL-60 cells was found to correlate positively with temperature from 30 to 42 °C, with higher temperatures inducing a concomitant increase in cell detachment. The migration persistence time of differentiated HL-60 cells was higher at lower temperatures (30-33 °C), while the migration persistence length stayed constant throughout the temperature range. Coupled with the increased speed observed at high temperatures, this suggests that neutrophils are primed to migrate more effectively at the elevated temperatures characteristic of inflammation. Temperature gradients exist on both cell and tissue scales. Taking this into consideration, we also investigated the ability of differentiated HL-60 cells to sense and react to the presence of temperature gradients, a process known as thermotaxis. Using a two-dimensional temperature gradient chamber with a range of 27-43 °C, we observed a migration bias parallel to the gradient, resulting in both positive and negative thermotaxis. To better mimic the extracellular matrix (ECM) environment in vivo, a three-dimensional collagen temperature gradient chamber was constructed, allowing observation of biased neutrophil-like differentiated HL-60 migration toward the heat source.

Human macrophages utilize a wide range of pathogen recognition receptors to recognize Legionella pneumophila, including Toll-Like Receptor 4 engaging Legionella lipopolysaccharide and the Toll-like Receptor 3 nucleic-acid sensor

Cytokines made by macrophages play a critical role in determining the course of Legionella pneumophila infection. Prior murine-based modeling indicated that this cytokine response is initiated upon recognition of L. pneumophila by a subset of Toll-like receptors, namely TLR2, TLR5, and TLR9. Through the use of shRNA/siRNA knockdowns and subsequently CRISPR/Cas9 knockouts (KO), we determined that TRIF, an adaptor downstream of endosomal TLR3 and TLR4, is required for full cytokine secretion by human primary and cell-line macrophages. By characterizing a further set of TLR KO's in human U937 cells, we discerned that, contrary to the viewpoint garnered from murine-based studies, TLR3 and TLR4 (along with TLR2 and TLR5) are in fact vital to the macrophage response in the early stages of L. pneumophila infection. This conclusion was bolstered by showing that i) chemical inhibitors of TLR3 and TLR4 dampen the cytokine output of primary human macrophages and ii) transfection of TLR3 and TLR4 into HEK cells conferred an ability to sense L. pneumophila. TLR3- and TLR4-dependent cytokines promoted migration of human HL-60 neutrophils across an epithelial layer, pointing to the biological importance for the newfound signaling pathway. The response of U937 cells to L. pneumophila LPS was dependent upon TLR4, a further contradiction to murine-based studies, which had concluded that TLR2 is the receptor for Legionella LPS. Given the role of TLR3 in sensing nucleic acid (i.e., dsRNA), we utilized newly-made KO U937 cells to document that DNA-sensing by cGAS-STING and DNA-PK are also needed for the response of human macrophages to L. pneumophila. Given the lack of attention given them in the bacterial field, C-type lectin receptors were similarly examined; but, they were not required. Overall, this study arguably represents the most extensive, single-characterization of Legionella-recognition receptors within human macrophages.

Regulatory mechanisms of neutrophil migration from the circulation to the airspace

The neutrophil, a short-lived effector leukocyte of the innate immune system best known for its proteases and other degradative cargo, has unique, reciprocal physiological interactions with the lung. During health, large numbers of ‘marginated’ neutrophils reside within the pulmonary vasculature, where they patrol the endothelial surface for pathogens and complete their life cycle. Upon respiratory infection, rapid and sustained recruitment of neutrophils through the endothelial barrier, across the extravascular pulmonary interstitium, and again through the respiratory epithelium into the airspace lumen, is required for pathogen killing. Overexuberant neutrophil trafficking to the lung, however, causes bystander tissue injury and underlies several acute and chronic lung diseases. Due in part to the unique architecture of the lung’s capillary network, the neutrophil follows a microanatomic passage into the distal airspace unlike that observed in other end-organs that it infiltrates. Several of the regulatory mechanisms underlying the stepwise recruitment of circulating neutrophils to the infected lung have been defined over the past few decades; however, fundamental questions remain. In this article, we provide an updated review and perspective on emerging roles for the neutrophil in lung biology, on the molecular mechanisms that control the trafficking of neutrophils to the lung, and on past and ongoing efforts to design therapeutics to intervene upon pulmonary neutrophilia in lung disease.

Chemotaxis and swarming in differentiated HL-60 neutrophil-like cells

The human leukemia cell line (HL-60) is an alternative to primary neutrophils in research studies. However, because HL-60 cells proliferate in an incompletely differentiated state, they must undergo differentiation before they acquire the functional properties of neutrophils. Here we provide evidence of swarming and chemotaxis in differentiated HL-60 neutrophil-like cells (dHL-60) using precise microfluidic assays. We found that dimethyl sulfoxide differentiated HL-60 cells (DdHL-60) have a larger size, increased length, and lower ability to squeeze through narrow channels compared to primary neutrophils. They migrate through tapered microfluidic channels slower than primary neutrophils, but faster than HL-60s differentiated by other protocols, e.g., using all-trans retinoic acid. We found that dHL-60 can swarm toward zymosan particle clusters, though they display disorganized migratory patterns and produce swarms of smaller size compared to primary neutrophils.

PbrPOE21 inhibits pear pollen tube growth in vitro by altering apical reactive oxygen species content

Genome-wide identification, tissue-specific expression analysis and functional characterization of selected genes containing the pear Pollen Olea europaea I domain reveal their roles in pollen tube growth. Genes containing the Pollen Olea europaea I (POE) domain play crucial roles in diverse growth and developmental processes. Nevertheless, the specific functions of POE family members in progression of pollen tube growth (PTG) remain uncharacterized. We identified 45 PbrPOE genes in the pear (Pyrus bretschneideri) genome, clustered into seven subclasses. PbrPOE genes contained 1 to 11 exons and 0 to 10 introns, with exon/intron structure mostly conserved within each subclass. Whole-genome duplication has mainly contributed to the duplication pattern of PbrPOE genes in pear. Expression profiles of 45 PbrPOE genes in 12 different pear tissues revealed that six PbrPOE genes (PbrPOE6, 12, 21, 29, 35 and 41) of subclass B were highly expressed during the growth of the pear pollen tube in vitro. PbrPOE21 was selected for further functional analysis on the basis of its high and differential expression pattern in pollen. Antisense oligodeoxynucleotide assays demonstrated that PTG was augmented in vitro when PbrPOE21 expression was significantly inhibited. Moreover, pollen tube length in vitro was reduced when PbrPOE21 was transitorily over-expressed using particle bombardment technology. Exogenous PbrPOE21 recombinant protein inhibited PTG in vitro at an optimum concentration of 1.8 µM. PbrPOE21 also affected reactive oxygen species content in the pear pollen tube apex. We suggest that PbrPOE21 inhibits PTG in vitro by altering apical reactive oxygen species content.

CFTR Modulators Dampen Aspergillus-Induced Reactive Oxygen Species Production by Cystic Fibrosis Phagocytes

Excessive inflammation by phagocytes during Aspergillus fumigatus infection is thought to promote lung function decline in CF patients. CFTR modulators have been shown to reduce A. fumigatus colonization in vivo, however, their antifungal and anti-inflammatory mechanisms are unclear. Other treatments including azithromycin and acebilustat may dampen Aspergillus-induced inflammation due to their immunomodulatory properties. Therefore, we set out in this study to determine the effects of current CF therapies on ROS production and fungal killing, either direct or indirect by enhancing antifungal immune mechanisms in peripheral blood immune cells from CF patients upon A. fumigatus infection. Isolated peripheral blood mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs) from CF patients and healthy volunteers were challenged with A. fumigatus following pre-treatment with CFTR modulators, azithromycin or acebilustat. Ivacaftor/lumacaftor treated CF and control subject PMNs resulted in a significant reduction (p < 0.05) in Aspergillus-induced ROS. For CF PBMC, Aspergillus-induced ROS was significantly reduced when pre-treated with ivacaftor alone (p < 0.01) or in combination with lumacaftor (p < 0.01), with a comparable significant reduction in control subject PBMC (p < 0.05). Azithromycin and acebilustat had no effect on ROS production by CF or control subject phagocytes. None of the treatments showed an indirect or direct antifungal activity. In summary, CFTR modulators have potential for additional immunomodulatory benefits to prevent or treat Aspergillus-induced inflammation in CF. The comparable effects of CFTR modulators observed in phagocytes from control subjects questions their exact mechanism of action.

Neutrophil swarming delays the growth of clusters of pathogenic fungi

Neutrophils employ several mechanisms to restrict fungi, including the action of enzymes such as myeloperoxidase (MPO) or NADPH oxidase, and the release of neutrophil extracellular traps (NETs). Moreover, they cooperate, forming “swarms” to attack fungi that are larger than individual neutrophils. Here, we designed an assay for studying how these mechanisms work together and contribute to neutrophil's ability to contain clusters of live Candida. We find that neutrophil swarming over Candida clusters delays germination through the action of MPO and NADPH oxidase, and restricts fungal growth through NET release within the swarm. In comparison with neutrophils from healthy subjects, those from patients with chronic granulomatous disease produce larger swarms against Candida, but their release of NETs is delayed, resulting in impaired control of fungal growth. We also show that granulocyte colony-stimulating factors (GCSF and GM-CSF) enhance swarming and neutrophil ability to restrict fungal growth, even during treatment with chemical inhibitors that disrupt neutrophil function.

Neutrophils employ several mechanisms to control the growth of fungi, including enzymes, reactive oxygen species, extracellular traps, and formation of “swarms”. Here, Hopke et al. study how the different mechanisms work together, using an in vitro assay with human neutrophils and clusters of live Candida cells.

Vestitol drives LPS-activated macrophages into M2 phenotype through modulation of NF-κB pathway

Previously, we demonstrated the anti-inflammatory properties of vestitol in a neutrophil model. Here, we show the effects of vestitol on macrophage activation and function. Vestitol was obtained from Brazilian red propolis after bioguided fractionation and tested at different concentrations in LPS-activated RAW 264.7 murine macrophages for nitric oxide (NO) production and cell viability. The levels of TNF-α, IL1-β, TGF-β, IL-4, IL-6, IL-10, IL-12, GM-CSF, IFN-ɣ and gene expression related to cytokines, NO, PI3K-AKT and signal transduction pathways were assayed by ELISA and RT-qPCR, respectively. Differences were determined by one-way ANOVA followed by Tukey-Kramer. Vestitol inhibited NO production by 83% at 0.55 μM without affecting cell viability when compared to the vehicle control (P < 0.05). Treatment with vestitol reduced GM-CSF, IL-6, TNF-α, IL-4 and TGF-β levels and increased IL-10 release (P < 0.05). Vestitol affected the expression of genes related to NF-κB pathway, NO synthase, and inhibition of leukocyte transmigration, namely: Ccs, Ccng1, Calm1, Tnfsf15, Il11, Gata3, Gadd45b, Cdkn1b, Csf1, Ccl5, Birc3 (negatively regulated), and Igf1 (positively regulated). Vestitol diminished the activation of NF-κB and Erk 1/2 pathways and induced macrophages into M2-like polarization. The modulatory effects of vestitol are due to inhibition of NF-κB and Erk 1/2 signaling pathways, which are associated with the production of pro-inflammatory factors.

TREM-1 regulates neutrophil chemotaxis by promoting NOX-dependent superoxide production

Neutrophil migration across tissue barriers to the site of injury involves integration of complex danger signals and is critical for host survival. Numerous studies demonstrate that these environmental signals fundamentally alter the responses of extravasated or "primed" neutrophils. Triggering receptor expressed on myeloid cells 1 (TREM-1) plays a central role in modulating inflammatory signaling and neutrophil migration into the alveolar airspace. Using a genetic approach, we examined the role of TREM-1 in extravasated neutrophil function. Neutrophil migration in response to chemoattractants is dependent upon multiple factors, including reactive oxygen species (ROS) generated either extracellularly by epithelial cells or intracellularly by NADPH oxidase (NOX). We, therefore, questioned whether ROS were responsible for TREM-1-mediated regulation of migration. Thioglycollate-elicited peritoneal neutrophils isolated from wild-type (WT) and TREM-1-deficient mice were stimulated with soluble and particulate agonists. Using electron paramagnetic resonance spectroscopy, we demonstrated that NOX2-dependent superoxide production is impaired in TREM-1-deficient neutrophils. Consistent with these findings, we confirmed with Clark electrode that TREM-1-deficient neutrophils consume less oxygen. Next, we demonstrated that TREM-1 deficient neutrophils have impaired directional migration to fMLP and zymosan-activated serum as compared to WT neutrophils and that deletion or inhibition of NOX2 in WT but not TREM-1-deficient neutrophils significantly impaired direction sensing. Finally, TREM-1 deficiency resulted in decreased protein kinase B (AKT) activation. Thus, TREM-1 regulates neutrophil migratory properties, in part, by promoting AKT activation and NOX2-dependent superoxide production. These findings provide the first mechanistic evidence as to how TREM-1 regulates neutrophil migration.

G-quadruplex-forming oligodeoxyribonucleotides activate leukotriene synthesis in human neutrophils

Human polymorphonuclear leukocytes (PMNLs, neutrophils) play a major role in the immune response to bacterial and fungal infections and eliminate pathogens through phagocytosis. During phagocytosis of microorganisms, the 5-lipoxygenase (5-LOX) pathway is activated resulting in generation of leukotrienes, which mediate host defense. In this study, a library of oligodeoxyribonucleotides (ODNs) with varying numbers of human telomeric repeats (d(TTAGGG)_n) and their analogues with phosphorothioate internucleotide linkages and single-nucleotide substitutions was designed. These ODNs with the potential to fold into G-quadruplex structures were studied from structural and functional perspectives. We showed that exogenous G-quadruplex-forming ODNs significantly enhanced 5-LOX metabolite formation in human neutrophils exposed to Salmonella Typhimurium bacteria. However, the activation of leukotriene synthesis was completely lost when G-quadruplex formation was prevented by substitution of guanosine with 7-deazaguanosine or adenosine residues at several positions. To our knowledge, this study is the first to demonstrate that G-quadruplex structures are potent regulators of 5-LOX product synthesis in human neutrophils in the presence of targets of phagocytosis. Communicated by Ramaswamy H. Sarma.

Stepwise phosphorylation of leukotriene B4 receptor 1 defines cellular responses to leukotriene B4

Leukotriene B₄ (LTB₄) receptor type 1 (BLT1) is abundant in phagocytic and immune cells and plays crucial roles in various inflammatory diseases. BLT1 is phosphorylated at several serine and threonine residues upon stimulation with the inflammatory lipid LTB₄ Using Phos-tag gel electrophoresis to separate differentially phosphorylated forms of BLT1, we identified two distinct types of phosphorylation, basal and ligand-induced, in the carboxyl terminus of human BLT1. In the absence of LTB₄, the basal phosphorylation sites were modified to various degrees, giving rise to many different phosphorylated forms of BLT1. Different concentrations of LTB₄ induced distinct phosphorylation events, and these ligand-induced modifications facilitated additional phosphorylation events at the basal phosphorylation sites. Because neutrophils migrate toward inflammatory sites along a gradient of LTB₄, the degree of BLT1 phosphorylation likely increases in parallel with the increase in LTB₄ concentration as the cells migrate. At high concentrations of LTB₄, deficiencies in these two types of phosphorylation events impaired chemotaxis and β-hexosaminidase release, a proxy for degranulation, in Chinese hamster ovary (CHO-K1) and rat basophilic leukemia (RBL-2H3) cells, respectively. These results suggest that an LTB₄ gradient around inflammatory sites enhances BLT1 phosphorylation in a stepwise manner to facilitate the precise migration of phagocytic and immune cells and the initiation of local responses, including degranulation.

Too much of a good thing: How modulating LTB4 actions restore host defense in homeostasis or disease

The ability to regulate inflammatory pathways and host defense mechanisms is critical for maintaining homeostasis and responding to infections and tissue injury. While unbalanced inflammation is detrimental to the host; inadequate inflammation might not provide effective signals required to eliminate pathogens. On the other hand, aberrant inflammation could result in organ damage and impair host defense. The lipid mediator leukotriene B₄ (LTB₄) is a potent neutrophil chemoattractant and recently, its role as a dominant molecule that amplifies many arms of phagocyte antimicrobial effector function has been unveiled. However, excessive LTB₄ production contributes to disease severity in chronic inflammatory diseases such as diabetes and arthritis, which could potentially be involved in poor host defense in these groups of patients. In this review we discuss the cellular and molecular programs elicited during LTB₄ production and actions on innate immunity host defense mechanisms as well as potential therapeutic strategies to improve host defense.

Functional characterization of the copper transcription factor AfMac1 from Aspergillus fumigatus

Although copper functions as a cofactor in many physiological processes, copper overload leads to harmful effects in living cells. Thus, copper homeostasis is tightly regulated. However, detailed copper metabolic pathways have not yet been identified in filamentous fungi. In this report, we investigated the copper transcription factor AfMac1 ( Aspergillus fumigatusMac1 homolog) and identified its regulatory mechanism in A. fumigatus AfMac1 has domains homologous to the DNA-binding and copper-binding domains of Mac1 from Saccharomyces cerevisiae, and AfMac1 efficiently complemented Mac1 in S. cerevisiae Expression of Afmac1 resulted in CTR1 up-regulation, and mutation of the DNA-binding domain of Afmac1 failed to activate CTR1 expression in S. cerevisiae The Afmac1 deletion strain of A. fumigatus failed to grow in copper-limited media, and its growth was restored by introducing ctrC We found that AfMac1 specifically bound to the promoter region of ctrC based on EMSA. The AfMac1-binding motif 5'-TGTGCTCA-3' was identified from the promoter region of ctrC, and the addition of mutant ctrC lacking the AfMac1-binding motif failed to up-regulate ctrC in A. fumigatus Furthermore, deletion of Afmac1 significantly reduced strain virulence and activated conidial killing activity by neutrophils and macrophages. Taken together, these results suggest that AfMac1 is a copper transcription factor that regulates cellular copper homeostasis in A. fumigatus.

Evidence of a Redox-Dependent Regulation of Immune Responses to Exercise-Induced Inflammation

We used thiol-based antioxidant supplementation (n-acetylcysteine, NAC) to determine whether immune mobilisation following skeletal muscle microtrauma induced by exercise is redox-sensitive in healthy humans. According to a two-trial, double-blind, crossover, repeated measures design, 10 young men received either placebo or NAC (20 mg/kg/day) immediately after a muscle-damaging exercise protocol (300 eccentric contractions) and for eight consecutive days. Blood sampling and performance assessments were performed before exercise, after exercise, and daily throughout recovery. NAC reduced the decline of reduced glutathione in erythrocytes and the increase of plasma protein carbonyls, serum TAC and erythrocyte oxidized glutathione, and TBARS and catalase activity during recovery thereby altering postexercise redox status. The rise of muscle damage and inflammatory markers (muscle strength, creatine kinase activity, CRP, proinflammatory cytokines, and adhesion molecules) was less pronounced in NAC during the first phase of recovery. The rise of leukocyte and neutrophil count was decreased by NAC after exercise. Results on immune cell subpopulations obtained by flow cytometry indicated that NAC ingestion reduced the exercise-induced rise of total macrophages, HLA⁺ macrophages, and 11B⁺ macrophages and abolished the exercise-induced upregulation of B lymphocytes. Natural killer cells declined only in PLA immediately after exercise. These results indicate that thiol-based antioxidant supplementation blunts immune cell mobilisation in response to exercise-induced inflammation suggesting that leukocyte mobilization may be under redox-dependent regulation.

DHA Suppresses Primary Macrophage Inflammatory Responses via Notch 1/ Jagged 1 Signaling

Persistent macrophages were observed in the lungs of murine offspring exposed to maternal LPS and neonatal hyperoxia. Maternal docosahexaenoic acid (DHA) supplementation prevented the accumulation of macrophages and improved lung development. We hypothesized that these macrophages are responsible for pathologies observed in this model and the effects of DHA supplementation. Primary macrophages were isolated from adult mice fed standard chow, control diets, or DHA supplemented diets. Macrophages were exposed to hyperoxia (O₂) for 24 h and LPS for 6 h or 24 h. Our data demonstrate significant attenuation of Notch 1 and Jagged 1 protein levels in response to DHA supplementation in vivo but similar results were not evident in macrophages isolated from mice fed standard chow and supplemented with DHA in vitro. Co-culture of activated macrophages with MLE12 epithelial cells resulted in the release of high mobility group box 1 and leukotriene B₄ from the epithelial cells and this release was attenuated by DHA supplementation. Collectively, our data indicate that long term supplementation with DHA as observed in vivo, resulted in deceased Notch 1/Jagged 1 protein expression however, DHA supplementation in vitro was sufficient to suppress release LTB₄ and to protect epithelial cells in co-culture.

Callicarpa japonica Thunb. attenuates cigarette smoke-induced neutrophil inflammation and mucus secretion

ETHNOPHARMACOLOGICAL RELEVANCE

Callicarpa japonica Thunb. (CJT) is traditionally used as an herbal remedy for the treatment of inflammatory diseases in Korea, China, and Japan. In this study, we evaluated the effects of C. japonica Thunb. (CJT) on the development of COPD using a Cigarette smoke (CS)-induced murine model and cigarette smoke condensate (CSC)-stimulated H292 cells, human pulmonary mucoepidermoid cell line.

MATERIAL AND METHODS

C. japonica Thunb. was isolated from the leaves and stem of C. japonica. The methanol extract profile was obtained by UPLC Q-TOF-MS analysis. In in vivo experiment, the mice received 1h of cigarette smoke for 10 days. C. japonica Thunb. was administered to mice by oral gavage 1h before cigarette smoke exposure for 10 days. In in vitro experiment, we evaluated the effect of C. japonica Thunb. on the expression of MUC5AC and proinflammatory cytokines in H292 cells stimulated with CSC.

RESULTS

CJT treatment effectively suppressed the infiltration of neutrophils, and decreased the production of ROS and the activity of neutrophil elastase in the bronchoalveolar lavage fluid (BALF) induced by CS. CJT also significantly attenuated production of proinflammatory cytokines such as IL-6 and TNF-α in the BALF, and reduced the infiltration of inflammatory cells and the production of mucus in lung tissue induced by CS. In in vitro experiments, CJT decreased the expression of MUC5AC and proinflammatory cytokines in CSC-stimulated H292 cells. Furthermore, CJT attenuated the phosphorylation of ERK induced by CSC in H292 cells. Taken together, CJT effectively reduced the neutrophil airway inflammation and mucus secretion induced by CS in murine model, and inhibited the expression of MUC5AC in CSC-stimulated H292 human lung cell line. These findings suggest that CJT has a therapeutic potential for the treatment of COPD.

Secreted adenosine triphosphate from Aggregatibacter actinomycetemcomitans triggers chemokine response

Extracellular ATP (eATP) is an important intercellular signaling molecule secreted by activated immune cells or released by damaged cells. In mammalian cells, a rapid increase of ATP concentration in the extracellular space sends a danger signal, which alerts the immune system of an impending danger, resulting in recruitment and priming of phagocytes. Recent studies show that bacteria also release ATP into the extracellular milieu, suggesting a potential role for eATP in host-microbe interactions. It is currently unknown if any oral bacteria release eATP. As eATP triggers and amplifies innate immunity and inflammation, we hypothesized that eATP secreted from periodontal bacteria may contribute to inflammation in periodontitis. The aims of this study were to determine if periodontal bacteria secrete ATP, and to determine the function of bacterially derived eATP as an inducer of inflammation. Our results showed that Aggregatibacter actinomycetemcomitans, but not Porphyromonas gingivalis, Prevotella intermedia, or Fusobacterium nucleatum, secreted ATP into the culture supernatant. Exposure of periodontal fibroblasts to filter sterilized culture supernatant of A. actinomycetemcomitans induced chemokine expression in an eATP-dependent manner. This occurred independently of cyclic adenosine monophosphate and phospholipase C, suggesting that ionotrophic P2X receptor is involved in sensing of bacterial eATP. Silencing of P2X7 receptor in periodontal fibroblasts led to a significant reduction in bacterial eATP-induced chemokine response. Furthermore, bacterial eATP served as a potent chemoattractant for neutrophils and monocytes. Collectively, our findings provide evidence for secreted ATP of A. actinomycetemcomitans as a novel virulence factor contributing to inflammation during periodontal disease.

The absence of the leukotriene B4 receptor BLT1 attenuates peripheral inflammation and spinal nociceptive processing following intraplantar formalin injury

BACKGROUND

Leukotriene B4 (LTB4) is a potent lipid mediator of inflammation, and its biological effects are mediated primarily through the high affinity LTB4 receptor BLT1. Although numerous studies have reported that LTB4-BLT1 signaling is involved in inflammatory diseases, the role of BLT1 signaling in pain remains undefined. To clarify the role of LTB4-BLT1 signaling in acute inflammatory pain induced by tissue injury, we performed pain behavioral analysis and assessment of local inflammation induced by peripheral formalin injections in BLT1 knockout mice. We examined the phosphorylation of cAMP response element-binding protein (CREB) in the spinal cord both in wild-type and BLT1 knockout mice because phosphorylation of CREB in spinal cord neurons is important for nociceptive sensitization following peripheral injury. We also examined the effect of a BLT1 antagonist on formalin-induced pain responses in mice.

RESULTS

BLT1 knockout mice exhibited markedly attenuated nociceptive responses induced by intraplantar formalin injections. Edema formation and neutrophil infiltration in the paw were significantly decreased in BLT1 knockout mice compared with wild-type mice. Phosphorylation of CREB in the spinal cord after the intraplantar formalin injection was decreased in BLT1 knockout mice. In addition, mice pretreated with a BLT1 antagonist showed reduced nociception and attenuated CREB phosphorylation in the spinal cord after the formalin injection.

CONCLUSIONS

Our data suggest that LTB4-BLT1 axis contributes not only to the peripheral inflammation but also to the neuronal activation in the spinal cord induced by intraplantar formalin injections. Thus, LTB4-BLT1 signaling is a potential target for therapeutic intervention of acute and persistent pain induced by tissue injury.

Identification of high-affinity copper transporters in Aspergillus fumigatus

We investigated the copper metabolism of Aspergillus fumigatus, which has not been characterized well. We cloned the putative copper transporters ctrA2 and ctrC from A. fumigatus and investigated the functions of these transporters in copper metabolism. Four putative copper transporters were identified in the A. fumigatus genome; ctrA2 and ctrC complemented CTR1 functionally and localized to the plasma membrane in Saccharomyces cerevisiae. ctrA2 and ctrC single-deletion mutants and a double-deletion mutant of ctrA2 and ctrC were constructed in A. fumigatus. The ctrA2 and ctrC double-deletion mutant exhibited a growth defect on Aspergillus minimal medium (AMM) supplemented with bathocuproine disulfonic acid (BCS) and was sensitive to H2O2. Furthermore, the deletion of ctrA2 and ctrC reduced superoxide dismutase (SOD) activity, laccase activity, and intracellular copper contents. The activities of the ctrA2 and ctrC genes were up-regulated by BCS treatment. In addition, the deletion of ctrA2 up-regulated ctrC and vice versa. ctrA2 and ctrC were localized to the A. fumigatus plasma membrane. Although ctrA2 and ctrC failed to affect the mouse survival rate, these genes affected conidial killing activity. Taken together, these results indicate that ctrA2 and ctrC may function as membrane transporters and that the involvement of these genes in pathogenicity merits further investigation.

Pulmonary function changes in rats with taurocholate-induced pancreatitis are attenuated by pretreatment with melatonin

Melatonin is a free radical scavenger and broad-spectrum antioxidant with immunomodulatory effects. We studied the effects of melatonin on changes in lung function, oxidative/nitrosative stress, and inflammatory cell sequestration in an acute pancreatitis (AP)-associated lung inflammation model. Acute pancreatitis was induced by injection of 5% sodium taurocholate into the pancreatic duct of rats. Animals were randomized into control, AP, and a melatonin pretreatment (10 mg/kg)/AP group. Functional residual capacity (FRC), lung compliance (Cchord), expiratory flow rate at 50% (FEF50), airway resistance index (RI), and peak expiratory flow rate (PEF) were evaluated. White blood cell count (WBC) and hydrogen peroxide, lung lavage fluid WBC, methylguanidine, protein, lactic dehydrogenase (LDH), nitric oxide (NO), and leukotriene B4 (LTB4) levels were determined. Lung wet-to-dry weight ratio, peroxynitrite, and inducible nitric oxide synthase (NOS) mRNA and protein were measured. AP induction resulted in reductions in FRC, Cchord, FEF50, and PEF, and increase in RI and lung wet-to-dry weight ratio. Blood and lung lavage fluid WBC, lavage fluid LDH, protein, and blood hydrogen peroxide also increased. Levels of hydroxyl radicals, nitric oxide, and LTB4 in lung lavage fluid, inducible NOS mRNA, protein expression, and peroxynitrite in lung tissue also were significantly elevated. Pretreatment with melatonin attenuated obstructive and restrictive ventilatory insufficiency induced by AP. Blood and lavage WBC, lavage LDH and protein, lung edema, oxidative/nitrosative stress, and lipoxygenase pathway derivatives were also significantly attenuated by melatonin. We conclude that melatonin decreases AP-induced obstructive and restrictive lung function changes via its antioxidant and anti-inflammatory properties.

Resolvins: Endogenously-Generated Potent Painkilling Substances and their Therapeutic Perspectives

The efficacy of many of pain-relieving drugs is based on mechanisms by which the drugs interfere with the body’s natural pain-mediating pathways. By contrast, although it is less popular, other drugs including opioids exert more powerful analgesic actions by augmenting endogenous inhibitory neural circuits for pain mediation. Recently, a novel endogenous pain-inhibitory principle was suggested and is now attracting both scientific and clinical attentions. The central players for the actions are particular body lipids: resolvins. Although research is in the preclinical phase, multiple hypotheses have actively been matured regarding the potency and molecular and neural processes of the analgesic effects of these substances. Consistently, accumulating experimental evidence has been demonstrating that treatment with these lipid substances is strongly effective at controlling diverse types of pain. Treatment of resolvins does not appear to disturb the body homeostasis as severely as many other therapeutic agents that interrupt the body’s natural signaling flow, which enables us to predict their fewer adverse effects. This paper serves as a review of currently documented painkilling actions of resolvins, summarizes the potential cellular and receptor-mediated mechanisms to date, and discusses the many clinical uses for these therapeutic lipids that have not yet been tested. Future scientific efforts will more concentrate to unveil such aspects of the substances and to construct clear proofs of concept for pain relief.

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

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

Neutrophil cell surface receptors and their intracellular signal transduction pathways

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

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Neutrophils are crucial players in innate and adaptive immunity.

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Neutrophils also participate in autoimmune and inflammatory diseases.

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Various neutrophil receptors recognize pathogens and the inflammatory environment.

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The various cell surface receptors trigger diverse intracellular signaling.

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Neutrophil receptors and signaling are potential targets in inflammatory diseases.

EGb 761 promotes osteoblastogenesis, lowers bone marrow adipogenesis and atherosclerotic plaque formation

AIM OF THE STUDY

Our earlier study has demonstrated that EGb 761 (standardized extract of Ginkgo) has the bone sparing effect on the estrogen deficiency induced bone loss model. In the present study, we have addressed the question whether treatment of osteoporosis benefits arterial calcification or vice versa, because both adipocyte and osteoblast originate from the same mesenchymal cell of the bone marrow cell (BMC) population.

MATERIALS AND METHODS

Bone marrow cells were isolated to study the effect of EGb 761 on osteoblast and adipocytes. For in vivo effect hamsters were fed high fat diet and the effect of EGb 761 studied on atherosclerotic plaque formation and endothelial function.

RESULTS

BMC's undergoing induced osteogenic or adipogenic differentiations in the presence of EGb 761 show increase and decrease in mineralization and adipogenesis respectively. Osteogenic and adipogenic mRNAs, reveal lineage dependent expression patterns. Runx-2 (osteoblast transcription factor) showed a progressive increase, whereas PPAR-γ (adipogenic regulator) was attenuated, with same pattern of expression being for late osteogenic and adipogenic genes. EGb 761 led to increase in apoptotic cells and ROS, an important upstream signal. In vivo experiments in hamsters after induction with high cholesterol diet (HCD) show improvement in endothelial function by EGb 761 with lowering in total plasma cholesterol levels. EGb 761 led to vascular preservation of the aortic lumen with impairment of the endothelium dependent relaxation which was corroborated by micro-CT and histological sections of the thoracic region of the aorta.

CONCLUSION

From this data, it can be implied that EGb 761 controls bone loss, adiposity and lowers atherogenic risk factor after HCD induction.

Intracellular superoxide dismutase activity defines invasiveness of the murine T-lymphoma cell line L5187Y-ML25 in vitro and in vivo

Superoxide anion in the tumor microenvironment promotes a malignant phenotype. Here, we examined superoxide in a murine T-lymphoma cell line L5187Y-ML25. Clones with high and low intracellular superoxide dismutase (SOD) activities were obtained from parental L5187Y-ML25 cells and were subjected to assays determining cell invasiveness, motility, and in vivo dissemination. Cells with lower SOD activity exhibited higher invasiveness in vitro and in vivo. NADPH oxidase inhibitor suppressed intracellular free radical levels and cell motility, suggesting NADPH oxidase as a source of superoxides that stimulates cell motility. These results implicate superoxide as a potential anti-metastatic therapy for hematopoietic cell malignancies.

Macrophage killing of bacterial and fungal pathogens is not inhibited by intense intracellular accumulation of the lipoglycopeptide antibiotic oritavancin

Intact phagocytic effector function is fundamental to host defense against microbial pathogens. Concern has been raised regarding the potential that accumulation of certain agents, including cationic amphiphilic antibiotics, within macrophages could cause a mixed-lipid storage disorder, resulting in macrophage dysfunction in recipients. The ability of 2 macrophage cell lines (HL-60; RAW 264.7) to kill archetypal Gram-positive (Staphylococcus aureus), Gram-negative (Acinetobacter baumannii), and fungal (Candida albicans) pathogens was tested following exposure of the macrophages to the lipoglycopeptide antibiotic oritavancin. Oritavancin did not affect killing of C. albicans but markedly enhanced killing of S. aureus by both macrophages. Oritavancin modestly reduced killing of A. baumannii by HL-60 cells but not by RAW 264.7 cells. Thus, macrophage killing of microbes remains intact despite substantial intracellular accumulation with a lipoglycopeptide antibiotic.

Bioactive lipoxygenase metabolites stimulation of NADPH oxidases and reactive oxygen species

In mammalian cells, reactive oxygen species (ROS) are produced via a variety of cellular oxidative processes, including the activity of NADPH oxidases (NOX), the activity of xanthine oxidases, the metabolism of arachidonic acid (AA) by lipoxygenases (LOX) and cyclooxygenases (COX), and the mitochondrial respiratory chain. Although NOX-generated ROS are the best characterized examples of ROS in mammalian cells, ROS are also generated by the oxidative metabolism (e.g., via LOX and COX) of AA that is released from the membrane phospholipids via the activity of cytosolic phospholipase A(2) (cPLA(2)). Recently, growing evidence suggests that LOX- and COX-generated AA metabolites can induce ROS generation by stimulating NOX and that a potential signaling connection exits between the LOX/COX metabolites and NOX. In this review, we discuss the results of recent studies that report the generation of ROS by LOX metabolites, especially 5-LOX metabolites, via NOX stimulation. In particular, we have focused on the contribution of leukotriene B(4) (LTB(4)), a potent bioactive eicosanoid that is derived from 5-LOX, and its receptors, BLT1 and BLT2, to NOX stimulation through a signaling mechanism that leads to ROS generation.

Low-dose UVB irradiation stimulates matrix metalloproteinase-1 expression via a BLT2-linked pathway in HaCaT cells

Skin exposure to low-dose ultraviolet B (UVB) light up-regulates the expression of matrix metalloproteinase-1 (MMP-1), thus contributing to premature skin aging (photo-aging). Although cyclooxygenase-2 (COX- 2) and its product, prostaglandin E(2) (PGE((2))), have been associated with UVB-induced signaling to MMP expression, very little are known about the roles of lipoxygenases and their products, especially leukotriene B((4)) (LTB((4))) and 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), in MMP-1 expression in skin keratinocytes. In the present study, we demonstrate that BLT2, a cell surface receptor for LTB((4)) and 12(S)-HETE, plays a critical role in UVB-mediated MMP-1 upregulation in human HaCaT keratinocytes. Moreover, our results demonstrated that BLT2-mediated MMP-1 upregulation occurs through a signaling pathway dependent on reactive oxygen species (ROS) production and the subsequent stimulation of ERK. Blockage of BLT2 via siRNA knockdown or with the BLT2-antagonist LY255283 completely abolished the up-regulated expression of MMP-1 induced by low-dose UVB irradiation. Finally, when HaCaT cells were transiently transfected with a BLT2 expression plasmid, MMP-1 expression was significantly enhanced, along with ERK phosphorylation, suggesting that BLT2 overexpression alone is sufficient for MMP-1 up-regulation. Together, our results suggest that the BLT2-ROS- ERK-linked cascade is a novel signaling mechanism for MMP-1 upregulation in low-dose UVB- irradiated keratinocytes and thus potentially contributes to photo-aging.

Blocking the leukotriene B4 receptor 1 inhibits late-phase airway responses in established disease

Most of the studies investigating the effectiveness of blocking the leukotriene B4 (LTB4) receptor 1 (BLT1) have been performed in models of primary or acute allergen challenge. The role of the LTB4-BLT1 pathway in secondary challenge models, where airway hyperresponsiveness (AHR) and airway inflammation have been established, has not been defined. We investigated the effects of blocking BLT1 on early- and late-phase development of AHR and airway inflammation in previously sensitized and challenged mice. Female BALB/c mice were sensitized (Days 1 and 14) and challenged (primary, Days 28-30) with ovalbumin. On Day 72, mice were challenged (secondary) with a single OVA aerosol, and the early and late phases of AHR and inflammation were determined. Specific blockade of BLT1 was attained by oral administration of a BLT1 antagonist on Days 70 through 72. Administration of the antagonist inhibited the secondary ovalbumin challenge-induced alterations in airway responses during the late phase but not during the early phase, as demonstrated by decreases in AHR and in bronchoalveolar lavage neutrophilia and eosinophilia 6 and 48 hours after secondary challenge. The latter was associated with decreased levels of KC protein, macrophage inflammatory protein 2, and IL-17 in the airways. These data identify the importance of the LTB4-BLT1 pathway in the development of late-phase, allergen-induced airway responsiveness after secondary airway challenge in mice with established airway disease.

The biocontrol fungus Trichoderma stromaticum downregulates respiratory burst and nitric oxide in phagocytes and IFN-gamma and IL-10

Trichoderma stromaticum, a biocontrol agent of the cacao witches' broom pathogen Moniliophthora perniciosa, has been used in Brazil as part of the integrated pest management of cacao. At the present time, little is known about the effects of T. stromaticum on the modulation of in vitro or in vivo immune responses. The present study examined the interaction of T. stromaticum spores with cellular and molecular components of the immune system following intranasal sensitization of mice. Our results showed that T. stromaticum spores prevented the expression and production of inflammatory mediators in macrophages stimulated with interferon (IFN)-γ plus lipopolysaccharide (LPS) and neutrophils stimulated with phorbol myristate 13-acetate (PMA). Quantitative polymerase chain reaction (qPCR) assays revealed that T. stromaticum spores inhibited the expression of dectin-1 and Toll-like-receptor (TLR)2/TLR4. Intranasal injection of BALB/c mice and subsequent challenge with spores of T. stromaticum induced a discrete inflammatory response in the lungs. Interestingly, the spores inhibited local and systemic production of the regulatory IL-10 and proinflammatory IFN-γ cytokines. In addition the spores presented an antiproliferative effect on spleen cells. These findings showed that the biopesticide T. stromaticum may exert immunosuppressive effects in vitro and in vivo.

Gelatinase contributes to the pathogenesis of endocarditis caused by Enterococcus faecalis

The Gram-positive pathogen Enterococcus faecalis is a leading agent of nosocomial infections, including urinary tract infections, surgical site infections, and bacteremia. Among the infections caused by E. faecalis, endocarditis remains a serious clinical manifestation and unique in that it is commonly acquired in a community setting. Infective endocarditis is a complex disease, with many host and microbial components contributing to the formation of bacterial biofilm-like vegetations on the aortic valve and adjacent areas within the heart. In the current study, we compared the pathogenic potential of the vancomycin-resistant E. faecalis V583 and three isogenic protease mutants (ΔgelE, ΔsprE, and ΔgelE ΔsprE mutants) in a rabbit model of enterococcal endocarditis. The bacterial burdens displayed by GelE(-) mutants (ΔgelE and ΔgelE ΔsprE mutants) in the heart were significantly lower than those of V583 or the SprE(-) mutant. Vegetations on the aortic valve infected with GelE(-) mutants (ΔgelE and ΔgelE ΔsprE mutants) also showed a significant increase in deposition of fibrinous matrix layer and increased chemotaxis of inflammatory cells. In support of a role for proteolytic modulation of the immune response to E. faecalis, we also demonstrate that GelE can cleave the anaphylatoxin complement C5a and that this proteolysis leads to decreased neutrophil migration in vitro. In vivo, a decreased heterophil (neutrophil-like cell) migration was observed at tissue sites infected with GelE-producing strains but not at those infected with SprE-producing strains. Taken together, these observations suggest that of the two enterococcal proteases, gelatinase is the principal mediator of pathogenesis in endocarditis.

Neutrophils and macrophages cooperate in host resistance against Leishmania braziliensis infection

Neutrophils play an active role in the control of infections caused by intracellular pathogens such as Leishmania. In the present study, we investigated the effect of neutrophil depletion at the time of Leishmania braziliensis infection of BALB/c mice and how neutrophils interact with the infected macrophage to promote parasite elimination. The in vivo depletion of neutrophils led to a significant increase in parasite load and enhanced the Th1-Th2 immune response in this experimental model of infection. BALB/c mice coinoculated with both parasites and live neutrophils displayed lower parasite burdens at the site of infection and in the draining lymph nodes. In vitro, we observed that live neutrophils significantly reduced the parasite load in L. braziliensis-infected murine macrophages, an effect not observed with Leishmania major. L. braziliensis elimination was dependent on the interaction between neutrophils and macrophages and was associated with TNF-alpha as well as superoxide production. Furthermore, cooperation between neutrophils and macrophages toward parasite elimination was also observed in experiments performed with L. braziliensis-infected human cells and, importantly, with two other New World Leishmania species. These results indicate that neutrophils play an important and previously unappreciated role in L. braziliensis infection, favoring the induction of a protective immune response.

High susceptibility to respiratory Acinetobacter baumannii infection in A/J mice is associated with a delay in early pulmonary recruitment of neutrophils

Acinetobacter baumannii is an important cause of both community-associated and nosocomial pneumonia, which have become increasingly difficult to treat because of the rapid development of resistance to multiple antibiotics. Despite its clinical importance, the pathogenesis of and host defense against respiratory A. baumannii infection remains largely unknown. To examine host factors that could contribute to the defense, we compared the susceptibilities of A/J and C57BL/6 mice to intranasal (i.n.) inoculation with A. baumannii. We found that A/J mice were significantly more susceptible to infection with higher mortality (P<0.05) and tissue bacterial burdens (P<0.01) as well as greater histopathology in the lung and spleen than C57BL/6 mice. More importantly, the high susceptibility of A/J mice was associated with a reduced local proinflammatory cytokine/chemokine (particularly IL-1beta, MIP-2 and TNF-alpha) responses and a significant delay and reduction in the early influx of neutrophils in the lung (P<0.05). Intranasal administration of neutrophil-inducing chemokine MIP-2 to A/J mice enhanced pulmonary neutrophil influx and partially restored host resistance to A. baumannii to a level comparable to the more resistant C57BL/6 mice. Our results imply that the early recruitment of neutrophils into the lung is critical for initiating an efficient host defense against respiratory A. baumannii infection.

Role of the low-affinity leukotriene B4 receptor BLT2 in VEGF-induced angiogenesis

OBJECTIVE

The leukotriene B(4) (LTB(4)) receptor BLT2 is expressed in endothelium, but no clear physiological function for it has yet been identified, especially in vascular angiogenesis. The purpose of this study is to characterize the potential function of BLT2 in vascular endothelial growth factor (VEGF)-induced angiogenesis.

METHODS AND RESULTS

VEGF significantly upregulates BLT2 expression in human umbilical vein endothelial cells (HUVECs), and BLT2 knockdown by siRNA or inhibition of BLT2 by a specific BLT2 antagonist LY255283 attenuates VEGF-induced angiogenesis, which was determined by its effect on the formation of tube-like structures and on transmigration. The role of BLT2 in VEGF-induced angiogenesis was more evident in vivo, where BLT2 inhibition by LY255283 almost completely blocked VEGF-induced vessel formation in Matrigel-plug assays. In addition, we found that VEGF upregulates synthesis of the BLT2 ligand, 12(S)-hydroxyeicosatetraenoic acid (HETE). siRNA knockdown of 12-lipoxygenase (12-LO) expression attenuates VEGF-induced angiogenesis in HUVECs, and the addition of 12(S)-HETE to the 12-LO knockdown-HUVECs restores VEGF-induced angiogenesis. The activation of BLT2 itself by either 12(S)-HETE or LTB(4) evoked significant angiogenic phenotypes, both in vitro and in vivo.

CONCLUSIONS

Our findings indicate that BLT2 plays an essential role in mediating VEGF-induced angiogenesis.

Mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2-dependent pathways are essential for CD8+ T cell-mediated airway hyperresponsiveness and inflammation

BACKGROUND

Ligation of the leukotriene B(4) (LTB(4)) receptor 1 on effector memory CD8(+) T cells by LTB(4) is important for the recruitment of CD8(+) T cells into the airways, which appears central to the induction of airway hyperresponsiveness (AHR) and allergic inflammation. Phosphorylation of extracellular signal-regulated kinase (ERK) is important in activation and cytokine production from many cell types.

OBJECTIVE

The roles of ERKs in effector CD8(+) T-cell function and on CD8(+) T cell-mediated AHR were determined.

METHODS

Effector CD8(+) T cells were generated from OVA(257-264) (SIINFEKL) peptide-primed mononuclear cells from OT-1 mice. The effects of U0126, an ERK inhibitor, on effector CD8(+) T-cell function and on CD8(+) T cell-mediated AHR and allergic inflammation were examined.

RESULTS

Pretreatment of effector CD8(+) T cells with U0126 suppressed anti-CD3/anti-CD28-induced ERK1/2 phosphorylation and cytokine production, but did not affect LTB(4)-induced Ca(2+) mobilization or chemotaxis. Adoptive transfer of U0126-treated CD8(+) T cells into sensitized mice before secondary allergen challenge resulted in significant decreases in AHR, eosinophilic inflammation, goblet cell metaplasia, and IL-5 and IL-13 levels in bronchoalveolar lavage fluid of recipient mice. The number of transferred CD8(+) T cells accumulating in bronchoalveolar lavage fluid or lungs was unaffected by treatment.

CONCLUSION

ERK1/2-dependent pathways are essential for the effector functions of CD8(+) T cells, including T(H)2 cytokine production, allergic inflammation, and development of AHR. Inhibition of ERK1/2 signaling has potential therapeutic benefit in preventing CD8(+) T cell-mediated AHR.

Pulmonary toxicity and environmental contamination: radicals, electron transfer, and protection by antioxidants

The atmosphere is replete with a mixture of toxic substances, both natural and man-made. Inhalation of toxic substances produces a variety of insults to the pulmonary system. Lung poisons include industrial materials, particulates from mining and combustion, agricultural chemicals, cigarette smoke, ozone, and nitrogen oxides, among a large number of other chemicals and environmental contaminants. Many proposals have been advanced to explain the mode of action of pulmonary toxicants. In this review we focus on mechanisms of pulmonary toxicity that involve ET, ROS, and OS. The vast majority of toxicants or their metabolites possess chemical ET functionalities that can undergo redox cycling. Such recycling may generate ROS that can injure various cellular constituents in the lung and in other tissues. ET agents include quinones, metal complexes, aromatic nitro compounds, and conjugated iminium ions. Often, these agents are formed metabolically from parent toxicants. Such metabolic reactions are often catalytic and require only small amounts of the offending material. Oxidative attack is commonly associated with lipid peroxidation and oxidation of DNA, and it may result in strand cleavage and 8-OH-DG production. Toxicity is often accompanied by depletion of natural AOs, which further exacerbates the toxic effect. It is not surprising that the use of AOs, both natural in fruits and vegetables, as well as synthetic, may provide protection from the adverse effects of toxicant exposure. The mechanistic framework described earlier is also applicable to some of the more prominent pulmonary illnesses, such as asthma, COPD, and cancer.

TNF-alpha-induced up-regulation of intercellular adhesion molecule-1 is regulated by a Rac-ROS-dependent cascade in human airway epithelial cells

Up-regulation of intercellular adhesion molecule-1 (ICAM-1) in the lung airway epithelium is associated with the epithelium-leukocyte interaction, critical for the pathogenesis of various lung airway inflammatory diseases such as asthma. However, little is known about how ICAM-1 is up-regulated in human airway epithelial cells. In this study, we show that tumor TNF-alpha induces monocyte adhesion to A549 human lung airway epithelium and also up-regulation of ICAM-1 expression. These effects were significantly diminished by pre-treatment with diphenyliodonium (DPI), an inhibitor of NADPH oxidase-like flavoenzyme. In addition, the level of reactive oxygen species (ROS) was increased in response to TNF-alpha in A549 cells, suggesting a potential role of ROS in the TNF-alpha-induced signaling to ICAM-1 expression and monocyte adhesion to airway epithelium. Further, we found out that expression of RacN17, a dominant negative mutant of Rac1, suppressed TNF-alpha-induced ROS generation, ICAM-1 expression, and monocyte adhesion to airway epithelium. These findings suggest that Rac1 lies upstream of ROS generation in the TNF-alpha-induced signaling to ICAM-1 expression in airway epithelium. Finally, pretreatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of NF-kappaB, reduced TNF-alpha-induced ICAM-1 expression and both DPI and RacN17 significantly diminished NF-kappaB activation in response to TNF-alpha. Together, we propose that Rac1-ROS-linked cascade mediate TNF-alpha-induced ICAM-1 up-regulation in the airway epithelium via NF-kappaB-dependent manner.

Acute lung injury induced by lipopolysaccharide is independent of complement activation

Although acute lung injury (ALI) is an important problem in humans, its pathogenesis is poorly understood. Airway instillation of bacterial LPS, a known complement activator, represents a frequently used model of ALI. In the present study, pathways in the immunopathogenesis of ALI were evaluated. ALI was induced in wild-type, C3(-/-), and C5(-/-) mice by airway deposition of LPS. To assess the relevant inflammatory mediators, bronchoalveolar lavage fluids were evaluated by ELISA analyses and various neutralizing Abs and receptor antagonists were administered in vivo. LPS-induced ALI was neutrophil-dependent, but it was not associated with generation of C5a in the lung and was independent of C3, C5, or C5a. Instead, LPS injury was associated with robust generation of macrophage migration inhibitory factor (MIF), leukotriene B(4) (LTB4), and high mobility group box 1 protein (HMGB1) and required engagement of receptors for both MIF and LTB4. Neutralization of MIF or blockade of the MIF receptor and/or LTB4 receptor resulted in protection from LPS-induced ALI. These findings indicate that the MIF and LTB4 mediator pathways are involved in the immunopathogenesis of LPS-induced experimental ALI. Most strikingly, complement activation does not contribute to the development of ALI in the LPS model.

Corticosteroids enhance CD8+ T cell-mediated airway hyperresponsiveness and allergic inflammation by upregulating leukotriene B4 receptor 1

BACKGROUND

Leukotriene B4 (LTB4) is a potent inflammatory lipid mediator that binds to LTB4 receptor 1 (BLT1). Ligation of BLT1 by LTB4 plays an important role in the recruitment of effector memory CD8+ T cells into the airways of sensitized and challenged mice.

OBJECTIVES

The effects of the corticosteroid dexamethasone (DEX) on BLT1-expressing effector memory CD8+ T cells and effector memory CD8+ T cell-mediated airway hyperresponsiveness (AHR) and allergic inflammation were determined.

METHODS

Effector memory CD8+ T cells were generated from ovalbumin(257-264)-primed mononuclear cells from OT-1 mice in the presence of IL-2. In some cultures DEX was added. The effects of DEX on BLT1 expression, LTB4-induced Ca2+ influx, phosphorylation of extracellular signal-regulated kinase 1/2, chemotaxis, and effector memory CD8+ T cell-mediated AHR were examined.

RESULTS

DEX-treated effector memory CD8+ T cells showed significant increases in surface expression of BLT1, LTB4-induced intracellular Ca2+ influx, phosphorylation of extracellular signal-regulated kinase 1/2, and chemotaxis. Upregulation of BLT1 by DEX was accompanied by increased IL-2 receptor expression. Adoptive transfer of DEX-treated effector memory CD8+ T cells into ovalbumin-sensitized and ovalbumin-challenged CD8-/- mice resulted in significant increases in AHR, allergic inflammation, goblet cell metaplasia, and numbers of both CD8+ and CD4+ T cells in the bronchoalveolar lavage fluid and lungs.

CONCLUSIONS

Corticosteroids upregulate BLT1 on effector memory CD8+ T cells and related signaling pathways and potentiate allergic airway inflammation and AHR induced by these cells.

Essential role of protein kinase C zeta in transducing a motility signal induced by superoxide and a chemotactic peptide, fMLP

Under various pathological conditions, including infection, malignancy, and autoimmune diseases, tissues are incessantly exposed to reactive oxygen species produced by infiltrating inflammatory cells. We show augmentation of motility associated with morphological changes of human squamous carcinoma SASH1 cells, human peripheral monocytes (hPMs), and murine macrophage-like cell line J774.1 by superoxide stimulation. We also disclose that motility of hPMs and J774.1 induced by a chemotactic peptide (N-formyl-methionyl-leucyl-phenylalanine [fMLP]) was inhibited by superoxide dismutase or N-acetylcystein, indicating stimulation of motility by superoxide generated by fMLP stimulation. In these cells, protein kinase C (PKC) ζ was activated to phosphorylate RhoGDI-1, which liberated RhoGTPases, leading to their activation. These events were inhibited by dominant-negative PKCζ in SASH1 cells, myristoylated PKCζ peptides in hPMs and J774.1, or a specific inhibitor of RhoGTPase in SASH1, hPMs, and J774.1. These results suggest a new approach for manipulation of inflammation as well as tumor cell invasion by targeting this novel signaling pathway.