Neutrophil chemotactic factors

Biological Cells as Therapeutic Delivery Vehicles

One of the significant challenges remaining in the field of drug delivery is insufficient targeting of diseased tissues or cells. While efforts to perform targeted drug delivery by engineered nanoparticles have shown some success, there are underlying targeting, toxicity, and immunogenicity challenges. By contrast, live cells usually have innate targeting mechanisms, and can be used as drug-delivery vehicles to increase the efficiency with which a drug accumulates to act on the intended tissue. In some cases, when no native cell types exhibit the desired therapeutic phenotype, preferred outcomes can be achieved by genetically modifying and reprogramming cells with gene circuits. This review highlights recent advances in the use of cells to deliver therapeutics. Specifically, we discuss how red blood cells (RBCs), platelets, neutrophils, mesenchymal stem cells (MSCs), and bacteria have been utilized to advance drug delivery.

Activation of inflammation and resolution pathways of lipid mediators in synovial fluid from patients with severe rheumatoid arthritis compared with severe osteoarthritis

Background

The upregulation of the cyclooxygenase and lipoxygenase pathways of arachidonic acid is thought to be involved in the development of rheumatoid arthritis. Recently, the presence of specialized pro-resolving lipid mediators in synovial tissues from patients with osteoarthritis has been reported.

Objective

To clarify the quantitative and qualitative changes in lipid mediators in the synovium of severe rheumatoid arthritis patients, we compared the profiles of lipid mediators in synovial fluid obtained from patients with severe rheumatoid arthritis and from those with severe osteoarthritis.

Methods

We enrolled 18 patients with rheumatoid arthritis and 26 patients with osteoarthritis. All the patients had undergone total knee replacement surgery. Synovial fluid samples had been obtained during the surgery. Lipid profiling in the synovial fluid from these patients was performed using liquid chromatography-tandem mass spectrometry/mass spectrometry.

Results

Among the 150 oxidized fatty acids examined so far, 119 were substantially detected in synovial fluid from the patients. Not only the concentrations of pro-inflammatory lipid mediators such as prostaglandins and leukotrienes, but also those of specialized pro-resolving lipid mediators such as lipoxins, resolvins, and protectin D1 were significantly higher in synovial fluid obtained from rheumatoid arthritis patients than from synovial fluid obtained from osteoarthritis patients.

Conclusion

The activation of both inflammation and resolution pathways of lipid mediators might be a fatty acid signature in the synovial fluid of patients with severe rheumatoid arthritis. Inflammatory, anti-inflammatory and pro-resolving mediators in synovial fluid could be good biomarkers for differentiating between severe rheumatoid arthritis and severe osteoarthritis.

Primary Macrophage Chemotaxis Induced by Cannabinoid Receptor 2 Agonists Occurs Independently of the CB2 Receptor

Activation of CB₂ has been demonstrated to induce directed immune cell migration. However, the ability of CB2 to act as a chemoattractant receptor in macrophages remains largely unexplored. Using a real-time chemotaxis assay and a panel of chemically diverse and widely used CB₂ agonists, we set out to examine whether CB₂ modulates primary murine macrophage chemotaxis. We report that of 12 agonists tested, only JWH133, HU308, L-759,656 and L-759,633 acted as macrophage chemoattractants. Surprisingly, neither pharmacological inhibition nor genetic ablation of CB₂ had any effect on CB₂ agonist-induced macrophage chemotaxis. As chemotaxis was pertussis toxin sensitive in both WT and CB₂^-/- macrophages, we concluded that a non-CB₁/CB₂, G_i/o-coupled GPCR must be responsible for CB₂ agonist-induced macrophage migration. The obvious candidate receptors GPR18 and GPR55 could not mediate JWH133 or HU308-induced cytoskeletal rearrangement or JWH133-induced β-arrestin recruitment in cells transfected with either receptor, demonstrating that neither are the unidentified GPCR. Taken together our results conclusively demonstrate that CB₂ is not a chemoattractant receptor for murine macrophages. Furthermore we show for the first time that JWH133, HU308, L-759,656 and L-759,633 have off-target effects of functional consequence in primary cells and we believe that our findings have wide ranging implications for the entire cannabinoid field.

Immune antibodies and helminth products drive CXCR2-dependent macrophage-myofibroblast crosstalk to promote intestinal repair

Helminth parasites can cause considerable damage when migrating through host tissues, thus making rapid tissue repair imperative to prevent bleeding and bacterial dissemination particularly during enteric infection. However, how protective type 2 responses targeted against these tissue-disruptive multicellular parasites might contribute to homeostatic wound healing in the intestine has remained unclear. Here, we observed that mice lacking antibodies (Aid^-/-) or activating Fc receptors (Fcrg^-/-) displayed impaired intestinal repair following infection with the murine helminth Heligmosomoides polygyrus bakeri (Hpb), whilst transfer of immune serum could partially restore chemokine production and rescue wound healing in Aid^-/- mice. Impaired healing was associated with a reduced expression of CXCR2 ligands (CXCL2/3) by macrophages (MΦ) and myofibroblasts (MF) within intestinal lesions. Whilst antibodies and helminths together triggered CXCL2 production by MΦ in vitro via surface FcR engagement, chemokine secretion by intestinal MF was elicited by helminths directly via Fcrg-chain/dectin2 signaling. Blockade of CXCR2 during Hpb challenge infection reproduced the delayed wound repair observed in helminth infected Aid^-/- and Fcrg^-/- mice. Finally, conditioned media from human MΦ stimulated with infective larvae of the helminth Ascaris suum together with immune serum, promoted CXCR2-dependent scratch wound closure by human MF in vitro. Collectively our findings suggest that helminths and antibodies instruct a chemokine driven MΦ-MF crosstalk to promote intestinal repair, a capacity that may be harnessed in clinical settings of impaired wound healing.

To complete their lifecycles, helminth parasites have to migrate through tissues such as the skin, lung, liver and intestine. This migration causes severe tissue damage, resulting in the need for rapid repair to restore the integrity and function of damaged tissues. Protective type 2 immune responses against helminths can repair acute lung damage, but they can also promote liver fibrosis. However, how protective immune mechanisms might contribute to wound healing during enteric nematode infection has remained unclear. Here we show that during a protective antibody response, where helminth larvae are trapped in the intestinal mucosa, macrophages and myofibroblasts secrete chemokines, which promote the repair of helminth-caused lesions. Chemokine secretion by macrophages was triggered by antibodies and helminth products, whilst myofibroblasts produced chemokines directly in response to innate recognition of helminth products. The same chemokines that instructed intestinal repair in mice were also secreted by human macrophages, when co-cultured with immune serum and helminths. Finally, human myofibroblasts closed in vitro scratch wounds more rapidly, when stimulated with the chemokine secretions of helminth-antibody activated human macrophages. Thus, our findings reveal a novel mechanism, by which a protective antibody response can promote the repair of intestinal injury during helminth infection.

Chemotactic tripeptides incorporating at position 2 alpha-aminoacid residues with unsaturated side chains

New N-For-Met-Leu-Phe-OMe (fMLF-OMe) analogues incorporating three different gamma-delta-didehydro-alpha-aminoacid residues (namely: Alg = (S)-Allylglycine; Dag = Diallylglycine; Cpg = 1-Aminocyclopent-3-ene-1-carboxylic acid) replacing the native (S)-Leucine have been synthesized and their activity towards human neutrophils has been evaluated in comparison with that shown by the reference tripeptide fMLF-OMe. Chemotaxis, lysozyme release and superoxide anion production have been measured. (1)H NMR titration experiments and NOESY spectrum of the Cpg containing model 10 have been discussed in order to ascertain the preferred solution conformations. A fully extended (C(5)) conformation at position 2 and a folded conformation with two consecutive gamma-turns (C(7) structure) have been proposed for the Dag and Cpg containing tripeptides, respectively.

Pasteurella multocida Infection in Heterophil-Depleted Chickens

The present study was aimed at elucidating the role of heterophil granulocytes during the initial infection with Pasteurella multocida subsp. multocida in chickens. Chickens (17 and 19 wk old) were depleted of their heterophil granulocytes by 5-fluorouracil treatment. When the heterophil blood counts were significantly reduced, the birds were inoculated intratracheally with 1.8-4.3 x 10(4) colony-forming units of P. multocida. Twelve, 24, or 48 hr postinoculation, the birds were euthanatized and examined for macroscopic and histologic lesions in the lungs. Bacterial invasion was determined by culture of P. multocida from the spleen. Recruitment of heterophils into the respiratory tract during infection was found to contribute considerably to the lung lesions in chickens and was found to mediate tissue damage, possibly allowing a more rapid systemic spread of P. multocida. However, during progression of the infection, the heterophil-mediated necrosis in chickens seemed to stimulate giant cell demarcation of infected lung tissue, which coincided with the clearance of P. multocida from the spleen, thus hampering further invasion. Consequently, heterophil activation plays a dual role for the outcome of a P. multocida infection in chickens, where it initially seems to promote invasion and systemic spread but subsequently helps limit the infection by giant cell formation and bacterial clearance.

Human neutrophils as a source of nociceptin: a novel link between pain and inflammation

Nociceptin is a neuropeptide sharing sequence homology with classical opioid peptides but with a distinct pharmacological profile. Through activation of its receptor, NociR, nociceptin has been linked with several physiological functions in the central nervous system including memory, locomotion, and processing of pain signals. Recently, peripheral blood neutrophils (PMNs) were demonstrated to express a functional NociR, a result suggesting that additional functions of the neuropeptide remain to be elucidated. The present study investigated the possibility that PMNs may be a source of nociceptin and whether the neuropeptide elicits PMN early responses. We observed the presence of nociceptin in the synovial fluids from arthritic patients, an inflammatory milieu typically containing high numbers of PMNs. In addition, freshly isolated PMNs were found to express and secrete nociceptin following degranulation, identifying these inflammatory cells as a novel source of the neuropeptide. Incubation of PMNs with nociceptin elicited a specific pattern of cellular protein phosphorylation on tyrosine residues in a rapid and transient fashion. Moreover, nociceptin prevented intracellular accumulation of cAMP in fMLP-stimulated PMNs, an effect mimicked by the specific NociR synthetic agonist, Ro 64-6198. Taken together, these results show that nociceptin/NociR is present and functional in human neutrophils, and the results identify a novel dialogue pathway between neural and immune tissues.

Granulocytes from chronic myeloid leukemia (CML) patients show differential response to different chemoattractants

Binding of chemoattractant to polymorphonuclear leukocytes (PMNL) triggers a series of events like polymerization of actin and tubulin, orientation of cells, chemotaxis, increase in fluid pinocytosis and phagocytosis, and stimulation of microbicidal pathways which includes lysosomal degranulation and generation of reactive oxygen species. Earlier studies from our laboratory have shown that stimulation of chemotaxis, fluid pinocytosis, and actin polymerization of CML PMNL in response to a synthetic chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP) is significantly lower than that in normal PMNL. It is not known whether this lower response of CML PMNL to fMLP is a global phenomenon involving different chemoattractant receptors or is restricted to the fMLP pathway. We have evaluated chemoattractant induced degranulation process in normal and CML PMNL to fMLP, platelet activating factor (PAF), leukotriene B4 (LTB4), and an analogue of fMLP viz formyl-methionine-1 aminocyclooctane 1 carboxylic acid-phenylalanine-O-methionine (FACC8) using release of lysozyme as a parameter. We find that after stimulation with fMLP and FACC8, the mean percent release of lysozyme was significantly lower in CML PMNL as compared to that in normal cells (P < 0.001). There was no significant difference between the two after stimulation with PAF and LTB4. The results indicate that the fMLP pathway is suppressed in CML granulocytes whereas PAF and LTB4 pathways appear unaltered in these cells. We therefore also studied the kinetics of peptide-receptor interaction with a labelled hexapeptide fNLPNTL which binds to the fMLP receptor. Our results show that the number of fMLP receptors/cell is significantly lower in CML PMNL (P < 0.05) than in normal PMNL, while their affinity constants and dissociation constants were comparable.

Shape, F-actin, and surface morphology changes during chemotactic peptide-induced polarity in human neutrophils

BACKGROUND

The exposure of human neutrophils to uniform concentrations of chemoattractants, such as N-formyl peptides, induces morphological cell polarization. In this study we report the temporal sequence of changes in cell shape, F-actin, and cell surface morphology during cellular polarization induced by N-formylmethionyl-leucyl-phenylalanine (fMLP) in human neutrophils in suspension.

METHODS

Neutrophil shape changes induced by 10(-8) M fMLP were observed with DIC microscopy. Size and cellular granularity were analyzed by flow cytometry measuring their forward and side scattered light. To visualize F-actin distribution, neutrophils were labeled with the fluorescence probe FITC-phalloidin, and were examined with fluorescence and confocal laser scanning microscopy. Cell surface morphology was assessed with scanning electron microscopy (SEM).

RESULTS

The stimulation of round-smooth neutrophils with nanomolar concentrations (10(-8) M) of fMLP in suspension induced a temporal sequence of morphological changes during cell polarization, characterized by 1) increase in size as determined by forward angle scattered light, 2) rapid redistribution of F-actin from a diffuse cytoplasmic localization to the cell periphery, and 3) rapid reorganization of cell surface morphological features, with accumulation of plasma membrane in the front of polar cells. Four cell shapes were identified with SEM after stimulation of round-smooth neutrophils: round-ridged, round-ruffled, nonpolar ruffled, and polar cells. These cell shapes were correlated with a cortical localization, focal aggregates, and multipolar distribution of F-actin. In polar neutrophils, F-actin became concentrated in the front of the cell.

CONCLUSIONS

These findings show the relation between reorganization of the microfilamentous cytoskeleton and modifications in cell shape and surface features during cell polarization induced after fMLP activation in neutrophils. This approach offers a powerful tool for further analysis of receptor distribution in polarized, motile neutrophils.

Human neutrophil motility: time-dependent three-dimensional shape and granule diffusion

The locomotion of human polymorphonuclear leukocytes (PMNs) was studied with two complementary methods: Three-dimensional shapes were reconstructed from time series of optical sectioning microscopy using differential interference contrast (DIC) optics, and the diffusion of cytoplasm granules within individual cells was measured using quasielastic laser light scattering (QELS). The three-dimensional cell edges outlined in the optical sections were analyzed qualitatively in time-lapse film strips and quantitatively from morphometry. The fastest locomotion occurred in chemotactic gradient with cell velocity that oscillated between 10 and 30 microns/min with a period of 50-55 seconds. Within the periodic bursts of speed, a fibroblast-like locomotory cycle was observed, with leading lamella extended and contacts formed with the substrate surface, followed by rapid motion of the cell body and nucleus over the immobile contacts. Consistent with this apparent staged motion, correlation analysis revealed a phase lag of 2-3 seconds in velocities between the bottom (ventral) and the top layers of the cell. In addition there was a tendency to a lower cell profile at times of higher velocity. The diffusion of natural cytoplasmic granules within resting PMNs was not affected by cytoskeleton disrupting drugs. During the stage of most rapid motion, when cytoplasmic streaming could be seen, diffusion of the granules decreased two- to 2.5-fold, and then returned to resting levels. These observations suggest that PMN locomotion consists of extensions near the surface to form forward contacts and then stiffening or possibly contraction of the cytoskeleton when the body of the cell is moved forward. Three-dimensional movies of PMN cells are included in the video supplement.

Synthesis and chemotactic activity of the fMLP analog HCO-Hmb-Leu-Phe-OMe

The new fMLP analog HCO-Hmb-Leu-Phe-OMe (1), containing (S)-2-hydroxy-4-(methylthio)butyric acid (Hmb) in place of L-methionine at the N-terminal position, has been synthesized and fully characterized. The peptide 1 has been designed in order to improve the understanding of the role exerted by the formamido group in the binding interaction with the formylpeptide chemotactic receptors. Chemotaxis, superoxide anion production, and lysozyme release have been measured for both 1 and its deformylated analog Hmb-Leu-Phe-OMe 2. Results indicate that a strong hydrogen bond of the OH....O = C type may complement a weak H-bonding interaction involving the formylic proton as H-bond donor.

Poxvirus-induced alteration of arachidonate metabolism

Recent evidence suggests that orthopoxviruses have an obligate requirement for arachidonic acid metabolites during replication in vivo and in vitro. Our report indicates that a virus family (Poxviridae) possesses multiple genes that function to regulate arachidonate metabolism. Analyses of BS-C-1 cells infected with cowpox virus or vaccinia virus detected enhanced arachidonate product formation from both the cyclooxygenase (specifically prostaglandins E2 and F2 alpha) and lipoxygenase (specifically 15-hydroxyeicosatetraenoic acid and 12-hydroxyeicosatetraenoic acid) pathways. In contrast, human parainfluenza type 3 or herpes simplex virus type 1 infections did not increase arachidonate metabolism. Results were consistent with a virus early-gene product either directly mediating or inducing a host factor that mediated the up-regulation of arachidonate metabolism, although vaccinia growth factor was not responsible. In addition, the cowpox virus 38-kDa protein-encoding gene, which is associated with inhibition of an inflammatory response, correlated with inhibition of formation of a product biochemically characteristic of (14R,15S)-dihydroxyeicosatetraenoic acid. We propose that orthopoxvirus-induced up-regulation of arachidonic acid metabolism during infection renders the infected cells susceptible to generation of inflammatory mediators from both the cyclooxygenase and the lipoxygenase pathways, and poxviruses, therefore, possess at least one gene (38K) that can alter the lipoxygenase-metabolite spectrum.

Human chemotaxis receptor genes cluster at 19q13.3-13.4. Characterization of the human C5a receptor gene

The human C5a anaphylatoxin and formyl peptide receptor genes, as well as two genes with high sequence identity to the formyl peptide receptor, FPRH1 and FPRH2, have been mapped to chromosome 19 (Lu et al., 1992). Further analysis reveals that these genes are present in the 19q13.3 band adjacent to the 13.3-13.4 interface. MRNAs for the C5a and formyl peptide receptors, as well as for FPRH1, are expressed in cAMP differentiated U937 cells and human eosinophils, while all four transcripts are expressed in human lung. This observation opens the possibility for coordinate regulation of these genes. In order to initiate the mapping of fine structure at this locus, genomic clones have been analyzed. All four of the genes have a similar structure, with the receptor protein encoded in a single exon. Detailed characterization of the C5a receptor gene reveals a two exon structure, with the 5' untranslated sequence and initiating methionine located in the first exon. An intron of approximately 9 kb separates exon 1 from the receptor-encoding exon 2. The region of genomic DNA flanking the 5' untranslated sequence possesses promoter activity when transfected into the myeloid-derived rat basophilic leukemia RBL-1 cells, but the same region is inactive when transfected into nonmyeloid cells. Deletional analyses indicate that C5a receptor 5' flanking region contains both cell-specific suppressor and promoter regions.