Activation of endothelial extracellular signal-regulated kinase is essential for neutrophil transmigration: potential involvement of a soluble neutrophil factor in endothelial activation

Cytokine inflammatory response in dairy cows with mastitis caused by Streptococcus agalactiae

Introduction

The aim of the study was evaluation of the concentrations of interleukin (IL)-1β, IL-8, IL-12β and tumour necrosis factor alpha (TNF-α) in the serum and milk of cows with mastitis caused by Streptococcus agalactiae.

Material and Methods

A total of 60 milk samples from diseased cows and 30 milk samples from healthy cows were included in the study. Blood and milk samples were taken from Holstein-Friesian cows from three herds (two in tie-stall and one in a free-stall housing system) in Lublin Province in Poland. The concentrations of cytokines in blood serum and quarter milk samples were determined by ELISA.

Results

The levels of IL-1β, IL-8, IL-12β and TNF-α were significantly higher in the milk of cows suffering from mastitis caused by S. agalactiae compared to the milk of healthy cows (263.03 vs 55.36 pg/mL, 298.34 vs 131.82 pg/mL, 604.10 vs 139.17 pg/mL and 460.86 vs 78.82 pg/mL, respectively). In the group of sick cows, cytokine levels were significantly higher in milk than in serum (263.03 vs 55.25 pg/mL for IL-1β, 298.34 vs 164.22 pg/mL for IL-8, 604.10 vs 70.34 pg/mL for IL-12β and 460.86 vs 104.78 pg/mL for TNF-α).

Conclusion

The results confirm the involvement of the entire bovine immune system to protect against the bacteria first locally in the udder. The response of the mammary gland to infection caused by S. agalactiae is rapid and already very strong at the beginning of the infection.

Primary adhered neutrophils increase JNK1-MARCKSL1-mediated filopodia to promote secondary neutrophil transmigration

During inflammation, leukocytes extravasate the vasculature to areas of inflammation in a process termed transendothelial migration. Previous research has shown that transendothelial migration hotspots exist, areas in the vasculature that are preferred by leukocytes to cross. Several factors that contribute to hotspot-mediated transmigration have been proposed already, but whether one leukocyte transmigration hotspot can be used subsequently by a second wave of leukocytes and thereby can increase the efficiency of leukocyte transmigration is not well understood. Here, we show that primary neutrophil adhesion to the endothelium triggers endothelial transmigration hotspots, allowing secondary neutrophils to cross the endothelium more efficiently. Mechanistically, we show that primary neutrophil adhesion increases the number of endothelial apical filopodia, resulting in an increase in the number of adherent secondary neutrophils. Using fluorescence resonance energy transfer (FRET)-based biosensors, we found that neutrophil adhesion did not trigger the activity of the small GTPase Cdc42. We used kinase translocation reporters to study the activity of mitogen-activated protein (MAP) kinases and Akt in endothelial cells on a single-cell level with a high temporal resolution during the process of leukocyte transmigration and found that c-Jun N-terminal kinase (JNK) is rapidly activated upon neutrophil adhesion, whereas extracellular regulated kinase (ERK), p38, and Akt are not. Additionally, we show that short-term chemical inhibition of endothelial JNK successfully prevents the adhesion of neutrophils to the endothelium. Furthermore, we show that neutrophil-induced endothelial JNK1 but not JNK2 increases the formation of filopodia and thereby the adhesion of secondary neutrophils. JNK1 needs its downstream substrate MARCKSL1 to trigger additional apical filopodia and consequently neutrophil adhesion. Overall, our data show that primary neutrophils can trigger the endothelial transmigration hotspot by activating JNK1 and MARCKSL1 to induce filopodia that trigger more neutrophils to transmigrate at the endothelial hotspot area.

Mead acid inhibits retinol-induced irritant contact dermatitis via peroxisome proliferator-activated receptor alpha

Retinol is widely used in topical skincare products to ameliorate skin aging and treat acne and wrinkles; however, retinol and its derivatives occasionally have adverse side effects, including the induction of irritant contact dermatitis. Previously, we reported that mead acid (5,8,11-eicosatrienoic acid), an oleic acid metabolite, ameliorated skin inflammation in dinitrofluorobenzene-induced allergic contact hypersensitivity by inhibiting neutrophil infiltration and leukotriene B₄ production by neutrophils. Here, we showed that mead acid also suppresses retinol-induced irritant contact dermatitis. In a murine model, we revealed that mead acid inhibited keratinocyte abnormalities such as keratinocyte hyperproliferation. Consistently, mead acid inhibited p38 MAPK (mitogen-activated protein kinase) phosphorylation, which is an essential signaling pathway in the keratinocyte hyperplasia induced by retinol. These inhibitory effects of mead acid were associated with the prevention of both keratinocyte hyperproliferation and the gene expression of neutrophil chemoattractants, including Cxcl1 and Cxcl2, and they were mediated by a PPAR (peroxisome proliferator-activated receptor)-α pathway. Our findings identified the anti-inflammatory effects of mead acid, the use of which can be expected to minimize the risk of adverse side effects associated with topical retinoid application.

Anthocyanins and their gut metabolites attenuate monocyte adhesion and transendothelial migration through nutrigenomic mechanisms regulating endothelial cell permeability

Cardioprotective effects of dietary anthocyanins are partly attributed to their ability to maintain endothelial function. However, the underlying cellular and molecular mechanisms of action are not fully understood. This study aimed to evaluate the effect of anthocyanins and their gut metabolites, at physiologically-relevant conditions, on endothelial cell (EC) function and decipher the underlying molecular mechanisms of action using integrated omics approaches. Primary EC were treated with a mixture of 0.1 μM cyanidin-3-arabinoside, 0.1 μM cyanidin-3-galactoside, 0.1 μM cyanidin-3-glucoside, 0.1 μM delphinidin-3-glucoside, 0.1 μM peonidin-3-glucoside and 0.5 μM 4-hydroxybenzaldehyde for 3 h or a mixture of gut metabolites: 0.2 μM protocatechuic, 2 μM vanillic, 1 μM ferulic and 2 μM hippuric acids for 18 h. Also, successive exposure of EC to both mixtures was performed to mimic anthocyanin pharmacokinetics following their intake. Inflammatory stress was induced using TNFα and monocytes added to assess adhesion and transmigration. Effects of these mixtures on gene, miRNA expression and their potential interaction with cell signalling were investigated. Anthocyanins and their gut metabolites significantly reduced monocyte adhesion and transendothelial migration. Gene expression analysis, using macroarrays, showed that tested compounds modulated the expression of genes involved in cell-cell adhesion, cytoskeleton organisation or focal adhesion. Bioinformatics analyses of gene expression data identified potential transcription factors involved in the observed nutrigenomic effects and signalling proteins regulating their activity. Molecular docking revealed cell signalling proteins to which these bioactives may bind to and potentially affect their activity and the activation of downstream signalling, effects that were in agreement with the results of Western blot analyses. Microarray analysis showed that anthocyanins and their gut metabolites affected miRNA expression in EC, especially those involved in regulation of EC permeability, contributing to the observed changes in EC function. Integration of these results revealed endothelial-protective properties of anthocyanins and their gut metabolites and deciphered new underlying multi-target and multi-layered mode of action.

Endothelial MAPKs Direct ICAM-1 Signaling to Divergent Inflammatory Functions

Lymphocyte transendothelial migration (TEM) is critically dependent on intraendothelial signaling triggered by adhesion to ICAM-1. Here we show that endothelial MAPKs ERK, p38, and JNK mediate diapedesis-related and diapedesis-unrelated functions of ICAM-1 in cerebral and dermal microvascular endothelial cells (MVECs). All three MAPKs were activated by ICAM-1 engagement, either through lymphocyte adhesion or Ab-mediated clustering. MAPKs were involved in ICAM-1-dependent expression of TNF-α in cerebral and dermal MVECs, and CXCL8, CCL3, CCL4, VCAM-1, and cyclooxygenase 2 (COX-2) in cerebral MVECs. Endothelial JNK and to a much lesser degree p38 were the principal MAPKs involved in facilitating diapedesis of CD4⁺ lymphocytes across both types of MVECs, whereas ERK was additionally required for TEM across dermal MVECs. JNK activity was critical for ICAM-1-induced F-actin rearrangements. Furthermore, activation of endothelial ICAM-1/JNK led to phosphorylation of paxillin, its association with VE-cadherin, and internalization of the latter. Importantly ICAM-1-induced phosphorylation of paxillin was required for lymphocyte TEM and converged functionally with VE-cadherin phosphorylation. Taken together we conclude that during lymphocyte TEM, ICAM-1 signaling diverges into pathways regulating lymphocyte diapedesis, and other pathways modulating gene expression thereby contributing to the long-term inflammatory response of the endothelium.

Annexin A1: novel roles in skeletal muscle biology

Annexin A1 (ANXA1, lipocortin-1) is the first characterized member of the annexin superfamily of proteins, so called since their main property is to bind (i.e., to annex) to cellular membranes in a Ca(2+) -dependent manner. ANXA1 has been involved in a broad range of molecular and cellular processes, including anti-inflammatory signalling, kinase activities in signal transduction, maintenance of cytoskeleton and extracellular matrix integrity, tissue growth, apoptosis, and differentiation. New insights show that endogenous ANXA1 positively modulates myoblast cell differentiation by promoting migration of satellite cells and, consequently, skeletal muscle differentiation. This suggests that ANXA1 may contribute to the regeneration of skeletal muscle tissue and may have therapeutic implications with respect to the development of ANXA1 mimetics.

Febrile-range hyperthermia modifies endothelial and neutrophilic functions to promote extravasation

Acute respiratory distress syndrome (ARDS) is a neutrophil (polymorphonuclear leukocyte; PMN)-driven lung injury that is associated with fever and heat-stroke, and involves approximately 40% mortality. In murine models of acute lung injury (ALI), febrile-range hyperthermia (FRH) enhanced PMN accumulation, vascular permeability, and epithelial injury, in part by augmenting pulmonary cysteine-x-cysteine (CXC) chemokine expression. To determine whether FRH increases chemokine responsiveness within the lung, we used in vivo and in vitro models that bypass the endogenous generation of chemokines. We measured PMN transalveolar migration (TAM) in mice after intratracheal instillations of the human CXC chemokine IL-8 in vivo, and of IL-8-directed PMN transendothelial migration (TEM) through human lung microvascular endothelial cell (HMVEC-L) monolayers in vitro. Pre-exposure to FRH increased in vivo IL-8-directed PMN TAM by 23.5-fold and in vitro TEM by 7-fold. Adoptive PMN transfer demonstrated that enhanced PMN TAM required both PMN donors and recipients to be exposed to FRH, suggesting interdependent effects on PMNs and endothelium. FRH exposure caused the activation of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase in lung homogenates and circulating PMNs, with an associated increase in HSP27 phosphorylation and stress-fiber formation. The inhibition of these signaling pathways with U0126 and SB203580 blocked the effects of FRH on PMN extravasation in vivo and in vitro. Collectively, these results (1) demonstrate that FRH augments chemokine-directed PMN extravasation through direct effects on endothelium and PMNs, (2) identify ERK and p38 signaling pathways in the effect, and (3) underscore the complex effects of physiologic temperature change on innate immune function and its potential consequences for lung injury.

Mechanisms for vascular cell adhesion molecule-1 activation of ERK1/2 during leukocyte transendothelial migration

BACKGROUND

During inflammation, adhesion molecules regulate recruitment of leukocytes to inflamed tissues. It is reported that vascular cell adhesion molecule-1 (VCAM-1) activates extracellular regulated kinases 1 and 2 (ERK1/2), but the mechanism for this activation is not known. Pharmacological inhibitors of ERK1/2 partially inhibit leukocyte transendothelial migration in a multi-receptor system but it is not known whether VCAM-1 activation of ERK1/2 is required for leukocyte transendothelial migration (TEM) on VCAM-1.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we identified a mechanism for VCAM-1 activation of ERK1/2 in human and mouse endothelial cells. VCAM-1 signaling, which occurs through endothelial cell NADPH oxidase, protein kinase Cα (PKCα), and protein tyrosine phosphatase 1B (PTP1B), activates endothelial cell ERK1/2. Inhibition of these signals blocked VCAM-1 activation of ERK1/2, indicating that ERK1/2 is activated downstream of PTP1B during VCAM-1 signaling. Furthermore, VCAM-1-specific leukocyte migration under physiological laminar flow of 2 dynes/cm(2) was blocked by pretreatment of endothelial cells with dominant-negative ERK2 K52R or the MEK/ERK inhibitors, PD98059 and U0126, indicating for the first time that ERK regulates VCAM-1-dependent leukocyte transendothelial migration.

CONCLUSIONS/SIGNIFICANCE

VCAM-1 activation of endothelial cell NADPH oxidase/PKCα/PTP1B induces transient ERK1/2 activation that is necessary for VCAM-1-dependent leukocyte TEM.

Deciphering the key molecular and cellular events in neutrophil transmigration during acute inflammation

Recruitment of leukocytes circulating in our blood to the sites of infection or tissue damage is the key phenomenon in the acute inflammatory response(s). Among the leukocytes, neutrophils are primarily recruited into the areas of acute inflammation. When neutrophils interact with activated endothelium of the blood vessels, they become migratory and cross the endothelial layer of the blood vessel wall in a process called as leukocyte extravasation. Identifying and understanding the gene regulation of this extravasation phenomenon is one of the key objective of biomedical research aimed at ameliorating or alleviating the symptoms of various diseases, such as rheumatoid arthritis, asthma, anaphylaxis, atherosclerosis, ulcerative colitis etc., that are exacerbated by inappropriate inflammatory stimuli. Here, we decipher and discuss the key genes implicated in the leukocyte transmigration using the acute inflammation model called as the Dextran Sulphate Sodium (DSS) induced Colitis in mice as a classic paradigm.

A proinflammatory role for proteolytically cleaved annexin A1 in neutrophil transendothelial migration

Neutrophil extravasation, a critical component of innate immunity must be tightly regulated to prevent inadvertent or prolonged inflammation and subsequent tissue damage. We have shown previously that endothelial ERK1/2 signaling essential for neutrophil transendothelial migration is induced by a soluble factor produced by activated neutrophils. In this study, we demonstrate that the soluble neutrophil factor is a truncated form of annexin A1 (AnxA1) that can be generated by calpain 1 cleavage of the N terminus, thus identifying a novel proinflammatory function to AnxA1. In contrast, neither the full-length protein nor the N-terminal 26 aa peptide, previously shown to be antiinflammatory, were able to activate Erk. Our data suggest that two different fragments of AnxA1 have opposing functions in inflammation. We also provide evidence that C-terminal AnxA1 functions by increasing ICAM1 clustering around adherent neutrophils to anchor them to the endothelium and promote transmigration through the transcellular route.

Gender-dependent differential phosphorylation in the ERK signaling pathway is associated with increased MMP2 activity in rat aortic smooth muscle cells

BACKGROUND

The present experiments were conducted to explore the role of mitogen-activated protein kinase (MAPK) pathways, potential upstream regulators of MMPs, in abdominal aortic aneurysms (AAAs).

METHODS

Rat aortic smooth muscle cells (RASMCs) from males and females were treated with media containing interleukin (IL)-1beta (2 ng/mL), a concentration known to be present in AAAs. Levels of both total and phosphorylated (activated) extracellular signal-regulated kinase (ERK), c-Jun amino terminal kinase/stress-activated protein kinase (JNK/SAPK), and p38 were examined by Western blotting at various time intervals up to 60 min. Similar experiments were conducted following exposure of RASMCs to elastase (6 U/mL), a concentration known to induce AAA formation in rodents. Finally, media was assayed for MMP activity by zymography.

RESULTS

Total ERK (t-ERK) was consistently no different in females compared with males prior to or following IL-1beta exposure. In contrast, levels of phosphorylated ERK (p-ERK) were significantly higher in males than females throughout the postexposure period (P < 0.0001). Levels of t-p38, p-p38, and t-JNK were not altered in a gender-dependent manner. The lack of p-JNK levels detected in both male and female RASMCs did not allow for conclusions to be drawn regarding gender disparities in this pathway. Results were similar following RASMC elastase exposure, although t-ERK levels were consistently higher in females than males (P < 0.0001). Pro-MMP2 levels were significantly higher (P = 0.0035) in males than females at each time point following elastase exposure.

CONCLUSIONS

These data provide evidence implicating alterations in p-ERK signaling via the up-regulation of MMPs as a potential explanation for gender-related discrepancies in AAA formation.

ADAM15 regulates endothelial permeability and neutrophil migration via Src/ERK1/2 signalling

AIMS

Endothelial barrier dysfunction is a key event in the pathogenesis of vascular diseases associated with inflammation. ADAM (a disintegrin and metalloprotease) 15 has been shown to contribute to the development of vascular inflammation. However, its role in regulating endothelial barrier function is unknown. The aim of this study was to examine the effect of ADAM15 on endothelial permeability and its underlying mechanisms.

METHODS AND RESULTS

By measuring albumin transendothelial flux and transendothelial electric resistance in cultured human umbilical vein endothelial cell monolayers, we found that depletion of ADAM15 expression via siRNA decreased endothelial permeability and attenuated thrombin-induced barrier dysfunction. In contrast, endothelial cells overexpressing either wild-type or catalytically dead mutant ADAM15 displayed a higher basal permeability and augmented hyperpermeability in response to thrombin. In addition, ADAM15 knockdown inhibited whereas ADAM15 overexpression promoted neutrophil transendothelial migration. Further molecular assays revealed that ADAM15 did not cleave vascular endothelial-cadherin or cause its degradation. However, overexpression of ADAM15 promoted extracellular signal-regulated kinase (ERK)1/2 phosphorylation in both non-stimulated and thrombin-stimulated endothelial cells in a protease activity-independent manner. Pharmacological inhibition of Src kinase or ERK activation reversed ADAM15-induced hyperpermeability and neutrophil transmigration.

CONCLUSION

The data provide evidence for a novel function of ADAM15 in regulating endothelial barrier properties. The mechanisms of ADAM15-induced hyperpermeability involve Src/ERK1/2 signalling independent of junction molecule shedding.

Carbon dioxide directly suppresses spontaneous migration, chemotaxis, and free radical production of human neutrophils

BACKGROUND

Carbon dioxide (CO(2)) insufflation during laparoscopy has been shown to dampen the systemic stress response to surgery. This is related to a suppression of peritoneal macrophage functions. In vivo data suggest that CO(2) can also affect neutrophils (polymorphonuclear cells, PMNs), the most abundant cell type in the inflamed peritoneal cavity. Nonetheless, the direct effects of CO(2) on PMNs have not yet been investigated.

METHOD

PMNs were isolated from peripheral blood of healthy volunteers and incubated with (1) CO(2) (100% CO(2), pH 6.2), (2) hypoxic control (95% helium/5% CO(2), pH 7.4), and (3) control (95% air/5% CO(2), pH 7.4). Spontaneous and IL-8-induced migrations (chemokinesis and chemotaxis) during 2 h of exposure to different gases were measured with a transwell chamber system. The release of reactive oxygen species (ROS, luminometry) was determined after 15-min and 2-h exposures. In other sets of experiments, PMNs were exposed for 2 h or 4 h and kept under normal conditions for 18 h with lipopolysaccharide (LPS) stimulation thereafter. Final viability and apoptosis were assessed with fluorometry.

RESULTS

Exposure to 100% CO(2) completely blocked spontaneous and IL-8 induced migration of PMNs (p < 0.001 vs. controls). Neutrophil migration was slightly diminished in the hypoxic control group. PMA-stimulated ROS production was reduced even after short exposure to 100% CO(2)(p < 0.05). We observed a slight increase of caspase-3/7 activity after exposure to 100% CO(2) and/or hypoxia; however, total viability was not affected.

CONCLUSIONS

CO(2) incubation directly and temporarily suppresses the proinflammatory functions of PMNs; this is caused only partially by the concomitant hypoxia. This effect will contribute to the dampened inflammatory response to laparoscopic surgery. Further studies are needed to investigate whether the temporary suppression of neutrophil functions could affect the clearance of bacterial contaminations.

Innate immune response of bovine mammary gland to pathogenic bacteria responsible for mastitis

Mastitis (mammary gland inflammation) is one of the most important bovine diseases causing economic losses to dairy producers. Mammary gland inflammation is a consequence of the activity of a number of cell and soluble factors that function together to eliminate invading microorganisms. The factors involved in this inflammatory response differ depending on the infectious agent. This review analyzes the factors involved in the immunologic mechanisms against the main pathogenic bacteria causing mastitis, and emphasizes the innate immune response of the mammary gland. Knowledge, at the molecular level, of the mammary gland immune response during infection by pathogenic bacteria is fundamental to the design of effective therapies to control and eradicate bovine mastitis.

Tissue inhibitor of metalloproteinase-2 inhibits T-cell infiltration and preserves pancreatic β-cell function in an in vitro type 1 diabetes mellitus model

Type 1 diabetes mellitus (T1DM) results from autoreactive T-cells that attack and destroy insulin producing pancreatic beta-cells. This knowledge has provided a framework for numerous efforts to prevent or mitigate T1DM at various stages of the disease. In this study, we utilized an organ culture model of type 1 diabetes to determine whether tissue inhibitors of metalloproteinases (TIMPs) could block T-cell migration into the pancreas and ultimately preserve beta-cell function. We measured T-cell repertoires, insulin secretion, and performed immunohistochemistry and confocal laser microscopy in order to evaluate the effect of TIMP-1, TIMP-2, and TIMP-3 on our in vitro T1DM organ culture model. TIMP-2 decreased T-cell transmigration and preserved insulin production in our T1DM organ culture model. Moreover, TIMP-2 inhibited transmigration of diabetogenic T-cells across an islet microvascular endothelial cell layer. Our findings suggest that TIMP-2 is effective at blocking infiltration of autoreactive T-cells into target pancreas tissue thereby preserving pancreatic beta-cell mass.

PECAM-1 isoform-specific activation of MAPK/ERKs and small GTPases: implications in inflammation and angiogenesis

Platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) is expressed on the surface of endothelial cells (EC) and leukocytes. PECAM-1 plays an important role in endothelial-leukocyte and endothelial-endothelial cell-cell interactions. The anti-PECAM-1 antibody-mediated blockade of these interactions inhibits transendothelial migration (TEM) of leukocytes and angiogenesis. PECAM-1 may accommodate these processes through the regulation of cell adhesive and migratory mechanisms. How PECAM-1 regulates these dynamic processes remain unknown. Here we show that PECAM-1 transduces outside-in signals, which activate MAPK/ERKs and small GTPases. This occurs through PECAM-1-mediated formation of intracellular-signaling complexes, Shc/Grb2/SOS1 and/or Crkl/C3G, which is initiated by PECAM-1 engagement on the surface of leukocytes and/or EC. Src, SHP2, and alternative PECAM-1 pre-mRNA splicing play a regulatory role in these signaling events. Our findings reveal that PECAM-1 engagement on the cell surface can transduce "outside-in" signals and activate MAPK/ERKs and small GTPases, impacting both cadherin-mediated cell-cell and integrin-mediated cell-matrix interactions. Thus, we propose PECAM-1 is an important mediator of vascular barrier and regulator of leukocyte and EC adhesion and migration.

Interaction between integrin alpha9beta1 and vascular cell adhesion molecule-1 (VCAM-1) inhibits neutrophil apoptosis

According to the prevailing paradigm, neutrophils are short-lived cells that undergo spontaneous apoptosis within 24 hours of their release from the bone marrow. However, neutrophil survival can be significantly prolonged within inflamed tissue by cytokines, inflammatory mediators, and hypoxia. During screening experiments aimed at identifying the effect of the adhesive microenvironment on neutrophil survival, we found that VCAM-1 (CD106) was able to delay both spontaneous and Fas-induced apoptosis. VCAM-1-mediated survival was as efficient as that induced by the cytokine IFN-beta and provided an additive, increased delay in apoptosis when given in combination with IFN-beta. VCAM-1 delivered its antiapoptotic effect through binding the integrin alpha9beta1. The alpha9beta1 signaling pathway shares significant features with the IFN-beta survival signaling pathway, requiring PI3 kinase, NF-kappaB activation, as well as de novo protein synthesis, but the kinetics of NF-kappaB activation by VCAM-1 were slower and more sustained compared with IFN-beta. This study demonstrates a novel functional role for alpha9beta1 in neutrophil biology and suggests that adhesive signaling pathways provide an important extrinsic checkpoint for the resolution of inflammatory responses in tissues.

Rebamipide reduces indomethacin-induced gastric injury in mice via down-regulation of ICAM-1 expression

Non-steroidal anti-inflammatory drugs (NSAIDs) induced gastric mucosal injury occurs through subsequent events following free radical production derived from activated neutrophils. In this study, we hypothesized that rebamipide, a novel anti-ulcer agent, exerts a protective effect on NSAID-induced gastric injury through its antioxidant properties. The protective effect of rebamipide in a mouse model of indomethacin-induced gastric injury and mechanisms for this effect were investigated. Pre-treatment with rebamipide significantly inhibited indomethacin-induced gastric mucosal injury in mice. Gastric thiobarbituric acid reactive substances (TBARS) levels and myeloperoxidase (MPO) activity substantially increased 3 hr after indomethacin administration. These increases were significantly inhibited by pre-treatment with rebamipide. Furthermore, rebamipide pre-treatment notably decreased intercellular adhesion molecule-1 (ICAM-1) expression that was up-regulated in gastric tissue treated with indomethacin. Therefore, rebamipide may reduce indomethacin-induced gastric mucosal injuries through its antioxidant effect, which inhibits the neutrophil activation step following up-regulation of ICAM-1 expression on endothelial cells.

Regulation of haematopoiesis by growth factors - emerging insights and therapies

Haematopoiesis is regulated by a wide variety of glycoprotein hormones, including stem cell factor, granulocyte-macrophage colony-stimulating factor, thrombopoietin and IL-3. These haematopoietic growth factors (HGFs) share a number of properties, including redundancy, pleiotropy, autocrine and paracrine effects, receptor subunit oligomerisation and similar signal transduction mechanisms, yet each one has a unique spectrum of haematopoietic activity. Ongoing studies with knockout mice have discovered previously unrecognised physiological roles for HGFs, linking haematopoiesis to innate immunity, pulmonary physiology and bone metabolism. The regulation of stem cells by HGFs within niches of the bone marrow microenvironment is now well recognised and similar mechanisms appear to exist in the regulation of other stem cell compartments. Alternative signalling strategies, other than tyrosine kinase activation and phosphotyrosine cascades, may account for some of the more subtle differences between HGFs. Accumulating evidence suggests that some, but not all, HGF receptors can transduce a genuine lineage-determining signal at certain points in haematopoiesis. Further studies, primarily at the receptor level, are needed to determine the mechanisms of instructive signalling, which may include phosphoserine cascades. Novel haematopoietic regulators, as well as the development of biological therapies, including growth factor antagonists and peptide mimetics, are also discussed.

Tumour necrosis factor-α mediates neutrophil migration to the knee synovial cavity during immune inflammation

Tumour necrosis factor (TNF)-alpha, interleukin-1beta, interleukin-8 and leukotriene B4 have an important role on neutrophil recruitment during immune-inflammation. Here we evaluated the participation of several inflammatory mediators on ovalbumin-induced neutrophil recruitment in the knee articular space of immunized rats. Ovalbumin administration in immunized, but not in control, rats induced a dose- and time-dependent neutrophil accumulation, which was inhibited by dexamethasone, pentoxifylline or thalidomide, but not by selective inhibitors of nitric oxide (nitro-L-arginine), platelet-activating factor (BN50730 or UK74505), prostaglandins (indomethacin), histamine (meclisine) or leukotriene B4 (MK 886 and CP105,696). Anti-TNF-alpha antiserum, but not anti-interleukin-1beta or anti-CINC-1 (cytokine-induced neutrophil chemoattractant 1) antisera, impaired ovalbumin-induced neutrophil accumulation. High amounts of TNF-alpha were detected in the exudates, which was inhibited by dexamethasone, pentoxifylline and thalidomide. These results suggest a specific role for TNF-alpha in this model, and the ability of pentoxifylline and thalidomide to inhibit both neutrophil influx and TNF-alpha release may have therapeutic implications in arthritis.