Mast cell and macrophage chemokines CXCL1/CXCL2 control the early stage of neutrophil recruitment during tissue inflammation

Analysis of mechanical ventilation and lipopolysaccharide‑induced acute lung injury using DNA microarray analysis

Gene expression profiles of samples taken from patients with acute lung injury (ALI) induced by mechanical ventilation (MV) and lipopolysaccharide (LPS) were analyzed in order to identify key genes, and explore the underlying mechanisms. The GSE2411 microarray data set was downloaded from the Gene Expression Omnibus. This data set contained microarray data from 24 mouse lung samples, which were equally divided into four groups: Control group, MV group, LPS group and MV+LPS group. Differentially expressed genes (DEGs) were identified in the MV, LPS and MV+LPS groups, as compared with the control group, using packages of R software. Hierarchical clustering and between‑group comparisons were performed for each group of DEGs. Overrepresented biological processes were revealed by functional enrichment analysis using the Database for Annotation, Visualization and Integrated Discovery. Unique DEGs in the LPS and MV+LPS groups were selected, and pathway enrichment analyses were performed using the Kyoto Encyclopedia of Genes and Genomes Orthology Based Annotation system. A total of 32, 264 and 685 DEGs were identified in the MV, LPS and MV+LPS groups, respectively. The MV+LPS group had more DEGs, as compared with the other two treatment groups. Genes associated with the immune and inflammatory responses were significantly overrepresented in both the LPS and MV+LPS groups, suggesting that LPS dominated the progression of ALI. Unique DEGs in the LPS and MV+LPS groups were associated with cytokine‑cytokine receptor interaction. The Janus kinase‑signal transducer and activator of transcription signaling pathway was shown to be enriched in the LPS+MV‑unique DEGs. The results of the present study demonstrated that MV could exaggerate the transcriptional response of the lungs to LPS. Numerous key genes were identified, which may advance knowledge regarding the pathogenesis of ALI.

Approaches for analyzing the roles of mast cells and their proteases in vivo

The roles of mast cells in health and disease remain incompletely understood. While the evidence that mast cells are critical effector cells in IgE-dependent anaphylaxis and other acute IgE-mediated allergic reactions seems unassailable, studies employing various mice deficient in mast cells or mast cell-associated proteases have yielded divergent conclusions about the roles of mast cells or their proteases in certain other immunological responses. Such "controversial" results call into question the relative utility of various older versus newer approaches to ascertain the roles of mast cells and mast cell proteases in vivo. This review discusses how both older and more recent mouse models have been used to investigate the functions of mast cells and their proteases in health and disease. We particularly focus on settings in which divergent conclusions about the importance of mast cells and their proteases have been supported by studies that employed different models of mast cell or mast cell protease deficiency. We think that two major conclusions can be drawn from such findings: (1) no matter which models of mast cell or mast cell protease deficiency one employs, the conclusions drawn from the experiments always should take into account the potential limitations of the models (particularly abnormalities affecting cell types other than mast cells) and (2) even when analyzing a biological response using a single model of mast cell or mast cell protease deficiency, details of experimental design are critical in efforts to define those conditions under which important contributions of mast cells or their proteases can be identified.

The chemokine system in innate immunity

Chemokines are chemotactic cytokines that control the migration and positioning of immune cells in tissues and are critical for the function of the innate immune system. Chemokines control the release of innate immune cells from the bone marrow during homeostasis as well as in response to infection and inflammation. They also recruit innate immune effectors out of the circulation and into the tissue where, in collaboration with other chemoattractants, they guide these cells to the very sites of tissue injury. Chemokine function is also critical for the positioning of innate immune sentinels in peripheral tissue and then, following innate immune activation, guiding these activated cells to the draining lymph node to initiate and imprint an adaptive immune response. In this review, we will highlight recent advances in understanding how chemokine function regulates the movement and positioning of innate immune cells at homeostasis and in response to acute inflammation, and then we will review how chemokine-mediated innate immune cell trafficking plays an essential role in linking the innate and adaptive immune responses.

Severe acute respiratory syndrome coronaviruses with mutations in the E protein are attenuated and promising vaccine candidates

Severe acute respiratory syndrome coronavirus (SARS-CoV) causes a respiratory disease with a mortality rate of 10%. A mouse-adapted SARS-CoV (SARS-CoV-MA15) lacking the envelope (E) protein (rSARS-CoV-MA15-ΔE) is attenuated in vivo. To identify E protein regions and host responses that contribute to rSARS-CoV-MA15-ΔE attenuation, several mutants (rSARS-CoV-MA15-E*) containing point mutations or deletions in the amino-terminal or the carboxy-terminal regions of the E protein were generated. Amino acid substitutions in the amino terminus, or deletion of regions in the internal carboxy-terminal region of E protein, led to virus attenuation. Attenuated viruses induced minimal lung injury, diminished limited neutrophil influx, and increased CD4(+) and CD8(+) T cell counts in the lungs of BALB/c mice, compared to mice infected with the wild-type virus. To analyze the host responses leading to rSARS-CoV-MA15-E* attenuation, differences in gene expression elicited by the native and mutant viruses in the lungs of infected mice were determined. Expression levels of a large number of proinflammatory cytokines associated with lung injury were reduced in the lungs of rSARS-CoV-MA15-E*-infected mice, whereas the levels of anti-inflammatory cytokines were increased, both at the mRNA and protein levels. These results suggested that the reduction in lung inflammation together with a more robust antiviral T cell response contributed to rSARS-CoV-MA15-E* attenuation. The attenuated viruses completely protected mice against challenge with the lethal parental virus, indicating that these viruses are promising vaccine candidates.

IMPORTANCE

Human coronaviruses are important zoonotic pathogens. SARS-CoV caused a worldwide epidemic infecting more than 8,000 people with a mortality of around 10%. Therefore, understanding the virulence mechanisms of this pathogen and developing efficacious vaccines are of high importance to prevent epidemics from this and other human coronaviruses. Previously, we demonstrated that a SARS-CoV lacking the E protein was attenuated in vivo. Here, we show that small deletions and modifications within the E protein led to virus attenuation, manifested by minimal lung injury, limited neutrophil influx to the lungs, reduced expression of proinflammatory cytokines, increased anti-inflammatory cytokine levels, and enhanced CD4(+) and CD8(+) T cell counts in vivo, suggesting that these phenomena contribute to virus attenuation. The attenuated mutants fully protected mice from challenge with virulent virus. These studies show that mutations in the E protein are not well tolerated and indicate that this protein is an excellent target for vaccine development.

The P2X1 receptor is required for neutrophil extravasation during lipopolysaccharide-induced lethal endotoxemia in mice

Extracellular ATP is becoming increasingly recognized as an important regulator of inflammation. However, the known repertoire of P2 receptor subtypes responsible for the proinflammatory effects of ATP is sparse. We looked at whether the P2X1 receptor, an ATP-gated cation channel present on platelets, neutrophils, and macrophages, participates in the acute systemic inflammation provoked by LPS. Compared with wild-type (WT) mice, P2X1(-/-) mice displayed strongly diminished pathological responses, with dampened neutrophil accumulation in the lungs, less tissue damage, reduced activation of coagulation, and resistance to LPS-induced death. P2X1 receptor deficiency also was associated with a marked reduction in plasma levels of the main proinflammatory cytokines and chemokines induced by LPS. Interestingly, macrophages and neutrophils isolated from WT and P2X1(-/-) mice produced similar levels of proinflammatory cytokines when stimulated with LPS in vitro. Intravital microscopy revealed a defect in LPS-induced neutrophil emigration from cremaster venules into the tissues of P2X1(-/-) mice. Using adoptive transfer of immunofluorescently labeled neutrophils from WT and P2X1(-/-) mice into WT mice, we demonstrate that the absence of the P2X1 receptor on neutrophils was responsible for this defect. This study reveals a major role for the P2X1 receptor in LPS-induced lethal endotoxemia through its critical involvement in neutrophil emigration from venules.

Leukocyte migration into inflamed tissues

Leukocyte migration through activated venular walls is a fundamental immune response that is prerequisite to the entry of effector cells such as neutrophils, monocytes, and effector T cells to sites of infection, injury, and stress within the interstitium. Stimulation of leukocytes is instrumental in this process with enhanced temporally controlled leukocyte adhesiveness and shape-changes promoting leukocyte attachment to the inner wall of blood vessels under hydrodynamic forces. This initiates polarized motility of leukocytes within and through venular walls and transient barrier disruption facilitated sequentially by stimulated vascular cells, i.e., endothelial cells and their associated pericytes. Perivascular cells such as macrophages and mast cells that act as tissue inflammatory sentinels can also directly and indirectly regulate the exit of leukocytes from the vascular lumen. In this review, we discuss current knowledge and open questions regarding the mechanisms involved in the interactions of different effector leukocytes with peripheral vessels in extralymphoid organs.

C/EBPα controls mast cell function

CCAAT/enhancer binding protein alpha (C/EBPα) is a transcription factor that influences immune cell fate and differentiation. However, the effect of C/EBPα on mast cells is not fully understood. In this study, we showed that C/EBPα suppressed granule formation in mast cells and increased macrophage inflammatory protein (MIP)-2 production from mast cells upon bacterial stimulation. These results indicate that C/EBPα regulates the balance between the allergic response and the innate immune response of mast cells. Furthermore, we showed that stimulation of mast cells with the Lactobacillus casei JCM1134(T) strain during late differentiation up-regulated C/EBPα expression in differentiated mast cells. This suggests that intestinal commensal bacteria modulate C/EBPα expression and thereby regulate mast cell function.

The role of mast cells in atherosclerosis

Rupture of an atherosclerotic plaque is the major underlying cause of adverse cardiovascular events such as myocardial infarction or stroke. Therapeutic interventions should therefore be directed towards inhibiting growth of atherosclerotic lesions as well as towards prevention of lesion destabilization. Interestingly, the presence of mast cells has been demonstrated in both murine and human plaques, and multiple interventional murine studies have pointed out a direct role for mast cells in early and late stages of atherosclerosis. Moreover, it has recently been described that activated lesional mast cells correlate with major cardiovascular events in patients suffering from cardiovascular disease. This review focuses on the effect of different mast cell derived mediators in atherogenesis and in late stage plaque destabilization. Also, possible ligands for mast cell activation in the context of atherosclerosis are discussed. Finally, we will elaborate on the predictive value of mast cells, together with therapeutic implications, in cardiovascular disease.

Anti-inflammatory effects of cannabinoid CB(2) receptor activation in endotoxin-induced uveitis

BACKGROUND AND PURPOSE

Cannabinoid CB2 receptors mediate immunomodulation. Here, we investigated the effects of CB2 receptor ligands on leukocyte-endothelial adhesion and inflammatory mediator release in experimental endotoxin-induced uveitis (EIU).

EXPERIMENTAL APPROACH

EIU was induced by intraocular injection of lipopolysaccharide (LPS, 20 ng·μL(-1) ). Effects of the CB2 receptor agonist, HU308 (1.5% topical), the CB2 receptor antagonist, AM630 (2.5 mg·kg(-1) i.v.), or a combination of both compounds on leukocyte-endothelial interactions were measured hourly for 6 h in rat iridial vasculature using intravital microscopy. Anti-inflammatory actions of HU308 were compared with those of clinical treatments for uveitis - dexamethasone, prednisolone and nepafenac. Transcription factors (NF-κB, AP-1) and inflammatory mediators (cytokines, chemokines and adhesion molecules) were measured in iris and ciliary body tissue.

KEY RESULTS

Leukocyte-endothelium adherence was increased in iridial microvasculature between 4-6 h after LPS. HU308 reduced this effect after LPS injection and decreased pro-inflammatory mediators: TNF-α, IL-1β, IL-6, CCL5 and CXCL2. AM630 blocked the actions of HU-308, and increased leukocyte-endothelium adhesion. HU-308 decreased levels of the transcription factors NF-κB and AP-1, while AM630 increased levels of NF-κB. Topical treatments with dexamethasone, prednisolone or nepafenac, failed to alter leukocyte adhesion or mitigate LPS-induced increases in inflammatory mediators during the 6 h of EIU.

CONCLUSION AND IMPLICATIONS

Activation of CB2 receptors was anti-inflammatory in a model of acute EIU and involved a reduction in NF-κB, AP-1 and inflammatory mediators. CB2 receptors may be promising drug targets for the development of novel ocular anti-inflammatory agents.

LINKED ARTICLES

This article is part of a themed section on Cannabinoids 2013. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-6.

SIRT2 Regulates LPS-Induced Renal Tubular CXCL2 and CCL2 Expression

Sirtuin 2 (SIRT2), a NAD(+)-dependent histone deacetylase, is involved in carcinogenesis and genomic instability and modulates proinflammatory immune responses. However, its role in renal inflammatory injury has not been demonstrated. In this study, we explored the expression patterns of CXCL2 and CCL2 in kidney tissue from Sirt2(-/-) and Sirt2(+/+) mice and in mouse proximal tubular epithelial (MPT) cells. CXCL2 and CCL2 were significantly downregulated at both the mRNA and the protein levels in kidneys of LPS-treated Sirt2(-/-) mice compared with those of LPS-treated Sirt2(+/+) mice. Furthermore, SIRT2 deficiency ameliorated LPS-induced infiltration of neutrophils and macrophages, acute tubular injury, and decrease of renal function. Supporting these observations, CXCL2 and CCL2 expression levels were lower in MPT cells treated with SIRT2-siRNA than in cells treated with control-siRNA, and adenovirus-mediated overexpression of SIRT2 in MPT cells significantly increased the LPS-induced expression of CXCL2 and CCL2 at the mRNA and protein levels. In addition, SIRT2 interacted with mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1), and SIRT2-knockdown increased the acetylation of MKP-1 and suppressed the phosphorylation of p38 MAPK and c-Jun N-terminal kinase in LPS-treated MPT cells. SIRT2 also regulated p65 binding to the promoters of CXCL2 and CCL2. Taken together, these findings indicate that SIRT2 is associated with expression of renal CXCL2 and CCL2 and that regulation of SIRT2 might be an important therapeutic target for renal inflammatory injury.

Mast cell function: a new vision of an old cell

Since first described by Paul Ehrlich in 1878, mast cells have been mostly viewed as effectors of allergy. It has been only in the past two decades that mast cells have gained recognition for their involvement in other physiological and pathological processes. Mast cells have a widespread distribution and are found predominantly at the interface between the host and the external environment. Mast cell maturation, phenotype and function are a direct consequence of the local microenvironment and have a marked influence on their ability to specifically recognize and respond to various stimuli through the release of an array of biologically active mediators. These features enable mast cells to act as both first responders in harmful situations as well as to respond to changes in their environment by communicating with a variety of other cells implicated in physiological and immunological responses. Therefore, the critical role of mast cells in both innate and adaptive immunity, including immune tolerance, has gained increased prominence. Conversely, mast cell dysfunction has pointed to these cells as the main offenders in several chronic allergic/inflammatory disorders, cancer and autoimmune diseases. This review summarizes the current knowledge of mast cell function in both normal and pathological conditions with regards to their regulation, phenotype and role.

Proinflammatory role of neutrophil extracellular traps in abdominal sepsis

Excessive neutrophil activation is a major component in septic lung injury. Neutrophil-derived DNA may form extracellular traps in response to bacterial invasions. The aim of the present study was to investigate the potential role of neutrophil extracellular traps (NETs) in septic lung injury. Male C57BL/6 mice were treated with recombinant human (rh)DNAse (5 mg/kg) after cecal ligation and puncture (CLP). Extracellular DNA was stained by Sytox green, and NET formation was quantified by confocal microscopy and cell-free DNA in plasma, peritoneal cavity, and lung. Blood, peritoneal fluid, and lung tissue were harvested for analysis of neutrophil infiltration, NET levels, tissue injury, as well as CXC chemokine and cytokine formation. We observed that CLP caused increased formation of NETs in plasma, peritoneal cavity, and lung. Administration of rhDNAse not only eliminated NET formation in plasma, peritoneal cavity, and bronchoalveolar space but also reduced lung edema and tissue damage 24 h after CLP induction. Moreover, treatment with rhDNAse decreased CLP-induced formation of CXC chemokines, IL-6, and high-mobility group box 1 (HMGB1) in plasma, as well as CXC chemokines and IL-6 in the lung. In vitro, we found that neutrophil-derived NETs had the capacity to stimulate secretion of CXCL2, TNF-α, and HMGB1 from alveolar macrophages. Taken together, our findings show that NETs regulate pulmonary infiltration of neutrophils and tissue injury via formation of proinflammatory compounds in abdominal sepsis. Thus we conclude that NETs exert a proinflammatory role in septic lung injury.

Neutrophils at work

In this Review we discuss data demonstrating recently recognized aspects of neutrophil homeostasis in the steady state, granulopoiesis in 'emergency' conditions and interactions of neutrophils with the adaptive immune system. We explore in vivo observations of the recruitment of neutrophils from blood to tissues in models of blood-borne infections versus bacterial invasion through epithelial linings. We examine data on novel aspects of the activation of NADPH oxidase and the heterogeneity of phagosomes and, finally, consider the importance of two neutrophil-derived biological agents: neutrophil extracellular traps and ectosomes.

Neutrophils mediate blood-spinal cord barrier disruption in demyelinating neuroinflammatory diseases

Disruption of the blood-brain and blood-spinal cord barriers (BBB and BSCB, respectively) and immune cell infiltration are early pathophysiological hallmarks of multiple sclerosis (MS), its animal model experimental autoimmune encephalomyelitis (EAE), and neuromyelitis optica (NMO). However, their contribution to disease initiation and development remains unclear. In this study, we induced EAE in lys-eGFP-ki mice and performed single, nonterminal intravital imaging to investigate BSCB permeability simultaneously with the kinetics of GFP(+) myeloid cell infiltration. We observed a loss in BSCB integrity within a day of disease onset, which paralleled the infiltration of GFP(+) cells into the CNS and lasted for ∼4 d. Neutrophils accounted for a significant proportion of the circulating and CNS-infiltrating myeloid cells during the preclinical phase of EAE, and their depletion delayed the onset and reduced the severity of EAE while maintaining BSCB integrity. We also show that neutrophils collected from the blood or bone marrow of EAE mice transmigrate more efficiently than do neutrophils of naive animals in a BBB cell culture model. Moreover, using intravital videomicroscopy, we demonstrate that the IL-1R type 1 governs the firm adhesion of neutrophils to the inflamed spinal cord vasculature. Finally, immunostaining of postmortem CNS material obtained from an acutely ill multiple sclerosis patient and two neuromyelitis optica patients revealed instances of infiltrated neutrophils associated with regions of BBB or BSCB leakage. Taken together, our data provide evidence that neutrophils are involved in the initial events that take place during EAE and that they are intimately linked with the status of the BBB/BSCB.

Gene expression profiling of peri-implant healing of PLGA-Li+ implants suggests an activated Wnt signaling pathway in vivo

Bone development and regeneration is associated with the Wnt signaling pathway that, according to literature, can be modulated by lithium ions (Li+). The aim of this study was to evaluate the gene expression profile during peri-implant healing of poly(lactic-co-glycolic acid) (PLGA) implants with incorporated Li+, while PLGA without Li+ was used as control, and a special attention was then paid to the Wnt signaling pathway. The implants were inserted in rat tibia for 7 or 28 days and the gene expression profile was investigated using a genome-wide microarray analysis. The results were verified by qPCR and immunohistochemistry. Histomorphometry was used to evaluate the possible effect of Li+ on bone regeneration. The microarray analysis revealed a large number of significantly differentially regulated genes over time within the two implant groups. The Wnt signaling pathway was significantly affected by Li+, with approximately 34% of all Wnt-related markers regulated over time, compared to 22% for non-Li+ containing (control; Ctrl) implants. Functional cluster analysis indicated skeletal system morphogenesis, cartilage development and condensation as related to Li+. The downstream Wnt target gene, FOSL1, and the extracellular protein-encoding gene, ASPN, were significantly upregulated by Li+ compared with Ctrl. The presence of β-catenin, FOSL1 and ASPN positive cells was confirmed around implants of both groups. Interestingly, a significantly reduced bone area was observed over time around both implant groups. The presence of periostin and calcitonin receptor-positive cells was observed at both time points. This study is to the best of the authors' knowledge the first report evaluating the effect of a local release of Li+ from PLGA at the fracture site. The present study shows that during the current time frame and with the present dose of Li+ in PLGA implants, Li+ is not an enhancer of early bone growth, although it affects the Wnt signaling pathway.

Xilei san ameliorates experimental colitis in rats by selectively degrading proinflammatory mediators and promoting mucosal repair

Xilei san (XLS), a herbal preparation widely used in China for erosive and ulcerative diseases, has been shown to be effective in ulcerative colitis (UC). The present experiments were conducted to assess its efficacy and determine its mechanism of action in a rat model that resembles human UC. The model was induced by adding 4% dextran sulfate sodium (DSS) to the rats' drinking water for 7 days. XLS was administered daily by retention enema from day 2 to day 7; the rats were sacrificed on day 8. The colon tissues were obtained for further experiments. A histological damage score and the activity of tissue myeloperoxidase were used to evaluate the severity of the colitis. The colonic cytokine levels were detected in a suspension array, and epithelial proliferation was assessed using Ki-67 immunohistochemistry. Intrarectal administration of XLS attenuated the DSS-induced colitis, as evidenced by a reduction in both the histological damage score and myeloperoxidase activity. It also decreased the levels of proinflammatory cytokines, but increased the mucosal repair-related cytokines. In addition, the epithelial Ki-67 expression was upregulated by XLS. These results suggest that XLS attenuates DSS-induced colitis by degrading proinflammatory mediators and promoting mucosal repair. XLS could be a potential topical treatment for human UC.

CXCL1 inhibits airway smooth muscle cell migration through the decoy receptor Duffy antigen receptor for chemokines

Airway smooth muscle cell (ASMC) migration is an important mechanism postulated to play a role in airway remodeling in asthma. CXCL1 chemokine has been linked to tissue growth and metastasis. In this study, we present a detailed examination of the inhibitory effect of CXCL1 on human primary ASMC migration and the role of the decoy receptor, Duffy AgR for chemokines (DARC), in this inhibition. Western blots and pathway inhibitors showed that this phenomenon was mediated by activation of the ERK-1/2 MAPK pathway, but not p38 MAPK or PI3K, suggesting a biased selection in the signaling mechanism. Despite being known as a nonsignaling receptor, small interference RNA knockdown of DARC showed that ERK-1/2 MAPK activation was significantly dependent on DARC functionality, which, in turn, was dependent on the presence of heat shock protein 90 subunit α. Interestingly, DARC- or heat shock protein 90 subunit α-deficient ASMCs responded to CXCL1 stimulation by enhancing p38 MAPK activation and ASMC migration through the CXCR2 receptor. In conclusion, we demonstrated DARC's ability to facilitate CXCL1 inhibition of ASMC migration through modulation of the ERK-1/2 MAPK-signaling pathway.

Defining a pro-inflammatory neutrophil phenotype in response to schistosome eggs

Neutrophils contribute to the pathological processes of a number of inflammatory disorders, including rheumatoid arthritis, sepsis and cystic fibrosis. Neutrophils also play prominent roles in schistosomiasis japonica liver fibrosis, being central mediators of inflammation following granuloma formation. In this study, we investigated the interaction between Schistosoma japonicum eggs and neutrophils, and the effect of eggs on the inflammatory phenotype of neutrophils. Our results showed significant upregulated expression of pro-inflammatory cytokines (IL-1α, IL-1β and IL-8) and chemokines (CCL3, CCL4 and CXCL2) in neutrophils after 4 h in vitro stimulation with S. japonicum eggs. Furthermore, mitochondrial DNA was released by stimulated neutrophils, and induced the production of matrix metalloproteinase 9 (MMP-9), a protease involved in inflammation and associated tissue destruction. We also found that intact live eggs and isolated soluble egg antigen (SEA) triggered the release of neutrophil extracellular traps (NETs), but, unlike those reported in bacterial or fungal infection, NETs did not kill schistosome eggs in vitro. Together these show that S. japonicum eggs can induce the inflammatory phenotype of neutrophils, and further our understanding of the host-parasite interplay that takes place within the in vivo microenvironment of schistosome-induced granuloma. These findings represent novel findings in a metazoan parasite, and confirm characteristics of NETs that have until now, only been observed in response to protozoan pathogens.

[Chemokines and attraction of myeloid cells in peripheral neuropathic pains]

Chronic neuropathic pain has become a real social issue, due to the difficulty of its treatment and by the major impairment to quality of life that it causes in every day behavior. Understanding neurobiological basis and pathophysiological causes of diverse painful syndromes constantly evolves and reports the complexity of its mechanisms. Unfortunately this complexity makes it difficult to discover effective treatments against chronic pain syndromes, in particular as regards peripheral neuropathic pains. Recent studies reveal that, during chronic peripheral neuropathy, inflammatory mediators (in particular chemokines), besides their implications in the modulation of nociceptive messages and central neuroinflammatory mechanisms, play a critical role in the orchestration of the immune response induced by a peripheral nerve lesion. In this review, after a brief introduction about chemokines and their role in neuromodulation of the nociceptive message, we will attempt to define their functions and implications in the immune response associated to peripheral neuropathies. Thus, perfectly understanding the molecular and cellular communications between the nervous system and the immune system will be useful for the future development of novel and innovative therapeutic strategies against these highly disabling pathologies.

Microfluidic platform for measuring neutrophil chemotaxis from unprocessed whole blood

Neutrophils play an essential role in protection against infections and their numbers in the blood are frequently measured in the clinic. Higher neutrophil counts in the blood are usually an indicator of ongoing infections, while low neutrophil counts are a warning sign for higher risks for infections. To accomplish their functions, neutrophils also have to be able to move effectively from the blood where they spend most of their life, into tissues, where infections occur. Consequently, any defects in the ability of neutrophils to migrate can increase the risks for infections, even when neutrophils are present in appropriate numbers in the blood. However, measuring neutrophil migration ability in the clinic is a challenging task, which is time consuming, requires large volume of blood, and expert knowledge. To address these limitations, we designed a robust microfluidic assays for neutrophil migration, which requires a single droplet of unprocessed blood, circumvents the need for neutrophil separation, and is easy to quantify on a simple microscope. In this assay, neutrophils migrate directly from the blood droplet, through small channels, towards the source of chemoattractant. To prevent the granular flow of red blood cells through the same channels, we implemented mechanical filters with right angle turns that selectively block the advance of red blood cells. We validated the assay by comparing neutrophil migration from blood droplets collected from finger prick and venous blood. We also compared these whole blood (WB) sources with neutrophil migration from samples of purified neutrophils and found consistent speed and directionality between the three sources. This microfluidic platform will enable the study of human neutrophil migration in the clinic and the research setting to help advance our understanding of neutrophil functions in health and disease.

Hepatitis C-associated mixed cryoglobulinemic vasculitis induces differential gene expression in peripheral mononuclear cells

This study examines the distinct gene expression profile of peripheral blood mononuclear cells from patients with chronic hepatitis C infection and mixed cryoglobulinemic (MC) vasculitis. Our DNA microarray analysis indicates that hepatitis C virus (HCV)-associated MC vasculitis is characterized by compromised neutrophil function, impaired chemotaxis, and increased interferon-stimulated gene (ISG) expression, contributing to overall MC pathogenesis and end-organ damage. Increased ISG expression is suggestive of an enhanced endogenous interferon gene signature. PBMC depletion assays demonstrate that this increased expression is likely due to an activation of monocytes and not a direct result of B cell expansion. Notably, this monocyte activation of ISG expression in HCV-associated MC vasculitis suggests a poor predictor status of interferon-based treatment. Further analysis of PBMC gene expression profiles before and after in vivo B cell depletion therapy is critical to completely understanding the mechanisms of MC vasculitis pathogenesis.

Attenuation of collagen-induced arthritis in mice by salmon proteoglycan

Rheumatoid arthritis (RA) is a serious autoimmune disease caused by chronic inflammation of connective tissues. The basic principle of RA treatment is aimed to reduce joint inflammation. Our previous studies demonstrated that salmon cartilage proteoglycan (PG) suppresses excess inflammation in different mouse inflammatory diseases. In this study, we investigated the prophylactic effect of PG on the progression of RA using an experimental mouse model, collagen-induced arthritis (CIA). Clinical and histological severity of CIA was attenuated by daily oral administration of PG. In the joints of PG-administered mice, infiltration of macrophages and neutrophils and also osteoclast accumulation were limited. In comparison to nonadministered mice, anti-collagen antibodies in the sera of PG-administered mice did not alter. On the other hand, local expression of interleukin-17A (IL-17A), IL-6, IL-1β, interferon-γ (IFN-γ), C-C chemokine ligand 2 (CCL2), C-X-C chemokine ligand 1 (CXCL1), and CXCL2 in the joints of PG-administered mice decreased. Moreover, in the response of type II collagen- (CII-) restimulation ex vivo, IL-17A and IFN-γ production by splenocytes from PG-administered mice was less than that of control mice. These data suggested that daily ingested PG attenuated CIA pathogenesis by modulating immune response of splenocytes to CII stimulation and local production inflammatory cytokines and chemokines in the joints.

Loss of Lkb1 and Pten leads to lung squamous cell carcinoma with elevated PD-L1 expression

Lung squamous cell carcinoma (SCC) is a deadly disease for which current treatments are inadequate. We demonstrate that biallelic inactivation of Lkb1 and Pten in the mouse lung leads to SCC that recapitulates the histology, gene expression, and microenvironment found in human disease. Lkb1;Pten null (LP) tumors expressed the squamous markers KRT5, p63 and SOX2, and transcriptionally resembled the basal subtype of human SCC. In contrast to mouse adenocarcinomas, the LP tumors contained immune populations enriched for tumor-associated neutrophils. SCA1(+)NGFR(+) fractions were enriched for tumor-propagating cells (TPCs) that could serially transplant the disease in orthotopic assays. TPCs in the LP model and NGFR(+) cells in human SCCs highly expressed Pd-ligand-1 (PD-L1), suggesting a mechanism of immune escape for TPCs.

A mystery unraveled: nontumorigenic pluripotent stem cells in human adult tissues

INTRODUCTION

Embryonic stem cells and induced pluripotent stem cells have emerged as the gold standard of pluripotent stem cells and the class of stem cell with the highest potential for contribution to regenerative and therapeutic application; however, their translational use is often impeded by teratoma formation, commonly associated with pluripotency. We discuss a population of nontumorigenic pluripotent stem cells, termed Multilineage Differentiating Stress Enduring (Muse) cells, which offer an innovative and exciting avenue of exploration for the potential treatment of various human diseases.

AREAS COVERED

This review discusses the origin of Muse cells, describes in detail their various unique characteristics, and considers future avenues of their application and investigation with respect to what is currently known of adult pluripotent stem cells in scientific literature. We begin by defining cell potency, then discuss both mesenchymal and various reported populations of pluripotent stem cells, and finally delve into Muse cells and the characteristics that set them apart from their contemporaries.

EXPERT OPINION

Muse cells derived from adipose tissue (Muse-AT) are efficiently, routinely and painlessly isolated from human lipoaspirate material, exhibit tripoblastic differentiation both spontaneously and under media-specific induction, and do not form teratomas. We describe qualities specific to Muse-AT cells and their potential impact on the field of regenerative medicine and cell therapy.

The regulation of inflammatory mediators in acute kidney injury via exogenous mesenchymal stem cells

Acute kidney injury (AKI) remains to be an independent risk factor for mortality and morbidity. Inflammation is believed to play a major role in the pathophysiology of AKI. Exogenous mesenchymal stem cells (MSCs) are now under extensive investigation as a potential therapy for AKI. Various preclinical studies indicated the beneficial effects of MSCs in alleviating renal injury and accelerating tissue repair. However the mechanisms responsible for these effects are incompletely understood. In the recent years, anti-inflammatory/immunoregulatory properties of MSCs have become one of the important issues in the treatment of AKI. This review will summarize the current literature on the regulation of inflammatory mediators via exogenous MSCs contributing to the recovery from AKI.

A TLR2/S100A9/CXCL-2 signaling network is necessary for neutrophil recruitment in acute and chronic liver injury in the mouse

BACKGROUND & AIMS

Neutrophils are important immune effectors required for sterile and non-sterile inflammatory responses. However, neutrophils are associated with pathology in drug-induced liver injury, acute alcoholic liver disease, and ischemia-reperfusion injury. An understanding of the complex mechanisms that control neutrophil recruitment to the injured liver is desirable for developing strategies aimed at limiting neutrophil-mediated cellular damage.

METHODS

Wt, tlr2(-/-), tlr4(-/-), and s100a9(-/-) mice were administered CCl4 either acutely (8, 24, 48, or 72 h) or chronically (8 weeks) and livers investigated by histological (IHC for neutrophils, fibrogenesis, proliferation, and chemotactic proteins) or molecular approaches (qRT-PCR for neutrophil chemoattractant chemokines and cytokines as well as pro-fibrogenic genes).

RESULTS

Mice lacking TLR2 or S100A9 failed to recruit neutrophils to the injured liver and had a defective hepatic induction of the neutrophil chemokine CXCL-2. Hierarchy between TLR2 and S100A9 proved to be complex. While induction of S100A9 was dependent on TLR2 in isolated neutrophils, there was a more complicated two-way signalling cross-talk between TLR2 and S100A9 in whole liver. However, wound-healing and regenerative responses of the liver were unaffected in these genetic backgrounds as well as in wild type mice, in which neutrophils were depleted by infusion of Ly-6G antibody.

CONCLUSIONS

We have identified TLR2 and S100A8/S100A9 as key regulators of hepatic CXCL-2 expression and neutrophil recruitment. This novel TLR2-S100A9-CXCL-2 pathway may be of use in development of new strategies for selectively manipulating neutrophils in liver disease without impairing normal wound healing and regenerative responses.

Mast cells as targets for immunotherapy of solid tumors

Mast cells have historically been studied mainly in the context of allergic disease. In recent years, we have come to understand the critical importance of mast cells in tissue remodeling events and their role as sentinel cells in the induction and development of effective immune responses to infection. Studies of the role of mast cells in tumor immunity are more limited. The pro-tumorigenic role of mast cells has been widely reported. However, mast cell infiltration predicts improved prognosis in some cancers, suggesting that their prognostic value may be dependent on other variables. Such factors may include the nature of local mast cell subsets and the various activation stimuli present within the tumor microenvironment. Experimental models have highlighted the importance of mast cells in orchestrating the anti-tumor events that follow immunotherapies that target innate immunity. Mast cells are long-lived tissue resident cells that are abundant around many solid tumors and are radiation resistant making them unique candidates for combined treatment modalities. This review will examine some of the key roles of mast cells in tumor immunity, with a focus on potential immunotherapeutic interventions that harness the sentinel role of mast cells.

Mast cell mediator responses and their suppression by pathogenic and commensal microorganisms

Mast cells (MCs) are selectively found at the host environment interface and are capable of secreting a wide array of pharmacologically active mediators, many of which are prepackaged in granules. Over the past two decades, it has become clear that these cells have the capacity to recognize a range of infectious agents allowing them to play a key role in initiating and modulating early immune responses to infectious agents. However, a number of pathogenic and commensal microbes appear to have evolved distinct mechanisms to suppress MC mediator release to avoid elimination in the host. Understanding how these microbes suppress MC functions may have significant therapeutic value to relieve inflammatory disorders mediated by MCs.

Functional annotation of rheumatoid arthritis and osteoarthritis associated genes by integrative genome-wide gene expression profiling analysis

Background

Rheumatoid arthritis (RA) and osteoarthritis (OA) are two major types of joint diseases that share multiple common symptoms. However, their pathological mechanism remains largely unknown. The aim of our study is to identify RA and OA related-genes and gain an insight into the underlying genetic basis of these diseases.

Methods

We collected 11 whole genome-wide expression profiling datasets from RA and OA cohorts and performed a meta-analysis to comprehensively investigate their expression signatures. This method can avoid some pitfalls of single dataset analyses.

Results and Conclusion

We found that several biological pathways (i.e., the immunity, inflammation and apoptosis related pathways) are commonly involved in the development of both RA and OA. Whereas several other pathways (i.e., vasopressin-related pathway, regulation of autophagy, endocytosis, calcium transport and endoplasmic reticulum stress related pathways) present significant difference between RA and OA. This study provides novel insights into the molecular mechanisms underlying this disease, thereby aiding the diagnosis and treatment of the disease.

Chemokines and chemokine receptors: positioning cells for host defense and immunity

Chemokines are chemotactic cytokines that control the migratory patterns and positioning of all immune cells. Although chemokines were initially appreciated as important mediators of acute inflammation, we now know that this complex system of approximately 50 endogenous chemokine ligands and 20 G protein-coupled seven-transmembrane signaling receptors is also critical for the generation of primary and secondary adaptive cellular and humoral immune responses. Recent studies demonstrate important roles for the chemokine system in the priming of naive T cells, in cell fate decisions such as effector and memory cell differentiation, and in regulatory T cell function. In this review, we focus on recent advances in understanding how the chemokine system orchestrates immune cell migration and positioning at the organismic level in homeostasis, in acute inflammation, and during the generation and regulation of adoptive primary and secondary immune responses in the lymphoid system and peripheral nonlymphoid tissue.

Traps and hyper inflammation - new ways that neutrophils promote or hinder survival

For a long time neutrophil granulocytes were considered simply as terminally differentiated cells with a limited life span and pathogen killing by phagocytosis and chemical toxicity being the sole mode of action. However, work during the last 10 years has started to change this view fundamentally. Modern understanding is that neutrophils have an enormous complexity of functions. This review discusses very recent findings on how neutrophils can control the spread of pathogens and mediate their killing by mechanisms such as formation of DNA nets, how they influence tumour growth and adaptive immune responses and how they manoeuvre inside the diverse compartments of the body. It will also describe how the normally protective functions of neutrophils can have deleterious consequences if they occur in an uncontrolled fashion. These exciting novel findings are likely to completely and permanently change our view of this central leucocyte population.

Elevated CXCL1 expression in gp130-deficient endothelial cells impairs neutrophil migration in mice

Neutrophils emigrate from venules to sites of infection or injury in response to chemotactic gradients. How these gradients form is not well understood. Some IL-6 family cytokines stimulate endothelial cells to express adhesion molecules and chemokines that recruit leukocytes. Receptors for these cytokines share the signaling subunit gp130. We studied knockout mice lacking gp130 in endothelial cells. Unexpectedly, gp130-deficient endothelial cells constitutively expressed more CXCL1 in vivo and in vitro, and even more upon stimulation with tumor necrosis factor-α. Mobilization of this increased CXCL1 from intracellular stores to the venular surface triggered β2 integrin-dependent arrest of neutrophils rolling on selectins but impaired intraluminal crawling and transendothelial migration. Superfusing CXCL1 over venules promoted neutrophil migration only after intravenously injecting mAb to CXCL1 to diminish its intravascular function or heparinase to release CXCL1 from endothelial proteoglycans. Remarkably, mice lacking gp130 in endothelial cells had impaired histamine-induced venular permeability, which was restored by injecting anti-P-selectin mAb to prevent neutrophil rolling and arrest. Thus, excessive CXCL1 expression in gp130-deficient endothelial cells augments neutrophil adhesion but hinders migration, most likely by disrupting chemotactic gradients. Our data define a role for endothelial cell gp130 in regulating integrin-dependent adhesion and de-adhesion of neutrophils during inflammation.