Novel mechanisms of the transendothelial migration of leukocytes

CD47: role in the immune system and application to cancer therapy

BACKGROUND

CD47 is a widely expressed cellular receptor well known for its immunoregulatory functions. By interacting with its ligands, including thrombospondin-1 (TSP-1), signal regulatory protein α (SIRPα), integrins, and SH2-domain bearing protein tyrosine phosphatase substrate-1 (SHPS-1), it modulates cellular phagocytosis by macrophages, transmigration of neutrophils and activation of dendritic cells, T cells and B cells. Ample studies have shown that various types of cancer express high levels of CD47 to escape from the immune system. Based on this observation, CD47 is currently considered as a prominent target in cancer therapy.

CONCLUSIONS

Here, we review the role of CD47 in the maintenance of immune system homeostasis. We also depict three emerging CD47-targeting strategies for cancer therapy, including the use of mimicry peptides, antibodies, and gene silencing strategies. Among these approaches, the most advanced one is the use of anti-CD47 antibodies, which enhances cancer cell phagocytosis via inhibition of the CD47-SIRPα axis. These antibodies can also achieve higher anti-cancer efficacies when combined with chemotherapy and immunotherapy and hold promise for improving the survival of patients with cancer.

Expression Profile of Immune-Associated Genes in Nasal Polyps

Objectives:

We performed this study to investigate the expression profile of immune-associated genes and to probe the role of related genes in the immune pathogenesis of nasal polyps.

Methods:

Microarray analysis was used to find the expression profile of 491 immune-associated genes in nasal polyps. In validation studies, immunohistochemical staining and Western blot analysis were used to detect interleukin (IL)–17 and IL-17 receptor (IL-17R) in nasal polyps and controls.

Results:

Eighty-seven genes were differentially expressed in the immune-associated gene profile of nasal polyps, and 15 genes showed differential expression in both chips. In nasal polyp tissues, IL-17 was expressed mainly in the cytoplasm of plasma cells and to a lesser degree in the prickle cell layer of the epithelium and the acinus of the serous gland. In turbinates, IL-17 was also expressed in the same location, but the expression of IL-17 in nasal polyps and that in turbinates differed significantly (p > .05). Both IL-17 and IL-17R displayed specific bands in nasal polyps and turbinates, but the bands of IL-17 and IL-17R in nasal polyps were stronger than those in turbinates.

Conclusions:

The differentially expressed genes in immune-associated gene chips will provide clues about, and a theoretical foundation for, the pathogenesis of nasal polyps. Furthermore, IL-17 may play an important role in the occurrence of nasal polyps by overexpression.

Critical but divergent roles for CD62L and CD44 in directing blood monocyte trafficking in vivo during inflammation

Using noninvasive in vivo imaging and experimental autoimmune uveoretinitis as a model, we show for the first time that the mechanisms controlling blood monocyte recirculation through peripheral and lymphoid tissues alter during inflammation. The recirculation of monocytes in mice with ocular inflammation but not controls was found to depend on the selectin CD62-ligand (CD62L) and on CD44. Not only was rolling efficiency ablated or markedly reduced in antibody-treated mice, but most of the labeled monocytes also disappeared from the circulation within seconds, anti-CD44–treated monocytes homing to the lymph nodes and anti–CD62L-treated monocytes homing to the spleen. Our data indicate that, although PSGL-1 has a partial role in the transmigration of monocytes into the inflamed retina, CD62L has a key role in regulating recruitment of monocytes to lymphoid tissue from the blood during inflammation and that CD44 is required to maintain CD62L⁺ inflammatory monocytes within the circulation during inflammation. This effect was systemic, because sequestered monocytes accumulated in mesenteric as well as draining cervical lymph nodes, and inflammation dependent, because depletion of circulating blood monocytes was much reduced or absent in normal mice and accumulations of adoptively transferred monocytes in the lymphoid tissues did not occur.

Chemokines and chemokine receptors in neurological disease: raise, retain, or reduce?

Chemokines and chemokine receptors comprise a large number of molecules implicated in a wide range of physiological and pathological functions. Numerous studies have demonstrated the roles of chemokines and chemokine receptors: 1) during development, by regulating hematopoiesis, cardiogenesis, and vascular and cerebellar development; 2) during tumor biology, by controlling cell proliferation, angiogenesis, and metastasis; and 3), especially during leukocyte migration, by acting on firm adhesion, locomotion, diapedesis, and chemotaxis. This review focuses on chemokine and chemokine receptor involvement in diverse neurological diseases and their therapeutic potentials. Because of its induction or upregulation during CNS pathologies, members of the chemokine system can be used as biological markers. CXCR4 and CXCL12, by the correlation between their expression and the glioblastoma tumor progression, could be a marker to grade this type of CNS tumor. CCR1, by virtue of specific expression in Abeta plaques, may be a marker for Alzheimer pathology. Downregulation of CCL2 in cerebrospinal fluid may be a candidate to characterize multiple sclerosis (MS), but needs additional investigation. Moreover, chemokines and chemokine receptors represent interesting therapeutic targets. Using chemokine receptor antagonists, several studies provided exciting findings for potential neurological disease treatment. Chemokine receptor antagonists reduce disease severity in animal models of MS. In glioblastoma, a CXCR4 antagonist (AMD3100) showed an inhibition of tumor growth. Inhibition of chemokine receptor signaling is not the only therapeutic strategy: for example, CXCR4-CXCL12 has anti-inflammatory properties and CX3CL1-CX3CR1 controls neurotoxicity. Thus, chemokine biology suggests several approaches for treating neurological disease.

Coxsackievirus group B type 3 infection upregulates expression of monocyte chemoattractant protein 1 in cardiac myocytes, which leads to enhanced migration of mononuclear cells in viral myocarditis

Coxsackievirus group B type 3 (CVB3) is an important cause of viral myocarditis. The infiltration of mononuclear cells into the myocardial tissue is one of the key events in viral myocarditis. Immediately after CVB3 infects the heart, the expression of chemokine(s) by infected myocardial cells may be the first trigger for inflammatory infiltration and immune response. However, it is unknown whether CVB3 can induce the chemokine expression in cardiac myocytes. Monocyte chemoattractant protein 1 (MCP-1) is a potent chemokine that stimulates the migration of mononuclear cells. The objective of the present study was to investigate the effect of CVB3 infection on MCP-1 expression in murine cardiac myocytes and the role of MCP-1 in migration of mononuclear cells in viral myocarditis. Our results showed that the expression of MCP-1 was significantly increased in cardiac myocytes after wild-type CVB3 infection in a time- and dose-dependent manner, which resulted in enhanced migration of mononuclear cells in mice with viral myocarditis. The migration of mononuclear cells was partially abolished by antibodies specific for MCP-1 in vivo and in vitro. Administration of anti-MCP-1 antibody prevented infiltration of mononuclear cells bearing the MCP-1 receptor CCR2 in mice with viral myocarditis. Infection by UV-irradiated CVB3 induced rapid and transient expression of MCP-1 in cardiac myocytes. In conclusion, our results indicate that CVB3 infection stimulates the expression of MCP-1 in myocardial cells, which subsequently leads to migration of mononuclear cells in viral myocarditis.

Adhesion mechanisms of endothelial cells

Endothelial cells express a diverse and exquisite array of adhesion molecules and cell surface receptors. Adhesion molecules expressed on endothelial cells not only maintain structural integrity of the vasculature, but also mediate more dynamic processes such as the highly regulated movement of leukocytes from free flow into different tissue compartments. Recent studies have focused on the molecular processes that mediate endothelial cell function and their ability to respond rapidly to changes in their immediate microenvironment, as well as maintaining routine cell trafficking through specialist tissue compartments. Adhesion molecules expressed on the endothelium mediate the movement of leukocytes into the underlying extravasculature to mediate a diverse array of functions including immune effector responses, cellular interactions in specialist lymphatic microenvironments and recirculation back into the vasculature. The true diversity and capacity of adhesion molecules capable of being expressed on the endothelium is now beginning to emerge, demonstrating new levels of complexity as specialist subsets of endothelium are characterised that define specific, yet diverse functions. In this chapter, the role of cell adhesion molecules in mediating endothelial cell function is discussed, from how their different physiochemical properties contribute to function, to how specific ligand interactions expressed on leukocyte cell populations contribute to functions ranging from constitutive cell trafficking to inflammation.

Expression of vascular adhesion protein-1 in normal and inflamed mice lungs and normal human lungs

Recently, vascular adhesion protein-1 (VAP-1) was implicated in adhesion and transmigration of lymphocytes across endothelial cells in liver and other organs. There is very little information on VAP-1 expression in normal and inflamed lungs. Therefore, we conducted a study to localize VAP-1 in normal mice and human lungs and in two distinct murine models of lung inflammation. Normal mice and human lungs revealed VAP-1 expression in the endothelium of large and mid-sized pulmonary vessels but not in alveolar septae, airway epithelium or blood cells. Mice that lack the lpr(-/-) gene and develop extensive lymphocytic infiltration in their lungs showed VAP-1 expression similar to the normal mice lungs. Mice subjected to cecal ligation and puncture developed acute lung inflammation and showed VAP-1 not only in endothelial cells but also in inflammatory cells in perivascular areas at 72 h after the procedure. We concluded that VAP-1 expression may contribute to the functional heterogeneity of endothelial cells within the lung to create distinct sites for the recruitment of inflammatory cells. Furthermore, since VAP-1 is expressed over a longer period of time in inflamed lungs, it may even be a suitable target for drug delivery and therapeutic manipulations.

Tumor necrosis factor-alpha and angiostatin are mediators of endothelial cytotoxicity in bronchoalveolar lavages of patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterized by an extensive alveolar capillary leak, permitting contact between intra-alveolar factors and the endothelium. To investigate whether factors contained in the alveolar milieu induce cell death in human lung microvascular endothelial cells, we exposed these cells in vitro to bronchoalveolar lavage fluid (BALF) supernatants from control patients, patients at risk of developing ARDS, and patients with early- and late-phase ARDS. In contrast to BALF from control patients, a significant cytotoxicity was found in BALF from patients at risk of developing ARDS, with late-phase ARDS, and especially from patients with early-phase ARDS. Subsequently, we determined the levels of factors known to exert cytotoxicity in endothelial cells, i.e., tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, and angiostatin. BALF from patients at risk of developing ARDS, with early-phase ARDS, and with late-phase ARDS, contained increased levels of TNF-alpha and angiostatin, but not of TGF-beta1, as compared with BALF from control patients. Whereas inhibition of TGF-beta1 had no effect in this setting, neutralization of TNF-alpha or angiostatin inhibited the cytotoxic activity on endothelial cells of part of the early-phase ARDS BALF. These results indicate that TNF-alpha and angiostatin may contribute to ARDS-related endothelial injury.