Interleukin-1β Reduces Transcellular Monocyte Diapedesis and Compromises Endothelial Adherens Junction Integrity

Polymorphism of Interleukin-1 Gene Cluster in Polish Patients with Acute Coronary Syndrome

Background and objectives: Some experimental studies demonstrated adverse modulation of atherothrombosis by interleukin-1beta (IL-1b). To assess the relationship between the five most common variants of three polymorphisms of the IL1b gene cluster and the complexity of coronary atherosclerosis expressed in Gensini Score (GS), and the age of onset of the first acute coronary syndrome (ACS), we assessed the patients (pts) hospitalized due to ACS in this aspect. Materials and Methods: 250 individuals were included. The single nucleotide polymorphisms of IL1b gene: transition T/C at -31 position, C/T at -511, and those of IL1 receptor antagonist gene (IL1RN)—variable number of tandem repeats allele 1, 2, 3, or 4—were determined by PCR. GS was calculated from the coronary angiogram performed at the index ACS. The impact of the presence of T or C and allele 1 to 4 at the investigated loci on the mean GS, GS greater than 40, mean age of onset of ACS, and the fraction of pts over 60 years of age at ACS were compared between the five most common genotype variants. Results: The five most common variants were present in 203 pts (81.2%). Patients with pair 22 in ILRN had the lowest rate and those with pair 12 had the highest rate of ACS before 60 years of age (29.4 vs. 67.8%; p = 0.004). GS > 40 entailed an eight-fold increase of risk, as observed when pts with one T allele at locus -31 were compared with carriers of 2 or no T allele at this locus: OR 8.73 [CI95 4.26–70.99] p = 0.04. Conclusion: Interleukin-1 beta is subject to frequent genetic variability and our results show a potential relationship of this polymorphism with the extent of coronary atherosclerosis and age at the first ACS.

Alternative Pathways of IL-1 Activation, and Its Role in Health and Disease

Cytokines activate or inhibit immune cell behavior and are thus integral to all immune responses. IL-1α and IL-1β are powerful apical cytokines that instigate multiple downstream processes to affect both innate and adaptive immunity. Multiple studies show that IL-1β is typically activated in macrophages after inflammasome sensing of infection or danger, leading to caspase-1 processing of IL-1β and its release. However, many alternative mechanisms activate IL-1α and IL-1β in atypical cell types, and IL-1 function is also important for homeostatic processes that maintain a physiological state. This review focuses on the less studied, yet arguably more interesting biology of IL-1. We detail the production by, and effects of IL-1 on specific innate and adaptive immune cells, report how IL-1 is required for barrier function at multiple sites, and discuss how perturbation of IL-1 pathways can drive disease. Thus, although IL-1 is primarily studied for driving inflammation after release from macrophages, it is clear that it has a multifaceted role that extends far beyond this, with various unconventional effects of IL-1 vital for health. However, much is still unknown, and a detailed understanding of cell-type and context-dependent actions of IL-1 is required to truly understand this enigmatic cytokine, and safely deploy therapeutics for the betterment of human health.

Adhesion Molecules: Master Controllers of the Circulatory System

This manuscript will review our current understanding of cellular adhesion molecules (CAMs) relevant to the circulatory system, their physiological role in control of vascular homeostasis, innate and adaptive immune responses, and their importance in pathophysiological (disease) processes such as acute lung injury, atherosclerosis, and pulmonary hypertension. This is a complex and rapidly changing area of research that is incompletely understood. By design, we will begin with a brief overview of the structure and classification of the major groups of adhesion molecules and their physiological functions including cellular adhesion and signaling. The role of specific CAMs in the process of platelet aggregation and hemostasis and leukocyte adhesion and transendothelial migration will be reviewed as examples of the complex and cooperative interplay between CAMs during physiological and pathophysiological processes. The role of the endothelial glycocalyx and the glycobiology of this complex system related to inflammatory states such as sepsis will be reviewed. We will then focus on the role of adhesion molecules in the pathogenesis of specific disease processes involving the lungs and cardiovascular system. The potential of targeting adhesion molecules in the treatment of immune and inflammatory diseases will be highlighted in the relevant sections throughout the manuscript.

Monocyte trafficking across the vessel wall

Monocytes fundamentally contribute to immune surveillance and the inflammatory response in immunoinflammatory diseases like atherosclerosis. Recruitment of these cells to the site of injury requires their trafficking across the blood vessel wall. A series of events, including capture, rolling, slow rolling, arrest, adhesion strengthening, and lateral locomotion, precede monocyte transmigration. Recent investigations have revealed new aspects of this cascade. This article revisits some conventional paradigms and selectively highlights new findings, including novel insights into monocyte differentiation and recently identified functional mediators, signalling pathways, and new structural aspects of monocyte extravasation. The emerging roles of endothelial junctional molecules like vascular endothelial-cadherin and the junctional adhesion molecule family, adhesion molecules such as intercellular adhesion molecule-1, molecules localized to the lateral border recycling compartment like cluster of differentiation 99, platelet/endothelial cell adhesion molecule-1, and poliovirus receptor (CD155), as well as other cell surface molecules such as cluster of differentiation 146 and ephrins in transendothelial migration are discussed.

Interleukin-1β induces an inflammatory response and the breakdown of the endothelial cell layer in an improved human THBMEC-based in vitro blood-brain barrier model

BACKGROUND

The blood-brain barrier is necessary to provide an optimal environment for cerebral function. It consists of endothelial cells that interact through interendothelial tight junctions and form a barrier with low permeability. Therefore, the infiltration of lymphocytes into the central nervous system is limited. Pathological conditions, such as chronic-inflammatory diseases and viral infections, induce a breakdown in the blood-brain barrier, which facilitates the accumulation of immune cells in the brain.

NEW METHOD

Using the endothelial cell line "transfected human brain microvascular endothelial cells", we established an improved in vitro blood-brain barrier model. Using interleukin-1β, we refined this model into an inflammatory blood-brain barrier model.

RESULTS

The model is characterised by a transendothelial electrical resistance of 250 Ohm cm(2) and a permeability coefficient of 1×10(-6) cm/s for sodium fluorescein. IL-1β induces a strong inflammatory response, resulting in the increased expression of the adhesion molecule ICAM-1 and the pro-inflammatory cytokines IL-6, IL-8, and TNFα. Furthermore, the transendothelial electrical resistance decreased and the paracellular permeability increased in the presence of IL-1β. Additionally, the expression of the tight junction protein ZO-1 was reduced. As a consequence, an increased number of leukocytes were able to cross the cell layer.

COMPARISON WITH EXISTING METHODS

The model presented here exhibits improved characteristics with regards to TEER and permeability. The influence of IL-1β has not been described before in this model system.

CONCLUSION

The inflammatory in vitro blood-brain barrier model provides a useful tool for studying inflammatory processes at the blood-brain barrier, especially processes provoked by IL-1β.

Exposing endothelial cells to tumor necrosis factor-α and peripheral blood mononuclear cells damage endothelial integrity via interleukin-1ß by degradation of vascular endothelial-cadherin

BACKGROUND AND PURPOSE

We demonstrated previously that the administration of tumor necrosis factor alpha (TNF-α) for the treatment of solid tumors enhanced the response to chemotherapy by augmenting intratumoral drug accumulation. TNF-α changes the integrity of the endothelial cell monolayer in combination with interferon gamma (IFN-γ), which is further enhanced by the addition of peripheral blood mononuclear cells (PBMCs). The improved effect of PBMCs was mostly induced by the endogenous production of interleukin-1beta (IL-1ß) after TNF-α stimulation. In the current study, we demonstrate that exposing endothelial cells to TNF-α and PBMCs mediates the loss of vascular endothelial (VE)-cadherin, an important adherens junction protein for maintaining endothelial integrity, through endogenous IL-1ß. This loss increases permeability of the endothelial layer, thereby explaining the augmented passage of chemotherapeutics into the tumor.

METHODS

Human umbilical vein endothelial cells were exposed to TNF-α, IFN-γ, PBMCs, or IL-1ß, and the effects on the endothelial integrity were assessed by morphological changes and permeability changes with the use of fluorescein isothiocyanate-labeled bovine serum albumin flux. The loss of VE-cadherin was assessed using immunofluorescence, western blotting, and polymerase chain reaction.

RESULTS

Incubating endothelial cells with TNF-α, IFN-γ, and PBMCs increased cell elongation, gap formation, and subsequently the permeability of fluorescein isothiocyanate-labeled bovine serum albumin compared with control or TNF-α and IFN-γ-treated cells (P < .05). When PBMCs were replaced with IL-1ß, identical changes were observed. These changes in integrity were associated with a loss of VE-cadherin at the membrane.

CONCLUSION

We conclude that VE-cadherin is lost at the membrane when endothelial cells are exposed to TNF-α, IFN-γ, and PBMCs, which results in loss of integrity. IL-1ß can mimic the effects of PBMCs, indicating a dominant role of endogenously produced IL-1ß in this process.

On, around, and through: neutrophil-endothelial interactions in innate immunity

This manuscript will review our current understanding of neutrophilic polymorphonuclear leukocyte (neutrophil) interactions with the endothelium during immune and inflammatory responses, focusing on the molecular mechanisms regulating neutrophil adhesion to and migration through the endothelium in response to infection or tissue injury. This is a complex and dynamic area of research and one that has been the topic of several recent comprehensive reviews to which the interested reader is referred (64, 118, 131). By design, this review will begin with a brief review of some basic aspects of neutrophil biology and endothelial adhesion to provide a foundation. The remainder of the review will focus on selected areas of this complex field, specifically the role of the endothelial glycocalyx in regulating neutrophil adhesion and the mechanisms and consequences of migration of neutrophils between (paracellular) and through (transcellular) endothelial cells during egress from the vasculature.

Monocyte trans-endothelial migration augments subsequent transmigratory activity with increased PECAM-1 and decreased VE-cadherin at endothelial junctions

BACKGROUND

Although the importance of monocyte trans-endothelial migration in early atherogenesis is well recognized, it is unclear whether and how one transmigration event affects endothelium to facilitate subsequent ones. In this study, we tested the hypothesis that monocyte transmigration alters endothelial junctional organization to facilitate subsequent transmigration.

METHODS AND RESULTS

When human monocytes were added twice at intervals of ≈30 min to IL-1beta-prestimulated human umbilical vein endothelial cells in vitro, significant augmentation of transmigration was observed at the second addition (≈1.5-fold, analyzed from a total of 231 monocytes in 3 experiments). Endothelial surface expressions of two major junctional molecules, PECAM-1 and VE-cadherin, increased and decreased respectively, in response to monocyte addition, which could facilitate subsequent transmigration. To further investigate spatiotemporal dynamics of the increasing molecule, PECAM-1, we constructed a PECAM-1-GFP expression system and found that monocyte transmigration induced local accumulation of endothelial PECAM-1 around the transmigration spot, which was followed by transmigration of subsequent monocyte around the same location. Detailed analysis revealed that within the defined region around one transmigration event, 50% of later transmigrating monocytes used the same or similar location as the previous one (10 out of 20 transmigrating monocytes in 11 experiments).

CONCLUSIONS

These findings show that monocyte trans-endothelial migration alters endothelial junctional organization to a more monocyte-permeable state (increased PECAM-1 and decreased VE-cadherin), resulting in the augmented transmigratory activity at a later stage. This positive feedback mechanism is partially associated with monocyte transmigration-induced local accumulation of endothelial PECAM-1, which promotes transmigration of following monocytes at the same location.

Targeting Robo4-dependent Slit signaling to survive the cytokine storm in sepsis and influenza

The innate immune system provides a first line of defense against invading pathogens by releasing multiple inflammatory cytokines, such as interleukin-1beta and tumor necrosis factor-alpha, which directly combat the infectious agent and recruit additional immune responses. This exuberant cytokine release paradoxically injures the host by triggering leakage from capillaries, tissue edema, organ failure, and shock. Current medical therapies target individual pathogens with antimicrobial agents or directly either blunt or boost the host's immune system. We explored a third approach: activating with the soluble ligand Slit an endothelium-specific, Robo4-dependent signaling pathway that strengthens the vascular barrier, diminishing deleterious aspects of the host's response to the pathogen-induced cytokine storm. This approach reduced vascular permeability in the lung and other organs and increased survival in animal models of bacterial endotoxin exposure, polymicrobial sepsis, and H5N1 influenza. Thus, enhancing the resilience of the host vascular system to the host's innate immune response may provide a therapeutic strategy for treating multiple infectious agents.

IL-1B-511 polymorphism is associated with increased risk of certain subtypes of gastric cancer in Chinese: a case-control study

OBJECTIVES

The association of interleukin-1B (IL-1B)-511 polymorphism with gastric cancer is still controversial, and the association of IL-1B-511 polymorphism with subtypes of gastric cancer is still largely unknown. We investigated whether the association between IL-1B-511 polymorphism and gastric cancer risk varies by clinically important tumor characteristics and the prognostic value of this polymorphism in a large population-based case-control study among Chinese.

METHODS

A population-based case-control study was conducted between 1999 and 2006 in Guangdong Province, China. A total of 1,010 gastric cancer patients and 1,500 healthy controls were enrolled in this study. Polymorphism in IL-1B-511 was analyzed by PCR-restriction fragment length polymorphism on 501 gastric cancers and 500 healthy controls.

RESULTS

Compared with the CC genotype, carriers of IL-1B-511 TT genotype had an increased gastric cancer risk (odds ratio (OR)=1.97, 95% confidence interval (CI)=1.29-3.01, P=0.0016). TT genotype was significantly associated with intestinal type of gastric cancer (OR=3.16, 95% CI=1.74-5.71, P=0.0001) but not with diffuse or mixed-type gastric cancer. The test for OR heterogeneity between the intestinal-type and non-intestinal-type gastric cancers was statistically significant (P=0.02). In subgroup analyses, TT genotype was found to be associated with poorly differentiated gastric cancer (OR=3.31, 95% CI=1.43-3.60, P<0.0001), but not with moderately or well-differentiated gastric cancer. IL-1B-511 genotypes were not associated with the prognosis of gastric cancer patients.

CONCLUSIONS

IL-1B polymorphism influences certain subtypes of gastric cancer according to the clinical and pathological features. Understanding the etiologic heterogeneity of gastric cancer may result in improvements in controlling this disorder.

Recent developments and complexities in neutrophil transmigration

PURPOSE OF REVIEW

As the migration of neutrophils from blood to inflamed tissues is an essential component of innate immunity and a key contributing factor to the pathogenesis of inflammatory disorders, this aspect of leukocyte biology continues to be a highly dynamic field of research. This review summarizes recent findings in this area, focusing on the mechanisms that mediate neutrophil transmigration, an area where significant progress has been made.

RECENT FINDINGS

The topics to be covered will include responses that are prerequisite to neutrophil migration through venular walls, such as leukocyte luminal crawling and cellular and molecular changes in leukocytes and endothelial cells (e.g. formation of protrusions) that collectively support leukocyte transendothelial cell migration. Advances in both paracellular and transcellular neutrophil migration through endothelial cells will be discussed, addressing the associated roles and regulation of expression of endothelial cell luminal and junctional adhesion molecules. Beyond the endothelium, migration through the vascular pericyte coverage and basement membrane will be reviewed.

SUMMARY

The unquestionable role of neutrophils in the development and progression of inflammatory conditions suggests that a better understanding of the tissue-specific and stimulus-specific mechanisms that mediate this response may identify novel pathways that could be exploited for the development of more specific anti-inflammatory interventions.

Mechanisms for transcellular diapedesis: probing and pathfinding by 'invadosome-like protrusions'

Immune-system functions require that blood leukocytes continuously traffic throughout the body and repeatedly cross endothelial barriers (i.e. diapedese) as they enter (intravasate) and exit (extravasate) the circulation. The very earliest studies to characterize diapedesis directly in vivo suggested the coexistence of two distinct migratory pathways of leukocytes: between (paracellular pathway) and directly through (transcellular pathway) individual endothelial cells. In vivo studies over the past 50 years have demonstrated significant use of the transcellular diapedesis pathway in bone marrow, thymus, secondary lymphoid organs, various lymphatic structures and peripheral tissues during inflammation and across the blood-brain barrier and blood-retinal barrier during inflammatory pathology. Recently, the first in vitro reports of transcellular diapedesis have emerged. Together, these in vitro and in vivo observations suggest a model of migratory pathfinding in which dynamic 'invadosome-like protrusions' formed by leukocytes have a central role in both identifying and exploiting endothelial locations that are permissive for transcellular diapedesis. Such 'probing' activity might have additional roles in this and other settings.

Smooth muscle alpha-actin and calponin expression and extracellular matrix production of human coronary artery smooth muscle cells in 3D scaffolds

For a tissue-engineered coronary artery substitute to be a viable clinical option in the treatment of vascular diseases, it is necessary to use tissue-specific human cells. Coronary artery smooth muscle cells are the main resident cells in the tunica media of arteries. In this work, we examined the behavior and differentiation state of human coronary artery smooth muscle cells (HCASMCs) when cultured on 3D polyurethane scaffolds to fabricate hybrid vascular tissues. As the mechanical strength of the scaffold is an important element in engineered hybrid vascular substitutes, porous 3D polyurethane scaffolds fabricated using paraffin spheres and ammonium chloride particles were tested for their mechanical properties both in tension and in compression. The use of ammonium chloride particles as porogen generated scaffolds with superior mechanical properties, which are suitable for vascular tissue engineering. When seeded on uncoated, fibronectin-coated, and Matrigel-coated scaffolds, HCASMCs were well spread and started producing collagen as judged by histochemical analysis but appeared to lack elastin production. Fibronectin coating appeared to promote the infiltration of HCASMCs into the scaffold better than Matrigel coating but did not appear to affect the expression of collagen and elastin. Western blot analyses after successful cell recovery from the scaffolds indicated that HCASMCs, after culturing for 4 and 7 days, expressed similar amounts of smooth muscle alpha-actin and calponin regardless of extracellular matrix coating. Taken together, our data showed that the behavior and differentiation phenotype of HCASMCs can be analyzed after culture in 3D polyurethane scaffolds to establish appropriate conditions that will favor the fabrication of hybrid-engineered vascular substitutes.

Endothelial signaling in paracellular and transcellular leukocyte transmigration

As the primary physical barrier between blood and tissue compartments within the body, blood vessel endothelial cells and integrity of the cell junctions connecting them must be carefully regulated to support leukocyte transendothelial migration only when necessary. Leukocytes utilize two independent routes across the endothelium: the paracellular route involves migration in-between adjacent endothelial cells and requires the transient disassembly of endothelial cell junctions, while the transcellular route occurs directly through an individual endothelial cell, likely requiring the formation of a channel or pore. In this review, I will first summarize the signaling events that are transduced by leukocyte engagement of endothelial cell-surface receptors like ICAM-1 and VCAM-1. Some of these signals include activation of GTPases, production of reactive oxygen species, and phosphorylation of target proteins. These signaling pathways converge to cause junctional disruption, cytoskeletal remodeling, and/or the membrane fusion events that are associated with leukocyte transendothelial migration. The review will conclude with a detailed discussion of the newly characterized transmigratory cup structure, and the recent advances made towards understanding the mechanisms of transcellular transendothelial migration.

Trans-cellular migration: cell-cell contacts get intimate

Trans-cellular migration, the movement of one cell directly through another, seems an unlikely, counterintuitive, and even bizarre process. Trans-cellular migration has been reported for nearly half a century in leukocyte transendothelial migration in vivo, but is not well enough accepted to widely feature in textbook accounts of diapedesis. Recently, the first in vitro and additional in vivo observations of trans-cellular diapedesis have been reported. Mechanisms by which this occurs are just beginning to be elucidated and point to podosome-like protrusive activities in leukocytes and specific fusogenic functions in endothelial cells. Emerging evidence for a quantitatively significant contribution of trans-cellular migration to leukocyte trafficking in increasingly diverse settings suggests that this phenomenon represents an important and physiologic cell biological process.

Polyurethane biomaterials for fabricating 3D porous scaffolds and supporting vascular cells

Successful tissue engineering of vascular grafts largely depends on synthetic scaffolds that support the survival, proliferation, and differentiation of seeded cells. To investigate the utility of polyurethanes for vascular tissue engineering, three-dimensional porous polyurethane scaffolds with highly interconnected pore structures were fabricated by a pressure differential/particulate leaching technique. Ammonium chloride and paraffin porogens were prepared to fabricate the scaffolds. Grinding of ammonium chloride resulted in particulates with uniform particle sizes but irregular shapes. Paraffin particulates made by a dispersion method, on the other hand, had spherical shapes and uniform particle sizes. Polyurethane scaffolds fabricated from these particulates had open faced, highly interconnected channels that could allow cellular infiltration and nutrient delivery. Human coronary artery smooth muscle and endothelial cell interactions with polyurethane surfaces revealed these biomaterials to maintain the contractile phenotype of human coronary artery smooth muscle cells and the formation of endothelial monolayers. During longer culture times, surface modification with cell adhesive extracellular matrix (ECM) protein promoted vascular cell proliferation, maintenance of the differentiated phenotype and endothelial monolayer integrity. Our results suggest that these polyurethanes, in conjunction with cell adhesive ECM proteins, could also support vascular cells in three-dimensional bioreactor-based culture conditions.

ICAM-1-Mediated, Src- and Pyk2-Dependent Vascular Endothelial Cadherin Tyrosine Phosphorylation Is Required for Leukocyte Transendothelial Migration

Leukocyte transendothelial migration (TEM) has been modeled as a multistep process beginning with rolling adhesion, followed by firm adhesion, and ending with either transcellular or paracellular passage of the leukocyte across the endothelial monolayer. In the case of paracellular TEM, endothelial cell (EC) junctions are transiently disassembled to allow passage of leukocytes. Numerous lines of evidence demonstrate that tyrosine phosphorylation of adherens junction proteins, such as vascular endothelial cadherin (VE-cadherin) and beta-catenin, correlates with the disassembly of junctions. However, the role of tyrosine phosphorylation in the regulation of junctions during leukocyte TEM is not completely understood. Using human leukocytes and EC, we show that ICAM-1 engagement leads to activation of two tyrosine kinases, Src and Pyk2. Using phospho-specific Abs, we show that engagement of ICAM-1 induces phosphorylation of VE-cadherin on tyrosines 658 and 731, which correspond to the p120-catenin and beta-catenin binding sites, respectively. These phosphorylation events require the activity of both Src and Pyk2. We find that inhibition of endothelial Src with PP2 or SU6656 blocks neutrophil transmigration (71.1 +/- 3.8% and 48.6 +/- 3.8% reduction, respectively), whereas inhibition of endothelial Pyk2 also results in decreased neutrophil transmigration (25.5 +/- 6.0% reduction). Moreover, overexpression of the nonphosphorylatable Y658F or Y731F mutants of VE-cadherin impairs transmigration of neutrophils compared with overexpression of wild-type VE-cadherin (32.7 +/- 7.1% and 38.8 +/- 6.5% reduction, respectively). Our results demonstrate that engagement of ICAM-1 by leukocytes results in tyrosine phosphorylation of VE-cadherin, which is required for efficient neutrophil TEM.