Degranulation of eosinophils mediated by intercellular adhesion molecule-1 and its ligands is involved in adhesion molecule expression on endothelial cells-selective induction of VCAM-1

Value of Absolute Eosinophil Count in Patients with Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention

Background and Aims

Elevated eosinophils typically indicate hypersensitive inflammation; however, their involvement in cardiovascular events remains incompletely understood. We investigated the association between the absolute eosinophil count (AEC) and major adverse cardiovascular and cerebrovascular events (MACCEs) in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI). Additionally, we determine whether the integration of AEC with the SYNTAX II score could improve predictive ability.

Methods and Results

The AECs of 1711 patients with ACS undergoing PCI from June 2016 to November 2017 were analyzed on admission. All recruitments were splitted into three groups based on AEC tertiles and 101 participants underwent one or more noteworthy outcomings. The association between AEC and MACCEs (defined as a composite of cardiovascular death, myocardial infarction [MI], and stroke) was tested by Cox proportional-hazards regression analysis. After adjusting for confounders, AEC was independently associated with MACCEs (HR 11.555, 95% CI: 3.318-40.239). Patients in the lowest AEC tertile (T1) as a reference, those in the higher tertiles had an incrementally higher risk of MACCEs (T3: HR 1.848 95% CI: 1.157-2.952; P for trend=0.008). Inclusion of AEC enhanced the predictive accuracy of the SYNTAX II score for MACCEs (AUC: from 0.701 [95% CI: 0.646-0.756] to 0.728 [95% CI: 0.677-0.780]; DeLong's test, P = 0.020).

Conclusion

AEC is independently linked to MACCEs in ACS patients who underwent PCI, and adds incremental predictive information to the SYNTAX II score.

Eosinophil-platelet interactions promote atherosclerosis and stabilize thrombosis with eosinophil extracellular traps

Clinical observations implicate a role of eosinophils in cardiovascular diseases because markers of eosinophil activation are elevated in atherosclerosis and thrombosis. However, their contribution to atherosclerotic plaque formation and arterial thrombosis remains unclear. In these settings, we investigated how eosinophils are recruited and activated through an interplay with platelets. Here, we provide evidence for a central importance of eosinophil-platelet interactions in atherosclerosis and thrombosis. We show that eosinophils support atherosclerotic plaque formation involving enhanced von Willebrand factor exposure on endothelial cells and augmented platelet adhesion. During arterial thrombosis, eosinophils are quickly recruited in an integrin-dependent manner and engage in interactions with platelets leading to eosinophil activation as we show by intravital calcium imaging. These direct interactions induce the formation of eosinophil extracellular traps (EETs), which are present in human thrombi and constitute a substantial part of extracellular traps in murine thrombi. EETs are decorated with the granule protein major basic protein, which causes platelet activation by eosinophils. Consequently, targeting of EETs diminished thrombus formation in vivo, which identifies this approach as a novel antithrombotic concept. Finally, in our clinical analysis of coronary artery thrombi, we identified female patients with stent thrombosis as the population that might derive the greatest benefit from an eosinophil-inhibiting strategy. In summary, eosinophils contribute to atherosclerotic plaque formation and thrombosis through an interplay with platelets, resulting in mutual activation. Therefore, eosinophils are a promising new target in the prevention and therapy of atherosclerosis and thrombosis.

Emerging Roles of Vascular Cell Adhesion Molecule-1 (VCAM-1) in Immunological Disorders and Cancer

Tumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine that triggers the expression of inflammatory molecules, including other cytokines and cell adhesion molecules. TNFα induces the expression of intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 (VCAM-1). VCAM-1 was originally identified as a cell adhesion molecule that helps regulate inflammation-associated vascular adhesion and the transendothelial migration of leukocytes, such as macrophages and T cells. Recent evidence suggests that VCAM-1 is closely associated with the progression of various immunological disorders, including rheumatoid arthritis, asthma, transplant rejection, and cancer. This review covers the role and relevance of VCAM-1 in inflammation, and also highlights the emerging potential of VCAM-1 as a novel therapeutic target in immunological disorders and cancer.

Soluble vascular cell adhesion molecule-1 induces human eosinophil migration

BACKGROUND

Tissue eosinophilia is one of the hallmarks of allergic diseases and Th2-type immune responses including asthma. Adhesion molecules are known to play an important role in the accumulation of eosinophils in allergic inflammatory foci, and they contribute to eosinophil activation. Elevated levels of the soluble forms of adhesion molecules in the body fluid of asthmatic patients have been observed, although their pathophysiological significance remains to be fully elucidated.

METHODS

Peripheral blood eosinophils were purified, and the effect of soluble vascular cell adhesion molecule-1 (sVCAM-1) on eosinophil migration was investigated using in vitro systems.

RESULTS

We found that sVCAM-1 (1 to 10 mug/ml) induced eosinophil chemotaxis, rather than chemokinesis, in a concentration-dependent fashion. In addition, sVCAM-1 induced cell shape change and actin polymerization, which are necessary for cell movement. Manipulations with very late antigen (VLA)-4-neutralizing antibody and signal inhibitors indicated that the sVCAM-1-induced chemotaxis was mediated through ligand-dependent activation of tyrosine kinase Src, p38 mitogen-activated protein kinase (MAPK), and extracellular signal-regulated kinase (ERK) MAPK. Rapid phosphorylation of these signaling molecules was observed using a bead-based multiplex assay.

CONCLUSION

Our results raise the possibility of sVCAM-1 in the fluid phase as a significant contributor to the heightened eosinophilic inflammatory response.

Targeted inactivation of endothelial lipase attenuates lung allergic inflammation through raising plasma HDL level and inhibiting eosinophil infiltration

Endothelial lipase (EL) is a novel phospholipase that determines plasma high-density lipoprotein cholesterol (HDL-C) levels. We have investigated the role of HDL-C in lung allergic inflammation by using EL knockout (EL-KO) mice that are high in HDL-C. EL-KO and wild-type control mice were sensitized and challenged with ovalbumin to evoke eosinophilic inflammation in the lung. EL was expressed in epithelial cells, alveolar type II cells, and endothelial cells in the lung, and its expression was upregulated during inflammation. Concomitant with attenuated hyperresponsiveness of the airway smooth muscles, the number of eosinophils in bronchoalveolar lavage and the expression of VCAM-1 were lower in EL-KO mice than in control mice. HDL reduced cytokine-induced VCAM-1 expression in cultured endothelial cells. When plasma HDL levels were decreased to similar levels in both mouse groups by adenovirus-mediated overexpression of EL, however, eosinophil infiltration was still lower in EL-KO mice. In vitro adhesion assays revealed that EL expression on the cell surface promoted the interaction of eosinophils through the ligand-binding function of EL. In summary, targeted inactivation of EL attenuated allergic inflammation in the lung, and the protective effects in EL-KO mice were associated with high plasma HDL levels, downregulation of VCAM-1, and loss of the direct ligand-binding function of EL. Thus EL is a novel modulator of the progression of allergic asthma.

Coexpression of IL-5 and eotaxin-2 in mice creates an eosinophil-dependent model of respiratory inflammation with characteristics of severe asthma

Mouse models of allergen provocation and/or transgenic gene expression have provided significant insights regarding the cellular, molecular, and immune responses linked to the pathologies occurring as a result of allergic respiratory inflammation. Nonetheless, the inability to replicate the eosinophil activities occurring in patients with asthma has limited their usefulness to understand the larger role(s) of eosinophils in disease pathologies. These limitations have led us to develop an allergen-naive double transgenic mouse model that expresses IL-5 systemically from mature T cells and eotaxin-2 locally from lung epithelial cells. We show that these mice develop several pulmonary pathologies representative of severe asthma, including structural remodeling events such as epithelial desquamation and mucus hypersecretion leading to airway obstruction, subepithelial fibrosis, airway smooth muscle hyperplasia, and pathophysiological changes exemplified by exacerbated methacholine-induced airway hyperresponsiveness. More importantly, and similar to human patients, the pulmonary pathologies observed are accompanied by extensive eosinophil degranulation. Genetic ablation of all eosinophils from this double transgenic model abolished the induced pulmonary pathologies, demonstrating that these pathologies are a consequence of one or more eosinophil effector functions.

Expression and regulation of intercellular adhesion molecule-1 on airway parasympathetic nerves

BACKGROUND

Eosinophils cluster along airway nerves in patients with asthma and release eosinophil major basic protein, an antagonist of inhibitory M2 muscarinic receptors on nerves. Blocking M2 function increases bronchoconstriction, leading to airway hyperreactivity. Intercellular adhesion molecule-1 (ICAM-1) mediates eosinophil adhesion to nerves.

OBJECTIVE

We investigated mechanisms of ICAM-1 expression by parasympathetic nerves.

METHODS

ICAM-1 expression was examined by immunocytochemistry of lung sections from ovalbumin-sensitized and challenged guinea pigs. ICAM-1 was measured in parasympathetic nerves isolated from subjects and guinea pigs and in human neuroblastoma cells by real-time RT-PCR, immunocytochemistry, and Western blot.

RESULTS

ICAM-1 was not detected in control airway parasympatheric nerves in vivo or in cultured cells. ICAM-1 was expressed throughout antigen-challenged guinea pig lung tissue and was selectively decreased by dexamethasone only in nerves. ICAM-1 was induced in human and guinea pig parasympathetic nerves by TNF-alpha and IFN-gamma and was inhibited by dexamethasone and by an inhibitor of nuclear factor-kappaB (NF-kappaB). In neuroblastoma cell lines TNF-alpha and IFN-gamma-induced ICAM-1 was blocked by an inhibitor of NF-kappaB but not by inhibitors of mitogen-activated protein kinases. Dexamethasone did not inhibit ICAM-1 expression in neuroblastoma cells.

CONCLUSIONS

ICAM-1 induced in nerves by antigen challenge and proinflammatory cytokines is sensitive to dexamethasone. ICAM-1 expression is also sensitive to inhibitors of NF-kappaB. Neuroblastoma cells mimic many, but not all, characteristics of ICAM-1 expression in parasympathetic nerves.

CLINICAL IMPLICATIONS

Dexamethasone and NF-kappaB inhibitors could prevent eosinophils from adhering to nerves by blocking ICAM-1 expression on parasympathetic nerves, thus protecting inhibitory M2 muscarinic receptors and making this pathway a potential target for asthma treatment.

The effect of overexpression of endothelial nitric oxide synthase on eosinophilic lung inflammation in a murine model

The effects of nitric oxide (NO) on allergic inflammation are controversial. In particular, the role of endothelial nitric oxide synthase (eNOS) in asthma remains uncertain. In the present study, we examined the effects of overexpression of eNOS on allergic inflammation using eNOS transgenic (eNOS-Tg) mice, in which eNOS protein is overexpressed in the vascular endothelium and airway epithelium. We found that eNOS-Tg mice showed a reduction of the asthmatic response to allergen challenge. Eosinophilic accumulation in the airspaces, eosinophilic activity, and bronchial responsiveness to acetylcholine were significantly attenuated in eNOS-Tg mice, as compared with wild-type mice following ovalbumin sensitization/challenge, even though the levels of circulating eosinophils were comparable in the wild-type and eNOS-Tg mice. The concentrations of eotaxin in the bronchoalveolar lavage fluid were significantly less in eNOS-Tg mice than in the wild-type mice. In addition, immunohistochemical analysis showed that the expressions of both intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 on the pulmonary endothelium of eNOS-Tg mice was decreased compared with the controls. These results suggest that chronic eNOS overexpression contributes to the suppression of allergic inflammation by reducing the production of eotaxin in the airspaces and/or the expression of adhesion molecules in the vascular endothelium.

Vascular adhesion and transendothelial migration of eosinophil leukocytes

Tissues respond to injury with inflammation in an effort to protect and repair the damaged site. During inflammation, leukocytes typically accumulate in response to certain chemicals produced within the tissue itself. The passage of leukocytes through the vascular lumen into tissues occurs in several phases, including rolling, activation, firm adhesion, transendothelial migration, and subendothelial migration. Although infiltration of eosinophil leukocytes is one of the most important aspects of allergic inflammatory reactions, eosinophils also participate in nonallergic inflammation. Eosinophil accumulation is regulated not only by endothelial adhesion molecules, but also by interactions between eosinophil adhesion molecules and extracellular matrix elements. This review summarizes the regulation of eosinophil leukocyte adhesion and migration. A better understanding of eosinophil recruitment responses may lead to the development of novel therapeutics for chronic allergic diseases.

Altered tissue expression pattern of cell adhesion molecules, ICAM-1, E-selectin and VCAM-1, in bullous pemphigoid during methotrexate therapy

Little is known about how eosinophils accumulate in bullous pemphigoid (BP) and why these cells rapidly disappear during immunosuppressive therapy. Eosinophils can produce cytokines such as IL-4, IL-5, IL-6, IL-10 and IL13, which can induce endothelial cells to express cellular adhesion molecules (CAMs) such as E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) necessary for the recruitment of eosinophils from the bloodstream to the skin. The present aim was to investigate the cellular expression of these three CAMs in serial biopsies before and during oral low-dose methotrexate therapy. Seventy-four biopsy specimens, 37 from active lesions and 37 from normal skin, were taken at different intervals from eight patients with bullous pemphigoid and stained immunohistochemically with specific monoclonal antibodies for these three CAMs. The expression and distribution of CAMs in the biopsies was evaluated and scored with light-microscopic examination. The basal keratinocytes in active lesions expressed ICAM-1. A strong VCAM-1 expression of endothelial cells and pericytes was correlated to a perivascular inflammatory cell infiltrate that also showed intense immunoreactivity to ICAM-1. Endothelial cell/pericytes also expressed E-selectin strongly in the BP patients before therapy. The expression of CAMs faded during therapy and, to the best of our knowledge, this has not been previously reported. Thus we suggest that the rapid reduction of tissue eosinophils may reflect the altered pattern of cell adhesion molecules during immunosuppressive therapy, which could explain the prompt clinical improvement seen in BP patients treated with methotrexate.

Modification of eosinophil function by suplatast tosilate (IPD), a novel anti-allergic drug

Suplatast tosilate (IPD), a new dimethylsulfonium agent, is used therapeutically in allergic diseases. Suplatast has been reported to attenuate airway hyperresponsiveness in guinea pigs, human IgE synthesis, and murine peritoneal eosinophilia. However, the effect of suplatast on human eosinophils is not known. In this study, we examined the effects of suplatast in human eosinophils on platelet activating factor (PAF, 1 microM)-induced chemotaxis by the blind well chamber technique, eosinophil adhesion to TNF-alpha (10 ng/ml) or IL-4 (10 ng/ml)-stimulated human umbilical vein endothelial cells (HUVECs), and expression of very late antigen-4 (VLA-4) on eosinophils and vascular cell adhesion molecule-1 (VCAM-1) on HUVECs by flow cytometry. Suplatast suppressed IL-4-induced eosinophil adhesion to HUVECs in a dose-dependent manner. Eosinophils from the normal subjects did not express VLA-4. However, there was a significant increase (P < 0.01) in the basal expression of VLA-4 in allergic patients. PAF or IL-4 did not enhance VLA-4 expression on eosinophils, and there was no significant effect of suplatast on VLA-4 expression in allergic patients. Suplatast did not affect TNF-alpha-induced VCAM-1 expression. Interestingly, suplatast significantly suppressed IL-4 induced VCAM-1 expression on HUVECs and PAF-induced eosinophil chemotaxis. These data suggest that suplatast may modify eosinophil participation in airway inflammation by attenuating inflammatory mediators-induced chemotaxis and adhesion to endothelial cells, and thus might be useful in the treatment of bronchial asthma.

IL-12-dependent vascular cell adhesion molecule-1 expression contributes to airway eosinophilic inflammation in a mouse model of asthma-like reaction

Bronchial-alveolar eosinophilic inflammation is among the characteristic pathological changes in asthma, which has been shown to be correlated with type 2 cytokine and chemokine production. Exogenous IL-12 has been found to be inhibitory for pulmonary eosinophilia in reported studies. Using a murine asthma-like model induced by OVA, we found in the present study that IL-12 gene knockout (KO) mice showed substantially reduced airway recruitment of eosinophils compared with wild-type control mice following OVA sensitization/challenge, although the levels of circulating eosinophils were comparable in these two groups of mice. Cytokine analysis showed Ag-driven Th1 (IFN-gamma) and Th2 (IL-4, IL-5, IL-10, and IL-13) cytokine production by CD4 T cells from local draining lymph nodes and spleen. Similarly, local eotaxin production was comparable in wild-type and IL-12 KO mice. In contrast, immunohistochemical analysis showed that the expression of VCAM-1 on the lung endothelium of IL-12 KO mice was dramatically less than that in wild-type mice. Furthermore, administration of rIL-12 at the stage of sensitization and challenge with OVA restored airway eosinophilia and VCAM-1 expression in IL-12 KO mice. The results suggest that endogenous IL-12 contributes to the recruitment of eosinophils into airways observed in asthma, possibly via enhancement of the expression of VCAM-1 on local vascular endothelial cells.

Expression of vascular cell adhesion molecule-1, alpha4-integrin and L-selectin during inner ear immunity reaction

The expression of vascular cell adhesion molecule-1 (VCAM-1), alpha4-integrin and L-selectin was dynamically observed using an immunohistochemical approach during labyrinthitis induced by inoculation of keyhole limpet hemocyanin into the scala tympani of animals that had been systemically sensitized to it. At the same time, we used ELISA to monitor interleukin-1(IL-1) in the peripheral blood of these animals. The expression of alpha4-integrin and L-selectin on the surface of leukocytes in peripheral blood was examined by flow cytometry. VCAM-1 was found on the endothelial surface of the spiral modiolar vein (SMV) and its collecting venules (CV) at 24 h post-challenge; the VCAM-1 level reached a maximum on day 2, which was maintained until 1 week post-challenge, and then declined gradually. Alpha4-integrin was found on the surface of leukocytes, mainly monocytes and lymphocytes, that had infiltrated the SMV, CV, cochlear nerve and perilymph by 24 h post-challenge; the alpha4-integrin level reached a maximum on day 2 and then decreased rapidly. At 1 week post-challenge, no significant expression of alpha4-integrin was seen. Expression of alpha4-integrin and L-selectin was also observed on leukocytes in peripheral blood. No L-selectin was observed on the surface of leukocytes during inner ear inflammation. The expression of L-selectin on the surface of leukocytes in the peripheral blood appeared to be downregulated during inflammation. The concentrations of IL-1 in the peripheral blood increased commensurately during inner ear inflammation. These results further elucidate the role of adhesion molecules during inner ear immune responses. The increased expression of VCAM-1 on SMV and CV was correlated with the concentration of IL-1 in peripheral blood during inner ear inflammation.

Signaling through the beta2 integrin prolongs eosinophil survival

BACKGROUND

Recently, adhesion molecules have been suggested to play an important role in allergic inflammatory diseases such as bronchial asthma. It is unclear whether eosinophil activation and paracrine or autocrine synthesis of eosinophilopoietic growth cytokines is mediated through signaling by intercellular adhesion molecule-1 (ICAM-1) and the beta2 integrin family.

OBJECTIVE

We examined whether signaling by ICAM-1 and its ligands (beta2 integrins) could prolong eosinophil survival.

METHODS

Eosinophils were isolated from patients with hypereosinophilia by modified CD16 negative selection. After culture with or without recombinant soluble ICAM-1, eosinophil viability was measured by trypan blue dye exclusion.

RESULTS

Eosinophil survival was prolonged in cultures with recombinant soluble ICAM-1 compared with cultures without it (P <.01 on days 2, 4, and 6); this effect was dose-dependent. Eosinophil survival in cultures with recombinant soluble ICAM-1 was significantly inhibited by antibodies against ICAM-1 (P <.01), complement receptor 3 (P <.01), and lymphocyte function-associated antigen-1beta (P <.01). Anti-IL-3 showed no effect on eosinophil survival, whereas anti-IL-5 caused partial inhibition of survival. Interestingly, anti-granulocyte/macrophage colony-stimulating factor caused the complete inhibition of eosinophil survival in cultures with recombinant soluble ICAM-1.

CONCLUSION

These results suggested the importance of the beta2 integrins in eosinophil-mediated allergic inflammation.

Human eosinophil-airway smooth muscle cell interactions

Eosinophils are present throughout the airway wall of asthmatics. The nature of the interaction between human airway smooth muscle cells (ASMC) and eosinophils was investigated in this study. We demonstrated, using light microscopy, that freshly isolated eosinophils from healthy donors rapidly attach to ASMC in vitro. Numbers of attached eosinophils were highest at 2 h, falling to 50% of maximum by 20 h. Eosinophil attachment at 2 h was reduced to 72% of control by anti-VCAM-1, and to 74% at 20 h by anti-ICAM-1. Pre-treatment of ASMC for 24h with TNF-alpha, 10 nM, significantly increased eosinophil adhesion to 149 and 157% of control after 2 and 20 h. These results provide evidence that eosinophil interactions with ASMC involve VCAM-1 and ICAM-1 and are modulated by TNF-alpha.