Dendritic cell adhesion is enhanced on endothelial cells preexposed to calcineurin inhibitors

The immunosuppressant drug Cyclosporin A aggravates irradiation effects in endothelial cells

The immunosuppressant drug Cyclosporin A (CsA) has been widely used to prevent the development of Graft-versus-Host Disease (GvHD) that can occur after transplantation, including allogeneic graft after accidental high-dose irradiation in humans. Here, we show that CsA alone stimulates ICAM-1 overexpression in human pulmonary microvascular endothelial cells (HPMECs) through Toll-Like Receptor 4 (TLR4) and NF-κB activation. In HPMECs, CsA treatment significantly worsened the overexpression of ICAM-1 induced by high-dose irradiation (15 Gy). This additive effect of CsA was also observed when ICAM-1 overexpression was induced by another pathway (Ca²⁺ entry) in macrovascular endothelial cells. In addition, CsA triggered apoptosis as well as rearrangement of the actin cytoskeleton and adherens junctions (VE-Cadherin) in microvascular endothelial monolayers. High-dose irradiation triggered similar deleterious effects in endothelial monolayers and, again, CsA treatment strongly aggravated the effects of irradiation. Altogether, these results suggest that post-transplant CsA treatment may exacerbate the deleterious effects of irradiation on the endothelium.

Inflammation research sails through the sea of immunology to reach immunometabolism

Inflammation occurs as a result of acute trauma, invasion of the host by different pathogens, pathogen-associated molecular patterns (PAMPs) or chronic cellular stress generating damage-associated molecular patterns (DAMPs). Thus inflammation may occur under both sterile inflammatory conditions including certain cancers, autoimmune or autoinflammatory diseases (Rheumatic arthritis (RA)) and infectious diseases including sepsis, pneumonia-associated acute lung inflammation (ALI) or acute respiratory distress syndrome (ARDS). The pathogenesis of inflammation involves dysregulation of an otherwise protective immune response comprising of various innate and adaptive immune cells and humoral (cytokines and chemokines) mediators secreted by these immune cells upon the activation of signaling mechanisms regulated by the activation of different pattern recognition receptors (PRRs). However, the pro-inflammatory and anti-inflammatory action of these immune cells is determined by the metabolic stage of the immune cells. The metabolic process of immune cells is called immunometabolism and its shift determined by inflammatory stimuli is called immunometabolic reprogramming. The article focuses on the involvement of various immune cells generating the inflammation, their interaction, immunometabolic reprogramming, and the therapeutic targeting of the immunometabolism to manage inflammation.

Epidermal Growth Factor–Like Domain 7 Is a Novel Inhibitor of Neutrophil Adhesion to Coronary Artery Endothelial Cells Injured by Calcineurin Inhibition

Background—

We investigated the effect of epidermal growth factor–like domain 7 (Egfl7) on nuclear factor-κB activation, intercellular adhesion molecule-1 expression, and neutrophil adhesion to human coronary artery endothelial cells after calcineurin-inhibition–induced injury.

Methods and Results—

Human coronary endothelial cells were incubated with cyclosporine (CyA) 10 μg/mL with or without Egfl7 (100 ng/mL) or the Notch receptor activator Jagged1 (200 ng/mL) for 6 to 48 hours. CyA upregulated nuclear factor-κB (p65) activity (128±2% of control, P <0.001) in nuclear extracts, as determined with a DNA-binding activity ELISA. This activity was inhibited by Egfl7 (86±3% of control; P <0.001 versus CyA alone). Jagged1 blocked Egfl7-induced nuclear factor-κB inhibition (105±4% of control; P <0.05 versus CyA plus Egfl7). CyA upregulated cell-surface intercellular adhesion molecule-1 expression (215±13% of control; P <0.001), as determined by flow cytometry. This expression was suppressed by Egfl7 (148±5%; P <0.001 versus CyA alone). Jagged1 attenuated the intercellular adhesion molecule-1–suppressive effect of Egfl7 when administered with CyA (193±3% versus 148±5%; P <0.01). CyA increased neutrophil adhesion to human coronary endothelial cells (control 20±5%, CyA 37±3%; P <0.001 versus control) in a nonstatic neutrophil adhesion assay. This increase was attenuated by Egfl7 (22±6%; P <0.001 versus CyA alone). Jagged 1 attenuated the effect of Egfl7 on neutrophil adhesion (31±3%; P <0.001 versus Egfl7 plus CyA).

Conclusions—

Our study reveals that Egfl7 is a potent inhibitor of neutrophil adhesion to human coronary endothelial cells subsequent to calcineurin-inhibition–induced injury. Mechanistically, Egfl7 blocked nuclear factor-κB pathway activation and intercellular adhesion molecule-1 expression, which suggests that it may have significant antiinflammatory properties. Because Jagged1 blocked the effect of Egfl7, Notch receptor antagonism may contribute to the mechanism of action of Egfl7.

Role of dendritic cells in cardiovascular diseases

Dendritic cells (DCs) are potent antigen-presenting cells that bridge innate and adaptive immune responses. Recent work has elucidated the DC life cycle, including several important stages such as maturation, migration and homeostasis, as well as DC classification and subsets/locations, which provided etiological insights on the role of DCs in disease processes. DCs have a close relationship to endothelial cells and they interact with each other to maintain immunity. DCs are deposited in the atherosclerotic plaque and contribute to the pathogenesis of atherosclerosis. In addition, the necrotic cardiac cells induced by ischemia activate DCs by Toll-like receptors, which initiate innate and adaptive immune responses to renal, hepatic and cardiac ischemia reperfusion injury (IRI). Furthermore, DCs are involved in the acute/chronic rejection of solid organ transplantation and mediate transplant tolerance as well. Advancing our knowledge of the biology of DCs will aid development of new approaches to treat many cardiovascular diseases, including atherosclerosis, cardiac IRI and transplantation.

Inhibition of T cells provides protection against early invasive pneumococcal disease

Infections caused by Streptococcus pneumoniae are major causes of morbidity and mortality, which are in part mediated by immune cell-dependent mechanisms. Yet, the specific contributions of individual cell types to immunopathology are only partially understood. T cells are well characterized with respect to their function in protective humoral immune responses; however, their roles during early stages of infection and invasive pneumococcal disease (IPD) are less well defined. Using a mouse model of pneumococcal sepsis, we found that CD4(+) T cells were recruited to the lung as early as 12 h after intranasal infection. Recruitment was accompanied by upregulation of CD69 and B7-H1, reflecting T-cell activation. Unexpectedly, major histocompatibility complex (MHC) class II-deficient mice, which lack CD4(+) T cells, displayed an increased survival despite comparable bacterial titers in the blood, spleen, and lung. The higher survival correlated with a lower cytokine and chemokine response upon S. pneumoniae challenge in MHC class II-deficient mice, suggesting that inflammation may contribute to the mortality of IPD. Comparable to the case for MHC class II-deficient mice, antibody-mediated depletion of CD4(+) T cells and drug-induced inhibition of T-cell function with cyclosporine, or interference with T-cell activation using CTLA4-immunoglobulin (Abatacept), led to significant increases in survival during IPD. Our results reveal an important and adverse role of CD4(+) T cells in the pathogenesis of IPD and suggest that modulation of T-cell activation during early phases of S. pneumoniae invasive infection may provide a therapeutic option.

LFA-1 activity state on dendritic cells regulates contact duration with T cells and promotes T-cell priming

A key event in the successful induction of adaptive immune responses is the antigen-specific activation of T cells by dendritic cells (DCs). Although LFA-1 (lymphocyte function-associated antigen 1) on T cells is considered to be important for antigen-specific T-cell activation, the role for LFA-1 on DCs remains elusive. Using 2 different approaches to activate LFA-1 on DCs, either by deletion of the αL-integrin cytoplasmic GFFKR sequence or by silencing cytohesin-1-interacting protein, we now provide evidence that DCs are able to make use of active LFA-1 and can thereby control the contact duration with naive T cells. Enhanced duration of DC/T-cell interaction correlates inversely with antigen-specific T-cell proliferation, generation of T-helper 1 cells, and immune responses leading to delayed-type hypersensitivity. We could revert normal interaction time and T-cell proliferation to wild-type levels by inhibition of active LFA-1 on DCs. Our data further suggest that cytohesin-1-interacting protein might be responsible for controlling LFA-1 deactivation on mature DCs. In summary, our findings indicate that LFA-1 on DCs needs to be in an inactive state to ensure optimal T-cell activation and suggest that regulation of LFA-1 activity allows DCs to actively control antigen-driven T-cell proliferation and effective immune responses.

Dual mode of HMG-CoA reductase inhibition on dendritic cell invasion

Atherosclerosis is a chronic disease triggered by lipid disturbances, endothelial injury and sustained by inflammation. Dendritic cells (DCs) are critical for the cell-mediated arm of an immune response and are known to initiate inflammatory immunity. We investigated the role of statins and the mevalonate pathway on DC invasion. DC incubation with atorvastatin (ATV; 0.05-1 microM) for 24h decreased DC adhesion capacity. DC invasion (adhesion/transmigration) was decreased after exposing DCs to low and moderate concentrations of statins, which was reversible by mevalonate (but not geranyl- or farnesyl-pyrophosphate) and cholesterol. Inhibition of the phosphoinositide 3-kinase (with wortmannin) and inhibition of the NO-synthase (with asymmetric dimethyl ADMA) partially reversed statin-mediated effects. High-dose statins markedly decreased DC invasion, which was reversible by adding geranyl pyrophosphate and cholesterol. Inhibition of geranylgeranyltransferase but not inhibition of farnesyltransferase significantly decreased DC invasion. Statin-mediated alteration in DC-cholesterol synthesis and subsequent activation of the Akt/NOS pathway accounts for the statin-induced decrease in DC invasion at low-moderate concentrations (0.05-0.5 microM). Additionally, at high statin concentrations (1 microM) DC invasion is reduced by inhibition of protein geranylgeranylation. As DCs control immunity, regulating DC/endothelial cell interaction by statins may have relevance to inflammation and atherogenesis.

Renal ischemia-reperfusion injury: new implications of dendritic cell-endothelial cell interactions

In renal ischemia/reperfusion (I/R) injury endothelial cells are a main target. The disturbance of endothelial cell physiology leads to endothelial swelling and narrowing of the blood vessel lumen. We attribute this effect to impairment of endothelial cell nitric oxide synthase (NOS). NO is significantly reduced in the course of hypoxia causing dysfunction of the vascular smooth muscle tone. Subsequently to an I/R injury, the inflammatory response results in endothelial activation with enhanced dendritic cell (DC) adhesion and migration. Thus, alloreactive leukocytes are recruited to the inflammatory site. Finally, dendritic cell-endothelial cell interactions may play a crucial role in antigen-specific allograft rejection in I/R renal injury. DCs, which activate naïve alloreactive T cells, play a central role in the establishment of alloantigen-specific immunity. In the course of hypoxia rejection is initiated at the activated layer of foreign endothelial cells (EC), which forms an immunogenic barrier for migrating DCs and T cells. Host DCs that bind to postischemic activated ECs invade the allografted tissues, or remain stationary in the subendothelial layer, or transmigrate into lymphoid vessels and secondary lymphoid organs, where they present alloantigens to naïve host T cells. Organ rejection is mediated by host alloreactive T cells, which are activated by donor DCs (direct activation) or host DCs (indirect activation). We hypothesized that DC-EC binding and migration is the first step in the renal I/R injury that mediates allotransplant rejection. We sought to better understand the downstream events of a renal I/R injury by understanding DC binding and migration, thereby seeking new strategies for more specific immunomodulatory interventions. Herein we developed a new allotransplant-rejection model after renal I/R injury.