Cigarette smoke-induced CXCR3 receptor up-regulation mediates endothelial apoptosis

Y-Chromosome Gene, Uty, Protects Against Pulmonary Hypertension by Reducing Proinflammatory Chemokines

Rationale: Idiopathic pulmonary arterial hypertension (PAH) is a terminal pulmonary vascular disease characterized by increased pressure, right ventricular failure, and death. PAH exhibits a striking sex bias and is up to four times more prevalent in females. Understanding the molecular basis behind sex differences could help uncover novel therapies. Objectives: We previously discovered that the Y chromosome is protective against hypoxia-induced experimental pulmonary hypertension (PH), which may contribute to sex differences in PAH. Here, we identify the gene responsible for Y-chromosome protection, investigate key downstream autosomal genes, and demonstrate a novel preclinical therapy. Methods: To test the effect of Y-chromosome genes on PH development, we knocked down each Y-chromosome gene expressed in the lung by means of intratracheal instillation of siRNA in gonadectomized male mice exposed to hypoxia and monitored changes in right ventricular and pulmonary artery hemodynamics. We compared the lung transcriptome of Uty knockdown mouse lungs to those of male and female PAH patient lungs to identify common downstream pathogenic chemokines and tested the effects of these chemokines on human pulmonary artery endothelial cells. We further inhibited the activity of these chemokines in two preclinical pulmonary hypertension models to test the therapeutic efficacy. Measurements and Main Results: Knockdown of the Y-chromosome gene Uty resulted in more severe PH measured by increased right ventricular pressure and decreased pulmonary artery acceleration time. RNA sequencing revealed an increase in proinflammatory chemokines Cxcl9 and Cxcl10 as a result of Uty knockdown. We found CXCL9 and CXCL10 significantly upregulated in human PAH lungs, with more robust upregulation in females with PAH. Treatment of human pulmonary artery endothelial cells with CXCL9 and CXCL10 triggered apoptosis. Inhibition of Cxcl9 and Cxcl10 expression in male Uty knockout mice and CXCL9 and CXCL10 activity in female rats significantly reduced PH severity. Conclusions:Uty is protective against PH. Reduction of Uty expression results in increased expression of proinflammatory chemokines Cxcl9 and Cxcl10, which trigger endothelial cell death and PH. Inhibition of CLXC9 and CXLC10 rescues PH development in multiple experimental models.

Polymorphisms in CXCR3 ligands predict early CXCL9 recovery and severe chronic GVHD

Chronic graft-versus-host disease (cGVHD) is a major cause of mortality and morbidity after allogeneic stem cell transplantation (alloSCT). The individual risk of severe cGVHD remains difficult to predict and may involve CXCR3 ligands. This study investigated the role of single-nucleotide polymorphisms (SNPs) of CXCL4, CXCL9, CXCL10, and CXCL11, and their day +28 serum levels, in cGVHD pathogenesis. Eighteen CXCR3 and CXCL4, CXCL9-11 SNPs as well as peri-transplant CXCL9-11 serum levels were analyzed in 688 patients without (training cohort; n = 287) or with statin-based endothelial protection cohort (n = 401). Clinical outcomes were correlated to serum levels and SNP status. Significant polymorphisms were further analyzed by luciferase reporter assays. Findings were validated in an independent cohort (n = 202). A combined genetic risk comprising four CXCR3 ligand SNPs was significantly associated with increased risk of severe cGVHD in both training cohort (hazard ratio (HR) 2.48, 95% confidence interval (CI) 1.33-4.64, P = 0.004) and validation cohort (HR 2.95, 95% CI 1.56-5.58, P = 0.001). In reporter assays, significantly reduced suppressive effects of calcineurin inhibitors in constructs with variant alleles of rs884304 (P < 0.001) and rs884004 (P < 0.001) were observed. CXCL9 serum levels at day +28 after alloSCT correlated with both genetic risk and risk of severe cGVHD (HR 1.38, 95% CI 1.10-1.73, P = 0.006). This study identifies patients with high genetic risk to develop severe cGVHD.

HIV-Nef Protein Persists in the Lungs of Aviremic Patients with HIV and Induces Endothelial Cell Death

It remains a mystery why HIV-associated end-organ pathologies persist in the era of combined antiretroviral therapy (ART). One possible mechanism is the continued production of HIV-encoded proteins in latently HIV-infected T cells and macrophages. The proapoptotic protein HIV-Nef persists in the blood of ART-treated patients within extracellular vesicles (EVs) and peripheral blood mononuclear cells. Here we demonstrate that HIV-Nef is present in cells and EVs isolated from BAL of patients on ART. We hypothesize that HIV-Nef persistence in the lung induces endothelial apoptosis leading to endothelial dysfunction and further pulmonary vascular pathologies. The presence of HIV-Nef in patients with HIV correlates with the surface expression of the proapoptotic endothelial-monocyte-activating polypeptide II (EMAPII), which was implicated in progression of pulmonary emphysema via mechanisms involving endothelial cell death. HIV-Nef protein induces EMAPII surface expression in human embryonic kidney 293T cells, T cells, and human and mouse lung endothelial cells. HIV-Nef packages itself into EVs and increases the amount of EVs secreted from Nef-expressing T cells and Nef-transfected human embryonic kidney 293T cells. EVs from BAL of HIV⁺ patients and Nef-transfected cells induce apoptosis in lung microvascular endothelial cells by upregulating EMAPII surface expression in a PAK2-dependent fashion. Transgenic expression of HIV-Nef in vascular endothelial-cadherin⁺ endothelial cells leads to lung rarefaction, characterized by reduced alveoli and overall increase in lung inspiratory capacity. These changes occur concomitantly with lung endothelial cell apoptosis. Together, these data suggest that HIV-Nef induces endothelial cell apoptosis via an EMAPII-dependent mechanism that is sufficient to cause pulmonary vascular pathologies even in the absence of inflammation.

Endothelial cells are a source of Nestin expression in Pulmonary Arterial Hypertension

Uncontrolled proliferation of endothelial cells is essential to the pathogenesis of pulmonary arterial hypertension (PAH). Both proliferation and cytoskeleton reorganization are associated with upregulation of the intermediate filament protein Nestin. Recently, accumulation of Nestin-expressing cells was found in pulmonary vascular lesions of PAH patients. The goal of this study is to determine if Nestin expression contributes to endothelial proliferation in pulmonary arterial hypertension, using both lung tissues and endothelial cells. Here we found that endothelial cells from complex and plexiform lesions of PAH patients expressed Nestin. These Nestin+ cells further stained positive for the angiogenic factors CXC chemokine ligand 12 and Wnt1. Likewise, in the chronic hypoxia/SU5416 animal model of pulmonary hypertension, Nestin+ endothelial cells were found in occlusive pulmonary vascular lesions. In vitro, both growing rat and human lung endothelial cells expressed Nestin protein. When Nestin was overexpressed in endothelial cells (both rat and human), Nestin overexpression promoted proliferation and expression of CXC chemokine ligand 12. Nestin overexpression further increased angiogenic tube formation in vitro. Conclusions: We found increased Nestin expression from endothelial cells of occlusive lung vascular lesions in severe pulmonary hypertension. Elevated Nestin expression likely contributes to unchecked pulmonary vascular proliferation and angiogenesis, possibly via induction of CXC chemokine ligand 12. Additional studies are required to determine whether targeting Nestin would be beneficial to treat PAH.

Subcutaneous administration of neutralizing antibodies to endothelial monocyte-activating protein II attenuates cigarette smoke-induced lung injury in mice

Proapoptotic and monocyte chemotactic endothelial monocyte-activating protein 2 (EMAPII) is released extracellularly during cigarette smoke (CS) exposure. We have previously demonstrated that, when administered intratracheally during chronic CS exposures, neutralizing rat antibodies to EMAPII inhibited endothelial cell apoptosis and lung inflammation and reduced airspace enlargement in mice (DBA/2J strain). Here we report further preclinical evaluation of EMAPII targeting using rat anti-EMAPII antibodies via either nebulization or subcutaneous injection. Both treatment modalities efficiently ameliorated emphysema-like disease in two different strains of CS-exposed mice, DBA/2J and C57BL/6. Of relevance for clinical applicability, this treatment showed therapeutic and even curative potential when administered either during or following CS-induced emphysema development, respectively. In addition, a fully humanized neutralizing anti-EMAPII antibody administered subcutaneously to mice during CS exposure retained anti-apoptotic and anti-inflammatory effects similar to that of the parent rat antibody. Furthermore, humanized anti-EMAPII antibody treatment attenuated CS-induced autophagy and restored mammalian target of rapamycin signaling in the lungs of mice, despite ongoing CS exposure. Together, our results demonstrate that EMAPII secretion is involved in CS-induced lung inflammation and cell injury, including apoptosis and autophagy, and that a humanized EMAPII neutralizing antibody may have therapeutic potential in emphysema.

EMAPII Monoclonal Antibody Ameliorates Influenza A Virus-Induced Lung Injury

Influenza A virus (IAV) remains a major worldwide health threat, especially to high-risk populations, including the young and elderly. There is an unmet clinical need for therapy that will protect the lungs from damage caused by lower respiratory infection. Here, we analyzed the role of EMAPII, a stress- and virus-induced pro-inflammatory and pro-apoptotic factor, in IAV-induced lung injury. First, we demonstrated that IAV induces EMAPII surface translocation, release, and apoptosis in cultured endothelial and epithelial cells. Next, we showed that IAV induces EMAPII surface translocation and release to bronchoalveolar lavage fluid (BALF) in mouse lungs, concomitant with increases in caspase 3 activity. Injection of monoclonal antibody (mAb) against EMAPII attenuated IAV-induced EMAPII levels, weight loss, reduction of blood oxygenation, lung edema, and increase of the pro-inflammatory cytokine TNF alpha. In accordance with the pro-apoptotic properties of EMAPII, levels of caspase 3 activity in BALF were also decreased by mAb treatment. Moreover, we detected EMAPII mAb-induced increase in lung levels of M2-like macrophage markers YM1 and CD206. All together, these data strongly suggest that EMAPII mAb ameliorates IAV-induced lung injury by limiting lung cell apoptosis and shifting the host inflammatory setting toward resolution of inflammation.

Effects of cigarette smoke on pulmonary endothelial cells

Cigarette smoking is the leading cause of preventable disease and death in the United States. Cardiovascular comorbidities associated with both active and secondhand cigarette smoking indicate the vascular toxicity of smoke exposure. Growing evidence supports the injurious effect of cigarette smoke on pulmonary endothelial cells and the roles of endothelial cell injury in development of acute respiratory distress syndrome (ARDS), emphysema, and pulmonary hypertension. This review summarizes results from studies of humans, preclinical animal models, and cultured endothelial cells that document toxicities of cigarette smoke exposure on pulmonary endothelial cell functions, including barrier dysfunction, endothelial activation and inflammation, apoptosis, and vasoactive mediator production. The discussion is focused on effects of cigarette smoke-induced endothelial injury in the development of ARDS, emphysema, and vascular remodeling in chronic obstructive pulmonary disease.

Blockade of CXC chemokine receptor 3 on endothelial cells protects against sepsis-induced acute lung injury

BACKGROUND

CXCR3, a G-protein coupled chemokine receptor, has been shown to play a critical role in recruiting inflammatory cells into lungs in several studies. However, its roles in polymicrobial septic acute lung injury (ALI) is yet unknown. Therefore, the purpose of this study was to elucidate the protective effects of CXCR3 blockade on pulmonary microvascular endothelial cells (PMVECs) in septic ALI and explore potential mechanisms.

MATERIALS AND METHODS

ALI was induced by polymicrobial sepsis through cecal ligation and puncture surgery. The expression of CXCR3 on pulmonary microvascular endothelial cells was measured 24 h after cecal ligation and puncture surgery. In addition, the protective effects of neutralizing antibody were detected, including protein concentration, inflammation cell counts, lung ​wet-to-dry ratio, and lung damages. In human umbilical vein endothelial cells (HUVECs) culture condition, CXCR3 expression was measured after exposure to tumor necrosis factor-α. The permeability and apoptosis ratio were detected through CXCR3 gene silencing on HUVECs. The p38 mitogen-activated protein kinase (MAPK) was analyzed with Western blot.

RESULTS

CXCR3 expression was upregulated both in vivo and in vitro. After CXCR3 neutralizing antibody administrated intraperitoneally, the protein concentration, inflammatory cell counts in BALF and lung ​wet-to-dry ratio were decreased significantly, as well as the lung tissue damages. In vitro, CXCR3 gene silencing inhibited tumor necrosis factor-α and CXCL10-induced hyperpermeability and apoptosis in HUVECs. In addition, p38 mitogen-activated protein kinase activation was essential for CXCR3-mediated apoptosis.

CONCLUSIONS

CXCR3 blockade exerts protective effects on ALI at least partly by inhibiting endothelial cells apoptosis and decreasing the leakage of protein-rich fluid and inflammatory cells. Blockade of CXCR3 may be a promising therapeutic strategy for severe sepsis-induced ALI.

Pulmonary Microvascular Blood Flow in Mild Chronic Obstructive Pulmonary Disease and Emphysema. The MESA COPD Study

RATIONALE

Smoking-related microvascular loss causes end-organ damage in the kidneys, heart, and brain. Basic research suggests a similar process in the lungs, but no large studies have assessed pulmonary microvascular blood flow (PMBF) in early chronic lung disease.

OBJECTIVES

To investigate whether PMBF is reduced in mild as well as more severe chronic obstructive pulmonary disease (COPD) and emphysema.

METHODS

PMBF was measured using gadolinium-enhanced magnetic resonance imaging (MRI) among smokers with COPD and control subjects age 50 to 79 years without clinical cardiovascular disease. COPD severity was defined by standard criteria. Emphysema on computed tomography (CT) was defined by the percentage of lung regions below -950 Hounsfield units (-950 HU) and by radiologists using a standard protocol. We adjusted for potential confounders, including smoking, oxygenation, and left ventricular cardiac output.

MEASUREMENTS AND MAIN RESULTS

Among 144 participants, PMBF was reduced by 30% in mild COPD, by 29% in moderate COPD, and by 52% in severe COPD (all P < 0.01 vs. control subjects). PMBF was reduced with greater percentage emphysema-950HU and radiologist-defined emphysema, particularly panlobular and centrilobular emphysema (all P ≤ 0.01). Registration of MRI and CT images revealed that PMBF was reduced in mild COPD in both nonemphysematous and emphysematous lung regions. Associations for PMBF were independent of measures of small airways disease on CT and gas trapping largely because emphysema and small airways disease occurred in different smokers.

CONCLUSIONS

PMBF was reduced in mild COPD, including in regions of lung without frank emphysema, and may represent a distinct pathological process from small airways disease. PMBF may provide an imaging biomarker for therapeutic strategies targeting the pulmonary microvasculature.

Activation of p38-MAPK by CXCL4/CXCR3 axis contributes to p53-dependent intestinal apoptosis initiated by 5-fluorouracil

Chemotherapy-induced mucositis (CIM) is a major does limiting side-effect of chemoagents such as 5-fluorouracil (5-FU). Molecules involved in this disease process are still not fully understood. We proposed that the homeostatically regulated genes during CIM may participate in the disease. A cluster of such genes were previously identified by expression gene-array from the mouse jejunum in 5-FU-induced mucositis model. Here, we report that CXCL4 is such a homeostatically regulated gene and serves as a new target for the antibody treatment of CIM. CXCL4 and its receptor CXCR3 were confirmed at both the gene and protein levels to be homeostatically regulated during 5-FU-induced mucositis. Using of CXCL4 neutralizing monoclonal antibody (CXCL4mab) decreased the incidence, severity, and duration of the chemotherapy-induced diarrhea, the major symptom of CIM, in a 5-FU mouse CIM model. Mechanistically, CXCL4mab reduced the apoptosis of the crypt epithelia by suppression of the 5-FU-induced expression of p53 and Bax through its receptor CXCR3. The downstream signaling pathway of CXCL4 in activation of the epithelial apoptosis was identified in an intestinal epithelial cell line (IEC-6). CXCL4 activated the phosphorylation of p38 MAPK, which mediated the stimulated expression of p53 and Bax, and resulted in the ultimate activation of Caspase-8, -9, and -3. Taken together, activation of CXCL4 expression by 5-FU in mice participates in 5-FU-induced intestinal mucositis through upregulation of p53 via activation of p38-MAPK, and CXCL4mab is potentially beneficial in preventing CIM in the intestinal tract.

Transfer of intracellular HIV Nef to endothelium causes endothelial dysfunction

With effective antiretroviral therapy (ART), cardiovascular diseases (CVD) are emerging as a major cause of morbidity and death in the aging HIV-infected population. To address whether HIV-Nef, a viral protein produced in infected cells even when virus production is halted by ART, can lead to endothelial activation and dysfunction, we tested Nef protein transfer to and activity in endothelial cells. We demonstrated that Nef is essential for major endothelial cell activating effects of HIV-infected Jurkat cells when in direct contact with the endothelium. In addition, we found that Nef protein in endothelial cells is sufficient to cause apoptosis, ROS generation and release of monocyte attractant protein-1 (MCP-1). The Nef protein-dependent endothelial activating effects can be best explained by our observation that Nef protein rapidly transfers from either HIV-infected or Nef-transfected Jurkat cells to endothelial cells between these two cell types. These results are of in vivo relevance as we demonstrated that Nef protein induces GFP transfer from T cells to endothelium in CD4.Nef.GFP transgenic mice and Nef is present in chimeric SIV-infected macaques. Analyzing the signal transduction effects of Nef in endothelial cells, we found that Nef-induced apoptosis is mediated through ROS-dependent mechanisms, while MCP-1 production is NF-kB dependent. Together, these data indicate that inhibition of Nef-associated pathways may be promising new therapeutic targets for reducing the risk for cardiovascular disease in the HIV-infected population.

Inflammatory Markers of the Systemic Capillary Leak Syndrome (Clarkson Disease)

OBJECTIVES

The Systemic Capillary Leak Syndrome (SCLS) is a rare and potentially fatal disorder resembling systemic anaphylaxis that is characterized by transient episodes of hypotensive shock and peripheral edema. The pathogenesis of SCLS is unknown, and triggers for attacks are apparent only in a minority of patients. We introduce a clinical algorithm for the diagnosis of SCLS, and we investigated potential serum biomarkers of acute SCLS episodes.

METHODS

We analyzed serum cytokines in a cohort of 35 patients with an established diagnosis of SCLS and characterized the effects of SCLS sera on endothelial cell function. We investigated the cellular source(s) of CXCL10, a chemokine that was significantly elevated in both basal and acute SCLS sera, by flow cytometry.

RESULTS

Several cytokines were elevated in acute SCLS sera compared to baseline or sera from healthy controls, including CXCL10, CCL2, IL-1β, IL-6, IL-8, IL-12 and TNFα. The majority of acute sera failed to activate endothelial cells as assessed by surface adhesion marker expression. Monocytes appear to be the major source of serum CXCL10, and the percentage of CXLC10+ monocytes in response to IFNγ stimulation was increased in SCLS subjects compared to controls.

CONCLUSIONS

The presence of proinflammatory cytokines in acute SCLS sera suggests that inflammation or infection may have a role in triggering episodes. The enhanced capacity of monocytes from SCLS patients to produce CXCL10 suggests a new therapeutic avenue for SCLS.

HIV envelope protein gp120-induced apoptosis in lung microvascular endothelial cells by concerted upregulation of EMAP II and its receptor, CXCR3

Chronic lung diseases, such as pulmonary emphysema, are increasingly recognized complications of infection with the human immunodeficiency virus (HIV). Emphysema in HIV may occur independent of cigarette smoking, via mechanisms that are poorly understood but may involve lung endothelial cell apoptosis induced by the HIV envelope protein gp120. Recently, we have demonstrated that lung endothelial apoptosis is an important contributor to the development of experimental emphysema, via upregulation of the proinflammatory cytokine endothelial monocyte-activating polypeptide II (EMAP II) in the lung. Here we investigated the role of EMAP II and its receptor, CXCR3, in gp120-induced lung endothelial cell apoptosis. We could demonstrate that gp120 induces a rapid and robust increase in cell surface expression of EMAP II and its receptor CXCR3. This surface expression occurred via a mechanism involving gp120 signaling through its CXCR4 receptor and p38 MAPK activation. Both EMAP II and CXCR3 were essentially required for gp120-induced apoptosis and exposures to low gp120 concentrations enhanced the susceptibility of endothelial cells to undergo apoptosis when exposed to soluble cigarette smoke extract. These data indicate a novel mechanism by which HIV infection causes endothelial cell loss involved in lung emphysema formation, independent but potentially synergistic with smoking, and suggest therapeutic targets for emphysema prevention and/or treatment.

Nonclassically Secreted Regulators of Angiogenesis

Many secreted polypeptide regulators of angiogenesis are devoid of signal peptides. These proteins are released through nonclassical pathways independent of endoplasmic reticulum and Golgi. In most cases, the nonclassical protein export is induced by stress. It usually serves to stimulate repair or inflammation in damaged tissues. We review the secreted signal peptide-less regulators of angiogenesis and discuss the mechanisms and biological significance of their unconventional export.