A monoclonal rat anti-mouse EMAP II antibody that functionally neutralizes pro- and mature-EMAP II in vitro

Mice with humanized immune system as novel models to study HIV-associated pulmonary hypertension

People living with HIV and who receive antiretroviral therapy have a significantly improved lifespan, compared to the early days without therapy. Unfortunately, persisting viral replication in the lungs sustains chronic inflammation, which may cause pulmonary vascular dysfunction and ultimate life-threatening Pulmonary Hypertension (PH). The mechanisms involved in the progression of HIV and PH remain unclear. The study of HIV-PH is limited due to the lack of tractable animal models that recapitulate infection and pathobiological aspects of PH. On one hand, mice with humanized immune systems (hu-mice) are highly relevant to HIV research but their suitability for HIV-PH research deserves investigation. On another hand, the Hypoxia-Sugen is a well-established model for experimental PH that combines hypoxia with the VEGF antagonist SU5416. To test the suitability of hu-mice, we combined HIV with either SU5416 or hypoxia. Using right heart catheterization, we found that combining HIV+SU5416 exacerbated PH. HIV infection increases human pro-inflammatory cytokines in the lungs, compared to uninfected mice. Histopathological examinations showed pulmonary vascular inflammation with arterial muscularization in HIV-PH. We also found an increase in endothelial-monocyte activating polypeptide II (EMAP II) when combining HIV+SU5416. Therefore, combinations of HIV with SU5416 or hypoxia recapitulate PH in hu-mice, creating well-suited models for infectious mechanistic pulmonary vascular research in small animals.

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.

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.

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.

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

Endothelial monocyte-activating polypeptide II (EMAP II) and interferon-inducible protein (IP)-10 are proinflammatory mediators, which in addition to their chemokine activities, selectively induce apoptosis in endothelial cells and are up-regulated in the lungs of cigarette smoke-exposed humans. Previously, we showed that EMAP II is an essential mediator of cigarette smoke-induced lung emphysema in mice linking endothelial cell apoptosis with inflammation. Here we addressed the role of the CXCR3 receptor in EMAP II-induced and IP-10-induced apoptosis in endothelial cells and its regulation by cigarette smoke. We found that both neutralizing antibodies and small inhibitory RNA to CXCR3 abrogated EMAP II-induced and IP-10-induced endothelial caspase-3 activation and DNA fragmentation. CXCR3 receptor surface expression in human lung microvascular endothelial cells and in lung tissue endothelium was up-regulated by exposure to cigarette smoke. In tissue culture conditions, EMAP II-induced and IP-10-induced apoptosis was enhanced by preincubation with cigarette smoke extract. Interestingly, serum starvation also induced CXCR3 up-regulation and enhanced EMAP II-induced endothelial apoptosis. Signal transduction via p38 mitogen-activated protein kinase activation was essential for CXCR3-induced cell death, but not for CXCR3 receptor up-regulation by cigarette smoke. In turn, protein nitration was required for CXCR3 receptor up-regulation by cigarette smoke and consequently for subsequent CXCR3-induced cell death. In conclusion, the concerted up-regulation of proinflammatory EMAP II, IP-10, and CXCR3 by cigarette smoke could sustain a cascade of cell death that may promote the alveolar tissue loss noted in human emphysema.

Lung endothelial monocyte-activating protein 2 is a mediator of cigarette smoke-induced emphysema in mice

Pulmonary emphysema is a disease characterized by alveolar cellular loss and inflammation. Recently, excessive apoptosis of structural alveolar cells has emerged as a major mechanism in the development of emphysema. Here, we investigated the proapoptotic and monocyte chemoattractant cytokine endothelial monocyte-activating protein 2 (EMAPII). Lung-specific overexpression of EMAPII in mice caused simplification of alveolar structures, apoptosis, and macrophage accumulation, compared with that in control transgenic mice. Additionally, in a mouse model of cigarette smoke-induced (CS-induced) emphysema, EMAPII levels were significantly increased in murine lungs. This upregulation was necessary for emphysema development, as neutralizing antibodies to EMAPII resulted in reduced alveolar cell apoptosis, inflammation, and emphysema-associated structural changes in alveoli and small airways and improved lung function. The mechanism of EMAPII upregulation involved an apoptosis-dependent feed-forward loop, since caspase-3 instillation in the lung markedly increased EMAPII expression, while caspase inhibition decreased its production, even in transgenic EMAPII mice. These findings may have clinical significance, as both current smokers and ex-smoker chronic obstructive pulmonary disease (COPD) patients had increased levels of secreted EMAPII in the bronchoalveolar lavage fluid compared with that of nonsmokers. In conclusion, we suggest that EMAPII perpetuates the mechanism of CS-induced lung emphysema in mice and, given its secretory nature, is a suitable target for neutralization antibody therapy.