Myeloid cells are key factors in the progression of bronchopulmonary dysplasia (BPD) pathogenesis. Endothelial monocyte-activating polypeptide II (EMAP II) mediates myeloid cell trafficking. The origin and physiological mechanism by which EMAP II affects pathogenesis in BPD is unknown. The objective was to determine the functional consequences of elevated EMAP II levels in the pathogenesis of murine BPD and to investigate EMAP II neutralization as a therapeutic strategy. Three neonatal mouse models were used: (1) BPD (hyperoxia), (2) EMAP II delivery, and (3) BPD with neutralizing EMAP II antibody treatments. Chemokinic function of EMAP II and its neutralization were assessed by migration in vitro and in vivo. We determined the location of EMAP II by immunohistochemistry, pulmonary proinflammatory and chemotactic gene expression by quantitative polymerase chain reaction and immunoblotting, lung outcome by pulmonary function testing and histological analysis, and right ventricular hypertrophy by Fulton's Index. In BPD, EMAP II initially is a bronchial clubcell-specific protein-derived factor that later is expressed in galectin-3 1 macrophages as BPD progresses. Continuous elevated expression corroborates with baboon and human BPD. Prolonged elevation of EMAP II levels recruits galectin-3 1 macrophages, which is followed by an inflammatory state that resembles a severe BPD phenotype characterized by decreased pulmonary compliance, arrested alveolar development, and signs of pulmonary hypertension. In vivo pharmacological EMAP II inhibition suppressed proinflammatory genes Tnfa, Il6, and Il1b and chemotactic genes Ccl2 and Ccl9 and reversed the severe BPD phenotype. EMAP II is sufficient to induce macrophage recruitment, worsens BPD progression, and represents a targetable mechanism of BPD development.
Alveolar growth abnormalities and severe respiratory dysfunction are often fatal. Identifying mechanisms that control epithelial proliferation and enlarged, poorly septated airspaces is essential in developing new therapies for lung disease. The membrane-bound ligand ephrin-B2 is strongly expressed in lung epithelium, and yet in contrast to its known requirement for arteriogenesis, considerably less is known regarding the function of this protein in the epithelium. We hypothesize that the vascular mediator ephrin-B2 governs alveolar growth and mechanics beyond the confines of the endothelium. We used the in vivo manipulation of ephrin-B2 reverse signaling to determine the role of this vascular mediator in the pulmonary epithelium and distal lung mechanics. We determined that the ephrin-B2 gene (EfnB2) is strongly expressed in alveolar Type 2 cells throughout development and into adulthood. The role of ephrin-B2 reverse signaling in the lung was assessed in Efnb2LacZ/6YFDV mutants that coexpress the intracellular truncated ephrin-B2-b-galactosidase fusion and an intracellular point mutant ephrin-B2 protein that is unable to become tyrosine-phosphorylated or to interact with either the SH2 or PDZ domain-containing downstream signaling proteins. In these viable mice, we observed pulmonary hypoplasia and altered pulmonary mechanics, as evidenced by a marked reduction in lung compliance. Associated with the reduction in lung compliance was a significant increase in insoluble fibronectin (FN) basement membrane matrix assembly with FN deposition, and a corresponding increase in the a5 integrin receptor required for FN fibrillogenesis. These experiments indicate that ephrin-B2 reverse signaling mediates distal alveolar formation, fibrillogenesis, and pulmonary compliance.Keywords: arterial; fibronectin; a5b1 integrin; alveoli; pulmonary mechanics Lung development in mammalian species occurs through a series of overlapping stages, distinguished in terms of their histological appearance, and specifically the growth and differentiation of pulmonary epithelial structures. Although the proximal airways are completely formed by the end of gestation, the distal airways and alveoli continue their growth and maturation beyond the time of birth. Concurrent to the development of the epithelial structures, the pulmonary vasculature develops in a sequential fashion, via the coordinated processes of angiogenesis and vasculogenesis (1). Because of the close proximity of the developing airways and vasculature in the lung, vascular mediators have been suggested to influence pulmonary development. For instance, Chen and colleagues (2) and Schwarz and colleagues (3-5) used a mouse fetal lung allograft model to show that endothelial-monocyte activating polypeptide II can not only inhibit neovascularization, but can also significantly impair epithelial morphogenesis. Based on these and similar findings, our laboratory has focused on the role of vascular mediators during pulmonary development.Our studies have focused on the ephrin-B2 (EfnB2)...
Calcium channel blocker (CCB) toxicity is associated with refractory hypotension and can be fatal. A 13 year old young woman presented to the emergency department(ED) six hours after an intentional overdose of amlodipine, barbiturates, and alcohol. She remained extremely hypotensive despite the administration of normal saline and calcium chloride and despite infusions of norepinephrine, epinephrine, insulin, and dextrose. Due to increasing evidence of end organ dysfunction, Extracorporeal Life Support (ECLS) was initiated 9 hours after presentation to the ED. The patient's blood pressure and end organ function immediately improved after cannulation. She was successfully decannulated after 57 hours of ECLS and was neurologically intact. Patients with calcium channel blocker overdose who are resistant to medical interventions may respond favorably to early ECLS.
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