Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Bärnthaler, T.
Effects of PGE2 on the alveolar epithelial barrier function
Humanmedizin; [ Diplomarbeit ] Medical University of Graz; 2014. pp. 57
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- Autor*innen der Med Uni Graz:
- Bärnthaler Thomas
- Betreuer*innen:
- Heinemann Akos
- Konya Viktoria
- Altmetrics:
- Abstract:
- Background: Impairment of the epithelial-endothelial barrier is a hallmark of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). The dysfunctional air-blood barrier does not only result in pulmonary infiltration of leukocytes, but also triggers edema formation in the alveoli resulting in respiratory failure. PGE2, regardless of its known pro-inflammatory features, is considered to be protective in the lung (Vancheri et al., 2004). Our group recently reported about the barrier enhancing effect of the PGE2 receptor EP4 on human pulmonary microvascular endothelial cells (Konya et al., 2012). Additionally, our preliminary observations reveal that PGE2 is able to prevent the pathogenesis of LPS-induced acute lung injury in mice. Despite its importance, the impact of PGE2 on the alveolar epithelial barrier function is not well understood. Research Focus: My Master thesis aims to investigate the effect of PGE2 on the alveolar epithelial barrier function and to identify the involved EP receptor subtype. To this end, alveolar epithelial cells were isolated from male BALB/c mice as previously described (Corti et al., 1996; Marsh et al., 2009) and by additionally using negative magnetic separation. The obtained cells, being mainly alveolar type II (AT2) epithelial cells, were cultured on laminin 1 for six days resulting in transdifferentiation of AT2 cells towards alveolar type I (AT1)-like cells as described previously (Demaio et al., 2009). Changes of the epithelial barrier function were measured by using Electric Cell-substrate Impedance Sensing (ECIS). Phenotypic characterization and EP receptor expression of the isolated cells were assessed by using flow cytometry. Results: The obtained alveolar epithelial cells represented 89% viability and, after six days of culturing on laminin 1, formed tight monolayers with the electrical resistance of typically 2000 Ω/cm2. Phenotypic characterization of the isolated cells revealed minimal amounts of alveolar macrophages, endothelial cells and fibroblasts. Strikingly, upon exposure of AT1-like cells to PGE2, the electrical resistance rapidly decreased. PGE2 acted very potently on AT1-like cells, by inducing 20% barrier loss already at 10 nM concentration, while at 30 nM, PGE2 caused irreversible barrier disruption. This function was mimicked by the EP2 agonist butaprost and by the EP4 agonist ONO AE1-329. Interestingly, only blocking of EP2 receptor by using a selective antagonist PF-04418948 could reverse this barrier disrupting effect, while the EP4 receptor antagonist ONO AE3-208 did not have any influence. In accordance with these findings, AT1-like cells expressed EP2 and EP4 receptors as well as EP3 receptor. Discussion: Taken together, PGE2 induced disintegration of the alveolar epithelial cell barrier on an EP2 receptor-dependent manner. These findings suggest that the way PGE2 controls the alveolar epithelial - capillary endothelial barrier might be very complex. On the circulation side the endothelial barrier is strengthened by PGE2, while the air-exposed alveolar epithelial layer becomes more permeable, due to different EP receptor subset activation by PGE2. Further investigations are required for establishing the physiological relevance of the EP2 receptor-mediated increase of alveolar permeability. These preliminary findings suggest that EP2 receptor antagonists might represent new therapeutic options for diseases with compromised air-blood barrier such as ALI and ARDS.