Hyperoxia induces paracellular leak and alters claudin expression by neonatal alveolar epithelial cells

Abstract

Background Premature neonates frequently require oxygen supplementation as a therapeutic intervention that, while necessary, also exposes the lung to significant oxidant stress. We hypothesized that hyperoxia has a deleterious effect on alveolar epithelial barrier function rendering the neonatal lung susceptible to injury and/or bronchopulmonary dysplasia (BPD). Materials and Methods We examined the effects of exposure to 85% oxygen on neonatal rat alveolar barrier function in vitro and in vivo. Whole lung was measured using wet-to-dry weight ratios and bronchoalveolar lavage protein content and cultured primary neonatal alveolar epithelial cells (AECs) were measured using transepithelial electrical resistance (TEER) and paracellular flux measurements. Expression of claudin-family tight junction proteins, E-cadherin and the Snail transcription factor SNAI1 were measured by Q-PCR, immunoblot and confocal immunofluorescence microscopy. Results Cultured neonatal AECs exposed to 85% oxygen showed impaired barrier function. This oxygen-induced increase in paracellular leak was associated with altered claudin expression, where claudin-3 and claudin-18 were downregulated at both the mRNA and protein level. Claudin-4 and claudin-5 mRNA were also decreased, although protein expression of these claudins was largely maintained. Lung alveolarization and barrier function in vivo were impaired in response to hyperoxia. Oxygen exposure also significantly decreased E-cadherin expression and induced expression of the SNAI1 transcription factor in vivo and in vitro. Conclusions These data support a model in which hyperoxia has a direct impact on alveolar tight and adherens junctions to impair barrier function. Strategies to antagonize the effects of high oxygen on alveolar junctions may potentially reverse this deleterious effect.

Age-Dependent Translocation of Gold Nanoparticles across the Air–Blood Barrier

“…The high NP translocation in 3-day-old rats (~23%) progressively decreased with age and reached the low levels typically characteristic for adults 8,12,13 (≤1%). These findings and the observation that 5 and 100 nm NPs translocated with equal efficiency in infants are consistent with the hypothesis that potential paracellular transport 5 of NPs may also be significantly involved in the NP translocation process in immature animals. Epithelial cells are connected with each other by complex structures forming cell–cell junctions that include tight junctions, adherent junctions, gap junctions, and desmosomes.…”

Signaling Pathways Involved in the Development of Bronchopulmonary Dysplasia and Pulmonary Hypertension

“…Tight junctions are located at alveolar type I–type II cell interfaces and regulate para-cellular fluid permeability through the expression of claudins, a transmembrane family of proteins. In in-vitro studies, neonatal alveolar epithelial cells on exposure to hyperoxia have shown to exhibit increased para-cellular leak and significant reduction in the mRNA and protein levels of claudin 3 and in the mRNA levels of claudin 18 and claudin 5 [ 90 ]. Mizobuchi M. et al [ 91 ] have shown 44% (total 54) of premature infants (<28 wks gestational age) requiring ventilatory support beyond one week developed severe leaky lung syndrome.…”

2018 year in review: Part 2 of 4: Neonatal lung disease

“…Identifying relevant model systems is a major challenge, and a task in sore need of refinement. Vyas‐Read and colleagues studied neonatal rat alveolar epithelium obtained from newborn rats exposed to 85% O 2 , showing increased paracellular leak which they attributed to reduced integrity of inter‐cellular connection measured in part by claudin expression . Such studies are limited by the differing redox conditions in vivo and several hours later after cell isolation and culture.…”