How to Measure Alterations in Alveolar Barrier Function as a Marker of Lung Injury

Abstract

The alveolar capillary membrane maintains the proper water and solute content of the epithelial lining fluid at the alveolar air-liquid interface, which is critical for adequate gas exchange in the lung. This is possible due to the alveolar fluid clearance (AFC) capacity of this membrane that assists in the removal of salt and water from the alveolar air spaces. The alveolar capillary membrane also provides a barrier that restricts the passage of proteins and water from the interstitial and vascular compartments into the alveolar air spaces. This restricted passage is due to the presence of tight junctions between adjacent alveolar epithelial cells. Severe injury to the alveolar epithelial/endothelial membrane results in increased protein permeability and impairment of AFC, which leads to the formation of protein-rich edema with the consequent deterioration of gas exchange. Many animal models of lung injury, focused on damage of the alveolar-capillary membrane, assess the AFC capacity and the barrier function. We describe a simple method to assess the AFC rate in normal and pathological conditions in mice. We also describe two complementary methods to assess the alveolar-capillary barrier function, which require measuring the concentration of endogenous plasma proteins in bronchoalveolar lavage fluid and detection of tight-junction proteins in lung tissue by immunofluorescence.

Effects of Orally Ingested Arsenic on Respiratory Epithelial Permeability to Bacteria and Small Molecules in Mice

“…Bacterial penetration may in principle either be paracellular, via penetration through intercellular tight junctions, or transcellular, following invasion and/or damage to cells. Measurement in BALF of the levels of two plasma proteins, albumin (MW, ) and IgM (MW, in pentameric form), is commonly used as a metric of endothelial permeability in the lung to circulating medium-sized and large molecules, respectively ( Herrero and Matute-Bello 2015 ). BALF albumin and IgM were both increased after exposure of mice to inhaled LPS, as expected; however, levels were equivalent between control and arsenic-exposed mice in both the naïve and post-LPS condition ( Figure 6b, c ).…”

Trimetazidine, a metabolic modulator, attenuates silica‐induced pulmonary fibrosis and decreases lactate levels and LDH activity in rats

“…Silica group also increased TGF‐β levels (6.8 ± 0.14 vs. 1.2 ± 0.04 pg/ml) and triggered accumulation of proteins in BALF (3.7 ± 0.4 vs. 1.9 ± 0.3 μg/ml), which is considered a marker of damage to the alveolar–capillary barrier. [ 47 ] Both changes were significantly inhibited by TMZ, where it caused 81.3% and 91.5% decreases in silica‐induced increase in TGF‐β levels and total protein concentration in BALF, respectively (Figure 4A–C).…”