Abstract
BackgroundWe tested the hypothesis that normal human bronchial epithelial (NHBE) cells 1) grown submerged in media and 2) allowed to differentiate at air-liquid interface (ALI) demonstrate disparities in the response to particle exposure.ResultsFollowing exposure of submerged NHBE cells to ambient air pollution particle collected in Chapel Hill, NC, RNA for IL-8, IL-6, heme oxygenase 1 (HOX1) and cyclooxygenase 2 (COX2) increased. The same cells allowed to differentiate over 3, 10, and 21 days at ALI demonstrated no such changes following particle exposure. Similarly, BEAS-2B cells grown submerged in media demonstrated a significant increase in IL-8 and HOX1 RNA after exposure to NIST 1648 particle relative to the same cells exposed after growth at ALI. Subsequently, it was not possible to attribute the observed decreases in the response of NHBE cells to differentiation alone since BEAS-2B cells, which do not differentiate, showed similar changes when grown at ALI. With no exposure to particles, differentiation of NHBE cells at ALI over 3 to 21 days demonstrated significant decrements in baseline levels of RNA for the same proteins (i.e. IL-8, IL-6, HOX1, and COX2). With no exposure to particles, BEAS-2B cells grown at ALI showed comparable changes in RNA for IL-8 and HOX1. After the same particle exposure, NHBE cells grown at ALI on a transwell in 95% N2-5% CO2 and exposed to NIST 1648 particle demonstrated significantly greater changes in IL-8 and HOX1 relative to cells grown in 95% air-5% CO2.ConclusionsWe conclude that growth of NHBE cells at ALI is associated with a diminished biological effect following particle exposure relative to cells submerged in media. This decreased response showed an association with increased oxygen availability.
Highlights
We tested the hypothesis that normal human bronchial epithelial (NHBE) cells 1) grown submerged in media and 2) allowed to differentiate at air-liquid interface (ALI) demonstrate disparities in the response to particle exposure
Relative to submerged cells, normal human bronchial epithelial cells (NHBE) cells grown at air–liquid interface (ALI) for 21 days showed evidence of differentiation with 18.6 ± 3.9 and 11.8 ± 3.0 fold increased RNA for alpha tubulin and muc5b respectively [6]
NHBE cells grown submerged in media demonstrated a significant increase in RNA for the pro-inflammatory mediators IL-8 and IL-6 at 4 hr following exposure to ambient air pollution particle collected from Chapel Hill, North Carolina (Figures 1A and 1B)
Summary
We tested the hypothesis that normal human bronchial epithelial (NHBE) cells 1) grown submerged in media and 2) allowed to differentiate at air-liquid interface (ALI) demonstrate disparities in the response to particle exposure. The airway epithelium provides a critical interface between the body and the external environment In the human, this epithelium is a pseudostratified layer consisting of basal cells, secretory cells, and columnar ciliated cells [1]. When cultured at an air–liquid interface (ALI) in an appropriate medium, normal human bronchial epithelial cells (NHBE) form a polarized, pseudostratified epithelium composed of ciliated and mucus-secreting cells [5,6]. This culture system provides a useful tool for the in vitro study of airway epithelial biology and cell differentiation (i.e. increasing specialization leading to the formation of structurally and functionally distinct cells, tissues, and organs). The in vitro response of differentiated airway epithelial cells may more accurately predict that of the lung relative to that of submerged cells [7]
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