Inflammation Increases the Opening State of Channels in the Epithelium, Releasing High Levels of ATP that Resulted in a Decrease on Mucociliary Transport Velocity in the Airways

Abstract

ATP is one of the chemical signals locally released by the airway epithelium associated with an autocrine/paracrine mechanism to control basal ciliary beat frequency (CBF). A recent study has reported that ATP has a dual effect on CBF, since ATP (μM) increases CBF, but high levels of ATP (mM) significantly decreases CBF in cultures of mouse tracheal epithelial cell. This nucleotide can be released by different mechanisms that include hemichannels of connexins (Cx43) and pannexins (Panx1), and more recently the Calhm1 channel. In several cell types it has recently reported that in pathophysiological conditions, connexins and pannexins channels could modify their opening state. Furthermore, high levels of ATP have been measured in the bronchoalveolar fluid of asthmatic patients and ovoalbumin‐induced asthmatic mouse model (OVA). The asthmatic patients also have infiltration of inflammatory cells in the pulmonary epithelium, reduced CBF and mucociliary transport effectiveness. Mucociliary transport is the first defense mechanism in the airways, where particles are trapped in the mucus and removed by the ciliary beating to the pharynx. We proposed the following objective: Determine the relation between levels of ATP of an asthmatic OVA mouse model, the opening state of the channels that control the release of this nucleotide and the effectiveness of mucociliary transport in the airways. The protocols used in this study were approved, by the ethics committee of the university that follow international guidelines for animal care. We measured extracellular ([ATP]e) with a luminometric assay and evaluated the infiltration of inflammatory cells in the lung parenchyma by histochemistry (H&E). The ethidium bromide (5μM) capture was recorded with a camera mounted on an Olympus upright microscope. The microspheres (6μm) velocity on the surface of the trachea epithelium was registered with a videomicroscopy system and analyzed with the ImageJ program. We observed greater infiltration of inflammatory cells in the pulmonary parenchyma of the asthmatic mouse, compared with the control mouse. Also, we established that high levels of ATP were present in asthmatic mice trachea lavage compared to control animals. The microspheres velocity was diminished in OVA mouse model compare to control mice and addition of 1mM of ATP in control or asthmatic mice transiently stopped the microspheres movement. Furthermore, we observed a significant increase in the percentage of ethidium bromide capture by the epithelium of asthmatic mice compare to controls. These results demonstrated that in an inflammatory condition, channels involved in the ATP release increased their opening state in the airways epithelium. This effect could be associated to high levels of ATP measured in asthma, condition that resulted in a deleterious effect on mucociliary transport effectiveness.Support or Funding InformationCONICYT 21160416, LL.A. Millennium Institute on Immunology and Immunotherapy (P09/016‐F) MV.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.