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A2776 - Transient Receptor Potential Vanilloid 4 (TRPV4) Channels as Trigger Mechanisms of Ventilator Induced Brain Injury (VIBI)
Author Block: A. Gonzalez-Lopez1, P. Pickerodt1, I. Lopez-Alonso2, C. von Haefen1, M. A. Prado3, H. M. Reimann4, G. Albaiceta2, R. Francis1, C. Spies1; 1Anesthesiology and Intensive Care Medicine, Charité-Universitätsmedizin Berlin CVK, Berlin, Germany, 2Unidad de Cuidados Intensivos Cardiológicos, Área del Corazón, Hospital Universitario Central de Ast, Instituto de Investigación Biosanitaria del Principado de Asturias., Oviedo, Spain, 3Department of Cell Biology, Harvard Medical School, Boston, MA, United States, 4Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany.
RATIONALE: Mechanical ventilation (MV) is a leading precipitation factor in the development of neuropsychological disorders in critically ill patients. An interplay between mechanical forces, mechanosensing and release of mediators within the lung might be the base of these disorders. Hyperdopaminergia and Dopamine receptor D2 (DRD2) activation have showed to play a role during VIBI. The aim of this study was to identify VIBI triggering mechanisms. METHODS: Broncho Alveolar Lavage Fluid (BALF), lungs and hippocampal formation from mechanically ventilated mice lacking TRPV4 and their wild-type counterparts were harvested, and hippocampal DRD2-dependent proapoptotic pathway studied (phosphor-AKT, phospho-GSK3-Beta, Caspase-7, PARP-1 and Tyrosine Hydroxylase). These measurements were repeated in wildtype mice treated with vehicle, lidocaine (intratracheal or intravenous), isso-PPADS (P2X purinoreceptor channel antagonist) and trpv4 knockout mice treated with ATP, right before mechanical ventilation. Hippocampus from sham, ventilated and lidocaine pretreated animals were use for Tandem-mass-tag proteomics. Brain fMRI was used to assess differences in hippocampal activation between trpv4 knockout and wild type mice. Beas-2B human lung epithelial cells were submitted to cyclic mechanical stretch in presence or absence of lidocaine. Levels of TRPV4 were assessed in lung samples from ventilated patients. RESULTS: Pharmacologic pan-inhibition of ion channels using intratracheal, but not intravenous, lidocaine protected mice from VIBI and improved survival. TRPV4 channels activation, mechanoreceptors with a role in ATP extracellular transport, was increased after mechanical ventilation, as well as alveolar levels of extracellular ATP. Expression levels of trpv4 and p2x channels were reduced after mechanical ventilation showing a mid-term compensatory mechanism to the activation of TRPV4-ATP-P2X axis. This result was confirmed in lung samples from ventilated patients. Mechanical stretch of Beas-2B cells resulted in TRPV4 activation and reduced trpv4 and p2x expression, the latter two ameliorated by lidocaine treatment. Isso-PPADS and trpv4 genetic deficiency resulted in protection against VIBI, while a gain of function model using ATP resulted in restoration of VIBI in trpv4 Knockout mice. Proteomics and pathway analysis showed a network of proteins related to neurological disorders disrupted during mechanical ventilation, several of them were restored to sham values after lidocaine treatment. fMRI showed differential hippocampal activation in response to mechanical ventilation between wildtype and knockout mice. CONCLUSIONS: Lung neuronal pan-inhibition abrogates ventilator induced brain injury (VIBI). The TRPV4/ATP/P2X axis seems to play a key role in triggering lung stretch induced hippocampal apoptosis. The use of specific inhibitors for these channels could represent a novel therapeutic approach for critically ill patients.