STRETCH INDUCED ACTIVATION OF MAP KINASES IN THE LUNG

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The treatment of adult respiratory distress syndrome (ARDS) requires the use of positive pressure mechanical ventilation with high levels of inspired oxygen to provide adequate oxygenation to vital organs. Since ARDS is an inhomogeneous disease, some areas are less affected and therefore more compliant. These areas may be mechanically overdistended by ventilator breaths. This ventilatory induced lung injury is characterized by non-cardiogenic pulmonary edema, release of inflammatory cytokines and influx of neutrophils. Little is understood about the effects of lung tissue overdistention at the cellular level. Interleukin 8 (IL-8) is an inflammatory cytokine and chemoattractant for neutrophils in the lung. The MAP kinases, including stress activated protein kinase (SAPK), p38 and ERK-1/2, regulate cellular response to extracellular stimuli, such as oxidant stress, heat shock, growth factors and radiation. We hypothesize that lung cell stretch induced IL-8 production is dependent on activation of the stress responsive MAP kinases, SAPK and/or p38. To examine the effects of stretch at the cellular level we use a cell stretch device that applies uniform biaxial strain to flexible cell culture membranes. Lung cells, including type II alveolar cells and pulmonary artery endothelial cells, are grown on fibronectin coated silicone elastomeric membranes. The applied strain varies from two to 25 percent at 12 to 24 cycles/minute. Our preliminary data show that stretch activates the SAPKs and p38, and increases production of IL-8. Combined pharmacological blockade of both SAPK and p38 activation blocked stretch-induced IL-8 production. This proposal seeks to: 1) define the role MAP kinases, including SAPK, p38, and ERK-1/2, in regulation of stretch induced IL-8 production, through the use of recombinant adenoviruses encoding dominant inhibitory mutants of SAPKs and p38 activation; 2) determine the effect of MAP kinase activation on transcription regulation of IL-8 mRNA and 3) define the pathway of cell stretch-induce MAP kinase activation by determining the upstream activators in the MAP kinase pathways are activated by cell stretch.