Mechanical ventilation is frequently used in the intensive care unit to support critically ill patients. Studies have shown that mechanical stretch leads to ventilator induced lung injury (VILI) through overdistension of alveolar tissue and augmentation of inflammatory cytokines. The cell signaling involved in VILI is incompletely understood. The mitogen activated protein kinase pathways, particularly the cJun amino terminal kinase (JNK) are implicated in the pathogenesis of VILI. The upstream signaling of JNK in response to mechanical stretch is not well described. In other models of mechanical stretch, integrin signaling is key to mechanotransduction and JNK phosphorylation. This occurs through integrin clustering at focal adhesion complexes and signaling through multiple proteins including focal adhesion kinase (FAK). Results of my initial studies show that: 1) JNK phosphorylation and subsequent early growth response gene (Egr1) expression is increased with mechanical stretch;2) stretch-induced Egr1 expression is dependent on JNK;and 3) JNK activation requires signaling by integrins containing the ?1 subunit. Based on these data, the specific hypothesis for this proposal is that stretch induced JNK phosphorylation in alveolar epithelial cells requires activation of a ?1 containing integrin and subsequent focal adhesion complex formation.
The specific aims are to: 1) Identify the specific integrin(s) involved in stretch-induced JNK phosphorylation and subsequent gene expression in lung epithelial cells. Using a dominant negative ?1 construct, I will confirm that ?1 containing integrins are important for stretch-induced JNK phosphorylation. Then, by using blocking antibodies and/or RNA interference directed towards different integrin a subunits, I will further delineate the specific integrin(s) responsible for JNK phosphorylation. 2) Identify the mechanism by which cyclical stretch-induced integrin activation causes downstream JNK phosphorylation. I will stain focal adhesion complexes with and without stretch as well as using FAK siRNA to examine the role of focal adhesion complex formation and FAK activation in stretch-induced JNK activation.
Mechanical ventilation is used frequently in the intensive care unit and is known to augment lung injury, which carries a high mortality. Further understanding of the cellular pathways involved in lung mechanical stretch could help with potential therapies and approaches to patients on ventilators.
| Klaff, Lindy S; Gill, Sean E; Wisse, Brent E et al. (2012) Lipopolysaccharide-induced lung injury is independent of serum vitamin D concentration. PLoS One 7:e49076 |
