GADD45a is a novel candidate gene in inflammatory lung injury via influences on Akt signaling

We explored the mechanistic involvement of the growth arrest and DNA damage‐inducible gene GADD45a in lipopolysaccharide (LPS)‐ and ventilator‐induced inflammatory lung injury (VILI). Multiple biochemical and genomic parameters of inflammatory lung injury indicated that GADD45a–/– mice are modestly susceptible to intratracheal LPS‐induced lung injury and profoundly susceptible to high tidal volume VILI, with increases in microvascular permeability and bronchoalveolar lavage levels of inflammatory cytokines. Expression profiling of lung tissues from VILI‐ challenged GADD45a–/– mice revealed strong dysregulation in the B‐cell receptor signaling pathway compared with wild‐type mice and suggested the involvement of PI3 kinase/Akt signaling components. Western blot analyses of lung homogenates confirmed ~50% reduction in Akt protein levels in GADD45a–/– mice accompanied by marked increases in Akt ubiquitination. Electrical resistance measurements across human lung endothelial cell monolayers with either reduced GADD45a or Akt expression (siRNAs) revealed significant potentiation of LPS‐induced human lung endothelial barrier dysfunction, which was attenuated by over‐expression of a constitutively active Aktl transgene. These studies validate GADD45a as a novel candidate gene in inflammatory lung injury and a significant participant in vascular barrier regulation via effects on Akt‐mediated endothelial signaling.— Meyer, N. J., Huang, Y., Singleton, P. A., Sammani, S., Moitra, J., Evenoski, C. L., Husain, A. N., Mitra, S., Moreno‐ Vinasco, L., Jacobson, J. R., Lussier, Y. A., Garcia, J. G. N. GADD45a is a novel candidate gene in inflammatory lung injury via influences on Akt signaling. FASEBJ. 23, 1325–1337 (2009)