Inhibition of PKR ameliorates lipopolysaccharide-induced acute lung injury by suppressing NF-κB pathway in mice

Abstract

Acute lung injury (ALI) is characterized by dramatic lung inflammation and alveolar epithelial cell death. Although protein kinase R (PKR) (double-stranded RNA-activated serine/threonine kinase) has been implicated in inflammatory response to bacterial cell wall components, whether it plays roles in lipopolysaccharide (LPS)-induced ALI remains unclear. This study was aimed to reveal whether and how PKR was involved in LPS-induced ALI pathology and the potential effects of its specific inhibitor, C16 (C13H8N4OS). During the experiment, mice received C16 (100 or 500 ug/kg) intraperitoneally 1 h before intratracheal LPS instillation. Then, whole lung lavage was collected for analysis of total protein levels and proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6. The lungs were tested for Western blot, transferase-mediated dUTP nick-end labeling (TUNEL) stain and immunohistochemistry. Results showed that PKR phosphorylation increased significantly after LPS instillation. Furthermore, PKR specific inhibition attenuated LPS-induced lung injury (hematoxylin and eosin stain), reduced lung protein permeability (total protein levels in whole lung lavage) and suppressed proinflammatory cytokines (TNF-α, IL-1β and IL-6) and lung apoptosis (TUNEL stain and caspase3 activation). Moreover, mechanism-study showed that C16 significantly suppressed I kappa B kinase (IKK)/I kappa B alpha (IκBα)/NF-κB signaling pathway after LPS challenge. These findings suggested that PKR inhibition ameliorated LPS-induced lung inflammation and apoptosis in mice by suppressing NF-κB signaling pathway.