Differential Requirement for c-Jun N-terminal Kinase 1 in Lung Inflammation and Host Defense

The c-Jun N-terminal kinase (JNK) - 1 pathway has been implicated in the cellular response to stress in many tissues and models. JNK1 is known to play a role in a variety of signaling cascades, including those involved in lung disease pathogenesis. Recently, a role for JNK1 signaling in immune cell function has emerged. The goal of the present study was to determine the role of JNK1 in host defense against both bacterial and viral pneumonia, as well as the impact of JNK1 signaling on IL-17 mediated immunity. Wild type (WT) and JNK1 −/− mice were challenged with Escherichia coli, Staphylococcus aureus, or Influenza A. In addition, WT and JNK1 −/− mice and epithelial cells were stimulated with IL-17A. The impact of JNK1 deletion on pathogen clearance, inflammation, and histopathology was assessed. JNK1 was required for clearance of E. coli, inflammatory cell recruitment, and cytokine production. Interestingly, JNK1 deletion had only a small impact on the host response to S. aureus. JNK1 −/− mice had decreased Influenza A burden in viral pneumonia, yet displayed worsened morbidity. Finally, JNK1 was required for IL-17A mediated induction of inflammatory cytokines and antimicrobial peptides both in epithelial cells and the lung. These data identify JNK1 as an important signaling molecule in host defense and demonstrate a pathogen specific role in disease. Manipulation of the JNK1 pathway may represent a novel therapeutic target in pneumonia

JNK1 modulates the inflammatory response to IL-17A in vivo.

<p>WT and JNK1 −/− mice were challenged with 5×10⁸ pfu of adenovirus expressing IL-17A for 3 days (A–C) (N = 8, 7) or 1 µg of recombinant IL-17A for 24 hours (D–F)(N = 6, 7). A – inflammatory cells in BAL fluid. B, C, D, E – inflammatory cytokines in lung homogenate. F – antimicrobial peptide expression in lung tissue. * p<0.05, # p<0.10, nd – not detected.</p

JNK1 is required for host defense against gram-negative bacterial pneumonia.

<p>WT and JNK1 −/− mice were challenged with 10⁷ cfu of <i>E. coli</i> for 24 hours (N = 8, 10). A – bacterial colony counts in lung homogenate. B – inflammatory cells in BAL fluid. C, D – inflammatory cytokines in lung homogenate. E – antimicrobial peptide expression in lung tissue. F – inflammatory cells in BAL fluid from mice challenged with PBS for 24 hours (N = 6, 6). * p<0.05, # p<0.10.</p

JNK1 modulates Influenza A induced inflammation.

<p>WT and JNK1 −/− mice were challenged with 150 pfu of Influenza A PR/8/34 H1N1 for 7 days. A – inflammatory cells in BAL fluid. B, C, D, E – inflammatory cytokines in lung homogenate. * p<0.05, # p<0.10.</p

JNK1 is required for the epithelial cell response to IL-17A.

<p>MTEC from WT and JNK1 −/− mice were treated with IL-17A (10 ng/ml) for 24 hours. A – JNK1 activation by in vitro kinase assay. B, C – inflammatory cytokines produced (N = 6). D, E – inflammatory cytokine gene expression by RT-PCR (N = 3). F – antimicrobial peptide expression by RT-PCR (N = 3). * p<0.05.</p

JNK1 is not required for host defense against gram-positive pneumonia.

<p>WT and JNK1 −/− mice were challenged with 10⁸ cfu of <i>S. aureus</i> for 24 hours (N = 5, 8). A – bacterial colony counts in lung homogenate. B – inflammatory cells in BAL fluid. C, D, E – inflammatory cytokines in lung homogenate. * p<0.05.</p

JNK1 alters lung histopathology during Influenza A infection.

<p>WT and JNK1 −/− mice were challenged with 150 pfu of Influenza A PR/8/34 H1N1 for 7 days. A – lung histology 200× (N = 9, 8). B – lung histology scoring (N = 9, 8). C – mucin gene expression by RT-PCR (N = 9, 8).</p

JNK1 regulates host defense against Influenza A infection.

<p>WT and JNK1 −/− mice were challenged with 150 pfu of Influenza A PR/8/34 H1N1 for 7 days. A – weight loss during infection (N = 9, 8). B – viral burden by plaque assay (N = 4, 4). C – viral burden by RT-PCR for M protein expression (N = 9, 8). * p<0.05.</p

JNK1 is not required for antiviral interferon or T cell recruitment in response to Influenza A.

<p>WT and JNK1 −/− mice were challenged with 150 pfu of Influenza A PR/8/34 H1N1 for 7 days. A – type I interferon expression by RT-PCR (N = 9, 8). B – T cell profile in lung homogenate by flow cytometry (N = 7, 9).</p

JNK1 is required for peribronchial inflammation during gram-negative bacterial pneumonia.

<p>WT and JNK1 −/− mice were challenged with 10⁷ cfu of <i>E. coli</i> for 24 hours (N = 8, 10). A – lung histology 100× (top panels), 200× (lower panels). B – lung histology scoring. * p<0.05.</p