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A3833 - The Bcl-2 Family Protein, Noxa, Inhibits NF-κB-Mediated Inflammation in Airway Epithelia by Delaying IκBα Degradation
Author Block: J. T. Jones1, C. Zhang2, H. S. Chand3, C. M. Evans4, B. F. Dickey5, Y. A. Mebratu6, Y. Tesfaigzi7; 1COPD, Lovelace Respiratory Research Institute, Albuquerque, NM, United States, 2COPD program, Lovelace Respiratory Research Institute, Albuquerque, NM, United States, 3Immunology, Florida International University, MIAMI, FL, United States, 4Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Denver School of Medicine, Aurora, CO, United States, 5Pulmonary Medicine, Univ Texas M D Anderson Cancer Ctr, Houston, TX, United States, 6Lovelace Resp Rsch Inst, Albuquerque, NM, United States, 7COPD Program, Lovelace Respiratory Research Institute, Albuquerque, NM, United States.
Introduction: The Bcl-2 family of proteins regulates cell numbers in airway epithelia and the apoptotic death of hyperplastic mucous cells during resolution of inflammation. Noxa, a pro-apoptotic protein, does not affect mucous cell hyperplasia (MCH), despite being expressed in the airway epithelium, but affects inflammation. The present studies investigated the mechanisms by which Noxa blocks inflammation. Methods: Wild-type (noxa+/+) or Noxa-deficient (noxa-/-) mice on C57Bl/6 background were exposed to house dust mite (HDM) and bronchoalveolar lavage (BAL) was analyzed for inflammatory cell numbers. We tested activation of Nuclear Factor-kappaB (NF-κB) by evaluating nuclear content of transcription factor p65 in primary mouse airway epithelial cells from noxa+/+ and noxa-/- mice. We performed MALDI-TOF Mass Spectrometry to evaluate Noxa-interacting proteins. Transgenic mice that inducibly express Noxa in airway epithelia were generated and exposed to HDM. Additionally, we used peptides derived from the different domains of Noxa and instilled HDM-exposed mice with the active peptide. Results: Noxa-/- compared to noxa+/+ mice exposed to HDM showed increased inflammatory cells in the lung. MALDI-TOF Mass Spectrometry identified that Noxa interacted with phosphorylated heat shock protein 27 (p-HSP-27). Reduced Noxa/p-HSP-27 interaction or suppression of HSP-27 expression prevented the anti-inflammatory role of Noxa. Adenoviral expression of Noxa and treatment with the N-terminal peptide of Noxa reduced TNFα-induced p65 nuclear translocation and stabilized its inhibitor, IκBα. Noxa protein and peptide did not affect phosphorylation of IκBα, but delayed the degradation of K48-ubiquitylated IκBα. Both transgenic expression of Noxa in airway epithelia and instillation of the N-terminal Noxa-derived peptide significantly attenuated HDM-induced eosinophilia. Conclusions: Noxa inhibits inflammation by stabilizing ubiquitylated IκBα. This inhibitory effect of Noxa involves a Noxa/p-HSP-27 interaction that blocks nuclear translocation of NF-κB and inflammation. These findings show a novel non-cell death-related role for Noxa that can have therapeutic significance.