Investigation of Chromatin Remodeling and Akt-Dependnet mTOR/S6K Mediate Thrombin-Induced IL-8/CXCL8 in Lung Epithelial Cells

Chronic obstructive pulmonary disease (COPD) and asthma are major global health problem. Almost of COPD and asthma cases are associated with inflammation in small airways and lung parenchyma. There is increasing evidence that chromatin remodeling plays a critical role in the regulation of genes expression. Chromatin modifying complexes can be classified into two major groups. One is histone acetylation by histone acetyltransferase (HAT) and revised by histone deacetylase (HDAC). The second is Switch in mating type/sucrose nonfermentation (SWI/SNF), which containing ATPase activity can facilitate the binding of transcription factor to the nucleosome core. In bronchial biopsies obtained from patients with asthma and COPD, there is an increased HAT activity and reduction HDAC activity, and this correlated with disease severity and with increased IL-8/CXCL8 gene expression. These results indicated that chromatin modification play a crucial role in regulation of IL-8/CXCL8 gene expression. Thrombin generated at sites of vascular injury and well known for its pivotal role in the coagulation cascade, but also plays an important role in lung inflammation such as induces IL-8/CXCL8 espression. Several reports have shown that thrombin levels and activities are increased in bronchoalveolar lavage fluid from asthma patients. Thus, the presence of thrombin in airway fluids appears to be a common feature of a variety of inflammatory lung diseases and plays critical roles in lung inflammation. Our previously study data has showed that thrombin, acting through PAR1 and PAR4, activates the c-Src/IKKα/β signaling pathway to induce NF-κB activation and IL-8/CXCL8 expression in human lung epithelial cells. Little is known, however, regarding the mechanism underlying chromatin remodeling and Akt dependent downstream signal pathway involved in thrombin-induced IL-8/CXCL8 expression. In this project, we further investigate the role of chromatin remodeling and Akt-dependent mTOR/S6K pathway in thrombin-induced IL-8/CXCL8 expression in human lung epithelial cells. Akt also plays a critical role in the induction of inflammatory gene transcription. Furthermore, Akt regulate gene expression through multiple intracellular signaling pathways including the mTOR/S6K. Our preliminary data showed that dominant negative mutant of Akt (AktDN) and rapamycin (an mTOR inhibitor) inhibit thrombin-induced IL-8/CXCL8 release in lung epithelial cells. In addition, thrombin-induced IL-8/CXCL8 expression was potentiates by trichostatin (a HDAC inhibitor), but inhibits by anacardic acid (a HAT inhibitor). Therefore, we suggest that HAT, HDAC, and Akt-dependent mTOR/S6K may be mediated thrombin-induced IL-8/CXCL8 expression. The Central Hypothesis of this project is that chromatin remodeling and Akt/mTOR/S6K mediate thrombin-induced IL-8/CXCL8 expression. In this project, we will test the following 3 hypotheses: Hypothesis 1: HAT and HDAC dependent p65 and histone acetylation contribute to uced IL-8/CXCL8 expression in lung epithelial cell Hypothesis 2: Akt/mTOR/S6K dependent p300 phosphorylation mediates thrombin-induced n and IL-8/CXCL8 expression Hypothesis 3: Thrombin-induced IL-8/CXCL8 expression via Akt/S6K-dependent SWI/SNF omplex formation and MSK1 dependent p65 and histone phosphorylation erstanding of the es become activated in airway inflammatory diseases, which can be useful in therapy of airway inflammatory diseases.