Submitted on October 21, 2007
Revised on January 30, 2008
IKK
Causes Chromatin Modification on Pro-inflammatory Genes by Cigarette Smoke in Mouse Lung
Se-Ran Yang1, Samantha Valvo1, Hongwei Yao1, Aruna Kode1, Saravanan Rajendrasozhan1, Indika Edrisinghe1, Samuel Caito1, David Adenuga1, Ryan Henry1, George Fromm2, Sanjay Maggirwar3, Jian-Dong Li3, Michael D Bulger2, and Irfan Rahman1*
1 Department of Environmental Medicine, University of Rochester Medical Center, Rochester, New York, USA,
2 Department of Pediatrics, University of Rochester Medical Center, Rochester, New York, USA,
3 Department of Microbiology and Immunology, University of Rochester Medical Center, Rochester, New York, USA
* To whom correspondence should be addressed. E-mail: Irfan_Rahman{at}urmc.rochester.edu.
Cigarette smoke (CS) induces abnormal and sustained lung inflammation, however the molecular mechanism underlying sustained inflammation is not known. It is well known that activation of I
B kinase
(IKK) leads to transient translocation of active NF-B (RelA/p65-p50) in the nucleus and transcription of pro-inflammatory genes, whereas the role of IKK
in perpetuation of sustained inflammatory response is not known. We hypothesized that CS activates IKK and causes histone acetylation on the promoters of pro-inflammatory genes leading to sustained transcription of pro-inflammatory mediators in mouse lung in vivo and in human monocyte/macrophage cell line (MonoMac6) in vitro. CS exposure to C57BL/6J mice resulted in activation of IKK leading to phosphorylation of ser10 and acetylation of lys9 on histone H3 on the promoters of IL-6 and MIP-2 genes in mouse lung. The increased level of IKK was associated with increased acetylation of lys310 RelA/p65 on pro-inflammatory gene promoters. The role of IKK in CS-induced chromatin modification was confirmed by gain and loss of IKK in MonoMac6 cells. Over-expression of IKK was associated with augmentation of CS-induced pro-inflammatory effects, and phosphorylation of ser10 and acetylation of lys9 on histone H3 whereas transfection of IKK dominant negative mutants reduced CS-induced chromatin modification and pro-inflammatory cytokine release. Moreover, phosphorylation of ser276 and acetylation of lys310 of RelA/p65 was augmented in response to CSE in MonoMac6 cells transfected with IKK. Taken together, these data suggest that IKK plays a key role in CS-induced pro-inflammatory gene transcription through phospho-acetylation of both RelA/p65 and histone H3.
