title: Keap1 silencing boosts lipopolysaccharide-induced transcription of interleukin 6 via activation of nuclear factor κB in macrophages.
abstract: Interleukin-6 (IL6) is a multifunctional cytokine that regulates immune and inflammatory responses. Multiple transcription factors, including nuclear factor κB (NF-κB) and nuclear factor E2-related factor 2 (Nrf2), regulate IL6 transcription. Kelch-like ECH-associated protein 1 (Keap1) is a substrate adaptor protein for the Cullin 3-dependent E3 ubiquitin ligase complex, which regulates the degradation of many proteins, including Nrf2 and IκB kinase β (IKKβ). Here, we found that stable knockdown of Keap1 (Keap1-KD) in RAW 264.7 (RAW) mouse macrophages and human monocyte THP-1 cells significantly increased expression of Il6, and Nrf2-target genes, under basal and lipopolysaccharide (LPS, 0.001-0.1 μg/ml)-challenged conditions. However, Nrf2 activation alone, by tert-butylhydroquinone treatment of RAW cells, did not increase expression of Il6. Compared to cells transduced with scrambled non-target negative control shRNA, Keap1-KD RAW cells showed enhanced protein levels of IKKβ and increased expression and phosphorylation of NF-κB p65 under non-stressed and LPS-treated conditions. Because the expression of Il6 in Keap1-KD RAW cells was significantly attenuated by silencing of Ikkβ, but not Nrf2, it appears that stabilized IKKβ is responsible for the enhanced transactivation of Il6 in Keap1-KD cells. This study demonstrated that silencing of Keap1 in macrophages boosts LPS-induced transcription of Il6 via NF-κB activation. Given the importance of IL6 in the inflammatory response, the Keap1-IKKβ-NF-κB pathway may be a novel target for treatment and prevention of inflammation and associated disorders.
authors.affiliation: Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China; Institute for Chemical Safety Sciences, The Hamner Institutes for Health Sciences, 6 Davis Drive, Research Triangle Park, NC 27709, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Lv
authors.forename: Peng
authors.initials: P
authors.lastname: Xue
authors.forename: Jian
authors.initials: J
authors.lastname: Dong
authors.forename: Hui
authors.initials: H
authors.lastname: Peng
authors.forename: Rebecca
authors.initials: R
authors.lastname: Clewell
authors.forename: Aiping
authors.initials: A
authors.lastname: Wang
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: Shuangqing
authors.initials: S
authors.lastname: Peng
authors.forename: Weidong
authors.initials: W
authors.lastname: Qu
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Melvin E
authors.initials: ME
authors.lastname: Andersen
authors.forename: Jingbo
authors.initials: J
authors.lastname: Pi
mesh_terms: D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D020868:Gene Silencing / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis / Q000235:genetics*; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D000072019:Kelch-Like ECH-Associated Protein 1; D008070:Lipopolysaccharides / Q000633:toxicity*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation / Q000235:genetics*
chemical_list: C508600:IL6 protein, human; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D008070:Lipopolysaccharides; D016328:NF-kappa B
keywords: IKKβ; IL6; Keap1; Macrophage; NF-κB; Nrf2