title: NRF2 Signaling Negatively Regulates Phorbol-12-Myristate-13-Acetate (PMA)-Induced Differentiation of Human Monocytic U937 Cells into Pro-Inflammatory Macrophages.
abstract: Blood monocytes are recruited to injured tissue sites and differentiate into macrophages, which protect against pathogens and repair damaged tissues. Reactive oxygen species (ROS) are known to be an important contributor to monocytes' differentiation and macrophages' function. NF-E2-related factor 2 (NRF2), a transcription factor regulating cellular redox homeostasis, is known to be a critical modulator of inflammatory responses. We herein investigated the role of NRF2 in macrophage differentiation using the human monocytic U937 cell line and phorbol-12-myristate-13-acetate (PMA). In U937 cells with NRF2 silencing, PMA-stimulated cell adherence was significantly facilitated when compared to control U937 cells. Both transcript and protein levels for pro-inflammatory cytokines, including interleukine-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNFα) were highly elevated in PMA-stimulated NRF2-silenced U937 compared to the control. In addition, PMA-inducible secretion of monocyte chemotactic protein 1 (MCP-1) was significantly high in NRF2-silenced U937. As an underlying mechanism, we showed that NRF2-knockdown U937 retained high levels of cellular ROS and endoplasmic reticulum (ER) stress markers expression; and subsequently, PMA-stimulated levels of Ca2+ and PKCα were greater in NRF2-knockdown U937 cells, which caused enhanced nuclear accumulation of nuclear factor-ҡB (NFҡB) p50 and extracellular signal-regulated kinase (ERK)-1/2 phosphorylation. Whereas the treatment of NRF2-silenced U937 cells with pharmacological inhibitors of NFҡB or ERK1/2 largely blocked PMA-induced IL-1β and IL-6 expression, indicating that these pathways are associated with cell differentiation. Taken together, our results suggest that the NRF2 system functions to suppress PMA-stimulated U937 cell differentiation into pro-inflammatory macrophages and provide evidence that the ROS-PKCα-ERK-NFҡB axis is involved in PMA-facilitated differentiation of NRF2-silenced U937 cells.
authors.affiliation: College of Pharmacy, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 712-749, Republic of Korea.
authors.forename: Min-Gu
authors.initials: MG
authors.lastname: Song
authors.affiliation: College of Pharmacy, The Catholic University of Korea, Bucheon, Gyeonggi-do 420-743, Republic of Korea.
authors.forename: In-Geun
authors.initials: IG
authors.lastname: Ryoo
authors.affiliation: College of Pharmacy, The Catholic University of Korea, Bucheon, Gyeonggi-do 420-743, Republic of Korea.
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Choi
authors.affiliation: College of Pharmacy, The Catholic University of Korea, Bucheon, Gyeonggi-do 420-743, Republic of Korea.
authors.forename: Bo-Hyun
authors.initials: BH
authors.lastname: Choi
authors.affiliation: Seoul National University Bundang Hospital, Sungnam, Gyeonggi-do 463-707, Republic of Korea.
authors.forename: Sang-Tae
authors.initials: ST
authors.lastname: Kim
authors.affiliation: College of Pharmacy, The Catholic University of Korea, Bucheon, Gyeonggi-do 420-743, Republic of Korea.
authors.forename: Tae-Hwe
authors.initials: TH
authors.lastname: Heo
authors.affiliation: College of Pharmacy, The Catholic University of Korea, Bucheon, Gyeonggi-do 420-743, Republic of Korea.
authors.forename: Joo Young
authors.initials: JY
authors.lastname: Lee
authors.affiliation: College of Pharmacy, Yeungnam University, Gyeongsan, Gyeongsangbuk-do 712-749, Republic of Korea.
authors.forename: Pil-Hoon
authors.initials: PH
authors.lastname: Park
authors.affiliation: College of Pharmacy, The Catholic University of Korea, Bucheon, Gyeonggi-do 420-743, Republic of Korea.
authors.forename: Mi-Kyoung
authors.initials: MK
authors.lastname: Kwak
mesh_terms: D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D016207:Cytokines / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress; D055785:Gene Knockdown Techniques; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000378:metabolism; D051571:Protein Kinase C-alpha / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D016207:Cytokines; D051267:NF-E2-Related Factor 2; D052002:NF-kappa B p50 Subunit; C495635:NFE2L2 protein, human; C489548:NFKB1 protein, human; D017382:Reactive Oxygen Species; C496628:PRKCA protein, human; D051571:Protein Kinase C-alpha; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium