title: Inflammasomes Induced by 7-Ketocholesterol and Other Stimuli in RPE and in Bone Marrow-Derived Cells Differ Markedly in Their Production of IL-1β and IL-18.
abstract: OBJECTIVE
  The inflammatory process plays a major role in the pathogenesis of AMD, and recent data indicate the involvement of inflammasomes. Inflammasomes are intracellular structures that trigger inflammation by producing mature interleukin-(IL)-1β and IL-18. This study examined the capacity of 7-ketocholesterol (7KCh), an oxysterol that accumulates in the retinal pigmented epithelium (RPE) and choroid, to initiate inflammasome formation in RPE and bone marrow-derived cells.
  
  
  METHODS
  Tested cells included fetal human RPE (fhRPE), human ARPE-19 cells, primary human brain microglia cells, and human THP-1 monocyte cells. 7-Ketocholesterol and other compounds were added to the cell cultures, and their stimulatory effects were determined by quantitative PCR and release of cytokines, measured by ELISA and Western blotting.
  
  
  RESULTS
  7-Ketocholesterol efficiently induced inflammasome formation by all primed cell populations, but secreted cytokine levels were higher in cultures of bone marrow-derived cells (microglia and THP-1 cells) than in RPE cultures. Interestingly, inflammasomes formed in cells of the two populations differed strikingly in their preferential production of the two cytokines. Thus, whereas bone marrow-derived cells produced levels of IL-1β that were higher than those of IL-18, the opposite was found with RPE cells, which secreted higher levels of IL-18. Importantly, Western blot analysis showed that IL-18, but not IL-1β, was expressed constitutively by RPE cells.
  
  
  CONCLUSIONS
  7-Ketocholesterol efficiently stimulates inflammasome formation and is conceivably involved in the pathogenesis of AMD. In contrast to bone marrow-derived cells, RPE cells produced higher levels of IL-18 than IL-1β. Further, IL-18, a multifunctional cytokine, was expressed constitutively by RPE cells. These observations provide new information about stimuli and cells and their products assumed to be involved in the pathogenesis of AMD.
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Guangpu
authors: G
authors: Shi
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Siqi
authors: S
authors: Chen
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Wambui S
authors: WS
authors: Wandu
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Osato
authors: O
authors: Ogbeifun
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Lindsey F
authors: LF
authors: Nugent
authors: Section on Epithelial and Retinal Physiology and Disease, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Arvydas
authors: A
authors: Maminishkis
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Samuel J H
authors: SJ
authors: Hinshaw
authors: Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Ignacio R
authors: IR
authors: Rodriguez
authors: Laboratory of Immunology, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors: Igal
authors: I
authors: Gery
mesh_terms: D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000187:drug effects* / Q000502:physiology*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D058847:Inflammasomes / Q000187:drug effects* / Q000502:physiology*; D020382:Interleukin-18 / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism*; D007653:Ketocholesterols / Q000494:pharmacology*; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000502:physiology*
chemical_list: D058847:Inflammasomes; D020382:Interleukin-18; D053583:Interleukin-1beta; D007653:Ketocholesterols; C003001:7-ketocholesterol
keywords: IL-1; IL-18; RPE cells; bone marrow–derived cells; inflammasomes