title: Effects of proinflammatory cytokines on the claudin-19 rich tight junctions of human retinal pigment epithelium.
abstract: OBJECTIVE
  Chronic, subclinical inflammation contributes to the pathogenesis of several ocular diseases, including age-related macular degeneration. Proinflammatory cytokines affect tight junctions in epithelia that lack claudin-19, but in the retinal pigment epithelium claudin-19 predominates. We examined the effects of cytokines on the tight junctions of human fetal RPE (hfRPE).
  
  
  METHODS
  hfRPE was incubated with interleukin 1-beta (IL-1β), interferon-gamma (IFNγ), or tumor necrosis factor-alpha (TNFα), alone or in combination. Permeability and selectivity of the tight junctions were assessed using nonionic tracers and electrophysiology. Claudins, occludin, and ZO-1 were examined using PCR, immunoblotting, and confocal immunofluorescence microscopy.
  
  
  RESULTS
  Only TNFα consistently reduced transepithelial electrical resistance (TER) >80%. A serum-free medium revealed two effects of TNFα: (1) decreased TER was observed only when TNFα was added to the apical side of the monolayer, and (2) expression of TNFα receptors and inhibitors of apoptosis were induced from either side of the monolayer. In untreated cultures, tight junctions were slightly cation selective, and this was affected minimally by TNFα. The results were unexplained by effects on claudin-2, claudin-3, claudin-19, occludin, and ZO-1, but changes in the morphology of the junctions and actin cytoskeleton may have a role.
  
  
  CONCLUSIONS
  Claudin-19-rich tight junctions have low permeability for ionic and nonionic solutes, and are slightly cation-selective. Claudin-19 is not a direct target of TNFα. TNFα may protect RPE from apoptosis, but makes the monolayer leaky when it is presented to the apical side of the monolayer. Unlike other epithelia, IFNγ failed to augment the effect of TNFα on tight junctions.
authors: Department of Surgery, Yale University School of Medicine, New Haven, Connecticut, USA.
authors: Shaomin
authors: S
authors: Peng
authors: Geliang
authors: G
authors: Gan
authors: Veena S
authors: VS
authors: Rao
authors: Ron A
authors: RA
authors: Adelman
authors: Lawrence J
authors: LJ
authors: Rizzolo
mesh_terms: D002478:Cells, Cultured; D057167:Claudins / Q000032:analysis; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D053583:Interleukin-1beta / Q000494:pharmacology*; D008565:Membrane Proteins / Q000032:analysis; D062793:Occludin; D010539:Permeability; D010750:Phosphoproteins / Q000032:analysis; D055213:Retinal Pigment Epithelium / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D019108:Tight Junctions / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D062826:Zonula Occludens-1 Protein
chemical_list: D057167:Claudins; D053583:Interleukin-1beta; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; D010750:Phosphoproteins; C569042:TJP1 protein, human; D014409:Tumor Necrosis Factor-alpha; D062826:Zonula Occludens-1 Protein; D007371:Interferon-gamma