title: Expression and functional roles of caspase-5 in inflammatory responses of human retinal pigment epithelial cells.
abstract: OBJECTIVE
  To investigate the expression, activation, and functional involvement of caspase-5 in human retinal pigment epithelial (hRPE) cells.
  
  
  METHODS
  Expression and activation of caspase-5 in primary cultured hRPE cells, telomerase-immortalized hTERT-RPE1 cells (hTERT-RPE1), or both, were measured after stimulation with proinflammatory agents IL-1β, TNF-α, lipopolysaccharide (LPS), interferon-γ, monocyte coculture, adenosine triphosphate (ATP), or endoplasmic reticulum (ER) stress inducers. Immunomodulating agents dexamethasone (Dex), IL-10, and triamcinolone acetonide (TA) were used to antagonize proinflammatory stimulation. Cell death ELISA and TUNEL staining assays were used to assess apoptosis.
  
  
  RESULTS
  Caspase-5 mRNA expression and protein activation were induced by LPS and monocyte-hRPE coculture. Caspase-5 activation appeared as early as 2 hours after challenge by LPS and consistently increased to 24 hours. Meanwhile, caspase-1 expression and protein activation were induced by LPS. Activation of caspase-5 was blocked or reduced by Dex, IL-10, and TA. Activation of caspase-5 and -1 was also enhanced by ATP and ER stress inducers. Expression and activation of caspase-5 were inhibited by a caspase-1-specific inhibitor. Caspase-5 knockdown reduced caspase-1 protein expression and activation and inhibited TNF-α-induced IL-8 and MCP-1. In contrast to caspase-4, the contribution of caspase-5 to stress-induced apoptosis was moderate.
  
  
  CONCLUSIONS
  Caspase-5 mRNA synthesis, protein expression, and catalytic activation were highly regulated in response to various proinflammatory stimuli, ATP, and ER stress inducers. Mutual activation between caspase-5 and -1 suggests caspase-5 may work predominantly in concert with caspase-1 in modulating hRPE inflammatory responses.
authors.affiliation: Department of Ophthalmology, University of Michigan, Ann Arbor, Michigan 48105, USA.
authors.forename: Zong-Mei
authors.initials: ZM
authors.lastname: Bian
authors.forename: Susan G
authors.initials: SG
authors.lastname: Elner
authors.forename: Hemant
authors.initials: H
authors.lastname: Khanna
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Murga-Zamalloa
authors.forename: Suresh
authors.initials: S
authors.lastname: Patil
authors.forename: Victor M
authors.initials: VM
authors.lastname: Elner
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D020170:Caspase 1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D020169:Caspases / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D018920:Coculture Techniques; D003907:Dexamethasone / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress / Q000276:immunology; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D015870:Gene Expression / Q000276:immunology; D055785:Gene Knockdown Techniques; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D016753:Interleukin-10 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects / Q000276:immunology*; D055213:Retinal Pigment Epithelium / Q000166:cytology* / Q000276:immunology*; D014221:Triamcinolone / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D000893:Anti-Inflammatory Agents; C111835:CCL2 protein, human; D018932:Chemokine CCL2; C508609:IL10 protein, human; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D014221:Triamcinolone; D003907:Dexamethasone; D007371:Interferon-gamma; D000255:Adenosine Triphosphate; C099217:CASP5 protein, human; D020169:Caspases; D020170:Caspase 1