title: Cross-talk between the Toll-like receptor 4 and Notch1 pathways augments the inflammatory response in the interstitial cells of stenotic human aortic valves.
abstract: OBJECTIVE
  Calcific aortic stenosis is a chronic inflammatory disease, and aortic valve interstitial cells (AVIC) play an important role in valvular inflammation. Whereas AVIC from stenotic aortic valves exhibit an augmented response to Toll-like receptor 4 (TLR4) stimulation, the underlying mechanism is unclear. This study tested the hypothesis that an excessive cross-talk between the TLR4 and Notch1 pathways is responsible for augmentation of the inflammatory response to lipopolysaccharide (LPS) in AVIC of stenotic valves.
  
  
  RESULTS
  Human AVIC were isolated from normal and stenotic leaflets. Nuclear factor kappa-B (NF-κB) activation and production of interleukin-8, monocyte chemoattactrant protein-1, and intercellular adhesion molecule-1 were analyzed after treatment with LPS. The role of Notch1 in the inflammatory response was determined using inhibitor, siRNA, and specific ligand. Cells from diseased valves produced greater levels of chemokines and intercellular adhesion molecule-1 that are associated with enhanced NF-κB activation. Interestingly, diseased cells exhibited augmented Jagged1 release and Notch1 activation after TLR4 stimulation. Inhibition and silencing of Notch1 each resulted in greater suppression of the TLR4-induced inflammatory response in diseased cells. Conversely, activation of Notch1 with a specific ligand, Jagged1, enhanced the LPS-induced inflammatory response in normal AVIC. Further, Notch1 intracellular domain was coimmunoprecipited with the inhibitor of NF-κB kinase after LPS stimulation, and inhibition of Notch1 abrogated the difference in the level of NF-κB activation between diseased and normal cells.
  
  
  CONCLUSIONS
  Notch1 enhances the inflammatory response to TLR4 stimulation in human AVIC through modulating NF-κB activation. Excessive cross-talk between the TLR4 and Notch1 pathways is responsible for augmentation of the TLR4 response in AVIC of stenotic valves.
authors.affiliation: Department of Surgery, University of Colorado Denver, Aurora, CO, USA.
authors.forename: Qingchun
authors.initials: Q
authors.lastname: Zeng
authors.forename: Chunhua
authors.initials: C
authors.lastname: Jin
authors.forename: Lihua
authors.initials: L
authors.lastname: Ao
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Cleveland
authors.forename: Rui
authors.initials: R
authors.lastname: Song
authors.forename: Dingli
authors.initials: D
authors.lastname: Xu
authors.forename: David A
authors.initials: DA
authors.lastname: Fullerton
authors.forename: Xianzhong
authors.initials: X
authors.lastname: Meng
mesh_terms: D000368:Aged; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors; D001024:Aortic Valve Stenosis / Q000378:metabolism / Q000473:pathology*; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured / Q000378:metabolism / Q000473:pathology; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D004151:Dipeptides / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007249:Inflammation / Q000473:pathology; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D000072100:Jagged-1 Protein; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D008875:Middle Aged; D016328:NF-kappa B / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D051881:Receptor, Notch1 / Q000502:physiology*; D000072099:Serrate-Jagged Proteins; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051197:Toll-Like Receptor 4 / Q000502:physiology*
chemical_list: D002135:Calcium-Binding Proteins; D016207:Cytokines; D004151:Dipeptides; D036341:Intercellular Signaling Peptides and Proteins; C000606273:JAG1 protein, human; D000072100:Jagged-1 Protein; D008070:Lipopolysaccharides; D008565:Membrane Proteins; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; D016328:NF-kappa B; C497761:NOTCH1 protein, human; D034741:RNA, Small Interfering; D051881:Receptor, Notch1; D000072099:Serrate-Jagged Proteins; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D053829:Amyloid Precursor Protein Secretases