title: Mast cell tryptase induces microglia activation via protease-activated receptor 2 signaling.
abstract: BACKGROUND
  Mast cell tryptase can stimulate peripheral mononuclear cells activation to cause widespread inflammation. However, the influence of tryptase on microglia, the resident immune cells in the brain, remains uninvestigated. Since microglia plays a pivotal role in immune surveillance of CNS, we studied the effect of tryptase on microglia activation.
  
  
  METHODS
  Induction of microglia activation by tryptase was examined with primary cultured microglia. TNF-alpha and IL-6 was measured with a commercial ELISA kit. Intracellular ROS was determined by dichlorodihydrofluorescein oxidation. Mitochondrial membrane potential was assessed with the MitoProbe™ JC-1 assay kit. And MAPK and NF-kappa B phosphorylation were evaluated by Western blot.
  
  
  RESULTS
  We found that tryptase stimulated microglia activation and subsequently produced proinflammatory factors TNF-alpha, IL-6 and ROS. Inhibition of PAR-2 activation reduced tryptase-induced TNF-alpha, IL-6 and ROS production, and mitochondrial membrane potential loss in microglia. Among the three members of MAPK pathway, ERK and p38, but not JNK mediated tryptase-induced microglia activation. Inhibition of PAR-2 suppressed tryptase-induced ERK and p38 MAPK pathway activation in microglia. Tryptase also activated NF-kappa B within 30 min, and ammonium pyrrolidinedithiocarbamate, an inhibitor of NF- kappa B, reduced tryptase-induced TNF-alpha and IL-6 release.
  
  
  CONCLUSIONS
  Our results suggest that tryptase can induce microglia activation and pro-inflammatory mediator release via PAR-2-MAPK-NF-kappa B signaling pathway, which will contribute to the development of microglia-mediated inflammation in brain.
authors.affiliation: Clinical Research Center, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Zhang
authors.forename: Xiaoning
authors.initials: X
authors.lastname: Zeng
authors.forename: Haiwei
authors.initials: H
authors.lastname: Yang
authors.forename: Gang
authors.initials: G
authors.lastname: Hu
authors.forename: Shaoheng
authors.initials: S
authors.lastname: He
mesh_terms: D000818:Animals; D015850:Interleukin-6 / Q000096:biosynthesis; D020935:MAP Kinase Signaling System; D017628:Microglia / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D044464:Receptor, PAR-2 / Q000378:metabolism*; D015398:Signal Transduction; D053802:Tryptases / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D015850:Interleukin-6; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D044464:Receptor, PAR-2; D014409:Tumor Necrosis Factor-alpha; D053802:Tryptases