title: Activation of microglial cells via protease-activated receptor 2 mediates neuronal cell death in cultured rat primary neuron.
abstract: The role of protease-activated receptor (PARs) in the regulation of microglial activation process is increasingly evident. In the present study, we have investigated the role of PAR-2, which can be activated by trypsin-like proteases, in microglial activation and neuronal cell death. In cultured rat primary microglia, activation of PAR-2 induced nitrite production by PKC- and MAPKs-dependent mechanism. Among the three members of MAPK pathway, ERK and JNK but not p38 mediated PAR-2-induced microglial activation. The down-stream regulator of PAR-2-PKC-MAPK pathway-induced microglial activation was NF-kappaB pathway. Besides nitrite, PAR-2 activation increased production of a variety of inflammatory mediators such as ROS and pro-inflammatory cytokines including TNF-alpha and IL-1beta. The addition of culture spent media from PAR-2 activated microglia induced neuronal cell death in primary rat cortical neuron cultures with apoptotic features such as increased number of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive neurons, dissipation of mitochondrial membrane potential, increased expression of pro-apoptotic Bax, decreased expression of anti-apoptotic Bcl-2, Bcl-X(L), and activation of caspase-3 in neurons. Interestingly, the increased production of cytoactive molecules as well as the neuronal cell death was normalized by PAR-2 or trypsin inhibitor or an NO synthase inhibitor, N(G)-nitro-l-arginine-methyl ester. Taken together, these results suggest that overt PAR-2 activation may induce microglial activation, which contributes to neuronal cell death.
authors.affiliation: Department of Pharmacology, College of Pharmacy, Seoul National University, Seoul, Republic of Korea.
authors.forename: Gyu Hwan
authors.initials: GH
authors.lastname: Park
authors.forename: Se Jin
authors.initials: SJ
authors.lastname: Jeon
authors.forename: Hyun Myung
authors.initials: HM
authors.lastname: Ko
authors.forename: Jae Ryun
authors.initials: JR
authors.lastname: Ryu
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Hahn-Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Seol-Heui
authors.initials: SH
authors.lastname: Han
authors.forename: Young Sun
authors.initials: YS
authors.lastname: Kang
authors.forename: Seung Hwa
authors.initials: SH
authors.lastname: Park
authors.forename: Chan Young
authors.initials: CY
authors.lastname: Shin
authors.forename: Kwang Ho
authors.initials: KH
authors.lastname: Ko
mesh_terms: D000818:Animals; D016923:Cell Death; D002478:Cells, Cultured; D016207:Cytokines / Q000096:biosynthesis; D017628:Microglia / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014357:Trypsin / Q000378:metabolism
chemical_list: D016207:Cytokines; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D044464:Receptor, PAR-2; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D014357:Trypsin