Activation of microglial cells via protease-activated receptor 2 mediates neuronal cell death in cultured rat primary neuron.
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.
Park
Gyu Hwan
GH
Department of Pharmacology, College of Pharmacy, Seoul National University, Seoul, Republic of Korea.
Jeon
Se Jin
SJ
Ko
Hyun Myung
HM
Ryu
Jae Ryun
JR
Lee
Jong Min
JM
Kim
Hahn-Young
HY
Han
Seol-Heui
SH
Kang
Young Sun
YS
Park
Seung Hwa
SH
Shin
Chan Young
CY
Ko
Kwang Ho
KH
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
D016207:Cytokines; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D044464:Receptor, PAR-2; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D014357:Trypsin