title: Upregulation of protease-activated receptor-1 in astrocytes in Parkinson disease: astrocyte-mediated neuroprotection through increased levels of glutathione peroxidase.
abstract: In the present study, we investigated the expression of protease-activated receptors (PARs), receptors for thrombin, in substantia nigra pars compacta (SNpc) of Parkinson disease (PD) brains and cultures of human neurons, astrocytes, oligodendrocytes, and microglia as determined by immunocytochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR). Expression of PAR-1 was demonstrated only in glial fibrillary acidic protein-positive astrocytes in SNpc, and the number of astrocytes expressing PAR-1 increased in SNpc of PD as compared with nonneurologic control brain. Immunoreactivity for thrombin and prothrombin was stronger in astrocytes and the vessel walls in SNpc of PD brains. PAR-1 was expressed in human astrocytes and neurons, but not in oligodendrocytes or microglia as determined by RT-PCR. We investigated thrombin-mediated activation of human astrocytes. Thrombin treatment activates human astrocytes and induces morphologic change and a marked increase in proliferation of astrocytes. Increased expression of glial cell line-derived growth factor and glutathione peroxidase (GPx) but no change in the expression of nerve growth factor and inflammatory cytokines/chemokine (IL-1beta, IL-6, IL-8, MCP-1) was found in thrombin/PAR-activated astrocytes. Next, we studied the neuroprotective effect exerted by thrombin-activated astrocytes in human cerebral neuron x human neuroblastoma hybrid neurons. Although thrombin showed neurotoxicity against human hybrid neurons in a dose-dependent manner, the conditioned media derived from thrombin-pretreated astrocyte cultures promoted the survival of human hybrid neurons. The protective effect was completely inhibited with a GPx inhibitor, mercaptosuccinic acid, indicating that GPx released from thrombin/PAR-activated astrocytes is responsible for neuroprotection of hybrid neurons against thrombin cytotoxicity. The present study suggests that the increased expression of PAR-1 in astrocytes in SNpc of PD brain is the restorative move taken by the brain to provide neuroprotection against neuronal degeneration and cell death of dopaminergic neurons caused by noxious insults during the progression of PD pathology.
authors.affiliation: Department of Neurology and Department of Laboratory Medicine, Shimane University School of Medicine, Izumo, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Ishida
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nagai
authors.forename: Shotai
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Seung U
authors.initials: SU
authors.lastname: Kim
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D016022:Case-Control Studies; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D009414:Nerve Growth Factors / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010300:Parkinson Disease / Q000378:metabolism / Q000473:pathology*; D011516:Prothrombin / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D044463:Receptor, PAR-1 / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013778:Tetrazolium Salts; D013844:Thiazoles; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
chemical_list: D016207:Cytokines; D005904:Glial Fibrillary Acidic Protein; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D013778:Tetrazolium Salts; D013844:Thiazoles; D011516:Prothrombin; D005979:Glutathione Peroxidase; D013917:Thrombin; C022616:thiazolyl blue