title: Inhibition of cathepsin X reduces the strength of microglial-mediated neuroinflammation.
abstract: Inflammation plays a central role in the processes associated with neurodegeneration. The inflammatory response is mediated by activated microglia that release inflammatory mediators to the neuronal environment. Microglia-derived lysosomal cathepsins, including cathepsin X, are increasingly recognized as important mediators of the inflammation involved in lipopolysaccharide (LPS)-induced neuroinflammation. The current study was undertaken to investigate the role of cathepsin X and its molecular target, γ-enolase, in neuroinflammation and to elucidate the underlying mechanism. We determined that the exposure of activated BV2 and EOC 13.31 cells to LPS led to increased levels of cathepsin X protein and activity in the culture supernatants in a concentration- and time-dependent manner. In contrast, LPS stimulation of these two cells reduced the release of active γ-enolase in a manner regulated by the cathepsin X activity. Cathepsin X inhibitor AMS36 significantly reduced LPS-induced production of nitric oxide, reactive oxygen species and the pro-inflammatory cytokines interleukin-6 and tumor necrosis factor-α from BV2 cells. Inhibition of cathepsin X suppressed microglial activation through the reduced caspase-3 activity, together with diminished microglial cell death and apoptosis, and also through inhibition of the activity of the mitogen-activated protein kinases. Further, SH-SY5Y treatment with culture supernatants of activated microglial cells showed that cathepsin X inhibition reduces microglia-mediated neurotoxicity. These results indicate that up-regulated expression and increased release and activity of microglial cathepsin X leads to microglia activation-mediated neurodegeneration. Cathepsin X inhibitor caused neuroprotection via its inhibition of the activation of microglia. Cathepsin X could thus be a potential therapeutic target for neuroinflammatory disorders.
authors.affiliation: Department of Pharmaceutical Biology, Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, SI-1000 Ljubljana, Slovenia. Electronic address: anja.pislar@ffa.uni-lj.si.
authors.forename: Anja
authors.initials: A
authors.lastname: Pišlar
authors.affiliation: Institute for Physiology and Biochemistry, Faculty of Biology, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia.
authors.forename: Biljana
authors.initials: B
authors.lastname: Božić
authors.affiliation: Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, SI-1000 Ljubljana, Slovenia.
authors.forename: Nace
authors.initials: N
authors.lastname: Zidar
authors.affiliation: Department of Pharmaceutical Biology, Faculty of Pharmacy, University of Ljubljana, Aškerčeva 7, SI-1000 Ljubljana, Slovenia; Department of Biotechnology, Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia.
authors.forename: Janko
authors.initials: J
authors.lastname: Kos
mesh_terms: D000613:Aminobutyrates / Q000008:administration & dosage*; D000818:Animals; D002403:Cathepsins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D004660:Encephalitis / Q000378:metabolism*; D008070:Lipopolysaccharides; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D017382:Reactive Oxygen Species; D013386:Succinates / Q000008:administration & dosage*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C000621155:AMS36 compound; D000613:Aminobutyrates; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D013386:Succinates; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D002403:Cathepsins; C000602812:cathepsin X, mouse; D010751:Phosphopyruvate Hydratase
keywords: Cathepsin X; Microglia; Neuroinflammation; Neuroprotection; γ-Enolase