Cysteine peptidase cathepsin X as a therapeutic target for simultaneous TLR3/4-mediated microglia activation

Pišlar, Anja (author), Božić Nedeljković, Biljana (author), Perić, Mina (author), Jakoš, Tanja (author), Zidar, Nace (author), Kos, Janko (author)

Microglia are resident macrophages in the central nervous system that are involved in immune responses driven by toll-like receptors (TLRs). Microglia-mediated inflammation can lead to central nervous system disorders, and more than one TLR might be involved in these pathological processes. The cysteine peptidase cathepsin X has been recognized as a pathogenic factor for inflammation-induced neurodegeneration. Here, we hypothesized that simultaneous TLR3 and TLR4 activation induces synergized microglia responses and that these phenotype changes affect cathepsin X expression and activity. Murine microglia BV2 cells and primary murine microglia were exposed to the TLR3 ligand polyinosinic-polycytidylic acid (poly(I:C)) and the TLR4 ligand lipopolysaccharide (LPS), individually and simultaneously. TLR3 and TLR4 co-activation resulted in increased inflammatory responses compared to individual TLR activation, where poly(I:C) and LPS induced distinct patterns of proinflammatory factors together with different patterns of cathepsin X expression and activity. TLR co-activation decreased intracellular cathepsin X activity and increased cathepsin X localization at the plasma membrane with concomitant increased extracellular cathepsin X protein levels and activity. Inhibition of cathepsin X in BV2 cells by AMS36, cathepsin X inhibitor, significantly reduced the poly(I:C)- and LPS-induced production of proinflammatory cytokines as well as apoptosis. Additionally, inhibiting the TLR3 and TLR4 common signaling pathway, PI3K, with LY294002 reduced the inflammatory responses of the poly(I:C)- and LPS-activated microglia and recovered cathepsin X activity. We here provide evidence that microglial cathepsin X strengthens microglia activation and leads to subsequent inflammation-induced neurodegeneration. As such, cathepsin X represents a therapeutic target for treating neurodegenerative diseases related to excess inflammation.

• Language: English
• Keywords: microglia, toll-like receptors, cathepsin X, proinfammatory mediators, neuroinfammation, neuroprotection
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FFA - Faculty of Pharmacy
• Publication status: Published
• Publication version: Version of Record
• Year: 2022
• Number of pages: Str. 2258–2276
• Numbering: Vol. 59, iss. 4
• PID: 20.500.12556/RUL-145265
• UDC: 616-097:616.8
• ISSN on article: 0893-7648
• DOI: 10.1007/s12035-021-02694-2
• COBISS.SI-ID: 95406083
• Publication date in RUL: 14.04.2023

Record is a part of a journal

• Title: Molecular neurobiology
• Shortened title: Mol. neurobiol.
• Publisher: Springer Nature
• ISSN: 0893-7648
• COBISS.SI-ID: 25975552

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: mikroglija, receptorji TLR, katepsin X, protivnetni mediatorji, nevrovnetje, nevroprotekcija, motnje živčnega sistema, imunski odziv