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Updated: Jul 10, 2026
Microglia as a Surrogate Biosensor to Determine Nanoparticle Neurotoxicity
Published on: October 25, 2016
Neurotoxicity of microglial cathepsin D revealed by secretome analysis
Sangseop Kim1, Jiyeon Ock, Ae Kyung Kim
1Department of Pharmacology, Kyungpook National University School of Medicine, Daegu, Korea.
Abstract:
Microglia-driven inflammatory responses have both neuroprotective and neurotoxic effects in the CNS. The excessive and chronic activation of microglia, however, may shift the balance towards neurotoxic effects. In this regard, proteins secreted from activated microglia likely play a key role in the neurotoxic effects. To characterize secreted proteins of activated microglia, conditioned media obtained from BV-2 mouse microglia cells were analyzed by two-dimensional gel electrophoresis or liquid chromatography coupled with tandem mass spectrometry. Among many proteins identified in the secretome of activated microglia, an aspartic endoprotease cathepsin D has been found to mediate microglial neurotoxicity based on the following results: (i) the expression of cathepsin D protein was markedly increased in lipopolysaccharide/interferon-γ-stimulated microglia compared with resting microglia as determined by western blot analysis of conditioned media; (ii) knockdown of cathepsin D expression in microglia using short hairpin RNA diminished the neurotoxicity in the coculture of microglia and neuroblastoma cells and (iii) recombinant procathepsin D protein exerted cytotoxic effects toward cultured neurons. In conclusion, cathepsin D appears to play a central role in the microglial neurotoxicity, and could be a potential biomarker or drug target for the diagnosis and treatment of neurodegenerative diseases that are associated with excessive microglial activation and subsequent neurotoxic inflammation.
Insights
Cathepsin D, secreted by activated microglia, drives neurotoxicity. Targeting this protein may offer new treatments for neurodegenerative diseases linked to microglial inflammation.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia-driven inflammation in the central nervous system (CNS) can be both beneficial and harmful.
- Chronic overactivation of microglia can lead to detrimental neurotoxic effects.
- Secreted proteins from activated microglia are implicated in mediating this neurotoxicity.
Purpose of the Study:
- To identify proteins secreted by activated microglia.
- To investigate the role of specific secreted proteins in microglial neurotoxicity.
- To explore potential therapeutic targets for neurodegenerative diseases.
Main Methods:
- Analysis of conditioned media from activated BV-2 mouse microglia cells using 2D gel electrophoresis and liquid chromatography-tandem mass spectrometry.
- Western blot analysis to quantify cathepsin D expression in stimulated versus resting microglia.
- Short hairpin RNA (shRNA) mediated knockdown of cathepsin D in microglia.
- Assessment of neurotoxicity in co-cultures of microglia and neuroblastoma cells.
- Evaluation of cytotoxic effects of recombinant procathepsin D on cultured neurons.
Main Results:
- Cathepsin D, an aspartic endoprotease, was identified as a key protein in the microglia secretome.
- Expression of cathepsin D was significantly upregulated in lipopolysaccharide/interferon-γ-stimulated microglia compared to resting microglia.
- Knockdown of cathepsin D reduced the neurotoxic effects in microglia-neuron co-cultures.
- Recombinant procathepsin D demonstrated direct cytotoxic effects on neurons.
Conclusions:
- Cathepsin D plays a critical role in mediating neurotoxicity driven by activated microglia.
- Cathepsin D represents a potential biomarker for diagnosing neurodegenerative conditions.
- Targeting cathepsin D could be a viable therapeutic strategy for diseases involving excessive microglial activation and neuroinflammation.
